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The author show the working process of this schematic

1.The proposed system waits until the PZT device stores the energy vibrations produce during the positive half of vibration period \$T_{VIB}\$ before engaging switches \$S_I\$ and \$S_N\$ to discharge \$C_{PZT}\$ into off-chip harvesting inductor \$L_H\$

2.The inductor current \$i_L\$ rises to reach the peak, then the switches \$M_{P1}\$ and \$S_I\$ de-energize \$L_H\$ into the battery via \$i_{BAT}^+\$

3.The system again waits for the transducer to energize \$C_{PZT}\$ (in the negative direction) through the negative half of \$T_{VIB}\$ before prompting \$S_I\$ and \$S_N\$ to discharge \$C_{PZT}\$ into \$L_H\$, after which \$M_{P2}\$ and \$S_N\$ deenergize \$L_H\$ into the battery

I sort out what the author said:

1.the PZT will produce energy first,then \$S_I\$ and \$S_N\$ be "on" to let the current flow from \$C_{PZT}\$ to \$L_H\$

2.\$M_{P1}\$ and \$S_I\$ disconnect,and let the \$i_{BAT}^+\$ flow from the \$L_H\$ to the battery

3.when the PZT produce the negative part voltage,\$S_I\$ and \$S_N\$ are "on",and the negative current flow from the \$C_{PZT}\$ to \$L_H\$(this current direction is the oppsite of 1. current direction in the \$L_H\$ ),then \$M_{P2}\$ and \$S_N\$ disconnect to let the current flow from the \$L_H\$ to the battery

Hold on a second,i have a question about the 2. and 3.,if the \$M_{P1}\$ and \$S_I\$ disconnect,why can the \$i_{BAT}^+\$ flow from the \$L_H\$ to the battery?why can \$M_{P2}\$ and \$S_N\$ disconnect to let the current flow from the \$L_H\$ to the battery?It seems that i misunderstand something from the author saying,but i don't know which part do i misunderstand,can anyone correct my mistake?


1 Answer 1


After +ve swing of Cpzt: Dump charge into L current then release low side of +ve current as V+ into Vbat with CP1.

After -ve swing of Cpzt: Dump -ve charge into L current then release hi side of -ve current also as V+ into Vbat with CP2.

  • \$\begingroup\$ Sir,i read the some part of the paper,the schematic is also from this paper,can you tell me your thinking or correct my mistake if i am wrong? \$\endgroup\$ Mar 31, 2018 at 3:16
  • \$\begingroup\$ I corrected your thinking in my answer. It’s a full wave rectifier \$\endgroup\$ Mar 31, 2018 at 4:11
  • \$\begingroup\$ but sir,the topic of this paper is "A 2um BiCMOS Rectifier-Free AC–DC Piezoelectric Energy Harvester-Charger IC " \$\endgroup\$ Mar 31, 2018 at 4:50
  • \$\begingroup\$ I did not read topic, but I can read schematics. This is a boost flyback rectified current from a sinusoid piezoelectric. Charge up voltage is shunted to inductor L current then switched to charged Vbat, based on current polarity. \$\endgroup\$ Mar 31, 2018 at 5:18
  • \$\begingroup\$ CP1 and CP2 are "active rectifiers", not rectifiers, not pn junctions. Their Vf can be far below the 0.7V of a junction rectifier. The circuit is not rectifier-free. Instead it avoids use of pn junction rectifiers. \$\endgroup\$
    – wbeaty
    Mar 31, 2018 at 5:21

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