Electronic equipment and systems
By using a level conversion IC to connect the main device's GND to the external device's GND through the frame GND, the solution addresses communication failures caused by leakage currents, ensuring reliable signal transmission and reception.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- RICOH CO LTD
- Filing Date
- 2021-12-27
- Publication Date
- 2026-05-11
AI Technical Summary
Existing electronic devices experience communication failures due to leakage currents generated between the main body and external devices, which cause mismatched ground potential references, leading to incorrect signal transmission and reception.
The implementation of a level conversion IC on the circuit board that connects the main device's GND to a separate GND terminal, which is then connected to the external device's GND via the frame GND, ensuring consistent reference potentials across both devices.
This solution reduces communication failures by maintaining consistent signal voltage levels and preventing misinterpretation of control signals, thus enhancing communication reliability.
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention relates to electronic devices and systems.
Background Art
[0002] For example, electronic devices such as image forming apparatuses, projectors, or electronic blackboards are configured to be able to connect various external devices such as wireless LAN (Local Area Network) devices, authentication devices, or USB (Universal Serial Bus) memories.
[0003] Also, in an electronic device including a circuit device and an external device, a technique is known in which a level shifter is provided between a processing circuit and a physical layer circuit of the circuit device, and a ground potential difference is corrected by the level shifter based on a measurement result of a signal voltage (see, for example, Patent Document 1).
Summary of the Invention
Problems to be Solved by the Invention
[0004] In an electronic device to which an external device is connected, the main body of the electronic device and the external device transmit and receive signals such as control signals or data signals via an interface such as a connector or a cable. At this time, in order to match the signal voltage levels, for example, the frame ground of the electronic device is set as a common GND, and the GND is used as a reference potential for circuit operation.
[0005] However, in an electronic device to which an external device is connected, communication failures may occur due to leakage current generated between the main body of the electronic device and the external device. Here, the leakage current is a current flowing to the GND when an IC (Integrated Circuit) or the like operates.
[0006] While the technology disclosed in Patent Document 1 can correct the signal voltage level, this method has the problem that it cannot track instantaneous potential differences in GND, such as leakage current, because it includes a step of measuring the signal voltage in the process of correcting the signal voltage level.
[0007] One embodiment of the present invention has been made in view of the above-mentioned problems, and reduces communication failures caused by leakage current generated between the main body of the electronic device and the external device in an electronic device that connects an external device. [Means for solving the problem]
[0008] To solve the above problems, an electronic device according to one embodiment of the present invention is Electronic device, the main body of the electronic device A controller mounted on the circuit board that controls external devices, and the aforementioned Main unit It is mounted on a circuit board and converts the signal voltage level of the controller to the signal voltage level of the external device. level conversion I C and, The GND terminal of the controller is connected to the first GND, which is the GND of the main board. The aforementioned level conversion I C GND terminal It is not connected to the first GND within the main board, and when the external device is connected to the main board, GND of the external device The second GND Connect The first GND is connected to the frame GND of the electronic device, and the second GND is connected to the frame GND of the electronic device when the external device is connected to the main board. [Effects of the Invention]
[0009] According to one embodiment of the present invention, in an electronic device that connects an external device, communication failures caused by leakage current occurring between the main body of the electronic device and the external device can be reduced. [Brief explanation of the drawing]
[0010] [Figure 1] This figure shows an example configuration of a system including electronic equipment according to the first embodiment. [Figure 2] This figure shows the equivalent circuit of the system according to the first embodiment. [Figure 3]This figure shows an example of the voltage level of the transmitted signal according to the first embodiment. [Figure 4] This figure shows an example of the voltage level of a received signal according to the first embodiment. [Figure 5] This figure shows an example configuration of a system including electronic equipment according to the second embodiment. [Figure 6] This diagram illustrates communication failures caused by leakage current. [Figure 7] This figure shows an example of the signal voltage level when no leakage current is occurring. [Figure 8] This figure shows an example of the signal voltage level when leakage current is occurring. [Modes for carrying out the invention]
[0011] Embodiments of the present invention will be described in detail below with reference to the drawings.
[0012] <Communication failure due to leakage current> Before describing the electronic device and the system including the electronic device according to this embodiment, we will explain the communication failure caused by leakage current, which is the problem of this application.
