The BridgeSwitch™ family of ICs employ high-side and low-side FREDFETs (Fast Recovery Epitaxial Diode Field Effect Transistors). This, combined with an integrated half-bridge’s (IHB) distributed thermal footprint, eliminates any need for an external heat sink, saving precious system weight. The ICs achieve conversion efficiency of up to 98.5% in brushless DC (BLDC) motor drive applications of up to 300 W.
The BridgeSwitch IC package. Image from Power Integrations
A First for Power Integrations
Power Integrations has a long track record in the field of AC-DC power converters but this is their first BLDC motor drive IC. According to Andrew Smith, Director of Training at Power Integrations, the jump to motor drives is natural because both types of products revolve around the efficient switching of power thousands of times per second.
Senior product marketing manager Cristian Ionescu-Catrina states that “We have taken a fresh look at the challenges posed by the burgeoning BLDC market and ever-tightening energy-use regulations worldwide, and produced an innovative solution that saves energy and space while reducing the BOM. This eases compliance with safety standards, simplifies circuitry, and reduces development time."
Simplifying Circuit Design
The BridgeSwitch ICs feature built-in device protection and system monitoring with a single-wire status update interface, enabling communication between the motor-microcontroller and up to three BridgeSwitch devices. The need to protect the system from open or shorted motor windings is eliminated by the new IHB’s facility to configure high-side and low-side current.
Hardware-based motor-fault protection simplifies the task of IEC60335-1 and IEC60730-1 compliance.
Losses during switching and noise generation are both reduced by the ultra-soft-recovery body-diodes that are incorporated by the 600 V FREDFETs used in BridgeSwitch ICs. EMI is reduced, making EMC easier.
Power Integrations’ BridgeSwitch family of ICs. Image source: Power Integrations.
Brushless DC Motors vs. AC Motors
Another reason Power Integrations feels comfortable entering this new space, according to Smith, is that much of the industry is switching from AC motors to BLDC motors.
In a motor commonly used in the past, brushes convey electrical power to an electric motor’s armature. They are troublesome mechanical parts that are a source of sparking, EMI, and motor failure.
Simplified diagram of a brushless DC motor. Image (modified) from the BLDC motor section of the AAC textbook
In this cross-section of a brushless DC motor, the north/south permanent magnet is mounted perpendicularly on the motor’s armature.
A driver like Power Integrations’ BridgeSwitch would sense the magnet’s south pole is adjacent to electromagnet H3, and send power to H3, causing it to become a north pole magnet, causing the armature’s permanent magnet to move away, pulling the armature along with it.
When the opposite end of the armature, the north-pole magnet, reaches the next coil, its position is sensed by the driver, which at the correct moment energizes the coil in a manner to keep the armature moving on its revolving pathway.
Thus, in this manner, troublesome mechanical brushes are eliminated in favor of reliable semiconductors.
Though brushless motors are more complex, Smith explains, they're more efficient, more compact, and have a longer lifespan.
BridgeSwitch™ Family Specifications
The ICs are compatible with all common control algorithms—field oriented control (FOC), sinusoidal, and trapezoidal modes with sensor- and sensorless detection.
- The units can operate at PWM frequencies of up to 20 kHz
- FREDFET drain current, mirroring positive motor winding current, is reported
- Over-temperature detection
- DC bus overvoltage and undervoltage protection and reporting
While the increase in efficiency to 98.5% may not seem drastic, because of the very large amounts of power involved, the 1% advantage over competition means that about a 1/3 reduction of heat that needs to be dissipated by the IC.
Inverter efficiency. Image source: Power Integrations
Because so many safety considerations are built into members of the BridgeSwitch family, there is less for the MCU to do. Much of the eliminated MCU software would otherwise be subjected to difficult to achieve certification requirements, thus eliminating a time-consuming design task.
BridgeSwitch is available in InSOP-24C packages, and creepage distances are 3.2 mm or greater. Samples of BridgeSwitch ICs are available now. You can learn more from Power Integrations' technical support.
Image source: Power Integrations
BridgeSwitch 3-Phase Inverter Reference Designs
At electronica 2018, Power Integrations is demoing three reference designs to show the BridgeSwitch family's capabilities. The designs vary in power, control method and microcontroller, though the latter two differ primarily to demonstrate their capabilities.
The current lineup of BridgeSwitch family reference designs.
First is the DER-653 reference design intended for high-voltage BLDC motor applications:
- BridgeSwitch IC: BRD1165C
- Inverter output power: 300W
- Microcontroller: Toshiba TMP375FSDMG
- Sensor: Sensorless
- Control method: FOC
The DER-653 reference design
The next is the DER-654, also for high-voltage BLDC motor applications:
- BridgeSwitch IC: BRD1265C
- Inverter output power: 300W
- Microcontroller: Any
- Sensor: Hall sensor
- Control method: Any
The DER-654 reference design
Finally, there is the DER-749, intended for high-voltage BLDC motors in fan applications:
- BridgeSwitch IC: BRD1260C
- Inverter output power: 40W
- Microcontroller: Princeton PT2505
- Sensor: Hall sensor
- Control method: Sinusoidal
The DER-749 reference design
The Growing Importance of Brushless DC Motors
Supporting the idea that BLDC motors are the way of the future is the long list of manufacturers involved in their production.
The DRV10983 from Texas Instruments can supply drive current of up to 2 Amps. Like members of the BridgeSwitch family, much is included within, and few external components are required.
TI's DRV10983 sensorless BLDC motor control driver. Image courtesy of Texas Instruments
The A4964 from Allegro, on the other hand, does not include internal power semiconductors. This device requires the use of external power MOSFETs.
It's clear that the dominance of this type of device is growing and Power Integrations is jumping into the fray.
What's your experience with BLDC motors? What's stood out to you this year in BLDC trends? Let us know in the comments below.