JPS60132202A - Control device - Google Patents

Abstract

PURPOSE:To prevent a danger caused by a thermal runaway of a microcomputer etc., by using a latching circuit by a transistor. CONSTITUTION:A transistor Q3 turns on and off a load RYA for performing a fail safe. A latching circuit is constituted of transistors Q1, Q2 and a start switch SWS is provided between a trigger input terminal C of the latching circuit and an output terminal 17 of a microcomputer 13. A power source of the latching circuit is supplied from output terminals A, VSS. When heating is ended, when an output terminal 23 of the microcomputer is made low, namely, the transistor Q3 is turned off, both Q1 and Q2 turn off and the latch is released. At the same time, a current of the RYA is also obstructed by Q2. Also, microcomputer runs away, and even in case its output terminals 23, 24 and 17 all turn on, Q2 does not turn on, therefore, the load RYA is not energized, and a fail safe is operated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applicable to a device operated by a user, such as a microwave oven or a household type C oven, and which uses a microcomputer.
The present invention relates to a safety circuit that prevents runaway logic circuits in equipment controlled by such logic circuits.

Conventional structure 11y and its problems Conventional logic circuitsFor example, in a microwave oven controlled by a microcomputer (hereinafter referred to as microcomputer), a relay is generally driven by the output terminal of the microcomputer, and the heating heat source ( magnetron) is energized.

However, if the logic circuit of a microcomputer or the like goes out of control due to noise or the like, there is a risk that the output will be lost and overheating will start on its own. In contrast, conventionally, a circuit using a cyrisk as shown in FIG. 1 has been used. dl, to explain the operation of the conventional example shown in Fig. 1, in Fig. 1, 1 is a logic circuit, which is composed of a microcomputer, and its outputs 2゜3.4 are the gate of Cyrisk SE, 1-Runnut Q4, respectively. is connected to the base of the l-ranginuta Q5. Further, one end of the Cyrisk SE is connected as a load to a coil RYA of a relay that switches on and off the power to the heating heat source, and the other end is connected to the collector of Q5. Now, after the microcomputer is given necessary human power such as heating time from an input section (not shown), it turns on point A as shown in FIG. turns on. After this, when the user presses the start switch SWS to start heating (b), the entire SWS is passed through terminal 2, which is already on, and the thyristor S'E is turned on.
-Rig (c), a current flows through RyA-5E-resistor R1-Q4, and SE maintains the on state. However, the value of the resistor R1 is determined so that the current in this lhi K Id-1 is such that the contact of the relay RyA does not close. After that (or at the same time), when terminal 4 is turned on (b), Q5 is also turned on, ←j→RyA is energized, its contact is completely closed, and power is supplied to the heating heat source.

In this way, in the conventional example, unless the SWS is closed, that is, unless the user performs an operation to start heating, even in a runaway state where all three outputs of the microcomputer are turned on, It is safe because RyA is not excited.

However, even the conventional grid diagram has the following drawbacks.

1. If a short circuit failure occurs in Q4, the operation of output terminal 3 of the microcomputer (determination 1 of whether there is a heating time input from the operation panel)
After the analysis, the SE is retained and discarded regardless of the output (output).

2. If Q4 has a short-circuit failure, it is impossible to turn off the SIRISK SE, which has been damaged by the 1-rigger once.

3. The holding current of Cyrisk SE is comparatively large (
3 to 8mA), so it does not save energy.

4. Cyrisk is more expensive than one I-lumf and two, so the safety circuit needs to be reduced in height.

5. There are unstable factors such as thyristor triggers malfunctioning due to noise, etc., and self-triggering when the sensitivity becomes high.

There are problems such as: 'Aspects of the Invention 11 The present invention solves all of the above-mentioned conventional drawbacks by providing a latch circuit using a 1-range nut and using a microcomputer 4:1. '
Our aim is to provide an inexpensive and reliable circuit that prevents the risk of heating occurring automatically due to runaway of the y.
'J.

Structure of the Invention In order to achieve the above objective ll'J, the safety circuit of the whitening 1 device of the present invention includes a 1-run resistor Q3 that turns on the load (relay) to be fail-safed, and two 1-run risks Q1. , Q2, and a 1-rigger input for keeping the transistor Q2 on, and also have a configuration in which the latch voltages ij', j of the U-Sochi circuit are obtained from the output terminal of the microcomputer. It has a configuration in which KniJ Q3 and 02 are connected in series through a diode, and even if the microcomputer 1 goes out of control, heating will not start unless the operator presses the start switch 1, which is a safe operation.

