A kind of method of protecting satellite television LNB from short circuit
Technical field
The present invention relates to the signal processing field, especially a kind of method of protecting satellite television LNB from short circuit.
Background technology
In the satellite digital TV system, because LNB (Low Noise Block, low noise block downconverter, its function is that the satellite-signal process that will be transmitted by feed is amplified and down-conversion, Ku or C-band signal are become L-band, send satellite receiver to through coaxial cable) be installed in the open air together with reception antenna, the rf signal line of receiver carries out feed and LNB needs via satellite.The LNB power supply circuits that are built in the receiver need produce H/V control voltage (H represents horizontal polarization, and V represents perpendicular polarization), also will be able to control simultaneously and open or close the output of H/V voltage.In case the holding wire short circuit of stack H/V control voltage will cause the receiver electric power system unusual, and the system that makes restarts, and can cause device failure when serious.
Generation for fear of above-mentioned phenomenon; LNB power supply circuits in satellite receiver need be considered short-circuit protection; common LNB short-circuit protection method seals in thermistor for the input at the LNB power supply circuits; when the LNB short circuit takes place when; the electric current of thermistor of flowing through will become very big; in case current value overrate thermistor will heat up rapidly and resistance moment will become very big, thereby disconnect power supply circuits.
Summary of the invention
The method that the purpose of this invention is to provide a kind of protecting satellite television LNB from short circuit in LNB short-circuit detecting task, is at first opened the output of H/V control voltage, waits for a period of time with regulated output voltage, reads the short circuit detection levpl value then immediately; If the LNB short circuit is removed, then stay open the output of H/V control voltage, program turns back to and begins the place and re-execute short-circuit detecting then; If LNB, then closes the output of H/V control voltage immediately still for short circuit, in video output, show the OSD information of " LNB short circuit " printed words simultaneously, program turns back to short-circuit detecting and begins the place after a period of time of delaying time then.Technical scheme response of the present invention is fast, and system can detect short circuit and disconnect the LNB power supply in 100 milliseconds; In case the LNB short circuit is removed, system can detect and recover the LNB power supply in 100 milliseconds, and recovers operate as normal immediately.
Description of drawings
The present invention will illustrate by example and with reference to the mode of accompanying drawing, wherein:
Fig. 1 is the theory diagram of LNB short-circuit protection circuit of the present invention.
Fig. 2 is a schematic flow sheet of the present invention.
Embodiment
Disclosed all features in this specification, or the step in disclosed all methods or the process except mutually exclusive feature and/or step, all can make up by any way.
Disclosed arbitrary feature in this specification (comprising any accessory claim, summary and accompanying drawing) is unless special narration all can be replaced by other equivalences or the alternative features with similar purpose.That is, unless special narration, each feature is an example in a series of equivalences or the similar characteristics.
The theory diagram of LNB short-circuit protection circuit as shown in Figure 1; comprise CPU and the voltage adjuster that links to each other with CPU thereof; input voltage at first enters voltage adjuster; voltage adjuster output H/V under CPU control controls voltage to LNB; CPU is by two output pin control voltage adjusters; one of them pin is as H/V voltage output control switch, and another pin is selected H or the output of V control voltage.CPU also uses an input pin to import as short-circuit detecting simultaneously.
When the LNB short circuit takes place, saltus step will take place in short-circuit detecting pin level, and in a single day CPU detects this level saltus step will close the output of H/V control voltage immediately.In order to confirm whether short circuit is removed, CPU (preferred 100 milliseconds) at set intervals detects the LNB short-circuit state.
Concrete control flow chart as shown in Figure 2, in LNB short-circuit detecting task, at first open the output of H/V control voltage, wait for a period of time (preferred 2 milliseconds) with regulated output voltage, read the short circuit detection levpl value then immediately, if the LNB short circuit is removed, then stay open the output of H/V control voltage, program turns back to and begins the place and re-execute short-circuit detecting then; If still be short circuit, then close the output of H/V control voltage immediately, the OSD information that in video output, shows " LNB short circuit " printed words simultaneously, delay time a period of time then (preferred 100 milliseconds) afterwards program turn back to beginning LNB short-circuit detecting place, reopen the output of H/V control voltage, repeat the testing process of foregoing description.
Technical scheme response of the present invention is fast, and system can detect short circuit and disconnect the LNB power supply in 100 milliseconds; In case the LNB short circuit is removed, system can detect and recover the LNB power supply in 100 milliseconds, and recovers operate as normal immediately.
The present invention is not limited to aforesaid embodiment.The present invention expands to any new feature or any new combination that discloses in this manual, and the arbitrary new method that discloses or step or any new combination of process.