WO2018147133A1 - Power supply device and television device - Google Patents

Power supply device and television device Download PDF

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Publication number
WO2018147133A1
WO2018147133A1 PCT/JP2018/003064 JP2018003064W WO2018147133A1 WO 2018147133 A1 WO2018147133 A1 WO 2018147133A1 JP 2018003064 W JP2018003064 W JP 2018003064W WO 2018147133 A1 WO2018147133 A1 WO 2018147133A1
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WIPO (PCT)
Prior art keywords
switching element
load
current
gate
power supply
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PCT/JP2018/003064
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French (fr)
Japanese (ja)
Inventor
豊田　友博
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シャープ株式会社
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Publication of WO2018147133A1 publication Critical patent/WO2018147133A1/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
    • H02M1/00—Details of apparatus for conversion
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • 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
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/63—Generation or supply of power specially adapted for television receivers

Definitions

  • the present invention relates to a power supply apparatus and a television apparatus, and more particularly, to a power supply apparatus and a television apparatus that reduce noise.
  • EMI Electro Magnetic Interference
  • the switching circuit of the power supply circuit is large in terms of power, it has a great influence on EMI.
  • a high frequency component is generated at the time of switching from a switching element such as an FET used in a DC-DC converter or the like, and EMI and noise terminal voltage are deteriorated.
  • Patent Document 1 allows the rising or falling characteristics of an output signal to be set from the outside without adding or modifying design countermeasure components, and dynamically EMI. It is not something that reduces.
  • the present invention has been made in view of these circumstances, and an object of the present invention is to provide a power supply circuit and a television apparatus that dynamically reduce switching noise at light load.
  • a first technical means of the present invention includes an inductor connected to a power source, a capacitor charged with a current from the power source via the inductor, and a charging current to the capacitor.
  • a power supply device that includes a switching element for turning on / off and a control circuit that controls on / off of the switching element, and that supplies power to a load, wherein the control circuit has a large load current of the load.
  • the gate resistance value of the switching element is changed according to the temperature of the switching element.
  • the control circuit changes the gate resistance value to a larger value as the average value of the load current is smaller or the temperature of the switching element is lower. It is characterized by this.
  • the load is a load whose magnitude of the load current is changed according to a predetermined load mode
  • the control circuit includes the load mode.
  • the gate resistance value of the switching element is changed according to the above.
  • the fourth technical means is a television apparatus provided with a power supply device which is any one of the first to third technical means.
  • the fifth technical means is characterized in that, in the fourth technical means, the change of the gate resistance value of the switching element by the control circuit is performed at the time of starting or at the time of a scene change of an image.
  • switching noise at light load can be dynamically reduced.
  • FIG. 1 is a diagram for schematically explaining an example of a power supply device according to the present invention.
  • the power supply circuit 1 of the present invention converts the input voltage Vin and the input current Iin from the DC power supply 2 into an output voltage Vout and an output current Iout and supplies them to the load 5.
  • a DC-DC converter 3 is provided.
  • the AC power source in the case of a television apparatus using an AC power source, the AC power source is passed through an EMI filter, a full-wave rectifier circuit, a PFC (power factor correction circuit), an LLC (series resonance circuit), and a rectifier circuit.
  • a voltage may be obtained or a battery may be used.
  • the gate resistance value of the switching element of the DC-DC converter 3 is changed according to the magnitude of the load current.
  • This example corresponds to the first embodiment of the present invention.
  • the gate resistance value of the switching element is changed according to the temperature of the switching element of the DC-DC converter 3.
  • the load 5 is a backlight of the liquid crystal television device, and the gate resistance value of the switching element is changed according to the mode of the video signal.
  • This example corresponds to the third embodiment of the present invention.
  • an electronic switching element such as an FET is used for the DC-DC converter 3. It is known that a high frequency component is generated at the time of switching, and EMI and noise terminal voltage are deteriorated. In this case, even if the average load current is large, there is no problem with EMI if it is close to the DC current, but even if the average load current is small, the EMI deteriorates if the pulse current has a large peak value. There is.
  • the gate pulse waveform of an electronic switching element such as an FET
  • the rise time and fall time of the switching element can be delayed, and the generation of high-frequency noise due to switching can be suppressed.
  • the gate pulse waveform is smoothed, there is a problem that the temperature of the switching element rises.
  • the gate pulse waveform is smoothed by increasing the resistance value of the gate line that drives the FET that is the switching element of the DC-DC converter 3, that is, The switching noise of the FET is suppressed by changing the slope of the rising and falling waveforms.
  • the switching element focusing on the temperature of the switching element, when the load is light, the switching element does not exceed the allowable operating temperature range, so the temperature of the switching element is detected and the temperature falls below a predetermined temperature.
  • the resistance value of the gate line is increased to suppress the generation of switching noise.
  • FIG. 2 is a diagram illustrating a configuration of an embodiment of a power supply device according to the present invention, and corresponds to the schematic diagram of FIG.
  • a direct current power source 2 is used as a power source and an LED (light emitting diode) 51 used for a backlight of a liquid crystal television device or a liquid crystal display device is used as a load 5
  • the battery 5 may be a battery, and the load 5 is not limited to the LED of the backlight but can be various loads.
  • the power supply device 1 of this embodiment includes a DC-DC converter 3, a gate control circuit 4, and a load current detection circuit 6.
  • the configuration surrounded by the broken line of the gate control circuit 4 may be configured by an IC (integrated circuit).
  • the DC-DC converter 3 is supplied with an input voltage Vin from a DC power supply 2 and is supplied with an input current Iin. One output terminal of the DC power supply 2 is grounded.
  • the DC-DC converter 3 includes a capacitor 31 connected in parallel to the output terminal of the DC power supply 2, an inductor 32 connected to one DC line of the capacitor 31, a switching element 33 provided at the subsequent stage of the inductor 32, and switching A backflow prevention diode 34 and a smoothing capacitor 35 provided in the subsequent stage of the element 33 are provided. Both ends of the smoothing capacitor 35 correspond to output terminals of the power supply device, and a load 5 is connected to the subsequent stage.
  • the inductor 32 is an inductance element for generating an electromotive force by storing a current flowing according to a voltage supplied from the DC power supply 2 and the capacitor 31 as energy.
  • the switching element 33 is composed of, for example, an N-channel field effect transistor (FET), and is turned on when a high level signal is supplied to the gate, and is turned off when a low level signal is supplied to the gate.
  • FET field effect transistor
  • a gate signal from the gate control circuit 4 is supplied to the gate of the switching element 33. Since the switching frequency of the switching element 33 is generally several tens of kHz to several MHz, it is important to reduce noise from the switching element 33 as an EMI countermeasure.
  • the gate control circuit 4 changes the duty ratio of the gate signal supplied to the switching element 33 in accordance with the output voltage of the DC-DC converter 3, and the output voltage of the DC-DC converter 3 is a predetermined value. It is controlled to become. That is, the power supply apparatus constitutes a feedback control system based on the output voltage. For example, the predetermined value of the output voltage of the DC-DC converter 3 is set to a voltage at which the LED as a load is sufficiently lit.
  • the gate control circuit 4 includes resistors 41 and 42, an error amplifier 43, a reference voltage generation circuit 44, a pulse width modulation (PWM) circuit 45, a gate resistance value change circuit 46, a threshold voltage generation circuit 47, and a comparator 48. .
  • the output voltage Vout of the DC-DC converter 3 is divided by the resistors 41 and 42, and the divided voltage is connected to the inverting input terminal of the error amplifier 43.
  • the reference voltage Vr from the reference voltage generation circuit 44 is input to the non-inverting input terminal of the error amplifier 43.
  • a difference voltage between the reference voltage Vr and the divided voltage is output as an output signal of the error amplifier 43.
  • the output signal of the error amplifier 43 is input to the pulse width modulation circuit 45, and the pulse width modulation circuit 45 has a predetermined pulse frequency (several tens of kHz to several MHz) according to the magnitude of the output signal of the error amplifier 43.
  • a pulse signal with a changed pulse duty ratio is output.
  • the pulse signal from the pulse width modulation circuit 45 is applied to the gate of the switching element 33 of the DC-DC converter 3 through the gate resistance value changing circuit 46.
  • the switching element 33 Since the pulse signal from the pulse width modulation circuit 45 becomes the gate signal of the switching element 33, the switching element 33 is turned on in an on time corresponding to the duty ratio of the pulse signal from the pulse width modulation circuit 45.
  • the voltage of the resistor 61 is input to the inverting input terminal of the comparator 48, and the threshold voltage Vth from the threshold voltage generating circuit 47 is input to the non-inverting input terminal of the comparator 48. Because One resistor 61 the other is connected in series to the load 5 is grounded, the load current I F equal load 5 to the output current Iout of the DC-DC converter 3 is detected as a voltage value V IF at the resistor 61.
  • the load current is not a direct current but includes an alternating current such as a pulse current
  • an average value circuit and a low-pass filter (not shown) are provided in front of the comparator 48 so that the non-inverting input terminal of the comparator 48 is provided.
  • the voltage corresponding to the average value of the load current flowing through the load 5 is input.
  • the resistor 61 constitutes the load current detection circuit 6.
  • the voltage V IF of the threshold voltage Vth and the resistor 61 are compared, as a comparison signal, a binary signal of high level or low level is outputted.
  • the binary output signal from the comparator 48 is input to the gate resistance value changing circuit 46 and used to change the resistance value of the gate line of the switching element 33. The change of the resistance value of the gate line will be described in detail later.
  • FIG. 3 is a diagram showing the voltage waveform or current waveform of each part of the power supply device shown in FIG. 2.
  • the input voltage Vin, the input current Iin of the DC-DC converter 3, the gate signal Q of the switching element 33, and the switching element 33 are shown.
  • the switching element 33 is turned on at time t1, turned off at time t2, turned on at time t3, turned off at time t4, turned on at time t5, and turned off at time t6.
  • a path of the DC power source 2 is generated. Therefore, the voltage of the DC power supply 2 is an inductor 32, is applied to the switching element 33, the current I L of the inductor 32 as an inductance element is increased.
  • a current IQ flows through the switching element 33.
  • the current I L and the current I Q is the same size. With increasing current I L in the inductor 32, the energy stored in the inductor 32 increases.
  • the DC power source 2 When the switching element 33 is turned off at time t2, the DC power source 2, the inductor 32, the diode 34, the parallel circuit of the load 5 and the smoothing capacitor 35, and the path of the DC power source 2 are generated. Then, power from the DC power source 2 is supplied to the smoothing capacitor 35 and the load 5 via the diode 34 as energy stored in the inductor 32.
