Power Supply Backup Circuit (X32: ) - Kenwood DP-7050 Service Manual

DP-7050
CIRCUIT DESCRIPTION
9. Power Supply Backup Circuit (X32 : )
9-1. Explanation of operation
This circuit memorize the ON/OFF operations of the
secondary power. For this circuit, the CE signals for
backing up the IC106 RAM for disc file and the power
of +5V for the system unit (which is turned on and off
by turning on and off the secondary power switch).
When the primary plug is disconnected, the CE sig-
nal changes from L to H to set the RAM in the backup
mode. This CE signal is set as CLK of the D flip-flop and
9-2. Block diagram
U-com +5V
YZ
RAM
1C106
C155
Super hi
capacitor
RAM CE
1C106
pin 18
y-» POWER | |
To PO terminal
of p-Com unit
+5V
O
Secondary O
power switch
the +5V for the system unit is set the data to maintain
H/L of the +5V for the system unit.
The flip-flop of the next stage is used for the AND
operation of the maintained data (1Q —>PR) and the
differential pulse of the RST signal which changes from
L to H when the primary plug is connected. Only when
the maintained data (PR) is L, the L pulse is output to
2Q to turn on the secondary power.
R224 100k
Super
capacitor
C218
N
> iS
&
vane,
= ik a =
| for system unit
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