CN2845356Y - Satellite digit set-top box with LNB voltage switching circuit - Google Patents
Satellite digit set-top box with LNB voltage switching circuit Download PDFInfo
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- CN2845356Y CN2845356Y CNU200520086874XU CN200520086874U CN2845356Y CN 2845356 Y CN2845356 Y CN 2845356Y CN U200520086874X U CNU200520086874X U CN U200520086874XU CN 200520086874 U CN200520086874 U CN 200520086874U CN 2845356 Y CN2845356 Y CN 2845356Y
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- lnb
- top box
- stabilizing chip
- voltage
- voltage stabilizing
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Abstract
The utility model discloses a satellite digit set-top box with an LNB voltage switching circuit, which comprises a CPU, a radio frequency head and a direct current power supply. A set-top box circuit comprises a voltage stabilizing chip KA317, the output voltage of which is adjustable; the voltage stabilizing chip takes the place of a traditional special control chip for an LNB, and is matched with a simple resistance regulating circuit, which realizes the effective switching of the output voltage; the voltage stabilizing chip provides a 13V/18V polarized voltage for the frequency converter under low noise LNB of an outdoor unit, and ensures the reliable reception of a satellite signal. Besides, a self-restoring fuse is additionally arranged on the output end of the voltage stabilizing chip KA317, which realizes the effective protection of an indoor unit and eliminates the trouble of maintenance resulting from the damage of a common fuse. The LNB voltage switching circuit of the utility model has the advantages of simple structure and low cost, and is suitable for the circuit of a basic satellite digit set-top box.
Description
Technical field
The utility model relates to a kind of improvement of satellite digital set-top box circuit, specifically, relates to a kind of control circuit that the set-top box circuit switches the supply power voltage of low noise block downconverter LNB that is used for.
Background technology
At present, for preparing comprehensive digital broadcasting service, but many people just are being devoted to research and develop the Digital Television and the set-top box of receiving digital broadcast and data broadcasting.Because simulated television in whole world extensive use, therefore, can receive digital broadcasting and data broadcasting signal for making existing simulated television, set-top box is extensively promoted and is used.For making the satellite digital set-top box can receive the digital broadcast signal of different satellites transmits, need 13V/18V (vertical/horizontal) be provided polarizing voltage for the low noise block downconverter LNB of outdoor unit by coaxial cable.In present set-top box circuit, all be the switching requirement of satisfying polarizing voltage by the LNB control chip of special use generally.But, use the control chip cost height of this special use, and in basic model satellite digital set-top box, can cause the waste of function, be unfavorable for extensively popularizing of equipment.
Summary of the invention
The utility model is for the cost height that the special-purpose LNB control chip of available technology adopting comes the low noise block downconverter LNB for outdoor unit to provide supply power voltage to cause is provided, in basic model satellite digital set-top box, can cause the problem of function waste, a kind of novel set-top box LNB voltage commutation circuit is provided, by adopting the LNB control chip of simple circuit configuration instead of dedicated, realized effective switching to low noise block downconverter LNB supply power voltage, thereby greatly reduce production cost of products, improved the competitiveness of product in market.
For solving the problems of the technologies described above, the utility model is achieved by the following technical solutions:
A kind of satellite digital set-top box with LNB voltage commutation circuit, comprise CPU, tuner and DC power supply, the voltage stabilizing chip that in described set-top box circuit, includes an Adjustable Output Voltage, the input of described voltage stabilizing chip connects DC power supply, output connects tuner, the adjustable side connects its output through a resistance on the one hand, adjusts circuit ground through resistance on the other hand.
As further qualification to technique scheme, in described resistance adjustment circuit, include a switch element, the control end of described switch element links to each other with the GPIO mouth of CPU, two gating end one end ground connection, the other end connects the adjustable side of described voltage stabilizing chip through a resistance, and the adjustable side of described voltage stabilizing chip is through another grounding through resistance.Wherein, described switch element can adopt a NPN type triode to realize, the base stage of described NPN type triode connects the GPIO mouth of CPU, and collector electrode connects the adjustable side of described voltage stabilizing chip through resistance, emitter is ground connection on the one hand, links to each other through the adjustable side of another resistance with described voltage stabilizing chip on the other hand.Certainly, described resistance is adjusted circuit and also can be adopted a potentiometer to realize.
