Switching AC to DC converter for LEDs (no resistor)

i need a schematic for convert 220v Ac to 40v dc with dont use resistor,and
only use diod and capacitor(switching power suplly use buck converter) ,please help me Immediately,please!

this circuit use in led light lamp :
**broken link removed**

SO you need an AC-DC power supply that is current regulated so it can power an LED without using a current limiting resistor? Is that what you mean by no resistor?

dknguyen said:

SO you need an AC-DC power supply that is current regulated so it can power an LED without using a current limiting resistor? Is that what you mean by no resistor?

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for example buck converter dont need any resistor,
so losses reduce in This type of circuites,
i want to use Bridge Rectifiers with buck converter to
reduce voltage to almost 40 volt dc,but i dont have any safe
diagram for this.
what kind of connection between elements do i need?