Power MOS Transistor Reverse Current Protection Circuit
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Solution Overview
Problem
Semiconductor apparatuses with power MOS transistors face malfunctions due to reverse currents, which cause abnormal voltages and prevent the protection circuit from returning to a normal state after the reverse current occurs, leading to persistent power MOS transistor shutdown.
Innovation Solution
A semiconductor apparatus with a timer block that counts up a value to a predetermined condition and a protection transistor that short-circuits the power MOS transistor's source and gate, resetting the count value when the output voltage no longer meets the condition, preventing malfunction and allowing the power MOS transistor to return to an on state after a reverse current is canceled.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protection circuit is added to protect the power MOS transistor, then the reliability is improved, but the device complexity increases
Solution Approach 1:
The protection transistor is merged with the power MOS transistor structure, sharing the same substrate and epitaxial layer. The protection circuit components (timer block, detection circuit) are integrated into the same semiconductor device, reducing overall system complexity while maintaining protection functionality.
Solution Approach 2:
The protection transistor serves multiple functions: it acts as both the main power switching device and the protected device simultaneously. The timer block and detection circuit work together to provide both timing control and abnormal voltage detection, eliminating the need for separate protection circuits.
2Reliability
If the protection transistor continuously monitors output voltage, then the reliability is improved, but the loss of energy increases
Solution Approach 1:
The timer block generates periodic clock signals to control the counting operation, and the detection circuit periodically checks the output voltage at specific intervals rather than continuously monitoring. This periodic operation reduces energy consumption while maintaining effective protection.
Solution Approach 2:
The protection transistor monitors its own output voltage through the integrated detection circuit, eliminating the need for external monitoring components that would consume additional power. The system uses its own operational parameters for self-diagnosis and protection.
Data Source
AI summary
There has been a problem in semiconductor apparatuses of related art in which a circuit operation cannot be returned after a reverse current occurred. In one embodiment, a semiconductor apparatus includes a timer block configured to count up a count value to a predetermined value in response to a control signal being enabled, the control signal instructing a power MOS transistor to be turned on, and a protection transistor including a drain connected to a gate of the power MOS transistor, a source and a back gate connected to a source of the power MOS transistor, and an epitaxial layer in which the power MOS transistor is formed, the epitaxial layer being supplied with a power supply voltage. The protection transistor short-circuits the source and gate of the power MOS transistor in response to an output voltage of the power MOS transistor meeting a predetermined condition and the count value reaching the predetermined value. The timer block resets the count value when the output voltage of the power MOS transistor no longer meets the predetermined condition.