JPH0589993A - Power unit and discharge lamp lighting device using it - Google Patents

Abstract

PURPOSE:To employ a simple constitution to make variable the output of a power unit which uses a power source such as a battery having a wide voltage fluctuation range and to apply the power unit to dimming control or the like. CONSTITUTION:In a power unit 2 using a power source 1 such as a battery having a wide voltage fluctuation range, a dropper circuit 5 having a transistor 7 which cuts the amount of voltage exceeding a predetermined voltage when outputting voltage to the power line of the power source 1 is provided and a control means 6 is provided for the PWM control of the transistor 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device using a power supply such as a battery having a wider voltage fluctuation range and a discharge lamp lighting device using the same.

[0002]

2. Description of the Related Art Generally, in office automation equipment such as rack-top type word processors, in-vehicle equipment, and the like, it is often the case that 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 it is used as a backlight power source for a liquid crystal display in a rack top type word processor, its brightness is required to be stable. Here, considering that the power supply voltage of this kind of power source decreases with time due to the life etc.,
It can be said that it is a good idea to set the supply voltage to a low level and control the supply power to be suppressed at the beginning of use.

In this respect, even when such a power source is used, it is possible to stabilize it by taking the same stabilizing measures as in the case of a normal power source device. For example, when considering a backlight power supply, a constant voltage chopper is combined with an inverter circuit for lighting a backlight (discharge lamp), or PWM control for turning on / off the power supply line in the preceding stage of the inverter circuit is combined. You can

[0004]

However, the method of combining the constant voltage chopper has a large number of parts and is inefficient for use in this type of simple power supply device.

Further, in the case of the PWM control, since the fluctuation of the power supply voltage having a large fluctuation width is directly applied to the inverter circuit, the breakdown voltage of the inverter circuit is apt to be defective, and the cost is increased if the breakdown voltage is designed. ..

Further, when the output is varied and the dimming of a discharge lamp is attempted, it is relatively easy to use a chopper, but when the chopper is used, the above-mentioned disadvantages occur.

[0007]

According to a first aspect of the present invention, in a power supply device using a power supply such as a battery having a wide voltage fluctuation range, a voltage of a predetermined voltage or more is cut in a power supply line of the power supply. A dropper circuit having a transistor for outputting is provided, and control means for PWM-controlling the transistor is provided.

In a second aspect of the present invention, in a power supply device using a power source such as a battery having a wider voltage fluctuation range, a dropper having a transistor for cutting and outputting a voltage equal to or more than a predetermined voltage to a power source line of the power source. Circuit is provided,
A control circuit is provided for switching control of the transistor in order to keep the voltage of the output portion of the dropper circuit constant based on the detected voltage on the load side.

According to the third aspect of the invention, such a power supply device is connected in front of the inverter circuit for lighting the discharge lamp.

[0010]

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.

When the power supply voltage is equal to or higher than the predetermined voltage, the dropper circuit cuts off the voltage exceeding the predetermined voltage and supplies a voltage having a small voltage fluctuation width. With such a small fluctuation range, the transistor in the dropper circuit is turned on / off by the feedback control by the control means.
By performing the OFF switching control, it is possible to stably supply the predetermined voltage. Here, the element that performs the drop operation and the element that performs the ON / OFF operation are shared by one transistor, and thus a simple configuration is sufficient.

In particular, by connecting such a power supply device to the preceding stage of the inverter circuit in the discharge lamp lighting device, the inverter circuit is hardly affected by the fluctuation of the power supply voltage, and the withstand voltage is low and the cost is low. It is possible to stabilize the brightness of the discharge lamp while using.

[0013]

An embodiment of the present invention will be described with reference to the drawings. This embodiment is applied to, for example, a power source for a backlight of a liquid crystal display in a rack-top type word processor, and a discharge lamp (for a power source device 2 having a power source 1 with a wide voltage fluctuation range) via an inverter circuit 3 ( Lamp) 4 is connected.

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 a transistor (FE) connected on the power line.
(Concept including T) 7, a resistor 8 connected between the collector and the base of the transistor 7, and a Zener diode 9 connected between the base of the transistor 7 and the other power supply line. The control means 6 turns on the transistor 10 in parallel with the Zener diode 9 and the transistor 10 by the PWM method according to the magnitude of the input voltage.
And a control circuit 11 for performing OFF control, and performs operation control based on a voltage detected by a detector 12 provided on the discharge lamp 4 side.

