link
Here is a small inverting "Cuk" type switcher. Input voltage is 3 to 17V and in this case Vout is -5V. The link has some reading that might help.

 

link
Here is a small inverting "Cuk" type switcher. Input voltage is 3 to 17V and in this case Vout is -5V. The link has some reading that might help.
View attachment 250282

For 1.5 W output power, the integrated solution has major advantages.

 

[QUOTE = "ronsimpson, postagem: 1674757, membro: 653142"]
Vout 5V 5A = 25W
Vout 45V 5A = 225 watts. ???
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Vin = 48V @ 5A, Vout = 45V @ 5A Isso parece bom.
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Vin - = 5 V @ 45 A, Vout = 45 V @ 5 A A corrente de entrada é muito grande.
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O que estou tentando apontar é que um switcher de 45W é moderadamente fácil, mas um de 225 watts é muito mais difícil.
Se você realmente precisa queimar 45A no lado da entrada, isso é difícil.
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É apenas uma forma de aprender ou você tem uma aplicação real? Podemos escolher números fáceis?
O que você começou a fazer não é fácil. Um intervalo de entrada de 10: 1 é difícil. Uma tensão de saída de 9: 1 e uma faixa de potência são difíceis.
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The mosfet i got ( SMN5R6-100BS ) can support that i think.
This is just a study for my thesis. I've never worked with eletronics and had to learn everything for myself. I already implemented the circuit but didn't got the expected results (i was getting 31v output always with no load (so, if i put some load, could it burn? someone said before it would be destroied)), thats why i'm here.
Thank for all guys, if i knew before that you would help me this much, i would ask for an advice for shure.
In fact, 10:1 input range is hard. Maybe the best solution is to rearange this values to get a smaller input and output ranges

 

The mosfet i got ( SMN5R6-100BS ) can support that i think.

You have a 300V input, but only 100V-rated transistor and diode?

 

You have a 300V input, but only 100V-rated transistor and diode?

Not 300, 48V max

 

Not 300, 48V max

Apologies - fooled by @Papabravo 's circuit in post #15.
But still - 48V in and 45V out - 93V across the transistor is a bit close for comfort.

 

You were not fooled. If the AC Input was 48 volts (RMS, Peak to Peak, what exactly!), the TS could have indicated that explicitly. To be fair, the AC voltage was never explicitly stated on the schematic of post #5. Post #7 mentioned 220VAC(RMS), and I specifically asked in post #8, point #3. The TS imperiously decided not to respond to that explicit request, and so I went with what seemed reasonable assumptions. Give us garbage input and you get garbage output.

He did say that Vin was 48 VDC, but I thought he was referring to the voltage in the divider network where the Zener is located. That network has no effect on the switching network, and even with 311 volts from the rectifier only gets to about 20.5 volts. This was perhaps the most confusing set of design inputs it has even been my misfortune to encounter.

I can easily change the input voltage on the simulation, but the behavior will look the same because the output is not regulated and the loop is not closed. It will still be an unregulated inverting buck-boost converter.

 

A common-mode choke won't work in this circuit, with either one winding or two windings in parallel. You need a choke with an iron powder core or a ferrite core with a GAP. Common mode chokes don't have a gap. They will saturate almost immediately. as @ronsimpson said back in post #5
In order to work they must have an equal and opposite current in the second winding.
Your simulation will work perfectly, because SPICE doesn't simulate inductor saturation. If you make it with a common mode choke it will blow up (rapidly). A 11.2mH inductor that works at 10A will be huge.
Micrometals' software predicts a toroidal inductor 132mm diameter x 40mm high.
You can download the design software here
http://www.iec-international.com/micrometals/micrometals/software.html

Can you please send a print of the parameters you have used and where did you insert it in the software to get that result?

 

Hello guys,

So, I've been trying to reformulate the inverting buck- boost and i end up concluding that for my application i can have lower currents and lower input/output ranges.
I will try to elaborate a buck-boost with:
Vin: 15V- 48V
Vout:-15V- -40V
Max output current: 2A
Min output current: 0,5A
Frequency: 100kHz.

The input voltage is provided by a generator that can generate between 0-50V, and i will use a full rectifier briedge with filter to retify AC to DC. In terms of MOSFET control I want to use a micro controller (wich will also only accept Vin between 15-48V). I already have some components:
MOSFET- PSMN5R6-100BS
mosfet driver - LTC7004
Diode: STTH2002G-TR
In terms of the inductor and capacitor, i'm still with some doubts about the values i should choose, thats why i'm asking now if you can help me explaining what should i use and how did you get the values.

I've used this formulas:
IL = Vi*D/R/((1-D)^2); %IL = Po/Vo + Po/Vi
DELTA_IL = IL/10;
DELTA_Vo = 2/100*Vo;
L = Vi*D/f/DELTA_IL;
C = Io*D/f/DELTA_Vo;

But I'm not shure if the formulas are 100% correct and depending on the Vi/Vo/Po i use (between my ranges) i will get different L and C values as expectable.

 

There's a few factors here which are your choice.
Do you want it to run in continuous-current mode or discontinuous-current mode?
If "continuous-current", how much ripple?
Discontinuous current mode minimises the switching losses, continuous-current mode minimises the core losses. Continuous current can use an iron-powder core, discontinuous current would require a gapped ferrite. (Neither could use a common mode choke!)
If low ripple is really important to you, then you should use the Čuk converter.

 

There's a few factors here which are your choice.
Do you want it to run in continuous-current mode or discontinuous-current mode?
If "continuous-current", how much ripple?
Discontinuous current mode minimises the switching losses, continuous-current mode minimises the core losses. Continuous current can use an iron-powder core, discontinuous current would require a gapped ferrite. (Neither could use a common mode choke!)
If low ripple is really important to you, then you should use the Čuk converter.

I would like to run in CCM. Current ripple i am not shure, but maybe between 2% and 10%(is there a common percentage? I read books in witch they use 2% and others 10%).

 

In CCM you would run 100% ripple at the smallest load. Example: If the current ramps from 0 to 1A and then back down to 0A the average of that is 0.5A. That is the smallest load to stay in CCM mode. (smallest load at highest input voltage)