阅读说明：本技术 一种基于二次电流模拟的llc同步整流电路 (LLC synchronous rectification circuit based on secondary current simulation ) 是由 谢小高 于海明 于 2021-07-16 设计创作，主要内容包括：本发明提出一种模拟二次电流的LLC同步整流驱动电路。针对实际的同步整流MOS漏源极中存在寄生电感,导致驱动关断时刻与理想驱动状态区别较大,造成占空比丢失的问题。采用谐振电感辅助绕组和变压器辅助绕组在二次侧串联连接,其输出信号输入到积分电路中,积分电路的输出信号v-(iSR)整流后的信号是与二次侧整流电流i-(SR)成比例的电压信号。采用此电压信号取代v-(ds-SR)产生SR的驱动信号,可有效解决因寄生电感导致SR驱动信号占空比丢失的问题,减小同步整流MOS损耗,提高变换器的效率。(The invention provides an LLC (logic link control) synchronous rectification drive circuit for simulating secondary current. The method aims at the problem that the duty ratio is lost due to the fact that parasitic inductance exists in an actual synchronous rectification MOS drain-source electrode, and the difference between the driving turn-off moment and an ideal driving state is large. The auxiliary winding of resonant inductor and the auxiliary winding of transformer are connected in series at the secondary side, the output signal is input into the integrating circuit, and the output signal v of the integrating circuit iSR The rectified signal is the rectified current i of the secondary side SR A proportional voltage signal. Using this voltage signal instead of v ds_SR The SR driving signal is generated, the problem that the duty ratio of the SR driving signal is lost due to parasitic inductance can be effectively solved, the loss of the synchronous rectification MOS is reduced, and the efficiency of the converter is improved.)

1. The utility model provides a LLC synchronous rectification circuit based on secondary current simulation which characterized in that includes: a power circuit and a control section;

the power circuit includes: DC input voltage V_inTwo main power transistors Q of a half-bridge circuit₁And Q₂Resonant capacitor C_rResonant inductance L_rLLC main transformer T₁Secondary side synchronous rectifier tube S₁And S₂And an output capacitor C_oAnd a load;

the control section includes: resonant inductor auxiliary winding L_auxAuxiliary winding W of transformer_auxAn integrating circuit and a synchronous rectification drive circuit;

the synchronous rectification drive circuit comprises: synchronous rectification MOS tube S₁Drive generation circuit and synchronous rectification MOS tube S₂The drive generation circuit of (1);

wherein the DC input voltage V_inThe positive pole is connected with a switching tube Q₁A drain electrode; switch tube Q₁Source electrode of the capacitor is connected with a resonance capacitor C_rOne end of (a); resonant capacitor C_rThe other end of the resonant inductor L is connected with_rThe same name end of (1); resonant inductor L_rThe different name end of T is connected with the main transformer₁The same name end of (1); main transformer T₁Different name end connected switch tube Q₂Source and input power supply V_inThe negative electrode of (1); transformer T₁Secondary winding W_s1Different name end-connected synchronous rectification MOS tube S₁A drain electrode of (1); transformer T₁Secondary winding W_s2Is connected with a synchronous rectification MOS tube S₂A drain electrode of (1); secondary winding W_s2Different name ends W_s1End of same name and output capacitor C_oThe positive electrode and the load end of (1); output capacitor C_oNegative pole of the rectifier is connected with the other end of the load and the synchronous rectifier tube S₁、S₂A source electrode of (a);

resonant inductor L_rOf the auxiliary winding L_auxEnd-connected transformer T of the same name₁Auxiliary winding W of_auxA homonymous terminal;

L_auxthe synonym end of the integrating circuit is connected with the input end of the integrating circuit, and the output end of the integrating circuit is connected with the input end of the synchronous rectification drive circuit; synchronous rectification driving circuit for generating synchronous rectification tube S₁Drive signal V of_{gs_SR1}And S₂Drive signal V of_{gs_SR2}。

2. The LLC synchronous rectification circuit based on secondary current simulation of claim 1, wherein said load is a post-stage circuit.

3. The LLC synchronous rectification circuit based on secondary current simulation of claim 1, wherein the integration circuit comprises an operational amplifier OP, an input resistor R of the operational amplifier OP₁Feedback resistor R of operational amplifier OP₂And a feedback capacitor C₁；

OP input resistor R of operational amplifier₁One end of is connected with a resonant inductor L_rAuxiliary winding L_auxA synonym terminal; r₁The other end of the operational amplifier is connected with the negative input end of the operational amplifier OP and the feedback resistor R₂And a feedback capacitor C₁One end of (a); the positive input end of the operational amplifier OP is connected with the secondary side ground GND-S; the output end of the operational amplifier OP is connected with a feedback resistor R₂Another terminal of (1), feedback capacitance C₁And the other end of the synchronous rectification MOS tube S₁Drive generation circuit of (1) and synchronous rectification MOS tube S₂The input terminal of the drive generation circuit is electrically connected.

