Diodes Incorporated — Brushed and Brushless DC Motors

Diodes Incorporated Brushed and Brushless DC Motors

Brushed DC motors are composed of a rotor with electromagnets and a stator with permanent magnets. The graphics below illustrate the construction and operation of a simple two-pole brushed DC motor works.

• The rotational speed of a DC motor is proportional to the back EMF across its coils.
• Torque is proportional to current.
• When the voltage remains constant an increase in load (torque) on the motor results in a decrease in speed.
• The relationship between speed and torque is shown in a motors speed - torque (below). Torque and speed are said to be inversely proportional.

Super Barrier Rectifier (SBR^®) combines both a lower forward loss compared to a Schottky Barrier diode (SBD) with thermal stability of a Fast Recovery diode (FRD)

These advantages over existing technologies translate to…

• Higher Efficiency and Higher Temperature Operation
  • SBR^® enables lower VF with more stable reverse leakage current allowing applications to run more efficiently at higher ambient temperature, resulting in more power savings and higher reliability

• Better Performance in Smaller Packages
  • SBR^® patented high density cellular technology enables SBR® to exceed customers’ ever increasing demand for high performance in smaller packages

• Scalable technology
  • Lack of metal Schottky barrier and use of CMOS process allows for a scalable technology from 0.1A to 60A and 20V to 400V without degradation of performance

Device Structure and Operation of SBR^®

• SBR^® is Patented and Proprietary Technology of Diodes Inc.
• Traditional (two terminal) device by shorting the gate and source together (shown in red)
• In forward mode, device operates as majority carrier (MOS) with low VF and fast switching
• In reverse mode, electrostatic behaviour causes depletion mode, substantially reducing leakage current
• Cellular design operates as thousands of individual devices working in parallel

Brushless DC Motors (BLDC)

• Improved battery performance suited for hand held power tools
• Government standards requiring more efficient energy usage
• 60 to 70% of industrial electricity usage is in motor drive
• All BLDC motors require electronic control to drive the motor
• Diodes Inc. offers Gate Drivers, MOSFETs, Hall Sensors, discretes

3-Phase BLDC Motor Driving Example

DMT Shielded Gate Technology

This MOSFET is designed to meet the stringent requirements of Automotive applications. It is qualified to AEC-Q101, supported by a PPAP.

Features

• Rated to +175°C – Ideal for High Ambient Temperature Environments
• Thermally Efficient Package for Cooler Running Applications
• High Conversion Efficiency
• Low RDS(ON) – Minimises On-State Losses
• Low Input Capacitance
• Fast Switching Speed
• <1.1mm Package Profile – Ideal for Thin Applications