CN1467557A

CN1467557A - Power supply circuit for camera

Info

Publication number: CN1467557A
Application number: CNA031407218A
Authority: CN
Inventors: 野中修
Original assignee: Olympus Optical Co Ltd
Current assignee: Olympus Corp
Priority date: 2002-06-12
Filing date: 2003-06-12
Publication date: 2004-01-14
Also published as: JP2004072991A

Abstract

Provided is a power supply circuit simplifying a constitution at low cost further with voltage control properly performed simultanesously with low current consumption. A current is allowed to repeatedly flow from a battery 2 to an inductor 3 by a switching means, and a voltage generated in the inductor 3 is smoothed by a capacitor 5 to be input to a regulator 6. An input to this regulator 6 is monitored by an A/D converter 1a in a CPU1. Reference voltage of the A/D converter 1a is stabilized by output voltage of the regulator 6.

Description

The power circuit of camera

Invention field

The present invention relates to power circuit, particularly with the improvement of battery as the power circuit of the portable electric appts of power supply such as camera.

Background technology

In recent years, along with the trend of portable set miniaturization, be extensive use of the battery that can only produce the low capacity low-voltage, in order to make equipment correct operation for a long time, people have carried out a large amount of trials.The technology of utilizing the DC/DC transducer is a kind of technology wherein.

On the other hand, for making device miniaturization, must reduce the part number.Applicant is not used special-purpose oscillator, but controls the ON/OFF of a port of the microcontroller that equipment integral is controlled, and constitutes the DC/DC transducer that utilizes electricity to lead.

But the DC/DC transducer that constitutes with this mode is difficult to its output voltage is managed.

In addition, in recent years, along with the progress of the Micrometer-Nanometer Processing Technology of technology, the chip of microcontroller is more and more littler, and cost is more and more lower.But the withstand voltage restriction that is caused by miniaturization has become important management project, specifically, when utilizing this device up-to-date, small inexpensive, must take measures to make supply voltage can not rise to more than the assigned voltage.

On the other hand, need certainly as the case may be the DC/DC transducer to be controlled more accurately, suppress current drain, the life-span of battery is prolonged, improve the measure of user's satisfaction.

Summary of the invention

Therefore, the present invention makes in view of above-mentioned condition, purpose provide a kind of simple in structure, cost is low, can correctly manage and can reduce the power circuit of current drain to voltage.

That is the supply unit of the camera of first aspect present invention is characterised in that to have: the boost switching circuit, and it comprises by pulse controlled switching device and inductance; Voltage detection department, it detects the output voltage of described boost switching circuit; Control circuit, its output and setting with described voltage detection department compares, and controls the applying regularly of gating pulse of described switching device.

The supply unit of the camera of second aspect present invention is characterised in that to have: switchgear, its from battery repeatedly to the inductance inflow current; Smoothing circuit, it makes the voltage smoothing that produces in the described inductance, and with its input voltage stabilizer; Monitoring circuit, it monitors the output of described smoothing circuit, the reference voltage of described monitoring circuit carries out voltage stabilizing by the output of described voltage stabilizer.

The supply unit of the camera of third aspect present invention is characterised in that to have: microcontroller, and it has pulse signal to the regulation pulsewidth control function of vibrating; The DC/DC transducer, it is by the control of pulse signal of described generation, with battery as power supply; Voltage stabilizer, its output transform with described DC/DC transducer is a low-voltage; After described pulse signal output, after official hour, described microcontroller compares the output of described voltage stabilizer and the output of described DC/DC transducer, and described pulse signal is controlled.

In power circuit of the present invention, by switchgear, repeatedly from battery to the inductance inflow current, the voltage that in above-mentioned inductance, produces, by smoothing circuit that it is level and smooth, be input to voltage stabilizer then.The output of this smoothing circuit is monitored circuit and monitors.And the reference voltage of above-mentioned monitoring circuit comes voltage stabilizing by the output voltage of above-mentioned voltage stabilizer.

In addition, in power circuit of the present invention, microcontroller has the vibrate function of control of pulse signal to the regulation pulsewidth, and the battery that will be controlled by the pulse signal of above-mentioned generation is as the power supply of DC/DC transducer.The output of above-mentioned DC/DC transducer is transformed to low-voltage by voltage stabilizer.And then, after above-mentioned pulse signal output, after official hour,, the output of above-mentioned voltage stabilizer and the output of DC/DC transducer are compared by above-mentioned microcontroller, above-mentioned pulse signal is controlled.

Up-to-date microcontroller is along with function improves constantly, the miniaturization technology is constantly made progress, in existing small chip, be provided with peripheral circuits such as LCD (LCD) driver, A/D transducer (analog/digital converter), hummer, PWM (pulse-length modulation) circuit isopulse generation circuit in mostly.

The present invention especially effectively utilizes A/D transducer and pulse generating circuit, and the battery of low capacity can be used for a long time, makes equipment operating stably for a long time.

Description of drawings

Fig. 1 is the structural representation of 1st embodiment relevant with power circuit of the present invention.

Fig. 2 is the timing diagram that the voltage-controlled method of operating that power circuit carried out to Fig. 1 describes.

Fig. 3 is the process flow diagram that the action to the camera with the power circuit in the 1st embodiment describes.

Fig. 4 is the structural representation of 2nd embodiment relevant with power circuit of the present invention.

Fig. 5 is the key diagram the when power circuit in the 2nd embodiment is boosted judgement.

Fig. 6 is the structural representation of 3rd embodiment relevant with power circuit of the present invention, is the system configuration example block scheme that expression is applied to this power circuit camera integral body.

Fig. 7 is the action timing diagram that is used for the each several part of system when boosting of key diagram 6.

Embodiment

Below, with reference to accompanying drawing, embodiments of the present invention are described.

In the 1st embodiment of the present invention, be that example describes to comprise movable members such as a lot of actuators in the portable electric appts and to make the very heavy camera of battery burden.

In Fig. 1, CPU1 is the parts of the whole sequence of control camera, is made of microcontroller.In this CPU1, have A/D transducer 1a described later and lcd driver 1b.

Battery 2 except utilizing 1 primary cells such as lithium battery, alkaline battery, in recent years, also utilizes NiH (ni-mh) or Li-ion 2 primary cells such as (lithium ions) as the energy of shutter 16 described later and flash unit 17.This battery 2 is connected to CPU1 by inductance 3, commutation diode 4, stable capacitor 5 and the voltage stabilizer 6 used of power supply.

In addition, connecting on this CPU1 the divider resistance 9 that constitutes by two resistance, transistor 10, by above-mentioned lcd driver 1b LCD driven 12, switch 13, capacitor 14, reset circuit 15, shutter 16 and flash unit 17.

In such structure, the response user is to the control of switch 13, and by the interior program of being located among the CPU1, the sequence that puts rules into practice drives shutter 16, flash unit 17, and the control photography is moved or shown.Utilize the energy of battery 2 as these shutters 16 and flash unit 17.

When using this battery, can not ignore the resistive component that is called internal resistance, when the electric current that flows into hundreds of milliamperes of levels in the electromagnet of shutter 16 usefulness or in the motor (not shown), when perhaps in the charging circuit (not shown) of flash unit 17, flowing into the electric current of several amperes of levels, cause pressure drop by above-mentioned internal resistance.Sometimes because cell voltage sharply changes or reduces, and CPU1 can carry out misoperation, perhaps depart from minimum voltage action and stop.

This internal resistance component changes because of the kind of battery behaviours in service such as environment temperature, battery consumption situation and above-mentioned battery or the difference of producer, therefore, preferably with above-mentioned factor irrespectively, under constant voltage, CPU and other each several part are controlled.

For this reason, present embodiment is by being added to base stage with pulse signal, makes the DC/DC transducer with transistor 10 high speed conductings or end by CPU1.Thus, in inductance 3, produce electric current and change,, charge with capacitor 5 by 4 pairs of power supplys of commutation diode are stable based on the electric current of the voltage that produces this moment.So, be expressed as DC in the drawings _OutThe voltage of part rise to cell voltage (V _Cc1) more than, by its power supply, just can form the above-mentioned power supply that can not be subjected to very big cell voltage influence of change as CPU1.

