Limited-power power adapter

Abstract

The power-limited power adapter comprises a constant current source, a universal serial bus interface, an output control switch tube which is connected to a power bus pin of the universal serial bus interface, and an output current detection resistor which is used for detecting the output current of the power-limited power adapter, the power-limited power supply adapter is configured as follows: after the power-limited power supply adapter is electrified to work but the mobile terminal equipment is not connected to the power-limited power supply adapter, the connection between a constant current source and a configuration channel pin of a universal serial bus interface is controlled to be disconnected for a preset time; a first sampling low voltage is obtained by sampling a voltage at a configuration channel pin within a predetermined time, and whether a combination failure of an output current detection resistor and an output control switch tube occurs or not is judged according to a combination of the first sampling low voltage and an output current sensing voltage at two ends of the output current detection resistor.

Description

Technical Field

[0001] The present invention relates to the field of circuits, and more particularly to a power-limited power adapter. Background Art

[0002] With the improvement of charging power level of mobile terminal devices and the promotion of USB Type-C & PD protocol, the Limited Power Source (LPS) adapter is required to have a single point failure protection function, that is, the LPS adapter can still meet the output power or output current requirements of the limited power source (output power less than 100W or maximum output current less than 8A) when there is a failure on its printed circuit board. Summary of the invention

[0003] A limited power adapter according to an embodiment of the present invention comprises a constant current source, a universal serial bus interface, an output control switch connected to a power bus pin of the universal serial bus interface, and an output current detection resistor for detecting the output current of the limited power adapter. The limited power adapter is configured to: after the limited power adapter is powered on but a mobile terminal device has not yet been connected to the limited power adapter, control the connection between the constant current source and the configuration channel pin of the universal serial bus interface to be disconnected for a predetermined time, obtain a first sampled low voltage by sampling the voltage at the configuration channel pin within the predetermined time, and determine whether a combination failure of the output current detection resistor and the output control switch occurs based on a combination of the first sampled low voltage and the output current sensing voltage at both ends of the output current detection resistor. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] The present invention can be better understood from the following description of specific embodiments of the present invention in conjunction with the accompanying drawings, in which:

[0005] Figures 1A to 1C This is a schematic diagram of the application circuit of a traditional LPS adapter.

[0006] Figure 2 yes Figure 1A The example waveforms of the related voltages and currents of the LPS adapter and the mobile terminal device are shown in the case of output current detection failure.

[0007] Figure 3 yes Figure 1A The example waveform diagrams of the related voltages and currents of the LPS adapter and the mobile terminal device are shown in the case where the resistance value of the interface plug-in detection resistor Rd changes dynamically.

[0008] Figure 4 yes Figure 1AThe illustrated waveform diagrams are of related voltages and currents when the LPS adapter implements the failure detection method according to the embodiment of the present invention. DETAILED DESCRIPTION

[0009] The features and exemplary embodiments of various aspects of the present invention will be described in detail below. In the detailed description below, many specific details are proposed to provide a comprehensive understanding of the present invention. However, it is obvious to those skilled in the art that the present invention can be implemented without the need for some of these specific details. The following description of the embodiments is only to provide a better understanding of the present invention by illustrating examples of the present invention. The present invention is by no means limited to any specific configuration and algorithm proposed below, but covers any modification, replacement and improvement of elements, parts and algorithms without departing from the spirit of the present invention. In the accompanying drawings and the following description, known structures and technologies are not shown to avoid unnecessary ambiguity in the present invention. In addition, it should be noted that the term "A is connected to B" used here can mean "A is directly connected to B" and can also mean "A is indirectly connected to B via one or more other elements".

