Overvoltage Protection Circuit Using Current Change Control
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Solution Overview
Problem
Conventional overvoltage protection circuits face challenges in suppressing conduction disturbing wave voltage, leading to increased noise and larger power supply apparatus sizes due to steep current fluctuations, especially when dealing with a wide range of commercial power supply voltages from 100 V to 240 V.
Innovation Solution
An overvoltage protection circuit with a semiconductor switch and a control circuit that gradually changes the current flowing through the switch, using a current change circuit to suppress conduction disturbing wave voltage by controlling the semiconductor switch's on and off states, and employing components like sense resistors, low-pass filters, and inductors to smooth current fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the semiconductor switch is turned on and off to clamp the input voltage, then the overvoltage protection function is achieved, but steep current fluctuations occur causing conduction disturbing wave voltage to increase
Solution Approach 1:
The control circuit detects the voltage potential difference between both ends of the semiconductor switch before turning it on, and only generates a control voltage to turn on the switch when this potential difference is zero or a predetermined minute value. This preliminary check prevents turn-on during high voltage differential, thereby suppressing conduction disturbing wave voltage and EMI while maintaining overvoltage protection capability
Solution Approach 2:
The control circuit continuously monitors the voltage potential difference across the semiconductor switch and uses this feedback information to determine the appropriate timing for turning the switch on or off. This feedback mechanism ensures that switching occurs only under favorable voltage conditions, minimizing harmful current fluctuations and EMI generation
2Speed
If the semiconductor switch is turned on when voltage potential difference is high, then the overvoltage protection response is faster, but large current flows causing large loss in the semiconductor switch
Solution Approach 1:
The control circuit prevents turn-on of the semiconductor switch when the voltage potential difference between both ends is high, by checking the potential difference first and only allowing turn-on when it is zero or a predetermined minute value. This preliminary anti-action avoids large inrush currents and reduces energy loss in the switch while maintaining effective overvoltage protection
3Adaptability or versatility
If the input capacitor is designed for wide voltage range (100V-240V), then the power supply apparatus can be used worldwide, but the input capacitor size becomes large
Solution Approach 1:
The overvoltage protection circuit actively clamps the input voltage to a predetermined value regardless of the commercial power supply voltage (100V-240V). By changing the operating voltage parameter through active control rather than passive design, the input capacitor can be sized for the clamped voltage level, significantly reducing its size while maintaining worldwide compatibility through the protection circuit's voltage regulation function
Data Source
AI summary
An overvoltage protection circuit is provided which is connected between a rectifier circuit and a load including an input capacitor element connected to both ends of the load. The overvoltage protection circuit includes a semiconductor switch connected between the rectifier circuit and the load, and a control circuit controls the semiconductor switch. When the rectified voltage exceeds a predetermined value, the control circuit turns off the semiconductor switch, and detects a voltage potential difference between both ends of the semiconductor switch, and then, for an interval when the voltage potential difference is zero or a predetermined minute value, the control circuit generates a control voltage for turning on the semiconductor switch, and outputs the control voltage to a control terminal of the semiconductor switch. The overvoltage protection circuit includes a current change circuit that gradually changes a current flowing through the semiconductor switch.