| 摘要 |
The invention relates to a current limiter for a switching regulator. The transistor current of the transistor (TS) which is located in the primary circuit of a transformer (TR) is measured via a current transformer (SW) and is compared with a reference voltage which is dependent on the duty cycle of the transistor current. If the maximum permissible transistor current is exceeded, then the transistor is switched off until the start of a new switching period. Switching-off occurs virtually always at the same output current, even in the case of different input voltages to the switching regulator, as a result of the reference voltage which is dependent on the duty ratio. The limiter circuit (BS) contains a differential amplifier (DV) to which a measurement voltage (ui) which is proportional to the transistor current (iT), and a reference voltage (Uc) are supplied. The reference voltage is produced via a switch (S), which is controlled in accordance with the duty ratio, a resistor (R1) which is connected downstream of the switch, a voltage divider (R2, R3) and a capacitor (C) which is used for filtering. <IMAGE>
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