[0013] Figure 6 illustrates a communication failure caused by leakage current. In electronic devices connected to external devices, the main body of the electronic device and the external device transmit and receive signals such as control signals and data signals via an interface such as a connector or cable. In the example in Figure 6, the main board 10, which is equipped with a controller IC 11 that controls the device IC (Integrated Circuit) 12, and the device board 20, which is equipped with the device IC 12, transmit and receive signals such as control signals 14 and data signals 15 via a cable 13. Note that the device IC 12 and the device board 20 are examples of external devices.
[0014] The main body substrate 10 and the device substrate 20 use, for example, the frame ground FG of an electronic device or the like including the main body substrate 10 as a common GND to match the signal voltage levels, and use this frame ground FG as the potential serving as the reference for circuit operation.
[0015] However, in reality, there is a minute resistance component (hereinafter referred to as parasitic resistance Rp1) between the GND of the main body substrate 10 and the frame ground FG, and there is a minute resistance component (hereinafter referred to as parasitic resistance Rp2) between the GND of the device substrate 20 and the frame ground FG.
[0016] Therefore, for example, when a leakage current occurs in the controller IC11, a current I1 flows through the parasitic resistance Rp1, and a voltage V1 is generated between the GND of the controller IC11 and the frame ground FG. Similarly, when a leakage current occurs in the device IC12, a current I2 flows through the parasitic resistance Rp2, and a voltage V2 is generated between the GND of the device IC12 and the frame ground FG. Here, the leakage current is the current flowing to the GND when an IC (Integrated Circuit) or the like operates.
[0017] As a result, the GND of the controller IC11 and the GND of the device IC12 are no longer at the same potential, and the reference of the GND level does not match, so that the control signal 14 and the data signal 15 cannot be correctly transmitted and received, and a communication failure may occur.
[0018] FIG. 8 shows an example of the signal voltage levels when no leakage current is occurring. The controller IC11 outputs, as an example for explanation, a HIGH level in an output voltage range 801 of 2.64 V to 3.3 V and a LOW level in an output voltage range 811 of 0 V to 0.66 V. On the other hand, the device IC12, as an example for explanation, recognizes a signal with a HIGH voltage threshold of 2.31 V or more as HIGH and a signal with a LOW voltage threshold of 0.99 V or less as LOW.
[0019] In this case, the HIGH voltage threshold of device IC12 (2.31V) is lower than the lower limit of the HIGH level of controller IC11 (2.64V), and the LOW voltage threshold of device IC12 (0.99V) is higher than the upper limit of the LOW level of controller IC11 (0.66V). Therefore, device IC12 can correctly recognize the HIGH and LOW levels of the signals output by controller IC11.
[0020] Figure 9 shows an example of signal voltage levels when leakage current is occurring. For illustrative purposes, assume that due to leakage current, the voltage V2 at the GND of device IC12 (hereinafter referred to as GND2) is higher than the voltage V1 at the GND of controller IC11 (hereinafter referred to as GND1). Generally, the path from the externally attached device board 20 to the frame ground FG is longer than that of the main board 10, so the parasitic resistance Rp2 is larger and the voltage V2 is often higher.
[0021] In Figure 9, controller IC 11 outputs a HIGH level in the output voltage range 901 of (2.64+V1)V to (3.3+V1)V, and a LOW level in the output voltage range 911 of (V1)V to (0.66+V1)V. On the other hand, device IC 12 recognizes signals above (2.31+V2)V as HIGH and signals below (0.99+V2)V as LOW. Therefore, as shown in Figure 9, when the difference between V1 and V2 becomes large, the HIGH level signal 900 output by controller IC 11 may become an intermediate potential that controller 12 cannot recognize as a HIGH level.
[0022] Here, we assume that this HIGH level signal 900 is the RESET_N signal, which is a reset control signal from controller IC11 to device IC12. The RESET_N signal is used to reset device IC12, with a LOW level indicating reset and a HIGH level indicating reset release.
[0023] In this case, for example, even though controller IC11 outputs a HIGH level RESET_N signal to release the reset, device IC12 may mistakenly determine that the voltage is below the HIGH voltage threshold. As a result, the device IC may misinterpret the RESET_N signal with a voltage below the HIGH voltage threshold as a LOW level signal, perform a reset operation, and disconnect communication with controller IC11.
