JP2018085868A - Electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve responsibility of a driving circuit that controls driving of a light emission element such as a light emission diode.SOLUTION: An electronic apparatus includes: a light emission diode part (9); DC-DC converters (4 to 7) in which an anode side of the light emission diode part is connected to an output terminal; a first feedback loop that allows each DC-DC converter to be operated by feed backing and flowing a predetermined current to the light emission diode part from a current control part that controls a current; a second feedback loop that feedbacks a voltage of a voltage detection part so that an output voltage value of each DC-DC converter becomes a predetermined voltage value, and allows each DC-DC converter to be operated; and a feedback switching part that switches to the first feedback loop or the second feedback loop.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electronic apparatus (such as a digital camera) having a drive circuit that controls driving of a light emitting element such as a light emitting diode (LED) element.

  Patent Document 1 describes a configuration in which a predetermined current drive is performed by boosting only a voltage corresponding to a forward voltage necessary for driving a light emitting diode. Patent Document 2 has a configuration in which only a forward voltage necessary for driving a light emitting diode is boosted to perform a predetermined current drive. A transistor is inserted into a current control loop of the light emitting diode, and light emission is performed by controlling the transistor. A configuration is described in which the circuit is turned on or off.

JP 2003-152224 A JP2012-49179A

  A case is assumed in which the configurations described in Patent Documents 1 and 2 are employed in an electronic device capable of flash photography. In the configuration described in Patent Document 1, it is difficult to flow a large current instantaneously because the start-up responsiveness of the DCDC converter is affected when the light emitting diode starts to emit light. Therefore, it is difficult to control minute light emission with a minute time pulse when performing strobe photography. Furthermore, even if it is going to improve the starting responsiveness of a DCDC converter, since there is a technical limit in the frequency characteristic and gain of ErrAmp, it is difficult to perform light emission control with good responsiveness.

  In the configuration described in Patent Document 2, a predetermined wait time is required between the start timing of the DCDC converter and the timing at which the transistor is turned on. If the predetermined wait time is too short, the peak value is not constant with insufficient light emission, and if it is too long, the anode potential of the light emitting diode becomes unnecessarily large and an abnormal current flows. Therefore, the predetermined wait time is fixed and cannot be arbitrarily set.

  Therefore, in the configuration described in Patent Document 2, the light emitting diode cannot emit light unless a predetermined wait time has elapsed after the trigger signal (X signal) for starting the light emission of the light emitting diode is generated. There are times when responsiveness is not good.

  Accordingly, an object of the present invention is to improve the responsiveness of a driving circuit that controls driving of a light emitting element such as a light emitting diode. Another object of the present invention is to improve the responsiveness at the start of light emission in a light emission system that performs preliminary light emission before the main light emission.

  In order to achieve the above object, one of the electronic devices according to the present invention includes a light emitting diode unit, a DCDC converter in which an anode side of the light emitting diode unit is connected to an output terminal, and a predetermined current in the light emitting diode unit. A first feedback loop that performs the operation of the DCDC converter by feeding back from a current control unit that controls current to flow, and a voltage of the voltage detection unit so that an output voltage value of the DCDC converter becomes a predetermined voltage value. It is characterized by having a second feedback loop that performs the operation of the DCDC converter by feeding back, and a feedback switching unit that switches between the first feedback loop and the second feedback loop.

  In order to achieve the above object, one of the electronic devices according to the present invention includes a light emitting diode section, a DCDC converter having an output terminal connected to the anode side of the light emitting diode section, and a predetermined current in the light emitting diode section. A first feedback loop for performing an operation of the DCDC converter by feeding back from a current control unit that controls a current so as to flow, and an output of the voltage detection unit so that an output voltage value of the DCDC converter becomes a predetermined voltage value. Even when any one of the second feedback loop that feeds back to the DCDC converter, and the first feedback loop and the second feedback loop are operating, based on the output of the voltage detection unit, The control unit 15 that monitors the anode potential of the light emitting diode unit, and a feedback cutoff that switches between the first feedback loop and the second feedback loop. In the main light emission, the anode potential of the light emitting diode part is boosted in advance in the second feedback loop with a voltage based on the anode potential of the light emitting diode part at the time of preliminary light emission. The light is emitted by the first feedback loop at the time of light emission.

  ADVANTAGE OF THE INVENTION According to this invention, the responsiveness of the drive circuit which controls the drive of light emitting elements, such as a light emitting diode, can be improved. Further, according to the present invention, in the light emitting system that performs preliminary light emission before the main light emission, the responsiveness at the start of light emission can be improved.

