Transformerless AC Line Isolator

• US 20160329830A1
• Filed: 05/06/2016
• Published: 11/10/2016
• Est. Priority Date: 05/07/2015
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Hussain, Asif, Mohtashemi, Behzad, Pandya, Manisha P., Navabi-Shirazi, Mohammad J.
• Granted Patent: US 10,075,095 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 1/0058 by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero using an auxiliary actively switched resonant commutation circuit connected to an intermediate DC voltage or between two push-pull branches of an inverter bridge H02M7/4811; in resonant inverters H02M7/4815; in inverters operating from a resonant DC source H02M7/4826
• CPC Class Codes: H02M 1/08 Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load
• CPC Class Codes: H02M 7/537 using semiconductor devices only, e.g. single switched pulse inverters
• 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

Various systems, apparatuses, and methods are disclosed herein, which provide a new power conversion topology for isolated systems that does not include a transformer. Embodiments of the inventive systems comprise: a switching system utilizing high voltage, low leakage switches, e.g., Silicon Carbide (SiC) MOS-FETs; a power source; an inductor and a capacitor operating as a link stage resonant LC circuit; and a load. The switching system may be configured to be controlled in a synchronized ‘four phase’ control loop process, wherein the input switches are prevented from being closed at the same time as the output switches, thereby providing electrical isolation between the input power source and the load—without the use of a transformer. The techniques disclosed herein are applicable to any number of isolated systems that supply power to electronic systems such as: digital cameras, mobile phones, watches, personal data assistants (PDAs), portable music players, displays, and computers.

Claims

1. An electrically-isolated power conversion circuit comprising:

a link stage incorporating a resonant LC circuit, the resonant LC circuit comprising a first inductor and a first capacitor;

an input stage comprising at least two simultaneously operated input switching devices that, in their closed position, couple the resonant LC circuit to an input power source and that, in their open position, de-couple the resonant LC circuit from the input power source;

an output stage comprising at least two simultaneously operated output switching devices that, in their closed position, couple the resonant LC circuit to a load and that, in their open position, de-couple the resonant LC circuit from the input power source; and

a control system operatively coupled to the input and output stages configured to prevent the input switching devices and the output switching devices from closing at the same time, thereby providing electrical isolation between the input power source and the load without the use of a transformer.

2. The power conversion circuit of claim 1, wherein the input switching devices open when peak current in the first inductor reaches a threshold value.

3. The power conversion circuit of claim 1, wherein the power conversion circuit does not contain a transformer.

4. The power conversion circuit of claim 1, wherein at least one of the input switching devices or the output switching devices comprises a Silicon Carbide (SiC) MOS-FET.

5. The power conversion circuit of claim 1, wherein the link stage operates in a resonant mode when each of the input switching devices and output switching devices are in their open position.

6. The power conversion circuit of claim 1, wherein the control system is further configured to place the input switching devices into their closed position when a voltage measured across the resonant LC circuit reaches an input voltage level.

7. The power conversion circuit of claim 1, wherein the control system is further configured to place the output switching devices into their closed position when a voltage measured across the resonant LC circuit reaches an output voltage level.

8. The power conversion circuit of claim 1, further comprising at least one optocoupler configured to transfer electrical signals between the output stage and the input stage and synchronize the operation of the input switching devices and the output switching devices.

9. A method of operating an electrically isolated power conversion circuit according to claim 1 through a power cycle, the method comprising:

closing the input switching devices to transfer energy to the resonant LC circuit;

opening the input switching devices thereby allowing the resonant LC circuit to begin resonating;

allowing the resonance to continue until the voltage across the resonant LC circuit inverts, and then closing the output switching devices, thereby transferring energy from the resonant LC circuit to the load;

opening the output switching devices when the current from the resonant LC circuit to the load reaches zero; and

allowing the resonant LC circuit to continue resonating until the voltage across the resonant LC circuit again inverts, and then closing the input switching devices under a zero voltage condition.

10. The method of claim 9, further comprising opening the input switching devices when peak current in the first inductor reaches a threshold value.

11. The method of claim 9, wherein the power conversion circuit does not contain a transformer.

12. The method of claim 9, wherein at least one of the input switching devices or the output switching devices comprises a SiC MOS-FET.

13. The method of claim 9, wherein the control system is further configured to close the input switching devices when a voltage measured across the resonant LC circuit reaches an input voltage level.

14. The method of claim 9, wherein the control system is further configured to close the output switching devices when a voltage measured across the resonant LC circuit reaches an output voltage level.

15. The method of claim 9, wherein the power conversion circuit further comprises at least one optocoupler configured to transfer electrical signals between the output stage and the input stage.

16. The method of claim 15, wherein the at least one optocoupler is further configured to synchronize the operation of the input switching devices and the output switching devices.

17. An electrically-isolated power conversion apparatus comprising:

a power source for generating an input voltage;

a power converter comprising;

an input system; and

output system; and

one or more switching devices, the one or more switching devices further comprising first input switching devices and first output switching devices;

a controller configured to operate the one or more switching devices, so as to convert an input voltage of the input system to a regulated output voltage for delivery to a load in the output system according to a control loop process, wherein;

a first phase of the control loop process comprises;

closing the first input switching devices to transfer energy from the power source to a resonant LC circuit, wherein the resonant LC circuit is connected between the power source and the load; and

opening the first output switching devices to electrically isolate the load from the input voltage;

a second phase of the control loop process comprises;

opening the first input switching devices to allow the resonant LC circuit to resonate until a voltage across the resonant LC circuit inverts;

a third phase of the control loop process comprises;

closing the first output switching devices to transfer energy from the resonant LC circuit to the load; and

a fourth phase of the control loop process comprises;

opening the output switching devices when a current from the resonant LC circuit to the load reaches zero;

allowing the resonant LC circuit to continue resonating until the voltage across the resonant LC circuit again inverts; and

closing the input switching devices under a zero voltage condition.

18. The power conversion apparatus of claim 17, wherein the power conversion circuit does not contain a transformer.

19. The power conversion apparatus of claim 17, wherein at least one of the input switching devices or the output switching devices comprises a SiC MOS-FET.

20. The power conversion apparatus of claim 17, further comprising at least one optocoupler configured to transfer electrical signals between the output system and the input system.