The Role of Passive Components in Power Modules

2022-12-13 10:15

　　As a critical component of power supply systems, power modules are increasingly vital in the field of power electronics and are widely used in telecommunications equipment, automotive applications, industrial systems, rail transit, and many other sectors. Serving as devices that convert between AC and DC, power modules feature numerous key performance parameters, including input and output voltage ranges, input and output voltage accuracy, temperature drift, voltage regulation, current regulation, and efficiency. In recent years, driven by rapid advances in power‑electronics technology, power modules have been evolving toward higher power density and lower‑voltage, high‑current designs. Throughout this evolution, passive components and power‑management ICs play an essential role, serving as the primary enablers for further performance improvements. Nevertheless, in many cases, the significance of RCL networks within system circuits is overlooked; selecting appropriately designed RCL networks can often deliver remarkable gains in efficiency, power density, and overall system footprint. High‑performance connectors also prove invaluable for enhancing both power density and efficiency. With that in mind, let’s explore the roles of passive components in power modules.

　　1. Resistance

　　Resistors, as passive components, are classified into fixed resistors, variable resistors, and sensing resistors. Fixed resistors further subdivide into wire-wound resistors, solid‑state resistors, thin‑film resistors, and others, while sensing resistors include potentiometers, thermistors, and similar devices.

　　Fixed resistor

　　Resistors with fixed resistance values play a crucial role in optimizing system efficiency. For instance, the resistor placed before the MOSFET input in a power module is often desired to be as large as possible. Consequently, low‑value resistors tend to dissipate significant heat, making it difficult to improve overall efficiency; however, increasing the resistance indefinitely is not advisable either. Otherwise, capacitor charging slows down, adversely affecting the startup time of the memory circuitry and preventing any further efficiency gains.

　　Variable resistor

　　The variable resistor in the circuit helps the system fine-tune the output accuracy and provides improved responsiveness to varying loads.

　　Sensitive resistor

　　Variable resistors and thermistors are common types of sensitive resistors used in power modules, typically to enhance the module’s reliability. For example, NTC (negative temperature coefficient) thermistors exhibit decreasing resistance as temperature rises, thereby helping to prevent large inrush currents during system startup. The selection of variable resistors is closely tied to their maximum allowable voltage rating, clamping voltage limit, and surge current capacity, enabling them to safeguard internal sensors when subjected to rapid voltage fluctuations.

　　2. Capacitor

　　When it comes to capacitors, there are quite a few types. Bypass capacitors, decoupling capacitors, and filtering capacitors are all common in power‑supply modules—so what roles do they play?

　　Due to the presence of bypass capacitors, alternating current in the system circuit does not have to pass through resistors, thereby preventing voltage drops. In AC signal‑processing circuits, the signal source and the signal‑processing stage are connected via coupling capacitors, ensuring that the DC operating points of the preceding and succeeding amplifier stages remain unaffected. Filtering capacitors at the output can eliminate unwanted AC components from the DC module, thus improving output quality. Furthermore, capacitors in power supply modules also serve functions such as frequency stabilization, tuning, timing, and compensation. 3. Inductors

　　Inductors in passive components exhibit the characteristic of blocking AC signals while allowing DC current to pass, making them suitable for isolating and filtering AC signals. By incorporating common-mode inductors at the input of power supply modules, radiated emissions can be reduced, thereby mitigating high-frequency common-mode noise. Inductors are used in conjunction with capacitors in both input and output filter circuits and are also commonly employed to smooth current.

　　4. Connector

　　As the power of power modules continues to increase, the associated passive components have become indispensable for high‑power‑density modules. Though compact in size, these connectors can meet the high‑current demands of power modules, deliver high‑power transmission, and offer exceptional design flexibility.

　　The above outlines the roles of passive components in power modules. For more information, please feel free to contact us!

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