CN104994664B - A kind of single-stage buck type LED drive circuit of leakage inductance energy feedback - Google Patents

Abstract

The invention relates to a single-stage step-down LED drive circuit for leakage inductance energy feedback, which includes an input AC power supply V _in and an LED lamp load, a power MOS switch tube Q ₁ , a power MOS switch tube Q ₂ , and a rectified power Diode D ₁ , a rectifying power diode D ₂ , a rectifying power diode D ₃ , a rectifying power diode D ₄ , a fast recovery diode D ₅ , a fast recovery diode D ₆ , a fast recovery diode D ₇ , a fast recovery diode D ₈ , a fast recovery diode D ₉ , a fast recovery diode D ₁₀ , an intermediate electrolytic capacitor C _B , an output electrolytic capacitor C _o , a pre-stage Buck circuit inductance L _Buck , a transformer T _r and its equivalent leakage inductance L _lk . The present invention integrates the front-stage BUCK circuit and the rear-stage leakage inductance energy feedback dual-tube flyback circuit into a single-stage LED drive circuit to realize functions such as low-voltage switching stress, high conversion efficiency, and constant current output.

Description

A single-stage step-down LED drive circuit with leakage inductance energy feedback

technical field

The invention relates to the technical field of power electronics, in particular to a single-stage step-down LED drive circuit for leakage inductance energy feedback.

Background technique

Leakage inductance is caused by incomplete coupling of coils, so leakage inductance mainly occurs in the occasions where coils are coupled, such as transformers and inductors. The leakage inductance of the transformer can be described as the magnetic flux generated by the primary coil of the transformer cannot completely pass through the secondary coil, so a leakage flux is generated, which is equivalent to the magnetic flux generated by the leakage inductance. Due to the existence of transformer leakage inductance, the energy of the primary side of the transformer cannot be transferred to the secondary side 100%, resulting in incomplete utilization of energy and increasing losses.

The existence of the high-frequency leakage inductance in the switching converter has a great influence on the stress of the switching devices in the circuit topology. When the main switching tube of the circuit is disconnected, the leakage inductance of the stored energy will generate a back electromotive force stress peak, which will easily cause the switching device to overheat. Voltage breakdown, leakage inductance may also form an oscillation circuit with the distributed capacitance in the circuit and the distributed capacitance of the transformer coil, causing the circuit to oscillate and radiate electromagnetic energy outward, causing electromagnetic interference. Because the flyback converter transformer is a transformer with an air gap, the leakage inductance value and stored energy of the flyback circuit are much larger than that of the forward circuit and other isolated converter circuits, that is, the influence of the leakage inductance on the flyback circuit is compared And other isolation circuits that use isolation transformers have a much greater impact.

Contents of the invention

In view of this, for the application of the flyback converter, the purpose of the present invention is to propose a single-stage step-down LED drive circuit with leakage inductance energy feedback, to achieve lower switching tube voltage stress and constant current output, and by constructing a transformer The leakage inductance energy feedback loop realizes the feedback and utilization of the leakage inductance energy of the transformer, reduces the switch stress, and improves the reliability of the device and the conversion efficiency of the circuit.

