Switching converter with pre-charging circuit

Abstract

The switching converter comprises an input end, an output end, an input switching circuit coupled between the input end and the output end, an energy storage circuit, an output switching circuit coupled to the energy storage circuit and the output end, and a pre-charging circuit. The input switch circuit comprises a first switch tube and a second switch tube which are coupled in series, and the common end of the first switch tube and the second switch tube is a first switch node. The tank circuit includes a first capacitor coupled to the first switch node. The pre-charging circuit is coupled between the input end and the first switch node and comprises a first voltage stabilizing diode and a first resistor which are coupled in series, and the cathode of the first voltage stabilizing diode is coupled to the input end. The pre-charging circuit charges the first capacitor in the starting process of the switching converter and automatically stops charging the first capacitor according to the input voltage of the switching converter. The pre-charging circuit does not need external control, the voltage stress borne by the switching tube close to the input end in the starting process can be reduced, and therefore the circuit cost is reduced.

Description

Technical Field

[0001] This invention relates to an electronic circuit, and more specifically, to a switching converter. Background Technology

[0002] In applications requiring high energy conversion efficiency, high energy density, and small size, switching converters incorporate capacitors as energy storage elements to perform energy transfer and voltage conversion. Typical topologies include switched-capacitor converters (SCCs). In some applications, magnetic components can be further incorporated into the switched-capacitor converter topology to form resonant switched-tank converters (STCs), further improving efficiency and energy density, enabling them to provide higher voltage conversion ratios.

[0003] However, during power-up, this type of switching converter experiences higher voltage stress on the switching transistors than in the steady-state phase because the initial voltage across the capacitor is zero or much lower than the capacitor voltage in the steady-state phase. This is especially true for switching transistors located near the input, where the voltage during power-up is significantly higher than in the steady-state phase. Therefore, only switching transistors with higher voltage ratings can be selected, leading to increased cost and wasted performance in the switching converter circuit. Summary of the Invention

[0004] Therefore, in order to solve the above-mentioned technical problems, the present invention proposes a switching converter with a pre-charging circuit.

[0005] According to an embodiment of the present invention, a switching converter is provided, including an input terminal, an output terminal, an input switching circuit, an output switching circuit, a first capacitor, a second capacitor, a third capacitor, and a pre-charge circuit. The input terminal of the switching converter is configurable to receive an input voltage, and the output terminal is configurable to provide an output voltage. The input switching circuit includes a first switch, a second switch, a third switch, and a fourth switch, each switch including a first terminal and a second terminal. The first terminal of the first switch is coupled to the input terminal of the switching converter, and the second terminal of the fourth switch is coupled to the output terminal of the switching converter. The second terminal of the first switch and the first terminal of the second switch are coupled to form a first switching node, the second terminal of the second switch and the first terminal of the third switch are coupled to form a second switching node, and the second terminal of the third switch and the first terminal of the fourth switch are coupled to form a third switching node. The output switching circuit includes at least one switch and is coupled to the output terminal of the switching converter and the input switching circuit. One end of the first capacitor is coupled to the first switching node, and the other end is coupled to the output switching circuit. One end of the second capacitor is coupled to the second switching node, and the other end is coupled to the output switching circuit. One end of the third capacitor is coupled to the third switching node, and the other end is coupled to the output switching circuit. The pre-charge circuit includes a first terminal and a second terminal. The first terminal of the pre-charge circuit is coupled to the input terminal of the switching converter, and the second terminal of the pre-charge circuit is coupled to at least one of the first to third switching nodes. The pre-charge circuit includes a first Zener diode and a first resistor coupled in series. The cathode of the first Zener diode is coupled to the input terminal of the switching converter.

[0006] According to an embodiment of the present invention, a switching converter is also provided, including an input terminal, an output terminal, a first switching transistor, a second switching transistor, a first capacitor, a first magnetic element, a second magnetic element, an output switching circuit, and a pre-charge circuit. The input terminal of the switching converter is configurable to receive an input voltage, and the output terminal is configurable to provide an output voltage. The first switching transistor and the second switching transistor each include a first terminal and a second terminal. The first terminal of the first switching transistor is coupled to the input terminal of the switching converter, and the second terminal of the first switching transistor is coupled to the first terminal of the second switching transistor to form a first switching node. The first capacitor has a first terminal and a second terminal, and the first terminal of the first capacitor is coupled to the first switching node. The first magnetic element and the second magnetic element each have a first terminal and a second terminal. The first terminal of the first magnetic element is coupled to the second terminal of the second switching transistor, the first terminal of the second magnetic element is coupled to the second terminal of the first capacitor, and the second terminals of the first magnetic element and the second magnetic element are coupled to the output terminal of the switching converter. The output switching circuit includes a third switching transistor and a fourth switching transistor. The third switching transistor is coupled between the second terminal of the second switching transistor and a reference ground, and the fourth switching transistor is coupled between the second terminal of the first capacitor and the reference ground. The pre-charge circuit is coupled between the input terminal of the switching converter and the second terminal of the first switching transistor, and includes a first Zener diode and a first resistor coupled in series. The cathode of the first Zener diode is coupled to the input terminal of the switching converter.

[0007] According to an embodiment of the present invention, a switching converter is also provided, including an input terminal, an output terminal, an input switching circuit, an energy storage circuit, an output switching circuit, and a pre-charge circuit. The input terminal of the switching converter is configurable to receive an input voltage, and the output terminal is configurable to provide an output voltage. The input switching circuit includes a first switching transistor and a second switching transistor connected in series, the common terminal of which forms a first switching node, and is coupled between the input terminal and the output terminal of the switching converter. The energy storage circuit includes a first capacitor, one end of which is coupled to the first switching node. The output switching circuit is coupled to the energy storage circuit and the output terminal of the switching converter, and includes at least one switching transistor. The pre-charge circuit is coupled between the input terminal of the switching converter and the first switching node, and includes a first Zener diode and a first resistor connected in series, the cathode of which is coupled to the input terminal of the switching converter. The pre-charge circuit is configured to charge the first capacitor during startup of the switching converter and is configured to automatically stop charging the first capacitor based on the input voltage.

