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I am reading this material for understanding the switch mode push pull power supplies. Push Pull Switched Mode Power Supplies

I am unable to understand the working though. Can someone provide a simple explanation for the circuit in 3.4.2 and its waveforms?

And it is mentioned as R3 and C2 are the timings components which I dont understand also. How do the internal transistors and the external transistors function? Please explain. Thanks.

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  • \$\begingroup\$ If you haven't already, strongly recommend reading modules 1-3.4.1 \$\endgroup\$ – K H Jan 16 at 4:39
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The working of the circuit is described here in this document which describes the functionality of PWM modulators.

RT and Ct are part of an oscillator circuit where

\$ f = \frac{1.18}{R_T C_T}\$

(Rt is in kΩ, Ct is in uF, f is in kHz)

Practical values of CT fall between 1 nF and 100 nF. Practical values of RT fall between 1.8 kW and 100 kW. This results in a frequency range typically from 120 Hz to 500 kHz.

Source: datasheet listed above

enter image description here

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  • \$\begingroup\$ Thanks. Can you provide a run through of the operation of the blocks during one on state and one off state? \$\endgroup\$ – Electronic_Maniac Jan 16 at 5:09
  • \$\begingroup\$ And sorry for the basic question, how does the capacitor charge and discharge through the resistor. From where the R and C get the charge and discharge? \$\endgroup\$ – Electronic_Maniac Jan 16 at 5:17
  • \$\begingroup\$ Is this homework? \$\endgroup\$ – laptop2d Jan 16 at 5:55
  • \$\begingroup\$ No I am trying to understand the working of the circuit \$\endgroup\$ – Electronic_Maniac Jan 16 at 6:03
  • \$\begingroup\$ I am unable to understand how the RC section works. We will get a ramp waveform at the timing capacitor pin only when RC is connected in series, right? But here R and C are not in series. How is this ramp generated? \$\endgroup\$ – Electronic_Maniac Jan 16 at 6:45

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