Research On A Novel Current Regulating Device And Its Applications

As the simplest constant current source,the CRD(Current Regulating Device)can output a stable current in the constant current interval.It is convenient to use and low in cost and has been widely applied to LED(Light Emitting Diode)driving,battery charging and discharging,device parameter testing and electronic circuit interface.At present,the LED driver basically adopts an integrated circuit solution,which can meet higher driving needs.But for applications where the driving functionalities are not high,it will increase the circuit complexity and driving cost,while the use of current regulating device will simplify the circuit structure and is economical and practical.The main research work of this paper is to design a novel current regulating device and carry out the tape-out experiments.In addition,several new LED driving circuits have been proposed and verified based on the electrical characteristics of the device in order to explore its new application scenarios.Nowadays,the existing current regulating devices all operate in unipolar conduction mode,the reverse output is similar to the forward characteristic of the diode,and they do not have the reverse blocking capability of an ideal constant current source.This paper proposes a new device structure based on the theories of current regulating devices.The biggest difference from the traditional device is that the proposed structure operates in bipolar conduction mode,that is,there are two kinds of carriers,electrons and holes,involved in conduction in the open state,and the introduction of the P-type substrate makes the device have reverse blocking characteristic.The conductivity modulation effect caused by the holes injected into the drift region reduces the series resistance,which not only increases the on-state current density,but also significantly reduces the pinch-off voltage of the new structure,which can be controlled below 2 V.TCAD tools such as MEDICI,TSUPREM4 and SENTAURUS were used to simulate and optimize the cell and terminal parameters in order to explore their influence on the forward and reverse characteristics of the device and obtain the optimal combination of the parameters.According to the low pinch-off voltage and reverse blocking characteristic of the novel current regulating device,the advantages of the device in low voltage DC input LED driving are proved,and two new LED driving circuits based on a new rectifier bridge and a bidirectional current regulating device,respectively,are proposed combined with the SENTAURUS circuit hybrid simulations.Under AC input,the LED current can be stabilized.Similar to the pulse driving method,the load current is a rectangular wave,which reduces the requirements for heat dissipation performance of the driving system and ensures the service life of LEDs.By adjusting the AC input amplitude and the number of LEDs,the current duty cycle and LED brightness can be changed to achieve the dimming function.On the basis of simulations,the process flow of the current regulating devices is established,and the layouts are designed to carry out the tape-out experiments,after that,the devices with better performance are used to build the LED driving circuits.The experimental results show that the new devices have reverse blocking characteristics,the reverse breakdown voltage reaches 200 V,and the forward breakdown voltage is higher than 50 V.The pinch-off voltage of a 40 mA device is only 1.56 V,and for a higher current class such as 110 mA,the pinch-off voltage is only 2.69 V,which is significantly lower than that of a conventional device.Besides,the 110 mA device has a current temperature coefficient as low as 0.12%/K.The constructed circuits successfully drive the LEDs and the test results are in agreement with the circuit simulations,indicating the proposed new circuits extend the application scenarios of current regulating devices for driving LEDs.