JP2017062274A - Driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stroboscope power supply circuit capable of restraining loss from occurring due to charging and discharging of the stroboscope power supply circuit even in a plurality of different light emitting forms.SOLUTION: A power supply circuit (100) includes: a battery voltage detection circuit for detecting the voltage of a battery; a chargeable unit charged until a prescribed voltage value through a charging circuit by the battery; and a power supply control circuit unit that is supplied power by a power supply unit composed of the battery and the chargeable unit and makes a light-emitting unit emit light by prescribed current. The voltage value of the chargeable unit is set to a first voltage level by preliminary charging performed before preliminary light emission, and after that to a second voltage level by main charging performed after the preliminary light emission.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power supply circuit applicable to an imaging apparatus using a light emitting diode (LED) as a strobe light source.

  Conventionally, when an LED is used for a strobe, a large amount of charge is required for light emission, so the capacitor is charged to emit light.

  In general, a capacitor has a large self-discharge, and the closed circuit voltage is not stable like a battery. Therefore, the capacitor always stands by in a state of being continuously charged at the upper limit of the use voltage, and prepares for the operation timing of the device. However, the usage method in which the capacitor is always charged and put in standby has problems that the power consumption of the circuit in the standby state is increased due to the leakage current, and that the capacitor is subjected to voltage load, and the deterioration proceeds.

  Patent Document 1 discloses a technique for avoiding continuous charging by charging a capacitor immediately before the operation timing of the device.

JP 2011-050229 A

  However, in Patent Document 1, even when the conditions for the charging time are the same, the amount of charge that can be charged differs depending on the battery voltage. Therefore, optimal charging cannot always be performed while the battery voltage changes.

  Moreover, since the amount of charge required for light emission differs depending on the light emission form, it is not desirable to charge the strobe at the upper limit of the operating voltage. With the technique disclosed in Patent Document 1, depending on the light emission mode, a charge residue is generated in the capacitor, resulting in a loss, and the capacitor is further deteriorated.

  Therefore, the present invention uses a battery voltage at the time of light emission, preset ISO and aperture conditions, and information on a light reception result of receiving a preliminary light emission, so that a strobe power supply can be used even in a plurality of different light emission forms. An object of the present invention is to provide a strobe power supply circuit capable of suppressing loss caused by charge / discharge of the circuit.

In order to achieve the above object, a power supply circuit according to the present invention includes:
A battery voltage detection circuit that detects the voltage of the battery, a charging unit that is charged from the battery through a charging circuit to a predetermined voltage value, power is supplied from the battery and the power supply unit that is the charging unit, and the light emitting unit is A power control circuit unit that emits light at a predetermined current, and the voltage value of the charging unit is set to the first voltage level by the preliminary charging performed before the preliminary light emission, and then the main charging performed after the preliminary light emission. Is set to the second voltage level.

  According to the power supply circuit of the present invention, it is possible to suppress loss caused by charging / discharging of the strobe power supply circuit even in a plurality of different light emission modes.

FIG. 3 is a diagram for explaining an example of components included in the LED strobe power supply circuit 100 according to the first embodiment. 6 is a flowchart for explaining an example of a strobe light emission sequence in the first embodiment. It is a time chart for demonstrating the case where a battery voltage is high and performs full light emission as main light emission. It is a time chart for demonstrating the case where a battery voltage is low and performs full light emission as main light emission. It is a time chart for demonstrating the case where a battery voltage is high and performs 1/2 light emission as main light emission.

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

[Embodiment 1]
FIG. 1 is a diagram for explaining an example of components included in the LED strobe power supply circuit 100 according to the first embodiment.

  The LED strobe power supply circuit 100 is a power supply circuit applicable to an imaging apparatus using a light emitting diode (LED) as a strobe light source.

  In FIG. 1, an LED strobe power supply circuit 100 includes a battery 101, a capacitor 102 as a charging unit, a charging circuit 103, a DCDC converter 104 as a power supply control circuit unit, a light emitting unit 105, a resistor 106, a power supply voltage detection circuit 107, and circuit control. A microcomputer 108 that is a scanning unit, an AE sensor 109 that is a photometric unit, and a memory 110. Battery 101 is also connected to other load circuit 111. The battery 101 and the capacitor 102 are a power supply unit to the DCDC converter 104.

  The battery 101 supplies power to the LED strobe power supply circuit 100 and the other load circuit 111. In the first embodiment, a lithium ion battery having a voltage in the range of 5.5 V to 8.5 V and a continuous allowable discharge current of 2000 mA is used, but other batteries may be used.

  The current value that can be supplied from the battery 101 to the LED strobe circuit 100 varies depending on the remaining battery level. For example, when the power supplied to the other load circuit 112 is 4.0 W, the current value supplied to the other load circuit 112 is 480 mA when the battery voltage is 8.5 V, and 730 mA when the battery voltage is 5.5 V. . Therefore, the current value that the battery 101 can supply to the LED strobe power supply circuit 100 varies in the range of 1270 mA to 1520 mA depending on the remaining battery level.

