Patent Abstract:
An alternating current input voltage detection circuit comprises: a first voltage waveform detection circuit that detects a voltage waveform of one alternating current input terminal of the diode rectification circuit, based on a reference potential of the device; a second voltage waveform detection circuit that detects a voltage waveform of the other alternating current input terminal of the diode rectification circuit, based on the reference potential of the device, and a voltage waveform generation circuit that: calculates a first detection voltage waveform, which is output from the first voltage waveform detection circuit, and a second detection voltage waveform, which is output from the second voltage waveform detection circuit; generates a voltage waveform signal, in which waveform distortions generated in the first detection voltage waveform and the second detection voltage waveform are eliminated; and outputs the voltage waveform signal as the voltage detection signal.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority from Japanese Patent Application No. 2012-069047 filed on Mar. 26, 2012, the entire subject matter of which is incorporated herein by reference. 
       TECHNICAL FIELD 
       [0002]    This disclosure relates to an alternating current input voltage detection circuit of a power supply device and the like having an alternating current power supply as an input source. 
       BACKGROUND 
       [0003]    It is known that a power supply device obtains a direct current power supply based on an alternating current power supply as an input source and an alternating current input voltage detection circuit detects an alternating current input voltage (a voltage of the alternating current power supply) to thus output a voltage detection signal.  FIG. 8  illustrates an example of the power supply device and the alternating current input voltage detection circuit of the background art. In  FIG. 8 , the power supply device  10  has a diode rectification circuit  2  and a smoothing capacitor  3 . Also, the alternating current input voltage detection circuit  20  is provided in the power supply device  10 . 
         [0004]    The diode rectification circuit  2  includes four diodes D 11  to D 14  that forms a full-wave rectification circuit having a bridge configuration. One alternating current input terminal  2   a  of the diode rectification circuit  2  is connected to one terminal of an alternating current power supply  1  through an alternating current power supply line L 1  and to a connection point of the diode D 11  and the diode D 12 . The other alternating current input terminal  2   b  of the diode rectification circuit  2  is connected to the other terminal of the alternating current power supply  1  through an alternating current power supply line L 2  and to a connection point of the diode D 13  and the diode D 14 . Also, a positive direct current output terminal  2   c  of the diode rectification circuit  2  is connected to a connection point of the diode D 11  and the diode D 13  and to one end of the smoothing capacitor  3 . A negative direct current output terminal  2   d  of the diode rectification circuit  2  is connected to a connection point of the diode D 12  and the diode D 14  and to the other end of the smoothing capacitor  3 . 
         [0005]    The other end of the smoothing capacitor  3  is grounded and thus becomes a reference potential of the power supply device  10 . Also, the smoothing capacitor  3  is connected in parallel with a load  30 . 
         [0006]    The alternating current input voltage detection circuit  20  includes resistances R 5  to R 7  and a diode D 15 . One end of the resistance R 5  is connected to the one terminal of the alternating current power supply  1  or one alternating current input terminal  2   a  of the diode rectification circuit  2 , one end of the resistance R 6  is connected to the other end of the alternating current power supply  1  or other alternating current input terminal  2   b  of the diode rectification circuit  2 , the other end of the resistance R 5  is connected to the other end of the resistance R 6  and to an anode of the diode D 15 , a cathode of the diode D 15  is connected to one end of the resistance R 7  and the other end of the resistance R 7  is grounded. Also, a connection point of the one end of the resistance R 5  and the one terminal of the alternating current power supply  1  or a connection point of the one end of the resistance R 5  and the one alternating current input terminal  2   a  of the diode rectification circuit  2  is referred to as a point A, a connection point of the one end of the resistance R 6  and the other terminal of the alternating current power supply  1  or a connection point of the one end of the resistance R 6  and the other alternating current input terminal  2   b  of the diode rectification circuit  2  is referred to as a point B, and a connection point of the cathode of the diode D 15  and the one end of the resistance R 7  is referred to as a point C. 
         [0007]    In the below, operations of the power supply device  10  and alternating current input voltage detection circuit  20  configured as described above will be described. 
