Oznog
Active Member
I was talking to some electric vehicle guys who have large battery packs which are not grounded to the frame who still need a 12v supply to accessories.
Some have used commercial converters intended to be line-driven. I'm not sure what the failure modes are but I'm hearing they didn't work all that well. The source voltage is not well matched to begin with and it can be quite noisy.
It would need to take in 80-225 vdc depending on pack design and put out around 12v-14v, and the input and output need to be isolated. The input may see large spikes due to being hooked up to a PWM converter driving a huge motor. Output current was something like 50-100 amps.
So a simple buck converter with an inductor would be out of the question since we require isolation. Buck converters would be pretty rough with a high input/output ratio anyways.
I'm thinking an SMPS power supply. 225v isn't much higher than a normal 120v SMPS rectifies to and is lower than a 220v rectifies to. 80v of course is lower.
The range of possible voltages seems to be a problem. My first thought would be to have multiple taps on the transformer that could be reconfigured according to the battery configuration. The batt voltage will of course have a high and low voltage due to load and charge state but it's not as wide as the 80v-225v configuration variance.
Another thought is we only use one tap and the SMPS controller modifies the pulse width. I think this is a good idea. The only problem is the entire input winding would need to be of a gauge which can handle 16 amps for the 80v input situation. With multiple taps the tap for 225v would have wire rated for 6 amps, so it would go in series with the 80v tap so about 2/3's of the total turns could be much smaller making it fit on the core much better.
What's out there for SMPS controllers? What about ones that can accept feedback from an isolated output stage through an optocoupler?
Some have used commercial converters intended to be line-driven. I'm not sure what the failure modes are but I'm hearing they didn't work all that well. The source voltage is not well matched to begin with and it can be quite noisy.
It would need to take in 80-225 vdc depending on pack design and put out around 12v-14v, and the input and output need to be isolated. The input may see large spikes due to being hooked up to a PWM converter driving a huge motor. Output current was something like 50-100 amps.
So a simple buck converter with an inductor would be out of the question since we require isolation. Buck converters would be pretty rough with a high input/output ratio anyways.
I'm thinking an SMPS power supply. 225v isn't much higher than a normal 120v SMPS rectifies to and is lower than a 220v rectifies to. 80v of course is lower.
The range of possible voltages seems to be a problem. My first thought would be to have multiple taps on the transformer that could be reconfigured according to the battery configuration. The batt voltage will of course have a high and low voltage due to load and charge state but it's not as wide as the 80v-225v configuration variance.
Another thought is we only use one tap and the SMPS controller modifies the pulse width. I think this is a good idea. The only problem is the entire input winding would need to be of a gauge which can handle 16 amps for the 80v input situation. With multiple taps the tap for 225v would have wire rated for 6 amps, so it would go in series with the 80v tap so about 2/3's of the total turns could be much smaller making it fit on the core much better.
What's out there for SMPS controllers? What about ones that can accept feedback from an isolated output stage through an optocoupler?