CN217741574U - Power conversion power supply, driving circuit thereof and clamping circuit of synchronous rectification switching tube - Google Patents
Power conversion power supply, driving circuit thereof and clamping circuit of synchronous rectification switching tube Download PDFInfo
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- CN217741574U CN217741574U CN202123383768.6U CN202123383768U CN217741574U CN 217741574 U CN217741574 U CN 217741574U CN 202123383768 U CN202123383768 U CN 202123383768U CN 217741574 U CN217741574 U CN 217741574U
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Abstract
A power conversion power supply, a driving circuit thereof and a clamping circuit of a synchronous rectification switching tube are provided, wherein the clamping circuit of the synchronous rectification switching tube comprises: current-limiting unit, voltage stabilizing unit, enable unit and clamp unit, wherein: the current limiting unit is coupled with the second port of the secondary winding of the synchronous rectification circuit and the voltage stabilizing unit and outputs current limiting current according to the voltage of the second port of the secondary winding; the voltage stabilizing unit is coupled with the clamping unit and used for receiving the current-limiting current to charge the voltage stabilizing unit, and the voltage stabilizing unit generates voltage to control the conduction of the clamping unit and clamp the grid voltage of the synchronous rectification switching tube at a low level; a voltage detection unit for detecting the power supply voltage and outputting the detection result; the enabling unit is connected with the voltage detection unit, receives the detection result and outputs an enabling signal; and the clamping unit is coupled with the enabling unit, receives the enabling signal and disconnects the grid electrode of the synchronous rectification switching tube from the ground. The scheme can prevent the synchronous rectification switching tube from being conducted by mistake.
Description
Technical Field
The utility model relates to the technical field of circuits, especially, relate to a power conversion power supply and drive circuit, synchronous rectifier switch tube's clamp circuit.
Background
Synchronous rectification is a method of using a synchronous rectification switching tube (MOSFET) with low on-resistance instead of a rectifier diode to reduce rectification loss. The synchronous rectification switching tube belongs to a voltage control type device, and the volt-ampere characteristic when the synchronous rectification switching tube is conducted is in a linear relation. When the synchronous rectification switching tube is used for rectification, the grid voltage of the synchronous rectification switching tube and the phase of the rectified voltage are kept synchronous, and then the rectification function can be completed.
Referring to fig. 1, a schematic diagram of a conventional power conversion power supply circuit is shown. A live wire L and a zero line N of commercial power are respectively connected to two input ends of a rectifier bridge, and two output ends of the rectifier bridge are respectively connected with a first primary winding and a second primary winding of a transformer. And a filter capacitor C1 is arranged between the two output ends of the rectifier bridge. And the absorption circuit is arranged on the first primary winding and used for absorbing the leakage inductance energy of the transformer, and the absorption circuit consists of a third resistor R3, a third capacitor C3 and a first diode D1. The first voltage-dividing resistor R1 and the second voltage-dividing resistor R2 are arranged on the second primary winding, the input end of the primary power switch tube control circuit is coupled to the second end of the first voltage-dividing resistor R1 and the first end of the second voltage-dividing resistor R2, the output end is coupled to the control end of the primary power switch tube M1, and the sampling end is coupled to the first end of the fourth sampling resistor R4. The first end of the primary side power switch tube M1 is connected with a first current source IP, and the second end of the primary side power switch tube M1 is connected with the first end of the fourth sampling resistor R4.
The second port of the secondary winding of the transformer is coupled with the ground GND, and a synchronous rectification switch tube M2 is arranged. And comparing the voltage VD of the secondary winding port with a first reference voltage VREF1 by using a starting comparator to obtain a starting signal ON. And comparing the port voltage VD of the secondary winding with a second reference voltage VREF2 by using a turn-OFF comparator to obtain a turn-OFF signal OFF. The logic control unit generates and outputs a control signal PWM according to the ON signal ON and the OFF signal OFF. After the control signal PWM passes through the driving circuit, a driving signal GATE (i.e., a driven control signal) is obtained and output to the GATE of the synchronous rectification switch tube M2, so as to control the on/off of the synchronous rectification switch tube M2.
In the power conversion power supply circuit shown in fig. 1, at the instant when the primary side power switching tube M1 is turned on, the power supply voltage VCC of the synchronous rectification controller is not reached to the start threshold voltage for a period of time, the internal logic is not yet established, and the synchronous rectification switching tube M2 should not be turned on. However, at this time, the Drain (Drain) of the synchronous rectification switch M2 receives the high voltage VD, the parasitic capacitance Cgd between the Drain and the Gate (Gate) is coupled to the Gate, and the Gate voltage rises accordingly. If the gate charges are not released in time, the synchronous rectification switch M2 may be turned on by mistake.
