KR20030075414A - Electronic ballasts circuit for fluorescent lamps - Google Patents

Abstract

PURPOSE: An electronic stabilizer circuit for fluorescent lamp is provided to lengthen a lifetime by preventing a dropping phenomenon of an output voltage to a negative voltage to remove a malfunction of an IC element. CONSTITUTION: An electronic stabilizer circuit for fluorescent lamp includes a power input portion, a rectification portion, a smoothing circuit portion, a power factor compensation portion, a power consumption maintenance portion(42), a transistor control portion, and an output frequency control portion(43). The rectification portion rectifies the voltage of the power input portion. The smoothing circuit portion smoothens the rectified voltage. The power factor compensation portion compensates a power factor of the smoothened voltage. The power consumption maintenance portion(42) maintains the power consumption of the compensated voltage. The transistor control portion controls the first and the second transistors. The output frequency control portion(43) controls an error of an output frequency when a fluorescent lamp is operated according to a control operation of the transistor control portion.

Description

Electronic ballasts circuit for fluorescent lamps

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic ballast circuit for fluorescent lamps, and more particularly, to an electronic ballast circuit using a power semiconductor device for high frequency switching.

Recently, in order to save energy, an electronic ballast has been developed to extend the power saving effect and the lamp life.

The electronic ballast is a commercial AC power supply unit, a line filter unit for removing noise from the AC power source, a bridge diode rectifier unit consisting of a rectifying diode and a capacitor for converting AC into DC, and an inverter unit having a MOSFET having a half bridge type switching function. And a lamp output unit including an inductor, a lamp, and a load capacitor.

Such an electronic ballast will be described in detail with reference to FIG. 1.

The operation according to FIG. 1 performs partial smoothing in the smoothing circuit B which performs partial smoothing by series charge and parallel discharge after full-wave rectification of the commercial AC power supply E in a rectifying circuit DB composed of a diode bridge. The half of the partially smoothed voltage is supplied to the transistor oscillation circuit (A).

The transistor oscillation circuit A converts the power supplied by oscillating at a frequency of several tens of kHz to high frequency power, and starts and discharges the discharge lamp La with high light emission efficiency or high power factor.

The smoothing circuit B is composed of capacitors C1, C2, charging diodes D1, and discharge diodes D1, D3. The smoothing circuit B connects the series circuits of the capacitor C1, the charging diode D1 and the capacitor C2 between the output terminals of the full-wave rectifying circuit DB, and is connected between the connection point of the capacitor C1 and the charging diode D1 and the ground point G. The discharge diode D2 is connected, and the discharge diode D3 is connected between the connection point and the F point of the capacitor C2 and the charging diode D1.

In this case, the voltages charged by the capacitors C1 and C2 are each 1/2 of the peak PEAK value of the full-wave rectified voltage, and the capacitors C1 and C2 start discharging when the full-wave rectified voltage reaches 1/2 or less of the peak value. When the full-wave rectified voltage becomes higher than the voltage of the capacitors C1 and C2, charging starts. Therefore, when the valley point of the full-wave rectified voltage is filled to the height of about 1/2 of the peak value, the partial smoothing voltage is applied.

In the transistor oscillation circuit A, the voltage across the capacitor C2 is connected to the base power supply of the oscillation transistors Q1 and Q2 of the transistor oscillation circuit A, that is, the base resistor R1 is connected to the connection points of the diodes D1 and C2. In this way, the voltage of the C2 (normally 1/2 of the peak value of the input voltage E) is applied to set the values of the base resistors R1, R2, and R3 to be small, thereby reducing the power loss.

Therefore, in the ballast shown in FIG. 1, when the commercial AC voltage is first applied, the power supply voltage which is full-wave rectified in the full-wave rectifying circuit DB and partially smoothed by the smoothing circuit B passes through the choke coil CH. The base current is supplied to Q2, and the collector current starts to flow to either of the oscillation transistors Q1 and Q2.

