Switching power supply type charger and its power limiting protection circuit

Abstract

A switching power supply type charger and an LPS protection circuit thereof are provided. The LPS protection circuit is configured to: detect a source-drain voltage difference between a source and a drain of an output switch tube, generate a first output switch tube voltage drop indication signal based on the source-drain voltage difference of the output switch tube and a first output switch tube voltage drop threshold, and generate a second output switch tube voltage drop indication signal based on the source-drain voltage difference of the output switch tube and a second output switch tube voltage drop threshold; detect a CC terminal voltage of the switching power supply type charger after the output switch tube is turned on and a load of the switching power supply type charger is pulled, generate a first CC terminal voltage indication signal based on the CC terminal voltage and a first CC terminal voltage threshold, and generate a second CC terminal voltage indication signal based on the CC terminal voltage and a second CC terminal voltage threshold; and determine whether LPS protection needs to be performed based on the first output switch tube voltage drop indication signal, the second output switch tube voltage drop indication signal, the first CC terminal voltage indication signal, and the second CC terminal voltage indication signal.

Description

Technical Field

[0001] This invention relates to the field of circuits, and more specifically to a switching power supply type charger and its power limiting protection circuit. Background Technology

[0002] As the battery capacity of mobile electronic devices increases and the required charging speed improves, the output power requirements for chargers also increase. Currently, most chargers on the market have increased their output power to the 80W-90W range and their maximum output current to around 7.5A. At the same time, these chargers must meet the Limited Power Sources (LPS) requirements, meaning their output power is less than 100W and their output current is less than 8A. Summary of the Invention

[0003] According to an embodiment of the present invention, an LPS protection circuit is used in a switching power supply charger. The LPS protection circuit includes: an output switching transistor voltage drop detection module configured to detect the source-drain voltage difference between the source and drain of the output switching transistor in the switching power supply charger, generate a first output switching transistor voltage drop indication signal based on the source-drain voltage difference of the output switching transistor and a first output switching transistor voltage drop threshold, and generate a second output switching transistor voltage drop indication signal based on the source-drain voltage difference of the output switching transistor and a second output switching transistor voltage drop threshold; a fast charging protocol communication detection module configured to detect the CC terminal voltage of the switching power supply charger after the output switching transistor is turned on and the load of the switching power supply charger is applied, generate a first CC terminal voltage indication signal based on the CC terminal voltage and a first CC terminal voltage threshold, and generate a second CC terminal voltage indication signal based on the CC terminal voltage and a second CC terminal voltage threshold; and a logic control module configured to determine whether LPS protection needs to be performed based on the first output switching transistor voltage drop indication signal, the second output switching transistor voltage drop indication signal, the first CC terminal voltage indication signal, and the second CC terminal voltage indication signal.

[0004] The switching power supply charger according to an embodiment of the present invention includes the above-described LPS protection circuit. Attached Figure Description

[0005] The invention can be better understood from the following description of specific embodiments of the invention in conjunction with the accompanying drawings, wherein:

[0006] Figure 1 The circuit diagram of a switching power supply charger with an output power of 65W is shown.

[0007] Figure 2 A circuit diagram of a portion of the circuitry of a switching power supply charger, according to an embodiment of the present invention, is shown, in which the LPS protection circuit is included in a fast charging protocol chip.

[0008] Figure 3 A schematic block diagram of an LPS protection circuit according to an embodiment of the present invention is shown.

[0009] Figure 4 A circuit diagram of a portion of the circuitry of another switching power supply charger, in which the LPS protection circuit is included in a fast charging protocol chip according to an embodiment of the present invention, is shown. Detailed Implementation

[0010] The features and exemplary embodiments of various aspects of the present invention will now be described in detail. Numerous specific details are set forth in the following detailed description to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The invention is by no means limited to any specific configurations and algorithms presented below, but covers any modifications, substitutions, and improvements to elements, components, and algorithms without departing from the spirit of the invention. Well-known structures and techniques are not shown in the drawings and the following description in order to avoid unnecessarily obscuring the invention.

[0011] Typically, in switching power supply type chargers (i.e., chargers implemented by switching power supplies) with an output power of less than 65W, the output current and output power of the charger are limited by a pulse width modulation (PWM) controller used to control the switching frequency of the charger, thereby achieving LPS protection, because the maximum output current of the charger is usually only 3.25A and 65W is far enough away from 100W. Figure 1 The circuit diagram of a switching power supply charger with an output power of 65W is shown.

