Phase Compensation Circuit for Voltage Regulators at Low Voltage Drop
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Solution Overview
Problem
Conventional voltage regulators face stability issues when the input/output voltage difference is small, as the auxiliary transistor fails to operate in the saturation region due to a lower source-drain voltage, hindering effective phase compensation.
Innovation Solution
Incorporating an offset voltage source connected to the gate of the auxiliary transistor, allowing it to operate in the saturation region even with small input/output voltage differences by adjusting the offset voltage to match or exceed the voltage drop across the resistor, thereby ensuring stable phase compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the auxiliary transistor is used for phase compensation in a conventional voltage regulator, then phase compensation is achieved, but the transistor cannot operate in the saturation region when the input/output voltage difference is small
Solution Approach 1:
An offset voltage source is introduced as an intermediary element between the error amplifier output and the auxiliary transistor gate. This offset voltage source mediates the voltage relationship by providing an additional voltage component that ensures the auxiliary transistor maintains sufficient gate-source voltage to operate in the saturation region, even when the input/output voltage difference is small. The offset voltage acts as a buffer that decouples the auxiliary transistor's operating conditions from the input/output voltage difference.
2Reliability
If the voltage drop across the resistor is increased to ensure the auxiliary transistor operates in saturation, then phase compensation stability is improved, but the required input/output voltage difference becomes unreasonably large
Solution Approach 1:
The invention changes the electrical parameters at the gate of the auxiliary transistor by introducing an offset voltage. This parameter change directly affects the gate-source voltage of the auxiliary transistor, allowing it to maintain saturation operation without requiring a large voltage drop across the resistor. By modifying the gate voltage parameter through the offset source, the system achieves stable phase compensation with a reasonable input/output voltage difference.
Data Source
AI summary
A voltage regulator includes an output transistor, a voltage division circuit, an error amplifier, a phase compensation circuit connected between the output terminal and the output terminal of the voltage division circuit, and an auxiliary transistor having a source connected to the input terminal, a drain connected to the phase compensation circuit, and a gate connected to the output terminal of the error amplifier through an offset voltage source.