JP6889082B2 - Flame sensor drive circuit - Google Patents

Description

The present invention relates to a drive circuit of a flame sensor that receives and discharges ultraviolet rays generated by the generation of a flame.

Conventionally, as a flame sensor for detecting the presence or absence of a flame, an ultraviolet sensor (UV sensor) that receives and discharges ultraviolet rays generated by the generation of a flame has been used.

This UV sensor uses a shutter for self-checking of the sensor. When the shutter is closed and the flame is invisible, the UV sensor is checked for self-discharge because no discharge is generated.

This UV sensor is used for flame monitoring of plants and the like, and alternately applies a high voltage (voltage that enables discharge) and a low voltage (voltage that disables discharge) between the anode electrode and the cathode electrode. A drive circuit is provided (see, for example, FIGS. 1 and 2 of Patent Document 1).

FIG. 4 shows a drive circuit (conventional drive circuit) of a UV sensor configured based on the circuit shown in Patent Document 1. In this drive circuit 200, a discharge occurs between the voltage application circuit 2 that selectively applies DC370V and DC55V to the anode electrode 1a of the UV sensor 1 and the anode electrode 1a and the cathode electrode 1b of the UV sensor 1. It is provided with a discharge detection circuit 3 for detecting the above, a monostable multivibrator 4, an unstable multivibrator 5, an RS flip-flop circuit 6, and an output circuit 7.

In the drive circuit 200, the voltage application circuit 2 includes resistors R11 to R16, capacitors C11, and transistors Q11 and Q12. The resistors R11 (30 kΩ) and R12 (47 kΩ) are connected in series between the input line L11 of DC370V and the anode electrode 1a of the UV sensor 1.

The resistor R13 (12 kΩ) is connected between the connection line L12 between the resistor R12 and the anode electrode 1a of the UV sensor 1 and the collector of the transistor Q11. The emitter of the transistor Q11 is connected to the collector of the transistor Q12, and the emitter of the transistor Q12 is connected to the ground line GND.

The resistor R14 (150 kΩ) is connected between the input line L11 of DC370V and the base of the transistor Q11, and the connection line L13 between the resistor R14 and the base of the transistor Q11 is a capacitor between the ground line GND. C11 (390pF) and resistor R15 (150kΩ) are connected in parallel. Further, a resistor R16 (520Ω) is connected to the base of the transistor Q12 with the ground line GND.

In the drive circuit 200, the unstable multivibrator 5 repeatedly generates a pulse signal, and outputs this pulse signal as an oscillation output from the first output terminal 5-1 and the second output terminal 5-2. The oscillation output output from the first output terminal 5-1 is given to the connection line L14 between the base of the transistor Q12 and the resistor R16. As a result, the transistor Q12 is turned ON / OFF.

When the transistor Q12 is turned off, DC370V from the input line L11 is applied to the anode electrode 1a of the UV sensor 1 through the resistors R11 and R12. When the transistor Q12 is turned on, a current flows through the paths of the resistors R11, R12, R13, and the transistors Q11 and Q12, the voltage at the connection point between the resistor R12 and the resistor R13 drops, and the lowered voltage (DC55V) becomes It is applied to the anode electrode 1a of the UV sensor 1.

As a result, when there is no flame and the UV sensor 1 does not discharge, DC370V and DC55V are alternately applied to the anode electrode 1a of the UV sensor 1 at regular intervals (see FIG. 5B). That is, the voltage application mode of the voltage application circuit 2 to the UV sensor 1 is a first mode in which a first voltage (high voltage (DC370V)) that enables discharge is applied, and a second mode in which discharge is disabled. The second mode in which the voltage (low voltage (DC55V)) is applied is alternately switched at regular intervals.

In this case, the period T1 in which DC370V is applied to the anode electrode 1a of the UV sensor 1 is defined as the discharge monitoring period, and the period T2 in which DC55V is applied is defined as the discharge monitoring stop period (see FIG. 5A). .. The time width between the discharge monitoring period T1 and the discharge monitoring stop period T2 can be adjusted by changing the duty ratio of the pulse signal output from the unstable multivibrator 5 by adjusting the sensitivity.