FIG. 3 is a block diagram for explaining a plurality of components included in the electronic apparatus A according to the first embodiment. 3 is a block diagram for explaining in detail some of a plurality of components included in the electronic apparatus A according to Embodiment 1. FIG. It is a block diagram for demonstrating the some component which the electronic device B in Embodiment 2 has. It is a block diagram for demonstrating the some component which the electronic device C in Embodiment 3 has. It is a block diagram for demonstrating the some component which the electronic device D in Embodiment 4 has. 6 is a timing chart for explaining operations of the electronic device A in the first embodiment and the electronic device C in the third embodiment. 12 is a timing chart for explaining the operation of the electronic apparatus B in the second embodiment. 10 is a timing chart for explaining the operation of the electronic device D in the fourth embodiment. It is a block diagram for demonstrating the some component which the electronic device E in Embodiment 5 has. 10 is a timing chart for explaining an operation of the electronic device E according to the fifth embodiment.

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

[Embodiment 1]
The first embodiment will be described with reference to FIGS. 1, 2, and 6. 1 and 2 are block diagrams for explaining a plurality of components included in the electronic apparatus A according to the first embodiment. In the first embodiment, a case where the electronic apparatus A operates as, for example, a digital camera will be described.

  Reference numeral 1 denotes a battery as a power source. Here, a two-cell battery (about 6 to 8.5 v) is assumed. Reference numeral 3 denotes a capacitor 3 that is charged from the battery 1 through the charging circuit 2, and is an auxiliary power source 1. Here, an electric double layer capacitor is assumed.

  4 to 7 constitute a DCDC converter for boosting, 4 is a control IC of the DCDC converter (4 to 7), 6 is a transistor controlled by the control IC 4, 5 is a coil, and 7 is a shot. It is a key diode. Reference numeral 8 denotes an output capacitor, which is connected to stabilize the output of the DCDC converter (4 to 7) and reduce the ripple voltage. The control IC 4 includes a feedback control unit 20, a reference voltage generation unit 21 of the feedback control unit, a triangular wave generation unit 22, an ON / OFF control unit 23 for converter operation, and a driver unit 24 for the drive transistor 6, and drives the drive transistor 6. By doing so, a constant boost converter operation is performed.

  The output terminals of the DCDC converters (4 to 7) are connected to the anode side of the light emitting diode unit 9. Here, the light emitting diode unit 9 is assumed to be a white light emitting diode having a Vf voltage of about 3.5 V (at 2A), and is configured by connecting four white light emitting diodes in series. For example, when the light emitting diode unit 9 is controlled with a current of 2 A, the anode voltage is assumed to be about 14 v. Furthermore, the cathode side of the light emitting diode unit 9 is connected to the current control unit 10, and the other end of the current control unit 10 is connected to GND. The current control unit 10 includes, for example, a current sense resistor and a SW element (switching element) (see FIG. 2).

  When the SW element of the current control unit 10 is in the ON state, the signal that has been subjected to current-voltage conversion by the current sense resistor is connected to the feedback control unit 20 inside the control IC 4 via the first SW element (first switching element) 12. And returned. As a result, the DCDC converter (4-7) uses the capacitor 3 as an input power source, and the anode terminal of the light emitting diode unit 9 is set so that the signal level converted by the current sense resistor in the current control unit 10 is constant. To control the voltage. That is, when the SW element of the current control unit 10 is in the ON state and the first SW element 12 is in the ON state, control is performed by the first feedback circuit in which a predetermined current flows through the light emitting diode unit 9. It is possible.

  11 is a voltage detection part, and one end is connected to the output end of a DCDC converter (4-7), and the other end is connected to GND. For example, the voltage detection unit 11 includes at least two resistors (see FIG. 2). A signal obtained by resistance-dividing the output voltage of the DCDC converter (4 to 7) by 11 is connected to the feedback control unit 20 via the second SW element (second switching element) 13 and fed back. As a result, the DCDC converter (4-7) is boosted by the second feedback circuit so that the voltage becomes a constant voltage based on the resistance division ratio set by the voltage detector 11 with the capacitor 3 as an input power supply.

  That is, when the second SW element 13 is ON, it is possible to perform a boosting operation by the second feedback circuit to a voltage based on the resistance division ratio.

  Reference numeral 15 denotes an LED drive control unit that performs light emission control of the light emitting diode unit 9 by performing operation control of the DCDC converter (4 to 7). An inverter circuit 14 exclusively controls the first SW element 12 that selects the first feedback loop of the DCDC converter (4 to 7) and the second SW element 13 that selects the second feedback loop. Circuit. That is, the DCDC converters (4 to 7) are controlled by the LED drive control unit 15 selecting and controlling the operation controlled by the first feedback loop and the operation controlled by the second feedback loop.

  In the first embodiment, the control IC 4 is a step-up drive control IC based on the output power supply range of the battery and the series number of the plurality of light emitting diodes included in the light emitting diode unit 9. Depending on the connection state, it is possible to cope with this by adopting a control IC for step-down driving or step-up / step-down driving.

  Next, the operation of the electronic apparatus A in the first embodiment will be described with reference to the timing chart of FIG.

  First, the LED drive control unit 15 sets the reference voltage to the reference voltage generation unit 21 of the feedback control unit of the control IC 4 by the communication control of the CTL 4 to set the current when the current flows through the light emitting diode unit 9. The peak value level is determined (CTL4 control in FIG. 4).

  Next, by setting the CTL2 signal to Hi from the LED drive control unit 15, the first SW element 12 is turned OFF and the second SW element 13 is turned ON, so that the second feedback loop is activated. .

  Next, the CTL1 signal is set to Hi from the LED drive control unit 15, and driving of the converter operation of the control IC 4 is started. As a result, the DCDC converters (4 to 7) operate to boost the voltage of the anode terminal of the light emitting diode unit 9 to the boost level based on the divided resistance ratio set by the voltage detection unit 11.

  In this case, the boosted level of the anode terminal is set to a voltage higher than the voltage assumed at the anode end (voltage generated by the diode Vf voltage + sense resistor) when a predetermined current is passed through the light emitting diode unit 9. The voltage level in the reference voltage generator 21 is determined. Next, by setting the CTL2 signal from the LED drive control unit 15 to Low and switching from the second feedback loop to the first feedback loop, the CTL3 signal is set to Hi at the same time by the first feedback loop, Current control is performed on the light emitting diode unit 9 with a current value based on the sense resistor of the current control unit 10 and the voltage level set by the reference voltage generation unit 21 of the feedback control unit.

  In this case, the anode potential of the light emitting diode unit 9 is controlled so as to boost only the voltage necessary for flowing the current with respect to the anode potential. Since the anode potential is boosted to a predetermined level in advance, the light emission operation starts with good responsiveness.

  Next, current control for a predetermined time is performed at a time determined in advance by the LED drive control unit 15, and after the predetermined time has elapsed, the CTL 3 is switched to Low to cut off the current. At the same time, CTL1 is switched to Low, and the boosting operation of the DCDC converter (4-7) is stopped.

  As long as the DCDC converter (4-7) is activated in advance by CLT2 by the operation as described above, at the same time, CTL2 is switched to Low and at the same time the CTL3 is switched to Hi. It is possible to pass a current to the light emitting diode portion 9 with high responsiveness.

[Embodiment 2]
The second embodiment will be described with reference to FIGS. 3 and 7. FIG. 3 is a block diagram for explaining a plurality of components included in the electronic device B according to the second embodiment. In the second embodiment, a case where the electronic device B operates as a digital camera, for example, will be described.

  In the second embodiment, the DCDC converters (4 to 7) have a first feedback loop of the current control unit 10 and a second feedback loop of the voltage detection unit 11, and the resistance from the voltage detection unit 11 The divided signal is connected to the feedback control unit 20 of the control IC 4 without passing through the SW element (switching element), and the signal from the current sense resistor of the current control unit 10 is passed through the first SW element 12. Thus, the control IC 4 is connected to the feedback control unit 20.

  Furthermore, the control signal of the transistor that controls the current control unit 10 and the control signal of the first SW element 12 that connects and disconnects the first feedback loop are controlled by the same CTL signal. Other portions are the same as those shown in FIG.

  Next, the operation of the electronic apparatus B in the second embodiment will be described with reference to the time chart of FIG. First, the LED drive control unit 15 sets the reference voltage to the reference voltage generation unit 21 of the feedback control unit of the control IC 4 by the communication control of the CTL 4 to set the current when the current flows through the light emitting diode unit 9. The peak value level is determined (CTL4 control in FIG. 7).

  Next, the CTL1 signal is set to Hi from the LED drive control unit 15, and driving of the converter operation of the control IC 4 is started. As a result, the DCDC converters (4 to 7) operate to boost the voltage of the anode terminal of the light emitting diode unit 9 to the boost level based on the divided resistance ratio set by the voltage detection unit 11.

  In this case, the step-up level of the anode terminal is determined by the voltage level set by the reference voltage generation unit 21 of the feedback control unit and the sense resistor in the current control unit 10, and the current value passed through the light emitting diode unit 9 is The voltage is higher than the voltage assumed at the anode end (the voltage generated by the diode + the sense resistor) when the light-emitting diode portion 9 is passed. By setting the CTL3 signal to Hi, the first feedback loop causes the sense resistor of the current control unit 10, the parallel sum of the resistance values on the GND side of the voltage detection unit 11, and the generation of the reference voltage of the feedback control unit. Current control is performed on the light emitting diode unit 9 with a current value based on the voltage level set in the unit 21.

  Here, the current sense resistor 10 of the current control unit 10 has a resistance value sufficiently smaller than the resistance value on the GND side of the voltage detection unit 11, so that the current value is approximately equal to or less than about 1 / 10,000. It is almost decided.

  The anode potential of the light emitting diode section 9 is controlled so as to boost only the voltage necessary for flowing the current to the anode potential. Since the anode potential is boosted to a predetermined level in advance, the light emission operation starts with good responsiveness.

  Next, current control for a predetermined time is performed at a time determined in advance by the LED drive control unit 15, and after the predetermined time has elapsed, the CTL 3 is switched to Low to cut off the current. At the same time, CTL1 is switched to Low, and the boosting operation of the DCDC converter (4-7) is stopped.

  By the operation as described above, the feedback loop 2 is always connected to the first embodiment, and the connection of the feedback loop 1 is turned ON or OFF for the state, and the feedback loop is turned ON. Even when there is a difference between the responsiveness of the / OFF SW elements 12 and 13 and the responsiveness of the SW elements of the current control unit 10, it is possible to switch seamlessly without dead time. Furthermore, it is unnecessary by setting the resistance value of the resistance divider 11 to a larger value at a level that can be controlled by the DCDC converter (4 to 7), and controlling the start timing of CTL1 only at a necessary timing. Power can be minimized.

[Embodiment 3]
The third embodiment will be described with reference to FIGS. 4 and 6. FIG. 4 is a block diagram for explaining a plurality of components included in the electronic device C according to the third embodiment. In the third embodiment, a case where the electronic device C operates as a digital camera, for example, will be described.

  In the third embodiment, as compared with the first embodiment, the current control unit 10 is connected to the anode side of the light emitting diode unit 9. Thus, the DCDC converter (4 to 7) has the first feedback loop of the current control unit 54 and the second feedback loop of the voltage detection unit 11, and is divided by the resistance from the voltage detection unit 11. The signal is connected to ErrAmp 52 inside the feedback control unit 20 of the control IC 4 via the SW element (switching element) 51 inside the power supply IC 4, and signals at both ends of the current sense resistor of the current control unit 54 are inside the power supply IC 4. It is connected to Amp 53 inside feedback control unit 20 and is connected to ErrAmp 52 inside feedback control unit 20 of control IC 4 via SW element (switching element) 50 inside feedback control unit 20.

  Other portions are the same as those shown in FIG. Also in the operation timing, the same control as in the time chart of FIG. 6 is performed, and thus the description thereof is omitted.

[Embodiment 4]
Embodiment 4 will be described with reference to FIGS. FIG. 5 is a block diagram for explaining a plurality of components included in the electronic device D according to the fourth embodiment. In the fourth embodiment, a case where the electronic device D operates as a digital camera, for example, will be described.

  Reference numeral 60 denotes a lens unit, 61 denotes a diaphragm drive mechanism, and 75 denotes a reflection mirror disposed at 45 degrees with respect to the optical axis, which is operated during imaging and is stored in a position that does not affect the imaging optical axis. . 62 is the front curtain of the focal plane shutter, and 63 is the rear curtain of the focal plane shutter. Reference numeral 74 denotes a detection member that detects that the front curtain of 62 has completed traveling. Reference numeral 64 denotes an image sensor, and here, a CMOS sensor is assumed. In the subject light, the lens unit 60, the apertures 61 and 62 are the front curtain of the focal plane shutter, and 63 is imaged on the image sensor via the rear curtain of the focal plane shutter.

  Apart from the imaging optical system, on the other hand, there is a photometric optical system that is reflected by a reflecting mirror 75 and forms an image on a photometric sensor 73 via a pentagonal prism 71 and a photometric lens 72. An image picked up by the image pickup device 64 is taken into the memory 68 after being processed by the DSP via the AD converter 65. Reference numeral 67 denotes a timing generator, which is controlled by the DSP 66 so that the DSP 66, the image sensor 64, and the AD converter 65 are synchronously controlled. Reference numeral 69 denotes an external liquid crystal, which is a member that displays an image captured by the image sensor 64 to the outside.

  Reference numeral 1 denotes a battery as a power source. Here, a two-cell battery (about 6 to 8.5 v) is assumed. Reference numeral 3 denotes a capacitor 3 that is charged from the battery 1 through the charging circuit 2, and is an auxiliary power source 1. Here, an electric double layer capacitor is assumed.

  4 to 7 constitute a DCDC converter for boosting, 4 is a control IC of the DCDC converter (4 to 7), 6 is a transistor controlled by the control IC 4, 5 is a coil, and 7 is a shot. It is a key diode. Reference numeral 8 denotes an output capacitor, which is connected to stabilize the output of the DCDC converter (4 to 7) and reduce the ripple voltage. The control IC 4 includes a feedback control unit 20, a reference voltage generation unit 21 of the feedback control unit, a triangular wave generation unit 22, an ON / OFF control unit 23 for converter operation, and a driver unit 24 for the drive transistor 6, and drives the drive transistor 6. By doing so, a constant boost converter operation is performed.

  The output terminals of the DCDC converters (4 to 7) are connected to the anode side of the light emitting diode unit 9. Here, the light emitting diode unit 9 is assumed to be a white light emitting diode having a Vf voltage of about 3.5 V (at 2A), and is configured by connecting four white light emitting diodes in series. For example, when the light emitting diode unit 9 is controlled with a current of 2 A, the anode voltage is assumed to be about 14 v.

  Furthermore, the cathode side of the light emitting diode unit 9 is connected to the current control unit 10, and the other end of the current control unit 10 is connected to GND. The current control unit 10 includes, for example, a current sense resistor and a SW element (switching element) (see FIG. 2). When the SW element of the current control unit 10 is in the ON state, the signal that has been subjected to current-voltage conversion by the current sense resistor is connected to the feedback control unit 20 inside the control IC 4 via the first SW element (first switching element) 12. And returned. As a result, the DCDC converter (4-7) uses the capacitor 3 as an input power source, and the anode terminal of the light emitting diode unit 9 is set so that the signal level converted by the current sense resistor in the current control unit 10 is constant. To control the voltage.

  That is, when the SW element of the current control unit 10 is in the ON state and the first SW element 12 is in the ON state, control is performed by the first feedback circuit in which a predetermined current flows through the light emitting diode unit 9. It is possible.

  11 is a voltage detection part, and one end is connected to the output end of a DCDC converter (4-7), and the other end is connected to GND. For example, the voltage detection unit 11 includes at least two resistors (see FIG. 2). A signal obtained by resistance-dividing the output voltage of the DCDC converter (4 to 7) by 11 is connected to the feedback control unit 20 via the second SW element (second switching element) 13 and fed back.

  As a result, the DCDC converter (4-7) is boosted by the second feedback circuit so that the voltage becomes a constant voltage based on the resistance division ratio set by the voltage detector 11 with the capacitor 3 as an input power supply. That is, when the second SW element 13 is ON, it is possible to perform a boosting operation by the second feedback circuit to a voltage based on the resistance division ratio.

  Reference numeral 15 denotes an LED drive control unit that performs light emission control of the light emitting diode unit 9 by performing operation control of the DCDC converter (4 to 7). An inverter circuit 14 exclusively controls the first SW element 12 that selects the first feedback loop of the DCDC converter (4 to 7) and the second SW element 13 that selects the second feedback loop. Circuit. That is, the DCDC converter (4-7) controls the case where it is controlled by the first feedback loop and the case where it is controlled by the second feedback loop by controlling by the LED drive control unit 15.

  The LED drive control unit 15 is connected to the DSP 66, the SW member 70, the front curtain 62 of the focal plane shutter, and a detection member 74 that detects that the front curtains of the rear curtains 63 and 62 of the focal plane shutter have completed running. As a result, the LED drive control unit 15 issues an imaging operation command to the DSP 66 based on the signal input from the SW member 70, and the focal plane shutter front curtain 62 and the focal plane shutter rear curtain 63. The electronic device D is controlled by the CTLs 1 to 4 in accordance with the timing of the travel detection signal 74 of the front curtain.

  Next, the operation of the electronic device D in the fourth embodiment will be described with reference to the timing chart of FIG.

  First, the reference voltage is set in advance for the reference voltage generation unit 21 of the feedback control unit of the control IC 4 by the CTL signal 4, and at the same time, the second voltage based on the voltage detection level of 11 is set by setting the CTL signal 2 to Hi. The second SW element 13 is set so as to form a feedback loop. Here, the current peak value during light emission is determined.

  Next, the control IC 4 is activated. Thus, the current peak value level when a current is passed through the light emitting diode section 9 is determined.

  When an imaging request signal is received from the SW member 70, energization of the shutter front curtain 62 and the shutter rear curtain 63 is started based on this signal (CTL5, CTL6), and the shutter is held in the set state. Furthermore, CTL1 is switched to Hi at that timing, and the DCDC converters (4 to 7) are activated in the second feedback loop. After the start of the DCDC converter (4 to 7) is completed, CTL3 is switched to Hi at a predetermined time, and at the same time, by switching CTL2 to Low, a predetermined current peak value for a predetermined time is determined. The preliminary light emission operation is performed.

  In this state, with the reflection mirror 75 disposed at a 45 ° position, the photometric sensor 73 performs preliminary photometry of the reflected light emission of the subject by preliminary light emission in the photometric optical system via 71 and 72. Based on the preliminary photometric value, the LED drive control unit 15 calculates a main light emission amount for proper exposure during the main light emission. Further, the light emission time is calculated in the case where the main light emission amount is equal to the current light peak value of the preliminary light emission.

  Next, after the preliminary light emission is completed, the aperture member 61 is started to drive the aperture. After the aperture operation is completed, the holding of the front curtain 62 of the focal plane shutter is released, and the front curtain of SH is run. . When the SH front curtain travels, the LED drive control unit 15 detects the SH front curtain travel completion signal from the detection unit 74, so that the LED drive control unit 15 switches the CTL3 signal to Hi, By switching the CTL signal 2 signal to Low, the light emitting diode unit 9 starts to emit light.

  Next, the LED drive control unit 15 performs light emission control based on the main light emission time calculated in advance, and then releases the holding of the rear curtain 62 of the focal plane shutter and causes the rear curtain to run. . Here, it is assumed that the main light emission time is within the fully open time of the shutters 61 and 62.

  As described above, in the case where the electronic device D operates as a digital camera, for example, an operation example is shown in which light emission control with good responsiveness can be performed without waiting time for the light emission trigger signal.

[Embodiment 5]
The fifth embodiment will be described with reference to FIGS. 9 and 10. FIG. 9 is a block diagram for explaining a plurality of components included in the electronic device E according to the fifth embodiment. In the fifth embodiment, a case where the electronic device E operates as, for example, a digital camera will be described.

  First, with reference to FIG. 9, the structure of the electronic device E in Embodiment 5 is demonstrated. In the fifth embodiment, parts different from the electronic device D (see FIG. 5) in the fourth embodiment will be described, and descriptions of other parts will be omitted.

  The output of the voltage detection unit 11 is connected to the feedback switching unit 12 while being connected to the LED drive control unit 15.

  Thereby, even when the light emitting diode unit 9 is controlled to emit light in the first feedback loop using the current control unit 10, the anode potential of the light emitting diode unit 9 can be monitored by the LED drive control unit 15. . Furthermore, it is possible to control the DAC 21 of the DCDC converter 4 from the LED drive control unit 15 based on the voltage, and to set the anode potential to an arbitrary voltage in the second feedback loop using the voltage detection unit 11.

  With the above configuration, when the light emitting diode unit 9 is caused to emit light in the first feedback loop, the anode potential of the light emitting diode unit 9 from the start of light emission is set to the anode potential expected in advance during light emission. Control by the drive control unit 15 becomes possible.

  Next, the operation of the electronic device E according to the fifth embodiment will be described with reference to FIG. The setting of the current peak value when the preliminary light emission is started is previously set in the DAC 21 of the DCDC converter control IC 4 by the CTL4 signal from the LED drive control unit 15 (# 201).

  When the photographing request signal from the user is acted on by the SW unit 70, it is received by the LED drive control unit 15 as a CTL5 signal (# 202). Next, CTL1 (step-up control) of the DCDC converter control IC4 is turned on (# 203), and at the same time, the current control unit 10 serving as the first feedback loop is turned on by CTL3 (# 204). As a result, the step-up operation of the DCDC converter is started, and current starts to flow through the light emitting diode unit 9 (# 205). When the current of the light emitting diode unit 9 becomes constant, the photometric sensor 73 acquires the brightness of the subject light through the imaging lens 60, the main mirror 75, the pentaprism 71, and the photometric lens 72, and the LED drive control unit. 15 is stored.

  Furthermore, when the current of the light emitting diode unit 9 becomes constant, the LED drive control unit 15 stores the anode potential of the light emitting diode unit 9 during preliminary light emission via the voltage detection unit 11 (# 206). .

  When the stop of the preliminary light emission is completed, the feedback switching unit 12 is switched by the LED drive control unit 15 from the first feedback loop using the current control unit 10 to the second feedback loop using the voltage detection unit 11 (# 207). When the feedback switching unit 12 is switched to the second feedback loop, the anode potential of the light emitting diode unit 9 is boosted to a voltage preset in the DAC 21 (# 208). On the camera side, when the preliminary light emission is stopped, the image pickup optical system retracts the 75 main mirrors in the Up direction so that light directly hits the image pickup device (# 209).

