Step _ Down Swiching Regulator

OmidbimO · 2017-12-15 8:49 pm

hello im not good at english exusme
i have a circuit for truck 24v to 12v (20 amps) for drive led and amplifirs and recevers and ...
lm2576 is good but i have 20 amps
can you help me?
thanks

Chris Daly · 2017-12-15 9:53 pm

I would determine how much current draw you actually have. The LM2576 has capability to 3 amps, you may find that it is sufficient already for some of the devices you are connecting
http://www.onsemi.com/pub/Collateral/LM2576-D.PDF

You could then load share some of the devices from the LM2576, and others from say a zener based transistor regulator

The LM2576 is a switching regulator , however a heatsink is still a good precaution for it.
If you are needing higher current capability you should be able to use a PNP transistor like a MJ15004 adapting the circuit shown on page 21 (applying to a 78xx series of regulator )
http://www.onsemi.com/pub/Collateral/MC7800-D.PDF , to give greater current than 3 amps.

nigelwright7557 · 2017-12-15 10:16 pm

Take a look at this:
24V to 12V DC-DC Car Power Supply Inverter Converter Conversion Device 30A UK | eBay

MarianB · 2017-12-16 2:04 pm

nigelwright7557 said:
Take a look at this:
24V to 12V DC-DC Car Power Supply Inverter Converter Conversion Device 30A UK | eBay

Hi.

Look at the pictures of it.
Would you run 30A trough such ridiculously thin wires?
Thus do you think that toy is really optimised for 30A?
Even it's price let's people know it's a joke...

MorbidFractal · 2017-12-16 3:16 pm

nigelwright7557 said:
Take a look at this:
24V to 12V DC-DC Car Power Supply Inverter Converter Conversion Device 30A UK | eBay

Apart from other concerns as to the quality of your suggestion Omid is in Iran and I don't think Ebay has a local branch. Otherwise he seems to be restricted to an LM2576 or other outdated stuff. Perhaps I have things wrong but Iran suffers from technology import restrictions, apart from StuxNet. Otherwise I do not mean to offend. If Omid can source stuff like CD4046, CD4013, LM324, LM339, passives, small signal transistors and diodes and some power components then, given a cunning plan, it would be possible for him to 'roll his own' general purpose solution?

MarianB · 2017-12-16 3:58 pm

If 20A is a required current then the linear way is far to wasteful to be usable ( you could waste up to more than 300W ).
Problem is, optimizing a buck converter for 20A isn't very simple, nor is it cheap.
Still it is doable, but i don't think 2576 is the way to go.

kodabmx · 2017-12-16 5:08 pm

Yes the wires are thin, but they are also short so it doesn't matter very much. 30A is pushing it though, I'd say 15A with 30A peaks is more likely.

This might be a better choice... 800W 30A DC Buck Converter Step-down Power Supply Module IN 20-70V OUT 2.5-58V | eBay

MorbidFractal · 2017-12-16 5:47 pm

kodabmx said:
Yes the wires are thin, but they are also short so it doesn't matter very much. 30A is pushing it though, I'd say 15A with 30A peaks is more likely.

This might be a better choice... 800W 30A DC Buck Converter Step-down Power Supply Module IN 20-70V OUT 2.5-58V | eBay

China might be happy to export to Canada but EBay does not have a presence in Iran. It does not really matter how thin or thick the wires are if you cannot buy one.

...

MorbidFractal · 2017-12-16 6:08 pm

Anyway Omid wants to turn 24V into 12V so it looks like he needs a buck converter. The duty cycle will be,

D = VOUT/VIN = 12/24 = 0.5 or 50%

Let's assume the things that are going to be using something near to 12V.

Code:

