1. A synchronous operating system for a plurality of DC-AC converters, oscillator capacitors of the plurality of DC-AC converters being commonly connected, AC power from the plurality of DC-AC converters being supplied to a plurality of loads, each of the plurality of DC-AC converters comprising:
a resonant circuit including a capacitor connected to at least one of primary and secondary windings of a transformer, an output thereof being connected to the load;
a plurality of switching elements of network configuration to supply AC power to the load through the resonant circuit;
a first oscillator configured to generate a first triangular wave signal whose inclination for charging the oscillator capacitor and inclination for discharging the oscillator capacitor are the same;
a second oscillator configured to generate a second triangular wave signal that is an inverted signal of the first triangular wave signal;
an error amplifier configured to amplify a voltage related to a current passing through the load with respect to a reference voltage;
a signal generator of an initialize signal configured to alternately allow a first drive signal and a second drive signal during every half period of the first triangular wave signal, wherein the first drive signal is generated for driving at least one of the plurality of the switching elements to supply current to the load, and
the second drive signal is generated for driving at least one of the rest of the plurality of the switching elements to supply current to the load in an opposite manner to that of the first drive signal; and wherein:
in a period while the first drive signal is allowed to generate, the first triangular wave signal and an output of the error amplifier are compared to generate the first drive signal with a pulse width related to the current of the load; and
in a period while the second drive signal is allowed to generate, the second triangular wave signal and the output of the error amplifier are compared to generate the second drive signal having a pulse width substantially equal to that of the first drive signal and an opposite phase with respect to the first drive signal.
2. A DC-AC converter comprising:
a resonant circuit including a capacitor connected to at least one of primary and secondary windings of a transformer, an output thereof being connected to a load;
a plurality of switching elements of network configuration to supply AC power to the load through the resonant circuit;
an first oscillator configured to generate a first triangular wave signal whose inclinations for charging and that for discharging are the same;
a second oscillator generating a second triangular wave signal that is an inverted signal of the first triangular wave signal;
an error amplifier configured to amplify a voltage related to a current passing through the load with respect to a reference voltage;
a signal generator of an initialize signal configured to alternately allow a first drive signal and a second drive signal during every half period of the first triangular wave signal, wherein the first drive signal is generated for driving at least one of the plurality of the switching elements to supply current to the load, and the second drive signal is generated for driving at least one of the rest of the plurality of the switching elements to supply current to the load in an opposite manner to that of the first drive signal, and wherein in a period while the first drive signal is allowed to generate, the first triangular wave signal and an output of the error amplifier are compared to generate the first drive signal with a pulse width related to the current of the load; and
in a period while the second drive signal is allowed to generate, the second triangular wave signal and the output of the error amplifier are compared to generate the second drive signal having a pulse width substantially equal to that of the first drive signal and an opposite phase with respect to the first drive signal.
3. A DC-AC converter according to claim 2, wherein the period while the first drive signal is allowed to generate is one of a rise inclination period and a fall inclination period of the first triangular wave signal and the period while the second drive signal is allowed to generate is another of the rise inclination period and the fall inclination period of the first triangular wave signal.
4. A DC-AC converter according to claim 2, wherein the period while the first drive signal is allowed to generate is one of that while potential of the first triangular wave signal is at or above a midpoint potential between upper and lower limit thereof and that while potential of the first triangular wave signal is at or below the midpoint potential and the period while the second drive signal is allowed to generate is another of that while potential of the first triangular wave signal is at or above the midpoint potential between upper and lower limit thereof and that while potential of the first triangular wave signal is at or below the midpoint potential.
5. An integration circuit for controlling a plurality of switching elements of network configuration to supply power to a load, comprising:
a first oscillator configured to generate a first triangular wave signal whose inclinations for charging and that for discharging are the same;
a second oscillator configured to generate a second triangular wave signal that is an inverted signal of the first triangular wave signal;
an error amplifier configured to amplify a voltage related to a current passing through the load with respect to a reference voltage;
a signal generator of an initialize signal configured to alternately allow a first drive signal and a second drive signal during every half period of the first triangular wave signal, the first drive signal being generated for driving at least one of the plurality of the switching elements to supply current to the load, and the second drive signal being generated for driving the rest of the plurality of the switching elements to supply current to the load in an inverted manner, wherein
in a period while the first drive signal is allowed to generate, the first triangular wave signal and an output of the error amplifier are compared to generate the first drive signal having a pulse width related with the current of the load; and
in a period while the second drive signal is allowed to generate, the second triangular wave signal and the output of the error amplifier are compared to generate the second drive signal having a pulse width substantially equal to that of the first drive signal and an opposite phase with respect to the first drive signal.
6. An integration circuit according to claim 5, wherein the period while the first drive signal is allowed to generate is one of a rise inclination period and a fall inclination period of the first triangular wave signal and the period while the second drive signal is allowed to generate is another of the rise inclination period and the fall inclination period of the first triangular wave signal.
7. An integration circuit according to claim 5, wherein the period while the first drive signal is allowed to generate is one of that where potential of the first triangular wave signal is at or above a midpoint potential between upper and lower limit thereof and that while potential of the first triangular wave signal is at or below the midpoint potential and the period while the second drive signal is allowed to generate is another of that where potential of the first triangular wave signal is at or above the midpoint potential between upper and lower limit thereof and that while potential of the first triangular wave signal is at or below the midpoint potential.
8. An integration circuit according to claim 5, wherein
the first and second drive signals each has a predetermined maximum ON duty being smaller than a duty of 50%.
9. An integration circuit according to claim 5, wherein
an operation of stopping each switching element starts when an ON duty of the first and second drive signals reaches a predetermined maximum ON duty being smaller than a duty of 50%.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. Apparatus for applying anti-copy-protection to a raster-scanned video signal to produce a modified video signal, the apparatus comprising:
an input for receiving a video signal, the video signal having a vertical synchronisation pulse defined between a leading edge and a trailing edge, wherein the leading edge and the trailing edge are consecutive edges in the video signal;
circuitry configured to modify the vertical synchronisation pulse between the leading edge and the trailing edge of the video signal received by the input to produce a modified video signal, the modified signal being viewable on a display device at or near to the quality intended by the originator of the video signal but such that after recording by a recording device, the recorded signal exhibits a reduction in vertical stability when played back and viewed on the display device, wherein the circuitry is further configured to modify the vertical synchronisation pulse such that after recording by the recording device, the average voltage level of a modified vertical synchronisation pulse is shifted towards a blanking level in comparison to the average level before recording; and
an output configured to output the modified video signal.
2. Apparatus according to claim 1, wherein the circuitry is further configured to modify the vertical synchronisation pulse such that a time duration of the vertical synchronisation pulse remains substantially unaltered.
3. Apparatus according to claim 1 wherein the circuitry comprises a waveform generator for adding a waveform to the vertical synchronisation pulse in the video signal received by the input such.
4. Apparatus according to claim 3 wherein the wave form generator is operable to add to the vertical synchronisation pulse a waveform that has a peak level above a blanking level of the video signal.
5. Apparatus according to claim 3 wherein the waveform generator is operable to add a square wave to the vertical synchronisation pulse.
6. Apparatus according to claim 1 wherein the circuitry is further configured to add a front porch to the video signal adjacent to the synchronisation pulse.
7. Apparatus according to claim 6 wherein the front porch has a voltage level substantially equal to that of the vertical synchronisation pulse.
8. Apparatus according to claim 6 wherein the circuitry is configured to modify the vertical synchronisation pulse of the video signal such that after recording by a recording device that amplifies and clamps the video signal, the recorded signal exhibits a reduction in vertical stability when played back and viewed on the display device.
9. Apparatus for applying anti-copy-protection to a raster-scanned video signal to produce a modified video signal, the apparatus comprising:
an input for receiving a video signal which is to be modified, the video signal having a vertical synchronisation pulse defined between a leading edge and a trailing edge, wherein the leading edge and the trailing edge are consecutive edges in the video signal;
circuitry configured to modify the vertical synchronisation pulse between the leading edge and the trailing edge of the video signal received by the input to produce a modified video signal, the circuitry adding a waveform to the vertical synchronisation pulse with an amplitude at least equal to that of the vertical synchronisation pulse, wherein the circuitry is further configured to modify the vertical synchronisation pulse such that after recording by a recording device, the average voltage level of a modified vertical synchronisation pulse is shifted towards a blanking level in comparison to the average level before recording, and
an output configured to output the modified video signal.
10. Apparatus according to claim 9 wherein the waveform has a frequency of at least 5000 KHz.
11. A method for adding anti-copy-protection to a raster-scanned video signal to produce a modified signal, comprising:
receiving a video signal which is to be modified, the video signal having a vertical synchronisation pulse defined between a leading edge and a trailing edge, wherein the leading edge and the trailing edge are consecutive edges in the video signal;
modifying the vertical synchronisation pulse of the video signal such that the modified video signal is viewable on a display device at or near to the quality intended by the originator of the video signal, but such that after recording by a recording device, the recorded signal exhibits a reduction in vertical stability when played back and viewed on the display device, wherein modifying the vertical synchronisation pulse further includes modifying the vertical synchronisation pulse such that the average voltage level of a modified vertical synchronisation pulse is shifted towards the blanking level in a comparison to the average level before recording; and
outputting the modified signal.
12. The method according to claim 11, wherein modifying the vertical synchronisation pulse further includes modifying the vertical synchronisation pulse such that a time duration of the vertical synchronisation pulse remains substantially unaltered.
13. The method according to claim 12 further comprising adding a front porch to the video signal adjacent to the synchronisation pulse.
14. A method for applying anti-copy-protection to a raster-scanned video signal to produce a modified video signal, the method comprising:
receiving a video signal which is to be modified, the video signal having a vertical synchronisation pulse defined between a leading edge and a trailing edge, wherein the leading edge and the trailing edge are consecutive edges in the video signal;
modifying the vertical synchronisation pulse of the video signal received by the input to produce a modified video signal, the modifying means adding a waveform to the vertical synchronisation pulse with a frequency of at least 500 KHz and with an amplitude at least equal to that of the vertical synchronisation pulse, wherein modifying the vertical synchronisation pulse further includes modifying the vertical synchronisation pulse such that the average voltage level of a modified vertical synchronisation pulse is shifted towards the blanking level in a comparison to the average level before recording, and
outputting the modified video signal.
15. The method of claim 14 wherein modifying the vertical synchronisation pulse of the video signal includes modifying the vertical synchronisation pulse such that a time duration of the vertical synchronisation pulse remains substantially unaltered.
16. A method comprising: outputting from an electronic device a raster-scanned video signal having a modified vertical synchronisation pulse defined between a leading edge and a trailing edge of the video signal such that the video signal can be viewed on a display device at or near the quality intended by the originator of the video signal, but such that after recording by a recording device, the recorded signal exhibits a reduction in vertical stability when played back and viewed on the display device, wherein the leading edge and the trailing edge are consecutive edges in the video signal prior to recording, and wherein the modified vertical synchronisation pulse is such that, after recording by the recording device, the average voltage level of a modified vertical synchronisation pulse is shifted towards the blanking level in comparison to the average level before recording.
17. An apparatus comprising: circuitry configured to output a raster scanned video signal having a vertical synchronisation pulse modified to include a waveform with an amplitude at least equal to that of the vertical synchronisation pulse such that a time duration of the modified vertical synchronisation pulse is substantially the same as a time duration of the vertical synchronisation pulse before modification, wherein the vertical synchronization pulse is defined between a leading edge and a trailing edge in the video signal, and wherein the leading edge and the trailing edge are consecutive edges in the video signal before modification, wherein the circuitry is further configured to modify the vertical synchronisation pulse such that after recording by a recording device, the average voltage level of a modified vertical synchronisation pulse is shifted towards a blanking level in comparison to the average level before recording.