Switching control circuit, charging control circuit and step-down converter

Abstract

The invention discloses a switch control circuit, a charging control circuit and a step-down converter, in the switch control circuit, a first end of a first switch unit is connected with an SW pin of the step-down converter, and a second end is connected with a grid electrode of a charging control switch tube; the first end of the second switch unit is connected with the BOOT pin of the buck converter, and the second end is connected with the grid electrode of the charging control switch tube; the first switch unit is used for accessing the voltage of the SW pin to the grid electrode of the charging control switch tube in the charging period of the BOOT capacitor of the step-down converter, so that the charging control switch tube is switched on, and charging current is accessed to the BOOT capacitor to charge the BOOT capacitor; and the second switch unit is used for accessing the voltage of the BOOT pin to the grid electrode of the charging control switch tube in the non-charging period of the BOOT capacitor so as to turn off the charging control switch tube. According to the invention, stable and orderly switching control can be carried out on the charging control switching tube, so that the BOOT capacitor can be stably and effectively charged.

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 suitable, and contribute to the stability of the output voltage VOUT of the buck converter. For example, if the buck converter includes Figure 1 The chip shown in the figure has BOOT, SW, VIN, GND, EN, SS, RT / CLK and FB pins as the pins of the chip. Capacitor C3 is the BOOT capacitor between the BOOT and SW pins. The BOOT capacitor can supply power to the upper bridge drive circuit when the negative end of the upper bridge drive buck converter floats with the SW pin, making the output voltage VOUT more stable. Because the charge and discharge current is required when driving the upper bridge switch device, the voltage of the BOOT capacitor itself will be reduced and must be charged and supplemented. Usually, when the lower bridge switch is turned on SW=GND, the BOOT capacitor is charged by the low-voltage power supply inside the chip. The relevant charging circuit can be referred to. Figure 2 As shown, the BOOT capacitor is charged by the internal low voltage VCC (such as 5V) of the chip through the relevant charging circuit.

[0003] Some BOOT capacitor charging circuits can refer to Figure 3 As shown in the figure, 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 internal low voltage VCC of the chip is used to charge the BOOT capacitor (such as Figure 3 CB) is charged, the difference between the voltage of the BOOT pin and the ground voltage (i.e. VBOOT-GND) is low voltage, and the charging control switch tube (such as Figure 3 The gate voltage of PM1 shown in the figure is the ground voltage (GND) and can be charged. When the upper bridge switch is turned on, the BOOT pin VBOOT is the sum of the input voltage VIN and the voltage of the BOOT capacitor, which is usually a high voltage. At this time, the gate voltage of the charging control switch tube must be equal to the voltage VBOOT of the BOOT pin to be turned off to ensure that the BOOT capacitor does not leak voltage input. Therefore, it is urgent to provide a switch control scheme corresponding to the charging control switch tube, to switch the charging control switch tube, so that the charging control switch tube can stably and effectively 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 switch 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; 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 charging 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 charging 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 for connecting 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.

[0006] 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.

[0007] 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, thereby turning on the first MOS tube.

[0008] 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 used to be broken down when the BOOT voltage of the BOOT pin is higher than the first preset voltage, and the input end voltage is lower than the output end voltage, thereby turning on the second MOS tube.

[0009] 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.

[0010] The present application also provides a charging control circuit, which includes any one of the above-mentioned switch control circuits.

[0011] 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.

[0012] Optionally, the charging control circuit also 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 electric 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.

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

[0014] In the above-mentioned switch control circuit, charging control circuit and buck converter of the present application, the first switch 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 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 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

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. 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.

[0016] Figure 1 It is a schematic diagram of the buck converter structure during the research process of this application; Figure 2 It is a partial structural schematic diagram of the buck converter in the research process of this application; Figure 3 It is a schematic diagram of the charging circuit structure during the research process of this application; Figure 4 is a schematic diagram of the structure of a switch control circuit according to an embodiment of the present application; Figure 5 is a schematic diagram of the switch control circuit structure of another embodiment of the present application; Figure 6 is a schematic diagram of the switch control circuit structure of another embodiment of the present application; Figure 7 It is a schematic diagram of the switch control circuit structure of an embodiment of the present application. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the present application are clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application. In the absence of conflict, the following embodiments and their technical features can be combined with each other.

