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Service manual WP 895/895F, CP885/885F, CP485F
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 V
TH1
= 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 V
in
voltage exceeds 22V (typ.)
Summary of Contents for CP-485F
Page 33: ... 32 Service manual WP 895 895F CP885 885F CP485F Block diagram TDA8944J ...
Page 36: ... 35 Service manual WP 895 895F CP885 885F CP485F ...
Page 38: ... 37 Service manual WP 895 895F CP885 885F CP485F Block diagram TDA6107Q ...
Page 43: ... 42 Service manual WP 895 895F CP885 885F CP485F 5 Circuit description 5 1 Block diagram ...
Page 61: ... 60 Service manual WP 895 895F CP885 885F CP485F 5 9 2 2 STR F6654 oscillating operation ...
Page 67: ... 66 Service manual WP 895 895F CP885 885F CP485F ...
Page 87: ...Service Manual WP 895 895F CP885 885F CP485F 86 7 Exploded View 7 1 DWX 28W5 ...
Page 88: ...Service Manual WP 895 895F CP885 885F CP485F 87 7 Exploded View 7 2 DWF 28W8 ...
Page 89: ...Service Manual WP 895 895F CP885 885F CP485F 88 7 Exploded View 7 3 DTF 29U8 ...
Page 90: ...Service Manual WP 895 895F CP885 885F CP485F 89 7 Exploded View 7 4 DTP 28A7 ...
Page 91: ...Service Man ual WP 895 895F CP885 885F CP485F 90 7 Exploded View 7 5 DTP 28B1 ...
Page 92: ...Service Man ual WP 895 895F CP885 885F CP485F 91 7 Exploded View 7 6 DTP 28G7 ...
Page 93: ...Service Manual WP 895 895F CP885 885F CP485F 92 7 Exploded View 7 7 DTP 28G8 ...
Page 94: ...Service Manual WP 895 895F CP885 885F CP485F 7 8 DWF 28W9 93 7 Exploded View ...
Page 95: ... 94 Service Manual WP 895 895F CP885 885F CP 485F 7 9 DTB 21U7 7 Exploded view ...
Page 96: ...SCHEMATIC DIAGRAM WP 895 CP 885 ...
Page 97: ...SCHEMATIC DIAGRAM WP 895F CP 885F ...
Page 98: ...SCHEMATIC DIAGRAM CP 485F ...
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