DC Motor Overcurrent Detection Using Microcomputer Voltage Sampling
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Solution Overview
Problem
Existing DC motor control systems for vehicles face challenges in efficiently detecting overcurrent without increasing circuit complexity and costs, particularly due to the need for differential amplifiers and comparators, which can lead to delays and overheating issues.
Innovation Solution
A control apparatus and method that eliminates the need for a differential amplifier and comparator by using a microcomputer to measure voltage differences across a half-bridge driver's on and off periods, counting threshold exceedances to determine overcurrent, and stopping the motor when a predetermined number of exceedances occur, thereby simplifying the circuit and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a differential amplifier and comparator are used to detect overcurrent, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts and removes the differential amplifier and comparator from the circuit, replacing them with a simplified microcontroller-based voltage sampling system. The microcontroller directly samples the voltage across the shunt resistor and compares it against threshold values stored in memory, eliminating the need for dedicated analog amplification and comparison circuits while maintaining overcurrent detection capability.
Solution Approach 2:
The patent replaces the analog electronic system (differential amplifier and comparator) with a digital processing system. The microcontroller uses its built-in ADC to convert the analog voltage signal to digital, then performs comparison operations in software, substituting analog circuitry with digital processing to reduce component count and circuit complexity.
2Measurement precision
If a differential amplifier is used to amplify current signal, then measurement precision is improved, but response speed decreases due to amplification delay
Solution Approach 1:
The patent eliminates the analog amplification stage entirely and uses the microcontroller's built-in ADC to directly convert the voltage signal across the shunt resistor into a digital value. This digital conversion happens in real-time without the delays associated with analog amplification, and the microcontroller immediately compares the converted value against stored thresholds to detect overcurrent conditions.
3Loss of energy
If shunt resistor with very small resistance value is used, then power loss is reduced, but measurement precision deteriorates due to small voltage difference
Solution Approach 1:
The patent uses the microcontroller's built-in ADC to create a digital copy of the analog voltage signal across the shunt resistor. By converting the small analog voltage to a digital value, the system can accurately represent and process even very small voltage differences without requiring expensive high-precision analog components, thus maintaining measurement precision while using a low-value shunt resistor to minimize power loss.
Data Source
AI summary
The present disclosure provides a control apparatus for sensing overcurrent of a DC motor of a vehicle. The control apparatus may include: a microcomputer configured to convert a pulse width modulation (PWM) signal into a digital signal for controlling the DC motor; a half-bridge driver configured to control switching of the DC motor; a regulator configured to supply power; and a noise removal filter. The microcomputer is configured to measure a voltage at an input of the half-bridge driver, compare a difference between on-voltage and off-voltage during each of PWM period with a predetermined threshold, and stop the DC motor when the difference exceeds the predetermined threshold a predetermined number of times.