CN212392660U - Power supply circuit, PCB and electronic device - Google Patents

Abstract

The utility model provides a power supply circuit, including input and output, the input is used for being connected with the power positive pole, and the output is used for being connected with the load, is provided with first field effect transistor between input and the output, and the grid of first field effect transistor is through first resistance ground connection, and the resistance of first resistance is big more, and the power supply circuit switch-on surge current in the twinkling of an eye is little. The utility model also provides a PCB board and electron device. The utility model provides a power supply circuit, PCB board and electron device is provided with field effect transistor between input and the output, utilizes the Miller electric capacity that exists between field effect transistor's grid and the drain electrode to lengthen the opening time of field effect transistor to reduce output voltage's rising slope, reduce surge current; because the field effect transistor has extremely low power consumption, under the condition of not increasing extra power consumption, the surge current at the moment of connecting the power supply circuit can be reduced, and the loading capacity of the power supply circuit can be ensured.

Description

Power supply circuit, PCB and electronic device

Technical Field

The utility model relates to an automotive filed, concretely relates to supply circuit, PCB board and electron device.

Background

The basic way of preventing the surge in the power supply circuit is to serially connect an NTC (Negative Temperature Coefficient resistor) or a small resistor on a power line, and the schemes can reduce the surge current to a certain degree, but can affect the load capacity of the circuit, because the NTC and the small resistor consume extra power.

Disclosure of Invention

Aiming at the problems in the prior art, the utility model aims to solve the problem of providing a power supply circuit, a field effect tube is arranged between an input end and an output end, and the opening time of the field effect tube is prolonged by utilizing Miller capacitance existing between a grid electrode and a drain electrode of the field effect tube, so that the rising slope of output voltage is reduced, and surge current is reduced; because the field effect transistor has extremely low power consumption, under the condition of not increasing extra power consumption, the surge current at the moment of connecting the power supply circuit can be reduced, and the loading capacity of the power supply circuit can be ensured.

The utility model provides a power supply circuit, including input, output and set up the first field effect transistor between input and output, the input is used for being connected with the power positive pole through the switch, and the output is used for being connected with the load, and the grid of first field effect transistor passes through first resistance ground connection, and the resistance of first resistance is big more, and the transient surge current of power supply circuit switch-on is little.

Further, the first field effect transistor is a P-type field effect transistor.

Furthermore, the source electrode of the first field effect transistor is connected with the input end, and the drain electrode of the first field effect transistor is connected with the output end.

Furthermore, the power supply circuit also comprises a first voltage-stabilizing diode, the source electrode of the first field effect transistor is connected with the cathode of the first voltage-stabilizing diode, and the grid electrode of the first field effect transistor is connected with the anode of the first voltage-stabilizing diode.

Further, the resistance value of the first resistor is greater than or equal to 1k and less than or equal to 100 k.

Further, a transient voltage suppressor is arranged between the input end of the power supply circuit and the ground.

The utility model also provides a PCB board sets up above-mentioned supply circuit on the PCB board.

The utility model also provides an electronic device, include the casing and set up the PCB board in the casing.

Further, the electronic device is a combination meter.

Compared with the prior art, the utility model provides a supply circuit, PCB board and electron device has following beneficial effect: a field effect tube is arranged between the input end and the output end, and the switching-on time of the field effect tube is prolonged by utilizing a Miller capacitor between a grid electrode and a drain electrode of the field effect tube, so that the rising slope of output voltage is reduced, and surge current is reduced; because the field effect transistor has extremely low power consumption, under the condition of not increasing extra power consumption, the surge current at the moment of connecting the power supply circuit can be reduced, and the loading capacity of the power supply circuit can be ensured.

Drawings

Fig. 1 is a schematic diagram of a power supply circuit of one embodiment of the present invention;

FIG. 2 is a waveform of an inrush current at a switch-on instant of the power supply circuit shown in FIG. 1;

fig. 3 is a graph of the output voltage waveform at the switch-on instant of the power supply circuit shown in fig. 1.

Detailed Description

The utility model discloses a supply circuit of an embodiment, as shown in the part in the virtual frame of fig. 1 for electron device, for example combination meter, supply circuit sets up on the PCB board in combination meter.

The power supply circuit comprises an input end and an output end, the input end is connected with the positive pole of the power supply Vdc through the switch UI, and the output end is connected with the load. The load is a capacitive load and is represented by a first capacitor C1, a second capacitor C2, a third capacitor C3 and a load resistor R0.

A first field effect transistor Q1 is disposed between the input end and the output end, in this embodiment, the first field effect transistor Q1 is a P-type field effect transistor, a gate of the first field effect transistor Q1 is grounded through a first resistor R1, a source S is connected to the input end, and a drain is connected to the output end.

