Power converter, PFC (Power Factor Correction) controller and electronic equipment

Abstract

The invention provides a power converter, a PFC (Power Factor Correction) controller and electronic equipment, when the voltage of an intermediate direct-current power supply is smaller than a first threshold voltage, the PFC controller controls a PFC booster circuit to maintain the voltage on a direct-current bus at a first target PFC voltage by using the intermediate direct-current power supply; when the voltage of the intermediate direct-current power supply is greater than a second threshold voltage, the PFC controller controls the PFC booster circuit to stop working, and the charge pump PFC circuit maintains the voltage on the direct-current bus at a second target PFC voltage under the driving of the resonant current generated by the LLC resonant conversion circuit; when the voltage of the intermediate DC power supply changes from the voltage smaller than the first threshold voltage or larger than the second threshold voltage to the voltage maintaining range, the PFC controller maintains the control action of the PFC booster circuit unchanged before the change.

Description

Technical Field

[0001] The present invention relates to the field of power supplies, and particularly to a power converter, a PFC controller, and an electronic device. Background Art

[0002] A common type of power converter includes an input rectifier filter circuit, a PFC (Power Factor Correction) circuit, a conversion circuit, and an output rectifier circuit. The input rectifier filter circuit rectifies and filters the input AC power supply AC into an intermediate DC power supply. The conversion circuit converts the intermediate DC power supply into an intermediate AC power supply. The output rectifier circuit then rectifies the intermediate AC power supply into an output DC power supply for use by a DC load (such as an LED). The PFC circuit provides power factor correction for the power converter.

[0003] Currently common PFC circuits include a charge pump PFC circuit (as described in CN216414184U), and an active PFC circuit (or APFC circuit). When using a charge pump PFC circuit, the conversion circuit usually needs to adopt an LLC resonant conversion circuit to drive the charge pump PFC circuit, while an active PFC circuit generally adopts a boost conversion circuit.

[0004] As Figure 1 shown, it is a circuit diagram of a power converter using a charge pump PFC circuit 120, including an input rectifier filter circuit 110, a charge pump PFC circuit 120, an LLC resonant conversion circuit 130, and an output rectifier circuit 140. Among them, the primary side of the transformer T is a component of the LLC resonant conversion circuit 130, and the secondary side is coupled to the output rectifier circuit 140. The output of the charge pump PFC circuit 120 is coupled to the DC bus of the power converter. The resonant current generated by the operation of the LLC resonant conversion circuit 130 drives the charge pump PFC circuit 120 to operate, so that the DC bus voltage is maintained at a certain target PFC voltage (which can be a value or a value range) designed, and the output DC power supply Vo of the output rectifier circuit 140 is for use by a DC load (such as an LED).

[0005] As Figure 2As shown, it is a circuit diagram of a power converter adopting an active PFC circuit 150 and an LLC resonant conversion circuit 130, including an input rectifier and filter circuit 110, an active PFC circuit 150, an LLC resonant conversion circuit 130, and an output rectifier circuit 140. Among them, the active PFC circuit 150 includes a PFC controller and a PFC boost circuit 151. The output of the PFC boost circuit 151 is coupled to the DC bus of the power converter. The primary side of the transformer T is a component of the LLC resonant conversion circuit 130, and the secondary side is coupled to the output rectifier circuit 140. A target PFC voltage can be set in the PFC controller. The PFC controller detects the voltage of the DC bus, and the PFC controller maintains the DC bus voltage at the target PFC voltage by controlling the operation of the PFC boost circuit 151.

[0006] In actual product applications, a power converter adopting a charge pump PFC circuit needs to be applied in countries or regions where the effective value of the AC input voltage is above 200V. The reason is that the charge pump PFC circuit needs to cooperate with the LLC resonant conversion circuit to work. In the case of the common effective values of AC voltages worldwide (for example, 120V in the United States, 220V in China, 200 - 264V in Europe), the LLC resonant conversion circuit usually requires that the effective value of the AC input voltage should be above 200V. Otherwise, if the effective value is lower than 200V, in order to maintain the output DC voltage constant, the switching frequency in the LLC resonant conversion circuit needs to be reduced. This frequency is easily reduced below the critical point frequency, and the LLC resonant conversion circuit will enter the ZCS (zero current switching) working region, resulting in the problem that the switches in the LLC resonant conversion circuit cannot achieve ZVS (zero voltage switching), thus leading to problems such as increased losses and reduced efficiency in the LLC resonant conversion circuit. More seriously, it will also lead to problems such as instability of the LLC resonant conversion circuit loop. In short, the charge pump PFC circuit is restricted by the input voltage. For actual products, the power converter adopting this charge pump PFC circuit has a narrow application voltage range and can only be applied in countries or regions where the voltage is above 200V (such as Europe).

[0007] In contrast, an active PFC circuit can operate more stably within the effective value range of common AC voltages worldwide, with a relatively wide application voltage range. To operate as much as possible within the effective value range of common AC voltages worldwide (for example, taking into account the US standard market of 100 - 277 VAC and the European standard market with an input of 200 - 264 VAC), some existing power converters with active PFC circuits set the target output voltage of the active PFC circuit to 400 V or above. In this way, regardless of whether the power converter is applied to a country or region with a relatively small AC input voltage (effective value less than 200 V) or a relatively large AC input voltage (effective value above 200 V), the active PFC circuit can perform power factor correction, so that the power factor (PF) and harmonic distortion THD of the power converter can meet the relevant requirements of the corresponding country or region. Otherwise, if the target output voltage of the active PFC circuit is set to less than 400 V, when the power converter is applied to a region with a relatively large AC input voltage (effective value above 200 V), the duty cycle D of the BOOST circuit in the active PFC circuit decreases, resulting in the inability of the active PFC circuit to operate normally, and further leading to a significant reduction in the power factor (PF) and a deterioration of the harmonic distortion THD. However, when the target output voltage of the active PFC circuit is set to 400 V or above, when the power converter is applied to a region with a relatively small AC input voltage (effective value less than 200 V), the duty cycle D of the BOOST circuit in the active PFC circuit will be relatively large, resulting in an increase in the effective value of the current in the BOOST circuit, further increasing the losses of the inductor and MOS (or other switching transistors) in the BOOST circuit, with low power conversion efficiency. In addition, to accommodate the relatively large current in the BOOST circuit, MOS and inductors with a relatively large rated current (larger volume) need to be used, further leading to an increase in cost. Summary of the Invention

[0008] In view of the above situation, the applicant has filed an invention application. In this invention application, both an active PFC circuit and a charge pump PFC circuit are used in the power converter. When the intermediate DC power supply voltage detected by the PFC controller is less than the threshold voltage, the PFC boost circuit is controlled to operate, and the charge pump PFC circuit "operates incidentally". When the intermediate DC power supply voltage detected by the PFC controller is greater than the threshold voltage, the PFC boost circuit is controlled to stop operating, and the charge pump PFC circuit is controlled to operate. In this way, the power converter can not only be applied under different common AC voltage effective values in various regions of the world currently, but also can perform power factor correction relatively efficiently.

[0009] However, in the above invention application, when the AC voltage of the AC power supply fluctuates frequently, it may cause the power converter to frequently control the PFC boost circuit to switch between working and stopping, thus bringing many problems, such as unstable DC bus voltage and the like.

[0010] Based on the current situation of the above invention application, the main object of the present invention is to provide a power converter, a PFC controller, a circuit board, an adapter and an electronic device, so that they can work with high efficiency and low cost on the premise that they can work within the range of the effective value of the common AC voltage in the current world.

[0011] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0012] A power converter includes an input rectifier filter circuit, an active PFC circuit, an LLC resonant conversion circuit and an output rectifier filter circuit. The active PFC circuit includes a PFC controller and a PFC boost circuit. The input rectifier filter circuit rectifies and filters the AC power supply to form an intermediate DC power supply. The power converter further includes a charge pump PFC circuit. The charge pump PFC circuit and the active PFC circuit are both coupled to the output terminal of the input rectifier filter circuit, the DC bus and the LLC resonant conversion circuit. The PFC controller detects the voltage magnitude of the intermediate DC power supply.

[0013] When the voltage of the intermediate DC power supply is less than the first threshold voltage, the PFC controller controls the PFC boost circuit to maintain the voltage on the DC bus at the first target PFC voltage by using the intermediate DC power supply.

[0014] When the voltage of the intermediate DC power supply is greater than the second threshold voltage, the PFC controller controls the PFC boost circuit to stop working, and the charge pump PFC circuit maintains the voltage on the DC bus at the second target PFC voltage under the drive of the resonant current generated by the LLC resonant conversion circuit.

[0015] When the voltage of the intermediate DC power supply changes from a voltage less than the first threshold voltage or greater than the second threshold voltage to the voltage maintenance range, the PFC controller maintains the control action on the PFC boost circuit before the change unchanged.

[0016] Wherein, the second target PFC voltage, the first target PFC voltage, the second threshold voltage and the first threshold voltage decrease in sequence, and the voltage maintenance range is the range from the first threshold voltage to the second threshold voltage.

[0017] When the voltage of the intermediate DC power supply is less than the first threshold voltage, the LLC resonant conversion circuit converts the voltage on the DC bus into an intermediate AC power supply, the output rectifier and filter circuit rectifies and filters the intermediate AC power supply into an output DC power supply for the DC load, and the charge pump PFC circuit can charge the DC bus under the drive of the resonant current generated by the LLC resonant conversion circuit.

[0018] When the voltage of the intermediate DC power supply is greater than the second threshold voltage, the LLC resonant conversion circuit converts the voltage on the DC bus into an intermediate AC power supply, the output rectifier and filter circuit rectifies and filters the intermediate AC power supply into an output DC power supply for the DC load, and the charge pump PFC circuit maintains the voltage on the DC bus at the second target PFC voltage under the drive of the resonant current generated by the LLC resonant conversion circuit.

[0019] Preferably, the power converter further includes a first diode, the anode of the first diode is coupled to the output terminal of the input rectifier and filter circuit, and the cathode is coupled to the DC bus.

[0020] Preferably, the charge pump PFC circuit includes a second diode, a third diode and a pump capacitor; the LLC resonant conversion circuit includes a half-bridge switch arm and a resonant element; the positive and negative terminals of the half-bridge switch arm are respectively coupled to the DC bus and the ground; the anode of the second diode is coupled to the output terminal of the input rectifier and filter circuit, and the cathode is coupled to the anode of the third diode; the cathode of the third diode is coupled to the DC bus; the common terminal of the second diode and the third diode is grounded through the pump capacitor and connected to the midpoint of the half-bridge switch arm through the resonant element.

[0021] Preferably, the charge pump PFC circuit includes a second diode, a third diode, a fourth diode, a fifth diode and a pump capacitor; the LLC resonant conversion circuit includes a half-bridge switch arm, a resonant inductor, a first resonant capacitor and a second resonant capacitor; the positive and negative terminals of the half-bridge switch arm are respectively coupled to the DC bus and the ground; the anode of the second diode is coupled to the output terminal of the input rectifier and filter circuit, and the cathode is coupled to the anode of the third diode; the cathode of the third diode is coupled to the DC bus; the common terminal of the second diode and the third diode is grounded through the pump capacitor and connected to the midpoint of the half-bridge switch arm through the first resonant capacitor and the resonant inductor; the anode of the fourth diode is coupled to the output terminal of the input rectifier and filter circuit, and the cathode is coupled to the anode of the fifth diode; the cathode of the fifth diode is coupled to the DC bus; the common terminal of the fourth diode and the fifth diode is connected to the midpoint of the half-bridge switch arm through the second resonant capacitor and the resonant inductor.

[0022] Preferably, the first target PFC voltage is greater than or equal to 250V and less than or equal to 270V.

[0023] The present invention also provides a PFC controller for a power converter. The power converter includes an input rectifier and filter circuit, an active PFC circuit, an LLC resonant conversion circuit, and an output rectifier and filter circuit. The active PFC circuit includes a PFC boost circuit and the PFC controller. The input rectifier and filter circuit rectifies and filters an AC power supply to form an intermediate DC power supply. The power converter further includes a charge pump PFC circuit. The charge pump PFC circuit and the active PFC circuit are both coupled to the output terminal of the input rectifier and filter circuit, the DC bus, and the LLC resonant conversion circuit. The PFC controller detects the magnitude of the voltage of the intermediate DC power supply.

[0024] When the voltage of the intermediate DC power supply is less than a first threshold voltage, the PFC controller controls the PFC boost circuit to maintain the voltage on the DC bus at the first target PFC voltage using the intermediate DC power supply.

[0025] When the voltage of the intermediate DC power supply is greater than a second threshold voltage, the PFC controller controls the PFC boost circuit to stop working, and the charge pump PFC circuit maintains the voltage on the DC bus at a second target PFC voltage under the drive of the resonant current generated by the LLC resonant conversion circuit.

[0026] When the voltage of the intermediate DC power supply changes from a voltage less than the first threshold voltage or greater than the second threshold voltage to a voltage maintenance range, the PFC controller maintains the control action on the PFC boost circuit before the change unchanged.

[0027] Wherein, the second target PFC voltage, the first target PFC voltage, the second threshold voltage, and the first threshold voltage decrease in sequence, and the voltage maintenance range is the range from the first threshold voltage to the second threshold voltage.

[0028] When the voltage of the intermediate DC power supply is less than the first threshold voltage, the LLC resonant conversion circuit converts the voltage on the DC bus into an intermediate AC power supply, and the output rectifier and filter circuit rectifies and filters the intermediate AC power supply into an output DC power supply for use by a DC load. The charge pump PFC circuit can charge the DC bus under the drive of the resonant current generated by the LLC resonant conversion circuit.

[0029] When the voltage of the intermediate DC power supply is greater than the second threshold voltage, the LLC resonant conversion circuit converts the voltage on the DC bus into an intermediate AC power supply, and the output rectifier and filter circuit rectifies and filters the intermediate AC power supply into an output DC power supply for use by the DC load.

[0030] Preferably, the power converter further includes a first diode, an anode of the first diode is coupled to an output terminal of the input rectifier and filter circuit, and a cathode of the first diode is coupled to the DC bus.

[0031] Preferably, the charge pump PFC circuit includes a second diode, a third diode, and a pump capacitor; the LLC resonant conversion circuit includes a half-bridge switch arm and a resonant element; a positive terminal and a negative terminal of the half-bridge switch arm are respectively coupled to the DC bus and ground; an anode of the second diode is coupled to the output terminal of the input rectifier and filter circuit, and a cathode of the second diode is coupled to an anode of the third diode; a cathode of the third diode is coupled to the DC bus; a common terminal of the second diode and the third diode is grounded through the pump capacitor and is connected to a midpoint of the half-bridge switch arm through the resonant element.

[0032] Preferably, the charge pump PFC circuit includes a second diode, a third diode, a fourth diode, a fifth diode, and a pump capacitor; the LLC resonant conversion circuit includes a half-bridge switch arm, a resonant inductor, a first resonant capacitor, and a second resonant capacitor; a positive terminal and a negative terminal of the half-bridge switch arm are respectively coupled to the DC bus and ground; an anode of the second diode is coupled to the output terminal of the input rectifier and filter circuit, and a cathode of the second diode is coupled to an anode of the third diode; a cathode of the third diode is coupled to the DC bus; a common terminal of the second diode and the third diode is grounded through the pump capacitor and is connected to a midpoint of the half-bridge switch arm through the first resonant capacitor and the resonant inductor; an anode of the fourth diode is coupled to the output terminal of the input rectifier and filter circuit, and a cathode of the fourth diode is coupled to an anode of the fifth diode; a cathode of the fifth diode is coupled to the DC bus; a common terminal of the fourth diode and the fifth diode is connected to the midpoint of the half-bridge switch arm through the second resonant capacitor and the resonant inductor.

[0033] Preferably, the first target PFC voltage is greater than or equal to 250V and less than or equal to 270V.

[0034] The present invention also provides a circuit board, including any one of the above-mentioned power converters.

[0035] The present invention also provides an LED adapter, including any one of the above-mentioned power converters.

[0036] The present invention also provides an electronic device, including any one of the above-mentioned power converters.

[0037] In the above solution, two different PFC circuits, namely an active PFC circuit and a charge pump PFC circuit, are provided in the power converter. The conversion circuit is selected as an LLC resonant conversion circuit that is applicable to both the active PFC circuit and the charge pump PFC circuit. Moreover, the PFC controller in the active PFC circuit coordinately controls the PFC boost circuit and the charge pump PFC circuit in the active PFC circuit. When the intermediate DC power supply voltage detected by the PFC controller is less than the first threshold voltage (indicating that the power converter is applied in an area with a relatively small effective value of the AC voltage at this time), it controls the PFC boost circuit to maintain the voltage VB on the DC bus at the first target PFC voltage, and the charge pump PFC circuit operates "incidentally". It can be seen that when applied in an area with a relatively small effective value of the AC voltage, the power converter of the present invention can perform power factor correction through the PFC boost circuit of the active PFC circuit that can work stably and relatively efficiently when the effective value of the AC voltage is small. When the intermediate DC power supply voltage detected by the PFC controller is greater than the second threshold voltage (indicating that the power converter is applied in an area with a relatively large effective value of the AC voltage at this time), it controls the PFC boost circuit to stop working and controls the charge pump PFC circuit to work. It can be seen that when applied in an area with a relatively large effective value of the AC voltage, the power converter of the present invention can perform power factor correction through the charge pump PFC that can work relatively efficiently when the effective value of the AC voltage is large. In this way, the power converter of the present invention can not only be applied under different common effective values of AC voltages in various different regions of the world at present, but also can perform power factor correction relatively efficiently.

[0038] When the current voltage of the detected intermediate DC power supply changes from a voltage less than the first threshold voltage or greater than the second threshold voltage to this maintained voltage range, the PFC controller maintains the previous control action on the PFC boost circuit (that is, before the current voltage change). In this way, compared with only using one threshold voltage (when the current voltage is less than the threshold voltage, the PFC boost circuit is controlled to work, and when the current voltage is greater than the threshold voltage, the PFC boost circuit is controlled to stop working), the solution of the present invention can avoid many problems (such as unstable DC bus voltage, etc.) caused by the fluctuation of the voltage of the intermediate DC power supply due to the fluctuation of the AC power supply AC voltage, and further cause the PFC controller to frequently control the PFC boost circuit to switch between working and stopping.

[0039] Other beneficial effects of the present invention will be described by introducing specific technical features and technical solutions in the specific implementation manner. Those skilled in the art should be able to understand the beneficial technical effects brought by the described technical features and technical solutions through these introductions. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. In the drawings:

[0041] Figure 1 is a circuit diagram of a power converter using a charge pump PFC circuit in the prior art;

[0042] Figure 2 is a circuit diagram of a power converter using an active PFC circuit and an LLC resonant conversion circuit in the prior art;

[0043] Figure 3 is a power converter according to a preferred embodiment of the present invention;

[0044] Figure 4 is a power converter according to another preferred embodiment of the present invention;

[0045] Figure 5 is a power converter according to another preferred embodiment of the present invention. Detailed Embodiment

[0046] The present invention will be described below based on embodiments, but the present invention is not limited to these embodiments. In the following detailed description of the present invention, some specific details are described in detail. In order to avoid obscuring the essence of the present invention, well-known methods, processes, procedures, and components are not described in detail.

[0047] In addition, those of ordinary skill in the art should understand that the drawings provided herein are for illustrative purposes only, and the drawings are not necessarily drawn to scale.

[0048] Unless the context clearly requires otherwise, the words "including", "comprising", and the like in the entire specification and claims should be construed in an inclusive sense rather than an exclusive or exhaustive sense; that is, the meaning of "including but not limited to".

[0049] In the description of the present invention, it should be understood that the terms "first", "second", etc. are only used for descriptive purposes and cannot be construed as indicating or implying relative importance. In addition, in the description of the present invention, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0050] As Figure 3 shown, is a power converter according to an embodiment of the present invention, including an input rectifier filter circuit 110, an active PFC circuit 150, a charge pump PFC circuit 120, a DC bus, an LLC resonant conversion circuit 130, and an output rectifier filter circuit 140. A bus capacitor with a relatively large capacity (such as a common electrolytic capacitor) is provided on the DC bus. The active PFC circuit 150 includes a PFC controller 152 and a PFC boost circuit 151.

[0051] The input rectifier and filter circuit 110 rectifies and filters the AC power supply AC to form an intermediate DC power supply, that is, the output terminal of the input rectifier and filter circuit 110 outputs this intermediate DC power supply. The magnitude of the voltage of the intermediate DC power supply reflects the magnitude of the effective value of the AC power supply AC. The larger the effective value of the AC power supply AC, the larger the voltage of this intermediate DC power supply; conversely, the smaller the effective value of the AC power supply AC, the smaller the voltage of this intermediate DC power supply. As an example, the magnitude of the voltage of the intermediate DC power supply is approximately equal to 1.4 times the effective value of the AC power supply AC. The input rectifier and filter circuit 110 includes a rectifier bridge B and a capacitor C1. The capacitor C1 is connected across the two output terminals of the rectifier bridge B. The two input terminals of the rectifier bridge are respectively coupled to the AC power supply AC, for example, through a filter, an overcurrent protection device (such as a fuse, etc.) and connected to the AC power supply AC.

[0052] The charge pump PFC circuit 120 and the active PFC circuit 150 are both coupled to the output terminal of the input rectifier and filter circuit 110, the DC bus, and the LLC resonant conversion circuit 130.

[0053] The PFC controller 152 detects the current voltage magnitude of the intermediate DC power supply output by the input rectifier and filter circuit 110. The PFC controller 152 compares it with the magnitude of a first threshold voltage (such as 200V, 210V, 220V, 230V, 240V) and a second threshold voltage (the second threshold voltage is greater than the first threshold voltage, for example, the second threshold voltage = the first threshold voltage + △V, where △V can be 7V, 8V, 9V, 10V, 11V, or 12V, etc.). According to the different comparison results, the PFC controller 152 makes different controls on the PFC boost circuit 151, so as to coordinately control the operation of the PFC boost circuit 151 of the active PFC circuit 150 and the charge pump PFC circuit 120 under corresponding conditions to play the role of power factor correction.

[0054] When the current voltage of the detected intermediate DC power supply is less than the first threshold voltage, the PFC controller 152 also detects the voltage VB on the DC bus and controls the operation of the PFC boost circuit 151, that is, controls the PFC boost circuit 151 to maintain the voltage VB on the DC bus at the first target PFC voltage (which can be a numerical value or a numerical range, such as 250V, 260V, 270V, 280V, 300V, 320V, or 250V - 260V, or 260V - 270V, or 270V - 280V, etc.). The LLC resonant conversion circuit 130 converts the voltage VB on the DC bus into an intermediate AC power supply, and the output rectification and filtering circuit 140 rectifies and filters the intermediate AC power supply into an output DC power supply for the DC load. The LLC resonant conversion circuit 130 generates a resonant current during the above process. The charge pump PFC circuit 120 can charge the bus capacitor on the DC bus under the drive of the resonant current generated by the LLC resonant conversion circuit 130. However, during this process, the voltage VB on the DC bus is maintained at the first target PFC voltage independently of the operation of the charge pump PFC circuit 120. On the contrary, it is precisely because the PFC boost circuit 151 maintains the voltage VB on the DC bus at the first target PFC voltage that the circuit operates stably, and then the charge pump PFC circuit 120 can operate stably "incidentally". Moreover, the stable operation of the charge pump PFC circuit 120 "incidentally" does not affect the normal operation of the PFC boost circuit 151. Therefore, there is no need to add an additional control circuit to turn off the charge pump PFC circuit 120 during this process, thus simplifying the circuit design. It can be seen that in this case, the PFC boost circuit 151 in the active PFC circuit 150 plays the role of maintaining the voltage VB on the DC bus at the first target PFC voltage, and the charge pump PFC circuit 120 only operates "incidentally".