4. The LLC synchronous rectification circuit based on secondary current simulation of claim 1, wherein the integration circuit comprises: resistance R₁And a capacitor C₁(ii) a Resistance R₁One end is connected with the auxiliary winding W of the transformer_auxA synonym terminal; resistance R₁The other end is connected with a capacitor C₁One end of (a); capacitor C₁The other end is connected with a secondary side ground GND-S; resistance R₁And a capacitor C₁Between the output voltage v of the integrating circuit_iSR。

5. The LLC synchronous rectification circuit based on secondary current simulation of claim 1, wherein the integration circuit comprises:

operational amplifiers OP1, OP2 and OP3, operational amplifier OP1 input resistor R₁Feedback resistance R₂Feedback capacitance C₁Input resistor R of operational amplifier OP2₃Feedback resistance R₄Feedback capacitance C₂Input resistance R of operational amplifier OP3₅And R₇Feedback resistance R₈Divider resistor R₆The operational amplifiers OP1 and OP2 form an integrator form, and the operational amplifier OP3 forms a differential operational amplifier form;

wherein the positive input terminal of the operational amplifier OP1 is grounded; the negative input end of the operational amplifier OP1 is connected with a resistor R₁The other end, a feedback capacitor C₁One terminal and a feedback resistor R₂One end; the output end of the operational amplifier OP1 is connected with a feedback resistor R₂The other end, a feedback capacitor C₁The other end and R₇One end; the positive input end of the operational amplifier OP2 is grounded; the negative input end of the operational amplifier OP2 is connected with the input resistor R₃Another terminal, feedback resistor R₄One terminal and a feedback capacitor C₂One end; the output end of the operational amplifier OP2 is connected with a feedback resistor R₄The other end, a feedback capacitor C₂The other end and a resistor R₅One end; the negative input end of the operational amplifier OP3 is connected with the input resistor R₇The other end and a feedback resistor R₈One end; the positive input end of the operational amplifier OP3 is connected with the input resistor R₅The other end and a divider resistor R₆One end; voltage dividing resistor R₆The other end is grounded; the output end of the operational amplifier OP3 is connected with a feedback resistor R₈The other end and a synchronous rectification MOS tube S₁Drive generation circuit of (1) and synchronous rectification MOS tube S₂The input terminal of the drive generation circuit is electrically connected.

6. The LLC synchronous rectification circuit based on secondary current simulation of claim 3, 4 or 5, wherein said synchronous rectification MOS transistor S₁The drive generation circuit of (1), comprising: the circuit comprises a comparator 1, a comparator 2, an SR trigger 1 and a driving circuit 1; the positive input end of the comparator 1 is connected with the output end of the operational amplifier OP of the integrating circuit 501 and the negative input end of the comparator 2; the negative input end of the comparator 1 is connected with a voltage source; the output end of the comparator 1 is connected with the SET end of the SR trigger 1; the RESST of the SR trigger 1 is connected with the output end of the comparator 2; the negative input end of the comparator 2 is grounded; the output Q end of the SR trigger 1 is connected with the input end of the driving circuit 1; the output end of the drive circuit 1 is connected with a synchronous rectification MOS tube S₁A gate electrode of (2).

7. The LLC synchronous rectification circuit based on secondary current simulation of claim 3, 4 or 5, wherein said synchronous rectification MOS transistor S₂The drive generation circuit of (1), comprising:

a comparator 3, a comparator 4, an SR flip-flop 2, a driving circuit 2; wherein the negative input terminal of the comparator 3 is connected to the output terminal of the operational amplifier OP of the integrating circuit 501 and the positive input terminal of the comparator 4; the positive input end of the comparator 3 is connected with a voltage source; the output end of the comparator 3 is connected with the SET end of the SR trigger 2; the RESET end of the SR trigger 2 is connected with the output of the comparator 4; the negative input terminal of the comparator 4 is grounded; the output end Q of the SR trigger 2 is connected with the input end of the driving circuit 2; the output of the driving circuit 2 is connected with the gate of the synchronous rectification MOS tube S2.

Technical Field

The invention relates to the technical field of electronics, in particular to an LLC synchronous rectification circuit based on secondary current simulation.

Background

Currently, with the miniaturization of consumer electronics and IT equipment, higher demands are placed on the miniaturization and high efficiency of DC-DC power supplies. The LLC circuit topology has many advantages, and particularly, it can realize zero-voltage turn-on (ZVS) of the primary switching tube and zero-current turn-off (ZCS) of the secondary rectifying tube without adding any auxiliary circuit, so that the switching losses of the switching tube and the rectifying tube can be reduced. The LLC circuit topology can easily achieve higher efficiency, and can be widely used in various current power supplies.

