JP2018113526A - Imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To implement driving having power supply efficiency higher than that of a linear regulator circuit.SOLUTION: An imaging apparatus includes: a first switching regulator circuit for converting an output voltage of a power supply into a first voltage; a second switching regulator circuit for converting the output voltage of the power supply or an output voltage of the first switching regulator circuit into a second voltage; selection means for selecting either a first drive mode of generating the second voltage by using the first switching regulator circuit and the second switching regulator circuit or a second drive mode of generating the second voltage by not using the first switching regulator circuit but using the second switching regulator circuit; and an imaging element for performing photoelectric conversion on an optical image to generate picture data. The selection means, depending on an operation mode of the imaging element, selects the first drive mode or the second drive mode.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an imaging apparatus capable of reducing the influence of radiation noise.

  In recent digital still cameras, downsizing of devices is progressing, and high-density mounting is progressing on a substrate in the device. Along with this, there is a tendency that an image pickup device for picking up an optical image and a power supply circuit for driving electronic components in the device are arranged closer to each other.

  In an image sensor such as a CMOS sensor that captures an optical image, if noise due to an external magnetic field or the like is large during driving of the image sensor, the noise affects the image. In addition, this phenomenon is easily affected when the image pickup element is driven, particularly when it occurs at the timing of reading processing of the pixel portion. On the other hand, it is known that the higher the ISO sensitivity (signal gain) of the pixel portion, the higher the influence on the output image, and the higher the sensitivity of the image sensor is progressing. Is becoming more susceptible to external noise.

  On the other hand, as a power supply circuit used for supplying power to each electronic component in a digital camera device, a switching regulator circuit is generally used in terms of efficiency. In particular, since a digital camera is driven by a battery, if the efficiency of the power supply circuit is low, the number of images that can be captured is affected, which is fatal. This switching regulator circuit is driven to sink and source a pulse current in the inductor.

  In other words, because a pulse current flows through the inductor, electromagnetic noise is radiated from the inductor during switching drive, and if the image sensor is placed near the power supply circuit, it is affected by the radiated noise from the inductor and affects the captured image. Will appear. The amount of noise radiated from this inductor is proportional to the current amplitude of the pulse current of the inductor.

  Furthermore, this current amplitude correlates with the output difference between the input voltage and the output voltage of the switching regulator circuit, and the current amplitude increases as the input / output potential difference increases. That is, it is known that the radiation noise increases as the difference between the input voltage and the output voltage of the switching regulator circuit (hereinafter referred to as input / output voltage difference) increases.

  As described above, the effects of radiation noise of the switching regulator circuit are becoming larger as the size of devices and the sensitivity of imaging devices increase, and a countermeasure for this problem is desired.

  As an idea for avoiding this problem, in Patent Document 1, when the sensitivity of the image sensor is equal to or higher than a predetermined value, the image sensor is affected by noise by switching the power supply circuit from a switching power source to a linear regulator. In a state where it is easy to receive, a proposal has been made to drive a power supply circuit in a system in which noise due to the power supply circuit is reduced.

  In Patent Document 2, a proposal is made to avoid the influence of radiation noise from the switching regulator circuit by switching the power supply circuit from the switching regulator circuit to the linear regulator circuit while driving the image sensor.

JP 2011-55308 A JP 2013-65939 A

  However, in Patent Document 1, when the sensitivity of the image sensor is higher than a predetermined value, the power supply circuit is driven by switching from the switching regulator circuit to the linear regulator circuit, so that it avoids noise to the image sensor. Although it is possible to change the efficiency from the switching regulator circuit to the linear regulator circuit, the efficiency is lowered. As a result, in the case of imaging when the sensitivity of the imaging device is higher than the predetermined value, it is always driven by a power circuit with low efficiency, which increases the power consumption of the camera and consequently affects the number of images that can be captured. Will be affected.

  In Patent Document 2, the power supply circuit is switched from the switching regulator circuit to the linear regulator circuit according to the drive mode of the image pickup device, and thus the power supply circuit is driven in the image pickup drive mode. In this case, the circuit loss is increased, and even in this case, the number of images that can be imaged is affected.

  One of the imaging devices according to the present invention includes a first switching regulator circuit that converts an output voltage of a power source into a first voltage, and an output voltage of the power source or an output voltage of the first switching regulator circuit as a second voltage. The first switching mode for generating the second voltage by using the second switching regulator circuit that converts the voltage to the first voltage, the first switching regulator circuit, and the second switching regulator circuit, By using the second switching regulator without using the first switching regulator circuit, the selecting means for selecting one of the second drive modes for generating the second voltage, and the optical image are photoelectrically converted. An image sensor for generating image data, and the selection unit is configured to perform the operation according to an operation mode of the image sensor. And selecting the first drive mode or the second driving mode.

