. Various DVDR985 Philips free download

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39 Figure 16 - Power Supply Circuit Power Supply components and large enough to turn On 7140, 7125 is turned Off by 7140. Diodes 6130, 6131 and 6132 protect the control circuit in case of This unit uses a stand alone Switch Mode Power failure of the MOSFET by providing an upperlimit Supply, SMPS. A MOSFET transistor turns On to the voltage that can remain on the source of and Off in an oscillator fashion, driving a trans- the MOSFET. former. The primary half of the supply uses a Hot Ground. The primary side of the circuit provides Coarse Regulation drive and coarse control of the power supply. The positive portion of the signal on Pins 7 and 8 The secondary side of the circuit rectifies and fil- will be rectified via R3150 and D6140, charging ters the output of the transformer to produce C2140 via R3140. In time, the voltage on C2140 many output voltages. It uses a cold ground, sig- will reach 15 to 20Vdc. This value depends on nal ground system. Two of the output voltages the value of the Mains voltage and the load. The are monitored for precise regulation. The 12Vdc negative portion of the signal on Pins 7 and 8 is supplied to the anode of the Optic Coupler's will be rectified via R3150 and D6142. This will diode, and the 5Vdc Standby is feed to the charge C2151 to approximately -15Vdc. This is Shunt Regulator. The regulation path includes an used as a regulation supply. Optic Coupler to accommodate the different grounding systems. The control circuit consists of T7140, D6141, C2144, C2145, C2147, R3147, and 3148. This Circuit Description circuit controls the conduction time and the switching frequency of the MOSFET. It switches AC Input Circuit Off the MOSFET as soon as the voltage on the Refer to Figure 16. The input circuit consists of sourc