Power supply circuit with current limiting function

Abstract

The invention relates to the technical field of power supply circuits, in particular to a power supply circuit with a current limiting function. According to the invention, the power supply circuit, the first current source circuit, the current limiting circuit and the output circuit are arranged, the power supply circuit and the first current source circuit are used for providing electric signals required by work for the current limiting circuit and the output circuit, and the output circuit can output stable electric signals to supply power to an external load; and meanwhile, the current limiting circuit can change the working state of the output circuit and reduce the output current when the output current of the output circuit is relatively large due to a fault of the circuit, and can recover the working state of the output circuit after the fault is eliminated, so that the output circuit can work normally. Therefore, the power supply circuit can realize automatic current limiting and automatic recovery after current limiting, and meanwhile, two low-voltage power supplies are simultaneously generated through one power supply circuit, so that the size of a chip can be reduced, and the development trend that an integrated circuit controls miniaturization of the chip is met.

Description

Technical Field

[0001] The present invention relates to the technical field of power supply circuits, and in particular to a power supply circuit with a current limiting function. Background Art

[0002] At present, in integrated circuit control chips, stable and reliable power supply inside the chip is one of the key factors to ensure the normal operation of the chip. With the continuous development of electronic technology, the functions of control chips are becoming increasingly complex, and the requirements for the power supply circuit inside the chip are also getting higher and higher.

[0003] In many practical application scenarios, the power supply circuit may face various abnormal situations, such as sudden load changes, short circuit faults, etc. These situations may cause the current of the power supply circuit to increase sharply instantly. Excessive current will not only damage the power supply circuit and shorten its service life, but may even cause serious problems such as overheating and burning of other components inside the chip, thereby affecting the stability and reliability of the entire integrated circuit control chip, causing adverse consequences such as failure and shutdown of the chip's external circuit, data loss, etc.

[0004] The structure of the power supply circuit with current limiting function inside the traditional chip is relatively complicated. Not only does it have problems such as low current limiting accuracy and inability to automatically recover, but it also requires the setting of multiple low-voltage power supplies generated by the power supply circuit inside the chip. And several low-voltage power supplies are required, that is, several internal power supply circuits must be set in the power supply circuit, which leads to an increase in the size of the power supply circuit, which does not conform to the development trend of miniaturization of integrated circuit control chips. Summary of the invention

[0005] In view of this, an embodiment of the present invention provides a power supply circuit with a current limiting function to solve the technical problems of low current limiting accuracy, inability to automatically recover and large size in the current limiting method used in the power supply circuit in the prior art.

[0006] The technical solution provided by the embodiment of the present invention is as follows: A first aspect of an embodiment of the present invention provides a power supply circuit with a current limiting function, comprising: a power supply circuit, a first current source circuit, a current limiting circuit and an output circuit; The first end of the power supply circuit is connected to an external power supply, the second end of the power supply circuit is grounded, the third end of the power supply circuit is connected to the first end of the first current source circuit, the first end of the current limiting circuit and the first end of the output circuit, the fourth end of the power supply circuit is connected to the second end of the current limiting circuit and the second end of the output circuit, and the power supply circuit is used to generate a first low-voltage power supply and a second low-voltage power supply at the same time after the external power supply is connected; The second end of the first current source circuit is connected to the third end of the current limiting circuit and the third end of the output circuit, the third end of the first current source circuit is grounded, and the first current source circuit is used to operate according to the first low-voltage power supply; The fourth end of the current limiting circuit is connected to the external power supply, the fifth end of the current limiting circuit is connected to the fourth end of the output circuit, the sixth end of the current limiting circuit is connected to the fifth end of the output circuit, and the seventh end of the current limiting circuit is grounded. The current limiting circuit is used to conduct according to the external power supply, the first low-voltage power supply, the second low-voltage power supply and the first current source circuit that is in conduction, and is in a first working state; The sixth end of the output circuit is connected to the external power supply, the seventh end of the output circuit is connected to the output end of the power supply circuit, and the eighth end of the output circuit is grounded. The output circuit is used to stabilize the voltage at the output end of the power supply circuit at a first preset value according to the external power supply, the first low-voltage power supply, the second low-voltage power supply and the first current source circuit that is turned on and in the second working state; When the output current of the output circuit is greater than the second preset value, the current limiting circuit switches from the first working state to the third working state according to the second low-voltage power supply and the current in the output circuit that is greater than the second preset value, and switches the output circuit from the second working state to the fourth working state, and the output current of the output circuit decreases; when the output current of the output circuit is less than the second preset value, the current limiting circuit returns to the first working state according to the second low-voltage power supply and the current in the output circuit that is less than the second preset value, and returns the output circuit to the second working state, and stabilizes the voltage at the output end of the power supply circuit at the first preset value.

[0007] In an optional embodiment, the first current source circuit includes: a first current source and a first resistor, one end of the first current source is connected to one end of the first resistor, a third end of the current limiting circuit and a third end of the output circuit, the other end of the first current source is grounded, and the other end of the first resistor is connected to the third end of the power supply circuit, the first end of the current limiting circuit and the first end of the output circuit.

[0008] In an optional implementation, the current limiting circuit includes: a first controllable current source, a second controllable current source, a fifth controllable current source, a seventh controllable current source, a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a second resistor, a fourth resistor and a tenth resistor; The positive control terminal and the input terminal of the first controllable current source are connected to the positive control terminal and the input terminal of the second controllable current source, the first terminal of the third switch tube, the third terminal of the power circuit, the first terminal of the first current source circuit and the first terminal of the output circuit; the negative control terminal of the first controllable current source is connected to the negative control terminal of the second controllable current source, the second terminal of the first current source circuit and the third terminal of the output circuit; the output terminal of the first controllable current source is connected to the first terminal of the first switch tube and the first terminal of the second switch tube; the second terminal of the first switch tube is connected to the fourth terminal of the power circuit and the second terminal of the output circuit; the third terminal of the first switch tube is connected to one terminal of the second resistor and the positive control terminal of the fifth controllable current source; the second terminal of the second switch tube is connected to the output terminal of the seventh controllable current source and one terminal of the tenth resistor; the third terminal of the second switch tube and the other terminal of the second resistor are grounded; The output end of the second controllable current source is connected to the second end of the third switch tube and the input end of the fifth controllable current source, the third end of the third switch tube is connected to the first end of the fourth switch tube and one end of the fourth resistor, the negative control end and the output end of the fifth controllable current source, the other end of the fourth resistor, the other end of the tenth resistor and the second end of the fourth switch tube are grounded, the third end of the fourth switch tube is connected to the fourth end of the output circuit, the positive control end and the input end of the seventh controllable current source are connected to an external power supply, and the negative control end of the seventh controllable current source is connected to the fifth end of the output circuit.

[0009] In an optional implementation, the current limiting circuit further includes a third resistor, one end of the third resistor is connected to the third end of the second switch tube, the other end of the third resistor is grounded, and the resistance of the third resistor is equal to the resistance of the second resistor.

[0010] In an optional implementation, the output circuit includes a third controllable current source, a fourth controllable current source, a sixth controllable current source, an eighth controllable current source, a fifth switch tube, a sixth switch tube, a seventh switch tube, a fifth resistor, a seventh resistor, an eighth resistor, a ninth resistor and an eleventh resistor; The positive control terminal and the input terminal of the third controllable current source are connected to the positive control terminal and the input terminal of the fourth controllable current source, the third terminal of the power supply circuit, the first terminal of the first current source circuit and the first terminal of the current limiting circuit; the negative control terminal of the third controllable current source is connected to the negative control terminal of the fourth controllable current source, the second terminal of the first current source circuit and the third terminal of the current limiting circuit; the output terminal of the third controllable current source is connected to the first terminal of the fifth switch tube and the first terminal of the sixth switch tube; the second terminal of the fifth switch tube is connected to the fourth terminal of the power supply circuit and the second terminal of the current limiting circuit; the third terminal of the fifth switch tube is connected to one terminal of the fifth resistor and the positive control terminal of the sixth controllable current source; the second terminal of the sixth switch tube is connected to one terminal of the ninth resistor and one terminal of the eleventh resistor; the third terminal of the sixth switch tube and the other terminal of the fifth resistor are grounded; The output end of the fourth controllable current source is connected to the first end of the seventh switch tube, the input end of the sixth controllable current source and the fifth end of the current limiting circuit, the second end of the seventh switch tube is connected to one end of the eighth resistor, the negative control end of the eighth controllable current source and the sixth end of the current limiting circuit, the third end of the seventh switch tube is connected to one end of the seventh resistor, the negative control end and the output end of the sixth controllable current source, the other end of the seventh resistor and the other end of the eleventh resistor are grounded, the other end of the eighth resistor is connected to the positive control end and the input end of the eighth controllable current source and the external power supply, and the output end of the eighth controllable current source is connected to the other end of the ninth resistor and the output end of the power supply circuit.

