CN216216520U

CN216216520U - High-voltage power supply control system for synchronous rectification

Info

Publication number: CN216216520U
Application number: CN202122186722.9U
Authority: CN
Inventors: 杨潺; 冯开勇; 杨光; 刘国
Original assignee: Wuxi Botong Microelectronics Technology Co ltd
Current assignee: Wuxi Botong Microelectronics Technology Co ltd
Priority date: 2021-09-09
Filing date: 2021-09-09
Publication date: 2022-04-05
Anticipated expiration: 2031-09-09

Abstract

The utility model provides a high-voltage power supply control system for synchronous rectification, and belongs to the technical field of switching power supplies. The problem of current high voltage power supply control system structure complicacy need special device JFET, area great cost is higher, when the primary side conduction time is short, the power supply demand is not enough is solved. The technical scheme is as follows: the synchronous rectification circuit comprises a transformer T1, a power tube MN1, an output capacitor Cout and a synchronous rectification control chip. The utility model has the beneficial effects that: the charge NMOS tube is driven by the internal charge pump, the maximum charge capacity of the charge NMOS tube can be released, the rapid charge can be ensured in a short enough time, and the area of a chip is further reduced.

Description

High-voltage power supply control system for synchronous rectification

Technical Field

The utility model relates to the technical field of switching power supplies, in particular to a high-voltage power supply control system for synchronous rectification.

Background

The synchronous rectification chip is more and more widely applied in the field of ACDC switching power supplies, and the power supply of the synchronous rectification chip is high-voltage power supply in order to reduce peripheral devices and reduce cost. As shown in fig. 1, when the synchronous rectifier is turned on, the voltage across the power transistor MN1 is close to 0. When the charging tube NM1 is turned off, the voltage across the power tube will have a high voltage drop when the primary side chip is turned on. The sampling end HV and the grounding end GND of the device chip have the same high voltage, and the power supply end VCC can be stored and supplied by the voltage difference.

The existing high-voltage power supply circuit such as CN106376145 adopts a JFET and two NMOS tubes connected in series to control power supply. But has the following disadvantages: JFETs require special process requirements for process implementation while potentially increasing mask cost. 2. The Vgs voltage of the NMOS is low during charging, so that the charging current is limited, and quick charging cannot be finished in a short time. The problem that the power supply is insufficient and the work cannot be carried out under a small duty ratio (the charging time is short) due to high power (more driving power consumption) is solved. 3. When the charging current is large, the area of JFEF and two NMOS in series needs to be increased to meet the current requirement. Another high-voltage power supply circuit CN109510484, which uses JFETs and diodes to control the implementation: the first disadvantage is also present, and if the JFET clamp voltage is higher than the VCC voltage, there is a problem of not being able to turn off. The circuit does not work properly.

How to solve the above technical problems is the subject of the present invention.

SUMMERY OF THE UTILITY MODEL

The utility model aims to provide a high-voltage power supply control system for synchronous rectification, which solves the problems that the existing high-voltage power supply control system is complex in structure, needs a special device JFET, is large in area and high in cost, and is insufficient in power supply requirement when the primary side is short in conduction time.

The idea of the utility model is as follows: the utility model carries out charging control on a power supply terminal VCC through a high-voltage LDMOS charging tube NM1, generates a driving voltage VPOW through a resistor R1, a Zener tube Z1 and a high-voltage driving tube NM2 in order to drive the charging tube NM1, a capacitor C2 is used for bootstrap driving of a charging tube NM1, a diode D2 prevents the capacitor on the C2 from reversely flowing to a HV pin of a sampling terminal, an OR gate OR1 and an inverter INV1 are used for logic control of charging of the power supply terminal VCC, a UVLO comparator is used for under-voltage front control, a Vclamp comparator controls the voltage of the power supply terminal VCC, a DRV signal, and the control can be carried out only when a secondary side is turned off, the HV voltage of the sampling terminal is higher.

The utility model is realized by the following measures: a high-voltage power supply control system for synchronous rectification comprises a transformer T1, a power tube MN1, an output capacitor Cout and a synchronous rectification control chip;

the synchronous rectification control chip consists of a high-voltage power supply circuit, a switching-on and switching-off detection circuit and a logic control driving circuit;

