Abstract:
A drive control circuit ( 100 ) performs drive control of a plurality of loads ( 111, 112 ) having different operating characteristics. The drive control circuit includes a plurality of connectors ( 106, 107 ) for connecting with the plurality of loads, a control portion ( 101 ) that supplies drive control signals to the plurality of loads via first electrodes of the plurality of connectors, and a comparing portion ( 110 ) that compares certain characteristic values at second electrodes concerning certain characteristics of signals applied to the first electrodes of the plurality of connectors and supplies a result of the comparison to the control portion, so that the drive control signals are decided in accordance with the result of the comparison.

Description:
This application is based on Japanese Patent Application No. 2006-252175 filed on Sep. 19, 2006, and the contents of which are hereby incorporated by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a drive control circuit, in particular a drive control circuit for performing drive control of a plurality of loads. The present invention also relates to a projection apparatus equipped with such a drive control circuit. 
   2. Description of Related Art 
   A projection apparatus has an optical system made up of a lamp to be a light source, a polarizing beam splitter, a polarizing plate, a liquid crystal panel and the like, an it has a problem of heat generated from the optical system. Therefore, a usual projection apparatus has a fan for cooling the entire optical system by letting air in the apparatus flow, and a drive control circuit for performing drive control of the fan, in order to deal with the generated heat. 
   Recently, there is widespread a projection apparatus having a plurality of fans and a drive control circuit for performing drive control of the plurality of fans for a purpose of securing a sufficient cooling effect, improving the cooling effect or reducing a noise.  FIG. 4  shows an example of a drive control circuit for performing drive control of a plurality of fans provided to a conventional projection apparatus. 
     FIG. 4  is a block diagram to show a general structure of the drive control circuit  900 . The drive control circuit  900  includes a microcomputer  901 , a first PWM conversion portion  902 , a second PWM conversion portion  903 , a first driver  904 , a second driver  905 , a first connector  906 , a second connector  907 , a first detecting portion  908  and a second detecting portion  909 . Here, the first connector  906  is a connector for connecting to a first fan  910 , while the second connector  907  is a connector for connecting to a second fan  911 . 
   The microcomputer  901  is connected to the first PWM conversion portion  902  and the second PWM conversion portion  903 . The first PWM conversion portion  902  is connected to the first driver  904 , while the second PWM conversion portion  903  is connected to the second driver  905 , respectively. The first driver  904  is connected to a plus terminal of the first connector  906 , while the second driver  905  is connected to a plus terminal of the second connector  907 , respectively. In addition, a minus terminal of the first connector  906  is connected to the first detecting portion  908 , while a minus terminal of the second connector  907  is connected to the second detecting portion  909 , respectively. Furthermore, the first detecting portion  908  and the second detecting portion  909  are connected to a terminal T 91  of the microcomputer  901 . 
   In the drive control circuit  900  having the structure described above, the microcomputer  901  delivers a control signal S 1  to the first PWM conversion portion  902  for performing drive control of the first fan  910  and delivers a control signal S 2  to the second PWM conversion portion  903  for performing drive control of the second fan  911 . Furthermore, the first PWM conversion portion  902  performs PWM conversion on the control signal S 1  and delivers an obtained signal to the first driver  904 . In addition, the second PWM conversion portion  903  performs PWM conversion on the control signal S 2  and delivers an obtained signal to the second driver  905 . 
   The first driver  904  delivers a drive control signal to the first fan  910  via the plus terminal of the first connector  906  based on a signal from the first PWM conversion portion  902 . In addition, the second driver  905  delivers a drive control signal to the second fan  911  via the plus terminal of the second connector  907  based on a signal from the second PWM conversion portion  903 . 
   The first detecting portion  908  includes an operational amplifier  912  having a non inverting input terminal that is connected to a minus terminal of the first connector  906 , an inverting input terminal to which a reference voltage is applied and an output terminal that is connected to the terminal T 91  of the microcomputer  901 , and a resistor R 91  having one end that is connected to the minus terminal of the first connector  906  and the other end that is connected to the ground. In addition, the second detecting portion  909  includes an operational amplifier  913  having a no inverting input terminal that is connected to the minus terminal of the second connector  907 , an inverting input terminal to which a reference voltage is applied and a output terminal that is connected to the terminal T 91  of the microcomputer  901 , and a resistor R 92  having one end that is connected to the minus terminal of the second connector  907  and the other end that is connected to the ground. 
