Secondary side bridge type synchronous rectification driving control circuit and switching power supply

Abstract

The utility model discloses a secondary side bridge type synchronous rectification driving control circuit and a switching power supply, the driving control circuit is applied to the switching power supply with a secondary side being a bridge type synchronous rectification module, and the driving control circuit comprises an enabling voltage stabilization power supply module and a driving control module; the driving control module is used for accessing a driving control signal and generating a driving signal according to the driving control signal to control the synchronous rectification module; and the enabling voltage-stabilizing power supply module is used for supplying power to the driving control module when the switching power supply works normally, and cutting off output when the switching power supply triggers input under-voltage protection or remote control cut-off under a no-load working condition, so that the voltage of the power supply input end of the driving control module is lowered. The problem that due to the fact that the leakage current of the drive control module is large, the output voltage of the switching power supply is high in input under-voltage turn-off and remote control turn-off under the no-load working condition is solved.

Description

Technical Field

[0001] The utility model relates to a switching power supply, in particular to a synchronous rectification drive control circuit applied to a secondary side of the switching power supply and the switching power supply. Background Art

[0002] In all switching power converter secondary bridge synchronous rectification circuits, the synchronous rectifiers on the secondary side need to be driven by high- and low-side driver chips. The high-side reference terminals of the high- and low-side driver chips are the source terminals of the upper tubes on the bridge arms. Therefore, the withstand voltage of the high-side reference pins of the high- and low-side driver chips needs to be greater than or equal to the voltage stress of the secondary synchronous rectifiers. In low-voltage output switching power supplies, due to the reverse recovery caused by transformer leakage inductance and high output current, the voltage stress spikes of the secondary synchronous rectifiers will be very high. Therefore, high- and low-side driver chips with higher withstand voltage levels are required to meet reliability requirements.

[0003] The existing high-side and low-side driver chips with a high withstand voltage level have a large static operating current at the high-side power supply end, generally reaching several hundred microamperes. This results in the output voltage still floating high when the switching power supply is shut down by input undervoltage or remote control under no-load conditions, although the drive signal is turned off. This voltage is actually provided by the power supply end of the drive control module. The existing solution is mainly to power the drive control chip by sampling or coupling the output voltage. Since the input voltage range of the existing drive control chip is relatively narrow, this method is suitable for switching power supplies with a narrow adjustable output voltage range. In addition, the coupling solution adds an extra winding, especially for planar transformers that are designed with the same board as the control circuit PCB. The design of adding a winding to the planar transformer will reduce the utilization rate of the PCB, making it difficult for the product design to meet the high power density requirements. Utility Model Content

[0004] In response to the problems existing in the related technology, the utility model discloses a secondary side bridge synchronous rectification drive control circuit and a switching power supply. By enabling and controlling the power supply of the high-side reference pins of the high-side and low-side driver chips, the switching power supply can be completely shut down when the input undervoltage is shut down under no-load conditions and the product is completely shut down when remote control is shut down.

[0005] To achieve the above purpose, the technical solution provided by the utility model is as follows:

[0006] In a first aspect, a secondary-side bridge synchronous rectification drive control circuit is provided. The drive control circuit is applied to a switching power supply with a bridge synchronous rectification module on the secondary side, and includes a signal control module, an enable voltage-stabilizing power supply module, a drive control module, and a synchronous rectification module; the signal control module generates a drive control signal as an input signal of the drive control module, controls the secondary-side drive control module to generate a drive signal to control the secondary-side synchronous rectification module; and simultaneously generates an enable control signal as an input signal of the enable voltage-stabilizing power supply module, controls the enable voltage-stabilizing power supply module to supply power to the drive control module.

[0007] Preferably, the enabling voltage-stabilized power supply module includes capacitor C2, capacitor C3, capacitor C4, resistor R9, resistor R10, and a voltage-stabilized power supply chip U1; pins 1 and 2 of the voltage-stabilized power supply chip U1 are connected to one end of capacitor C2 as the power input end of the chip; the connection points of pins 3 and 4 of the voltage-stabilized power supply chip U1 and one end of resistor R9, one end of capacitor C3, and one end of capacitor C4 are used as the output end of the enabling voltage-stabilized power supply module, and are connected to the power input end of the drive control module; pin 6 of the voltage-stabilized power supply chip U1 is connected to the other end of resistor R9, the other end of capacitor C3, and one end of resistor R10 as a voltage reference pin; pin 7 of the voltage-stabilized power supply chip U1 is connected to the other end of capacitor C2, the other end of resistor R10, and the other end of capacitor C4 as the reference ground of the voltage-stabilized power supply chip U1; pin 8 of the voltage-stabilized power supply chip U1 is used as the enable control pin of the chip, and is used to access the enable control signal LDO_EN.

