Control method, control device and switching power supply

Abstract

The invention provides a control method, a control device and a switching power supply. The control method comprises the following steps: a current sampling step: sampling a first voltage signal representing the magnitude of the current flowing through the boost inductor; a comparison output step: in each switch work period, comparing the first voltage signal with two different thresholds in the current power frequency half period to generate a first pulse signal and a second pulse signal; and an identification execution step: identifying whether the first pulse signal exists or not, if so, taking the first pulse signal as a trigger signal of the high-frequency main pipe, and otherwise, taking the second pulse signal as the trigger signal of the high-frequency main pipe. According to the invention, the problem that the main switch tube of the power factor correction circuit cannot realize zero-voltage switching-on due to inherent time delay in a high-switching-frequency application occasion can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of electric energy conversion, and in particular to a control method, a control device and a switching power supply. Background Art

[0002] The research on single-phase medium-power PFC rectification technology is developing towards high efficiency and high power density. In order to achieve high efficiency, the totem pole bridgeless PFC topology is proposed to follow this trend. Compared with the traditional bridge Boost PFC converter, the bridgeless PFC uses a controllable switch tube to replace the bridge arm diode to reduce the loss of the switch device in the open path, thereby improving efficiency. Among various bridgeless PFC topologies, the totem pole bridgeless PFC has become the mainstream because of its advantages such as fewer components and less common-mode noise. Figure 1 The figure shows a circuit diagram of a well-known totem pole bridgeless PFC, including a boost inductor L, a first switch tube Q1, a second switch tube Q2, a third switch tube Q3 and a fourth switch tube Q4; wherein the first switch tube Q1 and the second switch tube Q2 are high-frequency switch tubes, the third switch tube Q3 and the fourth switch tube Q4 are industrial frequency switch tubes, and the industrial frequency switch tubes can be replaced by diodes.

[0003] Specifically: in the positive half cycle of the power frequency AC of the PFC converter, the first switch tube Q1 serves as a high-frequency rectifier, the second switch tube Q2 serves as a high-frequency main tube, the third switch tube Q3 serves as a power frequency switch tube and remains turned off, and the fourth switch tube Q4 serves as a power frequency switch tube and remains turned on; in the negative half cycle of the power frequency AC of the PFC converter, the first switch tube Q1 serves as a high-frequency main tube, the second switch tube Q2 serves as a high-frequency rectifier, the third switch tube Q3 serves as a power frequency switch tube and remains turned on, and the fourth switch tube Q4 serves as a power frequency switch tube and remains turned off; its working principle takes the positive half cycle of the input voltage as an example, when the second switch tube Q2 is driven to turn on, the boost inductor L is excited, the current of the boost inductor L increases, and the voltage across the boost inductor L is Vin; when the second switch Q2 is driven to turn off, the first switch tube Q1 continues to flow, the boost inductor L is demagnetized, the current of the boost inductor L decreases, and the voltage across the boost inductor L is Vout-Vin.

[0004] The circuit application of the totem pole bridgeless PFC requires GaN or SiC devices in the continuous conduction mode (CCM mode) to reflect the efficiency advantage. Due to its hard switching, the switching frequency is usually not high; in the critical conduction mode (CRM), by controlling the negative inductor current, zero voltage switching (ZVS) can be achieved, which can further increase the switching frequency of the PFC and achieve higher power density. In order to achieve zero voltage switching of the high-frequency switch tube, most of the existing solutions trigger the high-frequency switch tube to turn on through the zero current detection signal (ZCD). Although this solution has a certain hardware delay, when the frequency is low, the boost inductance is large, so the resonant period is longer, and there is sufficient time to turn on and achieve zero voltage switching (ZVS). However, if Figure 2 As shown, with the increase of switching frequency, the decrease of inductance, the shorter resonance period, the smaller zero voltage turn-on area, the inherent delay influence of hardware detection and controller etc. becomes very large, and the use of zero current detection signal triggering will cause the first switch tube to miss the optimal time for zero voltage turn-on, thus hard switching leads to reduced efficiency.

