Minimising EM noise from PWM switched fairly lights?

[Tim Watts]

Hi,

This year's project is to drive 3 strings of 30V DC LED outdoor fairy
lights from Raspberry Pi's[1]


I've been on here before last year and took some greet advice with
respect to H-Bridges and found some, along with DC-DC converters that
will enable me to interface a 30V DC supply to the Pi and the Pi back to
the lights.


The only thing I am mindful of is not to inadvertantly blat out a ton of
EM noise.

So I was wondering if anyone (without guarantees of course) might be
able to offer any rule of thumb advice please?


1) I'll keep the PWM frequency as low as possible without causing
visible flickering to passing motor cars (which is sometime I can test
by driving by, road speed limit is 30mph so not super fast).

2) I'm thinking to pop a suitable choke inline with each string of
lights after the H-Bridge to block the higher harmonics. This is the bit
I'm not sure of. What would be a suitable number of Henrys as a function
of drive current and base frequency of the PWM?

3) Are there any inexpensive ways of doing a quick and dirty
verification of the amount of noise being emitted? I don't have a
'scope, though I could get a picoscope type unit if sticking an antenna
of some sort on it would provide useful tests???


Many thanks,

Tim

 

[Tim Watts]

On 24/10/2019 10:28, TTman wrote:

On 24/10/2019 09:57, Tim Watts wrote:

Why bother for a private project ?

I'd like to not piss the neighbours off when their TVs or radios stop
working

Or worse, interefere with some comms system that matters. I'm in
England, my plot is 100x75 feet so we're all fairly close to each other.

 

[Tim Watts]

On 24/10/2019 10:16, piglet wrote:

On 24/10/2019 09:57, Tim Watts wrote:
3) Are there any inexpensive ways of doing a quick and dirty
verification of the amount of noise being emitted? I don't have a
'scope, though I could get a picoscope type unit if sticking an
antenna of some sort on it would provide useful tests???


Cheapest, simplest, quickest: get an old-school battery powered pocket
AM/FM radio. Find a quiet spot on the AM broadcast band and start
sniffing your unit under test for RFI.

piglet

Thanks for that

I could baseline the current controller on the same lights with it first
to get some idea of what level is acceptable.

 

[TTman]

On 24/10/2019 09:57, Tim Watts wrote:

Hi,

This year's project is to drive 3 strings of 30V DC LED outdoor fairy
lights from Raspberry Pi's[1]


I've been on here before last year and took some greet advice with
respect to H-Bridges and found some, along with DC-DC converters that
will enable me to interface a 30V DC supply to the Pi and the Pi back to
the lights.


The only thing I am mindful of is not to inadvertantly blat out a ton of
EM noise.

So I was wondering if anyone (without guarantees of course) might be
able to offer any rule of thumb advice please?


1) I'll keep the PWM frequency as low as possible without causing
visible flickering to passing motor cars (which is sometime I can test
by driving by, road speed limit is 30mph so not super fast).

2) I'm thinking to pop a suitable choke inline with each string of
lights after the H-Bridge to block the higher harmonics. This is the bit
I'm not sure of. What would be a suitable number of Henrys as a function
of drive current and base frequency of the PWM?

3) Are there any inexpensive ways of doing a quick and dirty
verification of the amount of noise being emitted? I don't have a
'scope, though I could get a picoscope type unit if sticking an antenna
of some sort on it would provide useful tests???


Many thanks,

Tim
Why bother for a private project ?

--
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

 

[Phil Allison]

piglet wrote:

---------------

Cheapest, simplest, quickest: get an old-school battery powered pocket
AM/FM radio. Find a quiet spot on the AM broadcast band and start
sniffing your unit under test for RFI.

** Ah, the $10 portable spectrum analyser.

Analogue TVs with rabbit-ears are also good at the same task.

Built a simple, 18V linear reg once using a BD139 while watching CH9 on TV in the same room.

When energised, it wiped out the pix - a 10nF ceramic soon came to the rescue.

Another time, I was getting regular, slow impulse noise spikes breaking into my scope and guitar amps.

Tracked it down with a AM portable to a local Pharmacist, 65 metres away, with it a dodgy neon sign in the window.

Who woulda thunk ?



