Telecom power supplies provide a stable power supply 24 hours a day for various communication devices, including telephones and the Internet. They convert alternating current (AC) power supplied by commercial systems to direct current (DC) voltages and regulate the output voltage.
Depending on the application, power supply designs are driven by topology selection criteria, power requirements and efficiency goals. These challenges stimulate architectural innovation and the rapid evolution of converter topologies.
Purpose of Power Supplies
Telecom power supplies provide stable power for various communication devices, including the telephone and the Internet. These power supplies come in multiple forms, including direct current and alternating current power supplies.
The power supply must maintain continuous operation for telecommunication equipment even when there is a power failure. It is especially true for mobile phone base stations and other communications infrastructure.
A high-voltage power supply uses a voltage multiplier, a high turns ratio or a transformer to convert the bulk of its input energy into high voltage. This voltage is then passed through a special connector and applied to a voltage divider that converts it to a metering signal compatible with low-voltage circuitry.
A closed-loop controller then uses the metering signal to regulate the high voltage. In some cases, the metering signal is also conveyed out of the power supply so that it can be monitored by external circuitry.
Another type of power supply is an uninterruptible power supply (UPS). It takes its power from two or more sources simultaneously, and if one source fails, the UPS instantly transfers its power to another.
The power supply industry rapidly evolves to address diverse power requirements and a volatile telecommunications market. Telecom power suppliers must offer more efficient, reliable, and cost-effective power solutions for today’s communication equipment.
Power System Configuration
The power system configuration for telecom power supplies is a critical design consideration. It is essential when combining AC- and DC-powered loads. Telecommunications sites that host traditional telecommunication equipment typically have a mix of 85% to 95% AC-powered load and 5% to 15% DC-powered load, with the overall system requiring multiple rectifiers, lead-acid storage batteries, converters, or inverters, all configured as parallel-redundant systems (see Figure 1).
The type of conversion used in a telecommunications power supply depends on its application. Linear, switched, and battery-based converters all have pros and cons. For example, a linear converter uses less complex circuitry but produces more heat than a switched converter. A switched converter is more complicated but more relaxed but creates more noise than a battery-based converter.
A typical telecommunications site requires extended battery support to ensure critical loads can continue operating during sustained rectifier or AC power failures. Often, plant personnel will supplement the battery with an engine-generator system, which helps ensure the system can function during extended periods of inactivity.
Most power distribution systems have three lines and a neutral, allowing them to supply single-phase and three-phase loads. The two most common configurations are delta and Y, with a Y connection supplying phase and line voltage.
Input Power Requirements
The convergence of information technology (IT) and telecommunications equipment has brought about the need for power systems that meet a wide range of input requirements. It requires designers to configure a system that supports these requirements as reliably and economically as possible.
The input power required for these systems will vary, depending on the type of equipment used and the location. In general, telecom and data centers use a mix of AC-powered loads and DC-powered ones. For example, an Internet hosting site may have 85% to 95% AC-powered loads and 5% to 15% DC-powered ones.
Telecom power supplies typically consist of a high-power backplane connected by line cards. Each line card has its input-filter capacitor and low-voltage power converter.
The design is challenging because each value is limited to a few microfarads, so the power-supply circuit should be compact and efficient. The power-supply technology gurus say the best way to accomplish this is using a multichip multistage high-frequency, current-mode PWM controller.
This device should be designed to switch a wide input-voltage range while delivering low output power. It should also have an integrated under-voltage lockout feature, a fast internal comparator, and a power conversion output.
Uninterruptible Power Supply (UPS)
As part of their power supply, telecommunications companies also need uninterruptible power supplies (UPS). In the event of an outage or surge, these devices allow plugged-in components to receive energy for a certain amount of time until average utility power is restored.
It helps prevent any corruption of data or improper shutdowns during the outage. In the telecommunications industry, any disruption in power affects communications and can cause severe damage to equipment.
Many different types of UPS systems work in different ways. These include line-interactive models that actively regulate voltage and battery-based and flywheel-type systems.
Line-interactive models are best for applications that need protection from power anomalies but don’t have sensitive equipment. Communication closets, non-centralized servers, network rooms, and general IT enclosures are a good fit for this type of UPS system.
Regardless of the form factor of the UPS, it will usually contain batteries that store energy until a backup source is available. Choosing user-replaceable batteries can help reduce the cost of replacing the whole unit when they fail, and buying Lithium-ion batteries with a longer lifespan can be a good idea.
There are two primary output waveforms that most UPS models use to produce AC: pure sine and modified sine. Both are fine for most equipment, but pure sine is preferred for more sensitive gear like medical imaging machines and telecommunications systems.
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