Electronic device including distributed voltage conversion structure for image sensor

Abstract

The electronic device of the present invention includes a main board comprising a first voltage converter that converts an input voltage; and a sensor board connected to the main board and receiving voltage from the main board, wherein the sensor board may include a second voltage converter that converts the voltage received from the main board.

Description

Technology Field

[0001] The present invention relates to a power supply structure for an image sensor, and more specifically, to an electronic device that suppresses voltage fluctuations and provides a stable driving voltage by distributing voltage conversion between a main board and a sensor board for an image sensor with large load fluctuations. Background Technology

[0002] In general, electronic devices containing image sensors widely utilize a structure in which the main board converts the input voltage into multiple voltage levels and then transmits the converted voltage to the sensor board to drive it. In this structure, voltage conversion is primarily performed by the main board, and it is common for the sensor board to receive and use the voltage supplied by the main board.

[0003] However, in such conventional structures, the voltage delivered to the sensor board can be affected by voltage drop and noise as it passes through wiring and connectors. In particular, for image sensors with large load fluctuations, voltage fluctuations may occur due to rapid changes in current. This can lead to reduced operational stability or performance degradation of the sensor, and thus a more efficient power supply structure is required to address this. The problem to be solved

[0004] One objective of the present invention is to provide a power supply structure for providing a stable voltage to an image sensor. means of solving the problem

[0005] An electronic device according to one embodiment includes a main board comprising a first voltage converter that converts an input voltage; and a sensor board connected to the main board and receiving voltage from the main board, wherein the sensor board may include a second voltage converter that converts the voltage received from the main board.

[0006] Here, the first voltage converter may include a switching power supply that converts the input voltage by the periodic switching operation of a switching element.

[0007] Here, the second voltage converter may include a linear voltage converter that converts the voltage supplied from the main board by linear operation.

[0008] Here, the switching power supply includes a first converter connected to a first power line and a second converter connected to a second power line, and the linear voltage converter may include a first linear voltage converter corresponding to the first converter and a second linear voltage converter corresponding to the second converter.

[0009] Here, the sensor board may include a first capacitor group connected to the first linear voltage converter and a second capacitor group connected to the second linear voltage converter.

[0010] Here, a plurality of capacitors included in the first capacitor group are connected in parallel with one end connected to the first power line and the other end connected to the reference potential of the sensor board, and a plurality of capacitors included in the second capacitor group are connected in parallel with one end connected to the second power line and the other end connected to the reference potential of the sensor board.

[0011] Here, the sensor board is formed as a printed circuit board comprising a plurality of layers, and the plurality of layers may include a first layer corresponding to the first power line and a second layer corresponding to the second power line.

[0012] Here, the sensor board may include a third linear voltage converter connected to the first linear voltage converter to provide voltage to at least one input of the first linear voltage converter for a stepwise voltage drop.

[0013] Here, the first voltage converter may include at least one of a buck converter, a buck-boost converter, and a flyback converter.

[0014] Here, the second voltage converter may include at least one of a low drop voltage regulator (LDO), a source follower, and a pass transistor-based circuit.

[0015] Here, the second voltage converter includes a first transistor and a second transistor, the first transistor provides a voltage to the output node of the second voltage converter, and the second transistor may be configured to induce current from the output node of the second voltage converter to the reference potential of the sensor board.

[0016] Here, the second transistor is connected in series with at least one resistor, and the at least one resistor may be composed of a resistor network in which a plurality of resistor elements are combined in series and parallel.

[0017] Here, the target voltage of the linear voltage converter is varied by an external digital signal, and the reference potential of the sensor board may be the same as the reference potential of the target voltage.

[0019] An image sensor according to one embodiment includes a main board comprising a first voltage converter for converting an input voltage; and a sensor board connected to the main board and receiving voltage from the main board, wherein the sensor board may include a pixel array comprising a plurality of SPAD (Single-Photon Avalanche Diode) elements and a second voltage converter for converting the voltage received from the main board to provide a driving voltage to the pixel array. Effects of the invention

[0020] According to one embodiment of the present invention, a power supply structure for providing a stable voltage to an image sensor may be provided. Brief explanation of the drawing

[0021] FIG. 1 is a schematic diagram illustrating the configuration and signal flow of a power rail according to one embodiment. Figures 2 and 3 are drawings to explain the conventional board configuration and the problems associated therewith. FIG. 4 is a block diagram illustrating a board configuration according to an embodiment of the present invention. FIGS. 5 and 6 are drawings for explaining the signal flow for a board configuration according to an embodiment of the present invention. FIGS. 7 and FIGS. 8 are drawings for illustrating the signal flow for a board configuration according to another embodiment of the present invention. FIG. 9 is a drawing for explaining the effects according to the board configuration of the present invention. FIG. 10 is a drawing for specifically describing a sensor board according to one embodiment of the present invention. FIG. 11 is a drawing for specifically describing a sensor board according to another embodiment of the present invention. FIG. 12 is a drawing for explaining a sensor board according to a plurality of power lines according to an embodiment of the present invention. Specific details for implementing the invention

[0022] The embodiments described in this specification are intended to clearly explain the concept of the present invention to those skilled in the art to which the present invention belongs. Therefore, the present invention is not limited to the embodiments described in this specification, and the scope of the present invention should be interpreted to include modifications or variations that do not deviate from the concept of the present invention.

[0023] The terms used in this specification have been selected to be as widely used as possible, taking into account their functions in the present invention; however, these terms may vary depending on the intent of those skilled in the art to which the present invention pertains, case law, or the emergence of new technologies. However, if a specific term is defined and used with an arbitrary meaning, the meaning of that term will be described separately. Accordingly, the terms used in this specification should be interpreted based on their actual meaning and the content throughout this specification, rather than merely their names.

[0024] The drawings attached to this specification are intended to facilitate the explanation of the present invention. Since the shapes depicted in the drawings may be exaggerated as necessary to aid in understanding the present invention, the present invention is not limited by the drawings.

[0025] In this specification, if it is determined that a detailed description of known components or functions related to the present invention may obscure the essence of the present invention, such detailed description will be omitted as necessary.

[0027] FIG. 1 is a schematic diagram illustrating the configuration and signal flow of a power rail according to one embodiment.

[0028] Referring to FIG. 1, an electronic device (10) according to one embodiment may include a main board (100) and a sensor board (200). The electronic device (10) of the present invention may be a device including a sensor and may be a device for detecting physical quantities in various environments.

[0029] For example, the sensor may be a light sensor that detects light, and the light sensor may perform the function of converting an incident light signal from the outside into an electrical signal. The light sensor may be an image sensor for acquiring image information, or a sensor for detecting signals at the single-photon level. For example, the image sensor may be a sensor including a SPAD (Single-Photon Avalanche Diode), but is not limited thereto and can be implemented as an image sensor of various forms. Furthermore, the power supply structure of the present invention is not limited to image sensors and can also be applied to systems including various electronic loads with large current fluctuations.

[0030] The main board (100) and the sensor board (200) may be circuit boards on which electronic components are mounted. For example, the main board (100) and the sensor board (200) may be implemented as a Printed Circuit Board (PCB). The main board (100) may include various circuits for controlling the overall operation of the electronic device (10) and may perform power supply, signal processing, control functions, etc.

[0031] The sensor board (200) is a board that includes a sensor and may include a circuit for driving and signal processing of the sensor. Additionally, the main board (100) and the sensor board (200) may be electrically connected to each other, for example, through a connector, a flexible cable, or wiring.

[0032] The main board (100) can receive an input voltage from an external power source. Additionally, the main board (100) can convert the input voltage into multiple voltage levels suitable for the operation of the electronic device (10). For example, the main board (100) may include a power circuit for voltage conversion and may include multiple power lines for generating different voltages. These voltages may be provided to various components, including a sensor board (200).

[0033] The sensor board (200) can drive the sensor by receiving the voltage supplied from the main board (100). The sensor board (200) may include analog and digital circuits for the operation of the sensor. Additionally, the sensor board (200) may include a voltage conversion circuit for adjusting or further converting the voltage to suit the operating conditions of the sensor. This allows for providing a stable voltage to the sensor and improving the performance of the sensor.

[0034] In FIG. 1, the electronic device (10) is shown as including a main board (100) and a sensor board (200), but this is illustrated with a focus on the main components for convenience of explanation. Accordingly, the electronic device (10) is not limited thereto and may further include various components such as a power supply unit, a control unit, a communication unit, and a storage unit.

[0036] Figures 2 and 3 are drawings to explain the conventional board configuration and the problems associated therewith.

[0037] Referring to FIG. 2, a conventional electronic device (11) may include a main board (101) and a sensor board (201). Since a general description of the main board (101) and the sensor board (201) overlaps with the description of the main board (100) and the sensor board (200) in FIG. 1, a detailed description thereof is omitted.

[0038] The main board (101) may be a power board or a power processing board and may receive input voltages (VP, VN) from an external source. The main board (101) may include a Power Supply Unit (PSU) for converting the input voltages (VP, VN) to a voltage level required for the operation of the sensor board (201).

[0039] The power supply unit can convert input voltages (VP, VN) into output voltages (VOUT). For example, the power supply unit may include a Switched Mode Power Supply (SMPS) and can convert input voltages (VP, VN) into a predetermined output voltage (VOUT) by utilizing the switching operation of a switching element.

[0040] In a conventional electronic device (11), the voltage conversion required for the sensor board (201) can be substantially completed from the main board (101). That is, the sensor board (201) receives the output voltage (VOUT) generated from the main board (101) through the power terminals (VDD, GNDS), and can drive the sensor circuit or front-end circuit using the received output voltage (VOUT).

[0041] The sensor board (201) may include a sensor or a front-end circuit associated with the sensor. For example, the sensor board (201) may include a light sensor, an image sensor, a SPAD sensor, or an analog front-end circuit associated therewith. In FIG. 2, the load included in the sensor board (201) is depicted as a spiky load, which exemplifies a load with large instantaneous current fluctuations.

[0042] In particular, for image sensors operating with a global shutter or SPAD-based image sensors, a large amount of current can be consumed instantaneously during periods when multiple pixels operate simultaneously. While these sensors consume relatively small current over most of the time, they may exhibit characteristics where very large peak currents occur in specific intervals. Therefore, such loads are characterized by large instantaneous current fluctuations despite having a low average current, and can be defined as spiky loads.

[0043] When such a spiky load is placed on a sensor board (201) separated from the main board (101), and an output voltage (VOUT) generated from the main board (101) is transmitted to the sensor board (201) through wiring, connectors, or a board-to-board interface, the influence of parasitic resistance and parasitic inductance included in the power transmission path may increase. As a result, instantaneous voltage fluctuations may occur not only in the output voltage (VOUT) but also in the power nodes (VDD, GNDS) of the sensor board (201) and the power node (GNDP) of the main board (101).

[0044] Furthermore, while the switching power supply attempts to maintain a constant output voltage through an internal control loop, the response speed of the control loop is limited, making it difficult to respond immediately to sudden current changes occurring in the load. Consequently, a voltage drop may occur during a rapid increase in load current, and a voltage overshoot may occur during a rapid decrease in load current.

