A pfc control circuit and method

Abstract

The application discloses a PFC control circuit and method, relates to the technical field of PFC control, and achieves the following effects: the PFC control circuit rectifies alternating current of commercial power into direct current through an input rectification module; direct current voltage is obtained by collecting the direct current through an input voltage sampling module; inductance current is collected through an input current sampling module; current output voltage under the current duty cycle is collected through an output voltage sampling module; the second MOS tube is controlled to be turned off or turned on according to the voltage target value and the voltage setting value through a control module, so that the first MOS tube or the second MOS tube performs corresponding voltage reduction or voltage increase on the direct current voltage; the duty cycle at the next moment is obtained according to the voltage target value, the current output voltage, the inductance current, the direct current voltage and the current duty cycle, so that the first MOS tube or the second MOS tube performs corresponding voltage reduction or voltage increase on the direct current voltage, and the output voltage at the next moment reaches the voltage target value; and the application makes the output voltage controllable.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of PFC control, in particular to a PFC control circuit and method. BACKGROUND

[0002] The existing megasonic cleaning power supply is in AC-DC-AC mode, that is, the required frequency AC power is obtained by rectification by a diode rectifier bridge and then by full-bridge or half-bridge chopper inversion. With the increase of the rated working frequency of the cleaning power supply, it is difficult for the pre-stage of the rectification of the cleaning power supply to meet the requirement of a higher power factor using uncontrolled rectification or phase-controlled rectification. At the same time, the power output of the megasonic cleaning equipment on the market today is 100W-1500W, and thus the output voltage of the PFC (Power Factor Correction) circuit required by the megasonic cleaning equipment also needs to be controllable in a full range. Although the PFC circuit is mainly used for improving harmonic injection and reducing pollution of the load to the power grid, the output voltage control function is an indispensable function of the megasonic cleaning power supply. If the input voltage and input current of the inversion part are relatively pure, the Vds waveform of the switch tube turned on will be better. SUMMARY

[0003] The purpose of the present application is to provide a PFC control circuit and method, which can make the output voltage controllable.

[0004] To achieve the above purpose, the present application provides the following solutions:

[0005] A PFC control circuit, which is connected with an input end of commercial power and a load respectively, and comprises:

[0006] An input rectification module, which is connected with the input end of commercial power and is used for rectifying AC power of commercial power to obtain DC power;

[0007] A voltage conversion module, which is connected with the input rectification module and the load respectively; the voltage conversion module comprises a first MOS tube, a second MOS tube and an inductor; the positive pole of the input rectification module is connected with the first MOS tube, the inductor, the load and the negative pole of the input rectification module in sequence; the drain of the second MOS tube is connected with the negative pole of the input rectification module, and the source of the second MOS tube is connected between the circuit where the inductor and the load are connected; the DC current in the DC power obtains an inductor current through the inductor;

[0008] An input voltage sampling module, which is connected with the output end of the input rectification module and is used for collecting the DC power to obtain a DC voltage;

[0009] An input current sampling module, which is connected with the inductor and is used for collecting the inductor current;

[0010] An output voltage sampling module is connected with the load, and is configured to collect a current output voltage under a current duty cycle;

[0011] A control module is connected with the input voltage sampling module, the input current sampling module, the output voltage sampling module, the first MOS tube and the second MOS tube, and is configured to:

[0012] According to the voltage target value and the voltage setting value, the second MOS tube is controlled to be turned off or turned on, so that the first MOS tube or the second MOS tube performs corresponding voltage reduction or voltage increase on the direct current voltage;

[0013] According to the voltage target value, the current output voltage, the inductor current, the direct current voltage and the current duty cycle, a next time duty cycle is obtained, so that the first MOS tube or the second MOS tube performs corresponding voltage reduction or voltage increase on the direct current voltage, so that the next time output voltage reaches the voltage target value; wherein an initial duty cycle is determined according to the voltage target value and the voltage setting value.

[0014] Optionally, the control module comprises a voltage outer loop and a current inner loop.

[0015] The voltage outer loop is connected with the input voltage sampling module, the output voltage sampling module and the current inner loop respectively; and the current inner loop is connected with the voltage conversion module and the input current sampling module respectively.

[0016] The voltage outer loop is configured to obtain a current reference value according to the current output voltage, the voltage target value and the direct current voltage.

