LV 123 and LV 148: Testing Across the Voltage Window, Not Just at Nominal

EV & automotive · 3 min read · 22 cited facts

Automotive high-voltage testing is organised around bands rather than setpoints. A component is not asked to work at a voltage; it is asked to behave in a defined way across a window, and differently again above and below it. Specify a supply against nominal and you have specified for the least interesting part of the test.

The HV classes

An 800 V architecture sits in HV_3, so a supply for that work needs to reach the circuit limit rather than the operating maximum. The slew limit is equally load-bearing: the overvoltage pulse is defined by its rate as well as its amplitude, and a supply that cannot control the ramp cannot run the clause.

The 48 V board net is a different problem

Source impedance is specified, which is unusual and easy to miss. The supply is not merely required to produce a voltage — it has to present a defined impedance while doing it, because the device's behaviour depends on how stiff the bus is. Programmable output impedance is the specification to check.

Ripple on top of the window

Both documents ask for ripple superimposed on the DC level, and this is where benches most often fall short. Reaching the voltage window is straightforward; producing the specified ripple across it, at the specified frequencies, while sinking regenerated energy, is what actually determines the equipment.