Power supply switching circuit and power supply switching method

Abstract

To provide a power supply switching circuit and a power supply switching method.SOLUTION: The power switching circuit is disposed in the projection apparatus, and includes a universal serial bus (USB) port, a current limiting unit, a power converter, a detection circuit, and a processing unit, where the current limiting unit is connected to the USB port and the power converter, and when the projection apparatus is in a power-on state, the power converter provides an operating voltage to the USB port through the current limiting unit to perform power supply. The detection circuit outputs a detection signal based on an electrical feature of a connection terminal of the current limiting unit, and when the projection apparatus is switched from a power-on state to a standby state, the processing unit receives a standby voltage, determines whether the USB port is in a power supply state based on the detection signal after a predetermined time, and controls the current limiting unit to be an open circuit when the USB port is not in the power supply state, thereby controlling to stop supplying power through the USB port.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a power supply switching circuit and a power supply switching method, and more particularly to a power supply switching circuit and a power supply switching method that stop power supply via a Universal Serial Bus port after the operating state of a projection device is switched to a standby state. [Background technology]

[0002] The working states of the projection device can include a power-on state, a standby state, and a power-off state. In the standby state, the conventional projection device can support a power supply function via a universal serial bus (USB) port, a local area network (LAN) connection function, a wireless network (WiFi) connection function, and an operating system (e.g., Android) standby function, and the total power consumption is greater than 0.5 watts (W).

[0003] As environmental protection issues become increasingly important, and as related regulations become more stringent, energy conservation has become an urgent need, so how to put a projection device into standby mode and adjust the overall power consumption of the projection device according to usage has become an important development direction in the industry.

[0004] The contents of the "Background" section are intended to aid in understanding the present invention, and the contents of the "Background" section may include prior art other than that known to a person of ordinary skill in the art. The contents of the "Background" section, or those representative of the problems that one or more embodiments of the present invention attempt to solve, are not already known or recognized by a person of ordinary skill in the art prior to the filing of the present invention. Summary of the Invention [Problem to be solved by the invention]

[0005] The embodiments of the present invention provide a power supply switching circuit and a power supply switching method that can put a projection device into a standby state and adjust the overall power consumption of the projection device according to usage conditions, thereby achieving energy saving effects.

[0006] Other objects and advantages of the present invention will become more apparent from the technical features disclosed in the present invention. [Means for solving the problem]

[0007] In order to achieve one, part, or all of the above objects, or other objects, one embodiment of the present invention provides a power supply switching circuit disposed in a projection device, the power supply switching circuit including: a Universal Serial Bus port; a current limiting unit having an output terminal connected to the Universal Serial Bus port; a power converter connected to an input terminal of the current limiting unit, the power converter providing an operating voltage to the Universal Serial Bus port via the current limiting unit to supply power when the projection device is in a power-on state; a detection circuit connected to the input terminal or the output terminal of the current limiting unit, the detection circuit outputting a detection signal based on an electrical characteristic of the input terminal or the output terminal of the current limiting unit; and a processing unit connected to the detection circuit and the current limiting unit, the processing unit receiving a standby voltage when the projection device is switched from the power-on state to a standby state, determining whether the Universal Serial Bus port is in a power-supply state based on the detection signal after a first predetermined time, and controlling the current limiting unit to open circuit when the Universal Serial Bus port is not in the power-supply state.

[0008] In order to achieve one, part, or all of the above objects, or other objects, one embodiment of the present invention provides a power supply switching method applied to a power supply switching circuit of a projection device, the power supply switching circuit including: a universal serial bus port; a current limiting unit; a power converter; a detection circuit; and a processing unit, an input terminal of the current limiting unit is connected to the power converter; an output terminal of the current limiting unit is connected to the universal serial bus port; the detection circuit is connected to the input terminal or the output terminal of the current limiting unit; and the processing unit is connected to the detection circuit and the current limiting unit, providing an operating voltage to the Universal Serial Bus port via a current limiting unit; when the projection device is switched from the power-on state to a standby state, the processing unit receiving the standby voltage and counting a first predetermined time; after the first predetermined time, the processing unit determining whether the Universal Serial Bus port is in a powered state based on a detection signal output by the detection circuit based on an electrical characteristic of the output terminal or the input terminal of the current limiting unit; and when it is determined that the Universal Serial Bus port is not in the powered state, the processing unit controlling the current limiting unit to open circuit. [Effects of the Invention]

[0009] As described above, the embodiments of the present invention have at least one of the following advantages or effects. In the power supply switching circuit and power supply switching method according to the present invention, when the operating state of the projection device is in standby and after a first predetermined time has elapsed, the processing unit determines whether the Universal Serial Bus port is in a power supply state based on the detection signal output by the detection circuit, and if the Universal Serial Bus port is not in a power supply state, controls the current limiting unit to open a circuit, thereby controlling to stop power supply via the Universal Serial Bus port. When the operating state of the projection device is standby, the power supply switching circuit and power supply switching method according to the embodiments of the present invention perform correlation control depending on whether the function of supplying power via the Universal Serial Bus port is supported, thereby putting the operating state of the projection device to which the power supply switching circuit and power supply switching method are applied into standby and controlling whether to continuously support the power supply function depending on the usage status, thereby adjusting (reducing) the overall power consumption when the projection device is in standby and achieving energy saving effects.

