CN217693094U

CN217693094U - Resonant converter

Info

Publication number: CN217693094U
Application number: CN202221657955.0U
Authority: CN
Inventors: 侯帅丞; 刘晓霖; 徐学愚; 王云鹏
Original assignee: Neijiang Linghui Electronic Technology Co ltd
Current assignee: Neijiang Linghui Electronic Technology Co ltd
Priority date: 2022-06-30
Filing date: 2022-06-30
Publication date: 2022-10-28
Anticipated expiration: 2032-06-30

Abstract

The utility model discloses a resonant converter, it is including flowing the input end, former limit switch circuit, short-circuit protection control circuit, former limit resonant circuit, current sampling circuit, isolation transformer, vice limit rectifier filter circuit and direct current output, current sampling circuit is used for detecting resonant converter's current signal, former limit switch circuit includes two sets of switch tubes, short-circuit protection control circuit is arranged in the current signal that obtains detecting when predetermineeing the current threshold value, a set of switch tube that is in the on-state at present among two sets of switch tubes of control former limit switch circuit is turn-off, a set of switch tube that the while control is in the off-state at present switches on, thereby make the afterflow current that flows through the body diode of switch tube flow through the switch tube, reduce the switch tube heat by a wide margin. The utility model discloses short-circuit protection response speed is fast, requires lowly to the switch tube surplus, safe and reliable, and application scope is wide.

Description

Resonant converter

Technical Field

The utility model relates to a power electronic converter technical field especially relates to a resonant converter.

Background

When the load of the output end of the existing power resonant converter or a transformer is in short circuit, the short circuit protection is basically realized by improving the switching frequency, the driving of a switching tube can be cut off after a plurality of pulses, and the response speed is slow; or the short-circuit protection is realized by directly cutting off the drive of the switching tube, and the current flowing through the body diode of the switching tube is overlarge to cause overheating because the inductive current in the resonant converter can not change suddenly, so that the requirement of the power resonant converter on the allowance of the switching tube is high, and when the allowance of the switching tube is not large, the body diode in the switching tube is easy to be burnt due to high temperature.

SUMMERY OF THE UTILITY MODEL

The utility model aims at providing a short-circuit protection response speed is fast, the resonant converter that the switch tube surplus required to hang down to current power resonant converter short-circuit protection not enough.

In order to achieve the purpose, the utility model adopts the following technical scheme:

the utility model provides a resonant converter, which comprises a direct current input end, a primary side switch circuit, a short-circuit protection control circuit, a primary side resonant circuit, a current sampling circuit, an isolation transformer, a secondary side rectifying and filtering circuit and a direct current output end, wherein,

the direct current input end is used for connecting a direct current input source to input direct current voltage to the resonant converter;

the current sampling circuit is used for detecting a current signal of the resonant converter and at least comprises a primary side current sampling resistor;

the primary side switching circuit comprises two groups of switching tubes, the direct current input positive end of the primary side switching circuit is connected with the positive electrode of the direct current input end, the direct current input negative end of the primary side switching circuit is connected with the negative electrode of the direct current input end, the first end of the primary side resonant circuit is connected with the first end of the primary side current sampling resistor, the primary side resonant circuit is coupled with the primary side winding of the isolation transformer, and the two alternating current output ends of the primary side switching circuit are respectively connected with the second end of the primary side resonant circuit and the second end of the primary side current sampling resistor;

the two ends of the alternating current input of the secondary side rectifying and filtering circuit are respectively connected with the two ends of the secondary side winding of the isolation transformer, the positive direct current output end of the secondary side rectifying and filtering circuit is connected with the positive electrode of the direct current output end, and the negative direct current output end of the secondary side rectifying and filtering circuit is connected with the negative electrode of the direct current output end;

the direct current output end is used for connecting a direct current load to supply power to the direct current load;

the input end of the short-circuit protection control circuit is connected with the current sampling circuit, the output end of the short-circuit protection control circuit is connected with the control signal input end of the primary side switching circuit, and the short-circuit protection control circuit is used for controlling one group of switching tubes which are currently in a conducting state in two groups of switching tubes of the primary side switching circuit to be switched off when a current signal detected by the current sampling circuit exceeds a threshold current threshold value, and simultaneously controlling one group of switching tubes which are currently in a switching-off state to be switched on.

Preferably, the short-circuit protection control circuit comprises a threshold value storage, a comparator and a switch logic control circuit, wherein a first input end of the comparator is connected with the threshold value storage, a second input end of the comparator is connected with an output end of the current sampling circuit, an output end of the comparator is connected with an input end of the switch logic control circuit, and an output end of the switch logic control circuit is connected with a control signal input end of the primary side switch circuit.

