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Performance Characteristics

3.2 Air Flow

Prolonged operation at full power and high ambient temperature will cause the thermal shutdown circuit

within the regulator IC to activate. A fan with a minimum of 200 LFM should always be provided.

3.3 Powering Up

Using the ENABLE pin (J7) provided will allow powering up the input source with the current level set low.

It is suggested that the load power be kept low during the first power up. Set the current limit of the input

source to provide about 1.5 times the anticipated wattage of the load. As you remove the connection from

the ENABLE pin to GND (J5), immediately check for 5 volts at the output.

A quick efficiency check is the best way to confirm that everything is operating properly. If something is

amiss you can be reasonably sure that it will affect the efficiency adversely. Few parameters can be

incorrect in a switching power supply without creating losses and potentially damaging heat.

3.4 Over Current Protection

The evaluation board is configured with cycle-by-cycle over-current protection. This function is completely

contained in the LM5001. The Primary current is limited to approximately 1A. This equates to about 1.4A

load current when the input voltage is 16V, and about 2.1A load current when the input is 42V. The

thermal stress on various circuit components is quite severe while in an overloaded condition, therefore

limit the duration of the overload and provide sufficient cooling (airflow).

3.5 Synchronization

A SYNC pin (J6) has been provided on the evaluation board. This pin can be used to synchronize the

regulator to an external clock or multiple evaluation boards can be synchronized together by connecting

their SYNC pins together. Refer to the LM5001 High Voltage Switch Mode Regulator (SNVS484) data

sheet for complete information.

3.6 Flyback Topology

An excellent introduction to the isolated flyback converter is available on the Texas Instruments website.

The Application Note AN-1095(SNVA005) discusses both loop compensation with a secondary side error

amplifier and the phase-shift caused by opto-couplers.

4 Performance Characteristics

Efficiency Plots

Figure 1 shows the conversion efficiency versus output current for several input voltage conditions.

Figure 1. Conversion Efficiency vs Output Current

SNVA221B–February 2007–Revised April 2013 AN-1588 LM5001 Evaluation Board

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