KR101451822B1 - Driving apparatus for light emitting diode using ac power supply - Google Patents

Abstract

According to the LED driving apparatus using the AC power source according to the preferred embodiment of the present invention, even if the magnitude of the AC voltage as the commercial power source varies arbitrarily, the pulse width of the semiconductor switch is adjusted to supply the stable voltage, can do. Also, according to the present invention, a high power factor of 0.99 or more can be realized by switching the AC power supply to a high frequency so that voltage and current have the same phase and flowing a current according to the voltage level.
A light emitting diode driving apparatus using an AC power source according to a preferred embodiment of the present invention includes a converter for receiving an AC power source and outputting an AC voltage having a certain effective value by reducing a voltage; A full wave rectifier for full-wave rectifying and outputting the output voltage of the converter; And a controller for generating a control signal for controlling the operation of the transducer.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an LED driving apparatus using an AC power source,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an LED driving apparatus using an AC power source, and more particularly, to a photodiode driving apparatus capable of supplying a stable power while using an AC power source.

BACKGROUND ART In a light modulation apparatus using a light emitting diode (LED), the life of a light emitting diode itself is long, but a driving apparatus for driving a light emitting diode has a problem in that the position where the light emitting diode is installed is not generally convective, There is always a problem that reliability is deteriorated due to heat or the like disposed directly on the heat sink.

In order to improve this, an AC light emitting diode (AC LED) or an AC direct light emitting diode light modulating device which directly drives an AC power source has been introduced, but a flicker phenomenon occurs due to the instability of a system voltage Another problem is happening.

In order to solve this problem, a constant voltage source that synchronizes the system voltage and current while stabilizing the voltage in spite of the fluctuation of the system voltage and a constant current source for driving the light emitting diode by rectifying it are secured There is a demand for a light emitting diode driving apparatus that does not use an electrolytic capacitor which is highly related to the lifetime in order to increase the reliability of the light emitting diode driving apparatus.

KR 1020060071869 A KR 1020110100577 A

SUMMARY OF THE INVENTION It is an object of the present invention to solve the technical problems as described above, and it is an object of the present invention to provide a semiconductor light emitting device capable of adjusting a pulse width of a semiconductor switch, And to provide an LED driving apparatus using an AC power source.

It is still another object of the present invention to provide an LED driving apparatus using an AC power source capable of realizing a high power factor of 0.99 or more by switching an AC power supply to a high frequency so that voltage and current have the same phase, But also to provide.

According to a preferred embodiment of the present invention, there is provided an apparatus for driving an LED using an AC power source, the apparatus comprising: a converter for receiving an AC power source and outputting an AC voltage having a predetermined effective value; A full wave rectifier for full-wave rectifying and outputting the output voltage of the converter; And a controller for generating a control signal for controlling the operation of the transducer.

The controller may further include: a detector that detects at least one of an output of the converter, an output of the full-wave rectifier, or the input AC power; And a control signal generator for generating the control signal for controlling the operation of the converter by using at least one of the output of the converter, the output of the full-wave rectifier, and the AC power source detected by the detector .

It is also preferable that the control signal generator generates the control signal by modulating the pulse width of the square wave.

Specifically, the converter includes: a switching element unit including a first switching element, a second switching element, a third switching element, and a fourth switching element whose ON or OFF is controlled by the control signal; And an LC element part for outputting an AC voltage having a certain effective value by using the output of the switching element part. Further, the LC element portion includes a first inductor and a third capacitor.

Preferably, the one end of the first switching device is connected to the positive terminal of the AC power source, the other end of the first switching device is connected to one end of the third switching device and one end of the first inductor, The other end of the third switching element is connected to one end of the fourth switching element, the other end of the fourth switching element is connected to one end of the second switching element, and the other end of the fourth switching element is connected to the negative And is connected to the terminal.

One end of the first switching device connected to the positive terminal of the AC power source is connected to one end of the first capacitor and the other end of the first capacitor is connected to the other end of the third switching device and one end of the second capacitor And the other end of the second capacitor is connected to the other end of the second switching device.

Specifically, the controller controls the first switching element and the second switching element in a first predetermined period in which the AC power source changes from a 0 voltage to a positive voltage, and during a second predetermined period in which the AC power source changes from a positive voltage to a zero voltage, The first switching device and the third switching device are controlled such that the third switching device is turned off while the AC power source except for the first predetermined period and the second predetermined period is a positive voltage, The third switching element is turned off during the on period of the first switching element and the third switching element is turned on during the off period of the first switching element, And a control signal for controlling the element and the third switching element. The first predetermined period and the second predetermined period may have a value of 0 or a predetermined positive value.

The controller may control the second switching element and the second switching element in a third period during which the AC power is changed from a zero voltage to a positive voltage and during a fourth predetermined period during which the AC power is changed from a positive voltage to a zero voltage, The second switching device and the fourth switching device are turned on during a period in which the AC power source is in a positive voltage except for the third predetermined period and the fourth predetermined period, The control signal for controlling the second switching element and the fourth switching element is generated so as to maintain the state of the second switching element and the fourth switching element. Preferably, the third predetermined period and the fourth predetermined period have a value of 0 or a predetermined positive value.

In addition, the controller may control the second switching element and the second switching element in a fifth predetermined period in which the AC power source changes from a 0 voltage to a negative voltage, and during a sixth predetermined period in which the AC power source changes from a negative voltage to a zero voltage, The second switching device and the fourth switching device are controlled such that the fourth switching device is turned off while the AC power is negative during the fifth predetermined period and the sixth predetermined period, The fourth switching element is turned off during the on period of the second switching element and the fourth switching element is turned on during the off period of the second switching element, And a control signal for controlling the first switching element and the fourth switching element. Preferably, the fifth predetermined period and the sixth predetermined period have a value of 0 or a predetermined positive value.

The controller may control the first switching element and the second switching element during a seventh constant period in which the AC power source changes from a 0 voltage to a negative voltage and during an eighth predetermined period in which the AC power source changes from a negative voltage to a zero voltage, The first switching device and the third switching device are controlled such that the third switching device is turned off while the AC power source except for the seventh certain period and the eighth constant period is a negative voltage, The control signal for controlling the first switching device and the third switching device is generated. Preferably, the seventh predetermined period and the eighth predetermined period have a value of 0 or a predetermined positive value.

The full-wave rectifier of the present invention is characterized by being a diode bridge including a fifth diode, a sixth diode, a seventh diode and an eighth diode. The driving apparatus of the present invention may further include: a fourth capacitor connected in parallel to an output terminal of the full-wave rectifier; And a first resistor connected in series with the light emitting diode array including at least one light emitting diode.

According to the LED driving apparatus using the AC power source according to the preferred embodiment of the present invention, even if the magnitude of the AC voltage as the commercial power source varies arbitrarily, the pulse width of the semiconductor switch is adjusted to supply the stable voltage, can do. Also, according to the present invention, a high power factor of 0.99 or more can be realized by switching the AC power supply to a high frequency so that voltage and current have the same phase and flowing a current according to the voltage level.

FIG. 1 is a configuration diagram of an LED driving apparatus using an AC power source according to a preferred embodiment of the present invention. FIG.
2 is a circuit diagram showing a configuration diagram of the LED driving apparatus of FIG.
3 is a voltage waveform diagram of an input AC power source, an input of each switching element, and a light emitting diode array.

Hereinafter, an LED driving apparatus using an AC power source according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

It should be understood that the following embodiments of the present invention are only for embodying the present invention and do not limit or limit the scope of the present invention. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

1 is a configuration diagram of an LED driving apparatus 100 using an AC power supply according to a preferred embodiment of the present invention. 2 shows a circuit diagram embodying the configuration diagram of the LED driving apparatus 100 of FIG. However, the controller 30 is not shown in Fig. 1 and 2, an LED driving apparatus 100 using an AC power source according to an exemplary embodiment of the present invention receives an AC power, depressurizes it, and outputs an AC voltage having a certain effective value A full wave rectifier 20 for full-wave rectifying and outputting the output voltage of the converter 10 and a controller 30 for generating a control signal for controlling the converter 10.

Hereinafter, each component included in the LED driving apparatus 100 of the present invention will be described in more detail.

The converter 10 of the present invention includes a switching element portion 11, a diode portion 12 and an LC element portion 13.

The switching element unit 11 includes a first switching element Q1, a second switching element Q2, a third switching element Q3, a fourth switching element Q2, a third switching element Q3, A switching element Q4, a first capacitor C1, and a second capacitor C2. The first capacitor C1 and the second capacitor C2 serve to keep the voltage across the node where the first capacitor C1 and the second capacitor C2 meet. Therefore, the first capacitor C1 and the second capacitor C2 are preferably the same kind of capacitors having the same capacitance value.

