Air Conditioner Chip Set Is Way Cool

The analog block in IR's platform consists of the IRS2136D family of three-phase analog driver and protection ICs. These ICs incorporate three independent 600-V half-bridge inverter gate drivers with built-in bootstrap diodes, along with the IGBTs and FETs.

Typically in these air conditioners, the chips' target fan motor capacity is about 100 W, while the compressor motor can reach up to 1 kW, depending on the air conditioner's cooling capacity. FETs perform the fan switching, while IR's latest depletion-stop trench IGBTs accomplish the compressor motor's switching. These IGBTs provide lower collector-to-emitter saturation voltage (on the order of 1.7 V) and total switching loss (slightly more than 300 J) than punch-through and non-punch-through IGBTs.

MAKING IT WORK
Developing the user interface for an air-conditioner application takes place on a RAM-based evaluation system. Application programs that run on the 8051 controller are developed in C or assembly language using whatever third-party tools are the most familiar to the engineer. A JTAG emulator enables debugging. When using the reference design, developers can change set-points and read out diagnostic information on their PCs. Isolation lets designers run the reference design live during development.

At this time, IR mask-programs the apps code in the final product. Some customers who anticipate the need to update application features and don't want to be stuck with a large inventory of mask-programmed chips containing the old code are asking for flash memory. IR says it's working to accommodate those customers.

There are additional tools for adapting the generic motor-control engine that IR supplies with the reference design to any particular motor. These 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.

By staying in the graphical mode, engineers can configure the control loop quickly, with less chance of coding error than if they were writing code. In the development environment, the motor-control algorithm can be updated as required.

For more, see "Bringing It Home: AC Efficiency" online at Drill Deeper 12212, www.electronicdesign.com

International Rectifier
www.irf.com