Drive Device Gate Control for Power Switching Protection

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Solution Overview

Problem

Existing drive devices with protection circuits for power switching elements face issues with erroneous operation due to manufacturing variations and switching noise, leading to increased stress on the elements and incorrect short-circuit detection, as they either uniformly reduce gate voltage or rely on temperature-variant Zener diodes, causing waveform rounding and ringing.

Innovation Solution

A drive device with an on-side and off-side circuit connected in series, a protection circuit that includes a constant-current circuit and a collector current detector, which controls the gate current of the power switching element by drawing gate charge at a constant speed, reducing the gate voltage and collector current at a constant slew rate, and preventing erroneous operation through a filter circuit.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If resistance voltage division is used to reduce gate voltage for short-circuit protection, then the gate voltage is reduced uniformly, but waveform rounding occurs and the time constant increases, resulting in increased stress on the power switching element

Engineering Contradiction:

Improveshort-circuit protectionVSAvoidstress on power switching element

Core Design Contradiction:

ReliabilityVSStress or pressure

Solution Approach 1:

The patent changes the parameter of gate voltage reduction from uniform resistance division to controlled constant-current discharge. This allows precise control of the voltage reduction rate, maintaining protection reliability while minimizing waveform rounding and time constant increase, thereby reducing stress on the power switching element.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If a large short-circuit detection threshold is set to prevent erroneous release, then protection reliability improves, but the stress on the power switching element increases

Engineering Contradiction:

Improveprotection operation stabilityVSAvoidstress on power switching element

Core Design Contradiction:

ReliabilityVSStress or pressure

Solution Approach 1:

The patent employs feedback control by detecting the collector current and using it to control the gate voltage reduction process. The constant-current circuit adjusts the gate discharge current based on the detected collector current, ensuring protection activation at appropriate thresholds while preventing erroneous release, thus maintaining low stress on the power switching element.

Inventive Principle:

Principle #23Feedback

3Speed

If Zener diode is used to reduce gate voltage rapidly, then the time constant problem is solved, but characteristic variation due to temperature or manufacturing variations causes erroneous release

Engineering Contradiction:

Improvegate voltage reduction speedVSAvoidprotection operation accuracy

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent substitutes the Zener diode's passive voltage clamping mechanism with an active constant-current circuit controlled by collector current detection. This replacement enables rapid gate voltage reduction through controlled discharge while using feedback from collector current detection to maintain protection accuracy, eliminating the characteristic variation problems of Zener diodes.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Loss of time

If gate voltage is reduced without precise control, then protection response is fast, but ringing is generated in the current and surge voltage is applied to the power switching element

Engineering Contradiction:

Improveprotection response timeVSAvoidringing and surge voltage

Core Design Contradiction:

Loss of timeVSObject-affected harmful factors

Solution Approach 1:

The patent applies dynamic control by adjusting the gate discharge current based on real-time collector current detection. The constant-current circuit dynamically adapts the discharge rate, enabling fast protection response while preventing excessive discharge that would cause ringing and surge voltage, thus eliminating harmful factors.

Inventive Principle:

Principle #15Dynamics

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 configuration effectively reduces waveform rounding and ringing, allows for precise control of gate voltage reduction, and minimizes stress on the power switching element by maintaining a constant collector current, even with variations in gate capacitance, thereby reducing the risk of erroneous protection releases.

Implementation Method 1

a constant-current circuit that defines a constant current for drawing a gate charge of the power switching element

Methodology Applied

Scientific EffectCapacitance discharge: Capacitance

Data Source

PatentUS9660636B2Drive device

Publication Date: 2017.05.23 DENSO CORP

AI summary

A drive device includes: an on-side circuit turning on a power switching element; an off-side circuit turning off the power switching element; and a protection circuit controlling a gate current of the power switching element. The protection circuit includes: a constant-current circuit that defines a constant current for drawing a gate charge of the power switching element; a protection switch that controls electrical connection between the constant-current circuit and the gate of the power switching element; and a collector current detector. The collector current detector turns off the on-side circuit to disconnect the power switching element from the main power supply, and turns on the protection switch after a predetermined time has elapsed from when the current value of the collector current of the power switching element exceeds a first threshold.