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CR1 chassis (E)
9
3-2-2-3. Sub Converter
Fly-back type hard switching
This circuit consists of a control IC IC610 and a Q630 for switching FET.
It provides USB voltage.
D632 and D633 compose a snubber.
Shunt regulator IC680 feeds back the output.
The output voltage is supplied to the USB board and the heater circuit.
3-2-2-4. Main Converter
The Main Converter is a current resonance type converter of separately excited oscillating system.
The resonance frequency is decided by the 5-7 winding inductance of T620 and the resonance capacitor C658.
By turning on/off two MOSFET Q640 and Q641 alternately, the current is fed to the 5-7 winding of T620 to generate the voltage in the
secondary winding.
The output voltage is controlled by detecting the +B output voltage (+ pin of C650) by IC640, and varying the switching frequency of
Q640 and Q641, namely by the frequency modulation system.
As the load becomes heavy, the switching frequency lowers.
The +B2 and (15 V are outputted according to the turn ratio to the winding for +B output.
3-2-2-5. Degauss Circuit
The degauss operation is controlled by the DEGAUSS SW signal from the micro controller.
When the DEGAUSS SW signal goes High, Q611 turns on, and then RY603 (2 contacts) turns on.
When the relay turns on, the current flows to the degauss coil from CN601 through positive characteristic thermistor.
The positive characteristic thermistor increases its resistance value due to heating when the current flows, thus gradually attenuating
the current flowing into the degauss coil.
The DEGAUSS SW signal goes Low about 6 seconds after the degauss started. The RY603 turns off and the degauss operation
finishes.
3-2-2-6. ON/OFF Circuit
It consists of Q652, PH620, and Q610.
When the Power signal is outputted from the micro controller, Q610 turns on to supply Vcc from "Sub Converter" to the "Main
Converter" and "Active Filter Circuit".
3-2-2-7. Standby Voltage Output Circuit
The 2-output series regulator IC652 supplies standby 5 V and 3.3 V.
The 5 V power is outputted normally.
The ON/OFF of 3.3 V power is controlled by the Power signal from the micro controller.
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