[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:00.00,0:00:19.29,Default,,0000,0000,0000,,{\i1}36C3 preroll music{\i0}
Dialogue: 0,0:00:19.81,0:00:26.71,Default,,0000,0000,0000,,Herald: Okay, that was fast two minutes.\NThe next talk is going to be on DC to DC
Dialogue: 0,0:00:26.71,0:00:39.64,Default,,0000,0000,0000,,converters by Zoé Bőle. She's an\Nenthusiast for open hardware and fan of
Dialogue: 0,0:00:39.64,0:00:50.01,Default,,0000,0000,0000,,DIY and has been working on the topic of\NDC to DC converters for a long time and I
Dialogue: 0,0:00:50.01,0:00:58.90,Default,,0000,0000,0000,,have to keep on talking now because it\Nseems that her computer is not really
Dialogue: 0,0:00:58.90,0:01:07.42,Default,,0000,0000,0000,,communicating with the presentation\Ndevice. We do have a picture but we don't
Dialogue: 0,0:01:07.42,0:01:29.49,Default,,0000,0000,0000,,get it moving.\N{\i1}troubleshooting whispers in background{\i0}
Dialogue: 0,0:01:29.49,0:01:32.76,Default,,0000,0000,0000,,Herald: While they're still having some
Dialogue: 0,0:01:32.76,0:01:38.95,Default,,0000,0000,0000,,issues up here I might remind you that it\Nis very helpful if you take your trash
Dialogue: 0,0:01:38.95,0:01:44.97,Default,,0000,0000,0000,,with you and now please welcome Zoë and we\Nare ready to {\i1}inaudible{\i0}.
Dialogue: 0,0:01:44.97,0:01:47.59,Default,,0000,0000,0000,,Give her a warm hand!
Dialogue: 0,0:01:54.50,0:01:59.74,Default,,0000,0000,0000,,Zoé Bőle: Hi, my name is Zoë and this is
Dialogue: 0,0:01:59.74,0:02:05.52,Default,,0000,0000,0000,,the first time I'm standing here in a\Nchaos stage so I'm a little bit, like,
Dialogue: 0,0:02:05.52,0:02:13.03,Default,,0000,0000,0000,,anxious but I'm here to talk to you…\N{\i1}applause{\i0}
Dialogue: 0,0:02:13.03,0:02:23.11,Default,,0000,0000,0000,,Zoé: I'm here to talk about these DC\Nconverters and the talk's called "DC/DC
Dialogue: 0,0:02:23.11,0:02:28.10,Default,,0000,0000,0000,,converters and everything you wanted to\Nknow about them" but it's unlikely I can
Dialogue: 0,0:02:28.10,0:02:36.26,Default,,0000,0000,0000,,fit everything into a 50 minute talk, so\Nit's like not everything, but my goal is
Dialogue: 0,0:02:36.26,0:02:42.54,Default,,0000,0000,0000,,to provide you some starting points and\Ngive you an overview and hopefully if you
Dialogue: 0,0:02:42.54,0:02:50.15,Default,,0000,0000,0000,,already worked with DC/DC's then you're\Nalso not gonna be annoyed and not gonna be
Dialogue: 0,0:02:50.15,0:02:57.84,Default,,0000,0000,0000,,bored. Before I start with the DC/DC\Ntopic, I would like ask you to be
Dialogue: 0,0:02:57.84,0:03:04.16,Default,,0000,0000,0000,,excellent to each other and this is not\Nrelated to my talk but I hear people
Dialogue: 0,0:03:04.16,0:03:08.94,Default,,0000,0000,0000,,starting clapping when someone broke the\Nbottle accidentally and I think it's super
Dialogue: 0,0:03:08.94,0:03:18.83,Default,,0000,0000,0000,,not cool. Yesterday I saw someone breaking\Ndown in tears because they just broke a
Dialogue: 0,0:03:18.83,0:03:23.70,Default,,0000,0000,0000,,bottle and everybody was clapping and\Npaying attention to them
Dialogue: 0,0:03:23.70,0:03:31.96,Default,,0000,0000,0000,,and that was like harassment. So, please\Ndon't be the one who starts clapping. But
Dialogue: 0,0:03:31.96,0:03:42.02,Default,,0000,0000,0000,,also I'm not here to forbid you to clap\Nand… just know what's happening. So,
Dialogue: 0,0:03:42.02,0:03:49.01,Default,,0000,0000,0000,,brief introduction to DC/DC's and why:\Nquite often you need different voltages
Dialogue: 0,0:03:49.01,0:03:56.46,Default,,0000,0000,0000,,than what you have available. For example\Nyou have a microcontroller or you have an
Dialogue: 0,0:03:56.46,0:04:02.26,Default,,0000,0000,0000,,FPGA and you work with the battery\Nthen you need to provide a different
Dialogue: 0,0:04:02.26,0:04:14.95,Default,,0000,0000,0000,,voltage for that circuit and the trivial\Nsolution is to just use two resistors and
Dialogue: 0,0:04:14.95,0:04:21.16,Default,,0000,0000,0000,,make a voltage divider, but this is\Ntotally unsuited for power delivery
Dialogue: 0,0:04:21.16,0:04:27.60,Default,,0000,0000,0000,,because as you start loading the output,\Nthe output voltage starts dropping. Also,
Dialogue: 0,0:04:27.60,0:04:36.93,Default,,0000,0000,0000,,this circuit dissipates power even if\Nthere is no useful load on the output. So
Dialogue: 0,0:04:36.93,0:04:44.40,Default,,0000,0000,0000,,this is only useful for signals and to\Nhave some kind of feedback and regulate
Dialogue: 0,0:04:44.40,0:04:52.39,Default,,0000,0000,0000,,the output to a desired level you can use\Nan LDO, which is the same thing but you
Dialogue: 0,0:04:52.39,0:05:01.47,Default,,0000,0000,0000,,control, one resistor – very simplified –\Nto always keep a desired output voltage.
