Voltage detection circuit and switching power supply device

Abstract

The present application is applicable to the field of electronic circuit technology, and provides a voltage detection circuit and a switching power supply device. The voltage detection circuit includes a switch module and a voltage detection module. The switch module is respectively connected to the voltage detection module, the power module and the segmented drive circuit in the switching power supply. The voltage detection module is respectively used to connect to the switch node and the segmented drive circuit in the switching power supply, and the voltage detection module is also used for grounding. When the switching power supply operates in the intermittent conduction mode, the switch module is disconnected according to the drive signal in the segmented drive circuit, so that the voltage detection module is disconnected from the power module. After the voltage detection module is disconnected from the power module, the voltage detection module does not work, and no current is generated, thereby reducing the power consumption of the circuit. In summary, the voltage detection circuit provided in the embodiment of the present application solves the problem of high power consumption of the existing SW voltage detection circuit when the DC-DC switching power supply operates in the DCM mode.

Description

Technical Field

[0001] The present application belongs to the technical field of electronic circuits, and in particular, relates to a voltage detection circuit and a switching power supply device. Background Art

[0002] With the rapid development of science and technology, DC-DC (Direct Current to Direct Current) switching power supplies are widely used in various types of electronic devices, and consumer electronics AMOLED (Active-matrix organic light-emitting diode) is one of them. AMOLED has relatively high requirements for the efficiency and EMI (Electromagnetic Interference) of DC-DC switching power supplies. If the EMI performance is better, the dv / dt (voltage change rate) of the switch tube in the DC-DC switching power supply needs to be smaller, but too slow a driving speed will result in high switching losses, which in turn leads to low efficiency of the DC-DC switching power supply. In order to solve this problem, segmented driving can be used. In segmented driving, the SW (switch node) voltage detection circuit plays a vital role. It is used to generate corresponding control signals according to the voltage at SW to drive the switch tube to work in segments.

[0003] However, when the DC-DC switching power supply operates in DCM mode (Discontinuous Conduction Mode), the SW voltage detection circuit will face the problem of power consumption: when the DC-DC switching power supply operates in DCM mode, the NMOS power tube and PMOS power tube in the DC-DC switching power supply are disconnected, and the voltage at the SW will oscillate at the middle level between the power supply and the ground. When the voltage at the SW is at the middle level, the SW voltage detection circuit will have a current of hundreds of uA. This current will exist for a long time in the DCM mode, which will increase the power consumption of the circuit. Summary of the invention

[0004] The embodiments of the present application provide a voltage detection circuit and a switching power supply device, which can solve the problem of high power consumption of the existing SW voltage detection circuit when the DC-DC switching power supply operates in DCM mode.

[0005] In a first aspect, an embodiment of the present application provides a voltage detection circuit, including a switch module and a voltage detection module, wherein the switch module is respectively connected to the voltage detection module, a power module and a segmented drive circuit in a switching power supply, and the voltage detection module is respectively used to connect to a switch node in the switching power supply and the segmented drive circuit, and the voltage detection module is also used to be grounded;

[0006] When the switching power supply operates in the intermittent conduction mode, the switch module is disconnected according to the driving signal in the segmented driving circuit, so that the voltage detection module is disconnected from the power supply module.

[0007] In a possible implementation of the first aspect, when the voltage at the switch node changes, the switch module is turned on according to the drive signal, so that the voltage detection module is connected to the power supply module; the voltage detection module outputs a first control signal and a second control signal to the segmented drive circuit according to the voltage at the switch node.

[0008] In a possible implementation of the first aspect, the switch module includes a first field effect transistor, a gate of the first field effect transistor is used to connect to the segmented drive circuit, a source of the first field effect transistor is used to connect to the power supply module, and a drain of the first field effect transistor is connected to the voltage detection module.

[0009] In a possible implementation manner of the first aspect, the voltage detection module includes a first switch unit, a second switch unit, a resistance unit, a first logic unit, and a second logic unit, the resistance unit is respectively connected to the first switch unit, the second switch unit, the first logic unit, and the second logic unit, the first switch unit is respectively connected to the switch module, the second switch unit, and the switch node, the first logic unit and the second logic unit are respectively used to connect to the segmented drive circuit, and the second switch unit is also used to connect to the ground; the first control signal includes a first level signal and a fourth level signal, and the second control signal includes a second level signal and a third level signal;

[0010] When the switching power supply operates in the intermittent conduction mode, the switch module is disconnected according to the driving signal, so that the first switch unit is disconnected from the power supply module;

[0011] When the voltage at the switch node changes, the switch module is turned on according to the drive signal, so that the first switch unit is connected to the power module.

