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OPA2277: What is the best differential op amp for Voltage and Current sensing when making 500KWatt converter?

Manrae Kim
Prodigy 30 points
Part Number: OPA2277
Other Parts Discussed in Thread: INA2137, , OPA2206

Tool/software:

Hi guys

I'm making schematics for 500[KWatt] Converter.

In this design, I need your recommendation on differential OP AMP to sense both Voltage and current in -/+15V range.

First of all, I received the reference schematic from senior at work and INA2137 to converter from -/+10V to -/+3.3V and then to 3.3V for MCU input port.

However, I think that features of OPA2277 is better than that of INA2137.

What do you think about that?

But if you have the best differential OP-AMP for my schematic, I hope let me know it.

BR

Manrea

  • 0
    TI__Guru* 77541 points

    Hi Manrea, 

    Manrae Kim said:
    However, I think that features of OPA2277 is better than that of INA2137.

    Here is some comparisons and I added OPA2206 due to its input overvoltage protection and higher slew rate.  

    Manrae Kim said:
    In this design, I need your recommendation on differential OP AMP to sense both Voltage and current in -/+15V range.

    For the application, you would need high Aol, CMRR and PSRR features in the differential circuit. 500kW is huge power in converter. Since I do not have switching frequency, voltage and current information, I am unable to comment on it. 

    For the application, our thin film matching resistors may help if you are constructing discrete difference amplifier (INA2137 is integrated DA) for sensing application. 

    https://www.ti.com/lit/ds/symlink/res11a.pdf?ts=1746384751429&ref_url=https%253A%252F%252Fduckduckgo.com%252F

    https://www.ti.com/lit/ds/symlink/res60a-q1.pdf?ts=1746456737669&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FRES60A-Q1

    If you have other questions, please let me know. 

    Best,

    Raymond

  • 0 in reply to Raymond Zhang1
    Prodigy 30 points

    Hi Raymond

    Thank you for the detailed feedback.

    Sorry for the late reply, but last Monday and Tuesday were public holidays in Korea.

    It would not be appropriate but I don't have much experience about features of OP-AMP such as Aol, PSRR, etc.

    However, I know the concepts on CMRR, Vos Drift, rail-to-rail.

    Could you elaborate the concepts Aol, and PSRR, IQ typ(mA), Vn at 1kHz(nV/Hz)?

    Also, I have to use NACL2000B1S5/SP2 as current sensor and lv_25-1000 as voltage sensor. These datasheet are attached.

    So, now, could you recommend on differential OP AMP to sense both Voltage and current in -/+15V range?

    I know this is an unreasonable question, but I would really appreciate your help.

    sensor_datasheet.zip

    Have a nice day!

    Best Regards!

    Manrae.

  • 0 in reply to Manrae Kim
    TI__Guru* 77541 points

    Hi Manrae, 

    Manrae Kim said:
    Could you elaborate the concepts Aol, and PSRR, IQ typ(mA), Vn at 1kHz(nV/Hz)?

    When you are talking about 500kW switching power supply, the low noise specification in the op amp does not mean much. The dominated noise in your system is from switching power supply and switching PWM signal. The list below is captured from OPA2206. 

    However, higher Aol, CMRR and PSRR will help to attenuated unwanted signal from the switcher. That being said, it depends on how well you are able to filter out your +/-15Vdc fo drive a high Aol op amp, where it can take advantages of CMRR and PSRR in the op amp. The op amp selection is important, but it is more critical how to minimize your switching noise in your 500kW converter. 

    For instance, this is CMRR, +/-PSRR in OPA2206 op amp. If you are able to place a low frequency pole in your switching supply, say 5kHz to 10kHz, then the +PSRR rejection will be adequate. Here CMRR and -PSRR has better rejection than +PSRR. If your LC pole is placed at 30kHz, the +PSRR is still has 40dB rejection on the +15Vdc rail. Beyond the high switching frequency or harmonics, +PSRR won't work as well. But CMRR is still excellent at 30kHz,

    -PSRR is decent at 70dB in this part. 

    So it is difficult to answer your question - if you have the best differential OP-AMP for my schematic. 

    You can select the best op amps in the world. If you do not manage the switching frequency and harmonics in the converter, it is not going to help your design significantly. For 500kW converter, the common mode noise will be high. So OPA2206 may help.  You can always filter out +/-15Vdc supply rails with high PSRR LDO and use lower ripple voltage rails and sample the voltage and current in difference amplifier or instrumentation amplifier etc.

    If you have other questions, please let me know. 

    Best,

    Raymond