But, when unrestrictedly coming continuous drive transistor 10, during continuous drive DC/DC transducer, along with DC with pulse _OutExcessive rising, current drain is also wasted.For preventing its generation, DC _OutBe imported into voltage stabilizer 6, with the supply voltage V of its output as CPU1 _Cc2

When battery open circuit voltage is 3V, voltage stabilizer output V _Cc2Just be chosen near the 2.7V.Thereby, when battery is new battery, or under the situation of the circuit that does not drive big current system, stop the DC/DC transducer, to suppress current drain.

So, by by the voltage stabilizer of voltage stabilizing output V _Cc2Be located at the lcd driver 1b of CPU1, the reference voltage of A/D transducer 1a in being used as, can make the concentration of LCD12 not rely on the battery consumption state and keep constant, on this basis, can carry out correct A/D conversion.In addition, can make it be no more than the power supply upper limit (about 3.6V) of above-mentioned CPU1, CPU can stably be controlled.

If utilize above-mentioned A/D transducer 1a, by come the output DC of dividing potential drop DC/DC transducer with resistance 9 _Out, just can judge whether be necessary the DC/DC transducer is controlled.

That is, when CPU1 is changed to L (low level) with open-drain lead-out terminal 9a, in the ratio correspondent voltage of target generation with 2 resistance of divider resistance 9.Thereupon, this is also monitored by A/D transducer 1a, is not surpassing above-mentioned voltage stabilizer output (V _REG) 2.7V the time, make DC/DC transducer 10 work.

In addition, when stopping 10 work of DC/DC transducer immediately when surpassing 2.7V, immediately by the CPU1 current sinking, voltage V at this moment _Cc2Constantly descend.Therefore, after the short time, boosted continuously again, after about rising 0.5V (when becoming V _REG+ V ₀The back), stops the DC/DC transducer, to suppress current drain.

Fig. 2 is voltage-controlled method of operating is carried out in explanation with such circuit a timing diagram.

Among the figure, DC represents to control the pulse waveform of DC/DC transducer with transistor 10 base stages.DC _OutAnd V _Cc2Represent the input and output of voltage stabilizer 6 respectively.A/D represents the judgement timing of A/D transducer 1a.

It should be noted that as voltage stabilizer 6 V of outputting standard not also herein _REGThe time, because the reference voltage of A/D transducer 1a itself is not a right value, will consider after becoming right value, just begin to A/D conversion and judge.That is, after driving the DC/DC transducer, passing through official hour (T _AD) afterwards, just carry out the A/D conversion.

By this control,, just carry out judging (DC according to the voltage of A/D conversion because behind the correct reference voltage of input _OutJudge), so can carry out correct DC/DC convertor controls.In addition, when taking out battery, judge this situation, CPU1 is resetted by reset circuit 15.

Secondly, to the action of the camera of power circuit, describe with reference to the process flow diagram of Fig. 3 with this spline structure.

And this process flow diagram is the flow process of carrying out according to the agenda among the ROM that is located in being stored in the CPU1.

Behind the main switch of input camera, at first, at step S1, DC/DC transducer transistor 10 starting oscillations.As mentioned above, in a bit of time after this boost action since in be located at the reference voltage (V of the A/D transducer 1a among the CPU1 _Ref) itself exist unsettled possibility, therefore carry out following processing action.That is, at step S2, judge and whether passed through stipulated time t _ADAt this moment, if passed through stipulated time t _AD, at follow-up step S3, carry out LCD and show, and then, at step S4, beginning A/D conversion action.

Then, at step S5, judge whether the result of this A/D conversion satisfies following relation: DC _Out＞V _REG+ V ₀(than the voltage of the high approximately 0.5V of voltage stabilizer voltage).

At this moment, if DC _OutHigher, just transfer to step S6.And then, suppose that the action of DC/DC transducer can stop when action that needn't carrying out to flashlight charging and so on, judgement needs flashlamp is charged.

Under situation about need charge to flashlamp, transfer to step S7, setting charge complete flag is " 0 ", at step S8, begins the charging action.At this moment, owing to assert cell voltage step-down, therefore the DC/DC transducer is worked on, so that the voltage (V of CPU _Cc2) stable.

In addition, at above-mentioned steps S6, under the situation that flashlamp need not to charge, transfer to step S9, setting charge complete flag is " 1 ".Then,, after the charging that stops flashlamp,, the DC/DC transducer is stopped, to reduce current drain at step S11 at step S10.

