| 摘要 |
In a circuit arrangement for limiting the switching-on current peaks in a switching transistor (T), for example, a switching transistor in a direct voltage converter, rectangular switching pulses of the same height (UST) are applied to the control input of the switching transistor. In order to protect, for the largest possible number of types of application, the switching transistor (T) having an equally dimensioned coil (PW) from overload, the coil is included in a branch which is common both to the control circuit and to the operating circuit of the switching transistor. For simultaneously monitoring the operating current (I) in a direct voltage converter (UB, UA), the coil is the primary coil of a current transformer (STW), whose secondary circuit includes, inter alia, the series-combination of a saturable choke (DR) and a load resistor (RB2). The proportioning of all elements (RB1, DR, RB2, SW) in the secondary circuit of the current converter transformer can be chosen so that the voltage drop at the load resistor (RB2) is a measure of the current strength (i) through the switching transistor. When this voltage drop exceeds a threshold, the switching transistor is cut off by a pulse width modulator (PWM) until the next switching pulse occurs.
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