WO2014050165A1 - Power source device and display device - Google Patents

Power source device and display device Download PDF

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Publication number
WO2014050165A1
WO2014050165A1 PCT/JP2013/055324 JP2013055324W WO2014050165A1 WO 2014050165 A1 WO2014050165 A1 WO 2014050165A1 JP 2013055324 W JP2013055324 W JP 2013055324W WO 2014050165 A1 WO2014050165 A1 WO 2014050165A1
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WO
WIPO (PCT)
Prior art keywords
power supply
pwm signal
transformer
unit
duty ratio
Prior art date
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PCT/JP2013/055324
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French (fr)
Japanese (ja)
Inventor
崇 園田
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Eizo株式会社
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Application filed by Eizo株式会社 filed Critical Eizo株式会社
Publication of WO2014050165A1 publication Critical patent/WO2014050165A1/en

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33507—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters
    • H02M3/33523—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters with galvanic isolation between input and output of both the power stage and the feedback loop

Definitions

  • the present invention relates to a power supply device that drives a load by PWM control and a display device including the power supply device.
  • a liquid crystal monitor uses a power supply device to supply a required voltage or current to a load.
  • a power supply device For example, an AC voltage is induced on the secondary side of the transformer by connecting a transistor to the primary side of the switching transformer and switching the transistor by applying a pulse signal with a pulse width controlled to the base of the transistor.
  • a power supply device that supplies a DC voltage to a load by rectifying and smoothing the induced AC voltage is disclosed (Patent Document 1).
  • Such a power supply device can be used for a display device that dimmes the backlight of a liquid crystal monitor using a PWM control method.
  • FIG. 9 is a block diagram showing an example of the configuration of a conventional display device 300.
  • the power supply device includes a switching transformer 313, and a transistor 314 is connected to the primary side of the transformer 313.
  • a pulse signal having a required pulse width output from the control IC 335 is applied to the base of the transistor 314, and the transistor 314 performs a switching operation at a predetermined frequency.
  • a diode 315 and a smoothing capacitor 316 are connected to the secondary side of the transformer 313, and an LC filter including a coil 320 and a capacitor 330 is connected to the subsequent stage.
  • An LED driver 20 and a backlight 110 are connected to the output side of the power supply device.
  • a brightness value corresponding to the user setting is output to the microcomputer 120, and the microcomputer 120 generates a PWM signal corresponding to the input brightness value to generate an LED driver. 20 output.
  • the load current of the power supply device fluctuates greatly.
  • the transistor 314 performs a switching operation in an attempt to follow the fluctuation of the load current. Therefore, the magnetic flux change of the transformer 313 becomes large, and the core or winding of the transformer 313 vibrates due to the magnetic flux change, and abnormal noise is generated from the transformer 313.
  • an LC filter is provided at the output end of the power supply device to reduce the change in the current flowing through the transformer 313.
  • the parts used in the conventional LC filter are considerably large, and it is difficult to reduce the size of the power supply device.
  • the present invention has been made in view of such circumstances, and provides a power supply device capable of suppressing abnormal noise generated when a load is driven by PWM control, and a display device including the power supply device. It is in.
  • a power supply device includes a power supply unit, a drive unit that drives a load by PWM-controlling the output of the power supply unit in accordance with a PWM signal, and the power supply unit in response to output fluctuations of the power supply unit.
  • a power supply apparatus including a control unit that controls output includes an adjustment unit that adjusts a response speed of the control unit in accordance with a duty ratio of the PWM signal.
  • the power supply device is connected to the transformer on the secondary side and the primary side of the transformer, and is based on the frequency of the PWM signal.
  • the adjustment unit adjusts the change rate of the on period of the switching element from the on / off time of the PWM signal according to the duty ratio of the PWM signal. It is made to do so.
  • the adjustment unit includes the switching element when the duty ratio is greater than a first threshold value ( ⁇ 50%) and smaller than a second threshold value (> 50%).
  • a power supply apparatus further comprising a smoothing circuit that rectifies and smoothes the PWM signal, and the adjustment unit has a voltage smoothed by the smoothing circuit greater than a first threshold voltage, The rate of change of the ON period from the ON / OFF time point of the PWM signal of the switching element when the voltage is smaller than the threshold voltage (> the first threshold voltage), when the voltage is smaller than the first threshold voltage or the second
  • the PWM signal is adjusted so as to be slower than the rate of change of the ON period from the ON / OFF point of the PWM signal when it is larger than the threshold voltage.
  • a display device includes the power supply device according to any one of the foregoing inventions, and a backlight driven by a drive unit of the power supply device.
  • the power supply unit the drive unit that drives the load by PWM control of the output of the power supply unit according to the PWM signal, and the control that controls the output of the power supply unit in response to the output fluctuation of the power supply unit A part.
  • the power supply unit includes, for example, a switching transformer and a switching element.
  • the control unit controls the output so as to respond to the output fluctuation (for example, current fluctuation, voltage fluctuation, etc.) of the power supply section. For example, when the load current of the power supply unit increases, the control unit controls the switching operation of the switching element of the power supply unit to increase the current output from the power supply unit.
  • the adjustment unit adjusts the response speed of the control unit according to the duty ratio of the PWM signal.
  • the PWM signal is a signal in which an ON / OFF pulse waveform is repeated at a predetermined frequency
  • the duty ratio ⁇ can be a ratio of an ON period in one cycle of the PWM signal.
  • the duty ratio ⁇ is, for example, 10%, the current output from the power supply unit is small, and the change in current flowing through the transformer of the power supply unit (for example, the difference between the maximum value and the minimum value of the current waveform) is small.
  • the duty ratio ⁇ 90%, for example, the current output from the power supply unit is large, but the current change flowing through the transformer of the power supply unit (for example, the difference between the maximum value and the minimum value of the current waveform) is small.
  • the duty ratio ⁇ is, for example, about 50%, the change in current flowing through the transformer of the power supply unit (for example, the difference between the maximum value and the minimum value of the current waveform) becomes large, and the magnetic flux change of the transformer becomes large. It becomes large and causes abnormal noise in the transformer.
  • the power supply unit is connected to the primary side of the transformer having the drive unit connected to the secondary side, and is turned on / off at a frequency higher than the frequency of the PWM signal.
  • a repeated switching element can be set to 200 Hz, for example, and the operating frequency of the switching element can be set to 100 kHz, for example.
  • the control unit performs control so that the ON period of the switching element is lengthened / shortened according to the magnitude of the output of the power source unit. For example, when the load current of the power supply unit increases, the control unit increases the current output from the power supply unit by extending the ON period of the switching element of the power supply unit.
  • the adjusting unit adjusts the change rate of the ON period of the switching element controlled by the control unit according to the duty ratio of the PWM signal.
  • the duty ratio ⁇ is, for example, 10% or 90%
  • the change in current flowing through the transformer of the power supply unit for example, the difference between the maximum value and the minimum value of the current waveform
  • the adjustment unit does not adjust the change rate of the ON period of the switching element controlled by the control unit.
  • the duty ratio ⁇ is, for example, about 50%, a change in current flowing through the transformer of the power supply unit becomes large, and a change in magnetic flux of the transformer becomes large, causing abnormal noise generation in the transformer.
  • the adjustment unit adjusts so that the change rate of the ON period of the switching element controlled by the control unit becomes slow.
  • the change rate of the ON period of the switching element By slowing down the change rate of the ON period of the switching element, the current flowing in the transformer is suppressed from increasing rapidly, preventing the transformer magnetic flux from changing suddenly and reducing the occurrence of abnormal noise. can do.
  • the adjustment unit adjusts the change rate of the ON period of the switching element controlled by the control unit from the time when the PWM signal is turned on / off. Slowing the change rate of the ON period of the switching element prevents the current flowing in the transformer from increasing suddenly, prevents the transformer magnetic flux from changing suddenly, and reduces the occurrence of abnormal noise. can do.
  • the adjustment unit is configured to start from the ON / OFF time point of the PWM signal of the switching element when the duty ratio is larger than the first threshold value ( ⁇ 50%) and smaller than the second threshold value (> 50%).
  • the change rate of the ON period is adjusted to be slower than the change rate of the ON period from the ON / OFF point of the PWM signal when the duty ratio is smaller than the first threshold value or larger than the second threshold value.
  • the first threshold value Th1 can be set to a value such as 30% or 40%, for example.
  • the second threshold Th2 can be set to a value such as 70% or 60%, for example.
  • the smoothing circuit rectifies and smoothes the PWM signal. That is, the voltage smoothed by the smoothing circuit is high or low according to the duty ratio of the PWM signal.
  • the adjusting unit changes the on period from the on / off time of the PWM signal of the switching element when the voltage smoothed by the smoothing circuit is larger than the first threshold voltage and smaller than the second threshold voltage (> first threshold voltage). Is adjusted to be slower than the rate of change of the on period from the on / off time point of the PWM signal when the voltage is smaller than the first threshold voltage or larger than the second threshold voltage.
  • the first threshold voltage corresponds to the first threshold Th1 of the duty ratio
  • the second threshold voltage corresponds to the second threshold Th2 of the duty ratio.
  • FIG. 1 is a block diagram illustrating an example of a configuration of a display device 200 according to the present embodiment
  • FIG. 2 is an explanatory diagram illustrating an example of a circuit configuration of the display device 200 according to the present embodiment.
  • the display device 200 includes a power supply device 100, a backlight 110, a microcomputer 120, a liquid crystal panel 130, and the like.
  • the power supply apparatus 100 includes a power supply unit 10, an LED driver 20 as a drive unit, a control unit 30, an adjustment unit 40, and the like.
  • the power supply unit 10 includes a switching transformer 13 and a transistor 14 as a switching element, converts an AC voltage supplied from the commercial power supply 1 into a DC voltage, and converts the converted DC voltage to the LED driver 20. Output to. Details of the power supply unit 10 will be described later.
  • the LED driver 20 drives the backlight 110 as a load by PWM-controlling the output of the power supply unit 10 according to the PWM signal. That is, the backlight 110 can be dimmed by the PWM control method.
  • the control unit 30 controls the output of the power supply unit 10 to respond to output fluctuations (for example, current fluctuation, voltage fluctuation, etc.) of the power supply unit 10. For example, when the load current of the power supply unit 10 increases, the control unit 30 controls the switching operation of the switching element of the power supply unit 10 to increase the current output from the power supply unit 10. That is, the control unit 30 feeds back an output (for example, current, voltage, etc.) of the power supply unit 10 and controls the switching operation of the power supply unit 10. Details of the control unit 30 will be described later.
  • the adjustment unit 40 acquires the PWM signal output from the microcomputer 120 and adjusts the response speed of the control unit 30 according to the duty ratio of the acquired PWM signal.
  • the PWM signal is a signal in which an ON / OFF pulse waveform is repeated at a predetermined frequency, and the duty ratio ⁇ can be a ratio of an ON period in one cycle of the PWM signal.
  • the frequency of the PWM signal can be, for example, 200 Hz, but is not limited thereto.
  • the duty ratio ⁇ is, for example, 10%
  • the current output from the power supply unit 10 is small, and the change in current flowing through the transformer 13 of the power supply unit 10 (for example, the maximum value of the current waveform)
  • the change in current flowing through the transformer 13 of the power supply unit 10 for example, the maximum value of the current waveform
  • the difference from the minimum value is small. Therefore, the difference between the maximum value and the minimum value of the magnetic flux of the transformer 13 is also small.
  • the duty ratio ⁇ is about 50%, for example, the change in the current flowing through the transformer 13 of the power supply unit 10 (for example, the maximum value and the minimum value of the current waveform) (Difference) increases, and the magnetic flux change of the transformer 13 increases, causing abnormal noise in the transformer 13.
  • the 10%, 50%, and 90% described above are examples, and the numerical value of the duty ratio ⁇ is not limited to these.
  • the power supply unit 10 includes a rectifying element 11, a capacitor 12, a switching transformer 13, a transistor 14 as a switching element, a diode 15, a capacitor 16, and the like.
  • the adjustment unit 40 includes diodes 41 and 42, resistors 43 and 44, capacitors 45 and 46, resistors 47, 48, 49, 51, 52, 54, 55 and 56, transistors 50, 53 and 58, light emitting diodes 571 and a phototransistor.
  • the photocoupler 57 having the 572, the capacitor 59, and the like are provided.
  • the power supply unit 10 will be described. As shown in FIG. 2, the collector of the transistor 14 is connected to the primary side of the transformer 13, and the LED driver 20 as a drive unit is connected to the secondary side of the transformer 13 after the diode 15 and the capacitor 16. Is connected.
  • the LED driver 20 supplies required power (current, voltage) to the backlight 110 by performing PWM control on the output of the power supply unit 10 based on the PWM signal from the microcomputer 120.
  • the drive terminal D of the control IC 35 is connected to the base of the transistor 14.
  • a pulse signal having a required width which is repeatedly turned on and off at a predetermined frequency (for example, 100 kHz) from the drive terminal D of the control IC 35, the transistor 14 has a frequency higher than the frequency of the PWM signal.
  • the on / off operation is repeated at.
  • the switching operation frequency of the transistor 14 is not limited to 100 kHz, and may be other frequencies.
  • FIG. 4 is a schematic diagram showing the relationship between the PWM signal and the switching waveform of the transistor 14.
  • the transistor 14 performs a switching operation with a frequency of 100 kHz, for example.
  • the frequency of the PWM signal is, for example, 200 Hz.
  • a current is output to the backlight 110 via the LED driver 20 by the switching operation of the transistor 14.
  • no current is output to the backlight 110 regardless of whether or not the transistor 14 performs a switching operation.
  • the switching operation of the transistor 14 may be stopped or the switching operation may be continued.
  • Resistors 31 and 32 connected in series are connected between the power supply unit 10 and the LED driver 20, and a series circuit of a photocoupler 33 (light emitting diode 331) and a shunt regulator 34 is connected in parallel with the resistors 31 and 32. Connected. The reference of the shunt regulator 34 is connected to the connection node of the resistors 31 and 32.
  • the control IC 35 changes the pulse width of the pulse signal output from the drive terminal D according to the voltage value of the feedback terminal FB. More specifically, the control IC 35 increases the ON width of the pulse signal output from the drive terminal D as the voltage value of the feedback terminal FB is higher. The longer the ON width of the pulse signal, the longer the ON period of the transistor 14, and the power supply unit 10 can output more current.
  • the output of the power supply unit 10 is zero or extremely small, so that the current flowing through the light emitting diode 331 increases and the current that the phototransistor 332 flows out from the feedback terminal FB of the control IC 35 increases. , Lower the voltage value of the FB terminal.
  • the control IC 35 can stop the switching operation of the transistor 14 or operate it with a very short on-time by reducing the on width of the pulse signal output from the drive terminal D to zero or extremely short.
  • a series circuit of a diode 41 and a resistor 43 is connected to the output terminal P of the PWM signal of the microcomputer 120, and a capacitor 45 is connected to the subsequent stage of the resistor 43.
  • a series circuit of a diode 42 and a resistor 44 is connected to the output terminal P of the PWM signal of the microcomputer 120, and a capacitor 46 and a resistor 47 are connected to the subsequent stage of the resistor 44.
  • the diode 41, the resistor 43, and the capacitor 45 constitute a smoothing circuit.
  • the diode 42, the resistors 44 and 47, and the capacitor 46 also form a smoothing circuit.
  • the PWM signal of the microcomputer 120 is smoothed (integrated) by the capacitors 45 and 46.
  • the output end P of the PWM signal is separated from the output end to the LED driver, but the output end P of the PWM signal may also serve as the output end to the LED driver.
  • the base of the transistor 50 is connected to the connection node between the capacitor 46 and the resistor 44 via the resistor 49.
  • a resistor 48 is connected between the base and emitter of the transistor 50.
  • the base of the transistor 53 is connected to the connection node between the capacitor 45 and the resistor 43 via the resistor 51.
  • a resistor 52 is connected between the base and emitter of the transistor 53.
  • the emitter of the transistor 50 and the collector of the transistor 53 are connected to the base of the transistor 58.
  • a voltage obtained by dividing the required voltage Vcc by resistors 54 and 55 is applied to the base of the transistor 58.
  • a series circuit of a resistor 56 and a photocoupler 57 (light emitting diode 571) is connected to the collector of the transistor 58.
  • a series circuit of a capacitor 59 and a photocoupler 57 (phototransistor 572) is connected to the feedback terminal FB of the control IC 35.
  • FIG. 5 is an explanatory diagram showing an example of the operation of the adjustment unit 40.
  • FIG. 5 illustrates how the adjustment unit 40 operates in accordance with the duty ratio ⁇ of the PWM signal.
  • Th1 is a first threshold value and Th2 is a second threshold value.
  • the first threshold Th1 can be set to 30% and the second threshold Th2 can be set to 70%.
  • the first threshold Th1 may be 40% and the second threshold Th2 may be 60%.
  • the values of the first threshold value and the second threshold value are not limited to these numerical values.
  • the voltages V1 and V2 obtained by smoothing the PWM signal are medium voltages, and the transistor 50 53 are turned off.
  • This case corresponds to a case where the voltage smoothed by the smoothing circuit is larger than the first threshold voltage and smaller than the second threshold voltage (> first threshold voltage). Since both the transistors 50 and 53 are turned off, a voltage obtained by dividing the voltage Vcc is applied to the base of the transistor 58, and the transistor 58 is turned on. Since the transistor 58 is turned on, a current flows through the light emitting diode 571, and the phototransistor 572 is turned on. Therefore, the capacitor 59 is connected to the feedback terminal FB of the control IC 35 in parallel with the capacitor 36, and the capacitance of the capacitor of the feedback terminal FB becomes relatively large.
  • the change rate of the voltage value of the feedback terminal FB becomes slower as the capacitance of the feedback terminal FB of the control IC 35 is larger.
  • the control IC 35 shortens the ON width of the pulse signal output from the drive terminal D as the voltage value of the feedback terminal FB is lower. As the ON width of the pulse signal is shortened, the ON period of the transistor 14 is shortened, and the power supply unit 10 reduces the output current.
  • the change rate of the voltage value of the feedback terminal FB increases as the capacitance of the feedback terminal FB of the control IC 35 decreases.
  • the control IC 35 increases the ON width of the pulse signal output from the drive terminal D as the voltage value of the feedback terminal FB is higher. As the ON width of the pulse signal is increased, the ON period of the transistor 14 is increased, and the power supply unit 10 increases the output current.
  • the adjustment unit 40 adjusts so that the change rate of the ON period of the transistor 14 controlled by the control unit 30 is slow. That is, the capacitor 59 is connected to the feedback terminal FB of the control IC 35.
  • the adjustment unit 40 adjusts the changing speed of the ON period of the transistor 14 from the ON point of the PWM signal according to the duty ratio of the PWM signal.
  • the time when the PWM signal is turned on is the time when the power supply unit 10 starts to output current to the LED driver 20, and the time when the output fluctuation of the power supply unit 10 increases.
  • the adjustment unit 40 can change the change rate of the ON period of the transistor 14 controlled by the control unit 30 from the ON time of the PWM signal at time t0. Do not make adjustments. In this case, the ON width of the pulse signal applied to the base of the transistor 14 is T1, and the load current rises at time t0.
  • the adjustment unit 40 can change the ON period of the transistor 14 controlled by the control unit 30 from the ON point of the PWM signal at time t0. Make adjustments.
  • the ON width of the pulse signal applied to the base of the transistor 14 is T2 ( ⁇ T1).
  • the adjustment unit 40 adjusts the rate of change of the ON period of the transistor 14 controlled by the control unit 30 from the time when the PWM signal is turned off. By slowing down the change rate of the ON period of the transistor 14, it is possible to suppress a sudden increase in the current flowing through the transformer 13, thereby preventing the magnetic flux of the transformer 13 from changing suddenly and generating abnormal noise. Can be reduced.
  • FIG. 8 is an explanatory diagram showing an example of a switching waveform when the duty ratio ⁇ of the PWM signal is around 50%.
  • 8A shows the PWM signal
  • FIG. 8B shows the conventional switching waveform
  • FIG. 8C shows the switching waveform of the present embodiment.
  • the switching waveform changes sharply when the PWM signal is turned on / off.
  • the change of the switching waveform when the PWM signal is turned on / off is gradual.
  • the response performance of the power supply unit 10 is degraded at the point where the output current of the power supply unit 10 changes suddenly, that is, at the point where the magnetic flux of the transformer 13 swings to the maximum and abnormal noise increases (specifically).
  • the feedback gain is lowered and the follow-up performance with respect to the output fluctuation is lowered. Can be suppressed.
  • the magnitude of the magnetic flux change of the transformer 13 of the power supply unit 10 is determined by the backlight control PWM signal, and the response (following performance) to the load fluctuation of the power supply unit 10 is controlled, so that the transformer 13
  • the change in magnetic flux can be softened and the generation of abnormal noise from the transformer 13 can be suppressed.
  • the LC filter required in the conventional switching power supply can be omitted, and the apparatus can be reduced in size and cost. Can be planned.
  • an LC filter may be provided in the power supply unit 10 also in the present embodiment. In this case, the LC filter can be made smaller than the conventional one.
  • two capacitors are connected to the feedback terminal FB of the control IC 35, and one capacitor is connected or disconnected.
  • the number of capacitors is limited to two. However, three or more can be provided. When three or more capacitors are provided, the number of capacitors to be connected can be increased or decreased stepwise according to the duty ratio ⁇ of the PWM signal.
  • a database in which relationships such as the brightness value, the PWM signal, and the pulse width of the pulse signal are previously stored may be stored, and the microcomputer 120 may control the switching operation of the transistor 14. .
  • the microcomputer 120 performs the functions of the control unit 30 and the adjustment unit 40.

