The goal of the project is to build a universal regulated power supply that can be used to charge nickel or lead batteries, and not only car batteries. The charger will allow you to charge batteries with voltages from 4 to 30 V.
The first thing you will need to implement this project is a body. Suitable, for example, from a Chinese inverter 12-220 V. It is monolithic and made of aluminum.
You can take any other suitable size, for example, from a computer power supply.
The second is a network step-down switching power supply.
The output voltage of the unit used in this project is 19 V with a current of about 5 A.
This is a cheap universal laptop adapter. It is built on a PWM controller from the UC38 family, has stabilization and short circuit protection.
The third is a digital or analog voltammeter. The volt-ampere meter shown here was taken from a Chinese voltage stabilizer (30V, 5A).
Fourth is a few electronic components such as terminals and power cord.
The device is shown schematically in the following picture:
Now take a look at the power supply diagram. The TL431 chip is located near the optocoupler. It is this microcircuit that sets the output voltage. There are only 2 resistors in the harness, and by selecting them you can obtain the desired output voltage.
In this diagram it is designated as R13. In the existing block, its resistance is 20 kOhm. You need to connect a 10 kOhm variable in series to this resistor, approximately as in the picture:
By rotating the variable resistor, it is necessary to achieve an output voltage of around 30 V. Then you need to turn off the “variable” and measure its resistance, at which the output voltage was 30 V, and replace R13 with a resistor with a selected resistance. The result was approximately 27 kOhm. This completes the adapter conversion.
To limit the current, the PWM control method will be used, since the output current from the adapter from the laptop is very small.
In general, this circuit is a PWM voltage regulator without a separate current limiting unit. This square wave generator is based on the NE555 timer, which operates at a specific frequency. Diodes serve to constantly change the charging and discharging time of the frequency-setting capacitor. Thanks to this phenomenon, it is possible to change the duty cycle of the output pulses. Since the power transistor operates in switch mode (it is either open or closed), a fairly high efficiency can be observed. A variable resistor regulates the duty cycle of the pulses.
The required charging current can be set by changing the voltage, that is, by rotating a multi-turn variable resistor.
Literally any transistor will do. An n-channel field-effect transistor with a voltage of 60 V and a current of 20 A is used here.
Due to the key operating mode, its heating will not be great, unlike linear circuits, but heat removal will not interfere. This project uses an aluminum casing as a heat sink.
The PWM regulator circuit is really simple, economical and reliable, but also needs a little modification. The fact is that, according to the documentation, the NE555 microcircuit has a maximum permissible supply voltage of 16 V. And at the output of the converted adapter, the voltage is almost 2 times higher, and when the circuit is connected, the timer will definitely burn out.
There are several solutions to this situation. Take a look at 3 of them:
- Use a linear regulator, say 5 to 12 V from the 78xx family or
build a simple stabilizer according to the following scheme:
The simplest solution would be to introduce a linear stabilizer into the circuit, for example, 7805. But it should be remembered that the maximum supply voltage, depending on the manufacturer, varies from 24 to 35 V. This project uses a KA7805 stabilizer with a maximum input voltage of 35 V according to the datasheet. If you cannot get such a chip, you can build a stabilizer from just three parts.
After assembly, you need to check the PWM regulator.
On the adapter board there are 2 active components that are subject to heating - the power transistor of the high-voltage circuit of the converter and a dual diode at the output of the circuit. They were soldered and attached to an aluminum housing. In this case, they need to be isolated from the main body.
The front panel is made of a piece of plastic.
The adapter circuit has short circuit protection, but does not have reverse polarity protection. But this can be fixed.
Since the adapter output voltage exceeded 30 V during testing, the digital voltammeter burned out. Do not exceed the voltage by even 1 V. You will have to do without it. The charge current will be shown using a multimeter.
The charger turned out to be good - it also charges batteries from a screwdriver without any problems.
