A diode current bypass control circuit and control method thereof

Abstract

The present invention provides a diode current bypass control circuit and a control method thereof, wherein the control circuit comprises: a main module, a diode current sensing module and a driving module, wherein the main module comprises a main switch tube and a main diode, wherein the main diode is connected in parallel to the source and drain ends of the main switch tube; the diode current sensing module is connected to the two ends of the main diode, and is used to sense the current flowing through the main diode; the driving module is connected to the output end of the diode current sensing module and the gate end of the main switch tube, and is used to generate a driving current proportional to the sensing current to drive the main switch tube to conduct; wherein the main module, the diode current sensing module and the driving module constitute a negative feedback loop, and realize the reduction of the current of the main diode to a set current value. The present invention solves the heating problem caused by a large current flowing through a body diode or a freewheeling diode during the main switch tube off period in the prior art, and the circuit out of control problem caused by a large current introduced into the substrate.

Description

Technical Field

[0001] The present invention relates to the field of integrated circuits, and in particular to a diode current bypass control circuit and a control method thereof. Background Art

[0002] As society pays more and more attention to high efficiency and environmental protection, power devices that continuously improve efficiency, such as power MOSFET, IGBT, SiC, and GaN, are constantly developing. How to increase efficiency and reduce heat has become a goal that engineers strive for.

[0003] When power MOSFET, IGBT, SiC, GaN, etc. are used in power supplies or as main switch tubes, large currents widely flow through the body diode or freewheeling diode during the off cycle of these main switches; for example, when power MOSFET is used in a switching power supply, large currents flow through the body diode of the power MOSFET during the switching period; in portable device batteries, during the overvoltage protection and undervoltage protection of the MOSFET used for protection, large current discharge and charging currents will all flow through the body diode of the MOSFET isolation device; in high-efficiency and energy-saving DC motor drive applications, power switch tubes such as IGBT / SiC / GaN will have additional freewheeling diodes, so that when the upper and lower bridge driving main switch tubes are turned off, a current of tens or hundreds of amperes can flow through the freewheeling diode to drive the motor to work normally.

[0004] Since large currents flowing through body diodes or freewheeling diodes often cause heat, or even cause logic confusion due to excessive substrate current, making the circuit unable to work properly, how to reduce this negative effect has long been a direction that engineers have been constantly exploring. Summary of the invention

[0005] In view of the shortcomings of the prior art described above, the object of the present invention is to provide a diode current bypass control circuit and a control method thereof, which are used to solve the heating problem caused by large current flowing through the body diode or the freewheeling diode during the off period of the main switch tube in the prior art and the circuit out of control problem caused by the introduction of large current into the substrate.

[0006] To achieve the above-mentioned purpose and other related purposes, the present invention provides a diode current bypass control circuit, the control circuit comprising: a main module, a diode current sensing module and a driving module,

[0007] The main module includes a main switch tube and a main diode, and the main diode is connected in parallel to the source and drain ends of the main switch tube;

[0008] The diode current sensing module is connected to both ends of the main diode and is used to sense the current flowing through the main diode;

[0009] The driving module is connected to the output end of the diode current sensing module and the gate end of the main switch tube, and is used to generate a driving current proportional to the sensing current to drive the main switch tube to conduct;

[0010] The main module, the diode current sensing module and the driving module form a negative feedback loop to reduce the current of the main diode to a set current value.

[0011] Optionally, the diode current sensing module includes a sensing diode, which senses the current flowing through the main diode through the sensing diode by making the voltage across the sensing diode positively correlated or equal to the voltage across the main diode.

[0012] Optionally, the diode current sensing module includes: an error amplifier, a source follower tube and a sensing diode, the non-inverting input terminal of the error amplifier is connected to the anode terminal of the main diode, the inverting input terminal of the error amplifier is connected to the source terminal of the source follower tube and the anode terminal of the sensing diode, the output terminal of the error amplifier is connected to the gate terminal of the source follower tube, the drain terminal of the source follower tube serves as the output terminal of the diode current sensing module, and the cathode terminal of the sensing diode is connected to the cathode terminal of the main diode.

[0013] Optionally, the diode current sensing module includes: a bias current source, a first common-gate tube, a second common-gate tube, a sensing switch tube and a sensing diode, the input end of the bias current source is connected to the power supply voltage, the output end of the bias current source is connected to the drain end of the first common-gate tube, the source end of the first common-gate tube is connected to the anode end of the main diode, the gate end of the first common-gate tube is connected to the drain end of the first common-gate tube and the gate end of the second common-gate tube, the drain end of the second common-gate tube serves as the output end of the diode current sensing module, the source end of the second common-gate tube is connected to the source end of the sensing switch tube and the anode end of the sensing diode, the gate end of the sensing switch tube is connected to the source end of the sensing switch tube, and the drain end of the sensing switch tube is connected to the cathode end of the sensing diode and the cathode end of the main diode.

[0014] Optionally, the diode current sensing module further includes: a first resistor, wherein the first resistor is connected between the source end of the first common-gate tube and the anode end of the main diode.

[0015] Optionally, the diode current sensing module further includes: a first resistor and a second resistor, the first resistor being connected between the source end of the first common-gate tube and the anode end of the main diode, and the second resistor being connected between the source end of the second common-gate tube and the anode end of the sensing diode.

