Patent ID: 7679353
Filing Date: 2010-03-16
Classification: H05B,Y02B

Abstract:
1. A constant-current circuit, comprising: a first transistor formed of a MOS transistor and configured to supply a current based on a control signal input to a gate of the first transistor to serve as a current source; a second transistor formed of a MOS transistor having the same conductivity as the first transistor and configured to supply a current to a load based on the control signal input to a gate of the second transistor that includes a source connected to ground, the gate connected to the gate of the first transistor, and a drain connected to the load; a voltage regulation unit configured to control a drain voltage of the first transistor according to a drain voltage of the second transistor; a current detector configured to detect a value of a current flowing through the first transistor and output a current according to a detected value; a controller configured to control a gate voltage of the first transistor and a gate voltage of the second transistor according to the value detected by the current detector so that the current flowing through the first transistor becomes a predetermined value, wherein the controller comprises an error amplifier; and a delay circuit configured to delay a voltage output from the controller for a predetermined time and output a delayed voltage to the gates of the first and second transistors.