SYSTEM AND METHOD FOR POWER SUPPLY CONTROL

• US 20130099590A1
• Filed: 10/24/2012
• Published: 04/25/2013
• Est. Priority Date: 10/25/2011
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Ma, Tao, LU, Xi, SHI, Yimeng, ZHU, Pengcheng, MORRIS, Garron Koch, SABATE, Juan Antonio, SLOTNICK, Jeffrey Neal, SKEFFINGTON, Wesley Michael, WIZA, Margaret Ann
• Granted Patent: US 9,287,795 B2
• Time in Patent Office: Days
• US Class Current: 307/104
• CPC Class Codes: H02M 1/0003 Details of control, feedback or regulation circuits
• CPC Class Codes: H02M 3/3388 of the parallel type
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A resonant power supply is provided. The resonant power supply comprises a series resonant converter configured to convert an input DC voltage to an output DC voltage to generate an output DC voltage. The series resonant converter includes a switching stage, a resonant inductor, a resonant capacitor, and an isolation transformer. The resonant power supply further comprises a converter controller configured to obtain an actual trajectory radius signal based on a resonant inductor current, a resonant capacitor voltage, and a voltage in association with the isolation transformer. The converter controller is further configured to generate a trajectory radius command signal based on a DC voltage command signal and a DC voltage feedback signal, and to generate control signals to be applied to the switching stage based on the actual trajectory radius signal and the trajectory radius command signal.

Claims

1. A resonant power supply, comprising:

a series resonant converter configured to convert an input direct current (DC) voltage to generate an output DC voltage, the series resonant converter comprising;

a switching stage;

a resonant inductor coupled to the switching stage;

a resonant capacitor in series coupled to the resonant inductor; and

an isolation transformer coupled to the resonant capacitor; and

a converter controller coupled to the series resonant converter, wherein the converter controller is configured to;

obtain an actual trajectory radius signal based on a resonant inductor current measured at the resonant inductor, a resonant capacitor voltage measured at the resonant capacitor, and a voltage in association with the isolation transformer;

generate a trajectory radius command signal based on a DC voltage command signal and a DC voltage feedback signal measured at the output of the series resonant converter; and

generate control signals to be applied to the switching stage of the series resonant converter based on the actual trajectory radius signal and the trajectory radius command signal.

2. The resonant power supply of claim 1, wherein the converter controller comprises:

an average unit configured to receive the resonant inductor current, the resonant capacitor voltage, and the voltage in association with the isolation transformer, and to calculate an average resonant inductor current, an average resonant capacitor voltage, and an average voltage in association with the isolation transformer; and

a trajectory radius calculator coupled to the average unit, the trajectory radius calculator configured to calculate an average value of the actual trajectory radius signal according to the average resonant inductor current, the average resonant capacitor voltage, and the average voltage in association with the isolation transformer.

3. The resonant power supply of claim 2, wherein the average unit comprises a low pass filter for obtaining the average value of the actual trajectory radius signal by removing high frequency components of the resonant inductor current, the resonant capacitor voltage, and the voltage in association with the isolation transformer.

4. The resonant power supply of claim 2, wherein the voltage in association with the isolation transformer comprises a primary voltage measured at a primary winding of the isolation transformer, and wherein the trajectory radius calculator is configured to calculate an average value of the actual trajectory radius signal according to the following equation:

RADIUS²=(Z₀*I_Lr)²+(V_Cr+V_pri)²,

where Z₀ is the characteristic impedance of the resonant inductor and the resonant capacitor, I_Lr is the resonant inductor current, V_Cr is the resonant capacitor voltage, V_pri is the primary voltage, and RADIUS is the average radius of the state trajectory.

5. The resonant power supply of claim 2, wherein the voltage in association with the isolation transformer comprises an output voltage, and wherein the trajectory radius calculator is configured to calculate an average value of the actual trajectory radius signal according to the following equation:

6. The resonant power supply of claim 1, wherein the converter controller further comprises:

a summation element configured to receive the DC voltage command signal and the DC voltage feedback signal and generate a DC voltage error signal representing a difference between the DC voltage command signal and the DC voltage feedback signal; and

a voltage regulator configured to receive the DC voltage error signal and generate the trajectory radius command signal according to the DC voltage error signal.

7. The resonant power supply of claim 1, wherein the converter controller is further configured to generate the control signals at a fixed frequency to be applied to the switching stage of the series resonant converter.

8. The resonant power supply of claim 1, wherein the series resonant converter is configured to operate at a discontinuous current mode.

9. The resonant power supply of claim 3, wherein the converter controller further comprises a voltage limit module configured to detect the output voltage of the series resonant converter, and provide command signals to reduce the output voltage upon determination that the detected output voltage exceeds a predetermined voltage threshold value.

