JP3611214B2 - Power supply device and discharge lamp lighting device using the same - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a power supply device using a power source such as a battery having a wide voltage fluctuation range and a discharge lamp lighting device using the same.
[0002]
[Prior art]
In general, in office automation equipment such as a rack-top type word processor, in-vehicle equipment, etc., there are many cases in which a power source having a wide voltage fluctuation range such as a battery or a battery must be used. Even when such a power supply is used, it is necessary for the power supply device to stabilize the supply voltage by some means. For example, when used as a backlight power source for a liquid crystal display in a rack-top type word processor, the luminance is required to be stable. Here, considering that the power supply voltage drops over time due to the lifespan of this type of power supply, it is advisable to set the supply voltage to a low value and to control the supply power at the beginning of use. It can be said.
[0003]
In this regard, even when such a power supply is used, it is possible to stabilize it by taking the same stabilization measures as in the case of a normal power supply device. For example, in the case of a backlight power supply, a constant voltage chopper is combined with an inverter circuit for lighting a backlight (discharge lamp), and PWM control for turning on / off a power supply line in the previous stage of the inverter circuit is combined. Can.
[0004]
[Problems to be solved by the invention]
However, the method of combining the constant voltage chopper has a large number of parts and is inefficient for use in this type of simplified power supply device.
[0005]
Further, in the case of PWM control, since the fluctuation of the power supply voltage having a large fluctuation width is directly applied to the inverter circuit, the inverter circuit is liable to have a breakdown voltage failure. However, the design with the increased breakdown voltage increases the cost.
[0006]
Further, when the output is varied and, for example, dimming a discharge lamp, it is relatively easy to use a chopper, but using a chopper has the disadvantages described above.
[0007]
[Means for Solving the Problems]
According to the first aspect of the present invention, in a power supply device using a power source such as a battery having a wide voltage fluctuation range, a dropper circuit having a transistor that cuts and outputs a voltage equal to or higher than a predetermined voltage is provided in the power source line of the power source. A control means for PWM controlling the transistor is provided.
[0008]
According to a second aspect of the present invention, in a power supply apparatus using a power source such as a battery having a wide voltage fluctuation range, a dropper circuit having a transistor that cuts and outputs a voltage equal to or higher than a predetermined voltage is provided in the power source line of the power source. A control circuit is provided for switching control of the transistor in order to keep the voltage at the output portion of the dropper circuit constant based on the detection voltage on the load side.
[0009]
In the invention according to claim 3, such a power supply device is connected to the previous stage of the inverter circuit for lighting the discharge lamp.
[0010]
[Action]
The output can be varied by using the transistor of the dropper circuit and performing PWM control on the transistor, and for example, dimming control can be performed.
[0011]
When the power supply voltage is equal to or higher than the predetermined voltage, the portion exceeding the predetermined voltage is cut by the dropper circuit, and a voltage with a small voltage fluctuation width is supplied. In such a state where the fluctuation range is small, the transistor in the dropper circuit is ON / OFF-switched by feedback control by the control means, so that a stable predetermined voltage can be supplied. Here, since the element that performs the drop operation and the element that performs the ON / OFF operation are shared by a single transistor, a simple configuration is sufficient.
[0012]
In particular, by connecting such a power supply device to the front stage of the inverter circuit in the discharge lamp lighting device, the inverter circuit is hardly affected by fluctuations in the power supply voltage, while using an inexpensive inverter circuit with a low withstand voltage. The brightness of the discharge lamp can be stabilized.
[0013]
【Example】
An embodiment of the present invention will be described with reference to the drawings. This embodiment is applied to, for example, a power supply for a backlight of a liquid crystal display in a rack top type word processor, and a discharge lamp ( Lamp) 4 is connected.
[0014]
The power supply device 2 is obtained by adding a dropper circuit 5 and a control means 6 to the power supply 1. The dropper circuit 5 is connected between a transistor (concept including FET) 7 connected on a power supply line, a resistor 8 connected between the collector and base of the transistor 7, a base of the transistor 7 and the other power supply line. And a Zener diode 9. The control means 6 is composed of a transistor 10 in parallel with the Zener diode 9 and a control circuit 11 for controlling ON / OFF of the transistor 10 according to the magnitude of the input voltage by the PWM method, and a detector provided on the discharge lamp 4 side. The operation is controlled on the basis of the detection voltage of No. 12.
[0015]