[0055] When the current voltage of the detected intermediate DC power supply is greater than the second threshold voltage, the PFC controller 152 controls the PFC boost circuit 151 to stop working. At this time, the PFC controller 152 may no longer detect the voltage VB on the DC bus. The LLC resonant conversion circuit 130 converts the voltage VB on the DC bus into an intermediate AC power supply, and the output rectification and filtering circuit 140 rectifies and filters the intermediate AC power supply into an output DC power supply for the DC load. The LLC resonant conversion circuit 130 generates a resonant current during the above process. The charge pump PFC circuit 120 maintains the voltage VB on the DC bus at the second target PFC voltage (which can be a value or a value range) driven by the resonant current generated by the LLC resonant conversion circuit 130. Among them, the values of the second target PFC voltage, the first target PFC voltage, the second threshold voltage, and the first threshold voltage decrease in sequence. The second target PFC voltage can be 380V, 390V, or 400V, or 380V - 390V, or 390V - 400V, etc. It can be seen that in this case, only the charge pump PFC circuit 120 works for power factor correction, and the PFC boost circuit 151 in the active PFC circuit 150 stops working.

[0056] The range from the first threshold voltage to the second threshold voltage is called the maintenance voltage range (that is, the maintenance voltage range is the range from the first threshold voltage to the second threshold voltage). When the current voltage of the detected intermediate DC power supply changes from a voltage less than the first threshold voltage or greater than the second threshold voltage to this maintenance voltage range, the PFC controller 152 maintains the previous control action on the PFC boost circuit 151 unchanged; for example, if the previously detected current voltage of the intermediate DC power supply is less than the first threshold voltage, so the PFC controller 152 controls the PFC boost circuit 151 to work, and if the current voltage changes from less than the first threshold voltage to this maintenance voltage range, the PFC controller 152 maintains the control of the PFC boost circuit 151 to work unchanged; another example is that if the previously detected current voltage of the intermediate DC power supply is greater than the second threshold voltage, so the PFC controller 152 controls the PFC boost circuit 151 to stop working, and if the current voltage changes from greater than the second threshold voltage to this maintenance voltage range, the PFC controller 152 maintains the control of the PFC boost circuit 151 to stop working unchanged.

[0057] In this embodiment, two different PFC circuits, namely an active PFC circuit 150 and a charge pump PFC circuit 120, are provided in the power converter. The conversion circuit is selected as an LLC resonant conversion circuit that is applicable to both the active PFC circuit and the charge pump PFC circuit. Moreover, the PFC controller 152 in the active PFC circuit 150 coordinately controls the PFC boost circuit 151 in the active PFC circuit 150 and the charge pump PFC circuit 120 to operate. When the intermediate DC power supply voltage detected by the PFC controller 152 is less than the first threshold voltage (indicating that the power converter is applied in an area with a relatively small effective value of the AC voltage at this time), it controls the PFC boost circuit 151 to maintain the voltage VB on the DC bus at the first target PFC voltage, and the charge pump PFC circuit 120 operates "incidentally". It can be seen that when applied in an area with a relatively small effective value of the AC voltage, the power converter of the present invention can perform power factor correction through the PFC boost circuit 151 of the active PFC circuit 150 that can work stably and relatively efficiently when the effective value of the AC voltage is small; when the intermediate DC power supply voltage detected by the PFC controller 152 is greater than the second threshold voltage (indicating that the power converter is applied in an area with a relatively large effective value of the AC voltage at this time), it controls the PFC boost circuit 151 to stop operating and controls the charge pump PFC circuit 120 to operate. It can be seen that when applied in an area with a relatively large effective value of the AC voltage, the power converter of the present invention can perform power factor correction through the charge pump PFC that can work relatively efficiently when the effective value of the AC voltage is large. In this way, the power converter of the present invention can not only be applied under different common effective values of AC voltages in various different regions of the world at present, but also can perform power factor correction relatively efficiently.

[0058] When the currently detected voltage of the intermediate DC power supply changes from a voltage less than the first threshold voltage or greater than the second threshold voltage to this maintained voltage range, the PFC controller 152 maintains the control action on the PFC boost circuit 151 before (i.e., before the current voltage change). In this way, compared with using only one threshold voltage (controlling the PFC boost circuit 151 to operate when the current voltage is less than the threshold voltage and controlling the PFC boost circuit 151 to stop operating when the current voltage is greater than the threshold voltage), the solution of the present invention can avoid many problems (such as unstable DC bus voltage, etc.) caused by the fluctuation of the voltage of the intermediate DC power supply due to the fluctuation of the AC power supply AC voltage, and further cause the PFC controller 152 to frequently control the PFC boost circuit 151 to switch between operating and stopping.

[0059] Since the PFC boost circuit 151 of the active PFC circuit 150 only operates in regions where the effective value of the AC voltage is relatively small, the rated power and volume of the switches and inductors in the PFC boost circuit 151 do not need to be larger, resulting in lower costs. Additionally, the diodes and capacitors typically used in the charge pump PFC circuit 120 provided in the power converter have relatively small volumes and costs. Therefore, overall, it does not impose more costs on the power converter.

[0060] Furthermore, the PFC controller 152 detects the magnitude of the DC power supply voltage from the output terminal of the input rectifier filter circuit 110 as a basis for determining the effective value of the AC power supply AC, rather than directly detecting the effective value of the AC power supply AC on the input side of the input rectifier filter circuit 110. This makes full use of the rectification and filtering functions of the input rectifier filter circuit 110 and simplifies the detection circuit while achieving the detection purpose.

[0061] As Figure 4 shown, a power converter according to another embodiment of the present invention further includes a first diode D1. The anode of the first diode D1 is coupled to the output terminal of the input rectifier filter circuit 110, and the cathode is coupled to the DC bus. When the power converter is applied in a region where the effective value of the AC voltage is relatively small, at the moment of power-on of the power converter, the output terminal of the input rectifier filter circuit 110 can quickly charge the bus capacitor C2 to the same voltage as the output voltage of the input rectifier filter circuit 110 via the first diode D1. As a result, the PFC boost circuit 151 of the active PFC circuit 150 can perform boosting on the basis of the output voltage of the input rectifier filter circuit 110 until the first target PFC voltage. Therefore, the response speed of the PFC boost circuit 151 of the active PFC circuit 150 can be improved. When the power converter is applied in a region where the effective value of the AC voltage is relatively large, at the moment of power-on of the power converter, the output terminal of the input rectifier filter circuit 110 can also quickly charge the bus capacitor C2 to the same voltage as the output voltage of the input rectifier filter circuit 110 via the first diode D1. As a result, the charge pump PFC circuit 120 can perform boosting on the basis of the output voltage of the input rectifier filter circuit 110 until the second target PFC voltage. Therefore, the response speed of the charge pump PFC circuit 120 can also be improved. It can be seen that the setting of the first diode D1 realizes the promotion effect on the PFC boost circuit 151 of the active PFC circuit 150 and the charge pump PFC circuit 120.

[0062] As Figure 4As shown, the charge pump PFC circuit 120 includes a second diode D2, a third diode D3, and a pump capacitor C3; the LLC resonant conversion circuit 130 includes a half-bridge switch arm (formed by switching transistors Q2 and Q3), a controller 131, and resonant elements; the positive and negative terminals of the half-bridge switch arm are respectively coupled to the DC bus and ground; the anode of the second diode D2 is coupled to the output terminal of the input rectifier and filter circuit 110, and the cathode is coupled to the anode of the third diode D3; the cathode of the third diode D3 is coupled to the DC bus; the common terminal of the second diode D2 and the third diode D3 is grounded through the pump capacitor C3 and is connected to the midpoint of the half-bridge switch arm, that is, the common terminal of the switching transistors Q2 and Q3, and the controller 131 controls the conduction and cutoff of the switching transistors Q2 and Q3. Among them, the resonant elements include a resonant inductor L2 and a resonant capacitor C4, Figure 4 The shown series LLC resonant conversion circuit 130, in which the resonant inductor L2 and the resonant capacitor C4 are in series. As long as a series LLC is formed, the positions among the resonant inductor L2, the resonant capacitor C4, and the primary side of the transformer T can be adjusted. The resonant inductor L2 can adopt an inductor device independent of the transformer T, or a leakage inductance can be designed in the transformer T to form an equivalent resonant inductor L2. At this time, there is no physical such resonant inductor L2 in this power converter. The controller 131 controls the conduction and cutoff of the switching transistors Q2 and Q3. Cooperating with the above-mentioned resonant elements, the LLC resonant conversion circuit 130 can generate a resonant current, and further can drive the charge pump PFC circuit 120 to work. In this embodiment, there is only one resonant loop.

[0063] The following is for Figure 4A brief description of the operation process of the charge pump PFC circuit 120 shown is as follows. (1) Stage 1: When both the switching transistors Q2 and Q3 are turned off (the stage before Q2 is about to conduct), the current path is: resonant inductor L2 - body diode of switching transistor Q2 - bus capacitor C2 - capacitor C1 - second diode D2 - resonant capacitor C4 - primary side of transformer T - resonant inductor L2. During this process, the resonant current charges the bus capacitor C2. (2) Stage 2: When switching transistor Q2 is conducting and switching transistor Q3 is turned off, the current path is: bus capacitor C2 - switching transistor Q2 - resonant inductor L2 - primary side of transformer T - resonant capacitor C4 - pump capacitor C3 - bus capacitor C2. During this process, the bus capacitor C2 discharges. (3) Stage 3: Switching transistor Q2 continues to conduct and switching transistor Q3 continues to be turned off. The current path is: resonant capacitor C4 - third diode D3 - switching transistor Q2 - resonant inductor L2 - primary side of transformer T - resonant capacitor C4. (4) Stage 4: When both the switching transistors Q2 and Q3 are turned off (the stage before Q3 is about to conduct), the current path is: resonant inductor L2 - primary side of transformer T - resonant capacitor C4 - third diode D3 - bus capacitor C2 - body diode of switching transistor Q3 - resonant inductor L2. During this process, the resonant current charges the bus capacitor C2. (5) Stage 5: When switching transistor Q3 is conducting and switching transistor Q2 is turned off, the current path is: pump capacitor C3 - resonant capacitor C4 - primary side of transformer T - resonant inductor L2 - switching transistor Q3 - pump capacitor C3. (6) Stage 6: Switching transistor Q3 continues to conduct and switching transistor Q2 continues to be turned off. The current path is: capacitor C1 - second diode D2 - resonant capacitor C4 - primary side of transformer T - resonant inductor L2 - switching transistor Q3 - capacitor C1.

[0064] The active PFC circuit 150 includes a PFC controller 152 and a PFC boost circuit 151. Among them, the PFC boost circuit 151 includes a boost inductor L1, a boost diode D0, and a boost switch Q1. The anode of the boost diode D0 is coupled to the output terminal of the input rectifier and filter circuit 110 through the boost inductor L1. The cathode of the boost diode D0 is coupled to the DC bus. The common terminal of the boost inductor L1 and the boost diode D0 is grounded through the boost switch Q1. One voltage detection terminal of the PFC controller 152 is connected to the output terminal of the input rectifier and filter circuit 110 to detect the voltage of the intermediate DC power supply, and the other voltage detection terminal is connected to the DC bus to detect the voltage of the DC bus. The control terminal of the PFC controller 152 is connected to the control terminal of the boost switch Q1.

[0065] As Figure 5 shown, it is a power converter according to another embodiment of the present invention. In this power converter, the same Figure 4Different charge pump PFC circuits (with an additional fourth diode D4 and fifth diode D5 compared to Figure 4 's charge pump PFC circuit) and LLC resonant conversion circuits (with an additional second resonant capacitor C5 compared to Figure 4 's LLC resonant conversion circuit, for convenience of description).

