JPH08147051A - Power source controller - Google Patents

Abstract

PURPOSE: To surely monitor abnormality with simple circuit constitution by interposing a 1st capacitor between the power source side of a 1st transistor(TR) and a control terminal and a 2nd capacitor between the control terminal of the 1st TR and a 2nd TR, and turning OFF the 2nd TR and discharging the 2nd capacitor. CONSTITUTION: If the operation of a microcomputer 19 becomes abnormal and a port 19d is held at a low level while ports 19e-19g, etc., are still at a high level, the TR Q2 does not turn ON even the discharging of the capacitor C1 is completed, so the TR Q1 turns OFF, so that DC power Vcc is applied to none of the coils of relays 22-24. When the port 19d of the microcomputer 19 is held at the high level, on the other hand, the potential at the connection point between the capacitor C2 and a resistor R2 rises, the base-emitter voltage of the TR Q1 falls, and the TR Q1 turns OFF, so that the DC power Vcc is applied to none of the coils of the relays 22-24.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply control device for detecting an abnormality in a microcomputer and shutting off power supply to a load.

[0002]

2. Description of the Related Art In various equipments which control by using a microcomputer, it is necessary to shut off the power supply to a load for safety when the microcomputer is abnormal. For example, in the case of a hot water supply device, when the microcomputer is abnormal, it is dangerous unless the gas passage is forcibly closed by cutting off the power supply to the coil of Reele that controls the solenoid of the solenoid valve that opens and closes the gas passage.

Therefore, conventionally, in various devices which are controlled by using a microcomputer, for example, the actual fairness 5-7.
As described in Japanese Patent No. 601, the watchdog circuit monitors an abnormality of the microcomputer, and when the microcomputer is in an abnormal state, a signal from the watchdog circuit turns off the switching transistor to make a coil of the relay. It is configured to shut off power to loads such as.

[0004]

However, in the above-mentioned conventional configuration, a complicated circuit such as a watchdog circuit is required to monitor the abnormality of the microcomputer.
As the manufacturing cost rises, the watchdog circuit itself may be damaged.

The present invention has been proposed in view of the above points, and its object is to reliably monitor abnormality of a microcomputer with a simple circuit configuration.

[0006]

In order to solve the above problems, the present invention takes the following technical means.

That is, according to the first aspect of the invention of the present application, the first transistor interposed between the load and the power supply and the pulse signal from the microcomputer are input to the control end of the first transistor. A switching second transistor for controlling the voltage, a first capacitor interposed between the power supply side and the control end of the first transistor, a control end of the first transistor and the second transistor, It is characterized in that a second capacitor interposed between the second capacitor and a discharge circuit for discharging the electric charge of the second capacitor when the second transistor is turned off are provided.

The invention described in claim 2 of the present application is
A first transistor interposed between the load and the power supply,
A pulse signal of a predetermined cycle is input to a control end from a microcomputer, a switching second transistor for controlling the first transistor, and a first transistor interposed between a power supply side and the control end. No. 1 capacitor, a second capacitor interposed between the control terminal of the first transistor and the second transistor, and a discharge for discharging the electric charge of the second capacitor when the second transistor is turned off. A circuit is provided, and when the second transistor is turned off, the discharge current of the first capacitor keeps the first transistor on for a certain period of time.
The first transistor maintains the ON state during the period in which the transistor is ON / OFF in the predetermined cycle and the OFF state of the second transistor continues for the predetermined time or more, the discharge of the first capacitor progresses. Accordingly, when the first transistor is turned off and the on state of the second transistor continues for a predetermined time or more, the first transistor is turned off as the charging of the second capacitor progresses. There is.

The invention described in claim 3 of the present application is
A first transistor whose collector is connected to a load controlled by a microcomputer and whose emitter is connected to a power supply; and a pulse signal of a predetermined period is input to the base from the microcomputer, and whose emitter is grounded. A second transistor, a first capacitor interposed between the emitter and the base of the first transistor, and a first capacitor interposed between the base of the first transistor and the collector of the second transistor. A second capacitor, a cathode of which is connected to the emitter of the first transistor and an anode of which is connected to the first transistor side of the second capacitor; and a series circuit of the diode and the second capacitor in parallel. And a resistor connected to the second transistor when the second transistor is turned off.
The electric charge of the capacitor is discharged by a discharge circuit including a diode and a resistor, and the discharge current of the first capacitor keeps the first transistor on for a certain period of time. While the second transistor is on / off in a predetermined cycle, the first transistor maintains the on state, and when the off state of the second transistor continues for a predetermined time or longer, the discharge of the first capacitor proceeds. The first transistor is turned off in accordance with the above, and when the on state of the second transistor is continued for a predetermined time or longer, the first transistor is turned off as the charging of the second capacitor progresses. I am trying.

The invention described in claim 4 of the present application is
Based on a detection signal from a water amount sensor that detects the amount of water passing through the heat exchanger of the water heater, a water amount confirmation means for forcibly turning off or on the second transistor when the amount of water is equal to or less than a predetermined value is provided. The feature is that it is provided.

The invention described in claim 5 of the present application is
Flame that forcibly turns off or on the second transistor when a flame disappears after a predetermined time has elapsed from the start of ignition, based on a detection signal from a flame detector that detects the flame of the burner of the water heater. The feature is that a confirmation means is provided.

