Pulsed Measurement of Power Transistor Id-Vds Characteristics

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Solution Overview

Problem

Existing methods for measuring the current-voltage characteristic of power transistors, such as curve tracers, face challenges in accurately capturing high-current/high-voltage regions due to heat production and limited measurement ranges, leading to inaccuracies in device modeling.

Innovation Solution

A method involving a measurement device that sets and measures drain current and voltage in a switching transient state, acquiring the current-voltage characteristic by measuring gate-source voltage and gate current, which reduces heat production and improves accuracy by focusing on switching transient states and plateau regions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If a curve tracer is used to measure the current-voltage characteristic of a power transistor in high-current/high-voltage region, then the measurement range is extended, but heat production increases and measurement accuracy deteriorates

Engineering Contradiction:

Improvemeasurement rangeVSAvoidheat production

Core Design Contradiction:

Area of stationary objectVSTemperature

Solution Approach 1:

The patent applies periodic pulse action to the transistor instead of continuous DC measurement. By using pulsed measurements with duty cycles less than 1%, the transistor operates in transient states where heat accumulation is minimized, enabling measurement in high-power regions without excessive temperature rise

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The measurement method rapidly transitions through the high-current/high-voltage region by applying voltage pulses and measuring during the transient switching period. The measurement is completed before significant heat can be generated, effectively 'skipping' through the dangerous high-power zone without prolonged exposure

Inventive Principle:

Principle #21Skipping (Rushing through)

2Measurement precision

If a curve tracer is used to measure the current-voltage characteristic, then the measurement can be performed, but the measurement precision deteriorates in high-current/high-voltage region due to heat production

Engineering Contradiction:

Improvemeasurement accuracyVSAvoidheat production

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The measurement system rapidly traverses the high-power region by applying voltage pulses and capturing measurements during the transient switching period. The entire measurement sequence is completed before significant heat can be generated, effectively skipping through the region where heat would otherwise degrade measurement accuracy

Inventive Principle:

Principle #21Skipping (Rushing through)

Solution Approach 2:

By using periodic pulse measurements with appropriate duty cycles, the system maintains the transistor in a transient state during measurement, preventing heat accumulation that would otherwise cause thermal drift and measurement errors in the high-current/high-voltage region

Inventive Principle:

Principle #19Periodic action

3Device complexity

If the drain current is assumed to remain constant in the saturation region for Si-MOSFET, then the measurement process is simplified, but the measurement precision deteriorates for power transistors like SiC-MOSFET due to short-channel effects

Engineering Contradiction:

Improvemeasurement process complexityVSAvoidcurrent-voltage characteristic accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

Instead of assuming constant current in saturation and performing a simplified measurement, the patent applies voltage pulses that drive the transistor through the entire characteristic curve including the saturation region. This partial measurement approach captures the actual non-constant current behavior in power transistors, providing accurate data without requiring complex iterative measurement procedures

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The patent changes the measurement approach from DC steady-state assumptions to transient pulsed measurements. By applying time-varying voltage pulses and measuring the resulting transient current responses, the system captures the actual dynamic behavior of power transistors in the saturation region, where current does change with voltage due to short-channel effects

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS20240329111A1Method for measuring current-voltage characteristic

Publication Date: 2024.10.03 ROHM CO LTD

AI summary

A method for measuring a current-voltage characteristic (Id-Vds characteristic) representing the relationship between the drain current Id (or collector current) and the drain-source voltage Vds (or collector-emitter voltage) of a transistor M1 includes setting the drain current Id (or collector current) and the drain-source voltage Vds (or collector-emitter voltage), measuring the gate-source voltage Vgs (or gate-emitter voltage) and the gate current Ig of the transistor M1 in a switching transient state, and acquiring the current-voltage characteristic (Id-Vds characteristic) of the transistor M1 based on the measurement results of the gate-source voltage Vgs (or gate-emitter voltage) and the gate current Ig.