Voltage regulator provided with a current limiter

Abstract

A voltage regulator for converting an input voltage (V ) into an output voltage (V ). The input voltage may be burdened with a ripple. The output voltage (V ) supplied by the voltage regulator is virtually free from ripple. The voltage regulator comprises an input terminal ( ) for receiving the input voltage (V ), an output terminal for supplying the output voltage (V ) in response to the input voltage (V ), and current limiting means for limiting the maximum absolute value of an output current (I ) taken from the output terminal ( ). The current limiting means comprise a field effect transistor (T ). The voltage regulator further comprises a first current mirror (CM ) comprising transistors (T , T ), a second current mirror (CM ) comprising transistors (T , T ), and a third current mirror comprising transistors (T , T ). In a typical operation, the field effect transistor (T ) is in the linear region and thus behaves like a resistance. With an increasing output current (I ), the current through the field effect transistor (T ) also increases, and the voltage between the drain and the source of the field effect transistor (T ) increases. When the voltage between the drain and the source of the field effect transistor (T ) has exceeded a certain level, the field effect transistor (T ) enters its saturation region and accordingly behaves like a constant-current source. As a consequence the output current (I ) can no longer rise.