Abstract:
A light-source driver for a light-source, detachable from an endoscope body includes a first switch, a pilot lamp, a warning lamp, a second switch, and a light switcher. The first switch switches between the On-state and Off-state in connection with the attachment and detachment of the light-source to the endoscope body. The pilot lamp indicates that the illumination light source is energized. The warning lamp indicates that the output voltage of a battery has dropped below a predetermined value. The second switch switches the warning lamp between the On-state and Off-state in connection with the On-state and Off-state of the first switch. The light switcher switches the pilot lamp to the Off-state and enables the second switch when the second switch is set to the On-state and the output voltage has declined to or below the predetermined value.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a light-source driver applied to a battery-powered light-source unit for a portable endoscope where the light-source unit is detachable from the body of the endoscope. 
     2. Description of the Related Art 
     In general, a light-source unit is configured to be detachable from a portable endoscope. A battery is generally used as an electric power source of the light-source unit and a main switch for lighting the light source is provided on the body of the light-source unit. In mounting the light-source unit on the body of the endoscope, the light-source is inserted into the body of the endoscope. Light is emitted from the distal end of the portable endoscope via a light guide arranged in the body of the endoscope when the main switch is turned on and illuminates an object (refer to Japanese Laid-open Patent Publication No. 2003-319906). 
     SUMMARY OF THE INVENTION 
     However, in the conventional structure, if the main switch is left on even after the light-source unit is detached from the body of the portable endoscope, the light source continues emitting light, thus wasting the battery. In particular, if the main switch is left on when storing the portable endoscope after use, the battery will be depleted. 
     Therefore, an object of the present invention is to provide a light-source driver that securely prevents the light source from being left on when the light-source unit is detached from the endoscope body thereby saves electric energy. Furthermore, another aspect of the present invention is to provide a portable endoscope using the above-mentioned light-source driver. 
     According to the present invention, a light-source driver for a light-source unit detachable from the endoscope body of a portable endoscope is provided. 
     The light-source driver includes a first switch, a pilot lamp, a warning lamp, a second switch, and a light-switching block. 
     The first switch switches its status between an On-state and an Off-state in connection with the attachment and detachment of the light-source unit to the endoscope body. The pilot lamp indicates that the illumination light source is being energized. The warning lamp indicates that the output voltage of the battery has dropped to or below a predetermined value. The second switch switches the status of the warning lamp between the On-state and the Off-state in connection with the On-state and the Off-state of the first switch. The light switching block switches the pilot lamp to the Off-state and further enables the second switch when the second switch is set to the On-state and the output voltage has declined to or below the predetermined value. The second switch is set to the Off-state when the light-source unit is detached from the endoscope body. 
     Furthermore, according to another aspect of the present invention, a portable endoscope is provided that includes the above-mentioned light-source driver. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The objects and advantages of the present invention will be better understood from the following description, with reference to the accompanying drawings in which: 
         FIG. 1  is a block diagram that schematically illustrates the structure of an embodiment of the portable endoscope to which the present invention is applied; 
         FIG. 2  is a block diagram of a light-source drive circuit of the present embodiment; and 
         FIG. 3  shows a schematic of a voltage-detecting circuit device. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention is described below with reference to the embodiments shown in the drawings. 
       FIG. 1  is a block diagram that schematically illustrates the structure of an embodiment of a portable endoscope to which the present invention is applied. 
     The portable endoscope  10  is comprised of an endoscope body  11  and a light-source unit  12  which is detachable from the endoscope body  11 . Inside the endoscope body  11 , a light guide  13  and an image guide  14  are arranged. The light guide  13  is for transmitting illumination light to the distal end of the endoscope body  11  and the image guide  14  is for observing an image that is illuminated by the illumination light at the distal end of the endoscope body  11 . 
     One end of the light guide  13 , where light is made incident (the incident end face), is disposed at a manipulating portion of the endoscope body  11 . A lens  15  is arranged in front of the incident end face. When the light-source unit  12  is attached to the endoscope body  11 , light from the light-source unit  12  is concentrated onto the incident end face via the lens  15  and made incident onto the light guide  13 . The other end of the light guide  13 , where light is emitted (the emitting end face), is disposed at the distal end of an insertion portion of the endoscope body  11 . The light incident onto the light guide  13  is transmitted within the light guide  13  and emitted from the emitting end face, and thereby, illuminates a subject through a lens  16 . 
     Furthermore, one end of the image guide  14  is disposed at the distal end of the insertion portion of the endo scope body  11 . The illumination light from the light guide  13  is reflected by the subject and made incident onto the image guide  14  through an objective lens  17 . The other end of the image guide  14  is disposed at the manipulating portion of the endo scope body  11  and an optical image transmitted via the image guide  14  is observed through an ocular lens  18 . 