  One of the imaging devices according to the present invention includes a first switching regulator circuit that converts an output voltage of a power source into a first voltage, and an output voltage of the power source or an output voltage of the first switching regulator circuit as a second voltage. The first switching mode for generating the second voltage by using the second switching regulator circuit that converts the voltage to the first voltage, the first switching regulator circuit, and the second switching regulator circuit, By using the second switching regulator without using the first switching regulator circuit, the selecting means for selecting one of the second drive modes for generating the second voltage, and the optical image are photoelectrically converted. An image sensor that generates image data and means for changing sensitivity settings of the image sensor, and the selection means In response to said sensitivity setting value of the image sensor, and selects the first driving mode or the second driving mode.

  According to the present invention, since the power supply circuit is composed of only the switching regulator circuit as the power supply circuit, driving with higher power supply efficiency than the linear regulator circuit can be realized.

  According to the present invention, in a mode in which the imaging device is likely to be affected, the difference between the input and output potentials of the power supply circuit can be greatly reduced by using two stages of switching regulators. The radiation noise from the switching regulator can be suppressed.

  According to the present invention, the switching regulator circuit has two stages when operating in a mode that is susceptible to the imaging result of the imaging device, and the switching regulator circuit when operating in a mode that is not easily influenced by the imaging result of the imaging device. By making the circuit one stage, it is possible to drive with further improved power efficiency.

2 is a diagram for describing an example of a configuration of an imaging apparatus according to Embodiment 1. FIG. It is a figure for demonstrating the characteristic of the radiation noise from the inductor used in the switching regulator circuit. It is a figure for demonstrating the example of arrangement | positioning of an electronic component and a power supply circuit. It is a timing chart for explaining the 1st example of operation. It is a timing chart for demonstrating the 2nd operation example.

  Hereinafter, embodiments will be described with reference to the drawings. However, the present invention is not limited to the following embodiments.

[Embodiment 1]
With reference to FIG. 1, an example of the configuration of an imaging apparatus (example: digital camera) in the first embodiment will be described. In FIG. 1, an example of an electronic component related to an imaging process and a power supply circuit for supplying power to the electronic component will be described, and description of other parts will be omitted. Reference numeral 1 denotes a power source. Here, a lithium ion secondary battery is assumed. Reference numeral 2 denotes a first switching regulator circuit that receives power from the power source 1 and generates a first voltage from the output voltage of the power source 1. Here, a step-down converter is assumed, which includes an input / output capacitor, a high-side and low-side switching MOS, and an inductor.

  Here, the first switching regulator circuit 2 is connected to the microcomputer 5 and the SW input unit 9 operated by the user, and supplies power to the microcomputer 5 and the SW input unit 9. In addition, the control signal is connected to the input power supply so that it operates when the power supply 1 is turned on. Next, 3 is a second switching regulator circuit. The second switching regulator circuit 3 includes three systems of switching regulators. Each of the three systems of switching regulators receives power from the power source 1 or the first switching regulator circuit 2 and generates a second voltage from the output voltage of the power source 1 or the output voltage of the first switching regulator circuit 2. .

  The output of the second switching regulator circuit 3 is connected to a DSP (Digital Processing Unit) 6, an image sensor 7 and a memory 8 for each switching regulator of each system, and supplies power to the DSP 6, the image sensor 7 and the memory 8. Yes. Here, the second switching regulator circuit 3 is assumed to be a step-down converter in any system, and is composed of an input / output capacitor, a high-side switching MOS, and a low-side switching MOS and an inductor.

  Reference numeral 4 denotes a drive mode selection circuit, which is a circuit for selecting and switching between connecting the power source 1 to the input section of the second switching regulator circuit 3 and connecting the output of the first switching regulator circuit 2. It can be changed according to the timing of the imaging operation and the driving mode.

  A microcomputer 5 is connected to the SW input unit 9, DSP 6, drive mode selection circuit 4, and second switching regulator circuit 3. The SW input unit 9 accepts an imaging request signal from the user, and based on the information, The DSP 6 is driven, the image sensor 7 is driven from the DSP 6, and the imaging operation is started. The image sensor 7 is an image sensor that photoelectrically converts an optical image to generate image data. The image sensor 7 receives a notification of the start of the imaging operation from the DSP 6, performs imaging, transmits image data corresponding to the captured image to the DSP 6, and is recorded in the memory 8 after the DSP 6 performs a series of image processing. .

  Next, with reference to FIG. 2, the characteristic of the radiation noise from the inductor used in the switching regulator circuit will be described. Relationship 10 shows the relationship between the input / output potential difference of the switching regulator circuit and the inductor current. The horizontal axis is the input / output potential difference of the switching power supply, the vertical axis is the inductor current (more precisely, the current amplitude of the inductor), and the inductor current tends to increase as the input / output potential difference of the switching regulator circuit increases. There is.

