Why Engineers Use Parallel Capacitors to Increase Capacitance

Each consisting of two conductive plates separated by an insulator (dielectric), capacitors might seem very simple components, and they very much are. However, this doesn’t mean they are of merely peripheral importance. Quite the opposite; their behaviour with AC/DC, filtering, and timing helps to make them utterly crucial in virtually all electronic circuits.

This passive component stores electrical energy in an electric field, acting akin to a tiny, fast-charging (or discharging) battery. The usefulness of this behaviour has led to capacitors being incorporated into practically everything, from smartphones to industrial machinery.

Across the extremely broad range of such products and projects, though, there are inevitably times when a single capacitor doesn’t provide enough capacitance for the given job. Engineers respond to this by connecting capacitors in parallel, as a way of boosting overall capacitance.

Understanding The Basics of Capacitance

Capacitance is the ability of an object or component (a capacitor) to store electrical energy as an electric charge. This is measured as the ratio of stored charge (Q) to the voltage across it (V), as embodied in the formula: C = Q/V.

The standard unit of measurement for capacitance is the farad (F). It is used to determine the amount of charge a capacitor can hold at a given voltage.

In practice, though, most capacitors that an engineer will encounter will be rated in the subunits microfarads (µF), nanofarads (nF), or picofarads (pF).

What Does It Mean When Capacitors Are Linked in Parallel?

When you see a reference to capacitors being connected in a parallel configuration, this means their positive terminals are joined together, with their negative terminals being connected as well. To put it another way, the capacitors are wired side-by-side.

This setup allows for the voltage across each capacitor to be the same. However, the total capacitance adds up when a parallel arrangement is used. This effectively increases the overall storage capacity and plate area, similar to one large capacitor with combined plates.

You can work out the total capacitance of capacitors in parallel, then, by adding together the individual values. This formula is commonly expressed as: C_total = C₁ + C₂ + C₃ + ….

For What Reasons, Then, Do Engineers Turn to Parallel Capacitors?

There are various potential practical reasons for a parallel arrangement of capacitors being chosen by an engineer overseeing a given project. These encompass:

• A Need to Achieve Certain Custom Values

A particular design may require something slightly different to standard capacitor values. In such a situation, an engineer might decide to parallel multiple capacitors, so that they can fine-tune the total capacitance to match what is needed.

For example, a specific filter circuit might need 6.9µF. The engineer may look to fulfil this requirement by arranging a 4.7µF capacitor and a 2.2µF capacitor in parallel.

• Cost And Availability Issues

While an engineer may initially search for a high-capacitance capacitor for a given need in their project, they might later come to realise the options available are somewhat expensive or bulky.

This may lead them to conclude it would be a more economical course of action to use several smaller capacitors in parallel instead. Such components are readily available from trusted suppliers like RS. Indeed, they can be a godsend when engineers find themselves stymied by supply-chain problems, or when they need to prototype on a budget.

• The Opportunity for Enhanced Performance and Reliability

The linking of capacitors in parallel allows for the more even distribution of current. This, in turn, helps to reduce heat buildup and extend the lifespan of components. In power supplies, this helps with ripple filtering.

It is worth bearing in mind, too, that when a parallel configuration of capacitors is laid out, in the event of one capacitor later failing during use, the other capacitors would be able to keep the circuit operational. Such an additional layer of redundancy can be especially important in critical applications like medical devices or automotive electronics.

• The Handling of Particular Power Demands

Such applications as electric vehicles (EVs) and renewable energy systems frequently depend on the use of especially high-frequency or high-power circuits. In circuits like these, parallel capacitors can provide the energy storage required, without exceeding voltage ratings.

All in all, the linking of capacitors in parallel can be an invaluable strategy for engineers who need more capacitance. This type of configuration can be very flexible in line with a broad range of situations and requirements. It can also help save money and bolster circuit reliability.