Power control device, display device, power control method

Abstract

The present invention comprises: a first overcurrent detection unit (201) for detecting whether the current supplied from the power supply unit to an external device exceeds a first reference value; a second overcurrent detection unit (202) for detecting whether the current supplied from the power supply unit to the external device exceeds a second reference value, which is a reference value higher than the first reference value; a timer unit (203) for setting a time corresponding to a time from the point in time during which the power supplied from the power supply unit to the external device during the negotiation period is switched to power corresponding to the result of the negotiation between the power supply unit and the external device until the power supply stabilizes; and a control unit (204) for performing overcurrent detection using the second overcurrent detection unit before the negotiation ends, and when the negotiation ends and the time set by the timer unit has elapsed, invalidating the overcurrent detection performed by the second overcurrent detection unit and validating the overcurrent detection performed by the first overcurrent detection unit.

Description

Technical Field

[0001] This invention relates to power control devices, display devices, and power control methods. Background Technology

[0002] In recent years, cables have been used to connect display devices (source devices) to external devices (synchronization devices) and to supply power from the display device to the external device. The connection between the display device and the external device sometimes uses cables that correspond to the USB (Universal Serial Bus) Type-C standard.

[0003] In this USB (Universal Serial Bus) Type-C, the power supply function is called USB Power Delivery (USB Power Delivery / hereinafter referred to as USB-Type-C PD). By using this USB-Type-C cable, it is possible to receive power up to 100W.

[0004] When the display device is connected to an external device via a USB-Type-C cable, it supplies power to the external device at a specified voltage. The external device receives the supplied power at the specified voltage and uses this power to drive itself, thereby negotiating with the display device. After the negotiation is complete, the display device supplies power to the external device at a voltage increased to correspond to the negotiation result.

[0005] At this point, when the voltage is increased to the level corresponding to the negotiated result, there is a possibility that, as the voltage changes, the surge current flows from the display device to the external device.

[0006] As a technology to prevent inrush current, there is the technology described in Patent Document 1. In Patent Document 1, a timer is used to keep track of the time from when power is supplied to an external device until the current stabilizes. During the period when the timer is started, it is considered that a normal device is connected, and the power supply is not stopped even if an overcurrent is detected.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2004-094821 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] However, there is a situation where, during the period from when negotiation begins and power supply to external devices starts until the current stabilizes, an inrush current flows. If the value of this inrush current exceeds the upper limit of the current normally set, an overcurrent is considered to have occurred, and power supply is stopped. In other words, there is a situation where, when power is supplied in accordance with the result of the negotiation process, the inrush current exceeds the upper limit of the current set based on a stable voltage or current state, thereby stopping power supply.

[0012] In this situation, when the power supply is interrupted, users may sometimes mistakenly believe it is a malfunction of the display device's USB-Type-C PD function. Here, if the power supply is not stopped even if an overcurrent is detected during the period from when power is supplied to the external device until the current stabilizes, overcurrent cannot be prevented in abnormal situations.

[0013] The problem to be solved is the cessation of power supply in situations where a failure may not necessarily occur.

[0014] Technical solutions for solving the problem

[0015] One embodiment of the present invention includes: a first overcurrent detection unit that detects whether the current supplied from a power supply unit to an external device exceeds a first reference value; a second overcurrent detection unit that detects whether the current supplied from the power supply unit to the external device exceeds a second reference value, wherein the second reference value is a reference value higher than the first reference value; a timer unit that sets a time corresponding to a time from the point in time during which the power supplied from the power supply unit to the external device during the negotiation period is switched to power corresponding to the result of the negotiation between the power supply unit and the external device until the power supply stabilizes; and a control unit that performs overcurrent detection using the second overcurrent detection unit before the negotiation ends, and when the negotiation ends and the time set by the timer unit has elapsed, invalidates the overcurrent detection performed by the second overcurrent detection unit and makes the overcurrent detection performed by the first overcurrent detection unit valid.

[0016] Another embodiment of the present invention is a power control method, comprising the following processes: detecting whether the current supplied from a power supply unit to an external device exceeds a first reference value; detecting whether the current supplied from the power supply unit to the external device exceeds a second reference value, the second reference value being a reference value higher than the first reference value; timing whether a set time has elapsed, the set time being a time corresponding to a time from the point in time during negotiation when the power supplied from the power supply unit to the external device is switched to power corresponding to the result of negotiation with the external device until the power supply stabilizes; and performing overcurrent detection based on the second reference value before the negotiation ends, and when the negotiation ends and the set time has elapsed, invalidating the overcurrent detection based on the second reference value and validating the overcurrent detection based on the first reference value.

[0017] Invention Effects

[0018] According to the present invention, it is possible to prevent the power supply from stopping even when a failure may not occur. Attached Figure Description

[0019] Figure 1 This is a functional block diagram illustrating the structure of the power control device 1 in one embodiment of the present invention.

[0020] Figure 2 This is a diagram showing the relationship between the output voltage and output current that the power conversion unit 20 can output.

[0021] Figure 3 This is a timing diagram illustrating the operation of the power control device 1.

[0022] Figure 4 This is a timing diagram illustrating the operation of the power control device 1.

[0023] Figure 5 This is a functional block diagram illustrating the structure of the power control device 1A in one embodiment of the present invention. Detailed Implementation

[0024] Figure 1 This is a functional block diagram illustrating the structure of the power control device 1 in one embodiment of the present invention.

[0025] The power control device 1 can be mounted on electronic devices such as display devices, or can be connected to external devices.

[0026] The power control device 1 includes a power supply unit 101, a power conversion unit 102, an overcurrent detection circuit 103, a connector 104, a timer circuit 105, an overcurrent detection circuit 106, a control unit 107, an inverter circuit 108, a first AND circuit 109, a second AND circuit 110, a switch unit 111, a display control unit 112, and a display unit 113. The power control device 1 has functions corresponding to USB-Type-CPD.

