Isolated power transfer via coupled oscillators

Abstract

Isolated power transfer via coupled oscillators is disclosed. A system (200) includes a power receiver (110) including an oscillator having a first coil (112) and a second coil (114). The oscillator includes a first field effect transistor (FET) (120) having a first gate terminal, a first source terminal, and a first drain terminal, the first drain terminal coupled to the first coil (112), the first coil (112) adapted to inductively couple to a third coil (204) in a power sensor (102). The oscillator further includes a first capacitor (116) coupled to the first coil (112). The oscillator includes a second FET (122) having a second gate terminal, a second source terminal, and a second drain terminal, the second gate terminal coupled to the first capacitor (116), the second source terminal coupled to the first source terminal, and the second drain terminal coupled to the second coil (114), the second coil (114) adapted to inductively couple to a fourth coil (202) in a power transmitter (102). The oscillator includes a second capacitor (118) coupled to the first gate terminal and coupled to the second coil (114).

Description

Background Technology

[0001] Electronic isolation is a means of preventing the transmission of direct current (DC) and unwanted alternating current (AC) between two parts of a system while still allowing signal and power transmission between those parts. One method for electrical isolation is to use a transformer to transfer energy from the transmitter to the receiver. Electrical energy can be transferred between the individual coils of the transformer, without any conductive connection between the transmitter and receiver. Summary of the Invention

[0002] In at least one example, a system includes a power receiver comprising an oscillator, wherein the oscillator includes a first coil and a second coil. The oscillator further includes a first field-effect transistor (FET) having a first gate terminal, a first source terminal, and a first drain terminal, the first drain terminal being coupled to the first coil, the first coil being adapted for inductive coupling to a third coil in a power transmitter. The oscillator includes a first capacitor coupled to the first coil. The oscillator further includes a second FET having a second gate terminal, a second source terminal, and a second drain terminal, the second gate terminal being coupled to the first capacitor, the second source terminal being coupled to the first source terminal, and the second drain terminal being coupled to a second coil, the second coil being adapted for inductive coupling to a fourth coil in a power transmitter. The oscillator also includes a second capacitor coupled to the first gate terminal and coupled to the second coil.

[0003] In at least one example, a system includes a power transmitter that includes an oscillator. The oscillator includes a first FET having a first gate terminal, a first source terminal, and a first drain terminal, the first drain terminal being coupled to a first coil. The oscillator also includes a first capacitor coupled to the first coil. The oscillator further includes a second FET having a second gate terminal, a second source terminal, and a second drain terminal, the second gate terminal being coupled to the first capacitor, the second source terminal being coupled to the first source terminal, and the second drain terminal being coupled to a second coil. The oscillator also includes a second capacitor coupled to the first gate terminal and adapted to be coupled to the second coil.

[0004] In at least one example, a method includes providing an input voltage to a first oscillator in a power transmitter, the first oscillator including a first coil and a second coil. The method further includes driving a current through the first and second coils to generate a first magnetic field and a second magnetic field. The method also includes inducing a first electromotive force (EMF) in a second oscillator in a power receiver via the first magnetic field, the second oscillator including a third coil and a fourth coil. The method further includes inducing a second EMF in the second oscillator via the second magnetic field. The method also includes providing an output voltage to a load via the second oscillator, the output voltage being proportional to the input voltage. Attached Figure Description

[0005] Figure 1A These are schematic diagrams of power transmission systems based on various examples.

[0006] Figure 1B These are waveform diagrams from example oscillator systems based on various examples.

[0007] Figure 2 These are schematic diagrams of power transmission systems based on various examples.

[0008] Figure 3 These are schematic diagrams of power transmission systems based on various examples.

[0009] Figure 4 These are schematic diagrams of power transmission systems based on various examples.

[0010] Figure 5 These are schematic diagrams of power receivers based on various examples.

[0011] Figure 6 This is a flowchart of example methods for isolated power transmission based on various examples. Detailed Implementation

[0012] One technique for isolated power transmission uses a transmitter and a receiver, where power is transmitted via a transformer. An isolation barrier in the transformer prevents the DC component of the signal from traveling from the transmitter to the receiver, but allows the AC component of the signal to pass through the barrier. Power is transmitted via magnetic induction from a coil on the transmitter side to a coil on the receiver side. The voltage and current in the transmitter coil generate a magnetic flux, which induces an electromotive force (EMF) in the receiver coil, resulting in a current in the receiver coil.

[0013] In some conventional systems, the power transmitter uses a half-bridge or full-bridge structure to generate a square wave voltage, which is transmitted across an isolation barrier via magnetic induction. On the receiver side of a conventional system, some form of rectification is performed to convert the input AC or similar AC signal from the transmitter into a DC signal. Rectification can be passive (e.g., using a diode bridge rectifier) ​​or active (e.g., using active switches). Passive rectification is generally less complex to implement than active rectification. With passive rectification, the receiver does not need to be synchronized with the transmitter. However, the diode voltage drop in a diode bridge rectifier leads to power consumption that reduces the overall efficiency of the system. With active rectification, the switches in the receiver are configured to operate at a specific frequency related to the frequency of the input signal from the transmitter. Some conventional systems use a sensing coil at the receiver to sense the magnetic field from the transmitter coil and recover the frequency of the input signal, then use a controller to adjust the phase on the receiver side based on the recovered frequency to regulate the receiver output. Switches in receivers used for active rectification incur power losses (e.g., gate drive losses) as they drive the transistors that constitute the switches. These gate drive losses are proportional to the switching frequency. A higher switching frequency means that the transistor turns on and off more times per second, so a higher switching frequency will result in more gate drive losses.

