JP2002027299A - Power source system and image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the constitution of a power source system. SOLUTION: The power source system 200 switches/supplies power to the load of a unit from an outer power source 270 outside a unit and from an inner power source 250 provided in the unit. The system is provided with a voltage adjusting switch element 202 whose one end is connected to the outer power source 270, whose other end to the positive electrode and the load of the inner power source 250, and which adjusts a voltage supplied to the load by a switching operation; and a control part 300 controlling the switching operation of the voltage adjusting switch element 202. The control part 300 makes the voltage adjusting switch element 202 perform a switching operation, so that the voltage requested from the load is obtained at an outer power supply mode where the power of the outer power source 270 is supplied to the load. At an inner power charging mode where the power of the outer power source 270 is supplied to the inner power source 250 and the inner power source 250 is charged, the voltage adjusting switch element 202 is switch-operated so that the voltage required for charging the inner power source 250 is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a power supply system and an image pickup apparatus. In particular, the present invention relates to a power supply system that switches power from an external power supply outside the device and an internal power supply provided inside the device to a load of the device, and an imaging apparatus that can use the power supply system.

[0002]

2. Description of the Related Art A portable device such as a digital camera is equipped with a power supply system capable of switching and supplying power from an external power supply and an internal power supply to a load of the device. The power supply system boosts or steps down the voltage of each power supply and supplies the voltage to the load so that the voltage is required by the load. In order to convert the voltage, the power supply system includes a DC / DC converter circuit.

As a DC / DC converter circuit capable of highly efficient voltage conversion, for example, a synchronous rectification type DC / DC converter circuit is known. In the synchronous rectification method, a voltage is converted by a switching operation of two switch elements. According to the synchronous rectification method, the power of the power supply can be used efficiently, so that the power consumption of the portable device can be reduced.

[0004]

However, when the synchronous rectification method is employed, there is a problem that the number of required switching elements increases as compared with DC / DC converters of other methods. In order to reduce the size and weight of the entire portable device, it is preferable to minimize the number of elements mounted on the power supply system. It has been desired to develop a power supply system capable of achieving highly efficient voltage conversion with a circuit having a simple configuration.

Accordingly, an object of the present invention is to provide a power supply system and an image pickup apparatus that can solve the above-mentioned problems. This object is achieved by a combination of features described in the independent claims. The dependent claims define further advantageous embodiments of the present invention.

[0006]

According to one aspect of the present invention, there is provided a power supply for switching power from an external power supply external to a device and an internal power supply provided inside the device to a load of the device. A voltage adjustment switch element having one end connected to an external power supply and the other end connected to a positive electrode of an internal power supply and a load, for adjusting a voltage supplied to the load by a switching operation, and a switching operation of the voltage adjustment switch element And a control unit for controlling
In the external power supply mode in which the power of the external power supply is supplied to the load, the control unit performs a switching operation of the voltage adjustment switch element so as to have a voltage required from the load, and supplies the power of the external power supply to the internal power supply to perform the internal operation. In the internal power supply charging mode for charging the power supply, the voltage adjustment switch element performs a switching operation so as to have a voltage necessary for charging the internal power supply.

The power supply system further includes a coil element provided in series between the voltage adjustment switch element and the load. In the external power supply mode, the control unit controls the voltage adjustment switch element so that the power supply system functions as a switching regulator. It may be controlled.

[0008] In the internal power supply charging mode, the control unit may control the voltage adjustment switch element so that the power supply system functions as a series regulator.

A diode element having one end connected to the external power supply and the other end connected to the coil element and provided in parallel with the voltage adjustment switch element for flowing a current from the coil element to the external power supply; And a second switch element connected to the coil element. The control unit includes a coil element, a diode element, and a switching operation of the second switch element. The voltage of the power supply may be boosted.

Another embodiment of the present invention is an imaging apparatus for imaging an image, wherein power is supplied from an external power supply external to the imaging apparatus and an internal power supply provided inside the imaging apparatus to a load of the imaging apparatus. A power supply system for switching supply, one end of which is connected to an external power supply and the other end of which is connected to an internal power supply and a load, and a voltage adjustment switch element for adjusting a voltage supplied to the load by a switching operation; A control unit for controlling a switching operation of the switch element, wherein the control unit is configured to control a voltage in the external power supply mode for supplying power of the external power supply to the load such that a voltage required by the load is obtained. In the internal power supply charging mode, in which the elements are switched and the power of the external power supply is supplied to the internal power supply to charge the internal power supply, the voltage required for charging the internal power supply is obtained. A voltage adjustment switching element is a switching operation so.

