Flyback Converter Hybrid Clamp for ZVS Across Line and Load

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Solution Overview

Problem

Existing flyback converters face challenges in optimizing performance across the entire line and load ranges, particularly at light-load and low-input-voltage conditions where active clamp performance is inferior to RCD clamp performance.

Innovation Solution

A hybrid clamp circuit that combines the passive RCD clamp and active clamp properties, allowing the power management unit to configure the clamp circuit based on operating conditions, thereby optimizing performance across all operating ranges.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If switching frequency is increased to reduce power supply size, then passive component sizes are reduced, but switching losses increase

Engineering Contradiction:

Improvepower supply sizeVSAvoidswitching loss

Core Design Contradiction:

Volume of moving objectVSLoss of energy

Solution Approach 1:

The patent converts the harmful effect of leakage inductance (which causes voltage spikes and switching losses) into a beneficial effect by using it to charge the parasitic capacitance of the main switch before turn-on. This resonant charging process enables zero-voltage switching, eliminating turn-on switching losses even at high switching frequencies, thereby allowing high frequency operation with reduced component sizes without incurring excessive switching losses

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 hybrid clamp circuit enhances the efficiency and performance of flyback converters by dynamically switching between passive and active clamp configurations, achieving optimal performance at all line and load conditions.

Implementation Method 1

a capacitor (202) and a resistor (203) connected in parallel to each other and connected in series to a diode (204)

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

connected in series to a diode (204), wherein the diode (204) is connected in anti-parallel to the main switch (206)

Methodology Applied

Scientific EffectDiode rectification: Diode

Implementation Method 3

a flyback transformer (201) having a primary winding (201a) and a secondary winding (201b)

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUSRE50277E1Power converter and method of control thereof

Publication Date: 2025.01.21 DELTA ELECTRONICS INC(CN)

AI summary

A flyback power converter includes a hybrid clamp circuit and a corresponding power management unit that substantially optimizes the performance of the flyback power converter in its entire line and load ranges. The clamp circuit, which is connected in parallel to a primary winding of the flyback transformer, includes a parallel combination of a capacitor and resistor that is connected in series with a parallel combination of a switch and a diode. By sensing the operating conditions, the power management circuit configures the clamp circuit either as a passive clamp or as an active clamp. In the passive-clamp configuration, the switch is kept turned off. In the active-clamp configuration, the switch operates with pulse-width modulation (PWM) which enables ZVS turn-on of the main switch.