PWM Current Limiter Feedback for BLDC Motor Overcurrent Protection

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Solution Overview

Problem

Brushless DC motors in space-based vehicles face premature failure due to overcurrent events, which are life-limiting and cannot be repaired or replaced, reducing the system's useful life.

Innovation Solution

A self-correcting frequency controlled current limiter, integrated with a feedback loop, compares instantaneous motor current with a buffered filtered PWM control signal to prevent overcurrent events by temporarily halting the motor drive signal when the current exceeds the setpoint, using active filters and comparators.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If brushless DC motor operates without current limiting, then motor power and speed are maintained, but overcurrent events cause premature motor failure

Engineering Contradiction:

Improvemotor lifecycleVSAvoidovercurrent events

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The current limiter is configured to limit motor current before overcurrent events can occur by comparing instantaneous current with a reference level and interrupting the drive signal when the threshold is exceeded, preventing harmful current spikes that would otherwise damage the motor

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system continuously monitors instantaneous motor current through sensing circuitry and feeds this information back to the current limiter, which adjusts the PWM drive signal in real-time to maintain current below the reference level, creating a closed-loop control system that prevents overcurrent conditions

Inventive Principle:

Principle #23Feedback

2Reliability

If a current limiter is added to control motor current, then overcurrent events are prevented, but system complexity increases

Engineering Contradiction:

Improvemotor lifecycleVSAvoidcontrol system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The current limiting functionality is integrated directly into the PWM controller that already exists for motor control, combining current sensing, comparison, and PWM generation into a single control unit rather than adding separate standalone components

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The PWM controller is designed to perform multiple functions simultaneously: generating PWM drive signals for motor control, sensing instantaneous current through integrated circuitry, comparing current with reference levels, and adjusting output based on current feedback, making the controller a multi-functional device that reduces overall system complexity

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS20260005628A1Self-correcting frequency controlled voltage converter for brushless DC motor current limiting

Publication Date: 2026.01.01 HAMILTON SUNDSTRAND SPACE SYST INT INC

AI summary

A space based vehicle includes a controller configured to generate a pulse width modulation (PWM) control signal and output the PWM control signal at a control signal output. A self-correcting frequency controlled current limiter is connected to the control signal output. The self-correcting frequency current limiter provides a current limited control signal output and a buffered feedback loop output connected to a feedback input of the controller. A direct current (DC) motor includes a control input connected to the current limited control signal output and an instantaneous input current sensor.