400-W AC/DC Reference Design for Avionics
Description
This board is a compact, 30-V DC, 400-W reference design for avionics applications, working with mains frequency between 400 Hz and 800 Hz. A two-phase interleaved transition mode (TM) power factor correction (PFC) based on the UCC28064A is used to correct power factor and at the same time to minimizes harmonic content of input current. The DC/DC is implemented employing the HB-LLC stage, using UCC256404 device. The efficiency is further improved by using synchronous rectification on the secondary side.
The reference design PMP31179 Rev_A was built on the PMP30763 Rev_D PCB.
Features
- Maximum 400-W output power at 96 VAC–134 VAC grid connection
- Two-stage converter achieving 92.8% plug-to-plug efficiency:
- First stage: PFC interleaved Boost (97% efficiency) with UCC28064A, allows reduced EMI filter size and increases efficiency
- Second stage: half-bridge resonant LLC converter (95% efficiency) isolates HV input, and supplies 30 V, 13.3 A
- No need of an auxiliary power supply, since the second stage provides the bias voltage for the PFC
- Specifically designed to comply with DO160-G harmonic limits in avionics applications for mains frequency in the 400 Hz–800 Hz range
Applications
1 Test Prerequisites
1.1 Voltage and Current Requirements
| Parameter | Specifications |
|---|---|
| Input Voltage | 96 VAC–134 VAC |
| Frequency | 400 Hz–800 Hz |
| Output, Voltage | 30 VDC |
| Output, Current | 13.3 A |
1.2 Required Equipment
- 0–150 VAC, 400 Hz–800 Hz (minimum current limit 7 ARMS), AC constant voltage source (VS1)
- Electronic load, (constant current range 0–15 A)
- Oscilloscope (minimum 100-MHz bandwidth)
- Current probe (minimum 100-kHz bandwidth)
- Optional: infrared camera
1.3 Dimensions
The board dimensions are 218.44 mm x 102.26 mm, height 31.75 mm (transformer T1).
1.4 Test Setup
- Connect the source VS1 to J3-1 and J3-2; earth connection to J3-3
- Connect the load to terminals “30V” (plus) and “R_SENSE” (minus)
- Attach a current probe in series to VS1 to measure the input current
- Attach a current probe in series to L7 (by disconnecting one pin) to measure the resonant current
- Turn on VS1 (accepted range: 96 VAC…134 VAC).
- Increase the load on the
outputWARNING: The following step involves working with high voltage. To minimize the risk of personal injury, never touch the board or its electrical circuits, as they could be at high voltages capable of causing an electrical shock hazard.
- After turn off, discharge the capacitors C1A, C1B, and C1C (PFC capacitors) by means of an external resistor or active discharge circuit
2 Testing and Results
2.1 Efficiency Graphs
Figure 2-1 shows the plug-to-plug converter efficiency, versus output power.
The input voltage was set to 96 VAC, 115 VAC, and 134 VAC, while the mains frequency was 400 Hz.
Figure 2-1 Efficiency Graph for Three Different VAC Input
Voltages, Versus Output Power2.2 Efficiency Data
Efficiency data is shown in the following tables.
| V_pfc (V) | PIN (W) | PF (%) | iTHD (%) | VOUT (V) | IOUT (A) | POUT (W) | Efficiency (%) |
|---|---|---|---|---|---|---|---|
|
238.7 |
0.58 |
0.0 |
0.00 |
29.93 |
0.000 |
0.00 |
0.00% |
|
238.6 |
5.35 |
25.1 |
20.0 |
29.93 |
0.104 |
3.12 |
58.26% |
|
238.6 |
14.52 |
49.2 |
36.5 |
29.93 |
0.305 |
9.12 |
62.83% |
|
238.5 |
28.95 |
70.7 |
29.6 |
29.93 |
0.709 |
21.23 |
73.34% |
|
238.4 |
59.87 |
88.2 |
19.33 |
29.93 |
1.720 |
51.49 |
86.01% |
|
238.4 |
117.64 |
