WO2013038795A1 - Power circuit, illumination deice, and image display device - Google Patents

Abstract

This power circuit (1) is provided with a first rectifier circuit (20) which generates a pulsating voltage from an AC voltage, a first output circuit (30) which outputs a DC voltage generated from the pulsating voltage, a second output circuit (40) which outputs the pulsating voltage, and a switch for switching between the first output circuit (30) and the second output circuit (40).

Description

Power supply circuit, lighting device, and image display device

The present invention relates to a power supply circuit that obtains direct current from alternating current. The present invention also relates to an illumination device including a power supply circuit and an image display device.

In recent years, light-emitting diodes (hereinafter also referred to as LEDs) that can be driven with lower power consumption than incandescent bulbs and fluorescent lamps have been used as light sources for backlights of liquid crystal displays and lighting devices. LEDs are advantageous in that they are small in size and strong in impact resistance, and there is no fear of ball breakage.

At present, as a power source for causing the LED to emit light, an AC power source typified by a household power source is generally used. On the other hand, the LED is a DC drive element. For this reason, in order to drive an LED, which is a DC drive element, using an AC power supply, various power supply circuits that convert AC power into DC have been proposed.

For example, as shown in FIG. 7, Patent Document 1 includes a switching unit that switches ON / OFF of a bypass path that bypasses the next-stage LED block based on the energization amount of the LED block composed of a plurality of light-emitting diodes. A light emitting diode drive circuit is disclosed.

Japanese Patent Publication “Japanese Patent Laid-Open No. 2011-040701 (published on February 24, 2011)”

However, in the power supply circuit such as the light-emitting diode driving circuit described in Patent Document 1, the power supply efficiency has been reduced due to heat loss (heat generation loss) generated in each circuit for obtaining direct current from alternating current. .

Here, an example of heat loss that occurs in each circuit will be described with reference to FIG. FIG. 8 is a circuit diagram showing an example of a conventionally used power supply circuit.

As shown in FIG. 8, the power supply circuit includes an AC power supply 110 that supplies an AC voltage, a rectifier circuit 120 that rectifies the AC power supply to obtain a pulsating voltage, a smoothing circuit 130 that smoothes the pulsating voltage, and is smoothed. A high-frequency transformer circuit 140 that converts the value of the pulsating current voltage, a rectifying and smoothing circuit 150 that obtains a DC voltage from the voltage-converted pulsating voltage, and a stabilization circuit 160 that stabilizes the DC voltage output from the power supply circuit. It has. As a result, the power supply circuit generates a DC voltage from the AC voltage.

In the power supply circuit shown in FIG. 8, heat loss occurs in each of the rectifier circuit 120, the smoothing circuit 130, the high-frequency transformer circuit 140, the rectifying and smoothing circuit 150, and the stabilization circuit 160. Conventionally, in order to obtain a DC voltage from an AC voltage as described above, a large number of circuits are required, and heat loss occurs in each of the circuits, resulting in a decrease in power supply efficiency.

The present invention has been made in view of the above-described problems, and a main object of the present invention is to provide a power supply circuit that can suppress generation of heat loss and improve power supply efficiency.

In order to solve the above problems, a power supply circuit according to one embodiment of the present invention includes a rectifier circuit that generates a pulsating voltage by rectifying an AC voltage, and a DC voltage generated from the pulsating voltage generated by the rectifying circuit. A first output circuit that outputs a DC voltage generated by the smoothing circuit; a second output circuit that outputs a pulsating voltage generated by the rectifier circuit; A switch for switching between the first output circuit and the second output circuit is provided.

According to the above configuration, the power supply circuit switches between the first output circuit and the second output circuit by the switch, so that the voltage output from the power supply circuit is a DC voltage or a pulsating voltage. Switch to.

Here, when obtaining a pulsating voltage or a DC voltage from an AC voltage, the power efficiency is reduced due to power loss caused by heat generated in each circuit included in the power circuit, such as the rectifier circuit and the smoothing circuit. It will decline. The loss that occurs when the pulsating voltage is obtained is only the loss in the rectifier circuit, whereas the loss that occurs when the DC voltage is obtained is the loss that occurs in the rectifier circuit and the smoothing circuit. Will be included.

Therefore, when the output of the DC voltage is not necessary, the power supply circuit can eliminate the loss due to the smoothing circuit by switching the output to the pulsating voltage. Thus, the power supply circuit outputs a DC voltage when a DC voltage is required, and occurs in the power supply circuit when a DC voltage is not required (for example, when reduction of power consumption is prioritized). Loss can be suppressed and power supply efficiency can be improved.

In order to solve the above problems, a power supply circuit according to one embodiment of the present invention is generated by a rectifying and smoothing circuit that generates a pulsating voltage by rectifying and smoothing an AC voltage, and the rectifying and smoothing circuit. A first output circuit that outputs a DC voltage generated by the smoothing circuit, and a pulsating voltage generated by the rectifying and smoothing circuit; And a switch that switches between the first output circuit and the second output circuit.

According to the above configuration, the power supply circuit switches between the first output circuit and the second output circuit by the switch, so that the voltage output from the power supply circuit is a DC voltage or a pulsating voltage. Switch to.

