Bidirectional unipolar-bipolar DC-DC converter with digital-assisted common mode loop

Abstract

The invention relates to a bidirectional unipolar-bipolar DC-DC converter with a digitally assisted common mode loop. In one embodiment, a semiconductor device including a bidirectional unipolar-bipolar DC-DC circuit is disclosed. The bidirectional monopole-bipolar DC-DC circuit comprises a first transistor, a second transistor, a third transistor and a fourth transistor. The first transistor is connected between a reference ground connection and a first connection of the coil. The second transistor is connected between the positive bipolar input / output connection and the first connection of the coil. A third transistor is connected between the second connection of the coil and the negative bipolar input / output connection. A fourth transistor is connected between the second connection of the coil and the unipolar voltage input / output connection. The bidirectional DC-DC circuit is configured to simultaneously activate the second transistor and the third transistor to cause current to flow through the coil between the positive bipolar input / output connection and the negative bipolar input / output connection.

Description

Background Art

[0001] The present disclosure generally relates to apparatus and methods for converting between unipolar and bipolar DC power signals during power transfer between a wireless power transmitter and a wireless power receiver.

[0002] Wireless power systems typically include a power transmitter and a power receiver. When the transmission coil of the power transmitter and the receiver coil of the power receiver are placed close to each other, they form a transformer that facilitates the inductive transfer of alternating current (AC) power between the power transmitter and the power receiver. The power transmitter includes an inverter circuit that converts bipolar direct current (DC) power to AC power for wireless transmission across an isolation gap to the power receiver. The power receiver includes a rectifier circuit that converts the received AC power to bipolar DC power for use by various loads or components that require DC power to operate. The power transmitter is typically powered by unipolar DC power (e.g., from a 5V wall adapter), which is converted to bipolar DC power for input to the inverter circuit. Similarly, the loads or components supplied by the power receiver may require unipolar DC power to operate, which is converted from the bipolar DC power output of the rectifier circuit. Summary of the Invention

[0003] In one embodiment, a semiconductor device is disclosed that includes a bidirectional unipolar-bipolar DC-DC circuit. The bidirectional unipolar-bipolar DC-DC circuit may include a first transistor, a second transistor, a third transistor, and a fourth transistor. The first transistor may be connected between a reference ground connection and a first connection of a coil. The second transistor may be connected between a positive bipolar input / output connection and the first connection of the coil. The third transistor may be connected between a second connection of the coil and a negative bipolar input / output connection. The fourth transistor may be connected between the second connection of the coil and a unipolar voltage input / output connection. The bidirectional DC-DC circuit may be configured to concurrently activate the second transistor and the third transistor to cause current to flow through the coil between the positive bipolar input / output connection and the negative bipolar input / output connection.

[0004] In one embodiment, a semiconductor device is disclosed that includes a bidirectional single-pole - bipolar DC - DC circuit. The bidirectional single-pole - bipolar DC - DC circuit can include a first transistor, a second transistor, a third transistor, and a fourth transistor. The first transistor can be connected between a reference ground connection and a first connection of the coil. The second transistor can be connected between a positive bipolar input / output connection and the first connection of the coil. The third transistor can be connected between a second connection of the coil and a negative bipolar input / output connection. The fourth transistor can be connected between the second connection of the coil and a single-pole voltage input / output connection. The semiconductor device can additionally include a control and common-mode circuit. The control and common-mode circuit can include a linear common-mode loop that can be configured to maintain symmetry with respect to the reference ground connection between the positive bipolar input / output connection and the negative bipolar input / output connection. The control and common-mode circuit can additionally include a digital control loop that is configured to adjust the on-time pulse length of at least one of the first transistor, the second transistor, the third transistor, and the fourth transistor to drive the absolute value of a first current corresponding to the positive bipolar input / output connection and the absolute value of a second current corresponding to the negative bipolar input / output connection below a predetermined reference current value.

[0005] In one embodiment, a semiconductor device is disclosed that includes a bidirectional single-pole - bipolar DC - DC circuit. The bidirectional single-pole - bipolar DC - DC circuit can include a first transistor, a second transistor, a third transistor, and a fourth transistor. The first transistor can be connected between a reference ground connection and a first connection of the coil. The second transistor can be connected between a positive bipolar input / output connection and the first connection of the coil. The third transistor can be connected between a second connection of the coil and a negative bipolar input / output connection. The fourth transistor can be connected between the second connection of the coil and a single-pole voltage input / output connection. The bidirectional DC - DC circuit can be configured to concurrently activate the second transistor and the third transistor to cause current to flow through the coil between the positive bipolar input / output connection and the negative bipolar input / output connection. The semiconductor device can additionally include a bidirectional inverter / rectifier circuit that can be connected to the positive bipolar input / output connection, the negative bipolar input / output connection, a first AC connection, and a second AC connection. The bidirectional inverter / rectifier circuit can be configured to convert energy between a bipolar DC power supply defined by the positive bipolar input / output connection and the negative bipolar input / output connection and an AC power supply defined by the first AC connection and the second AC connection.

[0006] The foregoing summary is illustrative only and is not intended to be limiting in any way. In addition to the above-described illustrative aspects, embodiments, and features, additional aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description. In the drawings, like reference numerals indicate identical or functionally similar elements. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is a block diagram of an example system for wireless power transfer according to one embodiment.

[0008] Figure 2 is a block diagram of a system showing example components of a power transmitter and a power receiver according to one embodiment. Figure 1 of the system.

