AC-line supplies - under 1% loss

[Winfield Hill]

TI's TIDA-00961 PFC reference design, see
link: http://www.ti.com/tool/TIDA-00961
is for a 1.6kW offline PFC stage, with a
goal of under 1% total loss. In place
of the customary diode bridge there's a
totem-pole bridgeless PFC. It has two
GaN half-bridge MOSFET boost-converters,
plus a Silicon MOSFET active rectifier.
They include a bridge rectifier, but it's
bypassed by MOSFETs. The active rectifier
uses a pair of massive 500-volt MOSFETs,
STY105NM50N by ST, with Ron = 19 m-ohms!
Wow, but these beasts cost $20 each. The
LMG3410 GaN switches are wimpy, with Ron
over 100 m-ohms when hot, so they use two
interleaved sets. They cost $28 each, so
that's $152 total for the power MOSFETs.


--
Thanks,
- Win

 

[Winfield Hill]

Winfield Hill wrote...

TI's TIDA-00961 PFC reference design, see
link: http://www.ti.com/tool/TIDA-00961
is for a 1.6kW offline PFC stage, with a
goal of under 1% total loss. In place
of the customary diode bridge there's a
totem-pole bridgeless PFC. It has two
GaN half-bridge MOSFET boost-converters,
plus a Silicon MOSFET active rectifier.
They include a bridge rectifier, but it's
bypassed by MOSFETs. The active rectifier
uses a pair of massive 500-volt MOSFETs,
STY105NM50N by ST, with Ron = 19 m-ohms!
Wow, but these beasts cost $20 each. The
LMG3410 GaN switches are wimpy, with Ron
over 100 m-ohms when hot, so they use two
interleaved sets. They cost $28 each, so
that's $152 total for the power MOSFETs.

They could have used four STY105NM50N, for
$80 total, and spent more on the inductor.
The two serving as 60Hz active rectifiers
are driven by 5k gate resistors, turn-on
time constant Rg Ciss = 5k 10nF = 50us.


--
Thanks,
- Win

 

[Winfield Hill]

Winfield Hill wrote...

Winfield Hill wrote...

... The active rectifier
uses a pair of massive 500-volt MOSFETs,
STY105NM50N by ST, with Ron = 19 m-ohms!

They could have used four STY105NM50N, for
$80 total, and spent more on the inductor.
The two serving as 60Hz active rectifiers
are driven by 5k gate resistors, turn-on
time constant Rg Ciss = 5k 10nF = 50us.

Forgetting the PFC stage for the moment,
it'd be easy to make a 99.9% efficient
1.2 kW active full-bridge rectifier,
i.e., with loss < 0.1%.


--
Thanks,
- Win

 

[Winfield Hill]

klaus.kragelund@gmail.com wrote...

Active rectifiers for mains bridge replacement is easy

What is hard is to construct one that handles 4kV surge
and burst and keeping a price point not orders of
magnitude higher than a standard bridge

A standard bridge is dirt cheap, so a few orders
of magnitude higher isn't so bad. I have no
experience with MOSFETs as bridges, but the PFC
guys don't seem worried by it. It's not very
hard to protect the gates, and these big MOSFETs
can handle a lot of energy while in avalanche.


--
Thanks,
- Win

 

Active rectifiers for mains bridge replacement is easy

What is hard is to construct one that handles 4kV surge and burst and keeping a price point not orders of magnitude higher than a standard bridge

Cheers

Klaus

 

[Winfield Hill]

Winfield Hill wrote...

klaus.kragelund@gmail.com wrote...

Active rectifiers for mains bridge replacement is easy

What is hard is to construct one that handles 4kV
surge and burst and keeping a price point not orders
of magnitude higher than a standard bridge

A standard bridge is dirt cheap, so a few orders
of magnitude higher isn't so bad. I have no
experience with MOSFETs as bridges, but the PFC
guys don't seem worried by it. It's not very
hard to protect the gates, and these big MOSFETs
can handle a lot of energy while in avalanche.

I've studied avalanche breakdown in many types of
silicon devices, read papers, and have made many
measurements of MOSFET avalanche breakdown, and
would like to assert that it's not intrinsically
more vulnerable than a rectifier diode.