         [0008]    The power supply device  10  full-wave rectifies an alternating current input voltage, which is supplied from the alternating current power supply  1 , by the diode rectification circuit  2 , smoothes the full-wave rectified voltage by the smoothing capacitor  3  to convert into a direct current output voltage and thus outputs the direct current output voltage to the load  30  that is connected in parallel with the smoothing capacitor  3 . Also, a power supply device, in which the smoothing capacitor  3  is replaced with a power conversion unit (not shown) of a boost converter to has a function of improving a power factor of the alternating current power supply  1  and to output a direct current output voltage higher than the alternating current input voltage, and a power supply device, in which a power conversion unit (not shown) such as DC-DC converter and DC-AC converter is provided between the smoothing capacitor  3  (or boost converter) and the load  30  to convert the alternating current input voltage into a desired direct current output voltage or alternating current output voltage and to output the same, have been also known. 
         [0009]    The alternating current input voltage detection circuit  20  is a circuit that detects the alternating current input voltage supplied from the alternating current power supply  1  and thus outputs a voltage detection signal, inputs voltage waveforms of the points A and B, on the basis of the reference potential (ground) of the power supply device  10 , and outputs a voltage waveform of the point C as the voltage detection signal. The voltage detection signal is output from the alternating current input voltage detection circuit  20  is used to detect a voltage value such as average value and effective value of the alternating current input voltage and is used to detect a zero cross of the alternating current input voltage and to detect an abnormality (outage, voltage lowering, overvoltage and the like) of the alternating current power supply  1 , at an inside or outside of the power supply device  10 . 
         [0010]    Also, for example, JP-A-11-155284 discloses an outage detection circuit, as a related technology of the background art. 
       SUMMARY 
       [0011]    In the meantime, as shown in  FIG. 9 , during light load and heavy load, when there is no change in the voltage waveform of the point A and also in the voltage waveform of the point B, the voltage waveform of the point C does not change. That is, when the voltage detection signal that is output from the alternating input voltage detection circuit  20  is not influenced due to the load, according to the voltage detection signal that is output from the alternating input voltage detection circuit  20 , it is possible to precisely detect a voltage value such as average value and effective value of the alternating current input voltage, a zero cross of the alternating current input voltage and an abnormality of the alternating current power supply  1 . 
         [0012]    However, actually, as shown in  FIG. 11 , during the light load, a waveform distortion is generated in the vicinity of a zero voltage of the voltage waveforms of the points A and B. As shown in  FIG. 10 , it is thought that the generation of the waveform distortion is influenced by a parasitic capacitance (which is shown with the dotted line) of the alternating current power supply lines L 1 , L 2  or parasitic capacitance (which is shown with the dotted line) of the diode rectification circuit  2 , and the like. Since the voltage waveform of the point C is generated by combining the voltage waveform of the point A and the voltage waveform of the point B with the diode D 15 , the voltage waveform of the point C is increased in the vicinity of the zero voltage due to the waveform distortion. Since the generation of the waveform distortion causes a change in the voltage waveform of the point A and also in the voltage waveform of the point B during the light load and heavy load, a change is caused in the voltage waveform of the point C. That is, since the voltage detection signal that is output from the alternating input voltage detection circuit  20  is influenced due to the load, it is not possible to precisely detect the voltage value such as average value and effective value of the alternating current input voltage, the zero cross of the alternating current input voltage and the abnormality of the alternating current power supply  1  from the voltage detection signal. As can be also seen from  FIG. 11 , an average value of the alternating current input voltage during the light load is detected to be larger than an average value of the alternating current input voltage during the heavy load. 
         [0013]    Like this, since the waveform distortion is caused in the voltage detection signal that is output from the alternating input voltage detection circuit  20 , it is not possible to precisely detect the voltage value such as average value and effective value of the alternating current input voltage, the zero cross of the alternating current input voltage and the abnormality of the alternating current power supply  1 , from the voltage detection signal having the waveform distortion, at the inside or outside of the power supply device  10 . 
         [0014]    In view of the above, this disclosure provides at least an alternating current input voltage detection circuit that detects an alternating current input voltage supplied from an alternating current power supply and thus outputs a voltage detection signal without waveform distortion. 