[0009] Figure 3 is a circuit diagram of an example bidirectional single-pole - bipolar DC - DC circuit of a system that can be used by a power receiver and a power transmitter according to one embodiment. Figure 2 of the system.

[0010] Figure 4 is a circuit diagram of an example bidirectional power transmitter / receiver circuit of a system that can be used by a power receiver and a power transmitter according to one embodiment, also showing the single-pole - bipolar DC - DC conversion flow path during power transfer. Figure 2 of the system.

[0011] Figure 5 is a circuit diagram showing Figure 5 of the bidirectional power transmitter / receiver circuit, Figure 5 showing the single-pole - bipolar DC - DC conversion flow path during power reception according to one embodiment.

[0012] Figure 6 is a signal diagram of signals associated with the Figure 5 bidirectional power transmitter / receiver circuit during power transfer and power reception according to one embodiment.

[0013] Figure 7 is a circuit diagram showing the control and common-mode loop of the Figure 5 bidirectional power transmitter / receiver circuit according to one embodiment.

[0014] Figure 8 is a signal diagram of signals associated with the Figure 5 bidirectional power transmitter / receiver circuit during power transfer and power reception according to one embodiment, including precise control by the Figure 7 control and common-mode loop circuit. DETAILED DESCRIPTION

[0015] Figure 1 FIG. 1 is a schematic diagram showing an example system 100 that implements wireless power transfer and communication according to an illustrative embodiment. The system 100 includes a power transmitter 110 and a power receiver 120, which are configured to wirelessly transfer power and data therebetween via an inductive coupler. Although described herein as a power transmitter 110 and a power receiver 120, each of the power transmitter 110 and the power receiver 120 may be configured to transmit and receive power or data therebetween via inductive coupling.

[0016] The power transmitter 110 is configured to receive power from one or more power sources and wirelessly transmit AC power to the power receiver 120. For example, the power transmitter 110 may be configured to connect to a power source such as an AC power source or a DC power source. The power transmitter 110 includes a controller 112 and a power driver 114.

[0017] The controller 112 is configured to control and operate the power driver 114. The controller 112 includes, for example, a processor, a central processing unit (CPU), a field programmable gate array (FPGA), or any other circuitry configured to control and operate the power driver 114. Although described as a CPU in the illustrative embodiment, the controller 112 is not limited to a CPU in these embodiments and may include any other circuitry configured to control and operate the power driver 114. In an example embodiment, the controller 112 is configured to control the power driver 114 to drive the coil TX of the power driver 114 to generate a magnetic field. The power driver 114 is configured to drive the coil TX within a frequency and configuration range defined by a wireless power standard, such as the Wireless Power Consortium (Qi) standard, the Power Matters Alliance (PMA) standard, the Wireless Power Consortium (WP or Rezence) standard, or any other wireless power standard. The controller 112 may be configured as a component separate from the power driver 114 or may be included as a part of the power driver 114.

[0018] The power receiver 120 is configured to receive the AC power transmitted from the power transmitter 110 and supply power to one or more loads 126 or other components of the target device 140. The destination device 140 may include, for example, a computing device, a mobile device, a mobile phone, a smart device, a tablet computer, a wearable device, or any other electronic device configured to wirelessly receive power. In the illustrative embodiment, the destination device 140 includes the power receiver 120. In other embodiments, the power receiver 120 may be separate from the destination device 140 and connected to the destination device 140 via a wire or other component configured to supply power to the destination device 140.

[0019] The power receiver 120 includes a controller 122 and a power rectifier 124. The controller 122 includes, for example, a processor, a central processing unit (CPU), a field programmable gate array (FPGA), or any other circuitry that can be configured to control and operate the power rectifier 124. The power rectifier 124 includes a coil RX and is configured to rectify the power received via the coil RX into the type of power required by the load 126. For example, the power rectifier 124 can be configured to rectify the AC power received from the coil RX into DC power, which can then be supplied to the load 126.

[0020] As an example, when the power receiver 120 is placed near the power transmitter 110, a magnetic field generated by the coil TX of the power driver 114 induces a current in the coil RX of the power rectifier 124. The induced current causes the AC power 130 to be inductively transferred from the power driver 114 to the power rectifier 124. The power rectifier 124 receives the AC power 130 and converts the AC power 130 into DC power 132. The DC power 132 is then provided by the power rectifier 124 to the load 126. The load 126 can include, for example, a battery charger configured to charge the battery of the destination device 140, a DC-DC converter configured to supply power to the processor, display, or other electronic components of the destination device 140, or any other load of the destination device 140.

[0021] The power transmitter 110 and the power receiver 120 are also configured to exchange information or data, such as messages, via inductive coupling of the power driver 114 and the power rectifier 124. For example, before the power transmitter 110 begins to transmit power to the power receiver 120, a power protocol can be established and created between the power receiver 120 and the power transmitter 110. For example, the power receiver 120 can send a communication data packet or other data indicating power transfer information to the power transmitter 110, where the power transfer information can be, for example, the amount of power to be transferred to the power receiver 120, a command to increase, decrease, or maintain the power level of the AC power 130, a command to stop power transfer, or other power transfer information. In another example, in response to the power receiver 120 being brought near the power transmitter 110, for example, close enough such that a transformer can be formed by the coil TX and the coil RX to facilitate power transfer, the power receiver 120 can be configured to initiate communication by sending a signal requesting power transfer to the power transmitter 110. In such cases, the power transmitter 110 can respond to the request of the power receiver 120 by establishing a power protocol or beginning to transmit power to the power receiver 120, for example, if a power protocol already exists.

