JP2017121098A - Power supply system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply system that is related to a control unit implementing adaptive voltage scaling (AVS) and is able to reduce input power when a load is light, and an imaging device.SOLUTION: A power supply device detects load current, performs PWM control if the detected load current value is equal to or more than specified current, receives, by output voltage value communication reception means, a voltage value output by setting voltage value communication means, outputs the voltage value by power output means depending on the received setting voltage value, receives, by output voltage value communication reception means, the voltage value output by the setting voltage value communication output means if the detected load current value is equal to or less than the specified current, sets a setting voltage value of the output voltage setting means without changing to the received setting voltage value, switches to PFM control, and outputs it by power supply output means.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power supply system used for a control unit of an electrical apparatus such as an imaging apparatus, and more particularly to a power supply system using a switching regulator.

  In recent years, in a device using a battery such as a mobile phone or a digital camera, the importance of reducing the power consumed in the device is increasing from the viewpoint of extending the battery life. For this reason, a step-down switching regulator using a highly efficient inductor is widely used in power supply circuits and power supply systems. A general switching regulator uses PWM control (hereinafter referred to as PWM control) in which the frequency is constant and the voltage is controlled by the pulse width.

  The PWM control switching regulator maintains high efficiency during heavy load, for example, when shooting a moving image in a digital camera. However, since the current consumption of the switching regulator itself is relatively large, when the device operation is quiet, for example, in a digital camera, the efficiency is reduced during a reproduction operation or a power saving operation.

  Therefore, there is PFM (Pulse Frequency Modulation) control (hereinafter referred to as PFM control) as a technique for improving the efficiency at light load. The PFM control switching regulator is a technique for maintaining efficiency at light loads by reducing the switching frequency at light loads.

  Furthermore, a technique for detecting a load current and performing PWM / PFM switching control that operates by PWM control at a heavy load and operates by PFM control at a light load is realized.

  However, both the PFM control and the PWM / PFM switching control reduce the switching frequency at light load. For this reason, since a time for increasing the switching frequency is required for a sudden load fluctuation, the responsiveness is lowered. That is, the voltage drop when there is a sudden change from a light load to a heavy load increases.

  On the other hand, in a voltage system related to a control unit such as a CPU such as a digital camera, there is a technology called AVS (Adaptive Voltage Scaling) (hereinafter referred to as AVS). This is a technique for absorbing the process variation of the semiconductor of the control unit. First, an initial voltage is applied from the power supply unit to the control unit. Next, a necessary voltage is calculated in the control unit, and the calculated voltage is communicated to a power supply unit such as a power supply IC using communication means. The power supply unit outputs the received set voltage. The initial voltage is assumed to be the highest voltage assumed in consideration of semiconductor variations. In the case of a control unit having an average semiconductor performance, the voltage calculated by the control unit is lower than the initial voltage, thereby reducing power consumption.

  However, when the control unit calculates a necessary voltage, the set voltage is calculated by adding a voltage drop with respect to the set voltage of the power supply unit. That is, in the PWM / PFM switching control and PFM control, the responsiveness is low and the voltage drop is large. Therefore, it is necessary to increase the voltage value to be added. As a result, process variations cannot be absorbed and the power saving effect is reduced. For this reason, conventionally, when the AVS technique is implemented, it is driven by PWM control.

  FIG. 5 is a diagram for explaining the power saving effect of PWM / PFM switching drive and AVS.

  FIG. 5A is a log-log graph in which the horizontal axis represents the load current and the vertical axis represents the efficiency. However, FIG. 5 is an example assuming general DC load characteristics. In actual electrical equipment, the current value fluctuates transiently. The load current axis is logarithmic. A thick line 501 is a graph of the efficiency of PWM / PFM switching control. A dotted line 502 is a graph of the efficiency of PWM control. Reference numeral 503 denotes a current value for switching the PWM / PFM. In other words, in the PWM / PFM switching control, when the current is 503 or more, it is driven by PWM control, and when the current is less than 503, it is driven by PFM control. When the load is lighter than 503, the PWM / PFM switching control 501 maintains high efficiency with respect to the PWM control 502.