[0005] like Figure 3 As shown, in the Chinese patent application document with publication number CN104518656 A, the voltage on the PFC inductor is detected. When the voltage reverses, the first switch tube is triggered to soft switch or valley turn-on. The disadvantage of this method is that it can only detect the turning point of the inductor current, and cannot trigger the main switch tube to turn on according to the size of the inductor current. It is suitable for low switching frequency occasions where negative current is generated by diode reverse recovery to achieve ZVS, and the hardware delay existing in the winding detection method will also cause zero voltage turn-on, which is not suitable for high switching frequency occasions.

[0006] For high switching frequency applications, such as Figure 4 As shown, the existing solution is to detect the negative current of the inductor, change the high-frequency synchronous tube shutdown threshold through the controller and the digital-to-analog converter to control the negative current, and open the high-frequency main tube after a certain dead zone. Although this solution avoids the high-frequency main tube from over-ZVS due to hardware delay, the hardware delay causes a delay in shutting down the high-frequency synchronous tube, resulting in an increase in the negative current of the inductor on both sides of the power frequency input, a deterioration of THD, and a decrease in efficiency, while also increasing the cost of the hardware circuit.

[0007] In summary, further increasing the switching frequency to achieve higher power density is the future development trend. It is very necessary to propose a solution suitable for high switching frequency to achieve zero voltage switching of high-frequency main pipes.

[0008] It should be noted that the above information disclosed in the background technology section is only intended to deepen the understanding of the overall background technology of this application, and should not be regarded as admitting or suggesting in any form that the information constitutes prior art already known to those skilled in the art. Summary of the invention

[0009] In view of this, the technical problem to be solved by the present invention is to provide a control method, a control device and a switching power supply, which can at least to a certain extent solve one of the technical problems existing in the above-mentioned prior art.

[0010] As a first aspect of the present invention, the technical solution of the control method provided is as follows: A control method is applied to a power factor correction circuit, wherein the power factor correction circuit includes a boost inductor, a high-frequency main tube and a high-frequency rectifier tube; wherein the control method is used to control the conduction of the high-frequency main tube in a positive half cycle or a negative half cycle of a power frequency of the power factor correction circuit, and comprises: A current sampling step of sampling a first voltage signal representing the magnitude of the inductor current flowing through the boost inductor; A comparison and output step, in each switching operation cycle, respectively comparing the first voltage signal with two different thresholds in the current power frequency half cycle to generate a first pulse signal and a second pulse signal; The identification execution step is to identify whether the first pulse signal exists. If so, the first pulse signal is used as the trigger signal of the high-frequency main tube; otherwise, the second pulse signal is used as the trigger signal of the high-frequency main tube.

[0011] Furthermore, the comparison and output step includes: In the positive half cycle of the power frequency: in each switching working cycle, when the minimum value of the inductor current represented by the first voltage signal is less than the first set value, both the first pulse signal and the second pulse signal exist; when the minimum value of the inductor current represented by the first voltage signal is greater than or equal to the first set value and less than the second set value, the first pulse signal does not exist, and the second pulse signal exists; when the inductor current represented by the first voltage signal is always zero or the minimum value is greater than the second set value, both the first pulse signal and the second pulse signal do not exist; the first set value is a negative value, and the second set value is greater than the first set value; In the negative half cycle of the industrial frequency: in each switching working cycle, when the maximum value of the inductor current represented by the first voltage signal is greater than the third set value, both the first pulse signal and the second pulse signal exist; when the maximum value of the inductor current represented by the first voltage signal is less than or equal to the first set value and greater than the fourth set value, the first pulse signal does not exist, and the second pulse signal exists; when the inductor current represented by the first voltage signal is always zero or the maximum value is less than the fourth set value, both the first pulse signal and the second pulse signal do not exist; the third set value is a positive value, and the third set value is greater than the fourth set value.