  • the current ID flowing through the diode 34 is a current obtained by adding the current IC2 flowing through the smoothing capacitor 35 and the load current. Therefore, current obtained by subtracting the load current I F from the current flowing through the current I D flowing through the diode 34 but flows into the smoothing capacitor 35, decreasing charged in the smoothing capacitor 35 with time. Further, the output voltage Vout of the DC-DC converter 3 becomes higher than the input voltage Vin.
  • the switching element 33 is turned off at time t3, the path of the DC power source 2, the inductor 32, the switching element 33, and the DC power source 2 is generated as in the time t1, and the same current flows.
  • a load current is supplied from the smoothing capacitor 35 to the load 5. In this way, power is supplied to the load 5 both when the switching element 33 is on and when it is off.
  • the current I C1 flowing through the capacitor 31 and the current I C2 flowing through the smoothing capacitor 35 have an AC component corresponding to the on / off state of the switching element 33.
  • the load 5 is directed to the LED (light emitting diode) 51 used for the backlight of the liquid crystal television device or the liquid crystal display device, but the brightness of the backlight is dimming. It is adjusted by the switching signal from the signal generation circuit 9. More specifically, the current flowing through the LED 51 is switched at a frequency with no visual problem by a switching element 52 such as a field effect transistor (FET). The brightness is adjusted by the on-duty of the switching signal. Note that the switching frequency of the switching element 52 is at most several hundred Hz, and a frequency considerably lower than the switching frequency of the switching element 33 of the DC-DC converter 3 is used.
  • a switching element 52 such as a field effect transistor (FET).
  • FIG. 4 is a diagram illustrating a current flowing through the load of the power supply device illustrated in FIG. 2.
  • FIG. 4A illustrates a case where the backlight is lit brightly, and the on-duty of the switching signal of the switching element 52 is 100%. It is said. In this case, the load current I F becomes almost a direct current, the average load current I FAVE also increased.
  • FIG. 4B shows a case where the backlight does not need to be lit brightly, and the on-duty of the switching signal of the switching element 52 is, for example, 50%. In this case, the load current I F becomes substantially pulse-shaped current, the average load current I FAVE is smaller than when the on-duty of 100%. However, since the pulse current flows when the average current I FAVE shown in FIG.
  • the gate control circuit 4 tries to maintain the output voltage Vout of the DC-DC converter 3 at a voltage value necessary for lighting the LED 51.
  • the duty ratio D of 33 is increased. Thereby, current I Q flowing through the switching element 33 increases, the temperature of the switching element 33 of the DC-DC converter 3 is increased.
  • the gate control circuit 4 tries to maintain the output voltage Vout of the DC-DC converter 3 at a voltage value necessary for lighting the LED 51. Since F is small, it is not necessary to increase the duty ratio D of the switching element 33 and an attempt is made to maintain a small value. Thereby, current I Q flowing through the switching element 33 is decreased, the temperature of the switching element 33 is not large to increase. In this case, the temperature of the switching element 33 such as an FET and the temperature of the solder surface have a relatively margin with respect to the reference value.
  • the gate pulse waveform is smoothed by increasing the resistance value of the gate line that drives the switching element 33 of the DC-DC converter 3, and the switching element The rise time and fall time are slowed down to suppress the generation of high frequency noise due to switching.
  • FIG. 5 is a diagram for explaining a gate resistance value changing circuit and a gate signal waveform of the power supply device shown in FIG. 2, and will be described together with FIG.
  • the comparator 48 compares the threshold voltage Vth and the voltage V IF of the resistor 61, and the binary output signal from the comparator 48 is input to the gate resistance value changing circuit 46.
  • the resistance value of the resistor R 2 is greater than the resistance value of the resistor R 1, for example, resistor R 1 is 0 .OMEGA, resistance R 2 has a 200 [Omega.
  • the comparator 48 outputs a low level signal, the gate resistance value changing circuit 46, switching the switch SW so that the resistance value of the gate line becomes a value of less resistance R 1 of the switching element 33.
  • a gate signal having a good pulse waveform in which the rise and fall are not inclined is applied to the gate of the switching element 33, and the temperature rise of the switching element is suppressed.
  • the comparator 48 when the voltage V IF resistor 61 is smaller than the threshold voltage Vth, that is, when the load current I F is smaller than the predetermined value, the comparator 48 outputs a high signal, the gate resistance value changing circuit 46, switching Since the time constant of the RC circuit is large due to the resistance between the gate line of the element 33 having a large gate line resistance and the capacitance between the gate and source of the switching element 33, the waveform of the gate signal is as shown in FIG. It becomes a so-called sluggish shape with rising and falling slopes. Thereby, although the temperature of the switching element 33 rises, the generated noise can be suppressed.
  • the magnitude of the threshold voltage Vth, the resistance value of the resistor 61 for the load current I F detected, the resistance value of the resistor R 2 is set so that the switching element 33 falls within the allowable temperature range.
  • the switch the two values as the resistance value of the gate line of the switching element 33 may be switched to three or more resistance, further, the magnitude of the load current I F Accordingly, the resistance value of the gate line may be changed continuously.
  • FIG. 6 is a diagram showing the configuration of another embodiment of the power supply device according to the present invention, and corresponds to the schematic diagram of FIG.
  • a direct-current power source 2 is used as a power source
  • an LED (light emitting diode) 51 used as a backlight of a liquid crystal television device or a liquid crystal display device is used as a load 5 as in the first embodiment.
  • the power source may be a battery
  • the load 5 is not limited to the LED of the backlight but can be various loads.
  • the power supply device 1 of this embodiment includes a DC-DC converter 3, a gate control circuit 4, and an element temperature detection circuit 7.
  • the configuration surrounded by the broken line of the gate control circuit 4 can be configured by an IC (integrated circuit).
  • the basic configuration of the DC-DC converter 3 and the gate control circuit 4 is the same as that of the first embodiment shown in FIG. 2, and in the first embodiment, the magnitude of the load current IF is large.
  • the gate resistance value of the switching element 33 of the DC-DC converter 3 is changed accordingly, whereas in the present embodiment, the gate resistance of the switching element 33 depends on the temperature of the switching element 33 of the DC-DC converter 3. The value has been changed.
  • the description of the same configuration as that of the first embodiment will be omitted, and a different configuration will be described.
  • Element temperature detecting circuit 7 for detecting the temperature of the switching element 33 is provided.
  • the voltage V T obtained by dividing the constant voltage by the voltage dividing resistor circuit of the thermistor 71 and the resistor 72 is the temperature of the switching element 33.
  • the value increases with the rise.
  • the comparator 48 If the voltage V T is greater than the threshold voltage Vth, i.e., when the temperature of the switching element 33 is higher than the predetermined value, the comparator 48 outputs a low level signal, the gate resistance value changing circuit 46, the switching element the resistance of the gate line 33 assumes a value smaller resistor R 1 so switches the switch SW.
  • a gate signal having a good pulse waveform in which the rising and falling edges are not inclined is applied to the gate of the switching element 33, and the temperature rise of the switching element 33 is suppressed.
  • the gate resistance changing circuit 46 switches the switch SW to a value of the resistor R 2 the resistance value is large gate line of the switching element 33.
  • the time constant of the RC circuit due to the resistance of the gate line of the switching element 33 and the capacitance between the gate and source of the switching element 33 increases, so that the waveform of the gate signal rises and falls as shown in FIG.
  • the so-called slanted shape is inclined. Thereby, although the temperature of the switching element 33 rises, the generated noise can be suppressed.
  • the magnitude of the threshold voltage Vth, characteristic resistance value of the thermistor 71, the resistance value of the resistor 72, the resistance value of the resistor R 2, is set so that the switching element 33 becomes the allowable temperature range.
  • two values are switched as the resistance value of the gate line of the switching element 33.
  • three or more resistance values may be switched.
  • the resistance value of the gate line may be continuously changed according to the temperature of the switching element 33.
  • FIG. 7 is a diagram illustrating a configuration of an embodiment when a television apparatus is applied to the power supply device according to the present invention, and corresponds to the schematic diagram of FIG.
  • a DC power source 2 is used as a power source
  • an LED (light emitting diode) 51 used as a backlight of a liquid crystal television device is used as a load 5 as in the first embodiment.
  • the television apparatus of this embodiment includes a DC-DC converter 3, a gate control circuit 4, and a dimming signal generation circuit 9.
  • the configuration surrounded by the broken line of the gate control circuit 4 can be configured by an IC (integrated circuit).
  • the basic configuration of the DC-DC converter 3 and the gate control circuit 4 is the same as that of the first embodiment shown in FIG. 2, and in the first embodiment, the magnitude of the load current IF is large.
  • the gate resistance value of the switching element 33 of the DC-DC converter 3 is changed accordingly, in the present embodiment, in the television device, the current consumption of the backlight in a specific video mode such as a movie mode. Note that the gate resistance value of the switching element 33 of the DC-DC converter 3 is changed according to the mode of the video signal.
  • the description of the same configuration as that of the first embodiment will be omitted, and a different configuration will be described.
  • the gate control circuit 4 includes a mode analysis unit 49 that receives a mode signal input from the video signal mode input terminal.
  • the threshold voltage generation circuit 47 included in the first embodiment, and The comparator 48 is not provided.
  • the mode signal input from the video signal mode input terminal is also input to the dimming signal generation circuit 9.
  • the dimming signal generation circuit 9 adjusts the current flowing through the LED 51 in accordance with the mode signal input from the video signal mode input terminal. For example, when the mode signal is the movie mode, by inputting a switching signal having a small on-duty ratio to the switching element 52, the current flowing through the LED 51 is suppressed, and a dark image is displayed on a liquid crystal screen (not shown). When the mode signal is dynamic mode, a switching signal having a large on-duty ratio is input to the switching element 52, whereby the current flowing through the LED 51 is increased and an image with a large contrast is displayed. Thus, the magnitude of the load current of the backlight is changed according to a load mode such as a predetermined video mode.
  • a load mode such as a predetermined video mode.
  • the mode analysis unit 49 of the gate control circuit 4 analyzes the mode signal input from the video signal mode input terminal, and outputs a resistance change signal to the gate resistance value change circuit 46 according to the mode signal.
  • the mode signal when a movie mode, the gate resistance value changing circuit 46 outputs a resistance change signal to a value of the resistance value is large R 2 gate line of the switching element 33.
  • the waveform of the gate signal has a so-called distorted shape in which the rising edge and the falling edge are inclined as shown in FIG. Thereby, although the temperature of the switching element 33 rises, the generated noise can be suppressed.
