Transistor Drive Circuit Topology to Prevent Gate Undershoot
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing drive circuits using a normally-off-type transistor and a normally-on-type transistor in series suffer from undershooting in the drive voltage of the higher-side transistor when the lower-side transistor is in the OFF state, which cannot be sufficiently mitigated by conventional Zener diodes due to their limited reaction time.
Innovation Solution
A drive circuit design incorporating a diode, third, fourth, and fifth transistors, along with a control circuit unit, to manage the gate voltages of the transistors, ensuring the normally-off-type transistors remain in the ON state during normal operation, thereby preventing undershooting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Zener diode is used to curb undershooting in drive voltage, then the drive voltage stability is improved, but the reaction time is insufficient and undershooting cannot be sufficiently curbed
Solution Approach 1:
The control circuit unit proactively controls the third and fourth transistors to maintain the normally-off-type transistor in the ON state before undershooting occurs. By anticipating the voltage drop condition and pre-positioning the transistor in a safe state, the circuit prevents undershooting rather than reacting to it, thereby achieving both voltage stability and fast response without being limited by Zener diode reaction time.
2Extent of automation
If a normally-off-type transistor and a normally-on-type transistor are connected in series, then the transistor circuit can be normally-off driven, but undershooting occurs in drive voltage when the lower-side transistor is in OFF state
Solution Approach 1:
The control circuit unit acts as an intermediary that mediates the interaction between the normally-off-type and normally-on-type transistors. By introducing the third and fourth transistors under control circuit management, the system coordinates the switching states of both transistors to prevent the harmful interaction that causes undershooting, while maintaining the desired normally-off drive capability.
Solution Approach 2:
The control circuit unit applies preliminary anti-action by controlling the third and fourth transistors to counteract the potential undershooting effect before it can adversely affect the drive voltage. This proactive measure prevents the harmful voltage drop that would otherwise occur when the lower-side normally-on-type transistor is in the OFF state, thereby maintaining stable drive voltage while preserving normally-off drive operation.
Data Source
AI summary
A drive circuit normally-off drives a transistor circuit which is constituted of a normally-on-type first transistor and a normally-off-type second transistor connected in series. A power source voltage wiring is connected between first transistor and the second transistor. The drive circuit has a diode which is disposed between a drive terminal of the first transistor and the second transistor, a third transistor which is disposed between the power source voltage wiring and the drive terminal of the first transistor, a fourth transistor which is disposed between a ground and the drive terminal of the first transistor, a fifth transistor which is disposed between the drive terminal of the first transistor and the fourth transistor, and a control circuit unit which switches states of the second, third, fourth, and fifth transistors.