...... Phil

 

[piglet]

On 24/10/2019 09:57, Tim Watts wrote:

3) Are there any inexpensive ways of doing a quick and dirty
verification of the amount of noise being emitted? I don't have a
'scope, though I could get a picoscope type unit if sticking an antenna
of some sort on it would provide useful tests???

Cheapest, simplest, quickest: get an old-school battery powered pocket
AM/FM radio. Find a quiet spot on the AM broadcast band and start
sniffing your unit under test for RFI.

piglet

 

[Martin Brown]

On 24/10/2019 09:57, Tim Watts wrote:

Hi,

The only thing I am mindful of is not to inadvertantly blat out a ton of
EM noise.

So I was wondering if anyone (without guarantees of course) might be
able to offer any rule of thumb advice please?

1) I'll keep the PWM frequency as low as possible without causing
visible flickering to passing motor cars (which is sometime I can test
by driving by, road speed limit is 30mph so not super fast).

2) I'm thinking to pop a suitable choke inline with each string of
lights after the H-Bridge to block the higher harmonics. This is the bit
I'm not sure of. What would be a suitable number of Henrys as a function
of drive current and base frequency of the PWM?

You want a small capacitor across the load to provide a local path for
higher frequencies to attenuate them further. Try this simple URL:

https://www.electronics-notes.com/articles/radio/rf-filters/constant-k-simple-low-pass-lc-rf-filter-design-calculations.php

If you lowpass it to below 30kHz you probably won't annoy any hams.
(or jam local 60kHz radio clocks)

3) Are there any inexpensive ways of doing a quick and dirty
verification of the amount of noise being emitted? I don't have a
'scope, though I could get a picoscope type unit if sticking an antenna
of some sort on it would provide useful tests???

AM radio tuned to an otherwise quiet spot. You would have to be doing
something really silly to end up broadcasting MHz harmonics though.

--
Regards,
Martin Brown

 

[Bill Sloman]

On Thursday, October 24, 2019 at 7:57:56 PM UTC+11, Tim Watts wrote:

<snip>

1) I'll keep the PWM frequency as low as possible without causing
visible flickering to passing motor cars (which is sometime I can test
by driving by, road speed limit is 30mph so not super fast).

It's the edges that generate the high frequency content, so minimising the PWM frequency isn't all that helpful.

2) I'm thinking to pop a suitable choke inline with each string of
lights after the H-Bridge to block the higher harmonics. This is the bit
I'm not sure of. What would be a suitable number of Henrys as a function
of drive current and base frequency of the PWM?

The aim is to stop the high-frequency content getting out into the string of lights (which acts like an aerial broad-casting and high-frequenes you may push aronud the loop), so put the choke as close as possible to the H-bridge, and immediately follow it with a capacitor to the return connection of the H-bridge.

This is an L-section filter. As second one right up against it will attentuate any high frequency content even further.

Any wound inductor has interwinding capacitance, and a self-resonant frequency. It doesn't do much to attentuate frequencies higher than the self-resonant frequency. Ferrite beads and chips aren't wound, but don't have much inductance.

3) Are there any inexpensive ways of doing a quick and dirty
verification of the amount of noise being emitted? I don't have a
'scope, though I could get a picoscope type unit if sticking an antenna
of some sort on it would provide useful tests???

Transistor radio - as everybody else has pointed out.

--
Bill Sloman, Sydney

 

[Tim Watts]

On 24/10/2019 11:49, Martin Brown wrote:

You want a small capacitor across the load to provide a local path for
higher frequencies to attenuate them further. Try this simple URL:

https://www.electronics-notes.com/articles/radio/rf-filters/constant-k-simple-low-pass-lc-rf-filter-design-calculations.php

Hi Martin,

That's great - thanks! I'll play with some numbers and see what looks sane.

Sounds like a job for a bit of sold fashioned tagboard. I'll have 4
modules (filter, DC-DC, H-Bridge and Pi) to mount on an acrylic plate to
sit inside of an airtight food/fridge box which is ideal for the job.

Gland the cables in and out and it'll sit on the grass right next to the
lights it's driving. The plan is to use a Pi Zero/W and access it over
WiFi - 3 sets in total, one for each fairy string.

It's more for my son who wants to dabble with some coding and asked if
we could make a controller for our existing Xmas lights.

