5 Reasons You Need a Wide Input Voltage

May 8, 2018

Many DC-DC converters are designed with a relatively narrow input range to allow efficiency to be optimized, but the lack of flexibility can be a limitation for many applications. The Vicor Sine Amplitude Converter (SAC) topology allows the development of DC-DC converters with wide input ranges that retain high efficiency from the lowest to highest input voltage.

There are a number of reasons why you might want a wide input voltage.  Having worked with power designers worldwide we have developed a list of the top five.


Supporting Multiple Requirements or Standards

DCMs with 1% RegulationSome applications use power rails at different voltages. For example, both 72V and 110V are used to distribute power in rail applications. It’s obviously desirable for a single system to be able to support both voltages to reduce costs throughout the supply chain. Power systems using wide input range converters, such as Vicor DCMs that support inputs of 43V to 154V, will inherently support both power rails, eliminating the need to develop separate products for the different voltages.

In other applications, there may be a migration from one standard to another. For example, many industrial applications are moving from 12V to 24V and then 48V to deliver more power with less loss. A wide input range converter will allow a single board to be developed that can support all three voltages, allowing the same board to be retrofitted to existing equipment in the field as well as being deployed in new systems running at the higher voltage.


Making Full Use of Batteries

Battery Output Voltage Variations Regulators Must Deal With

Figure 1 – Battery Output Voltage Variations

As batteries discharge, their output voltage falls. A typical 12V battery might deliver 12.5V or more when fully charged, and fall to less than 10V as it discharges. To maximize the operation time on batteries and ensure that the full charge of the battery can be used, a wide input range is therefore required from the DC-DC converter.  For example, in automotive applications, during engine cranking, the battery can be subject to very high loads that can reduce the battery voltage further.  Vicor DCM converters with their 9-50V input voltage range can provide stable outputs for on-board applications, allowing them to operate through these periods of high load demand without the need to use bulky hold-up capacitance.

This capability also means that wide input range converters are ideal for improving the reliability of systems with poorly regulated power supplies. If a supply voltage droops because of changes in demand from the loads (a brownout), a converter with a wide input range can continue operating, ensuring the system does not fail.


Voltage Drop in Long Power Cables

Many applications, from tunnel boring to tethered UAVs, use long cables to connect to a remote vehicle or device. The resistance of the cable will cause a voltage drop. As most systems need to minimize the weight and cost of the cable, using the smallest cable that can carry the current, this voltage drop across the cable is further exacerbated.

Increasing the voltage being supplied to the cable will allow the use of smaller cables and help ensure the expected voltage is delivered at the load. A simpler approach is to use a wide input range converter at the load, which will function even when the voltage drop in the cable is at its maximum.


Reduced Inventory

Adding additional parts to inventory can be expensive. By choosing a wide input range converter, the same part can be used in several different situations, reducing the number of components needed in stock and thereby cutting the organization’s costs.


Variable Input Voltage

In some applications the input voltage is not well regulated and can fluctuate significantly. For example, the output voltage of photovoltaic (PV) panels increases as the light falling on the panel gets brighter and decreases as it gets darker. A wide input range allows a system to continue operating even when the supply voltage is not stable.


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