As to further the limiting again of technique scheme, between the output of described voltage stabilizing chip and tuner, be connected with one from the homing position type fuse, described tuner is by the provide supply power voltage of coaxial cable for the low noise block downconverter LNB of outdoor unit.
As the further qualification again to technique scheme, the model of described voltage stabilizing chip is KA317, or adopts other model identical with its function, realizes that as chips such as LM317T its input and output are respectively through filter capacitor ground connection.
Compared with prior art, advantage of the present utility model and good effect are: the utility model replaces traditional LNB special integrated circuit by adopting voltage stabilizing chip KA317, cooperate simple resistance to adjust effective switching that circuit has been realized output voltage, for the low noise block downconverter LNB of outdoor unit provides 13V/18V polarizing voltage, guaranteed the reliable reception of satellite-signal.In addition,, realized effective protection, and removed the maintenance trouble of using the general insurance silk to cause from because of damage to indoor unit by setting up the self-resetting type fuse at the output of voltage stabilizing chip KA317.LNB voltage commutation circuit of the present utility model is simple in structure, with low cost, is applicable in the basic model satellite digital set-top box circuit.
Description of drawings
Fig. 1 is the application principle figure of voltage stabilizing chip KA317;
Fig. 2 is the schematic circuit of the utility model LNB voltage commutation circuit.
Embodiment
Below in conjunction with the drawings and specific embodiments the utility model is done explanation in further detail.
Employed voltage stabilizing chip KA317 is present very general integrated circuit in the utility model, and its application principle as shown in Figure 1.The relational expression of output voltage is
V
O=1.25(1+R
2/R
1)+I
abjR
2 ①
Wherein, electric current I
AbjRelatively very little, maximum also has only 100 μ A, and remains unchanged substantially, so magnitude of voltage I
AbjR
2Can ignore, thus, 1. the above-mentioned relation formula can be reduced to
V
O=1.25(1+R
2/R
1) ②
The utility model utilizes described voltage stabilizing chip KA317 to cooperate suitable resistance to adjust the switching that circuit is realized the LNB supply power voltage, and its circuit theory diagrams are referring to shown in Figure 2.
Among Fig. 2, the input IN connection+22V DC power supply of voltage stabilizing chip U705, and through filter capacitor C705, C706 ground connection, output OUT is through the tuner of fuse F701 junctor top box, and links to each other with its adjustable side abj through resistance R 712.Described adjustable side abj connects the collector electrode of a NPN type triode VT701 through resistance R 711, and through resistance R 703 ground connection.The base stage of described NPN type triode VT701 is through the GPIO mouth of resistance R 704 connection CPU, grounded emitter.When needs provide 13V perpendicular polarization voltage for outdoor unit LNB, the GPIO mouth of Controlled CPU output high level signal (3.3V).At this moment, NPN type triode VT701 saturation conduction, collector voltage is dragged down, the 2. middle resistance R of above-mentioned relation formula
2Resistance be the resistance 2.031K in parallel of resistance R 711 and R703.So the magnitude of voltage of voltage stabilizing chip U705 output is 1.25 (1+2031/200)=13.94V, exports to outdoor unit LNB through the tuner of set-top box by coaxial cable, for it provides 13V supply power voltage.When the digital signal that receives from different satellites, in the time of need providing 18V horizontal polarization voltage for outdoor unit LNB, the GPIO mouth output low level signal of Controlled CPU.At this moment, NPN type triode VT701 ends, the 2. middle resistance R of relational expression
2Resistance be the resistance 2.7K of resistance R 703.So the magnitude of voltage of voltage stabilizing chip U705 output is 1.25 (1+2700/200)=18.13V, just in time satisfies the 18V supply power voltage requirement of low noise block downconverter LNB.
Among Fig. 2, fuse F701 adopts a self-resetting type fuse RXE030 to realize, when short circuit appears in outdoor unit LNB, and described fuse F701 automatic disconnection, thus effectively protected the indoor set top box to avoid damaging.When outdoor unit recovers just often, described fuse F701 can recover conducting automatically, thereby has removed the maintenance trouble that adopts the general insurance silk to cause because of damage from.
The utility model has been realized the reliable switching of outdoor unit LNB supply power voltage has been avoided the use of special-purpose LNB control chip, thereby reduced cost by adopting above-mentioned simple circuit configuration, has satisfied the designing requirement of basic model satellite digital set-top box.Certainly; above-mentioned explanation is not to be to restriction of the present utility model; the utility model also is not limited in above-mentioned giving an example, and variation, remodeling, interpolation or replacement that those skilled in the art are made in essential scope of the present utility model also should belong to protection range of the present utility model.
Claims (7)
1. satellite digital set-top box with LNB voltage commutation circuit, comprise CPU, tuner and DC power supply, it is characterized in that: the voltage stabilizing chip that in described set-top box circuit, includes an Adjustable Output Voltage, the input of described voltage stabilizing chip connects DC power supply, output connects tuner, the adjustable side connects its output through a resistance on the one hand, adjusts circuit ground through resistance on the other hand.
2. the satellite digital set-top box with LNB voltage commutation circuit according to claim 1, it is characterized in that: in described resistance adjustment circuit, include a switch element, the control end of described switch element links to each other with the GPIO mouth of CPU, two gating end one end ground connection, the other end connects the adjustable side of described voltage stabilizing chip through a resistance, and the adjustable side of described voltage stabilizing chip is through another grounding through resistance.
3. the satellite digital set-top box with LNB voltage commutation circuit according to claim 2, it is characterized in that: described switch element adopts a NPN type triode to realize, the base stage of described NPN type triode connects the GPIO mouth of CPU, collector electrode connects the adjustable side of described voltage stabilizing chip, grounded emitter through resistance; In addition, the adjustable side of described voltage stabilizing chip is also through the direct ground connection of another resistance.
4. the satellite digital set-top box with LNB voltage commutation circuit according to claim 1 is characterized in that: described resistance is adjusted circuit and can be adopted a potentiometer to realize.
5. according to claim 1 or 2 or 4 described satellite digital set-top box with LNB voltage commutation circuit, it is characterized in that: be connected with one from the homing position type fuse between the output of described voltage stabilizing chip and tuner, described tuner provides supply power voltage by coaxial cable for the low noise block downconverter LNB of outdoor unit.
6. the satellite digital set-top box with LNB voltage commutation circuit according to claim 1 is characterized in that: the input of described voltage stabilizing chip and output are respectively through filter capacitor ground connection.
7. the satellite digital set-top box with LNB voltage commutation circuit according to claim 1 is characterized in that: the model of described voltage stabilizing chip is KA317.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
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CNU200520086874XU CN2845356Y (en) | 2005-09-09 | 2005-09-09 | Satellite digit set-top box with LNB voltage switching circuit |
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CNU200520086874XU CN2845356Y (en) | 2005-09-09 | 2005-09-09 | Satellite digit set-top box with LNB voltage switching circuit |
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CN2845356Y true CN2845356Y (en) | 2006-12-06 |
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CNU200520086874XU Expired - Fee Related CN2845356Y (en) | 2005-09-09 | 2005-09-09 | Satellite digit set-top box with LNB voltage switching circuit |
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Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN101895698A (en) * | 2010-06-29 | 2010-11-24 | 苏州市华芯微电子有限公司 | Integrated circuit with functions of bias and polarization selection |
CN101741055B (en) * | 2009-12-31 | 2011-12-28 | 成都东银信息技术股份有限公司 | Method for protecting satellite television LNB from short circuit |
CN104254008A (en) * | 2014-09-16 | 2014-12-31 | 深圳市九洲电器有限公司 | LNB loop polarization voltage switching control circuit and device |
-
2005
- 2005-09-09 CN CNU200520086874XU patent/CN2845356Y/en not_active Expired - Fee Related
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN101741055B (en) * | 2009-12-31 | 2011-12-28 | 成都东银信息技术股份有限公司 | Method for protecting satellite television LNB from short circuit |
CN101895698A (en) * | 2010-06-29 | 2010-11-24 | 苏州市华芯微电子有限公司 | Integrated circuit with functions of bias and polarization selection |
CN101895698B (en) * | 2010-06-29 | 2012-10-03 | 苏州华芯微电子股份有限公司 | Integrated circuit with functions of bias and polarization selection |
CN104254008A (en) * | 2014-09-16 | 2014-12-31 | 深圳市九洲电器有限公司 | LNB loop polarization voltage switching control circuit and device |
CN104254008B (en) * | 2014-09-16 | 2017-11-07 | 深圳市九洲电器有限公司 | A kind of LNB rings wear polarizing voltage control switching circuit and device |
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C14 | Grant of patent or utility model | ||
GR01 | Patent grant | ||
C19 | Lapse of patent right due to non-payment of the annual fee | ||
CF01 | Termination of patent right due to non-payment of annual fee |