US-20260128669-A1 - Compensation of Leakage Current in Power Supplies

Abstract

A voltage converter may experience leakage current, which is an undesired current that may travel through a current path of the voltage converter and be felt by a human user or sensitive electrical components at a chassis. The voltage converter may be adapted to include a voltage source and an accompanying capacitor to generate a compensating current to compensate for the leakage current.

Inventors

• Desheng Guo
• Sheng-Yang Yu
• Brent McDonald

Assignees

• TEXAS INSTRUMENTS INCORPORATED

Dates

Publication Date

20260507

Application Date

20241104

Claims (20)

1. 1 . A circuit comprising: a first switching leg coupled between a first direct current (DC) terminal and a second DC terminal; a second switching leg coupled between the first DC terminal and the second DC terminal; a first switch and a second switch, arranged in the first switching leg, wherein the first switch and the second switch are coupled to a first alternating current (AC) line; a third switch and a fourth switch, arranged in the second switching leg, wherein the third switch and the fourth switch are coupled to a second AC line at a first node of the second switching leg, further wherein the fourth switch is coupled to a ground; and a voltage source, arranged between the ground and the first node of the second switching leg, wherein an output of the voltage source is coupled to a first capacitor.
2. 2 . The circuit of claim 1 , wherein the voltage source is configured to produce a first voltage that is proportional and opposite in polarity to a second voltage across the fourth transistor.
3. 3 . The circuit of claim 1 , wherein the voltage source comprises: an operational amplifier having an inverting input and a non-inverting input, wherein the non-inverting input is coupled to the first node of the second switching leg, and wherein the inverting input is coupled to the second DC terminal, further wherein an output of the amplifier is coupled to the ground via the first capacitor.
4. 4 . The circuit of claim 1 , wherein the voltage source comprises: an operational amplifier having an inverting input and a non-inverting input, wherein the non-inverting input is coupled to the first node of the second switching leg, and wherein the inverting input is coupled to the first DC terminal, further wherein an output of the amplifier is coupled to the ground via the first capacitor.
5. 5 . The circuit of claim 1 , wherein the voltage source comprises: an operational amplifier having an inverting input and a non-inverting input, wherein the inverting input is coupled to the first node of the second switching leg, and wherein the non-inverting input is coupled to the second DC terminal, further wherein an output of the amplifier is coupled to the first node of the second leg via the first capacitor.
6. 6 . The circuit of claim 1 , wherein the voltage source comprises: a transformer having a first winding and a second winding, wherein the first winding is coupled to the second AC line and coupled to the ground via the first capacitor.
7. 7 . The circuit of claim 6 , wherein the second winding is coupled to the first node of the second leg and to the second DC terminal.
8. 8 . The circuit of claim 7 , wherein the first winding and the second winding have different polarities.
9. 9 . The circuit of claim 6 , wherein the second winding is coupled to the first DC terminal and the first node of the second leg, and wherein the first winding and the second winding have a same polarity.
10. 10 . A system comprising: an alternating current (AC) input having a first AC terminal and a second AC terminal; a first switching leg and a second switching leg coupled between a first direct current (DC) terminal and a second DC terminal, wherein the first switching leg is coupled to the first AC terminal, and wherein the second switching leg is coupled to the second AC terminal; a filter disposed between the AC input and the first and second switching legs; a first transistor disposed in the second switching leg between the first DC terminal and a first node; a second transistor disposed in the second switching leg between the first node and the second DC terminal; and a voltage source coupled to the first node and coupled to a ground and having an output coupled to a capacitor.
11. 11 . The system of claim 10 , wherein the voltage source comprises an operational amplifier having a first input coupled to the second DC terminal and a second input coupled to the first node, wherein an output of the operational amplifier is coupled to the ground via the capacitor.
12. 12 . The system of claim 10 , wherein the voltage source comprises an operational amplifier having a first input coupled to the first DC terminal and a second input coupled to the first node, wherein an output of the operational amplifier is coupled to the ground via the capacitor.
13. 13 . The system of claim 10 , wherein the voltage source comprises an operational amplifier having a first input coupled to the second DC terminal and a second input coupled to the first node, wherein an output of the operational amplifier is coupled to the first node via the capacitor.
14. 14 . The system of claim 10 , wherein the voltage source comprises a transformer having a first winding coupled to the first node and to the ground via the capacitor.
15. 15 . The system of claim 14 , wherein the voltage source comprises a second winding coupled to the first node and to the second DC terminal.
16. 16 . The system of claim 14 , wherein the voltage source comprises a second winding coupled to the first DC terminal and the first node.
17. 17 . The system of claim 14 , wherein the voltage source comprises a second winding coupled to the first node and to the second DC terminal, and wherein the first winding has an opposite polarity relative to the second winding.
18. 18 . The system of claim 14 , comprising a totem pole bridgeless power factor correction rectifier that includes the first switching leg and the second switching leg.
19. 19 . A method comprising: controlling a voltage converter, including transmitting first control signals to switch a first switching leg at a first frequency and transmitting second control signals to switch a second switching leg at a second frequency that is lower than the first frequency; sensing a first voltage at a first node of the second switching leg; and applying a second voltage to a first capacitor, wherein a value of the second voltage is proportional to a value of the first voltage, thereby injecting a first current to ground via the first capacitor, wherein the first current compensates a second current between the first node and ground.
20. 20 . The method of claim 19 , wherein the first voltage comprises a voltage between the first node and a positive direct current (DC) terminal of the voltage converter or a voltage between the first node and a negative DC terminal of the voltage converter, and wherein the ground is an earth ground or a chassis ground.

Description

TECHNICAL FIELD The present disclosure relates to power supplies and, more specifically, to power supplies having compensation for leakage currents. BACKGROUND A switch-mode power supply (SMPS) transfers power from an input power source to a load by switching one or more power transistors. The power transistors are coupled through a switch node to an energy storage element (e.g., a capacitor) that is capable of coupling to the load. An SMPS may include an SMPS controller to provide one or more switching (e.g., PWM) control signals to drive the power transistor(s). SUMMARY In an arrangement, a circuit includes: a first switching leg coupled between a first direct current (DC) terminal and a second DC terminal; a second switching leg coupled between the first DC terminal and the second DC terminal; a first switch and a second switch, arranged in the first switching leg, wherein the first switch and the second switch are coupled to a first alternating current (AC) line; a third switch and a fourth switch, arranged in the second switching leg, wherein the third switch and the fourth switch are coupled to a second AC line at a first node of the second switching leg, further wherein the fourth switch is coupled to a ground; and a voltage source, arranged between the ground and the first node of the second switching leg, wherein an output of the voltage source is coupled to a first capacitor. In an arrangement, a system includes: an alternating current (AC) input having a first AC terminal and a second AC terminal; a first switching leg and a second switching leg coupled between a first direct current (DC) terminal and a second DC terminal, wherein the first switching leg is coupled to the first AC terminal, and wherein the second switching leg is coupled to the second AC terminal; a filter disposed between the AC terminals and the first and second switching legs; a first transistor disposed in the second switching leg between the first DC terminal and a first node; a second transistor disposed in the second switching leg between the first node and the second DC terminal; and a voltage source coupled to the first node and coupled to a ground and having an output coupled to a capacitor. In an arrangement, a method includes: controlling a voltage converter, including transmitting first control signals to switch a first switching leg at a first frequency and transmitting second control signals to switch a second switching leg at a second frequency that is lower than the first frequency; sensing a first voltage at a first node of the second switching leg; and applying a second voltage to a first capacitor, wherein a value of the second voltage is proportional to a value of the first voltage, thereby injecting a first current to ground via the first capacitor, wherein the first current compensates a second current between the first node and ground. BRIEF DESCRIPTION OF THE DRAWINGS Having thus described the invention in general terms, reference will now be made to the accompanying drawings, wherein: FIG. 1 is an illustration of an example voltage converter, according to some embodiments; FIG. 2 is an illustration of various waveforms, which may be present in the system of FIG. 1, according to some embodiments; FIG. 3 is an illustration of an example voltage converter, adapted according to some embodiments; FIG. 4 is an illustration of an example voltage converter, adapted according to some embodiments; FIG. 5 is an illustration of example voltage converter, according to some embodiments; FIG. 6 is an illustration of example voltage converter, according to some embodiments; FIG. 7 is an illustration of example voltage converter, according to some embodiments; and FIG. 8 is an illustration of example method, according to some embodiments. DETAILED DESCRIPTION The present disclosure is described with reference to the attached figures. The figures are not drawn to scale, and they are provided merely to illustrate the disclosure. Several aspects of the disclosure are described below with reference to example applications for illustration. It should be understood that numerous specific details, relationships, and methods are set forth to provide an understanding of the disclosure. The present disclosure is not limited by the illustrated ordering of acts or events, as some acts may occur in different orders and/or concurrently with other acts or events. Furthermore, not all illustrated acts or events are required to implement a methodology in accordance with the present disclosure. One example switch mode power supply may include a high-frequency switching leg and a low-frequency switching leg, coupled in parallel between a positive direct current (DC) output terminal and a negative DC output terminal (DC+ and DC− terminals). Furthermore, the negative DC output terminal may be coupled to an earth ground (GND) via a parasitic capacitance. In some instances, there may be a leakage current, which flows from the parasitic capacit