Panasonic KX-NS500AG, Service Manual

Page: 18 / 191

18
KX-NS500AG
4.9. Battery voltage input and output
This section describes the operation of battery input and output.
1) Battery voltage output (charge time)
Charge circuit has constant voltage and constant current.
When the battery voltage is high, a controlled fixed voltage of the main converter is output.
When the battery voltage is low, a controlled fixed current of main converter is output.
When the battery switch SW181 turns ON and CN102áB-áC is short circuited, the main converter output supplies voltage with
controlled circuit, and Q181, Q182, Q183 change to ON. The voltage from L201 (sub winding voltage) is applied to the gate ter-
minal of Q161, Q163 and the battery output.
When the battery voltage is low, battery output is limited to a fixed current controlled by R170, R171, R172, and Q162.
When voltage is even lower.
Consequently the fold back current limiting shuts down 41V output.
2) Battery voltage input (power outage)
Battery voltage conducts to FET Q163 and diode D163, and is supplied by main converter output (C101, C102, C109).
When the battery voltage is reduced, Q181, Q182, Q183 on the battery control circuit go OFF. Q163 of the battery input/output
DC switch circuit goes to OFF status and releases the battery which stops the power supply.