Output end power failure detection device and switching power supply system with the same

Abstract

The invention discloses an output end power-down detection device. The output end power-down detection device comprises a control unit, a transformer and a power-down detection unit, and the power-down detection unit comprises a voltage regulator, a power-down detection comparator, an interval control switch and an interval controller. When output voltage of a switch power source output end is smaller than a threshold value of the power-down detection comparator, the power-down detection comparator outputs an output end power-down detection signal to the interval controller, and the interval controller controls the interval control switch to be on so as to transmit the output end power-down detection signal to the control unit. The invention further discloses an on-off conversion power source system with the device.

Description

technical field [0001] The invention relates to a power-down detection device at an output end, in particular to a power-down detection device at an output end of an off-line primary-side adjusted AC / DC switch conversion power supply system. Background technique [0002] Please refer to figure 1 , figure 1 It is a schematic diagram of an output end power-down detection device in the prior art. Such as figure 1 The output terminal power-down detection device shown includes: a reference voltage source LT431, an optocoupler PC817, two voltage divider resistors R 3 , R 4 And a current-limiting resistor R5, the output voltage Vout is divided by resistors R3 and R4, and connected to the reference terminal of TL431, the cathode of TL431 is connected to the cathode of the light-emitting diode of the optocoupler, and the anode of the light-emitting diode of the optocoupler PC817 passes through the current-limiting resistor R5 Connect the output. During normal operation, the out...

AI Technical Summary

Problems solved by technology

[0005] 1. In the first way, the reference voltage source LT431 and the optocoupler PC817 cannot be integrated in an integrated circuit, and the cost is relatively high;

[0006] 2. In the second method, the reference voltage source, regulator, comparator and oscillator can be integrated in one integrated circuit. There is still a reference voltage source that needs to be trimmed, and the threshold of the comparator needs to output different voltages V according to the switching power supply. out to adjust and the oscillator output dynamic range is too small and other shortcomings

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