Flyback Converter Wakeup Circuit for Output Voltage Stability
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Solution Overview
Problem
Flyback converters experience a drop in output voltage if the primary power switch remains OFF for an extended period, potentially affecting the normal operation of subsequent stages.
Innovation Solution
A flyback converter with a wakeup circuit that includes a monitor circuit, a sample-hold circuit, and a comparison circuit. The monitor circuit generates an enable signal when the voltage at the wakeup terminal is lower than a reference voltage, allowing the sample-hold circuit to sample and hold feedback voltages based on the output voltage's comparison to a reference threshold, and the comparison circuit generates a comparison signal to wake up the primary power switch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the primary power switch remains OFF for an extended period to save energy, then energy consumption is reduced, but the output voltage drops below the required value
Solution Approach 1:
The wakeup circuit performs preliminary detection of the output voltage before the switch-off period ends. When the output voltage approaches the lower threshold, the circuit proactively generates a wakeup signal to turn on the primary power switch, preventing the voltage from dropping below the required level while still maintaining extended switch-off periods for energy savings.
2Reliability
If the primary power switch is turned on frequently to maintain output voltage, then output voltage stability is improved, but energy consumption increases
Solution Approach 1:
The wakeup circuit continuously monitors the output voltage and uses this feedback to determine when to generate a wakeup signal. The feedback mechanism allows the system to maintain output voltage stability only when necessary, rather than using frequent switching, thereby reducing unnecessary energy consumption while ensuring voltage stability is maintained.
3Device complexity
If a simple voltage monitoring mechanism is used, then device complexity is reduced, but the ability to detect and respond to voltage drops in time is insufficient
Solution Approach 1:
The wakeup circuit uses a lower threshold voltage for detection that is set below the minimum required output voltage. This preliminary detection approach allows the circuit to identify voltage drops early and generate wakeup signals before the voltage critically drops, providing timely response without requiring complex prediction algorithms.
Data Source
AI summary
A flyback converter with timely wakeup is discussed. The flyback converter adopts a wakeup circuit to monitor a voltage drop at the output voltage of the flyback converter. If the output voltage drops to a certain ratio of the previous voltage value, the wakeup circuit would notice the primary side of the flyback converter, to wake up the primary power switch.