Zero-cross detection circuit

Abstract

To provide a zero-cross detection circuit capable of supplying a drive power source to a photocoupler using a suitable structure and capable of reducing power consumption.SOLUTION: A zero-cross detection circuit for detecting the zero-cross timing of an AC power source includes: a power source part being an AC power source; a photocoupler; a zero-cross breaking circuit capable of breaking the drive current of the zero cross detector circuit by the operation of the photocoupler; and a control part for controlling the zero-cross breaking circuit. The drive source divided from the power source part is supplied to the photocoupler of the zero-cross breaking circuit.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The disclosed embodiments relate to a zero-crossing detection circuit. [Background technology]

[0002] Conventionally, various zero-cross detection circuits have been proposed that detect zero crossings at which the voltage of an AC power supply becomes 0 V (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-174574 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned conventional technology, a drive current is supplied to the zero-cross detection circuit at the detection timing for detecting a zero cross, and the drive current is cut off at times other than the detection timing, thereby reducing the power consumption in the zero-cross detection circuit. The cut-off of the drive current is performed, for example, by the operation of a photocoupler. However, the conventional technology has room for improvement in terms of supplying a drive power supply to the photocoupler in an appropriate configuration.

[0005] An object of one aspect of an embodiment is to provide a zero-crossing detection circuit that can supply a driving power supply to a photocoupler using an appropriate configuration and can reduce power consumption. [Means for solving the problem]

[0006] A zero-cross detection circuit according to one aspect of the embodiment detects zero-cross timing of an AC power supply. The zero-cross detection circuit includes a power supply unit which is an AC power supply, a zero-cross interruption circuit including a photocoupler and capable of interrupting a drive current of the zero-cross detection circuit by operation of the photocoupler, and a control unit which controls the zero-cross interruption circuit, and the photocoupler of the zero-cross interruption circuit is supplied with a drive power divided from the power supply unit.

[0007] In this way, by supplying the photocoupler with a drive power divided from the power supply unit, it is possible to supply the drive power to the photocoupler without providing a separate power supply, in other words, it is possible to supply the drive power to the photocoupler using an appropriate configuration. Also, for example, by providing a zero-cross cutoff circuit that cuts off the drive current of the zero-cross detection circuit at times other than the timing of detecting the zero cross, it is possible to reduce the power consumption in the zero-cross circuit.

[0008] In addition, the zero-crossing cutoff circuit is provided on a connection line connected to the power supply unit and includes a voltage dividing circuit unit that divides the voltage of the power supply unit, a rectifier circuit unit that is connected to the voltage dividing circuit unit and rectifies the voltage output from the voltage dividing circuit unit, and a charging circuit unit that is connected to the rectifier circuit unit and charges the voltage rectified by the rectifier circuit unit, and the voltage charged by the charging circuit unit is supplied to the photocoupler as a driving power source.

[0009] In this way, by rectifying the voltage divided by the voltage dividing circuit, it is possible to prevent a reverse bias from being applied to, for example, DC drive components. Also, by charging the divided voltage once in the charging circuit and then using it, it is less susceptible to the voltage fluctuations of the AC power supply, and the driving power supply for the photocoupler can be stabilized.

[0010] In addition, the zero-cross cutoff circuit includes a drive circuit unit that has the photocoupler and a transistor connected to the photocoupler, and when in an on state, makes the zero-cross timing detectable in the zero-cross detection circuit, and the control unit turns on the drive circuit unit after the charging circuit unit has completed charging the amount of charge required for the operation of the drive circuit unit.

[0011] This ensures that the drive current for the photocoupler and transistor required to drive the zero-cross cutoff circuit does not run short, allowing the control unit to stably capture the zero-cross signal.

[0012] The control unit also executes a confirmation process for confirming whether the charging of the charging amount is completed in the charging circuit unit, turning on the drive circuit unit, and whether the zero-cross detection circuit is in a state in which it is possible to detect the zero-cross timing.

