Gate Bias Control for Reverse Recovery Charge Reduction
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Solution Overview
Problem
Reverse recovery charge causes current and voltage transients in power switching applications, leading to inefficiencies and increased switching losses.
Innovation Solution
Control the gate of transistors with a non-zero turn-off voltage and apply backgate bias voltage to lower the reverse-threshold voltage, preventing reverse recovery charge accumulation and minimizing current and voltage transients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the body diode is forward biased to allow current flow, then current conduction is enabled, but reverse recovery charge is stored at the junction
Solution Approach 1:
The gate is turned off to a non-zero value (bias voltage greater than zero but less than threshold voltage) before the body diode becomes forward biased. This preliminary gate voltage reduction prevents excessive reverse recovery charge from being stored at the diode junction, thereby reducing reverse recovery current and voltage transients while maintaining proper current conduction during the on-state.
2Loss of energy
If the gate is turned off completely to prevent current flow, then reverse recovery charge is reduced, but the switch cannot conduct forward current
Solution Approach 1:
The gate voltage is dynamically adjusted to different states: during the off-state, it is reduced to a non-zero bias voltage (greater than zero but less than threshold voltage) to minimize reverse recovery charge; during the on-state, it is raised to a sufficient voltage to enable proper current conduction. This dynamic gate voltage control optimizes both reverse recovery performance and forward current conduction.
3Loss of energy
If a bias voltage greater than zero is applied to the gate during forward current, then reverse recovery charge is reduced, but the switch may not turn off completely
Solution Approach 1:
The gate voltage is periodically switched between two distinct states: a non-zero bias voltage state (greater than zero but less than threshold voltage) during the off-state to reduce reverse recovery charge, and a sufficient voltage state during the on-state to ensure complete turn-on and proper current conduction. This periodic voltage switching ensures both reverse recovery optimization and reliable switch operation.
Data Source
AI summary
A method for reducing or eliminating current and voltage transients in a device including: providing the device, wherein the device comprises a transistor with a gate; and controlling the gate, wherein the gate is turned off to a non-zero value in a presence of the positive current flow and wherein the gate is turned on in a presence of the negative current flow; reducing the negative current flow; and reducing or eliminating current and voltage transients in the device.