We are building a universal machine USB charger (attempt number one). Car charger for a mobile phone DIY car charger for a phone
Recently I ordered a tablet computer from one of the online auctions and, purely out of curiosity, decided to assemble it charging from on-board network car 12 Volts, although I don’t have a machine yet :) It was necessary to develop a circuit with an input power of 12 Volts, and an output of 5-6 with a load current of at least 3 Amps.
You cannot use a standard linear voltage stabilizer from the 78XX series here, since the maximum current of such stabilizer microcircuits is limited to 1.5-2 Amperes. It was decided to assemble a voltage stabilizer using a zener diode and a power transistor.
A powerful bipolar transistor KT818GM or any other similar power was used as a power component. The zener diode is a domestic low-power zener diode with a rated stabilization voltage of 4.7-5 Volts, the maximum value of the stabilized voltage is 10 Volts. You can use another zener diode with a similar stabilization voltage.
We install the power component (transistor) on the heat sink; heat generation may be observed.
The voltage of the electrolytic capacitor is selected to be 16, 25 or 50 Volts, the capacitance may deviate from the specified one by 20% in one direction or another………………
The output current of such charging directly depends on the transistor used; in our case, the current is about 4-5 Amperes, which is more than enough to charge any tablet computers.
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This circuit can be used to charge mobile phones, MP3 players and CD players and power them in a car.
The finished circuit turns out to be very compact and can fit in a compact case, no larger than a matchbox.
Buy ready-made charging to the phone not interested). Make with your own hands much more interesting, especially since such a simple and reliable device has already been tested. And she didn’t want to borrow the cigarette lighter. I found out about such a thing as KR142EN5A. Advantages of this microcircuit:
- Allowable output current 1A
- No external components required
- Internal thermal protection
- Output transistor protection
- Internal short circuit current limitation
The input voltage is up to 20 V, and the output is always 5 V. Actually, this is what is needed in order to reliably charge the phone battery. There is nothing complicated about assembly. We solder four wires to the circuit (we solder two terminals to the central leg - this will be “ground”). The left terminal is “+” input, the central one is ground, the right terminal is “+” output.
I had an old broken charger, I cut off the plug from it and soldered it to the microcircuit.” +” plug to “+” at the output from KR142EN5A, and “-” plug to circuit ground. It turns out that there is a common ground wire for the input and output. In the car I dragged the wires to a convenient place where the phone is always kept, and connected permanently via a button). I pressed the button, inserted the plug into the phone and started charging). Here I am posting photos...
But then I had to improve the circuit a little, since familiar “minds” recommended installing two 1000 uF capacitors. The result is this diagram. I recommend installing the condensers right away, although everything worked without them... And placing the microcircuit itself on a small radiator (just to be sure)
In order to charge any portable device, such as a phone or tablet, from the car’s 12-volt on-board network, you will have to use a DC-DC converter. But it is not necessary to buy an inverter when you can assemble, for example, a very simple design based on the 34063api chip yourself.
The chip is specially designed for this purpose, and many charger manufacturers use it as the main driver in car chargers. It was this microcircuit that became the base for most “chargers” powered by a cigarette lighter.
The microcircuit has a built-in output stage that delivers current up to 3A to the load. Thanks to this, it can be considered universal - it can charge almost any mobile device, including devices with large batteries, such as tablet computers.
The microcircuit provides a stable output voltage of 5 Volts. It is optimal for recharging the batteries of a wide variety of portable devices. The choke consists of 20 turns of 0.6 mm thick wire wound around a dumbbell. Drops and surges in on-board voltage are not dangerous for the microcircuit, since the input voltage range is from 7 to 40 Volts.
The microcircuit operates stably even with sudden temperature changes and weather changes, without overheating in the process. You can connect 34063api using several schemes. Here is the most reliable option, which is also simple and easy to reproduce.
A particularly valuable quality of this microcircuit is that it is possible to simultaneously connect several mobile phones to the output. At the same time, the quality of charging, even if all models are different, will be no worse than through a standard device. You can also exclude input and output capacitors from the circuit, which are needed only to filter noise.
The charger circuit is shown in Figure 2; it is a DC-DC converter that provides a stable voltage of +5V at a current of up to 0.5A, and an input voltage within 7..18V. Looking at the diagram, the question may arise - why such complexity, when, it would seem, you can get by with just one “crank”? It's a fair question. Indeed, similar Charger can be done, for example, according to the scheme in Figure 1.
