Gate Drive Circuit Startup Switching to Prevent False Turn-On

Solution Overview

Problem

Existing drive circuits for semiconductor switching elements experience power loss and false turn-on during start-up due to the short-circuiting of the gate and emitter, leading to potential defective start-up of the power supply system.

Innovation Solution

A drive circuit design incorporating a drive voltage generator, signal amplifier, resistive element, and switch elements that include a normally-off and normally-on switch, with a start-up sensor to cut off the current path until the control power supply is established, preventing power loss and false turn-on.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the switch short-circuits the gate and emitter during start-up to prevent false turn-on, then false turn-on is prevented, but power loss occurs at the gate resistor

Engineering Contradiction:

Improvefalse turn-on preventionVSAvoidpower loss at gate resistor

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The control signal is provided in advance to the gate through the gate resistor before the short-circuiting switch is activated. This preliminary action allows the gate voltage to rise gradually without causing false turn-on, while the switch remains in the off state to prevent power loss at the gate resistor during the start-up period.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The switch transitions from an off state during start-up to an on state after start-up is complete. This dynamic switching allows the circuit to adapt to different operational phases: preventing power loss during start-up when the switch is off, and enabling active short-circuiting for false turn-on prevention during normal operation when the switch is on.

Inventive Principle:

Principle #15Dynamics

2Ease of operation

If the gate resistance value is reduced to adjust driving conditions, then driving performance is improved, but power loss increases

Engineering Contradiction:

Improvedriving condition adjustmentVSAvoidpower loss at gate resistor

Core Design Contradiction:

Ease of operationVSLoss of energy

Solution Approach 1:

The control signal is provided in advance to the gate through the gate resistor before the short-circuiting switch is activated. This preliminary action allows the gate voltage to rise gradually without causing false turn-on, while the switch remains in the off state to prevent power loss at the gate resistor during the start-up period.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The switch transitions from an off state during start-up to an on state after start-up is complete. This dynamic switching allows the circuit to adapt to different operational phases: preventing power loss during start-up when the switch is off, and enabling active short-circuiting for false turn-on prevention during normal operation when the switch is on.

Inventive Principle:

Principle #15Dynamics

3Loss of energy

If the control power supply is established late, then power loss is reduced, but false turn-on cannot be prevented

Engineering Contradiction:

Improvepower loss reductionVSAvoidfalse turn-on prevention

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The control signal is provided in advance to the gate through the gate resistor before the short-circuiting switch is activated. This preliminary action allows the gate voltage to rise gradually without causing false turn-on, while the switch remains in the off state to prevent power loss at the gate resistor during the start-up period.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The switch transitions from an off state during start-up to an on state after start-up is complete. This dynamic switching allows the circuit to adapt to different operational phases: preventing power loss during start-up when the switch is off, and enabling active short-circuiting for false turn-on prevention during normal operation when the switch is on.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentEP3826156B1Drive circuit and electric power conversion apparatus

Publication Date: 2026.01.28 MITSUBISHI ELECTRIC CORP

Figure 1
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Figure 3~4

AI summary

A current path to a gate (203) is cut off by a normally-off first switch element (50) until start-up of a gate drive voltage generator (10) is sensed. Furthermore, a semiconductor switching element (200) is maintained in an off state as a normally-on second switch element (60) short-circuits the gate (203) to a source (202). As start-up of the gate drive voltage generator (10) is sensed, the second switch element (60) is turned off and the first switch element (50) is turned on. As the gate (203) is thus driven by an output from a signal amplifier (20) in accordance with a control signal (Sgc), the semiconductor switching element (202) is turned on and off in accordance with the control signal (Sgc).