This step-up dc-dc converter is designed to increase the voltage of the car's on-board network (+12V) up to 19V, making it possible to connect a laptop to the car's on-board cable network. Given the fact that a laptop is not uncommon in our time, the converter circuit presented in this article is very relevant for motorists.
This UC3845 automotive converter is built on the principle of a single-ended boost converter with a storage choke. The circuit has current protection.
Diagram of a car converter from 12V to 19V on UC3845
The operation of the circuit is described in detail in the article "". In the same article, you will read about how current protection works, as well as other interesting information on this scheme.
The UC3845 chip is a PWM controller and is similar in operation to the UC3843 PWM.
ICs UC3845 and UC3843 are identical in pinout and can be interchanged with each other in this circuit. When replacing these PWM controllers, it is worth considering the fact that with the same timing elements (R2, C6), the frequency at the outputs of these PWMs (pin 6) will almost double.
The fact is that the UC3845 has a trigger that divides the frequency in half, and also limits the pulse width to 50% (discussed below). And if you set the generators of the UC3845 and UC3843 microcircuits to the same frequency (we stand with an oscilloscope at pin 4), then at the very output of the UC3845 (pin 6) the frequency will be half the output frequency of the UC3843. Do not confuse the output frequency with the PWM generator frequency, it is not always the same (as in our case).
For example, I set R2 = 10kΩ and C6 = 1nF, the UC3845's oscillator frequency was about 160kHz, while the UC3843's was 135kHz. At the output of the UC3845, the frequency was approximately 80 kHz (that is, it was halved), while the frequency of the UC3843 was equal to the generator frequency (135 kHz).
Therefore, for the UC3845, the capacitor C6 must be installed with a capacitance of no more than 500pF, and the resistor R2 at 10kΩ, in order to obtain a frequency of approximately 160kHz at the output. I set 1nF and conducted all tests on this capacitance.
Another difference between these microcircuits is that the pulse duty cycle of the UC3845 PWM is 50%, unlike the UC3843, whose duty cycle is 100%.
In short, when adjusting the duty cycle, the UC3843 pulse width can be so large that it takes almost the entire period, and the UC3845 only half the period. How can you feel it, yes it is easy! Having assembled this car boost converter from 12V to 19V on the UC3845, when adjusting the voltage under a load of 3A, the voltage at the output of the converter will not be able to rise more than 21V-22V (the voltage depends on the parameters of the inductor), that is, the voltage will “sink”.
It seemed like trouble! But no, our converter needs to output 19V DC, and it does its job perfectly with a load of 3A and 5A. No wonder this microcircuit is one of the leaders in 12-19 Volt conversion circuits.
Some parameters of the microcircuit
Maximum input voltage no more than .......... 30V
Output current.......... 1A
Error signal current......... 10mA
Power dissipation (DIP package) .............. 1W
Maximum generator frequency .......... 500kHz
Duty factor.......... 50%
Operating current.......... 11mA
You will find other parameters and graphs in .
Circuit elements
The circuit resistors must be selected for a quarter watt (0.25W), with the exception of R4 = 0.5W and R6 = 2W.
Capacitors C1, C2, C8, C9 must be rated at 25V. At the output of the circuit, one electrolyte per 1000uF (C8 or C9) is sufficient.
Diodes VD1 and VD2 - Schottky, or other superfast diodes. I have an assembly of Schottky SB2040CT (20A, 40V), it is better not to install less than 40V. You can install a single diode on the board, but it is easier to attach a heatsink to the assembly.
R9 is a type 3296 multi-turn tuning resistor. Multi-turn resistors allow for smooth tuning.
The most interesting thing is the L1 choke. Its inductance should be in the range of 40-50 μH. Although the converter will work even with an inductance of 20 μH, only the efficiency will be lower than desired. To make it, you need to find a yellow-white powdered iron ring. The larger the ring diameter, the better. My ring has an outer diameter of 27mm, an inner diameter of 14mm and a thickness of 11mm. We wind 20-22 turns with double copper, varnished wire. Core diameter 1mm. I have a core diameter of 1.4mm, I wound it with a single wire. Such a choke holds a current of 3A for a long time at an output voltage of + 19V.
