TWI239378B - Power factor correcting circuit for electronic ballast - Google Patents

Abstract

Disclosed is a power factor correcting circuit for electronic ballast of fluorescent lamp. The power factor correcting circuit is arranged between a bridge rectifier circuit and a high frequency oscillation circuit of the electronic ballast and is comprised of a filtering capacitor charging/discharging circuit and a feedback circuit for feedback of lamp filament to provide power factor greater than 0.95, lamp current peak factor greater than 1.7, and overall harmonic distortion less than 10%.

Description

When the AC voltage is constant, the road is stable for the oscillating display, and the b-wave converter changes the frequency of the wave 6 彡 photon to the high-resolution filter 1 1, and the current device uses the first-order circuit C, and the direct current is determined by Pressure such as, tube capacity to save Zaizi electricity. ο Lamp electric, one, electric lamp 1 moves one. light. The streamer of the streamer drive has a small amount of flow. It ’s straightforward to know that after the electricity package, the main priority is to wait for Xi Liangliang to change, and then reorder, 2 single small devices, the following formula 4 Of course, the road body of the bridge 1 is safe and secure. The electric power including the bundled electric waves of the string lights and the high-frequency filter oscillating filter due to the optical connection is the first day. The frequency of direct money technology has been changed in the group of high frequency, high price, this way to high electricity and the former electric element-based electricity into electricity, its a priori, the market changes know 2. The inverse practice of method t equalizer flow 1 light do 1239378 V. Description of the invention (1) [Technical field to which the invention belongs] The present invention relates to a high-efficiency fluorescent lamp electronic ballast, or more specifically, to a Power factor correction circuit for electronic ballasts for fluorescent lamps. The input AC voltage V s is rectified by the bridge-type rectifier circuit 10 and then charged and discharged by the capacitor C 1 to form a DC voltage with ripples across the capacitor C 1. Because the AC voltage V s only has a sufficiently large voltage near its peak or valley, the capacitor C 1 is charged by the bridge rectifier circuit 10, so the input AC current will have a pulse waveform. Generally, in order to reduce the ripple of the DC voltage (that is, to improve the filtering effect), a capacitor C 1 with a larger capacitance is selected, but this will make the input AC current pulse sharper.

Page 5 1239378 V. Description of the invention (2) Sharp.

The second figure is a waveform diagram of the input AC voltage V s and the AC current I s of the conventional electronic ballast. As shown in the second figure, the input AC current I s is a sharp pulse with severe distortion, which results in an increase in the harmonic content (especially the third harmonic content) and a decrease in the power factor. The increase of harmonic content will increase electromagnetic interference. If a large number of such electronic ballasts are used, the power supply system may trip (burn out the fuse), and more serious situations may lead to fires. The reduction of the power factor increases the power consumption of the power supply system and increases the cost of electricity.

If the capacitance of capacitor C 1 is reduced, this will certainly reduce the distortion of the input AC current I s, reduce its harmonic content, and increase its power factor, but the DC voltage formed across capacitor C 1 will have a ripple amplitude. It will increase, which in turn will cause the crest factor (ratio of the current peak value to the effective value) of the lamp current to exceed the rated value of the lamp, thereby reducing the life of the lamp. The lamp life test standard is generally measured under the condition that the lamp current crest factor is 1.7 or less. It can be seen from the above that reducing the input current harmonics and increasing the power factor, and reducing the lamp current crest factor, the two are actually in conflict with the conventional electronic ballast. The so-called high-efficiency electronic ballasts currently on the market, the vast majority of the total harmonic distortion -10%, power factor and 0.50, lamp current crest factor -1.7, its harmonic content is very high and The power factor is very low, so it is highly efficient

Page 6 1239378 V. Description of the invention (3) The rate actually refers to the high frequency and high efficiency of the lighting. To achieve real high efficiency, it is necessary to add some circuits in the electronic ballast to solve the above problems. At present, the general electronic ballasts reduce the input AC current harmonic content and increase the power factor. The scheme mainly adopts active or passive power factor correction circuits. The active power factor correction circuit uses active components, so the structure is complex, bulky, and costly. However, the conventional passive power factor correction circuit has a poor improvement effect and is difficult to be practical.

[Summary of the Invention] "The technical problem to be solved"; The distortion of the input current of the current electronic stabilizer, which causes the current harmonic content (especially the third harmonic content) to increase and the power factor to decrease. Increasing the content of spectral waves will increase electromagnetic interference. If this type of electronic ballast is used in large quantities, it may cause tripping of the power supply system (burning the fuse), and more serious conditions may cause fires. The reduction of the power factor increases the power consumption of the power supply system and increases the cost of electricity.

In addition, the conventional passive power factor correction circuit has a poor improvement effect, the input current harmonic content is still high, the reliability is low, the lamp current crest factor is high, and the lamp life is reduced, which is difficult to be practical.

Page 7 1239378 V. Description of the invention (4) "Technical means to solve the problem"

The invention relates to a conventional electronic ballast bridge rectifier circuit and a high-frequency oscillation circuit. A plurality of diodes and a capacitor form a power factor correction circuit, replacing the conventional single capacitor filter circuit. This power factor correction circuit includes a filter capacitor charging and discharging circuit and a feedback circuit fed back from the lamp filament. The former reduces the equivalent capacitance of the power supply voltage when charging it, making the input AC current waveform smoother and the harmonic content. When the former is discharged to the load, the equivalent capacitance is increased, the discharge time constant is increased, and the amplitude of the DC voltage ripple is reduced. This also reduces the fluctuation of the current supplied to the lamp and reduces its crest factor. . The latter further superimposes the high-frequency voltage on the low-frequency DC voltage output by the rectifier circuit, making the input AC current waveform closer to a sine wave. "Effects of the prior art" The power factor correction circuit of the present invention can achieve low harmonic content of input AC current (total harmonic distortion < 10%), high power factor (power factor)

0. 9 5), the lamp current crest factor is lower than the rated value (lamp current crest factor < 1. 7), it also has a small volume, low cost, high working reliability, especially suitable for use in Small and medium power self-excited electronic ballasts. The object, features and advantages of the present invention can be further understood through the following detailed description and accompanying drawings. It should be understood that the foregoing general description, the following detailed description and the accompanying drawings are exemplary. And explain

Page 8 1239378 V. Description of the Invention (5) It is intended to provide a further explanation of the invention, and is not intended to impose any additional restrictions on the invention. [Embodiment] In order to explain the object, features, and effects of the present invention in detail, the present invention will be described in detail with reference to the following preferred embodiments and the accompanying drawings. The power factor correction circuit of the present invention is built on a conventional electronic ballast circuit and operates in combination with it. The third figure is a circuit diagram of an electronic ballast according to a preferred embodiment of the present invention. As shown in the third figure, the bridge rectifier circuit 10, the high-frequency oscillation circuit 14 and the lamp tube circuit 16 are all conventional electronic ballast circuits. The power factor correction circuit includes a filter capacitor charging and discharging circuit and a feedback circuit. The following describes the filter capacitor charging and discharging circuit. The filter capacitor charging / discharging circuit includes diodes D 1 to D 5 and filter capacitors C 1 and C 2. The output of the positive terminal of the bridge rectifier circuit 10 and a rectifying diode D 5 are connected in a forward direction to a point B. Between this point B and the output point C of the negative terminal of the bridge rectifier circuit 10, the filter capacitor C 1 and The diode D 4 is connected in series, and the diode D 4 is connected in a negative direction by its anode and point C. At the same time, between point B and the output C of the negative terminal 10 of the bridge rectifier circuit, the diode D 3 and the filter capacitor C 2 are connected in series.