In such a configuration, it is assumed that the inverter circuit 3 has an input voltage of 12V standard and the voltage of the power supply 1 is 18V at the initial stage. In such a case, the Zener voltage of the Zener diode 9 is, for example, 15V.
Is set to. Then, the transistor 7 provided in the power supply line shows a dropper operation, that is, a resistance operation such as a class A operation for the amount exceeding the Zener voltage of 15 V, and cuts consumption. When the on-duty is 100%, the inverter circuit 3 side does not A voltage of about 15V with a small fluctuation width is supplied. However, the transistor 10 is
By performing M control, the transistor 7 is also PWM-controlled and outputs a voltage (effective value) of 12V. The discharge lamp 4 is turned on by the inverter circuit 3 in response to such voltage supply, 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, if the detected voltage based on the lamp current is too high, the PWM
By ON / OFF controlling the transistor 10 by the method, the transistor 7 is also ON / OFF controlled so that the lamp voltage is constant, that is, the lamp brightness is 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.

It will be easily understood that any dimming lighting can be obtained by changing the detection voltage input to the control means 6 into a dimming signal (not shown). In this case, it is optional whether or not to finely adjust according to the detection voltage on the load side.

In this way, one transistor 7 has a simple structure in which it is used both as a dropper and for PWM control, and lighting of a discharge lamp with stable brightness or dimming becomes possible.

[0018]

Since the present invention is configured as described above, according to the invention of claim 1, in a power supply device using a power supply such as a battery having a wider voltage fluctuation range, a predetermined power supply line is used for the power supply. Since a dropper circuit having a transistor for cutting and outputting a voltage equal to or higher than the voltage is provided and a control means for PWM controlling the transistor is provided, the output can be varied by PWM controlling the transistor of the dropper circuit, and for dimming control or the like. Applicable.

According to the second aspect of the present invention, a dropper circuit having a transistor that cuts and outputs a voltage equal to or more than a predetermined voltage is provided on a power supply line of a power supply such as a battery having a wide voltage fluctuation range, and a load is provided. A control circuit is provided to control the switching of the transistor to keep the voltage of the output part of the dropper circuit constant based on the detected voltage on the side.When the power supply voltage is higher than a predetermined voltage, the dropper circuit cuts off the part exceeding the predetermined voltage. The voltage in the dropper circuit is turned on / off by the feedback control by the control circuit while the voltage with a small voltage fluctuation width is supplied.
By performing F switching control, it is possible to supply a stable predetermined voltage, and a single transistor can be used as both an element that performs a drop operation and an element that performs an ON / OFF operation. Therefore, a simple configuration is sufficient. Become.

In particular, according to the third aspect of the invention, 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 the fluctuation of the power supply voltage. It is possible to stabilize the brightness of the discharge lamp while using an inexpensive inverter circuit having a low breakdown voltage.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

[Explanation 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)

[Claims] 1. A power supply device using a power supply such as a battery having a wider voltage fluctuation range, wherein a dropper circuit having a transistor for cutting and outputting a voltage equal to or more than a predetermined voltage is provided on the power supply line of the power supply, and the transistor is provided. To PW
A power supply device comprising a control means for M control. 2. A power supply device using a power supply such as a battery having a wider voltage fluctuation range, wherein a dropper circuit having a transistor for cutting and outputting a voltage equal to or more than a predetermined voltage is provided on a power supply line of the power supply, and a load side is provided. The power supply device is provided with a control means for PWM-controlling the transistor in order to keep the voltage of the output part of the dropper circuit constant based on the detection voltage of. 3. A dropper circuit having a transistor that cuts and outputs a voltage equal to or more than a predetermined voltage to a power supply line of a power supply such as a battery having a wide voltage fluctuation range, and the dropper circuit output based on a detection voltage on the discharge lamp side. A discharge lamp lighting device, characterized in that a power supply device comprising a control means for PWM-controlling the transistor in order to keep a partial voltage constant is connected to a stage before an inverter circuit for lighting the discharge lamp.