Abstract

Provided are a power source device and a display device equipped with the power source device capable of suppressing an abnormal sound that is generated when driving a load via PWM control. A power source (10), which includes a transformer, a switching element and so forth, converts an AC voltage supplied from a commercial power source (1) to a DC voltage, and outputs the converted DC voltage to an LED driver (20). The LED driver (20) drives a backlight (110) using PWM control for the output from the power source (10) in accordance with a PWM signal. A control unit (30) controls the output from the power source (10) to respond to the output fluctuation of the power source (10). An adjustment unit (40) acquires the PWM signal output from a microcomputer (120), and adjusts the speed of response in the control unit (30) in response to the duty ratio of the acquired PWM signal.

Description

電源装置及び表示装置Power supply device and display device
　本発明は、ＰＷＭ制御して負荷を駆動する電源装置及び該電源装置を備える表示装置に関する。 The present invention relates to a power supply device that drives a load by PWM control and a display device including the power supply device.
　液晶モニタ（表示装置）を含む多くの電気機器又は電子機器には、負荷に所要の電圧又は電流を供給するため電源装置が用いられている。例えば、スイッチング用の変圧器の一次側にトランジスタを接続し、トランジスタのベースにパルス幅が制御されたパルス信号を加えてトランジスタをスイッチング動作させることにより、変圧器の二次側に交流電圧を誘起させ、誘起した交流電圧を整流・平滑することにより、直流電圧を負荷へ供給する電源装置が開示されている（特許文献１）。このような電源装置は、液晶モニタのバックライトをＰＷＭ制御方式で調光する表示装置に使用することができる。 Many electric devices or electronic devices including a liquid crystal monitor (display device) use a power supply device to supply a required voltage or current to a load. For example, an AC voltage is induced on the secondary side of the transformer by connecting a transistor to the primary side of the switching transformer and switching the transistor by applying a pulse signal with a pulse width controlled to the base of the transistor. A power supply device that supplies a DC voltage to a load by rectifying and smoothing the induced AC voltage is disclosed (Patent Document 1). Such a power supply device can be used for a display device that dimmes the backlight of a liquid crystal monitor using a PWM control method.
　図９は従来の表示装置３００の構成の一例を示すブロック図である。図９に示すように、電源装置は、スイッチング用の変圧器３１３を備え、変圧器３１３の一次側にはトランジスタ３１４を接続してある。トランジスタ３１４のベースには、コントロールＩＣ３３５から出力される所要のパルス幅のパルス信号が印加され、トランジスタ３１４は、所定の周波数でスイッチング動作を行う。変圧器３１３の二次側には、ダイオード３１５、平滑用のキャパシタ３１６を接続してあり、その後段には、コイル３２０及びキャパシタ３３０で構成されるＬＣフィルタを接続してある。電源装置の出力側には、ＬＥＤドライバ２０、バックライト１１０を接続してある。液晶モニタの明るさを設定すべくユーザが操作した場合、ユーザの設定に応じたブライトネス値がマイコン１２０へ出力され、マイコン１２０は、入力されたブライトネス値に応じたＰＷＭ信号を生成してＬＥＤドライバ２０へ出力する。 FIG. 9 is a block diagram showing an example of the configuration of a conventional display device 300. As shown in FIG. 9, the power supply device includes a switching transformer 313, and a transistor 314 is connected to the primary side of the transformer 313. A pulse signal having a required pulse width output from the control IC 335 is applied to the base of the transistor 314, and the transistor 314 performs a switching operation at a predetermined frequency. A diode 315 and a smoothing capacitor 316 are connected to the secondary side of the transformer 313, and an LC filter including a coil 320 and a capacitor 330 is connected to the subsequent stage. An LED driver 20 and a backlight 110 are connected to the output side of the power supply device. When the user operates to set the brightness of the liquid crystal monitor, a brightness value corresponding to the user setting is output to the microcomputer 120, and the microcomputer 120 generates a PWM signal corresponding to the input brightness value to generate an LED driver. 20 output.
実用新案登録第２５１３７４１号公報Utility Model Registration No. 2513741
　従来の電源装置にあっては、バックライト１１０をＰＷＭ制御方式で調光を行った際に、電源装置の負荷電流が大きく変動する結果、負荷電流の変動に追従しようとしてトランジスタ３１４がスイッチング動作を行うため、変圧器３１３の磁束変化が大きくなり変圧器３１３のコア又は巻き線が磁束変化により振動して変圧器３１３から異音が発生する。このため、変圧器３１３から発生する異音を減少させるために、電源装置の出力端にＬＣフィルタを設け、変圧器３１３に流れる電流の変化を少なくしている。しかし、従来のＬＣフィルタで使用する部品は相当程度大きく、電源装置を小型化することが困難であった。 In the conventional power supply device, when the backlight 110 is dimmed by the PWM control method, the load current of the power supply device fluctuates greatly. As a result, the transistor 314 performs a switching operation in an attempt to follow the fluctuation of the load current. Therefore, the magnetic flux change of the transformer 313 becomes large, and the core or winding of the transformer 313 vibrates due to the magnetic flux change, and abnormal noise is generated from the transformer 313. For this reason, in order to reduce the abnormal noise generated from the transformer 313, an LC filter is provided at the output end of the power supply device to reduce the change in the current flowing through the transformer 313. However, the parts used in the conventional LC filter are considerably large, and it is difficult to reduce the size of the power supply device.
　本発明は、斯かる事情に鑑みてなされたものであり、ＰＷＭ制御して負荷を駆動する場合に発生する異音を抑制することができる電源装置及び該電源装置を備える表示装置を提供することにある。 The present invention has been made in view of such circumstances, and provides a power supply device capable of suppressing abnormal noise generated when a load is driven by PWM control, and a display device including the power supply device. It is in.
　第１発明に係る電源装置は、電源部と、ＰＷＭ信号に応じて前記電源部の出力をＰＷＭ制御して負荷を駆動する駆動部と、前記電源部の出力変動に応答して該電源部の出力を制御する制御部とを備える電源装置において、前記ＰＷＭ信号のデューティ比に応じて、前記制御部の応答の遅速を調整する調整部を備えることを特徴とする。 A power supply device according to a first aspect of the present invention includes a power supply unit, a drive unit that drives a load by PWM-controlling the output of the power supply unit in accordance with a PWM signal, and the power supply unit in response to output fluctuations of the power supply unit. A power supply apparatus including a control unit that controls output includes an adjustment unit that adjusts a response speed of the control unit in accordance with a duty ratio of the PWM signal.
　第２発明に係る電源装置は、第１発明において、前記電源部は、二次側に前記駆動部が接続される変圧器と、該変圧器の一次側に接続され、前記ＰＷＭ信号の周波数よりも高い周波数でオン・オフ動作が繰り返されるスイッチング素子とを備え、前記制御部は、前記電源部の出力変動に応じて前記スイッチング素子のオン期間を制御するようにしてあり、前記調整部は、前記ＰＷＭ信号のデューティ比に応じて、前記制御部が制御する前記スイッチング素子のオン期間の変化速度を調整するようにしてあることを特徴とする。 According to a second aspect of the present invention, there is provided the power supply device according to the first aspect, wherein the power supply unit is connected to the transformer on the secondary side and the primary side of the transformer, and is based on the frequency of the PWM signal. A switching element that repeats an on / off operation at a higher frequency, and the control unit is configured to control an on period of the switching element according to an output variation of the power supply unit, and the adjustment unit includes: According to the duty ratio of the PWM signal, the change rate of the ON period of the switching element controlled by the control unit is adjusted.
　第３発明に係る電源装置は、第２発明において、前記調整部は、前記ＰＷＭ信号のデューティ比に応じて、前記ＰＷＭ信号のオン／オフ時点からの前記スイッチング素子のオン期間の変化速度を調整するようにしてあることを特徴とする。 According to a third aspect of the present invention, there is provided the power supply device according to the second aspect, wherein the adjustment unit adjusts the change rate of the on period of the switching element from the on / off time of the PWM signal according to the duty ratio of the PWM signal. It is made to do so.
　第４発明に係る電源装置は、第３発明において、前記調整部は、前記デューティ比が第１閾値（＜５０％）より大きく、第２閾値（＞５０％）より小さい場合の前記スイッチング素子の前記ＰＷＭ信号のオン／オフ時点からのオン期間の変化速度を、前記デューティ比が前記第１閾値より小さい場合又は前記第２閾値より大きい場合の前記ＰＷＭ信号のオン／オフ時点からの前記オン期間の変化速度より遅くすべく調整するようにしてあることを特徴とする。 According to a fourth aspect of the present invention, there is provided the power supply device according to the third aspect, wherein the adjustment unit includes the switching element when the duty ratio is greater than a first threshold value (<50%) and smaller than a second threshold value (> 50%). The on period from the on / off time of the PWM signal when the duty ratio is smaller than the first threshold value or larger than the second threshold value. It is characterized in that it is adjusted so as to be slower than the rate of change of.
　第５発明に係る電源装置は、第３発明において、前記ＰＷＭ信号を整流して平滑する平滑回路を備え、前記調整部は、前記平滑回路で平滑した電圧が第１閾値電圧より大きく、第２閾値電圧（＞前記第１閾値電圧）より小さい場合の前記スイッチング素子の前記ＰＷＭ信号のオン／オフ時点からのオン期間の変化速度を、前記電圧が前記第１閾値電圧より小さい場合又は前記第２閾値電圧より大きい場合の前記ＰＷＭ信号のオン／オフ時点からの前記オン期間の変化速度より遅くすべく調整するようにしてあることを特徴とする。 According to a fifth aspect of the present invention, there is provided a power supply apparatus according to the third aspect, further comprising a smoothing circuit that rectifies and smoothes the PWM signal, and the adjustment unit has a voltage smoothed by the smoothing circuit greater than a first threshold voltage, The rate of change of the ON period from the ON / OFF time point of the PWM signal of the switching element when the voltage is smaller than the threshold voltage (> the first threshold voltage), when the voltage is smaller than the first threshold voltage or the second The PWM signal is adjusted so as to be slower than the rate of change of the ON period from the ON / OFF point of the PWM signal when it is larger than the threshold voltage.
　第６発明に係る表示装置は、前述の発明のいずれか１つに係る電源装置と、該電源装置の駆動部により駆動されるバックライトとを備えることを特徴とする。 A display device according to a sixth aspect of the invention includes the power supply device according to any one of the foregoing inventions, and a backlight driven by a drive unit of the power supply device.
　第１発明にあっては、電源部、ＰＷＭ信号に応じて電源部の出力をＰＷＭ制御して負荷を駆動する駆動部、及び電源部の出力変動に応答して電源部の出力を制御する制御部を備える。電源部は、例えば、スイッチング用の変圧器及びスイッチング素子などを備える。制御部は、電源部の出力変動（例えば、電流変動、電圧変動など）に応答すべく出力を制御する。例えば、電源部の負荷電流が増加した場合には、制御部は、電源部のスイッチング素子のスイッチング動作を制御して電源部が出力する電流を増加させる。 In the first invention, the power supply unit, the drive unit that drives the load by PWM control of the output of the power supply unit according to the PWM signal, and the control that controls the output of the power supply unit in response to the output fluctuation of the power supply unit A part. The power supply unit includes, for example, a switching transformer and a switching element. The control unit controls the output so as to respond to the output fluctuation (for example, current fluctuation, voltage fluctuation, etc.) of the power supply section. For example, when the load current of the power supply unit increases, the control unit controls the switching operation of the switching element of the power supply unit to increase the current output from the power supply unit.
