JP3421560B2 - Triangular wave signal generation circuit - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a triangular wave signal generation circuit incorporated in, for example, a television IC, and more particularly to a triangular wave signal generation circuit in which the frequency of a triangular wave output signal changes according to the frequency change of an input signal. Regarding

[0002]

2. Description of the Related Art In a television IC or the like, a triangular wave signal is formed from an input pulse signal. In the conventional triangular wave signal generation circuit used for such an application, especially in the one in which the frequency of the triangular wave output signal changes according to the frequency change of the input pulse signal, an automatic adjustment loop is used to stabilize the triangular wave. There is a system in which the peak value or the amplitude value of the triangular wave is made constant even if the frequency of the input pulse signal changes.

[0003]

However, in the above-mentioned conventional system in which the peak value or the amplitude value is made constant, there is a disadvantage that the inclination angle of the triangular wave changes due to the change of the frequency of the input pulse signal.

It is desirable that the amplitude (peak value) is constant and the inclination angle of the triangular wave output signal is always constant with respect to the frequency change of the input pulse signal. However, in reality, such a thing does not exist in the past.

The present invention has been made in consideration of the above circumstances, and an object thereof is that the amplitude (peak value) is constant with respect to the frequency change of the input pulse signal and the inclination angle of the triangular wave is always constant. It is to provide a triangular wave signal generating circuit such that

[0006]

A triangular wave signal generating circuit according to a first aspect of the present invention is a pulse generating circuit which generates a pulse signal in synchronism with an input pulse signal, and a constant current after the generation period of the pulse signal. The pulse generator includes a triangular wave output circuit that outputs a triangular wave signal by charging a capacitor, and a comparator circuit that compares the peak value of the triangular wave signal with a first reference value and outputs a signal corresponding to the difference. The generation circuit charges the capacitor with a current proportional to the signal corresponding to the difference output from the comparison circuit, and stops the generation of the pulse signal when the charging voltage reaches the second reference value. It is characterized in that it is composed of.

A triangular wave signal generating circuit according to a second aspect includes a pulse generating circuit which generates a pulse signal in synchronization with an input pulse signal, a constant current source and a first capacitor, and the generation period of the pulse signal ends. After that, a triangular wave output circuit that outputs a triangular wave signal by charging the first capacitor with the current of the constant current source and a peak value of the triangular wave signal are compared with a first reference value, and the difference is determined according to the difference. A comparison circuit for outputting a signal, wherein the pulse generation circuit includes a second capacitor charged with a current proportional to the signal corresponding to the difference output from the comparison circuit,
It is characterized in that the generation of the pulse signal is stopped when the charging voltage of the second capacitor reaches the second reference value.

A triangular wave signal generation circuit according to a third aspect generates a first control pulse signal delayed from the input pulse signal by a predetermined time with respect to the input pulse signal and a second control pulse signal synchronized with the input signal. A control pulse signal generation circuit, a flip-flop circuit set by the first control pulse signal, a constant current source, a first capacitor connected to the constant current source, and a connection between both ends of the first capacitor. And a triangular wave output circuit which outputs a triangular wave signal from a connection point between the constant current source and the first capacitor, and a second switch which is conductively controlled by a signal at a set output terminal of the flip-flop circuit. Operation is controlled by the control pulse signal of 1., and the output voltage of the first comparison circuit for comparing the triangular wave signal with the first reference voltage and the output voltage of the first comparison circuit are supplied. A converting circuit for converting into a second capacitor charged by the converted current in the conversion circuit,
Comparing the charging voltage of the second capacitor with a second reference voltage, and generating a signal for resetting the flip-flop circuit when the charging voltage of the second capacitor is higher than the second reference voltage. 2 comparison circuit, and the second
A second switch which is connected between both ends of the capacitor and whose conduction is controlled by a signal from the reset output terminal of the flip-flop circuit.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 is a block diagram showing a schematic configuration of a triangular wave signal generating circuit according to the present invention, and FIG. 2 is a timing chart showing a signal waveform of a main part of the triangular wave signal generating circuit of FIG.