[0010] Figures 1A to 1C This is a schematic diagram of the application circuit of the traditional LPS adapter. Figures 1A to 1C As shown, the LPS adapter includes a fast charging protocol chip U1, a universal serial bus (USB) interface on the adapter side, an output control switch tube Q1 connected to the power bus (VBUS) pin of the USB interface on the adapter side, and an output current detection resistor R1 (or output current detection circuit) for detecting the output current of the LPS adapter. Specifically, Figure 1A It shows the application circuit where the output control switch tube Q1 and the output current detection resistor R1 are located outside the fast charging protocol chip U1 and the output current detection resistor R1 is on the low side; Figure 1B It shows the application circuit where the output control switch tube Q1 and the output current detection resistor R1 are located outside the fast charging protocol chip U1 and the output current detection resistor R1 is on the high side; Figure 1C The application circuit of the output control switch tube Q1 and the output current detection circuit (implemented together with the output control switch tube Q1) located inside the fast charging protocol chip U1 is shown.

[0011] like Figures 1A to 1CAs shown, the mobile terminal device includes a terminal device side USB interface and an interface plug-in detection resistor Rd connected between a configuration channel (CC) pin of the terminal device side USB interface and a circuit reference ground, wherein, when the mobile terminal device is connected to the LPS adapter via the USB interface and a cable, the VBUS pin, CC pin, and ground (GND) pin of the terminal device side USB interface are respectively connected to the VBUS pin, CC pin, and GND pin of the adapter side USB interface. The critical single point failure on the printed circuit board of the LPS adapter is a short circuit at both ends of the output current detection resistor R1 (i.e., output current detection failure) or a short circuit at both ends of the output control switch tube Q1 (i.e., output protection failure).

[0012] like Figures 1A to 1C As shown, when the mobile terminal device is connected to the LPS adapter, when the output current Io (not shown) of the LPS adapter increases, the voltage difference Vcd between the voltage Vc at the GND pin of the USB interface on the terminal device side and the voltage Vd at the GND pin of the USB interface on the adapter side gradually increases due to the GND line resistance Rcable_gnd between the two GND pins, and the voltage difference Vad between the voltage Va at the CC pin of the USB interface on the adapter side and the voltage Vd at the GND pin also increases due to the GND line resistance Rcable and the interface plug-in detection resistor Rd. The output current Io of the LPS adapter is Vcd / Rcable_gnd, Rcable_gnd is Rcontat1+Rcable+Rcontat2, where Rcable is the impedance of the cable itself between the two GND pins, Rcontat1 is the contact impedance between the cable between the two GND pins and the GND pin of the USB interface on the adapter side, and Rcontat2 is the contact impedance between the cable between the two GND pins and the GND pin of the USB interface on the terminal device side.

[0013] Below Figure 1A The LPS adapter shown in the figure is used as an example to illustrate the detection mechanism of the LPS adapter for output current detection failure and output protection failure. Figure 1AAs shown, when the mobile terminal device has not been connected to the LPS adapter, the constant current source Ip in the fast charging protocol chip U1 pulls up the voltage Va at the CC pin of the USB interface on the adapter side to Vdd. When the mobile terminal device is connected to the LPS adapter, the voltage Va at the CC pin of the USB interface on the adapter side is equal to Ip*Rd, wherein, according to the USB Type-C&PD protocol, the interface plug-in detection resistor Rd is usually 5.1KΩ. The LPS adapter can detect output current detection failure and output protection failure as follows: when a sudden change in the voltage Va at the CC pin of the USB interface on the adapter side is detected, the output current Io is detected by the output current detection resistor R1. If the output current sensing voltage across the output current detection resistor R1 is much smaller than the threshold Vth1, it is considered that there is an output current detection failure, triggering the single-point failure protection and controlling the output control switch tube Q1 from the on state to the off state; when the output control switch tube Q1 is in the off state, the output current Io is detected by the output current detection resistor R1 or the output protection failure is determined based on the voltage at the VBUS pin of the USB interface on the adapter side.

[0014] Figure 2 yes Figure 1A The example waveform diagram of the related voltage and current of the LPS adapter and the mobile terminal device in the case of output current detection failure is shown, where VBUS represents the voltage at the VBUS pin of the USB interface on the adapter side, CC represents the voltage at the CC pin of the USB interface on the adapter side, Current represents the actual load current of the mobile terminal device, and Current Sense represents the output current sensing voltage across the output current detection resistor R1. Figure 2 As shown, in the case of output current detection failure, when the voltage at the CC pin of the adapter-side USB interface suddenly changes, the actual load current of the mobile terminal device suddenly changes accordingly, but the output current sensing voltage across the output current detection resistor R1 remains unchanged.

