UEI30-050-Q12NL1-C 데이터 시트보기 (PDF) - Murata Manufacturing
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UEI30-050-Q12NL1-C Datasheet PDF : 16 Pages
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UEI30 Series
30W Isolated Wide-Range DC/DC Converters
APPLICATION NOTES
Input Fusing
Certain applications and/or safety agencies may require fuses at the inputs of
power conversion components. Fuses should also be used when there is the
possibility of sustained input voltage reversal which is not current-limited. For
greatest safety, we recommend a fast blow fuse installed in the ungrounded
input supply line.
The installer must observe all relevant safety standards and regulations. For
safety agency approvals, install the converter in compliance with the end-user
safety standard.
Input Reverse-Polarity Protection
If the input voltage polarity is reversed, an internal diode will become forward
biased and likely draw excessive current from the power source. If this source
is not current-limited or the circuit appropriately fused, it could cause perma-
nent damage to the converter.
Input Under-Voltage Shutdown and Start-Up Threshold
Under normal start-up conditions, converters will not begin to regulate properly
until the rising input voltage exceeds and remains at the Start-Up Threshold
Voltage (see Specifications). Once operating, converters will not turn off until
the input voltage drops below the Under-Voltage Shutdown Limit. Subsequent
restart will not occur until the input voltage rises again above the Start-Up
Threshold. This built-in hysteresis prevents any unstable on/off operation at a
single input voltage.
Users should be aware however of input sources near the Under-Voltage
Shutdown whose voltage decays as input current is consumed (such as capaci-
tor inputs), the converter shuts off and then restarts as the external capacitor
recharges. Such situations could oscillate. To prevent this, make sure the operat-
ing input voltage is well above the UV Shutdown voltage AT ALL TIMES.
Start-Up Delay
Assuming that the output current is set at the rated maximum, the Vin to Vout Start-
Up Delay (see Specifications) is the time interval between the point when the rising
input voltage crosses the Start-Up Threshold and the fully loaded regulated output
voltage enters and remains within its specified regulation band. Actual measured
times will vary with input source impedance, external input capacitance, input volt-
age slew rate and final value of the input voltage as it appears at the converter.
These converters include a soft start circuit to moderate the duty cycle of the
PWM controller at power up, thereby limiting the input inrush current.
The On/Off Remote Control interval from inception to VOUT regulated
assumes that the converter already has its input voltage stabilized above the
Start-Up Threshold before the On command. The interval is measured from the
On command until the output enters and remains within its specified accuracy
band. The specification assumes that the output is fully loaded at maximum
rated current.
Sometimes only a small ceramic capacitor is sufficient. Since it is difficult to
totally characterize all applications, some experimentation may be needed.
Note that external input capacitors must accept high speed switching currents.
Because of the switching nature of DC/DC converters, the input of these
converters must be driven from a source with both low AC impedance and
adequate DC input regulation. Performance will degrade with increasing input
inductance. Excessive input inductance may inhibit operation. The DC input
regulation specifies that the input voltage, once operating, must never degrade
below the Shut-Down Threshold under all load conditions. Be sure to use
adequate trace sizes and mount components close to the converter.
I/O Filtering, Input Ripple Current and Output Noise
All models in this converter series are tested and specified for input reflected
ripple current and output noise using designated external input/output compo-
nents, circuits and layout as shown in the figures below. External input capaci-
tors (CIN in the figure) serve primarily as energy storage elements, minimizing
line voltage variations caused by transient IR drops in the input conductors.
Users should select input capacitors for bulk capacitance (at appropriate
frequencies), low ESR and high RMS ripple current ratings. In the figure below,
the CBUS and LBUS components simulate a typical DC voltage bus. Your specific
TO
OSCILLOSCOPE
+
VIN –
+
–
LBUS
CBUS
CURRENT
PROBE 1
+INPUT
CIN
2
−INPUT
CIN = 33μF, ESR < 700mΩ @ 100kHz
CBUS = 220μF, ESR < 100mΩ @ 100kHz
LBUS = 12μH
Figure 2. Measuring Input Ripple Current
system configuration may require additional considerations. Please note that the
values of CIN, LBUS and CBUS will vary according to the specific converter model.
In critical applications, output ripple and noise (also referred to as periodic
and random deviations or PARD) may be reduced by adding filter elements
such as multiple external capacitors. Be sure to calculate component tempera-
ture rise from reflected AC current dissipated inside capacitor ESR. In figure 3,
the two copper strips simulate real-world printed circuit impedances between
the power supply and its load. In order to minimize circuit errors and standard-
ize tests between units, scope measurements should be made using BNC
connectors or the probe ground should not exceed one half inch and soldered
directly to the fixture.
Input Source Impedance
These converters will operate to specifications without external components,
assuming that the source voltage has very low impedance and reason-
able input voltage regulation. Since real-world voltage sources have finite
impedance, performance is improved by adding external filter components.
Floating Outputs
Since these are isolated DC/DC converters, their outputs are “floating” with
respect to their input. The essential feature of such isolation is ideal ZERO
CURRENT FLOW between input and output. Real-world converters however do
exhibit tiny leakage currents between input and output (see Specifications).
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03 Feb 2011 MDC_UEI Series 30W.A14 Page 6 of 16
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