[0008] Compared to traditional technologies, the switching converter of the present invention does not require external control. It pre-charges the capacitor during startup and automatically stops charging the first capacitor according to the input voltage, thereby reducing the voltage stress on the switching transistor near the input terminal during startup and thus reducing circuit cost. Attached Figure Description

[0009] To better understand this invention, it will be described in detail with reference to the following drawings. Identical or similar elements are referred to by the same reference numerals.

[0010] Figure 1 The circuit structure diagram of the existing switching converter 100 is shown below.

[0011] Figure 2 A circuit diagram of a switching converter 200 according to an embodiment of the present invention is shown;

[0012] Figure 3 A circuit diagram of a switching converter 300 according to an embodiment of the present invention is shown;

[0013] Figure 4 A circuit diagram of a switching converter 400 according to an embodiment of the present invention is shown;

[0014] Figure 5 Examples of embodiments of the present invention are shown. Figure 4 The signal waveform diagram 500 of the switching converter 400 shown during the pre-charging process is shown in Figure 500.

[0015] Figure 6 A circuit diagram of a switching converter 600 according to an embodiment of the present invention is shown;

[0016] Figure 7 A circuit diagram of a switching converter 700 according to an embodiment of the present invention is shown;

[0017] Figure 8 A circuit diagram of a switching converter 800 according to an embodiment of the present invention is shown;

[0018] Figure 9 A circuit diagram of a switching converter 900 according to an embodiment of the present invention is shown.

[0019] Figure 10 This is a flowchart of a pre-charging method 1000 for a switching converter according to an embodiment of the present invention. Detailed Implementation

[0020] Specific embodiments of the present invention will now be described in detail. It should be noted that the embodiments described herein are for illustrative purposes only and are not intended to limit the invention. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that these specific details are not necessary to practice the invention. In other instances, well-known circuits, materials, or methods have not been specifically described to avoid obscuring the invention.

[0021] Throughout this specification, references to “an embodiment,” “an example,” or “an example” mean that a particular feature, structure, or characteristic described in connection with that embodiment or example is included in at least one embodiment of the invention. Therefore, the phrases “in an embodiment,” “in an embodiment,” “an example,” or “an example” appearing in various places throughout the specification do not necessarily refer to the same embodiment or example. Furthermore, specific features, structures, or characteristics can be combined in one or more embodiments or examples in any suitable combination and / or sub-combination. Moreover, those skilled in the art will understand that the accompanying drawings provided herein are for illustrative purposes and are not necessarily drawn to scale. It should be understood that when an element is referred to as “coupled” or “connected” to another element, it can be directly coupled to the other element or there may be intermediate elements. Conversely, when an element is referred to as “directly coupled” or “directly connected” to another element, there are no intermediate elements. The same reference numerals indicate the same elements. The term “and / or” as used herein includes any and all combinations of one or more of the associated listed items.

[0022] Figure 1 This is a circuit diagram of an existing switching converter 100. Figure 1 As shown, the switching converter 100 receives an input voltage Vin at its input terminal 101 and provides an output voltage Vout at its output terminal 102. The switching converter 100 includes an input switching circuit 110, an energy storage circuit 120, and an output switching circuit 130. The input switching circuit 110 is coupled between the input terminal 101 and the output terminal 102 of the switching converter 100 and includes series-coupled switching transistors S1 to S4. Each of the switching transistors S1 to S4 has a first terminal and a second terminal. The first terminal of switching transistor S1 is coupled to the input terminal of the switching converter 100, and the second terminal of switching transistor S4 is coupled to the output terminal of the switching converter 100. The second terminal of switching transistor S1 is coupled to the first terminal of switching transistor S2 to form a switching node 111, the second terminal of switching transistor S2 is coupled to the first terminal of switching transistor S3 to form a switching node 112, and the second terminal of switching transistor S3 is coupled to the first terminal of switching transistor S4 to form a switching node 113. Figure 1 In the example, the energy storage circuit 120 includes capacitors Cd1, Cd2, and Cd3, each of which has a first terminal and a second terminal. The first terminal of capacitor Cd1 is coupled to switching node 111, the first terminal of capacitor Cd2 is coupled to switching node 112, and the first terminal of capacitor Cd3 is coupled to switching node 113. The output switching circuit 130 is coupled to the output terminal 102 of the switching converter 100 to provide the output voltage Vout. Figure 1In the example, the output switching circuit 130 includes two bridge arms composed of switching transistors S5 to S8. These two bridge arms are connected in parallel between the output terminal 102 of the switching converter 100 and the reference ground GND, and each has bridge arm nodes 131 and 132. Specifically, switching transistors S5 and S6 are connected in series between the output terminal 102 of the switching converter 100 and the reference ground GND, and switching transistors S7 and S8 are connected in series between the output terminal 102 of the switching converter 100 and the reference ground GND. The common terminal of switching transistors S5 and S6 forms bridge arm node 131, and the common terminal of switching transistors S7 and S8 forms bridge arm node 132. Figure 1 As shown, the output switching circuit 130 is coupled to the energy storage circuit 120. Figure 1 In the example, the second end of capacitor Cd1 and the second end of capacitor Cd3 are coupled to bridge arm node 131, and the second end of capacitor Cd2 is coupled to bridge arm node 132.