The above summary of the invention does not enumerate all of the necessary features of the present invention, and a sub-combination of these features can also be an invention.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described through embodiments of the present invention. However, the following embodiments do not limit the claimed invention and have the features described in the embodiments. Not all combinations are essential to the solution of the invention.

FIG. 1 shows the configuration of a digital camera 10 having a power supply system 200. The power supply system 200 will be described in detail in FIG. The digital camera 10 mainly includes an imaging unit 20, an imaging control unit 40, a processing unit 60, a display unit 100, an operation unit 110, and a power supply system 200.

The image pickup unit 20 includes a mechanism member and an electric member related to photographing and image formation. Imaging unit 20
First, a photographing lens 22 for capturing and processing images,
An aperture 24, a shutter 26, an optical LPF (low-pass filter) 28, a CCD 30, and an image signal processing unit 32 are included. The taking lens 22 includes a focus lens, a zoom lens, and the like. With this configuration, the subject image is
Image on the light receiving surface of. Charges are accumulated in each sensor element (not shown) of the CCD 30 according to the amount of light of the formed subject image (hereinafter, the charges are referred to as “accumulated charges”). The accumulated charge is read out to a shift register (not shown) by a read gate pulse, and is sequentially read out as a voltage signal by a register transfer pulse.

Since the digital camera 10 generally has an electronic shutter function, a mechanical shutter such as the shutter 26 is not essential. In order to realize the electronic shutter function, the CCD 30 is provided with a shutter drain via a shutter gate. When the shutter gate is driven, accumulated charges are swept out to the shutter drain. By controlling the shutter gate, the time for accumulating the electric charges in each sensor element, that is, the shutter speed can be controlled.

A voltage signal output from the CCD 30, that is, an analog signal is color-separated into R, G, and B components by an image signal processing unit 32, and the white balance is adjusted first.
Subsequently, the imaging signal processing unit 32 performs gamma correction, sequentially A / D converts the R, G, and B signals at necessary timing, and obtains digital image data (hereinafter, simply referred to as “digital image data”) obtained as a result. ) Is output to the processing unit 60.

The image pickup unit 20 further includes a finder 3
4 and a strobe 36. The finder 34 may be equipped with an LCD (not shown). In this case, various information from the main CPU 62 and the like described later can be displayed in the finder 34. The strobe 36 functions by emitting light when energy stored in a capacitor (not shown) is supplied to the discharge tube 36a.

The imaging control unit 40 includes a zoom drive unit 4
2. It has a focus drive unit 44, an aperture drive unit 46, a shutter drive unit 48, an imaging system CPU 50 that controls them, a distance measurement sensor 52, and a photometry sensor 54. The driving units such as the zoom driving unit 42 each have a driving unit such as a stepping motor. When a release switch 114 described later is pressed, the distance measurement sensor 52 measures the distance to the subject, and the photometry sensor 54 measures the brightness of the subject. The measured distance data (hereinafter simply referred to as “distance measurement data”) and the subject luminance data (hereinafter simply referred to as “photometry data”) are sent to the imaging system CPU 50. Imaging system CPU 50
Controls the zoom drive unit 42 and the focus drive unit 44 to adjust the zoom magnification and focus of the photographing lens 22 based on the photographing information such as the zoom magnification designated by the user.

The image pickup system CPU 50 controls the R of one image frame.
The aperture value and the shutter speed are determined based on the integrated value of the digital signal of GB, that is, the AE information. According to the determined values, the aperture driving unit 46 and the shutter driving unit 48 adjust the aperture amount and open and close the shutter 26, respectively.

The image pickup system CPU 50 controls the emission of the strobe light 36 based on the photometric data, and at the same time adjusts the aperture of the aperture 24. When the user instructs the capture of an image, the CCD 30 starts to accumulate electric charges, and the accumulated electric charges are output to the imaging signal processing unit 32 after a lapse of a shutter time calculated from the photometric data.

The processing unit 60 includes the digital camera 10
The main C that controls the whole, especially the processing unit 60 itself
PU 62 and memory control unit 6 controlled by PU 62
4, a YC processing unit 70, an optional device control unit 74, a compression / decompression processing unit 78, and a communication I / F unit 80. Main C
The PU 62 is connected to the imaging CPU 5 by serial communication or the like.
Necessary information is exchanged with 0. Main CPU6
The second operation clock is provided from a clock generator 88. The clock generator 88 also provides clocks having different frequencies to the imaging system CPU 50 and the display unit 100, respectively.

