Hi,
For full bridge circuit to convert from 300vdc to 220vac, if I use MOSFETs, I need isolated high side MOSFET gate drive. If I use MJE13009 NPN transistor instead, do I need high side isolated drive? Can I drive it directly from my SG3525 50Hz oscillator?
Thank you in advance.

 

Hi,
Will bootstrapping method work for frequencies such as 50Hz or 60Hz?
I tried IR2110 at 50Hz. Unfortunately, the full bridge was delivering no output. But when I used it at 30kHz there was appropriate output.

 

The MJE13009 requires around 2A base current to get roughly 10A out. No, your SG3525 would not supply enough current; it's limited to 200mA.

It wouldn't be able to directly drive high-side NPN transistors, either.

 

What about 2 H bridges inverted from each other?

 

Hi,
Will bootstrapping method work for frequencies such as 50Hz or 60Hz?
I tried IR2110 at 50Hz. Unfortunately, the full bridge was delivering no output. But when I used it at 30kHz there was appropriate output.

My best guess here is that you're attempting to run the bridge under no-load conditions. At 30kHz, there is enough parasitic LC in the bridge to get the high side caps charged, but not enough at low frequencies.

Try using a 220K resistor as a load.

Have a look at International Rectifier's Design Tip DT97-3
http://www.irf.com/technical-info/designtp/dt97-3.pdf

 

My best guess here is that you're attempting to run the bridge under no-load conditions. At 30kHz, there is enough parasitic LC in the bridge to get the high side caps charged, but not enough at low frequencies.

Try using a 220K resistor as a load.

Have a look at International Rectifier's Design Tip DT97-3
http://www.irf.com/technical-info/designtp/dt97-3.pdf

I ran the bridge with a 25W lamp as load.

 

The MJE13009 requires around 2A base current to get roughly 10A out. No, your SG3525 would not supply enough current; it's limited to 200mA.

It wouldn't be able to directly drive high-side NPN transistors, either.

But if I'm taking only 0.3A (100W load at 300v), I would require less than 100mA. That is within the capability of the SG3525.

 

If you are using the MJE13009 in the high side of a bridge, it will be functioning as an emitter follower. In order to have 300V on the emitter, you would need 300V on the base.

 

Hi,

Thank you. Now I have gotten the answer to my question. Once again, thank you.

Tahmid.

 

hi,

I used full bridge circuit with 4 X MJE13009.The bridge works properly and the load lamp of 25W lights, but after a few seconds, 2 of the transistors get shorted and the circuit ceases to function. I have replaced the transistors twice, but same thing happens.
The propagation delay time of MJE13009 is 1.6us. I have used SG3525 to drive the transistors with a driver transistor: MJE13001 for the high side. My guess is that the dead time set in the SG3525 is too narrow and the transistors are cross-conducting. That's why the upper and lower transistors are shorted. I have used 470 ohm resistor between the DISCHARGE and CT pin of SG3525 and this sets the dead time to the maximum possible.
Is my assumption correct? If not, what can be the cause?
What can be the remedy?


Thanks.

 

The datasheet lists minimum frequency of the SG3525 as 120Hz. Perhaps it is unstable when operating at 50Hz and is unable to provide dead time?

 

Hi,
Thingmaker 3, you are correct. I checked the datasheet of SG3525 of ST Microelectronics. Then, if SG3525 is becoming unstable, what is my solution? What oscillator should I use?

 

Hi,

I have found out about SG3526 which can operate from 1 hz to 400khz. Should I use this?
In the Microsemi datasheet, they have stated that at 40khz, if i use 22 ohm resistor as Rd, i get a dead time of 50%. If i use 10 ohm i get 25%.
I want to know: if i will still get the same dead time at 50hz?

Thanks.

 

why dont you incerase dead time and see the operation

 

why dont you incerase dead time and see the operation

Hi,
For SG3525, i have set maximum deadtime and it is not working.
I do not know how to set dead time in SG3526. That's why i require help. If you know, please let me know.

Thanks.

 

According to figure 6 of the SG3526 datasheet, dead time is proportional to the value of the resistor on pin 11.

 

According to figure 6 of the SG3526 datasheet, dead time is proportional to the value of the resistor on pin 11.

Hi,
I have seen the datasheet, but in the datasheet it specifies the dead time at 40khz. Will it be the same for 50hz?

Thanks.

 

I suggest experimenting with a resistor divider standing in for the transistors. You can then adjust the driver as needed without having to risk loosing more transistors.

 

Hi,

I have found out about SG3526 which can operate from 1 hz to 400khz. Should I use this?

The first thing I saw in the datasheet was a Vcc limit of 40V.

I thought you were working with a few hundred volts?

If so, and if you try this IC, you'll blow the lid right off of it.

You must ensure that the driver IC meets all of your requirements before you connect it, unless you enjoy seeing bright flashes and large clouds of acrid smoke, accompanied by loud "BANGs".

 

Can we see a drawing of the bridge?
Have you tried driving the transistors with a pulse tranformer?