JPH0545974B2 - - Google Patents

Description

Detailed Description of the Invention The present invention provides a method for setting the constant voltage circuit where the input voltage of the constant voltage circuit decreases due to a power outage, and the output voltage of the constant voltage circuit is higher than the lower limit of the operation guaranteed voltage of the electronic control circuit. The present invention relates to a program control device that provides a reset signal to the reset terminal of the electronic control circuit when the voltage becomes less than the output voltage.

Conventionally, an initialization circuit that resets an electronic control device when the power is turned on detects the input voltage of a constant voltage circuit, and when it detects a predetermined voltage that is slightly lower than the set voltage of the constant voltage circuit when the power is turned on, it triggers a switch, for example. The switching transistor is activated to start charging the capacitor of the time constant circuit, and the voltage generated between the terminals of this capacitor is supplied to the reset terminal of the electronic control circuit. The electronic control circuit remains in a reset state for a predetermined period of time until the lower threshold level of the reset terminal of the circuit is exceeded. However, with this configuration, it takes a certain amount of time for the capacitor in the time constant circuit to discharge after the power is turned off, so if the power is turned on again after a short power cut, the voltage across the terminals of the capacitor immediately after the power is turned off again. may already exceed the lower limit threshold level of the reset terminal of the electronic control circuit, and in this case there is a drawback that the electronic control circuit is not reset and malfunctions occur.

The present invention has been made in view of the above circumstances, and its purpose is to provide an initialization circuit that can reliably reset the electronic control circuit even when the power is turned on after being turned off for a short time, thereby preventing malfunctions. There is no program to provide a control device.

An embodiment in which the present invention is applied to an oven will be described below with reference to the drawings. 1 and 2 are AC power terminals, 3 is a heater as a load installed in the oven body 4, and 5 is an operation switch, which is connected to a normally closed switch 6, normally open switches 7, 8, and normally open switches 9, 10. Become. Although not shown, the operation switch 5 includes, for example, a first push button that operates the normally closed switch 6, a second push button that operates the normally open switches 7 and 9 in conjunction, and a normally open switch 8 and 10. The switches 6 to 10 operate only while each push button is operated, and return to a steady state when the operation is completed. Inside the operating switch 5, one end of each of the normally open switches 7 and 8 is connected to one end of the normally closed switch 6, and the other end of each of the normally open switches 7 and 8 and one end of each of the normally open switches 9 and 10 are connected in common. is connected to. Then, the other end of the normally closed switch 6 is connected to the power supply terminal 2, and the normally open switch 7 is connected to the power terminal 2.
A common connection point of 1 to 10 is connected to one end of a bidirectional three-terminal thyristor (hereinafter referred to as a triax) 12 as a control element via a power line 11, and the other end of the triax 12 is connected via a heater 3 and a power line 13. and connect it to power terminal 1. 14 is a DC power supply circuit, the primary coil 15a of the transformer 15 is connected between the power lines 11 and 13, the secondary coil 1515b of this transformer is connected between the input terminals 16a and 16b of the bridge rectifier circuit 16, and the A smoothing capacitor 17 is connected between the plus and minus output terminals 16c and 16d of the bridge rectifier circuit 16, and the minus output terminal 16d is grounded. 18 is a constant voltage circuit, and NPN type power transistor 19
The collector of is connected to the positive output terminal 16c of the bridge rectifier circuit 16 via the positive power supply line 16A, and the cathode of a constant voltage diode 20 for generating a reference voltage is connected to the base, and the anode of the constant voltage diode 20 is connected to the negative power supply. It is connected to the negative output terminal 16d of the bridge rectifier circuit 16 via the line 16B, and maintains the output voltage _V1 between the emitter of the transistor 19 and the negative power supply line 16B at a predetermined constant voltage.
The emitter 9 is connected to the power supply line 11 to have the same potential. Reference numeral 22 is an electronic control circuit that includes a microcomputer mainly based on, for example, an LSI. One of the stored control programs is selected and executed by a selection signal, and its positive power supply terminal 22a is connected to the emitter of the transistor 19, and its negative power terminal 22d is connected to the negative power supply terminal 22d. Connect to the power supply line 16B, connect the first selection terminal 22j to the other end of the normally open switch 9, and connect the second selection terminal 22j to the other end of the normally open switch 9.
k is connected to the other end of the normally open switch 10, the clock input terminal 22c is branched into two, one is connected to one end of the secondary coil 15b of the transformer 15 via the resistor 23, and the other is connected to the negative terminal via the capacitor 24. It is connected to the power supply line 16B. 25 is an initialization circuit for giving a reset signal to the reset terminal 22r of the electronic control circuit 22, and the cathode of a constant voltage diode 26 serving as a voltage detection circuit whose anode is connected to the negative power supply line 16B is connected to the positive power supply through a resistor 27. At the same time, connect the cathode of the constant voltage diode 26 to the base of the PNP type transistor 28 via the resistor 29, connect the emitter of the transistor 28 to the positive power supply line 16A, and connect the collector of the transistor 28 to the reset terminal 22r. and the negative power supply line 1 via the resistor 30.
Connected to 6B. The first and second output terminals O ₁ and O ₂ of the electronic control circuit 22 are designed to output output signals as described later, and the drive circuit is connected to the first output terminal O ₁ via a resistor 31. Connect the base of NPN type transistor 32 as , and connect it to the second output terminal O ₂ through resistor 33
The base of the NPN type transistor 34 is connected, the collector of the transistor 32 is connected to the gate of the triac 12 via the resistor 35, and the emitters of the transistors 32 and 34 are connected to each other to form an NPN type transistor 36 for switching. The emitter of the transistor 36 is grounded, and the base is connected to the collector of the transistor 28 of the initialization circuit 25 via a resistor 37. 38 is a relay as a second power-on circuit, and the relay contact 38a is connected to normally open switches 7 and 8.
One end of the relay coil 38b is connected to the power supply line 11, and the other end is connected to the collector of the transistor 34. 39 is a thermistor that detects the temperature inside the oven main body 4;
Connect one end of this to the power supply line 11, and the other end to the resistor 4.
It is grounded via 0. 41 is an A-D converter that converts an analog signal into a digital signal, and its input terminal 41a is connected to a thermistor 39 and a resistor 40.
The output terminal 41b is connected to the input terminal 22i of the electronic control circuit 22. That is, the A-D converter 41 converts the voltage, which is an analog signal, generated between both ends of the resistor 40 into a digital signal, and the resistance value of the thermistor 39 changes in accordance with the temperature change inside the oven main body 4. resistance 40
Since the voltage between both ends changes, the digital signal output to the output terminal 41b of the AD converter 41 changes in accordance with this voltage change.

Next, the effects of this embodiment configured as described above will be explained with reference to the timing diagram shown in FIG. 2. In FIG. Indicates on/off, second
Figure c shows the voltage change, Figure 2 d and e show the input/output signals of each input/output terminal of the electronic control circuit 22, which are indicated by the same symbols as in Figure 1, and Figure 2 f shows the relay 3.
8 indicates on/off of the relay contact 38a, and the second
Figure g shows the read timing of input signals in program selection of the electronic control circuit 22, Figure 2 h shows a set temperature program which is one of the control programs stored in the electronic control circuit 22;
Figure i shows temperature changes within the oven body 4.

Now, at time _t1 , push the operation switch 5, for example, normally open switches 7 and 9, as shown in FIG.
When it is closed (turned on) by pressing the button, the power line 11 is connected to the power terminal 2 via the normally open switch 7, and AC voltage is applied between the power lines 11 and 13, so that the transformer 15 is turned on. The low voltage alternating current that is stepped down is converted into direct current by the bridge rectifier circuit 16, and the positive and negative power lines 16A,
16B, but this power supply line 16A, 1
Voltage V ₀ between 6B and capacitor 17 when the power is turned on
, the charge gradually increases over time as shown by the solid line in Figure 2c. And constant voltage circuit 1
The output voltage _V1 of 8 is the voltage of _V0 , which is the reset release voltage.
When the voltage is lower than Vr, the voltage regulator diode 20 is cut off, so the voltage rises slightly lower than the voltage V ₀ following the voltage V ₀ , but when the voltage V ₀ reaches Vr, the voltage regulator diode 20 breaks over and becomes conductive, changing and adjusting the base current of transistor 19, so when voltage V ₀ is greater than Vr, voltage V ₁ is stabilized at a constant voltage V ₁ r slightly lower than Vr. be done. On the other hand, the constant voltage diode 26 of the initialization circuit 25 has a voltage V ₀ of
When it is detected that Vr has been reached (time t ₂ ), it breaks over and becomes conductive, turning on the transistor 28. Therefore, the reset terminal 22r of the electronic control circuit 22 is reset from time t ₁ as shown in FIG. 2d. It is maintained at a low level for t ₂ and rises to a high level at time t ₂ . Further, the electronic control circuit 22 has upper and lower operating voltage limits determined so that it can operate normally when the terminal voltage between the positive and negative power terminals 22s and 22d is within several percent above and below _V1r . Therefore, when the voltage V ₁ reaches its lower limit guaranteed operation voltage Vrmin (time t ₂ ′)
From then until the voltage V ₁ reaches V ₁ r (set voltage of the constant voltage circuit 18) (time t ₂ ), the reset terminal 2 is
The low level signal (reset signal) applied to 2r puts it into a reset state, clears the states of internal registers, etc., and outputs to output terminals _O1 and _O2 become low level. Now, although the normally open switch 9 has been closed since time _t1 , the first selection terminal 22j of the electronic control circuit 22 is connected to the second selection terminal 22j since the reset of the electronic control circuit 22 is completed at time _t2 . As shown in Fig. g, the reading ends at time _t3 , which is a predetermined time elapsed from time _t2 . That is, the electronic control circuit 22 reads the selection signal, for example, twice between time t ₂ and time t ₃ , determines that the reading results match, finishes the reading, and cancels the reading due to causes such as switch chattering. I try not to make any mistakes. Then time t ₃
The electronic control circuit 22 starts reading out one of the two stored control programs based on the selection signal that has been read out. Timing progression of the electronic control circuit 22 after time _t2 is performed by counting the AC waveform applied to the clock terminal 22c of the electronic control circuit 22. Now, after the electronic control circuit 22 finishes reading the selection signal at time _t3 , after a predetermined period of time has elapsed (time _t4 ), the output terminal _O2 is changed to high level, the transistor 34 is turned on, and the time _t2 is reached. Since the transistor 36 is already turned on with its base changed to a high level (see