[0027] The power supply unit 101 is electrically connected to the power conversion unit 102. The power supply unit 101 supplies power to the power conversion unit 102. The power supply unit 101 can supply either DC or AC power to the power conversion unit 102, but in this embodiment, the case of supplying DC power will be described.

[0028] The power conversion unit 102 is electrically connected to the power supply unit 101, the overcurrent detection circuit 103, and the control unit 107. The power conversion unit 102 receives power supplied from the power supply unit 101, converts it into an output voltage as the target voltage to be supplied, and outputs it to the overcurrent detection circuit 103.

[0029] The power conversion unit 102 is, for example, a DC-DC converter circuit. The power conversion unit 102 outputs a DC voltage equal to the input DC voltage. Alternatively, the power conversion unit 102 can also boost the input DC voltage to output a voltage higher than the input voltage.

[0030] The maximum current value that the power conversion unit 102 can supply is set to a current value corresponding to the inrush current. The inrush current may occur at the following times: when an external device is connected to the connector 104 and power for negotiation processing is supplied to the external device; and when negotiation occurs between the control unit 107 and the external device, and the voltage supplied to the external device during the negotiation process switches to a voltage corresponding to the result of the negotiation process. The main causes of such inrush currents include the capacitance of the input capacitor of the external device and the impedance of the external device. It is preferable to set the maximum current value of the power conversion unit 102 considering the peak value of this inrush current. Here, if the peak current value of the inrush current generated when power for negotiation processing is supplied to the external device is compared with the peak current value of the inrush current generated when switching to a voltage corresponding to the result of the negotiation process, the peak current value of the inrush current generated when switching to a voltage corresponding to the result of the negotiation process is larger. Therefore, the maximum current value of the power conversion unit 102 can be determined considering the peak current value of the inrush current generated when switching to a voltage corresponding to the result of the negotiation process. Therefore, even if a surge current larger than the surge current generated at the start of the negotiation process occurs when switching to a voltage corresponding to the result of the negotiation process, the power conversion unit 102 can determine whether to cut off the power supply based on whether an overcurrent caused by the connected external device flows through it. Therefore, as long as no overcurrent caused by the connected external device flows through it, power can continue to be supplied to the external device without cutting off the power supply.

[0031] Furthermore, regarding the maximum current value of the power conversion unit 102, for example, when the connected external device is a battery or motor, the inrush current is often larger compared to the case where the external device does not have a motor. Therefore, a power conversion unit 102 with a rated maximum current value that is assumed to be larger than that of such an external device without a motor can also be used. For example, if the maximum current value is assumed to be 7A when connecting an external device without a motor, a power conversion unit 102 with a maximum current value corresponding to 10A can also be used.

[0032] Figure 2 This is a graph showing the relationship between the output voltage and output current that the power conversion unit 20 can output, especially showing the relationship between the output voltage and output current when the supplied power exceeds 60W and is up to 100W.

[0033] In a USB Type-C PD, the maximum output current can vary depending on the output voltage. That is, the USB Type-C PD negotiates with the external device to set an arbitrary power level corresponding to the external device's request within the power range that the power control device can supply, and then supplies that set power to the external device. The supplied current varies according to the set power. For example, if the negotiated power supply is 60W, and the output voltage is set to any voltage between 5V and 20V, the supplied current can be fixed at 3A.

[0034] Here, in the USB-Type-C PD standard, the power supply can be set up to 100W. Therefore, if the negotiation results in a power supply ranging from over 60W to 100W, such as... Figure 2 As shown, the output voltage is set to 5V to 15V, and the output current is set to 3A. However, when the output voltage is set to 20V, the output current becomes 5A. Therefore, the peak value of the inrush current generated when switching to the voltage corresponding to the result of the negotiation process is larger when switching to 20V compared to the case where the output voltage changes from the negotiated output voltage to any of the 5V to 15V output voltages. In this embodiment, considering the case where the output current also changes when switching to the output voltage corresponding to the result of the negotiation process, and assuming that the inrush current increases accordingly as the output current increases, the maximum current value of the power conversion unit 102 is set accordingly.

[0035] The overcurrent detection circuit 103 is electrically connected to the power conversion unit 102, the control unit 107, the switch unit 111, the first AND circuit 109, and the second AND circuit 110. The overcurrent detection circuit 103 detects whether the current supplied from the power conversion unit 102 to the external device connected to the connector 104 exceeds a first reference value. The first reference value is used as a benchmark to determine whether there is an abnormality in the current value supplied after a VBUS voltage stabilization time (hereinafter referred to as the voltage stabilization time) has elapsed after switching to power corresponding to the result of the negotiation process.

[0036] The voltage stabilization time is determined based on the time from the point in time during which the voltage switches to the voltage corresponding to the result of the negotiation process until the fluctuation of the output power supplied from the power conversion unit 102 to the external device stabilizes. This voltage stabilization time can also use the standard value specified by USB PD3.0.

[0037] In addition, during the period when the overcurrent detection circuit 103 outputs the DC-DC converter EN signal from the control unit 107 (the DC-DC converter EN signal is on), it is driven according to the signal from the first AND circuit 109 or the second AND circuit 110. When there is no output of the DC-DC converter EN signal (the DC-DC converter EN signal is off), the overcurrent detection function is stopped.

[0038] In other words, when power is normally supplied to external devices, the overcurrent detection circuit 103 detects overcurrent.

[0039] Connector 104 connects to an external device, which is an external device of the power control device 1. The shape of the terminals of connector 104 corresponds to the USB-Type C standard. Connector 104 can be connected to the external device via a cable that corresponds to the USB-Type C standard.

