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I was trying to learn how the flyback and half bridge DC-DC converter is working. For Flyback circuit, enter image description here

Understood output waveform is as follows. enter image description here

Keeping this understanding in mind, I was trying to analyze the Half bridge DC-DC converter working. enter image description here

MOSFET Part number: BUK7K17-60E

Current flow as per my understanding is

For M1 is conducting: VIN -> M1 -> T1-> C2->GND

For M2 is conducting: VIN-> C1 -> T1 -> M2 -> GND

Please correct me if I am wrong.

Also, any direction to the current and mosfet drain voltage characteristics (plots) will be appreciated.

Datasheet of LM5109B: Link

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    \$\begingroup\$ The waveforms you have shown for the flyback converter are those of a converter operated in discontinuous conduction mode (DCM). This mode is usually encountered in light-load conditions or purposely adopted for low-power levels (< 20 W). You will find a comprehensive description of this converter here: cbasso.pagesperso-orange.fr/Downloads/PPTs/… \$\endgroup\$
    – Verbal Kint
    Commented Jan 11, 2018 at 20:08

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Your flyback analysis appears to be correct.

For the half-bridge type shown you can assume that the mid-point of C1 and C2 is Vin/2 (and DC) for analysis. Therefore I would put: -

For M1 is conducting: VIN -> M1 -> T1-> VIN/2

Also, any direction to the current and mosfet drain voltage characteristics (plots) will be appreciated.

Current flows into the left side of T1 when M1 activates and flows out from that point when M2 activates. Without a part number for the MOSFET the 2nd part cannot be answered.

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  • \$\begingroup\$ For M2 conducting, I believe current flow will be VIN/2 -> T1 -> M2 -> GND. Please note, added the MOSFET part number in the question (BUK7K17-60E) \$\endgroup\$
    – vt673
    Commented Jan 11, 2018 at 15:42
  • \$\begingroup\$ @vt673 Yes, that makes sense. \$\endgroup\$
    – Andy aka
    Commented Jan 11, 2018 at 15:44
  • \$\begingroup\$ The sparrow in the MOSFET symbol is misleading. Current flows contrary to this sparrow (and contrary to the diode). Why did they designed this symbol like this, is beyond me. An explanation here: electronics.stackexchange.com/questions/274370/… \$\endgroup\$
    – Fredled
    Commented Jan 11, 2018 at 22:34
  • \$\begingroup\$ Any help on current and mosfet drain voltage characteristics (plots)? \$\endgroup\$
    – vt673
    Commented Feb 22, 2018 at 14:22
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    \$\begingroup\$ If you are happy with this answer please consider formally accepting it or raise a comment if there's something you need help with understanding. \$\endgroup\$
    – Andy aka
    Commented Mar 2, 2018 at 10:05

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