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  • Hello my name is Andy Reiter, I'm with Microchips Power Supply Applications Group.

  • The topic we would cover today is our new CIP Hybrid Power Starter Kit.

  • This starter kit is introducing the PIC16F176X and 7X families of freely

  • programmable pwm microcontrollers. These microcontrollers

  • have specific peripherals that are running independently from the core and

  • are highly configurable so that it can configure them or interconnect them in

  • specific ways to form some PWM controller architectures. So the

  • advantage of this freely configurable peripherals are that you can tailor the

  • PWM controller capabilities specifically to your very application. To allow

  • designers to utilize these capabilities we also have introduced a new design

  • tool chain, which is encapsulated in our development environment MPLAB X. So this

  • is part of our Microchip Code Configurator tool called MCC, and is a

  • set of sub libraries that allows you to simplify the configuration of multiple

  • peripherals at the same time. We have set up this assembly in this demo here where

  • we have a starter kit on the left and here on the right on the screen you see

  • this MPLAB X environment with the specific switch mode power supply library

  • subset for Microchips Code Configurator. So this tool now can be used to set up

  • PWM controllers that support different control modes like peak current load

  • control, voltage mode control, average motor control. You can combine

  • multiple control loops, you can add in specific fault handlers and the device

  • itself then supports you with setting specific thresholds like shutdown levels

  • for maximum currents, voltage clamping, inputs under voltage

  • over voltage lockout and further features by utilizing the internal DACs.

  • So the variety of things you can do with these peripherals is really really wide.

  • So the switching power supply library helps you to abstract the

  • capabilities and tailor them to specific topologies. So therefore we also offer

  • different sets of pre-configurations for targeting specific topologies. So once

  • you have used that tool to set up a PWM controller for a specific application

  • and topology, that where you're generating the code, the code is

  • downloaded into the device, the codes that's generated with the device also

  • includes functional aspects like soft start, so that you're having a nice

  • behavior right from the beginning, so that when you fire up the power supply

  • for the very first time that you can be sure that it won't burn. So once you have

  • downloaded it, and this is what we are doing in this demo set, is then we have

  • connected a network analyzer to the output, we are injecting an error signal

  • and we're using our BODI 100 Network Analyzer to measure the total open-loop

  • gain in the closed-loop system. So depending on the additional tools you

  • might have used to design your power supply and to set up your compensation networks,

  • so to achieve a certain stability of your application, you can then

  • just measure directly from the kit the final results compared with your

  • simulation and then you take it from there and in further some iteration

  • steps you might have quickly achieved your goal.

  • so before we go into the details about this kit and its software and design

  • tool chain might be necessary to explain a little bit what hybrid power actually

  • means the work hybrid is often used in different contexts like hybrid power

  • supplies is something entirely different from hybrid power controllers so hybrid

  • in our context means that it's a device which is somewhere between the analog

  • control domain and the full digital control domain so analog controllers

  • usually come as fixed Asics covering very specific topologies or specific

  • applications so the conventional pol controllers for example or you have here

  • switch switching regulator for flight controllers or resonant converters and

  • for every single one of them so for every single application you might have

  • a set of specific Asics to choose from while full digital control then

  • digitizes even the feedback loop so everything is running and software the

  • interface is an A to D converter so analog signals continuous time domain

  • analog signals are converted into digital signals and then processed

  • through software and then some PWM is adjusted so this the letter 1 full

  • digital control gives you extreme flexibility in terms of what a

  • controller can do while analog circuitry is might have a significantly higher

  • performance but they are nailed to what they have been designed for so that

  • section between both worlds that is what we're trying to cover with hybrid

  • controls so it means we have a small device with relatively low power

  • consumption but and in within the architecture we're combining digital

  • logic with analog circuits so that we can leverage that in the advantages of

  • both worlds in one single device so and when we are focusing on these hybrid

  • devices then it's always a a device which is targeting the

  • application would have a specific requirement for very specific features

  • so the basic concept of these products is that in one chip you get a

  • microcontroller core and a PWM controller peripheral that PWM

  • controller peripheral always breaks down into three main major blocks consisting

  • of the compensator so Erin play fire basically and the modulator so the

  • modulator then determines which control loop control mode you're applying and

  • there's always an additional fault level that helps you to make sure that the

  • power supply stays within its safe operating range default is usually tied

  • into the modulator or uses inputs to the modulator to shut down the passerby in

