Leakage current compensation in power supply

Abstract

The invention relates to leakage current compensation in a power supply. A voltage converter (100) may experience a leakage current, which is an undesirable current that can travel through a current path of the voltage converter and can be perceived by a human user or a sensitive electrical component at a chassis. The voltage converter may be modified to include a voltage source (114) and a follower capacitor to generate a compensation current to compensate for the leakage current.

Description

Technical Field

[0001] This disclosure relates to power supplies, and more specifically, to power supplies with compensation for leakage current. Background Technology

[0002] A switch-mode power supply (SMPS) delivers power from an input source to a load by switching one or more power transistors. The power transistors are coupled via switching nodes to energy storage elements (e.g., capacitors) that can be coupled 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 transistors. Summary of the Invention

[0003] In the arrangement, a circuit includes: a first switching branch coupled between a first direct current (DC) terminal and a second DC terminal; a second switching branch coupled between the first DC terminal and the second DC terminal; a first switch and a second switch arranged in the first switching branch, 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 branch, wherein the third switch and the fourth switch are coupled to a second AC line at a first node of the second switching branch, and wherein the fourth switch is coupled to ground; and a voltage source arranged between the ground and the first node of the second switching branch, wherein the output of the voltage source is coupled to a first capacitor.

[0004] In the arrangement, a system includes: an alternating current (AC) input having a first AC terminal and a second AC terminal; a first switching branch and a second switching branch coupled between a first direct current (DC) terminal and a second DC terminal, wherein the first switching branch is coupled to the first AC terminal and wherein the second switching branch is coupled to the second AC terminal; a filter disposed between the AC terminal and the first and second switching branches; a first transistor disposed in the second switching branch between the first DC terminal and a first node; a second transistor disposed in the second switching branch between the first node and the second DC terminal; and a voltage source coupled to the first node and coupled to ground, and having an output coupled to a capacitor.

[0005] In one arrangement, a method includes: controlling a voltage converter, comprising transmitting a first control signal at a first frequency to switch a first switching branch, and transmitting a second control signal at a second frequency lower than the first frequency to switch a second switching branch; sensing a first voltage at a first node of the second switching branch; and applying a second voltage to a first capacitor, wherein the value of the second voltage is proportional to the value of the first voltage, thereby injecting a first current to ground via the first capacitor, wherein the first current compensates for a second current between the first node and ground. Attached Figure Description

[0006] Having thus generally described the invention, reference will now be made to the accompanying drawings, in which:

[0007] Figure 1 This is a schematic illustration of an example voltage converter based on some embodiments;

[0008] Figure 2 It is possible to exist according to some embodiments Figure 1 A graphical explanation of various waveforms in the system;

[0009] Figure 3 This is a graphical illustration of an example voltage converter adapted according to some embodiments;

[0010] Figure 4 This is a graphical illustration of an example voltage converter adapted according to some embodiments;

[0011] Figure 5 This is a schematic illustration of an example voltage converter based on some embodiments;

[0012] Figure 6 This is a schematic illustration of an example voltage converter based on some embodiments;

[0013] Figure 7 This is a schematic illustration of an example voltage converter based on some embodiments; and

[0014] Figure 8 This is a diagrammatic illustration of example methods based on some embodiments. Detailed Implementation

[0015] This disclosure is described with reference to the accompanying drawings. The drawings are not to scale and are provided for illustrative purposes only. Several aspects of this disclosure are described below with reference to illustrative examples. It should be understood that numerous specific details, relationships, and methods are set forth to provide an understanding of this disclosure. This disclosure is not limited to the described order of actions or events, as some actions may occur in a different order and / or simultaneously with other actions or events. Furthermore, not all described actions or events are required to implement the methods according to this disclosure.

