At Knowles Precision Devices, we purposely avoid commodity components. What we thrive on is doing the hard things. We handle the specialty components that go in systems that cannot fail and that operate at extremely high voltages, temperatures, or frequencies. Do you have a complex technical challenge with hard-to-meet performance, size, or other requirements? Bring it to us. It’s what we do.
As a fundamental component of circuit design, equivalent series resistance (ESR) is the measurement of all the non-ideal electrical resistances in series with a capacitor. When current flows through a multilayer ceramic capacitor (MLCC) due to application of alternating voltage, heat is generated in the MLCC due to the losses, specifically ESR. As a result, this self-heating can cause various performance and reliability issues in the circuits of today’s more complex and smaller electronic systems.
DC link capacitors are commonly used in power converters as an intermediary buffer between an input source to an output load that have different instantaneous power, voltages, and frequencies. In electric vehicle (EV) applications, DC link capacitors help offset the effects of inductance in inverters, motor controllers, and battery systems. They also serve as filters that protect EV subsystems from voltage spikes, surges, and electromagnetic interference (EMI).
To meet consumer demand for longer driving ranges and faster charging, electric vehicle (EV) manufacturers are redesigning vehicles to move from 400V to 800V battery systems. As a result of using higher operating voltages, EV designers and original equipment manufacturers (OEMs) need components, such as multi-layer ceramic capacitors (MLCCs), that can withstand voltages well beyond those expected under normal operating conditions. For example, a drivetrain running off an 800V battery system may be subjected to a withstand test of up to 4kV DC for 60 seconds, which is a standard safety test in high voltage systems.
CToday, the design and development of many applications, such as power electronics in electric vehicles (EVs), is driven largely by concerns about size and weight. This means the film capacitors traditionally used by electronics engineers aren’t always the best option. Instead, multi-layer ceramic capacitors (MLCCs) are emerging as an excellent alternative to film capacitors. Let’s review some of the considerations to keep in mind when you are deciding if making the switch is the right choice for your application.
When an engineer designs a circuit, he or she needs to ensure that each component will “do what it says on the box.” In multi-layer ceramic capacitor (MLCC) design, one area that often concerns engineers is the fact that capacitance can fluctuate with voltage, which is known as “DC bias” or “voltage coefficient.”
As countries around the world tighten emissions standards, the demand for fully electric vehicles (EVs) is increasing. However, for EVs to see mainstream adoption, manufacturers must address the primary consumer concerns: longer driving ranges and faster charging. To address these concerns, EV manufacturers are beginning to redesign their vehicles to switch from the 400V battery systems widely used today to 800V battery systems, which can offer twice the voltage and 2.7 times the power density compared to a 400V system.
Today’s advancements in power electronics are reaching all-new highs in performance. In the quest for increasing efficiency and power density of converters and inverters, manufacturers are looking to use WBG semiconductors, such as gallium nitride (GaN) and silicon carbide (SiC), for making metal-oxide semiconductor field-effect transistors (MOSFETs), metal-semiconductor field-effect transistors (MESFETs) and other devices.
These materials are capable of operating at faster switching frequencies – and therefore greater current and power – compared to traditional silicon-based materials. Their higher temperature rating also allows the semiconductors to be used in harsher environments found in electric vehicles, aerospace, energy production, and test equipment.
One of the primary goals in electric vehicles (EVs) is to increase the efficiency of its power conversion devices. The more efficiently power is converted, the further distance the EV can travel on one charge. For example, by reducing losses in a DC-to-DC (or DC/DC) converter, the converter (and overall vehicle) benefits from improved energy efficiency, a more streamlined design, and diminished heating from components.
In power electronics, rectification is the conversion of alternating current (AC) to direct current (DC). After the AC signal enters a rectifier circuit consisting of power diodes, the resulting raw rectified waveform yields a series of half sine waves with significant ripple. In order to minimize the pulsating DC voltage, a smoothing capacitor is placed in parallel with the load across the rectifier output. As the rectifier voltage rises, the capacitor charges and stores energy like a reservoir. Then when the rectifier voltage falls, the capacitor discharges, greatly reducing the ripple voltage.