In order to further improve the LLC topology efficiency, under the condition of heavy load, the synchronous rectification technology is usually adopted, i.e. low-voltage synchronous rectification is usedAnd a rectifying MOS (SR) tube replaces a rectifying diode. The low-voltage MOS tube has the advantage of very small conduction resistance, and the on-state voltage drop of the low-voltage MOS tube is far smaller than that of a rectifier diode. However, the synchronous rectification MOS transistor needs a driving circuit to function during conduction. There are many driving methods for the synchronous rectification driving problem, but most commercially used methods mainly detect the voltage across the drain (D) S (source) of the synchronous rectification MOS transistor to obtain the driving signal, as shown in fig. 1. Fig. 2 is an idealized waveform of its operation. When current flows through the synchronous rectification diode, a relatively large negative voltage drop V is generated at two ends of the DS of the synchronous rectification MOS_dsWhen V is_dsVoltage lower than drive turn-on voltage V_{th_on}The driving chip generates a driving signal V of the synchronous rectification MOS_{gs_SR}. At this time, the voltage drop of the synchronous rectification MOS is V_ds＝i_SR·R_onWherein i_SRIs the current of a synchronous rectification MOS, R_onIs a synchronous rectification MOS on-resistance. MOS tube i with synchronous rectification_SRDrop near zero, V_dsThe voltage is also close to zero when V_dsGreater than the turn-off voltage V_{th_}At off, the driving signal V_{gs_SR}Off, V_{th_}off is a voltage near zero volts. Thus, the diode turn-on time of the synchronous rectification MOS can be reduced to be very small.

However, the actual synchronous rectification MOS drain has various parasitic inductances, including MOS package inductance and PCB trace inductance, etc., and the model is shown in fig. 3, L_SRIs the total parasitic inductance of the synchronous rectification MOS. The DS terminal voltage of the actually detected synchronous rectification MOS tube is V_d′s。

The drive waveform start-up process is not repeated as in fig. 2. But the drive off instant is very different from the ideal drive. Since when the MOS current i is rectified synchronously_SRAt the time of falling, parasitic inductance L_SRThe induced voltage of the synchronous rectification MOS is reversed, and the DS terminal voltage of the actually detected synchronous rectification MOS isSo that the actually detected V_d′sV than ideal_dsEarlier reaching the drive turn-off threshold voltage V_{th_off}. Due to the fact thatHere, the actual drive signal V 'of the synchronous rectification MOS tube'_{gs_SR}Ideal drive signal V_{gs_SR}Earlier turn off, resulting in a loss of duty cycle. The diode conduction time of the synchronous rectification MOS tube is increased, the loss of the synchronous rectification MOS is increased, and the condition is more serious under the conditions of high frequency and heavy load.

Disclosure of Invention

The invention provides an LLC synchronous rectification control circuit for simulating secondary current, aiming at the problem that the duty ratio is lost due to the fact that the difference between the driving turn-off moment and the ideal driving state is large because parasitic inductance exists in the drain-source electrode of an actual synchronous rectification MOS. The auxiliary winding of resonant inductor and the auxiliary winding of transformer are connected in series at the secondary side, the output signal is input into the integrating circuit, and the output signal v of the integrating circuit_iSRThe rectified signal is the rectified current i of the secondary side_SRA proportional voltage signal. The voltage signal is used to replace V_{ds_SR}And a driving signal of the synchronous rectification MOS is generated, so that the problem of losing the duty ratio of the SR driving signal due to parasitic inductance is effectively solved, the loss of the synchronous rectification MOS is reduced, and the efficiency of the converter is improved.

Specifically, the present invention provides an LLC synchronous rectification circuit based on secondary current simulation, including: the power circuit includes: DC input voltage V_inTwo main power transistors Q of a half-bridge circuit₁And Q₂Resonant capacitor C_rResonant inductance L_rLLC main transformer T₁Secondary side synchronous rectifier tube S₁And S₂And an output capacitor C_oAnd a load;

the control section includes: resonant inductor auxiliary winding L_auxAuxiliary winding W of transformer_auxAn integrating circuit and a synchronous rectification drive circuit;

the synchronous rectification drive circuit comprises: synchronous rectification MOS tube S₁Drive generation circuit and synchronous rectification MOS tube S₂The drive generation circuit of (1);

