WO2013010459A1

WO2013010459A1 - Self-oscillating inverter power supply having variable output frequency slicing and power supply having variable output current

Info

Publication number: WO2013010459A1
Application number: PCT/CN2012/078653
Authority: WO
Inventors: 徐一珺; 叶小娟
Original assignee: 张曦春
Priority date: 2011-07-18
Filing date: 2012-07-13
Publication date: 2013-01-24

Abstract

Provided in the present invention is a self-oscillating inverter power supply of reliable operations and reduced costs and having variable output frequency or output power. The power supply is provided with an inverter switching circuit, a coupling circuit consisting of multiple current transformers, a switch, and a load circuit, constituting a self-oscillating inverter power supply circuit. The current transformers are wound with coils on magnetic cores. Primary windings of the transformers are serial-connected or parallel-connected to each other, and respectively are connected to a power switch and load circuit of the inverter switching circuit. Each transformer is provided with two secondary windings, respectively serial-connected or parallel-connected to a base electrode of an upper and a lower power switching tube of the inverter switching circuit. The switch controls some of the current transformers in the coupling circuit consisting of the multiple current transformers to engage in or disengage from self-oscillation to change the self-oscillation frequency. An advantage of this is the provision of the self-oscillating power supply of reliable operations and having variable output frequency or output power, applicable in self-oscillating electronic ballast of a gas-discharge lamp, providing a light-dimming feature and relatively reduced costs. Also disclosed is a power supply having variable output current.

Description

Description: Output self-oscillation inverter power supply with variable frequency segmentation, variable output power supply

The invention relates to a self-oscillating inverter power source with variable output segmentation, in particular to a gas discharge lamp with a dimming function, a self-excited oscillation electronic ballast inverter power source and a variable output power source.

Background technique

Self-oscillating inverter power supplies that convert DC into AC are widely used, especially in low-cost gas discharge lamp self-oscillating electronic ballasts or electronic transformers. However, it is more difficult for the self-oscillating inverter circuit to achieve an adjustable oscillation frequency or an adjustable output power.

U.S. Patent No. 5,596,247 discloses a relatively simple self-oscillating electronic ballast dimming scheme, but this solution will cause the opening and closing times of the upper and lower tubes of the half bridge to be different, so that the upper and lower tubes work in an asymmetrical state, bringing reliability to the circuit. influences.

Another US patent US6696803 discloses a self-oscillating power supply scheme that can work reliably and can change the operating frequency. However, the fluctuation of the auxiliary power supply voltage in the scheme will affect its oscillation frequency and output power, so the design of the auxiliary power supply is proposed. Higher requirements and higher costs.

China utility model patent CN91217582. 6 proposes an inexpensive segmented dimming self-excited oscillation electronic ballast. The scheme envisages using a toggle switch to short the different taps of the oscillating magnetic ring to realize segmental dimming. However, in fact, the switch short-circuits part of the winding will greatly reduce the output voltage, so the reliable operation of the circuit cannot be guaranteed.

Summary of the invention

In order to overcome the above inconveniences, it is a primary object of the present invention to provide a self-oscillating power supply having a variable output frequency or variable output power that can operate reliably.

The technical problem to be solved by the present invention is: how to make the self-oscillating inverter circuit work at different oscillation frequencies, and can change the operating frequency as required; when the load circuit forms an equivalent load of non-pure resistance, if the circuit can By changing the operating frequency, you can change the output power.

The working principle of the conventional self-oscillating inverter circuit is to use a magnetic ring as a current transformer, and couple the inverter output current to the secondary side of the magnetic ring to drive the inverter switch tube to form self-oscillation. When the parameters of other parts of the circuit are determined, the difference in the coupling relationship between the output current and the secondary side of the magnetic ring will produce different self-oscillation frequencies. For example, the saturation depth of the magnetic ring will cause the self-oscillation frequency to be different.

Based on the above principles, the object of the present invention is achieved as follows:

A self-oscillating inverter power supply with variable output segmentation, the power supply is provided with an inverter switch circuit, a coupling circuit composed of a plurality of current transformers, a switch and a load circuit, and constitutes a self-oscillating inverter power supply circuit, Switch controls multiple batteries A part of the current transformers in the coupling circuit composed of the book current transformer participates in or exits the self-oscillation to change the self-oscillation frequency.

The coupling circuit composed of the plurality of current transformers includes at least two current transformers whose coupling coefficients are independent of each other. The plurality of current transformers disposed in the circuit are wound with a coil on the magnetic core, and the primary windings of the transformer are connected in series with each other, and respectively connected to the power switch tube and the load circuit in the inverter switch circuit; The transformer has two secondary windings, one of which has a secondary winding in series with one secondary winding of the other transformer, and the base and emitter of the upper power switching tube of the inverter circuit through the driving resistor and the inverter circuit Connecting, the other two secondary windings are connected in series, and the driving resistor is connected to the base and the emitter of the power switching tube under the inverter switching circuit, and the at least one current transformer is controlled to participate in or exit the self-oscillation by means of a switch to control the circuit. Oscillation frequency.

The switch is connected to the primary winding of the coil in a current transformer; or is connected to at least one secondary winding of a current transformer.

A secondary side control winding is further wound in any of the current transformers, and the secondary side control winding is connected by a switch. The secondary side control winding is connected in series with a switch, or a resistor, or a DC power source.

The plurality of current transformers disposed in the circuit are wound with a coil on the magnetic core, and the primary windings of the transformer are connected in series with each other, and respectively connected to the power switch tube and the load circuit of the inverter switch circuit; The device has two secondary windings, and the secondary windings connected to one or more current transformers by the switch control are respectively connected in series with the bases of the upper and lower power switching tubes of the inverter switching circuit.

The plurality of current transformers disposed in the circuit are wound with a coil on the magnetic core, and the primary windings of the transformer are connected in parallel with each other, and the primary side of the transformer and the power of the inverter switching circuit are selected by the switch control. The switch tube and the load circuit are connected; each transformer has two secondary windings, which are respectively connected in series with the bases of the upper and lower power switch tubes of the inverter switch circuit, or respectively connected in parallel, and are connected by switch control to select one or The secondary windings of the plurality of current transformers are connected in series with the bases of the upper and lower power switching tubes of the inverter switching circuit.

The switch is a mechanical switch or an electronic switch.

When the self-oscillating inverter power supply circuit is powered on or receives an external start command, the control command is controlled to be placed at a certain position to reach a certain frequency.

