Design And Analysis Of Switch-Mode Power Supply Based On Bipolar Process

Along with the excellence in high gain and speedy velocity, bipolar integrated circuits are still dominant in products of small scale circuits. And the Switch-Mode Power Supply (SMPS) has the capability of improving high efficiency and attenuating hardware power loss to maximize battery run-time. Combined with the advantages of bipolar process and SMPS, a high efficient SMPS XD6912 is designed.XD6912 adopts the voltage-mode PWM control, operating at a switching frequency of 150 kHz, it has many advantages over those prior arts, such as wide input voltage changing range, adjustable output and high load current. Firstly, by following 40V bipolar process the device can be inexpensive in cost and small in size. Secondly, with TTL shutdown capability the standby quiescent current of the device can be reduced to 30μA. Thirdly, due to an internal frequency compensation circuit, it needs few external components to work properly. Finally, connecting with self-protection under fault conditions, the device can reach high performance in application. It is a detailed description about the design of the system structure and the sub-block circuits. And by comparison between voltage-mode PWM control and current-mode PWM control, it is pointed out that selecting the right control mode in special application is of importance.The simulation results of all critical functional blocks are given. Select appropiate components, simulate the system and give the results about system characters. The Hspice results show that the efficiency varies with the load resistance. While the input voltage is 20V, output voltage is 5V, and the output load current is 3A, the efficiency of XD6912 can reach much more than 80%.