[0045] Furthermore, if a large current flows repeatedly and instantaneously, the current flowing through the board-to-board connections or connectors may exceed the rated current, which can lead to a decrease in system reliability.

[0046] Such voltage fluctuations can degrade the operational stability of the sensor circuit included in the sensor board (201). In particular, if the sensor is an image sensor or a single photon detection sensor that operates based on the power supply voltage, voltage fluctuations can affect detection accuracy, signal quality, or reading performance.

[0047] Meanwhile, methods such as increasing the capacitance of decoupling capacitors or decreasing the Equivalent Series Resistance (ESR) may be considered to suppress voltage fluctuations. However, increasing the capacitor capacitance may degrade the response speed of the power supply, and the design of the compensation circuit may become complex for stable operation. In particular, such a design can be very difficult when the instantaneous current of the load reaches the level of tens of amperes (A).

[0048] Therefore, in a structure in which the final voltage is transmitted to the sensor board (201) after the voltage conversion is completed on the main board (101) as in the conventional method, there may be limitations in providing a stable voltage to the sensor having a spiky load. This problem can be explained in more detail with reference to FIG. 3.

[0049] Referring to Figure 3, the pattern of change in output voltage over time can be observed. In the graph, the target voltage is set to approximately 22V, and for the normal operation of the sensor, it is required that this voltage be maintained stably.

[0050] However, as the load on the sensor board operates as a spiky load, a phenomenon may occur where the output voltage drops sharply at the point where a large current is momentarily consumed by the load. As shown in Fig. 3, a voltage drop may occur at a specific point in time where the voltage drops significantly below the target voltage. For example, it can be observed that the voltage, which should be maintained at 22V, drops to about 13V at a specific point in time.

[0051] Such voltage drops are caused by a sharp increase in load current and can be further exacerbated by parasitic resistance and inductance in the power delivery path, as well as the response speed limits of the power supply unit. Additionally, it may take a certain amount of time to recover to the target voltage level after the voltage has dropped.

[0052] In such cases, if the output voltage momentarily drops below the target voltage, the driving voltage applied to the sensor may not meet the reference voltage, and the sensor may not operate normally. In particular, for devices sensitive to power supply voltage, such as image sensors or SPAD-based sensors, such voltage fluctuations can cause detection errors, signal distortion, or operation failure.

[0053] Therefore, it can be seen that in conventional power supply structures, it is difficult to sufficiently suppress voltage fluctuations caused by spiky loads, and there are limitations in providing a stable voltage to the sensor.

[0055] FIG. 4 is a block diagram illustrating a board configuration according to an embodiment of the present invention.

[0056] Referring to FIG. 4, an electronic device (12) according to one embodiment of the present invention may include a main board (102) and a sensor board (202). Since a general description of the main board (102) and the sensor board (202) overlaps with the description of the main board (100) and the sensor board (200) in FIG. 1, a detailed description thereof is omitted.

[0057] The main board (102) may include a first voltage conversion unit (110). The first voltage conversion unit (110) may convert a voltage input from the outside and provide it to the sensor board (202). For example, the first voltage conversion unit (110) may include a switching power supply unit and may convert the input voltage to a predetermined voltage level using the switching operation of a switching element.

[0058] The sensor board (202) may receive voltage from the main board (102). The sensor board (202) may include a second voltage converter (210) and a sensor element (220). The second voltage converter (210) may additionally convert the voltage supplied from the main board (102) and provide it to the sensor element (220). For example, the second voltage converter (210) may include a voltage conversion circuit that performs linear operation and may be implemented as a low drop voltage regulator (LDO), a source follower, or a pass transistor-based circuit. The second voltage converter may be placed on the same board as the sensor element, and the distance from the sensor element may be set to various values ​​depending on design conditions.

[0059] In this way, the present invention allows voltage conversion to be performed distributed across the main board (102) and the sensor board (202), rather than being completed at the main board (102). That is, the first voltage conversion unit (110) primarily converts the input voltage, and the second voltage conversion unit (210) can perform a second conversion to a voltage suitable for the sensor element (220).

[0060] Due to this structure, the second voltage converter (210) located on the sensor board (202) can generate or adjust the voltage at a location closer to the sensor element (220), thereby enabling more effective response to instantaneous current fluctuations occurring in the load. In particular, even in the case of a sensor element (220) having spiky load characteristics, voltage fluctuations can be suppressed and a stable voltage can be provided.

[0061] In addition, as the voltage conversion function is distributed, the effects of voltage drop and noise occurring in the power transfer path between the main board (102) and the sensor board (202) can be reduced, and the operational stability and performance of the sensor element (220) can be improved.

[0062] In particular, since the second voltage converter (210) is positioned close to the sensor element, the response to the current change occurring in the load can be made directly on the sensor board without going through the power transmission path.

[0063] In a conventional structure, voltage conversion is substantially completed on the main board and the sensor board uses the transmitted voltage, whereas in the present invention, the voltage conversion function can be functionally divided and disposed between the main board and the sensor board. In addition, the present invention differs in that voltage adjustment is performed at a location close to the load by a second voltage conversion unit performed on the sensor board.

[0064] Furthermore, as voltage conversion is additionally performed on the sensor board, instantaneous current changes occurring in the load can be locally absorbed and compensated within the sensor board rather than being transmitted to the main board through the power delivery path. Consequently, voltage fluctuations caused by parasitic resistance and inductance in the power lines are reduced, and peak currents flowing through the connectors between boards can be lowered, thereby improving system reliability.

[0066] FIGS. 5 and 6 are drawings for explaining the signal flow for a board configuration according to an embodiment of the present invention.

