CN113258766B

CN113258766B - Current-limiting tracking chip, switching power supply circuit and switching power supply system

Info

Publication number: CN113258766B
Application number: CN202110707783.7A
Authority: CN
Inventors: 陈博; 刘彬; 李瑞平
Original assignee: Shanghai Xinlong Semiconductor Technology Co ltd Nanjing Branch
Current assignee: Shanghai Xinlong Semiconductor Technology Co ltd Nanjing Branch
Priority date: 2021-06-25
Filing date: 2021-06-25
Publication date: 2021-10-01
Anticipated expiration: 2041-06-25
Also published as: CN113258766A

Abstract

The invention provides a current-limiting tracking chip, a switching power supply circuit and a switching power supply system, wherein the current-limiting tracking chip comprises a power tube, a logic controller and a current-limiting tracking module; the current-limiting tracking module comprises a constant current source unit, a first comparison unit, a second comparison unit, a timer and a counter. In the power-on starting stage of the current-limiting tracking chip, the power supply current and the power supply voltage input to the current-limiting tracking chip by the power supply module are continuously detected, and the reference voltage provided by the constant current source unit is continuously adjusted, so that the first trigger signal and the second trigger signal are alternately triggered to enable the current-limiting tracking chip to continuously perform current-limiting protection, thereby being beneficial to continuously establishing the power supply voltage, further realizing the normal starting of the current-limiting tracking chip, further avoiding the situation that the power supply voltage provided is continuously pulled down due to the triggering of the current-limiting current value of the power supply module, and further avoiding the situation that the switching power supply circuit cannot establish a normal input-output logic relationship.

Description

Current-limiting tracking chip, switching power supply circuit and switching power supply system

Technical Field

The invention relates to the technical field of power supply chips, in particular to a current-limiting tracking chip, a switching power supply circuit and a switching power supply system.

Background

In the field of switching power supplies, power supply modules generally have certain current capacity and rated output power, and in order to ensure safe and stable operation of the power supply modules, the power supply modules have current limiting measures, and the purpose of protecting the power supply modules is achieved by limiting the maximum value of the power supply current of the power supply modules; when the current value output by the power supply module after being pulled is larger than the current value provided by the power supply module, the power supply module enters a current-limiting state, which is embodied as the voltage drop of the output end of the power supply module.

In the field of switching power supplies, a chip is generally required to have a wider operating voltage range and a larger output power so as to adapt to a wider input voltage range and meet diversified load requirements. The chip is compatible with a lower input voltage, the threshold voltage of the chip triggering undervoltage protection function needs to be designed to be lower than the lowest working voltage of the chip (for example, the working voltage range of the chip is 4-40V, and the threshold voltage of the undervoltage protection function is designed to be 3.3V), at the initial stage of power-on starting of a switch power supply circuit (the switch power supply circuit comprises the chip) with a load (carrying a load module), after the input voltage of the switch power supply circuit is slightly higher than the threshold voltage of the chip triggering the undervoltage protection function, the chip starts to work, at the moment, the power supply module needs to simultaneously supply power to an input capacitor and an output capacitor of the switch power supply circuit and an external load module, but because the power supply module is still in the process of continuously establishing a normal output logic relationship at the moment, the input voltage of the switch power supply circuit is lower, and the input current of the switch power supply circuit at the initial stage of power-on is extremely large, the current-limiting current value of the power supply module is easily triggered, so that the input voltage of the chip is continuously reduced and cannot normally reach a preset value, the output voltage of the switching power supply circuit cannot be normally established, and the switching power supply circuit fails to be started. As shown in fig. 1, fig. 1 is a schematic diagram of a plurality of switching power supply circuits commonly connected to the same power supply module after being loaded, and similar to the situation of fig. 1, the output voltage logic relationship of the switching power supply circuits cannot be normally established, and the power supply module cannot configure normal output power exceeding several times to meet the input current required at the initial power-on stage of the switching power supply circuits after being loaded, which is not favorable for resource optimization configuration and is easy to cause excess of the output power margin of the power supply module at the working stage.

The reason for this is that a large current is required for the initial start-up of the switching power supply circuit after the load is applied to the switching power supply circuit at the time of low voltage input. In view of this, how to track and set the current-limiting current values of the chip in the startup stage, the normal operation stage, and other stages, improve the on-load startup characteristic of the switching power supply circuit, and ensure that the logic relationship of the output voltage can be normally established when the chip is started in various application scenarios, and how to configure more on-load switching power supply circuits for the power supply module under the limited output power supply power resource becomes an urgent problem to be solved by designers, so it becomes more important to study and design the tracking work of the current-limiting current of the chip.

Disclosure of Invention

The invention aims to provide a current-limiting tracking chip, a switching power supply circuit and a switching power supply system, and aims to solve the problem that when the existing current-limiting tracking chip is compatible with lower power supply voltage and the switching power supply circuit is at the initial stage of power-on starting, the current-limiting value of a power supply module is easy to trigger, so that the power supply voltage input to the switching power supply circuit is continuously pulled down, and the switching power supply circuit cannot establish a normal input-output logic relationship; the second purpose is to solve the problem that the output power margin of the power supply module is excessive in the working stage due to the existing switching power supply system.

To solve the above technical problem, according to an aspect of the present invention, there is provided a current-limiting tracking chip applied to a switching power supply circuit, the current-limiting tracking chip including: the power tube, the logic control module and the current-limiting tracking module;

the input end of the power tube is used for acquiring the power supply voltage input to the current-limiting tracking chip; the output end of the power tube is connected to the output end of the current-limiting tracking chip; the control end of the power tube is accessed to the logic control module;

the current-limiting tracking module comprises a constant current source unit, a first comparison unit, a second comparison unit, a timer and a counter;

the constant current source unit is used for providing a reference voltage for the first comparison unit; the real-time value of the reference voltage comprises a first expected value and a second expected value, and the first expected value is larger than the second expected value;

the first comparison unit is used for acquiring the corresponding sampling voltage after acquiring the power supply current input to the current-limiting tracking chip in real time, and then outputting a first trigger signal to the logic control module according to the comparison value of the sampling voltage and the reference voltage; when the sampling voltage is greater than the reference voltage, the first trigger signal is valid, the logic control module controls the constant current source unit to adjust a real-time value of the reference voltage from one of the first expected value and the second expected value to the other, and the logic control module outputs a current limiting signal to control the power tube to be cut off;

the second comparison unit is used for acquiring the power supply voltage at the moment when the first trigger signal is effective; the second comparison unit is further configured to detect the power supply voltage after the time when the first trigger signal is valid in real time until it is detected that a difference between the power supply voltage after the time when the first trigger signal is valid and the power supply voltage at the time when the first trigger signal is valid is greater than an expected voltage difference, and the second comparison unit outputs a second trigger signal to drive the logic control module to control the power tube to be turned on and off at an expected frequency;

the logic control module is used for controlling the timer to start countdown according to expected time length, and the timer is used for sending a counting signal to the counter after the countdown is finished so that the counter records the counting signal once; the counter is used for sending a third trigger signal to the logic control module when the number of times of recording the counting signal reaches an expected number of times in an accumulated mode so as to drive the logic control module to control the power tube to be switched on and switched off under the expected frequency, the constant current source unit latches a real-time value of the reference voltage as a first expected value, and the timer stops counting down;

when the first trigger signal is valid, the logic control module controls the timer to count down, suspend and reset; the logic control module is also used for controlling the timer to reset after one countdown is finished; the counter is used for resetting after acquiring the current limiting signal.