[0011] In an optional embodiment, the third end of the power supply circuit outputs a first low-voltage power supply, the fourth end of the power supply circuit outputs a second low-voltage power supply, the voltage of the first low-voltage power supply is greater than the voltage of the second low-voltage power supply, and the difference between the voltage of the first low-voltage power supply and the voltage of the second low-voltage power supply is greater than the threshold voltage of the first switch tube and the fifth switch tube.

[0012] In an optional implementation, the output circuit further includes a sixth resistor, one end of the sixth resistor is connected to the third end of the sixth switch tube, the other end of the sixth resistor is grounded, and the resistance value of the sixth resistor is the same as the resistance value of the fifth resistor.

[0013] In an optional embodiment, the ratio of the first controllable current generated by the first controllable current source to the second controllable current generated by the second controllable current source is two to one, and the ratio of the third controllable current generated by the third controllable current source to the fourth controllable current generated by the fourth controllable current source is two to one.

[0014] In an optional embodiment, the power supply circuit also includes: an isolation circuit, a first end of the isolation circuit is connected to one end of the eighth resistor, the negative control end of the seventh controllable current source and the negative control end of the eighth controllable current source, a second end of the isolation circuit is connected to the third end of the power supply circuit, the first end of the first current source circuit, the first end of the current limiting circuit and the first end of the output circuit, a third end of the isolation circuit is connected to the second end of the seventh switch tube, a fourth end of the isolation circuit is connected to the output end of the seventh controllable current source, a fifth end of the isolation circuit is connected to the second end of the second switch tube and one end of the tenth resistor, a sixth end of the isolation circuit is grounded, and a seventh end of the isolation circuit is connected to the output end of the eighth controllable current source, the other end of the ninth resistor and the output end of the power supply circuit.

[0015] In an optional implementation, the isolation circuit includes an eighth switch tube, a ninth controllable current source, a twelfth resistor and a thirteenth resistor; the first end of the eighth switch tube is connected to one end of the eighth resistor, the negative control end of the seventh controllable current source and the negative control end of the eighth controllable current source, the second end of the eighth switch tube is connected to the third end of the power supply circuit, the first end of the first current source circuit, the first end of the current limiting circuit and the first end of the output circuit, the third end of the eighth switch tube is connected to the second end of the seventh switch tube, the input end of the ninth controllable current source is connected to the output end of the seventh controllable current source, the output end of the ninth controllable current source is connected to the second end of the second switch tube and one end of the tenth resistor, the negative control end of the ninth controllable current source is connected to one end of the thirteenth resistor and one end of the twelfth resistor, the other end of the thirteenth resistor is grounded, and the positive control end of the ninth controllable current source is connected to the other end of the twelfth resistor, the output end of the eighth controllable current source, the other end of the ninth resistor and the output end of the power supply circuit.

[0016] In an optional implementation, a current capability of the ninth controllable current source is greater than a current capability of the seventh controllable current source.

[0017] The technical solution of the present invention has the following advantages: In the present invention, a power supply circuit, a first current source circuit, a current limiting circuit and an output circuit are provided, wherein the power supply circuit and the first current source circuit are used to provide the electric signal required for the current limiting circuit and the output circuit to work, and the output circuit can output a stable electric signal to supply power to an external load; at the same time, the current limiting circuit can change the working state of the output circuit and reduce the output current when a fault occurs in the circuit so that the output current of the output circuit is large, and restore the working state of the output circuit after the fault is eliminated, so that it works normally. Thus, the power supply circuit can realize automatic current limiting and automatic recovery after current limiting, and at the same time, two low-voltage power supplies are generated simultaneously through a power supply circuit, so that the chip volume can be reduced, which is in line with the development trend of miniaturization of integrated circuit control chips. Moreover, in this embodiment, a power supply circuit is provided in the power supply circuit, and the power supply circuit can output two low-voltage power supplies, thereby there is no need to set up multiple internal power supplies, therefore, the space originally used to set up other internal power supplies can be provided with functional structures such as current limiting, so that a power supply circuit with a current limiting function in this embodiment is provided with a functional structure of current limiting on the basis of meeting the chip volume design requirements, thereby retaining the small volume characteristics of the chip and improving the safety and reliability of the chip.

[0018] In the present invention, through the third resistor and the sixth resistor, it can be ensured that when the circuit is in a stable working state in the normal output mode, the current voltages of various paths in the output circuit are completely matched, and the gate voltage of the sixth switch tube is precisely equal to the voltage of the second low-voltage power supply. At the same time, it can be ensured that when the circuit is at a current limiting switching node where the normal working mode is switched to the current limiting mode, the gate voltage of the second switch tube is precisely equal to the voltage of the second low-voltage power supply. Therefore, the power supply circuit can improve the accuracy of the output voltage VOUT and the accuracy of the current limiting switching node, thereby further improving the safety and reliability of the circuit.

[0019] In the present invention, by setting up an isolation circuit, all devices below the isolation circuit can be low-voltage devices, ensuring that the leakage of the switch tube is small, thereby improving the safety and reliability of the circuit; and the isolation circuit prevents the disturbance of the external high-voltage power supply from being transmitted to one end of the tenth resistor, thereby ensuring that the current limiting switching node will not drift, further improving the safety and reliability of the circuit.

[0020] In the present invention, by setting only one power supply circuit, two high-precision low-voltage power supplies that are not affected by temperature can be generated, thereby improving the output voltage accuracy and current limiting accuracy of the power supply circuit and reducing the volume of the power supply circuit; at the same time, the power supply circuit can provide a first low-voltage power supply with current capability and a second low-voltage power supply without current capability, and the power supply circuit can be obtained after reasonable combination with a current limiting circuit and an output circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 is a structural block diagram of a power supply circuit with a current limiting function in an embodiment of the present invention; Figure 2 It is a schematic diagram of the structure of a power supply circuit with a current limiting function in an embodiment of the present invention; Figure 3 It is a structural schematic diagram of another power supply circuit with current limiting function in an embodiment of the present invention; Figure 4 is a structural block diagram of a power supply circuit in an embodiment of the present invention; Figure 5 Schematic diagram of the structure of the power supply circuit in the embodiment of the present invention. DETAILED DESCRIPTION

[0023] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0025] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, it can also be the internal connection of two components, it can be a wireless connection, or it can be a wired connection. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0026] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0027] The embodiment of the present invention provides a power supply circuit with a current limiting function, such as Figure 1 As shown, the power supply circuit includes: a power supply circuit 10, a first current source circuit 20, a current limiting circuit 30 and an output circuit 40; the first end of the power supply circuit 10 is connected to an external power supply, the second end of the power supply circuit 10 is grounded, the third end of the power supply circuit 10 is connected to the first end of the first current source circuit 20, the first end of the current limiting circuit 30 and the first end of the output circuit 40, the fourth end of the power supply circuit 10 is connected to the second end of the current limiting circuit 30 and the second end of the output circuit 40, and the power supply circuit 10 is used to simultaneously generate a first low-voltage power supply and a second low-voltage power supply after the external power supply is connected. The second end of the first current source circuit 20 is connected to the third end of the current limiting circuit 30 and the third end of the output circuit 40, the third end of the first current source circuit 20 is grounded, and the first current source circuit 20 is used to conduct and work according to the first low-voltage power supply.

[0028] The fourth end of the current limiting circuit 30 is connected to the external power supply, the fifth end of the current limiting circuit 30 is connected to the fourth end of the output circuit 40, the sixth end of the current limiting circuit 30 is connected to the fifth end of the output circuit 40, and the seventh end of the current limiting circuit 30 is grounded. The current limiting circuit 30 is used to conduct according to the external power supply, the first low-voltage power supply, the second low-voltage power supply, and the first current source circuit 20 that is turned on, and is in a first working state. The sixth end of the output circuit 40 is connected to the external power supply, the seventh end of the output circuit 40 is connected to the output end of the power supply circuit, and the eighth end of the output circuit 40 is grounded. The output circuit 40 is used to conduct according to the external power supply, the first low-voltage power supply, the second low-voltage power supply, and the first current source circuit 20 that is turned on, and is in a second working state, stabilizing the voltage at the output end of the power supply circuit at a first preset value.

