Single phase bi-directional AC-DC converter with reduced passive components size and common mode electro-magnetic interference
A bidirectional AC-DC converter is presented with reduced passive component size and common mode electro-magnetic interference. The converter includes an improved input stage formed by two coupled differential inductors, two coupled common and differential inductors, one differential capacitor and two common mode capacitors. With this input structure, the volume, weight and cost of the input stage can be reduced greatly. Additionally, the input current ripple and common mode electro-magnetic interference can be greatly attenuated, so lower switching frequency can be adopted to achieve higher efficiency.
1. An AC-DC converter, comprising:
a converter circuit configured to receive an AC input and operates to convert the AC input to DC output; and
an input filter interposed between the AC input and the AC-DC converter circuit, wherein the input filter comprising:
a pair of differential inductors coupled across an AC input, wherein a first differential inductor in the pair of differential inductors has a first terminal electrically connected to one side of the AC input, and a second differential inductor in the pair of differential inductors has a first terminal electrically connected to other side of the AC input, the first and second differential inductors being inductively coupled together and sharing a common core;
a pair of common inductors coupled in series with the pair of differential inductors, wherein a first common inductor in the pair of common inductors has a first terminal electrically coupled to a second terminal of the first differential inductor, and a second common inductor in the pair of common inductors has a first terminal electrically coupled to a second terminal of the second differential inductor, the first and second common inductors being inductively coupled together and sharing a common core;
a first common mode capacitor having a first terminal and a second terminal, where the first terminal of the first common mode capacitor is connected directly to the second terminal of the first differential inductor and the second terminal of the first common mode capacitor is connected directly to positive terminal of an output capacitor coupled across a load that receives the DC output;
a second common mode capacitor electrically coupled between the second terminal of the second differential inductor and ground; and
a differential capacitor electrically coupled across the AC input.
2. The AC-DC converter of claim 1 further comprises a second filter interposed between the input filter and the AC input and configured to filter electromagnetic interference from the AC input.
3. The AC-DC converter of claim 1 wherein coupling coefficient for the pair of differential inductors is on the order of one.
4. The AC-DC converter of claim 3 wherein coupling coefficient for the pair of common inductors is less than one.
5. The AC-DC converter of claim 4 wherein the differential capacitor having a first terminal electrically coupled to the second terminal of the first differential inductor and a second terminal electrically coupled to the second terminal of the second differential inductor.
6. The AC-DC converter of claim 1 further comprises a second pair of differential inductors coupled in series with the pair of common inductors, wherein a first differential inductor in the second pair of differential inductors has a first terminal electrically coupled to a second terminal of the first common inductor, and a second differential inductor in the second pair of differential inductors has a first terminal electrically coupled to a second terminal of the second common inductor, the first and second common inductors being inductively coupled together and sharing a common core.
7. The AC-DC converter of claim 1 wherein the converter circuit is further defined as a full bridge inverter having four switches.
8. The AC-DC converter of claim 7 further comprises a controller that generates driving signals to the four switches, wherein the driving signals are changed during both a first half and a second half of a switching period.
9. The AC-DC converter of claim 8 wherein the controller operates to control output of the converter circuit using a Kalman state estimator.
10. A high order filter circuit, comprising:
a pair of differential inductors coupled across an AC input, wherein a first differential inductor in the pair of differential inductors has a first terminal electrically connected to one side of the AC input, and a second differential inductor in the pair of differential inductors has a first terminal electrically connected to other side of the AC input, the first and second differential inductors being inductively coupled together and sharing a common core;
a pair of common inductors coupled in series with the pair of differential inductors, wherein a first common inductor in the pair of common inductors has a first terminal electrically coupled to a second terminal of the first differential inductor, and a second common inductor in the pair of common inductors has a first terminal electrically coupled to a second terminal of the second differential inductor, the first and second common inductors being inductively coupled together and sharing a common core;
a first common mode capacitor having a first terminal and a second terminal, where the first terminal of the first common mode capacitor is connected directly to the second terminal of the first differential inductor and the second terminal of the first common mode capacitor is connected directly to positive terminal of an output capacitor coupled across a load that receives the DC output;
a second common mode capacitor electrically coupled between the second terminal of the second differential inductor and ground; and
a differential capacitor electrically coupled across the AC input.
11. The high order filter of claim 10 wherein coupling coefficient for the pair of differential inductors is on the order of one.
12. The high order filter of claim 11 wherein coupling coefficient for the pair of common inductors is less than one.
13. The high order filter of claim 12 wherein the differential capacitor having a first terminal electrically coupled to the second terminal of the first differential inductor and a second terminal electrically coupled to the second terminal of the second differential inductor.
14. The high order filter of claim 10 further comprises a second pair of differential inductors coupled in series with the pair of common inductors, wherein a first differential inductor in the second pair of differential inductors has a first terminal electrically coupled to a second terminal of the first common inductor, and a second differential inductor in the second pair of differential inductors has a first terminal electrically coupled to a second terminal of the second common inductor, the first and second common inductors being inductively coupled together and sharing a common core.
15. The high order filter of claim 10 wherein the first common mode capacitor is electrically coupled in series with the second common mode capacitor.