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

Abstract

A switching power supply, an electronic ballast and an LED driving power supply. The switching power supply includes: a switching circuit; the switching circuit includes a parallel resonant sub-circuit, the parallel resonant sub-circuit is suitable for generating a resonance control signal, and the power supply of the LED load is controlled by the resonance control signal; wherein, The branch after the LED load is connected in series with the variable capacitance circuit is connected in parallel with the parallel resonant sub-circuit; the variable capacitance circuit is suitable for adjusting the capacitance value under the control of the dimming control signal to adjust the The LED load is dimmed. By applying the above solution, 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 technique

In the field of lighting, LED lighting has been used in more and more application scenarios due to its high light efficiency, long life and other advantages, and traditional fluorescent light sources are gradually replaced by LED light sources.

As the society's requirements for energy saving and situational perception are getting higher and higher, the requirements for dimming lighting systems are also increasing.

Since the LED light source needs a DC constant current source for power supply, it is necessary to control the current of the power supply when dimming it, so the dimming is difficult, and the self-excitation topology used for traditional fluorescent lamp ballasts is difficult to achieve.

At present, the usual practice is to select a special control chip to realize the dimming of the LED light source.

However, the above method will lead to high cost of the switching power supply and complicated circuit.

SUMMARY OF THE INVENTION

The problem to be solved by the present invention is: how to adjust the LED light source conveniently.

In order to solve the above problem, an embodiment of the present invention provides a switching power supply, which is characterized by comprising: a switch circuit; the switch circuit includes a parallel resonator circuit, and the parallel resonator circuit is suitable for generating a resonance control signal, The resonance control signal controls the power supply of the LED load;

Wherein, the branch after the LED load is connected in series with the variable capacitance circuit is connected in parallel with the parallel resonant sub-circuit; the variable capacitance circuit is suitable for adjusting the capacitance value under the control of the dimming control signal, so as to adjust the capacitance value. The LED load is dimmed.

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

Optionally, the variable capacitance circuit further includes:

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

Optionally, the variable capacitance circuit further includes:

A third capacitor, the third capacitor is connected in series with the first switch and connected in parallel with the first capacitor.

Optionally, the first switch is any one of the following: a diode, a triode, a MOS tube, a thyristor switch, and a relay switch.

Optionally, the switch circuit further includes:

a first switch sub-circuit, coupled to the output end of the DC power supply, suitable for opening or closing under the control of the resonance control signal;

A first DC-to-AC sub-circuit, coupled between the first switch sub-circuit and the parallel resonant sub-circuit, is adapted to convert the DC power input from the DC power output end into AC power, and input it to the the parallel resonant oscillator circuit;

a first start-up circuit, connected to the first switch sub-circuit, and adapted to start the switch tube of the first switch sub-circuit;

The parallel resonator circuit is coupled to the positive pole of the output terminal of the DC power supply through a fourth capacitor, and is coupled to the negative pole of the output terminal of the DC power supply through a fifth capacitor.

Optionally, the parallel resonant sub-circuit includes: 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 to the first DC-to-AC sub-circuit and the other end is coupled to the fourth capacitor and the fifth capacitor.

Optionally, the switch circuit further includes:

A second DC-to-AC subcircuit, coupled to the DC power output terminal, is adapted to convert the DC power input from the DC power output terminal into an AC power source and input it to the parallel resonant sub-circuit;

a second switch sub-circuit, coupled between the output end of the DC power supply and the parallel resonant sub-circuit, and adapted to be opened or closed under the control of the resonance control signal;

A second start-up circuit, connected to the second switch sub-circuit, is adapted to start the switch tube of the second switch sub-circuit.

Optionally, the parallel resonator circuit includes:

the second resonant inductor;

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

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

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

Optionally, the switching power supply further includes: a signal conversion circuit adapted to receive the dimming control signal and convert the dimming control signal into an electrical signal suitable for being applied to the variable capacitance circuit.

An embodiment of the present invention further provides an electronic ballast, where the electronic ballast includes any one of the switching power supplies described above.

An embodiment of the present invention further provides an LED driving circuit, where the LED driving circuit includes any one of the switching power supplies described above.

Compared with the prior art, the technical solutions of the embodiments of the present invention have the following advantages:

By applying the solution of the present invention, since the capacitance value of the variable capacitance circuit can be changed under the control of the dimming control signal, compared to using a dedicated chip to adjust the operating frequency and or duty cycle of the switching tube in the switching circuit for dimming In the present invention, only by changing the capacitance value of the LED load series capacitor, the dimming is more convenient.

Further, the variable capacitance circuit is composed of a capacitor and a switch in parallel, and the cost of dimming is lower than that of a dedicated chip for dimming.

Description of drawings

1 is a schematic structural diagram of a variable capacitance circuit of the present invention;

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

3 is a schematic structural diagram of another variable capacitance circuit of the present invention;

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

5 is a schematic structural diagram of another switching power supply in an embodiment of the present invention;

FIG. 6 is a schematic structural diagram of a signal conversion circuit in an embodiment of the present invention.