SUMMERY OF THE UTILITY MODEL
The utility model provides a problem be synchronous rectification switch tube have the technical problem that the mistake switched on.
In order to solve the above problem, the utility model provides a clamping circuit of synchronous rectification switch tube, include: current-limiting unit, voltage regulation unit, voltage detection unit, enable unit and clamp unit, wherein: the current limiting unit is coupled with a second port of a secondary winding of the synchronous rectification circuit and the voltage stabilizing unit and outputs current limiting current according to the voltage of the second port of the secondary winding; the voltage stabilizing unit is coupled with the clamping unit and used for receiving the current-limiting current, the current-limiting current charges the voltage stabilizing unit, and the voltage stabilizing unit generates voltage to control the conduction of the clamping unit and clamp the grid voltage of the synchronous rectification switching tube at a low level; the voltage detection unit is coupled with the first port of the secondary winding, detects the power voltage and outputs a detection result; the enabling unit is connected with the voltage detection unit, receives the detection result and outputs an enabling signal; and the clamping unit is coupled with the enabling unit, receives the enabling signal and disconnects the grid electrode of the synchronous rectification switching tube from the ground. .
Optionally, the voltage stabilizing unit generates a stabilizing voltage before the power supply voltage does not reach a threshold value, and triggers the clamping unit to be turned on; the enabling unit controls the clamping unit to be switched off when the power supply voltage reaches a threshold value.
Optionally, the current limiting unit includes: current-limiting resistor and freewheeling diode, wherein: the first end of the current limiting resistor is coupled with the input end of the current limiting unit, and the second end of the current limiting resistor is coupled with the anode of the fly-wheel diode; and the cathode of the freewheeling diode is coupled with the input end of the voltage stabilizing unit.
Optionally, the voltage stabilizing unit includes: a holding capacitor and a zener diode, wherein: the first end of the maintaining capacitor is coupled with the input end of the voltage stabilizing unit, and the second end of the maintaining capacitor is grounded; and the anode of the voltage stabilizing diode is coupled with the second end of the maintaining capacitor, and the cathode of the voltage stabilizing diode is coupled with the output end of the voltage stabilizing unit.
Optionally, the clamping unit includes: a first NMOS transistor; the grid electrode of the first NMOS tube is coupled with the output end of the voltage stabilizing unit and the output end of the enabling module, the source electrode of the first NMOS tube is grounded, and the drain electrode of the first NMOS tube is coupled with the grid electrode of the rectifying tube.
Optionally, the enabling unit includes: the enable circuit and the second NMOS tube; the input end of the enabling circuit is coupled with the input end of the enabling unit, and the output end of the enabling circuit is coupled with the grid electrode of the second NMOS tube; and the drain electrode of the second NMOS tube is coupled with the output end of the enabling unit, and the source electrode of the second NMOS tube is grounded.
The embodiment of the utility model provides a still provide a drive circuit of power conversion power, include: the clamp circuit of the synchronous rectification switching tube, the turn-on comparator, the turn-off comparator, the logic control unit and the driving unit, wherein: the first input end of the starting comparator inputs the secondary side port voltage, the second input end of the starting comparator inputs the first reference voltage, and the secondary side port voltage is compared with the first reference voltage to obtain a starting signal; the secondary side port voltage is a second port voltage of the secondary side winding; the first input end of the turn-off comparator inputs the secondary side port voltage, the second input end of the turn-off comparator inputs a second reference voltage, and the secondary side port voltage and the second reference voltage are compared to obtain a turn-off signal; the logic control unit inputs the turn-on signal and the turn-off signal, and logically combines the turn-on signal and the turn-off signal to obtain a control signal; the driving unit inputs the control signal, drives the control signal and outputs the driven control signal to the grid electrode of the synchronous rectification switching tube; and the clamping circuit of the synchronous rectification switching tube is coupled with the grid electrode of the synchronous rectification switching tube, and controls the grid electrode voltage of the synchronous rectification switching tube to be low level before the power supply voltage does not reach a preset voltage.
The embodiment of the utility model provides a power conversion power supply circuit is still provided, including former limit power switch tube, rectifier bridge, filter circuit, transformer, absorption circuit, former limit power switch tube control circuit, synchronous rectifier switch tube, and the aforesaid drive circuit of power conversion power supply, wherein: the rectifier bridge rectifies the input commercial power into high-voltage direct current; the filter circuit is coupled with the rectifier bridge and used for filtering the high-voltage direct current; the absorption circuit is coupled with the primary winding of the transformer and absorbs the leakage inductance energy of the transformer so as to reduce the voltage peak value when the primary power switching tube is turned off; the primary side power switching tube control circuit is coupled with the primary side power switching tube and is used for controlling the primary side power switching tube; the synchronous rectification switching tube is coupled with the secondary winding of the transformer and is used for synchronously rectifying secondary output voltage of the transformer; and the driving circuit of the power conversion power supply is coupled with the synchronous rectification switching tube and the second end of the secondary winding of the transformer, and outputs a driving signal to the grid electrode of the synchronous rectification switching tube so as to drive the synchronous rectification switching tube.