[0024] Thus, in conventional technology, communication failures may occur in electronic devices that connect external devices due to leakage current generated between the main body of the electronic device (main board 10) and the external device (device board 20).
[0025] Therefore, in this embodiment, in an electronic device that connects an external device, communication failures caused by leakage current occurring between the main body of the electronic device (main board 10) and the external device (device board 20) are reduced.
[0026] <System Configuration> Figure 1 shows an example of a system configuration of a system including an electronic device according to the first embodiment. System 100 includes an electronic device 110 and an external device 120 connected to the electronic device.
[0027] The electronic device 110 is a variety of devices to which an external device 120 can be connected. For example, the electronic device 110 may be an image forming apparatus, a PJ (Projector), an IWB (Interactive White Board: an electronic whiteboard with the ability to communicate with each other), or digital signage. The electronic device 110 may also be a HUD (Head Up Display) device, industrial machinery, imaging device, sound collection device, medical equipment, networked home appliance, automobile (Connected Car), game console, PDA (Personal Digital Assistant), or digital camera. Furthermore, the electronic device 110 may be a general-purpose information processing device such as a notebook PC (Personal Computer), mobile phone, smartphone, tablet terminal, wearable PC, or desktop PC.
[0028] (Configuration of electronic equipment) The electronic device 110 includes, for example, a main board 111, a controller IC 101, a conversion device 102, a connector 103, and a power supply IC 104.
[0029] The controller IC (controller) 101 is, for example, mounted on the main board 111 and is an IC that controls the external device 112. The controller IC 101 transmits and receives control signals and data signals to and from the external device 120, for example, via a conversion device 102 and a connector 103. Note that the controller IC 101 is an example of a controller mounted on a board that controls the external device 120. The controller that controls the external device 120 may be, for example, a module including the controller IC 101, a sub-board, a chipset, or a circuit.
[0030] As shown in Figure 1, the power terminal (+V) of the controller IC 101 is connected to the power supply voltage VCC1 output by the power supply IC 104. The GND terminal of the controller IC 101 is connected to GND1, which is the GND of the main board 111, and GND1 is connected to the frame ground FG of the electronic equipment 110. Note that GND is the reference potential (ground) for circuit operation.
[0031] The conversion device 102 is, for example, mounted on the main board 111 and is a signal voltage conversion device (IC) that converts the signal voltage level output by the controller IC 101 to the signal voltage level of the external device 120. It is also called a level shifter or level conversion IC. Preferably, the conversion device 102 further converts the signal voltage level output by the external device 120 to the signal voltage level for the controller IC 101.
[0032] Furthermore, in this embodiment, the GND terminal of the conversion device 102 is configured to be connected to GND2, which is the GND of the external device 120, and is not connected to the GND terminal of the controller IC 101 within the main board 111.
[0033] Preferably, the conversion device 102 is provided between the controller IC 101 and the connector (interface) 103, and when the external device 120 is connected to the connector 103, the GND terminal of the conversion device 102 is connected to the GND2 of the external device 120 via the connector 103. In other words, when the external device 120 is not connected to the electronic device 110, the GND terminal of the conversion device 102 is not connected to GND1, which is the GND of the main board 111. When the external device 120 is connected to the electronic device 110, the GND terminal of the conversion device 102 is connected to GND2, which is the GND of the external device 120, and to GND1, which is the GND of the main board 111, via the frame ground FG.
[0034] Furthermore, in the first embodiment, the power terminal (+V) of the conversion device 102 is connected to the power terminal (+V) of the controller IC 101 and the power supply voltage VCC1 output by the power supply IC 104, as shown in Figure 1.
[0035] Connector 103 is mounted on the main board 111 and is an example of an interface that electrically connects the main board 111 and the external device 120. In the example in Figure 1, the external device 120 is connected to the main board 111 using connector 103 and cable 130. However, it is not limited to this, and connector 103 may connect the main board 111 to a connector mounted on a device board, or to contacts formed on a device board, for example. Similarly, the main board 111 is not limited to connector 103, and may be connected to the external device 120 using cable 130 or contacts formed on the main board 111.
