Design Of The Highly Integrated AC/DC XD1456 With Constant Current/Constant Voltage Function

Although the switching power supply started very late, its existence changed the face of the world and brought vitality to people’s lives. Now it exists every part of our life, for which it has been paid more attention by national research personnel. The switching power supply is developed fast, especically its frequency, efficiency and volume size. As a variety of electronic devices has been introduced, the size and the efficient of the switching power supply is increasingly demanding, using easily. Design of the Highly Integrated AC/DC XD1456 with Constant Current/Constant Voltage Function is researched and designed base on the project “Theoretical Research and Design of Key Technique for Power Management IC.The constant current/voltage function is studied in this paper while improving the efficiency of the switching power supply. it is important that its size of the volume is reduced using highly integrated technology. This chip employs a variety of ways to reduce the chip’s power consumption, using PFM mode to achieve a precise constant current output. The constant voltage function is achieved by introducing PSM mode which adopts digital design in order to shorten the design cycle. By employing the ON/OFF control state machine, we can leave out the stability of the loop. So this method can improve the frequency of switching power supply. The chip adopts advanced compensation techniques so that the output value can be more accurate. It can use the restart function when the chip encounters a fault in order to improve the efficiency employing advanced protection measures. In order to reduce costs, the peripheral circuit of the chip apply inductively coupled feedback mode while the output accuracy has reached the user’s requirements. In order to improve the efficiency of the standby state, it adopts the method of bias supply. The conversion efficiency is high over the entire load range, so it is easy to achieve targets of efficiency that the international standard requires.In the design of the circuit, the results are calculated through using theoretical knowledge. In the circuit design, it is important that the reference voltage of the circuit is designed well, as the accuracy of the reference design affects the accurancy of other circuit modules. It is the second important that the circuit to achieve constant current is made perfectly. In order to achieve accurately constant current, the circuit is compensated through a variety of methods. It is last but equally important the circuit to complete constant voltage function is designed perfectly. To realize constant voltage of the client output terminal, the cable drop compensation circuit is added. In the chip, the implement of designing the cable compensation circuit alters the threshold of the constant voltage comparator according to the switch duty cycle and the value of limit current. The accuracy of outputting the constant voltage using this method is much larger than the design specifications. In order to improve the client’s feelings of use, decreasing the sampling current limit is to achieve constant voltage firstly. Some protection circuit modules are added to this chip to avoid damage in all the conditions, such as over-temperature protection, which uses hysteresis comparator to achieve this function, and over-voltage protection that is implemented by shunting current.In this paper, the power technology and the future development are analysed briefly. The working processes of the different converters are described in detail. The different topology structures of the peripheral are compared. The inverter power sources are introduced and many ways to reduce power consumption are raised. The selections of the external components are introduced. The device’s electrical specification requirements are put forward and the corresponding circuits are designed and are simulated to check the performance. At the last, the whole chip is simulated to check constant current/constant voltage function.