During discharge monitoring by alternately switching between the discharge monitoring period T1 and the discharge monitoring stop period T2, if a discharge occurs in the UV sensor 1 during the discharge monitoring period T1, the discharge detection circuit 3 detects the discharge generated in the UV sensor 1. Detect (t1, t2, t3, t4 points shown in FIG. 6C).

The monostable multivibrator 4 generates a one-shot pulse signal when the discharge detection circuit 3 detects that a discharge has occurred in the UV sensor 1 (points t1, t2, t3, t4 shown in FIG. 6D). ). The one-shot signal generated by the monostable multivibrator 4 is given to the RS flip-flop circuit 6. Further, the one-shot pulse signal informs the output circuit 7 that a flame has been detected.

The RS flip-flop circuit 6 is set by a one-shot signal from the monostable multivibrator 4 and turns on the transistor Q12. As a result, the voltage applied to the anode electrode 1a of the UV sensor 1 is switched from DC370V to DC55V (points t1, t2, t3, t4 shown in FIG. 6B).

In this way, when the discharge is detected in the discharge monitoring period T1, the voltage applied to the anode electrode 1a of the UV sensor 1 drops to DC55V, and the discharge stops. After that, the RS flip-flop circuit 6 is reset by the oscillation output from the second output terminal 5-2 of the unstable multivibrator 5, that is, by the pulse signal sent next. As a result, the next discharge monitoring is started.

U.S. Pat. No. 4,407,038B

The UV sensor is used for flame monitoring of plants and the like, and its usage environment becomes high temperature because it receives direct sunlight and heat from a combustion part. On the other hand, since a drip-proof / explosion-proof structure is required as the structure of the product, the internal substrate is in a sealed state and cannot be cooled by ventilation. Therefore, the internal temperature of the product rises.

In the drive circuit 200 shown in FIG. 4, the voltage applied to the UV sensor 1 is reduced to DC55V after discharge detection or when discharge monitoring is not performed. However, when the voltage applied to the UV sensor 1 is reduced to DC55V, the power consumption increases and the internal temperature of the product further rises. Due to this increase in the internal temperature, there is a high risk that the self-checking shutter will not operate or a component failure will occur.

FIG. 7 shows the path of the current flowing through the voltage application circuit 2 when the discharge is being monitored and no discharge is generated. In this case, since the transistor Q12 is turned off, a current flows only in the paths of the resistors R14 and R15, and the current at this time is 1.2 mA. As a result, the voltage application circuit 2 consumes 370 V × 1.2 mA = 0.44 W of electric power.

FIG. 8 shows the path of the current flowing through the voltage application circuit 2 after the discharge is detected or when the discharge is not monitored. In this case, since the transistor Q12 is turned on, a current of 4.1 mA flows through the paths of the resistors R11, R12, R13 and the transistors Q11 and Q12. Further, a current of 2.5 mA flows through the base of the transistor Q11. As a result, the voltage application circuit 2 consumes 370 V × (4.1 mA + 2.5 mA) = 2.44 W of electric power.

The present invention has been made to solve such a problem, and an object of the present invention is to stabilize the drive of the shutter by reducing the power consumption and suppressing the rise in the internal temperature of the product. It is an object of the present invention to provide a drive circuit of a flame sensor which can be implemented and can reduce the risk of component failure.