[0014] Therefore, conventional systems suffer from power losses on both the transmitter and receiver sides. The transformer itself also experiences power losses. Transformer efficiency is a strong function of the coil's quality factor Q. The quality factor Q is a dimensionless unit representing the ratio of the magnetic energy stored in the coil to the energy loss (typically in ohms) over one cycle (usually defined by the multiplier factor 2π). The quality factor Q is the ratio of inductance L to coil resistance R at a given frequency ω; Q = (ωL) / R. Miniaturized coils (e.g., coils on electronic chips using air cores) have a reasonable Q at high switching frequencies ω. However, as mentioned above, higher switching frequencies lead to higher gate drive losses due to driving transistors in the receiver at higher frequencies. Therefore, using miniaturized coils to achieve high Q values ​​at high switching frequencies results in higher gate drive losses.

[0015] The examples described herein include switching receivers that do not use passive diodes and do not suffer from high gate drive losses. Instead, the examples here include a power oscillator in the receiver that uses a switch to excite one or more inductors and one or more capacitors in an LC circuit. The transistor in the power oscillator is driven resonantly; this phenomenon is called resonant gate drive. In conventional systems, the switch is driven by hard charging (or ohmic charging) and then hard discharging (or ohmic discharging) the gate capacitance of the transistor. However, resonant gate drive recovers the energy used to charge and discharge the gate capacitance of the transistor by utilizing an LC oscillating circuit. In the examples described herein, resonant gate drive enables a wireless power transmission system with lower power losses than conventional systems. In another example described herein, both the transmitter and receiver include power oscillators. Different types of oscillators are used in the various examples.

[0016] Figure 1A This is a schematic diagram of example system 100. System 100 is a system for wireless power transmission using a transmitter and receiver. The transmitter (left) side of system 100 includes components coupled to a voltage source V. in Power transmitter 102 of 104. Power transmitter 102 is represented as a block and includes any suitable type of power transmitter. Power transmitter 102 can use a half-bridge topology, a full-bridge topology, or any other suitable topology. Voltage source V in 104 provides DC voltage to power transmitter 102. The transmitter side of system 100 also includes transformer coils. In this example, the transformer coils include two coils, 106 and 108. In this example, coil 106 is substantially the same as coil 108. Figure 1A The points associated with each coil 106 and 108 in the diagram represent the winding direction in coils 106 and 108, which in turn represent the direction of the mutual inductance voltage in coils 114 and 112, respectively, according to the point convention.

[0017] According to the example, system 100 also includes a power receiver 110, which includes a cross-coupled oscillator. Power receiver 110 includes coils 112 and 114, capacitors 116 and 118, and field-effect transistors (FETs) 120 and FET 122. Coil 112 has a first terminal coupled to a first terminal of coil 114. Coil 112 has a second terminal coupled to a first terminal of capacitor 116 and a drain terminal of FET 120. The second terminal of capacitor 116 is coupled to a gate terminal of FET 122. The source terminal of FET 120 is coupled to a source terminal of FET 122. The second terminal of coil 114 is coupled to a first terminal of capacitor 118 and a drain terminal of FET 122. The second terminal of capacitor 118 is coupled to a gate terminal of FET 120. A capacitor 124 coupled to power receiver 110 is also included on the right side of system 100. Capacitor 124 is also coupled across load 126. During the operation of the power receiver 110, an output voltage V is provided across the load 126. out .

[0018] In power receiver 110, the capacitance values ​​of capacitors 116 and 118 are substantially the same in one example. Additionally, in this example, coils 112 and 114 are substantially the same. In system 100, mutual inductance causes the current flowing in coils 106 and 108 to induce voltages in coils 112 and 114. Specifically, the current flowing in coil 106 induces the voltage in coil 114, and the current flowing in coil 108 induces the voltage in coil 112. The amount of inductive coupling between coils 106 and 114 and between coils 108 and 112 is expressed as a decimal between -1 and 1, where 1 represents full or maximum inductive coupling, 0 represents zero inductive coupling, and -1 represents full inductive coupling with a polarity change. This number is called the coupling coefficient and is denoted as k. If k equals 1, the two coils are perfectly coupled. If k > 0.5, the two coils are relatively tightly coupled. If 0 < k < 0.5, the two coils are relatively loosely coupled. In system 100, the coupling coefficient between coils 108 and 112 is represented as k. A And the coupling coefficient between coils 106 and 114 is expressed as k. B In one example, k A Approximately equal to k B .

[0019] The example here uses resonant gate drive and zero-voltage switching to reduce power loss and / or increase switching frequency. Zero-voltage switching is performed using a zero-voltage switching topology. System 100 uses a resonant LC network, where the voltage and current waveforms vary sinusoidally during one or more intervals of the switching cycle. A resonant LC network can also be referred to as a tank network or LC tank. The LC network stores energy oscillating at the resonant frequency of the circuit. The resonant frequency is determined by the capacitance and inductance values ​​in the LC network. In operation, energy oscillates between the capacitors and inductors in the LC network. In system 100, energy from coils 106 and 108 on the transmitter side drives the LC network in power receiver 110. The energy oscillating between capacitors 116, 118 and coils (inductors) 112, 114 in power receiver 110 drives the gate terminals of FETs 120 and 122 to turn FETs 120 and 122 on and off to provide output power to load 126.

