Flux detection circuit for detecting magnetic flux via magnetic flux probe, and method therein
The magnetic flux probe integrated with a magnetic core and adjustable circuit elements addresses the challenge of magnetic interference in miniaturized power supplies, enhancing the detection of time-varying magnetic flux and improving power converter control.
Patent Information
- Application Number
- JP2024205051
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2024-11-22
- Filing Date
- 2024-11-25
- Publication Date
- 2025-07-15
AI Technical Summary
Conventional switching power supplies face challenges in miniaturization due to the need to isolate magnetic components from circuit components, which is exacerbated by the integration of magnetic components with circuit components, leading to magnetic interference and degraded performance.
A magnetic flux probe forms a loop around a magnetic core, allowing trace wiring to traverse the winding window, with adjustable circuit elements to measure electromotive force, enabling accurate detection of time-varying magnetic flux and reducing interference.
The solution allows for precise detection of magnetic flux signals, improving control of power converters by minimizing interference, particularly in switching power converters, and enabling efficient operation of synchronous rectifiers.
Smart Images
Figure 2025106191000001_ABST
Abstract
Description
Technical Field
[0001] Cross - Reference to Related Applications
[0001] This application claims priority from U.S. Provisional Patent Application No. 63 / 610,775, filed on December 15, 2023, the entire disclosure of which is incorporated herein by reference.
[0002]
[0002] The present invention relates to a circuit approach for detecting a time - varying magnetic field by utilizing Faraday's law.
Background Art
[0003]
[0003] Many electronic devices, such as mobile phones, laptop computers, etc., are powered by electric power of direct current (DC) obtained from a power source. Conventional wall outlets generally transmit high - voltage alternating current (AC) power that needs to be converted to regulated DC power for use as a power source for consumer - oriented electronic devices. Switching converters, also called switching power supplies, are commonly used to convert high - voltage AC power to regulated DC power because of their high efficiency, small size, and light weight.
[0004]
[0004] A switching power supply may further include a magnetic circuit for transferring energy. A magnetic circuit is similar to an electric circuit. For example, a magnetic circuit provides a path for magnetic flux, and an applied magnetomotive force similar to an electromotive force causes the magnetic flux to follow the magnetic - circuit path.
Summary of the Invention
[0005]
[0005] Non - limiting and non - exhaustive embodiments of a flux detection circuit for detecting magnetic flux are described with reference to the following figures, and like reference numerals indicate like parts throughout the various drawings, unless otherwise specified.
Brief Description of the Drawings
[0006]
Figure 1A
[0006] Figure 1A shows a magnetic flux probe according to an embodiment.
Figure 1B
[0007] Figure 1B shows a magnetic flux probe according to another embodiment.
Figure 2A
[0008] Figure 2A shows a top perspective view of a magnetic core and interconnect routing for receiving probe signals according to an embodiment.
Figure 2B
[0009] Figure 2B shows a top perspective view of a magnetic core and interconnect routing for receiving probe signals according to another embodiment.
Figure 2C
[0010] Figure 2C shows a top perspective view of a magnetic core and interconnect routing for receiving one or more probe signals according to an embodiment.
Figure 2D
[0011] Figure 2D shows a top perspective view of a magnetic core and interconnect routing for receiving one or more probe signals according to another embodiment.
Figure 3A
[0012] Figure 3A shows a schematic diagram including a magnetic flux probe according to an embodiment.
Figure 3B
[0013] Figure 3B shows a schematic diagram including a magnetic flux probe according to another embodiment.
Figure 4A
[0014] Figure 4A shows a schematic diagram of a flyback converter according to an embodiment.
Figure 4B
[0015] Figure 4B shows a schematic diagram of a flyback converter according to another embodiment.
Figure 4C
[0016] Figure 4C shows a schematic diagram of a flyback converter according to another embodiment.
Figure 4D
[0017] Figure 4D shows a schematic diagram of a flyback converter according to another embodiment.
Figure 5A
[0018] Figure 5A shows a three-dimensional (3D) upper perspective view of a flyback converter according to an embodiment of a printed circuit board (PCB).
Figure 5B
[0019] Figure 5B shows a three-dimensional (3D) upper perspective view of a flyback converter according to the embodiment of FIG. 5A.
Figure 5C
[0020] Figure 5C shows a three-dimensional (3D) upper perspective view of a flyback converter according to the embodiment of FIG. 5A.
Figure 6A
[0021] Figure 6A shows the interconnection routing of the magnetic flux probes and the interconnection routing according to the embodiment of FIG. 5A.
Figure 6B
[0022] Figure 6B shows the interconnection routing of the magnetic flux probes and the interconnection routing according to another embodiment.
Figure 7A
[0023] Figure 7A shows a schematic diagram of a flyback converter according to the embodiment of FIG. 6A.
Figure 7B
[0024] Figure 7B shows a schematic diagram of a flyback converter according to the embodiment of FIG. 6A.
Figure 8A
[0025] Figure 8A shows waveforms according to the teachings herein.
Figure 8B
[0026] Figure 8B shows waveforms according to the teachings herein.
Figure 9
[0027] Figure 9 shows a conceptual flowchart for controlling a synchronous rectifier during a switching cycle.
DETAILED DESCRIPTION OF THE INVENTION
[0007]
[0028] Throughout the several views of the drawings, corresponding reference numerals indicate corresponding components. Those skilled in the art will understand that the elements in the figures are drawn to be simple and clear, and are not necessarily drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to make the various embodiments of the teachings herein easier to understand. Further, common but well-understood elements that are useful or necessary in a commercially suitable embodiment are often not shown so as not to obscure the view of these various embodiments of the flux detection circuit.