Dialogue: 0,0:05:01.47,0:05:08.78,Default,,0000,0000,0000,,Of course this can only go lower than your\Ninput and your efficiency is limited to
Dialogue: 0,0:05:08.78,0:05:17.38,Default,,0000,0000,0000,,the ratio of the output voltage and the\Ninput voltage, and this is even in ideal
Dialogue: 0,0:05:17.38,0:05:26.40,Default,,0000,0000,0000,,situation. So, instead of burning up power\Nin your converter you can just use
Dialogue: 0,0:05:26.40,0:05:31.74,Default,,0000,0000,0000,,switches and this is the idea behind\Nswitching supplies that you use a switch
Dialogue: 0,0:05:31.74,0:05:36.20,Default,,0000,0000,0000,,element which is either \Nfully on or fully off.
Dialogue: 0,0:05:36.20,0:05:41.34,Default,,0000,0000,0000,,And if it's fully on then there\Nis no loss on a switch and if it's
Dialogue: 0,0:05:41.34,0:05:46.30,Default,,0000,0000,0000,,fully off there is no current flowing\Nthrough it so there is no loss either.
Dialogue: 0,0:05:46.30,0:05:51.56,Default,,0000,0000,0000,,There are some practical problems\Nwith this approach but
Dialogue: 0,0:05:51.56,0:06:01.64,Default,,0000,0000,0000,,but this works for LEDs and heaters if your\Nswitching frequency is high enough.
Dialogue: 0,0:06:01.64,0:06:08.93,Default,,0000,0000,0000,,To think of a DC/DC converter is a\Nbox with four terminals. It has an input
Dialogue: 0,0:06:08.93,0:06:15.75,Default,,0000,0000,0000,,side and an output side. Right now I'm\Ntalking about buck step-down DC/DC
Dialogue: 0,0:06:15.75,0:06:21.71,Default,,0000,0000,0000,,converters which are non isolated. This\Nmeans the ground in the input side and the
Dialogue: 0,0:06:21.71,0:06:31.72,Default,,0000,0000,0000,,ground on the output side are connected\Ntogether inside and this limits certain uses.
Dialogue: 0,0:06:31.72,0:06:37.94,Default,,0000,0000,0000,,Also you should not connect these\NDC/DC converters in series, so if you have
Dialogue: 0,0:06:37.94,0:06:44.07,Default,,0000,0000,0000,,a block like this and you think "oh, I\Ncould use two or three of them and just
Dialogue: 0,0:06:44.07,0:06:50.08,Default,,0000,0000,0000,,connect them in series to give it higher\Ninput voltages," that's gonna blow up very
Dialogue: 0,0:06:50.08,0:07:03.34,Default,,0000,0000,0000,,quickly. A block looks like this on a\Nscreen and might look like this in reality.
Dialogue: 0,0:07:03.34,0:07:13.30,Default,,0000,0000,0000,,Let's take a look inside. So all of these\NDC/DC converters consist of a power stage,
Dialogue: 0,0:07:13.30,0:07:23.62,Default,,0000,0000,0000,,a control system, and the feedback.\NThe feedback is there to provide a
Dialogue: 0,0:07:23.62,0:07:31.17,Default,,0000,0000,0000,,regulated output regardless of the\Noperating conditions. So what's inside a
Dialogue: 0,0:07:31.17,0:07:38.46,Default,,0000,0000,0000,,power stage? To have a deeper look inside\Nwe can consider this asynchronous buck
Dialogue: 0,0:07:38.46,0:07:46.10,Default,,0000,0000,0000,,converter where a switching element – a\NMOSFET – is controlled by an analog and
Dialogue: 0,0:07:46.10,0:07:53.49,Default,,0000,0000,0000,,digital circuitry. Feedback is provided\Nfrom the output voltage and we see a diode
Dialogue: 0,0:07:53.49,0:07:59.49,Default,,0000,0000,0000,,in the middle which I'm going to talk\Nabout soon. You also see two capacitors on
Dialogue: 0,0:07:59.49,0:08:04.43,Default,,0000,0000,0000,,the input side and on the output side,\Nwhich are also very important.
Dialogue: 0,0:08:04.43,0:08:07.74,Default,,0000,0000,0000,,More about them later.
Dialogue: 0,0:08:07.74,0:08:14.79,Default,,0000,0000,0000,,Let's consider the first situation:\Nthe switch is on – this is
Dialogue: 0,0:08:14.79,0:08:26.29,Default,,0000,0000,0000,,so-called "the on state" – and this forms\Na loop from the input to the output. The
Dialogue: 0,0:08:26.29,0:08:36.78,Default,,0000,0000,0000,,input capacitor we can neglect and in an\Nideal situation the output capacitor is,
Dialogue: 0,0:08:36.78,0:08:46.41,Default,,0000,0000,0000,,um, I will talk more about more about the\Noutput later.
Dialogue: 0,0:08:46.41,0:09:07.91,Default,,0000,0000,0000,,{\i1}pause{\i0}
Dialogue: 0,0:09:07.91,0:09:14.44,Default,,0000,0000,0000,,All right, I don't wanna make this into a\Nlecture and everybody is sleeping in
Dialogue: 0,0:09:14.44,0:09:19.53,Default,,0000,0000,0000,,and the fun part will start very soon.
