CN106550512A - A kind of resonant type soft-switch single stage type LED drive circuit - Google Patents

Abstract

The invention discloses a resonant soft-switching single-stage LED drive circuit, which includes an AC input terminal, a rectifier circuit, a PFC circuit, a DC/DC circuit, an LED load and a control circuit, and the PFC circuit includes an inductor L _B and a diode D ₁ , diode D ₂ , capacitor C _B and switch tube S ₁ ; the DC/DC circuit includes inductor L _r , capacitor C _r , capacitor C _s , capacitor C _o , switch tube S ₂ , transformer T, diode D _o1 and diode D _o2 , the cathode of the diode D _o2 is connected to the capacitor C _o and one end of the LED load at the same time; the other end of the secondary winding of the transformer T is connected to the anode of the diode D _o1 , the capacitor C _o and one end of the LED load at the same potential; _The gates _of the switch tube S1 and the switch tube S2 are connected to the drive signal output end of the control circuit at the same time. The circuit structure of the invention is simple, and can improve efficiency and power factor.

Description

A resonant soft-switching single-stage LED drive circuit

technical field

The invention relates to the technical field of circuits, in particular to a resonant soft-switching single-stage LED drive circuit.

Background technique

LED is a semiconductor device that emits light and belongs to a new light source. It has many advantages such as energy saving and environmental protection, high luminous efficiency, long life, and various colors. It gradually replaces traditional lighting fixtures and becomes a new generation of lighting tools. China Quality Certification Center (English abbreviation CQC) developed and launched the energy-saving certification business of AC electronic control devices for LED modules in 2014. The standard for AC electronic control devices for LED modules is CQC3146-2014 "AC electronic control devices for LED modules Technical Specifications for Energy Conservation Certification. The specification requires that when the power of the isolated LED drive power supply is less than 5W, the efficiency must be greater than 78.5%, and there is no power factor requirement; when the power of the LED drive power supply is between 5W and 25W, the efficiency must be greater than 84%, and the power factor must be greater than 0.8. As the power of LED driving power increases, the requirements for its efficiency and power factor are higher.

In the existing small and medium power LED drive circuits, two-stage or single-stage are often used. Two-stage type: the front stage (PFC stage) realizes power factor correction, and the rear stage (DC/DC stage) realizes constant voltage and constant current output, which requires two sets of processing components and corresponding control circuits, and its circuit is complex, high in cost and low in efficiency. Therefore, the single-stage circuit has become a research hotspot: it integrates the PFC stage and the DC/DC stage, shares the switch tube and the control circuit, and has fewer components, low cost, and improved efficiency and power density. However, most single-stage LED drive circuits are in a hard switching state, which limits the improvement of circuit efficiency. Moreover, due to the leakage inductance of the transformer in the actual circuit, it will resonate with the parasitic capacitance in the circuit, and other absorption circuits are often added to suppress the resonance, which will sacrifice the performance of the single-stage LED drive circuit. Therefore, it is of great significance to design and develop a fully soft-switching single-stage LED drive circuit with high efficiency, high power factor and simple circuit structure.

Contents of the invention

In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a resonant soft-switching single-stage LED driving circuit, which has a simple circuit structure and can improve efficiency and power factor.

In order to solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a resonant soft-switching single-stage LED drive circuit, including an AC input terminal, a rectifier circuit, a PFC circuit, a DC/DC circuit, an LED load and a control circuit, It is characterized by:

The rectifier circuit is used to convert the alternating current at the AC input terminal into direct current;

The PFC circuit includes an inductor L _B , a diode D ₁ , a diode D ₂ , a capacitor C _B and a switch tube S ₁ , wherein: one end of the inductor L _B is connected to an output end of the rectifier circuit, and the other end of the inductor L _B At the same time, it is connected to the _anodes of diode D1 and diode D2 _; the cathode of diode D1 is connected to the source _of switch tube S1, and the cathode of diode D2 is connected to _one end of capacitor _{CB ;} the other end of capacitor _CB , switch tube The drain of S ₁ and the other output terminal of the rectifier circuit are grounded simultaneously;

The DC/DC circuit includes an inductor L _r , a capacitor C _r , a capacitor C _s , a capacitor C _o , a switch tube S ₂ , a transformer T, a diode D _o1 and a diode D _o2 , wherein: the capacitor C _r and the inductor L _{r One} end of the inductor L r is connected to the cathode of the diode D2 at the same time, the other end of the inductor L _r is connected to one end of the primary winding of the transformer T, and the other end of the primary winding of the transformer T and the drain of the switch tube _S2 are simultaneously connected to the source _of the switch tube S1 The other end of the capacitor C _r is connected to the source of the switch tube S2 _; one end of the secondary winding of the transformer T is connected to one end of the capacitor C _s , and the other end of the capacitor C _s is simultaneously connected to the cathode of the diode D _o1 and The anode of diode D _o2 is connected, and the cathode of diode D _o2 is connected with capacitor C _o and one end of LED load at the same time; the other end of the secondary winding of transformer T is equipotential with diode D _o1 anode, capacitor C _o and one end of LED load at the same time connected;

_The gates _of the switch tube S1 and the switch tube S2 are connected to the drive signal output end of the control circuit at the same time.