[0022] The power transmitter 110 and the power receiver 120 can transmit and receive communication data packets, data, or other information via the inductive coupling of the coil TX and the coil RX. As an example, the communication data packet sent from the power transmitter 110 to the power receiver 120 may include a frequency shift keying (FSK) signal 134. The FSK signal 134 is a frequency modulation signal that uses changes in the carrier frequency to represent digital data. The communication data packet sent from the power receiver 120 to the power transmitter 110 may include an amplitude shift keying (ASK) signal 136. The ASK signal 136 is an amplitude modulation signal that uses changes in the carrier amplitude to represent digital data. Although the power transmitter 110 is described as sending the FSK signal 134 and the power receiver 120 is described as sending the ASK signal 136, in other embodiments, the power receiver 120 may alternatively send an FSK signal and the power transmitter 110 may alternatively send an ASK signal. Alternatively, any other means of transmitting communication data packets, data, or other information between the power transmitter 110 and the power receiver 120 may be used.

[0023] Now referring to Figure 2 , an example interface between the power transmitter 210 and the power receiver 220 will be described according to one embodiment. The power transmitter 210 and the power receiver 220 may include components and functionality similar to those of the power transmitter 110 and the power receiver 120 described above.

[0024] As Figure 2 shown, VUtx–GNDtx is the unipolar DC power supply of the power transmitter 210, where GNDtx is the local ground on the transmitter side and can be, for example, 0V or any other value. VUrx–GNDrx is the unipolar DC output power supply of the power receiver 220, where GNDrx is the local ground on the receiver side, which can be, for example, 0V or other values.

[0025] Some wireless power transfer systems stipulate that the DC component of the power supply should not appear at the isolated interface with respect to the local ground, also known as canceling the DC component. For example, the average AC voltage at the isolated interface should be equal to the local ground, for example, 0V or other values. For example, in one embodiment, such a system can be satisfied by a unipolar-bipolar conversion centered on the local ground.

[0026] The power transmitter 210 includes a DC / DC circuit 212 and a DC / AC circuit 214. The DC / DC circuit 212 is configured to convert the unipolar energy received from a unipolar DC power supply VUtx - GNDtx into bipolar DC energy having a positive component VBPtx and a negative component VBNtx. VBPtx - VBNtx is the bipolar intermediate DC power supply for the DC / AC converter 214, which is configured to convert the bipolar DC energy into AC energy for transmission, for example, to the coil RX of the power receiver 220 across an isolation gap using the coil TX. In one embodiment, the DC component can be set to zero according to Equation (1):

[0027] (VBPtx + VBNtx) / 2 = GNDtx (1)

[0028] The power receiver 220 includes an AC / DC circuit 224 and a DC / DC circuit 222. The AC / DC circuit 224 is configured to receive AC energy from the coil RX and convert the received AC energy into bipolar DC energy having a positive component VBPrx and a negative component VBNrx. VBPrx - VBNrx is the bipolar intermediate DC power supply to the DC / DC circuit 222, which is configured to convert the bipolar DC energy into unipolar DC energy and output the unipolar DC energy as the DC power supply VUrx - GNDrx. In one embodiment, the DC component can be set to zero according to Equation (2):

[0029] (VBPrx + VBNrx) / 2 = GNDrx (2)

[0030] Now referring to Figure 3 , an example DC / DC circuit 300 that can be used to convert between unipolar DC energy and bipolar DC energy will now be described according to one embodiment. In one embodiment, the DC / DC circuit 330 is bidirectional and can be used in one or both of the DC / DC circuits 212( Figure 2 ) and 222( Figure 2 ), which will be described in more detail below.

[0031] The DC / DC circuit 300 is connected to VU, GND, VBP, and VBN. As an example, for the DC / DC circuit 212, VU may correspond to VUtx, GND may correspond to GNDtx, VBP may correspond to VBPtx, and VBN may correspond to VBNtx. Similarly, for the DC / DC circuit 222, VU may correspond to VUrx, GND may correspond to GNDrx, VBP may correspond to VBPrx, and VBN may correspond to VBNrx.

[0032] The DC / DC circuit 300 can also utilize an external coil L0, which is connected to the DC / DC circuit 300 via connectors SW1 and SW2. In some embodiments, the coil L0 can also be integrated into the DC / DC circuit 300.

[0033] As shown, the DC / DC circuit 300 includes transistors M1, M2, M3, and M4 disposed between VU, GND, VBP, VBN, SW1, and SW2. The transistors M1, M2, M3, and M4 can include any type of transistor commonly used in semiconductor devices, including, for example, field effect transistors (FETs), metal oxide semiconductor field effect transistors (MOSFETs), bipolar junction transistors (BJTs), or any other transistor or switching technology. The transistors M1, M2, M3, and M4 can be controlled by corresponding control circuits, such as power drivers, for example, using pulse width modulation or another type of signal.

[0034] As Figure 3 shown, transistor M1 is connected to GND, transistor M2 is connected to VBP, transistor M3 is connected to VBN, and transistor M4 is connected to VU. SW1 is connected between transistors M1 and M2, while SW2 is connected between transistors M3 and M4.

[0035] The transistors M1, M2, M3, and M4 are configured to control the energy flow through the coil L0 during the conversion between unipolar DC energy and bipolar DC energy. For example, depending on the activation state of each transistor M1, M2, M3, M4, current can flow through the coil L0 in a specific direction and along a specific path within the DC / DC circuit 300 to reversibly achieve the corresponding conversion.

