UEI15-033-Q12N-C 查看數據表（PDF） - Murata Manufacturing
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UEI15-033-Q12N-C Datasheet PDF : 16 Pages
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UEI15 Series
Isolated Wide Input Range 15-Watt DC/DC Converters
COPPER STRIP
C1
C2
SCOPE
RLOAD
COPPER STRIP
C1 = 0.1μF CERAMIC
C2 = 10μF TANTALUM
LOAD 2-3 INCHES (51-76mm) FROM MODULE
Figure 3. Measuring Output Ripple and Noise (PARD)
and a DC leakage resistance. When using the isolation feature, do not allow
the isolation voltage to exceed specifications. Otherwise the converter may
be damaged. Designers will normally use the negative output (-Output) as
the ground return of the load circuit. You can however use the positive output
(+Output) as the ground return to effectively reverse the output polarity.
Minimum Output Loading Requirements
These converters employ a synchronous rectifier design topology. Models
UEI15-033-Q12, UEI15-120-Q12, and UEI15-050-Q12 require 10% minimum
load to meet specifications. Operation under less than 10% load may slightly
increase regulation, ripple, and noise.
Thermal Shutdown
To prevent many over temperature problems and damage, these converters
include thermal shutdown circuitry. If environmental conditions cause the
temperature of the DC/DC’s to rise above the Operating Temperature Range
up to the shutdown temperature, an on-board electronic temperature sensor
will power down the unit. When the temperature decreases below the turn-on
threshold, the converter will automatically restart. There is a small amount of
hysteresis to prevent rapid on/off cycling.
CAUTION: If you operate too close to the thermal limits, the converter may shut
down suddenly without warning. Be sure to thoroughly test your application to
avoid unplanned thermal shutdown.
Temperature Derating Curves
The graphs in the next section illustrate typical operation under a variety of
conditions. The Derating curves show the maximum continuous ambient air
temperature and decreasing maximum output current which is acceptable
under increasing forced airflow measured in Linear Feet per Minute (“LFM”).
Note that these are AVERAGE measurements. The converter will accept brief
increases in temperature and/or current or reduced airflow as long as the aver-
age is not exceeded.
Note that the temperatures are of the ambient airflow, not the converter
itself which is obviously running at higher temperature than the outside air.
Also note that “natural convection” is defined as very flow rates which are not
using fan-forced airflow. Depending on the application, “natural convection” is
usually about 30-65 LFM but is not equal to still air (0 LFM).
MPS makes Characterization measurements in a closed cycle wind tunnel
with calibrated airflow. We use both thermocouples and an infrared camera
system to observe thermal performance. As a practical matter, it is quite diffi-
cult to insert an anemometer to precisely measure airflow in most applications.
Sometimes it is possible to estimate the effective airflow if you thoroughly un-
derstand the enclosure geometry, entry/exit orifice areas and the fan flowrate
specifications. If in doubt, contact MPS to discuss placement and measurement
techniques of suggested temperature sensors.
CAUTION: If you routinely or accidentally exceed these Derating guidelines,
the converter may have an unplanned Over Temperature shut down. Also, these
graphs are all collected at slightly above Sea Level altitude. Be sure to reduce
the derating for higher density altitude.
Output Overvoltage Protection
This converter monitors its output voltage for an over-voltage condition using
an on-board electronic comparator. The signal is optically coupled to the pri-
mary side PWM controller. If the output exceeds OVP limits, the sensing circuit
will power down the unit, and the output voltage will decrease. After a time-out
period, the PWM will automatically attempt to restart, causing the output volt-
age to ramp up to its rated value. It is not necessary to power down and reset
the converter for the this automatic OVP-recovery restart.
If the fault condition persists and the output voltage climbs to excessive levels,
the OVP circuitry will initiate another shutdown cycle. This on/off cycling is referred
to as “hiccup” mode. It safely tests full current rated output voltage without damag-
ing the converter.
Output Fusing
The converter is extensively protected against current, voltage and temperature
extremes. However your output application circuit may need additional protec-
tion. In the extremely unlikely event of output circuit failure, excessive voltage
could be applied to your circuit. Consider using an appropriate fuse in series
with the output.
Output Current Limiting
As soon as the output current increases to approximately 125% to 150% of
its maximum rated value, the DC/DC converter will enter a current-limiting
mode. The output voltage will decrease proportionally with increases in output
current, thereby maintaining a somewhat constant power output. This is com-
monly referred to as power limiting.
Current limiting inception is defined as the point at which full power falls
below the rated tolerance. See the Performance/Functional Specifications. Note
particularly that the output current may briefly rise above its rated value. This
enhances reliability and continued operation of your application. If the output
current is too high, the converter will enter the short circuit condition.
Output Short Circuit Condition
When a converter is in current-limit mode, the output voltage will drop as
the output current demand increases. If the output voltage drops too low, the
magnetically coupled voltage used to develop primary side voltages will also
drop, thereby shutting down the PWM controller. Following a time-out period,
the PWM will restart, causing the output voltage to begin ramping up to its ap-
propriate value. If the short-circuit condition persists, another shutdown cycle
will initiate. This on/off cycling is called “hiccup mode”. The hiccup cycling
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14 Mar 2011 MDC_UEI15W.B42 Page 13 of 16
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