The Design And Realization Of20A High Power Constant Current Driver

With the development of modern science and technology, electronic technologyhas penetrated into almost every area of industrial production and our daily life. Thedemand of stabilized power supply is increasing gradually. As a kind of stabilized powersupply, the constant current source has the extremely broad development space in thefield of power supply. Particularly, with the widely using of laser Diode (LD) inindustrial and medical fields in recent years, research and production on LD constantcurrent driver get the attention of many manufacturers and research institutes. The paperdesign and realize a kind of20Ahigh power constant current driver, in order to provideconstant-current driver source for the20-75W semiconductor pump module or thecontinual high efficiency LD arrays.The technical specification and the system design program of the20A high powerconstant current source are determined according to the requirement of driving sourcefrom LD. The core circuit of the proposed constant current driver, which is based onvoltage controlled current source (VCCS) of negative-feedback system, in order toachieve high stability of output current. A circuit topology of Darlington compositestructure is designed to enhance the large current output capability of power amplifiermodule.In the power module, the topological structure of paralleled power transistors isdesigned to endure heavier load current, and to improve the circuit’s redundancy andreliability. In order to avoid current concentration effect on the influence of the powertransistors, the paper analyzed the various factors which may cause current unbalancedamong the paralleled power transistors, from the perspective of the E-M equations andI-V characteristics of the power transistor, respectively. Some measures are put forwardfor constructing the power transistors’ parallel circuit. Concrete and feasible solutions have been proposed, focusing on the theoretically derivation of the current-sharingresistances calculation method, and verify the correctness of the proposed method fromexperimental analysis.Whether the high power constant current driver can works normally or not isdetermined by radiator’s performance. Therefore a new kind of radiator is designedthrough researching heat theory, to reduce thermal resistance and improve their thermalperformance. The designed radiators are demonstrated experimentally that the heat ofthe power amplifier module can conduct equally, which can ensure the reliability andworking life of the constant-current driver.Through prototype testing, the proposed20A high power constant current driversatisfies the requirements of the indicators. It demonstrates through experiments that themaximum output current Iomaxis20.12A, the control sensitivity A_gof output current is2.11A/V, the long-term stability is less than0.1％and the ripple current is less than50mA. Various parameters satisfy the design request.