JPH0435520A - Voltage control oscillation circuit - Google Patents

Abstract

PURPOSE:To constitute the circuit so that a period of an output signal can be varied in direct proportion to a control voltage by providing a bistable circuit by which a stable point voltage is controlled, and a triangular signal generating circuit connected to this circuit so that this circuit generates a triangular wave signal corresponding to a stable point voltage difference of the bistable circuit. CONSTITUTION:The circuit is provided with a bistable circuit 2 by which a stable point voltage VS is controlled in accordance with a control voltage Vc, and a triangular wave signal generating circuit 3 connected to this bistable circuit 2, and this trianglar wave signal generating circuit 3 generates a triangular wave signal ST corresponding to a stable point voltage difference of the bistable circuit 2. Accordingly, in one stable point voltage VS1 varied in accordance with the control voltage VC, a voltage of the triangular wave signal ST in the triangular wave signal generating circuit 3 increases and when it reaches the other stable point voltage VS2, the bistable circuit 2 is inverted. Also, the triangular wave signal ST can be generated repeatedly so that the voltage of the triangular wave signal ST decreases as soon as the bistable circuit 2 is inverted. In such a way, a period of an output signal can be varied in direct proportion to the inputted control voltage V2.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is applicable to a CCD (Char
The present invention relates to a voltage controlled oscillation circuit suitable for use as a transfer lock of a GE Coupled Device.

[Summary of the Invention] The present invention provides a CCD (Charge
A voltage controlled oscillator circuit suitable for use as a transfer lock for a coupled device, comprising a bistable circuit in which a stable point voltage is controlled, and a triangular wave signal generation circuit connected to the bistable circuit, This triangular wave signal generation circuit generates a triangular wave signal according to the stable point voltage difference of the bistable circuit, so that the period of the output signal changes in direct proportion to the control voltage.

[Prior Art] For example, when a multi-disc player is used to reproduce a video signal from an optical disc, fluctuations occur in the video signal on the time axis due to the eccentricity of the multi-disc player's turntable, etc. When reproduced on a CRT screen, the quality of the image deteriorates.

Therefore, a time base collector is used to remove the above-mentioned fluctuation on the time axis, that is, jitter. For example, a CCD is used as this time base collector, and by changing the transfer lock period of this CCD in accordance with the eccentricity, a video signal without fluctuation on the time axis can be obtained.

[Problems to be Solved by the Invention] Generally, the transfer lock of a CCD is obtained as an output signal of a voltage controlled oscillation circuit. In this case,
It is said that it is desirable for a voltage controlled oscillator circuit to have a characteristic in which the period of an output signal changes in direct proportion to an input control voltage, that is, a so-called period linear characteristic.

This is because the configuration of the drive circuit of the voltage controlled oscillator circuit is simplified, and the circuit design and system configuration are also facilitated.

However, conventional voltage controlled oscillator circuits have a characteristic in which the frequency of the output signal changes in direct proportion to the input control voltage, a so-called frequency linear characteristic, which makes the configuration of the drive circuit of the voltage controlled oscillator circuit complicated. Furthermore, there was a problem in that circuit design and system configuration became difficult.

The present invention has been made in view of the above points, and provides a relatively simple voltage controlled oscillation circuit having a characteristic that the period of an output signal changes in direct proportion to an input control voltage, that is, a so-called period linear characteristic. The purpose is to

[Means for Solving the Problems] The present invention, for example, as shown in FIGS. 1 and 2,
A bistable circuit (2) whose stable point voltage VS (VS=VSI or VSZ) is controlled according to a control voltage VC, and a triangular wave signal generation circuit (2) connected to this bistable circuit (2).
3), and this triangular wave signal generation circuit (3) has a stable point voltage difference (VS+ VS2) of the above bistable circuit (2).
A triangular wave signal ST is generated according to the following.

[Operation] According to the present invention configured as described above, the control voltage ■c
The bistable circuit (2) is inverted when the voltage of the triangular wave signal ST in the triangular wave signal generating circuit (3) increases at one stable point voltage V S + which changes according to the voltage and reaches the other stable point voltage S2. do. Then, the triangular wave signal ST can be repeatedly generated by causing the voltage of the triangular wave signal ST to decrease at the same time as the bistable circuit (2) is inverted. Therefore, the cycle of the repetitive triangular wave signal ST is the control voltage ■. changes in direct proportion to.

[Embodiment] An embodiment of the voltage controlled oscillation circuit of the present invention will be described below with reference to the drawings. In Figure 1, (2) is a bistable circuit with a control voltage of ■. A Schmint trigger circuit is employed in which the stable point voltage VS (hereinafter, the higher stable point voltage will be referred to as VS, and the lower stable point voltage will be referred to as VS2) according to. (3) is a triangular wave signal generation circuit, which performs charging and discharging according to the stable point voltage ■S and generates a triangular wave signal ST.
A charging/discharging circuit is used that generates . The bistable circuit (2) and the triangular wave signal ordering circuit (3) constitute the voltage controlled oscillation circuit according to this embodiment.