　調整部は、ＰＷＭ信号のデューティ比に応じて、制御部の応答の遅速を調整する。ＰＷＭ信号は、オン・オフのパルス波形が所定の周波数で繰り返される信号であり、デューティ比αは、ＰＷＭ信号の１周期に占めるオン期間の割合とすることができる。デューティ比αが、例えば、１０％である場合、電源部が出力する電流は少なく、電源部の変圧器に流れる電流変化（例えば、電流波形の最大値と最小値との差）は小さい。また、デューティ比αが、例えば、９０％である場合、電源部が出力する電流は多いが、電源部の変圧器に流れる電流変化（例えば、電流波形の最大値と最小値との差）は小さい。他方、デューティ比αが、例えば、５０％程度である場合、電源部の変圧器に流れる電流変化（例えば、電流波形の最大値と最小値との差）は大きくなり、変圧器の磁束変化が大きくなり変圧器の異音発生の原因となる。 The adjustment unit adjusts the response speed of the control unit according to the duty ratio of the PWM signal. The PWM signal is a signal in which an ON / OFF pulse waveform is repeated at a predetermined frequency, and the duty ratio α can be a ratio of an ON period in one cycle of the PWM signal. When the duty ratio α is, for example, 10%, the current output from the power supply unit is small, and the change in current flowing through the transformer of the power supply unit (for example, the difference between the maximum value and the minimum value of the current waveform) is small. Further, when the duty ratio α is 90%, for example, the current output from the power supply unit is large, but the current change flowing through the transformer of the power supply unit (for example, the difference between the maximum value and the minimum value of the current waveform) is small. On the other hand, when the duty ratio α is, for example, about 50%, the change in current flowing through the transformer of the power supply unit (for example, the difference between the maximum value and the minimum value of the current waveform) becomes large, and the magnetic flux change of the transformer becomes large. It becomes large and causes abnormal noise in the transformer.
　調整部は、電源部の変圧器に流れる電流変化が大きくなるようなデューティ比αの場合、制御部の応答が遅くなるように調整する。制御部の応答を遅くすることにより、電源部が出力する電流が電源部の出力変動に追従して急激に変化することを抑制し、変圧器の磁束が急激に変化することを防止し、異音の発生を低減することができる。また、変圧器に流れる電流変化を小さくするためのＬＣフィルタが不要になるので、ＬＣフィルタに用いる比較的大きな部品が不要となり、またＬＣフィルタを実装するための基板面積も小さくすることができ、電源装置の小型化、コスト低減を図ることができる。 The adjustment unit adjusts the response of the control unit to be slow when the duty ratio α is such that a change in current flowing through the transformer of the power supply unit becomes large. By slowing down the response of the control unit, the current output from the power supply unit is prevented from abruptly changing following the output fluctuation of the power supply unit, and the transformer magnetic flux is prevented from changing suddenly. Generation of sound can be reduced. In addition, since an LC filter for reducing the current change flowing through the transformer is not required, relatively large parts used for the LC filter are not required, and the board area for mounting the LC filter can be reduced. The power supply device can be reduced in size and cost.
　第２発明にあっては、電源部は、二次側に駆動部が接続される変圧器と、当該変圧器の一次側に接続され、ＰＷＭ信号の周波数よりも高い周波数でオン・オフ動作が繰り返されるスイッチング素子とを備える。ＰＷＭ信号の周波数は、例えば、２００Ｈｚとすることができ、スイッチング素子の動作周波数は、例えば、１００ｋＨｚとすることができる。制御部は、電源部の出力の大／小に応じてスイッチング素子のオン期間を長／短にすべく制御する。例えば、電源部の負荷電流が増加した場合には、制御部は、電源部のスイッチング素子のオン期間を長くして電源部が出力する電流を増加させる。 In the second invention, the power supply unit is connected to the primary side of the transformer having the drive unit connected to the secondary side, and is turned on / off at a frequency higher than the frequency of the PWM signal. A repeated switching element. The frequency of the PWM signal can be set to 200 Hz, for example, and the operating frequency of the switching element can be set to 100 kHz, for example. The control unit performs control so that the ON period of the switching element is lengthened / shortened according to the magnitude of the output of the power source unit. For example, when the load current of the power supply unit increases, the control unit increases the current output from the power supply unit by extending the ON period of the switching element of the power supply unit.
　調整部は、ＰＷＭ信号のデューティ比に応じて、制御部が制御するスイッチング素子のオン期間の変化速度を調整する。デューティ比αが、例えば、１０％である場合、あるいは９０％である場合、電源部の変圧器に流れる電流変化（例えば、電流波形の最大値と最小値との差）は小さく、変圧器の異音が小さいので、制御部の応答を遅くする必要がない。そこで、調整部は、制御部が制御するスイッチング素子のオン期間の変化速度の調整を行わないようにする。他方、デューティ比αが、例えば、５０％程度である場合、電源部の変圧器に流れる電流変化は大きくなり、変圧器の磁束変化が大きくなり変圧器の異音発生の原因となる。そこで、制御部の応答を遅くすべく、調整部は、制御部が制御するスイッチング素子のオン期間の変化速度が遅くなるように調整する。スイッチング素子のオン期間の変化速度を遅くすることにより、変圧器に流れる電流が急激に増加することを抑制して、変圧器の磁束が急激に変化することを防止し、異音の発生を低減することができる。 The adjusting unit adjusts the change rate of the ON period of the switching element controlled by the control unit according to the duty ratio of the PWM signal. When the duty ratio α is, for example, 10% or 90%, the change in current flowing through the transformer of the power supply unit (for example, the difference between the maximum value and the minimum value of the current waveform) is small, and the transformer Since abnormal noise is small, there is no need to slow down the response of the control unit. Therefore, the adjustment unit does not adjust the change rate of the ON period of the switching element controlled by the control unit. On the other hand, when the duty ratio α is, for example, about 50%, a change in current flowing through the transformer of the power supply unit becomes large, and a change in magnetic flux of the transformer becomes large, causing abnormal noise generation in the transformer. Therefore, in order to slow down the response of the control unit, the adjustment unit adjusts so that the change rate of the ON period of the switching element controlled by the control unit becomes slow. By slowing down the change rate of the ON period of the switching element, the current flowing in the transformer is suppressed from increasing rapidly, preventing the transformer magnetic flux from changing suddenly and reducing the occurrence of abnormal noise. can do.
　第３発明にあっては、調整部は、ＰＷＭ信号のデューティ比に応じて、ＰＷＭ信号のオン／オフ時点からのスイッチング素子のオン期間の変化速度を調整する。ＰＷＭ信号のオン／オフ時点は、電源部が駆動部への電流出力を開始／終了する時点となり、電源部の出力変動が大きくなる時点である。 In the third aspect of the invention, the adjusting unit adjusts the changing speed of the ON period of the switching element from the ON / OFF time point of the PWM signal according to the duty ratio of the PWM signal. The on / off time of the PWM signal is a time when the power supply unit starts / ends current output to the drive unit, and is a time when output fluctuation of the power supply unit becomes large.
　デューティ比αが、例えば、５０％程度である場合、電源部の変圧器に流れる電流変化は大きくなり、変圧器の磁束変化が大きくなり変圧器の異音発生の原因となる。そこで、制御部の応答を遅くすべく、調整部は、ＰＷＭ信号のオン／オフ時点から制御部が制御するスイッチング素子のオン期間の変化速度が遅くなるように調整する。スイッチング素子のオン期間の変化速度が遅くすることにより、変圧器に流れる電流が急激に増加することを抑制して、変圧器の磁束が急激に変化することを防止し、異音の発生を低減することができる。 When the duty ratio α is, for example, about 50%, the change in current flowing through the transformer of the power supply unit becomes large, and the change in magnetic flux of the transformer becomes large, causing abnormal noise in the transformer. Therefore, in order to slow down the response of the control unit, the adjustment unit adjusts the change rate of the ON period of the switching element controlled by the control unit from the time when the PWM signal is turned on / off. Slowing the change rate of the ON period of the switching element prevents the current flowing in the transformer from increasing suddenly, prevents the transformer magnetic flux from changing suddenly, and reduces the occurrence of abnormal noise. can do.
　第４発明にあっては、調整部は、デューティ比が第１閾値（＜５０％）より大きく、第２閾値（＞５０％）より小さい場合のスイッチング素子のＰＷＭ信号のオン／オフ時点からのオン期間の変化速度を、デューティ比が第１閾値より小さい場合又は第２閾値より大きい場合のＰＷＭ信号のオン／オフ時点からのオン期間の変化速度より遅くすべく調整する。第１閾値Ｔｈ１は、例えば、３０％、４０％などの値とすることができる。また、第２閾値Ｔｈ２は、例えば、７０％、６０％などの値とすることができる。これにより、変圧器の磁束変化が大きくなるようなデューティ比α（Ｔｈ１＜α＜Ｔｈ２）である場合に、ＰＷＭ信号のオン／オフ時点でのトランジスタのオン期間の変化速度を遅くするので、変圧器に流れる電流が急激に増加することを抑制して、変圧器の磁束が急激に変化することを防止し、異音の発生を低減することができる。 In the fourth aspect of the invention, the adjustment unit is configured to start from the ON / OFF time point of the PWM signal of the switching element when the duty ratio is larger than the first threshold value (<50%) and smaller than the second threshold value (> 50%). The change rate of the ON period is adjusted to be slower than the change rate of the ON period from the ON / OFF point of the PWM signal when the duty ratio is smaller than the first threshold value or larger than the second threshold value. The first threshold value Th1 can be set to a value such as 30% or 40%, for example. The second threshold Th2 can be set to a value such as 70% or 60%, for example. As a result, when the duty ratio α (Th1 <α <Th2) is such that the magnetic flux change of the transformer becomes large, the change rate of the on period of the transistor at the time of turning on / off the PWM signal is slowed down. It is possible to suppress a sudden increase in the current flowing through the transformer, to prevent the magnetic flux of the transformer from changing abruptly, and to reduce the occurrence of abnormal noise.
　第５発明にあっては、平滑回路は、ＰＷＭ信号を整流して平滑する。すなわち、ＰＷＭ信号のデューティ比の大小に応じて平滑回路で平滑した電圧は高低となる。調整部は、平滑回路で平滑した電圧が第１閾値電圧より大きく、第２閾値電圧（＞第１閾値電圧）より小さい場合のスイッチング素子のＰＷＭ信号のオン／オフ時点からのオン期間の変化速度を、電圧が第１閾値電圧より小さい場合又は第２閾値電圧より大きい場合のＰＷＭ信号のオン／オフ時点からのオン期間の変化速度より遅くすべく調整する。第１閾値電圧は、デューティ比の第１閾値Ｔｈ１に対応し、第２閾値電圧は、デューティ比の第２閾値Ｔｈ２に対応する。これにより、変圧器に流れる電流が急激に増加することを抑制して、変圧器の磁束が急激に変化することを防止し、異音の発生を低減することができる。 In the fifth invention, the smoothing circuit rectifies and smoothes the PWM signal. That is, the voltage smoothed by the smoothing circuit is high or low according to the duty ratio of the PWM signal. The adjusting unit changes the on period from the on / off time of the PWM signal of the switching element when the voltage smoothed by the smoothing circuit is larger than the first threshold voltage and smaller than the second threshold voltage (> first threshold voltage). Is adjusted to be slower than the rate of change of the on period from the on / off time point of the PWM signal when the voltage is smaller than the first threshold voltage or larger than the second threshold voltage. The first threshold voltage corresponds to the first threshold Th1 of the duty ratio, and the second threshold voltage corresponds to the second threshold Th2 of the duty ratio. Thereby, it can suppress that the electric current which flows into a transformer increases rapidly, it can prevent that the magnetic flux of a transformer changes rapidly, and generation | occurrence | production of abnormal noise can be reduced.
　第６発明にあっては、ＰＷＭ制御して負荷を駆動する場合に発生する異音を抑制することができる表示装置を提供することができる。 According to the sixth aspect of the invention, it is possible to provide a display device that can suppress abnormal noise that occurs when a load is driven by PWM control.
　本発明によれば、ＰＷＭ制御して負荷を駆動する電源装置及び該電源装置を備える表示装置において、ＰＷＭ制御に起因して電源装置から発生する異音を抑制することができる。 According to the present invention, in a power supply device that drives a load by PWM control and a display device including the power supply device, abnormal noise generated from the power supply device due to PWM control can be suppressed.
本実施の形態の表示装置の構成の一例を示すブロック図である。It is a block diagram which shows an example of a structure of the display apparatus of this Embodiment. 本実施の形態の表示装置の回路構成の一例を示す説明図である。It is explanatory drawing which shows an example of the circuit structure of the display apparatus of this Embodiment. ＰＷＭ信号のデューティ比αと電源部の変圧器の磁束変化との関係を示す説明図である。It is explanatory drawing which shows the relationship between duty ratio (alpha) of a PWM signal, and the magnetic flux change of the transformer of a power supply part. ＰＷＭ信号とトランジスタのスイッチング波形との関係を示す模式図である。It is a schematic diagram which shows the relationship between a PWM signal and the switching waveform of a transistor. 調整部の動作の一例を示す説明図である。It is explanatory drawing which shows an example of operation | movement of an adjustment part. ＰＷＭ信号のデューティ比αがα＜Ｔｈ１又はα＞Ｔｈ２である場合のトランジスタのベースに印加されるパルス信号の一例を示す説明図である。It is explanatory drawing which shows an example of the pulse signal applied to the base of a transistor in case the duty ratio (alpha) of a PWM signal is (alpha) <Th1 or (alpha)> Th2. ＰＷＭ信号のデューティ比αがＴｈ１＜α＜Ｔｈ２である場合のトランジスタのベースに印加されるパルス信号の一例を示す説明図である。It is explanatory drawing which shows an example of the pulse signal applied to the base of a transistor in case the duty ratio (alpha) of a PWM signal is Th1 <(alpha) <Th2. ＰＷＭ信号のデューティ比αが５０％付近のスイッチング波形の一例を示す説明図である。It is explanatory drawing which shows an example of the switching waveform whose duty ratio (alpha) of a PWM signal is 50% vicinity. 従来の表示装置の構成の一例を示すブロック図である。It is a block diagram which shows an example of a structure of the conventional display apparatus.
　以下、本発明に係る電源装置及び表示装置を実施の形態を示す図面に基づいて説明する。図１は本実施の形態の表示装置２００の構成の一例を示すブロック図であり、図２は本実施の形態の表示装置２００の回路構成の一例を示す説明図である。図１に示すように、表示装置２００は、電源装置１００、バックライト１１０、マイコン１２０、液晶パネル１３０などを備える。また、電源装置１００は、電源部１０、駆動部としてのＬＥＤドライバ２０、制御部３０、調整部４０などを備える。 Hereinafter, a power supply device and a display device according to the present invention will be described with reference to the drawings showing embodiments. FIG. 1 is a block diagram illustrating an example of a configuration of a display device 200 according to the present embodiment, and FIG. 2 is an explanatory diagram illustrating an example of a circuit configuration of the display device 200 according to the present embodiment. As shown in FIG. 1, the display device 200 includes a power supply device 100, a backlight 110, a microcomputer 120, a liquid crystal panel 130, and the like. The power supply apparatus 100 includes a power supply unit 10, an LED driver 20 as a drive unit, a control unit 30, an adjustment unit 40, and the like.
　液晶パネル１３０の明るさを設定すべくユーザがブライトネス設定の操作した場合、ユーザの設定に応じたブライトネス値がマイコン１２０に入力される。マイコン１２０は、入力されたブライトネス値に応じたＰＷＭ信号を生成し、生成したＰＷＭ信号をＬＥＤドライバ２０及び調整部４０へ出力する。 When the user performs a brightness setting operation to set the brightness of the liquid crystal panel 130, a brightness value corresponding to the user setting is input to the microcomputer 120. The microcomputer 120 generates a PWM signal corresponding to the input brightness value, and outputs the generated PWM signal to the LED driver 20 and the adjustment unit 40.
　電源部１０は、後述のようにスイッチング用の変圧器１３及びスイッチング素子としてのトランジスタ１４などを備え、商用電源１から供給される交流電圧を直流電圧に変換し、変換した直流電圧をＬＥＤドライバ２０へ出力する。なお、電源部１０の詳細は後述する。 As will be described later, the power supply unit 10 includes a switching transformer 13 and a transistor 14 as a switching element, converts an AC voltage supplied from the commercial power supply 1 into a DC voltage, and converts the converted DC voltage to the LED driver 20. Output to. Details of the power supply unit 10 will be described later.
　ＬＥＤドライバ２０は、ＰＷＭ信号に応じて電源部１０の出力をＰＷＭ制御して負荷としてのバックライト１１０を駆動する。すなわち、バックライト１１０は、ＰＷＭ制御方式により調光することができる。 The LED driver 20 drives the backlight 110 as a load by PWM-controlling the output of the power supply unit 10 according to the PWM signal. That is, the backlight 110 can be dimmed by the PWM control method.
　制御部３０は、電源部１０の出力変動（例えば、電流変動、電圧変動など）に応答すべく電源部１０の出力を制御する。例えば、電源部１０の負荷電流が増加した場合には、制御部３０は、電源部１０のスイッチング素子のスイッチング動作を制御して電源部１０が出力する電流を増加させる。すなわち、制御部３０は、電源部１０の出力（例えば、電流、電圧など）をフィードバックし、電源部１０のスイッチング動作を制御する。なお、制御部３０の詳細は後述する。 The control unit 30 controls the output of the power supply unit 10 to respond to output fluctuations (for example, current fluctuation, voltage fluctuation, etc.) of the power supply unit 10. For example, when the load current of the power supply unit 10 increases, the control unit 30 controls the switching operation of the switching element of the power supply unit 10 to increase the current output from the power supply unit 10. That is, the control unit 30 feeds back an output (for example, current, voltage, etc.) of the power supply unit 10 and controls the switching operation of the power supply unit 10. Details of the control unit 30 will be described later.
　調整部４０は、マイコン１２０が出力したＰＷＭ信号を取得し、取得したＰＷＭ信号のデューティ比に応じて、制御部３０の応答の遅速を調整する。ＰＷＭ信号は、オン・オフのパルス波形が所定の周波数で繰り返される信号であり、デューティ比αは、ＰＷＭ信号の１周期に占めるオン期間の割合とすることができる。ＰＷＭ信号の周波数は、例えば、２００Ｈｚとすることができるが、これに限定されるものではない。 The adjustment unit 40 acquires the PWM signal output from the microcomputer 120 and adjusts the response speed of the control unit 30 according to the duty ratio of the acquired PWM signal. The PWM signal is a signal in which an ON / OFF pulse waveform is repeated at a predetermined frequency, and the duty ratio α can be a ratio of an ON period in one cycle of the PWM signal. The frequency of the PWM signal can be, for example, 200 Hz, but is not limited thereto.
　図３はＰＷＭ信号のデューティ比αと電源部１０の変圧器１３の磁束変化との関係を示す説明図である。磁束変化は、負荷電流の変動が発生させる変圧器１３の磁束変化である。図３Ａ、Ｂ、ＣはそれぞれＰＷＭ信号のデューティ比αが１０％、５０％、９０％の場合におけるＰＷＭ信号及び電源部１０の変圧器１３の磁束変化の様子を模式的に表している。 FIG. 3 is an explanatory diagram showing the relationship between the duty ratio α of the PWM signal and the change in magnetic flux of the transformer 13 of the power supply unit 10. The magnetic flux change is a magnetic flux change of the transformer 13 that is caused by fluctuations in the load current. 3A, 3B, and 3C schematically show how the PWM signal and the magnetic flux change of the transformer 13 of the power supply unit 10 change when the duty ratio α of the PWM signal is 10%, 50%, and 90%, respectively.
　図３Ａに示すように、デューティ比αが、例えば、１０％である場合、電源部１０が出力する電流は少なく、電源部１０の変圧器１３に流れる電流変化（例えば、電流波形の最大値と最小値との差）は小さい。したがって、変圧器１３の磁束の最大値と最小値との差も小さい。 As shown in FIG. 3A, when the duty ratio α is, for example, 10%, the current output from the power supply unit 10 is small, and the change in current flowing through the transformer 13 of the power supply unit 10 (for example, the maximum value of the current waveform) The difference from the minimum value is small. Therefore, the difference between the maximum value and the minimum value of the magnetic flux of the transformer 13 is also small.
　また、図３Ｃに示すように、デューティ比αが、例えば、９０％である場合、電源部１０が出力する電流は多いが、電源部１０の変圧器１３に流れる電流変化（例えば、電流波形の最大値と最小値との差）は小さい。したがって、変圧器１３の磁束の最大値と最小値との差も小さい。 As shown in FIG. 3C, when the duty ratio α is 90%, for example, a large amount of current is output from the power supply unit 10, but a change in current flowing through the transformer 13 of the power supply unit 10 (for example, the current waveform) The difference between the maximum and minimum values is small. Therefore, the difference between the maximum value and the minimum value of the magnetic flux of the transformer 13 is also small.
　これに対して、図３Ｂに示すように、デューティ比αが、例えば、５０％程度である場合、電源部１０の変圧器１３に流れる電流変化（例えば、電流波形の最大値と最小値との差）は大きくなり、変圧器１３の磁束変化が大きくなり変圧器１３の異音発生の原因となる。なお、上述の１０％、５０％、９０％は一例であって、デューティ比αの数値がこれらに限定されるものではない。 On the other hand, as shown in FIG. 3B, when the duty ratio α is about 50%, for example, the change in the current flowing through the transformer 13 of the power supply unit 10 (for example, the maximum value and the minimum value of the current waveform) (Difference) increases, and the magnetic flux change of the transformer 13 increases, causing abnormal noise in the transformer 13. The 10%, 50%, and 90% described above are examples, and the numerical value of the duty ratio α is not limited to these.
　調整部４０は、電源部１０の変圧器１３に流れる電流変化が大きくなるようなデューティ比αの場合、制御部３０の応答が遅くなるように調整する。制御部３０の応答を遅くすることにより、電源部１０が出力する電流が電源部１０の出力変動に追従して急激に変化することを抑制し、変圧器１３の磁束が急激に変化することを防止し、異音の発生を低減することができる。また、変圧器１３に流れる電流変化を小さくするためのＬＣフィルタが不要になるので、ＬＣフィルタに用いる比較的大きな部品が不要となり、またＬＣフィルタを実装するための基板面積も小さくすることができ、電源装置の小型化、コスト低減を図ることができる。 The adjustment unit 40 adjusts the response of the control unit 30 to be slow when the duty ratio α is such that a change in the current flowing through the transformer 13 of the power supply unit 10 increases. By slowing down the response of the control unit 30, the current output from the power supply unit 10 is suppressed from changing rapidly following the output fluctuation of the power supply unit 10, and the magnetic flux of the transformer 13 is changed rapidly. This can prevent the occurrence of abnormal noise. In addition, since an LC filter for reducing the change in the current flowing through the transformer 13 is not required, relatively large components used for the LC filter are not required, and the board area for mounting the LC filter can be reduced. Therefore, it is possible to reduce the size and cost of the power supply device.
　次に、本実施の形態の電源装置１００について詳細に説明する。図２に示すように、電源部１０は、整流素子１１、キャパシタ１２、スイッチング用の変圧器１３、スイッチング素子としてのトランジスタ１４、ダイオード１５、キャパシタ１６などを備える。 Next, the power supply device 100 of the present embodiment will be described in detail. As shown in FIG. 2, the power supply unit 10 includes a rectifying element 11, a capacitor 12, a switching transformer 13, a transistor 14 as a switching element, a diode 15, a capacitor 16, and the like.
　制御部３０は、抵抗３１、３２、発光ダイオード３３１及びフォトトランジスタ３３２を有するフォトカップラ３３、シャントレギュレータ３４、コントロールＩＣ３５、キャパシタ３６などを備える。 The control unit 30 includes resistors 31, 32, a photocoupler 33 having a light emitting diode 331 and a phototransistor 332, a shunt regulator 34, a control IC 35, a capacitor 36, and the like.
　調整部４０は、ダイオード４１、４２、抵抗４３、４４、キャパシタ４５、４６、抵抗４７、４８、４９、５１、５２、５４、５５、５６、トランジスタ５０、５３、５８、発光ダイオード５７１及びフォトトランジスタ５７２を有するフォトカップラ５７、キャパシタ５９などを備える。 The adjustment unit 40 includes diodes 41 and 42, resistors 43 and 44, capacitors 45 and 46, resistors 47, 48, 49, 51, 52, 54, 55 and 56, transistors 50, 53 and 58, light emitting diodes 571 and a phototransistor. The photocoupler 57 having the 572, the capacitor 59, and the like are provided.
　まず、電源部１０について説明する。図２に示すように、変圧器１３の一次側にはトランジスタ１４のコレクタを接続してあり、変圧器１３の二次側には、ダイオード１５及びキャパシタ１６の後段に駆動部としてのＬＥＤドライバ２０を接続してある。ＬＥＤドライバ２０は、マイコン１２０からのＰＷＭ信号に基づいて電源部１０の出力をＰＷＭ制御することにより、バックライト１１０に所要の電力（電流、電圧）を供給する。 First, the power supply unit 10 will be described. As shown in FIG. 2, the collector of the transistor 14 is connected to the primary side of the transformer 13, and the LED driver 20 as a drive unit is connected to the secondary side of the transformer 13 after the diode 15 and the capacitor 16. Is connected. The LED driver 20 supplies required power (current, voltage) to the backlight 110 by performing PWM control on the output of the power supply unit 10 based on the PWM signal from the microcomputer 120.
　トランジスタ１４のベースには、コントロールＩＣ３５のドライブ端子Ｄを接続してある。コントロールＩＣ３５のドライブ端子Ｄから所定の周波数（例えば、１００ｋＨｚ）でオン・オフが繰り返される所要幅のパルス信号をトランジスタ１４のベースへ出力することにより、トランジスタ１４は、ＰＷＭ信号の周波数よりも高い周波数でオン・オフ動作が繰り返される。なお、トランジスタ１４のスイッチング動作周波数は、１００ｋＨｚに限定されるものではなく、他の周波数でもよい。 The drive terminal D of the control IC 35 is connected to the base of the transistor 14. By outputting to the base of the transistor 14 a pulse signal having a required width which is repeatedly turned on and off at a predetermined frequency (for example, 100 kHz) from the drive terminal D of the control IC 35, the transistor 14 has a frequency higher than the frequency of the PWM signal. The on / off operation is repeated at. Note that the switching operation frequency of the transistor 14 is not limited to 100 kHz, and may be other frequencies.
　図４はＰＷＭ信号とトランジスタ１４のスイッチング波形との関係を示す模式図である。図４に示すように、トランジスタ１４は、例えば、周波数が１００ｋＨｚのスイッチング動作を行う。ＰＷＭ信号の周波数は、例えば、２００Ｈｚであり、ＰＷＭ信号のオン期間においては、トランジスタ１４のスイッチング動作により、ＬＥＤドライバ２０を介してバックライト１１０に電流が出力される。また、ＰＷＭ信号のオフ期間においては、トランジスタ１４がスイッチング動作を行うか否かに関わらず、バックライト１１０には電流が出力されない。ＰＷＭ信号のオフ期間においては、トランジスタ１４のスイッチング動作を停止させてもよく、あるいはスイッチング動作を続けてもよい。 FIG. 4 is a schematic diagram showing the relationship between the PWM signal and the switching waveform of the transistor 14. As shown in FIG. 4, the transistor 14 performs a switching operation with a frequency of 100 kHz, for example. The frequency of the PWM signal is, for example, 200 Hz. During the on period of the PWM signal, a current is output to the backlight 110 via the LED driver 20 by the switching operation of the transistor 14. In addition, during the OFF period of the PWM signal, no current is output to the backlight 110 regardless of whether or not the transistor 14 performs a switching operation. During the OFF period of the PWM signal, the switching operation of the transistor 14 may be stopped or the switching operation may be continued.
　次に、制御部３０について説明する。電源部１０とＬＥＤドライバ２０との間には、直列接続した抵抗３１、３２を接続してあり、抵抗３１、３２と並列にフォトカップラ３３（発光ダイオード３３１）とシャントレギュレータ３４との直列回路を接続してある。シャントレギュレータ３４のリファレンスは抵抗３１、３２の接続ノードに接続してある。 Next, the control unit 30 will be described. Resistors 31 and 32 connected in series are connected between the power supply unit 10 and the LED driver 20, and a series circuit of a photocoupler 33 (light emitting diode 331) and a shunt regulator 34 is connected in parallel with the resistors 31 and 32. Connected. The reference of the shunt regulator 34 is connected to the connection node of the resistors 31 and 32.
　フォトトランジスタ３３２のコレクタはコントロールＩＣ３５のフィードバック端子ＦＢに接続してあり、フィードバック端子ＦＢには、制御部３０の応答性を決定付けるためのキャパシタ３６を接続してある。 The collector of the phototransistor 332 is connected to the feedback terminal FB of the control IC 35, and a capacitor 36 for determining the responsiveness of the control unit 30 is connected to the feedback terminal FB.
　コントロールＩＣ３５は、フィードバック端子ＦＢの電圧値の高低に応じて、ドライブ端子Ｄから出力するパルス信号のパルス幅を変化させる。より具体的には、コントロールＩＣ３５は、フィードバック端子ＦＢの電圧値が高いほど、ドライブ端子Ｄから出力するパルス信号のオン幅を長くする。パルス信号のオン幅を長くするほど、トランジスタ１４のオン期間が長くなり、電源部１０は多くの電流を出力することが可能となる。 The control IC 35 changes the pulse width of the pulse signal output from the drive terminal D according to the voltage value of the feedback terminal FB. More specifically, the control IC 35 increases the ON width of the pulse signal output from the drive terminal D as the voltage value of the feedback terminal FB is higher. The longer the ON width of the pulse signal, the longer the ON period of the transistor 14, and the power supply unit 10 can output more current.
　上述の構成により、コントロールＩＣ３５は、電源部１０の出力変動の大小に応じてトランジスタ１４のオン期間を制御することができる。例えば、電源部１０の負荷電流が減少した場合には、抵抗３１、３２で分圧された電圧、すなわちシャントレギュレータ３４のリファレンス電圧が高くなり、発光ダイオード３３１に流れる電流が増加する。そうするとフォトトランジスタ３３２は、コントロールＩＣ３５のフィードバック端子ＦＢから多くの電流を流出させ、ＦＢ端子の電圧値を下げるので、電源部１０のトランジスタ１４のオン期間を短くして電源部１０が出力する電流を減少させる。 With the above configuration, the control IC 35 can control the ON period of the transistor 14 according to the output fluctuation of the power supply unit 10. For example, when the load current of the power supply unit 10 decreases, the voltage divided by the resistors 31 and 32, that is, the reference voltage of the shunt regulator 34 increases, and the current flowing through the light emitting diode 331 increases. Then, the phototransistor 332 causes a large amount of current to flow out from the feedback terminal FB of the control IC 35 and lowers the voltage value of the FB terminal. Therefore, the on period of the transistor 14 of the power supply unit 10 is shortened and the current output from the power supply unit 10 Decrease.
　なお、ＰＷＭ信号のオフ期間においては、電源部１０の出力はゼロ又は極めて小さくなるので、発光ダイオード３３１に流れる電流が増加し、フォトトランジスタ３３２がコントロールＩＣ３５のフィードバック端子ＦＢから流出させる電流が増加し、ＦＢ端子の電圧値を下げる。この場合、コントロールＩＣ３５は、ドライブ端子Ｄから出力するパルス信号のオン幅をゼロ又は極めて短くすることにより、トランジスタ１４のスイッチング動作を停止又は極めて短いオン時間で動作させることができる。 Note that, during the off period of the PWM signal, the output of the power supply unit 10 is zero or extremely small, so that the current flowing through the light emitting diode 331 increases and the current that the phototransistor 332 flows out from the feedback terminal FB of the control IC 35 increases. , Lower the voltage value of the FB terminal. In this case, the control IC 35 can stop the switching operation of the transistor 14 or operate it with a very short on-time by reducing the on width of the pulse signal output from the drive terminal D to zero or extremely short.
　次に、調整部４０について説明する。マイコン１２０のＰＷＭ信号の出力端Ｐには、ダイオード４１と抵抗４３の直列回路を接続してあり、抵抗４３の後段にはキャパシタ４５を接続してある。同様に、マイコン１２０のＰＷＭ信号の出力端Ｐには、ダイオード４２と抵抗４４の直列回路を接続してあり、抵抗４４の後段にはキャパシタ４６及び抵抗４７を接続してある。ダイオード４１、抵抗４３、キャパシタ４５は、平滑回路を構成する。また、ダイオード４２、抵抗４４、４７、キャパシタ４６も、平滑回路を構成する。かかる構成により、マイコン１２０のＰＷＭ信号は、それぞれのキャパシタ４５、４６で平滑（積分）される。なお、図２に示す構成ではＰＷＭ信号の出力端ＰはＬＥＤドライバへの出力端と分かれているが、ＰＷＭ信号の出力端ＰはＬＥＤドライバへの出力端を兼ねる構成としてもよい。 Next, the adjustment unit 40 will be described. A series circuit of a diode 41 and a resistor 43 is connected to the output terminal P of the PWM signal of the microcomputer 120, and a capacitor 45 is connected to the subsequent stage of the resistor 43. Similarly, a series circuit of a diode 42 and a resistor 44 is connected to the output terminal P of the PWM signal of the microcomputer 120, and a capacitor 46 and a resistor 47 are connected to the subsequent stage of the resistor 44. The diode 41, the resistor 43, and the capacitor 45 constitute a smoothing circuit. The diode 42, the resistors 44 and 47, and the capacitor 46 also form a smoothing circuit. With this configuration, the PWM signal of the microcomputer 120 is smoothed (integrated) by the capacitors 45 and 46. In the configuration shown in FIG. 2, the output end P of the PWM signal is separated from the output end to the LED driver, but the output end P of the PWM signal may also serve as the output end to the LED driver.
　キャパシタ４６と抵抗４４との接続ノードには、抵抗４９を介してトランジスタ５０のベースを接続してある。トランジスタ５０のベース・エミッタ間には抵抗４８を接続してある。同様に、キャパシタ４５と抵抗４３との接続ノードには、抵抗５１を介してトランジスタ５３のベースを接続してある。トランジスタ５３のベース・エミッタ間には抵抗５２を接続してある。 The base of the transistor 50 is connected to the connection node between the capacitor 46 and the resistor 44 via the resistor 49. A resistor 48 is connected between the base and emitter of the transistor 50. Similarly, the base of the transistor 53 is connected to the connection node between the capacitor 45 and the resistor 43 via the resistor 51. A resistor 52 is connected between the base and emitter of the transistor 53.
　トランジスタ５０のエミッタ、及びトランジスタ５３のコレクタは、トランジスタ５８のベースに接続してある。また、トランジスタ５８のベースには、所要の電圧Ｖｃｃを抵抗５４、５５で分圧した電圧が印加されるようにしてある。トランジスタ５８のコレクタには、抵抗５６とフォトカップラ５７（発光ダイオード５７１）の直列回路を接続してある。また、コントロールＩＣ３５のフィードバック端子ＦＢには、キャパシタ５９とフォトカップラ５７（フォトトランジスタ５７２）の直列回路を接続してある。 The emitter of the transistor 50 and the collector of the transistor 53 are connected to the base of the transistor 58. A voltage obtained by dividing the required voltage Vcc by resistors 54 and 55 is applied to the base of the transistor 58. A series circuit of a resistor 56 and a photocoupler 57 (light emitting diode 571) is connected to the collector of the transistor 58. A series circuit of a capacitor 59 and a photocoupler 57 (phototransistor 572) is connected to the feedback terminal FB of the control IC 35.
　次に、調整部４０の動作について説明する。図５は調整部４０の動作の一例を示す説明図である。図５は、ＰＷＭ信号のデューティ比αの大小に応じて調整部４０がどのように動作するかを例示したものである。図５において、Ｔｈ１は第１閾値、Ｔｈ２は第２閾値である。例えば、第１閾値Ｔｈ１を３０％とし、第２閾値Ｔｈ２を７０％とすることができる。あるいは、第１閾値Ｔｈ１を４０％とし、第２閾値Ｔｈ２を６０％としてもよい。第１閾値及び第２閾値の値は、これらの数値に限定されるものではない。 Next, the operation of the adjustment unit 40 will be described. FIG. 5 is an explanatory diagram showing an example of the operation of the adjustment unit 40. FIG. 5 illustrates how the adjustment unit 40 operates in accordance with the duty ratio α of the PWM signal. In FIG. 5, Th1 is a first threshold value and Th2 is a second threshold value. For example, the first threshold Th1 can be set to 30% and the second threshold Th2 can be set to 70%. Alternatively, the first threshold Th1 may be 40% and the second threshold Th2 may be 60%. The values of the first threshold value and the second threshold value are not limited to these numerical values.
　図５に示すように、マイコン１２０から出力されるＰＷＭ信号のデューティ比αが小さい（α＜Ｔｈ１）場合、ＰＷＭ信号を平滑した電圧Ｖ１、Ｖ２は小さいので、トランジスタ５０はオンとなり、トランジスタ５３はオフとなる。トランジスタ５０がオンとなるので、トランジスタ５８のベース電位は基準レベル（接地レベル）となり、トランジスタ５８はオフとなる。トランジスタ５８がオフであるので、発光ダイオード５７１に流れる電流はゼロ又は極めて少ない電流（漏電流程度）となり、フォトトランジスタ５７２はオフとなる。このため、コントロールＩＣ３５のフィードバック端子ＦＢには、キャパシタ３６だけが接続され、フィードバック端子ＦＢのキャパシタの容量は比較的小さくなる。 As shown in FIG. 5, when the duty ratio α of the PWM signal output from the microcomputer 120 is small (α <Th1), the voltages V1 and V2 obtained by smoothing the PWM signal are small, so that the transistor 50 is turned on and the transistor 53 is turned on. Turn off. Since the transistor 50 is turned on, the base potential of the transistor 58 is at the reference level (ground level), and the transistor 58 is turned off. Since the transistor 58 is off, the current flowing through the light-emitting diode 571 is zero or extremely small (about the leakage current), and the phototransistor 572 is turned off. For this reason, only the capacitor 36 is connected to the feedback terminal FB of the control IC 35, and the capacitance of the capacitor of the feedback terminal FB becomes relatively small.
　また、図５に示すように、マイコン１２０から出力されるＰＷＭ信号のデューティ比αが大きい（α＞Ｔｈ２）場合、ＰＷＭ信号を平滑した電圧Ｖ１、Ｖ２は大きい、トランジスタ５０はオフとなり、トランジスタ５３はオンとなる。トランジスタ５３がオンとなるので、トランジスタ５８のベース電位は基準レベル（接地レベル）となり、トランジスタ５８はオフとなる。トランジスタ５８がオフであるので、発光ダイオード５７１に流れる電流はゼロ又は極めて少ない電流（漏電流程度）となり、フォトトランジスタ５７２はオフとなる。このため、コントロールＩＣ３５のフィードバック端子ＦＢには、キャパシタ３６だけが接続され、フィードバック端子ＦＢのキャパシタの容量は比較的小さくなる。 As shown in FIG. 5, when the duty ratio α of the PWM signal output from the microcomputer 120 is large (α> Th2), the voltages V1 and V2 obtained by smoothing the PWM signal are large, the transistor 50 is turned off, and the transistor 53 Is turned on. Since the transistor 53 is turned on, the base potential of the transistor 58 is at the reference level (ground level), and the transistor 58 is turned off. Since the transistor 58 is off, the current flowing through the light-emitting diode 571 is zero or extremely small (about the leakage current), and the phototransistor 572 is turned off. For this reason, only the capacitor 36 is connected to the feedback terminal FB of the control IC 35, and the capacitance of the capacitor of the feedback terminal FB becomes relatively small.
　また、図５に示すように、マイコン１２０から出力されるＰＷＭ信号のデューティ比αが、Ｔｈ１＜α＜Ｔｈ２である場合、ＰＷＭ信号を平滑した電圧Ｖ１、Ｖ２は中程度の電圧となり、トランジスタ５０、５３はいずれもオフとなる。この場合、平滑回路で平滑した電圧が第１閾値電圧より大きく、第２閾値電圧（＞第１閾値電圧）より小さい場合に相当する。トランジスタ５０、５３がいずれもオフとなるので、トランジスタ５８のベースには、電圧Ｖｃｃを分圧した電圧が印加され、トランジスタ５８はオンとなる。トランジスタ５８がオンとなるので、発光ダイオード５７１に電流が流れ、フォトトランジスタ５７２はオンとなる。このため、コントロールＩＣ３５のフィードバック端子ＦＢには、キャパシタ３６と並列にキャパシタ５９が接続され、フィードバック端子ＦＢのキャパシタの容量は比較的大きくなる。 Further, as shown in FIG. 5, when the duty ratio α of the PWM signal output from the microcomputer 120 is Th1 <α <Th2, the voltages V1 and V2 obtained by smoothing the PWM signal are medium voltages, and the transistor 50 53 are turned off. This case corresponds to a case where the voltage smoothed by the smoothing circuit is larger than the first threshold voltage and smaller than the second threshold voltage (> first threshold voltage). Since both the transistors 50 and 53 are turned off, a voltage obtained by dividing the voltage Vcc is applied to the base of the transistor 58, and the transistor 58 is turned on. Since the transistor 58 is turned on, a current flows through the light emitting diode 571, and the phototransistor 572 is turned on. Therefore, the capacitor 59 is connected to the feedback terminal FB of the control IC 35 in parallel with the capacitor 36, and the capacitance of the capacitor of the feedback terminal FB becomes relatively large.
　フォトカップラ３３のフォトトランジスタ３３２がオンしたときに、コントロールＩＣ３５のフィードバック端子ＦＢのキャパシタの容量が大きいほど、フィードバック端子ＦＢの電圧値の変化速度は遅くなる。コントロールＩＣ３５は、フィードバック端子ＦＢの電圧値が低いほど、ドライブ端子Ｄから出力するパルス信号のオン幅を短くする。パルス信号のオン幅を短くするほど、トランジスタ１４のオン期間が短くなり、電源部１０は、出力する電流を少なくする。 When the phototransistor 332 of the photocoupler 33 is turned on, the change rate of the voltage value of the feedback terminal FB becomes slower as the capacitance of the feedback terminal FB of the control IC 35 is larger. The control IC 35 shortens the ON width of the pulse signal output from the drive terminal D as the voltage value of the feedback terminal FB is lower. As the ON width of the pulse signal is shortened, the ON period of the transistor 14 is shortened, and the power supply unit 10 reduces the output current.
　また、フォトカップラ３３のフォトトランジスタ３３２がオンしたときに、コントロールＩＣ３５のフィードバック端子ＦＢのキャパシタの容量が小さいほど、フィードバック端子ＦＢの電圧値の変化速度は速くなる。コントロールＩＣ３５は、フィードバック端子ＦＢの電圧値が高いほど、ドライブ端子Ｄから出力するパルス信号のオン幅を長くする。パルス信号のオン幅を長くするほど、トランジスタ１４のオン期間が長くなり、電源部１０は、出力する電流を多くする。 Also, when the phototransistor 332 of the photocoupler 33 is turned on, the change rate of the voltage value of the feedback terminal FB increases as the capacitance of the feedback terminal FB of the control IC 35 decreases. The control IC 35 increases the ON width of the pulse signal output from the drive terminal D as the voltage value of the feedback terminal FB is higher. As the ON width of the pulse signal is increased, the ON period of the transistor 14 is increased, and the power supply unit 10 increases the output current.
　上述のように、調整部４０は、ＰＷＭ信号のデューティ比に応じて、制御部３０が制御するトランジスタ１４のオン期間の変化速度を調整する。デューティ比αが、例えば、１０％である場合（α＜Ｔｈ１）、あるいは９０％である場合（α＞Ｔｈ２）、電源部１０の変圧器１３に流れる電流変化（例えば、電流波形の最大値と最小値との差）は小さく、変圧器１３の異音が小さいので、制御部３０の応答を遅くする必要がない。そこで、調整部４０は、制御部３０が制御するトランジスタ１４のオン期間の変化速度の調整を行わないようにする。すなわち、コントロールＩＣ３５のフィードバック端子ＦＢにはキャパシタ５９が接続されない状態とする。 As described above, the adjustment unit 40 adjusts the change rate of the ON period of the transistor 14 controlled by the control unit 30 according to the duty ratio of the PWM signal. When the duty ratio α is, for example, 10% (α <Th1) or 90% (α> Th2), a change in the current flowing through the transformer 13 of the power supply unit 10 (for example, the maximum value of the current waveform) (The difference from the minimum value) is small and the noise of the transformer 13 is small, so there is no need to slow down the response of the control unit 30. Therefore, the adjustment unit 40 does not adjust the change rate of the ON period of the transistor 14 controlled by the control unit 30. That is, the capacitor 59 is not connected to the feedback terminal FB of the control IC 35.
　他方、デューティ比αが、例えば、５０％程度である場合（Ｔｈ１＜α＜Ｔｈ２）、電源部１０の変圧器１３に流れる電流変化は大きくなり、変圧器１３の磁束変化が大きくなり変圧器１３の異音発生の原因となる。そこで、制御部３０の応答を遅くすべく、調整部４０は、制御部３０が制御するトランジスタ１４のオン期間の変化速度が遅くなるように調整する。すなわち、コントロールＩＣ３５のフィードバック端子ＦＢにキャパシタ５９が接続された状態とする。トランジスタ１４のオン期間の変化速度を遅くすることにより、変圧器１３に流れる電流が急激に増加することを抑制して、変圧器１３の磁束が急激に変化することを防止し、異音の発生を低減することができる。 On the other hand, when the duty ratio α is, for example, about 50% (Th1 <α <Th2), a change in current flowing through the transformer 13 of the power supply unit 10 becomes large, and a change in magnetic flux of the transformer 13 becomes large. Cause abnormal noise. Therefore, in order to slow down the response of the control unit 30, the adjustment unit 40 adjusts so that the change rate of the ON period of the transistor 14 controlled by the control unit 30 is slow. That is, the capacitor 59 is connected to the feedback terminal FB of the control IC 35. By slowing down the change rate of the ON period of the transistor 14, it is possible to suppress a sudden increase in the current flowing through the transformer 13, thereby preventing the magnetic flux of the transformer 13 from changing suddenly and generating abnormal noise. Can be reduced.
　また、調整部４０は、ＰＷＭ信号のデューティ比に応じて、ＰＷＭ信号のオン時点からのトランジスタ１４のオン期間の変化速度を調整する。ＰＷＭ信号のオン時点は、電源部１０がＬＥＤドライバ２０への電流出力を開始する時点となり、電源部１０の出力変動が大きくなる時点である。 Further, the adjustment unit 40 adjusts the changing speed of the ON period of the transistor 14 from the ON point of the PWM signal according to the duty ratio of the PWM signal. The time when the PWM signal is turned on is the time when the power supply unit 10 starts to output current to the LED driver 20, and the time when the output fluctuation of the power supply unit 10 increases.
　デューティ比αが、例えば、５０％程度である場合（Ｔｈ１＜α＜Ｔｈ２）、電源部１０の変圧器１３に流れる電流変化は大きくなり、変圧器１３の磁束変化が大きくなり変圧器１３の異音発生の原因となる。そこで、制御部３０の応答を遅くすべく、調整部４０は、ＰＷＭ信号のオン時点から制御部３０が制御するトランジスタ１４のオン期間の変化速度が遅くなるように調整する。トランジスタ１４のオン期間の変化速度を遅くすることにより、変圧器１３に流れる電流が急激に増加することを抑制して、変圧器１３の磁束が急激に変化することを防止し、異音の発生を低減することができる。 When the duty ratio α is, for example, about 50% (Th1 <α <Th2), a change in current flowing through the transformer 13 of the power supply unit 10 becomes large, a change in magnetic flux of the transformer 13 becomes large, and a difference in the transformer 13 occurs. Causes sound generation. Therefore, in order to slow down the response of the control unit 30, the adjustment unit 40 adjusts so that the change rate of the ON period of the transistor 14 controlled by the control unit 30 becomes slow from the time when the PWM signal is turned on. By slowing down the change rate of the ON period of the transistor 14, it is possible to suppress a sudden increase in the current flowing through the transformer 13, thereby preventing the magnetic flux of the transformer 13 from changing suddenly and generating abnormal noise. Can be reduced.
　図６はＰＷＭ信号のデューティ比αがα＜Ｔｈ１又はα＞Ｔｈ２である場合のトランジスタ１４のベースに印加されるパルス信号の一例を示す説明図であり、図７はＰＷＭ信号のデューティ比αがＴｈ１＜α＜Ｔｈ２である場合のトランジスタ１４のベースに印加されるパルス信号の一例を示す説明図である。 FIG. 6 is an explanatory diagram showing an example of a pulse signal applied to the base of the transistor 14 when the duty ratio α of the PWM signal is α <Th1 or α> Th2, and FIG. 7 shows the duty ratio α of the PWM signal. It is explanatory drawing which shows an example of the pulse signal applied to the base of the transistor in the case of Th1 <α <Th2.
　図６に示すように、ＰＷＭ信号のデューティ比αがα＜Ｔｈ１又はα＞Ｔｈ２である場合には、前述のように、電源部１０の変圧器１３に流れる電流変化は小さく、変圧器１３の異音が小さいので、制御部３０の応答を遅くする必要がない。そこで、コントロールＩＣ３５のフィードバック端子ＦＢにはキャパシタ５９が接続されない状態とすることにより、調整部４０は、時刻ｔ０のＰＷＭ信号のオン時点から制御部３０が制御するトランジスタ１４のオン期間の変化速度の調整を行わないようにする。この場合、トランジスタ１４のベースに印加されるパルス信号のオン幅はＴ１となり、負荷電流は、時刻ｔ０において立ち上がる。 As shown in FIG. 6, when the duty ratio α of the PWM signal is α <Th1 or α> Th2, as described above, the change in the current flowing through the transformer 13 of the power supply unit 10 is small. Since the abnormal noise is small, there is no need to delay the response of the control unit 30. Therefore, by setting the capacitor 59 not to be connected to the feedback terminal FB of the control IC 35, the adjustment unit 40 can change the change rate of the ON period of the transistor 14 controlled by the control unit 30 from the ON time of the PWM signal at time t0. Do not make adjustments. In this case, the ON width of the pulse signal applied to the base of the transistor 14 is T1, and the load current rises at time t0.
　また、図７に示すように、ＰＷＭ信号のデューティ比αがＴｈ１＜α＜Ｔｈ２である場合には、前述のように、電源部１０の変圧器１３に流れる電流変化は大きく、変圧器１３の異音が大きくなるので、制御部３０の応答を遅くする。そこで、コントロールＩＣ３５のフィードバック端子ＦＢにはキャパシタ５９が接続された状態とすることにより、調整部４０は、時刻ｔ０のＰＷＭ信号のオン時点から制御部３０が制御するトランジスタ１４のオン期間の変化速度の調整を行う。この場合、トランジスタ１４のベースに印加されるパルス信号のオン幅はＴ２（＜Ｔ１）となる。 As shown in FIG. 7, when the duty ratio α of the PWM signal is Th1 <α <Th2, the change in current flowing through the transformer 13 of the power supply unit 10 is large as described above, and Since abnormal noise becomes large, the response of the control unit 30 is delayed. Therefore, by setting the capacitor 59 to be connected to the feedback terminal FB of the control IC 35, the adjustment unit 40 can change the ON period of the transistor 14 controlled by the control unit 30 from the ON point of the PWM signal at time t0. Make adjustments. In this case, the ON width of the pulse signal applied to the base of the transistor 14 is T2 (<T1).
　このように、調整部４０は、デューティ比αが第１閾値Ｔｈ１（＜５０％）より大きく、第２閾値Ｔｈ２（＞５０％）より小さい場合のトランジスタ１４のＰＷＭ信号のオン時点からのオン期間の変化速度を、デューティ比αが第１閾値Ｔｈ１より小さい場合又は第２閾値Ｔｈ２より大きい場合のＰＷＭ信号のオン時点からのオン期間の変化速度より遅くすべく調整する。これにより、変圧器１３の磁束変化が大きくなるようなデューティ比α（Ｔｈ１＜α＜Ｔｈ２）である場合に、ＰＷＭ信号のオン時点からのトランジスタ１４のオン期間の変化速度を遅くするので、変圧器１３に流れる電流が急激に増加することを抑制して、変圧器１３の磁束が急激に変化することを防止し、異音の発生を低減することができる。 As described above, the adjustment unit 40 determines the ON period from the ON point of the PWM signal of the transistor 14 when the duty ratio α is larger than the first threshold Th1 (<50%) and smaller than the second threshold Th2 (> 50%). Is adjusted to be slower than the change rate of the ON period from the ON point of the PWM signal when the duty ratio α is smaller than the first threshold value Th1 or larger than the second threshold value Th2. As a result, when the duty ratio α (Th1 <α <Th2) is such that the magnetic flux change of the transformer 13 increases, the change rate of the ON period of the transistor 14 from the ON point of the PWM signal is slowed down. It is possible to suppress a sudden increase in the current flowing through the transformer 13, prevent the magnetic flux of the transformer 13 from changing suddenly, and reduce the occurrence of abnormal noise.
　同様に、調整部４０は、ＰＷＭ信号のデューティ比に応じて、ＰＷＭ信号のオフ時点からのトランジスタ１４のオン期間の変化速度を調整する。ＰＷＭ信号のオフ時点は、電源部１０がＬＥＤドライバ２０への電流出力を終了する時点となり、電源部１０の出力変動が大きくなる時点である。 Similarly, the adjustment unit 40 adjusts the change rate of the ON period of the transistor 14 from the OFF point of the PWM signal according to the duty ratio of the PWM signal. The time when the PWM signal is turned off is the time when the power supply unit 10 finishes outputting the current to the LED driver 20, and the time when the output fluctuation of the power supply unit 10 becomes large.
　デューティ比αが、例えば、５０％程度である場合（Ｔｈ１＜α＜Ｔｈ２）、電源部１０の変圧器１３に流れる電流変化は大きくなり、変圧器１３の磁束変化が大きくなり変圧器１３の異音発生の原因となる。そこで、制御部３０の応答を遅くすべく、調整部４０は、ＰＷＭ信号のオフ時点から制御部３０が制御するトランジスタ１４のオン期間の変化速度が遅くなるように調整する。トランジスタ１４のオン期間の変化速度を遅くすることにより、変圧器１３に流れる電流が急激に増加することを抑制して、変圧器１３の磁束が急激に変化することを防止し、異音の発生を低減することができる。 When the duty ratio α is, for example, about 50% (Th1 <α <Th2), a change in current flowing through the transformer 13 of the power supply unit 10 becomes large, a change in magnetic flux of the transformer 13 becomes large, and a difference in the transformer 13 occurs. Causes sound generation. Therefore, in order to slow down the response of the control unit 30, the adjustment unit 40 adjusts the rate of change of the ON period of the transistor 14 controlled by the control unit 30 from the time when the PWM signal is turned off. By slowing down the change rate of the ON period of the transistor 14, it is possible to suppress a sudden increase in the current flowing through the transformer 13, thereby preventing the magnetic flux of the transformer 13 from changing suddenly and generating abnormal noise. Can be reduced.
　図８はＰＷＭ信号のデューティ比αが５０％付近のスイッチング波形の一例を示す説明図である。図８ＡはＰＷＭ信号を示し、図８Ｂは従来のスイッチング波形を示し、図８Ｃは本実施の形態のスイッチング波形を示す。図８Ｂに示すように、従来のスイッチング波形では、ＰＷＭ信号のオン／オフ時におけるスイッチング波形の変化が急峻である。これに対して、本実施の形態では、図８Ｃに示すように、ＰＷＭ信号のオン／オフ時におけるスイッチング波形の変化が緩やかである。 FIG. 8 is an explanatory diagram showing an example of a switching waveform when the duty ratio α of the PWM signal is around 50%. 8A shows the PWM signal, FIG. 8B shows the conventional switching waveform, and FIG. 8C shows the switching waveform of the present embodiment. As shown in FIG. 8B, in the conventional switching waveform, the switching waveform changes sharply when the PWM signal is turned on / off. On the other hand, in the present embodiment, as shown in FIG. 8C, the change of the switching waveform when the PWM signal is turned on / off is gradual.
　上述のように、本実施の形態では、電源部１０の出力電流が急変するポイント、すなわち変圧器１３の磁束が最大に振れ、異音が大きくなるポイントで電源部１０の応答性能を落とす（具体的には、コントロールＩＣ３５のフィードバック端子ＦＢのキャッパシタの容量を大きくすることで、フィードバックゲインを下げ、出力変動に対する追従性能を下げる）ことにより、変圧器１３の磁束変化を和らげ、異音の発生を抑制することができる。 As described above, in the present embodiment, the response performance of the power supply unit 10 is degraded at the point where the output current of the power supply unit 10 changes suddenly, that is, at the point where the magnetic flux of the transformer 13 swings to the maximum and abnormal noise increases (specifically). Specifically, by increasing the capacity of the capacitor of the feedback terminal FB of the control IC 35, the feedback gain is lowered and the follow-up performance with respect to the output fluctuation is lowered. Can be suppressed.
　また、バックライト制御用のＰＷＭ信号によって、電源部１０の変圧器１３の磁束変化の大小を判別し、電源部１０の負荷変動に対する応答性（追従性能）を制御することにより、変圧器１３の磁束変化を和らげ、変圧器１３からの異音の発生を抑制することができる。また、変圧器１３からの異音の発生を抑制（削減又は微小化）することができるので、従来のスイッチング電源では必要としたＬＣフィルタを省略することができ、装置の小型化、コスト低減を図ることができる。なお、本実施の形態においても電源部１０にＬＣフィルタを設けてもよい。この場合には、ＬＣフィルタを従来のものより小さくすることができる。 Further, the magnitude of the magnetic flux change of the transformer 13 of the power supply unit 10 is determined by the backlight control PWM signal, and the response (following performance) to the load fluctuation of the power supply unit 10 is controlled, so that the transformer 13 The change in magnetic flux can be softened and the generation of abnormal noise from the transformer 13 can be suppressed. Further, since the generation of abnormal noise from the transformer 13 can be suppressed (reduced or miniaturized), the LC filter required in the conventional switching power supply can be omitted, and the apparatus can be reduced in size and cost. Can be planned. Note that an LC filter may be provided in the power supply unit 10 also in the present embodiment. In this case, the LC filter can be made smaller than the conventional one.
　上述の実施の形態では、コントロールＩＣ３５のフィードバック端子ＦＢに２個のキャパシタを接続する構成とし、一方のキャパシタを接続状態又は非接続状態とするものであったが、キャパシタの数は２個に限定されるものではなく、３個以上設けることもできる。キャパシタを３個以上設ける場合には、ＰＷＭ信号のデューティ比αの大小に応じて、接続状態にするキャパシタの数を段階的に増減させることができる。 In the above-described embodiment, two capacitors are connected to the feedback terminal FB of the control IC 35, and one capacitor is connected or disconnected. However, the number of capacitors is limited to two. However, three or more can be provided. When three or more capacitors are provided, the number of capacitors to be connected can be increased or decreased stepwise according to the duty ratio α of the PWM signal.
　また、上述の実施の形態において、ブライトネス値、ＰＷＭ信号、パルス信号のパルス幅などの関係を予め定めたデータベースを記憶しておき、マイコン１２０でトランジスタ１４のスイッチング動作を制御するようにしてもよい。この場合には、マイコン１２０が制御部３０及び調整部４０の機能を行うことになる。 In the above-described embodiment, a database in which relationships such as the brightness value, the PWM signal, and the pulse width of the pulse signal are previously stored may be stored, and the microcomputer 120 may control the switching operation of the transistor 14. . In this case, the microcomputer 120 performs the functions of the control unit 30 and the adjustment unit 40.
　１０　電源部
　１３　変圧器
　１４　トランジスタ（スイッチング素子）
　２０　ＬＥＤドライバ（駆動部）
　３０　制御部
　３１、３２　抵抗
　３３　フォトカップラ
　３４　シャントレギュレータ
　３５　コントロールＩＣ
　３６　キャパシタ
　４０　調整部
　４１、４２　ダイオード（平滑回路）
　４３、４４、４７　抵抗（平滑回路）
　４５、４６　キャパシタ（平滑回路）
　５９　キャパシタ
　１１０　バックライト（負荷）
　１２０　マイコン 10 Power Supply Unit 13 Transformer 14 Transistor (Switching Element)
20 LED driver (drive unit)
30 Control Unit 31, 32 Resistor 33 Photocoupler 34 Shunt Regulator 35 Control IC
36 capacitor 40 adjustment unit 41, 42 diode (smoothing circuit)
43, 44, 47 Resistance (smoothing circuit)
45, 46 Capacitor (smoothing circuit)
59 Capacitor 110 Backlight (Load)
120 microcomputer

Claims (6)

  1. 　電源部と、ＰＷＭ信号に応じて前記電源部の出力をＰＷＭ制御して負荷を駆動する駆動部と、前記電源部の出力変動に応答して該電源部の出力を制御する制御部とを備える電源装置において、
    　前記ＰＷＭ信号のデューティ比に応じて、前記制御部の応答の遅速を調整する調整部を備えることを特徴とする電源装置。     A power supply unit; a drive unit that drives a load by PWM-controlling an output of the power supply unit according to a PWM signal; and a control unit that controls the output of the power supply unit in response to an output fluctuation of the power supply unit. In power supply,
    A power supply apparatus comprising: an adjustment unit that adjusts a response speed of the control unit in accordance with a duty ratio of the PWM signal.
  2. 　前記電源部は、
    　二次側に前記駆動部が接続される変圧器と、
    　該変圧器の一次側に接続され、前記ＰＷＭ信号の周波数よりも高い周波数でオン・オフ動作が繰り返されるスイッチング素子と
    　を備え、
    　前記制御部は、
    　前記電源部の出力変動に応じて前記スイッチング素子のオン期間を制御するようにしてあり、
    　前記調整部は、
    　前記ＰＷＭ信号のデューティ比に応じて、前記制御部が制御する前記スイッチング素子のオン期間の変化速度を調整するようにしてあることを特徴とする請求項１に記載の電源装置。     The power supply unit is
    A transformer connected to the drive unit on the secondary side;
    A switching element connected to a primary side of the transformer, and repeatedly switching on and off at a frequency higher than the frequency of the PWM signal,
    The controller is
    The ON period of the switching element is controlled according to the output fluctuation of the power supply unit,
    The adjustment unit is
    2. The power supply device according to claim 1, wherein a change rate of an ON period of the switching element controlled by the control unit is adjusted according to a duty ratio of the PWM signal.
  3. 　前記調整部は、
    　前記ＰＷＭ信号のデューティ比に応じて、前記ＰＷＭ信号のオン／オフ時点からの前記スイッチング素子のオン期間の変化速度を調整するようにしてあることを特徴とする請求項２に記載の電源装置。     The adjustment unit is
    3. The power supply device according to claim 2, wherein a change speed of an on period of the switching element from an on / off time point of the PWM signal is adjusted according to a duty ratio of the PWM signal.
  4. 　前記調整部は、
    　前記デューティ比が第１閾値（＜５０％）より大きく、第２閾値（＞５０％）より小さい場合の前記スイッチング素子の前記ＰＷＭ信号のオン／オフ時点からのオン期間の変化速度を、前記デューティ比が前記第１閾値より小さい場合又は前記第２閾値より大きい場合の前記ＰＷＭ信号のオン／オフ時点からの前記オン期間の変化速度より遅くすべく調整するようにしてあることを特徴とする請求項３に記載の電源装置。     The adjustment unit is
    When the duty ratio is larger than the first threshold value (<50%) and smaller than the second threshold value (> 50%), the rate of change of the ON period from the ON / OFF time point of the PWM signal of the switching element is expressed as the duty ratio. The ratio is adjusted so as to be slower than the rate of change of the ON period from the ON / OFF time point of the PWM signal when the ratio is smaller than the first threshold value or larger than the second threshold value. Item 4. The power supply device according to Item 3.
  5. 　前記ＰＷＭ信号を整流して平滑する平滑回路を備え、
    　前記調整部は、
    　前記平滑回路で平滑した電圧が第１閾値電圧より大きく、第２閾値電圧（＞前記第１閾値電圧）より小さい場合の前記スイッチング素子の前記ＰＷＭ信号のオン／オフ時点からのオン期間の変化速度を、前記電圧が前記第１閾値電圧より小さい場合又は前記第２閾値電圧より大きい場合の前記ＰＷＭ信号のオン／オフ時点からの前記オン期間の変化速度より遅くすべく調整するようにしてあることを特徴とする請求項３に記載の電源装置。     A smoothing circuit for rectifying and smoothing the PWM signal;
    The adjustment unit is
    Change rate of ON period from ON / OFF time of PWM signal of switching element when voltage smoothed by smoothing circuit is larger than first threshold voltage and smaller than second threshold voltage (> first threshold voltage) Is adjusted to be slower than the rate of change of the ON period from the ON / OFF time point of the PWM signal when the voltage is lower than the first threshold voltage or higher than the second threshold voltage. The power supply device according to claim 3.
  6. 　請求項１乃至請求項５のいずれか１項に記載の電源装置と、該電源装置の駆動部により駆動されるバックライトとを備えることを特徴とする表示装置。 A display device comprising: the power supply device according to any one of claims 1 to 5; and a backlight driven by a drive unit of the power supply device.
PCT/JP2013/055324 2012-09-27 2013-02-28 Power source device and display device WO2014050165A1 (en)

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CN112087171A (en) * 2020-08-26 2020-12-15 湖南英迈智能科技有限公司 Current smoothing method and device

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JP2003299356A (en) * 2002-04-01 2003-10-17 Nanao Corp Dc-dc converter control method
JP2011229338A (en) * 2010-04-22 2011-11-10 Denso Corp Power conversion equipment

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CN112087171B (en) * 2020-08-26 2022-02-11 湖南英迈智能科技有限公司 Current smoothing method and device

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