JPH0210696A - Device for lighting discharge lamp - Google Patents

Abstract

PURPOSE:To stabilize energy accumulated in a choke by a method wherein a second smoothing capacitance C2 is charged by electric current fed back from a part of an inverter and C2 voltage is intermittently applied to a choke between homopoles of commutative output of a commercial power source VS and a first smoothing capacitance C1. CONSTITUTION:In addition to smoothing capacitance C1 of an input terminal of an inverter INV, capacitance C2 which is charged lower than voltage VC1 and the peak of a commercial power source C2 is provided and intermittently applied to a choke L0 between an output terminal of a full-wave rectifier DB and capacitance C1 via a transistor Q0. While the device Q0 is on, VC2 is added to L0, and while the device Q0 is off, self induction voltage of L0 overlaps the output of the all-wave rectifier so as to charge C1. As a result, while momentary voltage of VS is low, input current Iin from VS does not resume so that current of a discharge lamp L2 is stable, increasing input rate and decreasing higher harmonic component of input current. This constitution keeps voltage to be applied to L0 almost constant, stabilizes accumulated energy, compacts L0 and reduces pressure of a device 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a discharge lamp lighting device that receives a commercial AC voltage as an input and lights a discharge lamp at high frequency.

[Prior Art] Conventionally, a discharge lamp lighting device has been widely used that inputs a DC voltage obtained by rectifying and smoothing the AC voltage of a commercial power supply to an inverter, converts it to high frequency and supplies it to the discharge lamp, and lights the discharge lamp at high frequency. It is being In this type of lighting device, the rectified output of the commercial AC voltage is smoothed so that the envelope of the high-frequency current supplied to the discharge lamp does not fluctuate with the commercial AC cycle. This is to substantially eliminate the arc phenomenon, improve the luminous efficiency of the discharge lamp, reduce the power consumption of the device, and eliminate flickering of light, thereby improving the performance of the lighting device.

However, when the commercial AC voltage is rectified and smoothed, the current flowing from the commercial power supply to the smoothing capacitor will only flow near the peak value of the commercial AC voltage, and the current flowing into the smoothing capacitor from the commercial power supply will only flow around the peak value of the commercial AC voltage. Because it is a current, the input power factor is poor and it also contains many high-order harmonic current components relative to the AC fundamental frequency, which may cause high-frequency noise to be mixed into other equipment connected to the same AC power distribution system. There were other negative effects. Therefore, in order to increase the power factor of the input current, reduce harmonic components, and supply the inverter with a DC smoothed voltage as flat as possible, various measures have been taken as described below.

Low speed 1 FIG. 4 is a circuit diagram of a conventional example. In this conventional example, a push-pull type inverter is used as the inverter INV. The positive output terminal of the full-wave rectifier DB is connected to the primary winding N1 of the oscillation transformer T. The primary winding of the zero oscillation transformer T connected to each end of N + , N 2
The other ends of each transistor Q1.

A resonant capacitor C1° is connected to the primary windings N + and N2 of the zero oscillation transformer T, which is connected between the collector and emitter of Q2° and to the negative output terminal of the full-wave rectifier DB via the choke L1. are connected in parallel.

Transistor Q. The bases of transistors Q2 and Q2 are connected to resistors R1 and Rt. are connected to the positive input terminal of the full-wave rectifier DB via the oscillating transformer T, and to both ends of the feedback winding N3 of the oscillation transformer T, respectively.

A discharge lamp La is connected to the secondary winding UAN4 of the oscillation transformer T, and a high frequency voltage is obtained at both ends thereof.

A smoothing capacitor C0 is connected between the positive output terminal and the negative output terminal of the full-wave rectifier DB through a reverse diode D0.
is connected. Diode D0 and smoothing capacitor C
6 connection point is choke L 10 and diode D. ,
Dx. The primary winding N of the oscillation transformer T, ,
Connected to the middle tap of N2.

In other words, in this conventional example, each primary winding N of the oscillation transformer T in the push-pull inverter INV,
An intermediate tap is provided at N2, and a portion of the voltage generated in each primary winding N, , N, is fed back to the smoothing capacitor C0 on the input side. The feature of this method is that the smoothing capacitor C
The charging current of 0 is always the primary winding N + of the oscillation transformer T.
, Nx. Therefore, the input current Iin from the commercial power source Vs does not have a pulse-like waveform, but has a relatively smooth waveform as shown in FIG.

In this conventional example, during the period when the voltage of the commercial power supply Vs is higher than the voltage vc0 of the capacitor C0, the inverter IN
Current flows directly from the commercial power supply Vs to V, and the primary winding N
+, charges the smoothing capacitor C8 through a portion of N2. Conversely, the voltage of the commercial power supply Vs is the voltage ■ of the smoothing capacitor C0. . For periods lower than the inverter INV
Current flows from the capacitor C0 to the capacitor C0, and no longer flows from the commercial power supply Vs.

Therefore, the input voltage of the inverter INV has a waveform in which the pulsating voltage is filled in with the voltage VCO of the capacitor C6. This method provides a stable output even during periods when the input power factor is high and the pulsating voltage is low, but it has the disadvantage of a high distortion factor of the input current because there is a rest period in the waveform of the input current Iin. have

A1 Figure 6 is a circuit diagram of another conventional example. In this circuit, a step-up chopper CHP is inserted between the full-wave rectifier D B + and the smoothing capacitor C0. In the step-up chopper CHP, a choke L0 is connected to the rectified output terminal of a full-wave rectifier D B + via an L-transistor Q0 for switching, and a smoothing capacitor is connected to both ends of the transistor Q0 via a diode D0 for blocking reverse current. C0 is connected to the drive circuit A, and the switching transistor Q is connected to the drive circuit A. By switching at high frequency, a voltage higher than the peak voltage obtained at the rectified output terminal of the full-wave rectifier DB is obtained at the smoothing capacitor C0. That is, transistor Q. During the ON period of the transistor Q0, energy is stored in the choke L0, and during the OFF period of the transistor Q0, the self-induced electromotive force of the choke L0 is superimposed on the full-wave rectified output of the commercial power supply Vs to charge the smoothing capacitor C0. Therefore, even during a period when the instantaneous voltage value of the commercial power supply Vs is low, the electromotive force of the choke L0 is applied, so the input current Iin from the commercial power supply Vs has the advantage that almost no rest period occurs, and the input power factor is high. Furthermore, it is possible to suppress harmonic components of the input current to a low level.

[Problem M to be solved by the invention] In the conventional example 1 described above, by charging the smoothing capacitor C8 with the self-induced voltage generated in the primary winding of the oscillation transformer T in the inverter INV, the smoothing capacitor C8 is charged directly from the commercial power supply Vs. Avoiding charging the capacitor C0, the commercial power supply V
By providing a charging path for S, inverter INV, and smoothing capacitor C0, the current conduction period from commercial power supply Vs to smoothing capacitor C0 is extended, and the peak value of input current Iin is reduced. However, in this conventional example, since the smoothing capacitor C0 is provided in parallel with the output of the full-wave rectifier DB, the commercial power supply Vs
During the period when the instantaneous voltage value of is low, as shown in Fig. 5, a rest period T occurs in the input current Iin from the commercial power supply Vs, and it is possible to achieve an input power factor of 90% or more. , there is a drawback that the input current Iin contains many odd-order harmonic components.

In addition, in the above-mentioned conventional example 2, since the power source for storing energy on the choke of the boost chopper CHP is a full-wave rectified output, the stored energy is small during a period when the instantaneous voltage value of the commercial power source Vs is low. During high periods, the stored energy becomes large. For this reason, the commercial power supply V
When the instantaneous voltage value of s reaches the peak value, it is choked. The accumulated energy of the chopper increases, and therefore the self-induced electromotive force also increases.Therefore, the voltage of the smoothing capacitor C0 becomes more than twice as high as the peak voltage of the commercial power supply Vs. There is a drawback that a transistor with a high breakdown voltage is required for use in the CHP and the inverter INV, resulting in an increase in device cost. Also, based on the chopper operation, a full wave rectifier D
Since the chopper current flowing through B + becomes a high-frequency triangular wave, the high-frequency removal filter circuit RFT for preventing this from flowing to the commercial power supply ■s has the drawback of being large and expensive.

The present invention has been made in view of the above points, and its purpose is to reduce the harmonic components of the input current from a commercial power source, improve the input power factor, and improve the input current supplied to the discharge lamp. An object of the present invention is to provide a discharge lamp lighting device in which the envelope of a high-frequency current is substantially constant during a commercial AC cycle.