  The capacitor 102 is a charging device that is charged through the charging circuit 103. As a charging device used in the LED strobe power supply circuit 100, one having a large capacity and low ESR is desired. In particular, in order to suppress the loss caused by charging / discharging, it is desirable that the ESR which is the resistance component of the capacitor 102 is low. If the ESR is not sufficiently low, the voltage drop is large, and charging / discharging can be performed in a short time. Can not.

  The charging circuit 103 is a general charging circuit used for charging the capacitor 102 having a particularly low ESR, and is constituted by, for example, a battery charger.

The DCDC converter 104 is a voltage feedback type DCDC converter that uses the battery 101 or one of the capacitors 102 or both the battery 101 and the capacitor 102 as an input power source and causes the light emitting unit 105 to emit light with a constant current output. Emitting unit 105 in the first embodiment, _{V F} is using a white LED in the range of 3.0～4.0V, the resistance 106 is the sense resistor uses a 50 m [Omega, the output of the DCDC converter 104 The voltage is in the range of 3.1-4.1V. The light emitting unit 105 is not limited to a white LED, but may be another LED or a xenon tube.

  The battery voltage detection circuit 107 is a voltage dividing circuit composed of two resistors connected in series, for example, and the microcomputer 108 detects the divided battery voltage.

  The microcomputer 108 controls the circuits constituting the LED strobe power supply circuit 100, performs various calculations, and reads the memory 110.

  The AE sensor 109 is a photometric sensor that performs automatic exposure, performs pre-emission photometry, and sends information to the microcomputer 108.

  The memory 110 is a data storage device. In the first embodiment, at least the current level data that can be supplied to the LED strobe power supply circuit 100 according to the voltage value of the battery 101, the charge amount necessary for preliminary light emission, and the charge amount necessary for full light emission are stored. A device that stores other data may also be used.

  The other load circuit 111 is a general circuit constituting a digital camera, and includes, for example, an AF circuit and a lens communication circuit, but may be other circuits.

  Next, an example of the strobe light emission sequence in the first embodiment will be described with reference to FIG.

  In S101, the battery voltage detection circuit 107 controlled by the microcomputer 108 detects the current battery voltage value.

  In S <b> 102, the current that can be supplied to the LED strobe power circuit 100 by the battery at the current battery voltage value read in S <b> 101 from the current value that can be supplied to the LED strobe power circuit 100 at each battery voltage value stored in advance in the memory 110. Read the value.

  In S103, the microcomputer 108 reads a preset time from the preliminary light emission to the main light emission, and in the current value that can be supplied to the LED strobe power supply circuit 100 calculated in S102, the capacitor 102 between the preliminary light emission and the main light emission. Calculate the amount of charge that can be charged.

  In general, since the capacitor 102 is charged with a constant current, the charge amount Q [F] accumulated in the capacitor 102 is set to I [A] as the charging current, t [sec] as the charging time, and the capacitor 102. When the capacitor 102 is charged from 0 [V] to V [V], Q = I × t = V × F.

  In S104, the microcomputer 108 calculates the first voltage level by calculation. The first voltage level is the sum of the charge amount necessary for preliminary light emission and the charge amount necessary for full light emission stored in advance in the memory 110 as data, and the charge that can be charged between the preliminary light emission and the main light emission calculated in S103. Calculated from the difference in quantity. For example, when the charge amount necessary for preliminary light emission is 0.006 [C] and the charge amount necessary for full light emission is 0.1 [C], the charge amount necessary for preliminary light emission and the charge necessary for full light emission The sum of the amounts is 0.106 [C].

  Under the condition that the time from the preliminary light emission to the main light emission is 0.05 [sec] and the charging current is 1 [A], the charge amount that can be charged during the charge time from the preliminary light emission to the main light emission is 0.05 [C]. Therefore, the difference between the charge amount necessary for preliminary light emission and the charge amount necessary for full light emission, and the charge amount and the charge amount chargeable between the preliminary light emission and the main light emission calculated in S103 are 0.056C. When the capacitance of the capacitor 102 is 0.2 [F], the first voltage level is about 0.3 [V].

  In S105, the capacitor 102 is charged to the first voltage level obtained in S104.

  In S106, preliminary light emission is performed, and the AE sensor 109 transmits a light reception result when the preliminary light emission is received to the microcomputer 108.

  In S107, the microcomputer 108 calculates the second voltage level by calculation. The second voltage level is determined according to the preset emission and emission conditions determined by the preset ISO and aperture conditions, and the AE sensor 109 that performs photometry, based on the light reception result when the preliminary light emission is received. . For example, when the voltage level required for full light emission is 0.53 [V] and the light emission form of the main light emission determined based on the light reception result when the preliminary light emission is received is 1/2 light emission, The voltage level of 2 is 0.265 [V].