Preferably, the current sampling circuit further comprises an input current sampling resistor and/or an output current sampling resistor;

the input current sampling resistor is connected in series between the negative direct current input end of the primary side switching circuit and the negative electrode of the direct current input end;

the output current sampling resistor is connected in series between the negative DC output terminal of the secondary side rectifying and filtering circuit and the negative electrode of the DC output terminal.

Preferably, the primary side resonant circuit is an LC resonant circuit, an LLC resonant circuit, an LCC resonant circuit, a CLLC resonant circuit, or a CLLLC resonant circuit.

Preferably, the resonant converter further includes a secondary resonant capacitor, and the secondary resonant capacitor is connected in series between the dotted terminal of the secondary winding of the isolation transformer and the first ac input terminal of the secondary rectification filter circuit.

Preferably, the resonant converter further comprises a secondary side resonant inductor and a secondary side resonant resistor;

the secondary resonant inductor is connected in series between a non-homonymous end of a secondary winding of the isolation transformer and an alternating current input second end of the secondary rectifying and filtering circuit, and the secondary resonant resistor is connected in series between the secondary resonant capacitor and an alternating current input first end of the secondary rectifying and filtering circuit.

Preferably, the primary side switch circuit is a half-bridge type switch circuit, the half-bridge type switch circuit includes a first MOSFET tube and a second MOSFET tube, a drain of the first MOSFET tube is connected to an anode of the dc input terminal, a source of the first MOSFET tube is connected to a drain of the second MOSFET tube and a second end of the primary side resonance circuit, a source of the second MOSFET tube is connected to a cathode of the dc input terminal and a second end of the primary side current sampling resistor, and a gate of the first MOSFET tube and a gate of the second MOSFET tube are connected to an output terminal of the short-circuit protection control circuit.

Preferably, the primary side switch circuit is a full-bridge type switch circuit, the full-bridge type switch circuit includes a first MOSFET tube, a second MOSFET tube, a third MOSFET tube and a fourth MOSFET tube, a drain electrode of the first MOSFET tube and a drain electrode of the third MOSFET tube are respectively connected to an anode of the dc input terminal, a source electrode of the first MOSFET tube is respectively connected to a drain electrode of the second MOSFET tube and a second end of the primary side resonance circuit, a source electrode of the third MOSFET tube is respectively connected to a drain electrode of the fourth MOSFET tube and a second end of the primary side current sampling resistor, a source electrode of the second MOSFET tube and a source electrode of the fourth MOSFET tube are respectively connected to a cathode of the dc input terminal, and a gate electrode of the first MOSFET tube, a gate electrode of the second MOSFET tube, a gate electrode of the third MOSFET tube and a gate electrode of the fourth MOSFET tube are respectively connected to an output terminal of the short-circuit protection control circuit.

Preferably, the secondary side rectifying and filtering circuit comprises a full-bridge uncontrollable rectifying circuit and a filtering capacitor, wherein the full-bridge uncontrollable rectifying circuit is composed of 4 rectifying diodes and is connected with the filtering capacitor in parallel, the input two ends of the full-bridge uncontrollable rectifying circuit are respectively connected with the two ends of the secondary side winding of the isolation transformer, and the output two ends of the full-bridge uncontrollable rectifying circuit are respectively connected with the anode and the cathode of the direct current output end.

Preferably, the secondary side rectification filter circuit comprises a full-bridge full-control rectification circuit and a filter capacitor, wherein the full-bridge full-control rectification circuit is composed of 4 MOSFET tubes and is connected with the filter capacitor in parallel, the two input ends of the full-bridge full-control rectification circuit are respectively connected with the two ends of the secondary side winding of the isolation transformer, and the two output ends of the full-bridge full-control rectification circuit are respectively connected with the positive electrode and the negative electrode of the direct current output end.

The technical scheme of the utility model beneficial effect lies in:

the utility model discloses a resonant converter circuit simple structure, current signal through configuration current sampling circuit real-time detection resonant converter, through the configuration primary side switch circuit that includes two sets of switch tubes, and the current signal of configuration current sampling circuit real-time detection resonant converter, when overcurrent or short circuit appear in power resonator place circuit, switch over the break-make state of two sets of switch tubes through short-circuit protection control circuit, thereby make the afterflow current that flows through the body diode of switch tube behind the disconnection switch tube flow from the switch tube, thereby reduce the heat that the switch tube produced because of flowing through the body diode by a wide margin, restriction switch tube electric current does not rush through the switch tube limit. The utility model discloses short-circuit protection response speed is fast, requires lowly to the switch tube surplus, safe and reliable, and application scope is wide.

