| 摘要 |
<p>1494259 D.C.-D.C. converters SIEMENS AG 20 March 1975 [10 April 1974] 11558/75 Heading H2F [Also in Division G3] A current limiting and voltage stabilizing circuit comprises a blocking oscillator formed by a switching transistor 1 and transformer 3 having a primary winding 2 and feedback winding 8. A resistor 17 is included in series with the main current path of switching transistor 1. Control of output voltage is achieved by means of a thyristor 14 connected in parallel with the series arrangement of the input electrodes of switching transistor 1 and resistor 17 and controlled in dependence on the output of a comparator 23, responsive to the difference between a reference voltage 27 and a voltage dependent on the output voltage and arranged to stabilize the voltage and to protect the circuit against over-current conditions. The voltage across feed-back winding 8 is rectified by diode 13 to provide operating voltage for thyristor 14 and by diode 20 to provide inverse bias for the gate. As described, pulses in the secondary 40 are rectified at 41 ... 44 so as to provide D.C. outputs at 45 ... 48. The input is derived from A.C. mains 57 via rectifier 65 and via terminals 4 and 16. Starting.-A mains frequency starting pulse is derived by diode 31 and pulse shaping components 32, 33 and fed to the base of switching transistor 1. Voltage stabilization and over-current protection.-A voltage dependent on the output voltage is induced in winding 5 and is rectified by diode 6 and compared by transistor 23 with a reference voltage across Zener diode 27. If this voltage is excessive, thyristor 14 is turned on so as to block the base circuit of switching transistor 1 for some cycles until started by the next mains frequency pulse. A similar action occurs in the event of over-current, since this causes an increase in voltage across resistor 17.</p> |
