WTA charging circuit

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alpha91

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Hi, i am designing a charging circuit for a 48V battery from a dynamo for my assignment.
i want to ask that in between dynamo and the battery, is only a buck boost converter is enough? what else do i need ?
the dynamo is DC but the speed is variation.
 
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If the dynamo puts out a choppy waveform, then you'll probably need to add filtering so that it makes a stable power supply for your control circuit. (Or else install a separate power supply for your control circuit.)

An alternative might be to use the battery to power the control circuit, but the battery will be hooked up at inverse polarity (because a buckboost inverts the polarity).

Therefore your control circuit will need to be able to sense and interpret a negative voltage at the output.
 

may i ask what is choppy waveform? my dynamo spin in different speed along the time and i thought buck boost converter help in filtering the output.
do you mean that buck boost output is switching polarity when change from ON state to OFF state and so on?
 

alpha91 said:
may i ask what is choppy waveform?
Click to expand...

If the waveform is smooth DC, then it can be fed directly to a buck-boost.

However the dynamo could be similar to operating a DC motor in reverse. The waveform might not be smooth. It might be choppy. It ought to be made smooth.

do you mean that buck boost output is switching polarity when change from ON state to OFF state and so on?
Click to expand...

The buck-boost converter is suitable for your purposes. It can step a supply voltage up or down.

However the buck-boost is different from the buck and boost types. The buck and boost types output a positive polarity, from a positive supply.

The buck-boost outputs a negative polarity, from a positive supply. This means you'll connect zero ground to battery positive. You'll connect the buck-boost output to battery negative.
 

so, is that mean that i need a filter before buck-boost converter ?
and about the connection, is that mean from the output of the buck-boost converter, negative to the battery positive while positive to the battery negative ?

and i did some research online, i found that during ON state, my input is charging the inductor, when OFF state, the inductor is supply to the load. so isn't that mean the output polarity is constant?
 
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alpha91 said:
so, is that mean that i need a filter before buck-boost converter ?
Click to expand...

You need to find out whether the dynamo produces a smooth waveform or a 'choppy' one.

In fact, regardless of the waveform, in any case it is a good idea to put a smoothing capacitor at the input of the converter.


Simulations can be an excellent learning tool. A bit of experimenting will quickly reveal the inner workings of the different converters.

See my posts in the thread below. You'll find links to my tutorial simulations of switched-coil converters.

https://www.edaboard.com/threads/268178/
 
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    alpha91

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hi, i have watched the simulation that you posted. is the label 'load can go here' means the place that i can put my load? and is that circuit already insert the method that fix the output polarity? because i saw the current that flowing through the resistor is only one direction when ON and OFF.
 

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