UEI-12 データシートの表示（PDF） - Murata Power Solutions
部品番号
コンポーネント説明
メーカー
UEI-12 Datasheet PDF : 12 Pages
| |||
UEI Series
50-60W Isolated Wide-Range DC/DC Converters
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 mag-
netically 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 appro-
priate value. If the short-circuit condition persists, another shutdown cycle will
initiate. This on/off cycling is called “hiccup mode”. The hiccup cycling reduces
the average output current, thereby preventing excessive internal tempera-
tures. A short circuit can be tolerated indefinitely.
Remote Sense Input
Sense inputs compensate for output voltage inaccuracy delivered at the load.
This is done by correcting voltage drops along the output wiring such as mod-
erate IR drops and the current carrying capacity of PC board etch. Sense inputs
also improve the stability of the converter and load system by optimizing the
control loop phase margin.
Note: The Sense input and power Vout lines are internally connected through
low value resistors to their respective polarities so that the converter can
operate without external connection to the Sense. Nevertheless, if the Sense
function is not used for remote regulation, the user should connect +Sense to
+VOUT and –Sense to –VOUT at the converter pins.
2 −INPUT
4 ON/OFF
CONTROL
+OUTPUT
+SENSE
TRIM
−SENSE
Contact and PCB resistance
losses due to IR drops
6
5 I OUT
Sense Current
9
Sense Return
8
LOAD
1
+INPUT
-OUTPUT
I OUT Return
7
Contact and PCB resistance
losses due to IR drops
Figure 4 – Remote Sense Circuit Configuration
The remote Sense lines carry very little current. They are also capacitively
coupled to the output lines and therefore are in the feedback control loop to
regulate and stabilize the output. As such, they are not low impedance inputs
and must be treated with care in PC board layouts. Sense lines on the PCB
should run adjacent to DC signals, preferably Ground. In cables and discrete
wiring, use twisted pair, shielded tubing or similar techniques.
Please observe Sense inputs tolerance to avoid improper operation:
[VOUT(+) –VOUT(-)] – [ Sense(+) – Sense(-)] ≤ 10% of VOUT
Output overvoltage protection is monitored at the output voltage pin, not the
Sense pin. Therefore excessive voltage differences between Vout and Sense
together with trim adjustment of the output can cause the overvoltage protec-
tion circuit to activate and shut down the output.
Power derating of the converter is based on the combination of maximum
output current and the highest output voltage. Therefore the designer must insure:
(VOUT at pins) x (IOUT) ≤ (Max. rated output power)
Trimming the Output Voltage
The Trim input to the converter allows the user to adjust the output voltage over
the rated trim range (please refer to the Specifications). In the trim equations and
circuit diagrams that follow, trim adjustments use either a trimpot or a single
fixed resistor connected between the Trim input and either the +Sense or –Sense
terminals. (On some converters, an external user-supplied precision DC voltage
may also be used for trimming). Trimming resistors should have a low tempera-
ture coefficient (±100 ppm/deg.C or less) and be mounted close to the converter.
Keep leads short. If the trim function is not used, leave the trim unconnected.
With no trim, the converter will exhibit its specified output voltage accuracy.
There are two CAUTION’s to be aware for the Trim input:
CAUTION: To avoid unplanned power down cycles, do not exceed EITHER the
maximum output voltage OR the maximum output power when setting the trim.
Be particularly careful with a trimpot. If the output voltage is excessive, the
2
−INPUT
4 ON/OFF
CONTROL
1
+INPUT
6
+OUTPUT
5
+SENSE
9
TRIM
−SENSE 8
−OUTPUT 7
7 5-22
TURNS
LOAD
Figure 5 – Trim adjustments using a trimpot
2
−INPUT
6
+OUTPUT
5
+SENSE
4 ON/OFF
CONTROL
9
TRIM
R TRIM DOWN
−SENSE 8
1
+INPUT
7
−OUTPUT
LOAD
Figure 6 – Trim adjustments to decrease Output Voltage using a Fixed Resistor
www.murata-ps.com
Technical enquiries email: sales@murata-ps.com, tel: +1 508 339 3000
MDC_UEI Series 50-60W.B24 Page 8 of 12
Share Link: 