[0040] The timer circuit 105 is set with a time corresponding to the time from the start of negotiation until the power supply stabilizes and is switched to the power corresponding to the result of the negotiation. The time set in the timer circuit 105 can be based on the time when negotiation starts, or it can be based on the time when the external device on the docking side is detected to be connected to the connector 104 via a USB-Type C cable.

[0041] Furthermore, the setting time in the timer circuit 105 can be a time obtained by adding the voltage stabilization time to the time spent on negotiation, based on the start of the negotiation process or the detection of an external device connected to the mating side via a USB-Type C cable. Alternatively, the setting time may include the negotiation time, the voltage stabilization time, and the margin time. The timer value set in the timer circuit 105 can be any value corresponding to this setting time.

[0042] Here, the voltage stabilization time can be set arbitrarily. For example, connector 104 is a connector that corresponds to the USB Type-C standard. Based on the time point of connection with external devices according to the USB Type-C standard, the voltage stabilization time can be set as the voltage stabilization time based on the standard value of USB PD3.0 (maximum 270ms).

[0043] Additionally, during the timekeeping period, the timer circuit 105 outputs an enable signal to the overcurrent detection circuit 106 and the inverter circuit 108. The enable signal can be, for example, the signal representing "HI" from "HI" and "LOW".

[0044] Thus, during the period including the time required for negotiation and the voltage stabilization time, the timer circuit 105 outputs an enable signal to the overcurrent detection circuit 106, thereby enabling the overcurrent detection function in the overcurrent detection circuit 106 during the period of outputting the enable signal. Therefore, the overcurrent detection function of the overcurrent detection circuit 106 can be enabled during the period including the time required for negotiation and the voltage stabilization time, and the overcurrent detection function of the overcurrent detection circuit 106 can be disabled after this period.

[0045] Inrush currents primarily occur during periods of output voltage instability. Therefore, for inrush currents generated during the voltage stabilization period, a different detection method than during stabilization can be used by employing the timer circuit 105 and the overcurrent detection circuit 106 (details will be described later; a different second reference value is used for detection). Thus, during the voltage stabilization period, for inrush currents generated in response to output voltage switching, a higher reference value than normally used can be used to determine whether an overcurrent has occurred. Therefore, even if an inrush current is generated in response to output voltage switching, and in the case of an inrush current generated due to the characteristics of the source device, the power supply can be cut off.

[0046] The overcurrent detection circuit 106 is electrically connected to the overcurrent detection circuit 103, the timer circuit 105, and the control unit 107.

[0047] The overcurrent detection circuit 106 detects whether the current supplied from the power conversion unit 102 to the external device exceeds a second reference value, which is a reference value higher than the reference value set in the overcurrent detection circuit 103.

[0048] The second reference value can be a value corresponding to the maximum value of the inrush current flowing when switching to power corresponding to the negotiated result. For example, if the negotiated result is to supply power exceeding 60W up to 100W, the output current is 5A when the output voltage is 20V. Therefore, it is also possible to set it to 10A based on this output current as the current value assuming that an inrush current was generated.

[0049] When an enable signal is output from the timer circuit 105, the overcurrent detection circuit 106 performs overcurrent detection. During overcurrent detection, the overcurrent detection circuit 106 determines whether a second reference value, which is a current value higher than the first reference value detected by the overcurrent detection circuit 103, is supplied from the power conversion unit 102 to the connector 104. If it determines that the current value exceeds the second reference value, it outputs an error signal (e.g., an OCP (Open Core Protocol) ERR signal) indicating that the current value exceeds the second reference value to the control unit 107 and the display control unit 112.

[0050] In addition, when the supply of the start signal output from the timer circuit 105 stops, the overcurrent detection circuit 106 stops detecting the overcurrent.

[0051] The control unit 107 is electrically connected to the power conversion unit 102, the overcurrent detection circuit 103, the timer circuit 105, the overcurrent detection circuit 106, the switch unit 111, the connector 104, the first AND circuit 109, the second AND circuit 110, and the display control unit 112.

[0052] When an external device is connected to the connector 104, the control unit 107 detects that the external device is connected to the connector 104, negotiates with the external device, determines the voltage and current values ​​that can be handled between the power control device 1 and the external device, and begins to supply power to the external device.

[0053] Here, negotiation refers to the process in USB Power Delivery (power delivery based on a USB Type-C connector) of sending and receiving information related to the available power (voltage, current) between the source device (power control device 1) and the receiving device (external device) via the USB protocol, and of deciding whether to supply or receive power (voltage, current).

[0054] When the control unit 107 detects that an external device is connected to the connector 104, it outputs an instruction to the timer circuit 105 to start the timing.

[0055] When the control unit 107 outputs an instruction to start timing to the timer circuit 105, it enables the enable signal (hereinafter referred to as the DC-DC converter EN signal) output to the power conversion unit 102 and the overcurrent detection circuit 103 (activated).

[0056] When the control unit 107 receives an error signal indicating that an overcurrent has been detected from the overcurrent detection circuit 106, it turns off the DC-DC converter EN signal (enable signal) (inactive), and outputs an indication to stop the timing of the timer circuit 105, and outputs a cut-off signal to the switch unit 111 as an indication to cut off the circuit.

[0057] The control unit 107 outputs a switching signal (hereinafter referred to as the VBUS voltage switching signal) indicating a switch to a voltage determined through negotiation with an external device. Here, during the negotiation process, the control unit 107 outputs a VBUS voltage switching signal indicating 5V, and when the negotiation ends, it outputs a VBUS voltage switching signal specifying any one of the voltages corresponding to the negotiation result, namely 5V, 9V, 12V, 15V, and 20V.

