No Deadtime

[sudiptamandal]

There is no dead time in this code. sometimes pulses overlaps. Can't drive any MOSFET or IGBT with this code

[tvixen]

Hi Kurt
Could you please comment this comment.
Thanks in advance.

[Terbytes]

@sudiptamandal Dead time for a h-bridge I'm assuming. Feel free to make a PR

[johnnypeste]

can you modify the code to use 2 more pairs of pins with SPWM out of phase 120 degrees and 240 degrees. in order to make a 3 phase inverter. I guess Arduino mega is needed for that...

[Irev-Dev]

@johnnypeste I did have a quick go at making a three-phase version, but it was much more difficult than the single-phase with how resource-constrained these micros are.
I think with the cost of hardware, it's probably worth moving to something a bit more beefy than 8-bit.
Also, it's not as simple as making the same signal another two time out of phase. If you've ever looked at a three-phase bridge, it gets pretty tricky.
No shorting the bridge for a single-phase is trivial and can be handled with deadtime, much harder with three-phase.

[johnnypeste]

Thank you for the response but i i have plenty of deadtime and i will invest in 3 phase... If i have 3 one phase ac ources dephased each other by 120 degrees i dont understand why i cannot connect therm together with one common to the 3 and use the other  3 terminals as the 3 phases. Regards Joao Sent from Yahoo Mail on Android On Sat, 28 Sep 2019 at 7:27, Charlie<notifications@github.com> wrote: @johnnypeste I did have a quick go at making a three-phase version, but it was much more difficult than the single-phase with how resource-constrained these micros are. I think with the cost of hardware, it's probably worth moving to something a bit more beefy than 8-bit. Also, it's not as simple as making the same signal another two time out of phase. If you've ever looked at a three-phase bridge, it gets pretty tricky. No shorting the bridge for a single-phase is trivial and can be handled with deadtime, much harder with three-phase. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub, or mute the thread.

[AttonRisk]

Something like the AtTiny85 could make for a good candidate to offload the work onto. They are also cheap and pretty easy to integrate.

[johnnypeste]

Seems like a nice cheap microprocessor... I will give it a try... Thank you and i will let you know if i succeed. The 1 phase ac dc conversion is the more expensive part, requiring a 20 mF capacitor or a big inductance in order to have a decent dc ripple... the cheapest capacitors i found were kemet 10 mF 450 V. I will put 2 of them in parallel when my input is 1 phase and 2 of them in series when my input is 3 phase (in this case the arduino and igbt setup is only to have 3 phase with a varible frequency). Bye Sent from Yahoo Mail on Android On Sat, 28 Sep 2019 at 17:10, thenuke321<notifications@github.com> wrote: Something like the AtTiny85 could make for a good candidate to offload the work onto. They are also cheap and pretty easy to integrate. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub, or mute the thread.

[AttonRisk]

Do keep in mind the issues of power factor and harmonics when dealing with mains power

[johnnypeste]

What do you mean exactly? Sent from Yahoo Mail on Android On Sun, 29 Sep 2019 at 5:35, thenuke321<notifications@github.com> wrote: Do keep in mind the issues of power factor and harmonics when dealing with mains power — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub, or mute the thread.

[yo6ial]

Hi folks. Old thread, old code but beautiful code.
I'm in the process of converting a square wave inverter to sine and this piece of code struck me the second I saw it. Praises aside and to whom may this concern in the future, there is no overlap between pulses and there is no need to insert dead times in the code. Any sane inverter design implements shoot-trough prevention in hardware. The gate drivers like ir2110 have the needed internal logic for this. Here is a pic of my nano (328p) output on the scope: https://photos.app.goo.gl/U5djzXFAW4uBJ9dM7

Happy trails!

[Irev-Dev]

Really appreciate you sharing that. Thanks @yo6ial.

