What is SMPS Buck converter? I have still a newbie to the electronic, I don't know whether voltage divider is the good solution, just some one told me to consider it.

hi Kelvin,
A SMPS Buck converter, is a Switched Mode Power Supply, the incoming 28Vdc is is rapidly switched On/Off in order to create square wave voltage, whose On/Off period can be controlled to provide a lower voltage.
The Buck defines it as a voltage reducing SMPS ie: voltage input step down, a Boost SMPS steps up the incoming voltage.

This type of SMPS can be as efficient as 95% in Bucking/Boosting, so little power is lost as heat.

The Voltage divider, at your required current levels is very inefficient, a lot of battery power would be wasted as heat and the battery endurance reduced.

This is a very rough explanation of an SMPS, if you want to to get into detail, just ask.

E

 

Dear shteii01,

Sorry I don't understand what the Omega mean.

How can you find the 4.2 Ohm from the datasheet? I can't find it, is it by calculation? How? Do you mind teaching me?

By the way, Solve for R1, how about R2? Remove it?

Best regards,

Kelvin.

R2 is resistance of the motor. In datasheet the resistance of the motor is 4.2 Ω.
Ω: https://en.wikipedia.org/wiki/Ohm

 

Dear MrAI,

How is a modern converter? Is it a circuit design and individual electronic component?

Hello,

Well not so modern converters did not use MOSFETs but real modern ones do and also could use synchronous rectification rather than diodes.
Older converters were lucky if they did 80 percent efficiency but modern ones strive for over 90 percent.,

 

R2 is resistance of the motor. In datasheet the resistance of the motor is 4.2 Ω.
Ω: https://en.wikipedia.org/wiki/Ohm

Got it, have to click into the datasheet and found it. Thanks. How about R2? Is it not necessary and simply remove it?

 

You need to clarify the rules as to the 22V limit. Is that the max battery voltage or the max motor voltage?
If it is the max motor voltage, forget all about using a resistor as the motor voltage will be varying a great deal depending on the load.
A better way to go is to change your battery as even a switch mode supply to drop the volts to 22V may be breaking the rules.

 

the rule is the voltage should be limited below 22V,

Dear BobTPH,

By calculation, yes, 5 cell lithium battery is 21V, sorry that I forgot to mention the capacity is also the consideration, now my battery is 24v12ah.

Sorry, but there is a contradiction here.

Bob