JPS5945289B2 - Pulse generation circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pulse generating circuit that can freely change the period and duty ratio of an output pulse according to an input signal.

If a lamp malfunctions due to a disconnection of the lamp coil in a direction indicating device using a lamp flashing method for automobiles, etc., it will be in an extremely dangerous situation, so it is necessary to make the driver aware of the malfunction of the lamp by some means. There is a need.

By the way, in order to check the operating status of the direction indicator, the driver's seat is equipped with an indicator lamp that blinks in response to the direction indicator installed on the outer periphery of the car, and also a display lamp that blinks in response to the direction indicator installed on the outer periphery of the car. A pulse generating circuit is used for control.

Conventionally, the pulse generating circuit normally oscillates at a constant frequency, and when the lamp of the direction indicator fails, the change in the current flowing through the direction indicator is detected and the oscillation frequency is increased.

In this way, when the lamps of the direction indicating device fail, the indicator lamp provided at the driver's seat blinks at a faster rate, and the driver can confirm approximately how many lamps of the direction indicating device have failed.

However, as the oscillation frequency of the pulse generation circuit increases and the flashing cycle of the indicator lamp becomes shorter, the indicator lamp will continue to be lit, and if the blinking cycle exceeds a certain level, it becomes impossible to know how many lamps have failed. It becomes difficult to recognize.

Therefore, in order to clearly confirm the blinking state even if the blinking period becomes short, it is sufficient to change the duty ratio of the output pulse of the pulse generating circuit.

However, there is no conventional pulse generation circuit that can change both the oscillation frequency and the duty ratio in accordance with the input signal.

This invention was made in consideration of the above circumstances, and its purpose is to provide a pulse generation circuit that can freely change the oscillation frequency and duty ratio according to the input signal. be.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a pulse generation circuit according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a pulse generating circuit according to the present invention.

Reference numeral 1 denotes an input circuit for detecting current or voltage, and an output signal of this input circuit 1 is supplied in parallel to a charge/discharge circuit 2 and a reference voltage generation circuit 3.

The charging/discharging circuit 2 is composed of a constant current source, a variable current source whose current value changes according to the output signal of the input circuit 1, and a capacitor that is charged or discharged by the output current of each of these two current sources. The voltage at this capacitor is then supplied to the non-inverting input terminal of the comparator 4.

Further, the reference voltage generation circuit 3 is composed of a constant voltage source whose value is fixed and a variable voltage source whose value changes depending on the output signal of the input circuit 1. The output voltage is supplied to the inverting input terminal of the comparator 4.

The comparator 4 compares the output voltage of the charging/discharging circuit 2 and the output voltage of the reference voltage generating circuit 3, and the comparison output signal is supplied to the outside via the buffer circuit 5.

Furthermore, the comparison output signal of the comparator 4 is transmitted to the switching circuit 6.
is supplied to.

This switching circuit 6 is for switching the respective operations of the charging/discharging circuit 2 and the reference voltage generating circuit 3 according to the comparison output signal. For example, if the comparison output signal of the comparator 4 is I? 17 level, the operation is switched so that the capacitor in the charging/discharging circuit 2 is charged by the constant current source, and the output voltage of the constant voltage source is supplied to the comparator 4 in the reference voltage generating circuit 3. Its operation can be switched.

FIG. 2 is a block diagram showing in detail the pulse generating circuit shown in FIG. 1 above.

In FIG. 2, a resistor 11 whose one end is connected to the power supply VCC is a resistor for voltage detection, and the voltage drop across this resistor 11 is used as an input signal to the pulse generating circuit.

The other end of the above resistor is a multi-IL/IL with two collectors.
The transistor PNP l- is connected to the emitter of the transistor 12.

The base of this transistor is connected to a connection point between a diode 14 and a resistor 15 in a circuit in which a resistor 13, a diode 14, and a resistor 15 are connected in series between the power supply and the ground potential point.

One collector of the transistor 12 is connected to an inverting input terminal of a comparator 18 via a diode 17 connected in series in the forward direction.

