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Hello. I'm Dave Priscak with Texas Instruments, your host for the Power Tips "Ask the Expert" video series. I am back in Freising, Germany here with Bernd Geck who's going to talk to us about using microcontrollers in power supply design. Welcome back.

Hello, Dave. Thank you so much. So today we want to little bit talk on use of microprocessors inside power supplies. I'm not talking on digital loop compensation. So where we need a digital filter and [INAUDIBLE]. We are just adding some beneficial features to our power supplies to implement additional features and functions.

First we got two main groups. First group is monitoring. Second is control.

And if we talk on monitoring, we are talking on monitoring to AC voltage, the PFC voltage, the output voltage, the input current, and the output current. What we did in our two examples that I brought with me here, we had, in addition to the inner safety that we provide by decisions by the microprocessor, we always have, of course, an outer safety. This outer safety is still hardware. It means there is a certain sensory system. We have an overcurrent, we provide a shutdown-- a hard shutdown-- by the hardware-- by the controller.

But we have an inner safety where we could do, in addition, certain calculations. So if we have information on input voltage, output voltage, input current, output current, we are able to calculate input power, output power, and efficiency on the fly. That we can add.

From these two examples, you're saying the hardwire. This is inherent to the design of the power supply. And this is more of an outer system level, whether or not an outside force, if you will, wants to interact or shut down the power supply.

Exactly. We use a standard TI power controller, PWM controller, with all these features like current limitation, and so on. But we put, outside around this, we put the microprocessor that adds us all the monitoring functions that we perhaps need for some sophisticated designs here.

Our microprocessor also is able to provide us a certain fan speed, and checks if the fan is still OK by the current consumption. We can monitor various temperatures of our power supply with the microprocessor. And of course the main machine interface means the output of our power supply is done, we are display. And of course we have some push buttons just to decide the output voltage, just to adjust our output current, and so on. That we're going to show here with this power supply that I brought with me here.

So next that we have for our power supply, we have of course the control functions. Control function means we are able to enable and disable our power supply. We are able to adjust our output voltage. We are able to set our maximum output current.

And what we did with this design here, we are synchronizing our power supply with a microprocessor. It means first we are able to change the switching frequency; means if we have a certain baseband where we don't want to have spurious, we are able. So a microprocessor another processor could change the switching frequency to put the spurious out of band. Or on the other hand, if the microprocessor modulates my switching frequency, I'm able to provide dithering to my supply. So I'm lowering emissions there.

You're lowering your peak emissions.

The peak emissions. The average are constant, but the peak emissions, let's say, are attenuated, let's say, by minus 3, minus 4dBs there.

And what we did in this design as well, our microprocessor does a synchronous rectification of the bridge rectifier to increase our efficiency. Those decisions are made by the microprocessor as well.

And the big design that I brought with me here, that's a 2-kilowatt charger. Here we implemented the charger algorithm for our battery chemistry inside the microprocessor. So if the customer is going from a standard lead battery to an AGM battery, or whatever else, if he changes to chemistry, there is no need for changing the hardware of the power supply to change trickle loading or the-- I don't know-- the CD loading, and so on. That's just a software change in the microprocessor. We are flexible there.

And last but not least, that's a design for N+1 configuration. So you can parallel those power supplies. A charger. There are no special dynamic requirements to charge a battery. So we do all the current sharing and the information on the current to the module that we put in parallel to this one. We do it [INAUDIBLE] interface that is also provided by the microprocessor.

So they can talk to each other about current sharing, or even status of the power supplies themselves.

Exactly. Status and of course the current changing. That's exactly what we're going to do with this power supply.

Would you be able to also then use like a trimming function with the power supply for slightly changing to maximize the performance of an asynchronous or an FPGA?

Of course. Of course. You can also add VID interface very, very easily. So if your microprocessor with the output pins gives you information on the needed output voltage, you just influence your feedback pin there, and you can change the output voltage as well.

Very cool. You brought kind of a working model here. Can you kind of showcase what the MSP430 in this case is doing for us?

Yeah, of course. At the moment we are monitoring the output voltage, the output current. Of course at the moment there is no load applied. So we can see only that the output current is zero, of course. We're on standby. What we are able to see here is the input voltage, the AC input, and the PFC intermediate voltage. That's what we measure on the fly.

And next we see here the switching frequency. We selected here a constant switching frequency. We are able to change the switching frequency, or we are able to stop the ring mode, of course.

Next is we see the temperatures inside our power supply. We see the temperatures inside are fairly low, because there is no load applied-- no power losses and so on. We see the temperature of the PFC, and of the footbridge heatsink.

And in addition, here we going to see the inside temperature of the chassis. So the temperature inside the chassis. That's what we provide by the MSP430 very easily.

So it's very good. So not only does it help the operation, but also from a troubleshooting, from a monitoring of the temperature, to know when to bring the fans and all that, you get all that with a very, very low cost microcontroller.

Of course.

This is a great way to really take your power supplies to another level. And then it actually has communication involved with it as well as monitoring, as well as safety. So thank you very much for bringing this to our attention. Much more information on TI.com when you visit the MSP430, or any of the microcontroller websites at TI.com.

This is Dave Priscak again, with the Power Tips "Ask the Expert" video series. Thank you for attending. See you next time.

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