[0023] Figure 1 The switching converter 100 shown is illustrated using a switched capacitor converter (SCC) as an example, where capacitors Cd1 to Cd3 are flying capacitors. By controlling the on and off states of switches S1 to S8 in the input switching circuit 110 and the output switching circuit 130, the charging and discharging of capacitors Cd1 to Cd3 can be controlled, thereby achieving energy transfer and voltage conversion. The switching converter 100 has a voltage conversion ratio of 4:1. In steady state, the maximum voltage stress Vdsmax1 borne by switch S1 is equal to the output voltage Vout, and the maximum voltage stress Vdsmax2 borne by switch S2 is equal to twice the output voltage Vout. For example, when the input voltage Vin is 60V and the output voltage Vout is 15V in steady state, the maximum voltage stress Vdsmax1 borne by switch S1 in steady state is equal to 15V, and the maximum voltage stress Vdsmax2 borne by switch S2 is equal to 30V. However, during the startup of the switching converter 100, since the flying capacitors Cd1 to Cd3 have no initial charge, the voltage Vds1 across the switching transistor S1 increases with the increase of the input voltage Vin. When the input voltage Vin reaches 60V, the voltage Vds1 across the switching transistor S1 also reaches its maximum value (approximately 60V). That is, during the startup of the switching converter 100, the maximum voltage stress Vdsmax1 borne by the switching transistor S1 can reach approximately 60V. If the controller ( Figure 1 If the switching transistors S1 to S8 (not shown) are controlled to turn on and off, the maximum voltage stress Vdsmax2 borne by the switching transistor S2 will reach a level close to 60V before the switching converter 100 enters a steady state.

[0024] For switching transistors located near the input terminal (e.g.) Figure 1Regarding the switching transistors S1 and S2 in the switching converter 100, the aforementioned characteristics during startup significantly limit the selection of the models of switching transistors S1 and S2. For example, with an input voltage Vin of 60V and an output voltage Vout of 15V, although the required withstand voltage of switching transistors S1 and S2 during steady-state operation is much lower than 60V, models with a withstand voltage of 60V or higher must be selected, leading to increased overall losses and costs for the switching converter 100. Although Figure 1 Taking a switched-capacitor converter as an example only, those skilled in the art will know that other switched-capacitor converters that utilize capacitors for energy conversion also suffer from the aforementioned problems. Therefore, this invention proposes a switched-capacitor converter with a pre-charging circuit. This pre-charging circuit requires no external control, pre-charging the capacitors in the switched-capacitor during startup and automatically stopping charging the capacitors based on the input voltage, thereby preventing the switching transistors near the input terminal from experiencing excessive voltage stress during startup.

[0025] Figure 2 A circuit diagram of a switching converter 200 according to an embodiment of the present invention is shown. Figure 2 As shown, the switching converter 200 receives an input voltage Vin at its input terminal 101 and supplies it to the load at its output terminal 102. Figure 2(Not shown) provides an output voltage Vout. The switching converter 200 includes an input switching circuit 110, an energy storage circuit 120, and an output switching circuit 130. The circuit structure and connections of the input switching circuit 110, energy storage circuit 120, and output switching circuit 130 are consistent with those of the switching converter 100, forming a switched-capacitor converter. Those skilled in the art will understand that, in embodiments of the present invention, each of the switching transistors S1 to S8 may include, for example, a controllable switching device such as a metal-oxide-semiconductor field-effect transistor (MOSFET), a junction field-effect transistor (JFET), a bipolar junction transistor (BJT), a super junction transistor (SJT), or an insulated-gate bipolar transistor (IGBT). Unlike the switching converter 100, the switching converter 200 further includes a pre-charge circuit 140. A pre-charge circuit 140 is coupled between the input terminal 101 of the switching converter 200 and at least one of the switching nodes 111-112. Specifically, the pre-charge circuit 140 includes a first terminal and a second terminal. The first terminal of the pre-charge circuit 140 is coupled to the input terminal 101 of the switching converter 200, and the second terminal of the pre-charge circuit 140 is coupled to at least one of the capacitors Cd1-Cd3. During the startup process of the switching converter 200, the pre-charge circuit 140 charges at least one of the capacitors Cd1-Cd3 and automatically stops charging the corresponding capacitor based on the input voltage Vin. For example, after the input voltage Vin reaches a stable value, the pre-charge circuit 140 automatically stops charging the corresponding capacitor. Figure 2 In the illustrated embodiment, the pre-charge circuit 140 includes a Zener diode D1 and a resistor R1 connected in series between the input terminal 101 and the switching node 112. The cathode of the Zener diode D1 is coupled to the input terminal 101 of the switching converter 200. Those skilled in the art will understand that the pre-charge circuit 140 can also be coupled between the input terminal 101 and the switching node 111, or between the input terminal 101 and the switching node 113. Those skilled in the art should understand that in the embodiments of the present invention, when a component is referred to as "coupled" to another component, it can be directly coupled to the other component, or coupled to the other component through an intermediate component, such as a resistor, capacitor, inductor, or switching transistor.

[0026] Figure 2 The arrows in the diagram schematically illustrate the pre-charge path of the switching converter 200. Figure 2 In the illustrated embodiment, the Zener diode D1 has a stable voltage Vz1. For example... Figure 2 As indicated by the arrows, during the startup process of the switching converter 200, the input voltage Vin rises continuously from zero. When the voltage division of the Zener diode D1 reaches its stable voltage Vz1, the Zener diode D1 breaks down in reverse, and the input voltage Vin begins to generate a pre-charging current Ipre through the pre-charging circuit 140, charging the capacitor Cd2, and the voltage at the switching node 112 increases. In one embodiment, the switching transistors S1 to S8 are all MOSFETs with body diodes. The increased voltage at the switching node 112 further conducts the body diode of the switching transistor S2, causing the voltage at the switching node 111 to increase, thereby further charging the capacitor Cd1.