Drawings

Fig. 1 is a schematic block diagram of a circuit of a resonant converter according to an embodiment of the present invention;

fig. 2 is a schematic diagram of a partial circuit of a resonant converter according to an embodiment of the present invention.

Fig. 3 is a schematic circuit diagram of a short-circuit protection control circuit of a resonant converter according to an embodiment of the present invention;

fig. 4 is a main waveform diagram before and after protection of a resonant converter according to an embodiment of the present invention;

fig. 5 is a schematic circuit diagram of a part of a resonant converter disclosed in the second embodiment of the present invention;

fig. 6 is a schematic circuit diagram of a part of a resonant converter according to a third embodiment of the present invention;

fig. 7 is a schematic circuit diagram of a part of a resonant converter according to the fourth embodiment of the present invention;

fig. 8 is a schematic circuit diagram of a part of a resonant converter disclosed in the fifth embodiment of the present invention;

fig. 9 is a schematic circuit diagram of a part of a resonant converter according to a sixth embodiment of the present invention.

Detailed Description

Any feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving equivalent or similar purposes, unless expressly stated otherwise. That is, unless expressly stated otherwise, each feature is only an example of a generic series of equivalent or similar features. The technical solution of the present invention is further explained with reference to the accompanying drawings and the description of the specific embodiments.

The first embodiment is as follows:

as shown in fig. 1, it is a schematic block diagram of a circuit of a resonant converter according to an embodiment of the present invention, the resonant converter includes a dc input terminal, a primary switch circuit, a short-circuit protection control circuit, a primary resonant circuit, a current sampling circuit, an isolation transformer, a secondary rectification filter circuit, and a dc output terminal.

In this embodiment, the dc input terminal is used to connect a dc input source to input a dc voltage to the resonant converter; the current sampling circuit is used for detecting a current signal of the resonant converter and at least comprises a primary side current sampling resistor; the primary side switching circuit comprises two groups of switching tubes, the direct current input positive end of the primary side switching circuit is connected with the positive electrode of the direct current input end, the direct current input negative end of the primary side switching circuit is connected with the negative electrode of the direct current input end, the first end of the primary side resonant circuit is connected with the first end of the primary side current sampling resistor, the primary side resonant circuit is coupled with the primary side winding of the isolation transformer, and the two alternating current output ends of the primary side switching circuit are respectively connected with the second end of the primary side resonant circuit and the second end of the primary side current sampling resistor; the alternating current input ends of the secondary side rectifying and filtering circuit are respectively connected with the two ends of the secondary side winding of the isolation transformer, the direct current output positive end of the secondary side rectifying and filtering circuit is connected with the positive electrode of the direct current output end, and the direct current output negative end of the secondary side rectifying and filtering circuit is connected with the negative electrode of the direct current output end; the direct current output end is used for connecting a direct current load to supply power to the direct current load; the input end of the short-circuit protection control circuit is connected with the current sampling circuit, the output end of the short-circuit protection control circuit is connected with the control signal input end of the primary side switching circuit, and the short-circuit protection control circuit is used for controlling the on-off state of two groups of switching tubes of the primary side switching circuit according to current signals detected by the current sampling circuit.

Fig. 2 is a schematic diagram of a partial circuit of a resonant converter according to an embodiment of the present invention. In this embodiment, the primary side switching circuit is a full-bridge switching circuit, and includes two groups of switching tubes, the first group includes a first MOSFET tube Q1 and a fourth MOSFET tube Q4, and the second group includes a second MOSFET tube Q2 and a third MOSFET tube Q3; the primary side resonance circuit comprises a first primary side resonance capacitor Cr, a first primary side resonance inductor Lr and a second primary side resonance inductor Lm, and the first primary side resonance capacitor Cr, the first primary side resonance inductor Lr and the second primary side resonance inductor Lm form an LLC resonance circuit; the current sampling circuit comprises an input current sampling resistor Rcs1, a primary side current sampling resistor Rcs2 and an output current sampling resistor Rcs3; the secondary side rectifying and filtering circuit comprises a full-bridge uncontrollable rectifying circuit and a filtering capacitor Cf, wherein the full-bridge uncontrollable rectifying circuit is composed of 4 rectifying diodes D1, D2, D3 and D4.