[0067] Referring to FIG. 5, the electronic device (12) may include a main board (102) and a sensor board (202). FIG. 5 illustrates, for example, that the sensor board (202) is an image sensor board including a SPAD (Single-Photon Avalanche Diode) element.

[0068] The sensor board (202) may include a front side and a back side. A pixel array including a plurality of SPAD elements may be disposed on the front side of the sensor board (202), and each pixel may perform single photon detection.

[0069] A second voltage converter (210) and a plurality of capacitors may be disposed on the rear side of the sensor board (202). The second voltage converter (210) can convert the voltage supplied from the main board (102) and provide it to the sensor element (220). In FIG. 5, an exemplary case is shown where the second voltage converter (210) is implemented as a low drop voltage regulator (LDO). However, it is not limited thereto, and the second voltage converter (210) and a plurality of capacitors may be disposed on the front side of the sensor board (202).

[0070] The main board (102) may include a first voltage converter (110) that converts the input voltage. The first voltage converter (110) may convert the voltage input from the outside into a plurality of voltage levels. In FIG. 5, the first voltage converter (110) is exemplarily illustrated as including a buck converter, but is not limited thereto.

[0071] The main board (102) and the sensor board (202) can be connected via a power connector and a signal connector. The power connector can transmit a power voltage generated from the main board (102) to the sensor board (202), and the signal connector can transmit a control signal, a data signal, or a synchronization signal.

[0072] In one embodiment, the electronic device may include a plurality of power lines connecting the main board (102) and the sensor board (202). For example, in FIG. 5, the P23V power line, P5V power line, and P3V power line are shown sharing a return line. The SPAD power line can transmit a voltage used for biasing or driving the sensor element (220), the VDDA power line can transmit a voltage used for an analog circuit, and the VDDD power line can transmit a voltage used for a digital circuit.

[0073] A second voltage converter (210) may be disposed on the rear of the sensor board (202) in correspondence with each power line. For example, an LDO may be disposed for each of the SPAD power line, VDDA power line, and VDDD power line, and each second voltage converter (210) may additionally convert or adjust the voltage transmitted from the main board (102) on the sensor board (202).

[0074] Additionally, a plurality of capacitors may be disposed on the rear surface of the sensor board (202). The plurality of capacitors may be connected to each power line to perform a decoupling function. For example, the plurality of capacitors may include a first capacitor group connected to the SPAD power line, a second capacitor group connected to the VDDA power line, and a third capacitor group connected to the VDDD power line. The plurality of capacitors included in each capacitor group may be connected in parallel, with one end connected to the corresponding power line and the other end connected to the reference potential of the sensor board (202).

[0075] In this way, in the present embodiment, voltage conversion is not performed entirely on the main board (102), but rather a first voltage conversion is performed on the first voltage conversion unit (110) of the main board (102), and a second voltage conversion is performed on the second voltage conversion unit (210) of the sensor board (202). That is, the voltage conversion function can be distributed and arranged on the main board (102) and the sensor board (202).

[0076] According to this structure, since the second voltage converter (210) placed on the sensor board (202) can generate or adjust the voltage at a location close to the sensor element (220), voltage fluctuations can be effectively suppressed even for the sensor element (220) having spiky load characteristics. In addition, since the capacitor group placed on the sensor board (202) can mitigate voltage fluctuations of each power line, a stable voltage can be provided to the sensor element (220) and the related circuit.

[0077] FIG. 5 illustrates an exemplary case where the first voltage converter (110) is a buck converter and the second voltage converter (210) is an LDO, but the present invention is not limited thereto. For example, the first voltage converter (110) may include at least one of a buck converter, a buck-boost converter, and a flyback converter. Additionally, the second voltage converter (210) may include at least one of a low drop voltage regulator (LDO), a source follower, and a pass transistor-based circuit.

[0078] In one embodiment, the sensor board (202) may be implemented as a multilayer printed circuit board comprising a plurality of layers. For example, the sensor board (202) may include a first layer corresponding to a first power line and a second layer corresponding to a second power line. Each layer may be configured to transmit the voltage of the corresponding power line.

[0079] Specifically, the first layer may be formed as a power layer that transmits the voltage of the first power line. Additionally, the second layer may be formed as a power layer that transmits the voltage of the second power line. The number and configuration of the layers may vary depending on the number of power lines and design conditions.

[0080] These power layers are formed in a planar shape within the board to provide a low-impedance current path, and by separating power lines by layer, interference between power sources can be reduced, and voltage drop and noise can be decreased. Additionally, a separate return layer corresponding to the return line can be formed, and the parallel structure between the power layer and the return layer can reduce the impedance of the power distribution network and stabilize the current path.

[0081] A plurality of capacitors may be disposed on the sensor board (202) corresponding to the first power line and the second power line, respectively, and these capacitors may be connected in parallel to perform a power decoupling function. In particular, the plurality of capacitors may be disposed on the same layer, but may also be distributed across different layers, and each capacitor may be electrically connected to the corresponding power layer and return layer through vias.

[0082] In addition, one or more vias can be formed in parallel to reduce the resistance and inductance of the current path. As capacitors placed in multiple layers are connected in parallel through vias in this way, multiple low-impedance paths are formed between each power line and return line, and power noise can be effectively filtered.

[0083] In addition, the current path formed through the vias can form a structure that extends in the thickness direction of the board, thereby dispersing current density and reducing parasitic inductance. In particular, when a large current is required instantaneously, such as with a spiky load, current can be rapidly supplied through the low-impedance path formed by this multilayer structure and via connection. Accordingly, voltage drop and voltage ripple in each power line can be suppressed, and a more stable voltage can be provided to the sensor element.

[0085] FIG. 6 is a circuit diagram for more specifically explaining a power supply structure according to an embodiment of the present invention. FIG. 6 can be understood as illustrating the board configuration described in FIG. 5 in more detail.