Anyway, the central idea here is that if the HV
power-transmission guys can keep their losses well
under 1%, right up to our property boundary, why
can't we try to do the same in our consumption?

On the subject of cost, the 19 m-ohm STY105NM50N
is the best 500V part in my table, and is much
better than needed, even for 1.6kW. Alternates
might be the 28 m-ohm STY100NM60N, which Newark
has on sale for $7, or the 65 m-ohm FCH072N60F,
which is going for as little as $2.50. That one
would create about 0.06% loss at 1.6kW, or about
14x lower than a bridge rectifier. The $7 part
costs $28, but would save $70 on electricity,
after 15 years of service with a 20% duty cycle.


--
Thanks,
- Win

 

[Rick C]

On Thursday, September 12, 2019 at 1:53:18 PM UTC-4, klaus.k...@gmail.com wrote:

Active rectifiers for mains bridge replacement is easy

What is hard is to construct one that handles 4kV surge and burst and keeping a price point not orders of magnitude higher than a standard bridge

I wonder what Tesla does? With high efficiencies in the motor and battery, I'd hate to think they are tossing much in poor efficiency designs.

--

Rick C.

- Get 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209

 

[Lasse Langwadt Christense]

torsdag den 12. september 2019 kl. 23.21.13 UTC+2 skrev Rick C:

On Thursday, September 12, 2019 at 1:53:18 PM UTC-4, klaus.k...@gmail.com wrote:
Active rectifiers for mains bridge replacement is easy

What is hard is to construct one that handles 4kV surge and burst and keeping a price point not orders of magnitude higher than a standard bridge

I wonder what Tesla does? With high efficiencies in the motor and battery, I'd hate to think they are tossing much in poor efficiency designs.

not many details but still interesting, 97% @ 25kW

https://youtu.be/qy9pltNa0rY

 

[Tim Williams]

<klaus.kragelund@gmail.com> wrote in message
news:7caf24f3-4095-44d1-8f8d-40fb8c8ef243@googlegroups.com...

Active rectifiers for mains bridge replacement is easy

What is hard is to construct one that handles 4kV surge and burst and
keeping a price point not orders of magnitude higher than a standard
bridge

Not so bad with transistors that big, I would guess. You can keep it
switched on during the surge -- dumping the surge current into the filter
cap (perhaps use a nice PN diode to bypass from PFC input to bulk cap, to
handle both inrush and surge).

Tim

--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
Website: https://www.seventransistorlabs.com/

 

"Tim Williams" <tiwill@seventransistorlabs.com> wrote in
news:qleh4d$u15$1@dont-email.me:

klaus.kragelund@gmail.com> wrote in message
news:7caf24f3-4095-44d1-8f8d-40fb8c8ef243@googlegroups.com...
Active rectifiers for mains bridge replacement is easy

What is hard is to construct one that handles 4kV surge and burst
and keeping a price point not orders of magnitude higher than a
standard bridge


Not so bad with transistors that big, I would guess. You can keep
it switched on during the surge -- dumping the surge current into
the filter cap (perhaps use a nice PN diode to bypass from PFC
input to bulk cap, to handle both inrush and surge).

Tim

HV diodes are often a number of PN junction elements in series.

Not going to get the efficiency number, but not needed anyway to
that degree.

To get the surge protection, series together diodes. Yes the
junction potential also sums.

99.9%

That is relative. If one is only trying to rectify ten volts, the
losses would be greater than if one were trying to do 100 volts.

The same reason we use HV for distribution. The losses are
proportionately less.

 

On Thursday, 12 September 2019 20:25:33 UTC+2, Winfield Hill wrote:

klaus.kragelund@gmail.com wrote...

Active rectifiers for mains bridge replacement is easy

What is hard is to construct one that handles 4kV surge
and burst and keeping a price point not orders of
magnitude higher than a standard bridge

A standard bridge is dirt cheap, so a few orders
of magnitude higher isn't so bad. I have no
experience with MOSFETs as bridges, but the PFC
guys don't seem worried by it. It's not very
hard to protect the gates, and these big MOSFETs
can handle a lot of energy while in avalanche.