The working principle of the resonant converter in the embodiment is as follows:

when the resonant converter works, the short-circuit protection control circuit provides PWM pulse signals to control the on-off state of the two groups of switching tubes. When the direct current input end is electrified, PWM pulse signals control a first MOSFET tube Q1 and a fourth MOSFET tube Q4 to be switched on, current sequentially passes through the first MOSFET tube Q1, a primary current sampling resistor Rcs2, a second primary resonance inductor Lm, a primary winding of an isolation transformer T connected with the first MOSFET tube Q1 in parallel, a first primary resonance inductor Lr, a first primary resonance capacitor Cr, the fourth MOSFET tube Q4 and an input current sampling resistor Rcs1 and returns to the negative electrode of the direct current input end, current in a secondary winding of the isolation transformer T is filtered by a rectifier diode D3 and a filter capacitor Cf and then is output to the positive electrode of the direct current output end, the current returns to the negative electrode of the direct current output end through a load connected with the direct current output end, then flows through the output current sampling resistor Rcs3 and is filtered by the filter capacitor Cf, and flows through the rectifier diode D2 and returns to the secondary winding of the isolation transformer T; after a half period, a PWM pulse signal turns off a first MOSFET Q1 and a fourth MOSFET Q4, a third MOSFET Q3 and a second MOSFET Q2 are turned on, current sequentially passes through the third MOSFET Q3, a first primary resonant capacitor Cr, a first primary resonant inductor Lr and a second primary resonant inductor Lm and a primary winding, a primary current sampling resistor Rcs2, a second MOSFET Q2 and an input current sampling resistor Rcs1 of an isolation transformer T which are connected with the primary winding, the second primary resonant inductor Lm and the primary winding, the primary current sampling resistor Rcs2 and the input current sampling resistor Rcs1 in parallel, the current in a secondary winding of the isolation transformer T is filtered by a rectifier diode D1 and a filter capacitor Cf and then output to the anode of a direct current output end, and then returns to the cathode of the direct current output end through a load connected with the direct current output end, then flows through the output current sampling resistor Rcs3, is filtered by the filter capacitor Cf, and flows through D4 and returns to a secondary winding of the isolation transformer T;

when the primary side current sampling resistor Rcs2 detects that a set overcurrent or short circuit occurs, if the first MOSFET tube Q1 and the fourth MOSFET tube Q4 are turned on, and the third MOSFET tube Q3 and the second MOSFET tube Q2 are turned off, the short-circuit protection control circuit is turned on to immediately control the first MOSFET tube Q1 and the fourth MOSFET tube Q4 to be turned off, the third MOSFET tube Q3 and the second MOSFET tube Q2 to be turned on, and when the primary side current sampling resistor Rcs2 detects that the current returns to a set value (for example, the current returns to a zero point), the short-circuit protection control circuit controls all switch tubes of the primary side switch circuit to be turned off to wait for restarting; if the third MOSFET tube Q3 and the second MOSFET tube Q2 are turned on and the first MOSFET tube Q1 and the fourth MOSFET tube Q4 are turned off at present, the short-circuit protection control circuit is turned on to immediately control the turning off of the third MOSFET tube Q3 and the second MOSFET tube Q2, the first MOSFET tube Q1 and the fourth MOSFET tube Q4 are turned on, when the primary side current sampling resistor Rcs2 detects that the current returns to a set value, the short-circuit protection control circuit turns on to control the turning off of all the switching tubes of the primary side switching circuit to wait for restarting.

In this embodiment, the short-circuit protection control circuit controls the turn-on and turn-off sequence of the two groups of switching tubes of the primary side switching source circuit when an overcurrent or a short circuit occurs, so that the current does not rush through the limit of the switching tubes, and the follow current originally flowing through the body diode of the MOSFET tube in one group of switching tubes flows through the MOSFET tube in the other group of switching tubes, thereby realizing the rapid short-circuit protection.

Fig. 3 is a schematic circuit diagram of a short-circuit protection control circuit of a resonant converter according to an embodiment of the present invention. The short-circuit protection control circuit comprises a threshold memory (not shown in the figure) which stores an overcurrent reference current value and a reset reference current value in advance, two comparators U1 and U8 and a switch logic control circuit. The negative input end of the comparator U1 is connected with the threshold memory to read the overcurrent reference current value from the threshold memory, the positive input end is connected with the current sampling circuit to read the sampled current signal (in the embodiment, the current signal of the primary side is sampled by a primary side current sampling resistor Rcs 2) from the current sampling circuit, and the output end is connected with the switch logic control circuit; the negative input end of the comparator U8 is connected to the threshold memory to read the reset reference current value from the threshold memory, the positive input end is connected to the current sampling circuit to read the sampled current signal from the current sampling circuit (in this embodiment, the current signal on the primary side is sampled by the primary side current sampling resistor Rcs 2), and the output end is connected to the switch logic control circuit. The switch logic control circuit comprises two switch tube switch state signal input ends, a pulse delayer U2, an AND gate U7, two pulse retainers U4 and U5, two exclusive-OR gates U3 and U6 and two alternative switches K1 and K2, wherein the two switch tube switch state signal input ends respectively input switch state signals of two groups of switch tubes of a primary side switch circuit, and the switch logic control circuit controls the on-off states of the two alternative switches K1 and K2 according to level signals output by the comparators U1 and U8 and current on-off states of the first MOSFET tube Q1, the second MOSFET tube Q2, the third MOSFET tube Q3 and the fourth MOSFET tube Q4 in the two groups of switch tubes of the primary side switch circuit after carrying out logic operation through the logic gate chips, so as to control the on-off states of the first MOSFET tube Q1, the second MOSFET tube Q2, the third MOSFET tube Q3 and the fourth MOSFET tube Q4 in the two groups of switch tubes of the primary side switch circuit connected with the output end of the switch logic control circuit.