  FIG. 5B is a log-log graph in which the horizontal axis indicates the input power on the vertical axis with respect to the load current regarding the PWM / PFM switching control. 510 is a graph of load power against load current. The load power increases in proportion to the load current. Reference numeral 511 denotes input power when PWM / PFM switching control is performed. 512 is a graph of input power in PWM control. At a light load of 503 or less, the input power of 511 PWM / PFM switching control is less than the input current of 512 PWM control. This is because the drive is performed by PFM control, and the loss is small due to high efficiency.

  FIG. 5C is a log-log graph in which the horizontal axis indicates the input power on the vertical axis with respect to the load current with respect to AVS. Reference numeral 513 is an example of input power when AVS is implemented. Since the power is uniformly reduced with respect to the input power in the case of 512 PWM control, the graph is a graph in which the input power is translated downward in the entire load current range. The amount of movement depends on the individual process.

  FIG. 5D is a graph in which FIGS. 5A, 5B, and 5C are superimposed. The input power 511 when PWM / PFM switching control is performed is compared with the input power 513 when AVS is performed. In the range of the current range 521 shown in the figure, the input power is smaller in the case of 511 when the PWM / PFM switching control is performed than in the case of 513 when the AVS is performed. This is because the power saving effect by PFM control is higher than the power saving effect by AVS at light load.

  Patent Document 1 discloses a technique for switching a set voltage during PWM / PFM switching control.

JP 2005-341789 A

  However, in the conventional technique disclosed in Patent Document 1 described above, a technique for changing the reference voltage during PWM control and PFM control is disclosed for improving response. A block diagram of the prior art is shown in FIG. Using the above technique, it is possible to change the output voltage during PWM control and PFM control. However, there is no means for receiving the AVS set voltage value calculated by the control unit by communication. For this reason, AVS is performed in the PWM control state at light load, and it is impossible to reduce power at light load by PFM control.

  Accordingly, an object of the present invention is to reduce input power by not performing AVS or increasing a set voltage while performing PFM driving at a light load in a power supply system and an imaging apparatus in a control unit that performs AVS. It is to provide a power supply system that enables the above.

In order to achieve the above object, a power supply system according to the present invention includes:
PWM / PFM switching means for switching between PWM control and PFM control, load current detection means for detecting the load current of the power supply, output voltage setting means for setting the output voltage of the power supply, and receiving a set voltage from the outside by communication Set voltage value communication receiving means, power supply output means for outputting a voltage according to the set voltage value from the output voltage setting means and the set voltage value received by the set voltage value communication receiving means, and the power supply A control unit that controls the entire apparatus by a voltage supplied from an output voltage of the output unit, a necessary setting voltage determination unit that determines a necessary voltage while evaluating a processing speed performance of the control unit, and a necessary setting voltage determination unit. Setting voltage value communication output means for outputting the determined voltage by communication, and the load current detection means detects and detects the load current When the load current value is equal to or greater than a specified current, PWM control is performed by the PWM / PFM switching means, and the output voltage value communication receiving means receives and receives the voltage value output by the set voltage value communication output means. When the detected load current value is equal to or less than a specified current according to the set voltage value, the output voltage value communication receiving means outputs the voltage value output by the set voltage value communication output means. The setting voltage value of the output voltage setting means is set without being changed to the received setting voltage value, and the PWM / PFM switching means is switched to PFM control and output from the power output means.

  According to the present invention, in a power supply system in a control unit implementing AVS, a power system capable of reducing input power by not performing AVS or increasing a set voltage while performing PFM driving at a light load. In addition, an imaging device can be provided.

It is a block diagram which shows the power supply system structure of the imaging device regarding Example 1 of this invention. It is a flowchart which shows the power supply system operation | movement of an imaging device in connection with Example 1 of this invention. It is a flowchart which shows the power supply system operation | movement of an imaging device in connection with Example 2 of this invention. It is a flowchart which shows the operation | movement of AVS. It is a figure for demonstrating the power saving effect of PWM / PFM switching drive and AVS. It is a block diagram which shows the structure of the imaging device of a prior art example.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing the configuration of a power supply system of a photographing apparatus according to an embodiment of the present invention.

  The power supply unit 101 is a power supply circuit that outputs a voltage composed of a power supply IC and discrete components. The control unit 102 controls the entire electric device such as a digital camera. In the case of a digital camera, a display unit, a lens driving unit, an imaging unit, a storage medium control unit, and all devices (not shown) are controlled.

  The PWM / PFM switching means 111 determines whether to perform PWM control or PFM control.

  The load current detection unit 112 detects a load current. Although FIG. 1 illustrates a current detection method by voltage detection of the high-side FET, the method is not limited. The PWM / PFM switching means determines PWM control and PFM control based on the load current detected by the load current detection means 112.

  The output voltage setting unit 113 determines a voltage output from the power supply unit 101. Although FIG. 1 illustrates a method for setting the set voltage by changing the reference voltage in the power supply unit 101, the method is not limited. The present invention can also be implemented by a method of changing the feedback resistance.

  The set voltage value communication receiving unit 114 receives the voltage output from the set voltage value communication output unit 122 of the control unit 102. For example, the control unit 102 and the power supply unit 101 communicate using communication means such as I2C (Inter-Integrated Circuit) and SPI (Serial Peripheral Interface).

  The operation mode communication receiving unit 115 receives the operation mode output from the operation mode communication output unit 123 of the control unit 102. This is the same as the set voltage value communication receiving unit 114.

  The error amplifying unit 116 feeds back the voltage output from the power supply unit 101 by resistance division and amplifies the error. Negative feedback control is performed to maintain the output voltage constant by the error output from the error amplifying means 116.

  The high-side drive unit 117 and the low-side drive unit 118 are a high-side FET drive unit and a low-side FET drive unit. When the output of the error amplifying means 116 indicates that the output voltage of the power supply unit 101 is low, the output voltage is increased by increasing the on-time of the high-side FET and shortening the on-time of the low-side FET. .

The necessary set voltage determining unit 121 sets a necessary voltage in the control unit 102. The set value is set by comparing the evaluation value acquisition unit 124 and the target value setting unit 125.
The set voltage value communication output unit 122 outputs the voltage set by the necessary set voltage determination unit 121 to the power supply unit 101.

  The operation mode communication output unit 123 outputs the operation mode of the control unit 102, that is, the operation mode of the digital camera, to the power supply unit 101. For example, the state of shooting standby, movie shooting, playback, or power saving is notified.

  The evaluation value acquisition unit 124 acquires the current processing capability of the control unit 102 as an evaluation value. The target evaluation value setting unit 125 sets a value with which the control unit 102 can ensure performance as an evaluation value.

  The margin adding unit 126 adds, as an evaluation value, a margin in consideration of a voltage drop during operation to the voltage output from the power supply unit 101.

  The target evaluation value setting means 125 sets, as the target evaluation value, a value obtained by converting the margin with respect to the target evaluation value described by the control unit 102 at the time of shipment from the manufacturer.

Example 1
Hereinafter, with reference to the block diagram of FIG. 1 and the flowchart of FIG. 2, the configuration of the power supply system of the photographing apparatus according to the first embodiment of the present invention will be described.

  In a system in which power is supplied from the power supply unit 101 to the control unit 102, power is supplied from the power supply unit 101 and the control unit 102 is activated (step S201).

  First, the power supply unit 101 fixes the PWM / PFM switching means to PWM control and outputs a voltage. The voltage output at this time is the highest voltage among the set voltages of the control unit 102 among the set voltages (step S202).