[0029] When the output current of the output circuit 40 is greater than the second preset value, the current limiting circuit 30 switches from the first working state to the third working state according to the second low-voltage power supply and the current in the output circuit 40 that is greater than the second preset value, and switches the output circuit 40 from the second working state to the fourth working state, and the output current of the output circuit 40 decreases; when the output current of the output circuit 40 is less than the second preset value, the current limiting circuit 30 returns to the first working state according to the second low-voltage power supply and the current in the output circuit 40 that is less than the second preset value, and returns the output circuit 40 to the second working state, and stabilizes the voltage at the output end of the power supply circuit at the first preset value.

[0030] The power supply circuit with current limiting function can be arranged inside the chip. The power supply circuit is a power supply circuit arranged inside the chip, and can also be called an internal power supply. The external power supply is a power supply arranged outside the chip, and the power supply signal generated by the external power supply is a high-voltage power supply signal.

[0031] In the present invention, a power supply circuit, a first current source circuit, a current limiting circuit and an output circuit are provided, wherein the power supply circuit and the first current source circuit are used to provide the current limiting circuit and the output circuit with the electrical signals required for operation, and the output circuit can output a stable electrical signal to supply power to an external load; at the same time, the current limiting circuit can change the working state of the output circuit and reduce the output current when a circuit fault occurs and the output current of the output circuit is large, and at the same time, after the fault is eliminated, the working state of the output circuit is restored to enable it to work normally. Thus, the power supply circuit can realize automatic current limiting and automatic recovery after current limiting, and at the same time, two low-voltage power supplies are generated simultaneously through a power supply circuit, so that the chip volume can be reduced, which is in line with the development trend of miniaturization of integrated circuit control chips.

[0032] In addition, in the present embodiment, a power supply circuit is provided in the power supply circuit, and the power supply circuit can output two low-voltage power supplies, thereby eliminating the need to provide multiple internal power supplies. Therefore, the space originally used to provide other internal power supplies can be used to provide functional structures such as current limiting. This enables a power supply circuit with a current limiting function in the present embodiment to be provided with a current limiting functional structure on the basis of meeting the chip volume design requirements, thereby retaining the small volume characteristics of the chip and improving the safety and reliability of the chip.

[0033] In an optional embodiment, if Figure 2 As shown, the first current source circuit 20 includes: a first current source I1 and a first resistor R1, one end of the first current source I1 is connected to one end of the first resistor R1, the third end of the current limiting circuit 30 and the third end of the output circuit 40, the other end of the first current source I1 is grounded, and the other end of the first resistor R1 is connected to the third end of the power supply circuit (i.e., the internal power supply) 10, the first end of the current limiting circuit 30 and the first end of the output circuit 40. Specifically, when the power supply circuit is powered on, the external power supply is connected to the power supply circuit, and the power supply circuit 10 generates a first low-voltage power supply signal, thereby generating a first current in the first current source I1 that flows through the first resistor R1 and generates a voltage drop across the first resistor R1, i.e., the first current source circuit 20 is turned on.

[0034] In an optional embodiment, if Figure 2As shown, the output circuit 40 includes a third controllable current source G3, a fourth controllable current source G4, a sixth controllable current source G6, an eighth controllable current source G8, a fifth switch tube M5, a sixth switch tube M6, a seventh switch tube M7, a fifth resistor R5, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9 and an eleventh resistor R11; the ratio of the third controllable current generated by the third controllable current source G3 to the fourth controllable current generated by the fourth controllable current source G4 is two to one. The third terminal of the power supply circuit 10 outputs a first low-voltage power supply, and the fourth terminal of the power supply circuit 10 outputs a second low-voltage power supply, the voltage of the first low-voltage power supply is greater than the voltage of the second low-voltage power supply, and the difference between the voltage of the first low-voltage power supply and the voltage of the second low-voltage power supply is greater than the threshold voltage of the fifth switch tube M5.

[0035] The positive control terminal and the input terminal of the third controllable current source G3 are connected to the positive control terminal and the input terminal of the fourth controllable current source G4, the third terminal of the power supply circuit 10, the first terminal of the first current source circuit 20 and the first terminal of the current limiting circuit 30; the negative control terminal of the third controllable current source G3 is connected to the negative control terminal of the fourth controllable current source G4, the second terminal of the first current source circuit and the third terminal of the current limiting circuit; the output terminal of the third controllable current source G3 is connected to the first terminal of the fifth switch tube M5 and the first terminal of the sixth switch tube M6; the second terminal of the fifth switch tube M5 is connected to the fourth terminal of the power supply circuit and the second terminal of the current limiting circuit; the third terminal of the fifth switch tube M5 is connected to one terminal of the fifth resistor R5 and the positive control terminal of the sixth controllable current source G6; the second terminal of the sixth switch tube M6 is connected to one terminal of the ninth resistor R9 and one terminal of the eleventh resistor R11; the third terminal of the sixth switch tube M6 and the other terminal of the fifth resistor R5 are grounded; The output end of the fourth controllable current source G4 is connected to the first end of the seventh switch tube M7, the input end of the sixth controllable current source G6 and the fifth end of the current limiting circuit; the second end of the seventh switch tube M7 is connected to one end of the eighth resistor R8, the negative control end of the eighth controllable current source G8 and the sixth end of the current limiting circuit; the third end of the seventh switch tube M7 is connected to one end of the seventh resistor R7; the negative control end and the output end of the sixth controllable current source G6, the other end of the seventh resistor R7 and the other end of the eleventh resistor R11 are grounded; the other end of the eighth resistor R8 is connected to the positive control end and the input end of the eighth controllable current source G8 and the external power supply; the output end of the eighth controllable current source G8 is connected to the other end of the ninth resistor R9 and the output end of the power supply circuit.

[0036] Specifically, when the circuit is powered on, the external power supply is input into the power supply circuit, and the power supply circuit in the power supply circuit directly generates two low-voltage power supplies (a first low-voltage power supply and a second low-voltage power supply). At the same time, the first low-voltage power supply generated by the power supply circuit causes a voltage drop across the first resistor R1, thereby, a third controllable current and a fourth controllable current flow through the third controllable current source G3 and the fourth controllable current source G4, respectively. Therefore, the source voltages of the fifth switch tube M5 and the sixth switch tube M6 are both pulled up to the voltage V1 of the first low-voltage power supply. At the same time, since the gate voltage of the fifth switch tube M5 is equal to the voltage V2 of the second low-voltage power supply, the fifth switch tube M5 is turned on; at this time, current flows through the fifth resistor R5, and a voltage drop is generated across the fifth resistor R5. Therefore, a sixth controllable current flows through the sixth controllable current source G6, and the current coefficient of the sixth controllable current source G6 is designed to be 1. Therefore, at this time, it can be obtained that the current flowing through the fifth switch tube M5=the current flowing through the fifth resistor R5=the sixth controllable current.

[0037] At the same time, since the eighth controllable current source G8 is not turned on when the circuit is just powered on, the gate of the sixth switch tube M6 is grounded through the eleventh resistor R11. Therefore, the gate-source voltage difference of the fifth switch tube M5 is smaller than the gate-source voltage difference of the sixth switch tube M6. The current flowing through the sixth switch tube M6 is larger than the current flowing through the fifth switch tube M5. Since the sum of the current flowing through the sixth switch tube M6 and the current flowing through the fifth switch tube M5 is equal to the third controllable current, it can be obtained that the current flowing through the fifth switch tube M5 is smaller than half of the third controllable current. The fourth controllable current is equal to half of the third controllable current, and the current flowing through the fifth switch tube M5 is equal to the sixth controllable current. Therefore, the sixth controllable current is less than the fourth controllable current, the voltage at point B is pulled up, and the seventh switch tube M7 is turned on. At this time, current flows through the eighth resistor R8, and a voltage drop is generated across the eighth resistor R8. The voltage drop causes the eighth controllable current to be generated in the eighth controllable current source G8. At this time, the eighth controllable current flows through the ninth resistor R9 and the eleventh resistor R11. Therefore, the gate voltage of the sixth switch tube gradually increases.

