Laptops today are the what is called notebook computers, which now is becoming popular. Laptops can be brought into the bag making it suitable for business trips. And even as the “home entertainment center” laptop is more convenient, because it takes a little space. However, in my opinion, there is one very important which become shortcomings – most laptops which powered by an electric voltage of 19V, making it impossible for them to direct the power to an integrated network vehicle (12-14V). It is very important, especially when laptop battery capacity is not more than two hours in active mode. And what if you, at some object in the whole day want to process some data, but no other useful sources of electricity?
The adapter is based on chip LM3524, which is a high-frequency switching DC-DC converter with pumped inductance and output current up to 200mA, the output current which, in this scheme, will increased to 3.5-4A using a powerful transistor switch (on transistors VT1 and VT2).
Consider the circuit carefully. Voltage on-board vehicle network goes to supply circuit and output circuits D1 through key fuse F1 and low-resistance wire resistor R6, mitigating start the generator and the circuit operates in overload protection. Current consumption chip D1 determines the voltage at R6, enter the inputs of overload switching – Conclusions 4 and 5 D1. The voltage on the R6 increases with what greater than the load current (and actual current consumption from the source).
A pair of output transistors connected in parallel circuits D1 (emitter terminals 14 and 11, collectors – the outputs of 12 and 13). Loaded with collectors of output transistors a resistor R10. With this resistor pulses are fed to the non-inverting switch on transistors VT1 and VT2. Transistor VT1 is the pre-inverter, and s as the output transistor VT2 uses a powerful field-effect transistor with a small key resistance of the open channel. Due to the low impedance of the open channel, in spite of considerable current, power dissipated in it is small, and almost no heat sink required. Exclusively “to ensure” it is installed on the radiator plate output transistor Vertical TV type 3 USTST (plate size of approximately 25h35mm).
Pumping voltage is on the inductor L1. Diode VD2 rectifies the pulses of self-inductance and across the capacitor C11, there is a constant voltage.
In order to stabilize the output voltage using a comparator inputs are, pins 1 and 2 D1. On pin 2 through a divider R1-R2 is fed from the internal reference voltage regulator circuit (output of the stabilizer, – output 16). At the output a voltage is applied from the output of the power supply, low divider R3-R4-R5. The value of the output voltage depends on the ratio of the divider apart, and set trimmer R4 (in fact, ranging from 15 to 22 volts). It is desirable that the resistor R4 was multi-turn – so its installation is more accurate and more stable.
- The coil L1 is wound on a ferrite magnetic core ring outer diameter of 28mm. A total of 30 turns
- Diode VD2 (Schottky diode) should allow a direct constant current of at least 5A.
- BU278 transistor can be replaced by any other similar transistor, for example, BUZ21L
- LM3524 chip is desirable to select a DlP-body (easier to solder). You can replace a chip SG3524, but other production.
- Resistor R6 – wire, with a capacity not less than 2W.
- All capacitors must be rated for a voltage below 25V.
- When connected to a vehicle on-board network, you must strictly observe polarity. Otherwise, the inverter fails. Optimally – Connect directly to battery terminals. In this case it will be a minimum of interference. Converter housing must be shielded.