[0013] This allows the control unit to check whether the zero-cross detection circuit is in a state where it can detect a zero-cross, and to check (identify) the zero-cross timing, which enables the control unit to set the timing for turning on the drive circuit unit from the checked zero-cross timing, for example, from the next time onwards.

[0014] Furthermore, the control unit turns off the drive circuit unit after completing acquisition of a zero-cross signal indicating that the zero-cross timing has been detected.

[0015] This prevents the operation of the zero-cross cutoff circuit from being longer than necessary, resulting in further reduction in power consumption in the zero-cross detection circuit. Effect of the Invention

[0016] According to one aspect of the embodiment, it is possible to supply driving power to a photocoupler using an appropriate configuration, and to reduce power consumption. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a zero-crossing detection circuit according to an embodiment. [Diagram 2] FIG. 2 is a timing chart showing the operation of the zero-crossing detection circuit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, embodiments of the zero-crossing detection circuit disclosed in the present application will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to the embodiments described below.

[0019] A zero-cross detection circuit according to an embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram showing an example of the configuration of a zero-cross detection circuit 1 according to an embodiment.

[0020] The zero-cross detection circuit 1 shown in Fig. 1 is a circuit that detects zero-cross timing (hereinafter may be referred to as "zero cross") when the voltage of an AC power supply becomes 0V. The zero-cross detection circuit 1 includes a control unit 100. The control unit 100 is a microcomputer having a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), etc. The CPU of the microcomputer detects zero crosses and controls the driving of an electric load (not shown), such as a heater, by reading and executing a program stored in the ROM.

[0021] Specifically, when the control unit 100 detects a zero cross, it controls (ON / OFF control) the drive of an electric load such as a heater, thereby reducing noise, for example. On the other hand, when the drive control of this electric load is not required, that is, at a time other than the detection timing for detecting a zero cross, the drive current to the zero cross detection circuit 1 is cut off, thereby reducing power consumption in the zero cross detection circuit 1.

[0022] More specifically, the zero-crossing detection circuit 1 includes a power supply unit 10, a first diode 21, and a second diode 22. The power supply unit 10 is an AC power supply (commercial power supply (for example, 100 V)).

[0023] The first diode 21 has a cathode connected to one end of the power supply unit 10, and an anode connected to the anode of the second diode 22. The second diode 22 has a cathode connected to the other end of the power supply unit 10.

[0024] The zero-cross detection circuit 1 further includes a first photocoupler 31 and a zero-cross cutoff circuit 40. The first photocoupler 31 includes a light-emitting diode 31a and a transistor 31b, and turns on when the voltage of the AC power supply, which is the power supply unit 10, is positive. To be precise, the first photocoupler 31 turns on when a switching element 43, which will be described later, is on and the voltage of the AC power supply is positive.

[0025] In addition, a capacitor 32 and a resistor 33 are connected to the first photocoupler 31. More specifically, one end of the capacitor 32 and the resistor 33 is connected to the anode of the light-emitting diode 31a, and the other end is connected to the cathode of the light-emitting diode 31a. The capacitor 32 and the resistor 33 are components for absorbing noise to the first photocoupler 31.

[0026] In addition, resistors 51 and 52 are connected to the first photocoupler 31. One end of resistor 51 is connected to a power supply potential, and the other end is connected to the collector of transistor 31b. One end of resistor 52 is connected to the other end of resistor 51 and the collector of transistor 31b, and the other end is connected to control unit 100. Such resistors 51 and 52 are current limiting resistors.

[0027] The zero-crossing cutoff circuit 40 includes a second photocoupler 41, a resistor-built-in transistor 42, and the above-mentioned switching element 43, and is configured so that the drive current of the zero-crossing detection circuit 1 can be cut off by the operation of the second photocoupler 41 etc. The second photocoupler 41, the resistor-built-in transistor 42, and the switching element 43 are an example of a drive circuit section 45. The drive circuit section 45 is configured so that, when in an on state, the zero-crossing detection circuit 1 is in a state where it can detect zero crossings.