[0020] Zero-voltage switching is a technique used in the examples presented herein to reduce power losses. Resonant gate drive allows zero-voltage switching to turn on a FET when the drain-source voltage across the FET is zero or near zero. Zero-voltage switching involves a transition (e.g., turning on the FET) when the drain-source voltage is zero, which reduces power losses during FET transitions. Power losses occur if there is current through the FET and voltage across the FET during the transition (e.g., the transition is the point in time when the FET is turned on or off). These power losses can be reduced by driving the current through the FET to zero (zero-current switching) or driving the voltage across the FET to zero (zero-voltage switching) before the transition occurs. Therefore, zero-voltage switching reduces or eliminates switching losses caused by stored charge and device output capacitance.

[0021] Figure 1B It is a graph of waveform 150 based on a portion of an example oscillator (such as the oscillator in power receiver 110). Figure 1B This is a simplified model of how oscillations occur between the inductor and capacitor. Waveform 152 is an example waveform showing the on-time and off-time of a transistor switch. Waveform 154 shows the current i through the inductor. L The curve of i L This is plotted relative to time t. Waveform 156 represents the voltage v at the drain terminal of the FET. D The curve, where v D It is plotted relative to time t.

[0022] In response to the transistor switch closing as shown with respect to waveform 152 (e.g., FET 120 turning on), the voltage at the drain terminal of the FET is grounded. On waveform 156, during the time interval of the switch closing in waveform 152, vD = 0 volts. Therefore, a voltage v is applied across the inductor (such as coil 112) coupled to the drain terminal of the FET. in This increases the current in the inductor. On waveform 154, when the switch is closed, the current i... L The current increases linearly with time t. In response to the switch opening at time t1, current still flows through the inductor. This inductor current continues to flow and flows into a capacitor (such as capacitor 116) coupled to the drain terminal of the FET. This capacitor is charged, and the voltage at the drain terminal increases. This voltage increase is shown in waveform 156, where the voltage increase begins at time t1. At time t2, the current in the inductor is decreasing and reversing polarity, as shown in waveform 154 (at time v). D It reaches its peak at time t2, i L A drop below zero indicates that i L (The change in polarity). Therefore, these example waveforms are examples of oscillations between an inductor and a capacitor. Energy flows into the inductor as shown in waveform 154, and then flows out of the inductor and into the capacitor as shown in waveform 156. At time t3, v D It returns to zero. At that time, the switch closes again. This is an example of zero-voltage switching (e.g., closing the switch when the voltage is zero). After time t3, the pattern in the waveform will repeat. Therefore, Figure 1B The simplified illustration shows how energy oscillates between an inductor and a capacitor in the example presented in this article.

[0023] Refer again Figure 1A In system 100, a current flows through coils 106 and 108 on the transmitter side. This current induces voltages in coils 112 and 114 via mutual inductance. The induced voltages in coils 112 and 114 initiate the operation of the LC network in power receiver 110. The LC network drives FETs 120 and 122 at the receiver's resonant frequency, which generates power supplied to load 126. Therefore, system 100 transfers power from a voltage source V on the transmitter side. in Load 126 is wirelessly transmitted to the receiver. Additionally, FETs 120 and 122 experience reduced gate drive losses due to the use of an oscillator for resonant gate drive in the power receiver 110. Because of the reduced gate drive losses, system 100 can operate at a higher switching frequency than conventional systems. As mentioned above, the higher switching frequency allows for the use of miniaturized coils with a higher quality factor Q in some examples.

[0024] If the oscillator in power receiver 110 is allowed to operate at its natural frequency (as determined by the values ​​of L and C), power will not be delivered to load 126 because the frequencies on the transmitter side and the receiver side will be unrelated. However, if the oscillator is excited with a signal at a drive frequency that is not exactly the same as but close to its natural frequency, the oscillator's frequency can be pulled to resonate at the drive frequency. This phenomenon is called injection lock-in. As an example, if the inductive coupling between two oscillators is strong and the natural frequencies of the two oscillators resonate with each other, the first oscillator can trap the second oscillator and cause the second oscillator to adjust its frequency until the second oscillator has a frequency substantially the same as the first oscillator. Figure 1A In a transmitter and receiver coil, if the inductive coupling is strong and the natural frequency of the receiver LC oscillator is close to the transmitter drive frequency, the receiver LC oscillator adjusts its frequency by injection-locking to the transmitter drive frequency. Injection-locking allows the transmitter and receiver frequencies to synchronize, even if they naturally operate at slightly different frequencies. Injection-locking occurs if the frequencies of the receiver oscillator and transmitter driver are within an acceptable range.

[0025] The natural frequency of an oscillator (such as the oscillator in power receiver 110) depends on the values ​​of the inductors and capacitors, the gate capacitance of the FET, and other factors of the components in the oscillator. If the oscillator has a high Q, it is more difficult to pull the oscillator from its natural frequency to another frequency via injection lock. With a high Q, injection lock can be achieved on the transmitter side by operating at a frequency close to the natural frequency of the receiver oscillator. The closer the transmitter-side frequency is to the receiver-side natural frequency, the more likely the system is to achieve injection lock.