Rice. 1
And this scheme will work. But, please note that KR142EN5A is a regular linear stabilizer, and with an input voltage of 12V and a load current of 0.5A, the power that will be dissipated by the control transistor of the KR142 EH5A microcircuit can be more than 6W. The microcircuit will heat up and will require a fairly large and heavy radiator. Not to mention the low efficiency of such a scheme.
Rice. 2
The circuit shown in Figure 2 operates as a pulsed source, and during normal operation dissipates very little power. There is absolutely nothing here that requires heat removal. In addition to the fact that it has a very high efficiency, this scheme allows you to assemble the adapter in the form of a very light and compact structure.
Of course, there is also a minus - the circuit is much more complicated, it contains many parts, the total cost of which is significantly more than the price of KR142EN5A and a pair of capacitors.
The “charger” is connected to the car’s cigarette lighter. Just in case, diode VD1 protects the circuit from incorrect polarity of the input voltage (suddenly the cigarette lighter was changed and connected incorrectly). Zener diode VD2 - protection against short high voltage pulses that may be present in the network of a not very new car.
The A1 chip contains the main components of the converter - a pulse generator, a pulse width regulator and a measuring comparator that compares the output voltage with the reference voltage generated by the internal stabilizer of the chip. The input of the comparator is pin 5. It is supplied with voltage from the output of the circuit through a divider on resistors R4-R6. The division coefficient depends on the position of the slider of the adjusted resistor R5. When setting up the converter, this resistor is used to set the required output voltage (in this case it is 5V).
Details. Diode VD1 - any rectifying silicon diode with a permissible forward current of at least 0.7A. VD2 is a medium power zener diode, with a stabilization voltage of 20-30V. VD3 is a Schottky barrier diode with a maximum forward current of at least 2A. VD4 is a medium power zener diode with a stabilization voltage of 5.0-5.6V. HL1 - any indicator LED.
Please note that all diodes and zener diodes, the types of which are indicated in the diagram, have a CATHODE marked with a belt on the body.
Capacitors C1 and C4 are any electrolytic small-sized ones, for example, K50-35 or JAMICON, with a permissible voltage of C1 - not lower than 20V, C4 - not lower than 6.3V.
Resistors are ordinary. Resistors R1, R2, R3 can be replaced with one resistor with a power of 1W and a resistance of 0.3 Ot. The resistor must be non-wire.
Coil L1 is wound on a ferrite ring with a diameter of 16 mm; PEV wire - 0.47 is used for winding. The number of turns is 80. The winding is evenly distributed around the entire circumference of the ring.
If all parts are in working order and there are no errors in installation, adjustment is only an adjustment of the output voltage with resistor R5.
The same circuit can be used to charge the battery of an MP-3 player, for example, by making an output cable with a USB connector, you can charge the battery of an MP-3 player iPOD or other similar one. In principle, on the body of the charger you can install some kind of connector as X2, for example, USB (+5V on pin 1, -5V on pin 4), and make several replaceable cables (for a telephone, radio station, MP-3 player and etc.). If you need a different voltage, accordingly, reconfigure the divider R4-R5-R6 and replace the zener diode VD4.
Modern mobile devices have already become an indispensable part of our lives. First of all, we are talking about phones and tablets. We use them everywhere, at home, on the street, in the car. In the car, they are also supplemented by navigators, video recorders, etc. What is needed for the normal operation of these devices? Of course there is power, because any battery, even a very good one, will eventually run out.
You can buy a ready-made USB charger for everything we use in the car. But there may be problems with the number of sockets, power, etc. As a rule, the charger’s power is limited to a current of 0.5 A, although many are written at 1 A, but they are not able to withstand such a current.
As for my particular case, this charger, which is essentially a voltage stabilizer on the 7805 chip, was used to hide it under the instrument panel. As a result, having powered it from the cigarette lighter and hidden it under the instrument panel, only mini USB plugs were brought out to the instrument panel for the navigator and video recorder. This made it possible to provide power to gadgets while leaving the cigarette lighter sockets unoccupied. And perhaps the most important thing is to get rid of the wires that get in the way and their unsightly appearance.
So, in our article we will talk about an alternative, about making your own USB charger for a car based on a microcircuit - stabilizer 7805.
How to make a 1.5 Ampere USB charger in a car with your own hands (Option 1)
The voltage stabilizer of the L7805 series (current 1 A) or its analogue L7805CV (current 1.5 A) will be used as the “heart” of our charger. In fact, there can be a great variety of analogues used. In principle, the entire 7805 series of chips will be suitable for this. We will tell you more about analogues a little later.
