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recently I am researching the piezoelectric transducer (PET), which can convert the mechanical energy into electricity. And I found a strange phenomenon. I used the 10MΩ probe of oscilloscope to connect the two electrodes of PET, it measured about 9.9V output voltage and the current is around 1uA obtained by other equipment. However, after I connected a full-bridge rectifier after the PET, the output of rectifier is only around 2.4V. I remember it should be 9.9V-2*(forward voltage of diode), that is about 9.5V. I couldn’t find what is the problem. I just simulated this using TINA-TI software. The result is that the case as well. The PET can be modelled as a sinusoidal current source in parallel with its internal electrode capacitance and resistor. When I increased the current from 1uA to tens of uA, the output voltage after full-bridge circuit is correct. So I wonder why small current of PET will cause this problem. Can anybody help me solve this confusion. Thanks a lot!

PET model

PET model simulated result

PET with full-bridge rectifier

Simulated result of PET with rectifier

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I believe the problem is the reverse current of the diode (current which flows through the diode if it is reversed biased). For this diode, this current is about 2uA, thus during the positive half cycle, the source current will flow in the forward direction through D2 and part of it back to the source through D3 (reverse current).

Probably if you use ideal diodes in your simulation, the problem should be solved. Or as you already suggested, just increase the source current.

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  • \$\begingroup\$ Thank you so much. That is really the problem. \$\endgroup\$
    – Nick Long
    Commented Mar 28, 2020 at 3:14

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