An open source small DC/DC 3W switcher to drop 5V to 3V in a 7805 TO-220 pinout from Black Mesa Labs:
This post is an open source hardware design from Black Mesa Labs for a simple DC/DC converter for dropping 5V to 3.3V ( or adjustable to lower voltages via resistor selections ). The design is based on the PAM2305 from Diodes Incorporated, a great little 1 Amp step-down DC-DC converter in a small TSOT25 package. The PAM2305 supports a range of input voltages from 2.5V to 5.5V, allowing the use of a single Li+/Li-polymer cell, multiple Alkaline/NiMH cell, USB, and other standard power sources. The output voltage is adjustable from 0.6V to the input voltage.
More details at Black Mesa Labs site.
Application note form Würth Elektronik about EM radiation radiated from inductors in DC-DC converters. Link here (PDF)
This Application Note focuses on the Electro-Magnetic (EM) radiation behavior of power inductor(s) in DC-DC converters, which is dependent on several parameters such as ripple current, switching frequency, rise & fall time of a switching device, the core material and its permeability and suggests several design tips to mitigate these EMI effects.
Robert Gawron made a 3V3/30V DC/DC converter using SN6505A:
Recently I’v got my samples of SN6505A, it’s a really nice IC, so I decided to make a simple DC/DC converter to get familiar with it. What I like in this chip is that it can operate on input voltage as low as 2,5V – that makes it great for battery devices. It’s also nice, that it’s a very minimalist design – on primary side all what is needed is decoupling capacitor. One disadvantage is that it doesn’t have a feedback loop.
To increase efficiency, SN6505A can operate with more developed versions of transformers, but I used the simplest configuration – one coil on each side.
Project info at Robert Gawron’s blog.
Thomas Fischl writes:
Some applications needs to control the output voltage of a dc/dc converter instead using a fixed output voltage. For example battery chargers has to adjust the output voltage to the current battery level. This page shows how to add such a control function to a buck converter circuit.
Control output via external voltage source
Typically a voltage divider is used in dc converters to adjust the output voltage to the needed feedback voltage. To control the feedback signal by an external voltage source, a third resistor is added to the circuit.
More info at Fischl’s site.