Voltages and power
The 160V high voltage source for the Nixie tubes is a boost converter based around the TPS40210 from Texas Instruments. It handles all the boost control by itself, including overcurrent. The MCU enables or disables the converter operation.
The boost converter operates in Continuous Conduction Mode (CCM), its Duty Cycle is close to 0.95, and switching frequency is around 100KHz. It may seem an exreme operation case (due to its high voltage output), but keep in mind that individual digits glow with a current less than 2mA with full brightness. Besides, due to the multiplexing scheme, only one tube is active at a time. Thus, even when the voltage requirement is very high, the power requirement is very low.
The digital circuitry is powered with a simple linear regulator, but not directly from the regulator output: when external power is not present, the coin cell backup battery powers the MCU. This switching between these two sources is automatically performed using shottky diodes D11 and D12. The presence of external power is sensed through R30 and R31. That way, the MCU switches to sleep mode when no external power is sensed.