Optionally, the power tube includes a PMOS tube, the input end of the power tube is a source electrode of the PMOS tube, the output end of the power tube is a drain electrode of the PMOS tube, and the control end of the power tube is a gate electrode of the PMOS tube.

Optionally, the first comparing unit includes a first resistor, a second resistor, a third resistor, a fourth resistor, an amplifier, and a first comparator; the first end of the first resistor is used for being connected with the input end of an external sampling resistor; the second end of the first resistor is connected with the first end of the second resistor and is connected with the non-inverting input end of the amplifier in a common access mode; the second end of the second resistor is connected to the output end of the amplifier; the first end of the third resistor is used for being connected with the output end of the sampling resistor; the second end of the third resistor is connected with the first end of the fourth resistor and is commonly connected to the inverting input end of the amplifier; a second end of the fourth resistor is grounded; the non-inverting input end of the first comparator is connected with the output end of the amplifier, the inverting input end of the first comparator obtains the reference voltage, the output end of the first comparator is connected with the logic control module, and the output end of the first comparator is configured as the output end of the first comparing unit.

Optionally, the second comparing unit includes a fifth resistor, a sixth resistor, a first switch, a second switch, a third switch, a fourth switch, a diode, an energy storage capacitor, and a second comparator; the first end of the fifth resistor is used for acquiring the power supply voltage, and the second end of the fifth resistor is grounded through the sixth resistor; the first end of the first switch and the first end of the second switch are connected to the second end of the fifth resistor together; the second end of the first switch is used for being connected with the input end of the diode, and the output end of the diode is connected with the non-inverting input end of the second comparator; the second end of the second switch is used for realizing the connection with the inverting input end of the second comparator through the third switch, and the common end formed by the second switch and the third switch is grounded through the energy storage capacitor; the output end of the second comparator is connected with the logic control module through the fourth switch;

when the first trigger signal is valid, the second comparing unit is switched from a first switching state to a second switching state, and after the logic control module receives a second trigger signal, the second comparing unit is switched from the second switching state to the first switching state; when the second comparing unit is in the first switch state, the first switch, the third switch and the fourth switch are all opened, and the second switch is closed; when the second comparing unit is in the second switch state, the first switch, the third switch and the fourth switch are all closed, and the second switch is opened.

Optionally, the expected voltage difference is determined according to a resistance value of the fifth resistor, a resistance value of the sixth resistor, and a voltage drop of the diode.

Optionally, a ratio of the first expected value to the second expected value is greater than or equal to 1.5 and less than or equal to 2.

Optionally, the current-limiting tracking chip includes an under-voltage protection module, and the under-voltage protection module is configured to drive the logic control module to control the power tube to be turned off when the power supply voltage is less than a minimum start voltage of the current-limiting tracking chip.

Based on another aspect of the present invention, the present invention further provides a switching power supply circuit, which includes a first capacitor circuit, a sampling resistor, a freewheeling diode, an inductor, a second capacitor circuit, and the current-limiting tracking chip as described above; the input end and the output end of the sampling resistor are simultaneously connected to the first comparison unit, and the first comparison unit is used for sampling the power supply current according to the sampling resistor; the first end of the first capacitor circuit is connected with the input end of the sampling resistor, and the second end of the first capacitor circuit is grounded; the output end of the current-limiting tracking chip is connected with the output end of the freewheeling diode and then is connected to the first end of the inductor together; the input end of the freewheeling diode is grounded; the second end of the inductor is grounded through the second capacitor circuit; when the power tube is conducted, the first capacitor circuit, the sampling resistor, the power tube, the inductor and the second capacitor circuit form a first loop; when the power tube is cut off, the inductor, the second capacitor circuit and the freewheeling diode form a second loop.

Optionally, the switching power supply circuit is used for driving an external load module to operate; the switching power supply circuit comprises a sampling resistor, and the sampling resistor is used for sampling the load current of the load module in real time; the current-limiting tracking chip comprises a voltage feedback module, wherein the voltage feedback module is used for generating feedback sampling voltage according to the real-time sampling of the load current by the sampling resistor, and further forming a feedback signal to a logic control module according to the feedback sampling voltage so as to drive the logic control module to adjust the duty ratio of the power tube.

Based on still another aspect of the present invention, the present invention further provides a switching power supply system, which includes a power supply module, a plurality of switching power supply circuits as described above, and a plurality of load modules corresponding to the switching power supply circuits one to one; and the switching power supply circuit is connected to the power supply module after the corresponding load module is loaded.

In summary, in the current-limiting tracking chip, the switching power supply circuit and the switching power supply system provided by the present invention, the current-limiting tracking chip includes a power transistor, a logic controller and a current-limiting tracking module; the current-limiting tracking module comprises a constant current source unit, a first comparison unit, a second comparison unit, a timer and a counter. In the power-on starting stage of the current-limiting tracking chip, the power supply current and the power supply voltage input to the current-limiting tracking chip by the power supply module are continuously detected, and the reference voltage provided by the constant current source unit is continuously adjusted, so that the first trigger signal and the second trigger signal are alternately triggered to enable the current-limiting tracking chip to continuously perform current-limiting protection, thereby being beneficial to continuously establishing the power supply voltage, further realizing the normal starting of the current-limiting tracking chip, further avoiding the situation that the power supply voltage provided is continuously pulled down due to the triggering of the current-limiting current value of the power supply module, and further avoiding the situation that the switching power supply circuit cannot establish a normal input-output logic relationship. In addition, after a plurality of switching power supply circuits are loaded, the same power supply module is connected, the starting process of the current-limiting tracking chip of each switching power supply circuit can be optimized simultaneously, the purpose of maximizing the limited output power supply resource utilization rate of the power supply module is achieved, and the surplus of output power is avoided.

Drawings

It will be appreciated by those skilled in the art that the drawings are provided for a better understanding of the invention and do not constitute any limitation to the scope of the invention.

Fig. 1 is a schematic diagram of a plurality of switching power supply circuits commonly connected to the same power supply module after being loaded.

Fig. 2 is a schematic diagram of a switching power supply circuit according to an embodiment of the invention.

FIG. 3 is a diagram of a current-limiting tracking chip according to an embodiment of the invention.

Fig. 4 is a schematic diagram of a current limit tracking module according to an embodiment of the invention.

In the drawings:

100-current limiting tracking chip; 200-a power supply module; 300-a load module;

110-a logic control module; 120-a current limit tracking module; 130-undervoltage protection module; 140-a voltage feedback module; 121-a first comparing unit; 1211-amplifier; 1212-a first comparator; 122-a second comparison unit; 1220-a second comparator; 123-constant current source unit; 1230-constant current source; 124-a timer; 125-a counter;

p1-power input pin; p2-input voltage sampling pin; P3-GND pin; p4-power output pin; p5-feedback signal input pin;

c1 — first capacitance; c2 — second capacitance; c3-energy storage capacitor; rx-sampling resistance; ry-sampling resistance; r1 — first resistance; r2 — second resistance; r3 — third resistance; r4-fourth resistor; r5-fifth resistor; r6-sixth resistance; r7 — seventh resistor; d1-freewheeling diode; d2-diode; an L-inductor; q-power tube; k1 — first switch; k2 — second switch; k3 — third switch; k4-fourth switch;

VA — first reference voltage; VB-first sample voltage; VC-a current limit signal; VD-second sampling voltage; VE-a second reference voltage; VF-third trigger signal; VG-count signal; VH-first trigger signal; VP-second trigger signal.