  In S108, the capacitor 102 is charged up to the second voltage level determined in S107.

  In S109, the main light emission is performed under the conditions determined based on the preset ISO and aperture conditions and the light reception result when the preliminary light emission is received in the photometry unit that performs photometry.

  Next, how the first and second voltage levels change according to the battery voltage and the form of the main light emission will be described with reference to FIGS.

  FIG. 3 is a time chart for explaining the case where the battery voltage is high and full light emission is performed as the main light emission.

  In the time chart shown in FIG. 3, since the battery voltage is high as a condition, the current that can be supplied to the LED strobe power supply circuit 100 increases, and the voltage level of the capacitor 102 changes from the start of charging to the first voltage level and the second voltage level. The time to reach is short. In addition, since the full emission is performed in the main emission, the second voltage level is set high.

  FIG. 4 is a time chart for explaining the case where the battery voltage is low and full light emission is performed as the main light emission.

  In the time chart shown in FIG. 4, since the battery voltage is low as a condition, the current that can be supplied to the LED strobe power supply circuit 100 is small, and the voltage level of the capacitor 102 changes from the start of charging to the first voltage level and the second voltage level. It takes time to reach Therefore, the first voltage level is set to a high value.

  FIG. 5 is a time chart for explaining the case where the battery voltage is high and half light emission is performed as main light emission.

  In the time chart shown in FIG. 5, since the battery voltage is high as a condition, the current that can be supplied to the LED strobe power supply circuit 100 increases, and the voltage level of the capacitor 102 changes from the start of charging to the first voltage level and the second voltage level. The time to reach is short. Further, since 1/2 light emission is performed as the main light emission, the second voltage level is set to a lower value than in the case of performing full light emission as the main light emission.

100 LED strobe power supply circuit, 101 battery, 102 charging unit, 103 charging circuit,
104 power supply control circuit unit, 105 light emitting unit, 106 resistor, 107 battery voltage detection circuit,
108 circuit control unit, 109 photometry unit, 110 memory, 111 other load circuit,
112 Power supply unit

Claims (8)

A battery voltage detection circuit for detecting the voltage of the battery;
A charging unit charged to a predetermined voltage value from the battery through a charging circuit;
A power control circuit unit that is supplied with power from the battery and a power supply unit that is the charging unit, and causes the light emitting unit to emit light at a predetermined current;
The voltage value of the charging unit is set to a first voltage level by preliminary charging performed before preliminary light emission, and is then set to a second voltage level by main charging performed after preliminary light emission. Power supply circuit. A battery voltage detection circuit for detecting the voltage of the battery;
A charging unit charged to a predetermined voltage value from the battery through a charging circuit;
A power control circuit unit that is supplied with power from the battery and a power supply unit that is the charging unit, and causes the light emitting unit to emit light at a predetermined current;
The voltage value of the charging unit is set to a first voltage level by preliminary charging performed before preliminary light emission, and then set to a second voltage level by main charging performed after preliminary light emission.
The first voltage level is set by the circuit control unit based on a charge amount necessary for preliminary light emission, a charge amount necessary for full light emission, and a charge amount chargeable between preliminary light emission and main light emission. A power circuit characterized by. A battery voltage detection circuit for detecting the voltage of the battery;
A charging unit charged to a predetermined voltage value from the battery through a charging circuit;
A power control circuit unit that is supplied with power from the battery and a power supply unit that is the charging unit, and causes the light emitting unit to emit light at a predetermined current;
The voltage value of the charging unit is set to a first voltage level by preliminary charging performed before preliminary light emission, and then set to a second voltage level by main charging performed after preliminary light emission.
The second voltage level is set by the circuit control unit based on a light reception result when a preliminary light emission is received in a photometry unit that performs preset ISO and aperture conditions and photometry. Power supply circuit.   The first voltage level has a difference between the amount of charge necessary for preliminary light emission stored in the memory and the amount of charge necessary for full light emission and the amount of charge that can be charged during the time from preliminary light emission to main light emission. The power supply circuit according to any one of claims 1 to 3, wherein the power supply circuit is set by the circuit control unit.   The amount of charge that can be charged between the preliminary light emission and the main light emission can be supplied to the power supply circuit according to the preset time from the preliminary light emission to the main light emission and the voltage value of the battery stored in the memory. The power supply circuit according to claim 1, wherein the power supply circuit is calculated by the circuit control unit based on a current level.   The power supply circuit according to any one of claims 1 to 5, wherein the power supply unit is the charging unit.   The power circuit according to claim 1, wherein the power supply unit is the battery.   The power supply circuit according to any one of claims 1 to 7, wherein the power supply unit is both the charging unit and the battery.