Texas Instruments Evaluation Boards for LM25037 - Dual PWM Controller with Alternating Outputs LM25037EVAL/NOPB LM25037EVAL/NOPB Datenbogen
Produktcode
LM25037EVAL/NOPB
50 Volt , 5 Amp
Power Supply
With Current
Meter
100 W , 20 Amp
Electronic
Load
+
-
+
-
Volt- Meter
Volt- Meter
Current-Meter
IN
OUT
Evaluation
Board
Scope
Performance Characteristics
If it is desired to power up the evaluation board at maximum load, resistor banks can be used. This will
ensure a soft-start and evaluation board will perform as desired. The high output current requires thick
cables! If resistor banks are used there are certain precautions to be taken. The resistance for maximum
load is 0.5
ensure a soft-start and evaluation board will perform as desired. The high output current requires thick
cables! If resistor banks are used there are certain precautions to be taken. The resistance for maximum
load is 0.5
Ω
. The wattage and current ratings must be adequate for a 10A, 60W supply. Monitor both
current and voltage at all times. Ensure there is sufficient cooling provided for the load.
3.4
Air Flow
Full power loading should never be attempted without providing the specified 200 LFM of air flow over the
evaluation board. A stand-alone fan should be provided.
evaluation board. A stand-alone fan should be provided.
3.5
Powering Up
It is suggested to set the current limit of the source supply to provide about 1.5 times the wattage of the
load.
load.
A most common occurrence, that will prove unnerving, is when the current limit set on the source supply is
insufficient for the load. The result is similar to having the high source impedance referred to earlier. The
interaction of the source supply folding back and the evaluation board going into under-voltage shutdown
will start an oscillation, or chatter, that may have undesirable consequences.
insufficient for the load. The result is similar to having the high source impedance referred to earlier. The
interaction of the source supply folding back and the evaluation board going into under-voltage shutdown
will start an oscillation, or chatter, that may have undesirable consequences.
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.
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.
3.6
Over Current Protection
The evaluation board is configured with hiccup over-current protection. In the event of an output overload
(approximately 14A@16V Input) the unit will discharge the soft-start capacitor, which disables the power
stage. After a delay the soft-start is released. The shutdown, delay and slow recharge time of the soft-start
capacitor protects the unit, especially during a short circuit event where the stress is highest.
(approximately 14A@16V Input) the unit will discharge the soft-start capacitor, which disables the power
stage. After a delay the soft-start is released. The shutdown, delay and slow recharge time of the soft-start
capacitor protects the unit, especially during a short circuit event where the stress is highest.
Figure 2. Typical Evaluation Setup
4
Performance Characteristics
Once the circuit is powered up and running normally, the output voltage is regulated to 5.0V, with the
accuracy determined by feedback resistors and bandgap reference voltage inside the IC. When the load
current is varied from 5A to 10A, the regulator output should vary less than 100 mV. The frequency of
operation is selected to be 250 kHz, which is a good compromise between board size and efficiency. The
efficiency of the power converter is measured to be 88% at 24V and 10A. Please refer to
accuracy determined by feedback resistors and bandgap reference voltage inside the IC. When the load
current is varied from 5A to 10A, the regulator output should vary less than 100 mV. The frequency of
operation is selected to be 250 kHz, which is a good compromise between board size and efficiency. The
efficiency of the power converter is measured to be 88% at 24V and 10A. Please refer to
for
efficiency curves.
3
SNVA352C – July 2008 – Revised May 2013
AN-1861 LM25037 Evaluation Board
Copyright © 2008–2013, Texas Instruments Incorporated