[0028] Specifically, the second photocoupler 41 includes a light emitting diode 41a and a transistor 41b. The emitter of the transistor 41b is connected to a switching element 43 via a resistor 43a (described later). The second photocoupler 41 is an example of a photocoupler.

[0029] The resistor-embedded transistor 42 includes a transistor 42a, and the collector of the transistor 42a is connected to the cathode of the light-emitting diode 41a via a resistor 44. The base of the transistor 42a is connected to the control unit 100 via a resistor 42b, and the emitter is connected to the base via a resistor 42c. The resistor 44 is a current limiting resistor, the resistor 42b is a base resistor of the transistor 42a, and the resistor 42c is a resistor for stabilizing the voltage between the base and emitter of the transistor 42a.

[0030] The switching element 43 is an example of a transistor, and the collector is connected to the cathode of the light-emitting diode 31a, and the emitter is connected to the anode of the second diode 22. The base of the switching element 43 is connected to the emitter of the transistor 41b of the second photocoupler 41 via a resistor 43a. The emitter of the switching element 43 is connected to the base via a resistor 43b. The resistor 43a is a base resistor of the switching element 43, and the resistor 43b is a resistor for stabilizing the voltage between the base and emitter of the switching element 43. Note that, as the switching element 43, an NPN bipolar high-voltage transistor can be used, but is not limited thereto.

[0031] Incidentally, a driving power supply is supplied to the above-mentioned second photocoupler 41. More specifically, in the second photocoupler 41, a power supply is connected to the collector side of the transistor 41b, and driving power is supplied from the power supply.

[0032] In the prior art, the withstand voltage of the components in the second photocoupler was taken into consideration, and for example, the driving power was supplied from the auxiliary winding voltage of the power supply. However, for example, when the power supply is a modularized power supply unit, a new connection line is required to supply the auxiliary winding voltage inside the power supply module to the second photocoupler, and this is difficult to actually provide. For this reason, for example, it is conceivable to provide a terminal pin for the driving power of the second photocoupler on the board of the power supply unit, but in this case, there is a risk that the size of the power supply unit will increase and the cost will increase.

[0033] Therefore, in the zero-cross detection circuit 1 according to this embodiment, the drive power for the second photocoupler 41 can be supplied using an appropriate configuration.

[0034] Specifically, second photocoupler 41 of zero-crossing cutoff circuit 40 is supplied with a divided driving power from power supply unit 10. More specifically, zero-crossing cutoff circuit 40 further includes a voltage divider circuit unit 60, a rectifier circuit unit 70, a resistor 80, and a charging circuit unit 90.

[0035] The voltage divider circuit section 60 is provided on a connection line 10a connected to the power supply section 10, and divides the voltage of the power supply section 10. More specifically, the voltage divider circuit section 60 includes a first resistor 61 and a second resistor 62. One end of the first resistor 61 is connected to one end of the power supply section 10, and the other end is connected to one end of the second resistor 62. The other end of the second resistor 62 is connected to the other end of the power supply section 10. A connection point 60a is provided between the first resistor 61 and the second resistor 62, and a division line 60b is connected to the connection point 60a.

[0036] The voltage at the dividing line 60b is set according to the resistance value of the first resistor 61 and the resistance value of the second resistor 62, and is set to, for example, 30V. Although the voltage at the dividing line 60b is specifically shown above, this is merely an example and is not limiting. In this way, the voltage dividing circuit unit 60 divides the voltage of the power supply unit 10, and therefore it can also be said to be a voltage dividing circuit unit. Although the above shows an example in which the voltage dividing circuit unit 60 divides the voltage of the power supply unit 10 using the first and second resistors 61 and 62, the present invention is not limited to this, and may be configured in other ways, such as a circuit using an IC (Integrated Circuit).