When winding with a double (triple) wire, the winding may not fit in one layer, then the winding must be done in two layers, it is possible without insulation (if the wire enamel is not damaged).
A few words about protection
Fuse FU1 will save from a short circuit (short circuit). The short circuit withstands, my experiments showed it, the main thing is that the + 12V voltage source connected to the input of the converter has protection and is powerful enough, but it is better that it be a car battery.
The operation of the current protection is described in detail in the article about UC3843 (see the link above), here everything works in a similar way. The only thing I will add is that for the operation of the converter on the UC3845 for an output current of up to 5A, it is necessary to halve the resistance of the resistor R6 (current sensor), or connect two 0.1 Ohm resistors in parallel. If you do not do these manipulations, the output power (voltage and current) will be limited by the protection.
Two throttles of different sizes...
The converter with the throttle parameters described just above, I operated on a load with a resistance of 6.2 Ohms. The load current was 3A, with an output voltage of 19V. During thirty minutes of operation, the throttle heated up to 45 degrees Celsius, and the temperature rise stopped, which is very good. By the way, the efficiency at such a load was 82%.
After that, I installed a second choke, which is wound on a ring with an outer diameter of 18mm, an inner diameter of 8mm and a width of 7mm. Single wire, wire diameter 1.4mm, 20 turns (40µH). When operating at an output current of 3A for 30 minutes, the inductor heated up to a temperature of 50 degrees Celsius.
Now it’s a little clear to you what core dimensions to choose. Of course, if I wound with two wires, the heating would decrease a little, but even 55 degrees is quite normal.
It is difficult for a modern person to do without a computer. Today, people do not part with electronics, even in the bathroom. What can I say about long-distance travels, in which you must definitely look at the weather forecast, road map on your laptop and, out of habit, be in touch on social networks. It’s bad that the laptop’s battery lasts more than an hour, and you can’t directly plug it into the car’s cigarette lighter socket. To power a laptop or netbook, a voltage of 19 V is required, at a current of 4–5 A.
You will have to assemble a boost converter from 12 to 19 volts. Since the maximum load current reaches 5 A, a low-power voltage multiplier is indispensable. Exactly powerful inductive-pulse converter 12/19 V , for example, assembled according to the scheme below, is needed to power a laptop.
Adapter details
The heart of the converter is chip KR1006VI1 . The switching frequency of 40 kHz of this RS register is set by capacitor C3. The circuit has protection against lowering the input voltage. Since if it falls below 9 V, then the inductor, trying to maintain the set voltage at the output, will work at the limit, while an abnormally high current will flow through the power switch VT2.
There is also protection against overvoltage at the output above 25 V. An abnormal increase in voltage can be observed when the feedback line in the circuit is broken. Which is not dangerous for a laptop, but catastrophic for a converter.
Throttle L 1 with an inductance of 25 μH must be wound independently on a toroidal magnetic circuit of size TN27/15/11. Such a coil, as in the photo, covered with a yellow plastic shell, is available in any computer power supply.
Only 9 turns of 25 µH need to be wound, using the specified coil with a diameter of 27 mm. PEV-2 wire with a diameter of 1 mm is ideal for winding. It should be evenly distributed throughout the magnetic circuit.
To rectify the pulsed output voltage, you need Schottky diode VD 2 and electrolytic capacitor C5 capacitance 100–220 uF. From a faulty computer power supply, you can borrow an assembly of two MBR4045PT Schottky diodes, in which they are connected in parallel. This is a very powerful assembly, rated for current up to 40 A at low voltage up to 45 V, so the Schottky diodes will never heat up during operation of the laptop converter.
In the output key of the converter, to provide a large supply current, a powerful field transistor VT 2 , such as in the schematic or you can remove the T60N02R from the motherboard.
All other parts of the laptop adapter can also be replaced with domestic or imported counterparts.
