JPH087635B2 - Hot water temperature control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention prevents flickering (luminous flux flickering) from occurring in the brightness of a lighting device when a voltage fluctuation with a short cycle such as several times per second occurs. The present invention relates to a hot water temperature control device such as a suppressed water heater.

[Technical background of the invention]

In the temperature control of electric water heaters and electric water heaters (instantaneous) used in general households, the temperature detection sensor usually detects the hot water temperature, and the temperature has a high or low difference with respect to a predetermined temperature. In this case, the energization of the heater is controlled by a switching element such as a triac to maintain the hot water temperature at a predetermined temperature. In this case, if hot water is frequently used, the switching elements are turned on and off in a proportional manner to control the energization of the heater, which causes the voltage to fluctuate irregularly, which may cause a lighting fixture or TV set to change. A "flickering" of brightness occurs for the image receiver, which gives discomfort to the eyes of the viewer. This flicker has a different "flickering feeling" depending on the extent to which the magnitude of the power supply voltage changes and the repetition frequency or frequency.

Fig. 5 shows a flicker luminosity curve that is a standard for determining the presence or absence of flickering. This is commonly used by electric power companies. The higher the frequency of flickering sensitivity coefficient in the figure, the easier it is to perceive flickering and the illumination flickering. Will cause complaints and will cause discomfort.

[Problems of background technology]

Now, for example, if hot water is frequently used by a water heater or an instant water heater used in general households, the temperature control of the hot water is, for example, zero cross control (this control sends a pulse signal to the power supply terminal). When the output is performed in synchronization with the zero point of the input power supply voltage), flickering due to voltage fluctuation has the highest flicker sensitivity coefficient in FIG.
The frequency may reach 10 Hz, which causes a serious obstacle to the normal use of electricity.

On the other hand, in each electric power company, if the flicker sensitivity coefficient is 0.4 or less, it is generally accepted without judging it as a flickering, and this is when the voltage fluctuation is 2 Hz or less or 25 Hz or more in FIG. But it is acceptable as well. This is because flickering actually occurs even within the allowable range, but the human eye does not feel the flicker to that extent as unpleasant. However, it is necessary to take appropriate measures against flickers in a range that is uncomfortable, and when controlling the hot water temperature of a water heater or the like at zero-cross, the heater used for the water heater etc. is turned off once and then turned on again. Time to 2H
It is only necessary to turn on the heater for a time (0.5 to 0.04 seconds) corresponding to z to 25 Hz.

In addition, when an AC voltage is applied between the anode and cathode of the silicon-controlled rectifier and a current is applied to the gate of the silicon-controlled rectifier to change the ignition phase, the magnitude of the rectified voltage increases. It is also proposed that the flickering can be controlled, that is, a method of suppressing flickering by controlling the phase of the AC voltage. When controlling the phase of an AC voltage, flickers are generally less likely to occur, but electrical noise is likely to occur, and a special electrical circuit or the like to prevent this noise may be required or the phase may be delayed. Adopting the phase control method of the AC voltage in order to prevent the above, not only raises the price of electric equipment, but also causes problems such as adversely affecting the equipment itself, and is used for temperature control of water heaters and the like. There were few things.

[Object of the Invention]

In view of the above problems, the present invention has a simple configuration of flickering suppressing function that enables smooth control of hot water temperature even if flickering that is likely to occur when performing zero-cross control of hot water temperature in a water heater or the like is suppressed. It is to provide a hot water temperature control device provided with.

[Means for solving problems]

A temperature control circuit configured to control the energization of the heater by incorporating a reference voltage setting means and a control IC formed so that the output of the drive circuit can be pushed or pulled in parallel, and a reference voltage incorporated in the temperature control circuit. A zero-cross detection circuit configured to output a pulse signal to the control IC in synchronization with the zero point of the power supply voltage connected to the generation means and input to the power supply terminal, and the reference voltage output from the reference voltage setting means. In the middle of the energizing circuit supplied to the zero-cross detection circuit, a monostable multivibrator and a CR constant setting for insertion and connection between the terminal of the monostable multivibrator and the energizing circuit supplying the reference voltage to the zero-cross detection circuit. A flicker prevention circuit including a resistor and a capacitor; Depending on the output, the temperature control circuit does not output the gate signal for turning on the switching element for a time corresponding to 2 to 25 Hz, so that the occurrence of flickers can be suppressed without impairing the control of the hot water temperature. Characterize.

Example of Invention

The present invention will be described below with reference to FIGS. 1 to 4 by using an example of an electric instant water heater.

In FIG. 1, the hot water temperature control device 1 of the present invention is roughly classified into a zero cross detection circuit 11 and a flickering prevention circuit 21.
And the temperature control circuit 31. Before describing the configuration of each circuit, a control IC for a switching regulator power supply (hereinafter referred to as control IC ₃₎ which is inserted and connected to a temperature control circuit 31 which plays the most important role in the present invention, is called Texas IC. "T
The schematic structure of TL494M manufactured by "EXAS INSTRUMENT" will be described with reference to FIG.

32 is a reference voltage generator, which controls the reference voltage Vref
The oscillator 33, the first and second comparators 34 and 35, and the control circuit provided in the control IC ₃ are supplied to the zero-cross detection circuit 11 and the flickering prevention circuit 21 outside the IC _3.
It is supplied to the 36 as a stable operating power supply, and this reference voltage Vr
When 7 to 40V DC is supplied to the input terminal VIN side, ef is 5 ± 0.025V DC from the output terminal Vout side of the reference voltage.
It outputs Vref in a stable state.
The first comparator 34 has an offset voltage Vr (for example, 110 mv) on its inverting input terminal side, and its non-inverting input terminal is connected to one terminal CT of the oscillator 33. When the terminal CT voltage of the oscillator 33 is lower than the inverting input voltage of the first comparator 34, an "L" level signal is output from the output terminal of the comparator 34. That is, if the offset voltage Vr is 110 mv, D
When the T terminal is connected to the ground, when it is lower than 110 mv, the signal of “L” level is output from the output terminal of the comparator 34. Next, the second comparator 35 has its non-inverting input terminal connected to the terminal CT of the oscillator 33, and its inverting input terminal is connected to the wired OR output terminal W of the output terminals of the error amplifiers 37 and 38. The voltage input from the terminal CT of
If the voltage at the CT terminal side is larger than the wired OR output voltage by comparing with the voltage at the wired OR output terminal W,
An "H" level signal is output from the output terminal of the second comparator 35. The wired OR output end is a control IC ₃
It is also connected to the feed back terminal FB of.

Next, the output control circuit 36 will be described. The output terminal of the AND gate 39 to which the output terminals of the first and second comparators 34 and 35 are connected is connected to the input terminal of the bistable circuit FF via the not gate 40. In addition to being connected, it is connected to one input end of a first gate circuit 41a composed of two AND gates 41, 41 '. The output terminal of the bistable circuit FF is connected to one input terminal of a second gate circuit 42a composed of two NAND gates 42 and 42 ', and the other input terminal of the second gate circuit 42a is controlled. It is connected to a control terminal OC for receiving signals output from other than IC ₃ , and the output end of the second gate circuit 42a is connected to the other input end of the first gate circuit 41a. . The output terminal of the first gate circuit 41a is connected to a drive circuit 43 composed of _two transistors T ₁ and T ₂ .

Then, "L" input from the output control terminal OC
Depending on the level or "H" level signal, the transistor T of the drive circuit 43 is passed through the first and second gate circuits 41a and 42a.
_1, Putsushiyupuru the on operation T ₂ (T ₁ and T ₂ are alternately repeated on operation) is selected to either of or parallel operation (both T ₁ and T ₂ is turned on). That is, when an "L" level signal is input to the control terminal OC, the output of the second gate circuit 42a becomes "H" level, so the output of the drive circuit 43 becomes a parallel operation output, and conversely to the OC terminal. When the "H" level signal is input, the second gate circuit
The output of 42a is an "L" level signal when the output from the bistable circuit FF is "H" level, and an "H" level signal when the output of the bistable circuit FF is "H" level. Is output, the output of the drive circuit 43 becomes push-pull.

The GND in Fig. 2 is the ground terminal of the control IC ₃ .

Next, an electric circuit of the hot water temperature control device having the flickering suppression function of the present invention shown in FIG. 3 will be described.

