I'm looking for a small number (<10) who would like to run the NexGen BB board through some testing.
The Nextgen as it stands has two modes which makes for an interesting converter board.
The IC used has a soft start mode which limits output power till regulation is achieved and then it kicks over to full power mode. Because of the LED Vf being log instead of being linear it compresses the voltage range seen on the output with changing current. This results in the current feedback to typically never reach the threshold as in the case of a standard voltge feedback network. Hopefully, I'm explaining this well enough.
Anyway, the two modes (safe) and (full) are what I'll call them.
I'll be frank here and say that (safe) mode actually is a performer all by itself. While semi-regulated (constant power) mode it delivers almost a whopping 1A to a 1W/3W with 3V input. On the one I tested I was seeing 980mA with 3V input and approx 700mA to the LED with 2V input. That's nothing to sneeze at and safe mode is very useable and kicks some arse. BTW: that's 90+% efficient at these levels.
If the input rises fast enough or Vin is high enough such that the constant power is enough for full output power the IC then throttles over to full regulation. If the feedback is set for 1A for example it will regulation 1A down to 2V or so and at some point switch back to safe mode down to 1.8V and then go into some limp mode below 1.8V.
The regulator behaves well with a two stage switch, has connector holes to make a sandwich.
The converter board has what appears to be a silicon diode across the output P MOSFET. This means that if Vin rises above Vout the silicon diode forward biases and the internal logic shuts down. This is now in DD with headroom of 0.6V and this is the configuration I'm running in my FF. I'm running a 1A CC Nexgen with a R123 from JS (Thx JS!). You can use Li-ION with Lux3 K bins and higher. As long as Vin does not rise more than the 0.6V above Vf, I'm thinking this is safe. At least my FF hasn't smoked yet. Be extremely careful here since this IC fry's just looking at it. I've smoked more of these ICs than any other design.
The R123 voltage is high enough to bring the converter board into regulation from the low level switch mode to full.
Raising the input voltage slowely requires the converter input of approx 3.2V before full regulation starts (with 1A setting). Lower output current settings would result in startup at lower input voltages.
A kick start circuit has been implemented and if the input is hot switched as in the standard flashlight configuration without a two stage switch the IC will kick start on the input transient with inputs as low as 2.2V - 2.3V.
Since this is complicated in description and behavior, I'm looking for ueers that can test and verify safe, full, standard 123, two AA, R123 and Li-ION configurations.
I'll need to know if it indeed does work and is stable and how to best lock in the specifications for this dual mode converter.
The converter will use the same 0603 sense resistor to set the output current and the feedback scaling is such that the online calculator for output current is the same.
Iout = 0.050V / Rsense.
Please post here and give me a little background of your test equipment (ie power supply, meter, scopes etc).
I have not decided how many I will give each person, but, if you are lucky the board will be useable after you are done testing and you are more then welcome to keep the beta board when testing is completed.
The board has the standard anode contact on the backside and is 0.55" in diameter.
Board size constraints limit the size of the inductor and if the board was made larger or a better inductor was loaded the efficiency should rise to around 95% with 1A output.
Wayne
The Nextgen as it stands has two modes which makes for an interesting converter board.
The IC used has a soft start mode which limits output power till regulation is achieved and then it kicks over to full power mode. Because of the LED Vf being log instead of being linear it compresses the voltage range seen on the output with changing current. This results in the current feedback to typically never reach the threshold as in the case of a standard voltge feedback network. Hopefully, I'm explaining this well enough.
Anyway, the two modes (safe) and (full) are what I'll call them.
I'll be frank here and say that (safe) mode actually is a performer all by itself. While semi-regulated (constant power) mode it delivers almost a whopping 1A to a 1W/3W with 3V input. On the one I tested I was seeing 980mA with 3V input and approx 700mA to the LED with 2V input. That's nothing to sneeze at and safe mode is very useable and kicks some arse. BTW: that's 90+% efficient at these levels.
If the input rises fast enough or Vin is high enough such that the constant power is enough for full output power the IC then throttles over to full regulation. If the feedback is set for 1A for example it will regulation 1A down to 2V or so and at some point switch back to safe mode down to 1.8V and then go into some limp mode below 1.8V.
The regulator behaves well with a two stage switch, has connector holes to make a sandwich.
The converter board has what appears to be a silicon diode across the output P MOSFET. This means that if Vin rises above Vout the silicon diode forward biases and the internal logic shuts down. This is now in DD with headroom of 0.6V and this is the configuration I'm running in my FF. I'm running a 1A CC Nexgen with a R123 from JS (Thx JS!). You can use Li-ION with Lux3 K bins and higher. As long as Vin does not rise more than the 0.6V above Vf, I'm thinking this is safe. At least my FF hasn't smoked yet. Be extremely careful here since this IC fry's just looking at it. I've smoked more of these ICs than any other design.
The R123 voltage is high enough to bring the converter board into regulation from the low level switch mode to full.
Raising the input voltage slowely requires the converter input of approx 3.2V before full regulation starts (with 1A setting). Lower output current settings would result in startup at lower input voltages.
A kick start circuit has been implemented and if the input is hot switched as in the standard flashlight configuration without a two stage switch the IC will kick start on the input transient with inputs as low as 2.2V - 2.3V.
Since this is complicated in description and behavior, I'm looking for ueers that can test and verify safe, full, standard 123, two AA, R123 and Li-ION configurations.
I'll need to know if it indeed does work and is stable and how to best lock in the specifications for this dual mode converter.
The converter will use the same 0603 sense resistor to set the output current and the feedback scaling is such that the online calculator for output current is the same.
Iout = 0.050V / Rsense.
Please post here and give me a little background of your test equipment (ie power supply, meter, scopes etc).
I have not decided how many I will give each person, but, if you are lucky the board will be useable after you are done testing and you are more then welcome to keep the beta board when testing is completed.
The board has the standard anode contact on the backside and is 0.55" in diameter.
Board size constraints limit the size of the inductor and if the board was made larger or a better inductor was loaded the efficiency should rise to around 95% with 1A output.
Wayne
