Resonant Power Converter Control for Low-Loss Load Adaptation

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Solution Overview

Problem

Resonant switching power converters face significant switching losses due to parasitic capacitances and inductances, which are not effectively reduced by existing methods, leading to inefficiencies and increased power dissipation, especially at light to no-load conditions.

Innovation Solution

The implementation of a resonant circuit with a transformer and a switch controller that adjusts the duration of power transfer intervals and energy recycling intervals based on load current variations, utilizing zero voltage switching (ZVS) and zero current switching (ZCS) techniques to minimize switching losses, along with a gate drive circuit that operates primary and secondary switches to optimize energy transfer and reduce power dissipation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If resonant switching power converters use fixed switching intervals, then the converter structure is simple, but switching losses increase significantly at light to no-load conditions

Engineering Contradiction:

Improveconverter structureVSAvoidswitching losses

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The patent implements dynamic adjustment of the power transfer interval duration based on load conditions. The controller modifies the duration of power transfer intervals in response to detected load levels, transitioning from fixed to variable timing. This dynamic adaptation allows the converter to optimize switching behavior across different operating conditions, reducing switching losses at light loads while maintaining effective power transfer at full load.

Inventive Principle:

Principle #15Dynamics

2Productivity

If the power transfer interval duration is extended to improve energy transfer, then energy transfer efficiency improves, but switching losses increase due to prolonged capacitor charging/discharging

Engineering Contradiction:

Improveenergy transfer efficiencyVSAvoidswitching losses

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

The patent changes the temporal parameter of the power transfer interval duration based on operating conditions. By adjusting this time parameter dynamically, the system optimizes the balance between energy transfer effectiveness and switching loss minimization. The controller modifies the interval duration to match load requirements, preventing excessive capacitor charging/discharging cycles that would increase switching losses.

Inventive Principle:

Principle #35Parameter changes

3Volume of moving object

If resonant frequency is increased to reduce converter size, then device volume decreases, but switching losses increase due to higher frequency switching

Engineering Contradiction:

Improveconverter volumeVSAvoidswitching losses

Core Design Contradiction:

Volume of moving objectVSLoss of energy

Solution Approach 1:

The patent implements dynamic control of switching intervals that adapts to operating conditions. By optimizing the timing and duration of power transfer intervals rather than relying solely on high frequency, the system achieves effective power transfer without proportionally increasing switching losses. This dynamic timing control allows the use of resonant frequencies that reduce size while compensating for switching losses through intelligent interval management.

Inventive Principle:

Principle #15Dynamics

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 approach significantly reduces switching losses by up to 99% and improves efficiency by adapting the operating cycle to load conditions, maintaining a narrow converter operating period and minimizing power dissipation in the converter.

Implementation Method 1

A resonant circuit including the transformer may be formed having a characteristic resonant frequency and period

Methodology Applied

Scientific EffectResonance: Resonance

Implementation Method 2

ZVS ideally causes the voltage across the switch to decline to zero volts, essentially eliminating switching loss associated with the capacitive discharge of the switch

Methodology Applied

Scientific EffectZero voltage switching:

Implementation Method 3

Turning switches ON and OFF at times when zero or minimal current is flowing through the switch, called zero current switching ('ZCS'), can also reduce losses and reduce noise

Methodology Applied

Scientific EffectZero current switching:

Data Source

PatentUS11831246B1Adaptive control of resonant power converters

Publication Date: 2023.11.28 VICOR CORPORATION

AI summary

A power converter including a transformer, a resonant circuit including the transformer and a resonant capacitor having a characteristic resonant frequency and period, and output circuitry connected to the transformer for delivering a rectified output voltage to a load. Primary switches drive the resonant circuit, a switch controller operates the primary switches in a series of converter operating cycles which include power transfer intervals of adjustable duration during which a resonant current at the characteristic resonant frequency flows through a winding of the transformer. The operating cycles may also include energy recycling intervals of variable duration for charging and discharging capacitances within the converter. A gate driver includes a transformer, a plurality of switches, a current monitor, and a controller that operates the switches in a series of driver operating cycles having adjustable ON periods and adjustable transition periods during which capacitances are resonantly charged and discharged.