Switching power supply circuit

Abstract

The present invention discloses a switching power supply circuit, comprising a high-frequency switching network that receives a low-frequency AC input signal and performs high-frequency chopping on the low-frequency AC input signal to output a high-frequency AC signal; a transformer whose primary winding receives the high-frequency AC signal and converts the high-frequency AC signal into a voltage before outputting it from a secondary winding of the transformer; and a rectifier module that rectifies the output signal of the secondary winding to output a DC signal. The switching power supply circuit of the present invention eliminates the need for a rectifier bridge and directly converts the AC signal into a DC signal. This reduces the number of switching transistors, reduces the number of network stages and energy loss, and improves efficiency.

Description

Technical Field

[0001] The present invention relates to the field of power electronics, and more particularly to a switching power supply circuit. Background Art

[0002] In daily life, many semiconductor electronic devices require a switching power supply circuit to convert AC power into DC power so that they can obtain the DC power required for operation from the AC mains network. In most cases, in order to meet safety requirements, it is necessary to isolate the load end and the power supply end. Figure 1 As shown, it includes a rectifier bridge, a DC-DC converter and a transformer. The rectifier bridge receives an AC input voltage, and its output end is connected to the input end of the DC-DC converter. The output end of the DC-DC converter is coupled to the primary winding of the transformer, and the secondary winding of the transformer is coupled to the load. The rectifier bridge converts the received AC signal into a DC signal, and then transfers the energy to the load through the DC-DC converter and the transformer.

[0003] Due to the presence of a rectifier bridge in the switching power supply circuit of the prior art, a large number of switching tubes are required, resulting in large energy losses and low efficiency, which is more obvious when the AC input voltage is low. Summary of the Invention

[0004] In view of this, the present invention proposes a switching power supply circuit that directly converts AC signals into DC signals without the need for a rectifier bridge, solving the technical problems in the prior art caused by the presence of a rectifier bridge, such as the need for a large number of switching tubes, large energy loss, and low efficiency.

[0005] The present invention provides a switching power supply circuit, comprising: a high-frequency switching network, which receives a low-frequency AC input signal, performs high-frequency chopping on the low-frequency AC input signal, and outputs a high-frequency AC signal;

[0006] a transformer, wherein a primary winding of the transformer receives the high-frequency AC signal, performs voltage conversion on the high-frequency AC signal, and outputs the voltage from a secondary winding of the transformer;

[0007] The rectifier module rectifies the output signal of the secondary winding and outputs a DC signal.

[0008] Preferably, the high-frequency switching network includes an energy storage module. When the first loop of the high-frequency switching network is operating, the low-frequency AC input signal charges the energy storage module and the primary winding; when the second loop of the high-frequency switching network is operating, the energy storage module discharges the primary winding. The first loop and the second loop do not operate at the same time.

[0009] Preferably, the high-frequency switching network further includes a low-frequency AC input end, a first switching tube, a second switching tube, a third switching tube, a fourth switching tube and an energy storage module. The low-frequency AC input end, the first switching tube, the second switching tube, the primary winding and the energy storage module are connected to form a first loop, and the third switching tube, the fourth switching tube, the primary winding and the energy storage module are connected to form a second loop. The first loop and the second loop do not operate simultaneously.

[0010] Preferably, the first end of the first switching tube and the first end of the second switching tube are respectively connected to the two ports of the low-frequency AC input end, the second end of the first switching tube is connected to the first end of the third switching tube, the second end of the second switching tube is connected to the first end of the fourth switching tube, and the second end of the third switching tube is connected to the second end of the fourth switching tube. The energy storage module and the primary winding are connected between the first node and the second node.

[0011] The first node is a common end of the first switch tube and the third switch tube, and the second node is a common end of the second switch tube and the fourth switch tube.

[0012] Preferably, the first switching tube, the second switching tube, the third switching tube and the fourth switching tube are connected in series in sequence, the first end of the first switching tube and the second end of the fourth switching tube are respectively connected to the two ports of the low-frequency AC input end, and the energy storage module and the primary winding are connected between the first node and the second node.

[0013] The first node is a common terminal of the second switch tube and the third switch tube, and the second node is a common terminal of the fourth switch tube and the low-frequency AC input terminal.

[0014] Preferably, the high-frequency switching network includes a low-frequency AC input terminal, first to eighth switching transistors, a third capacitor, a fourth capacitor, and an energy storage module. The first, second, third, and fourth switching transistors are sequentially connected in series, and the fifth, sixth, seventh, and eighth switching transistors are sequentially connected in series. The first end of the first switching transistor and the first end of the fifth switching transistor are respectively connected to two ports of the low-frequency AC input terminal, the second end of the fourth switching transistor is connected to the second end of the eighth switching transistor, one end of the third capacitor is connected to a common terminal of the first and second switching transistors, and the other end is connected to a common terminal of the third and fourth switching transistors. One end of the fourth capacitor is connected to a common terminal of the fifth and sixth switching transistors, and the other end is connected to a common terminal of the seventh and eighth switching transistors. The energy storage module and the primary winding are connected between the first node and the second node.

[0015] The first node is a common end of the second switch tube and the third switch tube, and the second node is a common end of the sixth switch tube and the seventh switch tube.

[0016] Preferably, the energy storage module includes N inductors and / or N capacitors, where N is greater than or equal to 0.

[0017] Preferably, the high-frequency switching network operates in one of a resonant state and a half-bridge buck state.

[0018] Preferably, the energy storage module includes a first capacitor, and the first capacitor and the primary winding are connected in series and connected between the first node and the second node.

[0019] Preferably, the energy storage module further includes a first inductor, and the first inductor, the first capacitor and the primary winding are connected in series and connected between the first node and the second node.

[0020] Preferably, the energy storage module further includes a second capacitor, and the second capacitor is connected in parallel with the primary winding.

[0021] Preferably, during the positive half cycle of the low-frequency AC input signal, the first switch tube and the third switch tube are always turned on, and the second switch tube and the fourth switch tube are alternately turned on in a high-frequency PWM manner; during the negative half cycle of the low-frequency AC input signal, the second switch tube and the fourth switch tube are always turned on, and the first switch tube and the third switch tube are alternately turned on in a high-frequency PWM manner.

[0022] Preferably, during the positive half cycle of the low-frequency AC input signal, the fifth switch tube, the sixth switch tube, the seventh switch tube and the eighth switch tube are always turned on, and the first switch tube, the second switch tube, the third switch tube and the fourth switch tube are turned on or off in a high-frequency PWM manner; during the negative half cycle of the low-frequency AC input signal, the first switch tube, the second switch tube, the third switch tube and the fourth switch tube are always turned on, and the fifth switch tube, the sixth switch tube, the seventh switch tube and the eighth switch tube are turned on or off in a high-frequency PWM manner.

[0023] Preferably, when the high-frequency switching network operates in the first mode, during the positive half cycle of the low-frequency AC input signal, the fifth, sixth, seventh and eighth switching transistors are always on, the first and second switching transistors are turned on or off simultaneously, the third and fourth switching transistors are turned on or off simultaneously, and the first and second switching transistors and the third and fourth switching transistors are alternately turned on in a high-frequency PWM manner; during the negative half cycle of the low-frequency AC input signal, the first, second, third and fourth switching transistors are always on, the fifth and sixth switching transistors are turned on or off simultaneously, the seventh and eighth switching transistors are turned on or off simultaneously, and the fifth and sixth switching transistors and the seventh and eighth switching transistors are alternately turned on in a high-frequency PWM manner.

[0024] Preferably, when the high-frequency switching network operates in the second mode, during the positive half cycle of the low-frequency AC input signal, the fifth, sixth, seventh and eighth switching tubes are always turned on, the first and fourth switching tubes are turned on or off in opposite ways, and the second and third switching tubes are turned on or off in opposite ways; during the negative half cycle of the low-frequency AC input signal, the first, second, third and fourth switching tubes are always turned on, the fifth and eighth switching tubes are turned on or off in opposite ways, and the sixth and seventh switching tubes are turned on or off in opposite ways.