[0012] In a possible implementation of the first aspect, when the voltage at the switch node starts to drop from the power supply voltage and the voltage at the switch node is greater than or equal to a first threshold voltage, the first switch unit is turned on and provides a first signal to the first logic unit; the first logic unit outputs a first level signal according to the first signal; the second switch unit is turned on, so that the resistance unit is connected to the ground; the resistance unit provides a second signal to the second logic unit; the second logic unit outputs a second level signal according to the second signal; when the voltage at the switch node is less than the first threshold voltage, the first switch unit maintains a turned-on state; the second switch unit is turned off, so that the resistance unit is disconnected from the ground; the resistance unit provides a third signal to the second logic unit; the second logic unit outputs a third level signal according to the third signal.

[0013] In a possible implementation of the first aspect, when the voltage at the switch node starts to rise from 0V and the voltage at the switch node is less than or equal to a second threshold voltage, the first switch unit is turned on and provides a first signal to the first logic unit; the first logic unit outputs a first level signal according to the first signal; the second switch unit is turned on, so that the resistance unit is connected to the ground; the resistance unit provides a second signal to the second logic unit; the second logic unit outputs a second level signal according to the second signal; when the voltage at the switch node is greater than the second threshold voltage, the second switch unit maintains a turned-on state; the first switch unit is turned off; the resistance unit provides a fourth signal to the first logic unit; the first logic unit outputs a fourth level signal according to the fourth signal.

[0014] In a possible implementation of the first aspect, the first switch unit includes a second field effect transistor, a gate of the second field effect transistor is used to be connected to the switch node, a source of the second field effect transistor is connected to the switch module, and a drain of the second field effect transistor is respectively connected to the first logic unit and the resistance unit.

[0015] In a possible implementation of the first aspect, the second switch unit includes a third field effect transistor, a gate of the third field effect transistor is used to be connected to the switch node, a drain of the third field effect transistor is respectively connected to the resistance unit and the second logic unit, and a source of the third field effect transistor is used to be grounded.

[0016] In a possible implementation of the first aspect, the resistance unit includes a first resistor and a second resistor, the first end of the first resistor is respectively connected to the first switch unit and the first logic unit, the second end of the first resistor is connected to the first end of the second resistor, and the second end of the second resistor is respectively connected to the second switch unit and the second logic unit.

[0017] In a second aspect, an embodiment of the present application provides a switching power supply device, comprising the voltage detection circuit described in any one of the first aspects.

[0018] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0019] An embodiment of the present application provides a voltage detection circuit, including a switch module and a voltage detection module, the switch module is respectively connected to the voltage detection module, the power module and the segmented drive circuit in the switching power supply, the voltage detection module is respectively used to connect to the switch node and the segmented drive circuit in the switching power supply, and the voltage detection module is also used for grounding.

[0020] When the switching power supply operates in the intermittent conduction mode, the switch module is disconnected according to the driving signal in the segmented driving circuit, so that the voltage detection module is disconnected from the power module. After the voltage detection module is disconnected from the power module, the voltage detection module does not work, and no current is generated, thereby reducing the power consumption of the circuit.

[0021] In summary, the voltage detection circuit provided in the embodiments of the present application solves the problem of high power consumption of the existing SW voltage detection circuit when the DC-DC switching power supply operates in the DCM mode.

[0022] It can be understood that the beneficial effects of the second aspect mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0024] Figure 1 It is a circuit connection diagram of segmented drive in DC-DC switching power supply;

[0025] Figure 2 is a principle block diagram of a voltage detection circuit provided in an embodiment of the present application;

[0026] Figure 3is a principle block diagram of a voltage detection circuit provided in another embodiment of the present application;

[0027] Figure 4 Schematic diagram of circuit connection of a voltage detection circuit provided in one embodiment of the present application.

[0028] In the figure: 10, switch module; 20, voltage detection module; 21, first switch unit; 22, second switch unit; 23, resistance unit; 24, first logic unit; 25, second logic unit; 30, power supply module; 40, switching power supply; 41, segmented drive circuit. DETAILED DESCRIPTION

[0029] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application may also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present application.

[0030] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, wholes, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or combinations thereof.

[0031] It should also be understood that the term “and / or” used in the specification and appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0032] As used in the specification and appended claims of this application, the term "if" can be interpreted as "when" or "uponce" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" can be interpreted as meaning "uponce it is determined" or "in response to determining" or "uponce [described condition or event] is detected" or "in response to detecting [described condition or event]", depending on the context.

