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TPS61158: Lower PWM frequency then recommended range 20k~100kHz

Takashi Onawa
Genius 13200 points
Part Number: TPS61158

Hi Team,

My customer wants to use 10kHz PWM frequency for dimming if possible. 
We are understanding our recommendation is 20k~100kHz for CTRL control though, what side effect will be expected if they use the lower frequency for CTRL control?

In my customer's evaluation, it looks switching cycle was skipped when CTRL rising edge in 10kHz PWM duty 20% case.

Regards,

Takashi Onawa

  • 0
    TI__Genius 13001 points

    Hi,

    If the PWM frequency is lower than 20kHz, the RC low-pass filter's voltage is unstable, which means the reference voltage of EA has large ripple. Then the output current's accuracy cannot be guaranteed. 

    BR,

    Robin

  • 0 in reply to Yuting Shao
    TI__Genius 13200 points

    Hi Robin-san,

    Thanks for your prompt response on this. I understood.

    One quick confirmation.

    Am I correct in my understanding that this problem will not occur under any conditions when used at the recommended range of PWM frequencies? Or Do they need to consider additional margins, e.g. using 40kHz PWM against the 20k~100kHz recommended range?

    Regards,

    Takashi Onawa

  • 0 in reply to Takashi Onawa
    TI__Genius 13001 points

    Hi Takashi,

    Yes, you're right. 20Khz is enough.

    BR,

    Robin