JP5159050B2 - Display circuit for portable endoscope - Google Patents

Description

  The present invention relates to a display circuit for a portable endoscope using a battery, and more particularly, to a display circuit for displaying and warning a low battery level of a portable endoscope.

  In a portable endoscope (such as a fiberscope), a battery is used as a power source. In general, a portable endoscope has a warning display function for notifying that the remaining battery level is low and for prompting battery replacement in order to prevent the battery from running out while observing the subject. Have. In order to inform the endoscope operator of the decrease in the remaining battery level, a light emitting element such as an LED that is controlled to emit light only when the battery voltage falls below a predetermined reference is used. A light emitting element such as an LED usually emits light using a current based on an input voltage from a battery.

In addition, in order to observe a subject in a dark body, an illumination light source may be provided at the distal end of the scope of the endoscope apparatus. As this light source, it is known to use an LED or the like (see, for example, Patent Document 1). In order to use a light source for illumination, even if the voltage of the battery changes, the current flowing to the LED is stabilized, the brightness to be illuminated is stabilized, and a larger current is passed to the LED to stabilize the illumination. Since a high voltage is required to increase the brightness, a booster circuit is generally used.
Japanese Patent No. 3315809 (see paragraphs [0013] and [0014], FIG. 3)

  An LED or the like for informing a decrease in the remaining battery level due to long-term use or the like emits light with a current due to an input voltage from the battery. For this reason, the LED or the like emits light by the already lowered voltage, and the brightness of the light is lowered, and the warning display may become unclear.

  An object of the present invention is to provide a display circuit that uses a booster circuit to reliably notify a decrease in the remaining battery level.

  The first display circuit of the present invention is a display circuit connected to a boosting unit that boosts an input voltage input from a battery to obtain a predetermined boosted voltage. The first display circuit includes a voltage determining unit that determines whether or not the input voltage is lower than a predetermined reference voltage, a display unit that emits light when a current is supplied, and a voltage determining unit. Current control means for controlling the current to be supplied to the display means based on a predetermined boosted voltage when it is determined that the voltage is lower than the voltage.

  The boosting unit includes, for example, a DC / DC converter. The DC / DC converter preferably operates by a step-up converter method. The display means is preferably an LED. The current control means preferably supplies current to the display means so that the display means can be recognized from outside the endoscope apparatus in order to indicate that the input voltage is lower than a predetermined reference voltage. The current control means includes, for example, an n-channel FET.

  Further, the display circuit is supplied with a current based on a predetermined boosted voltage, so that the bright light emitting means for emitting illumination light includes a plurality of LEDs, the plurality of LEDs are connected in series, and a power supply to the display means is provided. It is preferable that the supply is performed from a node where the anode terminal of the lower LED in the plurality of LEDs and the cathode terminal of the upper LED are connected.

  The lower LED is preferably the lowermost LED. Further, the display circuit includes, for example, an LED as a pilot light source that displays the lighting of the illumination emitting means, and the anode power terminal of the lower LED and the cathode terminal of the upper LED are connected to the pilot light source. This is preferably done from connected nodes.

  An endoscope apparatus according to the present invention includes a first display circuit. The endoscope apparatus preferably has illumination light emitting means for emitting illumination light when supplied with a current based on a predetermined boosted voltage. And it is more preferable that an illumination light emission means contains LED.

  The second display circuit of the present invention includes a voltage determining unit that determines whether or not an input voltage input from a battery is lower than a predetermined reference voltage, a display unit that emits light when a current is supplied, and a display unit. And a current control means for controlling the current supply from the power supply to the display means when the voltage judgment means judges that the input voltage is lower than the reference voltage.

  ADVANTAGE OF THE INVENTION According to this invention, the display circuit for alert | reporting reliably the fall of battery remaining charge using a booster circuit can be provided.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a portable endoscope apparatus (fiber scope) in the first embodiment.

  First and second LEDs 14 and 16 for illuminating the subject S and first and second light distribution lenses 18 and 20 are provided at the tip of the fiberscope 10. The first and second LEDs 14 and 16 emit illumination light to the subject S by the power supplied from the battery 12 under the control of the lighting drive unit 20. The reflected light of the illumination light reflected on the surface of the subject S enters the operator's eyes via the objective lens 22, the light guide 24, and the eye lens 26. Thus, the subject S is observed by the operator.

