Quick Search: Power Supplies
Glossary
Ambient temperature
Temperature of inactive air which surrounds the power supply. It is usually measured approx. 10 mm apart from the running power supply.
Class B
Protection against electric shock with special consideration of the leakage currents.
Class BF
Like B, but considering the so-called „F-parts“ which sometimes may get in contact with a patient and which are isolated from other parts.
Class CF
Class with the highest protection among all classes.
Current limited
Electronic overload protection which limits the max. output to a preset value.
Efficiency ratio
The efficiency ratio concerns the ratio between output and input and is always smaller than 1. To reduce the power loss under the given load prerequisites, the maximum efficiency ratio is aspired. For a power supply it is measured at full load and at nominal input. The difference between input and output is transposed into heat, hence each increase of the efficiency ratio means less thermal stress on the components and therefore a life cycle increase. Even a minor improvement of the efficiency ratio can have a dramatic impact on the life cycle.
EMC
“Electromagnetic Compatibility” is the ability of a device, equipment, or system to function satisfactorily in its electromagnetic environment without introducing intolerable electromagnetic disturbances to anything in that environment.
Power supplies should at least comply with two minimum technical standards of the EMC standards: 1. standard for transient emissions (grid-bound interferences emitted by the power supply) and 2. standard for interference resistance (external interferences). These standards comprise a multitude of substandard's which stipulate thresholds for particular sub areas (for example particular types of interferences).
FRIWO power supplies meet these standards even tighter than required since we believe that we should make the most of EMC to guarantee a trouble-free service.
Leakage current
Current which discharges via a protective earth conductor against ground during service by passing the capacitances and the insulating resistor of the working circuit.
Life cycle
Life cycle of a power supply. After the expiration of life cycles power supplies tend to break down because of worn components.
MTBF (meantime between failures)
MTBF stands for Mean Time Between Failures (average time between two power supply breakdowns). The MTBF specifies the statistic average time during which a power supply is likely to break down because of production or material problems before it is worn out.
NTC
A temperature-sensitive resistor with negative coefficient which constantly reduces the resistance value at increasing heat. It is therefore also called thermal resistor. In addition to its temperature monitoring function it also limits the switch on current of power supplies.
Operating temperature
The range of temperature which can neither be exceeded nor fallen below during operation.
Over voltage resistance
A circuitry within the power supplies monitors the output. If a preset threshold value is exceeded, the power supply will be turned off.
Short circuit proof
Short circuit proof means that a temporary short circuit of some seconds can be absorbed without any damages.
Single range
Power supplies with limited input voltage for usage in the corresponding countries.
SMT
SMT (surface-mounting technology) means a special surface mounting technology during which surface-mountable components (components without wire bonding's) are directly soldered onto a PCB.
Standby losses
Power consumption of a power supply during idle service.
Storage temperature
Ambient temperature in which a switch mode unit may be stored (not operated) without being damaged.
Sustained short circuit proof
A short circuit might occur without damaging the output. As soon as the problem is solved, the output will return to normal service.
THT
Stands for “through-hole technology“ and concerns the transfix montage. Components to be used for this mode of montage have wire bonding's (“through-hole components“) and are inserted by vias into the PCB. Afterwards the components are soldered in a special THT soldering process.
Voltage regulated
A servo loop within the power supply ensures a stable output voltage, independent of all other factors (e.g. temperature).
Wide range
Wide range power supplies can be operated at different rated voltages without having to be readjusted (manually or automatically) by a switch.
Battery Chemistry and Charging Information
| Chemistry | Lead Acid | Ni-Cd | Ni-MH | Li-Ion | |
|---|---|---|---|---|---|
| Cobalt | Manganese | ||||
| Cell voltage | 2.0V | 1.2V | 1.2V | 3.6 resp. 3.7V | |
| Energy density (Wh/kg) | 30-50 | 45-80 | 60-120 | 110-190 | 110-120 |
| Self-discharge ratio per month | 5% | 20% | 30% | 8% | |
| Overload tolerance | high | moderate | low | very low | |
| Charging cycles | 200-400 | 1500 | 300-500 | 300-500 | |
| Charging method | U= const. | I= const. | I= const. | 300-500 | |
| Charging characteristic | IU0U, IUIa | I0I | I0I | IUa | |
| Phase 1: constant current | Charging criteria: -dV, dT/dt, dU/dt, T max | Phase 1: constant current | |||
| Phase 2: constant voltage | Identification and control via microcontroller | Phase 2: constant voltage | |||
| Phase 3: trickle charge | |||||
