Hi Neko,

Seems the filtered Line should be less noisy than the "raw" Line.

Really?

 

Hi Neko,

Really?
View attachment 218062

Hi Danko,

Thanks for your comments. So I don't quite understand why there would be more noise on the lowpass filtered side of the Line compared to the raw Line. I see what you are pointing out, but the sync circuit should provide more reliable zero crossing transitions if no high frequency noise is present on the Line input, correct?

Also, does this noise really matter in the operation of the PWM controller?

Thanks,

Neko

 

Hi Neko,

Thanks for your comments. So I don't quite understand why there would be more noise on the lowpass filtered side of the Line compared to the raw Line. I see what you are pointing out, but the sync circuit should provide more reliable zero crossing transitions if no high frequency noise is present on the Line input, correct?

You can see noise intensity before filter V(D_M1)
and after filter V(Line).
Filter prevents mains connected appliances from affect
by high frequency, high intensity noise of PWM power module.

 

Hi Neko,

You can see noise intensity before filter V(D_M1)
and after filter V(Line).
Filter prevents mains connected appliances from affect
by high frequency, high intensity noise of PWM power module.

View attachment 218097
View attachment 218090
View attachment 218089
Hi Danko,

This totally makes sense to keep the AC line clean; the FFT clearly shows the difference.

Seems though that this LC lowpass filter would work better with C1 terminated on the line side of L1. With C1 on the IN side, it acts as a highpass filter, injecting high frequencies created into the neutral port.

Right now, the filter only relies the reactance of L1 to attenuate these high frequency components.

If you have a chance, could you simulate this change?

Thanks,

Neko

 

Hi Danko,

Moving the capacitor termination to the Line side apparently works well as shown in the quick AC sweep below:



Thoughts or comments?

Thanks,

Neko

 

Hi Neko,

Hi Danko,
Moving the capacitor termination to the Line side apparently works well as shown in the quick AC sweep below:

Thoughts or comments?

With capacitor moved to the Line side, simulation shows:


For simulation used file https://forum.allaboutcircuits.com/attachments/pwm-test-asc.217528/

 

Hi Neko,


With capacitor moved to the Line side, simulation shows:
View attachment 218235
View attachment 218237
For simulation used file https://forum.allaboutcircuits.com/attachments/pwm-test-asc.217528/

Hi Danko,

Does not look good with capacitor on the line side. Well tomorrow after a final check, I'll apply power. The only unpowered module so far is the FET driver module. I did however do a point to point twice against the schematic.

Below a photo shows the modules wired together.



I will ramp up the line voltage with the variac and also monitor for hot spots with my FLIR infrared camera.

Neko

 

Hi Danko,

Does not look good with capacitor on the line side. Well tomorrow after a final check, I'll apply power. The only unpowered module so far is the FET driver module. I did however do a point to point twice against the schematic.

Below a photo shows the modules wired together.

View attachment 218278 a

I will ramp up the line voltage with the variac and also monitor for hot spots with my FLIR infrared camera.

Neko

Hi Danko,

First application of power after checking conditions. Fan was the load. I hesitate to bring up to full AC line voltage:



PWM waveform would come and go at different Line voltages. Also PWM appeared spikey, didn't want to blow a component. Sync timing is not at the zero crossing; looked good in an earlier test without the power module.

Temperature rise was not too high; max about 42C on the power module:



Thoughts, comments?

Thanks,

Neko

 

Hi Neko,

PWM waveform would come and go at different Line voltages.
Also PWM appeared spikey, didn't want to blow a component.
Sync timing is not at the zero crossing; looked good in an earlier test without the power module.

1. Irregular spikes on PWM and synchro signal:
Unstable connections in receptacles, variac wiper, breadboards?

2. Distorted positive part of PWM pulses envelope:
Damaged transistor M4 or distorted line voltage from variac?

3. PWM zero crossing appears before synchro signal:
Change load from fan to incandescent bulb 15...40W and see what is difference.
=============
I sent you private message (click on envelope in top-right corner of screen) .

BTW, show on this setup (with fan) oscillogram PWM and V(D_M1) simultaneously.