95.8 |
15.54 |
29.92 |
3.538 |
105.86 |
89.99% |
|
238.3 |
214.08 |
98.8 |
7.740 |
29.92 |
6.566 |
196.47 |
91.77% |
|
238.2 |
442.00 |
99.8 |
4.970 |
29.90 |
13.41 |
401.07 |
90.74% |
| V_pfc (V) | PIN (W) | PF (%) | iTHD (%) | VOUT (V) | IOUT (A) | POUT (W) | Efficiency (%) |
|---|---|---|---|---|---|---|---|
|
238.8 |
0.56 |
0.0 |
0.00 |
29.94 |
0.000 |
0.00 |
0.00% |
|
238.7 |
5.19 |
18.7 |
15.0 |
29.94 |
0.104 |
3.12 |
60.09% |
|
238.7 |
14.09 |
38.3 |
29.9 |
29.94 |
0.305 |
9.13 |
64.79% |
|
238.6 |
28.82 |
59.7 |
35.7 |
29.94 |
0.710 |
21.25 |
73.72% |
|
238.5 |
59.68 |
80.2 |
24.28 |
29.93 |
1.721 |
51.50 |
86.30% |
|
238.4 |
117.23 |
92.4 |
17.83 |
29.93 |
3.539 |
105.91 |
90.34% |
|
238.3 |
212.78 |
97.6 |
9.230 |
29.92 |
6.567 |
196.49 |
92.34% |
|
238.3 |
437.50 |
99.5 |
5.207 |
29.91 |
13.42 |
401.28 |
91.72% |
| V_pfc (V) | PIN (W) | PF (%) | iTHD (%) | VOUT (V) | IOUT (A) | POUT(W) | Efficiency (%) |
|---|---|---|---|---|---|---|---|
|
238.7 |
0.54 |
0.0 |
0.00 |
29.93 |
0.000 |
0.00 |
0.00% |
|
238.6 |
5.04 |
14.2 |
10.2 |
29.93 |
0.105 |
3.13 |
62.08% |
|
238.5 |
13.59 |
30.7 |
21.4 |
29.93 |
0.305 |
9.14 |
67.26% |
|
238.5 |
28.23 |
49.7 |
32.8 |
29.92 |
0.710 |
21.24 |
75.25% |
|
238.4 |
59.38 |
72.3 |
29.54 |
29.92 |
1.721 |
51.49 |
86.72% |
|
238.3 |
115.69 |
87.8 |
17.03 |
29.92 |
3.539 |
105.87 |
91.52% |
|
238.2 |
211.73 |
95.4 |
12.69 |
29.91 |
6.568 |
196.44 |
92.78% |
|
238.2 |
435.10 |
99.0 |
5.810 |
29.90 |
13.42 |
401.23 |
92.22% |
2.3 Power Factor and iTHD Versus Load, VAC and Frequency
The power factor value was measured by varying the converter output power in the whole load range, for different VAC, repeated at 400-Hz and 800-Hz mains frequency.
Figure 2-2 Power Factor Versus Output
Power at 400 Hz
Figure 2-3 Power Factor Versus Output
Power at 800 Hz
Figure 2-4 iTHD Versus Output Power at
400 Hz
Figure 2-5 iTHD Versus Output Power at
800 Hz2.3.1 Power Factor and iTHD Tables
The following tables show all values of power factor (PF) and input current harmonic distortion (iTHD) versus output power.
| PF (%) | iTHD (%) | POUT (W) |
|---|---|---|
|
0.00 |
0.00 |
0.00 |
|
10.8 |
10.2 |
3.12 |
|
24.0 |
28.1 |
9.13 |
|
40.4 |
46.7 |
21.25 |
|
61.2 |
37.07 |
51.50 |
|
80.4 |
25.90 |
105.91 |
|
92.5 |
14.52 |
196.49 |
|
98.6 |
6.38 |
401.28 |
| PF (%) | iTHD (%) | POUT (W) |
|---|---|---|
|
0.00 |
0.00 |
0.00 |
|
14.7 |
17.8 |
3.12 |
|
31.9 |
38.2 |
9.12 |
|
50.9 |
42.3 |
21.23 |
|
72.4 |
30.40 |
51.49 |
|
88.9 |
20.17 |
105.86 |
|
96.5 |
9.84 |
196.47 |
|
99.6 |
5.56 |
401.07 |
| PF (%) | iTHD (%) | POUT (W) |
|---|---|---|
|
0.00 |
0.00 |
0.00 |
|
8.0 |
0.0 |
3.13 |
|
18.9 |
19.7 |
9.14 |
|
33.1 |
34.4 |
21.24 |
|
53.1 |
42.06 |
51.49 |
|
70.8 |
30.97 |
105.87 |
|
87.1 |
19.88 |
196.44 |
|
96.7 |
8.05 |
401.23 |
2.4 Thermal Image
Figure 2-6 and Table 2-7 show the thermal picture of the converter supplied at 115 VAC and 400 Hz, taken after 30 minutes soak time, at 25°C ambient temperature.
The board runs at full load with a fan, placed on the side (DC/DC output).
Figure 2-6 Thermal Image, 30 Minutes, Full Load| Name | Temperature | Emissivity | Background |
|---|---|---|---|
|
D3 |
64.9°C |
0.96 |
25.5°C |
|
L2 |
42.7°C |
0.96 |
25.5°C |
|
L1 |
37.3°C |
0.96 |
25.5°C |
|
Q1 |
37.1°C |
0.96 |
25.5°C |
|
D1 |
43.8°C |
0.96 |
25.5°C |
|
D5 |
41.5°C |
0.96 |
25.5°C |
|
L7 |
35.5°C |
0.96 |
25.5°C |
|
T1 |
75.5°C |
0.96 |
25.5°C |
|
Q5 |
45.1°C |
0.96 |
25.5°C |
|
Q7 |
44.1°C |
0.96 |
25.5°C |