A PFC converter, current control method and device

Abstract

A power factor correction (PFC) converter, a current control method and a device are disclosed, wherein the PFC converter comprises: an AC voltage source, a rectifier bridge, a switch device, a freewheeling electronic device, a filter capacitor, and further comprises a boost inductor, a first resistor, a power module and a control circuit, wherein the inductance value of the boost inductor is variable; the boost inductor is connected to the power module through the first resistor; the control circuit is connected to the power module, and is used to control the power module to output a first auxiliary current, so that the first auxiliary current generates a first inductance value in the boost inductor; the control circuit is also connected to the switch device, and is used to control the on or off of the switch device so that the converter outputs a stable voltage. The inductance value of the boost inductor is variable, so that the inductance value can be obtained above the critical inductance value, so that the inductance margin of the PFC converter is fully utilized, and the efficiency of the PFC converter is improved.

Description

Technical Field

[0001] The present application relates to the field of converter control, and in particular to a PFC converter, a current control method and a device. Background Art

[0002] Power Factor Correction (PFC) converters can reduce input current harmonics and improve input power factor, and have been widely used. PFC converters can be divided into two types: active and passive. Compared with passive methods, active methods have the advantages of high input power factor, small size, and low cost. Active PFC converters can adopt various circuit topologies and control methods. Among them, Boost PFC converters have the following advantages:

[0003] 1. The boost inductor is connected in series at the input end, and the high-frequency ripple of the input current is small;

[0004] 2. High output voltage, large output filter capacitor energy storage and small size;

[0005] 3. A high power factor can be maintained within the entire input high voltage range;

[0006] 4. The circuit structure is simple, the cost is low and the working reliability is high.

[0007] Based on whether the inductor and current are continuous or not, they can be divided into three operating modes: continuous current mode (CCM), critical conduction mode (CRM), and discontinuous conduction mode (DCM). Compared with CRM, the DCM BoostPFC converter has the advantages of zero-current turn-on of the switch tube and no reverse recovery of the boost diode. In addition, the switching frequency is constant, which facilitates the design of the inductor and EMI filter.

[0008] Working principle of DCM Boost PFC converter, Figure 1 This is the main circuit of the DCM Boost PFC converter. For ease of analysis, the following assumptions are made: all components are ideal, the output voltage ripple is very small compared to its DC value, and the switching frequency is much higher than the input voltage frequency.

[0009] Figure 2 The inductor current waveform in one switching cycle is shown in Figure 1. b When the freewheeling diode D b Cut-off; boost inductor L b The voltage across the two ends is v g, its current i Lb Starting from zero with v g / L b The slope increases linearly. b When off, i Lb By D b Continue current, at this time L b The voltage across the two ends is v g -V0,i Lb -(V0-v g ) / L b Since the Boost PFC converter operates in DCM mode, before the end of the switching cycle, i Lb Dropped to zero.

[0010] Generally, the input AC voltage v in The expression is:

[0011] v in =V m sinωt (1)

[0012] Among them, v in is the AC input voltage, V m is the amplitude of the AC input voltage, and ω is the angular frequency of the AC input voltage.

[0013] Then the rectified input voltage v g for:

[0014] v g =V m ·|sinωt| (2)

[0015] When the duty cycle D y When fixed, the peak value of the inductor current i in a switching cycle is Lb _ pk It can be expressed as:

[0016]

[0017] Among them, D y is the duty cycle, T s is the switching period, f s is the switching frequency, and f s =1 / T s .

[0018] In each switching cycle, L b The volt-second area at both ends is balanced, that is

[0019] v g ·D y ·T s =(V0-v g )·DR ·T s (4)

[0020] Where V0 is the output voltage, D R is the duty cycle corresponding to the inductor current dropping to zero.

[0021] From formula (4), we can get the proportion of the inductor current rise time D in a switching cycle: y and the proportion of the inductor current fall time D R The relationship between:

[0022]

[0023] Where α is the voltage ratio, and α=V m / V0.

[0024] The inductor is located in the input branch. According to equations (3) and (5), the input current is equal to the average value of the inductor current i Lb _ ave :

[0025]

[0026] Assuming the converter efficiency is 100%, the input power P in Equal to the output power P0, and then the duty cycle D can be obtained y The expression is:

[0027]

[0028] Keeping the converter operating in DCM, there are:

[0029] D y +D R ≤1 (8)

[0030] Substituting equations (5) and (7) into equation (8), we can obtain:

[0031]

[0032] It can be seen from the above formula (9) that when the converter parameters are constant, the critical inductance values ​​required at different angles within half the power frequency cycle are different. Among them, the critical inductance value corresponding to π / 2 is the smallest, that is, the critical inductance value L under constant duty cycle control is b1 for:

[0033]

[0034] Where α = V m / V0, the amplitude of the AC input voltage V m The value range is The output voltage V0 is 400V, the output power P0 is 120W, and the switching frequency f s The frequency is 100kHz. The above parameters are prototype parameters.

