Power Module Surge Voltage Limiting Element

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Solution Overview

Problem

High voltage gate driver circuits are susceptible to electrical overstress failures due to surge voltages induced by stray inductance in printed circuit board patterns and shunt resistors, particularly affecting low-side transistor switches.

Innovation Solution

A power module is designed with an integrated surge voltage limiting element between the low-side power transistor's second load path terminal and the low-side voltage pin, providing a current path for a portion of the load current to mitigate surge voltages, thereby preventing electrical overstress failures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a low-side transistor switch is turned on to enable current flow, then the circuit functionality is improved, but surge voltage is induced due to stray inductance causing electrical overstress failures

Engineering Contradiction:

Improvecircuit functionalityVSAvoidelectrical overstress failure

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

A surge voltage limiting element is introduced as an intermediary component between the low-side transistor switch and the low-side voltage source. This element acts as a mediator that limits the surge voltage caused by stray inductance when current flows through the transistor, thereby preventing electrical overstress failures while maintaining circuit functionality.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The surge voltage limiting element is positioned in advance before the surge voltage can cause damage to the low-side transistor switch and gate driver circuit. By having this protective element already in place, the circuit is cushioned against potential electrical overstress failures before they occur.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Measurement precision

If stray inductance in PCB pattern and shunt resistor is present during current flow, then current measurement and circuit operation are enabled, but surge voltage is induced causing electrical overstress

Engineering Contradiction:

Improvecurrent measurementVSAvoidsurge voltage

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The surge voltage limiting element converts the harmful effect of stray inductance into a beneficial protective function. By intentionally adding this element, the circuit transforms the potential harm of voltage surges into a controlled situation where the surge voltage is limited to safe levels, protecting the low-side transistor switch and gate driver circuit.

Inventive Principle:

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

3Power

If gate driver circuit operates at high voltage to drive power transistors, then power switching capability is improved, but susceptibility to electrical overstress failures increases

Engineering Contradiction:

Improvepower switching capabilityVSAvoidelectrical overstress failure

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The surge voltage limiting element is specifically applied to the low-side gate driver circuit where the electrical overstress risk is highest. This localized protection approach targets the specific area vulnerable to surge voltage damage while maintaining the overall high voltage power switching capability of the gate driver circuit.

Inventive Principle:

Principle #3Local quality

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

The integration of a surge voltage limiting element within the power module effectively reduces surge voltages, enhancing the reliability of high voltage gate driver circuits by preventing electrical overstress failures and ensuring stable operation.

Implementation Method 1

a surge voltage may be induced due to stray inductance of a printed circuit board (PCB) pattern and the shunt resistor

Methodology Applied

Scientific EffectElectrical Inductance: Inductor

Data Source

PatentUS11349303B2Power module with integrated surge voltage limiting element

Publication Date: 2022.05.31 INFINEON TECH AUSTRIA AG

AI summary

One or more embodiments provide a power module that includes a high-side power transistor; a low-side power transistor coupled to the high-side power transistor, the low-side power transistor including a first load path terminal through which a load current enters the low-side power transistor and a second load path terminal through which the load current exits the low-side power transistor; a gate driver integrated circuit (IC) configured to drive the high-side power transistor and/or the low-side power transistor; a leadframe having a low-side voltage pin configured to be coupled to a low-side voltage source; a surge voltage limiting element coupled between the second load path terminal of the low-side power transistor and the low-side voltage pin; and a module package, where the high-side power transistor, the low-side power transistor, the gate driver IC, the leadframe, and the surge voltage limiting element are encapsulated in the module package.