The diode unit 12 includes a first diode D1 and a second diode D2 connected in parallel to the first through fourth switching devices Q1, Q2, Q3, and Q4 of the switching device unit 11, A third diode D3, and a fourth diode D4. The LC element part 13 of the present invention outputs an AC voltage having a certain effective value by using the output of the switching element part 11 and includes a first inductor L1 and a third capacitor C3. The first to fourth switching elements Q1, Q2, Q3 and Q4 of the present invention can be implemented as semiconductor devices, and in particular, can be implemented using FETs (Field Effect Transistors). Also, the first to fourth diodes D1, D2, D3, and D4 may be implemented using a diode incorporated in the FET.

Specifically, as can be seen from Fig. 1, the connection of each element of the transducer 10 is as follows.

One end of the first switching device Q1 is connected to the positive terminal of the AC power source and the other end of the first switching device Q1 is connected to one end of the third switching device Q3 and one end of the first inductor L1 The other end of the third switching device Q3 is connected to one end of the fourth switching device Q4 and the other end of the fourth switching device Q4 is connected to one end of the second switching device Q2, The other end of the second switching element Q2 is connected to the negative terminal of the AC power source.

One end of the first switching device Q1 connected to the positive terminal of the AC power source is connected to one end of the first capacitor C1 and the other end of the first capacitor C1 is connected to the other end of the third switching device Q3 And the other end of the second capacitor C2 is connected to the other end of the second switching device Q2.

The controller (30) of the present invention includes a detecting section (31), a control signal generating section (32), and a driving section (33).

The detecting unit 31 serves to detect at least one of the output (voltage or current) of the converter 10, the output (voltage or current) of the full-wave rectifier 20 or the inputted alternating current power (voltage or current).

The control signal generating unit 32 uses the at least one of the output of the converter 10 detected by the detecting unit 31, the output of the full-wave rectifier 20, or the input AC power to detect the operation of the converter 10 And generates a control signal for controlling. In particular, the control signal generator 32 modulates (Pulse Width Modulation, PWM) the pulse width of the square wave for controlling the operation of the first to fourth switching elements Q1, Q2, Q3, and Q4 And generates a control signal.

The driving unit 33 drives the converter 10 to drive the control signal generated by the control signal generating unit 32, particularly the first to fourth switching devices Q1, Q2, Q3 and Q4 Signal.

3 shows an input AC power source Vac using a control signal generated by the controller 30 according to a preferred embodiment of the present invention and the inputs V _Q1 and V V2 of the switching elements Q 1, Q 2, Q 3 and Q 4 _Q2 , _VQ3 , _VQ4 ) and the voltage (V _LED ) of the light emitting diode array (LED).

3, in the controller 30 of the present invention, the ON period and the OFF period of the first switching device Q1 and the third switching device Q3 are set to be The third switching device Q3 is turned off during the on period of the first switching device Q1 and the third switching device Q3 is turned on during the off period of the first switching device Q1, And generates a control signal for controlling the switching element Q1 and the third switching element Q3.

That is, during a period in which the AC power source is a positive voltage, the converter 10 of the present invention has the level of the output voltage according to the pulse width of on and off of the first switching device Q1 and the third switching device Q3 The pulse width modulation is performed.

It is more preferable that the first switching device Q1 is turned on during a first predetermined period in which the alternating current power source changes from the zero voltage to the positive voltage and in a second predetermined period in which the alternating current power source changes from the positive voltage to the zero voltage, And the third switching element Q3 are controlled to be off so as to prevent the switching element unit 11 from short-circuiting.

That is, the first predetermined period and the second predetermined period may have a value of zero or a constant value.

It is preferable that the second switching device Q2 and the fourth switching device Q4 are kept on and short-circuited during a period in which the AC power source is a positive voltage. However, it is more preferable that the second switching device Q2 and / or the fourth switching device Q2 are turned on for a certain period of time after the AC power source is switched from the zero voltage to the positive voltage and before the AC power source is switched from the positive voltage to the zero voltage. It is necessary to prevent the switching element section 11 from being short-circuited by turning off the switching element Q4. In other words, during a fourth predetermined time period in which the AC power source changes from the 0 voltage to the positive voltage and the AC power source changes from the positive voltage to the 0 voltage, the second switching device Q2 and the fourth switching device (Q4) must be controlled to be off. That is, the third schedule interval and the fourth schedule interval may have 0 or a constant value. The second switching device Q2 and the fourth switching device Q4 are turned on during a period in which the AC power source is a positive voltage except for the third predetermined period and the fourth predetermined period, Need to control the second switching device Q2 and the fourth switching device Q4.

