| 摘要 |
<p>PURPOSE:To form a power supply circuit including a power supply section by a semiconductor integrated circuit by consuming excess power from the power supply circuit by one power transistor (TR) so as to eliminate the need for the use of a power TR for a power supply section. CONSTITUTION:Power supply sections 14, 14 supplying power to a load circuit such as a telephone set 3 via a power supply circuit 12 such as a telephone line, a detection circuit 15 detecting the combined resistance between the feeding line and the load circuit by a change in a voltage level at power supply terminals 2, 3, and one power control TR Qa driven by a detection signal obtained from the detection circuit 15 and provided in a current path comprising the power supply section, the power supply circuit and the load circuit, are provided. The power control TR Qa provided at the outside of a semiconductor integrated circuit 11 is driven by a detection signal obtained corresponding to the combined resistance to supply stable power to the load circuit and the excess power when the combined resistance is small is consumed by the power control TR Qa.</p> |