Dialogue: 0,0:09:19.53,0:09:26.58,Default,,0000,0000,0000,,So, this DC/DC has two states: either the \Nswitch is on or switch is off. Right now
Dialogue: 0,0:09:26.58,0:09:30.88,Default,,0000,0000,0000,,the switch is on and you see that the \Ncurrent can flow from the input through
Dialogue: 0,0:09:30.88,0:09:41.43,Default,,0000,0000,0000,,this inductor to the output. The inductor\Nresists the change of current. It's like
Dialogue: 0,0:09:41.43,0:09:49.34,Default,,0000,0000,0000,,pushing a heavy mass and once it starts\Nmoving it wants to keep moving. That's why
Dialogue: 0,0:09:49.34,0:09:57.61,Default,,0000,0000,0000,,in this "on" state the input current flows\Nthrough the inductor and starts to
Dialogue: 0,0:09:57.61,0:10:06.37,Default,,0000,0000,0000,,increase while it's also flowing to the\Noutput. Then the converter turns the
Dialogue: 0,0:10:06.37,0:10:14.86,Default,,0000,0000,0000,,switch off, which comes to the off state,\Nand now the diode comes into play, which
Dialogue: 0,0:10:14.86,0:10:22.94,Default,,0000,0000,0000,,will keep the current recirculating. In\Nthis "off" state there is no current from
Dialogue: 0,0:10:22.94,0:10:29.39,Default,,0000,0000,0000,,the power from the source to the output,\Nbut the output is still powered from this
Dialogue: 0,0:10:29.39,0:10:40.72,Default,,0000,0000,0000,,decaying magnetic field through the\Ninductor. Sometimes you hear about
Dialogue: 0,0:10:40.72,0:10:48.78,Default,,0000,0000,0000,,synchronous DC/DC converters where this\Ndiode is replaced by another switch.
Dialogue: 0,0:10:48.78,0:10:58.00,Default,,0000,0000,0000,,In that case efficiency's increased since\Nthe voltage drop across MOSFET is lower
Dialogue: 0,0:10:58.00,0:11:04.51,Default,,0000,0000,0000,,than the forward voltage of the diode. In \Nthis case, as you can see, current is still
Dialogue: 0,0:11:04.51,0:11:10.18,Default,,0000,0000,0000,,being delivered to the output. And this is\Nthe big advantage of the buck converter
Dialogue: 0,0:11:10.18,0:11:16.76,Default,,0000,0000,0000,,that in both an "on" and an "off" state \Nthe output is sourced with current.
Dialogue: 0,0:11:16.76,0:11:25.15,Default,,0000,0000,0000,,What the output capacitor\Ndoes there is it provides the difference
Dialogue: 0,0:11:25.15,0:11:33.07,Default,,0000,0000,0000,,between the inductor current. On the lower\Nend you can see the inductor current.
Dialogue: 0,0:11:33.07,0:11:39.32,Default,,0000,0000,0000,,As the switch is on it ramps up and as switch\Nis off it ramps down, and in the middle
Dialogue: 0,0:11:39.32,0:11:48.93,Default,,0000,0000,0000,,you see this line which is the output\Ncurrent. So you see these triangles and
Dialogue: 0,0:11:48.93,0:11:57.04,Default,,0000,0000,0000,,this is what's provided by the output\Ncapacitor. Alright, so this is an actual
Dialogue: 0,0:11:57.04,0:12:01.62,Default,,0000,0000,0000,,part without the simplifications and I\Nwould like to talk a bit about the
Dialogue: 0,0:12:01.62,0:12:08.01,Default,,0000,0000,0000,,reference voltage and how that works. So\Nthis device creates an internal 0.7V
Dialogue: 0,0:12:08.01,0:12:18.15,Default,,0000,0000,0000,,reference and you can program the output\Nvoltage by choosing R1 and R2 on the
Dialogue: 0,0:12:18.15,0:12:27.36,Default,,0000,0000,0000,,left side so at your desired output\Nexactly 0.7V will be at this voltage
Dialogue: 0,0:12:27.36,0:12:36.73,Default,,0000,0000,0000,,divider and this converter will keep\Nregulating to reach the state.
Dialogue: 0,0:12:45.19,0:12:53.35,Default,,0000,0000,0000,,If you're looking for DC/DC converter to\Nyour next project then you might see
Dialogue: 0,0:12:53.35,0:12:58.15,Default,,0000,0000,0000,,a bunch of parameters and \NI'm gonna talk about those.
Dialogue: 0,0:12:58.15,0:13:04.24,Default,,0000,0000,0000,,So first you see a 3.3 volt 2 amp \Nconverter. What does it mean?
Dialogue: 0,0:13:07.06,0:13:12.39,Default,,0000,0000,0000,,This depends on how and \Nwho specifies that output
Dialogue: 0,0:13:12.39,0:13:19.11,Default,,0000,0000,0000,,because someone says it's two amps if it\Ncan provide two amps for a second and
Dialogue: 0,0:13:19.11,0:13:25.22,Default,,0000,0000,0000,,someone says it's two amps if it can\Ncontinuously provide the two amps even in
Dialogue: 0,0:13:25.22,0:13:32.67,Default,,0000,0000,0000,,a warm environment, so it's important to\Ntalk about if it's a peak or continuous
Dialogue: 0,0:13:32.67,0:13:40.40,Default,,0000,0000,0000,,current rating. Then there is this so\Ncalled "output ripple." You saw that
Dialogue: 0,0:13:40.40,0:13:48.76,Default,,0000,0000,0000,,switching action going on and off and that\Nwill create a ripple on the output voltage
Dialogue: 0,0:13:48.76,0:13:58.01,Default,,0000,0000,0000,,so it won't be 3.3V it will be oscillating\Naround that. This can be as low as a few
Dialogue: 0,0:13:58.01,0:14:07.74,Default,,0000,0000,0000,,microvolts and as high as a few volts,\Ndepending on the parameters. Also there is
Dialogue: 0,0:14:07.74,0:14:18.04,Default,,0000,0000,0000,,a voltage accuracy: maybe it's labeled \Nas 3.3V but actually it's 3.5 or 3.0.
Dialogue: 0,0:14:18.04,0:14:30.42,Default,,0000,0000,0000,,Load regulation: it's maybe 3.3V when it's\Nunloaded and as you increase the output it
Dialogue: 0,0:14:30.42,0:14:37.89,Default,,0000,0000,0000,,starts changing the output voltage. There\Nis the line regulation which means the
Dialogue: 0,0:14:37.89,0:14:46.57,Default,,0000,0000,0000,,input voltage has influence over the\Noutput, which is undesired. Then there is
Dialogue: 0,0:14:46.57,0:14:52.80,Default,,0000,0000,0000,,this maximum input voltage rating. Let's\Nsay this converter can tolerate seven
Dialogue: 0,0:14:52.80,0:15:00.26,Default,,0000,0000,0000,,volts on its input so you think "oh let's\Njust hook it up to USB, that's 5V, right?"
Dialogue: 0,0:15:00.26,0:15:12.40,Default,,0000,0000,0000,,Yes, but no, because when you use cables\Nand non-ideal conditions, you can create
Dialogue: 0,0:15:12.40,0:15:24.19,Default,,0000,0000,0000,,transients which overshoot the voltage \Npossibly way above this maximum rating and
Dialogue: 0,0:15:24.19,0:15:33.18,Default,,0000,0000,0000,,this can lead to very nasty surprises.\NBecause sometimes they fail short, which
Dialogue: 0,0:15:33.18,0:15:38.33,Default,,0000,0000,0000,,means they connect their input\Ndirectly to their output.
Dialogue: 0,0:15:38.33,0:15:45.36,Default,,0000,0000,0000,,In this case the device you connected to\Nthe converter might also go up in flames.
Dialogue: 0,0:15:45.36,0:15:50.89,Default,,0000,0000,0000,,So mind the transients and always\Nhave some margin between
Dialogue: 0,0:15:50.89,0:15:57.82,Default,,0000,0000,0000,,your desired input voltage and the\Nmaximum the converter can tolerate.
Dialogue: 0,0:15:57.82,0:16:06.80,Default,,0000,0000,0000,,Then you might see 95% efficiency\Nand that's also question at
Dialogue: 0,0:16:06.80,0:16:18.38,Default,,0000,0000,0000,,which load because at maximum specified\Nload it will be lower, and at lower/less load it
Dialogue: 0,0:16:18.38,0:16:23.81,Default,,0000,0000,0000,,will be also lower, so there is this\Nefficiency peak. That marketing people love
Dialogue: 0,0:16:23.81,0:16:29.17,Default,,0000,0000,0000,,to specify. There's also this so called\N"quiescent current" which means your
Dialogue: 0,0:16:29.17,0:16:38.72,Default,,0000,0000,0000,,converter draws current from your input\Neven when there is nothing on its output
Dialogue: 0,0:16:38.72,0:16:45.83,Default,,0000,0000,0000,,and if it runs from a battery this can\Ndrain your battery in days or weeks, so
Dialogue: 0,0:16:45.83,0:16:53.91,Default,,0000,0000,0000,,you must pay attention to this. And there is\Nthis other factor called "switching
Dialogue: 0,0:16:53.91,0:17:00.60,Default,,0000,0000,0000,,frequency" so how fast, how often the\Ninternal switch changes state, but this
Dialogue: 0,0:17:00.60,0:17:06.29,Default,,0000,0000,0000,,might not be a constant value, especially\Nwith the previously mentioned quiescent
Dialogue: 0,0:17:06.29,0:17:16.96,Default,,0000,0000,0000,,current feature, the converters that excel\Nat having a low quiescent current don't
Dialogue: 0,0:17:16.96,0:17:23.64,Default,,0000,0000,0000,,have fixed switching frequency, so you\Nmight have noise at different frequency
Dialogue: 0,0:17:23.64,0:17:35.04,Default,,0000,0000,0000,,bands and disturb your circuits or radio\Nnoise. Let's talk about a few features,
Dialogue: 0,0:17:35.04,0:17:43.13,Default,,0000,0000,0000,,you might want to look for. "Enable": enable\Nfunctionality. This is very useful to
Dialogue: 0,0:17:43.13,0:17:50.60,Default,,0000,0000,0000,,easily disable your DC/DC converter and \Nwithout having to interrupt either the
Dialogue: 0,0:17:50.60,0:18:01.90,Default,,0000,0000,0000,,input side or the output side. Let's say\Nyou have a 20 amp output converter – you
Dialogue: 0,0:18:01.90,0:18:09.08,Default,,0000,0000,0000,,really don't want to switch the 20 amp\Nwith a mechanical big switch. Instead
Dialogue: 0,0:18:09.08,0:18:15.65,Default,,0000,0000,0000,,of that you have a logic input to\Nyour DC/DC converter with which you can
Dialogue: 0,0:18:15.65,0:18:23.44,Default,,0000,0000,0000,,turn this completely off. Then there is so\Ncalled "undervoltage lockout": you might
Dialogue: 0,0:18:23.44,0:18:31.75,Default,,0000,0000,0000,,want to prevent it from running below a\Ncertain input voltage to prevent draining