10. The resonant power supply of claim 3, wherein the converter controller further comprises a current limit module configured to detect the resonant inductor current of the resonant inductor, and provide command signals to reduce the resonant inductor current upon determination that the resonant inductor current exceeds a predetermined current threshold value.

11. A method of operating a series resonant converter, the method comprising:

obtaining an actual trajectory radius signal based on a resonant inductor current measured at a resonant inductor of the series resonant converter, a resonant capacitor voltage measured at a resonant capacitor of the series resonant converter, and a voltage measured in association with an isolation transformer of the series resonant converter;

generating a trajectory radius command signal based on a DC voltage command signal indicative of a desired DC voltage to be achieved at the output of the series resonant converter and a DC voltage feedback signal measured at the output of the series resonant converter; and

generating control signals to be applied to a switching stage of the series resonant converter based on the obtained actual trajectory radius signal and the trajectory radius command signal.

12. The method of claim 11, wherein obtaining an actual trajectory radius signal comprises calculating an average resonant inductor current, an average resonant capacitor voltage;

and an average voltage in association with the isolation transformer according to the resonant inductor current, the resonant capacitor voltage, and the voltage in association with the isolation transformer.

13. The method of claim 12, wherein calculating an average resonant inductor current, an average resonant capacitor voltage, and an average voltage in association with the isolation transformer comprises using a low pass filter to process the resonant inductor current, the resonant capacitor voltage, and the voltage in association with the isolation transformer.

14. The method of claim 12, wherein obtaining an actual trajectory radius signal comprises calculating an average value of the actual trajectory radius signal according to the following equation:

RADIUS²=(Z₀*I_Lr)²+(V_Cr+V_pri)²,

where Z₀ is the characteristic impedance of the resonant inductor and the resonant capacitor, I_Lr is the resonant inductor current, V_Cr is the resonant capacitor voltage, V_pri is the primary voltage of a primary winding of the isolation transformer, and RADIUS is the average radius of the state trajectory.

15. The method of claim 12, wherein obtaining an actual trajectory radius signal comprises calculating an average value of the actual trajectory radius signal according to the following equation:

16. A magnetic resonance system, comprising:

a main magnet for generating a main magnetic field;

a gradient coil for applying gradient magnetic field to the main magnetic field along selected gradient axes;

a gradient amplifier coupled to the gradient coil for driving the gradient coil;

a series resonant converter coupled to the gradient amplifier for supplying power to the gradient amplifier, wherein the series resonant converter is configured to convert an input direct current (DC) voltage to generate an output DC voltage, the series resonant converter comprising a switching stage, a resonant inductor, a resonant capacitor, and an isolation transformer; and

a converter controller coupled to the series resonant converter, wherein the converter controller is configured to;

obtain an actual trajectory radius signal based on a resonant inductor current measured at the resonant inductor, a resonant capacitor voltage measured at the resonant capacitor, and a voltage measured in association with the isolation transformer;

generate a trajectory radius command signal based on a DC voltage command signal indicative of a desired DC voltage to be achieved at the output of the series resonant converter and a DC voltage feedback signal measured at the output of the series resonant converter; and

generate control signals to be applied to the switching stage of the series resonant converter based on the actual trajectory radius signal and the trajectory radius command signal.

17. The magnetic resonance system of claim 16, wherein the converter controller comprises:

an average unit configured to receive the resonant inductor current, the resonant capacitor voltage, and the voltage in association with the isolation transformer, and to calculate an average resonant inductor current, an average resonant capacitor voltage, and an average voltage in association with the isolation transformer; and

a trajectory radius calculator coupled to the average unit, the trajectory radius calculator configured to calculate an average value of the actual trajectory radius signal according to the average resonant inductor current, the average resonant capacitor voltage, and the average voltage in association with the isolation transformer.

18. The magnetic resonance system of claim 17, wherein the average unit comprises a low pass filter for obtaining the average value of the actual trajectory radius signal by removing high frequency components of the resonant inductor current, the resonant capacitor voltage, and the voltage in association with the isolation transformer.

19. The magnetic resonance system of claim 17, wherein the voltage in association with the isolation transformer comprises a primary voltage of a primary winding of the isolation transformer, and wherein the trajectory radius calculator is configured to calculate an average value of the actual trajectory radius signal according to the following equation:

RADIUS²=(Z₀*I_Lr)²+(V_Cr+V_pri)²,

where Z₀ is the characteristic impedance of the resonant inductor and the resonant capacitor, I_Lr is the resonant inductor current, V_Cr is the resonant capacitor voltage, V_pri is the primary voltage, and RADIUS is the average radius of the state trajectory.

20. The magnetic resonance system of claim 17, wherein the voltage in association with the isolation transformer comprises an output voltage of the series resonant converter, and wherein the trajectory radius calculator is configured to calculate an average value of the actual trajectory radius signal according to the following equation: