PRELIMINARY CHL8511 HIGH EFFICIENCY 6A BUCK MOSFET DRIVER. External MOSFETs in a synchronous buck converter. It is intended for use with CHiL Digital PWM controllers to. HIGH EFFICIENCY 6A BUCK MOSFET DRIVER Page 2 of 11 CHiL Semiconductor Confidential DS0021 Rev 0.91, July 22, 2010.
- Typically, buck converters have a bootstrap gate driver 1 and an N-channel MOSFET, or a P-channel MOSFET. 1 Bootstrap gate driver (see also here) is not the only option for N-challel MOSFETS. Other options: gate driver transformer, additional supply rail for gate driving with elevated voltage.
- The NJW4161 is a MOSFET Drive switching regulator IC for Buck Converter that operates wide input range from 3.1V to 40V. It can provide large current application because of built-in highly effective Pch MOSFET 10V drive circuit. There are two types, Hiccup type and Latch type, of over current protection version.
- PWM from PIC to drive MOSFET of Buck Converter. You should use some of hi side mosfet gate driver chips to work with n type mosfets. MC has nice one with their own charge pumps (not likr IRxxxx that uses mosfet drive signal). Switching speed is very important cause it defines losses in mosfet.
- A buck converter (step-down converter) is a DC-to-DC power converter which steps down voltage (while stepping up current) from its input (supply) to its output (load). To achieve this, MOSFET gate drivers typically feed the MOSFET output voltage back into the gate driver.
- The RT9610A/B is a high frequency, dual MOSFET driver specifically designed to drive two power N-MOSFETS in a synchronous-rectified buck converter topology. It is especially suited for mobile computing applications that require high efficiency and excellent thermal performance.
- Buck converter using pic microcontroller and IR2110, what is buck conveter. Implementation of buck converter using IR2110, Gate driver circuit for Buck.
I designed a simple buck converter to meet the following specs (I have attached the schematic):
- Vin = 17.4V
- Vout = 12V
- D = 0.69
- Switching Frequency = 50kHz
- Inductor Ripple Current = 20% of Output Current
- Output Voltage Ripple = 2% of Vout
Background Info: All the parts and component values listed on the schematic are parts I'm implementing in the circuit. I know the inductor and capacitor values are not matched perfectly to the specs listed above, but they are the closest that I could find. The PWM signal is being generated by the Arduino Uno and I am using the TC4427 IC to drive the signal at the gate of my MOSFET.
Problem:My MOSFET is not turning on. I know for it to turn on Vgs > Vth. I am using the TC4427, because the max output voltage of the Arduino is only 5V. What I'm confused about is why my gate driver isn't supplying the necessary turn on voltage. I thought I understood how it works, but not apparently. The max output of the TC4427 is only as high as the supply voltage I feed into it (from measurements I've taken), which doesn't make sense to me. I've looked on the TC4427 datasheet, but it doesn't give me any information on the max voltage output coming from the gate driver. Does this mean I need to supply an input volts higher than V1 to the supply just to turn on my MOSFET? Or how exactly is a gate driver supposed to work?
simulate this circuit – Schematic created using CircuitLab
Dave Tweed♦2 Answers
$begingroup$The TC4427 by itself can not generate a gate drive voltage greater than its own supply voltage. That follows from the functional block diagram on p.2 of the datasheet.
It would make the question clearer, if you add the gate driver to the schematic on the O.P. and show its supply rails.
For the time being, I'll assume that the TC4427 is powered from the same +17.4V that goes to the input of the buck. In that case, the source of the N-channel MOSFET will not be any higher than 17.4 V - Vth.
Typically, buck converters have a bootstrap gate driver1 and an N-channel MOSFET, or a P-channel MOSFET.
1Bootstrap gate driver (see also here) is not the only option for N-challel MOSFETS. Other options: gate driver transformer, additional supply rail for gate driving with elevated voltage.
$endgroup$$begingroup$Your N ch fet is wired as a source follower and this is bad for this type of power supply (switching) but OK for a linear regulator! You should either: -
- Consider using a P channel MOSFET
- Use a bootstrapped driver
If you use a bootstrapped driver it will provide a gate volate that is at least 10V higher than the source voltage and turn the damn thing on properly.
Ti Mosfet Driver
What you have at the moment is (at best) 17.4V delivered to the gate and maybe 14 or 15 volts out of the source - now that is hardly turning the MOSFET on is it?
Andy akaAndy akaNot the answer you're looking for? Browse other questions tagged buckpower-electronicsgate-driving or ask your own question.
How to turn on a buck transistor via a bootstrap circuit?
In my circuit, I use a AVR microcontroller to turn on and off a buck switch. What circuit should I use here?
Previously, I used optocoupler which does not have a fast response. I like to turn on and off the transistor for no more than 500 ns on/off transition.
There are some high side low side ICs which are designed for bridges and I am not sure if they would work for here.
Solutions with BJT/Capacitor/Diodes are very pleasant to me though I dont limit myself to only those solutions.
1 Answer
$begingroup$You're using an N-channel MOSFET, for it to come into an 'on' (low-resistance) state Vgs must be large, let's say 5V. The highest voltage you have is 36 V (+ node of battery). Even this will not fully turn-on the NMOS. You would need at least 41 V on the gate.Instead I would use a PMOS, then you can just pull the gate low.But to switch it OFF the gate of the PMOS must be pulled to 36 V !An AVR cannot handle this so you would need an additional transistor to pull the gate of the PMOS down.
A 1n4001 is not fast enough for these type of applications, better use a Schottky diode.
There is a fundamental flaw in your circuit! It has no current limiting !This is an issue, especially when the battery pack has a low voltage and the inductor saturates. The current would only be limited by the series resistance of the batteries and this is BAD, avoid at all cost ! (Your wires could melt !)
Have a look at this document form TI and learn how it's done !
If you want to actually build this then I strongly advise you to use an IC for that but pay attention to the 36V battery voltage, not all ICs can handle that.Also there are a lot of ready-built modules for sale on eBay, that would be more convenient as the layout of a switched converter is not something for a beginner.
In general, you don't want an AVR or any micro Controller to control a DC-DC converter switch. They're too slow, software could get stuck with the switch turned on. The current will be uncontrolled. AVOID !!!
Mosfet Driver Circuit Design
I do not understand what you mean by 'designed for bridges' ?
Bimpelrekkie