Average inductive current compensation method in PFC (Power Factor Correction) circuit

Abstract

The invention discloses an average inductive current compensation method in a PFC circuit, and the method comprises the steps: comparing the current actual duty ratio D of a PWM control signal of the PFC circuit with the duty ratio DCCM of the PWM control signal when the PFC circuit is in a CCM continuous conduction mode, so as to judge whether the PFC circuit is in the DCM discontinuous conduction mode or not; when the PFC circuit is in a DCM discontinuous conduction mode, compensating the high-level conduction duration Ton of the PWM control signal in the CCM mode so as to realize the compensation of the average inductive current Iin; according to the method provided by the invention, the PF / THD performance of the CCM-PFC circuit running in the DCM interval is improved; meanwhile, an auxiliary winding is not needed, inductance value (Lm) information is not needed, the design complexity is simplified, and the system cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of integrated circuits, and in particular to an average inductor current compensation method in a PFC circuit. Background Art

[0002] For a PFC circuit operating in continuous conduction mode (CCM), the voltage outer loop is generally used to control the power output to achieve constant voltage output, while the current inner loop controls the average inductor current I of the PFC circuit. in (AC current), achieving an average inductor current I in The shaping function is called PFC function.

[0003] In order to make the current inner loop work correctly, the target inductor current waveform I ref (I ref Generally, it is a sine wave. By adjusting the AC voltage waveform V in Shape detection), the average inductor current I in When the PFC circuit in CCM mode operates in heavy / medium load state, the inductor current is in continuous conduction mode; when the PFC circuit operates in light load state, it will inevitably enter discontinuous conduction mode (DCM), especially near the AC valley, such as Figure 1 As shown. Inductor current detection is generally carried out in two ways: full-wave detection and half-wave detection. The advantage of full-wave detection is that it can detect the complete inductor current waveform, whether the switch is closed or disconnected, whether in CCM or DCM mode, full-wave detection can detect the correct average inductor current I in Therefore, full-wave detection can provide the current loop with an accurate average inductor current I in either CCM or DCM. in The average inductor current I in PFC shaping. However, the limitations of full-wave detection are obvious, including: 1. The power loss of the detection resistor is large; 2. The detected waveform is a negative voltage, which needs to be processed into a positive voltage in a complex way before it can be used by the current loop; 3. It is not suitable for high-power multi-channel interleaved PFC circuits, and all channel currents can only be detected together, making it impossible to achieve single-channel precise control.

[0004] At the same time, half-wave detection can only detect the inductor current when the switch is on, that is, it is necessary to "predict" the inductor current when the switch is off for use in the current inner loop. The advantages of half-wave detection can just make up for the disadvantages of full-wave detection: small loss, positive voltage, and the average inductor current I of each channel can be achieved in the multi-channel interleaved PFC circuit. inAnd independent control of power. However, the defects of half-wave detection are also very obvious, that is, half-wave detection cannot obtain the complete inductor current waveform. Half-wave detection is not accurate in detecting the average inductor current in DCM mode, resulting in deviation in the output of the current inner loop. The main reason is that when the median sampling method is used, that is, the current of the current detection resistor is sampled in half of the time when the power tube is ON. Since the inductor current waveform rises linearly in the ON state and decreases linearly in the OFF state, the rising median can represent the average waveform of the inductor current. However, this method has a large deviation when entering the DCM mode. Because the inductor current has a dead zone under DCM, that is, the inductor current is zero, the median current is smaller than the true average current. This will "mislead" the current inner loop to produce the switch tube closing time T on Insufficient, resulting in the average inductor current I in Shaping distortion, the total harmonic THD index of the PFC circuit is poor.

[0005] It can be seen that the prior art needs a method that can more accurately generate the switch tube closing time T during half-wave detection. on Methods to increase the average inductor current I in The accuracy of shaping. Summary of the invention

[0006] The technical purpose to be achieved by the present invention is to provide a method for compensating an average inductor current in a PFC circuit. Based on this method, the PFC circuit can more accurately determine the inductor current when the switch tube is in the off state when performing half-wave detection, thereby improving the total harmonic performance of the PFC circuit.

[0007] Based on the above technical objectives, the present invention provides a method for compensating an average inductor current in a PFC circuit, the method comprising:

[0008] When performing half-wave detection on the PFC circuit, the duty cycle D of the actual PWM control signal of the PFC circuit is 实际 The duty cycle D of the PWM control signal when the PFC circuit is in CCM continuous conduction mode CCM Compare to determine whether the PFC circuit is in DCM discontinuous conduction mode;

[0009] When the PFC circuit is in DCM discontinuous conduction mode, the high level conduction time T of the PWM control signal in CCM mode on Compensation is performed to achieve an average inductor current I in compensation;

[0010] The high level conduction time T of the PWM control signal in the CCM mode on Compensation is satisfied if:

[0011] Where T on ' is the high level conduction time of the compensated PWM control signal.

[0012] In one embodiment, determining whether the PFC circuit is in the DCM discontinuous conduction mode includes: 实际 <D CCM Then, the PFC circuit is in DCM discontinuous conduction mode. 实际 =D CCM Then, the PFC circuit is in CCM continuous conduction mode.

[0013] In one embodiment, determining whether the PFC circuit is in the DCM discontinuous conduction mode includes: 实际 <K×D CCM Then, the PFC circuit is in DCM discontinuous conduction mode. 实际 ≧K×D CCM Then, the PFC circuit is in CCM continuous conduction mode, and the coefficient K is less than 1.

[0014] In one embodiment, the high level conduction time T of the PWM control signal in the CCM mode is on Compensation is satisfied if:

[0015]

[0016] Compared with the prior art, one or more embodiments of the present invention may have the following inventive features and advantages:

[0017] On the basis of the half-wave of the prior art, the present invention further sets the high level conduction time T of the PWM control signal. on Compensation is performed so that the existing median sampling can obtain a more accurate average inductor current value. The method according to the present invention improves the PF / THD performance of the CCM-PFC circuit when it operates in the DCM range; at the same time, the average inductor current measurement method of the present invention does not require an auxiliary winding, does not require inductance (Lm) information, simplifies the design complexity and reduces system cost.

[0018] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0020] Figure 1 It is a schematic diagram of the average inductor current waveform of the PFC of the present invention in the DCM mode and the CCM mode;

[0021] Figure 2 It is a schematic diagram of the compensation effect of the average inductor current compensation method of the PFC circuit of the present invention. DETAILED DESCRIPTION

[0022] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings.

[0023] Before proceeding to the following detailed description, it may be necessary to set forth the definitions of certain words and phrases used throughout the present invention. The terms "coupling", "connection" and their derivatives refer to any direct or indirect communication or connection between two or more elements, regardless of whether those elements are in physical contact with each other. The terms "transmission", "reception" and "communication" and their derivatives cover direct and indirect communication. The terms "include" and "comprising" and their derivatives refer to including but not limited to. The term "or" is inclusive, meaning and / or. The phrase "associated with..." and its derivatives refer to including, including within, interconnecting, containing, contained within, connecting or with...connecting, coupling or with...coupling, communicating with, cooperating, interweaving, parallel, approaching, binding or with...binding, having, having attributes, having a relationship or with...having a relationship, etc. The term "controller" refers to any device, system or part thereof that controls at least one operation. Such a controller can be implemented with hardware, or a combination of hardware and software and / or firmware. The functions associated with any particular controller can be centralized or distributed, whether local or remote. The phrase "at least one of", when used with a list of items, means that different combinations of one or more of the listed items may be used, and only one of the items in the list may be required. For example, "at least one of A, B, C" includes any of the following combinations: A, B, C, A and B, A and C, B and C, A and B and C.

[0024] The description of the first end and the second end of a resistor, capacitor or inductor in the present invention is only to distinguish the two connection ends of the device, so as to facilitate the description of the connection relationship between the device and other devices, and does not specifically specify a certain end of the resistor, capacitor or inductor in actual situations. Those skilled in the art should know that when constructing an actual circuit, any end of the resistor, capacitor or inductor in an actual device can be defined as the first end, and when the first end is defined, the other end of the device is automatically defined as the second end.

[0025] When describing various components or elements in the present invention, the description methods of "first", "second", "third", etc. are used only to distinguish the various components and to express the different relationships between the various components. The description methods used above do not contain any implicit meaning of the relationship between the components. For example, when only the descriptions of "first" and "third" appear, it does not mean that there is a "second" between the two. The descriptions of "first" and "third" here only mean that there are two different independent components.

[0026] Definitions of other specific words and phrases are provided throughout this disclosure. Those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior and future uses of such defined words and phrases.

[0027] In the present invention, the application combination of modules and the division level of sub-modules are only used for illustration, and the application combination of modules and the division level of sub-modules may have different modes without departing from the scope of the present disclosure.

[0028] Example

[0029] In the PFC circuit, the inductor auxiliary winding can directly detect the inductor current zero crossing to determine whether the PFC circuit is in DCM mode, or according to the calibrated inductance Lm information, through T r =I pk ×Lm / (V out -V in ) to determine whether the PFC circuit is in DCM mode, where T r is the inductor discharge time, I pk is the inductor peak current, V out is the output voltage of the PFC circuit, V in is the rectified voltage. However, the above methods either rely on hardware support or on the accuracy of the calibrated inductance Lm.

[0030] The PFC circuit average inductor current compensation method of this embodiment includes:

[0031] S100, the duty cycle D of the actual PWM control signal of the PFC circuit is 实际 The duty cycle D of the PWM control signal when the PFC circuit is in CCM continuous conduction mode CCM The comparison is used to determine whether the PFC circuit is in DCM discontinuous conduction mode.

[0032] In this embodiment, when the Boost circuit in the PFC circuit is in the CCM continuous conduction mode, the duty cycle D of the PWM control signal used to control the switch tube to close or open is CCM Should be satisfied with:

[0033]

[0034] Among them, T on T is the high level conduction time of the PWM control signal in CCM mode; p is the cycle length of the PWM control signal in CCM mode. out and the rectified voltage V in Get the duty cycle D of the PWM control signal when the PFC circuit is in CCM continuous conduction mode CCM . Using this duty cycle D CCM The actual duty cycle D of the PFC current PWM control signal 实际 By comparison, it can be determined whether the PFC circuit is in DCM discontinuous conduction mode. 实际 <D CCM Then, the PFC circuit is in DCM discontinuous conduction mode. 实际 =D CCM Then, the PFC circuit is in CCM continuous conduction mode.

[0035] In practical applications, since the output voltage V out and the rectified voltage V in There are tolerances or slight changes, and the starting current and ending current of the inductor current are not exactly the same value, so D 实际 >D CCM Therefore, in this embodiment, in order to more accurately determine whether the PFC circuit is in the DCM discontinuous conduction mode, the above judgment relationship is further limited to when D 实际 <K×D CCM Then, the PFC circuit is in DCM discontinuous conduction mode. 实际 ≧K×D CCM Then, the PFC circuit is in CCM continuous conduction mode. The coefficient K is less than 1, and its specific value is determined according to the actual parameters of the PFC circuit.

[0036] S101, when the PFC circuit is in the DCM discontinuous conduction mode, the high level conduction time T of the PWM control signal in the CCM mode on Compensation is performed to achieve an average inductor current I in compensation.

[0037] In this embodiment, in the DCM discontinuous conduction mode, the current I obtained by the median sampling method is mid The size cannot correctly reflect the average inductor current I in (i.e., AC current) value, causing the current loop to misjudge the high-level conduction time T of the PWM control signal onTherefore, the compensated time T can be calculated by the formula of the inductor current in DCM discontinuous conduction mode: on , to achieve the median sampling current I mid = Average inductor current I in The average inductor current formula in DCM discontinuous conduction mode is:

[0038]

[0039] At the same time, in DCM discontinuous conduction mode:

[0040]

[0041] Thus, we have:

[0042]

[0043] In the above formula, T on and I mid These are all compensated parameters, not values ​​obtained by measurement. Therefore, if T is defined on ' is the compensated T on , I mid ' is the compensated I mid , and I mid '=I mid ×(T on ' / T on ), then the formula is rewritten as:

[0044]

[0045] In order to make the median detection method still applicable in DCM discontinuous conduction mode, it is necessary to achieve the following conditions for T on 'After compensation, I can be satisfied in =I mid , the above formula can be simplified to:

[0046]

[0047] Right now: In the above formula, only the high-level conduction time T of the compensated PWM control signal is on ' is an unknown parameter, and the remaining parameters can be obtained by real-time detection of the PFC circuit. And according to the above derivation, it can be known that D CCM =1-(V out / V in ), D 实际 =T on ' / T p . So we have:

[0048]

[0049] Right now: As mentioned above, after the PFC circuit enters the DCM discontinuous conduction mode, there is a D 实际 <D CCM Therefore, according to the above formula, Ton'>Ton, the out-of-loop compensation of the current in the DCM discontinuous conduction mode is realized. Figure 2 shown.

[0050] In this embodiment, since the RMS calculation complexity is relatively high, in order to simplify the operation, the above compensation relationship is simplified as follows:

[0051]

[0052] The present invention may be a system, method and / or computer program product at any possible level of integrated technical detail. The computer program product may include a computer-readable storage medium (or multiple media) having computer-readable program instructions thereon for causing a processor to perform various aspects of the present invention.

[0053] A computer readable storage medium may be a tangible device that can retain and store instructions used by an instruction execution device. The computer readable storage medium may be, for example, but not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. A non-exhaustive list of more specific examples of computer readable storage media includes the following: a portable computer floppy disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disk read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanical encoding device such as a punch card or a raised structure in a groove on which instructions are recorded, and any suitable combination of the above. A computer readable storage medium, as used herein, should not be interpreted as a transient signal itself, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium (e.g., a light pulse through a fiber optic cable), or an electrical signal transmitted by a wire.

[0054] The computer-readable program instructions described herein may be downloaded from a computer-readable storage medium to a corresponding computing / processing device, or downloaded to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network may include copper transmission cables, optical transmission fibers, wireless transmissions, routers, firewalls, switches, gateway computers, and / or edge servers. The network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions to be stored in a computer-readable storage medium within the corresponding computing / processing device.

[0055] The computer-readable program instructions for performing the operation of the present invention may be assembler instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state setting data, configuration data for integrated circuits, or source code or object code written in any combination of one or more programming languages ​​and process programming languages. The computer-readable program instructions may be executed entirely on the user's computer, partially on the user's computer, as an independent software package, partially on the user's computer, partially on a remote computer, or entirely on a remote computer or server. In the latter case, the remote computer may be connected to the user's computer by any type of network including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., by using the Internet of an Internet service provider). In certain embodiments, the electronic circuit including, for example, a programmable logic circuit, a field programmable gate array (FPGA) or a programmable logic array (PLA) may execute the computer-readable program instructions by utilizing the state information of the computer-readable program instructions to personalize the electronic circuit, thereby performing aspects of the present invention.

[0056] Various aspects of the present invention are described herein with reference to flowcharts and / or block diagrams of methods, devices (systems) and computer program products according to embodiments of the present invention. It is understood that each block of the flowchart illustration and / or block diagram, and the combination of blocks in the flowchart illustration and / or block diagram, can be implemented by computer-readable program instructions.

[0057] These computer-readable program instructions may be provided to a processor of a computer or other programmable data processing device to produce a machine so that the instructions executed by the processor of the computer or other programmable data processing device create instructions for implementing the flowcharts and / or block diagrams. Figure 1These computer-readable program instructions may also be stored in a computer-readable storage medium capable of booting a computer, a programmable data processing device and / or other device that operates in a specific manner, so that the computer-readable storage medium having the instructions stored therein includes a manufactured product that includes instructions that implement aspects of the functions / actions specified in the flowchart and / or block diagram blocks.

[0058] Computer readable program instructions may also be loaded into a computer, other programmable data processing device, or other device to cause a series of operating steps to be performed on the computer, other programmable devices or other devices for producing a computer-implemented process, so that the instructions executed on the computer, other programmable device or other device implement the functions / actions specified in the flowchart and / or block diagram blocks.

[0059] The flowcharts and block diagrams in the accompanying drawings illustrate the possible implementation architecture, functions and operations of the system, method and computer program product according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagram may represent a module, segment or portion of an instruction, which includes one or more executable instructions for implementing a specified logical function. In some optional implementations, the functions indicated in the block may occur outside the order indicated in the figure. For example, in fact, two blocks shown in succession can be completed as a step, and depending on the functions involved, they can be executed concurrently, substantially concurrently, in a partially or fully time-overlapping manner, or sometimes these blocks can be executed in reverse order. It will also be noted that each block of the block diagram and / or flowchart illustration, as well as the combination of blocks in the block diagram and / or flowchart illustration, can be implemented by a dedicated hardware-based system that performs a specified function or action or performs a combination of dedicated hardware and computer instructions.

[0060] The embodiments of the present application are described with reference to the flowcharts and / or block diagrams of the methods, apparatuses (devices) and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0061] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0062] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

Claims

1. A method for compensating average inductor current in a PFC circuit, characterized in that: The method comprises: When performing half-wave detection on the PFC circuit, the duty cycle D of the actual PWM control signal of the PFC circuit is 实际 The duty cycle D of the PWM control signal when the PFC circuit is in CCM continuous conduction mode CCM Compare to determine whether the PFC circuit is in DCM discontinuous conduction mode; When the PFC circuit is in DCM discontinuous conduction mode, the high level conduction time T of the PWM control signal in CCM mode on Compensation is performed to achieve an average inductor current I in compensation; The high level conduction time T of the PWM control signal in the CCM mode on Compensation is satisfied if: Where T on ' is the high level conduction time of the compensated PWM control signal.

2. The average inductor current compensation method according to claim 1, characterized in that: The method of judging whether the PFC circuit is in the DCM discontinuous conduction mode comprises: when D 实际 <D CCM Then, the PFC circuit is in DCM discontinuous conduction mode. 实际 =D CCM Then, the PFC circuit is in CCM continuous conduction mode.

3. The average inductor current compensation method according to claim 1, characterized in that: The method of judging whether the PFC circuit is in the DCM discontinuous conduction mode comprises: when D 实际 <K×D CCM Then, the PFC circuit is in DCM discontinuous conduction mode. 实际 ≧K×D CCM Then, the PFC circuit is in CCM continuous conduction mode, and the coefficient K is less than 1.

4. The average inductor current compensation method according to claim 1, characterized in that: The high level conduction time T of the PWM control signal in the CCM mode on Compensation is satisfied if:

5. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer instructions, and the computer instructions are used to enable the computer to execute the average inductor current compensation method according to any one of claims 1 to 4.

6. An integrated circuit structure, in which the average inductor current compensation method according to any one of claims 1 to 4 is used to perform half-wave detection of a PFC circuit.

Images