Design PWM to cope with supercapacitor and battery(help)

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Discussion Overview

The discussion revolves around the design of an electric circuit that utilizes Pulse Width Modulation (PWM) to manage the operation of a battery and supercapacitor in supplying current to loads. The participants explore the stages of operation, issues with circuit functionality, and potential design alternatives.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant outlines a three-stage operation for the circuit involving charging the supercapacitor with the battery, switching to supercapacitor supply, and then reverting back to battery supply as the supercapacitor discharges.
  • Issues are reported with the PWM and switch functionality, specifically mentioning damping oscillation in the positive input signal and the NMOS switch not turning off when Vs > Vg.
  • Another participant points out a discrepancy in the use of NMOS versus PMOS FETs in the schematic, suggesting that the schematic shows a PMOS while the participant intended to use an NMOS.
  • A suggestion is made to consider replacing PWM with comparators for the circuit design.

Areas of Agreement / Disagreement

Participants express differing views on the appropriate FET type to use and the effectiveness of PWM versus comparators, indicating that multiple competing views remain and the discussion is unresolved.

Contextual Notes

There are potential limitations regarding the assumptions made about the circuit components and their interactions, as well as unresolved issues related to the circuit's operational stability and design choices.

Who May Find This Useful

Individuals interested in circuit design, particularly those working with power management systems involving batteries and supercapacitors, may find this discussion relevant.

shanver
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I need to design an electric circuit which require PWM to let the battery and supercapacitor take turn to supply current to the loads.

stage1: battery charge up supercap and supply current to the load

stage2: supercap voltage increase to a certain level, battery current is cut, supercap supply current to the loads

stage3: voltage of supercap decrease to certain level, again, battery supply current to load and supercap.
http://www.freeimagehosting.net/3eguo

image http://www.freeimagehosting.net/3eguo

my pwm and switch is not functioning well,
the positive input signal undergoes damping oscillation
and the switch (nmos) does not switch off as Vs>Vg

can anyone help me in this project? I will provide any information if require to..
 
Last edited:
Engineering news on Phys.org
http://img43.imageshack.us/img43/8094/projecto.png

here is the problem circuits
 
Last edited by a moderator:
shanver said:
I need to design an electric circuit which require PWM to let the battery and supercapacitor take turn to supply current to the loads.

stage1: battery charge up supercap and supply current to the load

stage2: supercap voltage increase to a certain level, battery current is cut, supercap supply current to the loads

stage3: voltage of supercap decrease to certain level, again, battery supply current to load and supercap.
http://www.freeimagehosting.net/3eguo

image http://www.freeimagehosting.net/3eguo

my pwm and switch is not functioning well,
the positive input signal undergoes damping oscillation
and the switch (nmos) does not switch off as Vs>Vg

can anyone help me in this project? I will provide any information if require to..

shanver said:
http://img43.imageshack.us/img43/8094/projecto.png

here is the problem circuits

You mention using an nmos FET, but your schematic shows a pmos FET...
 
Last edited by a moderator:
berkeman said:
You mention using an nmos FET, but your schematic shows a pmos FET...

thank for correcting , should be nmos as in schematic,
it would be fine for pmos/nmos as long as 1 of them are functioning
 
I'm thinking of replacing pwm to comparators.. any suggestion?
 

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