JPH0123005B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a waveform conversion circuit that operates an input signal applied as a pulse width in the time domain and outputs the resultant signal.

Conventionally, there is a pulse width conversion circuit having the configuration shown in FIG. 1a, where b indicates the waveform of each part. As is well known, this circuit is called a pulse stretcher and performs waveform manipulation on the time axis. In this configuration, the transistor T _r1 is conductive while the input signal A is at a positive potential with respect to ground, and the capacitor C ₁
The terminal voltage e ₁ of is almost the ground potential. When the input signal goes to ground potential, the transistor T ₁ becomes non-conducting, and the capacitor C ₁ passes the voltage E ₁ through the resistor R ₁ .
The terminal voltage e ₁ increases exponentially as shown in (b). Furthermore, the terminal voltage e ₁ of the capacitor C ₁ is applied to the inverting input of the voltage comparator 11, and the reference voltage e ₂ is applied to the non-inverting input. When voltage e ₁ exceeds reference voltage e ₂ , the output potential of voltage comparator 11 is inverted. Therefore, the output waveform of the voltage comparator 11 is as shown in (c). That is, if the pulse width of the input signal is τ _x , the pulse width of the output signal is τ _y , and the time until the voltage e ₁ exceeds the reference voltage e ₂ is τ _b , the relationship between the input and output pulse widths is τ _y =
τ _x + τ _b . Here, τ _b is E ₁ , R ₁ , C ₁ and e ₂
is a constant pulse width determined by . Therefore _, according to _this pulse width conversion circuit, it is possible to obtain an output _signal with a pulse width corresponding to the input signal pulse width _τ The drawback was that it was not possible to obtain the pulse width.

As another _conventional example, after A/D conversion is performed by sampling an input signal with _a pulse width of τ There was a method that made _y = a・τ _x . According to this method, the constant a determined by the sampling period can be made less than 1, so it is possible to obtain an output that is less than the pulse width of the input signal, but the circuit becomes complicated and A/D conversion is not required. This has disadvantages such as the output pulse width becoming discontinuous with respect to changes in the input pulse width, and when the input pulse width is narrow, the sampling frequency must be increased, which is accompanied by technical difficulties. .

In order to solve the above-mentioned drawbacks, the present invention is characterized in that the input pulse width is converted into a voltage and applied to the control input of the pulse width modulator, and the input pulse width is proportional to the input pulse width and narrower than the input pulse width. A circuit for obtaining an output pulse containing a pulse component is provided.

FIG. 2 is a diagram showing an embodiment according to the present invention, in which a shows the configuration and b shows waveforms of each part. The main components include a constant current source 12 consisting of resistors R ₂ , R ₃ , and R ₄ transistors T _r2 , an integrating capacitor C ₂ , an electronic discharge switch 13 a, and a pulse width modulator 16 a. Furthermore, the pulse width modulator 16a is a capacitor.
C ₃ , resistor R ₁ , R ₆ , R ₇ , R ₈ , R ₉ , transistor
It consists of T _r3 , voltage comparators 11a and 11b, and flip-flop 15. First, when a discharge pulse is input, the electronic discharge switch 13a
The charge on the integrating capacitor C ₂ is rapidly discharged. Inverter 13b is also used as an electronic switch, and when input signal RO is applied, it drives constant current source 12 during the logic level "1" period. Therefore, if the instantaneous voltage is v, the constant current is i, and the time is t, then the terminal voltage C of the integrating capacitor _C2 increases linearly with time _, and the final The value is proportional to the pulse width of the input signal. The terminal voltage of _C2 is then held until a discharge pulse is applied. on the other hand,
When the trigger pulse N is applied to the inverter 14, the input of the voltage comparator 11a becomes a logic level "0", setting the flip-flop 15, and the Q output H rises. At this time, the base of transistor T _r3 is
Since it is connected to the output of flip-flop 15 through resistor _R9 and is therefore non-conducting, capacitor _C3 is charged with +5V through resistor _R1 , and the voltage at the terminals of _C3 rises in an exponential curve. Furthermore, when the terminal voltage of capacitor _C3 exceeds the voltage applied to the inverting input of voltage comparator 11b, flip-flop 15 is reset and transistor T _r3
becomes conductive and the charge on _C3 rapidly discharges.
By the way, if the combined resistance value of R _5a , R ₆ , R ₇ , and R ₈ is sufficiently large, the terminal voltage of capacitor C ₂ will be proportional to the pulse width of the input signal. When the terminal voltage of the capacitor _C2 is at ground potential and the pulse width modulator 16a is activated by the trigger pulse 2, the output pulse width of the pulse width modulator 16a is the minimum value τ _b shown in E.
The pulse width will be as follows. However, when an input pulse with a width τ _x drives the constant current source 12, the terminal voltage of the capacitor _C2 corresponding to the input pulse width is added to the inverting input of the voltage comparator 11b through the resistor _R5a , and the comparison voltage increases. The output pulse width increases. When the input pulse width is τ _x , the output becomes the pulse width τ _y as shown in E. Therefore, the relationship between the input and output pulse widths is a linear function of τ _y =a·τ _x +τ _b , and the output pulse width τ _y is related to the input pulse width τ _x . Here, the control sensitivity a of the pulse width modulator 16a is a constant set by the output current of the constant current 12, the capacitor _C2 , and the resistors _R5a , _R6 , _R7 , and _R8 . Further, τ _b is a constant value determined by the values of the resistor R ₁ and the integrating capacitor C ₃ of the pulse width modulator 16a.
By selecting a≦1, the present invention makes the change Δτ _y in τ _y relative to the change Δτ _x in τ _x proportional to Δτ _x , and Δτ
_x
The value can be made much smaller.

As described above, according to the present invention, it is possible to provide a pulse width conversion circuit which is proportional to the input pulse width and obtains a minute deviation smaller than the input pulse width with a simple circuit configuration.

[Brief explanation of drawings]

FIG. 1 is a diagram of a conventional pulse width conversion circuit, and FIG. 2 is a pulse width conversion circuit showing a first embodiment of the present invention. 11a, 11b... Voltage comparator, 12... Constant current source, 13a... Electronic discharge switch, 15... Flip-flop, 16a... Pulse width modulator, C ₂ , C ₃
… Integrating capacitor, R ₁ , R _5a , R ₆ , R ₇ , R ₈ … Resistor.

Claims (1)

[Claims] 1. A constant current source driven in proportion to an input signal with a pulse width τ _x , and a first integrating capacitor that is linearly charged with the output current of the constant current source to a terminal voltage proportional to the pulse width τ _x . a second integrating capacitor whose terminal voltage increases exponentially; and a first integrating capacitor whose terminal voltage is applied to one input terminal and compared with the voltage applied to the other input terminal. a voltage comparator; means for adding a weight a (a≦1) to the terminal voltage of the first integrating capacitor to the voltage applied to the other input terminal of the first voltage comparator; a second voltage comparator that applies the terminal voltage of the first integrating capacitor to its input terminal and outputs an output in response to a trigger pulse applied to the other input terminal while the terminal voltage is at a high level; and the second voltage comparator. a flip-flop that is set by the output of the voltage comparator and reset by the output of the first voltage comparator, and a pulse width τ _b determined by the charging time constant from the output terminal of the flip-flop to the second integrating capacitor and the pulse. A pulse width conversion circuit characterized in that a pulse width τ _y =aτ _x +τ _b is obtained by adding a pulse width aτ _x with a weight a to the width τ _x .