[0036] In the example shown in Figure 1, the connector 103 and cable 130 include a signal line S1 for transmitting control signals, a signal line S2 for transmitting data signals, and a signal line G2 connecting the GND of the conversion device 102 to the GND of the device IC 105. The connector 103 and cable 130 may further include a signal line G1 that connects GND2, which is the GND of the device board, to the frame ground FG of the electronic equipment 110.
[0037] The power supply IC 104 is a device (IC) that supplies the power supply voltage VCC1 (3.3V in the example shown in Figure 1) to the controller IC 101. In the first embodiment, the power supply IC 104 also supplies the power supply voltage VCC1 to the conversion device 102.
[0038] The main board 111 is a board on which interfaces such as a controller IC 101, a conversion device 102, and a connector 103, as well as a power supply IC 104, are mounted.
[0039] (External device configuration) The external device 120 includes, for example, a device board 121, a device IC 105, and a power supply IC 106.
[0040] Device IC 105 is mounted on the device board 121 and is an IC that transmits and receives control signals and data signals to and from the controller IC 101, for example, via cable 130 and connector 103. Device IC 105 performs various controls according to the functions provided by the external device 120.
[0041] As shown in Figure 1, the power supply terminal (+V) of device IC 105 is connected to the power supply voltage VCC2 (3.3V in the example in Figure 1) output by power supply IC 106. The GND terminal of device IC 105 is connected to GND2, which is the GND of device board 121, and GND2 is connected to the frame ground FG of electronic equipment 110 via signal line G1. Furthermore, when external device 120 is connected to electronic equipment 110, the GND terminal of device IC 105 and GND2, which is the GND of external device 120, are connected to the GND terminal of conversion device 102 mounted on the main board 111 via signal line G2.
[0042] The power supply IC 106 is a device (IC) that supplies the power supply voltage VCC2 (3.3V in the example shown in Figure 1) to the device IC 105. The device board 121 is a board on which the device IC 105 and the power supply IC 106 are mounted, for example. The device board 121 is electrically connected to the electronic equipment 110 by, for example, a connector mounted on the device board 121, a cable 130, or contacts formed on the device board 121.
[0043] (Equivalent circuit) Figure 2 shows the equivalent circuit of the system according to the first embodiment. As explained in Figure 6, there is a parasitic resistor Rp1 between GND1, which is the GND of the main board 111, and the frame ground FG, and there is a parasitic resistor Rp2 between GND2, which is the GND of the device board 20, and the frame ground FG.
[0044] Therefore, for example, when leakage current occurs in controller IC 101, current I1 flows through parasitic resistor Rp1, and a voltage V1 = I1 × Rp1 is generated between GND1 of the main board 111 and the frame ground FG. As a result, when leakage current occurs, as shown in Figure 2, the potential of GND1 of the main board 111 becomes (V1)V, and the potential of the power supply voltage VCC1 output by power supply IC 104 becomes (V1 + 3.3)V.
[0045] Similarly, when leakage current occurs in device IC121, current I2 flows through the parasitic resistor Rp2, generating a voltage V2 ~ I2 × Rp2 between GND2 of device IC121 and the frame ground FG. As a result, when leakage current occurs, as shown in Figure 2, the potential of GND2 on the device board 121 becomes (V2)V, and the potential of the power supply voltage VCC2 output by power supply IC106 becomes (V2 + 3.3V).
[0046] Furthermore, in this embodiment, as shown in Figure 2, when an external device 120 is connected to the connector 103, the potential of the GND terminal of the conversion device 102 is configured to be approximately the same as the GND2 (potential V2) of the device board 121. As a result, the potential of the conversion device 102 and the reference potential for the circuit operation of the device IC 106 become the same, and communication failures like those described in Figure 9 will not occur. Note that, in this case, an error of a certain degree that does not impair the effects of the present invention is permissible for "same potential".
[0047] (Voltage level of the transmitted signal) Figure 3 shows an example of the voltage level of the transmission signal according to the first embodiment. This figure shows an example of the voltage level of the transmission signal that the controller IC 101 transmits to the external device 120.
