Control circuit for displaying the same video simultaneously to two or more panels
A display panel control circuit includes a voltage controlled oscillator (VCO) for outputting a clock signal, a first-panel horizontal system pulse generation section, a second-panel horizontal system pulse generation section, a vertical system pulse generation section which is commonly used among the first and second panels, a phase comparator, and a smoothing element. The first-panel horizontal system pulse generation section and the second-panel horizontal system pulse generation section respectively generate a reference signal of a first-panel horizontal system output group and a reference signal of a second-panel horizontal system output group from signal VCOCLK 1 output from the VCO. Thus, it is possible to simultaneously drive two different panels.
1. A display panel control circuit for controlling display of a first panel and a second panel, the control circuit comprising:
a voltage controlled oscillator (VCO) for outputting a VCO clock signal;
a first-panel horizontal system pulse generation section for outputting a horizontal system output pulse group for the first panel, the first-panel horizontal system pulse generation section including a first frequency divider for dividing the frequency of the VCO clock signal by N (N is a positive integer) and a first counter for counting an output signal of the first frequency divider, the first counter being reset synchronously with a horizontal synchronization signal of a video signal; and
a second-panel horizontal system pulse generation section for outputting a horizontal system output pulse group for the second panel, the second-panel horizontal system pulse generation section including a second frequency divider for dividing the frequency of the VCO clock signal by M (M is a positive integer different from N) and a second counter for counting an output signal of the second frequency divider, both the second frequency divider and the second counter being reset at a timing when the first counter is reset.
2. The display panel control circuit of claim 1 , further comprising a vertical system pulse generation section for outputting a horizontal system output pulse group for the first and second panels, the vertical system pulse generation section including a third counter for counting an output signal of the first-panel horizontal system pulse generation section as a clock, the third counter being reset by a vertical synchronization signal.
3. The display panel control circuit of claim 1 , further comprising:
a phase comparator for comparing the phase of an output signal of the first-panel horizontal system pulse generation section and the phase of a horizontal synchronization signal; and
a smoothing element which receives a comparison result from the phase comparator to feed back a phase error voltage to the voltage controlled oscillator.