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 VNW50N04 FOR AIR CONDITIONING In small to medium size vehicles, control of air conditioning blower powered by adjustable resistor baffles in the air channels is still the preferred solution. However, this necessitates a power switch in the dashboard with extensive wiring for currents up to 25A. A new, fully protected OMNIFET from ST, the VNW50N04, now takes over this task. With an Ron of 12m½ this blower fans up to 300W in economic linear operation. Key features of the device are overvoltage clamping at 40V, 50A current limiting and overtemperature protection. The device comes in a TO247 package which, under certain assembly conditions, allows an extremely efficient coupling to the heatsink. Shown in the illustration above, the advantage of this concept is that only one analog signal wire runs from the operating unit to the OMNIFET, which sits on a heat sink in the air channel. The resistance between drain and gate sends a current back to the operation unit, with which the drain voltage of the OMNIFET can almost be reconstructed. This allows a virtual control of the motor voltage.   The power of the blower can therefore be controlled stepless or in any number of steps, without influencing the wiring costs. Of particular interest is that in place of manual power control, electronic air conditioning can control the blower power. ST offers OMNIFET types from 400m½ to 12m½ with clamping voltages ranging from 40V to 70V for each application area.  |
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