  Next, the anode potential of the light emitting diode unit 9 at the time of preliminary light emission stored in the LED drive control unit 15 is set in the DAC 21 of the DCDC converter control IC 4 (# 210). Thus, when the peak value during the main light emission is the same as the preliminary light emission, the anode potential is set in advance in the second feedback loop to the anode potential of the light-emitting diode unit 9 predicted during the main light emission. Is possible.

  Next, at the timing when the shutter front curtain 62 is operated and the shutter front curtain is fully opened, the feedback switching control unit is switched to the first feedback loop (# 211), and the current control unit 10 is operated by the light emission signal CTL3. (# 212), current is passed through the light emitting diode unit 9 to emit light. In this case, since the anode potential is set to a voltage having a peak value assumed at the time of light emission, the light emission is controlled with the peak value aimed at a good response from the start of light emission. Finally, at the timing when the light emission operation ends, the boost control signal CTL1 and the light emission signal CTL3 are stopped.

  In the fifth embodiment, the case where the peak values of the preliminary light emission and the main light emission are the same is taken as an example. As another assumption example, when the peak values of the preliminary light emission and the main light emission are different, an approximate expression, a table, and the like indicating the correlation between the drive current and the brightness of the light emitting diode unit 9 determined in advance are stored. Keep it. Then, based on the anode potential of the light emitting diode unit 9 at the time of preliminary light emission and the correlation table, control is performed by predicting the anode potential at the time of main light emission.

  As described above, by controlling the DAC 21 of the DCDC converter 4 so that the anode potential at the time of main light emission is predicted in advance before the start of main light emission even when the peak value is different between the preliminary light emission and the main light emission. Therefore, it is possible to emit light with good responsiveness. In the light emission control sequence without preliminary light emission, the anode potential assumed at the time of main light emission is predicted from the anode potential of the light emitting diode unit 9 at the time of light emission at the closest timing in the past, and the DAC 21 of the DCDC converter 4 is controlled and set in advance. This makes it possible to emit light with good responsiveness.

  As described above, when the electronic device E operates as a digital camera, for example, in a system having preliminary light emission and main light emission, light emission control with better responsiveness can be performed.

1 Battery 2 Charge Control Unit 3 Capacitor 4 Control IC
5 Inductor 6 Drive Transistor 7 Schottky Diode 8 Output Capacitor 9 Light-Emitting Diode Unit 10 Current Control Unit 11 Voltage Detection Unit 12 Feedback Switching Unit 15 LED Drive Control Unit

Claims (12)

