This can be used as a 24v to 12v DC-DC converter, suitable to run 12v equipment from a 24v battery system. The input voltage I chose for testing was 26v, this is a typical running voltage for a 24v battery system.
The Circuit
+26v -------*-----------------*--------,
| | | Q1
| 1k R1 | PNP
| | E BC327
15k RZ *------B
| | C
| | | (measured:)
| 2k7 R2 | 470uH (460uH, 0.7 dc ohms)
| | | |
100uF | NPN BC337 | *----L1-------*------ +12.5v out
63v | C Q2 | |
| *----*----*-----B | |
| | | E--------|-------------*
| | | | |
| | | | |
| | '------C2--------* |
zener | | 470pF | | 100uF
ZD1 - | - C 25v
13.0v ^ C1 ^ D1 1A |
400mW | | | schottky |
| | 4.7nF | 1N5819 |
| | | |
Gnd --------*----*---------------------*-------------*------ Gnd
(these are the actual parts values as used in the test,
note the 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 (%) 26v 1.5mA 0.0390w 12.48v 0.8mA 0.0100w chaos 0.53 25.6% 26 2.4 0.0624 12.48 2.4 0.0300 chaos 1.00 48.0 26 6.7 0.1742 12.49 10 0.1249 205 1.49 71.7 26 12.3 0.3198 12.47 20 0.2494 165 1.63 78.0 26 17.7 0.4602 12.46 30 0.3738 135 1.69 81.2 26 22.7 0.5902 12.45 40 0.4980 115 1.76 84.4 26 27.8 0.7228 12.44 50 0.6220 99 1.80 86.1 26 33.3 0.8658 12.42 60 0.7452 89 1.80 86.1 26 38.3 0.9958 12.41 70 0.8687 80 1.83 87.2 26 43.4 1.1284 12.41 80 0.9928 73 1.84 88.0 26 48.3 1.2558 12.40 90 1.1160 67 1.86 88.9 26 52.6 1.3676 12.40 100 1.2400 61 1.90 90.7 26 63.0 1.6380 12.38 120 1.4856 53 1.90 90.7 26 73.0 1.8980 12.37 140 1.7318 48 1.92 91.2 26 82.7 2.1502 12.35 160 1.9760 43 1.93 91.9 26 92.4 2.4024 12.35 180 2.2230 43 1.95 92.5 26 102.0 2.6520 12.35 200 2.4700 43 1.96 93.1 !! 26 128.0 3.3280 12.34 250 3.0850 42 1.95 92.7 !! 26 154.7 4.0222 12.34 300 3.7020 42 1.94 92.0 26 182.0 4.7320 12.34 350 4.3190 42 1.92 91.3 26 208.0 5.4080 12.34 400 4.9360 42 1.92 91.3 26 235.0 6.1100 12.34 450 5.5530 42 1.91 90.9 26 263.0 6.8380 12.34 500 6.1700 42 1.90 90.2 26 292.0 7.5920 12.34 550 6.7870 42 1.88 89.4 26 320.0 8.3200 12.34 600 7.4040 42 1.88 89.0 26 350.0 9.1000 12.34 650 8.0210 42 1.86 88.1 26 380.0 9.8800 12.34 700 8.6380 42 1.84 87.4
Parts List
Transistor Q1 TO92 BC327 10c Transistor Q2 TO92 BC337 7c Inductor L1 0.7ohm 470uH 50c Schottky Diode D1 1A 1N5819 20c Zener Diode Z1 400mW 13.0v 6c Capacitor C1 ceramic 470pF 5c Capacitor C2 polyester 4.7nF 5c Capacitor CL 25v electro 100uF 10c Capacitor CS 63v electro 100uF 15c Resistor RZ 1/4w 15k 2c Resistor R1 1/4w 1k 2c Resistor R2 1/4w 2k7 2c TOTAL $1.34 AUD (in US dollars: $0.74 USD )
Notes
This version of the Black regulator can be used as a high efficiency 24v to 12v converter.
Warning! If using this in a running vehicle, you will need to add a filter of some type to the input. You can use a commercial 24v filter sold for auto use, or use the filter circuit below. The Zener is optional, and recommended. A 500mA fuse on the input is also recommended.
+26v ----R---*------*------*---- to input of circuit
3.3 ohm | | |
| | |
1000uF | 0.1 | |
Ca Cb Zener
| | | 35v 3W
| | |
| | |
| | |
Gnd ---------*------*------*----- to gnd of circuit
- end -
[Back to Home Page]