CN211859934U

CN211859934U - Bootstrap capacitor charging circuit

Info

Publication number: CN211859934U
Application number: CN202020796509.2U
Authority: CN
Inventors: 高红波; 黄必亮
Original assignee: Joulwatt Technology Hangzhou Co Ltd
Current assignee: Joulwatt Technology Co Ltd
Priority date: 2020-05-14
Filing date: 2020-05-14
Publication date: 2020-11-03
Anticipated expiration: 2030-05-14

Abstract

The utility model provides a bootstrap capacitor charging circuit, the charging circuit includes one-way conduction circuit and current-limiting circuit, the one-way conduction circuit and current-limiting circuit are connected in series; the supply voltage charges the bootstrap capacitor through the charging circuit, and the current limiting circuit limits the charging current of the bootstrap capacitor. The utility model discloses avoid bootstrapping electric capacity charging current to flow the body diode in the one-way conduction circuit to avoid the influence that the body diode parasitic effect brought.

Description

Bootstrap capacitor charging circuit

Technical Field

The utility model relates to a power electronics field, in particular to bootstrap capacitor charging circuit.

Background

FIG. 1 illustrates a schematic diagram of a prior art switching power supply, wherein a supply voltage VDD is supplied to a switching power supply driving circuit through two MOS tubes connected in series; however, when the synchronous rectifier M1 is turned on, the voltage at SW is pulled down to be less than zero, so that the voltage at the high potential of the bootstrap capacitor C0 is pulled down, and thus the voltage difference between the input terminal and the positive electrode of the bootstrap capacitor C0 is large, which causes leakage current to flow through the body diode of the main switch M2. Leakage current flowing through the body diode can affect circuit performance due to parasitic effects of the body diode.

SUMMERY OF THE UTILITY MODEL

The utility model aims at providing an avoid leaking current and flow through body diode's bootstrap capacitor charging circuit for solve the problem that the parasitic effect that the leakage current that prior art exists flows through body diode and brings.

In order to achieve the above object, the present invention provides a bootstrap capacitor charging circuit, which comprises a unidirectional conducting circuit and a current limiting circuit, wherein the unidirectional conducting circuit is connected in series with the current limiting circuit; the power supply voltage charges the bootstrap capacitor through the charging circuit, and the current limiting circuit limits the charging current of the bootstrap capacitor;

optionally, when the main power tube of the switching power supply is turned off, the current limiting circuit is turned off, and when the turn-off time reaches the first time, the current limiting circuit is turned on.

Optionally, when the main power tube of the switching power supply is turned off, the current limiting circuit is turned off; when the voltage of the high potential end of the bootstrap capacitor or the voltage of the low potential end of the bootstrap capacitor reaches a corresponding threshold value, the current limiting circuit is conducted.

Optionally, the current limiting circuit includes a switching tube, and the switching tube is connected to the unidirectional conducting circuit; when a main power tube of the switching power supply is turned off, the switching tube is turned off, and when the turn-off time reaches the first time, the switching tube is turned on.

Optionally, the unidirectional circuit includes two MOS transistors, and body diodes of the two MOS transistors are connected in series in an inverse direction.

Optionally, the two MOS transistors are both PMOS transistors.

Optionally, the two MOS transistors are NMOS transistors.

Optionally, one of the two MOS transistors is an NMOS transistor, and the other is a PMOS transistor.

Compared with the prior art, the utility model has the advantages of it is following: the utility model is based on a one-way conduction circuit and a current-limiting circuit, wherein the one-way conduction circuit is connected in series with the current-limiting circuit; the power supply voltage charges the bootstrap capacitor through the one-way conduction circuit and the current limiting circuit, and the current limiting circuit limits the charging current of the bootstrap capacitor. When a main power tube of the switching power supply is turned off, the current limiting circuit is turned off, and when the turn-off time reaches the first time or the voltage at one end of the bootstrap capacitor reaches the corresponding threshold voltage, the current limiting circuit is turned on. The utility model discloses can avoid bootstrapping electric capacity charging current to flow the body diode in the one-way conduction circuit to avoid the influence that the body diode parasitic effect brought.

Drawings

FIG. 1 is a schematic diagram of a prior art switching power supply;

FIG. 2 is a schematic diagram of a bootstrap capacitor charging circuit of the present invention;

FIG. 3 is a schematic diagram of a real-time embodiment II of the unidirectional conducting circuit of the present invention;

FIG. 4 is a diagram of three schematic diagrams of a real-time embodiment of the unidirectional conducting circuit of the present invention;

FIG. 5 is a schematic diagram of a real-time embodiment of a unidirectional conducting circuit of the present invention;

Detailed Description

The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but the present invention is not limited to only these embodiments. The present invention covers any alternatives, modifications, equivalents, and alternatives falling within the spirit and scope of the present invention.

In the following description of the preferred embodiments of the present invention, specific details are set forth in order to provide a thorough understanding of the present invention, and it will be apparent to those skilled in the art that the present invention may be practiced without these specific details.

The invention is described in more detail in the following paragraphs by way of example with reference to the accompanying drawings. It should be noted that the drawings are simplified and in non-precise proportion, so as to facilitate and clearly assist in explaining the embodiments of the present invention.

As shown in fig. 2, the utility model discloses bootstrap capacitor charging circuit schematic diagram, including current-limiting circuit, one-way conduction circuit, current-limiting circuit and one-way conduction circuit connection, supply voltage VDD charges for switching power supply's bootstrap capacitor C0 through current-limiting circuit and one-way conduction circuit. The current limiting circuit comprises a switching tube M0, a driving circuit U01 and a timing circuit U02. When the main power tube of the switching power supply is turned off, the voltage of the high potential end of the bootstrap capacitor is pulled down, the conduction voltage drop of the unidirectional conduction circuit is increased, and parasitic oscillation can occur for a period of time due to the influence of the parasitic capacitor of the unidirectional conduction circuit. Therefore, when the main power tube of the switching power supply is turned off, the switching tube M0 is controlled to be turned off, and when the turn-off time reaches a first time or the voltage at one end of the bootstrap capacitor reaches a corresponding threshold, the switching tube M0 is controlled to be turned on.

The unidirectional turn-on circuit in this embodiment includes 2 NMOS transistors M1, M2, the body diodes of the two NMOS transistors are connected in series in reverse, the drain of one of the NMOS transistors M1 is connected to the gates of the two NMOS transistors, the drain of the NMOS transistor M1 is the positive electrode of the unidirectional turn-on circuit, and the drain of the other NMOS transistor M2 is the negative electrode of the unidirectional turn-on circuit.

As shown in fig. 3, the second schematic diagram of the embodiment of the unidirectional conducting circuit of the present invention is illustrated, including two PMOS transistors M1, M2 connected in series with two diodes, wherein the drain of one PMOS transistor M2 is connected to the gates of two PMOS transistors, the drain of this PMOS transistor M2 is the negative electrode of the unidirectional conducting circuit, and the drain of the other MOS transistor M1 is the positive electrode of the unidirectional conducting circuit.

As shown in fig. 4, the utility model discloses a three principle pictures of unidirectional current conducting circuit embodiment, including a PMOS pipe M1 and an NMOS pipe M2, the body diode reverse series connection of two MOS pipes, NMOS pipe M2's grid is connected to PMOS pipe M1's drain electrode, and its drain electrode and NMOS pipe M2's source electrode are connected to PMOS pipe M1's grid, and PMOS pipe M1 source electrode is the unidirectional current conducting circuit positive pole, and NMOS pipe M2 drain electrode is the unidirectional current conducting circuit negative pole.

As shown in fig. 5, the four schematic diagrams of the unidirectional conducting circuit embodiment of the present invention are illustrated, including a PMOS transistor M1 and an NMOS transistor M2, the body diode reverse series connection of two MOS transistors, the source electrode of the NMOS transistor M2 is connected to the gate electrode of the PMOS transistor M1, the gate electrode and the drain electrode of the NMOS transistor M2 are connected to the source electrode of the PMOS transistor M1, the drain electrode of the PMOS transistor M1 is the unidirectional conducting circuit anode, and the source electrode of the NMOS transistor M2 is the cathode of the unidirectional conducting circuit.

Persons of ordinary skill in the art will recognize that substitutions and integrations between embodiments may be made without reference to any explicitly recited embodiment.

The above-described embodiments do not limit the scope of the present invention. Any modification, equivalent replacement, and improvement made within the spirit and principle of the above-described embodiments should be included in the protection scope of the technical solution.

Claims

1. A bootstrap capacitor charging circuit, comprising: the power supply comprises a one-way conduction circuit and a current limiting circuit, wherein the one-way conduction circuit is connected with the current limiting circuit in series; the power supply voltage charges the bootstrap capacitor through the charging circuit, and the current limiting circuit limits the charging current of the bootstrap capacitor; the bootstrap capacitor is used for supplying power to a driving circuit on the switching power supply, and the switching power supply receives input voltage.

2. The bootstrap capacitor charging circuit of claim 1, wherein: when the main power tube of the switching power supply is turned off, the current limiting circuit is turned off, and when the turn-off time reaches the first time, the current limiting circuit is turned on.

3. The bootstrap capacitor charging circuit of claim 1, wherein: when a main power tube of the switching power supply is turned off, the current limiting circuit is turned off; when the voltage of the high potential end of the bootstrap capacitor or the voltage of the low potential end of the bootstrap capacitor reaches a corresponding threshold value, the current limiting circuit is conducted.

4. A bootstrap capacitor charging circuit as claimed in claim 2 or 3, characterized in that: the current limiting circuit comprises a switching tube, and the switching tube is connected with the one-way conduction circuit; when a main power tube of the switching power supply is turned off, the switching tube is turned off, and when the turn-off time reaches the first time, the switching tube is turned on.

5. The bootstrap capacitor charging circuit of claim 4, wherein: the unidirectional conduction circuit comprises two MOS tubes, and body diodes of the two MOS tubes are connected in series in a reverse direction.

6. The bootstrap capacitor charging circuit of claim 5, wherein: and the two MOS tubes are PMOS tubes.

7. The bootstrap capacitor charging circuit of claim 5, wherein: the two MOS tubes are NMOS tubes.

8. The bootstrap capacitor charging circuit of claim 5, wherein: one of the two MOS tubes is an NMOS tube, and the other MOS tube is a PMOS tube.