[0008] Preferably, when the switching power supply operates normally, the enable control signal LDO_EN is at a high level, and when the switching power supply triggers input undervoltage protection or remote control shutdown under no-load conditions, the enable control signal LDO_EN is at a low level.

[0009] Preferably, the drive control signal includes PWM 1A and PWM 0A; the drive control module includes a diode D1, a diode D2, a diode D3, a capacitor C5, a capacitor C6, a resistor R11, a resistor R12, and a drive control chip U2; the connection point between pin 1 of the drive control chip U2 and one end of the capacitor C5 and the anode of the diode D1 is connected to the output end of the enable voltage-stabilized power supply module as the power input end of the drive control chip U2; pins 2 and 3 of the drive control chip U2 are connected to PWM 1A and PWM 0A as the signal input ends of the chip, respectively. 0A; Pins 4, 5 and 11 of the drive control chip U2 are connected to the other end of the capacitor C5 as the reference ground of the chip; Pin 6 of the drive control chip U2 is connected to the cathode of the diode D3 and one end of the resistor R12 as the low-side output end of the chip; the anode of the diode D3 and the other end of the resistor R12 are used as the low-side output end of the drive control module to be connected to the control end of the low-side switch tube of the synchronous rectification module; Pin 9 of the drive control chip U2 is connected to the cathode of the diode D2 and one end of the resistor R11 as the high-side output end of the chip; the anode of the diode D2 and the other end of the resistor R11 are used as the high-side output end of the drive control module to be connected to the switch tube of the high-side switch tube of the synchronous rectification module; the connection point between Pin 8 of the drive control chip U2 and one end of the capacitor C6 is connected to the middle point of the bridge arm of the synchronous rectification module as the high-side reference end of the drive control module; Pin 10 of the drive control chip U2 is connected to the cathode of the diode D1 and the other end of the capacitor C6 as the high-side power supply end of the chip.

[0010] In a second aspect, a switching power supply is provided, comprising a primary circuit, a transformer, a secondary bridge synchronous rectification module and the secondary synchronous rectification drive control circuit as described above.

[0011] Compared with the prior art, the utility model has the following improvements:

[0012] 1. The utility model can effectively control the power supply of the secondary side drive control module, thereby ensuring that the switching power supply is completely shut down when the input is undervoltage shut down under no-load conditions and the output voltage is completely shut down when the remote control is shut down, and the performance of the switching power supply is further improved.

[0013] 2. The utility model simplifies the implementation scheme of the synchronous rectification drive circuit by optimizing the existing synchronous rectification drive circuit scheme, and effectively improves the power density of the high-power power supply.

[0014] 3. The utility model is suitable for switching power supply products with a wide output voltage range by optimizing the existing synchronous rectification drive circuit solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a control block diagram of the secondary side bridge type synchronous rectification drive circuit of the utility model;

[0016] Figure 2 A specific circuit diagram of the secondary side bridge type synchronous rectification driving circuit of the utility model applied to a switching power supply;

[0017] Figure 3 It is the output signal of the signal control module of the utility model. DETAILED DESCRIPTION

[0018] The following is a more clear and complete description of the technical solution of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0019] Figure 1 This is the control block diagram of the secondary side bridge synchronous rectification drive control circuit of the utility model. Figure 2 This is a specific implementation principle diagram of the secondary bridge synchronous rectification drive control circuit of the utility model applied to a switching power supply. The switch power supply applied to the bridge synchronous rectification module, the drive control circuit includes an enabling voltage stabilization power supply module and a drive control module.

[0020] The signal control module generates a drive control signal as an input signal of the drive control module, controls the secondary side drive control module to generate a drive signal to control the secondary side synchronous rectification module; and at the same time generates an enable control signal as an input signal of the enable voltage regulated power supply module, controls the enable voltage regulated power supply module to supply power to the drive control module.

[0021] like Figure 2 As shown, the enabling voltage-stabilized power supply module includes capacitor C2, capacitor C3, capacitor C4, resistor R9, resistor R10, and a voltage-stabilized power supply chip U1; pins 1 and 2 of the voltage-stabilized power supply chip U1 are connected to one end of the capacitor C2 as the power input end of the chip; the connection points of pins 3 and 4 of the voltage-stabilized power supply chip U1 and one end of the resistor R9, one end of the capacitor C3, and one end of the capacitor C4 are used as the output end of the enabling voltage-stabilized power supply module, and are connected to the power input end of the drive control module; pin 6 of the voltage-stabilized power supply chip U1 is connected to the other end of the resistor R9, the other end of the capacitor C3, and one end of the resistor R10 as the voltage reference pin; pin 7 of the voltage-stabilized power supply chip U1 is connected to the other end of the capacitor C2, the other end of the resistor R10, and the other end of the capacitor C4 as the reference ground of the voltage-stabilized power supply chip U1; pin 8 of the voltage-stabilized power supply chip U1 is used as the enable control pin of the chip, and is connected to the enable control signal LDO_EN output by the signal control module.

