Starter Generator Gate Driver Power Supply for Back-EMF Faults

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Solution Overview

Problem

Starter generator systems face failure during fault conditions due to back electromotive force (BEMF) exceeding voltage rails, causing components to fail, and the smaller power supply may not be able to turn on low-side switches, leading to system failure.

Innovation Solution

Implementing a floating low-side power supply for each phase, which compensates for shorts on the smaller power supply pin and phases, ensuring adequate power to turn on low-side switches during fault conditions by using a diode and current source circuit to block shorts and charge capacitors from the increasing supply voltage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a smaller power supply is used to power the motor driver IC, then the system complexity is reduced, but the power supply may not be able to turn on low-side switches during fault conditions, leading to system failure

Engineering Contradiction:

Improvepower supply structureVSAvoidsystem operation during fault conditions

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent implements a bootstrap capacitor that is pre-charged during normal operation to store energy in advance. During fault conditions when the power supply voltage drops, this pre-stored energy enables the low-side switches to be turned on successfully, resolving the reliability issue without adding complex power supply circuitry.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces a bootstrap capacitor as an intermediary energy storage element between the power supply and the low-side switch gate drivers. This capacitor mediates the power delivery, providing the necessary voltage boost during fault conditions when the main power supply cannot maintain adequate voltage levels.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Power

If the power supply voltage increases during fault conditions, then more power is available to turn on switches, but back electromotive force (BEMF) exceeds voltage rails, causing components to fail

Engineering Contradiction:

Improvepower supply voltageVSAvoidBEMF damage to components

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The patent implements a clamp circuit with a diode and resistor that is pre-configured to activate when the power supply voltage exceeds safe levels. This circuit proactively clamps the voltage to prevent BEMF from damaging components, countering the harmful effect before it can cause damage.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The patent utilizes the increasing power supply voltage during fault conditions beneficially by directing excess voltage through a clamp circuit that dissipates the energy safely through a resistor. The harmful BEMF energy is converted into harmless heat dissipation, protecting components while still allowing adequate power for switch operation.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This solution ensures consistent power supply to the motor driver IC, allowing low-side switches to turn on during fault conditions, preventing system failure and protecting components from BEMF damage.

Implementation Method 1

using a diode and current source circuit to block shorts

Methodology Applied

Scientific EffectDiode blocking: Diode

Implementation Method 2

charge capacitors from the increasing supply voltage

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS11764664B2Methods and apparatus for protecting starter generator systems during a fault condition

Publication Date: 2023.09.19 TEXAS INSTRUMENTS INC

AI summary

An example apparatus includes a level shifter having a first supply input, a gate driver having a second supply input coupled to the first supply input and adapted to be coupled to a cathode of a diode, the gate driver having an output adapted to be coupled to a control terminal of a switch, and a current source circuit having an input and an output, the input adapted to be coupled to a power supply and the output adapted to be coupled to the first supply input, the second supply input and to a capacitor.