If you lowpass it to below 30kHz you probably won't annoy any hams.
(or jam local 60kHz radio clocks)

Thank you - good design limit. I have 60kHz radio clocks, so hopefully
any badness will be apparant to me fairy quickly.

3) Are there any inexpensive ways of doing a quick and dirty
verification of the amount of noise being emitted? I don't have a
'scope, though I could get a picoscope type unit if sticking an
antenna of some sort on it would provide useful tests???

AM radio tuned to an otherwise quiet spot. You would have to be doing
something really silly to end up broadcasting MHz harmonics though.

I'd hope it would be hard Actual drive frequency depends on whether
the Pi's 2 hardware PWMs are phase locked which which case I will use 2
to drive a single H-Bridge. If not, I'll have to do it in software and
it will be really slow. I have an el-cheapo logic analyser USB widget so
I'll test that soon.

If this works, next will be to make a 4th box but drive some neopixels
in fairy string format which will add a dash of colour to the whole thing.

Many many thanks for your kind suggestions

 

[Rick C]

On Thursday, October 24, 2019 at 4:57:56 AM UTC-4, Tim Watts wrote:

Hi,

This year's project is to drive 3 strings of 30V DC LED outdoor fairy
lights from Raspberry Pi's[1]


I've been on here before last year and took some greet advice with
respect to H-Bridges and found some, along with DC-DC converters that
will enable me to interface a 30V DC supply to the Pi and the Pi back to
the lights.


The only thing I am mindful of is not to inadvertantly blat out a ton of
EM noise.

So I was wondering if anyone (without guarantees of course) might be
able to offer any rule of thumb advice please?


1) I'll keep the PWM frequency as low as possible without causing
visible flickering to passing motor cars (which is sometime I can test
by driving by, road speed limit is 30mph so not super fast).

2) I'm thinking to pop a suitable choke inline with each string of
lights after the H-Bridge to block the higher harmonics. This is the bit
I'm not sure of. What would be a suitable number of Henrys as a function
of drive current and base frequency of the PWM?

3) Are there any inexpensive ways of doing a quick and dirty
verification of the amount of noise being emitted? I don't have a
'scope, though I could get a picoscope type unit if sticking an antenna
of some sort on it would provide useful tests???


Many thanks,

Tim

Why not deal with the RFI by not creating it? I'm not sure what your setup is at the moment but driving with a DC current should be pretty much as simple as PWM. You talk about adding a choke. I'd be willing to bet if you look at the resulting circuit it is a short stone's throw from being a DC/DC converter.

Drive with DC and you only need to deal with residual high frequency noise you can stop with a simple filter.

I'm one of those people who see and are very annoyed by the blinking taillights on so many cars. Cadillac was the first car I noticed it on many years ago and have always been the worst offenders with huge taillights on some of their vehicles. More recently they seem to have changed their design, either by bumping up the frequency or by using DC.

Interesting that you can't effectively google this effect because there is a distinct effect from replacement LED turn signals blinking too fast because they don't draw enough current for the blink circuit to work correctly, called hyper flashing.

Do cars get EMI tested?

--

Rick C.

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

 

On Thu, 24 Oct 2019 09:57:49 +0100, Tim Watts <tw@example.com> wrote:

Hi,

This year's project is to drive 3 strings of 30V DC LED outdoor fairy
lights from Raspberry Pi's[1]


I've been on here before last year and took some greet advice with
respect to H-Bridges and found some, along with DC-DC converters that
will enable me to interface a 30V DC supply to the Pi and the Pi back to
the lights.


The only thing I am mindful of is not to inadvertantly blat out a ton of
EM noise.

So I was wondering if anyone (without guarantees of course) might be
able to offer any rule of thumb advice please?


1) I'll keep the PWM frequency as low as possible without causing
visible flickering to passing motor cars (which is sometime I can test
by driving by, road speed limit is 30mph so not super fast).

2) I'm thinking to pop a suitable choke inline with each string of
lights after the H-Bridge to block the higher harmonics. This is the bit
I'm not sure of. What would be a suitable number of Henrys as a function
of drive current and base frequency of the PWM?

3) Are there any inexpensive ways of doing a quick and dirty
verification of the amount of noise being emitted? I don't have a
'scope, though I could get a picoscope type unit if sticking an antenna
of some sort on it would provide useful tests???