[0027] Figure 3 A circuit diagram of a switching converter 300 according to an embodiment of the present invention is shown. Figure 3 As shown, the switching converter 300 receives an input voltage Vin at input terminal 101 and provides an output voltage Vout at output terminal 102. The switching converter 300 includes an input switching circuit 110, an energy storage circuit 320, an output switching circuit 130, and a pre-charge circuit 140. The circuit structure and connections of the input switching circuit 110, output switching circuit 130, and pre-charge circuit 140 are consistent with those of the switching converter 200. The difference from the switching converter 200 is that the energy storage circuit 320 includes a resonant tank circuit 321 coupled between switching node 111 and bridge arm node 131, a resonant tank circuit 322 coupled between switching node 113 and bridge arm node 131, and a capacitor Cd coupled between switching node 112 and bridge arm node 132. The resonant tank circuit 321 includes a capacitor Cr1 and an inductor Lr1 coupled in series, and the resonant tank circuit 322 includes a capacitor Cr2 and an inductor Lr2 coupled in series. Compared to the switching converter 200, Figure 3 The shown switching converter 300 further incorporates inductors Lr1 and Lr2 into the energy storage circuit 320, forming a resonant switched-capacitor converter (STC). Figure 3 In the embodiment shown, the pre-charge circuit 140 pre-charges capacitors Cd and Cr1 during the startup process of the switching converter 300. The pre-charge path of the switching converter 300 is similar to that of the switching converter 200, and will not be described again here.

[0028] Figure 4 A circuit diagram of a switching converter 400 according to an embodiment of the present invention is shown. Similar to switching converter 300, switching converter 400 is also a resonant switched-capacitor converter. Figure 4As shown, the switching converter 400 receives an input voltage Vin at input terminal 101 and provides an output voltage Vout at output terminal 102. The switching converter 400 includes an input switching circuit 110, an energy storage circuit 320, an output switching circuit 430, and a pre-charge circuit 140. The circuit structure and connections of the input switching circuit 110, energy storage circuit 320, and pre-charge circuit 140 are consistent with those of the switching converter 300. The difference between the switching converter 400 and the switching converter 300 is that the output switching circuit 430 of the switching converter 400 includes three bridge arms composed of switching transistors S5 to S10. These three bridge arms are connected in parallel between the output terminal 102 of the switching converter 400 and the reference ground GND, and have bridge arm nodes 431, 432, and 433, respectively. Figure 4 In the illustrated embodiment, resonant tank circuit 321 is coupled between switch node 111 and bridge arm node 431, capacitor Cd is coupled between switch node 112 and bridge arm node 432, and resonant tank circuit 322 is coupled between switch node 113 and bridge arm node 433. Those skilled in the art will understand that in the embodiments of the present invention, each of the switching transistors S1 to S10 may include, for example, a controllable switching device such as a metal-oxide-semiconductor field-effect transistor (MOSFET), a crystal field-effect transistor (JFET), a bipolar junction transistor (BJT), a superjunction transistor (SJT), or an insulated gate bipolar transistor (IGBT).

[0029] Similar to the switching converter 300, in Figure 4 In the illustrated embodiment, the pre-charge circuit 140 pre-charges capacitors Cd and Cr1 during the startup process of the switching converter 400. Once the switching converter has completed startup and is operating in steady state, it should be ensured that no current flows through the pre-charge circuit 140. That is, the voltage between input terminal 101 and switching node 112 in steady state should be less than the stable voltage Vz1 of the Zener diode D1 to ensure that the Zener diode D1 does not break down in steady state. For example, when the input voltage Vin is 60V and the output voltage Vout is 15V in steady state, the maximum voltage between input terminal 101 and switching node 112 is 30V. Therefore, a Zener diode D1 with a stable voltage Vz1 greater than 30V (e.g., Vz1 = 33V) needs to be selected. In the pre-charge circuit 140, the resistor R1 adjusts the magnitude of the pre-charge current Ipre. When the resistor R1 is small, the pre-charge current Ipre is large, and the charging speed of capacitors Cr1 and Cd is fast; when the resistor R1 is large, the pre-charge current Ipre is small, which can prevent the Zener diode D1 from overheating. In one embodiment, the value of the resistor R1 can be between 1 and 20 Ω. Although Figure 4The illustrated embodiment uses a resonant switched capacitor converter as an example for illustration, but those skilled in the art should understand that the energy storage circuit 320 of the switch converter 400 can also be replaced by the energy storage circuit 120 in the switch converter 200 to form a non-resonant switched capacitor converter.

[0030] Figure 5 Examples of embodiments of the present invention are shown. Figure 4 The signal waveform diagram 500 of the switching converter 400 during the pre-charging process is shown. Figure 5 The waveforms of the input voltage Vin, the voltage Vds1 across switch S1, the voltage Vds2 across switch S2, and the pre-charge current Ipre of the switching converter 400 are shown from top to bottom. Figure 5 In the illustrated embodiment, the example uses an input voltage Vin of 60V in steady state, a Zener diode D1 voltage Vz1 of 33V, and a resistor R1 of 10Ω. However, those skilled in the art will understand that the input voltage Vin, the Zener diode D1 voltage Vz1, and the resistor R1 in steady state can all be any other suitable values. Figure 5 As shown, at time t0, the input voltage Vin increases from 0V. Since the voltage at switch node 111 is still 0V, the voltage Vds1 across switch S1 also increases from 0V. At time t1, the voltage drop across Zener diode D1 reaches its stable voltage Vz, causing reverse breakdown. The voltage stress Vds1 across switch S1 reaches 33V. The pre-charge circuit 140 begins to generate a pre-charge current Ipre, which charges capacitor Cd. Subsequently, the body diode of switch S2 conducts, and the pre-charge current Ipre flows through the body diode of switch S2 and further charges capacitor Cr1. Therefore, the voltage stress Vds2 across switch S2 decreases slightly, approximately equal to the negative value of the forward voltage drop of the body diode of switch S2 (e.g., Vds2 = -2V). After time t1, the input voltage Vin continues to increase, and the body diode of switch S2 remains conducting. Therefore, the voltage stress Vds2 on switch S2 remains unchanged. Due to the voltage drop across resistor R1, the voltage stress Vds1 on switch S1 continues to increase slowly. At time t2, the input voltage Vin reaches 60V and no longer changes. The pre-charge current Ipre decreases until it reaches 0A, meaning the pre-charge circuit 140 no longer charges capacitors Cd and Cr1. The voltage stress Vds1 on switch S1 reaches its maximum value of approximately 35V between times t1 and t2, and the pre-charge current Ipre also reaches its maximum value between times t1 and t2. After time t2, as resistor R1 and capacitor Cd begin their RC discharge process, the voltage stress Vds1 on switch S1 decreases slightly and gradually stabilizes.

[0031] At some time after time t2 ( Figure 5 (Not shown), switching transistors S1 to S10 begin to turn on and off under the control of the controller, causing the switching converter 400 to gradually enter a steady state. Therefore, the maximum voltage stress Vdsmax2 experienced by switching transistor S2 in steady state is approximately 30V, and the maximum voltage stress Vdsmax1 experienced by switching transistor S1 in steady state is approximately 15V. Therefore, for Figure 4 In the switch converter 400 shown, switching transistors S1 and S2 can be, for example, devices with a withstand voltage of 40V. However, if the switch converter 400 does not include the pre-charge circuit 140, then switching transistors S1 and S2 can only be devices with a withstand voltage of 60V or higher. Therefore, embodiments of the present invention avoid subjecting the switching transistors near the input terminal to excessive voltage stress during startup without external control, thereby reducing waste of device performance and lowering the overall circuit cost of the switch converter.

[0032] Figure 6 A circuit diagram of a switching converter 600 according to an embodiment of the present invention is shown. Similar to switching converter 400, switching converter 600 is also a resonant switched-capacitor converter. Figure 6 As shown, the switching converter 600 receives an input voltage Vin at input terminal 101 and provides an output voltage Vout at output terminal 102. The switching converter 600 includes an input switching circuit 110, an energy storage circuit 320, an output switching circuit 430, and a pre-charge circuit 640. The circuit structure and connections of the input switching circuit 110, energy storage circuit 320, and output switching circuit 430 are consistent with those of the switching converter 400. The difference from the switching converter 400 is that in the switching converter 600, the pre-charge circuit 650, in addition to including a Zener diode D1 and a resistor R1 connected in series between input terminal 101 and switching node 112, also includes a Zener diode D2 and a resistor R2 connected between input terminal 101 and switching node 111. Figure 6 In the embodiment shown, the cathode of the Zener diode D2 is coupled to the input terminal 101 of the switching converter 600.

[0033] Figure 6 The arrows in the diagram schematically illustrate the pre-charge path of the switching converter 600. Figure 6 In the illustrated embodiment, Zener diode D2 has a stable voltage Vz2, which is less than the stable voltage Vz1 of Zener diode D1. Figure 6As shown by the arrows, during the startup process of the switching converter 500, the input voltage Vin gradually increases and first causes the voltage division of Zener diode D2 to reach its stable voltage Vz2. Zener diode D2 then breaks down in reverse, and the input voltage Vin begins to generate a pre-charging current Ipre to charge capacitor Cr1 through Zener diode D2 and resistor R2, causing the voltage at switching node 111 to rise. When the input voltage Vin further increases and causes the voltage division of Zener diode D1 to reach its stable voltage Vz1, Zener diode D1 breaks down in reverse, and the input voltage Vin begins to generate a pre-charging current Ipre' to charge capacitor Cd through Zener diode D1 and resistor R1, causing the voltage at switching node 112 to rise.

[0034] Figure 7 A circuit diagram of a switching converter 700 according to an embodiment of the present invention is shown. Figure 7 As shown, the switching converter 700 receives an input voltage Vin at its input terminal 101 and provides an output voltage Vout at its output terminal 102. The switching converter 700 includes an input switching circuit 810, an energy storage circuit 820, an output switching circuit 830, and a pre-charge circuit 840. The input switching circuit 810 is coupled between the input terminal 101 and the output terminal 102 of the switching converter 700 and includes series-coupled switching transistors S1 and S2, each having a first terminal and a second terminal. The first terminal of switching transistor S1 is coupled to the input terminal of the switching converter 700, and the second terminal of switching transistor S1 is coupled to the first terminal of switching transistor S2 to form a switching node 711. Figure 8In the illustrated embodiment, the energy storage circuit 820 includes a capacitor C1, a magnetic element L1, and a magnetic element L2, each having a first terminal and a second terminal. The first terminal of capacitor C1 is coupled to a switching node 711, the first terminal of magnetic element L2 is coupled to the second terminal of capacitor C1, the first terminal of magnetic element L1 is coupled to the first terminal of switching transistor S2, and the second terminals of magnetic elements L1 and L2 are coupled to the output terminal 102 of the switching converter 700. In one embodiment, magnetic elements L1 and L2 may be discrete inductors; in another embodiment, magnetic elements L1 and L2 may be two windings of a transformer, or two windings electromagnetically coupled to each other in other ways. The output switching circuit 730 includes switching transistors S3 and S4, with switching transistor S3 coupled between the second terminal of switching transistor S2 and reference ground GND, and switching transistor S4 coupled between the second terminal of capacitor C1 and reference ground GND. The pre-charge circuit 740 includes a Zener diode D1 and a resistor R1 connected in series. The cathode of the Zener diode D1 is coupled to the input terminal 101 of the switching converter 700. During the startup process of the switching converter 700, when the input voltage Vin rises and the voltage division of the Zener diode D1 reaches its stable voltage Vz1, the Zener diode D1 breaks down in reverse, and the input voltage Vin begins to pre-charge the capacitor C1 through the pre-charge circuit 740.

[0035] Figure 8 A circuit diagram of a switching converter 800 according to an embodiment of the present invention is shown. Figure 8 As shown, the switching converter 800 receives an input voltage Vin at input terminal 101 and provides an output voltage Vout at output terminal 102. The switching converter 800 includes an input switching circuit 810, an energy storage circuit 820, an output switching circuit 830, and a pre-charge circuit 840. The input switching circuit 810 is coupled between the input terminal 101 and the output terminal 102 of the switching converter 800 and includes switching transistors S1 to S4, each of which has a first terminal and a second terminal. Switches S1 and S2 are connected in series, with the first terminal of switch S1 coupled to the input terminal 101 of the switching converter 800, and the second terminal of switch S1 coupled to the first terminal of switch S2 to form a switching node 811. Switches S3 and S4 are connected in series, with the first terminal of switch S3 connected to the input terminal of the switching converter 800, and the second terminal of switch S3 coupled to the first terminal of switch S4 to form a switching node 812. Figure 8In the illustrated embodiment, the energy storage circuit 820 includes capacitors C1 and C2, magnetic element L1, and magnetic element L2. Each of capacitors C1, C2, L1, and L2 has a first terminal and a second terminal. The first terminal of capacitor C1 is coupled to switching node 811, the first terminal of capacitor C2 is coupled to switching node 812, the first terminal of magnetic element L2 is coupled to the second terminal of capacitor C1, the first terminal of magnetic element L1 is coupled to the second terminal of capacitor C2, and the second terminals of magnetic elements L1 and L2 are coupled to the output terminal 102 of the switching converter 800. The output switching circuit 830 includes switching transistors S5 and S6. Switch S5 is coupled between the second terminal of switching transistor S2 and reference ground GND, and switching transistor S6 is coupled between the second terminal of switching transistor S4 and reference ground GND. The pre-charge circuit 840 includes a series-coupled Zener diode D1 and resistor R1, and a series-coupled Zener diode D2 and resistor R2. The cathode of Zener diode D1 is coupled to the input terminal 101 of the switching converter 800, and Zener diode D1 has a stable voltage Vz1. The cathode of Zener diode D2 is coupled to the input terminal 101 of the switching converter 800, and Zener diode D2 has a stable voltage Vz2. During the startup process of the switching converter 800, when the input voltage Vin rises to the point that the voltage division of Zener diode D1 reaches its stable voltage Vz1, Zener diode D1 breaks down in reverse, and the input voltage Vin begins to charge capacitor C1 through the series-coupled Zener diode D1 and resistor R1; when the input voltage Vin rises to the point that the voltage division of Zener diode D2 reaches its stable voltage Vz2, Zener diode D2 breaks down in reverse, and the input voltage Vin begins to pre-charge capacitor C2 through the series-coupled Zener diode D2 and resistor R2.

[0036] Figure 9 A circuit diagram of a switching converter 900 according to an embodiment of the present invention is shown. Figure 9 In the illustrated embodiment, the switching converter 900 is a three-level buck converter circuit. For example... Figure 9 As shown, the switching converter 900 receives an input voltage Vin at its input terminal 101 and provides an output voltage Vout at its output terminal 102. The switching converter 900 includes an input switching circuit 910, an energy storage circuit 920, an output switching circuit 930, and a pre-charge circuit 940. The input switching circuit 910 is coupled between the input terminal 101 and the output terminal 102 of the switching converter 900 and includes series-coupled switches S1 and S2. The output switching circuit 930 is coupled between the output terminal 102 of the switching converter 900 and reference ground GND and includes series-coupled switches S3 and S4. Figure 9In the illustrated embodiment, both the input switch circuit 910 and the output switch circuit 930 are coupled to the output terminal 102 of the switch converter 900 via inductor L1. Each of the switching transistors S1 to S4 has a first terminal and a second terminal. The first terminal of switch transistor S1 is coupled to the input terminal 101 of the switch converter 900, and the second terminal of switch transistor S1 is coupled to the first terminal of switch transistor S2 to form a switching node 911. The first terminal of switch transistor S3 is coupled to reference ground GND, and the second terminal of switch transistor S3 is coupled to the first terminal of switch transistor S4 to form a switching node 931. Figure 9 In the illustrated embodiment, the energy storage circuit 920 includes a capacitor C1 and an inductor L1, both having a first terminal and a second terminal. The first terminal of capacitor C1 is coupled to switching node 1011, and the second terminal of capacitor C1 is coupled to switching node 931. The first terminal of inductor L1 is coupled to the second terminals of switching transistors S2 and S4, and the second terminal of inductor L1 is coupled to the output terminal 102 of switching converter 900. That is, the input switching circuit 910 and the output switching circuit 930 are coupled to the output terminal 102 of switching converter 900 through inductor L1. The pre-charge circuit 940 includes a Zener diode D1 and a resistor R1 coupled in series, with the cathode of Zener diode D1 coupled to the input terminal 101 of switching converter 900. During the startup process of the switching converter 900, when the input voltage Vin rises, causing the voltage division of Zener diode D1 to reach its stable voltage Vz1, Zener diode D1 breaks down in reverse, and the input voltage Vin begins to precharge capacitor C1 through pre-charge circuit 940. Although Figure 9 The embodiment shown is illustrated using a three-level buck converter circuit as an example, but those skilled in the art should understand that the pre-charge circuit 940 can also be applied to other multi-level converter circuits.

[0037] Figure 10 This is a flowchart of a pre-charging method 1000 for a switching converter according to an embodiment of the present invention. The switching converter has an input terminal for receiving an input voltage and an output terminal for providing an output voltage. The switching converter includes an input switching circuit, an energy storage circuit, and an output switching circuit. The input switching circuit includes a first switching transistor and a second switching transistor connected in series, the common terminal of the first switching transistor and the second switching transistor forming a switching node, wherein the input switching circuit is coupled between the input terminal and the output terminal of the switching converter. The energy storage circuit includes a capacitor, one end of which is coupled to the switching node. The output switching circuit is coupled to the energy storage circuit and the output terminal of the switching converter, and the output switching circuit includes at least one switching transistor. The pre-charging method 1000 includes steps S11 to S14.