[0022] Specifically, when the switching power supply operates normally, the enable control signal LDO_EN is at a high level, and when the switching power supply triggers input undervoltage protection or remote control shutdown under no-load conditions, the enable control signal LDO_EN is at a low level.

[0023] The drive control module includes a diode D1, a diode D2, a diode D3, a capacitor C5, a capacitor C6, a resistor R11, a resistor R12, and a drive control chip U2; the connection point between pin 1 of the drive control chip U2 and one end of the capacitor C5 and the anode of the diode D1 is used as the power input end of the drive control chip U2 and is connected to the output end of the enable voltage-stabilized power supply module; pins 2 and 3 of the drive control chip U2 are used as the signal input ends of the chip and are respectively connected to the output signals PWM 1A and PWM 1A of the signal control module. 0A is connected; the 4th, 5th and 11th pins of the drive control chip U2 are connected to the other end of the capacitor C5 as the reference ground of the chip; the 6th pin of the drive control chip U2 is connected to the cathode of the diode D3 and one end of the resistor R12 as the low-side output end of the chip; the anode of the diode D3 and the other end of the resistor R12 are connected to the input signal G2 (the control end of the low-side switch tube) of the synchronous rectifier module as the low-side output end of the drive control module; the 9th pin of the drive control chip U2 is connected to the cathode of the diode D2 and one end of the resistor R11 as the high-side output end of the chip; the anode of the diode D2 and the other end of the resistor R11 are connected to the input signal G1 (the control end of the high-side switch tube) of the synchronous rectifier module as the high-side output end of the drive control module; the connection point between the 8th pin of the drive control chip U2 and one end of the capacitor C6 is connected to the middle point of the bridge arm of the synchronous rectifier module as the high-side reference end of the drive control module; the 10th pin of the drive control chip U2 is connected to the cathode of the diode D1 and the other end of the capacitor C6 as the high-side power supply end of the chip.

[0024] Specifically, Figure 2 As shown, the switching power supply includes a primary circuit, a transformer and a secondary bridge synchronous rectification module. The primary circuit includes a switch tube TR1, a switch tube TR2, a switch tube TR3, a switch tube TR4, a resistor R1, a resistor R2, a resistor R3, and a resistor R4. The secondary bridge synchronous rectification module includes a switch tube TR5 (a high-side switch tube), a switch tube TR6 (a low-side switch tube), a switch tube TR7, a switch tube TR8, a resistor R5, a resistor R6, a resistor R7, a resistor R8, an inductor L1 and a capacitor C1. The specific connection relationship is as follows: Figure 2 As shown, no further description is given here.

[0025] The specific working process of the circuit is as follows:

[0026] like Figure 3As shown, the signal control module generates PWM 0A / PWM 1A control signals and transmits them to the LI / HI signal input port of the driver control chip U2. When the LI signal input port of the driver control chip U2 receives a high level, the LO drive output port of the driver control chip U2 outputs a high level, and provides a drive signal to the gate of the switch tube TR6 through the resistor R12. At this time, the switch tube TR6 is turned on, and its drain level is pulled to the reference ground. Similarly, the level of the high-side reference terminal SW of the driver control chip is also pulled to the reference ground. At this time, the capacitor C6 is charged through the diode D1 to provide driving energy for the switch tube TR5 to turn on. When the HI signal input port of the driver control chip receives a high level, the HO drive output port of the driver control chip outputs a high level, and the energy stored in the capacitor C6 provides driving energy to the gate of the switch tube TR5 through the resistor R11. When the LI / HI signal input port of the driver control chip receives a low level, the LO / HO drive output port of the driver control chip outputs a low level, and the gate drive charge of the switch tube TR6 / TR5 is quickly discharged through the diode D3 / D2.

[0027] The enable voltage-stabilized power supply module configures a suitable output voltage through the internal reference and external resistors R9 and R10 to supply power to the drive control module. The signal control module generates an enable control signal LDO_EN, which is transmitted to the enable pin EN of the enable voltage-stabilized power supply module; when the switching power supply is working normally, the signal control module generates a high-level enable control signal LDO_EN, which enables the enable voltage-stabilized power supply module to supply power to the drive control module normally; when the switching power supply triggers input undervoltage protection or remote control shutdown under no-load conditions, the signal control module generates a low-level enable control signal LDO_EN, which enables the enable voltage-stabilized power supply module to be shut down, thereby lowering the voltage at the power input end of the drive control module, and avoiding the problem of high output voltage when the switching power supply is turned off when the no-load drive signal is turned off.