Likewise, during a period in which the AC power source is a negative voltage, the converter 10 of the present invention changes the level of the output voltage according to the pulse width of turning on and off the second switching device Q2 and the fourth switching device Q4 The pulse width modulation is performed.

That is, during the interval in which the AC power source is a negative voltage, the ON period and the OFF period of the second switching device Q2 and the fourth switching device Q4 are repeated. During the ON period of the second switching device Q2, The fourth switching device Q4 is turned off and the fourth switching device Q4 is turned on during the off period of the second switching device Q2 so that the controller 30 of the present invention turns on the second switching device Q2, It is preferable to generate a control signal for controlling the switching element Q4.

It is more preferable that the second switching device Q2 is turned on during the fifth predetermined period in which the AC power source changes from the zero voltage to the negative voltage and in the sixth predetermined period in which the AC power source changes from the negative voltage to the zero voltage, And the fourth switching element Q4 are controlled to be off so as to prevent the switching element unit 11 from short-circuiting. That is, the fifth predetermined period and the sixth predetermined period may have a value of 0 or a constant value.

It is also preferable that the first switching device Q1 and the third switching device Q3 are kept on and short-circuited during a period in which the AC power source is a negative voltage. However, it is more preferable that the first switching device Q1 and / or the third switching device Q2 are turned on for a certain time after the AC power source is switched from the zero voltage to the negative voltage and before the AC power source is switched from the negative voltage to the zero voltage. It is necessary to prevent the switching element section 11 from being short-circuited by turning off the switching element Q3. In other words, during the seventh constant period in which the AC power source changes from the zero voltage to the negative voltage and during the eighth predetermined period in which the AC power source changes from the negative voltage to the zero voltage, the first switching device Q1 and the third switching device (Q3) must be controlled to be off. That is, the seventh predetermined period and the eighth predetermined period may have zero or a constant value. The first switching device Q1 and the third switching device Q3 are controlled by the controller 30 so that the on state is maintained during a period in which the AC power source is negative except for the seventh constant period and the eighth constant period. It is necessary to control the first switching device Q1 and the third switching device Q3.

The full wave rectifier 20 of the present invention can be implemented using a diode bridge circuit including the fifth to eighth diodes D5, D6, D7 and D8. It is also preferable to connect a fourth capacitor C4 connected in parallel to the output end of the full-wave rectifier 20 for DC link setting.

The output of the full-wave rectifier 20 exhibits a certain level of the effective voltage value. In order to utilize the output voltage characteristic of the full-wave rectifier 20, a constant current source can be constituted by connecting a first resistor R1 in series with a light emitting diode array (LED) including at least one light emitting diode .

The overall operation of the LED driving apparatus 100 using the AC power according to the preferred embodiment of the present invention will be summarized again. When the AC power source of the system AC is a positive voltage, the first switching device Q1 is turned on to store energy in the first inductor L1, and the energy is supplied to the fifth diode D5, And is subjected to full-wave rectification through a diode array (LED) and an eighth diode (D8). The fourth capacitor (C4) supplies power in the form of a pulse current to the LED array (LED). On the other hand, when the first switching device Q1 is turned off, the energy stored in the first inductor L1 is subjected to a flywheel operation through the fourth switching device Q4 and the third diode D3, The energy stored in the inductor L1 is reset. When the AC power of the system AC is a negative voltage, the power is supplied to the LED array through an opposite process.

The output of the full wave rectifier 20 by the fifth to eighth diodes D5, D6, D7 and D8 is a full-wave rectified pulsating current but the duty of the first switching device Q1 The constant current is controlled by the pulse width PWM control in accordance with the first resistor R1 and is converted into the constant current by the first resistor R1 and supplied to the light emitting diode array LED.

Also, since the output of the converter 10 has the same voltage and current due to the high-frequency switching of the first inductor L1, a high power factor of 0.99 or more can be realized.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the technical problems as described above, and it is an object of the present invention to provide a semiconductor light emitting device capable of adjusting a pulse width of a semiconductor switch, And an LED driving apparatus (100) using the AC power source.

