JP3009387B2 - Heater control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a heater control circuit using a commercial AC power supply.

[0002]

2. Description of the Related Art There are a method in which a bimetal is connected in series between an AC power supply terminal and a heater, a method in which a temperature sensor circuit and a relay are provided instead of a bimetal, or a method in which a temperature sensor circuit and a semiconductor switching element are provided to perform on / off control. .

For example, as shown in FIG. 8, a semiconductor switching element 3 such as a thyristor is provided between an AC power supply terminal 1 and a heater 2, and the switching element 3 is connected to a trigger circuit 4.
Trigger with it.

By the way, in such a circuit, when the power supply voltage changes from 100 V to 200 V, for example, electric power is applied to the heater 2 four times in proportion to the square of the power supply voltage.

For this reason, the heater 2 for 100 V is set to 200 V
Use in an environment may cause damage. Conversely, if the 200 V heater 2 is used in a 100 V environment, the required heat generation cannot be obtained.

As shown in FIG. 8, when a temperature sensor (a heater may be used as a sensor) 5 is provided and the trigger circuit 4 is controlled based on the detected temperature, the heat generated by the heater 2 is controlled by feedback from the sensor 5. Therefore, it is conceivable that the 100 V heater 2 can be used in a 200 V environment. However, the heater 2 has a time delay from when the voltage is applied to when the temperature reaches the set temperature, and the heater 2 is damaged by the voltage applied during that time. I do.

As a method for solving this, conventionally, 10
It was necessary to prepare the 0V heater 2 and the 200V heater 2 to deal with the respective environments, or to match the voltage environment using a transformer.

[0008]

However, the method of preparing the above-described heaters for 100 V and 200 V is costly. Further, the method using a transformer has a problem that it is large and heavy, in addition to the cost.

Accordingly, an object of the present invention is to provide a heater control circuit for automatically and automatically restricting the power supplied to a heater for a 100 V heater even when the power supply voltage is 200 V, and a power supply to the heater while limiting the power supplied to the heater. An object of the present invention is to provide a heater control circuit capable of controlling the temperature.

[0010]

According to the present invention, there is provided a circuit for connecting a semiconductor switching element and a heater in series between an AC power supply terminal and energizing the circuit.
Depending on the power supply voltage applied between the AC power supply terminals,
Charged by the ON current of the semiconductor switching element
Charge / discharge to set a pause period to suspend power supply to the
This configuration employs a circuit and a circuit for preventing the semiconductor switching element from being energized based on the charged voltage of the charge / discharge circuit .

[0011]

[0012]

By adopting such a configuration, the charging / discharging circuit is charged with the ON current of the semiconductor switching element, and while the charged voltage is discharged to a predetermined voltage, the semiconductor switching element is regulated. The heater can be controlled while the power supply cycle to the heater is thinned out (intermittently) in accordance with the power supply voltage applied between the terminals, and the average supply power to the heater is limited within the allowable loss of the heater.

Further, by providing the charge / discharge circuit with a voltage discriminating function, it is possible to easily set the voltage of the charge / discharge circuit to be operated according to the power supply voltage.
The setting of the pause cycle according to the rise of the power supply voltage is facilitated.

By making such a configuration and setting,
When the power supply voltage is low, the thinning of the power supply cycle does not occur, and the thinning starts with the rise of the power supply voltage, and the thinning cycle can be increased in accordance with the rise of the power supply voltage.

In this case, the heater control circuit is provided in a temperature control circuit for connecting a semiconductor switching element and a heater in series between AC power supply terminals and for controlling on / off of energization of the semiconductor switching element by a measurement signal of a temperature sensor. That is why the configuration was adopted.

For example, a semiconductor switching element and a heater are connected in series between commonly used AC power supply terminals,
A temperature control circuit that controls on / off of energization of the semiconductor switching element by a measurement signal of a temperature sensor (a heater that can measure the temperature of the heater itself by a change in electric resistance of the heater may be used as the sensor) And an ON signal to the semiconductor switching element of the temperature control circuit is blocked by a gate circuit or the like so as to be in a quiescent period according to the power supply voltage applied between the AC power supply terminals.

At this time, the semiconductor switching element includes:
Use of a bidirectional thyristor or unidirectional thyristor is suitable.However, if an element such as a field-effect transistor that can be turned on and off at any time is adopted, the power supply to the heater can be limited even if the phase is smaller than 180 degrees of the AC power cycle. Control becomes possible, and more detailed control can be performed.

Since the above control is performed instantaneously when power is supplied or power is supplied to the heater, it is possible to provide a heater control circuit that safely and automatically supports a wide range of commercial power supply voltage without damaging the heater. Can be.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a heater control circuit according to the first embodiment.

In the heater control circuit of this embodiment, a unidirectional thyristor (hereinafter, thyristor) 3 is provided as a semiconductor switching element between an AC power supply terminal 1 and a ceramic heater 12.

As shown in FIG. 1, this circuit includes a thyristor 3, a zero-cross circuit 6, a comparison circuit 7, a temperature setting circuit 8, a trigger circuit 9, a charge / discharge circuit 10, a gate circuit 11,
It comprises a ceramic heater 12 and a measuring current circuit 13.

The zero-cross circuit 6 detects the zero-cross of the AC input voltage. The zero-cross circuit 6 drives the transistor Tr with the detected zero-cross, and supplies power to the comparison circuit 7 as shown in FIG. Constant current resistance 1
A constant current is supplied to the ceramic heater 12 via the reference numeral 4.

The comparison circuit 7 has one input connected to the temperature setting circuit 8 and the other input to which a measurement voltage is input via a resistor, and outputs a comparator output of both voltages to the trigger circuit 9.

The trigger circuit 9 generates a trigger pulse Vtg from the output of the comparator and outputs it to the gate of the thyristor 3.

The charging / discharging circuit 10 connects the capacitor C1 and the discharging resistor R1 in parallel, and connects one end of the capacitor C1 and the discharging resistor R1 to the cathode of the thyristor 3 via a voltage dividing resistor. It is designed to be charged with the ON current of the battery.

A Zener diode 15 is provided between the backflow preventing diode D1 and the capacitor C1 as switching means.

The Zener diode 15 is connected with the cathode terminal on the side of the backflow preventing diode D1 and is turned on only when the voltage applied when the thyristor 3 is turned on is 100 V or more, and the capacitor C1 is charged. It is supposed to be.

As described above, in this embodiment, the work of setting the discharge time is simplified by allowing the charge / discharge circuit 10 to operate only at a specific voltage or higher by the Zener diode 15.

The other output of the charge / discharge circuit 10 is connected to the gate of an FET 11 provided as a gate circuit.

The FET 11 has a drain connected to the trigger circuit 9 and a source connected to a common com of the circuit. When the FET 11 is turned on, the trigger pulse Vtg can be regulated.

Reference numeral 16 denotes a hysteresis circuit, and reference numeral 17 denotes an LED for display.

This embodiment is configured as described above.
Hereinafter, the operation will be described based on the voltage waveforms of the respective parts in FIGS. 2 and 3.

FIG. 2 shows the waveform of each part when the power supply voltage is 100 V, and FIG. 3 shows the waveform when the power supply voltage is 200 V.

FIG. 2A (hereinafter, FIG. 2 is omitted) shows a power supply voltage waveform. (B) is an output waveform of the transistor Tr, which supplies a measurement current synchronized with zero crossing to the ceramic heater 12 and simultaneously supplies power to the comparison circuit 7.

When the power is supplied, the set voltage of the temperature setting circuit 8 and the measured voltage are input to the comparison circuit 7. Therefore, a comparator output comparing the two inputs is output to the trigger circuit 9 as shown in (h).

That is, at the time of startup, the ceramic heater 1
Since 2 is cold, the trigger circuit 9 outputs a trigger signal to the thyristor 3 as shown in (nu) at each zero cross. Therefore, the thyristor 3 is turned on every half cycle of the AC power supply, and the flowing current causes the ceramic heater 1 to turn on.
2 generates heat.