[0016] Optionally, the driving module includes: a first current mirror tube, a second current mirror tube and a driving resistor, the source end of the first current mirror tube is connected to the source end of the second current mirror tube and connected to the power supply voltage, the drain end of the first current mirror tube is connected to the output end of the diode current sensing module, the gate end of the first current mirror tube is connected to the drain end of the first current mirror tube and the gate end of the second current mirror tube, the drain end of the second current mirror tube is connected to one end of the driving resistor and serves as the output end of the driving module, and the other end of the driving resistor is connected to the switch control signal of the main switch tube.

[0017] Optionally, the driving module includes: a first current mirror tube, a second current mirror tube, a sampling resistor, an NMOS driving tube and a PMOS driving tube, the source end of the first current mirror tube is connected to the source end of the second current mirror tube and connected to the power supply voltage, the drain end of the first current mirror tube is connected to the output end of the diode current sensing module, the gate end of the first current mirror tube is connected to the drain end of the first current mirror tube and the gate end of the second current mirror tube, the drain end of the second current mirror tube is connected to one end of the sampling resistor, the gate end of the NMOS driving tube and the gate end of the PMOS driving tube, the other end of the sampling resistor is connected to the source end of the main switch tube, the drain end of the NMOS driving tube is connected to the power supply voltage, the source end of the NMOS driving tube is connected to the source end of the PMOS driving tube, and at the same time as the output end of the driving module is connected to the gate end of the main switch tube, the drain end of the PMOS driving tube is connected to the source end of the main switch tube; wherein the threshold voltage of the PMOS driving tube is less than the threshold voltage of the main switch tube.

[0018] Optionally, the driving module further includes: a PMOS switch tube, whose source terminal is connected to the power supply voltage, whose drain terminal is connected to the gate terminal of the NMOS driving tube, and whose gate terminal is connected to the switch control signal of the PMOS switch tube.

[0019] Optionally, the driving module includes: a first current mirror tube, a second current mirror tube, a sampling resistor, a first transistor and a second transistor, the source end of the first current mirror tube is connected to the source end of the second current mirror tube and connected to the power supply voltage, the drain end of the first current mirror tube is connected to the output end of the diode current sensing module, the gate end of the first current mirror tube is connected to the drain end of the first current mirror tube and the gate end of the second current mirror tube, the drain end of the second current mirror tube is connected to one end of the sampling resistor, the base of the first transistor and the base of the second transistor, the other end of the sampling resistor is connected to the source end of the main switch tube, the collector of the first transistor is connected to the power supply voltage, the emitter of the first transistor is connected to the emitter of the second transistor, and at the same time as the output end of the driving module is connected to the gate end of the main switch tube, and the collector of the second transistor is connected to the source end of the main switch tube; wherein the turn-on voltage of the second transistor is less than the threshold voltage of the main switch tube.

[0020] Optionally, the driving module further includes: a PMOS switch tube, a source end of which is connected to a power supply voltage, a drain end of which is connected to the base of the first transistor, and a gate end of which is connected to a switch control signal of the PMOS switch tube.

[0021] Optionally, the control circuit also includes: a current threshold module, connected between the diode current sensing module and the driving module, used to compare the sensing current and the set threshold current, and turn off the driving module when the sensing current is less than the set threshold current, and turn on the driving module when the sensing current is greater than the set threshold current.

[0022] Optionally, the current threshold module includes: a threshold current source, an input end of the threshold current source is connected to a power supply voltage, and an output end of the threshold current source is connected to an output end of the diode current sensing module and an input end of the driving module.

[0023] The present invention also provides a diode current bypass control method for bypassing a main diode connected in parallel to the source and drain ends of a main switch tube in a main module. The control method includes:

[0024] sensing a current flowing through the main diode based on a diode current sensing module;

[0025] The driving module generates a driving current proportional to the induced current to drive the main switch tube to conduct;

[0026] The main module, the diode current sensing module and the driving module form a negative feedback loop to reduce the current of the main diode to a set current value.

[0027] Optionally, the method for sensing the current flowing through the main diode based on the diode current sensing module includes: sensing the current flowing through the main diode by making the voltage across the sensing diode in the diode current sensing module positively correlated or equal to the voltage across the main diode.

[0028] Optionally, after the diode current sensing module senses the current flowing through the main diode, the control method further includes: comparing the sensed current with a set threshold current, and turning off the drive module when the sensed current is less than the set threshold current, and turning on the drive module when the sensed current is greater than the set threshold current.

[0029] As described above, a diode current bypass control circuit and control method of the present invention utilizes a negative feedback loop constructed by a main module, a diode current sensing module and a driving module to control the opening of a main switch tube to bypass and adjust the main diode current, thereby reducing the main diode current to a set current value, thereby controlling the main diode current within a limited range. The present invention has a negative feedback property, and an opening threshold (i.e., a set threshold current) can also be added to automatically open or close the circuit. At the same time, the circuit structure of the present invention is simple and easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It shows the implementation method of the diode current bypass control circuit described in the first embodiment of the present invention.

[0031] Figure 2 It shows another implementation of the diode current sensing module in the diode current bypass control circuit of the present invention.

[0032] Figure 3 It shows another implementation of the driving module in the diode current bypass control circuit of the present invention.

[0033] Figure 4 It shows another implementation of the driving module in the diode current bypass control circuit of the present invention.

[0034] Figure 5 It shows another implementation of the driving module in the diode current bypass control circuit of the present invention.

[0035] Figure 6 It shows another implementation of the driving module in the diode current bypass control circuit of the present invention.

[0036] Figure 7 It shows the implementation method of the diode current bypass control circuit described in the second embodiment of the present invention.