The short-circuit protection control circuit has the following specific working principle:

when the comparator U1 detects that overcurrent occurs, an overcurrent signal is output, after the overcurrent signal is subjected to logic and operation through an AND gate U7 together with a reset signal output by a pulse delayer U2 and a comparator U8, the two-choice switches K1 and K2 are switched, input signals of the first MOSFET tube Q1/fourth MOSFET tube Q4 and the second MOSFET tube Q2/third MOSFET tube Q3 are subjected to logic exclusive-OR operation through a pulse retainer U4 and U5 and delayed overcurrent signals through an exclusive-OR gate U3 and U6 respectively, and control signals are output through the two-choice switches K1 and K2 respectively to control the on-off states of the first MOSFET tube Q1, the second MOSFET tube Q2, the third MOSFET tube Q3 and the fourth MOSFET tube Q4. Specifically, when the input of the first MOSFET tube Q1/the fourth MOSFET tube Q4 is at a high level, a low level is output after being logically xored with an overcurrent signal, the input of the second MOSFET tube Q2/the third MOSFET tube Q3 is at a low level, a high level is output after being logically xored with an overcurrent signal, the second MOSFET tube Q2 and the third MOSFET tube Q3 shown in fig. 2 are turned on through the one-of-two switch, and the first MOSFET tube Q1 and the fourth MOSFET tube Q4 are turned off; when the input of the second MOSFET Q2/the third MOSFET Q3 is at a high level, the low level is output after the logical XOR with the over-current signal, the input of the first MOSFET Q1/the fourth MOSFET Q4 is at a low level, the high level is output after the logical XOR with the over-current signal, the first MOSFET Q1 and the fourth MOSFET Q4 shown in the figure 2 are switched on through the one-of-two switch, and the second MOSFET Q2 and the third MOSFET Q3 are switched off; when the current is reduced to the reset reference current value, the reset signal level is reversed, and after the logic AND of the delayed overcurrent signal, the alternative switch is reset, and simultaneously the pulse delayer and the pulse retainer are reset, and the normal working mode is entered.

As shown in fig. 4, it is a main oscillogram around the protection of the first embodiment of the present invention discloses a resonant converter, the first MOSFET tube Q1, the driving signal waveform of the fourth MOSFET tube Q4, the second MOSFET tube Q2, the driving signal waveform of the third MOSFET tube Q3, and the current signal waveform sampled by the primary side current sampling resistor Rcs2 are sequentially provided from top to bottom in the graph, as shown in the graph, when an overcurrent or a short circuit occurs, a set of switching tubes in the primary side switching circuit (i.e., the second MOSFET tube Q2 and the third MOSFET tube Q3) is turned off, another set of switching tubes in the primary side switching circuit (i.e., the first MOSFET tube Q1 and the fourth MOSFET tube Q4) is turned on, the current drops to zero (a reset reference current value), all switching tubes in two sets of switching tubes in the primary side switching circuit are turned off, and the resonant converter is waited to restart.

The second embodiment:

fig. 5 is a schematic diagram of a partial circuit of a resonant converter according to a second embodiment of the present invention. In this embodiment, the primary side switching circuit is a half-bridge switching circuit, and includes two groups of switching tubes, the first group includes a first MOSFET tube Q1, the second group includes a second MOSFET tube Q2, the primary side resonant circuit includes a first primary side resonant capacitor Cr and a first primary side resonant inductor Lr, the first primary side resonant capacitor Cr and the first primary side resonant inductor Lr form an LC series resonant circuit, and other circuit structures are the same as embodiment 1 (an isolation transformer and subsequent circuits are omitted in the figure), and the resonant converter in this embodiment operates according to the following principle:

when the direct current input end is electrified, the first MOSFET tube Q1 is switched on, and then the current returns to the negative electrode of the direct current input end through the positive electrode of the direct current input end, the first MOSFET tube Q1, the first primary side resonant capacitor Cr, the first primary side resonant inductor Lr, the primary side current sampling resistor Rcs2 and the input current sampling resistor Rcs 1; after half a period, the first MOSFET Q1 is turned off, the second MOSFET Q2 is turned on, and the energy on the first primary side resonant capacitor Cr returns to the first primary side resonant capacitor Cr through the second MOSFET Q2, the primary side current sampling resistor Rcs2, and the first primary side resonant inductor Lr.

