Hi Pavel, On 16/4/19 9:19, Pavel Machek wrote: > Hi! > >> This patch exposes a new property, similar to input current limit, to >> re-configure the maximum voltage from the external supply at runtime >> based on system-level knowledge or user input. > > Well, and I suspect it should expose input power limit, not input > voltage limit. >
Oh, ok, I thought we were agree that input voltage had sense after had some discussion in v3. Seems that no, let me try to give you another example... > DC-DC convertor efficiency normally does not much depend on input > voltage.... > > Pavel > As we said we have a heat "problem" due the internal voltage conversions. Lets assume you have a linear regulator instead with a Vin range from 5V to 9V and we want an output of 3.3V/1A For 9V: Input power : P(in) = 9V x 1A = 9W Output power: P(out) = 3.3V x 1A = 3.3W Regulator power dissipated: P(reg) = P(in) - P(out) = 9W - 3.3W = 5.7W For 5V: Input power : P(in) = 5V x 1A = 5W Output power: P(out) = 3.3V x 1A = 3.3W Regulator power dissipated: P(reg) = P(in) - P(out) = 5W - 3.3W = 1,7W In the first case the regulator needs to dissipate more power, hence the temperature is greater than the second case. Thanks, Enric