In general since flash lamp circuit to utilize the high voltage energy that flashlamp is carried out luminous, therefore need the charging action, be accompanied by very big current drain this moment.In addition, when making release-push be ON, the action of shutter etc. also can be accompanied by very big current drain.Therefore,, judge the state of release-push, when release-push is ON, transfer to step S13, make the DC/DC transducer carry out work at step S12.Then,, shutter is controlled at step S14, and then, at step S15, to carrying out flashlamp light emitting control etc.

Behind this current drain EO, transfer to above-mentioned steps S4, after carrying out the A/D conversion once more, judge whether be necessary the DC/DC transducer is controlled once more.

On the other hand, at above-mentioned steps S12, when not being changed to ON, transfer to step S18 as if release-push.

In addition, at above-mentioned steps S5, if concern DC _Out＞V _REG+ V ₀Be false, transfer to step S16, make the DC/DC transducer continue vibration with transistor 10, and then, at step S17, stop the big current drain control of flashlight charging etc.Transfer to step S18 thereafter.

At step S18, judge the mode of operation of main switch.At this moment,, transfer to step S19, whenever through after the official hour, the A/D of above-mentioned steps S4 is judged (supply voltage judgement) if main switch is not operating as OFF.

In addition,, when main switch is changed to OFF, transfer to step S20, make demonstration become OFF at above-mentioned steps S18.Then,, the action of DC/DC transducer is stopped, to reduce current drain at step S21.

As mentioned above,, owing to be located at A/D converting means (transducer) in the CPU in effectively utilizing, the ON/OFF of DC/DC transducer is carried out appropriate control according to the 1st embodiment, thus operating stably can be guaranteed, and can extending battery life.

And then, because, therefore can only just can hold the power circuit that mini-plant is used with very little space by the Nch open-drain terminal with CPU1 being come measures such as the ON/OFF that the ground connection (GND) of divider resistance 9 is held controls are reduced the part number.

In addition, because during, necessarily make the work of DC/DC transducer, to prevent V at control flashlamp or actuator and with the action of big current drain _Cc2Reduction, thereby can eliminate misoperation, the flicker that can be used for preventing to show etc.

Below, the 2nd embodiment of the present invention is described.

In this 2nd embodiment, the part identical with the 1st embodiment shown in Figure 1 given identical Ref. No. and omitted its explanation.

In this 2nd embodiment, because the V of A/D transducer _RefUtilized the forward voltage V of the diode 20a of bleeder circuit 20 _F, therefore from the circuit structure of Fig. 1, delete voltage stabilizer 6, to obtain cheap more circuit.

That is A/D transducer 1a is this V _FWhether compare with the output by the DC/DC transducer after divider resistance 9 dividing potential drops, can judge needs to boost.Only when this was judged, as shown in Figure 5, the open-drain port 9a ' of CPU1 was ON, only constantly at this, and just to the voltage detection unit inflow current that constitutes by diode, resistance etc.And in other cases, will open a way, to suppress current drain. herein

If by the voltage ratio of being undertaken, control the ON/OFF of DC/DC transducer continually, because the V of diode 20a by this A/D transducer 1a _FBe generally 0.6～0.7V, therefore also can be with DC _OutDeviation suppress to be 0.3～0.4V of 3～4 times as its difference 0.1V.

By these measures, just can glimmer with the voltage minimizing of regulation on one side and drive LCD12, the decline of camera 21 caused supply voltages such as shutter, flash unit can prevent on one side owing to can provide the power circuit that can supply with stabilized supply voltage.Because this 2nd embodiment has been cancelled voltage stabilizer, can make cost lower.

Below, the 3rd embodiment of the present invention is described.

Fig. 6 is the structural representation of 3rd embodiment relevant with power circuit of the present invention, is the system configuration example block scheme that expression utilizes the camera integral body of external power supply circuit.

The 3rd embodiment of the present invention is provided with voltage stabilizer 6 in the same chip of single chip microcomputer (CPU) 1.The output of this voltage stabilizer 6 is supplied with A/D transducer 1a, lcd driver 1b, D/A transducer 1c, when resetting (RESET) circuit 25, also can it be fetched into the outside of CPU by impact damper 26.

