PICl is a double row 8 foot device, a careful observation of the PIC1 circuit connection method, found that the common UC3842 application circuit does not match. To find the same type of machine after comparison, determine the KA7552 is PICl, PFET1 is K793. As never exposed to KA7552, its performance is not understood, then the Internet to download the KA7552 of the original data. KA7552 is produced by Fairchild switching power supply control IC, it has various protection functions and external circuit is simple, convenient application and is used in imported DVDs machine, fax machine, Printer Rent display electronic equipment of switching power supply. KA7552 working voltage 10V-30V can direct drive power MOSFET, drive current is up to + 1.5A and driving pulse duty ratio of 70%; 5kHz-600kHz operating frequency range, it is easy to get higher conversion efficiency and reduce the heat quantity of the electric power; in the locked mode has an overvoltage cutoff function; with perfect over-current, overload, under voltage protection circuit and soft start circuit, standby current only 90 [mu] a. KA7552 uses 8 pin DIP or SOP two kinds of packaging methods. KA7552's internal block diagram and other details can refer to the manufacturer's original English use technical manual.

KA7552 each pin symbol and function table.

Samsung DV-350KV player circuit see figure.

220V PRl, PR2, PC2, PC1 and other components of the filter to filter out various high-frequency interference in the power grid, and then by the PDl rectifier, PCEl filter to get the 300V DC voltage. 300V voltage divided into two branches: a path switch transformer PTL main winding and to PFETl drain, the other path start resistance PRll, PRl2 and back coupling capacitor PCE3 to P1C1 6 feet, for Pici start voltage is provided. Also PICl 6 foot internal circuit undervoltage protection circuit, when the supply voltage is lower than 8.7v, the internal start-up circuit in stop working state, the oscillation circuit to stop oscillation. The pin is normally operating at about 12V. Starting time of the power switch to IC is determined by PRl2, PRll, and PCE3. When the PICl pin voltage is greater than 16V, PICl began to work.

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