Load Control Unit PWM Accuracy via Battery Voltage Tracking
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Solution Overview
Problem
Existing load control units for vehicles face challenges in efficiently managing PWM outputs due to the complexity and cost of circuit designs that accommodate both fixed and pulse inputs, with the omission of a constant voltage source leading to accuracy issues in frequency and duty ratio when voltage variations occur from the vehicle's battery or wiring resistance.
Innovation Solution
A load control unit is designed with a reference voltage generating unit, first and second charging/discharging units, and comparing units to generate a triangle wave and PWM pulse, where the capacity ratio between the units approximates the resistance ratio, ensuring the reference, divided, and triangle wave voltages vary together with battery voltage, thus stabilizing PWM output without a constant voltage source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a constant voltage source is used to maintain accurate PWM output, then the frequency and duty ratio accuracy is improved, but the device complexity and cost increase
Solution Approach 1:
The patent removes the constant voltage source from the circuit, extracting only the essential components needed for PWM generation. The triangle wave generating unit and comparing unit work directly with the battery voltage to produce accurate PWM output without requiring voltage stabilization circuitry.
Solution Approach 2:
The circuit uses the battery voltage itself as the reference for generating the triangle wave and comparing signals. The triangle wave generating unit generates a triangle wave based on the battery voltage, and the comparing unit compares this triangle wave with a signal derived from the same battery voltage, allowing the system to self-reference without external constant voltage sources.
2Adaptability or versatility
If the circuit is designed to accommodate both fixed and pulse inputs with general-purpose characteristics, then the adaptability is improved, but the circuit complexity increases
Solution Approach 1:
The load control unit is designed with a universal input interface that can accept both fixed input signals and pulse input signals through the same control terminal. The comparing unit is configured to generate PWM output based on either input type, eliminating the need for separate circuit paths for different input patterns and reducing overall circuit complexity.
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 maintains high accuracy of PWM output, reduces device size, and lowers costs by compensating for voltage variations from the battery and wiring resistance, ensuring reliable operation without a constant voltage source.
Implementation Method 1
a first charging/discharging unit that charges and discharges to generate the triangle wave at a constant current proportional to the voltage of the battery
Implementation Method 2
a first comparing unit that compares the voltage of the first charging/discharging unit with the reference voltage and switches between the charge and discharge of the first charging/discharging unit to generate the triangle wave
Data Source
AI summary
A load control unit for controlling the supply of an electric power to a load from battery in accordance with a pulse-width modulation control includes: a reference voltage generating unit; a first charging/discharging unit; a second charging/discharging unit connected in series to the first charging/discharging unit to charge and discharge in reverse to those of the first charging/discharging unit; a first comparing unit that compares the voltage of the first charging/discharging unit with the reference voltage and switches between the charge and discharge of the first charging/discharging unit to generate a triangle wave; and a second comparing unit that compares a divided voltage by dividing the voltage of the battery with the voltage of the triangle wave generated by the first comparing unit to generate a PWM pulse. The ratio of capacities between the first and second charging/discharging units approximates to the ratio of resistances for obtaining the divided voltage.