[0015] Figure 3 yes Figure 1A The example waveform diagram of the related voltage and current of the LPS adapter and the mobile terminal device when the resistance value of the interface plug-in detection resistor Rd changes dynamically is shown, where VBUS represents the voltage at the VBUS pin of the USB interface on the adapter side, CC represents the voltage at the CC pin of the USB interface on the adapter side, and Current represents the actual load current of the mobile terminal device. Figure 3As shown, when the resistance value of the interface plug-in detection resistor Rd changes dynamically, when the voltage at the CC pin of the USB interface on the adapter side changes suddenly, the real load current of the mobile terminal device remains unchanged, so the output current sensing voltage across the output current detection resistor R1 will also remain unchanged, which will cause the LPS adapter to mistakenly believe that there is an output current detection failure. In actual applications, the charging chip of the mobile terminal device usually uses VBUS power supply to reduce power consumption. When the charging chip does not activate VBUS power supply, the impedance of the interface plug-in detection resistor Rd is small. After the charging chip activates VBUS charging, the impedance of the interface plug-in detection resistor Rd increases, which causes the voltage at the CC pin of the USB interface on the adapter side to fluctuate in the no-load state. At this time, the LPS adapter may mistakenly believe that there is an output current detection failure and mistakenly trigger the single-point failure protection.

[0016] However, there is currently no detection mechanism to achieve Figures 1A to 1C The output current detection failure and output control failure of the LPS adapter shown in the figure are detected simultaneously. In view of this, a failure detection method used in an LPS adapter according to an embodiment of the present invention is proposed, which can realize the simultaneous detection of output current detection failure and output control failure. Figure 1A The LPS adapter shown is used as an example for explanation. Figure 4 yes Figure 1A The illustrated waveform diagrams are of related voltages and currents when the LPS adapter implements the failure detection method according to the embodiment of the present invention.

[0017] like Figure 1A and Figure 4 As shown, after the LPS adapter is powered on but the mobile terminal device has not yet been connected to the LPS adapter, the fast charging protocol chip U1 controls the constant current source Ip to disconnect from the CC pin of the USB interface on the adapter side for a predetermined time Δt1. During the predetermined time Δt1, the voltage at the CC pin of the USB interface on the adapter side is sampled to obtain a first sampled low voltage Vcc_L1, and based on the combination of the first sampled low voltage Vcc_L1 and the output current sensing voltage at both ends of the output current detection resistor R1, it is determined whether there is a combined failure of the output current detection resistor R1+output control switch tube Q1. If the first sampled low voltage Vcc_L1 is greater than the threshold value Vth1 and the output current sensing voltage at both ends of the output current detection resistor R1 is less than the threshold value Vth_Io, it is considered that there is a combined failure of the output current detection resistor R1+output control switch tube Q1.

