Switch control circuit, charging control circuit and buck converter

Abstract

The present application discloses a switch control circuit, a charging control circuit, and a buck converter. In the switch control circuit, a first end of a first switch unit is connected to the SW pin of the buck converter, and a second end is connected to the gate of a charging control switch tube; a first end of a second switch unit is connected to the BOOT pin of the buck converter, and a second end is connected to the gate of the charging control switch tube; the first switch unit is used to connect the voltage of the SW pin to the gate of the charging control switch tube during the charging period of the buck converter's BOOT capacitor, thereby turning on the charging control switch tube and connecting the charging current to the BOOT capacitor to charge the BOOT capacitor; the second switch unit is used to connect the voltage of the BOOT pin to the gate of the charging control switch tube during the non-charging period of the BOOT capacitor, thereby turning off the charging control switch tube. The present application can stably and orderly control the switching of the charging control switch tube, thereby stably and effectively charging the BOOT capacitor.

Description

Technical Field

[0001] The present application relates to the field of circuit technology, and in particular to a switch control circuit, a charging control circuit, and a buck converter. Background Art

[0002] The buck converter usually includes a BOOT pin (boost pin) and a SW pin (switch pin). A charging capacitor is provided between the BOOT pin and the SW pin. The charging capacitor can also be called a BOOT capacitor. The BOOT capacitor can make the voltage difference between the BOOT pin and the SW pin appropriate, and contribute to the stability of the buck converter output voltage VOUT. For example, if the buck converter includes Figure 1 In the chip shown, the BOOT, SW, VIN, GND, EN, SS, RT / CLK, and FB pins are the chip's pins. Capacitor C3 is the BOOT capacitor between the BOOT and SW pins. This BOOT capacitor provides power to the high-side driver circuit when the negative terminal of the high-side buck converter floats with the SW pin, making the output voltage VOUT more stable. Because charging and discharging currents are required to drive the high-side switching device, the BOOT capacitor's voltage will be reduced and must be recharged. Typically, when the low-side switch is turned on (SW = GND), the BOOT capacitor is charged from the chip's internal low-voltage power supply. For related charging circuits, see Reference. Figure 2 As shown, the BOOT capacitor is charged by the low voltage VCC (such as 5V) inside the chip through the relevant charging circuit.

[0003] Some BOOT capacitor charging circuits can refer to Figure 3 As shown, when the lower bridge switch is turned on, the voltage at the SW pin is equivalent to the ground voltage, that is, SW=GND. At this time, the BOOT capacitor (such as Figure 3 As shown in the figure, the difference between the voltage of the BOOT pin and the ground voltage (ie VBOOT-GND) is low voltage, and the charging control switch tube (such as Figure 3 The charging process can be performed as long as the gate voltage of PM1 (shown) is at ground voltage (GND). When the high-side switch is on, the BOOT pin (VBOOT) is the sum of the input voltage (VIN) and the voltage of the BOOT capacitor, typically a high voltage. At this point, the gate voltage of the charge control switch must be equal to the BOOT pin voltage (VBOOT) before it can be turned off to prevent leakage from the BOOT capacitor. Therefore, a switching control solution for the charge control switch is urgently needed to control the charging control switch on and off, ensuring that the charging control switch can stably and efficiently charge the BOOT capacitor. Summary of the Invention

[0004] In view of this, the present application provides a switch control circuit, a charging control circuit and a buck converter to perform switching control on the charging control switch tube, so that the charging control switch tube can stably and effectively charge the BOOT capacitor.

[0005] The present application provides a switch control circuit, the switch control circuit comprising a first switch unit and a second switch unit;

[0006] The first end of the first switch unit is connected to the SW pin of the buck converter, and the second end is connected to the gate of the charge control switch tube in the buck converter; the first end of the second switch unit is connected to the BOOT pin of the buck converter, and the second end is connected to the gate of the charge control switch tube;

[0007] The first switch unit is used to connect the gate of the charging control switch tube to the voltage of the SW pin during the charging period of the BOOT capacitor of the buck converter, so as to turn on the charging control switch tube and connect the charging current to the BOOT capacitor to charge the BOOT capacitor;

[0008] The second switch unit is used to connect the gate of the charging control switch tube to the voltage of the BOOT pin during the non-charging period of the BOOT capacitor, so as to turn off the charging control switch tube.

[0009] Optionally, the first switch unit includes a first MOS tube; the source of the first MOS tube serves as the first end of the first switch unit and is connected to the SW pin, and the drain serves as the second end of the first switch unit and is connected to the gate of the charging control switch tube, and the gate is used to access a switch control signal; the switch control signal is used to control the first MOS tube to be turned on during the charging period of the BOOT capacitor, and to control the first MOS tube to be turned off during the non-charging period of the BOOT capacitor.

[0010] Optionally, the first switching unit also includes a first diode and a first current source; the input end of the first diode is connected to the SW pin, and the output end is respectively connected to the output end of the first current source and the gate of the first MOS tube; the first current source is used to apply a reverse current to the first diode during the charging period of the BOOT capacitor to reversely break down the first diode, so that the voltage at the output end of the first diode is higher than the voltage at the input end of the first diode, thereby turning on the first MOS tube.

[0011] Optionally, the second switch unit includes a second MOS tube and a second diode; the source of the second MOS tube serves as the first end of the second switch unit, connected to the BOOT pin, and the drain serves as the second end of the second switch unit, connected to the gate of the charging control switch tube, and the gate is connected to the input end of the second diode; the output end of the second diode is connected to the BOOT pin; the second diode is configured to be broken down when the voltage of the BOOT pin is higher than a first preset voltage, so that the voltage at the input end of the second diode is lower than the voltage at the output end of the second diode, thereby turning on the second MOS tube.

[0012] Optionally, the switch control circuit also includes a third diode and a second current source; the input end of the third diode is used to access the second preset voltage, and the output end is respectively connected to the input end of the second current source and the gate of the second MOS tube; the output end of the second current source is connected to the SW pin.

[0013] The present application also provides a charging control circuit, which includes any of the above-mentioned switch control circuits.

[0014] Optionally, the charging control circuit also includes a charging control switch tube; the drain of the charging control switch tube is used to access the charging current, the gate is respectively connected to the second end of the first switch unit and the second end of the second switch unit, and the source is connected to the BOOT pin of the buck converter.

[0015] Optionally, the charging control circuit further includes a reference voltage providing module, a comparator, a current providing module and a comparison voltage protection module; the positive input end of the comparator is connected to the output end of the reference voltage providing module, the negative input end is respectively connected to the output end of the current providing module, the drain of the charging control switch tube and the first end of the comparison voltage protection module, and the output end is connected to the input end of the current providing module; the second end of the comparison voltage protection module is grounded; the reference voltage providing module is used to provide a reference voltage; the comparison voltage protection module is used to limit the maximum value of the comparison voltage; the comparator is used to output a high-level signal to the current providing module when the reference voltage is greater than the comparison voltage; the current providing module is used to provide a charging current to the charging control switch tube when a high-level signal is connected.

[0016] The present application also provides a buck converter, which includes any of the above-mentioned charging control circuits.

[0017] In the above-mentioned switching control circuit, charging control circuit and buck converter of the present application, the first switching unit can connect the gate of the charging control switch tube to the voltage of the SW pin during the charging period of the BOOT capacitor of the buck converter, so that the gate voltage of the charging control switch tube is lower than its source voltage, the charging control switch tube is turned on, and the charging current of the drain of the charging control switch tube is connected to the BOOT capacitor to charge the BOOT capacitor; the second switching unit is used to connect the gate of the charging control switch tube to the voltage of the BOOT pin during the non-charging period of the BOOT capacitor, so that the gate voltage of the charging control switch tube is equal to its source voltage, the charging control switch tube is turned off, and the charging of the BOOT capacitor is stopped; thereby, the charging control switch tube can be stably and orderly switched, so that the charging control switch tube can charge the BOOT capacitor stably and effectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 This is a schematic diagram of the buck converter structure used in the research process of this application;

[0020] Figure 2 This is a partial structural diagram of the buck converter used in the research process of this application;

[0021] Figure 3 This is a schematic diagram of the charging circuit structure during the research process of this application;

[0022] Figure 4 This is a schematic diagram of the switch control circuit structure of an embodiment of the present application;

[0023] Figure 5 is a schematic structural diagram of a switch control circuit according to another embodiment of the present application;

[0024] Figure 6 is a schematic structural diagram of a switch control circuit according to another embodiment of the present application;

[0025] Figure 7 2 is a schematic diagram of the switch control circuit structure of an embodiment of the present application. DETAILED DESCRIPTION

[0026] The following, in conjunction with the accompanying drawings, clearly and completely describes the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of this application. In the absence of conflict, the following embodiments and their technical features can be combined with each other.

[0027] In a first aspect, the present application provides a switch control circuit that can be provided within a buck converter. The buck converter includes a charge control switch and a boot capacitor. When the charge control switch is on, it can connect a charging current to the boot capacitor for charging. The switch control circuit can be connected to the gate of the charge control switch to control the on and off of the charge control switch. In some embodiments, the boot capacitor can also be referred to as a bootstrap capacitor.

[0028] refer to Figure 4 As shown, the switch control circuit includes a first switch unit 210 and a second switch unit 220. The first end of the first switch unit 210 is connected to the SW pin of the buck converter, and the second end is connected to the gate of the charge control switch tube PM1 in the buck converter; the first end of the second switch unit 220 is connected to the BOOT pin of the buck converter, and the second end is connected to the gate of the charge control switch tube PM1.

[0029] The first switch unit 210 is used to connect the gate of the charging control switch tube PM1 to the voltage of the SW pin during the charging period of the BOOT capacitor CB of the buck converter, so that the gate voltage of the charging control switch tube PM1 is lower than its source voltage, the charging control switch tube PM1 is turned on, and the charging current I0 of the drain of the charging control switch tube PM1 is connected to the BOOT capacitor CB to charge the BOOT capacitor CB.

[0030] The second switch unit 220 is used to connect the gate of the charging control switch tube PM1 to the voltage of the BOOT pin during the non-charging period of the BOOT capacitor CB, so that the gate voltage of the charging control switch tube PM1 is equal to its source voltage, and the charging control switch tube PM1 is turned off to stop charging the BOOT capacitor CB.

[0031] Optionally, both the first switch unit 210 and the second switch unit 220 may further include control terminals, which are respectively connected to corresponding control signals to control the first switch unit 210 to be turned on and the second switch unit 220 to be turned off during the charging period of the BOOT capacitor CB of the buck converter, and to control the first switch unit 210 to be turned off and the second switch unit 220 to be turned on during the non-charging period of the BOOT capacitor CB.

[0032] Optionally, the buck converter may further include a control module. Optionally, the buck converter's control module may pre-set the charging period and non-charging period of the BOOT capacitor CB based on factors such as the control logic and / or operating mode of the upper and lower bridge switches. Optionally, the buck converter's control module may further monitor the charge level and / or charging status of the BOOT capacitor CB via relevant components, and determine the charging period and non-charging period of the BOOT capacitor CB based on the monitoring results.

[0033] In the above-mentioned switch control circuit, the first switch unit 210 can connect the gate of the charging control switch tube PM1 to the voltage of the SW pin during the charging period of the BOOT capacitor CB of the buck converter, so that the gate voltage of the charging control switch tube PM1 is lower than its source voltage, and the charging control switch tube PM1 is turned on, and the charging current I0 of the drain of the charging control switch tube PM1 is connected to the BOOT capacitor CB to charge the BOOT capacitor CB; the second switch unit 220 is used to connect the gate of the charging control switch tube PM1 to the voltage of the BOOT pin during the non-charging period of the BOOT capacitor CB, so that the gate voltage of the charging control switch tube PM1 is equal to its source voltage, and the charging control switch tube PM1 is turned off, stopping charging the BOOT capacitor CB; thereby, the charging control switch tube can be stably and orderly switched, so that the charging control switch tube can stably and effectively charge the BOOT capacitor.

[0034] In some embodiments, reference Figure 5 As shown, the first switch unit 210 includes a first MOS transistor NM1; the first MOS transistor NM1 can be an NMOS transistor. The source of the first MOS transistor NM1 serves as the first end of the first switch unit 210 and is connected to the SW pin. The drain of the first MOS transistor NM1 serves as the second end of the first switch unit 210 and is connected to the gate of the charge control switch transistor PM1. The gate of the first MOS transistor NM1 is connected to a switch control signal CK1. The switch control signal CK1 is used to control the first MOS transistor PM1 to conduct during the charging period of the BOOT capacitor CB, so that the gate voltage of the charge control switch transistor PM1 is equal to the SW pin voltage VSW, and the source voltage of the charge control switch transistor PM1 is equal to the BOOT pin voltage VBOOT. The gate voltage of the charge control switch transistor PM1 is lower than its source voltage, and the first MOS transistor PM1 is turned off during the non-charging period of the BOOT capacitor CB.

[0035] In some examples, reference Figure 6As shown, the first switch unit 210 further includes a first diode D1 and a first current source CS1. The input end of the first diode D1 is connected to the SW pin, and the output end is respectively connected to the output end of the first current source CS1 and the gate of the first MOS transistor NM1. Optionally, the first diode D1 may be a voltage regulator diode or a Zener diode. Optionally, the input end of the first current source CS1 may be connected to the internal voltage of the buck converter, such as the second preset voltage VDD.

[0036] The first current source CS1 is used to apply a reverse current to the first diode D1 during the charging period of the BOOT capacitor CB, so as to reversely break down the first diode D1, so that the voltage at the output end of the first diode D1 is higher than the voltage at the input end of the first diode D1 (for example, the voltage at the output end of the first diode D1 is higher than the voltage at its input end by a breakdown voltage corresponding to the first diode D1). At this time, the switch control signal CK1 connected to the gate of the first MOS transistor NM1 includes the sum of the SW pin voltage VSW corresponding to the input end of the first diode D1 and the breakdown voltage of the first diode D1. The first MOS transistor NM1 is turned on, so that the gate voltage of the charging control switch tube PM1 is the SW pin voltage VSW.

[0037] Optionally, the first current source CS1 may further include a control terminal (not shown). The control terminal of the first current source CS1 is configured to receive an on signal (e.g., a high level) during the charging period of the boot capacitor CB to apply reverse current to the first diode D1, and receive a off signal (e.g., a low level) during the non-charging period of the boot capacitor CB to stop applying current to the first diode D1. Optionally, the on signal and / or off signal corresponding to the first current source CS1 may originate from the control module of the buck converter.

[0038] In some embodiments, reference Figure 5 and Figure 6 As shown, the second switch unit 220 includes a second MOS transistor PM2 and a second diode D2; optionally, the second MOS transistor PM2 may be a PMOS transistor; the second diode D2 may be a voltage regulator diode or a Zener diode.

[0039] The source of the second MOS transistor PM2 serves as the first end of the second switch unit 220 and is connected to the BOOT pin. The drain of the second MOS transistor PM2 serves as the second end of the second switch unit 220 and is connected to the gate of the charge control switch transistor PM1. The gate of the second MOS transistor PM2 is connected to the input end of the second diode D2. The output end of the second diode D2 is connected to the BOOT pin.

[0040] The second diode D2 is configured to be broken down when the voltage at the BOOT pin is higher than a first preset voltage. The voltage at the input terminal of the second diode D2 is lower than the voltage at the output terminal of the second diode D2, thereby turning on the second MOS transistor PM2. At this time, the gate voltage of the charging control switch tube PM1 is the BOOT pin voltage VBOOT, and the source voltage of the charging control switch tube PM1 is the BOOT pin voltage VBOOT. The gate voltage of the charging control switch tube PM1 is equal to its source voltage, the charging control switch tube PM1 is turned off, and the charging of the BOOT capacitor CB at the BOOT pin stops.

[0041] Optionally, the first preset voltage includes a voltage indicating that charging of the BOOT capacitor CB is complete. After charging of the BOOT capacitor CB is complete, the BOOT pin voltage VBOOT increases. The increased BOOT pin voltage VBOOT reversely breaks down the second diode D2. At this time, the voltage at the input terminal of the second diode D2 is lower than the voltage at the output terminal of the second diode D2 by the breakdown voltage of the second diode D2, thereby turning on the second MOS transistor PM2.

[0042] In some embodiments, as Figure 6 As shown, the switch control circuit 220 further includes a third diode D3 and a second current source CS2. The input terminal of the third diode D3 is connected to the second preset voltage VDD, and the output terminal is connected to the input terminal of the second current source CS2 and the gate of the second MOS transistor PM2, respectively. The output terminal of the second current source CS2 is connected to the SW pin. The second current source CS2 is configured to cooperate with the third diode D3 to provide a required signal to the gate of the second MOS transistor PM2. Furthermore, the third diode D3 prevents the gate current of the second MOS transistor PM2 from flowing back to the terminal providing the second preset voltage VDD, thereby ensuring the stability of the buck converter in which the switch control circuit is located during operation.

[0043] Optionally, the second preset voltage VDD may be an internal voltage of the buck converter (such as a 5V voltage inside the buck converter, etc.).

[0044] In the above switch control circuit, the first switch unit 210 can connect the gate of the charging control switch tube PM1 to the voltage of the SW pin during the charging period of the BOOT capacitor CB of the buck converter, so that the gate voltage of the charging control switch tube PM1 is lower than its source voltage, and the charging control switch tube PM1 is turned on, and the charging current I0 of the drain of the charging control switch tube PM1 is connected to the BOOT capacitor CB to charge the BOOT capacitor CB; the second switch unit 220 is used to connect the gate of the charging control switch tube PM1 to the voltage of the BOOT pin during the non-charging period of the BOOT capacitor CB, so that the gate voltage of the charging control switch tube PM1 is equal to its source voltage, and the charging control switch tube PM1 is turned off, stopping charging the BOOT capacitor CB; thereby, the charging control switch tube can be stably and orderly switched, so that the charging control switch tube can stably and effectively charge the BOOT capacitor.

[0045] A second aspect of the present application provides a charging control circuit, which includes the switch control circuit described in any one of the above embodiments.

[0046] Specifically, the charging control circuit also includes a charging control switch transistor PM1; the drain of the charging control switch transistor PM1 is used to receive the charging current I0, the gate is connected to the second end of the first switch unit 210 and the second end of the second switch unit 220, and the source is connected to the BOOT pin of the buck converter. During the charging period of the buck converter's BOOT capacitor CB, the first switch unit 210 connects the voltage of the SW pin to the gate of the charging control switch transistor PM1, so that the gate voltage of the charging control switch transistor PM1 is lower than its source voltage. The charging control switch transistor PM1 is turned on and the charging current I0 from the drain of the charging control switch transistor PM1 is connected to the BOOT capacitor CB to charge the BOOT capacitor CB. During the non-charging period of the BOOT capacitor CB, the second switch unit 220 connects the voltage of the BOOT pin to the gate of the charging control switch transistor PM1, so that the gate voltage of the charging control switch transistor PM1 is equal to its source voltage. The charging control switch transistor PM1 is turned off and stops charging the BOOT capacitor CB.

[0047] In some embodiments, reference Figure 7 As shown, the charging control circuit further includes a reference voltage supply module 110, a comparator 120, a current supply module 130, and a comparison voltage protection module 140. The positive input of comparator 120 is connected to the output of reference voltage supply module 110; the negative input of comparator 120 is connected to the output of current supply module 130, the drain of charge control switch PM1, and the first terminal of comparison voltage protection module 140; the output of comparator 120 is connected to the input of current supply module 130. The second terminal of comparison voltage protection module 140 is grounded.

[0048] The reference voltage providing module 110 is configured to provide a reference voltage VREF.

[0049] The comparison voltage protection module 140 is configured to limit a maximum value of the comparison voltage VFB.

[0050] The comparator 120 is configured to output a high-level signal to the current providing module 130 when the reference voltage VREF is greater than the comparison voltage VFB, so as to turn on the current providing module 130 .

[0051] The current providing module 130 is configured to provide a charging current I0 to the charging control switch tube PM1 when a high level signal is input.

[0052] In some examples, the reference voltage providing module 110 includes a third current source CS3, a voltage-controlling resistor R1, and a first switch S1. The input end of the third current source CS3 is connected to the voltage input end VIN, and the second end of the third current source CS3 serves as the output end of the reference voltage providing module 110, and is respectively connected to the positive input end of the comparator 120 and the first end of the voltage-controlling resistor R1. The second end of the voltage-controlling resistor R1 is grounded through the first switch S1. The voltage-controlling resistor R1 can provide a voltage signal that is a preset voltage higher than the voltage at the first switch S1 after the first switch S1 is closed. This voltage signal is the reference voltage VREF. Optionally, when the first switch S1 is closed, the magnitude of the reference voltage VREF is VREF=I1*R1, where I1 is the magnitude of the output current of the third current source CS3 and R1 is the resistance value of the voltage-controlling resistor R1. Optionally, the parameters of the third current source CS3 and the voltage-controlling resistor R1 can be determined based on the magnitude of the reference voltage VREF required to be connected to the positive input end of the comparator 120, where the reference voltage VREF is generally a voltage value greater than the comparison voltage VFB.

[0053] Optionally, the reference voltage providing module 110 further includes a second switch S2. A first end of the second switch S2 is connected to the second end of the voltage-controlling resistor R1, and a second end of the second switch S2 is connected to the SW pin of the buck converter. The second switch S2 is configured to connect the voltage-controlling resistor R1 to the SW pin of the buck converter, so that the reference voltage VREF is VSW + I1*R1, where VSW is the voltage at the SW pin.

[0054] In some examples, the current supply module 130 includes a fourth current source CS4, a setting switch K2, and a current mirror 131. The setting switch K2 can be an NMOS transistor. The gate of the setting switch K2 serves as the input of the current supply module 130 and is connected to the output of the comparator 120. The source of the setting switch K2 is connected to the input of the fourth current source CS4. The drain of the setting switch K2 is connected to the input of the current mirror 131. The output of the fourth current source CS4 is grounded. The output of the current mirror 131 serves as the output of the current supply module 130 and is connected to the drain of the charge control switch PM1. The setting switch K2 is configured to conduct when its gate is connected to a high level, thereby connecting the current provided by the fourth current source CS4 to the input of the current mirror 131. The current mirror 131 is configured to output the current connected to the input to the drain of the charge control switch PM1, so that the current charges the BOOT capacitor CB through the charge control switch PM1.