Converter setup
To test the output of the converter, you should connect a string of resistors assembled in total for a resistance of 5 ohms and a power of at least 50 watts. Now you can check if the circuit holds the voltage within 17-20 V at a load current of 4-5 A.
After this setup, it will be possible to connect most LCD monitors powered by 19 volts through the adapter. In case of organizing a cinema in the car.
Device assembly
It is convenient to place the finished device for the car in a case from a faulty computer power supply. Most of the elements are located on its circuit board. Since the source of the VT2 field effect transistor is also its case, it should be insulated with a mica or synthetic film when installed on a radiator.
At full load, the transistor on the heatsink becomes warm. Cooling can be enhanced by using the fan in the computer unit. Such a cooler is connected from the factory through a thermistor installed close to the radiator. The resistance of the thermistor at room temperature is about 400 ohms, as the temperature rises, it decreases, and the fan starts to rotate faster.
It remains only to connect the cigarette lighter plug to connect to the car's on-board network.
The circuit is also available at //radiokot.ru/circuit/power/converter/45 and on the author's website //microscheme.blogspot.ru/2011/03/blog-post.html
Automotive chokeless PSU on IRS2153 for laptops and mobile phones External USB socket in car radio We connect the mobile phone to the radio Do-it-yourself USB socket in the car
The goals were set as follows:
1. First of all, the author set himself the commercial interest of this project, so the cost should tend to zero.
2. Simple circuit and practical implementation (100% repeatability).
3. Small dimensions, low heating (no radiators sticking up and forced cooling), low profile (the latter is due to the fact that the author has cases from PSU printers, scanners :).
4. The converter must be suitable for ALL LAPTOPs (if necessary, it could provide power of at least 120 W for a certain time, which is typical for starting to charge the batteries of powerful laptops).
I started my search from the Internet and this is what he gave birth to me:
1. Scheme by an unknown author.
Having assembled this circuit and confirmed our assumptions that the UC3843 output driver at a switching frequency of 150 kHz (this frequency corresponds to the indicated ratings R2, C2) gives such blockages of the fronts of the control pulses at the VT1 gate, which leads to an unacceptable (according to the author) key heating due to dynamic losses during switching. By adding an external driver on discrete elements, the situation improved, but the result still did not satisfy the set goals. From it at normal temperature (not higher than 60 degrees), more than 3.5A cannot be squeezed out. And the losses in the current-measuring resistor are quite large, which gives it not only dimensions, but also heating, and in a closed case this will decide a lot. It is impossible not to say about the advantages of this circuit solution. A high switching frequency automatically reduces the values of the input and output capacitors, although at the same time it places high demands on their quality (low Equivalent Series Resistance), and the value of the inductance is relatively small, which makes it possible to reduce its dimensions with good hardware .
2. Scheme from the author Michael Schon.
Everything would be fine (except for the 96% efficiency declared in the efficiency, although the author did not find such possible data in any reference literature on the design and practical implementation of these converters, and everywhere the bar was indicated at 89% with which I absolutely agree), but this scheme and especially its practical implementation did not meet any requirement. Therefore, the author did not collect and experiment with it. Maybe abroad you can buy everything or even order it, but where can you get so many capacitors, and the size of the throttle with radiators was not satisfactory.