[11Naweed11]

hello everyone, I tried this code with an inverter but unfortunately couldn't get it to working. here is my setup:

MOSFETs Q1 to Q4 are IRFP460
U1 and U2 are IR2110
The input voltage of the H-bridge is 300 ~ 350 VDC (J1)
Gate drive voltage is 12 ~ 15 VDC for driving the FETs. (J1)
Logic level is 5 volts.
The LC filter after the H-bridge uses 3.3 mH inductor with 4 ohms of resistance and 2.2 uF capacitor. (J3)
Signal from Arduino comes in from J2.

The output of the Arduino after filter is pure sinewave but the output of the H-bridge after the filter is nowhere near sinewave. it also takes a lot of current from power supply without any load at the output.

I am sure there is nothing wrong with my build because I have used it with EGS002 spwm driver module and everything works fine. The output is pure sinewave and it takes negligable current from supply.

After doing some investigation 2 things stoodout to me. One that in default configuration EGS002 does unipolar modulation while Arduino with your code does bipolar, and second is the dead time, which EGS002 by default has a 300ns of dead time.
Now you could argue that if EGS002 is working fine for me why would I try something else? the answer is that EGS002 is an ASIC meaning you don't have the freedom of customization. For example I want to change the inverters parameters with a graphical user interface such as output voltage or frequency. This is hard and expensive to do with EGS002.

If you wanted to know anything more, I am very much willing to provide. Thanks.

[Irev-Dev]

Just guessing @11Naweed11, but I suspect that the dead time is the most likely culprit, only because that would explain why the current is high even with no load, if it's shorting the h-bridge during the crossing, and if it is shorting it wouldn't surprise me if that would have a knock on effect of distorting the output shape. 🤷

[11Naweed11]

Well, the problem with bipolar modulation (meaning we feed both sides with spwm) is that it requires a better filter at the end which is difficult. This type of modulation is ok when used with low voltage low frequency transformers (because they don't require a filter) but not high voltage. But the problem with low frequency transformers are that they waste a lot of energy.
I tried unipolar codes using Timer1 library but could never get the dead time to be less than 4.5 us which is alot. The dead time should be more or less 500 ns.

[yo6ial]

hello everyone, I tried this code with an inverter but unfortunately couldn't get it to working. here is my setup:

MOSFETs Q1 to Q4 are IRFP460 U1 and U2 are IR2110 The input voltage of the H-bridge is 300 ~ 350 VDC (J1) Gate drive voltage is 12 ~ 15 VDC for driving the FETs. (J1) Logic level is 5 volts. The LC filter after the H-bridge uses 3.3 mH inductor with 4 ohms of resistance and 2.2 uF capacitor. (J3) Signal from Arduino comes in from J2.

The output of the Arduino after filter is pure sinewave but the output of the H-bridge after the filter is nowhere near sinewave. it also takes a lot of current from power supply without any load at the output.

I am sure there is nothing wrong with my build because I have used it with EGS002 spwm driver module and everything works fine. The output is pure sinewave and it takes negligable current from supply.

After doing some investigation 2 things stoodout to me. One that in default configuration EGS002 does unipolar modulation while Arduino with your code does bipolar, and second is the dead time, which EGS002 by default has a 300ns of dead time. Now you could argue that if EGS002 is working fine for me why would I try something else? the answer is that EGS002 is an ASIC meaning you don't have the freedom of customization. For example I want to change the inverters parameters with a graphical user interface such as output voltage or frequency. This is hard and expensive to do with EGS002.

If you wanted to know anything more, I am very much willing to provide. Thanks.

Your problem comes from the incorrect filtering.
When you pwm both branches of the line you need to use an inductor on each branch for the output filter.
You go with an inductor from each half-bridge output and one (or more) capacitor between the inductors at the very end.

Your output filtering part of the schematic is for half-pwm where one of the half-bridges modulates a 50/60hz square wave with 50% pwm fill rate.
Add another identical inductor and please move low voltage lines (physically) away from high voltage lines and outputs.
Take extra care of EMC, EMF and ground loops.