Attached files:
How to make a simple Power Bank with your own hands: diagram of a homemade power bank
A power supply is a device used to convert (lower or increase) alternating mains voltage into a given direct voltage. Power supplies are divided into: transformer and pulse. Initially, only transformer designs of power supplies were created. They consisted of a power transformer powered from a 220V, 50Hz household network and a rectifier with a filter and voltage stabilizer. Thanks to the transformer, the network voltage is reduced to the required values, followed by rectification of the voltage by a rectifier consisting of diodes connected in a bridge circuit. After rectification, the constant pulsating voltage is smoothed out by a parallel connected capacitor. If it is necessary to accurately stabilize the voltage level, voltage stabilizers on transistors are used.
The main disadvantage of a transformer power supply is the transformer. Why is that? All because of the weight and dimensions, since they limit the compactness of the power supply, while their price is quite high. But these power supplies are simple in design and this is their advantage. But still, in most modern devices, the use of transformer power supplies has become irrelevant. They were replaced by switching power supplies.
Switching power supplies include:
1) mains filter (input choke, electromechanical filter providing noise rejection, mains fuse);
2) rectifier and smoothing filter (diode bridge, storage capacitor);
3) inverter (power transistor);
4) power transformer;
5) output rectifier (rectifier diodes connected in a half-bridge circuit);
6) output filter (filter capacitors, power chokes);
7) inverter control unit (PWM controller with wiring)
The switching power supply provides stabilized voltage through the use of feedback. It works as follows. The mains voltage is supplied to a rectifier and a smoothing filter, where the mains voltage is rectified and the ripples are smoothed out through the use of capacitors. In this case, an amplitude of about 300 volts is maintained. At the next stage, the inverter is connected. Its task is to generate rectangular high-frequency signals for the transformer. Feedback to the inverter is carried out through the control unit. From the output of the transformer, high-frequency pulses are supplied to the output rectifier. Due to the fact that the pulse frequency is about 100 kHz, it is necessary to use high-speed semiconductor Schottke diodes. At the final phase, the voltage on the filter capacitor and inductor is smoothed. And only after this, a voltage of a given value is supplied to the load. That's it, enough theory, let's move on to practice and start making a power supply.
Power supply housing
Every radio amateur who deals with radio electronics, wanting to design his devices, often faces the problem of where to get the housing. This problem also befell me, which in turn prompted me to think, why not make the case with my own hands. And then my search began... The search for a ready-made solution on how to make a body did not lead to anything. But I didn't despair. After thinking for a while, I had an idea, why not make a case from a plastic box for laying wires. It was the right size for me, and I started cutting and gluing. See the pictures below.
The dimensions of the box were chosen based on the size of the power supply board. See the picture below.
Also, the housing should also accommodate an indicator, wires, a regulator and a network connector. See the picture below.
To install the above elements, the necessary holes were cut in the housing. Look at the pictures above. And finally, to give the power supply case an aesthetic appearance, it was painted black. See the pictures below.
Measuring device
I’ll say right away that I didn’t have to look for a measuring device for long; the choice immediately fell on the combined digital voltammeter TK1382. See the pictures below.
The measuring ranges of the device are for voltage 0-100 V and current up to 10 A. The device also has two calibration resistors for adjusting voltage and current. See the picture below.
As for the connection diagram, it has some nuances. See the pictures below.
Power supply diagram
To measure current and voltage, we will use circuit 2, see the figure above. And so on in order. For the laptop power supply I have, let’s first find an electrical circuit diagram. The search must be carried out using a PWM controller. In this power supply it is CR6842S. See the diagram below.
Now let's touch on the alterations. Since an adjustable power supply will be made, the circuit will have to be redone. To do this, we will make changes to the diagram; these areas are circled in orange. See the picture below.
Circuit section 1.2 provides power to the PWM controller. And it is a parametric stabilizer. The stabilizer voltage of 17.1 V was chosen due to the operating characteristics of the PWM controller. In this case, to power the PWM controller, we set the current through the stabilizer to about 6 mA. “The peculiarity of this controller is that to turn it on you need a supply voltage greater than 16.4 V, a current consumption of 4 mA” excerpt from the datasheet. When converting the power supply in this way, it is necessary to abandon the self-powering winding, since its use is not advisable at low output voltages. In the picture below you can see this unit after the modification.