[0035] In V m When the corresponding AC voltage is within the range of 90 to 264 V AC input voltage and the output voltage is 400 V, the range of α is from 0.32 to 0.94. According to formula (10), the critical inductance curve can be drawn, as shown in Figure 3 As shown. Figure 3 It can be seen from the figure that for a fixed inductor under a wide input voltage range, keeping the PFC converter operating in DCM requires an output inductance value of only 92μH. This 92μH is the value of the inductor at 264V AC. However, the inductance margin in the medium and low voltage regions is high and not fully utilized. This results in a large inductor current peak, great current stress on the power devices, and a large effective value of the inductor current. This, in turn, increases the copper loss and core loss of the power devices, including the inductor, the switching loss and conduction loss of the MOS tube, and the conduction loss of the diode and rectifier bridge, resulting in low converter efficiency. Summary of the Invention

[0036] This application utilizes variable inductance technology to adjust the inductance value according to the grid voltage, thereby improving the efficiency of the converter. In order to solve the above technical problems, the technical solutions provided by this application are as follows:

[0037] In a first aspect, the present application provides a power factor correction (PFC) converter, which includes: an AC voltage source, a rectifier bridge, a switching device, a freewheeling electronic device, and a filter capacitor. Furthermore, the converter also includes: a boost inductor, a first resistor, a power module, and a control circuit, wherein the inductance value of the boost inductor is variable.

[0038] Furthermore, the boost inductor is connected to the power module through the first resistor; the control circuit is connected to the power module, and is used to control the power module to output a first auxiliary current, so that the first auxiliary current generates a first inductance value in the boost inductor; the control circuit is also connected to the switching device, and is used to control the conduction or shutdown of the switching device so that the converter outputs a stable voltage.

[0039] The PFC converter provided in this application generates an auxiliary current through a newly added power module and control circuit, and uses this auxiliary current to control the inductance of the boost inductor, making the inductance of the boost inductor variable. This allows the inductance to be adjusted to a value above the critical inductance value, fully utilizing the inductance margin of the PFC converter, reducing the peak value and effective value of the inductor current, and improving the efficiency of the PFC converter.

[0040] Optionally, the converter further includes components such as an LC filter and a load.

[0041] In conjunction with the first aspect, in one possible implementation of the first aspect, the boost inductor includes a main winding coil and an auxiliary winding coil, and the main winding coil and the auxiliary winding coil are wound around the same magnetic core. Under the action of the first auxiliary current, the auxiliary winding coil causes the main winding coil to generate the first inductance value.

[0042] One end of the main winding coil is connected to the rectifier bridge, and the other end is connected to the switch device and the freewheeling electronic device. Specifically, one end of the main winding coil is connected to the output end of the rectifier bridge RB, and the other end of the main winding coil is connected to the switch tube Q. b The source and freewheeling diode D b connected to the cathode.

[0043] One end of the auxiliary winding coil is connected to the power module through the first resistor, and the other end is grounded.

[0044] In conjunction with the first aspect, in another possible implementation of the first aspect, the control circuit is further configured to control the power module to output a second auxiliary current when the amplitude of the AC input voltage provided by the AC voltage source changes, wherein the second auxiliary current generates a second inductance value in the boost inductor. In this implementation, when the amplitude of the AC input voltage changes, the second auxiliary current is used to change the inductance value of the boost inductor from the first inductance value to the second inductance value, thereby achieving flexible change of the desired inductance value.

[0045] In conjunction with the first aspect, in another possible implementation of the first aspect, the auxiliary winding coil, under the action of the second auxiliary current, causes the main winding coil to generate the second inductance value. In this implementation, the inductance value of the main winding coil is variable by adding the auxiliary winding coil. One end of the auxiliary winding coil is connected to the power module, and the other end is grounded. Thus, the inductance value of the main winding coil can be changed by providing an auxiliary current or auxiliary voltage through the power module.

[0046] Optionally, the power module is a low-dropout linear regulator (LDO). Since the LDO has a wide power range, it can provide a wide range of current and voltage for the boost inductor, thereby expanding the variable range of the boost inductor's inductance value.

[0047] In combination with the first aspect, in another possible implementation of the first aspect, the control circuit is integrated into a controller, and the controller also includes a first analog-to-digital conversion module, a second analog-to-digital conversion module and a processing module; the first analog-to-digital conversion module is connected to the rectifier bridge, and is used to perform analog-to-digital conversion on the input voltage signal passing through the rectifier bridge, and send it to the processing module; the second analog-to-digital conversion module is connected to the freewheeling electronic device, and is used to perform analog-to-digital conversion on the output voltage signal passing through the freewheeling electronic device, and send it to the processing module; the processing module is used to determine a first duty cycle based on the input voltage signal processed by the first analog-to-digital conversion module and the output voltage signal processed by the second analog-to-digital conversion module, and control the power supply module to output the first auxiliary current according to the first duty cycle.

[0048] Optionally, the controller is a digital signal processor (DSP). The first analog-to-digital conversion module is ADC1, and the second analog-to-digital conversion module is ADC2.

[0049] This embodiment utilizes a controller, such as a DSP, to output a PWM drive through an LC low-pass filter to achieve auxiliary power supply, so that the number of components required for the PFC controller is reduced compared to that achieved by using an LDO method, thereby saving costs.

[0050] In conjunction with the first aspect, in another possible implementation of the first aspect, the controller further includes a signal output module, one end of the signal output module being connected to the processing module and the other end being connected to the switching device; the signal output module being configured to send a control signal to the switching device under the control of the processing module, thereby turning the switching device on or off. In this implementation, the signal output module outputs the control signal, thereby providing a stable environment for the power module to output the auxiliary current, thereby ensuring that the converter outputs a stable voltage.

[0051] Optionally, the signal output module is a pulse width modulator PWM.

[0052] In a second aspect, the present application also provides a current control method, which is applied to a PFC converter, wherein the converter includes an AC voltage source, a rectifier bridge, a switching device, a freewheeling electronic device, and a filter capacitor. In addition, the PFC converter also includes a boost inductor, a first resistor, a power module, and a control circuit, wherein the inductance value of the boost inductor is variable.

[0053] The method includes: a control circuit obtaining a first reference inductance value of the boost inductor; the control circuit determining a first inductance value based on the first reference inductance value; the control circuit determining a first voltage ratio corresponding to the first inductance value, and determining a first duty cycle based on the first voltage ratio, wherein the first voltage ratio is a ratio between a first amplitude of an AC input voltage provided by the AC voltage source and an output voltage of the PFC converter; the control circuit determining a first auxiliary current based on the first duty cycle, and controlling the power supply module to output the first auxiliary current so that the boost inductor generates the first inductance value.

[0054] This method changes the inductance of the boost inductor by changing the DC bias of the boost inductor auxiliary winding, thereby changing the saturation of the inductor core and thus changing the inductance value, and controlling the boost inductor to output a desired inductance value. Since the desired inductance value is a preset ratio of the reference inductance value, the critical inductance margin of the PFC converter under a wide range of input voltages is fully utilized, the peak value and effective value of the inductor current are reduced, and the efficiency of the PFC converter is improved.

[0055] In combination with the second aspect, in a possible implementation of the second aspect, the method further includes: the control circuit generating a control signal according to the first duty cycle while controlling the power supply module to output the first auxiliary current; and the control circuit sending the control signal to the switching device to control the duty cycle of the switching device to be on and off to the first duty cycle, so that the PFC converter outputs the output voltage.

[0056] Wherein, the output voltage is a DC voltage.

[0057] In combination with the second aspect, in another possible implementation of the second aspect, the converter stores an inductance correspondence relationship, wherein the inductance correspondence relationship includes a correspondence relationship between the first inductance value and the first voltage ratio; the control circuit determines the first voltage ratio corresponding to the first inductance value, including: the control circuit determines the first voltage ratio based on the inductance correspondence relationship and the first inductance value.

[0058] In combination with the second aspect, in another possible implementation of the second aspect, the method also includes: when the AC input voltage provided by the AC voltage source changes to a second amplitude, the control circuit determines a second voltage ratio, which is the ratio between the second amplitude and the output voltage; the control circuit determines a second duty cycle based on the second voltage ratio; the control circuit determines a second auxiliary current based on the second duty cycle, and controls the power supply module to output the second auxiliary current, so that the boost inductor generates a second inductance value.

[0059] In combination with the second aspect, in another possible implementation of the second aspect, the converter stores a correspondence between the first inductance value and the first voltage ratio, and the control circuit obtains the first inductance value based on the first reference inductance value and a preset ratio; the control circuit establishes a correspondence between the first inductance value and the first voltage ratio, and stores the correspondence.

[0060] In a third aspect, the present application further provides a device comprising the PFC converter described in the first aspect and various implementations of the first aspect. The PFC converter can implement the current control method described in the second aspect and various implementations of the second aspect.

[0061] In a fourth aspect, the present application also provides a computer-readable storage medium, which stores instructions. When the instructions are run on a computer or a processor, they are used to execute the methods in the aforementioned second aspect and various implementations of the second aspect.

[0062] In a fifth aspect, an embodiment of the present application further provides a computer program product, which includes computer instructions. When the instructions are executed by a computer or a processor, the method in the aforementioned second aspect or various implementations of the second aspect can be implemented. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 A circuit diagram of a DCM Boost PFC converter main circuit provided by this application;

[0064] Figure 2 This is a waveform diagram of the inductor current in one switching cycle when working in DCM provided by the present application;

[0065] Figure 3 A schematic diagram of a reference inductance value curve provided in this application;

[0066] Figure 4 A circuit diagram of a PFC converter main circuit provided in an embodiment of the present application;

[0067] Figure 5 A schematic structural diagram of a boost inductor provided in an embodiment of the present application;

[0068] Figure 6 A circuit diagram of another PFC converter main circuit provided in an embodiment of the present application;

[0069] Figure 7a A circuit diagram of another PFC converter main circuit provided in an embodiment of the present application;

[0070] Figure 7bA circuit diagram of another PFC converter main circuit provided in an embodiment of the present application;

[0071] Figure 7c A circuit diagram of another PFC converter main circuit provided in an embodiment of the present application;

[0072] Figure 7d A circuit diagram of another PFC converter main circuit provided in an embodiment of the present application;

[0073] Figure 8 A flow chart of a current control method provided in an embodiment of the present application;

[0074] Figure 9 A schematic diagram of an expected inductance curve provided in an embodiment of the present application. DETAILED DESCRIPTION

[0075] In order to enable people in this technical field to better understand the technical solutions in the embodiments of the present application, and to make the above-mentioned purposes, features and advantages of the embodiments of the present application more obvious and easy to understand, the technical solutions in the embodiments of the present application are further described in detail below with reference to the accompanying drawings.

[0076] First, the technical scenarios and related concepts applied in the embodiments of this application are introduced.

[0077] The technical solution of the embodiment of the present application can be applied to a PFC converter or a power grid structure including a PFC converter. In one example, the PFC converter is a discontinuous conduction mode (DCM) Boost PFC converter, and its basic structure is shown in FIG. Figure 1 As shown in the figure, the DCM Boost PFC converter has the advantages of zero-current turn-on of the switch tube, no reverse recovery of the diode, and constant switching frequency. However, for a fixed inductor within a certain range of input voltage, the inductance value in the PFC converter is small, and the inductance margin in the medium and low voltage areas is not fully utilized, resulting in increased conduction losses of the components in the converter and low converter efficiency.

[0078] To solve this technical problem, an embodiment of the present application provides a new PFC converter, which uses variable inductance technology and controls the inductance value of the variable inductor according to the grid current, thereby improving the efficiency of the PFC converter.

[0079] The circuit structure and working principle of the PFC converter in this embodiment are introduced below.

[0080] like Figure 4The figure shows a circuit diagram of the main circuit of a PFC converter provided in this embodiment. The PFC converter includes: an AC voltage source, a rectifier bridge RB, a switch device, a freewheeling electronic device, and a filter capacitor. The AC voltage source AC is used to provide an AC voltage v in The rectifier bridge RB is connected to the AC voltage source AC to convert the AC voltage v in After sorting, the voltage v is obtained g , where the AC voltage v is expressed by the above formula (2) in With v g The relationship is: v g =V m ·|sinωt|. V m is the amplitude of the AC input voltage, such as the first amplitude.

[0081] Optionally, the freewheeling electronic device includes but is not limited to a MOS tube, a diode, a triode, a relay, etc. The filter capacitor is an output filter capacitor.

[0082] In addition, the PFC converter further includes: a boost inductor, a first resistor R1, a power module and a control circuit, wherein the inductance value of the boost inductor is L b 'variable.

[0083] See also Figure 4 One end of the boost inductor is connected to the rectifier bridge RB, and the other end is connected to the freewheeling electronic device and the switch device. In addition, the boost inductor also includes two pins, one of which is connected to the power module through the first resistor R1, and the other pin is grounded. Specifically, Figure 5 As shown, the boost inductor includes a main winding coil and an auxiliary winding coil, which are wound on the same magnetic core, with the main winding coil at the top and the auxiliary winding coil at the bottom. One end of the auxiliary winding coil is connected to a first resistor R1, which acts as a voltage divider and current limiter. The other end of the auxiliary winding coil is grounded.

[0084] exist Figure 5 In the boost inductor shown, the inductance generated by the main winding coil is L b ', the auxiliary winding is used to change the inductance of the main winding to L b ', one implementation method is to change the inductance of the main winding coil to L by inputting different currents or voltages to the auxiliary winding coil b ′.

[0085] In addition, the control circuit is connected to the power module, and the control circuit is used to control the power module to output the first auxiliary current I m , so that the first auxiliary current I mThe first inductance value L is generated in the boost inductor b In this embodiment, the auxiliary winding coil is at the first auxiliary current I m Under the action of the first inductance value L, the main winding coil generates b ′, and then control the boost inductor to obtain an L b ’ first inductance value.

[0086] The control circuit is also connected to the switching device and is configured to control the duty ratio of the switching device to turn on and off, so that the PFC converter generates a certain output voltage. The other end of the switching device is grounded. Specifically, the control circuit is configured to send a control signal to the switching device, which turns the switch in the switching device on or off, thereby providing a stable environment for the power module to output auxiliary current.

[0087] The duty cycle is the ratio of the pulse duration to the total duration during a continuous working period. The duty cycle is determined by the voltage ratio, which is the amplitude V of the AC input voltage provided by the AC voltage source. m The ratio between the output voltage V0 of the PFC converter.

[0088] The boost inductor is further connected to a freewheeling electronic device, which is connected to a filter capacitor and a load. The freewheeling electronic device is used to charge the filter capacitor and generate a load voltage V0.

[0089] It should be noted that the positions and connections of the various components of the PFC converter, including the AC voltage source, the rectifier bridge, the switching device, the freewheeling electronic device, and the filter capacitor, can refer to the circuit structure of the DCM Boost PFC converter. In addition, the PFC converter may further include an LC filter and a load, etc., which is not limited in this embodiment.

[0090] The converter provided in this embodiment generates an auxiliary current through a newly added power module and control circuit. This auxiliary current is used to control the inductance of the boost inductor, making the inductance of the boost inductor variable. This allows the inductance to be set above the critical inductance value, fully utilizing the inductance margin of the PFC converter, reducing the peak value and effective value of the inductor current, and improving the efficiency of the PFC converter.

[0091] When the amplitude of the AC input voltage provided by the AC voltage source AC changes, for example, from a first amplitude to a second amplitude, the control circuit controls the power module to output a second auxiliary current, which generates a second inductance value L in the boost inductor. b2 Specifically, under the action of the second auxiliary current, the auxiliary winding coil of the boost inductor causes the main winding coil of the boost inductor to generate the second inductance value Lb2 ′.

[0092] like Figure 6 As shown, in the PFC converter, the AC voltage source AC, the rectifier bridge RB, the LC filter (LC Filter), the boost inductor, the switch tube Q b , freewheeling diode D b , filter capacitor C o and load R Ld Connect in sequence.

[0093] Specifically, the switch tube Q b The drain and freewheeling diode D b The anode of the switch tube Q b The drain of the boost inductor is also connected to one end of the boost inductor, and the other end of the boost inductor is connected to the LC filter, which is used to output the filter current i L ' b . Freewheeling diode D b The cathode and filter capacitor C o The positive electrode is connected.

[0094] Load R Ld Connect in parallel to the filter capacitor C o At both ends, the switch tube Q b The source and output filter capacitor C o The negative pole is connected to the rectifier bridge RB through the other end of the LC filter, thereby returning to the AC voltage source AC to form a loop.

[0095] The auxiliary winding coil of the boost inductor is connected to the first resistor R1, and the other end of the first resistor R1 is connected to the power module. The power module is used to provide auxiliary current or auxiliary voltage to the auxiliary winding coil, thereby adjusting the inductance value of the main winding coil.

[0096] The specific circuit and structural relationship between the power module and the control circuit can be obtained by the following Figures 7a to 7d Various possible implementations are shown.

[0097] In one possible implementation, Figure 7a As shown, the power module is a low-dropout linear regulator (LDO), which is used to output an auxiliary current or auxiliary power to the boost inductor to obtain a desired inductance value. The control circuit is used to control the LDO to output the corresponding auxiliary current or auxiliary power. This embodiment uses an LDO to provide auxiliary current or auxiliary power to the boost inductor. Due to the large power range of the LDO, it can provide a wide range of current and voltage for the boost inductor, thereby expanding the variable range of the boost inductor's inductance value.

[0098] Optionally, the control circuit can be implemented by a controller or a control chip.

[0099] In another possible implementation, Figure 7b As shown, the power module can be implemented by a circuit consisting of a filter and a pulse width modulator (PWM). Specifically, a first resistor R1 is connected to the filter, the filter is connected to the PWM, and the PWM is connected to a control circuit. The control circuit is used to control the PWM and filter to jointly output a DC auxiliary current or auxiliary voltage, and output the auxiliary current or auxiliary voltage to the auxiliary winding coil of the boost inductor.

[0100] In a specific implementation, the PMW and the control circuit can be integrated into one controller.

[0101] In another possible implementation, Figure 7c As shown, the control circuit can be implemented by a controller. The controller is connected to the power module and is used to control the power module to output an auxiliary current or auxiliary voltage. In addition, the power module is connected to a filter, which is used to filter ripple.

[0102] Furthermore, the controller includes a first analog-to-digital conversion module, a second analog-to-digital conversion module, and a processing module. The processing module can realize the functions of the control circuit.

[0103] Among them, one end of the first analog-to-digital conversion module is connected to the rectifier bridge RB, and the other end is connected to the processing module, which is used to perform analog-to-digital conversion on the input voltage signal passing through the rectifier bridge RB and send the converted signal to the processing module. One end of the second analog-to-digital conversion module is connected to the freewheeling diode D b The other end is connected to the processing module, which is used to b The output voltage signal of the first analog-to-digital conversion module is converted into analog-to-digital, and the converted signal is sent to the processing module; the processing module is used to determine a first duty cycle according to the input voltage signal processed by the first analog-to-digital conversion module and the output voltage signal processed by the second analog-to-digital conversion module, and control the power supply module to output a first auxiliary current according to the first duty cycle.

[0104] Furthermore, the first analog to digital converter (ADC) is referred to as ADC1, and the second analog to digital converter is referred to as ADC2. ADC1 obtains the voltage v output by the rectifier bridge RB. g After that, the voltage v gThe analog signal is converted into a digital signal and then transmitted to the processing module. After receiving the signal, the processing module obtains the amplitude V of the AC input voltage through amplitude detection. m .

[0105] Similarly, ADC2 obtains the current through the freewheeling diode D b After the cathode output voltage is obtained, the output voltage is converted from an analog signal to a digital signal and then transmitted to the processing module. The processing module receives the output voltage V0. The processing module calculates the output voltage V0 according to the amplitude of the AC input voltage V m and the output voltage V0 to calculate a first voltage ratio, which is represented by "α", α = V m / V0. Since there is a corresponding relationship between the first voltage ratio α and the first duty cycle, and the first duty cycle is D y1 With the first auxiliary current I m There is a corresponding relationship between them, so the first auxiliary current I can be controlled by adjusting the first voltage ratio α m size.

[0106] Optionally, the controller is a digital signal processor (DSP). Further, the processing module in the DSP is a DSP chip, and the DSP chip is TMS320F28335.

[0107] Figure 7c A controller is used, such as a DSP output PWM drive, to achieve auxiliary power supply through an LC low-pass filter, so that the number of devices required for the PFC controller is reduced compared to that achieved by using an LDO method, thereby saving costs.

[0108] exist Figure 7c In the circuit structure shown, the first pin of the processing module is connected to the power module, the power module is connected to the filter, and the filter outputs auxiliary current or auxiliary voltage to the boost inductor; the second pin of the processing module is connected to the switch tube Q b The processing module is used to send a signal to the switch tube Q through the second pin. b Send control signal S0 to control the switch tube Q b The switch is turned on or off.

[0109] In another possible implementation, Figure 7d As shown, the controller Figure 7c The controller shown in the figure also includes a signal output module, one end of which is connected to the processing module and the other end is connected to the switch tube Q. b The signal output module is used to generate and send a signal to the switch tube Q under the control of the processing module. b Send control signal S0 to control switch Qb The switch is turned on or off, thereby providing a stable output environment for the power module to output the first auxiliary current or the first auxiliary voltage. For example, when the first duty cycle is generated by turning on and off the switch tube in the switching device, the PFC converter outputs the output voltage V0, so that the boost inductor generates a first inductance value L b ′.

[0110] Wherein, the signal output module is a PWM.

[0111] The present application also provides a current control method, which is applied to any of the PFC converters in the above embodiments. The PFC converter includes an AC voltage source AC, a rectifier bridge RB, a switch tube Q, and a b , freewheeling diode D b , filter capacitor C o and load R Ld In addition, it also includes a boost inductor, a first resistor R1, a power module and a control circuit. The specific connection relationship of each component can be seen in Figure 4 、 Figure 6 The circuit structure shown will not be described in detail here.

[0112] Among them, the inductance value of the boost inductor is L b ' changes with the auxiliary current in the auxiliary winding. The inductance value of the boost inductor L b ′ is the inductance of the main winding coil.

[0113] like Figure 8 As shown, the current control method includes:

[0114] 101: The control circuit obtains a first reference inductance value of the boost inductor.

[0115] Specifically, one implementation is that the control circuit obtains a reference inductance curve, wherein the reference inductance curve includes a corresponding relationship between the reference inductance and the voltage ratio. Figure 9 As shown, the horizontal coordinate of each point in the above reference inductance curve is the amplitude of the AC input voltage V m The voltage ratio α between the output voltage and the output voltage V0 is plotted on the vertical axis as the first reference inductance value. For example, when the first voltage ratio α is 0.475, the first reference inductance value obtained according to the reference inductance curve is 375 μH; when the first voltage ratio α is 0.940, the corresponding first reference inductance value is 92 μH.

[0116] Furthermore, the reference inductance curve can be obtained by the above formula (10):

[0117]

[0118] Using the prototype parameters, the AC input voltage range of the AC voltage source output is 90~264V, and the amplitude of the AC input voltage is V m The value range is The output voltage V0 is constant at 400V, the output power P0 is 120W, and the switching frequency f s is 100kHz.

[0119] Furthermore, the first voltage ratio α=V m / V0,

[0120] So the AC input voltage amplitude V is obtained by measuring m The first voltage ratio can be determined by the output voltage V0 of the PFC converter. Figure 7c Or the circuit structure described in 7d. Specifically, the processing module or the control circuit measures and obtains the amplitude V m The process of generating and outputting the voltage V0 can be found in the above description of the controller embodiment, which will not be repeated here.

[0121] The control circuit substitutes each first voltage ratio α measured and calculated into formula (10) to obtain the first reference inductance value, thereby establishing a corresponding relationship between the first voltage ratio and the first reference inductance value, and stores and displays it in the form of a reference inductance value curve.

[0122] 102: The control circuit determines a first inductance value according to the first reference inductance value.

[0123] The control circuit includes a storage unit, which stores a first inductance value L b The corresponding relationship between ′ and the first voltage ratio is the reference inductance curve.

[0124] The control circuit obtains the first inductance value according to the first reference inductance value and a preset ratio, establishes a corresponding relationship between the first inductance value and the first voltage ratio, and stores the corresponding relationship. Figure 9 As shown, the preset ratio is 80%, then the first inductance value is 80% of the first reference inductance value. For example, if the first inductance value is 375μH, the corresponding first reference inductance value is 300μH. And the first reference inductance value 300μH and the first voltage ratio 0.475 are a set of corresponding relationships, which can also be called an inductance corresponding relationship. Thus, according to the inductance corresponding relationship, Figure 9 The desired inductance curve is shown.

[0125] Wherein, the first inductance value L b ' is also called the expected inductance value, the first inductance value L b ′ is the inductance value of the desired boost inductor output.

[0126] In addition, the preset ratio can be freely set according to the parameter requirements of the controller, and this embodiment does not limit this.

[0127] 103: The control circuit determines a first voltage ratio corresponding to the first inductance value, and determines a first duty cycle based on the first voltage ratio, where the first voltage ratio is a ratio between a first amplitude of an AC input voltage provided by the AC voltage source and an output voltage of the PFC converter, where the output voltage is a DC voltage.

[0128] Specifically, the storage unit of the converter stores the inductance correspondence relationship ( Figure 9 The inductance correspondence includes a correspondence between a first inductance value and a first voltage ratio. The process of determining the first voltage ratio includes: a control circuit determining the first voltage ratio according to the inductance correspondence and the first inductance value.

[0129] 104: The control circuit determines a first auxiliary current according to the first duty cycle, and controls the power module to output the first auxiliary current, so that the boost inductor generates the first inductance value.

[0130] Specifically, the first duty cycle α, the first auxiliary current I m and the first inductance value L b The relationship between ′ is as follows:

[0131] The first auxiliary current I output by the power module m and the first inductance value L b The relationship between ′ can be expressed as I m =f1(L b ′);

[0132] According to the above formula (10), the first inductance value L can be obtained b The relationship between ' and the first duty cycle α is L b ′=f2(α);

[0133] Then the first auxiliary current I is obtained m The relationship between the first duty cycle α is expressed as I m =f1[f2(α)].

[0134] According to the first auxiliary current I m and the first resistor R1 to determine the first auxiliary voltage, such as the high-level voltage V output by the PWM in the DSP controller. pulse .

[0135] Specifically, V pwm =I m ·R;

[0136] And, V pwm=V pulse ·D y1 ;

[0137] So we can get, I m R = V pulse ·D y1 ;

[0138]

[0139] Therefore, according to the amplitude of the AC input voltage V m The PWM duty cycle D can be obtained y1 , thereby adjusting the auxiliary current I m , so that the first inductance value L b ′According to the objective function L b ′=f2(α) outputs the desired inductance value.

[0140] In addition, during step 104, the method further includes: the control circuit generating a control signal when controlling the power module to output the first auxiliary current; and the control circuit sending the control signal to the switching device to control the switching device to have a first duty cycle for turning on and off, so that the PFC converter outputs the output voltage V0.

[0141] The method provided in this embodiment changes the DC bias of the boost inductor's auxiliary winding, thereby changing the saturation of the inductor core and thereby changing the inductor's inductance. This controls the boost inductor to output a desired inductance value. Because the desired inductance value is a preset ratio of the reference inductance value, the critical inductance margin of the PFC converter over a wide input voltage range is fully utilized, reducing the peak and effective value of the inductor current, thereby improving the efficiency of the PFC converter.

[0142] In addition, the method is also applicable to changing the first auxiliary current when the first inductance value changes, so that the boost inductor outputs the corresponding inductance value. Specifically, the method further includes:

[0143] When the AC input voltage provided by the AC voltage source changes to a second amplitude, the control circuit determines a second voltage ratio, which is the ratio between the second amplitude and the output voltage; the control circuit determines a second duty cycle based on the second voltage ratio, determines a second auxiliary current based on the second duty cycle, and controls the power supply module to output the second auxiliary current, so that the boost inductor generates a second inductance value.

[0144] In one example, the first inductance value before the change is represented by L b1 ′, the corresponding amplitude is the first amplitude V m1 , the first duty cycle is D y1 The second inductance value after the change is expressed as Lb2 ′, the corresponding amplitude is the second amplitude V m2 , the second duty cycle is D y2 ; According to the following relationship, the second duty cycle D y2 ;

[0145]

[0146] Among them, I m2 is the second auxiliary current, α2 is the second voltage ratio, V pulse2 is the high-level voltage output by the PWM at the second voltage ratio α2.

[0147] Finally, according to I m2 R = V pulse2 ·D y2 , and obtain the second auxiliary current I m2 .

[0148] The boost inductor is in the second auxiliary current I m2 Under the action of the second inductance value L, the main winding coil generates b2 ′.

[0149] The method provided in the embodiments of the present application utilizes variable inductor technology to control the duty cycle of the DCM Boost PFC converter through a newly added control circuit and power module, thereby optimizing the inductance value under a wide range of input voltages, effectively reducing power loss, and improving the efficiency of the converter.

[0150] It should be noted that the execution subject in the above method embodiment may be a control circuit, or a processing module or controller, a control chip, etc., and this embodiment does not limit this.

[0151] In addition, an embodiment of the present application further provides a device, which includes the PFC converter described in the aforementioned embodiment. The device has the functions of the PFC converter and can output an auxiliary current or auxiliary voltage to a boost inductor, thereby controlling the inductance of the boost inductor so that the inductance of the boost inductor reaches a desired inductance, fully utilizing the inductance margin of the PFC converter and improving the efficiency of the PFC converter.

[0152] Specifically, the device may be a primary power module or a primary power device. Specifically, models of the primary power module or primary power device include AX1200i, PS48600, XVE-120100, and the like. When the primary power module is connected to a load, it can supply power to the load. The load includes various electrical devices, such as computers, servers, switches, routers, and the like, but this is not limited in this embodiment of the present application.

[0153] In addition, an embodiment of the present application further provides a chip, which is connected to a memory and is used to read and execute a software program stored in the memory to implement the functions performed by the PFC converter in the above method embodiment.

[0154] The memory may be a read-only memory, or other types of static storage devices that can store static information and instructions, a random access memory, or other types of dynamic storage devices that can store information and instructions, or an electrically erasable programmable read-only memory or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and can be accessed by a computer, but is not limited thereto.

[0155] The terms "first," "second," and the like in the specification and claims of this application and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a particular order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, such that the embodiments described herein can be practiced in an order other than that shown or described herein.

[0156] In this specification, references to the same or similar parts between the various embodiments are sufficient. In particular, since the application environment of the method embodiment is similar to the circuit structure of the PFC converter, the circuit structure and component relationships of the PFC converter in the method embodiment are relatively simple. For relevant parts, references to the description of the device embodiment are sufficient.

[0157] The above-described embodiments of the present application do not constitute a limitation on the scope of protection of the present application.

Claims

1. A power factor correction (PFC) converter, comprising: AC voltage source, rectifier bridge, switch device, freewheeling electronic device, filter capacitor, characterized in that the converter further comprises: a boost inductor, a first resistor, a power module and a control circuit, wherein the inductance value of the boost inductor is variable; The boost inductor is connected to the power module through the first resistor; The control circuit is connected to the power module and is used to control the power module to output a first auxiliary current so that the first auxiliary current generates a first inductance value in the boost inductor; The control circuit is also connected to the switch device, and is used to control the switch device to be turned on or off so that the PFC converter outputs a stable voltage; The control circuit is integrated in a controller, and the controller further includes a first analog-to-digital conversion module, a second analog-to-digital conversion module and a processing module; The first analog-to-digital conversion module is connected to the rectifier bridge, and is used to perform analog-to-digital conversion on the input voltage signal passing through the rectifier bridge, and send the analog-to-digital conversion to the processing module; The second analog-to-digital conversion module is connected to the freewheeling electronic device, and is used to perform analog-to-digital conversion on the output voltage signal passing through the freewheeling electronic device, and send the analog-to-digital conversion to the processing module; The processing module is used to determine a first duty cycle based on an input voltage signal processed by the first analog-to-digital conversion module and an output voltage signal processed by the second analog-to-digital conversion module, and control the power supply module to output the first auxiliary current according to the first duty cycle.

2. The converter according to claim 1, characterized in that The boost inductor comprises a main winding coil and an auxiliary winding coil; One end of the main winding coil is connected to the rectifier bridge, and the other end is connected to the switch device and the freewheeling electronic device; one end of the auxiliary winding coil is connected to the power module through the first resistor, and the other end is grounded; The auxiliary winding coil causes the main winding coil to generate the first inductance value under the action of the first auxiliary current.

3. The converter according to claim 2, characterized in that The control circuit is further used to control the power supply module to output a second auxiliary current when the amplitude of the AC input voltage provided by the AC voltage source changes, and the second auxiliary current generates a second inductance value in the boost inductor.

4. The converter according to claim 3, characterized in that The auxiliary winding coil causes the main winding coil to generate the second inductance value under the action of the second auxiliary current.

5. The converter according to any one of claims 1 to 4, characterized in that: The power supply module is a low dropout linear regulator LDO.

6. The converter according to claim 1, characterized in that The controller further comprises a signal output module, one end of which is connected to the processing module, and the other end of which is connected to the switch device; The signal output module is used to send a control signal to the switch device under the control of the processing module, so that the switch device is turned on or off.

7. A current control method, the method is applied to a power factor correction (PFC) converter, the converter includes an AC voltage source, a rectifier bridge, a switch device, a freewheeling electronic device, and a filter capacitor, characterized in that: The PFC converter further includes a boost inductor, a first resistor, a power module and a control circuit, wherein the inductance value of the boost inductor is variable; and the method includes: The control circuit obtains a first reference inductance value of the boost inductor; The control circuit determines a first inductance value according to the first reference inductance value; The control circuit determines a first voltage ratio corresponding to the first inductance value, and determines a first duty cycle according to the first voltage ratio, wherein the first voltage ratio is a ratio between a first amplitude of an AC input voltage provided by the AC voltage source and an output voltage of the PFC converter; The control circuit determines a first auxiliary current according to the first duty cycle, and controls the power module to output the first auxiliary current, so that the boost inductor generates the first inductance value.

8. The method according to claim 7, characterized in that The method further comprises: The control circuit generates a control signal while controlling the power module to output the first auxiliary current; The control circuit sends the control signal to the switching device to control the switching device to have a duty cycle of turning on and off to the first duty cycle, so that the PFC converter outputs the output voltage.

9. The method according to claim 7 or 8, characterized in that: The converter stores an inductance correspondence relationship, wherein the inductance correspondence relationship includes a correspondence relationship between the first inductance value and the first voltage ratio; The control circuit determines a first voltage ratio corresponding to the first inductance value, including: The control circuit determines the first voltage ratio according to the inductance correspondence relationship and the first inductance value.

10. The method according to claim 7, characterized in that The method further comprises: When the AC input voltage provided by the AC voltage source changes to a second amplitude, the control circuit determines a second voltage ratio, where the second voltage ratio is a ratio between the second amplitude and the output voltage; The control circuit determines a second duty cycle according to the second voltage ratio; The control circuit determines a second auxiliary current according to the second duty cycle, and controls the power module to output the second auxiliary current, so that the boost inductor generates a second inductance value.

11. The method according to claim 7, characterized in that The converter stores a corresponding relationship between the first inductance value and the first voltage ratio. The control circuit obtains the first inductance value according to the first reference inductance value and a preset ratio; The control circuit establishes a corresponding relationship between the first inductance value and the first voltage ratio, and stores the corresponding relationship.

12. An electronic device, characterized in that: The electronic device comprises the PFC converter according to any one of claims 1 to 6.

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