It's not so much about energy, but dv/dt over drain source during burst. EN61000-4 test define 2kV/5ns, which is far higher than most MOSFET dv/dt can handle.

Cheers

Klaus

 

On Friday, 13 September 2019 00:33:54 UTC+2, Tim Williams wrote:

klaus.kragelund@gmail.com> wrote in message
news:7caf24f3-4095-44d1-8f8d-40fb8c8ef243@googlegroups.com...
Active rectifiers for mains bridge replacement is easy

What is hard is to construct one that handles 4kV surge and burst and
keeping a price point not orders of magnitude higher than a standard
bridge


Not so bad with transistors that big, I would guess. You can keep it
switched on during the surge -- dumping the surge current into the filter
cap (perhaps use a nice PN diode to bypass from PFC input to bulk cap, to
handle both inrush and surge).

If you switch it on during the surge, how do you do than with confidence in sub us. Surge is up to 4kV at 1.2us

And when do you turn off? If you do not turn off in time, you connect the cap to the line and bad things happen

Cheers

Klaus

 

On Friday, 13 September 2019 11:01:04 UTC+2, klaus.k...@gmail.com wrote:

On Thursday, 12 September 2019 20:25:33 UTC+2, Winfield Hill wrote:
klaus.kragelund@gmail.com wrote...

Active rectifiers for mains bridge replacement is easy

What is hard is to construct one that handles 4kV surge
and burst and keeping a price point not orders of
magnitude higher than a standard bridge

A standard bridge is dirt cheap, so a few orders
of magnitude higher isn't so bad. I have no
experience with MOSFETs as bridges, but the PFC
guys don't seem worried by it. It's not very
hard to protect the gates, and these big MOSFETs
can handle a lot of energy while in avalanche.

It's not so much about energy, but dv/dt over drain source during burst. EN61000-4 test define 2kV/5ns, which is far higher than most MOSFET dv/dt can handle.

Cheers

Klaus

https://www.infineon.com/dgdl/mosfet.pdf?fileId=5546d462533600a4015357444e913f4f

Page 11

 

[Jan Panteltje]

On a sunny day (Fri, 13 Sep 2019 02:01:00 -0700 (PDT)) it happened
klaus.kragelund@gmail.com wrote in
<bbcb097a-e72a-4b73-8560-f50ef1600f2a@googlegroups.com>:

On Thursday, 12 September 2019 20:25:33 UTC+2, Winfield Hill wrote:
klaus.kragelund@gmail.com wrote...

Active rectifiers for mains bridge replacement is easy

What is hard is to construct one that handles 4kV surge
and burst and keeping a price point not orders of
magnitude higher than a standard bridge

A standard bridge is dirt cheap, so a few orders
of magnitude higher isn't so bad. I have no
experience with MOSFETs as bridges, but the PFC
guys don't seem worried by it. It's not very
hard to protect the gates, and these big MOSFETs
can handle a lot of energy while in avalanche.

It's not so much about energy, but dv/dt over drain source during burst. EN61000-4 test define 2kV/5ns, which is far higher than
most MOSFET dv/dt can handle.

I would not expact 5nS to pass the mains filter L C.
That is 200 MHz.

 

On Friday, 13 September 2019 11:17:33 UTC+2, Jan Panteltje wrote:

On a sunny day (Fri, 13 Sep 2019 02:01:00 -0700 (PDT)) it happened
klaus.kragelund@gmail.com wrote in
bbcb097a-e72a-4b73-8560-f50ef1600f2a@googlegroups.com>:

On Thursday, 12 September 2019 20:25:33 UTC+2, Winfield Hill wrote:
klaus.kragelund@gmail.com wrote...

Active rectifiers for mains bridge replacement is easy

What is hard is to construct one that handles 4kV surge
and burst and keeping a price point not orders of
magnitude higher than a standard bridge

A standard bridge is dirt cheap, so a few orders
of magnitude higher isn't so bad. I have no
experience with MOSFETs as bridges, but the PFC
guys don't seem worried by it. It's not very
hard to protect the gates, and these big MOSFETs
can handle a lot of energy while in avalanche.

