Active Clamp Load Drive Circuit for Back-EMF Heat Distribution
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Solution Overview
Problem
In semiconductor devices with inductive loads, high counter electromotive voltage generation during power transistor interruption leads to high power consumption and heat generation, which can cause device breakdown, and existing solutions either increase transistor size or face challenges in heat dissipation and wiring resistance.
Innovation Solution
A load drive device with a first transistor connected to an inductive load, an active clamp circuit that activates when the terminal voltage exceeds a threshold, and a second transistor connected in parallel to the first transistor, which is turned on when the first transistor is turned off to distribute the counter electromotive force and reduce heat concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the power transistor size is increased to suppress heat generation, then heat dissipation performance is improved, but chip cost increases
Solution Approach 1:
The power transistor is divided into multiple sections (first power transistor and second power transistor) that are arranged at intervals on the chip. This segmentation allows heat to dissipate more effectively from each individual transistor while maintaining a compact overall design, resolving the contradiction between heat dissipation performance and chip cost.
2Temperature
If the power transistor is divided into multiple sections to enhance heat dissipation, then temperature reduction is achieved, but wiring resistance increases
Solution Approach 1:
A current distribution circuit is introduced as an intermediary component to connect the multiple power transistor sections. This current distribution circuit efficiently distributes current to each transistor section while minimizing wiring resistance, allowing the system to achieve both good heat dissipation and low energy loss.
3Ease of operation
If the power transistor is interrupted to control the inductive load, then load control is achieved, but high counter electromotive voltage is generated
Solution Approach 1:
A clamp circuit is provided as a protective measure that activates when the power transistor is interrupted. The clamp circuit clamps the counter electromotive voltage to a safe level, preventing voltage spikes that could damage the transistor. This allows the system to achieve effective load control while protecting against harmful voltage transients.
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 suppresses local temperature concentration during counter electromotive force absorption while maintaining a smaller power transistor size, improving heat dissipation efficiency and preventing device destruction.
Implementation Method 1
an active clamp circuit that causes current to flow when a terminal voltage of a second control electrode between the first transistor and the inductive load exceeds a threshold
Data Source
AI summary
Achieved is a load drive device capable of suppressing local concentration of temperature at the time of absorbing a counter electromotive force of an inductive load while suppressing a size of a power transistor. The load drive device includes a first transistor connected between a first control electrode and an inductive load. Further, the load drive device includes an active clamp circuit that becomes conductive when a terminal voltage of a second control electrode between the first transistor and the inductive load exceeds a threshold. Furthermore, the load drive device includes a second transistor connected to the second control electrode and connected in parallel to the first transistor.