[0037] The rectifier circuit section 70 is connected to the voltage divider circuit section 60. In other words, the rectifier circuit section 70 is provided on the division line 60b. The rectifier circuit section 70 rectifies the voltage output from the voltage divider circuit section 60. For example, a rectifier diode can be used as the rectifier circuit section 70. The rectifier diode, which is the rectifier circuit section 70, has an anode connected to the voltage divider circuit section 60 (more precisely, the connection point 60a of the voltage divider circuit section 60) and a cathode connected to the charging circuit section 90 via a resistor 80. The resistor 80 is a resistor that sets a time constant for charging the charging circuit section 90.

[0038] The charging circuit section 90 is connected to the rectifier circuit section 70 via a resistor 80. The charging circuit section 90 charges the voltage rectified by the rectifier circuit section 70. A capacitor can be used as the charging circuit section 90, and for example, an electrolytic capacitor can be used, but the present invention is not limited thereto.

[0039] The voltage charged by the charging circuit section 90 is supplied to the second photocoupler 41 as a driving power source.

[0040] Thus, the zero-cross detection circuit 1 according to this embodiment includes the zero-cross interruption circuit 40, and the second photocoupler 41 of the zero-cross interruption circuit 40 is supplied with a drive power divided from the power supply unit 10. This makes it possible to supply drive power to the second photocoupler 41 without providing a new connection line and a separate power supply using, for example, the above-mentioned auxiliary winding voltage or a terminal pin of the power supply unit; in other words, the drive power for the second photocoupler 41 can be supplied using an appropriate configuration.

[0041] Next, a description will be given of the operation of the zero-cross detection circuit 1 configured as above. The control unit 100 controls the zero-cross detection circuit 1 including the zero-cross interruption circuit .

[0042] For example, the control unit 100 turns on / off the output signal to the resistor built-in transistor 42. In detail, the control unit 100 turns on the output signal to the resistor built-in transistor 42 at the detection timing for detecting a zero cross.

[0043] When the output signal to the resistor built-in transistor 42 is turned on, the resistor built-in transistor 42 is turned on. When the resistor built-in transistor 42 is turned on, the second photocoupler 41 is turned on. When the second photocoupler 41 is turned on, the switching element 43 is turned on. In other words, the drive circuit unit 45 is turned on.

[0044] When the switching element 43 is on and the voltage of the AC power supply is positive, the first photocoupler 31 is on. As a result, the voltage of the input signal to the control unit 100 switches from a Hi signal from the power supply voltage to a reference voltage Lo signal, and the control unit 100 detects a zero-cross signal indicating that a zero-cross timing has been detected.

[0045] It should be noted that the second diode 22 does not conduct electricity when the voltage of the AC power supply is negative, thereby preventing the application of a reverse voltage to the switching element 43.

[0046] On the other hand, the control unit 100 turns off the output signal to the resistor-built-in transistor 42 at times other than the detection timing for detecting the zero crossing. When the output signal to the resistor-built-in transistor 42 is turned off, the resistor-built-in transistor 42 turns off. When the resistor-built-in transistor 42 turns off, the second photocoupler 41 turns off. When the second photocoupler 41 turns off, the switching element 43 turns off. In other words, the drive circuit unit 45 is turned off.

[0047] When the switching element 43 is in the off state, the first photocoupler 31 is not turned on even if the voltage of the AC power supply is positive. In this way, the drive current to the zero-cross detection circuit 1 is cut off except at the detection timing for detecting the zero-cross, so that the power consumption in the zero-cross detection circuit 1 can be reduced.

[0048] Next, a description will be given of the timing of the operation of the zero-cross detection circuit 1 configured as above. Fig. 2 is a diagram showing a timing chart of the operation of the zero-cross detection circuit 1. In Fig. 2, from the top, the power supply voltage waveform of the power supply unit 10, the zero-cross signal, the output signal to the resistor built-in transistor 42, the discharge current of the capacitor which is the charging circuit unit 90, the charging current of the capacitor which is the charging circuit unit 90, and the voltage across the capacitor which is the charging circuit unit 90 are shown.