Many thanks,

Tim

At a low PWM rate, say 100 Hz, anything radiated in the AM band will
be ballpark the 10,000th harmonic of the switch frequency. The energy
will be nil.

Slow down the switching edges a bit if you like. Add mosfet gate
resistors to soften the edges.



--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Tim Williams]

Easiest: use a low frequency like 1kHz to avoid flicker, and a switching
speed that's ponderously slow like 10us to avoid much radiation. Maybe
still put an LC across it (with a cutoff of some 100s kHz), with damping so
it doesn't ring, to be sure.

Slow switching can be done by putting an R+C across the MOSFET D-G and a
relatively generous series gate drive resistor. The R's prevent oscillation
(capacitance from G to D/S is a no-no, you'll make an oscillator at 100s MHz
that way) and the feedback network sets bandwidth as if it were an amplifier
(which it clearly is during switching edges ).

Best efficiency: use an adjustable DC converter. Filtered input and output,
high switching frequency, steady output. Typically you'd use a buck or
boost converter (depending on supply, you might need a flyback or SEPIC
configuration rather than boost, but, close enough) and either control the
current setpoint node (external compensation type) or tease the voltage
feedback pin with a resistor (thus shifting Vout).

In the first case, you try to avoid generation of harmonics; in the second
case, you go all in, then filter them as close as possible to the source.

Additional filtering may still apply, on account of the first case, the
impedances between all the nodes mean that the ~5ns edge you get from the
MCU pin driver or IO expander or whatever it is, can feed forwards through
everything and get into the wires. An RC in front of the gate R can help
with that, for example. Or in both cases, there may be ground-loop noise,
due to return currents from logic signals, or switching currents.

Tim

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

"Tim Watts" <tw@example.com> wrote in message
news:h1d7cdF8c75U1@mid.individual.net...

Hi,

This year's project is to drive 3 strings of 30V DC LED outdoor fairy
lights from Raspberry Pi's[1]


I've been on here before last year and took some greet advice with respect
to H-Bridges and found some, along with DC-DC converters that will enable
me to interface a 30V DC supply to the Pi and the Pi back to the lights.


The only thing I am mindful of is not to inadvertantly blat out a ton of
EM noise.

So I was wondering if anyone (without guarantees of course) might be able
to offer any rule of thumb advice please?


1) I'll keep the PWM frequency as low as possible without causing visible
flickering to passing motor cars (which is sometime I can test by driving
by, road speed limit is 30mph so not super fast).

2) I'm thinking to pop a suitable choke inline with each string of lights
after the H-Bridge to block the higher harmonics. This is the bit I'm not
sure of. What would be a suitable number of Henrys as a function of drive
current and base frequency of the PWM?

3) Are there any inexpensive ways of doing a quick and dirty verification
of the amount of noise being emitted? I don't have a 'scope, though I
could get a picoscope type unit if sticking an antenna of some sort on it
would provide useful tests???


Many thanks,

Tim

 

[Tim Watts]

On 24/10/2019 17:36, Tim Williams wrote:

Easiest: use a low frequency like 1kHz to avoid flicker, and a switching
speed that's ponderously slow like 10us to avoid much radiation.  Maybe
still put an LC across it (with a cutoff of some 100s kHz), with damping
so it doesn't ring, to be sure.

Slow switching can be done by putting an R+C across the MOSFET D-G and a
relatively generous series gate drive resistor.  The R's prevent
oscillation (capacitance from G to D/S is a no-no, you'll make an
oscillator at 100s MHz that way) and the feedback network sets bandwidth
as if it were an amplifier (which it clearly is during switching edges
).

As mentioned in another reply just now, I won't be able to influence the
switching speed as I'm using an L298N prebuilt H-Bridge module (because
H-Bridges are hard for simple plebs like me - I'm more about the software

But interesting all the same - thanks

Best efficiency: use an adjustable DC converter.  Filtered input and
output, high switching frequency, steady output.  Typically you'd use a
buck or boost converter (depending on supply, you might need a flyback
or SEPIC configuration rather than boost, but, close enough) and either
control the current setpoint node (external compensation type) or tease
the voltage feedback pin with a resistor (thus shifting Vout).

