Heater Device

Abstract

To appropriately perform a malfunction detection regardless of a control method of a drive switch.SOLUTION: A heater device comprises: a heater drive circuit in which a heater and a drive switch are serially connected to an AC power supply; a zero-cross detection circuit; a malfunction detection circuit; a determination part; and a control part. The malfunction detection circuit includes: a photo coupler containing a light emission diode and a photo transistor, connected in parallel to the drive switch; and a diode reversely connected in parallel to the light emission diode. The determination part determines a malfunction of the heater or the heater drive circuit on the basis of an output of the malfunction detection circuit. The control part prevents the drive switch from generating an off period in a period when a direction of a current flowing in the heater drive circuit becomes a forward direction of the light emission diode on the basis of detecting a zero cross detected by the zero-cross detection circuit in the case of controlling the drive switch in a duty ratio different from 100%.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a heater device, and more particularly to a heater device including an abnormality detection device. [Background technology]

[0002] Conventionally, a heater device including this type of abnormality detection device has been proposed that includes a photocoupler having a light-emitting diode connected in series to a toilet seat heater and a heater switch and a phototransistor that receives light from the light-emitting diode, and a Zener diode connected in anti-parallel to the light-emitting diode, and that determines whether or not there is a disconnection in the toilet seat heater by monitoring the output of the photocoupler when the heater switch is on (see, for example, Patent Document 1).

[0003] Also proposed is a toilet seat heater that includes a heater driver (triac) that drives the toilet seat heater, a heater drive detector connected to both ends of the heater driver to detect the conduction state of the triac, an AC voltage detector that outputs a signal synchronized with the zero crossing of the AC voltage, and a controller that controls the heater driver and detects abnormalities in the heater driver and the heat generating unit based on the output of the heater drive detector and the output of the AC voltage detector (see, for example, Patent Document 2). The controller controls the energization of the toilet seat heater using three control methods: full-wave control, which receives a zero-cross signal and energizes the AC voltage for the entire period of one cycle, half-wave control, which energizes for half the period, and phase control, which energizes part of the AC voltage with a certain time delay from the zero-cross signal. During full-wave control and phase control, an abnormality is detected if the waveform of the output signal from the heater drive detector is clearly different from the normal waveform. During half-wave control, the normal output differs depending on whether the voltage applied is positive or negative, so no abnormality is detected. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-145471 A [Patent Document 2] JP 2009-61138 A Summary of the Invention [Problem to be solved by the invention]

[0005] The circuit described in Patent Document 1 is a circuit configuration assuming full-wave control, and in duty control such as half-wave control, the output during normal operation differs depending on whether the applied voltage is positive or negative, so abnormality detection cannot be performed. In addition, the circuit described in Patent Document 2 can detect abnormalities during full-wave control and phase control, but requires a heater drive detection unit, which increases costs. Also, like the circuit described in Patent Document 1, in half-wave control, the output during normal operation differs depending on whether the applied voltage is positive or negative, so abnormality detection cannot be performed.

[0006] A main object of the present invention is to provide a heater device capable of appropriately detecting an abnormality, regardless of the control method of the drive switch. [Means for solving the problem]

[0007] In order to achieve the above-mentioned main object, the heater device of the present invention employs the following means.

[0008] The heater device of the present invention comprises: a heater drive circuit in which a heater and a drive switch are connected in series to an AC power source; a zero-cross detection circuit for detecting a zero-cross of a voltage of the AC power supply; an abnormality detection circuit including a photocoupler including a light-emitting diode connected in parallel to the drive switch and a phototransistor receiving light from the light-emitting diode, and a diode connected in anti-parallel to the light-emitting diode; a determination unit that determines an abnormality in the heater or the heater drive circuit based on an output of the abnormality detection circuit; a control unit that controls the drive switch based on the detection of a zero cross by the zero cross detection circuit when the drive switch is controlled with a duty ratio different from 100%, so that an off period of the drive switch does not occur during a period in which a current flowing through the heater drive circuit is in a forward direction of the light emitting diode; The gist of the invention is to provide the following:

[0009] In the heater device of the present invention, when the drive switch is controlled with a duty ratio different from 100%, the drive switch is controlled based on the detection of a zero cross so that an off period of the drive switch does not occur during a period in which the direction of the current flowing through the heater drive circuit is the forward direction of the light-emitting diode. When the drive switch is controlled with a duty ratio of 100%, there is no off period of the drive switch, so that the current from the AC power source flows through the drive switch throughout the entire period and does not flow through the light-emitting diode. Therefore, if the device is normal, the output of the abnormality detection circuit will be the same in both cases. Therefore, in both cases of control with a duty ratio different from 100% and control with a duty ratio of 100%, the output of the abnormality detection circuit can be compared with the output during normal operation to appropriately determine an abnormality in the heater device.

