Pulse laboratory power unit 0... 30В, 0.01... 5Ао
The offered device stabilizes supply voltage of loading and limits a current consumed by it, passing to a mode of stabilization of a current. The pulse operating mode provides high efficiency in any operating modes. The device is not afraid of long short circuits of an exit. It can be a current source for processes of electrolysis, a galvanoplasty and others for which the stable or limited current is necessary. The device can be used for a charging of accumulators of almost all types. In radio amateur literature the set of descriptions of laboratory power units is published. The offered source differs wide functionality, simplicity, in high efficiency. On fig. 1 is shown its function chart.
a device Basis - a lowering voltage stabilizer with pulse-width regulation on the switching VT1 transistor. After accumulative elements - L1 and C1 condenser throttle - the limiter of current А1 and A3 voltage stabilizer are switched on consistently adjustable linear. The VD1 diode provides course of a current of a throttle of L1 in the C1 condenser and loading when the switching VT1 transistor is closed. The current of loading is limited from above by the A1 hub from 10 мА to 5 A.Stabilizator napryazheniya A3 allows to regulate target tension from 0 to 30 Century. Differential amplifiers A2 and А4 with factor of strengthening about 5 supervise power failure on blocks A1 and A3. When at least one of them is too great, the switching VT1 transistor is closed on a signal of pulse-width regulator А5. It reaches high efficiency and stabilization not only target tension, but also a current. The small disseminated capacity on regulating elements increases reliability of the device, allows to reduce its weight and dimensions at the expense of reduction of the sizes of heat-conducting paths in comparison with linear regulation. On fig. 2 is shown the schematic diagram of the device.
the Components VT4, VD5, L1, С8 correspond to VT1, VD1, L1, С1 on fig. 1. On the elements VT1-VT3, С1, VD3, HL1, R3-R8 is accurate pulse-width regulator А5. The limiter of current А1 is transistorized according to the circuit of the stabilizer of a current of VT6 and VT7, VD6-VD10 diodes and the R10-R20 resistors one of which is connected by the SA2 switch. The adjustable voltage stabilizer of A3 is accurate on DA4 chip. The differential A2 amplifier (see fig. 1) - high-voltage OU Kr1408ud1 (DA3) with resistors R21, R23, R25, R26. The similar differential A4 amplifier - DA5, R28, R31.R33, R34. Lowered to 30 In the T1 transformer mains voltage from a winding of II straightens diode Bridge VD4 and smoothes the C4 condenser. This tension (about 40 In) - entrance for the pulse stabilizer. The R1 resistor and stabilitron of VD1 form a parametrical voltage stabilizer of a food of the setting generator executed on the one-transitional VT2 transistor. The VT3 transistor - the amplifier of a current of the setting generator. The KT825G transistor choice as switching (VT4) is caused by its high reliability and wide availability. Frequency of generation of 40 kHz is chosen according to frequency properties of the KT825G transistor. On the R2 resistor and a light-emitting diode of HL1 the parametrical voltage stabilizer about 2 In for fixing of level of tension on the emitter of the regulating VT1 transistor is accurate. The VD3 diode interferes with giving of return tension on emitterny transition of this transistor. Opening, the switching VT4 transistor connects L1 throttle to a rectifier exit on diode Bridge VD4. L1 proceeding through a throttle a current charges the accumulative C8 condenser. Changing tension on the basis of the VT1 transistor, it is possible to regulate width of the impulses opening the VT4 transistor, and respectively tension on the accumulative C8 condenser. The limiter of current А1 is executed on discrete elements. Refusal of use of a chip of LT1084 is caused by its insufficiently high maximum entrance voltage (37 In). Besides, application of discrete elements increases efficiency. Power failure on the tokozadayushchy resistor of the integrated stabilizer equally 1,25 In, at a current 5 And on this resistor dissipates capacity of 6,25 W. Power failure on the tokozadayushchy UR resistor is equal in the applied limiter of a current to a power failure difference on a diode chain of VD6-VD10 and tension base emitter of the compound VT6VT7 transistor. In this case UR is approximately equal 0,6 V.Moshchnost, disseminated on the R20 resistor (on a limit 5 And), is approximately equal 3 W. Resistance of the tokozadayushchy resistor R count on R=UR/I formula, where I - a demanded current of restriction.