Preferably, the method further includes a control module and a sampling circuit, and the current sampling of the load circuit is collected by the sampling circuit, and fed back to the control module, and the control module controls the PWM duty ratio to open or close the switch according to the duty ratio to keep the current average value constant. Near the target value.

Preferably, the circuit further comprises a rectifying circuit, wherein the external AC live line and the neutral line are rectified and connected to the inverter switch circuit, and the signal ground of the control module is connected to the negative end of the rectified output, and the external AC live line or the neutral line forms a loop and has Any voltage source with a voltage difference is connected to the signal input terminal of the control module via a command switch, and the control module outputs a connection switch. When the specification causes the switch to be closed, the control module receives the voltage signal of the voltage source and regards the signal as a control command to close or open the switch, so that the circuit operates at a self-oscillating frequency or a duty cycle Combining with the formed frequency, or causing the circuit to operate at an output current target value, when the command switch is turned off, the control module regards the disappearance of the voltage signal as another command, causing the switch to open or close, so that the circuit operates Another self-oscillating frequency or a combination of frequencies formed by another P-Liture duty cycle, or the circuit operates at another output current target value.

A gas discharge lamp electronic ballast comprising any of the above self-oscillating inverter power sources.

An output current variable power supply is provided with an inverter switch circuit, a control module, a switch, a plurality of current transformers, a resonant inductor, a resonant capacitor, an output rectifier circuit, and a DC load, and the resonant inductor and the resonant capacitor are connected in series The resonant circuit, the resonant capacitor is connected to the output rectifier circuit, and the output of the output rectifier circuit is connected to the DC load. The control module closes or opens the switch according to an external command, so that at least one current transformer participates or exits the self-oscillation to change the self-oscillation. Frequency, change the amount of current output to the DC load.

Preferably, the DC load comprises at least one light emitting diode.

Preferably, the output rectifier circuit comprises at least one light emitting diode.

The plurality of current transformers are wound with a coil on the magnetic core, and the primary windings of the transformer are connected in series with the resonant inductor in series, and each transformer has two secondary windings, which are respectively driven in series. The upper and lower power switch tubes of the variable-switching circuit, wherein one current transformer or a secondary side control winding is connected, and the switch is connected to one winding of any current transformer, and the control module opens or closes the switch, so that the current transformer participates or Exit the self-oscillation to control the oscillation frequency of the circuit.

Preferably, the control module outputs a PWM signal to cause the switch to be closed or opened according to the P signal, so that the current transformer controlled by the switch exits or participates in self-oscillation according to the P-signal, so that the self-excited oscillation frequency is according to the pulse width of the PWM signal. Switching between the two frequencies, changing the ratio of the time of operation to the two self-oscillating frequencies by changing the P-pulse ratio, changes the average value of the current output to the DC load.

Preferably, the power supply further comprises: a sampling module that feeds back the sampling signal of the average value of the output current to the control module, and the control module changes the pulse width ratio of the output P signal according to the difference between the sampled value and the target value, so that the output is output to the DC load. The average value of the current is constant near the target value.

The power supply further comprises a rectifier circuit, and the external AC live wire and the neutral wire are rectified and connected to the inverter switch circuit, and the signal ground of the control module is connected to the negative terminal of the rectified output, and the external AC live wire or the neutral wire forms a loop and has a voltage Any voltage source with a difference is connected to the signal input end of the control module through a command switch, and the control module outputs a connection switch. When the command switch is closed, the control module receives the voltage signal of the voltage source and regards the signal as a control. Commanding, closing or opening the switch to operate the circuit at a self-oscillating frequency or a combination of frequencies formed by the PWM duty cycle, or causing the circuit to operate at an output current target value, when the command switch is turned off, The control module regards the disappearance of the voltage signal as another command. The instructions cause the switch to open or close, to operate the circuit at another self-oscillating frequency or at a frequency formed by another P-reducing duty cycle, or to operate the circuit at another output current target value.

The beneficial effects of the invention are:

The invention provides a self-excited oscillation power source with variable output frequency or output power, or a self-excited oscillation electronic ballast with a dimming function, and the invention adopts self-oscillation mode. To achieve a change in output frequency or output power, compared to his oscillating circuit, the relatively low cost is achieved. The present invention can also provide a power supply having a variable output current.

DRAWINGS

The invention will now be further described with reference to the drawings and embodiments.

Figure 1 is a block diagram showing the overall structure of the present invention;

Figure 2 is a schematic view of an embodiment of the present invention;

Figure 3 is a schematic view of another embodiment of the present invention;

Figure 4 is a schematic view of another embodiment of the present invention;

Figure 5 is a schematic view of another embodiment of the present invention;

Figure 6 is a schematic view of another embodiment of the present invention;

Figure 7 is a schematic view of another embodiment of the present invention;

Figure 8 is a detailed circuit diagram of an embodiment of the present invention for an electronic ballast;

Figure 9 is a schematic view of a startup process of the present invention;

Figure 10 is a diagram showing an example of an LED driving power supply of the present invention.

The symbols in the drawings indicate:

101—inverter switching circuit;

102—a coupling circuit composed of a plurality of current transformers;

103—load circuit; 104—switch;

201—upper tube; 202—lower tube;

203—load matching circuit; 204—control circuit; 205—electric control switch;

206a—the primary side of the magnetic ring; 206b—the upper side of the magnetic ring drives the secondary side;

206c—the lower side of the magnetic ring drives the secondary side;

207a—the primary side of the magnetic ring; 207b—the upper side of the magnetic ring drives the secondary side;

207c—the lower side of the magnetic ring drives the secondary side;

208—upper tube drive resistance; 209—lower tube drive resistance; Instruction manual

210—the DC blocking capacitor; 211—the DC blocking capacitor;

301—upper tube; 302—lower tube; 303—load matching circuit;

304—control circuit; 305—double-pole electric control switch;

306a—the primary side of the magnetic ring; 306b—the upper side of the magnetic ring drives the secondary side;

306c—the lower side of the magnetic ring drives the secondary side;

307a—the primary side of the magnetic ring; 307b—the upper side of the magnetic ring drives the secondary side;

307c—the lower side of the magnetic ring drives the secondary side;

308—upper tube drive resistance; 309—lower tube drive resistance;

310—the DC blocking capacitor; 311—the DC blocking capacitor;

401—upper tube; 402—down tube;

403 - load matching circuit; 404 - DC blocking capacitor; 405 - DC blocking capacitor; 406a - magnetic ring primary; 406b - magnetic ring upper tube driving secondary;

406c—the lower side of the magnetic ring drives the secondary side;