Detailed ways

At present, most of the control chips are used to control the operating frequency or duty cycle of the switching tube for dimming. Specifically, the output current is adjusted by adjusting the operating frequency or duty cycle of the switching tube, so as to control the output current and achieve the purpose of dimming. The entire solution is costly and complicated to control.

In view of the above problems, in the embodiment of the present invention, the capacitor connected in series with the LED load is a variable capacitor circuit, and the capacitance value of the variable capacitor circuit can be changed under the control of the dimming control signal, so that the Dimming LED loads more easily.

In order to make the above objects, features and advantages of the present invention more clearly understood, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

1 to 3 , an embodiment of the present invention provides a switching power supply, and the switching power supply may include: a switching circuit; the switching circuit includes a parallel resonator circuit 11 .

The parallel resonator circuit 11 is adapted to generate a resonance control signal, and control the power supply of the LED load 12 through the resonance control signal;

The branch of the LED load 12 in series with the variable capacitance circuit 13 is connected in parallel with the parallel resonator circuit 11; the variable capacitance circuit 13 is suitable for adjusting the capacitance under the control of the dimming control signal value to dim the LED load 12 .

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

However, in the embodiment of the present invention, the capacitance value of the capacitor connected in series with the LED load 12 is variable. Since the voltage across 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 of the variable capacitor circuit 13. By adjusting the variable capacitor circuit 13 The capacitance value of , can change the current of the LED load 12 to achieve the purpose of dimming the LED load 12 .

In specific implementation, the variable capacitance circuit 13 may have various circuit structures, which are not specifically limited. Only the variable capacitance circuit 13 can 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 suitable for opening or closing 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 is connected in series with the LED load 12, and is connected with the first capacitor C2. A circuit composed of the capacitor C1 and the first switch SW1 is connected in series.

In yet 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 connected in parallel with the first capacitor C1.

In a specific implementation, the first switch SW1 may be any one of the following: a diode, a triode, a MOS tube, a thyristor switch, and a relay switch.

It can be understood that the specific type of the first switch SW1 does not constitute a limitation to the present invention, as long as the first switch SW1 can be opened or closed under the control of the dimming control signal, thereby changing the dimming control signal. The capacitance value of the variable capacitance circuit 13 is sufficient.

In a specific implementation, there may be various specific structures of the switching power supply, which are not specifically limited, as long as the switching power supply includes the above-mentioned variable capacitance circuit 13, it is within the protection scope of the present invention.

The following is a detailed description of the specific switching power supply circuit:

Referring to FIG. 4 , the switch circuit 40 may be a half-bridge circuit. Specifically, the switch circuit 40 may include: a first switch sub-circuit, a first DC-to-AC sub-circuit 42 , and a parallel resonant sub-circuit 11 .

in:

the first switch sub-circuit, coupled to the output terminal of the DC power supply, is suitable for opening or closing under the control of the resonance control signal;

The first DC-to-AC sub-circuit 42 is coupled between the first switch sub-circuit and the parallel resonator sub-circuit 43, and is adapted to convert the DC power input from the output terminal of the DC power source into AC power, and input to the parallel resonator circuit 11;

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

The parallel resonator circuit 11 is coupled to the positive pole of the output terminal of the DC power supply through a fourth capacitor C4, and is coupled to the negative pole of the output terminal of the DC power supply through a fifth capacitor C5.

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

One end of the first resonant capacitor C6 is coupled to the first DC-to-AC sub-circuit 42, and the other end is 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 . The first switch module 411 may include: a first switch tube Q1, a first diode D1, a third diode D3, a first resistor R1, and a first winding T1C. The second switch module 412 may include: 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, and the first resonant inductor T1A, are windings of the same transformer. The gate of the second switch transistor Q2 is connected to the first start-up circuit 43 .

In an embodiment of the present invention, the first DC-to-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 transistor Q2, so that the second switch transistor Q2 is turned on. The DC voltage applied to the seventh capacitor C7 is converted into an AC voltage through the fourth winding T2B and applied to the parallel resonant sub-circuit 11 .

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

After the parallel resonant sub-circuit 11 is applied with a voltage, 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 on the first resonant inductor T1A to couple to the first winding T1C. The AC voltage obtained on 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 transistor Q1, so that the first switch transistor Q1 is turned on.

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

In a specific implementation, after the first start-up circuit 43 controls the second switch transistor Q2 to be turned on, it no longer controls the second switch transistor Q2. Subsequently, through the resonance control signal, the voltage on the first resonant inductor T1A can be coupled to the second winding T1D, and the AC voltage obtained on the second winding T1D is converted into a DC power supply through the second resistor R2 and the fourth diode D4 Then, it is input to the gate of the second switch tube Q2 to control the second switch tube Q2 to be turned on, thereby changing the circuit for supplying power to the LED load 12 .

Through the dimming control signal, the first switch SW1 is controlled to open or close, so that the capacitance value of the series capacitor of the LED load 12 can be changed, thereby changing the current of the LED load 12 to achieve the purpose of dimming.

It should be noted that, in a specific implementation, the transformer where the first resonant inductor T1A is located may be an isolation transformer or a non-isolation transformer, which is not specifically limited.

