Patent ID: 6424131
Filing Date: 2002-07-23
Classification: H03K

Abstract:
A power control device comprising:a bridge circuit consisting of a first branch, a second branch, a third branch and a fourth branch, wherein each of said first to fourth branches includes a first terminal and a second terminal, the first terminal of said first branch and the first terminal of said third branch are connected to a first power-source-connecting terminal at a substantially constant potential, the second terminal of said second branch and the second terminal of said fourth branch are connected to a second power-source-connecting terminal at a substantially constant potential, the second terminal of said first branch and the first terminal of said second branch are mutually connected at a first node, the second terminal of said third branch and the first terminal of said fourth branch are mutually connected at a second node, said second branch includes a load and a switch circuit connected in series with said load, said first branch includes an output circuit for driving said load, said third branch includes an auxiliary circuit for outputting an adjusting current adjusted to an amount smaller substantially by a predetermined ratio than an output current outputted from said output circuit in the case of applying substantially the same input voltage as that of said output circuit, and said fourth branch includes a current setting circuit for holding at a substantially constant level or changing quasistatically said adjusting current; a potential difference detector for detecting a potential difference between said first node and said second node; a control circuit for making said output circuit interlock with said auxiliary circuit and controlling said output circuit; a switch control circuit for turning on or off said switch circuits in a manner synchronized with the operation of said control circuit; and a current ratio compensator for feeding back said detected potential difference detected by said potential difference detector and controlling the equivalent impedance across said first terminal and said second terminal of one of said first to fourth branches so that said bridge circuit keep the balance, thereby holding said ratio at a substantially constant level.