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DP-4X POWER SUPPLY SW +115V REGULATION EXPLANATION
Hi-Voltage Power Supply Regulation Circuit Diagram explanation:
(See Power Supply SW+115V Regulation Circuit Diagram for details)
THIS POWER SUPPLY RUNS ONLY WHEN THE SET IS TURNED ON:
TURNING ON THE SW +115V POWER SUPPLY: (See Relay Controls on previous page).
RY102 AC Supply to the Deflection Power Supply Relay
When the set is turned on, the POWER DEF command is supplied from pin 58 of the Microprocessor I004.
(This high also turns on the Power LED on the front of the set). This high is sent to Q023 and Q024 then to the
PPS1 connector pin 11 labeled POWER 3. From here this high goes to the Deflection PWB through R125,
R122, D110 to the Base of Q102. The base goes high and the transistor turns on. This action supplies a ground
return for the coil inside RY102 and the relay turns on supplying AC to the connector PC2. Then to the Deflec-
tion Power Supply rectifier DP01 and the Deflection Power Supply begins to operate.
DP01 develops raw 300V via the doubler circuit comprised by CP03 and CP04. This voltage is routed through
FP01 to the Drain of QP01. A sample of this DC is routed through RP03 as Start Up voltage for IP01 at around
309V. From the Source of QP01 (when switched) the pulsed DC is routed to pin 9 of TP01. This voltage is
routed through the primary coil inside TP01 and out pins 7. One path from here is sent to pin 9 of IP01 which is
the Over Current Detection pin. The Ground return path for the primary voltage is routed through three 0.22 ohm
resistors R911, R912 and R913.
The Source of QP01 is also connected to the Drain of QP02. In this way, QP01 acts to connect raw B+ to the
primary of TP01 during the field build up period and QP02 acts as a ground switch during the collapse of the
primary field. QP01 gate control is via pin 16 of IP01. QP02 gate control is via pin 12 of IP01.
After the Deflection Power Supply begins to operate, IP01 needs Run Voltage. This is accomplished by the pulse
from TP01 pin 5 being rectified by DP04, filtered by CP13 and the DC component arrives at pin 8 of IP01.
SW +115 REGULATION
SW +115V pulse is generated from pin 10 and 11 of T901. This pulse is rectified by DP34, filtered by CP45 and
then routed through the Excessive Current sensing circuit RP34 and QP05.
The primary route for the SW +115V is through EP02, LP37 and output as SW +115V to the Deflection and
High Voltage generation circuit.
However, the regulation route is to pin 1 of IP03. Internally, the regulator circuit works as a variable resistor
whose resistance is dependant upon the SW +115V voltage fluctuations. The internal variable resistor manipu-
lates the current flow from pin 6 to pin 7 ground. This will cause the voltage at pin 2 of IP02 to be controlled.
Internally, the LED is illuminated by degrees dependant upon the SW +115V voltage fluctuations. The internal
receiver receives this light and acts as a variable resistor from pin 4 which is the regulation control signal to pin 3
hot ground.
This action causes pin 2 of IP01 to manipulate the internal oscillator within IP01. This in turn causes the timing
of the drive pulses delivered to the Gate of QP01 and QP02 SMOSFET (Switch Metal Oxide Semiconductor
Field Effect Transistor) to manipulate the frequency of the pulse generated on the primary of TP01. The current
drain of these SMOSFETs is monitored by three low ohm resistors mentioned above. If this current exceeds a
specific value, the voltage developed by these low ohm resistors is routed through RP14 back into pin 9 of IP01
which is the Over Current Protection circuit. This pin will inhibit the drive signal to the gate of the SMOSFETs.
As soon as the excessive current situation is eliminated, the IC will recover and continue functioning.
B+ GENERATION FOR THE POWER SUPPLY DRIVER IC:
Vcc for the Driver IC is first generated by the AC input. This voltage is called Start Up Voltage. IP01 requires
23.3V DC to operate normal. However, it will begin operation at a much smaller voltage on pin 18.
When AC is applied to the main full wave bridge rectifier DP01 where it is converted to Raw 300V DC voltage,
voltage doubler filter CP03 and CP04, routed through RP03 and made available to pin 18 of IP01 as start up
voltage. This voltage climbs to 300Vdc and the internal Regulator of IP01 is turned On and begins operation.
When the power supply begins to operate, the magnet field collapses and the EMF is coupled over to the secon-
dary windings, as well as the drive windings. The drive windings at pin (5) produce a run voltage pulse of around
43 V p/p which is rectified by DP04, filtered by CP13 and becomes run voltage (20.3V) for IP01 pin 8.
PAGE 01-17
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