The present invention is realized by the following scheme: a single-stage step-down LED drive circuit for leakage inductance energy feedback, including an input AC voltage source V _in and an LED lamp load, the L terminal of the input single-phase AC voltage source V _in is connected to The anode of a first power diode _D1 and the cathode of a third power diode _D3 , the N _terminal of the input single-phase AC voltage source Vin is connected to the cathode of a fourth power diode _D4 and a second power diode D ₂ ; the cathode of the first power diode _D1 is connected to the cathode of the second power diode _D2 , the cathode of a fifth power diode _D5 , and one end of an inductor L _Buck ; the fourth power diode D The anode of ₄ is connected to the anode of the third power diode _D3 , the anode of a sixth power diode _D6 , and the source of a second power MOS transistor _Q2 ; the drain of the second power MOS transistor _Q2 is connected to An anode of an eighth power diode _D8 , a cathode of a seventh power diode _D7 , and a primary opposite end of a transformer _Tr , the gate of the second power MOS transistor _Q2 is connected to the first PWM control signal ; The anode of the fifth power diode _D5 is connected to the anode of the seventh power diode _D7 , the cathode of the sixth power diode _D6 , the anode of a ninth power diode _D9 , and the negative terminal of an intermediate capacitor C _B ; The positive end of the intermediate capacitor C _B is connected to the other end of the inductor L _Buck , the cathode of the eighth power diode _D8 , and the drain of a first power MOS transistor _Q1 , and the gate of the first power MOS transistor _Q1 is connected to The second PWM control signal; the source of the first power MOS transistor _Q1 is connected to the cathode of the ninth power diode _D9 and the same-named end of the primary side of the transformer _Tr ; the different name of the secondary side of the transformer _Tr The terminal is connected to the anode of a tenth power diode D ₁₀ ; the cathode of the tenth diode D ₁₀ is connected to the positive end of an output capacitor C _O , and the negative end of the output capacitor C _O is connected to the secondary side of the transformer T _r terminal with the same name; the positive and negative terminals of the output capacitor _CO are connected to the LED lamp load.

Further, the transformer T _r is a high-frequency transformer, and the terminals with the same name on the primary and secondary sides of the transformer T _r are excited in opposite directions.

Further, the first power diode D ₁ , the second power diode D ₂ , the third power diode D ₃ and the fourth power diode D ₄ are rectifying power diodes; the fifth power diode D ₅ and the sixth power diode D ₆ , the seventh power diode D ₇ , the eighth power diode D ₈ , the ninth power diode D ₉ , and the tenth power diode D ₁₀ are fast recovery power diodes.

Further, the intermediate capacitor C _B is an electrolytic capacitor.

Further, the output capacitor C _O is an electrolytic capacitor.

Further, the first power MOS transistor _Q1 and the second power MOS transistor _Q2 adopt a working mode of being turned on and turned off at the same time.

Further, the front-stage BUCK circuit and the rear-stage dual-transistor flyback circuit of the single-stage step-down LED drive circuit for leakage inductance energy feedback are designed to work in a current discontinuous mode.

Compared with the prior art, the present invention has the following beneficial effects:

1. The single-stage circuit only needs a set of control schemes, uses fewer semiconductor devices, reduces the complexity of the control circuit, saves costs, and improves the conversion efficiency of the whole machine at the same time;

2. Compared with the general circuit, the invention adds an energy feedback loop to the leakage inductance of the transformer, effectively utilizes the energy of the leakage inductance, and reduces the voltage stress of the switch tube.

Description of drawings

FIG. 1 is a single-stage step-down LED drive circuit for leakage inductance energy feedback of the present invention.

Fig. 2 is a single-stage step-down LED drive circuit for leakage inductance energy feedback of the present invention, which works in the inductance L _Buck current discontinuous mode. When the power MOS transistor _Q1 and the power MOS transistor _Q2 are turned on, the input AC voltage is rectified Output a schematic diagram of the working mode of charging the L _Buck inductor and the intermediate capacitor C _B.

Fig. 3 shows that the single-stage step-down LED drive circuit of the present invention with leakage inductance energy feedback works in the inductance L _Buck current discontinuous mode, the power MOS transistor _Q1 and the power MOS transistor _Q2 are turned on, and they are in the working dead zone of the Buck circuit , Schematic diagram of the working mode in which the intermediate capacitor C _B excites the excitation inductance and leakage inductance L _lk of the flyback transformer.

Fig. 4 The single-stage step-down LED drive circuit _of the present invention with leakage inductance energy feedback works in the inductance L _Buck current discontinuous mode, when the power MOS transistor Q ₁ and the power MOS transistor Q ₂ are turned on, when the When the current is less than the current flowing through the primary side of the flyback transformer, the input AC voltage is rectified and then output together with the intermediate capacitor C _B to excite the excitation inductance and leakage inductance of the flyback transformer.

Fig. 5 shows that the single-stage step-down LED drive circuit _of the present invention with leakage inductance energy feedback works in the inductance L _Buck current discontinuous mode, when the power MOS transistor _Q1 and the power MOS switch transistor _Q2 are turned on, when the When the current of the inductor is greater than the current flowing through the primary side of the flyback transformer, the input AC voltage is rectified and output to charge the intermediate capacitor C _B , and at the same time it also excites the excitation inductance and leakage inductance of the flyback transformer.

Fig. 6 is a single-stage step-down LED drive circuit for leakage inductance energy feedback of the present invention that operates in the discontinuous current mode of the inductor L _Buck , and when the power MOS transistor _Q1 and the power MOS transistor _Q2 are turned off, the L _Buck inductor continues to flow, Schematic diagram of the working mode of the flyback transformer leakage inductance energy feedback.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

As shown in Figure 1, this embodiment provides a single-stage step-down LED drive circuit for leakage inductance energy feedback, including an input single-phase AC voltage source V _in and an LED lamp load, the input AC voltage source V _in The L terminal of the input AC voltage source Vin is connected to the anode of a first power diode _D1 and the cathode of a third power diode _D3 , and the N terminal of the input AC voltage source V _in is connected to the cathode of a fourth power diode _D4 and a second power diode D4. The anode of the diode D ₂ ; the cathode of the first power diode D ₁ is connected to the cathode of the second power diode D ₂ , the cathode of a fifth power diode D ₅ , and one end of an inductor L _Buck ; the fourth power The anode of the diode _D4 is connected to the anode of the third power diode _D3 , the anode of a sixth power diode _D6 , and the source of a second power MOS transistor _Q2 ; the drain of the second power MOS transistor _Q2 The pole is connected to the anode of an eighth power diode _D8 , the cathode of a seventh power diode _D7 , and the primary opposite end of a transformer _Tr , and the gate of the second power MOS transistor _Q2 is connected to the first PWM Control signal; the anode of the fifth power diode _D5 is connected to the anode of the seventh power diode _D7 , the cathode of the sixth power diode _D6 , the anode of a ninth power diode _D9 , and the negative terminal of an intermediate capacitor C _B ; The positive end of the intermediate capacitor C _B is connected to the other end of the inductance L _Buck , the cathode of the eighth power diode _D8 , the drain of a first power MOS transistor _Q1 , and the gate of the first power MOS transistor _Q1 The pole is connected to the second PWM control signal; the source of the first power MOS transistor _Q1 is connected to the cathode of the ninth power diode _D9 and the same-named end of the primary side of the transformer _Tr ; the secondary side of the transformer _Tr The opposite end is connected to the anode of a tenth power diode D ₁₀ ; the cathode of the tenth diode D ₁₀ is connected to the positive end of an output capacitor C _O , and the negative end of the output capacitor C _O is connected to the transformer _Tr The terminal with the same name as the secondary side; the positive and negative terminals of the output capacitor _CO are connected to the LED lamp load.

In this embodiment, the transformer _Tr is a high-frequency transformer, and the terminals with the same name on the primary and secondary sides of the transformer _Tr are excited in opposite directions. The first power diode D ₁ , the second power diode D ₂ , the third power diode D ₃ , and the fourth power diode D ₄ are rectifying power diodes; the fifth power diode D ₅ , the sixth power diode D ₆ , The seventh power diode D ₇ , the eighth power diode D ₈ , the ninth power diode D ₉ , and the tenth power diode D ₁₀ are fast recovery power diodes. Preferably, the intermediate capacitor C _B and the output capacitor C _O are electrolytic capacitors. Further, the first power MOS transistor _Q1 and the second power MOS transistor _Q2 adopt a working mode of being turned on and turned off at the same time. At the same time, the front-stage BUCK circuit and the rear-stage dual-tube flyback circuit of the single-stage step-down LED drive circuit for leakage inductance energy feedback are designed to work in a current discontinuous mode.

