QLS30 DC-DC Series Data Sheet
30A Quarter-Brick Converter
Industrial Standard Positive Trim (suffix –T)
The -T option units trim up with a resistor from the TRIM
pin to the +Sense pin and trim down with a resistor from
the TRIM pin to the –Sense pin as shown in the Figure 9.
Safety Considerations
The QLS30 Series converters feature 1500 Volt DC
isolation from input to output.
The input-to-output
resistance is greater than 10MOhm. These converters are
provided with Basic insulation between input and output
circuits according to all IEC60950 based standards.
Nevertheless, if the system using the converter needs to
receive safety agency approval, certain rules must be
followed in the design of the system. In particular, all of
the creepage and clearance requirements of the end-use
safety requirements must be observed. These documents
include UL60950, CSA60950-00 and EN60950, although
other additional requirements may be needed for user’s
specific applications.
The QLS30 Series converters have no internal fuse. An
external fuse must be provided to protect the system from
catastrophic failure, as illustrated in Figure 7. The fuse
with a rating of 4A or less is recommended. The user can
select a lower rating fuse based upon the highest inrush
transient at the maximum input voltage and the maximum
input current of the converter at the minimum input voltage.
Both input traces and the chassis ground trace (if
applicable) must be capable of conducting a current of 1.5
times the value of the fuse without opening. The fuse must
not be placed in the grounded input line, if any.
Figure 9. QLS30 Series Positive Trim Schematic
The equations below determine the trim resistor value
required to achieve a ΔV change in the output voltage.
In order for the output of the QLS30 Series converter to be
considered as SELV (Safety Extra Low Voltage) or TNV-1,
according to all IEC60950 based standards, one of the
following requirements must be met in the system design:
Vout(100+ ΔV%) 100+ 2ΔV%
⎛
⎞
⎟
R =5.11
−
,kΩ
⎜
UP
1.225ΔV%
ΔV%
⎝
⎠
100
⎛
⎝
⎞
⎠
RDOWN = 5.11
− 2 , kΩ
⎜
⎟
●
●
If the voltage source feeding the module is SELV or
TNV-2, the output of the converter may be grounded
or ungrounded.
If the voltage source feeding the module is ELV, the
output of the converter may be considered SELV only
if the output is grounded per the requirements of the
standard.
If the voltage source feeding the module is a
Hazardous Voltage Secondary Circuit, the voltage
source feeding the module must be provided with at
least Basic insulation between the source to the
converter and any hazardous voltages. The entire
system, including the QLS30 converter, must pass a
dielectric withstand test for reinforced insulation.
Design of this type of systems requires expert
engineering and understanding of the overall safety
requirements and should be performed by qualified
personnel.
ΔV %
For QLS30ZY use the following equations.
Vout(100+ ΔV%)
1.225ΔV%
⎛
⎞
⎟
R =5.11
,KΩ
⎜
UP
●
⎝
⎠
100
1
⎛
⎝
⎞
⎠
RDOWN = 5.11
−
,KΩ
⎜
⎟
2ΔV % 2
where ΔV% is the output voltage change expressed in
percents of the nominal output voltage, Vout.
Notes:
1. When the output voltage is trimmed up, the output power
from the converter must not exceed its maximum rating. The
power is determined by measuring the output voltage on the
output pins, and multiplying it by the output current.
Thermal Considerations
The QLS30 Series converters are designed for both
natural and forced convection cooling. The maximum
allowable output current of the converters is determined by
meeting the derating criteria of all electronic components
used in the power supplies. An example of the derating
criteria for the semiconductor junction temperature is not to
exceed 120°C to provide reliable long-term operation of the
converters.
2. In order to avoid creating apparent load regulation
degradation, it is important that the trim resistors are
connected directly to the remote sense pins, and not to the
load or to traces going to the load.
3. The QLS30 Series converters will trim down further than the
10% limit. In general, this is permissible. The user must
confirm that the results are acceptable in the application.
MCD10053 Rev. 1.0
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