A switching circuit and a control method thereof

Abstract

The application discloses a switching circuit and a control method thereof. The switching circuit comprises a power input module, a resonant capacitor, a resonant inductor, a transformer, a voltage output module and a working mode control module. The voltage output module comprises a voltage output path, an LLC mode path and an AHB mode path connected with the voltage output path respectively. The AHB mode path comprises a first triode, and the LLC mode path comprises a second triode. When the first triode is turned on and the second triode is turned off, the switching circuit works in the AHB mode. When the first triode is turned off and the second triode is turned on, the switching circuit works in the LLC mode. The application has the advantages of LLC topology and AHB topology, can adopt the LLC topology to ensure the efficiency and EMI performance of high-frequency application, and can adopt the AHB topology to meet the demand of large input-output variation range.

Description

Technical Field

[0001] This invention relates to the field of switching circuit technology, and in particular to a switching circuit and its control method. Background Technology

[0002] Currently, the most common switching circuits are LLC topologies and AHB topologies. LLC topologies offer good electromagnetic interference (EMI) performance, but their efficiency is only high near the resonant point, making them unsuitable for wide input voltage ranges and requiring a small input / output variation range. While AHB topologies can accommodate a wide range of input / output variations, their efficiency is lower than LLC topologies in high-frequency applications, and they are also larger. Furthermore, the control strategy for AHB topologies is more complex, requiring more precise design and debugging. Summary of the Invention

[0003] This invention provides a switching circuit and its control method to solve the technical problem that current switching circuits cannot simultaneously handle large variations in power input and output efficiency and EMI performance.

[0004] To address the aforementioned technical problems, in a first aspect, the present invention provides a switching circuit, comprising a power input module, a resonant capacitor, a resonant inductor, a transformer, a voltage output module, and a working mode control module. The transformer comprises a primary winding and a secondary winding. One end of the power input module is connected to the resonant capacitor, the resonant capacitor and the resonant inductor are connected in series with one end of the primary winding, and the other end of the power input module is connected to the other end of the primary winding. The voltage output module includes a voltage output path and an LLC mode path and an AHB mode path respectively connected to the voltage output path. The AHB mode path includes a first transistor, and the LLC mode path includes a second transistor. The voltage output path, the LLC mode path, and the AHB mode path are connected to the secondary winding and generate an output voltage. The operating mode control module receives the output voltage and is connected to the base of the first transistor and the base of the second transistor. When the first transistor is on and the second transistor is off, the switching circuit operates in AHB mode; when the first transistor is off and the second transistor is on, the switching circuit operates in LLC mode.

[0005] In some embodiments, the AHB mode path further includes a first diode, the LLC mode path further includes a second diode, and the secondary winding includes a first winding and a second winding. One end of the first transistor is connected to the voltage output path, the other end of the first transistor is connected to one end of the first winding, the other end of the first winding is connected to the positive terminal of the first diode, and the negative terminal of the first diode is connected to the voltage output path. One end of the second transistor is connected to the voltage output path, the other end of the second transistor is connected to one end of the second winding, the other end of the second winding is connected to the positive terminal of the second diode, and the negative terminal of the second diode is connected to the voltage output path.

[0006] In some embodiments, the voltage output path includes a third diode and an RC circuit, and the secondary winding further includes a third winding; The positive terminal of the third diode is connected to one end of the third winding, and the other end of the third winding is connected to one end of the first transistor, one end of the second transistor, and one end of the RC circuit. The other end of the RC circuit is connected to the negative terminal of the first diode, the negative terminal of the second diode, and the negative terminal of the third diode.

[0007] In some embodiments, the operating mode control module includes a control chip that receives the output voltage, and a first pin of the control chip is connected to the base of the first transistor, and a second pin of the control chip is connected to the base of the second transistor.

[0008] In some embodiments, the voltage output path is connected to several Buck circuits and outputs a Buck voltage, and the control chip also receives the Buck voltage.

[0009] In some embodiments, the third pin of the control chip is connected to an output voltage adjustment unit, which includes a first resistor, a second resistor, a fourth diode, and a third resistor. One end of the first resistor, one end of the third resistor, the cathode of the fourth diode, and the third pin are connected. The other end of the third resistor is grounded. The other end of the first resistor, one end of the second resistor, and the voltage output terminal of the voltage output path are connected. The other end of the second resistor is connected to the anode of the fourth diode.

