JPH0241476Y2 - - Google Patents

Description

[Detailed description of the invention] [Purpose of the invention] (Field of industrial application) The present invention is a combustion control circuit, particularly a combustion control circuit that indicates an abnormality in a microcomputer when performing combustion control using a microcomputer. Regarding.

(Prior Art) When controlling gas combustion using a microcomputer, a failsafe operation is performed while confirming the presence of flame. However, even if it is possible to reliably detect the presence or absence of a flame, for example, no measures have been taken to prevent other abnormalities. That is, since the microcomputer may run out of control due to noise, temperature rise, etc., some countermeasures must be taken against these as well.

Therefore, the applicant previously proposed the safety circuit shown in FIG. 1 as Utility Application No. 58-74667. The outline of the overall operation shown in FIG. 1 is as follows. That is, the flame detection circuit 1 outputs the "L" level when there is a flame, and the "H" level when there is no flame, so that when the microcomputer 2 is reset, all ports are at the "H" level. configured and also reset target of microcomputer 2.
RST is set so that it is reset when it becomes an "L" level input. First, when the power is turned on, there is no flame, so the flame detection circuit 1 outputs the "H" level, and the microcomputer 2 is in the reset state, so the output port _P0 is at the "H" level, and when the power is turned on, the voltage is divided. Since the potential rise at the point is small and the level is "L", the logic circuit 6
The output becomes "L" level and is input to the reset terminal of the microcomputer 2 and the reset terminal of the monostable multi 3. In this state, the microcomputer 2 is in the reset state, so each output port P ₀ , P ₁ , P ₂ is at the "H" level as described above, and the monostable multi 3 is also in the reset state, and the output Q is "H" level. It becomes L level.
Therefore, the output of the inverter 10 becomes "H" level, and the switching transistor TR1 is turned off. As a result, the excitation coil GV1 of the gas main valve, the excitation coil GV2 of the gas auxiliary valve, and the ignition coil GV
3 are not energized.

Next, as a predetermined time elapses, the potential at the voltage dividing point rises, and when this exceeds the threshold point of the logic circuit 5, the output of the logic circuit 5 is inverted to the "L" level, and as a result, the logic circuit 6 The output becomes "H" level, and the microcomputer 2 starts executing the program.

Well, a capacitor Ct and a resistor Rt are connected to the monostable multi 3, and when a trigger pulse from the output port P _A of the microcomputer 2 is input, the output is delayed by the time constant determined by Ct and Rt. It is designed to derive signals. Therefore, if you prepare a subroutine that outputs one predetermined pulse in the program and distribute it at regular intervals by calling it, the output will be simple as long as the microcomputer system is operating normally. The stable multi-channel 3 can be used as a continuous operation output, and the output of the inverter 10 can be maintained at "L" level, so that the switching transistor
Turn on TR1, and each excitation coil GV1, GV2
and GV3 can be activated.

Note that in the operating state, both the power lamp LED1 and the combustion lamp LED2 are lit.

(Problem to be solved by the invention) The previously proposed device described above uses a monostable multi as a watchdog timer for detecting runaway, and attempts to turn off the power in the event of an abnormality.・When the dog timer is operating, no abnormality is displayed to the user.

Additionally, although it is extremely easy to install a new abnormality lamp, for example, increasing the number of cables between the water heater, which is a device to be combusted, and the controller not only reduces reliability, but also increases the cost considerably. There is a problem.

The present invention was made in order to solve the above-mentioned problems, and aims to provide a combustion control circuit that can indicate an abnormality with only slight circuit changes.

[Structure of the invention] (Means for solving the problem) In order to achieve the above object, the present invention provides combustion control using a microcomputer that checks the presence of flame by a flame detection circuit and controls the opening and closing of the gas main valve. In the circuit, when the microcomputer is in a normal operating state, there is a monostable multiplier that derives continuous output, a power supply circuit that is controlled on and off by the output of the monostable multiplier, and an energization state of the power supply circuit that is displayed. A switching circuit bypasses the power lamp circuit and can display an on/off signal depending on the nature of the abnormality in response to an abnormality processing program from a microcomputer.

(Function) When operating normally, the output of the monostable multi is maintained in the "H" state by pulses at predetermined time intervals in the control program, the switching transistor is turned on, and the power lamp is turned on. are doing. Furthermore, when the microcomputer becomes abnormal, a switching circuit provided in parallel with the power lamp circuit is turned on and off based on the output from the blinking processing program, thereby causing the power lamp to blink.