  • case something is going wrong so when we're looking into the modulator so here

  • on the right side we see a specific setup for a voltage or an average

  • current mode and on the top we see an implementation for a classical picker

  • remote controller so here on the upper writes in the current note section we

  • find a subset of codes lay or labeled with PRG so that stands for programmable

  • RAM generator so we are utilizing this ramp generator to generate a negative

  • ramp which is modulated onto the reference input to our modulator that

  • then is used usually in Picard mode for slope computation but it can also be

  • used in voltage mode this is when you look below you also see a voltage range

  • on the upper right where we use a positive ramp to generate an analog PWM

  • signal the next therefore we find in this modulator are fast comparators so

  • in the current mode section on the top we find that comparative

  • between the RAM generator and our so-called Co G which is actually our PWM

  • output logic block so that comparator is used to tie in the current feedback so

  • that we can trip on peaks of the inductor current while in voltage and

  • average card mode that comes very same comparator is now used to compare the

  • reference from the Aaron profile to the artificially generated ramp and when the

  • ramp exceeds the reference voltage level then it changes its output strips and

  • and it's our latch and this then influences our PWM output so in both

  • motivators we always use a PWM module and the so called CEO cheese or the

  • complimentary output generator or in other devices it's called

  • a complimentary waveform generator cwg but these blocks to is actually said

  • they give to get to the capability to start out from a single PWM signal and

  • split it up into complementary waveforms allowing you to adjust that x or you can

  • split it up up to a full bridge drive so it also offers additional inputs for

  • false signals so fault triggers that come from different peripherals or from

  • external circuits can also be fed into the PWM logic and some additional glue

  • logics and also would allow you to establish something like conditional

  • fault handing so the third level is the compensator the compensator on these

  • devices usually just a are just consisting of an errand to fire so this

  • is actually a general-purpose operational amplifier then you get a

  • deck to adjust reference and then the reference itself which is called the

  • fixed voltage reference F we are

  • so in addition to help you to condition signals for especially false signals of

  • to define fault levels to trip on there is a an additional set of comparators

  • and attack with a lower resolution so usually you get five bit tags that help

  • you to set up thresholds that five bits might not be sufficient for in some

  • cases so when you need a higher resolution then it is possible to use

  • external resistors to create a window which is then still scalable with five

  • bit and then you send it around a threshold range you would like to set up

  • so once we have picked these three blocks we now can use these to set up an

  • entire analog feedback loop here we see the first architecture so on the right

  • we have a power supply so in this case it's just for the purposes of a sake of

  • an example it's a boost converter that offers a voltage feedback coming from a

  • voltage divider and we have a peak current signal which is taken from below

  • the boost mains which using a shunt resistor so the voltage feedback now is

  • fed into the outer loop portion of our architecture which is then our air

  • amplifier so the amplifier compares that signal to our reference which is

  • internally set by attack the output of that amplifier is fed into the

  • programmable Ram generator and this part we are modulating a negative frame onto

  • this reference voltage to apply a slope compensation for our inner p-card load

  • control loop then we are entering then or we are taking this output of this

  • program of a ramp generator feed it into a comparator that comparator compares

  • that reference signal to the peak current signal that's coming from our

  • shunt resistor and then that output of that comparator trips our

  • PWM output logic and effectively true hates the duty cycle so to set up the

  • switching frequency we are now using a digital PWM oniel which allows us to set

  • up a fixed period with a maximum duty cycle so in case the comparator does not

  • trip the pwm module in time it's the only time base of the pwm module which

  • makes sure that the duty cycle is not hitting hundred percent and maybe with a

  • bad outcome when your inductor saturates and then your power supplies effectively

  • going out of control

  • so one thing we see here in this particular example is because of these

  • devices are highly configurable and can practically drive any kind of topology

  • it is very hard to define our C Network values that might be necessary to set up

  • an appropriate computation for every single different topology out there so

  • therefore all of the compensation networks need to be external with these

  • devices so we see here in the lower around the OPA so the operational

  • amplifier that the input as well as it's the output is connected to a device pin

  • so these device pins are usually sitting right next to each other so that it's

  • very easy that it can place your RC components of the conversation that are

  • very close to the device so after having established this basic feedback loop we

  • are now adding the fault level so the fault level consists of a comparator

  • with five attack in this case we are using it as an additional over current

  • shut down and then we can feed that output of the comparator directly into

  • the CG so that it asynchronously overrides anything that's coming from

  • the software from the rest of the European architecture

  • and we can truncate the duty cycle and turn off the PWM immediately as fast as

  • possible so usually these comparators have a propagation delay of between 30

  • and 50 nanoseconds and this is the timeframe in which she can shut down can

  • you respond to fault and shut down the power supply economy so what we can do

  • with these PWM controllers now is a lot so as I said potentially you can support