[0058] The control unit 107 outputs a voltage setting signal indicating which output voltage (VBUS voltage) is being used to either the first AND circuit 109 or the second AND circuit 110. For example, when the output voltage is any one of 5V, 9V, 12V, or 15V, the control unit 107 outputs a first voltage setting signal to the first AND circuit 109, and when the VBUS voltage is 20V, it outputs a second voltage setting signal to the second AND circuit 110.

[0059] When the result of the negotiation is to supply power of 60W or more up to 100W, the first voltage setting signal is output when the output voltage is 5V, 9V, 12V, or 15V, but the output current is 3A in all cases. The second voltage setting signal is output when the output voltage is 20V, but the output current is 5A in all cases. In this embodiment, the case where the control unit 107 outputs either the first or second voltage setting signal will be described. However, when there are three or more types of output current, the number of voltage setting signals can be set to correspond to the number of types. Therefore, even when power is supplied to an external device according to specifications other than the USB Type-C PD standard, the overcurrent reference value can be set for the overcurrent detection circuit 103 based on the output current value.

[0060] If the overcurrent detection circuit 103 detects that the current value exceeds the first reference value, or if the overcurrent detection circuit 106 detects that the current value exceeds the second reference value, the control unit 107 disconnects the switch unit 111 to stop the power supply from the power conversion unit 102 to the external device.

[0061] Before the negotiation ends (e.g., at the start of the negotiation and during the negotiation process), the control unit 107 performs overcurrent detection using the overcurrent detection circuit 106. When the negotiation ends and the time set in the timer circuit 105 has elapsed, the overcurrent detection performed by the overcurrent detection circuit 106 is invalidated, and the overcurrent detection performed by the overcurrent detection circuit 103 is valid.

[0062] During the negotiation period and until the time set in the timer circuit 105 has elapsed, the control unit 107 disables the overcurrent detection circuit 103.

[0063] The inverter circuit 108 is electrically connected to the timer circuit 105, the first AND circuit 109, and the second AND circuit 110.

[0064] The inverter circuit 108 inverts the signal input from the timer circuit 105 and outputs the inverted signal to the first AND circuit 109 and the second AND circuit 110.

[0065] Specifically, when an on signal (e.g., "HI") is output from timer circuit 105, inverter circuit 108 inverts it into an off signal (e.g., "LOW") and outputs it to the first AND circuit and the second AND circuit. When an off signal (e.g., "LOW") is output from timer circuit 105, inverter circuit 180 inverts it into an on signal (e.g., "HI") and outputs it to the first AND circuit 109 and the second AND circuit 110.

[0066] The inverter circuit 108 can be, for example, a NOT gate circuit.

[0067] The first AND circuit 109 is connected to the control unit 107, the inverter circuit 108, and the overcurrent detection circuit 103. One input of the first AND circuit 109 is connected to the terminal of the control unit 107 that can output a first voltage setting signal, and the other input is connected to the inverter circuit 108.

[0068] When at least one of the signals input from the inverter circuit 108 and the control unit 107 is "LOW", the first AND circuit 109 outputs "LOW" to the overcurrent detection circuit 106. For example, when the first AND circuit 109 is in a state where the signal input from the inverter circuit 108 is an on signal and no first voltage setting signal is input from the control unit 107 ("LOW state"), it outputs a "LOW" signal to the overcurrent detection circuit 103; when the signal input from the inverter circuit 108 is an on signal and the first voltage setting signal is input from the control unit 107 ("HI state"), it outputs a "HI" signal to the overcurrent detection circuit 103.

[0069] In other words, when the timer circuit 105 is not performing timekeeping based on the timer function and a first voltage setting signal is input, the first AND circuit 109 outputs "HI" to the overcurrent detection circuit 103, and outputs "LOW" otherwise.

[0070] The second AND circuit 110 is connected to the control unit 107, the inverter circuit 108, and the overcurrent detection circuit 103. One input of the second AND circuit 110 is connected to the terminal of the control unit 107 that can output a second voltage setting signal, and the other input is connected to the inverter circuit 108.

[0071] When at least one of the signals input from the inverter circuit 108 and the control unit 107 is "LOW", the second AND circuit 110 outputs "LOW" to the overcurrent detection circuit 106. For example, when the signal input from the inverter circuit 108 is an on signal and no second voltage setting signal is input from the control unit 107 ("LOW state"), the second AND circuit 110 outputs a "LOW" signal to the overcurrent detection circuit 103; when the signal input from the inverter circuit 108 is an on signal and a second voltage setting signal is input from the control unit 107 ("HI state"), it outputs a "HI" signal to the overcurrent detection circuit 103.

[0072] In other words, when the second AND circuit 110 is in a period when the timer circuit 105 is not performing timer-based timing and a second voltage setting signal is input, it outputs "HI" to the overcurrent detection circuit 103, and outputs "LOW" otherwise.

[0073] In this embodiment, two circuits, a first AND circuit 109 and a second AND circuit 110, are used to supply the first voltage setting signal, the second voltage setting signal, and the signal corresponding to the timing state of the timer function to the overcurrent detection circuit 103. However, as long as each output current value corresponding to the VBUS voltage is set separately, there can be three or more AND circuits. Here, the output current is 3A when the VBUS voltage is 5V, 9V, 12V, or 15V, and 5A when the VBUS voltage is 20V, so there are two types of output current. Therefore, the AND circuit is provided with a first AND circuit 109 for 3A and a second AND circuit 110 for 5A. In addition, when there are three or more types of output current, the AND circuits can be set separately according to their types (the number of types of voltage setting signals). Thus, even when power is supplied to an external device in a manner other than that of the USB-Type C PD standard, the overcurrent reference value can be set for the overcurrent detection circuit 103 according to the value of the output current.