When a collector current starts to flow in the oscillation transistor Q1 on the collector winding N1 side of the oscillation transformer OT, it is induced in the base winding N3 in the direction in which the base current increases, and the collector current increases and reaches saturation. However, when the collector current becomes saturated, there is no voltage induced in the base winding N3, and the collector current begins to decrease, and the oscillation transistor Q1 is turned into a non-conduction state and becomes non-conducting soon.

On the other hand, the base current of the oscillation transistor Q2 on the collector winding N2 side begins to increase as the voltage induced in the base winding N3 becomes a forward bias at the time when the oscillation transistor Q1 on the collector winding N1 side saturates, and the collector current also increases. do. Therefore, in the base winding N3, the voltage is induced in the forward bias direction to reach saturation at once. When saturated, there is no increase in collector current and no voltage is induced in the base winding N3, causing the collector current to begin to decrease and turn into non-conduction. This returns to the initial state, and the oscillation is continued repeatedly thereafter.

However, the conventional technique, which is constructed and operated as described above, has a large no-load because the discharge holding voltage becomes considerably higher than the normal lamp voltage when the lamp is at the end of its life and the lamp is not lit when the filament is broken or when the lamp is detached when necessary. There is a problem in that the power is consumed and the resonant current flows largely without maintaining the discharge sustain voltage of the lamp, which can destroy the main switch transistor or destroy the circuit.

In addition, even when the phase difference between the input voltage and the input current is too large or even when the voltage is divided by the capacitor voltage dividing method, the power factor can be lower than the high power factor. Of course, lowering the capacitance of the voltage dividing capacitor may improve the power factor, but the ripple becomes severe and the circuit operation becomes unstable.

An example of a technique for solving the above problems is disclosed in Korean Patent Publication No. 2001-88753.

The technique disclosed in the above publication will be described with reference to FIG. 2.

The electronic ballast shown in FIG. 2 rectifies the input AC signal and rectifies and smoothes the DC voltage supply unit 200, a lighting unit which receives the voltage applied from the rectifying and smoothing unit and oscillates at a given resonance frequency to light the lamp. 600, an inverter unit 400 which receives the rectified voltage from the rectifying and smoothing unit to cause resonance of the lighting unit, and a starting circuit unit 300 which performs initial start-up of the inverter unit, and the lighting unit 600 is for resonance. Capacitors C12, C5, and C6 and an inductor L2, the inverter unit 400 of the drive transformer (T1, T2, T3) and the drive transformer of which one winding is electrically connected to the resonant inductor (L2) It is turned off by whether the secondary or tertiary windings are energized and includes trigger elements Q1 and Q2 for triggering the resonant circuit of the lighting unit to generate a high frequency output. The start circuit unit 300 is triggered when the lamp is started. A starter circuit C8, R6, TD for operating any one of the elements and circuits R8, D13 for stopping the operation of the starter circuit after the lamp is turned on, and the trigger element Q1 of the inverter unit 400. A switching element Q3 connected to any one of Q2, a constant voltage diode D11 connected to the control terminal of the switching element Q3, and a secondary side or tertiary side winding T2, T3 of the drive transformer. Further comprising a negative electrode preheating current control circuit portion 500 consisting of voltage divider resistors R7 and R8 whose connection points are connected to the constant voltage diode, wherein the output voltage divider voltage detected by the voltage divider resistors R7 and R8 is the brake of the diode D11. In the case of an overvoltage higher than the down voltage, the switching element Q3 is operated to control the gate supply voltage of one of the trigger elements Q1 and Q2, and the resonance voltage across the resonance capacitor C12 connected to the lamp is lowered to cause fluorescence. Control cathode preheat current of filament of lamp And soft start the lamp.

The source side of the switching element Q3 of the cathode preheat current control circuit 500 is connected to the gates of any one of the trigger elements Q1 and Q2 through the resistor R4, and the gate side thereof is connected to the constant voltage diode D11. At the same time, it is connected to ground through the capacitor C9.