Further, the driving signals _of the switching tube S1 and the switching tube S2 output by the control circuit are complementary pulse width driving signals, and are used to respectively control the switching _on and off _of the switching tube _S1 and the switching tube S2.

Further, the LED load is an LED lamp row formed by connecting several LED lamps.

Further, the inductor L _r is a resonant inductor, and the capacitor C _s is a resonant capacitor.

Compared with the prior art, the present invention has the following advantages: simple structure, fewer components and high efficiency; on the single-stage LED drive circuit, the resonant soft switching technology is combined, and the excitation inductance of the transformer is used to participate in the resonance to realize soft switching. Switch, reduce EMI interference caused by traditional hard switching, can work at high frequency, and can obtain high power factor at the same time; at the same time, it can keep the intermediate DC capacitor voltage within an acceptable range under high AC voltage input.

Description of drawings

Fig. 1 is the block diagram of circuit principle of the present invention.

Figure 2 shows the average input current waveform of the inductor L _B in half the power frequency cycle.

Figure 3 is an equivalent schematic diagram of a DC/DC circuit.

Fig. 4 is a circuit simulation waveform diagram of the present invention.

detailed description

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

Embodiment: Referring to FIG. 1 , a resonant soft-switching single-stage LED drive circuit includes an AC input terminal, a rectifier circuit, a PFC circuit, a DC/DC circuit, an LED load and a control circuit. The LED load is an LED lamp row formed by connecting several LED lamps.

The rectifier circuit is used to convert the alternating current at the AC input terminal into direct current; in specific implementation, it includes D _R1 , D _R2 , D _R3 and D _R4 , and one end of the AC input terminal (V _ac ) is simultaneously connected with the anode of D _R1 and the The cathode of _DR3 is connected, and the other end of the AC input terminal is connected with the anode of _DR2 and the cathode of _DR4 at the same time. The anode of _DR1 and _DR2 is connected as an output terminal of the rectifier circuit, and the cathode of _DR3 and _DR4 are connected. As the other output terminal of the rectifier circuit.

The PFC circuit includes an inductor L _B , a diode D ₁ , a diode D ₂ , a capacitor C _B and a switch tube S ₁ . Wherein: one end of the inductor L _B is connected to an output end of the rectifier circuit, and the other end of the inductor L _B is connected to the _{anodes of} the diode D1 and the diode D2 at the same time. _The cathode of the diode D1 is connected to the source _of the switching tube S1, and the cathode of the diode _D2 is connected to one end of the capacitor _CB . The other end of the capacitor C _B , the drain _of the switch tube S1 and the other output end of the rectifier circuit are simultaneously grounded; thereby realizing the power factor correction function.

The DC/DC circuit includes an inductor L _r , a capacitor C _r , a capacitor C _s , a capacitor C _o , a switch tube S ₂ , a transformer T, a diode D _o1 and a diode D _o2 . Wherein _: one end of the capacitor C _r and the inductance L _r is connected to the cathode of the diode D2 at the same time, the other end of the inductance L _r is connected to one end of the primary winding of the transformer T, and the other end of the primary winding of the transformer T is connected to the switch tube _S2 The drain of the switch tube S1 is connected to the source at the same time _; in the actual implementation process, the inductance L _r is a resonant inductance, and the capacitor C _s is a resonant capacitor; the inductance L _r can be obtained by the transformer T according to the working conditions of the circuit existing leakage inductance instead. The other end of the capacitor C _r is connected to the source of the switch tube S2 _; one end of the secondary winding of the transformer T is connected to one end of the capacitor C _s , and the other end of the capacitor C _s is simultaneously connected to the cathode of the diode D _o1 and the diode D _o2 The anode of the diode D o2 is connected to the anode of the diode D _o2 , and the cathode of the diode D _o2 is connected to the capacitor C _o and one end of the LED load _; Grounding); in order to realize the adjustment of output voltage and current.

_The gates _of the switch tube S1 and the switch tube S2 are connected to the drive signal output end of the control circuit at the same time _; wherein, the drive signals _of the switch tube S1 and the switch tube S2 output by the control circuit are driven by complementary pulse widths. The signal is used to control the turn-on and turn _- off _of the switch tube S1 and the switch tube S2 respectively.

The PFC circuit composed of inductance L _B , diode D ₁ , diode D ₂ , capacitor C _B and switch tube S ₁ determines the value of inductance _LB and the duty of the drive signal input to the gate of switch tube S ₁ by the control circuit The ratio can make the Boost topology of the PFC unit work in DCM mode, and the Boost topology can automatically realize the PFC function in this mode. As shown in Figure 2, on means that the switch tube is turned on, and off means that the switch tube is turned off; ILB,avg is the average input current waveform of half _a power frequency cycle in the inductor L _B , and Q1 is the gate drive _of the switch tube S1 waveform.