  On the surface of the main body (portion held by the operator) of the fiberscope 10, a battery remaining amount warning lamp 28 is provided. The battery level warning lamp 28 includes a warning LED (not shown). The warning LED automatically turns on when the voltage of the battery 12 decreases due to long-term use or the like in order to inform the operator that the remaining battery level is low.

  FIG. 2 is a circuit diagram illustrating a power supply circuit, an illumination lighting circuit, and a display circuit provided in the lighting driving unit 20. FIG. 3 is a circuit diagram showing the display circuit. FIG. 4 is a circuit diagram showing a conventional display circuit.

  The lighting drive unit 20 is provided with a power supply circuit 30, an illumination lighting circuit 50, and a display circuit 60. The power supply circuit 30 includes a step-up DC / DC converter IC 32, a transistor 42, and the like, and includes a DC / DC converter provided in the step-up DC / DC converter IC 32 for boosting a voltage input from the battery 12. , Switch 38, capacitor 40, coil 44, Schottky diode 46, and smoothing capacitor 48. The illumination lighting circuit 50 is provided with two series of LEDs, that is, the first and second LEDs 14 and 16, and the first resistor 45. The display circuit 60 is provided with a warning LED 34, a display drive circuit 36, and a second resistor 58.

  Then, when the voltage input from the battery 12 is boosted by the DC / DC converter and the generated boosted voltage is applied to the anode terminal of the first LED 14, the first and second LEDs 14, 16 emit currents so as to emit illumination light. Flows. This current is monitored by a first resistor 45 connected to the first node 39. Then, the DC / DC converter IC 32 operates so that a constant current always flows through the first node 39.

  The battery 12 supplies a voltage of 3.5 (V) to the DC / DC converter block immediately after the start of use, for example, if it is a lithium battery. descend. When the input voltage of the battery 12 falls below a predetermined voltage, the OUT terminal of the display drive circuit 36 provided in the display circuit 60 is switched so that a current flows through the warning LED 34, and the warning LED 34 is lit. .

  When the switch 38 is turned on, a current is supplied to the third terminal 32C of the DC / DC converter IC 32 via the second node 41. The DC / DC converter IC 32 supplies a base current to the transistor 42 connected to the fifth terminal 32E. Here, during the active period of the drive voltage that the DC / DC converter IC 32 supplies to the transistor 42 via the fifth terminal 32E, that is, the period when the terminal is HI, at the first node 39 detected by the first terminal 32A. It is variable according to the voltage. That is, as the voltage at the first node 39 is lower, the fifth terminal 32E extends the period during which the base terminal voltage per unit time is HI, and the on-time of the transistor 42 is increased. As a result, according to the principle of the step-up converter, the voltage at the first node 39 and the voltage supplied to the first and second LEDs 14 and 16 are kept constant.

  Between the second node 41 and the third node 43, a coil 44 that performs a step-up inductor as a step-up inductor is provided, and between the third node 43 and the first LED 14, a reverse current is prevented. Schottky diode 46 and a smoothing capacitor 48 for smoothing the current are provided.

  Next, the operation of the display drive circuit 36 will be described (see FIG. 3). The display drive circuit 36 is provided with a reference voltage generation circuit 52. The reference voltage generation circuit 52 generates a reference voltage of 2.3 (V), for example. A voltage obtained by dividing the reference voltage and the input voltage input from the battery 12 by the resistance ratio is input to the comparator 54. The comparator 54 compares the levels of these voltages and determines whether or not the input voltage from the battery 12 is lower than the reference voltage 2.3 (V).

  When the comparator 54 determines that the voltage obtained by resistance-dividing the voltage of the battery 12 is lower than the reference voltage, the comparator 54 applies a voltage of HI to the gate of the n-channel FET 56. For this reason, when the voltage obtained by resistance-dividing the input voltage of the battery 12 is lower than the reference voltage, the voltage at the output terminal of the comparator 54 increases, the voltage at the gate of the n-channel FET 56 increases, and the drain, source Current flows between them. As a result, a current flows through the second resistor 58 to the warning LED 34 connected to the n-channel FET 56, and the warning LED 34 is lit.

  Thus, in the display circuit 60 in the present embodiment, the warning LED 34 is caused to emit light using the current obtained through the resistance from the boosted voltage for light emission of the first and second LEDs 14 and 16. That is, not the current due to the voltage directly input from the battery 12 but the current is supplied to the warning LED 34 through the second resistor 58 from the voltage boosted by the control of the power supply circuit 30.