  • all kind of different configurations for specific topologies it does not only

  • cover fixed frequency you can also setup the peripherals to support user 80

  • controls like internal time constant of time quasi resonant converters resonant

  • converters so the variety of possibilities is really really wide so

  • for just to keep things simple let's just start with fixed frequency

  • operation off a standard topology and this is what we are doing with this

  • starter kit so this starter kit we have used a simple synchronous buck converter

  • not only because it's safe to operate it easy to compensate but also because

  • everyone is very familiar with this topology so this starter kit now comes

  • with multiple options so that it can play an experiment and explore a little

  • bit the capabilities of the part play with different configurations and see

  • how you can solve different design challenges by using different

  • modifications of a preset of provided examples so when we are looking into the

  • hardware we find that this port is as a power supply on the lower side so this

  • is where we find our synchronous buck converter so that buck converter has

  • been designed for a power level of approximately 25 watts so the maximum

  • current call from the outputs at 3.3 volt is

  • roughly at around 8 m/s so you're above this is where we have find our

  • controller so that controller is bigger than it would be necessary for that

  • single topology so we have picked our superset device providing up to four

  • independent pwm controller peripheral sets the reason why we have done that is

  • to allow you to switch between different control modes so we have set up one PWM

  • control of the voltage mode another one for pico remote control in the third one

  • for average current mode control we use the peripherals of the fourth one to add

  • more advanced functions one of them for example is VCR sensing so one of the

  • current feedback options provided by the power plant is a RC network which is

  • tied in parallel to the main inductor and which can be used to to use a

  • lossless sensing technique which is fairly popular especially in low voltage

  • here will applications to implement that function we need an additional append so

  • as the op-amp is still available from the fourth PWM controller architecture

  • we can now utilize it to create an additional option which then is tied

  • into one of the other PDM controllers so that kit now is supported by the power

  • supply library NCC so when we are now trying to utilize

  • this extreme flexibility of the Percel we really rely on tools which try to

  • keep the complexity as low as possible during the design process so for that

  • particular purpose we have created this switching power supply library which is

  • available in the microchip code configurator

  • so the basic architecture so the ones of you who are familiar with MCC might know

  • that it is a graphical tool that helps you to configure specific settings of

  • one independent peripheral so usually when you set up an application you pick

  • one person like a UART and then you use that school to set up moderate or very

  • specific details of that very powerful and then you're generating hold and the

  • generated code is then called during startup of the device and putting that

  • function provided by the person in place so now as we have seen that a switchman

  • power supply controller is more than just one single peripheral the

  • configuration of multiple blocks can get very tricky so eventually you might end

  • up with seven to nine different peripheral blocks that need to be

  • connected in a very specific way to achieve a certain function so to

  • simplify that design process we have now added additional layers to our MCC

  • design tool so here on the bottom of that diagram we see that classical MCC

  • layer this is what most of you are maybe familiar with and this is what contains

  • all the different configuration sets of every single powerful so here in that

  • list you see all the peripherals that are used to form that function of a PWM

  • controller so here we find this program a program generator the complimentary

  • output output generator the PWM module a timer comparators digital to analog

  • converters fixed voltage references op amps and so forth so these blocks mell

  • are merged into that functional blocks of a modulator here on the left for peak

  • current mode control and compensator block which consists of an op-amp attack

  • and the fixed voltage reference here in the right we

  • another set and this is the model a box for voltage not control or average more

  • control so once you have you know which control mode you would like to use then

  • we can tie together compensator and model a the block to form a control mode

  • block in this case we have two options the card mode control or voltage or

  • average mode control now this block is still very generic and it's not really

  • tailored to a specific topology so to make the right position on the

  • switch configuration which kind of dead times you need we now need to nail down

  • the topology you would like a pro apply this control block for so this brings us

  • up to the next level which is the topology level until specifically for

  • our starter kits we are using a synchronous buck converter block so that

  • block now when we pick one of these blocks we know exactly what the PWM

  • output configuration needs to be we know which feedback signals we need to

  • consider and we can pick all the peripherals to form a PWM controller so

  • that you as a designer and up with a system that is already pre-configured

  • and the only remaining options that need to be picked to make this block work or

  • where should the feedback signals go into the device where is the pillar of

  • iam coming out of the device and what is your preference value for your feedback

  • and what is the definition of your switch node so switching frequency and

  • that times need to be specified so eventually instead of diving into the

  • peripherals and spending quite some time to set up all these different blocks

  • functional blocks you now practically just configure the entire system on a

  • very high level by just using physical values coming from your area application

