QHS DC-DC Series Data Sheet
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.
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
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.
QHS converter, must pass
a
dielectric
withstand test for Reinforced insulation.
Design of this type of systems requires expert
engineering and under-standing of the overall
safety requirements and should be performed
by qualified personnel.
3. The QHS 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.
Thermal Considerations
Safety Considerations
The QHS Series converters are designed for
The QHS Series converters feature 1500 VDC isolation
from input to output. The input to output resistance is
greater than 10 MΩ. 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 or additional requirements
may be needed for specific applications.
natural or forced convection cooling.
The
maximum allowable output current of the
converters is determined by meeting the derating
criteria for all components used in the converters.
For example, the maximum semiconductor
junction temperature is not allowed to exceed
120 °C to ensure reliable long-term operation of
the converters.
Contact Power-One for the
complete list of the derating criteria.
The graphs in Figures 11-14 show the maximum
output current of the QHS Series converters at
different ambient temperatures under both natural
and forced (longitudinal airflow direction, from pin
1 to pin 3) convection.
The QHS Series converters have no internal fuse. The
external fuse must be provided to protect the system
from catastrophic failure as shown in Figure 7. The
user can select a fuse based upon the highest inrush
transient at the maximum input voltage and the
maximum input current of the converter, which occurs
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.
For example, from Figure 11, the QHS40ZE
operating at 55 °C can deliver up to 18 A reliably
with 100 LFM forced air, while up to 25 A reliably
with 400 LFM forced air.
12
10
8
In order for the output of the QHS 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:
6
0
4
100LFM
200LFM
2
300LFM
400LFM
•
If the voltage source feeding the module is SELV or
TNV-2, the output of the converter may be
grounded or ungrounded.
0
25 30 35 40 45 50 55 60 65 70 75 80 85
Ambient Temperature (C)
Figure 11. QHS12ZH (12V) Derating Curves
•
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
DEC 09, 2004 revised to APR 12, 2006
Page 8 of 10
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