Patent ID: 9380657
Filing Date: 2016-06-28
CPC Classification: H05B,Y02B

Claim Text:
1. An LED lighting device comprising: an LED string including a first LED string and a second LED string connected in series; a rectifier to which an alternating-current power source is input and which outputs an undulating voltage to the LED string; a current limit circuit connected in series to the LED string, and having a variable resistor element and a current limit transistor connected with the variable resistor element in series; a bypass circuit having a bypass first input terminal connected between the first LED string and the second LED string, a bypass current control terminal, a bypass variable resistor element and a bypass transistor connected with the bypass variable resistor element in series; and a control circuit configured to control a current flowing through the LED string by controlling the resistor element, thereby to perform light control of the LED string; wherein the bypass circuit causes a constant current to flow via the bypass first input terminal in a case where the undulating voltage output from the rectifier is between a threshold voltage of the first LED string and a total threshold voltage of the threshold voltages of the first and second LED strings, and shuts off the current via the bypass first input terminal in a case where the undulating voltage exceeds the total threshold voltage, and the control circuit inputs a bypass current control signal for controlling a current value of the constant current flowing via the bypass first input terminal by controlling the bypass variable resistor element to the bypass current control terminal.