It's Blowing Hot and Cold

It looks like a normal British summer so far, some barbeque weekends, some get-out-the-appropriate-clothing weekends.
Although we have had a strong web presence since 1998, you will have noticed that we have now launched our brand new website.

The rugged power supplies we designed and made for a road research vehicle was fully installed earlier this year.  It powers a variety of flat panel displays, video cameras and splitters, network switches etc.  The prototype chargers for special rechargeable batteries are being thoroughly tested and we have been doing some preliminary design studies for a multi-cell Li-Ion battery simulator.

Rugged Power Supply

This power supply was designed for a road research vehicle that is fitted with several touch screens, video cameras, network switches, etc. Originally this equipment was powered from 230V ac mains plug adaptors which tend to occasionally fall out with the vibration from road imperfections. Two variants of this power supply have been commissioned, each to power up to 12 low voltage loads with a total output of 180W per unit.

Battery Charger

We were asked to develop a prototype battery charger with constant current and then constant voltage control.  Unusually, the constant current was the maximum current allowed from the power supply, not the current into the battery.  The production charger may be required to work with different battery chemistries so we needed a flexible solution. We developed the prototype shown below (before the inductors were fitted) with a PIC microcontroller to adjust the output of a buck-topology switch mode DC to DC converter.

We had hoped to use the PIC16F785 microcontroller for the overall management of the charger as the application note says that the features of this device are well suited for switch mode battery charging.  Unfortunately, the errata for the data sheet says that anomalies in Rev. A silicon means that this device will not operate as the buck converter shown in the application note.  So, we designed a work-around to prove the principles.

Battery Simulator

A potential customer was looking for a Lithium Ion battery simulator to test a piece of equipment they were putting into production.  This equipment had similar circuitry for battery charging to that in a portable computer.  The requirement was to simulate a four cell battery.
The enquiry came from finding information on our web site about the tester for smart battery chargers that we designed some eight years ago.  A new approach was required as the customer wanted the simulator to source as well as sink power with a seamless switch-over.  We responded with an outline design that matched this customer’s requirements.  Although these plans have been temporarily shelved due to the recession, we will expand on them in a forthcoming case study with a modular approach simulating a Li-Ion battery of up to six cells.

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