Capacitor manufacturers provide a maximum temperature rise or operating temperature to prevent overheating of the capacitor. For convenience, most manufacturers provide AC voltage or current limits that correspond to the maximum temperature limit. The maximum rms voltage and current are typically provided in a graph versus frequency. The AC voltage and current limits provide a way to limit power dissipation and prevent capacitor overheating.

For audio LC filter applications, the losses due to AC voltage and current are a result of the ripple voltage from the inductor charge and discharge cycles. The charge and discharge cycle frequency occurs at the class-D switching frequency.

To estimate power losses and temperature rise, first use the ripple current calculation in Equation 12 and then use the following equations for power losses in the capacitor.

ESR					Dissipation Factor
Equation 16.					Equation 17.
	Parameter	Description	Units			Parameter	Description	Units
	Plosses	Power Dissipation in Capacitor	W			Plosses	Power Dissipation in Capacitor	W
	Vripple	RMS Ripple Voltage	VRMS			Vripple	RMS Ripple Voltage	VRMS
	Iripple	RMS Ripple Current	IRMS			f	Ripple Frequency	Hz
	ESR	Equivalent series resistance	Ω			C	Capacitance	F
						tan δ	Dissipation Factor	-
Note: Use the ESR value at the same frequency as the ripple current.					Note: Use the dissipation factor value at the same frequency as the ripple current.

Using the power losses calculated in Equation 16 and Equation 17, the capacitor temperature due to self-heating can be calculated using the heat coefficient in the capacitor data sheet. Typically, there is a heat coefficient represented as the ratio of temperature rise to the power dissipated in watts. The thermal coefficient typically takes into account the capacitor size and surface area.

Equation 18 is read, “For every 1 W of power dissipated, there is a temperature change of Δ°C.”