Page 9 1239378 V. Description of the invention (6) Type connection, in which the diode D 3 is connected in a negative direction, and its cathode is connected to point B. Between the connection point of the filter capacitor C 1 and the diode D 4 and the connection point of the diode D 3 and the filter capacitor C 2, the diodes D 1 and D 2 are connected in series in a forward direction, of which two The cathode of the pole D 4 is connected to the anode of the diode D 1, and the cathode of the diode D 2 is connected to the anode of the diode D 3. In this filter capacitor charging and discharging circuit, the filter capacitors C 1 and C 2

The charging path is from point B to C 1, via diodes D 1, D 2, to C

2. Then go to point C. The discharge path of filter capacitor C1 is from C1 through point B, load, point C, and finally through diode D4, and then back to C

1 . The discharge path of the filter capacitor C 2 is from C 2 through the diode D 3, point B, load, point C, and then back to C 2. The DC voltage of the bridge rectifier circuit 10 and the diode D 5 supplies power to the high-frequency oscillation circuit 14 on the one hand from the point B, and charges the filter capacitors C 1 and C 2 via the charging path on the other hand. C 1 and C 2 form a series relationship. Assuming that the diodes D 1 and D 2 are ideal diodes (that is, regardless of their electrical resistance), and the capacitances of C 1 and C 2 are both C, etc. Effective filtering capacitance = (CxC) / (C + C) = C / 2, that is, the equivalent filtering capacitance is 50% less than the capacitance of a single capacitor C 1 or C2. As the equivalent filtering capacitance is reduced, the input AC current waveform will be smoother, and the harmonic content will be reduced, thereby increasing its power factor.

Page 10 1239378 V. Description of the invention (7) When the voltage at point B is less than the sum of the voltages of the filter capacitors C 1 and C 2, then C 1 and C 2 discharge the load in parallel with their respective discharge paths, assuming two poles The bodies D 1 and D 2 are ideal diodes (that is, their conductive resistance is not considered), and the capacitances of C1 and C2 are both C, then the equivalent discharge capacitance = C + C = 2C, which is equivalent The discharge capacitance is twice as large as that of the single capacitor C1 or C2, and the time constant of the discharge is also twice as large as the time constant of the single capacitor C1 or C2. This reduces the DC voltage ripple amplitude. The fluctuation amplitude of the current supplied to the lamp tube 17 is reduced, so that its crest factor is reduced. Electricity and electricity three C's one transistor is connected to the second device with a frequency of two lamps. The electricity and the other two are known as high school and D. Their habits and examples are coupled. The 6 application of this 1 connection shows that the C real warp D point is connected to the good point C of the device. The picture size is compared with the B, the electricity, the telecommunication, the second 3, and the C 6 in this frequency. If the high-frequency circuit breaker D is sold. The end of the capacitor body is connected with a wire discharge electrode, and the lamp is charged with one or two points of feed wire, and the capacitor is opposite to the B lamp. For electricity, 4 is connected to the 1-point and 1-point C-series tracing tube with filter A, and the lamp is out to this yin yin, and the output is connected to the connection from the electrical connection. 6 6 4 1 1 points, point D Road Figure 6 A string

Page 11 1239378 V. Description of the invention (8) These two will further make the waveform of the input AC current I s smoother and closer to the sinusoidal waveform, and also reduce the DC voltage ripple amplitude further, making the lamp tube 1 7 The current crest factor decreases. Please refer to the fourth figure, which is a waveform diagram of the input AC voltage: V s and the parent current I s in this preferred embodiment of the present invention. As shown in the fourth figure, the power factor correction circuit of the present invention precisely inputs the pulse waveform of the alternating current I s, which approaches a sinusoidal waveform. This is sharper than the sharp pulse shape of the conventional electronic ballast shown in the second figure. Significant improvement. The high-efficiency power factor correction circuit of the present invention has the following advantages: (a) The third harmonic content of the input AC voltage V s is reduced, the total harmonic distortion is reduced to less than 10%, the electromagnetic pollution is reduced, and the application efficiency is improved. Electrical safety. (b) Increase the power factor to above 0.95 and reduce the power loss of the power supply system. (c) Reduce the amplitude of the DC voltage fluctuation, reduce the crest factor of the current of the lamp tube 17 to less than 1.7, extend the service life of the lamp and tube 17, and also improve the reliability of the components of the high-frequency oscillation circuit 14, The overall reliability of the electronic ballast has also improved a lot. (d) Reduce the capacitance and required withstand voltage of the filter capacitor, reduce the cost of the filter capacitor and increase its reliability. For those familiar with this technology, it is clear that various modifications and changes can be applied.

