CN203774776U - Surge current suppression circuit and power supply circuit with same - Google Patents

Abstract

The utility model discloses a surge current suppressing circuit, which comprises: a resistor R1 and a resistor R2 connected in series between the live wire and the neutral wire of an AC input power supply; a capacitor branch connected in parallel with the resistor R1; The common terminal and the source of R2 are connected to the fire wire of the AC input power supply, and the drain is used as the output terminal of the MOS transistor Q1; the resistor R5 is connected between the source and the drain of the MOS transistor Q1. The utility model also discloses a power supply circuit with a surge current suppression circuit. The utility model is turned on by delaying the MOS transistor Q1, and when the MOS transistor Q1 is turned on, the current is controlled within the range of the allowable value through the resistor R5, thereby achieving the purpose of suppressing the surge current when the power circuit is started, and has a simple circuit structure , High reliability, suitable for high-power power supply circuits and frequent switching power supply circuits.

Description

Surge current suppression circuit and power supply circuit with surge current suppression

technical field

The utility model relates to a power supply circuit, in particular to a surge current suppression circuit and a power supply circuit with the surge current suppression circuit

Background technique

Inrush current refers to the peak current flowing into electronic equipment at the moment when the power is turned on.

FIG. 1 is a schematic structural diagram of an existing DC power supply. After the input AC power U _in is filtered by the filter circuit, the required voltage amplitude is obtained through the step-down circuit, and then the DC power U _out is output through the rectification circuit. Wherein, the filter circuit can be a filter capacitor, an RC filter circuit or even a more complex combination. However, when the AC input power supply U _in is turned on, the filter capacitor in the filter circuit is charged rapidly, so the peak current is far greater than the steady-state input current, that is, a surge current is generated. The surge current not only shortens the life of the filter capacitor, but also has a great impact on the rectifier bridge and fuse of the rectifier circuit, and also destroys the quality of power supply of the grid, causing serious electromagnetic interference to affect the electrical equipment of the same grid.

In order to eliminate the surge generated at the moment when the power is turned on, the existing traditional circuit for suppressing the surge current is to connect a suitable power type negative temperature coefficient thermistor or/and pre-filter circuit in series before the rectifier circuit, such as CN201320430852 .5 The technical solution disclosed in the Chinese patent application. The thermistor has a relatively large resistance value under normal conditions. When the power is turned on, the thermistor limits the charging current to the filter capacitor, thereby suppressing the surge current, and the resistance value of the thermistor becomes smaller after heating, so as to Reduce the power consumption of the resistor itself and reduce the influence of the circuit.

But there is following technical defect in this technical scheme:

1. The existing series-connected thermistors are only suitable for low-power power supply circuits, and high-power power supply circuits need multiple parallel and series connections. In high-power power supply circuits, the surge current is often not well suppressed.

2. The thermistor has a certain cooling time constant. The larger the cooling time constant, the longer the recovery time required, and vice versa. The thermistor must completely recover from the high temperature and low resistance state to the normal temperature and high resistance state. The same surge suppression effect as last time is achieved, so thermistors are not suitable for power circuits with frequent switching.

Utility model content

In order to overcome the deficiencies of the prior art, the utility model proposes a surge current suppression circuit with simple circuit structure and high reliability and a power supply circuit with surge current suppression. The surge current suppression circuit is suitable for high-power power supply circuits And frequent switching power supply circuit.

The utility model is realized by adopting the following technical solutions: a surge current suppression circuit, which includes: a resistor R1 and a resistor R2 connected in series between the live wire and the neutral wire of the AC input power supply; a capacitor branch connected in parallel with the resistor R1; Connect the common end of the resistor R1 and the resistor R2, the source is connected to the fire wire of the AC input power supply, and the drain is used as the output terminal of the MOS transistor Q1; the resistor R5 is connected between the source and the drain of the MOS transistor Q1.

Wherein, the suppression circuit further includes a resistor R3 and a resistor R4 connected in series between the live wire and the neutral wire of the AC input power supply, and the resistor R3 is connected in parallel with the resistor R1, and the resistor R4 is connected in parallel with the resistor R2.

Wherein, the capacitance branch includes a capacitor C1 and a capacitor C2 connected in series.

Wherein, the MOS transistor Q1 is a P-type MOS transistor.

Wherein, the resistance value of the resistor R5 is greater than or equal to the AC input power divided by the maximum start-up surge current allowed by the power circuit.

