KR810000566B1 - Stabilizer for electronic fluorescnet lamp - Google Patents

Abstract

A fluorescent lamp ballast circuit includes a tunned OSC coupled to a pulsed DC potential source and to a transformer having a first winding directly connected to the OSC and in series connection with a capacitor to form a series resonant circuit. A second winding of the transformer inductively couples the first winding of the transformer to the OSC, a hird winding includively couples a load across the capacitor of the series resonant circuit, and a forth winding is inductively coupled to the first winding of the transformer and clamps the DC potential source to a given poential level.

Description

Electronic fluorescent ballast

1 is a circuit diagram for lighting a fluorescent lamp with a known direct current.

2 is an example of a circuit for lighting a fluorescent lamp using a known inverter circuit.

3 is a basic circuit of an electronic fluorescent ballast according to the present invention.

4 is an equivalent circuit for explaining the basic operation principle of FIG.

5 is a waveform diagram showing the switching operation of FIG.

6 is an example in which the basic circuit of the present invention is composed of a full bridge.

7 is an embodiment in which one fluorescent lamp is connected to the basic circuit of the present invention.

8 is an embodiment in which two fluorescent lamps are connected to the basic circuit of the present invention.

9 is an embodiment in which three fluorescent lamps are connected to the basic circuit of the present invention.

10 is an embodiment in which several fluorescent lamps are connected in parallel to the basic circuit of the present invention.

The present invention relates to an operation circuit for an antistatic lamp, in particular a lighting circuit system of a fluorescent lamp.

A general object of the present invention is to realize instantaneous lighting and high efficiency lighting of fluorescent lamps as a lighting device using a novel inverter inverter circuit for lighting a load, in particular, various kinds of general fluorescent lamps.

The present invention is a direct current power supply, two transistors connected in series to a direct current power supply, a current transformer (Currnt Transformer) for maintaining the oscillation operation of the two transistors, is connected to the connection point of the two transistors composed of an inductor and a capacitor The present invention relates to an operation circuit based on a type including a series resonant circuit, and a fluorescent lamp connected between a capacitor of a resonant circuit and another capacitor connected to a power source, and in particular, a connection with an inverter, a series resonant circuit, and a fluorescent lamp. It relates to a reconstruction method for.

Regarding the conventional fluorescent lamp lighting device, except for the conventional method of using the most commonly used choke, the method of lighting a fluorescent lamp by rectifying an alternating current as shown in FIG. 1 as a direct current (Korean Patent Publication 78) Transistor inverter systems as shown in (561) and (Fig. 2) are known.

The scheme of FIG. 1 connects capacitors CF1 and CF2 respectively across bridge diodes DF1-DF4 and diodes DF2 and DF4 connected to an AC power source, and another capacitor across the bridge diodes. (CF3) is connected, and a fluorescent lamp is connected to the capacitor and CF3 through resistor RF.

The method initially multiplies the voltage by the role of diodes DF1, DF2 and capacitors CF1, DF2. When the fluorescent lamp is lit by the multiplied voltage, the main current flows through the diodes CF1-DF4, and the limit of power is controlled by the resistance RF. It can be adjusted.

The advantage of this method is that it lights up without the need for a starter lamp and is smaller and lighter than conventional choke stabilizers. However, since the power is limited by the resistance, the power loss is large and the current flowing through the fluorescent lamp is direct current, so the photoelectric efficiency of changing to light is poor even at the same power consumption.In addition, only one filament of the fluorescent lamp is deteriorated when it is lit for a long time. The difference in efficiency is large, and it is difficult to design for various kinds of fluorescent lamps with different power consumption for a given input voltage.

The disadvantages of such ballasts can be eliminated by using electronic ballasts using transistor inverters.

As a representative example of a known electronic ballast, a transistor inverter method of the type shown in FIG. 2 will be considered. The method has one primary and one secondary ferrite transformer, respectively, and connects two transistors Q.1, Q.2, and a DC power supply to the primary side of the main transport T1 as shown in the drawing, and the secondary side n2. The fluorescent lamp is connected via an inductor Ld1 to the first winding of the auxiliary transformer T2 by simultaneously winding some windings to heat the filament of the fluorescent lamp and connecting the two transistors in the secondary of the auxiliary transformer. It is configured to supply the base current of (Q1, Q2). The method is a self-osillasion type inverter whose frequency is determined by the magnetic saturation characteristic of the transporter T1, and is a high frequency transistor inverter operating in the range of about 20KHz-50KHz. . Lighting of the fluorescent lamp is made possible by causing high voltage to be induced in the secondary by adjusting the primary and secondary turns ratios of the main transistor T1.

However, in the above scheme, as the secondary voltage is increased, the value of the choke Ld1 increases, which causes a spike of high voltage during switching of the transistors Q1 and Q2, and a current larger than the load current (n2>). In case of n1), it is very difficult to increase efficiency because it repeats the operation of flowing out and upside down from the power source through the transistor.

Since the switching operation of the transistors Q1 and Q2 occurs in the state where the most current flows, the time for turning off the transistor becomes long and the loss is increased. Connecting capacitor Cd1 to make the series resonance with Choke Ld1 as shown in the drawing can be improved a little, but anyway, the high cost and high voltage (high voltge) It is a big disadvantage to make it inevitable to use high speed power transistor.

SUMMARY OF THE INVENTION The object of the present invention relates to a novel type of inverter inverter circuit which is characterized by low cost, high efficiency, high reliability and instantaneous lighting while solving these various disadvantages.

The basic configuration of the present invention is as shown in FIG.

The basic circuit consists of two transistors (Q1, Q2) connected in series to a DC power supply, and a primary (N1) winding of the current transformer To and the inductor (Lo) at the connection points of the two transistors. Connect one end of the fluorescent lamp to the connection point of the two capacitors (C1) connected in series at both ends of the direct power, and the other end of the fluorescent lamp (7) is the connection point of the other two capacitors (C0) connected to the DC power supply at both ends The other end of the lamp and the two capacitors (Co) at the connection point (e ') of the two diodes (10, 11) connected to both ends of the DC power supply in the opposite direction to the polarity of the power supply depending on the type of fluorescent lamp. It is possible to connect or open between the connection point (e) of the, and the base current of the two transistors (Q1, Q2) to the polarity as shown in the figure so that can be supplied by the secondary winding of the current transformer (Curret Transfomer To) Results and is through the direct-current power supply 12, resistor 17 and capacitor 16 via the operating switch (So) in the form attached to the base of the transistor (Q2).

Where C1 is a lighting capacitor and Co is a power control capacitor. The basic circuit is a half bridge type, but as shown in FIG. 6, two transistors 14 and 15 may be added to the full bridge to form a full bridged type. In this case, the current transformer 3a further has two secondary windings N2 for the base current supply of the two additional transistors 14,15.

That is, in the full bridge type, a total of four secondary windings N2 are required for driving four different transistors 1, 2, 14, and 15, and the polarities of the respective windings are 1, 15 and (2, 14) are connected with the same polarity, respectively, so as to be turned on and off in synchronization with each other during the inverter operation.

In this case, the connection method of the capacitors Cl and Co is different from that of FIG. Detailed configuration of this is shown as including the series and parallel connection method of a plurality of fluorescent lamps from (Fig. 7) to (Fig. 10). In the above configuration, the capacitor Co is for filament heating of the fluorescent lamp and the start of lighting of the lamp, and the capacitor Co is for controlling the power of the lamp. A detailed description thereof will be provided later.

In order to explain the operation principle of the present invention will be considered with a focus on the basic configuration shown in (Fig. 3). (Figure 3) is, in principle, equivalent to (Figure 4). That is, transistors Q1 and Q2 are replaced by two switches S1 and S2, respectively, and capacitors 5 and 6 are equivalently synthesized.

However, in this case (Fig. 3), the points e and e 'are considered to be open. When the two circuits are equivalent, when the inverter of the present invention is operating at a high frequency, the power supply is applied to the AC component. Since the impedance of (12) is 0, the capacitors Cl and Co can be considered to be summed in one direction, respectively, and thus can be replaced by one capacitor each having a value of 2Cl and 2Co.

Also, in Fig. 4, the resistance ro denotes the separation of the copper wire resistance of the inductor Lo itself.

In other words, the basic principle of this circuit is to switch on and off the switches S1 and S2 at high speed alternately, and when the frequency matches the resonant frequency of the inductor Lo and the capacitor 2Cl, a very large voltage is generated by series resonance between the capacitors. Will appear.

(Because 2Co is not affected because the lamp is not lit yet.) When this voltage becomes higher than the discharge start voltage of the fluorescent lamp, the discharge occurs and the voltage across the lamp gradually decreases to reach a constant potential (this is a characteristic of the lamp. The power dissipated in the lamp is limited by the capacitor 2Co. Therefore, returning to (Fig. 3), the operation of the inverter circuit starts by stepping on the external switch So 18, because the transistors Q1 and Q2 are in the off state before the operation starts. 18) is because a short pulse current is applied to the base of the transistor Q2 through the capacitor 16 and the resistor 17 at the moment of closing, and once the operation occurs, the states of the transistors Q1 and Q2 are (Q1: Qn, Q2: Off) (Q1: Off, Q2: On) In either of these states, the voltage applied to the transistor in the off state is relatively low withstand voltage due to the supply voltage Vs and no voltage spike. The stable operation can be expected even with the transistor of.

