Daewoo WP-895 Overcurrent protection function OCP, Latch circuit, Thermal shutdown circuit TSD

Page 61

Service manual WP 895/895F, CP885/885F

When the MOSFET is ON, the STR-F6654 internal capacitor C1 is charged at the constant voltage 6.5V.

At the same time, the voltage at pin 1 (OCP / FB) increases with the same waveform as the MOSFET drain current.

When the pin 1 voltage reaches the threshold voltage VTH1 = 0.73V, the STR-F6654 internal comparator 1 starts operating. The STR-F6654 internal oscillator is inverted and the MOSFET turns OFF.

When the MOSFET turns OFF, charging of STR-F6654 internal capacitor C1 is released and C1 starts discharging by the STR-F6654 internal resistance R1. So, C1 voltage starts falling in accordance with the gradient regulated by the constant discharging time of C1 and R1. So, this means that the fixed time determined by C1 and R1 is the OFF-time of the MOSFET.

When C1 voltage falls to around 3.7V, the STR-F6654 internal oscillator is reversed again and the MOSFET turns ON. C1 is quickly charged to around 6.5V

The MOSFET continues to oscillate by repeating the above procedure.

5-9-2-3 STR-F6654 protection circuits

overcurrent protection function (OCP)

Overcurrent protection is performed pulse by pulse detecting at STR-F6654 pin 1 (OCP) the peak of the MOSFET drain current in every pulse.

• latch circuit

This circuit sustains an output low from the STR-F6654 internal oscillator and stops operation of the power supply when overvoltage protection (OVP) and thermal shutdown (TSD) circuit are under operation

• thermal shutdown circuit (TSD)

This circuit triggers the latch circuit when the frame temperature of STR-F6654 IC exceeds 140°C

• overvoltage protection circuit (OVP)

This circuit triggers the latch circuit when the Vin voltage exceeds 22V (typ.)

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Contents Colour Television Contents Circuit description PCB Layout Circuit Diagram Power consumption Main FeaturesSound Output Power Tuning systemSpecification matrix Pin Signal Description Matching value Page C02 C01C03 C04C42 S11 S10S12 S13Special case Country selection = Others Program Group SkipITV RAY Radiation Precaution Safety instructionAlignment instructions Order Default settingh for wpParabola HOR WidthDisable HOR Paral BOW Corner EW Trapez IC description Page Page Chassis IC marking OSD languages Atss countries Text IC version VCT 3832APin Name Type Short Description Gndaf Supply VCT Page Analogue Section DSP-Section Audio Baseband ProcessingNicam plus FM/AM-Mono German 2-Carrier System Dual FM SystemSECAM-L PALUssr AdrselDvsup ANAIN1 FeaturesTesten XtalinPin Symbol Function GND1 OUT1OUT1+ ModeBlock diagram TDA8944J GND Page Page Inverting input Block diagram TDA6107Q SCL SDAPage Description IC PIN Symbol Rating Unit OCH -F MINCircuit description If section Block diagram Vision if Amplifier Standard Features Page Page Adaptive Comb Filter VCT3834A only Video Sync Processing CRT Measurement and Control Page Stand by ConfigurationDescription Application Page Page Quadrature Mixers ESCPage Page STR-F6654 general description Power supply primary part operationsPage STR-F6654 oscillating operation Latch circuit Overcurrent protection function OCPThermal shutdown circuit TSD Overvoltage protection circuit OVPTV start-up operations TV normal run and stand-by mode operations Page FBT CP885/885F N T R O L L E D Rectifier 6V DC High Service Parts List Spark GAP CBXF1H104Z Cera Semi 50V F 0.1MF Z Tapping CZSL1H220J Cera 50V SL 22PF J Axial CCZB1H222K Cera Coil Peaking Wire Copper Carbon Comp Exploded View Exploded View DTF-29U8 DTP-28A7 Service Man ual WP-895/895F, CP885/885F DTP-28G7 DTP-28G8 Printed Circuit Board Page Page 686, AHYEON-DONG MAPO-GU SEOUL, Korea

CP-885F, CP-885, WP-895, WP-895F specifications

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