Push-Pull Piezo Driver Circuit for Low Voltage SCBA Alert

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Solution Overview

Problem

Existing Personal Alert Safety Systems (PASS) devices for firefighters may not function effectively at low battery voltages and can consume excessive power, leading to potential failure in distress situations.

Innovation Solution

A PASS device integrated with a piezoelectric sound generator, a power supply, and a piezoelectric driver circuit utilizing a push-pull configuration with bipolar junction transistors and resistors, which operates efficiently at low voltages and reduces power consumption, ensuring the device can alert others even when the battery voltage is below 4 volts and minimizing current draw in no-load states.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional driver circuits are used in PASS devices, then the device can operate at normal battery voltages, but the device cannot function effectively when battery voltage drops below 4 volts

Engineering Contradiction:

Improveoperation reliability at low voltageVSAvoidvoltage range adaptability

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The driver circuit uses a push-pull configuration with bipolar junction transistors that can operate across a wide voltage range. The circuit parameters (transistor switching thresholds, resistor values) are designed to maintain proper operation from 4 volts down to lower voltages, allowing the PASS device to remain reliable even as battery voltage depletes

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The push-pull driver circuit dynamically adjusts its operation based on the input signal from the piezoelectric controller. The complementary transistor pair (one NPN, one PNP) allows the circuit to efficiently switch between sourcing and sinking current, maintaining consistent piezoelectric actuator performance across varying battery voltages

Inventive Principle:

Principle #15Dynamics

2Duration of action of moving object

If traditional driver circuits are used, then the circuit can drive the piezoelectric actuator, but the current draw is excessive leading to reduced battery life

Engineering Contradiction:

Improvebattery lifeVSAvoidpower consumption

Core Design Contradiction:

Duration of action of moving objectVSUse of energy by moving object

Solution Approach 1:

The piezoelectric controller generates periodic square wave signals to drive the piezoelectric actuator through the push-pull driver circuit. This periodic switching operation allows the transistors to spend most time in low-power cutoff states rather than continuous conduction, significantly reducing average current draw and extending battery life

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent replaces traditional electromagnetic buzzer or speaker mechanisms with a piezoelectric actuator driven by a solid-state push-pull circuit. This substitution eliminates mechanical friction and electromagnetic losses, reducing overall power consumption while maintaining the audible alert function

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Use of energy by moving object

If a piezoelectric driver circuit with push-pull configuration is implemented, then power consumption is reduced, but the circuit complexity increases

Engineering Contradiction:

Improvepower consumptionVSAvoidcircuit complexity

Core Design Contradiction:

Use of energy by moving objectVSDevice complexity

Solution Approach 1:

The push-pull driver circuit combines two complementary transistors (NPN and PNP) and associated resistors into a single integrated driving stage. This merged configuration achieves efficient push-pull operation with reduced component count compared to alternative low-power designs, balancing circuit complexity with power savings

Inventive Principle:

Principle #5Merging (Combining)

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 ensures the PASS device can emit a loud audible alert consistently, even at low battery voltages, and reduces power consumption to extend battery life, ensuring reliable operation during emergencies.

Implementation Method 1

a piezoelectric sound generator

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS9044625B2Piezo driver having low current quiesent operation for use in a personal alert safety system of a self-contained breathing apparatus

Publication Date: 2015.06.02 HONEYWELL SAFETY PRODUCTS USA INC

AI summary

Embodiments relate generally to personal alert safety systems (PASS) as well as the use of piezoelectric sound generators which may be located within a PASS device operable to alert others when user is in danger. Some embodiments further relate to the use of a PASS device in an SCBA. Embodiments may also relate to the design of piezoelectric driver circuits operable to sound one or more piezoelectric sound generators, wherein the driver circuit design may be low cost and energy efficient.