407a - the primary side of the magnetic ring; 407b - - the upper side of the magnetic ring drives the secondary side;

407c—magnetic ring lower tube drive secondary side; 407d—magnetic ring control winding; 408—upper tube drive resistance; 409—lower tube drive resistance; 410—control switch;

501 - upper tube; 502 - lower tube;

503 - load matching circuit; 504 - control circuit;

505a—the upper portion of the linkage switch; 505b—the lower tube portion of the linkage switch; 506a—the primary side of the magnetic ring; 506b—the upper side of the magnetic ring drives the secondary side; 506c—the lower side of the magnetic ring drives the secondary side;

507a—the primary side of the magnetic ring; 507b—the upper side of the magnetic ring drives the secondary side; 507c—the lower side of the magnetic ring drives the secondary side;

508—upper tube drive resistance; 509—lower tube drive resistance;

510 - DC blocking capacitor; 511 - DC blocking capacitor;

601 - upper tube; 602 - lower tube;

603 - load matching circuit; 604 - control circuit;

605a—the upper tube portion of the linkage switch; 605b—the lower tube portion of the linkage switch; 605c—the primary side portion of the linkage switch magnetic ring; Instruction manual

606a—the primary side of the magnetic ring; 606b—the upper side of the magnetic ring drives the secondary side;

606c—the lower side of the magnetic ring drives the secondary side;

607a—the primary side of the magnetic ring; 607b—the upper side of the magnetic ring drives the secondary side;

607c—the lower side of the magnetic ring drives the secondary side;

608—upper tube drive resistance; 609—lower tube drive resistance;

610 - DC blocking capacitor; 611 - DC blocking capacitor;

701—upper tube; 702—lower tube;

703 - load matching circuit; 704 - control circuit;

705—two position switch;

706a—the primary side of the magnetic ring; 706b—the upper side of the magnetic ring drives the secondary side;

706c—the lower ring of the magnetic ring drives the secondary side;

707a—the primary side of the magnetic ring; 707b—the upper side of the magnetic ring drives the secondary side;

707c—the lower ring of the magnetic ring drives the secondary side;

708—upper tube drive resistance; 709—lower tube drive resistance;

710—the DC blocking capacitor; 711—the DC blocking capacitor;

D1—rectifier circuit or PFC circuit;

R1—starting voltage charging resistor; C1 together with shaking capacitor; D2—bidirectional triggering diode;

D3—diode; R2—half bridge upper tube drive resistor; R3—half bridge lower tube drive resistor;

Q1—half bridge upper tube; Q2—half bridge lower tube; Tla—oscillation magnetic ring T1 primary side;

Tib—oscillating magnetic ring T1 upper tube driving secondary side; Tic-oscillating magnetic ring T1 lower tube driving secondary side;

T2a—oscillation magnetic ring T2 primary side; T2b—oscillation magnetic ring T2 upper tube driving secondary side;

T2c—oscillating magnetic ring T2 lower tube driving secondary side; T2d—oscillating magnetic ring T2 controlling winding;

S1—control switch; VDC—auxiliary DC voltage power supply; R4—auxiliary resistor;

Lr-resonant inductor; TL-fluorescent lamp; Cr-resonant capacitor;

C2—the DC blocking capacitor; C3—the DC blocking capacitor;

901—power on or receive a start command;

902 - the switch is at a position where the starting frequency is generated;

903 - Is the startup completed?

904—According to the control command, set the switch to the position where the desired frequency is generated.

D1001—rectifier circuit; Z1001—voltage regulator tube; Instruction manual

R1001 - start-up charging resistor; C1001 - start-up capacitor; D1002 - bi-directional trigger diode;

D1003—diode; R1002 half-bridge upper tube drive resistor;

R1003 half bridge lower tube drive resistor;

Q1001—half bridge upper tube; Q1002—half bridge lower tube;

TlOOla—oscillation magnetic ring T1001 primary side;

TlOOlb—oscillation magnetic ring T1001 upper tube drive secondary side;

TlOOlc—oscillation magnetic ring T1001 lower tube drive secondary side;

T1002a—oscillation magnetic ring T1002 primary side;

T1002b—oscillating magnetic ring T1002 upper tube driving secondary side;

T1002c—oscillating magnetic ring T1002 lower tube driving secondary side;

DC1001—auxiliary DC voltage source; R1004 resistor;

C1002 half-bridge capacitor; C1003 half-bridge capacitor;

LrlOOl—resonant inductor; C1004—resonant capacitor; D1004—output rectifier circuit;

Semiconductor light emitting device group;

ASIC—control module; VCMD—command power supply; S1001—command switch;

S1002—Electric control switch.

detailed description

Referring to FIG. 1, the output frequency segmentation variable self-oscillation power supply of the present invention is composed of an inverter switching circuit (101), a coupling circuit (102) composed of a plurality of current transformers, a load circuit (103), and The switch (104) is configured, wherein an output of the inverter switch circuit (101) is connected to a series circuit composed of a coupling circuit (102) and a load circuit (103) composed of a plurality of current transformers, and a coupling circuit composed of a plurality of current transformers ( 102) The output is connected to the inverter switching circuit (101) as a driving of the inverter switching circuit (101).

The external control command can control the switch (104) to cause a part of the coupling circuit (102) composed of the plurality of current transformers to participate in or exit the self-oscillation to change the self-oscillation frequency. The coupling circuit (102) composed of the plurality of current transformers is composed of at least two current transformers whose coupling coefficients are independent of each other.

Some loads have specific requirements on the frequency or power delivered to the load at power-on startup. Only the required frequency or power can guarantee the normal startup of the load. When connecting such loads, the output frequency or output shown in Figure 1 The self-oscillation power supply with variable power can meet the requirement of the starting frequency according to the load starting characteristic, and the frequency at which some specific transformers in the coupling circuit (102) composed of the plurality of current transformers participate in the oscillation is the starting frequency; Then, according to the method described in FIG. 9, when the self-oscillating power supply is powered on or when an external command is given to the start command, the switch (104) is controlled to control the specific mutual It is stated that the book sensor participates in the oscillation, thereby generating the starting oscillation frequency. Until the load is started, follow the control command to set the switch (104) to the position where the desired frequency is generated.

