Semiconductor Switch Control Circuit Suppressing Self-Oscillation
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Solution Overview
Problem
Wide band gap semiconductor switches in switching power source devices are prone to self-oscillation during turn-off periods, especially when large switching currents flow or overloads occur, leading to potential semiconductor switch or circuit failure.
Innovation Solution
A semiconductor switch control circuit that includes a pulse signal generator, drive current generator, gate voltage detector, and drive current controller, which adjusts the drive current to control the gate voltage's lowering or rising speed based on detected self-oscillation phenomena, setting multiple voltage levels and current thresholds to minimize self-oscillation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a wide band gap semiconductor is used as a semiconductor switch, then high speed switching is realized, but self-oscillation is generated during turn-off period due to parasitic capacitor or inductor
Solution Approach 1:
The control circuit performs preliminary action by detecting gate voltage before self-oscillation occurs and proactively adjusting the drive current to prevent oscillation. The system monitors the gate voltage during the turn-off period and modifies the drive current in advance to maintain stable operation, rather than reacting after oscillation begins.
Solution Approach 2:
The control circuit implements feedback by continuously detecting the gate voltage of the semiconductor switch and using this information to adjust the drive current. The detection unit monitors gate voltage, and the control unit modifies drive current based on detected voltage levels, creating a closed-loop system that suppresses self-oscillation while maintaining high-speed switching.
2Reliability
If a negative-voltage-use power source is added to bias gate voltage during turn-off period, then self-oscillation is suppressed, but device complexity increases
Solution Approach 1:
The control circuit changes parameters by dynamically adjusting the drive current magnitude based on detected gate voltage levels. Instead of using a negative voltage power source, the system modifies the drive current parameter in response to gate voltage detection, achieving self-oscillation suppression through parameter adaptation rather than additional hardware components.
Solution Approach 2:
The control circuit introduces an intermediary function by using the detection unit and control unit as mediators between the power source and semiconductor switch. Rather than directly adding a negative voltage source to the circuit, the system uses the control circuit as an intermediary that processes gate voltage information and adjusts drive current accordingly, achieving suppression without increasing fundamental circuit complexity.
3Speed
If drive current is increased to improve switching speed, then switching performance is enhanced, but self-oscillation is more likely to occur during turn-off
Solution Approach 1:
The control circuit applies dynamics by making the drive current adaptive rather than fixed. The system dynamically adjusts drive current magnitude based on real-time gate voltage detection, allowing high drive current for fast switching when conditions permit, while automatically reducing drive current when gate voltage indicates risk of self-oscillation during turn-off.
Solution Approach 2:
The control circuit changes parameters by adjusting drive current magnitude in response to gate voltage conditions. The system maintains high drive current for fast switching performance but modifies the current parameter when detection unit identifies gate voltage levels that could lead to self-oscillation, achieving dynamic parameter optimization that balances speed and stability.
Data Source
AI summary
A semiconductor switch control circuit configured to perform an ON/OFF control of a semiconductor switch and includes: a pulse signal generating part configured to generate a pulse signal; a drive current generating part configured to generate a drive current based on the pulse signal which the pulse signal generating part generates and supplies the drive current to a gate electrode of the semiconductor switch; a gate voltage detecting part configured to detect a gate voltage VGS of the semiconductor switch; and a drive current control part configured to control the drive current which the drive current generating part generates based on the pulse signal which the pulse signal generating part generates and the gate voltage VGS which the gate voltage detecting part detects.