As shown in Figure 3, in the DC/DC circuit, the capacitor C _B can be regarded as a DC voltage source V _g , when the switching tube S ₂ is in the off state, the switching tube S ₁ starts to conduct (t ₀ ~t ₁ ), the parasitic capacitance (C _oss ) of the switching tube S ₁ starts to resonate with the inductance L _r and the excitation inductance L _m of the transformer T, when the parasitic capacitance voltage (V _coos ) of the switching tube S ₁ drops from the current value to zero, here Turning on the switch tube S ₁ at time (t ₁ ) can realize ZVS (Zero Voltage Switching).

During the period when the switch S ₁ starts to conduct and the diode D _o1 turns off (t ₁ ~t ₂ ), the DC voltage V _g is applied to the transformer excitation inductance L _m and the inductance L _r , and at the same time, only the diode D _o1 is on the secondary side of the transformer The forward bias starts, and at this time the transformer excitation inductance L _m , inductance L _r and capacitor C _s start to resonate. When the voltage of capacitor C _s rises to the maximum value, the current through diode D _o1 is zero, so diode D _o1 Realize ZCS (Zero Current Switching).

During the period before the switching tube S ₁ is turned off and the switching tube S ₂ is turned on (t ₃ ~ t ₄ ), the current flowing through the inductor Lr charges the parasitic capacitance C _oss of the switching tube S ₁ , when the voltage rises to the DC voltage V When the voltage of _g and the capacitor C _r is summed, at this moment (t ₄ ) the switch tube S ₂ is turned on, that is, ZVS (zero voltage switching) can be realized.

During the period when the switch S ₂ starts to conduct and the diode D _o2 turns off (t ₄ ~ t ₅ ), it can be understood that the voltage V _r on the capacitor C _r is added to the transformer excitation inductance L _m and the inductance L _r , and the transformer secondary Only the diode D _o2 starts to be forward-biased on one side. At this time, the transformer excitation inductance L _m and inductance L _r start to resonate with the capacitor C _s . When the voltage of the capacitor C _s drops to the minimum value, the current through the diode D _o1 is zero. , Then, the diode D _o2 realizes ZCS (zero current switching).

As shown in Figure ₄ , V _coss and V _S2 are the drain _- source voltage waveforms _of the switch tube S1 and the switch tube S2 respectively, and Q1 and _Q2 are the gate drive waveforms _of the switch tube S1 and the switch tube S2 _respectively , I _Do1 and I _Do2 are the current waveforms of diode D _o1 and diode D _o2 respectively.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than limit the technical solutions. Those skilled in the art should understand that those who modify or replace the technical solutions of the present invention without departing from the present technology The purpose and scope of the scheme should be included in the scope of the claims of the present invention.

Claims (4)

1. a kind of resonant type soft-switch single stage type LED drive circuit, including AC input end, rectification circuit, pfc circuit, DC/DC are electric Road, LED load and control circuit, it is characterised in that：

The rectification circuit, for AC input end alternating current is converted into unidirectional current；

The pfc circuit includes inductance L_B, diode D₁, diode D₂, electric capacity C_BWith switching tube S₁, wherein：The inductance L_B's One end is connected with an outfan of rectification circuit, inductance L_BThe other end simultaneously with diode D₁With diode D₂Anode be connected； Diode D₁Negative electrode and switching tube S₁Source electrode be connected, diode D₂Negative electrode and electric capacity C_BOne end be connected；Electric capacity C_BIt is another One end, switching tube S₁Drain electrode and another outfan of rectification circuit be simultaneously grounded；

The DC/DC circuits include inductance L_r, electric capacity C_r, electric capacity C_s, electric capacity C_o, switching tube S₂, transformator T, diode D_o1With two Pole pipe D_o2, wherein：The electric capacity C_rWith inductance L_rOne end simultaneously with diode D₂Negative electrode is connected, inductance L_rThe other end with become One end of the armature winding of depressor T is connected, the other end and switching tube S of the armature winding of transformator T₂Drain electrode simultaneously with switch Pipe S₁Source electrode be connected；Electric capacity C_rOther end end and switching tube S₂Source electrode be connected；One end of the secondary windings of transformator T with Electric capacity C_sOne end be connected, electric capacity C_sThe other end simultaneously with diode D_o1Negative electrode and diode D_o2Anode be connected, two poles Pipe D_o2Negative electrode simultaneously with electric capacity C_oIt is connected with one end of LED load；The other end of the secondary windings of transformator T simultaneously with two poles Pipe D_o1Anode, electric capacity C_oAnd one end isoelectric level of LED load is connected；

The switching tube S₁With switching tube S₂Grid be simultaneously connected with the drive signal outfan of control circuit.

2. a kind of resonant type soft-switch single stage type LED drive circuit according to claim 1, it is characterised in that：Control circuit The switching tube S of output₁With switching tube S₂Drive signal, be complementary pulsewidth drive signal, for controlling switch pipe S respectively₁With Switching tube S₂Turn-on and turn-off.

3. a kind of resonant type soft-switch single stage type LED drive circuit according to claim 1, it is characterised in that：The LED bears Carry and arrange for the LED that some LEDs are connected to form.

4. a kind of resonant type soft-switch single stage type LED drive circuit according to claim 1, it is characterised in that：The inductance L_r For resonant inductance, the electric capacity C_sFor resonant capacitance.