120-Hz ripple reduction with PIR controller for LLC converter
An LLC converter includes a transformer that includes a primary winding and a secondary winding, a resonant stage that includes the primary winding, a switching stage that includes switches and that is connected to an input voltage and the resonant stage, a rectifying stage that is connected to the secondary winding and that provides an output voltage, and a controller that senses the output voltage and that controls switching of the switches based on proportional-integral control of the output voltage to reduce errors in the output voltage with respect to a DC voltage and based on quasi-resonant control of the output voltage to reduce errors in the output voltage with respect to a range of voltages with a frequency bandwidth.
1. An LLC converter comprising:
a transformer that includes a primary winding and a secondary winding;
a resonant stage that includes the primary winding;
a switching stage that includes switches and that is connected to an input voltage and the resonant stage;
a rectifying stage that is connected to the secondary winding and that provides an output voltage; and
a controller that senses the output voltage and that controls switching of the switches based on proportional-integral control of the output voltage to reduce errors in the output voltage with respect to a DC voltage and based on quasi-resonant control of the output voltage to reduce errors in the output voltage with respect to a range of voltages with a frequency bandwidth.
2. The LLC converter of claim 1 , wherein a first sampling period of the proportional-integral control is shorter than a second sampling period of the quasi-resonant control.
3. The LLC converter of claim 1 , wherein the controller controls the switching of the switches using pulse-frequency modulation.
4. The LLC converter of claim 1 , wherein the proportional-integral control and the quasi-resonant control are both discrete control.
5. The LLC converter of claim 4 , wherein a transfer function of the quasi-resonant control is provided by:
G
R
2
(
z
)
=
k
r
T
R
2
(
1
-
z
-
1
)
2
+
2
ω
c
T
R
(
1
-
z
-
1
)
+
(
ω
T
R
)
2
=
k
R
(
1
-
z
-
1
)
2
+
α
(
1
-
z
-
1
)
+
θ
2
where ω is a line angular frequency, ω c is a bandwidth angular frequency, k r is resonant gain in continuous quasi-resonant control, α=2ω c T R , k R =k r T R 2 , θ=ωT R , k R is a discrete resonant gain, and T R is the second sampling period of the quasi-resonant control.
6. The LLC converter of claim 1 , wherein the range of voltages includes a voltage with a frequency of 120 Hz.
7. The LLC converter of claim 1 , wherein the resonant stage further includes a resonant inductor, a resonant capacitor, and a magnetizing inductor.
8. The LLC converter of claim 1 , wherein the switching stage includes first and second primary switches that are controlled by the controller.
9. The LLC converter of claim 1 , wherein the rectifying stage includes first and second synchronous rectifiers.
10. The LLC converter of claim 1 , wherein the controller is a digital signal controller.
11. A method of controlling an LLC converter comprising:
sensing an output voltage of the LLC converter; and
switching switches connected to a primary winding of a transformer included in the LLC converter based on proportional-integral control of the output voltage to reduce errors in the output voltage with respect to a DC voltage and based on quasi-resonant control of the output voltage to reduce errors in the output voltage with respect to a range of voltages with a frequency bandwidth.
12. The method of claim 11 , further comprising:
sampling the output voltage with a first sampling period with respect to the proportional-integral control; and
sampling the output voltage with a second sampling period with respect to the quasi-resonant control; wherein
the second sampling period is longer than the first sampling period.
13. The method of claim 11 , wherein the switching uses pulse-frequency modulation.
14. The method of claim 11 , wherein the proportional-integral control and the quasi-resonant control are both discrete control.
15. The method of claim 14 , wherein a transfer function of the quasi-resonant control is provided by:
G
R
2
(
z
)
=
k
r
T
R
2
(
1
-
z
-
1
)
2
+
2
ω
c
T
R
(
1
-
z
-
1
)
+
(
ω
T
R
)
2
=
k
R
(
1
-
z
-
1
)
2
+
α
(
1
-
z
-
1
)
+
θ
2
where ω is a line angular frequency, ω c is a bandwidth angular frequency, k r is resonant gain in a continuous quasi-resonant controller, α=2ω c T R , k R =k r T R 2 , θ=ωT R , k R is a discrete resonant gain, and T R is a sampling period of the quasi-resonant control.
16. The method of claim 11 , wherein the range of voltages includes a voltage with a frequency of 120 Hz.
17. The method of claim 11 , wherein the switches are connected to a resonant stage that includes a resonant inductor, a resonant capacitor, a magnetizing inductor, and the primary winding.
18. The method of claim 11 , wherein the switching includes switching first and second primary switches connected to the primary winding.
19. The method of claim 11 , further comprising rectifying a voltage from a secondary winding of the transformer to provide the output voltage.
20. The method of claim 11 , wherein the switching is controlled using a digital signal controller.