Phase-shifted resonant converter having reduced output ripple
View Patent ↗A power converter comprises a pair of resonant converter circuits coupled together in parallel and operated at respective switching frequencies that are out of phase. The power converter includes a first resonant converter circuit and a second resonant converter circuit operatively coupled together. The first resonant converter circuit includes at least one power switch adapted to convey power to a first resonant circuit and a first rectification stage adapted to rectify the conveyed power from the first resonant circuit. The second resonant converter circuit includes at least one power switch adapted to convey power to a second resonant circuit and a second rectification stage adapted to rectify the conveyed power from the second resonant circuit. A filter capacitor is coupled to the first and second rectification stages to provide DC output power therefrom. A regulator is operatively coupled to the first and second resonant converters to control switching frequency of the power switches, such that the switching frequency of the at least one power switch of the second resonant converter is shifted in phase with respect to the switching frequency of the at least one power switch of the second resonant converter. In a preferred embodiment, the switching frequency of the at least one power switch of the second resonant converter is shifted in phase by approximately 90° with respect to the switching frequency of the at least one power switch of the second resonant converter.
1. A power converter comprising:
a first resonant converter circuit including at least one power switch adapted to convey power to a first resonant circuit and a first rectification stage adapted to rectify said conveyed power from said first resonant circuit;
a second resonant converter circuit including at least one power switch adapted to convey power to a second resonant circuit and a second rectification stage adapted to rectify said conveyed power from said second resonant circuit;
a filter capacitor coupled to said first and second rectification stages to provide DC output power therefrom;
a regulator operatively coupled to said first and second resonant converters to control switching frequency of said at least one power switch of each of said first and second resonant converters, such that switching frequency of said at least one power switch of said second resonant converter is shifted in phase with respect to switching frequency of said at least one power switch of said first resonant converter;
wherein rms ripple current (I r ) applied to said filter capacitor may be characterized in accordance with the following equation:
I
r
=
2
π
∫
0
π
2
(
I
p
sin
t
+
I
p
cos
t
-
I
out
)
2
ⅆ
t
wherein I p is a sinusoidal current waveform applied to said first and second rectification stages and I out is DC output current; and
wherein said ripple current I r applied to said filter capacitor is approximately 9.5% of the DC output current I out .
2. A power converter comprising:
a first resonant converter circuit including at least one power switch adapted to convey power to a first resonant circuit and a first rectification stage adapted to rectify said conveyed power from said first resonant circuit;
a second resonant converter circuit including at least one power switch adapted to convey power to a second resonant circuit and a second rectification stage adapted to rectify said conveyed power from said second resonant circuit;
a filter capacitor coupled to said first and second rectification stages to provide DC output power therefrom;
a regulator operatively coupled to said first and second resonant converters to control switching frequency of said at least one power switch of each of said first and second resonant converters, such that switching frequency of said at least one power switch of said second resonant converter is shifted in phase with respect to switching frequency of said at least one power switch of said first resonant converter;
wherein, each of said first and second resonant circuit further comprises an inductor, a transformer having a primary winding in series with said inductor, first and second capacitors in series with said primary winding and connected across an input voltage source, and first and second diodes coupled in parallel respectively with said first and second capacitors.
3. A power converter of claim 2 , wherein said switching frequency of said at least one power switch of said second resonant converter is shifted in phase by approximately 90° with respect to said switching frequency of said at least one power switch of said first resonant converter.
4. The power converter of claim 2 , wherein rms ripple current (I r ) applied to said filter capacitor may be characterized in accordance with the following equation:
I
r
=
2
π
∫
0
π
2
(
I
p
sin
t
+
I
p
cos
t
-
I
out
)
2
ⅆ
t
wherein I p is a sinusoidal current waveform applied to said first and second rectification stages and I out is DC output current.
5. The power converter of claim 2 , further comprising an additional capacitor operatively coupled between said primary winding and said first and second capacitors.
6. The power converter of claim 2 , further comprising additional first and second capacitors coupled in series respectively with said first and second capacitors.
7. A power converter comprising:
a first resonant converter circuit including at least one power switch adapted to convey power to a first resonant circuit and a first rectification stage adapted to rectify said conveyed power from said first resonant circuit;
a second resonant converter circuit including at least one power switch adapted to convey power to a second resonant circuit and a second rectification stage adaoted to rectify said conveyed power from said second resonant circuit;
a filter capacitor coupled to said first and second rectification stages to provide DC output power therefrom;
a regulator operatively coupled to said first and second resonant converters to control switching frequency of said at least one power switch of each of said first and second resonant converters, such that switching frequency of said at least one power switch of said second resonant converter is shifted in phase with respect to switching frequency of said at least one power switch of said first resonant converter; and
means for limiting current that passes through at least one of said first and second resonant circuits.
8. A power converter comprising:
a first resonant converter circuit including at least one power switch adapted to convey power to a first resonant circuit and a first rectification stage adapted to rectify said conveyed power from said first resonant circuit;
a second resonant converter circuit including at least one power switch adapted to convey power to a second resonant circuit and a second rectification stage adapted to rectify said conveyed power from said second resonant circuit;
a filter capacitor coupled to said first and second rectification stages to provide DC output power therefrom; and
a regulator operatively coupled to said first and second resonant converters to control switching frequency of said at least one power switch of each of said first and second resonant converters, such that switching frequency of said at least one power switch of said second resonant converter is shifted in phase with respect to switching frequency of said at least one power switch of said first resonant converter;
wherein said at least one power switch of each of said first and second resonant converters further comprises a first power switch operatively coupled to an input voltage source and a second power switch operatively coupled to ground with a phase node defined between said first and second power switches, a corresponding one of said first and second resonant circuits being coupled to said phase node.
9. The power converter of claim 8 , wherein each of said first and second resonant circuit further comprises an inductor, a transformer having a primary winding in series with said inductor, and first and second capacitors in series with said primary winding and connected across an input voltage source.
10. The power converter of claim 8 , further comprises means for preventing an overvoltage condition of at least one of said first and second resonant converter circuits.