Building a BLDC motor controller from scratch is one of the most demanding tasks in embedded systems engineering. At Entlar, we have spent the last fourteen months designing, testing, and refining the custom motor controller that sits at the heart of every Entlar ceiling fan.
The Challenge
Traditional ceiling fans use simple AC induction motors with triac phase-cut dimmers. They are cheap, reliable, and well-understood — but they are also wildly inefficient at partial loads, generate audible hum at low speeds, and offer no intelligence whatsoever. We wanted something fundamentally better.
Our requirements were ambitious:
- Efficiency above 92% across the entire operating range, not just at peak load
- Zero audible noise at any speed — 0 to 280 RPM
- True sinusoidal commutation to eliminate torque ripple
- Self-calibrating — no factory tuning required per fan unit
- Under ₹320 BOM cost at 10,000-unit volume
Gate Driver Selection
After evaluating seven different gate driver ICs over six weeks, we settled on the IR2136. Its integrated bootstrap diodes, built-in shoot-through protection, and 600 V absolute maximum rating gave us the headroom we needed without adding external protection circuitry.
FOC Implementation
Field-Oriented Control on a 48 MHz Cortex-M4 with floating-point hardware is surprisingly achievable. Our Clarke-Park transformation pipeline runs at 20 kHz — fast enough to cancel torque ripple on a 14-pole motor at any speed in our range.
The breakthrough came when we abandoned textbook PID tuning and moved to an adaptive gain scheduler that recalculates kP and kI every 50 ms based on measured back-EMF phase noise. This alone cut our low-speed vibration from 12 mg to under 2 mg.
What’s Next
We are currently validating our second-generation thermal protection algorithm, which predicts winding temperature from a Kalman-filtered model rather than a direct thermistor read. Early results show 30% faster fault detection without false positives.
More details in the next engineering post.