wherein the DC input voltage V_inThe positive pole is connected with a switching tube Q₁A drain electrode; switch tube Q₁Source electrode of the capacitor is connected with a resonance capacitorC_rOne end of (a); resonant capacitor C_rThe other end of the resonant inductor L is connected with_rThe same name end of (1); resonant inductor L_rThe different name end of T is connected with the main transformer₁The same name end of (1); main transformer T₁Different name end connected switch tube Q₂Source and input power supply V_inThe negative electrode of (1); transformer T₁Secondary winding W_s1Different name end-connected synchronous rectification MOS tube S₁A drain electrode of (1); transformer T₁Secondary winding W_s2Is connected with a synchronous rectification MOS tube S₂A drain electrode of (1); secondary winding W_s2Different name ends W_s1End of same name and output capacitor C_oThe positive electrode and the load end of (1); output capacitor C_oNegative pole of the rectifier is connected with the other end of the load and the synchronous rectifier tube S₁、S₂A source electrode of (a);

resonant inductor L_rOf the auxiliary winding L_auxEnd-connected transformer T of the same name₁Auxiliary winding W of_auxA homonymous terminal; l is_auxThe synonym end of the integrating circuit is connected with the input end of the integrating circuit, and the output end of the integrating circuit is connected with the input end of the synchronous rectification drive circuit; synchronous rectification driving circuit for generating synchronous rectification tube S₁Drive signal V of_{gs_SR1}And S₂Drive signal V of_{gs_SR2}。

Preferably, the load is a post-stage circuit.

Preferably, the integration circuit includes an operational amplifier OP and an input resistor R₁A feedback resistor R₂And a feedback capacitor C₁. Wherein:

input resistance R₁One end of the input resistor R is connected with the output end of the synthetic voltage source₁The other end of the operational amplifier is connected with the negative input end of the operational amplifier OP and the feedback resistor R₂And a feedback capacitor C₁The positive input end of the operational amplifier OP is connected with the secondary side ground GND-S, and the output end of the operational amplifier OP is connected with the feedback resistor R₂Another terminal of (1), feedback capacitance C₁The other end of the operational amplifier OP outputs a voltage signal v_iSR。

Preferably, the integration circuit includes: resistance R₁And a capacitor C₁(ii) a Resistance R₁One end of the jointAn output terminal of the voltage source; resistance R₁The other end is connected with a capacitor C₁One end of (a); capacitor C₁The other end is connected with a secondary side ground GND-S; resistance R₁And a capacitor C₁With the output voltage signal v of the integrating circuit therebetween_iSR。

Preferably, the synchronous rectification drive circuit includes: synchronous rectification MOS tube S₁Drive generation circuit and synchronous rectification MOS tube S₂The drive generation circuit of (1).

Preferably, the synchronous rectification MOS tube S₁The drive generation circuit of (1), comprising: the circuit comprises a comparator 1, a comparator 2, an RS trigger 1 and a driving circuit 1; the positive input end of the comparator 1 is connected with the output end of the operational amplifier OP of the integrating circuit 501 and the negative input end of the comparator 2; the negative input end of the comparator 1 is connected with a voltage source V_{th_SR1}(ii) a The positive input end of the comparator 2 is grounded; the output end of the comparator 1 is connected with the SET end of the RS trigger 1; the output end of the comparator 2 is connected with the RESET end of the RS trigger 1; the output Q end of the RS trigger 1 is connected with the input end of the driving circuit 1; the output end of the drive circuit 1 is connected with a synchronous rectification MOS tube S₁A gate electrode of (2).

Preferably, the synchronous rectification MOS tube S₁The drive generation circuit of (1), comprising: the circuit comprises a comparator 1, a comparator 2, an RS trigger 1 and a driving circuit 1; the positive input end of the comparator 1 is connected with a negative voltage source V_{th_on}The negative input end of the comparator 1 is connected with a synchronous rectification MOS tube S₁A drain electrode of (1); the output end of the operational amplifier OP of the integrating circuit 501 is connected with the negative input end of the comparator 2, and the positive input end of the comparator 2 is grounded; the output end of the comparator 1 is connected with the SET end of the RS trigger 1; the RESET end of the RS trigger 1 is connected with the output end of the comparator 2; the output Q end of the RS trigger 1 is connected with the input end of the driving circuit 1; the output end of the drive circuit 1 is connected with a synchronous rectification MOS tube S₁A gate electrode of (2).

Preferably, the synchronous rectification MOS tube S₂The drive generation circuit of (1), comprising: comparator 3, comparator 4, RS flip-flop 2, drive circuit 2. Wherein the negative input terminal of the comparator 3 is connected to the output terminal of the operational amplifier OP of the integrating circuit 501 and the positive input terminal of the comparator 4; the positive input end of the comparator 3 is connected with a voltage source V_{th_SR2}(ii) a The output end of the comparator 3 is connected with RS triggerThe SET end of the device 2; the RESET end of the RS trigger 2 is connected with the output of the comparator 4; the negative input terminal of the comparator 4 is grounded; the output end Q of the RS trigger 2 is connected with the input end of the drive circuit 2; the output of the drive circuit 2 is connected with a synchronous rectification MOS tube S₂A gate electrode of (2).

