CN111818698A

CN111818698A - Switching power supply, electronic ballast and LED drive circuit

Info

Publication number: CN111818698A
Application number: CN202010623827.3A
Authority: CN
Inventors: 陈亮
Original assignee: Zhejiang Arc Light Intelligent Electric Appliance Co ltd
Current assignee: Zhejiang Arc Light Intelligent Electric Appliance Co ltd
Priority date: 2020-07-01
Filing date: 2020-07-01
Publication date: 2020-10-23

Abstract

A switching power supply, an electronic ballast and an LED driving power supply are provided. The switching power supply includes: a switching circuit; the switch circuit comprises a parallel harmonic oscillator circuit, the parallel harmonic oscillator circuit is suitable for generating a resonance control signal, and the power supply of the LED load is controlled through the resonance control signal; the branch circuit formed by connecting the LED load and the variable capacitance circuit in series is connected with the parallel harmonic oscillator circuit in parallel; the variable capacitance circuit is suitable for adjusting a capacitance value under the control of a dimming control signal so as to dim the LED load. By applying the scheme, the LED light source can be dimmed more conveniently.

Description

Switching power supply, electronic ballast and LED drive circuit

Technical Field

The invention relates to the technical field of electronic circuits, in particular to a switching power supply, an electronic ballast and an LED driving power supply.

Background

In the field of lighting, LED lighting has been used in more and more application scenes due to its advantages of high light efficiency, long life, etc., and the traditional fluorescent lamp light source is gradually replaced by the LED light source.

As society demands energy saving and situational awareness, the demand for dimming lighting systems is increasing.

Because the LED light source needs the power supply of the direct current constant current source, when the LED light source is dimmed, the current of the power supply needs to be controlled, so the dimming difficulty is higher, and the self-excitation topology used for the traditional fluorescent lamp ballast is difficult to realize.

At present, the common practice is: and a special control chip is selected to realize the dimming of the LED light source.

However, the above method results in high cost and complicated circuit of the switching power supply.

Disclosure of Invention

The invention aims to solve the problems that: how to dim the LED light source conveniently.

In order to solve the above problem, an embodiment of the present invention provides a switching power supply, including: a switching circuit; the switch circuit comprises a parallel harmonic oscillator circuit, the parallel harmonic oscillator circuit is suitable for generating a resonance control signal, and the power supply of the LED load is controlled through the resonance control signal;

the branch circuit formed by connecting the LED load and the variable capacitance circuit in series is connected with the parallel harmonic oscillator circuit in parallel; the variable capacitance circuit is suitable for adjusting a capacitance value under the control of a dimming control signal so as to dim the LED load.

Optionally, the variable capacitance circuit comprises: a first capacitor; and a first switch in parallel with the first capacitor; wherein the first switch is adapted to be opened or closed under the control of the dimming control signal.

Optionally, the variable capacitance circuit further comprises:

and the second capacitor is connected with the LED load in series and is connected with a circuit formed by the first capacitor and the first switch in series.

Optionally, the variable capacitance circuit further comprises:

a third capacitor in series with the first switch and in parallel with the first capacitor.

Optionally, the first switch is any one of: diode, triode, MOS pipe, silicon controlled switch, relay switch.

Optionally, the switching circuit further comprises:

the first switch sub-circuit is coupled with the output end of the direct-current power supply and is suitable for being opened or closed under the control of the resonance control signal;

the first direct current-to-alternating current sub-circuit is coupled between the first switch sub-circuit and the parallel resonant sub-circuit, is suitable for converting a direct current power supply input by the direct current power supply output end into an alternating current power supply and inputting the alternating current power supply to the parallel resonant sub-circuit;

the first starting circuit is connected with the first switch sub-circuit and is suitable for starting a switching tube of the first switch sub-circuit;

the parallel harmonic oscillator circuit is coupled with the anode of the direct-current power supply output end through a fourth capacitor and coupled with the cathode of the direct-current power supply output end through a fifth capacitor.

Optionally, the parallel resonator sub-circuit comprises: a first resonant inductor; a first resonant capacitor connected in parallel with the first resonant inductor; one end of the first resonant capacitor is coupled with the first direct current to alternating current sub-circuit, and the other end of the first resonant capacitor is coupled with the fourth capacitor and the fifth capacitor.

Optionally, the switching circuit further comprises:

the second DC-AC sub-circuit is coupled with the output end of the DC power supply, is suitable for converting the DC power supply input by the output end of the DC power supply into an AC power supply and inputs the AC power supply to the parallel harmonic oscillator circuit;

the second switch sub-circuit is coupled between the output end of the direct-current power supply and the parallel resonance sub-circuit and is suitable for being opened or closed under the control of the resonance control signal;

and the second starting circuit is connected with the second switch sub-circuit and is suitable for starting a switching tube of the second switch sub-circuit.

Optionally, the parallel resonator sub-circuit comprises:

a second resonant inductor;

a third resonant inductor in series with the second resonant inductor;

the second resonant capacitor is connected in parallel with a branch where the second resonant inductor and the third resonant inductor are located;

and the second switch sub-circuit is connected with the second resonant inductor and the third resonant inductor.

Optionally, the switching power supply further includes: and the signal conversion circuit is suitable for receiving the dimming control signal and converting the dimming control signal into an electric signal suitable for being applied to the variable capacitance circuit.

The embodiment of the invention also provides an electronic ballast, which comprises any one of the switching power supplies.

The embodiment of the invention also provides an LED drive circuit, which comprises any one of the switch power supply.

Compared with the prior art, the technical scheme of the embodiment of the invention has the following advantages:

by applying the scheme of the invention, the capacitance value of the variable capacitance circuit can be changed under the control of the dimming control signal, and compared with the scheme of adjusting the working frequency and/or the duty ratio of a switching tube in a switching circuit by adopting a special chip to perform dimming, the dimming is more convenient and faster only by changing the capacitance value of the LED load series capacitor.

Furthermore, the variable capacitance circuit is formed by connecting a capacitor and a switch in parallel, and compared with a scheme of dimming by a special chip, the variable capacitance circuit is lower in dimming cost.

Drawings

FIG. 1 is a schematic diagram of a variable capacitor circuit according to the present invention;

FIG. 2 is a schematic diagram of another variable capacitance circuit of the present invention;

FIG. 3 is a schematic diagram of a variable capacitance circuit according to another embodiment of the present invention;

fig. 4 is a schematic structural diagram of a switching power supply of the present invention;

fig. 5 is a schematic structural diagram of another switching power supply according to an embodiment of the present invention;

fig. 6 is a schematic structural diagram of a signal conversion circuit according to an embodiment of the present invention.

Detailed Description

At present, the control chip is mostly used to control the operating frequency or duty ratio of the switching tube for dimming. Specifically, the output current is adjusted by adjusting the working frequency or duty ratio of the switching tube, so that the output current is controlled, the purpose of dimming is achieved, and the whole scheme is high in cost and complex in control.

In view of the above problem, in the embodiment of the present invention, the capacitor connected in series to the LED load is a variable capacitor circuit, and a capacitance value of the variable capacitor circuit can be changed under the control of the dimming control signal, so that the LED load can be dimmed more conveniently.

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.

Referring to fig. 1 to 3, an embodiment of the present invention provides a switching power supply, which may include: a switching circuit; the switching circuit comprises a parallel harmonic oscillator circuit 11.

The parallel resonant sub-circuit 11 is adapted to generate a resonance control signal, and the power supply of the LED load 12 is controlled by the resonance control signal;

the branch circuit formed by connecting the LED load 12 and the variable capacitance circuit 13 in series is connected in parallel with the parallel resonator circuit 11; the variable capacitance circuit 13 is adapted to adjust a capacitance value under the control of a dimming control signal to dim the LED load 12.

In the prior art, the capacitance value of the capacitor connected in series with LED load 12 is fixed.

In the embodiment of the present invention, the capacitance value of the capacitor connected in series with the LED load 12 is variable. Because the voltage at the two ends of the parallel resonator circuit 11 is fixed, and the impedance of the variable capacitor circuit 13 is much larger than the load impedance, the current of the LED load 12 depends on the capacitance value of the variable capacitor circuit 13, and the current of the LED load 12 can be changed by adjusting the capacitance value of the variable capacitor circuit 13, so as to achieve the purpose of dimming the LED load 12.

In specific implementation, the circuit structure of the variable capacitance circuit 13 may be various, and is not limited, and only the variable capacitance circuit 13 may change the capacitance value under the control of the dimming control signal.

In an embodiment of the present invention, referring to fig. 1, the variable capacitance circuit 13 may include: a first capacitor C1, and a first switch SW1 connected in parallel with the first capacitor C1. Wherein the first switch SW1 is adapted to open or close under the control of the dimming control signal.

In another embodiment of the present invention, referring to fig. 2, the variable capacitance circuit 13 may further include: a second capacitor C2, the second capacitor C2 being connected in series with the LED load 12 and in series with the circuit of the first capacitor C1 and the first switch SW 1.

In still another embodiment of the present invention, referring to fig. 3, the variable capacitance circuit 13 may further include: a third capacitor C3. The third capacitor C3 is connected in series with the first switch SW1 and in parallel with the first capacitor C1.

In a specific implementation, the first switch SW1 may be any one of the following: diode, triode, MOS pipe, silicon controlled switch, relay switch.

It is understood that, how the type of the first switch SW1 is, it is not limited to the present invention, as long as the first switch SW1 can be opened or closed under the control of the dimming control signal, so as to change the capacitance of the variable capacitance circuit 13.

In specific implementation, there may be a plurality of specific structures of the switching power supply, and the specific structure is not limited as long as the switching power supply includes the variable capacitance circuit 13, which is within the protection scope of the present invention.

The following is described in detail with reference to specific switching power supply circuits:

referring to fig. 4, the switching circuit 40 may be a half-bridge line, and specifically, the switching circuit 40 may include: a first switch sub-circuit, a first dc-to-ac sub-circuit 42, and a parallel resonator sub-circuit 11.

Wherein:

a first dc-ac sub-circuit 42, coupled between the first switch sub-circuit and the parallel resonator sub-circuit 43, adapted to convert the dc power input from the dc power output terminal into an ac power, and input the ac power to the parallel resonator sub-circuit 11;

a first starting circuit 43 connected to the first switch sub-circuit and adapted to start the switching tube of the first switch sub-circuit;

the parallel resonant sub-circuit 11 is coupled to the positive electrode of the dc power supply output terminal through a fourth capacitor C4, and coupled to the negative electrode of the dc power supply output terminal through a fifth capacitor C5.

In an embodiment of the present invention, referring to fig. 1 to 3 and fig. 4, the parallel resonator sub-circuit 11 may include: a first resonant inductor T1A, and a first resonant capacitor C6 connected in parallel with the first resonant inductor T1A;

the first resonant capacitor C6 has one end coupled to the first dc-ac sub-circuit 42 and the other end coupled to the fourth capacitor C4 and the fifth capacitor C5.

In an embodiment of the present invention, the first switch sub-circuit may include a first switch module 411 and a second switch module 412. Wherein the first switch module 411 may include: the switch comprises a first switch tube Q1, a first diode D1, a third diode D3, a first resistor R1 and a first winding T1C. The second switching module 412 may include: the switch comprises a second switch tube Q2, a second diode D2, a fourth diode D4, a second resistor R2 and a second winding T1D. The first winding T1C and the second winding T1D are windings of the same transformer as the first resonant inductor T1A. The gate of the second switching tube Q2 is connected to the first start-up circuit 43.

In an embodiment of the present invention, the first dc-ac sub-circuit 42 may include a third winding T2A and a fourth winding T2B located in the same transformer.

In a specific implementation, the dc power output from the dc power output terminal is applied to both ends of the seventh capacitor C7. The first start-up circuit 43 first applies a voltage to the gate of the second switch Q2, so that the second switch Q2 is turned on. The dc voltage applied to the seventh capacitor C7 is converted into an ac voltage by the fourth winding T2B and applied to the parallel resonator sub-circuit 11.

At this time, the circuit for supplying power to the LED load 12 is: the seventh capacitor C7 → the second switch module 412 → the fourth winding T2B → the parallel resonator sub-circuit 11 → the fourth capacitor C4.

When a voltage is applied to the parallel resonator sub-circuit 11, the first resonant inductor T1A and the first resonant capacitor C6 oscillate to generate a resonant control signal. The resonant control signal causes the voltage across the first resonant inductor T1A to couple to the first winding T1C. The ac voltage obtained from the first winding T1C is converted into a dc voltage through the first resistor R1 and the third diode D3, and is applied to the gate of the first switch Q1, so that the first switch Q1 is turned on.

At this time, the circuit for supplying power to the LED load 12 is: the seventh capacitor C7 → the first switch module 411 → the third winding T2A → the parallel resonator circuit 11 → the fifth capacitor C5.

In a specific implementation, after the first start circuit 43 controls the second switch Q2 to be turned on, the second switch Q2 is not controlled any more. Subsequently, the voltage of the first resonant inductor T1A can be coupled to the second winding T1D by the resonance control signal, and the ac voltage obtained from the second winding T1D is converted into a dc power supply through the second resistor R2 and the fourth diode D4, and then is input to the gate of the second switch tube Q2 to control the conduction of the second switch tube Q2, so as to change the loop for supplying power to the LED load 12.

By means of the dimming control signal, the first switch SW1 is controlled to be opened or closed, so that the capacitance value of the series capacitor of the LED load 12 can be changed, and the current of the LED load 12 can be changed, thereby achieving the purpose of dimming.

In a specific implementation, the transformer in which the first resonant inductor T1A is located may be an isolation transformer, or may be a non-isolation transformer, and is not limited specifically.

Referring to fig. 5, the switching circuit 50 may be a push-pull line. Specifically, the switching circuit 50 may include: a second dc-ac sub-circuit 52 and a second switch sub-circuit. Wherein:

the second dc-ac sub-circuit 52 is coupled to the dc power output end, and is adapted to convert the dc power input from the dc power output end into an ac power and input the ac power to the parallel resonator circuit 11;

the second switch sub-circuit is coupled between the output end of the direct-current power supply and the parallel resonance sub-circuit 11 and is suitable for being opened or closed under the control of the resonance control signal;

and the second starting circuit 53 is connected with the second switching sub-circuit and is suitable for starting a switching tube of the second switching sub-circuit.

In an embodiment of the present invention, referring to fig. 5, the parallel resonator sub-circuit 11 may include:

a second resonant inductance T3A;

a third resonant inductor T3B connected in series with the second resonant inductor T3A;

a second resonant capacitor C8 connected in parallel with the branch of the second resonant inductor T3A and the third resonant inductor T3B;

the second switch sub-circuit is connected to the second resonant inductor T3A and the third resonant inductor T3B.

In an embodiment of the present invention, the second switch sub-circuit may include: a third switching module 511 and a fourth switching module 512. Wherein, the third switching module 511 may include: a third switch tube Q3, a fifth diode D5, a seventh diode D7, a third resistor R3, and a fifth winding T3C. The second switching module 412 may include: a fourth switch tube Q4, a sixth diode D6, an eighth diode D8, and a fourth resistor R4. The fifth winding T3C, the second resonant inductor T3A and the third resonant inductor T3B are windings of the same transformer. The gate of the second switching tube Q2 is connected to the second start-up circuit 53.

In a specific implementation, the dc power output from the dc power output terminal is applied to both ends of the ninth capacitor C9. The second start-up circuit 53 first applies a voltage to the gate of the fourth switching transistor Q4, so that the fourth switching transistor Q4 is turned on. The dc power applied to the ninth capacitor C9 is converted into an ac voltage by the second dc-ac sub-circuit 52, and applied to the parallel resonator sub-circuit 11.

When a voltage is applied to the parallel resonator circuit 11, the second resonant inductor T3A and the third resonant inductor T3B oscillate with the second resonant capacitor C8 to generate a resonance control signal. The resonant control signal causes the voltages across the second resonant inductor T3A and the third resonant inductor T3B to couple to the fifth winding T3C. The ac voltage obtained from the fifth winding T3C is converted into dc power through the third resistor R3 and the seventh diode D7, and is applied to the gate of the third transistor Q3, so that the third transistor Q3 is turned on.

At this time, the third switching module 511, the parallel resonant sub-circuit 11, and the fourth switching module 512 form a circuit for supplying power to the LED load 12.

In a specific implementation, after the second start circuit 53 controls the fourth switching transistor Q4 to be turned on, the fourth switching transistor Q4 is no longer controlled.

In another embodiment of the present invention, the switch circuit may be a full bridge circuit.

It is understood that, in the embodiment of the present invention, the specific structure of the switch circuit is not limited, and it is within the scope of the present invention that only the switch circuit includes the above-mentioned variable capacitance circuit 13.

In an embodiment of the present invention, the switching power supply may further include: and the signal conversion circuit is suitable for receiving the dimming control signal and converting the dimming control signal into an electric signal suitable for being applied to the variable capacitance circuit.

Specifically, taking the first switch in the variable capacitance circuit 13 as an example of a relay switch, referring to fig. 6, the signal conversion circuit 60 may include a rectifier sub-circuit 61, a filter sub-circuit 62, a signal conversion sub-circuit 63, and a control sub-circuit.

Wherein the rectifying sub-circuit 61 is composed of two parallel-connected diode pairs DS51 and DS 52. The filtering sub-circuit 62 comprises a filtering capacitor CS 50. Referring to fig. 4, the voltage obtained by the first resonant inductor T1A is coupled to the sixth winding T1E, rectified by the rectifier sub-circuit 61, filtered by the filter sub-circuit 62, and applied to two ends of the signal converter sub-circuit 63.

The signal conversion sub-circuit 63 may include: a clamping diode ZS50, a fifth resistor RS53, a tenth capacitor CS51, a sixth resistor RS52, a seventh resistor RS51, and a fifth switch tube QS 51. The clamping diode ZS50 is connected with the dimming signal output ends (D + and D-), the fifth resistor RS53 is connected with the clamping diode ZS50 in series, and the tenth capacitor CS51 is connected with the clamping diode ZS50 and the fifth resistor RS53 in parallel. The sixth resistor RS52 and the tenth capacitor CS51 are connected to the clamping diode ZS 50. The seventh resistor RS51 is connected to the drain of the fifth switch tube QS 51.