2゜In the explanation of the conventional example, it has the effect of eliminating all unnecessary public telephone calls.

3. Detailed description of the invention The following is an example of the present invention based on the drawings - C dazzling 1
I will clarify. FIG. 3 shows operation E1 of the safety circuit using the present invention;
It is the same. FIG. 5 shows a more detailed embodiment in which the present invention is applied to flj' control of a microwave oven at home. In Figure 5, 5 is the power outlet, 6 is the heating chamber 1! α Lighting lamp, 7 is a door switch that operates in conjunction with the opening and closing of the heating chamber door, 8 is also for Shinblade 1.
In the figure, the door opens with the switch and the pancreas is exposed.”
C, 9il-i relay R3'A opens and closes by coil ``11Lilj; Lil-18 points, 10 is ji'
ii II: l-lance, i, lu-macneto 1-1
12 is a lamp relay contact which is opened and closed by relay RyB coil/l/Ic. Now, with the normal lamp relay contact 12 closed and the door closed, relay J"i
When p, l:j, 9 is closed, the magnetron 11 starts oscillating and heating is performed by 4T.

13B is the power supply for the i+ control circuit, and supplies power to the production circuit 1 shown in FIG. Reference numeral 13 denotes a logic circuit, which is composed of a P-channel horizontal one MO5 microcontroller.

14 is a display (,',;, 15 is an operation switch 11, which constitutes an operation section.
Funjista Q3. It is sold to a concubine in 1] so that it is energized when two of Q2 are turned on. Ql
, Q2. The circuit consisting of the transistor Q3 is the circuit according to the present invention. The operation section 15 is provided with a start switch 16 for starting heating manually. Now, in order to read the input from the operating section, the microcomputer 13 sequentially turns on the output terminals 17 and 18, and reads the human power at the input terminals 19, 20, 21 and 22 at that time, thereby controlling the switch group. It is possible to know which switch has been pressed. When the necessary operation input to start heating, such as heating time and heating output, is received, the microcomputer turns on the output terminal 23 (high level). 1
-Runcista Q1. Q2゜The third explanation of the dynamic f1 of Q3 is
It is shown in the figure. In order to make the operation of FIG. 5 easier to understand, unnecessary components such as capacitors and diodes are omitted.

This figure indicates the same thing as the F:isS diagram with the same symbol.

When terminal 23 is turned on, the MOS l inside the microcontroller
- When the run transistor 23' is turned on, a voltage source is supplied from Vdd. This is shown by the verse point (a) in Figure 4. Now, the start switch is marked 5VVS (16) in No. 31 No. 1, and when it is pressed (Fig. 4 (B)), the output terminal of the microcomputer 13 is 1
Since the transistor Q2 is connected so that current flows from the transistor Q2, the transistor Q2 is turned on.

(Figure 4 (c)). Transinuta Q1 and Q2un531
m, as shown in Figure 5, each collector is connected to its respective base, so that the base of Q2 and Ql
When the current at point XK, which is connected to the collector of
2, it is pulled out and Ql is also turned on. Then,
Since the base'+IU flow is supplied from the collector of Ql to Q2, Q2 is turned on (1 held 4, so the point C(d
, Q, is the 1-rigger input terminal of the child circuit consisting of 1 and Q2, and is a small latch.

fAll, microcomputer output terminal 'i'
23 B salary]9. I'm here. Here 5WS (16
) is opened (see FIG. 4), transistors Q1 and Q2 remain on. Here, after appropriate logic separation 1, the microcomputer turns on the output terminal 24 of the output transistor 24'.
(Fig. 4 (e)), the base current flows through the 1 to Q3 whose bases are connected to their output terminals, passes through the diode L11, and the emitter of Q3- flows to the collector of 2.
Since it is connected, transinutor Q3 is also turned on, and its load, relay coil yvHyA, is also excited. Therefore, the power supply relay contact 9 of No. 51 No. 1 is also started with a closing force of 1''.

[At the end of the first heat, the output terminal of the microcomputer is LOW, that is, the output transition y,
If it is set to 23'f/(-), I.Lancystar Ql
Since the latch C source for the Q2 launch circuit is no longer supplied, both Ql and Q2 are turned off and the latch is released. At the same time, the coil current of 1-1yA is also blocked by Q2.
i, so contact 9 is also opened and heating is also stopped.

However, in order to temporarily open the contact 9 for controlling the heating output, etc., it is possible to turn only the output 24 on and off.