The main CPU 62 is provided with a character generator 84 and a timer 86. The timer 86 is backed up by a battery and always counts the date and time.
From this count value, information about the shooting date and time and other time information are given to the main CPU 62. The character generation unit 84 generates character information such as a shooting date and time and a title, and the character information is appropriately combined with the captured image.

The memory control unit 64 includes a nonvolatile memory 66
And the main memory 68. Non-volatile memory 66
Is composed of an EEPROM (electrically erasable and programmable ROM), a flash memory, and the like, and stores data to be retained even when the power of the digital camera 10 is off, such as setting information by a user and adjustment values at the time of shipment. ing. The non-volatile memory 66 may have a main CP
A boot program or a system program of U62 may be stored. On the other hand, the main memory 68 generally has a D
It is composed of a relatively inexpensive and large-capacity memory such as a RAM. The main memory 68 has a function as a frame memory for storing data output from the imaging unit 20, a function as a system memory for loading various programs, and a function as a work area. The non-volatile memory 66 and the main memory 68
Data is exchanged with each unit inside and outside the unit 0 via the main bus 82.

The YC processing section 70 performs YC conversion on the digital image data, and outputs a luminance signal Y and a color difference (chroma) signal B-
Generate Y, RY. The luminance signal and the color difference signal are temporarily stored in the main memory 68 by the memory control unit 64.
The compression / decompression processing unit 78 sequentially reads out the luminance signal and the color difference signal from the main memory 68 and compresses them. The data thus compressed (hereinafter simply referred to as “compressed data”) is written to a memory card, which is a type of the optional device 76, via the optional device control section 74.

The processing unit 60 further includes an encoder 72
With. The encoder 72 receives a luminance signal and a color difference signal, converts them into a video signal (NTSC or PAL signal), and outputs the video signal from a video output terminal 90. When a video signal is generated from data recorded in the optional device 76, the data is first supplied to the compression / decompression processing unit 78 via the optional device control unit 74. Subsequently, the data subjected to the necessary expansion processing by the compression / expansion processing unit 78 is converted into a video signal by the encoder 72.

The optional device control unit 74 generates necessary signals between the main bus 82 and the optional device 76, performs logical conversion, or converts voltage according to the signal specifications recognized by the optional device 76 and the bus specifications of the main bus 82. And so on. The digital camera 10 may include, for example, a PCM as an optional device 76 in addition to the above-described memory card.
A standard CIA-compliant standard I / O card may be supported. In that case, the optional device control unit 74
It may be constituted by an IA bus control LSI or the like.

The communication I / F unit 80 is a digital camera 10
Communication specifications supported by, for example, USB, RS-23
It performs control such as protocol conversion according to specifications such as 2C and Ethernet (registered trademark). The communication I / F unit 80 includes a driver IC as necessary, and communicates with an external device including a network via a connector 92. In addition to such standard specifications, data may be exchanged with an external device such as a printer, a karaoke machine, a game machine, or the like by a unique I / F.

The display unit 100 includes an LCD monitor 10
2 and an LCD panel 104. These are the LCD driver monitor driver 106, panel driver 10
8 respectively. LCD monitor 102
Is provided on the back of the camera with a size of, for example, about 2 inches, and displays a current shooting and playback mode, a zoom ratio for shooting and playback, a remaining battery level, a date and time, a screen for mode setting, a subject image, and the like. . The LCD panel 104 is, for example, a small black-and-white LCD provided on the upper surface of the camera and has an image quality (FINE).
/ NORMAL / BASIC etc.), information such as strobe light emission / non-light emission, standard number of recordable images, number of pixels, battery capacity, etc. are simply displayed.

The operation unit 110 includes mechanisms and electrical members necessary for the user to set or instruct the operation and the mode of the digital camera 10. The power switch 112 determines whether the power of the digital camera 10 is turned on or off. The release switch 114 has a two-stage pressing structure of half pressing and full pressing. As an example, AF and AE are locked by a half-press, captured images are captured by a full-press, and are recorded in the main memory 68, the optional device 76, etc. after necessary signal processing, data compression, and the like. The operation unit 110 may receive a setting using a rotary mode dial, a cross key, or the like in addition to these switches, and these are collectively referred to as a function setting unit 116 in FIG. Examples of operations or functions that can be specified by the operation unit 110 include “file format”, “special effects”, “printing”, “determine / save”, and “display switching”. The zoom switch 118 determines a zoom magnification.

The power supply system 200 includes the digital camera 1
And a mechanism for supplying power to the zero load. The power supply system 200 switches the power of the external power supply and the internal power supply to the load of the digital camera 10.
When no external power supply is available, the power system 200
Supplies the power of the internal power supply to the load. When an external power supply is available, the power supply system 200 supplies the power of the external power supply to the load. At this time, the power supply system 200
Converts the voltage of each power supply into a voltage required by a load and supplies the voltage. Generally, a secondary battery such as a lithium ion battery is used as the internal power supply. The power supply system 200 also has a function of supplying power from an external power supply to the internal power supply and charging the internal power supply.

