With growing demand for energy efficiency, longer product life, and cost optimization in smart home appliances, electrolytic capacitor-free variable frequency control technology is attracting attention in refrigerator applications. As a cost-effective and efficient control solution for PMSMs, this approach replaces traditional electrolytic capacitors with film capacitors, significantly reducing system cost and extending service life. It also suppresses harmonic current from single-phase AC input without complex active PFC circuits, simplifying design and improving reliability.

To meet the requirements for low harmonics, high power factor, and cost efficiency in refrigerator compressors, Geehy introduces its electrolytic capacitor-free variable frequency control solution. This solution combines the APM32F035 motor control MCU with three GHD1620T motor gate drivers, working in conjunction with film capacitors and an IGBT circuit. Without an external PFC circuit, it suppresses harmonic current and improves board-level power factor, delivering an efficient and practical inverter control solution.

APM32F035 Electrolytic Capacitor-Free Variable Frequency Control Solution

This solution delivers low noise, reduced harmonics, high reliability, and stable motor speed. It lowers cost, extends service life, and enhances system reliability.

Electrolytic Capacitor-Free Variable Frequency Control Solution Board

After AC rectification and filtering, film capacitors are applied. The APM32F035 MCU acts as the main controller, detecting AC voltage and motor phase current for vector control. Using TIM1, three sets of complementary PWM signals are generated and sent to the GHD1620T drivers, which control IGBT switches for voltage inversion to drive the PMSM.

Block Diagram

Advantages of the Electrolytic Capacitor-Free Variable Frequency Control Solution

■ Single-Chip Control: APM32F035 MCU (72 MHz, with M0CP co-processor, high-speed ADC, and op-amps) handles AC voltage sampling and FOC on a single core.

■ Reliable Drive Performance: Motor speed accuracy and load capability match traditional capacitor-based drives, ensuring stable operation.

■ Advanced Algorithm: Proprietary voltage-following algorithm adapts to dynamic load changes, reduces harmonics, and removes the need for a PFC circuit.

■ High Cost Efficiency: Film capacitors cut system cost by 15–20%, reduce board size by 30%, and extend product lifetime.

■ High Drive Power: A 4μF film capacitor supports up to 400W inverter power.

Key Performance Parameters

Electrolytic Capacitor-Free Speed Control Data

Electrolytic Capacitor-Free Control Test Waveform

AC 176V at 4500rpm: Yellow = bus voltage, Blue = motor current

APM32F035 Motor Control MCU

■ Efficient Performance: Cortex-M0+ with M0CP co-processor reduces CPU load and supports sensorless FOC.

■ High-Speed ADC: Up to 1MHz sampling rate with segmented operation for accurate voltage and current separation.

■ Precision Timer: TIM1 outputs four complementary PWM groups with built-in dead-time and ADC interconnection for precise motor control.

■ High-Performance Op-Amps: Four integrated op-amps with configurable gain or preset options, 10 V/μs slew rate, and 10MHz gain-bandwidth product (GBWP) for fast response.

GHD1620T Dedicated Motor Gate Driver (Coming Soon)

■ 600 V dual N-channel gate driver for single-phase motors

■ Wide voltage range: 10–20V; 3.3V/5V logic compatible

■ Floating offset voltage: +600V; supports BLDC and brushed DC motors

■ Built-in 500ns deadband, undervoltage/overtemperature protection, and shoot-through prevention

■ Integrated bootstrap diode for stable high-side switching

■ Built-in temperature sensor for compensation and adaptive motor efficiency control

Geehy provides a full-stack motor control portfolio of MCU + Driver + IPM, supported by proprietary algorithms, development platforms, and a dedicated motor control team. Backed by expertise across applications, middleware, devices, and hardware, Geehy offers a complete ecosystem to help customers enhance motor performance and accelerate product development.