   In this case, if the first fan  910  is not connected to the first connector  906  or if the first driver  904  does not deliver the drive control signal to the first fan  910 , no current flows in the minus terminal of the first connector  906 . Therefore, the output terminal of the operational amplifier  912  delivers an L-level signal. In addition, if the first fan  910  is connected to first connector  906  and if the first driver  904  delivers the drive control signal to the first fan  910 , current flows in the minus terminal of the first connector  906 . Therefore, the output terminal of the operational amplifier  912  delivers an H-level signal. 
   In the same manner, if the second fan  911  is not connected to the second connector  907  or if the second driver  905  does not deliver the drive control signal to the second fan  911 , current does not flow in the minus terminal of the second connector  907 . Therefore, an L-level signal is delivered from the output terminal of the operational amplifier  913 . In addition, if the second fan  911  is connected to the second connector  907  and if a drive control signal is delivered from the second driver  905  to the second fan  911 , current flows in the minus terminal of the second connector  907 . Therefore, an H-level signal is delivered from the output terminal of the operational amplifier  913 . 
   For this reason, if the signal supplied to the terminal T 91  is an L-level signal, the microcomputer  901  detects that the first fan  910  is not connected to the first connector  906 , or that the drive control signal is delivered from the first driver  904  to the first fan  910 , or that the second fan  911  is connected to the second connector  907 , or that the drive control signal is delivered from the second driver  905  to the second fan  911 . 
   In addition, if the signal supplied to the terminal T 91  is an H-level signal, the microcomputer  901  detects that the first fan  910  is connected to the first connector  906 , and that the drive control signal is delivered from the first driver  904  to the first fan  910 , and that the second fan  911  is connected to the second connector  907 , and that the drive control signal is delivered from the second driver  905  to the second fan  911 . 
   In the drive control circuit  900  having the structure described above, the microcomputer  901  delivers the control signal S 1  for performing drive control of the first fan  910  to the first PWM conversion portion  902 , and it delivers the control signal S 2  for performing drive control of the second fan  911  to the second PWM conversion portion  903 . In this case, there is no problem if the first fan  910  and the second fan  911  has the same operating characteristic and the drive control method is the same between them. However, if the operating characteristic is different between the first fan  910  and the second fan  911 , and if the drive control method is also different between them, it is impossible to perform drive control correctly for the first fan  910  and the second fan  911  in the case where the first fan  910  is connected to the second connector  907  and the second fan  911  is connected to the first connector  906 , incorrectly. 
   Therefore, in the drive control circuit  900  the first connector  906  and the second connector  907  have different shapes so as to prevent the first fan  910  from being connected to the second connector  907  and prevent the second fan  911  from being connected to the first connector  906  incorrectly. 
   In addition, a control unit that can protect the incorrect connection is proposed (see JP-A-2005-076993), which is provided to an air conditioner using a power supply circuit that can delivers voltage generated by a voltage double rectifier from voltage after full wave rectification. It maintains the output voltage from the power supply circuit to be the voltage after the full wave rectification until it recognizes that an indoor unit and an outdoor unit have the same rated power voltage value, so as to protect components when incorrect connection is performed between units having different rated power voltage values. 
   However, when the drive control circuit  900  shown in  FIG. 4  is manufactured, it is necessary to provide different manufacturing steps for the first connector  906  and the second connector  907  because the first connector  906  and the second connector  907  have different shapes. This may cause a problem of lowering production efficiency. 
   In addition, if the projection apparatus having the drive control circuit  900  shown in  FIG. 4  is assembled manually, it is difficult to attach first one of the two connectors that is easier to attach since the first connector  906  and the second connector  907  have different shapes. This may also cause a problem of lowering production efficiency. 