FIG. 2 shows the configuration of the power supply system 200. The power supply system 200 includes a DC terminal 230 for connecting the AC adapter 270. AC adapter 27
0 supplies the digital camera 10 with power from an external power supply outside the device. AC adapter 270 may be connected to, for example, a commercial AC power supply provided by a power company. At this time, the AC adapter 270 may convert the commercial AC voltage into a DC voltage and supply it to the DC terminal 230. When the AC adapter 270 is connected to the DC terminal 230, the power of the external power supply is supplied to the digital camera 10 via the terminal 228.
Supplied to At this time, although not shown, the terminal 22
Since the terminal 8 is connected to the terminal 220, the terminal 220 is also supplied with the power of the external power supply.

The power supply system 200 includes a lithium ion battery 250 as an example of an internal power supply provided inside the device.
Is provided. Further, the power supply system 200 includes a control unit 300 for controlling the switching operation of the switch element.

The power supply system 200 includes an FET 202 as an example of a voltage adjustment switch element. FET20
2 has one end connected to the external power supply via the terminal 220 and the other end connected to the positive electrode of the lithium ion battery 250. FET2
02 is further connected to the load of the digital camera 10 via the transistor 210. FET202
The on / off state of is controlled by a signal transmitted from a “SYNC / CHARGE” terminal of the control unit 300.

The power supply system 200 further includes a coil 214 as an example of a coil element. Coil 214
Is connected in series between the FET 202 and the load of the digital camera 10. More specifically, the coil 214
One end corresponds to the FET 202 and the FET 204, and the other end corresponds to the positive electrode of the lithium ion battery 250 and the transistor 210.
Connected to.

The power supply system 200 further includes an FET 204 as an example of a second switch element. FET
204 has an FET 202 at one end and an FET 208 at the other end.
And the ground of the DC terminal 230. FE
ON / OFF of T204 is controlled by a signal transmitted from a “SYNC / SW” terminal of the control unit 300.

The power supply system 200 further includes a diode 216 as an example of a diode element. Diode 216 is connected in parallel with FET 202. The diode 216 is connected to the terminal 2 from the lithium ion battery 250.
The connection is made such that the direction toward 20 is the forward direction.

The power supply system 200 further includes an FET 20
6 is provided. The FET 206 has one end connected to the negative electrode of the lithium ion battery 250 and the other end grounded. F
The ON / OFF of the ET 206 is controlled by a signal transmitted from the “Li_SW” terminal of the control unit 300. FET
The 206 is kept on when the lithium ion battery 250 is used, and functions to ground the negative electrode of the lithium ion battery 250. When the lithium ion battery 250 is not used, the FET 206 is kept off.

The power supply system 200 further includes an FET 20
8 is provided. The FET 208 has one end connected to the ground of the FET 204 and the DC terminal 230 and the other end grounded. The FET 208 is connected to the “ADP” of the control unit 300.
ON / OFF is controlled by a signal transmitted from the “SW_SHORT” terminal. FET 208 is an AC adapter 2
When the terminal 70 is not connected to the DC terminal 230, the terminal 70 is kept on, and functions to ground one end of the FET 204. When the AC adapter 270 is connected to the DC terminal 230, the FET 208 is kept off.

The transistor 210 is connected to the power supply system 20
0 and the load of the digital camera 10 are controlled. When the transistor 210 is turned on, power is supplied to the load of the digital camera 10 via the terminal 224. The transistor 212 controls on / off of the transistor 210. The terminal 226 for controlling the on / off of the transistor 212 is connected to, for example, the power switch 112, and the on / off of the transistor 212 may be controlled by the on / off of the power switch 112. A signal for controlling the on / off of the transistor 226 is a main C signal.
It may be transmitted from the PU 62 or the like.

The capacitor 218 is connected in parallel with the lithium ion battery 250. The capacitor 218 performs a function of smoothing a voltage supplied to a load of the digital camera 10.

The terminal 228 connects an external power supply to the digital camera 10 via the DC terminal 230. Terminal 228
Are also connected to the terminal 220. That is, when the AC adapter 270 is connected to the DC terminal 230, the power supplied from the external power supply is supplied to the power supply system 200 via the terminal 220. The terminal 220 is connected to the lithium ion battery 2 of the load of the digital camera 10.
It is also connected to loads that require voltages higher than 50. When power is supplied to these loads from the lithium ion battery 250, power is supplied through the terminal 220.