However, even when the cathode preheating current control circuit portion as described in the above publication is employed in the electronic ballast, the high-side MOSFET and the low-side MOSFET are driven with the oscillation coil as the third, so that the gate current of the transistor is used. There was a problem that there is no path to cause the defect.

In addition, since soft start is performed using SCR, there is a problem that the time for which the lamp is ON is not constant and the tolerance of the output frequency becomes large.

Due to these reasons, the lamp life is shortened due to the initial sputtering of low temperature power generation, the loss of power saving effect due to the small input voltage fluctuation (± 10%) and the sudden change of the light output, the aging of the lamp, the end of the life of the lamp and incorrect wiring There was a problem that the internal switching element is destroyed in stability.

An object of the present invention is to solve the problems of the prior art as described above, it is possible to solve the problems caused by uneven input power compared to the rated voltage to extend the life of the ballast and the lamp.

Another object of the present invention is to provide an electronic ballast circuit for a fluorescent lamp which protects the ballast from overcurrent, overvoltage, low voltage, high temperature and bad lamps, and can achieve a power factor of 0.95 or more.

It is still another object of the present invention to provide an electronic ballast circuit for fluorescent lamps that is low in electromagnetic interference, excellent in continuous dimming ability, and capable of remarkably eliminating the light blurring shape of the lamp.

1 is a circuit diagram of a conventional electronic ballast for fluorescent lamps,

2 is a circuit diagram of a conventional electronic ballast for solving the problem of the electronic ballast shown in FIG.

3 is a block diagram of an electronic ballast circuit according to the present invention;

4 is a detailed circuit diagram of the block diagram shown in FIG. 3;

5 is an internal block diagram of the integrated circuit IC2 shown in FIG.

Explanation of symbols on the main parts of the drawings

31: AC 220V input unit 41: transistor driver

32: full-wave rectifier 42: power consumption maintenance unit

33: smoothing circuit section 43: output frequency control section

34: IC circuit section 44: first IC

36: resonance circuit 45: second IC

37: lamp

The electronic ballast circuit for fluorescent lamps of the present invention for achieving the above object is a electronic ballast circuit for controlling the lighting of the lamp using a semiconductor device, the commercial power input unit, a radio wave for full-wave rectifying the voltage supplied from the commercial power input unit A rectifying unit, a smoothing circuit unit for smoothing the voltage rectified by the full-wave rectifying unit, a power factor correction unit for compensating a power factor of the voltage smoothed in the smoothing circuit unit, a power consumption maintaining unit for maintaining power consumption of the voltage compensated by the power factor correction unit, A transistor control unit controlling first and second transistors driven according to the voltage adjusted by the power consumption maintaining unit, and an output frequency control unit adjusting an error of an output frequency thereof when the lamp is driven according to the control of the transistor control unit Includes,

In the electronic ballast circuit according to the present invention, the output frequency control section includes a second IC section, a capacitor, and a variable capacitor connected in parallel with the capacitor.

Further, in the electronic ballast circuit according to the present invention, the power consumption holding unit includes a first IC unit, a resistor, and a variable resistor connected in series with the resistor.

In addition, the electronic ballast circuit according to the invention, characterized in that it further comprises a circuit protection unit for protecting the ballast circuit by sensing the voltage of both ends of the lamp when the lamp is aging.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

In addition, in the description part of the Example which concerns on this invention, the same code | symbol is attached | subjected about the same part and the repeated description is abbreviate | omitted.

3 is a block diagram of an electronic ballast circuit according to the present invention, FIG. 4 is a detailed circuit diagram of the block diagram shown in FIG. 3, and FIG. 5 is an internal block diagram of the integrated circuit IC2 shown in FIG.

In Fig. 3, reference numeral 31 denotes an input of AC220V, which is a commercial power supply, 32 denotes a full-wave rectifier composed of a bridge circuit, and 33 denotes a smoothing circuit portion having a smoothing capacitor.