[0016] An example switch-mode power supply may include a high-frequency switching branch and a low-frequency switching branch coupled in parallel between a positive DC output terminal and a negative DC output terminal (DC+ and DC- terminals). Additionally, the negative DC output terminal may be coupled to ground (GND) via parasitic capacitance. In some cases, leakage current may exist, flowing from the parasitic capacitance through the transistor in the low-frequency switching branch to the AC neutral line and back to GND at the filter of the switch-mode power supply. Leakage current is generally considered undesirable. In practice, leakage current is sometimes referred to as touch current because in some applications, leakage current can be conducted through the device housing or other components that a human user may touch, where the user may actually experience an electric shock from the leakage current. For ease of illustration, leakage current will also be referred to as Itouch in this disclosure.

[0017] Various embodiments compensate for leakage current by including a compensating voltage source between the node of the low-frequency switching branch and GND. The compensating voltage source and the compensating capacitor are arranged in series to generate a current equal in magnitude to but opposite in polarity to the leakage current. When the switch-mode power supply is operating, the compensating voltage source and the compensating capacitor can reduce the leakage current to zero or near zero.

[0018] Such embodiments offer advantages over other solutions. For example, they allow for wider adoption of switch-mode power architectures that might otherwise be prone to leakage current. Examples may include totem-pole bridgeless power factor correction rectifiers, which can have desired operating characteristics, such as reduced conduction losses. In other words, such embodiments allow for wider adoption of totem-pole bridgeless power factor correction rectifiers. Furthermore, such embodiments can further enhance device safety by further isolating human users and sensitive electrical components from unwanted leakage current.

[0019] Figure 1 This is a schematic illustration of an example voltage converter 100 according to some embodiments. The voltage converter 100 has an architecture conforming to a totem-pole bridgeless power factor correction (PFC) rectifier that receives AC voltage from an AC voltage source 106 and outputs DC voltage between DC+ and DC- terminals. In this example, the AC power source 106 is coupled to an AC input, which includes a first AC line terminal 102 and a second AC line terminal 104. For ease of illustration, the first AC line terminal 102 and the second AC line terminal 104 will be referred to as AC line terminal 102 and AC neutral terminal 104, respectively.

[0020] The voltage converter 100 also includes a chassis ground or earth ground, denoted as GND 112. In this context, chassis refers to a physical structure, such as a conductive enclosure or conductive portion of an enclosure in which the voltage converter 100 is implemented. Network 108 may be a test network for measuring an iPod touch, and the designed product may not necessarily include network 108. GND 112 at network 108 and filter 116 may represent part of a chassis that may potentially be exposed to human touch or contact with sensitive electrical components in some cases.

[0021] The voltage converter 100 also includes a parasitic capacitance Cp, which is represented as coupled between GND 112 and the DC terminal. Component Lcm is an inductor implemented as a common-mode choke. Various capacitors CX (e.g., CX1 and CX2) and CY (e.g., CY3 and CY4), together with the inductor Lcm, form a passive electromagnetic interference (EMI) filter 116, which is coupled to the AC power supply 106 at AC line terminal 102 and AC neutral terminal 104. Network 108 is coupled between the AC voltage source 106 and GND 112. Additionally, in this example, AC line terminal 102 is coupled to node A, and AC neutral terminal 104 is coupled to node B.

[0022] exist Figure 1 In this example, capacitor CX1 is coupled between AC line terminal 102 and AC neutral terminal 104; capacitor CX2 is also coupled between terminals 102 and 104, but on the opposite side of inductor Lcm relative to capacitor CX1. Capacitor CY3 is coupled between AC neutral terminal 104 and GND 112, and capacitor CY4 is coupled between AC line terminal 102 and GND 112. Filter 116 is coupled to GND 112 via capacitors CY3 and CY4. The CX capacitors are configured to attenuate differential-mode noise occurring between terminals 102 and 104. Additionally, in this example, inductor Lcm is implemented as a choke to provide high impedance for common-mode noise, for example, that may be attributed to rapid voltage changes within voltage converter 100. The CY capacitors may be configured to redirect common-mode noise to GND 112.