[0026] Figure 2 This is a schematic diagram of example system 200. System 200 is a system for isolated power transmission that includes a transmitter side and a receiver side. The receiver (right) side is similar to the one described above. Figure 1A The receiver side is described. In system 200, the transmitter (left) side also includes a cross-coupled oscillator matched to the cross-coupled oscillator in power receiver 110. Using this oscillator on the transmitter side, the transmitter... Figure 1A The power receiver 110 in the example achieves efficient high-frequency operation in the same way, including the use of resonant gate drive and zero-voltage switching. In the example, resonant gate drive is used to drive the transistors on the transmitter side, which allows the transistors to operate with zero-voltage switching. Therefore, power losses on the transmitter side are reduced, just as they are on the receiver side, as described above. Additionally, due to the reduction or elimination of gate drive losses, the frequency of the system 200 can be increased, resulting in a higher quality factor Q in the example system using miniaturized coils.

[0027] refer to Figure 2 The transmitter side of system 200 includes a voltage source V. in 104. The cross-coupled oscillator on the transmitter side includes coils 202 and 204, capacitors 206 and 208, and FETs 210 and 212. The structure of the oscillator on the transmitter side is similar to that of the oscillator in the power receiver 110. In this example, the components of the oscillator in the transmitter are the same as or nearly the same as those of the oscillator in the power receiver 110. Voltage source V in Terminal 104 is coupled to the first terminal of coil 202 and the first terminal of coil 204. The second terminal of coil 202 is coupled to the first terminal of capacitor 206 and the drain terminal of FET 210. The second terminal of capacitor 206 is coupled to the gate terminal of FET 212. The source terminal of FET 210 is coupled to the source terminal of FET 212. The second terminal of coil 204 is coupled to the first terminal of capacitor 208 and the drain terminal of FET 212. The second terminal of capacitor 208 is coupled to the gate terminal of FET 210. In this example, the values ​​of capacitor 206 and capacitor 208 are substantially the same. Additionally, in this example, coils 202 and 204 are substantially the same.

[0028] In system 200, the voltage source V in The voltage and oscillator components of coil 104 generate current in coils 202 and 204 in an oscillating manner. The current flowing in coil 202 induces a voltage in coil 114, and the current flowing in coil 204 induces a voltage in coil 112. Therefore, power is wirelessly transmitted across the barrier between the transmitter and receiver sides. The coupling coefficient between coils 204 and 112 is k. A And the coupling coefficient between coils 202 and 114 is k. B In one example, k A Approximately equal to k B If the components of the oscillator on the transmitter side are manufactured similarly to those of the oscillator in the power receiver 110, and the transmitter and receiver are manufactured to be physically close to each other, then k A and k B The value can be very high (e.g., close to 1). Furthermore, if the inductors and capacitors in each oscillator are similar, and the FETs in each oscillator are similar, then the switching frequencies of each oscillator will also be close to each other. Similar switching frequencies on the transmitter and receiver sides of system 200 will result in easier injection locking to synchronize the operation on both the transmitter and receiver sides.

[0029] If the two oscillators in system 200 are identical or nearly identical, then the voltage V across load 126 is... outequals V in -I load R out Output voltage V out The turns ratio of the coils (112, 114, 202, and 204) of the two oscillators can be adjusted. Furthermore, if the oscillators are identical or nearly identical, the power transmission of system 200 is bidirectional. For example, if the voltage source V... in With 104 placed on the receiver side and load 126 and capacitor 124 placed on the transmitter side, system 200 will operate "in reverse" due to the symmetry in the system, where the right-side voltage source and oscillator drive the left-side oscillator and load.

[0030] Figure 3 This is a schematic diagram of example system 300. System 300 includes a transmitter side on the left and a receiver side on the right. System 300 uses a capacitively coupled oscillator instead of the one described above. Figure 1A and Figure 2 The inductively coupled oscillator described herein is used to transmit power. System 300 provides similar benefits to those provided by systems 100 and 200 as described above.

[0031] System 300 includes voltage source V in 302. The cross-coupled oscillator on the transmitter (left) side of system 300 includes coils 304 and 306, capacitors 308 and 310, and FETs 312 and 314. The structure of the oscillator on the transmitter side of system 300 is similar to... Figure 2 The structure of the oscillator on the transmitter side of system 200 is shown. However, system 300 uses capacitors 340 and 342 coupled to nodes 316 and 318 to transfer power to the receiver side of system 300. In system 300, the voltage source V in Terminal 302 is coupled to the first terminals of coils 304 and 306. The second terminal of coil 304 is coupled to the first terminal of capacitor 308 and the drain terminal of FET 312. The second terminal of capacitor 308 is coupled to the gate terminal of FET 314. The source terminal of FET 312 is coupled to the source terminal of FET 314. The second terminal of coil 306 is coupled to the first terminal of capacitor 310 and the drain terminal of FET 314. The second terminal of capacitor 310 is coupled to the gate terminal of FET 312. The drain terminal of FET 312 is coupled to node 316, and the drain terminal of FET 314 is coupled to node 318. In this example, the values ​​of capacitors 308 and 310 are substantially the same. Additionally, in this example, coils 304 and 306 are substantially the same.