[0049] The control unit 100 according to the present embodiment executes a confirmation process to confirm whether the zero-cross detection circuit 1 is in a state where the zero-cross can be detected before the normal process of detecting the zero-cross. In detail, the control unit 100 executes the confirmation process at a predetermined timing such as at the time of startup or before energizing an electric load. In the confirmation process, for example, the charging circuit unit 90 completes the charging amount required for the operation of the drive circuit unit 45 including the second photocoupler 41, etc., turns on the drive circuit unit 45 including the second photocoupler 41, etc., and executes a process to confirm whether the zero-cross detection circuit 1 is in a state where the zero-cross can be detected. In the example of FIG. 2, the confirmation process is performed from time T1 to time T7, and the normal process of detecting the zero-cross is performed from time T8 onwards.

[0050] More specifically, when the zero-cross detection circuit 1 is started at time T1 and AC power is supplied to the zero-cross detection circuit 1, the charging circuit unit 90 is charged during a period in which the voltage of the AC power supply (specifically, the voltage across the capacitor) is positive. In other words, the charging circuit unit 90 is charged with an amount of charge necessary for the operation of the drive circuit unit 45.

[0051] After charging of charging circuit unit 90 is completed (see time T2), control unit 100 turns on drive circuit unit 45 at a preset arbitrary timing (see time T3). More specifically, control unit 100 turns on the output signal to resistor-built-in transistor 42, and turns on resistor-built-in transistor 42, second photocoupler 41, etc. This causes drive power to be supplied from charging circuit unit 90 to second photocoupler 41, and charging circuit unit 90 discharges.

[0052] Next, after the zero cross occurs at time T4, the control unit 100 detects a zero cross signal indicating that the zero cross has been detected (see time T5). When the control unit 100 completes the capture of the zero cross signal (see time T6), it turns off the drive circuit unit 45. In detail, the control unit 100 turns off the output signal to the resistor built-in transistor 42, and turns off the resistor built-in transistor 42 and the second photocoupler 41, etc. Since the control unit 100 detects the zero cross signal and completes the capture of the zero cross signal, it determines that the zero cross detection circuit 1 is in a state where it can detect a zero cross. Furthermore, by this confirmation process, the control unit 100 can confirm (identify) the zero cross timing, and can set the timing for turning on the output signal to the resistor built-in transistor 42 from the confirmed zero cross timing from the next time onwards.

[0053] Next, the control unit 100 executes normal processing to detect zero crossing. The charging circuit unit 90 is charged during the period (times T4 to T7) when the voltage of the AC power supply (specifically, the voltage across the capacitor) is positive. In other words, the charging circuit unit 90 is charged with the amount of charge required for the operation of the drive circuit unit 45.

[0054] After charging of charging circuit unit 90 is completed (see time T7), control unit 100 turns on drive circuit unit 45 at a predetermined timing (here, time T8) set from the zero-cross timing confirmed in the confirmation process. In detail, control unit 100 turns on the output signal to resistor-integrated transistor 42, and turns on resistor-integrated transistor 42, second photocoupler 41, etc. This causes drive power to be supplied from charging circuit unit 90 to second photocoupler 41, and charging circuit unit 90 discharges.

[0055] Next, after the zero cross occurs at time T9, the control unit 100 detects a zero cross signal indicating that the zero cross has been detected (see time T10). When the control unit 100 has completed capturing the zero cross signal (see time T11), it turns off the drive circuit unit 45. More specifically, the control unit 100 turns off the output signal to the resistor built-in transistor 42, and turns off the resistor built-in transistor 42, the second photocoupler 41, etc. After that, the normal processing described above continues.