[0017] The current inner loop is connected with the first MOS tube and the second MOS tube, and is configured to:

[0018] According to the voltage target value and the voltage setting value, the second MOS tube is controlled to be turned off or turned on, so that the first MOS tube or the second MOS tube performs corresponding voltage reduction or voltage increase on the direct current voltage;

[0019] According to the current reference value, the inductor current and the current duty cycle, a next time duty cycle is obtained, so that the first MOS tube or the second MOS tube performs corresponding voltage reduction or voltage increase on the direct current voltage, so that the next time output voltage reaches the voltage target value.

[0020] Optionally, the voltage outer loop comprises:

[0021] A first adder is connected with the output voltage sampling module, and is configured to obtain a voltage error value according to the voltage target value and the current output voltage.

[0022] a voltage loop compensator connected with the first subtractor, configured to obtain a voltage compensation value according to the voltage error value;

[0023] a multiplier connected with the input voltage sampling module and the voltage loop compensator, configured to obtain a current reference value according to the DC voltage and the voltage compensation value.

[0024] Optionally, the current inner loop comprises:

[0025] a second adder connected with the input current sampling module and the multiplier, configured to obtain a current error value according to the inductor current and the current reference value;

[0026] a current loop compensator connected with the second subtractor, configured to obtain a voltage tracking value according to the current error value;

[0027] a third adder connected with the current loop compensator, configured to obtain a modulation value according to the current duty cycle and the voltage tracking value;

[0028] a PWM modulation sub-module connected with the third subtractor, configured to obtain a next time duty cycle according to the modulation value;

[0029] a power conversion sub-module connected with the PWM modulation sub-module, the first MOS tube and the second MOS tube, configured to obtain a modulated next time duty cycle according to the next time duty cycle and the DC voltage, so that the first MOS tube or the second MOS tube performs step-down or step-up on the DC voltage to make the next time output voltage reach a voltage target value.

[0030] Optionally, the voltage conversion module further comprises:

[0031] a first diode, a positive electrode of the first diode connected with a negative electrode of the input rectification module, a negative electrode of the first diode connected between a circuit in which the first MOS tube and the inductor are connected, configured to perform freewheeling for the second MOS tube.

[0032] Optionally, the voltage conversion module further comprises:

[0033] a filter capacitor, one end of the filter capacitor connected with the negative electrode of the input rectification module, the other end of the filter capacitor connected between a circuit in which the inductor and the load are connected;

[0034] a second diode, a positive electrode of the second diode connected with the inductor, a negative electrode of the second diode connected with the load.

[0035] To achieve the above object, the application further provides the following schemes:

[0036] A PFC control method, the PFC control method applies the PFC control circuit, the PFC control method comprises:

[0037] The AC power of the mains is rectified to obtain DC power based on the input rectifier module;

[0038] The DC voltage in the DC power is collected based on the input voltage sampling module;

[0039] The inductor current in the voltage conversion module is collected based on the input current sampling module;

[0040] The current output voltage under the current duty cycle is collected based on the output voltage sampling module;

[0041] The second MOS tube in the voltage conversion module is controlled to be turned off or turned on according to the voltage target value and the voltage set value based on the control module, so that the first MOS tube or the second MOS tube in the voltage conversion module performs corresponding voltage reduction or voltage increase on the DC voltage;

[0042] The next time duty cycle is obtained based on the control module according to the voltage target value, the current output voltage, the inductor current, the DC voltage and the current duty cycle, so that the first MOS tube or the second MOS tube performs corresponding voltage reduction or voltage increase on the DC voltage, so that the next time output voltage reaches the voltage target value; wherein the initial duty cycle is determined according to the voltage target value and the voltage set value.

[0043] Optionally, the next time duty cycle is obtained based on the control module according to the voltage target value, the current output voltage, the inductor current, the DC voltage and the current duty cycle, so that the first MOS tube or the second MOS tube performs corresponding voltage reduction or voltage increase on the DC voltage, so that the next time output voltage reaches the voltage target value, specifically including:

[0044] The current reference value is obtained based on the voltage outer loop according to the current output voltage, the voltage target value and the DC voltage;

[0045] The next time duty cycle is obtained based on the current inner loop according to the current reference value, the inductor current and the current duty cycle, so that the first MOS tube or the second MOS tube performs corresponding voltage reduction or voltage increase on the DC voltage, so that the next time output voltage reaches the voltage target value.

[0046] Optionally, the current reference value is obtained based on the voltage outer loop according to the current output voltage, the voltage target value and the DC voltage, specifically including:

[0047] The voltage error value is obtained based on the first adder according to the voltage target value and the current output voltage;

[0048] a voltage compensator based on the voltage error value to obtain a voltage compensation value;

[0049] a multiplier based on the DC voltage and the voltage compensation value to obtain a current reference value.

[0050] Optionally, a current inner loop based on the current reference value, the inductor current and the current duty cycle to obtain a next time duty cycle, so that the first MOS tube or the second MOS tube correspondingly step down or step up the DC voltage to make the next time output voltage reach the voltage target value, specifically comprising:

[0051] a second adder based on the inductor current and the current reference value to obtain a current error value;

[0052] a current loop compensator based on the current error value to obtain a voltage tracking value;

[0053] a third adder based on the current duty cycle and the voltage tracking value to obtain a modulation value;

[0054] a PWM modulation submodule based on the modulation value to obtain a next time duty cycle;

[0055] a power conversion submodule based on the next time duty cycle and the DC voltage to obtain a modulated next time duty cycle, so that the first MOS tube or the second MOS tube correspondingly step down or step up the DC voltage to make the next time output voltage reach the voltage target value.

[0056] According to the specific embodiments of the present application, the following technical effects are provided:

[0057] The PFC control circuit and method provided by the application, through input rectification module, rectifies the alternating current of the mains to obtain direct current; the voltage conversion module comprises a first MOS tube, a second MOS tube and an inductor; the direct current in the direct current is subjected to the inductor to obtain inductor current; the input voltage sampling module is used to collect the direct current to obtain direct current voltage; the input current sampling module is used to collect the inductor current; the output voltage sampling module is used to collect the current output voltage under the current duty cycle; the control module is connected with the input voltage sampling module, the input current sampling module, the output voltage sampling module, the first MOS tube and the second MOS tube; the control module controls the second MOS tube to be disconnected or turned on according to the voltage target value and the voltage setting value, so that the first MOS tube or the second MOS tube performs corresponding voltage reduction or voltage increase on the direct current voltage; the control module obtains the next time duty cycle according to the voltage target value, the current output voltage, the inductor current, the direct current voltage and the current duty cycle, so that the first MOS tube or the second MOS tube performs corresponding voltage reduction or voltage increase on the direct current voltage, so that the next time output voltage reaches the voltage target value; wherein, the initial duty cycle is determined according to the voltage target value and the voltage setting value; the output voltage can be controlled by the application.

[0058] Compared with the prior art, the application makes the output voltage of the required PFC circuit controllable. BRIEF DESCRIPTION OF DRAWINGS

[0059] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description only constitute some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0060] Figure 1 The PFC structure schematic diagram of the PFC control circuit of the application;

[0061] Figure 2 The control module structure schematic diagram of the PFC control circuit of the application;

[0062] Figure 3 The current inner loop structure schematic diagram of the PFC control circuit of the application;

[0063] Figure 4 The voltage outer loop (including the current inner loop) structure schematic diagram of the PFC control circuit of the application;

[0064] Figure 5The schematic diagram of the current loop compensator of the PFC control circuit of the present application;

[0065] Figure 6 The schematic diagram of the voltage loop compensator of the PFC control circuit of the present application;

[0066] Figure 7 The first waveform schematic diagram of the output voltage of the embodiment of the PFC control circuit of the present application;

[0067] Figure 8 The second waveform schematic diagram of the output voltage of the embodiment of the PFC control circuit of the present application;

[0068] Figure 9 The input voltage waveform schematic diagram of the embodiment of the PFC control circuit of the present application;

[0069] Figure 10 The input current waveform schematic diagram of the embodiment of the PFC control circuit of the present application;

[0070] Figure 11 The flow schematic diagram of the PFC control method of the present application.

[0071] Symbol explanation:

[0072] Input rectification module-1, voltage conversion module-2, first MOS tube-21, second MOS tube-22, inductor-23, first diode-24, filter capacitor-25, second diode-26, load-3, control module-4, first adder-41, voltage loop compensator-42, multiplier-43, second adder-44, current loop compensator-45, third adder-46, PWM modulation sub-module-47, power conversion sub-module-48. DETAILED DESCRIPTION

[0073] The technical solutions in the embodiments of the present application will be described clearly and completely below with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0074] The purpose of the present application is to provide a PFC control circuit, which can make the output voltage controllable.

[0075] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below with the accompanying drawings and specific embodiments.

[0076] As Figure 1As shown, the PFC control circuit provided by the application is connected with the input end of the commercial power and the load 3 respectively, and comprises an input rectification module 1, a voltage conversion module 2, an input voltage sampling module, an input current sampling module, an output voltage sampling module and a control module 4.