[0012]

According to the invention described in claim 1, when the second transistor is turned on, the first and second capacitors are charged, and the voltage across the first capacitor becomes equal to or more than a predetermined value. , The first transistor is turned on and power is supplied to the load. If the second transistor turns off,
Since the electric charge of the first capacitor is discharged through the power source side and the control end of the first transistor, the ON state of the first transistor is continued for a predetermined time. In addition, the charge of the second capacitor flows through the discharge circuit and is discharged. Therefore, if the operation in which the second transistor returns from the off state to the on state is repeated while the first transistor continues to be in the on state due to the discharge current of the first capacitor, the first transistor is turned on. The state will be retained. That is, the first transistor maintains the ON state while the pulse signal from the microcomputer is output to the control terminal of the second transistor at a predetermined cycle. On the other hand, when the signal supplied from the microcomputer to the control terminal of the second transistor is held at the low level due to the abnormal operation of the microcomputer, the off state of the second transistor continues for a predetermined time or longer. At this time, the voltage across the first capacitor decreases as the charge of the first capacitor discharges, and the voltage between the power supply side and the control end of the first transistor also decreases.
Finally, the first transistor is turned off, and the load is not supplied with power. On the contrary, when the signal supplied from the microcomputer to the control terminal of the second transistor is held at the high level due to the abnormal operation of the microcomputer, the ON state of the second transistor continues for a predetermined time or longer. At this time, the voltage across the second capacitor increases as the charge of the second capacitor is charged, and the potential at the control end of the first transistor also rises, thereby controlling the power supply side of the first transistor. Since the voltage between the terminals is reduced, the first transistor is finally turned off, and the load is not supplied with power.

According to the second aspect of the present invention, when the second transistor is turned off, the charge of the second capacitor flows through the discharge circuit and is discharged, and the discharge current of the first capacitor causes The on state of the first transistor continues for a certain period of time. Therefore, the first transistor maintains the on state while the second transistor is on / off in a predetermined cycle by the pulse signal from the microcomputer. On the other hand, when the off state of the second transistor continues for a predetermined time or longer, the voltage between the power supply side and the control end of the first transistor decreases as the discharge of the first capacitor progresses. Transistor turns off. On the contrary, when the ON state of the second transistor continues for a predetermined time or longer, the voltage across the second capacitor increases as the charging of the second capacitor progresses, which causes the control terminal of the first transistor to increase. Rises, the voltage between the power supply side of the first transistor and the control terminal decreases, and the first transistor is turned off.

According to the invention described in claim 3, when the second transistor is turned off, the charge of the second capacitor flows through the discharge circuit including the diode and the resistor and is discharged. The discharge state of the capacitor causes the ON state of the first transistor to continue for a certain period of time. Therefore, the first transistor maintains the on state while the second transistor is on / off in a predetermined cycle by the pulse signal from the microcomputer. On the other hand, when the off state of the second transistor continues for a predetermined time or longer, the voltage across the first capacitor decreases as the discharge of the first capacitor progresses, whereby the base-emitter of the first transistor is reduced. The voltage across reduces the first transistor to turn off. Conversely, the second
When the on state of the transistor of 1 continues for a predetermined time or more, the voltage across the second capacitor increases as the charging of the second capacitor progresses, which increases the base potential of the first transistor, Since the base-emitter voltage of the first transistor decreases, the first transistor turns off.

According to the fourth aspect of the invention, the water amount confirmation means determines the amount of water based on the detection signal from the water amount sensor for detecting the amount of water passing through the heat exchanger of the water heater. The second transistor is forcibly turned off or on in the following cases. As a result, the first transistor is turned off by the same operation as above.

According to the invention as set forth in claim 5, the flame confirmation means is provided after a predetermined time has elapsed from the start of ignition based on the detection signal from the flame detector for detecting the flame of the burner of the water heater. The second transistor is forced off or on when the flame disappears. As a result, the first transistor is turned off by the same operation as above.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The preferred embodiments of the present invention will be described below.
A specific description will be given with reference to the drawings.

(Embodiment 1) FIG. 2 shows Embodiment 1 of the present invention.
FIG. 2 is a schematic configuration diagram of a water heater including the power supply control device according to the first embodiment, in which a burner 2 for generating a flame is provided inside a casing 1.
A fuel supply path 3 for supplying a fuel such as gas or oil to the burner 2, a heat exchanger 4 for giving heat from combustion of the fuel to water to turn it into hot water, and water passing through the heat exchanger 4. Waterway 5
Are installed, and the fuel supply path 3 has solenoid valves 6,
7, 8 are interposed. In the vicinity of the burner 2,
A flame detector 9 for detecting the flame of the burner 2 is installed. A fan motor 12 that drives a sirocco fan for supplying secondary air to the inside of the casing 1 is installed inside a fan case 11 that is continuous with the lower end of the casing 1. An igniter 13 for igniting the burner 2 is installed outside the casing 1, and a water amount sensor 14 for detecting the amount of water flowing through the water passage 5 is provided in the water passage 5.
And a thermistor 15 for detecting the incoming water temperature. Further, detection signals are input to the outside of the casing 1 from the flame detector 9, the water amount sensor 14, and the thermistor 15, and the controller 16 for controlling the solenoid valves 6, 7, 8 and the fan motor 12, the igniter 13, and the remote operation. And a remote controller 17 for are installed.