The operating states of the transistors Q1 and Q2 at this time are shown in (Fig. 5). When the transistor (Q1 is in the ON state, the voltage vb at point b is

이기 때문)가 되고(because

Because)

When transistor Q2 is in the on state

Eventually, the voltage Vb at point b is maintained in the same state as opening and closing the switches S1 and S2 of FIG.

Current transformer To is needed to turn transistors Q1 and Q2 on and off in accordance with the resonant frequency.

Due to the role of the current transformer To, at any moment, only one transistor is in an on state, and a current equal to N1 / N2 times the current flowing through the emitter in the collector of this transistor is turned on. As it flows into the base of the transistor in the On state, it remains on after it is once turned on. Therefore, when the current flowing through the emitter from the collector (= current through inductor Lo) becomes zero, the transistor is automatically turned off, and the current of inductor Lo charges the capacitor (2 Cl + 2Co). After that, it automatically becomes 0. At this time, the voltages of the capacitors 2Cl and 2Co are overcharged by the role of the inductor Lo, which causes the current direction to change, which is off together with the magnetizing of the current transformer To. Since the transistor in the (Off) state is turned on, a regenerative operation occurs, so that oscillation is maintained.

Negative voltage spike occurs in the waveform of V _{BE in} the operating waveform of (Fig. 5) because the overcharge voltage of the capacitor causes the current to flow from the transformer To and the transistor Q2 (or Q1). ) Flows backward through the base-collector junction, and the interval becomes the length until the opposite transistor Q1 (or Q2) is turned on.

As can be seen from this process, the oscillation process is related to the mechanism of resonance of the inductor Lo and the capacitance 2Cl, so a very large voltage across the capacitor (Cl: 5 and 6), that is, the quality factor of the inductor Lo ( Qo, Qo. Vs is generated, and since this value exceeds the discharge start voltage of the lamp, the discharge is started and turned on.

After the lighting has occurred, the current flowing in the lamp is limited by the capacitor 2CO, and the oscillation frequency is lowered because the value of the entire capacitor increases from 2Cl to (2Cl + 2Co).

However, when the capacitor 2Cl for starting the discharge is directly connected to the inductor Lo without passing through the filament of the fluorescent lamp as shown in (Fig. 3), the resistance of the filament is excluded from the series resonant loop composed of Lo and 2Cl. As the quality factor Qo is large, it is advantageous to generate a large voltage across the capacitor Cl, but it is always necessary to remove the lamp with the power switch on when the worst condition is in mind. After the lamp is removed and the new lamp is not inserted, the oscillation continues, resulting in useless power consumption, and the capacitor Cl is destroyed when the idle voltage Qo Vs exceeds the internal voltage of the capacitor Cl.

Therefore, as shown in (Fig. 7), when the capacitor Cl for starting the discharge is connected after passing through the lamp filament, the oscillation is stopped when the lamp is removed, and the quality factor of the resonant circuit is reduced due to the resistance of the filament during operation. Becomes the idle voltage Qo. Vs is lowered, but instead, current flows through the filament and heats it, causing hot electrons to be released and discharge starts even at a lower voltage than if the filament had not actually passed through.

(Fig. 7) illustrates the case where one lamp is connected, and if the capacity of the capacitor is equivalent, (i) (ii) (iii) (iv) will be 2Cl and 2CO, and the inductor capacity will be Resonance frequency f is constant because all are Lo, but for equivalent resistance, if one resistance of filament is r, (i) is r, (ii) (iii) is r / 2 and (iv) is 2r, so Qo is Will be different.

Therefore, in the case of (ii) (iii), the equivalent resistance is relatively small, so Qo can be increased and idle voltage Qo, Vs can be moderately high, and discharge is started even at low input voltage. I can do it. In the case of (Fig. 8) and (Fig. 9), only different lamps are connected, but they are equivalent to (Fig. 7), and the filament connection method is slightly different.

(I) in FIG. 8 is 4r, (ii) is r, (iii) (iv) is 2r (v) and (vi) is r

(I) in Figure 9 is 6r, (ii) is 4r / 3, (iii) (iv) is 2r and (v) (vi) is r.

It is easy to see from the previous example that the connection in both (v) and (vi) is the most preferable in the case of (FIG. 8) and (FIG. 9).

In practice, however, the operating characteristics of the connecting lamps are slightly different, and the capacity of the capacitor Cl also differs, so that all the lamps are turned on in sequence instead of being turned on at the same time. By taking the secondary N2 out of the inductor Lo (iii) (iv) (v) When connected as in the case of (vi), the filament is heated and a current flows evenly through the lamp to enable the lighting.

However, in case of connecting the lamps in series as in (Fig. 8) and (Fig. 9), if one of the lamps is removed, the other lamp will not be lit. This can be complemented.

That is, since all of the connected lamps form their own resonant loops, removing other lamps does not affect the operation. Again (FIG. 3), when the discharge holding voltage V _F of the lamp is high (usually, the larger the power consumption, the higher the discharge holding voltage is), the diodes 10 and 11 are not affected. Removing 11 does not significantly affect the operation of the lamp.

If there is no influence of diodes 10 and 11, we will approximate the integer value of the circuit. If the pulsation voltage of the DC power supply is sufficiently small compared to the peak voltage, define Vs as the average DC voltage, and if the average load current supplied from the power supply is Is, then the total amount of power Ps supplied to the load can be expressed as Can be. In other words

In this case, if the resonant frequency at which the transistors Q1 and Q2 are synchronized on and off is represented by f, the load current will be equal to the current flowing through the capacitor.

Can be displayed as

to be. In this case, the lamp can be thought of as a resistor with an appropriate value during high frequency operation, and this value is defined as Ro.

Therefore, at this time, the operating frequency of the inverter coincides with the resonance frequency of the circuit and may be expressed as

In other words

here

Therefore, from the equations (2) and (5), Is is

Where Z is

From the equations (1) and (7), the following relation regarding Z is obtained. In other words

If the power consumed by the lamp during one cycle of inverter operation is W1

It may be displayed as follows.

In this case, when the inverter's efficiency is very good, the power Ps supplied to the load should be the same as the power consumed by the lamp.

If you rearrange equation (11)

Becomes So from (8), (12)

Can be obtained. However, the integer value of the circuit is from (6), (8)

Where Wo is given as a function of frequency f from equations (5) and (12), and therefore the average supply voltage (Vs) and the power consumption of the lamp (Ps) are given, and the operation of the inverter When the frequency f is selected, the constants L ₀ and C of the circuit can be obtained from the equations (13), (14) and (15).

The above calculations are approximated when the pulsation of the DC power supply voltage is small enough so that there is no significant difference between the average value and the effective value, and when the pulsation voltage is large, a significant error is obtained. Therefore, the exact integer value needs to be adjusted by experiment.

(Fig. 6) shows the form of a full bridge type, whereas (Fig. 3) is made of a half bridge type. will be.

Current transformer 3 _a has four secondary N2 coupled to one core with the same polarity as shown in the figure, and 1 and 15 of the four transistors (1, 2, 14, 15) and 2 and 14 are 1 Drive in pairs. Therefore, the operation principle can be easily understood from the description so far.

In the effect of the present invention, the test results of the present invention and known products with respect to the 40W × 2 fluorescent lamps are as follows.

1. Test report

(Compared to the 40W × 2 rapid start ballast case and 40W × 2 case of the electronic ballast of the present invention)

TABLE 1

(Note: Notices are in accordance with Korean Industrial Standards (KSC) 7601 and (KSC) 8109)

Finally, briefly summarized the features of the present invention.

First, power efficiency is good. That is, since the ON / OFF changes as the current goes to zero, there is no problem at the moment of change, and thus high efficiency can be obtained even by using a transistor having poor switching characteristics.

Second, if a voltage spike does not occur in the collector of the transistor and only the input voltage Vs can be tolerated, a transistor having a relatively low breakdown voltage can be used.

Third, the production cost can be greatly reduced because no ferrite transformer is used, and there is no power loss by the transformer.

Fourth, it is a momentary light.

Fifth, the lamp can be easily turned on even in the low voltage area, and stable angle is achieved without overwhelming voltage fluctuation (± 30%).

Sixth, compact and light weight is possible.

Seven, the heat rate is remarkably improved so that no reactive current flows to the power supply.

Claims (1)

As described above and illustrated in the drawings, in the method of lighting a discharge lamp such as a fluorescent lamp using a transistor inverter, two transistors Q ₁ and Q ₂ are connected in series at both ends of the DC power supply, An inductor L _o and a capacitor Cl constitute a first series resonant circuit, and connect a primary winding of the current transformer T _o in series with the first series resonant circuit, and electrically connect each other in the current transformer. Extracted by insulated secondary windings and connected between the base emitters of the two transistors (Q ₁ , Q ₂ ) so that their polarities are opposite to each other, and the fluorescent lamp and the capacitor (C _o ) at both ends of the capacitor (Cl). but by the connection in series with the inductor (L _o) to form a second series resonance circuit, the filament of the fluorescent lamp is configured to be inserted into the equivalent resistance in series with the first series resonant circuit Electronic fluorescent ballast circuit.

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