In the first case, you try to avoid generation of harmonics; in the
second case, you go all in, then filter them as close as possible to the
source.

Additional filtering may still apply, on account of the first case, the
impedances between all the nodes mean that the ~5ns edge you get from
the MCU pin driver or IO expander or whatever it is, can feed forwards
through everything and get into the wires.  An RC in front of the gate R
can help with that, for example.  Or in both cases, there may be
ground-loop noise, due to return currents from logic signals, or
switching currents.

Tim

 

[Tim Watts]

On 24/10/2019 16:37, Rick C wrote:

Why not deal with the RFI by not creating it? I'm not sure what your setup is at the moment but driving with a DC current should be pretty much as simple as PWM. You talk about adding a choke. I'd be willing to bet if you look at the resulting circuit it is a short stone's throw from being a DC/DC converter.

Drive with DC and you only need to deal with residual high frequency noise you can stop with a simple filter.

I'm one of those people who see and are very annoyed by the blinking taillights on so many cars. Cadillac was the first car I noticed it on many years ago and have always been the worst offenders with huge taillights on some of their vehicles. More recently they seem to have changed their design, either by bumping up the frequency or by using DC.

Interesting that you can't effectively google this effect because there is a distinct effect from replacement LED turn signals blinking too fast because they don't draw enough current for the blink circuit to work correctly, called hyper flashing.

Interesting idea - so I'd need a programmable bi directional constant
current drive to do that.

However, not really something I could use here as I'd still have to
strobe as the LEDs are in 2 sets, back to back wired on a single feed
pair of wires - hence the H-Bridge.

 

[Tim Watts]

On 24/10/2019 16:30, jlarkin@highlandsniptechnology.com wrote:

At a low PWM rate, say 100 Hz, anything radiated in the AM band will
be ballpark the 10,000th harmonic of the switch frequency. The energy
will be nil.

That was about as much as I understood about the whole thing

Slow down the switching edges a bit if you like. Add mosfet gate
resistors to soften the edges.

Interesting... Sadly won't be able to do that as I'm using pre built
H-Bridge modules based on the L298N

https://www.ebay.co.uk/itm/Dual-L298N/172822867116

Sorry for wimping out there ;->

 

[John Larkin]

On Thu, 24 Oct 2019 18:09:55 +0100, Tim Watts <tw@example.com> wrote:

On 24/10/2019 16:30, jlarkin@highlandsniptechnology.com wrote:

At a low PWM rate, say 100 Hz, anything radiated in the AM band will
be ballpark the 10,000th harmonic of the switch frequency. The energy
will be nil.

That was about as much as I understood about the whole thing

Slow down the switching edges a bit if you like. Add mosfet gate
resistors to soften the edges.

Interesting... Sadly won't be able to do that as I'm using pre built
H-Bridge modules based on the L298N

https://www.ebay.co.uk/itm/Dual-L298N/172822867116

Sorry for wimping out there ;-

Hard to beat for the price!

I don't think there will be detectable EMI from a low frequency PWM.
But you could add some sort of lowpass if you want to, a small
inductor or ferrite bead or something. I wouldn't bother.

I have some under-counter dimmable LED lights that switch at about 4
KHz. Doesn't radiate much, doesn't show up in my bench testing.

But then, we're two miles from Sutro Tower.

--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[Tim Watts]

On 24/10/2019 19:08, whit3rd wrote:

On Thursday, October 24, 2019 at 4:57:56 AM UTC-4, Tim Watts wrote:
Hi,

This year's project is to drive 3 strings of 30V DC LED outdoor fairy
lights from Raspberry Pi's[1]

The only thing I am mindful of is not to inadvertantly blat out a ton of
EM noise

That's very considerate of you.

That and I don't want Ofcom paying a visit

My only addition to the other suggestions (AM radio to snoop, try to
keep repetition frequency low) is to put a CM choke (ferrite
torus, snap-on choke, or even wrap a turn on a rusty iron
item) in one or more places on the long string, including near
the power-source end.

A slew-rate-limiting Miller capacitor or emitter-series-inductor can
be very effective, as well (and for mass production, would usually be employed).


Putting the Rasberry Pi in a metal container is also useful (if some RF
is being generated, the OTHER wiring deserves some attention as well).

Thanks for those other suggestions

 

[whit3rd]

On Thursday, October 24, 2019 at 4:57:56 AM UTC-4, Tim Watts wrote:

Hi,

This year's project is to drive 3 strings of 30V DC LED outdoor fairy
lights from Raspberry Pi's[1]

The only thing I am mindful of is not to inadvertantly blat out a ton of
EM noise

That's very considerate of you.

My only addition to the other suggestions (AM radio to snoop, try to
keep repetition frequency low) is to put a CM choke (ferrite
torus, snap-on choke, or even wrap a turn on a rusty iron
item) in one or more places on the long string, including near
the power-source end.

A slew-rate-limiting Miller capacitor or emitter-series-inductor can
be very effective, as well (and for mass production, would usually be employed).


Putting the Rasberry Pi in a metal container is also useful (if some RF
is being generated, the OTHER wiring deserves some attention as well).

 

[Bill Sloman]

On Friday, October 25, 2019 at 5:31:52 AM UTC+11, John Larkin wrote:

On Thu, 24 Oct 2019 18:09:55 +0100, Tim Watts <tw@example.com> wrote:

On 24/10/2019 16:30, jlarkin@highlandsniptechnology.com wrote:

At a low PWM rate, say 100 Hz, anything radiated in the AM band will
be ballpark the 10,000th harmonic of the switch frequency. The energy
will be nil.

That was about as much as I understood about the whole thing

Slow down the switching edges a bit if you like. Add mosfet gate
resistors to soften the edges.

Interesting... Sadly won't be able to do that as I'm using pre built
H-Bridge modules based on the L298N

https://www.ebay.co.uk/itm/Dual-L298N/172822867116

Sorry for wimping out there ;-

Hard to beat for the price!

I don't think there will be detectable EMI from a low frequency PWM.

John Larkin doesn't think very hard.

But you could add some sort of lowpass if you want to, a small
inductor or ferrite bead or something. I wouldn't bother.

John Larkin doesn't mind irritating his neighbours by screwing up their AM reception.

I have some under-counter dimmable LED lights that switch at about 4
KHz. Doesn't radiate much, doesn't show up in my bench testing.

John Larkin doesn't seem to spend much on bench testing

> But then, we're two miles from Sutro Tower.

https://en.wikipedia.org/wiki/Sutro_Tower

Not everybody can rely on a nearby radio-transmitter to swamp the consequences of their incompetence.

--
Bill Sloman, Sydney

 

[Bill Sloman]

On Friday, October 25, 2019 at 2:30:23 AM UTC+11, jla...@highlandsniptechnology.com wrote:

On Thu, 24 Oct 2019 09:57:49 +0100, Tim Watts <tw@example.com> wrote:

Hi,

This year's project is to drive 3 strings of 30V DC LED outdoor fairy
lights from Raspberry Pi's[1]


I've been on here before last year and took some greet advice with
respect to H-Bridges and found some, along with DC-DC converters that
will enable me to interface a 30V DC supply to the Pi and the Pi back to
the lights.


The only thing I am mindful of is not to inadvertantly blat out a ton of
EM noise.

So I was wondering if anyone (without guarantees of course) might be
able to offer any rule of thumb advice please?


1) I'll keep the PWM frequency as low as possible without causing
visible flickering to passing motor cars (which is sometime I can test
by driving by, road speed limit is 30mph so not super fast).

2) I'm thinking to pop a suitable choke inline with each string of
lights after the H-Bridge to block the higher harmonics. This is the bit
I'm not sure of. What would be a suitable number of Henrys as a function
of drive current and base frequency of the PWM?

3) Are there any inexpensive ways of doing a quick and dirty
verification of the amount of noise being emitted? I don't have a
'scope, though I could get a picoscope type unit if sticking an antenna
of some sort on it would provide useful tests???

Many thanks,

At a low PWM rate, say 100 Hz, anything radiated in the AM band will
be ballpark the 10,000th harmonic of the switch frequency. The energy
will be nil.

Not true. AM transmitters are delectable for miles. Even a small high frequency component from a radiator next door can be big enough to create problems.

Slow down the switching edges a bit if you like. Add mosfet gate
resistors to soften the edges.

Which increases the switching losses. If you slow down the edges enough, you will cook your MOSFETs.

--
Bill Sloman, Sydney