[0037] Component number description

[0038] 101 Main Module

[0039] 102 Diode Current Sensing Module

[0040] 103 Driver Module

[0041] 104 Comparison detection module DETAILED DESCRIPTION

[0042] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0043] See also Figures 1 to 7 It should be noted that the illustrations provided in this embodiment are only schematic illustrations of the basic concept of the present invention. Although the illustrations only show components related to the present invention and are not drawn according to the number, shape and size of components in actual implementation, the form, quantity and proportion of each component in actual implementation may be changed arbitrarily, and the component layout may also be more complicated.

[0044] Embodiment 1

[0045] like Figure 1 As shown, this embodiment provides a diode current bypass control circuit, the control circuit comprising: a main module 101, a diode current sensing module 102 and a driving module 103,

[0046] The main module 101 includes a main switch tube Mmain and a main diode Dmain, wherein the main diode Dmain is connected in parallel to the source and drain ends of the main switch tube Mmain;

[0047] The diode current sensing module 102 is connected to both ends of the main diode Dmain, and is used to sense the current flowing through the main diode Dmain;

[0048] The driving module 103 is connected to the output end of the diode current sensing module 102 and the gate end of the main switch tube Mmain, and is used to generate a driving current proportional to the sensing current to drive the main switch tube Mmain to turn on;

[0049] The main module 101 , the diode current sensing module 102 and the driving module 103 form a negative feedback loop to reduce the current of the main diode Dmain to a set current value.

[0050] As an example, the main switch tube Mmain includes: one of: a power MOSFET, an IGBT, a SiC tube or a GaN tube, and the main diode Dmain is a body diode or a freewheeling diode of the main switch tube Mmain; of course, whether the main diode Dmain is a body diode or a freewheeling diode depends on the actual application.

[0051] As an example, the diode current sensing module 102 includes a sensing diode Dsns, which senses the current flowing through the main diode Dmain through the sensing diode Dsns by making the voltage across the sensing diode Dsns positively correlated or equal to the voltage across the main diode Dmain.

[0052] Specifically, Figure 1 As shown, in one example, the diode current sensing module 102 includes: an error amplifier ERROR AMP, a source follower tube Md0 and a sensing diode Dsns, the non-inverting input terminal of the error amplifier ERROR AMP is connected to the anode terminal of the main diode Dmain, the inverting input terminal of the error amplifier ERROR AMP is connected to the source terminal of the source follower tube Md0 and the anode terminal of the sensing diode Dsns, the output terminal of the error amplifier ERROR AMP is connected to the gate terminal of the source follower tube Md0, the drain terminal of the source follower tube Md0 serves as the output terminal of the diode current sensing module 102, and the cathode terminal of the sensing diode Dsns is connected to the cathode terminal of the main diode Dmain. The sensing diode Dsns and the main diode Dmain are the same type of diodes, and the two are different only in junction area, and the ratio of the junction area of ​​the sensing diode Dsns to the junction area of ​​the main diode Dmain is 1 / N, and N is a positive number.

[0053] In this example, the error amplifier ERROR AMP and the source follower tube Md0 form a negative feedback circuit to make the anode terminal voltage of the sensing diode Dsns equal to the source terminal voltage of the main switch tube Mmain, that is, the anode terminal voltage of the sensing diode Dsns is equal to the anode terminal voltage of the main diode Dmain, and because the cathode terminal of the sensing diode Dsns is connected to the cathode terminal of the main diode Dmain, the cathode terminal voltage of the sensing diode Dsns is also equal to the cathode terminal voltage of the main diode Dmain, so that the voltage across the sensing diode Dsns is equal to the voltage across the main diode Dmain; at this time, the current ID_main flowing through the main diode Dmain and the current ID_sns flowing through the sensing diode Dsns satisfy the following formula: ID_sns:ID_main=1:N, thereby realizing accurate sensing of the current flowing through the main diode Dmain through the sensing diode Dsns.

[0054] Specifically, Figure 2 As shown, in another example, the diode current sensing module 102 includes: a bias current source Ibias, a first common-gate transistor MN0, a second common-gate transistor MN1, a sensing switch transistor Msns and a sensing diode Dsns, the input end of the bias current source Ibias is connected to the power supply voltage VDD, the output end of the bias current source Ibias is connected to the drain end of the first common-gate transistor MN0, the source end of the first common-gate transistor MN0 is connected to the anode end of the main diode Dmain, and the gate end of the first common-gate transistor MN0 is connected to the gate end of the first common-gate transistor MN0. The drain end of the first common-gate transistor MN0 and the gate end of the second common-gate transistor MN1, the drain end of the second common-gate transistor MN1 is used as the output end of the diode current sensing module 102, the source end of the second common-gate transistor MN1 is connected to the source end of the sensing switch transistor Msns and the anode end of the sensing diode Dsns, the gate end of the sensing switch transistor Msns is connected to the source end of the sensing switch transistor Msns, and the drain end of the sensing switch transistor Msns is connected to the cathode end of the sensing diode Dsns and the cathode end of the main diode Dmain. The sensing switch transistor Msns and the main switch transistor Mmain are the same type of switch transistors, and the two are different only in size. The size ratio of the sensing switch transistor Msns to the main switch transistor Mmain is 1 / N, and N is a positive number.

