Patent ID: 6084960
Filing Date: 2000-07-04
Classification: H04M

Abstract:
A power supply circuit for a telephone apparatus, provided with an input terminal, an output terminal and a reference terminal whose potential is intended to serve as a reference potential for the whole circuit, the input terminal and the reference terminal being intended to be connected via a rectifier bridge to a telephone line and to receive and supply a current referred to as power supply current, said power supply circuit comprising:a capacitance arranged between the output terminal and the reference terminal,a first transistor with its collector-emitter path arranged between the first input terminal and the output terminal,a second transistor with its collector-emitter path arranged between the input terminal and the reference terminal, anda control module intended to make a comparison between the potential of the input terminal and that of the output terminal and to introduce a conduction current and a current complementary thereto into the bases of the first and the second transistor, respectively, the values of said currents depending on the result of the comparison and their sum being referred to as the bias current,power supply circuit characterized in that it also comprises a measuring module provided with means for making a comparison between the value of the power supply current and a predetermined threshold, and for varying the value of the bias current in the reverse direction of the variations of the result of said comparison.