Car charger for cell phone. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Car charger for cell phone. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Chargers, batteries, galvanic cells

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The charger circuit is shown in Figure 2, it is a DC-DC converter that provides a stable voltage of +5 V at a current of up to 0,5 A and an input voltage within 7 ... 18 V. Looking at the circuit, the question may arise - why such difficulties, when, it would seem, you can get by with one "roll"? The question is fair. Indeed, a similar charger can be made, for example, according to the diagram in Fig. 1.

And such a scheme will work. But, pay attention to the fact that KR142EN5A is a conventional linear stabilizer, and with an input voltage of 12 V and a load current of 0,5 A, the power that will be dissipated in the control transistor of the KR142 microcircuit. EH5A can be more than 6 watts. The microcircuit will heat up, a sufficiently voluminous and heavy radiator will be required. Not to mention the low efficiency of such a scheme.

The scheme shown in fig. 2 operates as a switching source and dissipates very little power during normal operation. There is absolutely nothing here that needs heat dissipation. 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 design.

(click to enlarge)

Of course, there is also a minus - the circuit is much more complicated, contains many parts, the total cost of which is significantly higher than the price of KR142EN5A and a pair of capacitors.

"Charging" is connected to the car's cigarette lighter. The diode VD1, just in case, protects the circuit from the wrong 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 in the network of a not very new car.

The main components of the converter are assembled on the A1 chip - 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 microcircuit. 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 factor depends on the position of the slider of the tuned resistor R5.

With this resistor, when setting up the converter, the required output voltage is set (in this case, it is 5 V).

Details. Diode VD1 - any rectifying silicon diode with a permissible forward current of at least 0,7 A. VD2 - a medium power zener diode, with a stabilization voltage of 20-30 V, VD3 - a diode with a Schottky barrier with a permissible forward current of at least 2A. VD4 - medium power zener diode with a stabilization voltage of 5,0 ... 5,6 V. HL1 - any indicator LED.

Please note that for all diodes and zener diodes, the types of which are indicated in the diagram, the cathode is marked with a belt on the case.

Capacitors C1 and C4 are any electrolytic small-sized ones, for example, K50-35 or JAMICON, with a permissible voltage C1 - not less than 20 V, C4 - not less than 6,3 V.

Resistors are common. Resistors R1, R2, R3 can be replaced with one 1 W resistor with a resistance of 0,3 ohms. The resistor must be non-conductive.

Coil L1 is wound on a ferrite ring with a diameter of 16 mm, wire PEV - 0,47 is used for winding. The number of turns is 80. The winding is evenly distributed over the entire circumference of the ring.

All parts are placed on a printed circuit board, the installation and wiring of which is shown in Figure 3.

The board is placed in a plastic case measuring approximately 120x30x20 mm. Two cables come out from the ends, one of which ends with a standard connector for connecting a portable lamp to a car cigarette lighter, and the second with a plug like that of your mobile phone charger.

If all the parts are in good condition and there are no installation errors, adjustment is just adjusting the output voltage with resistor R5.

The same circuit can be used to charge the battery. MP3 player, for example, by making an output cable with a USB connector, you can charge the battery. MP3 player iPOD or similar. In principle, on the case of the charger, you can install some kind of connector as X2, for example, USB (+5 V on pin 1, -5V on pin 4), and make several interchangeable cables (for a telephone, radio station, MP3 player, etc. .). If you need a different voltage, reconfigure the R4-R5-R6 divider accordingly and replace the VD4 zener diode.

Author: Kuleshov M.

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Charity slightly corrupts 09.12.2015

You can often hear that you need to help a hungry person not with money or food, but give him a fishing rod or a gun so that he can get this food for himself. Otherwise, with money in hand, a person will become lazy, lose all activity and sink even deeper into poverty, expecting that sooner or later everything will fall into his hands. Although the theory is controversial, we are already somewhat accustomed to it. But researchers from the University of Amsterdam claim something more strange - they believe that selfless donations have a bad effect on the moral character of the one who donates.

Psychologists used a charity fundraising campaign that took place on Christmas Eve in several Dutch cities: people were invited right on the street to make a donation to the Red Cross and other similar organizations. Those who were noticed near the fundraising point were asked to answer several questions about whether they made a donation and how large, whether they are involved in charity at all, and whether they are ready, for example, to live in a way that does less harm to the environment (relatively speaking, I wanted to would a person pay for environmentally friendly electricity, and whether he would like to sign some kind of environmental petition). In their article in Social Influence, the authors of the work write that those of those surveyed who made a donation during the last week were less likely to do so afterwards. That is, the same environmental problems touched them less, and they were less willing to pay more for green energy and sign petitions than those who had not yet had time to perform an act of charity. Moreover, the size of the contribution, which is curious, did not play a role, the desire to participate in something similar fell regardless of whether the person contributed five euros or a thousand.

In fact, psychologists have long been discussing the so-called "license effect", when a good deed, as it were, gives permission to be slightly bad. Such psychological bargaining with oneself generally occurs often: for example, when a person, after going to the gym, immediately goes to some eatery to eat something fatty and sweet. In the socio-economic sphere, this is manifested in the fact that we, as it were, get from another source what we spent in the right (good, altruistic) act. So, two years ago, an article was published in Energy Policy, which described how people who agreed to save water for environmental reasons began to use more electricity.

However, this effect is not too large (although statistically significant) and depends on other factors. For example, in the case of Christmas donations, those who donated money frequently in general responded very readily to environmental proposals. That is, let's say, the general moral character of a person plays a role: one who is greedy by nature can give in to a momentary impulse, but then he will try to compensate for the "damage". In addition, as psychologists themselves say, we still need to figure out the motivation for donation: it is possible that someone just drowns out the feeling of guilt because of some misconduct in the past, and his subsequent “slightly bad” behavior is quite a common thing, not related to the charity gesture just made.

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