[0038] When the gate voltage of the sixth switch tube gradually increases to a voltage greater than the voltage V2 of the second low-voltage power supply, the gate-source voltage difference of the fifth switch tube M5 is greater than the gate-source voltage difference of the sixth switch tube M6, and the current flowing through the sixth switch tube M6 is less than the current flowing through the fifth switch tube M5. Since the sum of the current flowing through the sixth switch tube M6 and the current flowing through the fifth switch tube M5 is equal to the third controllable current, it can be obtained that the current flowing through the fifth switch tube M5 is greater than half of the third controllable current, and the fourth controllable current is equal to half of the third controllable current, and the current flowing through the fifth switch tube M5 is equal to the sixth controllable current. Therefore, the sixth controllable current is greater than the fourth controllable current, the voltage at point B is pulled down, the seventh switch tube M7 is turned off, no current flows through the eighth resistor R8, the gate voltage of the sixth switch tube gradually decreases, and the circuit enters the next cycle. Therefore, when the power supply circuit enters a stable state, the gate voltage of the sixth switch tube is equal to the voltage V2 of the second low-voltage power supply. Therefore, at this time, it can be obtained that the voltage of the second low-voltage power supply , output voltage That is, after the power supply circuit enters the stable state, the power supply circuit is in the normal output mode, and the output circuit is in the second working state.

[0039] In an optional embodiment, if Figure 2 As shown, the current limiting circuit 30 includes: a first controllable current source G1, a second controllable current source G2, a fifth controllable current source G5, a seventh controllable current source G7, a first switch tube M1, a second switch tube M2, a third switch tube M3, a fourth switch tube M4, a second resistor R2, a fourth resistor R4 and a tenth resistor R10. The ratio of the first controllable current generated by the first controllable current source G1 to the second controllable current generated by the second controllable current source G2 is two to one.

[0040] The positive control terminal and the input terminal of the first controllable current source G1 are connected to the positive control terminal and the input terminal of the second controllable current source G2, the first terminal of the third switch tube M3, the third terminal of the power supply circuit 10, the first terminal of the first current source circuit 20 and the first terminal of the output circuit 40; the negative control terminal of the first controllable current source G1 is connected to the negative control terminal of the second controllable current source G2, the second terminal of the first current source circuit 20 and the third terminal of the output circuit 40; the output terminal of the first controllable current source G1 is connected to the first terminal of the first switch tube M1 and the first terminal of the second switch tube M2; the second terminal of the first switch tube M1 is connected to the fourth terminal of the power supply circuit and the second terminal of the output circuit; the third terminal of the first switch tube M1 is connected to one terminal of the second resistor R2 and the positive control terminal of the fifth controllable current source G5; the second terminal of the second switch tube M2 is connected to the output terminal of the seventh controllable current source G7 and one terminal of the tenth resistor R10; the third terminal of the second switch tube M2 and the other terminal of the second resistor R2 are grounded.

[0041] The output end of the second controllable current source G2 is connected to the second end of the third switch tube M3 and the input end of the fifth controllable current source G5, the third end of the third switch tube M3 is connected to the first end of the fourth switch tube M4 and one end of the fourth resistor R4, the negative control end and the output end of the fifth controllable current source G5, the other end of the fourth resistor R4, the other end of the tenth resistor R10 and the second end of the fourth switch tube M4 are grounded, the third end of the fourth switch tube M4 is connected to the fourth end of the output circuit, the positive control end and the input end of the seventh controllable current source G7 are connected to the external power supply, and the negative control end of the seventh controllable current source G7 is connected to the fifth end of the output circuit.

[0042] Specifically, the first low-voltage power supply generated by the power supply circuit causes a voltage drop across the first resistor R1, thereby, the first controllable current and the second controllable current flow through the first controllable current source G1 and the second controllable current source G2 respectively, therefore, the source voltages of the first switch tube M1 and the second switch tube M2 are both pulled up to the voltage V1 of the first low-voltage power supply, and at the same time, since the gate voltage of the first switch tube M1 is equal to the voltage V2 of the second low-voltage power supply, the first switch tube M1 is turned on; at this time, current flows through the second resistor R2, and a voltage drop is generated across the second resistor R2, therefore, a fifth controllable current flows through the fifth controllable current source G5, and the current coefficient of the fifth controllable current source G5 is designed to be 1, so at this time, it can be obtained that the current flowing through the first switch tube M1 = the current flowing through the second resistor R2 = the fifth controllable current.

[0043] Since the seventh controllable current source G7 is not turned on when the circuit is just powered on, the gate of the second switch tube M2 is grounded through the tenth resistor R10. Therefore, the gate-source voltage difference of the first switch tube M1 is smaller than the gate-source voltage difference of the second switch tube M2, and the current flowing through the second switch tube M2 is larger than the current flowing through the first switch tube M1. Since the sum of the current flowing through the first switch tube M1 and the current flowing through the second switch tube M2 is equal to the first controllable current, it can be obtained that the current flowing through the first switch tube M1 is less than half of the first controllable current, and the second controllable current is equal to half of the first controllable current. The current flowing through the first switch tube M1 is equal to the fifth controllable current. Therefore, the fifth controllable current is less than the second controllable current, the voltage at point A is pulled up, and the third switch tube M3 is turned on. After being turned on, the third switch tube M3 pulls up the gate voltage of the fourth switch tube M4, and the fourth switch tube M4 is turned off. At the same time, when current flows through the eighth resistor R8 of the output circuit, a voltage drop is generated across the eighth resistor R8, and the voltage drop causes the seventh controllable current to be generated in the seventh controllable current source G7 (the ratio of the seventh controllable current to the eighth controllable current is 1:N). Therefore, the gate voltage of the second switch tube M2 gradually increases.

[0044] Moreover, when the power supply circuit is in normal output mode, the eighth controllable current almost entirely flows to the power supply load through the output end, and only a very small proportion of the eighth controllable current flows to the ninth resistor R9 and the eleventh resistor R11. Therefore, by detecting the seventh controllable current that is proportional to the eighth controllable current, the current flowing to the power supply load can be detected. Therefore, at this time, by selecting a suitable proportional coefficient N and the resistance value of the tenth resistor R10, the design value of the seventh controllable current is calculated, so that when the eighth controllable current (i.e., the load current) is greater than the threshold current, the seventh controllable current is greater than the design value, and the power supply circuit enters the current limiting mode.

[0045] Specifically, when the eighth controllable current (i.e., the load current) is greater than the threshold current, the seventh controllable current is greater than the design value. Therefore, at this time, the gate voltage of the second switch tube is greater than the voltage V2 of the second low-voltage power supply, the gate-source voltage difference of the first switch tube M1 is greater than the gate-source voltage difference of the second switch tube M2, and the current flowing through the second switch tube M2 is less than the current flowing through the first switch tube M1. Since the sum of the current flowing through the first switch tube M1 and the current flowing through the second switch tube M2 is equal to the first controllable current, it can be obtained that the current flowing through the first switch tube M1 is greater than half of the first controllable current, and the second controllable current is equal to half of the first controllable current. The current flowing through the first switch tube M1 is is equal to the fifth controllable current. Therefore, the fifth controllable current is greater than the second controllable current. The voltage at point A is pulled down, the third switch tube M3 is turned off, and the gate voltage of the fourth switch tube M4 is pulled down by the fourth resistor R4 (that is, the current limiting circuit enters the third state from the first state). At the same time, when the current limiting circuit enters the third state from the first state, current must flow through the seventh switch tube M7. Therefore, the voltage at point B is at a high level. That is, at this time, the source voltage of the fourth switch tube M4 is also at a high level. Therefore, at this time, the fourth switch tube M4 is turned on, the voltage at point B is pulled down through the fourth switch tube M4, and the seventh switch tube M7 is turned off, thereby realizing the current limiting function (that is, the output circuit enters the fourth state from the second state).

[0046] Afterwards, when the circuit fault disappears and the eighth controllable current (i.e., the load current) is less than the threshold current, the seventh controllable current is less than the design value. Therefore, at this time, the gate voltage of the second switch tube is less than the voltage V2 of the second low-voltage power supply. Therefore, the gate-source voltage difference of the first switch tube M1 is less than the gate-source voltage difference of the second switch tube M2. The current flowing through the second switch tube M2 is greater than the current flowing through the first switch tube M1. Since the sum of the current flowing through the first switch tube M1 and the current flowing through the second switch tube M2 is equal to the first controllable current, it can be obtained that the current flowing through the first switch tube M1 is greater than the current flowing through the second switch tube M2. The current of the switch tube M1 is less than half of the first controllable current, and the second controllable current is equal to half of the first controllable current. The current flowing through the first switch tube M1 is equal to the fifth controllable current. Therefore, the fifth controllable current is less than the second controllable current. The voltage at point A is pulled up, and the third switch tube M3 is turned on. After being turned on, the third switch tube M3 pulls up the gate voltage of the fourth switch tube M4, and the fourth switch tube M4 is turned off (that is, the current limiting circuit is restored from the second state to the first state). The circuit enters the normal output mode, and the output circuit is restored from the fourth state to the first state.

[0047] In an optional embodiment, if Figure 2 As shown, the current limiting circuit 30 further includes a third resistor R3, one end of the third resistor R3 is connected to the third end of the second switch tube M2, the other end of the third resistor R3 is grounded, and the resistance of the third resistor R3 is equal to the resistance of the second resistor R2. The output circuit 40 further includes a sixth resistor R6, one end of the sixth resistor R6 is connected to the third end of the sixth switch tube M6, the other end of the sixth resistor R6 is grounded, and the resistance of the sixth resistor R6 is the same as the resistance of the fifth resistor R5.

[0048] Specifically, when the power supply circuit is in a stable working state in the normal output mode, the current flowing through the fifth switch tube M5 is equal to the current flowing through the sixth switch tube M6. Therefore, at this time, a sixth resistor R6 is set in the branch of the sixth switch tube M6, and the resistance value of the sixth resistor R6 is designed to be equal to the resistance value of the fifth resistor R5. Therefore, when the current flowing through the fifth switch tube M5 is equal to the current flowing through the sixth switch tube M6, the voltage drop in the fifth resistor R5 and the sixth resistor R6 are the same, so that when the circuit is in a stable working state in the normal output mode, the fifth switch tube M5 and the sixth switch tube M6 are 6 are completely equal, so at this time it can be obtained that when the current flowing through the fifth switch tube M5 is equal to the current flowing through the sixth switch tube M6, and the voltages of the drains of the fifth switch tube M5 and the sixth switch tube M6 are also completely equal, the gate voltages of the fifth switch tube M5 and the sixth switch tube M6 must be completely equal, thereby ensuring that when the circuit is in a stable working state in the normal output mode, the current voltages of various paths in the output circuit are completely matched, and the gate voltage of the sixth switch tube M6 is accurately equal to the voltage V2 of the second low-voltage power supply. Therefore, through the above structure, the accuracy of the output voltage VOUT can be improved.

[0049] At the same time, it can be seen from the above analysis that when the circuit is at the current limiting switching node where the normal working mode is switched to the current limiting mode, the current flowing through the second switch tube M2 is equal to the current flowing through the first switch tube M1. Therefore, at this time, the third resistor R3 is set in the branch of the second switch tube M2, and the resistance value of the third resistor R3 is designed to be equal to the resistance value of the second resistor R2. Therefore, when the current flowing through the first switch tube M1 is equal to the current flowing through the second switch tube M2, the voltage drop in the second resistor R2 and the third resistor R3 is the same, so that when the circuit is at the current limiting switching node where the normal working mode is switched to the current limiting mode, the first switch tube M1 The gate voltage of the first switch tube M1 is completely equal to the voltage of the drain of the second switch tube M2. Therefore, it can be obtained that when the current flowing through the first switch tube M1 is equal to the current flowing through the second switch tube M2, and the voltages of the drains of the first switch tube M1 and the second switch tube M2 are also completely equal, the gate voltages of the first switch tube M1 and the second switch tube M2 must be completely equal, thereby ensuring that when the circuit is at a current limiting switching node where the normal working mode is switched to the current limiting mode, the gate voltage of the second switch tube M2 is accurately equal to the voltage V2 of the second low-voltage power supply. Therefore, through the above structure, the accuracy of the current limiting switching node can be improved, thereby further improving the safety and reliability of the circuit.

[0050] According to the above circuit, since the eighth resistor R8, the seventh controllable current source G7 and the eighth controllable current source G8 are all connected to an external high-voltage power supply, the devices connected below the eighth resistor R8 and the seventh controllable current source G7 must all use high-voltage devices, that is, the seventh switch tube M7 must use a high-voltage switch tube, and the high-voltage switch tube has a large leakage, which may cause the seventh switch tube M7 to not be correctly turned on or off when the circuit is at the current limiting switching node where the normal working mode is switched to the current limiting mode. At the same time, the disturbance of the external high-voltage power supply may be transmitted to one end of the tenth resistor R10, thereby causing the current limiting switching node to drift, reducing the accuracy of the current limiting switching node and the safety and reliability of the circuit.

[0051] Therefore, if Figure 3 As shown, the power supply circuit also includes: an isolation circuit, a first end of the isolation circuit is connected to one end of the eighth resistor R8, the negative control end of the seventh controllable current source G7 and the negative control end of the eighth controllable current source G8, a second end of the isolation circuit is connected to the third end of the power supply circuit 10, the first end of the first current source circuit 20, the first end of the current limiting circuit 30 and the first end of the output circuit 40, a third end of the isolation circuit is connected to the second end of the seventh switch tube M7, a fourth end of the isolation circuit is connected to the output end of the seventh controllable current source G7, a fifth end of the isolation circuit is connected to the second end of the second switch tube M2 and one end of the tenth resistor R10, a sixth end of the isolation circuit is grounded, and a seventh end of the isolation circuit is connected to the output end of the eighth controllable current source G8, the other end of the ninth resistor R9 and the output end of the power supply circuit.

[0052] Specifically, Figure 3As shown, the isolation circuit includes an eighth switch tube M8, a ninth controllable current source G9, a twelfth resistor R12 and a thirteenth resistor R13; a first end of the eighth switch tube M8 is connected to one end of the eighth resistor R8, a negative control end of the seventh controllable current source G7 and a negative control end of the eighth controllable current source G8, a second end of the eighth switch tube M8 is connected to a third end of the power supply circuit 10, a first end of the first current source circuit 20, a first end of the current limiting circuit 30 and a first end of the output circuit 40, a third end of the eighth switch tube M8 is connected to a second end of the seventh switch tube M7, and The input end of the ninth controllable current source G9 is connected to the output end of the seventh controllable current source G7, the output end of the ninth controllable current source G9 is connected to the second end of the second switch tube M2 and one end of the tenth resistor R10, the negative control end of the ninth controllable current source G9 is connected to one end of the thirteenth resistor R13 and one end of the twelfth resistor R12, the other end of the thirteenth resistor R13 is grounded, and the positive control end of the ninth controllable current source G9 is connected to the other end of the twelfth resistor R12, the output end of the eighth controllable current source G8, the other end of the ninth resistor R9 and the output end of the power supply circuit.

[0053] Among them, the eighth switch tube M8 plays a role of isolating high voltage, so that the device (seventh switch tube M7) below the eighth switch tube M8 can use a low-voltage device, thereby ensuring that the leakage of the seventh switch tube M7 is small, thereby improving the safety and reliability of the circuit; at the same time, a ninth controllable current source G9 with a larger current coefficient is set in the circuit, so that the ninth controllable current generated by the ninth controllable current source G9 according to the twelfth resistor R12 is greater than the seventh controllable current, that is, the current capacity of the ninth controllable current source G9 is greater than the current capacity of the seventh controllable current source G7. Therefore, when the power supply circuit is working, the current flowing through the branch of the seventh controllable current source G7, the ninth controllable current source G9 and the tenth resistor R10 is equal to the seventh controllable current, thereby ensuring that the isolation circuit will not affect the operation of the power supply circuit; and, due to the provision of the isolation circuit, the disturbance of the external high-voltage power supply will not be transmitted to one end of the tenth resistor R10, thereby ensuring that the current limiting switching node will not drift, thereby improving the safety and reliability of the circuit.

[0054] It should be noted that the switch tubes in the output circuit, the current limiting circuit and the isolation circuit can be implemented by MOS tubes.

[0055] An embodiment of the present invention provides a power supply circuit, such as Figure 4As shown, the power supply circuit includes a second current source circuit 50, a starting circuit 60, a regulating circuit 70 and a voltage output circuit 80. The second current source circuit 50 is used to conduct after the external power supply is connected, the starting circuit 60 is used to provide a starting voltage for the regulating circuit 70 according to the external power supply and the conducting second current source circuit 50, the regulating circuit 70 is used to regulate the current of the voltage output circuit 80 and stabilize it, and the voltage output circuit 80 is used to output the first low-voltage power supply and the second low-voltage power supply after the current is stable.

[0056] Among them, the first end of the second current source circuit 50 is connected to the external power supply, the first end of the starting circuit 60, the first end of the regulating circuit 70 and the first end of the voltage output circuit 80, the second end of the second current source circuit 50 is connected to the second end of the starting circuit 60 and the second end of the regulating circuit 70, and the third end of the second current source circuit 50 is grounded; the third end of the starting circuit 60 is connected to the third end of the regulating circuit 70 and the second end of the voltage output circuit 80, the fourth end of the starting circuit 60 is grounded, and the fifth end of the starting circuit 60 is connected to the seventh end of the regulating circuit 70; the fourth end of the regulating circuit 70 is connected to the third end of the voltage output circuit 80, the fifth end of the regulating circuit 70 is connected to the fourth end of the voltage output circuit 80, and the sixth end of the regulating circuit 70 is grounded; the fifth end of the voltage output circuit 80 outputs the first low-voltage power supply, the second end of the voltage output circuit 80 outputs the second low-voltage power supply, and the sixth end of the voltage output circuit 80 is grounded.

[0057] Specifically, the second current source circuit 50 includes a second current source I2 and a twenty-second resistor R22; the starting circuit 60 includes an eleventh controllable current source G11, a fifteenth controllable current source G15, a fourteenth resistor R14, a fourteenth MOS tube M14, a fifteenth MOS tube M15 and a second diode D2; the regulating circuit 70 includes a tenth controllable current source G10, a twelfth controllable current source G12, a thirteenth controllable current source G13, a fourteenth controllable current source G14, a first transistor Q1, a second transistor Q2, a ninth MOS tube M9, a tenth MOS tube M10, a fifteenth resistor R15, a sixteenth resistor R16, a seventeenth resistor R17, an eighteenth resistor R18 and a first diode D1; the voltage output circuit 80 includes a thirteenth MOS tube M13, a third transistor Q3, a nineteenth resistor R19, a twentieth resistor R20, a twenty-first resistor R21 and a fourth transistor Q4. The connection between the various components is as follows: Figure 5 shown.

[0058] The working principle of the power supply circuit is as follows: When the circuit is powered on, the external high-voltage power supply of the chip is input into the power supply circuit, and the second current source I2 generates a second current that flows into the twenty-second resistor R22. At this time, the tenth controllable current and the eleventh controllable current flow through the tenth controllable current source G10 and the eleventh controllable current source G11 respectively; the eleventh controllable current flows into the fourteenth resistor R14. At this time, the twelfth controllable current, the thirteenth controllable current, the fourteenth controllable current and the fifteenth controllable current flow through the twelfth controllable current source G12, the thirteenth controllable current source G13, the fourteenth controllable current source G14 and the fifteenth controllable current source G15 respectively. The thirteenth controllable current (wherein the ratio of the thirteenth controllable current to the fourteenth controllable current is 1:1) is applied to the fourteenth MOS tube M14 and the fifteenth MOS tube M15. At this time, the gate voltages of the fourteenth MOS tube M14 and the fifteenth MOS tube M15 are pulled up through the fifteenth controllable current source G15. At the same time, the source of the fourteenth MOS tube M14 is grounded through the second diode D2. Since the voltage VIN of the external high-voltage power supply is greater than the sum of the gate-source voltage difference VGS of the fourteenth MOS tube M14 and the forward conduction voltage drop VD2 of the second diode D2, at this time, the fourteenth MOS tube M14 and the second diode D2 are both turned on. At this time, the Figure 3 As shown in the structural schematic diagram, the gate voltage of the fourteenth MOS tube M14 and the gate voltage of the fifteenth MOS tube M15 are both equal to VGS+VD2. Therefore, when the source voltage of the fifteenth MOS tube M15 is less than VD2, the fifteenth MOS tube M15 is turned on. At this time, the source voltage of the fifteenth MOS tube M15 can be clamped at VD2. When the source voltage of the fifteenth MOS tube M15 is greater than VD2, although the fifteenth MOS tube M15 is not turned on, at this time, the base voltage of the first transistor Q1 is greater than VD2. Therefore, in the present application, the base voltage of the first transistor Q1 is greater than VD2. At least VD2, the base voltage of the second triode Q2 is at least close to VD2, and since the emitters of the first triode Q1 and the second triode Q2 are grounded through the tenth controllable current source G10, at this time, when the base voltage of the first triode Q1 is at least VD2, and the base voltage of the second triode Q2 is at least close to VD2, the first triode Q1 and the second triode Q2 can be smoothly turned on; at the same time, in order to further ensure that the first triode Q1 and the second triode Q2 are smoothly turned on, M diodes can be connected in series in the branch of the second diode D2, so as to ensure that the base voltage of the first triode Q1 is about M VD2, the base voltage of the second transistor Q2 is close to M VD2.

[0059] After the first transistor Q1 and the second transistor Q2 are turned on, the cathode of the first diode D1 is pulled low, and the first diode D1 is turned on. Therefore, current flows through the first transistor Q1 and the second transistor Q2. At this time, since the ratio of the number of the first transistor Q1 to the number of the second transistor Q2 is 1:K, and when the circuit is just powered on, the base voltage of the first transistor Q1 and the base voltage of the second transistor Q2 are very small, at this time, the number ratio of the transistors has a greater impact on the current flowing through the transistors. Therefore, the current IC1 flowing through the first transistor Q1 is less than the current IC2 flowing through the second transistor Q2. Since the resistance values ​​of the fifteenth resistor R15 and the sixteenth resistor R16 are equal, the voltage drop across the fifteenth resistor R15 is The gate voltage of the ninth MOS tube M9 connected to the fifteenth resistor R15 is greater than the gate voltage of the tenth MOS tube M10 connected to the sixteenth resistor R16. Since the source voltages of the ninth MOS tube M9 and the tenth MOS tube M10 are equal, the source-gate voltage difference of the ninth MOS tube M9 is less than the source-gate voltage difference of the tenth MOS tube M10, so that the current flowing through the tenth MOS tube M10 is greater than the current flowing through the ninth MOS tube M9. At this time, since the resistance values ​​of the seventeenth resistor R17 and the eighteenth resistor R18 are equal, the voltage drop across the eighteenth resistor R18 is greater than the voltage drop across the seventeenth resistor R17. Therefore, the eleventh MOS tube M The source voltage of the twelfth MOS tube M11 is less than the source voltage of the twelfth MOS tube M12, so the gate-source voltage difference of the twelfth MOS tube M12 is less than the gate-source voltage difference of the eleventh MOS tube M11, and thus the current flowing through the eleventh MOS tube M11 is greater than the current flowing through the twelfth MOS tube M12. Since the thirteenth controllable current and the fourteenth controllable current are equal, it can be obtained that the current flowing into point C = the fourteenth controllable current = the current flowing through the eleventh MOS tube M11, and the current flowing out of point C = the current flowing through the twelfth MOS tube M12. Therefore, the current flowing into point C is greater than the current flowing out of point C, and the voltage at point C is pulled up, that is, the gate voltage of the thirteenth MOS tube M13 is pulled up to the voltage VIN, and at the same time When the voltage VIN is much larger than the voltage difference VBE between the base and the emitter of the third transistor Q3 + the voltage difference VBE between the base and the emitter of the fourth transistor Q4 + the gate-source voltage difference VGS of the thirteenth MOS transistor M13, the thirteenth MOS transistor M13 is turned on. At this time, the internal current IM is generated in the branch composed of the thirteenth MOS transistor M13, the third transistor Q3, the nineteenth resistor R19, the twentieth resistor R20, the twenty-first resistor R21 and the fourth transistor Q4. As the internal current IM increases,The base voltage of the first transistor Q1 and the base voltage of the second transistor Q2 are gradually increased, and because the voltage drop across the twentieth resistor R20 is increasing, the base voltage of the first transistor Q1 is increasing relative to the base voltage of the second transistor Q2. Therefore, the voltage difference VBE1 between the base and emitter of the first transistor Q1 is increasing relative to the voltage difference VBE2 between the base and emitter of the second transistor Q2. In addition, the influence of the voltage difference between the base and emitter of the transistor on the current is greater than the influence of the number of transistors connected in parallel on the current. Therefore, it can be obtained at this time that as the internal current IM increases, the current IC1 flowing through the first transistor Q1 gradually becomes greater than the current IC2 flowing through the second transistor Q2. At this time, combined with the above analysis, it can be seen that the current flowing into C is less than the current flowing out from point C. The voltage at point C is pulled down, that is, the gate voltage of the thirteenth MOS tube M13 is pulled down. At this time, by designing the parameters of the eighteenth resistor R18 and the current flowing through the twelfth MOS tube M12, the terminal voltage of the eighteenth resistor R18 is lower than the voltage difference VBE between the base and the emitter of the third transistor Q3 + the voltage difference VBE between the base and the emitter of the fourth transistor Q4 + the gate-source voltage difference VGS of the thirteenth MOS tube M13. Therefore, when the voltage at point C is pulled down, the thirteenth MOS tube M13 is turned off, the internal current IM decreases, and the base voltage of the first transistor Q1 and the base voltage of the second transistor Q2 are both reduced. Afterwards, when the current IC1 flowing through the first transistor Q1 is less than the current IC2 flowing through the second transistor Q2, the circuit enters the next cycle.

