JPS63245280A - Power-supply device - Google Patents

Abstract

PURPOSE:To lower a cost, by avoiding the smoothing capacitor of a chopper, and by using a smoothing choke serving also as the constant current choke of an inverter. CONSTITUTION:A power-supply device is provided with a chopper circuit 2 connected to a pulse width controlling circuit PWM, and a constant current push-pull type inverter 3, and from the secondary winding Ws of an output transformer T1, current is fed to a fluorescent lamp FL for a load. Then, a chopper switching element Qcp, a choke (inductor) Lcp, and said inverter 3 are connected in series. By the choke Lcp, the inverter 3 is constant-current-push-pull- formed, and ON/OFF-output from the chopper 2 is smoothed by the choke Lcp, and continuous DC output is fed to the inverter 3, and so the choke Lcp is worked also for smoothing the chopper 2.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention uses a constant current push-pull type inverter to generate high frequency output from a DC power supply, and at this time, uses a step-down type chopper to control the input of the inverter. The present invention relates to a power supply device that controls the high frequency output.

[Prior Art] Conventionally, a discharge lamp lighting device having the configuration shown in FIG. 1 has been known as an application of this type of power supply device. In the figure, 1 is a DC power source such as a battery or a rectifier circuit, 2 is a step-down chopper, and 3 is a constant current push-pull inverter.

The chopper 2 varies the input voltage to the inverter 3 to dim the fluorescent lamp FL, stabilizes the input voltage to the inverter 3, and lights the fluorescent lamp FL at a constant power.
Alternatively, when the DC power supply 2 is a rectifier circuit, it is used for various purposes such as smoothing the rectified output and reducing the light output ripple of the fluorescent lamp FL.

[Problems to be Solved by the Invention] However, such a power supply device has a problem in that the cost is high due to the step-down chopper installed therein.

The present invention aims to reduce the cost of a power supply device including such a step-down chopper and a constant current push-pull inverter.

[Means for Solving the Problems] In order to achieve the above object, the present invention removes the smoothing capacitor of the chopper and replaces the smoothing choke (inductor) of the chopper and the inverter with respect to the conventional power supply device of the same type. It is characterized by being used also as a constant current choke.

[Operation] In the device of the present invention, as shown in FIG. 1, a chopper switching element, a choke (inductor), and a push-pull inverter are connected in series. Therefore, if this choke is included in the inverter, this inverter is a constant current push-pull type inverter.

Furthermore, since the on/off output from the chopper is smoothed by the choke and a continuous DC output is supplied to the inverter, this choke also has the function of smoothing the chopper.

Note that the discharge lamp lighting device shown in FIG. 1 of Japanese Patent Publication No. 57-37239 is very similar to the structure of the present invention in terms of the drawing. However, if this lighting device does not have an auxiliary power source, a section of the lamp current 11 will occur as shown in FIG. 2C of the publication. In other words, the on/off output from the switch 14 shown in FIG. 1 of the publication is supplied to the inverter 7 without being substantially smoothed. This is because the OFF frequency of the switch 14 is about 1 to 2 kHz, which is 10 to 20 times higher than the oscillation frequency of the inverter 7, which is 20 kHz.

On the other hand, since the choke of the present invention also serves as a smoothing choke for the chopper, it has a sufficient smoothing effect on the on/off frequency of the chopper.

In the present invention, the oscillation frequency of the inverter is preferably set to 20
~100 kHz, more preferably 40 to 50 kHz, and the on/off frequency of the chopper is equal to or lower than the oscillation frequency of the inverter and is 1/3 times or more, preferably 1/2 times or more. In this case, the constant current choke of the inverter and the smoothing choke of the chopper have approximately the same inductance, but one may be left in place and the other removed.

In addition, the on/off frequency of the chopper is set lower,
It is also possible to leave chalk for smoothing the chopper. However, in this case, since the inverter input voltage drop is large due to the constant current action of the inverter, it is necessary to increase the DC power supply voltage and to increase the withstand voltage and capacity of each element.

[Effects] According to the present invention configured as described above, the number of parts can be reduced, and the device can be made smaller and lower in cost.

Further, although an electrolytic capacitor is generally used as a smoothing capacitor, eliminating the electrolytic capacitor, which is a short-lived component, improves the lifespan and reliability of the device.

In addition, if the power supply device of the present invention is applied as a discharge lamp lighting device, it is possible to supply an output without any pause period to the discharge lamp without providing an auxiliary power source, etc., making the discharge lamp highly efficient and with no ripple in the light output. can be lit less.

[Example] The present invention will be described in detail below using the drawings.

