• • • CIRCUIT PROTECTION • • • How is inrush current
managed today? Various methods are available, but all come with their own compromises. Some involve the use of specialist components in the power supply design (ohmic resistors, NTC thermistors, PTC thermistors or a soft-start circuit), which introduce cost, complexity and energy waste. In cases where the power supply design does not actively manage inrush current, system installers must upgrade circuit breakers or limit the number of LED drivers, power supplies or battery chargers that are connected to a single wiring circuit, adding time and cost.
Darrel Kingham
overall energy consumption while delivering a range of other benefits. It offers engineers complete flexibility to adapt and scale for virtually any application from just 20W to several kW, with evaluation boards and reference design document packages available online to simplify the design process.
What are the benefits of no inrush current?
It goes without saying that a circuit without inrush current delivers significant advantages:
Design phase
• Overall system design is simplified • Reduction in component count, PCB space and assembly time
• A scalable solution for different applications
End applications • Reduce manufacturing costs • Improve reliability • Extend product lifetime
Installations Figure 2. How is inrush current managed?
How has Pulsiv eliminated inrush current?
In a conventional power supply design, a series inductor is used to achieve power factor correction (PFC). Pulsiv has developed and patented a completely different method for AC to DC power conversion by charging a capacitor in parallel. This approach enables greater control and prevents a large current from flowing into the circuit. Measured using accepted techniques, Pulsiv OSMIUM designs have been proven to completely eliminate inrush current.
Kingham explains: “Inrush current has always been a problem in certain applications due to the behaviour of legacy power electronics. The obvious safety and reliability implications mean that it must be addressed somewhere in the system design or installation process. By completely eliminating inrush current, Pulsiv OSMIUM technology reduces cost, complexity and risk in any application where it currently needs managing.” Pulsiv OSMIUM technology provides manufacturers with a cost-effective method of designing highly efficient power supplies to reduce
• System installation is simplified • Reduction of cabling • Installation time/cost reduced
Figure 4. Pulsiv OSMIUM eliminates inrush current Figure 3. Pulsiv OSMIUM design circuit schematic
Fire alarm system example In a typical fire detection system used for large commercial buildings, there will be several notification devices on a 24Vdc circuit that may be several kilometres long. Due to strict regulations, it is not possible to increase voltage or add equipment to address voltage drops caused by inrush current. Output lines from the fire panel are protected, so the combined effect of inrush from multiple devices can cause fuses to blow and lead to complete system failure. Alarm sounder manufacturers do not always document inrush current data for their devices, so the problem is often discovered, and must then be resolved, during installation. Using a power supply based on a Pulsiv OSMIUM design will eliminate inrush current, reducing application cost, complexity and ultimately, risk.
electricalengineeringmagazine.co.uk
ELECTRICAL ENGINEERING • JULY/AUGUST 2025 37
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