Optionally, a positive input end of the rectifier bridge is connected to the live wire of the utility power, and an inverted input end of the rectifier bridge is connected to the ground wire of the utility power.
Optionally, the filter circuit is coupled between the first output terminal of the rectifier bridge and the second output terminal of the rectifier bridge, and one port of the filter circuit is grounded.
Optionally, the transformer includes a first primary winding, and the first primary winding is coupled to the first output end of the rectifier bridge; the absorption circuit includes: first diode, third resistance and third electric capacity, wherein: the anode of the first diode is coupled to the first port of the first primary winding, and the cathode of the first diode is coupled to the first end of the third resistor and the first end of the third capacitor; a second end of the third resistor is coupled to a second port of the first primary winding; and a second end of the third capacitor is coupled to the second port of the first primary winding.
Optionally, the transformer includes a first primary winding and a second primary winding, the first primary winding is coupled to the first output terminal of the rectifier bridge, and the second primary winding is coupled to the second output terminal of the rectifier bridge; the power conversion power supply circuit further includes: first divider resistance, second divider resistance, first current source and fourth sampling resistor, wherein: a first end of the first voltage-dividing resistor is coupled to the second output end of the rectifier bridge, and a second end of the first voltage-dividing resistor is coupled to a first end of the second voltage-dividing resistor and an input end of the primary side power switch tube control circuit; a second end of the second voltage-dividing resistor is coupled with a first port of the second primary winding; a second port of the second primary winding is grounded; a first end of the first current source is coupled to the first port of the first primary winding, and a second end of the first current source is coupled to the first end of the primary power switching tube; the output end of the primary side power switching tube control circuit is coupled with the control end of the primary side power switching tube; and a first end of the fourth sampling resistor is coupled with the second end of the primary side power switch tube and the sampling end of the primary side power switch tube control circuit, and a second end of the fourth sampling resistor is grounded.
Compared with the prior art, the technical scheme of the utility model have following advantage:
the voltage stabilizing unit is charged through the current limiting unit, generates a stable voltage before the power supply voltage does not reach the preset voltage, and clamps the grid voltage of the synchronous rectification switching tube at a low level through the clamping unit. After the power supply voltage reaches a preset voltage, the enabling unit outputs a high-level enabling signal, the shielding clamping unit controls the grid electrode of the synchronous rectification switching tube, and the synchronous rectification switching tube works normally. Therefore, before the power supply voltage does not reach the preset voltage, the grid voltage of the synchronous rectification switching tube is clamped at a low level through the clamping unit, and the synchronous rectification switching tube can be effectively prevented from being conducted by mistake.
Drawings
Fig. 1 is a schematic structural diagram of a conventional power conversion power supply circuit;
fig. 2 is a schematic structural diagram of a power conversion power supply circuit in an embodiment of the present invention;
fig. 3 is a schematic structural diagram of a clamping circuit of a synchronous rectification switching tube according to an embodiment of the present invention;
fig. 4 is a timing diagram of the clamp circuit of the synchronous rectification switch tube according to an embodiment of the present invention.
Detailed Description
As described in the background art, the conventional power conversion power supply circuit may have a technical problem of erroneous conduction of the synchronous rectification switching tube.
The embodiment of the utility model provides an in, charge for voltage stabilizing unit through the current-limiting unit, voltage stabilizing unit produces a steady voltage before mains voltage does not reach predetermined voltage, through the grid voltage clamping of clamping unit with synchronous rectification switch tube at the low level. After the power supply voltage reaches a preset voltage, the enabling unit outputs a high-level enabling signal, the shielding clamping unit controls the grid electrode of the synchronous rectification switching tube, and the synchronous rectification switching tube works normally. Therefore, before the power supply voltage does not reach the preset voltage, the grid voltage of the synchronous rectification switching tube is clamped at a low level through the clamping unit, and the synchronous rectification switching tube can be effectively prevented from being conducted by mistake.
In order to make the aforementioned objects, features and advantages of the present invention more comprehensible, embodiments accompanied with figures are described in detail below.