  • so we have seen the basic concept of the MCC smps library I would say just let's

  • give it a try and configure or switch mode power supply so for that purpose I

  • take my starter kit and I plug it it with my using the micro USB cable and

  • what happens now when I do this when we look into MPLAB X as soon as the tool

  • connects we see the product page coming up so MPLAB X is detecting the board and

  • the board comes with a specific feature that it mounts a thumb drive on which

  • all the information is stored that is now displayed in that window so now from

  • that window on you can directly click on go to the kids home page and on that

  • development kids home page you find all the documents and collaterals we offer

  • with the device so as of today what you find is a user guide for the kids the

  • configuration user guide for the switch composed by libraries which concludes

  • the installation process the library itself so did not be already included in

  • your envelop X installation you can always download the latest version from

  • that website and then you find further documentation like schematics and the

  • detailed data sheet of the chip we are using which is in this case the

  • pic16f877a so let's get started so to set up a power supply controller on on

  • that chip what I do first is I create a new project

  • so I create a standalone project continue I picked the device I'm using

  • but just pick 16 F one seven seven nine

  • okay next now I have to check when my tool is and here I think to find the CIP

  • hyper tower starter kit so I select this one click next choose my compiler and

  • then I need to give it project name so I call this CIP high HP test choose a

  • directory

  • and click finish

  • so now with in this new generators project I'm now opening MCC

  • and as well as the mcc modules have floated I can save the configuration I'm

  • going to build in a specific file which is usually stored in the project

  • directory so the very first thing and this might be a little bit out of the

  • scope of normal power supply designs is I have to determine which frequency I

  • would like to have running on that device so to make sure that all the

  • peripherals including pwms interrupts input capture you are and everything

  • else you might use in your application works at decent performance we pick the

  • eight megahertz oscillator and we enable the PLL which then gives us an effective

  • CPU frequency of thirty-two megahertz so based on that timing this is the base

  • for all the other timings we are going to set up in on that chip so later on in

  • the modules we will find specifications for switching frequencies for dead times

  • and so forth and all these timings always refer to the specific frequency

  • we have set in this window so from that point on we are ready to go and dive

  • into the configuration of the power supply peripherals so to make our life

  • easy we are now referring to the switching power supply library so when

  • we look into the device resources we find here this SMPS power controllers so

  • when we open those then we find either soft blocks or the highest level would

  • then be power supply topologies so when you recall that diagram we have just

  • seen at the bottom there were all the peripherals then above they were already

  • pre-configured sets of peripherals forming modulators and compensators

  • above that we found encapsulated blocks for control modes and above that there

  • was our topology so we going to start at the highest level let's say this highest

  • abstraction layer and as we see there are a couple of different topologies

  • already with can pick from in this case we pick a

  • generic synchronous buck converter double click it and now it's loaded into

  • our project resources when we load that project item then first we end up in a

  • short page with some short description about what this block is all about the

  • second one is then our configuration window so if you consider the number of

  • peripherals who would have to put together for one PWM controller so all

  • of that is now already pre-configured so we know exactly which peripherals we

  • need to pick how they need to be interconnected because we know what you

  • are going to design so the number of parameters then need to be set now comes

  • down to a very very short list so this now is starts with the switching

  • frequency so for this particular starter kit we pick 500 kilohertz the maximum

  • duty cycle this determines some certain clamping value so for that starter kit

  • it's 90% but it's really highly the application dependent and it really

  • depends on the topology and your safety levels you're trying to achieve so we

  • leave it at the 90% for that for our demo setup here the reference voltage

  • relies on your feedback signal so the voltage divider we used on the starter

  • kit gives us feedback signals of exactly 2.5 volts when the converter is

  • producing 3.3 volt at the output so to achieve that 3.3 volts stable output

  • control we need to set the reference at 2.5 volt then we have leading-edge

  • blanking so and that depends on the current feedback we are going to use so

  • the starter kit offers three different current sensing options the first one is

  • a current Stinson's fauna which is located above the high side switch so

  • when we switch over into the third top then we see

  • a simplified schematic that gives us some indication where we find our

  • current sensing option and how feedbacks and interconnects are done so here we

  • see that complementary PWM that's connected to the highside and low-side

  • switch of our half bridge then the current sense gives us the inductor

  • current so the first option would be this is the one we're going use would be

  • the currents in some format so that guy is located here just before the hiset

  • switch that location that is indicated here in is just idolized indicating that

  • we are always measuring the inductor current in truth the second option would

  • be the shunt which is located between the inductor and the output capacitor so

  • at this place and then we have a third option which is called TC our sensing so