[0008]
[0029] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the flux detection circuit. However, it will be apparent to those skilled in the art that specific details are not necessarily used to practice the teachings herein. In other instances, well-known materials or methods have not been described in detail so as not to obscure the present disclosure.
[0009]
[0030] In the context of the present disclosure, power may be transferred from an input (e.g., primary) side to an output (e.g., secondary) side according to a switching cycle via an energy transfer element (e.g., a transformer). For example, a primary switch may switch according to a switching cycle, in which case a winding (i.e., a primary winding) receives input power over a portion of the switching cycle and one or more secondary windings provide power over another portion of the switching cycle. Since energy from the input source may be stored in an element during a portion of the switching cycle and the stored energy may be transferred to the output during another portion of the switching cycle, the energy transfer element may also be an energy storage element. Since energy from the circuit may be stored in an element during a portion of the switching cycle and the stored energy, although not necessarily transferred to the output, may be taken out of the element during another portion of the switching cycle, a magnetic energy storage element may include only one winding.
[0010]
[0031] According to the teachings herein, when a transistor is in the "off state" or "off", the transistor blocks current and / or substantially does not conduct current. Conversely, when a transistor is in the "on state" or "on", the transistor can substantially conduct current. By way of example, in one embodiment, a high-voltage transistor comprises an N-channel metal-oxide-semiconductor (NMOS) field-effect transistor (FET) that supports a high voltage between a drain, which is a first terminal, and a source, which is a second terminal. In some embodiments, an integrated control device circuit can be used to drive a power switch when regulating the energy provided to a load. Further, for the purposes of the present disclosure, "ground" or "ground potential" represents a reference voltage or reference potential with respect to which all other voltages or potentials of an electronic circuit or integrated circuit (IC) are defined or measured.
[0011]
[0032] A switching power supply can include a magnetic component. In the context of the present disclosure, a magnetic component can be an energy transfer element and / or a magnetic energy storage element.
[0012]
[0033] A switching power supply can further include a magnetic circuit for transferring energy. The magnetic circuit can then channel a magnetic field and / or magnetic flux in a magnetic core (e.g., a transformer or inductor core).
[0013]
[0034] Conventionally, magnetic components (such as energy transfer elements, integrated transformers, coupled inductors, etc.) can be located away from circuit components (such as power transistors, control devices, analog circuits, digital circuits, etc.) to isolate susceptible signals (such as relatively small voltage signals) from magnetic interference. However, with the trend of miniaturizing switching power supplies, there is a need to eliminate this constraint by integrating magnetic components (energy transfer elements) together with circuit components.
[0014]
[0035] For example, a magnetic core can be incorporated into a multilayer printed circuit board (PCB), in which case the winding is formed by trace wiring surrounding the core. Further, there may be a window (such as a space) within the core called a winding window.
[0015]
[0036] Conventionally, as a best practice, susceptible trace wiring (such as circuit trace wiring that transmits susceptible signals) can be routed around or away from the winding window to avoid magnetic interference and / or the half-winding effect. Unfortunately, this constraint conflicts with the need to integrate and miniaturize switching power supplies. Therefore, there is a need to develop a method for transmitting susceptible signals through the winding window without degrading circuit performance.
[0016]
[0037] A flux detection circuit for detecting magnetic flux through a magnetic flux probe and a method therein are presented herein. A magnetic flux probe having circuit elements forming a loop around a magnetic core enables the interconnection of trace wiring that is susceptible to the flux traversing the winding window. The flux detection circuit is configured to measure the electromotive force (emf) of one or more elements of the loop, and at least one of the circuit elements can be adjustable (e.g., can include a variable resistor). By this approach, the magnetic flux probe and the flux detection circuit can be calibrated to accurately detect a signal proportional to the time-varying magnetic flux and to provide a signal across the winding window. One example use for such a signal disclosed herein is to provide an alternative approach for detecting a time-varying current in a magnetic transmission element and for using that information to control the operation of circuit elements within a power converter by a method that is less susceptible to interference than more conventional control methods. A particular exemplary use of the magnetic flux probe disclosed herein is to control the switching of a synchronous rectifier switch on the secondary side of a switching power converter.
[0017]
[0038] FIG. 1A shows a magnetic flux probe 50 according to an embodiment. The magnetic flux probe 50 includes a resistor R1, a resistor R2, an interconnect 61a, and an interconnect 61b. The resistors R1 - R2 are electrically coupled to the interconnects 61a - b so as to generate a loop (i.e., a "loop" according to circuit and network theory).
[0018]
[0039] A magnetic core 102 (e.g., a ferrite core) and a winding 60 (e.g., a primary winding) are further shown. The magnetic core 102 can be the "E" section (e.g., an E-type core) of an incorporated transformer, and the winding 60 can be formed using printed circuit board (PCB) trace wiring (e.g., copper PCB trace wiring). The magnetic core 102 includes an outer leg 49a, an outer leg 49b, and a center leg 49c.
[0019]
[0040] The magnetic flux density B can be generated in the magnetic core 102 due to the current in the winding 60. The magnetic flux probe 50 forms a loop surrounding the magnetic core 102, and an electromotive force (emf) and current ILOOP can be induced in response to the time-varying magnetic flux density B.
[0020]
[0041] The magnetic flux probe 50 is shown as surrounding the central leg 49c of the magnetic core 102, but other configurations are possible. For example, the magnetic flux probe 50 can surround (i.e., encircle) any portion of the magnetic core 102 (such as the outer leg 49a, the outer leg 49b) that channels the magnetic flux density B. Further, other magnetic core types are possible.