FIG. 1 is an electric circuit diagram of a main part of the controller 16. Inside the controller 16, detection signals of the flame detector 9, the water amount sensor 14, the thermistor 15 and the like are input, and the solenoid valves 6 and 6. Microcomputer 19 for outputting signals for controlling 7, 8 and fan motor 12, igniter 13 and the like, and a constant voltage circuit 2 with a reset function for supplying the microcomputer 19 with power of a predetermined voltage.
0, and a power supply control device 21 that shuts off the supply of power to a relay, which will be described later, which constitutes the switch means, and solenoid valves 6, 7, 8 except when a pulse signal of a predetermined cycle is input from the microcomputer 19. Relays 22, 23, 24 that control the energization of the solenoid of the, and diodes 26, 2
7, 28, transistors 29, 30, 31 and resistors 32, 33, 34 are installed. Power control device 2
1 denotes transistors Q1 and Q2 and capacitors C1 and C
2, a diode D1, and resistors R1 to R6.

The input terminal of the constant voltage circuit 20 is a DC power source Vcc.
The output terminal of the constant voltage circuit 20 is connected to the power supply port 19a of the microcomputer 19. The reset end of the constant voltage circuit 20 is connected to the reset port 19b of the microcomputer 19, and the ground port 19c of the microcomputer 19 is grounded. The port 19d of the microcomputer 19 is connected to the base of the transistor Q2 via the resistor R6, and the emitter of the transistor Q2 is grounded.
One end of the resistor R5 is connected to the base of the transistor Q2, and the other end of the resistor R5 is connected to the emitter of the transistor Q2. The collector of the transistor Q2 is connected to the base of the transistor Q1 via the resistor R4, the capacitor C2 and the resistor R2. The emitter of the transistor Q1, the one end of the resistor R1, the capacitor C1
, A cathode of the diode D1, and an end of the resistor R3 are connected to the DC power source Vcc, respectively.
The other end of 1 is connected to the connection point between the base of the transistor Q1 and the resistor R2. The other end of the capacitor C1 and the anode of the diode D1 are connected to the resistor R2 and the capacitor C2.
And the other end of the resistor R3 is connected to the connection point between the capacitor C2 and the resistor R4.
Relays 22, 23, 2 are connected to the collector of the transistor Q1.
One end of the coil of No. 4 and the cathodes of the diodes 26, 27, 28 are connected, and the diodes 26, 27, 2 are connected.
The anode of 8 is connected to the other ends of the coils of the relays 22, 23, 24. The other ends of the coils of the relays 22, 23, 24 are connected to the collectors of the transistors 29, 30, 31 and the emitters of the transistors 29, 30, 31 are grounded via the resistors 32, 33, 34. The bases of the transistors 29, 30, 31 are connected to the ports 19e, 19f, 19g of the microcomputer 19. Note that the transistor Q1 constitutes a first transistor, the transistor Q2 constitutes a second transistor, the capacitor C1 constitutes a first capacitor, and the capacitor C2 constitutes a second capacitor. Therefore, the diode D1 and the resistor R3 form a discharge circuit. Further, the capacitor C1 constitutes a part of the integrating circuit, and the capacitor C2 constitutes a part of the differentiating circuit. Further, the coils of the relays 22, 23, 24 form a load of the power supply control device 21.

FIG. 3 is an electric circuit diagram of a main part of a water heater provided with the power supply control device according to the first embodiment of the present invention. Inside the controller 16, an AC power supply 36 and a relay (not shown) are provided. The normally open contact 37, the rectifier 38, and the power supply circuit 39 that generates the DC power supply Vcc are installed.
Series circuit of igniter 13 and normally open contact 37 and rectifier 3
The parallel circuit of 8 and the power supply circuit 39 is connected to the AC power supply 36, and one end on the output side of the rectifier 38 is connected to one end of the normally open contact 22a of the relay 22. The other end of the normally open contact 22a of the relay 22 is connected to one end of the solenoid 6a of the solenoid valve 6, one end of the normally open contact 23a of the relay 23, and one end of the normally open contact 24a of the relay 24. The other end of the normally open contact 23a of the relay 23 is connected to one end of the solenoid 7a of the solenoid valve 7, and the other end of the normally open contact 24a of the relay 24 is connected to one end of the solenoid 8a of the solenoid valve 8. The other ends of the solenoids 6a, 7a, 8a of the solenoid valves 6, 7, 8 are connected to the other end on the output side of the rectifier 38.

