Comparison of MC34063 circuit structures

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Comparison of MC34063 circuit structures [Copy link]

 

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The same buck-boost series structure, but the efficiency measured is different.

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The other component parameters are the same, except that SEPIC has an additional coupling capacitor.

The input is 4.5-20V, the output is 5-12V, and the actual efficiency measurement shows that the flyback structure is 3-5 points more efficient than the sepic structure.

maychang

Wei Lin Power published on 2019-10-3 22:05 The other component parameters are the same, except that SEPIC has an additional coupling capacitor. The input is 4.5-20V, the output is 5-12V, and the measured efficiency is...

The flyback efficiency is slightly higher, so why use Sepic? If the efficiency is equal, you should use flyback, at least you can save a coupling capacitor.

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maychang posted on 2019-10-4 07:21 The flyback efficiency is slightly higher, so why use Sepic? If the efficiency is equal, you still need to use flyback, at least you can save a coupling capacitor.

Master maychang:

I needed to make a buck-boost circuit at the beginning, which was not isolated, so I first considered using SEPIC. During the design, due to size reasons, the two inductors shared a magnet, but suddenly I found that removing the coupling capacitor would result in a flyback, and after removing it, I found that the efficiency was actually improved a lot. I was wondering, since the flyback circuit structure is simpler and more efficient, and the flyback can be isolated or non-isolated, then what is the meaning of SEPIC?

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Moreover, the difference in loss between the two is not just one or two points. What is the specific difference in loss? Can Master Maychang give a detailed analysis?

PowerAnts

The purpose of sepic is to "earn" back the leakage energy of flyback, otherwise what's the point?

Reason for modification: Correction of typos

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PowerAnts posted on 2019-10-4 14:28 The meaning of sepic is to "earn" back the leakage energy of flyback, otherwise it will be too high

Professor Jiang, maybe I didn't express myself clearly. The efficiency I measured so far is that flyback is higher than sepic. Of course, it is possible that this may be caused by unreasonable parameters in my design.

maychang

Weilin Power Supply published on 2019-10-4 13:47 Moreover, the difference in loss between the two is not just one point or two points. What is the specific difference in loss? Can Master Maychang give a detailed analysis?

"Moreover, the difference in loss between the two is not just one or two points. What is the specific difference in loss?"

I don’t know about that.

I have used capacitor-coupled circuits and have tried Cuk topologies, but not other topologies.

maychang

Weilin Power Supply published on 2019-10-4 13:47 Moreover, the difference in loss between the two is not just one point or two points. What is the specific difference in loss? Can Master Maychang give a detailed analysis?

I don’t deserve the title of “Master”.

PowerAnts is much better at using switching power supplies than I am.

PowerAnts

Weilin Power Supply published on 2019-10-4 15:40 Mr. Jiang, maybe I didn’t express myself clearly. At present, the efficiency I measured is that flyback is higher than sepic. Of course, it is not ruled out that this may be due to the inappropriate parameters of my design...

As an old bird, you should know how to post. There are no input and output parameters, no transformer parameters, just like a gangster, haha

PowerAnts

maychang posted on 2019-10-4 16:08 I don’t dare to call myself a “master”. PowerAnts is much better at switching power supplies than I am.

Mr. Zhang is too modest. You are a senior and you have been in this industry for much longer than me. I have only really entered this industry in recent years.

PowerAnts

Have you checked the specifications of the two electrolytic capacitors pretending to be non-polar capacitors? What are the ripple current and ESR? What is the ripple voltage?

PowerAnts

A controller like 34063, which cannot perform duty cycle by voltage sampling but can only perform pulse burst output by shutting down pulse groups by current sampling, is somewhat ridiculous to use for flyback and SEPIC! It is normal to come up with some counterintuitive conclusions. If you show the waveform, it will scare people to death.

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PowerAnts posted on 2019-10-4 18:48 As an old bird, you should know how to post. There are no input and output parameters, no transformer parameters, just like a gangster, haha

You are wronging me. The input and output parameters are on the 3rd floor. I will repeat them here: input 4.5-20vdc, output 5-12vdc, maximum current 3a, inductance 47uH, 1:1 double wire parallel winding, yellow and white magnetic ring.

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maychang posted on 2019-10-4 16:08 I don’t dare to call myself a “master”. PowerAnts is much better at switching power supplies than I am.

You deserve the title of master.

PowerAnts

Wei Lin Power Supply published on 2019-10-4 22:59 You have wronged me. There are input and output parameters on the third floor. I repeat them here. Input 4.5-20vdc, output 5-12vdc maximum current 3a, inductance...

There is current on the third floor, transformer parameters?

PowerAnts

Did you brag to the client that you got it done for two dollars? You are doomed

zhuyebb

Support the host.

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PowerAnts posted on 2019-10-5 07:20 Is there current on the 3rd floor, transformer parameters?

No, because I feel there is no need to mention it for now, so I didn’t write it down.