[Means for Solving the Problems] In the present invention, in order to solve the above problems, the first
As shown in the figure, the AC voltage of the commercial power supply Vs is rectified, smoothed by the first smoothing capacitor CI, and then connected to the inverter IN.
In this device, a second smoothing capacitor C2 is provided which is charged with the current fed back from a part of the inverter INV, and the second smoothing capacitor C2 is charged with the current fed back from a part of the inverter INV. While intermittently applying the voltage of C2 to the choke L0 connected between the rectified output of the commercial power supply Vs and the same pole of the first smoothing capacitor C5,
This is characterized in that the voltage of the second smoothing capacitor C2 is set lower than the peak voltage of the commercial power supply Vs.

[Function] In this way, in the present invention, the voltage of the second smoothing capacitor C2 charged with the current fed back from a part of the inverter INV driven by the rectified and smoothed voltage of the commercial AC voltage is Rectified output of power supply Vs and first smoothing capacitor C
Since the voltage is applied intermittently to the choke L0 connected between the same poles of the choke L. The voltage value that is intermittently applied to becomes substantially constant, and the energy stored in the choke L0 is stabilized compared to the conventional example using the chopper CHP. Moreover, since the voltage of the second smoothing capacitor C2 is set lower than the peak voltage of the commercial power supply Vs, the choke L0 can be made smaller and the circuit elements used can be designed to have lower breakdown voltages.

"Example 1" Fig. 1 is a circuit diagram of an embodiment of the present invention, and Fig. 2 is an operating waveform diagram of the above circuit. Connected.Commercial power supply Vs
A filter capacitor C for high frequency removal is arranged between the full-wave rectifier D B + and the full-wave rectifier D B +. full wave rectifier DB,
The positive output terminal of is connected to the positive terminal of the first smoothing capacitor C1 via a choke L0. Full wave rectifier DP
The negative output terminal of I is connected to the negative terminal of the first smoothing capacitor C1, and the voltage across this smoothing capacitor CI is the input voltage of the inverter %NV.

The high frequency output of the inverter INV is applied to a load such as the discharge lamp La. The current fed back from a part of the inverter INV is full-wave rectified by a full-wave rectifier DB2,
Charge the second smoothing capacitor C2. The second smoothing capacitor C2 is a transistor Q. choke L0 through
connected to both ends. Transistor Q0 is turned on and off at high speed by drive circuit A1. The voltage of the second smoothing capacitor C2 is set lower than the voltage of the first smoothing capacitor CI and lower than the peak voltage of the rectified output by the full-wave rectifier DB, and during the on period of the transistor Q0, The polarity is set so that the current flows from the second smoothing capacitor C2 to the choke L0 in the same direction as the charging current flowing from the full-wave rectifier DB to the first smoothing capacitor C1.

In this way, in the circuit of FIG. 1, in addition to the first smoothing capacitor C connected to the input terminal of the inverter INV, the voltage of this capacitor C3. , and is charged to a voltage lower than the peak voltage of the commercial power supply Vs.
A capacitor C2 is provided, and the voltage Vc2 of the capacitor C2 is
is intermittently applied to the choke L0 connected between one end of the rectified output terminal of the full-wave rectifier DB and one end of the first capacitor C9 through the transistor Q0, so that the second capacitor The voltage of C2 is applied to the choke L0, energy is stored in the choke L0, and during the off period of the transistor Q0, the self-induced voltage of the choke Lo is superimposed on the full-wave rectified output, and the first
The smoothing capacitor C8 is charged. Since the voltage of the second capacitor C2 is lower than the peak voltage of the commercial power supply Vs and has a substantially constant value, the self-induced voltage of the choke L0 is effectively superimposed during a period when the instantaneous voltage value of the commercial power supply Vs is low. First smoothing capacitor C1
When the input current Iin from the commercial power supply Vs is passed through the input current Iin from the commercial power supply Vs, conversely, during the period when the instantaneous voltage value of the commercial power supply Vs is higher, the current change in the choke L0 due to the on/off of the transistor Qo is small, so the self-induced voltage of the choke L0 itself becomes smaller, and the superposition effect becomes smaller. As a result, during a period when the instantaneous voltage value of the commercial power source Vs is low, there is no pause period for the input current Iin from the commercial power source Vs, the current ILa flowing through the discharge lamp La becomes stable, the input power factor increases, and the input current The harmonic components of are reduced, and the voltage VC of the first capacitor C3 can also be made approximately 1.2 to 1.5 times the peak voltage of the commercial power supply Vs.

[Example 2] FIG. 3 is a circuit diagram of another embodiment of the present invention.

This embodiment is an example of a circuit using a self-excited inverter as the inverter INV. A positive output terminal of the first smoothing capacitor CI, which serves as a power source for the inverter INV, is connected to one end of the primary winding nl of the oscillation transformer T.

The other end of the primary winding n is connected to the negative output terminal of the first smoothing capacitor C1 via a switching transistor Q1 and a diode D1. Primary winding n
A discharge lamp L is connected to the secondary winding n2 of the zero oscillation transformer T, to which a resonance capacitor C4 is connected in parallel to both ends of the zero oscillation transformer T.
A load consisting of a is connected. One end of a parallel circuit of a choke resistor R4 is connected to the base of the transistor Q, and the other end of the parallel circuit is connected to the positive output terminal of a smoothing capacitor CI via a starting resistor R3.
Feedback winding via capacitor C6! connected to one end of the ins. The other end of the feedback winding n3 is a smoothing capacitor CI.
A second smoothing capacitor C2 is connected to the primary winding n1 of the zero oscillation transformer T connected to the negative output terminal of the transformer T through a feedback charging circuit B consisting of a series circuit of a choke L2 and a diode D2. There is. When the transistor Q is off, the oscillating voltage induced at the primary winding port 1 of the oscillation transformer T is applied to the second smoothing capacitor C2 via the feedback charging circuit B. It charges to the polarity set. Second smoothing capacitor C
2 is connected to both ends of choke L0 via transistor Q0. Transistor Q. is turned on and off at high speed by the drive circuit A1, whereby the voltage of the smoothing capacitor C2 is intermittently applied to the choke L0. The voltage of the smoothing capacitor C2 is set lower than the peak voltage of the rectified output from the full-wave rectifier DB, as in the first embodiment described above.

When the power is turned on, the base current flows through the starting resistor R1 to the transistor Q1, turning on the transistor Q1. From then on, due to the oscillation principle of a ringing choke type inverter, the transistor Q is turned on and off at high frequency, and the discharge lamp La is turned on. A high frequency current flows through it. The envelope is determined according to the voltage of the first smoothing capacitor C1 and does not vary with respect to the commercial AC cycle.When the transistor Q1 is off, the second smoothing capacitor C2 is charged via the feedback charging circuit B. Other operations are the same as in the first embodiment.

[Effects of the Invention] As described above, the present invention converts the voltage of the second smoothing capacitor charged with the current fed back from a part of the inverter driven by the rectified and smoothed voltage of the commercial AC voltage to the voltage of the commercial power source. !
! Since the voltage is intermittently applied to the choke connected between the output output and the same pole of the first smoothing capacitor, the voltage value intermittently applied to the choke is approximately constant, which is different from the conventional method using a step-up chopper. Compared to the example above, this has the effect of stabilizing the energy stored in the choke. Moreover, since the voltage of the second smoothing capacitor is set lower than the peak voltage of the commercial power supply, the choke can be made smaller, and the parts that make up the inverter, especially the switching elements, can be designed to have a lower withstand voltage. This has the effect that the device can be made smaller and cheaper.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a first embodiment of the present invention, FIG. 2 is an operation waveform diagram of the same as above, FIG. 3 is a circuit diagram of a second embodiment of the present invention, and FIG. 4 is a circuit diagram of a conventional example. FIG. 5 is an operating waveform diagram similar to the above, and FIG. 6 is a circuit diagram of another conventional example. Vs is a commercial power supply, C3 is a first smoothing capacitor, C2 is a second smoothing capacitor, INV is an inverter, La is a discharge lamp, Q is a transistor, and L is a choke.

Claims (1)

[Claims] (1) In a device that rectifies the AC voltage of a commercial power supply, smooths it with a first smoothing capacitor, inputs it to an inverter, and lights a discharge lamp with the high frequency output of the inverter, the current returned from a part of the inverter A second smoothing capacitor to be charged is provided, and the voltage of the second smoothing capacitor is intermittently applied to a choke connected between the rectified output of the commercial power supply and the same polarity of the first smoothing capacitor, and the second smoothing capacitor is charged. A discharge lamp lighting device characterized in that the voltage of a smoothing capacitor is set lower than the peak voltage of a commercial power supply.