[0077] The input rectification module 1 is connected with the input end of the commercial power. The input rectification module 1 is used to rectify the alternating current of the commercial power to obtain direct current.

[0078] The voltage conversion module 2 is connected with the input rectification module 1 and the load 3 respectively. The voltage conversion module 2 comprises a first MOS tube 21, a second MOS tube 22 and an inductor 23; the positive pole of the input rectification module 1 is connected with the first MOS tube 21, the inductor 23, the load 3 and the negative pole of the input rectification module 1 in sequence; the drain of the second MOS tube 22 is connected with the negative pole of the input rectification module 1, and the source of the second MOS tube 22 is connected between the circuit where the inductor 23 and the load 3 are connected; the direct current in the direct current is converted into inductor current through the inductor 23.

[0079] The input voltage sampling module is connected with the output end of the input rectification module 1. The input voltage sampling module is used to collect the direct current to obtain direct current voltage.

[0080] The input current sampling module is connected with the inductor 23. The input current sampling module is used to collect the inductor current.

[0081] The output voltage sampling module is connected with the load 3. The output voltage sampling module is used to collect the current output voltage under the current duty cycle.

[0082] The control module 4 is connected with the input voltage sampling module, the input current sampling module, the output voltage sampling module, the first MOS tube 21 and the second MOS tube 22.

[0083] The control module 4 is used to control the second MOS tube 22 to be disconnected or turned on according to the voltage target value and the voltage setting value, so that the first MOS tube 21 or the second MOS tube 22 performs corresponding voltage reduction or voltage increase on the direct current voltage.

[0084] The control module 4 is used to obtain the next time duty cycle according to the voltage target value, the current output voltage, the inductor current, the direct current voltage and the current duty cycle, so that the first MOS tube 21 or the second MOS tube 22 performs corresponding voltage reduction or voltage increase on the direct current voltage, so that the next time output voltage reaches the voltage target value; wherein the initial duty cycle is determined according to the voltage target value and the voltage setting value.

[0085] The input rectifier module 1 is internally provided with a bridge circuit to rectify AC power to obtain DC power.

[0086] The voltage conversion module 2 has one of a boost mode and a buck mode; the boost mode is a boost mode; the buck mode is a buck mode; in the buck mode, the first MOS tube 21 controls the circuit switch, and the second MOS tube 22 is turned off; in the boost mode, the second MOS tube 22 controls the circuit switch, and the first MOS tube 21 is turned on.

[0087] In a specific embodiment, the voltage setting value is 330V; when the voltage target value is less than the voltage setting value, the voltage conversion module 2 has the buck mode.

[0088] That is, the first MOS tube duty cycle D can be obtained by the following formula 1(t) :

[0089]

[0090] V bus is the current output voltage, V 交 is the AC voltage in the AC power, ω is the angular frequency in the rectification process, t is the time in the rectification process, and V 直 is the DC voltage in the DC power.

[0091] When the voltage target value is greater than the voltage setting value, the voltage conversion module 2 has the boost mode.

[0092] That is, the second MOS tube duty cycle D can be obtained by the following formula 2(t) :

[0093]

[0094] In order to maintain the stability of the output voltage, reduce the output ripple, reduce the total harmonic distortion (THD), and improve the current control effect, the control module 4 (as shown in Figure 2 ) includes a voltage outer loop and a current inner loop.

[0095] The voltage outer loop is connected with the input voltage sampling module, the output voltage sampling module, and the current inner loop. The current inner loop is connected with the voltage conversion module 2 and the input current sampling module.

[0096] The voltage outer loop is used to obtain a current reference value according to the current output voltage, the voltage target value, and the DC voltage.

[0097] The current inner loop is connected with the first MOS transistor 21 and the second MOS transistor 22.

[0098] The current inner loop is used to control the second MOS transistor 22 to be turned off or turned on according to the voltage target value and the voltage setting value, so that the first MOS transistor 21 or the second MOS transistor 22 performs corresponding voltage reduction or voltage increase on the direct current voltage.

[0099] The current inner loop is used to obtain a next time duty cycle according to the current reference value, the inductor current and the current duty cycle, so that the first MOS transistor 21 or the second MOS transistor 22 performs corresponding voltage reduction or voltage increase on the direct current voltage, so that the next time output voltage reaches the voltage target value.

[0100] Further, as shown in Figure 4 The voltage outer loop includes a first adder 41, a voltage loop compensator 42 and a multiplier 43.