[0010] In order to make the above features and advantages of the present invention more clearly apparent, the following detailed description of preferred embodiments will be given with reference to the accompanying drawings. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a block diagram of a first embodiment of a power supply switching circuit according to the present invention. [Figure 2] 3 is a flowchart of a first embodiment of a power supply switching method according to the present invention. [Figure 3] 5 is a flowchart of a second embodiment of a power supply switching method according to the present invention. [Figure 4] FIG. 4 is a block diagram of a second embodiment of a power supply switching circuit according to the present invention. [Figure 5] 10 is a flowchart of a third embodiment of a power supply switching method according to the present invention. [Figure 6] 10 is a flowchart of a fourth embodiment of a power supply switching method according to the present invention. [Figure 7] FIG. 10 is a block diagram of a third embodiment of a power supply switching circuit according to the present invention. [Figure 8] 10 is a flowchart of a fifth embodiment of a power supply switching method according to the present invention. [Figure 9] 10 is a flowchart of a sixth embodiment of a power supply switching method according to the present invention. [Figure 10] FIG. 10 is a block diagram of a fourth embodiment of a power supply switching circuit according to the present invention. [Figure 11] 10 is a flowchart of a seventh embodiment of a power supply switching method according to the present invention. [Figure 12] 10 is a flowchart of an eighth embodiment of a power supply switching method according to the present invention. [Figure 13] FIG. 10 is a block diagram of a fifth embodiment of a power supply switching circuit according to the present invention. [Figure 14] 13 is a flowchart of a ninth embodiment of a power supply switching method according to the present invention. [Figure 15] 16 is a flowchart of a power supply switching method according to a tenth embodiment of the present invention. [Figure 16] FIG. 10 is a block diagram of a sixth embodiment of a power supply switching circuit according to the present invention. [Figure 17] 11 is a flowchart of an eleventh embodiment of a power supply switching method according to the present invention. [Figure 18] 12 is a flowchart of a power supply switching method according to a twelfth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] The above and other technical contents, features, and advantages of the present invention will be apparent from the detailed description of preferred embodiments with reference to the following drawings. Directional terms such as "upper," "lower," "left," "right," "front," and "rear" used in the following embodiments are merely descriptive terms referring to directions when referring to the drawings, and the present invention is not limited to those indicated by the directional terms.

[0013] FIG. 1 is a block diagram of a first embodiment of a power supply switching circuit according to the present invention. As shown in FIG. 1, the power supply switching circuit 100 is disposed in a projection device (not shown) and includes a universal serial bus port 110, a current limiting unit 120, a power converter 130, a detection circuit 140, and a processing unit 150. An input terminal 122 of the current limiting unit 120 is connected to the power converter 130, an output terminal 124 of the current limiting unit 120 is connected to the universal serial bus port 110, the detection circuit 140 is connected to the power converter 130 and the input terminal 122 of the current limiting unit 120, and the processing unit 150 is connected to the detection circuit 140 and the current limiting unit 120. The universal serial bus port 110 may be a Type-A universal serial bus port or a Type-C universal serial bus port. The current limiting unit 120 may be a switching element (e.g., a transistor, which may be an N-channel metal oxide semiconductor field effect transistor or an NPN bipolar transistor) for overcurrent protection. The power converter 130 may be a direct current / direct current (DC / DC) converter. The processing unit 150 may include a central processing unit (CPU), a microprocessor, a digital signal processor (DSP), a programmable controller, a programmable logic device (PLD), or other similar devices, or a combination of these devices. The projection device is, for example, a projector.

[0014] When the operating state of the projection device is in a power-on state, the power converter 130 provides an operating voltage to the Universal Serial Bus port 110 via the current limiting unit 120 to supply power. Specifically, the power converter 130 may convert a DC voltage Vin (e.g., 12 volts) supplied by a system (e.g., the main board side of the projector) into an operating voltage (e.g., 5 volts) and supply the operating voltage to the Universal Serial Bus port 110 via the current limiting unit 120 to supply power. Therefore, when the operating state of the projection device is in a power-on state, the projection device can be charged by supplying power to an external electronic device via the Universal Serial Bus port 110. The external electronic device may be, for example, a smartphone, a smart tablet, a computer, a TV stick, or other electronic device.

[0015] The detection circuit 140 outputs a detection signal based on an electrical characteristic of the input terminal 122 of the current limiting unit 120. The electrical characteristic may include a voltage. In this embodiment, when no external electronic device is connected to the Universal Serial Bus port 110, the detection circuit 140 may output a corresponding detection signal based on the operating voltage supplied to the Universal Serial Bus port 110, which is received by the input terminal 122 of the current limiting unit 120. When an external electronic device is being charged via the Universal Serial Bus port 110 (the operating voltage supplied to the Universal Serial Bus port 110 is extracted), the detection circuit 140 may output a corresponding detection signal in response to a voltage drop occurring in synchronization with the input terminal 122 of the current limiting unit 120 (in this case, the voltage at the input terminal 122 of the current limiting unit 120 is lower than the operating voltage).

[0016] When the operating state of the projection device is switched from the power-on state to the standby state, the processing unit 150 receives the standby voltage Vsb. After a first predetermined time (e.g., 20 minutes), the processing unit 150 determines whether the Universal Serial Bus port 110 is in a powered state based on the detection signal. If the Universal Serial Bus port 110 is not in a powered state, the processing unit 150 controls the current limiting unit 120 to open circuit. Specifically, a user may operate the projection device by pressing the power key of the projection device or by operating the remote control of the projection device to switch the operating state of the projection device from the power-on state to the standby state. When the projection device is in the standby state, a power supply (not shown) of the projection device can still supply the standby voltage Vsb to the processing unit 150 so that the processing unit 150 can continue to operate. Therefore, the processing unit 150 may count the first predetermined time when the projection device is switched from the power-on state to the standby state. When the projection device is in standby mode, the power converter 130 can still supply power by supplying an operating voltage to the Universal Serial Bus port 110 via the current limiting unit 120. After the first predetermined time has elapsed, the processing unit 150 determines whether the Universal Serial Bus port 110 is in a power supply state (i.e., whether the Universal Serial Bus port 110 is supplying power to an external electronic device) based on whether a voltage drop occurs at the input terminal 122 of the current limiting unit 120. If the processing unit 150 subsequently determines that the Universal Serial Bus port 110 is not in a power supply state, it controls the current limiting unit 120 to open circuit (i.e., turns off the switch element functioning as the current limiting unit 120), controls to stop the power supply via the Universal Serial Bus port 110, and switches the operating state of the projection device from standby mode to an energy-saving mode.