Here, when a pulsating voltage or a DC voltage is obtained from an AC circuit, the power supply is caused by power loss caused by heat generated in each circuit included in the power supply circuit, such as the rectifying and smoothing circuit and the smoothing circuit. Efficiency will decrease. The loss that occurs when the pulsating voltage is obtained is only the loss in the rectifier circuit, whereas the loss that occurs when the DC voltage is obtained is the loss that occurs in the rectifier circuit and the smoothing circuit. Will be included.

Therefore, when the output of the DC voltage is not necessary, the power supply circuit can eliminate the loss due to the smoothing circuit by switching the output to the pulsating voltage. Thus, the power supply circuit outputs a DC voltage when a DC voltage is required, and occurs in the power supply circuit when a DC voltage is not required (for example, when reduction of power consumption is prioritized). Loss can be suppressed and power supply efficiency can be improved.

Further, since the power supply circuit outputs a pulsating voltage obtained by rectifying and smoothing the AC voltage from the second output circuit, it is more direct current than when outputting a pulsating voltage obtained by only rectifying the AC voltage. A pulsating voltage close to the voltage can be output.

In order to solve the above-described problem, an illumination device according to one embodiment of the present invention includes the above-described power supply circuit and a light source, and the light source is driven by the power supply circuit.

According to the above configuration, the lighting device drives the light source with a DC voltage when a DC voltage is required to drive the light source, and generates a loss in the power supply circuit when a DC voltage is not required. It can suppress and can improve power supply efficiency.

An image display device including the above-described illumination device as a backlight device for a display panel is also included in the scope of the present invention.

As described above, the power supply circuit according to the present invention includes a rectifying circuit that generates a pulsating voltage by rectifying an AC voltage, and a smoothing circuit that generates a DC voltage from the pulsating voltage generated by the rectifying circuit. A first output circuit that outputs the generated DC voltage; a second output circuit that outputs a pulsating voltage generated in the rectifier circuit; the first output circuit and the second output circuit; And a switch for switching.

According to the above configuration, the power supply circuit outputs a DC voltage when a DC voltage output is required, and suppresses a loss generated in the power supply circuit when a DC voltage is not required, thereby improving the power efficiency. Can be improved.

It is a circuit diagram which shows the structure of the power supply circuit which concerns on one Embodiment of this invention. It is a block diagram which shows the outline of the television which concerns on one Embodiment of this invention. It is a figure which shows the waveform of the voltage in each circuit with which the power supply circuit which concerns on one Embodiment of this invention is provided, (a) shows the waveform of the alternating voltage in alternating current power supply, (b) is output from the 2nd output circuit. (C) shows the waveform of the DC voltage output from the first output circuit. It is a circuit diagram which shows the structure of the power supply circuit which concerns on other embodiment of this invention. It is a block diagram which shows the outline of the television which concerns on other embodiment of this invention. It is a figure which shows the waveform of the voltage in each circuit with which the power supply circuit which concerns on other embodiment of this invention is equipped, (a) shows the waveform of the alternating voltage in an alternating current power supply, (b) is output from a 2nd output circuit. (C) shows the waveform of the DC voltage output from the first output circuit. It is a circuit diagram which shows the structure of the light emitting diode drive circuit based on patent document 1. FIG. It is a circuit diagram which shows an example of a structure of the power supply circuit in a prior art.

<First Embodiment>
A power supply circuit according to an embodiment of the present invention will be described with reference to FIGS. However, unless otherwise specified, the configuration described in this embodiment is not merely intended to limit the scope of the present invention, but is merely an illustrative example.

In the present embodiment, a lighting device including a power supply circuit is provided in a television receiver (image display device) (hereinafter also referred to as a television), and a backlight (light source) of a liquid crystal display panel provided in the television is provided. A case will be described as an example in which the display panel functions as a backlight driving circuit for driving the TV (in other words, the television includes a lighting device including a power supply circuit as a backlight device for a display panel).

[Configuration of TV]
First, an outline of a television provided with a power supply circuit according to the present embodiment will be described with reference to FIG. FIG. 2 is a block diagram illustrating an outline of the television 100 according to the present embodiment. As shown in FIG. 2, the television 100 includes a power supply circuit 1 and a display device 50.

The power supply circuit 1 includes an AC power supply 10, a first rectifier circuit (rectifier circuit) 20, a first output circuit 30, a second output circuit 40, and a switch 45. The details of the power supply circuit 1 will be described later with different drawings.

The display device 50 includes a liquid crystal drive circuit 51, a liquid crystal display panel 52, and an LED group (backlight) 53. The liquid crystal driving circuit 51 is supplied with a DC voltage generated from a pulsating voltage generated in the first rectifier circuit 20 described later, and drives the liquid crystal display panel 52 to display an image. The liquid crystal display panel 52 is driven by the liquid crystal driving circuit 51 to display an image.

The LED group 53 is a backlight of the liquid crystal display panel 52 and has a plurality of light emitting diodes (LEDs). The LED group 53 is driven by a DC voltage supplied from the first output circuit 30 included in the power supply circuit 1 or a pulsating voltage supplied from the second output circuit 40.

[Configuration of power supply circuit]
Next, the power supply circuit 1 according to the present embodiment will be described with reference to FIG. FIG. 1 is a circuit diagram showing a configuration of a power supply circuit 1 according to the present embodiment.