It was decided to do it yourself and from what is! And since the author is part-time engaged in repairing computers, then there was something to do from. The main direction of constructing the circuit was to increase the operating frequency of the input and output filters in order to reduce their capacitance and dimensions, respectively, as well as load distribution and, consequently, heat losses, due to the introduction of a second power channel. Such a circuit technique was prompted by the study of the multi-phase formation of the power supply of processors on motherboards. Where, in principle, all the necessary details were taken. Only the well-worn TL494 was chosen as a PWM controller (it is in almost every PSU for a PC older than 2-3 years), but not the 4-phase SC2643VX from the motherboard. Almost all the necessary components were taken from the EPOX motherboard (the author has a pile of such under the ceiling). Well, here's what happened:
The TL494 piping is almost identical to the standard piping in a PC power supply, except that the oscillator has an operating frequency of about 290 kHz (unfortunately, the 300 kHz bar is indicated in the documentation for the microcircuit). I would like to note that the soft start circuit (R12, C7) in any boost converter having such a circuit technique is simply mandatory, since the converter operating in the continuous mode of the inductor current (the code stored energy in the inductor is stored until the next charge cycle) has a slow transient response, then the probability overvoltage is very large. A soft start eliminates overvoltage on T1 and T2, although there is a possibility of overvoltage as a result of load shedding, but this is a disaster for all converters of this kind. Fortunately, this converter can only enter this mode at a duty cycle of 50% or higher, but this is limited by the microcircuit itself, so there is nothing to worry about, but it does not hurt to play it safe. As for measuring and limiting the current, a piece of wire shunt from an old Tseshka about 10-15mm long (10-12 mOhm) was used for measurement. The top amplifier, which is part of IC1, provides current limiting, and by varying the resistors R3, R4, you can set the desired level. I would like to note that in any galvanically non-isolated boost converter, the concept of current limitation is rather relative, because in the event of a short circuit in the load, the current cannot be limited using a PWM controller - after all, even with private keys T1 and T2, a short-circuit current will flow through diodes D1 and D2, and the "current limiting level" implies that the circuit will limit the current through the inductor and switches, and as a result, when the load is exorbitant, the output voltage of the converter will simply drop. Therefore, fuse F1 is simply mandatory for emergencies.
The converter uses specialized SC1211 microcircuits, which are drivers for a buck converter with a synchronous rectification function (for those who do not have a motherboard with them, you can use other suitable ones such as RT9601, RT9602 and many others, which, by the way, are also on video cards, with the corresponding circuit correction, but below there will be a driver circuit on discrete elements). There was an idea to implement synchronous rectification in this device, but since the SC1211 is a driver for a buck converter, it does not implement the locking of the upper synchronous key in the function of the direction of the inductor current, but on the contrary is implemented for the lower one (the author uses the concept of "upper" and "lower" taking into account the fact that instead of D1 and D2 there are MOS transistors and with the keys T1 and T2 they form half-bridges). And without this driver function in the intermittent current mode of the inductor, there will definitely come a moment when the stored energy in the inductor runs out and the time for the output capacitor to work comes, only this stage will not be monitored, and the current from the capacitor will flow not only into the load, but also into the + 12V bus through a synchronous rectifier switch and a choke. This is the unwanted mode. Therefore, this project is still in development, and its use at low capacities is not economically justified.
As for the binding of the SC1211, I do not recommend increasing the ratings of R5 and R6, since at a value of 10 kOhm, the signal at the switching input of CO (4) -SC1211 has a sawtooth shape (due to the capacitance of the input), which leads to a delay in the trailing edge of the turning off key and, as a result introduces an additional zero into the transfer characteristic of the control loop, and because of this, instability and excitation of the system may occur. Capacitances C8 and C9 should be sufficient to ensure that they are enough for a guaranteed charge of the capacitance of the gates of the keys, otherwise all the work will fall on the internal source of the stabilized voltage SC1211 with its subsequent overheating (during the commissioning work, an accidentally fallen off capacitor led to the instant formation of a hole in the SC1211) .
Details.
As I said, almost all the necessary parts were taken from motherboards. I am enclosing a photo of the donor (Elitegroup motherboard model K7S5A, although the author prefers to use boards with SC1211 drivers, he simply assumes that those who want to assemble the converter may not be able to get such boards):
The green arrow in photo No. 5 indicates the desired "organs". This instance has on board and ring chokes, switches, Schottky diodes and input capacitors with good ESR (ATTENTION! On K7S5A, the voltage of the input capacitor, depending on the version of the board, can be 6.3V), and even TL494, and green ovals in photo No. 6 planar field-effect transistors are marked (marking on the case sSG25 or 702, these are all 2N7002 from different manufacturers) for use in a discrete driver. Such on any "mother" shaft just look closely. By the way, in the area of \u200b\u200bthe sound chip (usually marked ALC668: depending on the installed one), there is also a 78L05 stabilizer that can be used to power the gates of power switches. You can raise the level using two diode assemblies marked A7W to the level of 7-8V, since many sources indicate a voltage of 8.5V as optimal for low-level switches in terms of reducing dynamic losses. In the diagram, this node is in the red dotted line; it can also be implemented with a conventional parametric stabilizer. I do not recommend making it higher than 8V, since the difference between +11V at the input (in the worst case "battery is low") and +8V will be small, and this level will be used to control the upper half-bridge key of the driver.