[0023] As noted above, voltage converter 100 is configured to convert the AC input voltage across terminals 102 and 104 into a DC output voltage (VBUS) between DC+ and DC-. In one example, voltage converter 100 may be implemented as a boost converter to convert an AC input voltage (e.g., 120 V AC or 240 V AC at a frequency of 50 Hz or 60 Hz) into a DC output voltage (e.g., approximately 400 V DC). Figure 1In one example, the voltage converter 100 includes an arrangement of an inductor LPFC and transistors Q1, Q2, Q3, and Q4. In this example, the inductor LPFC and transistors Q1, Q2, Q3, and Q4 are configured as a totem-pole power factor correction boost AC-DC converter. For example, transistors Q1, Q2, Q3, and Q4 can be implemented as N-type metal-oxide-semiconductor field-effect transistors (NFETs). Alternatively, Q1, Q2, Q3, and Q4 can be implemented as P-type metal-oxide-semiconductor field-effect transistors (PFETs). In other examples, other types of semiconductor switches can be used, including bipolar junction transistors, such as insulated-gate bipolar transistors (IGBTs), laterally diffused metal-oxide-semiconductor (LDMOS) transistors, thyristors, GaN devices, or mixtures of the above.

[0024] Transistors Q1 and Q2 are coupled in series between the DC+ and DC- terminals, forming a first switching branch. The DC+ and DC- terminals are adapted to couple to a load (not shown) to supply the output DC voltage. For example, AC line terminal 102 can be coupled to the drain of Q1 and the source of Q2, the drain and source being coupled together at a high-frequency switching node (node ​​A). Transistors Q3 and Q4 can also be coupled in series between the DC+ and DC- outputs, forming a second switching branch. AC neutral terminal 104 can be coupled to the source of Q3 and the drain of Q4 at a low-frequency switching node (node ​​B).

[0025] The voltage converter 100 also includes a switching controller 130 configured to provide switching signals to the control terminals of transistors Q1-Q4. In this example, each of the respective transistors Q1-Q4 receives its own corresponding switching signal. Each of the switching signals may include, for example, a pulse width modulation (PWM) control signal configured to turn its respective transistor on or off.

[0026] exist Figure 1 In this example, transistors Q1 and Q2 can be configured as high-frequency transistors, and transistors Q3 and Q4 can be configured as low-frequency transistors. Therefore, the corresponding switching signals to transistors Q1 and Q2 can be configured as high-speed switching signals, for example, having a frequency greater than 1 kHz (e.g., 10 kHz to 100 kHz or greater). The switching signals to transistors Q3 and Q4 can be configured as low-speed switching signals having the same frequency as the AC input voltage (e.g., 50 Hz or 60 Hz). Therefore, the voltage converter 100 can be configured to convert the AC voltage received at terminals 102 and 104 into a corresponding DC output voltage VBUS across output terminals DC+ and DC-.

[0027] Figure 2This is a graphical illustration of example waveforms of voltages 202 and 203 and example current 204, which can be implemented within voltage converter 100 according to some embodiments. In this example, AC voltage 202 can be generated by AC voltage source 106 across terminals 102 and 104. AC voltage 202 can be applied across nodes A and B. As noted above, parasitic capacitance Cp is illustrated as being disposed between the DC-terminal and GND 112. Voltage 203 represents the voltage across parasitic capacitance Cp.

[0028] According to the totem-pole bridgeless PFC operating mechanism, for the entire positive or negative half-cycle, the voltage across Q4 is VBUS (DC+ minus DC-) or zero, and Q4 transitions from on to off or from off to on at the zero-crossing point of AC voltage 202. This means that at the zero-crossing point, there can be a sharp change in the drain-source voltage of Q4, and the magnitude of this change is equal to VBUS for a very short time. This phenomenon can cause a sudden voltage change across Cp, which causes current to flow through Q4 through the low-impedance path "GND-Cp-Q4-Lcm-network-GND". This is leakage current, and it is... Figure 1 The text is a jumbled mess of characters and doesn't form coherent sentences. It's impossible to translate it meaningfully without the original context or a clearer understanding of the intended meaning. Figure 2 The current is shown as 204. The charging and discharging of Cp is completed through Q4 according to equation (1), and except for the conversion rate of Q4, the peak value of the Itouch current spike (i p It is also proportional to the capacitance value of Cp.

