Hello,
I'm building a voltage controlled relay using an LM358 to monitor charge of two batteries and two Pmosfets that will turn on an Nmosfet if either of the battery's voltage rises above 13.8v. This will allow them both to be connected together in parallel if either battery is receiving a charge enough to push it over the 13.8v threshold.
This is the basic schematic -but the front end is duplicated for each battery.(Only one comparator shown). Although both can drive the final Nmosfet.
The circuit does work, only not as well as I had modelled in Spice. In practice the voltage rise from a battery charger is incredibly slow, and this seems to be causing a Pmosfet to enter its linear region for a lot longer than desired. This in turn causes the same effect in the Nmos and the current slowly builds in the relay until it turns on. I was hoping for a digital toggle effect from the LM358. Instead I am getting a sweep.
Can anyone explain what is happening and more importantly a correct method to drive the Mosfets for me. Maybe a different comparator.
Thank you for your time and any input.
I'm building a voltage controlled relay using an LM358 to monitor charge of two batteries and two Pmosfets that will turn on an Nmosfet if either of the battery's voltage rises above 13.8v. This will allow them both to be connected together in parallel if either battery is receiving a charge enough to push it over the 13.8v threshold.
This is the basic schematic -but the front end is duplicated for each battery.(Only one comparator shown). Although both can drive the final Nmosfet.
The circuit does work, only not as well as I had modelled in Spice. In practice the voltage rise from a battery charger is incredibly slow, and this seems to be causing a Pmosfet to enter its linear region for a lot longer than desired. This in turn causes the same effect in the Nmos and the current slowly builds in the relay until it turns on. I was hoping for a digital toggle effect from the LM358. Instead I am getting a sweep.
Can anyone explain what is happening and more importantly a correct method to drive the Mosfets for me. Maybe a different comparator.
Thank you for your time and any input.