Detailed Description

To further clarify the objects, advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. It is to be noted that the drawings are in greatly simplified form and are not to scale, but are merely intended to facilitate and clarify the explanation of the embodiments of the present invention. Further, the structures illustrated in the drawings are often part of actual structures. In particular, the drawings may have different emphasis points and may sometimes be scaled differently.

As used in this application, the singular forms "a", "an" and "the" include plural referents, the term "or" is generally employed in a sense including "and/or," the terms "a" and "an" are generally employed in a sense including "at least one," the terms "at least two" are generally employed in a sense including "two or more," and the terms "first", "second" and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicit to the number of technical features indicated. Thus, features defined as "first", "second" and "third" may explicitly or implicitly include one or at least two of the features, "one end" and "the other end" and "proximal end" and "distal end" generally refer to the corresponding two parts, which include not only the end points, but also the terms "mounted", "connected" and "connected" should be understood broadly, e.g., as a fixed connection, as a detachable connection, or as an integral part; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. Furthermore, as used in the present invention, the disposition of an element with another element generally only means that there is a connection, coupling, fit or driving relationship between the two elements, and the connection, coupling, fit or driving relationship between the two elements may be direct or indirect through intermediate elements, and cannot be understood as indicating or implying any spatial positional relationship between the two elements, i.e., an element may be in any orientation inside, outside, above, below or to one side of another element, unless the content clearly indicates otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the prior art, a conventional chip generally realizes the undervoltage protection function of the chip through an enabling pin and then through an undervoltage protection circuit arranged by a set resistor and a voltage stabilizing diode, and the main principle is that the chip does not work when the input voltage of the chip is low, and works after the input voltage is established, but the chip is limited by the working level state of the enabling pin of the chip, and the selected voltage stabilizing diode is determined, so the lowest input voltage of the chip is determined; in addition, the selection of the regulated voltage value of the voltage stabilizing diode cannot be too low, otherwise, the meaning of undervoltage protection is lost, and the initial stage of the chip on-load starting is still caused, and the current limiting current value of the power supply module, which is easy to trigger, causes the input voltage of the chip after the chip is on-load to be continuously pulled down, so that the normal input and output logic relationship cannot be established.

The core idea of the invention is as follows: in the initial stage of the chip load starting, the chip works alternatively with a small current (the current corresponding to the second expected value of the reference voltage provided by the constant current source unit) and a normal current (the current corresponding to the first expected value of the reference voltage provided by the constant current source unit) by continuously detecting the input current provided by the power supply module for the chip and continuously adjusting the threshold voltage (namely the reference voltage provided by the constant current source unit) arranged in the chip according to the change of the input current; after the input voltage of the chip (namely the power supply voltage provided by the power supply module for the chip) is completely established, maintaining the reference voltage provided by the constant current source unit as a first expected value to continuously complete the loading start of the chip; after the chips are started, the reference voltage provided by the constant current source unit is locked at a first expected value, so that the starting process is optimized after a plurality of chips are connected into the same power supply module in a loading mode, and the phenomenon that the chips cannot enter a normal working state after being started repeatedly in the loading mode is avoided.

Based on the core idea of the present invention, the present embodiment provides a current-limiting tracking chip, a switching power supply circuit and a switching power supply system according to the above chip, and aims to solve the problem that when the current-limiting tracking chip is compatible with a lower power supply voltage and the switching power supply circuit is at the initial stage of power-on start, the current-limiting value of the power supply module itself is easily triggered to cause the power supply voltage input to the switching power supply circuit to be continuously pulled down, so that the switching power supply circuit cannot establish a normal input/output logic relationship; the second purpose is to solve the problem that the output power margin of the power supply module is excessive in the working stage due to the existing switching power supply system.

The following describes the current-limiting tracking chip and the switching power supply circuit of the present embodiment with reference to the drawings.

As shown in fig. 2, fig. 2 is a schematic diagram of a switching power supply circuit according to an embodiment of the present invention, where the switching power supply circuit provided in this embodiment includes a first capacitor circuit, a sampling resistor Rx, a freewheeling diode D1, an inductor L, a second capacitor circuit, a current-limiting tracking chip 100, and a sampling resistor Ry; as shown in fig. 3, fig. 3 is a schematic diagram of a current-limiting tracking chip according to an embodiment of the invention, a power tube Q is disposed in the current-limiting tracking chip 100, the current-limiting tracking chip 100 has five pins, which are a power input terminal pin P1, an input voltage sampling pin P2, a GND pin P3, a power output terminal pin P4, and a feedback signal input pin P5, an input terminal of the power tube Q is connected to a power input terminal pin P1, and an output terminal of the power tube Q is connected to a power output terminal pin P4. With reference to fig. 2 and fig. 3, an input terminal of the sampling resistor Rx is connected to the input voltage sampling pin P2, an output terminal of the sampling resistor Rx is connected to the power input terminal pin P1, a first terminal of the first capacitor circuit is connected to the input terminal of the sampling resistor Rx, and a second terminal of the first capacitor circuit is grounded; the output end (power output end pin P4) of the current-limiting tracking chip 100 is connected with the output end of the freewheeling diode D1 and then is connected to the first end of the inductor L together; the input end of the freewheeling diode D2 is grounded; the second end of the inductor L is grounded through the second capacitor circuit; when the power tube Q is turned on, the first capacitor circuit, the sampling resistor Rx, the power tube Q, the inductor L, and the second capacitor circuit form a first loop; when the power tube Q is turned off, the inductor L, the second capacitor circuit, and the freewheeling diode D1 form a second loop.

Specifically, the external power supply module 200 provides a power supply voltage and a power supply current (input current) to the switching power supply circuit, a first end of the power supply module 200 is simultaneously connected to an input end of the sampling resistor Rx and a first end of the first capacitor circuit, and a second end of the power supply module 200 is connected to a second end of the second capacitor circuit; the switching power supply circuit processes the electric energy provided by the power supply module 200 and outputs a constant current to drive the load module 300 to work, and it should be noted that the load module 300 described in this embodiment is actually an LED load, and a voltage relationship thereof may be automatically established after the constant current is obtained. The first end of load module 300 inserts inductance L's second end and the first end of second capacitor circuit simultaneously, and the second end ground connection of second capacitor circuit, sampling resistance Ry's first end be used for with load module 300's second end is connected, sampling resistance Ry's second end ground connection (sampling resistance Ry establishes ties on load module 300's second end and the circuit of ground promptly), and sampling resistance Ry is used for sampling load module 300's load current in real time. The first loop can realize normal output of the load current and supply energy to the load module 300, and the second loop can be understood as a follow current loop, so that the switch current circuit can continuously supply energy to the load module 300 after the power tube Q is cut off, and stable operation of the load module 300 is ensured. In the switching power supply circuit of this embodiment, the supply voltage provided by the power supply module 200 is filtered by the first capacitor circuit, and then is input into the current-limiting tracking chip 100 from the input terminal (power input terminal pin P1) of the current-limiting tracking chip 100, and after being processed by the current-limiting tracking chip 100, a controllable pulse-type power switch voltage is output from the power output terminal pin P4, and after being stored by the inductor L and filtered by the second capacitor circuit, a constant load current (i.e., a direct current) is output and provided to the load module 300, so as to satisfy the load-carrying characteristics of the load module 300. In this embodiment, the first capacitor circuit is the first capacitor C1 shown in fig. 2, and the second capacitor circuit is the second capacitor C2 shown in fig. 2, but in this embodiment, the first capacitor circuit may also be a parallel structure of a plurality of capacitors, and the second capacitor circuit may also be a parallel structure of a plurality of capacitors. The freewheel diode D1 in this embodiment may be a schottky diode.