Example three:

fig. 6 is a schematic diagram of a partial circuit of a resonant converter according to a third embodiment of the present invention. In this embodiment, the first primary resonant capacitor Cr and the first primary resonant inductor Lr form an LC parallel resonant circuit, and other circuit structures are the same as those in embodiment 2 (the isolation transformer and subsequent circuits are omitted in the figure), and the resonant converter in this embodiment operates according to the following principle:

when the direct current input end is powered on, the first MOSFET Q1 is switched on, and then the positive electrode of the direct current input end, the first MOSFET Q1, the first primary side resonant capacitor Cr, the first primary side resonant inductor Lr connected with the first primary side resonant capacitor Cr in parallel, the primary side current sampling resistor Rcs2 and the input current sampling resistor Rcs1 return to the negative electrode of the direct current input end; after half a period, the first MOSFET tube Q1 is turned off, the second MOSFET tube Q2 is turned on, and then the energy on the first primary side resonant capacitor Cr and the first primary side resonant inductor Lr returns to the first primary side resonant capacitor Cr and the first primary side resonant inductor Lr through the second MOSFET tube Q2 and the primary side current sampling resistor Rcs 2.

Example four:

fig. 7 is a schematic diagram of a partial circuit of a resonant converter according to a fourth embodiment of the present invention. In this embodiment, the second primary side resonant capacitor Cp is added to the primary side resonant circuit on the basis of the second embodiment, the second primary side resonant capacitor Cp is connected in parallel with the first primary side resonant inductor Lr, and the first primary side resonant capacitor Cr, the first primary side resonant inductor Lr and the second primary side resonant capacitor Cp form an LCC resonant circuit, and the resonant converter in this embodiment has the following operating principle:

when the direct current input end is electrified, the first MOSFET tube Q1 is switched on, and then current returns to the negative electrode of the direct current input end through the positive electrode of the direct current input end, the first MOSFET tube Q1, the first primary side resonant capacitor Cr, the second primary side resonant capacitor Cp, the first primary side resonant inductor Lr, the primary side current sampling resistor Rcs2 and the input current sampling resistor Rcs1 which are connected in parallel with the first primary side resonant capacitor Cp; after a half period, the first MOSFET tube Q1 is turned off, and the second MOSFET tube Q2 is turned on, so that energy on the first primary side resonant capacitor Cr, the second primary side resonant capacitor Cp and the first primary side resonant inductor Lr returns to the first primary side resonant capacitor Cr, the second primary side resonant capacitor Cp and the first primary side resonant inductor Lr through the second MOSFET tube Q2 and the primary side current sampling resistor Rcs 2.

Example five:

fig. 8 is a schematic diagram of a partial circuit of a resonant converter according to a fifth embodiment of the present invention. In this embodiment, the primary side switch circuit is configured such that the third MOSFET tube Q3 and the fourth MOSFET tube Q4 are removed on the basis of embodiment 1, the other end of the primary side current sampling resistor Rcs2 is connected to the connection between the source of the second MOSFET tube Q2 and the input current sampling resistor Rcs1, and a secondary side resonant capacitor Cr1 connected in series is added between the dotted terminal of the secondary winding of the isolation transformer T and the first ac input terminal of the secondary side rectifier and filter circuit, and the resonant converter in this embodiment operates according to the following principle:

