JPH0352271B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a synchronization generator, which has a circuit configuration suitable for integration into an integrated circuit (IC), and can generate a synchronization signal for a desired television system with a simple switch by sharing most of the circuit. An object of the present invention is to provide a synchronization signal generator. Among the world's television systems, the black and white television systems are A, B, C, D, E, G, H, I, K,
There are K ₁ , L, M, N, etc., but A method has the number of scanning lines.
405 lines, and the E method has 819 scanning lines, and these systems are gradually becoming obsolete. Of the methods other than both A and E mentioned above, only M method has 525 scanning lines and a horizontal synchronization frequency of 15.75kHz.
(However, in the case of the color television system described later, the frequency is slightly different.) The remaining systems all have 625 scanning lines and a horizontal scanning frequency of 15.625k.
It is Hz. On the other hand, there are three color television signal systems in the world depending on the color signal transmission format: NTSC, PAL, and SECAM. Several color television systems can be created by combining these and the above methods, but color Looking at the relationship between carrier frequency _SC and horizontal synchronization frequency _H , M/NTSC, M/PAL, B, G, H,
I/PAL (hereinafter simply referred to as B/PAL), N/PAL
and B, D, G, H, K, K ₁ , and L/SECAM (hereinafter simply referred to as SECAM). Here, the relationship between the color subcarrier frequency _SC and the horizontal synchronization frequency _H of these five types of color television systems is as shown below. M/NTSC _SC = 455/2 _H (1) M/PAL _SC = 909/4 _H (2) B/PAL _SC = (1135/4 + 1/625 _H (3) N/PAL _SC = (917/4 + 1/625 ) _H (4) SECAM _OB = 272 _{H OR} = 282 _H (5) As shown in equations (1) to (4), in the four types of color television systems except the SECAM system, the color subcarrier frequency _SC and the horizontal Since the synchronization frequency _H does not have a simple integer ratio relationship, it has been difficult to obtain the horizontal synchronization frequency _H by dividing the color subcarrier frequency _SC.For this reason, with conventional synchronization signal generators, A balanced modulator or the like is used to calculate the sum or difference of frequencies, which results in a complex circuit configuration.Also, both analog circuits and digital circuits coexist, and the precision of analog circuits is It has been difficult to integrate into a single IC due to the necessary adjustment.Furthermore, conventional synchronization signal generators can only synchronize one of the five color television systems mentioned above. The present invention eliminates the above-mentioned drawbacks.
An embodiment will be described below with reference to the drawings. The figure shows a block system diagram of an embodiment of the synchronization signal generator according to the present invention. In the figure, 1 is the first frequency generator, M/NTSC, M/PAL, B/PAL
or synchronization signal or color subcarrier frequency _SC of any one of N/PAL color television systems.
When generating, the color subcarrier frequency of that method
A frequency that is four times _SC or a predetermined integer multiple thereof is generated, and when generating the SECAM color subcarrier frequency _OB , a frequency that is four times 272 _H or a predetermined integer multiple thereof is generated. Which of the five frequencies the frequency generator 1 generates is determined by the system of the device, such as a television camera, into which this synchronizing signal generator is incorporated, and the output frequency of the frequency generator 1 is switched accordingly. . This switching method is to replace the five crystal oscillators that generate each of the five types of frequencies with a socket and connect only one of the crystal oscillators, or to connect only one of the five crystal oscillators. Possible methods include attaching each one and switching between them using a switch. 7 is a voltage controlled oscillator (VCO) which is a second frequency generator, and its output oscillation frequency is the horizontal sync frequency _H of the color television system used.
616×l times (l is any positive integer). Here, the horizontal synchronization frequency _H is M/NTSC
For the M/PAL method, the frequency is 15.734264kHz, so the frequency of 616×l× _H above is 9.692306461
l [MHz], and the horizontal synchronization frequency of the other three systems
Since _H is 15.625kHz, the output frequency of VCO7 is
It becomes 9.625×l [MHz]. Note that l is any positive integer, but in reality, the value of l is sufficient. This is true when the oscillation frequency of VCO7 is l≧2.
