uoficowboy
Full Member level 3
- Joined
- Apr 4, 2009
- Messages
- 169
- Helped
- 6
- Reputation
- 12
- Reaction score
- 5
- Trophy points
- 1,298
- Location
- Seattle, Wa, USA
- Activity points
- 2,964
boost converter in battery charger
Hi there - I'd like to build a circuit that charges a high voltage battery pack. The pack will start out at 30V discharged, and will be full at 43V or so. I will have a 12VDC input. I'd like to charge at a constant current until the pack gets to 43V, and then I want to maintain a constant voltage while the current tapers off. I will have a microcontroller that can supervise to some extent - but I'd like most everything to be handled by a dedicated DC/DC controller.
My idea is to use a simple DC/DC boost converter that has a voltage feedback pin. Let's say that reference is 1V. Let's say that I want to charge at 5A. I would then have a shunt resistor on the high side of the battery with a high side current monitor watching it. This would generate a ground referenced signal of 0.2V/A. This would be getting summed with a signal that was equal to (battery voltage - 40)/3, except that that signal would not be driven below zero. That sum would be fed into the feedback pin of the boost converter. So the idea is simple in that when the pack voltage is below 40V only the current will affect the voltage at the feedback pin, while once you get past 40V the pack voltage will start getting added in to the current signal, slowing down the charge rate till it hits zero.
Any thoughts? It makes sense to me, though I'm still trying to figure out how to do some of this. For example - I'm worried that the high side current sense amp will be seeing a lot of high speed common mode noise. I'll have to find a part with really good PSRR.
Thanks!
Hi there - I'd like to build a circuit that charges a high voltage battery pack. The pack will start out at 30V discharged, and will be full at 43V or so. I will have a 12VDC input. I'd like to charge at a constant current until the pack gets to 43V, and then I want to maintain a constant voltage while the current tapers off. I will have a microcontroller that can supervise to some extent - but I'd like most everything to be handled by a dedicated DC/DC controller.
My idea is to use a simple DC/DC boost converter that has a voltage feedback pin. Let's say that reference is 1V. Let's say that I want to charge at 5A. I would then have a shunt resistor on the high side of the battery with a high side current monitor watching it. This would generate a ground referenced signal of 0.2V/A. This would be getting summed with a signal that was equal to (battery voltage - 40)/3, except that that signal would not be driven below zero. That sum would be fed into the feedback pin of the boost converter. So the idea is simple in that when the pack voltage is below 40V only the current will affect the voltage at the feedback pin, while once you get past 40V the pack voltage will start getting added in to the current signal, slowing down the charge rate till it hits zero.
Any thoughts? It makes sense to me, though I'm still trying to figure out how to do some of this. For example - I'm worried that the high side current sense amp will be seeing a lot of high speed common mode noise. I'll have to find a part with really good PSRR.
Thanks!