Dialogue: 0,0:18:31.75,0:18:40.18,Default,,0000,0000,0000,,your battery too deep and turning it\Ncompletely off. There's "power good" that
Dialogue: 0,0:18:40.18,0:18:45.80,Default,,0000,0000,0000,,can provide information to your processor\Nthat the output voltage is in regulation
Dialogue: 0,0:18:45.80,0:18:51.47,Default,,0000,0000,0000,,and stabilized. So if you hook up the\N"power good" output to let's say a reset
Dialogue: 0,0:18:51.47,0:18:58.68,Default,,0000,0000,0000,,line or "enable", then you can be sure\Nthat the output voltage is always stable
Dialogue: 0,0:18:58.68,0:19:07.27,Default,,0000,0000,0000,,and your processors are not going to go\Ninto glitch. Overtemperature shutdown is
Dialogue: 0,0:19:07.27,0:19:16.05,Default,,0000,0000,0000,,very common these days and that makes\Nthese tiny converters almost
Dialogue: 0,0:19:16.05,0:19:22.46,Default,,0000,0000,0000,,indestructible because if they get too hot\Nthey just turn off completely before they
Dialogue: 0,0:19:22.46,0:19:30.77,Default,,0000,0000,0000,,get permanently damaged. Efficient\Nstandby: this is the so called low
Dialogue: 0,0:19:30.77,0:19:37.76,Default,,0000,0000,0000,,quiescent current option. That means if\Nyour output is off, your processor is
Dialogue: 0,0:19:37.76,0:19:45.75,Default,,0000,0000,0000,,sleeping, then it willl reduce switching\Naction to reduce switching losses and
Dialogue: 0,0:19:45.75,0:19:51.90,Default,,0000,0000,0000,,might only draw a few micro amps or even\Nnano amps. Very important for battery
Dialogue: 0,0:19:51.90,0:19:59.13,Default,,0000,0000,0000,,powered applications. Then you might see\Novercurrent protection which makes the
Dialogue: 0,0:19:59.13,0:20:04.80,Default,,0000,0000,0000,,output very robust. You can even make a\Nshort circuit and the overcurrent protection
Dialogue: 0,0:20:04.80,0:20:17.42,Default,,0000,0000,0000,,will limit the output current to this\Nvalue and this prevents damaging of the
Dialogue: 0,0:20:17.42,0:20:24.44,Default,,0000,0000,0000,,converter and also damage to the cables\Nand switches if they are rated to
Dialogue: 0,0:20:24.44,0:20:33.00,Default,,0000,0000,0000,,withstand the overcurrent protection\Nlimit. Now let's talk about noise. The
Dialogue: 0,0:20:33.00,0:20:43.74,Default,,0000,0000,0000,,output ripple is not exactly noise. Output\Nripple is there because the output
Dialogue: 0,0:20:43.74,0:20:55.16,Default,,0000,0000,0000,,capacitor is non-ideal and usually this\Nthis is very low on a properly designed
Dialogue: 0,0:20:55.16,0:21:02.44,Default,,0000,0000,0000,,converter but if you measure the output\Nyou might see spikes on the output and
Dialogue: 0,0:21:02.44,0:21:14.87,Default,,0000,0000,0000,,that's not ripple. That's conducted EMI\Nbecause on that inductor the windings are
Dialogue: 0,0:21:14.87,0:21:21.78,Default,,0000,0000,0000,,coupled very closely, there is some\Ncapacitive coupling between the wires, so
Dialogue: 0,0:21:21.78,0:21:28.80,Default,,0000,0000,0000,,the digital on-off action from the\Nswitches will propagate to some extent to
Dialogue: 0,0:21:28.80,0:21:35.25,Default,,0000,0000,0000,,the output. This is attenuated by the\Ncapacitors but they cannot be completely
Dialogue: 0,0:21:35.25,0:21:42.03,Default,,0000,0000,0000,,filtered off and you will see the\Nswitching frequency and even upper
Dialogue: 0,0:21:42.03,0:21:50.79,Default,,0000,0000,0000,,harmonics of it but this can also be\Nfiltered. There is also radiated EMI,
Dialogue: 0,0:21:50.79,0:21:56.98,Default,,0000,0000,0000,,which comes mostly from the switching node\Nand capacitive coupling to the ground
Dialogue: 0,0:21:56.98,0:22:05.92,Default,,0000,0000,0000,,plane, and also the inductor – if it's not\Nshielded then a magnetic field can also
Dialogue: 0,0:22:05.92,0:22:15.96,Default,,0000,0000,0000,,radiate out and cause interference. On\Nthis picture what you see is that gray
Dialogue: 0,0:22:15.96,0:22:27.28,Default,,0000,0000,0000,,block, that's a shielded inductor, and the\Ntwo blue connectors at the end of this PCB
Dialogue: 0,0:22:27.28,0:22:34.75,Default,,0000,0000,0000,,are screw terminals. I personally advise\Nagainst using this style of screw
Dialogue: 0,0:22:34.75,0:22:41.70,Default,,0000,0000,0000,,terminals because the wires can easily\Nslip out, make a short, or you don't
Dialogue: 0,0:22:41.70,0:22:52.90,Default,,0000,0000,0000,,notice that they are not connected, so I\Nprefer a different style of connectors.
