Flyback Power Converter PSR Control With Feedback Voltage Limiting

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Solution Overview

Problem

Accurately detecting output voltage in flyback power converters using primary side regulation (PSR) is challenging due to the reflective voltage not always accurately representing the output voltage, especially under conditions of parasitic resistance, capacitance, or inductance.

Innovation Solution

The implementation of a voltage limiter in the power controller, which constrains the feedback voltage to a predetermined condition, ensures that the feedback voltage accurately reflects the output voltage, thereby improving voltage regulation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If PSR method is used to regulate output voltage, then device complexity is reduced by eliminating secondary side detection circuitry, but measurement precision deteriorates because reflective voltage does not accurately represent output voltage under parasitic conditions

Engineering Contradiction:

Improvedetection circuitryVSAvoidoutput voltage detection

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent introduces an intermediary calculation process that uses multiple measurable parameters (reflective voltage, primary current, duty cycle) to indirectly determine output voltage. Instead of directly measuring reflective voltage alone, the controller calculates output voltage using a formula that incorporates these intermediate measurements, compensating for parasitic effects and improving measurement precision while maintaining PSR simplicity

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces the traditional direct electrical measurement approach with a computational method. Instead of using complex hardware circuitry to directly sense output voltage, the system uses software-based calculation algorithms that process readily available electrical parameters (reflective voltage, current, duty cycle) to derive accurate output voltage information, substituting mechanical/electrical measurement complexity with computational processing

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Ease of operation

If reflective voltage is used directly to represent output voltage, then ease of operation is improved by simplifying control, but reliability deteriorates due to inaccurate voltage representation under parasitic conditions

Engineering Contradiction:

Improvecontrol simplicityVSAvoidvoltage regulation accuracy

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent implements an enhanced feedback mechanism where the controller continuously monitors multiple parameters (reflective voltage, primary current, duty cycle) and uses this feedback to calculate and adjust the output voltage regulation. The calculated output voltage feeds back into the control algorithm, creating a reliable closed-loop system that maintains accuracy while preserving the simplicity of PSR operation

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent changes the parameters used for voltage regulation from relying solely on reflective voltage to using a combination of parameters (reflective voltage, primary current, duty cycle) in a calculation formula. This parameter transformation approach maintains the ease of PSR operation while significantly improving reliability by accounting for parasitic effects through multi-parameter analysis

Inventive Principle:

Principle #35Parameter changes

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 voltage limiter effectively stabilizes the feedback voltage, allowing for accurate representation of the output voltage, which enhances the regulation of output voltage in flyback power converters using PSR.

Implementation Method 1

a power controller, which controls a main power switch to make an input power source in a primary side energize a transformer, and to release the energy stored in the transformer to an output power source in a secondary side

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

Methodology Applied

Scientific EffectVoltage clamping:

Data Source

PatentUS12308747B2Control method and power controller for flyback power converter

Publication Date: 2025.05.20 LEADTREND TECH

AI summary

A control method is disclosed to have a voltage sample capable of more correctly representing an output voltage of a power converter. The power converter has a primary side and a secondary side galvanically isolated from each other. A feedback voltage is received in the primary side. A main power switch is turned OFF, starting an OFF time, during which the feedback voltage is constrained in response to the voltage sample. In a sampling time within the OFF time, the feedback voltage is sampled to update the voltage sample representing the output voltage in the secondary side. A driving signal is provided in response to the voltage sample to control the main power switch.