Proposal For Applying Short Protection - Sanyo VHR-VK210A Service Manual

PROPOSAL FOR APPLYING SHORT PROTECTION

• The Contents of Examination
As all the IC that is applied to VCR is controlled by IIC, mutual communication, if Vcc of IC is short or open
with detecting 'Acknowledge' data of the specific IC according to each power(5V, 5VT) µ-COM gets unable to
detect 'ACK' data.
µ-COM regards this case as abnormal one and if it can't detect 'ACK' data for a certain time(3.5 sec) the sig-
nal of 'Power Control' and 'Timer Control' are switched to 'Low'. As a result POWER Switching TR is kept from
generating heat and fire.
Conception
BLOCK Diagram
• POWER for each IC
5.2V
5.3VA
• IC to detect 'ACK' data is selected as below because IC is different in accordance to region and option
W 5V POWER
Series 5VT POWER
SLAVE with 5V
SLAVE with 5V
Modulator
Hi-Fi IC
NICAM IC
Power Control
Modulator
AVCP IC
5VT SW
IIC BUS
5VT SW
5.2VT
VCC
5.3VA
*Short protection off mode : DJ01 Diode in
1-4
TIMER
CONTROL
MASTER
POWER
CONTROL
AVCP IC
TUNER
OSD
Timer Control
VCC