Referring to fig. 3, the current-limiting tracking chip 100 provided in this embodiment is preferably a synchronous rectification power switching power supply integrated circuit chip using an advanced integrated circuit manufacturing process, and the current-limiting tracking chip 100 further includes a logic control module 110 and a current-limiting tracking module 120; the input end of the power tube Q is connected to the input end (i.e. the power input end pin P1) of the current-limiting tracking chip 100 to obtain the power supply voltage input to the current-limiting tracking chip 100; the output end of the power tube Q is connected to the output end of the current-limiting tracking chip 100; the control end of the power tube Q is connected to the logic control module 110. The logic control module 110 is configured to send a control signal to the power transistor Q to drive the power transistor Q to turn on or off.

In an exemplary embodiment, the power transistor Q is a PMOS transistor, the input terminal of the power transistor Q is a source of the PMOS transistor, the output terminal of the power transistor Q is a drain of the PMOS transistor, the control terminal of the power transistor Q is a gate of the PMOS transistor, when the control signal sent to the power transistor Q by the logic control module 110 is at a low level, the voltage of the control signal is lower than the source voltage of the power transistor Q, and the absolute value of the voltage difference between the gate and the source is greater than the minimum turn-on voltage of the power transistor Q, so the power transistor Q is turned on; when the control signal is at a high level, and the absolute value of the voltage difference between the gate and the source is smaller than the minimum turn-on voltage of the power tube Q, the power tube Q is cut off.

Further, referring to fig. 4, fig. 4 is a schematic diagram of a current limit tracking module 120 according to an embodiment of the present invention, where the current limit tracking module 120 includes a constant current source unit 123, a first comparing unit 121, a second comparing unit 122, a timer 124, and a counter 125.

In this embodiment, the constant current source unit 123 is configured to provide a reference voltage to the first comparing unit 121; the real-time value of the reference voltage includes a first expected value and a second expected value, and the first expected value is greater than the second expected value. Specifically, the constant current source unit 123 includes a seventh resistor R7 and a constant current source 1230, a first end of the constant current source 1230 is connected to the logic control module 110, a second end of the constant current source 1230 is grounded through the seventh resistor R7, and another line is led out from a common line of the seventh resistor R7 and the constant current source 1230 and is connected to the first comparing unit 121. The seventh resistor R7 samples the output current of the constant current source 1230 in real time to form a reference voltage to the first comparing unit 121, and the real-time value of the output current of the constant current source 1230 driven by the logic control module 110 is the first preset current value or the second preset current value (c:)The first preset current value is larger than the second preset current value), the first expected value of the reference voltage is obtained by sampling the first preset current value corresponding to the seventh resistor R7, and the second expected value of the reference voltage is obtained by sampling the second preset current value corresponding to the seventh resistor R7. Preferably, the ratio of the first preset current value to the second preset current value is greater than or equal to 1.5 and less than or equal to 2, and the ratio of the first expected value to the second expected value is also greater than or equal to 1.5 and less than or equal to 2, in an example, the ratio is set to 2, and then the first expected value may be V₀The second desired value is 0.5V₀. For convenience of description, the first reference voltage VA is used to represent the reference voltage provided by the constant current source unit 123.

In this embodiment, the first comparing unit 121 is configured to obtain a corresponding sampling voltage after obtaining the power supply current input to the current-limiting tracking chip 100 in real time, and further output a first trigger signal VH to the logic control module according to a comparison value between the sampling voltage and the reference voltage (a first reference voltage VA). For convenience of description, the first sampling voltage VB is hereinafter referred to as a sampling voltage obtained by the first comparing unit 121. Specifically, the first comparing unit 121 includes a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, an amplifier 1211, and a first comparator 1212; a first end of the first resistor R1 is used for being connected with an input end of an external sampling resistor Rx; the second end of the first resistor R1 is connected to the first end of the second resistor R2, and is connected to the non-inverting input terminal of the amplifier 1211 in common; a second end of the second resistor R2 is connected to an output end of the amplifier 1211; the first end of the third resistor R3 is used for being connected with the output end of the sampling resistor Rx; a second end of the third resistor R3 is connected to a first end of the fourth resistor R4, and is commonly connected to an inverting input terminal of the amplifier 1211; a second end of the fourth resistor R4 is grounded; the non-inverting input terminal of the first comparator 1212 is connected to the output terminal of the amplifier 1211, the inverting input terminal of the first comparator 1212 obtains the reference voltage (first reference voltage VA), the output terminal of the first comparator 1212 is connected to the logic control module 110, and the output terminal of the first comparator 1212 is configured as the output terminal of the first comparing unit 121. The external sampling resistor Rx samples the power supply current input to the current-limiting tracking chip 100 in real time to form a sampling value, the sampling value is provided to the amplifier 1211, the amplifier 1211 performs an amplification operation to form a first sampling voltage VB, the first sampling voltage VB is provided to the first comparator 1212, the first comparator 1212 compares the first sampling voltage VB with the first reference voltage VA, and the comparison result between the first sampling voltage VB and the first reference voltage VA is output in the form of the first trigger signal VH. It should be noted that, in the present embodiment, the amplification factor of the amplifier 1211 has been adjusted in advance, so that the first sampling voltage VB is approximately equal to the product of the real-time magnitude of the supply current and the sampling resistor Rx.

Further, when the first sampling voltage VB is greater than the first reference voltage VA, the first trigger signal VH is considered to be valid (for example, the first trigger signal VH may be considered to be valid at a high level), the logic control module 110 receives the valid first trigger signal VH and then controls the constant current source unit 123 to adjust a real-time value of the reference voltage from one of the first desired value and the second desired value to the other, and receives the valid first trigger signal VH and then outputs the current-limiting signal VC to drive the power tube Q to turn off, so that a condition is provided for continuously establishing the power supply voltage, so that the input power supply voltage continuously increases. That is, after the logic control module 110 acquires the first trigger signal VH, the real-time value of the first reference voltage VA is adjusted, if the current value is the first expected value, the real-time value is adjusted to the second expected value, and if the current value is the second expected value, the real-time value is adjusted to the first expected value, so that the first reference voltage VA is alternately changed, and the logic control module 110 turns off the power tube Q at intervals, thereby implementing the continuous triggering of the current-limiting tracking chip for current-limiting protection, and enabling the input power supply voltage to be continuously established upwards.