In such a configuration, for example, a case is assumed in which the inverter circuit 3 has an input voltage of 12 V standard and the voltage of the power source 1 is 18 V in the initial stage. In such a case, the Zener voltage of the Zener diode 9 is set to 15V, for example. Then, the transistor 7 provided in the power supply line cuts the consumption by showing a dropper operation, that is, a resistive operation such as a class A operation, exceeding the Zener voltage of 15 V. When the on-duty is 100%, the inverter circuit 3 side A voltage of about 15 V with a small fluctuation width is supplied. However, when the transistor 10 is PWM-controlled, the transistor 7 is also PWM-controlled and outputs a voltage (effective value) of 12V. Upon receiving such voltage supply, the discharge lamp 4 is turned on by the inverter circuit 3, and the lamp current at this time is detected by the detector 12 and sent to the control circuit 11. In the control circuit 11, when the detection voltage based on the lamp current is too high, the transistor 10 is ON / OFF controlled by the PWM method, so that the transistor 7 is also ON / OFF controlled so that the lamp voltage is constant, that is, the lamp brightness is high. Control to be constant. In this case, since the fluctuation range of the input voltage to the inverter circuit 3 is reduced by the dropper function, the PWM control by the transistors 10 and 7 has a fine adjustment meaning and is extremely stable.
[0016]
It can be easily understood that any dimming lighting can be obtained by changing the detection voltage input to the control means 6 to a dimming signal (not shown). In this case, whether or not to finely adjust according to the detection voltage on the load side is arbitrary.
[0017]
In this manner, a simple configuration in which one transistor 7 is used for both a dropper and PWM control can be used to turn on a discharge lamp with stable luminance or dimming.
[0018]
【The invention's effect】
Since the present invention is configured as described above, according to the first aspect of the present invention, in a power supply apparatus using a power source such as a battery having a wide voltage fluctuation range, a voltage component equal to or higher than a predetermined voltage is applied to the power source line of the power source. the provided dropper circuit having a transistor for outputting the cut, is provided with the control means for PWM control of the transistor, can be output variable by PWM control transistor dropper circuit, applied can be a dimming control or the like, also, Since the element that performs the drop operation and the element that performs the ON / OFF operation can be shared by one transistor, a simple configuration is required, and the manufacturing cost can be reduced .
[0019]
According to a second aspect of the present invention, a dropper circuit having a transistor that cuts and outputs a voltage equal to or higher than a predetermined voltage is provided on a power supply line of a power source such as a battery having a wide voltage fluctuation range, and detection on the load side In order to keep the voltage of the output part of the dropper circuit constant based on the voltage, a control circuit for switching control of the transistor is provided, and when the power supply voltage is equal to or higher than a predetermined voltage, the voltage exceeding the predetermined voltage is cut by the dropper circuit. Supplying a stable predetermined voltage by supplying a voltage with a small fluctuation range and performing ON / OFF switching control of the transistors in the dropper circuit by feedback control by the control circuit in such a state where the fluctuation range is small. An element that performs a drop operation and an element that performs an ON / OFF operation. Since it combined in one transistor, seen already with a simple configuration, and it can reduce the manufacturing cost.
[0020]
In particular, according to the invention described in claim 3, since such a power supply device is connected to the preceding stage of the inverter circuit in the discharge lamp lighting device, the inverter circuit is hardly affected by fluctuations in the power supply voltage, and the breakdown voltage is reduced. The luminance of the discharge lamp can be stabilized while using a low-priced inexpensive inverter circuit.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Power supply 2 Power supply device 3 Inverter circuit 4 Discharge lamp 5 Dropper circuit 6 Control means 7 Transistor

Claims (3)

In a power supply apparatus using a power supply such as a battery having a wide voltage fluctuation range, a control is provided for providing a dropper circuit having a transistor that cuts and outputs a voltage equal to or higher than a predetermined voltage on the power supply line of the power supply, and performs PWM control of the transistor A power supply device comprising means. In a power supply apparatus using a power source such as a battery having a wide voltage fluctuation range, a dropper circuit having a transistor that cuts and outputs a voltage equal to or higher than a predetermined voltage is provided in the power source line of the power source, and is based on a detection voltage on the load side A power supply apparatus comprising: control means for performing PWM control on the transistor in order to maintain a constant voltage at the output portion of the dropper circuit. A dropper circuit having a transistor that cuts and outputs a voltage equal to or greater than a predetermined voltage to a power supply line of a power source such as a battery having a wide voltage fluctuation range, and the voltage at the output portion of the dropper circuit is constant based on a detection voltage on the discharge lamp side A discharge lamp lighting device comprising: a power supply device including a control unit that performs PWM control of the transistor to maintain the current level in front of an inverter circuit for lighting the discharge lamp.

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