Design Approach (1) The design was simulated to look like the figure below After searching for the needed parts, it was found that buying commercial products could save a lot from the budget The design still have the same basic blocks, but designed to fit in less number of blocks. The Intended design, before substitutes were found Senior Design :: May 04-08

Design Approach (2) A commercial power supply is used to replace the EMI filer, bridge rectifier, and the Flyback converter. The transformer that was planned to be used in the flyback is expensive and hard to find. But those blocks will work in the same methods our simulation worked on. Senior Design :: May 04-08

Design Approach (3) Definitions: PWM : Pulse Width Modulation Duty Ratio (D) : Time ON divided by the total time Lm : Magnetizing Inductance of a transformer For the simulation, 2 choice: Pspice: Available and have a lot of parts Electronic Work Bench : Easy and more visual Sample from the simulation Electronic Work Bench was used to simulate the design Senior Design :: May 04-08

Design Approach (4) A Quick review : Vo=Vs(D/(1-D)) N2/N1 (Flyback) Vo=Vs*D ( Buck ) PWM : Generate a square wave. (see figure) Trig.source Comparator The Reason behind using Flyback then a __buck converter is to create an isolation. Senior Design :: May 04-08

How does it work Figure 1: Buck Converter Figure 2: Flyback converter, it store energy in Lm when closed. When the switch is open the energy transfers from Lm Using commercial power supply have minimized a lot of the problems: like to keep the current and the voltage stable, finding transformer and also saved time Fig. 1 Fig. 2 Senior Design :: May 04-08

Summery of Design Approach The Astrodyne ® commercial power supply creates and isolation and provides 48 Vdc. The fixed buck converter will bring the voltage down to 25 Vdc. The variable buck provides 2.5-24 Vdc Senior Design :: May 04-08

Variable Buck Converter The new design Fixed Buck Converter TL499ACD Variable Outputs 120 VAC Wall outlet 48VDC 25VDC High Freq. Switch Variable Buck Converter Power Supply Senior Design :: May 04-08