TI's Advanced Microprocessor

TI's Advanced Microprocessor Allows Replacement of Mechanical Parts to Create Energy-Efficient, Less Expensive Appliances

Maintenance-prone belts, gears, and clutches could soon be eliminated from washing machines, heating/ventilation/air conditioning (HVAC) systems, and other appliances, thanks to a powerful new microprocessor from Texas Instruments (TI). The new electronic microprocessor combines an extensive set of motor control features with enough processing power to execute complex control equations needed for adaptive and variable speed control of brushless motors. Because these computer chips allow appliance designers to reduce mechanical coupling elements and generate optimized output waveforms to drive the motor, appliances can be made smaller, cheaper, quieter, and more energy efficient.

Known as a digital signal processor, or DSP, this advanced computer chip adds and multiplies tens of millions of complex formulas every second. A DSP chip is 10 to 50 times more powerful than other computer chips in handling math intensive tasks, and it enables numbers to be processed in "real time." TI is the world's leading provider of DSP solutions, having patented its first DSPs in 1982.

A Revolution in Appliance Motors

The rapid growth of DSPs, a market expected to reach $9 billion by the year 2000, is enabling the creation of new and improved products such as appliances. Because TI's TMS320C240 DSP enables bi-directional variable speed control, inexpensive AC induction, SR, or DC brushless motors can now be used in major appliance designs. The low-cost motors can be connected, for example, directly to washer drums that were traditionally coupled to single-speed motors via a system of belts, pulleys, clutches, or gears to collectively vary drum speed. Such mechanical couplings have long been appliance mainstays, but they are a very maintenance-prone and noise-producing subsystem in the appliance. Control systems that use the 'C240 in direct-drive electronics are quieter and can reduce appliance power consumption by as much as 40 percent. These DSP-enabled variable-speed AC motor systems may also weigh far less than their mechanical predecessors, can be easier to install and maintain, and can occupy less physical space, placing fewer design constraints on appliance design engineers.

The DSP uses advanced control formulas that can significantly lower motor induced vibration, making motor driven appliances quieter. One example would be in the case of HVAC blowers which, if a motor runs roughly, can produce significant fan vibration noise. The 'C240 allows engineers to design a robust motor controller with minimal torque ripple, thereby reducing the audible noise that is propagated by the blower in HVAC systems. Advanced control algorithms can also be used to estimate system information to eliminate costly feedback sensors such as motor tachometers or Hall effect sensors in the motor windings.

Because the 'C240 DSP is an "intelligent" control processor, the all-electronic control systems enabled by the chip can be programmed to behave far more flexibly than traditional mechanical systems. In the washing machine example, a wash cycle can use electronically programmed speed changes to specifically optimize wash programs and spin cycles for different kinds of fabrics. When a washer enters various parts of the wash cycle, DSP control allows a soft start after each motor direction reversal, helping quiet the appliance and reducing wear on parts. A programmed smooth start at the beginning of spin cycles helps to more evenly distribute laundry in the drum to avoid out-of-balance thumping conditions.

The Power of a DSP

TI's breakthrough 'C240 DSP controller is a DSP solution that includes a 20 MIPS processor CPU that runs sophisticated motor control formulas, a specialized motor control circuit called an "event manager," plus a comprehensive group of motor control peripherals, all on a single microprocessor.

Integrated with the DSP core, the 'C240's unique motor control event manager directly supports generation of pulse width modulated (PWM) outputs to drive the motor power amplifier, and contains motor control features that include timers, comparators, dead-band generation logic, a state space vector generator, and direct inputs for optical encoders. Additional chip peripherals include two serial interfaces, dual analog-to-digital converters, digital input and output lines, a low-voltage detector, and on-chip memory.

The processing power of the 'C240 DSP allows the use of math-intensive motor control algorithms, which enable sensorless and adaptive controller designs to be used in mainstream product designs for the first time. System cost can be lowered by reducing part count, such as external sensors, memory chips, and mechanical gearing and through the use of inexpensive motors such as DC brushless, switched reluctance, and AC induction. A 'C240-based system can also provide improved energy efficiency and reliability, along with reduced vibration and noise.

DSP Enables Use of Low-Cost Brushless Motors

Brushless motors offer many advantages over traditional brush-type motors including lower cost, lighter weight, and reduced maintenance, but they require real-time execution of mathematically intensive control algorithms for robust control. The 'C240 supports this need by enabling the use of complex DSP-based formulas which allow precise, adaptive control of brushless motors, with the ability to reduce the number of expensive sensors used for position and loading feedback.

'C240-based motor systems can provide precise torque control and speed regulation of brushless motors, and superb response to rapid speed or load changes, but without the weight, high maintenance costs, and energy consumption of a DC brush or universal motor system. These advanced DSP controllers for brushless motors can deliver full torque, even at standstill.

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