| 摘要 |
The invention relates to a stand-by power supply apparatus meant to be used within some electronic products such as radio and t.v. sets, personal computers, microcontrollers systems and the like. According to the invention, the stand-by power supply comprises a transformer (T3) which is connected to the load by means of two of its windings (N4 and N5), and by means of its primary winding (Npr) the transformer is connected, on the one hand, to a voltage source (E), and, on the other hand, to the collector of a transistor (Q3) which has the emitter connected to ground (GND) and which is controlled by the base-emitter junction as follows:-for the direct polarization of the base-emitter junction, the base of the transistor (Q3) is connected with a resistor (R3) to the voltage source (E) and with a resistor (R9) to the ground;- for increasing the period of functioning and stabilizing the load voltage, the base of the transistor (Q3) is connected through a resistor (Rp) to the terminal with polarity "-" of a capacitor (C7) which, having the polarity "+" connected to the ground (GND), is charged, through a diode (D6) connected with the anode to the polarity "-" of the capacitor (C7) and with the cathode to the reaction winding (Nr), with a voltage proportional to the load voltage, from the reaction winding (Nr) which is connected to ground (GND);-the base-emitter junction is pulse controlled through a capacitor (C3) connected with a terminal to the base of the transistor (Q3), while the other terminal is connected to the reaction winding (Nr) through a resistor (R8) and to the cathode of a diode (Dp) having the anode connected to the ground (GND). |
