Texas Instruments Evaluation Board for the LM5045 LM5045EVAL/NOPB LM5045EVAL/NOPB 数据表
产品代码
LM5045EVAL/NOPB
User's Guide
SNVA468C – February 2011 – Revised May 2013
AN-2111 LM5045 Evaluation Board
1
Introduction
The LM5045 evaluation board is designed to provide the design engineer with a fully functional power
converter based on the full-bridge topology to evaluate the LM5045 PWM controller. The evaluation board
is provided in an industry standard quarter brick footprint.
converter based on the full-bridge topology to evaluate the LM5045 PWM controller. The evaluation board
is provided in an industry standard quarter brick footprint.
The performance of the evaluation board is as follows:
•
Input operating range: 36V to 75V
•
Output voltage: 3.3V
•
Measured efficiency at 48V: 92% @ 30A
•
Frequency of operation: 420kHz
•
Board size: 2.28 x 1.45 x 0.5 inches
•
Load Regulation: 0.2%
•
Line Regulation: 0.1%
•
Line UVLO (34V/32V on/off)
•
Hiccup Mode Current Limit
The printed circuit board consists of 6 layers; 2 ounce copper outer layers and 3 ounce copper inner
layers on FR4 material with a total thickness of 0.062 inches. The unit is designed for continuous
operation at rated load at <40°C and a minimum airflow of 200 LFM.
layers on FR4 material with a total thickness of 0.062 inches. The unit is designed for continuous
operation at rated load at <40°C and a minimum airflow of 200 LFM.
2
Theory of Operation
Power converters based on the full-bridge topology offer high-efficiency and good power handling
capability up to 500W.
capability up to 500W.
illustrates the circuit arrangement for the full-bridge topology. The
switches, in the diagonal, Q1,Q3 and Q2,Q4 are turned alternatively with a pulse width determined by the
input and output voltages and the transformer turns ratio. Each diagonal (Q1 and Q3 or Q2 and Q4), when
turned ON, applies input voltage across the primary of the transformer. The resulting secondary voltage is
then rectified and filtered with an LC filter to provide a smoothened output voltage. In a full-bridge
topology, the primary switches are turned on alternatively energizing the windings in such a way that the
flux swings back and forth in the first and the third quadrants of the B-H curve. The use of two quadrants
allows better utilization of the core resulting in a smaller core volume compared to the single-ended
topologies such as a forward converter. Further, in a half-bridge topology, during power transfer when one
of the primary switches is active, the voltage across the primary of the power transformer is 1/2 the input
voltage (VIN) compared to a full VIN in a full-bridge topology. Therefore, for a given power, the primary
current will be half as much for the full-bridge as compared to the half-bridge. The reduced primary current
enables higher efficiency as compared to a half-bridge at high load currents.
input and output voltages and the transformer turns ratio. Each diagonal (Q1 and Q3 or Q2 and Q4), when
turned ON, applies input voltage across the primary of the transformer. The resulting secondary voltage is
then rectified and filtered with an LC filter to provide a smoothened output voltage. In a full-bridge
topology, the primary switches are turned on alternatively energizing the windings in such a way that the
flux swings back and forth in the first and the third quadrants of the B-H curve. The use of two quadrants
allows better utilization of the core resulting in a smaller core volume compared to the single-ended
topologies such as a forward converter. Further, in a half-bridge topology, during power transfer when one
of the primary switches is active, the voltage across the primary of the power transformer is 1/2 the input
voltage (VIN) compared to a full VIN in a full-bridge topology. Therefore, for a given power, the primary
current will be half as much for the full-bridge as compared to the half-bridge. The reduced primary current
enables higher efficiency as compared to a half-bridge at high load currents.
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1
SNVA468C – February 2011 – Revised May 2013
AN-2111 LM5045 Evaluation Board
Copyright © 2011–2013, Texas Instruments Incorporated