The input to the inverter switch circuit (101) is a DC input that can come from a pre-stage rectification or PFC circuit, or from an external DC power supply. After the inverter switch circuit (101) obtains the DC input, the start-up trigger pulse is generated by the internal oscillating circuit or the external circuit of the inverter switch circuit (101), so that the inverter switch circuit (101) starts to work, and the DC input is converted into an AC. Outputting a series circuit composed of a coupling circuit (102) composed of a plurality of current transformers and a load circuit (103), wherein a coupling circuit (102) composed of a plurality of current transformers generates an alternating current output from the inverter switching circuit (101) The coupled output is coupled to the inverter switching circuit (101) for driving the inverter switching circuit (101) to generate self-oscillation. When the external control command controls the switch (104) to cause a part of the transformers in the coupling circuit (102) composed of the plurality of current transformers to participate in or exit the self-oscillation, the inverter switch circuit (101) outputs to the load circuit (103) The current oscillation frequency changes; when the load circuit (103) is not purely resistive, the change in the current oscillation frequency causes the power output to the load circuit (103) to change.

Figure 2 is a schematic illustration of an embodiment of the invention. The upper tube (201), the lower tube (202), the DC blocking capacitor (210) and the DC blocking capacitor (211) form a half bridge inverter circuit, and the upper tube (201) and the lower tube (202) are connected to the midpoint output in turn. Connected to the primary side of the magnetic ring (206a), the primary side of the magnetic ring (207a) and the load matching circuit (203), the other end of the load matching circuit (203) and the DC blocking capacitor (210) and the DC blocking capacitor (211) The connection points are connected; two magnetic rings are arranged in the circuit, the magnetic ring primary side (207a), the magnetic ring upper tube driving secondary side (207b) and the magnetic ring lower tube driving secondary side (207c) are different windings of the same magnetic ring, The magnetic ring primary side (206a), the magnetic ring upper tube driving secondary side (206b) and the magnetic ring lower tube driving secondary side (206c) are different windings of the other magnetic ring; the magnetic ring upper tube drives the secondary side (206b) and magnetic The upper tube driving secondary side (207b) and the upper tube driving resistor (208) are connected in series to form a driving circuit of the upper tube (201); the magnetic ring lower tube driving secondary side (206c), the magnetic ring lower tube driving secondary side (207c) and The lower tube drive resistor (209) is connected in series to form the drive circuit of the lower tube (202). When the external pulsation pulse turns on the lower tube (202), the half bridge starts to vibrate. The control circuit (204) outputs a control signal to close or open the electric control switch (205) according to the request of the external control command; when the electric control switch (205) is opened, the load current flows through the magnetic ring primary side (206a) and the magnetic ring original The side (207a), after the two sets of secondary side outputs of the two magnetic rings are respectively superposed, respectively drive the upper tube (201) and the lower tube (202) to form a fixed self-oscillation frequency; when the electric control switch (205) When closed, the primary side of the magnetic ring (207a) is short-circuited, the load current flows only through the primary side of the magnetic ring (206a), the upper side of the magnetic ring drive (207b) and the lower side of the magnetic ring drive (207c) output voltage All are zero, only the upper side of the magnetic ring drive (206b) and the lower side of the magnetic ring drive (206c) drive the upper tube (201) and the lower tube (202), respectively, forming another fixed self-oscillating frequency. Therefore, the control circuit (204) can turn the electrical control switch (205) on or off in accordance with the requirements of the external control command, that is, the self-oscillation frequency can be changed, or the power output through the load matching circuit (203) can be changed.

Figure 3 is a schematic view of another embodiment of the present invention, which is basically the same as the working principle of the embodiment shown in Figure 2, only The specification is to change the control switch to the double-knife electric control switch (305) and control the auxiliary side of the oscillating magnetic ring; when the control circuit (304) controls the double-knife electric control switch (305) to be closed, the upper side of the magnetic ring drives the secondary side (307b) And the magnetic ring lower tube driving secondary side (307c) is short-circuited respectively, and the oscillation is exited, and the self-oscillation frequency is determined only by another magnetic ring; when the double-pole electric control switch (305) is open, both magnetic rings participate in oscillation. Another oscillation frequency is formed.

Figure 4 is a schematic view of another embodiment of the present invention, the upper tube (401) and the lower tube (402) constitute an inverter half bridge, and the output is sequentially connected to the primary side of the magnetic ring (406a), the primary side of the magnetic ring (407a) And a load matching circuit (403), which is connected to a connection point between the DC blocking capacitor (404) and the DC blocking capacitor (405); the DC blocking capacitor (404) and the DC blocking capacitor (405) are connected in series, Both ends are connected to both ends of the DC input; two magnetic rings are arranged in the circuit, the magnetic ring primary side (407a), the magnetic ring upper tube driving secondary side (407b), the magnetic ring lower tube driving secondary side (407c) and the magnetic ring The control windings (407d) are different windings of the same magnetic ring, the magnetic ring primary side (406a), the magnetic ring upper tube driving secondary side (406b) and the magnetic ring lower tube driving secondary side (406c) being different windings of the other magnetic ring The magnetic tube upper tube driving secondary side (406b), the magnetic ring upper tube driving secondary side (407b) and the upper tube driving resistor (408) are connected in series and connected to the base and emitter of the upper tube (401) to form an upper tube ( 401) drive circuit; magnetic ring lower tube drive secondary side (406c), magnetic ring lower tube drive secondary side (407c) and lower tube drive resistance (409) Connected in series with the base and emitter of the lower tube (402) to form the drive circuit of the lower tube (402); the control switch (410) is connected to the magnetic ring control winding (407d).

When the external pulsation pulse turns on the lower tube (402), the half bridge starts to vibrate. When the control switch (410) is turned on, the two magnetic rings participate in self-oscillation to form a fixed oscillation frequency; when the control switch (410) is closed, the upper side of the magnetic ring drives the secondary side

(407b) and the output voltage of the magnetic tube lower tube driving secondary side (407c) are clamped to zero to exit the oscillation, and the self-oscillation is determined by another magnetic ring to form another fixed oscillation frequency, which realizes the output frequency. change. If the load matching circuit (403) matches the external load to non-pure resistance, a controlled change in the oscillation frequency results in a controlled change in output power for the purposes of the invention.