 

Hi Danko,

Started looking at the fallout from yesterday's test run. What I've found so far is the following damage:

• Two of four FETs shorted
• M1 shorted G to D
• M4 shorted D to S
• U3 nonfunctional
• First -12V isolated DC/DC has 0V out

Also checked the variac output from very low to full voltage and observed:
• No wiper noise, waveform looked clean as I increased voltage
• Waveform appeared visually to be symmetrical
• Did not use scopes math function to integrate pos and neg cycles to confirm symmetry

I'll need to check my parts inventory to confirm if I need to place an order. I know that I don't have the TO-263 SIP header boards.

Measuring the 40W lightbulb resistance, I get 31Ω; this is probably what is blowing my variac's 2A fuse. The lightbulb does not come on which would raise the filament resistance.

I think it makes more sense to use a fixed resistor maybe 220Ω; this will draw about .5A; probably a safer load to check out functionality.

As soon as I get things working again, I'll show on this setup (with fan) oscillogram PWM and V(D_M1) simultaneously. But first with resistive load.
Thoughts? Comments?

Thanks,

Neko

 

Thoughts? Comments?

I know my comments aren't wanted in this thread but... I still don't understand how PMW is going to work on AC. If it would or does why do they make VFD's to do the job, and before someone says that VFD's only work on 3 phase, they do make them for single phase. The single phase ones are just not needed as much so are way more expensive and harder to find.

 

I know my comments aren't wanted in this thread but... I still don't understand how PMW is going to work on AC. If it would or does why do they make VFD's to do the job, and before someone says that VFD's only work on 3 phase, they do make them for single phase. The single phase ones are just not needed as much so are way more expensive and harder to find.

Hi Shortbus,

Your comments on VFDs are most welcome. When I started my search for a variable solidstate AC source, I did run across some example VFD circuits. In trying to keep the controller as simple as possible, I ruled out VFD controllers because all the ones I found either required a uC or FPGA. If you can post a simple VFD controller circuit, I'd be happy to entertain it.
Thanks,

Neko

 

Hi Neko,

Hi Shortbus,

Your comments on VFDs are most welcome. When I started my search for a variable solidstate AC source, I did run across some example VFD circuits. In trying to keep the controller as simple as possible, I ruled out VFD controllers because all the ones I found either required a uC or FPGA. If you can post a simple VFD controller circuit, I'd be happy to entertain it.
Thanks,

Neko

If you are interesting in VFD, look at this US $9.19 module:

Pure Sine Wave Inverter Driver Board EGS002 "EG8010 + IR2110" Driver+LCD Module
Feature:
Voltage,current,real time temperature feedback
Overvoltage,undervoltage,overcurrent and overheating protection
Serial communication to set the output voltage,frequency and other parameters External
Comes with deadband control,pin set up 4 dead time:300nS dead time;500nS dead time;1.0uS dead time;1.5uS dead time
Pin set up four kinds of pure sine wave output frequency:fixed frequency 50 hz pure sine wave;60 hz fixed frequency pure sine wave;0-100 hz pure sine wave frequency is adjustable;0-400 hz pure sine wave frequency is adjustable
Unipolar and bipolar modulation
External 12MHz crystal oscillator
PWM carrier frequency 23.4KHz
Soft-start mode pin setting the response time of 1S
External serial port 128 * 32 LCD module 1602 display the voltage,frequency,temperature and electric current of the inverter and other information
Applications:
Single phase pure sine wave inverter
PV Inverter
Wind power inverter
Uninterruptible Power Supply UPS System
Digital generator system
IF power
Single-phase motor speed controller
Single-phase inverter
Sine wave dimmer
Sine wave regulator
Sine wave generator
Size:3.1x1.4cm/1.22x0.55inch
3.5x2.2x1.2cm/1.38x0.87x0.47
Package includes:
1x Pure sine wave inverter driver board
1x LCD
-----------------------------------------------------
Also download "Project Work.pdf"

 

If you are interesting in VFD, look at this US $9.19 module:

I posted a link to that, from a different seller , long ago in the thread and got told it's not what he wants to do. I still don't understand how this PWM is ever going to work with AC and a motor, which I also said earlier. ac motors for the most part(but not all) are frequency based when it comes to speed control. Take running a motor made for 60Hz on a 50Hz mains, it will run slower for it's number of poles. But hey, what do I know.