[0036] In an example embodiment, M1 can include a 5V n-type transistor, M2 can include a 5V p-type transistor, M3 can include a 12V n-type transistor, and M4 can include a 12V p-type transistor. In such embodiments, the power supply VU-GND can have a value of 5V, VBP has a value of +6V, and VBN has a value of -6V. Any other values of the power supply, VBP, VBN, and transistors M1, M2, M3, and M4 can also be used.

[0037] Referring Figure 4 and Figure 5 , it is shown that the DC / DC circuit 300 is integrated into the bidirectional power transmitter / receiver circuit 400 together with the inverter / rectifier circuit 500. Either or both of the power transmitter 210 and the power receiver 220 can include a corresponding bidirectional power transmitter / receiver circuit 400, which is configured to perform conversions between AC energy, DC bipolar energy, and DC unipolar energy in either direction on the same silicon.

[0038] The bidirectional power transmitter / receiver circuit 400 includes a control and common-mode (CM) loop circuit 402 configured to finely control the symmetric bipolar behavior of the DC / DC circuit 300. Some or all of the functionality of the control and CM loop 402 may be implemented by the controller 112( Figure 1 ), the controller 122, or another processing device. In some embodiments, the control and CM loop 402 is configured to consume little or no power when the circuit 300 is in a steady state.

[0039] The inverter / rectifier circuit 500 is configured to perform the conversion between bipolar DC energy and AC energy in either direction of the power transmitter 210 or the power receiver 220. The inverter / rectifier circuit 500 includes transistors HS1, LS1, HS2, and LS2 connected to VBP, VBN, AC1, and AC2, as shown. The transistors HS1, LS1, HS2, and LS2 may include any type of transistor described above for transistors M1, M2, M3, and M4. AC1 and AC2 are respectively connected to the coil TX or the coil RX. The transistor HS1 is disposed between VBP and AC1, the transistor HS2 is disposed between VBP and AC2, the transistor LS1 is disposed between VBN and AC1, and the transistor LS2 is disposed between VBN and AC2. The transistors HS1, LS1, HS2, and LS2 are selectively activated to convert the bipolar DC power VBP-VBN into an AC output for transmission between the coil TX and the coil RX. For example, in some embodiments, two symmetric square waves are generated on AC1 and AC2.

[0040] Figure 4 An example flow of the DC / DC circuit 300 during power transfer is illustrated. For example, when the bidirectional power transmitter / receiver circuit 400 is used as the power transmitter 210, it is also referred to herein as the TX mode. During the TX mode, the DC / DC circuit 300 is provided with VU referenced to GND. The transistors M1, M2, M3, and M4 are used as a single-inductor dual-output (SIDO) to perform DC-DC conversion and single-pole to bipolar conversion.

[0041] The TX mode conversion involves a two-stage process. In the first stage, as shown in process 404tx, the coil L0 is magnetized by turning on transistors M4 and M1. The current flows from VU through transistor M4 to SW2, through coil L0 to SW1, and then through transistor M1 to GND. The current magnetizes coil L0, allowing coil L0 to store energy. Once coil L0 is sufficiently energized, M4 and M1 can be turned off. In other embodiments, for example, if VU provides a negative voltage or GND has a reference value greater than the voltage provided by VU, the current can flow from GND to VU to energize coil L0.

[0042] In the second stage, coil L0 is demagnetized and the stored energy is dumped to VBP-VBN by turning on transistors M3 and M2, as shown in process 406tx. The current flows from VBN through transistor M3 to SW2, through coil L0 to SW1, and through transistor M2 to VBP, increasing the voltage of VBP and concurrently decreasing the voltage of VBN until coil L0 is completely demagnetized. In this way, the positive voltage on VBP can be balanced with the negative voltage on VBN. In the TX mode, the inverter / rectifier 500 acts as an inverter and converts the bipolar DC energy provided by VBP-VBN into AC energy for output by AC1 and AC2, for example, as a symmetric rectangular wave. The two-stage process of the TX mode can be repeated as needed to continue providing VBP and VBN to the inverter / rectifier 500 for DC-AC conversion.

[0043] Figure 5 An example process of the DC / DC circuit 300 during power reception is illustrated. For example, when the bidirectional power transmitter / receiver circuit 400 acts as the power receiver 220, it is also referred to as the RX mode in this document. During the RX mode, the inverter / rectifier circuit 500 is operated as a rectifier to generate VBP and VBN from the AC energy received by the coil RX. Transistors M1, M2, M3, and M4 act as bipolar-input, unipolar-output DC-DC converters that perform DC-DC conversion and bipolar-to-unipolar conversion.

[0044] The conversion involves a two-stage process. In the first stage, as shown in process 404rx, the coil L0 is magnetized by turning on transistors M2 and M3. The current flows from VBP through transistor M2 to SW1, through coil L0 to SW2, and through transistor M3 to VBN, decreasing the voltage of VBP and concurrently increasing the voltage of VBN. The current magnetizes coil L0, allowing coil L0 to store energy.

[0045] In the second stage, by turning on transistors M4 and M1, coil L0 is demagnetized or dumped to VU-GND, as shown in process 406rx. Current flows from GND through transistor M1 to SW1, through coil L0 to SW2, and through transistor M4 to VU, increasing the voltage of VU until coil L0 is completely demagnetized or discharged. In this way, a single-pole DC energy source VU-GND can be generated for output to load 126( Figure 1 ). The two-stage RX mode process can be repeated as needed to continue outputting the single-pole DC energy source VU-GND.

[0046] During the TX mode process and the RX mode process, controllers 112 and 122 use control and CM loop 402 to ensure that (VBP + VBN) / 2 = GND.