As shown in FIG. 1, the power supply circuit 1 according to this embodiment includes an AC power supply 10, a first rectifier circuit (rectifier circuit) 20, a first output circuit 30, a second output circuit 40, and an LED group 53. It has.

The first rectifier circuit 20 is a circuit that generates a pulsating voltage by full-wave rectifying the AC voltage supplied from the AC power supply 10. As shown in FIG. 1, the first rectifier circuit 20 has four diodes 21 to 24, and the diodes 21 to 24 constitute a so-called diode bridge circuit.

The cathode terminal of the diode 21 is connected to one end of the AC power supply 10, the anode terminal is connected to the anode terminal of the diode 23, and the cathode terminal of the diode 23 is connected to the other end of the AC power supply 10. The anode terminal of the diode 22 is connected to the cathode terminal of the diode 21, the cathode terminal is connected to the cathode terminal of the diode 24, and the anode terminal of the diode 23 is connected to the cathode terminal of the diode 23. The cathode terminals of the diode 22 and the diode 24 are connected to an input terminal of a switch 45 described later.

(First output circuit)
The first output circuit 30 is a circuit that outputs a DC voltage generated from the pulsating voltage generated in the first rectifier circuit 20, and outputs a DC voltage to the LED group 53 in FIG. 1. The LED group 53 is driven by a DC voltage supplied from the first output circuit 30.

As shown in FIG. 1, the first output circuit 30 includes a first smoothing circuit (smoothing circuit) 31, a high-frequency transformer circuit 32, a second rectifier circuit 33, a second smoothing circuit 34, and a stabilization circuit. 35.

The first smoothing circuit 31 is a circuit that smoothes the pulsating voltage generated in the first rectifier circuit 20. The first smoothing circuit 31 has a capacitor 311 as shown in FIG. One end of the capacitor 311 is connected to one end of the output terminal of the switch 45, and the other end is connected to the anode terminals of the diode 21 and the diode 23, and one end of the input terminal of the switching circuit 353 provided in the stabilization circuit 35 described later. It is connected.

The high-frequency transformer circuit 32 is a circuit that changes the smoothed pulsating voltage to a desired (necessary) voltage. As shown in FIG. 1, the high-frequency transformer circuit 32 includes a primary coil 321 and a secondary coil 322. One end of the primary coil 321 is connected to one end of the capacitor 311, and the other end is connected to the output terminal of the switching circuit 353.

The second rectifier circuit 33 is a circuit that rectifies the voltage converted in the high-frequency transformer circuit 32 and brings it close to a DC voltage. The second rectifier circuit includes a diode 331 and a diode 332. The anode terminal of the diode 331 is connected to one end of the secondary coil 322, the cathode terminal is connected to the cathode terminal of the diode 332, and the anode terminal of the diode 332 is connected to the other end of the secondary coil 322.

The second smoothing circuit 34 is a circuit that further smoothes the voltage rectified in the second rectifier circuit 33 to obtain a DC voltage. The second smoothing circuit 34 includes a choke coil 341 and a capacitor 342. One end of the choke coil 341 is connected to the diode 331 and the cathode terminal of the diode 332, the other end is connected to one end of the capacitor 342, and the other end of the capacitor 342 is connected to the anode terminal of the diode 332.

The stabilization circuit 35 is a feedback circuit that operates so that the DC output voltage is always a constant value. The stabilization circuit 35 includes a detection circuit 351, a pulse width conversion circuit 352, and a switching circuit 353. The input terminal of the detection circuit 351 is connected to one end of the capacitor 342 and the anode terminal of the LED group 53, and the output terminal is connected to the input terminal of the pulse width conversion circuit 352. The input terminal of the pulse width conversion circuit 352 is connected to the output terminal of the detection circuit 351, and the output terminal is connected to the other end of the input terminal of the switching circuit 353. One end of the input terminal of the switching circuit 353 is connected to the other end of the capacitor 311, the other end of the input terminal is connected to the output terminal of the pulse width conversion circuit 352, and the output terminal is connected to the other end of the primary coil 321. It is connected.

The detection circuit 351 detects the output voltage of the first output circuit 30 and supplies the detection result to the pulse width conversion circuit 352. The pulse width conversion circuit 352 generates a pulse signal that controls ON / OFF in the switching circuit 353 based on the detection result supplied from the detection circuit 351.

The switching circuit 353 switches ON / OFF of the primary coil 321 according to the pulse signal supplied from the pulse width conversion circuit 352. Note that the switching circuit 353 can be configured by a transistor, a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), or the like.

The high-frequency transformer circuit 32, the second rectifier circuit 33, the second smoothing circuit 34, and the stabilization circuit 35 constitute a voltage changing circuit that changes the value of the output DC voltage. Specifically, the pulsating voltage whose value has been converted by the high-frequency transformer circuit 32 and the stabilization circuit 35 is rectified and smoothed by the second rectifier circuit 33 and the second smoothing circuit 34 to output a direct current. The voltage value has been changed.

In the present embodiment, the first smoothing circuit 31 and the second smoothing circuit 34 constitute a smoothing circuit, but the present invention is not limited to this. For example, the smoothing circuit may be configured by only the first smoothing circuit 31, or the smoothing circuit may be configured by only the second smoothing circuit 34.