[0060] From the above records, it can be seen that when the power supply circuit enters a stable working state, the current IC1 flowing through the first transistor Q1 is equal to the current IC2 flowing through the second transistor Q2. At the same time, the power supply circuit structure diagram shows that Figure 4 It can be seen that VBE1=VBE2+VR20, where VR20 is the voltage difference across the twentieth resistor R20, and , at this time, combined with the transistor current formula, we can get: , it can be seen that the internal current IM , where Vt is the thermal voltage and R20 is the resistance of the twentieth resistor.

[0061] Therefore, the voltage of the first low-voltage power supply of the power supply circuit is expressed by the following formula: ; The output voltage of the second low-voltage power supply is expressed by the following formula: ; At this time, first, the third transistor Q3 and the fourth transistor Q4 are designed to be transistors with exactly the same parameters, so it can be obtained that VBE3 of the third transistor Q3 = VBE4 of the fourth transistor Q4, recorded as VBE, therefore, , Secondly, the VBE of the transistor is a negative temperature parameter, and the thermal voltage Vt of the transistor is a positive temperature parameter. Therefore, by matching the parameters of K, R19, R20 and R21 appropriately, the output voltage V1 of the first low-voltage power supply and the voltage V2 of the second low-voltage power supply are not affected by temperature, so that the voltage generator outputs two voltages and improves the accuracy of the output voltage.

[0062] In addition, when the power supply circuit is just powered on, the current in the first transistor Q1 and the second transistor Q2 is small, so at this time, the voltage drop across the fifteenth resistor R15 and the sixteenth resistor R16 is small. At this time, if the first diode D1 does not exist, the fifteenth resistor R15 and the sixteenth resistor R16 are directly connected to the external high-voltage power supply, then the terminal voltage of the fifteenth resistor R15 and the sixteenth resistor R16 away from the external high-voltage power supply will be large, close to the voltage VIN of the external high-voltage power supply, thereby causing the gate voltage of the ninth MOS tube M9 and the tenth MOS tube M10 to be large, so that the ninth MOS tube M9 and the tenth MOS tube M10 cannot be turned on; therefore, at this time, the first diode D1 is set in the power supply circuit, so that the terminal voltage of the fifteenth resistor R15 and the sixteenth resistor R16 close to the external high-voltage power supply is VIN-VD1, wherein VD1 is the forward conduction voltage drop of the first diode D1; and by the attached Figure 4 It can be known that the twelfth controllable current source G12 pulls up the source voltage of the ninth MOS tube M9 and the tenth MOS tube M10 to the voltage VIN of the external high-voltage power supply. Therefore, when the gate voltage of the ninth MOS tube M9 and the tenth MOS tube M10 is less than VIN-VGS, they can be smoothly turned on. It can be known from the relevant technology that the forward conduction voltage drop of the diode is slightly less than the gate-source voltage difference VGS after the MOS tube is turned on. Therefore, when the first diode D1, the fifteenth resistor R15 and the sixteenth resistor R16 are provided in the circuit, it can be basically ensured that the fifteenth resistor R15 and the sixteenth resistor R16 are far away from the terminal voltage of the external high-voltage power supply, that is, the gate voltage of the ninth MOS tube M9 and the tenth MOS tube M10 is less than VIN-VGS, so that the ninth MOS tube M9 and the tenth MOS tube M10 are smoothly turned on.

[0063] At the same time, in order to further ensure that the ninth MOS tube M9 and the tenth MOS tube M10 are smoothly turned on, N diodes can be connected in series in the branch of the first diode D1, thereby further ensuring that the gate voltage of the ninth MOS tube M9 and the tenth MOS tube M10 is less than VIN-VGS.

[0064] When the power circuit enters a stable working state, the voltage V2 of the second low voltage power supply output by the power circuit is set to be greater than VGS, thereby ensuring that the fifteenth MOS tube M15 is in an off state and will not affect the magnitude of the two voltages output by the power circuit.

[0065] The first low-voltage power supply output end of the power supply circuit is connected to the external high-voltage power supply through the thirteenth MOS transistor M13. Therefore, the current outputted by the first low-voltage power supply output end to the current limiting circuit and the output circuit all comes from the external high-voltage power supply. The current outputted to the current limiting circuit and the output circuit does not affect the magnitude of the internal current IM. Therefore, the first low-voltage power supply output end has current capacity. The second low-voltage power supply output end is connected to the external high-voltage power supply through the nineteenth resistor R19, the third transistor Q3 and the thirteenth MOS transistor M13. Since the twentieth resistor R20, the twenty-first resistor R21 and the fourth transistor Q4 are regulated by the circuit, the current flowing through the above three devices remains unchanged. Therefore, at this time, if the second low-voltage power supply output end outputs current to the current limiting circuit and the output circuit, the internal current IM will inevitably increase, thereby making the voltage V1 of the first low-voltage power supply too large. Therefore, the second low-voltage power supply output end does not have current capacity.

[0066] In the present embodiment, only one power supply circuit is provided in the power supply circuit to generate two low-voltage power supplies that are not affected by temperature and have high precision, thereby improving the output voltage precision and current limiting precision of the power supply circuit and reducing the volume of the power supply circuit; at the same time, the power supply circuit can provide a first low-voltage power supply with current capability and a second low-voltage power supply without current capability, and after reasonable combination with the current limiting circuit and the output circuit, the above-mentioned power supply circuit with current limiting function can be obtained.

[0067] Although the exemplary embodiments and their advantages have been described in detail, those skilled in the art may make various changes, substitutions and modifications to these embodiments without departing from the spirit of the present invention and the scope of protection defined by the appended claims, and such modifications and variations all fall within the scope defined by the appended claims. For other examples, those of ordinary skill in the art should readily understand that the order of the process steps may be changed while maintaining the scope of protection of the present invention.

[0068] In addition, the scope of application of the present invention is not limited to the processes, mechanisms, manufactures, material compositions, means, methods and steps of the specific embodiments described in the specification. From the disclosure of the present invention, it will be easily understood by those skilled in the art that the processes, mechanisms, manufactures, material compositions, means, methods or steps that currently exist or will be developed in the future, which perform substantially the same functions as the corresponding embodiments described in the present invention or obtain substantially the same results, can be applied according to the present invention. Therefore, the claims attached to the present invention are intended to include these processes, mechanisms, manufactures, material compositions, means, methods or steps within their scope of protection.

Claims

1. A power supply circuit with current limiting function, characterized in that: include: A power supply circuit, used to simultaneously generate a first low-voltage power supply and a second low-voltage power supply after an external power supply is connected; A first current source circuit, configured to operate according to a first low-voltage power supply; A current limiting circuit is used to conduct according to an external power supply, two low-voltage power supplies and a first current source circuit that is conducting and is in a first working state; The output circuit is used to stabilize the voltage at the output end of the power supply circuit at a first preset value according to the external power supply, the two low-voltage power supplies and the first current source circuit that is turned on and is in a second working state; When the output current of the output circuit is greater than the second preset value, the current limiting circuit switches from the first working state to the third working state according to the second low-voltage power supply and the current in the output circuit that is greater than the second preset value, and switches the output circuit from the second working state to the fourth working state, and the output current of the output circuit decreases; when the output current of the output circuit is less than the second preset value, the current limiting circuit returns to the first working state according to the second low-voltage power supply and the current in the output circuit that is less than the second preset value, and returns the output circuit to the second working state, stabilizing the voltage at the output end of the power supply circuit at the first preset value.

