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Original question:

SN6507-Q1: Deadtime Influence

SN6507: SN6507

Gang Du
Prodigy 30 points
Part Number: SN6507

Tool/software:

Hi,

At a frequency of 1 MHz, the static power consumption should be 5-6 mA. In actual testing, it reaches 27 mA. I suspect that this is because there is a conduction path in Q1 and Q2. If there is no way to set the dead time through CLK, how should I solve this problem?

I am trying to reduce the frequency. I will update again when there is new progress.

Regards,

Gang DU

  • 0
    TI__Mastermind 23035 points

    Hello Gang, 

    Thank you for reaching out. The 5-6mA in the datasheet is the total current consumption for the SN6507. Even when you reduce the switching frequency, the current will not change much. This is the normal current. The 27mA is likely the current consumption for the whole application.

    The dead time (break before make time, or TBBM) is a fixed parameter. The internal BBM logic block makes sure that Q1 and Q2 are not conducting at the same time; this feature ensures operates irrespective of the device settings. 

    Best,
    Andrew

  • 0 in reply to Andrew J
    Prodigy 30 points

    Hello Andrew,

    Thanks for your apply.

    When I disconnected all secondary-side loads of the transformer, the static working current was 27 mA. I think the whole application is just in the schematic.

    Now, when the frequency is reduced to 350 kHz and the duty cycle is designed to be reduced to 40% (the actual effect of the duty cycle is not obvious), the current reduction is still relatively obvious, only 10.5 mA.

    Let me explain one point. The aforementioned 27 mA and 10.5 mA are both currents measured on R1 (1 ohm). The whole power consumption current is from 17mA to 5mA.

    I think the reduced 16.5mA on R1 comes from the conducting of Q1 and Q2 at the same time. Is that right?

  • +1 in reply to Gang Du
    TI__Mastermind 23035 points

    Hello Gang, 

    Gang Du said:

    The aforementioned 27 mA and 10.5 mA are both currents measured on R1 (1 ohm). The whole power consumption current is from 17mA to 5mA.

    Thank you for the clarification. I understand that you are measuring the consumption of the SN6507 and the transformer together. The current consumption above is expected.  

    Gang Du said:
    I think the reduced 16.5mA on R1 comes from the conducting of Q1 and Q2 at the same time. Is that right?

    The internal break-before-make logic stops Q1 and Q1 from conducting at the same time. There is no way for Q1 and Q2 to have the same conduction. Instead, the 16.5mA comes from the switching losses of the transformer.

  • 0 in reply to Andrew J
    Prodigy 30 points

    Hello Andrew，

        Thank you very much!

        The 16.5mA comes from the switching losses of the transformer. —— I think this is a correct interpretation.