[0066] The charge pump PFC circuit includes a second diode D2, a third diode D3, a fourth diode D4, a fifth diode D5, and a pump capacitor C3; the LLC resonant conversion circuit includes a half - bridge switch arm (including switching transistors Q2 and Q3), a resonant inductor L2, a first resonant capacitor C4, and a second resonant capacitor C5; the positive and negative terminals of the half - bridge switch arm are respectively coupled to the DC bus and ground; the anode of the second diode D2 is coupled to the output terminal of the input rectifier and filter circuit, and the cathode is coupled to the anode of the third diode D3; the cathode of the third diode D3 is coupled to the DC bus; the common terminal of the second diode D2 and the third diode D3 is grounded through the pump capacitor C3 and is connected to the mid - point of the half - bridge switch arm (the common terminal of the switching transistors Q2 and Q3) through the first resonant capacitor C4 and the resonant inductor L2; the anode of the fourth diode D4 is coupled to the output terminal of the input rectifier and filter circuit, and the cathode is coupled to the anode of the fifth diode D5; the cathode of the fifth diode D5 is coupled to the DC bus; the common terminal of the fourth diode D4 and the fifth diode D5 is connected to the mid - point of the half - bridge switch arm through the second resonant capacitor C5 and the resonant inductor L2.

[0067] The following is a description of Figure 5A brief description of the operation process of the charge pump PFC circuit 120 shown is as follows. (1) Stage 1: When both the switching transistors Q2 and Q3 are turned off (the stage before Q2 is about to conduct), there are two current paths. One path is: resonant inductor L2 - body diode of switching transistor Q2 - bus capacitor C2 - capacitor C1 - second diode D2 - first resonant capacitor C4 - primary side of transformer T - resonant inductor L2. The other path is: resonant inductor L2 - body diode of switching transistor Q2 - bus capacitor C2 - capacitor C1 - fourth diode D4 - second resonant capacitor C5 - primary side of transformer T - resonant inductor L2. During this process, the resonant current charges the bus capacitor C2. (2) Stage 2: When Q2 is conducting and Q3 is turned off, there are two current paths. One path is: bus capacitor C2 - switching transistor Q2 - resonant inductor L2 - primary side of transformer T - first resonant capacitor C4 - pump capacitor C3 - bus capacitor C2. The other path is: switching transistor Q2 - resonant inductor L2 - primary side of transformer T - second resonant capacitor C5 - fifth diode D5 - switching transistor Q2. During this process, the bus capacitor C2 discharges. (3) Stage 3: Q2 continues to conduct and Q3 continues to be turned off. There are two current paths. One path is: first resonant capacitor C4 - third diode D3 - switching transistor Q2 - resonant inductor L2 - primary side of transformer T - first resonant capacitor C4. The other path is: second resonant capacitor C5 - fifth diode D5 - switching transistor Q2 - resonant inductor L2 - primary side of transformer T - second resonant capacitor C5. (4) Stage 4: When both Q2 and Q3 are turned off (the stage before Q3 is about to conduct), there are two current paths. One path is: resonant inductor L2 - primary side of transformer T - first resonant capacitor C4 - third diode D3 - bus capacitor C2 - body diode of switching transistor Q3 - resonant inductor L2. The other path is: resonant inductor L2 - primary side of transformer T - second resonant capacitor C5 - fifth diode D5 - bus capacitor C2 - body diode of switching transistor Q3 - resonant inductor L2. During this process, the resonant current charges the bus capacitor C2. (5) Stage 5: When Q3 is conducting and Q2 is turned off, there are two current paths. One path is: pump capacitor C3 - first resonant capacitor C4 - primary side of transformer T - resonant inductor L2 - switching transistor Q3 - pump capacitor C3. The other path is: capacitor C1 - fourth diode D4 - second resonant capacitor C5 - primary side of transformer T - resonant inductor L2 - switching transistor Q3 - capacitor C1;(6) Stage 6: The switching transistor Q3 continues to conduct, and the switching transistor Q2 continues to be off. There are two current paths. One path is: capacitor C1 - second diode D2 - first resonant capacitor C4 - primary side of transformer T - resonant inductor L2 - switching transistor Q3 - capacitor C1. The other path is: capacitor C1 - fourth diode D4 - second resonant capacitor C5 - primary side of transformer T - resonant inductor L2 - switching transistor Q3 - capacitor C1.;

[0068] The present invention also provides a circuit board, including any one of the power converters, and this circuit board can be assembled on any component or device that can provide an output DC power supply for a DC load (such as an LED).

[0069] The present invention also provides an LED adapter, including any one of the power converters. The LED adapter may include a housing, and the above-mentioned power converter is disposed within the housing to provide a DC power supply for the LED as a DC load.

[0070] The present invention also provides an electronic device, including any one of the power converters. The electronic device may further include a DC load (such as an LED), and the power converter provides an output DC power supply for the DC load.

[0071] Those skilled in the art can understand that, on the premise of no conflict, the above preferred solutions can be freely combined and superimposed.

[0072] It should be understood that the above embodiments are merely exemplary and not restrictive. Without departing from the basic principles of the present invention, various obvious or equivalent modifications or substitutions made by those skilled in the art to the above details will all be included within the scope of the claims of the present invention.

Claims

1. A power converter, comprising an input rectifier and filter circuit, an active PFC circuit, an LLC resonant conversion circuit, and an output rectifier and filter circuit. The active PFC circuit includes a PFC controller and a PFC boost circuit. The input rectifier and filter circuit rectifies and filters an AC power supply to form an intermediate DC power supply, characterized in that, The power converter further includes a charge pump PFC circuit; both the charge pump PFC circuit and the active PFC circuit are coupled to the output terminal of the input rectifier filter circuit, the DC bus, and the LLC resonant conversion circuit; the PFC controller detects the voltage magnitude of the intermediate DC power supply, when the voltage of the intermediate DC power supply is less than the first threshold voltage, the PFC controller controls the PFC boost circuit to maintain the voltage on the DC bus at the first target PFC voltage by using the intermediate DC power supply; when the voltage of the intermediate DC power supply is greater than the second threshold voltage, the PFC controller controls the PFC boost circuit to stop working, and the charge pump PFC circuit maintains the voltage on the DC bus at the second target PFC voltage under the drive of the resonant current generated by the LLC resonant conversion circuit; when the voltage of the intermediate DC power supply changes from a voltage less than the first threshold voltage or greater than the second threshold voltage to the voltage maintenance range, the PFC controller maintains the control action on the PFC boost circuit before the change unchanged; wherein, the second target PFC voltage, the first target PFC voltage, the second threshold voltage, and the first threshold voltage decrease in sequence, and the voltage maintenance range is the range from the first threshold voltage to the second threshold voltage.

