JP2011130069A - Filter device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a filter device capable of performing filtering process using small power. <P>SOLUTION: A switch control section 13 brings a power feed switch 17 into an electrical connection state by 1 clock out of 8 clocks of a clock control signal ϕ, that is, the 1/8 the period by a clock control signal ϕ1 in an operation phase. Then, the switch control part 13 brings a signal input switch 12 into an electrical connection state by 1/2 the clock from among 8 clocks of the clock control signal ϕ, that is, the 1/16 period by a clock control signal ϕ2. By controlling switching of each switch so as to make the electrical connection state intermittent by using the period other than that as a pause phase, power consumed in the filtering process can be restrained. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a filter device, and particularly to a filter device capable of performing a filtering process with a small amount of power.

In an electronic circuit, for example, a small level detection signal output from a high-precision sensor, a signal boosted by a booster circuit, an unnecessary noise component included in an audio signal, etc. Various filter circuits are used. As an example of such a filter circuit, there is a filter circuit disclosed in Patent Document 1.
The operation of the conventional filter circuit will be described with reference to FIGS. FIG. 5 is a circuit diagram showing the configuration of a conventional filter circuit, and FIG. 6 is a time chart showing the movement of the waveform of the output signal in the conventional filter circuit.

  A filter circuit 100 illustrated in FIG. 5 includes a resistor 101 and a capacitor 102. The filter circuit 100 is a circuit that functions as a low-pass filter from the resistor 101 and the capacitor 102. An analog circuit 103 or the like is connected to the input side of the filter circuit 100, and the filter circuit 100 performs a filtering process of allowing only a specific low-frequency signal of the output signal Va_out from the analog circuit 103 to pass.

  In the filter circuit 100 illustrated in FIG. 6, when power is continuously supplied to the analog circuit 103 and the output signal Va_out from the analog circuit 103 becomes 0 V or more, the output signal Vlpf_out from the filter circuit 100 rises. Further, when the output signal Va_out from the analog circuit 103 becomes 0 V or less, the output signal Vlpf_out from the filter circuit 100 falls.

  Then, by continuously supplying power to the analog circuit 103 and changing the pulse width at which the output signal Va_out from the analog circuit 103 is 0 V or more or 0 V or less, the output signal Vlpf_out from the filter circuit 100 is changed. The size can be changed. For example, as shown in the drawing, the magnitude of the output signal Vlpf_out from the filter circuit 100 is gradually reduced by gradually reducing the pulse width at which the output signal Va_out from the analog circuit 103 is 0 V or more or 0 V or less. Can continue.

JP 2006-5439 A

However, since the above-described filter circuit requires a resistor having a large resistance value and a capacitor having a large capacitance, the power tends to increase. In addition, since power must be constantly supplied to the analog circuit, the power is further increased.
In view of the above problems, an object of the present invention is to provide a filter device that can perform a filtering process with a small amount of power.

In order to achieve the above object, the filter device according to the present invention is configured as follows.
The first filter device according to the present invention receives an electric signal and inputs the signal through the signal input switching element and a signal input switching element that switches between an electrical connection state and an electrical disconnection state. A filter circuit that performs filtering of the electrical signal, and switch control means that switches and controls the signal input switching element so that the electrical connection state becomes intermittent.

  According to the above filter device, the switch control means performs signal input switching only in a period of 1/2 clock, that is, 1/16 of 8 clock control signals in the operation phase of inputting an electrical signal to the filter circuit. The element is brought into an electrical connection state. Further, the switch control means puts the signal input switching element into an electrically disconnected state in a pause phase in which an electric signal is not input to the filter circuit. Thus, by controlling the switching of the signal input switching element so that the electrical connection state of the signal input switching element becomes intermittent, the resistance and the capacitance having a smaller resistance value than when the power is continuously consumed. Even with a small capacitor, it is possible to obtain the same output as when power is continuously consumed. In other words, it is possible to suppress the power consumed in the filtering process while the filtering process can obtain the same output as the conventional one.

  In the second filter device according to the present invention, the switch control means is a power supply for controlling an operation of switching a power supply switching element for supplying power to the circuit, which is included in the circuit that outputs the electrical signal. Generating a switch control signal and a signal input switch control signal for controlling an operation of switching the signal input switching element to an electrically connected state when the power supply switching element is in an electrically connected state; To do.