[0056] As shown in FIG. 2, the charging circuit unit 90 is charged while discharging, but the present invention is not limited thereto, and may be charged after discharging (after discharging is completed). However, it is preferable that the charging circuit unit 90 is charged while discharging. That is, for example, if the charging circuit unit 90 is configured to discharge before charging, it is necessary to advance the timing of completing the discharge. In such a case, the current flows to the zero-cross detection circuit 1 side earlier by the amount of the advance. Therefore, there is a risk of more loss occurring compared to when charging is performed while discharging. Therefore, it is preferable that the charging circuit unit 90 is charged while discharging.

[0057] The above-mentioned confirmation process may be performed only the first time when the device is started up, but is not limited to this. That is, the confirmation process may be performed every time before an electric load such as a heater is operated, assuming that the commercial power supply unit 10 may not be supplied normally due to a momentary power outage or momentary drop in the power supply voltage.

[0058] As described above, the zero-cross detection circuit 1 according to this embodiment detects the zero-cross timing of an AC power supply. The zero-cross detection circuit 1 is equipped with a power supply unit 10 which is an AC power supply, a zero-cross interruption circuit 40 which includes a second photocoupler 41 (an example of a photocoupler) and can interrupt the drive current of the zero-cross detection circuit 1 by operation of the second photocoupler 41, and a control unit 100 which controls the zero-cross interruption circuit 40. A divided drive power supply is supplied from the power supply unit 10 to the second photocoupler 41 of the zero-cross interruption circuit 40.

[0059] This makes it possible to supply drive power to the second photocoupler 41 without providing a separate power supply, in other words, it is possible to supply drive power to the second photocoupler 41 using an appropriate configuration. Furthermore, by providing the zero-crossing cutoff circuit 40, it is possible to reduce power consumption.

[0060] Furthermore, the zero-crossing cutoff circuit 40 includes the voltage divider circuit section 60, the rectifier circuit section 70, and the charging circuit section 90, and the voltage charged by the charging circuit section 90 is supplied to the second photocoupler 41 as a drive power source. By rectifying the voltage divided by the voltage divider circuit section 60 in this manner, it is possible to prevent a reverse bias from being applied to, for example, a DC-driven component. Furthermore, by charging the divided voltage once in the charging circuit section 90 and then using it, the drive power source for the second photocoupler 41 can be stabilized without being affected by voltage fluctuations in the AC power source (power supply section 10).

[0061] Zero-cross cutoff circuit 40 also includes drive circuit 45 which has a second photocoupler 41 and a switching element 43 (an example of a transistor) and which, when on, sets zero-cross timing in detectable state in zero-cross detection circuit 1. Control unit 100 turns on drive circuit 45 after charging circuit 90 has completed charging the amount of charge required for the operation of drive circuit 45.

[0062] As a result, the drive current required for driving second photocoupler 41 and switching element 43 to drive zero-cross cutoff circuit 40 is not insufficient, and control unit 100 can stably capture the zero-cross signal.

[0063] The control unit 100 also executes a confirmation process. For example, the control unit 100 executes the confirmation process before normal processing. In the confirmation process, the charging circuit unit 90 completes charging, turns on the drive circuit unit 45, and confirms whether the zero-cross timing can be detected in the zero-cross detection circuit 1. This allows the control unit 100 to confirm whether the zero-cross detection circuit 1 is in a state where it can detect a zero cross, and also to confirm (identify) the zero-cross timing. This allows the control unit 100 to set the timing for turning on the output signal to the resistor built-in transistor 42 from the confirmed zero-cross timing, for example, from the next time onwards.

[0064] Furthermore, after control unit 100 has completed receiving the zero-cross signal indicating that the zero-cross timing has been detected, it turns off drive circuit unit 45. This prevents zero-cross cutoff circuit 40 from operating for longer than necessary, and as a result, power consumption in zero-cross detection circuit 1 can be further reduced.