[0017] In this way, the power supply switching circuit 100 can be used to place the projection device in a standby state, and it can control whether to continuously support the function of supplying power via the Universal Serial Bus port 110 depending on the usage status (i.e., whether the Universal Serial Bus port 110 is in a power supply state), thereby adjusting (reducing) the overall power consumption of the projection device in a standby state and achieving energy conservation. Furthermore, the projection device can meet the standby power consumption requirements of the Energy-Related Products Directive (ErP Directive) 2023 / 826 issued by the European Commission on April 17, 2023.

[0018] The following description will be given with reference to FIGS. 1 and 2. FIG. 2 is a flowchart of a first embodiment of a power supply switching method according to the present invention. The power supply switching method of FIG. 2 may be applied to the power supply switching circuit 100 of FIG. 1. In step S210, if the projection device is in a power-on state, the power converter 130 provides an operating voltage to the Universal Serial Bus port 110 via the current limiting unit 120 to supply power. In step S220, if the projection device is switched from the power-on state to a standby state, the processing unit 150 receives the standby voltage Vsb and counts a first predetermined time. In step S230, after the first predetermined time, the processing unit 150 determines whether the Universal Serial Bus port 110 is in a power supply state based on the detection signal output by the detection circuit 140 based on the electrical characteristics of the input terminal 122 of the current limiting unit 120. In step S240, if it is determined that the Universal Serial Bus port 110 is not in a power supply state, the processing unit 150 controls the current limiting unit 120 to open circuit. In one embodiment, the processing unit 150 repeatedly executes step S230 when it determines that the Universal Serial Bus port 110 is in a powered state. The details of the implementation of steps S210 to S240 are described in detail in the embodiment of FIG. 1, and therefore will not be described here.

[0019] The following description will be given with reference to FIGS. 1 and 3. FIG. 3 is a flowchart of a second embodiment of a power supply switching method according to the present invention. The power supply switching method of FIG. 3 may be applied to the power supply switching circuit 100 of FIG. 1. The power supply switching method of FIG. 3 differs from the power supply switching method of FIG. 2 in that, in addition to steps S210 to S240, the power supply switching method of FIG. 3 may further include a step (step S350) in which, if it is determined that the Universal Serial Bus port 110 is in a power supply state, the processing unit 150 counts a second predetermined time, and then determines again whether the Universal Serial Bus port 110 is in a power supply state based on the detection signal output by the detection circuit 140. Here, the first predetermined time and the second predetermined time may be the same or different and may be set according to actual needs. In one embodiment, both the first predetermined time and the second predetermined time may be 20 minutes.

[0020] Specifically, if the processing unit 150 determines that the Universal Serial Bus port 110 is in a power supply state after a first predetermined time has elapsed, it counts a second predetermined time, and after the second predetermined time has elapsed, it again determines whether the Universal Serial Bus port 110 is in a power supply state based on whether a voltage drop has occurred at the input terminal 122 of the current limiting unit 120 (i.e., it determines whether the Universal Serial Bus port 110 is supplying power to an external electronic device). If the processing unit 150 determines that the Universal Serial Bus port 110 is in a power supply state, it repeatedly executes step S350. If the processing unit 150 determines that the Universal Serial Bus port 110 is not in a power supply state, it executes step S240.

[0021] Fig. 4 is a block diagram of a second embodiment of a power supply switching circuit according to the present invention. A power supply switching circuit 400 in Fig. 4 differs from the power supply switching circuit 100 in Fig. 1 in that the detection circuit 140 in Fig. 4 is a voltage divider circuit, one end of which is connected to the input terminal 122 of the current limiter 120, the other end of which is grounded, and a voltage-dividing point P of the voltage-dividing circuit is connected to the processing unit 150. The processing unit 150 determines whether the universal serial bus port 110 is in a powered state based on the voltage at the voltage-dividing point P. The detection signal output by the detection circuit 140 is the voltage at the voltage-dividing point P. The voltage-dividing circuit may include a first resistor 141 and a second resistor 142. One end of the first resistor 141 is connected to the input terminal 122 of the current limiting unit 120, the other end of the first resistor 141 is connected to one end of the second resistor 142, the other end of the second resistor 142 is grounded, the connection point between the first resistor 141 and the second resistor 142 is a voltage division point P, and the voltage division point P is connected to a pin of the processing unit 150.

[0022] The voltage at the voltage divider point P changes in synchronization with the voltage at the input terminal 122 of the current limiter 120 (i.e., the voltage at the voltage divider point P corresponds to the electrical characteristics of the input terminal 122 of the current limiter 120). In this embodiment, the detection circuit 140 may supply the voltage at the voltage divider point P to the processing unit 150. When an external electronic device is charged via the Universal Serial Bus port 110 (i.e., when the operating voltage supplied to the Universal Serial Bus port 110 is extracted), the detection circuit 140 may supply the voltage at which a voltage drop occurs at the voltage divider point P to the processing unit 150. Therefore, the processing unit 150 determines whether the Universal Serial Bus port 110 is in a powered state (i.e., whether the Universal Serial Bus port 110 is supplying power to the external electronic device) based on whether a voltage drop occurs at the voltage divider point P after a first predetermined time has elapsed. If the processing unit 150 determines that the universal serial bus port 110 is not in a powered state, it controls the current limiting unit 120 to open circuit, and controls the power supply via the universal serial bus port 110 to stop.