[0101] The first adder 41 is connected with the output voltage sampling module. The first adder 41 is used to obtain a voltage error value according to the voltage target value and the current output voltage.

[0102] The voltage loop compensator 42 (as shown in Figure 6 The voltage loop compensator 42 is connected with the first subtractor. The voltage loop compensator 42 is used to obtain a voltage compensation value according to the voltage error value.

[0103] The multiplier 43 is connected with the input voltage sampling module and the voltage loop compensator 42. The multiplier 43 is used to obtain a current reference value according to the direct current voltage and the voltage compensation value.

[0104] Because the current loop is errorless;

[0105] V bus =I L ×R s =K×I SINE ×V EAOUT ×R C

[0106] Wherein, I SINE is the effective value of the input sine current; V EAOUT is the voltage compensation value; R C is the sampling resistance of the input sine current, K is the input current sampling coefficient, R s is the sampling resistance of the inductor, and I L is the inductor current.

[0107] At this time,

[0108]

[0109] Among them, V rms R is the effective value of the input sinusoidal voltage. L I is the load resistance. bus This represents the current output current.

[0110] That is, the transfer function of the forward channel is:

[0111]

[0112] Among them, G VOL (s) is the transfer function of the previous forward channel, V bus (s) represents the current output voltage after Laplace transform, V EAOUT (s) represents the voltage compensation value after Laplace transform.

[0113] The voltage compensation value V is obtained using the following formula (transfer function of the voltage loop compensator). EAOUT :

[0114]

[0115] Among them, G V (s) is the transfer function of the previous voltage loop compensator; V ref For voltage setting; R a For protection resistors; S is t in the real domain corresponding to the Laplace transform; C3 is the third capacitor.

[0116] Meanwhile, the open-loop transfer function of the voltage loop is obtained by applying the following formula to the overall loop until the target voltage value is reached:

[0117]

[0118] Among them, G VK (s) is the open-loop transfer function of the previous voltage loop.

[0119] like Figure 6 As shown, Giv(s) is the transfer function from the inductor current to the current output voltage.

[0120] In addition, such as Figure 3 As shown, the inner current loop includes: a second adder 44, a current loop compensator 45, a third adder 46, a PWM modulation submodule 47, and a power conversion submodule 48.

[0121] The second adder 44 is connected to the input current sampling module and the multiplier 43. The second adder 44 is used to obtain the current error value based on the inductor current and the current reference value.

[0122] The current loop compensator 45 is connected with the second subtractor. The current loop compensator 45 is used to obtain a voltage tracking value according to the current error value.

[0123] The third adder 46 is connected with the current loop compensator 45. The third adder 46 is used to obtain a modulation value according to the current duty cycle and the voltage tracking value.

[0124] The PWM modulation sub-module 47 is connected with the third subtractor. The PWM modulation sub-module 47 is used to obtain a next time duty cycle according to the modulation value.

[0125] The power conversion sub-module 48 is connected with the PWM modulation sub-module 47, the first MOS tube 21 and the second MOS tube 22. The power conversion sub-module 48 is used to obtain a modulated next time duty cycle according to the next time duty cycle and the direct current voltage, so that the first MOS tube 21 or the second MOS tube 22 performs step-down or step-up on the direct current voltage to make the next time output voltage reach a voltage target value.

[0126] The next time duty cycle D' is obtained by the following formula (transfer function of the PWM modulator): (t) :

[0127]

[0128] Wherein, G PWM (s) is the last time PWM modulation function; K PWM is the current PWM modulation function; V -1 is the voltage tracking value, that is, V CAO .

[0129] The modulated next time duty cycle D is obtained by the following formula (transfer function of the power conversion sub-module): (t)

[0130]

[0131] Wherein, G id (s) is the last time power conversion circuit transfer function; K id is the current power conversion circuit transfer function.

[0132] As Figure 5 shown, the current loop compensator 45 is a PI controller with a current amplifier.

[0133] The current output voltage is obtained by the following formula (transfer function of the current loop compensator):

[0134] ​

[0135] wherein G i (s) is the last current loop compensator transfer function; V CAO is the voltage tracking value; R1 is the first resistor; R2 is the second resistor; R3 is the third resistor; C1 is the first capacitor; C2 is the second capacitor.

[0136] By setting the current loop compensator 45, the direct current voltage can be tracked without error.

[0137] In order to maintain the stability of the circuit, the voltage conversion module 2 further comprises a first diode 24.