[0086] Referring to FIG. 6, the electronic device (12) may include a main board (102) and a sensor board (202). Additionally, as indicated by the dotted line in FIG. 6, the left area may correspond to the main board (102) and the right area may correspond to the sensor board (202).

[0087] The main board (102) may include a first voltage converter (110) for converting the input voltage. In FIG. 6, the first voltage converter (110) is shown in a form that includes a plurality of buck converters, and each buck converter can convert the input voltage to different voltage levels and provide it to the sensor board (202).

[0088] The sensor board (202) may include a second voltage converter (210) for receiving and further converting the voltage supplied from the main board (102). FIG. 6 illustrates an example in which the second voltage converter (210) is implemented with a plurality of low-drop voltage regulators (LDOs), and each LDO can adjust the voltage for a corresponding power line.

[0089] Each power line can be connected to a sensor element (220) included in the sensor board (202). For example, a SPAD power line, a VDDA power line, and a VDDD power line can be formed, and each power line can be supplied to the sensor element (220) after the voltage is adjusted through a corresponding second voltage converter (210). The sensor element (220) may be a pixel array including a SPAD.

[0090] Additionally, capacitors may be placed on the sensor board (202) corresponding to each power line. For example, a capacitor of relatively large capacity may be connected to the output terminal of each second voltage converter (210), which can perform a decoupling function to mitigate voltage fluctuations.

[0091] In this way, in the present embodiment, a first voltage conversion is performed at the first voltage conversion unit (110) of the main board (102), and a second voltage conversion can be performed at the second voltage conversion unit (210) of the sensor board (202). That is, a stepwise voltage conversion structure can be formed for each power line.

[0092] Due to this structure, the second voltage converter (210) located on the sensor board (202) can adjust the voltage at a position close to the sensor element (220), thereby enabling a more rapid response to instantaneous current changes occurring in the load. Additionally, since independent voltage conversion and decoupling can be performed for each power line, interference between power sources is reduced and a more stable power supply is possible.

[0093] FIG. 6 illustrates a case where the first voltage converter (110) is a buck converter and the second voltage converter (210) is an LDO, but this is merely an exemplary configuration. The first voltage converter (110) may include at least one of a buck converter, a buck-boost converter, and a flyback converter, and the second voltage converter (210) may include at least one of a low drop voltage regulator (LDO), a source follower, and a pass transistor-based circuit.

[0095] FIGS. 7 and FIGS. 8 are drawings for illustrating the signal flow for a board configuration according to another embodiment of the present invention.

[0096] FIG. 7 illustrates a structure similar to the configuration described in FIG. 5, but with additional voltage conversion performed on the sensor board. Descriptions of configurations and operations that overlap with FIG. 5 are omitted.

[0097] Referring to FIG. 7, the second voltage converter (210) may include an additional linear voltage converter. There may be cases where the voltage margin required by the sensor board (202) is limited. For example, if it is difficult to secure a sufficient voltage drop with only a single voltage converter, the voltage can be lowered stepwise using multiple voltage converters. Additionally, since voltage fluctuations can be distributed at each step, a more stable voltage supply is possible.

[0098] Specifically, the second voltage converter (210) may include a first linear voltage converter and a second linear voltage converter. For example, the first linear voltage converter and the second linear voltage converter may be LDOs shown on the sensor board of FIG. 7, but are not limited thereto. At this time, the second voltage converter (210) may include a third linear voltage converter connected to the first linear voltage converter.

[0099] The third linear voltage converter may be configured to provide an input voltage to the first linear voltage converter. At this time, the voltage supplied to the third linear voltage converter may be a voltage provided without passing through the first voltage converter (110) of the main board (102), but is not limited thereto.

[0100] For example, the third linear voltage converter may directly receive the voltage provided by the main board (102), or it may receive the voltage provided through an external power source or a separate power path. Additionally, the third linear voltage converter may use the voltage that has not passed through the first voltage converter (110) as an input.

[0101] In this way, the path of the input voltage provided to the third linear voltage converter can be configured in various ways, and accordingly, the voltage conversion structure can be flexibly designed to meet the voltage conditions required by the sensor board (202).

[0102] For example, consider a case where a voltage of about 25V is supplied from the main board (102) to the sensor board (202), and a voltage of about 22V is required to drive the sensor element (220).

[0103] In this case, when directly converting 25V to 22V using a single linear voltage converter, a voltage drop of approximately 3V is required, and if the load current is large, it may be difficult to stably secure the dropout voltage and operating margin. In particular, if the instantaneous current increases due to a spiky load, the required dropout voltage increases, which may degrade the stability of the output voltage.

[0104] Accordingly, a stepwise voltage drop structure can be applied in which a voltage of 25V is first converted to, for example, about 23.5V using a third linear voltage converter, and then the 23.5V is secondarily converted to 22V using a first linear voltage converter.

[0105] In this case, since a voltage drop of about 1.5V is achieved in the third linear voltage converter and about 1.5V in the first linear voltage converter, the required dropout voltage and operating margin in each voltage converter can be more easily secured.

[0106] In addition, since voltage fluctuations caused by variations in load current can be distributed and processed at each stage, a more stable voltage can be provided to the sensor element (220) even under spiky load conditions.

[0108] FIG. 8 is a circuit diagram for more specifically explaining a power supply structure according to another embodiment of the present invention. FIG. 8 is similar to the circuit configuration described in FIG. 6, but shows a structure including an additional linear voltage converter in the sensor board (202). Descriptions of configurations and operations that overlap with FIG. 6 and FIG. 7 are omitted.

