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kell
Guest
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 Posted:
Sat Nov 26, 2005 9:35 am Post subject:
forward converter duty cycle question |
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Looking at the forward converter topology illustrated here:
http://schmidt-walter.fbe.fh-darmstadt.de/smps_e/edw_hilfe_e.html
They specify a maximum duty cycle of 50%.
Is this predicated on N1 and N1' having an equal number of turns?
It seems to me you get a longer duty cycle by reducing the number of
turns on N1'.
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John - kd5yi
Guest
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Sun Nov 27, 2005 8:56 am Post subject:
Re: forward converter duty cycle question |
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"kell" <kellrobinson@billburg.com> wrote in message
news:1132981991.437785.129000@o13g2000cwo.googlegroups.com...
I think it's to keep the transformer from saturating.
John |
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kell
Guest
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| Posted:
Mon Nov 28, 2005 7:45 am Post subject:
Re: forward converter duty cycle question |
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John - kd5yi wrote:
| Quote: | "kell" <kellrobinson@billburg.com> wrote in message
news:1132981991.437785.129000@o13g2000cwo.googlegroups.com...
Looking at the forward converter topology illustrated here:
http://schmidt-walter.fbe.fh-darmstadt.de/smps_e/edw_hilfe_e.html
They specify a maximum duty cycle of 50%.
Is this predicated on N1 and N1' having an equal number of turns?
It seems to me you get a longer duty cycle by reducing the number of
turns on N1'.
I think it's to keep the transformer from saturating.
John
I know. The magnetic field needs time to collapse. I'm asking does |
the mag field collapse faster with fewer
turns on N1'.
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John - kd5yi
Guest
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| Posted:
Mon Nov 28, 2005 5:35 pm Post subject:
Re: forward converter duty cycle question |
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"kell" <kellrobinson@billburg.com> wrote in message
news:1133142350.536572.230710@o13g2000cwo.googlegroups.com...
| Quote: |
John - kd5yi wrote:
"kell" <kellrobinson@billburg.com> wrote in message
news:1132981991.437785.129000@o13g2000cwo.googlegroups.com...
Looking at the forward converter topology illustrated here:
http://schmidt-walter.fbe.fh-darmstadt.de/smps_e/edw_hilfe_e.html
They specify a maximum duty cycle of 50%.
Is this predicated on N1 and N1' having an equal number of turns?
It seems to me you get a longer duty cycle by reducing the number of
turns on N1'.
I think it's to keep the transformer from saturating.
John
I know. The magnetic field needs time to collapse. I'm asking does
the mag field collapse faster with fewer
turns on N1'.
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Yes. However, note that the transistor's drain voltage would then be
Vin+(N1*Vin/N1'). The series diode on the secondary would also see higher
voltage (Vin*N2/N1').
John |
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kell
Guest
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| Posted:
Tue Nov 29, 2005 9:35 am Post subject:
Re: forward converter duty cycle question |
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| Quote: | Yes. However, note that the transistor's drain voltage would then be
Vin+(N1*Vin/N1').
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Ouch. |
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kell
Guest
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| Posted:
Tue Nov 29, 2005 9:35 am Post subject:
Re: forward converter duty cycle question |
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| Quote: | Yes. However, note that the transistor's drain voltage would then be
Vin+(N1*Vin/N1').
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That means when N1=N1', drain voltage is 2Vin. I didn't know that. |
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John - KD5YI
Guest
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| Posted:
Tue Nov 29, 2005 5:35 pm Post subject:
Re: forward converter duty cycle question |
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kell wrote:
| Quote: | Yes. However, note that the transistor's drain voltage would then be
Vin+(N1*Vin/N1').
That means when N1=N1', drain voltage is 2Vin. I didn't know that.
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You must have missed it. 5th paragraph below the schematic it says...
"Due to this the transistor drain-source voltage steps up to Vds > 2Vin when
the transistor is turned off."
Sorry.
John |
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