Version 4
SHEET 1 1004 984
WIRE -576 0 -608 0
WIRE -608 32 -608 0
WIRE -496 32 -608 32
WIRE -400 32 -496 32
WIRE 112 32 -400 32
WIRE 240 32 112 32
WIRE 288 32 240 32
WIRE 368 32 288 32
WIRE 496 32 464 32
WIRE 560 32 496 32
WIRE 688 32 640 32
WIRE 800 32 688 32
WIRE 832 32 800 32
WIRE -496 64 -496 32
WIRE 112 112 112 32
WIRE 288 112 288 32
WIRE 384 112 384 80
WIRE -400 176 -400 32
WIRE 240 176 240 32
WIRE -496 224 -496 144
WIRE -464 224 -496 224
WIRE 112 224 112 192
WIRE 176 224 112 224
WIRE 384 224 384 192
WIRE 416 224 384 224
WIRE -400 304 -400 272
WIRE 240 304 240 272
WIRE 384 304 384 224
WIRE 384 304 240 304
WIRE 384 336 384 304
WIRE 288 384 288 192
WIRE 320 384 288 384
WIRE -400 416 -400 384
WIRE 16 416 -400 416
WIRE 192 416 16 416
WIRE -400 448 -400 416
WIRE 112 448 112 224
WIRE 288 448 288 384
WIRE 16 496 16 416
WIRE 48 496 16 496
WIRE 192 496 192 416
WIRE 224 496 192 496
WIRE -400 544 -400 512
WIRE 16 576 -224 576
WIRE 112 576 112 544
WIRE 288 576 288 544
WIRE -224 688 -224 576
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WIRE 112 688 -32 688
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WIRE -224 928 -400 928
WIRE 384 928 384 432
WIRE 384 928 -224 928
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WIRE 496 928 384 928
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WIRE 800 928 800 896
WIRE 800 928 688 928
WIRE -608 960 -608 928
FLAG -112 640 0
FLAG -112 784 0
FLAG -192 784 0
FLAG -256 736 CLK
IOPIN -256 736 Out
FLAG 320 688 A
IOPIN 320 688 Out
FLAG 320 736 B
IOPIN 320 736 Out
FLAG 832 32 VOUT
IOPIN 832 32 Out
FLAG -608 960 0
FLAG 416 224 VG
IOPIN 416 224 Out
FLAG -400 544 0
FLAG -576 0 VIN
IOPIN -576 0 Out
SYMBOL pmos 464 80 M270
WINDOW 0 93 85 VLeft 2
WINDOW 3 72 83 VLeft 2
SYMATTR InstName M1
SYMATTR Value RSR020P05
SYMBOL Digital\\dflop -112 640 R0
WINDOW 0 -81 -15 Left 2
SYMATTR InstName A1
SYMATTR SpiceLine VHigh=12 VLow=0 Td=10n
SYMBOL npn 48 448 R0
WINDOW 0 41 35 Left 2
WINDOW 3 41 60 Left 2
SYMATTR InstName Q2
SYMATTR Value 2N3904
SYMBOL npn 224 448 R0
WINDOW 0 32 34 Left 2
WINDOW 3 35 60 Left 2
SYMATTR InstName Q3
SYMATTR Value 2N3904
SYMBOL res 128 672 R180
WINDOW 0 49 71 Left 2
WINDOW 3 37 50 Left 2
SYMATTR InstName R4
SYMATTR Value 22K
SYMBOL res 304 672 R180
WINDOW 0 57 71 Left 2
WINDOW 3 41 50 Left 2
SYMATTR InstName R5
SYMATTR Value 22K
SYMBOL pnp 320 432 M180
WINDOW 0 50 60 Left 2
WINDOW 3 47 35 Left 2
SYMATTR InstName Q5
SYMATTR Value 2N3906
SYMBOL res 368 96 R0
WINDOW 0 39 54 Left 2
SYMATTR InstName R8
SYMATTR Value 22R
SYMBOL res 272 96 R0
WINDOW 0 40 52 Left 2
SYMATTR InstName R7
SYMATTR Value 22K
SYMBOL pnp 176 272 M180
WINDOW 0 -41 21 Left 2
WINDOW 3 -42 -7 Left 2
SYMATTR InstName Q4
SYMATTR Value 2N3906
SYMBOL res 96 96 R0
WINDOW 0 37 50 Left 2
WINDOW 3 38 71 Left 2
SYMATTR InstName R6
SYMATTR Value 2K2
SYMBOL npn -464 176 R0
WINDOW 0 57 37 Left 2
WINDOW 3 56 64 Left 2
SYMATTR InstName Q1
SYMATTR Value 2N3904
SYMBOL res -512 48 R0
WINDOW 0 36 47 Left 2
WINDOW 3 37 72 Left 2
SYMATTR InstName R1
SYMATTR Value 22K
SYMBOL res -512 800 R0
WINDOW 0 41 47 Left 2
WINDOW 3 41 68 Left 2
SYMATTR InstName R2
SYMATTR Value 22K
SYMBOL cap -416 832 R0
WINDOW 0 40 15 Left 2
WINDOW 3 44 42 Left 2
SYMATTR InstName C1
SYMATTR Value 220n
SYMBOL voltage -224 800 R0
WINDOW 0 40 59 Left 2
WINDOW 3 24 96 Invisible 2
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName VCLK
SYMATTR Value PULSE(0 12 0 100n 100n 5u 10u)
SYMBOL ind 544 48 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 5 56 VBottom 2
SYMATTR InstName L1
SYMATTR Value 100µ
SYMBOL schottky 512 752 R180
WINDOW 0 -41 41 Left 2
WINDOW 3 -134 18 Left 2
SYMATTR InstName D1
SYMATTR Value RBR5L60A
SYMATTR Description Diode
SYMATTR Type diode
SYMBOL voltage -608 800 R0
WINDOW 0 40 45 Left 2
WINDOW 3 41 68 Left 2
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName VIN
SYMATTR Value 24V
SYMBOL cap 672 688 R0
WINDOW 0 38 17 Left 2
WINDOW 3 39 40 Left 2
SYMATTR InstName COUT
SYMATTR Value 4700µ
SYMBOL res 672 800 R0
WINDOW 0 35 47 Left 2
WINDOW 3 37 70 Left 2
SYMATTR InstName RESR
SYMATTR Value 50m
SYMBOL res 784 800 R0
WINDOW 0 37 47 Left 2
WINDOW 3 38 69 Left 2
SYMATTR InstName RLOAD
SYMATTR Value 2R4
SYMBOL res -416 288 R0
WINDOW 0 35 51 Left 2
SYMATTR InstName R3
SYMATTR Value 100R
SYMBOL cap -416 448 R0
WINDOW 0 40 21 Left 2
WINDOW 3 41 43 Left 2
SYMATTR InstName C2
SYMATTR Value 10µ
TEXT -560 968 Left 2 !.tran 0 10m 1u

A1 is a D type flip-flop, CD4013, and it divides CLK by two so A and B are 50% duty cycle signals. CLK comes from a CD4046. Level shift and stuff using small signal transistors.

Circuit plus start up. It would seem we need a current limit and perhaps some other bits but there's about 12V out at 5A.

kodabmx · 2017-12-16 6:34 pm

MorbidFractal said:
China might be happy to export to Canada but EBay does not have a presence in Iran. It does not really matter how thin or thick the wires are if you cannot buy one.

...

Then use Alibaba.

MarianB · 2017-12-16 6:35 pm

At 20 Amps you really need synchronous rectification, and there are dedicated IC's that make most of the control job ( current limiting included ), may not be cheap but it would be of good performance.

MorbidFractal · 2017-12-16 6:54 pm

kodabmx said:
Then use Alibaba.

Sounds good.

خرید بلیط هواپیما و بلیط قطار |علی‌بابا خرید اینترنتی بلیط هواپیما خارجی

Omid's English is infinitely better than my Farsi so perhaps you might be able to find him something similar to your Canadian Ebay suggestion via the local Alibaba site.

Given you appear to understand it I will have to assume Farsi is similar to French.

I also assume that, if and when you find a suitable product, the FOB, free on board, 10,000 minimum units condition will not be a problem.

MorbidFractal · 2017-12-16 7:39 pm

OK... so I mentioned a current limit might be in order. Adding some extra dirt and it is likely to be imprecise dirt.

Code:

Version 4
SHEET 1 1312 984
WIRE -576 -64 -608 -64
WIRE -608 -32 -608 -64
WIRE -496 -32 -608 -32
WIRE -400 -32 -496 -32
WIRE -352 -32 -400 -32
WIRE -304 -32 -352 -32
WIRE -192 -32 -224 -32
WIRE 352 -32 -192 -32
WIRE 480 -32 352 -32
WIRE 528 -32 480 -32
WIRE 608 -32 528 -32
WIRE 736 -32 704 -32
WIRE 800 -32 736 -32
WIRE 1008 -32 880 -32
WIRE 1120 -32 1008 -32
WIRE 1152 -32 1120 -32
WIRE -496 0 -496 -32
WIRE -192 32 -192 -32
WIRE 352 48 352 -32
WIRE 528 48 528 -32
WIRE 624 48 624 16
WIRE -352 96 -352 -32
WIRE -400 96 -400 -32
WIRE -240 96 -352 96
WIRE 480 112 480 -32
WIRE -496 144 -496 80
WIRE -464 144 -496 144
WIRE 352 160 352 128
WIRE 416 160 352 160
WIRE 624 160 624 128
WIRE 656 160 624 160
WIRE -400 240 -400 192
WIRE 480 240 480 208
WIRE 624 240 624 160
WIRE 624 240 480 240
WIRE 624 272 624 240
WIRE 528 320 528 128
WIRE 560 320 528 320
WIRE -400 352 -400 320
WIRE 256 352 -400 352
WIRE 432 352 256 352
WIRE -400 384 -400 352
WIRE 352 384 352 160
WIRE 528 384 528 320
WIRE 256 432 256 352
WIRE 288 432 256 432
WIRE 432 432 432 352
WIRE 464 432 432 432
WIRE -400 480 -400 448
WIRE -144 512 -144 96
WIRE 256 512 16 512
WIRE 352 512 352 480
WIRE 528 512 528 480
WIRE 16 624 16 512
WIRE 48 624 16 624
WIRE 352 624 352 592
WIRE 352 624 208 624
WIRE 560 624 352 624
WIRE 736 624 736 -32
WIRE 1008 624 1008 -32
WIRE 16 672 -16 672
WIRE 48 672 16 672
WIRE 256 672 256 512
WIRE 256 672 224 672
WIRE 528 672 528 592
WIRE 528 672 256 672
WIRE 560 672 528 672
WIRE -144 768 -144 592
WIRE 128 768 128 720
WIRE 128 768 -144 768
WIRE 160 768 128 768
WIRE -496 784 -496 144
WIRE -400 784 -496 784
WIRE -608 816 -608 -32
WIRE -496 816 -496 784
WIRE -144 816 -144 768
WIRE 16 816 16 672
WIRE 1008 816 1008 688
WIRE 1120 816 1120 -32
WIRE -400 832 -400 784
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WIRE -496 928 -496 896
WIRE -496 928 -608 928
WIRE -400 928 -400 896
WIRE -400 928 -496 928
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WIRE 1120 928 1120 896
WIRE 1120 928 1008 928
WIRE -608 960 -608 928
FLAG 128 576 0
FLAG 48 720 0
FLAG -16 672 CLK
IOPIN -16 672 Out
FLAG 560 624 A
IOPIN 560 624 Out
FLAG 560 672 B
IOPIN 560 672 Out
FLAG 1152 -32 VOUT
IOPIN 1152 -32 Out
FLAG -608 960 0
FLAG 656 160 VG
IOPIN 656 160 Out
FLAG -400 480 0
FLAG -576 -64 VIN
IOPIN -576 -64 Out
FLAG 160 768 CLR
IOPIN 160 768 Out
SYMBOL pmos 704 16 M270
WINDOW 0 93 85 VLeft 2
WINDOW 3 72 83 VLeft 2
SYMATTR InstName M1
SYMATTR Value RSR020P05
SYMBOL Digital\\dflop 128 576 R0
WINDOW 0 -81 -15 Left 2
SYMATTR InstName A1
SYMATTR SpiceLine VHigh=12 VLow=0 Td=10n
SYMBOL npn 288 384 R0
WINDOW 0 41 35 Left 2
WINDOW 3 41 60 Left 2
SYMATTR InstName Q2
SYMATTR Value 2N3904
SYMBOL npn 464 384 R0
WINDOW 0 32 34 Left 2
WINDOW 3 35 60 Left 2
SYMATTR InstName Q3
SYMATTR Value 2N3904
SYMBOL res 368 608 R180
WINDOW 0 49 71 Left 2
WINDOW 3 37 50 Left 2
SYMATTR InstName R4
SYMATTR Value 22K
SYMBOL res 544 608 R180
WINDOW 0 57 71 Left 2
WINDOW 3 41 50 Left 2
SYMATTR InstName R5
SYMATTR Value 22K
SYMBOL pnp 560 368 M180
WINDOW 0 50 60 Left 2
WINDOW 3 47 35 Left 2
SYMATTR InstName Q5
SYMATTR Value 2N3906
SYMBOL res 608 32 R0
WINDOW 0 39 54 Left 2
SYMATTR InstName R8
SYMATTR Value 22R
SYMBOL res 512 32 R0
WINDOW 0 40 52 Left 2
SYMATTR InstName R7
SYMATTR Value 22K
SYMBOL pnp 416 208 M180
WINDOW 0 -41 21 Left 2
WINDOW 3 -42 -7 Left 2
SYMATTR InstName Q4
SYMATTR Value 2N3906
SYMBOL res 336 32 R0
WINDOW 0 37 50 Left 2
WINDOW 3 38 71 Left 2
SYMATTR InstName R6
SYMATTR Value 2K2
SYMBOL npn -464 96 R0
WINDOW 0 57 37 Left 2
WINDOW 3 56 64 Left 2
SYMATTR InstName Q1
SYMATTR Value 2N3904
SYMBOL res -512 -16 R0
WINDOW 0 36 47 Left 2
WINDOW 3 37 72 Left 2
SYMATTR InstName R1
SYMATTR Value 22K
SYMBOL res -512 800 R0
WINDOW 0 41 47 Left 2
WINDOW 3 41 68 Left 2
SYMATTR InstName R2
SYMATTR Value 22K
SYMBOL cap -416 832 R0
WINDOW 0 40 15 Left 2
WINDOW 3 44 42 Left 2
SYMATTR InstName C1
SYMATTR Value 220n
SYMBOL voltage 16 800 R0
WINDOW 0 40 59 Left 2
WINDOW 3 24 96 Invisible 2
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName VCLK
SYMATTR Value PULSE(0 12 0 100n 100n 5u 10u)
SYMBOL ind 784 -16 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 5 56 VBottom 2
SYMATTR InstName L1
SYMATTR Value 100µ
SYMBOL schottky 752 688 R180
WINDOW 0 -41 41 Left 2
WINDOW 3 -134 18 Left 2
SYMATTR InstName D1
SYMATTR Value RBR5L60A
SYMATTR Description Diode
SYMATTR Type diode
SYMBOL voltage -608 800 R0
WINDOW 0 40 45 Left 2
WINDOW 3 41 68 Left 2
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName VIN
SYMATTR Value 24V
SYMBOL cap 992 624 R0
WINDOW 0 38 17 Left 2
WINDOW 3 39 40 Left 2
SYMATTR InstName COUT
SYMATTR Value 4700µ
SYMBOL res 992 800 R0
WINDOW 0 35 47 Left 2
WINDOW 3 37 70 Left 2
SYMATTR InstName RESR
SYMATTR Value 50m
SYMBOL res 1104 800 R0
WINDOW 0 37 47 Left 2
WINDOW 3 38 69 Left 2
SYMATTR InstName RLOAD
SYMATTR Value 2R4
SYMBOL res -416 224 R0
WINDOW 0 43 49 Left 2
SYMATTR InstName R3
SYMATTR Value 100R
SYMBOL cap -416 384 R0
WINDOW 0 40 21 Left 2
WINDOW 3 41 43 Left 2
SYMATTR InstName C2
SYMATTR Value 10µ
SYMBOL res -208 -48 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R9
SYMATTR Value 50m
SYMBOL pnp -144 32 R90
WINDOW 0 -33 -27 VRight 2
WINDOW 3 -4 -83 VRight 2
SYMATTR InstName Q6
SYMATTR Value 2N3906
SYMBOL res -160 496 R0
SYMATTR InstName R10
SYMATTR Value 22K
SYMBOL res -160 800 R0
SYMATTR InstName R11
SYMATTR Value 22K
TEXT -560 968 Left 2 !.tran 0 10m 1u

12A limit start up.

OmidbimO · 2017-12-24 4:29 pm

ok merci but i havd a swiching regulator

OmidbimO · 2017-12-24 4:41 pm

Chris Daly said:
I would determine how much current draw you actually have. The LM2576 has capability to 3 amps, you may find that it is sufficient already for some of the devices you are connecting
http://www.onsemi.com/pub/Collateral/LM2576-D.PDF

You could then load share some of the devices from the LM2576, and others from say a zener based transistor regulator

The LM2576 is a switching regulator , however a heatsink is still a good precaution for it.
If you are needing higher current capability you should be able to use a PNP transistor like a MJ15004 adapting the circuit shown on page 21 (applying to a 78xx series of regulator )
http://www.onsemi.com/pub/Collateral/MC7800-D.PDF , to give greater current than 3 amps.

ok merci but i havd a swiching regulator

OmidbimO · 2017-12-24 4:50 pm

MarianB said:
If 20A is a required current then the linear way is far to wasteful to be usable ( you could waste up to more than 300W ).
Problem is, optimizing a buck converter for 20A isn't very simple, nor is it cheap.
Still it is doable, but i don't think 2576 is the way to go.

I,M now this problem but a have a Discrete swiching(for example lm2576) for 24 volt to 12 volt 30 amps

OmidbimO · 2017-12-24 5:00 pm

MorbidFractal said:
China might be happy to export to Canada but EBay does not have a presence in Iran. It does not really matter how thin or thick the wires are if you cannot buy one.

...

it is a big problem!

sanaz5 · 2020-04-13 10:03 pm

EBay does not presence in Iran.. Alibaba does not presence in Iran .. Amazon does not presence in Iran..
but we have digikala

))
خرید ردیاب کودک قیمت مناسب با کیفیت در آراسیستم

Step _ Down Swiching Regulator

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