[0029] Equation (1)

[0030] Notice Figure 2 The diagram shows the first current spike at time T0, which corresponds to the zero-crossing of AC voltage 202, and the second current spike at time T1, which corresponds to the next subsequent zero-crossing of AC voltage 202. The spike at time T0 is positive, while the spike at time T1 is negative, and this pattern repeats with each cycle of AC voltage 202.

[0031] In addition, it should be noted that Figure 1 The text demonstrates that iPod Touch has a direction, but the direction is only a defined direction, and as shown in the image. Figure 2 As shown in the image, iTunes sometimes displays a positive value and sometimes a negative value.

[0032] Various embodiments compensate for the leakage current Itouch by including a compensation voltage source 114. In this example, the compensation voltage source 114 is coupled between node B and GND 112. A compensation capacitor Ccomp is coupled between the compensation voltage source 114 and GND 112. The compensation capacitor Ccomp is positioned between the compensation voltage source 114 and GND 112 to generate a compensation current Icomp, the magnitude of which is approximately equal to Itouch and the opposite polarity to Itouch at a given time. In other words, the compensation current Icomp should be approximately equal in magnitude to the waveform of current 204 and opposite in polarity at a given time. Therefore, at time T0, the compensation current Icomp should be negative, and at time T1, the compensation current Icomp should be positive.

[0033] In some instances, the compensation voltage source 114 can be configured to sense an appropriate voltage as input to produce a voltage output whose magnitude is proportional to the voltage across Q4. Furthermore, the size of the compensation capacitor Ccomp can be determined using Equation 2, where ∆t is the switching time of the low-frequency switching branch with Q2 and Q4, and ∆V is the voltage difference between node B and the DC terminal. Therefore, the compensation current Icomp can be zeroed or at least the leakage current Itouch can be reduced, at least at network 108.

[0034] Equation (2)

[0035] Figure 3 This is a schematic illustration of an example voltage converter 300 adapted according to some embodiments. The voltage converter 300 is similar to... Figure 1 The voltage converter 100, as both are totem-pole bridgeless power factor correction rectifiers. One difference between voltage converter 300 and voltage converter 100 is that voltage converter 300 moves capacitor CY3 outside of filter 116 and uses CY3 as a compensation capacitor (in Figure 1 (Shown as Ccomp in the image). Please note that... Figure 3 Provided for illustrative purposes only. In some embodiments, the voltage converter 300 may still retain capacitor CY3 (e.g. Figure 1 (As shown), and a separate capacitor Cp is used as the compensation capacitor. The size of CY3 can be set according to Equation 2.

[0036] The voltage converter 300 employs an operational amplifier (op amp) 310 as a compensation voltage source, as discussed above with respect to compensation voltage source 114. The op amp 310 has a non-inverting (+) input connected to the AC neutral terminal 104 at node B, and an inverting (-) input coupled to the DC- terminal. Furthermore, the op amp 310 has an internal ground reference 311 coupled to the AC neutral terminal 104. The ground reference 311 provides a reference point for the output voltage of the op amp 310. Additionally, the ground reference 311 serves as a loop for the compensation current Icomp. The output of the op amp 310 is coupled to node C (GND 112 at filter 116) via capacitor CY3. In other words, capacitor CY3 is connected in series between the output of the op amp 310 and node C.

[0037] Op amp 310 senses the voltage difference between node B and the DC terminal, and the op amp has an internal ground reference 311 coupled to node B. Therefore, op amp 310 outputs a voltage proportional to the voltage across transistor Q4 and with the same polarity as the voltage across transistor Q4 from drain to source. Capacitor CY3 is configured to charge and discharge, thereby generating a compensation current Icomp. The compensation current Icomp is approximately the same in magnitude as Itouch but has the opposite polarity, thereby eliminating or at least reducing Icomp.

[0038] Figure 4 This is a schematic illustration of an example voltage converter 400 adapted according to some embodiments. Voltage converter 400 is configured as a totem-pole bridgeless power factor correction rectifier similar to voltage converters 100 and 300 discussed above. Similar to voltage converter 300, voltage converter 400 moves capacitor CY3 outside of filter 116 and uses CY3 as a compensation capacitor (e.g., Ccomp). The size of CY3 as a compensation capacitor can be set according to Equation 2.