     The manipulation portion of the endoscope body  11  is provided with a light-source unit connector  11 A for attaching the light-source unit  12 . The light-source unit connector  11 A has a cylindrical shape and a male thread  11 M is provided on the outer surface of the cylinder. At the center of the light-source unit connector  11 A, a cylindrical recessed portion  11 R is provided coaxially with the light-source unit connector  11 A, and the lens  15  is arranged at the bottom of the recessed portion  11 R. The recessed portion  11 R is a void where a light-source portion  12 L of the light-source unit  12  is inserted, as described later. 
     Inside a casing  12 C of the light-source unit  12 , a battery(s)  19  is installed. The positive pole of the battery  19  is connected to a light-source drive circuit  30  (see  FIG. 2 ) provided on a light-source circuit board  22  via a main switch  21 . The negative pole of the battery  19  is connected to the ground of the light-source drive circuit  30 . 
     The light-source drive circuit  30  is provided with a sensor  24  for detecting attachment of the light-source unit  12  onto the endoscope body  11 . An example of the sensor  24  is a push switch that has a pin  25  and a switch  26 . The base end of the pin  25  is connected with the switch  26  and the pin  25  is biased toward the tip end direction by a biasing member such as a spring. Namely, the switch  26  is maintained in the Off-state while an external force other than the biasing force from the spring acts on the pin  25 . When the tip of the pin  25  is depressed against the biasing force of the biasing member, the pin  25  is pushed inward and thus the switch  26  is switched to the On-state. 
     A light source for illumination, such as LED  28  (LED 1 ), is provided on the light-source circuit board  22 . The light source  28  is driven by the light-source drive circuit  30  provided on the light-source circuit board  22 , thus, the lighting of the light source  28  is controlled by the light-source drive circuit  30  and light from the light source  28  is emitted through the illumination lens  29 . Furthermore, a green colored pilot lamp LED 2  and a yellow colored warning lamp LED 3  are also provided on the light-source circuit board  22 . 
     An endoscope connector  12 A is provided on the casing  12 C of the light-source unit  12 . The endoscope connector  12 A is a connector half that is connected to the light-source connector  11 A when attaching the light-source unit  12  to the endoscope body  11 . In this embodiment, the endoscope connector  12 A has as a cylindrical shape with the same diameter as the light-source unit connector  11 A and the outer surface of connector  12 A is provided with a male thread  12 M. In addition, a rotational ring member  12 R with a female thread on the inner surface is engaged with the male thread  12 M. 
     A cylindrical light-source portion  12 L, where the light source  28  and the illumination lens  29  are installed, is provided at the center of the top face of the endoscope connector  12 A and extends out along the axis of the cylindrical endoscope connector  12 A. Furthermore, the push switch, i.e., sensor  24 , is provided on the end face of the endoscope connector  12 A which connects the outer periphery of the endoscope connector  12 A to the base end of the light-source portion  12 L, of which an area is surrounded by the rotational ring member  12 R that is engaged with the male thread  12 M. Moreover, the sensor  24  (push switch) is arranged such that its axis is parallel with the cylindrical axis of the endoscope connector  12 A. 
     When connecting the light-source unit  12  with the endoscope body  11 , the light-source portion  12 L is inserted into the recessed portion  11 R of the light-source unit connector  11 A. The female thread of the rotational ring member  12 R is then manually engaged with the male thread  11 M of the light-source unit connector  11 A. Namely, when the rotational ring member  12 R is rotated, the rotational ring member  12 R is threaded out from the male thread  12 M of the endoscope connector  12 A and at the same time engaged with the male thread  11 M of the light-source unit connector  11 A. Thus, the attachment of the light-source unit  11  to the endoscope body  11  is complete. Note that the endoscope connector  12 A is provided with a stop mechanism (not shown) that prevents the rotational ring member  12 R from coming out of the endoscope connector  12 A. 
     When the light-source portion  12 L of the light-source unit  12  is being inserted into the recessed portion  11 R of the light-source unit connector  11 A, the tip end of the pin  25  abuts on the top face of the light-source unit connector  11 A, which surrounds the recessed portion  11 R. Thereby, the pin  25  is pushed into the casing  12  and the switch  26  is turned on. Incidentally, the switch  26  is kept in the Off-state when the light-source unit  12  is disconnected from the endoscope body  11 , since no force other than the biasing force of the spring acts on the pin  25 . 
     With reference to  FIG. 2 , the structures of the light-source drive circuit  30  of the present embodiment will be explained. 