when the direct current input end is electrified, a PWM pulse signal controls a first MOSFET tube Q1 to be switched on, current sequentially passes through the first MOSFET tube Q1, a first primary side resonant capacitor Cr, a first primary side resonant inductor Lr, a second primary side resonant inductor Lm, a primary side winding of an isolation transformer T connected with the first MOSFET tube Q1 in parallel, a primary side current sampling resistor Rcs2 and an input current sampling resistor Rcs1 to return to the negative electrode of the direct current output end, current in a secondary side winding of the isolation transformer T is filtered by a rectifier diode D1 and a filter capacitor Cf and then is output to the positive electrode of the direct current output end, the current returns to the negative electrode of the direct current output end through a load, flows through an output current sampling resistor Rcs3, is filtered by the filter capacitor Cf, flows through a rectifier diode D4 and the secondary side resonant capacitor Cr1 to return to the secondary side winding of the isolation transformer T; after a half period, a PWM pulse signal turns off a first MOSFET tube Q1, turns on a second MOSFET tube Q2, the energy of a first primary side resonance capacitor Cr and a first primary side resonance inductor Lr sequentially passes through the first primary side resonance capacitor Cr, the second MOSFET tube Q2, a primary side current sampling resistor Rcs2, a second primary side resonance inductor Lm and a primary side winding of an isolation transformer T connected in parallel with the first primary side resonance inductor Lr, the current in a secondary side winding of the isolation transformer T is filtered by a secondary side resonance capacitor Cr1, a rectifier diode D3 and a filter capacitor Cf, then is output to the anode of a direct current output end, returns to the cathode of the direct current output end through a load, flows through an output current sampling resistor Rcs3, is filtered by the filter capacitor Cf, and flows through the rectifier diode D2 and returns to the secondary side winding of the isolation transformer T;

example six:

fig. 9 is a schematic diagram of a partial circuit of a resonant converter according to a sixth embodiment of the present invention. In this embodiment, on the basis of the first embodiment, the secondary resonant inductor Lr1, the secondary resonant capacitor Cr1, and the secondary current sampling resistor Rcs4 are added to the secondary side of the isolation transformer T, and the full-bridge uncontrollable rectifier circuit composed of 4 rectifier diodes D1, D2, D3, and D4 is replaced by the full-bridge fully-controlled rectifier circuit composed of 4 MOSFET rectifier tubes Qa, qb, qc, and Qd, and the resonant converter in this embodiment operates according to the following principle:

when the direct current input end is electrified, PWM pulse signals control a first MOSFET tube Q1 and a fourth MOSFET tube Q4 to be switched on, current sequentially passes through the first MOSFET tube Q1, a first primary side resonant capacitor Cr, a first primary side resonant inductor Lr, a second primary side resonant inductor Lm, a primary side winding of an isolation transformer T connected in parallel with the first MOSFET tube Q1, the first primary side resonant capacitor Lr, the second primary side resonant inductor Lm, a primary side current sampling resistor Rcs2, the fourth MOSFET tube Q4 and an input current sampling resistor Rcs1 to return to a negative electrode of the direct current output end, current in a secondary side winding of the isolation transformer T is filtered by the secondary side resonant inductor Lr1, the MOSFET rectifier tube Qa and a filter capacitor Cf to be output to a positive electrode of the direct current output end, returns to a negative electrode of the direct current output end through a load, flows through an output current sampling resistor Rcs3, is filtered by the filter capacitor Cf, flows through the MOSFET rectifier tube Qd, the secondary side current sampling resistor Rcs4 and the secondary side resonant capacitor Cr1 to return to a secondary side winding of the isolation transformer T; after half period, the PWM pulse signal turns off the first MOSFET tube Q1 and the fourth MOSFET tube Q4, turns on the second MOSFET tube Q2 and the third MOSFET tube Q3, the current passes through the third MOSFET tube Q3, the primary side current sampling resistor Rcs2, the second primary side resonant inductor Lm, the primary side winding of the isolation transformer T connected in parallel therewith, the first primary side resonant inductor Lr, the first primary side resonant capacitor Cr, the second MOSFET tube Q2, and the input current sampling resistor Rcs1 in sequence, and returns to the negative electrode, the current in the secondary winding of the isolation transformer T is filtered by the secondary side resonant capacitor Cr1, the secondary side current sampling resistor Rcs4, the MOSFET rectifier Qc, and the filter capacitor Cf and then output to the positive electrode of the dc output terminal, and returns to the negative electrode of the dc output terminal through the load, flows through the output current sampling resistor Rcs3, is filtered by the filter capacitor Cf, flows through the rectifier MOSFET rectifier tube Qb and the secondary side inductor Lr1 and returns to the secondary winding of the isolation transformer T.

In the specification of the present invention, a large number of specific details are explained. It is understood, however, that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the scope of the embodiments of the present invention, and are intended to be covered by the claims and the specification.