  The control unit 102 performs AVS. The AVS will be described later with reference to a flowchart (step S203).

  A load current is detected using the load current detection means 112 of the power supply unit 101, and it is confirmed whether the detected load current is equal to or greater than a specified current. In this block, the current is detected by detecting the drain voltage of the high-side FET. By detecting that the drain voltage becomes negative, it is confirmed that the load current has decreased, and it is confirmed that the current has decreased (step S204).

  If the detected load current is equal to or greater than the specified current, the operation is maintained while the PWM control is being performed, and the process ends. If the current is less than the specified current, the AVS set voltage is released. The output voltage setting unit 113 of the power supply unit 101 does not change the set voltage to the voltage input from the set voltage value communication receiving unit 114, and sets the set voltage to the initial setting. That is, the highest voltage is set. This is because in the case of PFM control, the responsiveness is low, and a voltage drop may occur due to a sudden load change (step S211).

  Next, PFM control is performed using the PWM / PFM switching means of the power supply unit 101 (step S212).

  Next, AVS is performed by PFM control, and the process ends. Note that power saving can be realized without performing this step. This is because, during PFM control, it is necessary to add a large margin by the margin adding means 126 of the control unit 102, and the voltage set here is likely to be the initial set voltage (step S213).

  As described above, according to the first embodiment, in the current range 521 in FIG. 5, the input power becomes the power 511 at the time of PWM / PFM switching control, the input power is reduced, and the input power 521 in FIG.

(Example 2)
Hereinafter, with reference to the block diagram of FIG. 1 and the flowchart of FIG. 3, the configuration of the power supply system of the photographing apparatus according to the second embodiment of the present invention will be described.

  In a system in which power is supplied from the power supply unit 101 to the control unit 102, power is supplied from the power supply unit 101 and the control unit 102 is activated (step S301).

  First, the power supply unit 101 fixes the PWM / PFM switching means to PWM control and outputs a voltage. The voltage output at this time is the highest voltage among the set voltages of the control unit 102 (step S302).

  The control unit 102 performs AVS. The AVS will be described later using a flowchart (step S303).

  The load current is detected using the load current detecting means 112 of the power supply unit 101 (step S304).

  If the detected load current is equal to or greater than the specified current, the operation is maintained with the PWM control (step S305).

  The operation mode is communicated from the operation mode communication output unit 123 of the control unit 102 to the operation mode communication reception unit 115 of the power supply unit 101. When the received mode is a specific mode, for example, the standard moving image shooting mode or the full HD moving image shooting mode, the process proceeds to (Step S312) and PFM control is performed. In the flowchart of the present embodiment, the configuration for determining the operation mode is described, but the present invention can also be implemented by detecting the current. For example, when a current is measured by the current detection means and a second threshold value higher than the specified current is set and is equal to or higher than the second threshold value, that is, when there is more power (step) The same effect can be obtained even when the process proceeds to S312) and the PFM control is performed.

  When the mode is other than the specific mode, the operation is maintained while the PWM control is being performed (step S305). This is considered to be the case where switching noise of the power supply unit 101 during PWM control in a specific mode such as the full HD moving image shooting mode affects an imaging unit (not shown) to generate noise in an image. In this case, the object is to reduce the image noise by changing the switching frequency by PFM control even when the current exceeds the specified current.

  If the current is smaller than the specified current in (Step S304), the process proceeds to (Step S311).

  The operation mode is communicated from the operation mode communication output unit 123 of the control unit 102 to the operation mode communication reception unit 115 of the power supply unit 101. When the received mode is the photographing standby mode, the process proceeds to (Step S305). This is because, in the shooting standby state, even in a light load state, there is a possibility that a heavy load current may flow when the shooting switch is pressed by the user and the moving image shooting button is pressed. . The purpose is to maintain the voltage quality by maintaining the PWM control even when the load is light (step S311).