  Relationship 11 shows the relationship between the input / output potential difference of the switching regulator circuit and the leakage magnetic flux (radiated noise) from the inductor. The horizontal axis represents the input / output potential difference of the switching power supply, the vertical axis represents the leakage magnetic flux (radiated noise) from the inductor, and the larger the input / output potential difference of the switching regulator circuit, the greater the radiation noise from the inductor. This is because the current amplitude of the inductor increases as shown in relation 10, and as a result, radiation noise increases.

  The characteristics of FIG. 2 will be specifically described with reference to FIG. 1. Assuming that the power source 1 is 8.0 v, the output of the first switching regulator circuit 2 is 3.3 v, and the DSP 6 in the second switching regulator circuit 3 is the same. When the power supply for the memory 8 is 1.0 v and the power supply for the memory 8 is 1.2 v, when the power supply 1 is selected in the drive mode selection circuit 4, the power supply circuit for the DSP 6 in the second switching regulator circuit 3 Is the input / output potential difference: Δ7.0v, and in the power supply circuit for the memory 8, the input / output potential difference is Δ6.8v.

  On the other hand, when the first switching regulator circuit 2 is selected in the drive mode selection circuit 4, the input / output potential difference is Δ2.3v in the power supply circuit for the DSP 6, and the power supply circuit for the memory 8 is in the power supply circuit for the memory 8. Since the input / output potential difference is Δ2.1v and the drive mode selection circuit 4 selects the power supply 1, the input / output potential difference is about 30%, so that the radiation noise of the inductor is also suppressed to about 30%.

  On the other hand, also in terms of power supply efficiency, when the efficiency characteristics of the first and second switching regulator circuits 3 are about 90%, the drive mode selection circuit 4 selects the first switching regulator circuit 2. However, in general, the power supply efficiency is about 80%, and the efficiency is overwhelmingly higher than when either one is a linear regulator circuit. If either one is a linear regulator circuit, the efficiency is about 30%.

  FIG. 3 is a diagram for explaining an arrangement example of electronic components related to the imaging process and a power supply circuit for supplying power to these electronic components. Reference numeral 20 denotes a substrate on which the image pickup element 7, DSP 6, memory 8, microcomputer 5 and the second switching regulator circuit 3 for supplying power are mounted. The second switching regulator circuit 3 is a power supply circuit that supplies power to the DSP 6, the memory 8, and the microcomputer 5. The second switching regulator circuit 3 is an electronic device related to the imaging process from the viewpoint of reducing transmission line loss as well as downsizing the substrate. Mounted close to the component. Therefore, this is an example in which the image sensor 7 is susceptible to external noise, and it is necessary to reduce radiation noise from the inductor of the switching regulator circuit at the time of operation timing and operation setting.

  Next, a first operation example will be described with reference to the timing chart of FIG. In the timing chart of FIG. 4, the signal from the SW input unit 9, the operation status of the image sensor 7, DSP 6 and memory 8, the selection state of the drive mode selection circuit 4, and the inductor current (≈inductor of the second switching regulator circuit 3). The operation timing is shown for the state of (radiation noise).

  First, in the status of 30, the SW input unit 9 is in a state where an imaging request signal is received from the user. The microcomputer 5 receives a signal from the SW input unit 9 and starts an accumulation status from the DSP 6 to the image sensor 7. In this mode, since the image sensor 7 is not easily affected by external noise, the drive mode selection circuit 4 selects the power supply 1 side, the second switching regulator circuit 3 has a single stage configuration, and the inductor radiation noise is It becomes a relatively large state (efficiency is a good mode).

  Next, at 31, the accumulation operation of the image sensor 7 at 30 is finished, and the pixel reading operation of the image sensor 7 is started. In this mode, since the image sensor 7 is susceptible to external noise, the drive mode selection circuit 4 selects the first switching regulator circuit 2 side, and the second switching regulator circuit 3 has a two-stage configuration. Inductor radiation noise is relatively small.

  Next, in 32, the reading process of the image sensor 7 is completed, and the image processing operation (development process, compression process, etc.) of the captured image is performed in the DSP 6. Next, when image processing in the DSP 6 is completed, writing processing (recording processing) to the memory 8 is performed. In this mode, since the image sensor 7 is not easily affected by external noise, the drive mode selection circuit 4 selects the power source 1 side, the second switching regulator circuit 3 has a single stage configuration, and the inductor radiation noise is compared. The large state continues (efficiency is a good mode). Next, in operation 33 and 35, a state in which a new user's imaging request is generated and operation similar to operations 30 to 32 continues.