[0055] In this example, the first common-gate transistor MN0 and the second common-gate transistor MN1 form a common-gate circuit, the source terminal voltage of the first common-gate transistor MN0 is regarded as a reference voltage, and the source terminal voltage of the second common-gate transistor MN1 is regarded as an adjustment voltage. The source terminal of the first common-gate transistor MN0 generates a voltage due to the current flowing through the main diode Dmain, and the sum of this voltage and the gate-source voltage of the first common-gate transistor MN0 is used as the gate voltage of the second common-gate transistor MN1. The second common-gate transistor MN1 will generate a current flowing through the sensing diode Dsns under the bias of its gate voltage. As the current flowing through the sensing diode Dsns increases, the source terminal voltage of the second common-gate transistor MN1 will increase to be equal to the source terminal voltage of the first common-gate transistor MN0, so that the source terminal adjustment voltage of the second common-gate transistor MN1 is adjusted according to the source terminal reference voltage of the first common-gate transistor MN0, and the adjustment voltage is equal to the reference voltage. Thereby, the source terminal voltage of the second common-gate transistor MN1 is always equal to the source terminal voltage of the first common-gate transistor MN0, that is, the anode terminal voltage of the sensing diode Dsns is equal to the anode terminal voltage of the main diode Dmain. At the same time, since the cathode terminal of the sensing diode Dsns is connected to the cathode terminal of the main diode Dmain, the cathode terminal voltage of the sensing diode Dsns is also equal to the cathode terminal voltage of the main diode Dmain, so that the voltage across the sensing diode Dsns is equal to the voltage across the main diode Dmain. At this time, the current ID_main flowing through the main diode Dmain and the current ID_sns flowing through the sensing diode Dsns satisfy the following formula: ID_sns:ID_main=1:N, thereby realizing accurate sensing of the current flowing through the main diode Dmain through the sensing diode Dsns.

[0056] Specifically, Figure 2 As shown, in another example, the diode current sensing module 102 further includes: a first resistor R0, the first resistor R0 is connected between the source end of the first common-gate transistor MN0 and the anode end Dmain of the main diode, and is used to introduce a corresponding DC component to fine-tune the voltage relationship between the main diode Dmain and the sensing diode Dsns. Of course, the diode current sensing module 102 can also add a second resistor R1 on the basis of the first resistor R0, and at this time, the second resistor R1 is connected between the source end of the second common-gate transistor MN1 and the anode end of the sensing diode Dsns.

[0057] As an example, Figure 1 and 2As shown, the driving module 103 includes: a first current mirror tube MP0, a second current mirror tube MP1 and a driving resistor Rg, the source end of the first current mirror tube MP0 is connected to the source end of the second current mirror tube MP1 and connected to the power supply voltage VDD, the drain end of the first current mirror tube MP0 is connected to the output end of the diode current sensing module 102, the gate end of the first current mirror tube MP0 is connected to the drain end of the first current mirror tube MP0 and the gate end of the second current mirror tube MP1, the drain end of the second current mirror tube MP1 is connected to one end of the driving resistor Rg, and serves as the output end of the driving module 103, and the other end of the driving resistor Rg is connected to the switch control signal Crl_main of the main switch tube. It should be noted that the switch control signal Crl_main of the main switch tube is a control signal generated by an external circuit, which is used to control the conduction or shutdown of the main switch tube Mmain, so as to control whether the main switch tube Mmain is in a conduction cycle or a shutdown cycle.

[0058] In this example, the first current mirror tube MP0 and the second current mirror tube MP1 form a current mirror, which is used to generate a driving current Idrv proportional to the induced current ID_sns (the induced current ID_sns and the driving current Idrv satisfy the following formula: Idrv=M*ID_sns, M is the amplification factor of the current mirror), and the main switch tube Mmain is driven to turn on by applying the driving current Idrv to the driving resistor Rg to generate a corresponding driving voltage, thereby realizing the conduction of the main switch tube Mmain during the shutdown period.

[0059] As another example, Figure 3As shown, the driving module 103 includes: a first current mirror tube MP0, a second current mirror tube MP1, a sampling resistor Rg, an NMOS driving tube MNdrv and a PMOS driving tube MPdrv, the source end of the first current mirror tube MP0 is connected to the source end of the second current mirror tube MP1 and connected to the power supply voltage VDD, the drain end of the first current mirror tube MP0 is connected to the output end of the diode current sensing module 102, the gate end of the first current mirror tube MP0 is connected to the drain end of the first current mirror tube MP0 and the gate end of the second current mirror tube MP1, the drain end of the second current mirror tube MP1 is connected to one end of the sampling resistor Rg, the NMOS driving tube MNdrv and the gate end of the second current mirror tube MP1. The gate end of the S driving tube MNdrv and the gate end of the PMOS driving tube MPdrv, the other end of the sampling resistor Rg is connected to the source end of the main switch tube Mmain, the drain end of the NMOS driving tube MNdrv is connected to the power supply voltage VDD, the source end of the NMOS driving tube MNdrv is connected to the source end of the PMOS driving tube MPdrv, and at the same time, as the output end of the driving module 103, it is connected to the gate end of the main switch tube Mmain, and the drain end of the PMOS driving tube MPdrv is connected to the source end of the main switch tube Mmain; wherein the threshold voltage of the PMOS driving tube MPdrv is less than the threshold voltage of the main switch tube Mmain.