In this embodiment, a single-stage step-down LED drive circuit with leakage inductance energy feedback is used to realize high-efficiency constant current output, reduce the voltage stress of circuit switch tubes, reduce semiconductor power devices and improve efficiency, and simultaneously realize power factor correction. The specific working mode of the leakage inductance energy feedback single-stage step-down LED drive circuit of the present invention is described below in conjunction with Fig. 2 to Fig. 6. Both the front and rear stages are in the current discontinuous mode (DCM mode). as an example.

As shown in Figure 2, in this embodiment, when the power MOS transistors _Q1 and _Q2 are turned on, the input AC voltage source V _in is rectified by the rectifier bridge and output to the L _Buck inductance through the diode _D7 and the switch tube _Q2 And the intermediate capacitor C _B is charged, and the settling time is very short. The secondary output capacitor C _O discharges the load. At this time, fast recovery power diodes D ₅ , D ₈ , D ₉ , and D ₁₀ are cut off due to reverse voltage, and D ₆ is short-circuited.

As shown in Figure 3, in this embodiment, when the power MOS transistors _Q1 and _Q2 are turned on and the Buck circuit is in the working dead zone, the intermediate capacitor C _B passes through the switch tube _Q1 , the primary side of the flyback transformer _Tr , The switch tube Q ₂ and the diode D ₆ excite the excitation inductance and leakage inductance L _lk of the flyback transformer, and the secondary output capacitor C _O discharges the load. At this time, the fast recovery power diodes D ₅ , D ₇ , D ₈ , D ₉ , and D ₁₀ are cut off due to the reverse voltage.

As shown in Figure 4, in this embodiment, when the power MOS transistors _Q1 and _Q2 are turned on, when the current flowing through the Buck inductance L _Buck is smaller than the current flowing through the primary side of the flyback transformer, the input AC voltage source V After being rectified and output by the rectifier bridge _{, in} excites the excitation inductance and leakage inductance of the flyback transformer through the switch tube Q ₁ , the primary side of the flyback transformer, and the switch tube Q ₂ . The intermediate capacitor C _B excites the excitation inductance and leakage inductance of the flyback transformer through the switch tube Q ₁ , the primary side of the flyback transformer, the switch tube Q ₂ and the diode D ₆ , and the secondary output capacitor C _O discharges the load. At this time, the fast recovery power diodes D ₅ , D ₇ , D ₈ , D ₉ , and D ₁₀ are cut off due to the reverse voltage.

As shown in Figure 5, in this embodiment, when the power MOS transistors _Q1 and _Q2 are turned on, when the current flowing through the Buck inductance L _Buck is greater than the current flowing through the primary side of the flyback transformer, the input AC voltage source V _After being rectified and output by the rectifier bridge, part of the energy charges the Buck inductance and the intermediate capacitor C _B through the diode D ₇ ; the other part of the energy passes through the switch tube Q ₁ , the primary side of the flyback transformer, and the switch tube Q ₂ to the flyback transformer excitation inductance and The leakage inductance excites, and the secondary output capacitor C _O discharges the load. At this time, fast recovery power diodes D ₅ , D ₈ , D ₉ , and D ₁₀ are cut off due to reverse voltage, and D ₆ is short-circuited.

As shown in Figure 6, in this embodiment, when the power MOS transistors _Q1 and _Q2 are turned off, the Buck inductance L _Buck freewheels through the intermediate capacitor C _B and diode _D5 , and the flyback transformer transfers the energy to the secondary side , charge the output capacitor C _O through D ₁₀ , and supply power to the load LED lamp. At the same time, the leakage inductance energy of the flyback transformer is fed back to the intermediate capacitor C _B through the diodes D ₈ and D ₉ . At this time, the fast recovery power diodes D ₆ and D ₇ are cut off due to the reverse voltage.

The above is the equivalent circuit of the five working modes of one switching cycle when the embodiment is working in a steady state. This embodiment will repeat the working process of FIG. 2 to FIG. 6 , repeating itself.

