Active Gate Bias Driver for Switching Loss Reduction
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Solution Overview
Problem
High voltage switches in IPMs for low power motor drive applications face significant switching losses due to reverse recovery losses of the internal body diode, which conventional techniques fail to adequately address, especially at high voltages and varying temperatures.
Innovation Solution
A gate driver system that actively drives the gate voltage of a switch to a bias voltage during dead times, dynamically adjusting to reduce reverse recovery charge and account for temperature variations, thereby minimizing switching losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional gate driver techniques are used to deactivate a switch by providing ground voltage to the gate, then the switch is fully deactivated, but reverse recovery charge accumulates in the body diode during dead time, causing high switching losses
Solution Approach 1:
The gate driver dynamically adjusts the gate voltage during dead time periods by switching between different voltage levels (Vbias1 and Vbias2) based on the operational state of the switch. This dynamic voltage adjustment reduces reverse recovery charge in the body diode without requiring a completely new gate driver architecture, thereby reducing switching losses while maintaining manageable device complexity
Solution Approach 2:
The invention changes the gate voltage parameter from a fixed ground level to variable bias voltages (Vbias1 and Vbias2) during dead time periods. By adjusting the gate voltage parameter according to the switch state and temperature conditions, the reverse recovery charge is reduced, leading to lower switching losses
2Adaptability or versatility
If a single bias voltage is applied to the gate during dead time, then the circuit is simple, but it cannot account for temperature variations and dynamic effects like shoot through and undesired turn-on
Solution Approach 1:
The gate bias driver uses dynamic control to switch between two different bias voltages (Vbias1 and Vbias2) based on temperature conditions and switch state. This dynamic adaptation allows the system to account for temperature variations and prevent shoot-through and undesired turn-on events while maintaining reasonable control complexity through structured voltage selection
Solution Approach 2:
The system incorporates feedback mechanisms to monitor temperature and switch state, then adjusts the gate bias voltage accordingly. This feedback-based adaptation enables the gate driver to respond to temperature variations and dynamic conditions, improving system adaptability while maintaining controlled complexity through systematic voltage selection
3Loss of energy
If dead time is extended to prevent shoot-through, then switching losses from reverse recovery increase, but if dead time is reduced to minimize losses, then shoot-through risk increases
Solution Approach 1:
The gate driver dynamically adjusts bias voltages during dead time periods to actively manage the switch transition. By applying appropriate bias voltages (Vbias1 or Vbias2) during dead time, the system can maintain shorter dead times while still preventing shoot-through, thereby reducing reverse recovery losses while maintaining reliability
Solution Approach 2:
The gate driver applies preliminary bias voltages to the gate during dead time periods before the switch is fully activated or deactivated. This preliminary action prepares the switch for the upcoming transition, reducing reverse recovery charge accumulation and enabling shorter dead times without shoot-through risk
Data Source
AI summary
A device includes a gate driver configured to output, to a gate of a switch, a turn-on voltage for activating the switch. The active gate bias driver is configured to actively drive a voltage at the gate of the switch to a first bias voltage during a first dead time of the switch and actively drive the voltage at the gate of the switch to a second bias voltage during a second dead time of the switch. The second bias voltage is different from the first bias voltage.