Texas Instruments Evaluation Board for the LM5045 LM5045EVAL/NOPB LM5045EVAL/NOPB Datenbogen
Produktcode
LM5045EVAL/NOPB
Vout
T1
T1
Vin
ISOLATED
FEEDBACK
VCC
REF
AGND
PGND
SS SR
RES
RT
UVLO
VIN
HO1 BST1
HS1
LO1
CS
LO2
HS2 BST2
HO2
COMP
FULL-BRIDGE
CONTROLLER
WITH INTEGRATED GATE
DRIVERS
RD1
RD2
GATE
DRIVE
ISOLATION
SR1
SR2
VCC
VCC
SS
SLOPE
OVP
Q4
Q1
Q2
Q3
Powering and Loading Considerations
Figure 1. Simplified Full-Bridge Converter
The secondary side employs synchronous rectification scheme, which is controlled by the LM5045. In
addition to the basic soft-start already described, the LM5045 contains a second soft-start function that
gradually turns on the synchronous rectifiers to their steady-state duty cycle. This function keeps the
synchronous rectifiers off until the error amplifier on the secondary side soft-starts, allowing a linear start-
up of the output voltage even into pre-biased loads. Then the SR output duty cycle is gradually increased
to prevent output voltage disturbances due to the difference in the voltage drop between the body diode
and the channel resistance of the synchronous MOSFETs. Once the soft-start is finished, the synchronous
rectifiers are engaged with a non-overlap time programmed by the RD1 and RD2 resistors. Feedback from
the output is processed by an amplifier and reference, generating an error voltage, which is coupled back
to the primary side control through an opto-coupler. The LM5045 evaluation board employs peak current
mode control and a standard “type II” network is used for the compensator.
addition to the basic soft-start already described, the LM5045 contains a second soft-start function that
gradually turns on the synchronous rectifiers to their steady-state duty cycle. This function keeps the
synchronous rectifiers off until the error amplifier on the secondary side soft-starts, allowing a linear start-
up of the output voltage even into pre-biased loads. Then the SR output duty cycle is gradually increased
to prevent output voltage disturbances due to the difference in the voltage drop between the body diode
and the channel resistance of the synchronous MOSFETs. Once the soft-start is finished, the synchronous
rectifiers are engaged with a non-overlap time programmed by the RD1 and RD2 resistors. Feedback from
the output is processed by an amplifier and reference, generating an error voltage, which is coupled back
to the primary side control through an opto-coupler. The LM5045 evaluation board employs peak current
mode control and a standard “type II” network is used for the compensator.
3
Powering and Loading Considerations
When applying power to the LM5045 evaluation board certain precautions need to be followed. A
misconnection can damage the assembly.
misconnection can damage the assembly.
4
Proper Connections
When operated at low input voltages the evaluation board can draw up to 3.5A of current at full load. The
maximum rated output current is 30A. Be sure to choose the correct connector and wire size when
attaching the source supply and the load. Monitor the current into and out of the evaluation board. Monitor
the voltage directly at the output terminals of the evaluation board. The voltage drop across the load
connecting wires will give inaccurate measurements. This is especially true for accurate efficiency
measurements.
maximum rated output current is 30A. Be sure to choose the correct connector and wire size when
attaching the source supply and the load. Monitor the current into and out of the evaluation board. Monitor
the voltage directly at the output terminals of the evaluation board. The voltage drop across the load
connecting wires will give inaccurate measurements. This is especially true for accurate efficiency
measurements.
2
AN-2111 LM5045 Evaluation Board
SNVA468C – February 2011 – Revised May 2013
Copyright © 2011–2013, Texas Instruments Incorporated