• State
  • Locked Locked
  • Replies 0 replies
  • Subscribers 62 subscribers
  • Views 265 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LM3478 block diagram

Guillaume LEVANT
Prodigy 120 points
Other Parts Discussed in Thread: LM3478

Hi,

I am about to make a boost converter with the LM3478 but I don't understand some of the features in the block diagram :

  • The slope compensation generates a voltage ramp going from VSENSE to VSENSE-D*VSL where D is the duty cycle, correct ?
  • When the voltage across the current sensor resistor is equal to the value of the voltage ramp, the switching node is set to 0 and the MOSFET is off, that is what defines the duty cycle, correct ?
  • The thing I don't understand is that since the feedback voltage pin is connected to the negative pin of the error amplifier, and the output of this error amplifier is added to the ramp generator output voltage (or substracted, it is not very clear in the block diagram), which is connected to the negative pin of the PWM comparator, it means that if the output voltage is too low, the duty cycle will go down, which will logically reduce more the ouput voltage


I maybe missed something, but I want to understand this because I am currently feeling quite stupid :)

Does somebody could help me ?

Regards,

Guillaume