the turn-on and turn-off detection circuit consists of a comparator COM1, a comparator COM2 and a comparator COM3, wherein two ends of the comparator COM1 and two ends of the comparator COM2 are respectively connected with a sampling end HV, a first reference Vref1 and a second reference Vref2, and are used for judging the turn-on slope of the voltage at two ends of the power tube MN 1; the two ends of the comparator COM3 are respectively connected with the sampling end HV and the grounding end GND, and the comparator COM3 is used for detecting that the voltage at the two ends approaches to 0 along with the current reduction when the power tube MN1 starts, and is used for judging the turn-off voltage at the two ends of the power tube MN 1; the input of the logic control driving circuit is a comparator COM1, a comparator COM2 and a comparator COM3, a control signal is output to a control port DRV of a power tube MN1 through logic combination, and the control signal is input into a high-voltage power supply circuit to synchronously control the charging management of the power supply circuit;

the high-voltage power supply circuit is connected with the output end VOUT through a pin of the sampling end HV, and when the power tube MN1 is closed, the voltage difference between the output end VOUT and the ground end GND supplies power to the power supply end VCC through the high-voltage power supply circuit; when the power tube MN1 is opened, the voltage difference between the output terminal VOUT and the ground terminal GND is close to 0V, at the moment, the connection with the power supply terminal VCC is cut off through a high-voltage power supply circuit, and the internal module is powered by the energy stored in the capacitor of the power supply terminal VCC.

As a further optimized scheme of the high-voltage power supply control system for synchronous rectification provided by the utility model, the driving tube NM2 of the high-voltage power supply circuit is controlled by charging, the source end of the driving tube NM2 is connected with a one-way conduction diode D1 and an external driving capacitor C1, the comparator COM compares the voltage of the power supply end VCC with the reference Vref1 by detecting, and when the voltage of the power supply end VCC is higher, the driving circuit is controlled by logic to conduct the charging tube NM 1.

As a further optimized scheme of the high-voltage power supply control system for synchronous rectification provided by the utility model, a clamp resistor R1 and a clamp tube Z1 of the high-voltage power supply circuit form a clamp circuit, the clamp circuit drives a driving tube NM2, a unidirectional conducting diode D1 and a driving capacitor C1 respectively, a hysteresis comparator COM4 and a comparator COM5 detect a power supply terminal VCC voltage, and the charging tube NM1 is controlled to be opened and closed through a logic gate OR1 and an inverter INV 1. .

In order to better achieve the object of the present invention, the present invention further provides a control method for a high voltage power supply control system for synchronous rectification, the control method comprising the steps of:

step one, when starting and not needing to charge, a clamp circuit consisting of a resistor R1 and a clamp tube Z1 controls the voltage of VGATE to be about 5V through a driving tube NM 2;

step two, when the voltage of the power supply end VCC is low during starting, and meanwhile, the capacitor on the driving capacitor C1 needs a certain time to reach a clamp point, the lower stage plate of the driving capacitor C1 is pulled to 0V through the comparator UVLO, and the power supply end VCC is charged and rises along with the voltage of VGATE;

step three, when the voltage of the power supply terminal VCC is higher than the reference voltage of the comparator UVLO, the voltage of the power supply terminal VCC is still lower than the clamp voltage and needs to be charged, and after the synchronous rectifier is turned off, the voltage of the lower stage board of the driving capacitor C1 is higher than the voltage of the power supply terminal VCC, so that the voltage of VGATE of the charging tube NM1 is the sum of the voltage of the power supply terminal VCC and the voltage of the VPOW node, the voltage of VGATE of the charging tube NM1 is the voltage of the VPOW node, and the charging tube NM1 is turned on to start charging the power supply terminal VCC.

Compared with the prior art, the utility model has the beneficial effects that:

1. the utility model can realize charging control through the high-voltage LDMOS without using a JFET.

2. According to the utility model, the NMOS is bootstrapped to drive, so that the Vgs voltage of the charging tube is raised, and the charging current is increased. Meanwhile, the area of the NMOS tube is reduced, and the cost is reduced.

3. According to the utility model, the charging path is controlled by combining the driving signal and the VCC charging threshold voltage of the power supply terminal, so that the circuit is simplified without an additional charge pump control circuit.

Drawings

The accompanying drawings, which are included to provide a further understanding of the utility model and are incorporated in and constitute a part of this specification, illustrate embodiments of the utility model and together with the description serve to explain the principles of the utility model and not to limit the utility model.

Fig. 1 is a synchronous rectification operation block diagram of the synchronous rectification high-voltage power supply control system of the utility model.

Fig. 2 is a block diagram of the VCC power supply internal structure of the synchronous rectification high-voltage power supply control system of the present invention.

Fig. 3 is a circuit operation timing diagram of the synchronous rectification high-voltage power supply control system of the utility model.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. Of course, the specific embodiments described herein are merely illustrative of the utility model and are not intended to be limiting.

