Flyback Converter Dynamic UVP to Prevent Restart Loops
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Solution Overview
Problem
Asymmetric half-bridge flyback converters face issues with output voltage drop before the input voltage reaches the under voltage protection threshold, leading to system restart and inefficiencies in standby power consumption and low load efficiency.
Innovation Solution
A flyback converter with a dynamic under voltage protection threshold is introduced, where the under voltage protection threshold is proportional to the output voltage, preventing system restart and optimizing power consumption by turning off the PFC circuit in fast charging applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the under voltage protection threshold is set low to enable operation at low voltage input, then the converter can work at low voltage input, but the output voltage drops before the input voltage reaches the threshold, causing system restart
Solution Approach 1:
The patent implements a dynamic under voltage protection threshold that changes based on operating conditions. The threshold is adjusted according to the output voltage and load conditions, allowing the system to adapt to different input voltage levels while maintaining stable operation. This resolves the contradiction by making the threshold flexible rather than fixed, enabling low voltage operation without causing unwanted system restarts.
Solution Approach 2:
The patent changes the protection threshold parameter dynamically based on output voltage levels and operating conditions. By adjusting the threshold parameter according to real-time system state, the converter can operate reliably at low input voltages without triggering false undervoltage protection and system restart. This parameter adaptation resolves the contradiction between low voltage adaptability and system stability.
2Loss of energy
If the PFC circuit is turned off in standby state to optimize power consumption, then standby power consumption is reduced, but the input voltage becomes relatively low which requires lower protection thresholds
Solution Approach 1:
The dynamic protection threshold adapts to the operating mode of the PFC circuit. When PFC is turned off in standby mode, the threshold automatically adjusts to accommodate the lower input voltage range, enabling the system to maintain low power consumption while still operating reliably across the full input voltage range.
Solution Approach 2:
The protection mechanism is designed to work universally in both PFC-on and PFC-off modes. The dynamic threshold adjustment enables the same converter to operate efficiently in both full-power mode (with PFC) and standby mode (without PFC), providing multi-functional adaptability across different operating conditions.
3Adaptability or versatility
If a single-transistor flyback converter is used to achieve wide input and output range, then the PFC circuit can be turned off in standby state, but the efficiency and power consumption are not optimized compared to asymmetric half-bridge
Solution Approach 1:
The asymmetric half-bridge converter with dynamic protection threshold achieves both wide operating range and low standby power consumption. The dynamic threshold enables reliable operation without PFC in standby mode, while the asymmetric half-bridge topology provides wider input/output range than single-transistor designs, resolving the contradiction between adaptability and energy efficiency.
Data Source
AI summary
The present disclosure relates to a flyback converter and a power supply system. The flyback converter comprises: a transformer; a first switching transistor and a second switching transistor; a first inductor and a first capacitor; and a control circuit. The control circuit includes an under voltage protection module configured to determine an under voltage protection threshold proportional to an output voltage of the flyback converter and to trigger an under voltage protection action of the flyback converter in a case that an input voltage of the flyback converter is less than the under voltage protection threshold. By setting an adaptive under voltage protection threshold, a system-restart phenomenon of the flyback converter after an input power failure or a shutdown may be avoided, and a PFC circuit may be turned off to optimize the standby power consumption and the low load efficiency in fast charging applications using an flyback topology.