1. An electric power supply apparatus comprising: a power-supply unit that supplies low noise block driving electric power through an electric power line to a low noise block down converter in compliance with the digital satellite equipment control standard; a transmission unit that transmits a control command for a digital satellite equipment control apparatus through the electric power line; a receiving unit that receives a response from the digital satellite equipment control apparatus corresponding to the control command through the electric power line; and a suppression unit that suppresses a level of noise that can occur in response to a switching of the switching unit that switches between a TX mode in which the control command is transmitted and an RX mode in which a response is received.

2. The electric power-supply apparatus according to Claim 1  further comprising a choke coil that suppresses attenuation of the response from the digital satellite equipment control apparatus through the power supply line  wherein when the switching unit is switched from the TX mode to the RX mode  noise is a counter-electromotive force that can occur as a result of the low noise block driving electric power being made to flow into the choke coil.

3. The electric power-supply apparatus according to Claim 2  further comprising a control unit that outputs a switching signal for the switching unit  wherein the suppression unit integrates and delays the switching signal that is output from the control unit and supplies the switching signal to the switching unit  thereby causing the switching unit to be gradually switched from the TX mode to the RX mode.

4. The electric power-supply apparatus according to Claim 2  wherein the switching unit is formed of a plurality of switches  and wherein the suppression unit causes the plurality of switches to be switched with a predetermined time difference  thereby switching in a step-like manner from the TX mode to the RX mode.

5. A receiving apparatus comprising: a power-supply unit that supplies low noise block driving electric power through an electric power line to a low noise block down converter in compliance with the digital satellite equipment control standard; a tuner that inputs an IF signal that is reflected and converged by a parabolic antenna and that is converted from an RF signal by the low noise block down converter; a transmission unit that transmits a control command for a digital satellite equipment control apparatus through the electric power line; a receiving unit that receives a response from the digital satellite equipment control apparatus corresponding to the control command through the electric power line; and a suppression unit that suppresses a level of noise that can occur in accordance with a switching of the switching unit that switches between a TX mode in which the control command is transmitted and an RX mode in which a response is received.

FIELD OF THE INVENTION
The present disclosure relates to an electric power-supply apparatus and a receiving apparatus. More particularly  the present disclosure relates to an electric power-supply apparatus suitable for use in a case where electric power is supplied to a low noise block (LNB) down converter of a parabolic antenna in compliance with  for example  digital satellite equipment control (DiSEqC) Ver. 2.0 standard  and to a receiving apparatus.

