It never hurts to have your own car, in addition to the cigarette lighter socket, and even first connector, adapted to USB or even mini USB. Such adapters are useful in many cases, for example, to power peripheral equipment of PC, charging mobile phones, video recorders of events and everything is designed under USB power. This is quite possible.
With a relatively small load currents (0.5 A) when not required to achieve maximum efficiency, can be greatly simplified circuit diagram for the voltage regulators, provided that the input voltage is already quite stable. It’s like one of those times.
The device is made on the basis of the DC-DC Converter on the chip МС34063А company ON Semiconductor. МС34063А combines a comparator, a pulse generator (100 kHz), the driver’s internal temperature-compensated voltage reference and a powerful output key (Fig. 1).
Photo 1. Appearance modified splitter
Photo 2. The appearance of the printed circuit Board with mounted discrete elements and a microchip
The input voltage of IC – 3 to 40V, maximum output current, specified in the reference data, and 1.5 A. However, in my opinion, the current chip in the hull DIP-8 (photo 1) can be given only in emergency, disaster and short-term mode. The safe current for this chip installed without the radiator and other elements of the ventilated cooling, must not exceed 0,3…0,4 A. In our case, this is consistent with the task.
Electric Converter circuit is shown in figure 2.
By the way, there are different ways of increasing the output current IC МС34063А. About these options can be independently read in literature and on Internet forums. For example, if you increase the inductance of the inductor, the voltage and current in the load can also be increased.
The output of the Converter no need to install oxide super capacitor. First, the input voltage is in the car and so is quite stable, and second, internal chip protection МС34063А is triggered, not allowing the Converter to operate normally.
Analog IC МС34063А – КР1156ЕУ5; possible replacement for АР34063, NJM2360, KS34063.
The device used resistors MLT-0,25 or similar imported type MF-25. Oxide capacitors C1 and Sz – type K50-29 or similar.
VD2 diode – Schottky diode 1N5819 replacement for the 1N5817 or 1N5818. This diode is designed for a current equal to the load current.
Fig. 1. Diagram of the internal nodes МС34063А and its analogues
Fig. 2. Electric diagram of the device adapter for USB on-chip МС34063А
Inductor L1 is a coil on a rod length of 8 mm ferrite brand 2000НЦ contains 40 turns of wire of PEV in diameter of 0.75 mm. the resistance of L1 does not exceed 0.1 Ohm. Such a coil can be purchased at the shop of electronic components in finished form (for example, the DM inductors with magnetic core). The only condition: the throttle And must be able to withstand current up to 1A inclusive (with a reserve).
Zener diode VD1 in this case to protect the input circuits on the chip DА1 surge. You can replace 1N4745А (with voltage stabilization 16 In) or even exclude entirely, because this chip is designed for input voltage up to 40 V.
Figure 4 shows the USB connector, built-in car splitter, inside of which is fixed a printed circuit Board device (photo 1).
A. KASHKAROV, St. Petersburg
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