### Author Topic: I want an opinion on this boost converter 5 volt to 50 volt  (Read 411 times)

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#### alexaamnda

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##### I want an opinion on this boost converter 5 volt to 50 volt
« on: August 06, 2024, 08:42:13 pm »
Is this circle worth developing, knowing that I am a beginner?

https://i.postimg.cc/7hGrG92w/Screenshot-2024-08-06-185557.png

#### mariush

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##### Re: I want an opinion on this boost converter 5 volt to 50 volt
« Reply #1 on: August 06, 2024, 09:02:04 pm »
30 milli Henry , 5000 uF capacitors ... why?

Do you even need to connect so many leds in series?  Your input is 5v, just have three leds at a time in series with a current limiting resistor.  or use a step-up led driver to boost 5v to 12-24v. Parallel a bunch of groups of leds in series. ex 8 groups of  4 leds in series  paralleled.

#### PGPG

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##### Re: I want an opinion on this boost converter 5 volt to 50 volt
« Reply #2 on: August 06, 2024, 11:29:24 pm »
Is this circle worth developing, knowing that I am a beginner?

Each circuit you try to make working makes you learning and thanks to this being less and less beginner

I would start first from trying to make 5V->12V converter.

#### peter-h

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##### Re: I want an opinion on this boost converter 5 volt to 50 volt
« Reply #3 on: August 07, 2024, 06:27:08 am »
It is easy to go 5V to 50V with a flyback design (I use it a lot) but the above circuit won't work. You need a pulse generator, with a variable duty cycle, to control the output voltage, and some means of feedback. Or you can vary the pulse frequency but the control loop gets messy.

However LED drivers are not constant-voltage. They are constant-current or "constant energy rate".
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#### pcprogrammer

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##### Re: I want an opinion on this boost converter 5 volt to 50 volt
« Reply #4 on: August 07, 2024, 08:19:53 am »
Like peter-h wrote this won't work as there is no oscillator to be seen.

There are many boost converter IC's on the market so why make up your own circuit with discrete components. Finding one to do 50V on the output might be a bit more tedious but they do exist.

For driving LED's there are also complete modules to be found. Much easier.

Unless this is an exercise for learning, but it shows more study is needed.

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#### Phil1977

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##### Re: I want an opinion on this boost converter 5 volt to 50 volt
« Reply #5 on: August 07, 2024, 08:31:53 am »
A boost converter is a nice teaching object, and a series of LEDs is a well suited load, because the series of LEDÂ´s limit the output voltage by themselves, but they don't conduct current through the freewheeling diode when the switching transistor is not active.

That means you could test this circuit even just with a NE555 or any other PWM-generator at the gate of the FET. I would discard SW1, because if you disconnect the load but operate the converter then the voltage will rise until something gets destroyed. But as long as the LEDs are connected they will limit the voltage and dissipate all the power going through the converter.

But if you just want to get the LEDs light up, then please just take an out-of-the-shelf LED driver or step-up-converter with constant current mode.
Every time you think you designed something foolproof, the universe catches up and designs a greater fool.

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#### PGPG

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##### Re: I want an opinion on this boost converter 5 volt to 50 volt
« Reply #6 on: August 07, 2024, 10:12:02 am »
but the above circuit won't work.

Are you sure?
I'm not.

You need a pulse generator, with a variable duty cycle, to control the output voltage, and some means of feedback.
Like peter-h wrote this won't work as there is no oscillator to be seen.

Not sure, but can't it be the generator?
First both transistors are on. When current in L reaches the saturation voltage at MOS drain rises (provided supply source and MOS isn't too strong) switching both transistors off (VR1 is the positive feedback). When whole energy from L will be transferred through diode voltage at drain jumps down starting cycle from beginning.

Not being sure I can expect that VR1 can be a feedback regulating the output voltage.

Or you can vary the pulse frequency but the control loop gets messy.
It is the other way around.
Control loop happens to have stability problems when you want frequency being constant and only duty cycle being variable. But when you don't care about frequency things are much simpler.
And this circuit (if working) is certainly not constant frequency converter.

In 2014 I've selected to use in our products LM5017 from TI converters new family (developed in 2012). It is able to step down from 100V down to 3V3 using simple choke (without taps). I like its COT (Constant On Time) mode. Taking advantage of the fact that it doesn't keep frequency constant COT is free from feedback stability problems. I specially like its very fast reaction on load changes. COT changes duty cycle in single pulse time while constant frequency, current mode converters need 5..10 pulses to notice that duty cycle change is needed. I also like that it works in exactly the same mode being not loaded (internal key not simulate diode and if load is too small energy from L is transferred back to source).

I assume that if someone emphasizes that he is a beginner than learning is in front of getting ready to use complete module. If this circuit will work (which I do not rule out) the lesson will be learned. If not the lesson also will be learned

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#### pcprogrammer

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##### Re: I want an opinion on this boost converter 5 volt to 50 volt
« Reply #7 on: August 07, 2024, 11:01:15 am »
Not sure, but can't it be the generator?
First both transistors are on. When current in L reaches the saturation voltage at MOS drain rises (provided supply source and MOS isn't too strong) switching both transistors off (VR1 is the positive feedback). When whole energy from L will be transferred through diode voltage at drain jumps down starting cycle from beginning.

Not being sure I can expect that VR1 can be a feedback regulating the output voltage.

I'm in no way an expert on this, but why would the MOSFET turn off when the drain voltage rises due to saturation in the coil. As long as Q1 is turned on won't Q3 (IRFZ44) also stay on?
If initially the base of Q1 does not see a low enough voltage to turn on, the whole thing would not start anyway, so it would need an overshoot in the voltage to turn Q1 off. Will a coil do this when only turned on?

I assume that if someone emphasizes that he is a beginner than learning is in front of getting ready to use complete module. If this circuit will work (which I do not rule out) the lesson will be learned. If not the lesson also will be learned

This is certainly true, if the will to learn and understand is there.

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##### Re: I want an opinion on this boost converter 5 volt to 50 volt
« Reply #8 on: August 07, 2024, 11:02:06 am »
i would have stayed in 12vdc or 24vdc led strips, not higher than that

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##### Re: I want an opinion on this boost converter 5 volt to 50 volt
« Reply #9 on: August 07, 2024, 11:17:46 am »
Like peter-h wrote this won't work as there is no oscillator to be seen.

There are many boost converter IC's on the market so why make up your own circuit with discrete components. Finding one to do 50V on the output might be a bit more tedious but they do exist.

For driving LED's there are also complete modules to be found. Much easier.

Unless this is an exercise for learning, but it shows more study is needed.

https://www.lcsc.com/product-detail/LED-Drivers_Legend-Si-LGS63042B5_C5123978.html
https://www.lcsc.com/product-detail/DC-DC-Converters_Legend-Si-LGS6302EP_C5280693.html

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