In order to achieve such an object, the present invention presents a flame sensor (1) configured to receive and discharge an ultraviolet ray generated by the generation of a flame, and a voltage to an anode electrode (1a) of the flame sensor. As the application mode, a voltage application circuit (2A) including a first mode for applying a first voltage that enables discharge and a second mode for applying a second voltage that disables discharge, and a voltage. The first mode switching circuit (5) configured to alternately switch the voltage application mode to the anode electrode of the flame sensor in the application circuit between the first mode and the second mode, and the flame sensor are discharged. When the discharge detection circuit (3) configured to detect the occurrence and the discharge detection circuit detect that a discharge has occurred in the flame sensor, the voltage of the voltage to the anode electrode of the flame sensor in the voltage application circuit The drive circuit of the flame sensor including the second mode switching circuit (4, 6) configured to switch the application mode from the first mode to the second mode, and the voltage application circuit is the first. The first transistor (Q1) in which the collector and the emitter are connected between the voltage input line (L1) of the above and the anode electrode of the flame sensor with the emitter as the anode electrode side, and the first voltage input line. A second transistor (Q2) in which the collector and the emitter are connected between the connection line (L2) with the base of the first transistor and the ground line (GND) with the emitter as the ground line side is provided. The mode switching circuit 1 and the second mode switching circuit are characterized in that the potential of the emitter of the first transistor is switched from the first voltage to the second voltage by turning on the second transistor.

In the present invention, the first mode switching circuit and the second mode switching circuit have a first voltage (for example,) that enables discharge of the potential of the emitter of the first transistor by turning on the second transistor. , DC370V) to a second voltage (eg, DC55V) that disables discharge.

In the present invention, when the second transistor is turned off, the first voltage from the input line of the first voltage is the anode of the flame sensor through the PN connection between the base and the emitter of the first transistor. It is applied to the electrodes. In this case, power is not consumed in the voltage application circuit because the current does not flow only by applying the voltage.

In the present invention, when the second transistor is turned on, a current flows between the collector and emitter of the second transistor, and the voltage applied to the base of the first transistor decreases. This reduced voltage is applied as a second voltage to the anode electrode of the flame sensor through the PN junction between the base and emitter of the first transistor. In this case, the current flowing between the collector and emitter of the second transistor is small (for example, 0.2 mA), and the power consumption in the voltage application circuit is small.

In the above description, as an example, the components on the drawing corresponding to the components of the invention are indicated by reference numerals in parentheses.

As described above, according to the present invention, the potential of the emitter of the first transistor is discharged by connecting the emitter of the first transistor to the anode electrode side of the flame sensor and turning on the second transistor. Since the first voltage that enables the discharge is switched to the second voltage that disables the discharge, the power consumption can be reduced and the rise in the internal temperature of the product can be suppressed. As a result, the shutter can be driven stably, and the risk of component failure can be reduced. In addition, energy saving can be achieved because power consumption is reduced.

FIG. 1 is a block diagram showing a main part of a drive circuit of a flame sensor (UV sensor) according to an embodiment of the present invention. FIG. 2 is a diagram showing a voltage application path to the anode electrode of the UV sensor when discharge is being monitored and no discharge is generated in the drive circuit shown in FIG. FIG. 3 is a diagram showing a path of a current flowing through the voltage application circuit after discharge detection or when discharge monitoring is not performed in the drive circuit shown in FIG. FIG. 4 is a block diagram showing a main part of a conventional drive circuit. FIG. 5 is a time chart showing the discharge monitoring period T1 and the discharge monitoring stop period T2. FIG. 6 is a time chart showing an operation when a discharge occurs in the discharge monitoring period T1. FIG. 7 is a diagram showing a path of a current flowing through a voltage application circuit when discharge is being monitored and no discharge is generated in the drive circuit shown in FIG. FIG. 8 is a diagram showing a path of a current flowing through the voltage application circuit after discharge detection or when discharge monitoring is not performed in the drive circuit shown in FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a main part of a drive circuit of a flame sensor according to an embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 4 indicate the same or equivalent components as those described with reference to FIG. 4, and the description thereof will be omitted.

In the drive circuit 100 of the present embodiment, the configuration other than the voltage application circuit 2 is the same as that of the drive circuit 200 shown in FIG. That is, the discharge detection circuit 3, the monostable multivibrator 4, the unstable multivibrator 5, the RS flip-flop circuit 6 and the output circuit 7 have the same configuration as the drive circuit 200 shown in FIG.

Hereinafter, in order to distinguish from the voltage application circuit 2 in the drive circuit 200 shown in FIG. 4, the voltage application circuit 2 in the drive circuit 100 of the present embodiment is set to 2A, and the voltage in the conventional drive circuit 200 shown in FIG. 4 is defined. Let the application circuit 2 be 2B.

In the drive circuit 100 of the present embodiment, the voltage application circuit 2 includes resistors R1 to R8 and transistors Q1 and Q2. The resistors R1 (24 kΩ) and R2 (27 kΩ) are connected in series between the input line L1 of DC370V and the collector of the transistor Q1.

The resistor R3 (27 kΩ) is connected between the emitter of the transistor Q1 and the anode electrode 1a of the UV sensor 1, and the resistors R4 (510 kΩ), R5 (510 kΩ) and R6 (510 kΩ) are the input line L1 of DC370 V and the transistor. It is connected in series with the base of Q1.

The resistor R7 (270 kΩ) is connected between the connection line L2 between the resistor R6 and the base of the transistor Q1 and the collector of the transistor Q2, and the emitter of the transistor Q2 is connected to the ground line GND. The resistor R8 (620Ω) is connected between the base of the transistor Q2 and the ground line GND.

In this drive circuit 100, the oscillation output (repeatedly generated pulse signal) output from the first output terminal 5-1 of the unstable multivibrator 5 is given to the connection line L3 between the base of the transistor Q2 and the resistor R8. Be done. As a result, the transistor Q2 is turned ON / OFF. The unstable multivibrator 5 corresponds to the first mode switching circuit in the present invention.

When the transistor Q2 is turned off, DC370V from the input line L1 is sent to the anode electrode 1a of the UV sensor 1 through the paths of the resistors R4, R5, R6, and R3 through the PN connection between the base and the emitter of the transistor Q1. It is applied.

When the transistor Q2 is turned on, a current flows through the paths of the resistors R4, R5, R6, R7 and the transistor Q2, the voltage at the connection point between the resistor R6 and the resistor R7 drops, and the lowered voltage (DC55V) becomes It is applied to the anode electrode 1a of the UV sensor 1 through the PN connection between the base and the emitter of the transistor Q1.

As a result, when there is no flame and the UV sensor 1 does not discharge, DC370V and DC55V are alternately applied to the anode electrode 1a of the UV sensor 1 at regular intervals (see FIG. 5B). That is, the voltage application mode of the voltage application circuit 2 to the UV sensor 1 is a first mode in which a first voltage (high voltage (DC370V)) that enables discharge is applied, and a second mode in which discharge is disabled. The second mode in which the voltage (low voltage (DC55V)) is applied is alternately switched at regular intervals.

In this case, the period T1 in which DC370V is applied to the anode electrode 1a of the UV sensor 1 is defined as the discharge monitoring period, and the period T2 in which DC55V is applied is defined as the discharge monitoring stop period (see FIG. 5A). .. The time width between the discharge monitoring period T1 and the discharge monitoring stop period T2 can be adjusted by changing the duty ratio of the pulse signal output from the unstable multivibrator 5 by adjusting the sensitivity.

During discharge monitoring by alternately switching between the discharge monitoring period T1 and the discharge monitoring stop period T2, if a discharge occurs in the UV sensor 1 during the discharge monitoring period T1, the discharge detection circuit 3 detects the discharge generated in the UV sensor 1. Detect (t1, t2, t3, t4 points shown in FIG. 6C).

The monostable multivibrator 4 generates a one-shot pulse signal when the discharge detection circuit 3 detects that a discharge has occurred in the UV sensor 1 (points t1, t2, t3, t4 shown in FIG. 6D). ). The one-shot signal generated by the monostable multivibrator 4 is given to the RS flip-flop circuit 6. Further, the one-shot pulse signal informs the output circuit 7 that a flame has been detected.

The RS flip-flop circuit 6 is set by a one-shot signal from the monostable multivibrator 4 and turns on the transistor Q2. As a result, the voltage applied to the anode electrode 1a of the UV sensor 1 is switched from DC370V to DC55V (points t1, t2, t3, t4 shown in FIG. 6B). The combination of the monostable multivibrator 4 and the RS flip-flop circuit 6 corresponds to the second mode switching circuit of the present invention.

In this way, when the discharge is detected in the discharge monitoring period T1, the voltage applied to the anode electrode 1a of the UV sensor 1 drops to DC55V, and the discharge stops. After that, the RS flip-flop circuit 6 is reset by the oscillation output from the second output terminal 5-2 of the unstable multivibrator 5, that is, by the pulse signal sent next. As a result, the next discharge monitoring is started.

When the UV sensor 1 is discharged, a current flows through the base of the transistor Q1, the transistor Q1 is turned on, a current flows through the paths of the resistors R1, R2, and R3, and the discharge is maintained.

FIG. 2 shows a voltage application path to the anode electrode 1a of the UV sensor 1 when discharge is being monitored and no discharge is generated. In this case, since the transistor Q2 is turned off, DC370V from the input line L1 passes through the PN connection between the base and the emitter of the transistor Q1 through the paths of the resistors R4, R5, R6, and R3, and the anode of the UV sensor 1. It is applied to the electrode 1a. In FIG. 2, the PN connection between the base and the emitter of the transistor Q1 is shown by a dotted line as the diode D1. In this case, power is not consumed in the voltage application circuit 2A because the current does not flow only by applying the voltage.

FIG. 3 shows the path of the current flowing through the voltage application circuit 2A after the discharge is detected or when the discharge is not monitored. In this case, since the transistor Q2 is turned on, a current of 0.2 mA flows through the paths of the resistors R4, R5, R6, R7 and the transistor Q2, and a voltage of DC55V is generated at the connection point between the resistors R6 and R7. The voltage of DC55V is applied to the anode electrode 1a of the UV sensor 1 through the PN connection between the base and the emitter of the transistor Q1. As a result, the voltage application circuit 2A consumes 370V × 0.2mA = 0.047W of electric power.

That is, in the drive circuit 100 of the present embodiment, by using the transistor Q1 in the voltage application circuit 2A as an emitter follower circuit, only 0.2 mA flows in the voltage application circuit 2A after discharge detection or when discharge monitoring is not performed. In this way, power saving is planned.

Although the circuit configuration of this drive circuit 100 is not shown in FIG. 1, in addition to the voltage application circuit 2A, a circuit that promptly lowers the voltage when the power is cut off to prevent electric shock (electric shock prevention circuit). Is provided, and a current of 0.164 mA is passed through this electric shock prevention circuit. In the conventional drive circuit 200 shown in FIG. 4, the resistors R14 and R15 act as electric shock prevention circuits.

Here, let us compare the power consumption of the voltage application circuit 2B in the conventional drive circuit 200 and the voltage application circuit 2A in the drive circuit 100 of the present embodiment, including the current for preventing electric shock.

When no discharge was generated during discharge monitoring, the voltage application circuit 2B in the conventional drive circuit 200 consumed 370 V × 1.2 mA = 0.44 W of electric power (see FIG. 7). On the other hand, in the voltage application circuit 2A in the drive circuit 100 of the present embodiment, no current flows in the voltage application circuit 2A (see FIG. 2), but the current for preventing electric shock is also included. 370V x 0.164mA = 0.061W, and the power consumption is reduced to about 1/7.

After the discharge was detected or when the discharge was not monitored, the voltage application circuit 2B in the conventional drive circuit 200 consumed 370 V × (4.1 mA + 2.5 mA) = 2.44 W (see FIG. 8). On the other hand, in the voltage application circuit 2A in the drive circuit 100 of the present embodiment, when the current for preventing electric shock is included, 370V × (0.2mA + 0.164mA) = 0.135W (FIG. 3). (See), power consumption is reduced to about 1/18.

In this way, the drive circuit 100 of the present embodiment can reduce power consumption and suppress an increase in the internal temperature of the product as compared with the conventional drive circuit 200. As a result, the shutter can be driven stably, and the risk of component failure can be reduced. In addition, energy saving can be achieved because power consumption is reduced.

In the voltage application circuit 2A shown in FIG. 1, two resistors R1 and R2 are connected between the input line L1 of DC370V and the collector of the transistor Q1, but the two resistors are not necessarily connected. It may be used as one resistor, or the like. The same applies to the resistors R4, R5 and R6 in the connection line L2. Further, the resistor R3 may be omitted.

In addition, the voltage for driving the shutter may be changed from AC to DC. For example, it receives signals of AC85V to AC121V and outputs DC24V to the shutter. As a result, a constant power can be supplied to the shutter without depending on the AC voltage, and the state of low power consumption can be continued. Further, by setting the DC to 24V, the power consumption of the shutter can be reduced from 3W to 2W, and the rise in the internal temperature of the product can be suppressed.

[Extension of Embodiment]
Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above embodiments. Various changes that can be understood by those skilled in the art can be made to the structure and details of the present invention within the scope of the technical idea of the present invention.

1 ... UV sensor (flame sensor), 1a ... anode electrode, 1b ... cathode electrode, 2 (2A) ... voltage application circuit, 3 ... discharge detection circuit, 4 ... monostable multivibrator, 5 ... unstable multivibrator, 6 ... RS flip-flop circuit, 7 ... output circuit, Q1, Q2 ... transistor, R1 to R8 ... resistor, L1 ... input line, L2, L3 ... connection line, GND ... ground line, 100 ... drive circuit.

Claims (3)

A flame sensor configured to receive and discharge ultraviolet rays generated by the generation of a flame,
As the voltage application mode to the anode electrode of the flame sensor, a first mode in which the first voltage that enables the discharge is applied and a second mode in which the second voltage that disables the discharge is applied are applied. A voltage application circuit equipped with
A first mode switching circuit configured to alternately switch a voltage application mode to the anode electrode of the flame sensor in the voltage application circuit between the first mode and the second mode.
A discharge detection circuit configured to detect that the discharge has occurred in the flame sensor, and
When it is detected by the discharge detection circuit that the discharge has occurred in the flame sensor, the mode of applying the voltage to the anode electrode of the flame sensor in the voltage application circuit is changed from the first mode to the second mode. It is a drive circuit of a flame sensor including a second mode switching circuit configured to switch to.
The voltage application circuit
A first transistor in which a collector and an emitter are connected between the input line of the first voltage and the anode electrode of the flame sensor with the emitter as the anode electrode side.
A second transistor is provided in which the collector and the emitter are connected between the connection line between the input line of the first voltage and the base of the first transistor and the ground line with the emitter as the ground line side. ,
The first mode switching circuit and the second mode switching circuit are
A drive circuit for a flame sensor, characterized in that the potential of the emitter of the first transistor is switched from the first voltage to the second voltage by turning on the second transistor. In the drive circuit of the flame sensor according to claim 1,
The first mode switching circuit is
It consists of an unstable multivibrator that repeatedly generates a pulse signal.
The second mode switching circuit is
A monostable multivibrator that generates a one-shot pulse when the flame sensor detects that the discharge has occurred by the discharge detection circuit.
A flame sensor characterized in that it is composed of an RS flip-flop circuit that is set by a one-shot pulse generated by the monostable multivibrator and reset by a pulse signal repeatedly generated by the unstable multivibrator. Drive circuit. In the drive circuit of the flame sensor according to claim 1 or 2.
First and second resistors are connected in series between the input line of the first voltage and the collector of the first transistor.
A third resistor is connected between the emitter of the first transistor and the anode electrode of the flame sensor.
Fourth, fifth and sixth resistors are connected in series between the first voltage input line and the base of the first transistor.
A seventh resistor is connected between the connection line between the sixth resistor and the base of the first transistor and the collector of the second transistor.
A drive circuit for a flame sensor, characterized in that an eighth resistor is connected between the base of the second transistor and the ground line.

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