Another object of the present invention is to provide an LED driving apparatus using an AC power source capable of realizing a high power factor of 0.99 or more by switching an AC power supply to a high frequency so that voltage and current have the same phase, 100).

100: LED driving device using AC power source of the present invention
10: converter 20: full-wave rectifier
30: Controller
11: switching element part 12: diode part
13: LC element part
31: detection unit 32: control signal generation unit
33:
Q1: first switching element Q2: second switching element
Q3: third switching element Q4: fourth switching element
D1: first diode D2: second diode
D3: Third diode D4: Fourth diode
D5: fifth diode D6: sixth diode
D7: seventh diode D8: eighth diode
C1: first capacitor C2: second capacitor
C3: third capacitor C4: fourth capacitor
L1: first inductor R1: first resistance
LED: light emitting diode array AC: grid power

Claims (22)

A converter receiving an AC power and outputting an AC voltage having a certain effective value;
A full wave rectifier for full-wave rectifying and outputting the output voltage of the converter; And
And a controller for generating a control signal for controlling operation of the transducer,
The converter comprising:
A switching element including a first switching element, a second switching element, a third switching element, and a fourth switching element whose ON or OFF is controlled by the control signal; And
And an LC element part which outputs an AC voltage having a certain effective value by using the output of the switching element part and includes a first inductor and a third capacitor,
Wherein one terminal of the first switching element is connected to a positive terminal of the AC power source and the other terminal of the first switching element is connected to one end of the third switching element and one end of the first inductor, The other end of the fourth switching device is connected to one end of the second switching device and the other end of the fourth switching device is connected to the negative terminal of the AC power source Wherein the light emitting diode driving device uses an AC power source. The method according to claim 1,
The controller comprising:
A detector for detecting at least one of an output of the converter, an output of the full-wave rectifier, or the input AC power; And
And a control signal generator for generating the control signal for controlling the operation of the converter by using at least one of the output of the converter, the output of the full wave rectifier, and the AC power source detected by the detector Wherein the light emitting diode driving device uses an AC power source. 3. The method of claim 2,
Wherein the control signal generator comprises:
And the control signal is generated by modulating the pulse width of the square wave. delete delete delete The method according to claim 1,
One end of the first switching element connected to the positive terminal of the AC power source is connected to one end of the first capacitor,
The other end of the first capacitor is connected to the other end of the third switching device and one end of the second capacitor,
And the other end of the second capacitor is connected to the other end of the second switching device. 8. The method according to any one of claims 1 to 7,
The controller comprising:
The first switching element and the third switching element are turned on during a first predetermined period in which the AC power source changes from a 0 voltage to a positive voltage and during a second predetermined period in which the AC power source changes from a positive voltage to a zero voltage, Off,
The first switching device and the third switching device are repeatedly turned on and off during a period in which the AC power source is a positive voltage except for the first predetermined period and the second predetermined period, The third switching element is turned off during the ON period of the first switching element and the third switching element is turned on during the off period of the first switching element, And generates a control signal based on the control signal. 9. The method of claim 8,
Wherein the first predetermined period and the second predetermined period have a value of 0 or a predetermined positive value. 8. The method according to any one of claims 1 to 7,
The controller comprising:
The second switching element and the fourth switching element are turned off during a third predetermined period in which the AC power source changes from a 0 voltage to a positive voltage and during a fourth predetermined period in which the AC power source changes from a positive voltage to a zero voltage, Respectively,
The second switching device and the fourth switching device are turned on during a period in which the AC power source is a positive voltage except for the third predetermined period and the fourth predetermined period, And generates a control signal for controlling the fourth switching device. 11. The method of claim 10,
Wherein the third predetermined period and the fourth predetermined period have a value of 0 or a predetermined positive value. 8. The method according to any one of claims 1 to 7,
The controller comprising:
The second switching element and the fourth switching element are turned on during a fifth predetermined period in which the AC power source changes from a zero voltage to a negative voltage and during a sixth predetermined period in which the AC power source changes from a negative voltage to a zero voltage, Off,
The second switching element and the fourth switching element are repeatedly turned on and off during a period in which the AC power source is a negative voltage except during the fifth predetermined period and the sixth predetermined period, The fourth switching element is turned off during the on period of the first switching element and the fourth switching element is turned on during the off period of the second switching element, And generates a control signal based on the control signal. 13. The method of claim 12,
