Canon fax basic 2000 서비스 매뉴얼

FACSIMILE SYSTEM

6–24

6. POWER SUPPLY UNIT

The “power supply unit (regulator)” converts the alternating current (

for household use into a direct current (

) constant voltage power

source. A “constant voltage power source” refers to a power source whose

output is maintained at a fixed output voltage even if the input voltage or

output current fluctuate.

Series regulators and switching regulators are generally used as a DC con-

stant voltage power supply. Facsimiles mainly use switching regulators.

The reason why a switching regular has been selected is that even though

its circuit is more complicated than that of a series regulator, it is ideal for

downsizing and allows the power supply unit itself to be made compact.

Another reason why a switching regulator has been selected is that it dem-

onstrates good stable power supply efficiency and generates little heat.

The following describes what sort of power supply a switching regulator is

as switching regulators are used on almost all facsimiles.

6.1

Switching Regulator

Switching regulators supply only voltage that has dropped due to the load,

and turn semiconductor switches ON and OFF (“switching”) to control the

supply voltage for maintaining a constant voltage. This is why this kind of

regulator is called a “switching regulator.”

Switching regulators compare fluctuations in the output voltage with the

reference voltage, and change the time ratio (duty ratio) of the ON and

OFF states of the input DC voltage switch according to the result of this

comparison to control the output voltage to a constant voltage.

Table 6-1   Features of Switching Regulators and Series Regulators

Power Supply Type

Features

Switching regulator

• Compact size and light weight

• High efficiency

• Complicated circuit

• Large noise

Series regulator

• Large size and heavy weight

• Low efficiency

• Simple circuit

• Small noise