[0033] In addition, in the description of the present application specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0034] References to "one embodiment" or "some embodiments" etc. described in the specification of this application mean that one or more embodiments of the present application include specific features, structures or characteristics described in conjunction with the embodiment. Therefore, the statements "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear in different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0035] With the rapid development of science and technology, DC-DC switching power supplies are widely used in consumer electronics AMOLED, which has relatively high requirements for the efficiency and EMI of DC-DC switching power supplies. If the EMI performance is better, the dv / dt of the switch tube in the DC-DC switching power supply needs to be smaller, but too slow a driving speed will lead to high switching losses, which in turn leads to low efficiency of the DC-DC switching power supply. In order to solve this problem, segmented driving can be used. It should be noted that segmented driving is only for NMOS power tubes in DC-DC switching power supplies.

[0036] like Figure 1 As shown, the pull-up drive circuit for the NMOS power tube is divided into two sections, P1 and P2, for control. The size of the P1 tube is relatively small, and it is used to control the time for the NGATE voltage to change from 0 to the Miller platform. The NGATE voltage changes very slowly in the Miller platform interval. If the driving speed is always slow, the switching loss will be too high. By increasing the larger P2 tube to control the time from the Miller platform to VDD, the switching loss can be effectively reduced. Similarly, the pull-down drive circuit for the NMOS power tube is divided into two sections, N1 and N2, for control. The size of the N1 tube is relatively small, and it controls the time for the NGATE voltage to change from VDD to the Miller platform. The NGATE voltage changes very slowly in the Miller platform interval. If the driving speed is always slow, the switching loss will be too high. By increasing the larger N2 tube to control the time from the Miller platform to 0, the switching loss can be effectively reduced.

[0037] The specific principle of segmented driving is: when the gate voltage of the P1 tube is low, the NGATE voltage rises slowly. When the first control signal P_control becomes high, the gate voltage of the P2 tube is low (the input voltage and output voltage of buf are in opposite phases), the P2 tube is turned on, and the NGATE voltage rises rapidly to the power supply voltage VDD. Similarly, when the gate voltage of the N1 tube is high, the N1 tube is turned on, and the NGATE voltage drops slowly. When the second control signal N_control becomes low, the gate voltage of the N2 tube is high, the N2 tube is turned on, and the NGATE voltage drops rapidly to VSS. Among them, the first control signal P_control is used to control the turn-on time of the P2 tube, and the second control signal N_control is used to control the turn-on time of the N2 tube. The first control signal P_control and the second control signal N_control are generated by the SW voltage detection circuit.

[0038] As can be seen from the above, the SW voltage detection circuit plays a vital role in segmented driving. However, when the DC-DC switching power supply operates in DCM mode, the SW voltage detection circuit will face the problem of power consumption: when the DC-DC switching power supply operates in DCM mode, the NMOS power tube and PMOS power tube in the DC-DC switching power supply are disconnected, and the voltage at the SW will oscillate at the middle level between the power supply and the ground. When the voltage at the SW is at the middle level, the SW voltage detection circuit will have a current of hundreds of uA. This current will exist for a long time in the DCM mode, which will increase the power consumption of the circuit.

[0039] In view of the above problems, the present application provides a voltage detection circuit. Figure 2 As shown, the voltage detection circuit includes a switch module 10 and a voltage detection module 20. The switch module 10 is respectively connected to the voltage detection module 20, the power module 30 and the segmented drive circuit 41 in the switching power supply 40. The voltage detection module 20 is respectively used to connect to the switch node SW in the switching power supply 40 and the segmented drive circuit 41. The voltage detection module 20 is also used for grounding.

[0040] Specifically, when the switching power supply 40 operates in the intermittent conduction mode, the switch module 10 is disconnected according to the drive signal NDRIV in the segmented drive circuit 41, so that the voltage detection module 20 is disconnected from the power module 30. After the voltage detection module 20 is disconnected from the power module 30, the voltage detection module 20 does not work, and no current is generated, thereby reducing the power consumption of the circuit. It should be noted that when the switching power supply 40 operates in the intermittent conduction mode, the PMOS power tube and the NMOS power tube in the switching power supply 40 are both disconnected, and the power supply module 30 is disconnected. Figure 1It can be seen that if the NMOS power tube is disconnected, the NGATE voltage is low. If the NGATE voltage is low, the N2 tube is controlled to be turned on. If the N2 tube is controlled to be turned on, the drive signal NDRIV is high. Therefore, when the switching power supply 40 operates in the intermittent conduction mode, the drive signal NDRIV is high.

[0041] In summary, the voltage detection circuit provided in the embodiments of the present application solves the problem of high power consumption of the existing SW voltage detection circuit when the DC-DC switching power supply operates in the DCM mode.