FIG. 1 shows the configuration of a power supply device according to an embodiment of the present invention. The device shown in FIG. 2 is the same as that shown in FIG. 2, with the smoothing capacitor Ccp and constant current choke Lv removed.

In FIG. 1, the chopper circuit 2 includes the positive output terminal of the DC power supply 1 and the output voltage T1 of the inverter 3 and the secondary winding W.
A switching transistor Qcp and a choke Lcp are connected in series between the midpoint (center tap) of p, and a connection point between the transistor Qcp and the choke Lcp and a DC power supply 1
A diode Dcp is connected in the opposite direction between the negative side output terminal of the transistor QCp, and a pulse width control circuit PWM for turning on and off the transistor QCp is connected to the base of the transistor QCp.
is connected.

The constant current push-pull type inverter 3 has an output transformer T
The middle point of the first primary winding Wp is connected to the smoothing choke Lcp which also serves as a constant current choke, and transistors Qvl are connected to both ends of the second primary winding Wp.

Connect the collector of Qvl and connect the resonant capacitor C1, and connect the transistors Qvl and Qvl.
Connect the emitter of the transistor Q to the common terminal of the DC power supply 1 and the chopper (the negative output terminal of the DC power supply 1).
The bases of vl and Q vl are each output Lance T1
It is connected to both ends of the base feedback winding wb of the output transformer Tl, and to the midpoint of the primary winding Wp of the output transformer Tl via bias resistors R1 and R2.

For example, a fluorescent lamp FL is connected as a load to the secondary winding Ws of the output transformer T1.

Next, the operation of this power supply device will be explained.

When the DC power supply 1 is turned on, the control circuit PWM turns on and off the transistor Qcp with a pulse signal of a predetermined width.

As a result, a rectangular wave voltage corresponding to the pulse signal is generated at the emitter of the transistor Qcp. choke lcp
smoothes this rectangular wave voltage and supplies continuous DC output to the inverter.

In inverter 3, this DC output is bias resistor R1, R
2 to the transistors Q vl and Q v2 as a base current. Then the transistor Q vl
, Qv2, one of them turns on first due to a slight imbalance. Now, if the transistor Qvl is turned on first, an upward current flows through the primary winding Wp of the output transistor Tl. Therefore, a voltage is induced in the base feedback winding wb, which is positive on the base side of the transistor QvL and negative on the base side of the transistor Qvl, and a base current further flows through the transistor Qvl.

This positive feedback drives the primary winding Wp of the output transformer TI, and in this state, an oscillating voltage is generated due to the inductance of the primary winding Wp and the resonance of the resonant capacitor CI. When the polarity of this oscillating voltage is reversed, an electromotive force is generated in the opposite direction in the base winding wb and the transistor Qv
Turn on 2. Therefore, similarly below, the transistor Q
vl, Qv2 are alternately turned on and off to oscillate, generating a high frequency output in each winding of the output transformer T1.

The lamp FL is supplied with a high frequency output without a pause period induced in the secondary winding Ws of the output transformer T1, and is lit with high efficiency.

In this device, the lamp FL can be dimmed by making the output of the chopper 2 variable, and the on/off duty of the transistor Qcp can be adjusted by detecting a desired physical quantity such as the output of the chopper 2, the lamp current, or the lamp brightness. These physical quantities can be stabilized by feedback control. In addition, if ripples remaining in the DC input to the inverter 3 adversely affect these controls, a CR filter should be added to the detection system that detects the above physical quantities to remove the ripples in the detection signal. do it.

In the above, if a rectifier circuit is connected to the output of the inverter 3 instead of the discharge lamp and the output of the inverter 3 is rectified, a DC voltage with less ripple can be obtained.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a power supply device according to an embodiment of the present invention. 1: DC power supply, 2: Step-down chopper, 3: Constant current push-pull inverter, L cp: Smoothing choke, Lv: Constant current choke, Ccp: Smoothing capacitor, FL: Discharge lamp load.

Claims (1)

[Claims] 1. A step-down chopper that includes a DC power source, a smoothing choke, and a smoothing capacitor, and converts DC input from the DC power source into a lower voltage DC output; and a chopper that includes a constant current choke. In a power supply device equipped with a constant current push-pull type inverter that converts DC output to high frequency output, the smoothing capacitor is removed and a single choke serves as the smoothing choke and the constant current choke. Features a power supply device. 2. The chopping frequency of the step-down chopper is 1 to 1/of the output frequency of the constant current push-pull inverter.
3. The power supply device according to claim 1, which has a frequency of 3. 3. The power supply device according to claim 1 or 2, wherein the load of the inverter is a discharge lamp.