   The control unit described in JP-A-2005-076993 can only detect incorrect connection due to a difference of the rated power voltage value. Therefore, even if this control unit is applied to the drive control circuit  900  shown in  FIG. 4 , it is necessary to arrange that the first connector  906  and the second connector  907  have different shapes. Further more, it is still difficult to attach first one of the two connectors that is easier to attach. Therefore, it is difficult to expect improvement of production efficiency. 
   SUMMARY OF THE INVENTION 
   In view of the above described problem, it is an object of the present invention to provide a drive control circuit for performing drive control of a plurality of loads with high production efficiency. Further it is another object of the present invention to provide a projection apparatus having such a drive control circuit. 
   To attain the above described first object, a drive control circuit according to a first aspect of the present invention includes: a plurality of connectors for connecting with a plurality of loads having different operating characteristics; a control portion that supplies drive control signals to the plurality of loads via first electrodes of the plurality of connectors; and a comparing portion that compares certain characteristic values at second electrodes of the plurality of connectors concerning certain characteristics of signals applied to the first electrodes, so that a result of the comparison is supplied to the control portion, and the drive control circuit is characterized by a structure in which the drive control signal is determined in accordance with the result of the comparison. 
   A drive control circuit according to a second aspect of the present invention, as to the drive control circuit according to the above mentioned first aspect, has a structure in which the certain characteristics of the signals applied to the first electrodes are voltages, the voltages applied to the first electrodes have substantially the same value, and the certain characteristic values at the second electrode is current values. 
   A drive control circuit according to a third aspect of the present invention, as to the drive control circuit according to the above mentioned first aspect, further includes a detecting portion that detects whether or not current flows in the second electrodes of the plurality of connectors. 
   A projection apparatus according to a fourth aspect of the present invention is equipped with a drive control circuit according to any one of the above mentioned first to third aspects, and the loads are fans. 
   A projection apparatus according to a fifth aspect of the present invention is equipped with first and second fans having different voltage and current characteristics, and a drive control circuit. The drive control circuit includes two connectors for connecting with the first and the second fans, a control portion that supplies drive control signals to the first and the second fans via first electrodes of the two connectors, a comparing portion that compares current values at second electrodes of the two connectors, so that a result of the comparison is supplied to the control portion, and a detecting portion that detects whether or not current flows in the second electrodes of the two connectors. The drive control circuit determines which of the first and the second fans is connected to which of the two connectors based on the result of the comparison when substantially the same voltage is applied to the first and the second fans and voltage and current characteristics of the first and the second fans, so as to decide the drive control signals in accordance with a result of the determination. 
   According to the present invention, it is possible to provide a drive control circuit that can perform drive control correctly of a plurality of loads having different operating characteristics regardless of which of the loads is connected to which of a plurality of connectors. Therefore, it is not necessary to make the plurality of connectors have different shapes. As a result, it is not necessary to provide manufacturing steps of the plurality of connectors separately. In addition, when a certain load is attached manually, it can be attached to any one of unoccupied connectors that is easy to attach. Therefore, production efficiency can be improved. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram to show a general structure of a drive control circuit  100  according to the present invention. 
       FIG. 2  is a graph to show voltage and current characteristics of an 80 mm square fan and a blower fan used in a conventional projection apparatus. 
       FIG. 3  is a flowchart to show an action of fan determination performed by a microcomputer  101 . 
       FIG. 4  is a block diagram to show a general structure of a drive control circuit  900  according to a conventional technique. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   An embodiment of the present invention will be described with reference to the attached drawings. In the embodiment described below, a plurality of loads having different operating characteristics are different types of fans, and the operating characteristics are the voltage and current characteristics. However, the present invention is not limited to this embodiment, and it can be applied generally to a plurality of loads of any type having any different operating characteristics. 
     FIG. 1  is a block diagram to show a general structure of the drive control circuit  100  according to the embodiment of the present invention. The drive control circuit  100  includes a microcomputer  101 , a first PWM conversion portion  102 , a second PWM conversion portion  103 , a first driver  104 , a second driver  105 , a first connector  106 , a second connector  107 , a first detecting portion  108 , a second detecting portion  109  and a comparing portion  110 . Here, one of the first connector  106  and the second connector  107  is a connector for connecting a first fan  111  as an example of the plurality of loads, and the other is a connector for connecting a second fan  112  as the other example of the plurality of loads. 