[0039] Operational amplifier 410 is similar to Figure 1The op amp 410 functions by using a compensation voltage source 114. In this example, the op amp 410 includes a non-inverting input coupled to the AC neutral terminal 104 (node ​​B) and an inverting input coupled to the DC+ terminal. A ground reference 411 is coupled to the AC neutral terminal 104. Similarly, the ground reference 411 provides a reference point for the output voltage of the op amp 410. Additionally, the ground reference 411 can serve as a loop for the compensation current Icomp. The output of the op amp 410 is coupled to node C (GND 112 at filter 116) via capacitor CY3. Therefore, capacitor CY3 is connected in series between the output of the op amp 410 and node C. The op amp 410 senses the voltage across transistor Q3 in the low-frequency switching branch with transistor Q4. In this example, the voltage across transistor Q3 is proportional to the voltage across transistor Q4. Furthermore, in instances where transistors Q3 and Q4 are of the same magnitude, the voltage across Q3 is expected to be the same magnitude as the voltage across Q4, but with the opposite polarity (drain to source). The arrangement of the inverting and non-inverting inputs of op amp 410 ensures that the output voltage of op amp 410 is proportional to the voltage across Q4 and has the same polarity as the voltage across Q4.

[0040] The output voltage of op amp 410 charges and discharges capacitor CY3, thereby generating a compensation current Icomp that is approximately equal in magnitude to the leakage current Itouch and opposite in polarity to the leakage current Itouch.

[0041] Figure 5 This is a schematic illustration of an example voltage converter 500 according to some embodiments. The voltage converter 500 is a totem-pole bridgeless power factor correction rectifier, and it removes capacitor CY3 from the filter and uses said capacitor as a compensation capacitor, for example... Figure 1 The size of CY3 can be determined using Equation 2.

[0042] Op-amp 510 is configured to generate an output voltage that is proportional to and opposite in polarity to the voltage across transistor Q4. The inverting input of op-amp 510 is coupled to node B at AC neutral terminal 104. The non-inverting input of op-amp 510 is coupled to the DC terminal. Ground reference 511 is coupled to node C (GND 112). Ground reference 511 provides a reference point for the output voltage of op-amp 510. Additionally, ground reference 511 can be used as a loop for compensating current Icomp.

[0043] Capacitor CY3 is coupled between the output of op amp 510 and node B. In this example, the output voltage of op amp 510 charges and discharges capacitor CY3, which generates a compensation current Icomp injected at node B. The compensation current Icomp is approximately equal in magnitude to the leakage current Itouch but opposite in polarity.

[0044] therefore, Figure 3-5 Examples employ corresponding op amps 310, 410, and 510 as compensation voltage sources, and use capacitor CY3 to generate compensation current Icomp. Op amps 310, 410, and 510 are each arranged to couple to GND 112 at node B and node C, but each arrangement is different. In all three cases, voltage converters 300-500 use their respective op amps 310, 410, and 510 to inject compensation current Icomp to offset or substantially offset leakage current Itouch, at least as seen at network 108. In some embodiments, each of the corresponding op amps 310, 410, and 510 can be configured for unity gain, but various embodiments may use any suitable gain configuration.

[0045] The scope of the implementation is not limited to using an op amp as a compensation voltage source. In fact, other implementations can use any suitable compensation voltage source, such as a transformer or another component.

[0046] Figure 6 This is a schematic illustration of an example voltage converter 600 according to some embodiments. The voltage converter 600 is a totem-pole bridgeless power factor correction rectifier, and it uses a transformer 610 as a compensation voltage source, for example, utilizing... Figure 1 The compensation voltage source 114. Similarly, capacitor CY3 has been moved outside the filter and used as a compensation capacitor, for example, in conjunction with the above. Figure 1 The value of capacitor CY3 can be determined using Equation 2, as discussed in Ccomp.