It's not so much about energy, but dv/dt over drain source during burst. EN61000-4 test define 2kV/5ns, which is far higher than
most MOSFET dv/dt can handle.

I would not expact 5nS to pass the mains filter L C.
That is 200 MHz.

At 200MHz and saturated current, the CM inductor is nothing but a capacitor. But you are somewhat right, might not be as bad as I wrote, but something to dig deeper into

Cheers

Klaus

 

[Winfield Hill]

klaus.kragelund@gmail.com wrote...

If you switch it on during the surge, how do you do than
with confidence in sub us. Surge is up to 4kV at 1.2us

As stated, it can handle avalanche.

And when do you turn off? If you do not turn off in time,
you connect the cap to the line and bad things happen

TI uses a 50us filter for turnon, but 10ns for turn off.


--
Thanks,
- Win

 

[Winfield Hill]

legg wrote...

I've heard of transmission system losses
nearing 20% (2009). Perhaps that was a
worst-case scenario for places that
don't generate much of their own.

A number like that isn't surprising, for
the entire system input-to-output. It's
individual elements, xfmr, etc., that are
under 1%, have to be I guess, to allow a
bit more for long transmission lines and
still keep the total loss to under 20%.


--
Thanks,
- Win

 

[legg]

On 12 Sep 2019 14:03:11 -0700, Winfield Hill <winfieldhill@yahoo.com>
wrote:

Winfield Hill wrote...

klaus.kragelund@gmail.com wrote...

Active rectifiers for mains bridge replacement is easy

What is hard is to construct one that handles 4kV
surge and burst and keeping a price point not orders
of magnitude higher than a standard bridge

A standard bridge is dirt cheap, so a few orders
of magnitude higher isn't so bad. I have no
experience with MOSFETs as bridges, but the PFC
guys don't seem worried by it. It's not very
hard to protect the gates, and these big MOSFETs
can handle a lot of energy while in avalanche.

I've studied avalanche breakdown in many types of
silicon devices, read papers, and have made many
measurements of MOSFET avalanche breakdown, and
would like to assert that it's not intrinsically
more vulnerable than a rectifier diode.

Anyway, the central idea here is that if the HV
power-transmission guys can keep their losses well
under 1%, right up to our property boundary, why
can't we try to do the same in our consumption?

Where'd you get that number?

I've heard of transmission system losses nearing 20% (2009).
Perhaps that was a worst-case scenario for places that
don't generate much of their own.

RL

 

[Tim Williams]

<klaus.kragelund@gmail.com> wrote in message
news:41d03d8c-1c2a-49c7-bce3-b25488430dd0@googlegroups.com...

If you switch it on during the surge, how do you do than with confidence
in sub us. Surge is up to 4kV at 1.2us

And when do you turn off? If you do not turn off in time, you connect the
cap to the line and bad things happen

Fast switching is half of all we do..?

No need for fast switching anyway, the body diodes are already pointing in
the right direction.

Unless you read that as, short out mains during a surge, which would be
interesting, and risky, but the transistors could be dimensioned to handle
it. 2.5kV /diff/ surge at 2 ohms is 1.25kA. We're talking big transistors
already, so this isn't too too ludicrous, at least in the kW range.

Also the possibility to use 1800V SiC FETs to ride through it, using MOVs to
clamp the brunt of it.

CM surge doesn't really matter, which is nice.

Tim

--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
Website: https://www.seventransistorlabs.com/

 

[Tim Williams]

<klaus.kragelund@gmail.com> wrote in message
news:4d0dfae5-1c8b-4b18-aef6-61ebcd1c9d63@googlegroups.com...

I would not expact 5nS to pass the mains filter L C.
That is 200 MHz.

At 200MHz and saturated current, the CM inductor is nothing but a
capacitor. But you are somewhat right, might not be as bad as I wrote, but
something to dig deeper into

More important is that the pulse is tall enough to saturate CMCs. It won't
be saturated due to mains current, because that's still balanced.

Diff mode, the 50 ohm transient just bounces off the input X1 cap. What's
left isn't all that much, and the CMC will not be saturated in leakage mode
(for obvious reasons).

Tim

--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
Website: https://www.seventransistorlabs.com/