(Second output circuit)
The second output circuit 40 is a circuit that directly outputs the pulsating voltage generated in the first rectifier circuit 20. In FIG. 1, the pulsating voltage is directly output to the LED group 53. In addition, the 2nd output circuit 40 can mention conducting wire as the simplest structure. One end of the second output circuit 40 is connected to the other end of the output terminal of the switch 45, and the other end is connected to the anode terminal of the LED group 53.

In the present embodiment, the case where the second output circuit 40 is a conductive wire will be described as an example as shown in FIG. 1, but the present invention is not limited to this. For example, a configuration in which a circuit with a smaller loss than the power loss in the first output circuit 30 described later (for example, a configuration in which only the first smoothing circuit 31 is provided) may be employed.

(switch)
The switch 45 is a circuit that switches between the first output circuit 30 and the second output circuit 40 as a circuit that outputs a voltage to the LED group 53. The input terminal of the switch 45 is connected to the cathode terminals of the diode 22 and the diode 24, and one end of the output terminal is connected to one end of the capacitor 311 included in the first smoothing circuit 31 included in the first output circuit 30. The other end is connected to one end of the second output circuit 40.

[Operation of power supply circuit]
Next, the operation of the power supply circuit 1 will be described with reference to FIG. FIG. 3 is a diagram illustrating voltage waveforms in each circuit included in the power supply circuit 1 according to the present embodiment. 3A is a diagram showing a waveform of an AC voltage in the AC power supply 10, and FIG. 3B is a pulsating voltage rectified in the first rectifier circuit 20 (that is, output from the second output circuit 40). (C) is a diagram illustrating a waveform of a DC voltage output from the first output circuit 30. FIG.

(Operation in the first output circuit)
First, the operation of the power supply circuit 1 when the switch 45 connects the first rectifier circuit 20 and the first output circuit 30 will be described. Hereinafter, a state in which the first rectifier circuit 20 and the first output circuit 30 are connected via the switch 45 is also referred to as a normal mode.

The power supply circuit 1 first full-wave rectifies the AC voltage shown in FIG. 3A supplied from the AC power supply 10 into the pulsating voltage shown in FIG. In the normal mode, the pulsating voltage rectified in the first rectifier circuit 20 is supplied to the first smoothing circuit 31 included in the first output circuit 30 via the switch 45. The first smoothing circuit 31 smoothes the supplied pulsating voltage and supplies the smoothed pulsating voltage to the high-frequency transformer circuit 32.

The high frequency transformer circuit 32 converts the voltage supplied from the first smoothing circuit 31 into a desired voltage. The voltage converted in the high-frequency transformer circuit 32 is further rectified by the second rectifier circuit 33 and then smoothed by the second smoothing circuit 34 to become a DC voltage shown in FIG.

Further, the DC voltage smoothed by the second smoothing circuit 34 is always kept constant by appropriately switching between conduction and interruption of the primary coil 321 in the switching circuit 353 provided in the stabilization circuit 35.

(C) A DC voltage is generated from the AC voltage shown in FIG. 3A by the operation of the first output circuit 30 described above. The DC voltage generated in the first output circuit 30 is supplied to the LED group 53. That is, the LED group 53 is driven by a DC voltage supplied from the first output circuit 30.

Note that, as described above, the power supply circuit 1 is the value of the DC voltage output in the voltage changing circuit configured by the high-frequency transformer circuit 32, the second rectifier circuit 33, the second smoothing circuit 34, and the stabilization circuit 35. The value of the DC voltage output from the first output circuit 30 can be arbitrarily changed by changing. Therefore, the power supply circuit 1 can drive the LED group 53 with a DC voltage having a desired value by arbitrarily changing the value of the voltage output from the first output circuit 30 in the normal mode. That is, the power supply circuit 1 can arbitrarily change the luminous intensity of the LED group 53 in the normal mode.

For example, the luminous intensity (luminance) of the LED group 53 can be increased by increasing the value of the DC voltage output from the first output circuit 30, and the luminous intensity of the LED group 53 can be decreased by decreasing the value.

(Operation in the second output circuit)
Next, the operation of the power supply circuit 1 when the switch 45 connects the first rectifier circuit 20 and the second output circuit 40 will be described. Hereinafter, the state where the first rectifier circuit 20 and the second output circuit 40 are connected via the switch 45 is also referred to as a power saving mode.

The power supply circuit 1 first rectifies the AC voltage shown in FIG. 3A supplied from the AC power supply 10 into the pulsating voltage shown in FIG. In the power saving mode, the pulsating voltage rectified in the first rectifier circuit 20 is supplied to the second output circuit 40 via the switch 45. In other words. The second output circuit 40 supplies the supplied pulsating voltage to the LED group 53 as it is. Accordingly, the LED group 53 is driven by the pulsating voltage supplied from the second output circuit 40 and shown in FIG.

Thus, in the power saving mode, the power efficiency (conversion efficiency from the AC power source to the output voltage of the power source circuit 1) can be improved by driving the LED group 53 with the pulsating voltage.

