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BQ51221EVM-520: How to measure AC/DC Efficiency with BQ51221EVM and BQ501210 ?

user4797263
Prodigy 30 points

Part Number: BQ51221EVM-520

Hello

I'm stuggling with measurement Efficiecy with RX( BQ51221EVM) and TX(BQ501210).

How to measure Rx input voltage and current on AC1, AC2?

I measured voltage with  probe(active probe) AC1-AC2. And Current probing coil current.

And product  RMS Votage(AC1-AC2) and RMS coil.

Is it correct?

Let me know in detail.

Thanks in advance.

  • 0
    TI__Guru* 75886 points
    The difficulty with AC power measurement is Power Factor and distortion of current and voltage waveforms. A good solution is to use a Power Analyzer to for this problem, Yokogawa make a number of instruments for this. This will give an answer in watts that can be compared with DC output power.
    RMS voltage and RMS current will give apparent power (VA) and will be a larger value.

    The bq51221 will use synchronous rectification on the AC 1 and AC2 to RECT output to reduce power loss. Control loop will keep the RECT voltage about 300mV above output set point at full load. Combination of the above will put efficiency of the bq51221 at about 90%.