First, the zero-cross detection circuit 11 connects the AC input end of a diode bridge DB having diodes D _{1 to} D ₄ formed in a bridge circuit to the power supply terminal 2 via resistors R ₁ and R ₂ , and connects the diode bridge DB to the diode bridge DB. the DC output terminal connected to the base-emitter of the transistor Q _1, together with the base-emitter inserting a resistor R ₃ of the transistor Q _1, the reference voltage of the control IC ₃ collector via a resistor R ₄ Raw ware 3
2 is connected to the output terminal Vout, and a diode is connected between the collector of the transistor Q ₁ and the resistor R ₄ and the ground.
It is configured by inserting and connecting D ₅ and the resistor R ₅ in series, and the connection point Z between the resistors R ₄ and R ₅ becomes the output end of the zero-cross signal (pulse signal) and is connected to the terminal CT of the control IC ₃ , The voltage divided by the resistors R ₄ and R ₅ is sent to the control IC ₃ as a zero-cross signal. In addition,
In FIG. 3, the diode D ₆ has its anode connected to the connection point between the resistors R ₁ and R _2, and its cathode is the input terminal VIN of the control IC _3.
Directly connected to the transistor of the drive circuit 43
T _1, the collector C _1, C ₂ of T ₂ is connected via a resistor R _6.
A constant voltage diode ZD for protecting the control IC ₃ from abnormal voltage by keeping the voltage (about 40V) supplied to the control IC ₃ below a certain voltage between the cathode of the diode D ₆ and the ground. , And a smoothing capacitor C ₅ that reduces the pulsation of the current is connected in parallel, rectified by the diode D ₆ , and the direct current determined by the CR time constant of the resistor R ₁ and the smoothing capacitor C _5. (In this embodiment,
20V) is input to the input terminal VIN as the input voltage of the control IC ₃ .

Next, the flicker prevention circuit 21 adds a monostable multivibrator (hereinafter referred to as a monostable circuit) IC to the conduction circuit of the reference voltage Vref output from the output terminal Vout of the control IC _3.
It is constructed by inserting a ₂ and the transistor Q _3, wherein the monostable circuit IC _2, the reference voltage Vref of the control IC ₃ to the input terminal VIN is input, The terminal Rt, the energizing circuit of Ct and the reference voltage Vref A resistor 8 and a capacitor C ₇ are inserted between and. The output terminal Q of the monostable circuit IC ₂ is connected to the base of the transistor Q ₂ via the resistor R _13, and a pulse having a width (time) set by the CR time constant of the resistor R ₈ and the capacitor C ₇ . Output a signal. Furthermore, the input terminal A of the monostable circuit IC ₂
Is always set to the “L” level because it is connected to the ground, and the input terminal B has a resistor 7 and a transistor Q ₃ connected in series between the conducting circuit of the reference voltage Vref and the ground.
It is connected to the connection end with the collector of and is controlled via the collector → base → resistor 15 of the transistor Q ₃
Connected to feed back pin FB of IC ₃ . R ₁₄ is a ground resistor connected to the base of transistor Q ₃ .

Next, the temperature control circuit 31 includes the control IC ₃ and the variable resistor V
R, a hot water temperature detection sensor S, a transistor Q ₂ and a switching element TR such as a triac, the terminal RT of the control IC ₃ is connected to the output terminal Vout of the reference voltage Vref, and the first comparator. The terminal DT on the inverting input side of 34 and the control terminal OC are both grounded. On the other hand, the error amplifier 37IN (−) of the control IC ₃ and the non-inverting input terminal 38IN (+) of the error amplifier 38 are connected to the reference voltage Vr.
Variable resistance VR and hot water temperature detection sensor (for example, a thermistor with negative characteristics) inserted and connected in series between the energization circuit of ef and the ground
Connect to the connection point with S. At the connection point between the sensor S and the variable resistor VR, an output obtained by converting the temperature detected by the sensor S into a voltage is obtained, and the variable resistor VR can variably set the detected temperature. Also, the non-inverting input terminal of the error amplifier 37
37IN (+), of the reference voltage Vref of the energizing circuit and the resistor R ₉ inserted in series between the ground, R _10, R _11, connected to the connection point R between R _10, R _11, connection point The voltage output from R becomes the reference voltage VC for controlling the hot water temperature. Also, the error amplifier 38
The inverting input terminal 38IN (−) is connected to the connection point between the resistors R ₉ and R _10, and the voltage output from this connection point is higher than the reference voltage at the connection point R. Further control IC
Transistors T ₁ to form a driving circuit 43 for _3, of T ₂ emitter
E ₁ and E ₂ are connected to the collector of the transistor Q ₂ , and the anode of a reverse current blocking diode D ₇ is connected to the connection point of the emitters E ₁ and E ₂ of the transistors T ₁ and T ₂ , and this diode D The cathode of ₇ is the power supply terminal 2 via the heater H.
It is connected to the gate of the switching element TR consisting of a triac connected to the. R ₁₂ is a ground resistance connected to the base of transistor Q ₂ .

