Source for 28V needed to be lighter, reliable and portable

New solid-state X-ray technology allows medical X-ray scanners to be more portable and battery operated, enabling medical professionals to check patients in any location. Medical X-rays typically need a short pulse of high-intensity radiation energy, which can conveniently be stored and supplied to the X-ray diode by a supercapacitor, in this case charged to 28V. Normally the 28V would be sourced from a number of Li-ion batteries in series. However, in a portable application, this type of battery array and charging system is too large and too heavy. The key goals were:

• Find an alternative to heavy and bulky multiple-cell battery solutions
• Fast charging of the supercapacitor requires a high current pulse
• Long battery life to minimize the need for recharging

Bi-directional converter allowed for just one battery array

Use of a bi-directional DC-DC converter reduced the battery array to just one 2.7V Li-ion cell, reducing size and weight significantly compared to a typical boost converter solution. In addition, the bi-directional converter delivered higher efficiencies when charging the supercapacitor from a low voltage source, extending battery life. Key benefits were:

• Ultra-small, lightweight solution (8.6cm² footprint, 16g weight) compared to a boost converter solution
• Unique bi-directional converters (DC-DC transformer) available as standard products
• Higher efficiency achieved using low-loss Sine Amplitude Conversion topology