PSoC™ 4: Designing a washing machine inverter control

The consumer washing machine market is highly price competitive. Designing a cost-effective and reliable line-powered appliance involves careful component selection, and meeting internationally recognized safety specifications dictates the need for incorporating protection features. In a washing machine, controlling the three-phase brushless motor adds another requirement to achieve a safe, stable, and efficient drive. Sensing motor drive currents, performing complex algorithms, and managing the motor drive PWM waveforms requires a high-performance processor and many analog components.

Ideal product specifications include -

• A high-performance process capable of performing complex calculations quickly
• An analog signal chain to accurately sense motor phase drive currents for Hall-effect sensor and sensorless-based motor control
• Achieve a stable and efficient motor drive
• Meet all safety and Class B energy efficiency certifications

Design solution based on PSoC™ 4 - Your problem solver on chip

The recommended solution illustrated uses a PSoC™ 4 processor to achieve a single-chip field-oriented control (FOC) inverter drive. In a compact package, the PSoC™ 4 programmable system-on-chip integrates a powerful 48 MHz Arm Cortex-M0+ core with a host of configurable analog and digital functions, termed blocks. Programmable analog blocks include opamps, low-power comparators, a 12-bit SAR ADC, and an 8-bit current digital to analog converter (IDAC). Multiple configurable TCPWMs (timer, counter, pulse-width modulator), GPIOs, and universal digital blocks (UDBs) are some of the digital blocks. Serial configuration blocks (SCBs) provide flexibility in serial communication and can support UART, I2C, and SPI protocols. 

PSoC™ 4 also features a hardware divide & square-root accelerator, which significantly assists in achieving rapid and accurate floating point algorithmic computations, an essential aspect of maintaining a stable and safe motor rotation.

Communication with the washing machine's host processor uses an SCB configured as a UART and an external EEPROM through SPI.

PSoC™ 4 - Your problem solver on chip

PSoC™ 4 provides an optimized, cost-effective single-chip, high-performance design approach for a field-oriented control of a washing machine motor.