Protection Circuit; Abnormal Condition Detection Circuit; Over Heat Detection Circuit; Battery Reverse Connection Protection Circuit - Panasonic KX-TDA0103XJ Service Manual

8.1.1.6.

Protection Circuit

This section explains about the Over Voltage Protection Circuit and Over Heat Protection Circuit and Battery Reverse
Connection Protection Circuit.

1) Abnormal Condition Detection Circuit

Abnormal condition detection circuit consists of thyristors Q524 and Q525 (on Sub board). When power supply operation
becomes abnormal, the abnormal detection signal is sent and Q524 and Q525 are turned ON. A current flows through the diode
of PC4 (on Sub board), which is sent to the latch circuit of main converter, and the operation of main converter is stopped.
Refer to Fig. 6 (D).

2) Over Heat Detection Circuit

When internal temperature of power supply rises abnormally, resistance value of thermistor NTC501 becomes low, transistor
Q590 (on Sub board) turns OFF, and voltage from pin 8 of IC301 is sent to the abnormal detection circuit.
Refer to Fig. 6 (A).

3) Battery Reverse Connection Protection Circuit

When the battery is connected to the unit in the wrong direction by mistake, the voltage of plus terminal becomes minus. Then
diodes D523, D524 and D525 turn ON. The transistor Q511 (on Sub board) turns ON, and the voltage from dropper circuit
(Refer to Alarm Signal Sending Circuit (P.28)) is sent to the abnormal detection circuit through zener diode D529 (on Sub
board).
Refer to Fig. 6 (B).
4) Over Voltage Protection Circuit
When any of 15V, 15VPT, 30V and main converter 41V output becomes abnormal, the voltage is sent to the abnormal detection
circuit through zener diode D529 (on Sub board).
Refer to Fig. 6 (C).
KX-TDA0103XJ / KX-TDA0104XJ / KX-TDA0108XJ / KX-TDA0103X / KX-TDA0104X / KX-TDA0108X
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