The control section 300 receives information from a plurality of input terminals connected to each section of the circuit of the power supply system 200. The voltage supplied to the load of the digital camera 10 via the terminal 220 is input to the “FB_UP” terminal.
The voltage supplied to the load of the digital camera 10 via the terminal 224 is input to the “FB_DOWN” terminal.
The “Li_GND” terminal has a lithium ion battery 250
Is input. A reference voltage for constant current control is input to the “ADP_GND” terminal.

The control section 300 controls the switch elements based on the input information. Control unit 300 transmits an on / off control signal from an output terminal to a switch element of power supply system 200. The “SYNC / CHARGE” terminal outputs a signal for controlling the FET 202.
The “SYNC / SW” terminal outputs a signal for controlling the FET 204. "Li_SW" terminal is FET2
06 is output. "ADPSW_
The “SHORT” terminal outputs a signal for controlling the FET 208.

The control unit 300 may be realized as hardware by a circuit, or some functions of the control unit 300 may be realized as software. For example, analysis of an input signal and determination of an output signal may be performed by a program loaded into the main CPU 62.

As an operation mode of the power supply system 200,
There are four main types: First, the first operation mode is an internal power supply mode. In the internal power supply mode, the power of the lithium ion battery 250 is supplied to the load of the digital camera 10 via the terminal 224. The internal power supply mode is used when the power switch 112 of the digital camera 10 is turned on when the AC adapter 270 is not connected to the DC terminal 230. In the internal power supply mode, the FETs 202, 204, and 2
08 is kept off by the control unit 300. F
ET 206 is kept on by control unit 300. The configuration of the power supply system 200 at this time is shown in FIG. The operation in the internal power supply mode will be described in detail in the description of FIG.

The internal power supply boosting supply mode may be realized together with the internal power supply mode according to the configuration and specifications of the power supply system 200 and the equipment. May be done. Depending on the configuration and specifications of the power supply system 200 and the equipment, a plurality of modes may be appropriately used in combination.
The same applies to other modes.

The second operation mode is an external power supply mode. In the external power supply mode, the power of the external power
It is supplied to the load of the digital camera 10 via the terminal 224. In the external power supply mode, the AC adapter 270
It is connected to the C terminal 230 and is used when the power switch 112 of the digital camera 10 is on. In the external power supply mode, the control unit 300 keeps the FET 206 off. FET 208
It is kept on by the control unit 300. FET20
2 and 204 are switched by the control unit 300. The configuration of the power supply system 200 at this time is shown in FIG.
Is shown in an easy-to-understand manner. The operation in the external power supply mode will be described in detail in the description of FIG.

The third operation mode is an internal power supply charging mode. In the internal power supply charging mode, the power of the external power supply is supplied to the lithium ion battery 250, and the lithium ion battery 250 is charged. The internal power supply charging mode is used when the AC adapter 270 is connected to the DC terminal 230 and the power switch 112 of the digital camera 10 is off. In the external power supply mode, the FET
204 and 208 are kept off by the control unit 300. The FET 206 is kept on by the control unit 300. The FET 202 is switched by the control unit 300. Power supply system 20 at this time
The configuration of 0 is shown in FIG. The operation in the external power supply mode will be described in detail in the description of FIG.

The fourth operation mode is an internal power supply boosting mode. In the internal power supply boosting supply mode, the power of the lithium ion battery 250 is supplied to the load of the digital camera 10 via the terminal 224. The internal power supply boosting supply mode is used when the power switch 112 of the digital camera 10 is turned on when the AC adapter 270 is not connected to the DC terminal 230. Among the loads of the digital camera 10, a load that requires a voltage higher than the voltage of the lithium ion battery 250 is supplied with the voltage using the internal power supply boosting supply mode. In the internal power supply boost mode, the FET 202 is kept off by the control unit 300. FET 206 and FET
208 is kept on by the control unit 300.
The FET 204 is switched by the control unit 300. The configuration of the power supply system 200 at this time is shown in FIG. The operation in the external power supply mode will be described in detail in the description of FIG.

As described above, the power supply system 200
The power supplied from the adapter 270 and the power supplied from the lithium ion battery 250 are
The load is switched to the load within 0. Details of the operation of the power supply system 200 in each mode will be described below.

FIG. 3 is a diagram for explaining the operation of power supply system 200 in the internal power supply mode. At this time, since the FETs 202, 204, and 208 have been turned off by the control unit 300, these FETs
The part of the circuit directly connected to does not affect the operation. Further, since the AC adapter 270 is not connected to the DC terminal 230, a circuit portion directly connected to the DC terminal 230 does not affect the operation. In order to make the drawing easier to see, FIG. 3 omits the circuit part irrelevant to the operation from the circuit shown in FIG.

The FET 206 is connected to the “Li_
It is turned on by a signal transmitted from the “SW” terminal. Therefore, the negative electrode of the lithium ion battery 250 is grounded. At this time, the user operates the power switch 11
When the camera is turned on by operating the transistor 2, the transistor 2
12 turns on and transistor 210 also turns on.
As a result, the positive electrode of the lithium ion battery 250 is connected to the load of the digital camera 10, and power is supplied to the load. Capacitor 218 performs the function of smoothing the voltage supplied to the load.

In general, the voltage of a lithium ion battery is
Digital camera 1 is about 2.8 to 4.2 volts
Since the voltage required for the operation of 0 is about 3 volts, the voltage of the lithium ion battery 250 is supplied to the load of the digital camera 10 as it is. Lithium ion battery 250
Is input to the “FB_DOWN” terminal of the control unit 300. The control unit 300 includes a lithium ion battery 250
Monitor voltage. When the voltage of the lithium-ion battery 250 falls with the discharge and falls below a predetermined threshold, the digital camera 10 may issue a warning prompting charging and stop the operation.

With the above operation, the power supply system 200
Is a digital camera 10 from the lithium ion battery 250.
, The voltage required by the load can be supplied stably.

FIG. 4 is a diagram for explaining the operation of the power supply system 200 in the external power supply mode. At this time, since the FET 206 is turned off by the control unit 300, the circuit portion directly connected to the FET 206 does not affect the operation. To make the figure easier to see,
In FIG. 2, circuit portions irrelevant to the operation are omitted from the circuit shown in FIG.

The FET 202 and the FET 204 together with the coil 214 form a synchronous rectification step-down DC / DC converter. When AC adapter 270 is connected to DC terminal 230, the voltage of the external power supply is applied to terminal 228. Since the terminal 228 is connected to the terminal 220, the voltage of the external power supply is also applied to the terminal 220. Where FE
When T202 is on and the FET 204 is off, the voltage of the external power supply is applied to the coil 214. FET20
2 is off and the FET 204 is on, the coil 21
4, a ground voltage of an external power supply is applied. FET
By turning on and off the 202 and the FET 204 in synchronization, a voltage between the voltage of the external power supply and the ground voltage can be output with high efficiency. The output voltage is smoothed by the capacitor 218.

The voltage supplied to the load is “FB_DOW”.
The signal is input to the control unit 300 via the “N” terminal. Control unit 3
00 is set so that the voltage supplied to the load becomes an appropriate value.
The on / off duty ratio of the FET 202 and the FET 204 is controlled. That is, the control unit 300 controls the power supply system 2
00 controls the FET 202 and the FET 204 so that 00 functions as a switching regulator.

With the above operation, power supply system 200
Can stably supply a voltage required by the load from an external power supply to the load of the digital camera 10 with high efficiency.

FIG. 5 is a diagram for describing the operation of power supply system 200 in the internal power supply charging mode. At this time, the FET 204 and the FET 208
Since it is turned off by 0, the circuit portion directly connected to the FET 204 and the FET 208 does not affect the operation. In order to make the drawing easier to see, FIG. 5 omits circuit parts that are not related to the operation from the circuit shown in FIG.

The FET 202 forms a step-down DC / DC converter. AC adapter 270 is DC terminal 230
, The voltage of the external power supply is applied to the terminal 228. Since the terminal 228 is connected to the terminal 220, the voltage of the external power supply is also applied to the terminal 220. At this time,
By controlling the ON / OFF duty ratio of the FET 202, a voltage between the voltage of the external power supply and the ground voltage can be supplied to the lithium ion battery 250.

The voltage supplied to the lithium ion battery 250 is input to the control unit 300 via the “FB_DOWN” terminal. The control unit 300 controls the lithium ion battery 25
So that the voltage supplied to the FET 20 becomes an appropriate value.
2 is controlled. That is, the control unit 3
00 controls the FET 202 so that the power supply system 200 functions as a series regulator.

