The best type of converter for LEDs has a constant-current output, not constant-voltage output, for highest efficiency, since you don't need any series resistor, with its power loss.
It doesn't appear to have current limiting built in. If you use a MC34063 it has facility to connect a current set resistor and you can run it as a current regulated buck, it's a cheap chip and needs less parts count, but if you use the internal switch it's linited to under 1 amp LED current.
If you use a MC34063 it has facility to connect a current set resistor and you can run it as a current regulated buck, it's a cheap chip and needs less parts count, but if you use the internal switch it's linited to under 1 amp LED current.
It is an older chip and uses a bipolar transistor in a Darlington connection for the switch transistor. This means, unless you have a higher bias voltage than the normal input supply, the switch saturation voltage is about 1V. This will reduce the efficiency somewhat as compared to those switching regulators that use MOSFETs which will typically have an "on" voltage well below 1V.