EMI noise reduction circuit and method for bridgeless PFC circuit
View Patent ↗A circuit and method for improving EMI noise performance in a bridgeless PFC boost converter. Such a converter comprises a boost inductor having a first end connected to a first AC input terminal and a second end connected to a first junction defined between the anode of a first diode and a first terminal of a first switch; a second terminal of the first switch connected to a common line; a parallel circuit of a capacitance and a load connected between the cathode of the first diode and the common line; a series circuit of a second diode and a second switch connected between the cathode of the first diode and the common line; and a second AC input terminal connected to a second junction defined between the anode of the second diode and the second switch. High-frequency EMI noise is bypassed by placing a first filter capacitor between the first AC terminal and the common line. A second boost inductor may be connected between the second AC input terminal and the second junction, and a second filter capacitor may be connected between the second AC terminal and the common line. The first and/or second filter capacitor has a lower impedance in a high frequency range than the corresponding first or second boost inductor. Preferably the first and second capacitors have substantially the same capacitance.
1. A bridgeless PFC boost converter comprising:
a boost inductor having a first end connected to a first AC input terminal and a second end connected to a first junction defined between the anode of a first diode and a first terminal of a first switch;
a second terminal of the first switch connected to a common line;
a parallel circuit of a capacitance and a load connected between the cathode of the first diode and the common line;
a series circuit of a second diode and a second switch connected between the cathode of the first diode and the common line;
a second AC input terminal connected to a second junction defined between the anode of the second diode and the second switch; and
a first filter capacitor connected between said first AC terminal and said common line.
2. A bridgeless PFC boost converter according to claim 1 , wherein said first and second switches are MOSFETs.
3. A bridgeless PFC boost converter according to claim 2 , wherein said first and second switches are bidirectional MOSFETs.
4. A bridgeless PFC boost converter according to claim 1 , wherein said first and second switches are bidirectional switches.
5. A bridgeless PFC boost converter according to claim 4 , wherein said bidirectional switches are GaN devices.
6. A bridgeless PFC boost converter according to claim 1 , further comprising a second boost inductor connected between said second AC input terminal and said second junction, and a second filter capacitor connected between said second AC terminal and said common line.
7. A bridgeless PFC boost converter according to claim 6 , wherein said second filter capacitor has a lower impedance in a high frequency range than said second boost inductor.
8. A bridgeless PFC boost converter according to claim 6 , wherein said first and second capacitors have substantially the same capacitance.
9. A bridgeless PFC boost converter according to claim 1 , wherein said first and second switches are MOSFETs, each having a respective body diode whose cathode is connected to the corresponding one of said first and second junction points.
10. A bridgeless PFC boost converter according to claim 9 , wherein said MOSFETs each have a pair of main terminals connected respectively to said common line and to the corresponding one of said first and second junctions; and a gate terminal for controlling the MOSFET.
11. A bridgeless PFC boost converter according to claim 1 , wherein said first filter capacitor has a lower impedance in a high frequency range than said first boost inductor.
12. A method of reducing EMI noise in a bridgeless PFC boost converter comprising:
a boost inductor having a first end connected to a first AC input terminal and a second end connected to a first junction defined between the anode of a first diode and a first terminal of a first switch;
a second terminal of the first switch connected to a common line;
a parallel circuit of a capacitance and a load connected between the cathode of the first diode and the common line;
a series circuit of a second diode and a second switch connected between the cathode of the first diode and the common line; and
a second AC input terminal connected to a second junction defined between the anode of the second diode and the second switch;
the method comprising the step of connecting a first filter capacitor between said first AC terminal and said common line.
13. The method according to claim 12 , wherein a second boost inductor is connected between said second AC input terminal and said second junction, and further comprising the step of connecting a second filter capacitor between said second AC terminal and said common line.
14. The method according to claim 13 , further comprising the step of selecting said second filter capacitor to have a lower impedance in a high frequency range than said second boost inductor.
15. The method according to claim 13 , further comprising the step of providing said first and second filter capacitors with substantially the same capacitance.
16. The method according to claim 12 , further comprising the step of selecting said first filter capacitor to have a lower impedance in a high frequency range than said first boost inductor.