Further, the other collector of the transistor 12 is connected to a pair of NPN transistors 19 forming a so-called current mirror circuit.
, 20 is connected to the collector of one of the transistors 19.

Furthermore, a constant current source 21 is connected to the power source, and the anodes of two diodes 22 and 23 are connected in parallel to the other end of this constant current source.

Diodes 24 and 25 are connected in series to the diodes 22 and 23, respectively, and the cathodes of these two diodes 24 and 25 are connected in parallel.

A constant current source 26 is connected between the connection point of the two diodes 24 and 25 and the ground potential point.

Furthermore, one end of a resistor 27 is connected to the connection point, and the other end of this resistor 27 is connected to the collector of the transistor 20 constituting the current mirror circuit.

A resistor 28 is connected between the connection point of the diodes 22 and 24 and the power supply, and this connection point is connected to the collector of an NPN transistor 29 whose emitter is connected to the ground potential point. There is.

Further, the anode of the diode 17 is connected to the collector of an NPN transistor 30 whose emitter is connected to a connection potential point.

A capacitor 31 is connected between the connection point of the two diodes 23 and 25 and the ground potential point, and this connection point is connected to the non-inverting input terminal of the comparator 18.

Furthermore, there are two resistors 32°3 between the power supply and the ground potential point.
3 are connected in series, and there are two resistors 3 at this connection point.
4.35 are connected in parallel.

The other end of this one resistor 34 is connected to the inverting input terminal of the comparator 18, and the other end of the other resistor 35 is connected to the collector of an NPN transistor 36 whose emitter is connected to the ground potential point. ing.

Further, the output terminal of the comparator 18 is connected to a buffer circuit 37.
The transistor 2 is connected to the input terminal of the transistor 2.
9, 30, and 36 respectively.

In the circuit shown in FIG. 2 above, resistors 11, 13°15,
The transistor 12 and the diode 14 correspond to the input circuit 1, and when the base potential of the transistor 12 becomes higher than the collector current, a collector current flows.

Note that the diode 14 is a diode for canceling VBB of the transistor 12.

Furthermore, in FIG. 2, transistors 19 and 20, constant current sources 21 and 26, diodes 22 to 25, resistor 28, and capacitor 31 correspond to the charging/discharging circuit 2.

Further, the resistors 32 to 35 correspond to the reference voltage generating circuit 3, and the transistors 29, 30, and 36 correspond to the switching circuit 6, respectively.

The comparator 18 and the buffer circuit 37 correspond to the comparator 4 and the buffer circuit 5, respectively.

Next, the operation of the circuit connected as shown in FIG. 2 will be described with reference to the waveform diagrams shown in FIGS. 3 and 4.

First, the output current values of the constant current sources 21 and 26 are set to 11. I2
Assume that the capacitor 31 is in a discharged state and that the output signal P of the comparator 18 is at the "0" level (ground level).

If the voltage drop across the resistor 11, that is, the input signal voltage, is greater than the voltage drop across the resistor 13, the transistor 12 is turned off and no collector current flows through the transistor 20 constituting the current mirror circuit.

Furthermore, the transistors 29, 30, and 36 whose base input signal is the output signal P of the comparator 18 are turned off.

When the transistor 29 is turned off, the output current 1 of the constant current source 21 flows into the capacitor 31 via the diode 23, and the capacitor 31 is charged.

The voltage Vc at the capacitor 31 during charging is input to the non-inverting input terminal of the comparator 18.

Since the one-way transistor 36 is off, the resistor 32
The voltage at the connection point a of ゜33 is the resistance 3 of the power supply voltage vCC.
2 and the voltage v1 divided according to the resistance ratio of the resistor 33.
becomes.

Also, at this time, the base input signal of the transistor 30 is ``0''.
'' level, this transistor 30 is off, but no current flows through the diode 17, so the above a.
The voltage ■1 at the point is directly input to the inverting input terminal of the comparator 18 via the resistor 34.

