Primary Side Flyback Converter Voltage Regulation
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Solution Overview
Problem
Existing Flyback power converters face challenges in achieving stringent output voltage regulation, especially at low loads, due to transformer copper loss variations and resonant waveforms, leading to high costs with secondary side control configurations.
Innovation Solution
A primary side controlled power converter with a voltage sensing means, feedback sampling and hold circuit, and adaptive frequency adjustment to regulate output voltage and current, eliminating the need for costly secondary side control circuits and optical couplers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If secondary side control configuration is used to achieve stringent output voltage regulation, then voltage regulation accuracy is improved, but device complexity and cost increase due to additional components and optical couplers
Solution Approach 1:
The patent extracts the control function from the secondary side to the primary side by eliminating the optical coupler and secondary control IC. The primary side controller directly senses output voltage through the auxiliary winding and regulates it without requiring secondary side control components, thereby reducing device complexity while maintaining regulation accuracy.
Solution Approach 2:
The patent implements a feedback mechanism where the primary side controller senses the output voltage through the auxiliary winding of the transformer and uses this feedback information to regulate the output voltage. The controller adjusts the duty cycle of the primary switch based on the sensed voltage to maintain precise regulation without requiring secondary side control components.
2Device complexity
If primary side control is used to reduce cost, then device complexity is reduced, but output voltage regulation accuracy deteriorates especially at low loads
Solution Approach 1:
The patent applies preliminary action by pre-charging the auxiliary winding capacitor through a dedicated charge pump circuit before the main switching cycle begins. This ensures that the voltage sensing circuit has a stable reference voltage available for accurate feedback control from the start of operation, improving regulation accuracy at all load conditions including low loads.
Solution Approach 2:
The patent changes the operating parameters of the auxiliary winding by using a charge pump circuit to maintain a constant voltage on the auxiliary capacitor regardless of load conditions. This parameter stabilization allows the primary side controller to accurately sense and regulate output voltage even when the transformer operates in discontinuous current mode at light loads.
3Loss of energy
If Flyback converter operates in discontinuous current mode, then efficiency is improved, but resonant waveforms in auxiliary winding cause regulation deterioration
Solution Approach 1:
The patent converts the harmful resonant waveforms generated in discontinuous current mode into a beneficial signal. The charge pump circuit captures the resonant voltage spikes on the auxiliary winding and uses them to charge the auxiliary capacitor, transforming what was previously a source of regulation error into a useful charging mechanism that maintains stable voltage sensing.
Solution Approach 2:
The patent applies dynamics by making the auxiliary winding voltage dynamic rather than static. The charge pump circuit actively manages the auxiliary capacitor voltage to compensate for variations caused by discontinuous current mode operation, allowing the system to adapt to changing load conditions while maintaining accurate voltage regulation.
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
This solution provides accurate voltage regulation from 0% to 100% of rated load with reduced component costs and improved reliability by using current compensation and adaptive sampling techniques, while minimizing electromagnetic interference.
Implementation Method 1
a transformer 201 which has three windings
Implementation Method 2
the output voltage is fed back to the primary side via the auxiliary winding, rectified and filtered by rectifier 107 and capacitor 110
Data Source
AI summary
A primary side controlled power converter having a voltage sensing means coupled to a transformer of the power converter and configured to provide a voltage feedback waveform representative of an output of the transformer is provided. A primary switching circuit operates to control energy storage of a primary side of the transformer. The primary switching circuit is operable during an on time and inoperable during an off time. The on and off time is switched at a system frequency. A feedback amplifier generates an error signal indicative of a difference between the voltage feedback waveform and a reference voltage. A sample and hold circuit samples the error signal at a periodic frequency during the off time. An error signal amplifier is configured to provide the sampled value to the primary switching circuit wherein the primary switching circuit controls the transformer and thereby regulates an output of the power converter.