Recent content by rfhv

I experimented to find the value of C9. I do have some overshoot at startup. I get a spike of about 2 A that lasts for less than 1 ms. I do not expect this to be a problem for the 445nm diodes that everyone uses but if you wanted to use this for a 405 nm diode for example, you should probably...

Here is the driver with the ripple removed. Ripple is less than 10 mA at 2.4 MHz. The scope shots are 10 mA per division. Coupling is AC, probe is 10X. The bench meter shows output current. The green meter in the center shows the voltage across the load. The power supply is putting out 4 V...

Yes, I just used a single ground. I think split grounds are a bit overrated. In any case, I got the driver stable. I was able to remove all the ripple from the output with the addition of a capacitor and a resistor. The Russian suggestion was correct. All I needed to do was limit the high...

I suspect the ripple is a consequence of the TPS chip itself and the fact that I am in current mode rather than voltage mode. No value of capacitor can remove the ripple. If you can show that with low side sensing you have no ripple then I may redesign my circuit to have a much higher bandwidth...

My sensing scheme allows a common ground for everything. I use three wires in my design. I predict that using low side sensing you will not hit quite the maximum current out that my driver can hit. This is because the TPS has a feedback voltage of 0.5 V. If you use low side sensing and do not...

I added the zener to mine for overvoltage protection. I know that the TPS63020 has built in OVP but I do not know where it limits. If the limit is above 6.3 V then you may destroy your output caps unless you are using 10 V caps. I went the safe route and added the 5.1 V zener to be sure I do not...

The board is 0.7 inches by 0.55 inches.

A diode would have at least a 0.5 V drop. My MOSFET has a resistance of about 0.03 Ohms worst case. At 3 A, I will loose about 0.09 V across the FET. The choice was 0.5 V or 0.09 V. I chose the more efficient option. A FET can make the difference between 65% efficiency and 80% efficiency.

The MOSFET provides reverse polarity protection.

The ZXCT1009 is a voltage to current converter. It takes the voltage between its + and - terminals and puts out a current that is proportional to that voltage difference on its out pin. The TPS needs a voltage input though, so I made a current to voltage converter with a resistor and a pot and...

Here is a 445nm build I did with an Ehgemus host. There is a separate thread for the driver in the drivers board. A full write up and large images can be found at Chris's Electronics Page

This is very similar to what another member posted a few weeks ago. I built this driver and found it can do 2 A with 4 V input. It shuts off when the battery gets to 3 V. Mine is currently driving an M140 diode at 1.25 A and barely gets warm. I calculated the efficiency to be 82% into my diode...

I got about 70% efficiency at 2A out if I recall. About the low battery protection: I used a TC54 with a threshold of 2.9V on the enable pin of the TPS63020. The TPS does have low voltage protection, but the cutoff is too low. By the time it turns off, your battery may already be destroyed. How...

I hope you don't mind me asking if this is a TPS63020 based driver. I did one that is 17.7 x 13.7 mm. Mine is single sided and has a solid ground plane on the back side. I also have open circuit protection, low battery protection, and reverse polarity protection. I have yet to do full tests...