Why are DC-DC buck converters so limited?

[Fordulike]

In my recent search to find a solution to step down 48v DC to 36v, I found them to have very limited use in a high current role. The few I found that could convert to 36v, were very limited in output current and would be useless when used in an electric bike role.

Could anyone explain in layman's terms, why they are so limited in their abilities, when in this day and age of technology, almost anything is possible.

I honestly thought that stepping down DC power would be simple

 

[Woosh]

they are usually limited by the inductance of the coil that is used to transfer energy from the input to the output.
You can increase the size of the coil but that increases the size and weight of the circuit, and the operating frequency but there is a limit, the efficiency of the coil drops with high frequency.

 

[Danidl]

In my recent search to find a solution to step down 48v DC to 36v, I found them to have very limited use in a high current role. The few I found that could convert to 36v, were very limited in output current and would be useless when used in an electric bike role.

Could anyone explain in layman's terms, why they are so limited in their abilities, when in this day and age of technology, almost anything is possible.

I honestly thought that stepping down DC power would be simple

Stepping down voltage is indeed much simpler than using a DC to DC conversation. A simple zener diode or a zener diode driving a power transistor, would be the simplest technique. The circuit is placed in seriess with the load and it's effective resistance changes , so that the voltage accross the load remains constant. .. look up series regulators for circuits. In these circuits the extra voltage is converted into heat as the current flows via the regulator into the load.
In the case of dropping from 48 to 36 volts, the efficiency of the circuit will mean that exactly 25% of the original battery power is wasted as heat. 12v x current in load will exit as heat.the efficiency would be 75%.

While DC to DC convertors can be designed with efficiencies up to 90% or higher can be achieved, it would be likely that mid 80s% would be more common. , Since this is only 10% more than the simple 3 component series regulator, it is not worthwhile . Particularly as the current and power levels are high. . As Woosh has said, a high switching speed would be needed , if the inductor was to be small and light, and this would mean the production of plenty of radio frequency interference rfi. , Which would need to be filtered out for CE marking.
.... Now if you wanted 5v out from a 48v supply, a DC DC convertor would make sense...