RB-XLS&RB-XLD Series
Technical notes
ISOLATION VOLTAGE
"Hi Pot Test","Flash Tested","Withstand Voltage","Dielectric Withstand Voltage"&”Isolation Test Voltage" are all terms that relate to the same thing, a test voltage.
Applied for a specified time, across a component designed to provide electrical isolation, to verify the integrity of that isolation.
Professional Power Module B_XLS series of DC/DC converters are all 100% production tested at their stated isolation voltage. This is 1KVDC for 1 second.
A question commonly asked is,"What is the continuous voltage that can be applied across the part in normal operation?"
For a part holding no specific agency approvals, such as the B_XLS series ,both input and output should normally be maintained within SELV limits i.e. less than 42.4V peak, or
60VDC.The isolation test voltage represents a measure of immunity to transient voltages and the part should never be used as an element of a safety isolation system. The part
could be expected to function correctly with several hundred volts offset applied continuously across the isolation barrier, but then the circuitry on both sides of the barrier must
be regarded as operating at an unsafe voltage and further isolation/insulation systems must form a barrier between these circuits and any user-acssible circuitry according to
safety standard requirements.
REPEATED HIGH-VOLTAGE ISOLATION TESTING
It is well known that repeated high-voltage isolation testing of a barrier component can actually degrade isolation capability, to a lesser or greater degree depending on materials.
Construction and environment. The B_XLS series has toroidal isolation transformers, with no additional insulation between primary and secondary windings of enameled wire. While
parts can be expected to withstand several times the stated test voltage, the isolation capability does depend on the wire insulation. Any material, including this enamel (typically
polyurethane) is susceptible to eventual chemical degradation when subject to very high applied voltages thus implying that the number of tests should be strictly limited. We
therefore strongly advise against repeated high voltage isolation testing. but if it is absolutely required, that the voltage be reduced by 20% from specified test voltage.
This consideration equally applies to agency recognized parts for better than functional isolation where the wire enamel insulation is always supplemented by a further
insulation system of physical spacing or barriers.
OUTPUT RIPPLE REDUCTION
Output ripple reduction
By using the values of inductance and capacitance stated, the output ripple at the rated load is lowered to 5mV p-p max.
Component selection
Capacitor: Ceramic chip capacitors are recommended. It is required that the ESR(Equivalent Series Resistance)should be as low as possible.X7R types are recommended.
The voltage rating should be at least twice(except for 15V output),the rated output voltage of the DC/DC converter.
Inductor: The rated current of the inductor should not be less than of the output of the DC/DC converter. At the rated current, the DC resistance of the inductor should be
such that the voltage drop across the inductor is <2% of the rated voltage of the DC/DC converter. The SRF(Self Resonant Frequency) should be >20MHz.
CHARACTERISATION TEST METHODS
Ripple & Noise Characterization Method
Ripple and noise measurements are performed with the following test configuration.
C1
C2
1μF X7R multilayer ceramic capacitor, voltage rating to be a minimum of 3 times the output voltage of the DC/DC converter
10μF tantalum capacitor, voltage rating to be a minimum of 1.5 times the output voltage of the DC/DC converter with an ESR of less than 100mΩ at 100 KHz
100nF multilayer ceramic capacitor, general purpose
C3
R1
450Ω resistor, carbon film, ±1% tolerance
R2
50Ω BNC termination
T1
3T of the coax cable through a ferrite toroid
RLOAD
Resistive load to the maximum power rating of the DC/DC converter. Connections should be made via twisted wires
Measured values are multiplied by 10 to obtain the speciffied values.
Differential Mode Noise Test Schematic
http://www.microdc.cn Technical Enquiries-Email:tech@microdc.cn Tel:0086-20-86000646
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