Figure 5 is a schematic view of another embodiment of the present invention, the upper tube (501) and the lower tube (502) constitute a half-bridge inverter circuit, and the output is sequentially connected to the primary side of the magnetic ring (506a), the primary side of the magnetic ring (507a) And the load matching circuit (503), and then connected to the connection between the DC blocking capacitor (510) and the DC blocking capacitor (511); the DC blocking capacitor (510) and the DC blocking capacitor (511) are connected in series. Termination of DC input; two magnetic rings are arranged in the circuit, the primary side of the magnetic ring (507a), the upper side of the magnetic ring drive the secondary side

(507b) and the magnetic ring lower tube driving secondary side (507c) are different windings of the same magnetic ring, the magnetic ring primary side (506a), the magnetic ring upper tube driving secondary side (506b) and the magnetic ring lower tube driving secondary side (506c) ) is the different winding of the other magnetic ring; the upper side of the magnetic ring drives the secondary side

(506b) or the magnetic tube upper tube driving secondary side (507b) is selected by the upper switch upper tube portion (505a) to be connected in series with the upper tube driving resistor (508) and connected to the base and emitter of the upper tube (501); The magnetic ring lower tube driving secondary side (506c) or the magnetic ring lower tube driving secondary side (507c) is selected by the linkage switch lower tube portion (505b) and one of the lower tube driving resistors (509) is connected in series to the lower tube (502) Base and emitter; set the coupling coefficients of the two magnetic rings differently, so that each magnetic ring is separate The oscillation frequency formed when the book is connected to the circuit is different, wherein the oscillation frequency of the upper side (506b) of the upper ring of the magnetic ring and the secondary side (506c) of the lower side of the magnetic tube is connected to the circuit to meet the requirements of the load starting characteristic. At initial power-on, the control circuit (504) always controls the linkage switch to cause the magnetic tube upper tube driving secondary side (506b) and the magnetic ring lower tube driving secondary side (506c) to be connected to the circuit to ensure that the load starting characteristics are satisfied; The oscillating pulse causes the inverter half-bridge to start, and the circuit operates according to the starting frequency formed by the magnetic ring upper tube driving secondary side (506b) and the magnetic ring lower tube driving secondary side (506c) accessing the circuit. When the load is started, the control circuit (504) can switch the upper switch tube portion (505a) and the linkage switch lower tube portion (505b) between the secondary sides of the two magnetic rings according to the requirements of the external control command, so that the magnetic ring The upper tube driving secondary side (506b) and the magnetic ring lower tube driving secondary side (506c) are connected to the circuit, or the magnetic ring upper tube driving secondary side (507b) and the magnetic ring lower tube driving secondary side (507c) are connected to the circuit, Thereby, the circuit is switched between two different oscillation frequencies. When the load matching circuit (503) forms a non-pure resistive equivalent load, the change of the output frequency causes a change in the output power to achieve the object of the invention.

Figure 6 is a schematic view of another embodiment of the present invention, which is substantially similar to the working principle of the embodiment shown in Figure 5, except that the primary sides of the two magnetic rings are also selected by the primary side portion (605c) of the interlocking switch magnetic ring. Into the circuit; set the coupling coefficient of the two magnetic rings differently, so that the oscillation frequency formed when each magnetic ring is separately connected to the circuit is different. When the control circuit (604) controls the linkage switch to switch between the two magnetic rings as required by the external control command, the circuit is switched between two different oscillation frequencies for the purpose of the invention.

Figure 7 is a schematic view of another embodiment of the present invention, which is substantially similar to the working principle of the embodiment shown in Figure 5, except that the primary sides of the two magnetic rings are selected by the two-position switch (705) to access the circuit, and The secondary sides of the two magnetic rings are changed into a series; the coupling coefficients of the two magnetic rings are set differently, so that the oscillation frequency formed when each magnetic ring is separately connected to the circuit is different. When the control circuit (704) controls the two-position switch (705) to switch between the two magnetic rings according to the requirements of the external control command, the output voltage of the secondary side of the magnetic ring that is not connected to the primary side is zero, and the oscillation frequency is accessed by The magnetic loop of the circuit is determined; therefore, switching between the two magnetic loops, even if the circuit switches between two different oscillation frequencies, achieves the object of the invention.

8 is a specific circuit diagram of an embodiment of the present invention for an electronic ballast. The rectifier circuit or the PFC circuit D1 outputs an inverter half bridge connected to the half bridge upper tube Q1 and the half bridge lower tube Q2; The resistor R1, the starting capacitor C1 and the bidirectional trigger diode D2 form a starting line, and the diode D3 clamps the starting capacitor C1 at a low level after the circuit starts to oscillate; the inverse of the half bridge upper tube Q1 and the half bridge lower tube Q2 The output of the half bridge is connected to the primary side T1 of the oscillating magnetic ring T1, the primary side T2a of the oscillating magnetic ring T2, the resonant inductor Lr, the filament of the fluorescent lamp TL, and the resonant capacitor Cr. The other side of the fluorescent lamp TL is connected to the DC blocking capacitor C2. And the midpoint of the connection of C3 under the DC blocking capacitor; two magnetic rings are arranged in the circuit, the primary side Tla of the oscillating magnetic ring T1, the upper side Tib of the oscillating magnetic ring T1, and the secondary side of the oscillating magnetic ring T1 are the Tic Different windings of the same magnetic ring, the oscillating magnetic ring T2 primary side T2a, the oscillating magnetic ring T2 upper tube driving secondary side T2b, the oscillating magnetic ring T2 lower tube driving secondary side T2c and the oscillating magnetic ring T2 control winding T2d are another magnetic ring Different windings; oscillating magnetic ring T1 upper tube driving secondary side Tlb, oscillating magnetic ring T2 upper tube The driving sub-side T2b and the half-bridge upper tube driving resistor R2 are connected in series to the base and emitter of the half-bridge upper tube Q1; the oscillating magnetic ring T1 lower tube driving the secondary side Tlc, the oscillating magnetic ring T2, the lower tube driving the secondary side T2c And the half bridge lower tube driving resistor R3 is connected in series with the base and emitter of the half bridge lower tube Q2; the DC blocking capacitor C2 and the DC blocking capacitor C3 are connected in series and the two ends are connected to the output of the rectifier circuit or the PFC circuit D1; The DC voltage power supply VDC, the auxiliary resistor R4, and the control switch SI are connected in series to be connected to both ends of the oscillating magnetic ring T2 control winding T2d; the voltage value of the auxiliary DC voltage power supply VDC is sufficient to saturate the oscillating magnetic ring T2 through the auxiliary resistor R4. The value, or the voltage value of the auxiliary DC voltage source VDC is zero and the auxiliary resistor R4 is set to an appropriate value. When the auxiliary resistor R4 is connected to the oscillating magnetic ring T2 control winding T2d, the upper side of the oscillating magnetic ring T2 drives the secondary side T2b and The output of the oscillating magnetic ring T2 lower tube driving secondary side T2c is clamped to zero.

