Electronic Design

Washing-Machine Controller Wrings Multiple Design Wins From One Platform

Recently, International Rectifier released its iMotion control platform for air conditioners in China and Japan (see "Air Conditioner Chip Set Is Way Cool," March 30, 2006, p. 36). This month, IR released a version for washing machines with a global market.

The iMotion platform comprises a digital-control IC and a driver IC with on-board power devices. The control IC's 8051 core handles the user interface and a custom motion-control engine (MCE) that controls one or more synchronous permanent magnet motors (two in the air conditioner version, one in the washer). The two cores communicate via a RAM register block. A mixed-signal block integrates all signal-conditioning and conversion circuits for sensorless motor control.

From the OEM's perspective, the architecture makes a hard job easy and saves money by eliminating some parts elsewhere in the product. IR also wanted to offer a product with higher margins than discrete power switches and a platform with a lot of potential for design reuse.

(The air conditioner market designs and desirable product features are quite different in Japan and China, and iMotion lets OEMs deal with both markets.)

So with minor tweaking, IR easily adapted the same architecture to next-generation washing machines with synchronous permanent magnet (PM) motors, even though designers of those goods have different needs. PM motors are a big step forward in washer efficiency because they be directly connected to the tub, eliminating belts, pulleys, and the gearbox.

The problem is that they operate in two speed/torque regimes (see the figure). Agitating a tub full of water and clothes during the wash cycle takes lots of torque low speed. Spinning the water out of the washed clothes takes less torque at substantially higher rpms. In fact, faster spins wring more water out of the clothes, saving consumers a lot of money on drying and encouraging them to buy new washers.

The iMotion platform's MCE makes that possible. In fact, the implementation of control algorithms as different as those for air conditioners and washing machines is facilitated by the graphical tools used to customize the MCE. These tools consist of a library of analog blocks that can be graphically configured and simulated using the Mathworks' MatLab and a compiler that converts the results to a netlist.

The iMotion washer platform is being sampled to qualified users. The IRMCS3041 reference design costs $995.

International Rectifier

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