Gate Driver Circuit Startup Control for Negative Rail Undershoot

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Solution Overview

Problem

Existing gate driver circuits for high-power switches in electric vehicle inverters experience undershoot in negative output voltage during startup, which can damage components due to unregulated energy dissipation and potential voltage undershoot.

Innovation Solution

Incorporating a short-circuit transistor and regulation control circuit to short the negative output rail to ground until the positive output voltage reaches a sufficient threshold, powered by a shunt regulator to prevent undershoot and regulate the negative output voltage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a shunt regulator is used to regulate the negative output voltage, then the negative output voltage can be controlled, but the shunt regulator cannot operate until the positive output voltage reaches a sufficient threshold, causing undershoot

Engineering Contradiction:

Improvenegative output voltage regulationVSAvoidstartup delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The circuit performs preliminary action by pre-charging the negative output capacitor through the flyback converter before enabling the shunt regulator. This ensures that the negative output voltage is established and stabilized before the regulator needs to operate, eliminating the startup delay and undershoot issue.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The circuit applies preliminary anti-action by using the flyback converter to pre-charge the negative output capacitor in opposition to the potential undershoot that would occur later. This preliminary charging action counteracts the voltage drop that would otherwise happen when the shunt regulator starts operating, preventing the harmful undershoot effect.

Inventive Principle:

Principle #9Preliminary anti-action

2Use of energy by moving object

If the negative output capacitor is charged during startup, then energy is stored, but unregulated energy dissipation can damage components

Engineering Contradiction:

Improveenergy storage in negative output capacitorVSAvoidunregulated energy dissipation

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The circuit uses feedback control through the shunt regulator to monitor and control the negative output voltage. The regulator continuously adjusts the shunt transistor conduction based on the actual voltage level, ensuring that energy dissipation is regulated and preventing component damage from unregulated energy release during startup and operation.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS20250337401A1Gate driver circuit

Publication Date: 2025.10.30 NXP USA INC

AI summary

A driver circuit for controlling a high-power switch. The driver circuit comprises a flyback converter having a positive output rail and a negative output. The driver circuit also comprises: a driving stage that is connected between the positive output rail and the negative output rail; a shunt regulator configured to regulate the negative output voltage on the negative output rail based on a difference between the negative output voltage and a target negative voltage value, wherein the shunt regulator is powered by the positive output voltage on the positive output rail; a short-circuit transistor having a conduction channel that is connected between the negative output rail and a ground terminal; and a regulation control circuit configured to: provide a short-circuit control signal to a control terminal of the short-circuit transistor in order to short the negative output rail to the ground terminal until the positive output voltage reaches a positive threshold.