TPS7H5005-SEP: Synchronous Switching

Jarrett Blythe

Part Number: TPS7H5005-SEP

Is there recommended topology on the secondary for synchronous operation? I plan to use GaN drivers at secondary output and there should probably be a power source to drive the secondary GaN FETs. Can you please point me in the correct direction?

10 months ago

0 Daniel Hartung 10 months ago

TI__Mastermind 24485 points

Hey Jarrett,

What you use to create this power supply can depend on what converter you are working with.
Flybacks can work off an AUX winding, you can power it through a diode from the switch node and then down through an LDO.

What is the isolated converter you plan to make this power supply for?

Thanks,
Daniel

0 Jarrett Blythe 10 months ago in reply to Daniel Hartung

Prodigy 50 points

Understood. I am planning to build a Push Pull topology.

0 Daniel Hartung 10 months ago in reply to Jarrett Blythe

TI__Mastermind 24485 points

Hey Jarrett,

For the secondary side, what is the maximum voltage you expect on the switch node (including parasitic spike)?
It may be easiest to make a low current supply through a diode into an LDO with that condition.

Thanks,
Daniel

0 Jarrett Blythe 10 months ago in reply to Daniel Hartung

Prodigy 50 points

There is a 40V output not including diode drop. It would appear that I would not be able to get switching on the secondary without getting power to the LDO. if there is no power on the secondary, there is no power for switching. So that would be a tough task. Unless I place diodes in shunt with the GaN FET and use them for initial turn ON. Then have synchronous switching once power is applied to the secondary.

+1 Daniel Hartung 10 months ago in reply to Jarrett Blythe

TI__Mastermind 24485 points

Hey Jarrett,

With GaN FETs we practically require a diode in shunt with the GaN FET.
The TPS7H5005-SEP controller doesn't have the synchronous rectifiers on during start-up.

While Silicon FETs can often handle the start-up current GaN generally cannot.
In that case, depending on the output of your converter you could run it off of the output voltage.

Thanks,
Daniel

0 Jarrett Blythe 10 months ago in reply to Daniel Hartung

Prodigy 50 points

Thank you, Daniel. I believe this will assist with the design. I will use this information for our design.

0 Daniel Hartung 10 months ago in reply to Jarrett Blythe

TI__Mastermind 24485 points

Welcome

Thanks,
Daniel

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TPS7H5005-SEP: Synchronous Switching