Dialogue: 0,0:22:52.90,0:23:00.35,Default,,0000,0000,0000,,It's good to know about non-ideal\Ncomponents. The capacitors that are used
Dialogue: 0,0:23:00.35,0:23:10.12,Default,,0000,0000,0000,,have a so called DC bias. These multi-\Nlayer ceramic capacitors are very
Dialogue: 0,0:23:10.12,0:23:17.72,Default,,0000,0000,0000,,sensitive to the DC voltage across the\Nterminals and if they are rated, let's say
Dialogue: 0,0:23:17.72,0:23:24.83,Default,,0000,0000,0000,,20 microfarads, at the rated voltage they\Nmight lose up to 90 percent of their
Dialogue: 0,0:23:24.83,0:23:30.66,Default,,0000,0000,0000,,capacity. So you always have to pick a\Ncapacitor that's rated to a higher voltage
Dialogue: 0,0:23:30.66,0:23:38.33,Default,,0000,0000,0000,,than what your output is to compensate for\Nthis effect, and you also need to put more
Dialogue: 0,0:23:38.33,0:23:47.77,Default,,0000,0000,0000,,capacitors at your output than what you\Nwould think in an ideal situation. Mind
Dialogue: 0,0:23:47.77,0:23:55.00,Default,,0000,0000,0000,,the transients! As I said, if you plan to\Nhotplug, connect to live wires to your
Dialogue: 0,0:23:55.00,0:24:01.29,Default,,0000,0000,0000,,converter, you have to keep in mind the\Ninrush current. Those capacitors, when
Dialogue: 0,0:24:01.29,0:24:11.75,Default,,0000,0000,0000,,they are fully discharged and you connect\Nthat to the input, then they will try to
Dialogue: 0,0:24:11.75,0:24:21.49,Default,,0000,0000,0000,,charge to the input voltage as fast\Nas the cabling lets that happen, and the
Dialogue: 0,0:24:21.49,0:24:28.98,Default,,0000,0000,0000,,cables have inductance which will store\Nenergy and overshoot the input voltage.
Dialogue: 0,0:24:28.98,0:24:39.35,Default,,0000,0000,0000,,When fiddling with MOSFETs, don't forget\Nthe ESD protection. MOSFETs are very
Dialogue: 0,0:24:39.35,0:24:49.79,Default,,0000,0000,0000,,sensitive at their gate, because the oxide\Nlayer is so thin that even 20V voltage is
Dialogue: 0,0:24:49.79,0:24:57.45,Default,,0000,0000,0000,,enough to break it down, and a 20V ESD\Nstrike is something you probably don't
Dialogue: 0,0:24:57.45,0:25:08.92,Default,,0000,0000,0000,,even notice, but it can damage the\NMOSFETs. And ever avoid the 7800 series
Dialogue: 0,0:25:08.92,0:25:17.48,Default,,0000,0000,0000,,LDO, because it's a very old part and I\Nstill see it in new designs, while there
Dialogue: 0,0:25:17.48,0:25:25.93,Default,,0000,0000,0000,,are much better ones with better\Nregulation, less quiescent current, and
Dialogue: 0,0:25:25.93,0:25:39.99,Default,,0000,0000,0000,,it's also an LDO, so it's like just\Nmarginally related to DC/DCs. If
Dialogue: 0,0:25:39.99,0:25:46.30,Default,,0000,0000,0000,,you make your own DC/DC converters instead\Nof buying one, you should read the
Dialogue: 0,0:25:46.30,0:25:57.67,Default,,0000,0000,0000,,datasheet and follow the instructions\Nbecause the manufacturers give you a
Dialogue: 0,0:25:57.67,0:26:05.34,Default,,0000,0000,0000,,proven tested layout, which is typically\Ngood advice to follow and you should only
Dialogue: 0,0:26:05.34,0:26:25.90,Default,,0000,0000,0000,,deviate from that if you know what you're\Ndoing. {\i1}I'm sorry{\i0}
Dialogue: 0,0:26:25.90,0:26:48.30,Default,,0000,0000,0000,,{\i1}pause{\i0}\NAlright, that mostly concludes what I was trying
Dialogue: 0,0:26:48.30,0:26:56.81,Default,,0000,0000,0000,,to talk about and now it's time for your\Nquestions.
Dialogue: 0,0:26:56.81,0:27:02.07,Default,,0000,0000,0000,,{\i1}applause{\i0}
Dialogue: 0,0:27:02.07,0:27:09.03,Default,,0000,0000,0000,,Herald: Now there are two microphones one\Nthere and one over there, usually they
Dialogue: 0,0:27:09.03,0:27:18.72,Default,,0000,0000,0000,,are… ah, here comes the light. Are there\Nany questions? How about the signal angel,
Dialogue: 0,0:27:18.72,0:27:25.19,Default,,0000,0000,0000,,does the internet have any questions? The\Ninternet doesn't have a question but
Dialogue: 0,0:27:25.19,0:27:29.11,Default,,0000,0000,0000,,here's one up front.\NQ: What would you recommend instead of
Dialogue: 0,0:27:29.11,0:27:35.65,Default,,0000,0000,0000,,screw terminals?\NZoé: That's a very good question and that
Dialogue: 0,0:27:35.65,0:27:42.29,Default,,0000,0000,0000,,really depends on the application. You can\Nhave different kind of screw terminals,
Dialogue: 0,0:27:42.29,0:27:56.37,Default,,0000,0000,0000,,which use either crimped therminals on the\Ncable so you have a cable shoe.
Dialogue: 0,0:27:56.37,0:28:01.64,Default,,0000,0000,0000,,Q: Like a ring or something?\NZoé: Yes. Because then there is no way that it can
Dialogue: 0,0:28:01.64,0:28:09.61,Default,,0000,0000,0000,,slip out. For less current you can use\Ndupont connectors, they can take like
Dialogue: 0,0:28:09.61,0:28:22.88,Default,,0000,0000,0000,,2 to 3A per contact. You know the standard\Npin header and that kind of thing. And
Dialogue: 0,0:28:22.88,0:28:29.80,Default,,0000,0000,0000,,there are also latching connectors from\Nmolex and other manufacturers. The problem
Dialogue: 0,0:28:29.80,0:28:39.31,Default,,0000,0000,0000,,is with that you need crimping tools and\Nthose can be very expensive. So it first
Dialogue: 0,0:28:39.31,0:28:48.54,Default,,0000,0000,0000,,makes sense to get those when you have a\Nhackerspace or you can share it with other
Dialogue: 0,0:28:48.54,0:28:52.82,Default,,0000,0000,0000,,people.\NHerald: The next question, please?
Dialogue: 0,0:28:52.82,0:28:58.99,Default,,0000,0000,0000,,Q: Thank you for your talk. On your last\Nslide last point you mentioned stability
Dialogue: 0,0:28:58.99,0:29:07.17,Default,,0000,0000,0000,,analysis. What is your experience with\Nrunning such converters in parallel for
Dialogue: 0,0:29:07.17,0:29:13.65,Default,,0000,0000,0000,,redundancy and how would you do the\Nanalysis there?
Dialogue: 0,0:29:13.65,0:29:22.92,Default,,0000,0000,0000,,Zoé: Running current mode converters\Nparallel is typically okay, but they won't
Dialogue: 0,0:29:22.92,0:29:30.25,Default,,0000,0000,0000,,do current sharing automatically. So this\None converter has a certain output voltage
Dialogue: 0,0:29:30.25,0:29:37.72,Default,,0000,0000,0000,,set and the other one has little bit\Ndifferent voltage, and that will create a
Dialogue: 0,0:29:37.72,0:29:44.09,Default,,0000,0000,0000,,difference in their output currents, and\Nthere are topologies and there are
Dialogue: 0,0:29:44.09,0:29:50.62,Default,,0000,0000,0000,,converters which are prepared for parallel\Noperation and they can provide current
Dialogue: 0,0:29:50.62,0:29:56.30,Default,,0000,0000,0000,,information to all of the parallel\Nconverters, and they can ultimately
Dialogue: 0,0:29:56.30,0:30:07.41,Default,,0000,0000,0000,,synchronize. For stability, that should\Nnot influence the stability of it. What I
Dialogue: 0,0:30:07.41,0:30:14.76,Default,,0000,0000,0000,,should have mentioned is stability\Nanalysis because we have a control loop.
Dialogue: 0,0:30:14.76,0:30:22.78,Default,,0000,0000,0000,,The control loop takes the output and\Ncreates a control signal that influences
Dialogue: 0,0:30:22.78,0:30:36.60,Default,,0000,0000,0000,,the output, but this loop has a delay, and\Nbecause of this delay, basically you can
Dialogue: 0,0:30:36.60,0:30:47.23,Default,,0000,0000,0000,,make an oscillator of this, and to avoid\Nthat, you can use a network analyzer and
Dialogue: 0,0:30:47.23,0:30:56.86,Default,,0000,0000,0000,,inject a signal into the converter.\NQ: Thank you.
Dialogue: 0,0:30:56.86,0:31:09.17,Default,,0000,0000,0000,,Herald: Yeah, you go ahead, over there.\NQ: Hi, what would you say the choice is
Dialogue: 0,0:31:09.17,0:31:13.52,Default,,0000,0000,0000,,between a dis-synchronous mode or\Na forced-synchronous mode?
Dialogue: 0,0:31:13.52,0:31:33.01,Default,,0000,0000,0000,,Zoé: That's a very good question. All\Nright so when I talked about this briefly
Dialogue: 0,0:31:33.01,0:31:39.97,Default,,0000,0000,0000,,and mentioned the synchronous converters,\Nwith forced synchronous converters you
Dialogue: 0,0:31:39.97,0:31:49.29,Default,,0000,0000,0000,,have a control switch and those have\Ntypically fixed switch frequency. If the
Dialogue: 0,0:31:49.29,0:31:55.03,Default,,0000,0000,0000,,output current is zero, then during half\Nof the period current will flow backward
Dialogue: 0,0:31:55.03,0:32:01.75,Default,,0000,0000,0000,,from the output capacitor to the input\Nside and then the next half period that
Dialogue: 0,0:32:01.75,0:32:06.43,Default,,0000,0000,0000,,current will flow back from the input to\Nthe output, so basically energy swings
Dialogue: 0,0:32:06.43,0:32:15.66,Default,,0000,0000,0000,,between input and output and this causes\Nefficiency loss, but this also avoids
Dialogue: 0,0:32:15.66,0:32:30.77,Default,,0000,0000,0000,,operation in discontinuous mode, which\Nreduces ripple and reduces EMI. So it
Dialogue: 0,0:32:30.77,0:32:34.85,Default,,0000,0000,0000,,depends on your application.\NQ: Thanks.
Dialogue: 0,0:32:34.85,0:32:38.70,Default,,0000,0000,0000,,Zoé: You're welcome.\NHerald: The next question?
Dialogue: 0,0:32:38.70,0:32:48.39,Default,,0000,0000,0000,,Q: Hi, Zoé, thank you for the talk! I have\Na question about: you mentioned linear
Dialogue: 0,0:32:48.39,0:32:54.22,Default,,0000,0000,0000,,regulators at the end, what are they used\Nfor in this context?
Dialogue: 0,0:32:54.22,0:33:02.01,Default,,0000,0000,0000,,Zoé: you mean 7800 series?\NQ: Yes.
Dialogue: 0,0:33:02.01,0:33:13.91,Default,,0000,0000,0000,,Q: Not, the one before, I think.\NZoé: Those were very good regulators in
Dialogue: 0,0:33:13.91,0:33:22.13,Default,,0000,0000,0000,,the 70s and those are linear regulators,\Nand the problem with the 7800 series is
Dialogue: 0,0:33:22.13,0:33:28.54,Default,,0000,0000,0000,,everybody knows about them because books\Nare full of them but they have quite a few
Dialogue: 0,0:33:28.54,0:33:41.27,Default,,0000,0000,0000,,milli amps of quiescent current. They also\Nhave bad regulation against load and line
Dialogue: 0,0:33:41.27,0:33:48.14,Default,,0000,0000,0000,,transients and they are not cheaper than\Nmuch of their alternatives, so there's
Dialogue: 0,0:33:48.14,0:33:56.02,Default,,0000,0000,0000,,really no reason to use those. You can use\Nfor example a DC/DC pre-regulator and then
Dialogue: 0,0:33:56.02,0:33:59.59,Default,,0000,0000,0000,,an LDO afterward to smooth out the\Nvoltage.