Preferably, the synchronous rectification MOS tube S₂The drive generation circuit of (1), comprising: comparator 3, comparator 4, RS flip-flop 2, drive circuit 2. Wherein the positive input of the comparator 3 is connected with a negative voltage source V_{th_on}The negative input end of the comparator 3 is connected with a synchronous rectification MOS tube S₂A drain electrode of (1); the output end of the operational amplifier OP of the integrating circuit 501 is connected with the positive input end of the comparator 4, and the negative input end of the comparator 4 is grounded; the output end of the comparator 3 is connected with the SET end of the RS trigger 2; the RESET end of the RS trigger 2 is connected with the output of the comparator 4; the output end Q of the RS trigger 2 is connected with the input end of the drive circuit 2; the output of the driving circuit 2 is connected with the gate of the synchronous rectification MOS tube S2.

Preferably, the LLC synchronous rectification control circuit based on secondary current simulation can be used in an LLC resonant converter, an LC resonant converter, or an LCC resonant converter.

The substantial advantages of the invention are: according to the LLC synchronous rectification circuit based on secondary current simulation, the problem of loss of the duty ratio of the drive signal of the secondary synchronous rectification tube caused by parasitic inductance can be effectively solved, the high-precision synchronous rectification drive signal can be realized, and the LLC efficiency is improved. The circuit has the characteristics of simple structure, low circuit cost, high reliability and the like.

Drawings

FIG. 1 is a schematic block diagram of a driving signal generated by detecting the voltage across the DS of a synchronous rectification MOS transistor;

FIG. 2 shows an ideal waveform of a driving signal generated by detecting the voltage across the synchronous rectification MOS transistor DS;

FIG. 3 shows a model of a synchronous rectifier MOS transistor with parasitic inductance;

FIG. 4 is a schematic block diagram of an LLC synchronous rectification control circuit based on secondary current simulation according to the present invention;

FIG. 5 shows a first embodiment of an LLC synchronous rectification control circuit based on secondary current simulation according to the invention;

FIG. 6 shows a second embodiment of the LLC synchronous rectification control circuit based on secondary current simulation according to the invention;

FIG. 7 shows a third embodiment of the LLC synchronous rectification control circuit based on secondary current simulation according to the invention;

FIG. 8 is a diagram showing a comparison between an actual waveform and an ideal waveform of a driving signal generated by detecting the voltage across the synchronous rectification MOS transistor DS;

in the figure: 400. synthetic voltage source 401, integrating circuit 402, synchronous rectification drive circuit 4021, synchronous rectification MOS tube SR₁4022, and a synchronous rectification MOS transistor SR₂The drive generation circuit of (1).

Detailed Description

In order to make the technical solution and advantages of the present invention more apparent, the following detailed description of the present invention with reference to the accompanying drawings is provided for more complete understanding of the present invention without describing the details thereof.

Fig. 4 shows a schematic block diagram of an LLC synchronous rectification control circuit based on secondary current simulation, which is presented in the present invention, and for easy understanding, the diagram also shows the electrical connection of the synchronous rectification control circuit with the LLC resonant converter main circuit.

Referring to fig. 4, the synchronous rectification control circuit includes: resonant inductor L_rOf the auxiliary winding L_auxTransformer T₁Auxiliary winding W of_auxAn integration circuit 401 and a synchronous rectification drive circuit 402;

wherein the resonant inductor L_rOf the auxiliary winding L_auxAnd the transformer T₁Auxiliary winding W of_auxAre connected in series to form a combined voltage source 400, wherein a resonant inductor L_rOf the auxiliary winding L_auxEnd-connected transformer T of the same name₁Auxiliary winding W of_auxOne end of the synthesized voltage source 400 is connected with the secondary side ground GND-S, the other end of the synthesized voltage source 400 is connected with the input end of the integrating circuit 401, and the output end of the integrating circuit 401 is connected with the synchronous rectification drive circuitAt the input end of 402, a synchronous rectification drive circuit 402 generates a drive signal v of a synchronous rectification MOS tube_{gs_SR1}And v_{gs_SR2}。

The LLC resonant converter main circuit comprises a direct current input voltage V_inTwo main power transistors Q constituting a half-bridge circuit₁And Q₂Resonant capacitor C_rResonant inductance L_rTransformer T₁Secondary side synchronous rectifier SR₁And SR₂And an output capacitor C_oAnd a load. Wherein, the resonant inductor L_rPrimary side winding of the transformer T₁The dotted terminal of the primary winding.

