An Efficient and Flexible DC to DC Converter With Feedback Control for Communication System Agus Harjoko 1 , Tri Wahyu Supardi 2 1,2 Dept. Computer Science and Electronics, Gadjah Mada University, Yogyakarta, Indonesia Abstract— Many industrial, sciencetific, medical, communication and defence equipments require 32 or 48 volt power suppply. These equipments can be operated in a fixed placed as well as in a mobile unit. Unfortunately, many power supply, especially in a mobile unit, available only in 12 volts. These 12 volt power may come from car battery or solar cell. In this research, a 12 volt DC to 48 volt DC converter is designed, implemented and tested. The power supply is designed as a swithcing mode power supply (SMPS) with feedbcak regulator for efficiency and operasional flexibility. This way, the output voltage can be adjusted by the user to meet their need. The performance of the power supply is obtained by varying the input voltage and varying the output voltage. The power supply is also tested by applying the converter using car battery as its input and loading the power supply. Test results show that the power supply could deliver power from 26.6 to 55 volt DC for input voltage of 9.8 to 12 volt. For output of 48 volt, the converter yields an efficiency of 85% with ripple voltage of 50 milli volt peak to peak. Keywords— DC converter, SMPS, power supply I. INTRODUCTION DC – DC converter is an electronic device used to convert efficiently from one voltage level to another. DC – DC converter is used in many applications such as power supply for personal computer, office equipment, laptops, communication devices, DC motor driver [1] and particle accelerator [2, 3]. In automotive industry, DC – DC converter is needed in the electrical system. In electric and hybrid car, the deivce is used in power regulator to gain car efficiency [4]. In renewable energy system, DC – DC converter is used to convert voltage level from energy source to the battery for storing energy. It could also be used for converting voltage level from battery or energy source to a device [5]. In a computer system, the converter could be used to convert voltage to 3.5V, 5V and 12V [6]. In a satellite communication system, DC – DC converter is used to provide higher voltage from lower voltage sources such as battery or solar cell. In a lower radio frequency communication system, MOSFET and LDMOS RF power amplifier require voltage between 28V to 50V. Thus, also requiring DC – DC converters [7,8,9,10]. A number of converters have been reported in the literatures. For example, Hartwell II [5] developed 120V DC to 1500V DC converter. The input source is a single phase 120V or 240V AC. The output is between 1100 – 1500V and 50 - 570mA. Motorola [11] developed a switch mode pulse width modulation control circuit which converts 8 – 20V power supply to 28 volt, 0.2 ampere power supply. The development of a 12V DC to 48V DC converter is discussed in this paper. The converter is suitable for MOSFET and LDMOS-based RF power amplifier. II. THE PROPOSED CONVERTER The proposed DC – DC converter is shown in Fig. 1. The converter consists of four main modules and a number of supporting modules. The output voltage sensor is part of the feedback control element of the converter. The main modules are PWM generator and controller, Push-pull driver, Push-pull MOSFET switching, and high frequency transformer. 12 V DC input 48 V DC output Filter Filter High Frequency Transformer Push‐Pull Mosfet Switching Driver Push‐Pull Controller and PWM Generator ON‐OFF Voltage Sensor Fig 1. The proposed DC to DC converter The feedback controller module is intended to control and stabilize output voltage of the converter. The module consists of oscillator, reference voltage, voltage sensor and voltage scale regulator, comparator, OR logic gate, D flip- flop, MOSFET driver, amplifier differentiator, soft start system, and protection system. The oscillator is used as a clock generator to produce saw tooth signal and PWM generator and MOSFET array switching controller. The oscillator is set at 80 KHz. The output voltage sensor is made of voltage divider circuit using variable resistor. The soft start system is used to control the conversion process to avoid sudden current change that may damage the transformer. Agus Harjok et al, / (IJCSIT) International Journal of Computer Science and Information Technologies, Vol. 5 (6) , 2014, 6936-6938 www.ijcsit.com 6936