Referring to fig. 2, a schematic structural diagram of a power conversion power supply circuit according to an embodiment of the present invention is shown. In an embodiment of the present invention, the power conversion power supply circuit may include: the power conversion circuit comprises a primary side power switching tube M1, a rectifier bridge, a filter circuit, a transformer, an absorption circuit, a primary side power switching tube control circuit, a synchronous rectification switching tube M2 and a driving circuit 20 of a power conversion power supply.
In a specific implementation, the first input of the rectifier bridge may be coupled to the live line L of the mains supply and the second input of the rectifier bridge may be coupled to the neutral line N of the mains supply. The input commercial power can be rectified into high-voltage direct current through the rectifier bridge.
The first output end of the rectifier bridge is connected with the first primary winding, and the second output end of the rectifier bridge is connected with the second primary winding. The first output end of the rectifier bridge is a plus output end of the rectifier bridge, and the second output end of the rectifier bridge is a minus output end of the rectifier bridge.
And a filter circuit is arranged between the first output end of the rectifier bridge and the second output end of the rectifier bridge. And filtering the high-voltage direct current output by the rectifier bridge through a filter circuit.
In the embodiment of the present invention, the filter circuit may include a filter capacitor C1. The first end of the filter capacitor C1 is coupled to the first output end of the rectifier bridge, and the second end of the filter capacitor C1 is coupled to the second output end of the rectifier bridge and grounded.
The first primary winding is connected with an absorption circuit. The absorption circuit can absorb the leakage inductance energy of the transformer, so that the voltage peak value of the primary side power switch tube M1 is reduced when the primary side power switch tube M1 is turned off.
In an embodiment of the present invention, the absorption circuit includes a first diode D1, a third resistor R3, and a third capacitor C3, wherein:
a first diode D1, an anode of which is coupled to the first port of the first primary winding, and a cathode of which is coupled to the first end of the third resistor R3 and the first end of the third capacitor C3;
a second end of the third resistor R3 is coupled to the second port of the first primary winding;
and a second terminal of the third capacitor C3 is coupled to the second port of the first primary winding.
And a primary side power switching tube control circuit is connected to the second primary side winding, and the primary side power switching tube M1 is controlled through the primary side power switching tube control circuit.
The transformer further comprises a second primary winding, the second primary winding is coupled with a second output end of the rectifier bridge, and the power conversion power circuit further comprises: first divider resistor R1, second divider resistor R2, first current source IP and fourth sampling resistor R4, wherein: a first end of the first voltage-dividing resistor R1 is coupled to the second output end of the rectifier bridge, and a second end of the first voltage-dividing resistor R1 is coupled to the first end of the second voltage-dividing resistor R2 and the input end of the primary side power switch tube control circuit;
a second end of the second voltage-dividing resistor R2 is coupled to the first port of the second primary winding; a second port of the second primary winding is grounded;
a first current source IP, a first end of which is coupled to the first port of the first primary winding, and a second end of which is coupled to the first end of the primary power switching tube M1;
the output end of the primary side power switching tube control circuit is coupled with the control end of the primary side power switching tube M1;
a first end of the fourth sampling resistor R4 is coupled to the second end of the primary power switching tube M1 and the sampling end of the primary power switching tube control circuit, and a second end thereof is grounded.
The primary side power switching tube control circuit can adjust the voltage output by the output end of the primary side power switching tube through the voltage division ratio of the internal reference voltage of the VFB to the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2; the current is sampled by a fourth sampling resistor R4 to control the power level.
The embodiment of the utility model provides an in, synchronous rectification switch pipe M2 is suitable for and carries out synchronous rectification to the secondary output voltage of transformer. The synchronous rectification switching tube M2 is arranged at a second port of the secondary winding, and the second port of the secondary winding is connected with GND.
The grid electrode and the drain electrode of the synchronous rectification switch tube M2 are coupled and input with the port voltage VD of the secondary winding; the source of the synchronous rectification switch tube M2 is grounded.
The driving circuit 20 of the power conversion power supply is coupled to the GATE of the synchronous rectification switch transistor M2 and the second port of the complex winding of the transformer, and outputs a driving signal GATE to the GATE of the synchronous rectification switch transistor M2 to drive the synchronous rectification switch transistor M2.
In an embodiment of the present invention, the driving circuit 20 of the power conversion power supply includes: the circuit comprises a starting comparator 201, a turning-off comparator 202, a logic control unit 203, a driving unit 204 and a clamping circuit of a synchronous rectification switch tube, wherein: a start comparator 201 adapted to compare a secondary port voltage VD of the transformer with a first reference voltage VREF1 to obtain a start signal ON; a shutdown comparator 202 adapted to compare the secondary side port voltage VD of the transformer with a second reference voltage VREF2 to obtain a shutdown signal OFF; a logic control unit 203 adapted to logically combine the ON signal ON and the OFF signal OFF to obtain a control signal PWM; the driving unit 204 is adapted to drive the control signal PWM and output the driven control signal (i.e., the driving signal GATE) to the GATE of the synchronous rectification switching tube M2; and the clamping circuit of the synchronous rectification switching tube is coupled with the grid electrode of the synchronous rectification switching tube M2, and controls the grid electrode voltage of the synchronous rectification switching tube M2 to be low level before the power supply voltage VCC does not reach the preset voltage.