[0042] In some embodiments, when the voltage at the switch node SW changes, the switch module 10 is turned on according to the drive signal NDRIV, so that the voltage detection module 20 is connected to the power module 30. After the voltage detection module 20 is connected to the power module 30, the voltage detection module 20 starts to work and outputs the first control signal P_control and the second control signal N_control to the segmented drive circuit 41 according to the voltage at the switch node SW. It should be noted that during the change of the voltage at the switch node SW, the drive signal NDRIV is at a low level.

[0043] In some embodiments, Figure 3 As shown, the voltage detection module 20 includes a first switch unit 21, a second switch unit 22, a resistor unit 23, a first logic unit 24 and a second logic unit 25, the resistor unit 23 is respectively connected to the first switch unit 21, the second switch unit 22, the first logic unit 24 and the second logic unit 25, the first switch unit 21 is respectively connected to the switch module 10, the second switch unit 22 and the switch node SW, the first logic unit 24 and the second logic unit 25 are respectively used to connect to the segment drive circuit 41, and the second switch unit 22 is also used to connect to the ground. Among them, the first control signal P_control includes a first level signal and a fourth level signal, and the second control signal N_control includes a second level signal and a third level signal.

[0044] Specifically, when the switching power supply 40 operates in the intermittent conduction mode, the switch module 10 is disconnected according to the driving signal NDRIV, so that the first switch unit 21 is disconnected from the power module 30. After the first switch unit 21 is disconnected from the power module 30, the voltage detection module 20 does not work, and no current is generated, thereby reducing the power consumption of the circuit.

[0045] When the voltage at the switch node SW changes, the switch module 10 is turned on according to the drive signal NDRIV, so that the first switch unit 21 is connected to the power module 30. After the first switch unit 21 is connected to the power module 30, the voltage detection module 20 starts to work.

[0046] In some embodiments, when the voltage at the switch node SW starts to drop from the power supply voltage VDD (indicating that the NMOS power tube in the switching power supply 40 starts to turn on), and the voltage at the switch node SW is greater than or equal to the first threshold voltage VTHn (VTHn is the turn-on threshold voltage of the NMOS tube), the first switch unit 21 is turned on and provides a first signal (the first signal is a high level) to the first logic unit 24; the first logic unit 24 outputs a first level signal according to the first signal (the first level signal is a high level, that is, the second control signal N_control is a high level); the second switch unit 22 is turned on, so that the resistor unit 23 is connected to the ground; the resistor unit 23 provides a second signal (the second signal is a low level) to the second logic unit 25; the second logic unit 25 outputs a second level signal according to the second signal (the second level signal is a low level, that is, the first control signal P_control is a low level). When the voltage at the switch node SW is less than the first threshold voltage VTHn, the first switch unit 21 maintains the on state; the second switch unit 22 is turned off, so that the resistor unit 23 is disconnected from the ground; the resistor unit 23 provides the third signal (the third signal is a high level) to the second logic unit 25; the second logic unit 25 outputs a third level signal (the third level signal is a high level, that is, the first control signal P_control becomes a high level) according to the third signal. Figure 1 When the first control signal P_control becomes a high level, the P2 tube is turned on, and the NGATE voltage is quickly pulled to the power supply voltage VDD, which speeds up the rising speed of the NGATE voltage and reduces the switching loss.

[0047] In some embodiments, when the voltage at the switch node SW starts to rise from 0V (indicating that the NMOS power tube in the switching power supply 40 starts to disconnect), and the voltage at the switch node SW is less than or equal to the second threshold voltage VDD-VTHp (VTHp is the turn-on threshold voltage of the PMOS tube), the first switch unit 21 is turned on and provides a first signal (the first signal is a high level) to the first logic unit 24; the first logic unit 24 outputs a first level signal according to the first signal (the first level signal is a high level, that is, the second control signal N_control is a high level); the second switch unit 22 is turned on, so that the resistor unit 23 is connected to the ground; the resistor unit 23 provides a second signal (the second signal is a low level) to the second logic unit 25; the second logic unit 25 outputs a second level signal according to the second signal (the second level signal is a low level, that is, the first control signal P_control is a low level). When the voltage at the switch node SW is greater than the second threshold voltage VDD-VTHp, the second switch unit 22 maintains the on state; the first switch unit 21 is turned off; the resistor unit 23 provides the fourth signal (the fourth signal is low level) to the first logic unit 24; the first logic unit 24 outputs a fourth level signal (the fourth level signal is low level, that is, the second control signal N_control becomes low level) according to the fourth signal. Figure 1 When the second control signal N_control becomes a low level, the N2 tube is turned on and the NGATE voltage is quickly pulled to VSS, which speeds up the drop of the NGATE voltage and reduces the switching loss.