Page 12 1239378 V. Description of the invention (9) The power factor correction circuit based on the present invention without departing from the spirit or scope of the present invention. Therefore, it can be expected that the modifications and changes of the present invention are covered by the present invention if they conform to the scope of the attached application patent and its equivalent definitions.

Page 13 1239378 Brief description of the diagram The first diagram is a circuit diagram of a conventional electronic ballast. The second figure is a waveform diagram of the input AC voltage V S and the AC current Is of the conventional electronic ballast. The third figure is a circuit diagram of an electronic ballast according to a preferred embodiment of the present invention. The fourth figure is a waveform diagram of the input AC voltage V s and the AC current I s of the electronic ballast according to a preferred embodiment of the present invention. [Description of component symbols]

10 Bridge rectifier circuit 12 DC filter circuit 14 Surface frequency vibration surplus circuit 1 5 AC / DC converter 16 Lamp tube circuit 17 Lamp tube

Vs input AC voltage

Is Input AC current C1, C2, C3, C4, C5, C6 capacitors Q1, Q2, transistor

L 1 inductor D, D 2, D 3, D 4, D 5, D 6, D 7, D 8, D 9, D 10, D11, D12 diodes

Page 14

Claims (1)

Ρ # | ι 6. Application for patent application HI. A kind of power factor correction circuit for fluorescent lamp electronic mouth fluorescent lamp electronic safety lamp-crying girl benefit, which is located between a rectifier circuit and a high-frequency oscillating circuit. Correction circuit: Yu You: l The commercial power is rectified into a direct current voltage, and the power is turned on. Among them, this function is a high-frequency oscillation circuit. The correction circuit for the point-to-wave capacitor number of the lamp tube includes: The capacitor is composed of a plurality of capacitors in series, and the feedback circuit is a discharge circuit which will discharge electric current in parallel with t; it is high frequency with one of the Γ filament contacts to which the filter capacitor is charged and discharged. Signal feedback voltage. In the circuit, add the straight 2 to the output of the rectifier circuit. • If a special correction circuit is applied, a diode D is connected, and its cathode and capacitor C 4 are connected in series with the negative diameter of the output of the 1 diode; The polar body D 2 is a series of cathodes and current circuits. The power factor of the fluorescent lamp electronic ballast is 1%. The filter capacitor charging and discharging circuit includes: 1 ^ its anode system and the output of the rectifier circuit The positive terminal is connected to the positive terminal of the input of the high-frequency oscillation circuit; diode D4, this capacitor C1 and the diode! ^ = Formula, from the cathode of the diode D5, through the anode of the capacitor ^, the anode of the diode _, to the rectifier circuit 鳊, this connection constitutes one of the capacitor c 丄, and a capacitor 02, The diode 03 is the same as the capacitor c, from the cathode of the diode D5, through the anode of the diode D to the diode D3, through the capacitor c2, to the negative terminal of the whole, this one The wiring constitutes one of this capacitor c 2 1239378 Case No. 93106509 Amendment VI. Patent application scope Electric path; a diode D 1 and a diode D 2, the diodes D 1 and D 2 are connected in series by the cathode of D 1 and the anode of D 2 The method lies between the two discharge paths of the aforementioned capacitors C 1 and C 2, from the capacitor C 1, via the diodes D 1, D 2, to the capacitor C 2, constituting the capacitors C 1, C 2 A charging path. 3. The power factor correction circuit of the fluorescent lamp electronic ballast according to item 1 of the scope of patent application, wherein the feedback circuit includes: a capacitor C 6 which is connected to a filament contact of a lamp tube and the diode D 1, At the junction between D 2, a capacitor C 3 is connected between the junction between the diodes D 1 and D 2 and the negative terminal of the output of the rectifier circuit; a capacitor C 4 and a diode D 6, The capacitor C4 and the diode D 6 are connected in series from the junction between the diodes D 1 and D 2, through the capacitor C 4, the anode of the diode D 6, and the cathode of the diode D 6 to The positive terminal of the output of the rectifier circuit. Page 16