[0012] However, when the output power of a switching power supply charger increases to 80W-90W and the output current approaches 8A, the PWM controller can no longer be used to implement LPS protection due to accuracy issues. Therefore, a fast charging protocol chip is usually used to implement LPS protection. Specifically, the fast charging protocol chip can use high-precision, low-temperature-drift precision resistors (e.g., 5mohm resistors) to accurately detect the charger's output current and output power. However, when the precision resistor is short-circuited, the fast charging protocol chip cannot detect the charger's output current, and therefore cannot implement LPS protection. In addition, when the drain and source of the metal-oxide-semiconductor field-effect transistor (MOSFET, or MOS switch) connected to the VBUS output terminal are short-circuited, the fast charging protocol chip can detect that the charger's output current and output power exceed the limit but cannot turn off the MOSFET, and therefore cannot implement LPS protection either.

[0013] In view of one or more of the above problems, an LPS protection circuit according to an embodiment of the present invention is proposed, which can realize LPS protection in the event of a single-point failure (i.e., a short circuit occurs between adjacent pins of a device in the charger) in a switching power supply charger.

[0014] Figure 2 A circuit diagram of a portion of the circuitry of a switching power supply charger, according to an embodiment of the present invention, is shown, in which the LPS protection circuit is included in a fast charging protocol chip. Figure 3 A schematic block diagram of an LPS protection circuit according to an embodiment of the present invention is shown. The following is in conjunction with... Figure 2 and Figure 3 The circuit structure and working principle of the LPS protection circuit according to embodiments of the present invention are described in detail. Figure 2 and Figure 3 As shown, the LPS protection circuit 300 includes:

[0015] The output switch voltage drop detection module 302 is configured to detect the source-drain voltage difference Vds1 between the source and drain of the output switch Q1, generate a first output switch voltage drop indication signal T1a based on the source-drain voltage difference Vds1 of the output switch Q1 and a first output switch voltage drop threshold Vref1a, and generate a second output switch voltage drop indication signal T1b based on the source-drain voltage difference Vds1 of the output switch Q1 and a second output switch voltage drop threshold Vref1b.

[0016] The resistance current detection module 304 is configured to detect the voltage difference across the precision resistor Rcs as the resistance carrying voltage Vcs, generate a first resistance carrying voltage indication signal T2a by comparing the resistance carrying voltage Vcs with a first resistance carrying voltage threshold Vref2a, and generate a second resistance carrying voltage indication signal T2b by comparing the resistance carrying voltage Vcs with a second resistance carrying voltage threshold Vref2a.

[0017] The synchronous rectification (SR) switch voltage drop detection module 306 is configured to detect the source-drain voltage difference Vds2 between the source and drain of the SR switch Q2 during the conduction period, generate a first SR switch voltage drop indication signal T3a by comparing the source-drain voltage difference Vds2 of the SR switch Q2 with a first SR switch voltage drop threshold Vref3a, and generate a second SR switch voltage drop indication signal T3b by comparing the source-drain voltage difference Vds2 of the SR switch Q2 with a second SR switch voltage drop threshold Vref3b.

[0018] The fast charging protocol communication detection module 308 is configured to detect the CC terminal voltage of the switching power supply charger after the output switch Q2 is turned on and the load of the switching power supply charger is applied, generate a first CC terminal voltage indication signal T4a based on the CC terminal voltage and a first CC terminal voltage threshold Vref4a, and generate a second CC terminal voltage indication signal T2b based on the CC terminal voltage and a second CC terminal voltage threshold Vref4b.

[0019] The switching frequency detection module 310 is configured to detect the switching frequency Fsw of the switching power supply charger, generate a first switching frequency indication signal T5a by comparing the switching frequency Fsw with a first switching frequency threshold Fref5a, and generate a second switching frequency indication signal T5b by comparing the switching frequency Fsw with a second switching frequency threshold Fref5b; and

[0020] The logic control module 312 is configured to determine whether LPS protection needs to be performed based on the first output switch voltage drop indication signal T1a, the second output switch voltage drop indication signal T2a, the first resistor carrying voltage indication signal T1b, the second resistor carrying voltage indication signal T2b, the first SR switch voltage drop indication signal T3a, the second SR switch voltage drop indication signal T3b, the first CC terminal voltage indication signal T4a, the second CC terminal voltage indication signal T4b, the first switching frequency indication signal T5a, and the second switching frequency indication signal T5b.

