PWM signal power-up and power-down protection circuit

Abstract

The invention discloses a PWM signal power-up and power-down protection circuit comprising a hysteresis comparison circuit, an AND gate circuit, a first power supply monitoring circuit, a second power supply monitoring circuit and a buffer circuit. The AND gate circuit is respectively connected with the hysteresis comparison circuit, the first power supply monitoring circuit, the second power supply monitoring circuit and the buffer circuit. The power supply monitoring and comparison circuits are arranged so that the situation of circuit power supply can be monitored at any time. When the circuit is in the power-up state and voltage is lower than the preset threshold value, output of a PWM signal is limited. When the circuit is in the power-off state, the arranged triode is not conducted, output of the PWM signal from the buffer module is prohibited and thus the PWM signal is locked and a semiconductor device is protected. When the circuit is in the power-up state, the PWM signal is unlocked when all stages of level reaches a certain limit so that damage to the semiconductor switch device caused by initial power-up or power-down of certain stage of level is avoided, the service life of the semiconductor switch device is prolonged and product cost is saved.

Description

technical field [0001] The invention discloses a PWM signal power-up and power-down protection circuit, which belongs to the technical field of circuit design. Background technique [0002] With the rapid development and maturity of power electronics technology, the application of active filter products in power systems is increasing. The PWM signal controls the on and off of the semiconductor switching device, so that the output terminal obtains a series of pulses with equal amplitude and unequal width, and these pulses are used to replace sine waves or other required waveforms. The width of each pulse is modulated according to certain rules, which can not only change the output voltage of the inverter circuit, but also change the output frequency. [0003] PWM is a method of digitally encoding the level of an analog signal. Through the use of high-resolution counters, the duty cycle of the square wave is modulated to encode the level of a specific analog signal. The PWM...

AI Technical Summary

Problems solved by technology

[0007] In the existing application circuit, the circuit will cause certain damage to the semiconductor switching device when the circuit is initially powered on or powered off at a certain level. The degree of this damage will determine the service life of the semiconductor. The semiconductor device may If there is a problem of not being able to work at the beginning, it may also stop working during normal work in the future. This unpreventable life stop will bring certain losses to the enterprise. When a key semiconductor device is damaged, it will often Cause irreparable huge losses, so it is necessary to develop a PWM signal power-on and power-down protection circuit to solve the problems and deficiencies in the existing technology

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