Design PWM to cope with supercapacitor and battery(help)

AI Thread Summary
The discussion focuses on designing a PWM circuit to alternate power supply between a battery and a supercapacitor for an electric load. The proposed stages include charging the supercapacitor with the battery, switching to supercapacitor supply once its voltage reaches a certain level, and reverting to the battery as the supercapacitor discharges. The user is experiencing issues with the PWM and NMOS switch, specifically damping oscillations in the input signal and the NMOS not turning off properly. There is a suggestion to consider using comparators instead of PWM for better functionality. The conversation highlights the importance of correct component selection and circuit design for effective power management.
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..
 
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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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