JPH0574753B2 - - Google Patents

Description

[Detailed Description of the Invention] Purpose of the Invention [Field of Industrial Application] The present invention provides a load that is capable of detecting the presence or absence of failures such as short-circuiting or damage to output elements such as power transistors or disconnection of circuits while driving the load. This relates to a control device.

[Prior Art] Conventionally, electromagnetic valves that open and close fuel gas in gas appliances such as water heaters and boilers are driven based on the main drive current from a load control device. In such a load control device, when a power transistor is used as a driving element of a solenoid valve, the power transistor is destroyed by heat or external surge and becomes constantly in a conductive state or in a non-conductive state, resulting in a lack of reliability. In particular, if the electromagnetic valve is always in a conductive state and is always open, there is a risk of a gas leakage accident. Therefore, it has been proposed to open and close a solenoid valve using a contact relay that is unlikely to be constantly conductive.

[Problems to be Solved by the Invention] However, when the above-mentioned contact relay is used, the load control device increases in size, and
Since the life of the contacts of the contact relay is short, there is a problem in that the contact relay needs to be replaced at predetermined intervals. The purpose of this invention is to improve reliability by using a power transistor as an output element to drive a load such as a solenoid valve, and by automatically cutting off the power supply when the transistor is short-circuited and reliably preventing the solenoid valve from being constantly open. The object of the present invention is to provide an excellent and compact load control device.

Structure of the Invention [Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a power transistor for driving a solenoid valve, a detection means for detecting an excitation current flowing through the solenoid valve, and a power transistor for driving the solenoid valve. a first control means that outputs an operating signal to turn on the power transistor and a diagnostic signal to momentarily turn off the power transistor at regular intervals; The configuration includes a determining means for determining whether the power transistor is short-circuited, and a second control means for cutting off the power to the power transistor based on the output of the determining means.

[Operation] When a short circuit state of the power transistor is detected by the above means based on the output signal, the operation signal, and the diagnostic signal of the detection means, the power to the power transistor is cut off, and the driving of the solenoid valve is stopped.

[Embodiment] Hereinafter, an embodiment embodying the present invention will be described with reference to the drawings.A load control device 1 shown in FIG.
operates based on an output signal from a control circuit 2 connected to the preceding stage, and is capable of driving a gas opening/closing solenoid valve 3 connected as a load. The solenoid valve 3
Explaining this with reference to FIG. 2, the main body 4 has gas communication holes 5 formed therein. A core 6 is fixed to the upper part of the main body 4, and a plunger 7 is supported by the core 6 so as to be movable up and down, and a spring receiver 8 and a valve seat 9 are fitted to the lower end of the plunger 7.
A return spring 1 is inserted between the spring receiver 8 and the core 6.
0 is disposed so that the plunger 7 is normally lowered by its biasing force so that the valve seat 9 closes the communication hole 5.

A coil 11 is disposed around the plunger 7, and when an excitation current is supplied through a power line 12 connected to the control circuit 2, the coil 11 is excited and the plunger 7 is pulled upward. Therefore, when the coil 11 is excited, the valve seat 9 is moved upward as the plunger 7 is moved, so that the communication hole 5 is opened.

A magnetic core 13 is fitted onto the core 6 above the plunger 7. An auxiliary core 14 is attached to the upper part of the core 6, and a Hall element 15 is attached between the auxiliary core 14 and the magnetic core 13. The power line 12 is branched and connected to the Hall element 15 to supply power, and the signal line 1
6 is connected. Then, the coil 11 is excited while power is being supplied to the Hall element 15, and the magnetic flux generated in the coil 11 is transferred to the auxiliary core 14.
When the current is shunted from the magnetic flux density to the magnetic core 13, a voltage corresponding to the magnetic flux density is output from the Hall element 15 via the signal line 16.

A power supply voltage Vcc is supplied to the power supply line 17 of the load control device 1, and the coil 11 is connected between the power supply line 17 and the collector terminal of the power transistor 18 constituting the final output stage of the load control device 1. are connected in series via a power supply line 12. The emitter terminal of the power transistor 18 is grounded, and the base terminal is connected to the control circuit 2 via a resistor R1 to receive an operating signal SG1 shown in FIG. 3a.

The collector terminal of a diagnostic transistor 19 for outputting a pulse signal for failure diagnosis to the base terminal of the power transistor 18 is connected to the base terminal of the power transistor 18, and the emitter terminal of the diagnostic transistor 19 is grounded. The base terminal is connected to the control circuit 2 via a resistor R2. The control circuit 2 outputs a diagnostic signal SG2 to the diagnostic transistor 19 in the form of a constant cycle pulse signal as shown in section 3b.

The signal line 16 of the Hall element 15 is connected to an amplifier 20 in the load control device 1.
The output signal of the Hall element 15 is amplified, and the output signal of the amplifier 20 is outputted to the non-inverting input terminal of the comparator 21. Resistors R3, R4 and a variable resistor are connected to the inverting input terminal of the comparator 21 in advance.
The reference voltage set by VR is input. Therefore, the comparator 21 outputs an H level signal when the output voltage of the amplifier 20 becomes higher than the reference voltage, that is, when the power transistor 18 is turned on and the coil 11 is excited. Then, the output signal of the comparator 21 is output to the first AND circuit 22, and is also sent to the second AND circuit via the inverting circuit 23.
The signal is output to an AND circuit 24.

The operation signal SG1 output from the control circuit 2 to the power transistor 18 is also output to the first and second AND circuits 22 and 24, and the operation signal SG1 is output to the power transistor 18 from the control circuit 2.
The diagnostic signal SG2 outputted to the circuit 9 is outputted to the first AND circuit 22 and is also outputted to the second AND circuit 24 via the inversion circuit 25. Also,
The output signals of the first and second AND circuits 22 and 24 are output to self-holding circuits 26 and 27, respectively.
Each self-holding circuit 26, 27 is connected to each AND circuit 22,
After the H level output signal is output from the control circuit 24, the H level signal is continued to be output to the control circuit 2. The control circuit 2 is configured to stop supplying power to the power supply line 17 when an H level signal is output from at least one of the self-holding circuits 26 and 27.

Next, load control device 1 configured as described above
Explain the effect of

Now, the power transistor 1 of the load control device 1
8, the operation signal SG shown in FIG. 3a is sent from the control circuit 2.
When 1 is output, the power transistor 18 is turned on and excitation current flows through the coil 11 of the solenoid valve 3, and the plunger 7 is moved upward to open the communication hole 5. When the coil 11 is excited, the Hall element 15 outputs a signal voltage, and the comparator 21 outputs an H level signal based on the signal voltage.

When the diagnostic signal SG2 shown in FIG. 3b is output from the control circuit 2 together with the operating signal SG1 at regular intervals, the diagnostic transistor 19 is turned on at regular intervals. When the diagnostic transistor 19 is turned on, the base voltage of the power transistor 18 decreases, and the power transistor 18 is temporarily turned off. At this time, no excitation current flows through the coil 11, so the output of the comparator 21 is The signal is L
level. Therefore, the output signal of the comparator 21 becomes the output signal SG3 which has the opposite phase to the diagnostic signal SG2 as shown in FIG.
Since at least one of the input signals of the AND circuit 22 becomes L level, the first AND circuit 22
The output signal never becomes H level. Similarly, when the power transistor 18 is operating normally, at least one of the input signals of the second AND circuit 24 is at L level.
The output signal of the AND circuit 24 never becomes H level.

On the other hand, when the power transistor 18 is short-circuited, even if the diagnostic signal SG2 is output and the diagnostic transistor 19 is turned on, the collector current continues to flow through the power transistor 18 and the coil 11
continues to be excited, the output signal SG3 of the comparator 21 becomes the diagnostic signal SG2, as shown by the broken line in FIG. 3c.
Even if it becomes H level, it continues to be in the H level state. Then, since all the input signals of the first AND circuit 22 become H level, the output signal SG4 of the first AND circuit 22 becomes H level as shown in FIG. 3c. Then, based on the output signal SG4, the self-holding circuit 26 outputs an output signal SG5 shown in FIG. 3e to the control circuit 2, and the control circuit 2 cuts off the power supply voltage Vcc based on the output signal SG5.
Therefore, when the power transistor 18 is short-circuited, the control circuit 2 lowers the power supply voltage of the load control device 1.
Since Vcc is automatically cut off, even if the power transistor 18 is short-circuited, the excitation current will not continue to flow through the coil 11.

In addition, when the power transistor 18 becomes unable to conduct, or when a disconnection occurs in the load control device 1, the operating signal SG1 is at H level and the diagnostic signal SG2 is
Even if the output signal SG3 of the comparator 21 is at the L level as shown in FIG. 4c, the output signal SG3 of the comparator 21 is at the L level.
All the input signals of the second AND circuit 24 become H level, and the output signal SG6 of the second AND circuit 24 becomes H level as shown in FIG. 4d. Then, based on the output signal SG6, the self-holding circuit 2
7 outputs an output signal SG7 of H level, and the control circuit 2 cuts off the power supply voltage Vcc of the load control device 1 based on the output signal SG7.

As described above, in this load control device 1, when the power transistor 18 is short-circuited, the control circuit 2 automatically cuts off the power supply voltage Vcc, so when the power transistor 18 is short-circuited, the solenoid valve 3 opens. Even when this electromagnetic valve 3 is used as an on-off valve for a gas combustion system, problems such as gas leakage can be prevented. Furthermore, when the power transistor 18 becomes unable to conduct, or when a disconnection occurs in the load control device 1, the power supply voltage Vcc is cut off and the operation of the solenoid valve 3 is stopped.

Therefore, this load control device 1 uses the power transistor 18 as an output element for driving the solenoid valve 3, and can automatically cut off the power supply in the event of a failure to prevent the solenoid valve 3 from malfunctioning.

Effects of the Invention As detailed above, the present invention uses a power transistor as an output element to drive a load such as a solenoid valve, and when the transistor is short-circuited, the power is automatically cut off to ensure that the solenoid valve is always open. By preventing this, it is possible to provide an excellent effect of providing a highly reliable and compact load control device.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a load control device embodying the present invention, Fig. 2 is a sectional view showing a solenoid valve, and Fig. 3 is a sectional view showing a solenoid valve.
FIG. 4 is a timing chart showing the operation of the load control device. Control circuit (first and second control means)...2,
Solenoid valve...3, Hall element (detection means)...1
5. Power transistor...18. First AND
Circuit (discrimination means)...22, Operation signal...SG1,
Diagnostic signal...SG2.

Claims (1)

[Claims] 1. Power transistor 18 that drives the solenoid valve 3
, a detection means 15 for detecting the excitation current flowing through the solenoid valve 3, an operation signal SG1 for turning on the power transistor 18, and a diagnostic signal for turning off the power transistor 18 momentarily at regular intervals.
a first control means 2 that outputs an output signal SG2; and an output signal of the detection means 15 and an operation signal SG1.
and a determining means 22 for determining the short-circuit state of the power transistor 18 based on the diagnostic signal SG2, and a second control means 2 for cutting off the power to the power transistor 18 based on the output of the determining means 22.
A load control device equipped with a self-diagnosis function consisting of and.