[0023] The following description will be given with reference to FIGS. 4 and 5. FIG. 5 is a flowchart of a third embodiment of a power supply switching method according to the present invention. The power supply switching method of FIG. 5 may be applied to the power supply switching circuit 400 of FIG. 4. The power supply switching method of FIG. 5 differs from the power supply switching method of FIG. 2 in that step S230 of FIG. 2 is replaced with step S530. In step S530, the processing unit 150 determines whether the Universal Serial Bus port 110 is in a powered state based on the voltage at the voltage dividing point P after a first predetermined time. In one embodiment, if the processing unit 150 determines that the Universal Serial Bus port 110 is in a powered state, it repeatedly executes step S530. The details of the implementation of step S530 have been described in detail in the embodiment of FIG. 4, and therefore will not be described again here.

[0024] The following description will be given with reference to FIGS. 4 and 6. FIG. 6 is a flowchart of a fourth embodiment of a power supply switching method according to the present invention. The power supply switching method of FIG. 6 may be applied to the power supply switching circuit 400 of FIG. 4. The power supply switching method of FIG. 6 differs from the power supply switching method of FIG. 5 in that, in addition to steps S210, S220, S530, and S240, the power supply switching method of FIG. 6 may further include a step (step S650) in which, if it is determined that the Universal Serial Bus port 110 is in a powered state, the processing unit 150 counts a second predetermined time, and then re-determines whether the Universal Serial Bus port 110 is in a powered state based on the voltage from the voltage dividing point P of the detection circuit 140. Here, the first predetermined time and the second predetermined time may be the same or different and may be set according to actual needs. Specifically, if the processing unit 150 determines that the universal serial bus port 110 is in a power supply state after a first predetermined time has elapsed, it counts a second predetermined time, and after the second predetermined time has elapsed, it again determines whether the universal serial bus port 110 is in a power supply state based on whether a voltage drop has occurred at the voltage division point P (i.e., it determines whether the universal serial bus port 110 is supplying power to an external electronic device). If the processing unit 150 determines that the universal serial bus port 110 is in a power supply state, it repeatedly executes step S650. If the processing unit 150 determines that the universal serial bus port 110 is not in a power supply state, it executes step S240.

[0025] Fig. 7 is a block diagram of a third embodiment of a power supply switching circuit according to the present invention. The power supply switching circuit 700 of Fig. 7 differs from the power supply switching circuit 400 of Fig. 4 in that the power supply switching circuit 700 further includes a power management unit 710 and a control unit 720. The power management unit 710 is connected to the processing unit 150, and the control unit 720 is connected to the processing unit 150, the power management unit 710, and the current limiting unit 120. When the Universal Serial Bus port 110 is not in a powered state, the processing unit 150 activates the power management unit 710 to supply power to the control unit 720 and controls the current limiting unit 120 via the control unit 720 to open the circuit.

[0026] When the projection device is in standby mode, the power supply (not shown) of the projection device supplies only standby voltage Vsb to the processing unit 150 to maintain operation of the processing unit 150, while the power management unit 710 and control unit 720 are inoperable due to lack of power (i.e., the power management unit 710 and control unit 720 are in sleep mode). Therefore, when a user operates the projection device by pressing the power key or by operating the remote control of the projection device to switch the projection device from the power-on mode to the standby mode, the processing unit 150 counts a first predetermined time, and the power converter 130 can supply the operating voltage to the Universal Serial Bus port 110 via the current limiting unit 120 to supply power. After the first predetermined time has elapsed, the processing unit 150 determines whether the Universal Serial Bus port 110 is in a powered state (i.e., determines whether the Universal Serial Bus port 110 is supplying power to an external electronic device) based on whether a voltage drop has occurred at the voltage dividing point P. Thereafter, when the processing unit 150 determines that the Universal Serial Bus port 110 is not in a powered state, it enables the power management unit 710 through a general purpose input / output (GPIO) setting, supplies a system voltage to the control unit 720 via the power management unit 710, and wakes up the control unit 720. Next, the processing unit 150 controls the current limiting unit 120 to be an open circuit, and transmits a change in power mode setting via a transmission interface (e.g., an inter-integrated circuit (I / F) bus) so that the control unit 720 sends a stop signal to the current limiting unit 120 to cut off the operating voltage supplied from the power converter 130 to the Universal Serial Bus port 110 via the current limiting unit 120. 2 C) interface) to the control unit 720. Next, the power management unit 710 and control unit 720 return to a sleep state because the operating state of the projection device remains in a standby state. The power management unit 710 is, for example, a power management circuit (Power Management IC). The control unit 720 is, for example, a DDP processing circuit.

[0027] In this way, a projection device employing the power supply switching circuit 700 can control whether or not to continuously support the function of supplying power via the Universal Serial Bus port 110 while in standby mode, depending on the usage status (i.e., whether or not the Universal Serial Bus port 110 is in a power supply state), thereby adjusting (reducing) the overall power consumption of the projection device in standby mode and achieving an energy-saving effect.

[0028] The following description will be given with reference to FIGS. 7 and 8. FIG. 8 is a flowchart of a fifth embodiment of a power supply switching method according to the present invention. The power supply switching method of FIG. 8 may be applied to the power supply switching circuit 700 of FIG. 7. The power supply switching method of FIG. 8 differs from the power supply switching method of FIG. 5 in that step S240 of FIG. 5 is replaced with step S840. If the processing unit 150 determines in step S840 that the Universal Serial Bus port 110 is not in a powered state, the processing unit 150 activates the power management unit 710 to supply power to the control unit 720 and controls the current limiting unit 120 via the control unit 720 to open circuit. In one embodiment, if the processing unit 150 determines that the Universal Serial Bus port 110 is in a powered state, the processing unit 150 repeatedly executes step S530. The details of the implementation of step S840 have been described in detail in the embodiment of FIG. 7, and will not be described again here.