Then, the resistance value of the ceramic heater 12 increases with the heat generation. At this time, the measurement current is supplied to the ceramic heater 12 at each zero cross as described above, and the measurement voltage Vm detected at each zero cross is increased by the measurement current as shown in (g). Then, when the measured voltage Vm exceeds the set value Vref at t1, the comparator output of the comparison circuit 7 becomes zero, and the trigger pulse Vtg from the trigger circuit 9 stops.

Therefore, the thyristor 3 is no longer triggered, and the temperature of the ceramic heater 12 drops.

When the temperature drops, the ceramic heater 12
, The measured voltage Vm decreases. And
When the measured voltage Vm falls below the set value Vref, the comparison circuit 7
Output a comparator output, and the trigger circuit 9 outputs a trigger pulse Vtg. Therefore, thyristor 3
Is triggered, and the ceramic heater 12 is heated.

The on / off control of the thyristor 3 as described above keeps the ceramic heater 12 at a set temperature.

At this time, a voltage corresponding to 100 V is applied to the charge / discharge circuit 10 every time the thyristor 3 is turned on. At this voltage, the Zener diode 15 is off, and no charging current flows through the capacitor C1. for that reason,
The voltage Vcg of the charging / discharging circuit 10 remains at zero as shown in (e), the FET 11 does not turn on, and the gate is opened as shown in (i), and the trigger signal is not regulated.

Next, as shown in FIG. 3, when 200 V is applied to the heater control circuit, the comparator circuit 7 outputs a comparator output because it is cold at the time of startup, as in the case of 100 V. 3 is triggered.

At this time, the charge / discharge circuit 10
Is applied, the Zener diode 15 is turned on, and the capacitor C1 is charged, for example, as shown by (e) at t2.

The FET 11 is turned on by this charging voltage, and the trigger pulse Vtg is regulated. As a result, the thyristor 3 is not triggered, and the ceramic heater 1
No current flows through 2.

Therefore, no current is supplied to the charging / discharging circuit 10, and the electric charge of the capacitor C1 is discharged by the discharging resistor R1. Then, when the voltage drops as shown in (e) at t3, the FET 11 turns off and the trigger pulse V
The regulation of tg is released, and the thyristor 3 enters a triggerable state. Then, the charging / discharging circuit 10 is charged with the triggered on-current of the thyristor 3, so that the FE is again charged.
T11 is turned on, and the trigger pulse Vtg is regulated. Therefore, no current flows through the ceramic heater 12.

As described above, since the current flowing through the ceramic heater 12 is intermittently caused by the discharge time at the same time as the start-up, the allowable loss can be prevented from being exceeded even when a 200 V AC power supply is applied.

A measurement current is supplied to the ceramic heater 12 at each zero cross, and a comparison operation with a set voltage is performed by the comparison circuit 7.

Therefore, when the measured voltage exceeds the set value as at t4, the comparator output of the comparison circuit 7 becomes zero, the trigger pulse Vtg is not output, the thyristor 3 is turned off, and the temperature of the ceramic heater 12 decreases. .

When the temperature drops, the ceramic heater 12
, The measured voltage Vm decreases. And
When the measured voltage Vm falls below the set value Vref, the comparison circuit 7
Output a comparator output, the trigger circuit 9 outputs a trigger pulse Vtg, the thyristor 3 is turned on, and the ceramic heater 12 is heated.

At this time, the charging circuit 10 includes the thyristor 3
Therefore, the trigger pulse Vtg is regulated during the discharge time every time the thyristor 3 is triggered, so that no current flows through the ceramic heater 12.

For this reason, the average power of the ceramic heater 2 can be limited so that the allowable loss is not always exceeded even with a 200 V AC power supply.

As described above, the heater for 100 V can be used even at 200 V with a simple circuit, and further, even if a sensor is used, the heater can be prevented from being damaged.

Further, the charging / discharging circuit 10 is turned on when the applied voltage is 100 V or more by the Zener diode 15, so that the discharge time can be easily set.

FIG. 4 shows a charge / discharge circuit 1 according to a second embodiment.
0 shows another embodiment.

This circuit uses a transistor switch circuit 15 'instead of the Zener diode 15, and connects the base of the transistor 15' to the power supply Vcc.
When a voltage of 0 V is applied, the transistor 15 'is turned on and a charging current flows.

By doing so, the transistor 1
It is possible to set the 5 'operating voltage accurately only by the resistor.

The other configuration and operation are the same as those of the first embodiment, and the description is omitted.

FIG. 5 shows a third embodiment in which a bidirectional thyristor (hereinafter, triac) 3 ′ is used instead of the unidirectional thyristor 3.

In this case, the heater 2 is zero-cross controlled by the temperature control circuit 20. The control circuit 20 is isolated by triggering using the photocoupler 21.

The charge / discharge circuit 10 connects a capacitor C1 and a discharge resistor R1 in parallel, and connects one of them to a bridge circuit D
3 and a voltage dividing resistor connected to the cathode of the triac 3 '.

By doing so, the triac 3 '
The charging / discharging circuit 10 can be charged with the ON current in both directions.

In the heater control circuit configured as described above, each time the triac is turned on by the bridge circuit D3, the capacitor C1 is charged with an on-state current in both directions, and the trigger signal is regulated as in the case of the first embodiment. be able to.

Therefore, the heater for 100 V can be used even at 200 V, and even if a sensor is used, the heater 2 can be prevented from being damaged.

Although the switching means 15 is not used in this embodiment, even if the voltage dividing resistor and the time constant of the charging / discharging circuit are appropriately selected, it is possible to use even 100 V without any trouble.

FIG. 6 shows another embodiment of the charge / discharge circuit of the third embodiment as a fourth embodiment.

(A) shows the case where the Zener diode 15 is connected to the first
FIG. 4B shows a device in which the Zener diode 15 is used between the gate circuit 11 and the device used in the same position as the embodiment. (C) shows the one using the transistor switch 15 'as in (b).

In any case, the same operation as in the first embodiment can be exhibited, and the description thereof will be omitted.

[0070]

[0071]

[0072]

[0073]

[0074]

[0075]

In the above embodiment, the temperature control based on feedback is described. However, the present invention is not limited to this. Applicable regardless of feedback.

[0077]

The present invention is configured as described above, and the power supply to the heater can be regulated according to the voltage.
The heater for 00V can be used even at 200V.

Further, even when a sensor is used, it is possible to prevent the heater from being damaged.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a first embodiment.

FIG. 2 is a voltage waveform diagram of the first embodiment.

FIG. 3 is a voltage waveform diagram of the first embodiment.

FIG. 4 is a circuit diagram of a second embodiment.

FIG. 5 is a circuit diagram of a third embodiment.

FIG. 6 is a circuit diagram of a fourth embodiment.

FIG. 7 is a block diagram of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 AC power supply terminal 2 Heater 3 Switching element 3 'Switching element 6 Zero cross circuit 7 Comparison circuit 9 Trigger circuit 10 Charge / discharge circuit 11 Gate circuit 12 Ceramic heater 13 Measurement current circuit 15 Discrimination circuit D1 Backflow prevention diode D3 Bridge circuit C1 Capacitor R1 Discharge resistance Vtg Trigger pulse Vm Measurement voltage Vref Set value

Claims (2)

(57) [Claims] 1. A circuit in which a semiconductor switching element and a heater are connected in series between an AC power supply terminal and energized, wherein the semiconductor switching element and the heater are energized according to a power supply voltage applied between the AC power supply terminals.
Charged by the ON current of the semiconductor switching element, the heater
Charge / discharge times to set a rest period to suspend power to the
A heater control circuit provided with a path and a circuit for preventing conduction of the semiconductor switching element based on a charged voltage of the charge / discharge circuit. 2. The heater control circuit according to claim 1,
The semiconductor switching element and heater between the AC power supply terminals
Are connected in series, and the semiconductor
Temperature control to control ON / OFF of energization of switching element
Heater control circuit provided in the circuit.