Specifically, in the normal mode, the first rectifier circuit 20, the first smoothing circuit 31, the high-frequency transformer circuit 32, the second rectifier circuit 33, and the second included in the power supply circuit 1 for converting an AC voltage into a DC voltage. The power supply efficiency is reduced by power loss (heat generation loss) caused by heat generated in each element included in the smoothing circuit 34 and the stabilization circuit 35.

On the other hand, in the power saving mode, since the circuit except the first rectifier circuit 20 is bypassed by the second output circuit 40, the first smoothing circuit 31, the high-frequency transformer circuit 32, the second rectifier circuit 33, and the second smoothing are performed. Losses that occur in the circuit 34 and the stabilization circuit 35 can be eliminated. That is, in the power saving mode, the loss generated in the power supply circuit 1 is only the loss generated in the first rectifier circuit 20. That is, when the output of the DC voltage is not required, the power supply circuit 1 can eliminate the loss due to the circuits other than the first rectifier circuit 20 by switching the output to the pulsating voltage.

Therefore, the power supply circuit 1 can reduce the decrease in power supply efficiency and efficiently drive the LED group 53 by the power saving mode. In other words, the power supply circuit 1 suppresses loss generated in the power supply circuit 1 and improves power supply efficiency when output of a DC voltage is not necessary (for example, when reduction of power consumption is given priority). be able to.

Further, the power supply circuit 1 can switch between the first output circuit 30 and the second output circuit 40 by the switch 45. That is, the power supply circuit 1 can switch between the normal mode and the power saving mode by the switch 45.

Thereby, the power supply circuit 1 can change the luminous intensity of the LED group 53 by switching to the normal mode, and further reduces the decrease in power supply efficiency by switching to the power saving mode, and efficiently drives the LED group 53. be able to.

<Embodiment 2>
Another embodiment of the present invention will be described with reference to FIGS. For convenience of explanation, constituent elements having the same functions as those of the constituent elements according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted. In the present embodiment, differences from the first embodiment will be mainly described.

[Configuration of TV]
First, an outline of a television provided with a power supply circuit according to the present embodiment will be described with reference to FIG. FIG. 4 is a block diagram illustrating an outline of the television 200 according to the present embodiment. As shown in FIG. 4, the television 200 includes a power supply circuit 2 and a display device 50.

The power supply circuit 2 includes an AC power supply 10, a rectifying / smoothing circuit 60, a first output circuit 30 ′, a second output circuit 40, and a switch 45. The details of the power supply circuit 2 will be described later with different drawings.

The LED group 53 is a backlight of the liquid crystal display panel 52 and has a plurality of light emitting diodes (LEDs). The LED group 53 is driven by a DC voltage supplied from the first output circuit 30 ′ included in the power supply circuit 2 or a pulsating voltage supplied from the second output circuit 40.

[Configuration of power supply circuit]
Next, the power supply circuit 2 according to the present embodiment will be described with reference to FIG. FIG. 5 is a circuit diagram showing a configuration of the power supply circuit 2 according to the present embodiment.

As shown in FIG. 5, the power supply circuit 2 according to this embodiment includes an AC power supply 10, a rectifying / smoothing circuit 60, a first output circuit 30 ′, a second output circuit 40, and an LED group 53. Yes.

(Rectifying and smoothing circuit)
The rectifying / smoothing circuit 60 is a circuit that generates a pulsating voltage by rectifying and smoothing an AC voltage supplied from the AC power supply 10. The rectifying / smoothing circuit 60 includes a first rectifying circuit 61 and a first smoothing circuit 62 as shown in FIG. 5 in order to generate a pulsating voltage.

The first rectifier circuit 61 is a circuit that rectifies an AC voltage supplied from the AC power supply 10. The first rectifier circuit 61 includes four diodes 611 to 614 as shown in FIG.

The cathode terminal of the diode 611 is connected to one end of the AC power supply 10, the anode terminal is connected to the anode terminal of the diode 613, and the cathode terminal of the diode 613 is connected to the other end of the AC power supply 10. The anode terminal of the diode 612 is connected to the cathode terminal of the diode 611, the cathode terminal is connected to the cathode terminal of the diode 614, and the anode terminal of the diode 613 is connected to the cathode terminal of the diode 613. The cathode terminals of the diode 612 and the diode 614 are connected to one end of a capacitor 621 described later.

The first smoothing circuit 62 is a circuit that smoothes the voltage rectified in the first rectifier circuit 61. The first smoothing circuit 62 includes a capacitor 621 as shown in FIG. One end of the capacitor 621 is connected to the cathode terminals of the diode 612 and the diode 614, and the other end is connected to the anode terminals of the diode 611 and the diode 613.

The rectifying / smoothing circuit 60 rectifies the AC voltage supplied from the AC power supply 10 in the first rectifying circuit 61 and smoothes it in the first smoothing circuit 62, thereby generating a pulsating voltage.

(First output circuit)
The first output circuit 30 ′ is a circuit that outputs a DC voltage generated from the pulsating voltage generated in the rectifying and smoothing circuit 60, and outputs a DC voltage to the LED group 53 in FIG. 5. The LED group 53 is driven by a DC voltage supplied from the first output circuit 30 ′.

As shown in FIG. 5, the first output circuit 30 ′ includes a high-frequency transformer circuit (voltage change circuit) 32, a second rectifier circuit 33, a second smoothing circuit (smoothing circuit) 34, and a stabilization circuit 35. It has.

The high frequency transformer circuit 32 is a circuit that converts (changes) the voltage supplied from the AC power supply 10 into a desired voltage. As shown in FIG. 5, the high-frequency transformer circuit 32 includes a primary coil 321 and a secondary coil 322. One end of the primary coil 321 is connected to one end of an output terminal of a switch 45 described later, and the other end is connected to an output terminal of the switching circuit 353.

(Second output circuit)
The second output circuit 40 is a circuit that directly outputs the pulsating voltage generated in the rectifying / smoothing circuit 60. In FIG. 5, the pulsating voltage is directly output to the LED group 53. In addition, the 2nd output circuit 40 can mention conducting wire as the simplest structure. The LED group 53 is driven by a DC voltage supplied from the second output circuit 40. One end of the second output circuit 40 is connected to the other end of the output terminal of the switch 45, and the other end is connected to the anode terminal of the LED group 53.

In the present embodiment, the case where the second output circuit 40 is a conductive wire will be described as an example as shown in FIG. 5, but the present invention is not limited to this. For example, a configuration in which a circuit with a smaller loss than the power loss in the first output circuit 30 ′ described later may be employed.

(switch)
The switch 45 is a circuit that switches between the first output circuit 30 ′ and the second output circuit 40 as a circuit that outputs a voltage to the LED group 53. The input terminal of the switch 45 is connected to one end of the capacitor 621, one end of the output terminal is connected to one end of the primary coil 321 included in the high-frequency transformer circuit included in the first output circuit 30 ′, and the other end of the output terminal is the first. 2 is connected to one end of the output circuit 40.

[Operation of power supply circuit]
Next, the operation of the power supply circuit 2 will be described with reference to FIG. FIG. 6 is a diagram illustrating voltage waveforms in each circuit included in the power supply circuit 2 according to the present embodiment. 6A is a diagram showing a waveform of an AC voltage in the AC power supply 10, and FIG. 6B is a pulsating voltage rectified and smoothed by the rectifying / smoothing circuit 60 (that is, the second output circuit). (C) is a diagram illustrating a waveform of a DC voltage output from the first output circuit 30 ′.

(Operation in the first output circuit)
First, the operation of the power supply circuit 2 when the switch 45 connects the rectifying / smoothing circuit 60 and the first output circuit 30 ′ will be described. Hereinafter, a state in which the rectifying / smoothing circuit 60 and the first output circuit 30 ′ are connected via the switch 45 is also referred to as a normal mode.

The power supply circuit 2 first full-wave rectifies the AC voltage shown in FIG. 6A supplied from the AC power supply 10 in the first rectifier circuit 61 provided in the rectifying / smoothing circuit 60. The voltage rectified in the first rectifier circuit 61 is supplied to the first smoothing circuit 62. The first smoothing circuit 62 smoothes the supplied voltage. The rectifying / smoothing circuit 60 rectifies and smoothes the first rectifying circuit 61 and the first smoothing circuit 62 to generate a pulsating voltage shown in FIG.

In the normal mode, the pulsating voltage generated in the rectifying / smoothing circuit 60 is supplied to the high-frequency transformer circuit 32 included in the first output circuit 30 ′ via the switch 45.

The high-frequency transformer circuit 32 converts the pulsating voltage supplied from the rectifying / smoothing circuit 60 into a desired voltage. The voltage converted in the high-frequency transformer circuit 32 is further rectified by the second rectifier circuit 33 and then smoothed by the second smoothing circuit 34 to become a DC voltage shown in FIG. 6C.

Further, the DC voltage smoothed by the second smoothing circuit 34 is always kept constant by appropriately switching between conduction and interruption of the primary coil 321 in the switching circuit 353 provided in the stabilization circuit 35.

(C) A DC voltage is generated from the AC voltage shown in FIG. 6A by the operation of the first output circuit 30 'described above. The DC voltage generated in the first output circuit 30 ′ is supplied to the LED group 53. That is, the LED group 53 is driven by the DC voltage shown in FIG. 6C supplied from the first output circuit 30 '.

The power supply circuit 2 can arbitrarily change the value of the voltage output from the first output circuit 30 ′ by changing a desired voltage obtained in the high-frequency transformer circuit 32. Therefore, the power supply circuit 2 can drive the LED group 53 with a DC voltage having a desired value by arbitrarily changing the value of the voltage output from the first output circuit 30 ′ in the normal mode. That is, the power supply circuit 2 can change the luminous intensity of the LED group 53 in the normal mode.

For example, the luminous intensity (luminance) of the LED group 53 can be increased by increasing the value of the DC voltage output from the first output circuit 30 ′, and the luminous intensity of the LED group 53 can be decreased by decreasing the value. .

(Operation in the second output circuit)
Next, the operation of the power supply circuit 2 when the switch 45 connects the rectifying / smoothing circuit 60 and the second output circuit 40 will be described with reference to FIG. Hereinafter, the state where the rectifying / smoothing circuit 60 and the second output circuit 40 are connected via the switch 45 is also referred to as a power saving mode.

The power supply circuit 2 first rectifies the AC voltage shown in FIG. 6A supplied from the AC power supply 10 in the first rectifier circuit 61 provided in the rectifying and smoothing circuit 60. The voltage rectified in the first rectifier circuit 61 is supplied to the first smoothing circuit 62. The first smoothing circuit 62 smoothes the supplied voltage. The rectifying / smoothing circuit 60 rectifies and smoothes the first rectifying circuit 61 and the first smoothing circuit 62 to generate a pulsating voltage shown in FIG.

In the power saving mode, the pulsating voltage rectified in the rectifying / smoothing circuit 60 is supplied to the second output circuit 40 via the switch 45. The second output circuit 40 supplies the supplied pulsating voltage to the LED group 53 as it is. In other words, the LED group 53 is driven by the pulsating voltage supplied from the second output circuit 40 and shown in FIG.

Thus, in the power saving mode, the power efficiency can be improved by driving the LED group 53 with the pulsating voltage.

Specifically, in the normal mode, a rectifying / smoothing circuit 60, a high-frequency transformer circuit 32, a second rectifying circuit 33, a second smoothing circuit 34, and the like included in the power supply circuit 2 for converting an AC voltage into a DC voltage; The power supply efficiency is reduced due to power loss (heat generation loss) caused by heat generated in each element included in the stabilization circuit 35.

On the other hand, in the power saving mode, since the circuit other than the rectifying / smoothing circuit 60 is bypassed by the second output circuit 40, the high-frequency transformer circuit 32, the second rectifying circuit 33, the second smoothing circuit 34, and the stabilization Loss generated in the circuit 35 can be eliminated. That is, in the power saving mode, the loss generated in the power supply circuit 2 is only the loss generated in the rectifying / smoothing circuit 60. That is, when the output of the DC voltage is not necessary, the power supply circuit 2 can eliminate the loss due to the circuits other than the rectifying and smoothing circuit 60 by switching the output to the pulsating voltage.

Therefore, the power supply circuit 2 can reduce the decrease in power supply efficiency and efficiently drive the LED group 53 by the power saving mode. In other words, the power supply circuit 2 suppresses the loss generated in the power supply circuit 2 and improves the power supply efficiency when the output of the DC voltage is not necessary (for example, when reduction of power consumption is given priority). be able to.

Further, the power supply circuit 2 can switch between the first output circuit 30 ′ and the second output circuit 40 by the switch 45. That is, the power supply circuit 2 can switch between the normal mode and the power saving mode by the switch 45.

Therefore, the power supply circuit 2 can change the luminous intensity of the LED group 53 by switching to the normal mode, and further reduces the decrease in power supply efficiency by switching to the power saving mode, thereby driving the LED group 53 efficiently. Can do.

In addition, since the power supply circuit 2 outputs the pulsating voltage obtained by rectifying and smoothing the AC voltage from the second output circuit 40, compared with the case where the pulsating voltage obtained by only rectifying the AC voltage is output. A pulsating voltage close to a DC voltage can be output.

The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and the embodiments can be obtained by appropriately combining technical means disclosed in different embodiments. The form is also included in the technical scope of the present invention.

[Additional Notes]
As described above, a power supply circuit according to one embodiment of the present invention includes a rectifier circuit that generates a pulsating voltage by rectifying an AC voltage, and a smoothing that generates a DC voltage from the pulsating voltage generated by the rectifier circuit. A first output circuit that outputs a DC voltage generated by the smoothing circuit, a second output circuit that outputs a pulsating voltage generated by the rectifier circuit, and the first output circuit. And a switch for switching between the output circuit and the second output circuit.

According to the above configuration, the power supply circuit switches between the first output circuit and the second output circuit by the switch, so that the voltage output from the power supply circuit is a DC voltage or a pulsating voltage. Switch to.

Here, when obtaining a pulsating voltage or a DC voltage from an AC voltage, the power efficiency is reduced due to power loss caused by heat generated in each circuit included in the power circuit, such as the rectifier circuit and the smoothing circuit. It will decline. The loss that occurs when the pulsating voltage is obtained is only the loss in the rectifier circuit, whereas the loss that occurs when the DC voltage is obtained is the loss that occurs in the rectifier circuit and the smoothing circuit. Will be included.

Therefore, when the output of the DC voltage is not necessary, the power supply circuit can eliminate the loss due to the smoothing circuit by switching the output to the pulsating voltage. Thus, the power supply circuit outputs a DC voltage when a DC voltage is required, and occurs in the power supply circuit when a DC voltage is not required (for example, when reduction of power consumption is prioritized). Loss can be suppressed and power supply efficiency can be improved.

As described above, a power supply circuit according to one embodiment of the present invention includes a rectifying / smoothing circuit that generates a pulsating voltage by rectifying and smoothing an AC voltage, and a pulse generated by the rectifying / smoothing circuit. A first output circuit that outputs a DC voltage generated by the smoothing circuit, and a pulsating voltage generated by the rectifying and smoothing circuit; A second output circuit and a switch for switching between the first output circuit and the second output circuit are provided.

According to the above configuration, the power supply circuit switches between the first output circuit and the second output circuit by the switch, so that the voltage output from the power supply circuit is a DC voltage or a pulsating voltage. Switch to.