   Although the first fan  111  is connected to the first connector  106 , and the second fan  112  is connected to the second connector  107  in  FIG. 1 , it is possible to connect the second fan  112  to the first connector  106  and to connect the first fan  111  to the second connector  107 . Note that the detail of this will be described later. 
   The microcomputer  101  is connected to the first PWM conversion portion  102  and the second PWM conversion portion  103 . The first PWM conversion portion  102  is connected to the first driver  104 , while the second PWM conversion portion  103  is connected to the second driver  105 . The first driver  104  is connected to the plus terminal of the first connector  106 , while the second driver  105  is connected to the plus terminal of the second connector  107 . In addition, the minus terminal of the first connector  106  is connected to the first detecting portion  108  and the comparing portion  110 , while the minus terminal of the second connector  107  is connected to the second detecting portion  109  and the comparing portion  110 . Then, the first detecting portion  108  and the second detecting portion  109  are connected to the terminal T 1  of the microcomputer  101 , while the comparing portion  110  is connected to the terminal T 2  of the microcomputer  101 . 
   In the drive control circuit  100  having the structure described above, the microcomputer  101  supplies the first PWM conversion portion  102  with a control signal S 1  for performing drive control of the fan connected to the first connector  106  and supplies the second PWM conversion portion  103  with a control signal S 2  for performing drive control of the fan connected to the second connector  107 . Then, the first PWM conversion portion  102  performs the PWM conversion on the control signal S 1  and delivers the obtained signal to the first driver  104 . In addition, the second PWM conversion portion  103  performs the PWM conversion on the control signal S 2  and delivers the obtained signal to the second driver  105 . 
   The first driver  104  delivers the drive control signal to the fan connected to the first connector  106  via the plus terminal of the first connector  106  based on the signal from the first PWM conversion portion  102 . In addition, the second driver  105  delivers the drive control signal to the fan connected to the second connector  107  via the plus terminal of the second connector  107  based on the signal from the second PWM conversion portion  103 . 
   In other words, the microcomputer  101 , the first PWM conversion portion  102 , the second PWM conversion portion  103 , the first driver  104  and the second driver  105  constitute the control portion that delivers the drive control signal to the fan connected to the first connector  106  via the plus terminal of the first connector  106  and delivers the drive control signal to the fan connected to the second connector  107  via the plus terminal of the second connector  107 . 
   The first detecting portion  108  includes an operational amplifier  113  having a non inverting input terminal connected to the minus terminal of the first connector  106 , an inverting input terminal to which a reference voltage is applied, and an output terminal that is connected to the terminal T 1  of the microcomputer  101 , and a resistor R 1  having one end connected to the minus terminal of the first connector  106  and the other end connected to the ground. In addition, the second detecting portion  109  includes an operational amplifier  114  having a non inverting input terminal connected to the minus terminal of the second connector  107 , an inverting input terminal to which a reference voltage is applied, and an output terminal that is connected to the terminal T 1  of the microcomputer  101 , and a resistor R 2  having one end connected to the minus terminal of the second connector  107  and the other end connected to the ground. Here, resistance values of the resistor R 1  and the resistor R 2  are substantially equal to each other. 
   In this case, if no fan is connected to the first connector  106  or if the first driver  104  does not deliver the drive control signal to the fan connected to the first connector  106 , no current flows in the minus terminal of the first connector  106 . Therefore, the output terminal of the operational amplifier  113  delivers an L-level signal. In addition, if a fan is connected to the first connector  106  and if first driver  104  delivers the drive control signal to the fan connected to the first connector  106 , current flows in the minus terminal of the first connector  106 . Therefore, an H-level signal is delivered from the output terminal of the operational amplifier  113 . 
   In the same manner, if no fan is connected to the second connector  107  or if the second driver  105  does not deliver the drive control signal to the fan connected to the second connector  107 , current does not flow in the minus terminal of the second connector  107 . Therefore, an L-level signal is delivered from the output terminal of the operational amplifier  114 . In addition, if a fan is connected to the second connector  107  and if the second driver  105  delivers the drive control signal to the fan connected to the second connector  107 , current flows in the minus terminal of the second connector  107 . Therefore, an H-level signal is delivered from the output terminal of the operational amplifier  114 . 
