1. By: P. Liang, M. Shi, Y. Wang University of Ottawa November 24, 2006 ELG 4135 Course Project

2. The continuing increasing of the portable system results more and more complex electronic system. The increasing of automobile is incorporate with the electronic system, and causes some problem. One of the major problem is the requirement of multiple supply voltages for different portion of the portable system.

3. A DVD based GPS navigation system can has six or more different supplies: 12V, 5V, 3.3V, 2.5V, 1.5V, and 1.2V. Each voltage supply different part of the system, and need different current input as well. Other mobile system such as notebooks, PDAs, and cellular phones also need multiple voltage supplies.

4. The most common solution is designing a switching regulator. A switching regulator is a circuit that uses a power switch, low loss component such as inductors, and capacitors to transfer energy from input to output.

5. Even switching regulator has variety of choices. One of the solution is using Gallium Arsenide power switches. It has following features: Relatively high switching frequency of 40MHz. Power efficiency of 77%

6. Below is the diagram of this switching regulator: Fig. 1 : Square - Wave DC/DC step-down or Buck Converter

7. This is one of the solution to meet the requirements for mobile system. But It has following drawbacks: Not applicable for multiple voltages supply. Power efficiency is not high enough.

8. In order to make an improvement. We are using 2 LTC1624 switching regulator controller to design a 24V input, 12V/1A & 5V/3A dual DC/DC step-down converter. This is our method which is better than the previous solution. Due to the limitation of time and finance, we can only design a 2 voltages supply converter instead of 6.

10. Our new circuit makes following improvements: Power efficiency increases up to 95% Be able to drive two different voltages supply. Add additional capacitor to minimize the ripple.

13. From the simulation results, we observed the following data: Input stage: 24V/1.25A Output stage 1: 12V/1A Output stage 2: 5V/3A Rising time: 0.2ms~2.5ms Efficiency:90%

14. Using capacitor can change the ripple and the rising time. Increasing/Decreasing capacitor value. Decreasing/Increasing ripple Increasing/Decreasing rising time

15. With one capacitor (100uF)

16. With two capacitors (200uF each)

17. With four capacitors (200uF each)

18. We cannot optimize both the rising time and ripple, we choose a certain value (four 200uF capacitors ) trying to make a balance between those two parameters.

21. Our design makes improvement in the power efficiency; the number of power supply; and the ripples. But our design also makes a drawback in the rising time. As we shown, there is a trade-off in our design, we cannot optimize every part. Although our design is not perfect, it is a better choice than others.

22. Thank you! Questions?