[0060] In this example, the first current mirror tube MP0 and the second current mirror tube MP1 form a current mirror, which is used to generate a driving current Idrv proportional to the induced current ID_sns (the induced current ID_sns and the driving current Idrv satisfy the following formula: Idrv=M*ID_sns, M is the amplification factor of the current mirror). The driving current Idrv generates a corresponding driving voltage after passing through the sampling resistor Rg to drive the NMOS driving tube MNdrv and the PMOS driving tube MPdrv to turn on, thereby controlling the main switch tube Mmain to turn on, thereby realizing the turning on of the main switch tube Mmain during the shutdown period. Since the threshold voltage of the PMOS driving tube MPdrv is lower than the threshold voltage of the main switch tube Mmain, the driving module 103 in this example has its own current shutdown threshold, wherein the shutdown current threshold is the ratio of the difference between the threshold voltage of the main switch tube Mmain and the threshold voltage of the PMOS driving tube MPdrv to the sampling resistor Rg, that is, (Vth_main-Vth_MPdrv) / Rg.

[0061] As another example, Figure 4 As shown, compared with the previous example (i.e. Figure 3In the example, the driving module 103 in this example further includes: a PMOS switch tube MP, whose source end is connected to the power supply voltage VDD, whose drain end is connected to the gate end of the NMOS driving tube MNdrv, and whose gate end is connected to the switch control signal Ctl_MP of the PMOS switch tube. It should be noted that the switch control signal Ctl_MP of the PMOS switch tube is an external control signal, which is used to control whether the NMOS driving tube MNdrv and the PMOS driving tube MPdrv are turned on, so as to realize the external control of the driving module 103.

[0062] As another example, Figure 5 As shown, the driving module 103 includes: a first current mirror tube MP0, a second current mirror tube MP1, a sampling resistor Rg, a first transistor NPN and a second transistor PNP, the source end of the first current mirror tube MP0 is connected to the source end of the second current mirror tube MP1 and connected to the power supply voltage VDD, the drain end of the first current mirror tube MP0 is connected to the output end of the diode current sensing module 102, the gate end of the first current mirror tube MP0 is connected to the drain end of the first current mirror tube MP0 and the gate end of the second current mirror tube MP1, and the drain end of the second current mirror tube MP1 is connected to the sampling resistor Rg. g, the base of the first transistor NPN and the base of the second transistor PNP, the other end of the sampling resistor Rg is connected to the source end of the main switch tube, the collector of the first transistor NPN is connected to the power supply voltage VDD, the emitter of the first transistor NPN is connected to the emitter of the second transistor PNP, and at the same time, as the output end of the driving module 103, it is connected to the gate end of the main switch tube Mmain, and the collector of the second transistor PNP is connected to the source end of the main switch tube Mmain; wherein, the turn-on voltage of the second transistor PNP is less than the threshold voltage of the main switch tube Mmain.

[0063] In this example, the first current mirror tube MP0 and the second current mirror tube MP1 form a current mirror, which is used to generate a driving current Idrv proportional to the induced current ID_sns (the induced current ID_sns and the driving current Idrv satisfy the following formula: Idrv=M*ID_sns, M is the magnification of the current mirror), and the driving current Idrv generates a corresponding driving voltage after passing through the sampling resistor Rg to drive the first transistor NPN and the second transistor PNP to turn on, thereby controlling the main switch tube Mmain to turn on, thereby realizing the turning on of the main switch tube Mmain in the off period. Since the on-voltage of the second transistor PNP is less than the threshold voltage of the main switch tube Mmain, the driving module 103 in this example has a turn-off current threshold, wherein the turn-off current threshold is the ratio of the difference between the threshold voltage of the main switch tube Mmain and the base-emitter voltage of the second transistor PNP to the sampling resistor Rg, that is, (Vth_main-Vbe_PNP) / Rg.

[0064] As another example, Figure 6 As shown, compared with the previous example (i.e. Figure 5 In the example, the driving module 103 in this example further includes: a PMOS switch tube MP, whose source end is connected to the power supply voltage VDD, whose drain end is connected to the base of the first transistor NPN, and whose gate end is connected to the switch control signal Ctl_MP of the PMOS switch tube. It should be noted that the switch control signal Ctl_MP of the PMOS switch tube is an external control signal, which is used to control whether the first transistor NPN and the second transistor PNP are turned on, so as to realize the external control of the driving module 103.

[0065] Accordingly, this embodiment further provides a diode current bypass control method for bypassing a main diode Dmain connected in parallel to the source and drain ends of the main switch tube Mmain in the main module 101. The control method includes:

[0066] Based on the diode current sensing module 102 sensing the current flowing through the main diode Dmain;

[0067] The driving module 103 generates a driving current proportional to the induced current to drive the main switch tube Mmain to turn on;

[0068] The main module 101 , the diode current sensing module 102 and the driving module 103 form a negative feedback loop to reduce the current of the main diode Dmain to a set current value.

[0069] As an example, a method for sensing the current flowing through the main diode Dmain based on the diode current sensing module 102 includes: sensing the current flowing through the main diode Dmain by making the voltage across the sensing diode Dsns in the diode current sensing module 102 positively correlated or equal to the voltage across the main diode Dmain.

[0070] See below Figure 1 The working principle of the diode current bypass control circuit described in this embodiment is described in detail, wherein the main switch tube Mmain is in an off period under the action of the main switch tube switch control signal Ctl_main generated by the external circuit.

