UPSs are used to protect various types of electrical equipment, primarily computer equipment, from power surges, and can also support their operation for several minutes, hours or even days during a complete power outage
An uninterruptible power supply is able to cope with the following problems in the electrical network: complete shutdown of the mains supply, high-voltage impulse noise, long-term and short-term voltage surges; high-frequency noise or interference occurring in the mains, frequency deviation of more than 3 Hz.
Important parameters of the UPS are the load transfer time to battery power and the battery backup time.
Uninterruptible power supply is the basis of the construction scheme |
Redundant UPS design in operating mode, the load is powered from the electrical network, which is filtered by the uninterruptible power supply for high-voltage impulses and electromagnetic interference with passive filters.
If the mains voltage deviates beyond the rated values, the load is automatically connected to battery power using the inverter circuit, which is available in each UPS. As soon as the voltage in the network returns to normal, the uninterruptible power supply will switch the load to the power supply from the network.
UPS Interactive Diagram similar to the backup circuit, but in addition, a step voltage regulator based on an autotransformer is installed at the input, which allows you to adjust the output voltage. During normal operation, the interactive UPS does not regulate the frequency, but in the event of a power failure, it starts to be powered by an inverter with a battery. The advantage of this scheme is a shorter switching time. In addition, the inverter is synchronized with the input voltage.
UPS Double Conversion Diagram It works as follows: The input AC voltage is converted to DC, then back to AC with the help of an inverter. In the absence of input voltage, switching the load to battery power occurs instantly, because the batteries are constantly connected to the circuit.
The main blocks and nodes that may be part of the UPS:
Switching device
Network filter
Charger
Accumulator battery
Inverter: AC to DC Converter, DC Voltage Stabilizer, DC to AC Converter
bypass switching device
current sensor
Source Filter
temperature sensor
Interface
Display device
Input mains voltage 220V, 50Hz is supplied through the switching device and mains filter to the charger. A surge protector is necessary to prevent interference from entering the mains, the charger charges the battery when mains voltage is present.
The inverter is part of any UPS. It is built on the basis of a semiconductor DC voltage converter AB into an alternating voltage supplied to the load. Often the inverter combines the functions of both the inverter itself and the charger. Depending on the type of UPS, the inverter produces voltage of various forms.
Bypass - switching device. This device is used to directly link the input and output of the UPS, excluding the power backup circuit.
The bypass performs the following functions:
turn the UPS on or off
load transfer from inverter to bypass in case of overloads and short circuits at the output
load transfer from inverter to bypass to reduce power losses
The static bypass is assembled on the basis of a thyristor key from back-to-back thyristors. Key management comes from the UPS management system
The switching power supply was taken ready-made for 28 V, 50A, but you can assemble the circuits yourself and there are a great many. Two 12 volt car batteries connected in series are connected to the switching power supply. The inverter was also used ready-made, because the price of its components is almost twice as high as the finished device. This UPS is enough for almost a day of power consumption of a small private house. In the event of a long shutdown, which often happens in our Siberian expanses, I turn on the diesel generator for 6 hours.
UPS Diagram |
Our UPS is designed for the following features: Direct conversion from DC 12V to AC 220V at 50Hz. The maximum power of this UPS circuit is 220W. The reverse conversion is used to charge the battery. Charge current 6 A. The circuit provides fast switching from direct conversion to reverse mode.
On the radio components VT3, VT4, R3 ... R6, C5, C6, a clock generator is made that generates pulses with a repetition rate of 50 Hz. The generator sets the operating mode of the bipolar transistors VT1, VT6. Windings IIa, IIb of the transformer are connected to their collector circuit. The network filter is assembled on passive components C1, C2, L1, and on the radio elements VD1, C3, C4 the clock generator filter.
The UPS is a very profitable device. While it works, the user has no problems with the power supply. But the functionality of this device does not end there. The simplest refinement of an uninterruptible power supply makes it possible to create on its basis such devices as a converter, power supply and charging.
How to convert an uninterruptible power supply into a 12/220 V voltage converter
The voltage converter (inverter) turns the 12-volt direct current into alternating current, simultaneously increasing the voltage to 220 volts. The average cost of such a device is 60-70 US dollars. However, even owners of worn-out uninterruptible power supplies with a battery start function have a very real chance of getting a working converter for nothing. To do this, do the following:
Open the UPS case.