BACKGROUND
At present  digital television broadcasts transmitted via satellites have been becoming increasingly popular.
In particular  in Europe  a plurality of different satellites for digital television broadcasts have been launched  and the current situation is that a plurality of digital television signals that are broadcast through different respective satellites can be received at the same spot. For this reason  in Europe  also  in general consumer households  (the digital television signals transmitted from) the satellites are selectively switched from the receiving apparatus side  and television programs are received.
Specifically  the receiving apparatus side in compliance with the DiSEqC Ver. 2.0 standard bidirectionally communicates a control signal with an RF selection apparatus of the DiSEqC standard (hereinafter referred to as a DiSEqC apparatus) that selectively switches between LNBs provided in a plurality of respective parabolic antennas  so that satellites from which signals are received are switched between.
Furthermore  the receiving apparatus side in compliance with the DiSEqC Ver. 2.0 standard also supplies LNB driving electric power to the LNB of the parabolic antenna.
Fig. 1 illustrates an example of the configuration of a receiving apparatus of the related art in compliance with the DiSEqC Ver. 2.0 standard. This receiving apparatus 10 is provided as a single body  and is also installed into a television receiver  a video recorder  or the like.
The receiving apparatus 10 is mainly formed of a tuner 11  an MPEG-2 decoding unit 18  a video signal processing unit 19  and a DC power-supply unit 20.
The tuner 11 includes an antenna I/F 12  a high-frequency choke coil 13  a capacitor 14  an amplifier 15  a zero IF conversion unit 16  and a phase shift keying (PSK) demodulation unit 17.
The antenna I/F 12 is connected to an LNB 2 of the parabolic antenna 1 by using an antenna cable  and inputs  to the tuner 11  a Sat-IF signal of 1 to 2 GHz  which is reflected and converged by the parabolic antenna 1 and which is converted from an RF signal (digital television signal) of a 12 GHz band by the LNB 2. Furthermore  the antenna I/F 12 outputs LNB driving electric power that is supplied through the high-frequency choke coil 13 from the DC power-supply unit 20 to the LNB 2.
The high-frequency choke coil 13 prevents leakage of the Sat-IF signal that is input to the tuner 11 from the antenna I/F 12 to the DC power-supply unit 20 side. The capacitor 14 removes the DC components of the Sat-IF signal and outputs the signal to the amplifier 15. The amplifier 15 amplifies the Sat-IF signal in which the DC components are removed and outputs the signal to the zero IF conversion unit 16.
The zero IF conversion unit 16 frequency-converts the Sat-IF signal into an IQ orthogonal signal of the baseband and outputs the signal to the PSK demodulation unit 17 by using a digital/tuning circuit for station selection  which is formed of a built-in PLL synthesizer. The PSK demodulation unit 17 performs PSK demodulation including error correction on the IQ orthogonal signal  and outputs a transport stream (TS) of the MPEG2 format  which is obtained thereby  to the MPEG-2 decoding unit 18.
The MPEG-2 decoding unit 18 decodes the TS  and outputs the video signal obtained thereby to the video signal processing unit 19. The video signal processing unit 19 performs a predetermined signal process on the input video signal  and outputs the signal to the subsequent stage (display unit  etc.). The decoding result of the MPEG-2 decoding unit 18 contains an audio signal  and this is output to the subsequent stage (speaker  etc.) after the predetermined signal process. The illustration thereof is omitted.
The DC power-supply unit 20 supplies  through the tuner 11 to the LNB 2  LNB driving electric power of DC of a voltage of 18 V when the LNB 2 of the parabolic antenna 1 receives a horizontal polarized wave  and LNB driving electric power of DC of a voltage of 13 V when the LNB 2 of the parabolic antenna 1 receives a vertical polarized wave. Furthermore  the DC power-supply unit 20 transmits a DiSEqC command signal (TX) for a DiSEqC apparatus (not shown) through the tuner 11 and also  receives a DiSEqC command signal (RX) that is sent back through the tuner 11 from the DiSEqC apparatus.
Fig. 2 illustrates an example of the detailed configuration of the DC power-supply unit 20. The DC power-supply unit 20 is constituted by a power-supply unit 31  a tone modulation unit 32  a choke unit 33  a bypass switch 34  a demodulation unit 35  and a control unit 36.
The power-supply unit 31 outputs the LNB driving electric power of DC of a voltage of 18 V or 13 V to the power supply line connected to the tuner 11. The tone modulation unit 32 generates a 22 kHz tone signal as a DiSEqC command signal (TX)  and modulates the LNB driving electric power in response to the 22 kHz tone signal.
The choke unit 33 is constituted by a coil (22 ?H) and a resistor (15 ?) connected in parallel in compliance with the DiSEqC standard. The control unit 36 causes the bypass switch 34 to be turned on when the bypass switch 34 transmits a DiSEqC command signal (TX) for the DiSEqC apparatus  and causes the bypass switch 34 to be turned off when the bypass switch 34 receives a DiSEqC command signal (RX) from the DiSEqC apparatus. As a result  the 22 kHz tone signal as a DiSEqC command signal (TX)  which is transmitted  will be output to the tuner 11 after passing through the bypass switch 34. Furthermore  the 22 kHz tone signal as a DiSEqC command signal (RX)  which is received  will be input to the demodulation unit 35 as a result of the flow-into the power-supply unit 31 side being blocked by the choke unit 33.
The demodulation unit 35 demodulates the DiSEqC command signal (RX) to be received  and outputs the signal to the control unit 36. The control unit 36 controls each unit of the DC power-supply unit 20. For example  the control unit 36 outputs  to the bypass switch 34  a TX/RX mode switching signal for switching between the TX mode (transmission mode) and the RX mode (reception mode).
Fig. 3 illustrates an example of the waveform of control data for DiSEqC.
The tone modulation unit 32 adds an odd-number parity to binary data as control data forming various commands  and performs PWM (Pulse Width Modulation) modulation on this data to a pulse width of 0.5 ms (corresponding to 1 of binary data) or 1.0 ms (binary data corresponding to 0 of binary data)  thereby generating a 22 kHz tone signal.
For example  in a case where control data of 1 byte of E2h = 1110 0010b in hexadecimal notation is to be transmitted  a tone signal having the waveform shown in the figure is transmitted.
Fig. 4 illustrates timing of two-way communication in the DiSEqC Ver. 2.0 standard.
In a case where an RF selection apparatus as a DiSEqC apparatus is to be reset  in the DC power-supply unit 20  the bypass switch 34 is turned on (TX mode)  and 3-byte control data formed of E2h  14h  and 01h is transmitted as a 22 kHz tone signal. After that  in order to immediately switch to the RX mode  the bypass switch 34 is turned off  and waiting for the control data of 22h of 1 byte  which is a response that indicates reset completion  to be transmitted from the selector apparatus as a 22 kHz tone signal  is performed.

