AN3306

Benefits of using STPMxx with Rogowski coil-based sensors

Doc ID 18182 Rev 1

11/21

Equation 4

This leads to an offset error in power measurement and to a residual sinusoidal ripple at

twice the line frequency after the LP filtering. Real power should be averaged within a line

period.

The STPMxx family implements a new proprietary algorithm for power calculation that

removes this ripple and the offset by digital cancellation, providing an accurate and flat

power calculation without the need for an additional integrator in the analog section.

Figure 6.

STPMxx power calculation approach

Referring to Figure 6, the device calculates, then subtracts, and then divides by two the

following powers:

Equation 5

PGA

Signal

conditioning

ADC

v(t)

v dt

p(t)

v(t)

di/dt

ADC

Signal

conditioning

i(t)

di/dt

Subtractor &

:2 divider

v(t)

11-bit

16-bit

16-bit

Real power

AM00183v1

ϕ/