[0138] The anode of the first diode 24 is connected to the negative electrode of the input rectifier module 1. The cathode of the first diode 24 is connected between the circuit where the first MOS tube 21 and the inductor 23 are connected. The first diode 24 is used to freewheel the second MOS tube 22.

[0139] In order to filter out the influence of the circuit itself on the current output voltage, the voltage conversion module 2 further comprises a filter capacitor 25 and a second diode 26.

[0140] One end of the filter capacitor 25 is connected to the negative electrode of the input rectifier module 1. The other end of the filter capacitor 25 is connected between the circuit where the inductor 23 and the load 3 are connected.

[0141] The anode of the second diode 26 is connected to the inductor 23. The cathode of the second diode 26 is connected to the load 3.

[0142] The second diode 26 is used to prevent the influence of the discharge of the filter capacitor 25 on the safety of the circuit.

[0143] For example, as shown in the specific embodiments of Figure 9 , Figure 10 and Figure 11 , the voltage setting value is 330V. Among them, Δt is the frequency; ΔY is the voltage error. The ripple voltage is less than 6V, i.e. less than 2%.

[0144] In order to achieve the above-mentioned purpose, as shown in the specific embodiments of Figure 11 , the present application also provides a PFC control method. The PFC control method applies the above-mentioned PFC control circuit; the PFC control method comprises:

[0145] S1, based on the input rectifier module 1, the alternating current of the mains is rectified to obtain direct current.

[0146] S2, based on the input voltage sampling module, the direct current voltage in the direct current is collected.

[0147] S3, collecting the inductor current in the voltage conversion module 2 based on the input current sampling module.

[0148] S4, collecting the current output voltage under the current duty cycle based on the output voltage sampling module.

[0149] S5, controlling the second MOS tube 22 in the voltage conversion module 2 to be turned off or turned on according to the voltage target value and the voltage set value based on the control module 4, so that the first MOS tube 21 or the second MOS tube 22 in the voltage conversion module 2 performs corresponding voltage reduction or voltage increase on the direct current voltage.

[0150] S6, obtaining the duty cycle at the next moment according to the voltage target value, the current output voltage, the inductor current, the direct current voltage and the current duty cycle based on the control module 4, so that the first MOS tube 21 or the second MOS tube 22 performs corresponding voltage reduction or voltage increase on the direct current voltage so that the output voltage at the next moment reaches the voltage target value; wherein the initial duty cycle is determined according to the voltage target value and the voltage set value.

[0151] Preferably, step S6 obtains the duty cycle at the next moment according to the voltage target value, the current output voltage, the inductor current, the direct current voltage and the current duty cycle based on the control module 4, so that the first MOS tube 21 or the second MOS tube 22 performs corresponding voltage reduction or voltage increase on the direct current voltage so that the output voltage at the next moment reaches the voltage target value, specifically including:

[0152] S61, obtaining the current reference value according to the current output voltage, the voltage target value and the direct current voltage based on the voltage outer loop.

[0153] S62, obtaining the duty cycle at the next moment according to the current reference value, the inductor current and the current duty cycle based on the current inner loop, so that the first MOS tube 21 or the second MOS tube 22 performs corresponding voltage reduction or voltage increase on the direct current voltage so that the output voltage at the next moment reaches the voltage target value.

[0154] Further, step S61 obtains the current reference value according to the current output voltage, the voltage target value and the direct current voltage based on the voltage outer loop, specifically including:

[0155] S611, obtaining the voltage error value according to the voltage target value and the current output voltage based on the first adder 41.

[0156] S612, obtaining the voltage compensation value according to the voltage error value based on the voltage loop compensator 42.

[0157] S613, obtaining the current reference value according to the direct current voltage and the voltage compensation value based on the multiplier 43.

[0158] Further, step S62 obtains the duty cycle at the next moment based on the current inner loop according to the current reference value, the inductor current and the current duty cycle, so that the first MOS tube 21 or the second MOS tube 22 performs step-down or step-up on the direct current voltage correspondingly to make the output voltage at the next moment reach the voltage target value, and specifically comprises the following steps.

[0159] S621, obtaining a current error value based on the second adder 44 according to the inductor current and the current reference value.

[0160] S622, obtaining a voltage tracking value based on the current loop compensator 45 according to the current error value.

[0161] S623, obtaining a modulation value based on the third adder 46 according to the current duty cycle and the voltage tracking value.

[0162] S624, obtaining the duty cycle at the next moment based on the PWM modulation submodule 47 according to the modulation value.

[0163] S625, obtaining the modulated duty cycle at the next moment based on the power conversion submodule 48 according to the duty cycle at the next moment and the direct current voltage, so that the first MOS tube 21 or the second MOS tube 22 performs step-down or step-up on the direct current voltage correspondingly to make the output voltage at the next moment reach the voltage target value.

[0164] The PFC control circuit and method can be applied to the power supply of the megasonic cleaning device, solve the problems of controllable output voltage of the megasonic cleaning power supply PFC circuit and pure driving circuit power supply, and solve the problem of low conversion efficiency.

[0165] The current inner loop and the current outer loop of the control circuit are used to feed back the current output voltage to the duty cycle part, so that the voltage control is more perfect. That is, the voltage outer loop and the current inner loop are used to adjust the duty cycle of the first MOS tube 21 or the second MOS tube 22 in real time, so as to reduce the input current harmonic distortion, increase the accuracy of feedback control, and improve the robustness of the PFC control circuit.

[0166] The embodiments in the specification are described in a progressive manner, and each embodiment focuses on the difference from other embodiments. The same or similar parts of each embodiment can be referred to each other. For the method disclosed in the embodiments, the description is relatively simple because it corresponds to the circuit disclosed in the embodiments. The relevant parts can be referred to the description of the circuit part.

[0167] The principles and implementation manners of the present application are described by using specific examples in the present application, and the above examples are only used to help understand the method of the present application and its core idea; meanwhile, for the general technical personnel in the art, the specific implementation manners and application ranges will be changed according to the idea of the present application. In conclusion, the content of the present specification should not be understood as the limitation of the present application.

Claims

1. A PFC control circuit, characterized in that, The PFC control circuit is connected to both the mains power input and the load, and the PFC control circuit includes: The input rectifier module is connected to the input terminal of the mains power supply and is used to rectify the AC power from the mains power supply to obtain DC power. A voltage conversion module is connected to the input rectifier module and the load, respectively. The voltage conversion module includes a first MOSFET, a second MOSFET, and an inductor. The positive terminal of the input rectifier module is sequentially connected to the first MOSFET, the inductor, the load, and the negative terminal of the input rectifier module. The drain of the second MOSFET is connected to the negative terminal of the input rectifier module, and the source of the second MOSFET is connected between the inductor and the load. The DC current in the DC power supply is converted into inductor current through the inductor. The voltage conversion module operates in either boost or buck modes. The boost mode is boost mode, and the buck mode is buck mode. In buck mode, the first MOSFET controls the circuit switch, and the second MOSFET is off. In boost mode, the second MOSFET controls the circuit switch, and the first MOSFET is on. An input voltage sampling module is connected to the output terminal of the input rectifier module and is used to collect the DC current to obtain the DC voltage; An input current sampling module, connected to the inductor, is used to collect the inductor current; An output voltage sampling module, connected to the load, is used to collect the current output voltage under the current duty cycle. The control module, connected to the input voltage sampling module, the input current sampling module, the output voltage sampling module, the first MOSFET, and the second MOSFET, is used for: Based on the target voltage value and the set voltage value, the second MOSFET is controlled to be turned off or on, so that the first MOSFET or the second MOSFET performs corresponding voltage reduction or boost on the DC voltage. The duty cycle for the next moment is obtained based on the target voltage value, the current output voltage, the inductor current, the DC voltage, and the current duty cycle, so that the first MOSFET or the second MOSFET can correspondingly step down or boost the DC voltage so that the output voltage at the next moment reaches the target voltage value; wherein, the initial duty cycle is determined based on the target voltage value and the voltage setting value; The control module includes: an outer voltage loop and an inner current loop; The voltage outer loop is used to obtain a current reference value based on the current output voltage, the target voltage value, and the DC voltage; The inner current loop is used to control the second MOSFET to turn off or on according to the target voltage value and the set voltage value, so that the first MOSFET or the second MOSFET can perform corresponding voltage reduction or boost on the DC voltage. The inner current loop is used to obtain the duty cycle at the next moment based on the current reference value, the inductor current and the current duty cycle, so that the first MOSFET or the second MOSFET can correspondingly step down or step up the DC voltage so that the output voltage at the next moment reaches the voltage target value.

2. The PFC control circuit according to claim 1, characterized in that: The outer voltage loop is connected to the input voltage sampling module, the output voltage sampling module, and the inner current loop, respectively; the inner current loop is connected to the voltage conversion module and the input current sampling module, respectively. The inner current loop is connected to the first MOSFET and the second MOSFET.

