Driver Circuit Compensation for BLDC Supply Current Pulses
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Solution Overview
Problem
Existing driving methods for electrical loads, such as those used in brushless direct current (BLDC) motors, often result in abrupt current interruptions that produce negative current pulses in the power supply line, which can be detrimental to low-end power supplies that lack the necessary current sinking capability.
Innovation Solution
A driver circuit with a compensation circuit that modulates the driving signal to interrupt the load current and sinks a compensation current pulse from the power supply pin, mitigating or canceling negative current pulses by using a voltage clamp circuit to selectively activate the compensation current, which has a predetermined magnitude and duration with a falling slew rate lower than the rising slew rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If inductive sense procedure is applied to detect angular position of BLDC motor, then measurement precision is improved, but negative current pulses are produced in power supply line
Solution Approach 1:
The compensation circuit generates a compensation current pulse before and during the negative current pulse event to counteract its harmful effects. The compensation current is activated when the load current is interrupted and maintains opposite polarity to the negative pulse, thereby preemptively neutralizing the harmful effect on the power supply line.
Solution Approach 2:
The invention converts the harmful negative current pulse into a beneficial compensation mechanism. By detecting the load current interruption and generating a compensating current pulse with opposite polarity, the system transforms the harmful electromagnetic disturbance into a controlled signal that can be used to maintain power supply stability and even provide additional measurement information.
2Productivity
If load current is abruptly interrupted during inductive sense procedure, then productivity is improved, but negative current pulses damage low-end power supplies
Solution Approach 1:
The compensation circuit is activated in advance when load current interruption is detected, generating a compensation current pulse that counteracts the harmful negative pulse before it can damage the power supply. This preliminary protective action maintains power supply reliability without slowing down the inductive sense procedure.
Solution Approach 2:
The compensation circuit acts as an intermediary between the driver circuit and the power supply line. It introduces a compensating current that mediates the harmful interaction between the abrupt load current interruption and the power supply, protecting the power supply while maintaining the speed of the inductive sense procedure.
3Reliability
If compensation current pulse is generated to cancel negative current pulses, then power supply stability is improved, but device complexity increases
Solution Approach 1:
The compensation circuit is integrated into the existing driver circuit structure, sharing common components such as the power supply connection and control logic. The compensation current generation utilizes available circuit elements and combines the compensation function with the existing inductive sense procedure control, thereby reducing the increase in device complexity.
Solution Approach 2:
The driver circuit is designed to perform multiple functions: normal motor driving, inductive sense procedure, and compensation current generation. By making the driver circuit universal and capable of handling multiple operations, the need for separate dedicated compensation hardware is reduced, thereby limiting the increase in device complexity while maintaining power supply stability.
Data Source
AI summary
A method of driving an electrical load includes coupling a power supply source to a power supply pin of a driver circuit, and coupling an electrical load to at least one output pin of the driver circuit. A driver sub-circuit of the driver circuit produces at least one driving signal for driving the electrical load. The at least one driving signal is provided to the electrical load via the at least one output pin. The at least one driving signal is modulated to supply the electrical load with a load current and to subsequently interrupt the load current. A compensation current pulse is sunk from the power supply pin, at a compensation circuit of the driver circuit, in response to the load current being interrupted.