An output voltage detection circuit

Abstract

The invention provides an output voltage detection circuit. The output voltage detection circuit comprises a flyback transformer, a discharging detection circuit, a pulse generator, a RS trigger and an output voltage detection circuit, wherein the discharging detection circuit comprises a first comparator, the first comparator is used for sampling to acquire a voltage when a secondary winding is discharged and comparing the voltage with a first reference voltage, the pulse generator is used for generating a pulse signal according to a comparison result of the comparator and a periodic drivingsignal, the RS trigger is used for outputting a level signal of indicating whether discharging of the secondary winding is ended or not according to the pulse signal, the output voltage detection circuit comprises a second comparator, a delay circuit and a D trigger, the second comparator is used for sampling a voltage when the secondary winding is discharged and comparing the voltage with a second reference voltage, the delay circuit is used for delaying an output of the second comparator, and the D trigger is used for locking an output signal of the delay circuit according to the level signal, indicating the discharging ending of the secondary winding, output from the RS trigger and outputting a voltage, acquired by sampling, of the flyback transformer after delay time and before delay time of the delay circuit. By the output voltage detection circuit, the output voltage state can be detected after the secondary winding is approximate to complete discharging.

Description

technical field [0001] The present invention relates to the technical field of electronic circuits, in particular to the technical field of primary-side feedback power supply, in particular to an output voltage detection circuit. Background technique [0002] The primary-side feedback power supply, especially the primary-side feedback flyback power supply, omits the secondary feedback circuit, has a simple structure and low cost, and is widely used. The primary side feedback power supply uses a coupled winding to detect the output voltage. During normal operation, the secondary winding discharges during the switch off period. At this time, the voltage across the secondary winding is the output voltage Vout plus the conduction voltage V of the output rectifier diode. D . The voltage at both ends of the secondary winding can be coupled by using the third winding wound on the same magnetic core, so the output voltage can be detected by sampling the voltage of the third winding...

AI Technical Summary

Problems solved by technology

[0009] In view of the shortcomings of the prior art described above, the purpose of the present invention is to provide an output voltage detection circuit for solving the problem of low sampling accuracy due to sampling time when detecting the output voltage of the primary side feedback power supply in the prior art. question

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