  • we are using a parallel RC network which is sitting in parallel to the inductor

  • and that would actually give us that indicated current position although this

  • is more an an emulated current feedback signal so precise but is lossless

  • because it's not sitting really in the power path so it doesn't create losses

  • that is the advantage of DC are the penalty is it's not that accurate so the

  • three different current sensing options have three very different

  • characteristics so the advantage of a current sentence former is that it's

  • very fast and it gives you a very nice resolution so it's a large signal so the

  • signal noise ratio is very good the downside is because it's located above

  • the high sites which is that we only see half of the current waveform so we only

  • see current feedbacks when the current when the switch is closed and current is

  • flowing through that current transformer so we don't see the discharge current

  • towards the node and the output capacitor the second sensing option the

  • shunt has the advantage that it shows us the entire current waveform

  • however the shunt needs to be very small to create as little losses as possible

  • so we need to amplify that signal to get it up to a size that we can actually

  • work with it so this is done with a high set current sense amplifier these

  • amplifiers have limited bandwidth which usually results in a tiny phase shift

  • and usually some damping on the amplitude so instead of a razor-sharp

  • triangular current waveform you might get I mean something that's a little bit

  • more sinusoidal and face shifted the third option the DCR sensing is equally

  • sensitive so the signal won't be very large so we also need to amplify it and

  • it is a signal which need also needs to be taken from the high side so we need a

  • high cycle or higher voltage differential amplifier so the advantage

  • in this low voltage buck providing 3.3 volt is that the output voltage is still

  • below the supply voltage of our device so what we can do nervous we can utilize

  • an on-board amplifier as differential amplifier for the DCR sensing so these

  • are the three options we have in this first configuration we will start out

  • with the current sensors form so the Continentals former has a very

  • particular signal waveform so every time the switch closes it creates a tiny

  • spike so we see a turn-on spike and that peak of that spike might be higher than

  • the peak or peak current mode control is triggering on so we have to make sure

  • that this peak is not accidentally tripping our comparator we're achieving

  • this by setting up a so-called leading edge blanking window so this time frame

  • we are setting will disable the comparator during that time between the

  • start of the cycle until the end of our leading edge blanking period so when we

  • are going to set this up okay on this particular design we know already it

  • needs to be 200 15 nanoseconds so the 250 nanoseconds

  • are counted from the point our internal pwm module is generating the leading

  • edge so there's the first delay we have to consider is the delay between our

  • signal generator and the propagation delay through the complementary output

  • generator logic to the through the pin driver towards the most driver the

  • propagation delay of the most driver until the MOSFET eventually turns on so

  • that delay is already 55 milliseconds and then we see that spike of that

  • current sentence former and the width of the spike is roughly 120 nanoseconds and

  • to be a little bit on the safe side to account for additional switching noise

  • we add some safety margin this altogether that delay chain that brings

  • us up to 250 nanoseconds so the third setting we have to make is dead times so

  • we have a half bridge converter that means when we are closing both switches

  • at the same time simultaneously we're practically shortening out the input

  • voltage and that will potentially or very probably blow our switches so we

  • have to make sure that this never ever happens this dead time setting is based

  • on a high resolution delay line which is part of the complimentary own output

  • generator so we cannot just dead times with a resolution of five nanoseconds

  • per tick so when we set up a value of three then we get 15 nanoseconds dead

  • time so here in this mask all the values were entering our physical values so

  • using physical units so in this case we're just entering 15 nanoseconds if

  • you try to enter 12 it might sit there with 12 but eventually it will just be

  • 15 anyways so your choices are 5 10 15 20 and so forth

  • so the rising edge with 50 nanoseconds sounds very short and that the reason

  • why the dead time needs to be support is the MOSFETs we're using on this starter

  • kit so these are high speed high speed silicon MOSFETs which turned on in

  • roughly eight nanoseconds so between five and eight nanoseconds is typically

  • rise and fall time of these MOSFETs so they're extremely fast and the edges

  • don't change so any Miller plateau or any additional delays so we can position

  • them very close to each other to ensure a most efficient operation of our power

  • stage so the rising edge is 15 in this case the falling edge that time is named

  • with 60 nanoseconds so the mismatch between both dead times also mainly come

  • from that delay between our signal generator edge through the entire output

  • logic MOSFET or our master travel delays and then we have to account for all

  • these additional and late delays in addition to our appropriate dead time

  • setting so the best way to figure out how what the appropriate dead time is is

  • always starting out with a very safe setting which is usually derived from

  • the data sheets of the components here using so look into your into the data

  • sheets of the most drivers try to figure out what the corrugation delay is there

