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The 2-transistor Black regulator

App a00; +5v output, small size + low cost


Specs

  • 80% efficiency (from 30mA to 90mA out)
  • Tiny cheap RF type inductor
  • Very cheap circuit (under 50 cents in parts!)
  • Good 5v regulation
  • Input: 8v to 20v
  • Output: 5v @ 150mA maximum





    The Circuit 

    
+14v -------*-----------------*--------,
            |                 |        |  Q1
            |            1k2  R1       |  PNP
            |                 |        E  BC327
      10k   RZ                *------B
            |                 |        C
            |                 |        |          (measured:)
            |            2k7  R2       |   1.5mH  (1406uH, 8.7 dc ohms)
            |                 |        |
            |      NPN BC337  |        *----L1-------*------ +5v out
            |                 C  Q2    |             |
            *----*----*-----B          |             |
            |    |    |       E--------|-------------*
            |    |    |                |             |
            |    |    |                |             |
            |    |    '------C2--------*             |
     zener  |    |           1nF       |             | 47uF
      ZD1   -    |                     -             C 16v
     5.6v   ^    C1                    ^ D1  1A      |
    400mW   |    |                     | schottky    |
            |    | 4.7nF               | 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      1.1mA  0.0154w   4.96v    0.3mA   0.0015w   104kHz   0.27      9.7%
   14       5.4    0.0756    4.92      10     0.0492     71      1.85     65.1
   14       9.4    0.1316    4.89      20     0.0978     48      2.13     74.3
   14      13.4    0.1876    4.88      30     0.1464     38      2.24     78.0
   14      17.5    0.2450    4.88      40     0.1952     37      2.29     79.7
   14      21.7    0.3038    4.88      50     0.2440     37      2.30     80.3
   14      26.2    0.3668    4.88      60     0.2928     37      2.29     79.8
   14      30.7    0.4298    4.87      70     0.3409     36      2.28     79.3
   14      35.4    0.4956    4.87      80     0.3896     36      2.26     78.6
   14      40.0    0.5600    4.87      90     0.4383     36      2.25     78.3
   14      45.2    0.6328    4.87      100    0.4870     35      2.21     77.0
   14      50.4    0.7056    4.86      110    0.5346     35      2.18     75.8
   14      56.2    0.7868    4.85      120    0.5820     35      2.14     74.0
   14      62.1    0.8694    4.84      130    0.6292     36      2.09     72.4
   14      68.6    0.9604    4.82      140    0.6748     36      2.04     70.3
   14      75.8    1.0612    4.80      150    0.7200     37      1.98     67.8

    Notes

    This circuit is only good for about 150mA maximum output current due to the high dc resistance of the tiny inductor. These tiny RF type inductors are wound with very fine wire and are only good for low current apps.

    To reduce price the 1N5819 schottky diode can be replaced with a common 1N4148 glass diode. A few percent efficiency will be lost.


    Parts List 

    Transistor	Q1	TO92		BC327		10c
Transistor	Q2	TO92		BC337		7c

Inductor	L1	8.7ohm		1500uH		12c  (small "RF choke" type)
Schottky Diode	D1	1A		1N5819		20c

Zener Diode	Z1	400mW		5.6v		6c

Capacitor	C1	polyester	1nF		5c
Capacitor	C2	polyester	4.7nF		5c
Capacitor	CL	16v electro	47uF		6c
Capacitor	CS	25v electro	47uF		6c

Resistor	RZ	1/4w		10k		2c
Resistor	R1	1/4w		1k2		2c
Resistor	R2	1/4w		2k7		2c
TOTAL						    $0.83 AUD
				 (in US dollars:    $0.46 USD )

    - end -

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