JP2007202267A - Power supply device and electrical apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply device that makes it possible to enhance the voltage increasing efficiency, and an electrical apparatus using this power supply device. <P>SOLUTION: The power supply device is so constructed that it includes: a direct-current voltage source 1 for generating a supply voltage Vbat; a regulator circuit 2 for generating a predetermined steady voltage Vi from the supply voltage Vbat; and a charge pump circuit 3 that charges and discharges capacitors C1 and C2 using switches SW1 to SW7, thereby increases an input voltage to generate an output voltage Vo. The charge pump circuit 3 is configured to charge the capacitors C1 and C2 using the steady voltage Vi in charging operation, and discharges the capacitors C1 and C2 using the supply voltage Vbat in pumping operation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a power supply device provided with a charge pump circuit, and an electric apparatus using the same.

  FIG. 6 is a block diagram (partly including circuit elements) showing a conventional example of a power supply device including a charge pump circuit.

  As shown in FIG. 6A, the battery 10 that generates the battery voltage Vbat, the regulator circuit 20 that generates a predetermined steady voltage Vi from the battery voltage Vbat, and the constant voltage Vi at a predetermined magnification (1. In the conventional power supply device having the charge pump circuit 30 that generates the output voltage Vo by boosting the voltage by 5 times, generally, the charge operation (FIG. 6B) and the pump operation (FIG. 6 (FIG. 6)). In any of c)), the charge pump circuit 30 uses the output of the regulator circuit 20 (that is, the steady voltage Vi) (see, for example, Patent Document 1).

JP 2003-348821 A

  Certainly, in the case of the above-described conventional power supply device, the charge pump circuit 30 always generates the desired output voltage Vo by using the steady voltage Vi of the regulator circuit 20 without depending on the fluctuation of the battery voltage Vbat. Is possible.

  However, as described above, the conventional power supply apparatus has the charge pump circuit 30 that controls the regulator circuit 20 in both the charge operation (FIG. 6B) and the pump operation (FIG. 6C). Since the steady voltage Vi is used, the on-resistance of the entire system during the pump operation is increased by the amount of insertion of the regulator circuit 20, and the boosting efficiency is reduced. As a result, in the conventional power supply device, the remaining amount of the battery 10 cannot be utilized to the maximum extent.

  An object of this invention is to provide the power supply device which can raise pressure | voltage rise efficiency in view of said problem, and an electric equipment using the same.

  In order to achieve the above object, a power supply device according to the present invention includes a DC voltage source that generates a power supply voltage, a regulator circuit that generates a predetermined steady voltage from the power supply voltage, and a capacitor using a plurality of switches. A charge pump circuit that boosts an input voltage by charging and discharging to generate an output voltage, wherein the charge pump circuit uses the steady voltage to perform the capacitor operation during a charge operation. In the pump operation, the power supply voltage is used to perform the pump operation to discharge the capacitor (first configuration).

  In the power supply device having the first configuration, the regulator circuit may have a configuration (second configuration) including overcurrent limiter means for suppressing the output current to a predetermined upper limit value.

  The power supply device having the second configuration includes a detection unit that detects whether or not the output voltage is lower than a predetermined threshold voltage, and a control that performs switching control of the charge pump circuit according to the detection result. The control unit stops the boosting operation of the charge pump circuit when the output voltage is lower than a predetermined threshold voltage, and the output terminal of the regulator circuit and the output A configuration (third configuration) for performing switching control of the charge pump circuit so as to short-circuit the voltage extraction terminal is preferable.

  In the power supply device having the third configuration, the charge pump circuit includes a first capacitor and a second capacitor for storing charge; one end is connected to the output terminal of the regulator circuit and the other end is the first capacitor. A first switch connected to one end of the first capacitor; one end connected to one end of the first capacitor and the other end connected to the output voltage extraction end; and one end connected to the other end of the first capacitor A third switch having the other end connected to one end of the second capacitor; a fourth switch having one end connected to the positive end of the DC voltage source and the other end connected to the other end of the first capacitor; A fifth switch having one end connected to the other end of the second capacitor and the other end connected to the ground end; one end connected to the positive end of the DC voltage source and the other end connected to the other end of the second capacitor Sixth switch A seventh switch having one end connected to one end of the second capacitor and the other end connected to the output voltage extracting terminal; and during the charge operation, the first switch, the third switch, and the 5 switches are turned on, and the other switches are turned off. During the pump operation, the second switch, the fourth switch, the sixth switch, and the seventh switch are turned on. When the other switches are turned off, and the output voltage is lower than a predetermined threshold voltage, the first switch and the second switch are turned on. A configuration (fourth configuration) in which switching control is performed so as to cut off a direct current path from the positive terminal of the voltage source to the output terminal of the output voltage. Better to).

  Moreover, the electric device according to the present invention has a configuration (fifth configuration) including a power supply device having any one of the first to fourth configurations as power supply means to the load.

  As described above, with the power supply device according to the present invention, the on-resistance of the entire system can be reduced and the boosting efficiency can be increased by disconnecting the regulator circuit from the system during pump operation. Therefore, when a battery is used as the DC voltage source, the remaining amount can be utilized to the maximum.

  Hereinafter, in the backlight device that irradiates the liquid crystal display panel from the back side, the case where the power supply device according to the present invention is applied as a power supply means to the light emitting diode that is the light source will be described as an example.

  FIG. 1 is a block diagram (partly including circuit elements) showing an embodiment of a backlight device according to the present invention. As shown in the figure, the backlight device of the present embodiment includes power supply means for a load (a light emitting diode array formed by connecting a plurality of light emitting diodes in parallel, hereinafter simply referred to as an LED or an LED array). As shown, the power supply IC is formed by integrating a DC voltage source 1, a regulator circuit 2, a charge pump circuit 3, a detection unit 4, a control unit 5, and current sources 61 to 6n.

  A liquid crystal display device using such an LED array as a backlight can achieve effects such as power saving, long life, low heat generation, and space saving as compared with a configuration using a fluorescent tube or the like. In addition, the power consumption and heat generation are lower than those of other backlights using LEDs.

  Moreover, each LED which comprises LED row | line | column consists of three LED elements which have red, green, and blue luminescent color as a group, By mixing the emitted light of each LED element, desired luminescent color ( In this embodiment, illumination light having a white color is generated. If the liquid crystal display device uses such a white LED as a backlight, the color reproduction range of the liquid crystal display panel can be expanded as compared with a configuration using a fluorescent tube or the like.

  The DC voltage source 1 is a means for generating a DC voltage. In this embodiment, a battery (secondary battery such as a lithium ion battery) that generates a battery voltage Vbat is used. The DC voltage source 1 may be an AC / DC converter that converts a commercial AC voltage into a DC voltage.

  The regulator circuit 2 is means for generating a predetermined steady voltage Vi from the battery voltage Vbat so that the feedback voltage having the lowest voltage value among the feedback voltages Vfb1 to Vfbn described later matches the predetermined reference voltage Vref. For example, a series regulator that performs on-resistance control of a power transistor connected in series in the current path between the DC voltage source 1 and the charge pump circuit 3 may be used.

  Note that the regulator circuit 2 of the present embodiment includes overcurrent limiter means (not shown) that suppresses the output current to a predetermined upper limit value. More specifically, the regulator circuit 2 according to the present embodiment includes, as the overcurrent limiter means, a current feedback circuit that performs current limit during steady state and a soft start circuit that performs current limit during startup. It consists of With the regulator circuit 2 having such an overcurrent limiter function, it is possible to suppress an excessive current flowing into the charge pump circuit 3 immediately after the device is started.

  The overcurrent limiter function of the regulator circuit 2 is also used to suppress overcurrent when the output is short-circuited. This will be described in detail later.

  The charge pump circuit 3 uses a plurality of switches SW1 to SW7 to charge and discharge the capacitors C1 to C2 (the same capacity as each other), thereby increasing the input voltage by a predetermined magnification (1.5 times boosting operation in this embodiment). The output voltage Vo is generated by boosting the output voltage Vo.

  The switch SW1 has one end connected to the output end of the regulator circuit and the other end connected to one end of the first capacitor. The switch SW2 has one end connected to one end of the capacitor C1 and the other end connected to the output voltage extraction terminal To. The switch SW3 has one end connected to the other end of the capacitor C1 and the other end connected to one end of the capacitor C2. The switch SW4 has one end connected to the positive terminal of the DC voltage source 1 and the other end connected to the other end of the capacitor C1. The switch SW5 has one end connected to the other end of the capacitor C2 and the other end connected to the ground terminal. The switch SW6 has one end connected to the positive terminal of the DC voltage source 1 and the other end connected to the other end of the capacitor C2. The switch SW7 has one end connected to one end of the capacitor C2, and the other end connected to the output voltage extraction terminal To.

  The detection unit 4 is means for detecting whether or not the output voltage Vo (or a divided voltage thereof) is lower than a predetermined threshold voltage Vth, and is configured using a comparison circuit or a resistance divider circuit. As the threshold voltage Vth, a low voltage value for detecting an output short circuit (ground fault) is set.

  The control unit 5 performs switching control of the charge pump circuit 3 (gate control of the clock signal for the switches SW1 to SW7) and overcurrent limiter enhancement control of the regulator circuit 2 in accordance with the detection result of the detection unit 4. It is. The control will be described in detail later.

  The current sources 61 to 6n are connected between the LED string and the ground terminal as means for controlling the drive current of the LED string and as means for generating the feedback voltages Vfb1 to Vfbn.

  Hereinafter, the operation of the power supply IC configured as described above will be described in detail.

  First, the normal operation (boost operation) of the charge pump circuit 3 will be described in detail.

  In the charge pump circuit 3 configured as described above, during the charging operation, the switch SW1, the switch SW3, and the switch SW5 are turned on, and the other switches are turned off. By such switching control, the equivalent circuit of the charge pump circuit 3 has a configuration in which capacitors C1 to C2 are connected in series between the output terminal of the regulator circuit 2 and the ground terminal, as shown in FIG. It becomes. Therefore, the capacitors C1 and C2 are charged until the potential difference between both ends becomes 1 / 2Vi.

  On the other hand, during the pump operation, the switch SW2, the switch SW4, the switch SW6, and the switch SW7 are turned on, and the other switches are turned off. By such switching control, the equivalent circuit of the charge pump circuit 3 has capacitors C1 to C2 in parallel between the positive terminal of the DC voltage source 1 and the output voltage extraction terminal To, as shown in FIG. It becomes a connected form. Accordingly, the other ends of the capacitors C1 and C2 are pulled up from the ground voltage GND to the battery voltage Vbat. Therefore, as the output voltage Vo, a voltage obtained by adding the charging voltage 1 / 2Vi to the battery voltage Vbat is drawn.

  As described above, the charge pump circuit 3 of the present embodiment charges the capacitors C1 and C2 using the steady voltage Vi during the charge operation, while performing the pump operation using the power supply voltage Vbat during the pump operation, and the capacitor C1. It is set as the structure which discharges -C2. By adopting such a configuration, the on-resistance of the entire system can be reduced by separating the regulator circuit 2 from the system during the pump operation, so that the boosting efficiency can be increased. Therefore, when a battery is used as the DC voltage source 1, the remaining amount can be utilized to the maximum.

  Next, the protection operation of the charge pump circuit 3 when the output is short-circuited will be described in detail with reference to FIGS. 1 and 2 and FIG.

  FIG. 3 is a flowchart for explaining the protection operation of the charge pump circuit 3 when the output is short-circuited.

  In step S1, while the normal operation of the charge pump circuit 3 (the 1.5-fold voltage boosting operation described above) is being performed, the detection unit 4 detects whether or not the output voltage Vo is lower than the threshold voltage Vth. Performed (step S2). Here, if it is determined that the output voltage Vo is lower than the threshold voltage Vth, the flow proceeds to step S3. On the other hand, when it is determined that the output voltage Vo is not lower than the threshold voltage Vth, the flow is returned to step S1, and the normal operation of the charge pump circuit 3 is continued.

  When it is determined in step S2 that the output voltage Vo is lower than the threshold voltage Vth, the control unit 5 stops the boosting operation of the charge pump circuit 3 with the recognition that the output short circuit has occurred, and the regulator Switching control of the charge pump circuit 3 is performed so that the output terminal of the circuit 2 and the output voltage extraction terminal To are short-circuited, in other words, the steady voltage Vi is directly output as the output voltage Vo (steps S3 and S4). .

  More specifically, when it is determined that the output voltage Vo is lower than the threshold voltage Vth, the switch SW1 and the switch SW2 are turned on in the charge pump circuit 3, and the other switches are connected to the DC voltage source. Switching control is performed so that a direct current path from the positive electrode terminal 1 to the output voltage extraction terminal To is cut off. In the simplest case, the switches SW1 and SW2 are turned on, and all the other switches are turned off.

  With such a configuration, when the output is short-circuited, the current path from the DC voltage source 1 to the output voltage extraction end To is only the route via the regulator circuit 2 as shown in FIG. Then, an excessive current flows in the regulator circuit 2, and the overcurrent limiter means always operates (step S5).

  Therefore, the power supply IC of the present embodiment reduces the on-resistance of the entire system by disconnecting the regulator circuit 2 from the system during pump operation, and the overcurrent limiter function provided in the regulator circuit 2 when the output is short-circuited. Since it can be used effectively, it is possible to prevent an excessive current from flowing when the output is short-circuited and to protect the power supply IC from destruction.

  In addition, the power supply IC of the present embodiment is configured to perform overcurrent limiter enhancement control of the regulator circuit 2 using the control unit 5 prior to the activation of the overcurrent limiter function in step S5. More specifically, the power supply IC according to the present embodiment includes a regulator circuit 2 that reaches a steady state and restarts the soft start circuit that has already finished its function (discharge of the soft start capacitor). The circuit 2 is configured to perform the strict current limitation similar to that at the time of startup. With such a configuration, it is possible to effectively suppress an excessive current when the output is short-circuited and to protect the power supply IC from destruction.

  In step S4, the detection unit 4 detects whether or not the output voltage Vo is lower than the threshold voltage Vth while the protection operation (single boosting operation) of the charge pump circuit 3 is being performed. (Step S6). If it is determined that the output voltage Vo is lower than the threshold voltage Vth, the flow is returned to step S4, and the protection operation of the charge pump circuit 3 is continued. On the other hand, if it is determined that the output voltage Vo is not lower than the threshold voltage Vth, the flow is returned to step S1, and the charge pump circuit 3 is returned to the normal operation.

  Therefore, at the time of normal startup of the power supply IC, the output voltage Vo is raised while the overcurrent limiter means of the regulator circuit 2 is operating. When the output voltage Vo becomes higher than the threshold voltage Vth, the charge pump circuit 3 is protected. To normal operation.

  In the above-described embodiment, the case where the present invention is applied to the charge pump circuit having a load connected to the LED strings connected in parallel has been described as an example. In addition, the present invention can be applied to a charge pump circuit (see FIG. 4) using a series of LED strings as a load, or a charge pump circuit using a single LED as a load.

  Further, in the above embodiment, the case where the power supply device according to the present invention is applied as an example of the power supply means to the LED that is the light source of the backlight device has been described, but the application target of the present invention is The present invention is not limited to this, and can be widely applied to all power supply devices including a charge pump circuit.

  The configuration of the present invention can be variously modified within the scope of the present invention in addition to the above embodiment.

  For example, in the above embodiment, the charge pump circuit 3 has been described as a 1.5-fold boost type, but the configuration of the present invention is not limited to this, and the boost magnification may be any value. Absent. That is, as shown in FIG. 5, the present invention can be applied to a double boost type charge pump circuit. Further, an external resistor R (see FIG. 4) may be used instead of the current sources 61 to 6n of FIG.

  Further, in the above embodiment, the description has been given by taking, as an example, an LED that generates white light by mixing red light, green light, and blue light as the light emitting means of the backlight device. The present invention is not limited to this, and the present invention is naturally applied to a configuration using a light emitting unit that emits a desired colored light by mixing other colored light or a light emitting unit that emits monochromatic light. Is possible.

  The present invention is a technique useful for improving the efficiency and reliability of a power supply device. The power supply device according to the present invention includes a white LED for a backlight of a liquid crystal display such as a mobile phone terminal or a portable game machine. It can be mounted on all electric devices in use and other electric devices equipped with a charge pump type booster circuit.

These are block diagrams which show one Embodiment of the backlight apparatus which concerns on this invention. FIG. 4 is a diagram for explaining the operation of the charge pump circuit 3; These are flowcharts for explaining the operation of the charge pump circuit 3. These are block diagrams which show the modification of the backlight apparatus which concerns on this invention. These are block diagrams which show another modification of the backlight apparatus which concerns on this invention. These are block diagrams which show one prior art example of a power supply device.

Explanation of symbols

1 DC voltage source (battery)
2 regulator circuit 3 charge pump circuit 4 detector 5 controller 61 to 6n current source LED load (light emitting diode array)
R External resistor To Output voltage extraction terminal C1 to C2 Capacitor SW1 to SW7 Switch

Claims (5)

  A DC voltage source that generates a power supply voltage, a regulator circuit that generates a predetermined steady voltage from the power supply voltage, and a capacitor that is charged and discharged using a plurality of switches to boost the input voltage and generate an output voltage A charge pump circuit, wherein the charge pump circuit charges the capacitor using the steady voltage during a charge operation, and performs a pump operation using the power supply voltage during a pump operation. And the capacitor is discharged.   2. The power supply device according to claim 1, wherein the regulator circuit includes an overcurrent limiter that suppresses the output current to a predetermined upper limit value.   A detection unit that detects whether or not the output voltage is lower than a predetermined threshold voltage; and a control unit that performs switching control of the charge pump circuit in accordance with the detection result. The charge pump circuit is stopped when the output voltage is lower than a predetermined threshold voltage, and the output terminal of the regulator circuit and the output terminal of the output voltage are short-circuited. The power supply device according to claim 2, wherein switching control of the pump circuit is performed.   The charge pump circuit includes a first capacitor and a second capacitor for storing charge; a first switch having one end connected to the output terminal of the regulator circuit and the other end connected to one end of the first capacitor; A second switch connected to one end of the first capacitor and having the other end connected to the output voltage extracting terminal; one end connected to the other end of the first capacitor and the other end connected to one end of the second capacitor; A third switch; one end connected to the positive terminal of the DC voltage source and the other end connected to the other end of the first capacitor; and one end connected to the other end of the second capacitor; A fifth switch having one end connected to the ground terminal; a sixth switch having one end connected to the positive terminal of the DC voltage source and the other end connected to the other end of the second capacitor; and one end of the second capacitor Connected to one end and the other end And a seventh switch connected to the output voltage extraction terminal. During the charge operation, the first switch, the third switch, and the fifth switch are turned on, and the other switches The second switch, the fourth switch, the sixth switch, and the seventh switch are turned on during the pump operation, and the other switches are turned off, and When the output voltage is lower than a predetermined threshold voltage, the first switch and the second switch are turned on, and the remaining switches are connected from the positive end of the DC voltage source to the output end of the output voltage. 4. The power supply device according to claim 3, wherein each switching control is performed so as to cut off a direct current path.   An electric apparatus comprising the power supply device according to any one of claims 1 to 4 as means for supplying power to a load.

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