This power supply is a 140-W, full-bridge reference design for applications requiring high density and low component heights due to the planar transformer. The design is based on a hard-switched full bridge topology, using Schottky diodes on the secondary side, driven by the LM5045. A planar transformer is used to minimize the footprint and height. The printed circuit board (PCB) has six layers and the components are assembled top and bottom. The unit is designed for continuous operation at a rated load at TA < 40°C. A minimum airflow of 200 linear feet per minute (LFM) is recommended for higher ambient temperature.
Parameter | Specifications |
---|---|
Input Voltage | 19 VDC to 30 VDC |
Output Voltage | 56 VDC |
Output Current | 2.5 A |
The board is built on PCB PMP30900RevA.
The board dimensions are 88.9 mm × 46.99 mm, with the height of 11.34 mm (Transformer T1), while the net PCB area dimensions are 84.22 mm x 43.2 mm.
The copper thickness of the six layer board is 70 µm on the outer layers and 35 µm on the inner layers (70-30-30-30-30-70).
Figure 2-1 shows the efficiency graph of the power supply versus output current. The input voltage has been set to 18 VDC, 24 VDC, and 30 VDC.
Efficiency data is shown in the following tables.
VIN (V) | IIN (A) | PIN (W) | VOUT (V) | IOUT (A) | POUT (W) | Efficiency (%) |
---|---|---|---|---|---|---|
18.010 | 0.022 | 0.398 | 56.300 | 0.000 | 0 | 0.0% |
18.010 | 0.242 | 4.357 | 56.300 | 0.050 | 2.815 | 64.61% |
18.000 | 0.406 | 7.306 | 56.300 | 0.101 | 5.703 | 78.06% |
18.050 | 0.723 | 13.050 | 56.290 | 0.200 | 11.281 | 86.44% |
18.040 | 1.724 | 31.101 | 56.290 | 0.503 | 28.291 | 90.97% |
18.018 | 3.327 | 59.946 | 56.210 | 1.007 | 56.603 | 94.42% |
18.023 | 6.681 | 120.412 | 56.260 | 2.002 | 112.63 | 93.54% |
18.030 | 8.384 | 151.164 | 56.250 | 2.501 | 140.68 | 93.07% |
VIN (V) | IIN (A) | PIN (W) | VOUT (V) | IOUT (A) | POUT (W) | Efficiency (%) |
---|---|---|---|---|---|---|
24.070 | 0.016 | 0.378 | 56.300 | 0.000 | 0 | 0.0% |
24.040 | 0.205 | 4.938 | 56.300 | 0.051 | 2.866 | 58.04% |
24.000 | 0.336 | 8.059 | 56.300 | 0.101 | 5.664 | 70.28% |
24.000 | 0.567 | 13.603 | 56.290 | 0.200 | 11.264 | 82.80% |
24.000 | 1.305 | 31.320 | 56.280 | 0.503 | 28.326 | 90.44% |
24.080 | 2.559 | 61.621 | 56.260 | 1.004 | 56.491 | 91.67% |
24.070 | 5.084 | 122.372 | 56.250 | 2.016 | 113.40 | 92.67% |
24.070 | 6.343 | 152.676 | 56.240 | 2.506 | 140.94 | 92.31% |
VIN (V) | IIN (A) | PIN (W) | VOUT (V) | IOUT (A) | POUT (W) | Efficiency (%) |
---|---|---|---|---|---|---|
30.03 | 0.0170 | 0.511 | 56.25 | 0 | 0 | 0.0% |
30.02 | 0.1817 | 5.455 | 56.26 | 0.0507 | 2.852 | 52.29% |
30.02 | 0.3012 | 9.042 | 56.27 | 0.1004 | 5.650 | 62.48% |
30.01 | 0.4733 | 14.204 | 56.27 | 0.2014 | 11.333 | 79.79% |
30.05 | 1.0913 | 32.794 | 56.27 | 0.5035 | 28.332 | 86.39% |
30.04 | 2.096 | 62.964 | 56.26 | 1.004 | 56.479 | 89.70% |
30.01 | 4.130 | 123.941 | 56.24 | 2.014 | 113.27 | 91.39% |
30.03 | 5.153 | 154.745 | 56.24 | 2.508 | 141.05 | 91.15% |
The graphs in Figure 2-2 and Figure 2-3 show the thermal pictures of the converter supplied at 24 VDC at full load. Table 2-4 and Table 2-5 represent the corresponding values of the main image markers.
Thermal shots were taken after the board was running for 30 minutes at an ambient temperature of 25°C.
The board runs at full load with a fan, placed on the right side of the prototype.
Name | Temperature | Emissivity | Background |
---|---|---|---|
T1 | 59.9°C | 0.96 | 25.5°C |
T1 Core | 55.3°C | 0.96 | 25.5°C |
Diodes (secondary side) | 56.4°C | 0.96 | 25.5°C |
L4 | 39.8°C | 0.96 | 25.5°C |
Name | Temperature | Emissivity | Background |
---|---|---|---|
Q9 | 55.9°C | 0.96 | 25.5°C |
Q7 | 55.5°C | 0.96 | 25.5°C |
D19 | 69.6°C | 0.96 | 25.5°C |
D18 | 65.3°C | 0.96 | 25.5°C |
R11 | 66.5°C | 0.96 | 25.5°C |
R17 | 68.5°C | 0.96 | 25.5°C |
Q1 | 46.3°C | 0.96 | 25.5°C |
D15 | 66.0°C | 0.96 | 25.5°C |
U1 | 44.6°C | 0.96 | 25.5°C |
Q8 | 52.2°C | 0.96 | 25.5°C |
Q6 | 54.5°C | 0.96 | 25.5°C |
The graph in Figure 2-4 shows the bode plot of the converter, when supplied at 24 VDC and loaded at 2.5 A. Here are the results, in terms of crossover frequency, phase margin, and gain margin:
Parameter | Full Load |
---|---|
Crossover frequency | 2.859 kHz |
Phase margin | 80.84° |
Gain margin | 29.25 dB |
The switching waveforms were measured by supplying the converter at 30 VDC and full load.
The waveform in Figure 3-1 represents the switching behavior measured on diode D4-cathode to IGND.
The output voltage ripple was measured by supplying the converter at 24 VDC and full load; the bandwidth limit of the scope was set to 20 MHz.
The output voltage variation, during load transients, was measured by supplying the converter at 24 VDC and by switching the load current between 1.25 A and 2 A. For all waveforms, the bandwidth limit of the oscilloscope was set to 20 MHz
The screen shots in Figure 3-7 and Figure 3-8 show the output voltage behavior during start-up, at VIN = 24 VDC.
The following screen shots (Figure 3-9 and Figure 3-10) show the output voltage during start-up and overload protection, when the converter was loaded at 3.5 A.
The same condition as in Figure 3-9 with different time base results in Figure 3-10.
The output voltage has been measured by switching off the DC voltage source while the load was set to 2.5 A and VIN to 24 VDC
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