  • look into the most read data sheets look for the typical rise and fall times when

  • driven by a driver at a certain voltage and then you get some good ballpark

  • number where that data might be at a little bit of safety margin and fire up

  • your power supply for the first time look at the scope measure it and

  • optimize it so this is the more typical a little bit pragmatic but not a useful

  • way in setting up these values good so once we have gone through that list so

  • now the last setting here would be this computation so slope computation is not

  • available yet because we first have to have a peripheral which we need to

  • program so at that point there's nothing else we can do so now we have all the

  • settings we need to at least set up the architecture we're doing this by

  • selecting one out of four pwm controllers so the peak current mode

  • control controller is located here in a specific corner of the device so the pin

  • out of the device is divided in four sections so I'm here in the upper left

  • this is where we find the in and outputs of the first PWM controller then here is

  • number two number three and number four so that peanut has been arranged in a

  • way that when you're designing multiple power supplies that it can route the

  • signals on to the device in the most ideal way without crossing other lines

  • especially trying to keep analog separated from digital and so forth to

  • prevent any conflicts with signal integrity so on the starter kits the

  • peak current load control is wired up to PWM controller number three so I pick

  • that one from the list and now I can upload all the modules that are required

  • so I'm uploading the configuration for all the people peripherals so this takes

  • a moment

  • and here we are now in the project resources we see decide that one power

  • supply topology we have added first there is now a list of peripherals so

  • now we see all the sub blocks so which is then here

  • for example the comparative digital to analog converter and op-amp for the area

  • fire our fixed voltage reference at the complementary output generator the ramp

  • generator and the basic period is switching on PWM so and as you soon see

  • every time I click on one of these modules I see all the configurations

  • which are available for that particular powerful so if you go into the register

  • map you see this there are endless options of configurations that could

  • potentially be done but as we have done all this already all these settings have

  • been done for you ready so I can just skip that peripheral level go back into

  • my sync rectifier and now as attack is loaded and I know what the resolution of

  • the deck is now we can set a new revenue rate of our slope compensation ramp

  • generator so for that particular design we need a slope of 0.35 volt per

  • microsecond so that ramp that is modulated onto the reference of the air

  • amplifier now decreases over time with a ratio of 350 millivolt per microsecond

  • so now we are all set so I save my configuration and now I generate the

  • code

  • and in which the help would we know

  • until the process has completed

  • and I see this is stunned first when the progress bras have disappeared and when

  • I find a line that says save configuration' in final my path so when

  • I now switch over into the project and I open the header then I see that the MCC

  • generated files folder in which all the search and possible configurations have

  • been generated - and then there's another folder called SPS and in this

  • folder I find software functions that already have been generated in addition

  • to the basic peripheral configurations so what we providing as a standard

  • generated code block is a soft starter team especially in half bridge

  • configurations at high input voltages if you would just snap on the PWM with a

  • certain duty cycle the chances are very high that it will just blow up or not to

  • be switches so usually half which drives especially with high speed MOSFETs like

  • those needs needed is vitally need to be soft starter so and that code is now

  • part of your project already so this is a function you can call the right key

  • and you don't have to be concerned about your some sort behavior anymore

  • so when we go into the source files we find also a main which contains the main

  • program and years our MCC generated block with all the peripheral

  • configurations and here also this which will power supply software function

  • blocks so why did I look into my main the first line within Maine is system

  • initialize so inside that system initialize I see the configuration of my

  • pin out oscillator settings what's your timer settings and then all

  • the peripherals for most which one power supply PWM

  • controller including the to sink park and PCM C Block software blocks which

  • include the soft start

  • within Maine there's nothing else to find so there's just a while loop so the

  • only modification we have to do manually is to decide when that power supply

  • should be turned on so where to place my soft start function call so the first

  • thing is we have to figure out how that function is called so we have to go into

  • the PCMC header to learn how that function Hall looks like and how its

  • named so it's called PCMC underscore soft start easy to remember and we would

  • like to soft start that over to start the power supply immediately it just

  • before we enter the while loop so I place that function call here and this

  • is it now we are ready to go so now I hit compile compile the project

  • just to make sure that the generated code doesn't produce any errors

  • and I get a built succeed and now can program my device

  • okay so now we see programming verify complete so the program has been

  • successfully programmed okay so now here we are with a programmed board now we

  • have to test if it's really working now I'm connecting this port to the power

  • supplies and the load which is part of that development kit so for that purpose

  • I'm stealing the input voltage from that input terminals connected to my freshly