That is, the comparator 18 compares the voltage Vc when the capacitor 31 is charged with the voltage v1 at point a.

When the voltage Vc in the capacitor 31 rises and reaches vl, the output signal P of the comparator 18 is inverted to the 1'' level as shown in FIG.

When the output signal P of the comparator 18 is inverted to the "1" level, the transistors 29, 30.3, which have been off until now,
6 are all turned on.

When the transistor 29 is turned on, the output current 1 of the constant current source 21 that has been flowing into the capacitor 31 flows to the ground potential point via the diode 22 and the transistor 29, and the charge that has been accumulated in the capacitor 31 until now flows into the ground potential point. is discharged by the output current 2 of the constant current source 26.

The voltage Vc at the capacitor 31 during discharge is input to the non-inverting input terminal of the comparator 18.

Further, since the base input signal of the transistor 36 is at the "1" level, the transistor 36 is turned on.

At this time, the voltage at point a is a voltage v2 obtained by dividing the power supply voltage vCC according to the resistance ratio between the resistance value of the resistor 32 and the parallel resistance value of the resistors 33 and 35.

However, it is assumed that this divided voltage v2 satisfies the relationship of V<Vl.

Furthermore, since the transistor 30 is on at this time, the voltage v2 at the point a is directly input to the inverting input terminal of the comparator 18 via the resistor 34, regardless of whether or not current is flowing through the diode 17.

That is, the comparator 18 compares the voltage Vc when the capacitor 31 is discharged with the voltage 2 at point a.

Then, when the voltage Vc at the capacitor 31 decreases and reaches 2, the output signal P of the comparator 18 is again inverted to the "0" level as shown in FIG.

When the output signal P of the comparator 18 is again inverted to the "0" level, the transistor 29°30.36
Each of them is turned off, and the capacitor 31 is charged again by the output current 1 of the constant current source 21, and Vc rises again.

When Vc reaches vl, the output signal P of the comparator 18 is inverted to the "1" level as shown in FIG.

Similarly, the output signal P of the comparator 18 repeats the ``1'' level uOu level at a constant period.

Now, as shown in FIG. 3, one period of the output signal P is T.

When the period in which the signal is closed and the level is l'' is 'r, and the period in which the level is ?+07 is I2, T1.I2.To can be respectively expressed by the following equations.

T, = (V, -V2)-C/L -...--
=・(1)I2-(V,-V2)-C/I2-
・−・−・−・−(2) To−T1+T2 −(Vl−V2) rl/I, +1/I2)・C・・・(
3) (where C is the capacitance value of capacitor 31) Also, if the period during which the output signal P of the comparator 18 is at the °1" level is defined as the capability level period, the output signal P duty ratio can be expressed by the following formula. .

D=T1/To=I2. /(11+I2) −・−・
- (4) Therefore, the voltage drop across the resistor 11, that is, the input signal voltage is constant, and its value is the same as that of the resistor 11.
3, the period T of the output pulse of the buffer circuit 37.

or frequency f.

(fo=1/To) and the duty ratio are constant.

Next, when the current flowing through the resistor 11 decreases and the voltage drop across the resistor 11 becomes lower than the voltage drop across the resistor 13, the transistor 12 turns on in accordance with the voltage drop across the resistor 11, and the transistor 12
A collector current flows through each of the two collectors.

As the collector current of the transistor 12 flows, a forward current flows through the diode 17, and a collector current flows through the transistor 20 forming the current mirror circuit.

As a result, when the capacitor 31 is discharged, the charge accumulated in the capacitor 31 is combined with the output current 2 of the constant current source 26 and the transistor 2
It is discharged by the sum current 12' with the collector current of 0.

At this time, the slope when Vc decreases becomes steep as shown in FIG. 4, and the period T, / during which the output signal P of the comparator 18 is at the "1'" level becomes shorter than T1.