2. The power converter according to claim 1, wherein when the voltage of the intermediate DC power supply is less than the first threshold voltage, the charge pump PFC circuit can charge the DC bus under the drive of the resonant current generated by the LLC resonant conversion circuit.

3. The power converter according to claim 1, wherein it further includes a first diode, the anode of the first diode is coupled to the output terminal of the input rectifier filter circuit, and the cathode is coupled to the DC bus.

4. The power converter according to any one of claims 1 to 3, wherein the charge pump PFC circuit includes a second diode, a third diode, and a pump capacitor; the LLC resonant conversion circuit includes a half-bridge switch arm and a resonant element; the positive terminal and the negative terminal of the half-bridge switch arm are respectively coupled to the DC bus and the ground; the anode of the second diode is coupled to the output terminal of the input rectifier filter circuit, and the cathode is coupled to the anode of the third diode; the cathode of the third diode is coupled to the DC bus; the common terminal of the second diode and the third diode is grounded through the pump capacitor and is connected to the midpoint of the half-bridge switch arm through the resonant element.

5. The power converter according to any one of claims 1 to 3, wherein the charge pump PFC circuit includes a second diode, a third diode, a fourth diode, a fifth diode, and a pump capacitor; the LLC resonant conversion circuit includes a half-bridge switch arm, a resonant inductor, a first resonant capacitor, and a second resonant capacitor; the positive terminal and the negative terminal of the half-bridge switch arm are respectively coupled to the DC bus and the ground; The anode of the second diode is coupled to the output terminal of the input rectifier and filter circuit, and the cathode is coupled to the anode of the third diode; the cathode of the third diode is coupled to the DC bus; The common terminal of the second diode and the third diode is grounded through the pumping capacitor, and is connected to the midpoint of the half-bridge switch arm through the first resonant capacitor and the resonant inductor; The anode of the fourth diode is coupled to the output terminal of the input rectifier and filter circuit, and the cathode is coupled to the anode of the fifth diode; the cathode of the fifth diode is coupled to the DC bus; The common terminal of the fourth diode and the fifth diode is connected to the midpoint of the half-bridge switch arm through the second resonant capacitor and the resonant inductor.

6. A PFC controller for a power converter, the power converter comprising an input rectifier and filter circuit, an active PFC circuit, an LLC resonant conversion circuit, and an output rectifier and filter circuit, the active PFC circuit comprising a PFC boost circuit and the PFC controller, the input rectifier and filter circuit rectifying and filtering an AC power supply to form an intermediate DC power supply, characterized in that, The power converter further includes a charge pump PFC circuit; both the charge pump PFC circuit and the active PFC circuit are coupled to the output terminal of the input rectifier and filter circuit, the DC bus, and the LLC resonant conversion circuit; the PFC controller detects the magnitude of the voltage of the intermediate DC power supply, When the voltage of the intermediate DC power supply is less than the first threshold voltage, the PFC controller controls the PFC boost circuit to maintain the voltage on the DC bus at the first target PFC voltage using the intermediate DC power supply; When the voltage of the intermediate DC power supply is greater than the second threshold voltage, the PFC controller controls the PFC boost circuit to stop working, and the charge pump PFC circuit maintains the voltage on the DC bus at the second target PFC voltage under the drive of the resonant current generated by the LLC resonant conversion circuit; When the voltage of the intermediate DC power supply changes from a voltage less than the first threshold voltage or greater than the second threshold voltage to the maintenance voltage range, the PFC controller maintains the control action on the PFC boost circuit unchanged before the change; Wherein, the second target PFC voltage, the first target PFC voltage, the second threshold voltage, and the first threshold voltage decrease in sequence, and the maintenance voltage range is the range from the first threshold voltage to the second threshold voltage.

7. The PFC controller according to claim 6, wherein, When the voltage of the intermediate DC power supply is less than the first threshold voltage, the charge pump PFC circuit can charge the DC bus under the drive of the resonant current generated by the LLC resonant conversion circuit.

8. The PFC controller according to claim 6, wherein, The power converter further includes a first diode, the anode of the first diode is coupled to the output terminal of the input rectifier and filter circuit, and the cathode is coupled to the DC bus.

9. The PFC controller according to any one of claims 6 to 8, wherein, The charge pump PFC circuit includes a second diode, a third diode, and a pumping capacitor; The LLC resonant conversion circuit includes a half-bridge switch arm and resonant elements; the positive terminal and the negative terminal of the half-bridge switch arm are respectively coupled to the DC bus and the ground; The anode of the second diode is coupled to the output terminal of the input rectifier and filter circuit, and the cathode is coupled to the anode of the third diode; the cathode of the third diode is coupled to the DC bus; The common terminal of the second diode and the third diode is grounded through the pumping capacitor and connected to the midpoint of the half-bridge switch arm through a resonant element.

10. The PFC controller according to any one of claims 6 to 8, characterized in that The charge pump PFC circuit includes a second diode, a third diode, a fourth diode, a fifth diode, and a pumping capacitor; The LLC resonant conversion circuit includes a half-bridge switch arm, a resonant inductor, a first resonant capacitor, and a second resonant capacitor; the positive terminal and the negative terminal of the half-bridge switch arm are respectively coupled to the DC bus and the ground; The anode of the second diode is coupled to the output terminal of the input rectifier and filter circuit, and the cathode is coupled to the anode of the third diode; the cathode of the third diode is coupled to the DC bus; The common terminal of the second diode and the third diode is grounded through the pumping capacitor and connected to the midpoint of the half-bridge switch arm through the first resonant capacitor and the resonant inductor; The anode of the fourth diode is coupled to the output terminal of the input rectifier and filter circuit, and the cathode is coupled to the anode of the fifth diode; the cathode of the fifth diode is coupled to the DC bus; The common terminal of the fourth diode and the fifth diode is connected to the midpoint of the half-bridge switch arm through the second resonant capacitor and the resonant inductor.

11. A circuit board, characterized in that, Comprising a power converter according to any one of claims 1-5.

12. An LED adapter, characterized in that, Comprising a power converter according to any one of claims 1-5.

13. An electronic device, characterized in that, Comprising a power converter according to any one of claims 1-5.

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