[0029] The following description will be given with reference to FIGS. 7 and 9. FIG. 9 is a flowchart of a sixth embodiment of a power supply switching method according to the present invention. The power supply switching method of FIG. 9 may be applied to the power supply switching circuit 700 of FIG. 7. The power supply switching method of FIG. 9 differs from the power supply switching method of FIG. 8 in that, in addition to steps S210, S220, S530, and S840, the power supply switching method of FIG. 9 may further include a step (step S650) in which, if it is determined that the Universal Serial Bus port 110 is in a powered state, the processing unit 150 counts a second predetermined time, and then determines again whether the Universal Serial Bus port 110 is in a powered state based on the voltage from the voltage-dividing point P of the detection circuit 140. The details of the implementation of step S650 have been described in detail in the embodiment of FIG. 6, and therefore will not be described here.

[0030] Fig. 10 is a block diagram of a fourth embodiment of a power supply switching circuit according to the present invention. The power supply switching circuit 1000 of Fig. 10 differs from the power supply switching circuit 100 of Fig. 1 in that the detection circuit 140 is connected to the output terminal 124 of the current limiting unit 120, the output terminal 124 of the current limiting unit 120 is indirectly connected to the Universal Serial Bus port 110 (i.e., the detection circuit 140 is provided between the current limiting unit 120 and the Universal Serial Bus port 110), the electrical characteristic includes a current, and the detection circuit 140 outputs a detection signal based on the electrical characteristic of the output terminal 124 of the current limiting unit 120.

[0031] The following description will be given with reference to FIGS. 10 and 11. FIG. 11 is a flowchart of a seventh embodiment of a power supply switching method according to the present invention. The power supply switching method of FIG. 11 differs from the power supply switching method of FIG. 2 in that step S230 of FIG. 2 is replaced with step S1130. In step S1130, the processing unit 150 determines whether the Universal Serial Bus port 110 is in a powered state after a first predetermined time based on a detection signal output by the detection circuit 140 based on the electrical characteristics of the output terminal 124 of the current limiting unit 120. In one embodiment, if the processing unit 150 determines that the Universal Serial Bus port 110 is in a powered state, it repeatedly executes step S1130. The details of the implementation of step S1130 are similar to the details of the implementation of step S230, and therefore will not be described again here.

[0032] The following description will be given with reference to FIGS. 10 and 12. FIG. 12 is a flowchart of an eighth embodiment of a power supply switching method according to the present invention. The power supply switching method of FIG. 12 may be applied to the power supply switching circuit 1000 of FIG. 10. The power supply switching method of FIG. 12 differs from the power supply switching method of FIG. 11 in that the power supply switching method of FIG. 12 may further include a step (step S1250) in which, when it is determined that the Universal Serial Bus port 110 is in a powered state, the processing unit 150 counts a second predetermined time, and then determines again whether the Universal Serial Bus port 110 is in a powered state based on a detection signal from the detection circuit 140. The first predetermined time and the second predetermined time may be the same or different and may be set according to actual needs. Specifically, if the processing unit 150 determines that the Universal Serial Bus port 110 is in a power supply state after a first predetermined time has elapsed, it counts a second predetermined time, and after the second predetermined time has elapsed, it again determines whether the Universal Serial Bus port 110 is in a power supply state based on whether a voltage drop has occurred at the output terminal 124 of the current limiting unit 120 (i.e., it determines whether the Universal Serial Bus port 110 is supplying power to an external electronic device). If the processing unit 150 determines that the Universal Serial Bus port 110 is in a power supply state, it repeatedly executes step S1250. If the processing unit 150 determines that the Universal Serial Bus port 110 is not in a power supply state, it executes step S240.

[0033] Fig. 13 is a block diagram of a fifth embodiment of a power supply switching circuit according to the present invention. The power supply switching circuit 1300 of Fig. 13 differs from the power supply switching circuit 1000 of Fig. 10 in that the detection circuit 140 of Fig. 13 includes a shunt resistor 143 and a current sense amplifier 144. One end of the shunt resistor 143 is connected to the output terminal 124 of the current limiter 120, the other end of the shunt resistor 143 is connected to the Universal Serial Bus port 110, and the current sense amplifier 144 is connected in parallel with the shunt resistor 143. The current sense amplifier 144 outputs a corresponding sense voltage signal to the processing unit 150 based on the current flowing through the shunt resistor 143 so that the processing unit 150 can determine whether the Universal Serial Bus port 110 is in a powered state based on the sense voltage signal. The detection signal output by the detection circuit 140 is the sense voltage signal.

[0034] The magnitude of the current flowing through the shunt resistor 143 is equal to the current at the output terminal 124 of the current limiting unit 120 (i.e., the current flowing through the shunt resistor 143 corresponds to the electrical characteristics of the output terminal 124 of the current limiting unit 120). When an external electronic device is charged via the Universal Serial Bus port 110, the current flowing through the shunt resistor 143 increases, and the current sense amplifier 144 can supply a sense voltage signal corresponding to the increase in current flowing through the shunt resistor 143 to the processing unit 150. Therefore, after a first predetermined time has elapsed, the processing unit 150 determines whether the Universal Serial Bus port 110 is in a power supply state based on the received sense voltage signal (i.e., whether the Universal Serial Bus port 110 is supplying power to the external electronic device). If the processing unit 150 determines that the Universal Serial Bus port 110 is not in a power supply state, the processing unit 150 controls the current limiting unit 120 to open circuit, controls to stop power supply via the Universal Serial Bus port 110, and switches the operating state of the projection device from a standby state to an energy-saving state.