Reference numeral 34 denotes an IC circuit section consisting of two IC1s and an IC as a main feature of the present invention, a detailed description of which will be described with reference to Figs.

In FIG. 3, reference numeral 35 denotes a zero voltage switching (ZVS) inverter, which is controlled by receiving the drain voltage of the switching transistor from the IC circuit 34.

Denoted at 36 is a resonant circuit section comprising an inductor and a resonant capacitor, and 37 is a fluorescent lamp.

Next, the configuration shown in FIG. 3 will be described in detail with reference to FIG. 4.

First, in Fig. 4, ⓐ is a full-wave rectified output that is a low side output, ⓑ is a PFC output that is a high side output, and the ⓐ part of the upper part and the ⓐ part of the lower part, and the ⓑ part of the upper part and the ⓑ part of the lower part are mutually different. The connection is shown separately in the notation of the drawing.

In Fig. 4, reference numeral 41 denotes a transistor driver for driving transistors Q2 and Q3, and reference numeral 42 denotes a consumption in which a resistor R12 and a variable resistor R18 are connected in series and the variable resistor R18 is adjusted to maintain a constant power consumption. The power holding unit 43 is an output frequency control unit for adjusting the error of the output frequency by connecting the capacitor C11 and the variable capacitor TC1 in parallel.

44 and 45 are the first IC unit and the second IC, each having eight terminals and constituting the IC circuit unit 34, and the power consumption maintaining unit 42 is the first IC unit 44. Pin 1 is connected to the output frequency control unit 43 is connected to pin 2 of the second IC unit 45.

Next, the configuration and operation of FIG. 4 will be described in detail.

First, when a commercially rated voltage of AC220V, 60 Hz is applied to the power supply terminal AC INPUT, the voltage input through the full-wave rectifier 32 composed of diodes D1 to D4 is rectified.

The rectified voltage is smoothed by the capacitor C5 forming the smoothing circuit section 33, and the smoothed voltage is compensated for by the inductor L3, the resistors R7, R8, the transistor Q1, and the first IC 44, and compensated. The voltage of the high and low stages is adjusted through the resistor R12 and the variable resistor R18 constituting the power consumption holding unit 42.

Next, the half-bridge inverter unit 35 is operated by the transistors Q2 and Q3 according to the power source adjusted by the power consumption maintaining unit 42, and the inverter unit 35 is driven by the manufacturing voltage switching (ZVS) method.

By driving the transistors Q2 and Q3, the VCC voltage is obtained through the diode D8, the resistor R14, the diode D9, and the capacitor C15, and the lamp 37 is turned on while the second IC 45 operates. At this time, the resistor R11 senses the voltage across the lamp 37 when the lamp 37 is deteriorated to protect the ballast circuit.

In the configuration shown in Fig. 4, when the VCC exceeds 12 Volts, which is the start threshold voltage, the start-up circuit starts to operate and the operating current consumes about 10 mA. When the VCC falls below the UVLO hysteresis width, the IC section stops operating and all internal circuits are reset and enter standby. At this time, the standby current consumes about 0.9 mA.

In addition, initial setup is made into the voltage charged by C15 by Q2 and Q3, and a part of the output is fed back from D8 and D9, and VCC is supplied. In this way, when VCC is fed back to zero switching, the protection of the circuit is applied during the operation. In order to restart it, the circuit inside the IC must be reset. For this purpose, the VCC is supplied from the output to drop the VCC below the UVLO hysteresis.

In addition, in the present invention, the three-stage soft start preheats the filament for about 0.7 sec at a frequency 20 Hz higher than the normal control frequency of the second IC unit 45 to control the sudden voltage current at the initial stage for about 0.4 sec. The fluorescent lamp is turned on while decreasing linearly to the normal frequency.

In addition, in the configuration of FIG. 4, the second IC unit is operated by detecting the presence or absence of the lamp 37 and when the lamp is mounted and the lamp when the lamp is mounted. The output of (45) is shunted down, and when the lamp is mounted at the top of the lamp, the lamp reset function is restarted from the three-stage soft start so that the newly mounted lamp is turned on after the lamp filament preheats.