FIG. 2d), the relay coil 38a of the relay 38 is energized through the transistors 34 and 36, and after a short period of time, the transistor 36 is turned on. When the time has elapsed (time _t4 '), the relay contact piece 38a is closed (on) (the period from time _t4 to time _t4 ' is the time required for switching the relay contact piece 38a). After the relay contact piece 38a is closed at time _t4 ' (time _t5 ), the second push button (not shown) of the operation switch 5 is released and the normally open switches 7 and 9 are closed. Even when the power supply line 11 is opened (off), the power supply line 11 continues to be connected to the power supply terminal 2 via the relay contact 38a, so that it is so-called self-maintained, and the electronic control circuit 22 continues to be supplied with power. On the other hand, at time _t4 , the set temperature program as shown in _FIG .
2 is turned on periodically, so the tri-attack 12
By grounding the gates of the transistors 32 and 36, the triac 12 is ignited and the heater 3 is energized to generate heat. Due to the heat generated by the heater 3, the temperature inside the oven body 4 rises as shown in FIG. is converted into a digital signal by the A-D converter 41 and sent to the electronic control circuit 2.
2 input terminal 22i. On the other hand, the electronic control circuit 22 constantly compares the temperature information given to the input terminal 22i with the temperature set in the temperature setting program and changes the timing of the firing pulse outputted to the output terminal _O1 . The amount of heat generated by the heater 3 is adjusted by controlling the phase. That is, when the temperature _T1 is read out from the temperature setting program at time _t4 as shown in FIG. 2h, the temperature inside the oven body 4 at that time is low as shown in FIG. Since the difference from the temperature T ₁ is large, the timing of the ignition pulse output to the output terminal O ₁ of the electronic control circuit 22 is set so that the heater 3 generates a high amount of heat. Then, after that, the oven body 4
When the temperature inside the heater 3 rises and the difference from the temperature _T1 decreases, the output terminal is
The timing of the ignition pulse output to O ₁ is changed, so that the temperature inside the oven body 4 reaches the set temperature.
T is set to ₁ . Then, over time the set temperature program changes the temperature from T ₁ to T ₂ (time t ₆ )
and from T ₂ to T ₃ (time t ₇ ),
In the same way as described above, the electronic control circuit 22 compares the set temperatures T ₂ and T ₃ with the temperature inside the oven and adjusts the amount of heat generated by the heater 3, so the temperature inside the oven main body 4 changes according to the set temperature program. controlled. In addition to the set temperature, the set temperature program also stores cooking end data, and when a predetermined period of time has elapsed from time _t4 and the cooking ends,
By setting the output of the output terminal _O2 to a low level and turning off the transistor 34, the current to the relay coil 38b is cut off and the relay contact piece 38a is operated to return (off), thereby turning off the heater 3 and the electronic control circuit 2.
The power supply to 2 is automatically cut off. Now, if you want to interrupt cooking in the middle, such as when you want to check the cooking status or add something to be cooked, you can manually turn off the power by pressing the first push button (not shown) of the normally closed switch 6 of the operation switch 5. can do. That is, for example, when the normally closed switch 6 is opened (off) at time t ₈ , the supply of AC power between the power lines 11 and 13 is cut off, so that the power line 16
The voltage V ₀ between A and 16B gradually decreases due to the discharge from the capacitor 17, and as shown in FIG. 2c, at time t ₉
It drops to Vr at . Then, as the constant voltage diode 26 is suddenly disconnected, the transistor 28 is suddenly disconnected, and the reset terminal 22r becomes low level and the transistor 36 is turned off, so that the relay coil 3 via the transistor 34
The power to 8b is cut off. As a result, the relay contact piece 38a is opened (turned off). Therefore, even if the press of the first push button of the operating switch 5 is released and the normally closed switch 6 is turned back on (turned on) after time t ₉ (time t ₁₀ ), the relay 38 will not operate again. Cooking is interrupted.

