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CUI Inc │ SERIES: VWRBS1 │ DESCRIPTION: DC-DC CONVERTER
date 09/05/2012 │ page 5 of 6
APPLICATION NOTES
1. Requirement on Output Load
In order to ensure the product operates efficiently and reliably, make sure the specified range of input voltage is not exceeded and
the minimum output load is not less than 10% load. If the actual load is less than the specifi ed minimum load, the output ripple may
increase sharply while its effi ciency and reliability will reduce greatly. If the actual output power is very small, please add an
appropriate resistor as extra loading.
2. Overload Protection
Under normal operating conditions, the output circuit of these products has no protection against overload. The simplest method is to
connect a self-recovery fuse in series at the end or add a circuit breaker to the circuit.
5 Vdc models
12 Vdc models
24 Vdc models
48 Vdc models
1,000 mA slow-blow type
500 mA slow-blow type
250 mA slow-blow type
120 mA slow-blow type
3. Recommended Circuit
All VWRBS1 converters have been tested according to the following recommended testing circuit before leaving the factory. This
series should be tested under load, never under no load (Figure 1).
Ic
D1
R
Vc
Figure 1
3
Lin
2
1
6
8
Vi n
+Vo
0V
Cin
Co ut
Cs
GND
7
However, the capacitance of the output filter capacitor must be proper. If the capacitance is too big, a startup problem might arise.
For every channel of output, provided the safe and reliable operation is ensured, the greatest capacitance of its filter capacitor sees
(Table 1).
General:
5, 12 V
100 μF
10 μF
Vout
(Vdc)
Cout
(μF)
Table 1
Cin
24, 48 V
3.3
5
2,200
1,000
680
Cout
Lin
47 μF typ.
4.7~120 μH
2.2~10 μH
10~22 μF
9
Lout
Cs
12
15
470
330
4. CTRL Terminal
When open or high impedance, the converter work well; When this pin is ‘high’; the converter shutdown; It should be note that the
input current should between 5~10 mA, exceeding the maximum 20 mA will cause permanence damage to the converter.
The value of R can be derived as follows:
VC-VD-1.0
R=
IC
5. Input Current
While using unstable power source, please ensure the output voltage and ripple voltage do not excced indexes of the converter. The
preceding power source must be able to provide for converter sufficient starting current Ip.
General: Ip ≤1.4*Iin-max
Ip
Input Voltage
Range
Input Voltage (V)
6. No parallel connection or plug and play
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