Method for overcurrent protection of power device and circuit

Abstract

A method for overcurrent protection of a power device comprises the steps of collecting saturation voltage drop of a power device and a preset overcurrent threshold voltage to make a comparison to judge whether an overcurrent occurs; when the overcurrent occurs, instantly cutting off a driving voltage or a driving current of the power device to achieve cut-off of the power device, further applying a detection pulse to be used for detecting and judging whether the overcurrent is relieved; continuing to apply the protection if the overcurrent is not relieved; and enabling a protection circuit to quit from protection if the overcurrent is relieved. The circuit comprises a power unit, an overcurrent collecting unit, an overcurrent threshold unit, a frequency unit and a driving unit. The first end of the power unit is connected with the driving unit, the second end of the power unit is a power output end, and the third end of the power unit is connected with a power supply positive pole. The overcurrent collecting unit collects saturation voltage drop of the power unit. The overcurrent collecting unit and the frequency unit are connected with the first input end of the driving unit. The overcurrent threshold unit is connected with the second input end of the driving unit. When the power unit is subjected to the overcurrent, the driving unit makes the power unit achieve cut-off so that the power unit can be protected. The circuit has the advantages of being quick to open and close, simple in structure and high in reliability.

Description

technical field [0001] The invention belongs to the technical field of electromechanical control, and in particular relates to an overcurrent protection method and circuit of a power device. Background technique [0002] Switching power amplifier circuit is a kind of control circuit which is widely used. As a key component, its power tube generally has a large working current. It is often damaged by overcurrent due to load overload, load short circuit, etc., so that the circuit control equipment is damaged, making the control process and The production link is blocked, resulting in production loss. [0003] Generally, the power tube overcurrent protection circuit uses a current sampling resistor connected in series in the power tube output current loop, and judges whether the power tube is overcurrent through the voltage drop on the sampling resistor to implement protection, but this circuit has the following disadvantages: [0004] (1) It is difficult to accommodate larger...

AI Technical Summary

Problems solved by technology

[0004] (1) It is difficult to accommodate larger sampling resistors in the case of limited circuit area;

[0005] (2) Sampling resistance causes power loss and high heat generation leads to increased failure rate;

[0006] (3) The resistance value of the sampling resistor is very small and difficult to manufacture, and some use printed circuit copper foil instead of the sampling resistor, which increases the discreteness of the sampling resistor in batch products and causes sampling inaccuracy;

[0007] (4) The change of the resistance value of the sampling resistor and the change of the circuit contact resistance will make the sampling inaccurate;

[0008] (5) Some protection circuits using MCU for over-current sampling signal processing have complex structures and increased costs. At the same time, due to program operation, the circuit action speed is low and the anti-interference performance is low.

[0009] Based on the above, this kind of overcurrent protection circuit with sampling resistor or the circuit using MCU to implement overcurrent protection is very limited.

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