[0010] In the heater device of the present invention, the abnormality detection circuit may be configured to make the direction of the current flowing through the heater drive circuit the forward direction of the light-emitting diode during the period from the time when a half cycle has elapsed since the detection of a zero cross by the zero-cross detection circuit to the next zero cross. In this way, when the drive switch is controlled with a duty ratio other than 100%, the drive switch can be controlled to be turned on with a delay of a time according to the duty ratio from the time when the zero cross is detected, thereby reducing the effect of the delay time of the drive switch.

[0011] Alternatively, in the heater device of the present invention, the abnormality detection circuit may be configured so that the direction of current flowing through the heater drive circuit is the forward direction of the light-emitting diode during the period from the time when the zero crossing is detected by the zero crossing detection circuit to the next zero crossing.

[0012] In addition, in the heater device of the present invention, the determination unit may determine that an open failure has occurred in the drive switch when the output of the abnormality detection circuit is repeatedly switched between a low level signal and a high level signal while the control unit is controlling the drive switch to be turned on.

[0013] Furthermore, in the heater device of the present invention, when the control unit is controlling the drive switch to be turned off, the judgment unit may determine that the heater has been broken or that the drive switch has suffered a short-circuit failure if the output of the abnormality detection circuit is constant. [Brief description of the drawings]

[0014] [Figure 1] 1 is a schematic configuration diagram of a heater device including an abnormality detection device according to an embodiment of the present invention; [Diagram 2] FIG. 4 is an explanatory diagram illustrating the operation of a heater switch during full-wave control. [Diagram 3] FIG. 11 is an explanatory diagram illustrating the operation of a heater switch during half-wave control. [Figure 4] FIG. 11 is an explanatory diagram showing the relationship between the drive signal to the heater switch, the state of the heater switch, the state of the toilet seat heater, and the output voltage of the abnormality detection circuit when the heater switch is normal, when the toilet seat heater is disconnected, when the heater switch has an open fault, and when the heater switch has a short fault. [Diagram 5] 10 is an explanatory diagram showing the time change in the output voltage of the abnormality detection circuit when half-wave control is performed under normal conditions; FIG. [Figure 6] 11 is an explanatory diagram showing the time change in the output voltage of the abnormality detection circuit when half-wave control is performed when a disconnection fault occurs in the toilet seat heater. FIG. [Figure 7] 11 is an explanatory diagram showing the time change in the output voltage of the abnormality detection circuit when half-wave control is performed when an open fault occurs in a heater switch; FIG. [Figure 8] 11 is an explanatory diagram showing the time change in the output voltage of the abnormality detection circuit when half-wave control is performed when a short circuit occurs in a heater switch; FIG. [Figure 9]1 is an explanatory diagram showing the output voltage of the abnormality detection circuit during full-wave control in a normal state and the output voltage of the abnormality detection circuit during half-wave control (upper half-wave on, lower half-wave on). FIG. [Figure 10] FIG. 11 is an explanatory diagram showing an example of a heater input voltage with a duty of 70%. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings.

[0016] Fig. 1 is a schematic diagram of a heater device including an abnormality detection device of this embodiment. The heater device 10 heats the toilet seat 2 of a toilet seat device installed in a Western-style toilet, and as shown in Fig. 1, includes a toilet seat heater 11 built into the toilet seat 2, a heater drive circuit 15 that drives the toilet seat heater 11 by turning on a heater switch 16 and applying a voltage of an AC power source 1 to the toilet seat heater 11, a zero-cross detection circuit 20 that detects zero crosses of the voltage of the AC power source 1, an abnormality detection circuit 30 that detects abnormalities in the toilet seat heater 11 and the heater drive circuit 15, and a control device 40 that controls the entire device.

[0017] The heater switch 16 of the heater drive circuit 15 is configured, for example, by a triac or a solid state relay including a light emitting diode. The triac of the heater switch 16 and the toilet seat heater 11 are connected in series to the AC power supply 1. The heater switch 16 is turned on by a drive signal (on signal) from the control device 40, and is automatically turned off when the voltage of the AC power supply 1 passes the next zero crossing.

