This power supply voltage from 5 to give 15V, stable set within those limits, with a maximum current of 20A. Current not exceeding 22A triggered the protection.
AC 220V voltage from the mains is supplied through 4-amp fuse F1 on the primary winding of the transformer T1. This is the finished primary transformer winding on 230V and secondary to 20V operating current up to 20A. If necessary, this transformer can be made independently based on the power transformer from the hundred was colored tube tv, or on the basis of low-frequency power transformer capacity not lower than 500W to power halogen lamps ( 12V) or to obtain equipment for power supplies having rewound respectively its secondary winding.
With the secondary winding voltage 20V arrives at the rectifier bridge Here. This is the finished bridge Assembly type MB356, calculated on the maximum permanent current th 35 a. Rectified voltage pulsation smoothed condenser C1 capacity 22000 µF. In the absence of such a large-capacity capacitor it can replace multiple condenser Rami smaller capacity included in parallel, so add at least 20000 µF.
DC voltage on the capacitor C1 at idle is 28V.
Stabilizer stabilizer is composed of a scheme on the A1 and IC output transistor voltage regulator VT1-VT2 transistors, VT5-VT5 which included in parallel. Resistors R5-R8 serve to equalize current through the transistors, so as a result of differences in the rates of transfer they can, under equal conditions open to varying degrees. Resistors included in automatic help chains Ceska emitter installation base-emitter voltages under the action of load current in which the transistors open up equally.
LM723 chip is an integrated stabilizer with a adjustable output voltage and overload protection scheme. Adjusting the output voltage using the resistor R3, which, together with the resistors R2 and forms a voltage divider. Adjustable output voltage dependency set 4 A1 from output voltage. Comparator ICS is running so that the voltage at the output (10) adjusts so that the voltage at its output 4 proposal was unchanged. Consequently, the voltage at pin 10 is almost equal to the output. But Maxey as valid output current is small, so for maximum load current 20A requires current amplifier, which is circuit transistor VT1-VT5.
Protection circuit from over-current works with voltage measurement protivlenii on sequence ably load. Current sensor inputs are conclusions 2 and 3 A1. These conclusions are connected in parallel, resistance resistors R9-R12, which is included in series with the load. It is clear that Ohm's law voltage at the resistance will grow with increasing current. Until the voltage between the findings of proposal 2 and 3 below 0, 6V protection fails, perceiving it as what load current does not exceed the maximum permissible value. Current approaching to mark 22-23 and voltage between the 2 and 3 reaches 0, 6V and more. This leads to the triggering of protection, which reduces the output voltage paradise 10 A1 to zero and, thus, disconnects the load.
The maximum output current can be set and other, respectively changing the resulting resistance R9-R12, which in this case, subject to the choice of the upper threshold of the load current is equal to 0.025 Ohm 23A. Or you can even arrange Maxi mum adjustment output current if the parallel nizkoomnym rezistoram R9-R12 include one variable resistor resistance somewhere 10-100 Om, and control voltage to shoot with his engine and one of the most extreme conclusions. Resistor voltage divider will be R9-R12. But in this case, resistance R9-R12 need looked at the lower limit of the adjustment account maximum load current.
The scheme provides enough good Shui stability established output leg strain, for example, when the output voltage is 13V, Nom under load voltage is reduced to just 20A 40-60 mV.
HL1 led serves to display the status of network-enabled. Led indicates normal release of HL2. That is, it illuminates when there is voltage at the output. If it is not lit, but burning HL1 this suggests that there is a SHORT-CIRCUIT on the load or overload and output disconnect regulator current protection system, or the fuse burns out the F2 included the output of the rectifier.
Транзисторы VT2-VT5 обязательно должны быть на объемных радиаторах, обеспечивающих их эффективное охлаждение. Хороший вариант – использование пластинчатого алюминиевого радиатора совместно с вентилятором. В этом случае радиатор и вентилятор можно использовать от неисправного блока питания персонального компьютера типа АТ или АТХ. Моторчик вентилятора можно подключить параллельно конденсатору С1 через резистор, уменьшающий напряжение на вентиляторе до 12V.
Детали. О трансформаторе сказано в начале статьи. Конденсатор С1 – аналог К50-35, импортный, на 22000 мкф. Можно заменить несколькими конденсаторами меньшей емкости, включенными параллельно, в сумме не менее 20000 мкФ.
Rectifier bridge can be replaced by another in DC not lower than 30A, or collect it at the diodes designed at the same current, for example, 2D 2997, KD, KD 2997 2998.
You can replace the 1N3055 transistors CT 819. You need to take the transistors as possible similar parameters. Desirable but, with one letter, from one party, and even better before mounting the pick on them as near as possible h21je ratios.
Светодиоды – обычные, индикаторные, практически любые. Можно использовать AЛ307. При недостаточной яркости свечения можно понизить сопротивления резисторов R1 и R13.
Резисторы R5-R12 – пятиваттные, проволочные, сопротивлением 0,1 Ом.
If parallel rezistoram R9-R12 to connect switch PF Millivolt meter, so scale the load current can be measured (respectively, altering its scale in units of amperage).
Author: Gorchuk, N. V.