In the initial state, the control switch S 1 is opened. When the AC voltage of the appropriate voltage is input to the rectifier circuit or the PFC circuit D1, the rectifier circuit or the PFC circuit D1 converts the AC input into a DC output, and charges the oscillating capacitor C1 through the oscillating charging resistor R1, and the voltage on the oscillating capacitor C1 gradually rises. High until the bidirectional trigger diode D2 breakdown, the starting capacitor C1 is discharged to the base of the half bridge lower tube Q2 via the bidirectional trigger diode D2 and the half bridge lower tube drive resistor R3, and the half bridge lower tube Q2 is turned on, the circuit starts to oscillate; The switch S1 is open, the two magnetic rings are involved in oscillation, the circuit oscillates at a fixed frequency, and the inverter half-bridge output current composed of the half bridge upper tube Q1 and the half bridge lower tube Q2 flows through the resonant inductor Lr, the resonant capacitor Cr and the fluorescent lamp TL The filament, which generates a high voltage across the resonant capacitor Cr, eventually causes the fluorescent lamp TL to break down and the fluorescent lamp TL to illuminate. When dimming is required, the control switch S1 is closed. If the voltage value of the auxiliary DC voltage source VDC is set to a sufficiently high value, the current flowing through the auxiliary resistor R4 and the oscillating magnetic ring T2 controls the winding T2d to saturate the magnetic ring. And exiting the oscillation, the oscillation frequency is changed to the self-oscillation frequency determined by the other magnetic ring; when the control switch S 1 is closed, if the voltage value of the auxiliary DC voltage source VDC is set to zero and the auxiliary resistor R4 is set to an appropriate value, The output of the upper side T2b of the upper side of the oscillating magnetic ring T2 and the lower side of the lower side of the oscillating magnetic ring T2 are clamped to zero to exit the oscillation, and the oscillation frequency is changed to the self-oscillation frequency determined by the other magnetic ring; The fluorescent lamp TL has broken down, and a part of the output current of the inverter half bridge flows to the fluorescent lamp TL through the resonant inductor Lr, and the change of the self-oscillation frequency causes the current flowing through the resonant inductor Lr and the fluorescent lamp TL to change, so that the power output to the fluorescent lamp TL is changed. A change occurs to achieve the dimming effect.

Figure 9 is a schematic illustration of a method of starting up the present invention. When the load connected to the frequency segment variable self-oscillation power supply according to the present invention has a specific requirement on the starting frequency, the power supply of the present invention can set the coupling of the plurality of current transformers according to the load to the starting frequency requirement. The frequency at which certain specific transformers in the circuit (102) participate in the oscillation is the starting frequency. Then, the power supply of the present invention can be gradually started according to the method described in FIG. 9. When the power is turned on in step (901) or the start command is received, the process proceeds to step (902), where the switch is set to generate the start frequency, so that the switch The specific transformer is controlled to participate in the oscillation to generate the starting frequency. Then, according to step (903), it is judged whether the startup is completed. If it is not completed, the switch position remains unchanged; if the startup is completed, the process proceeds to step (904), and the control command is set to set the position at which the desired frequency is generated. The present method can be manually controlled, or can be accomplished by a control circuit provided in the power supply of the present invention.

In the above examples, a control module and a sampling circuit may also be provided, and the current sampling of the load circuit is collected by the sampling circuit, and fed back to the control module, and the control module controls the PWM duty ratio, thereby achieving the output average current constant at the target value. Nearby effects. This is merely an implementation, but is not intended to limit the invention, but is merely illustrative. Application example one

The power supplies of the above examples can be directly applied to gas discharge lamp electronic ballasts. Electronic ballast (Electricalbal last) refers to an electronic device that uses electronic technology to drive an electric light source to produce the desired illumination. Corresponding to this is an inductive ballast (or ballast). Modern fluorescent lamps are increasingly using electronic ballasts, which are light and compact, and can even integrate electronic ballasts with lamps. At the same time, electronic ballasts can usually have a function as a starter, thus saving Go to a separate starter. Electronic ballasts can also have more functions, such as the ability to use a DC power supply for fluorescent lamps through a power inverter process. Applying the power supply of the above example to an electronic ballast can also achieve dimming efficiency.

This application is for illustrative purposes only and is not intended to limit the invention. The field of power supply applications of the present invention is extremely broad and is merely an application implementation.

Application Example 2

The power supply of the above examples can be directly applied to a power source with variable output current, such as an LED driving power source, and of course, it can also be a driving power source of other lighting devices.

The DC load includes at least one light emitting diode.

The output rectifier circuit includes at least one light emitting diode.

In addition, the control module outputs a P medical signal to cause the switch to be closed or opened according to the PWM signal, so that the current transformer controlled by the switch exits or participates in self-oscillation according to the PWM signal, so that the self-oscillation frequency is proportional to the pulse width ratio of the PWM signal. Switch between two frequencies, The specification changes the average value of the current output to the DC load by changing the P-pulse ratio to change the proportion of time that operates at two self-oscillating frequencies.

The power supply further includes a sampling module that feeds the sampling signal of the average value of the output current to the control module, and the control module changes the pulse width ratio of the output P signal according to the difference between the sampled value and the target value, so that the average of the current output to the DC load is The value is constant near the target value.

The power supply further includes a rectifier circuit, and the external AC live wire and the neutral wire are rectified and connected to the inverter switch circuit, and the signal ground of the control module is connected to the negative terminal of the rectified output, and the external AC live wire or the neutral wire forms a loop and has a voltage difference. Any voltage source is connected to the signal input end of the control module through a command switch, and the control module outputs a connection switch. When the command switch is closed, the control module receives the voltage signal of the voltage source and regards the signal as a control command. Turning the switch on or off, causing the circuit to operate at a self-oscillating frequency or a combination of frequencies formed by a P-reducing duty cycle, or to cause the circuit to operate at an output current target value, when the command switch is turned off, The control module regards the disappearance of the voltage signal as another command, causing the switch to open or close, causing the circuit to operate at another self-oscillating frequency or a combination of frequencies formed by another P-reducing duty cycle, or to make the circuit Operates at another output current target value.