[0047] Refer to Figure 6 , and an example signal diagram 600 of the TX mode process and the RX mode process will now be described. The TX mode process is performed by power transmitter 210 including bidirectional power transmitter / receiver circuit 400, and the RX mode process is performed by power receiver 220 including another bidirectional power transmitter / receiver circuit 400.

[0048] Signal diagram 600 illustrates the TX mode and RX mode processes for timestamps t0 - t3. At time t0, the TX DC-DC enable signal TxEn is set high, initializing the TX-side DC / DC circuit 300 to start converting energy from the single-pole power source VUtx-GNDtx to the bipolar power source VBPtx-VBNtx, also known as the soft start of VBPtx-VBNtx. At time t0, the TX inverter enable signal TxInvEn, which controls the activation of the TX-side inverter / rectifier circuit 500, is set low, and the inverter is inactive.

[0049] On the RX side, at time t0, the RX DC-DC enable signal RxEn, which controls the activation of the RX-side DC / DC circuit 300, is also set low, and the RX-side DC / DC circuit 300 has not yet converted the bipolar DC power from the RX-side inverter / rectifier circuit 500 to single-pole DC power.

[0050] Initially, at time t0, VUtx is equal to the target voltage, e.g., 5V, and VBPtx, GNDtx, VBNtx, AC1tx, and AC2tx are all 0V (or equal to the reference voltage). The TX-side DC / DC circuit 300 has not yet started converting the VUtx - GNDtx from unipolar DC energy to bipolar DC energy to supply VBPtx - VBNtx, and no power is being transferred to the power receiver 220. VUrx, VBPrx, GNDrx, VBNrx, ACrtx, and AC2rx are all 0 because no power is received from the power transmitter 210.

[0051] Between time t0 and time t1, since TxEn is set high, the TX-side DC / DC circuit 300 starts converting the unipolar power supply VUtx - GNDtx to a bipolar power supply VBPtx - VBNtx during soft start. Due to the TX-side DC / DC circuit 300, VBPtx starts to increase while VBNtx concurrently starts to decrease, ensuring that (VBPtx + VBNtx) / 2 = GNDtx. AC1tx and AC2tx are also powered by the TX-side inverter rectifier circuit 500 during soft start.

[0052] At time t1, TxInvEn is set high, activating the TX-side inverter / rectifier circuit 500 to transfer the AC power output generated by AC1tx and AC2tx to the coil TX. RxEn remains low.

[0053] Between time t1 and time t2, as the TX-side inverter / rectifier circuit 500 starts transferring the AC power output converted from the bipolar DC power supply VBPtx - VBNtx to the coil tx, VBPtx and VBNtx each slope towards GNDtx, then continue to rise, and finally flatten out after time t2 and t3, where |VBPtx| = |VBNtx| = |VUtx|. As Figure 6 shown by the shaded area in, AC1tx and AC2tx are driven by the TX-side inverter / rectifier circuit 500 to output a symmetric rectangular wave that starts powering the coil tx to transfer AC energy to the coil RX. AC1tx and AC2tx can be driven to the target frequency, e.g., 6.78 MHz or another frequency value.

[0054] Between time t1 and time t2, AC1rx and AC2rx receive AC energy from the coils RX and RX side. The inverter / rectifier circuit 500 converts the AC energy into a bipolar DC power supply VBPrx-VBNrx and symmetrically generates VBPrx and VBNrx. Since RxEn has not been enabled yet, the RX side DC / DC circuit 300 has not started to convert the bipolar DC power supply VBPrx-VBNrx into a unipolar DC power supply VUrx-GNDrx, and VUrx remains at 0V.

[0055] At time t2, RxEn is set high and the RX side DC / DC circuit 300 starts to convert the bipolar DC power supply VBPrx-VBNrx into a unipolar DC power supply VUrx-GNDrx, as indicated by the increase in VUrx. By time t3, |VUrx| = |VBPrx| = |VBNrx| and power is being transferred between the power transmitter 210 and the power receiver 220.

[0056] Reference Figure 7 , the example control and CM loop 402 functionality will now be described. During conversion and power transfer, the bidirectional power transmitter / receiver circuit 400 may need to precisely control the common mode. For example, in one embodiment, the precise control can be configured to ensure that VBP = |VBN|. This can be particularly important when on the RX side, where the bidirectional power transmitter / receiver circuit 400 operating in RX mode rectifies the received AC energy AC1rx and AC2rx into a DC bipolar power supply VBPrx-VBNrx and then converts it into a DC unipolar power supply VUrx-GNDrx. In an ideal conversion, the current consumption from VBP should be perfectly balanced with the current consumption from VBN at both the TX and RX ends. In one embodiment, such balance of VBP and VBN currents is achieved by using a CM loop.

[0057] A typical linear (analog) CM loop typically seeks to absorb any mismatch between the VBP and VBN currents into GND to ensure symmetry, at the cost of power consumption and efficiency loss. In one embodiment, as Figure 7 shown, a digital assisted common mode loop is disclosed that suppresses or reduces the efficiency loss associated with absorbing the mismatch.

[0058] Figure 7 Illustrated is an example control and CM loop 402 that can be used for the RX mode of the bidirectional power transmitter / receiver circuit 400, although the same functionality can also be applied to the TX mode.