Dialogue: 0,0:33:59.59,0:34:07.20,Default,,0000,0000,0000,,Q: Okay, thank you.\NHerald: Go ahead
Dialogue: 0,0:34:07.20,0:34:13.49,Default,,0000,0000,0000,,Q: Thank you very much! My question is,\Nyou mentioned the noise coupled via the
Dialogue: 0,0:34:13.49,0:34:18.44,Default,,0000,0000,0000,,inductor to the output. Which sort of\Nfilter do you recommend: differential
Dialogue: 0,0:34:18.44,0:34:24.06,Default,,0000,0000,0000,,noise or common mode noise, and input or\Noutput? Which is most important from your
Dialogue: 0,0:34:24.06,0:34:32.04,Default,,0000,0000,0000,,perspective?\NZoé: So lots of the noise goes actually
Dialogue: 0,0:34:32.04,0:34:40.46,Default,,0000,0000,0000,,back to the input supply and I said that\Nin an ideal circuit the input capacitor is
Dialogue: 0,0:34:40.46,0:34:46.97,Default,,0000,0000,0000,,not necessary, but in a real circuit the\Ninput capacitor is critical because the
Dialogue: 0,0:34:46.97,0:35:03.52,Default,,0000,0000,0000,,input inductance is seen by by the switch.\NIf you let me show you. On this chart you
Dialogue: 0,0:35:03.52,0:35:11.66,Default,,0000,0000,0000,,see the inductor current and the input\Ncurrent, it follows the inductor current
Dialogue: 0,0:35:11.66,0:35:17.72,Default,,0000,0000,0000,,only during the on phase which means after\Nthe end of the on phase and beginning of
Dialogue: 0,0:35:17.72,0:35:25.52,Default,,0000,0000,0000,,the off phase it falls from maximum value\Nto zero and later on at the end of the off
Dialogue: 0,0:35:25.52,0:35:32.46,Default,,0000,0000,0000,,phase and the beginning of the on phase\Nthe current jumps from zero to the output
Dialogue: 0,0:35:32.46,0:35:42.38,Default,,0000,0000,0000,,current, and these jumps in the supply\Ncurrent create an awful lot of EMI if the
Dialogue: 0,0:35:42.38,0:35:51.61,Default,,0000,0000,0000,,input capacitor is not large enough so\Nthis is a very critical thing. I saw quite
Dialogue: 0,0:35:51.61,0:35:56.81,Default,,0000,0000,0000,,a few converters where the input capacitor\Nis under dimensioned and when you run it
Dialogue: 0,0:35:56.81,0:36:03.37,Default,,0000,0000,0000,,over longer wires with more parasitic\Ninductance, that can create a lot of EMI.
Dialogue: 0,0:36:03.37,0:36:12.09,Default,,0000,0000,0000,,For ways of reducing the the noise on the\Noutput, the best way is to have proper
Dialogue: 0,0:36:12.09,0:36:20.71,Default,,0000,0000,0000,,filtering capacitors. If you use ceramic\Ncapacitors and enough high enough value
Dialogue: 0,0:36:20.71,0:36:33.67,Default,,0000,0000,0000,,you can get rid of almost all of the\Nnoise. I made a design which had microvolt
Dialogue: 0,0:36:33.67,0:36:43.61,Default,,0000,0000,0000,,noise because I found a capacitor with its\Nresonance frequency exactly at the
Dialogue: 0,0:36:43.61,0:36:48.61,Default,,0000,0000,0000,,switching frequency, so basically all that\Nnoise that was coming from switching
Dialogue: 0,0:36:48.61,0:36:55.26,Default,,0000,0000,0000,,action was reflected away and higher\Nfrequency ranges where it got filtered
Dialogue: 0,0:36:55.26,0:37:05.27,Default,,0000,0000,0000,,dissipated much faster. You can\Nuse PI filters at the output but mind
Dialogue: 0,0:37:05.27,0:37:16.89,Default,,0000,0000,0000,,that you worsen the transient behavior of\Nyour converters. So if your load suddenly
Dialogue: 0,0:37:16.89,0:37:23.06,Default,,0000,0000,0000,,needs a lot more power and starts drawing\Nmore current, then your converter will
Dialogue: 0,0:37:23.06,0:37:35.94,Default,,0000,0000,0000,,react slower because of the\Nfilter you just added. PI filters or RC
Dialogue: 0,0:37:35.94,0:37:38.89,Default,,0000,0000,0000,,filters if you don't need that much\Ncurrent.
Dialogue: 0,0:37:38.89,0:37:44.62,Default,,0000,0000,0000,,Q: Okay, thanks.\NHerald: Okay great I don't see any more
Dialogue: 0,0:37:44.62,0:37:52.54,Default,,0000,0000,0000,,questions, so everything seems to be fully\Nexplained. Thank you and give her a
Dialogue: 0,0:37:52.54,0:37:55.22,Default,,0000,0000,0000,,applause and good night.
Dialogue: 0,0:37:55.22,0:37:56.67,Default,,0000,0000,0000,,{\i1}applause{\i0}
Dialogue: 0,0:37:56.67,0:38:02.96,Default,,0000,0000,0000,,Zoé: Thank you
Dialogue: 0,0:38:02.96,0:38:06.84,Default,,0000,0000,0000,,{\i1}postroll music{\i0}
Dialogue: 0,0:38:06.84,0:38:30.00,Default,,0000,0000,0000,,Subtitles created by c3subtitles.de\Nin the year 2020. Join, and help us!