The Circuit
+14v -------*-----------------*--------,
| | | Q1
| 470 ohm R1 | PNP
| | E BC327
4k7 RZ *------B
| | C
| | | (measured:)
| 2k7 R2 | 2.2mH (1960uH, 2.4 dc ohms)
| | |
| NPN BC337 | *----L1-------*------ +5v out
| C Q2 | |
*----*----*-----B | |
| | | E--------|-------------*
| | | | |
| | | | |
| | '------C2--------* |
zener | | 2nF | | 47uF
ZD1 - | - C 16v
5.6v ^ C1 ^ D1 1A |
400mW | | | schottky |
| | 6.8nF | 1N5819 |
| | | |
Gnd --------*----*---------------------*-------------*------ Gnd
(these are the actual parts values as used in the test, as
well as a 100uF cap on the power input)
Chart
Test Data
V in I in P in V out I out P out Freq I gain Eff (%) 14v 2.2mA 0.0308w 5.00v 0.3mA 0.0015w dc! 0.14 4.9% 14 5.1 0.0714 4.97 5.1 0.0253 78kHz 1.00 35.5 14 12.4 0.1736 4.95 25 0.1238 44 2.02 71.3 14 22.4 0.3136 4.95 50 0.2475 44 2.23 78.9 14 32.4 0.4536 4.95 75 0.3713 43 2.31 81.8 14 42.9 0.6006 4.94 100 0.4940 43 2.33 82.3 14 53.4 0.7476 4.94 125 0.6175 43 2.34 82.6 14 64.4 0.9016 4.94 150 0.7410 43 2.33 82.2 14 75.8 1.0612 4.94 175 0.8645 42 2.31 81.5 14 87.4 1.2236 4.93 200 0.9860 42 2.29 80.6 14 112.2 1.5708 4.93 250 1.2325 41 2.23 78.5 14 142.4 1.9936 4.93 300 1.4790 40 2.11 74.2 14 172.9 2.4206 4.91 350 1.7185 40 2.02 71.0
Notes
Regulation droop between 25mA and 175mA is only 0.02v! The powerband is big and flat with good efficiencies from 25mA to 250mA. Decreasing RZ caused better load regulation, but cost a few percent efficiency.
Parts List
Transistor Q1 TO92 BC327 10c Transistor Q2 TO92 BC337 7c Inductor L1 2.4ohm 2200uH 50c Schottky Diode D1 1A 1N5819 20c Zener Diode Z1 400mW 5.6v 6c Capacitor C1 polyester 2nF 5c Capacitor C2 polyester 6.8nF 5c Capacitor CL 16v electro 47uF 6c Capacitor CS 25v electro 47uF 6c Resistor RZ 1/4w 4k7 2c Resistor R1 1/4w 470 ohms 2c Resistor R2 1/4w 2k7 2c TOTAL $1.21 AUD (in US dollars: $0.67 USD )
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