In addition, the utility model also discloses a power supply circuit with surge current suppression, which includes a surge current suppression circuit, a step-down circuit, a rectifier circuit and a lightning protection circuit connected in sequence, wherein the surge current suppression circuit includes: Resistor R1 and resistor R2 between live wire and neutral wire of AC input power supply, capacitor branch connected in parallel with resistor R1; gate connected to common end of resistor R1 and resistor R2, source connected to live wire and drain of AC input power supply MOS transistor Q1 of the step-down circuit; resistor R5 connected between the source and drain of the MOS transistor Q1.

Among them, the lightning protection circuit includes: a capacitor C3 connected between the two output terminals of the rectifier circuit; a bipolar gas discharge tube Q1 and a transient suppression diode TVS1 connected between the positive output terminal of the rectifier circuit and the ground; The variable resistor R9 between the gas discharge tube Q1 and the transient suppression diode TVS1.

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

The utility model controls the rising speed of the gate voltage of the MOS transistor Q1 through the RC delay circuit, and the MOS transistor Q1 is turned on through the delay, and the current is controlled within the range of the allowable value through the resistor R5 when the MOS transistor Q1 is turned on. So as to achieve the purpose of suppressing the surge current when the power circuit is started. In addition, the utility model has the characteristics of simple circuit structure and high reliability, and is suitable for high-power power supply circuits and frequent switching power supply circuits.

Description of drawings

FIG. 1 is a schematic structural diagram of an existing DC power supply.

Fig. 2 is a schematic circuit diagram of an embodiment of the power supply circuit of the present invention.

FIG. 3 is a schematic diagram of a simulation waveform of the output current at the output terminal of the surge current suppression circuit when the power supply circuit shown in FIG. 2 is started.

Detailed ways

As shown in Figure 2, the utility model proposes a power supply circuit with a surge current suppression circuit, which includes: a surge current suppression circuit connected to the AC power supply U _in ; sequentially connected to the output terminal of the surge current suppression circuit And the step-down circuit, rectifier circuit and lightning protection circuit at the output end of the power circuit.

Wherein, the inrush current suppression circuit includes: a first voltage dividing branch and a second voltage dividing branch respectively connected between the live line (L) and the neutral line (N) of the AC input power supply U _in , the first voltage dividing branch The branch includes a resistor R1 and a resistor R2 connected in series between the live wire and the neutral wire of the AC input power supply U _in , and the second voltage division branch includes a resistor R3 and a resistor R3 connected in series between the live wire and the neutral wire of the AC input power U _in . Resistor R4; and the common terminal of resistor R1 and resistor R2 is connected to the common terminal of resistor R3 and resistor R4 (that is, resistor R3 is connected in parallel with resistor R1, and resistor R4 is connected in parallel with resistor R2); the capacitor branch connected in parallel with resistor R1 and resistor R3 The capacitor branch circuit includes capacitor C1 and capacitor C2 connected in series; the gate is connected to the common terminal of resistor R1 and resistor R2, the source is connected to the fire wire of the AC input power supply U _in , and the drain is connected to the P-type MOS transistor of the step-down circuit Q1; a resistor R5 connected between the source and the drain of the MOS transistor Q1.

Wherein, the resistance value of the resistor R5 needs to be greater than or equal to the AC input power U _in divided by the maximum start-up surge current allowed by the power circuit.

In addition, the normal turn-on driving voltage of MOS transistor Q1 is generally around 12V, so the ratio of resistor R1 and resistor R2 is selected so that when the AC input power supply U _in fluctuates within the working range, the divided voltage on resistor R2 can drive MOS Transistor Q1 is turned on.

The values of the resistors R1 , R2 , R3 and R4 , and the capacitors C1 and C2 affect the turn-on time from the startup of the power supply circuit to the conduction of the MOS transistor Q1 . The longer the conduction time of the OS transistor Q1 is, the better the startup surge current can be suppressed. However, if the conduction time of the OS transistor Q1 is too long, it will affect the back-end filter circuit and the DC-DC circuit, so it is necessary to select an appropriate resistance value and capacitance value to balance the above effects.

