Electrical – driving high and low side mosfet for synchronous buck converter

arduinomosfetmosfet-drivermpptpower electronics

I am designing an MPPT charge controller. I have chosen my MOSFETs to be both NMOS https://www.sparkfun.com/products/10213 (FQP30N06L) 60V, 30A. Since the gate voltage is 3 to 5V. I can drive the low side, however, how can drive the high side? since \$V_g\$ should be higher than \$V_s\$, which in this case is \$V_{in}\$ (around 37 V). A lot of people say using a half bridge driver. But also there is a problem. The output voltage is present always (battery voltage), which causes a problem for the driver.

input voltage is 5-37V and I max is 9A
the shared node is Dutycycle*Vin during Ton and it is 0.7V during toff

Any suggestions?
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Best Answer

Typically supplying the high side gate driver is accomplished with a "bootstrap capacitor".

While the low side is switched on, the switching node gets pulled low and the capacitor gets charged through the diode. After the low side switches off and the high side switches on, the high side gate driver remains powered by the stored charge. This does limit the maximum duty cycle and minimum switching frequency (as you cannot let the capacitor voltage sag too much), but is cheap and easy to implement.

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