The Design Of A Switching Power Supply Chip For Driving High Voltage EL Lamp

Electroluminescent (EL) lamp is a cold light source with surface light-emitting.There are many advantages which can be seen in the EL lamp such as uniform flat lightsource, lower energy consumption and so on. It has been applied in many fields such astraffic signs, instrument backlighting, etc. The EL lamp driver circuit has been improvedwith the development of microelectronic technique. Features of the EL lamp drivercircuit are high voltage and low current. The lowest working voltage amplitude is60V.It is necessary that designing an efficient high voltage switching power supply to driveEL lamp.An EL lamp driver circuit is designed in this dissertation. And the sample chipshave been produced by the CSMC120V BCD process. The main research content in thepaper includes whole chip circuit designing scheme, three sub-blocks’ design andsimulation, layout design and the chip test.Firstly, the dissertation presents the whole circuit diagram based on the demand ofdriving EL lamp. The designed chip has many advantages such as wide working voltagerange(2~6.5V), low power consumption(420μA working supply current), etc. The color,life and power consumption of the EL lamp can be controlled by changing its workingfrequency. The enable module has also been integrated to protect this chip.Secondly, the designing plan and simulating result of three sub-blocks are presentsin the paper. The above sub-blocks are Boost negative feedback circuit, H-Bridgecontrolling circuit, H-Bridge driver circuit. The designed Boost negative feedbackcircuit is a novel circuit which achieves PWM by comparing the current. Then, alocking signal circuit is designed to improve the H-Bridge’s working stability. Duringdesigning the H-Bridge driver circuit, the high voltage diodes are used to clamp thetransistors in upside of the H-bridge. The driving current of the H-Bridge can beregulated conveniently by changing the number of high voltage diodes. According to thewithstand voltage(100V) of the high-voltage transistor, a new kind of LDMOS is usedin the chip.Then, in the process of layout design, the paper researches some problems of device match, high-low voltage isolation, the current ability of switching powertransistor, etc. Then the whole chip layout and PCM layout are designed. The outcomeof chip testing is presented in the end.Finally, the simulation of the whole circuit proves that the principles analysis andthe design of the EL lamp driver chip are correct and feasible. The chip has been tested.According to the test report, this high voltage EL lamp driver switching power supply isfit for the design requirement.