UC3825: Synchronized operation

Mason Noh

Expert 2490 points

Part Number: UC3825
Other Parts Discussed in Thread: UCC28220

Hi TI team,

I have a question about the synchronized operation of the UC3825 IC.

In synchronized operation, PWM outputs of master and slave also can be synchronized?

over 5 years ago

0 Peter Meaney over 5 years ago

TI__Mastermind 31580 points

Hi Mason,

In the UC3825 when it is synchronized to an external clock the rising edge of the gate drive signals should be closely aligned but the duty cycle of the PWM may be slightly different due to internal offsets and variations in the current sense, voltage error amplifier and PWM circuits.

Regards

Peter

0 Mason Noh over 5 years ago in reply to Peter Meaney

Expert 2490 points

Thank you for your kindly reply.

Actually, when I measured gate signals of master and slave, it was not slightly different.

example, The output A of master is high when out B of master is high. is it normal?

0 Peter Meaney over 5 years ago in reply to Mason Noh

TI__Mastermind 31580 points

Hi Mason,

Are they both synchronised to the same source or are you synchronising one from the other contoller and if so what signal are you using?

Regards

Peter

0 Mason Noh over 5 years ago in reply to Peter Meaney

Expert 2490 points

Same source you mentioned means VCC? They are synchronized to the same source.
And I confirmed that both CLK and CT were in sync.

0 Peter Meaney over 5 years ago in reply to Mason Noh

TI__Mastermind 31580 points

Hi Mason,

The A and B outputs may not be synchronised as there is no way to predict which output either A or B will start to switch first when Vcc is applied.

How about two controllers on one IC like UCC28220 device ?

Regards

Peter

0 Mason Noh over 5 years ago in reply to Peter Meaney

Expert 2490 points

Do you have external schematic for syncronized operation?
Actually I have no option to change IC.

0 Peter Meaney over 5 years ago in reply to Mason Noh

TI__Mastermind 31580 points

Hi Mason,

Sorry for the late response, TI does have some examples of syncronisation circuits in its application notes, www.ti.com.cn/.../slua125.pdf, these are relatively simple but I dont know of a way to ensure that A output of two UC3825 controllers will start up first.

Regards

Peter

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UC3825: Synchronized operation