| 摘要 |
PURPOSE:To correct even fluctuation of a high CRT voltage supply by controlling a vertical amplitude correction circuit correcting an amplitude of a triangle wave outputted from a vertical amplitude reference oscillation circuit for a specific period so as to make the vertical amplitude constant over all the period of a change in the beam current. CONSTITUTION:When a voltage of a FBT output terminal 10 is changed attended with fluctuation of a beam current, for example, the beam current is decreased, a high voltage supply of the CRT is increased and the voltage at a FBT output terminal 10 is also increased. Then a base level of a correction transistor(TR) 11a is increased by a bias resistor 11d, the correction TR 11a is operated, the collector current of a vertical amplitude correction TR 3a is increased and the voltage change in a charge/discharge capacitor 2b is increased. That is, the amplitude of a reference oscillation triangle wave voltage is increased to correct the vertical amplitude of the pattern to be increased. Thus, the amplitude of the pattern is made constant in this way. |
