Linear Current Booster Pump Driver

Re: Linear Current Booster Pump Driver

Yes, you have it correct...

For a bit more detail. A solar panel is (for the most part) a current source--The panel will output a fixed amount of current from zero volts to around Vmp--With the current proportional to the amount of sunlight hitting it. The first amount of useful power is around sun up with weak sun hitting the panel (when panel reaches near Vmp and Ipanel is more than zero amps).

The "simple" pump motors are typically Brushed (Universal) DC motors (there are others types which I will ignore for the moment). The output torque of the motor is, mostly, based on the amount of current flowing through the windings.

So, here is the delema--A solar panel wants to output Vmp * I_{whatever-current} is available. And the motor wants all the current at what ever voltage is available.

And, if the pump plus the Vmp down towards zero volts, and still low current--The available power is V_near-zero * I_whatever = a small amount of energy.

What a linear current booster does is (through the use of a switching power supply circuit--probably similar to an MPPT type solar charge controller) is find the maximum output power (Psolar=Vmp*I_whatever) and then down convert it to Pmotor = Vmotor * Imotor) and what it can take. You can think of the LCB sort of as a version of a DC variable transformer--The ability to adjust/down convert/"transform" high voltage/low current from the array to low voltage/high current needed by the load (motor).

With weak sun on panels (morning, evening, cloudy weather) the linear current booster makes more current available to get the pump turning for more hours in a day, and drawing the maximum available power from the solar array (maximum power point tracking MPPT). You will not get a lot of water (GPH--gallons per hour)) at the begining and end of the day--But the pump will run, overall, more hours per day, and the solar panels will supply more efficiently--giving more total water moved in a day.

I believe some LCB controllers will also limit solar panel voltage to a fixed amount (say 12 or 24 volts) so the motor is not fed too much power.

Hope this makes things clear.

-Bill