Wherein the fifth predetermined period and the sixth predetermined period have a value of 0 or a predetermined positive value. 8. The method according to any one of claims 1 to 7,
The controller comprising:
The first switching element and the third switching element are turned off during a seventh constant period in which the AC power source changes from a 0 voltage to a negative voltage and during an eighth predetermined period in which the AC power source changes from a negative voltage to a zero voltage, Respectively,
The first switching device and the third switching device are maintained in an ON state during a period in which the AC power source is a negative voltage except for the seventh predetermined time period and the eighth predetermined time period, And a control signal for controlling the first to third switching elements is generated. 15. The method of claim 14,
Wherein the seventh constant period and the eighth constant period have a value of 0 or a predetermined positive value. The method according to claim 1,
The full-
Wherein the diode bridge is a diode bridge including a fifth diode, a sixth diode, a seventh diode and an eighth diode. 17. The method according to any one of claims 1 to 16,
The LED driving apparatus includes:
And a fourth capacitor connected in parallel to an output terminal of the full-wave rectifier. 18. The method of claim 17,
The LED driving apparatus includes:
And a first resistor connected in series with the light emitting diode array including at least one light emitting diode. A converter that receives an AC power and outputs an AC voltage having a certain effective value, and includes a first switching device, a second switching device, a third switching device, and a fourth switching device;
A full wave rectifier for full-wave rectifying and outputting the output voltage of the converter; And
And a controller for generating a control signal for controlling operation of the transducer,
The controller comprising:
The first switching element and the third switching element are turned on during a first predetermined period in which the AC power source changes from a 0 voltage to a positive voltage and during a second predetermined period in which the AC power source changes from a positive voltage to a zero voltage, Off,
The first switching device and the third switching device are repeatedly turned on and off during a period in which the AC power source is a positive voltage except for the first predetermined period and the second predetermined period, The third switching element is turned off during the ON period of the first switching element and the third switching element is turned on during the off period of the first switching element, And generates a control signal based on the control signal. A converter that receives an AC power and outputs an AC voltage having a certain effective value, and includes a first switching device, a second switching device, a third switching device, and a fourth switching device;
A full wave rectifier for full-wave rectifying and outputting the output voltage of the converter; And
And a controller for generating a control signal for controlling operation of the transducer,
The controller comprising:
The second switching element and the fourth switching element are turned off during a third predetermined period in which the AC power source changes from a 0 voltage to a positive voltage and during a fourth predetermined period in which the AC power source changes from a positive voltage to a zero voltage, Respectively,
The second switching device and the fourth switching device are turned on during a period in which the AC power source is a positive voltage except for the third predetermined period and the fourth predetermined period, And generates a control signal for controlling the fourth switching device. A converter that receives an AC power and outputs an AC voltage having a certain effective value, and includes a first switching device, a second switching device, a third switching device, and a fourth switching device;
A full wave rectifier for full-wave rectifying and outputting the output voltage of the converter; And
And a controller for generating a control signal for controlling operation of the transducer,
The controller comprising:
The second switching element and the fourth switching element are turned on during a fifth predetermined period in which the AC power source changes from a zero voltage to a negative voltage and during a sixth predetermined period in which the AC power source changes from a negative voltage to a zero voltage, Off,
The second switching element and the fourth switching element are repeatedly turned on and off during a period in which the AC power source is a negative voltage except during the fifth predetermined period and the sixth predetermined period, The fourth switching element is turned off during the on period of the first switching element and the fourth switching element is turned on during the off period of the second switching element, And generates a control signal based on the control signal. A converter that receives an AC power and outputs an AC voltage having a certain effective value, and includes a first switching device, a second switching device, a third switching device, and a fourth switching device;
A full wave rectifier for full-wave rectifying and outputting the output voltage of the converter; And
And a controller for generating a control signal for controlling operation of the transducer,
The controller comprising:
The first switching element and the third switching element are turned off during a seventh constant period in which the AC power source changes from a 0 voltage to a negative voltage and during an eighth predetermined period in which the AC power source changes from a negative voltage to a zero voltage, Respectively,
The first switching device and the third switching device are maintained in an ON state during a period in which the AC power source is a negative voltage except for the seventh predetermined time period and the eighth predetermined time period, And a control signal for controlling the first to third switching elements is generated.

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