Delay start soft-start

Thread Starter

adrien69

Joined Dec 19, 2019
3
Hi,

I need to make a delayed start circuit for starting two motors after 5 seconds when the the power suppy is on. the imput voltage is 48V and the current consumption is 30A.

Have anyone some good information about it using a circuit with MOSFET?

Thanks
 

Marley

Joined Apr 4, 2016
346
Just bear in mind that if the motors take 30A when running the start current will be at least 10-20x the continuous current.

Switching can be done with MOSFETs but size them carefully and drive the gates with a proper gate driver.
At high currents with large MOSFETs it is important that the device is switched on very fast. Also, a large MOSFET will have a large gate-channel capacitance so a large peak current will be required to get a quick charge. Hence proper gate driver.

A large MOSFET is really hundreds of thousands of tiny MOSFETS in parallel. Vital they all turn on at the same time or the device will be destroyed. Hence fast rise time on the gate voltage, proper driver needed.

The timing can be done with a simple resistor, capacitor, comparator circuit.
 

Thread Starter

adrien69

Joined Dec 19, 2019
3
hi,
Thanks for your reply

The NE555 supports a big current of 30A and 50 V of voltage ?

Thanks a lot

Adrien
Just bear in mind that if the motors take 30A when running the start current will be at least 10-20x the continuous current.

Switching can be done with MOSFETs but size them carefully and drive the gates with a proper gate driver.
At high currents with large MOSFETs it is important that the device is switched on very fast. Also, a large MOSFET will have a large gate-channel capacitance so a large peak current will be required to get a quick charge. Hence proper gate driver.

A large MOSFET is really hundreds of thousands of tiny MOSFETS in parallel. Vital they all turn on at the same time or the device will be destroyed. Hence fast rise time on the gate voltage, proper driver needed.

The timing can be done with a simple resistor, capacitor, comparator circuit.
 

Bordodynov

Joined May 20, 2015
2,538
hi,
Thanks for your reply

The NE555 supports a big current of 30A and 50 V of voltage ?

Thanks a lot

Adrien
30 A and 48 V provides a p-channel powerful transistor. The transistor is controlled by the NE555, which is powered by a parametric stabilizer on the Zener and the resistor.
 
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