In a specific implementation, reference may be made to the prior art for specific implementation and principles of the primary power switching tube M1, the rectifier bridge, the filter circuit, the transformer, the absorption circuit, the primary power switching tube control circuit, the synchronous rectification switching tube M2, the on comparator 201, the off comparator 202, the logic control unit 203, and the driving unit 204 provided in fig. 2.
In a specific implementation, the clamping circuit of the synchronous rectification switching tube may include a current limiting unit 101, a voltage stabilizing unit 102, an enabling unit 103, a clamping unit 104, and a voltage detecting unit 105.
In a specific implementation, the current limiting unit 101 may be used to supply power to the voltage stabilizing unit 102;
the voltage stabilizing unit 102 generates a stabilizing voltage before the power supply voltage VCC does not reach a predetermined voltage to control the clamping unit 104, and the gate voltage of the synchronous rectification switching tube M2 is clamped at a low level by the clamping unit 104;
the voltage detection unit 105 outputs a detection result when detecting that the power supply voltage VCC reaches the starting voltage of the synchronous rectification switch tube M2;
an enable unit 103 outputting an enable signal when receiving the detection result;
the clamping unit 104 releases the clamping control of the gate voltage of the synchronous rectification switch tube M2 upon receiving the enable signal.
The following describes in detail the specific structure and connection relationship of the clamp circuit of the synchronous rectification switching tube.
In the embodiment of the present invention, the input end of the current limiting unit 101 may be coupled to the second port of the secondary winding of the transformer, and the input voltage is VD; an output terminal of the current limiting unit 101 may be coupled to an input terminal of the voltage stabilizing unit 102. The current limiting unit 101 limits the magnitude of the current input to the voltage stabilizing unit 102.
An input terminal of the voltage regulation unit 102 is coupled to an output terminal of the current limiting unit 101.
An output of the enabling unit 103 may be coupled to an output of the current limiting unit 101 and an input of the clamping unit 104. An output terminal of the clamping unit 104 may be coupled to an output terminal of the driving unit 204 and a control terminal of the synchronous rectification switch M2.
An input terminal of the voltage detection unit 105 may be connected to a second port of the secondary winding, which outputs the power supply voltage VCC. An output of the voltage detection unit 105 is coupled to an input of the enable unit 103.
The embodiment of the utility model provides an in, voltage detection unit 105 when detecting that mains voltage VCC reaches synchronous rectification switch tube M2's starting voltage, output testing result, at this moment, testing result can be the high level. The enable unit 103 generates and outputs an enable signal of a high level upon receiving the detection result of the high level. On the contrary, if the voltage detection unit 105 detects that the power supply voltage VCC does not reach the start voltage of the synchronous rectification switch tube M2, the detection result does not need to be output, and at this time, the input terminal of the enabling unit 103 is at a low level, so the output of the enabling unit 103 is at a low level.
The first terminal of the synchronous rectification switch tube M2 may be coupled to the second port of the secondary winding, and the second terminal of the synchronous rectification switch tube M2 may be grounded GND. The first port of the secondary winding is the output end of the transformer and outputs the power supply voltage VCC. An output capacitor C2 is arranged between the first port of the secondary winding and the second port of the secondary winding.
Referring to fig. 3, a schematic structural diagram of a clamp circuit of a synchronous rectification switch tube in an embodiment of the present invention is shown.
In a specific implementation, the current limiting unit 101 may include a current limiting resistor R5 and a freewheeling diode D2. Through the current limiting unit 101, the current magnitude in the corresponding branch, that is, the current magnitude input to the voltage stabilizing unit 102, may be limited.
In the embodiment of the present invention, the connection mode between the current limiting resistor R5 and the freewheeling diode D3 may be a series connection. Specifically, a first terminal of the current limiting resistor R5 is coupled to the input terminal of the current limiting unit 101, and a second terminal of the current limiting resistor R5 is coupled to the anode of the freewheeling diode D3. The anode of the freewheeling diode D3 is coupled to the second terminal of the current-limiting resistor R5, and the cathode of the freewheeling diode D3 is coupled to the input terminal of the voltage stabilizing unit 102.
In a specific implementation, the voltage stabilizing unit 102 may include a holding capacitor C4 and a voltage stabilizing diode D3.
In the embodiment of the present invention, the connection mode of the holding capacitor C4 and the zener diode D3 may be a parallel connection. Specifically, a first terminal of the holding capacitor C4 is coupled to the input terminal of the voltage stabilizing unit 102, and a second terminal of the holding capacitor C4 is grounded. The anode of the zener diode D3 is coupled to the second terminal of the sustain capacitor C4, and the cathode of the zener diode D3 is coupled to the output terminal of the current limiting unit 101.
In a specific implementation, the clamping unit 104 may include a first NMOS transistor MN1.
In the embodiment of the present invention, when the clamping unit 104 includes the first NMOS transistor MN1, the gate of the first NMOS transistor MN1 can be coupled to the output of the current limiting unit 101 and the output of the enabling unit 103, the source of the first NMOS transistor MN1 is grounded, and the output of the drain driving unit 204 of the first NMOS transistor MN1 is coupled.
In a specific implementation, the enabling unit 103 may include an enabling circuit and a second NMOS transistor MN2.
In an embodiment of the present invention, the input of the enabling circuit may be coupled with the input of the enabling unit 103; the output end of the enabling circuit is coupled with the grid electrode of the second NMOS tube MN2.
The source of the second NMOS transistor MN2 is grounded, and the drain of the second NMOS transistor MN2 may be coupled to the output terminal of the enable unit 103.
In the embodiment of the present invention, the synchronous rectification switch tube M2 may be an NMOS tube. The first end of the synchronous rectification switch tube M2 is the drain electrode of the synchronous rectification switch tube M2, the second end of the synchronous rectification switch tube M2 is the source electrode of the synchronous rectification switch tube M2, and the control end of the synchronous rectification switch tube M2 is the gate electrode of the synchronous rectification switch tube M2.
Referring to fig. 4, a timing diagram of an operation of a synchronous rectification circuit according to an embodiment of the present invention is shown. The working principle of the clamping circuit of the synchronous rectification switch tube provided in the above embodiment of the present invention is described with reference to fig. 2 to 4.
In a specific implementation, the power supply voltage VCC is realized by charging and discharging the output capacitor C2, and therefore, a certain time is required for the power supply voltage VCC to reach a predetermined voltage. When the power supply voltage VCC does not reach the predetermined voltage VCCon, the gate of the synchronous rectification switch tube M2 is in a floating or weak conduction state. After the control circuit of the primary side power switch tube is conducted, voltage is generated on the primary side winding, and then the voltage on the first port and the voltage on the second port of the secondary side winding are rapidly increased. The Drain (Drain) voltage of the synchronous rectification switch tube M2 rises rapidly correspondingly. A current-limiting resistor R5 and a freewheeling diode D3 in the current-limiting unit 101 generate a current-limiting current, which is input to a holding capacitor C4 of the voltage stabilizing unit 102.
The capacitance value of the holding capacitor C4 of the voltage stabilizing capacitor is small, and the capacitor can store less charges, and is usually full of charges in several switching periods, so that the voltage VC1 of the first end of the holding capacitor C4 reaches a preset voltage value. The voltage VC1 on the maintaining capacitor C4 is always maintained near a preset voltage value through the discharge of the voltage stabilizing diode D3, and the preset voltage value is larger than the threshold voltage of the first NMOS transistor MN1. At this time, the first NMOS transistor MN1 is turned on, so as to clamp the gate voltage Vgate of the synchronous rectification switch transistor M2.
When the synchronous rectification switch tube M2 works normally, the gate of the synchronous rectification switch tube M2 does not need to be clamped by voltage, the gate of the second NMOS tube MN2 inputs the enable signal EN with high level, and the second NMOS tube MN2 is turned on. The grid voltage of the first NMOS transistor MN1 is pulled down, and the first NMOS transistor MN1 is turned off, so that the voltage clamp of the grid of the synchronous rectification switch transistor M2 is shielded.
The high-level enable signal EN input to the gate of the second NMOS transistor MN2 is generated when the power supply voltage VCC reaches a predetermined voltage, and the driving signal is also generated when the power supply voltage VCC reaches the predetermined voltage.
In a specific implementation, the enable signal EN and the driving signal may be generated and output by a synchronous rectification controller. The supply voltage VCC is the supply of the synchronous rectification controller. When the power supply voltage VCC reaches a predetermined voltage, the synchronous rectification controller generates and outputs an enable signal to the enable unit 103, and generates and outputs a drive signal to the drive unit 105.
In the embodiment of the present invention, the predetermined voltage is a synchronous rectification start voltage point (also called start threshold voltage), that is, a voltage at which the synchronous rectification controller can normally operate.
The embodiment of the utility model provides a still provide a clamp circuit of synchronous rectification switch tube, concrete structure of the clamp circuit of specific synchronous rectification switch tube can refer to fig. 2 and fig. 3. The embodiment of the utility model provides a still provide a drive circuit of power conversion power supply, its specific structure and the relation of connection between each part can correspond and refer to fig. 2 and fig. 3, and the no longer repeated description is done here.
Therefore, when the power supply voltage of the synchronous rectification circuit does not reach the preset voltage, namely the synchronous rectification circuit does not work normally, a stable voltage is generated through the voltage stabilizing unit, and the grid voltage of the synchronous rectification switching tube is clamped at a low level through the clamping unit. After the power supply voltage reaches a preset voltage, the enabling unit outputs a high-level enabling signal, the shielding clamping unit controls the grid electrode of the synchronous rectification switching tube, and the synchronous rectification switching tube works normally. Therefore, the grid voltage of the synchronous rectification switch tube is clamped at a low level through the clamping unit, and the synchronous rectification switch tube can be effectively prevented from being conducted by mistake.
Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one of ordinary skill in the pertinent art without departing from the scope or spirit of the present invention, and the scope of the present invention is defined by the appended claims.
Claims (12)
1. A clamping circuit of a synchronous rectification switching tube is characterized by comprising:
current-limiting unit, voltage stabilizing unit, enable unit, voltage detection unit and clamp unit, wherein:
the current limiting unit is coupled with a second port of a secondary winding of the synchronous rectification circuit and the voltage stabilizing unit, and outputs current limiting current according to the voltage of the second port of the secondary winding;
the voltage stabilizing unit is coupled with the clamping unit and used for receiving the current-limiting current, the current-limiting current charges the voltage stabilizing unit, and the voltage stabilizing unit generates voltage to control the conduction of the clamping unit and clamp the grid voltage of the synchronous rectification switching tube at a low level;
the voltage detection unit is coupled with the first port of the secondary winding, detects the power supply voltage and outputs a detection result;
the enabling unit is connected with the voltage detection unit, receives the detection result and outputs an enabling signal;
the clamping unit is coupled with the enabling unit, receives the enabling signal and disconnects the grid electrode of the synchronous rectification switching tube from the ground.
2. The clamp circuit of the synchronous rectification switch tube as claimed in claim 1, wherein the voltage stabilizing unit generates a stable voltage before the power supply voltage reaches a threshold value, and triggers the clamp unit to conduct; the enabling unit controls the clamping unit to be switched off when the power supply voltage reaches a threshold value.
3. The clamping circuit of the synchronous rectification switching tube according to claim 1, wherein the current limiting unit comprises: current-limiting resistor and freewheeling diode, wherein:
the first end of the current limiting resistor is coupled with the input end of the current limiting unit, and the second end of the current limiting resistor is coupled with the anode of the fly-wheel diode;
and the cathode of the freewheeling diode is coupled with the input end of the voltage stabilizing unit.
4. The clamping circuit of a synchronous rectification switching tube according to claim 1, wherein the voltage stabilizing unit comprises: a holding capacitor and a zener diode, wherein:
the first end of the maintaining capacitor is coupled with the input end of the voltage stabilizing unit, and the second end of the maintaining capacitor is grounded; and the anode of the voltage stabilizing diode is coupled with the second end of the maintaining capacitor, and the cathode of the voltage stabilizing diode is coupled with the output end of the voltage stabilizing unit.
5. The clamping circuit of a synchronous rectifier switching tube according to claim 1, wherein said clamping unit comprises: a first NMOS transistor; the grid electrode of the first NMOS tube is coupled with the output end of the voltage stabilizing unit and the output end of the enabling unit, the source electrode of the first NMOS tube is grounded, and the drain electrode of the first NMOS tube is coupled with the grid electrode of the synchronous rectification switch tube.
6. The clamp circuit of a synchronous rectifier switching tube according to claim 1, wherein the enabling unit comprises: the enable circuit and the second NMOS tube; the input end of the enabling circuit is coupled with the input end of the enabling unit, and the output end of the enabling circuit is coupled with the grid electrode of the second NMOS tube; and the drain electrode of the second NMOS tube is coupled with the output end of the enabling unit, and the source electrode of the second NMOS tube is grounded.