I would like to dwell a little on the manufacture of parallel step-up chokes L2 and L3. On motherboards there are ring ones, and pin ones in an anti-ringing casing (square). Preferably ring, as the manufacturing process will be easier. It is necessary to wind the existing wire and wind it, two are wired in parallel (I couldn’t fit more than two) with a diameter of 0.6 mm each, about 18-20 turns (this can be difficult because the window is small). During the operation of the inductor, they heat up, but not the iron itself, but the wire, which indicates a lack of conductor cross-section and a decent effect of the skin effect, but, unfortunately, this is the price for low profile, by the way, this is one of the reasons why the decision was made about the use of two parallel coils. The repeatability of the coils is 100% since they all stood in one place and also worked in parallel. And the search for a core that meets the requirements did not bring anything, because most of the available ones worked in the range of 60-100 kHz, and on the motherboard each of the cores worked at approximately a switching frequency of 300 kHz and with a duty cycle of no more than 20%, which indicates its good magnetic properties.
The operating mode of the converter is mixed. Each channel separately operates in intermittent current mode, which provides a fast transient response and a decrease in losses during switching on the key, since when it closes it does not break the current of its inductor that flows into the load (by that time another channel is already working and the diode of this channel is biased in the opposite direction). And working together for one load, two channels provide a continuous current in the load due to their inductor currents, practically without resorting to the help of a capacitor at the output. The output capacitor works significantly only at a low duty cycle, when there are dips between the inductor currents. I would like to note that the inductance calculations were carried out as for a single-channel converter operating in the intermittent choke current mode, and the output capacitance calculations were carried out as for a single-channel converter with doubled frequency and continuous choke current. Tests have shown that the two-channel scheme has absorbed the advantages of two modes. Namely: the intermittent current mode of the inductor of each of the channels gives a fast transient response and low losses on the key, and since the currents of the two inductors are superimposed on each other, the result is a continuous current of both double-frequency inductors and the output capacitor is required very small ( according to calculations, about 50uF per 100mV ripple at the output). But the author decided not to skimp, so an output capacitor of 100-470uF with an ESR of no more than 0.3 Ohm will be enough, especially since the size will be small (the ESR can be slightly reduced by paralleling it with a ceramic or polymer capacitor).
As for the T1 and T2 switches, these are N-channel UltraFEETs with very low Rdson (open channel resistance) and they are all from the same place, and their typical parameters are 30V drain-source voltage and 50-80A peak current. Be careful on some boards there are 20V instances, which will be fraught with: I suggest IRFL44 as their replacement (the choice is determined by price and availability).
Inductors L1, C18 and C19 are an optional high-frequency noise suppression filter in the car's on-board network and, if the design is budget-friendly, they can be omitted.
The device can be supplemented with circuits for signaling the presence of a +19V output and warning that the battery is low. Here are my options:
It may be necessary to match the ZD6 zener voltage to the red LED firing level, depending on your warning preference. With an LED that has a forward drop of about two volts and a 6V zener diode, the threshold is about 11V across the battery (because the output is stabilized).
In the circuit with drivers based on discrete elements, a classical two-phase field-switch circuit is used (any modern low-power N-channel transistors can be used). The author deliberately did not use the driver on N and P-channel keys, since there are not very many P-channel on mothers, and non-mainstream media do not inspire confidence.
And here is the circuit with drivers on discrete elements:
Assembly and adjustment
1. We breed the board while separating the power circuits from the signal circuits.
2. We solder all the components and check the frequency at the gates of the power switches (about 145 kHz), and also look at the steepness of the fronts.
