Power Chain for Road Toll Stations

February 20, 2015
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One of the latest Whiteboard Power Chains of the Week is an AC-DC power system for road toll stations that was developed by Alexander Mezin, one of our technical sales engineers. Here’s what he told us about this power chain he developed.

 

Can you briefly describe the application?

Road Toll Station Power ChainThe power system is a complete AC- DC power system for road toll stations. Modern toll stations are fully automated and have multiple loads that need to be powered with different voltages.

The power chain was required to accept a universal 115 / 230 V ac and to provide three DC output rails. LED lighting systems needed a 12 V, 2 A supply, the electronic control unit required 3.3V at 1 A and the motor to lift the barrier is driven by 24 V at 10 A.

 

What were the key criteria for the system?

Efficiency and robustness were very important to the design.  Reliability was particularly important as if the system were to fail, traffic jams may be the result – not something anyone would want! Size, however, was not a problem.

 

You need to power a large DC motor in the system: were there any design decisions made to ensure electrical noise from the motor didn’t interfere with other systems?

There was the potential for the electrical noise issues, but due to the isolation of BCM the noise will remain close to the load. A filter on the input of the ZVS Buck Regulators will be needed, the design of which would be finalized after taking measurements on the prototype.

 

Can you explain the benefits of using an AC Front End and a BCM compared with more integrated AC-DC converters from other vendors?

This architecture allows the user to replace the BCM with other parts, in case there is a need voltages other than 24 Vdc that was needed by the fan that was chosen initially. This flexibility is a significant benefit of using Vicor power components.

 

The system delivers 260 W of power: does it need any heatsinking?

The system does need heatsinking, although the overall efficiency of the system minimizes the heat that has to be removed, meaning that only convective cooling is required. This was an important criterion as convective cooling is inherently more reliable than forced-air and would reduce maintenance cycles.

 

Are there any other aspects of the design you would like to highlight?

Flexibility. The system is scalable, so you can choose what voltage you will need for each load. For example, it would be possible to switch to different DC motors or LEDs using components with the same footprint.

The scalability is one of the key benefits of designing power chains using the Vicor power component design methodology. In addition to making it quicker and easier to develop systems, the methodology also allows one component to be replaced by another – usually pin compatible – device to respond to changes in requirements. This flexibility ensures the design has a longer production life as changes can be made without requiring a new PCB layout.

 

 

You can view Alexander Mezin’s power chain for road toll stations by clicking here.

 

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