[0028] The above are only preferred embodiments of the present invention. It should be pointed out that the above preferred embodiments should not be regarded as limitations of the present invention. For technicians in this technical field, several improvements and modifications can be made without departing from the spirit and scope of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention. The embodiments will not be repeated here. The protection scope of the present invention should be based on the scope defined by the claims.

Claims

1. A secondary side bridge synchronous rectification drive control circuit, applied to a switching power supply with a bridge synchronous rectification module as the secondary side, characterized in that: The drive control circuit includes an enabling voltage-stabilized power supply module and a drive control module; The drive control module is used to access the drive control signal and generate a drive signal according to the drive control signal to control the synchronous rectification module; the enabling voltage stabilizing power supply module is used to supply power to the drive control module when the switching power supply is working normally, and when the switching power supply triggers input undervoltage protection or remote control shutdown under no-load conditions, the output is shut down, thereby lowering the voltage at the power input end of the drive control module.

2. The secondary side bridge synchronous rectification drive control circuit according to claim 1, characterized in that: The enabling voltage-stabilized power supply module includes capacitor C2, capacitor C3, capacitor C4, resistor R9, resistor R10, and a voltage-stabilized power supply chip U1; pins 1 and 2 of the voltage-stabilized power supply chip U1 are connected to one end of the capacitor C2 as the power input end of the chip; the connection points of pins 3 and 4 of the voltage-stabilized power supply chip U1 and one end of the resistor R9, one end of the capacitor C3, and one end of the capacitor C4 are used as the output end of the enabling voltage-stabilized power supply module, and are connected to the power input end of the drive control module; pin 6 of the voltage-stabilized power supply chip U1 is connected to the other end of the resistor R9, the other end of the capacitor C3, and one end of the resistor R10 as a voltage reference pin; pin 7 of the voltage-stabilized power supply chip U1 is connected to the other end of the capacitor C2, the other end of the resistor R10, and the other end of the capacitor C4 as the reference ground of the voltage-stabilized power supply chip U1; pin 8 of the voltage-stabilized power supply chip U1 is used as the chip enable control pin, which is used to access the enable control signal LDO_EN.

3. The secondary side bridge synchronous rectification drive control circuit according to claim 2, characterized in that: When the switching power supply operates normally, the enable control signal LDO_EN is at a high level. When the switching power supply triggers input undervoltage protection or remote control shutdown under no-load conditions, the enable control signal LDO_EN is at a low level.

4. The secondary side bridge synchronous rectification drive control circuit according to claim 1, characterized in that: The drive control signal includes PWM 1A and PWM 0A; the drive control module includes a diode D1, a diode D2, a diode D3, a capacitor C5, a capacitor C6, a resistor R11, a resistor R12, and a drive control chip U2; the connection point between the 1st pin of the drive control chip U2 and one end of the capacitor C5 and the anode of the diode D1 is connected to the output end of the enable voltage-stabilized power supply module as the power input end of the drive control chip U2; the 2nd and 3rd pins of the drive control chip U2 are connected to the PWM 1A and PWM 0A respectively as the signal input ends of the chip 0A; Pins 4, 5 and 11 of the drive control chip U2 are connected to the other end of the capacitor C5 as the reference ground of the chip; Pin 6 of the drive control chip U2 is connected to the cathode of the diode D3 and one end of the resistor R12 as the low-side output end of the chip; the anode of the diode D3 and the other end of the resistor R12 are used as the low-side output end of the drive control module to be connected to the control end of the low-side switch tube of the synchronous rectification module; Pin 9 of the drive control chip U2 is connected to the cathode of the diode D2 and one end of the resistor R11 as the high-side output end of the chip; the anode of the diode D2 and the other end of the resistor R11 are used as the high-side output end of the drive control module to be connected to the switch tube of the high-side switch tube of the synchronous rectification module; the connection point between Pin 8 of the drive control chip U2 and one end of the capacitor C6 is connected to the middle point of the bridge arm of the synchronous rectification module as the high-side reference end of the drive control module; Pin 10 of the drive control chip U2 is connected to the cathode of the diode D1 and the other end of the capacitor C6 as the high-side power supply end of the chip.

5. A switching power supply, characterized in that: It comprises a primary circuit, a transformer, a secondary bridge synchronous rectification module and a secondary bridge synchronous rectification drive control circuit as described in any one of claims 1 to 4.

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