3. We wind the throttle (18-20 turns, but leave one end about 10 cm long).
4. Solder one inductor, turn on and check the + 19V output (adjust using R7-R11.).
5. We find a suitable load and load the ampere by 3.
6. With simple manipulations, we measure the efficiency (with a stable load and input voltage, you can focus on the input current) and if it is within 88-89%, then everything is normal.
7. Turn off and wind up, if there is where, three turns. We repeat point 6 and conclude that it is better.
Having thus chosen the best value of the inductance for this coil, we unsolder it and carry out the same manipulations for the other, equalizing their readings. This is necessary to evenly distribute the load and losses.
8. We solder both coils and turn on, load, check:
9. After we made sure that everything works, we set up the current limit. This is done by applying the maximum selected load (output current 8A, 6A, 5A :) and reducing the value of R3 until the output voltage starts to drop. This will be the current limiting threshold. If a very short and low-resistance shunt is used, then it is possible that R3 is short-circuited, and the output voltage has not dropped. Then it is necessary to increase the value of R4 by two to three times and repeat the setting.
Thermal regime
I would like to especially note that the main losses and heating are quite localized and limited by the diodes D1 and D2 and the actual losses in the copper coils. At a load of 6A (19V), the diodes gradually and steadily heat up to about 40-50 degrees (planar mounting), therefore, by soldering small copper plates near the diodes, you can slightly improve their condition, taking into account the fact that with an increase in their temperature, losses on them also increase (the reverse leakage current increases, which at such a frequency and at such currents is already not small), from which the loss of efficiency percentage follows. I hope synchronous rectification will solve these issues.
The photo shows one of the sides of the finished board. Despite the permissible deviations from the recommended ratings and manufacturing methods, this instance showed its full performance at an output current of 8A and an output voltage of 19V. Also in the photo you can see the same plates near one of the diode assemblies. Do not be surprised that the diode assembly is in D2PAC, and the key is in DPAC. At a load of less than 100 W, the key practically does not heat up, and the copper to which it is soldered is quite enough to cool it.
Outcome
So, it turned out that from one motherboard with a 4-phase processor power supply and using SC1211, you can assemble two such converters, even if you burn a couple of three keys during commissioning (there are at least 12 of them on the board, 3 for each phase) and there's still a whole bunch of other details left. You can get such boards at the nearest computer service for a couple of bottles of valerian, but the author prefers to advertise the purchase of non-working computer junk and they are delivered to him directly at home for 1.5 - 2 USD.
What does the technical and economic comparison of this option show? For a couple of c.u. having bought a board and bought two TL494s, two pieces of textolite 6x10cm, two cases, two pairs of connectors and about 5m of a suitable wire, you can assemble two converters in one day, which are sold in the nearest store for at least 30-35 USD. every. And this despite the fact that the total cost of two converters, as a rule, does not exceed 6-8 USD. It is possible to earn or save decently on this, and this is no longer a question for the author. But will you do it? This remains a question.
The photo shows a finished device in a case from an HP printer with alarm circuits and a scaling
Section: [Voltage converters (inverters)]
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A laptop is undoubtedly a necessary device, but the problem is that its battery does not allow you to work with it offline for more than 2 - 3 hours.
Therefore, it will be logical, when moving by car, to power and recharge the laptop from the on-board network of the car. But, unfortunately, most laptops run on 19 volts, not 12 volts.
There are few options here ... The solution to this problem can be do-it-yourself car adapter for laptop in the form of a DC voltage converter (DC - DC), which raises the battery voltage from 12 to 19 volts.
To date, there are many electrical circuits of DC-DC converters, changing the ratio of the resistance of the measuring voltage divider. which it is possible to obtain various values of the output voltage, practically from zero to 50 V.
Description of the laptop adapter
This laptop car adapter can operate from 10 to 15 V, and at the output it will be able to provide 19 V at a load current of up to 2.5 amperes. With the adapter, there is also an electrical circuit for protection against lowering the input voltage. less than 10 V and against output overload.