Now, the above explanation is about the operation when the normally closed switch 6 is manually turned off, but the same operation is performed even when the AC power supply is cut off due to a power outage. That is,
If a power outage occurs at time _t8 , the DC power supply circuit 14
As the output voltage of the voltage regulator gradually decreases, the input voltage _V0 of the voltage regulator circuit 18 reaches the reset release voltage Vr at time _t9 , but at this point, the voltage regulator diode 26, which is the voltage detection circuit, is gradually disconnected and reset is performed. When the terminal 22r becomes low level, the electronic control circuit 22
is reset. This means that the input voltage V ₀ of the constant voltage circuit 18 is the set voltage V ₁ of the constant voltage circuit 18.
When the output voltage of the constant voltage circuit 18 is slightly lower than the voltage that outputs r and is sufficiently higher than the lower limit value Vrmin of the guaranteed operation voltage of the electronic control circuit 22,
Electronic control circuit 22 may be reset. For this reason, even if the power outage is for a very short time and the power is re-energized slightly after time _t9 , the electronic control circuit 22
is reliably reset, and the electronic control circuit 22 is reliably prevented from malfunctioning due to a short power outage.

By the way, for example, set the normally open switches 7 and 9 to the time.
When it is closed at t ₁ , the output terminal O ₂ immediately becomes high level as shown by the two-dot chain line in Figure 2e, and the relay contact 38a is turned on as shown by the two-dot chain line in Figure 2f. Considering the case where the timing of the output of the electronic control circuit ₂₂ is set so that Although no problem occurs, the normally open switch 7 is turned off at time _t5 ' as shown by the two-dot chain line in Fig. 2b.
and 9 is turned on only for a short time so that it is turned off, the normally open switch 9 is opened before the time _t3 when the selection input terminal 22j of the electronic control circuit 22 completes reading the selection signal. As a result, the electronic control circuit 22 cannot read the selection signal and malfunctions. However, in this embodiment, the output terminal O ₂ changes to high level and the relay 38 is activated after reading the selection signal is completed, so there is no risk of malfunction. If the electronic control circuit 22 is turned on for a short period of time so as to be turned off at time _t5 ', the power to the electronic control circuit 22 is cut off at time _t5 ' and the operation is interrupted, so there is no risk of malfunction. If the operation time of the second push button of the operation switch 5 is too short as described above, the operation may be repeated from the beginning.

