1. 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

2. 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

3. 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

4. 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

5. 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

6. 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 Vdc
Senior Design :: May 04-08

7. 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