Technology of Chandler, AZ, U.S. has introduced a family of 8-bit Flash microcontrollers (MCUs) with advanced motor control peripherals designed to improve efficiency and extend motor life in several applications, including appliances.
The new PICMicro MCU family contains three modules specifically designed
for advanced motion and power-control applications, which are key to
improving the efficiency in motor control applications, says Cheri Keller,
product marketing manager of Microchip Technology's Advanced Microcontroller
and Automotive Division. The first module is a 14-bit power control PWM.
The second is a high-speed analog-to-digital (A/D) converter that can
be synchronized with the PWM. The third module has motion-feedback capabilities
and contains a quadrature encoder, which is used to track the speed and
position of the motor. "These three features can be used in a closed-loop
a.c. induction motor (ACIM) and brushless d.c. (BLDC) motor applications,
thus providing improved efficiency, quieter operation, and more reliable
operation," Ms. Keller notes.
Technology's new MCU product family is said to be the only MCU
that has hardware available to drive three-phase motor control applications.
The devices contain 256 bytes of on-board, high-endurance data EEPROM,
and up to 10 MIPS performance at 40 MHz. The MCUs have a 16-level programmable
low-voltage detection module and nanoWatt Technology feature that provides
enhanced power-management capabilities.
Appliance designers and engineers are able to eliminate the use of
external A/D converters, resonators, PWM controllers, and quadrature
encoders because the three modules are available within the MCU, which
lowers the overall component costs and the PCB costs due to board space
The advanced power control and motor control applications can be used
in the appliance industry for items such a dishwashers, refrigerators,
washing machines, and ventilation fans. The new MCU devices include up
to eight PWM channels with 14-bit resolution, center alignment, programmable
dead time (950 to 250 ns), and two external fault-protection inputs.
They also have capture/compare/PWM modules, an internal PC oscillator
with eight selectable frequencies that range from 8MHz to 31.25 KHz,
and an enhanced USART supporting RS 485, RS232, and the LIN protocol.
The flexibility of the modules allow designers to add variable-speed
control that can improve efficiency by 30 percent in some appliance applications
- such as a refrigerator compressor - by controlling the pace at which
it operates, Ms. Keller tells APPLIANCE. "Rather than turn the motor
completely off and then back on to full speed, which takes a great amount
of power, designers can incorporate variable-speed control through the
use of a PWM module," she explains. "This significantly reduces the amount
of energy needed to operate the motor, just by varying the speed."
Any MCU in the series can be used in conjunction with a drive to provide
the variable-speed control. "The PIC18Fxx31 family also [incorporates]
the use of fail-safe clock monitors that use the internal Resistor-Capacitor
(RC), a back-up clock, in the event an external clock were to fail," Ms.
"In addition," she continues, "there are two external fault pins that
can be used to safely shut down the motor in the event there was some
sort of disturbance to the motor."