| 摘要 |
A switched mode power supply comprising a transformer (T180) that is provided with a primary winding (W2) and at least one secondary winding (W3), whereby the primary winding and a switching transistor (V160) are series connected to a direct current supply voltage (Up), and a rectifier (Glr) and a charging capacitor (CL) are mounted upstream from the secondary winding. A control circuit (ASA) for the switching transistor has a fixed frequent, astable multivibrator (V121, V130), and an output signal from the multivibrator is fed to the input of a controlled power source (V140, V143, R140) via an isolating transformer (V131). The output of the power source is connected to the control electrode of the switching transistor (V160) in the primary circuit in order to join the latter to the first flank of the multivibrator output signal. The control electrode of the switching transistor can be connected to a tripping potential via a controlled thyristor (V142, V141). The actuating signal (Us') and the output signal (UI) of the current sensor (R161) are fed to the thyristor in the form of a control signal and the respective second flanks of the multivibrator output signal are supplied to the thyristor as turn-off pulses. |