         [0015]    An alternating current input voltage detection circuit of this disclosure is provided at an inside or outside of a device rectifying an alternating current input voltage supplied from an alternating current power supply by a diode rectification circuit having a bridge configuration to detect the alternating current input voltage and output a voltage detection signal. The alternating current input voltage detection circuit comprises; a first voltage waveform detection circuit that detects a voltage waveform of one alternating current input terminal of the diode rectification circuit, based on a reference potential of the device; a second voltage waveform detection circuit that detects a voltage waveform of the other alternating current input terminal of the diode rectification circuit, based on the reference potential of the device, and a voltage waveform generation circuit that: calculates a first detection voltage waveform, which is output from the first voltage waveform detection circuit, and a second detection voltage waveform, which is output from the second voltage waveform detection circuit; generates a voltage waveform signal, in which waveform distortions generated in the first detection voltage waveform and the second detection voltage waveform are eliminated; and outputs the voltage waveform signal as the voltage detection signal. 
         [0016]    According to this disclosure, it is possible to provide the alternating current input voltage detection circuit that detects the alternating current input voltage supplied from the alternating current power supply and thus outputs the voltage detection signal without waveform distortion. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The foregoing and additional features and characteristics of this disclosure will become more apparent from the following detailed descriptions considered with the reference to the accompanying drawings, wherein: 
           [0018]      FIG. 1  illustrates an alternating current input voltage detection circuit according to a first illustrative embodiment of this disclosure; 
           [0019]      FIG. 2  illustrates waveforms of respective units of the alternating current input voltage detection circuit shown in  FIG. 1 ; 
           [0020]      FIG. 3  illustrates an alternating current input voltage detection circuit according to a second illustrative embodiment of this disclosure; 
           [0021]      FIG. 4  illustrates waveforms of respective units of the alternating current input voltage detection circuit shown in  FIG. 3 ; 
           [0022]      FIG. 5  illustrates an alternating current input voltage detection circuit according to a third illustrative embodiment of this disclosure; 
           [0023]      FIG. 6  illustrates waveforms of respective units of the alternating current input voltage detection circuit shown in  FIG. 5 ; 
           [0024]      FIG. 7  illustrates an alternating current input voltage detection circuit according to a fourth illustrative embodiment of this disclosure; 
           [0025]      FIG. 8  illustrates an example of a power supply device and an alternating current input voltage detection circuit of the background art; 
           [0026]      FIG. 9  illustrates waveforms of respective units of the alternating current input voltage detection circuit shown in  FIG. 8 ; 
           [0027]      FIG. 10  illustrates the power supply device of  FIG. 8  in which a parasitic capacitance is applied; and 
           [0028]      FIG. 11  illustrates waveforms of respective units of the alternating current input voltage detection circuit shown in  FIG. 10 . 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    Hereinafter, illustrative embodiments, in which this disclosure is applied to an alternating current input voltage detection circuit of a power supply device having an alternating current power supply as an input source, will be described with reference to the drawings. Also, in the respective drawings, the same parts are indicated with the same reference numerals, and the overlapping descriptions will be omitted. 
       First Illustrative Embodiment 
       [0030]      FIG. 1  illustrates an alternating current input voltage detection circuit according to a first illustrative embodiment of this disclosure. In  FIG. 1 , a power supply device  10   a  has a diode rectification circuit  2  and a smoothing capacitor  3 . Also, an alternating current input voltage detection circuit  20   a  is provided in the power supply device  10   a . Therefore, the power supply device  10   a  is a device, in which the alternating current input voltage detection circuit  20  of the power supply device  10  shown in  FIG. 10  is replaced with the alternating current input voltage detection circuit  20   a.  Since the other configurations are the same as those shown in  FIG. 10 , the same parts are indicated with the same reference numerals, and the descriptions thereof will be omitted. Here, only the alternating current input voltage detection circuit  20   a  will be described. The alternating current input voltage detection circuit  20   a  has a first voltage waveform detection circuit  21 , a second voltage waveform detection circuit  22  and a voltage waveform generation circuit  23   a.  Also, the alternating current input voltage detection circuit  20   a  may be provided at an outside of the power supply device  10   a.    