Above-mentioned D/A transducer 1c with amplifier 27, be included in amplifier 31 in the AF portion 30 and be connected in, also be connected with an input end of

comparer

32,33,34 respectively.Another input end of above-mentioned comparer 32 is connected with AF portion 30 with above-mentioned A/D transducer 1a.And then another input end of

comparer

33,34 is connected with light interrupted ciruit 52, divider resistance 9 respectively.And decision circuit 35 is supplied with in the output of

comparer

32,33, and decision circuit 36 is supplied with in the output of comparer 34.

The output of this decision circuit 36 is supplied with vibration with the output of above-mentioned reset circuit 25, oscillator 37 and is closed (OFF) circuit 38.In addition, reset circuit 25 is connected to the clock circuit 41 that is connected with the oscillator 40 of CPU1 outside by multiple circuit 42.

And, between the input and output of above-mentioned amplifier 27, be connected with the driving transistor 45 of motor driver 44.In addition, by being connected to the demonstration LED46 of impact damper 26, be connected to I/O portion 47.

Voltage stabilizer 6 in the above-mentioned CPU1 is connected to the diode 4 and the capacitor 5 of DC/DC transducer.And then above-mentioned diode 4 is connected to motor driver 44 and transistor 45 by inductance 3, battery 2.In addition, above-mentioned diode 4 is connected to vibration shut-off circuit 38 also by transistor 10 and resistance 48,49.And then vibration shut-off circuit 38 is connected to flash unit 17.

Be connected in the motor 51 of above-mentioned motor driver 44, detect its rotation by light interrupted ciruit 52.And then, when this light interrupted ciruit 52 is connected to I/O portion 47 by

resistance

53,54, is also connected to CPU1 inside, EEPROM55, and is connected to AF portion 30 and photoelectricity testing part 56.

In addition, the lcd driver 1b in LCD12 and the CPU1 is connected and by its driving.

In such structure, at first, stable and describe as the part of power utilization to the output that makes battery.

Herein, in the same chip of CPU1, in be provided with voltage stabilizer 6, the output of this voltage stabilizer 6 can be fetched into the outside of CPU1 by impact damper 26.Depend on the output DC of DC/DC transducer _OutVoltage, by divider resistance 9, be input to A/D transducer 1a and be arranged on comparer 34 in the CPU1.

Be located in the utilization oscillator 37 among the CPU1 make transistor 10 conductings or by the time because the electric current that flows into from battery 2, the voltage that produces in inductance 3 charges by 4 pairs of capacitors 5 of diode.This charging voltage DC _OutCarry out dividing potential drop by divider resistance 9,1a monitors it by the A/D transducer.

The timing diagram that circuit operation this moment is described is identical with the timing diagram of Fig. 2.But the program that always monitors the result of A/D transducer 1a is not perfectly, has some restriction.That is, carry out for a long time under the situation of High-speed Control at needs, be used to judge that the required time of this A/D conversion causes delaying, thereby can not accurately control.For example, judge when on film, writing the date to write under the situation regularly, perhaps when controls lens is focused, under the situation of detector lens position, monitor that the control ratio that boosts of DC/DC transducer is difficult.

For this reason, be provided for the comparer 34 of comparison assigned voltage DA1 and DA2 in the present embodiment.Thereby, work as DC _OutIn the time of in the specified level scope, decision circuit 36 just cuts out vibration halt circuit 38, and boost action is stopped.

This vibration halt circuit 38 not only makes vibration stop, and when vibration was stopped, the output voltage in the time of also will stopping to be changed to " L (low level) " so that transistor 10 can not keep conducting state.

By the circuit of such formation, just can control DC _Out, it is limited within the level of regulation.

In addition, according to the program of CPU1, D/A transducer 1c can switch the judgement voltage that is input in the comparer 34, and the DA shown in the timing diagram of Fig. 7 is such, can select two outputs of DA1, DA2.Set high-end upper limit DA1 when boosting, boost and set the lower limit DA2 of low side when stopping, when surpassing these restrictions, decision circuit 36 is just judged the output and the output signal of comparer 34, and the program of switching vibration halt circuit 38 and CPU1 is controlled.The timing diagram of this moment as shown in Figure 7.

Like this, only have the effect of similar window comparator, prevent that invalid circuit from maximizing, and makes circuit inexpensive with a comparer.