[0048] In summary, the voltage detection circuit provided in the embodiment of the present application accelerates the driving speed of the NMOS power tube in the switching power supply 40 by detecting the rising and falling time of the voltage at the switching node SW, improves the efficiency at light load, and reduces the power consumption in the DCM mode.

[0049] In some embodiments, Figure 4 As shown, the switch module 10 includes a first field effect transistor M1, a gate of the first field effect transistor M1 is used to connect to the segmented driving circuit 41, a source of the first field effect transistor M1 is used to connect to the power module 30, and a drain of the first field effect transistor M1 is connected to the voltage detection module 20.

[0050] Specifically, when the switching power supply 40 operates in the DCM mode, the driving signal NDRIV is at a high level, and the first field effect transistor M1 is disconnected, so that the voltage detection module 20 is disconnected from the power module 30. After the voltage detection module 20 is disconnected from the power module 30, the voltage detection module 20 does not work, and no current is generated, thereby reducing the power consumption of the circuit.

[0051] When the voltage at the switch node SW changes, the drive signal NDRIV is at a low level, the first field effect transistor M1 is turned on, and the voltage detection module 20 is connected to the power module 30. After the voltage detection module 20 is connected to the power module 30, the voltage detection module 20 starts to work and outputs the first control signal P_control and the second control signal N_control to the segment drive circuit 41 according to the voltage at the switch node SW.

[0052] In some embodiments, Figure 4 As shown, the first switch unit 21 includes a second field effect transistor M2, the gate of the second field effect transistor M2 is used to connect to the switch node SW, the source of the second field effect transistor M2 is connected to the switch module 10, and the drain of the second field effect transistor M2 is connected to the first logic unit 24 and the resistance unit 23 respectively. Figure 4 It can be seen that the source of the second field effect transistor M2 is connected to the drain of the first field effect transistor M1 in the switch module 10 .

[0053] Specifically, when the switching power supply 40 operates in the DCM mode, the driving signal NDRIV is at a high level, the first field effect transistor M1 is disconnected, and the source of the second field effect transistor M2 is disconnected from the power module 30. After the source of the second field effect transistor M2 is disconnected from the power module 30, the voltage detection module 20 does not work, and no current is generated, thereby reducing the power consumption of the circuit.

[0054] When the voltage at the switch node SW changes, the drive signal NDRIV is at a low level, the first field effect transistor M1 is turned on, and the source of the second field effect transistor M2 is connected to the power module 30. After the source of the second field effect transistor M2 is connected to the power module 30, the voltage detection module 20 starts to work: when the voltage at the switch node SW starts to drop from the power supply voltage VDD (indicating that the NMOS power transistor in the switch power supply 40 starts to turn on), and the voltage at the switch node SW is greater than or equal to the first threshold voltage VTHn (VTHn is the conduction threshold voltage of the NMOS transistor), the second field effect transistor M2 is turned on and provides a first signal (the first signal is a high level) to the first logic unit 24; the first logic unit 24 outputs a first level signal according to the first signal (the first level signal is a high level, that is, the second control signal N_control is a high level). When the voltage at the switch node SW is less than the first threshold voltage VTHn, the second field effect transistor M2 remains in the on state. That is, when the voltage at the switch node SW is in the process of decreasing, the second field effect transistor M2 is always in the on state, that is, the second control signal N_control is always kept at a high level.

[0055] When the voltage at the switch node SW starts to rise from 0V (indicating that the NMOS power tube in the switch power supply 40 starts to disconnect), and the voltage at the switch node SW is less than or equal to the second threshold voltage VDD-VTHp (VTHp is the conduction threshold voltage of the PMOS tube), the second field effect tube M2 is turned on and provides the first signal (the first signal is a high level) to the first logic unit 24; the first logic unit 24 outputs a first level signal according to the first signal (the first level signal is a high level, that is, the second control signal N_control is a high level). When the voltage at the switch node SW is greater than the second threshold voltage VDD-VTHp, the second field effect tube M2 is turned off, and the second switch unit 22 maintains the on state, then the resistor unit 23 provides the fourth signal (the fourth signal is a low level) to the first logic unit 24; the first logic unit 24 outputs a fourth level signal according to the fourth signal (the fourth level signal is a low level, that is, the second control signal N_control becomes a low level). That is, when the voltage at the switch node SW is in the rising process, the second field effect transistor M2 changes from the on state to the off state, so that the second control signal N_control changes from the high level to the low level.

