Font Size: a A A

High-power Illumination Led Constant Current Driver Chip Design

Posted on:2007-02-16Degree:MasterType:Thesis
Country:ChinaCandidate:H ShenFull Text:PDF
GTID:2208360182970887Subject:Microelectronics and Solid State Electronics
Abstract/Summary:PDF Full Text Request
Semiconductor lighting is gradually replacing incandescent and fluorescent lighting due to its unique attributes such as high efficiency, low energy consumption, low pollution, long life and high reliability. As the quality of power LED improves and the cost of power LED reduces, its application field has gradually turned from signal lighting and display lighting to general room lighting. Along with the development of power LED, the research of its driving IC has also been greatly accelerated.In this research, two driving ICs are separately designed to drive a 1W power LED, working in 3.5V and 350mA, with constant current. Both chips are fabricated in CSMC 0.6um double poly, double metal, 5V operational voltage CMOS process. The output driving MOSFET is integrated on chip, which makes possible the compatible integration of power device with conventional CMOS signal processing circuits. One unit is taken from the output driving MOSFET as sampling MOSFET, which ensures that the power driving MOSFET and sampling MOSFET are in the same temperature zone and have the same current density, therefore improving the control accuracy of driving current. PWM constant current driving IC is designed to increase the power efficiency up to 87%. Power efficiency can be further improved by increasing the W/L of output driving MOSFET. Besides, in order to minimize the area of output driving MOSFET, high W/L density structure is adopted with effective W/L density being doubled compared with normal MOS structure.The DC mode constant current driving IC is consisted of an on-chip power MOSFET, a bandgap reference, sample-feedback control circuits and output buffers. The sample and feedback circuit is used to stabilize the sampling current, which is 1/604 of the 350mA driving current conducted by power MOSFET, so as to stabilize the driving current. It is shown that variance of the driving current can be controlled within the range of 1.7% when voltage supply changes by 10%. When ambient temperature varies from 25 ℃ to 85℃, the driving current decreases only by 1.1 %.The PWM (Pulse Width Modulation) constant current driving IC is consisted of a power MOSFET, a frequency divider, a shaping circuit, an integrator, a bandgap reference, a comparator and digital control circuits. Unlike the DC constant current driving IC, in which the power LED is driven with a DC current, the PWM constant current driving IC dirives the power LED with PWM current. By adjusting the duty cycle of pulse driving current according to the peak sampling current, output average driving current is maintained around 350mA. Test results show that the variance of average driving current can be controlled within range of 4.5% when power supply changes by 10%. Efficiency of 87% is readily achievable with improvement of nearly 25% compared with DC mode constant current driving IC. By increasing the W/L of output driving MOSFET, power efficiency can be further improvedThe two constant current driving ICs has been successfully applied into 1W power LED lamp with pictures shown in Appendix A.
Keywords/Search Tags:Semiconductor Lighting, CMOS IC, High brightness high power LED, Pulse Width Modulation, Constant-Current Driving, Current control accuracy, Power Efficiency
PDF Full Text Request
Related items