The control sub-circuit may include: a sixth switching tube QS50, an eleventh capacitor CS52, and a ninth diode DS 53. When the first switch in the variable capacitance circuit 13 is a relay switch, the control sub-circuit may further include a control coil REA of a relay.

With reference to fig. 4, when the dimming signal voltage is lower than the clamping voltage of the clamping diode ZS50, the fifth switching tube QS51 is in an off state, the sixth switching tube QS50 is in an on state, the control coil REA of the relay is turned on, the relay switch REB is closed, the first capacitor C1 is short-circuited, and the current of the LED load 12 is limited only by the second capacitor C2;

when the dimming signal voltage is higher than the clamping voltage of the clamping diode ZS50, the fifth switching tube QS51 is in an on state, the sixth switching tube QS50 is in an off state, the control coil REA of the relay is turned off, the first switch SW1 is turned on, the first capacitor C1 is connected into the circuit, the current of the LED load 12 is limited by the capacitance value of the first capacitor C1 and the second capacitor C2 which are connected in series, the series capacitance value of the first capacitor C1 and the second capacitor C2 is the capacitance value of the second capacitor C2, the impedance of the whole branch of the LED load 12 is increased, and the output current is reduced. The current of the LED load 12 is reduced, the brightness of the lamp tube is reduced, and the purpose of dimming is achieved.

In specific implementation, the dimming control signal may be a 0-10V control signal, or may also be a silicon controlled dimming signal or a motion sensor signal, and is not limited specifically.

In a specific implementation, the dimming control signal may be a wireless control signal, such as WIFI, bluetooth, or the like. The capacitance value of the first capacitor C1 in the variable capacitance circuit 13 may be selected according to the load dimming requirement, and may be composed of one capacitor or a plurality of capacitors.

As can be seen from the above, the switching power supply in the embodiment of the present invention can be applied to a conventional fluorescent lamp electronic ballast, and the fixed voltage connected in series with the LED load is replaced by a variable capacitor circuit, so that the dimming function can be realized without changing the duty ratio and frequency of the switching tube by using a dedicated chip. The scheme of the invention is independent of the circuit outside the control chip and is not limited by the control chip, so the dimming is more convenient, the use is simple, the cost is low and the system reliability is high.

The embodiment of the invention also provides an electronic ballast, which can comprise the switching power supply in any one of the above embodiments.

The embodiment of the invention also provides an LED driving circuit, which can comprise any one of the switching power supplies in the embodiments.

Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A switching power supply, comprising: a switching circuit; the switch circuit comprises a parallel harmonic oscillator circuit, the parallel harmonic oscillator circuit is suitable for generating a resonance control signal, and the power supply of the LED load is controlled through the resonance control signal;

2. The switching power supply according to claim 1, wherein the variable capacitance circuit comprises:

a first capacitor;

and a first switch in parallel with the first capacitor;

wherein the first switch is adapted to be opened or closed under the control of the dimming control signal.

3. The switching power supply of claim 2, wherein the variable capacitance circuit further comprises:

4. The switching power supply of claim 2, wherein the variable capacitance circuit further comprises:

5. The switching power supply according to claim 2, wherein the first switch is any one of: diode, triode, MOS pipe, silicon controlled switch, relay switch.

6. The switching power supply according to any one of claims 1 to 5, wherein the switching circuit further comprises:

7. The switching power supply of claim 6, wherein the parallel resonant subcircuit comprises:

a first resonant inductor;

a first resonant capacitor connected in parallel with the first resonant inductor;

one end of the first resonant capacitor is coupled with the first direct current to alternating current sub-circuit, and the other end of the first resonant capacitor is coupled with the fourth capacitor and the fifth capacitor.

8. The switching power supply according to any one of claims 1 to 5, wherein the switching circuit further comprises:

9. The switching power supply of claim 8, wherein the parallel resonant subcircuit comprises:

a second resonant inductor;

a third resonant inductor in series with the second resonant inductor;

10. The switching power supply of claim 1, further comprising: and the signal conversion circuit is suitable for receiving the dimming control signal and converting the dimming control signal into an electric signal suitable for being applied to the variable capacitance circuit.

11. An electronic ballast comprising a switching power supply according to any one of claims 1 to 10.

12. An LED driving circuit comprising the switching power supply according to any one of claims 1 to 10.