[0025] Preferably, the switching power supply circuit acts as a high-frequency transformer to open-loop control the switching state of the high-frequency switching network.

[0026] Preferably, the switching state of the high-frequency switch network is controlled so that the output voltage and / or current of the rectifier module meets the load requirement.

[0027] Preferably, the switching frequency of the high-frequency switching network is controlled so that the output voltage and / or current of the rectifier module meets the load requirement.

[0028] Preferably, the high-frequency switching network operates only during a period of time in a cycle of the low-frequency AC input signal, so that the rectifier module outputs current in a pulsed form.

[0029] Preferably, when the absolute value of the low-frequency AC input signal voltage is greater than a first threshold, the high-frequency switch network operates; otherwise, the high-frequency switch network does not operate, so that the rectifier module outputs a pulsating current.

[0030] Preferably, the high-frequency switching network further includes an EMI filtering circuit, which is arranged at the low-frequency AC input end to control the switching state of the high-frequency switching network so that the input current changes synchronously with the low-frequency AC input signal.

[0031] Preferably, the rectifier module is one of a full-wave rectifier circuit and a full-bridge rectifier circuit.

[0032] Preferably, the high-frequency switching network further includes a low-frequency AC input terminal, a first switching tube and a second switching tube. The low-frequency AC input terminal, the first switching tube, the second switching tube and the primary winding are connected in series to form a loop.

[0033] Preferably, the rectifier module includes a first rectifier tube, a second rectifier tube, an inductor and a capacitor, one end of the series structure formed by the inductor and the capacitor being connected in series is connected to the first end of the first rectifier tube, the second end of the first rectifier tube is connected to the first end of the secondary winding, the other end of the series structure is connected to the middle end of the secondary winding, the first end of the second rectifier tube is connected to the second end of the secondary winding, and the second end of the second rectifier tube is connected to the common end of the first rectifier tube and the series structure.

[0034] Preferably, the rectifier module includes a first rectifier tube, a second rectifier tube, a third rectifier tube, a fourth rectifier tube, a capacitor and an inductor. One end of the series structure composed of the inductor and the capacitor is connected to the first end of the first rectifier tube and the first end of the second rectifier tube, and the other end of the series structure is connected to the second end of the third rectifier tube and the second end of the fourth rectifier tube. The second end of the first rectifier tube is connected to the first end of the third rectifier tube, and the second end of the second rectifier tube is connected to the first end of the fourth rectifier tube. The secondary winding is connected between the first node and the second node.

[0035] The first node is a common end of the first rectifier tube and the third rectifier tube, and the second node is a common end of the second rectifier tube and the fourth rectifier tube.

[0036] Preferably, during the positive half cycle of the low-frequency AC input signal, the first switch tube is always on or off, and the second switch tube is turned on or off in a high-frequency PWM manner; during the negative half cycle of the low-frequency AC input signal, the second switch tube is always on or off, and the first switch tube is turned on or off in a high-frequency PWM manner.

[0037] Compared with the prior art, the technical solution of the present invention has the following advantages: The switching power supply circuit of the present invention directly converts a low-frequency AC input signal into a high-frequency AC signal, and then converts the high-frequency AC signal into a DC output via a transformer and a secondary rectifier circuit. The switching power supply circuit of the present invention does not require a rectifier bridge and directly converts the AC signal into a DC signal, using a smaller number of switching transistors, reducing the number of network stages and energy loss, and improving efficiency. Furthermore, the switching power supply circuit of the present invention can achieve power factor adjustment during the process of converting the AC signal into the DC signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0039] Figure 1 A circuit diagram of a switching power supply circuit in the prior art;

[0040] Figure 2 This is a principle block diagram of the switching power supply circuit of the present invention;

[0041] Figure 3 1 is a circuit diagram of a switching power supply circuit according to a first embodiment of the present invention;

[0042] Figure 4 This is a working waveform diagram of the switching power supply circuit of the first embodiment of the present invention when the input voltage is in the positive half cycle;

[0043] Figure 5 This is a working waveform diagram of the switching power supply circuit of the first embodiment of the present invention when the input voltage is in the negative half cycle;

[0044] Figure 6 This is a signal waveform diagram of the switching power supply circuit according to the first embodiment of the present invention;

[0045] Figure 7 1 is a circuit diagram of a switching power supply circuit according to a second embodiment of the present invention;

[0046] Figure 8 2 is a working waveform diagram of the switching power supply circuit according to the second embodiment of the present invention;

[0047] Figure 9 1 is a circuit diagram of a switching power supply circuit according to a third embodiment of the present invention;

[0048] Figure 10 2 is a working waveform diagram of the switching power supply circuit according to the third embodiment of the present invention;

[0049] Figure 11 2. This is a signal waveform diagram of the switching power supply circuit in the first mode according to the third embodiment of the present invention;

[0050] Figure 12 2. This is a signal waveform diagram of the switching power supply circuit in the second mode according to the third embodiment of the present invention;

[0051] Figure 13 1 is a circuit diagram of a switching power supply circuit according to a fourth embodiment of the present invention;

[0052] Figure 14 1 is a circuit diagram of a switching power supply circuit according to a fifth embodiment of the present invention;

[0053] Figure 15 The operating waveforms of the switching power supplies according to the fourth and fifth embodiments of the present invention are shown;

[0054] Figure 16 A schematic diagram of a circuit in which the switching power supply circuit of the present invention is applied to power factor adjustment;

[0055] Figure 17 The input voltage and current waveforms of the switching power supply circuit of the present invention after power factor adjustment;

[0056] Figure 18 This is a circuit diagram of a switching power supply circuit of the present invention applied to output current control;

[0057] Figure 19 This is a working waveform diagram of the driving circuit of the switching power supply circuit of the present invention;

[0058] Figure 20 This is a circuit diagram of a switching power supply circuit of the present invention applied to outputting discontinuous current;

[0059] Figure 21 This is a working waveform diagram of the switching power supply circuit of the present invention applied to output discontinuous current. DETAILED DESCRIPTION

[0060] The present invention is described below based on the following embodiments, but the present invention is not limited to these embodiments. In the detailed description of the present invention below, certain specific details are described in detail. Those skilled in the art can fully understand the present invention without these details. To avoid obscuring the essence of the present invention, well-known methods, processes, procedures, components, and circuits are not described in detail.

[0061] Furthermore, persons of ordinary skill in the art will appreciate that the figures provided herein are for illustration purposes only and are not necessarily drawn to scale.

[0062] At the same time, it should be understood that in the following description, "circuit" refers to a conductive loop composed of at least one element or subcircuit connected electrically or electromagnetically. When an element or circuit is said to be "connected to" another element or an element / circuit is said to be "connected" between two nodes, it can be directly coupled or connected to the other element or there can be intermediate elements. The connection between the elements can be physical, logical, or a combination thereof. Conversely, when an element is said to be "directly coupled to" or "directly connected to" another element, it means that there are no intermediate elements between the two.

[0063] Figure 2 This is a principle block diagram of the switching power supply circuit of the present invention, which includes:

[0064] The high-frequency switching network 1 receives a low-frequency AC input signal (generally a power frequency AC signal), performs high-frequency chopping on the low-frequency AC input signal, and outputs a high-frequency AC signal;

[0065] A transformer 2, wherein the primary winding of the transformer 2 receives a high-frequency AC signal, converts the high-frequency AC signal into a voltage, and outputs the voltage from the secondary winding of the transformer 2;

[0066] The rectifier module 3 rectifies the output signal of the secondary winding and outputs a DC signal.

[0067] It should be noted that the low-frequency AC input signal can be a sine wave, or other types of AC signals such as a rectangular wave. For ease of explanation, the following description of the present invention uses a sine wave, but the present invention is not limited to this. The transformer can be a conventional transformer or a piezoelectric transformer, and the present invention is not limited to this.

[0068] Furthermore, the high-frequency switching network includes an energy storage module. When the first loop of the high-frequency switching network is operating, the low-frequency AC input signal charges the energy storage module and the primary winding. The polarity of the voltage on the primary winding does not necessarily correspond to the polarity of the low-frequency AC input signal, and can be the same or opposite. When the second loop of the high-frequency switching network is operating, the energy storage module discharges the primary winding. The first loop and the second loop do not operate simultaneously.

[0069] Furthermore, the energy storage module includes N inductors and / or N capacitors, where N is greater than or equal to 0. Preferably, the energy storage module includes a capacitor and a first inductor. Preferably, the energy storage module includes a capacitor. Preferably, the energy storage module includes two capacitors and one inductor.

[0070] Furthermore, the high-frequency switching network also includes a low-frequency AC input end, a first switching tube, a second switching tube, a third switching tube, a fourth switching tube and an energy storage module. The low-frequency AC input end, the first switching tube, the second switching tube, the primary winding and the energy storage module are connected to form a first loop, and the third switching tube, the fourth switching tube, the primary winding and the energy storage module are connected to form a second loop. The first loop and the second loop do not operate at the same time.

[0071] Furthermore, the high-frequency switching network operates in one of a resonant state and a half-bridge buck state.

[0072] The switch tube described in the invention can adopt various existing electrically controllable switch devices, such as metal oxide semiconductor field effect transistor (MOSFET), bipolar junction transistor (BJT), or insulated gate bipolar transistor (IGBT), without limitation.

[0073] The output end of the switching power supply circuit of the present invention can be directly coupled to a load to provide power, such as powering an LED or charging a battery. The switching power supply circuit of the present invention can be actively controlled in a single stage, such as by adjusting the frequency, to control the output voltage and / or current. In this case, when the output voltage and / or current are controlled, the output voltage and / or current can be controlled by adjusting the switching state of the high-frequency switching network 1, such as the switching frequency. The switching power supply circuit of the present invention can also be operated in a single stage without active frequency control, with an open-loop output, thereby utilizing the switching power supply circuit as a high-frequency transformer. The switching power supply circuit of the present invention can also be connected to a second-stage circuit at a subsequent stage. The second-stage circuit is coupled to a load to provide power, such as powering an LED or charging a battery. The second-stage circuit is typically a DC-DC circuit. In this case, when the output voltage and / or current are controlled, the output voltage and / or current can be controlled by adjusting the switching state of the high-frequency switching network and / or the DC-DC circuit, such as the switching frequency. When the output voltage and / or current are controlled solely by adjusting the switching frequency of the DC-DC circuit, the switching frequency of the high-frequency switching network is open-loop controlled. Furthermore, the switching power supply circuit of the present invention can be applied in PFC. Furthermore, the switch in the rectifier module of the present invention can be controlled by the primary side or independently controlled by the secondary side, without limitation. The switching power supply circuit of the present invention directly converts the low-frequency AC input signal into a high-frequency AC signal, and then converts the high-frequency AC signal into a DC output through a transformer and a secondary rectifier circuit. The switching power supply circuit of the present invention does not require a rectifier bridge, directly converts the AC signal into a DC signal, uses a smaller number of switching tubes, reduces the number of network stages and energy loss, improves efficiency, and solves the technical problems in the prior art caused by the presence of a rectifier bridge, such as the need for a large number of switching tubes, large energy loss, and low efficiency.

[0074] Figure 3 This is a circuit diagram of a switching power supply circuit according to a first embodiment of the present invention. The switching power supply circuit includes a high-frequency switching network 1, a transformer 2, and a rectifier module 3. The high-frequency switching network 1 includes a low-frequency AC input terminal, a first switching transistor Q1, a second switching transistor Q2, a third switching transistor Q3, a fourth switching transistor Q4, and an energy storage module. The first end of the first switching transistor Q1 and the first end of the second switching transistor Q2 are respectively connected to two ports N and L of the low-frequency AC input terminal. The second end of the first switching transistor Q1 is connected to the first end of the third switching transistor Q3, the second end of the second switching transistor Q2 is connected to the first end of the fourth switching transistor Q4, and the second end of the third switching transistor Q3 is connected to the second end of the fourth switching transistor Q4. The energy storage module and the primary winding L2 of the transformer 2 are connected between a first node and a second node. The first node is a common terminal of the first switching transistor Q1 and the third switching transistor Q3, and the second node is a common terminal of the second switching transistor Q2 and the fourth switching transistor Q4.

[0075] The energy storage module includes N inductors and / or N capacitors, where N is greater than or equal to 0. In this embodiment, the energy storage module includes a first inductor L1 and a first capacitor C1, and the first capacitor C1, the first inductor L1, and the primary winding L2 are connected in series between the first node and the second node. In other embodiments, the energy storage module may include only the first capacitor, and the first capacitor and the primary winding are connected in series between the first node and the second node; in other embodiments, the energy storage module includes a first capacitor, a second capacitor, and a first inductor, and the first capacitor, the first inductor, and the primary winding are connected in series between the first node and the second node, and the second capacitor and the primary winding are connected in parallel; in some embodiments, the energy storage module includes only the first inductor, and the first inductor and the primary winding are connected in series between the first node and the second node. In other embodiments, the energy storage module may also be in other combinations of inductors and capacitors, all of which are within the scope of protection of the present invention.

[0076] The transformer 2 also includes two secondary windings L3 and L4, which are connected in series. The common end of the secondary winding L3 and the secondary winding L4 is the middle end of the secondary winding. The other end of the secondary winding L3 is the first end of the secondary winding, and the other end of the secondary winding L4 is the second end of the secondary winding. In other embodiments, the transformer 2 includes a secondary winding with a center tap, wherein the center tap is the middle end of the secondary winding, and the other two ends are the first end and the second end of the secondary winding, respectively.

[0077] The rectifier module 3 is a full-wave rectifier circuit comprising a first rectifier D1 and a second rectifier D2. The first end of the first rectifier D1 is connected to the first end of the secondary winding, and the second end of the first rectifier D1 serves as the high-potential terminal of the output voltage. The first end of the second rectifier D2 is connected to the second end of the secondary winding, and the second end of the second rectifier D2 is connected to the second end of the first rectifier D1. The middle end of the secondary winding serves as the low-potential terminal of the output voltage. In other embodiments, the rectifier module 3 may be another type of rectifier circuit, such as a full-bridge rectifier circuit, and the present invention is not limited thereto. In this embodiment, the rectifier is a diode, but various existing electrically controllable switching devices, such as metal oxide semiconductor field-effect transistors (MOSFETs), bipolar junction transistors (BJTs), or insulated gate bipolar transistors (IGBTs), may also be used, without limitation. When the rectifiers in the secondary rectifier module are existing electrically controllable switching devices, the rectifiers can be turned on and off by controlling the primary side or the secondary side.

[0078] In this embodiment, the switching power supply circuit further includes a capacitor C2 connected to the output end of the rectifier module 3 for filtering the output signal of the rectifier module 3 .

[0079] Figure 4 The operating waveform diagram of the switching power supply circuit of the first embodiment of the present invention is given in the positive half cycle of the input voltage; Figure 4 (a) is the flow diagram of the average current in the positive half cycle of the input voltage, Figure 4 (b) is the working waveform of the switching power supply circuit in the positive half cycle of the input voltage. Figure 4 As shown, when the low-frequency AC input signal Vin is in a positive half-cycle, that is, the voltage at the L terminal is greater than that at the N terminal, the first switch tube Q1 and the third switch tube Q3 are always turned on, and the second switch tube Q2 and the fourth switch tube Q4 are alternately turned on in a high-frequency PWM manner. At this time, the first capacitor C1, the first inductor L1, and the primary winding L2 in the first embodiment form an LLC resonant circuit, and the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, and the fourth switch tube Q4 operate in a resonant state, thereby achieving high-frequency chopping. If the first capacitor C1 is too large and cannot resonate, the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, and the fourth switch tube Q4 operate in a half-bridge buck state, thereby achieving high-frequency chopping. The frequency of the high-frequency PWM is much greater than the frequency of the low-frequency AC input signal.

