Switched Resonant Capacitor-Inductor Tuning With Zero-Cross Feedback

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Solution Overview

Problem

Existing tunable resonant circuits face challenges in achieving high efficiency and stable operation across high frequency ranges, particularly in maintaining resonance frequency stability independent of amplitude variations and minimizing diode conduction losses, which affect dynamic behavior and control input responsiveness.

Innovation Solution

The solution involves coupling a capacitance or inductance with controlled switches, using a zero crossing detector to generate a pulse width modulation signal, and modifying the coupling control signal to reduce diode current flow intervals, thereby minimizing losses and ensuring independent control of resonance frequency based on a single control variable.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a PWM signal is generated synchronized with deflection frequency using a sawtooth generator, then the coupling control can be implemented, but the system becomes unstable when resonance frequency is tuned because the PWM signal is independent from the resonant circuit period

Engineering Contradiction:

Improvecoupling control implementationVSAvoidsystem stability

Core Design Contradiction:

Ease of operationVSStability of the object's composition

Solution Approach 1:

The patent implements feedback by detecting the actual resonant circuit period through zero-crossing detection and using this detected period to generate the PWM signal. This creates a closed-loop system where the PWM signal automatically adapts to changes in resonance frequency, eliminating the instability caused by using a fixed-frequency sawtooth generator.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system uses its own output signal (the resonant circuit period) to control its input (the PWM signal). The zero-crossing detector monitors the resonant circuit's natural oscillation and feeds this information back to the PWM generator, allowing the system to self-regulate without external synchronization.

Inventive Principle:

Principle #25Self-service

2Stability of the object's composition

If integration or low-pass filtering is applied to control variables to minimize positive feedback behavior, then system stability is improved, but the dynamic behavior deteriorates with slower transient response

Engineering Contradiction:

Improvesystem stabilityVSAvoidtransient response speed

Core Design Contradiction:

Stability of the object's compositionVSSpeed

Solution Approach 1:

Instead of continuous integration or low-pass filtering, the patent uses periodic zero-crossing detection that naturally samples the resonant circuit period at appropriate intervals. This periodic sampling approach provides stability without the sluggishness introduced by continuous filtering, maintaining fast transient response while minimizing positive feedback effects.

Inventive Principle:

Principle #19Periodic action

3Device complexity

If diode current flow interval is not reduced, then the circuit operation is simpler, but conduction losses increase proportionally to diode threshold voltage and current

Engineering Contradiction:

Improvecircuit operation simplicityVSAvoiddiode conduction losses

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The patent dynamically controls the switch timing based on the detected resonant circuit period, optimizing the switching moments to minimize diode conduction intervals. The PWM signal width is adjusted according to the actual resonance conditions, creating a dynamic operation mode that reduces losses while maintaining circuit simplicity through automated control.

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 enables fast transient response and efficient operation by reducing diode conduction losses and maintaining resonance frequency stability, allowing for dynamic range variation within resonant circuit periods without affecting frequency tuning.

Implementation Method 1

A current or voltage zero crossing detector generates a trigger signal

Methodology Applied

Scientific EffectZero crossing detection:

Implementation Method 2

which generates a pulse width modulation signal. The pulse width is controlled by an electronic control variable. The state of the switch is defined by the pulse width signal

Methodology Applied

Scientific EffectPulse width modulation:

Implementation Method 3

the capacitor CS and the inductance LH form a series resonant circuit

Methodology Applied

Scientific EffectResonance: Resonance

Data Source

PatentUS8854151B2Controlled large signal capacitor and inductor

Publication Date: 2014.10.07 REHM MARKUS

AI summary

An electrical resonance network comprising a first capacitor and a first inductor whose resonance frequency can be tuned by means of a second capacitor and/or a second inductor. The resulting effective capacitor- or inductor value of a network period is controlled by a variable coupling respectively decoupling interval by means of at least one coupling switch. The coupling respectively decoupling interval is synchronized by a sign change of a current and/or voltage in the network.