Transistor Switch Control Circuit for Shoot-Through Restraint
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Solution Overview
Problem
Conventional power circuits experience shoot-through current issues due to the inability of transistor switches to promptly switch between on and off states, leading to power consumption and potential damage from overheating.
Innovation Solution
A circuit comprising a master selecting unit and a logic unit that generates control signals to manage the switching sequence of two transistor switches, ensuring one switch is turned off before the other is turned on, thereby minimizing simultaneous on-states and preventing shoot-through current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If two transistor switches are controlled to switch simultaneously based on input signal, then the power circuit can efficiently control power transmission, but shoot through current occurs causing power consumption and potential damage
Solution Approach 1:
The control circuit introduces a delay mechanism where the lower-arm transistor switch is turned off before the upper-arm transistor switch is turned on. Specifically, when the input signal transitions from low to high, the lower-arm switch is turned off first, and only after a predetermined delay period does the upper-arm switch turn on. This preliminary action prevents both switches from being simultaneously on, eliminating shoot through current while maintaining efficient power transmission control.
2Device complexity
If two transistor switches are controlled to switch simultaneously, then the control circuit is simple, but the transistor switches may be damaged due to overheat from shoot through current
Solution Approach 1:
The control circuit uses a delay circuit (such as a RC circuit or dedicated delay element) to create a time gap between the turn-off of the lower-arm switch and the turn-on of the upper-arm switch. This preliminary delay action ensures that the transistor switches never overlap in the on-state, preventing overheating and damage while adding only minimal complexity to the control circuit through the inclusion of the delay mechanism.
3Speed
If the transistor switches switch quickly, then the power transmission response is fast, but shoot through current occurs during switching transitions
Solution Approach 1:
The control circuit applies a preliminary anti-action by intentionally delaying the turn-on of the upper-arm transistor switch until after the lower-arm switch has been turned off. This counter-intuitive delay prevents the harmful shoot through current that would otherwise occur during simultaneous switching transitions, allowing fast switching overall while eliminating the harmful overlap period through the predetermined delay mechanism.
Data Source
AI summary
A circuit for restraining a shoot through current comprises a master selecting unit and a logic unit. The master selecting unit receives an input signal, and outputs first and second master selecting signals. The logic unit comprises first and second logic elements which generate first and second control signals for controlling two transistor switches connected in series. The first and second logic elements change the logic states of the first and second control signals according to the first and second master selecting signals. When the input signal is at a first logic level, the first logic element acquires a control privilege to change the logic state of the first control signal and trigger the second logic element to change the logic state of the second control signal. When the input signal is at a second logic, the second logic element acquires the control privilege.