[0080] When the second switch tube Q2 is turned on and the fourth switch tube Q4 is turned off, the low-frequency AC input signal Vin charges the energy storage module and the primary winding. At this time, the direction of the average current is as follows: Figure 4As shown by the dotted line with an arrow in (a); when the second switch tube Q2 is turned off and the fourth switch tube Q4 is turned on, the energy storage module discharges the primary winding. At this time, the direction of the average current is as follows: Figure 4 Indicated by the dotted line with arrows in (a).

[0081] Figure 5 The operating waveform diagram of the switching power supply circuit of the first embodiment of the present invention is given in the negative half cycle of the input voltage; Figure 4 (a) is the flow diagram of the average current in the negative half cycle of the input voltage, Figure 4 (b) is the working waveform of the switching power supply circuit in the negative half cycle of the input voltage. Figure 4 As shown, when the low-frequency AC input signal Vin is in the negative half cycle, that is, the voltage at the N terminal is greater than that at the L terminal, the second switch tube Q2 and the fourth switch tube Q4 are always turned on, and the first switch tube Q1 and the third switch tube Q3 are alternately turned on in a high-frequency PWM manner. At this time, the first capacitor C1, the first inductor L1, and the primary winding L2 in the first embodiment form an LLC resonant circuit, and the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, and the fourth switch tube Q4 operate in a resonant state, thereby achieving high-frequency chopping. If the first capacitor C1 is too large and cannot resonate, the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, and the fourth switch tube Q4 operate in a half-bridge buck state, thereby achieving high-frequency chopping. The frequency of the high-frequency PWM is much greater than the frequency of the low-frequency AC input signal.

[0082] When the first switch tube Q1 is turned on and the third switch tube Q3 is turned off, the low-frequency AC input signal Vin charges the energy storage module and the primary winding. At this time, the direction of the average current is as follows: Figure 4 As shown by the dotted line with an arrow in (a); when the first switch tube Q1 is turned off and the third switch tube Q3 is turned on, the energy storage module discharges the primary winding. At this time, the direction of the average current is as follows: Figure 4 Indicated by the dotted line with arrows in (a).

[0083] Figure 6 : is a signal waveform diagram of the switching power supply circuit according to the first embodiment of the present invention; Figure 6 As shown, when the low-frequency AC input signal Vin is in the positive half cycle, the second switch tube Q2 and the fourth switch tube Q4 are alternately turned on in a high-frequency PWM manner; when the input voltage Vin is in the negative half cycle, the first switch tube Q1 and the third switch tube Q3 are alternately turned on in a high-frequency PWM manner.

[0084] It should be noted that complementary conduction is a special case of alternating conduction. Complementary conduction achieves the highest efficiency. However, to prevent a transient short circuit caused by a switch turn-off delay, a dead time is inserted between the state switching of the second switch Q2 and the fourth switch Q4, or the first switch Q1 and the third switch Q3. Subsequent alternating conduction includes this scenario and will not be further described.

[0085] Figure 7 This is a circuit diagram of a switching power supply circuit according to a second embodiment of the present invention. The switching power supply circuit includes a high-frequency switching network 1, a transformer 2, and a rectifier module 3. The high-frequency switching network 1 includes a low-frequency AC input terminal, a first switching tube Q1, a second switching tube Q2, a third switching tube Q3, a fourth switching tube Q4, and an energy storage module. The first switching tube Q1, the second switching tube Q2, the third switching tube Q3, and the fourth switching tube Q4 are connected in series in sequence. The first end of the first switching tube Q1 and the second end of the fourth switching tube Q4 are respectively connected to the two ports N and L of the low-frequency AC input terminal. The energy storage module and the primary winding L2 are connected between the first node and the second node.

[0086] The first node is a common terminal of the second switch tube Q2 and the third switch tube Q3, and the second node is a common terminal of the fourth switch tube Q4 and the low-frequency AC input terminal.

[0087] The energy storage module, transformer 2 and rectifier module 3 in this embodiment are similar to the energy storage module, transformer and rectifier module in the first embodiment, and are not described in detail here.

[0088] Figure 8This is an operating waveform diagram of the switching power supply circuit according to the second embodiment of the present invention. When the low-frequency AC input signal Vin is in the positive half-cycle, that is, the voltage at the L terminal is greater than that at the N terminal, the first switch tube Q1 and the third switch tube Q3 are always on, and the second switch tube Q2 and the fourth switch tube Q4 are alternately turned on in a high-frequency PWM manner. At this time, the first capacitor C1, the first inductor L1, and the primary winding L2 in the second embodiment form an LLC resonant circuit, and the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, and the fourth switch tube Q4 operate in a resonant state. If the first capacitor is too large and resonance cannot be achieved, the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, and the fourth switch tube Q4 operate in a half-bridge buck state. When the low-frequency AC input signal Vin is in the negative half cycle, that is, the voltage at the N terminal is greater than that at the L terminal, the second switch tube Q2 and the fourth switch tube Q4 are always turned on, and the first switch tube Q1 and the third switch tube Q3 are alternately turned on in a high-frequency PWM manner. At this time, the first capacitor C1, the first inductor L1, and the primary winding L2 in the second embodiment form an LLC resonant circuit, and the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, and the fourth switch tube Q4 operate in a resonant state. If the first capacitor is too large and resonance cannot be achieved, the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, and the fourth switch tube Q4 operate in a half-bridge buck state, thereby achieving high-frequency chopping.

[0089] Figure 9 This is a circuit diagram of a switching power supply circuit according to a third embodiment of the present invention; the switching power supply circuit includes a high-frequency switching network 1, a transformer 2, and a rectifier module 3. The high-frequency switching network 1 includes a low-frequency AC input terminal, a first switching tube Q1, a second switching tube Q2, a third switching tube Q3, a fourth switching tube Q4, a fifth switching tube Q5, a sixth switching tube Q6, a seventh switching tube Q7, and an eighth switching tube Q8, a capacitor C3, a capacitor C4, and an energy storage module. The first switching tube Q1, the second switching tube Q2, the third switching tube Q3, and the fourth switching tube Q4 are connected in series in sequence, and the fifth switching tube Q5, the sixth switching tube Q6, the seventh switching tube Q7, and the eighth switching tube Q8 are connected in series in sequence. The first end of the first switching tube Q1 and the first end of the fifth switching tube Q5 are respectively connected to the two ports L and N of the low-frequency AC input terminal. The second end of the fourth switching tube Q4 is connected to the second end of the eighth switching tube Q8. One end of the capacitor C3 is connected to the common end of the first switching tube Q1 and the second switching tube Q2, and the other end is connected to the common end of the third switching tube Q3 and the fourth switching tube Q4. One end of the capacitor C4 is connected to the common end of the fifth switching tube Q5 and the sixth switching tube Q6, and the other end is connected to the common end of the seventh switching tube Q7 and the eighth switching tube Q8. The energy storage module and the primary winding are connected between the first node and the second node.

[0090] The first node is a common end of the second switch tube Q2 and the third switch tube Q3 , and the second node is a common end of the sixth switch tube Q6 and the seventh switch tube Q7 .

[0091] The energy storage module, transformer 2 and rectifier module 3 in this embodiment are similar to those in the first embodiment, and are not described in detail here.

[0092] Figure 10 This is an operating waveform diagram of the switching power supply circuit according to the third embodiment of the present invention. When the low-frequency AC input signal Vin is in a positive half-cycle, that is, the voltage at the L terminal is greater than that at the N terminal, the fifth switch transistor Q5, the sixth switch transistor Q6, the seventh switch transistor Q7, and the eighth switch transistor Q8 are always on, and the first switch transistor Q1, the second switch transistor Q2, the third switch transistor Q3, and the fourth switch transistor Q4 are turned on or off in a high-frequency PWM manner. At this time, the first capacitor C1, the first inductor L1, and the primary winding L2 in the third embodiment form an LLC resonant circuit, and the first switch transistor Q1, the second switch transistor Q2, the third switch transistor Q3, and the fourth switch transistor Q4 operate in a resonant state. If the first capacitor is too large and resonance is impossible, the first switch transistor Q1, the second switch transistor Q2, the third switch transistor Q3, and the fourth switch transistor Q4 operate in a half-bridge buck state. During the negative half-cycle of the low-frequency AC input signal Vin, that is, the voltage at the N terminal is greater than that at the L terminal, the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, and the fourth switch tube Q4 are always on, and the fifth switch tube Q5, the sixth switch tube Q6, the seventh switch tube Q7, and the eighth switch tube Q8 are turned on or off in a high-frequency PWM manner. At this time, the first capacitor C1, the first inductor L1, and the primary winding L2 in the third embodiment form an LLC resonant circuit, and the fifth switch tube Q5, the sixth switch tube Q6, the seventh switch tube Q7, and the eighth switch tube Q8 operate in a resonant state. If the first capacitor is too large and resonance is impossible, the fifth switch tube Q5, the sixth switch tube Q6, the seventh switch tube Q7, and the eighth switch tube Q8 operate in a half-bridge buck state, thereby achieving high-frequency chopping.