7. A driver circuit for a power conversion power supply, comprising: the clamping circuit of the synchronous rectification switching tube, a starting comparator, a switching-off comparator, a logic control unit and a driving unit according to any one of claims 1 to 6, wherein:
the first input end of the starting comparator inputs the secondary side port voltage, the second input end of the starting comparator inputs the first reference voltage, and the secondary side port voltage is compared with the first reference voltage to obtain a starting signal; the secondary side port voltage is a second port voltage of the secondary side winding;
the first input end of the turn-off comparator inputs the secondary side port voltage, the second input end of the turn-off comparator inputs a second reference voltage, and the secondary side port voltage and the second reference voltage are compared to obtain a turn-off signal;
the logic control unit inputs the turn-on signal and the turn-off signal, and logically combines the turn-on signal and the turn-off signal to obtain a control signal;
the driving unit inputs the control signal, drives the control signal and outputs the driven control signal to the grid electrode of the synchronous rectification switching tube;
and the clamping circuit of the synchronous rectification switching tube is coupled with the grid electrode of the synchronous rectification switching tube, and controls the grid electrode voltage of the synchronous rectification switching tube to be low level before the power supply voltage does not reach a preset voltage.
8. A power conversion power supply circuit, comprising a primary side power switch tube, a rectifier bridge, a filter circuit, a transformer, an absorption circuit, a primary side power switch tube control circuit, a synchronous rectification switch tube, and a driving circuit of the power conversion power supply according to claim 7, wherein:
the rectifier bridge rectifies the input commercial power into high-voltage direct current;
the filter circuit is coupled with the rectifier bridge and used for filtering the high-voltage direct current;
the absorption circuit is coupled with the primary winding of the transformer and absorbs the leakage inductance energy of the transformer so as to reduce the voltage peak value when the primary power switch tube is turned off;
the primary side power switch tube control circuit is coupled with the primary side power switch tube and is used for controlling the primary side power switch tube;
the synchronous rectification switching tube is coupled with the secondary winding of the transformer and is used for synchronously rectifying the secondary output voltage of the transformer;
and the driving circuit of the power conversion power supply is coupled with the synchronous rectification switching tube and the second end of the secondary winding of the transformer, and outputs a driving signal to the grid electrode of the synchronous rectification switching tube so as to drive the synchronous rectification switching tube.
9. The power conversion power supply circuit according to claim 8, wherein the rectifier bridge has a positive input connected to a live line of the commercial power and an inverted input connected to a ground line of the commercial power.
10. The power conversion power supply circuit according to claim 8, wherein the filter circuit is coupled between the first output terminal of the rectifier bridge and the second output terminal of the rectifier bridge, and one port of the filter circuit is grounded.
11. The power conversion power supply circuit according to claim 8, wherein the transformer comprises a first primary winding, the first primary winding being coupled to the first output terminal of the rectifier bridge; the absorption circuit includes: first diode, third resistance and third electric capacity, wherein:
the anode of the first diode is coupled to the first port of the first primary winding, and the cathode of the first diode is coupled to the first end of the third resistor and the first end of the third capacitor;
a second end of the third resistor is coupled to a second port of the first primary winding;
and a second end of the third capacitor is coupled to the second port of the first primary winding.
12. The power conversion power supply circuit according to claim 8, wherein the transformer comprises a first primary winding and a second primary winding, the first primary winding being coupled to the first output terminal of the rectifier bridge, the second primary winding being coupled to the second output terminal of the rectifier bridge; the power conversion power supply circuit further includes: first divider resistance, second divider resistance, first current source and fourth sampling resistor, wherein:
a first end of the first voltage-dividing resistor is coupled to the second output end of the rectifier bridge, and a second end of the first voltage-dividing resistor is coupled to a first end of the second voltage-dividing resistor and an input end of the primary side power switch tube control circuit;
a second end of the second voltage-dividing resistor is coupled with a first port of the second primary winding; a second port of the second primary winding is grounded;
a first end of the first current source is coupled to the first port of the first primary winding, and a second end of the first current source is coupled to the first end of the primary power switching tube;
the output end of the primary side power switching tube control circuit is coupled with the control end of the primary side power switching tube;
and a first end of the fourth sampling resistor is coupled with the second end of the primary side power switch tube and the sampling end of the primary side power switch tube control circuit, and a second end of the fourth sampling resistor is grounded.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202123383768.6U CN217741574U (en) | 2021-12-29 | 2021-12-29 | Power conversion power supply, driving circuit thereof and clamping circuit of synchronous rectification switching tube |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116760286A (en) * | 2023-08-21 | 2023-09-15 | 深圳市力生美半导体股份有限公司 | Switching power supply driving circuit and switching power supply |
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2021
- 2021-12-29 CN CN202123383768.6U patent/CN217741574U/en active Active
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116760286A (en) * | 2023-08-21 | 2023-09-15 | 深圳市力生美半导体股份有限公司 | Switching power supply driving circuit and switching power supply |
| CN116760286B (en) * | 2023-08-21 | 2024-02-02 | 深圳市力生美半导体股份有限公司 | Switching power supply driving circuit and switching power supply |
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