  • the mode analyzing portion 49 of the gate control circuit 4 if the mode signal is in the dynamic mode, so that the gate resistance value changing circuit 46 becomes a value of the resistor R 1 a small resistance value of the gate line of the switching element 33 Outputs a resistance change signal.
  • a gate signal having a good pulse waveform in which the rising and falling edges are not inclined is applied to the gate of the switching element 33, and the temperature rise of the switching element 33 is suppressed.
  • the movie mode and the dynamic mode have been described as examples of the video signal mode.
  • the video signal mode need not be limited to this.
  • the backlight load current IF is reduced by receiving the mode signal of the dark mode, and the switching element 33 may be controlled to a value of the resistor R 2 the resistance value is large gate lines.
  • the resistance R the resistance of the gate line is larger switching element 33 It can be controlled to be a value of 2 .
  • a scene change or the like is performed in order to avoid a visual influence when the output voltage of the DC-DC converter 3 varies by changing the resistance value of the gate line of the switching element 33. It is desirable to change the resistance value at the video switching timing.
  • SYMBOLS 1 Power supply device, 2 ... DC power supply, 3 ... DC-DC converter, 4 ... Gate control circuit, 5 ... Load, 6 ... Load current detection circuit, 7 ... Element temperature detection circuit, 9 ... Dimming signal generation circuit, 31 DESCRIPTION OF SYMBOLS Capacitor 32 ... Inductor 33 ... Switching element 34 ... Diode 35 ... Smoothing capacitor 41, 42 ... Resistor 43 ... Error amplifier 44 ... Reference voltage generation circuit 45 ... Pulse width modulation circuit 46 ... Gate Resistance value changing circuit, 47... Threshold voltage generating circuit, 48... Comparator, 49... Mode analysis unit, 51... LED, 52.

Abstract

Provided are a power supply device and a television device which dynamically reduce a switching noise under a light load. This power supply device is provided with: an inductor (32) connected to a direct current power source (2); a capacitor (35) in which a current is charged from the power source through the inductor (32); and a switching element (33) for the on-off control of the charging current to the capacitor (35), and supplies power to a load (5). When the magnitude of a load current IF of the load (5) is small, the occurrence of noise is prevented by increasing a gate resistance value of the switching element (33) to attenuate a gate pulse waveform. In addition, when the temperature of the switching element (33) is low, the gate resistance value of the switching element (33) may also be increased.

Description

電源装置およびテレビジョン装置Power supply device and television device
本発明は、電源装置およびテレビジョン装置に関し、詳しくは、ノイズの低減を図った電源装置およびテレビジョン装置に関する。 The present invention relates to a power supply apparatus and a television apparatus, and more particularly, to a power supply apparatus and a television apparatus that reduce noise.
　テレビジョン装置等の家電において、不要輻射であるＥＭＩ（Electro Magnetic Interference）を低減することが常に求められている。特に、電源回路のスイッチング回路は、電力的にも大きいことからＥＭＩへの影響も大きい。例えば、ＤＣ－ＤＣコンバータなどに使用されているＦＥＴ等のスイッチング素子から、スイッチング時に高周波成分が発生し、ＥＭＩや雑音端子電圧が悪化することが知られている。 In home appliances such as television devices, it is always required to reduce EMI (Electro Magnetic Interference), which is unnecessary radiation. In particular, since the switching circuit of the power supply circuit is large in terms of power, it has a great influence on EMI. For example, it is known that a high frequency component is generated at the time of switching from a switching element such as an FET used in a DC-DC converter or the like, and EMI and noise terminal voltage are deteriorated.
　このため、従来から、ＥＭＩ低減のためにフィルタ等が用いられていた。また、例えば、特許文献１には、液晶表示装置において、回路基板やシステム全体が完成した後でも、表示信号および転送クロックを出力制御する出力回路の出力電流能力あるいは出力電圧の立ち上がりまたは立ち下がり特性を、外部から可変可能なように構成することによって、設計的に変更することなく、容易に不要輻射防止のためのＥＭＩ対策を実施することができる集積回路が提案されている。 For this reason, filters and the like have been conventionally used to reduce EMI. Further, for example, in Patent Document 1, in the liquid crystal display device, even after the circuit board and the entire system are completed, the output current capability of the output circuit that controls the output of the display signal and the transfer clock, or the rising or falling characteristics of the output voltage Therefore, an integrated circuit has been proposed that can easily implement EMI countermeasures for preventing unnecessary radiation without changing the design, so that the circuit can be varied from the outside.
特開平１１－１７４４０６号公報Japanese Patent Laid-Open No. 11-174406
　ＥＭＩ低減のためにフィルタを用いることは有効ではあるものの、フィルタの数や実装スペースが必要となるため、ある程度以上のＥＭＩの低減は難しかった。また、特許文献１に開示された集積回路は、設計的な対策部品の追加や修正をすることなく、出力信号の立ち上がりまたは立ち下り特性を外部から設定可能にするものであり、動的にＥＭＩを低減するものではない。 Although it is effective to use filters to reduce EMI, it is difficult to reduce EMI to some extent because the number of filters and mounting space are required. Further, the integrated circuit disclosed in Patent Document 1 allows the rising or falling characteristics of an output signal to be set from the outside without adding or modifying design countermeasure components, and dynamically EMI. It is not something that reduces.
　本発明は、これらの実情に鑑みてなされたものであり、軽負荷時のスイッチングノイズを動的に軽減する電源回路およびテレビジョン装置を提供することをその目的とする。 The present invention has been made in view of these circumstances, and an object of the present invention is to provide a power supply circuit and a television apparatus that dynamically reduce switching noise at light load.
　上記課題を解決するために、本発明の第１の技術手段は、電源に接続されたインダクタと、該インダクタを介して前記電源からの電流が充電されるコンデンサと、該コンデンサへの充電電流をオン・オフするためのスイッチング素子と、該スイッチング素子のオン・オフを制御する制御回路とを備え、負荷へ電力を供給する電源装置であって、前記制御回路は、前記負荷の負荷電流の大きさまたは前記スイッチング素子の温度に応じて、前記スイッチング素子のゲート抵抗値を変更することを特徴とするものである。 In order to solve the above problems, a first technical means of the present invention includes an inductor connected to a power source, a capacitor charged with a current from the power source via the inductor, and a charging current to the capacitor. A power supply device that includes a switching element for turning on / off and a control circuit that controls on / off of the switching element, and that supplies power to a load, wherein the control circuit has a large load current of the load. Alternatively, the gate resistance value of the switching element is changed according to the temperature of the switching element.
　第２の技術手段は、第１の技術手段において、前記制御回路は、前記負荷電流の平均値が小さいほど、または、前記スイッチング素子の温度が低いほど、前記ゲート抵抗値を大きな値に変更することを特徴とするものである。 According to a second technical means, in the first technical means, the control circuit changes the gate resistance value to a larger value as the average value of the load current is smaller or the temperature of the switching element is lower. It is characterized by this.
　第３の技術手段は、第１または第２の技術手段において、前記負荷は所定の負荷モードに応じて前記負荷電流の大きさが変更される負荷であって、前記制御回路は、前記負荷モードに応じて前記スイッチング素子のゲート抵抗値を変更することを特徴とするものである。 According to a third technical means, in the first or second technical means, the load is a load whose magnitude of the load current is changed according to a predetermined load mode, and the control circuit includes the load mode. The gate resistance value of the switching element is changed according to the above.
　第４の技術手段は、第１から第３のいずれか１の技術手段である電源装置を備えたテレビジョン装置である。 The fourth technical means is a television apparatus provided with a power supply device which is any one of the first to third technical means.
　第５の技術手段は、第４の技術手段において、前記制御回路による前記スイッチング素子のゲート抵抗値の変更は、起動時、または、映像のシーンチェンジ時に行うことを特徴とするものである。 The fifth technical means is characterized in that, in the fourth technical means, the change of the gate resistance value of the switching element by the control circuit is performed at the time of starting or at the time of a scene change of an image.
　本発明によれば、電源装置およびこの電源装置を備えたテレビジョン装置において、軽負荷時のスイッチングノイズを動的に軽減することができる。 According to the present invention, in a power supply apparatus and a television apparatus equipped with the power supply apparatus, switching noise at light load can be dynamically reduced.
本発明に係る電源装置の例を模式的に説明するための図である。It is a figure for demonstrating typically the example of the power supply device which concerns on this invention. 本発明に係る電源装置の一実施形態の構成を示す図である。It is a figure which shows the structure of one Embodiment of the power supply device which concerns on this invention. 図２に示す電源装置の各部の電圧波形または電流波形を示す図である。It is a figure which shows the voltage waveform or current waveform of each part of the power supply device shown in FIG. 図２に示す電源装置の負荷に流れる電流を示す図である。It is a figure which shows the electric current which flows into the load of the power supply device shown in FIG. 図２に示す電源装置のゲート抵抗値変更回路とゲート信号波形を説明するための図である。It is a figure for demonstrating the gate resistance value change circuit and gate signal waveform of the power supply device shown in FIG. 本発明に係る電源装置の他の実施形態の構成を示す図である。It is a figure which shows the structure of other embodiment of the power supply device which concerns on this invention. 本発明に係る電源装置をテレビジョン装置に適用した際の一実施形態の構成を示す図である。It is a figure which shows the structure of one Embodiment at the time of applying the power supply device which concerns on this invention to a television apparatus.
　以下、図面を参照しながら、本発明の電源装置およびテレビジョン装置に係る好適な実施形態について説明する。以下の説明において、異なる図面においても同じ符号を付した構成は同様のものであるとして、その説明を省略する場合がある。 Hereinafter, preferred embodiments of the power supply device and the television device of the present invention will be described with reference to the drawings. In the following description, the configurations denoted by the same reference numerals in different drawings are the same, and the description thereof may be omitted.
　図１は、本発明に係る電源装置の例を模式的に説明するための図である。本発明の電源回路１は、図１（Ａ）～（Ｃ）に示すように、直流電源２からの入力電圧Ｖinと入力電流Ｉinを出力電圧Ｖoutと出力電流Ｉoutに変換して負荷５に供給するＤＣ－ＤＣコンバータ３を有している。なお、電源としては、交流電源を用いるテレビジョン装置の場合は、交流電源から、ＥＭＩ用フィルタ、全波整流回路、ＰＦＣ（力率改善回路）、ＬＬＣ（直列共振回路）、整流回路を経て直流電圧を得るものでもよく、また、電池であっても構わない。 FIG. 1 is a diagram for schematically explaining an example of a power supply device according to the present invention. As shown in FIGS. 1A to 1C, the power supply circuit 1 of the present invention converts the input voltage Vin and the input current Iin from the DC power supply 2 into an output voltage Vout and an output current Iout and supplies them to the load 5. A DC-DC converter 3 is provided. As a power source, in the case of a television apparatus using an AC power source, the AC power source is passed through an EMI filter, a full-wave rectifier circuit, a PFC (power factor correction circuit), an LLC (series resonance circuit), and a rectifier circuit. A voltage may be obtained or a battery may be used.