To sum up, the present invention proposes a single-stage step-down LED drive circuit with leakage inductance energy feedback, which is to feed back the leakage inductance energy of the transformer to an intermediate capacitor when the switch tube is turned off. When the switch tube is turned on again , The leakage inductance energy is recycled again. This not only reduces the voltage stress of the main switch tube, reduces the voltage stress of the secondary output diode, reduces the loss, but also improves the EMI characteristics of the circuit.

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.

Claims (5)

1. A single-stage step-down LED drive circuit for leakage inductance energy feedback, comprising an input AC voltage source V _in and an LED lamp load, characterized in that: the L end of the input single-phase AC voltage source V _in is connected to a The anode of the first power diode _D1 and the cathode of a third power diode _D3 , the N _terminal of the input single-phase AC voltage source Vin is connected to the cathode of a fourth power diode _D4 and a second power diode _D2 the anode of the first power diode _D1 ; the cathode of the first power diode D1 is connected to the cathode of the second power diode _D2 , the cathode of a fifth power diode _D5 , and one end of an inductor L _Buck ; the fourth power diode _D4 The anode of the anode is connected to the anode of the third power diode _D3 , the anode of a sixth power diode _D6 , and the source of a second power MOS transistor _Q2 ; the drain of the second power MOS transistor _Q2 is connected to a The anode of the eighth power diode D ₈ , the cathode of a seventh power diode D ₇ , the primary side asymmetric terminal of the transformer T _r , the gate of the second power MOS transistor Q ₂ is connected to the first PWM control signal; The anode of the fifth power diode _D5 is connected to the anode of the _seventh power diode D7, the cathode of the sixth power diode _D6 , the anode of a ninth power diode _D9 , and the negative end of an intermediate capacitor C _B ; The positive end of the capacitor C _B is connected to the other end of the inductor L _Buck , the cathode of the eighth power diode _D8 , and the drain of a first power MOS transistor _Q1 , and the gate of the first power MOS transistor _Q1 is connected to the second Road PWM control signal; the source of the first power MOS transistor _Q1 is connected to the cathode of the ninth power diode _D9 and the same-named end of the primary side of the transformer _Tr ; the opposite-named end of the secondary side of the transformer _Tr is connected An anode of a tenth power diode D ₁₀ ; the cathode of the tenth diode D ₁₀ is connected to the positive end of an output capacitor C _O , and the negative end of the output capacitor C _O is connected to the secondary side of the transformer _Tr with the same name terminal; the positive and negative terminals of the output capacitor _CO are connected to the LED lamp load; The first power MOS transistor _Q1 and the second power MOS transistor _Q2 adopt a working mode of being turned on and turned off at the same time; The front-stage BUCK circuit and the rear-stage dual-tube flyback circuit of the single-stage step-down LED drive circuit for leakage inductance energy feedback are designed to work in a current discontinuous mode. 2. A kind of leakage inductance energy feedback single-stage step-down LED drive circuit according to claim 1, characterized in that: said transformer _Tr is a high-frequency transformer, and the terminal with the same name of the original secondary side of said transformer _Tr It is excited in the opposite direction. 3. A single-stage step-down LED drive circuit with leakage inductance energy feedback according to claim 1, characterized in that: the first power diode D ₁ , the second power diode D ₂ , and the third power diode D _3. The fourth power diode D ₄ is a rectifying power diode; the fifth power diode D ₅ , the sixth power diode D ₆ , the seventh power diode D ₇ , the eighth power diode D ₈ , the ninth power diode D ₉ , The tenth power diode D ₁₀ is a fast recovery power diode. 4 . The single-stage step-down LED drive circuit for leakage inductance energy feedback according to claim 1 , wherein the intermediate capacitor C _B is an electrolytic capacitor. 5. The single-stage step-down LED drive circuit for leakage inductance energy feedback according to claim 1, wherein the output capacitor _CO is an electrolytic capacitor.