Voltage Regulator Dropout Reduction via Positive Temperature Coefficient Cascode
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Solution Overview
Problem
In voltage regulators with a voltage control transistor, the negative temperature coefficient of the drain current limits the ability to increase the gate voltage, making it difficult to reduce the dropout voltage without exceeding the gate breakdown voltage of the output transistor.
Innovation Solution
A voltage regulator design incorporating a source-grounded amplifier circuit with a cascode circuit having a positive temperature coefficient, which helps maintain a constant drain current and gate voltage, reducing the dropout voltage while preventing output transistor breakdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a voltage control transistor with constant gate voltage is used to limit the gate voltage of the output transistor, then the gate breakdown voltage is protected, but the dropout voltage cannot be reduced due to negative temperature coefficient at low temperatures
Solution Approach 1:
The patent changes the temperature coefficient parameter from negative to positive by using a cascode circuit configuration. The cascode circuit with current source creates a positive temperature coefficient in the gate voltage of the voltage control transistor, allowing the gate voltage to increase at low temperatures and thereby reducing the dropout voltage while still protecting against gate breakdown at high temperatures.
2Power
If the constant voltage applied to the gate of the voltage control transistor is increased to reduce dropout voltage, then the dropout voltage is reduced, but the gate breakdown voltage is exceeded
Solution Approach 1:
The patent makes the gate voltage of the voltage control transistor dynamic rather than constant. The cascode circuit causes the gate voltage to vary with temperature, being higher at low temperatures to reduce dropout voltage and lower at high temperatures to prevent gate breakdown, thus resolving the contradiction between reducing dropout voltage and preventing gate breakdown.
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
The solution effectively reduces the dropout voltage of the output voltage while ensuring the output transistor does not exceed its breakdown voltage, maintaining stability across temperature variations.
Implementation Method 1
a cascode circuit controlled by a voltage having a positive temperature coefficient
Data Source
AI summary
A source-grounded amplifier circuit supplied with a signal of an error amplifier circuit, and an output transistor supplied with a control voltage of the source-grounded amplifier circuit are provided. The source-grounded amplifier circuit has, in a signal path, a current limiting circuit including a cascode circuit controlled by a voltage having a positive temperature coefficient. A voltage regulator capable of reducing a dropout voltage of an output voltage without exceeding a gate breakdown voltage of the output transistor is provided.