[0074] Furthermore, this explanation focuses on the case where two AND circuits, first AND circuit 109 and second AND circuit 110, are used to supply the first voltage setting signal, the second voltage setting signal, and a signal corresponding to the timing state of the timer function to the overcurrent detection circuit 103. However, other structures can be used without first AND circuit 109 and second AND circuit 110. For example, a selection signal supply unit 120, which includes the functions of first AND circuit 109 and second AND circuit 110, can be used. This selection signal supply unit 120 outputs a selection signal to the overcurrent detection circuit 103 based on a selection signal output from the control unit 107 for selecting the output voltage of the power supplied according to the negotiation result, and the timing result of the timer circuit 105. Alternatively, it can be implemented using software-based information processing instead of a logic circuit like an AND circuit.

[0075] The switch unit 111 is electrically connected to the overcurrent detection circuit 103, the control unit 107, and the connector 104.

[0076] Here, the switch unit 111 can be connected between the power conversion unit 102 and the connector 104. In this embodiment, an overcurrent detection circuit 103 is provided in front of the switch unit 111.

[0077] Normally, the switch provided in the switch unit 111 is closed. When a cut-off signal is received from the control unit 107, the switch is opened, thereby cutting off the power supply path between the overcurrent detection circuit 103 and the connector 104.

[0078] The display control unit 112 is electrically connected to the overcurrent detection circuit 106 and the display unit 113.

[0079] The display control unit 112 outputs an overcurrent detection signal indicating that an overcurrent has been detected by the overcurrent detection circuit 106. For example, an OCP ERR signal can be used as the overcurrent detection signal.

[0080] When the display control unit 112 receives an overcurrent detection signal from the overcurrent detection circuit 106, it displays a screen indicating that an overcurrent has been detected on the display unit 113. This screen may also show a situation where, although the negotiation based on the USB-Type-C standard ended normally, a subsequent power supply malfunction occurred.

[0081] The display control unit 112 can use a microcomputer (microcontroller).

[0082] The display unit 113 is electrically connected to the display control unit 112.

[0083] Display unit 113 displays the signals output from display control unit 112.

[0084] The display unit 113 can be a display device such as a liquid crystal display panel. Based on an instruction from the display control unit 112, the display unit 113 displays a screen indicating that an overcurrent has been detected. Alternatively, the display unit 113 may include a drive circuit for driving the liquid crystal display panel. While the description focused on the case where the display unit 113 is located inside the power control device 1, if the power control device 1 is located within the display device, the display panel of that display device can also be used as the display unit 113. In this case, the display control unit 112 can display a screen indicating that an overcurrent has been detected on the display screen of that display device.

[0085] The description covers the case where the display unit 113 displays the signal output from the display control unit 112, but it is also possible for the signal output from the display control unit 112 to be output to an external output unit. For example, it could be a speaker that outputs the signal via sound, or a lamp that indicates that the signal has been output.

[0086] The power control device 1 described above can be installed inside the display device as one of its functions. Alternatively, the power control device 1 can be connected between the display device and an external device.

[0087] Next, the operation of the power control device 1 will be explained.

[0088] Figure 3 This is a timing diagram illustrating the operation of power control device 1. Additionally, this... Figure 3 This illustrates a situation where power is being supplied to external devices normally, i.e., the power supply is not cut off by the switch 111. In the initial state, the switch 111 is in the on state.

[0089] First, when an external device is connected to connector 104 (time t1), control unit 107 detects the connection and begins negotiation with the external device (reference numeral B1). Additionally, control unit 107 outputs an instruction to start timing to timer circuit 105, outputs an indication of a 5V VBUS voltage to power conversion unit 102, and activates the DC-DC converter EN signal (reference numeral L1).

[0090] The timer circuit 105 starts timing based on an instruction from the control unit 107 (reference numeral C1). After starting timing, the timer circuit 105 outputs an enable signal to the overcurrent detection circuit 106 and the inverter circuit 108. Upon receiving the enable signal from the timer circuit 105, the overcurrent detection circuit 106 activates its overcurrent detection function (reference numeral F1). Furthermore, by activating the overcurrent detection function, the overcurrent detection circuit 106 monitors the current value of the power supplied from the power conversion unit 102 to the connector 104 and determines whether the current value exceeds a second reference value.

[0091] Here, inverter circuit 108 inverts the enable signal and outputs an enable signal to first AND circuit 109 and second AND circuit 110. Since the input signal to one of the first AND circuits 109 and 110 is an enable signal, they respectively output enable signals to overcurrent detection circuit 103. Therefore, since enable signals are input from both first AND circuit 109 and second AND circuit 110, overcurrent detection circuit 103 does not perform overcurrent detection. As a result, overcurrent detection circuit 103 outputs power from power conversion unit 102 to connector 104 without overcurrent detection.

[0092] The power conversion unit 102 receives an instruction from the control unit 107 to output a 5V VBUS voltage as the voltage for negotiation processing, and when the DC-DC converter EN signal output from the control unit 107 becomes active, it outputs a 5V voltage to the overcurrent detection circuit 103 based on the power supplied from the power supply unit 101. Thus, a 5V VBUS voltage (reference numeral G1) is supplied from the power conversion unit 102 to the overcurrent detection circuit 103 and its subsequent stages.

[0093] When a VBUS voltage is output from the power conversion unit 102 to the overcurrent detection circuit 103, a VBUS current flows from the power conversion unit 102 to the overcurrent detection circuit 103 along with the output of this VBUS voltage. At this time, regarding the VBUS current, an inrush current (labeled H1) flows immediately after the current begins to flow, and the current value stabilizes (labeled H2) after a certain period of time. At this time, since the VBUS voltage is 5V, therefore according to... Figure 2The relationship between the output voltage and output current is shown. When the current value is stable, the VBUS current value is 3A. The inrush current becomes a current value higher than this 3A, but the peak value of the inrush current as the VBUS current is, for example, about 110% of the 3A (when the voltage is stable), which is approximately 3.3A. At this time, since the overcurrent detection circuit 103 is in the off state (labeled D1, labeled E1), the overcurrent detection function in the overcurrent detection circuit 103 does not work. The overcurrent detection function of the overcurrent detection circuit 106, which receives the turn-on signal from the timer circuit 105, works, so it determines whether the reference current value (second reference value) set in the overcurrent detection circuit 106 is exceeded. Here, the reference value set in the overcurrent detection circuit 106 is the second reference value (e.g., 10A). Therefore, since the peak value of the inrush current after the initial flow through VBUS is about 3.3A and less than the second reference value (10A), the overcurrent detection circuit 106 does not detect an overcurrent. Therefore, the power control device 1 continues to supply power from the power conversion unit 102 to the connector 104.

[0094] Next, at time t2, when the negotiation ends, the control unit 107 outputs a VBUS switching signal to the power conversion unit 102. This VBUS switching signal is an indication to switch the 5V VBUS voltage to a voltage corresponding to the negotiation result (e.g., 20V). This time t2 corresponds to the start time of the voltage stabilization time (reference numeral I1). Based on this VBUS switching signal, the power conversion unit 102 switches the output voltage from 5V to the voltage represented by the VBUS switching signal. Here, when the power conversion unit 102 receives a VBUS switching signal that switches the VBUS voltage to, for example, 20V, it boosts the voltage to make the output voltage 20V (reference numeral G2).

[0095] As this voltage switches, the inrush current flows as the VBUS current (labeled H3). At this time, since the VBUS voltage is 20V, therefore according to... Figure 2The relationship between output voltage and output current is shown, with a VBUS current value of 5A. Since the VBUS current value is 5A, the inrush current is higher than 5A. The peak value of the inrush current also depends on the impedance of the external device connected to connector 104; for example, it may sometimes be approximately 110% of the stable 5A (approximately 5.5A). Furthermore, assuming the impedance of the connected external device is higher than that of a typical external device, there may be a case where the current value is approximately 150% of the stable 5A (approximately 7.5A) (reference H4). In this case, the overcurrent detection circuit 103 is in the off state (reference D1, reference E1) and does not operate, while the overcurrent detection circuit 106 operates, comparing the inrush current value with a second reference value (10A). Since the inrush current is approximately 7.5A and less than the second reference value of 10A, the overcurrent detection circuit 106 does not detect an overcurrent. Therefore, the power control device 1 continues to supply power from the power conversion unit 102 to connector 104.

[0096] Subsequently, the VBUS current value converges to its normal value (5A) (labeled H5) over time. Furthermore, the VBUS voltage also reaches 20V (labeled G3) during the voltage stabilization period.

[0097] On the other hand, when the control unit 107 finishes negotiation at time t2 and outputs a VBUS voltage switching signal to the power conversion unit 102, it outputs a voltage setting signal indicating the set VBUS voltage to either the first AND circuit 109 or the second AND circuit 110. When the VBUS voltage is any one of 5V, 9V, 12V, or 15V, the control unit 107 outputs a voltage setting signal to the first AND circuit 109; when the VBUS voltage is 20V, it outputs a voltage setting signal to the second AND circuit 110. That is, it outputs a voltage setting signal to either the first AND circuit 109 or the second AND circuit 110 based on the output current corresponding to the VBUS voltage. For example, if the negotiation process results in a VBUS voltage of 20V, the control unit 107 outputs a voltage setting signal to the second AND circuit 110.

[0098] When the voltage stabilization time (time t3, labeled I2) has elapsed since time t2, and time t4 (the voltage stabilization time plus a margin) arrives, the timing value of the timer circuit 105 reaches the timing value corresponding to the timer value (labeled C2). When the timing value reaches the timing value corresponding to the timer value, the timer circuit 105 switches the on signal for the overcurrent detection circuit 106 to an off signal (labeled F2), and outputs the off signal to the inverter circuit 108.

[0099] Therefore, when the signal input from the timer circuit 105 switches to a shutdown signal, the overcurrent detection circuit 106 stops its overcurrent detection function. Additionally, the inverter circuit 108 inverts the input shutdown signal and outputs it as an enable signal to the first AND circuit 109 and the second AND circuit 110.

[0100] The first AND circuit 109 is in a state where the inverter circuit 108 inputs an enable signal and the control unit 107 does not input a voltage setting signal (i.e., "LOW"), so it outputs the "LOW" signal to the overcurrent detection circuit 103.

[0101] The second AND circuit 110 is in a state where an enable signal is input from the inverter circuit 108 and a voltage setting signal is input from the control unit 107 (i.e., "HI"), and therefore outputs the "HI" signal to the overcurrent detection circuit 103.

[0102] When a "LOW" signal is input from the first AND circuit 109 and a "HI" signal is input from the second AND circuit 110, the overcurrent detection circuit 103 determines that the VBUS voltage is set to 20V and sets the reference value for determining the overcurrent to the current value corresponding to the output current of 5A, namely 5.5A (labeled E2). Here, the overcurrent detection circuit 103 sets the reference value to 5.5A after the voltage stabilization time has elapsed, so the inrush current generated in the VBUS current has converged and the current value has stabilized at 5A. Therefore, after the voltage stabilization time has elapsed, the reference value can be set to 5.5V for overcurrent detection processing.

[0103] According to the above-described embodiment, when an external device is inserted into the USB Type-C connector, negotiation is initiated by a signal already connected via USB Type-C. A timer circuit measures the VBUS voltage stabilization period (e.g., 270ms: standard value) plus a margin of several hundredms. During this measurement, the overcurrent detection circuit 106, which has a maximum current value higher than usual, is activated. Conversely, the overcurrent detection circuit 103 remains inactive during this period. Thus, overcurrent detection can be performed using a higher-than-usual overcurrent setting only from the time the device is inserted into the USB Type-C connector until the VBUS stabilization period ends. Therefore, even if an inrush current occurs when switching to a negotiated power level (e.g., from an output voltage of 5V / output current of 3A to an output voltage of 20V / output current of 5A), the power supply will not stop as long as no overcurrent caused by the impedance of the external device connected to connector 104 flows.