The capacitor C1 and capacitor C2 connected in series form an RC delay circuit with the first voltage dividing branch and the second voltage dividing branch, so that the rising speed of the gate voltage of the MOS transistor Q1 can be controlled, and the delay MOS transistor Q1 conducts When the MOS transistor Q1 is turned on, the current is controlled within the allowable range by the resistor R5, thereby achieving the purpose of suppressing the surge current when the power supply circuit is started. As shown in the simulated current waveform diagram in Figure 3, during the start-up process of the power circuit, the voltage at the output terminal of the surge current suppression circuit will quickly stabilize at a fixed value, effectively suppressing the surge current.

In addition, the step-down circuit is generally a transformer. And the rectification circuit adopts the full-bridge rectification circuit VD1 connected to the secondary winding of the transformer.

The lightning protection circuit includes: a capacitor C3 connected between the positive and negative output terminals of the full-bridge rectifier circuit VD1; a bipolar gas discharge tube Q1 and a transient suppression diode TVS1 connected between the positive output terminal of the full-bridge rectifier circuit VD1 and ground ; The variable resistor R9 connected between the bipolar gas discharge tube Q1 and the transient suppression diode TVS1. When the external power supply has a surge overcurrent due to lightning strike or other reasons, the resistance value of the variable resistor R9 increases rapidly, and the surge energy gathers rapidly at the front end of the variable resistor R9, so that the two-pole gas discharge tube G1 can be discharged more quickly. It is broken down, reaches the conduction state, and discharges in advance; if there is a continuous overcurrent at the output end of the external power supply, the variable resistor R9 will maintain a high-impedance state until the overcurrent subsides, thereby playing the role of overvoltage protection. Therefore, in addition to assisting the transient suppression diode TVS1 and the two-pole gas discharge tube G1 to achieve the same function of operation, the variable resistor R9 can also effectively inhibit the damage of the electrical equipment connected to the output end of the power circuit by continuous overcurrent, and play a role in overcurrent protection. The function of overvoltage double protection.

The above descriptions are only preferred embodiments of the present utility model, and are not intended to limit the present utility model. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present utility model shall be included in this utility model. within the scope of protection of utility models.

Claims (8)

1. A surge current suppression circuit is characterized in that it comprises: a resistor R1 and a resistor R2 between the live wire and the neutral wire of the AC input power supply connected in series; a capacitor branch connected in parallel with the resistor R1; the gate connection resistor R1 and The common terminal and the source of the resistor R2 are connected to the fire wire of the AC input power supply, and the drain is used as the output terminal of the MOS transistor Q1; the resistor R5 is connected between the source and the drain of the MOS transistor Q1. 2. The surge current suppression circuit according to claim 1, characterized in that the suppression circuit also includes a resistor R3 and a resistor R4 connected in series between the live wire and the neutral wire of the AC input power supply, and the resistor R3 is connected in parallel with the resistor R1, and the resistor R4 is connected in parallel with resistor R2. 3 . The surge current suppression circuit according to claim 1 , wherein the capacitor branch circuit includes a capacitor C1 and a capacitor C2 connected in series. 4 . 4. The surge current suppression circuit according to claim 1, wherein the MOS transistor Q1 is a P-type MOS transistor. 5. The surge current suppressing circuit according to claim 1, wherein the resistance value of the resistor R5 is greater than or equal to the AC input power divided by the maximum start-up surge current allowed by the power circuit. 6. A power supply circuit with inrush current suppression, comprising a sequentially connected inrush current suppression circuit, a step-down circuit, a rectifier circuit and a lightning protection circuit, characterized in that the inrush current suppression circuit includes: serially connected AC input power supply Resistor R1 and resistor R2 between the live wire and the neutral wire, and a capacitor branch connected in parallel with resistor R1; the gate is connected to the common terminal of resistor R1 and resistor R2, the source is connected to the live wire of the AC input power supply, and the drain is connected to the step-down circuit MOS transistor Q1; a resistor R5 connected between the source and drain of the MOS transistor Q1. 7. The power supply circuit with surge current suppression according to claim 6, characterized in that the suppression circuit also includes a resistor R3 and a resistor R4 connected in series between the live wire and the neutral wire of the AC input power supply, and the resistor R3 and the resistor R1 In parallel, resistor R4 is connected in parallel with resistor R2. 8. The power supply circuit with surge current suppression according to claim 6, wherein the lightning protection circuit comprises: a capacitor C3 connected between the two output terminals of the rectifier circuit; connected between the positive output terminal of the rectifier circuit and The two-pole gas discharge tube Q1 and the transient suppression diode TVS1 between the ground; the variable resistor R9 connected between the two-pole gas discharge tube Q1 and the transient suppression diode TVS1.