[0038] In step S11, a Zener diode and a resistor are connected in series between the input terminal and the switching node of the switching converter to form a pre-charge circuit. This pre-charge circuit can pre-charge the capacitor during the startup process of the switching converter.

[0039] In step S12, the switching converter is started, and the input voltage increases from an initial voltage (e.g., 0V).

[0040] In step S13, when the input voltage continues to increase and causes the Zener diode to break down in reverse, a pre-charging current is generated through the pre-charging circuit to charge the capacitor.

[0041] In step S14, charging of the capacitor is automatically stopped based on the input voltage.

[0042] It should be noted that the execution order of the steps in the flowchart above is not limited to... Figure 10 As shown, two consecutive function blocks can be executed simultaneously or in reverse order.

[0043] Although the invention has been described with reference to several exemplary embodiments, it should be understood that the terminology used is descriptive and exemplary, and not restrictive. Since the invention can be embodied in many forms without departing from the spirit or essence of the invention, it should be understood that the above embodiments are not limited to any of the foregoing details, but should be interpreted broadly within the spirit and scope defined by the appended claims. Therefore, all variations and modifications falling within the scope of the claims or their equivalents should be covered by the appended claims.

Claims

1. A switching converter, comprising: an input terminal configurable to receive an input voltage; an output terminal configurable to provide an output voltage; an input switching circuit comprising a first switch, a second switch, a third switch, and a fourth switch, each switch comprising a first terminal and a second terminal, wherein the first terminal of the first switch is coupled to the input terminal of the switching converter, the second terminal of the fourth switch is coupled to the output terminal of the switching converter, the second terminal of the first switch is coupled to the first terminal of the second switch to form a first switching node, the second terminal of the second switch is coupled to the first terminal of the third switch to form a second switching node, and the second terminal of the third switch is coupled to the first terminal of the fourth switch to form a third switching node; an output switching circuit comprising at least one switch, the output switching circuit coupled to the output terminal of the switching converter and the input switching circuit; a first capacitor having one terminal coupled to the first switching node and another terminal coupled to the output switching circuit; a second capacitor having one terminal coupled to the second switching node and another terminal coupled to the output switching circuit; a third capacitor having one terminal coupled to the third switching node and another terminal coupled to the output switching circuit; and a pre-charge circuit comprising a first terminal and a second terminal, the first terminal of the pre-charge circuit coupled to the input terminal of the switching converter, the second terminal of the pre-charge circuit coupled to at least one of the first to third switching nodes, the pre-charge circuit comprising a first zener diode and a first resistor coupled in series, wherein the cathode of the first zener diode is coupled to the input terminal of the switching converter. 2.The switching converter of claim 1, wherein the first zener diode and the first resistor are coupled in series between the input terminal of the switching converter and the second switching node. 3.The switching converter of claim 1, wherein the output switching circuit further comprises: a first bridge leg and a second bridge leg coupled in parallel between the output terminal of the switching converter and a reference ground, wherein the first bridge leg has a first bridge leg node and the second bridge leg has a second bridge leg node; wherein the first capacitor is coupled between the first switching node and the first bridge leg node, the second capacitor is coupled between the second switching node and the second bridge leg node, and the third capacitor is coupled between the third switching node and the first bridge leg node. 4.The switching converter of claim 1, wherein the output switching circuit further comprises: a first bridge leg, a second bridge leg, and a third bridge leg coupled in parallel between the output terminal of the switching converter and a reference ground, wherein the first bridge leg has a first bridge leg node, the second bridge leg has a second bridge leg node, and the third bridge leg has a third bridge leg node; wherein the first capacitor is coupled between the first switching node and the first bridge leg node, the second capacitor is coupled between the second switching node and the second bridge leg node, and the third capacitor is coupled between the third switching node and the third bridge leg node. 5.The switching converter of claim 4, further comprising: a first inductor coupled in series with the first capacitor between the first switching node and the first bridge leg node to form a first resonant tank circuit; and a second inductor coupled in series with the third capacitor between the third switching node and the third bridge leg node to form a second resonant tank circuit. ​ ​ 6. The switching converter of claim 2, wherein the pre-charge circuit further comprises a third terminal coupled to the first switching node, a second zener diode, and a second resistor, the second zener diode and the second resistor coupled in series between an input of the switching converter and the first terminal, wherein a cathode of the second zener diode is coupled to the input of the switching converter.

7. A switching converter, comprising: an input configurable to receive an input voltage; an output configurable to provide an output voltage; a first switch and a second switch, each switch comprising a first terminal and a second terminal, wherein the first terminal of the first switch is coupled to the input of the switching converter and the second terminal of the first switch is coupled to the first terminal of the second switch to form a first switching node; a first capacitor having a first terminal and a second terminal, the first terminal of the first capacitor coupled to the first switching node; a first magnetic element and a second magnetic element, each magnetic element having a first terminal and a second terminal, the first terminal of the first magnetic element coupled to the second terminal of the second switch and the first terminal of the second magnetic element coupled to the second terminal of the first capacitor, the second terminals of the first and second magnetic elements coupled to the output of the switching converter; an output switching circuit comprising a third switch and a fourth switch, the third switch coupled between the second terminal of the second switch and a reference ground, and the fourth switch coupled between the second terminal of the first capacitor and the reference ground; and a pre-charge circuit coupled between the input of the switching converter and the second terminal of the first switch, the pre-charge circuit comprising a first zener diode and a first resistor coupled in series, wherein a cathode of the first zener diode is coupled to the input of the switching converter.