  Therefore, even when the voltage of the battery 12 decreases, as long as the power supply circuit 30 operates, current is supplied from the boosted voltage to the warning LED 34 via the second resistor 58. For this reason, since sufficient current can be supplied to the warning LED 34, the warning LED 34 emits bright light, and the battery remaining amount warning lamp 28 can reliably notify the operator of the voltage drop of the battery 12. In the present embodiment, the DC / DC converter operates when, for example, a voltage of 2.0 (V) or more is supplied from the battery 12.

  On the other hand, like the conventional display circuit 61 shown in FIG. 4, while the illumination lighting circuit 50 is driven by the voltage obtained by boosting the input voltage from the battery 12 by the power supply circuit 30, the warning LED 34 is connected to the battery. 12, when light is emitted directly using the current obtained from the input voltage from the battery 12 via a resistor, the luminance of the light is reduced due to a decrease in the amount of current accompanying a decrease in the input voltage. . For this reason, when the warning LED 34 emits light in order to notify that the remaining amount of the battery 12 is low, the current flowing through the warning LED 34 is small, and a warning display with low-luminance light is recognized by the operator. There is a risk that it will not be.

  FIG. 5 is a diagram showing the change with time of the input voltage of the battery 12. FIG. 6 is a diagram showing a change with time of the voltage output from the power supply circuit 30. FIG. 7 is a diagram showing the change with time of the voltage at the output terminal OUT of the display drive circuit 36 when the voltage of the battery 12 changes with time as in FIG.

  The voltage input by the battery 12 decreases as the use time t elapses from 3.5 (V) at the use time t = 0, which is the use start time. When the input voltage from the battery 12 is 2.0 (V) or higher, the DC / DC converter operates, so the voltage output from the DC / DC converter is about 7.5 (V), for example. It is constant (see FIG. 6). When the input voltage from the battery 12 falls below 2.0 (V), the DC / DC converter does not operate because it falls below the lower limit voltage at which the DC / DC converter IC 32 can operate, and the voltage supplied from the battery 12 Is directly output via the coil 44, the Schottky diode 46, the second resistor 58, and the like. At this time, since the display circuit 50 is switched to turn on the warning LED 34, the warning LED 34 can be turned on.

  When the input voltage drops below the reference voltage of 2.3 (V), the n-channel FET 56 of the display drive circuit 36 is turned on, and the voltage at the output terminal OUT drops (see FIG. 7). As a result, a current corresponding to the voltage drop is supplied to the warning LED 34, and the warning LED 34 emits light. How the luminance of the light from the warning LED 34 changes in the display circuit 60 as the input voltage from the battery 12 shown in FIGS.

  FIG. 8 is a diagram showing the luminance of light emitted from the warning LED 34 corresponding to the current flowing through the warning LED 34 in the conventional display circuit 61 when the power supply from the battery 12 is directly used. FIG. 9 is a diagram showing the luminance of light emitted from the warning LED 34 in the display circuit 60 in FIG.

  When the input voltage of the battery 12 indicated by the one-dot chain line in FIGS. 8 and 9 is equal to or higher than the reference voltage 2.3 (V), both in the conventional circuit (see FIG. 4) and in the display circuit 60 of the present embodiment. The warning LED 34 does not emit light. When the input voltage of the battery 12 gradually decreases from the reference voltage 2.3 (V), in the conventional display circuit 61, the luminance of the light from the warning LED 34 is the reference voltage 2.3 (V ) Gradually decreases in proportion to the input voltage from a luminance level proportional to (hereinafter referred to as level 1). On the other hand, the warning LED 34 in the display circuit 60 is supplied with a stable voltage that is proportional to the output voltage of the DC / DC converter (see FIG. 6) and significantly higher than level 1, so that it is large as a result. The current value can be stably supplied, and light having a constant high luminance level can be emitted (see FIG. 9).

  When the input voltage of the battery 12 is reduced to 2.0 (V), the DC / DC converter does not operate in any of the display circuits 60 and 61. Therefore, the voltage supply from the DC / DC converter is stopped, and the warning LED 34 The luminance of the emitted light becomes a luminance level (hereinafter referred to as level 2) proportional to the input voltage of 2.0 (V) via the coil 44, the Schottky diode 46, the second resistor 58, and the like. When the input voltage further decreases, the luminance of light from the warning LED 34 further decreases according to the input voltage.

  As described above, the luminance of the light emitted from the warning LED 34 in the conventional display circuit 61 continues to decrease from level 1 to level 2 or less regardless of whether the DC / DC converter operates. On the other hand, the light emitted from the warning LED 34 in the display circuit 60 has a luminance level significantly higher than level 1 until the DC / DC converter stops operating.

  As described above, according to the present embodiment, the warning LED 34 emits high-luminance light immediately before the DC / DC converter can no longer operate, and during the period when there is the highest need to notify the input voltage drop of the battery 12. Therefore, it is possible to reliably notify the operator of a decrease in the remaining battery level.

  Further, since the boosted voltage is used for the power supply, the resistance value of the second resistor 58 can be set to a large value. Thereby, the change of the current value with respect to the fluctuation of the power supply voltage can be suppressed to be small, and the luminance change of the light source can be stabilized.

  In this embodiment, the DC / DC converter operates when a voltage of 2.0 (V) or higher is supplied, so the reference voltage is set to 2.3 (V), which is slightly higher than 2.0 (V). Although set, the magnitude of the reference voltage can be adjusted according to the magnitude of the minimum input voltage required for operating a circuit used for boosting, such as a DC / DC converter.

  FIG. 10 is a circuit diagram illustrating a power supply circuit, an illumination lighting circuit, and a display circuit in the second embodiment. In FIG. 10, the same components as those in the first embodiment are denoted by the same reference numerals.

  In the display circuit 70 of the present embodiment, the warning LED 34 is connected to the battery 12 in parallel with the DC / DC converter, and the display power supply 35 for the warning LED 34 is provided. This is different from the display circuit 60 of the first embodiment. When the input voltage of the battery 12 falls below the reference voltage of 2.3 (V), the current from the display power supply 35 is supplied to the warning LED 34 instead of from the battery 12 under the control of the display drive circuit 36. The warning LED 34 is lit.

  Therefore, in this embodiment, even when the input voltage of the battery 12 decreases to 2.0 (V) or less and the DC / DC converter does not operate, the luminance of the light from the warning LED 34 is set to the level 2 described above. It can be maintained above. For this reason, also in the display circuit 70, the fall of a battery remaining charge can be alert | reported reliably.

  FIG. 11 is a circuit diagram showing a power supply circuit, an illumination lighting circuit, and a display circuit in the third embodiment. The third embodiment will be described with reference to FIG. In FIG. 11, the same reference numerals are used for the same components as those in the first embodiment, and the description thereof is omitted.

  In the first embodiment, the lighting power of the warning LED 34 is supplied from the uppermost stage of the illumination LEDs (14, 16), that is, from the input terminal of the illumination lighting circuit 50. However, in this embodiment, the illumination LED is used. Are connected to the warning LED 34 from the node 80 corresponding to the connection point of the lowermost LED 16 and the upper LED 14 in the potential order. That is, the lighting power to the warning LED 34 is supplied from the position where the anode terminal of the lowermost illumination LED 16 and the cathode terminal of the upper illumination LED 14 are connected.

  Thereby, in addition to the effect of the first embodiment, it is possible to prevent a high voltage from being applied to the warning LED 34 even when the number of stages of LEDs for illumination is increased and the brightness is increased. Further, the warning LED 34 does not need to flow as much current as that of the lighting LED (lighting LED current value >> warning LED current value), so that the warning LED is sufficiently bright even in such a configuration. And the original brightness of the illumination LED is not impaired.

  Therefore, there is no limit to the number of stages of the illumination LEDs, and it is possible to increase the brightness, stabilize the voltage of the warning LED, and keep the brightness constant. Practically, it is possible to supply the warning LED power from a position where it can withstand pressure, such as one level higher than the position of the present embodiment, but the safety coefficient is based on the lowest level. It is preferable that

  Next, FIGS. 12 and 13 show a modification of the third embodiment. FIG. 12 is a block diagram of the portable endoscope apparatus 100 in the present modification, and FIG. 13 is a circuit diagram showing a power supply circuit, an illumination lighting circuit, and a display circuit in the modification. In the present modification, a pilot LED 82 that indicates lighting of the illumination LED is added. As shown in the figure, the lighting power is supplied from the node 80 to the pilot LED 82 via the resistor 84.

  FIG. 14 shows an on / off state of the pilot LED 82 due to a change in the voltage of the battery 12 over time. As shown in the figure, the pilot LED 82 is turned off when the voltage of the battery 12 falls below 2.0 (V) and the DC / DC converter is turned off.