Section 3 of circuit provides voltage regulation; with these element ratings, regulation is carried out within 4.5-24.5 V. For such a modification, it is necessary to unsolder the resistors marked in orange in the figure below, and in their place solder a variable resistor to regulate the voltage.
This completes the alteration. And you can do a test run. IMPORTANT!!! Due to the fact that the power supply is powered from a 220 V network, you must be careful to avoid being exposed to mains voltage! THIS IS LIFE DANGEROUS!!! Before starting the power supply for the first time, it is necessary to check the correct installation of all elements, and then connect it to a 220 V network through a 220 V, 40 W incandescent light bulb to avoid failure of the power elements of the power supply. You can see the first launch in the picture below.
Also, after the first start, we will check the upper and lower limits of voltage regulation. And as intended, they lie within the specified limits of 4.5-24.5 V. See the figures below.
And finally, when testing with a load of 2.5 A, the case began to heat up well, which did not suit me and I decided to make perforations in the case for cooling. The location for perforation was chosen based on the location of the greatest heating. To perforate the case, I made 9 holes with a diameter of 3 mm. See the picture below.
To prevent accidental penetration of conductive elements into the housing, a safety flap is glued to the back of the cover at a short distance. See the picture below.
I have long had a need to purchase a universal power supply for laptops. So that it has different connectors and can regulate the voltage. And if we need it, we buy it.
I chose this one:
LED Indicator.
Input power:100w.
Output power:96w.
Input voltage range: Ac110-240v.
Adjustable Output Voltage:12v/15v/16v/18v/19v/20v/24v.
Overload and short circuit protection.
Compatible with SONY/HP/IBM notebook, etc.
8 DC Plug as picture.
The parcel took a long time to arrive. The power supply was packaged poorly, in a regular bag, but surprisingly, nothing was broken.
Replaceable elements are plugged into such a socket on the wire. Contacts of different thicknesses, foolproof.
Before switching on, I performed an external inspection.
The power supply has a standard three-pin socket with grounding for connecting a standard computer cable.
Cable included... terrible.
Even upon external examination, it is so thin...
The cable says 250V 10A. Well, there is also a lot written on the fence.
The wire also indicates some second-rate Chinese brand and a thickness of 3x0.5mm.sq. Well, where does 10 Amps come from here? Why is the brand second-rate? A normal manufacturer will not make such poor and unsafe cables. Here the pursuit is only on low cost, the rest has been neglected.
To be honest, I think that 0.5 square is also too high, in reality there is even less, a couple of tiny hairs, and not copper, but steel, copper-plated. They burn out so spectacularly... With a bang and sparks.
This cable will certainly handle this power supply. But since it has a standard computer connector, it is better to immediately cut it into pieces and throw it away. Why cut? So that someone does not accidentally find and turn on any energy-consuming electrical appliance with its help, since this is an almost 100% guarantee of heating and burning of this cable, at a minimum with a stench and sparks, and at a maximum - a short circuit, blown fuses or a fire .
An external review revealed the following: if you shake the power supply, something rattles in it, and quite loudly. It was decided not to plug the power supply into the outlet, but to immediately open it and check it.
Looking ahead, I will say that this was the right decision, which allowed us to avoid repairs.
So, the block is opened. A decent amount of solder snot falls out of it, about 7x2mm.
This piece of solder rattled inside. It could very well short-circuit something and cause the power supply to fail.
The board is of fairly high quality, but both installation and soldering are a pitiful sight.
In the "hot" part, some elements are not installed. Some parts were installed with underestimated parameters and not as envisaged during the design. The board is marked with which elements should be installed and how.
But there is an NTC thermistor that prevents an inrush of current when the power supply is plugged into an outlet. It’s strange that they didn’t replace it with a jumper; they could have saved a couple of cents.
The high-voltage capacitor costs only 22 µF (this is extremely small), even on the board it says 47 µF, there is no filter choke in the input circuits, there is no filter capacitor, the power capacitor of the PWM chip is standing vertically, although it should be on the board, the fuse is of dubious rating and quality is installed so that replaces the filter choke.
Switching the stabilization voltage of the power supply is done by switching resistors in the divider arm on the TL431 chip. The soldering is terrible.
The entire board is covered in flux, no one tried to clean it.