Claims

1. A resonant converter is characterized by comprising a direct current input end, a primary side switch circuit, a short-circuit protection control circuit, a primary side resonant circuit, a current sampling circuit, an isolation transformer, a secondary side rectification filter circuit and a direct current output end,

the primary side switching circuit comprises two groups of switching tubes, the positive direct current input end of the primary side switching circuit is connected with the positive pole of the direct current input end, the negative direct current input end of the primary side switching circuit is connected with the negative pole of the direct current input end, the first end of the primary side resonance circuit is connected with the first end of the primary side current sampling resistor, the primary side resonance circuit is coupled with the primary side winding of the isolation transformer, and two alternating current output ends of the primary side switching circuit are respectively connected with the second end of the primary side resonance circuit and the second end of the primary side current sampling resistor;

the input end of the short-circuit protection control circuit is connected with the current sampling circuit, the output end of the short-circuit protection control circuit is connected with the control signal input end of the primary side switching circuit, and the short-circuit protection control circuit is used for controlling one group of switching tubes which are currently in a conducting state in two groups of switching tubes of the primary side switching circuit to be switched off and simultaneously controlling one group of switching tubes which are currently in a switching-off state to be switched on when a current signal detected by the current sampling circuit exceeds a preset current threshold value.

2. The resonant converter according to claim 1, wherein the short-circuit protection control circuit comprises a threshold memory, a comparator and a switching logic control circuit, wherein a first input terminal of the comparator is connected to the threshold memory, a second input terminal of the comparator is connected to the output terminal of the current sampling circuit, an output terminal of the comparator is connected to the input terminal of the switching logic control circuit, and an output terminal of the switching logic control circuit is connected to the control signal input terminal of the primary side switching circuit.

3. The resonant converter of claim 1, wherein the current sampling circuit further comprises an input current sampling resistor and/or an output current sampling resistor;

4. A resonant converter according to any of claims 1-3, characterized in that the primary resonant circuit is an LC resonant circuit, an LLC resonant circuit, an LCC resonant circuit, a CLLC resonant circuit or a CLLLC resonant circuit.

5. The resonant converter according to claim 4, further comprising a secondary resonant capacitor connected in series between the dotted terminal of the secondary winding of the isolation transformer and the first ac input terminal of the secondary rectifier filter circuit.

6. The resonant converter of claim 5, further comprising a secondary resonant inductor and a secondary resonant resistor;

7. The resonant converter according to claim 1, 2, 3, 5 or 6, wherein the primary side switching circuit is a half-bridge type switching circuit, the half-bridge type switching circuit comprises a first MOSFET tube and a second MOSFET tube, a drain of the first MOSFET tube is connected to an anode of the dc input terminal, a source of the first MOSFET tube is connected to a drain of the second MOSFET tube and a second end of the primary side resonant circuit, a source of the second MOSFET tube is connected to a cathode of the dc input terminal and a second end of the primary side current sampling resistor, and a gate of the first MOSFET tube and a gate of the second MOSFET tube are connected to an output terminal of the short-circuit protection control circuit.

8. The resonant converter according to claim 1, 2, 3, 5 or 6, wherein the primary side switching circuit is a full-bridge type switching circuit, the full-bridge type switching circuit comprises a first MOSFET tube, a second MOSFET tube, a third MOSFET tube and a fourth MOSFET tube, a drain electrode of the first MOSFET tube and a drain electrode of the third MOSFET tube are respectively connected to an anode of the dc input terminal, a source electrode of the first MOSFET tube is respectively connected to a drain electrode of the second MOSFET tube and a second end of the primary side resonant circuit, a source electrode of the third MOSFET tube is respectively connected to a drain electrode of the fourth MOSFET tube and a second end of the primary side current sampling resistor, a source electrode of the second MOSFET tube and a source electrode of the fourth MOSFET tube are respectively connected to a cathode of the dc input terminal, and a gate electrode of the first MOSFET tube, a gate electrode of the second MOSFET tube, a gate electrode of the third MOSFET tube and a gate electrode of the fourth MOSFET tube are respectively connected to an output terminal of the short-circuit protection control circuit.

9. The resonant converter according to claim 1, 2, 3, 5 or 6, wherein the secondary side rectifying and filtering circuit comprises a full-bridge uncontrollable rectifying circuit and a filtering capacitor composed of 4 rectifying diodes, the full-bridge uncontrollable rectifying circuit and the filtering capacitor are connected in parallel, two input ends of the full-bridge uncontrollable rectifying circuit are respectively connected with two ends of the secondary side winding of the isolation transformer, and two output ends of the full-bridge uncontrollable rectifying circuit are respectively connected with a positive electrode and a negative electrode of the DC output end.

10. The resonant converter according to claim 1, 2, 3, 5 or 6, wherein the secondary side rectifying and filtering circuit comprises a full-bridge fully-controlled rectifying circuit and a filtering capacitor formed by 4 MOSFET tubes, the full-bridge fully-controlled rectifying circuit and the filtering capacitor are connected in parallel, two input ends of the full-bridge fully-controlled rectifying circuit are respectively connected with two ends of the secondary side winding of the isolation transformer, and two output ends of the full-bridge fully-controlled rectifying circuit are respectively connected with a positive electrode and a negative electrode of the DC output end.