Furthermore, when the transistor 30 is off, the diode 1
Since a forward current flows through 1, the voltage at the inverting input terminal of the comparator 18 at this time becomes a voltage 1' which is lower than the voltage v1 at the point a by the voltage drop across the resistor 34.

Therefore, when the voltage drop across the resistor 11 becomes smaller than the voltage drop across the resistor 13, the comparator 18 compares the voltage Vc across the capacitor 31 with the voltage 1' or V2 as shown in FIG.

As a result, the period T of the output signal P of the comparator 18.

' is the early period T. will be shorter than

Now, when the voltage drop across the resistor 11 decreases and the discharge current 2 when the capacitor 31 is discharged becomes 12', and the voltage v1 input to the inverting input terminal of the comparator 18 becomes v1', the output signal P of the comparator 18 becomes Period T.

' and duty ratio D' can be expressed by the following formula.

To'=(■1'-v2)・(1/■1+1/■2')
・C・・・・・・・・・・・・(5) D'=I 2' / (I 1 + I 2')
(6) Therefore, by changing the discharge current value in the capacitor 31 and the voltage v1 at the connection point of the resistors 32 and 33 according to the voltage drop in the resistor 11, or vice versa. the charging current value in the capacitor 31 and the resistor 33 connected in parallel with the resistor 32,
By changing the potential v2 at the connection point with 35 and further by changing the resistance value of the resistor 13,
Characteristics having frequency (f) changes and duty ratio CD) changes as shown in Figures a to d can be obtained.

That is, in FIGS. 5a to 5d, the horizontal axis represents the input signal voltage Vin.
The vertical axis shows the frequency f1 and the duty ratio, respectively, where the solid line is the frequency change curve and the one-dot chain line is the duty ratio change curve.

FIG. 6 shows an example of application of the present invention, in which the pulse generating circuit shown in FIG. 2 is used in a direction indicating device using a flashing lamp system for automobiles and the like.

In FIG. 6, a resistor 41 whose l end is connected to the power supply vCC corresponds to the resistor 11, and this resistor 41
The other end is connected to the normally closed contact S of the relay device 42.

Furthermore, the other end of this contact S is connected to a movable contact Ca of the left/right changeover switch 43.

Between the fixed contact Cb1 of the left/right selector switch 43 and the ground potential point, a large lamp L-1 is installed on the outer periphery of the vehicle and is driven to blink when the vehicle turns right.
A lamp LR2 that is slightly smaller than this lamp LR1, a medium-sized lamp LR3 that is slightly smaller than this lamp LR2, and a small lamp LR4 are connected in parallel.

The fixed contact Cb2 of the left/right selector switch 43 is in an open state, and a contact is installed on the outer periphery of the vehicle between the fixed contact Cb3 and the ground potential point, and is driven to blink when the vehicle turns left. The lamps LBH and LR2
.

Lamp IJ whose size corresponds to LR3, LR, respectively
R1, LR2, LR3, and LR are connected in parallel.

An input end of a pulse generating circuit 44 is connected to the connection point between the resistor 41 and the contact S of the relay device 42.

Further, a resistor 45 is connected to the connection point between the contact S and the left/right changeover switch 43, and the other end of this resistor 45 is connected to the input end of the starting circuit 46.

Furthermore, a resistor 47 is connected between the input terminal of this starting circuit 46 and the power supply.

The output signal of the starting circuit 46 controls the opening and closing of a contact C which is connected in series between the pulse generating circuit 44 and the inverter 4B.

Furthermore, the output end of the inverter 48 is connected to the other end of the relay coil LR of the relay device 42, one end of which is connected to a power source.

The starting circuit 46 is a movable contact C of the left/right changeover switch 43.
a is the fixed contact Cb1. This is to detect that it is connected to either Cb3, and at the time of detection, the pulse generation circuit 4
A contact C inserted in series between 4 and the inverter 48
It is designed to output a signal that closes the

Further, the frequency change characteristics and duty ratio change characteristics with respect to the input signal of the pulse generating circuit 44 are shown in FIG.
Assume that the characteristics are as shown in .

Now move the movable contact Ca of the left/right selector switch 43 to the fixed contact C.
Connect to b1.

Then, the input terminal voltage of the starting circuit 46 decreases, and the contact C is then closed.

In addition, the movable contact Ca of the left/right selector switch 43 is replaced with the fixed contact C.
By connecting to b1, the lamp LR.

~If each of LR4 is not broken, these lamps LR
A current flows through the lamps LR1 to LR, and each lamp LRt to LR4 lights up.

By operating the left/right selector switch 43, the resistor 41
A current flows through the pulse generating circuit 44, and an input signal is applied to the pulse generating circuit 44.

As a result, the pulse generating circuit 44 outputs a pulse with a predetermined frequency and a predetermined duty ratio.

The output pulse of this pulse generation circuit 44 is transmitted to the inverter 48.
After being inverted by , it is input to relay coil LR.

Therefore, the contact S of the relay device 42 is closed only during the period when the output pulse of the pulse generation circuit 44 is at the level 1'', and the lamps LR1 to LR4 are connected to the output pulse of the pulse generation circuit 44.
It will blink depending on the frequency and duty ratio of the output pulse.

It is assumed that the blinking frequency and duty ratio when all of the lamps LR1 to LR, fJ3 are controlled to blink are at position A shown in FIG.

Next, the smallest lamp LR was broken and this lamp LR4
When current stops flowing through the resistor 41, the voltage drop across the resistor 41 decreases.

At this time, if the frequency and duty ratio of the output pulse of the pulse generating circuit 44 are set to the position shown in FIG. 7, the remaining lamps LR1 to LR3 blink more frequently than before.

Furthermore, if the next medium-sized lamp LR3 fails, resistor 4
The voltage drop at 1 further decreases.

At this time, if the frequency and duty ratio of the output pulse 2 of the pulse generating circuit 44 are set to the position C shown in FIG. 7, the remaining lamp L R1.

L R2y L R4 blinks more frequently.

Hereinafter, if the frequency and duty ratio of the output pulse of the pulse generating circuit 44 are set to 2 and E when the medium-sized and large-sized lamps LR2 and LR3 fail, respectively, the remaining lamps blink more frequently.

At this time, as the blinking frequency of the lamp increases, the duty ratio of the output pulse decreases, so even if the blinking frequency increases, the blinking state of the lamp can be confirmed.

Therefore, by looking at the display lamp provided for the operating level, it is possible to recognize at a glance which lamp is out of order according to its blinking state.

As explained above, according to the present invention, it is possible to provide a pulse generation circuit that can freely change the oscillation frequency and duty ratio according to the input signal.

[Brief explanation of drawings]

FIG. 1 is a block configuration diagram of one example of the pulse generation circuit of the present invention, FIG. 2 is a detailed circuit configuration diagram thereof, and FIGS. 3 and 4 are waveform diagrams for explaining the above embodiment, respectively. FIGS. 5a and 5d are characteristic diagrams for explaining the above embodiments, respectively;
FIG. 6 is a configuration diagram showing an application example of the present invention, and FIG. 7 is a characteristic diagram for explaining the above application example. 1...Input circuit, 2...Charging/discharging circuit,
3...Reference voltage generation circuit, 4...Comparator, 5...Buffer circuit, 6...
・Switching circuit, 41, 45, 47...Resistance, raw λ
...Relay device, 43...Right/left selector switch, 44...Pulse generation circuit, 46...
Starting circuit, 48... impark.

Claims (1)

[Claims] 1. A charging/discharging circuit consisting of a capacitor that is charged with a current of a predetermined value and discharged with a current whose value changes depending on an input signal, and a voltage at the capacitor and a first reference voltage of a predetermined value or the input signal. a comparison circuit that compares the voltage with a second reference voltage that changes according to the output of the comparison circuit; a charging/discharging operation in the charging/discharging circuit according to the output of the comparing circuit; 1. A pulse generating circuit comprising: a switching circuit for simultaneously switching reference voltages of