Hardware-Software Solution for Three-Phase BLDC Motor Inverters Enables Greater Than 98 Percent Efficiency, Saves PCB Space and Speeds Time-to-Market
Power Integrations , the leader in high-voltage integrated circuits (ICs) for energy-efficient power conversion, unveiled new control software for three-phase BLDC motor drives. Combined with Power Integrations’ BridgeSwitch™ integrated half-bridge motor driver and easy-to-use Motor-Expert™ configuration and diagnostics tool, this complete hardware-software solution enables 98.2 percent efficiency, reduces board space by more than 70 percent and requires just three components for current feedback circuitry, compared to 30 components in a discrete solution. The solution is ideal for residential and commercial appliances with three-phase motors, such as air conditioner fans, high-speed hair dryers, refrigerator compressors, range hood fans and water pumps.
“Traditional three-shunt field-oriented control (FOC) solutions require expensive and bulky operational amplifiers (op-amps) and matching circuitry for motor-current signal conditioning,” states Cristian Ionescu-Catrina, senior product marketing manager for Power Integrations. “Our BridgeSwitch integrated half-bridge ICs provide lossless current feedback for the positive half cycle, and our three-phase FOC software reconstructs the negative half-cycle current information from data present in the other phase current signals. This eliminates the need for costly and inefficient external current sense resistors, op-amps and matching circuitry and the associated complexity.”
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Power Integrations’ new software adds three-phase FOC to the existing library of single-phase code. It allows real-time adjustment of motor speed and torque via the Motor-Expert graphical user interface (GUI). The code runs on any Arm® Cortex®-M0 at 48 MHz and does not require a hardware accelerator block. It can also be ported to other equivalent MCUs. The current modeling algorithm is robust and reliable and has passed extensive static and dynamic test conditions, including low latency response to real-time events. The high degree of current accuracy ensures low jitter operation. The new code is MISRA C-compliant (Motor Industry Software Reliability Association), portable, modular and allows the user to modify any of the software layers.
How Three-Phase Motor Control Works with BridgeSwitch ICs
Power Integrations’ BridgeSwitch ICs provide a motor current output signal that maps the current passing through the low-side FREDFET. An internal sense-FET provides lossless current sensing. The sense circuit cannot provide current information when the anti-parallel body diode is conducting during commutation.
Built-in gain amplification allows direct connection of the current phase signal to the microcontroller ADC input. The local sense circuit provides an accurate analog of current with a high signal-to-noise ratio and a correspondingly high degree of accuracy.
The new software includes a reconstruction algorithm that uses the phase-shifted trigonometric relationship between current signals of all three phases to accurately deduce negative phase-current information.