Electronic – Mosfet to save power

h-bridgel298low-powermosfet

I am making a battery powered project which involves bi-directional motor control. However motor needs to turn rarely (about 10-20 seconds in 24 hour period). I am using L298 motor driver. However the quiescent current is in mA range. To reduce current consumption, I am planning to use a mosfet switch as shown in the figure below:

VM = 9 V

VCC = 4.5 V or 6 V (I will decide after a little experiment)

Motor current consumption < 1 A

H Bridge with mosfet switch

Whenever I need to use the motor, I will turn the mosfet ON and keep it OFF while the motor is not in use. (I am using logic level mosfet.) The quiescent current of mosfet is in uA range and that's how I am planning to save a lot of battery power.

Will it work?

Any suggestions/improvements are welcome.

Best Answer

I suggest using high-side switches rather than a low-side switch.

Edit: One high side switch for each power supply.

Something like this: (Edit: x2)

enter image description here

It needs a base resistor for the BJT or use a logic-level MOSFET. R1 could be something like 10K and the base resistor 20K or so. The p-channel MOSFET should be logic level for your conditions. You can find dual p/n channel units in an SO8 that can handle some amperes.

The problem with switching the ground connection (low side switch) is that there are two power supplies on the chip and the inputs will end up biased at some voltage above ground, which may draw unnecessary current and/or be bad for your micro.

You still have to bring the outputs of your micro low or you will drive unnecessary current into the L298 inputs.

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