  • program port

  • and I take the load module we have here on this side and connect it to the

  • output and then here on the display you see an operative of 3.3 volt at already

  • close to four amps so regulation seems to work to make sure that it's really

  • working we're just changing the load turning it off and it's the regulating

  • to 3.3 volts so seems that we have an active controller that controls the

  • voltage to a constant level overload how well it really works

  • our controller what did eventual performance is and our bandwidth the

  • transient response that obviously requires a little bit of more thorough

  • analysis and for that purpose we have a network analyzer which is connected to

  • that kit so I will just remove these blocks again give it a look the load

  • module back in

  • and the software which is currently running on that kit and that kit is

  • identical so this is exactly the same basic p-card mode control we have just

  • generated so when we are now letting this board run then we have on this side

  • our network lies analyzers running and it's continuously measuring the loop so

  • the way we do this is that we have a tiny resistor on top of our output

  • voltage divider so voltage dividers at the output I have usually resistors in

  • the kilo ohm range and we put a tiny 10 ohm resistor on top of this high

  • resistance and then we use a injection transformer so this is a one-to-one

  • current transformer and that is connected to the signal generator within

  • our OD analyzer so this frequency now is applied to the primary winding is

  • injecting a current that current is then showing up in on the secondary side and

  • is injecting an error signal in that Tang ohm resistor on top of our voltage

  • divider so this artificial error signal is now traveling through the voltage

  • divider entering our feedback loop that's their amplifier the area fire

  • starts to respond to that error signal and is injecting this error into our

  • modulator and so our PWM starts to be to modulate against that error that is

  • showing up at the feedback input and so our output voltage starts to change so

  • the network analyzer now looks at the signal that has been injected on one

  • side and then looks at the output of the power supply on the other side of the

  • Tarin ohm resistor and just measures the sinusoidal response of the system and

  • measures the difference in amplitude which gives us the game and the phase

  • shift which gives us the face and plotted as a bode plot

  • and the port button allows us to do stability analysis where we can measure

  • it across our frequency the slope of the gain at the crossover frequency the face

  • at the point where in the game hit zero and the value of the gain when the face

  • hits the minus hundred eighty degree sole point of instability so the

  • so-called gain margin so then with phase margin gain margin in Kosova frequency

  • we now have all the parameters that determine the total bandwidth and

  • performance basic performance parameter instability of our power supply so

  • before we have a closer look at the measurement let's briefly revisit what

  • we are actually going to measure so this is a block diagram of our system

  • consisting of the power plant which is the transfer function G of s in the S

  • domain and then we have the second transfer function which is our

  • compensator H H of s in the S plane so our feedback in our system is closed

  • with a voltage divider and this feedback signal is then fed into the compensator

  • and the compensator and is and comparing just into a reference and the difference

  • is then applied by our modulator to the plant and that changes when we change

  • the duty cycle for example the optical burst goes up or down and any transients

  • that might hit the system from outside or no transients or from the input will

  • then be compensated by our control system so to make sure that this system

  • is stable we have to have a look at the total transfer function of this entire

  • block from input to output and this is the gain the closed-loop gain so g

  • closed-loop equals the plant gain over 1 plus the plant gain times the

  • compensator gain so when we look at this term and one thing becomes obvious that

  • thing is always stable as long as G of s times H of s is different than minus one

  • because imagine when this tends to go to minus 1 then we have 1 plus minus 1 this

  • goes to what 0 so the gain of the system will go to infinity which means that the

  • system is coding getting out of control and the gain becomes infinite and the

  • game the system is gone and will most probably blow up in our case so this is

  • why we call this G of s times H of s equals minus 1 is the sole point of

  • instability so in any other condition the system is de facto stable and only

  • in that point it becomes uncontrollable so when we are making a stability

  • analysis the whole stability analysis is now about how far are we away from the

  • sole point of instability so and this is the so-called open loop gain within the

  • closed loop system so while the system is operating a closed loop we are only

  • having a look at the open loop gain of the system so now when we have a closer

  • look at the bode plot so what you are seeing here is a continuous measurement

  • of the open loop gain and closed loop system so this term of open loop in a

  • closed loop system comes from the open loop component that looks for how far

  • away are we from the sole point of instability which is the point when the

  • system hits a phase lag of - degrees so in this region the system

  • should not be able to respond to any transient in any reasonable form so we

  • need to have a large negative gain in that region the bode measurement is as

  • always when we look at the face there's always one kind of misleading thing

  • about the scale of the face and this is the minus 180 degree line is actually a