[0035] The following description will be given with reference to FIGS. 13 and 14. FIG. 14 is a flowchart of a ninth embodiment of a power supply switching method according to the present invention. The power supply switching method of FIG. 14 may be applied to the power supply switching circuit 1300 of FIG. 13. The power supply switching method of FIG. 14 differs from the power supply switching method of FIG. 11 in that step S1130 of FIG. 11 is replaced with step S1430 in the power supply switching method of FIG. 14. In step S1430, after a first predetermined time, the processing unit 150 determines whether the Universal Serial Bus port 110 is in a powered state based on a corresponding sense voltage signal output by the current sense amplifier 144 based on the current flowing through the shunt resistor 143. In one embodiment, if the processing unit 150 determines that the Universal Serial Bus port 110 is in a powered state, it repeatedly executes step S1430. The details of the implementation of step S1430 have been described in detail in the embodiment of FIG. 13, and therefore will not be described again here.

[0036] The following description will be given with reference to FIGS. 13 and 15. FIG. 15 is a flowchart of a tenth embodiment of a power supply switching method according to the present invention. The power supply switching method of FIG. 15 may be applied to the power supply switching circuit 1300 of FIG. 13. The power supply switching method of FIG. 15 differs from the power supply switching method of FIG. 14 in that, in addition to steps S210, S220, S1430, and S240, the power supply switching method of FIG. 15 may further include a step (step S1550) in which, if it is determined that the Universal Serial Bus port 110 is in a powered state, the processing unit 150 counts a second predetermined time, and then re-determines whether the Universal Serial Bus port 110 is in a powered state based on the sensed voltage signal from the detection circuit 140. Here, the first predetermined time and the second predetermined time may be the same or different and may be set according to actual needs. Specifically, if the processing unit 150 determines that the Universal Serial Bus port 110 is in a power supply state after a first predetermined time has elapsed, it counts a second predetermined time, and after the second predetermined time has elapsed, it again determines whether the Universal Serial Bus port 110 is in a power supply state based on the sensed voltage signal (i.e., determines whether the Universal Serial Bus port 110 is supplying power to an external electronic device). If the processing unit 150 determines that the Universal Serial Bus port 110 is in a power supply state, it repeatedly executes step S1550. If the processing unit 150 determines that the Universal Serial Bus port 110 is not in a power supply state, it executes step S240.

[0037] FIG. 16 is a block diagram of a sixth embodiment of a power supply switching circuit according to the present invention. The power supply switching circuit 1600 of FIG. 16 differs from the power supply switching circuit 1000 of FIG. 10 in that the detection circuit 140 of FIG. 16 includes a magnetic field detector 145 and a detection amplifier 146. One end of the magnetic field detector 145 is connected to the output terminal 124 of the current limiting unit 120, and the other end of the magnetic field detector 145 is connected to the Universal Serial Bus port 110 (i.e., the magnetic field detector 145 connects the output terminal 124 of the current limiting unit 120 to the Universal Serial Bus port 110). The magnetic field detector 145 measures a magnetic field. The detection amplifier 146 is connected in parallel with the magnetic field detector 145. The detection amplifier 146 outputs a corresponding measurement voltage signal to the processing unit 150 based on the measurement result of the magnetic field detector 145, so that the processing unit 150 can determine whether the Universal Serial Bus port 110 is in a powered state based on the measurement voltage signal. Here, the detection signal output by the detection circuit 140 is the measurement voltage signal. The magnetic field detector 145 is, for example, an iron core or a Hall element. If the magnetic field detector 145 is an iron core, a magnetic field is generated in the iron core by a current flowing through the iron core. The detection amplifier 146 is a current sensing amplifier that outputs a corresponding measurement voltage signal to the processing unit 150 based on the current flowing through the iron core (the measurement result of the magnetic field detector 145). If the magnetic field detector 145 is a Hall element, the Hall element converts the magnetic field generated by the current flowing through the Hall element into a Hall voltage by the Hall effect. The detection amplifier 146 is a voltage sensing amplifier that outputs a corresponding measurement voltage signal to the processing unit 150 based on the Hall voltage.

[0038] The magnitude of the current flowing through the magnetic field detector 145 is equal to the current at the output terminal 124 of the current limiting unit 120 (i.e., the current flowing through the magnetic field detector 145 corresponds to the electrical characteristics of the output terminal 124 of the current limiting unit 120). When an external electronic device is charged via the Universal Serial Bus port 110, the current flowing through the magnetic field detector 145 increases, and the detection amplifier 146 can provide a measurement voltage signal corresponding to the increase in current flowing through the magnetic field detector 145 to the processing unit 150. Therefore, after a first predetermined time has elapsed, the processing unit 150 determines whether the Universal Serial Bus port 110 is in a power supply state (i.e., whether the Universal Serial Bus port 110 is supplying power to the external electronic device) based on the received measurement voltage signal. If the processing unit 150 determines that the Universal Serial Bus port 110 is not in a power supply state, the processing unit 150 controls the current limiting unit 120 to open circuit, controls to stop power supply via the Universal Serial Bus port 110, and switches the operating state of the projection device from a standby state to an energy-saving state.

[0039] The following description will be given with reference to FIGS. 16 and 17. FIG. 17 is a flowchart of an eleventh embodiment of a power supply switching method according to the present invention. The power supply switching method of FIG. 17 may be applied to the power supply switching circuit 1600 of FIG. 16. The power supply switching method of FIG. 17 differs from the power supply switching method of FIG. 11 in that step S1130 of FIG. 11 is replaced with step S1730. In step S1730, after a first predetermined time, the processing unit 150 determines whether the Universal Serial Bus port 110 is in a powered state based on a corresponding measurement voltage signal output by the detection amplifier 146 based on the measurement result of the magnetic field measured by the magnetic field detector 145. In one embodiment, if the processing unit 150 determines that the Universal Serial Bus port 110 is in a powered state, it repeatedly executes step S1730. The details of the implementation of step S1730 have been described in detail in the embodiment of FIG. 16, and therefore will not be described again here.

