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Alignment and Adjustments
5. Output Circuit
The voltages, which are detected form an error detection
circuit of PWM IC (Differential AMP) and Dead Time, each
is applied to PWM conparator . Due to these detection
coltages, Q1, Q2 (Output TR) parallel operate. Q482
(External TR), however, functions as a buffer; natches
inpedance between the output port of PWM IC and the
final output TR(IRFS640). The PWM pulse (applied to the
final output FET (IRFS640 GATE) varies the IC current of
high voltage TR(Q473) by adjusting the load impedance of
starage Trans (T431). Due to this variation of current, the
gain for Q473 emitter pulse changes T444(FBT)makes this
emitter pulse became high voltage. Such change keeps
both dynamic and static changes fixed. The output
waveform of high valtage TR emitter is as shown in the
figure below.
6. Paraneters according to beam
To maintain the set high voltage value (31kV), parmaters
such as +Ve (DC), Vcp High Voltage change (See the table
below).
7. Response Waveform
To reduce unstable high voltage fluctuation, the existing
high voltage type REG circuit controls dynamic fluctuation
by using C-block capacitor. But, it can't detect actual
dynamic fluctuation. Also, its velocity of response to static
fluctuation is late because +B power supply changes per
about 1V. A PWM modulation type REG detects static,
dynamic high voltage fluctuation for only Ton Time (when
the current of the output TR collector flows) each 1H, and
modulates the width of PWM pulse. So, this PWM type has
better improvement in the characteristic of high voltage
2-34
REG as compared to the existing type.
8. Application Effects
1) Improvement of horizontal size fluctuation
2) Linearity improved
3) Embodiment of X-ray protection circuit
The figures below show characteristics when a PWM high
voltage REG circuit is applied.
Samsung Electronics
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