[0109] Referring to FIG. 8, the electronic device (12) may include a main board (102) and a sensor board (202), and the main board (102) may include a first voltage converter (110) for converting an input voltage. The first voltage converter (110) may include a plurality of buck converters and may convert the input voltage to different voltage levels and provide it to the sensor board (202).

[0110] The sensor board (202) may include a second voltage converter (210) for receiving and further converting the voltage supplied from the main board (102). The second voltage converter (210) may include a plurality of linear voltage converters and may adjust the voltage corresponding to each power line.

[0111] In particular, FIG. 8 illustrates a structure including additional linear voltage converters for a specific power line. For example, the second voltage converter (210) may include a first linear voltage converter and a second linear voltage converter, and may further include a third linear voltage converter connected to provide voltage to at least one input of the first linear voltage converter. Accordingly, a structure in which a plurality of linear voltage converters are connected in stages for a single power line may be formed.

[0112] The third linear voltage converter may be configured to provide an input voltage to the first linear voltage converter, and the voltage supplied to the third linear voltage converter may be a voltage provided through the first voltage converter (110) of the main board (102), but is not limited thereto. For example, the third linear voltage converter may directly receive a voltage provided from the main board (102), or receive a voltage from a separate power path or an external power source.

[0113] In this way, as a plurality of linear voltage converters are connected in stages, the voltage can be dropped in stages. For example, if a voltage of about 25V is provided from the main board (102) and a voltage of about 22V is required for the sensor element (220), it can be first converted to about 23.5V through the third linear voltage converter and then secondarily converted to about 22V through the first linear voltage converter. In this case, the voltage drop required at each voltage converter is distributed, making it easier to secure the dropout voltage and operating margin.

[0114] In addition, since voltage fluctuations can be distributed and processed at each stage, instantaneous current changes can be responded to more effectively even in the case of a sensor element (220) having spiky load characteristics. Accordingly, a more stable voltage can be provided to the sensor element (220).

[0115] FIG. 8 illustrates a case where the first voltage converter (110) is a buck converter and the second voltage converter (210) includes an LDO, but this is merely an exemplary configuration. The first voltage converter (110) can be implemented with various switching power supply circuits, and the second voltage converter (210) can be implemented with various linear voltage conversion circuits.

[0117] FIG. 9 is a drawing for explaining the effects according to the board configuration of the present invention.

[0118] Referring to FIG. 9, changes in voltage and current at each power node in a power supply structure according to an embodiment of the present invention are illustrated. In particular, voltage stability can be verified through the V(spad) graph, which represents the voltage supplied to the sensor element.

[0119] In the case of the conventional structure described in Fig. 3, a phenomenon may occur where the voltage drops significantly relative to the target voltage at a certain point due to a spiky load. For example, a voltage drop may occur in which the voltage that should be maintained at about 22V suddenly drops to about 13V.

[0120] On the other hand, when the power supply structure of the present invention is applied as shown in FIG. 9, it can be confirmed that voltage fluctuation is significantly reduced even under the same load conditions. For example, even if the voltage temporarily decreases at a specific point in time on the V(spad) graph, the magnitude of the decrease is relatively small, and the state close to the target voltage level can be maintained.

[0121] As the magnitude of the voltage drop is reduced in this way, the voltage applied to the sensor element can be maintained more stably. In particular, voltage fluctuations can be effectively suppressed even when instantaneous current changes occur due to a spiky load.

[0122] This is because the response to load changes occurs near the sensor due to the voltage conversion structure distributed across the main board and the sensor board, and the second voltage conversion unit and capacitor placed on the sensor board. Accordingly, the influence of parasitic components occurring in the power delivery path can be reduced, and voltage fluctuations can be compensated locally.

[0123] Consequently, according to the power supply structure of the present invention, the operational stability of the sensor element can be improved, and signal quality and detection performance can be improved even in the case of a sensor sensitive to power noise.

[0125] FIG. 10 is a drawing for specifically describing a sensor board according to one embodiment of the present invention.

[0126] Referring to FIG. 10, the sensor board (202) may include a power supply unit placed on the same board as the load. The power supply unit may provide voltage (VDD) to the load included in the sensor board (202), for example, a spiky load.

[0127] At this time, the power supply unit may be an embodiment of the second voltage converter (210) described in the present invention. That is, the power supply unit can be understood as a linear voltage converter that additionally converts the voltage supplied from the main board to generate a voltage suitable for the sensor element.

[0128] The power supply unit can be implemented as a linear voltage conversion circuit. For example, the power supply unit may be a linear voltage conversion unit comprising a reference voltage (Vref), an op-amp, and a transistor. The op-amp can control the output voltage (VDD) based on the reference voltage (Vref), and the transistor can regulate the current supplied to the load according to the output of the op-amp.

[0129] As such, when the power supply unit is implemented in a linear manner rather than a switching manner, noise caused by switching operations can be reduced. Additionally, since a dominant pole can be formed by a capacitor connected to the output terminal, the loop compensation design of the power supply unit can be simplified.

[0130] The sensor board (202) may include a plurality of capacitors positioned in close proximity to the load. The plurality of capacitors may be connected between the output voltage (VDD) and the reference potential of the sensor board (202), and may serve to supply the corresponding current when a large current is instantaneously required by the load. Accordingly, the large instantaneous current generated by the load may flow mainly through a local closed loop containing the capacitors.

[0131] The power supply unit can operate to replenish charge instantaneously consumed by the load. For example, if the charge stored in a capacitor is discharged due to the instantaneous current demand of the load, the linear voltage converter can recharge the capacitor within the design-allowed current range. Therefore, the power supply unit or the board-to-board connector does not have to directly handle the entire instantaneous peak current.