[0018] like Figure 1A and Figure 4As shown, after the mobile terminal device is connected to the LPS adapter but the LPS adapter has not yet turned on the power bus output, the fast charging protocol chip U1 obtains the first sampled high voltage Vcc_H1 by sampling the voltage at the CC pin of the USB interface on the adapter side, and records the first voltage difference Vcc_Δ1 between the first sampled high voltage Vcc_H1 and the first sampled low voltage Vcc_L1 as a comparison benchmark. When the single-point failure protection is triggered for the first time, the fast charging protocol chip U1 obtains the second sampled high voltage Vcc_H2 by sampling the voltage at the CC pin of the USB interface on the adapter side, controls the connection between the constant current source Ip and the CC pin of the USB interface on the adapter side to be disconnected for a predetermined time Δt1, obtains the second sampled low voltage Vcc_L2 by sampling the voltage at the CC pin of the USB interface on the adapter side during the predetermined time Δt1, records the second voltage difference Vcc_Δ2 between the second sampled high voltage Vcc_H2 and the second sampled low voltage Vcc_L2, and determines whether there is an output current detection failure by comparing the second voltage difference Vcc_Δ2 with the first voltage difference Vcc_Δ1. Here, if the second voltage difference Vcc_Δ2 is equal to the first voltage difference Vcc_Δ1 and the output current sensing voltage across the output current detection resistor R1 is less than the threshold Vth_Io, it is considered that there is an output current detection failure; if the second voltage difference Vcc_Δ2 is not equal to the first voltage difference Vcc_Δ1, it is considered that there is no output current detection failure and the comparison reference is reset to the second voltage difference Vcc_Δ2. Figure 4 As shown, when the single-point failure protection is triggered for the first time, the output current Io of the LPS adapter does not change, and the voltage mutation at the CC pin of the USB interface on the adapter side is caused by the resistance change of the interface plug-in detection resistor Rd in the mobile terminal device. The failure protection signal at this time needs to be ignored and the comparison benchmark is reset to the second voltage difference Vcc_Δ2.

[0019] like Figure 1A and Figure 4As shown, when the single-point failure protection is triggered for the second time, the fast charging protocol chip U1 obtains a third sampling high voltage Vcc_H3 by sampling the voltage at the CC pin of the USB interface on the adapter side, controls the connection between the constant current source Ip and the CC pin of the USB interface on the adapter side to be disconnected for a predetermined time Δt1, and obtains a third sampling low voltage Vcc_L3 by sampling the voltage at the CC pin of the USB interface on the adapter side during the predetermined time Δt1, records a third voltage difference Vcc_Δ3 between the third sampling high voltage Vcc_H3 and the third sampling low voltage Vcc_L3, and determines whether there is an output current detection failure by comparing the third voltage difference Vcc_Δ3 with the second voltage difference Vcc_Δ2. Here, if the third voltage difference Vcc_Δ3 is equal to the second voltage difference Vcc_Δ2 and the output current sensing voltage across the output current detection resistor R1 is less than the threshold Vth_Io, it is considered that there is an output current detection failure; if the third voltage difference Vcc_Δ3 is not equal to the second voltage difference Vcc_Δ2, it is considered that there is no output current detection failure and the comparison reference is reset to the third voltage difference Vcc_Δ3. Figure 4 As shown in the figure, when the single-point failure protection is triggered for the second time, the output current Io of the LPS adapter changes suddenly, but the output current sensing voltage across the output current detection resistor R1 remains unchanged. The voltage surge at the CC pin of the USB interface on the adapter side is caused by the change in the output current Io of the LPS adapter. At this time, the failure protection will be triggered and the power bus output will be shut down.

[0020] When the single point failure protection is triggered one or more times subsequently, the comparison benchmark reset when the single point failure protection is triggered last time can be used to repeat the same operation as when the single point protection failure is triggered for the second time to detect output current detection failure and / or reset the comparison benchmark.

[0021] like Figure 4 and Figure 1A As shown, after the LPS adapter turns off the power bus output but the mobile terminal device is still connected to the LPS adapter, the fast charging protocol chip U1 controls the constant current source Ip to disconnect from the CC pin of the USB interface on the adapter side for a predetermined time Δt1, and during the predetermined time Δt1, the voltage at the CC pin of the USB interface on the adapter side is sampled to obtain a fourth sampled low voltage Vcc_L4, and based on the combination of the fourth sampled low voltage Vcc_L4 and the output current sensing voltage across the output current detection resistor R1, it is determined whether there is a combined failure of the output current detection resistor R1+output control switch tube Q1, wherein, if the fourth sampled low voltage Vcc_L4 is greater than the threshold value Vth1 and the output current sensing voltage across the output current detection resistor R1 is less than the threshold value Vth_Io, it is considered that there is a combined failure of the output current detection resistor R1+output control switch tube Q1.