[0040] The following description will be given with reference to FIGS. 16 and 18. FIG. 18 is a flowchart of a twelfth embodiment of a power supply switching method according to the present invention. The power supply switching method of FIG. 18 may be applied to the power supply switching circuit 1600 of FIG. 16. The power supply switching method of FIG. 18 differs from the power supply switching method of FIG. 17 in that, in addition to steps S210, S220, S1730, and S240, the power supply switching method of FIG. 18 may further include a step (step S1850) in which, if it is determined that the Universal Serial Bus port 110 is in a powered state, the processing unit 150 counts a second predetermined time, and then determines again whether the Universal Serial Bus port 110 is in a powered state based on the measured voltage signal from the detection circuit 140. Here, the first predetermined time and the second predetermined time may be the same or different and may be set according to actual needs. Specifically, if the processing unit 150 determines that the Universal Serial Bus port 110 is in a power supply state after a first predetermined time has elapsed, it counts a second predetermined time, and after the second predetermined time has elapsed, it again determines whether or not the Universal Serial Bus port 110 is in a power supply state based on the measured voltage signal (i.e., determines whether or not the Universal Serial Bus port 110 is supplying power to an external electronic device). If the processing unit 150 determines that the Universal Serial Bus port 110 is in a power supply state, it repeatedly executes step S1850. If the processing unit 150 determines that the Universal Serial Bus port 110 is not in a power supply state, it executes step S240.

[0041]

[0013] From the above, the power supply switching circuit and power supply switching method according to the embodiments of the present invention have at least one of the following advantages or effects:

[0014] In the power supply switching circuit and power supply switching method according to the present invention, when the operating state of the projection device is in standby and a first predetermined time has elapsed, the processing unit determines whether the Universal Serial Bus port is in a power supply state based on the detection signal output by the detection circuit, and if the Universal Serial Bus port is not in a power supply state, controls the current limiting unit to open a circuit, thereby controlling to stop power supply via the Universal Serial Bus port.

[0015] When the operating state of the projection device is standby, the power supply switching circuit and power supply switching method according to the embodiments of the present invention perform correlation control depending on whether the function of supplying power via the Universal Serial Bus port is supported, thereby putting the operating state of the projection device to which the power supply switching circuit and power supply switching method are applied into standby and controlling whether to continuously support the power supply function depending on the usage status, thereby adjusting (reducing) the overall power consumption when the projection device is in standby, thereby achieving energy saving effects. In addition, the projection device can meet the standby power consumption requirements of Directive 2023 / 826 on Energy-related Products issued by the European Commission on April 17, 2023.

[0042] The above description is merely a preferred embodiment of the present invention and does not limit the scope of the present invention. Any changes and modifications may be made by those skilled in the art based on the claims and the contents of the specification, and the scope of protection of the present invention is determined by the claims. Furthermore, neither the embodiments nor the claims of the present invention necessarily achieve all of the objectives, advantages, or features disclosed by the present invention. Furthermore, the abstract and the title of the invention are merely intended to aid in patent document searches and are not intended to limit the scope of the present invention. Furthermore, terms such as "first," "second," etc. in the specification or claims are merely intended to name elements or distinguish between different embodiments or scopes, and are not intended to limit the number of elements. [Explanation of symbols]

[0043] 100, 400, 700, 1000, 1300, 1600: Power supply switching circuit 110: Universal Serial Bus port 120: Current limiter 122: Input terminal 124: Output terminal 130: Power converter 140: Detection circuit 141: The First Resistance 142: The Second Resistance 143: Shunt resistance 144: Current sense amplifier 145: Magnetic field detector 146: Detect amplifier 150: Processing section 710: Power management section 720: Control unit P: partial pressure point S210, S220, S230, S240, S350, S530, S650: Step S840, S1130, S1250, S1430, S1550, S1730, S1850: Step Vin: DC voltage Vsb: Standby voltage

Claims

1. A power supply switching circuit disposed in a projection device, Universal Serial Bus port and a current limiting unit having an output terminal connected to the Universal Serial Bus port; a power converter connected to an input terminal of the current limiting unit, the power converter providing an operating voltage to the Universal Serial Bus port through the current limiting unit to perform power supply when the projection device is in a power-on state; a detection circuit connected to the input terminal or the output terminal of the current limiting unit, the detection circuit outputting a detection signal based on an electrical characteristic of the input terminal or the output terminal of the current limiting unit; a processing unit connected to the detection circuit and the current limiting unit, the processing unit receiving a standby voltage when the projection device is switched from the power-on state to a standby state, determining whether the Universal Serial Bus port is in a powered state based on the detection signal after a first predetermined time, and controlling the current limiting unit to open circuit when the Universal Serial Bus port is not in the powered state.

2. The power supply switching circuit of claim 1 , wherein the electrical characteristic includes at least one of a voltage and a current.

3. 2. The power supply switching circuit according to claim 1, wherein the processing unit determines again whether the Universal Serial Bus port is in the power supply state based on the detection signal output by the detection circuit after a second predetermined time has elapsed since the processing unit determined that the Universal Serial Bus port is in the power supply state.

4. The power supply switching circuit according to claim 3 , wherein the first predetermined time and the second predetermined time are the same or different.

5. the detection circuit is a voltage divider circuit, one end of the voltage divider circuit is connected to the input terminal of the current limiting unit, the other end of the voltage divider circuit is grounded, and a voltage division point of the voltage divider circuit is connected to the processing unit; 2. The power supply switching circuit according to claim 1, wherein the processing unit determines whether the Universal Serial Bus port is in the power supply state based on a voltage at the voltage division point, and the detection signal is the voltage at the voltage division point.