In this embodiment, the second comparing unit 122 is configured to obtain the power supply voltage at a time when the first trigger signal VH is valid; the second comparing unit 122 is further configured to detect the power supply voltage after the moment that the first trigger signal VH is valid in real time until it is detected that a difference between the power supply voltage after the moment that the first trigger signal VH is valid and the power supply voltage at the moment that the first trigger signal is valid is greater than an expected voltage difference, and the second comparing unit 122 outputs a second trigger signal VP to drive the logic control module 110 to control the power tube Q to be turned on and off at an expected frequency. Specifically, at the time when the first trigger signal VH is valid (this paragraph is summarized as "valid time"), the second comparing unit 122 obtains and stores the value of the supply voltage at the valid time, and thereafter the second comparing unit 122 continuously detects and obtains the value of the supply voltage after the valid time until it detects that the difference between the supply voltage at a certain subsequent time and the supply voltage at the valid time is greater than the expected voltage difference (specifically, set according to the actual situation), the second comparing unit 122 outputs the second trigger signal VP, and drives the logic control module 110 to control the power tube Q to be turned on and off at the expected frequency (for example, 120KHz, 140KHz, 150 KHz).

Further, the second comparing unit 122 includes a fifth resistor R5, a sixth resistor R6, a first switch K1, a second switch K2, a third switch K3, a fourth switch K4, a diode, an energy storage capacitor C3, and a second comparator 1220; a first end of the fifth resistor R5 is connected to the input terminal of the current-limiting tracking chip 100 (i.e. connected to the power input terminal pin P1) for obtaining the power supply voltage input to the current-limiting tracking chip 100, and a second end of the fifth resistor R5 is grounded through the sixth resistor R6; a first end of the first switch K1 and a first end of the second switch K2 are connected to a second end of the fifth resistor R5 in common; a second terminal of the first switch K1 is configured to be connected to an input terminal of the diode, and an output terminal of the diode is connected to a non-inverting input terminal of the second comparator 1220; the second terminal of the second switch K2 is connected to the inverting input terminal of the second comparator 1220 through the third switch K3, and the common terminal formed by the second switch K2 and the third switch K3 is grounded through the energy storage capacitor C3; the output end of the second comparator 1220 is used for being connected with the logic control module 110 through the fourth switch K4; when the first trigger signal VH is valid, the second comparing unit 122 is switched from the first switching state to the second switching state, and after the logic control module 110 receives the second trigger signal VP, the second comparing unit 122 is switched from the second switching state to the first switching state; when the second comparing unit 122 is in the first switching state, the first switch K1, the third switch K3 and the fourth switch K4 are all open, and the second switch K2 is closed; when the second comparing unit 122 is in the second switching state, the first switch K1, the third switch K3 and the fourth switch K4 are all closed, and the second switch K2 is open. A first terminal of the fifth resistor R5 is configured as an input terminal of the second comparing unit 122, and a terminal of the fourth switch K4, which is used for connecting with the logic control module 110, is configured as an output terminal of the second comparing unit 122.

It is further known that, when the second comparing unit 122 is in the first switching state, the energy storage capacitor C3 is continuously charged to store the sampled value of the sixth resistor R6 to the supply voltage, and when the first trigger signal VH is active, the switching state is switched, and at this time, the voltage across the energy storage capacitor C3 is equal to the sampled value of the sixth resistor R6 to the supply voltage (referred to as the second reference voltage VE); when the second comparing unit 122 is in the second switch state, the non-inverting input terminal of the second comparator 1220 obtains a second sampling voltage VD in real time, the second sampling voltage VD is the difference between the sampling value of the supply voltage after the moment when the sixth resistor R6 is effective to the first trigger signal and the voltage drop of the diode, the inverting input terminal of the second comparator 1220 obtains a second reference voltage VE provided by the energy storage capacitor C3, the second comparator 1220 then performs a comparison operation on the second sampled voltage VD and the second reference voltage VE until it is detected that the second sampled voltage VD is greater than the second reference voltage VE, it means that the supply voltage has been increased by a larger amplitude than before, and the second comparator 1220 outputs the second trigger signal VP (for example, the second trigger signal VP may be at a high level) to the logic control module 110, so that the logic control module 110 controls the power tube Q to be turned on and off at the desired frequency. It can be understood that, considering the problem of loss during transmission, the second reference voltage VE is approximately equal to the last real-time sampled value of the power supply voltage by the sixth resistor R6, and the second sampled voltage VD is approximately equal to the next sampled value of the power supply voltage by the sixth resistor R6 minus the voltage drop of the diode D2. In short, the second comparing unit 122 is used to determine whether the rising amplitude of the input power supply voltage exceeds the preset expected voltage difference. At the initial stage of power-on of the switching power supply circuit, the power supply voltage provided by the power supply module 200 continuously rises (rises in a step shape approximately), the second sampling voltage VD and the second reference voltage VE also rise correspondingly, the difference between the two is greater than the expected voltage difference, which indicates that the input power supply voltage is still continuously established, and if the difference between the two is less than or equal to the expected voltage difference, which indicates that the power supply voltage is completely established, the current-limiting tracking chip 100 is started up.

It should be understood that the expected voltage difference is determined according to the resistance value of the fifth resistor R5, the resistance value of the sixth resistor R6 and the voltage drop of the diode. In an exemplary embodiment, the ratio of the resistance of the fifth resistor R5 to the resistance of the sixth resistor R6 is 4: 1, the voltage drop of the diode D2 is 0.5V, and a formula can be obtained according to the second sampling voltage VD being greater than the second reference voltage VE:

further it can be seen that

WhereinVin1A value of the supply voltage representing a moment when the first trigger signal is active,Vin2indicating the real-time magnitude of the supply voltage after the time when the first trigger signal is active (which can also be understood as the time when the power transistor Q is turned off), the supply voltage needs to be increased by more than 2.5V to allow the second comparator 1220 to output the second trigger signal VP.

In the above description, the first comparator 1212 and the second comparator 1220 are preferably high-speed comparators, and the delay is generally less than 100ns, which is beneficial to reducing the delay and improving the operation rate.

In this embodiment, the logic control module 110 is configured to control the timer 124 to start counting down according to a desired time length (which may be set according to an actual situation, and is not described herein again), and the timer 124 is configured to send a count signal VG to the counter 125 after counting down is finished, so that the counter 125 records the count signal VG once; the counter 125 is configured to send a third trigger signal VF to the logic control module 110 when the number of times of recording the count signal VG reaches a desired number of times, so as to drive the logic control module 110 to control the power tube Q to be turned on and off at a desired frequency, the constant current source unit 123 latches a real-time value of the reference voltage (the first reference voltage VA) as a first desired value, and the timer 124 stops counting down (stops working); when the first trigger signal VH is valid, the logic control module 110 controls the timer 124 to count down, suspend and reset, where "suspend" is to reset the timer when the timer is not timed out; the logic control module 110 is further configured to control the timer 124 to reset after a countdown is finished; the counter 125 is configured to reset after acquiring the current limit signal VC.