[0032] On the receiver (right) side of system 300, the cross-coupled oscillator includes coils 320 and 322, capacitors 324 and 326, and FETs 328 and 330. The structure of the oscillator on the receiver side of system 300 is similar to... Figure 1A The system 100 shown illustrates the structure of an oscillator on the receiver side. Coil 320 has a first terminal coupled to a first terminal of coil 322 and a second terminal coupled to a first terminal of capacitor 324 and the drain terminal of FET 328. The second terminal of capacitor 324 is coupled to the gate terminal of FET 330. The source terminal of FET 328 is coupled to the source terminal of FET 330. The second terminal of coil 322 is coupled to a first terminal of capacitor 326 and the drain terminal of FET 330. The second terminal of capacitor 326 is coupled to the gate terminal of FET 328. The receiver side of system 300 also includes a capacitor 336 coupled across load 338. Output voltage V out Provided across load 338 during operation.

[0033] Cross-coupled oscillators on the transmitter side provide resonant gate drive and zero-voltage switching for FETs 312 and 314. These features reduce power losses on the transmitter side. Similarly, cross-coupled oscillators on the receiver side provide resonant gate drive and zero-voltage switching for FETs 328 and 330.

[0034] In system 300, coils 304 and 306 on the transmitter side do not transfer power to coils 320 and 322 on the receiver side via inductive coupling. Instead, coupling capacitors 340 and 342 transfer power from the transmitter side to the receiver side via capacitive coupling. Coupling capacitor 340 has a first terminal coupled to node 316 on the transmitter side and a second terminal coupled to node 332 on the receiver side. Coupling capacitor 342 has a first terminal coupled to node 318 on the transmitter side and a second terminal coupled to node 334 on the receiver side. The function of the oscillator on the transmitter side causes voltage changes at nodes 316 and 318. These voltage changes cause voltage changes across coupling capacitors 340 and 342. Power is transferred from the transmitter side to the receiver side via an AC signal across coupling capacitors 340 and 342. The operation of the cross-coupled oscillator on the receiver side of system 300 is similar to that described above. Figure 1A The operation of the power receiver 110 described herein. The operation of the cross-coupled oscillator on the receiver side transmits power to the load 338.

[0035] If the frequency values ​​of each oscillator are close to each other, capacitive coupling between the transmitter and receiver sides of system 300 causes oscillator injection lock-in on each side. If the two oscillators in system 300 are identical or nearly identical, the voltage V across load 338... outequals V in -I load R out Furthermore, if the oscillators are the same or nearly the same, the power transmission of system 300 is bidirectional, as described above.

[0036] The above Figure 1A , Figure 2 and Figure 3 The oscillator shown is an example of a Class E oscillator. A Class E oscillator is a highly tuned switching oscillator. As mentioned above, Class E oscillators achieve high efficiency solely by operating the switching element at a point with zero current (on-to-off switching) or zero voltage (off-to-on switching), which reduces power losses in the switching process. The transistors in a Class E oscillator are driven to operate in the saturation region to function as switches with two discrete states (on and off).

[0037] Other examples can use other types of oscillators, such as Class D or Class F oscillators. Class D oscillators use some form of pulse width modulation in operation. The transistors in a Class D oscillator act as switches with two discrete states (on and off). Class F oscillators function similarly to Class E oscillators. In some examples, Class F oscillators improve efficiency and output by using harmonic resonators in the output network to shape the output waveform into a square wave.

[0038] Figure 4 This is a schematic diagram of example system 400. System 400 is a system for isolated power transmission that includes a transmitter side and a receiver side. System 400 is similar to the one described above, except that it uses Class F oscillators instead of Class E oscillators on both the transmitter and receiver sides. Figure 2 The system 200 shown is an example. The Class F oscillator uses a harmonic shaping filter as shown in system 400.

[0039] System 400 includes voltage source V in 402. The cross-coupled oscillator on the transmitter (left) side of system 400 includes coils 404 and 406, capacitors 408 and 410, and FETs 412 and 414. System 400 also includes ground 416. The structure of the oscillator on the transmitter side of system 400 is similar to... Figure 2 The system 200 shown illustrates the structure of an oscillator on the transmitter side. However, system 400 also includes a harmonic shaping filter 418, which includes an inductor 420 and a capacitor 422. The harmonic shaping filter 418 is coupled to the drain terminal of the FET 414. System 400 also includes a harmonic shaping filter 424, which includes an inductor 426 and a capacitor 428. In system 400, the voltage source V... in402 is coupled to the first terminal of coil 404 and the first terminal of coil 406. The second terminal of coil 404 is coupled to the first terminal of capacitor 408 and the drain terminal of FET 412. The second terminal of capacitor 408 is coupled to the gate terminal of FET 414. The source terminal of FET 412 is coupled to the source terminal of FET 414. The second terminal of coil 406 is coupled to the first terminal of capacitor 410 and the drain terminal of FET 414. The second terminal of capacitor 410 is coupled to the gate terminal of FET 412. In this example, coils 404 and 406 are substantially identical.

[0040] On the receiver (right) side of system 400, the cross-coupled oscillator includes coils 430 and 432, capacitors 434 and 436, and FETs 438 and 440. The structure of the oscillator on the receiver side of system 400 is similar to... Figure 2 The structure of the oscillator on the receiver side of system 200 is shown. System 400 also includes a capacitor 442 coupled across load 444. Output voltage V out During operation, a load 444 is provided. Capacitor 442 is also coupled to ground 446, which in this example is equivalent to ground 416. System 400 also includes a harmonic shaping filter 448, which includes an inductor 450 and a capacitor 452. Harmonic shaping filter 448 is coupled to the drain terminal of FET 438. System 400 also includes a harmonic shaping filter 454, which includes an inductor 456 and a capacitor 458. In system 400, a first terminal of coil 430 is coupled to a first terminal of coil 432. A second terminal of coil 430 is coupled to a first terminal of capacitor 434 and the drain terminal of FET 438. A second terminal of capacitor 434 is coupled to the gate terminal of FET 440. The source terminal of FET 438 is coupled to the source terminal of FET 440. A second terminal of coil 432 is coupled to a first terminal of capacitor 436 and the drain terminal of FET 440. The second terminal of capacitor 436 is coupled to the gate terminal of FET 438. In this example, coils 430 and 432 are essentially the same.