[0055] Optionally, the current mirror 131 includes a first MOS transistor P1, a second MOS transistor P2, and a third switch S3; both the first MOS transistor P1 and the second MOS transistor P2 are PMOS transistors. The drain of the first MOS transistor P1 serves as the input terminal of the current mirror 131 and is respectively connected to the drain of the setting switch transistor K2, the gate of the first MOS transistor P1, the gate of the second MOS transistor P2, and the first terminal of the third switch S3. The source of the first MOS transistor P1 is respectively connected to the voltage input terminal VIN, the second terminal of the third switch S3, and the source of the second MOS transistor P2. The drain of the second MOS transistor P2 serves as the output terminal of the current mirror 131 and is connected to the drain of the charge control switch transistor PM1.

[0056] In some examples, the comparison voltage protection module 140 includes a fourth diode D4 and a fourth switch S4. The input terminal of the fourth diode D4 is grounded via the fourth switch S4. In this case, the ground terminal can be the second terminal of the comparison voltage protection module 140. The output terminal of the fourth diode D4 serves as the first terminal of the comparison voltage protection module 140 and is connected to the drain of the first switch K1. The fourth diode D4 is a voltage stabilizing diode, such that the maximum voltage difference between the output terminal (e.g., ) and the input terminal of the fourth diode D4 is its breakdown voltage. In this case, the first terminal of the comparison voltage protection module 140 is the breakdown voltage of the fourth diode D4, and the maximum value of the comparison voltage VFB output to the negative input terminal of the comparator 120 is the breakdown voltage of the fourth diode D4.

[0057] The on-off control logic of the fourth switch S4 may be consistent with the on-off control logic of the first switch S1 . For example, the fourth switch S4 may be turned on when the first switch S1 is turned on, and may be turned off when the first switch S1 is turned off.

[0058] The charging control circuit includes the switch control circuit described in any of the above embodiments, and has all the beneficial effects of the switch control circuit described in any of the above embodiments, which will not be described in detail here.

[0059] A third aspect of the present application provides a buck converter, which includes the charging control circuit described in any one of the above embodiments.

[0060] Specifically, the buck converter further includes a BOOT capacitor CB; the BOOT capacitor CB is connected between the BOOT pin and the SW pin.

[0061] The buck converter includes the charging control circuit described in any of the above embodiments, and has all the beneficial effects of the charging control circuit described in any of the above embodiments, which will not be described in detail here.

[0062] Although the present application has been shown and described with respect to one or more implementations, equivalent variations and modifications will occur to those skilled in the art upon reading and understanding this specification and the accompanying drawings. This application includes all such modifications and variations and is limited only by the scope of the appended claims. In particular, with respect to the various functions performed by the components described above, the terms used to describe such components are intended to correspond to any component (unless otherwise indicated) that performs the designated function of the component (e.g., which is functionally equivalent), even if the structure is not identical to the disclosed structure that performs the function in the exemplary implementation of this specification shown herein.

[0063] That is, the above description is merely an embodiment of the present application and does not limit the patent scope of the present application. Any equivalent structural or equivalent process transformations made using the contents of the description and drawings of this application, such as the mutual combination of technical features between the various embodiments, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the present application.

[0064] In addition, in the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present application. In addition, for structural elements with the same or similar characteristics, the present application may use the same or different reference numerals to identify them. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more features. In the description of the present application, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0065] In this application, the word "exemplary" is used to mean "serving as an example, illustration or description". Any embodiment described in this application as "exemplary" is not necessarily to be construed as being more preferred or more advantageous than other embodiments. The above description is provided to enable any person skilled in the art to implement and use the present application. In the above description, various details are listed for the purpose of explanation. It should be understood that a person of ordinary skill in the art can recognize that the present application can be implemented without using these specific details. In other embodiments, well-known structures and processes will not be elaborated in detail to avoid obscuring the description of the present application with unnecessary details. Therefore, the present application is not intended to be limited to the embodiments shown, but is consistent with the widest scope consistent with the principles and features disclosed in this application.

Claims

1. A switch control circuit, characterized in that: The switch control circuit includes a first switch unit and a second switch unit; A first end of the first switch unit is connected to the SW pin of the buck converter, and a second end of the first switch unit is connected to the gate of the charge control switch tube in the buck converter; a first end of the second switch unit is connected to the BOOT pin of the buck converter, and a second end of the second switch unit is connected to the gate of the charge control switch tube; The first switch unit is used to connect the gate of the charging control switch tube to the voltage of the SW pin during the charging period of the BOOT capacitor of the buck converter, so as to turn on the charging control switch tube and connect the charging current to the BOOT capacitor to charge the BOOT capacitor; The second switch unit is used to connect the gate of the charging control switch tube to the voltage of the BOOT pin during the non-charging period of the BOOT capacitor, so as to turn off the charging control switch tube; The first switch unit includes a first MOS transistor, a first diode, and a first current source; the source of the first MOS transistor serves as the first end of the first switch unit and is connected to the SW pin; the drain of the first MOS transistor serves as the second end of the first switch unit and is connected to the gate of the charge control switch tube, and the gate of the first MOS tube is used to receive a switch control signal; the input end of the first diode is connected to the SW pin, and the output end of the first diode is respectively connected to the output end of the first current source and the gate of the first MOS transistor; The input end of the first current source is used to connect to a second preset voltage; The switch control signal is used to control the first MOS transistor to be turned on during the charging period of the BOOT capacitor, and to control the first MOS transistor to be turned off during the non-charging period of the BOOT capacitor; The first current source is used to apply a reverse current to the first diode during the charging period of the BOOT capacitor to reversely break down the first diode, so that the voltage at the output end of the first diode is higher than the voltage at the input end of the first diode, thereby turning on the first MOS transistor.

2. The switch control circuit according to claim 1, wherein: The second switch unit includes a second MOS tube and a second diode; The source of the second MOS transistor serves as the first end of the second switch unit and is connected to the BOOT pin. The drain of the second MOS transistor serves as the second end of the second switch unit and is connected to the gate of the charge control switch tube. The gate of the second MOS transistor is connected to the input end of the second diode. The output end of the second diode is connected to the BOOT pin. The second diode is configured to be broken down when the voltage of the BOOT pin is higher than a first preset voltage, so that the voltage at the input end of the second diode is lower than the voltage at the output end of the second diode, thereby turning on the second MOS transistor.

3. The switch control circuit according to claim 2, wherein: The switch control circuit further includes a third diode and a second current source; The input end of the third diode is used to connect to the second preset voltage, and the output end of the third diode is connected to the input end of the second current source and the gate of the second MOS transistor respectively; The output end of the second current source is connected to the SW pin.

4. A charging control circuit, characterized in that: The charging control circuit includes the switch control circuit according to any one of claims 1 to 3.

5. The charging control circuit according to claim 4, characterized in that: The charging control circuit also includes a charging control switch tube; The drain of the charging control switch tube is used to access the charging current, the gate of the charging control switch tube is connected to the second end of the first switch unit and the second end of the second switch unit respectively, and the source of the charging control switch tube is connected to the BOOT pin of the buck converter.

6. The charging control circuit according to claim 5, characterized in that: The charging control circuit further includes a reference voltage providing module, a comparator, a current providing module and a comparison voltage protection module; The positive input terminal of the comparator is connected to the output terminal of the reference voltage providing module, the negative input terminal of the comparator is respectively connected to the output terminal of the current providing module, the drain of the charging control switch tube and the first terminal of the comparison voltage protection module, and the output terminal of the comparator is connected to the input terminal of the current providing module; The second terminal of the comparison voltage protection module is grounded; The reference voltage providing module is used to provide a reference voltage; The comparison voltage protection module is used to limit the maximum value of the comparison voltage; The comparator is configured to output a high level signal to the current providing module when the reference voltage is greater than the comparison voltage; The current providing module is used to provide charging current to the charging control switch tube when a high level signal is input.

7. A buck converter, characterized in that: The buck converter comprises the charging control circuit according to any one of claims 4 to 6.

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