[0059] The control and CM loop 402 includes a linear CM loop 408 configured to ensure symmetry between VBP and VBN, e.g., VBP = |VBN|. Even at high frequencies, any current mismatch between VBP and VBN is compensated for by current Ip or current In. The control and CM loop 402 also includes a digital control loop 410 configured to maintain Ip and In within a certain window of a steady state, e.g., |Ip| < Iref and |In| < reference current Iref). In some embodiments, the linear CM loop 408 is configured to operate at a higher frequency than the digital control loop 410, and the bandwidth of the control and CM loop 402 is controlled by the frequency of a low-frequency clock connected to the UP / DN counter 414 of the digital control loop 410.

[0060] During operation of the control and CM loop 402, the digital control loop 410 samples the current values Ip and In of the linear CM loop 408. Comparators 412p and 412n are configured to compare the sampled Ip and In current values with the reference current Iref, respectively. Comparator 412p is configured to output a determination of whether the absolute value of Ip is greater than Iref, and comparator 412n is configured to output a determination of whether the absolute value of In is greater than Iref. As an example, in some embodiments, the output of comparator 412p can be simplified to determine whether Ip is greater than Iref, and the output of comparator 412n can be simplified to determine whether Iref is greater than In.

[0061] The outputs of comparators 412p and 412n are provided as inputs to an UP / DOWN (UP / DN) counter 414. The UP / DN counter 414 is configured to adjust the pulse length of the turn-on time control signal provided to the control circuitry of transistors M1, M2, M3, and M4 based on the values received from comparators 412p and 412n and based on which of the TX or RX modes the bidirectional power transmitter / receiver circuit 400 is operating in. For example, the UP / DN counter 414 can increase (e.g., stretch) the pulse length, decrease (e.g., shrink) the pulse length, or adjust the pulse length in any other way. Increasing the pulse length increases the turn-on time of the corresponding transistor M1, M2, M3, or M4, while decreasing the pulse length decreases the turn-on time of the corresponding transistor M1, M2, M3, or M4. In some embodiments, the pulse length can have a minimum value below which the UP / DN counter 414 will not decrement, thus ensuring a minimum turn-on time for the corresponding transistor. In some embodiments, transistors M1, M2, M3, and M4 are initialized with a predetermined turn-on time pulse length. As an example, the turn-on time pulse lengths of transistors M1 and M4 can initially be equal. Similarly, the turn-on time pulse lengths of transistors M2 and M3 can initially be equal.

[0062] As an example, in RX mode, as Figure 7 shown, the UP / DN counter 414 is configured to increase the pulse length of the control signal of transistor M2 if |Ip| > Iref, and to increase the pulse length of the control signal of transistor M3 if |In| > Iref. Similarly, the UP / DN counter 414 is configured to decrease the pulse length of the control signal of transistor M2 if |Ip| <= Iref, and to decrease the pulse length of the control signal of transistor M3 if |In| <= Iref. These increases and decreases in pulse length can be performed independently of each other by the UP / DN counter 414 based on the values of Ip and In. In some embodiments, the mismatch in conduction time between transistors M2 and M3 is used to drive any current mismatch between |Ip| and |In| towards Iref.

[0063] As another example, in TX mode, the UP / DN counter 414 is configured to increase the pulse length of the control signal of transistor M1 if |Ip| > Iref, and to increase the pulse length of the control signal of transistor M4 if |In| > Iref. Similarly, the UP / DN counter 414 is configured to decrease the pulse length of the control signal of transistor M1 if |Ip| <= Iref, and to decrease the pulse length of the control signal of transistor M4 if |In| <= Iref. These increases and decreases in pulse length can be performed independently of each other by the UP / DN counter 414 based on the values of Ip and In.

[0064] Referring Figure 8 to

[0065] Signal diagram 800 illustrates the TX mode and RX mode processes for time stamps t0 - t3. Initially at time t0, VUtx is equal to the target voltage, e.g., 5V, and VBPtx, GNDtx, VBNtx are all 0V (or equal to the reference voltage), and Iptx and Intx are at 0A. The TX side DC / DC circuit 300 has not yet started converting the VUtx - GNDtx from unipolar DC energy to bipolar DC energy to supply VBPtx - VBNtx, and no power is being transferred to the power receiver 220. VUrx, VBPrx, GNDrx, VBNrx are all 0V (or equal to the reference voltage), and Iprx and Inrx are 0A because no power is received from the power transmitter 210. The M1TXStretch and M2RXStretch signals are equal to 0, indicating that there is no valid pulse length increase or decrease on the TX side for transistor M1, and no valid pulse length increase on the RX side for transistor M2. Note that the units of M1TXStretch and M2RXStretch are nV, e.g., 1nV corresponds to an increase or decrease in pulse length of 1ns.

[0066] Between time t0 and time t1, the TX side DC / DC circuit 300 starts converting the unipolar power supply VUtx - GNDtx to the bipolar power supply VBPtx - VBNtx during soft start. Due to the TX side DC / DC circuit 300, VBPtx starts to increase while VBNtx concurrently starts to decrease, ensuring that (VBPtx + VBNtx) / 2 = GNDtx. As the TX side DC / DC circuit 300 is activated, the values of Iptx and Intx also spike, and in this example, Iptx goes as high as 150mA.

[0067] Between time t1 and time t2, when the TX side inverter / rectifier circuit 500 starts delivering the AC power output converted from the bipolar DC power supply VBPtx - VBNtx to the coil tx, VBPtx and VBNtx each slope towards GNDtx, then continue to rise, and finally flatten out after time t2 and t3, where |VBPtx| = |VBNtx| = |VUtx|. The TX side digital control loop 410 also determines that |Iptx| is greater than Iref and starts incrementing M1TXStretch to increase the on - time of transistor M1 in order to drive the current back down to Iref. As seen after time t3, both |Iptx| and |Intx| are in a steady state close to Iref, e.g., less than 100μA.

