Active Clamp Flyback Controller with Predicted Timing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional active-clamp circuits for flyback power converters experience high power loss at light loads due to high circulated current, and inefficiency at heavy loads, limiting the ability to operate at higher switching frequencies and reducing transformer size.
Innovation Solution
A control circuit for flyback power converters that includes a low-side transistor, an active-clamper in parallel with the transformer, and a high-side drive circuit, with a controller generating switching and active-clamp signals based on input and output voltages and predicted transformer demagnetizing time to recycle leakage inductance energy and enable soft switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of stationary object
If switching frequency is increased to reduce transformer size, then device volume is reduced, but efficiency deteriorates due to increased power losses
Solution Approach 1:
The control circuit performs preliminary calculation of the predicted demagnetizing time based on input voltage, output voltage, and switching signal characteristics before generating the active-clamp signal. This preliminary timing prediction allows the circuit to prepare the optimal clamp activation moment in advance, enabling efficient operation at higher switching frequencies where timing precision is critical for maintaining efficiency while using smaller transformers.
2Device complexity
If active-clamp signal timing is not optimized, then device complexity is reduced, but efficiency deteriorates at both light and heavy loads
Solution Approach 1:
The control circuit uses feedback from the switching signal characteristics (input voltage, output voltage, on-time) to calculate and adjust the predicted demagnetizing time. This feedback mechanism allows the circuit to automatically adapt the active-clamp timing to current operating conditions, achieving high efficiency across varying loads without requiring complex external control systems or manual tuning.
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
The solution achieves high efficiency across both light and heavy loads by recycling transformer leakage inductance energy, allowing the flyback power converter to operate at higher switching frequencies and reduce transformer size.
Implementation Method 1
a transformer (10) connected to an input voltage (VIN) of the power converter
Implementation Method 2
recycling the leakage inductance's energy of the transformer in the light load
Data Source
AI summary
A control circuit of a flyback power converter according to the present invention comprises a low-side transistor, an active-clamper, a high-side drive circuit, and a controller. The low-side transistor is coupled to switch a transformer. The active-clamper is coupled in parallel with the transformer. The high-side drive circuit is coupled to drive the active-clamper. The controller generates a switching signal and an active-clamp signal. The switching signal is coupled to drive the low-side transistor. The switching signal is generated in accordance with a feedback signal for regulating an output voltage of the flyback power converter. The active-clamp signal is coupled to control the high-side drive circuit and the active-clamper. The active-clamp signal is generated in response to a predicted time of the transformer. The predicted time is determined in accordance with an input voltage, the output voltage and an on time of the switching signal.