uPC1237 speaker protection schematic

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uPC1237 by a single power supply, operating voltage range of 25v ~ 60v, usually the direct use of the amplifier as a positive power source + Vcc power.
uPC1237 speaker protection schematic - schematic

Relay coil voltage is DC 24v, because foot relay driver-side current limit is 80mA, in energize the relay timely, pin voltage is about 0v, if the average voltage Vcc 24v, must be inserted step-down current limiting resistor R12, the relay and integrated circuit are not caused by over-current heat damage, the correspondence between the resistance R12, the average power consumption and Vcc voltage in Table 1. Buffs can look-up table 1 to determine the average voltage value R12 according to vcc own amplifier. uPC1237 foot end is power-on delay, determined by R7, c3 boot parameters quiet time after that is energized until the amplifier circuit reaches a stable equilibrium, let the delay circuit relay contacts connected speakers. This can eliminate the power-up impact noise, increased c3 or R7 extended boot mute time. uPC1237 feet supply side, the maximum limit is 8v. When Vcc is not the same, R8 respective different resistance, determined look-up table 1. uPC1237 foot AC power detection terminal for the amplifier off mute. When the amplifier power switch is off, the transformer secondary AC voltage immediately disappear, c2 small capacitor discharges through foot resistance quickly, pin voltage drops rapidly, internal circuit control relay, the output of the amplifier and the speakers disconnected to prevent during the transition the power output zero level when the speaker out of balance current impact (ie impact noise off) after a power outage. foot maximum limit voltage 10v, when the monitored power amplifier transformer secondary winding AC voltage values are different, the partial pressure of the current limiting resistor R6 respective different values, are too big too small speaker protection circuit will not work, Ac AC voltage and resistance R6 correspondence between Table 2.

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