Ironic
Newbie level 4
Hi guys.
A tricky one here:
This is for a robotics application, but similar to uses in RC world. However since the topic is very specific to power electronics i posted it here.
The robot has two lipos (4s - 16V) and a DC input (from a power supply that can do 50A)
I want to be able to use an arduino to select from which power source to draw current.
This means transistors or relays. I need this to handle 50A (so i have a good safety margin).
High side switching is desirable so that everything is at ground level.
I think the high current requirement means Bipolar, or IGBT are out of the question because heating and power loss would be excessive.
One approach wolud be to use N-Channel Mosfet in series with battery and dc input positive terminal.
**broken link removed**
The arduino(trough a high side driver) would then turn one mosfet to power the circuit. (i have already found mosfets suitable for the task)
The problem with this is that because of the body diode found in mosfets if for example battery 1 is discharged, and battery 2 was selected as the power source, current would flow into bat 1 trough the body diode of it's mosfet, despite the mosfet being off, which must be avoided.
Simple solution would be to add diodes in series, but i would like to avoid that because for 50A even low drop diodes would cause excessive power waste and heating.
Based on a similar problem found here which recommends this chip it seems that one solution is to use a another mosfet in series, in a reverse direction to use it's body diode as a very low drop out diode. The circuit recommended in the datasheet seems to have other uses (charging) but i do not require that.
However given the complexity and cost of these solutions maybe a relay would be better.
I am going to use a hot swap controller to limit inrush currents. The system will be designed in a way that the relays would only turn on or off when current is 0, so they only have to handle the steady state current.
However relays for 50A will take up some space and weigh (what i found so far is about 2.5cm side cube and 40g weight).
Any advice?
Regards
A tricky one here:
This is for a robotics application, but similar to uses in RC world. However since the topic is very specific to power electronics i posted it here.
The robot has two lipos (4s - 16V) and a DC input (from a power supply that can do 50A)
I want to be able to use an arduino to select from which power source to draw current.
This means transistors or relays. I need this to handle 50A (so i have a good safety margin).
High side switching is desirable so that everything is at ground level.
I think the high current requirement means Bipolar, or IGBT are out of the question because heating and power loss would be excessive.
One approach wolud be to use N-Channel Mosfet in series with battery and dc input positive terminal.
**broken link removed**
The arduino(trough a high side driver) would then turn one mosfet to power the circuit. (i have already found mosfets suitable for the task)
The problem with this is that because of the body diode found in mosfets if for example battery 1 is discharged, and battery 2 was selected as the power source, current would flow into bat 1 trough the body diode of it's mosfet, despite the mosfet being off, which must be avoided.
Simple solution would be to add diodes in series, but i would like to avoid that because for 50A even low drop diodes would cause excessive power waste and heating.
Based on a similar problem found here which recommends this chip it seems that one solution is to use a another mosfet in series, in a reverse direction to use it's body diode as a very low drop out diode. The circuit recommended in the datasheet seems to have other uses (charging) but i do not require that.
However given the complexity and cost of these solutions maybe a relay would be better.
I am going to use a hot swap controller to limit inrush currents. The system will be designed in a way that the relays would only turn on or off when current is 0, so they only have to handle the steady state current.
However relays for 50A will take up some space and weigh (what i found so far is about 2.5cm side cube and 40g weight).
Any advice?
Regards
