DD266457A1 - MONOSTABLE MULTIVIBRATOR WITH PROGRAMMABLE IMPULSE DURATION - Google Patents

Abstract

Monostable multivibrator with programmable pulse duration, which can be used anywhere with advantage, where an adjustable hold time is required. Specifically, it can be used to build circuits for generating pulses and Impulsverzoegerungsschaltungen whose pulse width or Impulsverzoegerung should be programmable. The object of the invention is to provide a monostable multivibrator circuit which is programmable in its hold time and terminates the hold state when the inverse of the input trigger frequency is less than the hold time. According to the invention, the object is achieved in that the trigger pulse input of the monostable multivibrator is the clock input of a D flip-flop whose Q output is routed to the D input and via a resistor to the base of a transistor. The emitter of the transistor is connected to the reference potential and the collector to a programmable current source, the input of a voltage comparator and a terminal of a capacitor, wherein the second terminal of the capacitor is connected to the reference potential. The second input of the voltage comparator is coupled to a programmable voltage source and its output is coupled to a level shifter. The output of the level shifter is routed to the reset input of the D flip-flop. The invention can be seen in FIG. Fig. 1

Description

For this 2 pages drawings

Field of application of the invention

Monostable multivibrator with programmable pulse duration, which can be used with advantage wherever an adjustable dwell time is required, so that it can be used to set up impulse and pulse delay circuits whose pulse width or pulse delay should be programmable.

Characteristic of the known technical solutions

A device for temporal Vorzögurunrj a signal is vorgostollt in DE-OS 2638950. With oinom flipflop oino discharge stage is disabled and a capacitor with oinor gotaktoton DC tensions aufgoladon. Dor capacitor is connected directly to the return path of the flip-flop. This has the disadvantage that the charging process breaks off slots with the sole charging voltage of the condutor. The Vorzörgorungszoit can be adjusted only with Hilfo the Gotaktoton DC quill. Furthermore, the charging process can not be carried out in advance.

The circuit to a stollbaron monoflop is vorgostollt in DE-OS 3219682. Sio is based on discharging oin capacitor with a controllable current source. Dor disadvantage of the solution bostoht is that the Ladovorgang can not be aborted vorzoitig and that holds the holding time umgokohrt proportional to the Stouorspannung. The DD-WP shows oinon non-triggorbaron monostable multivibrator, boi dom oin condenser is charged via o toktflonkongestouortes D flip-flop. After dom Erroichon of an adjustable threshold voltage, the flip-flop is back-blocked with a comparator and discharged the capacitor with oinor current source. The comparator has a fost adjustable hysteresis, so that the Ausgangsimpulsdauor can be varied only with Hilfo the power source. The disadvantage here is also that the holding time behaves inversely proportional to the current and that the charging process not vorzoitig aborted wordon kenn. Dos weitoren there is a minimum delay between dor Triggnrflanke and the output pulse, which is given by the Schaltzoit dos, flip-flop, dor charging time of the capacitor and the switching time of the comparators.

ZIoI the invention

The ZIoI of the invention is oino monostable multivibrator circuit with programmable pulse duration to ontworfon, dio oino has high resolution and programmable in einom woiten Boreich.

Explanation of the essence of the invention

The object of the invention is to provide a monostable multivibrator circuit, Hie is programmable in their hold time and the holding state aborts when the keying dor input trigger frequency is less than the hold time

Erfindungsgomäß the object is achieved in that the Triggorimpulselngang dos monostable multivibrator of

Clock input is a D-type Mip-flop whose O-tail is routed to the D input and a resistor to the base of a transistor. The emitter of the transistor is connected to the reference potential and the collector is connected to a programmable current source, the input of a voltage comparator and a terminal of a capacitor, the two terminal of the capacitor being connected to the reference potential. The second input of the Qpannungsverglcichers is with a

programmable voltage source and its output coupled to a Pogolumsotzor. The output of the level converter

is routed to the reset input of the D flip-flop.

The voltage comparator is composed of a current source and a differential amplifier.

Dor Pegolumsetzer is designed as a switchable power source.

Ausführungsbolspiol

The invention is intended to be explained in more detail below with reference to the detailed description. In don associated Zoichnungon? Oigon

Fig. 1: Blockscholtunt; dos monostabllon multivibrators

Fig. 2: Circuit arrangement dos monostable multivibrator

Fig. 3a: Zoltdlagramm dos monostable multivibrator, wonn dor Kohrwort dor Eingangstriggorfroquonz greater than dio

Haltozoitlst

 Fig. 3b: Zoitdiagramm dos mnnn <- »:> l> ilen multivibrators, if the Kohrwort dor Eingangstriggorfroquonz is smaller than dio hold time.

In figure 1 in the block diagram gozoigto monostable multivibrator bostoht from the following Hauptbostandtnilon:

- D flip flop

- discharge transistor T1

- Electric Quartet 11

- Ladokondeneator C

- voltage equalizer SV

- Pegelumsouer PU

In the Ausführungsbelspiol a flankongostouortos D flip-flop with positivor switching edge was used, as well as the use oforer flip-flop types is possible.

The description of the circuit is shown in FIG. 2.

It is assumed that at the 5-output of the flip-flop a logic high is possible. As a result, the transistor T1 is durchgestouort. He takes over all the electricity from the Electricity 11 and simultaneously discharges the capacitor. At the input E delta voltage comparator, which is designed as difforonzvorstörkor oino fixed voltage U 2> Oanliogon. Dor transistor T3 is thereby conductive, wihrond dor transistor T2 is blocked. Dor current 12 flows through don R1. Dor transistor T4 steers through with it, while at Rücksotzoingang the flip flop oin high pegol forms itself. If a low-Hlgh switching edge is applied to the clock input T dos flip-flop, then the d ohm output of the flip-flop wochsolt from high to low, since the flip-flop was connected as a divider. A low state at the output Q dos flip-flop causes the transistor T1 is turned off, which Doror R2 causes a faster degradation dor base carrier.

Nachdom the transistor has been blocked, the capacitor C with dom current 11 goladon. Neglecting the parasitic resistances, the Kondonsatorvorspannung U1 borechnon can be:

If U1 reaches the word of U 2, then the differential amplifier switches over, d. h., transistor T2 is turned on and transistor T3 is off. With dom blocking of transistor T3, transistor T4 is also blocking. The current through the resistor R3 decreases to the value of the output current of the flip-flop. Thus, on Rosotoingong oin low-pogol oin, who resets the flip-flop. The Q output of the flip-flop is thereby gosotzt high and the transistor T1 is durchgestouort. Thus, the capacitor C is discharged and the stable state orroicht.

This functional sequence is shown in FIG. 3a. Dor output Ados multivibrator is the output Q dos flip-flops, while the negative output Ä "is the output Q dos flip-flops.

t | = t ₀ + At,

where to represents the minimum Schaltzoit dor feedback coupler without capacitor charge. Here, t ₀ depends on the parameters of the wounded components. The charging time of the capacitor is Δι, ie it is the time after which U1 has word U 2 orroight. Thus, for tu:

It can be seen from this equation that t _{H increases} linearly with AU 2, and then enters the gloichung proportionally at the point of view.

Thus, 11 is suitable for range selection, while with AU 2 the concrete word dor holding time can be set linearly in this range.

In FIG. 3b, the provision of the circuit is depicted if the keying word of the input triggering frequency is smaller than the programmed holding range. In this case the flip-flop will arboit as a divider and the capacitor's laclo process will be aborted.

Claims (3)

A monostable multivibrator with programmable pulse duration and a D flip-flop, characterized in that the clock input of the D flip-flop is the trigger pulse input (T) and the Q output to the D input of the flip-flop and a resistor to the base of a transistor is guided, the emitter is connected to the reference potential and the collector of the transistor with a programmable current source 11, the input of a Spannungsvargleichers (SV) and a terminal of a capacitor, wherein the second terminal of the capacitor is connected to the reference potential, the second input of the Voltage comparator (SV) with a programmable Spannungsquello and the output of the voltage comparator with a level shifter (PU) is coupled, whose output is fed to the reset input of the D flip-flop. 2. Monostable multivibrator according to claim 1, characterized in that the voltage comparison ^! (SV) consists of a current source and a differential amplifier. 3. Monostable multivibrator according to claim 1, characterized in that the level converter is designed as a switchable power source,