[0047] Transformer 610 includes a primary winding 611 and a secondary winding 612. Windings 611 and 612 have opposite polarities indicated by their respective phase points. The primary winding 611 is coupled between node B and the DC terminal. The secondary winding 612 is coupled between node B and node C (GND 112 at filter 116).

[0048] The primary winding 611 is configured to sense the voltage across transistor Q4, and therefore the secondary winding 612 is configured to generate a voltage that is proportional to the voltage across transistor Q4 and has the opposite polarity.

[0049] Therefore, capacitor CY3 is charged and discharged to generate a compensation current Icomp. The corresponding number of turns in each of windings 611 and 612 can be configured such that the compensation current Icomp is approximately equal in magnitude to the leakage current Itouch but opposite in polarity.

[0050] Transformer 610 can be configured in any suitable manner, for example, having any suitable number of turns in the respective windings 611, 612. Furthermore, although not shown here, primary winding 611 may also include a DC blocking capacitor to ensure proper biasing of transformer 610. For example, the DC blocking capacitor may be one or more orders of magnitude larger than the compensation capacitor CY3, but the range of embodiments may include DC blocking capacitors of any suitable size. Additionally, although not shown here, primary winding 611 may also generate some current between node B and the DC terminal, but such current is not expected to affect the leakage current Itouch, because the current path through primary winding 611 passes through Q3 and is not coupled to GND 112 (except through Cp).

[0051] Figure 7 This is an illustrative diagram of an example voltage converter 700 according to some embodiments. The voltage converter 700 may be implemented similarly to the voltage converter 600, but with some of the modifications illustrated.

[0052] For example, transformer 710 has a primary winding coupled between node B and the DC+ terminal. In some instances where transistors Q3 and Q4 are of the same size, the primary winding 711 is expected to experience a voltage that is the same in magnitude but opposite in polarity to the voltage across transistor Q4. Furthermore, the primary winding 711 and the secondary winding 712 have the same polarity, as indicated by the phase point.

[0053] Secondary winding 712 is coupled between node B and node C (GND 112 at filter 116). The compensation voltage generated by secondary winding 712 is proportional in magnitude and opposite in polarity to the voltage across transistor Q4. Therefore, compensation capacitor CY3 charges and discharges to generate Icomp, which is approximately the same in magnitude and opposite in polarity to the leakage current Itouch.

[0054] Figure 6-7 Both implementations use a transformer as the compensation voltage source. The transformer is coupled between GND 112 at the filter and the AC neutral line (node ​​B), but the specific coupling arrangement differs in each of the two implementations.

[0055] Figure 8 This is an illustrated description of an example method 800 according to some embodiments. Method 800 can be performed by a voltage converter, such as the one described above. Figure 1-7The voltage converters described.

[0056] Action 802 involves controlling a voltage converter. An example of a voltage converter is given above. Figure 1 and 3 As explained in section -7. The control voltage converter may include a switching controller, such as... Figure 1 The switching controller 130 controls the switching on and off of the switching converter. Figure 1 and 3 Each of the different switching converters in the -7 series contains four transistors Q1-Q4, which operate as switches according to a switching signal from the switching controller 130.

[0057] For example, transistors Q1 and Q2 can be arranged as a high-frequency switching branch, wherein transistors Q1 and Q2 are positioned between the DC+ and DC- terminals, and the node (node ​​A) between transistors Q1 and Q2 is coupled to the AC line terminal. Each of transistors Q1 and Q2 can receive a corresponding switching signal from the switching controller 130, thereby turning each of transistors Q1 and Q2 on and off according to a mode suitable for a totem-pole bridgeless power factor correction rectifier.

[0058] Similarly, transistors Q3 and Q4 can be arranged as a low-frequency switching branch, with transistors Q3 and Q4 positioned between the DC+ and DC- terminals. The node (node ​​B) between transistors Q3 and Q4 can be coupled to the AC neutral terminal. Each of transistors Q3 and Q4 can receive a corresponding switching signal from the switching controller 130, thereby turning each of transistors Q3 and Q4 on and off according to a mode suitable for a fully bridgeless power factor correction rectifier. Therefore, transistors Q1-Q4 act as switches under the control of the switching controller 130.