 

I posted a link to that, from a different seller , long ago in the thread and got told it's not what he wants to do. I still don't understand how this PWM is ever going to work with AC and a motor, which I also said earlier. ac motors for the most part(but not all) are frequency based when it comes to speed control. Take running a motor made for 60Hz on a 50Hz mains, it will run slower for it's number of poles. But hey, what do I know.

shortbus and cmartinez

Thanks for the links; I just ordered two boards. Until I receive boards, I'll still play around with Danko's PWM circuit. I replaced what I thought were all the damaged components, but I must have missed something because I had smoke again today. :-(

Neko

 

shortbus and cmartinez

Thanks for the links; I just ordered two boards. Until I receive boards, I'll still play around with Danko's PWM circuit. I replaced what I thought were all the damaged components, but I must have missed something because I had smoke again today. :-(

Neko

Guys,

I looked at the schematic and see that additional circuitry is needed besides the board on eBay, see below:


I think that I looked at this when it was posted earlier in this thread. Did anybody find the outboard board that goes with the main board? Also, from what I see, the output AC voltage is adjusted via the serial bus- a pot is easier.

Neko

 

Hi Neko,

I replaced what I thought were all the damaged components, but I must have missed something because I had smoke again today. :-(

1. Please, check polarity of these signals:
Disconnect Line from L1, so Line connected only to +5V PS and to synchro module.
Short Source of M4 with Neutral (only for this measurement!).
Connect Ground to Neutral (for all experiments).
Scope Line and M4 Gate.
Gate trace should be positive, when Line is positive.


2. For safety, put resistors 10k between Gate and Source of each transistor (M1, M2, M3, M4).

Did anybody find the outboard board that goes with the main board? Also, from what I see, the output AC voltage is adjusted via the serial bus- a pot is easier.

Download "Project Work.pdf"
You can read there that AC voltage and AC frequency are controlled by potentiometers.
On page 21 picture show DIY outboard with connected to right side main board:


On page 24 is improved circuit of outboard:

 

Guys,

I looked at the schematic and see that additional circuitry is needed besides the board on eBay, see below:

View attachment 218559
I think that I looked at this when it was posted earlier in this thread. Did anybody find the outboard board that goes with the main board? Also, from what I see, the output AC voltage is adjusted via the serial bus- a pot is easier.

Neko

Hi Danko,

Before I saw your most recent post and suggestions, I made a measurement of the synchro signal with the original 3.92k resisitor and your suggested value of 150k.

I don't see any difference in timing with either resistor. See below:



Maybe the opamp is causing the delay? What do you think?

Thanks,

Neko

 

Hi Neko,


1. Please, check polarity of these signals:
Disconnect Line from L1, so Line connected only to +5V PS and to synchro module.
Short Source of M4 with Neutral (only for this measurement!).
Connect Ground to Neutral (for all experiments).
Scope Line and M4 Gate.
Gate trace should be positive, when Line is positive.
View attachment 218570

2. For safety, put resistors 10k between Gate and Source of each transistor (M1, M2, M3, M4).


Download "Project Work.pdf"
You can read there that AC voltage and AC frequency are controlled by potentiometers.
On page 21 picture show DIY outboard with connected to right side main board:
View attachment 218564

On page 24 is improved circuit of outboard:
View attachment 218575

Hi Danko,

Will try out your suggestions.
Thanks,

Neko

 

Hi Neko,


1. Please, check polarity of these signals:
Disconnect Line from L1, so Line connected only to +5V PS and to synchro module.
Short Source of M4 with Neutral (only for this measurement!).
Connect Ground to Neutral (for all experiments).
Scope Line and M4 Gate.
Gate trace should be positive, when Line is positive.
View attachment 218570

2. For safety, put resistors 10k between Gate and Source of each transistor (M1, M2, M3, M4).


Download "Project Work.pdf"
You can read there that AC voltage and AC frequency are controlled by potentiometers.
On page 21 picture show DIY outboard with connected to right side main board:
View attachment 218564

On page 24 is improved circuit of outboard:
View attachment 218575

Hi,

Was busy today and didn't read the full Project Work file. I will still try this out. One improvement that I see is that the Vdd in the circuit on page 24 improves from from the datasheet:


to:


Still need three supply voltages, but is doable.
Neko