Linear Regulator Reference Modulation for Stable Current Limiting
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Solution Overview
Problem
Conventional linear regulators lose regulation during current limit mode, leading to skewed nodes and large output voltage overshoot when exiting current limit operation, as the voltage error amplifier circuit becomes nonfunctional.
Innovation Solution
A current limit circuit is integrated with the voltage error amplifier circuit to modulate the output reference voltage, maintaining the voltage error amplifier's functionality during current limit mode and preventing load current from exceeding a predetermined threshold, thereby avoiding skewed nodes and overshoot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional current limit mode is implemented in linear regulators, then load current is limited to protect the circuit, but the voltage error amplifier becomes nonfunctional causing skewed nodes and large output voltage overshoot
Solution Approach 1:
The patent combines the current limit circuit with the voltage error amplifier circuit into a unified structure. The current limit switch element is integrated within the error amplifier, allowing both voltage regulation and current limiting functions to operate simultaneously through a single circuit architecture, preventing the error amplifier from becoming nonfunctional during current limit mode.
Solution Approach 2:
The patent implements dynamic switching between different operating states of the current limit switch element. The switch element can be turned on or off based on current conditions, allowing the circuit to dynamically transition between normal voltage regulation mode and current limit mode while maintaining error amplifier functionality throughout the transition.
2Reliability
If the voltage error amplifier is disabled during current limit mode, then current limiting is achieved, but skewed nodes and large output voltage overshoot occur when exiting current limit operation
Solution Approach 1:
By merging the current limit functionality into the voltage error amplifier circuit structure, the patent ensures that the error amplifier remains operational during current limiting. This integration allows continuous voltage regulation feedback while limiting current, preventing the loss of regulation and subsequent voltage overshoot that occurs when the error amplifier is completely disabled.
Solution Approach 2:
The patent changes the operating parameters of the error amplifier during current limit mode by modulating the output reference voltage. This parameter change allows the error amplifier to continue functioning in a modified state that enables both current limiting and voltage regulation, rather than completely disabling the amplifier.
3Reliability
If the current limit switch element is turned on to limit load current, then current protection is provided, but the output reference voltage becomes modulated requiring compensation
Solution Approach 1:
The patent merges the current limit switch element directly into the error amplifier circuit, combining current limiting control with voltage regulation control in a single integrated structure. This reduces overall circuit complexity compared to having separate independent current limit and voltage regulation circuits that would require additional coordination and control logic.
Data Source
AI summary
A linear regulator system is described. The linear regulator system includes a linear regulator core circuit including a pass element adapted to provide an output voltage, and a voltage error amplifier circuit coupled to the pass element and adapted to regulate the output voltage to form a regulated output voltage, based on an output reference voltage. The linear regulator core circuit further includes a current limit circuit comprising a current limit switch element coupled to the voltage error amplifier circuit and adapted to selectively modulate the output reference voltage of the voltage error amplifier circuit to form a current limited reference voltage, based on a current limit control signal received at a current limit control terminal associated therewith, in order to limit a load current through the pass element from exceeding a predefined maximum allowable load current limit.