Bidirectional Charging Circuit for Piezo Speaker Energy Recycling

Solution Overview

Problem

Conventional driving circuits, such as class-AB, -D, -G, and -H amplifiers, are inefficient when handling the highly capacitive loads of piezoelectric-actuated speakers due to their resistive and inductive assumptions, leading to energy wastage during charging and discharging cycles.

Innovation Solution

A bidirectional charging and discharging circuit is introduced, utilizing DC-DC converter circuits for energy recycling, allowing the capacitive load of the piezo speaker to act as an energy source during discharging, and incorporating a PWM controller to manage switching cycles and minimize distortion, enabling the circuit to handle voltage swings above, below, and across the power source voltage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If conventional class-AB, -D, -G, or -H amplifiers are used to drive piezo-speakers, then the circuit can operate with simple topology, but energy is wasted during discharging operation as the amplifiers drain energy from the capacitance to ground

Engineering Contradiction:

Improveenergy waste during dischargingVSAvoidcircuit topology complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent converts the previously wasted energy during discharging operation into a useful resource by capturing the energy that would otherwise be drained to ground and recycling it back to the voltage source. The bidirectional charging and discharging circuit enables energy to flow in both directions, transforming the harmful energy waste into a beneficial recycling mechanism that improves overall system efficiency.

Inventive Principle:

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

Solution Approach 2:

The patent implements energy recovery by capturing the energy stored in the capacitive load during discharging operation and returning it to the voltage source. Instead of discarding this energy to ground as conventional amplifiers do, the bidirectional circuit recovers and reusesthe energy, thereby reducing total energy consumption and improving efficiency.

Inventive Principle:

Principle #34Discarding and recovering

2Device complexity

If conventional amplifiers assume resistive and inductive loading, then the amplifier design can be simplified, but the amplifiers become inefficient when driving highly capacitive loads like piezo-speakers

Engineering Contradiction:

Improveamplifier design simplicityVSAvoidenergy efficiency with capacitive load

Core Design Contradiction:

Device complexityVSUse of energy by moving object

Solution Approach 1:

The patent changes the operating parameters of the amplifier system by implementing bidirectional charging and discharging cycles. This allows the system to adapt to the capacitive nature of piezo-speaker loads by controlling the flow of energy in both directions, thereby improving energy efficiency without requiring complete redesign of the amplifier topology.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces dynamic control of energy flow through the bidirectional circuit, allowing the system to switch between charging and discharging modes based on the operational requirements. This dynamic approach enables the circuit to efficiently handle the highly capacitive load characteristics of piezo-speakers while maintaining reasonable design complexity.

Inventive Principle:

Principle #15Dynamics

3Loss of energy

If the bidirectional charging and discharging circuit is implemented to recycle energy, then energy efficiency is improved, but the circuit complexity increases with multiple switches and inductors

Engineering Contradiction:

Improveenergy recycling efficiencyVSAvoidnumber of switches and inductors

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent achieves multi-functionality by designing a bidirectional circuit that can perform both charging and discharging operations through the same set of components. The switches and inductors serve dual purposes depending on the operational mode, thereby reducing the need for separate dedicated circuits for each function and optimizing the overall component utilization.

Inventive Principle:

Principle #6Universality (Multi-functionality)

4Ease of operation

If conventional amplifiers drain energy to ground during discharging, then the circuit operation is simple, but the energy stored in capacitive load is wasted

Engineering Contradiction:

Improvedischarging operation simplicityVSAvoidenergy stored in capacitive load

Core Design Contradiction:

Ease of operationVSLoss of energy

Solution Approach 1:

The patent converts the previously wasted energy during discharging operation into a useful resource by capturing the energy that would otherwise be drained to ground and recycling it back to the voltage source. The bidirectional charging and discharging circuit enables energy to flow in both directions, transforming the harmful energy waste into a beneficial recycling mechanism that improves overall system efficiency.

Inventive Principle:

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

Solution Approach 2:

The patent implements energy recovery by capturing the energy stored in the capacitive load during discharging operation and returning it to the voltage source. Instead of discarding this energy to ground as conventional amplifiers do, the bidirectional circuit recovers and reusesthe energy, thereby reducing total energy consumption and improving efficiency.

Inventive Principle:

Principle #34Discarding and recovering

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 solution improves energy efficiency by recycling energy stored in the capacitive load back to the voltage source, reducing wastage and achieving lower distortion and a broader output voltage range, suitable for both single-end and bridge-tied-load configurations.

Implementation Method 1

an inductor, comprising a first terminal coupled to the second terminal of the first switch and the first terminal of the second switch, and a second terminal

Methodology Applied

Scientific EffectElectromagnetic Induction: Electromagnetic Induction

Implementation Method 2

piezoelectric-actuated speakers (piezo-speakers) have emerged

Methodology Applied

Scientific EffectPiezoelectric Effect: Piezoelectric Effect

Data Source

PatentUS11336182B2Driving circuit with energy recycle capability

Publication Date: 2022.05.17 XMEMS LABS INC

AI summary

A bidirectional charging and discharging circuit is coupled between a voltage source and a capacitive load and configured to drive the capacitive load. The bidirectional charging and discharging circuit includes a first switch, comprising a first terminal coupled to the voltage source; a second switch, comprising a first terminal coupled to a second terminal of the first switch, and a second terminal coupled to a ground; an inductor, comprising a first terminal coupled to the second terminal of the first switch and the first terminal of the second switch; a third switch, comprising a first terminal coupled to a second terminal of the inductor, and a second terminal coupled to a first terminal of the capacitive load; and a fourth switch, comprising a first terminal coupled to the second terminal of the inductor and the first terminal of the third switch, and a second terminal coupled to a ground.