Resonant Flyback Switching Control for Safe Capacitor Discharge
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Solution Overview
Problem
Existing resonant flyback power converters experience over-current issues during the power-on period due to prolonged discharge of the resonant capacitor, leading to potential damage to transistors.
Innovation Solution
A switching control circuit that generates short-pulses of the second driving signal to discharge the resonant capacitor during power-on, with pulse-widths less than 1 μs to prevent over-current, and an open-loop feedback control during this period to manage the discharge process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the second driving signal is turned on for a long time to discharge the resonant capacitor during power-on, then the resonant capacitor is discharged, but the negative current becomes too large causing over-current damage
Solution Approach 1:
The patent applies periodic action by using multiple short-pulses instead of a continuous long-duration signal. The second driving signal is generated as a plurality of short-pulses during the power-on period, each pulse having a limited width that prevents excessive negative current while still achieving resonant capacitor discharge through repeated cycling.
Solution Approach 2:
The patent implements dynamics by making the pulse-width of the second driving signal adjustable and controllable. The controller dynamically adjusts the pulse-width to be sufficiently short to prevent over-current while maintaining enough duration to discharge the resonant capacitor, adapting the discharge process to real-time current conditions.
2Object-generated harmful factors
If short-pulses are used to discharge the resonant capacitor, then over-current is prevented, but the discharge efficiency may be reduced
Solution Approach 1:
The periodic short-pulses achieve discharge efficiency through cumulative effect. Multiple pulses are applied in sequence during the power-on period, with each pulse contributing to the discharge process. The periodic nature allows the resonant capacitor to discharge progressively without generating excessive current in any single pulse.
Solution Approach 2:
The patent maintains continuity of useful action by ensuring that the short-pulses are applied continuously throughout the power-on period. The plurality of pulses provides sustained discharge action, ensuring the resonant capacitor is fully discharged by the end of the power-on period while maintaining safe current levels throughout the process.
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
Prevents over-current damage to transistors by effectively discharging the resonant capacitor during power-on, ensuring safe and efficient operation of the resonant flyback power converter.
Implementation Method 1
a resonant capacitor which are connected in series and are coupled to the half-bridge circuit
Implementation Method 2
a transformer and a resonant capacitor which are connected in series and are coupled to the half-bridge circuit
Data Source
AI summary
A switching control circuit for use in controlling a resonant flyback power converter generates a first driving signal and a second driving signal. The first driving signal is configured to turn on the first transistor to generate a first current to magnetize a transformer and charge a resonant capacitor. The transformer and charge a resonant capacitor are connected in series. The second driving signal is configured to turn on the second transistor to generate a second current to discharge the resonant capacitor. During a power-on period of the resonant flyback power converter, the second driving signal includes a plurality of short-pulses configured to turn on the second transistor for discharging the resonant capacitor. A pulse-width of the short-pulses of the second driving signal is short to an extent that the second current does not exceed a current limit threshold.