The Miller capacitor between the grid electrode and the drain electrode of the first field effect transistor Q1 prolongs the turn-on time of the first field effect transistor Q1, so that the rising slope of the output voltage is reduced, and the surge current at the moment of switching on the power supply circuit is reduced; because the field effect transistor has extremely low power consumption, the surge current value can be reduced and the loading capacity of the circuit is ensured under the condition of not increasing extra power consumption.

The power supply circuit further comprises a first voltage-stabilizing diode Z1, the source electrode of the first field effect transistor Q1 is connected with the negative electrode of the first voltage-stabilizing diode, and the grid electrode of the first field effect transistor Q1 is connected with the positive electrode of the first voltage-stabilizing diode.

The first zener diode is used to protect the first fet Q1 and clamp the gate-source voltage of the first fet Q1 so that it does not exceed the maximum turn-on voltage.

The regulation value of the first regulation diode Z1 is selected to be, for example, 15V, so as to ensure that the gate-source voltage of the first field effect transistor Q1 does not exceed the breakdown voltage.

A transient voltage suppressor T1 is arranged between the input end of the power supply circuit and the ground.

A Transient Voltage Suppressor (TVS), which is a high-efficiency protection device in the form of a diode for short, is a Transient diode, and the TVS absorbs surge power and can bear reverse Voltage impact in a very short time, so that a Voltage clamp between two electrodes is at a specific Voltage to prevent a following circuit from being impacted. The overvoltage protection is simply done, similar to a zener diode, but without the need for a current limiting resistor.

The first resistor R1 can be selected from 1K-100K.

The simulation is carried out by referring to a circuit diagram shown in fig. 1, and specific parameters are as follows:

dc power supply Vdc ═ 13.5V

Capacitive load: 330uF for C1, 330uF for C2, 4.7uF for C3, and 6 Ω for R0

In the simulation, the switch U1 is used for simulating the surge current generated when the voltage is suddenly loaded to the load end, and the first resistor R1 selects 1K, 10K and 100K respectively for simulation.

Fig. 2 shows the inrush current waveform at the moment when the switch U1 is turned on, and fig. 3 shows the output voltage waveform at the moment when the switch U1 is turned on.

The curve with the slowest slope in fig. 3 (to

Expressed) as the load terminal voltage waveform at 100K of the first resistor R1, the corresponding curve in fig. 2 (to)

Indicated) the inrush current is also the smallest, the output voltage waveform when the steepest slope curve (indicated by □) in fig. 3 is 1K for the first resistor R1, and the corresponding surge current (indicated by □) in fig. 2 is also the largest. Therefore, the larger the resistance of the first resistor R1, the smaller the inrush current. In practical application, a power supply circuit with a large first resistor R1 is adopted.

The reverse withstand voltage of the first fet Q1 is generally the voltage (2 × 26.5V) passing the high voltage test of the vehicle, the current is generally 2 times or more the load current, and the parameter Qg is selected as large as possible. The transient current capability of the first fet Q1 is greater than the actual inrush current of the circuit, so as to avoid the inrush current from damaging the first fet Q1, and the breakdown voltage of the first fet Q1 may be selected to be 60V for cost reasons.

Although the present invention has been described with reference to the preferred embodiments, the present invention is not limited thereto. Various changes and modifications can be made by one skilled in the art without departing from the spirit and scope of the invention, and the scope of the invention is to be determined by the appended claims.

Claims (9)

1. The utility model provides a power supply circuit, its characterized in that, power supply circuit includes input, output and sets up the first field effect transistor between input and output, and the input is used for being connected with the power positive pole through the switch, and the output is used for being connected with the load, and the grid of first field effect transistor passes through first resistance ground connection, and the resistance of first resistance is big more, and the instantaneous surge current of power supply circuit switch-on is little more.

2. The power supply circuit of claim 1 wherein the first fet is a P-fet.

3. The power supply circuit of claim 2 wherein the first fet has a source connected to the input terminal and a drain connected to the output terminal.

4. The power supply circuit of claim 2 wherein the power supply circuit further comprises a first zener diode, the source of the first fet being connected to the cathode of the first zener diode and the gate being connected to the anode of the first zener diode.

5. The power supply circuit according to claim 1, wherein the first resistor has a resistance value greater than or equal to 1k and less than or equal to 100 k.

6. The power supply circuit of claim 1 wherein a transient voltage suppressor is provided between the input of the power supply circuit and ground.

7. A PCB board, characterized in that the power supply circuit of any one of claims 1 to 6 is arranged on the PCB board.

8. An electronic device, comprising a housing and the PCB of claim 7 disposed therein.

9. The electronic device of claim 8, wherein the electronic device is a combination meter.

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