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4. LOW-VOLTAGE POWER SUPPLY ASSY
4.1 Outline
The low-voltage power supply assy consists of the low-voltage generating block (hereinafter the
DC block) and the heater drive circuit block to turn the heater on (hereinafter the AC block).
When the power switch (SW1) is turned on, AC power is supplied to the low-voltage power supply
assy.
The DC block generates +5 VDC, and +24 VDC.
When the heater is turned on, AC power is supplied to the AC block under control of the heater
on-off signal from the engine controller.
+24V output is reserved in the DC block, for the cooling fan for the low-voltage power supply
assy.
4.2 Protection Functions
Each of the power supply circuits, +5V, and +24V, has a protection function to prevent the circuit
from accident by automatically cutting off the power supply in the case of a over-voltage or over-
current of the load.
When the cooling fan stops to rotating, an over-voltage protection or a short-circuit protection
function is activated, and all the DC power supplies are cutoff.
In this case check and clear the cause on the load after turning the power switch (SW1) off, and
then switch the power on again at least one minute after the power shut-down.