     The electric power is supplied from the battery (BATT)  19  through the main switch (SW 1 )  21  to the light-source drive circuit  30 . In the light-source drive circuit  30 , a switching regulator U 1  is adopted as a step-up DC-DC converter (a step-up controller), so that the voltage of the battery  19  is raised to a predetermined voltage before it is applied to the light source  28 . 
     The switching regulator U 1 , for example, has the following eight terminals or pins: 
     Pin # 1  (EaIn) is an error amplifier input terminal, at which the application of a voltage controls the pulse-width-modulation (PWM) output from the switching regulator; 
     Pin # 2  (SCP) is a terminal for triggering a soft start and a timer for a short circuit; 
     Pin # 3  (Vcc) is a power supply terminal. An output terminal (pin # 5 ) is fixed at Low when low voltage (e.g., Vcc&lt;1.3V) is input to this terminal in order to prevent an incorrect action of the system; 
     Pin # 4  (BR/CTL) is a break-control terminal for controlling the output current of the output terminal (pin # 5 ) and for setting the ON/OFF state of a standby mode. The standby mode, in which, for example, the power-source current is lower than 1 μA, is set when pin # 4  is opened or connected to Vcc; 
     Pin # 5  (Out) is a Totem-Pole type output terminal and connected to an external power transistor Q 1 ; 
     Pin # 6  (GND) is a ground terminal; 
     Pin # 7  (OSC) is a terminal for setting a PWM frequency by connecting a capacitor C 5  and a resistor R 1  in parallel; and 
     Pin # 8  (FB) is an error amplifier output terminal to which a capacitor C 3  for phase compensation is connected. 
     The step-up DC-DC converter is comprised of the switching regulator U 1 , the power transistor Q 1 , a coil L 1 , capacitors C 1  and C 2 , a Schottky diode D 1 , a switch device Q 2 , and so on. The positive pole of the battery BATT is connected to the DC-DC converter via the main switch SW 1 . When the main switch is set to the On-state, current is supplied to the power-supply terminal, such as pin # 3 , of the switching regulator U 1 , and in turn, the switching regulator U 1  is switched on. 
     The power transistor Q 1  is connected to the output terminal # 5  of the switching regulator U 1  and the base current is supplied from the output terminal # 5 . The output of the output terminal # 5  is controlled by the input voltage of EaIn terminal # 1 . The on-duty ratio of the output terminal # 5  is set higher when the input voltage of the EaIn terminal # 1  drops. Namely, as the input voltage of the EaIn terminal # 1  drops, the period in one cycle during which the base voltage of the power transistor Q 1  is set to high (i.e., where the power transistor Q 1  is set to the On-state) is elongated. 
     The output terminal of the DC-DC converter is connected to the anode of the LED 1  (the light source  28 ) and the output voltage Vout is applied to the anode of the LED 1 . The cathode of the LED 1  is connected to the ground via a resistor R 3  and the switch device Q 5 , as well as, to the EaIn terminal # 1  of the switching regulator U 1  through a resistor R 8 . Namely, the voltage of the cathode of the LED 1  is monitored by the EaIn terminal # 1  and the power transistor Q 1  is driven by a high on-duty ratio when the voltage of the cathode of the LED 1  drops. 
     According to the above structures, the voltage of the battery BATT is raised by the DC-DC converter on the basis of the principle of a step-up converter. Thereby, the switching regulator U 1  controls the output voltage Vout such that the current of LED 1  is maintained constant. 
     Furthermore, in the present embodiment, a switch device Q 2  is connected to the BR/CTL terminal # 4  of the switching regulator U 1 . An example of the switch device Q 2  is a semiconductor device, such as a resistor-built-in transistor which could be a bipolar transistor or an MOS transistor. The BR/CTL terminal # 4  is connected to the collector terminal of the switch device Q 2  via a resistor R 2 . The emitter terminal of the switch device Q 2  is connected to ground. Furthermore, the base terminal to control the On/Off state of the switch device Q 2  is connected to the power-source line via a built-in resistor and the switch SW 2  ( 26 ), which switches in connection with the attachment of the light-source unit  12  to the endoscope body  11 . 
     Namely, if switch SW 2 , such as a push switch, is switched on when the main switch SW 1  is in the On-state, i.e., when the light-source unit  12  is attached to the endoscope body  11 , the switch device Q 2  is switched on, and thus the BR/CTL terminal # 4  of the switching regulator U 1  is connected to ground via the resistor R 2 . On the other hand, even when the main switch SW 1  is on, the switch device Q 2  is set to the Off-state when the switch SW 2  is switched off and thus the BR/CRT terminal # 4  is opened, and in turn, the switching regulator U 1  is set to the standby mode. 
