Primary Side Flyback Voltage Regulation via Copper Loss Compensation
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Solution Overview
Problem
Existing switching mode power supplies, particularly flyback converters, face challenges in achieving tight output voltage regulation across varying loads and modes of operation due to transformer copper loss and reliance on costly secondary side control circuits and optical couplers, limiting their efficiency and cost-effectiveness.
Innovation Solution
A primary side constant output voltage PWM controller system that includes a timing generator, sample-and-hold circuits, an error amplifier, comparator, and a PWM controller module, which uses a programmable current mirror and current sensing circuits to regulate output voltage independently of transformer copper loss and temperature variations, eliminating the need for secondary side circuits and optical couplers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If secondary side control circuits and optical couplers are used to achieve tight output voltage regulation, then output voltage regulation precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts and eliminates the secondary side control circuit and optical coupler from the system by implementing primary side control. The controller IC senses parameters on the primary side (switch current, auxiliary winding voltage) to regulate output voltage, removing the need for secondary side sensing components and simplifying the overall device structure while maintaining regulation precision.
Solution Approach 2:
The patent introduces an intermediary approach by using the auxiliary winding voltage as a mediator to sense output voltage information indirectly on the primary side. Instead of directly sensing secondary voltage, the system uses the auxiliary winding to provide proportional voltage information that enables regulation without optical couplers or secondary control circuits.
2Measurement precision
If transformer copper loss is compensated for tight regulation, then output voltage regulation precision is improved, but device complexity increases
Solution Approach 1:
The patent implements feedback by using the auxiliary winding voltage as a feedback signal that contains information about output voltage and transformer copper loss. The controller IC processes this feedback to dynamically adjust the duty cycle and compensate for copper loss effects, achieving tight regulation without adding complex external compensation circuits.
Solution Approach 2:
The system performs self-service by using its own auxiliary winding and primary side parameters to automatically compensate for transformer copper loss. The controller IC internally processes the auxiliary voltage signal and adjusts switching parameters to maintain regulation, eliminating the need for external compensation components or complex circuitry.
3Device complexity
If primary side control is used to reduce component count, then device complexity is reduced, but output voltage regulation precision deteriorates
Solution Approach 1:
The controller IC performs multiple functions using primary side parameters: it senses switch current for peak current mode control, senses auxiliary winding voltage for output voltage regulation, and uses these same signals to compensate for copper loss. This multi-functionality enables tight regulation with minimal external components by maximizing the utility of primary side sensing.
Data Source
AI summary
A lower-cost and more precise control methodology of regulating the output voltage of a flyback converter from the primary side is provided, which works accurately in either continuous voltage mode (CCM) and discontinuous mode (DCM), and can be applied to most small, medium and high power applications such cell phone chargers, power management in desktop computers and networking equipment, and, generally, to a wide spectrum of power management applications. Two highly integrated semiconductor chips based on this control methodology are also described that require very few components to build a constant voltage flyback converter.