In an exemplary embodiment, the timer 124 starts counting down according to 100ms, if the 100ms count down reaches 0 normally, the timer 124 sends a count signal VG to the counter 125, the counter 125 records the count as "1", then the timer 124 resets and resets to start counting down next time, if the next 100ms count down still reaches 0, the timer 124 sends a count signal VG again, the counter 125 records the count as "2"; in the process of counting down by the timer 124 in 100ms, if the logic control module 110 receives the valid first trigger signal VH, the timer 124 stops counting down (for example, the first trigger signal VH is valid when counting down to 60ms, and stops at this time), and starts resetting to count down again, since a complete counting down is not completed, the counting signal VG is not generated, if the condition that the timer 124 stops is that the first trigger signal VH is valid, the logic control module 110 correspondingly generates the current limiting signal VC at this time, and the counter 125 resets the originally recorded times to "0" after acquiring the current limiting signal VC.

The specific operation of the current-limiting tracking chip of the present invention will be described with reference to the specific circuit diagram (fig. 4). From the initial stage of power-on of the current-limiting tracking chip 100, the second comparing unit 122 is in the first switching state, the energy-storage capacitor C3 is charged, the first comparator 1212 obtains the first reference voltage VA corresponding to the first expected value provided by the constant current source unit 123, when it is detected that the first sampling voltage VB obtained by sampling the supply current is greater than the first reference voltage VA, the first comparator 1212 outputs the effective first trigger signal VH for the first time, and after the logic control module receives the effective first trigger signal VH for this time, the logic control module controls the constant current unit 123 to output the first reference voltage VA corresponding to the second expected value, so as to adjust the second comparing unit 122 from the first switching state to the second switching state, and after receiving the effective first trigger signal VH, the logic control module 110 further sends the current-limiting signal VC to cut off the power tube Q, so as to reduce the load current output by the switching power supply circuit, the input power supply current also starts to drop, so that the power supply voltage is continuously and upwards established, and in addition, the voltage at the two ends of the energy storage capacitor C3 is equal to the sampling value of the power supply voltage of the sixth resistor R6 pair at the disconnection time of the second switch K2; the second comparing unit 122 is in the second switching state, when the input power supply voltage is set up to a certain value (i.e., the power supply voltage rises to a certain value), the second sampling voltage VD is greater than the second reference voltage VE provided by the energy storage capacitor C3 at this time, the second comparator 1220 outputs the second trigger signal VP to the logic control module 110 for the first time, the logic control module 110 is driven to turn on and off the power transistor Q at the desired frequency, and meanwhile, the second comparing unit 122 is switched from the second switching state to the first switching state. Then, the input power supply current rises again, after the first comparator 1212 detects that the first sampling voltage VB is greater than the first reference voltage VA corresponding to the second desired value again, the first comparator 1212 outputs the valid first trigger signal VH for the second time to drive the logic control module 110 to output the current limiting signal VC to turn off the power tube Q, the second comparison unit 122 switches from the first switching state to the second switching state, when the second sampling voltage VD obtained by sampling the power supply voltage at this time is greater than the second reference voltage VE provided by the energy storage capacitor C3 at this time (that is, when the first switching state is switched to the second switching state, the second switch K2 turns off the sampling value of the power supply voltage by the sixth resistor at this time), the second comparator 1220 outputs the second trigger signal VP to the logic control module 110 for the second time, and drives the logic control module 110 to turn on and turn off the power tube Q at the desired frequency, the second comparing unit 122 is then switched from the second switching state to the first switching state. Thus, after the current-limiting tracking module implements comparison of the real-time values of the first sampling voltage VB and the first reference voltage VA, comparison of the second sampling voltage VD and the second reference voltage VE, and switching of the first switching state and the second switching state of the second comparing unit 122 for multiple times, the input supply current does not increase, the first sampling voltage VB is not larger than the first reference voltage VA, and the input and the output of the current-limiting tracking chip 100 are completely established.

It is understood that the "supply voltage is fully established" condition described herein includes, but is not limited to, the last time the second comparing unit 122 obtains the supply voltage that can trigger the second trigger signal VP is just equal to the actual peak value of the supply voltage, and the difference between the last sampled value of the supply voltage and the actual peak value is smaller than or equal to the expected voltage difference.

In the process of establishing the supply voltage for the last time, if the rising amplitude of the supply voltage does not exceed the expected voltage difference, after the first trigger signal of the first comparator 1212 is valid for the last time, the current-limiting tracking chip 100 performs current-limiting protection, and the power tube Q is turned off, and then the second comparator 1220 does not output the second trigger signal VP to the logic control module 110 to drive the power tube Q to be turned on and off at the expected frequency, which may cause the current-limiting tracking chip 100 to fail to operate normally. Specifically, the second trigger signal VP is output from the second comparator 1220 for the first time, the logic control module 110 starts to drive the timer 124 to count down according to the expected time length, after the timer 124 counts down (it can be understood that one complete count down is completed), a count signal VG is sent to the counter 125, the counter 125 records the count signal VG, and when the timer 124 completes one complete count down, the reset is reset under the effect of the logic control module to start the next count down. Since the first comparison unit 121 outputs the valid first trigger signal VH in the early stage of power-on to drive the logic control module 110 to output the current-limiting signal VC, the counter 125 resets (clears) the number of times of recording the count signal VG after acquiring the current-limiting signal VC, and meanwhile, the timer 124 stops (the expected duration is set to be long enough according to actual conditions) and resets to start counting down again, so that the counter 125 does not trigger the third trigger signal VF to enable the logic control module 110 to latch the first reference voltage VA provided by the constant current source unit 123. After the current-limiting tracking chip 100 is started, that is, the supply current is not increased, the supply voltage is also stable, at this time, the first comparison unit 121 does not output the first trigger signal VH, the second comparison unit 122 does not output the second trigger signal VP, the counter 125 starts to perform cumulative recording on the number of times of the count signal VG after the current-limiting signal VC is obtained and cleared for the last time, which means that the timer 124 sends a count signal VG to the counter 125 after counting down is finished, and the counter 125 records a count signal VG; then the timer 124 resets and resets to count down again, and after the counting down is finished, the counter 125 records the counting signal VG twice in an accumulated mode; the timer 124 resets again to reset and count down again, the counter 125 records the count signal VG … … three times after the count down is finished, when the number of times of recording the count signal VG by the counter 125 reaches a desired number of times (which may be configured according to actual conditions), the third trigger signal VF is activated, the driving logic control module 110 controls the real-time value of the first reference voltage VA provided by the constant current source unit 123 to be latched in the first reference voltage VA corresponding to the first desired value, the power tube Q is turned on and off at the desired frequency, and the timer 124 also stops working, so that the current-limiting tracking chip 100 is started and starts to work normally. In addition, it should be noted that the expected number of times is generally set to be large, and it may happen that the expected duration is shorter than the duration between two adjacent valid times of the first trigger signal VH in the startup stage of the current-limiting tracking chip, then the number of times recorded by the counter 125 may be "2" or "3" (the number of times recorded is greater than "1", but the counter 125 will still reset to zero after receiving the current-limiting signal VC subsequently), and the expected number of times is set to be as large as possible, so as to avoid misjudgment of the counter 125 in the startup stage of the current-limiting tracking chip 100.