[0021] Here, to address the signal detection tolerance issue, a pair of reference thresholds, VrefXa and VrefXb (X = 1~4), is set for any one of the output switch voltage drop detection module 302, resistance current detection module 304, SR switch voltage drop detection module 306, and fast charging protocol communication detection module 308. A pair of reference thresholds, Fref5a and Fref5b, is also set for the switching frequency detection module 310. VrefXa > VrefXb (X = 1 / 2 / 3 / 4), Fref5a > Fref5b. VrefXa and Fref5a correspond to the LPS current protection threshold Io1, and VrefXb and Fref5b correspond to the LPS current protection threshold Io2. Typically, deviations in the electrical parameters of the detection circuit or the presence of a weak short circuit can lead to errors in the actual detection results. Therefore, it is necessary to appropriately widen the difference between Io1 and Io2. For example, the LPS current protection thresholds can be set to Io1 = 3A and Io2 = 1A.

[0022] In some embodiments, for any one of the output switch voltage drop detection module 302, resistance current detection module 304, SR switch voltage drop detection module 306, fast charging protocol communication detection module 308, and switching frequency detection module 310, TXa (X = 1 / 2 / 3 / 4 / 5) is a first logic value (e.g., TXa = logic 1) when the output current Io of the switching power supply charger is greater than Io1 and a second logic value (e.g., TXa = logic 0) when Io is not greater than Io1, and TXb (X = 1 / 2 / 3 / 4 / 5) is a first logic value (e.g., TXb = logic 1) when Io is greater than Io2 and a second logic value (e.g., TXb = logic 0) when Io is not greater than Io2.

[0023] In some embodiments, assuming the on-resistance of the output switch Q1 is Rdson1, the drain-source voltage difference Vds1 (Io = Vds1 / Rdson1) of the output switch Q1 can be detected through the VIN and VBUS pins of the fast charging protocol chip. The internal amplifier KA amplifies Vds1 by a factor of K1 and compares it with Vref1a = Io1 * Rdson1 * K1 and Vref1b = Io2 * Rdson1 * K1 (since Vds1 is usually small, amplification is relatively easy to implement). If the T1a / T1b signal output by the comparator CMP is logic 1, it indicates that the output current Io is greater than the LPS current protection threshold Io1 / Io2. That is, T1a is logic 1 when Vds1 is greater than Vref1a and logic 0 when Vds1 is not greater than Vref1a; T1b is logic 1 when Vds1 is greater than Vref1b and logic 0 when Vds1 is not greater than Vref1b.

[0024] In some embodiments, the voltage difference Vcs (Io = Vcs / Rcs) across the precision resistor Rcs can be detected via the ISP and ISN pins of the fast charging protocol chip. An internal amplifier KA amplifies Vcs by a factor of K2 and compares it with Vref2a = Io1 * Rcs * K2 and Vref2b = Io2 * Rcs * K2 (similarly, since Vcs is typically small, amplification is easier to implement). If the T2a / T2b signal output by the comparator CMP is logic 1, it indicates that the output current Io is greater than the LPS current protection threshold Io1 / Io2. That is, T2a is logic 1 when Vcs is greater than Vref2a and logic 0 when Vcs is not greater than Vref2a; T2b is logic 1 when Vcs is greater than Vref2b and logic 0 when Vcs is not greater than Vref2b.

[0025] In some embodiments, assuming the on-resistance of the SR switch Q2 is Rdson2, the drain-source voltage difference Vds2 (Io = Vds2 / Rdson2) of the SR switch Q2 can be detected through the Vd and GND pins of the fast charging protocol chip. The internal amplifier KA amplifies Vds2 by a factor of K3 and compares it with Vref3a = Io1 * Rdson2 * K3 and Vref3b = Io2 * Rdson2 * K3 (similarly, since Vds2 is usually small, amplification is easier to implement). If the T3a / T3b signal output by the comparator CMP is logic 1, it indicates that the output current Io is greater than the LPS current protection threshold Io1 / Io2. That is, T3a is logic 1 when Vds2 is greater than Vref3a and logic 0 when Vds2 is not greater than Vref3a; T3b is logic 1 when Vds2 is greater than Vref3b and logic 0 when Vds2 is not greater than Vref3b.