[0071] like Figure 1As shown, during the off period of the main switch tube, the diode current sensing module 102 senses and detects the forward current of the main diode Dmain, and the driving module 103 amplifies the sensed current by M times and forms a gate voltage at the gate end of the main switch tube Mmain through the driving resistor Rg, thereby driving the main switch tube Mmain to restart the conduction current during the off period; at this time, the current flowing through the main switch tube Mmain increases from zero at the time of shutdown to ID_Mmain. Since the total current flowing through the system is a fixed value at this working moment, the total current flowing through the main switch tube Mmain is a fixed value. When the flowing current increases to ID_Mmain, the current flowing through the main diode Dmain will decrease by ID_Mmain; at this time, the induced current of the diode current sensing module 102 is proportionally reduced, and the driving module 103 amplifies the reduced induced current by M times and forms a gate voltage at the gate end of the main switch tube Mmain through the driving resistor Rg. The smaller gate voltage will reduce the current ID_Mmain flowing through the main switch tube Mmain, and under the premise that the total system current is a fixed value, the current flowing through the main diode Dmain will increase, thereby forming a negative feedback loop. The negative feedback loop will put the entire loop in a steady state, so that the forward current flowing through the main diode Dmain is reduced to the current setting value; when the forward current flowing through the main diode Dmain is greater than the negative feedback loop start-up current threshold (i.e., Vth_main / Rg / M*N), the gate terminal voltage of the main switch tube Mmain will be greater than its own threshold voltage, and the main switch tube Mmain will be turned on, so that it can be reopened during the shutdown cycle, and the main switch tube Mmain will flow through the current ID_Mmain, thereby reducing the forward current flowing through the main diode Dmain to the current setting value; and when the forward current flowing through the main diode Dmain is less than the negative feedback loop start-up current threshold (i.e., Vth_main / Rg / M*N), the gate terminal voltage of the main switch tube Mmain will be less than its own threshold voltage, and the main switch tube Mmain will be turned off, so that it can automatically restore to the shutdown state during the shutdown cycle.

[0072] The main module 101, the diode current sensing module 102 and the driving module 103 are also constructed into an adaptive acceleration response circuit, which has the characteristic that the larger the current initially flowing through the main diode Dmain, the faster the negative feedback loop responds, thereby bypassing and reducing the current of the main diode Dmain to the set current value in a shorter time.

[0073] The above negative feedback loop reduces the forward current of the main diode Dmain to the current setting value, which is calculated as follows:

[0074] In the design, usually when the steady state is reached after the negative feedback loop is turned on, the conduction current ID_Mmain of the main switch tube Mmain that is selected to be reopened during the shutdown period is much larger than the current flowing through the main diode Dmain at this time, that is, the operating current flowing through the system at this time is Isys, which almost all flows through the main switch tube Mmain, and a very small part flows through the main diode Dmain. In the calculation, this very small part of the current flowing through the main diode can be ignored. Taking the MOSFET power tube as the main switch tube Mmain as an example, when the Isys current is small, the source-drain voltage difference of the MOSFET power tube is greater than the overdrive voltage (Vgs-Vth), and the MOSFET works in the saturation region. According to relevant basic knowledge, at this time:

[0075] Isys=1 / 2*μ n *Cox*W / L*(Vgs-Vth) 2

[0076] Vgs=Sqrt(2*Isys / (μ n *Cox*W / L))+Vth

[0077] When the negative feedback reaches a steady state, the main diode Dmain current setting value ID_set is:

[0078] ID_set=Vgs / Rg / M*N (1)

[0079] That is: ID_set=(Sqrt(2*Isys / (μ n *Cox*W / L))+Vth) / Rg / M*N

[0080] According to relevant basic knowledge, the forward voltage drop VD_main of the main diode Dmain is:

[0081] VD_main=VT*ln(ID_set / Is)

[0082] That is, VD_main=VT*ln((Sqrt(2*Isys / (μ n *Cox*W / L))+Vth) / Rg / M*N / Is)

[0083] Here is a design example to make it easier to understand. Figure 2As shown, the area ratio of the main diode Dmain and the sensing diode Dsns is selected to be 1E5 times (i.e., one hundred thousand times), the current amplification factor of the driving module 103 is 20 times, and the resistance value of the driving resistor is 50K ohms. At this time, if the system current is 10A. Without the present invention, this 10A current will flow through the main diode Dmain in the off cycle, causing the main diode Dmain to heat up, and the large current 10A flowing through the main diode Dmain will have a large forward voltage drop. Under the application of the present invention, the main switch tube Mmain is turned on again. The main switch tube Mmain usually has a very large width-to-length ratio. If the gate drive voltage is 3V at this time, according to the above formula (1), the current flowing through the main diode Dmain when the negative feedback loop is stable is: ID_set = Vgs / Rg / M*N = 3 / 50K / 20*1E5 = 300mA.

[0084] It can be seen that before the present invention is applied, a current of 10A flows through the main diode Dmain, causing it to heat up; when the present invention is applied, only a current of 300mA flows through the main diode Dmain when the negative feedback loop reaches a steady state, and the effect of reducing the current of the main diode Dmain is very obvious. Moreover, because the current of the main diode Dmain changes from 10A to 300mA, it is conservatively estimated that the voltage drop of the main diode Dmain will be reduced from 0.7V or more at 10A current to about 0.3V at 300mA current, and the voltage difference between the source and drain of the main switch tube Mmain connected in parallel at both ends of the main diode Dmain is also about 0.3V, that is, the system power consumption is sharply reduced from the 7W power consumption generated by the 0.7V forward voltage drop of the main diode Dmain 10A to the 3W power consumption generated by the 0.3V voltage drop of the main switch tube Mmain flowing through 10A, thereby greatly improving the system efficiency and reducing the heat during the shutdown period of the main switch tube Mmain.