Dismantle the battery by removing two wires from the drive terminals - red (to plus) and black (to minus).
Dismantle the speaker - an audible alarm device that looks like a centimeter washer.
Solder the fuse to the red wire. Most designers advise using 5 amp fuses.
Connect the fuse to the UPS "input" contact - the socket where the cable was inserted connecting the uninterruptible power supply to the outlet.
Connect the black wire to the free contact of the “input” socket.
Take a regular cable to connect the UPS to the outlet, cut off the plug. Connect the connector to the input jack and determine the colors of the wires corresponding to the red and black contacts.
Connect the wire from the red terminal to the battery positive, and from the black terminal to the negative.
Turn on the UPS.
Eaton 5P 1150i UPS internals
Such a transformation is only allowed by uninterruptible power supplies with a battery start function. That is, the UPS must initially be able to turn on from, without being connected to a power outlet.
If the UPS has a regular outlet, 220 volts can be removed from its contacts. If there is no such outlet, it will be replaced by an extension cord connected to the “output” socket of the uninterruptible power supply. The extension plug is removed, after which the wires are soldered to the contacts of the “output” socket.
The main disadvantages of such converters:
- The recommended operating time for such an inverter is up to 20 minutes, since the UPS is not designed for long-term battery operation. However, this disadvantage can be eliminated by inserting a 12 V computer fan into the UPS case.
- No battery charge controller. The user will have to periodically check the voltage at the drive terminals. To eliminate this drawback, you can embed a conventional automotive relay into the design of the converter by soldering the red wire behind the fuse to pin 87. When properly connected, such a relay will open the power supply when the battery voltage drops below 12 volts.
How to make a power supply from an uninterruptible power supply
In this case, only an uninterruptible power supply will be needed from the entire design. Therefore, the user who decides on such a remake of the UPS will either have to gut the entire UPS, leaving only the case and transformer, or remove this part, preparing a separate case for it. Then proceed according to the following plan:
Using an ohmmeter, the winding with the highest resistance is determined. Typical colors are black and white. These wires will be the input to the power supply. If the transformer remains in the UPS, then this step can be skipped - the input to the home-made power supply in this case will be the "input" socket on the end of the UPS, connecting the device with the outlet.
Next, the transformer is supplied with alternating current at 220 volts. After that, voltage is removed from the remaining contacts, looking for a pair with a potential difference of up to 15 volts. Typical colors are white and yellow. These wires will be the output from the power supply.
The input to the power supply is formed from wires, on one side of the core. The output from the block is formed from wires located on the opposite side.
A diode bridge is placed at the output of the power supply.
Consumers are connected to the contacts of the diode bridge.
Transformer
The typical voltage at the output of the transformer is up to 15 V, however, it will drop after connecting to a self-made load power supply. The output voltage of the designer of such a device will have to be selected through experiments. Therefore, the practice of using a UPS transformer as the basis of a computer power supply is far from the best idea.
Alteration of an uninterruptible power supply for charging
In this case, a minimal transformation similar to the one described in the paragraph above is not needed. After all, the uninterruptible power supply has its own battery, which is charged as needed. As a result, to turn the UPS into a charger, you need to do the following:
Locate the primary and secondary circuit of the transformer. This process is described in the paragraph above.
Apply 220 volts to the primary circuit by inserting a voltage regulator into the circuit - as such, you can use a rheostat for light bulbs that replaces the traditional switch.
The regulator will help calibrate the voltage at the output winding in the range from 0 to 14-15 volts. The insertion point of the regulator is in front of the primary winding.
Connect a 40-50 ampere diode bridge to the secondary winding of the transformer.
Connect the terminals of the diode bridge to the corresponding poles of the battery.
The battery charge level is monitored by its indicator or voltmeter.
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For any question, you can use this form.
All electronic equipment requires power supply, and most often we use an industrial current network 220V, 50 Hz.
But sometimes "force majeure" situations can arise when the electricity is suddenly "cut down". If a sudden power outage for household equipment is not very scary, then for, for example, computers, this can lead to irreversible consequences: uninstalled programs, loss of information, and so on.
If in large cities with power supply everything is more or less stable, but in rural areas this is a fairly common occurrence ...
To avoid annoying misunderstandings associated with a sudden power outage, many manufacturers recommend using uninterruptible power supplies(or whatever they are called uninterruptibles). Of course, they are produced by industry, but such a source can be collected on one's own.
In addition to providing protection in the event of a power outage, uninterruptable power source can be useful in the "field" conditions, when the need arises get 220 volts from a 12 volt battery.
We have already considered a similar circuit on our site, which allows you to get 220 Volts out of 12, here it is, here is another circuit taken from the Radio Amateur magazine, No. 2, 1999.
Homemade uninterruptible power supply circuit
Uninterruptable power source provides:
In direct mode, converting DC voltage 12 V to AC 220 V / 50 Hz with a maximum current consumption of not more than 6 A. Output power - up to 220 W (1 A):
Reverse mode (battery charge mode). In this case, the charge current is up to 6 A; .
Fast switching from direct to reverse mode.
The UPS diagram is shown in the figure. On the elements VT3, VT4, R3 ... R6, C5, C6, a clock generator is made that generates pulses with a frequency of about 50 Hz. He, in turn, controls the operation of transistors VT1, VT6, in the collector circuits of which the windings IIa, IIb of the transformer T1 are included. Diodes VD2, VD3 - protection elements of transistors VT1, VT6 in direct mode and rectifiers in reverse mode. Elements C1, C2, L1 form a network filter, VD1, C3, C4 - a clock generator filter. Consider how the circuit works in both modes.
Direct mode (=12V / -220V). A voltage of +12 V is alternately applied to the windings IIa or IIb, and the transformer T1 converts it to a voltage of 220 V / 50 Hz. This voltage is present on the XS1 socket, and all kinds of consumers are connected to it (incandescent lamps, TV, etc.)
The indicator of normal operation is the glow of the VD4, VD5 LEDs. The load current can reach 1A (220W).
Reverse mode (-220 V / =12 V). To work in reverse mode, you need to connect the network skins to the XP1 connector and apply -220 V to it. After that, the SB1 toggle switch switches. In this case, the mains voltage enters the primary winding of the transformer T1, and the clock generator is turned off. Due to this, two alternating voltages of 10V are obtained on the secondary windings of T1, which are rectified by diodes VD2, VD3. The indicator of normal operation in reverse mode is the glow of the VD5 LED. Boiling in the banks of the GB1 battery indicates the process of its charging.
details and design, T1 - any transformer that provides two voltages of 10V at a Current of up to 10 A. It is best to use cores of the SHL and PL type, which are easier to disassemble. Coil L1 is made on a K28x16x9 M2000NM ferrite ring and contains two windings of 10 turns of wire with a diameter of 0.5 ... 0.71 mm.
Transistors VT1, VT6 and diodes VD2, VD3 are mounted through mica gaskets, lubricated with heat-conducting paste, on one common radiator with an area of at least 200 cm2.
The device had the following requirements: small-sized, low-cost, silent operation with high efficiency, which can provide autonomous operation of the modem for three or more hours.
There are two types of uninterruptible power supplies: soft start and hard start. In our case, a system with a hard start is desirable.
In this case, the modem does not turn off due to a lack of mains voltage due to the instant operation of the uninterruptible power supply.
First what we need is batteries. The ideal option is 18650 batteries (4 pcs, capacity: the more, the better).
Second- this is the body. A case with a board from PowerBank will do. It has six compartments for 18650 batteries. We use two compartments to accommodate all electronics.
Third– DC-DC converter that provides 2 amps (hereinafter A) of output current
quadruple- Step-down stabilizer with the ability to stabilize current and voltage. It is needed to charge the battery of the uninterruptible power supply from the modem power adapter (its current is about 3 A).
Fifth- Electromagnetic relay (mandatory with a voltage of 12 volts). The relay current is basically irrelevant.
sixth- Two resistors of any power. One with a resistance of 150 ohms, the second with 1 kOhm.
seventh- Direct conduction transistor BD 140. It is important that it be direct conduction.
eighth– Any small latching switch. Current not less than 1 A.
