Voltage Regulator Fold-Back Overcurrent Protection Circuit
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Solution Overview
Problem
Semiconductor process deviations lead to uncertainty in overcurrent values in voltage regulators with fold-back overcurrent protection circuits, affecting the startup time and accuracy of the protection mechanism.
Innovation Solution
A voltage regulator design incorporating a current sensing unit, first and second mirroring units, a voltage to current converting unit, and a pull-up unit, which generates proportional currents to control the output voltage and current, minimizing the impact of semiconductor process deviations and ensuring accurate overcurrent protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fold-back overcurrent protection circuit is implemented, then power consumption is reduced and the voltage regulator is protected from burning, but semiconductor process deviations cause uncertainty in overcurrent values affecting protection accuracy
Solution Approach 1:
The patent changes the parameter being monitored from absolute current value to voltage difference. By comparing the voltage at node A (proportional to output voltage) with a reference voltage, the circuit detects overcurrent conditions based on voltage differential rather than absolute current, making the protection threshold independent of semiconductor process variations that would otherwise cause inconsistency in current-sensing components.
Solution Approach 2:
The patent introduces a voltage divider circuit as an intermediary between the output stage and the protection circuit. This voltage divider transforms the current information into voltage information that can be compared with the reference voltage, creating a mediation layer that isolates the protection logic from direct dependence on current-sensing component characteristics that vary with semiconductor manufacturing processes.
2Reliability
If the output voltage is lowered during overcurrent condition, then the output current is reduced to prevent damage, but the protection mechanism startup time becomes uncertain due to process deviations
Solution Approach 1:
The patent establishes a predetermined reference voltage that represents the desired voltage difference threshold before any overcurrent condition occurs. This preliminary setting of the reference voltage allows the circuit to immediately compare the actual voltage at node A against the pre-established threshold, enabling rapid and consistent protection activation without uncertainty about when the protection should engage.
Solution Approach 2:
The patent implements a feedback mechanism where the voltage at node A (which is proportional to output voltage) is continuously monitored and compared with the reference voltage. When the output voltage drops during overcurrent, this feedback loop immediately detects the voltage difference and triggers the protection response, ensuring consistent and predictable protection startup timing independent of semiconductor process variations.
Data Source
AI summary
A voltage regulator includes a constant voltage power circuit and an overcurrent protection circuit. The constant voltage power circuit generates an output voltage, an output current and a divided voltage. The overcurrent protection circuit includes a current sensing unit, a first mirroring unit, a voltage to current converting unit, a second mirroring unit, and a pull up unit. The current sensing unit generates a sensing current according to the output current. The first mirroring unit generates a first mirroring current. The first mirroring current is proportional to the output current. The voltage to current converting unit is used for converting the divided voltage into a first current. The second mirroring unit generates a second mirroring current. The second mirroring current is proportional to the second current. The pull up unit controls the output voltage and the output current according to the first mirroring current and the second mirroring current.