The following presents a simplified summary of the invention

Resonant inductor L_rAuxiliary winding L_auxVoltage v_LrIs represented as follows:

wherein L is_rIs a resonant inductance, n_LrIs a resonant inductor L_rThe primary winding being opposite the auxiliary winding L_auxTurn ratio of (i)_LrIs a resonant current.

Transformer T₁Auxiliary winding W_auxVoltage v_auxIs represented as follows:

wherein L is_mIs the primary side excitation inductance of the transformer, n_TIs a transformer T₁The primary winding being opposite to the auxiliary winding W_auxTurn ratio of (i)_LmIs the excitation current.

Referring to fig. 4, the output voltage v of the synthesized voltage source 400₁Is represented as follows:

v₁＝-(v_Lr-v_aux) (3)

the following current relationship can be obtained from the basic LLC working principle:

i_Lr-i_Lm＝i_SR/n_T (4)

wherein i_SRIs the sum of the rectification currents of the secondary side synchronous rectification MOS tube.

Simultaneous equations (1) to (3), the output signal v of the integrating circuit 401_iSRCan be expressed as follows:

the design circuit parameter satisfies L_r/n_Lr＝L_m/n_TIn conjunction with equation (4), equation (5) can be simplified as follows:

wherein k is L_r/(n_Lrn_T) Is the output signal v of the integrating circuit 401_iSRAbsolute value of and synchronous rectification current i_SRThe scaling factor of (c).

As can be seen from equation (6), the output signal v of the integrating circuit 401_iSRAbsolute value of and synchronous rectification current i_SRProportional relation, i.e. output signal v_iSRRectified signal waveform and synchronous rectification current i_SRProportional relationship of waveform, v_iSRWaveform of (a) and (i)_SRThe zero-crossing points of the waveforms are consistent. Thus, v can be detected_iSRA driving signal of the synchronous rectification MOS is generated. Compared with the traditional synchronous rectification scheme which detects the voltage at two ends of the DS of the synchronous rectification MOS tube to generate the driving signal of the synchronous rectification MOS tube, the scheme, especially the turn-off signal of the synchronous rectification MOS tube, is not influenced by parasitic inductance any more,

fig. 5 shows a first embodiment of the LLC synchronous rectification control circuit based on secondary current simulation of the present invention, and specifically shows an embodiment of the integrating circuit 401 and the synchronous rectification driving circuit 402. Also shown in fig. 5 for ease of understanding is the electrical connection of the synchronous rectifier circuit control circuit to the LLC resonant converter main circuit.

Referring to fig. 5, a transformer T₁Auxiliary winding W_auxThe end of the same name is connected with a resonant inductor L_rOf the auxiliary winding L_auxEnd of same name, resonant inductor L_rOf the auxiliary winding L_auxOutputs the output signal v of the synthesized voltage source 400₁。

The integration circuit 401 comprises an operational amplifier OP, an input resistor R of the operational amplifier OP₁Feedback resistor R of operational amplifier OP₂And a feedback capacitor C₁. OP input resistor R of operational amplifier₁One end of is connected with a resonant inductor L_rAuxiliary winding L_auxA synonym terminal; r₁The other end of the operational amplifier is connected with the negative input end of the operational amplifier OP and the feedback resistor R₂And a feedback capacitor C₁One end of (a); the positive input end of the operational amplifier OP is connected with the secondary side ground GND-S; the output end of the operational amplifier OP is connected with a feedback resistor R₂Another terminal of (1), feedback capacitance C₁And the other end of the same. Output voltage signal v of integration circuit 401 module to synthesis voltage source 400₁Integrating and outputting a signal v_iSR。

Output v of integrating circuit 401_iSRRectifying current i in synchronism with secondary side_SRThe frequency domain relationship of (a) is expressed as follows:

wherein f is_L＝1/2πR₂C₁Is the low frequency corner frequency of the integrating circuit 401. When the operating frequency f_s＞＞f_LWhen, v_iSRAnd i_SRThe time domain relationship can be simplified as follows:

wherein, K is L_r/(R₁C₁n_Lrn_T). Comparing equations (8) and (6), it can be seen that the particular embodiment of the integrating circuit 401 shown in fig. 5 can achieve the desired functionality of the integrating circuit 401.

The synchronous rectification driving circuit 402 comprises a synchronous rectification MOS tube SR₁Drive generation circuit 4021 and synchronous rectification MOS transistor SR₂The drive generation circuit 4022. Wherein the content of the first and second substances,

synchronous rectification MOS tube SR₁The drive generation circuit 4021 includes a comparator 1, a comparator 2, an RS flip-flop 1, and a drive circuit 1. The positive input end of the comparator 1 is connected with the output end of the operational amplifier OP of the integrating circuit 401 and the negative input end of the comparator 2; the negative input of the comparator 1 is connected to a voltage source V of very small positive voltage_{th_SR1}The positive input end of the comparator 2 is connected with the secondary side ground GND-S, and the output end of the comparator 1 is connected with the SET end of the RS trigger 1; the RESET end of the RS trigger 1 is connected with the output end of the comparator 2; the output Q end of the RS trigger 1 is connected with the input end of the driving circuit 1; the output end of the drive circuit 1 is connected with a synchronous rectification MOS tube SR₁A gate electrode of (2).

