Power dissipation calculation of H-Bridge

Hello TI Team ,

I found instruction (slva504a) about Pd calculation of H-Bridge , but if the duty cycle is variable during cycle time (for example , 10% duty in 1^st  periodic  , 20% duty cycle in 2^nd periodic ……..)how can we calculate the Pd of H-bridge ? 

And the “IL” is means RMS current or transient current shown in formula?  the total power dissipation of H- Bridge can be equal to PLS +PHS directly (Half Bridge Driver Using Low-Side Recirculation)?

"If we assume power dissipation in regions #4 and #6 are negligible, slews rate match for rising and falling edges,
dead times are equal, then power dissipation for each FET can be approximated as follows:
1. PLS = [RON × IL 2 x (1-D)] + [2 x VD x IL x tDEAD x fPWM]
2. PHS = [RON × IL 2 x D] + [VM x IL x (VM / SR) x fPWM]
Compared to a H-bridge driver, the power dissipation due to conduction losses is approximately cut in half,
however, the switching losses remain the same."

By the if you can provide thermal electronic mode of H-Bridge (DRV8144-Q1)to us?