JP6590397B2 - Power monitoring system - Google Patents

Description

  The present invention relates to an oscillation circuit and a power supply monitoring system.

  2. Description of the Related Art Oscillation circuits that output electrical signals having a predetermined frequency are widely used in various electrical devices today.

  An RC oscillation circuit including a resistor, a capacitor, and a transistor has been proposed (Patent Document 1). In this example, the RC oscillation circuit includes a voltage comparator to which a potential between a resistor and a capacitor to which a power supply voltage is applied and a divided potential of the power supply voltage are input. The transistor is connected in parallel with the capacitor and is controlled to be opened and closed by the output of the voltage comparator.

  Other RC oscillation circuits have also been proposed (Patent Document 2). In this example, the voltage generation circuit generates different first and second voltages. The selection circuit outputs one of the first and second voltages. The voltage from the selection circuit and the potential between the resistor and the capacitor to which the power supply voltage is applied are input to the voltage comparison circuit. The selection in the selection circuit is controlled by the output of the voltage comparison circuit, and determines the applied voltage to be applied to the resistor.

Japanese Utility Model Publication No. 60-30634 Japanese Utility Model Publication No. 60-32834

  However, the inventor has found the following problems. In the configurations described in Patent Documents 1 and 2, an inverter connected in two stages as a buffer circuit is provided as a buffer circuit in order to input a signal to the control terminal of the transistor. Therefore, in addition to the output signal of the oscillation circuit, electric power for driving the inverter is required, and the power consumption increases accordingly. In addition, the circuit area is increased by the buffer circuit, which is disadvantageous from the viewpoint of miniaturization.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a small-sized oscillation circuit with low power consumption.

  An oscillation circuit which is one embodiment of the present invention includes a Zener diode having a cathode connected to a power supply and an anode connected to a ground, a capacitor connected in parallel to the Zener diode, the Zener diode, and the capacitor. A resistor connected in series to the node, and an output terminal connected to a node between the Zener diode and the resistor, the Zener diode breaking down when the cathode becomes a first voltage. The cathode voltage becomes a Zener voltage, which is a second voltage smaller than the first voltage after breakdown.

  According to the present invention, it is possible to provide a small oscillation circuit with low power consumption.

1 is a circuit diagram schematically showing a configuration of an oscillation circuit according to a first exemplary embodiment; FIG. 3 is a circuit diagram showing a Zener diode characteristic evaluation circuit according to the first embodiment; It is a graph which shows an output voltage when changing the reverse voltage applied to a Zener diode. FIG. 3 is a circuit diagram showing an operation of the oscillation circuit according to the first exemplary embodiment. FIG. 3 is a circuit diagram showing an operation of the oscillation circuit according to the first exemplary embodiment. 3 is a graph showing an output voltage of the oscillation circuit according to the first embodiment and a current flowing through the Zener diode. 3 is a graph illustrating an example of a relationship between an output voltage and a power supply voltage of the oscillation circuit according to the first embodiment. FIG. 3 is a block diagram schematically showing a configuration of a power supply monitoring system according to a second exemplary embodiment. FIG. 6 is a block diagram schematically showing a configuration of a power supply monitoring system according to a third embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted as necessary.

Embodiment 1
The oscillation circuit 100 according to the first embodiment will be described. FIG. 1 is a circuit diagram schematically illustrating a configuration of the oscillation circuit 100 according to the first embodiment. The oscillation circuit 100 includes a Zener diode ZD, a resistor R, a capacitor C, and an output terminal TOUT.

  The cathode of the Zener diode ZD is connected to the power supply VCC via the resistor R. The anode of the Zener diode ZD is connected to the ground. The capacitor C is connected between the cathode and the anode of the Zener diode ZD, that is, connected in parallel with the Zener diode ZD. The output terminal TOUT is connected to a node N1 between the resistor R and the cathode of the Zener diode ZD. The power supply VCC is a DC power supply and outputs a constant power supply voltage VCC.

  The characteristics of the Zener diode ZD according to the present embodiment will be described. FIG. 2 is a circuit diagram illustrating the characteristic evaluation circuit 110 of the Zener diode ZD according to the first embodiment. The characteristic evaluation circuit 110 of the Zener diode ZD has a configuration in which the capacitor C is removed from the oscillation circuit 100 according to the present embodiment. Note that the resistor R10, the power supply V10, and the output terminal T10 of the Zener diode ZD characteristic evaluation circuit 110 correspond to the resistor R, the power supply VCC, and the output terminal TOUT of the oscillation circuit 100, respectively. The power supply V10 is a power supply that can change an output voltage. For example, the power supply V10 can output a sine wave signal as an output voltage.

  FIG. 3 is a graph showing the output voltage when the reverse voltage V10 applied to the Zener diode ZD is changed. In FIG. 3, the output voltage of the power source V10 is indicated as V10, and the voltage at the output terminal T10 is indicated as Vt. The Zener diode ZD is a Zener diode having hysteresis characteristics. In the Zener diode ZD, when the voltage V10 applied in the reverse direction exceeds the breakdown voltage Vb (section A1 to A2 in FIG. 3), a reverse current flows and the voltage of the cathode of the Zener diode drops to the Zener voltage Vz. (Section A3 in FIG. 3). At this time, even if the reverse applied voltage V10 further increases (section A4 in FIG. 3), the current flows so that the voltage drop at the Zener diode ZD does not change, so the voltage Vt at the output terminal T10 is the Zener voltage. Vb is maintained as it is.

  In the Zener diode ZD, even if the applied voltage V10 in the reverse direction becomes smaller than the breakdown voltage Vb, the above-described breakdown state is maintained and current continues to flow. When the reverse voltage V10 reaches the Zener voltage Vz (section A5 in FIG. 3), the Zener diode ZD exits the breakdown state and no current flows. That is, since the Zener voltage Vz is smaller than the breakdown voltage Vb, it can be understood that the Zener diode ZD exhibits a hysteresis behavior with respect to the applied reverse voltage V10.

  Next, the operation of the oscillation circuit 100 will be described. 4 and 5 are circuit diagrams illustrating the operation of the oscillation circuit 100 according to the first embodiment.

Step S1: When VOUT <Vb In this case, as shown in FIG. 4, since the Zener diode ZD is not in the breakdown state, no current flows through the Zener diode ZD. Therefore, the capacitor C is charged by the power supply voltage VCC. At this time, since the value of the current I flowing through the capacitor C is regulated by the resistor R, charging of the capacitor C has a predetermined time constant. Note that step S1 corresponds to the case where the power supply VCC starts applying voltage and the operation of the oscillation circuit 100 starts, and the state after step S3 described later.

Step S2: When VOUT> Vb When the output voltage VOUT becomes larger than the breakdown voltage Vb, as shown in FIG. 5, the Zener diode ZD enters the breakdown state. In this embodiment, the resistance value of the resistor R is the breakdown state. At that time, the resistance value of the Zener diode ZD is almost zero. Therefore, a reverse current I flows through the Zener diode ZD, and the charge charged in the capacitor C is also discharged through the Zener diode ZD. Therefore, the output voltage VOUT drops rapidly.

Step S3: When VOUT = Vr When the output voltage VOUT drops to the Zener voltage Vz, the Zener diode ZD is released from the breakdown state, so that no current flows through the Zener diode ZD. Therefore, as shown in FIG. 4, the charging of the capacitor C is resumed.

That is, in the oscillation circuit 100, it can be understood that the cycle from step S1 to step S3 is repeated. FIG. 6 is a graph showing the output voltage VOUT of the oscillation circuit 100 according to the first embodiment and the current flowing through the Zener diode ZD. As shown in FIG. 6, the output voltage VOUT rises in a slope shape from the Zener voltage Vz to the breakdown voltage Vb, and has a sawtooth or substantially sawtooth waveform that drops sharply to the Zener voltage Vz when the breakdown voltage Vb is reached. . The current I _ZD flowing through the Zener diode ZD becomes maximum at the start of the breakdown state, decreases in a slope shape toward the end of the breakdown, and becomes zero when not in the breakdown state.

式（１）のτ（τ＝ＣＲ）が時定数である。式（１）に示すように、時定数τ、すなわち容量Ｃの充電速度は、抵抗Ｒの抵抗値と容量Ｃの容量値とにより決定される。 Here, the oscillation frequency of the oscillation circuit 100 will be examined. A charging voltage of a capacitor in a series circuit of a resistor and a capacitor like the oscillation circuit 100 is generally expressed by the following formula (1).

In Equation (1), τ (τ = CR) is a time constant. As shown in Expression (1), the time constant τ, that is, the charging speed of the capacitor C is determined by the resistance value of the resistor R and the capacitance value of the capacitor C.

In the oscillation circuit 100, the time T during which the output voltage VOUT rises from the Zener voltage Vz of the Zener diode ZD to the breakdown voltage Vb is expressed by the following equation (2) using the time constant τ described above.

In step S2, the time for the output voltage VOUT to drop from the breakdown voltage Vb of the Zener diode ZD to the Zener voltage Vz is instantaneous, and is regarded as 0 here. Therefore, the time T shown in Expression (2) 2 is the oscillation cycle of the oscillation circuit 100. In this case, the oscillation period f of the oscillation circuit 100 is represented by the following formula (3).

  As described above, according to this configuration, it is possible to provide an oscillation circuit that can be simply configured using three components, ie, a Zener diode having hysteresis characteristics, a resistor, and a capacitor. This is advantageous from the viewpoint of reducing the size and weight of the oscillation circuit. In addition, since the number of parts is small, manufacturing at low cost can be realized. Furthermore, since the number of parts is small, a failure rate (Failure In Time: FIT) can be reduced, which can contribute to a reduction in parts replacement time.

  According to this configuration, as shown in the equation (1), increasing the value of the resistor R increases the time constant for charging the capacitor C. Therefore, as shown in Expression (3), the oscillation frequency of the oscillation circuit 100 can be reduced. Therefore, the oscillation frequency can be easily controlled by selecting the value of the resistor R. The value of the resistor R may be determined in advance, or may be configured to be dynamically controllable using a variable resistor.

  According to this configuration, as shown in Expression (1), the time constant for charging the capacitor C is increased by increasing the value of the capacitor C. Therefore, as shown in Expression (3), the oscillation frequency can be reduced. Therefore, the oscillation frequency can be easily controlled by selecting the value of the capacitor C. The value of the capacity C may be determined in advance, or may be configured to be dynamically controllable using a variable capacity.

  Further, as shown in Expression (3), the oscillation frequency can be changed by changing the value of the power supply voltage VCC. FIG. 7 is a graph showing an example of the relationship between the output voltage VOUT and the power supply voltage VCC of the oscillation circuit 100 according to the first embodiment. Here, RSB16V (ROHM Co., Ltd.) was used as the Zener diode ZD. In this case, the breakdown voltage Vb of the Zener diode ZD was 18.17V, and the Zener voltage Vz was 17.97V. The resistance value of the resistor R was 10 kΩ, and the value of the capacitor C was 0.1 μF (50 V). As shown in FIG. 7, the oscillation frequency can be increased by increasing the value of the power supply voltage VCC. In other words, the oscillation frequency can be easily controlled by changing the power supply voltage VCC.

  As described above, even if the values of the resistor R, the capacitor C, and the power supply voltage VCC are changed, the amplitude of the output voltage VOUT is maintained at Vb−Vr. Therefore, only the oscillation frequency of the output voltage VOUT can be changed. it can.

Embodiment 2
A power supply monitoring system 200 according to the second embodiment will be described. FIG. 8 is a block diagram schematically illustrating a configuration of the power supply monitoring system 200 according to the second embodiment. The power supply monitoring system 200 is configured as a system that monitors the voltage of the power supply line inside the electrical system 201.

  The electrical system 201 includes a 24V battery 1, switches SW1 to SW3, and loads 11 to 13. The output of the 24V battery 1 is connected to one end of the switches SW1 to SW3 through the power line W1.

  A load 11 is connected between the other end of the switch SW1 and the ground, and power is supplied through the power supply line W1. A load 12 is connected between the other end of the switch SW2 and the ground, and power is supplied through the power line W2. A load 13 is connected between the other end of the switch SW3 and the ground, and power is supplied through the power supply line W3.

  For example, when the electrical system 201 is an in-vehicle system, the power line W1 can be an ACC power line and the load 11 can be an ACC power socket. Further, the power line W2 can be a headlamp power source, and the load 12 can be a headlamp. The power supply line W3 can be a tail lamp power source, and the load 13 can be a tail lamp.

  The power supply monitoring system 200 includes oscillation circuits 101 to 104, a control unit 105, and capacitors C1 to C4. The oscillation circuit 100 according to the first embodiment is used for the oscillation circuits 101 to 104.

  The oscillation circuit 101 receives power supply from the power supply line W1, and outputs the output voltage VOUT1 to the control unit 105 via the capacitor C1. Therefore, the output voltage VOUT1 has an oscillation frequency corresponding to the voltage of the power supply line W1.

  The oscillation circuit 102 receives power supply from the power supply line W2, and outputs the output voltage VOUT2 to the control unit 105 via the capacitor C2. Therefore, the output voltage VOUT2 has an oscillation frequency corresponding to the voltage of the power supply line W2.

  The oscillation circuit 103 receives power supply from the power supply line W3 and outputs the output voltage VOUT3 to the control unit 105 through the capacitor C3. Therefore, the output voltage VOUT3 has an oscillation frequency corresponding to the voltage of the power supply line W3.

  The oscillation circuit 104 receives power supply from the power supply line W4 and outputs the output voltage VOUT4 to the control unit 105 through the capacitor C4. Therefore, the output voltage VOUT4 has an oscillation frequency corresponding to the voltage of the power supply line W4.

  Therefore, the control unit 105 can monitor the voltages of the power supply lines W1 to W4 by measuring the frequencies of the output voltages VOUT1 to VOUT4.

  Therefore, according to this configuration, it is possible to realize a power supply monitoring system that monitors the power supply voltage using the oscillation circuit according to the above-described embodiment as a voltage sensor.

Embodiment 3
A power supply monitoring system 300 according to the third embodiment will be described. FIG. 9 is a block diagram schematically illustrating a configuration of the power supply monitoring system 300 according to the third embodiment. The power supply monitoring system 300 is configured as a system that monitors the power supply voltage VCC. The power supply monitoring system 300 includes an oscillation circuit 100, a field effect transistor (FET) 31, a resistor R2, and a speaker 32.

  In the present embodiment, RSB16V (ROHM Co., Ltd.) is used as the Zener diode ZD. The resistance value of the resistor R was 10 kΩ, and the value of the capacitor C was 0.1 μF (50 V). For the FET 31, RSU002P03, which is a general-purpose P-type FET, was used.

  The source of the FET 31 is connected to the power supply VCC, and the drain is connected to the ground via the resistor R2 and the speaker 32.

  In the power supply monitoring system 300, 12V is supplied as the power supply voltage VCC. When the power supply voltage VCC is 12 V, which is a normal value, the oscillation circuit 100 does not oscillate. However, the oscillation circuit 100 oscillates when the power supply voltage VCC rises to 20 V or more due to an abnormality in the battery wiring or the like. When the difference between the output voltage VOUT of the oscillation circuit 100 and the power supply voltage VCC exceeds 2.5 V, the FET 31 is turned on, and sound corresponding to the oscillation frequency is output from the speaker 32.

  As described above, according to the present configuration, it is possible to realize the power supply monitoring system 300 that monitors the power supply voltage and detects the above and outputs an alarm sound when the power supply voltage rises or exceeds.

Other Embodiments The present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the spirit of the present invention. For example, in the above-described embodiment, any one of the capacitance value, the resistance value, and the power supply voltage may be changed, or two of the capacitance value, the resistance value, and the power supply voltage may be changed. Further, all of the capacitance value, the resistance value, and the power supply voltage may be changed.

  In the oscillation circuit according to the above-described embodiment, the resistor R is connected to the high potential side and the Zener diode ZD and the capacitor C are connected to the low potential side. However, this is merely an example. That is, the resistor R may be connected to the low potential side, and the Zener diode ZD and the capacitor C may be connected to the high potential side. In other words, the connection positions of the resistor R, the Zener diode ZD, and the capacitor C may be interchanged. In this case, unlike the waveform of FIG. 6, the waveform of the output voltage VOUT is a waveform that rises steeply and falls gently.

1 24V battery 11-13 Load 31 FET
32 Speaker 100, 101-104 Oscillator circuit 105 Control unit 110 Characteristic evaluation circuit 200, 300 Power supply monitoring system 201 Electrical system C Capacitance C1-C4 Capacitor N1 Nodes R, R2, R10 Resistors SW1-SW3 Switch T10 Output terminal TOUT Output terminal Vb Breakdown voltage VCC Power supply VOUT, VOUT1 to VOUT4 Output voltage Vz Zener voltage W1 to W4 Power supply line ZD Zener diode

Claims (5)

A Zener diode whose cathode is connected to the power supply and whose anode is connected to the ground;
A capacitor connected in parallel to the Zener diode;
A resistor connected in series with the zener diode and the capacitor;
An output terminal connected to a node between the Zener diode and the resistor;
The switch that closes when the voltage of the output terminal and the voltage of the power supply are input, and the difference between the voltage of the output terminal and the voltage of the power supply is greater than a predetermined value;
An alarm device connected between the switch and the ground and generating an alarm when the switch is closed,
The zener diode breaks down when the cathode is at a first voltage;
The cathode voltage becomes a Zener voltage, which is a second voltage smaller than the first voltage after breakdown,
Power monitoring system. The resistor is inserted between an end of the Zener diode and the capacitor on the power supply side and the power supply, or inserted between an end of the Zener diode and the capacitor on the ground side and the ground. And
The output terminal is connected to an end of the resistor on the Zener diode side;
The power supply monitoring system according to claim 1. The resistor is a variable resistor.
The power supply monitoring system according to claim 1 or 2. The capacity is a variable capacity,
The power supply monitoring system according to any one of claims 1 to 3. The power source is configured to be capable of adjusting a voltage to be output.
The power supply monitoring system according to any one of claims 1 to 4.

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