     According to the above-described structures, the LED 1  (light source  28 ) is prevented from being left on even when the light-source unit  12  is detached from the endoscope body  11  while the main switch SW 1  is left in the On-state. This is because the switch SW 2  of the sensor  24  (push switch) is set to the Off-state when the light-source unit  12  is detached from the endoscope body  11 , and thereby the switching regulator U 1  is set to the standby mode. Furthermore, the present embodiment has the advantage of reducing the size of the light-source unit  12 , since the current that flows in the switch SW 2  is reduced thus allowing the use of simpler switch SW 2 . 
     Moreover, abnormally high voltage caused by chattering of the switch SW 2 ( 26 ) induced while attaching and detaching the light-source unit  12  to the endoscope body  11  is prevented, and thus the circuit is kept safe, since the switch SW 2  is not connected to the coil L 1  in series. 
     Note that a resistor R 8  and a Zener diode D 2  are provided for protecting from over-voltage when an LED load is opened. Namely, when a feedback loop by the LED 1  is opened, a feedback loop via the Zener diode D 2  is activated, and thus destruction of the coil L 1  and the switching regulator U 1  is prevented. In the present embodiment, the description applied to the case of one LED being used, as well as to the case of a plurality of LEDs being used. 
     The light-source drive circuit  30  of the present embodiment also includes the green pilot lamp LED 2  and the yellow warning lamp LED 3 . The pilot lamp LED 2  is lit when the light-source drive circuit  30  is being energized and the warning lamp LED 3  is lit when the voltage of the battery BATT drops to a certain level. 
     The anode of the pilot LED 2  is connected to the output terminal (Vout) of the DC-DC converter, and the cathode is connected to ground via a resistor R 11  and a switch device Q 3 . Furthermore, the anode of the warning lamp LED 3  is also connected to the output terminal of the DC-DC converter just as the LED 2 , while the cathode of the warning lamp LED 3  is connected to the voltage-detecting circuit device U 2  via a resistor R 4  and a switch device Q 4 . 
     The voltage-detecting circuit device U 2  monitors the output voltage of the battery BATT while it also acts as a switch circuit that connects the cathode of the warning LED 3  when the output voltage drops to or below a predetermined value. Thereby, the warning lamp LED 3  is lit when the remaining electric power of the battery BATT is low and the output voltage decreases. 
     Both switch device Q 3  (which is provided between the resistor R 11  connected to the cathode of the pilot lamp LED 2  and ground) and the switch device Q 4  (which is provided between the resistor R 4  connected to the cathode of the warning lamp LED 3  and the voltage-detecting circuit device U 2 ) may be semiconductor devices, such as a resistor-built-in transistor which could be a bipolar transistor or an MOS transistor. 
     The switch device Q 4  is a switch for preventing the warning lamp LED 3  from being lit when the battery voltage drops to the level at which the warning lamp LED 3  is set to light but the DC-DC converter is in the Off-state because the switch SW 2  is in Off-state. 
     Namely, without the switch device Q 4 , the warning lamp LED 3  is lit if the main switch is set to the On-state even when the light-source unit  12  has been detached from the endoscope body  11 , i.e., the switch SW 2  is Off, and the DC-DC converter is in the Off-state, since the output side of the DC-DC converter is connected to the battery BATT through the coil L 1 . As for the warning lamp LED 3 , the lighting is suppressed if it has a high forward voltage drop VF. However, the VF of a color LED is generally low, therefore the switch device Q 4  is required. 
     The switch device Q 4  may be a device including a bipolar transistor. The collector terminal of the transistor is connected to a resistor R 4  and the emitter terminal is connected to the output terminal (the OUT terminal) of the voltage-detecting circuit device U 2 . Furthermore, the base terminal is connected to the switch SW 2  via a built-in resistor. Thereby, the switch device Q 3  is switched on only when the switch SW 2  is in the On-state. Therefore, lighting of the warning lamp LED 3  while the switch SW 2  is in the Off-state is prevented since the warning lamp LED 3  is opened when the switch SW 2  is in the Off-state. 
     The switch device Q 3  is a switch to turn off the pilot lamp LED 2  when the warning lamp LED 3  is turned on. Namely, if the warning lamp LED 3  is lighted, the lit of the pilot lamp LED 2  is not necessary, so that the lamp which is lit switches from the pilot lamp LED 2  to the warning lamp LED 3  to eliminate unnecessary electric consumption. 