Referring to FIG. 5 , the switch circuit 50 may be a push-pull circuit. Specifically, the switch circuit 50 may include: a second DC-to-AC sub-circuit 52 and a second switch sub-circuit. in:

The second DC-to-AC sub-circuit 52 is coupled to the output terminal of the DC power supply, and is adapted to convert the DC power input from the output terminal of the DC power supply into an AC power supply and input it to the parallel resonant sub-circuit 11;

The second switch sub-circuit is coupled between the output terminal of the DC power supply and the parallel resonant sub-circuit 11, and is suitable for opening or closing under the control of the resonance control signal;

The second start-up circuit 53 is connected to the second switch sub-circuit, and is adapted to start the switch tube of the second switch sub-circuit.

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

the second resonant inductor T3A;

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

The second resonant capacitor C8 is connected in parallel with the branch where the second resonant inductor T3A and the third resonant inductor T3B are located;

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 switch module 511 and a fourth switch module 512 . The third switch 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 switch module 412 may include: a fourth switch transistor 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 switch transistor 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 switch transistor Q4, so that the fourth switch transistor Q4 is turned on. The DC power applied to the ninth capacitor C9 is converted into an AC voltage through the second DC-to-AC sub-circuit 52 and applied to the parallel resonant sub-circuit 11 .

After a voltage is applied to the parallel resonant sub-circuit 11, the second resonant inductor T3A and the third resonant inductor T3B oscillate with the second resonant capacitor C8 to generate a resonant control signal. The resonance control signal causes the voltages on the second resonant inductor T3A and the third resonant inductor T3B to be coupled to the fifth winding T3C. The AC voltage obtained on the fifth winding T3C is converted into a DC power supply through the third resistor R3 and the seventh diode D7, and is applied to the gate of the third switch transistor Q3, so that the third switch transistor Q3 is turned on.

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

In a specific implementation, after the second start-up circuit 53 controls the fourth switch transistor Q4 to be turned on, it no longer controls the fourth switch transistor Q4.

Through the dimming control signal, the first switch SW1 is controlled to open or close, so that the capacitance value of the series capacitor of the LED load 12 can be changed, thereby changing the current of the LED load 12 to achieve the purpose of dimming.

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

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

In an embodiment of the present invention, the switching power supply may further include: a signal conversion circuit, adapted to receive the dimming control signal, and convert the dimming control signal into a signal suitable for applying to the variable capacitor Electrical signals on a circuit.

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

The rectifier circuit 61 is composed of two diode pairs DS51 and DS52 connected in parallel. The filter subcircuit 62 includes a filter capacitor CS50. Referring to FIG. 4 , the voltage obtained by the first resonant inductor T1A is coupled to the sixth winding T1E, rectified by the rectifier circuit 61 , filtered by the filter subcircuit 62 , and applied to both ends of the signal conversion subcircuit 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 QS51. The clamping diode ZS50 is connected to the dimming signal output terminals (D+ and D-), the fifth resistor RS53 is connected in series with the clamping diode ZS50, and the tenth capacitor CS51 is connected in parallel with the clamping diode ZS50 and the fifth resistor RS53. The sixth resistor RS52 is connected to the tenth capacitor CS51 and the clamping diode ZS50. The seventh resistor RS51 is connected to the drain of the fifth switch transistor QS51.

The control sub-circuit may include: a sixth switch tube QS50, an eleventh capacitor CS52, and a ninth diode DS53. 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 the relay.

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

When the dimming signal voltage is higher than the clamping voltage of the clamping diode ZS50, the fifth switch QS51 is turned on, the sixth switch QS50 is turned off, the control coil REA of the relay is turned off, the first switch SW1 is turned on, When the first capacitor C1 is connected to the circuit, the current of the LED load 12 is limited by the capacitance of the first capacitor C1 and the second capacitor C2 in series, and the series capacitance of the first capacitor C1 and the second capacitor C2 is the second capacitor C2. , the impedance of the entire LED load 12 branch increases, and the output current will decrease. The current of the LED load 12 is reduced accordingly, the brightness of the lamp tube is reduced, and the purpose of dimming is realized.

In a specific implementation, the dimming control signal may be a 0-10V control signal, or a thyristor dimming signal or a motion sensor signal, etc., which is not specifically limited.

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

It can be seen from the above content that the switching power supply in the embodiment of the present invention can be applied to a traditional fluorescent lamp electronic ballast, replacing the fixed voltage connected in series with the LED load to a variable capacitance circuit, and no special chip is required to change the duty cycle of the switching tube. and frequency, the dimming function can be realized. The solution of the present invention is independent of the circuit outside the control chip and is not restricted by the control chip, so the dimming is more convenient, the use is simple, the cost is low, and the system reliability is high.

An embodiment of the present invention further provides an electronic ballast, and the electronic ballast may include the switching power supply of any of the foregoing embodiments.

An embodiment of the present invention further provides an LED driving circuit, and the LED driving circuit may include the switching power supply of any of the foregoing embodiments.

Although the present invention is disclosed above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be based on the scope defined by the claims.

Claims (12)

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;

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.

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:

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.

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

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

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:

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.

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:

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.

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;

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.

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.

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