The duty cycle signal controller is made on a special chip UC3843 (A2). The electrical circuit of the car adapter is almost standard. The output signals go to the gate of a powerful key field effect transistor VT1. The conversion takes place at a frequency of approximately 50 kHz. Voltage pumping takes place on L1. The adapter rectifier is made on a VD5 Schottky diode. The ripples are smoothed out first by C10, after which there is a filter of 2 inductances L2 and L3 and 2 capacitors C9 and C8.
Output voltage size laptop car adapter is determined by the resistances R11-R12. They create a voltage divider, the ratio of the shoulders of which should be such that at the desired voltage. at the output, on pin 2 A2 there was a voltage of 2.5 V. With the values \u200b\u200bof the resistances R11 and R12 shown on the adapter circuit, the output voltage will be constantly at the level of 18.75 V.
Since the instances of resistors, as usual, have differences in ratings, when adjusting the size of R11 (and maybe R12) it is necessary to choose such that the output voltage is 19 V. This can be done by including additional resistors of a significantly larger value in parallel with this resistance. On the printed circuit board of the laptop adapter, there are places for them. By including resistors in parallel with R11, we reduce the output voltage, and in parallel with R12, we increase the output voltage.
The coils are assembled by hand on ferrite rings. Coil L1 is made on a ferrite ring with a diameter of 23 mm. It has 60 turns of PEV 0.61 wire. Coils L2 and L3 are assembled on ferrite rings with a diameter of 16 mm. They have 120 turns of wire PEV 0.43.
Coils L1-L3 are arranged vertically. Initially, they stand on their own conclusions, and at the end of the adjustment they are attached with a sealant. All capacities must be rated for voltages over 25 V. Diodes 1N4148 can be changed to KD522. Diode 1N4007 can be changed to KD209 or removed from the circuit altogether, however, in this case, if the polarity of the input voltage is connected incorrectly. the electrical circuit may burn out before the fuse FS1.
PCB with components and instructions in the package.
This kit will allow you to assemble a switching converter with an output voltage of 19 V and a maximum output current of 5 A to power portable computers: laptops, netbooks in a car. On long trips and long city traffic jams, your equipment will not suddenly turn off due to a dead battery.
The device is a powerful DC-DC converter for powering portable computers from the car's on-board network, car battery or any other 12...14 V voltage source of appropriate power.
The converter is based on the SG3845 PWM controller chip, which converts the DC input voltage into a high frequency AC voltage. Conversion frequency - 90 kHz. To control the output inductor, a powerful field-effect transistor VT1 is used. The stabilization of the output voltage is also carried out by the microcircuit, for which an error signal from the divider R9, R10 is applied to pin 2.
The output AC voltage is rectified by the VD2 diode assembly and smoothed by capacitors C7 ... C9.
The input choke L1 is necessary to prevent the penetration of high-frequency interference into the vehicle's on-board network.
Characteristics:
Supply voltage range: DC 12...14 V;
Rated output voltage: DC 19 V (±5%);
Maximum load current: 5 A;
Maximum current consumption: 10 A;
Conversion frequency: 90 kHz.
Assembly complexity: 2 points;
Assembly time: About 3 hours;
Operating temperature range: -10...+50 degrees Celsius;
Relative humidity: 5...95% (non-condensing);
Packing: Blister;
Package dimensions: 200 x 122 x 38 mm;
Device dimensions: 91 x 61 x 48 mm;
Total weight of the set: ~96 g.
Contents of delivery:
printed circuit board;
A set of radio components;
Coil of tubular solder POS-61 (0.5 m);
Wire coil PTV-2, 0.8 mm (2 m);
A set of hardware (M3);
Instruction manual.
Note:
Attention! It is strongly NOT recommended to connect the converter to the car's cigarette lighter socket! The device is connected directly to the battery terminals through a 30 A fuse included in the gap of the positive wire with a cross section of at least 6 mm 2
.
Connect the load (laptop computer) to the converter with a wire with a cross section of at least 1.5 mm 2
.
The manufacturer of this construction set is NOT responsible for any consequences for your car or portable electronics resulting from the use of this device.
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