[0104] In addition, it can prevent false alarms such as cutting off the power supply caused by detecting the surge current that accompanies the switching to the negotiated voltage as an overcurrent.

[0105] In addition, by locking based on the timer circuit, the overcurrent detection circuit 106 is turned off and the overcurrent detection circuit 103 is turned on, thereby enabling overcurrent detection using a first reference value corresponding to the output current (e.g., 3A or 5A) based on the power determined by negotiation after switching to the power.

[0106] then, Figure 4 This is a timing diagram illustrating the operation of power control device 1. Additionally, this... Figure 4 This example illustrates a situation where an overcurrent is detected when switching to a voltage determined by negotiation, i.e., the power supply is cut off by the switch unit 111. In the initial state, the switch unit 111 is in the on state.

[0107] Regarding the labels A11, B11, B12, C11, D11, E11, F11, G11, H11, H12, I11, and L11 from time t11 to time t12, due to... Figure 3 The labels A1, B1, B2, C1, D1, E1, F1, G1, H1, and L1 from time t1 to time t2 are the same, so their descriptions are omitted. The main focus is on the differences.

[0108] Next, at time t12, the power conversion unit 102 increases the output voltage from 5V to 20V (reference G12) based on the VBUS switching signal indicating 20V output from the control unit 107.

[0109] As the voltage switches, the inrush current flows as the VBUS current (labeled H13). At this time, since the VBUS voltage is 20V, the VBUS current value is output as 5A. Here, in Figure 3 The description explains the case where the current value becomes approximately 150% (approximately 7.5A) relative to the VBUS current value of 5A. However, when the impedance of the external device is higher than a certain value, the peak value of the inrush current may sometimes increase further. In this case, the peak value of the inrush current when the VBUS current value is switched to 5A may sometimes exceed 10A (reference H14), which is set as the second reference value of the overcurrent detection circuit 106. Between time t12 and time t13, the overcurrent detection circuit 106 compares the inrush current value with the second reference value (10A). When it is determined that the inrush current exceeds 10A as the second reference value, an error signal (OCP ERR signal) (reference J11) as "HI" is output to the control unit 107 at time t13.

[0110] When an error signal is output from the overcurrent detection circuit 106, the control unit 107 turns off the DC-DC converter EN signal (label L12), outputs an instruction to stop the timing to the timer circuit 105, and outputs a cut-off signal to the switch unit 111.

[0111] When the EN signal of the DC-DC converter is turned off (reference L12), the power conversion unit 102 stops outputting the VBUS voltage. As a result, the VBUS voltage output from the power conversion unit 102 decreases (reference G13), and along with the decrease in VBUS voltage, the VBUS current also decreases (reference H15).

[0112] When the DC-DC converter's EN signal is turned off, the overcurrent detection circuit 103 stops its overcurrent detection function. Furthermore, when a cut-off signal is output from the control unit 107 in response to the DC-DC converter's EN signal being turned off, the switch unit 111 opens the switch, cutting off the power supply path between the overcurrent detection circuit 103 and the connector 104. Thus, the power supply from the power conversion unit 102 to external devices is cut off.

[0113] Furthermore, when an error signal is output from the overcurrent detection circuit 106, the display control unit 112 causes the display unit 113 to activate the error display (reference numeral K11). The display unit 113 then displays an error screen. For example, the display unit 113 may display a string such as "Connection device error" as an error screen on the OSD (On-Screen Display) screen. By displaying an error screen on the display unit 113, the user can be notified that the power supply has been cut off due to an overcurrent flowing from the external device. Thus, the user can recognize that the power supply cutoff is not caused by a fault in the display device, power control unit 1, USB Type-C port, or USB Type-C cable, but rather by a fault on the external device side.

[0114] When the control unit 107 outputs an instruction to stop timing to the timer circuit 105, timing is stopped (labeled C12), and the supply of the start signal to the overcurrent detection circuit 106 and the inverter circuit 108 is stopped. When the supply of the start signal is stopped, the overcurrent detection circuit 106 stops its overcurrent detection function (labeled F12).

[0115] Since the supply of the turn-on signal is stopped, the inverter circuit 108 inverts the input signal, i.e. the turn-off signal, and outputs the turn-on signal to the first AND circuit 109 and the second AND circuit 110.

[0116] Here, the control unit 107 outputs a setting signal indicating 20V to the second AND circuit 110. Therefore, even if the output from the inverter circuit 108 is an on signal, since the setting signal indicating 5V is off, the first AND circuit 109 outputs the off output to the overcurrent detection circuit 103.

[0117] On the other hand, since the output from the inverter circuit 108 is an enable signal and the 20V setting signal is an enable signal, the second AND circuit 110 outputs an enable signal.

[0118] The overcurrent detection circuit 103 receives an enable signal from the second AND circuit 110 and is input a 20V setting signal, but since the DC-DC converter EN signal is off, the overcurrent detection function remains stopped.

[0119] At time t14, when the end of the voltage stabilization time arrives (labeled I12), before this time, the VBUS output voltage drops to 0V and the VBUS output current also drops to 0A.

[0120] According to the embodiment described above, when the external device connected to connector 104 is a high-impedance device, when switching from the power during negotiation to the power corresponding to the negotiation result, the overcurrent detection circuit 106 detects an overcurrent, and the display unit 113 displays an OSD indicating an abnormality caused by the connection of an external device with a large inrush current to the USB Type-C connector. Thus, the user is notified that the power was cut off because a high-impedance external device was connected, allowing the user to understand that the problem is not with the display device, power control device 1, USB Type-C port, or USB Type-C cable.