In addition, the electronic control circuit 22 has a voltage between the positive and negative power terminals 22s and 22d that is a guaranteed operation voltage.
If _the voltage drops below Vrmin, the operation is unstable and a high level may be output to the output terminals O ₁ and O ₂ even if a reset signal is applied to the reset terminal _22r . The transistors 32 and 34 connected to the voltage V ₁ may turn on when the voltage V 1 is lower than Vrmin. That is, from time t ₁ to t ₂
and between times t ₉ and t ₁₀ ,
If the relay 38 is activated before time _t2 and the normally open switches 7 and 9 are operated for only a short period of time, the electronic control circuit 22 may malfunction, or the time may change.
If the relay 38 operates after t ₉ , the electronic control circuit 22 may be re-energized even if the normally closed switch 6 is opened, or the heater may be turned on between times t ₁ and t ₂ and between times t ₉ and t ₁₀ . This causes problems such as temporary energization. However, in this embodiment, the initialization circuit 2
Transistor 36 turned on by the output of 5
is provided so that the transistor 36 changes from time t ₁ to t ₂
Since the emitters of the transistors 32 _{and 34} are connected in series with the transistor ₃₆ , the emitters of the transistors 32 and 34 are connected in series between the times _t1 and _t2 and between the times t9 _{and t9} . From t ₁₀ to t 10 , the transistors 32 and 34 are inactive, so even if the output terminals O ₁ and O ₂ output a HI level, the relay 38 is energized or the gate of the triac 12 is not activated. No ignition signal is given, and the various malfunctions described above are reliably prevented.

In the above embodiment, the electronic control circuit 22 itself sets the timing from when the reset of the electronic control circuit 22 ends at time _t2 until time _t4 when the output terminal _O2 outputs a high level. ₄ , the relay coil 38b is started to be energized. For example, a delay circuit is provided in the initialization circuit 25, and the output from the delay circuit turns on and off the transistor 34, etc. It is also possible to omit the output terminal _O2 of the control circuit 22.

Further, in the above embodiment, for convenience of explanation, the operation and effect when the normally open switches 7 and 9 are closed have been explained, but the same operation and effect can be achieved when the normally open switches 8 and 10 are closed. Of course, a different temperature setting program is read out.

Further, in the above-mentioned embodiment, the case where the voltage regulator diode 26 is provided as the voltage detection circuit is explained as an example, but the same effect can be obtained even if a NiCd battery is provided in place of the voltage regulator diode 26. I do.

As is clear from the above description, the present invention is a program control device that is equipped with an initialization circuit that can reliably reset the electronic control circuit even when the power is turned on again after being turned off for a short time, and that does not cause malfunction. can be provided.

[Brief explanation of drawings]

The drawings show an embodiment in which the present invention is applied to an oven device, and FIG. 1 is a circuit diagram and FIG. 2 is a timing diagram. In the drawing, 3 is a heater (load), 5 is an operation switch, 7 and 8 are normally open switches (first power supply circuit), 9 and 10 are normally open switches (selection circuit), 14
is a DC power supply circuit, 18 is a constant voltage circuit, 2 is an electronic control circuit, 25 is an initialization circuit, 26 is a constant voltage diode (voltage detection circuit), 38 is a relay (second power supply circuit), 41 is A-D It is a converter.

Claims (1)

[Claims] 1. A control element for controlling a load, and an electronic control circuit configured to include a microcomputer for controlling the control element via a drive circuit connected to the control element; a constant voltage circuit that converts an input voltage into a constant set voltage higher than a lower limit of guaranteed operation voltage of the electronic control circuit and supplies the same to the electronic control circuit; and a voltage detection circuit that detects the input voltage of the constant voltage circuit. When the input voltage starts to be supplied, a reset signal is applied to the reset terminal of the electronic control circuit until the input voltage reaches a reset release voltage higher than the lower limit of the operation guaranteed voltage, and the input voltage is an initialization circuit that applies a reset signal to the reset terminal of the electronic control circuit when the input voltage becomes less than the reset release voltage, and a switching circuit that stops the operation of the drive circuit by the reset signal of the initialization circuit. A program control device comprising: