Quasi-Resonant Flyback Ripple Suppression via Bus Voltage Compensation
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Solution Overview
Problem
Flyback isolated power supplies experience significant power frequency ripple in the output voltage due to fluctuations in the bus voltage, leading to reduced efficiency and output quality.
Innovation Solution
A ripple suppression circuit and method for quasi-resonant flyback power supplies, which generates a compensation signal based on bus voltage and uses a control circuit to compare signals, controlling the power switch to suppress ripples by adjusting the peak current on the primary side of the transformer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a capacitor Cbus is used to filter and compensate AC voltage, then the pulsation degree of AC voltage is reduced, but the capacitor still causes significant power frequency ripple in the bus voltage and output voltage
Solution Approach 1:
The patent implements a feedback mechanism by sampling the bus voltage and generating a compensation signal that is added to the reference signal. The control circuit continuously monitors the bus voltage fluctuations and adjusts the duty cycle of the power switch accordingly, creating a closed-loop control system that actively compensates for ripple rather than passively filtering it.
Solution Approach 2:
The patent changes the control parameter by introducing a compensation signal that dynamically adjusts the reference signal based on bus voltage conditions. By modifying the reference signal amplitude or offset in response to bus voltage ripple, the system adapts its operating parameters to maintain stable output despite input voltage fluctuations.
2Stability of the object's composition
If the flyback power supply operates with constant load, then the output voltage should remain unchanged, but bus voltage fluctuations cause output voltage to fluctuate, reducing efficiency and output quality
Solution Approach 1:
The control circuit uses feedback from the bus voltage sampling to generate a compensation signal that counteracts voltage fluctuations. This active feedback control prevents output voltage deviation caused by bus ripple, maintaining both voltage stability and conversion efficiency by optimizing the power switch duty cycle in real-time.
Solution Approach 2:
The compensation signal is generated in advance based on the sampled bus voltage before the ripple fully affects the output. By predicting and compensating for voltage fluctuations proactively rather than reactively, the system maintains stable output and efficient operation throughout the ripple cycle.
Data Source
AI summary
The application discloses a ripple suppression circuit and a ripple suppression method for quasi-resonant flyback power supply, wherein the ripple suppression circuit comprises a compensation circuit and a control circuit, the compensation circuit configured to generate a compensation signal based on bus voltage, and the control circuit configured to compare a first signal and a second signal to provide a first control signal to control the power switch of the quasi-resonant flyback power supply turning from the on state to the off state. Wherein the first signal is compensated by the compensating signal. Compared with traditional power switch control mode of quasi-resonant flyback power supply, the application takes the bus voltage as a part of the first signal, and compares the first signal with the second signal, then controls the status of the power switch according to the comparison result. Thus, the application can suppress the disturbance of the bus voltage to output voltage of the quasi-resonant flyback power supply, and improve output accuracy of the quasi-resonant flyback power supply.