Respirators are critical systems in the operating rooms and intensive care units. They precisely control invasive or non-invasive ventilation based on several measurement parameters such as air pressure, respiratory flow, oxygen saturation, pulse rate, or spontaneously triggered breaths.
Any failure can have severe or even fatal consequences, so the highest level of redundancy is required here. One potential failure mechanism is a power outage, which can be covered by an internal battery backup. This customer wanted the system to run up to eight hours on the internal battery backup. When the mains voltage comes back, the internal battery should be fully recharged in less than four hours. This means that robust AC-input and DC-input power supplies are required as 60-70% of the total input power may go into
battery charging. This configuration is also more resilient to intermittent power outages happening in areas with weaker infrastructure.
What if the mains voltage does not come back after eight hours? Exchanging an internal battery is stressful for the nurses and takes valuable time. The solution is to extend the backup time by simply plugging in external battery packs. In the worst case, customers should be able to connect to any 12V or 24V batteries, including those used in cars or trucks.
What happens if no mains is available at all or if the internal AC/DC power supply fails? Any external source providing a voltage in the range of 9 to 36V should be able to supply the respirator.
The customer’s first idea was a
fully custom design, but RECOM was able to provide a unique and clever solution. An AC/DC power supply paired with a wide input DC/DC converter generates an internal 24V bus voltage from the various inputs. From this 24V bus, a battery management system charges the internal battery, which then backs up this 24V bus if no input source is available. Lower power isolated DC/DC converters can then generate the necessary voltages for various loads. As sensors are connected to the patient, the converters must meet
2MOPP (2 Means of Patient Protection) requirements (e.g., 4kVAC/1minute, reinforced (double) insulation, 8 mm creepage, and clearances, as per IEC/EN 60601-1).
Another unique approach was used to generate isolated, 5V supply voltages for low-power sensors. From the internal 24V bus, a non-isolated, regulated 5W converter generates a stable 5V voltage. Isolated but non-regulated 1W converters then provide individual, galvanically separated voltages for each sensor.
