Capless Linear Voltage Regulator with Dual Current Mirrors
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Solution Overview
Problem
Conventional linear voltage regulators require external off-chip output capacitors, which are difficult to implement in integrated circuits and increase costs, while also needing to respond quickly to load variations in output voltage.
Innovation Solution
A capless linear voltage regulator design utilizing a control circuit with first and second current mirrors and an input stage, which controls the pass device to regulate output voltage without an external capacitor, allowing for rapid response to voltage variations by adjusting currents through the current mirrors based on reference voltages and feedback inputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a large off-chip output capacitor is connected to the output of the voltage regulator, then the response speed to load variations is improved, but the device complexity and cost increase
Solution Approach 1:
The patent removes the external output capacitor from the voltage regulator system, extracting this component entirely. Instead of using a large off-chip capacitor for output filtering, the invention implements an integrated solution where the control circuit directly drives the pass transistor, eliminating the need for external capacitive components while maintaining regulation functionality.
Solution Approach 2:
The patent introduces a control circuit with error amplifier and compensation network as an intermediary between the feedback input and pass transistor. This intermediary circuit provides the necessary phase compensation and stability control that would traditionally require external capacitors, enabling fast response without large off-chip capacitive elements.
2Stability of the object's composition
If a large off-chip output capacitor is connected to the output of the voltage regulator, then the output voltage stability is improved, but the manufacturing cost increases
Solution Approach 1:
The patent merges the functions of output filtering and voltage regulation into a single integrated control circuit. The error amplifier and compensation network work together to provide both stability and regulation functionality that would traditionally require separate external capacitors, reducing component count and manufacturing cost.
Solution Approach 2:
The patent changes the operational parameters of the control circuit, specifically using a compensation network with resistors and capacitors configured to provide phase compensation without requiring large external output capacitors. This parameter optimization enables stability with smaller, more cost-effective components.
3Speed
If the voltage regulator responds quickly to load variations, then the response speed is improved, but the control circuit complexity increases
Solution Approach 1:
The patent implements a dynamic control circuit with an error amplifier that continuously monitors the feedback voltage and adjusts the pass transistor gate voltage in real-time. This dynamic response mechanism enables fast reaction to load variations without requiring overly complex control logic, as the operational amplification naturally provides rapid error correction.
Solution Approach 2:
The patent employs a feedback mechanism where the output voltage is continuously monitored through a feedback network and compared against a reference voltage. The error amplifier processes this feedback signal to generate appropriate control signals for the pass transistor, enabling automatic and rapid correction of voltage deviations without complex external control circuitry.
Data Source
AI summary
A voltage regulator includes an output stage including a control terminal and a load path, with the load path coupled between the input terminal and the output terminal. The voltage regulator also includes a control circuit with an input stage, a first current mirror, and a second current mirror. The input stage includes a first control input configured to receive a first reference voltage, a second control input configured to receive a second reference voltage, a feedback input coupled to the output terminal, a first output terminal, and a second output terminal. The first current mirror includes a reference current path coupled between a first supply terminal and the first output terminal of the input stage, and an output current path coupled between the first supply terminal and the control terminal of the pass device.