Laboratory power unit 0... 20 In

Under such heading in "Radio", 1998, #5 was published the description of the simple power unit on KP142 series chips. Feature of new option of the block is possibility of smooth installation of a threshold of restriction of a target current from units a milliamper to the maximum size.

the Main difference of the modifed power unit (fig. 1) consists in introduction of the operational DA2 amplifier and installation of a chip of the stabilizer of negative tension-6 In instead of-1.25 V.Poka a target current is small also power failure on the current-measuring R2 resistor less established by the R3 resistor, on an exit of 6 OU and on an entrance of a chip of DA1 (a conclusion 2) values of tension are approximately equal, the VD4 diode is closed and OU does not participate in operation of the device. If power failure on the R2 resistor becomes more than on the R3 resistor, tension on an exit of a chip of DA2 will decrease, the VD4 diode and target tension of the block will open will decrease to the value corresponding to established restriction of the current. Transition of the block to a mode of stabilization of a current is displayed by inclusion of a light-emitting diode of HL1.

As in a mode of short circuit target tension of OU should be less than-1.25 In approximately on 2.4 In (power failure on the VD4 diode and HL1 light-emitting diode), tension of the OU negative power supply is chosen equal - 6 Century. Such value is necessary at all positions of the SA2 switch therefore it was necessary to switch and a rectifier VD2, VD3 entrance.

Chip КР1168ЕН6Б can replace with img src on similar with an index And, with MC79L06 with indexes of BP, CP and ACP, and also on КР1162ЕН6А (B) (see article: Nefedov A., Valyavsky And." Microcircuit stabilizers of the KP1162 series" in "Radio", 1995, #4), КР1179ЕН06, AN7906, µA7906, but at them dimensions and distance between conclusions is more (as at КР142ЕН12А). The pin-connection diagram coincides. Chip К140УД6 is replaceable on КР140УД608, К140УД7, КР140УД708. The light-emitting diode can be any type of a red luminescence. The R2 resistor - four in parallel connected C2-29B 2 Ohm, 0.125 W. To accuracy of its resistance no requirements are present, therefore the resistor can be made and is independent from a piece of a high-resistance wire. The R12 resistor - SP3-19a. Other elements - the same, as in the main option of the block, constructive registration is similar also. The drawing of the printed-circuit board is provided on fig. 2.

of Resistance of R3 and R4 resistors can differ from specified on the circuit twice, it is important only that their ratio was 1:10. It is possible to replace the R3 resistor also with two consistently included, and resistance of the second should make 5. . 10 % from the first, it will facilitate exact installation of a current of restriction.

At setup of the block by a selection of the R7 resistor establish to p target tension 20 In and R12 adjustment - 0 V.Poskolku these operations are interdependent, they should be repeated several times.

In a mode of the stabilizer of a current the SA2 switch should establish

in the situation corresponding to the minimum tension at which the necessary current of loading is provided. The block will stabilize a current and at bigger tension, but the capacity allocated on a chip of DA1, will exceed maximum permissible (10... 12 W), the thermal protection which has been built in a chip of DA1 also can work.

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