[0018] In a first aspect, the present application provides a switch control circuit, which can be arranged in a buck converter. The buck converter includes a charge control switch tube and a BOOT capacitor. When the charge control switch tube is turned on, the charge current can be connected to the BOOT capacitor for charging. The switch control circuit can be connected to the gate of the charge control switch tube to control the on and off of the charge control switch tube. In some embodiments, the BOOT capacitor can also be called a bootstrap capacitor.

[0019] 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 charging 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 charging control switch tube PM1.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] Optionally, the buck converter may further include a control module. Optionally, the control module of the buck converter may pre-set the charging period and non-charging period of the BOOT capacitor CB according to factors such as the control logic and / or working mode of the upper and lower bridge switches. Optionally, the control module of the buck converter may also monitor the amount of electricity and / or the charging state of the BOOT capacitor CB through relevant components, and determine the charging period and non-charging period of the BOOT capacitor CB according to the monitoring results.

[0024] 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, 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, the charging control switch tube PM1 is turned off, and the charging of the BOOT capacitor CB is stopped; 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.

[0025] 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 is used 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 is used as the second end of the first switch unit 210 and is connected to the gate of the charging control switch tube PM1; the gate of the first MOS transistor NM1 is used to access the switch control signal CK1. The switch control signal CK1 is used to control the first MOS transistor PM1 to turn on during the charging period of the BOOT capacitor CB, so that the gate voltage of the charging control switch tube PM1 is the SW pin voltage VSW, 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 lower than its source voltage, and the first MOS transistor PM1 is controlled to be turned off during the non-charging period of the BOOT capacitor CB.

[0026] In some examples, reference Figure 6As shown, the first switch unit 210 also 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 can be a voltage regulator diode or a Zener diode. Optionally, the input end of the first current source CS1 can be connected to the internal voltage of the buck converter such as the second preset voltage VDD.

[0027] 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 (for example, the voltage at the output end of the first diode D1 is higher than the voltage at its input end by the breakdown voltage corresponding to the first diode D1). At this time, the switch control signal CK1 connected to the gate of the first MOS tube 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 tube NM1 is turned on, so that the gate voltage of the charging control switch tube PM1 is the SW pin voltage VSW.

[0028] Optionally, the first current source CS1 may further include a control terminal (not shown in the figure), the control terminal of the first current source CS1 is used to access an on signal (such as a high level, etc.) during the charging period of the BOOT capacitor CB to apply a reverse current to the first diode D1, and access a off signal (such as a low level, etc.) 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 come from a control module of the buck converter.

[0029] 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.

[0030] The source of the second MOS transistor PM2 is used as the first end of the second switch unit 220, connected to the BOOT pin; the drain of the second MOS transistor PM2 is used as the second end of the second switch unit 220, connected to the gate of the charging control switch tube 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.

[0031] The second diode D2 is used to be broken down when the BOOT voltage of the BOOT pin is higher than the first preset voltage, and the voltage at the input end of the second diode D2 is lower than the voltage at the output end of the second diode D2, so that the second MOS tube PM2 is turned on. 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 BOOT capacitor CB at the BOOT pin stops charging.

[0032] Optionally, the first preset voltage includes a voltage indicating that the BOOT capacitor CB is fully charged. After the BOOT capacitor CB is fully charged, the BOOT pin voltage VBOOT increases, and the increased BOOT pin voltage VBOOT reversely breaks down the second diode D2. At this time, the voltage at the input end of the second diode D2 is lower than the voltage at the output end of the second diode D2 by the breakdown voltage of the second diode D2, so that the second MOS transistor PM2 is turned on.

[0033] In some embodiments, Figure 6 As shown, the switch control circuit 220 also includes a third diode D3 and a second current source CS2; the input end of the third diode D3 is used to access the second preset voltage VDD, and the output end is respectively connected to the input end of the second current source CS2 and the gate of the second MOS transistor PM2; the output end of the second current source CS2 is connected to the SW pin. The second current source CS2 is used to cooperate with the third diode D3 to provide a required signal for the gate of the second MOS transistor PM2. Furthermore, the third diode D3 can also prevent the gate current of the second MOS transistor PM2 from flowing back to the second preset voltage VDD providing end, so as to ensure the stability of the buck converter in which the switch control circuit is located during operation.

[0034] Optionally, the second preset voltage VDD may be an internal voltage of the buck converter (eg, a 5V voltage inside the buck converter, etc.).

[0035] 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, 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, the charging control switch tube PM1 is turned off, and the charging of the BOOT capacitor CB is stopped; 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.

[0036] 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.

[0037] Specifically, the charging control circuit further includes a charging control switch tube PM1; the drain of the charging control switch tube PM1 is used to access the charging current I0, the gate is respectively 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 BOOT capacitor CB of the buck converter, the first switch unit 210 connects the gate of the charging control switch tube PM1 to the voltage of the SW pin, 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; during the non-charging period of the BOOT capacitor CB, the second switch unit 220 connects the gate of the charging control switch tube PM1 to the voltage of the BOOT pin, so that 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 is stopped.

[0038] In some embodiments, reference Figure 7 As shown, the charging control circuit further includes a reference voltage providing module 110, a comparator 120, a current providing module 130 and a comparison voltage protection module 140. The positive input terminal of the comparator 120 is connected to the output terminal of the reference voltage providing module 110; the negative input terminal of the comparator 120 is respectively connected to the output terminal of the current providing module 130, the drain of the electric control switch tube PM1 and the first terminal of the comparison voltage protection module 140; the output terminal of the comparator 120 is connected to the input terminal of the current providing module 130. The second terminal of the comparison voltage protection module 140 is grounded.

[0039] The reference voltage providing module 110 is used to provide a reference voltage VREF.

[0040] The comparison voltage protection module 140 is used to limit the maximum value of the comparison voltage VFB.

[0041] The comparator 120 is used for outputting 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 .

[0042] The current providing module 130 is used to provide a charging current I0 to the charging control switch tube PM1 when a high level signal is connected.

[0043] In some examples, the reference voltage providing module 110 includes a third current source CS3, a voltage control 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 is used 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 control resistor R1. The second end of the voltage control resistor R1 is grounded through the first switch S1. The above-mentioned voltage control resistor R1 can provide a voltage signal with a preset voltage higher than the voltage at the first switch S1 after the first switch S1 is closed, and the 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, I1 is the magnitude of the output current of the third current source CS3, and R1 is the resistance value of the voltage control resistor R1. Optionally, the parameters of the third current source CS3 and the voltage control resistor R1 can be determined according to the magnitude of the reference voltage VREF required to be connected to the positive input end of the comparator 120, wherein the reference voltage VREF is usually a voltage value greater than the comparison voltage VFB.

[0044] Optionally, the reference voltage providing module 110 further includes a second switch S2. A first end of the second switch S2 is connected to a second end of the voltage control 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 used to connect the voltage control resistor R1 to the SW pin of the buck converter, so that the reference voltage VREF is VSW+ I1*R1; wherein VSW is the voltage of the SW pin.

[0045] In some examples, the current providing module 130 includes a fourth current source CS4, a setting switch tube K2 and a current mirror 131. The setting switch tube K2 may be an NMOS tube. The gate of the setting switch tube K2 is used as the input end of the current providing module 130, connected to the output end of the comparator 120, the source of the setting switch tube K2 is connected to the input end of the fourth current source CS4, and the drain of the setting switch tube K2 is connected to the input end of the current mirror 131; the output end of the fourth current source CS4 is grounded; the output end of the current mirror 131 is used as the output end of the current providing module 130, connected to the drain of the charging control switch tube PM1. The setting switch tube K2 is used to turn on when the gate is connected to a high level, so as to connect the current provided by the fourth current source CS4 to the input end of the current mirror 131. The current mirror 131 is used to output the current connected to the input end to the drain of the charging control switch tube PM1, so that the current charges the BOOT capacitor CB through the charging control switch tube PM1.