But unwashed flux is not the worst thing. The board is poorly soldered; some pins simply hang in the air.
For example here: dual Schottky diode. One of the terminals is not soldered, the second is torn off and the track is hanging in the air. The power supply will work in this state, but for how long?
It is clear that there is simply no talk of any quality control or debugging. It would be good if these power supplies were turned on at all...
The PWM chip - UC3843AN - is quite common. It makes many different power supplies and StepDown converters
The output part is also much simpler. After the rectifier diode there is a single electrolytic capacitor. There is no talk of any filter. There is not even shunt ceramic. It can be assumed that if everything is left as is, given that the case is practically sealed, the operation of such a power supply will not be long. The capacitor will swell very soon.
The power transistor and the rectifier dual diode are located on a common radiator (of course, there is no trace of thermal paste). The radiator is a poorly processed aluminum plate with burrs, it is not fixed in any way and rests on the transistor and diode itself. It is logical that the diode and transistor were soldered a little high and when the case was closed, force was applied and the transistor with the diode simply sank down and tore the tracks off the board.
It looks terrible, everything is hanging in the air, although I believe that there was contact and the power supply may have started even in this state. But I can’t leave such a disgrace as it is.
In short, this power supply is a set of jambs and defects. Almost everything in it requires modification or replacement: hot part, cold part, power cord.
First of all, I unsolder the “strategic” jumpers, a dubious fuse, a high-voltage capacitor, and a PWM power capacitor from the board.
I solder the filter choke, a normal 2 A fuse, a filter capacitor, and put the PWM power resistor sticking out to the side on its side. I am replacing the PWM power capacitor 47uF 63V with 100uF 63V. (47uF would be enough, but I didn’t have one with long leads on hand). The capacitor should be placed “lying” so as not to interfere with the installation of a high-voltage capacitor of larger capacity and, accordingly, larger size. I installed a high-voltage capacitor 47 μFx400V. This is exactly the denomination indicated on the board. A larger one would most likely be problematic to install, since it most likely would not fit into the case. It is clear that the board was not laid out very professionally. The high voltage capacitor is located horizontally above the PWM power capacitor, the PWM chip itself, and the power resistor. It's not lethal, but it's not very smart. But here it is, as it is.
The radiator has been removed. Thermal paste was not even planned there, the Chinese economy is visible in everything. The transistor is in a TO-218-ISO package, which is completely isolated from the heatsink, so you can do without insulating gaskets.
The proven KPT-8 will help us as always. It may not be the best thermal paste, but I trust it more than some unknown Chinese origin.
Well, the power elements are now on thermal paste. I hope this makes their life a little easier. The transistor and diode are placed lower so that the heatsink rests on the board.
The “hot” part is over.
I return the output electrolytic capacitor to its place, cut the long and wide positive track on the board, drill 2 holes and solder a choke into the gap. I solder a capacitor parallel to the power wires after the inductor.
I shunt the filtering electrolytic capacitor with “ceramics”.
I solder all the unsoldered parts (of which there are plenty on the board) and the torn tracks. I wash my board and dry it.
Builds and test activation. Everything is working.
Finally, I make several cuts in the housing with a Dremel for air exchange. This should allow heated air to escape from the housing and improve cooling slightly.
This may not be very pretty, but it will improve the thermal performance of the power supply.
Now this power supply has all the elements installed, everything is soldered, and the filtration has been improved. Now it’s not scary to connect it to a fairly expensive laptop or monitor.
Conclusions: this is a misunderstanding, this set of jambs, which was mistakenly called a universal power supply, cannot simply be used after purchase without modification and alteration. It's just dangerous.
Only the fact that the power supply was opened in time helped prevent its rapid failure.
Yes, it is inexpensive, much cheaper than normal power supplies, ready for use immediately after purchase. Refining it to a working condition does not require large financial investments, but it does require the presence of some parts, a soldering iron, direct hands and minimal knowledge. For people who have all this, this power supply is a good buy. For the rest of the population who do not know how to hold a soldering iron, this power supply is not recommended for purchase.