[0093] Figure 10 The high frequency switch network 1 of the third embodiment can work in mode 1, i.e., two-level mode, or mode 2, i.e., three-level mode. When the high frequency switch network 1 of the third embodiment works in mode 1, i.e., two-level mode, the signal waveform is as follows: Figure 11As shown, when the low-frequency AC input signal Vin is in a positive half-cycle, that is, the voltage at the L terminal is greater than that at the N terminal, the fifth switch transistor Q5, the sixth switch transistor Q6, the seventh switch transistor Q7, and the eighth switch transistor Q8 are always on, the first switch transistor Q1 and the second switch transistor Q2 are turned on or off simultaneously, the third switch transistor Q3 and the fourth switch transistor Q4 are turned on or off simultaneously, and the first switch transistor Q1 and the second switch transistor Q2 and the third switch transistor Q3 and the fourth switch transistor Q4 are alternately turned on in a high-frequency PWM manner. When Vin is in a negative half-cycle, that is, the voltage at the N terminal is greater than that at the L terminal, the first switch transistor Q1, the second switch transistor Q2, the third switch transistor Q3, and the fourth switch transistor Q4 are always on, the fifth switch transistor Q5 and the sixth switch transistor Q6 are turned on or off simultaneously, the seventh switch transistor Q7 and the eighth switch transistor Q8 are turned on or off simultaneously, and the fifth switch transistor Q5 and the sixth switch transistor Q6 and the seventh switch transistor Q7 and the eighth switch transistor Q8 are alternately turned on in a high-frequency PWM manner.

[0094] When the high frequency switch network 1 of the third embodiment operates in mode 2, i.e., the three-level mode, the signal waveform is as follows: Figure 12 As shown, when Vin is in a positive half cycle, that is, the voltage at the L terminal is greater than that at the N terminal, the fifth switch tube Q5, the sixth switch tube Q6, the seventh switch tube Q7, and the eighth switch tube Q8 are always turned on, the first switch tube Q1 and the fourth switch tube Q4 are turned on or off in opposite ways, and the second switch tube Q2 and the third switch tube Q3 are turned on or off in opposite ways; when Vin is in a negative half cycle, that is, the voltage at the N terminal is greater than that at the L terminal, the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, and the fourth switch tube Q4 are always turned on, the fifth switch tube Q5 and the eighth switch tube Q8 are turned on or off in opposite ways, and the sixth switch tube Q6 and the seventh switch tube Q7 are turned on or off in opposite ways.

[0095] Figure 13 This is a circuit diagram of a switching power supply circuit according to a fourth embodiment of the present invention. The switching power supply circuit includes a high-frequency switching network 1, a transformer 2, and a rectifier module 3. The high-frequency switching network 1 includes a low-frequency AC input terminal, a first switching tube Q1, and a second switching tube Q2. The low-frequency AC input terminal, the first switching tube Q1, the second switching tube Q2, and the primary winding L2 are connected in series to form a loop.

[0096] The rectifier module 3 includes a first rectifier tube D1, a second rectifier tube D2, an inductor L, and a capacitor C. One end of the series structure formed by the series connection of the inductor L and the capacitor C is connected to the first end of the first rectifier tube D1, the second end of the first rectifier tube D1 is connected to the first end of the secondary winding, the other end of the series structure is connected to the middle end of the secondary winding, the first end of the second rectifier tube D2 is connected to the second end of the secondary winding, and the second end of the second rectifier tube D2 is connected to the first rectifier tube D1 and the common end of the series structure. In this embodiment, the rectifier tube is a diode, and various existing electrically controllable switching devices can also be used, such as metal oxide semiconductor field effect transistors (MOSFETs), bipolar junction transistors (BJTs), or insulated gate bipolar transistors (IGBTs), without limitation. When the rectifier tube of the secondary rectifier module is an existing electrically controllable switching device, the opening and closing of the rectifier tube can be controlled by the primary side, or by the secondary side.

[0097] The energy storage module and transformer 2 in this embodiment are similar to those in the first embodiment, and are not described in detail here.

[0098] Figure 14 This is a circuit diagram of a switching power supply circuit according to a fifth embodiment of the present invention. The switching power supply circuit includes a high-frequency switching network 1, a transformer 2, and a rectifier module 3. The transformer 2 includes a primary winding L2 and a secondary winding L3. The high-frequency switching network 1 includes a low-frequency AC input terminal, a first switching tube Q1, and a second switching tube Q2. The low-frequency AC input terminal, the first switching tube Q1, the second switching tube Q2, and the primary winding L2 are connected in series to form a loop.

[0099] The rectifier module 3 includes a first rectifier tube S1, a second rectifier tube S2, a third rectifier tube S3, a fourth rectifier tube S4, a capacitor C and an inductor L. One end of the series structure composed of the inductor L and the capacitor C is connected in series to the first end of the first rectifier tube S1 and the first end of the second rectifier tube S2, and the other end of the series structure is connected to the second end of the third rectifier tube S3 and the second end of the fourth rectifier tube S4. The second end of the first rectifier tube S1 is connected to the first end of the third rectifier tube S3, and the second end of the second rectifier tube S2 is connected to the first end of the fourth rectifier tube S4. The secondary winding L3 is connected between a first node and a second node, wherein the first node is the common end of the first rectifier tube S1 and the third rectifier tube S3, and the second node is the common end of the second rectifier tube S2 and the fourth rectifier tube S4. The rectifier tube in this embodiment is a metal oxide semiconductor field effect transistor (MOSFET), but may also be a diode, or other existing electrically controllable switching devices, such as a bipolar junction transistor (BJT) or an insulated gate bipolar transistor (IGBT), without limitation. When the rectifier tube of the secondary rectifier module is an existing electrically controllable switching device, the turning on and off of the rectifier tube can be controlled by the primary side, or by the secondary side.

[0100] The energy storage module in this embodiment is similar to the energy storage module in the first embodiment and will not be described in detail here.

[0101] The operating waveforms of the switching power supply circuits according to the fourth and fifth embodiments of the present invention are shown in FIG. Figure 15 As shown; when the low-frequency AC input signal Vin is in a positive half cycle, that is, the voltage at the L terminal is greater than that at the N terminal, the first switch tube Q1 is always on, and the second switch tube Q2 is turned on in a high-frequency PWM manner, or the first switch tube Q1 is always off (the body diode of the first switch tube Q1 is turned on), and the second switch tube Q2 is turned on in a high-frequency PWM manner. At this time, the switching power supply circuit of this embodiment operates in a Buck state; when the circuit Vin is in a negative half cycle, that is, the voltage at the N terminal is greater than that at the L terminal, the second switch tube Q2 is always on, and the first switch tube Q1 is turned on in a high-frequency PWM manner, or the second switch tube Q2 is always off (the body diode of the second switch tube Q2 is turned on), and the first switch tube Q1 is turned on in a high-frequency PWM manner. At this time, the switching power supply circuit of this embodiment operates in a Buck state.

[0102] The switching power supply circuit of the present invention can achieve power factor control (PFC) by controlling the switching state of the high-frequency switching network so that the envelope of the input current Iin changes synchronously with the sinusoidal wave of the low-frequency AC input signal Vin. For ease of explanation, the following description will use Example 1, but any other embodiment can also be applied to power factor control, and the method for applying power factor control to Example 1 is similar.

