JP3945389B2 - Time-voltage converter and method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a time-voltage converter for simply and accurately measuring a pulse width time or period of a digital signal emitted from various devices into a voltage value proportional to its length, and the conversion The present invention relates to a time voltage conversion method using a measuring device.
[0002]
[Prior art]
Conventionally, a circuit combining a constant current circuit, a capacitor and a switch has been widely used for time-voltage conversion. FIG. 3 shows a typical circuit configuration and operation flow. In FIG. 3A, 1 is a constant current circuit, 2 is a capacitor, and 3 is a switch. Now, when the switch 3 is opened during the time T by the digital signal 10 having the width of the length T, the potential at Vout changes as indicated by 11 in the figure. At this time, if the constant current value is I and the capacitance of the capacitor is C, the amount of electricity Q stored in the capacitor during time T is expressed by
Q = IT = CV
Given in Therefore, by measuring the potential V,
[Formula 2]
T = CV / I
Thus, the time T can be obtained by calculation.
[0003]
However, this is an expression that is applied only when all the above-described elements operate ideally. In reality, the linearity of the time-voltage conversion line 11 is not guaranteed mainly due to the influence of the operation speed of the switch 3. . This state is shown in FIG. In the figure, t is a time required for the switch 3 in the connected state to be completely opened, and Vt is a potential charged in the capacitor during the same time. Including the effect of the state transition time of the switch, the above equation is expressed as follows.
[Formula 3]
V = I / C · (T−t) + Vt
However, when t is sufficiently small with respect to T,
t ≒ 0
By the way, Formula 3 is [Formula 4]
V = I / C · T
This agrees with Equation 2 and holds as an approximate equation.
[0004]
However, in recent years, various digital devices typified by an optical disc reproducing / recording apparatus and the like have been accelerating, and the pulse width of a signal to be detected becomes equal to the above t, and approximation by Equation 4 may be difficult.
[0005]
In order to solve this problem, for example, the time voltage conversion circuit of (a) is inputted while gradually changing the time length of a predetermined digital signal, and is induced according to each time length. There is a method of performing correction based on this recording during actual measurement by recording the potential.
Alternatively, as disclosed in, for example, Japanese Patent No. 1460182 “Time Voltage Converter”, the output potential from an oscillator that continuously changes at a constant period is measured at the start and stop of the signal under measurement. There is known a method of sampling a potential at, and obtaining a potential proportional to time by a difference between the potentials.
[0006]
[Patent Document 1]
Japanese Patent No. 1460182 [0007]
[Problems to be solved by the invention]
However, the time voltage conversion methods according to the conventional methods have problems such as an increase in cost due to an increase in circuit scale and a complicated procedure at the time of calibration.
[0008]
[Means for Solving the Problems]
In order to solve the above problem, the time-voltage converter according to claim 1 of the present invention comprises means for generating a pulse having a predetermined time width in synchronization with a measurement start edge of the signal under measurement, Time voltage converting means for inducing a potential corresponding to the time width thereof, means for receiving the input of the signal under measurement and delaying a predetermined time, and the signal under measurement output from the delay means And a means for holding the output potential of the time voltage conversion means at the time of each of the measurement start edge and the measurement end edge.
If this circuit configuration is used, a circuit such as a reference potential generator or a special calibration operation is not required, and a time voltage converter with low cost and excellent maintainability can be configured.
[0009]
According to a second aspect of the present invention, there is provided a time voltage conversion method using the time voltage converter according to the first aspect, wherein the output potential of the time voltage conversion means held at the measurement start edge and measurement end edge of the signal under measurement is measured. The difference is used as a voltage conversion result of the pulse width time or period of the signal under measurement.
By using this method, the non-linear region potential of the time voltage conversion means can be canceled, and a voltage proportional to the time without error can be obtained even in a short time.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of a circuit showing an embodiment of a time-voltage converter according to the present invention, and FIG. 2 is a timing diagram for explaining the operation of the circuit. However, it is assumed here that the rise time of the input signal is measured.
[0011]
In FIG. 1, 1 is a constant current circuit, 2 is a capacitor, and 3 is a switch, and constitutes time voltage conversion means for receiving a pulse input and inducing a potential according to its time width. . Hereinafter, this block is referred to as an integrator. 5 is a mono multivibrator which is a means for generating a pulse having a predetermined time width in synchronization with the measurement start edge of the signal under measurement, and 4 is for receiving a signal under measurement and delaying the predetermined time. Here, it is configured by digital buffer circuits connected in series by the number of necessary delay times. Also, 6 is an AND circuit, 7 is a NAND circuit, 8 is a flip-flop, and 9 is a sample-and-hold circuit. The time-voltage conversion means at each of the measurement start edge and measurement end edge of the signal under measurement is from 6 to 9. Means for holding the output potential. The operation of the time voltage converter configured as described above will be described below with reference to FIG.
[0012]
First, by setting data_set in the figure to HIGH, each circuit is initialized to prepare for input of a signal to be measured. The signal input from pulse_in is input to the integrator via the mono multivibrator 5. On the other hand, the signal input from pulse_in passes through the delay circuit 4, and then the S / H-1 and S / H-2 signals for the rising and falling edges of the delay pulse by the circuits 6, 7, and 8, respectively. Is generated. Since both timing signals are input to independent sample and hold circuits, potentials can be obtained as VS and VE in the figure, respectively, and the difference between these potentials is obtained as a voltage conversion result of the rising width time T of the input signal. To do.
[0013]
When this method is used, only the interval in which the linearity of the integrator is guaranteed is used. Therefore, even if the input time is short, a voltage that is accurately proportional to the time can be obtained. In addition, the calibration work during actual operation is as follows. A signal having a known rise time Tc (SEC.) Is input, and a constant current value and a capacitor capacity are appropriately combined so that the obtained time-voltage conversion result becomes a reference value Vc (V) determined as necessary. Thus, the proportionality coefficient K (V / SEC.) Is obtained using the following equation.
[Formula 5]
Vc = KTc
Thereafter, by dividing the potential changing according to the input signal by K, the rising width time of the input signal can be obtained accurately.
[0014]
【The invention's effect】
As described above, according to the present invention, even with a short input time, a voltage that is accurately proportional to the input time can be obtained with a very simple circuit configuration, and the calibration work is simple and excellent in handling and low cost. A simple time-voltage converter can be realized.
[Brief description of the drawings]
FIG. 1 is a block diagram of a time voltage converter according to an embodiment of the present invention. FIG. 2 is an operation explanatory diagram of the time voltage converter according to an embodiment of the present invention. Operation explanation diagram [Explanation of symbols]
1 constant current circuit 2 capacitor 3 switch 4 delay circuit 5 mono multivibrator 6 AND circuit 7 NAND circuit 8 flip-flop circuit 9 sample hold circuit 10 digital signal 11 time voltage conversion line

Claims (2)

A circuit for measuring a pulse width time or a period of a digital signal, a means for generating a pulse having a predetermined time width in synchronization with a measurement start edge of a signal under measurement, and a time width received by receiving the input of the pulse A time voltage converting means for inducing a potential according to the time, a means for delaying a predetermined time upon receipt of the input of the signal under measurement, a measurement start edge and a measurement end of the signal under measurement output by the delay means Means for holding the output potential of the time voltage conversion means at each edge time. A pulse of the signal under measurement is obtained by using the time voltage converter according to claim 1 and having a difference in output potential of the time voltage conversion means held at each time of measurement start edge and measurement end edge of the signal under measurement. A time-voltage conversion method, characterized in that a voltage conversion result of width time or period is used.

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