In this embodiment, when charging a lithium ion battery, charging is performed under a constant voltage and a constant current. Therefore, the power supply system 200 has a function of controlling the current supplied to the lithium ion battery 250 to be constant. “Li_GN” of the control unit 300
The voltage of the negative electrode of the lithium ion battery 250 is input to the “D” terminal. The difference between the voltage of the negative electrode of the lithium ion battery 250 and the voltage of the ground of the AC adapter 270 is
Current value flowing through lithium ion battery 250 and FET 20
6 corresponds to the product of the ON resistance value and the ON resistance value. Therefore, the current value to be supplied to the lithium ion battery 250 and the FET 20
6, the voltage value to be input to the “Li_GND” terminal can be calculated. The calculated voltage value is referred to as “ADP_GND” of the control unit 300 as a reference value.
The resistors 304a and 304b
Is set. The reference value may be calculated from the maximum value of the allowable current. That is, the reference value is a threshold value indicating the upper limit of the current.

The voltage input to the “Li_GND” terminal and the voltage input to the “ADP_GND” terminal are input to the comparator 302, respectively. The control unit 300 refers to the output of the comparator 302, and when the voltage input to the “Li_GND” terminal exceeds the voltage input to the “ADP_GND” terminal, sets the FET 202 through the “SYNC / CHARGE” terminal. The power is turned off, and the supply of current to the lithium ion battery 250 is stopped. Thus, the current supplied to lithium ion battery 250 can be kept constant.

By the above operation, the power supply system 200
Can stably supply a voltage and a current necessary for charging the lithium-ion battery 250 from an external power supply to the lithium-ion battery 250.

FIG. 6 is a diagram for explaining the operation of power supply system 200 in the internal power supply step-up / supply mode.
At this time, since the FET 202 is turned off by the control unit 300, the circuit portion directly connected to the FET 202 does not affect the operation. AC adapter 270
Is not connected to the DC terminal 230, so that the circuit portion directly connected to the DC terminal 230 does not affect the operation. In order to make the figure easier to see, FIG. 6 omits circuit parts that have nothing to do with the operation from the circuit shown in FIG.

In the internal power supply step-up supply mode shown in FIG. 6, unlike the case of the internal power supply mode shown in FIG. 3, power is supplied to the load of the digital camera 10 via the terminal 220 instead of the terminal 224. Digital camera 10
Among the loads that require a voltage higher than the voltage of the lithium ion battery 250,
It is necessary to boost and supply 50 voltages. Such a load is connected to the power supply system 200 via the terminal 220, and is supplied with power in the internal power supply boosting supply mode. At this time, the power of the internal power supply is boosted and supplied toward the external power supply.

The FET 206 is connected to the “Li_
It is turned on by a signal transmitted from the “SW” terminal. Therefore, the negative electrode of the lithium ion battery 250 is grounded. The FET 208 is connected to the “AD
It is turned on by a signal transmitted from the “PSW_SHORT” terminal. Therefore, one end of the FET 204 is grounded.

The FET 204, together with the coil 214 and the diode 216, forms a step-up DC / DC converter. A current flows to the terminal 220 via the coil 214 and the diode 216. The diode 216
This prevents current from flowing from the terminal 220 in the reverse direction. The coil 214 serves to store electric energy. In accordance with the operation principle of the step-up DC / DC converter, the FE
By turning on and off T204, lithium ion battery 2
The voltage of 50 can be boosted and supplied to the load of the digital camera 10.

The “FB_UP” terminal of the control unit 300
The voltage supplied to the load is input. The control unit 300
The voltage supplied to the load is monitored, and the ON / OFF duty ratio of the FET 204 is controlled so as to obtain an appropriate voltage value. That is, the control unit 300 controls the FE so that the power supply system 200 functions as a switching regulator.
It controls T204. When an appropriate voltage cannot be supplied to the load, the operation of the digital camera 10 may be stopped by issuing a warning prompting charging.

With the above operation, the power supply system 200
Is a digital camera 10 from the lithium ion battery 250.
, The voltage required by the load can be supplied stably.

As can be seen from the above description, in the power supply system 200 shown in FIG. 2, one switch element can have a plurality of functions. For example, FET2
02, in the external power supply mode, F
ET202 is used as a switch element of a synchronous rectification step-down DC / DC converter, and in an internal power supply charging mode,
The FET 202 is used as a switch element of a step-down series regulator. Focusing on the FET 204, in the external power supply mode, the FET 204 is used as a switch element of the synchronous rectification step-down DC / DC converter.
4 is used as a switch element of the step-up switching regulator. In this manner, by providing one switch element with a plurality of functions, the switch element can be shared in a plurality of operation modes. As a result, the number of necessary elements can be reduced, so that the circuit configuration can be simplified. As a result, the size and weight of the portable device can be reduced.

Further, since the synchronous rectification method can be used as the step-down DC / DC converter circuit, the power of the power supply can be used efficiently, which can contribute to the power saving of the equipment.