[0010] In some embodiments, the power input module includes a power supply, a fourth transistor, a fifth transistor, a fifth diode, a sixth diode, a first capacitor, and a second capacitor. The positive terminal of the power supply is connected to the collector of the fourth transistor, the negative terminal of the fifth diode, and one end of the first capacitor. The emitter of the fourth transistor, the positive terminal of the fifth diode, the other end of the first capacitor, one end of the resonant capacitor, the collector of the fifth transistor, the negative terminal of the sixth diode, and one end of the second capacitor are connected. The emitter of the fifth transistor, the positive terminal of the sixth diode, the other end of the second capacitor, the other end of the primary winding, and the negative terminal of the power supply are connected.

[0011] In some of these embodiments, the transformer employs a sandwich winding method.

[0012] In some embodiments, there is a dead time between the first transistor and the second transistor.

[0013] Secondly, the present invention also provides a control method for a switching circuit, comprising: Determine the output voltage value; If the output voltage value is less than the preset voltage value, a first level signal is sent to the first transistor and a second level signal is sent to the second transistor to turn on the first transistor and turn off the second transistor. The switching circuit operates in AHB mode. If the output voltage value is equal to the preset voltage value, a third level signal is sent to the first transistor and a fourth level signal is sent to the second transistor to turn off the first transistor and turn on the second transistor, and the switching circuit operates in LLC mode.

[0014] Compared with the prior art, the present invention has at least the following beneficial effects: The switching circuit of the present invention combines the advantages of LLC topology and AHB topology. It can use LLC topology to ensure efficiency and EMI performance in high-frequency applications, and can use AHB topology to meet the requirements of large input-output variation range. Attached Figure Description

[0015] Figure 1 This is a structural diagram of a switching circuit according to an embodiment of the present invention; Figure 2 This is a circuit diagram of a voltage output module shown in an embodiment of the present invention; Figure 3 This is an equivalent diagram of the secondary winding side of the AHB mode shown in an embodiment of the present invention; Figure 4 This is an equivalent diagram of the secondary winding side of the LLC mode shown in an embodiment of the present invention; Figure 5This is a circuit structure diagram of the control chip shown in an embodiment of the present invention; Figure 6 The diagram shows a plurality of Buck circuits according to an embodiment of the present invention. Figure 7 This is a flowchart illustrating the control method of the switching circuit according to an embodiment of the present invention. Detailed Implementation

[0016] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0017] It should be noted that when an element is said to be "fixed to" another element, it can be directly on the other element or there may be an intervening element. When an element is said to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. Conversely, when an element is said to be "directly on" another element, there is no intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0019] See Figure 1 The present invention illustrates a schematic diagram of a switching circuit, which includes a power input module 1, a resonant capacitor Cr, a resonant inductor Lr, a transformer T, a voltage output module 2, and a working mode control module 3. The transformer T includes a primary winding and a secondary winding. One end of the power input module 1 is connected to the resonant capacitor Cr, and the resonant capacitor Cr and the resonant inductor Lr are connected in series with one end of the primary winding. The other end of the power input module 1 is connected to the other end of the primary winding. The voltage output module 2 includes a voltage output path and an LLC mode path and an AHB mode path respectively connected to the voltage output path. The AHB mode path includes a first transistor Q1, and the LLC mode path includes a second transistor Q2. The voltage output path, the LLC mode path, and the AHB mode path are connected to the secondary winding and generate an output voltage V0. The operating mode control module 3 receives the output voltage and is connected to the base of the first transistor Q1 and the base of the second transistor Q2. When the first transistor Q1 is turned on and the second transistor Q2 is turned off, the switching circuit operates in AHB mode; when the first transistor Q1 is turned off and the second transistor Q2 is turned on, the switching circuit operates in LLC mode.

[0020] In this embodiment, the operating mode control module 3 controls the conduction or cutoff of the first transistor Q1 and the second transistor Q2 according to the output voltage, so as to switch the circuit to the AHB mode path or the LLC mode path, thereby combining the advantages of LLC topology and AHB topology. In high-frequency applications, LLC topology can be used to ensure the efficiency and EMI performance of high-frequency applications, and AHB topology can be used to meet the requirements of large input and output variation range.

[0021] Optionally, there is a dead time between the first transistor Q1 and the second transistor Q2 to ensure that there is a time lag in the switching process between AHB mode and LLC mode, thereby ensuring that the switching circuit switches normally between AHB mode and LLC mode.