(Example) An example will be described below with reference to the drawings. FIG. 2 is a configuration diagram of one embodiment of the combustion control circuit according to the present invention. In FIG. 2, the same symbols as in FIG. 1 have the same functions as those shown in FIG.
Therefore, in this embodiment, only the different parts will be explained.

In Figure 2, the switching transistor
The collector of TR1 is connected to the power lamp LED1 and the combustion lamp LED2 through the diode D1,
The other end of the power lamp is grounded, and the other end of the combustion lamp is connected to the output end of the inverter 7. Transistor TR2 has its base connected to port P _B of the microcomputer, which will be described later, and its emitter connected to ground.
Furthermore, the collector is connected to the base of transistor TR3. On the other hand, the base and emitter of the transistor TR3 are connected through a resistor _R7 , and this connection point is connected to the power source E, and the collector is connected to the output side of the diode D1. That is, transistor TR2
The power lamp LED1 is configured to blink by a so-called short circuit consisting of the TR3 and TR3. In addition, port P _B of the microcomputer
is an output terminal at the time of an abnormality, and in this case, by writing a blinking processing program in the abnormality processing routine, the transistor TR2 can be controlled to turn on and off. The other configurations are the same as in FIG. 1.

Next, the operation will be explained. First, the operations at startup and operation are similar to those shown in FIG. 1 described above. Therefore, at the time of reset, all ports are at the "H" level, and monostable multi (watch dog timer) 3 is at the "L" level, so the output of the inverter 10 is at the "H" level. Gatsute switching transistor TR1
is turned off, and both the combustion lamp LED2 and the power lamp LED1 are turned off. Next, when the reset of the microcomputer is completed and normal operation starts, the output of the monostable multi 3 goes to the "H" level, the output of the inverter 10 goes to the "L" level, and the switching transistor TR1 is turned on. Then, power supply E → switching transistor TR1 →
Power lamp LED through diode D1 circuit
1 lights up. When a combustion command is issued from the microcomputer, the port P ₀ goes to the "H" level, and the output of the inverter 7 goes to the "L" level, which energizes the excitation coil GV1 of the gas main valve, and the combustion lamp LED 2 is connected via the diode D1. lights up. This is a series of operations from startup to combustion.

Next, when an abnormality occurs, as already explained, the output of the monostable multi (watch dog timer) 3 becomes "L" level, the output of the inverter 10 becomes "H" level, and the switching transistor TR1 is turned off. shall be. In this case, port P ₀ is “L”
level, the output of the inverter 7 becomes the "H" level, the energization of the excitation coil GV1 of the gas main valve is released, and the combustion lamp LED2 is turned off. In this case, in order to start the abnormality processing routine, the program controls transistor TR2 by the flashing processing program from port P _B , and therefore, by the circuit of transistors TR2 and TR3,
The power lamp LED1 is turned on and off and starts blinking.

[Effects of the invention] As explained above, according to the invention, a bypass is provided for the power lamp circuit, and the power lamp circuit is turned on and off by outputting a flashing processing program when the microcomputer is abnormal. Therefore, we developed a combustion control circuit that allows the power lamp to blink with only a slight circuit change without increasing the number of cables between the water heater and the controller, and also allows the power lamp to be used as an error indicator lamp. Can be provided.

[Brief explanation of the drawing]

FIG. 1 is a combustion control circuit diagram previously proposed by the applicant, and FIG. 2 is a configuration diagram of an embodiment of the combustion control circuit according to the present invention. 1...Flame detection circuit, 2...Microcomputer, 3...Monostable multi (watch dog timer), 4-10...Logic circuit, GV1...Gas main valve excitation circuit, GV2...Gas auxiliary Excitation circuit, GV3...Ignition coil excitation circuit, TR1~
TR3...transistor, LED1...power lamp, LED2...combustion lamp.

Claims (1)

[Scope of utility model registration request] In a combustion control circuit using a microcomputer that controls the opening and closing of a gas main valve by confirming the presence of a flame using a flame detection circuit, a monostable multi-computer that derives a continuous output when the microcomputer is in a normal operating state, and a monostable A power supply circuit that is controlled on and off by the output of a stable multi-channel power supply, a power supply lamp that displays the energization state of the power supply circuit, and a power supply lamp that bypasses the power supply lamp circuit and responds to an abnormality processing program from a microcomputer. A combustion control circuit characterized by being equipped with a switching circuit that can display an on/off signal depending on the nature of the abnormality.