Although the present invention has been described with reference to the embodiment, the technical scope of the present invention is not limited to the scope described in the above embodiment. Various changes or improvements can be added to the above embodiment. It should be noted that such modified or improved embodiments may be included in the technical scope of the present invention.
It is clear from the description of the claims.

The following are examples of such modifications. In the present embodiment, the synchronous rectification method is used in the external power supply mode, but the voltage may be reduced by the series regulator method. At this time, FE
A diode element may be used instead of T204. Further, in the present embodiment, the step-down is performed by the series regulator method in the internal power supply charging mode.
A synchronous rectification method may be used. At this time, the control unit 300
Controls the FET 204 as in the case of the external power supply mode.

[0075]

As is apparent from the above description, according to the present invention, the configuration of the power supply system can be simplified.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of a digital camera 10. FIG.

FIG. 2 is a diagram showing a configuration of a power supply system 200.

FIG. 3 is a diagram illustrating an operation when the power supply system 200 is in an internal power supply mode.

FIG. 4 is a diagram for explaining an operation when the power supply system 200 is in an external power supply mode.

FIG. 5 is a diagram for explaining an operation when the power supply system 200 is in an internal power supply charging mode.

FIG. 6 is a diagram for explaining an operation when the power supply system 200 is in an internal power supply boosting supply mode.

[Explanation of symbols]

 Reference Signs List 10 digital camera 20 imaging unit 40 imaging control unit 60 processing unit 100 display unit 110 operation unit 200 power supply system 202, 204, 206, 208 FET 214 coil 216 diode 230 DC terminal 250 lithium ion battery 270 AC adapter 300 control unit

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H02J 7/00 H02J 7/00 H H02M 3/155 H02M 3/155 HF Term (Reference) 5C022 AA13 AB40 AC69 AC73 5G003 AA01 BA01 CA11 CC02 DA07 GA01 GB03 GC05 5G065 AA01 AA08 DA02 DA06 DA07 EA02 EA06 GA06 HA01 HA16 JA07 LA07 MA10 NA03 NA06 5H030 AA01 BB01 5H730 AA14 AA15 AS01 AS04 AS05 AS08 AS17 AS19 BB13 BB14 BB13 BB14 BB13 BB14

Claims (5)

[Claims] 1. A power supply system for switching power from an external power supply outside a device and an internal power supply provided inside the device to a load of the device, wherein one end is connected to the external power supply and the other end is connected to the internal power supply. A voltage adjustment switch element that is connected to the positive electrode and the load and adjusts a voltage supplied to the load by a switching operation; and a control unit that controls a switching operation of the voltage adjustment switch element. In the external power supply mode in which the power of the external power supply is supplied to the load, the voltage adjustment switch element performs a switching operation so as to have a voltage required from the load, and the power of the external power supply is supplied to the internal power supply. In the internal power supply charging mode for charging the internal power supply by supplying
A power supply system, wherein the voltage adjustment switch element performs a switching operation so as to have a voltage necessary for charging the internal power supply. 2. The power supply system according to claim 2, further comprising: a coil element connected in series between the voltage adjustment switch element and the load. In the external power supply mode, the control unit controls the power supply system to function as a switching regulator. 2. The power supply system according to claim 1, wherein the voltage control switch element is controlled. 3. The internal power supply charging mode, wherein the control unit controls the voltage adjustment switch element such that the power supply system functions as a series regulator or a switching regulator. A power supply system according to claim 1. 4. A diode element having one end connected to the external power supply, the other end connected to the coil element, and a diode element provided in parallel with the voltage adjustment switch element, and one end connected to the diode element and the coil element. A second switch element, wherein the control unit is configured to switch the coil element, the diode element, and a switching operation of the second switch element from the internal power supply to the external power supply, 4. The power supply system according to claim 2, wherein the power supply voltage is boosted and supplied. 5. An imaging apparatus for capturing an image, wherein power is switched from an external power supply external to the imaging apparatus and an internal power supply provided inside the imaging apparatus to a load of the imaging apparatus. A power supply system, the power supply system having one end connected to the external power supply and the other end connected to the internal power supply and the load, and a voltage adjustment switch element for adjusting a voltage supplied to the load by a switching operation; A control unit for controlling a switching operation of the voltage adjustment switch element, wherein the control unit is configured to control a voltage required by the load in an external power supply mode in which power of the external power is supplied to the load. The voltage adjusting switch element is operated to perform a switching operation so that the power of the external power supply is supplied to the internal power supply to charge the internal power supply. In the power charging mode,
An imaging apparatus, wherein the voltage adjustment switch element performs a switching operation so as to have a voltage necessary for charging the internal power supply.