[0056] In some embodiments, Figure 4 As shown, the second switch unit 22 includes a third field effect transistor M3, the gate of the third field effect transistor M3 is used to connect to the switch node SW, the drain of the third field effect transistor M3 is respectively connected to the resistance unit 23 and the second logic unit 25, and the source of the third field effect transistor M3 is used to ground.

[0057] Specifically, when the switching power supply 40 operates in the DCM mode, the driving signal NDRIV is at a high level, the first field effect transistor M1 is disconnected, and the source of the second field effect transistor M2 is disconnected from the power module 30. After the source of the second field effect transistor M2 is disconnected from the power module 30, the voltage detection module 20 does not work, and no current is generated, thereby reducing the power consumption of the circuit.

[0058] When the voltage at the switch node SW changes, the drive signal NDRIV is at a low level, the first field effect transistor M1 is turned on, and the source of the second field effect transistor M2 is connected to the power module 30. After the source of the second field effect transistor M2 is connected to the power module 30, the voltage detection module 20 starts to work: when the voltage at the switch node SW starts to drop from the power supply voltage VDD (indicating that the NMOS power transistor in the switch power supply 40 starts to be turned on), and the voltage at the switch node SW is greater than or equal to the first threshold voltage VTHn (VTHn is the conduction threshold voltage of the NMOS transistor), the third field effect transistor M3 is turned on, so that the resistor unit 23 is connected to the ground; the resistor unit 23 provides a second signal to the second logic unit 25 (the second signal is at a low level); the second logic unit 25 outputs a second level signal according to the second signal (the second level signal is at a low level, that is, the first control signal P_control is at a low level). When the voltage at the switch node SW is less than the first threshold voltage VTHn, the third field effect transistor M3 is turned off, so that the resistor unit 23 is disconnected from the ground; the resistor unit 23 provides a third signal (the third signal is a high level) to the second logic unit 25, so that the second logic unit 25 outputs a third level signal (the third level signal is a high level, that is, the first control signal P_control becomes a high level) according to the third signal. That is, when the voltage at the switch node SW is in the process of decreasing, the third field effect transistor M3 changes from the on state to the off state, so that the first control signal P_control changes from the low level to the high level.

[0059] When the voltage at the switch node SW starts to rise from 0V (indicating that the NMOS power tube in the switch power supply 40 starts to disconnect), and the voltage at the switch node SW is less than or equal to the second threshold voltage VDD-VTHp (VTHp is the conduction threshold voltage of the PMOS tube), the third field effect tube M3 is turned on, so that the resistance unit 23 is connected to the ground; the resistance unit 23 provides the second signal (the second signal is low level) to the second logic unit 25; the second logic unit 25 outputs the second level signal (the second level signal is low level, that is, the first control signal P_control is low level) according to the second signal. When the voltage at the switch node SW is greater than the second threshold voltage VDD-VTHp, the third field effect tube M3 remains in the on state. That is, when the voltage at the switch node SW is in the rising process, the third field effect tube M3 is always in the on state, that is, the first control signal P_control is always kept at a low level.

[0060] In some embodiments, the resistor unit 23 includes a first resistor R1 and a second resistor R2, wherein the first end of the first resistor R1 is connected to the first switch unit 21 and the first logic unit 24, respectively, the second end of the first resistor R1 is connected to the first end of the second resistor R2, and the second end of the second resistor R2 is connected to the second switch unit 22 and the second logic unit 25, respectively. Figure 4 It can be seen that the first end of the first resistor R1 is respectively connected to the drain of the second field effect transistor M2 in the first switch unit 21 and the first logic unit 24. The second end of the second resistor R2 is respectively connected to the drain of the third field effect transistor M3 in the second switch unit 22 and the second logic unit 25. Specifically, the first resistor R1 and the second resistor R2 are used to fix the threshold voltages of the second field effect transistor M2 and the third field effect transistor M3.

[0061] In some embodiments, the first logic unit 24 includes a first Schmitt trigger smit1, the input end of the first Schmitt trigger smit1 is connected to the first switch unit 21 and the resistor unit 23 respectively, and the output end of the first Schmitt trigger smit1 is used to connect to the segment drive circuit 41. Figure 4 It can be seen that the input end of the first Schmitt trigger smit1 is respectively connected to the drain of the second field effect transistor M2 in the first switch unit 21 and the first end of the first resistor R1 in the resistor unit 23. Specifically, the first Schmitt trigger smit1 is used to improve the anti-interference ability of the circuit.