  Next, a second operation example will be described with reference to the timing chart of FIG. In the timing chart of FIG. 5, the signal from the SW input unit 9, the operation status of the imaging device 7, DSP 6, and memory 8, the selection state of the drive mode selection circuit 4, and the inductor current (≈inductor of the second switching regulator circuit 3). The operation timing is shown for the state of (radiation noise).

  First, the status 40 indicates a state in which the user has set the ISO sensitivity of the image sensor 7. In the status 40, an example in which the sensitivity is set lower than a predetermined value is shown. Here, it is an example when set to ISO200. 41 is a state in which the user has received an imaging request signal from the user at the SW input unit 9, and the imaging device 7 is based on the ISO sensitivity value set at 40, as indicated by 30 to 32 in FIG. A series of imaging processes such as accumulation of the image sensor 7, reading of the pixel portion, DSP processing, and memory writing operate sequentially.

  Here, since the ISO sensitivity value set at 40 is lower than the predetermined value, the image pickup device 7 is not easily affected by external noise. Therefore, the drive mode selection circuit 4 selects the power supply 1 side, and the second switching regulator circuit. 3 has a one-stage configuration, and the operation is continued with a relatively large inductor radiation noise. As a result, the mode becomes efficient.

  Next, in status 42, the user is newly setting the ISO sensitivity of the image sensor 7. In 42, an example of a state in which the sensitivity is set higher than a predetermined value is shown. Here, it is an example when set to ISO6400. 43 is a state in which the user has received an imaging request signal from the user at the SW input unit 9, and the imaging element 7 is based on the ISO sensitivity value set in 42, as indicated by 30 to 32 in FIG. A series of imaging processes such as accumulation of the image sensor 7, reading of the pixel portion, DSP processing, and memory writing operate sequentially.

  Here, since the ISO sensitivity value set at 42 is higher than the predetermined value, the image pickup device 7 is susceptible to the influence of external noise. Therefore, the drive mode selection circuit 4 selects the first switching regulator circuit 2 side, The switching regulator circuit 3 of 2 has a two-stage configuration, and the operation is continued with a relatively small inductor radiation noise.

  As described above, according to the first embodiment, the power supply circuit (second switching regulator circuit 3) in the vicinity of the image sensor 7 depends on whether or not the image sensor 7 is in an imaging drive mode that is easily affected by external noise. The amount of noise from the power supply circuit (second switching regulator circuit 3) in the vicinity of the image sensor 7 can be controlled by switching the input power to the power source. As a result, according to the first embodiment, it is possible to perform power supply control that does not significantly reduce power supply efficiency and that is not affected by noise on the image sensor 7.

DESCRIPTION OF SYMBOLS 1 Power supply 2 1st switching regulator circuit 3 2nd switching regulator circuit 4 Drive mode selection circuit 5 Microcomputer 6 DSP
7 Image sensor 8 Memory 9 SW input section

Claims (4)

A first switching regulator circuit for converting an output voltage of the power source into a first voltage;
A second switching regulator circuit for converting an output voltage of the power source or an output voltage of the first switching regulator circuit into a second voltage;
By using the first switching regulator circuit and the second switching regulator circuit, the first driving mode for generating the second voltage or the second switching regulator circuit without using the first switching regulator circuit. Selecting means for selecting one of the second driving modes for generating the second voltage by using the switching regulator of
An image sensor that photoelectrically converts an optical image to generate image data,
The image pickup apparatus, wherein the selection unit selects the first drive mode or the second drive mode according to an operation mode of the image pickup device. The imaging apparatus according to claim 1,
The image pickup apparatus, wherein the selection unit selects the first drive mode during reading of a pixel signal of the image pickup device, and selects the second drive mode during storage of the image pickup device. . A first switching regulator circuit for converting an output voltage of the power source into a first voltage;
A second switching regulator circuit for converting an output voltage of the power source or an output voltage of the first switching regulator circuit into a second voltage;
By using the first switching regulator circuit and the second switching regulator circuit, the first driving mode for generating the second voltage or the second switching regulator circuit without using the first switching regulator circuit. Selecting means for selecting one of the second driving modes for generating the second voltage by using the switching regulator of
An image sensor that photoelectrically converts an optical image to generate image data;
Means for changing the sensitivity setting of the image sensor,
The image pickup apparatus, wherein the selection unit selects the first drive mode or the second drive mode according to a sensitivity setting value of the image pickup device. The imaging apparatus according to claim 3,
The selection unit selects the first drive mode when the sensitivity setting value of the image sensor is higher than a predetermined value, and the second driving mode when the sensitivity setting value of the image sensor is lower than a predetermined value. An image pickup apparatus that selects a driving mode.