P.S. When trying to use it with a laptop, after 20-30 minutes of operation, this power supply burned out with a loud bang, flash and smoke. At the same time, he took the laptop’s charging board with him; at least he managed to buy it on e-bay. A transistor burned out in the power supply, the PWM chip opened, and the transformer turned suspiciously black. The power supply went into the trash. I see no point in repairing this misunderstanding. I don't recommend anyone to buy it.
I am describing my personal experience of powering a laptop from external batteries. Getting ready to move to live in nature, I was puzzled by solving the problem of powering my laptop from a battery. Having rummaged through the forums, I didn’t find anything simple and accessible. Everyone suggested either a homemade adapter for power supply from a car generator, which is very difficult to assemble. Or ready-made solutions, such as auto adapters for laptops and current converters of 12 volts to 220 volts to use a regular power supply for a laptop. But all these adapters cost money, and I didn’t have the opportunity to buy something ready-made.
Here's how I got out of the situation. The laptop is powered by 19 volts, I took and purchased 3 batteries from UPS at 6 volts 4.5A. I connected them in series and got 19 volts. I cut off the wire from the power supply, the one from the unit to the laptop and connected it to the batteries, observing the plus or minus. Next, I took the battery out of the laptop and connected the power cord. I turned it on and the laptop started working.
Attention - if you power the laptop from batteries, then its own battery must be removed, otherwise the laptop will burn out. I'll explain why. A standard power supply provides a certain current, for example 4A, and its battery consumes all these 4A. And if you power it from external batteries, then the battery of the laptop itself will charge everything that is given to it, and external batteries can produce tens of Amperes. With such a charging current, the hardware of the laptop simply cannot withstand it and the built-in power supply of the laptop will burn out.
In order to not only power, but also charge a laptop from external batteries, you need to install a resistor that will limit the charging current. For example, if your laptop is powered by 19 volts 4A, then you need to install a 4A resistor. But I know that this option also causes some difficulties, since you need to find the right resistor. There is an even simpler option: instead of a current-limiting resistor, you just need to install a car light bulb with the required number of Amperes.
For example, if your laptop consumes 4 amps, then you need to install a 4 amp light bulb. It will work like a resistor, that is, passing only 4 amperes through itself, while it itself will consume the same amount. Yes, with this scheme, the electricity consumption from external batteries will be 2 times greater, but this will allow you to charge the internal battery of the laptop.
And so, look at the picture, in the first image the laptop is powered directly from 3 6-volt batteries. With this scheme, it is necessary to remove the internal battery, otherwise the internal power supply of the laptop will burn out.
In Figure “2” the laptop is powered and charged through a resistor. Turning on a resistor or light bulb will not only power, but also charge the built-up laptop battery.
I tested all the methods described above on my acer netbook, and it still works, I’m writing this article from it. Please note that for power supply I use 3 6.4 volt batteries, this gives 19 volts when connected in series. There are also laptops that are powered by 12…..16 volts. These laptops can be powered directly from 12 volts (auto battery), just remember to remove the internal battery. If you want to charge your laptop, then charge it through a resistor or a light bulb.
Another way to power a laptop if the laptop battery is dead
Power supply of the laptop from 12 volts, from the battery
The laptop's original battery failed, or rather it worked, but the charge lasted for about 20 minutes at most. And one fine day our electricity was cut off for 2 days, and I needed to correspond on the Internet. And I decided not to wait until the electricity was turned on, and to disassemble the built-in battery of the laptop, it was of no use anyway. There were 4 elements inside, the battery says 14.8 volts, which means each element is 3.7 volts.
Inside there are 2 main wires that are soldered to the ends of the element assembly, and several wires that are soldered between the elements. We need those 2 thick wires. which are on the sides of the element assembly. These wires are plus and minus for power, I connected a 12-volt battery to them and that’s it, we insert the empty battery case into its place and turn on the laptop, everything works.
By the way, depending on the model, the laptop may swear at the power supply and write that the battery is low, but don’t worry, this is because a regular car battery provides 12 volts, not 14 volts, which is why the laptop thinks that its battery is low , but at the same time it does not turn off and works normally until the battery is actually discharged.
This option is only suitable for 11.1 or 14.8 volt batteries. But these are emergency options, and it is better to use devices designed for this.