This is because the cost becomes too high for the VCO built into the IC. Also, set the oscillation frequency of VCO7 to 616×l× _H (=11
× 4 × 14 × _l For reasons such as making it possible. In other words, the horizontal synchronization frequency of each method is 15.734264kHz or 15.625kHz, as mentioned above.
There is almost no major difference between the methods, and the waveforms of the horizontal synchronizing signals of each method (front porch period, back porch period, etc.) are very similar, so one horizontal scanning period is the same number of times for each method. Can be divided. Furthermore, the oscillation frequency of the VCO 7 must be able to obtain the desired frequency by dividing the frequency division ratio of the programmable counter 8 by an integer in each case. This embodiment is designed to satisfy all of the five basic equations shown in equations (6) to (10) below, and as a result, the VCO
The oscillation frequency of 7 is 616×l× _H . When operating in M/NTSC mode 4 x a x _SC /65 = 616 x l x a x _H /44 x l (6) (a is a factor of 44 x l) If you transform this, _SC ] 65 x 616/44 x 4 _H = 455/2 _H , which satisfies the above formula (1). When operating in M/PAL mode 4 x b x _SC /909 = 616 x l x b x _H /616 x l (7) (b is a factor of 616 x l) If you transform this, _SC = 909/4 _H , satisfies equation (2) above. B/PAL mode operation 4 x c x _SC /64489=616 x l x c x _H /35000 x l
(8) (However, c is a factor of 35000×l) Transforming this equation, _SC = 64489×616/4×35000× _H = 1135.0064/4
_H = (1135/4 + 1/625) _H , which satisfies the above formula (3). When operating in N/PAL mode 4 x d x _SC /19537=616 x l x d x _H /13124 x l
(9) (However, d is a factor of 13124×l) Transforming this equation, _SC = 19537×616/4×13124 _H = 917.0064004/4
_H = (917/4 + 1/625 + 1/10000000) _H , and compared to the above equation (4), an error of 1/10,000,000 times the horizontal synchronization frequency _H occurs, but this level of error is practically impossible. Does not cause any trouble. During SECAM method operation 4×e× _OB /136=e×616×l× _H /77×l (10) (However, e is a factor of 77×l) If you transform this equation, _OB = 136×616/44 ×77 _H =272 _H , which satisfies the above formula (5). As is well known, the carrier color signal of the SECAM method is a color difference signal (R-Y) and has the first color subcarrier frequency.
FM signal obtained by frequency modulating _OR (=282 _H ),
The second color subcarrier frequency in the color difference signal (B-Y)
Since it is a line sequential signal in which the FM signal obtained by frequency modulating _OB (272 _H) is synthesized alternately and in time series every horizontal scanning period, when operating the SECAM method, the two color subcarrier frequencies _OR and If one of _{the OBs} can be generated, the other can be generated relatively accurately using an external circuit, so in this example, _{the OB} is generated.If _{the OR} is generated, can be according to the following basic formula: 4×n× _OR /282=n×616×l× _H /154×l(11) (where n is a factor of 154×l) If you transform this formula, _OR = 828×616/4×154 _H = 282 _H. Next, the operation of the device of the present invention for realizing the basic equations shown in equations (6) to (10) will be explained. First, M/
When operating in the NTSC system, the output frequency of the frequency generator 1 is selected to be 4a times the color subcarrier frequency _SC of the M/NTSC system as shown by equation (1). The frequency 4a _SC of the frequency generator 1 is divided into 1/4a by the frequency divider 2 and output as the NTSC color subcarrier frequency _SC from the output terminal 3 to an external circuit (not shown). 4a _SC is supplied to programmable counter 4, where it is divided into 1/65. Programmable counter 4 has the same switching control signal as programmable counters 8 and 12 and logic circuits 11 and 13, which will be described later, at the input terminal (pin if integrated)
5, the frequency division ratio is selected to be 1/65, and when operating in this M/NTSC system, the frequency division ratio of the programmable counter 8 is a/44×l, and the frequency division ratio of the programmable counter 12 is 1/525. are selected respectively. Here, the value of a during M/NTSC mode operation is a factor of 44×l as shown in equation (6), but
The values of b, c, d, and e shown in equations (7), (8), (9), and (10) during each operation of M/PAL system, B/PAL system, N/PAL system, and SECAM system are When all are made common (i.e. 44×l, 616×l, 35000
If the factor common to xl, 13124xl and 77xl; for example, "1"), the frequency divider 2 can use a fixed 1/4 frequency divider. However, when the values of a to c are not common to each system, the frequency divider 2 may be used as a programmable counter and switched in accordance with the values of each system. Frequency of programmable counter 4 above
The signal of 4a _SC /65 is supplied to the phase comparator 6, where the programmable counter 8 compares the phase with the signal obtained by dividing the output oscillation frequency 616×l× _H of the VCO 7 by a/44×l. After being converted into an error voltage according to the phase difference with the signal, it is applied as a control voltage to the VCO 7 through an appropriate filter (not shown) to variably control its output oscillation frequency. As a result, the loop consisting of the phase comparator 6, VCO 7, and programmable counter 8 constitutes a well-known phase locked loop (PLL), and operates so that the phase error in the phase comparator 6 is eliminated, and the output of the VCO 7 is The oscillation frequency 616×l× _H is phase-locked to the output signal of the programmable counter 4 and further to the output frequency 4a _SC of the frequency generator 1. At this time, what is the output signal frequency of programmable counter 4 shown on the left side of equation (6) and the output signal frequency of programmable counter 8 shown on the right side of equation (6)?
They are equal as shown in equation (6). In this way, the output frequency of frequency generator 1
4a The output oscillation frequency 616×l× _H of the VCO 7, which is phase-locked to _{the SC} , is supplied to the programmable counter 8 as described above, while being sequentially supplied to the 1/2 frequency divider 9 and the 1/308l frequency divider 10. is supplied to In the 1/2 frequency divider 9, the output signal of the VCO 7 often has distortion, and even if a signal with a constant period is obtained, the duty ratio is
Since it is difficult to obtain a symmetrical square wave with a cycle of 50%, it is provided to obtain a symmetrical square wave by dividing the output signal of the VCO 7 by 1/2. If you simply want to obtain the horizontal synchronization frequency _H , you don't need a symmetrical square wave, but as a synchronization signal, it is necessary to generate burst flag pulses or blanking pulses in small time increments as described later, so you can obtain a symmetrical square wave. It is. Further, the frequency dividers 9 and 10 may have a circuit configuration in which appropriate feedback is applied to a series of binary frequency dividing circuits to complete one cycle at 1/616×l. 1/2 from frequency divider 9
Repetition frequency extracted by frequency division 308×l
The _xH symmetrical square wave and each bit output of the frequency divider 10 are supplied to a logic circuit 11, respectively. logic circuit 1
1 is a circuit that counts the input signal mentioned above, determines its value, and generates various pulses, and it performs one horizontal scanning period.
Various pulse trains related to horizontal synchronization (for example, horizontal drive signals) with a narrow time step width divided by 616 × l
occurs. Among the various pulse trains taken out from the logic circuit 11, the pulse train with a repetition frequency of 2 _H is supplied to the programmable counter 12. In this pulse train with a repetition frequency of 2 _H , when the value of l is "1", the frequency divider 10 consisting of a counter converts the symmetric square wave from the frequency divider 9 into 308
Since the period of counting is one horizontal scanning period, the logic circuit 11 outputs when the values of the frequency divider 10 become "0" and "153". The programmable counter 12 divides the pulse train with the repetition frequency of 2 _H by 1/525 and supplies each bit output to the logic circuit 13. The logic circuit 13 generates various pulse trains (for example, vertical drive signals) related to vertical synchronization based on the same operating principle as the logic circuit 11. The various pulse trains taken out from the logic circuits 11 and 13 are supplied to the logic circuit 14, where they are converted into various pulse trains such as a composite synchronization signal, a composite blanking signal, and a burst flag signal with a frequency that conforms to the M/NTSC standard. is output. Note that when a=l=1 in the above M/NTSC system operation, the output frequency of the frequency generator 1 is 14.31818 MHz, and the output oscillation frequency of the VCO 7 is 9.692306461 MHz. Next, to explain the M/PAL method operation,
At this time, the frequency of frequency generator 1 is 4・b・
It can be switched to _SC . Set the value of b to “1”
Then, the value of 4 _SC is 909 _H from equation (2), so it is 14.30244573MHz. In addition, the frequency division ratio of programmable counter 4 is set to 1/909 by the switching control signal from input terminal 5, and the frequency division ratio of programmable counter 8 is set to 1/909.
The frequency division ratio of the programmable counter 12 is switched to b/616×l, and the frequency division ratio of the programmable counter 12 is switched to 1/525. As a result, the output signal frequency of the programmable counter 4 is shown by the left side of equation (7), and the output signal frequency of the programmable counter 4 is shown by the right side of equation (7). Output frequency _4b 616 × l × _H (l
= 1, a frequency of 9.692306461 MHz) is extracted, and various synchronization signals are obtained by the same operation as in the M/NTSC system operation. During each operation of B/PAL system, N/PAL system, and SECAM system, the frequency value of frequency generator 1,
The only difference is the frequency division ratio values of the programmable counters 4, 8, 12 and the pulse generation timing of the logic circuits 11, 13, and the basic operation is the same as that of the M/
This is the same as when operating in the NTSC system or M/PAL system. The frequency of frequency generator 1 is 4・c・_SC when operating in the B/PAL system (if c=1)
17.734475MHz), and when operating in N/PAL mode,
4d・_SC (14.328225MHz if d=1),
During SECAM method operation, 4e _SC (if e=1)
17.0MHz). In addition, the frequency division ratio of programmable counter 4 is 1/64489 during B/PAL operation.
When operating in N/PAL mode, it is 1/19537, and SECAM
When the system is operating, it can be switched to 1/136. In addition, the frequency division ratio of the programmable counter 8 is switched to c/35000×l when operating in the B/PAL method, to d/13124×l when operating in the N/PAL method, and to e/77×l when operating in the SECAM method. Furthermore, the frequency division ratio of the programmable counter 12 is B/PAL, N/PAL and
Both can be switched to 1/625 for SECAM mode operation. Note that the output oscillation frequency of the VCO 7 has the same frequency value 616×l× _H (9.625MHz when l=1) during operation of each of the above-mentioned B/PAL, N/PAL, and SECAM systems. The frequency division ratios of the programmable counters 4, 8, and 12 during operation of each of the above methods are summarized as shown in the following table.

[Table] In this way, according to this embodiment, most of the circuits except for the crystal oscillator connected to the frequency generator 1 and the time constant circuit of the VCO 7 can be configured with digital circuits, so they can be integrated into one IC. Moreover, it is possible to generate color subcarrier frequencies, horizontal synchronization signals, vertical synchronization signals, etc. that conform to the standards of any one of the five color television systems by simply switching the circuit. I can do it. Note that in the above embodiment, the VCO 7 was variably controlled by the output error voltage of the phase comparator 6, but the VCO 7 may be configured with a crystal oscillation circuit or the like with high frequency stability.
While generating a frequency of l × _H , the frequency generator is used as a VCO to supply the output error voltage of the phase comparator 6 as shown by the broken line in the figure, and its output frequency is 4 _SC.
Alternatively, the frequency of an integral multiple thereof may be variably controlled. Further, the logic circuits 11, 13 and 14 are
It may also be configured with read-only memory (ROM). As described above, the synchronization signal generator according to the present invention has a frequency equal to 4a times the color subcarrier frequency of the M/NTSC system (where a is a factor of 44×l, and l is any positive integer). 1 frequency and M/
4b times the color subcarrier frequency of the PAL system (however, b
is a factor of 616×l) and a second frequency equal to B,
G, H, I/PAL color subcarrier frequency 4c
the third equal to the factor of 35000 x c (where c is a factor of 35000 x c)
, a fourth frequency equal to 4d times the color subcarrier frequency of the N/PAL system (where d is a factor of 13124 x l), and a fourth frequency equal to 4e times the color subcarrier frequency _OB of the SECAM system (where e is 77×factor of l) or _OR
a fifth frequency equal to 4n times the horizontal synchronization frequency (where n is a factor of 154×l); A second frequency generator generates a frequency, and the frequency from the first frequency generator is 1/65, 1/909, 1/64489, 1/19537, or 1/136.
(or 1/282) and the output signal frequency of the first frequency divider whose frequency division ratio is switched to divide the frequency by a/44×l, b/616×l, c /35000×
a second frequency divider whose frequency division ratio is switched to divide the frequency by l, d/13124×l or e/77×l (or n/154×l);
a phase comparator that variably controls the output frequency of the second or first frequency generator using a phase error signal obtained by comparing the phases of the output signals of the first and second frequency dividers, respectively; A third frequency divider obtains the color subcarrier frequency from the output frequency of the second frequency generator, and a fourth frequency divider divides the output frequency of the second frequency generator by 1/308×l. Since it consists of frequency dividing circuit means for outputting a frequency and a vertical synchronization frequency, respectively, the frequency division ratios of the first to fourth frequency dividers and frequency dividing circuit means are all one integer, and the digital circuit A time constant circuit of the second or first frequency generator or a crystal of the first or second frequency generator whose frequency is controlled by the output phase error signal of the phase comparator. Almost the entire circuit, excluding the vibrator, etc., can be integrated into one IC, and when integrated into an IC, it can be made smaller and more reliable than conventional synchronization signal generators, and it can be used for five types of color TVs. Generates the color subcarrier frequency of any one of the color subcarrier frequencies and a synchronization signal that has an exact predetermined frequency ratio relationship with this by simply switching the circuit using a simple circuit configuration that shares most of the circuit. Furthermore, various pulse trains related to the horizontal scanning period can be generated from the output signal frequency of the second frequency generator at a fine time step width obtained by dividing one horizontal scanning period by 616×l. The number of divisions, 616 x l, is a number of divisions that fully satisfies all synchronization signal standards for each color television system, and has many features such as being able to be used satisfactorily even with high-end television cameras. be.

[Brief explanation of drawings]

The figure is a block system diagram showing one embodiment of the device of the present invention. 1...first frequency generator, 2, 9, 10...
Frequency divider, 3...Color subcarrier frequency output terminal, 4,
8, 12...Programmable counter, 6...Phase comparator, 7...Voltage controlled oscillator (VCO) which is a second frequency generator, 11, 13, 14...Logic circuit.

Claims (1)

[Claims] 1. A first frequency equal to a frequency that is 4a times the color subcarrier frequency of the M/NTSC system (where a is a factor of 44×l, and l is any positive integer);
4b times the color subcarrier frequency of the PAL system (however, b
is a factor of 616×l) and a second frequency equal to B,
G, H, I/PAL color subcarrier frequency 4c
the third equal to the factor of 35000 x l (where c is a factor of 35000 x l)
, a fourth frequency equal to 4d times the color subcarrier frequency of the M/PAL system (where d is a factor of 13124×l), and a fourth frequency equal to 4e times the color subcarrier frequency _OB of the SECAM system (however, e is a factor of 77×l)?
a first frequency generator that generates and outputs by switching one of the frequencies, and a fifth frequency equal to 4n times _{the OR} (where n is a factor of 154×l), and a first frequency generator that generates and outputs one frequency equal to 616×l times the horizontal sync frequency When the output frequency of the first frequency generator is the first frequency, this is divided by 1/65, and when the output frequency is the second frequency, this is For the third frequency above, divide this by 1/64489, and for the fourth frequency above, divide this by 1/19537.
Divide the frequency, and further divide it by 1/ for the fifth frequency above.
a first frequency divider whose frequency division ratio is switched to divide the frequency by 136 (or 1/282); and a first frequency divider whose frequency division ratio is switched to divide the frequency by 136 (or 1/282);
The frequency output from the frequency generator is the frequency output from the first frequency generator.
When the frequency is a/44×l, when the second frequency is b/616×l, when the third frequency is c/35000×l, and when the fourth frequency is d/13124. ×l, and a second frequency divider that is switched to e/77×l (or n/154×l) when the fifth frequency is selected, and output signals of the first and second frequency dividers. a phase comparator that variably controls the output frequency of the second or first frequency generator using phase error signals obtained by phase comparison; and a phase comparator that divides the first output frequency to be equal to the color subcarrier frequency. a third frequency divider that outputs a frequency, a fourth frequency divider that divides the output frequency of the second frequency generator by 1/308×l, and an output frequency of the fourth frequency divider. 1. A synchronization signal generating device comprising frequency dividing circuit means for dividing the frequency and outputting a horizontal synchronization frequency and a vertical synchronization frequency, respectively.