[0085] It can be seen from the above examples that, during the shutdown period of the main switch tube Mmain, if a forward current flows through the main diode Dmain and exceeds a certain current threshold, the present invention will restart the main switch tube Mmain to conduct, and most of the current will be bypassed by the main switch tube Mmain, leaving only a very small current to flow through the main diode Dmain; when the forward current of the main diode Dmain is less than the current threshold, the main switch tube Mmain will be automatically restored to be closed.

[0086] Embodiment 2

[0087] like Figure 7As shown, this embodiment provides a diode current bypass control circuit. Compared with the first embodiment, the control circuit of this embodiment further includes: a current threshold module 104, connected between the diode current sensing module 102 and the driving module 103, for comparing the sensing current ID_sns and the set threshold current Ith_adj, and turning off the driving module 103 when the sensing current ID_sns is less than the set threshold current Ith_adj, and turning on the driving module 103 when the sensing current ID_sns is greater than the set threshold current Ith_adj.

[0088] As an example, Figure 7 As shown, the current threshold module 104 includes: a threshold current source, the input end of the threshold current source is connected to the power supply voltage VDD, and the output end of the threshold current source is connected to the output end of the diode current sensing module 102 and the input end of the driving module 103.

[0089] In this example, when the sensed current ID_sns is less than the set threshold current Ith_adj provided by the threshold current source, the sensed current ID_sns is offset by the set threshold current Ith_adj. At this time, the gate voltage of the first mirror current tube MP0 is always high, that is, the first mirror current tube MP0 is in the off state, and the driving module 103 is in the off state; at this time, the bypass control circuit is in a dormant state, and the standby power consumption is very low. When the sensed current ID_sns is greater than the set threshold current Ith_adj provided by the threshold current source, there is a current (that is, the difference between the sensed current ID_sns and the set threshold current Ith_adj) flowing into the first mirror current tube MP0, and the driving module 103 is in the on state. It should be noted that when the diode current bypass control circuit includes a current threshold module 104, due to the existence of the set threshold current Ith_adj, the set current value corresponding to the circuit will be adjusted to (Vth_main / Rg / M+Ith_adj)*N.

[0090] Accordingly, this embodiment further provides a diode current bypass control method for bypassing a main diode Dmain connected in parallel to the source and drain ends of the main switch tube Mmain in the main module 101. The control method includes:

[0091] Based on the diode current sensing module 102 sensing the current flowing through the main diode Dmain;

[0092] Comparing the sensed current ID_sns with the set threshold current Ith_adj based on the current threshold module 104, and turning off the driving module 103 when the sensed current ID_sns is less than the set threshold current Ith_adj, and turning on the driving module 103 when the sensed current ID_sns is greater than the set threshold current Ith_adj;

[0093] When the driving module 103 is turned on, the driving module 103 generates a driving current Idrv proportional to the sensing current ID_sns to drive the main switch tube Mmain to turn on;

[0094] The main module 101 , the diode current sensing module 102 and the driving module 103 form a negative feedback loop to reduce the current of the main diode Dmain to a set current value.

[0095] In summary, a diode current bypass control circuit and control method of the present invention utilizes a negative feedback loop constructed by a main module, a diode current sensing module and a driving module to control the opening of a main switch tube to bypass and adjust the main diode current, thereby reducing the main diode current to a set current value, thereby controlling the main diode current within a limited range. The present invention has a negative feedback property, and a start threshold (i.e., a set threshold current) can also be added to automatically open or close the circuit. At the same time, the circuit structure of the present invention is simple and easy to implement. Therefore, the present invention effectively overcomes the various shortcomings of the prior art and has a high industrial utilization value.

[0096] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical ideas disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A diode current bypass control circuit, characterized in that: The control circuit includes: a main module, a diode current sensing module and a driving module. The main module includes a main switch tube and a main diode, and the main diode is connected in parallel to the source and drain ends of the main switch tube; The diode current sensing module is connected to both ends of the main diode and is used to sense the current flowing through the main diode; The driving module is connected to the output end of the diode current sensing module and the gate end of the main switch tube, and is used to generate a driving current proportional to the sensing current to drive the main switch tube to conduct; The main module, the diode current sensing module and the driving module form a negative feedback loop to reduce the current of the main diode to a set current value.

2. The diode current bypass control circuit according to claim 1, characterized in that: The diode current sensing module includes a sensing diode, which senses the current flowing through the main diode through the sensing diode by making the voltage across the sensing diode positively correlated or equal to the voltage across the main diode.

3. The diode current bypass control circuit according to claim 2, characterized in that: The diode current sensing module includes: an error amplifier, a source follower tube and a sensing diode. The non-inverting input terminal of the error amplifier is connected to the anode terminal of the main diode, the inverting input terminal of the error amplifier is connected to the source terminal of the source follower tube and the anode terminal of the sensing diode, the output terminal of the error amplifier is connected to the gate terminal of the source follower tube, the drain terminal of the source follower tube serves as the output terminal of the diode current sensing module, and the cathode terminal of the sensing diode is connected to the cathode terminal of the main diode.

4. The diode current bypass control circuit according to claim 2, characterized in that: The diode current sensing module includes: a bias current source, a first common-gate tube, a second common-gate tube, a sensing switch tube and a sensing diode. The input end of the bias current source is connected to the power supply voltage, the output end of the bias current source is connected to the drain end of the first common-gate tube, the source end of the first common-gate tube is connected to the anode end of the main diode, the gate end of the first common-gate tube is connected to the drain end of the first common-gate tube and the gate end of the second common-gate tube, the drain end of the second common-gate tube serves as the output end of the diode current sensing module, the source end of the second common-gate tube is connected to the source end of the sensing switch tube and the anode end of the sensing diode, the gate end of the sensing switch tube is connected to the source end of the sensing switch tube, and the drain end of the sensing switch tube is connected to the cathode end of the sensing diode and the cathode end of the main diode.

5. The diode current bypass control circuit according to claim 4, characterized in that: The diode current sensing module further includes: a first resistor connected between the source end of the first common-gate tube and the anode end of the main diode.

6. The diode current bypass control circuit according to claim 4, characterized in that: The diode current sensing module further includes: a first resistor and a second resistor, wherein the first resistor is connected between the source end of the first common-gate tube and the anode end of the main diode, and the second resistor is connected between the source end of the second common-gate tube and the anode end of the sensing diode.

7. The diode current bypass control circuit according to claim 1, characterized in that: The driving module includes: a first current mirror tube, a second current mirror tube and a driving resistor, wherein the source end of the first current mirror tube is connected to the source end of the second current mirror tube and connected to the power supply voltage, the drain end of the first current mirror tube is connected to the output end of the diode current sensing module, the gate end of the first current mirror tube is connected to the drain end of the first current mirror tube and the gate end of the second current mirror tube, the drain end of the second current mirror tube is connected to one end of the driving resistor and serves as the output end of the driving module, and the other end of the driving resistor is connected to the switch control signal of the main switch tube.

8. The diode current bypass control circuit according to claim 1, characterized in that: The driving module includes: a first current mirror tube, a second current mirror tube, a sampling resistor, an NMOS driving tube and a PMOS driving tube, wherein the source end of the first current mirror tube is connected to the source end of the second current mirror tube and connected to the power supply voltage, the drain end of the first current mirror tube is connected to the output end of the diode current sensing module, the gate end of the first current mirror tube is connected to the drain end of the first current mirror tube and the gate end of the second current mirror tube, the drain end of the second current mirror tube is connected to one end of the sampling resistor, the gate end of the NMOS driving tube and the gate end of the PMOS driving tube, the other end of the sampling resistor is connected to the source end of the main switch tube, the drain end of the NMOS driving tube is connected to the power supply voltage, the source end of the NMOS driving tube is connected to the source end of the PMOS driving tube, and is connected to the gate end of the main switch tube as the output end of the driving module, and the drain end of the PMOS driving tube is connected to the source end of the main switch tube; wherein the threshold voltage of the PMOS driving tube is less than the threshold voltage of the main switch tube.

9. The diode current bypass control circuit according to claim 8, characterized in that: The driving module also includes: The source end of the PMOS switch tube is connected to the power supply voltage, the drain end is connected to the gate end of the NMOS drive tube, and the gate end is connected to the switch control signal of the PMOS switch tube.

10. The diode current bypass control circuit according to claim 1, characterized in that: The driving module includes: a first current mirror tube, a second current mirror tube, a sampling resistor, a first transistor and a second transistor, the source end of the first current mirror tube is connected to the source end of the second current mirror tube and connected to the power supply voltage, the drain end of the first current mirror tube is connected to the output end of the diode current sensing module, the gate end of the first current mirror tube is connected to the drain end of the first current mirror tube and the gate end of the second current mirror tube, the drain end of the second current mirror tube is connected to one end of the sampling resistor, the base of the first transistor and the base of the second transistor, the other end of the sampling resistor is connected to the source end of the main switch tube, the collector of the first transistor is connected to the power supply voltage, the emitter of the first transistor is connected to the emitter of the second transistor, and is connected to the gate end of the main switch tube as the output end of the driving module, and the collector of the second transistor is connected to the source end of the main switch tube; wherein the turn-on voltage of the second transistor is less than the threshold voltage of the main switch tube.

11. The diode current bypass control circuit according to claim 10, characterized in that: The driving module further includes: a PMOS switch tube, a source end of which is connected to a power supply voltage, a drain end of which is connected to the base of the first transistor, and a gate end of which is connected to a switch control signal of the PMOS switch tube.

12. The diode current bypass control circuit according to any one of claims 1 to 11, characterized in that: The control circuit also includes: a current threshold module, connected between the diode current sensing module and the driving module, for comparing the sensing current with a set threshold current, and turning off the driving module when the sensing current is less than the set threshold current, and turning on the driving module when the sensing current is greater than the set threshold current.

13. The diode current bypass control circuit according to claim 12, characterized in that: The current threshold module includes: a threshold current source, an input end of the threshold current source is connected to a power supply voltage, and an output end of the threshold current source is connected to an output end of the diode current sensing module and an input end of the driving module.

14. A diode current bypass control method, used to bypass control the main diode connected in parallel to the source and drain ends of the main switch tube in the main module, characterized in that: The control method comprises: sensing a current flowing through the main diode based on a diode current sensing module; The driving module generates a driving current proportional to the induced current to drive the main switch tube to conduct; The main module, the diode current sensing module and the driving module form a negative feedback loop to reduce the current of the main diode to a set current value.

15. The diode current bypass control method according to claim 14, characterized in that: The method for sensing the current flowing through the main diode based on the diode current sensing module includes: sensing the current flowing through the main diode by making the voltage across the sensing diode in the diode current sensing module positively correlated or equal to the voltage across the main diode.

16. The diode current bypass control method according to claim 14, characterized in that: After the diode current sensing module senses the current flowing through the main diode, the control method further includes: comparing the sensed current with a set threshold current, and turning off the drive module when the sensed current is less than the set threshold current, and turning on the drive module when the sensed current is greater than the set threshold current.

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