The advantages of multilayer ceramic (MLC) capacitors over plastic film types include their smaller physical size, lower inductance, and ability to operate at higher temperatures. These advantages make MLC capacitors very well suited to high power applications, such as power converter systems in electric (EV) and hybrid electric (HEV) vehicles.
When selecting a capacitor to operate at high temperatures, it is useful to understand how its operating conditions can affect its working temperature. When AC (ripple) current passes through a capacitor, power will be dissipated inside the component, causing energy to be wasted in the form of heat. This mechanism is often called self-heating.
The temperature of the capacitor depends on the background (or ambient) temperature (TA) of the immediate surroundings, and also on the temperature rise (ΔT) caused by self-heating.
ΔT represents wasted energy. The lower its value, the longer the operational life of the capacitor and the more efficiently the circuit will operate.
Operating conditions that can affect ΔT include:
- The amplitude and frequency of the applied AC current
- The applied DC bias voltage
- The background (ambient) temperature.
Further, these factors vary depending on the class of capacitor used. Our engineering team recently put together an application note that examines how some of these factors impact capacitor self-heating. You can download the application note Factors Affecting Temperature Rise in MLC Capacitors and contact us to discuss your high power application.