According to the above filter device, the switch control means is 1 clock out of 8 clocks of the clock control signal, that is, a period of 1/8 in the operation phase of supplying power to the circuit that outputs the electrical signal to the filter circuit. Set the switch to electrical connection. Further, the switch control means puts the power supply switching element in an electrically disconnected state in the pause phase. In this way, by controlling the power supply switching element so as to operate intermittently, even if the circuit that outputs the electric signal is operated with less power than when the power is continuously consumed, the power supply switching element is continuously operated. To obtain the same output as when power is being supplied. In other words, it is possible to suppress the power consumed in the filtering process while the filtering process can obtain the same output as the conventional one. In addition, the power supply switch control signal for controlling the power supply switching element makes the signal input switching element for supplying power to the circuit that outputs the electric signal to the filter circuit in an electrically connected state, thereby stabilizing the power. Then, a signal input switch control signal for controlling the signal input switching element is output to the filter circuit. By operating in this way, the electric signal output from the circuit that outputs the electric signal to the filter circuit is also stabilized, and it becomes possible to output a stable signal from the filter circuit.
In a third filter device according to the present invention, the switch control means outputs a power supply switch control signal so as to bring the power supply switching element into an electrically connected state, and then electrically connects the signal input switching element. A signal input switch control signal is output so as to be in a state.

According to the above filter device, the power is supplied to the circuit that outputs the electrical signal from the normal filter circuit by raising the power supply switch control signal, for example, by 1/2 clock earlier than the rise of the signal input switch control signal. It is possible to secure a time until the output of the electric signal is stabilized after being supplied, and it is possible to obtain a stable output in the same manner as when the switching state of the switching element is continuously switched instead of being intermittent. Become.
According to a fourth filter device of the present invention, the filter circuit is a low-pass filter having a resistor and a capacitor.
According to the filter device described above, it is possible to use various low-pass filters in accordance with applications by changing only the control method of the control means.

  According to the filter device of the present invention, the electrical connection state of the power supply switching element for supplying power to the circuit that outputs the electrical signal to the filter circuit and the signal input switching element for inputting the electrical signal to the filter circuit is By switching the signal input switching element so as to be intermittent, the filter circuit and the filter are more effective than when switching the signal input switching element so that the electrical connection state of the switching element is not intermittent. Electric power required for filtering processing in a circuit that outputs an electrical signal to the circuit can be suppressed.

  At the same time, the resistance value of the resistor of the filter circuit and the capacitance value of the capacitor can be reduced. As a result, the volume of the resistor and the capacitor is also reduced. Therefore, even when a low pass filter is formed inside an LSI (Large Scale Integration), the area of the LSI itself can be significantly reduced. Furthermore, costs can be reduced.

It is a circuit diagram which shows the structure of the filter apparatus 10 which concerns on this invention. 3 is a circuit diagram showing a configuration of a switch control unit 13. FIG. 6 is a time chart showing the movement of each signal accompanying the signal output from the switch control unit 13; 6 is a time chart showing the movement of each signal accompanying the signal output from the switch control unit 13; It is a circuit diagram which shows the structure of the conventional filter circuit. It is a time chart which shows the motion of the waveform of the output signal in the conventional filter circuit.

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. In each drawing referred to in the following description, components equivalent to those in the other drawings are denoted by the same reference numerals.
(Configuration of filter device 10)
First, with reference to FIG. 1, the structure of the filter apparatus 10 which concerns on this invention is demonstrated. FIG. 1 is a circuit diagram showing a configuration of a filter device 10 according to the present invention.
A filter device 10 according to the present invention shown in FIG. 1 includes a low-pass filter circuit 11, a signal input switch 12, and a switch control unit 13.
An analog circuit 16 that outputs a signal to be filtered by the filter circuit of the filter device is connected to the input side of the filter device 10. The analog circuit 16 is a circuit composed of analog elements such as a booster circuit and an audio signal processing circuit. Inside the analog circuit 16, there is a power supply switch 17 for supplying and stopping power in accordance with the clock control signal φ 1 output from the switch control unit 13.

The low-pass filter circuit 11 includes a resistor 14 and a capacitor 15 and is a filter circuit for allowing only a specific low-frequency signal to pass through. The low-pass filter circuit 11 in the present embodiment will be described as a filter circuit that performs a filtering process that passes a signal in a low-frequency band.
The signal input switch 12 is a switching element such as a MOS transistor, for example, and is switched to either one of an electrically connected state and an electrically disconnected state by a clock control signal φ2 of the switch control unit 13, and a signal is sent to the low-pass filter circuit 11. Is input.

  The switch control unit 13 generates the clock control signal φ and the electrical connection state of the power supply switch 17 of the analog circuit 16 for supplying and stopping power to the analog circuit in accordance with the clock control signal φ. Electrical connection state of the power supply switch control clock control signal φ1 for controlling the switching operation to either one of the electrical disconnection state and the signal input switch 12 for inputting an analog signal to the low-pass filter circuit 11 And a circuit for generating a clock control signal φ2 for controlling a signal input switch for controlling an operation of switching to either one of an electrical disconnection state and an electrical disconnection state.

(Configuration of the switch control unit 13)
Next, the configuration of the switch control unit 13 will be described with reference to FIG. FIG. 2 is a circuit diagram showing a configuration of the switch control unit 13.
The switch control unit 13 shown in FIG. 2 includes a 3-bit counter 13a and AND circuits 13b and 13c.
The 3-bit counter 13a is a circuit that receives the clock control signal φ, counts 0 to 7, that is, (000) ₂ to (111) ₂ , and outputs the count value.

The AND circuit 13b inputs the count value output from the 3-bit counter 13a, outputs 1 (H level) when (111) ₂ is input, and outputs 0 (L level) otherwise. Circuit. The value output from the AND circuit 13b is the clock control signal φ1.
The AND circuit 13c receives the clock control signal φ and the value output from the AND circuit 13b, outputs the L level from the clock control signal φ, and outputs the H level when the H level is output from the AND circuit 13b. This is a circuit that outputs and outputs 0 (L level) at other times. The value output from the AND circuit 13c is the clock control signal φ2.

(Operation of the switch control unit 13)
Subsequently, the operation of the switch control unit 13 will be described with reference to FIGS. 3 and 4. FIG. 3 and FIG. 4 are time charts showing the movement of each signal accompanying the signal output from the switch control unit 13.
As shown in the time chart of FIG. 3, the switch control unit 13 outputs the clock control signal φ at a constant period.
First, in the operation phase of the power supply switch 17, the switch control unit 13 outputs the clock control signal φ1 at the H level only for one clock period, that is, one-eighth period of the eight clock periods of the clock control signal φ. The power supply switch 17 of the analog circuit 16 is brought into an electrical connection state. As a result, power is supplied to the analog circuit 16 and an analog signal is output from the analog circuit 16. This analog signal is shown as an output signal Va_out from the analog circuit 16 in FIG.

  The switch control unit 13 delays 1/2 of the 8 clocks of the clock control signal φ in the operation phase of the signal input switch 12 with a delay of 1/2 clock after the power supply switch 17 of the analog circuit 16 is in the electrically connected state. The clock input signal 12 is brought into an electrically connected state for the clock control signal φ2 for 2 clocks, that is, 1/16 time. As a result, an analog signal is input from the analog circuit 16 to the low-pass filter circuit 11.

The low-pass filter circuit 11 outputs a signal obtained by filtering the analog signal output from the analog circuit 16. A signal obtained by filtering the analog signal is shown as an output signal Vlpf_out from the low-pass filter circuit 11 in FIG.
The output signal Va_out from the analog circuit 16 starts to rise when the clock control signal φ1 becomes H level, and has finished rising before the clock control signal φ2 becomes H level. Further, the output signal Vlpf_out from the low-pass filter circuit 11 increases only in the phase in which the clock control signal φ2 becomes H level.

Next, in the idle phase of the signal input switch 12, the switch control unit 13 turns off the signal input switch 12 for 7 clocks out of 8 clocks of the clock control signal φ, that is, for 15/16 time. As a result, no analog signal is input from the analog circuit 16 to the low-pass filter circuit 11.
Further, in the pause phase of the power supply switch 17, the clock control signal φ 1 is output at the H level only during the period of 15/2 of the eight clocks of the clock control signal φ, that is, the period of 7/8. The power supply switch 17 is turned off. As a result, no power is supplied to the analog circuit 16 and no analog signal is output from the analog circuit 16.

  The pause phase is a phase in which the filtering process can be performed without the output signal Va_out from the analog circuit 16. Therefore, the power is supplied to the analog circuit 16 only in the operation phase, and the power supply switch 17 of the analog circuit 16 is not electrically connected, and is the same as when power is continuously supplied in the operation phase and the sleep phase. Output can be obtained.

  As described above, when the switch is controlled so that the electrical connection state of the signal input switch 12 and the power supply switch 17 is intermittent, the power consumed in the filtering process is continuously operated in the prior art. 1/8 of that. In addition, the time for which the signal input switch 12 for inputting an analog signal to the low-pass filter circuit 11 is in an electrically connected state is 1/16 that of the continuous operation in the prior art. For this reason, the frequency fc = 2π (1 / 16RC), and the resistance value R of the resistor 14 and the capacitance value C of the capacitor 15 can be reduced to 1/16 when continuously controlled.

  Thus, since the resistance value R of the resistor 14 and the capacitance value C of the capacitor 15 can be reduced, the volumes of the resistor 14 and the capacitor 15 are also reduced. Since the areas of the resistor 14 and the capacitor 15 are proportional to the values of the resistor 14 and the capacitor 15, if the resistance value R of the resistor 14 and the capacitance value C of the capacitor 15 are set to 1/16, the area can also be set to 1/16. it can. In particular, when a low-pass filter is formed inside an LSI (Large Scale Integration), the area of the LSI itself can be greatly reduced, and at the same time, the cost can be reduced.

  In general, the analog circuit 16 requires a certain time from when the power supply switch 17 is in an electrically connected state to when the output is stabilized after power is supplied. Therefore, the clock control signal φ1 is raised by 1/2 clock earlier than the clock control signal φ2. Further, when the clock control signal φ1 is raised, the clock control signal φ2 is raised and then the clock control signal φ1 is raised so that the signal input switch 12 is electrically disconnected, and then the analog control circuit 16 What is necessary is just to stop supply of electric power.

Further, as shown in the time chart of FIG. 4, when the time is made longer than that of the time chart of FIG. 3, the electric power is supplied only in the operation phase by the above operation, but the conventional filter shown in FIG. As described in the circuit, it can be seen that the same output can be obtained as when power is continuously supplied.
As described above, the analog circuit 16 connected to the previous stage of the filter device 10 can operate with less power than when continuously supplying power, but the filter device 10 is newly controlled. The same filtering process as that of the conventional filter circuit can be performed without providing the circuit.

In the filter device according to the present embodiment, the low-pass filter 11 has been described. However, the present invention is not limited to this. For example, a high-pass filter can be applied as long as it is a filter circuit that performs a filtering process on signals output from analog circuits. .
Further, if the time for setting the clock control signal φ2 to the H level is also shorter than the clock control signal φ1, that is, the time when there is no overlap, it can be set to any time according to the analog circuit and filter characteristics. .

(Summary)
In the operation phase, the switch control unit 13 causes the power supply switch 17 to be in an electrically connected state for one clock out of eight clocks of the clock control signal φ, that is, 1/8 of the clock control signal φ. Next, the switch control unit 13 causes the signal input switch 12 to be in an electrically connected state for a period of ½ clock, that is, 1/16 of the eight clocks of the clock control signal φ. By switching and controlling each switch so that the electrical connection state becomes intermittent, the power consumed in the filtering process is reduced to 1/8 compared to when continuously controlling, and the resistance 14 The resistance value R and the capacitance value C of the capacitor 15 can be reduced to 1/16.

  In particular, it is used as a filter device for electronic devices that are small and operate with low power.

DESCRIPTION OF SYMBOLS 10 Filter apparatus 11 Filter circuit 12 Signal input switch 13 Switch control part 14 Resistor 15 Capacitor 16 Analog circuit 17 Power supply switch

Claims (4)

A signal input switching element that inputs an electrical signal and switches between an electrical connection state and an electrical disconnection state;
A filter circuit that performs a filtering process on the electrical signal input via the signal input switching element;
Switch control means for switching and controlling the signal input switching element so that the electrical connection state is intermittent;
A filter device comprising:   The switch control means includes a power supply switch control signal for controlling an operation of switching a power supply switching element for supplying power to the circuit included in a circuit that outputs the electrical signal, and the power supply switching element includes: 2. The filter device according to claim 1, wherein a signal input switch control signal for controlling an operation of switching the signal input switching element to an electrical connection state when the electrical connection state is established.   The switch control means outputs a power supply switch control signal so as to place the power supply switching element in an electrically connected state, and then outputs a signal input switch control signal so as to place the signal input switching element in an electrically connected state. 3. The filter device according to claim 2, wherein the filter device outputs the filter device.   The filter device according to claim 1, wherein the filter circuit is a low-pass filter having a resistor and a capacitor.

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