Figure 10 is a detailed circuit diagram of another embodiment of the present invention which utilizes the present invention to effect dimmable driving of an LED. The rectifier circuit D1001 outputs an inverter half bridge connected to the half bridge upper tube Q1001 and the half bridge lower tube Q1002; the starting charging resistor R1001, the starting capacitor C1001 and the bidirectional trigger diode D1002 and the diode D1003 form a starting line; The output of the inverter half-bridge composed of the tube Q1001 and the half-bridge lower tube Q1002 is connected to the primary side T1001a of the oscillating magnetic ring T1001, the primary side T1002a of the oscillating magnetic ring T1002, the resonant inductor Lrl001, the resonant capacitor C1004, and the other end of the resonant capacitor C1004 is connected to the half-bridge capacitor. C1002 and half-bridge capacitor C1003 connection midpoint; resonant capacitor C1004 is connected to the output rectifier circuit D1004, the output rectifier circuit D1004 output is connected to the semiconductor light-emitting device group LEDs; the output rectifier circuit D1004 can also contain at least one Light-emitting diodes; the current value of the above-mentioned circuit structure outputted to the semiconductor light-emitting device group LEDs is less affected by the LED turn-on voltage drop, and is a better LED driving circuit. Two magnetic rings are arranged in the circuit, the oscillating magnetic ring T1001 primary side T1001a, the oscillating magnetic ring T1001 upper tube driving secondary side T1001lb and the oscillating magnetic ring T1001 lower tube driving secondary side TlOOlc are different windings of the same magnetic ring, the oscillating magnetic ring T1002 The primary side T1002a, the oscillating magnetic ring T1002 upper tube driving secondary side T1002b, the oscillating magnetic ring T1002 lower tube driving secondary side T1002c are different windings of the other magnetic ring; the oscillating magnetic ring T1001 upper tube driving secondary side T1001b, the oscillating magnetic ring T1002 The tube driving secondary side T1002b and the half bridge upper tube driving resistor R1002 are connected in series to the base and emitter of the half bridge upper tube Q1001; the oscillating magnetic ring T1001 lower tube driving the secondary side T1001c, the oscillating magnetic ring T1002, the lower tube driving the secondary side T1002c And the half bridge lower tube driving resistor R1003 is connected in series with the base and emitter of the half bridge lower tube Q1002; the half bridge capacitance on C1002 and the half bridge capacitor C1003 in series and the two ends connected to the output of the rectifier circuit D1001; auxiliary DC voltage source The DC1001 supplies power to the control module ASIC, and the control module ASIC output is connected to the control of the electronic control switch S1002. At the instruction end, the switch of the electronic control switch S1002 is connected to the oscillating magnetic ring T1002 and the lower side of the lower side of the tube drive T1002c; after the circuit starts to oscillate, the control module ASIC controls the electronic control switch S1002 to close or open, even if the oscillating magnetic ring T1002 exits or joins the self-excited Oscillation causes the circuit to output two different frequencies; because the resonant inductor Lrl001, the resonant capacitor C1004, the output rectifier circuit D1004, and the semiconductor light-emitting device group LEDs form an inductive load, the different output frequencies of the inverter circuit cause the load current to change, ultimately resulting in The magnitude of the current flowing through the LEDs of the semiconductor light-emitting device group changes to achieve the object of the invention.

When the control module ASIC outputs the PWM pulse width modulation signal, the electronic control switch S1002 is closed or turned off according to the duty ratio of the PWM signal, so that the self-oscillation circuit switches between the two operating frequencies according to the P-li duty ratio, thereby The load current causing the output is switched between the two magnitudes of the current according to the PWM duty cycle; changing the duty ratio of the P-signal, that is, changing the proportion of the two amplitudes in the load current, thereby changing the average output current, Therefore, the continuous change of the output average current is realized by the method of segment frequency modulation; if the current sampling circuit is connected in the current path of the LEDs of the semiconductor light emitting device group, the sampling signal is fed back to the control module ASIC, and the comparison result of the feedback signal and the target value is obtained. To change the PWM duty cycle, the average current that can control the output to the semiconductor light-emitting device group LEDs is kept constant near the target value.

In this embodiment, the signal ground of the control module ASIC is connected to the negative terminal outputted by the rectifier circuit D1001, and the signal input terminal of the control module ASIC and the signal ground are connected to the Zener diode Z1001, and the Zener diode Z1001 functions as a rectification of the signal voltage. The two functions of the clamp, the signal input end of the control module ASIC is connected to the command switch S1001 via the resistor R1004, and the other end of the command switch S1001 is connected to the command power supply VCMD, or connected to the live line input by the rectifier circuit D1001, or connected to the neutral line. The command power supply VCMD is any voltage source that forms a loop with a live or neutral line and has a voltage difference. When the command switch S1001 is closed, the control module ASIC receives the input voltage signal, and the voltage signal is used as a control command, and the control module ASIC controls the electronic control switch S1002 to be closed or opened according to a predetermined definition, or outputs a certain duty cycle PWM. Signal, the output frequency of the circuit is a combination of a self-excited oscillation frequency or a certain duty ratio of two self-excited oscillation frequencies; when the command switch S1001 is turned off, the input voltage signal is eliminated, and the control module ASIC signal receiving end is not Receiving the voltage signal again, the control module ASIC regards the disappearance of the voltage signal as another command, and the control module ASIC changes its output to change the switching state of the electronic control switch S1002, or outputs another P-signal of the duty cycle, so that The combination of the circuit output frequency being another self-oscillating frequency or another duty cycle of two self-oscillating frequencies achieves the object of the invention. It should be understood that the methods described herein can be implemented in various forms of hardware, software, firmware, special purpose processors, or combinations thereof. The connections between system modules (or logic flows of method steps) may vary, and those of ordinary skill in the relevant art will be able to devise these and similar embodiments of the present invention in light of the teachings herein. In the range. The various aspects and embodiments of the present invention are disclosed above, and other aspects and embodiments of the present invention will be apparent to those skilled in the art. The various aspects and embodiments disclosed in the present invention are for illustration only. The description is not intended to limit the invention, and the true scope and spirit of the invention should be determined by the claims.

Claims

The invention provides a self-oscillating inverter power supply with variable output segmentation, wherein the power supply is provided with an inverter switch circuit, a coupling circuit composed of a plurality of current transformers, a switch and a load circuit, which are formed by In the oscillating inverter power supply circuit, a part of the current transformers in the coupling circuit composed of a switch controlling a plurality of current transformers participate in or exit the self-oscillation to change the self-oscillation frequency.

The output frequency segmentation variable self-oscillation inverter power supply according to claim 1, wherein the coupling circuit composed of the plurality of current transformers comprises at least two current transformers whose coupling coefficients are independent of each other.

The output frequency segment variable self-oscillation inverter power supply according to claim 1, wherein the plurality of current transformers disposed in the circuit are wound with a coil on the magnetic core, and the transformer The primary windings are connected in series with each other and are respectively connected to the power switch tube and the load circuit in the inverter switch circuit; each transformer has two secondary windings, one of the secondary windings of one transformer and one of the other transformers After the secondary windings are connected in series, the driving resistor is connected to the base and the emitter of the upper power switch tube of the inverter switch circuit, and the other two secondary windings are connected in series, and the driving resistor and the base of the power switching tube under the inverter switching circuit are connected. Connected to the emitter, with a switch, controls at least one current transformer to participate in or exit the self-oscillation to control the oscillation frequency of the circuit.