[0065] <Additional Notes> (1) A zero-cross detection circuit for detecting zero-cross timing of an AC power supply, a power supply unit which is an AC power supply; a zero-crossing cutoff circuit including a photocoupler and capable of cutting off a drive current of the zero-crossing detection circuit by an operation of the photocoupler; a control unit for controlling the zero-crossing cutoff circuit; Equipped with A driving power source divided from the power supply unit is supplied to the photocoupler of the zero-cross cutoff circuit. Zero cross detection circuit. (2) The zero crossing cutoff circuit includes: a voltage division circuit section provided in a connection line connected to the power supply section and dividing a voltage of the power supply section; a rectification circuit section connected to the voltage division circuit section and configured to rectify a voltage output from the voltage division circuit section; a charging circuit section connected to the rectification circuit section and configured to charge the voltage rectified by the rectification circuit section; Including, The photocoupler is supplied with a voltage charged by the charging circuit as a driving power source. The zero-cross detection circuit according to (1). (3) The zero crossing cutoff circuit includes: a drive circuit section having the photocoupler and a transistor connected to the photocoupler, the drive circuit section turning on the transistor to a state in which the zero-cross timing can be detected by the zero-cross detection circuit; Including, The control unit is turning on the drive circuit unit after the charging circuit unit has completed charging the amount of charge required for the operation of the drive circuit unit; The zero-cross detection circuit according to (2). (4) The control unit is a confirmation process is executed to confirm whether the charging of the charging amount is completed in the charging circuit section, the driving circuit section is turned on, and whether the zero-cross timing is detectable in the zero-cross detection circuit; (3) A zero-cross detection circuit as described above. (5) The control unit is turning off the drive circuit unit after the acquisition of a zero-cross signal indicating that the zero-cross timing has been detected is completed; A zero-crossing detection circuit according to (3) or (4).

[0066] Further advantages and modifications may readily occur to those skilled in the art. Thus, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and equivalents thereof. [Explanation of symbols]

[0067] 1 Zero-cross detection circuit 10 Power supply section 40 Zero-cross cutoff circuit 100 Control section

Claims

1. A zero-cross detection circuit for detecting zero-cross timing of an AC power supply, a power supply unit which is an AC power supply; a zero-crossing cutoff circuit including a photocoupler and capable of cutting off a drive current of the zero-crossing detection circuit by an operation of the photocoupler; a control unit for controlling the zero-crossing cutoff circuit; Equipped with A driving power source divided from the power supply unit is supplied to the photocoupler of the zero-cross cutoff circuit. Zero cross detection circuit.

2. The zero crossing cutoff circuit includes: a voltage division circuit section provided in a connection line connected to the power supply section and dividing a voltage of the power supply section; a rectification circuit section connected to the voltage division circuit section and configured to rectify a voltage output from the voltage division circuit section; a charging circuit section connected to the rectification circuit section and configured to charge the voltage rectified by the rectification circuit section; Including, The photocoupler is supplied with a voltage charged by the charging circuit as a driving power source.

2. The zero crossing detection circuit of claim 1.

3. The zero crossing cutoff circuit includes: a drive circuit section having the photocoupler and a transistor connected to the photocoupler, the drive circuit section turning on the transistor to a state in which the zero-cross timing can be detected by the zero-cross detection circuit; Including, The control unit is turning on the drive circuit unit after the charging circuit unit has completed charging the amount of charge required for the operation of the drive circuit unit; 3. The zero crossing detection circuit according to claim 2.

4. The control unit is a confirmation process is executed to confirm whether the charging of the charging amount is completed in the charging circuit section, the driving circuit section is turned on, and whether the zero-cross timing is detectable in the zero-cross detection circuit; 4. The zero crossing detection circuit according to claim 3.

5. The control unit is turning off the drive circuit unit after the acquisition of a zero-cross signal indicating that the zero-cross timing has been detected is completed; 4. The zero crossing detection circuit according to claim 3.

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