[0103] like Figure 16 As shown, the switching power supply circuit in the first embodiment further includes an EMI filter circuit 4 and a control circuit 5. The EMI filter circuit 4 is arranged at the input end of the low-frequency AC input signal Vin, and the control circuit 5 controls the switching state of the high-frequency switching network 1 so that the input current Iin changes synchronously with the sinusoidal wave of the low-frequency AC input signal Vin to achieve the power factor adjustment (PFC) function.

[0104] The EMI filter circuit 4 includes a capacitor C4, a capacitor C5, and an inductor L5. The capacitors C4 and C5 are connected in parallel to the input terminal of the low-frequency AC input signal Vin, and the inductor L5 is connected between the capacitors C4 and C5. It should be understood that the EMI filter circuit 4 can be in other forms, and the present invention is not limited thereto.

[0105] The control circuit 5 includes a first error amplifier Gm1, a second error amplifier Gm2 and a drive circuit. The first error amplifier Gm1 is used to compare the input current sampling signal V Iin The second error amplifier Gm2 is used to compare the input current sampling signal V Iin The first error signal V1 is used to obtain a second error signal V2. The driving circuit is used to generate a driving signal according to the second error signal V2 to control the switching state of the switch tube in the high-frequency switching network 1.

[0106] Specifically, the first error amplifier Gm1 has a non-inverting input terminal inputting a current reference signal Iref, and an inverting input terminal inputting an input current sampling signal V Iin . Among them, the input current sampling signal is a voltage signal, which is used to characterize the input current Iin; the current reference signal Iref is used to characterize the current that changes synchronously with the sine wave of the low-frequency AC input signal Vin. In this way, an input current control loop can be formed to control the input current Iin to approach the current reference signal Iref. The first error signal V1 is used as the reference signal, which is input to the non-inverting input terminal of the second error amplifier Gm2, and the input current sampling signal V is input to the inverting input terminal of the second error amplifier Gm2. Iin , by comparing the input current sampling signal V Iinand the first error signal V1 to obtain a second error signal V2. The driving circuit includes a first comparator comp1, one end of which receives the second error signal V2, and the other end of which receives the ramp signal Vslope. The comparator outputs a driving signal for controlling the driving module to generate control signals G1 and G2, thereby controlling the switching states of the switches in the high-frequency switching network 1. Because the switching power supply circuit of the present invention has only two groups of switches alternately turned on during the positive and negative half-cycles of the AC input signal Vin, the control signals G1 and G2 are used to control the switching states of the two groups of switches alternately turned on during the positive and negative half-cycles of the AC input signal Vin.

[0107] The control circuit 5 further includes a capacitor C6 connected between the output terminal of the first error amplifier Gm1 and the ground terminal, and configured to convert the current signal output by the first error amplifier Gm1 into a voltage signal, namely, the first error signal V1. The control circuit 5 further includes a capacitor C7 connected between the output terminal of the second error amplifier Gm2 and the ground terminal, and configured to convert the current signal output by the second error amplifier into a corresponding voltage signal, namely, the second error signal V2.

[0108] The working waveform of the switching power supply circuit of the present invention after power factor adjustment is as follows Figure 17 As shown, the input current Iin varies synchronously with the sinusoidal waveform of the AC input signal Vin. The control circuit 5 used in the present invention to perform power factor adjustment is merely one embodiment. The control circuit 5 described above may also perform power factor adjustment using other methods, which are not limiting. It should be understood that the control circuit 5 is not limited to the method described herein, and those skilled in the art may employ other equivalent or existing methods to perform power factor adjustment.

[0109] The switching power supply circuit described in the present invention can also be connected to a second-stage circuit at the output end. The second-stage circuit is coupled to a load to power the load. The second-stage circuit is generally a DC-DC circuit. In this case, if the output voltage and / or current are controlled, the control of the output voltage and / or current can be achieved by adjusting the switching frequency of the high-frequency switching network and / or the DC-DC circuit; when the output voltage and / or current are controlled only by adjusting the switching frequency of the DC-DC circuit, the switching frequency in the high-frequency switching network is open-loop control.

[0110] The output end of the switching power supply circuit described in the present invention can be directly coupled to a load to provide power, such as powering an LED or charging a battery. The switching power supply circuit described in the present invention can be actively controlled at a single stage to adjust the frequency, etc. to control the output voltage and current. At this time, if the output voltage and / or current are controlled, the control of the output voltage and / or current can be achieved by adjusting the switching frequency of the high-frequency switching network 1. The switching power supply circuit described in the present invention can also be used as a high-frequency transformer without actively controlling the frequency at a single stage and with open-loop output.

[0111] The present invention only provides a detailed description of the case where a single-stage switching power supply circuit is used to control the output current, but the present invention is not limited to this. Other situations should also be within the scope of protection of the present invention. By controlling the switching state of the switch tube in the high-frequency switching network, the output current meets the load requirements. For ease of explanation, the following description will use Example 1, but any other embodiment can be applied to power factor adjustment, and the method of applying power factor adjustment to the embodiment is similar.

[0112] like Figure 18 As shown, the switching power supply circuit also includes a control circuit 6 for controlling the output current Io to meet the load requirements. The control circuit 6 includes a first error amplifier Gm1, a second error amplifier Gm2, a compensation circuit, and a drive circuit. The first error amplifier Gm1 is configured to compare the output current sampling signal Vfb with the current reference signal Iref to obtain a first error signal Vref. The second error amplifier Gm2 is configured to compare the output current sampling signal Vfb with the first error signal Vref to obtain a second error signal Vcs. The compensation circuit is configured to generate a compensation signal Vcp based on the second error signal Vcs. The drive circuit is configured to generate drive signals (PWMH and PWML) based on the compensation signal Vcp to control the switching state of the switching transistors in the high-frequency switching network 1.

[0113] In this embodiment, the first error amplifier Gm1 receives a current reference signal Iref at its non-inverting input and an output current sampling signal Vfb at its inverting input. The output current sampling signal is a voltage signal representing the output current; the current reference signal Iref represents the required output current. Consequently, the output signal of the first error amplifier Gm1 represents the difference between the actual output current Io and the required output current Io. This forms an average current loop to control the average value of the output current Io to approach the current reference signal Iref. The first error signal Vref serves as a reference signal and is input to the non-inverting input of the second error amplifier Gm2. The output current sampling signal Vfb is input to the inverting input of the second error amplifier Gm2. The second error signal Vcs is generated by comparing the output current sampling signal Vfb with the first error signal Vref. This forms an instantaneous current loop that controls the instantaneous value of the output current Io by adjusting the operating frequency of the high-frequency switching network 1. A compensation circuit, comprising resistors R1 and R4, and an optocoupler, generates a compensation signal Vcp based on the second error signal Vcs. The drive circuit is configured to generate PWM (pulse width modulation) drive signals (PWMH and PWML) based on the compensation signal Vcp, which are used to control the drive module to generate control signals G1-G2, thereby controlling the switching states of the switches in the high-frequency switching network 1. Control signals G1 and G2 are used to control the switching states of two groups of switches that alternately conduct during the positive and negative half-cycles of the low-frequency AC input signal Vin. In one embodiment, the drive circuit generates the PWMH and PWML drive signals by comparing the compensation signal Vcp with the ramp signal Vsaw.

[0114] Furthermore, the control circuit 6 further includes a capacitor C4 connected between the output terminal of the first error amplifier Gm1 and the ground terminal, for converting the current signal output by the first error amplifier Gm1 into a voltage signal, namely, the first error signal Vref. The control circuit 6 further includes a capacitor C5 connected between the output terminal of the second error amplifier Gm2 and the ground terminal, for converting the current signal output by the second error amplifier into a corresponding voltage signal Vcs.

[0115] It should be understood that the control circuit 6 is not limited to the method described herein, and those skilled in the art may adopt other equivalent methods or existing methods to perform control.

