Totem pole power factor correction system

Abstract

A mechanism for monitoring the current through a first inductor in a totem pole power factor correction system. A sensing resistor, connected in series with a switch of a PFC system, monitors the inductor current whilst the switch is activated. An electrical property of an auxiliary inductor, magnetically coupled to the first inductor, monitors changes in the inductor current for determining the inductor current whilst the switch is deactivated.

Description

[0001] 2024PF80522

[0002] 1

[0003] TOTEM POLE POWER FACTOR CORRECTION SYSTEM

[0004] FIELD OF THE INVENTION

[0005] The present invention relates to the field of power factor correction systems.

[0006] BACKGROUND OF THE INVENTION

[0007] There is an increasing use of power factor correction (PFC) systems in a wide variety of electrical goods in order to improve the efficiency of such electrical devices.

[0008] Indeed, power factor correction systems are often seen as being indispensable or essential for many electrical devices in order to achieve required power factors for the electrical device(s). One example of a power factor correction system is a totem pole power factor correction system, which is sometimes called an asymmetrical bridgeless boost rectifier.

[0009] There has been a growing interest in different control schemes for power factor correction systems, with new modes of operation being introduced in recent times. These modes include: a peak current control mode, an average current control mode, the continuous conduction mode (CCM), the discontinuous conduction mode (DCM), the boundary / transition conduction mode (BCM) and the quasi-square wave (QSW) mode. A power factor correction system may employ a combination of such control modes or schemes.

[0010] There is an ongoing desire to improve the performance and reliability of PFC systems, and particularly totem pole PFC systems.

[0011] SUMMARY OF THE INVENTION

[0012] The invention is defined by the claims.

[0013] In accordance with a proposed approach, there is provided a totem pole power factor correction system for driving a load. The system comprises an input interface comprising a first input node and a second input node for receiving an AC input signal from an external power supply, an output interface for providing a driving signal to the load, the output interface comprising a first output node and a second output node for connecting to the load, and an output capacitor connected between the first output node and the second output node. The system further comprises a PFC converter comprising a first inductor2024PF80522

[0014] 2

[0015] coupled between the first input node and an intermediate node, a first switch connected between the intermediate node and the first output node, a second switch connected between the intermediate node and the second output node, a first rectifying component connected between the second input node and the first output node, and a second rectifying component connected between the second input node and the second output node. A control arrangement is configured to control the activation and deactivation of at least the first switch and the second switch responsive to a feedback signal representing a current through the first inductor. The system also comprises a feedback system configured to generate the feedback signal, the feedback system comprising a sensing resistor connected in series with a target switch, wherein the target switch is the first switch or the second switch, wherein a voltage across the sensing resistor defines the value of the feedback signal whilst the target switch is activated. The feedback system further comprises an auxiliary inductor magnetically coupled to the first inductor, and a current monitoring system configured to, whilst the target switch is deactivated, monitor one or more electrical properties of the auxiliary inductor to determine a change in current through the first inductor and define the value of the feedback signal responsive to the determined change in current.

[0016] The present disclosure provides a new mechanism for monitoring an inductor current within a totem pole power factor correction system. In particular, the proposed approach provides an energy-efficient and reliable mechanism for monitoring the current through the first inductor of the totem pole power factor correction system.

[0017] The proposed approach requires the use of only a single sensing resistor to monitor the inductor current, reducing losses and providing a more efficient feedback system.

[0018] In some embodiments, the current monitoring system is configured to monitor a voltage across the auxiliary inductor, integrate the monitored voltage across the auxiliary inductor over time to predict a change in current through the first inductor.

[0019] The integration-based current prediction method allows for accurate current estimation (for at least a part of the operation of the system) without direct measurement, reducing component count and improving system reliability. This approach enables seamless current monitoring across switching cycles, enhancing overall power factor correction efficiency.

[0020] In some embodiments, the current monitoring system comprises an integrating capacitor connected between the auxiliary inductor and a reference voltage for integrating the voltage across the auxiliary inductor. An integrating capacitor provides a simple yet effective means of performing voltage integration, enabling accurate current prediction with minimal2024PF80522

[0021] 3

[0022] additional components. This provides to a more compact and materially efficient power factor correction system.

[0023] In some embodiments, the auxiliary inductor is connected between the reference voltage and the integrating capacitor. This configuration aids in the performance of the integrating capacitor.

[0024] In some embodiments, the current monitoring system comprises a first resistance connected between the auxiliary inductor and the integrating capacitor. The inclusion of a resistance between the auxiliary inductor and integrating capacitor allows for control or tuning of the integration time constant. This feature enables control of the current prediction accuracy for particular operating conditions.

[0025] In some embodiments, the feedback system comprises a storage capacitor, wherein a voltage across the storage capacitor defines the value of the feedback signal, and a first feedback switch arrangement configured to, whilst the target switch is activated, electrically connect the sensing resistor to the storage capacitor and control the voltage across the storage capacitor using the voltage across the sensing resistor, and whilst the target switch is deactivated, electrically disconnect the sensing resistor from the storage capacitor.

[0026] This feedback system design allows for seamless transition between direct current sensing and predicted current values. The use of a storage capacitor maintains a continuous feedback signal, ensuring smooth operation of the power factor correction system across all phases of the AC input cycle.

[0027] In some embodiments, the first feedback switch arrangement comprises a first feedback switch configured to, whilst the target switch is activated and only whilst the AC input signal is positive, electrically connect the sensing resistor to the storage capacitor and control the voltage across the storage capacitor using the voltage across the sensing resistor, and whilst any first predetermined criteria is met, electrically disconnect the sensing resistor from the storage capacitor, wherein the first predetermined criteria comprises: the target switch being deactivated; and the AC input signal being negative.

[0028] This switching arrangement ensures that direct current sensing is only used when the sensing resistor is connected in series with the first inductor, such that a current through the sensing resistor represents the inductor current.

[0029] In some embodiments, the first feedback switch arrangement comprises a second feedback switch and an inverter connected in series, wherein the second feedback switch is configured to, whilst the target switch is activated and only whilst the AC input signal is negative, electrically connect the sensing resistor to the storage capacitor and control2024PF80522

[0030] 4

[0031] the voltage across the storage capacitor using the voltage across the sensing resistor, and whilst any second predetermined criteria is met, electrically disconnect the sensing resistor from the storage capacitor, wherein the second predetermined criteria comprises: the target switch being deactivated; and the AC input signal being positive.

[0032] The addition of a second feedback switch arrangement with an inverter allows for symmetrical operation during both positive and negative portions (e.g., half-cycles) of the AC input. This balanced approach ensures consistent performance across the entire AC cycle.

[0033] In some embodiments, the feedback system comprises a second feedback switch arrangement configured to, whilst the target switch is deactivated, electrically connect the auxiliary inductor to the storage capacitor and control the voltage across the storage capacitor using the voltage across the auxiliary inductor, and whilst the target switch is activated, electrically disconnect the auxiliary inductor from the storage capacitor.

[0034] This second feedback switch arrangement enables transition between direct current sensing (via the sensing resistor) and indirect current sensing via the auxiliary inductor. By automatically switching between these two modes, the feedback system is able to maintain a continuous and accurate feedback signal, ensuring optimal power factor correction performance throughout the entire switching cycle.

[0035] In some embodiments, the second feedback switch arrangement comprises a first feedback switch configured to, whilst the target switch is deactivated and only whilst the AC input signal is positive, electrically connect the auxiliary inductor to the storage capacitor and control the voltage across the storage capacitor using the voltage across the auxiliary inductor, and whilst any third predetermined criteria is met, electrically disconnect the auxiliary inductor from the storage capacitor, wherein the third predetermined criteria comprises: the target switch being activated; and the AC input signal being negative.

[0036] In some embodiments, the second feedback switch arrangement comprises a second feedback switch and an inverter connected in series, wherein the second feedback switch is configured to, whilst the target switch is deactivated and only whilst the AC input signal is negative, electrically connect the auxiliary inductor to the storage capacitor and control the voltage across the storage capacitor using the voltage across the auxiliary inductor, and whilst any fourth predetermined criteria is met, electrically disconnect the sensing resistor from the storage capacitor, wherein the fourth predetermined criteria comprises: the target switch being activated; and the AC input signal being positive.

[0037] The inclusion of a second feedback switch with an inverter completes the symmetrical operation for both positive and negative periods (e.g., half-cycles) of the AC2024PF80522

[0038] 5

[0039] input. This balanced design ensures consistent performance and accuracy across the entire AC cycle, contributing to improved overall power factor correction and reduced harmonic distortion.

[0040] In some embodiments, when the feedback system includes an integrating capacitor, the integrating capacitor and the storage capacitor are the same component.

[0041] This dual-purpose capacitor efficiently combines the current prediction and feedback signal generation processes, potentially improving system response time and reducing overall cost.

[0042] In some embodiments, the first and second rectifying components are third and fourth switches respectively, and the control arrangement performs synchronous control of these switches. Using switches for rectification facilitates synchronous rectification, which is able to significantly reduce conduction losses compared to traditional diode rectification. The synchronous control of these switches enables more efficient power conversion, leading to improved overall system efficiency and reduced heat generation.

[0043] In some embodiments, the first and second rectifying components are first and second diodes respectively, connected from the second input node to the first and second output nodes. Utilizing diodes for rectification provides a simple and robust rectification solution. While potentially less efficient than synchronous rectification, diode rectification offers increased reliability and simplified control, which is advantageous for some applications or use case scenarios.

[0044] In accordance with another proposed approach, there is provided an electronic device arrangement comprising the totem pole power factor correction system as described in any of the previous embodiments, and an electronic device connected to the output interface of the totem pole power factor correction system.

[0045] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment s) described hereinafter.

[0046] BRIEF DESCRIPTION OF THE DRAWINGS

[0047] For a better understanding of the invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which:

[0048] Fig. 1 illustrates an existing totem pole power factor correction system;

[0049] Fig. 2 illustrates a totem pole power factor correction system with a proposed feedback system;2024PF80522

[0050] 6

[0051] Fig. 3 illustrates a simple version of a proposed feedback system;

[0052] Fig. 4 illustrates another version of a proposed feedback system; and Figs. 5 and 6 illustrate exemplary waveforms of the proposed system.

[0053] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0054] The invention will be described with reference to the Figures.

[0055] It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the apparatus, systems and methods, are intended for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, systems and methods of the present invention will become better understood from the following description, appended claims, and accompanying drawings. It should be understood that the Figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the Figures to indicate the same or similar parts.

[0056] The invention provides a mechanism for monitoring the current through a first inductor in a totem pole power factor correction system. A sensing resistor, connected in series with a switch of a PFC system, monitors the inductor current whilst the switch is activated. An electrical property of an auxiliary inductor, magnetically coupled to the first inductor, monitors changes in the inductor current for determining the inductor current whilst the switch is deactivated.

[0057] In the context of the present disclosure, the term “whilst” is used to indicate that a first action is performed during the majority of the time that a second action is performed. Thus, a first action performed whilst a second action is performed indicates that, for a majority (e.g., >90%) of the time that the second action is performed, the first action is also performed.

[0058] In context of the present disclosure, a switch may be considered "activated" when it is in a conductive state, allowing current to flow through the switch. Conversely, a switch may be considered "deactivated" when it is in a non-conductive state, allowing no or negligible current to flow through the switch. The terms "on" and "off1may be used interchangeably with "activated" and "deactivated" respectively when referring to the state of a switch.

[0059] Figure 1 illustrates an existing totem pole power factor correction system 100 to aid in contextualizing the present invention.2024PF80522

[0060] 7

[0061] The system 100 comprises an input interface 110, an output interface 120 and a PFC converter 130.

[0062] The input interface 110 comprises a first input node NINI and a second input node NIN2 112 for receiving an AC input signal SAC from an external power supply 190.

[0063] Although not illustrated, the input interface may comprise an impedance connecting the first and second inputs nodes, such as a filtering capacitor. Similarly, the input interface may comprise an EMI filter for performing EMI filtering (i.e., electromagnetic interference filtering) on the AC input signal received by the input interface. The intention of the EMI filter is to suppress or attenuate any interferences generated the power factor correction system 100 to remain below a permitted level to which the external power supply may be exposed. The EMI filter may comprise the filtering capacitor connected between the first input node NINI and the second input node NIN2 and a filtering inductor connected between the first input node and a third input node. In such examples, the input interface 110 may be configured such that the AC input signal SAC is received between the second input node and the third input node.

[0064] Of course, the EMI filter may contain extra filtering components, as is well established in the art. The illustrated EMI filter describes what are usually considered to be the minimum components required for effectively performing EMI filtering of differential mode noise.

[0065] The output interface 120 is configured for providing a driving signal V(Co) to a load (not shown). The output interface 120 comprises a first output node Noi and a second output node N02 for connecting to the load. The output interface 120 also comprises an output capacitor Co connected between the first output node Noi and the second output node NO2.

[0066] The voltage V(Co) between the first output node Noi and the second output node N02 may also be labelled a bus voltage Vb. The second output node N02 is connected to a return line, which may in turn be connected to a ground GND or reference voltage.

[0067] Accordingly, the second output node NO2 may be at a ground voltage GND.

[0068] The PFC converter 130 is here embodied as a synchronous boost PFC converter. The PFC converter comprises a first inductor LI coupled between the first input node NINI and an intermediate node Nl. The synchronous boost PFC converter 130 also comprises a first switch SW1 connected between the intermediate node Nl and the first output node Noi; and a second switch SW2 connected between the intermediate node Nl and the second output node N02.2024PF80522

[0069] 8

[0070] The first switch SW 1 and the second switch SW2 may each be embodied as a MOSFET, although other forms of controllable switch (particularly a transistor-based switch) may be employed.

[0071] An alternative label for the first input node NINI is a boost input node. An alternative label for the second input node NIN2 is a rectifier node. An alternative label for the first output node Noi is a bus node. An alternative label for the second output node N02 is a ground node. An alternative label for the intermediate node N1 is a switch node, or a boost converter switch node.

[0072] The voltage Vz at the first input node 111 can be labelled a boost input voltage Vz. The voltage Vy at the second input node 112 can be labelled a rectifier node voltage Vy. The voltage Vb at the first output node 121 can be labelled a bus voltage Vb. The voltage at the second output node 122 can be labelled a ground voltage GND. The voltage Vx at the intermediate node 135 can be labelled an intermediate voltage Vx or a switch voltage Vx.

[0073] The PFC converter also comprises a rectifying system 140 comprising: a first rectifying component DI connected between the second input node NIN2 and the first output node Noi; and a second rectifying component D2 connected between the second output node N02 and the second input node NIN2.

[0074] The rectifying component may, for instance, be a diode (as illustrated) or a switch, such as a MOSFET.

[0075] Thus, the first rectifying component may be or comprise a first diode connected from the second input node to the first output node; and the second rectifying component may be or comprises a second diode connected from the second input node to the second output node.

[0076] Alternatively, the first rectifying component may comprise a third switch connected between the second input node and the first output node; the second rectifying component comprises a fourth switch connected between the second input node and the second output node.

[0077] The PFC converter 130 further comprises a control system 135 to control the switching of the first SW 1 and second SW2 switches, and (if present) the operation of the switches forming the first / second rectifying components.

[0078] When each rectifying component is embodied as a switch, then the control arrangement is configured to perform synchronous control of the third switch and the fourth switch. Thus, the second rectifying component D2 will be controlled to be conductive (i.e., activated) whilst the AC input signal SAC has a positive value. This allows the positive half-2024PF80522

[0079] 9

[0080] cycle of the AC input to flow through D2 to the second output node NO2 (ground), completing the circuit path for the positive half-cycle.

[0081] Similarly, the first rectifying component DI will be controlled to be conductive (i.e., activated) whilst the AC input signal SAC has a negative value. This enables the negative half-cycle of the AC input to flow through DI to the first output node NO1 (bus node), effectively inverting the negative half-cycle to contribute to the positive DC output.

[0082] This alternating activation of DI and D2 in sync with the AC input polarity ensures that both positive and negative half-cycles of the AC input are utilized, resulting in full-wave rectification. This rectification process is crucial for converting the AC input into a usable DC form for the subsequent stages of the power factor correction system.

[0083] The synchronous control of these rectifying components, when implemented as switches, can offer advantages over traditional diode-based rectification, such as lower conduction losses and improved efficiency.

[0084] In a totem-pole configuration, the control system 135 is configured so that only one of the first SW1 and second SW2 switches is conductive at a same time, leading to synchronous control. More particularly, the control system may be configured such that current is always able to flow between the intermediate node 135 and the first output node Noi or the second output node N02.

[0085] A wide variety of control schemes for controlling the operation of the first SW1 and second SW2 switches are known, such as the average current control mode, the peak current control mode, the continuous conduction mode (CCM), the discontinuous conduction mode (DCM), the boundary / transition conduction mode (BCM) and the quasisquare wave (QSW) mode. The control system 135 may be embodied to employ any one or more of these modes to control the operation of the switches.

[0086] The control system 135 controls the operation of the first SW1 and second SW2 switch responsive to at least one feedback signal SFB. The feedback signal may, for instance, indicate one or more electrical measurements (e.g., voltage, current and / or power) at one or more different points within the overall system 100. A wide variety of feedback systems are known.

[0087] In particular, it is common to facilitate measurement of a current Ii through the first inductor LI of the PFC converter 130 (i.e., an inductor current Ii) , which helps define a power in / to the PFC converter 130. Thus, it is known for the feedback signal SFB to carry a measure of current through the first inductor LI .2024PF80522

[0088] 10

[0089] More specifically, the current through the first inductor LI is a key parameter in various control schemes that may be employed by the control system 135 (e.g., as average current mode control or peak current mode control). These control schemes use the inductor current to modulate the duty cycle or control the switching of the switches, ensuring proper PFC operation.

[0090] In average current mode control, the average value of the inductor current over each switching cycle is monitored. The control system compares this average current to a reference waveform, which is typically derived from the rectified input voltage. The difference between the sensed current and the reference is used to adjust the duty cycle of the switches (SW1 and SW2). This control scheme aims to shape the input current waveform to closely match the input voltage waveform, thereby improving the power factor.

[0091] In a peak current control mode, the control system monitors the peak value of the inductor current during each switching cycle. When the inductor current reaches a predetermined threshold, the active switch is turned off. This threshold is typically modulated by a slower outer voltage control loop that maintains the desired output voltage. Peak current mode control offers advantages such as inherent cycle-by-cycle current limiting and improved transient response.

[0092] Moreover, even if the inductor current is not directly used in the general control scheme of the control system 135, over-current protection (OCP) is desirable for protecting the circuit for transients in the AC supply signal. OCP requires a fast turn off of the PFC switch when a current supplied to the system is too high. Over-currents can be detected by monitoring the current L through the first inductor LI (i.e., the inductor current Ii). The control system 135 may compares the sensed current against a predetermined threshold. This threshold is set based on the maximum safe operating current of the system components. When the threshold is exceeded, the control system 135 immediately deactivates both SW1 and SW2 switches. This action interrupts the current path, protecting the circuit. OCP is advantageously employed in any control scheme that may be employed by the control system.

[0093] There is therefore a demand for reliable monitoring of a current through the first inductor LI.

[0094] The present disclosure proposes a new feedback system for generating a feedback signal representing a current through the first inductor LI of the PFC converter.

[0095] Figure 2 illustrates a totem pole power factor correction system 200 with the proposed feedback system. As previously mentioned, the feedback signal is configured for2024PF80522

[0096] 11

[0097] generating a feedback signal SFB representing a current through the first inductor LI of the PFC converter.

[0098] The feedback system comprises a sensing resistor Rs, an auxiliary inductor L2 and a current monitoring system 210.

[0099] The sensing resistor Rs is connected in series with the first switch SW1 or the second switch SW2. In the illustrated example, the sensing resistor Rs is connected in series with the second switch SW2, but this is not essential. The switch SW1, SW2 connected in series with the sensing resistor is labelled a target switch, for ease of reference.

[0100] It will be appreciated that the voltage across the sensing resistor Rs will, when the target switch SW2 is activated or conductive, represent a current through the target switch SW2. It will similarly be appreciated that, as the switches SW1, SW2 are controlled such that only one of the first SW1 and second SW2 switches is conductive at a same time, the current through the target switch is the current through the first inductor LI .

[0101] Thus, the sensing resistor Rs may define a first sensing signal SI that defines or represents the current through the first inductor LI when the target switch SW1 is activated.

[0102] Accordingly, the feedback system is configured to define the value of the feedback system using the voltage across the sensing resistor. More particularly, the value of the feedback signal may be defined as the value or absolute magnitude of the first sensing signal SI whilst the target switch SW2 is activated.

[0103] The feedback system may comprise a feedback signal generator 235 configured to generate the feedback signal SFB. The feedback signal generator 235 receives the first sensing signal SI and, whilst the target switch SW2 is activated (e.g., as indicated by a target switch gate signal SG), defines the value of the feedback signal SFB using the first sensing signal S 1.

[0104] The auxiliary inductor L2 is magnetically coupled to the first inductor LI. Thus, a change in current flow through the first inductor LI induces a respective change in current flow through the auxiliary inductor.

[0105] The relationship between the currents in the two inductors is expressible as:

[0106]

[0107] 2024PF80522

[0108] 12

[0109] where Ni and N2 are the number of turns in LI and L2 respectively, and L and I2 are the currents through the first inductor LI and the auxiliary inductor L2 respectively.

[0110] The feedback system further comprises a current monitoring system 235 configured to, whilst the target switch is deactivated, monitor one or more electrical properties of the auxiliary inductor to determine a change in current through the first inductor. In particular, the current monitoring system 235 may generate a second sensing signal S2 that changes responsive to the change in current through the auxiliary inductor L2.

[0111] The feedback signal SFB is, whilst the target switch is deactivated, defined responsive to the determined change in current. In particular, the value of the current defined by the first sensing signal (used whilst the target switch is activated) defines the initial value for the current, which is modified by the determined change in current through the auxiliary inductor.

[0112] As a working example, the current monitoring system 235 may be configured to measure a voltage across the auxiliary inductor L2. The integration of this measured voltage over time is representative of the change in current through the first inductor LI.

[0113] More specifically, the derivative form of the current through the first inductor is expressible as:

[0114] dL N2V2

[0115] — = — (2) dt Ni L27

[0116] where V2 is the voltage across the auxiliary inductor L2 and L2 (in equations (2) and 3) represents the inductance of the auxiliary inductor L2. Equation (2) is derived from the well-known relationship between voltage across and inductor and current through an inductor: V = L*dl / dt.

[0117] Accordingly, the current Ii through the first inductor LI (the inductor current Ii) is expressible as:

[0118]

[0119] where I(to) is the initial value for the current through the first inductor, which is defined by the first sensing signal.

[0120] The feedback signal generator 235 may therefore receive the first sensing signal SI and the second sensing signal S2 and use these to define the feedback signal SFB. In2024PF80522

[0121] 13

[0122] some aspects, the feedback signal generator may integrate the second sensing signal S2 over time to determine the change in current through the first inductor LI, and combine this with the initial current value defined by the first sensing signal SI to generate the feedback signal SFB.

[0123] More particularly, the feedback signal generator 235 may define the value of the feedback signal SFB using only the first sensing signal whilst the target switch SW 1 is activated (which may be indicated by a gate signal for the target switch SW 1 received from the control system 135).

[0124] Moreover, the feedback signal generator 235 may, whilst the target switch SW1 is deactivated, define the value of the feedback signal SFB by integrating the second sensing signal S2 over time and combining the result with the initial current value defined by the first sensing signal S 1.

[0125] From the foregoing, it will be appreciated that the feedback signal generator 235 uses different mechanisms to define the value of the current through the first inductor dependent upon whether or not the target switch is activated.

[0126] In some examples, the feedback signal generator 235 can be embodied as a digital processor. Thus, the first sensing signal SI and the second sensing signal S2 may be transformed into the digital domain (e.g., using an ADC of the digital processor) and processed digitally to define the feedback signal SFB.

[0127] As such, the feedback signal SFB may be a digital signal for processing by the control system 135.

[0128] In such implementations, the control system 135 and the feedback signal generator 235 may represent different functional modules within a single digital processor. The digital processor may be embodied as a microcontroller, digital signal processor (DSP), field-programmable gate array (FPGA), or application-specific integrated circuit (ASIC). Within this processor, different sections of code or logic blocks may be designated to perform the functions of the control system 135 and the feedback signal generator 235.

[0129] For the control system 135, a module may be implemented to execute the control algorithms for switching the first SW1 and second SW2 switches. This module may process the feedback signal SFB and implement the chosen control scheme, such as CCM, DCM, BCM, or QSW.

[0130] The feedback signal generator 235 may be represented by another module within the same processor. This module may be responsible for processing the first sensing2024PF80522

[0131] 14

[0132] signal SI and second sensing signal S2, performing the necessary calculations and integrations, and generating the feedback signal SFB.

[0133] Any herein proposed inductor may be embodied as a respective winding. For instance, an inductor may be physically implemented as a coil of wire wound around a core material. For example, the first inductor LI and the auxiliary inductor L2 can each be realized as separate windings. These windings may be wound on the same core to achieve the magnetic coupling described earlier, or on separate cores in close proximity to one another.

[0134] Figure 3 illustrates a simple version of a feedback system 300 that may be employed in some embodiments.

[0135] The feedback system is configured to receive the first sensing signal SI and the second sensing signal S2. These are connected to a storage capacitor CFB by respective feedback switch arrangements SWA1, SWA2. For the purposes of the simple version of the feedback system 300, each feedback switch arrangement SWA1, SWA2 may comprise or be a respective switch.

[0136] The storage capacitor CFB may be connected (by its opposite plate) to a ground or reference plane. Thus, the storage capacitor CFB may connect the first and second sensing signal to the ground or reference plane GND.

[0137] More specifically, a first feedback switch arrangement SWA1 connects the first switching signal to the storage capacitor CFB.

[0138] A second feedback switch arrangement SWA2 connects the second switching signal S2 to the storage capacitor CFB. The second sensing signal S2 is defined by a voltage across the auxiliary inductor L2. In some examples, the feedback system comprises a first resistance R1 configured to connect the auxiliary inductor L2 to the storage capacitor (e.g., via the second feedback switch arrangement S4).

[0139] The voltage across the storage capacitor CFB defines the feedback signal SFB. In this way, the current monitoring system of the feedback system comprises a storage capacitor CFB connected between the auxiliary inductor and a reference voltage for integrating the voltage across the auxiliar inductor. More particularly, the storage capacitor CFB and the first resistance R1 (if present) function as an RC integrator for integrating the voltage across the auxiliary inductor.

[0140] The first feedback switch arrangement SWA1 is controlled by the gate or switching signal SG for the target switch. In particular, the first feedback switch arrangement SWA1 is activated responsive to the gate or switching signal SG controlling the target switch to be activated. In this way, the storage capacitor is set to the value of the first switching2024PF80522

[0141] 15

[0142] signal SI whilst the target switch is activated. Of course, the first feedback switch arrangement SWA1 is similarly deactivated responsive to the gate or switching signal SG controlling the target switch to be deactivated.

[0143] In the illustrated example, the second feedback switch arrangement SWA1 is controlled by the inverse of the gate or switching signal SGfor the target switch. In particular, the second feedback switch arrangement SWA2 is activated responsive to the gate or switching signal SG controlling the target switch to be deactivated. In this way, the storage capacitor receives the second switching signal S2 whilst the target switch is deactivated. In this way, the feedback signal SFB is set to be responsive to the second switching signal whilst the target switch is activated.

[0144] In an alternative example, the second feedback switch arrangement SWA1 is controlled by the gate or switching signal SGfor the other of the first / second switch (i.e., the first / second switch that is not the target switch). The use of the non-target switch's gate signal avoids the need to invert the gate / switching signal for the target switch, simplifying the control logic as the existing complementary control signals are used instead. Since the first and second switches in the totem pole PFC converter are typically controlled in a complementary manner, using the gate signal of the non-target switch directly aligns the feedback switch control with the main converter switching.

[0145] The storage capacitor CFB effectively functions as an integrator of the second sensing signal S2. More particularly, when the second feedback switch arrangement SWA2 is activated, it connects the second sensing signal S2 to the storage capacitor CFB. The voltage across the capacitor then change in response to the second sensing signal S2.

[0146] The rate of change of the voltage across the storage capacitor CFB is proportional to the magnitude of the second sensing signal S2. This relationship is expressible as:

[0147] dV(CFB)=V(S2)

[0148] dt CFB. R1( }

[0149] where V(CFB) is the voltage across the storage capacitor, R1 is the resistance of the first resistance (or the resistance between the auxiliary inductor and the storage capacitor) and CFB is the capacitance of the storage capacitor. By integrating both sides of equation (4), the voltage across the storage capacitor V(CFB) is expressible as:2024PF80522

[0150] 16

[0151]

[0152] where Vo is the initial voltage across the capacitor.

[0153] Equation (5) demonstrates that the voltage across the storage capacitor CFB is proportional to the time integral of the second sensing signal S2, plus an initial voltage Vo. The initial voltage is set by the first sensing signal SI when the target switch is activated.

[0154] In this way, the storage capacitor CFB functions as an integrator for the second sensing signal S2, i.e., functions as an integrating capacitor. The resulting voltage across the capacitor, which defines the feedback signal SFB, may thereby represent the integrated value of the second sensing signal S2 over time whilst the second feedback switch arrangement is activated.

[0155] As previously mentioned, the second sensing signal S2 represents the voltage across the auxiliary inductor L2 (Figure 2). Thus, the integration of S2 corresponds to the change in current through the auxiliary inductor L2, which in turn represents the change in current through the first inductor LI .

[0156] The feedback system may include additional components or circuitry to modify or condition the integration process.

[0157] For instance, the feedback signal may comprise one or more amplifiers Ul, U2, such as operational amplifiers, for amplifying the first and / or second switching signal. In particular, the amplification performed by the amplifier(s) Ul, U2 may be designed to scale the first and second switching signals to align with one another, e.g., to account for constant component values, such as N2, N1 or L2 (see Equation (3)). The amplifier(s) may therefore perform signal conditioning on the first and / or second switching signals.

[0158] If present, one of the one or more amplifiers Ul, U2 may be an inverting amplifier, dependent upon the polarity of the auxiliary inductor L2 with respect to the auxiliary inductor LI .

[0159] As previously explained, the first sensing signal SI represents a measured current across the first inductor LI. Thus, when the first sensing signal SI is connected to the storage capacitor, an increase in the current through the first inductor may result in a proportional increase in the first sensing signal and therefore (assuming no inversion) an increase in the voltage across the storage capacitor (i.e., in the feedback signal). The polarity of the auxiliary inductor defines whether the second sensing signal S2 will take a positive or negative value as there is a decrease in the current across the first inductor. The polarity of2024PF80522

[0160] 17

[0161] the auxiliary inductor and / or the configuration of the amplifiers Ul, U2 (if present) is / are chosen such that the second sensing signal S2 causes the opposite change in the voltage across the storage capacitor to the change resulting from the first sensing signal (when there is an increase in the current through the first inductor).

[0162] As previously explained, the polarity of the AC input signal SAC may switch between positive and negative, e.g., alternating every half-period of the AC input signal. This naturally causes the voltage across the sensing resistor to (when considering only times when the target switch is activated) alternate between positive and negative values to represent the change in direction of current flow through the first inductor.

[0163] Similarly, a change in polarity of the AC input signal SAC will induce a corresponding change in polarity of the second sensing signal S2. This change in polarity of the second sensing signal S2 is a direct result of the magnetic coupling between the first inductor LI and the auxiliary inductor L2. When the AC input signal SAC changes polarity, it causes a reversal in the direction of current flow through the first inductor LI . Due to the magnetic coupling, this reversal induces a corresponding change in the voltage across the auxiliary inductor L2, represented by the second sensing signal S2.

[0164] In this way, the previously described feedback system (such as that illustrated in Figure 3) would result in a feedback signal that changes in polarity with the AC input signal SAC.

[0165] In some scenarios, this is not desirable. In particular, it would be desirable (for the purposes of control consistency) to ensure that power flow from the input interface to the output interface results in a same polarity feedback signal.

[0166] To address this issue, the feedback system may incorporate additional circuitry or processing to ensure the feedback signal remains positive.

[0167] One approach to maintaining a positive feedback signal is to use absolute value circuitry to process a dual-polarity feedback signal SFB such as that produced by the feedback system of Figure 3. This can be implemented using diodes or operational amplifiers, e.g., configured as a precision absolute value circuit. Such circuitry would convert any negative voltage across the storage capacitor CFB into its positive equivalent, ensuring the feedback signal SFB always represents the magnitude of the current through the first inductor LI, regardless of its direction.

[0168] Another approach is to reconfigure the feedback system to invert the first and second sensing signals whilst the AC input signal is negative. This method involves2024PF80522

[0169] 18

[0170] modifying the feedback circuitry to automatically adjust the polarity of the sensing signals based on the polarity of the AC input.

[0171] Figure 4 illustrates an example version of a feedback system 400 that may be employed in some embodiments.

[0172] This version of the feedback system 400 addresses the issue of polarity changes in the AC input signal and ensures that the feedback signal remains positive regardless of the AC input polarity. The system employs multiple feedback switches and control signals to route the sensing signals appropriately based on the AC input polarity and the state of the target switch.

[0173] More particularly, the feedback system 400 comprises inverting paths for both the first SI and second S2 sensing signal, which are selectively conductive via feedback switches. A first set of feedback switches are activatable only when the AC input signal is positive. A second set of feedback switches are activatable only when the AC input signal is negative.

[0174] The first sensing signal SI is connected to the storage capacitor CFB through a first feedback switch SF1. This connection may comprise a connection via a non-inverting amplifier U3 (e.g., for signal conditioning). The first feedback switch SF1 is controlled by a first control signal SCI, which activates the first feedback switch SF1 when the AC input signal is positive and the target switch is activated (e.g., as indicated by a target switch gate signal SG).

[0175] In systems where the rectifying elements DI and D2 are implemented as switches, SCI can be generated as an AND operation between the target switch's gate control signal and the second rectifying element's gate signal. This recognizes that the second rectifying element will be activated when the AC input signal is positive.

[0176] The first sensing signal SI is also connected to the storage capacitor CFB through an inverter U4 (which may be an inverting amplifier) and a second feedback switch SF2. The second feedback switch SF2 is controlled by a second control signal SC2, which activates the second feedback switch SF2 when the AC input signal is negative and the target switch is activated. In systems where the rectifying elements DI and D2 are implemented as switches, the second control signal SC2 may be generated as an AND operation between the target switch's gate control signal SG and the first rectifying element's gate signal.

[0177] The second sensing signal S2 is similarly connected to the storage capacitor CFB via a third feedback switch SF3. The second sensing signal S2 may be generated in any manner previously disclosed, e.g., as a monitored voltage across the auxiliary inductor (not2024PF80522

[0178] 19

[0179] illustrated in Figure 4). The connection of the second sensing signal S2 via the third feedback switch SF3 may comprise a connection via an inverting amplifier U5 (e.g., for signal conditioning). The third feedback switch SF3 is controlled by a third control signal SC3, which activates when the AC input signal is positive but the target switch is deactivated.

[0180] In systems where the rectifying elements DI and D2 are implemented as switches, the third control signal SC3 can be generated as an AND operation between: the non-target switch's gate signal (or the inverse of the target switch's gate signal) and the second rectifying element's gate signal.

[0181] Similarly, the second sensing signal S2 is connected to the storage capacitor CFB through an inverter U6 (which may be a non-inverting amplifier) and the fourth feedback switch SF4. The fourth feedback switch is controlled by the fourth control signal SC4, which activates the fourth feedback switch SF4 when the AC input signal is negative and the target switch is deactivated. SC4 can be generated as an AND operation between either the nontarget switch's gate signal (or the inverse of the target switch's gate signal) and the first rectifying element's gate signal.

[0182] It will be appreciated that a respective resistance may be connected in series with the third and fourth feedback switches SF3, SF4, for the purposes of integrating the second sensing signal S2. Alternatively, a resistor may be connected in series with the auxiliary inductor (not illustrated in Figure 4) before a branching node NB.

[0183] This configuration for the feedback system 400 ensures that the feedback signal always represents the magnitude of the current through the first inductor, regardless of the AC input polarity. By selectively routing and inverting the sensing signals based on the AC input signal polarity and switch states, the system maintains a consistent and positive feedback signal for accurate control of the PFC converter.

[0184] The first SF1 and second SF2 feedback switches function as a first feedback switch arrangement SWA1, as they control the connection between the first sensing signal SI and the storage capacitor CFB. The third SF3 and fourth SF4 feedback switches function as the second feedback switch arrangement SWA2, as they control the connection between the second sensing signal S2 and the storage capacitor CFB.

[0185] The nature of the amplifiers U3, U4, U5, U6 (i.e., inverting or non-inverting) is above defined assuming that the polarity of the first inductor and the auxiliary inductor is such that a reduction in current through the first inductor LI results in the voltage across the auxiliary inductor increasing. In one alternative example, the amplification performed by the amplifiers U3, U4, U5, U6 is inverted (e.g., the third amplifier is inverting; the fourth2024PF80522

[0186] 20

[0187] amplifier is non-inverting; the fifth amplifier is inverting and the sixth amplifier is noninverting).

[0188] The skilled person would be readily capable of modifying the illustrated circuit for other relative polarities of the first inductor LI and the auxiliary L2. For instance, where the polarity of the first inductor and the auxiliary inductor is such that a reduction in current through the first inductor LI results in the voltage across the auxiliary inductor decreasing, then either: the fifth amplifier is non-inverting and the sixth amplifier is inverting or the third amplifier is inverting and the fourth amplifier is non-inverting.

[0189] Figures 5 and 6 illustrates waveforms of the proposed system. For the scenarios of Figures 5 and 6, the control system operates using a peak current control scheme and the feedback system is configured to produce a feedback signal representing a magnitude of the current through the inductor (e.g., for use with the peak current control scheme).

[0190] In particular, Figures 5 and 6 illustrates the activation (high) or deactivation (low) of the first switch SW 1 the activation (high) or deactivation (low) of the second switch SW2, the inductor current L, the voltage V2 across the auxiliary inductor L2 and the voltage of the feedback signal SFB.

[0191] For illustrative clarity, Figures 5 and 6 also illustrates a threshold voltage VT. The threshold voltage represents the switching trigger for the peak current control scheme. Thus, when the voltage of the feedback signal SFB reaches the threshold voltage, the control system switches which of the first switch and the second switch are activated and deactivated.

[0192] Figure 5 illustrates the waveforms whilst the AC input signal is positive.

[0193] Figure 6 illustrates the waveforms whilst the AC input signal is negative.

[0194] There is also proposed an electronic device arrangement comprising any herein disclosed totem pole power factor correction system and an electronic device connected to the output interface of the totem pole power factor correction system. This arrangement allows for efficient power factor correction in various electronic applications.

[0195] The electronic device may be any device that would benefit from a regulated DC power supply, such as a lighting element (e.g., a light source or luminaire). Other examples of suitable electronic devices include personal care devices, household appliances, computers, television or industrial equipment. By incorporating the proposed totem pole power factor correction system, the electronic device arrangement benefits from improved power efficiency, reduced harmonic distortion, and compliance with power quality standards.2024PF80522

[0196] 21

[0197] In some implementations, the electronic device may be directly connected to the first output node and the second output node of the totem pole power factor correction system. The regulated DC voltage provided by the power factor correction system may serve as the main power supply for the electronic device.

[0198] The electronic device arrangement may also include additional power conditioning or conversion stages between the totem pole power factor correction system and the electronic device. For example, a DC-DC converter may be used to further adjust the voltage level to meet the specific requirements of the electronic device.

[0199] In some cases, the electronic device arrangement may incorporate multiple totem pole power factor correction systems to support higher power demands or to provide redundancy for critical applications. The arrangement may also include control and monitoring systems to optimize the performance of both the power factor correction system and the electronic device.

[0200] Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

[0201] The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0202] If the term "adapted to" is used in the claims or description, it is noted the term "adapted to" is intended to be equivalent to the term "configured to". If the term "arrangement" is used in the claims or description, it is noted the term "arrangement" is intended to be equivalent to the term "system", and vice versa.

[0203] Any reference signs in the claims should not be construed as limiting the scope.

Claims

2024PF8052222CLAIMS:

1. A totem pole power factor correction system for driving a load, the totem pole power factor correction circuity comprising:an input interface comprising a first input node and a second input node for receiving an AC input signal from an external power supply;an output interface for providing a driving signal to the load, the output interface comprising: a first output node and a second output node for connecting to the load; and an output capacitor connected between the first output node and the second output node;a PFC converter comprising:- a first inductor coupled between the first input node and an intermediate node;- a first switch connected between the intermediate node and the first output node;- a second switch connected between the intermediate node and the second output node;- a first rectifying component connected between the second input node and the first output node;- a second rectifying component connected between the second input node and the second output node;- a control arrangement configured to control the activation and deactivation of at least the first switch and the second switch responsive to a feedback signal representing a current through the first inductor; and- a feedback system configured to generate the feedback signal, the feedback system comprising:a sensing resistor connected in series with a target switch, wherein the target switch is the first switch or the second switch, wherein a voltage across the sensing resistor defines the value of the feedback signal whilst the target switch is activated;an auxiliary inductor magnetically coupled to the first inductor; and a current monitoring system configured to, whilst the target switch is deactivated, monitor one or more electrical properties of the auxiliary inductor to determine a2024PF8052223change in current through the first inductor and define the value of the feedback signal responsive to the determined change in current.

2. The totem pole power factor correction circuit of claim 1, wherein the current monitoring system is configured to:monitor a voltage across the auxiliary inductor;integrate the monitored voltage across the auxiliary inductor over time to predict a change in current through the first inductor.

3. The totem pole power factor correction circuit of claim 2, wherein the current monitoring system comprises an integrating capacitor connected between the auxiliary inductor and a reference voltage for integrating the voltage across the auxiliar inductor.

4. The totem pole power factor correction circuit of claim 3, wherein the auxiliary inductor is connected between the reference voltage and the integrating capacitor.

5. The totem pole power factor correction circuit of claim 3 or 4, wherein the current monitoring system comprises a first resistance connected between the auxiliary inductor and the integrating capacitor.

6. The totem pole power factor correction circuit of any one of claims 1 to 5, wherein the feedback system comprises:a storage capacitor, wherein a voltage across the storage capacitor defines the value of the feedback signal;a first feedback switch arrangement configured to:- whilst the target switch is activated, electrically connect the sensing resistor to the storage capacitor and control the voltage across the storage capacitor using the voltage across the sensing resistor; and- whilst the target switch is deactivated, electrically disconnect the sensing resistor from the storage capacitor.

7. The totem pole power factor correction circuit of claim 6, wherein the first feedback switch arrangement comprises:2024PF8052224a first feedback switch configured to whilst the target switch is activated and only whilst the AC input signal is positive, electrically connect the sensing resistor to the storage capacitor and control the voltage across the storage capacitor using the voltage across the sensing resistor; andwhilst any first predetermined criteria is met, electrically disconnect the sensing resistor from the storage capacitor, wherein the first predetermined criteria comprises: the target switch being deactivated; and the AC input signal being negative.

8. The totem pole power factor correction circuit of any one of claims 6 to 7, wherein the first feedback switch arrangement comprises:a second feedback switch and an inverter connected in series, wherein the second feedback switch arrangement is configured to:- whilst the target switch is activated and only whilst the AC input signal is negative, electrically connect the sensing resistor to the storage capacitor and control the voltage across the storage capacitor using the voltage across the sensing resistor; and- whilst any second predetermined criteria is met, electrically disconnect the sensing resistor from the storage capacitor, wherein the second predetermined criteria comprises: the target switch being deactivated; and the AC input signal being positive.

9. The totem pole power factor correction circuit of any one of claims 6 to 8, wherein the feedback system comprises:a second feedback switch arrangement configured to:- whilst the target switch is deactivated, electrically connect the auxiliary inductor to the storage capacitor and control the voltage across the storage capacitor using the voltage across the auxiliary inductor; and- whilst the target switch is activated, electrically disconnect the auxiliary inductor from the storage capacitor.

10. The totem pole power factor correction circuit of claim 9, wherein the second feedback switch arrangement comprises:a third feedback switch configured to whilst the target switch is deactivated and only whilst the AC input signal is positive, electrically connect the auxiliary inductor to the storage capacitor and control the voltage across the storage capacitor using the voltage across the auxiliary inductor; and2024PF8052225whilst any third predetermined criteria is met, electrically disconnect the auxiliary inductor from the storage capacitor, wherein the third predetermined criteria comprises: the target switch being activated; and the AC input signal being negative.

11. The totem pole power factor correction circuit of any one of claims 9 to 10, wherein the second feedback switch arrangement comprises:a fourth feedback switch and an inverter connected in series, wherein the second feedback switch is configured to:- whilst the target switch is deactivated and only whilst the AC input signal is negative, electrically connect the auxiliary inductor to the storage capacitor and control the voltage across the storage capacitor using the voltage across the auxiliary inductor; and - whilst any fourth predetermined criteria is met, electrically disconnect the sensing resistor from the storage capacitor, wherein the fourth predetermined criteria comprises: the target switch being activated; and the AC input signal being positive.

12. The totem pole power factor correction circuit of any one of claims 6 to 11, when dependent upon claim 3, wherein the integrating capacitor and the storage capacitor are the same.

13. The totem pole power factor correction circuit of any one of claims 1 to 12, wherein:the first rectifying component comprises a third switch connected between the second input node and the first output node;the second rectifying component comprises a fourth switch connected between the second input node and the second output node; andthe control arrangement is configured to perform synchronous control of the third switch and the fourth switch.

14. The totem pole power factor correction circuit of any one of claims 1 to 12, wherein:the first rectifying component comprises a first diode connected from the second input node to the first output node; andthe second rectifying component comprises a second diode connected from the second input node to the second output node.2024PF805222615. An electronic device arrangement comprising:the totem pole power factor correction system of any of claims 1 to 14; and an electronic device connected to the output interface of the totem pole power factor correction system.

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