Isolated Voltage Converter Control for Low-Voltage Current Limiting
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Solution Overview
Problem
Isolated voltage conversion circuits face the risk of damaging electronic devices due to large output currents when the output voltage is low, as existing over-power protection mechanisms fail to adequately limit current under varying voltage conditions.
Innovation Solution
A control circuit is implemented with a duty cycle control circuit, feedback frequency control circuit, and secondary driving control circuit to manage the switching times of primary and secondary switches, limiting output current by controlling the switching period and frequency based on load conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If over-power protection is designed to limit maximum output power, then the electronic device is protected from large output power damage, but the electronic device may be damaged by large output current when output voltage is low
Solution Approach 1:
The patent implements a feedback mechanism where the output voltage is detected and fed back to the control circuit. When the output voltage drops below a threshold, the control circuit automatically adjusts the duty cycle of the primary power switch to limit the output current. This closed-loop feedback system dynamically responds to voltage changes and prevents excessive current from damaging the electronic device.
Solution Approach 2:
The patent changes the control parameter from fixed over-power protection to dynamic parameter adjustment based on output voltage. The control circuit monitors output voltage and modifies the duty cycle parameter in real-time. When output voltage is low, the duty cycle is reduced to limit output current, thereby preventing current-induced damage while maintaining protection against power overload.
2Adaptability or versatility
If the output voltage varies in a wide range, then the voltage conversion circuit adapts to different conditions, but the upper limit of output current becomes large when output voltage is low
Solution Approach 1:
The patent introduces dynamic control of the duty cycle based on real-time output voltage detection. Instead of a fixed duty cycle, the control circuit continuously adjusts the duty cycle parameter according to the detected output voltage level. This dynamic adjustment ensures that when output voltage varies widely, the output current remains within safe limits, preventing damage while maintaining adaptability to different voltage conditions.
Solution Approach 2:
The control circuit employs feedback from the output voltage detection to dynamically adjust the duty cycle. When the output voltage drops, the feedback signal triggers the control circuit to reduce the duty cycle, thereby limiting the output current. This feedback mechanism enables the circuit to maintain safe operating current levels across a wide output voltage range.
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 limits output current to protect electronic devices by ensuring the switching period is maintained within a safe range, even under low output voltage conditions, thereby preventing damage.
Implementation Method 1
The transformer has a primary winding and a secondary winding. The primary winding is coupled in series with the primary switch, and the secondary winding is coupled in series with the secondary switch.
Data Source
AI summary
A control circuit for a voltage conversion circuit is provided. The control circuit includes a duty cycle control circuit, a feedback frequency control circuit and a secondary driving control circuit. The duty cycle control circuit provides a switching time control signal based on an on-period of a secondary switch of the voltage conversion circuit. The switching time control signal indicates a first duration. The feedback frequency control circuit provides a feedback frequency control signal based on a feedback signal operable to indicate a load of the voltage conversion circuit. The feedback frequency control signal indicates a second duration. The secondary driving control circuit provides a switching release signal based on the switching time control signal and the feedback frequency control signal. The switching release signal turns on a primary switch of the voltage conversion circuit in response to the first duration and the second duration.