Synchronous rectification MOS tube SR₁The specific operation of the drive generation circuit 4021 is as follows: when the output signal v of the integrating circuit 401 is_iSRHigher than V_{th_SR1}The comparator 1 outputs high level to make the output end Q of the RS trigger 1 set to high level, and the synchronous rectifier tube S₁Drive signal v_{gs_SR1}And is switched from low level to high level. When the output signal v of the integrating circuit 401 is_iSRWhen zero-crossing is reduced, the comparator 2 outputs high level to reset the output end Q of the RS trigger 1 to low level, and the synchronous rectification MOS tube S₁Drive signal v_{gs_SR1}And is switched from low level to high level.

Synchronous rectification MOS tube SR₂The drive generation circuit 4022 of (1) includes a comparator 3, a comparator 4, an RS flip-flop 2, and a drive circuit 2. Wherein the negative input terminal of the comparator 3 is connected to the output terminal of the operational amplifier OP of the integrating circuit 501 and the positive input terminal of the comparator 4; the positive input of the comparator 3 is connected to a voltage source V of very low negative voltage_{th_SR2}The negative input end of the comparator 4 is connected with the secondary side ground GND-S; the output end of the comparator 3 is connected with the SET end of the RS trigger 2; the RESET end of the RS trigger 2 is connected with the output of the comparator 4; RS touchThe output end Q of the generator 2 is connected with the input end of the driving circuit 2; the output of the drive circuit 2 is connected with a synchronous rectification MOS tube SR₂A gate electrode of (2).

Synchronous rectification MOS tube SR₂The specific operation of the drive generation circuit 4022 is as follows: when the output signal v of the integrating circuit 401 is_iSRRatio V_{th_SR2}When the voltage is low, the comparator 3 outputs high level to make the output end Q of the RS trigger 2 set to high level, and the synchronous rectifier tube S₂Drive signal v_{gs_SR2}And is switched from low level to high level. When 401 output signal v_iSRWhen the zero-crossing time is increased, the comparator 4 outputs high level to reset the output end Q of the RS trigger 2 to low level, and the synchronous rectification MOS tube SR₂Drive signal v_{gs_SR2}Becomes inverted from a high level to a low level.

Fig. 6 shows a second embodiment of the LLC synchronous rectification control circuit based on secondary current simulation according to the present invention. The difference between the second embodiment shown in fig. 6 and the first embodiment shown in fig. 5 is the implementation of the synchronous rectification driver circuit 402.

Referring to fig. 6, the synchronous rectification driving circuit 402 includes a synchronous rectification MOS transistor SR₁Drive generation circuit 4021 and synchronous rectification MOS transistor SR₂The drive generation circuit 4022. Wherein the content of the first and second substances,

the synchronous rectification MOS tube SR₁The drive generation circuit of (1), comprising: the circuit comprises a comparator 1, a comparator 2, an RS trigger 1 and a driving circuit 1; the positive input end of the comparator 1 is connected with a negative voltage source V_{th_on}The negative input end of the comparator 1 is connected with the synchronous rectification MOS tube SR₁A drain electrode of (1); the output end of the operational amplifier OP of the integrating circuit 501 is connected with the negative input end of the comparator 2, and the positive input end of the comparator 2 is connected with the secondary side ground GND-S; the output end of the comparator 1 is connected with the SET end of the RS trigger 1; the RESET end of the RS trigger 1 is connected with the output end of the comparator 2; the output Q end of the RS trigger 1 is connected with the input end of the driving circuit 1; the output end of the drive circuit 1 is connected with a synchronous rectification MOS tube SR₁A gate electrode of (2).

Synchronous rectification MOS tube SR₁The specific operation of the drive generation circuit 4021 is as follows: when synchronous rectification MOS tube SR₁The drain voltage of is lower than V_{th_on}The comparator 1 outputs high level to make the output end Q of the RS trigger 1 set to high level, and the synchronous rectifier tube S₁Drive signal v_{gs_SR1}And is switched from low level to high level. When the output signal v of the integrating circuit 401 is_iSRWhen zero-crossing is reduced, the comparator 2 outputs high level to reset the output end Q of the RS trigger 1 to low level, and the synchronous rectification MOS tube S₁Drive signal v_{gs_SR1}And is switched from low level to high level.

