JP3209181B2 - Slow on / off signal generation circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a slow on / off signal generation circuit, and more particularly to a slow on / off signal generation circuit capable of generating a slow on / off signal even when a power supply voltage range is narrow.

[0002]

2. Description of the Related Art Conventionally, a slow on / off signal generation circuit which generates a slow on / off signal, which is constituted by a combination of an integrating circuit, a current switch and a current mirror circuit, is known.

FIG. 7 is a block diagram of a conventional slow on / off signal generation circuit. As shown in FIG. 7, a slow on / off signal generating circuit 1 includes an integrating circuit 2 including a resistor and a capacitor, a current switch 3 including a resistor and a transistor, and a resistor and a transistor. First current mirror circuit 4, a second current mirror circuit 5 including resistors and transistors, power supplies 6a and 6b for outputting predetermined voltages, and diodes 7a and 7
b, resistor 8a, transistor 8b, and capacitor 8
c.

A control signal a is input from an input terminal 9 to the integration circuit 2, a current b which is an input current of the slow on / off signal generation circuit 1 is output from the second current mirror circuit 5, and a transistor 8 b , The output current c of the slow on / off signal generation circuit 1 is output.

FIG. 8 is a time chart showing the operation of the slow on / off signal generation circuit of FIG. As shown in FIG. 8, when the control signal a changes from on to off (see (b)), the control signal a supplied from the input terminal 9 changes gradually with the lapse of time by the integration circuit 2. . When the output of the integration circuit 2 is input to the current switch 3, a slowly changing current is generated, and the current flows through the first current mirror circuit 4.

The second current mirror circuit 5 outputs a current mirror output current b (see (a)) obtained by multiplying the input current by n, and this current mirror output current b flows into the first current mirror circuit 4. The output current c gradually decreases to 0 (see (c)).

The control signal a changes from off to on ((b)
Then, the output current of the first current mirror circuit 4 gradually decreases to 0 due to the integration circuit 2 and the current switch 3. Therefore, the output current b of the second current mirror circuit 5 slowly flows as the output current c of the slow on / off signal generation circuit 1 via the diodes 7a and 7b, the resistor 8a, and the transistor 8b (see (c)). .

As described above, by combining the integrating circuit 2, the current switch 3, and the two current mirror circuits 4, 5, an output current c that is slowly turned on / off in response to the on / off of the control signal a is generated. Can be.

[0009]

However, the conventional slow on / off signal generating circuit 1 has a configuration in which the current switch 3 and the first and second current mirror circuits 4 and 5 are cascaded, so that the signal of the signal is generated. Considering the dynamic range, the circuit configuration must be wide in the power supply voltage range. For this reason, in the conventional slow on / off signal generation circuit 1, it was necessary to widen the power supply voltage range by using a negative power supply.

An object of the present invention is to provide a gradual on / off signal generating circuit capable of generating a gradual on / off signal even when a power supply voltage range is narrow.

[0011]

In order to achieve the above object, a slow on / off signal generating circuit according to the present invention comprises an input terminal.
And an input signal supplied to the input terminal , a reference voltage
An integration circuit that integrates with a first resistor and a capacitor ,
A switch connected between a second resistor connected to the input terminal and an output terminal of the reference voltage, the switch being turned on / off by a switch control signal; and an on / off signal input from the switch being connected to the reference voltage. And a filter that outputs an output based on the third resistor.
After the current conversion, the first resistor and the capacitor
A voltage-current conversion circuit for outputting to a connection point of the
An output terminal connected to a connection point between the resistor and the capacitor .

With the above configuration, the output signal voltage gradually changes from the predetermined reference voltage to the input signal voltage by switching the switch. As a result, a gentle on / off signal can be generated even when the power supply voltage range is narrow.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a slow on / off signal generation circuit according to an embodiment of the present invention. As shown in FIG. 1, the slow on / off signal generation circuit 10 includes an integration circuit 1
1, a switch 12, a filter 13, and a voltage-current conversion circuit 14.

The integrating circuit 11 is composed of a first resistor 15 and a capacitor 16, and converts an input signal supplied from an input terminal 17 connected to the first resistor 15 into a predetermined signal of a power supply 18 connected to the capacitor 16. Integrate by the reference voltage (VA). This reference voltage (VA) can be set arbitrarily.

The switch 12 is connected between a reference voltage terminal 19 connected to the power supply section 18 and a second resistor 20 connected to the input terminal 17, and is controlled by a switch control signal input from a control signal input terminal 21. On / off operation.

The filter 13 has an input terminal connected to the second resistor 20.
The output terminal is connected to the third resistor 22
The voltage-current conversion circuit 14 has an input terminal connected to the third resistor 22 and an output terminal connected to the output terminal 23 connected to the first resistor 15.

FIG. 2 is a circuit diagram of the filter of FIG.
As shown in FIG. 2, the filter 13 includes resistors 24, 2
5, 26, 27, capacitors 28, 29 and operational amplifier 3
0 is an inverting type secondary low-pass filter having an input terminal 31 and an output terminal 32. The filter characteristics include resistors 24, 25, 26, 27 and capacitor 2
By changing the values of 8, 29, desired characteristics can be obtained.

FIG. 3 is a circuit diagram of the voltage-current conversion circuit of FIG. As shown in FIG. 3, the voltage-current conversion circuit 14
It comprises an operational amplifier 33 and an NPN transistor 34, and has an input terminal 35 and an output terminal 36. The operational amplifier 33 has a predetermined reference voltage (VA) as a positive input and an input from an input terminal 35 connected to the third resistor 22 as a negative input. The NPN transistor 34 has a base connected to the output of the operational amplifier 33, an emitter connected to an input terminal 35 serving as a negative input of the operational amplifier 33, and a collector connected to an output terminal 36.
Are connected to the output terminal 23 of the integration circuit 11 through the respective terminals.

FIG. 4 is a time chart of the slow on / off signal generation circuit 10 of FIG. In FIG. 4, (a)
In the case where the input signal voltage VIN is more positively applied than the predetermined reference voltage (VA), (b) indicates that the control signal input terminal 21
3 shows ON / OFF of the switch 12 by the switch control signal input from the switch.

When the switch 12 changes from on to off (see (b)), the input terminal 31 of the filter 13
The input signal voltage VIN is applied. Since the filter 13 is an inverting filter, a voltage lower than the reference voltage with respect to a predetermined reference voltage (VA) is applied to the output of the filter 13. Therefore, a potential difference occurs between both ends of the third resistor 22, and a current flows.

As a result, a current flows through the transistor 34, and the output terminal 23 has a predetermined reference voltage (VA), so that the input signal voltage VIN is not transmitted. The voltage-current conversion circuit 14 has a current gain at which the transistor 34 is saturated in a steady state.

Since the gradual on / off signal generation circuit 10 is a combination of the filter 13 composed of an inversion type secondary low-pass filter and the integration circuit 11, the output signal voltage is changed by switching the switch control signal from on to off. It gradually changes to a predetermined reference voltage (VA) (see (c)).

When the switch 12 is changed from off to on by the switch control signal (see FIG. 2B), a predetermined reference voltage (VA) is applied to the input terminal 31 of the filter 13.
Is added. Since there is no potential difference between both ends of the third resistor 22, no current flows through the third resistor 22.

As a result, since no current flows through the transistor 34, the input signal voltage VIN is output to the output terminal 23 as it is. Then, as in the case where the switch control signal is switched from on to off, the output signal voltage gradually changes from the predetermined reference voltage (VA) to the input signal voltage VIN by switching from off to on of the switch control signal. Note that the collector saturation voltage VCE (sat) of the NPN transistor 34 is sufficiently small with respect to the input signal voltage VIN, and can be ignored.

FIG. 5 is a circuit diagram showing another example of the voltage-current conversion circuit. As shown in FIG.
7 has a configuration similar to that of the voltage-current conversion circuit 14 except that a PNP transistor 38 is used instead of the NPN transistor 34. The PNP transistor 38 has a base connected to the output of the operational amplifier 33, an emitter connected to the input terminal 35 serving as a negative input of the operational amplifier 33, and a collector connected to the output terminal 36.
Are connected to the output terminal 23 of the integration circuit 11 through the respective terminals. Note that the reference voltage (VA) can be set arbitrarily.

FIG. 6 is a time chart of the slow on / off signal generation circuit provided with the voltage / current conversion circuit 37 of FIG. 6A shows a case where the input signal voltage VIN is applied more negatively than a predetermined reference voltage (VA), and FIG.
Indicates ON / OFF of the switch 12 by the switch control signal input from the control signal input terminal 21.

When the switch 12 changes from on to off (see (b)), the input terminal 31 of the filter 13
The input signal voltage VIN is applied. Since the filter 13 is an inversion type filter, a voltage higher than the reference voltage with respect to a predetermined reference voltage (VA) is applied to the output of the filter 13. Therefore, a potential difference occurs between both ends of the third resistor 22, and a current flows.

As a result, a current flows through the transistor 38, and the output terminal 23 has a predetermined reference voltage (VA), so that the input signal voltage VIN is not transmitted. The voltage-current conversion circuit 14 has a current gain at which the transistor 38 is saturated in a steady state.

Since the gradual on / off signal generating circuit is a combination of the filter 13 composed of an inverting type secondary low-pass filter and the integrating circuit 11, the output signal voltage is moderated by switching the switch control signal from on to off. Then, the voltage changes to a predetermined reference voltage (VA) (see (c)).

When the switch 12 is turned on from the off state by the switch control signal (see (b)), a predetermined reference voltage (VA) is applied to the input terminal 31 of the filter 13.
Is output as is. Since there is no potential difference between both ends of the third resistor 22, no current flows through the third resistor 22.

As a result, since no current flows through the transistor 38, the input signal voltage VIN is output to the output terminal 23 as it is. The output signal voltage gradually changes from the predetermined reference voltage (VA) to the input signal voltage VIN due to the switching of the switch control signal from off to on, similarly to the switching from off to on of the switch control signal. Note that the collector saturation voltage VCE (sat) of the PNP transistor 38 is sufficiently small with respect to the input signal voltage VIN, and can be ignored.

As described above, according to the present invention, it is possible to provide a gradual on / off signal generation circuit which does not require a negative power supply and can generate a gradual on / off signal even when the power supply voltage range is narrow. it can.

In the above embodiment, the second resistor 20 and the switch 12 are exchanged, and the switch 12 is connected to the second resistor 20 connected to the output terminal of the reference voltage and the input terminal 1.
7, the switch 12 may be configured to invert the on / off polarity.

Further, in the above embodiment, the slow ON /
Although the off signal generation circuit has been described as an example of a voltage signal, it is needless to say that a current signal as in the conventional example can be easily realized by adding a voltage / current conversion circuit. Also,
Although an example in which a second-order low-pass filter of an inversion type is used as the filter has been described, the present invention is not limited to this, and various modifications are possible. Furthermore, it goes without saying that various changes in the configuration and combination can be made without departing from the spirit of the present invention.

[0036]

As described above, according to the present invention,
When the switch is switched, the output signal voltage gradually changes from a predetermined reference voltage to the input signal voltage, so that a gentle on / off signal can be generated even when the power supply voltage range is narrow.

[Brief description of the drawings]

FIG. 1 is a block diagram of a slow on / off signal generation circuit according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of the filter of FIG.

FIG. 3 is a circuit diagram of the voltage-current conversion circuit of FIG. 1;

FIG. 4 is a time chart of the slow on / off signal generation circuit of FIG. 1;

FIG. 5 is a circuit diagram showing another example of the voltage-current conversion circuit.

FIG. 6 is a time chart of a slow on / off signal generation circuit including the voltage / current conversion circuit of FIG. 5;

FIG. 7 is a block diagram of a conventional slow on / off signal generation circuit.

8 is a time chart showing the operation of the slow on / off signal generation circuit of FIG. 7;

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 Slow on / off signal generation circuit 11 Integrator circuit 12 Switch 13 Filter 14, 37 Voltage-current converter circuit 15 First resistor 16 Capacitor 17, 31, 35 Input terminal 18 Power supply unit 19 Reference voltage terminal 20 Second resistor 21 Control Signal input terminal 22 Third resistor 23, 32, 36 Output terminal 24, 25, 26, 27 Resistor 28, 29 Capacitor 30, 33 Operational amplifier 34 NPN transistor 38 PNP transistor

Claims (4)

(57) [Claims] [1 claim] an input terminal, an input signal supplied to the input terminal, the reference voltage first
An integration circuit that integrates with a resistor and a capacitor, a switch that is connected between a second resistor connected to the input terminal and an output terminal of the reference voltage, and that is turned on / off by a switch control signal; A filter that outputs the input on / off signal based on the reference voltage, and an output voltage from the filter that is input through a third resistor is connected to a connection point between the first resistor and the capacitor after current conversion. a voltage-current converting circuit for outputting, connected to the connection point of the capacitor and the first resistor
A slow on / off signal generation circuit having an output terminal . 2. The slow on / off signal generation circuit according to claim 1 , wherein said filter is an inversion type secondary low-pass filter. 3. The voltage-current conversion circuit according to claim 1, wherein said voltage-current conversion circuit comprises an operational amplifier
3. The slow on / off signal generation circuit according to claim 1, comprising a PN or PNP transistor. Wherein said switch is according to any one of claims 1 to 3, characterized in that connected between the second resistor and the input terminal connected to an output terminal of the reference voltage Slow on / off signal generation circuit.