         [0031]    The first voltage waveform detection circuit  21  includes a diode D 1  and resistances R 1 , R 3 . An anode of the diode D 1  is connected to one terminal of an alternating current power supply  1  and one alternating current input terminal  2   a  of the diode rectification circuit  2 , a cathode of the diode D 1  is connected to one end of the resistance R 1 , the other end of the resistance R 1  is connected to one end of the resistance R 3  and the other end of the resistance R 3  is grounded. Also, a connection point of the anode of the diode D 1  and the one terminal of the alternating current power supply  1  or a connection point of the anode of the diode D 1  and the one alternating current input terminal  2   a  of the diode rectification circuit  2  is referred to as a point A. 
         [0032]    The second voltage waveform detection circuit  22  includes a diode D 2  and resistances R 2 , R 4 . An anode of the diode D 2  is connected to the other terminal of the alternating current power supply  1  and the other alternating current input terminal  2   b  of the diode rectification circuit  2 , a cathode of the diode D 2  is connected to one end of the resistance R 2 , the other end of the resistance R 2  is connected to one end of the resistance R 4  and the other end of the resistance R 4  is grounded. Also, a connection point of the anode of the diode D 1  and the other terminal of the alternating current power supply  1  or a connection point of the anode of the diode D 1  and the other alternating current input terminal  2   b  of the diode rectification circuit  2  is referred to as a point B. 
         [0033]    The voltage waveform generation circuit  23   a  is configured as a subtraction circuit including resistances R 11  to R 14  and an operational amplifier (which is also referred to as dual power supply operational amplifier) IC 1  operating with both power supplies (+Vcc, −Vdd). An output voltage range of the subtraction circuit is −Vdd to +Vcc. An inverting input terminal (−) of the operational amplifier IC 1  is connected to a connection point of the resistance R 2  and the resistance R 4  via the resistance R 11  and is connected to an output terminal of the operational amplifier IC 1  via the resistance R 12 . Also, a non-inverting input terminal (+) of the operational amplifier IC 1  is connected to a connection point of the resistance R 1  and the resistance R 3  via the resistance R 13  and is connected to a ground via the resistance R 14 . Also, the output terminal of the operational amplifier IC 1  is referred to as a point C. 
         [0034]    Next, operations of the alternating current input voltage detection circuit according to the first illustrative embodiment of this disclosure will be described with reference to  FIG. 2 . 
         [0035]    In  FIG. 2 , time periods T 1 , T 2  indicate the vicinity of the zero voltages of the voltage waveforms of the points A, B. Also, in the time periods T 1 , T 2 , a solid waveform indicates voltage when a waveform distortion is caused, and a dotted line waveform indicates voltage when a waveform distortion is not caused. In this illustrative embodiment, in view of amounts of the generation of waveform distortion in the time periods T 1 , T 2  are substantially the same at the points A, B, the waveform distortion is eliminated by calculating the voltage waveforms of the points A, B. Since the waveform distortion is eliminated by the calculation, the voltage waveform of the point C becomes a waveform of a sinusoidal wave shape without waveform distortion. 
         [0036]    The first voltage waveform detection circuit  21  inputs the voltage waveform of the point A, on the basis of a reference potential (ground) of the power supply device  10   a,  and outputs a voltage waveform of one end of the resistance R 3  as a first detection voltage waveform. 
         [0037]    The second voltage waveform detection circuit  22  inputs the voltage waveform of the point B, on the basis of the reference potential (ground) of the power supply device  10   a,  and outputs a voltage waveform of one end of the resistance R 4  as a second detection voltage waveform. 
         [0038]    The voltage waveform generation circuit  23   a  receives the first detection voltage waveform, which is output from the first voltage waveform detection circuit  21 , and the second detection voltage waveform, which is output from the second voltage waveform detection circuit  22 , and subtracts the second detection voltage waveform from the first detection voltage waveform. Since the waveform distortions in the vicinity of the zero voltage, which are generated in the first detection voltage waveform and the second detection voltage waveform, are eliminated by the subtraction, they are not output to the point C. The voltage waveform of the point C becomes an alternating current waveform of a sinusoidal wave shape without waveform distortion. That is, the waveform distortion is not generated in the voltage detection signal that is output from the voltage waveform generation circuit  23   a.    