2. The power supply circuit with current limiting function according to claim 1, characterized in that: The power supply circuit has a first end connected to an external power supply, a second end connected to ground, a third end connected to a first end of the first current source circuit, a first end of the current limiting circuit and a first end of the output circuit, and a fourth end of the power supply circuit connected to a second end of the current limiting circuit and a second end of the output circuit; The first current source circuit has a second end connected to the third end of the current limiting circuit and the third end of the output circuit, and a third end connected to ground; The current limiting circuit has a fourth end connected to the external power supply, a fifth end connected to the fourth end of the output circuit, a sixth end connected to the fifth end of the output circuit, and a seventh end connected to ground; The output circuit has a sixth end connected to an external power source, a seventh end connected to an output end of a power supply circuit, and an eighth end connected to ground.

3. The power supply circuit with current limiting function according to claim 1, characterized in that: The first current source circuit includes: a first current source and a first resistor, one end of the first current source is connected to one end of the first resistor, the third end of the current limiting circuit and the third end of the output circuit, the other end of the first current source is grounded, and the other end of the first resistor is connected to the third end of the power supply circuit, the first end of the current limiting circuit and the first end of the output circuit.

4. The power supply circuit with current limiting function according to claim 1, characterized in that: The current limiting circuit includes: a first controllable current source, a second controllable current source, a fifth controllable current source, a seventh controllable current source, a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a second resistor, a fourth resistor and a tenth resistor; The positive control terminal and the input terminal of the first controllable current source are connected to the positive control terminal and the input terminal of the second controllable current source, the first terminal of the third switch tube, the third terminal of the power circuit, the first terminal of the first current source circuit and the first terminal of the output circuit; the negative control terminal of the first controllable current source is connected to the negative control terminal of the second controllable current source, the second terminal of the first current source circuit and the third terminal of the output circuit; the output terminal of the first controllable current source is connected to the first terminal of the first switch tube and the first terminal of the second switch tube; the second terminal of the first switch tube is connected to the fourth terminal of the power circuit and the second terminal of the output circuit; the third terminal of the first switch tube is connected to one terminal of the second resistor and the positive control terminal of the fifth controllable current source; the second terminal of the second switch tube is connected to the output terminal of the seventh controllable current source and one terminal of the tenth resistor; the third terminal of the second switch tube and the other terminal of the second resistor are grounded; The output end of the second controllable current source is connected to the second end of the third switch tube and the input end of the fifth controllable current source, the third end of the third switch tube is connected to the first end of the fourth switch tube and one end of the fourth resistor, the negative control end and the output end of the fifth controllable current source, the other end of the fourth resistor, the other end of the tenth resistor and the second end of the fourth switch tube are grounded, the third end of the fourth switch tube is connected to the fourth end of the output circuit, the positive control end and the input end of the seventh controllable current source are connected to an external power supply, and the negative control end of the seventh controllable current source is connected to the fifth end of the output circuit.

5. The power supply circuit with current limiting function according to claim 4, characterized in that: The current limiting circuit also includes a third resistor, one end of the third resistor is connected to the third end of the second switch tube, the other end of the third resistor is grounded, and the resistance of the third resistor is equal to the resistance of the second resistor.

6. The power supply circuit with current limiting function according to claim 4, characterized in that: The output circuit includes a third controllable current source, a fourth controllable current source, a sixth controllable current source, an eighth controllable current source, a fifth switch tube, a sixth switch tube, a seventh switch tube, a fifth resistor, a seventh resistor, an eighth resistor, a ninth resistor and an eleventh resistor; The positive control terminal and the input terminal of the third controllable current source are connected to the positive control terminal and the input terminal of the fourth controllable current source, the third terminal of the power supply circuit, the first terminal of the first current source circuit and the first terminal of the current limiting circuit; the negative control terminal of the third controllable current source is connected to the negative control terminal of the fourth controllable current source, the second terminal of the first current source circuit and the third terminal of the current limiting circuit; the output terminal of the third controllable current source is connected to the first terminal of the fifth switch tube and the first terminal of the sixth switch tube; the second terminal of the fifth switch tube is connected to the fourth terminal of the power supply circuit and the second terminal of the current limiting circuit; the third terminal of the fifth switch tube is connected to one terminal of the fifth resistor and the positive control terminal of the sixth controllable current source; the second terminal of the sixth switch tube is connected to one terminal of the ninth resistor and one terminal of the eleventh resistor; the third terminal of the sixth switch tube and the other terminal of the fifth resistor are grounded; The output end of the fourth controllable current source is connected to the first end of the seventh switch tube, the input end of the sixth controllable current source and the fifth end of the current limiting circuit, the second end of the seventh switch tube is connected to one end of the eighth resistor, the negative control end of the eighth controllable current source and the sixth end of the current limiting circuit, the third end of the seventh switch tube is connected to one end of the seventh resistor, the negative control end and the output end of the sixth controllable current source, the other end of the seventh resistor and the other end of the eleventh resistor are grounded, the other end of the eighth resistor is connected to the positive control end and the input end of the eighth controllable current source and the external power supply, and the output end of the eighth controllable current source is connected to the other end of the ninth resistor and the output end of the power supply circuit.

7. The power supply circuit with current limiting function according to claim 6, characterized in that: The third end of the power supply circuit outputs a first low-voltage power supply, and the fourth end of the power supply circuit outputs a second low-voltage power supply. The voltage of the first low-voltage power supply is greater than the voltage of the second low-voltage power supply, and the difference between the voltage of the first low-voltage power supply and the voltage of the second low-voltage power supply is greater than the threshold voltage of the first switch tube and the fifth switch tube.

8. The power supply circuit with current limiting function according to claim 6, characterized in that: The output circuit further includes a sixth resistor, one end of the sixth resistor is connected to the third end of the sixth switch tube, the other end of the sixth resistor is grounded, and the resistance value of the sixth resistor is the same as the resistance value of the fifth resistor.

9. The power supply circuit with current limiting function according to claim 6, characterized in that: The ratio of the first controllable current generated by the first controllable current source to the second controllable current generated by the second controllable current source is two to one, and the ratio of the third controllable current generated by the third controllable current source to the fourth controllable current generated by the fourth controllable current source is two to one.

10. The power supply circuit with current limiting function according to claim 6, characterized in that: The power supply circuit also includes: an isolation circuit, a first end of the isolation circuit connected to one end of the eighth resistor, the negative control end of the seventh controllable current source and the negative control end of the eighth controllable current source, a second end of the isolation circuit connected to the third end of the power supply circuit, the first end of the first current source circuit, the first end of the current limiting circuit and the first end of the output circuit, a third end of the isolation circuit connected to the second end of the seventh switch tube, a fourth end of the isolation circuit connected to the output end of the seventh controllable current source, a fifth end of the isolation circuit connected to the second end of the second switch tube and one end of the tenth resistor, a sixth end of the isolation circuit grounded, and a seventh end of the isolation circuit connected to the output end of the eighth controllable current source, the other end of the ninth resistor and the output end of the power supply circuit.

11. The power supply circuit with current limiting function according to claim 10, characterized in that: The isolation circuit includes an eighth switch tube, a ninth controllable current source, a twelfth resistor and a thirteenth resistor; The first end of the eighth switch tube is connected to one end of the eighth resistor, the negative control end of the seventh controllable current source and the negative control end of the eighth controllable current source. The second end of the eighth switch tube is connected to the third end of the power supply circuit, the first end of the first current source circuit, the first end of the current limiting circuit and the first end of the output circuit. The third end of the eighth switch tube is connected to the second end of the seventh switch tube. The input end of the ninth controllable current source is connected to the output end of the seventh controllable current source. The output end of the ninth controllable current source is connected to the second end of the second switch tube and one end of the tenth resistor. The negative control end of the ninth controllable current source is connected to one end of the thirteenth resistor and one end of the twelfth resistor. The other end of the thirteenth resistor is grounded. The positive control end of the ninth controllable current source is connected to the other end of the twelfth resistor, the output end of the eighth controllable current source, the other end of the ninth resistor and the output end of the power supply circuit.

12. The power supply circuit with current limiting function according to claim 11, characterized in that: The current capability of the ninth controllable current source is greater than the current capability of the seventh controllable current source.

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