[0026] In some embodiments, the output current Io of the switching power supply charger can be determined by the voltage difference between the CC terminal voltage (i.e., the voltage at the CC1 or CC2 pin) of the fast charging protocol chip before and after the switching power supply charger is loaded. Specifically, the CC terminal voltage Sample1 can be detected during the off-state of the output switch Q1 and after the CC terminal is stably connected to the pull-down resistor Rd, and the CC terminal voltage Sample2 can be detected after the output switch Q1 is turned on and the switching power supply charger is loaded. If tolerance is not considered, sample1 = Icc * Rd. However, according to the Type-C protocol, Icc = 330ua tolerance ±10%, Rd = 5.1K tolerance ±10%. Therefore, it is usually necessary to first calibrate Vref4a / Vref4b using Sample1, where Vref4a = Sample1 + Rgnd * Io1, Vref4b = Sample1 + Rgnd * Io2. By reverse calculation, Io = (Sample2 - Sample1) / Rgnd, where Rgnd is the ground impedance of the charging cable connecting the charging cable and the terminal device. If Sample2 is greater than Vref4a / Vref4b, it means that the output current Io exceeds the LPS protection current threshold Io1 / Io2. That is, T4a is logic 1 when Sample2 is greater than Vref4a and logic 0 when Sample2 is not greater than Vref4a, and T4b is logic 1 when Sample2 is greater than Vref4b and logic 0 when Sample2 is not greater than Vref4b.

[0027] In some embodiments, the logic control module 312 is further configured to determine that LPS protection needs to be performed when any one of T1a to T5a is logic 1 and any one of T1b to T5b is logic 0.

[0028] In some embodiments, the logic control module 312 is further configured to transmit LPS protection information to the PWM controller when it is determined that LPS protection needs to be performed and T1b is logic 1 (i.e., the output switch Q1 is not short-circuited). For example, the logic control module 312 may be configured to transmit LPS protection information to the PWM controller via an optocoupler or an SR switch.

[0029] In some embodiments, the logic control module 312 is further configured to control the output switch Q1 to change from the on state to the off state when it is determined that LPS protection needs to be performed and T1b is logic 0.

[0030] It should be noted that, according to the embodiments of the present invention, the LPS protection circuit, even when including only any two or more of the following detection modules: output switch voltage drop detection module 302, resistance current detection module 304, SR switch voltage drop detection module 306, fast charging protocol communication detection module 308, and switching frequency detection module 310, can also determine whether LPS protection needs to be executed in conjunction with the logic control module 312. Furthermore, the LPS protection circuit according to the embodiments of the present invention can also be located outside the fast charging protocol chip, as long as it can be combined with... Figure 3 The functions described above are sufficient.

[0031] Figure 4 A circuit diagram of a portion of the circuitry of another switching power supply charger, in which the LPS protection circuit is included in a fast charging protocol chip according to an embodiment of the present invention, is shown. Figure 4 The switching power supply type charger shown is Figure 2 The main difference between the switching power supply type chargers shown is that the output switching transistor Q1 is integrated into the fast charging protocol chip, and the output switching transistor voltage drop detection module 302 and the resistance current detection module 304 are combined into one module.

[0032] This invention can be implemented in other specific forms without departing from its spirit and essential characteristics. For example, the algorithm described in a particular embodiment can be modified without departing from the basic spirit of the invention. Therefore, the present embodiments are to be regarded as exemplary rather than limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and all changes falling within the meaning and scope of the claims and their equivalents are thus included within the scope of the invention.

Claims

1. A power limiting LPS protection circuit for use in a switching power supply charger, the switching power supply charger including a pulse width modulation (PWM) controller and a fast charging protocol chip, the power limiting LPS protection circuit being located within the fast charging protocol chip, the power limiting LPS protection circuit comprising: The output switch voltage drop detection module is configured to detect the source-drain voltage difference between the source and drain of the output switch in the switching power supply charger, generate a first output switch voltage drop indication signal based on the source-drain voltage difference of the output switch and a first output switch voltage drop threshold, and generate a second output switch voltage drop indication signal based on the source-drain voltage difference of the output switch and a second output switch voltage drop threshold. The fast charging protocol communication detection module is configured to detect the CC terminal voltage of the switching power supply charger after the output switch is turned on and the load of the switching power supply charger is applied, generate a first CC terminal voltage indication signal based on the CC terminal voltage and a first CC terminal voltage threshold, and generate a second CC terminal voltage indication signal based on the CC terminal voltage and a second CC terminal voltage threshold. as well as The logic control module is configured to determine whether power limiting power supply (LPS) protection needs to be performed based on the first output switch voltage drop indication signal, the second output switch voltage drop indication signal, the first CC terminal voltage indication signal, and the second CC terminal voltage indication signal.