[0041] In system 400, the voltage source V in The voltage at 402 oscillates to induce current in coils 404 and 406. The current flowing in coil 406 induces voltage in coil 430, and the current flowing in coil 404 induces voltage in coil 432. Thus, power is wirelessly transmitted across the barrier between the transmitter and receiver sides. The coupling coefficient between coils 406 and 430 is k. A And the coupling coefficient between coils 404 and 432 is k. B In one example, kA Approximately equal to k B In a system as described above, if the inductors and capacitors in each oscillator are similar, and the FETs in each oscillator are similar, then the switching frequencies of each oscillator will also be close to each other. Similar switching frequencies on each side of system 400 will result in easier injection locking to synchronize the operation of the transmitter and receiver sides.

[0042] If the two oscillators in system 400 are identical or nearly identical, then the voltage V across load 444 out equals V in -I load R out The output voltage V can be adjusted by changing the turns ratio of the coils (404, 406, 430, and 432) of the two oscillators. out Furthermore, if the oscillators are the same or nearly the same, then as mentioned above, the power transmission of system 400 is bidirectional.

[0043] Figure 5 This is a schematic diagram of example system 500. System 500 is an example of a power receiver and a load. System 500 includes an oscillator in the receiver that operates similarly to the oscillator in the receiver described above. System 500 also includes a DC gate biasing circuit for the FET in the bias oscillator. Although Figure 5 Not shown in the figure, but in other examples, DC gate bias can also be used for power transmitters.

[0044] System 500 includes a receiver with a cross-coupled oscillator, wherein the cross-coupled oscillator includes coils 502 and 504, capacitors 506 and 508, and FETs 510 and 512. FETs 510 and 512 are coupled to ground 514 at their respective source terminals. The structure of the oscillator on the receiver side of system 500 is similar to... Figure 2 The structure of the oscillator on the receiver side of system 200 shown is the same as that added to the DC gate bias of system 500. System 500 also includes a capacitor 516 coupled across load 518. Output voltage V out Provided across load 518 during operation.

[0045] In system 500, the first terminal of coil 502 is coupled to the first terminal of coil 504. The second terminal of coil 502 is coupled to the first terminal of capacitor 506 and the drain terminal of FET 510. The second terminal of capacitor 506 is coupled to the gate terminal of FET 512. The source terminal of FET 510 is coupled to ground 514, and the source terminal of FET 512 is coupled to ground 514. The second terminal of coil 504 is coupled to the first terminal of capacitor 508 and the drain terminal of FET 512. The second terminal of capacitor 508 is coupled to the gate terminal of FET 510. In one example, coils 502 and 504 are substantially identical.

[0046] System 500 also includes a DC gate bias circuit 520. The DC gate bias circuit 520 sets the gate-source voltage V of FETs 510 and 512. gs This generates the programming voltage and current for the operation of each FET 510 and 512. Any suitable circuitry is used to provide a DC gate bias. DC gate bias circuitry 520 is used to set the appropriate operating points for FETs 510 and 512. In one example, components 522 and 524 are used in conjunction with DC gate bias circuitry 520 to properly bias FETs 510 and 512. In some examples, components 522 and 524 may be resistors or inductors. Receivers or transmitters using DC gate bias can replace the above-mentioned... Figures 1A to 4 Any receiver or transmitter shown in the example described.

[0047] Figure 6 This is a flowchart of an example method 600 for isolated power transmission. Although combined... Figures 1A to 5 Method steps are described, but any system configured to execute method steps in any suitable order is within the scope of this description.

[0048] Method 600 begins at step 610, wherein a voltage source provides an input voltage to a first oscillator in the power transmitter. For example, the voltage source V in 104 provides an input voltage to the oscillator in the transmitter of the above system 200. The first oscillator is adapted to include a first coil and a second coil, such as coils 202 and 204 in the example.

[0049] Method 600 continues at step 620, wherein a first oscillator drive current passes through a first coil and a second coil in the first oscillator to generate a first magnetic field and a second magnetic field. (As stated above regarding...) Figure 1A and Figure 1B The oscillator is used to oscillate charges between an inductor and a capacitor to provide a repetitive waveform, which is then used to transfer power to a receiver via inductive or capacitive coupling.

[0050] Method 600 continues at step 630, wherein the first magnetic field induces a first electromotive force in the second oscillator, and the second oscillator is adapted to include a third coil. For example, as described above regarding... Figure 2 The first coil 204 in the transmitter is inductively coupled to the third coil 112 in the receiver, wherein the coupling coefficient is k. A The coupling coils can be manufactured to be identical or nearly identical and can reside on the chip physically close to each other to increase the value of the coupling coefficient and increase the overall power efficiency of the system.

[0051] Refer again Figure 6 Method 600 continues at step 640, wherein the second magnetic field induces a second electromotive force in the second oscillator, and the second oscillator is adapted to include a fourth coil. The third and fourth coils are components of the second oscillator in the power receiver. Similar to the coil described in step 630, the second coil 202 in the transmitter is inductively coupled to the fourth coil 114 in the receiver, wherein the coupling coefficient is k. B The coupling coils can be manufactured to be identical or nearly identical and can reside on the chip physically close to each other to increase the value of the coupling coefficient and increase the overall power efficiency of the system.

[0052] Method 600 continues at step 650, wherein the power receiver provides an output voltage to the load via a second oscillator, wherein the output voltage is proportional to the input voltage. In one example, the output voltage is approximately equal to the input voltage. In another example, the output voltage can be adjusted to be higher or lower than the input voltage by adjusting the number of turns of the coil in the oscillator.

[0053] While the examples in this paper use two oscillators, in other examples, a third oscillator can be injected and locked to the first oscillator on the transmitter side and the second oscillator on the receiver side. Any number of oscillators can be frequency-locked together in a process known as banding.

[0054] In this specification, the term "coupled" may encompass a connection, communication, or signal path that achieves a functional relationship consistent with this specification. For example, if device A generates a signal to control device B to perform an action, then: (a) in a first example, device A is coupled to device B; or (b) in a second example, if intermediate component C does not substantially alter the functional relationship between device A and device B, then device A is coupled to device B via intermediate component C such that device B is controlled by device A via control signals generated by device A. Additionally, in this specification, a device "configured" to perform a task or function may be configured (e.g., programmed and / or hardwired) at the time of manufacture to perform a function and / or may be user-configurable (or reconfigurable) after manufacture to perform a function and / or other additional or alternative functions. Configuration may be achieved through firmware and / or software programming of the device, through the construction and / or layout of the device's hardware components and interconnections, or a combination thereof. Furthermore, in this specification, circuitry or devices including certain components may conversely be adapted to be coupled to those components to form the described circuitry or device. For example, a structure described as including one or more semiconductor elements (such as transistors), one or more passive elements (such as resistors, capacitors and / or inductors) and / or one or more sources (such as voltage and / or current sources) may instead include only semiconductor elements within a single physical device (e.g., a semiconductor die and / or integrated circuit (IC) package) and may be adapted to couple to at least some of the passive elements and / or sources to form the described structure as if formed by an end user and / or a third party at the time of manufacture or after manufacture.

[0055] While some components may be described herein as having a specific process technology, these components may be interchanged with components of other process technologies. The circuits described herein are reconfigurable to include the replaced components to provide functionality at least partially similar to that available prior to the component replacement. Unless otherwise stated, components illustrated as resistors generally represent any one or more series and / or parallel couplings to provide the impedance represented by the resistor shown. For example, resistors or capacitors shown and described herein as single components may, in contrast, be multiple resistors or capacitors coupled in series or parallel between the same two nodes as a single resistor or capacitor. Additionally, the phrase "ground voltage potential" as used in this specification includes chassis ground, earth ground, floating ground, virtual ground, digital ground, common ground, and / or any other form of ground connection applicable to or suited to the teachings of this specification. Unless otherwise stated, "about," "approximately," "almost," or "substantially" preceding a value indicates + / - 10% of the stated value.

[0056] Within the scope of the claims, modifications are possible in the described examples, and in other examples as well.

Claims

1. A system for isolated power transmission, the system comprising: A receiver having an output, the receiver comprising: The first coil coupled to the output; A second coil coupled to the output; A first transistor having a first control terminal, a first current terminal, and a second current terminal, wherein the first current terminal is coupled to the output via the first coil, and the first transistor is configured to receive a first oscillation signal having a first frequency at the first current terminal; A second transistor having a second control terminal, a third current terminal and a fourth current terminal, the third current terminal being coupled to the output via a second coil, and the second transistor being configured to receive a second oscillation signal having the first frequency at the third current terminal; A first capacitor coupled between the first current terminal and the second control terminal; and A second capacitor coupled between the third current terminal and the first control terminal; The receiver is configured to: In response to the first oscillation signal and the second oscillation signal, a third oscillation signal and a fourth oscillation signal are generated, the third oscillation signal and the fourth oscillation signal having a second frequency based on the first frequency; and A voltage is provided at the output in response to the third and fourth oscillation signals.

2. The system of claim 1, wherein the first coil and the second coil, as well as the first transistor and the second transistor, are configured as a Class E oscillator.

3. The system of claim 1, wherein the first coil and the second coil, as well as the first transistor and the second transistor, are configured as a Class F oscillator.

4. The system of claim 1, wherein the first capacitor and the second capacitor, as well as the first coil and the second coil, are configured to resonate at the second frequency and lock the second frequency to the first frequency by injection locking.

5. The system according to claim 1, wherein: The first coil is magnetically or capacitively coupled to the third coil to receive the first oscillation signal, the first coil having a first number of turns, and the third coil having a second number of turns; The second coil is magnetically or capacitively coupled to the fourth coil to receive the second oscillation signal, the second coil having the first number of turns, and the fourth coil having the second number of turns; and The first number of turns is approximately equal to the second number of turns.

6. The system according to claim 1, wherein: The first coil is inductively coupled to the third coil to receive the first oscillation signal; The second coil is inductively coupled to the fourth coil to receive the second oscillation signal; as well as The first coupling coefficient between the first coil and the third coil is substantially equal to the second coupling coefficient between the second coil and the fourth coil.

7. The system according to claim 1, wherein: The first transistor is configured to switch states in response to the second oscillation signal when the voltage between the first current terminal and the second current terminal is zero; The second transistor is configured to switch states in response to the first oscillation signal when the voltage between the third and fourth current terminals is zero.

8. The system of claim 1, wherein the first oscillation signal and the second oscillation signal are generated based on a DC voltage; and The receiver is isolated from the DC voltage.

9. The system of claim 1, wherein the first oscillation signal and the second oscillation signal are received from an oscillator.

10. The system of claim 1, wherein the first coil is capacitively coupled to the third coil to receive the first oscillation signal; and The second coil is capacitively coupled to the fourth coil to receive the second oscillation signal.

11. The system of claim 1, wherein the first coil and the first capacitor are configured to generate a third oscillation signal when the first transistor is disabled in response to the second oscillation signal; and The second coil and the second capacitor are configured to generate a fourth oscillation signal when the second transistor is disabled in response to the first oscillation signal.

12. The system according to claim 1, further comprising a first filter and a second filter; The first current terminal is coupled to the first filter to shape the first oscillation signal; and The second current terminal is coupled to the second filter to shape the second oscillation signal.

13. A system for isolated power transmission, the system comprising: A transmitter with an input, the transmitter including a first coil and a second coil and configured to: A first voltage is received at the input, and the first voltage is a direct current voltage, i.e., a DC voltage. A first oscillation signal is generated at the first coil, the first oscillation signal having a first frequency; as well as A second oscillation signal is generated at the second coil, the second oscillation signal having the first frequency; as well as A receiver having an output and including a third coil and a fourth coil coupled to the output, the third coil and the fourth coil being inductively or capacitively coupled to corresponding first and second coils, the receiver being configured to: The first oscillation signal is received at the third coil; The second oscillation signal is received at the fourth coil; A third oscillation signal is generated at the third coil, the third oscillation signal having a second frequency based on the first frequency; A fourth oscillation signal is generated at the fourth coil, the fourth oscillation signal having the second frequency; and A second voltage is provided at the output in response to the third and fourth oscillation signals.

14. The system of claim 13, wherein the transmitter is configured to cause the receiver to resonate at the second frequency, and to lock the second frequency to the first frequency by injection locking.

15. The system of claim 14, wherein the transmitter and the receiver comprise corresponding Class E oscillators.

16. The system of claim 14, wherein the transmitter and the receiver comprise corresponding Class F oscillators.

17. The system of claim 13, further comprising a first capacitor and a second capacitor. The first coil is coupled to the third coil via the first capacitor; and The second coil is coupled to the fourth coil through the second capacitor.

18. The system of claim 17, wherein the first capacitor is configured to transmit the first oscillation signal from the first coil to the third coil; and The second capacitor is configured to transmit the second oscillation signal from the second coil to the fourth coil.

19. A method for isolated power transmission, the method comprising: In response to a first voltage, a first oscillation signal and a second oscillation signal are generated by the transmitter, wherein the first voltage is a direct current voltage (DC voltage) and the first and second oscillation signals have a first frequency; In response to the first oscillation signal, a third oscillation signal is generated at the first transistor of the receiver, the third oscillation signal having a second frequency based on the first frequency; In response to the second oscillation signal, a fourth oscillation signal is generated at the second transistor of the receiver, the fourth oscillation signal having the second frequency; and A second voltage is generated in response to the third and fourth oscillation signals.

20. The method of claim 19, wherein the first oscillation signal is generated at a first coil of the transmitter, the first coil being coupled between a third transistor of the transmitter and an input of the transmitter, and the first voltage is received at the input; The second oscillation signal is generated at the second coil of the transmitter, and the second coil is coupled between the input and the fourth transistor of the transmitter; and The third and fourth transistors are cross-coupled.

21. The method of claim 20, wherein the first coil is coupled to a first current terminal of the third transistor, and the first control terminal of the third transistor is coupled to the second coil via a first capacitor; The second coil is coupled to the second current terminal of the fourth transistor, and the second control terminal of the fourth transistor is coupled to the first coil through the second capacitor; The first coil and the first capacitor provide a first resonant gate drive for the fourth transistor; and The second coil and the second capacitor provide a second resonant gate drive for the third transistor.

22. The method of claim 20, wherein the first oscillation signal is received at the third coil of the receiver via a first coupling between the first coil and the third coil of the receiver, the third coil being coupled between the output of the receiver and the first transistor of the receiver, and providing the second voltage at the output; The second oscillation signal is received at the fourth coil of the receiver via a second coupling between the second coil and the fourth coil of the receiver, and the fourth coil is coupled between the output and the second transistor of the receiver; Wherein it is cross-coupled with the first transistor and the second transistor; and The first coupling and the second coupling include inductive coupling or capacitive coupling.

23. The method of claim 22, wherein the third coil is coupled to a third current terminal of the first transistor, and the third control terminal of the first transistor is coupled to the fourth coil via a third capacitor; The fourth coil is coupled to the fourth current terminal of the second transistor, and the fourth control terminal of the second transistor is coupled to the third coil via a fourth capacitor; The third coil and the third capacitor provide a third resonant gate drive for the second transistor; and The fourth coil and the fourth capacitor provide a fourth resonant gate drive for the first transistor.

24. The method of claim 19, wherein the third oscillation signal and the fourth oscillation signal are generated by resonating at the second frequency and locking the second frequency to the first frequency via injection locking.

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