| 摘要 |
<p>1,211,778. Pulse generators. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. 1 Feb., 1968 [4 Feb., 1967], No. 5253/68. Headings H3A, H3P and H3T. In a pulse generator a capacitor 18 is periodically discharged substantially linearly by a voltage A of opposite polarity and each time the voltage across the capacitor reaches a given value an amplifier element 4 conducts and the capacitor 18 is again charged, a rectifier element 19 which is conductive for the charging but is cut off by synchronization pulses is connected between the capacitor 18 and the control electrode of the amplifier element 4. The pulse generator produces an output at 12 for the vertical or frame deflection coils of a colour television receiver. A positive pulse from winding 15 is applied via differentiating circuit 16, 17 to the base of a transistor 4 and at the beginning of the fly-back period causes the transistor 4 to conduct to discharge a capacitor 3. The base of transistor 4 becomes negative due to the charge across capacitor 17 and at the end of the fly-back and start of the stroke the voltage feed-back via the differentiating circuit 16, 17 makes the base further negative and transistor 4 turns off. The diode 19 turns on and the capacitor 18 which stabilizes the frequency together with capacitor 17 discharge and charge reversely to the voltage at A. The positive voltage now at the base of the transistor 4 causes it to conduct and the above is repeated. Synchronizing pulses are applied at 26 to cut off the diode 19. The natural frequency of the circuit remains substantially constant since the charging and discharging voltages of the capacitors are proportional to the supply voltage. The conduction of the output valve 7 is dependent on the state of charge on the capacitor 3 and is also determined by the feedback network 13. The resistor 20 may be variable as may be resistor 1.</p> |