First, the configuration of the triangular wave signal generation circuit (3) will be explained. The triangular wave signal generation circuit (3) includes a charging/discharging capacitor c1 whose one end is grounded, and this capacitor C
1 is a constant current source CSI that supplies a constant charging current I.
are connected in series. Furthermore, the anode of a diode D1 is connected to the capacitor C1, and the cathode of this diode DI is connected to the emitter of a transistor Q1 whose collector is connected to the power supply VCC. In this case, the diode D1 and the transistor 1 constitute a current switch, and a discharge current I is supplied to the capacitor C1 from a constant current source CS2 connected to their common connection point.
Switch 2. Here, the stable point voltage vs is applied from the bistable circuit (2) to the base of the transistor Q1. In this embodiment, the charging current 11 of the constant current source CSI is compared to the discharging current 1 of the constant current source C52.
2 is set to double. This is to make all slopes related to charging and discharging of the capacitor C1 constant. It is not limited to 2 times, but may be selected to any number such as 0.5, 1, 3, etc. Further, a triangular wave signal ST is generated on the so-called hot side of the capacitor C1.

Next, the configuration of the bistable circuit (2) will be explained.

Bistable circuit (2) is transistor 2 for current switch
, Q3, whose emitters carry a current I.

is connected to the collector of a transistor Q6 through which a constant current source CS3 and a current I flow. Above transistor Q
The triangular wave signal ST is introduced into the base of the transistor Q2, and its collector is connected to one end of the resistor R1 and the base of the transistor Q4. Transistor Q4 operates as a voltage follower. The collector of this transistor Q4 is connected to the power supply VCC, and its emitter is connected to the resistor R
2 to the base of the transistor Q3 for positive feedback, and is also connected to the base of the transistor Q1 constituting the triangular wave signal generating circuit (3) and to the constant current source CS4 of the current I4. . Here, two stable point voltages vs=vs, vs=vs are generated at the base of the transistor Q3, as will be described later.

The transistor Q6 and the transistor Q7 through which current 16 flows constitute a current mirror circuit.

The collector of this transistor (17) is connected to the emitter of transistor Q8 via a resistor R4.

Control voltage ■ is applied to the bases of transistor Q8 and transistor Q5. are added, and each collector is connected to the power supply VCC
It is connected to the. Note that the emitter of the transistor Q5 is connected to the other end of the resistor R1. and,
A resistor R3 acting as a load resistance and a diode D2 acting as a limiter are connected in parallel between the collector of the transistor 3 and the power supply VCC.
The output voltage as a repetitive square wave voltage on the cathode side of ■
. OT occurs.

Next, the operation of the above embodiment will be explained. First, it is assumed that the stable point voltage ■S is on the high level side (see time t0 in FIG. 2). In this case, transistor 03 constituting the bistable circuit (2) is in an active state, and transistor Q2 is in an off state. Therefore, the output voltage■. . 7 is diode D
2 clamped by the diode D from the power supply Vec.
It is a low level value obtained by subtracting the forward direction voltage VD2 of 2. Incidentally, for high-speed operation, a Sigitky diode is preferably used as the diode D2. Alternatively, instead of clamping with a diode, the output voltage may be determined by a voltage drop across the resistor R3.

In this case, since the transistor ROE is also in the active state, the discharge current 2 of the constant current source CS2 all flows to the transistor Ql side and does not flow to the diode DI side. Therefore, the capacitor CI is charged by the charging current 11 supplied from the constant current source CSI. Therefore, the slope of the triangular wave signal ST generated at the base of the transistor Q20 becomes a positive slope (It/CI) as shown between times t6 and t3 in FIG.

In this way, the voltage of the triangular wave signal ST increases, and when the voltage reaches the stable point voltage VS2 on the high level side (see time t1), the base current of the transistor 02 begins to flow, and its collector The voltage goes in the negative direction. Therefore, the emitter voltage of transistor Q4 decreases, and eventually the base voltage of transistor Q3 decreases, and due to the positive feedback effect, transistor Q
2 becomes active, and transistor Q3 becomes off. At the same time, the transistor Ql is also turned off.

Therefore, the stable point voltage vS becomes the low level stable point voltage vSI. In this case, discharge current I2 will flow through diode D1, so 1. -1. =1. (It is set to 12=2.1.

) current will flow.

Therefore, the slope of the triangular wave signal ST appearing at the base of the transistor Q2 is as shown in FIG. The slope becomes negative (-1, /C,) from the point.

In this case, the output voltage V. 0A is at a high level voltage equal to the power supply voltage VCC because the transistor Q3 is in the off state.

In this way, when the voltage of the triangular wave signal ST reaches the low level stable point voltage vS1 (see time t2), the transistor Q2 turns from the active state to the off state, and its collector turns to the high level, causing the transistor Through the emitter of g4, the base of transistor 3 becomes a high level stable point voltage S2. In this state, the transistor Q3 and the transistor Ql become active, so that the capacitor C1 is charged again only by the charging current II supplied from the constant current source CSI (see after time t2). In this case, the output voltage ■. . 1 becomes v cc-v , t.

As described above, according to this embodiment, as can be understood from FIG. 2, the output voltage is . The waveform of at is such that the charging and discharging currents supplied to the capacitor CI are equal and a triangular wave signal ST is generated between the two stable point voltages vs, , vs,
The signal waveform has a duty ratio of 50%.

That is, the period T of the triangular wave signal ST=T1+T2=2・
In T1, time T1 is the amount of charge and discharge of the capacitor C1, and if we focus on the current switch transistors Q2 and C3, the following equations (1) and (2) can be obtained. Therefore, C1・( VSz-VS+)=II-Tl...(
1) VS, -VS, = R1・(I, + Is)
...(2) Expressed as shown in the following equation (3).

TI=CI・R1・(Is+Is)/I+...
(3) Here, since the current I flowing through the transistor 06 is equal to the current I flowing through the transistor Q6, the relationship shown in the following equation (4) is obtained.

l5=1. ! =iVC/R4・--(4) Note that the (4th
), the base-emitter forward voltage VIE of transistor Q8 and transistor Q7 is omitted to make the equation clearer.

Therefore, by substituting equation (4) into equation (3) and rearranging, time T1 and control voltage ■ can be obtained. The relationship with
5) It is expressed as shown in the formula.

T1=a・■o+b...(5) However, a
, b are constants, and are expressed by the following equations (6) and (7).

a=C1・R1/■1・R4...(6) b=ci・R
1.13/I l (7) As understood from equation (5), time T1 is the control voltage ■. The triangular wave signal ST and the output voltage ■ are expressed as −order numbers. . 1 is synchronized, so the output voltage is ■. . The period of , is directly proportional to the control voltage ,. In other words, the output voltage ■. . A is the control voltage ■. However, it changes linearly with the period.

Note that, as understood from equation (2), the stable point voltage difference (VS2-VS,) is directly proportional to current ■, and as understood from equation 4, current ■5 is directly proportional to control voltage ■ Since it is directly proportional to c, by changing (increasing or decreasing) the control voltage VC, as shown after time t1 in FIG. 2, the stable point voltage difference (VS).

VS+) can be changed (increased or decreased). In this case, in this embodiment, since the slope of the triangular wave signal ST is constant, the stable point voltage difference (VS,
The period can be changed in proportion to the magnitude of -VS, ). In other words, the output voltage■. . The period of A is the control voltage ■. In other words, it changes linearly with the period.

In this way, according to the above embodiment, a period linear voltage controlled oscillation circuit with a duty ratio of 50% can be constructed with a relatively simple configuration. Further, the circuit shown in FIG. 1 can be easily integrated into an integrated circuit.

Note that, not limited to the above embodiment, for example, the transistor Q
5 may be omitted and one end of the resistor R1 may be directly connected to the power supply voltage VCC. ilt
The configuration may be such that one of the stable point voltages S or VS2 changes depending on the voltage V.

Note that the present invention is not limited to the above-described embodiments, and it goes without saying that various configurations may be adopted without departing from the gist of the present invention.

[Effects of the Invention] As described above, according to the present invention, since the amplitude of the triangular wave signal with a constant slope changes in proportion to the control voltage, the period of the output signal related to the triangular wave signal is directly proportional to the control voltage. This has the advantage that it is possible to obtain a relatively simple voltage controlled oscillator circuit having characteristics that change over time, that is, so-called period linear characteristics.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the configuration of an embodiment of the voltage controlled oscillation circuit according to the present invention, and FIG. 2 is a waveform diagram illustrating the operation of the circuit shown in FIG. 1. (2) is a triangular wave signal generation circuit, and (3) is a bistable circuit. Agent Hidemori Matsukuma Time Hon Mitsuaki ◆υi Ei 1 舊p Mitsufuri former Tomari To row A η

Claims (1)

[Claims] It has a bistable circuit in which a stable point voltage is controlled, and a triangular wave signal generation circuit connected to this bistable circuit, and this triangular wave signal generating circuit controls the stable point voltage difference of the bistable circuit. A voltage controlled oscillator circuit characterized in that it generates a triangular wave signal according to.