Herself electrical diagram connecting the stabilizer is simple, it is similar to the power stabilizer, which we talked about in our other article “Power stabilizer in a 12-volt car.” We can say that these are brother microcircuits, only their stabilization voltages are different.
Everything can be assembled either by surface mounting or on a board. It can be done on a regular, simple universal circuit board. In order for the microcircuit to develop its maximum supply current, it must be placed on a radiator. In our case, the radiator is taken from a computer processor.
The stabilizer microcircuits themselves can be produced in various packages. Possible options housings and applied analogues are shown in the figure below.
Our assembly uses the TO-220 case... It is also possible to use microcircuits with the KIA 7805 index. A more detailed Data sheet for these microcircuits can be viewed.
Connecting a mini and micro USB plug from a charger in a car
After you have assembled the USB device, you need to connect the USB connectors correctly. You can take a wire with a factory-made mini, micro USB plug, or you can buy an “empty” plug in a store and solder the wire to it. Correct connection various types USB is shown in the figure below.
In my case, a mini USB plug was needed, which was soldered to the wire. The view is shown without the body.
Then, using a universal device, the voltage was checked again so as not to damage electronic gadgets. And then the battery of the audio player was already charged.
Subsequently, the charger was installed under the instrument panel, and mini USB plugs were brought out: one on the instrument panel for the navigator, the second under the roof for the DVR.
I apologize for the view in the garage.
A 5-volt car charger for a smartphone, navigator, DVR, tablet, built on the principle of PWM modulation (USB) at 4 Amps (Option 2)
However, the saga with the charger did not end there. Again, for a banal reason, when there is not enough supplied power or supply current for consumers, which is essentially the same thing, provided that the on-board voltage in the car is constant, since these values will be directly proportional.
So, during long-term joint operation of the navigator and the DVR, one microcircuit was not able to “pull” the power from these two devices, even with installed radiator. As a result, it overheated and briefly turned off. At the same time, the navigator “cussed” when the power was turned off.
There seem to be two solutions to the problem. The first is to “fence the garden” and create parallel circuits, each of which will have its own consumers. Let's say one is a DVR, the other is a navigator. In fact, in the photo above, where two microcircuits are mounted on one radiator, this is what was done. However, it’s good if everything is limited to this, and if you need to connect a smartphone, tablet, something else... There is no way to do without more serious currents, and therefore without alternative options. An alternative option would be to use microassemblies with PWM modulation. I won’t explain for a long time and in detail what this is, but the principle of all this is based on the fact that current is supplied to the load not constantly, but at a very high frequency. As a result, it becomes possible to reduce the heating of the microcircuit due to the very periods when it “rests”, and the load at such a high frequency perceives the power supply as constant, although it is not so...
So, such a scheme will not require large radiators for heat removal, and rather high currents will be provided. In general, everything will be as we need it. This option will be discussed further below. To reduce the voltage, a microcircuit, an inductor and elements for strapping are used. The microassembly is designated KIS3R33S,
Its installation can be done according to the diagram from Datasheet. However, by default with this configuration it has an output voltage of 3.3 volts, but for USB we need 5 volts.
In this case, it will be necessary to select resistors R1, R2. The table with recommended resistor values on which the supply voltage depends is also taken from the Datasheet. This feature of changing the voltage by selecting resistors makes this device a universal assistant if you need to power the load not only with a voltage of 5 volts as for USB.
It should be noted that this device confidently holds a load with a current consumption of 3A, and peak performance can reach 4A. If you are too lazy to assemble such a device, have no time, or cannot do it, then you can purchase such an assembly for about $2 on well-known sites and online stores.
I must say that this Chinese voltage converter KIS-3R33S (MP2307) is quite good for its price, and is capable of delivering high currents, which we already know, up to 4A. This means that such an assembly can replace a pair of KRENOK or the 7805 series, which we talked about in the first part of the article. At the same time, it will be more compact and with higher efficiency.
So, I bought this assembly. Then I also bought a distribution box, which are used for installing electrical wiring in apartments. This became the body of the converter - charger.
An LED was also attached in order to control whether voltage is supplied to this “box”. You can read about connecting an LED to 12 volts in a car in the article “How to connect an LED to 12 volts”. Everything was then installed under the dash, behind the glove box.
Connected to the cigarette lighter. Voltage appears on it only when the ignition is turned on, which is very successful for me.
The wires are still routed to the gadgets.
Now the charger current has increased to 4 Amps, which is still enough.
A special feature of this charger is that it can work both in passenger cars, where the on-board voltage is 12 volts, and in trucks, where it is 24 volts. At the same time, the charger does not require any modification or adjustment.