8. The switching converter of claim 7, further comprising: a fifth switch and a sixth switch, each switch comprising a first terminal and a second terminal, wherein the first terminal of the fifth switch is coupled to the input of the switching converter and the second terminal of the fifth switch is coupled to the first terminal of the sixth switch to form a second switching node; and a second capacitor coupled between the second switching node and the first terminal of the first magnetic element; wherein the pre-charge circuit further comprises a second zener diode and a second resistor, the second zener diode and the second resistor coupled in series between the input of the switching converter and the second terminal of the fifth switch, a cathode of the second zener diode coupled to the input of the switching converter.

9. A switching converter, comprising: an input configurable to receive an input voltage; an output configurable to provide an output voltage; an input switching circuit comprising a first switch and a second switch coupled in series, a common terminal of the first switch and the second switch forming a first switching node, wherein the input switching circuit is coupled between the input of the switching converter and the output; an energy storage circuit comprising a first capacitor, one terminal of the first capacitor coupled to the first switching node; an output switching circuit coupled to the energy storage circuit and the output of the switching converter, the output switching circuit comprising at least one switch; and a pre-charge circuit coupled between the input of the switching converter and the at least one switch of the output switching circuit, the pre-charge circuit comprising a first zener diode and a first resistor coupled in series, wherein a cathode of the first zener diode is coupled to the input of the switching converter. ​ The pre-charge circuit is coupled between an input of the switching converter and the first switching node, and includes a first zener diode and a first resistor coupled in series, a cathode of the first zener diode being coupled to the input of the switching converter; wherein The pre-charge circuit is configured to charge the first capacitor during a start-up process of the switching converter, and is configured to automatically stop charging the first capacitor according to the input voltage.

10. The switching converter of claim 9, wherein: The input switching circuit further includes a third switch and a fourth switch, each of the first switch, the second switch, the third switch and the fourth switch including a first terminal and a second terminal, wherein the first terminal of the third switch is coupled to the input of the switching converter, the second terminal of the third switch is coupled to the first terminal of the first switch to form a second switching node, the second terminal of the first switch is coupled to the first terminal of the second switch to form the first switching node, the second terminal of the second switch is coupled to the first terminal of the fourth switch to form a third switching node, and the second terminal of the fourth switch is coupled to the output of the switching converter; and The energy storage circuit further includes a second capacitor and a third capacitor, the second capacitor being coupled between the second switching node and the output switching circuit, and the third capacitor being coupled between the third switching node and the output switching circuit.

11. The switching converter of claim 10, wherein the energy storage circuit further includes a first inductor and a second inductor; wherein: The first inductor and the second capacitor are coupled in series between the second switching node and the output switching circuit, and the second inductor and the third capacitor are coupled in series between the third switching node and the output switching circuit.

12. The switching converter of claim 10, wherein the output switching circuit includes: a first bridge leg and a second bridge leg coupled in parallel between the output of the switching converter and a reference ground, wherein the first bridge leg has a first bridge leg node, and the second bridge leg has a second bridge leg node; wherein the first capacitor is coupled between the first switching node and the second bridge leg node, the second capacitor is coupled between the second switching node and the first bridge leg node, and the third capacitor is coupled between the third switching node and the first bridge leg node.

13. The switching converter of claim 10, wherein the output switching circuit includes: a first bridge leg, a second bridge leg and a third bridge leg coupled in parallel between the input of the switching converter and a reference ground, wherein the first bridge leg has a first bridge leg node, the second bridge leg has a second bridge leg node, and the third bridge leg has a third bridge leg node; wherein the first capacitor is coupled between the first switching node and the second bridge leg node, the second capacitor is coupled between the second switching node and the first bridge leg node, and the third capacitor is coupled between the third switching node and the third bridge leg node.

14. The switching converter of claim 10, wherein the pre-charge circuit further includes: a second zener diode and a second resistor coupled in series between the input of the switching converter and the second switching node, a cathode of the second zener diode being coupled to the input of the switching converter.

15. The switching converter of claim 9, wherein: The energy storage circuit further comprises a first magnetic element and a second magnetic element, each of the magnetic elements and each of the switch tubes comprises a first end and a second end, the second end of the first switch tube and the first end of the second switch tube are coupled to form a first switch node, the first end of the first magnetic element is coupled to the second end of the second switch tube, the first end of the second magnetic element is coupled to the second end of the first capacitor, the second end of the first magnetic element and the second end of the second magnetic element are coupled to an output terminal of the switch converter; and The output switch circuit comprises a third switch tube and a fourth switch tube, the third switch tube is coupled between the second end of the second switch tube and a reference ground, the fourth switch tube is coupled between the second end of the first capacitor and the reference ground.

16. The switch converter of claim 15, wherein: The input switch circuit further comprises a fifth switch tube and a sixth switch tube, each of the switch tubes comprises a first end and a second end, wherein the first end of the fifth switch tube is coupled to the input terminal of the switch converter, the second end of the fifth switch tube and the first end of the sixth switch tube are coupled to form a second switch node; a second capacitor coupled between the second switch node and the first end of the first magnetic element; and a second pre-charge circuit coupled between the first end of the fifth switch tube and the second end of the fifth switch tube, comprising a second zener diode and a second resistor coupled in series, wherein the cathode of the second zener diode is coupled to the first end of the fifth switch tube.

17. The switch converter of claim 9, wherein: The output switch circuit comprises a third switch tube and a fourth switch tube, each of the first to fourth switch tubes comprises a first end and a second end, the first end of the first switch tube is coupled to the input terminal of the switch converter, the second end of the first switch tube and the first end of the second switch tube are coupled to form a first switch node, the first end of the third switch tube is coupled to a reference ground, the second end of the third switch tube and the first end of the fourth switch tube are coupled to form a second switch node; and The energy storage circuit further comprises an inductor, a first end of the inductor is coupled to the second end of the second switch tube and the second end of the fourth switch tube, a second end of the inductor is coupled to an output terminal of the switch converter. ​

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