Voltage Regulator Gate Breakdown Prevention via Diode Clamping
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Solution Overview
Problem
Related-art voltage regulators experience breakdown of the input transistor's gate when an overshoot occurs at the output terminal due to increased gate voltage, leading to reduced output voltage and operational instability.
Innovation Solution
Incorporating a diode connected between the cathode and gate of the input transistor within the error amplifier circuit to limit the gate-source voltage and prevent breakdown, while maintaining a small area requirement and minimizing leakage current influence on the divided voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gate voltage of the input transistor increases during output overshoot, then the error amplifier circuit can respond to the voltage deviation, but the gate of the input transistor breaks down due to excessive voltage
Solution Approach 1:
A diode is introduced as an intermediary component between the gate and source of the input transistor. The diode's anode connects to the gate while its cathode connects to the source, serving as a voltage clamp that prevents the gate-source voltage from exceeding the diode's forward voltage drop. This intermediary structure allows the error amplifier to respond to voltage deviations while protecting the gate from breakdown.
Solution Approach 2:
The diode changes the voltage parameter at the gate by clamping it to approximately one diode forward voltage drop above the source voltage. This parameter change limits the maximum gate-source voltage to a safe value while still allowing sufficient voltage range for the error amplifier to function during normal regulation and overshoot conditions.
2Reliability
If a protective component is added to prevent gate breakdown, then the reliability improves, but the device complexity increases
Solution Approach 1:
The diode serves as a simple intermediary protective component that adds minimal complexity to the circuit. By placing the diode in parallel with the gate-source junction, the circuit structure remains straightforward while gaining robust gate protection against voltage spikes and overshoot conditions.
3Reliability
If the diode is placed between gate and source to limit voltage, then the gate breakdown is prevented, but the leakage current may affect the divided voltage
Solution Approach 1:
The diode configuration creates a voltage reference copy at the gate that mirrors the source voltage plus a fixed diode drop. This copied voltage relationship ensures stable gate voltage while the diode's low leakage characteristics minimize interference with the precision voltage division function performed by the resistive divider network.
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
Prevents breakdown of the input transistor's gate during overshoots and allows earlier recovery of the error amplifier circuit's operating point when power supply voltage drops, ensuring stable output voltage regulation.
Implementation Method 1
The diode includes a cathode connected to a source of the input transistor and an anode connected to a gate thereof
Data Source
AI summary
Provided is a voltage regulator capable of preventing breakdown of a gate of an input transistor even when an overshoot occurs at an output terminal. The voltage regulator includes a diode, which is provided to an input transistor to which a divided voltage of an error amplifier circuit is input. The diode includes a cathode connected to a source of the input transistor and an anode connected to a gate thereof.