Voltage Regulator Gate Protection Without Drivability Loss
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Solution Overview
Problem
The existing voltage regulators limit the drivability of NMOS transistors due to gate protection mechanisms, which restrict the output transistor's performance.
Innovation Solution
A voltage regulator with a clamp circuit and level shift circuit configuration that protects the gate of the output transistor without limiting its drivability, using PMOS transistors and a constant current circuit to control the clamp level and prevent breakdown, allowing operation in a high drivability region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gate of the NMOS transistor is clamped by a diode to protect from breakdown, then the gate is protected from exceeding withstand voltage, but the drivability of the NMOS transistor is limited
Solution Approach 1:
The clamp circuit is designed to be dynamic rather than static. The clamp level is adjusted based on the output voltage state: when output voltage is normal, the clamp circuit operates at a higher level that does not restrict drivability; when output voltage drops abnormally, the clamp circuit activates at a lower level to protect the gate. This dynamic adjustment resolves the contradiction between protection and drivability.
Solution Approach 2:
The invention changes the clamp voltage parameter dynamically based on operating conditions. By using a clamp circuit with adjustable threshold levels that respond to output voltage changes, the system maintains high drivability during normal operation while providing effective protection during abnormal conditions, thus resolving the fixed-parameter limitation of conventional diode clamping.
2Ease of operation
If a clamp circuit is added to protect the gate without limiting drivability, then the drivability is improved, but the device complexity increases
Solution Approach 1:
The clamp circuit is designed to perform multiple functions: it provides gate protection during abnormal conditions, maintains high drivability during normal operation, and integrates with the existing error amplifier and output transistor control. This multi-functionality justifies the added complexity by delivering multiple benefits from a single circuit addition.
Solution Approach 2:
The clamp circuit is designed to automatically activate based on the output voltage state without requiring external control signals. The circuit self-regulates by monitoring the output voltage and activating protection only when needed, reducing the need for additional control logic and minimizing the overall complexity increase.
Data Source
AI summary
Provided is a voltage regulator including a clamp circuit capable of protecting a gate of an output transistor without limiting a drivability of the output transistor. The voltage regulator includes a level shift circuit having an input terminal connected to the gate of the output transistor and an output terminal connected to an input of the clamp circuit. The clamp circuit is controlled by an output voltage of the level shift circuit.