  • serum at 0 degree phase in that ball plot the reason for that is that the

  • small signal model defines that monitored minus 180 degrees at the

  • reference of the system however the measurement now is done at the output of

  • the power supply so feed other side of the island and then we have that phase

  • lag of 180 degrees throughout the system doesn't really matter it's just if

  • you're wondering why we're always talking about minus 180 degrees as so

  • point of instability and here in that scale we look for that point at 0

  • degrees that's actually the same thing so what that Buddha plot here in an

  • active measurement is showing you is actually more for more tuned towards

  • stability analysis then a theoretical description of the system so that is the

  • only thing that's maybe interesting to keep in mind

  • so let's perform a measurement so as you see it's running here at the low

  • frequency range we see a lot of noise and that is the small signal model so

  • you're achieved best and most accurate results of the transit function when the

  • signal you're injecting is as small as possible so that it you don't drive some

  • components like especially the air amplifier into nonlinear regions at its

  • margin of its total input reading range so this is why we always try to keep

  • that injected error signal as small as possible

  • and at low frequencies this is getting tricky for the measurement equipment to

  • see the variation of the sinusoidal curve that is so small that the noise

  • floor starts to have a large influence on the measurement result so this is why

  • we see in that low frequency range it's always very noisy so luckily that

  • measurement tool we're using here the Buddhahood home that has a feature that

  • allows us to shape the gain of our input stage so that we can increase the gain

  • to reduce the noise but as you see it is may be good but still not good enough so

  • we would have to perform many many measurements of exactly the same

  • operation point and activate an averaging over that period to get rid of

  • that noise to also achieve a better more accurate result in that region but for

  • the moment we are not really interested in this local frequency range we are

  • more interested in the total performance of our feedback loop which is more about

  • stability so the stability criteria we are now looking for is start with the

  • crossover frequency of the game so when it does the creating of the game which

  • is the red line cross zero dB so this is pretty much exactly at 30

  • kilo Hertz we can make a more precise measurement if we go here into the scale

  • and say okay please give me the number at zero DB and we see exactly it's at

  • thirty point one point six kilohertz the other point that's important for its

  • instability at area is the gain margin which we find when the face which is the

  • blue line now hits minus one at eighty degrees or in our plot C or the green

  • line so we do the same I go into that table put zero and the cursor gives me

  • thanks the number of minus 14 DB which is a sufficient gain margin for a power

  • bond so when we are let me stop the

  • measurements to keep it really quiet so knowing we analyze it one of them the

  • third stability criteria would look fine four would then be the slope of the game

  • at the crossover point so ideally it should be minus 20 DB per decade so

  • we're looking into that decade so here we have a point which was very close to

  • 10 DB so that is easy to take and then it should be a linear minus 45 degrees

  • over minus 20 DB per decade slope and when we draw a line when we imagine the

  • line that has a slope of minus 20 DB per decade then it would be at minus 10 DB a

  • ton of kilohertz and the crossover point would right be in the middle of that

  • slope so we exactly hit that slope of minus 20 DB per decade so it's a

  • perfectly schoolbook stable system so the last and foremost designers most

  • important value would then be the phase margin so that is determined to be at

  • the crossover point so what's the phase lag at the crossover point so we take

  • that server cursor and we've framed when we reset this to zero again so we find a

  • phase margin of 60 degrees gain margin of 14 DB add a crossover frequency of 30

  • kilo Hertz and we are meeting so we have really good stability at the crossover

  • frequencies of phase margin a margin and the slope at the crossover frequency all

  • three major stability factors are in a really good region for a real stable

  • power supply so the bandwidth we have set at 30 kilo Hertz is a little bit is

  • at many of fifteenth of the switching frequency

  • which is also a good ratio and which allows us to have enough safety margin

  • to account for variations in inductor component values capacitor component

  • values and so forth

  • so what we have covered today is we saw a short introduction of the CFP

  • hyperpower starter kit our demo setup the design procedure using our switch

  • from power supply libraries in the microchip code configurator and finally

  • how we generate the project we built our pwm controller downloaded into the

  • device bring it into the system and then measure and analyze it so I hope also

  • that the measurement results have given you some idea about the performance

  • level you can expect from the analog peripherals on board of these chips it

  • is really a straightforward pwm controller as you can expect it to find

  • on any other ASIC in terms of performance nevertheless have a look at

  • the data sheets and every further information you can find on the

  • descriptions below just click on the links follow them and you will find all

  • the documentation about the board the devices that are imposed by libraries

  • and further information on generic topics of simulation of switching power

  • supplies and design practices thank you very much for watching hope to see you

  • soon

Hello my name is Andy Reiter, I'm with Microchips Power Supply Applications Group.

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