     The switch device Q 3  may be a device including an MOS transistor, and the drain terminal is connected to the resistor R 11  and the source terminal is connected to ground. Furthermore, the gate terminal is connected to the emitter terminal of the switch device Q 4  via a built-in resistor. 
     When the battery voltage drops below a predetermined level and the output terminal (OUT terminal) of the voltage-detecting circuit device U 2  is set to low (i.e., when the emitter terminal of the switch device Q 4  is connected to ground), the gate terminal of the switch device Q 3  is set to low and the switch device Q 3  is switched to the Off-state. Thus, the pilot lamp LED 2  is turned off. At the same time, the cathode of the warning lamp LED 3  is connected to ground so that the warning lamp LED 3  turns on. 
     Operation of the voltage-detecting circuit device U 2  will be explained with reference to  FIG. 3  which shows a schematic of the voltage detecting circuit device U 2 . A standard voltage-generating circuit  31  is provided with the voltage-detecting circuit device U 2 . For example, the standard voltage-generating circuit  31  outputs 2.3 V as a standard voltage. This standard voltage and the voltage (V DD -V SS ) between the positive pole and the negative pole of the battery BATT which is split by the resistance ratio, are input to a comparator  32 . The comparator  32  compares the values of the input voltages and determines whether the output voltage of the battery BATT is lower than the standard voltage (here, 2.3 V). 
     When the voltage in which the split voltage of the battery BATT is lower than the standard voltage, the comparator  32  applies a high voltage to the gate terminal of an N-channel FET  33 . Namely, when the output voltage of the battery BATT declines to a level below the predetermined voltage, the split voltage declines to a level lower than the standard voltage, thus the gate terminal of the N-channel FET  33  is set at a high level and current flows between the drain and the source. 
     Thus, the cathode of the warning lamp LED 3  is connected to the ground via the resistor R 4  and the switch device Q 4  when the switch device Q 4  is in the On-state, and in turn, the warning lamp LED 3  is lit. Furthermore, at this time, the gate terminal of the switch device Q 3  is switched to the low level and the switch device Q 3  is switched off, thus turning off the pilot lamp LED 2 . Namely, the lighting of the LED switches from the pilot lamp LED 2  to the warning lamp LED 3 . 
     In the present embodiment, a switch device Q 5  is provided between ground and the resistor R 3 , which is used to monitor the current of the illumination LED 1 . Just as with the switch devices Q 2 -Q 4 , the switch device Q 5  may be a semiconductor device such as a resistor-built-in transistor which could be a bipolar transistor or an MOS transistor. In the present embodiment, for example, the switch device Q 5  is a device including an MOS transistor and its drain terminal is connected to the resistor R 3 , and the source terminal is connected to ground. Furthermore, the gate terminal is connected to the switch SW 2  via a built-in resistor. 
     The switch device Q 5  is a switch to prevent the illumination LED 1  from lighting when the light-source unit  12  is detached from the endoscope body  11  despite switch SW 2  being in the Off-state and the DC-DC converter being in the Off-state. Namely, if the switch device Q 5  is not employed, the illumination LED 1  is lit when the main switch SW 1  is in the On-state while the battery voltage is maintained at a high level, since the output terminal of the DC-DC converter is connected to the battery BATT through the coil L 1 . 
     The lighting of the illumination LED 1  during the Off-state of switch SW 2  can be prevented if a plurality of LEDs is provided as a multi-level circuit to configure the illumination light-source. However, this increases the number of parts, cost, and heat generation, and reduces the efficiency of the circuit, thus it is not preferable. Therefore, in the present embodiment, the switch device Q 5  is provided between ground and the illumination LED 1  current-monitoring resistor R 3 , and the gate terminal is connected to the switch SW 2  via the built-in resistor. Thus, when the switch SW 2  is in the Off-state, the switch device Q 5  is set to the Off-state and the cathode of the illumination LED 1  is opened. 
     Accordingly, when the light-source unit  12  is detached from the endoscope body  11 , i.e., when the switch SW 2  is in the Off-state, the lighting of the illumination LED 1  is securely prevented. 
     As described above, according to the present embodiment, wasteful lighting of the illumination light source and the warning lamp is prevented when the light-source unit is detached from the endoscope body by implementing this simple configuration. Furthermore, the lighting of the pilot and warning lamps are mutually exclusive, thus electric waste is further prevented. 
     Although the embodiment of the present invention has been described herein with reference to the accompanying drawings, obviously many modifications and changes may be made by those skilled in this art without departing from the scope of the invention. 
     The present disclosure relates to subject matter contained in Japanese Patent Application No. 2006-342152 (filed on Dec. 20, 2006), which is expressly incorporated herein, by reference, in its entirety.