[0116] Because the switching circuit of the present invention has two groups of switches that alternately conduct during the positive and negative half-cycles of the AC input signal Vin, control signals G1 and G2 are used to control the switching states of the two groups of switches that alternately conduct during the positive and negative half-cycles of the AC input signal Vin. That is, in the high-frequency switching network 1, during the positive half-cycle of the AC input signal Vin, the first switch Q1 and the third switch Q3 are always on, and the control signals G1 and G2 control the switching states of the second switch Q2 and the fourth switch Q4, respectively. In the high-frequency switching network 1 of the present invention, during the negative half-cycle of the input voltage Vin, the second switch Q2 and the fourth switch Q4 are always on, and the control signals G1 and G2 control the switching states of the first switch Q1 and the third switch Q3, respectively.

[0117] Figure 19 The operating waveforms of the driver circuit are shown, showing the compensation signal Vcp, ramp signal Vsaw, and PWM (PWMH and PWML) waveforms during the time periods when the two groups of switches in the high-frequency switching network are alternately turned on or off. The abscissa is time t, and the ordinate is the various components.

[0118] Specifically, during the period when the first switch Q1 and the third switch Q3 (or the second switch Q2 and the fourth switch Q4) are in the alternating on or off state, at time t4, the ramp signal Vsaw begins to rise, PWMH switches to a high level, and PWML remains at a low level. At time t5, the ramp signal Vsaw rises to be equal to the compensation signal Vcp, PWMH switches to a low level, and PWML remains at a low level. After the reading time Δt (dead time), that is, at time t6, the ramp signal Vsaw begins to rise, PWMH remains at a low level, and PWML switches to a high level. This cycle continues so that the duty cycle of the PWM signal is always 50%, controlling the DC-DC converter 2 to operate at a fixed duty cycle at the operating frequency.

[0119] Thus, the operating frequency of the high-frequency switching network 1 can be adjusted based on the difference between the current reference signal Iref and the output current sampling signal Vfb, and the DC-DC converter 2 can be operated at a fixed duty cycle at the operating frequency, thereby adjusting the average value of the output current Io to meet the charging requirements to charge the battery. In this case, the controlled output current is continuous.

[0120] The first, second, third, and fourth switching transistors in the high-frequency switching network operate only during a period of time within the low-frequency AC input signal cycle, causing the rectifier module to output a pulsed current. Preferably, when the absolute value of the low-frequency AC input signal voltage is greater than a first threshold, the first, second, third, and fourth switching transistors in the high-frequency switching network operate; otherwise, the high-frequency switching network does not operate, causing the rectifier module to output a pulsed current. In this case, the circuit operates with high efficiency.

[0121] Figure 20 The present invention provides a switching power supply circuit for controlling output current to be discontinuous. The control circuit further includes a control circuit 6, a control circuit 7 and a logic circuit. The control circuit 6 is used to generate drive signals PWMH and PWML according to the output current requirement and the output current Io. Figure 20 The control circuit 6 and Figure 18 The control circuit 6 is similar and will not be described in detail here. The output of the control circuit 6 is connected to the input of the logic circuit, and the output of the control circuit 7 is connected to the logic circuit. The logic circuit outputs control signals G1 and G2 for controlling the switching states of the switches in the high-frequency switch network 1. The control circuit 7 is configured to generate a first control signal En based on the AC input signal Vin and a first threshold value Vth. The logic circuit is configured to control the operating state of the high-frequency switch network based on the first control signal En and the drive signals PWMH and PWML to regulate the output current Io.

[0122] Furthermore, the logic circuit is configured to control the high-frequency switch network 1 to operate at a fixed duty cycle at an operating frequency in response to the first control signal En being valid according to the driven signals PWMH and PWML; and to control the high-frequency switch network 1 not to operate in response to the first control signal En being invalid.

[0123] The control circuit 7 includes a comparison circuit and an input signal sampling circuit. The input signal sampling circuit includes resistors R2 and R3, which are connected in series between the AC input terminals L and N to sample the low-frequency AC input signal Vin to obtain an input voltage sampling signal Vs. The comparison circuit is configured to compare the input voltage sampling signal Vs with a first threshold value Vth to obtain the first control signal En.

[0124] When the absolute value of the low-frequency AC input signal voltage is greater than a first threshold, the first control signal EN is enabled, and EN is at a high level. When the absolute value of the low-frequency AC input signal voltage is less than the first threshold, the first control signal En is disabled, and En is at a low level. It should be understood that the control circuit 7 is not limited to the method described herein, and those skilled in the art may employ other equivalent or existing methods to generate the first control signal.

[0125] Furthermore, in response to the first control signal En being at a low level, the logic circuit does not output the control signals G1 and G2. In response to the first control signal En being at a high level, the logic circuit generates the control signals G1 and G2 based on the drive signals PWMH and PWML to control the high-frequency switch network 1 to operate at a fixed duty cycle at the operating frequency. It should be understood that the operation of the logic circuit is not limited to the above-described method. For example, in response to the first control signal En being at a low level, the control signals G1 and G2 are both output at a low level. In response to the first control signal En being at a high level, the drive signals PWMH and PWML are output as the control signals G1 and G2. Since the switching power supply circuit of the present invention has two groups of switch tubes that are alternately turned on during the positive and negative half-cycles of the AC input signal Vin, the control signals G1 and G2 are used to control the switching states of the two groups of switch tubes that are alternately turned on during the positive and negative half-cycles of the AC input signal Vin.

[0126] Figure 21 This is a working waveform diagram of the discontinuous current control of the present invention. Figure 21 The waveform diagram shows the absolute value VS' of the input voltage sampling signal Vs, the first threshold Vth, the first control signal En, the output current sampling signal Vfb and the control signals G1 and G2 (PWM signals), where the abscissa is time t and the ordinate is each component.

[0127] Specifically, at time t1, the absolute value VS' of the input voltage sampling signal drops to equal the first threshold Vth, the first control signal En switches to a low level, and the logic circuit 33 does not output the control signals G1 and G2, controlling the high-frequency switch network 1 to be inoperative. Specifically, the second switch Q2 and the fourth switch Q4 (or the first switch Q1 and the third switch Q3) are turned off, causing the output current Io to be zero (or close to zero), thereby causing the output current sampling signal Vfb to be 0. At time t2, the absolute value VS' of the input voltage sampling signal rises to equal the predetermined threshold Vth, the first control signal En switches to a high level, and the logic circuit 33 outputs the control signals G1 and G2, controlling the high-frequency switch network 1 to be operational. Specifically, the second switch Q2 and the fourth switch Q4 (or the first switch Q1 and the third switch Q3) are alternately turned on, resulting in a high output current Io and a high output current sampling signal Vfb. At time t3, the absolute value VS' of the input voltage sampling signal drops again to equal the predetermined threshold Vth, and the cycle repeats. During a certain period of time within each cycle, the second switch Q2 and the fourth switch Q4 (or the first switch Q1 and the third switch Q3) are simultaneously in the off state, making the output current Io zero. During another period of time within each cycle, they are alternately in the on state, making the output current Io higher. In this way, the output current Io can be a pulsed current.

[0128] Furthermore, in the high-frequency switch network 1 of the present invention, during the positive half-cycle of the AC input signal Vin, the first switch transistor Q1 and the third switch transistor Q3 are always turned on. At this time, if the first control signal En switches to a low level, the second switch transistor Q2 and the fourth switch transistor Q4 are turned off, so that the output current Io is zero. If the first control signal En switches to a high level at this time, the second switch transistor Q2 and the fourth switch transistor Q4 are alternately turned on, so that the output current Io is relatively high. In the high-frequency switch network 1 of the present invention, during the negative half-cycle of the AC input signal Vin, the second switch transistor Q2 and the fourth switch transistor Q4 are always turned on. At this time, if the first control signal En switches to a low level, the first switch transistor Q1 and the third switch transistor Q3 are turned off, so that the output current Io is zero. If the first control signal En switches to a high level at this time, the first switch transistor Q1 and the third switch transistor Q3 are alternately turned on, so that the output current Io is relatively high.

[0129] Although the embodiments are described and explained separately above, some common technologies are involved. It is the opinion of ordinary technicians in this field that they can be replaced and integrated between the embodiments. If there is anything not clearly recorded in one of the embodiments, reference can be made to another recorded embodiment.