   Therefore, if the signal supplied to the terminal T 1  is an L-level signal, the microcomputer  101  can detects that no fan is connected to the first connector  106 , or that the first driver  104  does not deliver the drive control signal to the fan connected to the first connector  106 , or that no fan is connected to the second connector  107 , or that the second driver  105  does not deliver the drive control signal to the fan connected to the second connector  107 . 
   In addition, if the signal supplied to the terminal T 1  is an H-level signal, the microcomputer  101  can detects that a fan is connected to the first connector  106 , and that the first driver  104  delivers the drive control signal to the fan connected to the first connector  106 , and that a fan is connected to the second connector  107 , and that the second driver  105  delivers the drive control signal to the fan connected to the second connector  107 . 
   The comparing portion  110  includes a resistor R 3  having one end connected to the minus terminal of the first connector  106 , an operational amplifier  115  having a non inverting input terminal connected to the other end of the resistor R 3 , an inverting input terminal connected to the minus terminal of the second connector  107  and the output terminal connected to the terminal T 2  of the microcomputer  101 , a resistor R 4  connected between the non inverting input terminal and the output terminal of the operational amplifier  115 , and a resistor R 5  having one end connected to the output terminal of the operational amplifier  115  and the other end connected to a DC power source VDD. 
   In this case, the comparing portion  110  compares a current value of current that flows in the minus terminal of the first connector  106  with a current value of current that flows in the minus terminal of the second connector  107  by converting them into voltage values. If a current value of the current that flows in the minus terminal of the first connector  106  is smaller than a current value of the current that flows in the minus terminal of the second connector  107 , the comparing portion  110  delivers an L-level signal to the terminal T 2  of the microcomputer  101 . In addition, if a current value of the current that flows in the minus terminal of the first connector  106  is larger than a current value of the current that flows in the minus terminal of the second connector  107 , the comparing portion  110  delivers an H-level signal to the terminal T 2  of the microcomputer  101 . 
   Here, in a projection apparatus having a plurality of fans, the plurality of fans have different voltage and current characteristics in many cases.  FIG. 2  is a graph to show voltage and current characteristics of fans in a conventional projection apparatus having an 80 mm square fan and a blower fan. 
   If one of the first fan  111  and the second fan  112  is the blower fan having the voltage and current characteristics shown in  FIG. 2  and the other is the 80 mm square fan having the voltage and current characteristics shown in  FIG. 2 , a current value of current that flows in the blower fan is smaller than a current value of current that flows in the 80 mm square fan in the case where a voltage applied to the fan connected to the first connector  106  via the plus terminal of the first connector  106  from the first driver  104  is substantially equal to a voltage applied to the fan connected to the second connector  107  via the plus terminal of the second connector  107  from the second driver  105 , as shown clearly in  FIG. 2 . 
   For example, the voltage applied to the fan connected to the first connector  106  from the first driver  104  via the plus terminal of the first connector  106  and the voltage applied to the fan connected to the second connector  107  from the second driver  105  via the plus terminal of the second connector  107  are both 10 volts, current that flows in the blower fan is 0.16 amperes while current that flows in the 80 mm square fan is 0.21 amperes, as shown in  FIG. 2 . 
   Therefore, if the blower fan is connected to the first connector  106  while the 80 mm square fan is connected to the second connector  107 , a signal supplied to the terminal T 2  of the microcomputer  101  is an L-level signal. On the contrary, if the blower fan is connected to the second connector  107  while the 80 mm square fan is connected to the first connector  106 , a signal supplied to the terminal T 2  of the microcomputer  101  is an H-level signal. 
   Therefore, the microcomputer  101  can determine that the fan connected to the first connector  106  is the blower fan while the fan connected to the second connector  107  is the 80 mm square fan if the signal supplied to the terminal T 2  is an L-level signal. In addition, if the signal supplied to the terminal T 2  is an H-level signal, the microcomputer  101  can determine that the fan connected to the first connector  106  is the 80 mm square fan while the fan connected to the second connector  107  is the blower fan. 
   Therefore, if the signal supplied to the terminal T 2  is an L-level signal, the microcomputer  101  should make the control signal S 1  be the control signal for performing drive control of the blower fan and make the control signal S 2  be the control signal for performing drive control of the 80 mm square fan. In addition, if the signal supplied to the terminal T 2  is an H-level signal, the microcomputer  101  makes the control signal S 1  be the control signal for performing drive control of the 80 mm square fan and makes the control signal S 2  be the control signal for performing drive control of the blower fan. 
   The above mentioned control procedure of the fan determination performed by the microcomputer  101  will be described more in detail below.  FIG. 3  is a flowchart to show the control procedure of fan determination performed by the microcomputer  101 . When the projection apparatus is powered on (S 1 ), the microcomputer  101  delivers the control signal S 1  and the control signal S 2  so that the voltage applied to the fan connected to the first connector  106  from the first driver  104  via the plus terminal of the first connector  106  becomes substantially equal to the voltage applied to the fan connected to the second connector  107  from the second driver  105  via the plus terminal of the second connector  107  (S 2 ). 
   Then, the microcomputer  101  first detects the signal supplied to the terminal T 1  (S 3 ). Here, if the signal supplied to the terminal T 1  is an L-level signal, it means that a fan is not connected to at least one of the first connector  106  and the second connector  107 . Therefore, the microcomputer  101  stops the operation of the projection apparatus (S 4 ). 
   In S 3 , if the signal supplied to the terminal T 1  is an H-level signal, the microcomputer  101  detects a signal that is supplied to the terminal T 2  next (S 5 ). Here, if the signal supplied to the terminal T 2  is an L-level signal, the fan connected to the first connector  106  is the blower fan while the fan connected to the second connector  107  is the 80 mm square fan. Therefore, the microcomputer  101  makes the control signal S 1  be the control signal for performing drive control of the blower fan and makes the control signal S 2  be the control signal for performing drive control of the 80 mm square fan (S 6 ). 
   On the other hand, if the signal supplied to the terminal T 2  is an H-level signal in S 5 , the fan connected to the first connector  106  is the 80 mm square fan while the fan connected to the second connector  107  is the blower fan. Therefore, the microcomputer  101  makes the control signal S 1  be the control signal for performing drive control of the 80 mm square fan and makes the control signal S 2  be the control signal for performing drive control of the blower fan (S 7 ). 
   Since the microcomputer  101  performs the above mentioned fan determination in the drive control circuit  100  shown in  FIG. 1 , drive control can be performed correctly by connecting the first fan  111  to one of the first connector  106  and the second connector  107  and the second fan  112  to the other even if the first fan  111  and the second fan  112  have different drive control methods. In other words, drive control can be performed correctly both in the case where the first fan  111  is connected to the first connector  106  while the second fan  112  is connected to the second connector  107  and in the case where the second fan  112  is connected to the first connector  106  while the first fan  111  is connected to the second connector  107 . 
   Therefore, when the drive control circuit  100  shown in  FIG. 1  is manufactured, it is not necessary to arrange the first connector  106  and the second connector  107  to have different shapes. Thus, it is not necessary to provide separately the step for manufacturing the first connector  106  and the step for manufacturing the second connector  107 , resulting in an improvement of production efficiency. 
   In addition, when the projection apparatus having the drive control circuit  100  shown in  FIG. 1  is assembled manually, one of the first fan  111  and the second fan  112  can be attached first to either one of the first connector  106  and the second connector  107  that is easier to attach. Therefore, production efficiency can be improved. 
   Note that the present invention is not limited to the embodiment described above, which can be modified variously in the scope of the present invention without deviating from its spirit. For example, it is possible that the number of fans to be driven and controlled by the drive control circuit  100  can be three or more. 
   The present invention is effective as a drive control circuit for performing drive control of a plurality of loads such as a drive control circuit for performing drive control of a plurality of fans. In addition, the present invention is effective as the projection apparatus having such a drive control circuit. 
   Although characteristics of the signal to be supplied to the first electrode is exemplified by voltage while a certain characteristic value of the second electrode is exemplified by current in the embodiment described above, these can be any characteristics of the signal to be supplied to the first electrode and any characteristic value generated in the second electrode.