　図１（Ａ）に示す例は、負荷電流の大きさに応じてＤＣ－ＤＣコンバータ３のスイッチング素子のゲート抵抗値を変更している。この例は本発明の第１の実施形態に相当する。また、図１（Ｂ）に示す例では、ＤＣ－ＤＣコンバータ３のスイッチング素子の温度に応じて、スイッチング素子のゲート抵抗値を変更している。この例は本発明の第２の実施形態に相当する。さらに、図１（Ｃ）に示す例では、負荷５を液晶テレビジョン装置のバックライトとし、映像信号のモードに応じて、スイッチング素子のゲート抵抗値を変更している。この例は本発明の第３の実施形態に相当する。これらの各例については、後で詳述する。 In the example shown in FIG. 1A, the gate resistance value of the switching element of the DC-DC converter 3 is changed according to the magnitude of the load current. This example corresponds to the first embodiment of the present invention. In the example shown in FIG. 1B, the gate resistance value of the switching element is changed according to the temperature of the switching element of the DC-DC converter 3. This example corresponds to the second embodiment of the present invention. Further, in the example shown in FIG. 1C, the load 5 is a backlight of the liquid crystal television device, and the gate resistance value of the switching element is changed according to the mode of the video signal. This example corresponds to the third embodiment of the present invention. Each of these examples will be described in detail later.
　本発明に係る電源装置では、ＤＣ－ＤＣコンバータ３にＦＥＴ等の電子スイッチング素子が用いられている。そして、スイッチング時に高周波成分が発生し、ＥＭＩや雑音端子電圧が悪化することが知られている。この場合、平均の負荷電流が大きくても、直流電流に近い場合は、ＥＭＩは問題がないが、平均の負荷電流が小さくても、ピーク値の大きなパルス電流の場合は、ＥＭＩが悪化することがある。 In the power supply device according to the present invention, an electronic switching element such as an FET is used for the DC-DC converter 3. It is known that a high frequency component is generated at the time of switching, and EMI and noise terminal voltage are deteriorated. In this case, even if the average load current is large, there is no problem with EMI if it is close to the DC current, but even if the average load current is small, the EMI deteriorates if the pulse current has a large peak value. There is.
　一方、ＦＥＴ等の電子スイッチング素子のゲートパルス波形をなまらせることによって、スイッチング素子の立ち上がり時間と立ち下がり時間を遅くし、スイッチングによる高周波ノイズの発生を抑えることができる。しかしながら、ゲートパルス波形をなまらせた場合、スイッチング素子の温度が上昇するという問題がある。 On the other hand, by smoothing the gate pulse waveform of an electronic switching element such as an FET, the rise time and fall time of the switching element can be delayed, and the generation of high-frequency noise due to switching can be suppressed. However, when the gate pulse waveform is smoothed, there is a problem that the temperature of the switching element rises.
　平均の負荷電流が低い場合は、ＦＥＴ等のスイッチング素子の温度や半田面の温度は、基準値に対して比較的マージンがある。そこで、本発明では、負荷電流が小さな軽負荷の場合に、ＤＣ－ＤＣコンバータ３のスイッチング素子であるＦＥＴを駆動するゲートラインの抵抗値を大きくすることによってゲートパルス波形をなまらせて、すなわち、立ち上がりと立ち下がりの波形傾きを変えて、ＦＥＴのスイッチングノイズを抑えている。 When the average load current is low, the temperature of the switching element such as FET and the temperature of the solder surface have a relatively margin with respect to the reference value. Therefore, in the present invention, in the case of a light load with a small load current, the gate pulse waveform is smoothed by increasing the resistance value of the gate line that drives the FET that is the switching element of the DC-DC converter 3, that is, The switching noise of the FET is suppressed by changing the slope of the rising and falling waveforms.
　また、負荷電流が大きな高負荷の場合は、スイッチング素子の温度が上昇し、部品の信頼性や半田の信頼性に影響を及ぼしてしまう。このため、通常の波形がなまっていないゲートパルスがスイッチング素子に印加されるようにしている。 Also, in the case of a high load with a large load current, the temperature of the switching element rises, affecting the reliability of parts and the reliability of solder. For this reason, a gate pulse whose normal waveform is not blurred is applied to the switching element.
　さらに、本発明では、スイッチング素子の温度に着目し、負荷が軽負荷の場合は、スイッチング素子は許容動作温度範囲を超えることがないため、スイッチング素子の温度を検出し、所定の温度を下回る場合にゲートラインの抵抗値を大きくし、スイッチングノイズの発生を抑えている。 Further, in the present invention, focusing on the temperature of the switching element, when the load is light, the switching element does not exceed the allowable operating temperature range, so the temperature of the switching element is detected and the temperature falls below a predetermined temperature. In addition, the resistance value of the gate line is increased to suppress the generation of switching noise.
（第１の実施形態）
　図２は、本発明に係る電源装置の一実施形態の構成を示す図であり、図１（Ａ）の模式図に対応している。
　本実施形態では、電源として直流電源２を用い、負荷５として、液晶テレビジョン装置や液晶表示装置のバックライトに使用されるＬＥＤ（発光ダイオード）５１を対象にした場合について説明するが、電源としては電池でもよく、また、負荷５としては、バックライトのＬＥＤに限らず種々の負荷を対象とすることができる。本実施形態の電源装置１は、ＤＣ－ＤＣコンバータ３、および、ゲート制御回路４、負荷電流検出回路６を備えている。ゲート制御回路４の破線で囲んだ構成をＩＣ（集積回路）で構成することも可能である。 (First embodiment)
FIG. 2 is a diagram illustrating a configuration of an embodiment of a power supply device according to the present invention, and corresponds to the schematic diagram of FIG.
In the present embodiment, a case where a direct current power source 2 is used as a power source and an LED (light emitting diode) 51 used for a backlight of a liquid crystal television device or a liquid crystal display device is used as a load 5 will be described. The battery 5 may be a battery, and the load 5 is not limited to the LED of the backlight but can be various loads. The power supply device 1 of this embodiment includes a DC-DC converter 3, a gate control circuit 4, and a load current detection circuit 6. The configuration surrounded by the broken line of the gate control circuit 4 may be configured by an IC (integrated circuit).
　ＤＣ－ＤＣコンバータ３は、直流電源２から入力電圧Ｖinが印加され入力電流Ｉinが供給される。直流電源２の一方の出力端は接地されている。ＤＣ－ＤＣコンバータ３は、直流電源２の出力端に並列接続されたコンデンサ３１と、コンデンサ３１の一方の直流ラインに接続されたインダクタ３２と、インダクタ３２の後段に設けたスイッチング素子３３と、スイッチング素子３３の後段に設けた逆流防止用のダイオード３４と、平滑用コンデンサ３５とを備えている。平滑用コンデンサ３５の両端が電源装置の出力端子に相当し、その後段には負荷５が接続される。 The DC-DC converter 3 is supplied with an input voltage Vin from a DC power supply 2 and is supplied with an input current Iin. One output terminal of the DC power supply 2 is grounded. The DC-DC converter 3 includes a capacitor 31 connected in parallel to the output terminal of the DC power supply 2, an inductor 32 connected to one DC line of the capacitor 31, a switching element 33 provided at the subsequent stage of the inductor 32, and switching A backflow prevention diode 34 and a smoothing capacitor 35 provided in the subsequent stage of the element 33 are provided. Both ends of the smoothing capacitor 35 correspond to output terminals of the power supply device, and a load 5 is connected to the subsequent stage.
　インダクタ３２は、直流電源２とコンデンサ３１から供給された電圧にしたがって流れる電流をエネルギーとして蓄え、起電力を発生させるためのインダクタンス要素である。スイッチング素子３３は、例えばＮチャンネルの電界効果トランジスタ（ＦＥＴ）で構成され、ゲートにハイレベルの信号が供給されてオンし、ゲートにローレベルの信号が供給されてオフする。スイッチング素子３３のゲートへは、ゲート制御回路４からのゲート信号が供給される。スイッチング素子３３のスイッチング周波数は、通常、数十ｋＨｚ～数ＭＨｚが一般的に用いられるため、スイッチング素子３３からのノイズを少なくすることがＥＭＩ対策として重要になる。 The inductor 32 is an inductance element for generating an electromotive force by storing a current flowing according to a voltage supplied from the DC power supply 2 and the capacitor 31 as energy. The switching element 33 is composed of, for example, an N-channel field effect transistor (FET), and is turned on when a high level signal is supplied to the gate, and is turned off when a low level signal is supplied to the gate. A gate signal from the gate control circuit 4 is supplied to the gate of the switching element 33. Since the switching frequency of the switching element 33 is generally several tens of kHz to several MHz, it is important to reduce noise from the switching element 33 as an EMI countermeasure.
　ゲート制御回路４は、本実施形態では、ＤＣ－ＤＣコンバータ３の出力電圧に応じて、スイッチング素子３３へ供給するゲート信号のデューティ比を変更し、ＤＣ－ＤＣコンバータ３の出力電圧が所定の値となるように制御している。すなわち、電源装置は、出力電圧によるフィードバック制御系を構成している。ＤＣ－ＤＣコンバータ３の出力電圧の所定の値は、例えば、負荷となるＬＥＤが十分点灯する電圧に設定される。ゲート制御回路４は、抵抗４１、４２、誤差増幅器４３、基準電圧発生回路４４、パルス幅変調（ＰＷＭ）回路４５、ゲート抵抗値変更回路４６、閾値電圧発生回路４７、比較器４８を備えている。 In this embodiment, the gate control circuit 4 changes the duty ratio of the gate signal supplied to the switching element 33 in accordance with the output voltage of the DC-DC converter 3, and the output voltage of the DC-DC converter 3 is a predetermined value. It is controlled to become. That is, the power supply apparatus constitutes a feedback control system based on the output voltage. For example, the predetermined value of the output voltage of the DC-DC converter 3 is set to a voltage at which the LED as a load is sufficiently lit. The gate control circuit 4 includes resistors 41 and 42, an error amplifier 43, a reference voltage generation circuit 44, a pulse width modulation (PWM) circuit 45, a gate resistance value change circuit 46, a threshold voltage generation circuit 47, and a comparator 48. .