6. a power management unit connected to the processing unit; a control unit connected to the processing unit, the power management unit, and the current limiting unit, 6. The power supply switching circuit according to claim 5, wherein, when the Universal Serial Bus port is not in the power supply state, the processing unit activates the power management unit to supply power to the control unit, and controls the current limiting unit to be an open circuit via the control unit.

7. the detection circuit includes a shunt resistor and a current sense amplifier, one end of the shunt resistor is connected to the output terminal of the current limiting unit, the other end of the shunt resistor is connected to the Universal Serial Bus port, and the current sense amplifier is connected in parallel to the shunt resistor; 2. The power supply switching circuit according to claim 1, wherein the current sense amplifier outputs a corresponding sense voltage signal to the processing unit based on the current flowing through the shunt resistor, so that the processing unit determines whether the Universal Serial Bus port is in the power supply state based on the sense voltage signal, and the detection signal is the sense voltage signal.

8. the detection circuit includes a magnetic field detector and a detection amplifier, the magnetic field detector is connected to the output terminal of the current limiting unit and the universal serial bus port to measure a magnetic field, and the detection amplifier is connected in parallel with the magnetic field detector; 2. The power supply switching circuit according to claim 1, wherein the detection amplifier outputs the corresponding measurement voltage signal to the processing unit based on the measurement result of the magnetic field detector, so that the processing unit determines whether the Universal Serial Bus port is in the power supply state based on the measurement voltage signal, and the detection signal is the measurement voltage signal.

9. The power supply switching circuit according to claim 8 , wherein the magnetic field detector is an iron core or a Hall element.

10. A power supply switching method applied to a power supply switching circuit of a projection device, comprising: the power supply switching circuit includes a universal serial bus port, a current limiting unit, a power converter, a detection circuit, and a processing unit, an input terminal of the current limiting unit is connected to the power converter, an output terminal of the current limiting unit is connected to the universal serial bus port, the detection circuit is connected to the input terminal or the output terminal of the current limiting unit, and the processing unit is connected to the detection circuit and the current limiting unit; The power supply switching method includes: When the projection device is in a power-on state, providing an operating voltage to the Universal Serial Bus port through the current limiting unit so that the power converter performs power supply; When the projection device is switched from the power-on state to a standby state, the processing unit receives a standby voltage and counts a first predetermined time; a step of determining, after the first predetermined time, whether the Universal Serial Bus port is in a powered state based on a detection signal output by the detection circuit based on an electrical characteristic of the output terminal or the input terminal of the current limiting unit; and when it is determined that the Universal Serial Bus port is not in the power supply state, the processing unit controls the current limiting unit to open circuit.

11. 11. The power supply switching method according to claim 10, further comprising the step of: when it is determined that the Universal Serial Bus port is in the power supply state, the processing unit counts a second predetermined time, and then determining again whether or not the Universal Serial Bus port is in the power supply state based on the detection signal output by the detection circuit.

12. the detection circuit is a voltage divider circuit, one end of the voltage divider circuit is connected to the input terminal of the current limiting unit, the other end of the voltage divider circuit is grounded, and a voltage division point of the voltage divider circuit is connected to the processing unit; the step of determining, after the first predetermined time, whether the Universal Serial Bus port is in the power supply state based on a detection signal output by the detection circuit based on the electrical characteristics of the output terminal or the input terminal of the current limiting unit, by the processing unit, 11. The power supply switching method according to claim 10, further comprising the step of: after the first predetermined time, the processing unit determining whether the Universal Serial Bus port is in the power supply state based on a voltage at the voltage divider point, wherein the detection signal is the voltage at the voltage divider point.

13. The power supply switching circuit a power management unit connected to the processing unit; a control unit connected to the processing unit, the power management unit, and the current limiting unit, When it is determined that the Universal Serial Bus port is not in the power supply state, the step of controlling the processing unit to open the current limiting unit includes:

13. The power supply switching method according to claim 12, further comprising the step of: when the Universal Serial Bus port is not in the power supply state, the processing unit activates the power management unit to supply power to the control unit, and controls the current limiting unit to open circuit via the control unit.

14. the detection circuit includes a shunt resistor and a current sense amplifier, one end of the shunt resistor is connected to the output terminal of the current limiting unit, the other end of the shunt resistor is connected to the Universal Serial Bus port, and the current sense amplifier is connected in parallel to the shunt resistor; the step of determining, after the first predetermined time, whether the Universal Serial Bus port is in the power supply state based on a detection signal output by the detection circuit based on the electrical characteristics of the output terminal or the input terminal of the current limiting unit, by the processing unit, 11. The power supply switching method of claim 10, further comprising the step of: after the first predetermined time, the processing unit determines whether the Universal Serial Bus port is in the power supply state based on a corresponding sense voltage signal output by the current sense amplifier based on the current flowing through the shunt resistor, wherein the detection signal is the sense voltage signal.

15. the detection circuit includes a magnetic field detector and a detection amplifier, the magnetic field detector is connected to the output terminal of the current limiting unit and the universal serial bus port, and the detection amplifier is connected in parallel with the magnetic field detector; the step of determining, after the first predetermined time, whether the Universal Serial Bus port is in the power supply state based on a detection signal output by the detection circuit based on the electrical characteristics of the output terminal or the input terminal of the current limiting unit, by the processing unit, 11. The power supply switching method according to claim 10, further comprising the step of: after the first predetermined time, determining whether the Universal Serial Bus port is in the power supply state based on a corresponding measurement voltage signal output by the detection amplifier based on a measurement result of a magnetic field measured by the magnetic field detector, wherein the detection signal is the measurement voltage signal.

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