[0021]
[0042] For example, FIG. 1B shows a magnetic flux probe 50 according to another embodiment. The embodiment of FIG. 1B may be similar to that of FIG. 1A except that it shows a single-phase core type configuration that includes the magnetic core 102, the winding 60 (e.g., primary winding), and the winding 99 (e.g., secondary winding). Further, similar to that of FIG. 1A, the magnetic flux probe 50 includes a resistor R1, a resistor R2, an interconnect 61a, and an interconnect 61b.
[0022]
[0043] Similar to that of FIG. 1A, the core 102 can be a ferrite core configured to maintain (channel) the magnetic flux density B generated by the current ISW in the winding 60. Further, the core 102 can include a gap of dimension LG to improve core saturation characteristics, and the windings 60, 99, and interconnects 61a - b can be realized by wire wiring (e.g., copper wire wiring).
[0023]
[0044] Further, similar to that of FIG. 1A, the magnetic flux probe 50 forms a loop surrounding the magnetic core 102. The current ILOOP can be induced in response to the time-varying magnetic flux density B. Thus, the magnetic flux probe 50 can provide a probe signal in response to the time-varying magnetic flux density B.
[0024]
[0045] Figures 2A and 2B show an upper perspective view of a magnetic core 102 and an interconnect routing for receiving a probe signal VR1 according to an embodiment. The upper perspective view shows the magnetic core 102 as an E-type core including an outer leg 49a, an outer leg 49b, and a central leg 49c. The magnetic flux density B is shown as entering the central leg 49c by a vector symbol of "X" and as exiting from the outer legs 48a - b by a vector symbol of "dot".
[0025]
[0046] As described herein, the magnetic flux density B can be generated from a time-varying signal (e.g., current ISW) within a winding (e.g., winding 60).
[0026]
[0047] The magnetic flux probe 50 surrounds the central leg 49c. According to the laws of electromagnetic induction (e.g., Faraday's law and Lenz's law), an electromotive force (emf) can be induced within the magnetic circuit probe 50 in response to a time-varying magnetic flux density B and, alternatively, in response to a time-varying magnetic flux Φ. The magnetic flux probe 50 surrounds a magnetic flux Φ which is a scalar quantity specified by the vector surface integral (i.e., dot product integral) of the total magnetic flux density B over the enclosed surface area of the central leg 49c.
[0027]
[0048] Interconnects 62a, interconnects 62b, and a comparator 120 are further shown. Interconnect 62a is electrically coupled to interconnect 61a at node N1, and interconnect 62b is electrically coupled to interconnect 61b at node N2.
[0028]
[0049] The comparator 120 can monitor and / or measure a probe signal VR1 that is at least partially specified by a time-varying magnetic flux Φ, a resistance RV1 of resistor R1, and a resistance RV2 of resistor R2. As shown, the probe signal VR1 can be an electromotive force (emf) induced in resistor R1 (i.e., the voltage across resistor R1).
[0029]
[0050] Furthermore, the measurement result (i.e., the value of the probe signal VR1 observed by the comparator 120) may further depend on the arrangement of the interconnects 62a - b. As shown, the interconnects 62a - b are arranged such that the probe signal VR1 observed by the comparator 120 can be given by Equation 1 in terms of the resistance RV1, the total loop resistance RTOT, and the time rate of change of the flux Φ enclosed by the magnetic flux probe 50.
Number
[0030]
[0051] The sign (plus or minus) of the probe signal VR1 may depend in part on the time rate of change (i.e., the derivative) of the flux Φ and the corresponding direction of the induced current ILOOP.
[0031]
[0052] When the interconnect resistance of the interconnects 61a - b is negligible compared to the resistances RV1 and RV2, the total resistance RTOT can be given by the sum of the resistances RV1 and RV2, and Equation 1 can be rewritten as the following Equation 2.
Number
[0032]
[0053] Thus, the magnitude of the voltage of the probe signal VR1 can be trimmed to a selected value by adjusting one or both of the resistances RV1 and RV2. For example, the resistor R2 can be a variable or trim - able resistor. This can beneficially enable trimming the magnitude of the voltage of the probe signal VR1 such that the output of the comparator changes state (i.e., changes the detection signal VO) according to the trimmed target value.
[0033]
[0054] The embodiment of FIG. 2B is similar to that of FIG. 2A, except that node N1 can be connected to ground GND so that the measured voltage of the probe signal VR1 is referenced to ground GND. FIGS. 2A and 2B show the flux probe 50 as including two resistors R1 - R2, although other configurations including more or fewer resistors may be possible.
[0034]
[0055] Furthermore, other configurations for measuring the probe signal VR1 and for providing the detection signal VO may be possible. Other configurations may include one or more flux probes for providing the probe signal to a comparator and / or other circuitry (such as an operational amplifier).
[0035]
[0056] For example, FIG. 2C shows an upper perspective view of a magnetic core 102 and interconnect routing for receiving one or more probe signals VR1, VR4 according to an embodiment. Different from the embodiments of FIGS. 2A and 2B, the embodiments of FIGS. 2C and 2D include additional flux probes 55, circuitry 220, and circuitry 221.
[0036]
[0057] The flux probe 55 includes a resistor R3, a resistor R4, an interconnect 65a, and an interconnect 65b. The resistors R3 - R4 are electrically coupled to the interconnects 65a - b to form a loop, and the above description related to the operation of the flux probe 50 and the resistors R1 - R2 may be applicable to the flux probe 55.
