3. Over-Voltage Protection and Over-CurrentThis function is effective when the horizontal frequency of
Protection Circuitthe input signal is 15 kHz (NTSC and PAL).
The +135 V voltage line of the main power supply has theBecause this circuit produces an ill effect when the stan-
over-voltage protection circuit and the over-currentdard TV signal is input, use or not-use of this circuit can be
protection circuit that protect the power supply circuit andselected from the on-screen menu.
the loads when an abnormality occurs in the respective
loads and in the voltage feedback system.2. PWM Control Circuit for +B Power Voltages
When an over-current occurs, the latch circuit consisting offor Horizontal Deflection and of High Voltage
Q616 and Q617 is turned on so that the VCC power toThe PWM control circuit for +B power voltage consists of
IC601 and IC602 is turned off through the isolator PH604IC515 and its peripheral circuit. The horizontal drive
to stop operation of the main power supply circuit.signal that is output from IC507 pin-21 is used as the
This protection circuit is released when the input power toPWM trigger signal.
the main power supply circuit is turned off once or whenThe PWM control for horizontal deflection system is
the standby mode is selected.performed by inputting the deflection distortion correction
signal that is output from IC507 pin-31 to which the H.
size control DC voltage super-imposed, to IC515 pin-8.
Deflection and High Voltage CircuitOn the other hand, the horizontal signal that is fed back
from the horizontal output circuit is inputted to IC515 pin-
1. Sync Signal and Deflection Signal Processing7. These two input signals are compared and the error
Circuitsignal between them, that is the PWM control signal is
The horizontal and vertical sync signals that are input fromoutput from IC515 pin-11. The PWM control output
CN501 (pins-1/-2) are sent to the H/V DELAY timingsignal is sent to the +B regulator circuit consisting of
circuit consisting of IC510, IC522, IC509 and IC526. TheQ2503 and its peripheral circuit that control the H. size and
H/V DELAY timing circuit outputs the sync signals thatthe deflection distortion correction.
have the same phase as those of the input signal duringThe PWM control for the high voltage circuit is performed
normal operation. However, during the H/V DELAYby inputting the reference signal generated by IC519, to
mode, it outputs the delayed sync signals to which delay isIC515 pin-16 that is compared with the FBT high voltage
given by IC509 and IC510. The output sync signals aredetected voltage that is input to IC515 pin-17. The error
processed of the waveforms by IC503 and are sent to thesignal between them, that is the PWM control signal is
deflection signal processor IC507.output from IC515 pin-13. The PWM control output
The deflection signal processor IC507 outputs the varioussignal is sent to the +B regulator circuit consisting of Q514
signals that are required for deflection, such as horizontaland its peripheral circuit that control the high voltage to be
drive circuit, parabola signal for dynamic focusing,supplied to CRT.
parabola signal for picture distortion correction, verticalThe PWM control signal that is output from IC515 re-
drive signal and H/V blanking signals. The output signalsceives the DTC (Dead Time Control) in order to protect
are controlled directly by the microprocessor in the MAthe horizontal output circuit and the high voltage output
board through I2C bus.circuit from damage caused by the sharp change of fre-
The horizontal free-running frequency is set for about 18quency of the input video signal. The DTC circuit works
kHz. The pull-in range of the input signal frequency isas follows. When frequency of the input sync signal is
from 15 kHz to 45 kHz.changed, the unlock signal that is output from IC507 pin-
The deflection signal processor IC507 has the built-in37 is sent to IC507 pin-6 as the DTC signal input via the
protector for X-ray protection. When its pin-15 is raised toswitches Q523 and Q504, so that the PWM is controlled to
8 V or higher, the X-ray protection circuit starts working todecrease the +B regulator output voltages to be supplied to
stop the horizontal and vertical outputs. The X-raythe horizontal and high voltage systems.
protector circuit can be reset by turning off the main power
once then back on, or by entering the standby mode.3. Horizontal Output Circuit
There can be a case that the monitor receives the non-The horizontal drive signal that is output form IC507 pin-
standard TV signal such as the output signal from VTR. In21 is amplified by the horizontal drive circuit consisting of
order to reduce the skew effect on screen caused byQ2501, Q2502, Q2505 and their peripheral circuit. The
irregular timing of the input sync signal, the PLL circuithorizontal drive signal then drives T2502 (HDT) and
inside the IC507 is stopped during the vertical blankingQ2508 (H. OUT). The H. pulse is induced by the reso-
period.nance between the capacitors C2528, C2530, C2531 and
6-2BVM-D14H1U/D14H5U/D14H1E/D14H5E/D14H1A/D14H5AtheH. winding impedance. |
ACEC
