EV Inverter Active Discharge Using Programmable Gate Voltage

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Solution Overview

Problem

Inverters used in electric vehicles face challenges in efficiently and safely discharging bulk capacitors during fault conditions, which can stress power switches and lead to potential failures due to temperature variations and uncontrolled discharge rates.

Innovation Solution

A system is implemented to dynamically control the linear active discharge of the inverter by adjusting the gate driver power supply output voltage and disabling under-voltage lockout (UVLO) and dead-time protection (DTP) faults using a serial peripheral interface (SPI), allowing for programmable and controllable gate voltage and pulse width modulation (PWM) signals to manage the discharge process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If active discharge of the bulk capacitor is performed using conventional methods, then the discharge function is provided, but stress on power switches increases and reliability decreases

Engineering Contradiction:

Improvepower switch reliabilityVSAvoidstress on power switches

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The gate driver power supply output voltage is dynamically adjusted during the discharge process. The controller modifies the gate voltage levels in real-time to optimize the discharge current flow through the power switches, reducing stress while maintaining discharge effectiveness. This dynamic control allows the system to adapt the switching conditions throughout the discharge sequence.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the operating parameters of the power switches by adjusting the gate driver power supply output voltage. By varying the gate voltage, the on-resistance and current handling characteristics of the power switches are modified to reduce stress during discharge. Additionally, the discharge current magnitude and duration are controlled as adjustable parameters.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the discharge time is reduced to meet safety requirements, then safety is improved, but the control precision and stress management become more difficult

Engineering Contradiction:

ImprovesafetyVSAvoidcontrol complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The discharge process is implemented as a periodic, multi-stage sequence rather than a single uncontrolled event. The controller executes predetermined discharge phases with specific timing, where each phase applies controlled current levels for defined durations. This periodic structure ensures safety requirements are met while maintaining manageable control complexity through automation.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The system incorporates feedback control where the controller monitors the bulk capacitor voltage and discharge current, automatically adjusting the gate driver power supply output voltage to maintain optimal discharge conditions. This closed-loop control ensures safety requirements are met while reducing the need for complex manual control procedures.

Inventive Principle:

Principle #23Feedback

3Productivity

If the gate driver power supply output voltage is increased to speed up discharge, then discharge speed is improved, but heat generation and stress on components increase

Engineering Contradiction:

Improvedischarge speedVSAvoidheat generation

Core Design Contradiction:

ProductivityVSTemperature

Solution Approach 1:

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

Inventive Principle:

Principle #19Periodic action

4Adaptability or versatility

If protection faults such as UVLO and DTP are disabled to enable discharge, then discharge controllability is improved, but system protection capability is reduced

Engineering Contradiction:

Improvedischarge controllabilityVSAvoidprotection capability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The controller temporarily disables protection faults such as UVLO and DTP only during the specific discharge time window when the bulk capacitor is being discharged. Before and after this window, the protection faults remain enabled. This preliminary planning of protection status changes allows discharge controllability while maintaining protection capability during normal operation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The protection fault status is dynamically changed based on the discharge phase. The controller enables or disables specific protection faults at different stages of the discharge process, allowing optimal controllability during discharge while maintaining adequate protection during normal operation and other critical phases.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS20260019021A1Systems for active discharge for inverter for electric vehicle

Publication Date: 2026.01.15 BORGWARNER US TECHNOLOGIES LLC

AI summary

A system includes: an inverter configured to convert DC power from a battery to AC power to drive a motor, wherein the inverter includes: a bulk capacitor; one or more switches; a gate driver; and one or more controllers, wherein the one or more controllers are configured to provide one or more of a gate voltage or a pulse width modulated (PWM) signal to the gate driver to control the one or more switches to discharge the bulk capacitor.