My Team is designing a DC:DC Boost power supply with 3.3~3.65VDC input (power cell Li-Ion battery able to supply up to 30A for short bursts).
The output stage needs to generate 23.0+ VDC @ 1.5A for a maximum of 30 seconds.
We've started out with a 555-based switching power supply utilizing a 47uH inductor, but we just could not get the voltage up to where it theoretically should be.
We can get to 14.1vdc @ 600mA with the 555 running at 4kHz, which gave us the best result so far.
But all the calculations suggest we should be able to reach the intended goal..... but such is not the case.
No matter which parameters we choose to change, we keep hitting a max efficiency ceiling of that 14v output at the current we require.
However if we parallel TWO such devices, the voltage drops but current remains almost constant.
Bad things happen is we try to (logically) just series the outputs... not a good idea :(
Research and scope analysis seems to indicate we cannot get the 555 MOSFET gate driver resistance low enough to keep efficiency losses to the required minimum (something like < 1 milliohm)
In a previous forum post on this subject (13 Dec 2023) it was suggested to use the 5156 as it was almost exclusively designed for this purpose.
And it has an internal MOSFET drive connection so we assume it is ultra-low resistance.
Also, it was suggested that we change to much smaller inductors.. in the 2uH range.
We have tried to utilize the Powerstage designer tool from TI.... but keep running into negative values and/or locked fields (frequency).....
Any possibility someone in the know can tell us we're headed in the right direction or if we're wasting our time with this?