[0130] While embodiments of the present invention have been described above, these embodiments do not exhaustively describe all details and do not limit the invention to the specific embodiments described. Obviously, many modifications and variations are possible based on the above description. These embodiments are selected and described in detail in this specification in order to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better utilize the present invention and its modifications. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A switching power supply circuit, characterized in that: include: a high-frequency switching network, receiving a low-frequency AC input signal, performing high-frequency chopping on the low-frequency AC input signal, and outputting a high-frequency AC signal; A transformer, wherein the primary winding of the transformer receives the high-frequency AC signal and performs voltage conversion on the high-frequency AC signal before outputting the signal from the secondary winding of the transformer; the high-frequency switching network includes an energy storage module; when the first loop of the high-frequency switching network is operating, the low-frequency AC input signal charges the energy storage module and the primary winding; when the second loop of the high-frequency switching network is operating, the energy storage module discharges the primary winding; the first loop and the second loop do not operate simultaneously; a rectifier module, for rectifying the output signal of the secondary winding and outputting a DC signal; When the absolute value of the low-frequency AC input signal voltage is greater than a first threshold, the high-frequency switch network operates; otherwise, the high-frequency switch network does not operate, so that the rectifier module outputs a pulsating current.

2. The switching power supply circuit according to claim 1, wherein: The high-frequency switching network includes a low-frequency AC input end, a first switching tube, a second switching tube, a third switching tube, a fourth switching tube, and an energy storage module. The low-frequency AC input end, the first switching tube, the second switching tube, the primary winding, and the energy storage module are connected to form a first loop. The third switching tube, the fourth switching tube, the primary winding, and the energy storage module are connected to form a second loop. The first loop and the second loop do not operate simultaneously.

3. The switching power supply circuit according to claim 2, wherein: The first end of the first switching tube and the first end of the second switching tube are respectively connected to the two ports of the low-frequency AC input end, the second end of the first switching tube is connected to the first end of the third switching tube, the second end of the second switching tube is connected to the first end of the fourth switching tube, and the second end of the third switching tube is connected to the second end of the fourth switching tube. The energy storage module and the primary winding are connected between the first node and the second node. The first node is a common end of the first switch tube and the third switch tube, and the second node is a common end of the second switch tube and the fourth switch tube.

4. The switching power supply circuit according to claim 2, wherein: The first switch tube, the second switch tube, the third switch tube and the fourth switch tube are connected in series in sequence, the first end of the first switch tube and the second end of the fourth switch tube are respectively connected to the two ports of the low-frequency AC input end, the energy storage module and the primary winding are connected between the first node and the second node, The first node is a common terminal of the second switch tube and the third switch tube, and the second node is a common terminal of the fourth switch tube and the low-frequency AC input terminal.

5. The switching power supply circuit according to claim 1, wherein: The high-frequency switch network includes a low-frequency AC input terminal, first to eighth switching transistors, a third capacitor, a fourth capacitor, and an energy storage module. The first, second, third, and fourth switching transistors are connected in series in sequence, and the fifth, sixth, seventh, and eighth switching transistors are connected in series in sequence. The first end of the first switching transistor and the first end of the fifth switching transistor are respectively connected to two ports of the low-frequency AC input terminal, the second end of the fourth switching transistor is connected to the second end of the eighth switching transistor, one end of the third capacitor is connected to the common end of the first and second switching transistors, and the other end is connected to the common end of the third and fourth switching transistors. One end of the fourth capacitor is connected to the common end of the fifth and sixth switching transistors, and the other end is connected to the common end of the seventh and eighth switching transistors. The energy storage module and the primary winding are connected between a first node and a second node. The first node is a common end of the second switch tube and the third switch tube, and the second node is a common end of the sixth switch tube and the seventh switch tube.

6. The switching power supply circuit according to any one of claims 1 to 5, characterized in that: The energy storage module includes N inductors and / or N capacitors, where N is greater than or equal to 0.

7. The switching power supply circuit according to any one of claims 1 to 5, characterized in that: The high-frequency switching network operates in one of a resonant state and a half-bridge buck state.

8. The switching power supply circuit according to any one of claims 3 to 5, wherein: The energy storage module includes a first capacitor, which is connected in series with the primary winding and connected between the first node and the second node.

9. The switching power supply circuit according to claim 8, wherein: The energy storage module further includes a first inductor, wherein the first inductor, a first capacitor and the primary winding are connected in series and connected between the first node and the second node.

10. The switching power supply circuit according to claim 9, wherein: The energy storage module further includes a second capacitor, which is connected in parallel with the primary winding.

11. The switching power supply circuit according to claim 3 or 4, characterized in that: During the positive half cycle of the low-frequency AC input signal, the first switch tube and the third switch tube are always turned on, and the second switch tube and the fourth switch tube are alternately turned on in a high-frequency PWM manner; during the negative half cycle of the low-frequency AC input signal, the second switch tube and the fourth switch tube are always turned on, and the first switch tube and the third switch tube are alternately turned on in a high-frequency PWM manner.

12. The switching power supply circuit according to claim 5, wherein: During the positive half cycle of the low-frequency AC input signal, the fifth, sixth, seventh and eighth switching tubes are always turned on, and the first, second, third and fourth switching tubes are turned on or off in a high-frequency PWM manner; during the negative half cycle of the low-frequency AC input signal, the first, second, third and fourth switching tubes are always turned on, and the fifth, sixth, seventh and eighth switching tubes are turned on or off in a high-frequency PWM manner.

13. The switching power supply circuit according to claim 12, wherein: When the high-frequency switching network operates in the first mode, during the positive half cycle of the low-frequency AC input signal, the fifth, sixth, seventh, and eighth switching transistors are always on, the first and second switching transistors are turned on or off simultaneously, the third and fourth switching transistors are turned on or off simultaneously, and the first and second switching transistors and the third and fourth switching transistors are alternately turned on in a high-frequency PWM manner. During the negative half cycle of the low-frequency AC input signal, the first, second, third, and fourth switching transistors are always on, the fifth and sixth switching transistors are turned on or off simultaneously, the seventh and eighth switching transistors are turned on or off simultaneously, and the fifth and sixth switching transistors and the seventh and eighth switching transistors are alternately turned on in a high-frequency PWM manner.

14. The switching power supply circuit according to claim 12, wherein: When the high-frequency switching network operates in the second mode, during the positive half cycle of the low-frequency AC input signal, the fifth, sixth, seventh and eighth switching tubes are always turned on, the first and fourth switching tubes are turned on or off in opposite ways, and the second and third switching tubes are turned on or off in opposite ways; during the negative half cycle of the low-frequency AC input signal, the first, second, third and fourth switching tubes are always turned on, the fifth and eighth switching tubes are turned on or off in opposite ways, and the sixth and seventh switching tubes are turned on or off in opposite ways.

15. The switching power supply circuit according to any one of claims 1 to 5, characterized in that: The switching power supply circuit acts as a high-frequency transformer to open-loop control the switching state of the high-frequency switching network.

16. The switching power supply circuit according to any one of claims 1 to 5, characterized in that: The switching state of the high-frequency switch network is controlled so that the output voltage and / or current of the rectifier module meets the load requirements.

17. The switching power supply circuit according to any one of claims 1 to 5, characterized in that: The switching frequency of the high-frequency switching network is controlled so that the output voltage and / or current of the rectifier module meets the load requirements.

18. The switching power supply circuit according to any one of claims 1 to 5, characterized in that: The high-frequency switch network only operates within a period of time in the low-frequency AC input signal cycle, so that the rectifier module outputs a pulsating current.

19. The switching power supply circuit according to any one of claims 1 to 5, characterized in that: The high-frequency switch network further includes an EMI filter circuit, which is arranged at the low-frequency AC input end and controls the switching state of the high-frequency switch network so that the input current changes synchronously with the low-frequency AC input signal.

20. The switching power supply circuit according to claim 1, wherein: The rectifier module is one of a full-wave rectifier circuit and a full-bridge rectifier circuit.

Images