Over-current protection circuit and over-current protection method for DC power supply

Abstract

The invention is applied in the field of power circuits, and provides an over-current protection circuit and an over-current protection method for a DC power supply. The over-current protection circuit for the DC power supply comprises a first hysteresis comparator and an over-current protection sub-circuit, wherein the first hysteresis comparator is used for detecting whether the output voltage of the DC power supply reaches a preset voltage threshold value or not; and the over-current protection sub-circuit is used for sampling the output current of the DC power supply, and executing an over-current protection operation on the DC power supply when the first hysteresis comparator judges that the output voltage of the DC power supply reaches the preset voltage threshold value and the over-current protection sub-circuit judges whether the output current of the DC power supply reaches a preset current threshold value. In the over-current protection circuit and the over-current protection method for the DC power supply, the detection of the output voltage of the DC power supply is combined with the detection of the current of the DC power supply, and the output voltage of the DC power supply is judged to make the over-current protection circuit stop working in the starting process of the DC power supply and start protecting the DC power supply after the starting is finished; therefore, a user is not required to worry about protection circuit malfunction caused by surge current produced in the starting when setting an over-current protection point.

Description

technical field [0001] The invention belongs to the field of power supply circuits, and in particular relates to an overcurrent protection circuit and an overcurrent protection method of a DC power supply. Background technique [0002] At present, there are many kinds of overcurrent protection circuits for DC power supplies. The principle is to convert the current signal into a voltage signal and then compare it to determine whether to perform a protection action. The protection mode is mainly divided according to the different sampling points and protection actions. From the different sampling points, it can be divided into inductor current sampling, MOSFET current sampling, resistance current sampling, etc., and from the different protection actions can be divided into over-current after-over-current protection. There are two types of signal lockout and overcurrent protection signal self-recovery after overcurrent. Among them, the protection signal lockout requires the cir...

AI Technical Summary

Problems solved by technology

However, there are the following disadvantages: 1. Using the average value to judge will cause the MOS tube to flow the same current, and the average value will be different due to the difference in duty cycle, resulting in a large error; 2. The current detection process after starting up The medium will still filter the short-term high current, and there will be no instantaneous high current that will damage the load in essence, so that it will not be able to protect the short-term high current after starting up; 3. If the power supply The power-on time is longer, and the duration of the surge current will be extended, and the protection circuit will still send out a protection signal

[0004] There is also an overcurrent protection technology to judge whether there is overcurrent by monitoring the current flowing through the inductor on the power filter, such as figure 2 As shown, although the current sampled by this scheme is a continuous value and will not be affected by the duty cycle, there is still a problem that it cannot protect the short-term high current after power-on. Disadvantages of sending out protection signals

[0005] In short, the existing over-current protection technology has the problem that the over-current protection circuit malfunctions due to the surge current when starting up, and the over-current protection function is not normal after starting up.

Images