Next, the operation will be described. The operation command from the remote controller 17 is input to the controller 16,
When a detection signal indicating that a predetermined amount or more of water is detected is input from the water amount sensor 14 to the microcomputer 19, the microcomputer 19 starts the processing of the main routine, and the microcomputer 19 stores it in advance. Based on the program, the port 19d outputs a pulse signal having a constant cycle as shown in FIG. For example, at the start of processing of the main routine, port 1
9d goes high, the port 19d goes low at the end of the main routine processing, and when the timer by the software that starts the timing operation from the start of the processing of the main routine times out, the main routine again starts. The operation that the port 19d becomes high level at the same time when the processing is started is repeated. When the pulse signal from the port 19d of the microcomputer 19 becomes high level, the transistor Q2 is turned on and a current flows through the capacitors C1 and C2, as shown in (b) of FIG.
The current flowing through the capacitor C2 sharply decreases with time as shown in FIG. 4C, and the voltage across the capacitor C1 gradually increases with time as shown in FIG. 4D. Due to the increase in the voltage across the capacitor C1, the voltage between the base and emitter of the transistor Q1 exceeds a predetermined level, and the transistor Q1 is turned on as shown in (e) of FIG. This allows the relays 22, 23,
The DC power supply Vcc is applied to one end of the coil of 24. When the pulse signal output from the port 19d of the microcomputer 19 becomes low level, the transistor Q2 is turned off, the charge of the capacitor C2 is discharged through the diode D1 and the resistor R3, and the capacitor C1 is discharged.
The charged electric charge of is discharged through the emitter-base of the transistor Q1 and the resistor R2. Therefore, the discharge current of the capacitor C1 keeps the transistor Q1 on, and by the time the transistor Q1 is turned off, the pulse signal output from the port 19d of the microcomputer 19 is inverted to a high level and the transistor Q2 is turned on. As a result, port 1 of the microcomputer 19
While the pulse signal output from 9d is repeatedly turned on and off in a predetermined cycle, the transistor Q1 always keeps the on state.

When the port 19e of the microcomputer 19 goes high as shown in FIG. 4 (f), the transistor 29 is turned on and the coil of the relay 22 is energized. As a result, the normally-open contact 22a of the relay 22 is closed, and the solenoid 6a of the solenoid valve 6 is energized.
The solenoid valve 6 is opened as shown in FIG. When the ports 19f and 19g of the microcomputer 19 become high level, the transistors 30 and 31 are turned on, the coils of the relays 23 and 24 are energized, and the normally open contacts 23a and 24a of the relays 23 and 24 are closed. The solenoids 7a and 8a of the solenoid valves 7 and 8 are energized to open the solenoid valves 7 and 8. Therefore, the fuel passes through the fuel supply passage 3 and the burner 2
Is supplied to. In this state, the microcomputer 19 controls a relay (not shown) to close the normally open contact 37, energize the igniter 13 and ignite the burner 2. As a result, the water in the water channel 5 is heated while passing through the heat exchanger 4, and is supplied to a predetermined place. Of course, only one of the solenoid valves 7 and 8 can be opened by setting only one of the ports 19f and 19g of the microcomputer 19 to a high level according to the amount of hot water supplied and the temperature of hot water supplied.

If an abnormality occurs in the operation of the microcomputer 19 and the ports 19e, 19f, 19g and the like remain at the high level and the port 19d remains at the low level, the discharge of the capacitor C1 is completed. Also, since the transistor Q2 does not turn on, the transistor Q1 turns off and the DC power supply V
cc is no longer applied. That is, when the voltage across the capacitor C1 decreases due to the discharge of the capacitor C1, the base-emitter voltage of the transistor Q1 also decreases, and when it becomes smaller than a predetermined threshold value, the transistor Q1 decreases.
1 turns off. As a result, the normally open contacts 22a, 23a, 24a of the relays 22, 23, 24 are opened, and the solenoid valves 6,
The energization of the solenoids 6a, 7a, 8a of 7, 8 is cut off, and the solenoid valves 6, 7, 8 are closed. Conversely, if the port 19d of the microcomputer 19 maintains a high level state, the potential at the connection point between the capacitor C2 and the resistor R2 rises as the capacitor C2 is charged, and the potential between the base and emitter of the transistor Q1 increases. Voltage becomes small, the transistor Q1 turns off at last, and the relay 22,
The DC power supply Vcc is not applied to the coils 23 and 24. That is, when the voltage across the capacitor C2 increases due to the charging of the capacitor C2, the base potential of the transistor Q1 increases, and as a result, the base potential of the transistor Q1 increases.
When the emitter-to-emitter voltage decreases and becomes smaller than a predetermined threshold value, the transistor Q1 turns off. As a result, the normally open contacts 22a, 23a of the relays 22, 23, 24,
24a is opened, the solenoids 6a of the solenoid valves 6, 7, 8
The energization of 7a, 8a is cut off, and the solenoid valves 6, 7, 8 are closed. Even when the transistor Q2 has a short circuit failure, the solenoid valves 6, 7, 8 are closed by the same operation as when the port 19d of the microcomputer 19 maintains the high level state.

As described above, due to an abnormal operation of the microcomputer 19, for example, the ports 19e, 19f, 19g are
Is maintained at a high level, the transistor Q1 is turned off in either case regardless of whether the output of the port 19d is maintained at a high level or a low level. It can be closed. Therefore, the fire can be surely extinguished, and the leakage of the fuel from the burner 2 can be surely prevented. Further, without using a complicated circuit such as a conventional watchdog circuit, an abnormality of the microcomputer 19 is detected by the power supply control device 21 having a simple circuit configuration using charging and discharging of the capacitors C1 and C2, and the load is detected. Since the power supply to the coils of a certain relay 22, 23, 24 can be cut off, the manufacturing cost can be reduced and the watchdog circuit itself does not break down.

(Second Embodiment) FIG. 5 shows a second embodiment of the present invention.
FIG. 2 is an electric circuit diagram of a main part of a controller provided in a water heater including the power supply control device according to the first embodiment, which is different from the circuit of the first embodiment shown in FIG. It is the point of control. That is, one end of the coil of the relay 41 and the cathode of the diode 42 are connected to the collector of the transistor Q1.
2, 23, 24 coil ends and diode 26,
The cathodes of 27 and 28 are connected to a DC power supply Vcc. The other end of the coil of the relay 41 and the anode of the diode 42 are connected to the collector of the transistor 43, and the base of the transistor 43 is connected to the port 19h of the microcomputer 19. Transistor 4
The emitter of 3 is grounded via a resistor 40.

FIG. 6 is an electric circuit diagram of a main part of a water heater equipped with a power supply control device according to the second embodiment of the present invention. The difference from the circuit of the first embodiment shown in FIG. The point is that the normally open contact 41 a of the relay 41 is connected between the 36 and the normally open contact 37.

In the second embodiment, the transistor Q1 is turned on by the same operation as in the first embodiment, as shown in FIG.
When the port 19h of the microcomputer 19 becomes high level as shown in (f), the coil of the relay 41 is energized and the normally open contact 41a of the relay 41 is closed. As a result, when the rectifier 38 is connected to the AC power supply 36 and the normally open contacts 22a, 23a, 24a of the relays 22, 23, 24 are closed, the solenoid valves 6, 7, 8 of the solenoid valves 6a, 7a, 7a, 7a, 7a are closed.
The solenoid valves 6, 7 and 8 are opened by energizing a and 8a. Here, when an abnormality occurs in the operation of the microcomputer 19 and the transistor Q1 is turned off by the same operation as in the first embodiment, the coil of the relay 41 is no longer energized as shown in FIG. The normally open contact 41a is opened. Therefore, the connection between the AC power supply 36 and the rectifier 38 is cut off, and the solenoids 6a, 7 of the solenoid valves 6, 7, 8 are
The solenoid valves 6, 7 and 8 are closed because the a and 8a are not energized. Note that FIG. 7A shows the microcomputer 1
9 shows the voltage waveform of the port 19d, FIG. 7 (b) is the on / off state of the transistor Q2, and FIG.
7 shows the waveform of the current flowing through the capacitor, FIG. 7 (d) shows the voltage waveform across the capacitor C1, and FIG. 7 (e) shows the on / off state of the transistor Q1.

As described above, regardless of whether the output of the port 19d is maintained at the high level or the low level due to the abnormal operation of the microcomputer 19, the transistor Q1 is turned off in any case, so that the solenoid valve is reliably operated. 6,
The valves 7 and 8 can be closed. Therefore, the fire can be surely extinguished, and the leakage of the fuel from the burner 2 can be surely prevented. Further, since the energization of the igniter 13 is also blocked, sparks for ignition do not occur.
Further, the power control device 21 causes the normally-open contact 4 of the relay 41 to
Since 1a is opened, the solenoid valves 6, 7, 8 can be surely closed even when the normally open contacts of the relays 22, 23, 24 are stuck and closed. Moreover, without using a complicated circuit such as a conventional watchdog circuit,
The microcomputer 19 is controlled by the power supply control device 21 having a simple circuit configuration using the charging and discharging of the capacitors C1 and C2.
Since the power supply to the coil of the relay 41, which is the load, can be shut off by detecting the abnormality of No. 1, the manufacturing cost can be reduced and
The watchdog circuit itself does not break down.

Although the normally open contact 41a of the relay 41 is provided on the input side of the rectifier 38 in the second embodiment, the normally open contact 41a may be provided on the output side of the rectifier 38.

(Third Embodiment) FIG. 8 shows a third embodiment of the present invention.
FIG. 9 is an electric circuit diagram of a main part of a controller provided in a water heater including the power supply control device according to the first embodiment, which is different from the circuit of the second embodiment shown in FIG. The point is that a water amount confirmation means including a circuit 44, a transistor Q3, and resistors R7 and R8 is added. That is, the output end of the water amount sensor 14 is connected to the input end of the F / V conversion circuit 44 and the port 19i of the microcomputer 19, and the output end of the F / V conversion circuit 44 is a resistor R.
It is connected to the base of the transistor Q3 via 7. The collector of the transistor Q3 is connected to the connection point between the resistor R6 and the base of the transistor Q2, and the emitter of the transistor Q3 is grounded. The connection point between the output terminal of the F / V conversion circuit 44 and the resistor R7 is a resistor R8.
Grounded through.

FIG. 9 is an electric circuit diagram of a main part of a water heater provided with a power supply control device according to the third embodiment of the present invention, and has the same configuration as the circuit of the second embodiment shown in FIG.

In the third embodiment, the water amount sensor 14
Is converted into a voltage by the F / V conversion circuit 44 and supplied to the base of the transistor Q3. That is, the water amount sensor 14 outputs a pulse signal having a frequency corresponding to the amount of water in the water channel 5, and the F / V conversion circuit 44 outputs a voltage inversely proportional to the frequency of the pulse signal from the water amount sensor 14. When the amount of water in the water channel 5 decreases, the frequency of the pulse signal from the water amount sensor 14 decreases, so that the output voltage of the F / V conversion circuit 44 increases, and the amount of water in the water channel 5 becomes a predetermined value as shown in (h) of FIG. When the value becomes less than the value, the transistor Q3 turns on. As a result, the base potential of the transistor Q2 decreases and the transistor Q2 turns off. Therefore, the transistor Q1 turns off by the same operation as in Example 2, and the coil of the relay 41 is energized as shown in FIG. Then, the normally open contact 41a of the relay 41 is opened. Therefore, the connection between the AC power supply 36 and the rectifier 38 is cut off, the solenoids 6a, 7a, 8a of the solenoid valves 6, 7, 8 are no longer energized, and the solenoid valves 6, 7, 8 are closed. 10A shows the port 19 of the microcomputer 19.
10D is a voltage waveform, FIG. 10B is a transistor Q2 on / off state, FIG. 10C is a current waveform flowing through the capacitor C2, and FIG. 10D is a voltage waveform across the capacitor C1. 10E shows the on / off state of the transistor Q1, and FIG. 10F shows the voltage waveform of the port 19h of the microcomputer 19.

As described above, even when the amount of water in the water channel 5 drops below a predetermined value, the transistor Q1 is turned off.
The solenoid valves 6, 7, 8 can be surely closed. Therefore, the fire can be reliably extinguished to prevent an abnormal supply of high-temperature water and damage to the heat exchanger 4, and the burner 2
It is possible to reliably prevent fuel leakage from the. Further, since the energization of the igniter 13 is also blocked, sparks for ignition do not occur. Further, since the power control device 21 opens the normally open contact 41a of the relay 41, the relay 22,
Even when the normally open contacts 23 and 24 are stuck and closed, the solenoid valves 6, 7 and 8 can be reliably closed.
Further, the load is detected by detecting an abnormality of the microcomputer 19 by the power supply control device 21 having a simple circuit configuration using charging and discharging of the capacitors C1 and C2 without using a complicated circuit such as a conventional watchdog circuit. Relay 4
Since the power supply to the coil No. 1 can be cut off, the manufacturing cost can be reduced and the watchdog circuit itself does not break down.

Although the normally open contact 41a of the relay 41 is provided on the input side of the rectifier 38 in the third embodiment, the normally open contact 41a may be provided on the output side of the rectifier 38.

In the third embodiment, the water amount sensor 14
The transistor Q3 was turned on when the amount of water detected by
The transistor Q3 may be turned on when the amount of water detected by the water amount sensor 14 is equal to or lower than a predetermined value for a predetermined time or longer.

In the third embodiment, the water amount sensor 14
The transistor Q2 is forcibly turned off when the amount of water detected by is equal to or less than the predetermined value, but the transistor Q2 is forcibly turned on when the amount of water detected by the water amount sensor 14 is equal to or less than the predetermined value. You may comprise.

(Embodiment 4) FIG. 11 is an electric circuit diagram of a main part of a controller provided in a water heater provided with a power supply control device according to Embodiment 4 of the present invention. The embodiment shown in FIG. The difference from the circuit of FIG.
In place of the / V conversion circuit 44, a flame detection circuit 46 that detects a flame by a signal from the flame detector 9 and a flame detection circuit 46 that is activated by a signal from the port 19e of the microcomputer 19 and is timed up. The point is to provide a flame confirmation means including a timer circuit 47 for supplying a signal to the base of the transistor Q3. That is, the output end of the flame detector 9 is connected to the input end of the flame detection circuit 46, and the output end of the flame detection circuit 46 is connected to the input end of the timer circuit 47 and the port 19j of the microcomputer 19. . The output end of the timer circuit 47 is connected to the base of the transistor Q3 via the resistor R7, and the start control end of the timer circuit 47 is the microcomputer 1.
9 is connected to the connection point between the port 19e and the base of the transistor 29.

FIG. 12 is an electric circuit diagram of a main part of a water heater equipped with a combustion control device according to a fourth embodiment of the present invention.
It has the same configuration as the circuit of the second embodiment shown in FIG. 6 and the circuit of the third embodiment shown in FIG.

In the fourth embodiment, the flame detection circuit 46 is used.
Outputs to the timer circuit 47 and the port 19j of the microcomputer 19 a signal according to the presence or absence of flame in the burner 2 based on the detection signal from the flame detector 9, and the timer circuit 47 causes the port of the microcomputer 19 to operate. The timing operation is started when the signal from 19e becomes high level, and after the time is up, the signal from the flame detection circuit 46 is supplied to the base of the transistor Q3. That is, when the burner 2 does not ignite or the flame of the burner 2 disappears, the detection signal output from the flame detector 9 becomes low level as shown in FIG. 13 (h), which causes the flame detection circuit 46. Output becomes high level. On the other hand, the timer circuit 47 starts a timing operation for a predetermined time from when the signal from the port 19e of the microcomputer 19 becomes high level, and outputs the output of the flame detection circuit 46 after the time is up. This is because there is no flame before the burner 2 is ignited, so that fuel can be supplied even during ignition. When the output of the timer circuit 47 becomes high level,
The transistor Q3 turns on. As a result, the base potential of the transistor Q2 is lowered and the transistor Q2 is turned off.
Is turned off, the coil of the relay 41 is no longer energized as shown in FIG.
a opens. Therefore, the connection between the AC power supply 36 and the rectifier 38 is cut off, and the solenoid 6 of the solenoid valves 6, 7, 8 is
a, 7a, 8a are no longer energized, the solenoid valves 6, 7,
8 closes. 13A is a voltage waveform of the port 19d of the microcomputer 19, and FIG.
13C is the on / off state of the transistor Q2, FIG. 13C is the current waveform flowing through the capacitor C2, FIG. 13D is the voltage waveform across the capacitor C1, and FIG. 13E is the on / off state of the transistor Q1. Off, FIG. 13 (f) shows the voltage waveform of the port 19h of the microcomputer 19, respectively.

As described above, the transistor Q1 is turned off even when the burner 2 does not ignite or the flame once ignited disappears, so that the solenoid valves 6, 7, 8 can be surely closed. it can. Therefore, the fire can be surely extinguished, and the leakage of the fuel from the burner 2 can be surely prevented. Further, since the energization of the igniter 13 is also blocked, sparks for ignition do not occur. Further, since the power control device 21 opens the normally open contact 41a of the relay 41, even when the normally open contacts of the relays 22, 23, and 24 are fixed in the closed state, the solenoid valve 6, is surely opened.
The valves 7 and 8 can be closed. Further, the load is detected by detecting an abnormality of the microcomputer 19 by the power supply control device 21 having a simple circuit configuration using charging and discharging of the capacitors C1 and C2 without using a complicated circuit such as a conventional watchdog circuit. Since the power supply to the coil of the relay 41 can be cut off, the manufacturing cost can be reduced and the watchdog circuit itself does not break down.

In the fourth embodiment, the normally open contact 41a of the relay 41 is provided on the input side of the rectifier 38, but the normally open contact 41a may be provided on the output side of the rectifier 38.

Further, in each of the above-described embodiments, an example in which the power supply control device according to the present invention is used for a water heater has been described, but the power supply control device according to the present invention is not limited to such an application, and a micro It can be used for any device that controls using a computer.

Further, both the water quantity confirming means of the third embodiment and the flame confirming means of the fourth embodiment may be provided in the power supply controller 21. For example, transistor Q3 and resistor R
7 and R8 may be commonly used, and the output end of the F / V conversion circuit 44 and the output end of the timer circuit 47 may be connected to the base of the transistor Q3 via the resistor R7.

[0045]

As described above, according to the first aspect of the invention, when the microcomputer does not output the pulse signal by utilizing the charge and discharge of the first and second capacitors, the circuit configuration is simple. Therefore, it is possible to reliably monitor the abnormality of the microcomputer. Therefore, a complicated circuit such as a watchdog circuit is unnecessary for monitoring the abnormality of the microcomputer, the manufacturing cost can be reduced, and the watchdog circuit itself does not break down.

According to the second aspect of the present invention, when the second transistor is turned off, the discharge current of the first capacitor causes the first transistor to remain in the on state for a certain period of time, whereby a pulse from the microcomputer is generated. While the second transistor is on / off in a predetermined cycle by the signal, the first transistor maintains the on state, and when the off state of the second transistor continues for a predetermined time or more, the first capacitor The first transistor is turned off with the progress of discharging, and the first transistor is turned off with the progress of charging of the second capacitor when the on state of the second transistor is continued for a predetermined time or longer. Therefore, the microcomputer outputs a pulse signal of a predetermined cycle by using the charge and discharge of the first and second capacitors. When it disappears, it is possible to reliably monitor the abnormality of the microcomputer with a simple circuit configuration, and therefore, a complicated circuit such as a watchdog circuit is not necessary for monitoring the abnormality of the microcomputer, and the manufacturing cost can be reduced. The watchdog circuit itself will not fail.

According to the third aspect of the invention, when the second transistor is turned off, the electric charge of the second capacitor is discharged by the discharge circuit including the diode and the resistor, and the first capacitor is discharged. By keeping the ON state of the first transistor for a certain time by the current, the second signal is generated by the pulse signal from the microcomputer.
The first transistor maintains the ON state during the period in which the transistor is ON / OFF in the predetermined cycle and the OFF state of the second transistor continues for the predetermined time or more, the discharge of the first capacitor progresses. Accordingly, when the first transistor is turned off and the on state of the second transistor continues for a predetermined time or longer, the first transistor is turned off as the charging of the second capacitor progresses. When the microcomputer does not output a pulse signal of a predetermined cycle by using the charge and discharge of the second capacitor, the abnormality of the microcomputer can be reliably monitored with a simple circuit configuration. Because the power supply to the load controlled by the microcomputer can be cut off without using a complicated circuit It is possible to reduce manufacturing costs, also eliminated can say, watchdog circuit itself fails.

Further, according to the invention of claim 4, even when the amount of water supplied to the heat exchanger falls below a predetermined value, the power supply to the load can be cut off. Therefore, it becomes possible to prevent abnormal supply of high-temperature water and damage to the heat exchanger.

Further, according to the invention of claim 5, the power to the load can be shut off even when the burner is not ignited or the flame once ignited disappears. Therefore, it becomes possible to prevent the leakage of the fuel due to the ignition failure or the disappearance of the flame.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram of a main part of a controller provided in a water heater including a power supply control device according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a water heater including the power supply control device according to the first embodiment of the present invention.

FIG. 3 is an electrical circuit diagram of a main part of a water heater including the power supply control device according to the first embodiment of the present invention.

FIG. 4 is a signal waveform diagram of each part of the controller provided in the water heater including the power supply control device according to the first embodiment of the present invention.

FIG. 5 is an electric circuit diagram of a main part of a controller provided in a water heater including a power supply control device according to a second embodiment of the present invention.

FIG. 6 is an electric circuit diagram of a main part of a water heater including a power supply control device according to a second embodiment of the present invention.

FIG. 7 is a signal waveform diagram of each part of the controller provided in the water heater including the power supply control device according to the second embodiment of the present invention.

FIG. 8 is an electric circuit diagram of a main part of a controller provided in a water heater including a power supply control device according to a third embodiment of the present invention.

FIG. 9 is an electric circuit diagram of a main part of a water heater including a power supply control device according to a third embodiment of the present invention.

FIG. 10 is a signal waveform diagram of each part of the controller provided in the water heater including the power supply control device according to the third embodiment of the present invention.

FIG. 11 is an electric circuit diagram of a main part of a controller provided in a water heater including a power supply control device according to a fourth embodiment of the present invention.

FIG. 12 is an electric circuit diagram of a main part of a water heater including a power supply control device according to a fourth embodiment of the present invention.

FIG. 13 is a signal waveform diagram of each part of the controller provided in the water heater including the power supply control device according to the fourth embodiment of the present invention.

[Explanation of symbols]

 9 Flame detector 14 Water amount sensor 19 Microcomputer 21 Power supply control device 22 Relay 23 Relay 24 Relay 41 Relay 44 F / V conversion circuit 46 Flame detection circuit 47 Timer circuit Q1, Q2, Q3 Transistor C1, C2 Capacitor D1 Diode R3, R7 , R8 resistor

Claims (5)

[Claims] 1. A first transistor interposed between a load and a power source, and a second transistor for switching, which receives a pulse signal from a microcomputer at a control terminal to control the first transistor. And the first transistor interposed between the power source side and the control end of the first transistor.
Capacitor, a second capacitor interposed between the control terminal of the first transistor and the second transistor, and a charge of the second capacitor when the second transistor is turned off. A power supply control device comprising a discharge circuit for discharging. 2. A first transistor interposed between a load and a power supply, and a second switching transistor for controlling the first transistor by inputting a pulse signal of a predetermined cycle from a microcomputer to a control terminal. Of the first transistor, a first capacitor interposed between the power supply side of the first transistor and the control terminal, and a first capacitor interposed between the control terminal of the first transistor and the second transistor. Second
And a discharge circuit that discharges the electric charge of the second capacitor when the second transistor is turned off, and the discharge current of the first capacitor is used when the second transistor is turned off. By keeping the ON state of the first transistor for a certain period of time,
During a period in which the second transistor is turned on / off in a predetermined cycle by a pulse signal from the microcomputer, the first transistor is kept in an on state, and the off state of the second transistor is kept for a predetermined time or more. When it continues, the first transistor turns off as the discharge of the first capacitor progresses, and when the on state of the second transistor continues for a predetermined time or longer, the charge of the second capacitor progresses. The power supply control device is characterized in that the first transistor is turned off in accordance with the above. 3. A first transistor whose collector is connected to a load controlled by a microcomputer and whose emitter is connected to a power supply; and a pulse signal of a predetermined cycle is input to the base from said microcomputer, and said emitter is A grounded second transistor for switching, a first capacitor interposed between an emitter and a base of the first transistor, a base of the first transistor and a collector of the second transistor. A second capacitor interposed between the second capacitor, a cathode connected to the emitter of the first transistor and an anode connected to the first transistor side of the second capacitor; And a resistor connected in parallel with the series circuit of the second capacitor and the second capacitor. When the transistor is turned off, the electric charge of the second capacitor is discharged by the discharge circuit including the diode and the resistor, and the on-state of the first transistor is kept on for a predetermined time by the discharge current of the first capacitor. By continuing the pulse signal from the microcomputer, the first transistor maintains the ON state while the second transistor is ON / OFF at a predetermined cycle, and the second transistor is OFF. When the state continues for a predetermined time or more, the first transistor is turned off as the discharge of the first capacitor progresses, and when the on state of the second transistor continues for a predetermined time or more, the second transistor is turned on. The first transistor is turned off as the charging of the capacitor progresses. , Power supply control device. 4. The second transistor is forcibly turned off or turned off when the amount of water is below a predetermined value based on a detection signal from a water amount sensor that detects the amount of water passing through the heat exchanger of the water heater. The power supply control device according to any one of claims 1 to 3, further comprising a water amount confirmation means for turning on. 5. The second transistor is forcibly activated based on a detection signal from a flame detector that detects the flame of the burner of the water heater after a predetermined time has elapsed from the start of ignition and when the flame disappears. The power supply control device according to any one of claims 1 to 4, further comprising a flame confirmation means for turning the power off or on.