When the power supply voltage is established for the last time, if the power supply voltage just reaches the actual peak value, then the power tube Q works at the expected frequency, after the timer 124 counts down repeatedly for many times, the number of times recorded by the counter 125 reaches the expected number of times, and the counter 125 sends a third trigger signal VF once, so that the power tube Q is turned on and off at the expected frequency. It can be understood that if the last established power supply voltage just reaches the actual peak value, the operation of the power tube Q at the desired frequency will be performed twice, so as to ensure that the circuit will not make a false determination.

As a preferred embodiment, the current-limiting tracking chip 100 includes an under-voltage protection module 130, and the under-voltage protection module 130 is configured to drive the logic control module 110 to control the power transistor Q to be turned off when the power supply voltage is less than a minimum start voltage of the current-limiting tracking chip 100. In this embodiment, the under-voltage protection module 130 may be an under-voltage protector or an under-voltage protection circuit.

As a more preferred embodiment, in practical use, the switching power supply circuit is used for driving an external load module 300 (specifically, an LED load) to operate, and specifically, the switching power supply circuit provides a constant driving current (load current) to the load module 300 to drive the LED load to operate; the sampling resistor Ry of the switching power supply circuit is used for sampling the load current of the load module 300 in real time; the current-limiting tracking chip 100 includes a voltage feedback module 140, where the voltage feedback module 140 is configured to generate a feedback sampling voltage according to the real-time sampling of the load current by the sampling resistor Ry, and further form a feedback signal according to the feedback sampling voltage to the logic control module 110, so as to drive the logic control module 110 to adjust the duty ratio of the power tube Q, thereby achieving a function of constant load current.

Based on the above switching power supply circuit, the present embodiment correspondingly provides a switching power supply system, which includes a power supply module 200, a plurality of switching power supply circuits as described above, and a plurality of load modules 300 corresponding to the switching power supply circuits one to one; the switching power supply circuit is connected to the power supply module 200 after the load module 300 is loaded. Specifically, referring to fig. 1, a plurality of switching power supply circuits are connected to the same power supply module 200 after loading respective corresponding load modules 300 to form the switching power supply system, and the switching power supply system has the switching power supply circuit and the switching power supply circuit includes the current-limiting tracking chip 100, so that the switching power supply system also has the beneficial effects brought by the switching power supply circuit (and the current-limiting tracking chip 100).

Based on the above current-limiting tracking chip 100, the switching power supply circuit and the switching power supply system, the present embodiment provides a control method of the switching power supply circuit based on the specific devices listed in the text, so as to further explain the working principle of the current-limiting tracking chip 100, which specifically includes the following steps:

the method comprises the following steps: the resistance of the sampling resistor Rx is pre-configured according to the parameters of the power supply module 200, the parameters of the load module 300, and the power conversion efficiency of the power supply module 200, so as to adjust the multiple of the amplifier 1211 in the following step, such that the first sampling voltage VB is equal to the product of the sampling resistor Rx and the real-time value of the power supply current. For example, the rated power of the power supply module 200 is 200W, the rated voltage is 20V, the rated current is 10A, the rated power of the load module 300 is 10W, the rated voltage is 5V, the rated current is 2A, and the electric energy conversion efficiency of the power supply module 200 is 90%; the maximum number N = (200/(10/(0.9))) -1=17 of the configurable switching power supply circuit and the load module 300, the maximum supply current provided by the power supply module 200 to the single switching power supply circuit is Imax =10A/17=0.588A, the supply current in normal operation of the single switching power supply circuit is Iin = (10/90%)/20 =0.556A, and the current limiting current (the first preset current value of the constant current source 1230) is set between 0.556A and 0.588A, which should be slightly larger than 0.556A. The resistance of the sampling resistor Rx is obtained according to the initial current-limiting voltage and the current-limiting current, i.e., the quotient of the first reference voltage VA (the product of the first preset current value of the constant current source 1230 and the seventh resistor R7) corresponding to the first desired value of the constant current source unit 123 and the current-limiting current (preferably, the value is close to 0.556A and slightly greater than 0.556A).

Step two: at the initial power-on start stage of the current-limiting tracking chip 100, that is, at the initial start stage, the output current of the constant current source 1230 is a first preset current value, the constant current source unit 123 outputs a first reference voltage VA corresponding to a first desired value, the first switch K1, the third switch K3, and the fourth switch K4 are all turned off, the second switch K2 is turned on, the energy storage capacitor C3 is continuously charged, thereafter, the current-limiting tracking chip 100 starts to establish an input-output logic relationship, and when the supply current input to the current-limiting tracking chip 100 gradually increases to a first sampling voltage VB and is greater than the first reference voltage VA, the first comparator 1212 outputs a first trigger signal VH to be active (active at a high level); after the logic control module 110 receives the effective first trigger signal VH, the first switch K1, the third switch K3 and the fourth switch K4 are all closed, the second switch K2 is opened, and at the same time, the logic control module 110 sends a current-limiting signal to cut off the power tube Q, so that the load current output by the switching power supply circuit can be reduced, and the input supply current also starts to fall, which is favorable for the continuous upward establishment of the supply voltage, in addition, the energy storage capacitor C3 provides the second comparator 1220 with a second reference voltage VE obtained by sampling the supply voltage by a sixth resistor R6 at the time when the second switch K2 is opened, the second comparator 1220 continuously detects the supply voltage, and when the second sampling voltage VD 1220 is detected to be greater than the second reference voltage VE, the second comparator outputs a second trigger signal VP, and at this time, the supply voltage has a certain amplitude rise compared with the previous supply voltage. After receiving the second trigger signal VP (the second trigger signal VP is received for the first time), the logic control module 110 starts the timer 124, so that the timer 124 starts to count down within the expected time length, if the logic control module 110 does not acquire the second trigger signal VP for multiple times continuously within the expected time length (or the second comparator 1220 does not output the second trigger signal VP for a long time), after the timer 124 times out (completes one complete count down), the timer 124 sends a count signal VG to the counter 125 once, the counter 125 records that the number of times of the count signal VG is "1", the logic control module 110 controls the power tube Q to be turned on and off at the expected frequency (normal switching frequency), and controls the constant current source unit 123 to output the first reference voltage VA corresponding to the second expected value.

Step three: and repeating the second step, wherein the output voltage of the constant current source unit 123 is the first reference voltage VA corresponding to the second desired value. In addition, the timer 124 stops and resets the reset at the time when the first trigger signal is valid, and the counter 125 operates after acquiring the current limit signal VC sent by the logic control module 110 and resetting the number of times of the clear count signal VG.

Step four: and repeating the second step and the third step until the input power supply voltage is completely established, which is characterized in that the power supplied by the power supply module 200 to the single switching power supply circuit is constant, the power supply current is constant, and the input voltage is increased (small amplitude rise cannot trigger the second comparator 1220 to output the second trigger signal VP). That is, after the first reference voltage VA is triggered for the last time, the power transistor Q is in the off state.

Step five: the logic control module 110 controls the constant current source unit 123 to output a first reference voltage VA corresponding to a first desired value, the first switch K1, the third switch K3 and the fourth switch K4 are all turned off, the second switch K2 is turned on, the input-output logic relationship of the current-limiting tracking chip 100 is completely established, the input power supply current is not increased, the first sampling voltage VB after operation is smaller than the first reference voltage VA, an effective first trigger signal VH cannot be generated, the power supply voltage is not increased in a large amplitude, the second sampling voltage VD cannot be larger than the second reference voltage VE, and the second comparator 1220 cannot output a second trigger signal VP. After the timer 124 can complete one complete countdown according to the preset duration, the timer 124 sends a counting signal VG to the counter 125 after the timing is finished, the counter 125 records the counting signal VG once, after the counter 125 records the counting signal VG, the timer 124 resets and resets again to restart the countdown, after the countdown is finished, the counter 125 accumulatively records two counting signals VG … …, because the current-limiting tracking chip 100 has established the input-output logic relationship, the current-limiting signal VC cannot be triggered, and the counter 125 cannot reset after counting each time, the counter 125 can accumulatively record the number of times of the counting signal VG, and after the counting operation for many times, the number of times of the counting signal VG accumulatively recorded by the counter 125 reaches the expected number of times. When the expected number of times is reached, the counter 125 sends a third trigger signal VF to the logic control module 110 once, the driving logic control module 110 latches the output voltage of the constant current source unit 123 as the first reference voltage VA corresponding to the first expected value, the power tube Q is turned on and off at the expected frequency, and the logic control module 110 also controls the timer 124 to stop working.

Step six: when the load module 300 is short-circuited, specifically referring to fig. 1, that is, when a load of a certain path or two paths of loads are short-circuited, the load current provided by the switching power supply circuit is continuously large current, and at this time, the current-limiting current is triggered (that is, the first sampling voltage VB is greater than the first reference voltage VA corresponding to the first desired value), the logic control module 110 in the current-limiting tracking chip 100 turns off the power tube Q, the current-limiting current of the current-limiting tracking chip 100 is always maintained under the set current-limiting condition, and at this time, the maximum switching current of the power tube Q is the set current (it is only required to ensure that the current-limiting current during normal operation is slightly greater than the maximum application current of the system design, for example, the current in the first step is between 0.556A and 0.588A, that the current can be understood as the first predetermined current value provided by the constant current source 1230), the output power of the current-limiting tracking chip 100 is limited, and the current-limiting tracking chip 100 is not damaged, the normal operation of the current-limiting tracking chip 100 of other paths in the switching power supply system is not affected.

Step seven: after the current-limiting tracking chip 100 is powered off, repeating the second step to the sixth step, so that the current-limiting tracking chip 100 can be powered on again and reset to a working state.

The above description is only for the purpose of describing the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention, and any variations and modifications made by those skilled in the art according to the above disclosure are within the scope of the present invention.

Claims

1. A current-limiting tracking chip applied to a switching power supply circuit is characterized by comprising: the power tube, the logic control module and the current-limiting tracking module;

2. The current-limiting tracking chip of claim 1, wherein the power transistor comprises a PMOS transistor, the input terminal of the power transistor is a source of the PMOS transistor, the output terminal of the power transistor is a drain of the PMOS transistor, and the control terminal of the power transistor is a gate of the PMOS transistor.

3. The current-limiting tracking chip of claim 1, wherein the first comparing unit comprises a first resistor, a second resistor, a third resistor, a fourth resistor, an amplifier, and a first comparator; the first end of the first resistor is used for being connected with the input end of an external sampling resistor; the second end of the first resistor is connected with the first end of the second resistor and is connected with the non-inverting input end of the amplifier in a common access mode; the second end of the second resistor is connected to the output end of the amplifier; the first end of the third resistor is used for being connected with the output end of the sampling resistor; the second end of the third resistor is connected with the first end of the fourth resistor and is commonly connected to the inverting input end of the amplifier; a second end of the fourth resistor is grounded; the non-inverting input end of the first comparator is connected with the output end of the amplifier, the inverting input end of the first comparator obtains the reference voltage, the output end of the first comparator is connected with the logic control module, and the output end of the first comparator is configured as the output end of the first comparing unit.

4. The current-limiting tracking chip of claim 1, wherein the second comparing unit comprises a fifth resistor, a sixth resistor, a first switch, a second switch, a third switch, a fourth switch, a diode, an energy-storage capacitor, and a second comparator; the first end of the fifth resistor is used for acquiring the power supply voltage, and the second end of the fifth resistor is grounded through the sixth resistor; the first end of the first switch and the first end of the second switch are connected to the second end of the fifth resistor together; the second end of the first switch is used for being connected with the input end of the diode, and the output end of the diode is connected with the non-inverting input end of the second comparator; the second end of the second switch is used for realizing the connection with the inverting input end of the second comparator through the third switch, and the common end formed by the second switch and the third switch is grounded through the energy storage capacitor; the output end of the second comparator is connected with the logic control module through the fourth switch;

5. The current-limiting tracking chip of claim 4, wherein the expected voltage difference is determined according to a resistance of the fifth resistor, a resistance of the sixth resistor, and a voltage drop of the diode.

6. The current-limiting tracking chip of claim 1, wherein a ratio of the first expected value to the second expected value is greater than or equal to 1.5 and less than or equal to 2.

7. The current-limiting tracking chip of claim 1, wherein the current-limiting tracking chip comprises an under-voltage protection module, and the under-voltage protection module is configured to drive the logic control module to control the power transistor to turn off when the supply voltage is less than a minimum start voltage of the current-limiting tracking chip.

8. A switching power supply circuit, characterized by comprising a first capacitor circuit, a sampling resistor, a freewheeling diode, an inductor, a second capacitor circuit and a current-limiting tracking chip according to any one of claims 1-7; the input end and the output end of the sampling resistor are simultaneously connected to the first comparison unit, and the first comparison unit is used for sampling the power supply current according to the sampling resistor; the first end of the first capacitor circuit is connected with the input end of the sampling resistor, and the second end of the first capacitor circuit is grounded; the output end of the current-limiting tracking chip is connected with the output end of the freewheeling diode and then is connected to the first end of the inductor together; the input end of the freewheeling diode is grounded; the second end of the inductor is grounded through the second capacitor circuit; when the power tube is conducted, the first capacitor circuit, the sampling resistor, the power tube, the inductor and the second capacitor circuit form a first loop; when the power tube is cut off, the inductor, the second capacitor circuit and the freewheeling diode form a second loop.

9. The switching power supply circuit according to claim 8, wherein the switching power supply circuit is configured to drive an externally connected load module to operate; the switching power supply circuit comprises a sampling resistor, and the sampling resistor is used for sampling the load current of the load module in real time; the current-limiting tracking chip comprises a voltage feedback module, wherein the voltage feedback module is used for generating feedback sampling voltage according to the real-time sampling of the load current by the sampling resistor, and further forming a feedback signal to a logic control module according to the feedback sampling voltage so as to drive the logic control module to adjust the duty ratio of the power tube.

10. A switching power supply system characterized by comprising a power supply module, a plurality of switching power supply circuits according to claim 8 or 9, and a plurality of load modules in one-to-one correspondence with the switching power supply circuits; and the switching power supply circuit is connected to the power supply module after the corresponding load module is loaded.