Example 1

Referring to fig. 1 to fig. 3, the present invention provides a high-efficiency high-voltage power supply circuit and method, and a high-voltage power supply control system for synchronous rectification, wherein the high-voltage power supply control system comprises a transformer T1, a synchronous rectification MOS transistor NM1, an output capacitor Cout, and a synchronous rectification control chip;

the turn-on and turn-off detection circuit consists of a comparator COM1, a comparator COM2 and a comparator COM3, wherein two ends of the comparator COM1 and the comparator COM2 are respectively connected with a power supply end HV, a first reference Vref1 and a second reference Vref2, and are used for judging the turn-on slope of the voltage at two ends of the power tube MN 1; the two ends of the comparator COM3 are respectively connected with the power supply end HV and the ground end GND, and the comparator COM3 is used for detecting that the voltage at the two ends approaches to 0 along with the current reduction when the power tube MN1 starts, and is used for judging the turn-off voltage at the two ends of the power tube MN 1;

the input of the logic control driving circuit is the output of a comparator COM1, a comparator COM2 and a comparator COM3, a control signal of a power tube MN1 is output to a control port DRV of the power tube MN1 through logic combination, and the control signal is input into a high-voltage power supply circuit to synchronously control the charging management of the power supply circuit;

the high-voltage power supply circuit is connected with the output terminal VOUT through a sampling terminal HV pin, and when the power tube MN1 is closed,

the voltage difference between the output end VOUT and the ground end GND supplies power to the power supply end VCC through the high-voltage power supply circuit; when the power tube MN1 is opened, the voltage difference between the output terminal VOUT and the ground terminal GND is close to 0V, at the moment, the connection with the power supply terminal VCC is cut off through a high-voltage power supply circuit, and the internal module is powered by the energy stored in the capacitor of the power supply terminal VCC.

Preferably, the driving tube NM2 of the high-voltage power supply circuit is controlled by charging, the source end of the driving tube NM2 is connected with the one-way conduction diode D1 and the external driving capacitor C1, the comparator COM compares the VCC voltage of the power supply end with the reference Vref1 by detecting, and when the VCC voltage of the power supply end is higher, the driving tube NM1 is controlled to be conducted by the logic control driving circuit.

Preferably, the clamp resistor R1 and the clamp tube Z1 of the high-voltage power supply circuit constitute a clamp circuit, the clamp circuit drives the driving tube NM2, the unidirectional diode D1 and the driving capacitor C1 respectively, the hysteresis comparator COM4 and the comparator COM5 detect the voltage of the power supply terminal VCC, and the charging tube NM1 is controlled to be turned on and off through the logic gate OR1 and the inverter INV 1.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the utility model, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims

1. A high-voltage power supply control system for synchronous rectification is characterized by comprising a transformer T1, a power tube MN1, an output capacitor Cout and a synchronous rectification control chip;

the turn-on and turn-off detection circuit consists of a comparator COM1, a comparator COM2 and a comparator COM3, wherein two ends of the comparator COM1 and two ends of the comparator COM2 are respectively connected with a sampling end HV, a first reference Vref1 and a second reference Vref2, and are used for judging the turn-on slope of the voltage at two ends of the power tube MN 1; the two ends of the comparator COM3 are respectively connected with the sampling end HV and the grounding end GND, and the comparator COM3 is used for detecting that the voltage at the two ends approaches to 0 along with the current reduction when the power tube MN1 starts, and is used for judging the turn-off voltage at the two ends of the power tube MN 1;

the input of the logic control driving circuit is a comparator COM1, a comparator COM2 and a comparator COM3, a control signal is output to a control port DRV of a power tube MN1 through logic combination, and the control signal is input into a high-voltage power supply circuit to synchronously control the charging management of the power supply circuit;

2. The high voltage power supply control system for synchronous rectification according to claim 1, wherein the driving transistor NM2 of the high voltage power supply circuit is used for charge control, and its source terminal is connected to a unidirectional conducting diode D1 and an external driving capacitor C1, the comparator COM compares the VCC voltage of the power supply terminal with a reference Vref1, and when the VCC voltage of the power supply terminal is higher, the conduction of the charging transistor NM1 is controlled by the logic control driving circuit.

3. The high-voltage power supply control system for synchronous rectification according to claim 2, wherein a clamp resistor R1 and a clamp tube Z1 of the high-voltage power supply circuit constitute a clamp circuit, the clamp circuit drives a driving tube NM2, a unidirectional diode D1 and a driving capacitor C1 respectively, a hysteresis comparator COM4 and a comparator COM5 detect a power supply terminal VCC voltage, and the charging tube NM1 is controlled to be turned on and off through a logic gate OR1 and an inverter INV 1.