I’m looking at the MP9488, which looks close to what I want to do. Basically, I have a solar array on one side that could be anywhere from 80VDC to 1200VDC and I’m building an MPPT + synchronous buck to down regulate to 380VDC constant DC bus managed by a microcontroller. Ultimately, my goal, since either the solar on the DC Bus could be unpowered at any time is to use a controller to choose the source based on availability. (this will also be used to convert highly variable 384VDC nominal battery that can be anywhere from 320V to 450VDC but should just fit in the MP9488’s profile as part of another section of this so no voltage divider necessary.)
The microcontroller can easily work within the MP9488 power output and my assumption is that I can use a voltage divider using the top 1200VDC to get a Voltage range that the MP9488 supports. (obviously this is less than ideal for efficiency). My issue comes in both the solar input controller (isn’t a charge controller, it directly powers the DC bus which shares power to many loads) and battery buck/boost controller driving SiCFET gates. That is, I’ll be using a half-bridge gate driver that will drive the SiCFETs. My initial design uses the MP9488 for 3.3V for the microcontroller and another for the Gate Voltage of the SiCFETs. The half-bridge gate driver will bootstrap the high side and drive the low.
The issue is that I’m concerned that 350mA may not be enough current to drive the FET’s gate even through the gate driver(s). This this a valid concern? Is there a better approach to handling powering the microcontroller and gate driver in this topology?
As an Aside: I would think there is an excellent opportunity for a new IC or series of ICs that work in this environment and can take high voltage (up to 1200VDC) and output 3.3VDC for microcontrollers and logic level and a secondary that outputs a fixed gate drive rail (12-18VDC). If you treated this as an input controller and also had RP, OC, OV, and soft startup built in that could just be hooked to an external PFET as well, you’d have a killer combination that would work phenomenally well for both solar and EVs. (i.e. this would solve the need for a 12V battery in most EVs if it had a low parasitic draw when the controller was in sleep mode and the gates weren’t being driven and given that CCS Type-2 supports 1000VDC and we’re seeing 800VDC batteries a 1200VDC max is appropriate for this as well) This would also work really well for highly efficient AC/DC power supplies too.
Confusing request, I got you want an 800- 1200VDC in to 12V 500mA out converter to power control circuits. You are in the world of discrete flybacks I would think , perhaps a two transistor flyback to keep voltages as low as possible.
High (and wide) Voltage In => 3.3V @ ~200 mA out, and 6-18VDC @ ~2A out for Gate drive is what I’m looking for.
This is the absolute requirement of any MPPT, Synchronous Buck/Boost, charge control, or even AC/DC charging and transformerless DC/AC Inverter systems with high voltage (i.e. lots of new solar batteries are 384VDC nominal and 600V + series strings of Solar is common now).
There’s lots of ICs that do this at low voltage but as far as I can tell none that do it at high voltage or wide voltage ranges.
The MP9488 does relatively high voltage and a wide range, but its current limits are an issue for gate drive especially for SiC and GaN.
All high side power systems will require 3.3V and Gate Drive rail (i.e. Gan will be 6-8V, SiC and Mos will be 12-18 for the Gate Drive)
I’m just trying to create a highly efficient supply for this and looking for a self-powered system that will supply these voltages, either separately, or ideally a single IC. What I don’t want to have to do is have a separate battery source that has its own charging circuit just to drive 3.3 and 6-18V for the microcontroller and gate drives.
Since every device like this also requires Over/Under Voltage, Over Current, Soft Start, and Reverse Voltage protection a single IC that has 2 outputs for 3.3V and Gate would be ideal but not required as I can use an LTC7860 or similar for that stuff.
So a 350-600V in to 12V out. converter. I expect you are overestimating your gate drive requirements. The drivers may put out a peak current of amps, but that is only on the turn on edges for 100nSec every switching cycle and not a continuous load. Anyway no the 9488 with a 500V switch won’t work for this application. I expect you need to go controller/discrete FET route to make this work.
This is a synchronous buck/boost converter that is cycling at 800kH or more. The amperage is directly from the datasheets of the GanFETs.
Basically I’m trying to come up with a way to power the synchronous buck from the high input voltage. That means powering the 3.3v microcontroller that does the monitoring, PID and PWM (very small mA) and getting source voltage + 12Vish at 2 amp. I can bootstrap this for the high side with a diode and 2 caps, but I need 12V at 2 amp for the low side from the high side and because of the switching frequency the inefficiency of using a linear regulator, voltage divider (which wouldn’t be accurate enough) or a zener diode becomes a major power loss.
Obviously, I could use a high-voltage zener for both applications, but they’re less than efficient, so some sort of self-powered buck IC that can output both 3.3v and 12V for the low side gate would be ideal. I can’t find anything like that. The uses are many:
Synchronous buck/boost/flyback/forward converters with no diodes.
Pure Sinewave AC Generators
MPPT charge controllers
AC to DC chargers
If I use discrete fets to get the low side voltage, I have the same problem in that I either have to use a low side diode which is inefficient or I have to have a 12v gate drive for the lowside on the synchronous buck.
New solar batteries come up with a compact design and updated work module.
Most of the time these batteries are having 384 VDC and 600V configurations.
As you are using the battery for two different purposes, surely the voltage requirement would be different for both scenarios.
Also for solar and EVs working systems selecting the right battery is very important for the effective working of the application.
High V batteries will be more useful as they can be used in both AC/DC supplies.