A light emitting diode part;
A DCDC converter in which the anode side of the light emitting diode part is connected to an output terminal;
A first feedback loop for performing an operation of the DCDC converter by feeding back from a current control unit that controls a current so that a predetermined current flows in the light emitting diode unit;
A second feedback loop for performing the operation of the DCDC converter by feeding back the voltage of the voltage detector so that the output voltage value of the DCDC converter becomes a predetermined voltage value;
An electronic apparatus comprising: a feedback switching unit that switches between the first feedback loop and the second feedback loop. The current control unit includes a transistor and a current detection resistor,
One end of the transistor is connected to the cathode side of the light emitting diode part, the other end of the transistor is connected to the current detection resistor,
2. The electronic apparatus according to claim 1, wherein one end of the current detection resistor is connected to the transistor and the feedback switching unit, and the other end of the current detection resistor is connected to GND. . The voltage detection unit has at least two divided resistors.
3. The electronic apparatus according to claim 1, wherein the other end of the resistor connected to the output end of the DCDC converter is connected to the feedback switching unit and a resistor connected to the GND side.   The feedback switching unit includes a first switching element that controls connection of feedback from the current control unit, and a second switching element that controls connection of feedback from the voltage detection unit. The electronic device of any one of Claims 1 thru | or 3. A light emitting diode part;
A DCDC converter in which the anode side of the light emitting diode part is connected to an output terminal;
A current control unit having a transistor and a current detection resistor, wherein the one end of the current control unit is connected to the cathode side of the light emitting diode unit, and the other end of the current control unit is connected to GND A control unit;
In order to operate the DCDC converter so that the drive current of the light emitting diode unit becomes a predetermined current, a signal obtained by voltage-converting the current detected by one end of the current control unit is passed through the first switching element. A first feedback circuit connected to a feedback control unit of the DCDC converter;
In order to operate the output voltage of the DCDC converter to be a predetermined voltage, the voltage detection unit outputs the output of the DCDC converter at a predetermined division ratio, and one end of the voltage detection unit is connected to the DCDC converter. The voltage detection unit connected to an output and the other end of the voltage detection unit connected to GND;
A second feedback circuit for connecting a divided voltage output from the voltage detection unit to a feedback control unit of the DCDC converter;
An electronic apparatus comprising: a drive control unit that controls the first switching element and the switching element of the current control unit. A light emitting diode part;
DCDC, wherein the cathode side of the light emitting diode part is connected to GND, the anode side of the light emitting diode part is connected to a current control part having a transistor and a current detection resistor, and the other end of the current control part is connected to an output terminal A converter,
In order to operate the DCDC converter so that the drive current of the light emitting diode unit becomes a predetermined current, a signal obtained by voltage-converting the current detected by both ends of the current detection resistor of the current control unit is converted into a signal of the DCDC converter. A first feedback circuit connected to one end of the feedback control unit;
In order to operate so that the output voltage of the DCDC converter becomes a predetermined voltage, one end for outputting the output of the DCDC converter at a predetermined division ratio is connected to the output of the DCDC converter, and the other end is connected to GND. A voltage detection unit,
A second feedback circuit for connecting a divided voltage output from the voltage detection unit to one end of a feedback control unit of the DCDC converter;
An electronic apparatus comprising: a drive control unit that controls a first switching element and a second switching element in a feedback control unit of the DCDC converter. A light emitting diode part;
A DCDC converter in which the anode side of the light emitting diode part is connected to an output terminal;
A current control unit having one end connected to the cathode side of the light emitting diode unit and the other end connected to GND;
In order to operate the DCDC converter so that the driving current of the light emitting diode unit becomes a predetermined current, a signal obtained by voltage-converting the current detected by the other end of the current control unit is converted into a first switching element. A first feedback circuit connected to the feedback control unit of the DCDC converter via
A voltage detector for outputting the output of the DCDC converter at a predetermined division ratio in order to operate the output voltage of the DCDC converter to be a predetermined voltage;
A second feedback circuit for connecting a detection voltage output from the voltage detection unit to a feedback control unit of the DCDC converter via a second switching element;
A drive control unit for controlling the first feedback circuit and the second feedback circuit;
The drive control unit controls the light emission time of the preliminary light emission and the light amount of the main light emission based on a predetermined amount of reflected light of the preliminary light emitted to the subject. A light emitting diode part;
A DCDC converter having an output terminal connected to the anode side of the light emitting diode unit;
A first feedback loop for performing an operation of the DCDC converter by feeding back from a current control unit that controls a current so that a predetermined current flows in the light emitting diode unit;
A second feedback loop for feeding back the output of the voltage detector to the DCDC converter so that the output voltage value of the DCDC converter becomes a predetermined voltage value;
Even when one of the first feedback loop and the second feedback loop is operating, a control unit 15 that monitors the anode potential of the light emitting diode unit based on the output of the voltage detection unit; ,
A feedback switching unit that switches between the first feedback loop and the second feedback loop;
At the time of the main light emission, the anode potential of the light emitting diode part is boosted in advance in the second feedback loop with a voltage based on the anode potential of the light emitting diode part at the time of preliminary light emission, and at the time of light emission, the first potential is increased. An electronic device that emits light in a feedback loop.   When the peak values of the preliminary light emission and the main light emission are the same, the voltage is boosted in advance in the second feedback loop to a voltage equivalent to the anode potential of the light emitting diode unit during the preliminary light emission, and then switched to the first feedback loop. The electronic device according to claim 8, wherein the electronic device emits light.   When the peak values of the preliminary light emission and the main light emission are different, the anode potential at the time of the main light emission is determined from the anode potential of the light emitting diode unit 9 at the time of the preliminary light emission and the predetermined correlation between the brightness of the light emitting diode unit 9 and the current. 9. The electronic apparatus according to claim 8, wherein a potential is predicted, the voltage is boosted to the predicted voltage in advance in the second feedback loop, and the main light emission is performed by switching to the first feedback loop.   In the case of a light emitting operation that does not perform preliminary light emission, the anode potential at the time of main light emission is predicted from the anode potential of the light emitting diode unit 9 at the time of the recent preliminary light emission, and the predicted voltage is set in advance in the second feedback loop. The electronic apparatus according to claim 8, wherein the electronic device emits light by boosting and switching to the first feedback loop.   In preliminary light emission, light is emitted only in the first feedback loop. In main light emission, the voltage is boosted to a predetermined voltage in the second feedback loop, and then the main light emission is performed by switching to the first feedback loop. The electronic apparatus according to claim 8, characterized in that: