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TLV3603: high common mode input for comparator without GND referance.

Part Number: TLV3603
Other Parts Discussed in Thread: TLV3601, , UCC27211

Hello Experts,

I am designing an Active bridge rectifier (Diodes replaced by FETs). In which, the voltage can go as high as +-45V which operates at 360KHz. Now to make it work, I need to detect a few on-off threshold voltages across the FETs (-75mV and -3.9mV).  To scale down the voltage and make it work, I am using the below documents from TI "Dual Polarity High-Voltage Differential Input Interface for Low-Voltage Comparators Reference Design" Which works fine with the low side MOSFETs. But unfortunately, I am unable to make it work for high-side FETs.

Can you help me with how to achieve this or is there any difference amplifier that can solve this problem?

Note: As of now, the MOSFETs are off in the simulations.

Regards

Vishal.

  • Hi Vishal,

    I'm unable to read your schematic. Can you draw some connections?

    Kai

  • Hello Vishal,

    Thank you for your post. I would like to understand what issues you are experiencing with the TLV3601. I am guessing this is the comparator you are using since your attached schematic is hard to read as Kai mentioned. I see that you are using the suggested 3 resistor network on the inputs for the dual polarity high voltage signal. Can you reattach your simulation/schematic and explain the issues you are having with the comparator?

    Best Regards,

    Joe

    Applications Engineer

    Linear Amplifiers Business Unit | Comparators Product Line (CMPS)

    All information in this correspondence and in any related correspondence is provided “as is” and “with all faults”, and is subject to TI’s Important Notice (http://www.ti.com/corp/docs/legal/important-notice.shtml)

  • Hello Vishal,

    Just as a follow-up, how will the lower FETs ever turn on with the gate and source tied to the same potential? Is this what you meant by keeping the mosfets off in simulation?

    Best Regards,

    Joe

    Applications Engineer

    Linear Amplifiers Business Unit | Comparators Product Line (CMPS)

    All information in this correspondence and in any related correspondence is provided “as is” and “with all faults”, and is subject to TI’s Important Notice (http://www.ti.com/corp/docs/legal/important-notice.shtml)

  • Hi Joe,

    Here I am attaching the simulation file. The reason for 3 resistor divider network is to scale down the voltages as the comparator cannot support the higher voltage. This works fine for Lower side MOSFETs. I want to know how can I make it work for high-side FETs?

    Also, If I want to add hysteresis to this with TLV3603, Do I need to buffer my signals after the resister divider?

    Regarding MOSFETs being off, Based on the output from the comparator, the MOSFETs will be driven.

    RECTIFIER ON OFF THRSHOLD DETECTION high-low side_12052022.TSC

    Regards

    Vishal

  • Hi Vishal,

    I'm sorry but it's not possible for me to read your schematic without spending lots of time, which I do not have, unfortunately.

    Kai

  • Hello Vishal,

    Thank you for providing your TINA sim. I now see that the configuration you showed was to turn off the FETs. Your simulation schematic allows for them to be turned on and off via the UCC27211 half-bridge gate driver. I will take a look at your circuit to see if the comparator is causing the issue. If not, then I will direct you to the team that is responsible for the UCC27211 because they are best equipped to troubleshoot this portion of the circuit. 

    As far as adding hysteresis, you are currently using the TLV3601 as confirmed by the macro of the comparators. If you use the TLV3603, there is a dedicated LE/HYST pin that will allow you to configure the hysteresis that you need via an external resistor. 

    snom712a.zip

    The ZIP file that I have inserted above has the TLV3603 comparator in it. 

    I will take a look at your circuit and update you by the end of the day tomorrow. 

    Best Regards,

    Joe

    Applications Engineer

    Linear Amplifiers Business Unit | Comparators Product Line (CMPS)

    All information in this correspondence and in any related correspondence is provided “as is” and “with all faults”, and is subject to TI’s Important Notice (http://www.ti.com/corp/docs/legal/important-notice.shtml)

  • Hello Vishal,

    Taking a look at each comparators inputs and outputs leads me to believe that they are behaving as expected. Please see the attached TINA file, as there were some unconnected or circular connections that led to convergence errors. If you would like I can redirect this post to the team responsible for the UCC27211 to help with the configuration of the active bridge rectifier.

    RECTIFIER ON OFF THRSHOLD DETECTION high-low side_No_Errors.TSC

    Best Regards,

    Joe

    Applications Engineer

    Linear Amplifiers Business Unit | Comparators Product Line (CMPS)

    All information in this correspondence and in any related correspondence is provided “as is” and “with all faults”, and is subject to TI’s Important Notice (http://www.ti.com/corp/docs/legal/important-notice.shtml)

  • Hi Joe,

    Thanks for your response. I am using TLV3603 in my simulations to solve ZCD issues. My concern is regarding the high common-mode voltage when connecting the comparator on the high side of the H-bridge. How Can I scale down the high common-mode on the high side of the bridge?

    Also, Can I use the TLV3603 hysteresis circuit for inverting comparator configuration?

    Regards

    Vishal

  • Hi Vishal,

    I would recommend dividing the voltage down on the high side of the H-bridge via a resistive divider to adhere to the input common mode requirements of the TLV3603.

    As far as implementing hysteresis, I would encourage you to take a look at section 8.1.1 in the datasheet where there is an explanation for the TLV3603 hysteresis pin.

    Please let me know if you have any questions.

    Best Regards,

    Joe

    Applications Engineer

    Linear Amplifiers Business Unit | Comparators Product Line (CMPS)

    All information in this correspondence and in any related correspondence is provided “as is” and “with all faults”, and is subject to TI’s Important Notice (http://www.ti.com/corp/docs/legal/important-notice.shtml)