         [0039]    According to the alternating current input voltage detection circuit of the first illustrative embodiment of this disclosure, it is possible to detect the alternating current input voltage, which is supplied from the alternating current power supply  1 , and to output the voltage detection signal without waveform distortion. Therefore, it is possible to precisely detect a voltage value such as average value and effective value of the alternating current input voltage, a zero cross of the alternating current input voltage and an abnormality of the alternating current power supply  1  from the voltage detection signal without waveform distortion, at an inside or outside of the power supply device  10   a.    
       Second Illustrative Embodiment 
       [0040]      FIG. 3  illustrates an alternating current input voltage detection circuit according to a second illustrative embodiment of this disclosure. In  FIG. 3 , a power supply device  10   b  has the diode rectification circuit  2  and the smoothing capacitor  3 . Also, an alternating current input voltage detection circuit  20   b  is provided in the power supply device  10   b.  Therefore, the power supply device  10   b  is a device, in which the alternating current input voltage detection circuit  20   a  of the power supply device  10   a  shown in  FIG. 1  is replaced with the alternating current input voltage detection circuit  20   b.  Since the other configurations are the same as those shown in  FIG. 1 , the same parts are indicated with the same reference numerals and the descriptions thereof will be omitted. Here, only the alternating current input voltage detection circuit  20   b  will be described. The alternating current input voltage detection circuit  20   b  has the first voltage waveform detection circuit  21 , the second voltage waveform detection circuit  22  and a voltage waveform generation circuit  23   b.  Also, the alternating current input voltage detection circuit  20   b  may be provided at an outside of the power supply device  10   b.    
         [0041]    The voltage waveform generation circuit  23   b  has a first subtraction circuit including resistances R 15  to R 18  and an operational amplifier (which is also referred to as single power supply operational amplifier) IC 2  operating with a single power supply (+Vcc), a second subtraction circuit including resistances R 19  to R 22  and an operational amplifier IC 3  operating with a single power supply (+Vcc), and a first adding circuit including resistances R 23  to R 26  and an operational amplifier IC 4  operating with a single power supply (+Vcc). Output voltage ranges of the first subtraction circuit, the second subtraction circuit and the first adding circuit are 0 to +Vcc. 
         [0042]    An inverting input terminal (−) of the operational amplifier IC 2  is connected to a connection point of the resistance R 2  and the resistance R 4  via the resistance R 15  and is connected to an output terminal of the operational amplifier IC 2  via the resistance R 16 . Also, a non-inverting input terminal (+) of the operational amplifier IC 2  is connected to a connection point of the resistance R 1  and the resistance R 3  via the resistance R 17  and is connected to a ground via the resistance R 18 . Also, the output terminal of the operational amplifier IC 2  is referred to as a point X. 
         [0043]    An inverting input terminal (−) of the operational amplifier IC 3  is connected to a connection point of the resistance R 1  and the resistance R 3  via the resistance R 19  and is connected to an output terminal of the operational amplifier IC 3  via the resistance R 20 . Also, a non-inverting input terminal (+) of the operational amplifier IC 3  is connected to a connection point of the resistance R 2  and the resistance R 4  via the resistance R 21  and is connected to a ground via the resistance R 22 . Also, the output terminal of the operational amplifier IC 3  is referred to as a point Y. 
         [0044]    An inverting input terminal (−) of the operational amplifier IC 4  is connected to a ground via the resistance  26  and is connected to an output terminal of the operational amplifier IC 4  via the resistance R 25 . Also, a non-inverting input terminal (+) of the operational amplifier IC 4  is connected to the output terminal of the operational amplifier IC 2  via the resistance R 23  and is connected to the output terminal of the operational amplifier IC 3  via the resistance R 24 . Also, the output terminal of the operational amplifier IC 4  is referred to as a point C. 
         [0045]    In the below, operations of the alternating current input voltage detection circuit according to the second illustrative embodiment of this disclosure are described also with reference to  FIG. 4 . 
