Constant Voltage Power Source Circuit Overload Protection
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Solution Overview
Problem
Conventional constant voltage power source circuits face instability in output voltage during overload states, leading to potential overheating or device breakdown, as the feedback loop is disrupted when the output transistor is turned off for protection, making it difficult to smoothly return to a constant voltage state after an overload is resolved.
Innovation Solution
A constant voltage power source circuit with integrated voltage and current feedback circuits that control output voltage by switching between reference voltage and current limitation signals based on detection states, using a differential amplifier and PMOS transistors to maintain stability and limit current during overloads, ensuring the output voltage does not overshoot and preventing excessive current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the output transistor is turned off to protect the circuit during overload, then the circuit is protected from damage, but the feedback loop is blocked and output voltage becomes unstable
Solution Approach 1:
The patent implements dynamic switching between two operational modes: constant voltage mode (normal operation) and constant current mode (overload protection). The circuit transitions between these modes based on load conditions, allowing the output transistor to remain partially conductive during overload while limiting current, thus maintaining feedback loop operation and voltage stability even during protection events
Solution Approach 2:
The patent changes the control parameter from fixed voltage control to adaptive parameter control. During overload, the control circuit dynamically adjusts the transistor gate voltage to maintain a controlled current level rather than completely shutting off the transistor. This parameter change allows the circuit to protect itself while preserving feedback loop functionality and enabling smooth transition back to constant voltage mode
2Object-affected harmful factors
If the output transistor is completely turned off during overload protection, then excessive current is prevented, but the circuit cannot smoothly return to constant voltage state after overload is eliminated
Solution Approach 1:
The patent prepares the circuit for smooth recovery by maintaining the feedback loop operation during overload protection. The control circuit continuously monitors output conditions and keeps the transistor in a controlled conduction state rather than completely turning it off, so that when overload is eliminated, the circuit can immediately resume constant voltage regulation without requiring complex recovery sequences or creating voltage spikes
Data Source
AI summary
According to an embodiment, a constant voltage power source circuit has a voltage feedback circuit that controls an output voltage depending on a control voltage. It has a current feedback circuit that detects an output current, keeps the control voltage at a constant voltage until the output current reaches a predetermined current value, and changes a value of the control voltage at a time when the output current reaches the predetermined current value.