why dc dc converter needs a design with PWM?

[juaneduardodelgado]

Im looking for a dc dc converter implementation in web, and I found that all designs use a pwm chip to this.
I Know how work a dc dc converter that uses a pwm, capacitors and inductances. What I dont know is why I cant use a design with a simple transformer to implement a basic dc converter. I just want to change de output voltage and to get the maximum current.

Thanks.

 

[FvM]

You at least nead some kind of periodical operated switch to convert DC to AC voltage. Early DC/DC converters
(e.g. in tube car radios) have been using a mechanical chopper, later models a self oscillating transistor circuit.

 

[jigshaw]

current change-->magnetic change-->current change

That is the basic law of electromagnetic induction.