[0037]
[0058] Unlike the embodiments of FIGS. 2A and 2B, the embodiment of FIG. 2C includes a circuit 220 instead of the comparator 120. Similar to the comparator 120, the circuit 220 may receive the probe signal VR1. The circuit 220 may include active components and / or passive components that enable the circuit 220 to provide a detection signal VO1 in response to the probe signal VR1. For example, the circuit 220 may comprise an operational amplifier and / or passive components that provide the detection signal VO1 as a continuous analog signal. Alternatively, the circuit 220 may comprise digital components including, but not limited to, an analog-to-digital converter, logic gates, a digital signal processor, and the like.
[0038]
[0059] Interconnects 65a and 65b are further shown, coupled respectively to nodes N4 and N3 for providing the probe signal VR4 (e.g., emf induced in resistor R4) to the circuit 221. The circuit 221 may be similar to that of the circuit 220 and may provide a detection signal VO2 in response to the probe signal VR4.
[0039]
[0060] FIG. 2D further shows an upper perspective view of the magnetic core 102 and interconnect routing according to another embodiment including one or more magnetic flux probes 50, 55. The embodiment of FIG. 2D is similar to that of FIG. 2C except that it includes a comparator 120, which receives the probe signal VSENSE via interconnects 62b and 65b. As shown, the comparator 120 may provide a detection signal VO in response to the potential between nodes N2 and N3.
[0040]
[0061] FIGS. 3A and 3B show circuit diagrams 301a - b including a magnetic flux probe 50. The circuit diagrams 301a - b include a magnetic core 102, a winding 60 (e.g., a primary winding), and a comparator 120. The winding 60 may receive a time-varying current ISW provided from a signal source 30. Next, a magnetic flux density B may be generated in the magnetic core 102.
[0041]
[0062] As shown in schematic diagram 301a, magnetic flux probe 50 includes a partial turn winding fT1, a partial turn winding fT2, a resistor R1, and a resistor R2. The partial turn winding fT1 and the resistor R2 are electrically coupled between node N1 and node N2, and the partial turn winding fT2 and the resistor R1 are electrically coupled between node N1 and node N2.
[0042]
[0063] As shown, the partial turn windings fT1, fT2, and the resistors R1, R2 can represent a loop surrounding the magnetic core 102 including nodes N1, N2. For example, the circuit path including the partial turn winding fT2 and the resistor R1 from node N1 to node N2 can depict interconnect 61a, interconnect 61b, and resistor R1 routed through the winding window between the outer leg 49a and the center leg 49c. Similarly, the circuit path including the partial turn winding fT1 and the resistor R2 can depict interconnect 61a, interconnect 61b, and resistor R2 routed through the winding window between the outer leg 49b and the center leg 49c.
[0043]
[0064] As shown in schematic diagram 301a, comparator 120 is configured to measure (i.e., receive) a probe signal VR1 from magnetic flux probe 50. Further, the probe signal VR1 can be the voltage across resistor R1. For example, as already described in connection with FIG. 2A, when interconnects 62a and 62b are routed such that they do not surround the time-varying magnetic flux density B, comparator 120 can receive the probe signal VR1 (i.e., the voltage across resistor R1). In this way, the inverting input and the non-inverting input of comparator 120 can be coupled (i.e., electrically coupled) to nodes N2 and N1, respectively, such that the comparator measures the probe signal VR1 as the voltage across resistor R1.
[0044]
[0065] As shown in schematic diagram 301b in FIG. 3B, the comparator 120 can be configured to measure (i.e., compare) the probe signal VR1 against a reference voltage Vref (e.g., 0.1 volts). Node N1 can be connected to ground GND. Accordingly, the inverting input of the comparator 120 can receive the node relative probe signal VR1X with respect to ground GND. Further, the non-inverting input of the comparator 120 can receive the node relative reference voltage Vrefx with respect to ground GND.
[0045]
[0066] Further, unlike that of schematic diagram 301a, the resistor R2 in schematic diagram 301b can include a variable resistor RV2. As already described in connection with FIGS. 2A and 2B, the resistor R2 can be trimmed and / or adjusted to obtain a target value (i.e., the target voltage of the probe signal VR1) for which the comparator 120 changes its state with respect thereto.
[0046]
[0067] FIG. 4A shows a schematic diagram of an isolated flyback converter 400a according to an embodiment. The flyback converter 400a can receive input power having an input voltage VIN and a current ISW (e.g., switch current). During the switching cycle of the primary switch 152, the winding 60 (e.g., primary winding) receives the current ISW and, in response thereto, generates a magnetic flux density B within the magnetic core 102. As a result of the magnetic flux density B, power is transferred to the winding 99 (e.g., secondary winding) and can be transferred to the load 142 in the form of an output power having an output voltage VO1 and a load current IL1.
[0047]
[0068] Further, while the input power signal (e.g., input voltage VIN) can be with respect to a primary ground (e.g., ground GND), the output power signal (e.g., output voltage VO1) can be with respect to a secondary ground (e.g., secondary ground RTN). For example, as shown, the primary control device 109 is referenced to ground GND, while the secondary control device 108 and the load 142 are referenced to a galvanically isolated secondary ground RTN.
[0048]
[0069] As shown, flyback converter 400a includes a primary control device 109, a primary switch 152, and a winding 60 (e.g., a primary winding). The primary control device 109 can drive the primary switch 152 with a gate signal VCS such that the winding 60 receives a current ISW according to a switching cycle. A magnetic flux density B can be generated in the magnetic core 102 in response to the current ISW in the winding 60.
[0049]
[0070] The peak value of the current ISW can be partially determined by a detection signal SENS. As shown, the detection signal SENS can be provided to the primary control device 109 via a detection element 454. When the current ISW reaches a target peak value, the primary control device can switch the primary switch 152 off in response to the detection signal SENS.