3. The PFC control circuit according to claim 2, characterized in that, The voltage outer loop includes: The first adder is connected to the output voltage sampling module and is used to obtain the voltage error value based on the target voltage value and the current output voltage. A voltage loop compensator, connected to the first subtractor, is used to obtain a voltage compensation value based on the voltage error value. The multiplier, connected to the input voltage sampling module and the voltage loop compensator, is used to obtain a current reference value based on the DC voltage and the voltage compensation value.

4. The PFC control circuit according to claim 3, characterized in that, The inner current loop includes: The second adder, connected to the input current sampling module and the multiplier, is used to obtain the current error value based on the inductor current and the current reference value. A current loop compensator, connected to a second subtractor, is used to obtain a voltage tracking value based on the current error value; The third adder, connected to the current loop compensator, is used to obtain a modulation value based on the current duty cycle and the voltage tracking value. The PWM modulation submodule, connected to the third subtractor, is used to obtain the duty cycle for the next time step based on the modulation value. The power conversion submodule, connected to the PWM modulation submodule, the first MOSFET, and the second MOSFET, is used to obtain the modulated duty cycle of the next time step based on the duty cycle of the next time step and the DC voltage, so that the first MOSFET or the second MOSFET can correspondingly step down or step up the DC voltage so that the output voltage of the next time step reaches the target voltage value.

5. The PFC control circuit according to claim 1, characterized in that, The voltage conversion module also includes: The first diode has its anode connected to the cathode of the input rectifier module, and its cathode connected between the first MOSFET and the inductor to provide freewheeling current for the second MOSFET.

6. The PFC control circuit according to claim 1, characterized in that, The voltage conversion module also includes: The filter capacitor has one end connected to the negative terminal of the input rectifier module and the other end connected between the inductor and the load circuit. The second diode has its anode connected to the inductor and its cathode connected to the load.

7. A PFC control method, characterized in that, The PFC control method uses the PFC control circuit according to any one of claims 1-6, and the PFC control method includes: The AC power from the mains is rectified by the input rectifier module to obtain DC power. The DC voltage in the DC power supply is acquired based on the input voltage sampling module; The inductor current in the voltage conversion module is acquired based on the input current sampling module; The current output voltage is acquired based on the current duty cycle using the output voltage sampling module. Based on the voltage target value and the voltage set value, the control module controls the second MOSFET in the voltage conversion module to turn off or on, so that the first MOSFET or the second MOSFET in the voltage conversion module can perform corresponding voltage reduction or boost on the DC voltage. The control module determines the duty cycle for the next moment based on the target voltage value, the current output voltage, the inductor current, the DC voltage, and the current duty cycle, so that the first MOSFET or the second MOSFET can correspondingly step down or boost the DC voltage so that the output voltage reaches the target voltage value at the next moment; wherein, the initial duty cycle is determined based on the target voltage value and the voltage setpoint. Based on the voltage outer loop, a current reference value is obtained according to the current output voltage, the voltage target value, and the DC voltage; Based on the current inner loop, the duty cycle for the next moment is obtained according to the current reference value, the inductor current, and the current duty cycle, so that the first MOSFET or the second MOSFET can correspondingly step down or step up the DC voltage so that the output voltage reaches the target voltage value at the next moment.

8. The PFC control method according to claim 7, characterized in that, The voltage outer loop derives a current reference value based on the current output voltage, the target voltage value, and the DC voltage, specifically including: The voltage error value is obtained by the first adder based on the target voltage value and the current output voltage; The voltage compensation value is obtained based on the voltage error value using the voltage loop compensator; The multiplier obtains the current reference value based on the DC voltage and the voltage compensation value.

9. The PFC control method according to claim 8, characterized in that, Based on the current inner loop, the duty cycle for the next moment is obtained according to the current reference value, the inductor current, and the current duty cycle. This allows the first or second MOSFET to correspondingly step down or boost the DC voltage so that the output voltage reaches the target value at the next moment. Specifically, this includes: The second adder obtains the current error value based on the inductor current and the current reference value; The voltage tracking value is obtained based on the current error value using the current loop compensator; The modulation value is obtained based on the current duty cycle and the voltage tracking value by the third adder; The duty cycle for the next moment is obtained based on the modulation value by the PWM modulation submodule; Based on the power conversion submodule, the next time duty cycle is modulated according to the next time duty cycle and the DC voltage, so that the first MOSFET or the second MOSFET can step down or step up the DC voltage so that the output voltage in the next time step reaches the target voltage value.

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