2. The power limiting power supply LPS protection circuit as described in claim 1, wherein, The output switch voltage drop detection module is further configured to generate a first output switch voltage drop indication signal by comparing the source-drain voltage difference of the output switch with the first output switch voltage drop threshold, and to generate a second output switch voltage drop indication signal by comparing the source-drain voltage difference of the output switch with the second output switch voltage drop threshold.

3. The power limiting power supply LPS protection circuit as described in claim 2, wherein, The fast charging protocol communication detection module is further configured to generate a first CC terminal voltage indication signal by comparing the CC terminal voltage with the first CC terminal voltage threshold, and to generate a second CC terminal voltage indication signal by comparing the CC terminal voltage with the second CC terminal voltage threshold.

4. The power limiting power supply LPS protection circuit as described in claim 3, wherein, The first output switch voltage drop threshold is greater than the second output switch voltage drop threshold. Furthermore, the first output switch voltage drop indication signal is a first logic value when the source-drain voltage difference of the output switch is greater than the first output switch voltage drop threshold, and a second logic value when the source-drain voltage difference of the output switch is not greater than the first output switch voltage drop threshold. Furthermore, the second output switch voltage drop indication signal is the first logic value when the source-drain voltage difference of the output switch is greater than the second output switch voltage drop threshold, and is the second logic value when the source-drain voltage difference of the output switch is not greater than the second output switch voltage drop threshold.

5. The power limiting power supply LPS protection circuit as described in claim 4, wherein, The first CC terminal voltage threshold is greater than the second CC terminal voltage threshold. The first CC terminal voltage indication signal is the first logic value when the CC terminal voltage is greater than the first CC terminal voltage threshold and is the second logic value when the CC terminal voltage is not greater than the first CC terminal voltage threshold. The second CC terminal indication signal is the first logic value when the CC terminal voltage is greater than the second CC terminal voltage threshold and is the second logic value when the CC terminal voltage is not greater than the second CC terminal voltage threshold.

6. The power limiting power supply LPS protection circuit as described in claim 5, wherein, The logic control module is further configured to determine that power limiting power supply (LPS) protection needs to be executed when either the first output switch voltage drop indication signal or the first CC terminal voltage indication signal is the first logic value and either the second output switch voltage drop indication signal or the second CC terminal voltage indication signal is the second logic value.

7. The power limiting power supply LPS protection circuit as described in claim 1, wherein, The fast charging protocol communication detection module is further configured to detect the CC terminal voltage during the period when the output switch is off and after the CC terminal of the switching power supply charger is stably connected to a pull-down resistor, and to use the CC terminal voltage to calibrate the first CC terminal voltage threshold and the second CC terminal voltage threshold.

8. The power limiting power supply LPS protection circuit as described in claim 6, further comprising: The resistance current detection module is configured to detect the voltage difference across a precision resistor as the resistance carrying voltage, generate a first resistance carrying voltage indication signal by comparing the resistance carrying voltage with a first resistance carrying voltage threshold, and generate a second resistance carrying voltage indication signal by comparing the resistance carrying voltage with a second resistance carrying voltage threshold.

9. The power-limiting power supply LPS protection circuit as described in claim 8, wherein, The first resistor carrying voltage threshold is greater than the second resistor carrying voltage threshold. The first resistor carrying voltage indication signal is the first logic value when the resistor carrying voltage is greater than the first resistor carrying voltage threshold and is the second logic value when the resistor carrying voltage is not greater than the first resistor carrying voltage threshold. The second resistor carrying voltage indication signal is the first logic value when the resistor carrying voltage is greater than the second resistor carrying voltage threshold and is the second logic value when the resistor carrying voltage is not greater than the second resistor carrying voltage threshold.

10. The power-limiting power supply LPS protection circuit as described in claim 9, wherein, The logic control module is further configured to determine that power limiting power supply (LPS) protection needs to be executed when any one of the first output switch voltage drop indication signal, the first CC terminal voltage indication signal, and the first resistor carrying voltage indication signal is the first logic value and any one of the second output switch voltage drop indication signal, the second CC terminal voltage indication signal, and the second resistor carrying voltage indication signal is the second logic value.

11. The power limiting power supply LPS protection circuit as described in claim 6, further comprising: The switching frequency detection module is configured to detect the switching frequency of the switching power supply charger, generate a first switching frequency indication signal by comparing the switching frequency with a first switching frequency threshold, and generate a second switching frequency indication signal by comparing the switching frequency with a second switching frequency threshold.

12. The power limiting power supply LPS protection circuit as described in claim 11, wherein, The first switching frequency threshold is greater than the second switching frequency threshold. The first switching frequency indication signal is the first logic value when the switching frequency is greater than the first switching frequency threshold and is the second logic value when the switching frequency is not greater than the first switching frequency threshold. The second switching frequency indication signal is the first logic value when the switching frequency is greater than the second switching frequency threshold and is the second logic value when the switching frequency is not greater than the second switching frequency threshold.

13. The power-limiting power supply LPS protection circuit as described in claim 12, wherein, The logic control module is further configured to determine that power limiting power supply LPS protection needs to be executed when any one of the first output switch voltage drop indication signal, the first CC terminal voltage indication signal, and the first switching frequency indication signal is the first logic value and any one of the second output switch voltage drop indication signal, the second CC terminal voltage indication signal, and the second switching frequency indication signal is the second logic value.

14. The power limiting power supply LPS protection circuit as described in claim 6, further comprising: A synchronous rectifier SR switch voltage drop detection module is configured to detect the source-drain voltage difference between the source and drain of the synchronous rectifier SR switch during the conduction period of the synchronous rectifier SR switch in the switching power supply charger, generate a first synchronous rectifier SR switch voltage drop indication signal by comparing the source-drain voltage difference of the synchronous rectifier SR switch with a first synchronous rectifier SR switch voltage drop threshold, and generate a second synchronous rectifier SR switch voltage drop indication signal by comparing the source-drain voltage difference of the synchronous rectifier SR switch with a second synchronous rectifier SR switch voltage drop threshold.

15. The power-limiting power supply LPS protection circuit as described in claim 14, wherein, The first synchronous rectifier SR switch voltage drop threshold is greater than the second synchronous rectifier SR switch voltage drop threshold. The first synchronous rectifier SR switch voltage drop indication signal is the first logic value when the source-drain voltage difference of the synchronous rectifier SR switch is greater than the first synchronous rectifier SR switch voltage drop threshold, and is the second logic value when the source-drain voltage difference of the synchronous rectifier SR switch is not greater than the first synchronous rectifier SR switch voltage drop threshold. The second synchronous rectifier SR switch voltage drop indication signal is the first logic value when the source-drain voltage difference of the synchronous rectifier SR switch is greater than the second synchronous rectifier SR switch voltage drop threshold, and is the second logic value when the source-drain voltage difference of the synchronous rectifier SR switch is not greater than the second synchronous rectifier SR switch voltage drop threshold.

16. The power limiting power supply LPS protection circuit as described in claim 15, wherein, The logic control module is further configured to determine that power limiting power supply LPS protection needs to be executed when any one of the first output switch voltage drop indication signal, the first CC terminal voltage indication signal, and the first synchronous rectifier SR switch voltage drop indication signal is the first logic value and any one of the second output switch voltage drop indication signal, the second CC terminal voltage indication signal, and the second synchronous rectifier SR switch voltage drop indication signal is the second logic value.

17. The power limiting power supply LPS protection circuit as described in claim 6, wherein, The logic control module is further configured to transmit the power limiting power supply LPS protection information to the pulse width modulation (PWM) controller in the switching power supply charger when it is determined that power limiting power supply LPS protection needs to be performed and the second output switch voltage drop indication signal is the first logic value.

18. The power-limiting power supply LPS protection circuit as described in claim 17, wherein, The logic control module is further configured to transmit the power limiting power supply LPS protection information to the pulse width modulation (PWM) controller via an optocoupler or synchronous rectifier switch.

19. The power-limiting power supply LPS protection circuit as described in claim 6, wherein, The logic control module is further configured to control the output switch to change from the on state to the off state when it is determined that power limiting power supply LPS protection needs to be performed and the voltage drop indication signal of the second output switch is the second logic value.

20. A switching power supply type charger, comprising the power limiting power supply LPS protection circuit according to any one of claims 1 to 19.

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