[0121] Figure 5 This is a functional block diagram illustrating the structure of the power control device 2 in one embodiment of the present invention.

[0122] The power control device 2 includes a first overcurrent detection unit 201, a second overcurrent detection unit 202, a timer unit 203, and a control unit 204.

[0123] The first overcurrent detection unit 201 detects whether the current supplied from the power supply unit to the external device exceeds a first reference value. The second overcurrent detection unit 202 detects whether the current supplied from the power supply unit to the external device exceeds a second reference value, which is a reference value higher than the first reference value.

[0124] The timer unit 203 is set with a time corresponding to the time from the point when the switch was made until the power supply is stable. The switch is the switch from the power supplied to the external device by the power supply unit 205 during the negotiation period to the power corresponding to the result of the negotiation between the power supply unit 205 and the external device.

[0125] Before the negotiation ends, the control unit 204 performs overcurrent detection using the second overcurrent detection unit 202. When the negotiation ends and the time set in the timer unit 203 has elapsed, the overcurrent detection of the second overcurrent detection unit 202 is invalidated, and the overcurrent detection of the first overcurrent detection unit 201 is made valid.

[0126] Therefore, it is possible to prevent the power supply from being interrupted even when there is no fault in the power control device.

[0127] Alternatively, it can be used to implement Figure 1 The functions of the processing unit are recorded on a computer-readable medium, allowing the computer system to read and execute the program recorded on that medium for construction management. Furthermore, the term "computer system" here includes hardware such as the operating system and peripheral devices.

[0128] In addition, when using a WWW system, "computer system" also includes the homepage providing environment (or display environment).

[0129] Furthermore, the term "computer-readable recording medium" refers to portable media such as floppy disks, optical disks, ROMs, and CD-ROMs, as well as storage devices such as hard disks built into computer systems. Moreover, "computer-readable recording medium" includes media that retain programs for a certain period of time, such as volatile memory within a computer system acting as a server or client. Additionally, the aforementioned program can be a program used to implement the above-mentioned functions, or it can be a program that can implement the above-mentioned functions by combining them with programs already recorded in the computer system. Furthermore, the aforementioned program can be stored on a designated server and distributed (downloaded, etc.) via communication lines upon request from other devices.

[0130] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the specific structure is not limited to these embodiments, and also includes designs that do not depart from the spirit of the present invention.

[0131] Label Explanation

[0132] 1…Power control device, 2…Power control device, 20…Power conversion unit, 101…Power supply unit, 102…Power conversion unit, 103…Overcurrent detection circuit, 104…Connector, 105…Timer circuit, 106…Overcurrent detection circuit, 107…Control unit, 108…Inverter circuit, 109…First AND circuit, 110…Second AND circuit, 111…Switch unit, 112…Display control unit, 113…Display unit, 180…Inverter circuit, 201…First overcurrent detection unit, 202…Second overcurrent detection unit, 203…Timer unit, 204…Control unit, 205…Power supply unit.

Claims

1. A power control device, comprising: a first overcurrent detection section that detects whether a current supplied from a power supply section to an external device exceeds a first reference value; a second overcurrent detection section that detects whether a current supplied from the power supply section to the external device exceeds a second reference value that is a higher reference value than the first reference value; a timer section that sets a time corresponding to a time from a point in time at which power supplied from the power supply section to the external device is switched to power corresponding to a result of negotiation performed with the external device to a time at which the supply of the power stabilizes; and a control section that, before the negotiation ends, performs overcurrent detection by the second overcurrent detection section, and, when the negotiation ends and the time set in the timer section elapses, invalidates overcurrent detection by the second overcurrent detection section and validates overcurrent detection by the first overcurrent detection section.

2. The power control device according to claim 1, wherein the control section invalidates the first overcurrent detection section during the negotiation and until the time set in the timer section elapses.

3. The power control device according to claim 1 or 2, wherein the second overcurrent detection section determines, as the second reference value, a value corresponding to a maximum value of an inrush current that flows at the time of switching to power corresponding to the result of the negotiation.

4. The power control device according to claim 1, wherein the power control device has an output section that outputs data indicating that overcurrent is detected by the second overcurrent detection section.

5. The power control device according to claim 4, wherein the power control device has a display section that displays the data output from the output section on a display panel.

6. The power control device according to claim 1, wherein the power control device has a switch connected between the power supply section and a connector connected to the external device, and the control section opens the switch to stop the supply of power from the power supply section to the external device when a current value exceeds the first reference value is detected by the first overcurrent detection section or when a current value exceeds the second reference value is detected by the second overcurrent detection section.

7. The power control device according to claim 1, wherein the power control device has a selection signal supply section that, on the basis of a selection signal output from the control section and a result of counting by the timer section, outputs the selection signal to the first overcurrent detection section when the time set in the timer section elapses, the selection signal selecting an output voltage based on power supplied in correspondence with the result of the negotiation.

8. A display device having the power control device according to any one of claims 1 to 7.

9. A power control method, comprising the processes of: detecting whether a current supplied from a power supply section to an external device exceeds a first reference value; ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ detecting whether or not a current supplied from the power supply section to the external device exceeds a second reference value which is a reference value higher than the first reference value; counting whether or not a set time elapses, the set time setting a time corresponding to a time from a point in time at which power supplied from the power supply section to the external device is switched to power corresponding to a result of negotiation between the external device when negotiation is performed to a time at which supply of the power stabilizes; and performing overcurrent detection based on the second reference value before the negotiation ends, invalidating overcurrent detection based on the second reference value when the negotiation ends and the set time elapses, and validating overcurrent detection based on the first reference value.

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