Dc Switch And Dc Output Circuit - Panasonic KX-NS700 Service Manual

3) Latch function for protection
Control IC U2 has the latch fonction to stop the PSU operation when over heat or over voltage is detected .
To release the latch status, release the abnormal state at first, then remove the AC cord from PSU and leave for 60 seconds
before restart.
1.4.

DC Switch and DC Output Circuit

Added into the Original Service Manual as section 4.8.
This section describes the operation of the 41V output circuit and 15V output circuit which consists of DC/DC converter.
1) DC Switch
Vout(41V), the output of Main Converter is supplied to post circuits via CN100 and DC Switch mounted on the cabinet.
2) 41V Output
2-1) 41V Overcurrent Protection Circuit
This circuit consists of mainly of Q19, R62, R105 and Q15
When Overcurrent flows to R62, the voltage potential defference between R62 and R105 is detected by Q19 and Q19 turns
ON.
Then Q15(FET Switch) turns OFF.
Consequently the fold back current limiting shuts down 41V output.
To control this circuit, +60V voltage which is generated in 15V Circuit.
2-2) 41V Output Converter Circuit
41V is devided to two outputs, "+41V" and "+41V_OP")
"+41V" is fed to the circuit on Base Board / CPU Boaerd.
"+41V_OP" is fed to the optional card via Base Board.
3) 15V Output
3-1) 15V Output Converter Circuit
This circuit generates +15V from +41V.
This circuit consists of mainly of F4, C12, U7, D14, L3, C26
3-2) 15V Output Overcurrent Detection Circuit
This circuit consists of mainly of R63, Q30, and Q31.
If overcurrent of 15V output is detected, Q30, Q31, and Q29 get ON, then SD(Shut Down) pin of U7 get high and U7 shut
downs.
3-3) 15V Output Overvoltage Detection Circuit
This circuit consists of mainly of Z12, Q28 and Q27.
If overvoltage of 15V output is detected, Q28, Q27, and Q29 get ON, then SD(Shut Down) pin of U7 get high and U7 shut
downs.
4) Overvoltage Detection Circuit-2
When 15V or 41V output becomes abnormally high, it makes Photo Coupler U3 ON via D13.
Then the control IC(U2) stops with the latch mode.
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