[0046] Optionally, the current mirror 131 includes a first MOS transistor P1, a second MOS transistor P2 and a third switch S3; the first MOS transistor P1 and the second MOS transistor P2 are both PMOS transistors. The drain of the first MOS transistor P1 is used as the input end of the current mirror 131, and is respectively connected to the drain of the setting switch tube K2, the gate of the first MOS transistor P1, the gate of the second MOS transistor P2 and the first end of the third switch S3, and the source of the first MOS transistor P1 is respectively connected to the voltage input terminal VIN, the second end of the third switch S3 and the source of the second MOS transistor P2; the drain of the second MOS transistor P2 is used as the output end of the current mirror 131, and is connected to the drain of the charging control switch tube PM1.

[0047] In some examples, the comparison voltage protection module 140 includes a fourth diode D4 and a fourth switch S4. The input end of the fourth diode D4 is grounded through the fourth switch S4, and the ground end can be the second end of the comparison voltage protection module 140; the output end of the fourth diode D4 is used as the first end of the comparison voltage protection module 140, and is connected to the drain of the first switch tube K1. The fourth diode D4 is a voltage stabilizing diode, so that the maximum value of the voltage difference between the output end (such as) and the input end of the fourth diode D4 is its breakdown voltage. At this time, the first end 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 end of the comparator 120 is the breakdown voltage of the fourth diode D4.

[0048] 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.

[0049] 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.

[0050] A third aspect of the present application provides a buck converter, wherein the buck converter includes the charging control circuit described in any one of the above embodiments.

[0051] Specifically, the buck converter further includes a BOOT capacitor CB; the BOOT capacitor CB is connected between the BOOT pin and the SW pin.

[0052] The above-mentioned buck converter includes the charging control circuit described in any of the above-mentioned embodiments, and has all the beneficial effects of the charging control circuit described in any of the above-mentioned embodiments, which will not be repeated here.

[0053] 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 based on reading and understanding this specification and the accompanying drawings. The present 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 above-mentioned components, the terms used to describe such components are intended to correspond to any component (unless otherwise indicated) that performs the specified function of the component (e.g., it is functionally equivalent), even if it is not structurally equivalent to the disclosed structure that performs the function in the exemplary implementation of the present specification shown herein.

[0054] That is, the above description is only an embodiment of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the specification and drawings of the present application, such as the mutual combination of technical features between the embodiments, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the present application.

[0055] 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 drawings, which are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying 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 a limitation on 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 for identification. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of 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, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0056] In this application, the word "exemplary" is used to mean "used as an example, illustration or description". Any embodiment described as "exemplary" in this application is not necessarily to be construed as being more preferred or more advantageous than other embodiments. In order to enable any technician in the field to implement and use the present application, the present application provides the above description. 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 unnecessary details that make the description of the present application obscure. Therefore, the present application is not intended to be limited to the embodiments shown, but is consistent with the widest range of principles and features disclosed in the present application.

Claims

1. A switch control circuit, characterized in that: The switch control circuit includes a first switch unit and a second switch unit; 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 charging 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 charging 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 for connecting 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.

2. The switch control circuit according to claim 1, characterized in that: 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 the switch control signal; 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.

3. The switch control circuit according to claim 2, characterized in that: The first switch unit further 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, thereby turning on the first MOS tube.

4. The switch control circuit according to claim 1, characterized in that: 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 and is connected to the BOOT pin. The drain serves as the second end of the second switch unit and is connected to the gate of the charge control switch tube. 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 used to be broken down when the BOOT voltage of the BOOT pin is higher than the first preset voltage, and the input terminal voltage is lower than the output terminal voltage, thereby turning on the second MOS tube.

5. The switch control circuit according to claim 4, characterized in that: 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.

6. A charging control circuit, characterized in that: The charging control circuit comprises the switch control circuit according to any one of claims 1 to 5.

7. The charging control circuit according to claim 6, characterized in that: The charging control circuit also includes a charging control switch tube; The drain of the electrically controlled 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.

8. The charging control circuit according to claim 7, characterized in that: The charging control circuit also 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 electric 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 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 used for outputting 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.

9. A buck converter, characterized in that: The buck converter comprises a charging control circuit as claimed in any one of claims 6 to 8.

Images