[0012] Furthermore, the identification execution step further includes: if the first pulse signal and the second pulse signal cannot be identified within the first time, opening the high-frequency main pipe at the end of the first time.

[0013] Furthermore, the first time is 1 / Fmin, wherein Fmin is the minimum switching frequency of the power factor correction circuit.

[0014] Furthermore, the Fmin is 25Khz.

[0015] Furthermore, the high-frequency main tube is turned off and then the high-frequency rectifier tube is turned on after a set dead time has passed.

[0016] Furthermore, the conduction time T of the high-frequency rectifier tube is off Determined by the following formula: T off =u*(V in ×T on ) / (V out -V in ); Where u is a constant, V in is the input voltage of the power factor correction circuit, V out is the output voltage of the power factor correction circuit, T on The conduction time of the high frequency tube As a second aspect of the present invention, the technical solution of the embodiment of the control device provided is as follows: A control device is applied to a power factor correction circuit, wherein the power factor correction circuit includes a boost inductor, a high-frequency main tube and a high-frequency rectifier tube; wherein the control device is used to control the conduction of the high-frequency main tube in a positive half cycle or a negative half cycle of the power factor correction circuit, and includes a module that performs the following functions: A current sampling module, used for sampling a first voltage signal representing the magnitude and direction of the current flowing through the boost inductor; A comparison output module, used for comparing the first voltage signal with two different thresholds in a current power frequency half cycle to generate a first pulse signal and a second pulse signal in each switch working cycle; The identification execution module is used to identify whether the first pulse signal exists. If so, the first pulse signal is used as the trigger signal of the high-frequency main tube; otherwise, the second pulse signal is used as the trigger signal of the high-frequency main tube.

[0017] As a third aspect of the present invention, the technical solution of the embodiment of the switching power supply provided is as follows: A switching power supply includes a power factor correction circuit, wherein the power factor correction circuit includes a boost inductor, a high-frequency main tube and a high-frequency rectifier tube; wherein: the switching power supply also includes the control device described in any one of the second aspects above.

[0018] The embodiment of the present invention sets different thresholds, wherein in the positive half cycle, the first threshold is less than the second threshold, and in the negative half cycle, the third threshold is greater than the fourth threshold. The first pulse signal and the second pulse signal are generated by comparing the first voltage signal with different thresholds in the positive half cycle and the negative half cycle, respectively. By identifying whether the first pulse signal exists, different control strategies are executed. Compared with the existing PFC control scheme, the embodiment of the present invention has the following beneficial effects: (1) In the embodiment of the present invention, when the first pulse signal exists, the first pulse signal is used as the trigger signal of the high-frequency main tube. Since the first threshold is less than the second threshold in the positive half cycle, and the third threshold is greater than the fourth threshold in the negative half cycle, the high-frequency main tube can be triggered to turn on in advance in both the positive half cycle and the negative half cycle, thereby offsetting the inherent delay of the hardware, ensuring the zero voltage switching of the high-frequency main tube, and improving the efficiency of the PFC converter; (2) In the embodiment of the present invention, when the inductor negative current is too small in transient working condition, the first pulse signal will not exist. At this time, the second pulse signal is used as the trigger signal of the high-frequency main tube, which can ensure that the high-frequency main tube is turned on and avoid entering the minimum operating frequency, which will cause abnormal operation of the switching power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a circuit diagram of a known PFC converter; Figure 2 It is a circuit waveform diagram of the prior art; Figure 3 It is a circuit schematic diagram of the prior art; Figure 4 It is a circuit schematic diagram of the prior art; Figure 5 A specific circuit schematic diagram for implementing the control method of the first embodiment of the present invention; Figure 6 This is one of the main waveform diagrams of the control method of the first embodiment of the present invention; Figure 7 This is the second main waveform diagram of the control method of the first embodiment of the present invention; Figure 8 A schematic diagram of an embodiment of a control device according to a second embodiment of the present invention applied to a power factor correction circuit; Fig. 9 for Figure 8 A schematic diagram of a first internal structure of a current sampling module and an identification processing module; Fig.10 for Figure 8 Schematic diagram of the second internal structure of the current sampling module and the identification processing module. DETAILED DESCRIPTION

[0020] Typical embodiments that embody the features and advantages of the present disclosure will be described in detail in the following description in conjunction with the accompanying drawings. It should be understood that the present disclosure can have various changes in different embodiments, and these changes do not depart from the scope of the present disclosure, and the description and drawings therein are essentially illustrative of these changes, rather than limiting the present disclosure.

[0021] In addition, the drawings of the present disclosure are only schematic diagrams of the present disclosure and are not necessarily drawn to scale. The same symbols in the drawings represent the same or similar parts, and thus repeated descriptions thereof will be omitted. Some of the block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented using software, or implemented in one or more hardware modules or integrated circuits, or implemented in different networks and / or processor devices and / or microcontroller devices.

[0022] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0023] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0024] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0025] It should be understood that, in the specification, claims and drawings, when a step is described as being connected to another step, the step may be directly connected to the other step, or be connected to the other step through a third step; when an element / unit is described as being "connected" to another element / unit, the element / unit may be "directly connected" to the other element / unit, or be "connected" to the other element / unit through a third element / unit.

[0026] In the existing power factor correction circuit system, based on the analysis of the background technology, it is necessary to timely and accurately detect the negative current of the inductor current, generate a signal in advance to trigger the opening of the high-frequency main tube, offset the delay caused by hardware detection, and be used for the timing control of the high-frequency switch tubes Q1 and Q2, thereby realizing ZVS control within the full input AC voltage and full load range under TCM / CRM mode.

[0027] In order to solve the above problems, the embodiments of the present invention provide a control method, a control device and a switching power supply. The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other arbitrarily.

[0028] First embodiment The present embodiment provides a control method, which is applied to a power factor correction circuit, wherein the power factor correction circuit includes a boost inductor, a high-frequency main tube, and a high-frequency rectifier tube; wherein the control method of the present embodiment is used to control the conduction of the high-frequency main tube in a positive half cycle or a negative half cycle of the power frequency of the power factor correction circuit, and includes: A current sampling step of sampling a first voltage signal representing the magnitude of the inductor current flowing through the boost inductor; A comparison and output step, in each switching operation cycle, respectively comparing the first voltage signal with two different thresholds in the current power frequency half cycle to generate a first pulse signal and a second pulse signal; The identification execution step is to identify whether the first pulse signal exists. If so, the first pulse signal is used as the trigger signal of the high-frequency main tube; otherwise, the second pulse signal is used as the trigger signal of the high-frequency main tube.

[0029] The control method of this embodiment sets the first threshold value in the positive half cycle of the industrial frequency and the third threshold value in the negative half cycle, so as to open the high-frequency main pipe in advance before the inductor current passes through zero, thereby offsetting the inherent delay of the circuit, achieving zero-voltage opening of the power factor correction circuit CRM mode over the full input range, and improving the efficiency of the switching power supply; and sets the second threshold value in the positive half cycle and the fourth threshold value in the negative half cycle, so as to prevent the high-frequency main pipe from being unable to be opened when the negative current is too small, thereby improving the reliability of the switching power supply.

[0030] Figure 5 A specific circuit schematic diagram of the control method of the first embodiment of the present invention is implemented, in which the sampling resistor for sampling the inductor current to obtain the first voltage signal is set Figure 5 As an example, the specific control process of the control method of this embodiment is analyzed in detail as follows: When the power factor correction circuit operates in the positive half cycle of the power frequency, the main waveforms of the control method of this embodiment are as follows: Figure 6 As shown, when the negative inductor current is large enough, the boost inductor current can reach the first set value I1. At this time, the minimum value of the first voltage signal is less than the first threshold value (the first threshold value is a negative voltage), and a first pulse signal is generated. The rising edge or falling edge of the first pulse signal is used as a signal to trigger the second switch tube to turn on. The second switch tube can only be turned on after a delay Tdelay. Since the first set value I1 is set to a negative current, even if there is a delay time Tdelay, the second switch tube can be turned on before the inductor current passes through zero, ensuring that the second switch tube achieves zero voltage turn-on (ZVS); when the negative inductor current is small , the boost inductor current cannot reach the first set value I1, but can ensure to reach the second set value I2. At this time, the minimum value of the first voltage signal is less than the second threshold value (the second threshold value is greater than the first threshold value), and a second pulse signal is generated. The rising edge or falling edge of the second pulse signal is used as a signal to trigger the second switch tube to turn on. The second switch tube can be turned on after a delay Tdelay. Since the second set value I2 is zero or a positive value, the inductor current has passed zero when the second switch tube is turned on after the delay. At this time, the voltage across the second switch tube has resonated to a certain voltage. At this time, the second switch tube is turned on as a hard switch.

[0031] When the power factor correction circuit operates in the negative half cycle of the power frequency, the main waveforms of the control method of this embodiment are as follows: Figure 7As shown, when the positive current is large enough, the boost inductor current can reach the third set value I3. At this time, the maximum value of the first voltage signal is greater than the third threshold value (the third threshold value is a positive voltage), and a first pulse signal is generated. The rising edge or falling edge of the first pulse signal is used as a signal to trigger the first switch tube to turn on. The first switch tube can only be turned on after a delay Tdelay. Since the third set value I3 is set to a positive current, even if there is a delay time Tdelay, the second switch tube can be turned on before the inductor current passes through zero, ensuring that the first switch tube achieves zero voltage turn-on (ZVS); when the inductor positive current is small In this case, the inductor current cannot reach the set value I3, but can ensure to reach the set value I4. At this time, the maximum value of the first voltage signal is greater than the fourth threshold value (the fourth threshold value is less than the third threshold value), and a second pulse signal is generated. The rising edge or falling edge of the second pulse signal is used as a signal to trigger the first switch tube to turn on. The first switch tube can be turned on after a delay Tdelay. Since the fourth set value I4 is zero or a negative value, the inductor current has passed zero when the first switch tube is turned on after a delay. At this time, the voltage across the first switch tube has resonated to a certain voltage. At this time, the first switch tube is turned on as a hard switch.

[0032] It should be noted that the above analysis takes the sampling resistor close to the input end of the power factor correction circuit as the reference ground. Figure 5 The connecting end of the sampling resistor and the boost inductor is used as the reference ground. When the power factor correction circuit works in the positive half cycle of the power frequency, the main waveforms of the control method of this embodiment are as follows: Figure 7 When the power factor correction circuit operates in the negative half cycle of the power frequency, the main waveforms of the control method of this embodiment are as shown in FIG. Figure 6 As shown, the present invention does not limit the sampling reference ground of the current sampling module.

[0033] In addition, if an abnormal operating condition or protection action occurs in the power factor correction circuit, and the first pulse signal and the second pulse signal cannot be detected within the first time T1, the high-frequency main pipe is controlled to be opened at the end of the first time T1, wherein the first time T1 is obtained by T1=1 / Fmin, and Fmin is the minimum switching frequency of the power factor correction circuit, which is usually set to 25Khz. The specific setting parameters are not limited by the present invention.

[0034] Second embodiment The present embodiment provides a control device, which generates a pulse signal for triggering the high-frequency main tube to be turned on in advance by detecting the inductor current, and the advance time offsets the hardware delay, thereby preventing the voltage at both ends of the high-frequency main tube from resonating to zero and then resonating to a larger voltage for hard turning on, thereby improving the efficiency of the totem pole bridgeless PFC circuit.

[0035] Specifically, the control device of this embodiment is used to control the conduction of the high-frequency main pipe in the positive half cycle or the negative half cycle of the power frequency of the power factor correction circuit, and includes modules that perform the following functions: A current sampling module, used for sampling a first voltage signal representing the magnitude of the current flowing through the boost inductor; A comparison output module, used for comparing the first voltage signal with two different thresholds in the current power frequency half cycle to generate a first pulse signal and a second pulse signal in each switch working cycle; The identification execution module is used to identify whether the first pulse signal exists. If so, the first pulse signal is used as the trigger signal of the high-frequency supervisor. Otherwise, the second pulse signal is used as the trigger signal of the high-frequency supervisor.

[0036] Figure 8 This is a schematic diagram of an embodiment of a control device of the second embodiment of the present invention applied to a power factor correction circuit, which includes one or more interleaved power factor correction circuits, a current sampling module, a comparison output module, and an identification execution module.

[0037] Fig. 9 The first internal structure diagram of the current sampling module and the identification processing module is shown in FIG. 1 . The current sampling module is connected to the power factor correction circuit. The current sampling module includes but is not limited to a sampling resistor, a current transformer, and a Hall sensor. The sampling module is connected in series with the boost inductor for sampling, and is used to detect the current flowing through the boost inductor in real time. The comparison output module is connected to the current sampling module, and generates a first pulse signal and a second pulse signal by receiving a detection signal from the sampling module. Specifically, the inductor current collected by the sampling module can be amplified by a common-mode amplifier to generate a current amplification signal IL. When in the positive half-cycle of the power frequency, the current amplification signal IL is compared with the threshold value Vth1 by a comparator to generate a pulse signal Pulse1+ of the positive half-cycle of the power frequency, and the current amplification signal IL is compared with the threshold value Vth2 by a comparator to generate a pulse signal Pulse2+ of the positive half-cycle of the power frequency; when in the negative half-cycle of the power frequency, the current amplification signal IL is compared with the threshold value Vth3 by a comparator to generate a pulse signal Pulse1- of the negative half-cycle of the power frequency, and the current amplification signal IL is compared with the threshold value by a comparator to generate a pulse signal Pulse2- of the negative half-cycle of the power frequency; the pulse signal Pulse1+ and the pulse signal Pulse1- and the polarity signal representing the positive and negative half-cycles of the power frequency are selected by an AND gate, and then the signal of the entire power frequency cycle is synthesized as the first pulse signal by an OR gate. The pulse signal Pulse2+ and the pulse signal Pulse2- and the polarity signal representing the positive and negative half cycles of the power frequency are selected through an AND gate, and then the signal of the entire power frequency cycle is synthesized through an OR gate as the second pulse signal.

[0038] From the above analysis, it can be known that the inductor current of the negative half-cycle of the power frequency is symmetrical with the inductor current of the positive half-cycle about zero. Therefore, the inductor current collected by the sampling module can be amplified by an inverting amplifier to generate a current amplification signal IL-, and then the current amplification signal IL+ and the current amplification signal IL- and the polarity signal representing the positive and negative half-cycles of the power frequency are selected through an AND gate, and then the signal of the entire power frequency cycle is synthesized through an OR gate. At this time, the first threshold and the third threshold can be set to the same, and the second threshold and the fourth threshold can be set to the same. Therefore, the current amplification signal is compared with the first threshold to generate a first pulse signal, and the current amplification signal is compared with the second threshold to generate a second pulse signal. According to the above analysis, the current sampling module and the comparison output module structure are as follows: Fig.10 shown.

[0039] Wherein, when in the positive half cycle of the power frequency, when the first pulse signal exists, the first pulse signal is used as the trigger signal for turning on the second switch tube; when the first pulse signal does not exist, the second pulse signal is used as the trigger signal for turning on the second switch tube; When in the negative half cycle of the power frequency, when the first pulse signal exists, the first pulse signal is used as the trigger signal for turning on the first switch tube; when the first pulse signal does not exist, the second pulse signal is used as the trigger signal for turning on the first switch tube.

[0040] In addition, the instantaneous value signal V of the AC voltage input to the PFC circuit can be obtained through real-time sampling. in ; Through real-time sampling, the signal V representing the output DC bus voltage of the PFC converter can be obtained out ; Set the preset voltage reference value V ref , usually set to 410V, the specific setting can be based on the actual circuit requirements, the present invention is not limited to this, V out and the preset voltage reference value V ref The PFC converter voltage loop output voltage V is obtained through an operational amplifier. comp ; Use a constant current source to charge the capacitor. When the charging voltage reaches the output voltage V comp , control the high frequency tube to turn off, the time from the high frequency tube to the turn-off is the high frequency tube conduction time T on After the high-frequency main tube is turned off, the high-frequency rectifier tube is turned on after a certain dead time. The conduction time of the high-frequency rectifier tube is T off Determined by the following formula: T off =u*(V in ×T on ) / (V out -V in ), where u is a constant, by controlling the conduction time T of the high-frequency rectifier tube off The negative current of the boost inductor can be controlled.

[0041] Among them, taking the positive half cycle of the industrial frequency as an example, when the power factor correction circuit is in steady-state operation, the input voltage maintains a sinusoidal change, and the output voltage is stable near the preset voltage parameter value. The conduction time of the high-frequency rectifier tube can make the negative current of the inductor reach a certain value according to the calculation formula of Toff. After passing through the sampling module, the current amplification signal IL reaches the first threshold value, and can generate a first pulse signal to trigger the second switch tube to turn on. When the power factor correction circuit is in a transient state, such as input voltage switching, output load switching causing output voltage fluctuations, etc., the conduction time of the high-frequency rectifier tube may be too short according to the calculation formula of Toff, resulting in a small negative current of the inductor. After passing through the sampling module, the current amplification signal IL cannot reach the first threshold value, so the first pulse signal cannot be generated. However, at this time, even if the conduction time of the high-frequency rectifier tube is too short, the inductor current can be reduced to zero voltage through the parasitic diode of the high-frequency rectifier tube. Therefore, the current amplification signal IL can reach the second threshold value, so a second pulse signal will be generated to trigger the second switch tube to turn on.

[0042] In addition, if the power factor correction circuit has an abnormal operating condition or a protective action, the identification and processing module cannot detect the pulse signal that triggers the first switch tube or the second switch tube to turn on for the first time T1, then at the end of the first time T1, the first switch tube or the second switch tube is controlled to turn on, wherein the first time T1 is obtained by T1=1 / Fmin, Fmin is the minimum switching frequency of the power factor correction circuit, which is usually set to 25Khz. The specific setting parameters are not limited by the present invention.

[0043] Third embodiment The present embodiment provides a switching power supply, including a power factor correction circuit, wherein the power factor correction circuit includes a boost inductor, a high-frequency main tube and a high-frequency rectifier tube; wherein: the switching power supply also includes any one of the control devices in the second embodiment described above.

[0044] The terms used in the above embodiments are illustrative and exemplary, rather than restrictive. Since the present invention can be implemented in various forms without departing from the spirit or nature of the invention, it should be understood that the above embodiments are not limited to any of the aforementioned details, but should be widely interpreted within the spirit and scope defined by the attached claims, so all changes and modifications falling within the scope of the claims or their equivalents should be covered by the attached claims.

Claims

1. A control method, applied to a power factor correction circuit, wherein the power factor correction circuit comprises a boost inductor, a high-frequency main tube and a high-frequency rectifier tube; characterized in that: The control method is used to control the conduction of the high-frequency main pipe in the positive half cycle or the negative half cycle of the power frequency of the power factor correction circuit, and includes: A current sampling step of sampling a first voltage signal representing the magnitude of the inductor current flowing through the boost inductor; A comparison and output step, in each switching operation cycle, respectively comparing the first voltage signal with two different thresholds in the current power frequency half cycle to generate a first pulse signal and a second pulse signal; The identification execution step is to identify whether the first pulse signal exists. If so, the first pulse signal is used as the trigger signal of the high-frequency main tube; otherwise, the second pulse signal is used as the trigger signal of the high-frequency main tube.

2. The control method according to claim 1, characterized in that: The comparison output step comprises: In the positive half cycle of the power frequency: in each switching working cycle, when the minimum value of the inductor current represented by the first voltage signal is less than the first set value, both the first pulse signal and the second pulse signal exist; when the minimum value of the inductor current represented by the first voltage signal is greater than or equal to the first set value and less than the second set value, the first pulse signal does not exist, and the second pulse signal exists; when the inductor current represented by the first voltage signal is always zero or the minimum value is greater than the second set value, both the first pulse signal and the second pulse signal do not exist; the first set value is a negative value, and the second set value is greater than the first set value; In the negative half cycle of the industrial frequency: in each switching working cycle, when the maximum value of the inductor current represented by the first voltage signal is greater than the third set value, both the first pulse signal and the second pulse signal exist; when the maximum value of the inductor current represented by the first voltage signal is less than or equal to the first set value and greater than the fourth set value, the first pulse signal does not exist, and the second pulse signal exists; when the inductor current represented by the first voltage signal is always zero or the maximum value is less than the fourth set value, both the first pulse signal and the second pulse signal do not exist; the third set value is a positive value, and the third set value is greater than the fourth set value.

3. The control method according to claim 1, characterized in that: The identification execution step further includes: if the first pulse signal and the second pulse signal cannot be identified within the first time, opening the high-frequency main pipe at the end of the first time.

4. The control method according to claim 3, characterized in that: The first time is 1 / Fmin, where Fmin is the minimum switching frequency of the power factor correction circuit.

5. The control method according to claim 4, characterized in that: The Fmin is 25Khz.

6. The control method according to claim 1, characterized in that: After the high-frequency main tube is turned off, the high-frequency rectifier tube is turned on after a set dead time has passed.

7. The control method according to claim 6, characterized in that: The conduction time T of the high frequency rectifier tube off Determined by the following formula: T off =u*(V in ×T on ) / (V out - V in ); Where u is a constant, V in is the input voltage of the power factor correction circuit, V out is the output voltage of the power factor correction circuit, T on is the conduction time of the high frequency tube.

8. The control method according to claim 7, characterized in that: By controlling the conduction time T of the high frequency rectifier tube off The negative current of the boost inductor is controlled to achieve zero voltage switching of the high frequency main tube in the next switching cycle.

9. A control device, applied to a power factor correction circuit, wherein the power factor correction circuit comprises a boost inductor, a high-frequency main tube and a high-frequency rectifier tube; characterized in that: The control device is used to control the conduction of the high-frequency main pipe in the positive half cycle or the negative half cycle of the power factor correction circuit, and includes a module that performs the following functions: A current sampling module, used for sampling a first voltage signal representing the magnitude of the current flowing through the boost inductor; A comparison output module, used for comparing the first voltage signal with two different thresholds in a current power frequency half cycle to generate a first pulse signal and a second pulse signal in each switch working cycle; The identification execution module is used to identify whether the first pulse signal exists. If so, the first pulse signal is used as the trigger signal of the high-frequency main tube; otherwise, the second pulse signal is used as the trigger signal of the high-frequency main tube.

10. A switching power supply, comprising a power factor correction circuit, wherein the power factor correction circuit comprises a boost inductor, a high-frequency main tube and a high-frequency rectifier tube; characterized in that: The switching power supply further comprises the control device as claimed in claim 9.

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