The synchronous rectification MOS tube SR₂The drive generation circuit 4022 includes: comparator 3, comparator 4, RS flip-flop 2, drive circuit 2. Wherein the positive input of the comparator 3 is connected with a negative voltage source V_{th_on}The negative input end of the comparator 3 is connected with a synchronous rectification MOS tube SR₂A drain electrode of (1); the output end of an operational amplifier OP of the integrating circuit 401 is connected with the positive input end of the comparator 4, and the negative input end of the comparator 4 is connected with the secondary side ground GND-S; the output end of the comparator 3 is connected with the SET end of the RS trigger 2; the RESET end of the RS trigger 2 is connected with the output of the comparator 4; the output end Q of the RS trigger 2 is connected with the input end of the drive circuit 2; the output of the drive circuit 2 is connected with a synchronous rectification MOS tube SR₂A gate electrode of (2).

Synchronous rectification MOS tube SR₂The specific operation of the drive generation circuit 4022 is as follows: when synchronous rectification MOS tube SR₂The drain voltage of is lower than V_{th_on}The comparator 3 outputs high level to make the Q position of the output end of the RS trigger 2 become high level, and the synchronous rectifier tube SR₂Drive signal v_{gs_SR2}And is switched from low level to high level. When the output signal v of the integrator 401 is_iSRWhen the zero-crossing time is increased, the comparator 4 outputs high level to reset the output end Q of the RS trigger 2 to low level, and the synchronous rectification MOS tube SR₂Drive signal v_{gs_SR2}And the high level is inverted into the low level.

Fig. 7 shows a third embodiment of the LLC synchronous rectification scheme based on secondary current simulation according to the present invention. In particular, this embodiment shows another, simpler implementation of the integrating circuit 401. Wherein, the resonant inductor L_rAuxiliary winding L_auxThe different name end is connected with the secondary side ground GND-S, the same name end is connected with the transformer T₁Auxiliary winding W_auxThe end of the same name of (c) is,transformer T₁Auxiliary winding W_auxOutput signal v of the different name terminal as the output terminal of the synthesized voltage source 400₁. The integrating circuit 401 includes a resistor R_a1And a capacitor C_a1. Resistance Ra₁One end is connected with the auxiliary winding W of the transformer_auxEnd of synonym, resistance R_a1The other end is connected with a capacitor C_a1And outputs a signal v_iSRCapacitor C₁The other end is connected with a secondary side ground GND-S.

Output signal v of synthesized voltage source 400 of integrating circuit 401₁The time domain is represented as follows:

the design parameter satisfies R_a1>>1/(2πf_sC₁) Then capacitance C_a1Is output voltage v_iSRAnd i_SRThe time domain relationship can be simplified as follows;

wherein K is L_r/(R_a1C_a1n_Lrn_T) Is the output signal v of the integrating circuit 401_iSRWith synchronous rectification of current i_SRThe scaling factor of (c). This relationship is the same as equation (10), and therefore can be determined by detecting v_iSRIn place of i_SRTo generate a synchronous rectifier tube S_R1And S_R2And this signal is not affected by parasitic inductance.

Further, the implementation of the synchronous rectification driving circuit 402 in the second embodiment of the present invention shown in fig. 6 may be adopted to replace the synchronous rectification driving circuit 402 in the third embodiment of the present invention shown in fig. 7, so as to form a new embodiment, and the detailed description thereof is omitted.

Further, the implementation of the synthesized voltage source 400 shown in the first embodiment of the present invention shown in fig. 5 and the implementation of the synthesized voltage source 400 shown in the second embodiment of the present invention shown in fig. 6 may be replaced with the implementation of the synthesized voltage source 400 shown in the third embodiment of the present invention shown in fig. 7, and the corresponding implementation of the synchronous rectification driving circuit 402 is adjusted to some extent, so as to form a new embodiment, which is not described in detail herein.

The following claims are provided to define and protect the broad concepts and principles of the present invention. The invention is intended to cover alternatives, modifications, equivalents, and alternatives which may be included within the spirit and scope of the invention. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. The above detailed description of embodiments of the invention is not intended to be exhaustive or to limit the invention to the precise form disclosed. The details of the above circuit configuration and its control may be varied accordingly in its practical implementation, while still being encompassed by the present invention.

As noted above, it should be noted that the use of particular terminology when describing certain features or aspects of the invention should not be taken to imply that the terminology is being re-defined herein to be restricted to certain specific characteristics, features, or aspects of the invention with which that terminology is associated. In general, the terms used in the following claims should not be construed to limit the invention to the specific embodiments disclosed in the specification, unless the above detailed description section explicitly defines such terms. Accordingly, the actual scope of the invention encompasses not only the disclosed embodiments, but also within the claims.