This is the circuit diagram of 5VDC single polarity to 12VDC dual polarity converter based on IC LM2595-12 from National Semiconductor. This circuit will convert 5V DC single voltage (+) become 12V DC dual polarity output (+), GND, (-).

Many electronic devices need a ?12V power supply. Typical examples include analog circuits or RS-232 driver power supplies. The ?12V typically needs to be generated from a 5V system bus. The solutions normally used involve a multiple secondary transformer or multiple switching regulators. These solutions can be complicated, may require custom transformer design and may have poor efficiency and poor regulation. The 5VDC single polarity to 12VDC dual polarity converter circuit shown in above image is simple, uses only one switching regulator IC, uses a small number of components, and provides good regulation at a high efficiency. Additionally, all the components used in this circuit are off the shelf components.

The converter circuit in above image uses an LM2595-12 (buck SIMPLE SWITCHER?) based switching regulator to generate both the +12V and the -12V outputs from 5V input. The LM2595 is configured as an inverting buck-boost converter to obtain the negative output. The positive output is generated using an additional winding in the off-the-self inductor (CTX250-4 from Coiltronics) used in this circuit. Only one additional diode (D3) and a capacitor (C3) are needed to generate the positive output.

This circuit come from Application Note #1118 by National Semiconductor about Simple Regulator Provides ?12V from 5V Source using LM2595-12.
Download the application note AN-1118:

AN-1118 - 5V to 12V DC Converter

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This is the circuit diagram of 3V to 9V DC converter which capable to deliver output voltage about 10.4v on no load and 9.6v @30mA. By using this circuit, You will be able to replace a 9v battery from 3V DC input.

The advantage is the voltage stays over 9v for the life of the cells, while a normal 9v battery drops to 7v very quickly.

The output voltage is set to 9-10v by the 6k8 and 390R resistors. The 470R gives the circuit an idling current of about 20mA and the spikes are about 75mV.

By increasing the 470R, the quiescent current decreases but the voltage drops more when the current is 30mA.

I hope this 3V to 9V DC converter circuit useful for you. Good luck.

Above schematic diagram is the circuit of the variable desktop power supply. Regulator IC LM317T is set up in its standard application. Diode D1 protects against polarity reversal and capacitor C1 is an additional buffer. The green LED (LED1) signifies the status of the power input. Diode D2 keeps the output voltage from increasing above the input voltage when a capacitive or inductive load is hooked up at the output. Similarly, capacitor C3 eliminates any residual ripple.

Connect a common digital voltmeter in parallel with the output leads to precisely set the wanted voltage with the support of variable resistor / potensiometer VR1. It is possible to also work with your digital multimeter in case the digital voltmeter isn’t around. Switch on S1 and set the needed voltage through potensiometer VR1 and start reading it on the digital voltmeter. Now the power supply is all set to be used.

The circuit could be built on a general purposed Printed Circuit Board (PCB). Refer refer to the following picture for the pin configuration of LM317, just before soldering it on the PCB.

When the circuit already build, then enclose the circuit inside a metallic box, the suggested power supply box shown below:

Then open up the case of the desktop computer and hook up the input line of is circuit to a free available (hanging) four-pin drive power connector of the SMPS properly.

Today, a lot of handheld gadgets (for example: portable reading lamps, smartphones, tablets, ipod) utilise this resource of the USB port to recharge their battery pack using the support of an internal circuitry. Typically 5V DC, 100mA electric current is needed to satisfy the input electrical power demand.

The above diagram shows the circuit of a versatile USB power socket that properly converts the 12V battery voltage into stable 5V. This car cigar lighter to USB circuit can make it possible to power / recharge any USB power-operated device. It work with in-dash board cigar lighter socket of the car.

The DC supply presented from the cigarette lighter socket is fed to an adjustable, three-pin regulator LM317L (IC1).

Capacitor C1 buffers any disorder in the input supply. Resistors R1 and R2 regulate the output of IC1 to constant 5V, that is accessible at the “A” type female USB socket. Red LED1 signifies the output condition and zener diode ZD1 acts as a protector against excessive voltage.

Assemble the circuit of car cigar lighter to USB power socket on a general purpose PCB and enclose inside a slim plastic cabinet as well as the indicator and USB socket. Whilst wiring the USB outlet, make sure proper polarity of the supply. For interconnection between the cigar plug pin as well as the device, use a long coil cord as shown in second image.

Here the Pin configuration of LM317L:

Download this car cigar lighter to USB circuit in PDF Version:

USB Power Socket Project

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Circuit parts list:

• Cin : 220 uF, 50V, Nichicon UPL1H221MPH
• C1: 270 uF, 63V, Nichicon UPL1J271MRH
• C2, C3: 47 uF, 35V, Nichicon UPL1V470MPH
• D1: MBR360,
• D2, D3: 1N459,
• C4, C5: 0.01 uF
• IC1: LM2596-3.3 (SIMPLE SWITCHER? Step-Down Voltage Regulator)
• IC2, IC3: LM78L05, and LM79L05. (3- Terminal Regulators)
• L1: Custom Inductor with three windings (W1, W2 and W3) with the following specs:

• W1: 47 uH; Peak Current: 2.6A, RMS Current ? 2.32A
• W2: Number of turns = 3.4 x Number of turns in W1; RMS Current; 113 mA
• W3: Same as W2

The +12V and ?12V outputs are regulated with ?20% accuracy. A typical application of this circuit is where the 3.3V output provides the power to the main circuit which is 3.3V logic, the ?5V outputs power the 5V logic and ?12V outputs provide the bias supply of op-amps.

The efficiency of the circuit with full load at all outputs is 75%. The ripple voltage across the 3.3V output is less than 20 mV and that across the ?12V outputs is less than 30 mV. The ripple across the ?5V is less than 10 mV.

Download the application notes fro this DC to DC converter circuit HERE

This is the fixed 5V to 12V DC to DC converter. The circuit application converts input voltage of 5V (range 4.5V-5.5v) to 12V fixed regulated DC output. The circuit built based National regulator monolithic IC LM2586 which is specifically designed for flyback, step-up (boost), and forward converter circuit applications. The LM2586 will require a heat sink to prevent overheat on its.

LM2586 pin assignment:

Download the datasheet of LM2586 for reference and more DC to DC converter circuits:
? Download Link

This is a 5VDC to 12VDC boost converter circuit built based LT1070. The LT^?1070/LT1071 are monolithic high power switching regulators. They can be operated in all standard switching configurations including buck, boost, flyback, forward,inverting and “Cuk”. A high current, high efficiency switch is included on the die along with all oscillator, control and protection circuitry.

5VDC to 12VDC LT1070 Boost Converter circuit Reference: LT1070 datasheet

Schematic diagram:

Components and its usage:

6V to 12V DC to DC voltage converter circuit works:

When the switch is closed an extra current flows through the inductance and stores energy there. The capacitor supplies the load with current during this time.

After the switch closes the capacitor is charged by the energy stored in the inductance and an extra current starts flowing through the load, causing the output voltage to rise (energy is supplied directly from the input source also as long as the diode is forward biased). During this time, the system behaves like a RLC-circuit, so, after a while, the current decreases. The switch is then closed again and the cycle repeats. One could say that charge is pumped from input to output, increasing the output voltage up to the point where there is an equilibrium between the discharging of the capacitor while the switch is closed and the charging by the inductor while the switch is open.

PCB layout:

This is the simple and easy built of PCB design layout for above 6V to 12V DC Voltage converter diagram.

The circuit will look like following image: