Protection Circuit - Pioneer M-AX10 Service Manual

M-AX10

7.2 PROTECTION CIRCUIT

The protection circuits are provided for this unit. When these protection
circuits are activated ,the hardware muting is activated and muting and the
output relays are controlled by the microcomputer.
There are two protection circuits.
1) DC voltage detection at the output
2) Overcurrent detection due to the short circuit at the load end
1. DC voltage detection circuit
At the High-CH (Low-CH) output current amp of C.AMP (L)ASSY,
DC voltage is detected by Q507 and Q509 (Q508 and Q510) and these
transistors turned ON and P-DET signal becomes Low. When P-DET
signal becomes Low ,relay control Tr. Q515 ,Q511 and Q512 becomes
open and shut down the relay RY501 and RY502. Also microcomputer
receive P-DET Low signal and activate the mute circuit and set OFF the
relay control Tr. Q513.
2. Overcurrent detection circuit
At the High-CH (Low-CH) output current amp of C.AMP (L)ASSY,
(+) side overcurrent is detected by Q503 and Q505 (Q518,Q504 and
Q506) and these transistors turned ON and P-DET signal becomes Low.
Following is same as above.
(–) side overcurrent is detected by Q517,Q503 and Q505 (Q504 and
Q506) and these transistors turned ON and P-DET signal becomes Low.
Following is same as above.
Refer to next page FIg.1 about the circuit description.
3. Starting condition of the protection circuit
The above protection circuits works under the following condition.
DC voltage detection
Overrcurrent detection
52
about over ± 3V
:
: about over 14~15A