Now, even if the microcomputer goes out of control and its output terminals 2G and 17.24 are both turned on, transistor Q2 is not turned on, so the relay coil/
l/RyA is not excited. Therefore, unless the user presses the start switch 16 to start heating, heating will not start, so W' is complete.

Also, even if transistor Q1 has a short circuit failure,
If the output 23 of the microcomputer is not turned on, even if the start switch 16 is pressed, Q1Q2
Since the latch operation (1-d) of the launch circuit is no longer performed, there is safety in that heating does not continue.This point greatly improves the drawback of the conventional example shown in Fig. 1. In 11-1, if the transistor Q4 is short-circuited, there is a drawback that when the start switch SWS is pressed, the xyrinutor SF remains on.

In addition, in the conventional example shown in FIG.
J7 circuit failure causes the relay to be energized by simply pressing the start switch even if the microcomputer is operating normally, whereas in the case of the 31st embodiment of the present invention, the and 92 are in series, so the microcomputer must not turn on output 23.
The 9th relay RyA has been improved in terms of safety by not being energized.

In the case of the conventional example shown in FIG. 1, there are a total of three active components, one thyristor and two transistors, but in this embodiment, there are three transistors. Although the number of pieces is the same, Zairinuta has the effect that Core 1 is cheaper because it has 1 High Sen.

In order to match the P-channel microcomputer, we have installed one PNP l/lancistor (Ql) and one NP
Although an example is shown in which N'l-972722 (Q2, Q3) are used, the combination can be easily changed to suit the driver at the output end of the microcomputer.

Effects of the Invention The safety circuit of the control device of the present invention constitutes a latch circuit with two transistors that are latched by operation of a start switch, and also connects at least one of the latch circuits with another 1-run nut connected in series with the load. Since it has a configuration in which two transistors and a diode are connected in series, and the latch source for the MiJ latch circuit is supplied from the output of the microcomputer, it has the effects listed in 1 below. .

Even if a short-circuit failure occurs in the 1, l-run transistor Q1, heating will not start spontaneously if the logic circuit is normal.

2. Since the components are composed of transistors, it is simple and easy to integrate and reduce costs.

Historically, when compared with the conventional example shown in Figure 1, it has the following effects.

3. Launch floor transistor Q in FIGS. 3 and 5 of the present invention corresponding to launch holding transistor Q4 in FIG. 1
Even if 1 is short-circuited, the latch cannot be configured unless the microcomputer turns on the output, so the current flowing through the load will not be latched, resulting in high safety.

4. Similarly, even if the transistor Q1 is short-circuited during operation, the launch can be canceled by turning off the output of the microcomputer, so safety is high.

5. Since no Zyristor is used to hold the launch, the current is just enough to turn on all two transistors (2 mA or less)
This saves energy.

6.1- Since only Runcista is used, it is cheaper than using Sirinuta.

7. Since it uses only transistors, it is easy to wire noise prevention capacitors, which are strong and wasteful due to noise.

It has effects such as:

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the safety circuit of a conventional microwave oven, and FIG. 2 is a time chart diagram of the circuit shown in FIG. Fig. 3 is a circuit diagram of a main part of a safety circuit according to an embodiment of the present invention, Fig. 4 is a time chart 1 of the same embodiment, and Fig. 5 is a circuit diagram of a main part of a safety circuit according to an embodiment of the present invention. FIG. 9.-1----Power switch relay contact, f(yA-
−−1−−−Coil of power switch relay, 1) l−=−
--1-diode, i i --effect 11 thermal heat source, 15
--------Operation unit, ia --------(s ws
)-11----Start switch. Name of agent: Patent attorney Kazuo Nakao and 1 other person Figure 1 Figure 2 A Figure 3 Figure 4

Claims (1)

[Claims] (11tlT1) 1i141 A power on/off relay that opens and closes energization to the target, an operation unit that sets the energization time, etc., a start switch that instructs to start energization, and these ?l!'I
A logic circuit such as a microcomputer that controls the 6i
a transistor Q3 whose load is a power supply switching relay written in J;
At least two transistors Q1. a latch circuit consisting of transistors Q2 and having a trigger input terminal for turning on at least one transistor Q2, and the i'+iJ start switch is connected to the niJ rough launch circuit trigger input terminal. , I) 11th I-Langinuta Q
The base of No. 3 is connected to one output terminal of the logic circuit, and the transistor Q3 of No. 011 is connected in series with the transistor Q2 via a diode. A safety circuit of the control device, in which the l'li source is supplied from the output of the logic circuit.