Here, when a pulsating voltage or a DC voltage is obtained from an AC circuit, the power supply is caused by power loss caused by heat generated in each circuit included in the power supply circuit, such as the rectifying and smoothing circuit and the smoothing circuit. Efficiency will decrease. The loss that occurs when the pulsating voltage is obtained is only the loss in the rectifier circuit, whereas the loss that occurs when the DC voltage is obtained is the loss that occurs in the rectifier circuit and the smoothing circuit. Will be included.

Therefore, when the output of the DC voltage is not necessary, the power supply circuit can eliminate the loss due to the smoothing circuit by switching the output to the pulsating voltage. Thus, the power supply circuit outputs a DC voltage when a DC voltage is required, and occurs in the power supply circuit when a DC voltage is not required (for example, when reduction of power consumption is prioritized). Loss can be suppressed and power supply efficiency can be improved.

Further, since the power supply circuit outputs a pulsating voltage obtained by rectifying and smoothing the AC voltage from the second output circuit, it is more direct current than when outputting a pulsating voltage obtained by only rectifying the AC voltage. A pulsating voltage close to the voltage can be output.

In the power supply device according to one aspect of the present invention, it is preferable that the first output circuit includes a voltage changing circuit that changes a value of a DC voltage to be output.

According to the above configuration, the power supply circuit can change the value of the DC voltage output from the first output circuit. As a result, the power supply circuit can drive a device connected to the power supply circuit with a DC voltage having a desired value.

For example, when a light emitting diode (LED) is connected to the power supply circuit, the luminous intensity (brightness) is increased by increasing the direct current voltage output from the first output circuit, and the first output circuit The luminous intensity can be lowered by reducing the output DC voltage.

Therefore, the power supply circuit can change the value of the output voltage by switching the output circuit to the first output circuit, and the power supply efficiency can be improved by switching to the second output circuit.

As described above, an illumination device according to one embodiment of the present invention includes the above-described power supply circuit and a light source, and the light source is driven by the power supply circuit.

According to the above configuration, the lighting device drives the light source with a DC voltage when a DC voltage is required to drive the light source, and generates a loss in the power supply circuit when a DC voltage is not required. It can suppress and can improve power supply efficiency.

In the lighting device according to one embodiment of the present invention, the light source is preferably a light emitting diode.

According to the above configuration, when the light emitting diode is driven, when the reduction of power consumption is required rather than the driving by the DC voltage, the lighting device suppresses the loss generated in the power supply circuit, and the power efficiency Can be improved.

Further, according to the above configuration, the lighting circuit can change the value of the output voltage by switching the output circuit of the power supply circuit to the first output circuit, and can change the luminous intensity of the light emitting diode. Furthermore, the power supply efficiency can be improved by switching the output circuit of the power supply circuit to the second output circuit.

An image display device including the above-described illumination device as a backlight device for a display panel is also included in the scope of the present invention.

The present invention can be suitably used as a power supply circuit for driving a lighting device and a backlight of a liquid crystal display.

DESCRIPTION OF SYMBOLS 1 Power supply circuit 10 AC power supply 20 1st rectifier circuit (rectifier circuit)
21 to 24 Diode 30, 30 ′ First output circuit 31 First smoothing circuit (smoothing circuit)
32 High-frequency transformer circuit (voltage change circuit)
33 Second rectifier circuit (voltage change circuit)
34 Second smoothing circuit (smoothing circuit, voltage changing circuit)
35 Stabilization circuit (voltage change circuit)
40 Second output circuit 45 Switch 50 Display device 51 Liquid crystal drive circuit 52 Liquid crystal display panel 53 LED group 60 Rectification smoothing circuit 100, 200 Television receiver 311 Capacitor 321 Primary coil 322 Secondary coil 331, 332 Diode 341 Choke coil 342 Capacitor 351 Detection circuit 352 Pulse width conversion circuit 353 Switching circuit

Claims (6)

A rectifier circuit that generates a pulsating voltage by rectifying an AC voltage;
A first output circuit that has a smoothing circuit that generates a DC voltage from the pulsating voltage generated by the rectifier circuit, and that outputs the DC voltage generated by the smoothing circuit;
A second output circuit for outputting a pulsating voltage generated by the rectifier circuit;
A power supply circuit comprising: a switch for switching between the first output circuit and the second output circuit. A rectifying and smoothing circuit that generates a pulsating voltage by rectifying and smoothing an alternating voltage;
A first output circuit that has a smoothing circuit that generates a DC voltage from the pulsating voltage generated by the rectifying and smoothing circuit, and that outputs the DC voltage generated by the smoothing circuit;
A second output circuit that outputs a pulsating voltage generated by the rectifying and smoothing circuit;
A power supply circuit comprising: a switch for switching between the first output circuit and the second output circuit. 3. The power supply circuit according to claim 1, wherein the first output circuit includes a voltage changing circuit that changes a value of a DC voltage to be output. A power supply circuit according to any one of claims 1 to 3 and a light source.
Driving the light source by the power circuit;
A lighting device characterized by that. The light source is a light emitting diode;
The lighting device according to claim 4. The lighting device according to claim 4 or 5 is provided as a backlight device of a display panel.
An image display device characterized by that.

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