ArchivalAudio, it depends on the microphone. 48-Volt phantom power is delivered through a matched pair of 6.8 kOhm resistors--so the more current a mike draws, the lower the actual DC voltage will be on the cable or at the microphone. In older phantom-powered designs (e.g. Neumann fet 80 series microphones such as the KM 84 and U 87), the supply current was < 1 mA, so the DC voltage actually delivered to the microphone was still in the 40s--high enough for that voltage to be simply filtered and applied to the capsule to polarize it. This arrangement didn't achieve the final dB or two of signal-to-noise performance, but the advantages of simpler powering and cabling and solid-state reliability were greatly preferred over tubes by most engineers.
Since the 1970s it has been more common for new designs to use DC converters as you described, where the DC supply voltage drives an RF oscillator (i.e. it is converted to AC at a frequency above the human hearing range) and then stepped up to a higher voltage, rectified back to DC and used to polarize the capsule, commonly at ca. 60 Volts. However, this (along with the lower noise and increased sensitivity and maximum SPL expected by then) demanded more supply current. This, in turn, because of the 6.8 kOhm resistors, meant that the incoming DC voltage at the microphone was distinctly lower, commonly in the 30s. So "in for a penny, in for a pound"--there was a definite generational difference between the kind of amplifier electronics seen in P48 designs from the late 1960s and those from the mid-70s and onwards.
Historically the two leaders in this respect were AKG with the original C 451 (not the present-day electret "tribute" microphone of the same name), which drew 6 mA at 48 Volts, and the Schoeps "Colette" (CMC 50) series, which drew about 4.5 mA. For years the DIN/IEC standard set a limit of 2 mA per microphone for 48-Volt phantom powering, and even after that standard was finally revised, there were real problems using these higher-current microphones with older mixers and recorders that didn't have enough current available from their phantom powering circuits. Both manufacturers were forced to offer alternative models that drew less current (AKG C 452, Schoeps CMT 50 series).
--best regards