  When not in the shooting standby state, the AVS setting voltage is canceled. The output voltage setting unit 113 of the power supply unit 101 ignores the voltage input from the set voltage value communication receiving unit 114 and sets the set voltage to the initial setting. That is, the highest voltage is set. For example, high efficiency is maintained by shifting to PFM control in the playback mode and power saving mode (step S312).

  At the same time, the PFM control is performed using the PWM / PFM switching means of the power supply unit 101 (step S313).

  Next, AVS is performed by PFM control, and the process ends. Note that power saving can be realized without performing this step. This is because, during PFM control, it is necessary to add a large margin by the margin adding means 126 of the control unit 102, and the voltage set here is likely to be the initial set voltage (step S314).

  AVS will be described with reference to the flowchart shown in FIG.

  A power supply is activated in a system in which a voltage is applied from the power supply unit 101 to the control unit 102. A voltage is applied from the power supply unit 101 to the control unit 102 (step S401).

  The control unit 101 acquires an evaluation value indicating the current performance using the evaluation value acquisition unit 124 (step S402).

  The control unit 102 acquires a target evaluation value stored in a storage unit such as a ROM or a fuse when the semiconductor is shipped (step S403).

  The margin adding unit 126 adds a margin to the acquired target evaluation value. The value to be added is a value that takes into account the voltage drop in the wiring resistance between the power supply unit 101 and the control unit 102 and the voltage drop due to load fluctuations (step S404).

  The necessary set voltage determination means 121 determines the set voltage by comparing the evaluation value with the target evaluation value to which the margin is added. For example, when the evaluation value approximates the target evaluation value added with the margin, the set voltage maintains the current applied voltage. For example, when the evaluation value is higher than the target evaluation value added with the margin, the voltage drop is calculated based on the ratio, and the voltage lower than the current applied voltage is set as the set voltage (step S405).

  The set voltage value communication output means 122 outputs the set voltage determined using communication means such as I2C (Inter-Integrated Circuit) and SPI (Serial Peripheral Interface) to the control unit 101. Of course, there is no problem even if communication means other than those described is used (step S406).

  The set voltage value communication receiving unit 114 of the power supply unit 101 that has received the set voltage sets the set voltage that has received the set voltage of the output voltage setting unit 113 of the power supply unit 101 (step S407).

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

101 power supply unit, 102 control unit, 111 PWM / PFM switching unit,
112 load current detection means, 113 output voltage setting means,
114 set voltage value communication receiving means, 115 operation mode communication receiving means,
121 required set voltage determining means, 122 set voltage value communication output means,
123 Operation mode communication output means

Claims (7)

PWM / PFM switching means for switching between PWM control and PFM control;
Load current detection means for detecting the load current of the power supply;
Output voltage setting means for setting the output voltage of the power supply;
A set voltage value communication receiving means capable of receiving a set voltage from outside by communication;
Power supply output means for outputting a voltage according to the set voltage value from the output voltage setting means and the set voltage value received by the set voltage value communication receiving means;
Control means for controlling the entire apparatus by the voltage supplied from the output voltage of the power output means;
Necessary set voltage determining means for determining a necessary voltage while evaluating the processing speed performance of the control means;
Setting voltage value communication output means for outputting the voltage determined by the necessary setting voltage determination means by communication,
The load current detection means detects the load current, and when the detected load current value is equal to or greater than a specified current, the PWM / PFM switching means performs PWM control, and the voltage output by the set voltage value communication output means A value is received by the output voltage value communication receiving means, and output from the power output means according to the received set voltage value,
When the detected load current value is less than or equal to a specified current, the output voltage value communication receiving means receives the voltage value output by the set voltage value communication output means, and the output voltage is not changed to the received set voltage value. A power supply system, wherein a setting voltage value of a setting means is set, the PWM / PFM switching means is switched to PFM control, and output from the power supply output means. The load current detection means detects the load current, and when the detected load current value is equal to or greater than a specified current, the PWM / PFM switching means performs PWM control, and the voltage output by the set voltage value communication output means A value is received by the output voltage value communication receiving means, and output from the power output means according to the received set voltage value,
When the detected load current value is less than or equal to a specified current, the output voltage value communication receiving means receives the voltage value output by the set voltage value communication output means, and the output voltage is not changed to the received set voltage value. After the setting voltage value of the setting means is set and the PWM / PFM switching means switches to PFM control, the output voltage value communication receiving means receives the voltage value output by the setting voltage value communication output means, and the received setting The power supply system according to claim 1, wherein the power supply system is changed to a voltage value and output from the power supply output unit. Having a first mode and a second mode,
An operation mode communication receiving means capable of receiving an operation mode from the outside;
Operation mode communication output means capable of outputting the operation mode of the control means,
When the operation mode received by the operation mode communication receiving means is the first mode, the PWM / PFM switching means is set to PWM control even when the load current value detected by the load current detecting means is equal to or less than a specified current. The power supply system according to claim 1, wherein: Has a first and second mode,
An operation mode communication receiving means capable of receiving an operation mode from the outside;
An operation mode communication output means capable of outputting the operation mode of the control means, and when the operation mode received by the operation mode communication reception means is the second mode, the load current detection means detects the operation mode. 2. The power supply system according to claim 1, wherein the PWM / PFM switching unit performs PFM control even when the load current value is equal to or greater than a specified current. In the case of the first mode having the first and second modes and waiting so that the captured image can be recorded as an image file on the recording medium,
An operation mode communication receiving means capable of receiving an operation mode from the outside;
An operation mode communication output means capable of outputting the operation mode of the control means, and the operation mode received by the operation mode communication receiving means is the first mode,
2. The power supply system according to claim 1, wherein the PWM / PFM switching unit performs PWM control even when a load current value detected by the load current detection unit is equal to or less than a specified current. In the case of the second mode that has the first and second modes and shoots a high-resolution video,
An operation mode communication receiving means capable of receiving an operation mode from the outside;
Operation mode communication output means capable of outputting the operation mode of the control means,
When the operation mode received by the operation mode communication receiving means is the second mode, the PWM / PFM switching means is set to PFM control even when the load current value detected by the load current detecting means is equal to or greater than a specified current. The power supply system according to claim 1, wherein: PWM / PFM switching means for switching between PWM control and PFM control;
Load current detection means for detecting the load current of the power supply;
A first threshold value for determining a load current detected from the load current detection means; a second threshold value set higher than the first threshold value; and an output voltage setting means for setting an output voltage of a power source;
A set voltage value communication receiving means capable of receiving a set voltage from outside by communication;
Power supply output means for outputting a voltage according to the set voltage value from the output voltage setting means and the set voltage value received by the set voltage value communication receiving means;
A control means for controlling the entire apparatus by a voltage supplied from an output voltage of the power supply output means, and a necessary setting voltage determination means for determining a necessary voltage while evaluating a processing speed performance of the control means,
Setting voltage value communication output means for outputting the voltage determined by the necessary setting voltage determination means by communication,
The load current detection means detects a load current, and when the detected load current value is equal to or greater than a first threshold value, the PWM / PFM switching means performs PWM control, and the set voltage value communication output means outputs A voltage value to be received by the output voltage value communication receiving means, and according to the received set voltage value, output from the power supply output means,
If the detected load current value is less than or equal to the first threshold, the output voltage value communication receiving means receives the voltage value output by the set voltage value communication output means, and does not change the received set voltage value, Set the set voltage value of the output voltage setting means, the PWM / PFM switching means switches to PFM control, and outputs from the power supply output means,
If the detected load current value is greater than or equal to a second threshold, the output voltage value communication receiving means receives the voltage value output by the set voltage value communication output means, and does not change the received set voltage value, A power supply system, wherein a set voltage value of an output voltage setting means is set, the PWM / PFM switching means is switched to PFM control, and the power is output from the power supply output means.