1.5V to 5V/12V DC/DC converter based on LT1073

1.5V to 5V/12V DC/DC converter, using LT1073

This is a small 1.5V to 5V or 12V DC/DC converter using the LT1073 chip. This integrated circuit comes in three different versions, depending on the output voltage. Two have fixed output voltages of 5V and 12V, while the most interesting is the adjustable version. Adjustment is achieved via a voltage divider consisting of two resistors connected to ground, the output, and terminal 8, internally connected to a voltage comparator IC responsible for stabilizing the output voltage.

The LT1073 integrates everything needed to build a small DC/DC converter, featuring a low operating voltage of only 1V and a no-load power consumption of only 95μA.

If you don't have an inductance meter, making the inductor section of the driver can be a bit complicated, but we'll see some possible solutions. The capacitors recommended by the manufacturer for the circuit are also a bit hard to come by; I used tantalum capacitors recycled from another power supply, and the output ripple voltage was quite low. Last but not least, the diodes must be fast. Unlike the 1N4002 rectifier, the 1N5818 Schottky type is recommended, characterized by high response time and low internal resistance, which is ideal for this type of converter.

From the photograph of the circuit in the low-energy lamp, we can see that a small toroidal core can be recycled. For this core, we wound 7 turns of 0.3mm enameled copper wire to achieve 82μH.

Another option is to use a Ferroxcube toroidal core, Farnell code 178-504, dimensions 13.25 x 7 mm, 35 x 5 mm, 7 mm, grade 3C85, AL value 1000. Using this core, we wound 8 turns to achieve 90 μH.