　ＤＣ－ＤＣコンバータ３の出力電圧Ｖoutは、抵抗４１、４２によって分圧され、分圧された電圧が誤差増幅器４３の反転入力端子に接続される。誤差増幅器４３の非反転入力端子には基準電圧発生回路４４からの基準電圧Ｖrが入力される。基準電圧Ｖrと分圧された電圧との差電圧が誤差増幅器４３の出力信号として出力される。誤差増幅器４３の出力信号はパルス幅変調回路４５に入力され、パルス幅変調回路４５は、誤差増幅器４３の出力信号の大きさに応じて、所定のパルス周波数（数十ｋＨｚ～数ＭＨｚ）を有するパルスのデューティ比を変更したパルス信号を出力する。パルス幅変調回路４５からのパルス信号は、ゲート抵抗値変更回路４６を介してＤＣ－ＤＣコンバータ３のスイッチング素子３３のゲートに加えられる。 The output voltage Vout of the DC-DC converter 3 is divided by the resistors 41 and 42, and the divided voltage is connected to the inverting input terminal of the error amplifier 43. The reference voltage Vr from the reference voltage generation circuit 44 is input to the non-inverting input terminal of the error amplifier 43. A difference voltage between the reference voltage Vr and the divided voltage is output as an output signal of the error amplifier 43. The output signal of the error amplifier 43 is input to the pulse width modulation circuit 45, and the pulse width modulation circuit 45 has a predetermined pulse frequency (several tens of kHz to several MHz) according to the magnitude of the output signal of the error amplifier 43. A pulse signal with a changed pulse duty ratio is output. The pulse signal from the pulse width modulation circuit 45 is applied to the gate of the switching element 33 of the DC-DC converter 3 through the gate resistance value changing circuit 46.
　パルス幅変調回路４５からのパルス信号は、スイッチング素子３３のゲート信号となるため、スイッチング素子３３は、パルス幅変調回路４５からのパルス信号のデューティ比に応じたオン時間でオンする。本実施形態では、ＤＣ－ＤＣコンバータ３の入力電圧Ｖinに対する出力電圧Ｖoutの比は、パルス幅変調回路４５からのパルス信号のデューティ比をＤ（０≦Ｄ＜１）とした場合、Ｖout／Ｖin＝１／（１－Ｄ）となる。したがって、パルス幅変調回路４５からのパルス信号のデューティ比が大きいほど、ＤＣ－ＤＣコンバータ３の出力電圧Ｖoutが大きくなる。このため、出力電圧Ｖoutが小さい場合は、パルス幅変調回路４５からのパルス信号のデューティ比が大きくなるように作用する。 Since the pulse signal from the pulse width modulation circuit 45 becomes the gate signal of the switching element 33, the switching element 33 is turned on in an on time corresponding to the duty ratio of the pulse signal from the pulse width modulation circuit 45. In this embodiment, the ratio of the output voltage Vout to the input voltage Vin of the DC-DC converter 3 is Vout / Vin when the duty ratio of the pulse signal from the pulse width modulation circuit 45 is D (0 ≦ D <1). = 1 / (1-D). Therefore, the output voltage Vout of the DC-DC converter 3 increases as the duty ratio of the pulse signal from the pulse width modulation circuit 45 increases. Therefore, when the output voltage Vout is small, the duty ratio of the pulse signal from the pulse width modulation circuit 45 is increased.
　一方、比較器４８の反転入力端子には、抵抗６１の電圧が入力され、比較器４８の非反転入力端子には閾値電圧発生回路４７からの閾値電圧Ｖthが入力される。抵抗６１は一方が負荷５に直列接続され他方が接地されているため、ＤＣ－ＤＣコンバータ３の出力電流Ｉoutに等しい負荷５の負荷電流ＩＦは、抵抗６１での電圧値ＶＩＦとして検知される。なお、負荷電流が直流ではなくパルス電流などの交流分を含む電流の場合は、比較器４８の前段に、図示しない平均値回路やローパスフィルタを設けることで、比較器４８の非反転入力端子に、負荷５を流れる負荷電流の平均値に応じた電圧が入力されるようにする。抵抗６１は負荷電流検出回路６を構成している。 On the other hand, the voltage of the resistor 61 is input to the inverting input terminal of the comparator 48, and the threshold voltage Vth from the threshold voltage generating circuit 47 is input to the non-inverting input terminal of the comparator 48. Because One resistor 61 the other is connected in series to the load 5 is grounded, the load current I F equal load 5 to the output current Iout of the DC-DC converter 3 is detected as a voltage value V IF at the resistor 61 The When the load current is not a direct current but includes an alternating current such as a pulse current, an average value circuit and a low-pass filter (not shown) are provided in front of the comparator 48 so that the non-inverting input terminal of the comparator 48 is provided. The voltage corresponding to the average value of the load current flowing through the load 5 is input. The resistor 61 constitutes the load current detection circuit 6.
　比較器４８では、閾値電圧Ｖthと抵抗６１との電圧ＶＩＦが比較され、比較信号として、ハイレベルまたはローレベルの２値信号が出力される。比較器４８からの２値出力信号はゲート抵抗値変更回路４６に入力され、スイッチング素子３３のゲートラインの抵抗値を変更するために用いられる。ゲートラインの抵抗値の変更については、後で詳述する。 In the comparator 48, the voltage V IF of the threshold voltage Vth and the resistor 61 are compared, as a comparison signal, a binary signal of high level or low level is outputted. The binary output signal from the comparator 48 is input to the gate resistance value changing circuit 46 and used to change the resistance value of the gate line of the switching element 33. The change of the resistance value of the gate line will be described in detail later.
　次に、ＤＣ－ＤＣコンバータ３の各部の動作について図３を参照して説明する。図３は、図２に示す電源装置の各部の電圧波形または電流波形を示す図であり、ＤＣ－ＤＣコンバータ３の入力電圧Ｖin、入力電流Ｉin、スイッチング素子３３のゲート信号Ｑ、スイッチング素子３３を流れる電流ＩＱ、ダイオード３４を流れる電流ＩＤ、インダクタ３２を流れる電流ＩＬ、コンデンサ３１を流れる電流ＩＣ１、平滑用コンデンサ３５を流れる電流ＩＣ２、ＤＣ－ＤＣコンバータ３の出力電圧Ｖout、および、出力電流Ｉoutの各波形を示している。 Next, the operation of each part of the DC-DC converter 3 will be described with reference to FIG. FIG. 3 is a diagram showing the voltage waveform or current waveform of each part of the power supply device shown in FIG. 2. The input voltage Vin, the input current Iin of the DC-DC converter 3, the gate signal Q of the switching element 33, and the switching element 33 are shown. Flowing current I Q , current I D flowing through diode 34, current I L flowing through inductor 32, current I C1 flowing through capacitor 31, current I C2 flowing through smoothing capacitor 35, output voltage Vout of DC-DC converter 3, and Each waveform of the output current Iout is shown.
　スイッチング素子３３のゲート信号Ｑによって、スイッチング素子３３は時刻ｔ１でオン、時刻ｔ２でオフ、時刻ｔ３でオン、時刻ｔ４でオフ、時刻ｔ５でオン、時刻ｔ６でオフする。まず、図３の時刻t１においてスイッチング素子３３がオンした場合、直流電源２、インダクタ３２、スイッチング素子３３、および直流電源２のパスが生じる。このため、直流電源２の電圧がインダクタ３２、スイッチング素子３３に印加され、インダクタンス素子としてのインダクタ３２の電流ＩＬが増加する。同様に、スイッチング素子３３に電流ＩＱが流れる。スイッチング素子３３がオンしている期間（ton）は、電流ＩＬと電流ＩＱとは同じ大きさである。インダクタ３２には電流ＩＬの増加とともに、インダクタ３２に蓄えられるエネルギーは増加する。 By the gate signal Q of the switching element 33, the switching element 33 is turned on at time t1, turned off at time t2, turned on at time t3, turned off at time t4, turned on at time t5, and turned off at time t6. First, when the switching element 33 is turned on at time t1 in FIG. 3, a path of the DC power source 2, the inductor 32, the switching element 33, and the DC power source 2 is generated. Therefore, the voltage of the DC power supply 2 is an inductor 32, is applied to the switching element 33, the current I L of the inductor 32 as an inductance element is increased. Similarly, a current IQ flows through the switching element 33. Period when the switching element 33 is ON (ton), the current I L and the current I Q is the same size. With increasing current I L in the inductor 32, the energy stored in the inductor 32 increases.
　時刻ｔ２において、スイッチング素子３３がオフすると、直流電源２、インダクタ３２、ダイオード３４、および、負荷５と平滑用コンデンサ３５との並列回路、直流電源２のパスが生じる。そして、インダクタ３２に蓄積されていたエネルギーに直流電源２からの電力がダイオード３４を介して平滑用コンデンサ３５と負荷５とに供給される。ダイオード３４を流れる電流ＩＤには、平滑用コンデンサ３５に流れる電流ＩＣ２と負荷電流を足した電流が流れる。このため、ダイオード３４を流れる電流ＩＤに流れる電流から負荷電流ＩＦを差し引いた電流が平滑用コンデンサ３５に流れ込むが、時間とともに平滑用コンデンサ３５に充電されて減少していく。また、ＤＣ－ＤＣコンバータ３の出力電圧Ｖoutは入力電圧Ｖinよりも高くなる。 When the switching element 33 is turned off at time t2, the DC power source 2, the inductor 32, the diode 34, the parallel circuit of the load 5 and the smoothing capacitor 35, and the path of the DC power source 2 are generated. Then, power from the DC power source 2 is supplied to the smoothing capacitor 35 and the load 5 via the diode 34 as energy stored in the inductor 32. The current ID flowing through the diode 34 is a current obtained by adding the current IC2 flowing through the smoothing capacitor 35 and the load current. Therefore, current obtained by subtracting the load current I F from the current flowing through the current I D flowing through the diode 34 but flows into the smoothing capacitor 35, decreasing charged in the smoothing capacitor 35 with time. Further, the output voltage Vout of the DC-DC converter 3 becomes higher than the input voltage Vin.
　次に、時刻ｔ３でスイッチング素子３３がオフすると、時刻t１の時と同様に、直流電源２、インダクタ３２、スイッチング素子３３、および直流電源２のパスが生じ、同様の電流が流れる。なお、スイッチング素子３３がオフしている期間中は平滑用コンデンサ３５から負荷５に対して負荷電流を供給する。このように、スイッチング素子３３がオンの状態の時もオフの状態の時も、負荷５には電力が供給される。コンデンサ３１に流れる電流ＩＣ１および平滑用コンデンサ３５に流れる電流ＩＣ２は、スイッチング素子３３のオン・オフに応じた交流成分を持つことになる。 Next, when the switching element 33 is turned off at time t3, the path of the DC power source 2, the inductor 32, the switching element 33, and the DC power source 2 is generated as in the time t1, and the same current flows. During the period when the switching element 33 is off, a load current is supplied from the smoothing capacitor 35 to the load 5. In this way, power is supplied to the load 5 both when the switching element 33 is on and when it is off. The current I C1 flowing through the capacitor 31 and the current I C2 flowing through the smoothing capacitor 35 have an AC component corresponding to the on / off state of the switching element 33.
　本実施形態において、先述したように負荷５は、液晶テレビジョン装置や液晶表示装置のバックライトに使用されるＬＥＤ（発光ダイオード）５１を対象にしているが、バックライトの明るさは、調光信号生成回路９からのスイッチング信号によって調整される。より具体的には、ＬＥＤ５１を流れる電流は、電界効果トランジスタ（ＦＥＴ）などのスイッチング素子５２によって、視覚上問題のない周波数でスイッチングされる。そして、スイッチング信号のオンデューティによって明るさが調整される。なお、スイッチング素子５２のスイッチング周波数は高くとも数百Ｈｚであり、ＤＣ－ＤＣコンバータ３のスイッチング素子３３のスイッチング周波数よりかなり低い周波数が用いられる。 In the present embodiment, as described above, the load 5 is directed to the LED (light emitting diode) 51 used for the backlight of the liquid crystal television device or the liquid crystal display device, but the brightness of the backlight is dimming. It is adjusted by the switching signal from the signal generation circuit 9. More specifically, the current flowing through the LED 51 is switched at a frequency with no visual problem by a switching element 52 such as a field effect transistor (FET). The brightness is adjusted by the on-duty of the switching signal. Note that the switching frequency of the switching element 52 is at most several hundred Hz, and a frequency considerably lower than the switching frequency of the switching element 33 of the DC-DC converter 3 is used.
　図４は、図２に示す電源装置の負荷に流れる電流を示す図であり、図４（Ａ）は、バックライトを明るく点灯させる場合であり、スイッチング素子５２のイッチング信号のオンデューティを１００％としている。この場合、負荷電流ＩＦはほぼ直流電流となり、平均負荷電流ＩＦＡＶＥも大きくなる。また、図４（Ｂ）は、バックライトを明るく点灯させる必要がない場合を示しており、スイッチング素子５２のイッチング信号のオンデューティを例えば５０％としている。この場合、負荷電流ＩＦはほぼパルス状の電流となり、平均負荷電流ＩＦＡＶＥはオンデューティ１００％の時よりも小さくなる。しかしながら、図４（Ａ）に示す平均電流ＩＦＡＶＥの大きな場合よりも、図４（Ｂ）に示す平均電流ＩＦＡＶＥが小さな場合の方が、パルス電流が流れるためＥＭＩが悪くなる場合がある。さらに、ＬＥＤ駆動のデューティに応じてＤＣ－ＤＣコンバータ３の出力電圧を高める制御を行う場合は、デューティが小さく平均電流が小さい場合でも最大電流値が大きくなってＥＭＩが悪くなる場合がある。 4 is a diagram illustrating a current flowing through the load of the power supply device illustrated in FIG. 2. FIG. 4A illustrates a case where the backlight is lit brightly, and the on-duty of the switching signal of the switching element 52 is 100%. It is said. In this case, the load current I F becomes almost a direct current, the average load current I FAVE also increased. FIG. 4B shows a case where the backlight does not need to be lit brightly, and the on-duty of the switching signal of the switching element 52 is, for example, 50%. In this case, the load current I F becomes substantially pulse-shaped current, the average load current I FAVE is smaller than when the on-duty of 100%. However, since the pulse current flows when the average current I FAVE shown in FIG. 4B is smaller than when the average current I FAVE shown in FIG. 4A is large, the EMI may deteriorate. Further, when control is performed to increase the output voltage of the DC-DC converter 3 in accordance with the duty of LED driving, even if the duty is small and the average current is small, the maximum current value may be large and EMI may deteriorate.
　そして、負荷電流ＩＦが大きな場合、すなわち高負荷の場合、ゲート制御回路４は、ＤＣ－ＤＣコンバータ３の出力電圧ＶoutをＬＥＤ５１の点灯に必要な電圧値に維持しようとするために、スイッチング素子３３のデューティ比Ｄが大きくなるように作用する。これによって、スイッチング素子３３を流れる電流ＩＱは大きくなり、ＤＣ－ＤＣコンバータ３のスイッチング素子３３の温度が上昇する。 When the load current IF is large, that is, when the load is high, the gate control circuit 4 tries to maintain the output voltage Vout of the DC-DC converter 3 at a voltage value necessary for lighting the LED 51. The duty ratio D of 33 is increased. Thereby, current I Q flowing through the switching element 33 increases, the temperature of the switching element 33 of the DC-DC converter 3 is increased.
　一方、負荷電流ＩＦが小さな場合、すなわち低負荷の場合、ゲート制御回路４は、ＤＣ－ＤＣコンバータ３の出力電圧ＶoutをＬＥＤ５１の点灯に必要な電圧値に維持しようとするが、負荷電流ＩＦが小さいため、スイッチング素子３３のデューティ比Ｄを大きくする必要はなく、小さな値を維持しようとする。これによって、スイッチング素子３３を流れる電流ＩＱは小さくなり、スイッチング素子３３の温度は大きく上昇することはない。この場合、ＦＥＴ等のスイッチング素子３３の温度や半田面の温度は、基準値に対して比較的マージンがある。したがって、本実施形態では、負荷電流ＩＦが小さな軽負荷の場合に、ＤＣ－ＤＣコンバータ３のスイッチング素子３３を駆動するゲートラインの抵抗値を大きくすることによってゲートパルス波形をなまらせ、スイッチング素子の立ち上がり時間と立ち下がり時間を遅くし、スイッチングによる高周波ノイズの発生を抑えている。 On the other hand, when the load current IF is small, that is, when the load is low, the gate control circuit 4 tries to maintain the output voltage Vout of the DC-DC converter 3 at a voltage value necessary for lighting the LED 51. Since F is small, it is not necessary to increase the duty ratio D of the switching element 33 and an attempt is made to maintain a small value. Thereby, current I Q flowing through the switching element 33 is decreased, the temperature of the switching element 33 is not large to increase. In this case, the temperature of the switching element 33 such as an FET and the temperature of the solder surface have a relatively margin with respect to the reference value. Therefore, in this embodiment, when the load current IF is small, the gate pulse waveform is smoothed by increasing the resistance value of the gate line that drives the switching element 33 of the DC-DC converter 3, and the switching element The rise time and fall time are slowed down to suppress the generation of high frequency noise due to switching.
　図５は、図２に示す電源装置のゲート抵抗値変更回路とゲート信号波形を説明するための図であり、図２とともに説明する。図２において、比較器４８では、閾値電圧Ｖthと抵抗６１の電圧ＶＩＦが比較され、比較器４８からの２値出力信号はゲート抵抗値変更回路４６に入力される。ゲート抵抗値変更回路４６は、スイッチング素子３３のゲートＧに接続された抵抗Ｒ１、Ｒ２と、これらの抵抗Ｒ１、Ｒ２を切換えるスイッチＳＷから構成されている。抵抗Ｒ２の抵抗値は抵抗Ｒ１の抵抗値よりも大きく、例えば、抵抗Ｒ１は０Ω、抵抗Ｒ２は２００Ωとなっている。 FIG. 5 is a diagram for explaining a gate resistance value changing circuit and a gate signal waveform of the power supply device shown in FIG. 2, and will be described together with FIG. In FIG. 2, the comparator 48 compares the threshold voltage Vth and the voltage V IF of the resistor 61, and the binary output signal from the comparator 48 is input to the gate resistance value changing circuit 46. Gate resistance value changing circuit 46, and a switch SW for switching the resistors R 1, R 2 connected to the gate G of the switching element 33, these resistors R 1, R 2. The resistance value of the resistor R 2 is greater than the resistance value of the resistor R 1, for example, resistor R 1 is 0 .OMEGA, resistance R 2 has a 200 [Omega.
　そして、抵抗６１の電圧ＶＩＦが閾値電圧Ｖthより大きい場合、すなわち負荷電流ＩＦが所定値よりも大きい場合は、比較器４８はローレベルの信号を出力し、ゲート抵抗値変更回路４６は、スイッチング素子３３のゲートラインの抵抗値が小さい抵抗Ｒ１の値となるようにスイッチＳＷを切換える。これにより、スイッチング素子３３のゲートには、立ち上がりと立ち下がりが傾斜していない良好なパルス波形のゲート信号が印加され、スイッチング素子の温度上昇が抑えられる。 Then, when the voltage V IF resistor 61 is greater than the threshold voltage Vth, that is, when the load current I F is larger than the predetermined value, the comparator 48 outputs a low level signal, the gate resistance value changing circuit 46, switching the switch SW so that the resistance value of the gate line becomes a value of less resistance R 1 of the switching element 33. As a result, a gate signal having a good pulse waveform in which the rise and fall are not inclined is applied to the gate of the switching element 33, and the temperature rise of the switching element is suppressed.
　また、抵抗６１の電圧ＶＩＦが閾値電圧Ｖthより小さい場合、すなわち負荷電流ＩＦが所定値よりも小さい場合は、比較器４８はハイの信号を出力し、ゲート抵抗値変更回路４６は、スイッチング素子３３のゲートラインの抵抗値が大きい３のゲートラインの抵抗とスイッチング素子３３のゲートソース間の容量によるＲＣ回路の時定数が大きくなるため、ゲート信号の波形は、図５に示すように、立ち上がりと立ち下がりが傾斜した、いわゆるなまった形状となる。これによって、スイッチング素子３３の温度は上昇するものの、発生ノイズは抑制することができる。 Further, when the voltage V IF resistor 61 is smaller than the threshold voltage Vth, that is, when the load current I F is smaller than the predetermined value, the comparator 48 outputs a high signal, the gate resistance value changing circuit 46, switching Since the time constant of the RC circuit is large due to the resistance between the gate line of the element 33 having a large gate line resistance and the capacitance between the gate and source of the switching element 33, the waveform of the gate signal is as shown in FIG. It becomes a so-called sluggish shape with rising and falling slopes. Thereby, although the temperature of the switching element 33 rises, the generated noise can be suppressed.
　閾値電圧Ｖthの大きさ、負荷電流ＩＦ検出のための抵抗６１の抵抗値、抵抗Ｒ２の抵抗値は、スイッチング素子３３が許容温度範囲内に収まるように設定される。なお、本実施形態では、スイッチング素子３３のゲートラインの抵抗値として２つの値を切換えるようにしているが、３つ以上の抵抗値を切換えるようにしてもよく、さらに、負荷電流ＩＦの大きさに応じてゲートラインの抵抗値を連続的に変更するようにしてもよい。 The magnitude of the threshold voltage Vth, the resistance value of the resistor 61 for the load current I F detected, the resistance value of the resistor R 2 is set so that the switching element 33 falls within the allowable temperature range. In the present embodiment, although the switch the two values as the resistance value of the gate line of the switching element 33, may be switched to three or more resistance, further, the magnitude of the load current I F Accordingly, the resistance value of the gate line may be changed continuously.
（第２の実施形態）
　図６は、本発明に係る電源装置の他の実施形態の構成を示す図であり、図１（Ｂ）の模式図に対応している。
　本実施形態では、電源として直流電源２を用い、負荷５として、第１の実施形態と同様に、液晶テレビジョン装置や液晶表示装置のバックライトに使用されるＬＥＤ（発光ダイオード）５１を対象にした場合について説明するが、電源としては電池でもよく、また、負荷５としては、バックライトのＬＥＤに限らず種々の負荷を対象とすることができる。本実施形態の電源装置１は、ＤＣ－ＤＣコンバータ３、および、ゲート制御回路４、素子温度検出回路７を備えている。第１の実施形態と同じく、ゲート制御回路４の破線で囲んだ構成をＩＣ（集積回路）で構成することも可能である。 (Second Embodiment)
FIG. 6 is a diagram showing the configuration of another embodiment of the power supply device according to the present invention, and corresponds to the schematic diagram of FIG.
In the present embodiment, a direct-current power source 2 is used as a power source, and an LED (light emitting diode) 51 used as a backlight of a liquid crystal television device or a liquid crystal display device is used as a load 5 as in the first embodiment. However, the power source may be a battery, and the load 5 is not limited to the LED of the backlight but can be various loads. The power supply device 1 of this embodiment includes a DC-DC converter 3, a gate control circuit 4, and an element temperature detection circuit 7. As in the first embodiment, the configuration surrounded by the broken line of the gate control circuit 4 can be configured by an IC (integrated circuit).
　本実施形態は、ＤＣ－ＤＣコンバータ３、ゲート制御回路４の基本的な構成は図２に示した第１の実施形態と同じであり、第１の実施形態では、負荷電流ＩＦの大きさ応じてＤＣ－ＤＣコンバータ３のスイッチング素子３３のゲート抵抗値を変更しているのに対して、本実施形態では、ＤＣ－ＤＣコンバータ３のスイッチング素子３３の温度に応じてスイッチング素子３３のゲート抵抗値を変更している。以下、第１の実施形態と同じ構成についてはその説明を省略し、異なる構成について説明する。 In the present embodiment, the basic configuration of the DC-DC converter 3 and the gate control circuit 4 is the same as that of the first embodiment shown in FIG. 2, and in the first embodiment, the magnitude of the load current IF is large. The gate resistance value of the switching element 33 of the DC-DC converter 3 is changed accordingly, whereas in the present embodiment, the gate resistance of the switching element 33 depends on the temperature of the switching element 33 of the DC-DC converter 3. The value has been changed. Hereinafter, the description of the same configuration as that of the first embodiment will be omitted, and a different configuration will be described.
　第１の実施形態では、負荷５の負荷電流ＩＦを検出するために、負荷電流検出回路６を設けていたが、本実施形態では、負荷電流検出回路６に代えて、ＤＣ－ＤＣコンバータ３のスイッチング素子３３の温度を検出するための素子温度検出回路７を設けている。素子温度検出回路７は、例えば、スイッチング素子３３の近傍にサーミスタ７１を設け、定電圧をサーミスタ７１と抵抗７２によって分圧し、この分圧した電圧ＶＴを比較器４８の反転入力端子に加えている。 In the first embodiment, in order to detect the load current I F of the load 5, it had provided the load current detecting circuit 6, in the present embodiment, instead of the load current detecting circuit 6, DC-DC converter 3 An element temperature detection circuit 7 for detecting the temperature of the switching element 33 is provided. Element temperature detecting circuit 7, for example, a thermistor 71 provided in the vicinity of the switching element 33, a constant voltage dividing by the thermistor 71 and the resistor 72, added to the divided voltage V T to the inverting input terminal of the comparator 48 Yes.
　サーミスタ７１は、スイッチング素子３３の温度上昇とともにその抵抗値が減少するため、サーミスタ７１と抵抗７２の分圧抵抗回路によって定電圧を分圧することによって得られた電圧ＶＴは、スイッチング素子３３の温度上昇とともにその値が大きくなる。そして、負荷５の負荷電流ＩＦが大きくなってスイッチング素子３３の温度が高くなると、素子温度検出回路７からの電圧ＶＴは大きくなる。電圧ＶＴが閾値電圧Ｖthよりも大きい場合、すなわち、スイッチング素子３３の温度が所定値よりも高い場合は、比較器４８はローレベルの信号を出力し、ゲート抵抗値変更回路４６は、スイッチング素子３３のゲートラインの抵抗値が小さい抵抗Ｒ１の値となるようにスイッチＳＷを切換える。これにより、スイッチング素子３３のゲートには、立ち上がりと立ち下がりが傾斜していない良好なパルス波形のゲート信号が印加され、スイッチング素子３３の温度上昇が抑えられる。 Since the resistance value of the thermistor 71 decreases as the temperature of the switching element 33 rises, the voltage V T obtained by dividing the constant voltage by the voltage dividing resistor circuit of the thermistor 71 and the resistor 72 is the temperature of the switching element 33. The value increases with the rise. When the temperature of the switching element 33 increases the load current I F of the load 5 increases, the greater the voltage V T from the element temperature detecting circuit 7. If the voltage V T is greater than the threshold voltage Vth, i.e., when the temperature of the switching element 33 is higher than the predetermined value, the comparator 48 outputs a low level signal, the gate resistance value changing circuit 46, the switching element the resistance of the gate line 33 assumes a value smaller resistor R 1 so switches the switch SW. As a result, a gate signal having a good pulse waveform in which the rising and falling edges are not inclined is applied to the gate of the switching element 33, and the temperature rise of the switching element 33 is suppressed.
　また、素子温度検出回路７からの電圧ＶＴが閾値電圧Ｖthより小さい場合、すなわちスイッチング素子３３の温度が所定値よりも低い場合は、比較器４８はハイレベルの信号を出力し、ゲート抵抗値変更回路４６は、スイッチング素子３３のゲートラインの抵抗値が大きい抵抗Ｒ２の値となるようにスイッチＳＷを切換える。これにより、スイッチング素子３３のゲートラインの抵抗とスイッチング素子３３のゲートソース間の容量によるＲＣ回路の時定数が大きくなるため、ゲート信号の波形は、図５に示すように、立ち上がりと立ち下がりが傾斜した、いわゆるなまった形状となる。これによって、スイッチング素子３３の温度は上昇するものの、発生ノイズは抑制することができる。 Further, when the voltage V T less than the threshold voltage Vth of the element temperature detecting circuit 7, that is, when the temperature of the switching element 33 is lower than a predetermined value, the comparator 48 outputs a high level signal, the gate resistance changing circuit 46 switches the switch SW to a value of the resistor R 2 the resistance value is large gate line of the switching element 33. As a result, the time constant of the RC circuit due to the resistance of the gate line of the switching element 33 and the capacitance between the gate and source of the switching element 33 increases, so that the waveform of the gate signal rises and falls as shown in FIG. The so-called slanted shape is inclined. Thereby, although the temperature of the switching element 33 rises, the generated noise can be suppressed.
　閾値電圧Ｖthの大きさ、サーミスタ７１の特性と抵抗値、抵抗７２の抵抗値、抵抗Ｒ２の抵抗値、スイッチング素子３３が許容温度範囲となるように設定される。なお、本実施形態では、スイッチング素子３３のゲートラインの抵抗値として２つの値を切換えるようにしているが、第１の実施形態と同様に、３つ以上の抵抗値を切換えるようにしてもよく、さらに、スイッチング素子３３の温度に応じてゲートラインの抵抗値を連続的に変更するようにしてもよい。 The magnitude of the threshold voltage Vth, characteristic resistance value of the thermistor 71, the resistance value of the resistor 72, the resistance value of the resistor R 2, is set so that the switching element 33 becomes the allowable temperature range. In the present embodiment, two values are switched as the resistance value of the gate line of the switching element 33. However, as in the first embodiment, three or more resistance values may be switched. Furthermore, the resistance value of the gate line may be continuously changed according to the temperature of the switching element 33.
（第３の実施形態）
　図７は、本発明に係る電源装置をテレビジョン装置の適用した際の一実施形態の構成を示す図であり、図１（Ｃ）の模式図に対応している。
　本実施形態では、電源として直流電源２を用い、負荷５として、第１の実施形態と同様に、液晶テレビジョン装置のバックライトに使用されるＬＥＤ（発光ダイオード）５１を対象にしている。本実施形態のテレビジョン装置は、ＤＣ－ＤＣコンバータ３、ゲート制御回路４、および、調光信号生成回路９を備えている。第１、第２の実施形態と同じく、ゲート制御回路４の破線で囲んだ構成をＩＣ（集積回路）で構成することも可能である。 (Third embodiment)
FIG. 7 is a diagram illustrating a configuration of an embodiment when a television apparatus is applied to the power supply device according to the present invention, and corresponds to the schematic diagram of FIG.
In the present embodiment, a DC power source 2 is used as a power source, and an LED (light emitting diode) 51 used as a backlight of a liquid crystal television device is used as a load 5 as in the first embodiment. The television apparatus of this embodiment includes a DC-DC converter 3, a gate control circuit 4, and a dimming signal generation circuit 9. As in the first and second embodiments, the configuration surrounded by the broken line of the gate control circuit 4 can be configured by an IC (integrated circuit).
　本実施形態は、ＤＣ－ＤＣコンバータ３、ゲート制御回路４の基本的な構成は図２に示した第１の実施形態と同じであり、第１の実施形態では、負荷電流ＩＦの大きさ応じてＤＣ－ＤＣコンバータ３のスイッチング素子３３のゲート抵抗値を変更しているのに対して、本実施形態では、テレビジョン装置において、映画モードなどの特定の映像モードでは、バックライトの消費電流が小さいことに注目し、映像信号のモードに応じて、ＤＣ－ＤＣコンバータ３のスイッチング素子３３のゲート抵抗値を変更している。以下、第１の実施形態と同じ構成についてはその説明を省略し、異なる構成について説明する。 In the present embodiment, the basic configuration of the DC-DC converter 3 and the gate control circuit 4 is the same as that of the first embodiment shown in FIG. 2, and in the first embodiment, the magnitude of the load current IF is large. Whereas the gate resistance value of the switching element 33 of the DC-DC converter 3 is changed accordingly, in the present embodiment, in the television device, the current consumption of the backlight in a specific video mode such as a movie mode. Note that the gate resistance value of the switching element 33 of the DC-DC converter 3 is changed according to the mode of the video signal. Hereinafter, the description of the same configuration as that of the first embodiment will be omitted, and a different configuration will be described.
　本実施形態では、ゲート制御回路４は、映像信号モード入力端子から入力されたモード信号を受けるモード解析部４９を有しており、第１の実施形態が備えていた閾値電圧発生回路４７、および、比較器４８を備えていない。また、調光信号生成回路９にも映像信号モード入力端子から入力されたモード信号が入力される。 In the present embodiment, the gate control circuit 4 includes a mode analysis unit 49 that receives a mode signal input from the video signal mode input terminal. The threshold voltage generation circuit 47 included in the first embodiment, and The comparator 48 is not provided. The mode signal input from the video signal mode input terminal is also input to the dimming signal generation circuit 9.
　調光信号生成回路９は、映像信号モード入力端子から入力されたモード信号に応じて、ＬＥＤ５１を流れる電流を調整する。例えば、モード信号が映画モードである場合は、オンデューティ比の小さなスイッチング信号をスイッチング素子５２に入力することによって、ＬＥＤ５１を流れる電流を小さく抑え、図示しない液晶画面に暗い映像を表示する。また、モード信号がダイナミックモードでは、オンデューティ比の大きなスイッチング信号をスイッチング素子５２に入力することによって、ＬＥＤ５１を流れる電流を大きくし、コントラストの大きな映像を表示する。このように、バックライトは、所定の映像モードなどの負荷モードに応じて負荷電流の大きさが変更される。 The dimming signal generation circuit 9 adjusts the current flowing through the LED 51 in accordance with the mode signal input from the video signal mode input terminal. For example, when the mode signal is the movie mode, by inputting a switching signal having a small on-duty ratio to the switching element 52, the current flowing through the LED 51 is suppressed, and a dark image is displayed on a liquid crystal screen (not shown). When the mode signal is dynamic mode, a switching signal having a large on-duty ratio is input to the switching element 52, whereby the current flowing through the LED 51 is increased and an image with a large contrast is displayed. Thus, the magnitude of the load current of the backlight is changed according to a load mode such as a predetermined video mode.
　ゲート制御回路４のモード解析部４９は、映像信号モード入力端子から入力されたモード信号を解析し、モード信号に応じて、ゲート抵抗値変更回路４６へ抵抗変更信号を出力する。例えば、モード信号が映画モードである場合は、ゲート抵抗値変更回路４６がスイッチング素子３３のゲートラインの抵抗値が大きいＲ２の値となるように抵抗変更信号を出力する。これによって、負荷電流ＩＦが小さい場合は、ゲート信号の波形は、図５に示すように、立ち上がりと立ち下がりが傾斜した、いわゆるなまった形状となる。これによって、スイッチング素子３３の温度は上昇するものの、発生ノイズは抑制することができる。 The mode analysis unit 49 of the gate control circuit 4 analyzes the mode signal input from the video signal mode input terminal, and outputs a resistance change signal to the gate resistance value change circuit 46 according to the mode signal. For example, the mode signal when a movie mode, the gate resistance value changing circuit 46 outputs a resistance change signal to a value of the resistance value is large R 2 gate line of the switching element 33. Thus, when the load current IF is small, the waveform of the gate signal has a so-called distorted shape in which the rising edge and the falling edge are inclined as shown in FIG. Thereby, although the temperature of the switching element 33 rises, the generated noise can be suppressed.
　また、ゲート制御回路４のモード解析部４９は、モード信号がダイナミックモードである場合は、ゲート抵抗値変更回路４６がスイッチング素子３３のゲートラインの抵抗値が小さい抵抗Ｒ１の値となるように抵抗変更信号を出力する。これにより、負荷電流ＩＦが大きい場合は、スイッチング素子３３のゲートには、立ち上がりと立ち下がりが傾斜していない良好なパルス波形のゲート信号が印加され、スイッチング素子３３の温度上昇が抑えられる。 The mode analyzing portion 49 of the gate control circuit 4, if the mode signal is in the dynamic mode, so that the gate resistance value changing circuit 46 becomes a value of the resistor R 1 a small resistance value of the gate line of the switching element 33 Outputs a resistance change signal. As a result, when the load current IF is large, a gate signal having a good pulse waveform in which the rising and falling edges are not inclined is applied to the gate of the switching element 33, and the temperature rise of the switching element 33 is suppressed.
　以上、本実施形態では、映像信号のモードとして、映画モード、ダイナミックモードを例に説明したが、例えば、映像信号のモードはこれに限る必要はない。例えば、映像信号の平均輝度レベルに応じて、所定の値以下の映像信号を表示する場合は、暗モードのモード信号を受信することによって、バックライトの負荷電流ＩＦを小さくするとともに、スイッチング素子３３のゲートラインの抵抗値が大きい抵抗Ｒ２の値となるように制御してもよい。また、明るさセンサーを有するテレビでは、周囲の明るさに応じて暗い映像を表示するモードでは、バックライトの負荷電流ＩＦを小さくするとともに、スイッチング素子３３のゲートラインの抵抗値が大きい抵抗Ｒ２の値となるように制御することができる。 As described above, in this embodiment, the movie mode and the dynamic mode have been described as examples of the video signal mode. However, for example, the video signal mode need not be limited to this. For example, when displaying a video signal of a predetermined value or less according to the average luminance level of the video signal, the backlight load current IF is reduced by receiving the mode signal of the dark mode, and the switching element 33 may be controlled to a value of the resistor R 2 the resistance value is large gate lines. Further, in the television having a brightness sensor, in the mode for displaying the dark image according to the ambient brightness, as well as reduce the load current I F of the backlight, the resistance R the resistance of the gate line is larger switching element 33 It can be controlled to be a value of 2 .
　また、テレビジョン装置の場合は、スイッチング素子３３のゲートラインの抵抗値を変更することによってＤＣ－ＤＣコンバータ３の出力電圧の変動があった際の視覚上の影響を避けるために、シーンチェンジなどの映像切り替えのタイミングで抵抗値を変更することが望ましい。 In the case of a television device, a scene change or the like is performed in order to avoid a visual influence when the output voltage of the DC-DC converter 3 varies by changing the resistance value of the gate line of the switching element 33. It is desirable to change the resistance value at the video switching timing.
１…電源装置、２…直流電源、３…ＤＣ－ＤＣコンバータ、４…ゲート制御回路、５…負荷、６…負荷電流検出回路、７…素子温度検出回路、９…調光信号生成回路、３１…コンデンサ、３２…インダクタ、３３…スイッチング素子、３４…ダイオード、３５…平滑用コンデンサ、４１，４２…抵抗、４３…誤差増幅器、４４…基準電圧発生回路、４５…パルス幅変調回路、４６…ゲート抵抗値変更回路、４７…閾値電圧発生回路、４８…比較器、４９…モード解析部、５１…ＬＥＤ、５２…スイッチング素子、６１…抵抗、７１…サーミスタ、７２…抵抗。 DESCRIPTION OF SYMBOLS 1 ... Power supply device, 2 ... DC power supply, 3 ... DC-DC converter, 4 ... Gate control circuit, 5 ... Load, 6 ... Load current detection circuit, 7 ... Element temperature detection circuit, 9 ... Dimming signal generation circuit, 31 DESCRIPTION OF SYMBOLS Capacitor 32 ... Inductor 33 ... Switching element 34 ... Diode 35 ... Smoothing capacitor 41, 42 ... Resistor 43 ... Error amplifier 44 ... Reference voltage generation circuit 45 ... Pulse width modulation circuit 46 ... Gate Resistance value changing circuit, 47... Threshold voltage generating circuit, 48... Comparator, 49... Mode analysis unit, 51... LED, 52.

Claims (5)

  1. 　電源に接続されたインダクタと、該インダクタを介して前記電源からの電流が充電されるコンデンサと、該コンデンサへの充電電流をオン・オフするためのスイッチング素子と、該スイッチング素子のオン・オフを制御する制御回路とを備え、負荷へ電力を供給する電源装置であって、
    　前記制御回路は、前記負荷の負荷電流の大きさまたは前記スイッチング素子の温度に応じて、前記スイッチング素子のゲート抵抗値を変更することを特徴とする電源装置。     An inductor connected to a power source, a capacitor charged with a current from the power source via the inductor, a switching element for turning on / off a charging current to the capacitor, and turning on / off the switching element A power supply device including a control circuit for controlling and supplying power to a load,
    The control circuit changes the gate resistance value of the switching element according to the magnitude of the load current of the load or the temperature of the switching element.
  2. 　前記制御回路は、前記負荷電流の平均値が小さいほど、または、前記スイッチング素子の温度が低いほど、前記ゲート抵抗値を大きな値に変更することを特徴とする請求項1に記載の電源装置。 2. The power supply device according to claim 1, wherein the control circuit changes the gate resistance value to a larger value as the average value of the load current is smaller or the temperature of the switching element is lower.
  3. 　前記負荷は所定の負荷モードに応じて前記負荷電流の大きさが変更される負荷であって、前記制御回路は、前記負荷モードに応じて前記スイッチング素子のゲート抵抗値を変更することを特徴とする請求項１または２に記載の電源装置。 The load is a load whose magnitude of the load current is changed according to a predetermined load mode, and the control circuit changes a gate resistance value of the switching element according to the load mode. The power supply device according to claim 1 or 2.
  4. 　請求項１から３のいずれか1に記載の電源装置を備えたテレビジョン装置。 A television device comprising the power supply device according to any one of claims 1 to 3.
  5. 　前記制御回路による前記スイッチング素子のゲート抵抗値の変更は、映像のシーンチェンジ時に行うことを特徴とする請求項４に記載のテレビジョン装置。 The television apparatus according to claim 4, wherein the gate resistance value of the switching element by the control circuit is changed at the time of a scene change of an image.
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JP2009296721A (en) * 2008-06-03 2009-12-17 Denso Corp Voltage boosting power supply and drive device
JP2013205717A (en) * 2012-03-29 2013-10-07 Panasonic Corp Light source drive device, display device, and on-vehicle device
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