[0062] In some embodiments, the second logic unit 25 includes a second Schmitt trigger smit2, the input end of the second Schmitt trigger smit2 is connected to the second switch unit 22 and the resistor unit 23 respectively, and the output end of the second Schmitt trigger smit2 is used to connect to the segment drive circuit 41. Figure 4 It can be seen that the input end of the second Schmitt trigger smit2 is respectively connected to the drain of the third field effect transistor M3 in the second switch unit 22 and the second end of the second resistor R2 in the resistor unit 23. Specifically, the second Schmitt trigger smit2 is used to improve the anti-interference ability of the circuit.

[0063] Combine the following Figure 1 and Figure 4 The working principle of this application is explained again.

[0064] When the switching power supply 40 operates in the DCM mode, the driving signal NDRIV is at a high level, the first field effect transistor M1 is disconnected, and the source of the second field effect transistor M2 is disconnected from the power module 30. After the source of the second field effect transistor M2 is disconnected from the power module 30, the voltage detection module 20 does not work, and no current is generated, thereby reducing the power consumption of the circuit.

[0065] When the voltage at the switch node SW changes, the drive signal NDRIV is at a low level, the first field effect transistor M1 is turned on, and the source of the second field effect transistor M2 is connected to the power module 30. After the source of the second field effect transistor M2 is connected to the power module 30, the voltage detection module 20 starts to work: when the voltage at the switch node SW starts to drop from the power supply voltage VDD (indicating that the NMOS power transistor in the switch power supply 40 starts to turn on), and the voltage at the switch node SW is greater than or equal to the first threshold voltage VTHn (VTHn is the turn-on threshold voltage of the NMOS transistor), the second field effect transistor M2 is turned on and provides a first signal (the first signal is a high level) to the first Schmitt trigger smit1; the first Schmitt trigger smit1 outputs a first level signal (the first level signal is a high level, that is, the second control signal N_control is a high level) according to the first signal. The third field effect transistor M3 is turned on, so that the second resistor R2 is connected to the ground; the second resistor R2 provides a second signal (the second signal is low level) to the second Schmitt trigger smit2; the second Schmitt trigger smit2 outputs a second level signal according to the second signal (the second level signal is low level, that is, the first control signal P_control is low level). When the voltage at the switch node SW is less than the first threshold voltage VTHn, the second field effect transistor M2 maintains the on state, and the third field effect transistor M3 is turned off, so that the second resistor R2 is disconnected from the ground; the second resistor R2 provides a third signal (the third signal is high level) to the second Schmitt trigger smit2; the second Schmitt trigger smit2 outputs a third level signal according to the third signal (the third level signal is high level, that is, the first control signal P_control becomes high level). That is, when the voltage at the switch node SW is in the process of decreasing, the second field effect transistor M2 is always in the on state, that is, the second control signal N_control is always kept at a high level. The third field effect transistor M3 changes from the on state to the off state, so that the first control signal P_control changes from a low level to a high level. Recombination Figure 1 When the first control signal P_control becomes a high level, the P2 tube is turned on, and the NGATE voltage is quickly pulled to the power supply voltage VDD, which speeds up the rising speed of the NGATE voltage and reduces the switching loss.

[0066] When the voltage at the switch node SW starts to rise from 0V (indicating that the NMOS power tube in the switch power supply 40 starts to disconnect), and the voltage at the switch node SW is less than or equal to the second threshold voltage VDD-VTHp (VTHp is the conduction threshold voltage of the PMOS tube), the second field effect tube M2 is turned on and provides a first signal (the first signal is a high level) to the first Schmitt trigger smit1; the first Schmitt trigger smit1 outputs a first level signal according to the first signal (the first level signal is a high level, that is, the second control signal N_control is a high level). The third field effect tube M3 is turned on, so that the second resistor R2 is connected to the ground; the second resistor R2 provides a second signal (the second signal is a low level) to the second Schmitt trigger smit2; the second Schmitt trigger smit2 outputs a second level signal according to the second signal (the second level signal is a low level, that is, the first control signal P_control is a low level). When the voltage at the switch node SW is greater than the second threshold voltage VDD-VTHp, the third field effect transistor M3 remains in the on state; the second field effect transistor M2 is turned off; since the third field effect transistor M3 still remains in the on state, the first resistor R1 provides the fourth signal (the fourth signal is a low level) to the first Schmitt trigger smit1; the first Schmitt trigger smit1 outputs a fourth level signal according to the fourth signal (the fourth level signal is a low level, that is, the second control signal N_control becomes a low level). That is, when the voltage at the switch node SW is in the rising process, the third field effect transistor M3 is always in the on state, that is, the first control signal P_control is always kept at a low level. The second field effect transistor M2 changes from the on state to the off state, causing the second control signal N_control to change from a high level to a low level. Combined with Figure 1 When the second control signal N_control becomes a low level, the N2 tube is turned on and the NGATE voltage is quickly pulled to VSS, which speeds up the drop of the NGATE voltage and reduces the switching loss.