[0048] As an example, the controller IC 101 outputs a HIGH level in the output voltage range 301 of (VCC1×0.8) to (VCC1), and outputs a LOW level in the output voltage range 302 of (GND1) to (VCC1×0.2). When a leakage current I1 occurs, the potential of GND1 is V1 = I1×Rp1, and the potential of VCC1 is, for example, V1 + 3.3V.
[0049] In this embodiment, for the conversion device (level shifter) 102, as shown in FIG. 3, a component with a sufficiently low HIGH voltage threshold VIHmin is selected. In the example of FIG. 3, the HIGH voltage threshold VIHmin is set to VCC1×0.6. Thereby, even when V1 < V2 due to the leakage current, the conversion device 102 can correctly recognize a HIGH level signal such as the RESET_N signal output by the controller IC 101 as a HIGH level. Also, since the conversion device 102 recognizes a signal with a LOW voltage threshold VILmax (VCC1×0.3) or lower as LOW, it can correctly recognize a LOW level signal output by the controller IC 101 as a LOW level.
[0050] Also, in the system 100 according to this embodiment, the GND terminal of the conversion device 102 is connected to GND2 of the device substrate 121 and is at substantially the same potential as the GND terminal of the device IC 105. Therefore, even when a leakage current occurs and V1 < V2, the device IC 105 can correctly recognize the HIGH level and LOW level of the RESET_N signal without being affected by the leakage current. Therefore, in the system 100 according to this embodiment, it is possible to prevent or reduce the communication failure due to the misrecognition of the RESET_N signal described in FIG. 8.
[0051] (Voltage level of received signal) FIG. 4 is a diagram showing an example of the voltage level of a transmission signal according to the first embodiment. This diagram shows an example of the voltage level of a received signal received by the controller IC 101 from the external device 120.
[0052] As an example, the device IC105 outputs a HIGH level within the output voltage range 401 of (VCC2 × 0.8) to (VCC2), and outputs a LOW level within the output voltage range 402 of (GND2) to (VCC2 × 0.2). When the leakage current I2 occurs, the potential of GND2 is V2 = I2 × Rp2, and the potential of VCC2 is, for example, V2 + 3.3V.
[0053] In this embodiment, as shown in FIG. 4, the conversion device (level shifter) 102 selects a component in which the LOW voltage threshold VILmax is higher than the upper limit value VOLmax of the LOW level of the device IC105. In the example of FIG. 4, the LOW voltage threshold VILmax is set to VCC1 × 0.3. Thereby, even when V1 < V2 due to the leakage current, the conversion device 102 can correctly recognize the LOW level signal output by the device IC105.
[0054] Also, as shown in FIG. 4, since the conversion device 102 recognizes a signal with a HIGH voltage threshold VIHmin (VCC1 × 0.6) or higher as HIGH, it can correctly recognize the HIGH level signal output by the device IC105 as HIGH. However, if the signal voltage of the HIGH level output by the device IC105 exceeds the rated voltage of the conversion device 102, the conversion device 102 will be damaged. Therefore, the conversion device 102 selects a component with a sufficiently high rated voltage.
[0055] Also, as shown in FIG. 4, the conversion device 102 outputs a HIGH level within the output voltage range 403 of (VCC1 × 0.9) to (VCC1), and outputs a LOW level within the output voltage range 414 of (GND2) to (VCC1 × 0.2).
[0056] In the example shown in Figure 4, the controller IC 101 recognizes signals above the HIGH voltage threshold VIHmin (Vcc1 × 0.7) as HIGH, so it can correctly recognize the HIGH level signal output by the conversion device 102 as a HIGH level. Furthermore, since the power terminal (+V) of the conversion device 102 is connected to the same VCC1 as the power terminal (+V) of the controller IC 101, it is also possible to prevent the HIGH level signal output by the conversion device 102 from exceeding the rated voltage of the controller IC 101.
[0057] Furthermore, as shown in Figure 4, the controller IC 101 recognizes signals below the LOW voltage threshold VILmax (VCC1 × 0.3) as LOW, so it can correctly recognize the LOW level signal output by the conversion device 102 as a LOW level.
[0058] Thus, in the system 100 according to the first embodiment, the reference potential for circuit operation is the same between the conversion device 102 on the main board 111 and the device IC 105 of the external device 120, so the communication failure described in Figure 8 will not occur.
[0059] Furthermore, in the system 100 according to the first embodiment, the power terminal (+V) of the conversion device 102 is connected to the power terminal (+V) of the controller IC 101, so that the output signal of the conversion device 102 does not exceed the rated voltage of the controller IC 101.
[0060] [Second Embodiment] In the first embodiment, the power terminal (+V) of the conversion device 102 was connected to the power terminal (+V) of the controller IC 101. However, this is just one example, and the power terminal (+V) of the conversion device 102 can be configured to be at the same potential as the power terminal (+V) of the controller IC 101.
[0061] Figure 5 shows an example of the configuration of a system including electronic equipment according to the second embodiment. The main board 111 according to the second embodiment has a power supply IC 501 in addition to the configuration of the main board 111 according to the first embodiment described in Figure 1. The power supply IC 501 outputs a power supply voltage VCC3 which is the same voltage as the power supply voltage VCC1 output by the power supply IC 104.
[0062] Furthermore, the power terminal (+V) of the conversion device 102 according to this embodiment is not connected to the power terminal (+V) of the controller IC 101, but is connected to the power supply voltage VCC3 output by the power supply IC 501. Note that other components or circuits other than the controller IC 101 may be connected to VCC3.
[0063] Thus, in this embodiment, the electronic device 110 is configured such that the power terminal (+V) of the conversion device 102 is at the same potential as the power terminal (+V) of the controller IC 101 within the main board 111. Note that "same potential" may include an error (potential difference) that does not impair the effects of the present invention.
[0064] The same effects as in the first embodiment can be obtained in the electronic device 110 and system 100 according to the second embodiment.
[0065] As described above, according to each embodiment of the present invention, in an electronic device 110 to which an external device 120 is connected, communication failures caused by leakage current generated between the main body of the electronic device 110 and the external device can be reduced.
[0066] Furthermore, the present invention is not limited to the embodiments described above, and various modifications or applications are possible within the scope of the gist of the invention as described in the claims.
[0067] For example, in the system 100 shown in Figure 1, the power terminal (+V) of the conversion device 102 may be connected to the power supply voltage VCC2 of the device board 121 via the connector 103 and the cable 130. Furthermore, the conversion device 102 is not limited to the main board 111, but may also be mounted on the device board 121. In addition, the conversion device 102 may be divided into, for example, one or more conversion devices that convert the signal voltage level of the transmission signal transmitted by the controller IC 101, and one or more conversion devices that convert the signal voltage level of the reception signal received by the controller IC 101. [Explanation of Symbols]
[0068] 100 Systems 101 Controller IC (Controller) 102 Conversion Devices 103 Connector (Example of an interface) 110 Electronic equipment 111 Main board (board) 120 External Devices 130 Cables (Example of an interface) [Prior art documents] [Patent Documents]
[0069] [Patent Document 1] Japanese Patent Publication No. 2019-219718
Claims
1. An electronic device, A controller mounted on the main circuit board of the aforementioned electronic device, which controls an external device, A level conversion IC mounted on the main board converts the signal voltage level of the controller to the signal voltage level of the external device, It has, The GND terminal of the controller is connected to the first GND, which is the GND of the main board. The GND terminal of the level conversion IC is not connected to the first GND within the main board, but is connected to the second GND, which is the GND of the external device, when the external device is connected to the main board. The first GND is connected to the frame GND of the electronic device, The second GND is connected to the frame GND of the electronic device when the external device is connected to the main board. electronic equipment.
2. The electronic device according to claim 1, wherein the power terminal of the level conversion IC is connected to the power terminal of the controller within the main board.
3. The electronic device according to claim 1, wherein the power terminal of the level conversion IC is configured to be at the same potential as the power terminal of the controller within the main board.
4. It is mounted on the main board and has an interface that electrically connects the main board and the external device, The level conversion IC is provided between the controller and the interface, The electronic device according to any one of claims 1 to 3, wherein when the external device is connected to the interface, the GND terminal of the level conversion IC is connected to the GND of the external device via the interface.
5. The electronic device according to any one of claims 1 to 4, wherein the level conversion IC further converts the signal voltage level of the external device to the signal voltage level of the controller.
6. A system comprising the electronic equipment described in any one of claims 1 to 5.