In FIGS. 1 and 3, 51 is an operation switch 52.
Solenoid valve connected to power supply terminal 2 via 53, heater H
Electric instant water heater with built-in.

 Next, the operation will be described.

First, connect the power supply terminal 2 to an AC power supply (eg AC100V, 60H
z), the AC power supply is rectified to DC by diode D ₆ and CR of resistance R ₁ and smoothing capacitor C ₅
By lowering (about 20V) by a constant, it is input to the input terminal VIN of the control IC _3, supplied from the output terminal Vout of the control IC ₃ a reference voltage Vref for operating the zero-cross detection circuit 11, the flicker prevention circuit 21. On the other hand, when the operation switch 52 is turned on, the solenoid valve 51 opens the valve path, and water flows through the water supply pipe 54 into the water heater 53. When a certain amount of water is passed through the water heater 53, the operation switch 52 is once opened to close the valve path of the solenoid valve 51 to stop the inflow of water. At the initial stage when water is passed through the water heater 53, the temperature control is performed because the water temperature is low, that is, the temperature detected by the water temperature detection sensor S is low and the resistance value of the sensor S is high. Control IC ₃ provided in circuit 31
The voltage input to the error amplifier 37 is 37IN (+) <37IN
(−), That is, the reference voltage VC at the connection point R is lower than the voltage obtained by converting the detection signal of the sensor S into a voltage, so that an “L” level signal is output from the output terminal of the error amplifier 37,
Further, the voltage input to the error amplifier 38 is 38IN (+) <37IN as in the above because the hot water temperature detection sensor S is not broken.
It becomes (-), and an "L" level signal is output from the output terminal. Therefore, the "L" level signal is input to the inverting input of the second comparator 35, and the "H" level signal is input to the non-inverting input when zero cross is detected.
An "H" level signal is output from the output end at the time of zero cross detection, and both the transistors T ₁ and T ₂ forming the drive circuit 43 of the control IC ₃ are turned on (see IC _{3 in} FIG. 4).

On the other hand, in the zero-cross detection circuit 11, when the point X is higher than the potential of the point Y, the current is R ₁ →
It flows through R ₂ → D ₂ → Q ₁ → D ₃ to the Y point, and conversely, when the potential at the Y point is higher than the X point, it goes through D ₄ → Q ₁ → D ₁ → R ₂ → R ₁ . About X
Flowing to the point. When a current is flowing through the base of the transistor Q _{1 in} such a state, Q ₁ turns on. However, when the potentials at the X point and the Y point are equal (when the zero point of the power supply voltage input to the power supply terminal 2 is crossed), the transistor Q ₁
Transistor Q ₁ is turned off because the base current does not flow in. When this transistor Q ₁ is turned off, i.e., controlled by the transistor Q ₁ to turn off at the zero point of the supply voltage, the pulse signal from the output terminal Z of the zero-crossing control circuit 11
It is sent to the terminal CT of IC ₃ (see CT in Fig. 4). On the other hand, when the transistor Q ₁ is on, the control
The current flowing from the output terminal Vout of IC ₃ through the resistor R ₄ flows to the ground through the transistor Q ₁ and the diode D ₅ and the resistor
Since it does not flow to the circuit to which R ₅ is connected, no pulse signal is output from the output terminal Z, and the terminal CT voltage of the control IC ₃ is 0 volt.

The monostable circuit IC ₂ of the anti-flicker circuit 21 sets one input terminal A to the “L” level and the other input terminal B to the “H” level.
When the "L" level falling signal is input from the level, a pulse having a CR constant time determined by the resistor R ₈ and the capacitor C ₇ is output. On the other hand, since the "L" level signal is output from the output terminals of the error amplifiers 37 and 38,
The “L” level signal is also output from the terminal FB of the control IC ₃ . As a result, the transistor Q ₃ are turned off and the "L" level signal from the output terminal Q of the monostable circuit IC ₂ is output, the transistor Q ₂ is also turned off. Transistor
Since Q ₂ is off, the drive circuit of the control IC ₃ 43
When both of the transistors T ₁ and T ₂ forming the circuit are turned on at the time of zero cross, a gate signal flows to the gate of the switching element TR by an ON command from the drive circuit 43 of the control IC ₃ , and the switching element TR is connected to the power supply terminal. The heater H is turned on in synchronization with the zero point of the power supply voltage input to 2 (see TR in FIG. 4). As a result, the water heater 53
The water inside is heated.