In a copy of the author are realized 11 limits of restriction of a current: 10, 50, 100, 250, 500, 750 мА; 1, 2, 3, 4, 5 A.Im correspond R10-R20 resistors. As tension on the C8 condenser changes largely, a current through a stabistor made of VD6-VD10 diodes, defines the stabilizer on the VT5 transistor and HL2 light-emitting diode. The R22 resistor in a chain of the emitter of the VT5 transistor establish a current through VD6-VD10 chain within 10... 12 мА. The adjustable voltage stabilizer of A3 is executed on DA4 chip. Diodes VD13, VD14 promote increase of its reliability. Via these diodes at disconnection of the power unit from a network the condensers C12 and С13 eliminating self-excitation of the stabilizer are discharged. For obtaining zero target tension tension of negative polarity is submitted to a chain of an operating electrode through a divider of R27R30 from the DA2 stabilizer. The rectifier on diode Bridge VD2 and integrated stabilizers DA1, DA2 feeds also digital voltmeter on chip КР572ПВ2А, collected according to the standard circuit. Target signals of operational DA3 and DA5 amplifiers via VD11 and VD12 diodes arrive on the general loading - a rezistorny divider of R3R4. The light-emitting diode of HL3 is deduced on the obverse panel and signals about transition of the power unit to a mode of restriction of stabilization of a current. The increase in power failure on the limiter of a current or a voltage stabilizer causes tension growth on the R4 resistor. When it will exceed threshold value (about 3 In), will open the VT1 transistor, shortening generator impulses on the VT2 transistor. />
Design and details. the Power unit is mounted by strong in the case in the sizes of 90x170x270 mm. The VT4 transistor and the VD5 diode are established without isolating laying on one heat-conducting path in the area of 200 cm2. On a heat-conducting path in the area of 400 cm2 are mounted the VT6 transistor (through isolating laying) and the DA4 stabilizer. For increase of temperature stability it is expedient to establish VD6-VD10 diodes on a heat-conducting path probably closer to the VT6 transistor. The device is assembled on a universal model payment, the printed-circuit board was not developed. The T1 transformer is made of the network transformer of the lamp TV. Magnitoprovod assort, remove coils. Take up nakalny windings (they are located in the top layer and are reeled up by a wire of the greatest diameter), counting up rounds. Having increased this number of rounds on 5, we receive number of rounds of a winding of II. Further completely take up anode windings from both coils on one шпулю. Then on each coil reel up внавал polovinny number of rounds of a winding of II in two wires of an anode winding. Diameter of a wire of an anode winding of 0,8 mm corresponds to section 0,5 mm2. Winding in two wires gives equivalent section 1 mm2 that allows to receive a current of load of 5 A.Umnozhiv number of rounds of a nakalny winding on 3, we receive number of rounds of a winding of III. This winding also in two wires can be reeled up on one of two coils. Due to the small consumption of a current from a winding the III asymmetry of a magnetic field of the transformer turns out insignificant. After assembly магнитопровода semi-windings of III connect consistently taking into account phasing, the beginning of one semi-winding of III connect to the end another, forming branch from the middle. A throttle of L1 reel up on магнитопроводе Б48 from ferrite 1500НМ1 внавал in two wires of an anode winding before framework filling. For creation of not magnetic gap between cups the textolite washer in thickness of 1 mm is enclosed. After tightening by the Mb bolt a ready throttle impregnate with BF-2 glue. Drying and polymerization of glue were carried out in an oven at temperature of 100 °C. At independent manufacturing of a throttle on other магнитопроводе it is necessary to mean that the current through a throttle has a triangular form. To an average consumed current 5 And there corresponds amplitude 10 And, at this current магнитопровод should not enter into saturation. It is possible to replace the LT1084 (DA4) stabilizer with domestic analog КР142ЕН22А. The variable R29 resistor for bigger durability is used wire PPB. Considering that via the SA2 switch the considerable current proceeds, the ceramic galetny switch 11П3Н is applied to increase of stability and durability, its contacts are connected in parallel. СветодиодАЛ307КМ it is possible to replace (HL3) foreign L-543SRC-E.
Adjustment. Selection of the R30 resistor establish zero target tension on a power unit exit at bottom according to the circuit the provision of a cursor of the variable R29 resistor, and R32 resistor selection - tension 30 In at top according to the circuit the provision of a cursor of R29. Connect the voltmeter to conclusions 2 both 3 DA4 stabilizers and selection of the R4 resistor establish 1,5 V.Na vremya's tension of adjustment possibly use of tuning resistors. But their use for continuous operation is not recommended because of instability of resistance of mobile contact system. Then connect to target plugs loading via the ampermeter. Changing the R29 resistor target tension, on the ampermeter and the built-in voltmeter supervise target parameters. On low-current limits because of existence of currents of management of the DA4 stabilizer correction of resistance of R10-R12 resistors in comparison with settlement is required. On inclusion of a light-emitting diode of HL3 it is necessary to check restriction of a current and its stability on all limits. The offered laboratory power unit is very convenient in work, including for a charging of accumulators and batteries - from 7D-0.1 to starterny automobile. On the built-in digital voltmeter establish final tension of a charging, as the SA2 switch choose a necessary current of a charging and connect the accumulator (battery). The charging goes a stable current, at achievement of the set tension on the accumulator the charging stops. In three years of operation of the offered device of refusals in its work was not.
of K.Moroz, Nadym Yamal-Nenets bus of the district, Radio No. 4, 2008!>
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