optocoupler for h-bridge

[--BawA--]

I am using a microcontroller to drive hbridge .
Is there any optocoupler which i can use between microcontroller and ir2110 to protect the microcontroller ?

 

[picgak]

There are opto drivers available TLP250 TLP350 etc . you can avoid ir2110.
check your requirements with data sheet before buying

 

[eiphan]

I am using a microcontroller to drive hbridge .
Is there any optocoupler which i can use between microcontroller and ir2110 to protect the microcontroller ?

You can use HCPL-3120. It is gate drive opto-coupler.

 

[dick_freebird]

I would be very concerned about the variability and asymmetry
of delay in optocouplers. If you want to keep (say) nonoverlap
timing between HIN and LIN, a skew between optocoupler LH
and HL times could easily slop that around by microseconds
if you use separate signals and separate couplers.

The Avago part indicates 300nS worth of asymmetry (pulse
width distortion) but other older types are likely much worse,
especially types that are just a NPN phototransistor, bring
your own pullup.

 

[goldsmith]

I am using a microcontroller to drive hbridge .
Is there any optocoupler which i can use between microcontroller and ir2110 to protect the microcontroller ?

Hi --BawA--
You'd better to mention your characteristics before ask your question . what's frequency of your PWM ? 6n136 / 6n137 / TLP250 / PC817 / PC819 or ... etc are good .

Best Wishes
Goldsmith

 

[--BawA--]

Hi goldsmith
I am using a unipolar spwm scheme of carrier frequency 20KHz.
Actually i am using a DSPIC33 series mcu to generate the desired spwm signal.
The output of dspic33 has an amplitude of 3.3v so i used 74HCT541 to level shift the 3.3v to 5v.
The output of the 74hct541 goes to ir2110 mosfet driver. I want an optocoupler to be placed between 74HCT541 and ir2110 in order to protect the mcu.
Since i have used 74hct541 so is it necessary to use an optocoupler.or 74hct541 itself is sufficient to provide the safety measures to MCU?

 

[FvM]

I fear, the problem isn't clearly specified. What do you exactly mean with "protect the microcontroller"?

In many designs, isolation between control circuit (e.g. microcprocessor) and DC bus is required. Of course, isolation involves protection against damage by a defective power stage, but that's not it's primary purpose.

If the control circuit is not isolated from DC bus, in other words both are powered by the same supply, opto couplers make no sense. Series resistors and clamp diodes would be sufficient to protect the control circuit against overvoltage feed back from the power stage.

The other aspect that comes into play is highside driver isolation. If an optocoupler is used for control circuit isolation, it might also povide the highside isolation. Driver power supply concept and required gate current are also determining the design.

Fast optocouplers and optoisolated gate drivers are available with different speed and respective delay skew. State-of-the-art optoisolated gate drivers have a maximum delay skew down to 100 ns, logic level couplers several 10 ns.

 

[--BawA--]

FvM, in my earlier design i was using pic16 series MCUs, i didn't use any optocoupler or any isolation between the pic16 and DC bus . When the H-Bridge gets damage the microcontroller also damages, so every time i had to change the microcontroller too. This time i am using DSPIC33 series mcu and i dont want to let the same thing happen again. So how to isolate the Dspic from dc bus? I mean which isolator must be used between dspic and dc bus?
Also if i isolate the mcu from dc bus then is there any need to use optocouplers for control signals??

 

[picgak]

As Fvm rightly pointed out If the control circuit DC is not isolated from HVDC bus then there is no point in using opto isolator to save your MCU

 

[--BawA--]

How to isolate the MCU from DC bus?
I am not using any feedback loop in DC-AC stage because the DC-DC stage is already regulated.

 

[picgak]

make another isolated winding in the DC-DC converter for powering MOSFET driver circuit after the optocoupler

 

[--BawA--]

one more thing, in the DC DC stage , i want to give the feedback through 4n35, so how to make a connections to 4n35 , i am using sg3525 as a pwm controller.?

 

[picgak]

see this link below
https://320volt.com/wp-content/uploads/2012/08/50khz-4n25-sg3525-smps-ir2110-smps-700w-50v-power-supply.png

 

[--BawA--]

**broken link removed**
what is the role of 510 ohm resistor and two 36v and 11v zener in 4n25,,and how to select this resistor and zener?

 

[picgak]

what is the role of 510 ohm resistor and two 36v and 11v zener in 4n25,,and how to select this resistor and zener?

In that circuit regulated voltage is 50V so 36 plus 11 plus voltage drop in 4n25 LED makes near 50 and thus regulated. 510 ohm resistor is for current limiting to the LED portion of opto 4n25