Qorvo Enhances Cordless Vacuums with Advanced Motor Control
Have you ever imagined that a compact, wireless vacuum cleaner could deliver suction power comparable to professional equipment? In the wave of smart home technology in the 21st century, once-simple electric motors are being revitalized through modern design concepts, permeating every aspect of our lives. From refrigerators and computers to washing machines and vacuum cleaners, electric motors are ubiquitous. Outdoors, they power garage doors and garden tools alike.
Looking back to the early 20th century, simple AC induction motors and brushed DC motors could meet basic needs. Today, brushless DC (BLDC) motor designs have become mainstream, not only meeting consumer demands for efficient, long-lasting wireless devices but also making appliances more compact, reliable, and durable.
The global vacuum cleaner market reached $9.2 billion in 2018 and continues to grow strongly. According to Grand View Research, the market is expected to expand at a compound annual growth rate (CAGR) of 9.1% between 2019 and 2025. This growth is primarily driven by the increasing number of working women and rising living standards that create new consumer expectations. Simultaneously, consumer attention to energy efficiency and environmental considerations in household appliances has become a significant market driver.
In this collaborative project, the vacuum cleaner design team and Qorvo engineers faced a series of demanding requirements. They needed to create a wireless vacuum cleaner that combined powerful suction from ultra-high rotational speeds with a lightweight, portable design and long product lifespan. The required suction power significantly exceeded that of most traditional portable products on the market.
The client's specifications explicitly called for a permanent magnet synchronous motor (PMSM) with field-oriented control (FOC) technology to achieve variable frequency drive (VFD) functionality, meeting the product's extreme performance requirements.
Qorvo and the design team recognized that the final product would be a high-performance wireless vacuum cleaner. Therefore, they selected a three-phase PMSM motor with sine wave commutation technology to maximize performance. The core of the design lies in FOC technology, which uses a sophisticated algorithm to control the stator's rotating magnetic field, adjusting flux generation through two orthogonal components and precisely determining the motor's available torque.
Modern handheld vacuum cleaners typically use BLDC motors that generate rotating magnetic fields internally. In this brushless design, the stator remains stationary with fixed coils, while permanent magnets are mounted on the rotor, which rotates according to the periodic magnetic field generated by the stator coils. Current is precisely delivered to the stator coils by an external electronic motor controller, enabling variable speeds.
Qorvo's PAC5225 chip, part of the Qorvo Power Application Controller (PAC) series, is the core of this vacuum cleaner design. This highly integrated system-on-chip (SoC) provides comprehensive functionality for building a simple, compact, and cost-effective motor control board. The design board integrates a power management system, a 50MHz 32-bit ARM Cortex-M0 microcontroller unit (MCU), gate drivers, operational amplifiers, comparators, and other auxiliary components.
Reaching exceptional motor speeds was a key parameter in this project's design, with the goal of significantly exceeding standard vacuum cleaner performance levels. To achieve mechanical speeds up to 150,000 rpm, precise coordination between the ARM Cortex M0 MCU-controlled analog-to-digital converter (ADC) and pulse-width modulator (PWM) was required.
A vacuum cleaner's suction power is affected by multiple factors, including the duct volume of different attachments, battery level, blockages from foreign objects, and filter saturation. Under these variable conditions, maintaining constant power output is crucial for maximizing suction power.
To ensure smooth, quick startup, the motor's starting algorithm needs rotor position information. Qorvo's SoC sends high-frequency signals to the motor to capture three-phase motor inductance data, which the startup algorithm uses to calculate rotor position.
Integrating all motor control functions into a single Qorvo PAC motor control chip was key to achieving a cost-effective product design. By avoiding discrete components, the design reduced bill of materials (BOM) costs while minimizing maintenance requirements and extending product lifespan.
The advanced algorithms developed by Qorvo enable numerous complex motor control functions through the existing SoC hardware. For example, the design implements sensorless FOC control using a single current sensing resistor method, eliminating the need for three sampling resistors as required in many earlier designs.