Timing pulse input (input pulse signal)
Is supplied to the trigger pulse generation circuit 11. As shown in FIG. 2, the trigger pulse generation circuit 11 has a trigger pulse delayed by a certain time with respect to a timing pulse input, a rising edge synchronized with a rising edge of the timing pulse input, and a falling edge synchronized with a rising edge of the trigger pulse. AG
C pulse and.

The trigger pulse is supplied to the pulse width variable type monostable multivibrator circuit 12. The multivibrator circuit 12 rises to "H" level in synchronization with the rise of the trigger pulse, and outputs a pulse signal whose pulse width is in proportion to the period of the "H" level, that is, the timing pulse input period. To do.

The pulse signal output from the multivibrator circuit 12 is supplied to the triangular wave output circuit 13.
The triangular wave output circuit 13 is provided with a constant current source and a capacitor, which will be described in detail later, and after the pulse signal output from the multivibrator circuit 12 drops from "H" level to "L" level. While the pulse signal is at the "L" level, the capacitor is charged by the current of the constant current source, and a triangular wave signal (triangular wave output) as shown in FIG. 2 is obtained.

This triangular wave signal is supplied to the AGC comparison circuit 14. Further, the AGC pulse generated by the trigger pulse generation circuit 11 is supplied to the AGC comparison circuit 14. The AGC comparison circuit 14 operates during the period in which the AGC pulse is supplied, compares the triangular wave signal with the internal reference voltage Vref during the operation period, and outputs the signal corresponding to the comparison result to the previous multivibrator. It is given to the circuit 12. The multivibrator circuit 12 performs control to drop the preceding pulse signal to "L" level based on the signal according to the comparison result.

In such a configuration, the period during which the pulse signal output from the pulse width variable type monostable multivibrator circuit 12 is at "H" level, that is, the pulse width is proportional to the cycle of the timing pulse input. Therefore, the period during which this pulse signal is at "L" level is always constant regardless of the cycle of timing pulse input. In the triangular wave output circuit 13, the capacitor is charged with the current of the constant current source to obtain the triangular wave while the pulse signal output from the multivibrator circuit 12 is at the “L” level. The inclination angle of the triangular wave output signal obtained in step 2 is always constant regardless of the cycle (frequency) of the timing pulse input. Further, since the period during which the pulse signal is "L" level when charging the capacitor with the current of the constant current source is always constant, the peak value (amplitude) of the triangular wave output signal can also be always constant.

Next, a detailed circuit configuration of the triangular wave signal generation circuit shown in FIG. 1 will be described with reference to FIG. The same reference numerals are given to the portions corresponding to those in FIG. 1 for the description. The trigger pulse generation circuit 11 delays a timing pulse input for a predetermined time to generate the trigger pulse, and
The delay circuit 21 is composed of an inverting circuit 22 for inverting the trigger pulse, and an adder 23 for adding the output of the inverting circuit 22 and the timing pulse input to generate the AGC pulse.

The pulse width variable type monostable multivibrator circuit 12 outputs one pulse signal in synchronization with the rising edge of the trigger pulse as described above, and is configured as follows. That is, the trigger pulse is a set / reset type flip-flop circuit 24.
Is supplied to the set input terminal (S). In addition, one end of this multivibrator circuit 12 is grounded and the value is CT.
The capacitor 25 of is provided, and this capacitor 2
The signal voltage VT at the other end of 5 is supplied to the non-inverting input terminal of the comparator 26. A current source Io for operation is connected to the comparator 26, and a reference voltage VS is supplied from a reference voltage source 27 to its inverting input terminal.

The comparator 26 compares the terminal voltage VT with the reference voltage VS when the capacitor 25 is charged, and the comparison output is the reset input terminal (R) of the flip-flop circuit 24. Is supplied to. Further, the collector of an NPN type transistor Q1 is connected to the other end of the capacitor 25. The emitter of the transistor Q1 is grounded, and the base thereof has an output terminal (/
The signal from Q) is supplied. Similarly, the other end of the capacitor 25 is connected to the collector of another NPN transistor Q2. The emitter of the transistor Q2 is grounded, and the AGC pulse generated by the trigger pulse generating circuit 11 is supplied to its base.

The signal from the set output terminal (Q) of the flip-flop circuit 24 is supplied to the triangular wave output circuit 13 as the pulse signal. The triangular wave output circuit 13 has one end connected to the power supply voltage Vcc and a constant current source 28 for flowing a constant current Iramp, and a capacitor 29 having a value Cramp connected between the constant current source 28 and ground.
And an NPN transistor Q3 having a collector connected to the connection point of the constant current source 28 and the capacitor 29 and an emitter grounded. The flip-flop circuit 2 is provided at the base of the transistor Q3.
A pulse signal which is the output signal of the output terminal (Q) at the time of setting 4 is supplied, and the triangular wave output is obtained from the connection point of the constant current source 28 and the capacitor 29.

As described above, the AGC comparison circuit 14 uses the AG
It operates during the period in which the C pulse is supplied, compares the triangular wave signal with the reference voltage Vref during the operating period, and gives a signal according to the comparison result to the multivibrator circuit 12. Is configured. That is, the triangular wave signal is supplied to the non-inverting input terminal of the comparator 30. Further, the reference voltage Vref from the reference voltage source 31 is supplied to the inverting input terminal of the comparator 30. Further, the current IAGC of the operating current source is supplied to the comparator 30 through the NPN type transistor Q4. The AGC pulse is supplied to the base of the transistor Q4, and the comparison operation of the comparator 30 is controlled by controlling the conduction of the transistor Q4 according to the AGC pulse.

A voltage smoothing capacitor 32 having a value of CAGC is connected between the output terminal of the comparator 30 and the ground. That is, the voltage difference between the triangular wave signal output from the comparator 30 and the reference voltage Vref is the capacitor 3
Smoothed by 2. Then, the voltage VAGC smoothed by the capacitor 32 is converted into the current IT by the voltage-current conversion circuit 33. Then, this current IT is supplied to the previous multivibrator circuit 12, and the capacitor 25 in the multivibrator circuit 12 is charged by this current IT.

Next, the operation of the circuit configured as shown in FIG. 3 will be described with reference to FIG.
The timing chart will be described. The generation of the trigger pulse and the AGC pulse from the timing pulse input has already been described with reference to FIGS.

First, when the AGC pulse rises to "H" level first, the transistor Q in the AGC comparator 14 is
4 becomes conductive, a current IAGC flows to the comparator 30, and this comparator 30 becomes active. By operating the comparator 30, the triangular wave in the previous cycle is compared with the reference voltage Vref. The period in which the AGC pulse is at the “H” level corresponds to the period in which the triangular wave has just the peak value as shown in FIG. 4, so in the comparator 30, the triangular wave peak value is the reference voltage Vref. And the voltage corresponding to the difference is output.

Further, since the capacitor 32 is connected to the output terminal of the comparator 30, the difference in the above-mentioned voltages output by comparison in each previous cycle is smoothed by the capacitor 32 and averaged. Becomes a voltage VAGC, which is applied to the voltage-current conversion circuit 33 and converted into a current.

Further, during the period when the AGC pulse is at "H" level, the transistor Q2 in the multivibrator circuit 12 becomes conductive, and the terminal of the capacitor 25 opposite to the ground side is grounded via this transistor Q2. And the capacitor 25 is discharged.

On the other hand, when the AGC pulse rises to "H" level and then falls to "L" level, the trigger pulse next rises to "H" level. In synchronization with this, the flip-flop circuit 24 in the multivibrator circuit 12 is set, the set output signal Q rises to "H" level, and conversely the reset output signal / Q falls to "L" level.

When the signal Q becomes "H" level, the transistor Q3 in the triangular wave output circuit 13 becomes conductive and the constant current source 2
Since the constant current Iramp flowing through 8 flows through the transistor Q3, the capacitor 29 is not charged and the triangular wave becomes almost 0V. Further, when the signal / Q goes low, the transistor Q1 in the multivibrator circuit 12 becomes non-conductive. At this time, since the other transistor Q2 connected to the capacitor 25 is already non-conductive, the capacitor 25 is converted by the current IT converted by the voltage-current conversion circuit 33 immediately after the transistor Q1 becomes non-conductive. Will start charging. After that, the terminal voltage (VT) of the capacitor 25 gradually increases as shown in FIG.

The terminal voltage (VT) of the capacitor 25 is constantly compared with the reference voltage VS by the comparator 26. When VT exceeds the reference voltage VS, the output of the comparator 26 becomes "H" level. . As a result, the flip-flop circuit 24 is reset, the output signal Q at the time of setting falls to the "L" level, and conversely, the output signal / Q at the time of reset rises to the "H" level.

When the signal Q drops to "L" level, the transistor Q3 in the triangular wave output circuit 13 becomes non-conductive, and the constant current source 2 which has been flowing through the transistor Q3 until now.
The constant current Iramp of 8 flows into the capacitor 29 this time. As a result, the charging of the capacitor 29 is started,
A triangular wave is output. The operation of generating the triangular wave is continued until the timing pulse signal is next input, the trigger pulse is generated in the trigger pulse generating circuit 11, and the flip-flop circuit 24 is set.

Here, if the cycle of the timing pulse signal becomes short (the frequency becomes high), the cycle in which the triangular wave and the reference voltage Vref are compared in the comparator 30 in the AGC comparison circuit 14 becomes short. The value of VAGC increases, and the value of the current IT for charging the capacitor 25 in the multivibrator circuit 12 increases. Conversely, if the cycle of the timing pulse signal becomes long (frequency is low),
Since the cycle in which the triangular wave is compared with the reference voltage Vref in the comparator 30 also becomes long, the value of the voltage VAGC becomes small and the capacitor 2 in the multivibrator circuit 12 becomes small.
The value of the current IT for charging 5 decreases. That is, the value of the charging current IT of the capacitor 25 is proportional to the cycle of the timing pulse signal, and therefore the inclination (inclination angle) of the terminal voltage VT when the capacitor 25 is charged is also proportional to the cycle of the timing pulse signal.

As shown in FIG. 4, the period of the timing pulse signal is T, and the period during which the capacitor 25 is charged by the current IT is TS (pulse period in which the Q signal of the flip-flop circuit 24 is at "H" level). ), Constant current Ira
If the period during which the capacitor 29 is charged by mp is Tramp, then T = TS + Tramp.

Further, the voltage VAGC and this voltage VAGC
If the relation IT = K * VAGC (K is a proportional constant) is established with the current IT obtained by being converted by the voltage-current conversion circuit 33, the above TS is
TS = CT * VS / K * VAGC. Also, since the peak value of the triangular wave is Vref, the above Tramp is Tramp =
It becomes Vref * Cramp / Iramp. Putting these together,
The cycle T of the timing pulse signal is as follows.

T = CT * VS / K * VAGC + Vref * Cramp / Iramp ... 1 The second item on the right side of the above equation 1 indicates the inclination angle and the peak value (amplitude) of the triangular wave. Inclination angle Cramp / Iramp
Cramp is a fixed value, and Iramp is also a constant current source current, so this is also constant. Further, since the peak value (amplitude) Vref is the voltage of the reference voltage source 31, this is also constant. That is, both the inclination angle and the peak value (amplitude) of the triangular wave are always constant even if the cycle T of the timing pulse signal changes.

On the other hand, the first item on the right side of the above equation 1 indicates the inclination angle and peak value (amplitude) of the signal obtained by charging the capacitor 25, and CT and VS are fixed respectively. However, K * VAGC changes according to the change of the cycle T of the timing pulse signal.

As described above, in the triangular wave signal generation circuit shown in FIG. 3, the amplitude (peak value) is constant with respect to the frequency change of the timing pulse input, and the inclination angle of the triangular wave is always constant.

The transistor Q2 provided in the multivibrator circuit 12 is, as described above,
When the AGC pulse is at "H" level, it becomes conductive,
At the rising edge of the timing pulse input, the charging voltage of the capacitor 25 is reliably lowered to the ground voltage of 0V. This is because when the range corresponding to the input frequency of the multivibrator circuit 12 extends over many octaves, unless this transistor Q2 is provided, there are some stable points with respect to frequency in proportion to the increase of octaves, When the power is turned on, it stabilizes at a point other than the original stable point,
This is because a normal triangular wave cannot be obtained. Therefore, when the frequency band of the timing pulse input is not so wide, the transistor Q2 can be omitted.

[0036]

As described above, according to the present invention,
Amplitude (peak value) with respect to the frequency change of the input pulse signal
It is possible to provide a triangular wave signal generation circuit in which the angle is constant and the inclination angle of the triangular wave is always constant.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a triangular wave signal generation circuit according to the present invention.

FIG. 2 is a timing chart showing signal waveforms of essential parts of the triangular wave signal generation circuit of FIG.

3 is a diagram showing a detailed circuit configuration of the triangular wave signal generation circuit shown in FIG.

FIG. 4 is a timing chart showing signal waveforms of the circuit of FIG.

[Explanation of symbols]

11 ... Trigger pulse generation circuit, 12 ... Pulse width variable type monostable multivibrator circuit, 13 ... Triangular wave output circuit, 14 ... AGC comparison circuit, 21 ... delay circuit, 22 inversion circuit, 23 ... adder, 24 ... Flip-flop circuit, 25, 29, 32 ... capacitors, 26, 30 ... Comparator, 27, 31 ... Reference voltage source, 28 ... Constant current source, 33 ... Voltage-current conversion circuit, Q1 to Q4 ... NPN type transistors.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-9-200003 (JP, A) JP-A-8-307216 (JP, A) JP-A-5-275985 (JP, A) JP-A-7- 264016 (JP, A) JP 10-13196 (JP, A) JP 63-275218 (JP, A) JP 63-131716 (JP, A) JP 57-178415 (JP, A) JP-A-50-45556 (JP, A) JP-A-54-116163 (JP, A) JP-A-50-33754 (JP, A) JP-A-63-99611 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H03K 4/06

Claims (6)

(57) [Claims] 1. A pulse generation circuit that generates a pulse signal in synchronization with an input pulse signal, and a triangular wave output circuit that outputs a triangular wave signal by charging a capacitor with a constant current after the generation period of the pulse signal has ended. A pulse comparator circuit that compares the peak value of the triangular wave signal with a first reference value and outputs a signal corresponding to the difference between the peak value and the first reference value, wherein the pulse generation circuit responds to the difference output from the comparison circuit. The triangular wave signal generating circuit is configured to charge the capacitor with a current proportional to the signal and stop the generation of the pulse signal when the charging voltage reaches the second reference value. 2. A pulse generator circuit for generating a pulse signal in synchronization with an input pulse signal, a constant current source and a first capacitor, and a current of the constant current source after the end of the pulse signal generation period. A triangular wave output circuit that outputs a triangular wave signal by charging the first capacitor, and a comparison circuit that compares the peak value of the triangular wave signal with a first reference value and outputs a signal according to the difference The pulse generation circuit includes a second capacitor charged with a current proportional to the signal corresponding to the difference output from the comparison circuit, and the charging voltage of the second capacitor is a second reference value. The triangular wave signal generating circuit is configured so as to stop the generation of the pulse signal when the pulse signal reaches the temperature. 3. The comparison circuit is configured to compare the peak value of the triangular wave signal with the first reference value and output a signal smoothed according to the difference. The triangular wave signal generation circuit according to claim 1. 4. A control pulse signal generation circuit for generating a first control pulse signal delayed from the input pulse signal by a predetermined time with respect to the input pulse signal and a second control pulse signal synchronized with the input signal, Flip-flop circuit set by the control pulse signal of 1, a constant current source, a first capacitor connected to the constant current source, and a set output terminal of the flip-flop circuit connected between both ends of the first capacitor A triangle wave output circuit that outputs a triangle wave signal from a connection point between the constant current source and the first capacitor; and an operation controlled by the second control pulse signal. A first comparison circuit that compares the triangular wave signal with a first reference voltage; a conversion circuit that converts the output voltage of the first comparison circuit into a current; The second capacitor charged by the current converted in the path and the charging voltage of the second capacitor are compared with the second reference voltage, and the charging voltage of the second capacitor is lower than the second reference voltage. Second comparator circuit for generating a signal for resetting the flip-flop circuit when it is extremely high, and a second comparison circuit connected between both ends of the second capacitor and controlled by a signal at a reset output terminal of the flip-flop circuit. A triangular wave signal generation circuit, comprising: 5. A smoothing circuit for smoothing an output voltage of the first comparison circuit is further provided between the first comparison circuit and the conversion circuit.
The triangular wave signal generation circuit described in 1. 6. The triangular wave signal generator according to claim 4, further comprising a third switch connected between both ends of the second capacitor and controlled to be conductive by the second control pulse signal. circuit.