[0022] In some embodiments, such as Figure 2 The circuit diagram of the voltage output module shown includes a first diode D1 in the AHB mode path, a second diode D2 in the LLC mode path, and a first winding and a second winding in the secondary winding. One end of the first transistor Q1 is connected to the voltage output path, the other end of the first transistor Q1 is connected to one end of the first winding, the other end of the first winding is connected to the positive terminal of the first diode D1, and the negative terminal of the first diode D1 is connected to the voltage output path. One end of the second transistor Q2 is connected to the voltage output path, the other end of the second transistor Q2 is connected to one end of the second winding, the other end of the second winding is connected to the positive terminal of the second diode D2, and the negative terminal of the second diode D2 is connected to the voltage output path.

[0023] In this embodiment, the bases of the first transistor Q1 and the second transistor Q2 respectively receive the level signals from the operating mode control module 3 to control the conduction or cutoff of the first transistor Q1 and the second transistor Q2; for example Figure 3 The equivalent diagram of AHB mode shown illustrates that when the first transistor Q1 is turned on and the second transistor Q2 is turned off, the switching circuit operates in AHB mode to meet the requirements of a wide input / output range; as shown... Figure 4 The equivalent diagram of LLC mode shown shows that when the first transistor Q1 is off and the second transistor Q2 is on, the switching circuit operates in LLC mode to meet the efficiency and EMI performance requirements of high-frequency applications.

[0024] In some embodiments, such as Figure 2 As shown, the voltage output path includes a third diode D3 and an RC circuit, and the secondary winding also includes a third winding; The positive terminal of the third diode is connected to one end of the third winding, and the other end of the third winding is connected to one end of the first transistor, one end of the second transistor, and one end of the RC circuit. The other end of the RC circuit is connected to the negative terminal of the first diode, the negative terminal of the second diode, and the negative terminal of the third diode.

[0025] The positive terminal of the third diode D3 is connected to one end of the third winding, and the other end of the third winding is connected to one end of the first transistor Q1, one end of the second transistor Q2, and one end of the RC circuit. The other end of the RC circuit, the negative terminal of the first diode D1, the negative terminal of the second diode D2, and the negative terminal of the third diode D3 are connected.

[0026] In this embodiment, as Figure 3 and Figure 4 As shown, when the switching circuit operates in AHB mode or LLC mode, the voltage is converted based on the transformer T and passed through the RC circuit composed of the first resistor R1 and the first capacitor C1 to obtain the output voltage.

[0027] For example, in fast charging applications, the stage following the output voltage Vo of the switching circuit has multiple DC-DC converters. To improve the efficiency of the DC-DC converters, Vo must vary with the output voltage. For instance, the output voltages of the PD3.1 fast charging protocol are 5V, 9V, 12V, 15V, 20V, and 28V. Therefore, when the output voltage is 5V, 9V, or 12V, Vo is set to 12.5V; at 15V, Vo is set to 15.5V; at 20V, Vo is set to 20.5V; and at 28V, Vo is set to 28.5V. Since LLC can only output a fixed voltage, to achieve the highest efficiency at the maximum power point, the highest voltage point can be selected, i.e., Vo = 28.5V. In other words, the LLC operating point is designed to be 28.5V. When Vo = 28.5V, the switching circuit operates in LLC mode, and its equivalent diagram is shown below. Figure 3 As shown, when Vo ≠ 28.5V, the switching circuit operates in AHB mode, and its equivalent diagram is shown below. Figure 4 As shown.

[0028] Optionally, the transformer T employs a sandwich winding method. For example... Figure 3 and Figure 4 As shown, when the switching circuit operates in AHB mode or LLC mode, the transformer T is sandwich wound, which can effectively improve the circuit efficiency.

[0029] In some embodiments, such as Figure 5 As shown, the working mode control module 3 includes a control chip IC. The control chip IC receives the output voltage, and the first pin of the control chip IC is connected to the base of the first transistor Q1, and the second pin of the control chip IC is connected to the base of the second transistor Q2.

[0030] In this embodiment, the control chip IC sends a level signal to the base of the first transistor Q1 through the first pin according to the received output voltage value, so as to control the first transistor Q1 to be turned on or off; and notifies the second pin to send a signal to the base of the second transistor Q2, so as to control the second transistor Q2 to be turned on or off.

[0031] In some embodiments, such as Figure 6 As shown, the voltage output path is connected to several Buck circuits and outputs Buck voltage, and the control chip also receives the Buck voltage.

[0032] In this embodiment, the Buck circuits are connected in parallel, and each Buck circuit outputs a Buck voltage. The input voltage V0 is adjusted according to the multiple Buck voltages so that it can be used to select the output high or low level from the first and second pins of the control chip IC.

[0033] In some embodiments, such as Figure 5As shown, the third pin of the control chip IC is connected to an output voltage adjustment unit. The output voltage adjustment unit includes a first resistor, a second resistor, a fourth diode, and a third resistor. One end of the first resistor, one end of the third resistor, the cathode of the fourth diode, and the third pin are connected. The other end of the third resistor is grounded. The other end of the first resistor, one end of the second resistor, and the voltage output terminal of the voltage output path are connected. The other end of the second resistor is connected to the anode of the fourth diode.

[0034] In this embodiment, the control chip IC adjusts the output voltage through optocoupler feedback to meet the output voltage judgment requirements when the control chip outputs a level signal.

[0035] For example, the output voltage of the Buck circuit is V1, V2, V3, V4. When fast charging is used to charge electronic devices such as mobile phones and computers, Vo will adjust according to the maximum value of (V1, V2, V3, V4). At this time, Vo will be slightly greater than the maximum value of (V1, V2, V3, V4). Therefore, Vo is set to (V1, V2, V3, V4)max + 0.5V. The maximum value of (V1, V2, V3, V4)max is detected by the control chip, and the output voltage Vo is adjusted through optocoupler feedback to make it meet Vo = (V1, V2, V3, V4)max + 0.5V. For the LLC operating point design, 28.5V is selected. When Vo is less than 28.5V, it operates in AHB mode, the first transistor Q1 is turned on, and the second transistor Q2 is turned off. When Vo = 28.5V, it operates in LLC mode, the first transistor Q1 is turned off, and the second transistor Q2 is turned on.

[0036] In some embodiments, the power input module 1 includes a power supply, a fourth transistor, a fifth transistor, a fifth diode, a sixth diode, a first capacitor, and a second capacitor. The positive terminal of the power supply is connected to the collector of the fourth transistor, the negative terminal of the fifth diode, and one end of the first capacitor. The emitter of the fourth transistor, the positive terminal of the fifth diode, the other end of the first capacitor, one end of the resonant capacitor, the collector of the fifth transistor, the negative terminal of the sixth diode, and one end of the second capacitor are connected. The emitter of the fifth transistor, the positive terminal of the sixth diode, the other end of the second capacitor, the other end of the primary winding, and the negative terminal of the power supply are connected.

[0037] In some embodiments, by providing a fourth transistor and a fifth transistor, the resonant frequency generated between the resonant inductor Lr, the resonant capacitor Cr, and the magnetizing inductance of the transformer T can be adjusted.

[0038] See Figure 7 , Figure 7This is a flowchart illustrating a control method for a switching circuit according to an embodiment of the present invention. The control method for the switching circuit of this invention can be applied to electronic devices, including but not limited to power adapters, fast chargers, etc. Figure 6 As shown, the control method of the switching circuit in this embodiment includes steps S101 to S103, which are described in detail below: Step S101: Determine the output voltage value; Step S102: If the output voltage value is less than the preset voltage value, a first level signal is sent to the first transistor and a second level signal is sent to the second transistor to turn on the first transistor and turn off the second transistor. The switching circuit operates in AHB mode. Step S103: If the output voltage value is equal to the preset voltage value, a third level signal is sent to the first transistor and a fourth level signal is sent to the second transistor to turn off the first transistor and turn on the second transistor, and the switching circuit operates in LLC mode.

[0039] In this embodiment, the output voltage value can be adjusted via optocoupler feedback to satisfy Vo = (V1, V2, V3)max + 0.5V. For example, with the LLC operating point designed to be 28.5V, when Vo is less than 28.5V, it operates in AHB mode, with the first transistor on and the second transistor off. When Vo = 28.5V, it operates in LLC mode, with the first transistor off and the second transistor on.

[0040] The switching circuit of the present invention combines the advantages of LLC topology and AHB topology. It can use LLC topology to ensure efficiency and EMI performance in high-frequency applications, and can use AHB topology to meet the requirements of large input-output variation range.

[0041] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0042] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A switching circuit, characterized in that, It includes a power input module, a resonant capacitor, a resonant inductor, a transformer, a voltage output module, and a working mode control module. The transformer includes a primary winding and a secondary winding. One end of the power input module is connected to the resonant capacitor, and the resonant capacitor and the resonant inductor are connected in series with one end of the primary winding. The other end of the power input module is connected to the other end of the primary winding. The voltage output module includes a voltage output path and an LLC mode path and an AHB mode path respectively connected to the voltage output path. The AHB mode path includes a first transistor, and the LLC mode path includes a second transistor. The voltage output path, the LLC mode path, and the AHB mode path are connected to the secondary winding and generate an output voltage. The operating mode control module receives the output voltage and is connected to the base of the first transistor and the base of the second transistor. When the first transistor is on and the second transistor is off, the switching circuit operates in AHB mode; when the first transistor is off and the second transistor is on, the switching circuit operates in LLC mode.

2. The switching circuit as described in claim 1, characterized in that, The AHB mode path further includes a first diode, the LLC mode path further includes a second diode, and the secondary winding includes a first winding and a second winding. One end of the first transistor is connected to the voltage output path, the other end of the first transistor is connected to one end of the first winding, the other end of the first winding is connected to the positive terminal of the first diode, and the negative terminal of the first diode is connected to the voltage output path. One end of the second transistor is connected to the voltage output path, the other end of the second transistor is connected to one end of the second winding, the other end of the second winding is connected to the positive terminal of the second diode, and the negative terminal of the second diode is connected to the voltage output path.

3. The switching circuit as described in claim 2, characterized in that, The voltage output path includes a third diode and an RC circuit, and the secondary winding also includes a third winding; The positive terminal of the third diode is connected to one end of the third winding, and the other end of the third winding is connected to one end of the first transistor, one end of the second transistor, and one end of the RC circuit. The other end of the RC circuit is connected to the negative terminal of the first diode, the negative terminal of the second diode, and the negative terminal of the third diode.

4. The switching circuit as described in claim 1, characterized in that, The operating mode control module includes a control chip, which receives the output voltage, and the first pin of the control chip is connected to the base of the first transistor, and the second pin of the control chip is connected to the base of the second transistor.

5. The switching circuit as described in claim 4, characterized in that, The voltage output path is connected to several Buck circuits and outputs Buck voltage. The control chip also receives the Buck voltage.

6. The switching circuit as described in claim 4, characterized in that, The third pin of the control chip is connected to an output voltage adjustment unit, which includes a first resistor, a second resistor, a fourth diode, and a third resistor. One end of the first resistor, one end of the third resistor, the cathode of the fourth diode, and the third pin are connected. The other end of the third resistor is grounded. The other end of the first resistor, one end of the second resistor, and the voltage output terminal of the voltage output path are connected. The other end of the second resistor is connected to the anode of the fourth diode.

7. The switching circuit as described in claim 1, characterized in that, The power input module includes a power supply, a fourth transistor, a fifth transistor, a fifth diode, a sixth diode, a first capacitor, and a second capacitor. The positive terminal of the power supply is connected to the collector of the fourth transistor, the negative terminal of the fifth diode, and one end of the first capacitor. The emitter of the fourth transistor, the positive terminal of the fifth diode, the other end of the first capacitor, one end of the resonant capacitor, the collector of the fifth transistor, the negative terminal of the sixth diode, and one end of the second capacitor are connected. The emitter of the fifth transistor, the positive terminal of the sixth diode, the other end of the second capacitor, the other end of the primary winding, and the negative terminal of the power supply are connected.

8. The switching circuit as described in claim 1, characterized in that, The transformer uses a sandwich winding method.

9. The switching circuit as described in claim 1, characterized in that, There is a dead time between the first transistor and the second transistor.

10. A control method for a switching circuit as described in any one of claims 1 to 9, characterized in that, include: Determine the output voltage value; If the output voltage value is less than the preset voltage value, a first level signal is sent to the first transistor and a second level signal is sent to the second transistor to turn on the first transistor and turn off the second transistor. The switching circuit operates in AHB mode. If the output voltage value is equal to the preset voltage value, a third level signal is sent to the first transistor and a fourth level signal is sent to the second transistor to turn off the first transistor and turn on the second transistor, and the switching circuit operates in LLC mode.

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