Improvement Strategy of Load Regulation of Boosting Power Supply Based on PID Algorithm

As one of the most important parameters of Direct Current (DC) power supply, Load regulation determines the performance of whole system. In this paper, the internal structure as well as performance parameters of LM2577 boosting converter were deeply investigated and based on this investigation we proposed two new methods of improving its Load Regulation. One method (method 1) is to replace the resistor connected to the feedback pin of LM2577 with a programmable potentiometer and sample the variation of output voltage using an AD converter. The potentiometer is adjusted under the control of feedback algorithm to keep the output voltage stable, thus the load regulation enhanced. In the other method (method 2), the feedback pin of LM2577 is connected to an adder to stabilize the output voltage of DC power supply and increase the load regulation. A voltage divider made up of resistors divides the output voltage and provide the divided voltage to one input of the adder. The other adder input comes from DA converter controlled by microcontroller. To reduce the adjust time and increase the efficiency, PID algorithm is applied in the software part of the system. We use 12-bit AD (ADS1115), 12-bit DA (TLV 5638) and 10-bit programmable potentiometer (AD5293) to test the methods above under the condition of 5V input voltage and 600mA load current. When output is set to 7V, the load regulation is improved from 1.043%, the rate from application circuit in LM2577’s Datasheet, to 0.700% and 0.042% by applying the first and second method, respectively. When output voltage equals 12V, the improvement is from 0.658% to 0.008% and 0.008%. Meanwhile, the method 2 suppresses output voltage ripple to be less than 10mV.