[0018] The zero-cross detection circuit 20 detects the zero-cross of the voltage of the AC power source 1, and in this embodiment, detects the falling zero-cross of the voltage of the AC power source 1 based on the change of the output voltage Vc from a low-level voltage to a high-level voltage. As shown in FIG. 1, the zero-cross detection circuit 20 includes a photocoupler 21, a diode 24, resistor elements 25 and 26, and a capacitor 27. The photocoupler 21 has a light-emitting diode 22 as a light-emitting element and a phototransistor 23 as a light-receiving element that receives light from the light-emitting diode 22. The light-emitting diode 22 and the resistor element 25 are connected in series with each other to the AC power source 1, and are connected in parallel with the toilet seat heater 11 and the heater switch 16. The diode 24 is connected in anti-parallel to the light-emitting diode 22 (so that the forward direction of the diode 24 and the forward direction of the light-emitting diode 22 are opposite). The emitter of the phototransistor 23 is grounded, and the collector of the phototransistor 23 is connected to a constant voltage source Vcc via the resistor element 26 and is also grounded via the capacitor 27. The voltage at a connection point Pc between the resistance element 26 and the capacitor 27 is output to the control device 40 as an output voltage Vc.

[0019] The abnormality detection circuit 30 detects a disconnection of the toilet seat heater 11 and an open fault and a short fault of the heater switch 16, and has a circuit configuration similar to that of the zero-cross detection circuit 20. That is, as shown in FIG. 1, the abnormality detection circuit 30 includes a photocoupler 31, a diode 34, resistor elements 35 and 36, and a capacitor 37. The photocoupler 31 includes a light-emitting diode 32 as a light-emitting element, and a phototransistor 33 as a light-receiving element that receives light from the light-emitting diode 32. The light-emitting diode 32 and the resistor element 35 are connected in series with each other to the AC power source 1 together with the toilet seat heater 11, and are also connected in parallel to the heater switch 16. The diode 34 is connected in anti-parallel to the light-emitting diode 32 (so that the forward direction of the diode 34 and the forward direction of the light-emitting diode 32 are opposite). The emitter of the phototransistor 33 is grounded, and the collector of the phototransistor 33 is connected to a constant voltage source Vcc via the resistor element 36 and is also grounded via the capacitor 37. The voltage at the connection point Po between the resistance element 36 and the capacitor 37 is output to the control device 40 as the output voltage Vo.

[0020] The control device 40 is configured as a microprocessor equipped with a CPU, ROM, and RAM. The control device 40 has, as its functional blocks, a control unit 41 that receives the output voltage Vc of the connection point Pc and outputs a drive signal to the heater switch 16 to control it, and a determination unit 42 that receives the output voltages Vc and Vo of the connection points Pc and Po to determine whether the toilet seat heater 11 or the heater drive circuit 15 is abnormal.

[0021] Next, the operation of the heater device 10 thus configured will be described. The control unit 41 controls the heater switch 16 using full-wave control or half-wave control to energize the toilet seat heater 11 so that the temperature of the toilet seat 2 detected by a temperature sensor (not shown) becomes the set temperature. Figures 2 and 3 are explanatory diagrams for explaining the operation of the heater switch 16. Figure 2 shows the operation of full-wave control, and Figure 3 shows the operation of half-wave control. As shown in Figure 2, full-wave control is performed by controlling the heater switch 16 so that a voltage is applied to the toilet seat heater 11 in the entire section (100% duty ratio) of the AC power supply voltage V in response to detection of a zero cross of the AC power supply voltage V (the output voltage Vc of the zero-cross detection circuit 20 has changed from a low-level voltage to a high-level voltage). As shown in Figure 3, half-wave control is performed by controlling the heater switch 16 so that a voltage is applied to the toilet seat heater 11 in a half section (50% duty ratio) of the AC power supply voltage V in response to detection of a zero cross of the AC power supply voltage V. In this embodiment, the half-wave control is performed by turning on the heater switch 16 when a half cycle has elapsed since the detection of the zero crossing (falling zero crossing) so that the voltage in the upper half-wave section of the AC power supply voltage V is applied to the toilet seat heater 11.

[0022] Here, when no abnormality occurs in the heater device 10 (toilet seat heater 11 or heater switch 16) (normal operation), the abnormality detection circuit 30 operates as follows. When the control device 40 turns off the heater switch 16, the current from the AC power supply 1 flows alternately to the light-emitting diode 32 and the diode 34 every half cycle. Therefore, the abnormality detection circuit 30 outputs a low-level voltage and a high-level voltage alternately every half cycle as the output voltage Vo. On the other hand, when the control device 40 turns on the heater switch 16, the current from the AC power supply 1 flows to the heater switch 16 and does not flow to the light-emitting diode 32. Therefore, the abnormality detection circuit 30 outputs a constant high-level voltage as the output voltage Vo.

[0023] Next, the operation of the determination unit 42 to determine an abnormality in the toilet seat heater 11 or the heater drive circuit 15 based on the output voltage Vo from the abnormality detection circuit 30 will be described. FIG. 4 is an explanatory diagram showing the relationship between the drive signal to the heater switch 16, the state of the heater switch 16, the state of the toilet seat heater 11, and the abnormality detection circuit output voltage in normal times, when the toilet seat heater 11 is disconnected, when the heater switch 16 has an open failure, and when the heater switch 16 has a short-circuit failure, respectively. FIGS. 5 to 8 are explanatory diagrams showing the time change in the abnormality detection circuit output voltage according to the state of the heater device 10 when half-wave control is performed. Note that FIG. 5 shows the normal state, FIG. 6 shows the state when the toilet seat heater 11 has an open failure, FIG. 7 shows the state when the heater switch 16 has an open failure, and FIG. 8 shows the state when the heater switch 16 has a short-circuit failure. The abnormality determination is performed by determining whether the output voltage Vo of the abnormality detection circuit 30 is different from that in normal times when the heater switch 16 is controlled to be on or off.

[0024] When the toilet seat heater 11 is disconnected, no current flows through the toilet seat heater 11 or the light-emitting diode 32, regardless of the state of the heater switch 16. For this reason, as shown in Fig. 6, a constant high-level voltage is output as the output voltage Vo from the abnormality detection circuit 30. As shown in Fig. 4, when the heater switch 16 is controlled to be off under normal conditions, the output voltage Vo of the abnormality detection circuit 30 alternates between a low-level voltage and a high-level voltage, so that the determination unit 42 determines that the toilet seat heater 11 is disconnected when it detects a constant high-level voltage as the output voltage Vo of the abnormality detection circuit 30 even though the heater switch 16 is controlled to be off.

[0025] When the heater switch 16 has an open fault, even if the control device 40 controls the heater switch 16 to be on, the heater switch 16 does not turn on, and so the current from the AC power supply 1 flows alternately through the light-emitting diode 32 and the diode 34 every half cycle. For this reason, as shown in Fig. 7, the abnormality detection circuit 30 outputs a low-level voltage and a high-level voltage alternately as the output voltage Vo. As shown in Fig. 4, when the heater switch 16 is controlled to be on during normal operation, the output voltage Vo of the abnormality detection circuit 30 becomes a constant high-level voltage. Therefore, when the determination unit 42 detects that a low-level voltage and a high-level voltage are alternately output as the output voltage Vo of the abnormality detection circuit 30 despite the heater switch 16 being controlled to be on, it determines that the heater switch 16 has an open fault.

[0026] When the heater switch 16 is short-circuited, even if the control device 40 controls the heater switch 16 to be off, the heater switch 16 continues to be on, so that the current from the AC power source 1 continues to flow through the heater switch 16 and does not flow through the light-emitting diode 32. For this reason, as shown in FIG. 8, the abnormality detection circuit 30 outputs a constant high-level voltage as the output voltage Vo. As shown in FIG. 4, when the heater switch 16 is controlled to be off under normal conditions, the output voltage Vo of the abnormality detection circuit 30 alternates between a low-level voltage and a high-level voltage. Therefore, when the determination unit 42 detects a constant high-level voltage as the output voltage Vo of the abnormality detection circuit 30 even though the heater switch 16 is controlled to be off, the determination unit 42 determines that the heater switch 16 is short-circuited. Note that in both the case of a disconnection failure of the toilet seat heater 11 and the case of a short-circuit failure of the heater switch 16, the abnormality detection circuit 30 outputs a constant high-level voltage as the output voltage Vo when the control device 40 controls the heater switch 16 to be off. Therefore, the determination unit 42 performs an abnormality determination without distinguishing between the two.

[0027] In this way, the toilet seat heater 11 and the heater switch 16 are judged to be abnormal by judging whether the output voltage Vo of the abnormality detection circuit 30 is different from that in the normal state. Therefore, if the output voltage Vo of the abnormality detection circuit 30 changes when the control method of the heater switch 16 (full-wave control, half-wave control, etc.) is switched during normal operation, it becomes impossible to compare with the normal state and to judge the abnormality. FIG. 9 is an explanatory diagram showing the output voltage of the abnormality detection circuit during full-wave control during normal operation and the output voltage of the abnormality detection circuit during half-wave control (upper half-wave on, lower half-wave on). During full-wave control, the heater switch 16 is turned on during the entire section of the AC power supply voltage V, so no current flows through the light-emitting diode 32, and a constant high-level voltage is output from the abnormality detection circuit 30 as the output voltage Vo (see FIG. 9(a)). On the other hand, in half-wave control, the heater switch 16 is turned off for half the interval of the AC power supply voltage V, so that if an off period of the heater switch 16 occurs during a period in which the direction of the current flowing through the heater drive circuit 15 is the forward direction of the light-emitting diode 32, a current flows through the light-emitting diode 32 during the off period, and the abnormality detection circuit 30 alternately outputs a low-level voltage and a high-level voltage as the output voltage Vo, unlike in full-wave control (see FIG. 9(c)). Therefore, in this embodiment, the control unit 41 controls the heater switch 16 in half-wave control so that an off period of the heater switch 16 does not occur during a period in which the direction of the current flowing through the heater drive circuit 15 is the forward direction of the light-emitting diode 32. Specifically, since the direction of current flowing through heater drive circuit 15 during the upper half-wave section of AC power supply voltage V is the forward direction of light-emitting diode 32, heater switch 16 is controlled to be turned on when a half cycle has elapsed since detection of the falling zero cross of AC power supply voltage V so that the upper half-wave of AC power supply voltage V is applied to toilet seat heater 11 (see FIG. 9(b)). As a result, under normal conditions, output voltage Vo of abnormality detection circuit 30 can be made the same during full-wave control and half-wave control, and abnormality detection can be performed appropriately whether full-wave control or half-wave control is performed.In addition, when duty control is performed within the range of 50% to 100%, in order to make the output voltage Vo of the abnormality detection circuit 30 the same as when full-wave control is performed, it is sufficient that the off period of the heater switch 16 does not occur during the period in which the direction of the current flowing through the heater drive circuit 15 is the forward direction of the light-emitting diode 32. Therefore, for example, as shown in Figure 10 (70% duty control), a number of cycles may be defined as a unit period, and the execution ratio of full-wave control and half-wave control within the unit period may be adjusted according to the duty ratio.

[0028] In the heater device 10 of the present embodiment described above, when the heater switch 16 is controlled with a duty ratio other than 100%, the heater switch 16 is controlled so that an off period of the heater switch 16 does not occur during a period in which the direction of the current flowing through the heater drive circuit 15 is the forward direction of the light-emitting diode 32 based on the detection of a zero cross by the zero cross detection circuit 20. As a result, in half-wave control, the output voltage Vo of the abnormality detection circuit 30 in the normal state can be made the same as that in full-wave control, so that with either control method, abnormalities such as a disconnection of the toilet seat heater 11 and an open failure or short circuit failure of the heater switch 16 can be appropriately detected by comparing the output voltage Vo of the abnormality detection circuit 30 with that in the normal state.

[0029] In this embodiment, the abnormality detection circuit 30 is configured so that the direction of the current flowing through the heater drive circuit 15 during the period (half cycle) from the time when a half cycle has elapsed since the detection of a zero cross (a falling zero cross of the AC power supply voltage V) by the zero cross detection circuit 20 until the next zero cross is the forward direction of the light emitting diode 32, but the abnormality detection circuit 30 may be configured so that the current flowing through the heater drive circuit 15 during the period from the time when a zero cross is detected by the zero cross detection circuit 20 until the next zero cross is the forward direction of the light emitting diode 32. In this case, for example, when the direction of the current flowing through the heater drive circuit 15 during the upper half-wave section of the AC power supply voltage V is the forward direction of the light emitting diode 32, and the zero cross detection circuit 20 detects a rising zero cross of the AC power supply voltage V, in half-wave control, the heater switch 16 may be turned on when the zero cross detection circuit 20 detects a rising zero cross or when one cycle has elapsed since the detection of the rising zero cross.

[0030] In this embodiment, as shown in FIG. 1, the heater switch 16 includes a triac, but may include a photorelay such as a solid-state relay.

[0031] In this embodiment, the heater device 10 is applied to determine an abnormality in the toilet seat heater 11 or heater switch 16 in a heater drive circuit 15 in which the toilet seat heater 11 and heater switch 16 are connected in series to an AC power source 1. However, the heater device is not limited to the toilet seat heater 11, and can be applied to any heater device that detects an abnormality in a heater or drive switch, such as a hot water heater for heating washing water sprayed from a nozzle onto the private parts of the human body in a sanitary washing device, or a drying heater for drying the private parts of the human body wetted during washing with hot air.

[0032] The correspondence between the main elements of the embodiment and the main elements of the invention described in the section on means for solving the problem will be described below. In the embodiment, the toilet seat heater 11 corresponds to the "heater", the heater drive circuit 15 corresponds to the "heater drive circuit", the heater switch 16 corresponds to the "drive switch", the zero-cross detection circuit 20 corresponds to the "zero-cross detection circuit", the photocoupler 31 corresponds to the "photocoupler", the diode 34 corresponds to the "diode", the abnormality detection circuit 30 corresponds to the "abnormality detection circuit", the control unit 41 corresponds to the "control unit", and the judgment unit 42 corresponds to the "judgment unit".

[0033] Note that the correspondence between the main elements of the embodiment and the main elements of the invention described in the Means for Solving the Problem column does not limit the elements of the invention described in the Means for Solving the Problem column, since the embodiment is an example for specifically explaining the form for implementing the invention described in the Means for Solving the Problem column. In other words, the interpretation of the invention described in the Means for Solving the Problem column should be made based on the description in that column, and the embodiment is merely a specific example of the invention described in the Means for Solving the Problem column.

[0034] Although the above describes the form for carrying out the present invention, the present invention is not limited to such an embodiment, and it is of course possible to carry out the present invention in various forms without departing from the spirit of the present invention. [Industrial Applicability]

[0035] The present invention can be used in the manufacturing industry of heater devices and abnormality detection circuits. [Explanation of symbols]

[0036] 1 AC power supply, 2 toilet seat, 10 heater device, 11 toilet seat heater, 15 heater drive circuit, 16 heater switch, 20 zero cross detection circuit, 21 photocoupler, 22 light emitting diode, 23 phototransistor, 24 diode, 25, 26 resistance element, 27 capacitor, 30 abnormality detection circuit, 31 photocoupler, 32 light emitting diode, 33 phototransistor, 34 diode, 35, 36 resistance element, 37 capacitor, 40 control device, 41 control unit, 42 judgment unit.

Claims

1. a heater drive circuit in which a heater and a drive switch are connected in series to an AC power source; a zero-cross detection circuit for detecting a rising zero-cross or a falling zero-cross of a voltage of the AC power supply; an abnormality detection circuit including a photocoupler including a light-emitting diode connected in parallel to the drive switch and a phototransistor receiving light from the light-emitting diode, and a diode connected in anti-parallel to the light-emitting diode; a determination unit that determines an abnormality in the heater or the heater drive circuit based on an output of the abnormality detection circuit; a control unit that controls the drive switch so that an off period of the drive switch does not occur during a period in which a direction of a current flowing through the heater drive circuit is a forward direction of the light emitting diode, based on a rising zero cross or a falling zero cross detected by the zero cross detection circuit, when the drive switch is controlled by half-wave control or when the drive switch is controlled by adjusting an execution ratio of full-wave control and half-wave control within a unit period having a plurality of cycles as a unit period. A heater device comprising:

2. 2. The heater device according to claim 1, the abnormality detection circuit is configured so that the direction of the current flowing through the heater drive circuit becomes the forward direction of the light emitting diode during a half cycle from the time when a falling zero cross is detected by the zero cross detection circuit until the next zero cross. Heater device.

3. 2. The heater device according to claim 1, the abnormality detection circuit is configured so that a direction of a current flowing through the heater drive circuit becomes a forward direction of the light emitting diode during a half cycle from a time when a falling zero cross is detected by the zero cross detection circuit until the next zero cross. Heater device.

4. The heater device according to any one of claims 1 to 3, the determination unit determines that an open fault has occurred in the drive switch when an output of the abnormality detection circuit is repeatedly switched between a low level signal and a high level signal while the control unit is controlling the drive switch to be turned on. Heater device.

5. The heater device according to any one of claims 1 to 4, the determination unit determines that the heater has been broken or that the drive switch has been short-circuited when an output of the abnormality detection circuit is constant while the control unit is controlling the drive switch to be turned off. Heater device.

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