[0022] The present invention can be implemented in other specific forms without departing from its spirit and essential features. For example, the algorithms described in the specific embodiments can be modified, and the system architecture does not depart from the basic spirit of the present invention. Therefore, the current embodiments are regarded as exemplary and non-restrictive in all aspects, and the scope of the present invention is defined by the appended claims rather than the above description, and all changes falling within the meaning and equivalent scope of the claims are thus included in the scope of the present invention.

Claims

1. A power-limited power adapter, comprising a constant current source, a universal serial bus interface, an output control switch connected to a power bus pin of the universal serial bus interface, and an output current detection resistor for detecting an output current of the power-limited power adapter, wherein the power-limited power adapter is configured as follows: After the limited-power power adapter is powered on but the mobile terminal device has not yet been connected to the limited-power power adapter, the connection between the constant current source and the configuration channel pin of the universal serial bus interface is controlled to be disconnected for a predetermined time, and during the predetermined time, a first sampled low voltage is obtained by sampling the voltage at the configuration channel pin, and it is determined whether there is a combination failure of the output current detection resistor and the output control switch tube according to a combination of the first sampled low voltage and the output current sensing voltage across the output current detection resistor.

2. The power-limited power adapter according to claim 1, further configured as: When the first sampling low voltage is greater than a first threshold and the output current sensing voltage is less than a second threshold, it is considered that there is a combined failure of the output current detection resistor and the output control switch tube.

3. The power-limited power adapter according to claim 1, further configured as follows: After the mobile terminal device is connected to the power-limited power adapter but the power-limited power adapter has not yet turned on the power bus output, a first sampled high voltage is obtained by sampling the voltage at the configuration channel pin, and a first voltage difference between the first sampled high voltage and the first sampled low voltage is recorded as a comparison reference; When the single point failure protection is triggered for the first time, a second sampling high voltage is obtained by sampling the voltage at the configuration channel pin, the connection between the constant current source and the configuration channel pin is controlled to be disconnected for the predetermined time, a second sampling low voltage is obtained by sampling the voltage at the configuration channel pin during the predetermined time, a second voltage difference between the second sampling high voltage and the second sampling low voltage is recorded, and whether there is an output current detection failure is determined by comparing the second voltage difference with the first voltage difference.

4. The power-limited power adapter according to claim 3, further configured as follows: When the second voltage difference is equal to the first voltage difference and the output current sensing voltage is less than the second threshold, it is considered that the output current detection failure exists; When the second voltage difference is not equal to the first voltage difference, it is considered that there is no output current detection failure and the comparison reference is reset to the second voltage difference.

5. The power-limited power adapter according to claim 4, further configured as follows: When the single point failure protection is not triggered for the first time, a third sampling high voltage is obtained by sampling the voltage at the configuration channel pin, the connection between the constant current source and the configuration channel pin is controlled to be disconnected for the predetermined time, a third sampling low voltage is obtained by sampling the voltage at the configuration channel pin during the predetermined time, a third voltage difference between the third sampling high voltage and the third sampling low voltage is recorded, and whether the output current detection failure exists is determined by comparing the third voltage difference with the second voltage difference.

6. The power-limited power adapter according to claim 5, further configured as follows: When the third voltage difference is equal to the second voltage difference and the output current sensing voltage is less than the second threshold, it is considered that there is an output current detection failure; In the case that the third voltage difference value is not equal to the second voltage difference value, it is considered that there is no output current detection failure and the comparison reference is reset to the third voltage difference value.

7. The power-limited power adapter according to claim 1, further configured as follows: After the power-limited power adapter turns off the power bus output but the mobile terminal device is still connected to the power-limited power adapter, the connection between the constant current source and the configuration channel pin is controlled to be disconnected for the predetermined time, and during the predetermined time, a fourth sampled low voltage is obtained by sampling the voltage at the configuration channel pin, and it is determined whether there is a combination failure of the output current detection resistor and the output control switch tube according to a combination of the fourth sampled low voltage and the output current sensing voltage.

8. The power-limited power adapter according to claim 7, further configured as follows: When the fourth sampling low voltage is greater than the first threshold and the output current sensing voltage is less than the second threshold, it is considered that there is a combination failure of the output current detection resistor and the output control switch tube.

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