Next, when the hot water temperature in the water heater 53 reaches a predetermined set temperature, the hot water temperature detection sensor S detects this temperature and stops driving the drive circuit 43 in the control IC ₃ to energize the heater H. Open the circuit. That is, when the detected temperature of the sensor S becomes higher than the set temperature, the resistance value of the sensor S becomes small (see S in FIG. 4), and therefore the input voltage of the error amplifier 37 is 37IN.
(+)> 37IN (-), an "H" level signal is output from the output terminal, and the input voltage of the other error amplifier 38 is 38IN (+) <38IN (-). Although an "L" level signal is output from the output terminal, the inverting input of the comparator 35 becomes "H" level because the outputs of the error amplifiers 37 and 38 are wired OR, and the second comparator An "L" level signal is output from the output terminal of 35 to stop the drive circuit 43 of the control IC ₃ (see IC ₃ and TR in FIG. 4). Then, when the driving circuit 43 is stopped and a "H" level signal is output from the terminal FB of the control IC ₃ , the transistor Q ₃ is turned on (see FB and Q _{3 in} FIG. 4),
When the transistor Q _{3 is} turned on, the input terminal B of the monostable circuit IC ₂ falls to "L" level. Then, the "H" level signal is output from the output terminal Q of the IC _{2 for} the time determined by the CR constant of the resistor R ₈ and the capacitor C ₇ , and then changes to the "L" level (see IC _{2 in} FIG. 4). Then, while outputting "H" level signal from the output terminal of the IC ₂ is the turns on the transistor Q ₂ and a base current flows through the transistor Q _2, the transistor T ₁ of the drive circuit 43 of the control IC ₃ With this , T ₂ is although on the emitter circuit is closed, no gate signal flows in the gate of the switching-element TR, switching-element TR is not turned on. Therefore, the heater H is not energized (see TR in FIG. 4).

Then, when the hot water temperature in the water heater 53 drops below the set temperature, the hot water temperature detection sensor S detects the temperature (see S in FIG. 4), and the control IC ₃ of the temperature control circuit 31 again operates. The drive circuit 43 is driven (see IC _{3 in} FIG. 4), the switching element TR is turned on to energize the heater H, and the hot water temperature is raised to the set temperature. At this time, by frequently using hot water heated by the water heater 53, the switching element
TR maintains the hot water temperature in the water heater 53 at the set temperature.
Heater H is repeatedly turned on and off a considerable number of times in a short time.
Since the energization control is performed, flickering is likely to occur. However, in the present invention, when the temperature of hot water is controlled by the zero-cross control, the "H" level signal output from the output terminal of the monostable circuit IC ₂ forming the flickering prevention circuit 21 of the hot water temperature control device 1 is output. , Depending on the CR constant, it is configured to output from the time when the drive circuit 43 of the control IC ₃ stops until about 0.5 seconds elapse, so the transistor Q ₂ turns on and drives during this time period. Transistor T ₁ , T of circuit 43
_Since the switching element TR is not turned on even when the energizing circuit of ₂ is closed, the occurrence of flickers can be suppressed smoothly.

In this case, after the energization start command for the heater H is output
The heater H is energized after 0.5 seconds, but energization of the heater H with such a time delay does not adversely affect the consumer when reheating the water or hot water.

When the temperature of the hot water in the water heater 53 is lower than or equal to the set temperature, the input terminal of the error amplifier 37 of the control IC ₃ has 37IN (+)
Since the voltage of <37IN (-) is input, the "H" level signal is output from the output terminal. At that time, since a voltage of 38IN (+) <38IN (−) is also input to the input terminal of the error amplifier 38, an “L” level signal is output from the output terminal. However, when the hot water temperature detection sensor S including a thermistor having a negative characteristic is used, if the detection temperature of the sensor S itself is lowered, the resistance value of the sensor S increases, and
When a voltage of (+)> 38IN (-) is input to the error amplifier 38, a "H" level signal is output from its output terminal,
Since the signal is input to the inverting input terminal of the second comparator 35 (the "L" level signal is input from the error amplifier 37 to the non-inverting input terminal of the comparator 35), the output of the comparator 35 Since an "L" level signal is output from the end, control
The drive circuit 43 of IC ₃ does not operate. Therefore, if the set temperature detected by the hot water temperature detecting sensor S is selected by a voltage corresponding to a temperature lower than −273 ° C., if the hot water temperature detecting sensor S is not disconnected, it is input to the input end of the error amplifier 38. Since the applied voltage has a relationship of 38IN (+) <38IN (-), an "L" level signal is output from the output terminal. However, when the hot water temperature detection sensor S is disconnected, the voltage 38IN (+)> 2IN (-) is input to the input terminal of the error amplifier 38 as described above, and the "H" level signal is output from the output terminal. The signal is output. Therefore, the second comparator 35 outputs an "L" level signal, and the control IC ₃ does not operate. That is, since the heater H cannot be energized, it is possible to detect the disconnection of the hot water temperature detection sensor S using a thermistor having a negative characteristic and prevent the heater H from running out of control.