         [0046]    The voltage waveform generation circuit  23   b  receives the first detection voltage waveform, which is output from the first voltage waveform detection circuit  21 , and the second detection voltage waveform, which is output from the second voltage waveform detection circuit  22 , then subtracts the second detection voltage waveform from the first detection voltage waveform with the first subtraction circuit, subtracts the first detection voltage waveform from the second detection voltage waveform with the second subtraction circuit, and thus adds an output (voltage waveform of the point X) from the first subtraction circuit and an output (voltage waveform of the point Y) from the second subtraction circuit with the first adding circuit. Since the waveform distortions in the vicinity of the zero voltage, which are generated in the first detection voltage waveform and the second detection voltage waveform, are eliminated by the subtraction, they are not output to the points X, Y. The voltage waveform of the point C becomes a full-wave rectified waveform of a sinusoidal wave shape without waveform distortion. That is, the waveform distortion is not generated in the voltage detection signal that is output from the voltage waveform generation circuit  23   b.    
         [0047]    Accordingly, even in the alternating current input voltage detection circuit according to the second illustrative embodiment of this disclosure, it is possible to obtain the same effects as those of the alternating current input voltage detection circuit according to the first illustrative embodiment of this disclosure. 
       Third Illustrative Embodiment 
       [0048]      FIG. 5  illustrates an alternating current input voltage detection circuit according to a third illustrative embodiment of this disclosure. In  FIG. 5 , a power supply device  10   c  has the diode rectification circuit  2  and the smoothing capacitor  3 . Also, an alternating current input voltage detection circuit  20   c  is provided in the power supply device  10   c.  Therefore, the power supply device  10   c  is a device, in which the alternating current input voltage detection circuit  20   a  of the power supply device  10   a  shown in  FIG. 1  is replaced with the alternating current input voltage detection circuit  20   c.  Since the other configurations are the same as those shown in  FIG. 1 , the same parts are indicated with the same reference numerals and the descriptions thereof will be omitted. Here, only the alternating current input voltage detection circuit  20   c  will be described. The alternating current input voltage detection circuit  20   c  has the first voltage waveform detection circuit  21 , the second voltage waveform detection circuit  22  and a voltage waveform generation circuit  23   c.  The alternating current input voltage detection circuit  20   c  may be provided at an outside of the power supply device  10   c.    
         [0049]    The voltage waveform generation circuit  23   c  is configured as a subtraction circuit including resistances R 27  to R 30  and an operational amplifier IC 5  operating with a single power supply (+Vcc). An output voltage range of the subtraction circuit is 0 to +Vcc. An inverting input terminal (−) of the operational amplifier IC 5  is connected to a connection point of the resistance R 2  and the resistance R 4  via the resistance R 27  and is connected to an output terminal of the operational amplifier IC 5  via the resistance R 28 . Also, a non-inverting input terminal (+) of the operational amplifier IC 5  is connected to a connection point of the resistance R 1  and the resistance R 3  via the resistance R 29  and is connected to a ground via the resistance R 30 . Also, the output terminal of the operational amplifier IC 5  is referred to as a point C. 
         [0050]    In the below, operations of the alternating current input voltage detection circuit according to the third illustrative embodiment of this disclosure are described also with reference to  FIG. 6 . 
         [0051]    The voltage waveform generation circuit  23   c  inputs the first detection voltage waveform, which is output from the first voltage waveform detection circuit  21 , and the second detection voltage waveform, which is output from the second voltage waveform detection circuit  22 , and subtracts the second detection voltage waveform from the first detection voltage waveform. Since the waveform distortions in the vicinity of the zero voltage, which are generated in the first detection voltage waveform and the second detection voltage waveform, are eliminated by the subtraction, they are not output to the point C. The voltage waveform of the point C becomes a half-wave rectified waveform of a sinusoidal wave shape without waveform distortion. That is, the waveform distortion is not generated in the voltage detection signal that is output from the voltage waveform generation circuit  23   c.    
         [0052]    Accordingly, even in the alternating current input voltage detection circuit according to the third illustrative embodiment of this disclosure, it is possible to obtain the same effects as those of the alternating current input voltage detection circuit according to the first illustrative embodiment of this disclosure. 
       Fourth Illustrative Embodiment 
       [0053]      FIG. 7  illustrates an alternating current input voltage detection circuit according to a fourth illustrative embodiment of this disclosure. In  FIG. 7 , a power supply device  10   d  has the diode rectification circuit  2  and the smoothing capacitor  3 . Also, an alternating current input voltage detection circuit  20   d  is provided in the power supply device  10   d.  Therefore, the power supply device  10   d  is a device, in which the alternating current input voltage detection circuit  20   a  of the power supply device  10   a  shown in  FIG. 1  is replaced with the alternating current input voltage detection circuit  20   d.  Since the other configurations are the same as those shown in  FIG. 1 , the same parts are indicated with the same reference numerals and the descriptions thereof will be omitted. Here, only the alternating current input voltage detection circuit  20   d  will be described. The alternating current input voltage detection circuit  20   d  has the first voltage waveform detection circuit  21 , the second voltage waveform detection circuit  22  and a voltage waveform generation circuit  23   d.  Also, the alternating current input voltage detection circuit  20   d  may be provided at an outside of the power supply device  10   d.    
         [0054]    The voltage waveform generation circuit  23   d  includes a microcomputer IC 6  having A/D (analog/digital) converters  61 ,  62 , a memory  63  and an output port  64 . The A/D converter  61  of the microcomputer IC 6  is connected to a connection point of the resistance R 1  and the resistance R 3 . Also, the A/D converter  62  of the microcomputer IC 6  is connected to a connection point of the resistance R 2  and the resistance R 4 . The memory  63  is connected to the A/D converters  61 ,  62  and to the output port  64 . Also, an output terminal of the output port  64  the microcomputer IC 6  is referred to as a point C. 
         [0055]    In the below, operations of the alternating current input voltage detection circuit according to the fourth illustrative embodiment of this disclosure are described. 
         [0056]    The voltage waveform generation circuit  23   d  inputs the first detection voltage waveform, which is output from the first voltage waveform detection circuit  21 , and the second detection voltage waveform, which is output from the second voltage waveform detection circuit  22 , samples the first detection voltage waveform by the A/D converter  61  and the second detection voltage waveform by the A/D converter  62  every predetermined period to thus convert the same into digital signals and stores the converted digital signals in the memory  63 , subtracts the second detection voltage waveform from the first detection voltage waveform, as digital processing (calculation function of the microcomputer), and stores the result of the subtraction in the memory  63 . The voltage waveform that is obtained by the subtraction of the digital processing is output from the output terminal of the output port  64 . Since the waveform distortions in the vicinity of the zero voltage, which are generated in the first detection voltage waveform and the second detection voltage waveform, are eliminated by the subtraction of the digital processing, they are not output to the point C. The voltage waveform of the point C becomes a half-wave rectified waveform of a sinusoidal wave shape without waveform distortion. That is, the waveform distortion is not generated in the voltage detection signal that is output from the voltage waveform generation circuit  23   d.    
         [0057]    Accordingly, even in the alternating current input voltage detection circuit according to the fourth illustrative embodiment of this disclosure, it is possible to obtain the same effects as those of the alternating current input voltage detection circuit according to the first illustrative embodiment of this disclosure. 
         [0058]    Also, this disclosure is not limited to the above illustrative embodiments. In the illustrative embodiments of this disclosure, the voltage waveform is output as the voltage detection signal. However, a voltage value such as average value and effective value may be generated from the voltage waveform by a well-known technology (which is not shown and described here) and the voltage waveform and voltage value may be output as the voltage detection signal. Also, the diodes D 1 , D 2  may be omitted. 
         [0059]    Also, in the illustrative embodiments of this disclosure, the negative direct current output terminal  2   d  of the diode rectification circuit  2  or the other end of the smoothing capacitor  3  is grounded and is thus set to be the reference potential of the power supply device  10   a  to  10   d.  However, in a power supply device having a boost converter, a DC-DC converter, a DC-AC converter and the like, one end of a current detector may be connected to the negative direct current output terminal  2   d  of the diode rectification circuit  2 . In this power supply device, the other end of the current detector may be grounded and thus set to be the reference potential. 
         [0060]    The alternating current input voltage detection circuit of this disclosure can be applied to a variety of power supply devices or control devices in which an alternating current input voltage supplied from an alternating current power supply is rectified by a diode rectification circuit having a bridge configuration.

Technology Classification (CPC): 6