LDO Voltage Regulator Floating Reference Stability
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Solution Overview
Problem
Conventional Low Dropout (LDO) voltage regulators face stability issues due to high open loop output impedance, making them susceptible to load variations, which complicates frequency stability and compensation, especially in modern circuits with multiple poles and zeros.
Innovation Solution
The proposed solution involves reducing the overall loop gain of LDO voltage regulators to enhance stability, using a simplified configuration with a PMOSFET as the pass device and a Zener diode-based feedback circuit that sets a floating voltage reference, allowing for easier stabilization and improved load response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If higher loop gain is used to enhance output voltage regulation accuracy, then voltage regulation accuracy is improved, but system stability becomes more difficult to maintain
Solution Approach 1:
The patent changes the loop gain parameter from high to low to resolve the contradiction. By reducing the loop gain, the system achieves improved stability while maintaining adequate voltage regulation accuracy for the application requirements.
2Speed
If high open loop output impedance is present to enable rapid output current adjustment, then load response capability is improved, but frequency stability becomes susceptible to load variations
Solution Approach 1:
The patent modifies the output impedance parameter by reducing it through the low loop gain configuration. This change reduces the susceptibility to load variations and improves frequency stability while maintaining the ability to respond to load changes.
3Ease of manufacture
If simplified configuration is used to reduce device complexity, then ease of manufacture is improved, but compensation difficulty may increase
Solution Approach 1:
The patent simplifies the compensation network by reducing the number of poles and zeros through the low loop gain approach. This parameter change eliminates the need for complex compensation circuits while maintaining system stability.
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
This approach results in a more stable LDO voltage regulator with reduced loop gain, suitable for applications requiring simplicity and stability, and is effective in maintaining a regulated output voltage despite load variations, as demonstrated by the DC and transient response plots.
Implementation Method 1
a Zener diode-based feedback circuit that sets a floating voltage reference
Data Source
AI summary
An embodiment of a voltage regulator (100, 200) includes a pass device (160, 260), a feedback circuit (170, 270), and an operational amplifier (opamp) (140, 240). A first current conducting terminal of the opamp is coupled to an input voltage node (114, 214), and a second current conducting terminal of the opamp is coupled to a regulated voltage node (122, 222). The feedback circuit is coupled between the regulated voltage node and the feedback node, and the feedback circuit is a floating voltage reference configured to produce a feedback signal. The opamp has an input (256) coupled to a feedback node (154, 254), and an output (258) coupled to a control terminal of the pass device. The opamp provides a signal to the control terminal based on the feedback signal from the feedback node. The control signal causes a current through the pass device to vary to maintain a voltage at the regulated voltage node at a target regulated voltage.