LDO Leakage Compensation Circuit for Output Voltage Stability
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Solution Overview
Problem
Low-dropout regulators (LDOs) face issues with leakage current when the source-to-drain voltage is increased, leading to unreliable output voltages that can exceed the reliability limits of connected devices, especially during stress testing or low-load conditions.
Innovation Solution
A leakage current compensation circuit that replicates the leakage current of the LDO's pass device using a current mirror circuit, providing a compensating current to counteract the leakage, while drawing minimal power during normal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the source-to-drain voltage of the pass device is increased to expand operational range, then the LDO can operate under stress conditions, but leakage current increases causing output voltage to drift beyond reliability limits
Solution Approach 1:
The patent creates a replica pass device that copies the electrical characteristics of the original pass device. This replica device replicates the leakage current behavior, allowing the compensation circuit to generate an equal and opposite current to counteract the leakage, thereby maintaining output voltage stability even when the source-to-drain voltage is increased for expanded operational range
Solution Approach 2:
The patent implements a feedback mechanism where the compensation circuit continuously monitors the output voltage and adjusts the compensating current accordingly. When leakage current causes output voltage to drift, the feedback loop detects this change and increases the compensating current to restore the output voltage to its regulated value, ensuring reliability across the expanded operational range
2Reliability
If a compensation circuit is added to counteract leakage current, then output voltage stability is maintained, but circuit complexity increases
Solution Approach 1:
Instead of using complex active compensation circuits that would require multiple transistors and control logic, the patent simply copies the pass device itself to create the replica. This approach maintains output voltage stability while minimizing added complexity, as the replica device is structurally identical to the original pass device and requires no additional control circuitry
Solution Approach 2:
The compensation circuit uses the replica pass device to automatically generate the compensating current without external control. The replica device self-adjusts its current based on its inherent electrical characteristics matching the original pass device, eliminating the need for complex control logic and reducing overall circuit complexity while maintaining reliability
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
Effectively maintains regulated output voltage within safe limits by counteracting leakage current, ensuring reliable operation even under stress conditions without constant power consumption.
Implementation Method 1
a current mirror circuit coupled to the replica device and configured to provide a compensating current to an output of the pass device
Data Source
AI summary
Circuits and methods that compensate for the problems created by low-dropout regulator (LDO) leakage current, particularly when stressed. Embodiments include an improved LDO configured to provide a load current, and which includes a leakage current compensation circuit. The leakage current compensation circuit generates a compensating current that offsets the leakage current through the pass device of the LDO during conditions that induce such leakage. More specifically, the leakage current compensation circuit can replicate the leakage current of the pass device of the LDO and feed a compensating current back into the LDO from a current mirror circuit while drawing zero-power during normal use, when leakage current is absent. LDO circuits that include a leakage current compensation circuit are particularly useful as voltage sources for positive or negative charge pumps, but are also quite useful in applications requiring a regulated voltage output.