[0132] In this case, it may take some time for the output voltage (VDD) to recover. However, since the capacitor capacitance and ESR can be designed to match the load's allowable voltage range and the sensor's operating characteristics, temporary changes in the output voltage (VDD) can be prevented from having a substantial impact on the sensor's operating performance.

[0133] In addition, since the power supply unit is placed on the same sensor board (202) as the load, the influence of parasitic resistance, parasitic inductance, or rated current issues of the connector present in the power transfer path between the main board and the sensor board can be reduced. Accordingly, instantaneous current fluctuations caused by the spiky load can be suppressed from being directly transmitted to the power line between the boards.

[0134] In one embodiment, the output voltage (VDD) may be determined by a reference voltage (Vref). The reference voltage (Vref) may be controlled by a control signal (CTRL) provided from the outside. For example, the control signal (CTRL) may be a digital control signal and may be provided by a communication method using a small number of signal lines, such as I2C communication.

[0135] In one embodiment, the target voltage can be variably set by an external digital signal (CTRL). For example, the external digital signal (CTRL) may be provided via I2C communication, SPI communication, or an equivalent digital interface, and the output voltage (VDD) can be changed by adjusting the reference voltage (Vref).

[0136] Additionally, the reference potential of the sensor board (202) may be the same as the reference potential of the target voltage. For example, the reference potential of the reference voltage (Vref) for generating the target voltage and the reference potential of the sensor board (203) may use the same reference potential. Accordingly, voltage errors that may occur due to differences in reference potentials can be reduced, and the accuracy and stability of the target voltage provided to the sensor element can be improved. Therefore, the sensor board (202) can adjust the output voltage (VDD) according to the control signal (CTRL) without receiving complex high-current power control signals from the outside. Accordingly, the required voltage can be flexibly set according to the operating conditions of the sensor, and power supply suitable for the characteristics of the load included in the sensor board (202) is possible.

[0137] In this way, the instantaneous peak current required by the load is mainly supplied through the capacitor, and the second voltage converter can operate to replenish the charge of the capacitor at the average current level.

[0139] FIG. 11 is a drawing for specifically describing a sensor board according to another embodiment of the present invention. FIG. 11 illustrates a structure similar to the configuration described in FIG. 10, but including an additional transistor to perform the sinking function of the output current. Descriptions of configurations and operations that overlap with FIG. 10 are omitted.

[0140] Referring to FIG. 11, the sensor board (203) may include a power supply unit placed on the same board as the load. The power supply unit may be an embodiment of the second voltage converter (210) described in the present invention and may provide voltage (VDD) to the load included in the sensor board (203), for example, a spiky load.

[0141] The power supply unit may be implemented as a linear voltage conversion circuit comprising a reference voltage (Vref), an op-amp, and a plurality of transistors. In this case, the plurality of transistors may include a first transistor and a second transistor.

[0142] Specifically, referring to FIG. 11, the first transistor may be a pass transistor connected between an input power supply (VP) and an output node (VDD) and may provide voltage and current to the output node (VDD). Additionally, the second transistor may be a sinking transistor connected between the output node (VDD) and a return line and may guide current from the output node (VDD) toward the return line.

[0143] The first transistor can be connected between the input power supply and the output of the op-amp, and can perform the role of providing voltage (VDD) to the load included in the sensor board (203). That is, the first transistor can form a sourcing path that supplies current to the output node.

[0144] The second transistor can be connected to the output node of the op-amp and configured to guide current from the output node to the return line. That is, the second transistor can form a sinking path that allows current to flow from the output node toward the return line. By adding this sinking path, a rise in the power supply (VDD) voltage caused by abnormal reverse current flow that may occur in the load can be prevented, thereby protecting the components connected to the node from being destroyed due to exceeding the rated voltage.

[0145] In one embodiment, the second transistor may be connected in series with at least one resistor. The resistor may be used to regulate or limit the current flowing through the second transistor.

[0146] The above resistor may be implemented as a single resistor element, but is not limited thereto. For example, the resistor may be implemented as a resistor network in which a plurality of resistor elements are connected in series and / or parallel.

[0147] By using multiple resistor elements in this way, a desired resistance value can be achieved, power consumption can be distributed, and the reliability of the circuit can be improved. In addition, the response characteristics of the current sinking operation performed by the second transistor can be adjusted, and the voltage stability of the output node can be improved.

[0148] A typical linear voltage conversion circuit only has the function of sourcing output current, and the sinking function is provided only to a limited extent. In some cases, a method of dissipating current by adding a resistor to the output terminal may be used, but this method is not desirable as it can cause unnecessary current consumption even during normal operation.

[0149] Meanwhile, for certain loads, current may flow in reverse toward the power supply depending on the operating mode. In such situations, if the voltage at the output node rises, the power supply voltage may exceed the allowable range and surpass the breakdown voltage of the connected circuit components, which can lead to permanent damage to the circuit components.

[0150] By forming a current sinking path using a second transistor as in this embodiment, the current flowing into the output node can be quickly guided to the return line. Accordingly, the rise in the output voltage (VDD) can be effectively suppressed, and damage to the circuit due to overvoltage can be prevented.

[0151] In addition, the current sinking function by the second transistor can enable rapid discharge of a large-capacity capacitor connected to the output terminal. Accordingly, the operating state of the system can be stabilized more quickly, and electrical response characteristics can be improved.

[0152] Accordingly, according to the present embodiment, the current sourcing function by the first transistor and the current sinking function by the second transistor are implemented together, thereby improving the control range and responsiveness of the output voltage (VDD). In particular, a more stable voltage can be provided even in environments with large current variations, such as spiky loads.

[0154] FIG. 12 is a drawing for explaining a sensor board according to a plurality of power lines according to an embodiment of the present invention.

[0155] Referring to FIG. 12, the sensor board (204) may include a plurality of power supply units corresponding to a plurality of power lines. Each power supply unit may be an embodiment of the second voltage conversion unit (210) described in the present invention and may be implemented as a linear voltage conversion circuit described in FIG. 10 or FIG. 11.

[0156] For example, the sensor board (204) may include a first power supply unit (PSU-1), a second power supply unit (PSU-2), and a third power supply unit (PSU-3). Each power supply unit may receive different input voltages (VP1 / VN1, VP2 / VN2, VP3 / VN3) and generate respective output voltages (VDD1, VDD2, VDD3).

[0157] Each output voltage (VDD1, VDD2, VDD3) can be supplied to different power nodes of a load included in the sensor board (204), for example, a spy load. For example, VDD1 can be used as the SPAD driving voltage, VDD2 as the analog circuit voltage, and VDD3 as the digital circuit voltage.

[0158] Each power supply unit may include a plurality of capacitors to stabilize the output voltage. The plurality of capacitors can be connected between the corresponding power line and return line to perform a decoupling function and can additionally satisfy the instantaneous current demands generated by spiky loads.

[0159] In addition, each power supply unit can be controlled by independent control signals (CTRL1, CTRL2, CTRL3). For example, the reference voltage (Vref) of each power supply unit can be set by the corresponding control signal, and accordingly, each output voltage can be adjusted independently.

[0160] As multiple power supply units are configured independently for each power line in this manner, the voltage conditions of each power line can be optimized individually. In particular, interference between circuits requiring different power characteristics can be minimized, and the propagation of voltage fluctuations to other power lines can be suppressed.

[0161] In addition, since each power supply unit is positioned close to the sensor board (204), the influence of parasitic resistance and inductance included in the power delivery path can be reduced. Accordingly, a stable voltage can be provided for each power line even under spiky load conditions.

[0162] In FIG. 12, three power supply units are shown, but this is merely an exemplary configuration. The number of power supply units can be varied depending on the configuration of the sensor board (204) and the number of required power lines.

[0164] Although the embodiments have been described above with reference to limited examples and drawings, those skilled in the art can make various modifications and variations from the description above. For example, suitable results can be achieved even if the described techniques are performed in a different order than described, and / or the components of the described system, structure, device, circuit, etc. are combined or assembled in a form different from described, or replaced or substituted by other components or equivalents.

[0165] Therefore, other implementations, other embodiments, and equivalents to the claims also fall within the scope of the claims set forth below.

Claims

Claim 1 An electronic device comprising: a main board including a first voltage converter that converts an input voltage; and a sensor board connected to the main board and receiving voltage from the main board, wherein the sensor board includes a second voltage converter that converts the voltage received from the main board, the target voltage of the second voltage converter is varied by an external digital signal, and the reference potential of the sensor board is the same as the reference potential of the target voltage. Claim 2 An electronic device according to claim 1, wherein the first voltage converter comprises a switching power supply that converts the input voltage by the periodic switching operation of a switching element. Claim 3 In paragraph 2, the electronic device comprises a linear voltage converter that converts the voltage supplied from the main board by linear operation, wherein the second voltage converter is a linear voltage converter. Claim 4 An electronic device according to paragraph 3, wherein the switching power supply comprises a first converter connected to a first power line and a second converter connected to a second power line, and the linear voltage converter comprises a first linear voltage converter corresponding to the first converter and a second linear voltage converter corresponding to the second converter. Claim 5 In paragraph 4, the sensor board is an electronic device comprising a first capacitor group connected to the first linear voltage converter and a second capacitor group connected to the second linear voltage converter. Claim 6 An electronic device according to claim 5, wherein a plurality of capacitors included in the first capacitor group are connected in parallel with one end connected to the first power line and the other end connected to the reference potential of the sensor board, and a plurality of capacitors included in the second capacitor group are connected in parallel with one end connected to the second power line and the other end connected to the reference potential of the sensor board. Claim 7 An electronic device according to claim 5, wherein the sensor board is formed as a printed circuit board comprising a plurality of layers, and the plurality of layers include a first layer corresponding to the first power line and a second layer corresponding to the second power line. Claim 8 In paragraph 4, the electronic device comprises a sensor board including a third linear voltage converter connected to the first linear voltage converter to provide voltage to at least one input of the first linear voltage converter for a stepwise voltage drop. Claim 9 In claim 1, the first voltage converter is an electronic device comprising at least one of a buck converter, a buck-boost converter, and a flyback converter. Claim 10 In claim 1, the second voltage converter is an electronic device comprising at least one of a low drop voltage regulator (LDO), a source follower, and a pass transistor-based circuit. Claim 11 An electronic device according to claim 1, wherein the second voltage converter comprises a first transistor and a second transistor, the first transistor provides voltage to the output node of the second voltage converter, and the second transistor is configured to induce current from the output node of the second voltage converter to a reference potential of the sensor board. Claim 12 An electronic device according to claim 11, wherein the second transistor is connected in series with at least one resistor, and the at least one resistor is composed of a resistor network in which a plurality of resistor elements are combined in series and parallel. Claim 13 delete Claim 14 An image sensor comprising: a main board including a first voltage converter for converting an input voltage; and a sensor board connected to the main board and receiving voltage from the main board, wherein the sensor board includes a pixel array including a plurality of SPAD (Single-Photon Avalanche Diode) elements and a second voltage converter for converting the voltage supplied from the main board to provide a driving voltage to the pixel array, wherein the target voltage of the second voltage converter is varied by an external digital signal, and the reference potential of the sensor board is the same as the reference potential of the target voltage.

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