One of my friends asked. Can we build the switching dc power supply circuit with 2 transistor? The applications IC that Sometimes is difficult. A some number IC is hard to find. and very expensive. When considering Applications for some time. We do not need to use a high current. and have sufficient space to install circuits. The selection use the transistors. Therefore as an alternative to saving, and extremely value for money. How it works In Figure 1 it is design of the switching regulator, which is a step down dc converter converts the voltage from 15-20 volts to a voltage of 12 volts. The important components is T1 act as switching and has a common components The main are L1, D1 transistors, NPN+PNP Acted to feed back to each other. Increased frequency generators or to Makes the switch to run continuously. Only in this circuit of coil is [...]

If friends would to want the DC to DC voltage converter is small that has a few output current. I would suggest the IC-555 is a key equipment that it is popular and easy to uses so can be used in many circuits. Doubler voltage 12vdc to 24vdc with NE555 This be Simple Doubler Voltage circuit, from voltage 12VDC to be 24VDC. By use Timer IC highly popular the number NE555 and other equipment a little again. It can give current get about 50mA convenient for the circuit, that use low current the small-sized. The principle works of the circuit be, When use Volt input 12VDC give with the circuit will touch Filter current smoothly with increasingly. The capacitors C5 give with IC1, The resistor R1,R2 and , capacitors C1, Which build the circuit model astable multi vibrator Square wave generator, at the frequency about 2KHz come out the way [...]

Suppose, you want to use the 5Vdc power supply levels up to 100mA, But there is only one single AA 1.5V battery. This working we need to use The DC to DC converter step up voltage. but will choose which is better circuit well, to create simple and small. I try to was looking on the internet, we should be use the IC packages best, because small and easy to build. I am interested in the number of IC LT1073, It is the micropower DC-DC Converter Adjustable and Fixed 5V, 12V, They has the shape as DIP 8 pin and Prodution by:http://www.linear.com/, can be get the input voltage minimum 1V and peak voltage to 30V, the high power output current is about 1A. You would not have as clear picture, let’s see a better examples. In this circuit, we use 1.5V battery increase the voltage is 5VDC or 12VDC or [...]

      When we need a constant voltage 5V at the current about 20mA, by there are power supply source voltage about 4V to 6V. In this circuit, We use the MAX635 IC number is the main equipment, that acts as Preset/Adjustable Output CMOS Inverting Switching Regulators. At pin A, a negative output dc-dc converter generates a -5V. First, a negative output voltage dc-dc converter generates a -5V output at pin A.       Then, the primary of the transformer (T1) must fly back to a diode drop more negative than -5V. If T1 has a tightly coupled 1:1 turns ratio (270uH), there will be a 5V positive voltage at diode across the secondary ‘s T1. The 1N5817 rectifies this secondary voltage to generate an isolated 5V output. The isolated output is not fully regulated since only -5V at point A is controlled by the IC1. Related link Isolated DC-DC converters 5 volt dc [...]

This circuit is power supply circuit, again the circuit that have the merit is if we want dc voltage 12V but , we have 6 volt only the circuit can modify DC voltage 6 Volt be 12VDC get. The principle works of the circuit is Q1, Q2, R1, R2, R3, R4, R5, D1, C1 and C2 build the circuit is model astable multi vibrator give output be Square Wave. Which be positive pulse signal at have many frequency. And have R6 perform be limit current already flow come to reach at a pin B of Q3 and a pin C of Q4 in this condition current at flow come in pin way B of Q3 make Q3 bias. But Q4 still not bias. Because of still have no current bias at a pin B. When Q3 bias make have current flow through L1, D2 change ZD1 cause drop voltage at [...]