Low-cost alternating-current input overvoltage protection circuit and switching power supply

Abstract

The invention discloses a low-cost alternating-current input overvoltage protection circuit and a switching power supply. The protection circuit comprises a voltage sampling end which is used for being connected to the output end of an AC (Alternating Current) / DC (Direct Current) module of a power supply, a high-voltage suppression diode, a divider resistor, a bias resistor and a switching tube, wherein the control end of the switching tube is connected to a series-connection joint of the divider resistor and the bias resistor so as to receive a high electric level for switching on the switching tube; one end of a switching channel of the switching tube is grounded, and the other end of the switching channel is used for being connected with the feedback input end of a power supply control chip. According to the invention, the high-voltage suppression diode is used as a detecting switch for use, and can be broken down when the input is extremely high to provide a bias voltage for the bias resistor for switching on the switching tube and quickly pulling down the voltage at the feedback end of a control chip, so that the control chip is controlled to stop working; a self-recovery function also can be realized after high voltage, so that detection protection for input overvoltage is realized by only four simple parts; moreover, the protection circuit is simple, safe and reliable in structure, low in cost and easy for wide popularization and application.

Description

technical field [0001] The invention relates to the technical field of switching power supplies, in particular to a low-cost AC input overvoltage protection circuit and a switching power supply. Background technique [0002] In the field of switching power supplies, PWM-type auxiliary power supplies that supply power to the main power conversion circuit are generally included. The auxiliary power supply generally directly uses the input high voltage of the main conversion circuit (the AC input is rectified and filtered by the rectifier diode) to obtain the required DC voltage through high-frequency conversion. In some countries or regions with underdeveloped power grids, such as India, the AC input voltage is quite unstable, sometimes high and sometimes low, and the power supply will be damaged instantly when the voltage is high. Therefore, it is necessary to design an input overvoltage protection circuit to achieve the purpose of protection. However, some of the existing ...

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Problems solved by technology

However, some of the existing switching power supplies do not have input overvoltage protection design, or simply add simple protection elements such as overvoltage protectors or fuses at the AC input end, while other switching power supplies are designed for input overvoltage protection voltage. The cost is too high, the circuit design is complicated and it is difficult to popularize and apply

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