The output frequency segmentation variable self-oscillation inverter power supply according to claim 3, wherein the switch is connected to a primary winding of a coil in a current transformer; or is connected to a current At least one secondary winding of the transformer.

The output frequency segment variable self-oscillation inverter power supply according to claim 3, wherein a secondary side control winding is further wound in any one of the current transformers, and the secondary side control winding is connected by a switch Pick up.

The output frequency segment variable self-oscillation inverter power supply according to claim 5, wherein the secondary side control winding is connected in series with a switch, or a resistor, or a DC power source.

The output frequency segmentation variable self-oscillation inverter power supply according to claim 1, wherein the plurality of current transformers disposed in the circuit are wound with a coil on the magnetic core, and the mutual inductance The primary windings of the device are connected in series with each other, and are respectively connected with the power switch tube and the load circuit of the inverter switch circuit; each transformer has two secondary windings, and the secondary winding of one or more current transformers is selected by the switch control. They are connected in series with the bases of the upper and lower power switch tubes of the inverter switch circuit.

The output frequency segmentation variable self-oscillation inverter power supply according to claim 1, wherein the plurality of current transformers disposed in the circuit are wound with a coil on the magnetic core, and the mutual inductance The primary windings of the device are connected in parallel with each other. The primary side of one of the transformers is connected to the power switch tube and the load circuit of the inverter switch circuit by the switch control; each transformer has two secondary windings, which are respectively connected in series and inversely The bases of the upper and lower power switch tubes of the variable switching circuit are connected in series, or respectively connected in parallel, and the secondary side of one or more current transformers is selected by the switch control. The winding of the claim is connected in series with the base of the upper and lower power switch tubes of the inverter switch circuit.

The output frequency segmentation variable self-oscillation inverter power supply according to claim 1, wherein the switch is a mechanical switch or an electronic switch.

0. The output frequency segment variable self-oscillation inverter power supply according to claim 1, wherein the self-oscillating inverter power supply circuit is controlled by a control command when the power is turned on or when an external start command is received. The switch is placed in a certain position to reach a certain frequency.

The output frequency segmentation variable self-oscillation inverter power supply according to claim 1, further comprising a control module and a sampling circuit, wherein the current sampling of the load circuit is collected by the sampling circuit, and fed back to the control module. The control module controls the Pli duty cycle to cause the switch to open or close at a duty cycle to keep the current average constant near the target value. The power supply according to claim 1, further comprising a rectifying circuit, wherein the external AC live line and the neutral line are rectified and connected to the inverter switch circuit, and the signal ground of the control module is connected to the negative end of the rectified output, An external AC live or neutral line forms a voltage and any voltage source with a voltage difference is connected to the signal input of the control module via a command switch. When the command switch is closed, the control module receives the voltage signal of the voltage source and The signal is treated as a control command that causes the switch to be closed or opened, allowing the circuit to operate at a self-oscillating frequency or a combination of frequencies formed by the PWM duty cycle, or to cause the circuit to operate at an output current target value, when commanded When the switch is turned off, the control module regards the disappearance of the voltage signal as another command, causing the switch to open or close, causing the circuit to operate at another self-oscillating frequency or a frequency formed by another P-life cycle. Combine, or cause the circuit to operate at another output current target value.

An electronic ballast for a gas discharge lamp, comprising any of the self-oscillating inverter power sources according to any one of claims 1 to 12.

An output current variable power supply, characterized in that the power supply is provided with an inverter switch circuit, a control module, a switch, a plurality of current transformers, a resonant inductor, a resonant capacitor, an output rectifier circuit, and a DC load, a resonant inductor And the resonant capacitor constitutes a series resonant circuit, the resonant capacitor is connected to the output rectifier circuit, the output of the output rectifier circuit is connected to the DC load, and the control module closes or opens the switch according to an external command, so that at least one current transformer participates or exits the self-oscillation, To change the self-oscillating frequency to change the amount of current output to the DC load.

5. The power supply of claim 14 wherein the DC load comprises at least one light emitting diode.

6. The power supply of claim 14 wherein the output rectifier circuit comprises at least one light emitting diode. The power supply according to claim 14, wherein the plurality of current transformers are wound with a coil on the magnetic core, and the primary windings of the transformer are connected in series with each other and connected in series with the resonant inductor. The transformer has two secondary windings, which are respectively connected in series to drive the upper and lower power switching tubes of the inverter switching circuit, wherein one current transformer or winding The secondary side controls the winding, and the switch is connected to one winding of any current transformer. The control module opens or closes the switch, so that the current transformer participates or exits the self-oscillation to control the oscillation frequency of the circuit.

The power supply according to any one of claims 14 to 17, wherein the control module outputs a PWM signal to cause the switch to be closed or opened according to the PWM signal, so that the current transformer controlled by the switch exits or participates in the PWM signal. Excitation oscillation, the self-oscillation frequency is switched between two frequencies according to the pulse width ratio of the PWM signal, and the current output to the DC load is changed by changing the PWM pulse width ratio to change the time ratio of the two self-excited oscillation frequencies. The average size.

The power supply of claim 18, further comprising: feeding back a sampling signal of the average value of the output current to the sampling module of the control module, wherein the control module changes the pulse width of the output PWM signal according to the difference between the sampled value and the target value. The average value of the current output to the DC load is kept constant near the target value.

The output current variable power supply according to claim 14 or 18 or 19, further comprising a rectifying circuit, wherein the external AC live line and the neutral line are rectified and connected to the inverter switch circuit, and the signal connection of the control module To the negative end of the rectified output, any voltage source that forms a loop with the external AC live or neutral line and has a voltage difference is connected to the signal input end of the control module via a command switch with a wire. When the command switch is closed, the control module receives a voltage signal to the voltage source and treating the signal as a control command to cause the switch to be closed or opened, causing the circuit to operate at a self-oscillating frequency or a combination of frequencies formed by a P-reducing duty cycle, or to make the circuit Working according to an output current target value, when the command switch is turned off, the control module regards the disappearance of the voltage signal as another command, causing the switch to open or close, causing the circuit to operate at another self-oscillating frequency or by another A combination of frequencies formed by the duty cycle of the P-Li, or the circuit operating at another output current target value.