A very simple and high efficiency step-up dc dc converter circuit that require few external components can be designed using the LM2700 step-up DC/DC converter with a 3.6A, 80mohms internal switch and pin selectable operating frequency.
With the ability to produce 500mA at 8V from a single Lithium Ion battery, the LM2700 is an ideal part for biasing LCD displays. The LM2700 can be operated at switching frequencies of 600kHz and 1.25MHz allowing for easy filtering and low noise. An external compensation pin gives the user flexibility in setting frequency compensation, which makes possible the use of small, low ESR ceramic capacitors at the output.
This circuit can be used for handheld devices and some other portable applications .
This step-up DC DC converter will provide a 12 volts DC output voltage from an input voltage range between 2.5 to 4.2volts .
In some electronics circuits you will need a dual 15 volts dc power supply . You can design a dual 15 volts power supply circuit using a 78L15 voltage regulator ( but in this case yo will need a power supply that will provide more than 15 volts ) or you can use this Flyback Regulator circuit designed using LM1577or LM2577 ( difference between them is the working temperature ) .
This power supply dc circuit will provide an dual 15 volts output ( plus and minus ) from an 5 volts input voltage . The circuit require few external components an can be very easy to design . This circuit will provide a maximum output current of 225 mA for each output .
The LM1577 LM2577 is available in different packages: 5-Lead TO-220 (T), 16-Lead DIP (N), 24-Lead Surface Mount (M), TO-263 (S) 5-Lead Surface-Mount and 4-Lead TO-3.
Pin numbers shown in the schematic are for the TO-220 package (LM2577T-15).
The 12V fixed voltage version and the ADJ version of the IC can be used too, for different output voltages. In case of the ADJ version if you must disconnect pin 2 from +Vout and connect it to the middle of a divisor made with 2 resistors in series. Calculate the resistors with the formula:
VOUT = 1.23V (1 + R1/R2)
T1 can be : PE-65300 (Pulse), 326-0637 (AIE), RL-2580 (Renco) or equivalents and D1, D2 are 1N5821 (Schottky Barrier Rectifier diodes) .
The L9407F is a monolithic multifunction alternator voltage regulator intended for use in automotive application.
It includes the control section, the field power stage, fault diagnostic circuit which drives a warning lamp, and the protection against short circuits.
As you can see in this schematic circuit you’ll don’t need any external components to use this regulator in your car .
The alternator voltage is compared with a reference voltage in an amplifier, whose output determines the switching frequency of output power MOS whose current excites the coil of the alternator; as the regulators are a self-oscillating type this frequency depends on the whole system parameter set including the alternator characteristics.
Main features of this car voltage regulator are : Low side field driver, Thermal protection , Field short circuit protection , Protected diagnostic lamp driver, Protected high side relay driver , Complex diagnostics , Load response control , DFM output .