At the output of this stabilizer, you need to set the voltage to about 4.1-4.2 V, which is equivalent to the voltage of fully charged lithium-ion batteries. And you also need to set the maximum charge current to about 1.5-2 A. This is done using trimmer resistors on the step-down stabilizer board.
The Dc-Dc boost converter board also needs to be configured. To do this, we connect it to one bank of a lithium battery and, using the built-in tuning resistor, set the output voltage to about 12 V. It is this converter that will power the modem.
Now let's see how this whole system works.
In the presence of mains voltage, power from the modem adapter (about 12 V) is supplied to a step-down stabilizer, which charges lithium batteries. In this case, the transistor is open, and power is supplied to the relay through its junction, and the latter operates, opening the power supply network of the Dc-dc converter. If there is no power from the adapter, for example, when the mains voltage is turned off, the transistor closes and the power supply to the relay winding stops. Contacts 1 and 2 close. Battery power is supplied to the converter, which increases the voltage from lithium batteries to 12 V, ensuring uninterrupted operation of the modem. The switch is designed for emergency shutdown of the uninterruptible power supply.
Please pay attention to the diode that is in the circuit.
It is connected in such a way that no current flows from the output of the boost converter to the input of the buck regulator.
Do-it-yourself washing machine repair
In general, this article was originally written a very long time ago, more than two years ago. But in this case, I decided that the information from it can be useful and used for the benefit of 3D printing masters.
The essence of this article is to turn an ordinary power supply into a small uninterruptible power supply with an output of about 11-13.5 volts.
As an example, there will be a PSU with a power of 36 watts, but with little or no modifications, the circuit is applicable to more powerful PSUs and with modifications to.
But first, just a mini-review of the PSU itself, sorry for the quality of the photo, it was filmed with a soldering iron.
Specifications are listed on the end.
The characteristics confused me a little, usually they either indicate the full range, or if there is a choice of 110/220, then, accordingly, there is a switch and inside the mains rectifier circuit with switching to doubling. There was no switch here. We'll take a closer look at what's inside later.
The dimensions are relatively small.
From the end there are connection terminals for 220 Volts, a ground terminal and output terminals for 12 Volts. Also here is an LED that shows the presence of the output voltage and a trimmer to adjust the output voltage.
After opening, the printed circuit board of this power supply appeared before my eyes.
A full-fledged input filter, a 33uF 400 V capacitor (quite normal for the declared power), a high-voltage part made according to the oscillator circuitry (when I ordered, I hoped that there would be a standard UC3842), an output filter of two 470uF 25 Volt capacitors and a choke. The capacity of the output filter is too small, I would put 2 times more.
Power transistor 5N60D - only in the TO-220 package.
The output diode - stps20h100ct - is similar in the TO-220 package.
The stabilization and feedback circuit is made on the TL431.
Reverse side of the board.
Nothing out of the ordinary, average quality soldering, flux washed out, pretty neat.
But I was surprised by the marking on the board (it is also on the top side).
SM-24W, maybe the PSU was originally 24 watts, then they decided that it would not be enough and wrote 36?
Experiments will show.
The first inclusion, nothing bang, already not bad.
I loaded the power supply with classic unkillable Soviet resistors, 10 ohms, 2 pieces in parallel.
Current is about 2.5 amps.
I measured the voltage after the wires to the resistors, so it sank a little.
I left it like that, went to have a cup of tea and smoke, waiting for it to explode.
It didn’t explode, it didn’t even get warm, it was 40 degrees, maybe 45, I didn’t measure it on purpose, it feels a little warm.
Loaded another 0.22 A (did not find anything suitable nearby), nothing has changed.
I decided not to stop there and hung another 10 Ohm resistor on the output.
The voltage dipped to 10.05 Volts, but the power supply continued to work hard.
By the way, I was skeptical about this power supply, mainly because of its circuitry, as I used to work with more expensive power supplies, where there is a PWM controller, current control, etc. Practice has shown that this option is also quite viable.
