PFC under-voltage protection circuit and protection method

Abstract

The invention provides a PFC under-voltage protection circuit and a protection method. The PFC under-voltage protection circuit comprises an under-voltage sampling unit used for carrying out peak value sampling of an voltage of an AC input end of a PFC power supply, and obtaining a high-voltage DC level, a first voltage division unit used for carrying out voltage division processing on the high-voltage DC level to obtain a low-voltage DC level, a threshold setting unit used for setting a voltage stabilization value for an FB pin of a main control chip U1, and an FB pull-down unit used for being switched on when the low-voltage DC level is greater than a set voltage stabilization value to enable the main control chip U1 to work normally, and being switched off when the low-voltage DC levelis smaller than the set voltage stabilization value to enable the main control chip U1 to stop working. Under-voltage protection can be realized without external power supply, the reliability is high,the efficiency is high, the structure is simple, the use is convenient, and a small size and low power consumption of the power supply are realized.

Description

technical field [0001] The invention relates to a PFC power supply, in particular to a PFC undervoltage protection circuit and a protection method. Background technique [0002] At present, more and more active power factor correction circuits (PFC) are required in switching power supply applications. However, in some areas where the input grid is unstable, the input AC voltage may fluctuate greatly. When the input voltage is low to a certain extent In this case, the power supply is likely to be damaged, and the power supply used in these scenarios usually requires an additional design of an AC undervoltage protection circuit to prevent power supply damage. [0003] The existing input under-voltage protection circuit has complex circuit structure and high cost. There are mainly the following two solutions: [0004] One is realized by a dedicated undervoltage protection IC. The undervoltage detection circuit detects the rectified voltage and performs voltage division process...

AI Technical Summary

Problems solved by technology

[0006] Both of the above two existing technical solutions use some high-cost devices, such as the under-voltage protection IC and high-voltage MOS tube of the first type of under-voltage protection circuit, and the comparator and relay in the second type of under-voltage protection circuit. The cost is high, which is not conducive to the control of the total cost of the power supply

In addition, both the undervoltage protection IC and the comparator need external power supply, and an additional power supply circuit needs to be designed. The circuit design is more complicated, and the size of the switch tube and the relay is larger, which increases the difficulty in the design of the power supply structure.

As a result, the working efficiency of the power supply is reduced, and at the same time, due to the large energy consumption, the generated heat will affect the reliability of the circuit

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