[0067] The embodiment of the present application also provides a switching power supply device, including the voltage detection circuit described above. Since the switching power supply device provided in the embodiment of the present application adopts all the technical solutions of all the above embodiments, it at least has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described one by one here.

[0068] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0069] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A voltage detection circuit, characterized in that: It includes a switch module and a voltage detection module, wherein the switch module is respectively connected to the voltage detection module, the power module and the segmented drive circuit in the switch power supply, the voltage detection module is respectively used to connect to the switch node in the switch power supply and the segmented drive circuit, and the voltage detection module is also used to ground; When the switching power supply operates in the intermittent conduction mode, the switch module is disconnected according to the driving signal in the segmented driving circuit, so that the voltage detection module is disconnected from the power supply module; When the voltage at the switch node changes, the switch module is turned on according to the drive signal, so that the voltage detection module is connected to the power supply module; the voltage detection module outputs a first control signal and a second control signal to the segment drive circuit according to the voltage at the switch node; The voltage detection module includes a first switch unit, a second switch unit, a resistance unit, a first logic unit and a second logic unit, the resistance unit is respectively connected to the first switch unit, the second switch unit, the first logic unit and the second logic unit, the first switch unit is respectively connected to the switch module, the second switch unit and the switch node, the first logic unit and the second logic unit are respectively used to connect to the segmented drive circuit, and the second switch unit is also used to connect to the ground; the first control signal includes a first level signal and a fourth level signal, and the second control signal includes a second level signal and a third level signal; When the switching power supply operates in the intermittent conduction mode, the switch module is disconnected according to the driving signal, so that the first switch unit is disconnected from the power supply module; When the voltage at the switch node changes, the switch module is turned on according to the drive signal, so that the first switch unit is connected to the power module.

2. The voltage detection circuit according to claim 1, characterized in that: The switch module includes a first field effect transistor, a gate of the first field effect transistor is used to connect to the segmented driving circuit, a source of the first field effect transistor is used to connect to the power module, and a drain of the first field effect transistor is connected to the voltage detection module.

3. The voltage detection circuit according to claim 1, characterized in that: When the voltage at the switch node starts to drop from the power supply voltage and the voltage at the switch node is greater than or equal to the first threshold voltage, the first switch unit is turned on and provides a first signal to the first logic unit; the first logic unit outputs a first level signal according to the first signal; the second switch unit is turned on, so that the resistance unit is connected to the ground; the resistance unit provides a second signal to the second logic unit; The second logic unit outputs a second level signal according to the second signal; when the voltage at the switch node is less than the first threshold voltage, the first switch unit maintains an on state; the second switch unit is disconnected, so that the resistance unit is disconnected from the ground; the resistance unit provides a third signal to the second logic unit; the second logic unit outputs a third level signal according to the third signal.

4. The voltage detection circuit according to claim 1, characterized in that: When the voltage at the switch node starts to rise from 0V and the voltage at the switch node is less than or equal to a second threshold voltage, the first switch unit is turned on and provides a first signal to the first logic unit; the first logic unit outputs a first level signal according to the first signal; the second switch unit is turned on, so that the resistance unit is connected to the ground; the resistance unit provides a second signal to the second logic unit; The second logic unit outputs a second level signal according to the second signal; when the voltage at the switch node is greater than the second threshold voltage, the second switch unit maintains a conducting state; and the first switch unit is disconnected; The resistance unit provides a fourth signal to the first logic unit; and the first logic unit outputs a fourth level signal according to the fourth signal.

5. The voltage detection circuit according to claim 1, characterized in that: The first switch unit includes a second field effect transistor, a gate of the second field effect transistor is used to connect to the switch node, a source of the second field effect transistor is connected to the switch module, and a drain of the second field effect transistor is respectively connected to the first logic unit and the resistance unit.

6. The voltage detection circuit according to claim 1, characterized in that: The second switch unit includes a third field effect transistor, a gate of the third field effect transistor is used to be connected to the switch node, a drain of the third field effect transistor is respectively connected to the resistance unit and the second logic unit, and a source of the third field effect transistor is used to be grounded.

7. The voltage detection circuit according to claim 1, characterized in that: The resistance unit includes a first resistor and a second resistor, the first end of the first resistor is connected to the first switch unit and the first logic unit respectively, the second end of the first resistor is connected to the first end of the second resistor, and the second end of the second resistor is connected to the second switch unit and the second logic unit respectively.

8. A switching power supply device, characterized in that: The invention comprises the voltage detection circuit as described in any one of claims 1 to 7.

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