class d output power estimation audio group applications 1
TRANSCRIPT
1
Class D Output Power Estimation
Audio Group
Applications
2
TI Widgets -
http://www.ti.com/general/docs/gencontent.tsp?contentId=45777&DCMP=TI_Gadgets&HQS=Other+OT+widgets
Output Power Estimation of Class D Amplifier• Simple Calculation:
POWERSE
Vcc2
8 Rspeaker POWERSE 18W
POWERBTL
Vcc2
2 Rspeaker POWERBTL 36W
Vcc 24V Dmax 97% Rspeaker 4
Rdson 240m RL 10m RESR 2m
POWERSE_Fine
Rspeaker
Rspeaker Rdson RL RESRDmax Vcc
2
8 Rspeaker POWERSE_Fine 14.988W
POWERBTL_Fine
Rspeaker
Rspeaker 2 Rdson RL Dmax Vcc
2
2 Rspeaker POWERBTL_Fine 30.005W
APA Circuit Impedances
• Audio power amplifier circuits includes many other impedances than load (Speaker). The voltage on the load is reduced due to these impedances.
• Power supply internal impedance, trance impedance, MOSFET turn on resistance and inductor DC resistance must be small compared to load impedance to maintain efficiency and output power.
Rds
Rds
Rtrace
PVCC
RL
Rload
Co
V
V
Rtrace
Rtrace
load
loadR
load trace dson L
RV PVCC
R R R R
POWERSE
Vcc2
8 Rspeaker POWERSE 18W
POWERBTL
Vcc2
2 Rspeaker POWERBTL 36W
Vcc 24V Dmax 97% Rspeaker 4
Rdson 240m RL 10m RESR 2m
POWERSE_Fine
Rspeaker
Rspeaker Rdson RL RESRDmax Vcc
2
8 Rspeaker POWERSE_Fine 14.988W
POWERBTL_Fine
Rspeaker
Rspeaker 2 Rdson RL Dmax Vcc
2
2 Rspeaker POWERBTL_Fine 30.005W
Output Power Estimation of Class D Amplifier
• Simple Calculation:
• Accurate Calculation: