Tool/software:
Dear E2E,
I'm attempting to follow the design procedure shown in the datasheet for my case...
- duty cycle control
- no LDO
- Vin_min = 18V
- Vin_nom = 24V
- Vin_max = 30V
- Vout = 24V
- I_outDC = 50mA .. 600mA
And the following questions arise.
The block diagram for duty cycle control does not show how it works, that is, what info the IC uses to adjust the duty cycle. Can you please clarify this?
On to the main question: the selection of the Rdc resistor depends on D, Rclk, Vcc (Vin_nom). It does not (according to the datasheet) depend on Vout or on the turns ratio, but of course the duty cycle and turns ratio affect the output voltage as well.
For example, I found the Coilcraft TX2-ZE2430-AED as a transformer with Ns/Np=1.43. If I follow the datasheet and use Rdc=51k, then I get nominal operation at 25% duty cycle. But for the push-pull converter, Vout = Vin*dc*2*(Ns/Np) (this equation is not mentioned in the datasheet). So with my transformer the nominal Vout at 25% duty-cycle is then 17V.
Can you please confirm that I need to set the nominal duty-cycle for this turns ratio to 35% which gives Rdc = 71.7k in order to achieve nominal Vout = 24.0 V?
Thanks in advance!
