Primary Power Supply; Start Up; Regulation - Sony KV-32XBR400 Training Manual

Primary Power Supply

The primary power supply on the A board consists of three parts:
1. Oscillator 2. Output stage 3. Regulator Stage

Start Up

The oscillator within IC6001 starts if the V Sense input voltage at pin 1 is
above 1.3Vdc. Sample voltage from pin 18 is then used to run the inter-
nal oscillator. The initial frequency is approximately 200kHz. The low
amplitude initial oscillator signal is output IC6001/pins 12 and 16 into the
driver/output stage.
Driver / Output stage
The oscillator voltage output at pins 12 and 16 use drivers Q6007 and
Q6008 to develop T6003 secondary voltages. IC6001's oscillator will shut
down if the driver transistor's current is excessive. To prevent premature
shutdown, the timer capacitor C6064 delays the shutdown.
VC1 Enables the Regulator
Although the oscillator is running, at this initial frequency of 200kHz, there
is insufficient current from T6003 to produce any unregulated 5, 7, or 11V
voltage because of the load. There is little load on D6005 and D6009,
producing about 15V each at the cathodes (normally about 18Vdc). The
voltage from D6005 is returned to IC6001/pin 8 to serve as regulated B+
for the internal drivers that amplify the oscillator signal leaving pin 12.
The VC1 voltage also enables the internal regulator circuit (responds to
the error voltage input IC6001/pin 2) to change the oscillator frequency.
B+ for IC6001's Internal Drivers
At start up IC6001 uses current limited B+ from pin 18 to amplify the
oscillator signal and get it out to pin 16 (internal drivers). When VC1 is
present, the internal drivers switch to this stable regulated B+. The B+ for
the internal drivers for IC6001/pin 16 comes from Vb at pin 14. D6003
and C6009, external to IC6001/pins 10 and 14 (Vb), complete an internal
voltage boost circuit. This boost circuit starts with VC1 voltage (input pin
8) that is connected internally to VC2 pin 10 (less 0.6Vdc). This VC2
voltage is filtered by C6009 and passes through blocking diode D6003
31
into pin 14. Internal pulses from IC6001/pin 14 add to D6003's DC volt-
age, producing the boost voltage at Vb pin 14. This boost voltage is
approximately +10V above the reference voltage at IC6001/pin 15 and
used internally to serve as the B+ for the top internal drivers that amplify
oscillator signal leaving IC6001/pin 16.
Secondary Power Supply Starting
The Pri Pre 15V output of D6009 is only approximately 10Vdc at start up
when the oscillator frequency is high (normally about 18Vdc). When is
reaches 15.6Vdc, it starts the Secondary Power Supply. Therefore, the
Secondary Supply cannot start until the Primary Supply is running.

Regulation

Concept
T6003's secondary output voltages are dependent upon the match be-
tween the output resonate circuit (T6003 = L, C6014 = C) and the oscilla-
tor frequency. When IC6001's oscillator frequency is the same as the
resonate circuit frequency, there is maximum power transferred in T6003
producing maximum output voltage. By setting the oscillator frequency
above resonance, T6003's output voltage can be regulated.
T6003
Output
Voltage
Output Voltage Control
The regulating stage uses error detector IC6002 and optical isolator
PH6001 to monitor the unregulated +7V output from T6003. If the un-
regulated +7V output is LOW as it is at initial start up, the voltage fed back
to IC6001/pin 2 goes HIGH, decreasing the oscillator frequency. The
decrease in frequency increases the output of the T6003 transformer,
until +7Vdc is reached.
Regulation Feedback Voltages
Unreg 7V Output (D6011)
Low
85kHz = Normal Operation
200kHz = Start Up
PH6001/pin 2 IC6001/pin 2
high high