  As described above, also in this modified example, the same effect as that of the third embodiment can be obtained, and the lighting state of the LED for illumination can be confirmed.

  In any of the embodiments, a lamp may be used in place of the first and second LEDs 14 and 16 or the warning LED 34 which are light sources for subject illumination. The number and arrangement of the light sources are not limited to the first and second embodiments. For example, one light source may be used for illumination, or two illumination light sources may be arranged in parallel.

  In any embodiment, the first and second LEDs 14 and 16 for subject illumination are, for example, white LEDs. In this case, since the forward voltage becomes high in the white LED, it is particularly preferable to use a current obtained from the boosted voltage.

  The power supply circuit 30 and the display circuits 60 and 70 can be configured by general-purpose elements. For example, “TK11840L” manufactured by “Toko Co., Ltd.” can be used as a DC / DC converter.

It is a block diagram of the portable endoscope apparatus in a 1st embodiment. It is a circuit diagram which shows the power supply circuit, illumination lighting circuit, and display circuit in 1st Embodiment. It is a circuit diagram which shows a display circuit. It is a circuit diagram which shows the conventional display circuit. It is a figure which shows the time-dependent change of the input voltage of a battery. It is a figure which shows the time-dependent change of the voltage output from a power supply circuit. It is a figure which shows the time-dependent change of the voltage in the output terminal of a display drive circuit. It is a figure which shows the brightness | luminance of the light which warning LED light-emits in the conventional display circuit. In the display circuit in 1st Embodiment, it is a figure which shows the brightness | luminance of the light which LED for warning light-emits. It is a circuit diagram which shows the power supply circuit, illumination lighting circuit, and display circuit in 2nd Embodiment. It is a circuit diagram which shows the power supply circuit, illumination lighting circuit, and display circuit in 3rd Embodiment. It is a block diagram of the portable endoscope apparatus in the modification of 3rd Embodiment. It is a circuit diagram which shows the power supply circuit, illumination lighting circuit, and display circuit in the modification of 3rd Embodiment. It is a figure which shows the on / off state of the light which pilot LED light-emits in the display circuit of a modification.

Explanation of symbols

10 Fiberscope (endoscope device)
12 battery 14 1st LED (illumination light emitting means / LED)
16 Second LED (illumination light emitting means / LED)
32 DC / DC converter IC (Boosting means)
34 Warning LED (Display means / LED)
35 Power supply for display (power supply)
36 Display drive circuit (voltage judgment means / current control means)
52 Reference Voltage Generation Circuit 54 Comparator (Voltage Judgment Unit)
56 n-channel FET (current control means)
60 Display circuit

Claims (9)

A boosting unit that boosts the input voltage from the battery to a predetermined boosted voltage and supplies power to the illumination light source, a warning light source connected in parallel with the illumination light source,
Voltage determining means for determining whether or not the input voltage is lower than a reference voltage;
When the voltage determining means determines that the input voltage is higher than the reference voltage, the current flowing through the warning light source is interrupted to keep the warning light source off, and the input voltage is higher than the reference voltage. when it is determined also low, and a current control means for lighting the warning light source supplying a current to the warning light from said boosting means,
The illumination light source includes a plurality of LEDs connected in series, and the supply of current from the booster to the warning light source is the anode terminal of the lower LED in the plurality of LEDs and the immediate upper side thereof A display circuit comprising a node connected to the cathode terminal of the LED . The display circuit according to claim 1 , wherein the lower LED is a lowermost LED. The display circuit further includes an LED as a pilot light source for displaying the lighting of the illumination light source, and the current supply from the boosting means to the pilot light source is the anode terminal of the lower LED and the upper side The display circuit according to claim 2 , wherein the display is performed from the node to which the cathode terminal of the LED is connected.   The display circuit according to claim 1, wherein the boosting unit includes a DC / DC converter. The display circuit according to claim 4 , wherein the DC / DC converter operates by a step-up converter system. The display circuit according to claim 1, wherein the warning light source is an LED. Wherein said current control means, the input voltage is to show that less than the predetermined reference voltage, wherein said warning light source to supply a current to the warning light source so that it can be recognized from the outside Item 4. The display circuit according to Item 1.   The display circuit according to claim 1, wherein the current control unit includes an n-channel FET.   An endoscope apparatus comprising the display circuit according to claim 1.

Images