[0059] Furthermore, in this example, transistor Q4 may be arranged such that it is coupled to GND 112 via parasitic capacitance Cp. In one example, parasitic capacitance Cp may represent the capacitance associated with a current path of leakage current (e.g., the path of Itouch). The path may start at GND 112 at the DC terminal, and travel through transistor Q4, filter 116, and inductor Lcm, across network 108 on AC neutral line 104, and reach GND 112 at the node of filter 116. Furthermore, in this example, turning transistor Q4 on and off can generate a recurring leakage current, described as Itouch and current 204.

[0060] At operation 804, the voltage converter senses a first voltage at the first node of the low-frequency switching branch. For example, the first node of the low-frequency switching branch may include node B, which is the node between transistors Q3 and Q4, wherein transistors Q3 and Q4 are coupled to AC neutral terminal 104.

[0061] Action 804 may include sensing voltage by a device acting as a compensation voltage source. Figure 3 In this example, op amp 310 senses the voltage across transistor Q4 and uses AC neutral terminal 104 as a ground reference. Figure 4 In this example, op amp410 senses the voltage across transistor Q3 and uses AC neutral terminal 104 as a ground reference. Figure 5 In this example, op amp510 senses the voltage across transistor Q4 and uses GND 112 as a ground reference. Figure 6 In this example, transformer 610 senses the voltage across transistor Q4 through primary winding 611, and in Figure 7 In this example, transistor 610 senses the voltage across transistor Q3 via primary winding 711.

[0062] Action 806 includes applying a second voltage to the first capacitor, wherein the second voltage is proportional in magnitude to the first voltage. Figure 3 In this example, the op amp 310 generates a second voltage at its output. Figure 4 In this example, the op amp410 generates a second voltage at its output, and in Figure 5 In this circuit, the op amp 510 generates a second voltage at its output. Figure 3-5 In each of the op amp instances, capacitor CY3 is connected in series with the op amp output and acts as a compensation capacitor (Ccomp), and the size of CY3 can be determined using Equation 2. Figure 6 and 7 In the example, the corresponding transformers 610 and 710 generate voltages on their secondary windings 612 and 712 with polarity opposite to the drain-to-source voltage across transistor Q4. Similarly, CY3 is a compensation capacitor whose size can be set using Equation 2.

[0063] At operation 808, the voltage converter injects current to ground via the first capacitor. Figure 1 and 3 In each of the -7 examples, the current is represented as a compensation current Icomp, which is approximately equal in magnitude to the leakage current Itouch but opposite in polarity. In other words, the injected current compensates for the leakage current flowing through the first node (node ​​B) to ground.

[0064] Furthermore, over time, the voltage sensed at point 804 can change from positive to negative and back again, and the leakage current can change from a positive peak value to a negative peak value and back again, repeating this cycle. Figure 2The current 204 is described. Therefore, the current injected at operation 808 can also change from negative to positive and back, and at each moment, it is described as... Figure 2 The leakage current of current 204 is opposite in polarity. Therefore, the compensation current Icomp can be zeroed or at least the leakage current Itouch can be reduced, at least as seen at network 108.

[0065] Despite Figure 1 and 3 -7 Not specifically described, but various components can be implemented using any suitable technique. In one example, various components of a voltage converter can be implemented on a substrate such as a printed circuit board (PCB), having metal lines in various layers of the PCB. Various capacitors and inductors can be mounted to the PCB and connected by wires. Transistors Q1-Q4 can be implemented on one or more semiconductor dies, wherein those one or more semiconductor dies can be mounted to the PCB and the PCB's metal lines. However, other manufacturing techniques suitable for a given application can be used as needed.

[0066] Although various examples of this disclosure have been described above, it should be understood that they are presented by way of example only and not by way of limitation. Many changes may be made to the disclosed examples based on the disclosure herein without departing from the spirit or scope of this disclosure. Modifications to the described embodiments are possible within the scope of the claims, and other embodiments are also possible. Therefore, the breadth and scope of the invention should not be limited to any of the examples described above. In fact, the scope of this disclosure should be defined according to the appended claims and their equivalents.

Claims

1. A circuit comprising: The first switching branch is coupled between the first DC terminal and the second DC terminal; The second switching branch is coupled between the first DC terminal and the second DC terminal; A first switch and a second switch are arranged in the first switching branch, wherein the first switch and the second switch are coupled to a first AC line; A third switch and a fourth switch are arranged in the second switching branch, wherein the third switch and the fourth switch are coupled to the second AC line at the first node of the second switching branch, and wherein the fourth switch is coupled to ground. as well as A voltage source is disposed between the ground and the first node of the second switching branch, wherein the output of the voltage source is coupled to a first capacitor.

2. The circuit of claim 1, wherein the voltage source is configured to generate a first voltage that is proportional to and opposite in polarity to a second voltage across the fourth transistor.

3. The circuit according to 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 branch, and wherein the inverting input is coupled to the second DC terminal, and wherein the output of the amplifier is coupled to ground via the first capacitor.

4. The circuit according to 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 branch, and wherein the inverting input is coupled to the first DC terminal, and wherein the output of the amplifier is coupled to ground via the first capacitor.

5. The circuit according to 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 branch, and wherein the non-inverting input is coupled to the second DC terminal, and wherein the output of the amplifier is coupled to the first node of the second branch via the first capacitor.

6. The circuit according to 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. The circuit of claim 6, wherein the second winding is coupled to the first node of the second branch and to the second DC terminal.

8. The circuit according to claim 7, wherein the first winding and the second winding have different polarities.

9. The circuit of claim 6, wherein the second winding is coupled to the first node of the first DC terminal and the second branch, and wherein the first winding and the second winding have the same polarity.

10. A system comprising: The AC input has a first AC terminal and a second AC terminal. A first switching branch and a second switching branch are coupled between a first DC terminal and a second DC terminal, wherein the first switching branch is coupled to the first AC terminal and wherein the second switching branch is coupled to the second AC terminal. A filter is disposed between the AC input and the first and second switching branches; A first transistor is disposed in the second switching branch between the first DC terminal and the first node; The second transistor is disposed in the second switching branch between the first node and the second DC terminal; as well as A voltage source coupled to the first node and to ground, and having an output coupled to a capacitor.

11. The system according to claim 10, The voltage source includes an operational amplifier having a first input coupled to the second DC terminal and a second input coupled to the first node, wherein the output of the operational amplifier is coupled to ground via the capacitor.

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 the output of the operational amplifier is coupled to ground via the capacitor.

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 the output of the operational amplifier is coupled to the first node via the capacitor.

14. The system of claim 10, wherein the voltage source comprises a transformer having a first winding coupled to the first node and coupled to ground via the capacitor.

15. The system of claim 14, wherein the voltage source includes a second winding coupled to the first node and coupled to the second DC terminal.

16. The system of claim 14, wherein the voltage source includes a second winding coupled to the first DC terminal and the first node.

17. The system of claim 14, wherein the voltage source includes a second winding coupled to the first node and coupled to the second DC terminal, and wherein the first winding has a polarity opposite to that of the second winding.

18. The system of claim 14, comprising a totem pole bridgeless power factor correction rectifier, the totem pole bridgeless power factor correction rectifier including the first switching branch and the second switching branch.

19. A method comprising: A control voltage converter includes transmitting a first control signal at a first frequency to switch a first switching branch, and transmitting a second control signal at a second frequency lower than the first frequency to switch a second switching branch. Sensing the first voltage at the first node of the second switching branch; as well as A second voltage is applied to a first capacitor, wherein the value of the second voltage is proportional to the value of the first voltage, thereby injecting a first current into ground via the first capacitor, wherein the first current compensates for a second current between the first node and ground.

20. The method of claim 19, wherein the first voltage includes the voltage between the first node and the positive DC terminal of the voltage converter or the voltage between the first node and the negative DC terminal of the voltage converter, and wherein the ground is earth ground or chassis ground.

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