Activity for Chupacabras
| Type | On... | Excerpt | Status | Date |
|---|---|---|---|---|
| Comment | Post #291003 |
I actually went through searching. BCM847 costs like 0.15€ and has hFE matching around 0.90 (so 10% tolerance).
But I found better part IMHO, DMMT3904W and DMMT3906W, they cost 0.04€, and have hFE matching 0.98 (so 2% tolerance). (more) |
— | 2 months ago |
| Comment | Post #289577 |
@#36396 The slope control actually doesn't start from 0V, but starts at 2 diode drops. Is it wise to remove R8 and change value of R7 to 10k? So the startup time is the same, but it starts at 1 diode drop, instead of 2 diode drops. (more) |
— | 8 months ago |
| Comment | Post #289577 |
I have stimulated this circuit to figure out how it works, it works perfectly well. I extremely like it :) thanks for sharing it and your experience.
How long it took one to develop such circuit? (more) |
— | 8 months ago |
| Comment | Post #282140 |
Thanks for answer. It's LMV431 (1.25V reference), not TL431 (2.5V reference), but that's probably not important in this case. About R21,D21,C21, now I found the same thing in another datasheet, for TPS23750 on page 31. It seems like TI's special recipe. (more) |
— | almost 3 years ago |
| Comment | Post #282205 |
The switching frequency of that flyback is 98kHz. So it corresponds with the chart of the compensator response you posted. Do I understand it correctly that it (R22, C22, C23) basically filters out 100kHz ripple from feedback? (more) |
— | almost 3 years ago |
| Comment | Post #280675 |
Thanks for XR46010ISBTR. It's not usable in this case, but I could use it somewhere else. (more) |
— | about 3 years ago |
| Comment | Post #280672 |
@Lundin Well, my question was not focused on alternative schematics or options how to modify that circuit. My question was really specifically about that one device, because I can't find any such device. I could use it in different circuits as well, it could be handy. btw. I already changed LED for m... (more) |
— | about 3 years ago |
| Comment | Post #280672 |
@Lundin There is no failing part. It is working correctly. My plan was to increase output power (so increase current). But there is a device that outputs constant current, which I would like to replace for part with higher constant current. Thus I would like to find such part (what is name of it gene... (more) |
— | about 3 years ago |
| Comment | Post #280676 |
As I wrote, there is booster and after that is the schematic I posted here (no point to put here booster from 1.5V to 3.3V). Those 2 parts are basically independent. Booster just boosts voltage to stable 3.3V. From this point it's not important, so I omitted it.
R1 could be as failsafe option. In ca... (more) |
— | over 3 years ago |
| Comment | Post #280675 |
I have seen NCR402 during my searching. That is current source, not sink. And it has much larger dropout voltage. In my case source is 3.3V, LED is at 3.1V, so there is just 0.2V difference. (more) |
— | over 3 years ago |
| Comment | Post #280676 |
I'm absolutely sure about that schematic. I have just verified it. The current keeps constant despite I have changed the value of that resistor (from 1 ohm to 0.5 ohm) (more) |
— | over 3 years ago |
| Comment | Post #280672 |
Yes, it is 1 ohm. Before I reverse engineered the circuit I thought it is current sense. But it is not. I changed it to 0.5 ohm and current did not change. Then I reverse engineered schematic. I assume it is there to limit the current in case that driver failed. (more) |
— | over 3 years ago |
| Comment | Post #280395 |
I was just hoping the device is better than it is :) Thanks for you answer. I'm going to read datasheets from a little bit different perspective. (more) |
— | over 3 years ago |
| Comment | Post #280395 |
Well, I always considered charts and graphs to be more relevant. I expected real data there and I could see data for the exact range I care about. I have added response from NXP support. (more) |
— | over 3 years ago |
| Comment | Post #276117 |
Interesting. How much faster will relay switch off with resistor compared to alone diode? (more) |
— | almost 4 years ago |