# How to power a gate driver to 15-20 volts in a low voltage circuit?

#### bkhan10000

Joined Jan 18, 2017
31
Hey guys,

Just a conceptual question. Say I have a microcontroller at logic level, 5 volts, and want to use that to control a mosfet, which is not a logic level mosfet. In this case I would then use a gate driver. To provide the required 15-20 volts for the mosfet and gate driver, in a regular circuit, what is the most common way to provide the required voltage for the mosfet and the gate driver?

-Khan

#### #12

Joined Nov 30, 2010
18,224
bootstrap capacitor
It has limited usefulness. It won't work at all for DC.

#### Alec_t

Joined Sep 17, 2013
13,337
Can't say which would be the most common, but one way would be to use a 15V supply (perhaps created by stepping up the 5V) in addition to the 5V supply, then use a level-shifter driven by the micro.

#### bkhan10000

Joined Jan 18, 2017
31
ThanKS for the replies guys. In this situation, do you think a buck converter would be feasible to step up 5 volts to 15 volts? The place this stems from is the examination of motor control circuits that work of 7.4 volts. Most mosfets need more than 7.4 volts to operate. What do you think these motor control circuits use to drive the gates of mosfets? When I say motor control circuits I am referring to electronic speed controls such as:
https://www.amazon.com/gp/aw/d/B00M90TJJM/ref=yo_ii_img?ie=UTF8&psc=1#

-khan

#### ronv

Joined Nov 12, 2008
3,770
ThanKS for the replies guys. In this situation, do you think a buck converter would be feasible to step up 5 volts to 15 volts? The place this stems from is the examination of motor control circuits that work of 7.4 volts. Most mosfets need more than 7.4 volts to operate. What do you think these motor control circuits use to drive the gates of mosfets? When I say motor control circuits I am referring to electronic speed controls such as:
https://www.amazon.com/gp/aw/d/B00M90TJJM/ref=yo_ii_img?ie=UTF8&psc=1#

-khan
A buck converter usually lowers the input voltage. Maybe you meant a boost converter? That would work.
I suspect the ESC you posted uses a logic level FET.
Or here is a simple voltage doubler.

#### bkhan10000

Joined Jan 18, 2017
31
A buck converter usually lowers the input voltage. Maybe you meant a boost converter? That would work.
I suspect the ESC you posted uses a logic level FET.
Or here is a simple voltage doubler.
View attachment 119127
Hi Ronv. You are right I meant a buck converter. I have heard that logic level fets are generally higher resistance? I am about to do something research but that is what I heard and why they are avoided for power switching applications. Currently looking into the voltage doubler. Thanks for the input? Are there any other methods? Do all low voltage ESCs utilize logic level fets?

#### ian field

Joined Oct 27, 2012
6,536
Hey guys,

Just a conceptual question. Say I have a microcontroller at logic level, 5 volts, and want to use that to control a mosfet, which is not a logic level mosfet. In this case I would then use a gate driver. To provide the required 15-20 volts for the mosfet and gate driver, in a regular circuit, what is the most common way to provide the required voltage for the mosfet and the gate driver?

-Khan
A blocking oscillator Joule thief circuit will easily generate the voltage you need, but the downside is having to wind an inductor.

There's no shortage of examples online, but most are designed to run off 1.5V single cell - for any higher Vcc; you have to add a capacitor to DC block the feedback circuit and you have to provide the tranistors base with a start up resistor.

If you need to regulate the voltage - clamp the BO transistor B/E with a regulation transistor, that is biased on via a Zener with a current limiting resistor in series with it from the output rail.

#### ronv

Joined Nov 12, 2008
3,770
Hi Ronv. You are right I meant a buck converter. I have heard that logic level fets are generally higher resistance? I am about to do something research but that is what I heard and why they are avoided for power switching applications. Currently looking into the voltage doubler. Thanks for the input? Are there any other methods? Do all low voltage ESCs utilize logic level fets?
I kind of like these little guys:
http://www.mouser.com/ds/2/260/SBT01-SPEC-806254.pdf

Lots of them:
http://www.mouser.com/Power/DC-DC-C...Z1z0k0exZ1y9kc4hZ1yxt7ffZ1yxt791&Ns=Pricing|0

You can get some pretty go logic level FETs.
http://www.mouser.com/ds/2/196/irl40b209-938002.pdf

More. But check the curves carefully. Not all are logic level.
http://www.mouser.com/Semiconductor...i&Ns=Vgs th - Gate-Source Threshold Voltage|0