US 9,814,107 B2
Drive circuit and illumination device comprising the drive circuit
Yongchang Dai, Shenzhen (CN); and Daxin Lin, Shenzhen (CN)
Assigned to OSRAM GmbH, Munich (DE)
Filed by OSRAM GmbH, Munich (DE)
Filed on Feb. 26, 2015, as Appl. No. 14/631,887.
Claims priority of application No. 2014 1 0066712 (CN), filed on Feb. 26, 2014.
Prior Publication US 2016/0255684 A1, Sep. 1, 2016
Prior Publication US 2017/0273151 A9, Sep. 21, 2017
Int. Cl. H05B 37/00 (2006.01); H05B 33/08 (2006.01); H05B 37/02 (2006.01)
CPC H05B 33/0815 (2013.01) [H05B 33/0845 (2013.01); Y02B 20/347 (2013.01)] 12 Claims
OG exemplary drawing
 
1. A drive circuit of an illumination device, wherein the drive circuit has an output terminal connected to a load of the illumination device, the drive circuit comprising: a power supply, a boost control unit connected to an output terminal of the power supply, a main control unit connected to the boost control unit, and a load current control unit connected between the main control unit and the load, and comprising a switch unit, wherein the switch unit comprises a first sub switch unit, wherein the first sub switch unit is configured to switch according to a dimming control signal from the main control unit, and the switch unit further comprises a second sub switch unit connected to the first sub switch unit, wherein the second sub switch unit is configured to be switched on in a situation where the first sub switch unit is switched on so as to switch off the first sub switch unit and thereby to maintain the peak of the current flowing through the first sub switch unit and to adjust the mean value of the current,
wherein the first sub switch unit comprises a first transistor and a third resistor, wherein the third resistor has an end connected to the control electrode of the first transistor, and the other end of the third resistor is connected to the main control unit, and the second sub switch unit comprises a second transistor, a fourth resistor, a fifth resistor, and a first diode, wherein the reference electrode of the second transistor is grounded, the fourth resistor has an end connected to the control electrode of the second transistor, and the other end of the fourth resistor is connected to the node between the reference electrode of the first transistor and the anode of the first diode, and the cathode of the first diode is grounded through the fifth resistor.