When pin # 5 and # 601 of the second IC unit 45 are equal to or less than 1.4 V, the output of the second IC unit 45 is shunted down and the DC link voltage is 1.4 to pin # 6 through R14 when the lamp is mounted. It is supplied with a voltage above V.

In the present invention, in the series resonant parallel load circuit, when the power switching element switches above the resonance frequency, zero voltage switching (ZVS) is performed, but when the switching frequency is lowered near the resonance frequency, the gate signals of the transistors Q2 and Q3 are used. As the dead time of the sensor increases, the zero voltage switching operation stops. At this time, the second IC 45 senses the drain voltages of the transistors Q2 and Q3 and controls the dead time of the gate signal according to switching to ensure ZVS at all times.

Next, the internal structure and each terminal (pin) of the 2nd IC part 45 shown in FIG. 4 are demonstrated with reference to FIG.

In Fig. 4, the terminal 1 is connected to the capacitors C9 and C10 to determine the period of soft start during the initial lighting of the lamp 37, and the terminal 2 is connected to the output frequency control unit to determine the frequency of the internal triangle wave generation. Then, the output frequency of terminal 7 of frequency output 1 and terminal 6 of output 2 is determined.

Terminal 3 is connected to resistor R10 to determine the current value at soft start when the lamp 37 is initially turned on. Terminal 4 is connected to resistor R11 and the lamp 37 is removed after input from the protection circuit. If the voltage is less than 2V, the gate output of the transistor is stopped.

Terminal 5 is the ground terminal of the second IC unit 42. Terminal 6 is an output terminal for driving transistor Q3, which is connected to the resistor R16 and is a power switching element. The voltage level is equal to the VCC level.

Terminal 7 is connected to the capacitor C13, and is an output terminal for forming transistor Q2, which is a power switching element, and f0 is varied up to 50 mA ± 30 mA, and the output voltage level is equal to the VCC level. Terminal 8 is the VCC output terminal.

As mentioned above, although the invention made by this inventor was demonstrated concretely according to the said Example, this invention is not limited to the said Example and can be variously changed in the range which does not deviate from the summary.

As described above, in the conventional driving method, the high-side MOSFET and the low-side MOSFET are driven. Due to the dead time for ZVS when the MOSFET is turned off, there is no gate current path, so that the IC output voltage falls negatively. , But the malfunction of the IC caused the failure, but according to the electronic ballast circuit for the fluorescent lamp of the present invention, there is no phenomenon that the output voltage falls negatively to prevent the malfunction of the IC circuit portion to extend the life of the product. The effect can be obtained.

In addition, according to the present invention, the power consumption is always constant despite the change in the input voltage, so that the effect of further improving the stability of the product is also obtained.

Claims (4)

In the electronic ballast circuit for controlling the lighting of the lamp using a semiconductor element, Commercial power input unit, A full-wave rectifier for full-wave rectifying the voltage supplied from the commercial power input unit; A smoothing circuit unit for smoothing the voltage rectified by the full-wave rectifying unit, A power factor correction unit for compensating for the power factor of the voltage smoothed by the smoothing circuit unit; A power consumption maintaining unit for maintaining power consumption of the voltage compensated by the power factor correction unit; A transistor controller for controlling the first and second transistors driven according to the voltage adjusted by the power consumption maintaining unit; And an output frequency controller configured to adjust an error of an output frequency when the lamp is driven under the control of the transistor controller. The method of claim 1, And the output frequency control section includes a second IC section, a capacitor, and a variable capacitor connected in parallel with the capacitor. The method of claim 2, And the power consumption maintaining unit comprises a first IC unit, a resistor and a variable resistor connected in series with the resistor. The method of claim 3, The electronic ballast circuit further comprises a circuit protection unit for protecting the ballast circuit by sensing the voltage across the lamp when the lamp is aging.