TDA2005 as a DC-to-DC Converter
The TDA2005 is a very popular audio amplifier chip that many of us have used for years in car stereos and home DIY amplifiers. While it is mainly built to amplify AF signals, its internal design is actually strong enough to be used for other interesting projects like this DC-to-DC converter. By using the two amplifier channels inside the chip to create a high-frequency signal, we can turn the IC into a power driver that works with a rectifier circuit.
The way this circuit works is quite simple. The TDA2005 stages (U1A and U1B) are set up to produce a high-frequency AC signal. This signal goes through 2200µF coupling capacitors and then into a full-bridge rectifier made of 1N5822 Schottky diodes. I chose these specific diodes because they have a very low voltage drop, which helps keep the efficiency high. To keep the TDA2005 stable while it drives this kind of load, I included 1Ω resistors and 0.1µF capacitors as stability networks. This stops the chip from oscillating at very high frequencies, which could otherwise cause it to overheat or fail. The final output is cleaned up by a 4700µF filter capacitor and a small RC snubber to give a steady DC voltage.
Even with this design, there are a few things to keep in mind. Since the circuit does not have a feedback loop, the output voltage will change a bit depending on how much load you connect or how the input voltage varies. Also, heat is a major factor. In my testing, I found the overall efficiency to be around 80%, but the TDA2005 will still get hot during long use. Because of this, use a proper heatsink and make sure the 1Ω stability resistors are 1W rated so they don't burn out under stress.
When assembling the PCB, start by soldering the smaller parts like the 1W carbon film resistors and ceramic capacitors first. Then, you can add the larger electrolytic capacitors. Please make sure all capacitors are rated for 35V or higher just to be safe. Finally, always bolt the TDA2005 to a good heatsink with some thermal paste before you turn it on.
Schematic and PCB files of this project are available in this Google drive location.