〔The invention's effect〕

Since the present invention is configured as described above, it has the following effects.

The present invention, when the switching element is turned on in synchronization with the output from the zero-cross detection circuit to perform zero-cross control of the temperature of the hot water, the output terminal of the monostable multivibrator that constitutes the flicker prevention circuit of the temperature control device. The "H" level signal output from is set by the resistor and capacitor provided in the flicker prevention circuit.
Control provided in temperature control circuit by CR constant
It outputs a gate signal that turns on the switching element by outputting it until a certain time has elapsed from the time when the IC drive circuit stopped.
In the present invention, even if the heater on / off operation concentrates for a short time due to frequent use of hot water, the heater on operation is provided in the flicker prevention circuit. Depending on the CR constant set by the resistor and the capacitor, the frequency that flicker is likely to occur, that is, the time zone corresponding to 2 Hz to 25 Hz (about 0.5 ~
Since it can be avoided for only 0.04 seconds), it is possible to surely eliminate the harmful effects caused by the occurrence of flicker. Moreover, even if the start of energization to the heater is delayed, the time is only delayed within 0.5 seconds, so there is no effect on the temperature control of the hot water, and the hot water can be smoothly and satisfactorily. Temperature control can be performed.

Further, according to the present invention, in order to suppress the occurrence of flicker, the start time of energization to the heater is controlled by the temperature control circuit.
The flicker prevention circuit receives a signal output from the IC and has a simple circuit configuration that sets the time limit in advance, so for example, you can control the energization of the heater at the timing when flicker occurs. Alternatively, as compared with the conventional control circuit in which the shortest energization time to the heater is shortened to suppress the occurrence of flicker, the present invention makes the energization start time to the heater flicker compared to the normal energization time. In order to avoid the frequency band that is apt to occur, it was mechanically delayed by about 0.5 seconds.Therefore, the control circuit configuration itself effectively suppresses the occurrence of flicker when the heater is energized and also suppresses flicker. As a result, the circuit configuration of the hot water temperature control device is simplified, the manufacturing cost is inevitably lowered, and the hot water temperature control device is simplified with the simplification of the configuration. Advantages can be manufactured by nil state close equipment failures are also provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a hot water temperature control device of the present invention, FIG. 2 is a block diagram of a control IC ₃ which is an essential part of the present invention, FIG. 3 is an electric circuit diagram of the present invention, and FIG. FIG. 5 is a timing chart for explaining the outline of the operation of the present invention, and FIG. 5 is a flicker sensitivity curve diagram for judging the occurrence of flickers. 11 …… Zero cross detection circuit 21 …… Flicker prevention circuit 31 …… Temperature control circuit, H …… Heater IC ₂ …… Monostable multivibrator IC ₃ …… Control IC

Claims (1)

[Claims] 1. A temperature control circuit configured to control the energization of a heater by incorporating a control IC in which a reference voltage setting means and an output of a drive circuit are formed to be capable of push-pull or parallel operation, and the temperature control circuit. A zero-cross detection circuit configured to output a pulse signal to the control IC in synchronization with the zero point of the power supply voltage connected to the built-in reference voltage generation means, and output from the reference voltage setting means. In the middle of the energizing circuit that supplies the reference voltage to the zero-cross detection circuit, a CR inserted and connected between the monostable multivibrator and the terminal of the monostable multivibrator and the energizing circuit that supplies the reference voltage to the zero-cross detection circuit. And a flicker prevention circuit configured by including a resistor and a capacitor for setting constants. In synchronization with the pulse signal output from the circuit to drive the drive circuit of the temperature control circuit of the switching elements for energization control of the heater is turned on, and,
The "H" level signal output from the flicker prevention circuit is output for a period of time set by the CR constant from the time when the driving of the drive circuit is stopped so that the temperature control circuit does not output the ON command of the switching element. A hot water temperature control device having a flicker suppressing function.