Quick Start Procedure - Linear Technology DC1929A Demo Manual

DEMO MANUAL DC1929A

Quick start proceDure

IMPORTANT NOTE TO CUSTOMERS:
HAZARDOUS HIGH VOLTAGES ARE PRESENTED ON
THE DEMO CIRCUIT. IMPROPER OR UNSAFE HAN-
DLING OF THIS DEMO BOARD CAN LEAD TO LETHAL
INJURIES TO HUMAN BODY. ONLY QUALIFIED PER-
SONEL SHOULD OPERATE IT. YOU ARE STRONGLY
RECOMMENDED TO USE SAFETY GLASSES AND
AN ISOLATION TRANSFORMER. IMPROPER COM-
PONENTS REPLACEMENT ON THE DEMO CIRCUIT
CAN CAUSE PERFORMANCE DETERIORATIONS,
CIRCUIT MALFUNCTION, PROPERTY DAMAGE, AND
EVEN LIFE-THREATHENING INJURIES. CONTACT
LINEAR TECHNOLOGY APPLICATIONS ENGINEERS
FOR PROPER COMPONENT REPLACEMENT AND
CIRCUIT MODIFICATION.
Demonstration circuit 1929A must be set up as follows
to evaluate the performance of the LT3752-1/LT8311.
Refer to Figure 1 for proper equipment setup and follow
the procedure below.
NOTE. Do not operate DC1929A unless you have the ap-
propriate safety precautions in place on your bench to
guarantee safety. Always remove power before touching,
servicing, or attaching probes to the demo board. Never
leave the DC1929A unattended when under power.
1. With power off, connect the input power supply to the
board. The power supply should be adjustable over
100V ~ 450V range, and at least 3A current capability.
An ammeter capable of measuring 3ADC can be put in
series with the input supply to measure the input cur-
rent. Connect the load to the terminals V
–
V (J2) on the board. The load should be adjustable
OUT
up to 20A. If efficiency measurements are desired, an
ammeter capable of measuring 20ADC or a resistor
shunt can be put in series with the load to measure the
output current. A voltmeter can be placed across the
output terminals (E4, E5) in order to get an accurate
output voltage measurement.
2. Direct airflow of 300LFM across the demo circuit for
sustained operation at full load. Refer to Figure 1 for
proper airflow direction.
2
3. Turn on the power at the input. Increase V
150V.
NOTE. Make sure that the input voltage does not exceed
400V. Make sure the load current does not exceed the
specifications.
NOTE. Check the standby current without any load applied
and it should be less or around 25mA at 150V input, or
20mA at 400V input. Any cross-conduction of the primary-
secondary switches will significantly increase the standby
current.
4. Check for the proper output voltages. The output should
be regulated at 12.0V (±2%).
NOTE. If there is no output, temporarily disconnect the
load to make sure that the load is not set too high.
NOTE. By removing the resistor R2, and applying the V
between V
nected from the control/bias circuits, and the control/bias
circuit can be debugged separately. The standby current
of the control/bias circuit should be less than 2mA.
NOTE. By removing R37 and R40, and adjusting R25 to
107k, the feedback loop is disabled, and the circuit runs
in no-opto bus converter mode.
5. Once the proper output voltage is established, adjust
the input voltage and load current within the operating
range and observe the output voltage regulation, ripple
voltage, efficiency and other parameters.
NOTE. When measuring the output voltage ripples, care
must be taken to avoid a long ground lead on the oscillo-
+
(J1) and
OUT
scope probe. See Figure 2 for proper scope probe technique.
NOTE. Airflow should be directed to the demo circuit ac-
cording to the direction shown in Figure 1. Running the
circuit at full load without airflow could overheat the power
components, and lead to damage of the board. Overload
operation of the demo circuit is feasible for short-term only.
Long term overcurrent operation is not recommended,
unless enhanced cooling methods are used.
6. Turn off the load at the output, the power at the input,
and then turn off the airflow.
and –V , the main power circuit is discon-
B IN
slowly to
IN
IN
dc1929afa