Then I decided to move on to the non-standard part of the tests and try to get from him what I wanted to take him for. Actually, regular readers of my reviews are used to the fact that I like not only to show the product in the review, but also to apply it, I will not upset you this time either.
Dope
It all started with the fact that a friend called and asked if it was possible to make a small uninterruptible power supply to power the electromagnetic lock and controller. He lives in the private sector, the light is sometimes for a short while, but disappear. He already had a battery, left from a computer uninterruptible power supply, he no longer draws a large current, but he copes with the lock quite normally.
In general, I threw a small additional scarf to this power supply.
Scarf, diagram and a short description of the process.
Scheme.
And the fee strated on it.
The circuit provides charge current limitation (in my case it is set to 400mA), protection against battery overdischarge (set to 10 Volts), simple protection against battery reversal (except if you reverse the polarity right on the go), and the actual function of supplying voltage from the battery to the output power supply.
I transferred the scarf to the textolite, covered it with solder.
Corrected the details.
I soldered the board, the relay is different, because at first I didn’t notice that it was 5 volts, I had to look for 12.
Explanations for the diagram.
C2, in principle, can not be set, then R5 and R6 are replaced by one at 9.1-10 kOhm.
It is needed to reduce false positives during a sharp change in load.
Ideally, of course, it would be better to wind a couple of turns in addition to the secondary winding, since the power supply operates with a voltage overload of 20%. Tests have shown that everything works fine, but it’s better to either wind up the secondary winding a little, or even better, modify the PSU to 15 Volt, not on 12 . In my case, I also had to change the value of the resistor in the feedback divider at the power supply, on the diagram it is R7, there are 4.7 kOhm, I set 4.3 kOhm, if a 15 Volt PSU is used, this most likely will not have to be done.
After assembling the board, I built it into the power supply.
The connection points are marked on the board and you can see the place where the negative track is cut (above the number 3).
I wrapped the board with adhesive tape, and laid it on a more or less free place.
After (in fact, it’s better before we isolate it with tape) I set the output voltage of the power supply to 13.8 Volts (this is the voltage that will be maintained on the battery, usually set in the range of 13.8-13.85.
Here is a view of the assembled and configured device.
I connected a small load and a battery. Charge current 0.39A (may drop a little as it warms up).
I disconnected the power supply from the mains, the load continues to work, on the multimeter, the load current + the current consumption of the relay + the current consumption of the measurement circuits.
A friend needed an uninterruptible power supply for a current of 0.8-1 Amperes, I loaded a little more.
After that, I connected the power to 220 Volts, on one multimeter the voltage on the load (it will still rise, the battery is not charged), on the second, the charge current (dipped a little due to warming up).
In general, in my opinion, the alteration was a success, small loads can be powered from such a PSU, up to 1-1.5 Amperes. I would not do it anymore, since the power supply unit is in emergency mode. If you use a 15 Volt PSU, then the current can be raised, but you must always take into account the battery charge current (it is determined by resistor R1. 1.6 Ohm gives a charge current of about 0.4 A, the lower the resistance, the greater the current and vice versa.
If someone disagrees with the configured charge current, charge end voltage and auto shutdown, then it's all easy to change, if necessary, I'll explain how to do it.
Of course, you will ask what 3D printers and this small power supply have to do with it.
Everything is simple, as I wrote at the very beginning, you can take a powerful power supply, use more powerful components in the board that I made and get an uninterruptible power supply that does not have such a thing as "switching time", i.e. actually online. And since printing takes a very long time, this can be very useful in terms of uninterrupted work. In addition, the efficiency of such a system is noticeably higher than that of traditional UPSs.
For use with high currents, it is necessary to replace the VD1 diode on my board with any Schottky with a current of more than 30 Amperes (for example, soldered from a computer PSU) and install it on a radiator, relay on any with a contact current of more than 20 Amperes and a winding with a current of not more than 100mA ( better up to 80). In addition, you may need to increase the charge current, this is done by reducing the value of the resistor R1 to 0.6-1 Ohm.
There are also industrial PSUs with such a function, at least I know a couple of them manufactured by Meanwell, but:
1. They are very expensive.
2. They are produced with a power of 55 and 150 watts, which is not so much.
That's all, if you have any questions, I'll be happy to discuss.
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