Panasonic KX-TVM200E Service Manual page 50

KX-TVM200E / KX-TVM200NE
6.1.12. DC-DC Converter Circuit
This system has external AC adaptor, and DC40V is supplied by an external AC adaptor to the system.
AC Adaptor specification
AC input (Primary)
DC output (Secondary)
In the power supply circuit, the DC-DC converter generates 12V, 5v for the HDD, 3.3v for logic, and 1.9v for the CPU from the
DC40 input from the AC adapter. An alarm circuit is provided in the 40V route by which a DC power stop generates a DC down
alarm signal when LOW is asserted. The overvoltage detection circuit monitors 12v, 5v, and 3.3v described below and shuts
off the supply of 40v when each voltage reaches the predetermined value or higher.
The DC-DC converter generates 12v and 5v necessary for the HDD power supply. 5v is generated branching off from 12v. 12v
supplies the backup circuit with a large-capacitance capacitor for backup in the event of a momentary power failure. The inrush
current prevention circuit is provided to ease the inrush current that is generated by the capacitor on startup.
The DC-DC converter also supplies 3.3v to logic components of the main board from the 40v. 3.3v is set to start after 40V and
5V are raised to 10v and 4.3v respectively. 3.3v mounts the backup circuit with a large-capacitance capacitor for backup in the
event of a momentary power failure. The inrush current prevention circuit is provided to ease the inrush current that is generated
by the capacitor on startup.
In addition, this 3.3v generates 1.9v that is supplied as the core power supply to the CPU, and 1.9v is generated for the CPU´s
RTC circuit that has the backup circuit by the lithium battery. Particularly because the load changes of 1.9v for the CPU are
large, a converter with high transient characteristics is used. The lithium battery circuit is provided with a battery alarm, and an
nBAT_ALM signal is asserted LOW when the amount of the lithium battery remaining is exhausted.
100 V AC to 240 V AC, 1.5A, 50 Hz/60 Hz
DC40 V, 1.38 A (55.2 W)
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