Variable Capacitance Unit for Inductive Charging

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Solution Overview

Problem

In inductive charging systems, particularly at high voltages and currents, variable capacitors face challenges due to high AC voltages and parameter fluctuations, leading to inefficiencies and increased costs, as existing solutions require oversized control ranges and significant installation space.

Innovation Solution

A capacitor unit with at least two capacitor devices, connected in series and supplied with control voltages in opposite directions, ensuring the capacitor unit remains neutral to external voltages, thus minimizing the impact of AC voltages and allowing for efficient control of capacitance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a single variable capacitor is used in inductive charging systems, then capacitance can be adjusted, but high AC voltages significantly affect the control voltage and cause parameter fluctuations

Engineering Contradiction:

Improvecapacitance adjustment rangeVSAvoidparameter stability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The capacitor is divided into two separate capacitor devices (first and second capacitor devices) with different terminals. Each capacitor device is controlled by opposite polarity control voltages, which isolates the effect of AC voltages on the total capacitance control and improves parameter stability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of applying control voltage in one polarity direction, the invention applies control voltages with opposite polarities to the two capacitor devices. This inversion approach causes the AC voltage effects to cancel out, allowing for stable capacitance adjustment despite high AC voltages in the circuit.

Inventive Principle:

Principle #13The other way round (Inversion)

2Productivity

If oversized adjustment ranges are used to compensate for parameter fluctuations, then low power levels can be maintained, but installation space and costs increase significantly

Engineering Contradiction:

Improvepower output rangeVSAvoidinstallation space

Core Design Contradiction:

ProductivityVSArea of stationary object

Solution Approach 1:

The invention changes the control parameter from single-polarity voltage to dual-polarity opposite voltage. This parameter change enables precise capacitance control over a wide power range without requiring oversized physical components, thus reducing installation space while maintaining productivity.

Inventive Principle:

Principle #35Parameter changes

3Power

If high AC currents flow through resonant capacitors, then power transfer can be achieved, but high AC voltage drops occur reaching the kV range

Engineering Contradiction:

Improvepower transfer capabilityVSAvoidvoltage stress

Core Design Contradiction:

PowerVSStress or pressure

Solution Approach 1:

The capacitor function is segmented into two capacitor devices with opposite polarity control. This segmentation allows the system to handle high AC currents for power transfer while the opposite polarity control stabilizes the voltage stress on each individual capacitor device.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The opposite polarity control voltages act as counterweights to the high AC voltage drops. By applying equal and opposite control voltages to the two capacitor devices, the net effect of high AC voltage stress is compensated, enabling safe operation at high power levels.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

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 configuration reduces the influence of AC voltages on the capacitor unit, enabling efficient and cost-effective operation by maintaining a neutral terminal voltage, thereby optimizing structure, efficiency, and costs in inductive energy transmission systems.

Implementation Method 1

at least a first capacitor device (22) with variable and/or voltage-dependent capacitance and at least a second capacitor device (24) with variable and/or voltage-dependent capacitance

Methodology Applied

Scientific EffectVoltage-dependent capacitance: Capacitance

Implementation Method 2

the capacitor unit (20) is at least temporarily supplied with a first control voltage (U1) and the second capacitor device (24) is at least temporarily supplied with a second control voltage (U2)

Methodology Applied

Scientific EffectElectrical neutrality through opposite polarity control: Electric Field

Implementation Method 3

a coil assembly (6, 26) which serves to output an electromagnetic field and an electrical voltage generation device (10) with which the coil assembly (6, 26) can be supplied

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentEP3793090A1Variable capacity capacitor unit, in particular for an induction device for charging motor vehicles

Publication Date: 2021.03.17 ZOLLNER ELEKTRONIK

Figure 1
Figure 2a~3b
Figure 4a~4b

AI summary

A circuit arrangement for an inductive power transfer device (50) with a coil assembly (6) for generating an electromagnetic field and an AC voltage generation device (10, 14a, 14b) for generating an AC voltage that can supply the coil assembly (6), wherein the circuit arrangement comprises at least one capacitor unit (20) with variable capacitance. According to the invention, the capacitor unit (20) comprises at least a first capacitor assembly (22) with variable capacitance (C1) and a second capacitor assembly (24) with variable capacitance (C2), wherein the first capacitor assembly (22) is supplied with a first control voltage (U1) at least intermittently and the second capacitor assembly (24) is supplied with a second control voltage (U2) at least intermittently.