Epson PC AX Technical Manual page 30

PRINCIPLES OF OPERATION
2.2 ATRPS POWER SUPPLY UNIT
REV.B
ATRPS Unit is available in both 115-volt supply and 230-volt supply.
Switch S1 selects either 115-volt supply or 230-v01t supply, and
simultaneously switches a fuse.
Basic Operation
ATRPS Unit uses the Forward Converter Switching Regulation way.
+
1 __ Ff'
MOS FET
FIGURE 2-2-1. BASIC OPERATION CIRCUIT
2.2.1 Primary Oscillation Circuit
The HA16654 controls the MOS-FET. By supplying power to the HA16654, current
flows in the liOS-FET.
2.2.1.1 Power supply circuit
Power supply circuit for the HA16654 is explained by the following 2 steps:
1. From power on till the transformer for switching oscillates correctly.
2. After the transformer for switching has oscillated correctly.
1. From POWER ON till the transformer for switching oscillates correctly.
The power supply circuit is shown in Figure 2-2-2.
Zenor Diode D10 and Dll works so as not to supply the HA16654 with a vol tage
until the input voltage V reaches the fixed-level voltage.
2-2