STATEMENT OF THE INVENTION
Accordingly  an embodiment of the present invention provides an electric power supply apparatus comprising a power-supply unit that supplies low noise block driving electric power through an electric power line to a low noise block down converter in compliance with the digital satellite equipment control standard  a transmission unit that transmits a control command for a digital satellite equipment control apparatus through the electric power line  a receiving unit that receives a response from the digital satellite equipment control apparatus corresponding to the control command through the electric power line  and a suppression unit that suppresses a level of noise that can occur in response to a switching of the switching unit that switches between a TX mode in which the control command is transmitted and an RX mode in which a response is received.

OBJECT OF THE INVENTION
One object according to an embodiment of the present disclosure  is to provide electric power supply apparatus to suppress the level of noise that can occur.

Another object according to an embodiment of the present disclosure  is to provide electric power supply apparatus to stably perform two-way communication with a DiSEqC apparatus.

SUMMARY
Since switching is performed from the TX mode (transmission mode) to the RX mode (reception mode) in the manner described above  in a case where the bypass switch 34 is switched instantly from an on state to an off state  the LNB driving electric power passing through the bypass switch 34 in the TX mode flows into the coil (220 ?H) of the choke unit 33. Therefore  if the electrical current value flowing through this coil is denoted as I and the differential change amount as dI/dt  a counter-electromotive force in proportion to the electrical current increase amount of 220 [?H] ? dI/dt will be generated in the power supply line across the coil. This counter-electromotive force will be described specifically.
Fig. 5 illustrates an example of the configuration of an equivalent circuit of the DC power-supply unit 20 in which the bypass switch 34 is considered.
In the figure  an FET T1 corresponds to the bypass switch 34. When the series resistor R4 of the FET T1 is assumed to be 300 m?  and the remaining resistance amount R2 of the coil L1 forming the choke unit 33 is assumed to be 600 m?  in the TX mode  an LNB driving electric power of approximately 150 mA flows through the FET T1. When switched to the RX mode  this power flows into the coil L1 and  as shown in Fig. 6  is generated as a counter-electromotive force (glitch noise) in the form of a spike of about 1 Vpp.
Since this glitch noise occurs immediately after the 22 kHz tone signal is transmitted  depending on the performance that receives the 22 kHz tone signal of the DiSEqC apparatus  this glitch noise is interpreted as part of a 22 kHz tone signal that falls within the standard value of 650 mVpp ±250 mV  and a reception process is continued by assuming that the transmission of the 22 kHz tone signal from the DC power-supply unit 20 is continued even after this.
On the other hand  in the DC power-supply unit 20 of the communication party  the transmission of the 22 kHz tone signal has already been completed. Consequently  in the LNB 2 that continues the reception process  after a predetermined time has passed  this glitch noise is processed as an error  and a situation can arise where a command using the 22 kHz tone signal that has been received before that time is not processed properly. That is  depending on the generation timing of the glitch noise  in the worst case  there may be a situation where two-way communication between the DC power-supply unit 20 and the LNB 2 is not established.
The present disclosure has been made in view of such circumstances  and aims to stably perform two-way communication with a DiSEqC apparatus.
An electric power supply apparatus according to a first embodiment of the present disclosure includes: a power-supply unit that supplies low noise block driving electric power through an electric power line to a low noise block down converter in compliance with the digital satellite equipment control standard; a transmission unit that transmits a control command for a digital satellite equipment control apparatus through the electric power line; a receiving unit that receives a response from the digital satellite equipment control apparatus corresponding to the control command through the electric power line; and a suppression unit that suppresses a level of noise that can occur in response to a switching of the switching unit that switches between a TX mode in which the control command is transmitted and an RX mode in which a response is received.
The electric power-supply apparatus according to the first embodiment of the present disclosure may further include a choke coil that suppresses attenuation of the response from the DiSEqC apparatus through the power supply line  wherein when the switching unit is switched from the TX mode to the RX mode  noise may be a counter-electromotive force that can occur as a result of the LNB driving electric power being made to flow into the choke coil.
The electric power-supply apparatus according to the first embodiment of the present disclosure may further include a control unit that outputs a switching signal for the switching unit  wherein the suppression unit may integrate and delay the switching signal that is output from the control unit and supplies the switching signal to the switching unit  thereby causing the switching unit to be gradually switched from the TX mode to the RX mode.
The switching unit may be formed of a plurality of switches  and the suppression unit may cause the plurality of switches to be switched with a predetermined time difference  thereby switching in a step-like manner from the TX mode to the RX mode.
A receiving apparatus according to a second embodiment of the present disclosure includes a power-supply unit that supplies low noise block driving electric power through an electric power line to a low noise block down converter in compliance with the digital satellite equipment control standard; a tuner that inputs an IF signal that is reflected and converged by a parabolic antenna and that is converted from an RF signal by the low noise block down converter; a transmission unit that transmits a control command for a digital satellite equipment control apparatus through the electric power line; a receiving unit that receives a response from the digital satellite equipment control apparatus corresponding to the control command through the electric power line; and a suppression unit that suppresses a level of noise that can occur in accordance with a switching of the switching unit that switches between a TX mode in which the control command is transmitted and an RX mode in which a response is received.
In the first and second embodiments of the present disclosure  the level of the noise is suppressed in accordance with the switching of the switching unit that switches between the TX mode that transmits a control command and an RX mode that receives a response.
According to the first embodiment of the present disclosure  it is possible to suppress the level of noise that can occur.
According to the second embodiment of the present disclosure  it is possible to stably perform two-way communication with a DiSEqC apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the invention will now be described with reference to the accompanying drawings  throughout which like parts are referred to by like references  and in which:
Fig. 1 is a block diagram illustrating an example of the configuration of a receiving apparatus of the related art;
Fig. 2 is a block diagram illustrating an example of the configuration of a DC power-supply unit of Fig. 1;
Fig. 3 illustrates an example of a transmission waveform of control data for DiSEqC;
Fig. 4 illustrates timing of two-way communication in the DiSEqC Ver. 2.0 standard;
Fig. 5 is a circuit diagram illustrating an example of the configuration of an equivalent circuit of a DC power-supply unit in which a bypass switch is considered according to the related art;
Fig. 6 illustrates glitch noise and the like  which can occur in the equivalent circuit of Fig. 5;
Fig. 7 is a circuit diagram illustrating a first configuration example of a DC power-supply unit according to an embodiment;
Fig. 8 illustrates glitch noise and the like  which can occur from the DC power-supply unit of Fig. 7;
Fig. 9 is a circuit diagram illustrating a second configuration example of a DC power-supply unit according to an embodiment; and
Fig. 10 illustrates glitch noise and the like  which can occur from the DC power-supply unit of Fig. 9.

DETAILED DESCRIPTION OF EMBODIMENTS
The best mode for embodying the present disclosure (hereinafter referred to as an embodiment) will be described below in detail with reference to the drawings.

1. Embodiment
First configuration example of DC power-supply unit
Fig. 7 is a circuit diagram illustrating a first configuration example of a DC power-supply unit according to an embodiment. A DC power-supply unit 40 is used for a receiving apparatus 10 in place of a DC power-supply unit 20 whose equivalent circuit is shown in Fig. 5.
The DC power-supply unit 40 is such that  with respect to the DC power-supply unit 20 of Fig. 5  a capacitor C1 having a capacitance 10 nF indicated using a dashed line 31 is added between the gate terminal of the FET T1 corresponding to the bypass switch 34  and GND. Since the rest of the construction is the same as that of Fig. 5  the description thereof is omitted.
Fig. 8 illustrates glitch noise  and the like  which can originate from the DC power-supply unit 40 shown in Fig. 7.
In the DC power-supply unit 40  as a result of a capacitor C1 being added  a TX/RX mode switching signal from the control unit 36 is integrated and delayed. As a result of this delay  the switching operation of the FET T1 from on to off becomes moderate  and the flow-in speed of the LNB driving electric power into the coil L1 forming the choke unit 33 can be moderated. Therefore  the differential change amount dI/dt of the electrical current value I flowing through the coil L1 decreases  and the counter-electromotive force 220 [?H] ? dI/dt that occurs across the coil L1 is reduced.
Specifically  in the case of the equivalent circuit of the DC power-supply unit 40 shown in Fig. 8  the glitch noise in the form of a spike  which occurs in the LNB driving electric power  is suppressed to 250 mVpp  which is smaller than the lower limit standard value 400 mVpp of the 22 kHz tone signal. Consequently  the glitch noise can be suppressed to glitch noise to such a degree as to not be interpreted as part of the 22 kHz tone signal in the DiSEqC apparatus.

Second configuration example of DC power-supply unit
Fig. 9 illustrates a second configuration example of a DC power-supply unit according to an embodiment. This DC power-supply unit 50 is used for the receiving apparatus 10 in place of the DC power-supply unit 20 whose equivalent circuit is shown in Fig. 5. The DC power-supply unit 50 is such that an FET T3 or the like encircled by the dashed line 51 is added to the DC power-supply unit 20 of Fig. 5  and the rest of the configuration is the same as that of Fig. 5. Thus  the description thereof is omitted.
Fig. 10 illustrates glitch noise and the like  which can occur from the DC power-supply unit 50 shown in Fig. 9.
In the DC power-supply unit 50  the FET T1 and the FET T2  which are connected in parallel  correspond to the bypass switch 34. The FET T3 is configured to be turned off in accordance with the switching pulse RX/TXd by being delayed by 300 ms from the timing at which the FET T1 is turned off in accordance with the switching pulse RX/TX. For example  in order to distribute the LNB driving electric power so that an electrical current of about 70% of the LNB driving electric power flows into the FET T1  and an electrical current of about 30% flows into the FET T3  it is sufficient that the series resistor R9 of the FET T3 be set at 4 ?.
In the case of the DC power-supply unit 50  even if switching is performed from the TX mode to the RX mode  LNB driving electric power does not suddenly flow into the coil L1 forming the choke unit 33. Therefore  glitch noise in the form of a spike  which occurs in the electric power line  can be suppressed to spike/noise components of approximately 250 mVpp  which is smaller than the lower limit standard value 400 mVpp of the 22 kHz tone signal. That is  in the DiSEqC apparatus  the glitch noise can be suppressed to glitch noise to such a degree as to not be interpreted as part of the 22 kHz tone signal.
Furthermore  in the case of the DC power-supply unit 50  by only delaying the switching pulse TX/RX for the FET T1 by a typical latch circuit  a switching pulse TX/RXd for the FET T3 can be obtained. Thus  it is possible to reduce the circuit scale of the entire DC power-supply unit 50.
In the DC power-supply unit 50  the bypass switch is realized by using FETs of two stages. Alternatively  the bypass switch may be realized by FETs of many stages.
In the DC power-supply unit 40 or 50 described in the foregoing  it is possible to suppress glitch noise that can occur when switched from the TX mode to the RX mode to the lower limit standard value of the 22 kHz tone signal of 400 mVpp or less.
Therefore  if the DC power-supply unit 40 or 50 is adopted as the receiving apparatus of digital television broadcast  it becomes possible to realize stable two-way communication between the receiving apparatus and the DiSEqC apparatus.
The present disclosure contains subject matter related to that disclosed in Japanese Priority Patent Application JP 2011-186746 filed in the Japan Patent Office on August 30  2011  the entire contents of which are hereby incorporated by reference.
It should be understood by those skilled in the art that various modifications  combinations  sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.

WE CLAIM:

1. An electric power supply apparatus comprising:
a power-supply unit that supplies low noise block driving electric power through an electric power line to a low noise block down converter in compliance with the digital satellite equipment control standard;
a transmission unit that transmits a control command for a digital satellite equipment control apparatus through the electric power line;
a receiving unit that receives a response from the digital satellite equipment control apparatus corresponding to the control command through the electric power line; and
a suppression unit that suppresses a level of noise that can occur in response to a switching of the switching unit that switches between a TX mode in which the control command is transmitted and an RX mode in which a response is received.

2. The electric power-supply apparatus according to Claim 1  further comprising a choke coil that suppresses attenuation of the response from the digital satellite equipment control apparatus through the power supply line 
wherein when the switching unit is switched from the TX mode to the RX mode  noise is a counter-electromotive force that can occur as a result of the low noise block driving electric power being made to flow into the choke coil.

3. The electric power-supply apparatus according to Claim 2  further comprising a control unit that outputs a switching signal for the switching unit 
wherein the suppression unit integrates and delays the switching signal that is output from the control unit and supplies the switching signal to the switching unit  thereby causing the switching unit to be gradually switched from the TX mode to the RX mode.

4. The electric power-supply apparatus according to Claim 2 
wherein the switching unit is formed of a plurality of switches  and
wherein the suppression unit causes the plurality of switches to be switched with a predetermined time difference  thereby switching in a step-like manner from the TX mode to the RX mode.

5. A receiving apparatus comprising:
a power-supply unit that supplies low noise block driving electric power through an electric power line to a low noise block down converter in compliance with the digital satellite equipment control standard;
a tuner that inputs an IF signal that is reflected and converged by a parabolic antenna and that is converted from an RF signal by the low noise block down converter;
a transmission unit that transmits a control command for a digital satellite equipment control apparatus through the electric power line;
a receiving unit that receives a response from the digital satellite equipment control apparatus corresponding to the control command through the electric power line; and
a suppression unit that suppresses a level of noise that can occur in accordance with a switching of the switching unit that switches between a TX mode in which the control command is transmitted and an RX mode in which a response is received.