[0050]
[0071] Further, flyback converter 400a can include a secondary control device 108, a synchronous rectifier 126, a feedback network 140, and a winding 99 (e.g., a secondary winding). The winding 99 can be electrically coupled to the (drain) of the synchronous rectifier 126 (e.g., an NFET having a gate, a source, and a drain) at a node NFW (e.g., a secondary winding node).
[0051]
[0072] The secondary control device 108 can receive a feedback signal FB1 and, in response, can transmit information to the primary control device 109 via a signal FL. For example, if the feedback signal FB1 indicates that the load requires more power (e.g., the output voltage VO1 is decreasing), the secondary control device 108 can provide a pulse via the signal FL. In response, the primary control device 109 can provide a gate signal VCS such that the primary switch 152 switches on.
[0052]
[0073] Thus, the power transmitted to the load 142 can be adjusted to a specified output voltage VO1 as the load current IL1 varies with the load demand. Further, an output capacitor C1 can be used to filter the output ripple.
[0053]
[0074] As shown, synchronous rectifier 126 can be implemented as an N-channel field effect transistor (NFET). During each switching cycle of primary switch 152, synchronous rectifier 126 can receive a control signal Vcr from secondary control device 108. As described herein, control signal Vcr can be provided to synchronous rectifier 126 based in part on the switching state of primary switch 152.
[0054]
[0075] For example, when primary switch 152 transitions from on to off, secondary control device 108 can provide control signal Vcr to turn on synchronous rectifier 126 such that winding 99 (e.g., the secondary winding) can maintain secondary current IS. This can beneficially enable efficient transfer of power to load 142 while magnetic flux density B is present within magnetic core 102.
[0055]
[0076] Further, when secondary current IS becomes small during a switching cycle such that the flyback converter operates in discontinuous mode (DCM), after the secondary current has become substantially zero, secondary control device 108 can turn off synchronous rectifier 126.
[0056]
[0077] Further, according to the teachings herein, magnetic flux probe 50 can beneficially provide a probe signal VR1 indicative of the switching state and operating mode (e.g., DCM) of the primary switch. For example, when primary switch 152 switches off, the rate of change of magnetic flux density B can abruptly change sign (e.g., from positive to negative). Thus, probe signal VR1 can abruptly change sign indicative of the transition of primary switch 152.
[0057]
[0078] Furthermore, the magnitude of the voltage of the probe signal VR1 may indicate when the magnetic flux density B has decreased below the target magnitude. Thus, the probe signal VR1 may further indicate the occurrence of DCM and ringing.
[0058]
[0079] As described herein, the secondary control device 108 may further provide a control signal Vcr to the synchronous rectifier 126, at least partially based on the detection signal VO from the flux detection circuit 153.
[0059]
[0080] As illustrated, the flux detection circuit 153 may include a comparator 120 that measures (i.e., compares) the probe signal VR1 as the differential voltage between the non-inverting input terminal and the inverting input terminal, similar to that of FIG. 3A. Thus, the comparator 120 may provide a detection signal VO based on the value of the probe signal VR1. The secondary control device 108 may then provide a control signal Vcr to switch the synchronous rectifier on and / or off, at least partially based on the detection signal VO.
[0060]
[0081] FIG. 4B shows a schematic diagram of a flyback converter 400b according to another embodiment. The flyback converter 400b is similar to the flyback converter 400a, except that the node N1 may be electrically coupled to the secondary ground RTN such that the inverting input of the comparator 120 may receive a node-relative probe signal VR1X with respect to the secondary ground RTN. Further, the non-inverting input of the comparator 120 may receive a node-relative reference voltage Vrefx with respect to the secondary ground RTN such that the comparator 120 may compare the probe signal VR1 with a reference voltage Vref.
[0061]
[0082] Figure 4C shows a schematic diagram of a flyback converter 400c according to another embodiment. The flyback converter 400c is similar to the flyback converter 400b, except that it includes an additional partial turn winding fT3. As described herein, the partial turn winding fT3 may represent a partial turn that does not completely surround the magnetic core. As shown, the partial turn winding fT3 may be coupled to the secondary ground RTN and to the routed secondary ground RTNX.
[0062]
[0083] Further, as presented herein, the routed secondary ground RTNX and the secondary ground RTN may be physically located on both sides of a winding window (e.g., a winding window defined by outer legs 49a and central leg 49c). As will be appreciated by those skilled in the art, the partial turn winding fT3 may create a half-turn effect and / or result in an undesirable variation in the turns ratio between the primary turns TP and the secondary turns TS. For example, when the synchronous rectifier 126 is on, the partial turn winding fT3 may effectively couple to a winding 99 (e.g., the secondary winding), thereby resulting in an additional partial turn.
[0063]
[0084] Under certain operating conditions and configurations, if the partial turn winding fT3 becomes part of a loop that surrounds the magnetic core 102, this may change the effective secondary turns TS. For example, if additional interconnects and / or external wire routing are connected to both the secondary ground RTN and the routed secondary ground RTNX, the loop may include the partial turn winding fT3. Ideally, the layout may follow best practices such that the partial turn winding fT3 is not part of a loop, and under the conditions of these best practices, the secondary ground RTN and the routed secondary ground RTNX may be substantially equal without magnetic interference.
[0064]
[0085] Thus, when the winding fT3 of the partial turn is not part of the loop surrounding the core (e.g., the central leg 49c), the node relative reference voltage Vrefx and the node relative probe signal VR1X of the flyback 400c can be equal to those of the flyback 400b.
[0065]
[0086] FIG. 4D shows a schematic diagram of a flyback converter 400d according to another embodiment. The flyback converter 400d is similar to the flyback converter 400b, except that the node N2 can be electrically coupled to a node NFW (e.g., a secondary winding node) such that the node relative probe signal VR1X is referenced to the winding voltage VFW instead of the secondary ground RTN.
[0066]
[0087] The winding voltage VFW changes during the switching cycle and can depend on the switching state of the synchronous rectifier 126. When the synchronous rectifier 126 is on, the winding voltage VFW can be substantially equal to the value of the secondary ground RTN (e.g., 0 volts) or less than the value of the secondary ground RTN (e.g., 0 volts). For example, the winding voltage VFW can be less than the value of the secondary ground RTN due to the drain-to-source voltage of the synchronous rectifier 126. Thus, when the synchronous rectifier 126 is on, the node relative probe signal VR1X can change, at least in part, due to the drain-to-source voltage of the synchronous rectifier 126. Thus, in the embodiment of the flyback converter 400d, the comparator 120 can provide the detection signal VO based at least in part on the drain-to-source voltage of the synchronous rectifier 126 and on the node relative probe signal VR1X.
[0067]
[0088] FIG. 5A shows a three-dimensional (3D) upper perspective view of a portion of a flyback converter 500 according to an embodiment of a printed circuit board (PCB). The flyback converter 500 includes a magnetic core 102, a synchronous rectifier 126, a resistor R1, a resistor R2, and a secondary control device 108. The magnetic core 102 can be an EI type core. According to the teachings herein, there can be a magnetic flux density B generated within the magnetic core 102, and it may be necessary to switch the synchronous rectifier 126 on and off based at least in part on a switching state (e.g., the switching state of a primary switch) and / or an operating mode (e.g., DCM).
[0068]
[0089] FIG. 5B shows a three-dimensional (3D) upper perspective view of a portion of a flyback converter 500 according to the embodiment of FIG. 5A. In FIG. 5B, a portion of the magnetic core 102 (e.g., an I type segment) is removed to more clearly show the associated underlying trace wiring and interconnects. The view of FIG. 5B shows interconnect 61a, trace wiring PT_Vcr, and trace wiring PT_RTN. Interconnect 61a is electrically coupled to resistor R1 and resistor R2. The synchronous rectifier 126 can be an NFET including a gate electrically coupled to trace wiring PT_Vcr, and trace wiring PT_RTN can be electrically coupled to a secondary ground RTN.
[0069]
[0090] FIG. 5C shows a three-dimensional (3D) upper perspective view of a portion of a flyback converter 500 according to the embodiment of FIG. 5A. In the upper view of FIG. 5C, material is removed to show a magnetic flux probe 50 in relation to the magnetic core 102 and in relation to a winding 99 (e.g., a secondary winding). The magnetic flux probe 50 includes interconnect 61a, interconnect 61b, resistor R1, and resistor R2. As shown, the magnetic flux probe 50 can form a loop around the central leg 49c of the magnetic core 102. Further, as described herein, the magnetic flux probe 50 can provide a probe signal VR1 in response to a time-varying magnetic flux density B.
[0070]
[0091] In an exemplary embodiment, the interconnect 61a may include printed circuit board (PCB) vias to route the interconnect 61a in more than one layer of the PCB. Further PCB vias may route the interconnect 61a at node NFW and electrically couple the node NFW to the interconnect 61a.
[0071]
[0092] Further, the interconnect 61b may be electrically coupled to the resistor R2 and the resistor R1 using vias. This may enable the interconnect 61b to be routed in a second layer of the PCB separate from the layer including the resistors R1, R2.
[0072]
[0093] FIG. 6A shows the interconnect routing 50 of the flux probe and the interconnect routing according to the embodiment of FIG. 5A. The flux probe 50 may include the interconnect 61a, the interconnect 61b, the resistor R1, and the resistor R2, and may form a loop around the central leg 49c of the core 102. The synchronous rectifier 126 may be an N-type field effect transistor (NFET) having a drain electrically coupled to the node NFW (e.g., the secondary winding node), a source electrically coupled to the secondary ground RTN, and a gate electrically coupled to the trace wiring PT_Vcr.
[0073]
[0094] According to the teachings herein, the flux probe 50 may provide a probe signal VR1. As shown, the probe signal VR1 may be a voltage with respect to the routed secondary ground RTNX thanks to the trace wiring PT_RTN routed across the winding window between the outer leg 49a and the central leg 49c. As already explained in connection with FIG. 4C, the routed secondary ground RTNX may be equal to the secondary ground RTN when the trace wiring PT_RTN is excluded from the loop surrounding the core 102.
[0074]
[0095] Comparator 120 can compare the node-relative probe signal VR1X with the node-relative reference voltage Vrefx and, in response, provide a detection signal VO. Further, similar to that of the flyback converter 400d, the node-relative probe signal VR1X can be with respect to the winding voltage VFW. The node-relative reference voltage Vrefx can be, for example, minus 0.3 volts (-0.3V) with respect to the routed secondary ground RTNX. Thus, according to the operation of comparator 120, when the node-relative probe signal VR1X is less than minus 0.3 volts (-0.3V), the detection signal VO can be high, and when the node-relative probe signal VR1X is higher than -0.3V, the detection signal VO can be low.
[0075]
[0096] FIG. 6B shows the interconnection routing 50 of the flux probe and the interconnection routing according to another embodiment. The embodiment of FIG. 6B can be similar to that of FIG. 6A except that node N2 is not connected to either a fixed potential (e.g., return ground RTN) or node NFW. As shown, the probe signal VR1 can be derived from the voltage across resistor R1. Thus, when the sum of the probe signal VR1 and the reference voltage Vref is greater than zero, the detection signal VO can be high, and when the sum of the probe signal VR1 and the reference voltage Vref is less than zero, the detection signal VO can be low.
[0076]
[0097] FIGS. 7A and 7B show a schematic diagram of a flyback converter 500 according to the embodiment of FIG. 6A. The flyback converter 500 can be similar to the flyback converter 400d except that the flux probe 50 and the flux detection circuit 153 can be routed according to the configuration of FIG. 6A and the resistor R2 can have a fixed resistance. FIG. 7B includes a partial winding fT4 so as to schematically represent a trace wiring PT_Vcr that crosses the winding window between the outer leg 49a and the center leg 49c.
[0077]
[0098] As described herein, when the trace wiring PT_Vcr is excluded from the loop surrounding the time-varying magnetic flux B (i.e., is not part of the loop surrounding the magnetic core 102), the control signal Vcr can drive the control terminal (i.e., the gate) of the synchronous rectifier 126 without magnetic interference from the core.
[0078]
[0099] FIG. 8A shows waveforms 801 - 804 according to the teachings herein. Waveform 801 may correspond to the current ISW in winding 60 during the switching cycle of the primary switch 152. Waveform 802 may correspond to the secondary current IS in winding 99 during the switching cycle of the primary switch 152. Waveform 803 may correspond to the magnetic flux Φ in the magnetic core 102 during the switching cycle of the primary switch 152, and waveform 804 may correspond to the detection signal VO and / or the control signal Vcr.
[0079]
[0100] From time point tx0 to time point tx1, and from time point tx3 to time point tx4, the current ISW in winding 60 increases, thereby generating a magnetic flux Φ in the magnetic core 102. Thus, the magnetic flux Φ may increase from time point tx0 to time point tx1, and from time point tx3 to time point tx4.
[0080]
[0101] From time point tx1 to time point tx2, and from time point tx4 to time point tx5, the current ISW is zero so that no current flows in winding 60. Thus, the magnetic flux Φ may decrease from time point tx1 to time point tx2, and from time point tx4 to time point tx5. As the magnetic flux Φ decreases, the secondary current IS may be provided to winding 99 according to waveform 802, and the magnetic flux Φ in the magnetic core 102 decreases.
[0081]
[0102] Further, as shown, the switching period TSW is represented from time point tx1 to time point tx4, and from time point tx2 to time point tx3, the magnetic flux Φ may decrease to zero or substantially zero during discontinuous conduction mode (DCM). Thus, the secondary current IS may decrease to zero or substantially zero in winding 99.
[0082]
[0103] According to the teachings herein, the flux probe 50 may provide a probe signal VR1 in response to the time derivative of the waveform 803 (i.e., in response to the time-varying magnetic flux Φ). In response to the probe signal VR1, the flux detection circuit 153 may provide a detection signal VO, and the secondary controller 108 may provide a control signal Vcr according to the waveform 804.
[0083]
[0104] FIG. 8B shows waveforms 801-805 according to the teachings herein. The waveform 805 may correspond to the difference between the node-relative probe signal VR1X (e.g., FIGS. 4D and / or 7B) and the routed secondary ground RTNX in an embodiment using the node-relative probe signal VR1X. As shown, the difference between the node-relative probe signal VR1X and the routed secondary ground RTNX may decrease below 0 volts at time points tx1, tx4, and may increase towards 0 volts at time points tx2, tx5, such that the waveform 804 transitions high at time points tx1, tx4 and transitions low at time points tx2, tx5.
[0084]
[0105] FIG. 9 shows a conceptual flow diagram 900 for controlling the synchronous rectifier 126 during the switching cycle TSW. Step 901 may correspond to using the flux probe 50 to measure the time-varying magnetic flux Φ. Step 902 may correspond to receiving the probe signal VR1 from the first resistor R1 of the flux probe 50. Step 903 may correspond to providing a detection signal VO in response to the probe signal VR1 using the flux detection circuit 153. Step 904 may correspond to driving (i.e., providing the control signal Vcr) the synchronous rectifier in response to the detection signal VO.
[0085] Summary
[0106] The foregoing description of the illustrated examples of the present disclosure, which includes the matters described in the abstract, is not intended to be exhaustive or to limit the disclosure to the forms shown. Specific embodiments and examples of a flux detection circuit and method for detecting flux via a flux probe are described herein for purposes of illustration, but various equivalent modifications are possible without departing from the broader spirit and scope of the present disclosure. In fact, it is understood that specific and exemplary voltages, currents, frequencies, output range values, times, etc. are presented for purposes of explanation and that other values may be used in other embodiments and examples in accordance with the teachings of this specification.
[0086]
[0107] The foregoing description may refer to elements or features that are "connected" or "coupled" together. As used herein, unless expressly stated otherwise, "connected" means that one element / feature is directly or indirectly connected to another element / feature and does not necessarily mean mechanically connected. Similarly, unless expressly stated otherwise, "coupled" means that one element / feature is directly or indirectly coupled to another element / feature and does not necessarily mean mechanically connected. Thus, while the various schematic diagrams shown in the figures illustrate exemplary configurations of elements and components, additional intervening elements, devices, features, or components may exist in actual embodiments (assuming that the functionality of the circuits shown is not adversely affected).
[0087]
[0108] Furthermore, references to "one embodiment", "an embodiment", "an example", or "an illustration" in this specification mean that a particular feature, structure, or characteristic described in connection with the embodiment or example is included in at least one embodiment of a flux detection circuit and method for detecting magnetic flux via a magnetic flux probe. Accordingly, the use of the phrases "in one embodiment", "in an embodiment", "an example", or "an illustration" in various places in this specification are not necessarily all referring to the same embodiment or example. Further, the particular features, structures, or characteristics may be combined in any suitable combination and / or sub-combination in one or more embodiments or examples. The particular features, structures, or characteristics may be included in an integrated circuit, an electronic circuit, a combinational logic circuit, or other suitable components that provide the described functionality. Additionally, it is understood that the figures provided with this specification are for purposes of explanation to those skilled in the art and that the drawings are not necessarily drawn to scale.
[0088]
[0109] Furthermore, conditional expressions used in this specification such as, but not limited to, "can", "able to", "may", "may be", "for example", "as an example", "such as", etc., generally convey that a particular embodiment includes a particular feature, element, and / or state, while other embodiments do not include the particular feature, element, and / or state, unless explicitly stated otherwise or understood differently in the context in which it is used. Accordingly, such conditional expressions are not generally intended to imply that a feature, element, and / or state is required in one or more embodiments by any means, and that one or more embodiments necessarily include logic for determining whether these features, elements, and / or states are included in, or implemented in, any particular embodiment.
[0089]
[0110] While specific embodiments have been described, these embodiments are presented by way of example only and are not intended to limit the scope of the disclosure. In fact, the novel apparatus, methods, and systems described herein may be embodied in a variety of other forms, and various omissions, substitutions, and changes in the forms of the methods and systems described herein may be made without departing from the spirit of the disclosure. For example, while the disclosed embodiments are shown with a given configuration, alternative embodiments may perform similar functions using different components and / or circuit topologies, and some elements may be deleted, moved, added, re-divided, combined, and / or changed. Each of these elements may be implemented in a variety of different ways. Any suitable combination of the elements and operations of the various embodiments described above may be combined to provide further embodiments. Accordingly, the scope of the invention is defined only by reference to the appended claims.
[0090]
[0111] The claims presented in this application are in a one-dependent form for filing in the USPTO, but it is understood that any claim may depend on any one of the preceding claims of the same kind, except where it is clearly not technically feasible.
Claims
1. An energy transfer element comprising a primary winding, a secondary winding, and a core, a primary switch electrically coupled to the primary winding, the primary switch configured to generate a magnetic flux in the core according to a switching cycle, a magnetic flux probe comprising a first resistor and a second resistor, the magnetic flux probe configured to form a loop surrounding the magnetic flux and to provide a probe signal proportional to a time derivative of the magnetic flux, a synchronous rectifier (SR) electrically coupled to the secondary winding and configured to receive a control signal based at least in part on the probe signal, A switching power supply comprising the above components.
2. The switching power supply is a flyback converter, The switching power supply according to claim 1.
3. The energy transfer element is a magnetic component, The switching power supply according to claim 1.
4. The magnetic component is an integrated transformer, The switching power supply according to claim 3.
5. The synchronous rectifier is an N-type field effect transistor (NFET), The switching power supply according to claim 1.
6. The magnetic flux probe comprises a first node electrically coupled to the first resistor, The switching power supply according to claim 1.
7. The probe signal is at least partially determined by an electromotive force (emf) of the first resistor, The switching power supply according to claim 1.
8. The probe signal is proportional to the resistance of the first resistor and inversely proportional to the total resistance of the magnetic flux probe, The switching power supply according to claim 1.
9. The total resistance of the magnetic flux probe includes the resistance of the first resistor and the resistance of the second resistor, The switching power supply according to claim 8.
10. The second resistor is a variable resistor, The switching power supply according to claim 1.
11. The second resistor is a trimmer resistor, The switching power supply according to claim 1.
12. The magnetic flux probe comprises a first node electrically coupled to the secondary winding, The switching power supply according to claim 1.
13. The first node is electrically coupled to the synchronous rectifier, The switching power supply according to claim 12.
14. A flux detection circuit configured to provide a detection signal in response to the probe signal, further comprising the flux detection circuit, wherein the synchronous rectifier is configured to receive a control signal based at least in part on the detection signal. The switching power supply according to claim 1.
15. The flux detection circuit includes a comparator configured to provide the detection signal in response to a comparison between the probe signal and a reference voltage. The switching power supply according to claim 14.
16. The reference voltage has a magnitude between 0.1V and 0.5V. The switching power supply according to claim 15.
17. The magnetic flux probe further comprises at least one interconnect electrically coupled between the first resistor and the second resistor. The switching power supply according to claim 1.
18. The at least one interconnect comprises printed circuit board trace wiring. The switching power supply according to claim 17.
19. The at least one interconnect comprises wire wiring. The switching power supply according to claim 17.
20. A method of controlling a synchronous rectifier during a switching cycle, the method comprising: using a magnetic flux probe to measure a time-varying magnetic flux; receiving a probe signal from a first resistor of the magnetic flux probe; using a flux detection circuit to provide a detection signal in response to the probe signal; driving the synchronous rectifier in response to the detection signal. A method, including.
21. Further comprising adjusting a variable resistor to determine the magnitude of the probe signal. The method according to claim 20.
22. The synchronous rectifier is an N-type field effect transistor (NFET). The method according to claim 20.
23. Using the flux detection circuit to provide the detection signal in response to the probe signal further includes using a comparison unit to compare the probe signal and a reference voltage. The method according to claim 20.
24. The reference voltage has a magnitude between 0.1V and 0.5V. The method according to claim 23.
25. The switching cycle is a switching cycle of a power converter. The method according to claim 20.
26. The power converter is a flyback converter. The method according to claim 25.
27. The magnetic flux probe surrounds the time-varying magnetic flux of the core The method according to claim 20
28. The core is a core of an energy transfer element The method according to claim 27
29. The core is a core of an incorporated transformer The method according to claim 27