DC Inverter Over-Current Protection Circuit with Dual Signal Paths
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Solution Overview
Problem
Traditional over-current protection methods for DC Inverters fail to simultaneously account for the current protection values of both the power module and motor, leading to inadequate protection when these values differ, and require hardware adjustments for motors with varying protection thresholds.
Innovation Solution
An over-current protection method and circuit that samples output currents from the power module, generates distinct over-current signals for the power module and motor using different amplification factors, and dynamically adjusts the motor's over-current threshold based on its specifications and running states, using a control unit with digital-to-analog conversion and pulse-width modulation for effective protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed over-current protection threshold is configured by voltage-division of an external resistance, then the protection threshold can be set, but it cannot simultaneously account for current protection values of both the power module and motor
Solution Approach 1:
The patent divides the over-current protection function into two independent signal paths: one path processes the sampling signal through a first amplifying circuit with a first magnification factor to generate a first over-current signal for power module protection; another path processes the same sampling signal through a second amplifying circuit with a second magnification factor to generate a second over-current signal for motor protection. This segmentation allows each path to be independently configured for its specific protection requirements.
Solution Approach 2:
The patent introduces dynamic adjustability by allowing the second magnification factor to be modified through software control, enabling the motor's over-current protection threshold to be dynamically changed. This is achieved through a magnification factor adjusting circuit that can receive control signals to modify the second magnification factor, while the first magnification factor remains fixed for power module protection.
2Reliability
If the over-current protection threshold is set to the motor's current protection value, then the motor is protected, but the over-current protection value of the motor cannot be dynamically changed by software when the power module's current protection value is greater than the motor's
Solution Approach 1:
The patent makes the second magnification factor dynamic and software-adjustable, allowing the motor's over-current protection threshold to be changed through software without hardware modifications. The magnification factor adjusting circuit receives control signals that modify the second magnification factor, enabling flexible adaptation to different motor requirements while maintaining hardware-based protection.
3Reliability
If hardware circuit adjustments are required to change the over-current protection threshold for different motors with equal powers, then accurate protection is achieved, but the device complexity and adjustment difficulty increase
Solution Approach 1:
The patent replaces hardware circuit adjustments with software control for modifying the second magnification factor. Instead of physically changing resistor values or circuit configurations, the system uses software to dynamically adjust the magnification factor through electronic control signals, eliminating the need for hardware modifications when adapting to different motors.
Data Source
AI summary
An over-current protection method and circuit for a DC Inverter is provided in the present invention. Said over-current protection circuit comprises: a sampling unit for sampling output currents from a power module to form a sampling signal; a signal-processing unit for amplifying with various magnification factors and low-pass filtering the sampling signal to generate a first over-current signal and a second over-current signal; a signal-generating unit for generating a first interrupt trigger signal based on the first over-current signal; a comparison unit for comparing the second over-current signal with a reference voltage corresponding to an over-current threshold of a motor, with a comparison result being a second interrupt trigger signal; and a control unit for controlling the power module based on the first interrupt trigger signal, and the motor based on the second interrupt trigger signal. The over-current protection method and circuit provided in the present invention are able to satisfy over-current protection of the power module and the motor of the inverter simultaneously.