Output as the voltage stabilizer 6 in the CPU1 of the feature of present embodiment, and when being supplied to as the reference voltage of above-mentioned D/A transducer 1c, A/D transducer 1a and lcd driver 1b, also, play a part each outer circuit constant voltage source of CPU1 by impact damper 26.For example, as the power supply that detects the light interrupted ciruit 52 that motor 51 rotates, show power supply with the EEPROM5 of LED46, store various kinds of data etc.

In addition, not shown, when light projector device being carried out light projector control, also can be as making AF portion 30 stable power, this AF portion 30 is used to detect the size of the light signal that incides photoelectricity testing part 56.

And the output pulse of oscillator 37 also can be as the charging pulse of flash unit 17, in be located at the function that A/D transducer 1a in the CPU1 has this charging voltage of judgement.In addition, the output of D/A transducer 1c is imported into amplifier 27, with transistor 45, motor driver 44 is carried out constant voltage driving, can control the speed of motor 51.

As mentioned above, above-mentioned oscillator 40 makes clock circuit 41 work that the date uses that write.After the output of this oscillator 40 is doubled by multiple circuit 42, produce the action major clock of CPU1.

Reset circuit 25 has the CPU1 that resets when battery 2 exhausts, when more renewing battery 2 by exchange etc., and the function that CPU1 is correctly restarted.

Like this, by system shown in Figure 6, not only AF portion 30, and main parts can be formed in the same chip together with CPU1, therefore can provide cost or space all to have the product of advantage.

As mentioned above, according to the present invention,, can provide the power circuit that the long-time portable set that effectively utilizes of the energy content of battery is used by not only simple but also cheap structure.

As mentioned above,, just may be provided in simple structure that this is cheap and carry out correct voltage management according to the present invention, and the very low power circuit of current drain.

Claims

1. the supply unit of a camera is characterized in that, has:

The boost switching circuit, it comprises by pulse controlled switching device and inductance;

Voltage detection department, it detects the output voltage of described boost switching circuit;

Control circuit, its output and setting with described voltage detection department compares, and controls the applying regularly of gating pulse of described switching device.

2. supply unit as claimed in claim 1 is characterized in that,

When described control circuit is no more than setting in the output of described voltage detection department, allow to apply gating pulse to described switching device, otherwise, forbid applying described gating pulse.

3. supply unit as claimed in claim 1 is characterized in that,

Also have voltage stabilizing circuit, it is connected in the output of described boost switching circuit, and supplies with constant voltage output.

4. supply unit as claimed in claim 3 is characterized in that,

Described voltage stabilizing circuit is the universal serial bus type.

5. the supply unit of a camera is characterized in that, has:

Switchgear, its from battery repeatedly to the inductance inflow current;

Smoothing circuit, it makes the voltage smoothing that produces in the described inductance, and with its input voltage stabilizer;

Monitoring circuit, it monitors the output of described smoothing circuit,

The reference voltage of described monitoring circuit carries out voltage stabilizing by the output of described voltage stabilizer.

6. supply unit as claimed in claim 5 is characterized in that,

Also have control device, this control device is according to the output of described monitoring circuit, control the pulse generation of described switchgear work, do not work.

7. supply unit as claimed in claim 6 is characterized in that,

Described control device is made of microcontroller; The device of described switchgear pulsing by setting the specified registers in the described microcontroller, is utilized the pulse generation function that takes place or stop to have the pulse of regulation make-to-break ratio.

8. supply unit as claimed in claim 5 is characterized in that,

Described voltage stabilizer be formed on the shared semiconductor circuit board of the pulse generating circuit that inductance is carried out switch control on.

9. supply unit as claimed in claim 5 is characterized in that,

Described monitoring circuit is made of comparer and D/A transducer, and described D/A transducer is input to described comparer with reference voltage.

10. camera supply unit is characterized in that having:

Microcontroller, it has the vibrate function of control of pulse signal to the regulation pulsewidth;

The DC/DC transducer, it is by the control of pulse signal of described generation, with battery as power supply;

Voltage stabilizer, its output transform with described DC/DC transducer is a low-voltage;

After described pulse signal output, after official hour, described microcontroller compares the output of described voltage stabilizer and the output of described DC/DC transducer, and described pulse signal is controlled.