[0068] Between time t1 and time t2, the RX-side inverter / rectifier circuit 500 converts AC energy into a bipolar DC power supply VBPrx-VBNrx and symmetrically generates VBPrx and VBNrx. Spikes also occur in Iprx and Inrx, for example up to 15 mA.

[0069] At time t2, the RX-side DC / DC circuit 300 begins to convert the bipolar DC power supply VBPrx-VBNrx into a unipolar DC power supply VUrx-GNDrx, as indicated by the increase in VUrx between time t2 and time t3. By time t3, |VUrx| = |VBPrx| = |VBNrx| and power is being transferred between the power transmitter 210 and the power receiver 220.

[0070] Between time t2 and time t3, the RX-side digital control loop 410 also determines that |Iprx| is greater than Iref and begins to increase M2RXStretch to increase the on-time of transistor M2, thereby driving the current back down to Iref. As shown after t3, the current on Iprx and Inrx is in a steady state close to Iref, for example less than 100 μA.

[0071] By providing a bidirectional power transmitter / receiver circuit 400 with a unipolar-bipolar DC / DC circuit, which is controlled by a control and CM circuit including linear common-mode and digital control components, the disclosed embodiments compensate for asymmetric current consumption from VBP and VBN by manipulating the on-time of the transistors performing the unipolar-bipolar DC-DC conversion. The disclosed embodiments can improve the efficiency of the power transmission and power reception circuits, reducing power losses in the conversion by eliminating the need to absorb any mismatch between VBP and VBN on the TX and RX sides. The disclosed embodiments additionally ensure that there is no DC component with respect to local ground at the isolation interface. The disclosed bidirectional power transmitter / receiver circuit 400 includes a unipolar-bipolar DC-DC circuit 300 that can be used in both TX and RX modes, enabling the use of the same silicon configuration for both TX and RX modes, which simplifies the production process, optimizes production costs, and shortens the time to market.

[0072] The terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the present invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the terms "comprises" and / or "comprising", when used in this specification, specify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or combinations thereof.

[0073] All corresponding structures, materials, acts, and equivalents of the means or step plus function elements (if any) in the following claims are intended to include any structure, material, or act for performing the function, as well as other claimed elements that are particularly claimed. For purposes of illustration and description, the disclosed embodiments of the present invention have been presented, but these embodiments are not intended to be exhaustive or to limit the present invention to the disclosed forms. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the present invention. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, and to enable others of ordinary skill in the art to understand the present invention for various embodiments with various modifications suitable for the particular purposes contemplated.

Claims

1. A semiconductor device comprising: A bidirectional unipolar-bipolar DC-DC circuit, comprising: a first transistor connected between a reference ground connection and a first connection of the coil; a second transistor connected between the positive bipolar input / output connection and the first connection of the coil; a third transistor connected between the second connection of the coil and the negative bipolar input / output connection; and a fourth transistor connected between the second connection of the coil and a unipolar voltage input / output connection, the bidirectional DC-DC circuit being configured to concurrently activate the second transistor and the third transistor to cause current to flow through the coil between the positive bipolar input / output connection and the negative bipolar input / output connection.

2. The semiconductor device of claim 1 , wherein when in a power delivery mode, the bidirectional unipolar-bipolar DC-DC circuit is configured to: concurrently activating the first transistor and the fourth transistor to magnetize the coil by current flowing from the unipolar voltage input / output connection to the reference ground connection; and The second transistor and the third transistor are activated concurrently to demagnetize the coil by a current flowing from the negative bipolar input / output connection to the positive bipolar input / output connection, the demagnetization simultaneously generating a positive voltage on the positive bipolar input / output connection and a negative voltage on the negative bipolar input / output connection.

3. The semiconductor device of claim 1 , wherein when in a power receiving mode, the bidirectional unipolar-bipolar DC-DC circuit is configured to: concurrently activating the second transistor and the third transistor to magnetize the coil by a current flowing from the positive bipolar input / output connection to the negative bipolar input / output connection; and The first transistor and the fourth transistor are activated concurrently to demagnetize the coil by a current flowing from the reference ground connection to the unipolar voltage input / output connection.

4. The semiconductor device of claim 1, wherein the semiconductor device comprises a control and common mode circuit configured to adjust an on-time pulse length of at least one of the first transistor, the second transistor, the third transistor, and the fourth transistor.

5. The semiconductor device of claim 4, wherein the control and common mode circuit comprises: a linear common mode loop configured to maintain symmetry between the positive bipolar input / output connection and the negative bipolar input / output connection with respect to the reference ground connection; as well as a digital control loop configured to adjust the on-time pulse length of at least one of the first transistor, the second transistor, the third transistor, and the fourth transistor to drive an absolute value of a first current corresponding to the positive bipolar input / output connection and an absolute value of a second current corresponding to the negative bipolar input / output connection below a predetermined reference current value.

6. The semiconductor device according to claim 5, wherein the digital control loop is configured as: Based on the first current being greater than the predetermined reference current, increasing the on-time pulse length of a corresponding one of the first transistor, the second transistor, the third transistor, and the fourth transistor; and Based on the second current being greater than the predetermined reference current, the on-time pulse length of a corresponding one of the first transistor, the second transistor, the third transistor, and the fourth transistor is increased.

7. The semiconductor device according to claim 5, wherein the digital control loop includes an up / down counter, and the up / down counter is configured to increase and decrease the on-time pulse length corresponding to the at least one of the first transistor, the second transistor, the third transistor and the fourth transistor based on the comparison of the absolute value of the first current with the reference current value. 8 . The semiconductor device of claim 5 , wherein the linear common mode loop operates at a higher frequency than the digital control loop. 9 . The semiconductor device of claim 8 , wherein the digital control loop comprises a low frequency clock, the low frequency clock being adjustable to adjust the operating frequency of the digital control loop.

10. A semiconductor device comprising: A bidirectional unipolar-bipolar DC-DC circuit, comprising: a first transistor connected between a reference ground connection and a first connection of the coil; a second transistor connected between the positive bipolar input / output connection and the first connection of the coil; a third transistor connected between the second connection of the coil and the negative bipolar input / output connection; and a fourth transistor connected between the second connection of the coil and a unipolar voltage input / output connection; and Control and common-mode circuits, including: a linear common mode loop configured to maintain symmetry between the positive bipolar input / output connection and the negative bipolar input / output connection with respect to the reference ground connection; and A digital control loop is configured to adjust the on-time pulse length of at least one of the first transistor, the second transistor, the third transistor and the fourth transistor to drive the absolute value of the first current corresponding to the positive bipolar input / output connection and the absolute value of the second current corresponding to the negative bipolar input / output connection to be lower than a predetermined reference current value.

11. The semiconductor device of claim 10 , wherein when in a power delivery mode, the bidirectional unipolar-bipolar DC-DC circuit is configured to: concurrently activating the first transistor and the fourth transistor to magnetize the coil by current flowing from the unipolar voltage input / output connection to the reference ground connection; and The second transistor and the third transistor are activated concurrently to demagnetize the coil by a current flowing from the negative bipolar input / output connection to the positive bipolar input / output connection, the demagnetization simultaneously generating a positive voltage on the positive bipolar input / output connection and a negative voltage on the negative bipolar input / output connection.

12. The semiconductor device of claim 10 , wherein when in a power receiving mode, the bidirectional unipolar-bipolar DC-DC circuit is configured to: concurrently activating the second transistor and the third transistor to magnetize the coil by a current flowing from the positive bipolar input / output connection to the negative bipolar input / output connection; and The first transistor and the fourth transistor are activated concurrently to demagnetize the coil by a current flowing from the reference ground connection to the unipolar voltage input / output connection.

13. The semiconductor device according to claim 10, wherein the digital control loop is configured as: increasing the on-time pulse length of a corresponding one of the first transistor, the second transistor, the third transistor, and the fourth transistor based on the first current being greater than the predetermined reference current; and Based on the second current being greater than the predetermined reference current, the on-time pulse length of a corresponding one of the first transistor, the second transistor, the third transistor, and the fourth transistor is increased.

14. The semiconductor device according to claim 10, wherein the digital control loop includes an up / down counter, and the up / down counter is configured to increase and decrease the on-time pulse length of the at least one of the first transistor, the second transistor, the third transistor and the fourth transistor based on the comparison of the absolute value of the first current with the reference current value.

15. The semiconductor device of claim 10, wherein the linear common mode loop operates at a higher frequency than the digital control loop. 16 . The semiconductor device of claim 15 , wherein the digital control loop comprises a low frequency clock, the low frequency clock being adjustable to adjust the operating frequency of the digital control loop.

17. A semiconductor device comprising: A bidirectional unipolar-bipolar DC-DC circuit, comprising: a first transistor connected between a reference ground connection and a first connection of the coil; a second transistor connected between the positive bipolar input / output connection and the first connection of the coil; a third transistor connected between the second connection of the coil and the negative bipolar input / output connection; and a fourth transistor connected between the second connection of the coil and a unipolar voltage input / output connection, the bidirectional DC-DC circuit being configured to concurrently activate the second transistor and the third transistor to cause current to flow through the coil between the positive bipolar input / output connection and the negative bipolar input / output connection; and A bidirectional inverter / rectifier circuit is connected to the positive bipolar input / output connection, the negative bipolar input / output connection, the first AC connection, and the second AC connection, and the bidirectional inverter / rectifier circuit is configured to convert energy between a bipolar DC power supply defined by the positive bipolar input / output connection and the negative bipolar input / output connection and an AC power supply defined by the first AC connection and the second AC connection.

18. The semiconductor device of claim 17, wherein the semiconductor device further comprises a control and common mode circuit, the control and common mode circuit comprising: a linear common mode loop configured to maintain symmetry between the positive bipolar input / output connection and the negative bipolar input / output connection with respect to the reference ground connection; as well as A digital control loop is configured to adjust the on-time pulse length of at least one of the first transistor, the second transistor, the third transistor and the fourth transistor to drive the absolute value of the first current corresponding to the positive bipolar input / output connection and the absolute value of the second current corresponding to the negative bipolar input / output connection to be lower than a predetermined reference current value.

19. The semiconductor device according to claim 18, wherein: The linear common mode loop operates at a higher frequency than the digital control loop; as well as The digital control loop includes a low frequency clock that is adjustable to adjust the operating frequency of the digital control loop.

20. The semiconductor device of claim 17, wherein the bidirectional unipolar-bipolar DC-DC circuit comprises a digital control loop configured to: increasing the on-time pulse length of a corresponding one of the first transistor, the second transistor, the third transistor, and the fourth transistor based on the first current being greater than a predetermined reference current; and Based on the second current being greater than the predetermined reference current, the on-time pulse length of a corresponding one of the first transistor, the second transistor, the third transistor, and the fourth transistor is increased.

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