CN201114925Y - Electronic Ballasts for External Electrode Fluorescent Lamps - Google Patents

Abstract

The utility model discloses an electronic ballast for an external electrode fluorescent lamp, which is composed of an EMI electromagnetic interference circuit, a rectification circuit, a power factor compensation circuit, a ballast controller, an inverter/boost circuit and a protection circuit. The feature is that: 220V AC input voltage passes through the EMI electromagnetic interference circuit to remove EMI electromagnetic interference and RFI high-frequency interference, and then rectifies through the rectifier circuit and corrects the power factor with the power factor compensation circuit. The output of the /boost circuit is a high-frequency voltage to drive the parallel-connected external electrode fluorescent lamps. The utility model provides an electronic ballast for parallel use of external electrode fluorescent lamp tubes, which can simultaneously drive multiple parallel external electrode fluorescent lamp tubes with one ballast. It has the advantages of high power factor, low power consumption, good ability to suppress electromagnetic interference and radio frequency interference, and has protection functions such as lamp head no-load, lamp head overload, lamp head short circuit, over-temperature, over-undervoltage, etc., suitable for large box type advertisements Lightbox use.

Description

Electronic Ballasts for External Electrode Fluorescent Lamps

technical field

The utility model relates to an electronic ballast used for an external electrode fluorescent lamp.

current technology

At present, the lighting occasions of large commercial and public buildings are still occupied by traditional magnetic ballasts and ordinary electronic ballasts. Traditional inductive ballasts have been used in the fluorescent lamp market because of their low price, high reliability, and long service life, but they also have some disadvantages, such as large volume and weight, high power consumption, low power factor, noise, It will cause stroboscopic flickering of fluorescent tubes, blackening of tube ends after long-term use, and easy damage to starters. With the development of the fluorescent lamp industry, there are many kinds of electronic ballasts supporting it, but their functional principles are similar. They all rectify the power frequency alternating current and then invert it into a high frequency signal to drive the fluorescent lamp. However, the electronic ballasts in the current market can only drive one lamp tube, and there will be some defects in the design of large advertising light boxes, because such occasions require the use of multiple sets of electronic ballasts, which will not only bring unnecessary Energy is wasted, and multiple groups of electronic ballasts are used intensively. The current harmonics generated by themselves will seriously distort the current waveform of the power supply grid, cause the zero line to be overloaded, and affect the safe operation of the power system.

In addition, the existing fluorescent lamp is a low-pressure arc hot-cathode discharge lamp, and the electrodes at both ends are relatively hot, so its service life can only reach 6000-8000 hours. The electrodes at both ends are prone to aging and the tube wall becomes black after long-term use. CCFL (Cold Cathode Fluorescence Lamp) was launched later, that is, cold cathode fluorescent lamp, also known as low-pressure glow gas discharge lamp, which uses glow discharge, so the electrode temperature is low, cathode sputtering is relatively slow, and the lamp life is long. Generally can reach 30000 hours. The fly in the ointment is that the color gamut that CCFL can achieve is relatively small, and the matching electronic ballasts can only correspond one-to-one. Therefore, these fluorescent lamps are not suitable for occasions such as the design of large advertising light boxes that require multiple groups of fluorescent lamps to be used together.

The latest external electrode fluorescent lamp EEFL (External Electrode Fluorescent Lamp), its electrodes are located outside the lamp tube, the tube itself does not generate heat, which also strengthens the life of the lamp tube, generally up to 60,000-80,000 hours. In addition, its unique external electrode design enables it to be driven in parallel, thus solving the problem of one ballast driving multiple fluorescent tubes. The lamp tube has high color rendering, and the light color is more pleasing and comfortable, and can be made into various colored decorative lighting with different color temperatures. Very suitable for advertising light boxes. The parallel use of such lamp tubes requires a special ballast for it.

Utility model content

The technical problem to be solved by the utility model is to provide an electronic ballast for parallel use of external electrode fluorescent lamps, which can simultaneously drive multiple parallel external electrode fluorescent lamps with one ballast.

The technical solution adopted by the utility model is: an electronic ballast for an external electrode fluorescent lamp, which is composed of an EMI filter circuit, a rectifier circuit, a power factor compensation circuit, a ballast controller, an inverter/boost circuit, and a protection circuit. The 220V AC input voltage passes through the EMI filter circuit to remove EMI electromagnetic interference and RFI high-frequency interference, and then rectifies through the rectifier circuit and corrects the power factor with the power factor compensation circuit. Under the control of the ballast controller, the inverter/boost circuit The output is a high-frequency voltage to drive parallel-connected external electrode fluorescent tubes.

In the EMI filter circuit, capacitors C4, C5, and inductor L1 form a double Π-type filter circuit, wherein the two windings of inductor L1 are symmetrically wound on the same magnetic core, and the inductance values on both sides are the same, which is the same as that of capacitor C4. , C5 form two groups of mutually symmetrical Π-type EMI filters.

The power factor compensation circuit adopts the active power factor correction special chip L6561, the AC input is rectified by the rectifier bridge, and filtered by the capacitor C6 at high frequency to become a DC input, and connected to pin 3 of the chip through resistors R4 and R5. C7 and resistor R6 form an RC filter. On the one hand, the secondary winding of the inductor L2 transmits the zero-crossing signal of the inductor current to the pin 5 of the chip through the resistor R8, and on the other hand, it is used as the power supply for the chip to work normally; The No. pin output is connected to the gate of the MOS tube through the resistor R9, and at the same time it is grounded through R11, and the resistors R12~R17 are connected in parallel. One end of the resistor is connected to the system ground, and the other end is connected to the source of the MOS tube and the No. pin; resistors R18~R22 form a resistor divider network to form a negative feedback loop for the output voltage; capacitor C10 is connected between pins 1 and 2 of the chip to form a compensation network for the voltage loop; resistor R7, capacitor C9, diode D1, the voltage regulator tube D2 and the secondary side of the inductor L2 together constitute the power supply of the chip, wherein the resistor R6 is connected between the capacitor C7 and the pin 8 of the chip to provide the startup voltage of the chip when the system is powered on.

The ballast controller, inverter/boost circuit, and protection circuit use a dedicated chip IR21571. The output voltage of the power factor compensation circuit is divided by R23, R24 and R25 to supply power to the IR21571 chip. Chips 2, 3, 4, Pins 5, 6, and 7 and peripheral resistance-capacitance components form a circuit for controlling the startup, preheating, ignition, and operating status of the electronic ballast, and pins 11 and 16 of the chip are low-end and high-end gate output drivers. The signal is used to drive the half-bridge field effect transistors Q2 and Q3 to turn on in turn, and the No. 1 pin of the chip detects the DC bus voltage. When the port voltage is lower than 5.1V, the chip stops working and the half-bridge power field effect transistors are cut off. , The voltage and current signals sampled from the lamp head are fed back to pins 9 and 10 of the chip.

The positive effects of the utility model are: the utility model can use one electronic ballast to drive multiple fluorescent tubes, its power factor is high, and its own power consumption is low; and it has better ability to suppress electromagnetic interference and radio frequency interference; With protective functions such as no-load lamp, lamp overload, lamp short circuit, over-temperature, over-undervoltage, etc., it is assembled into a large box-type advertising light box with EEFL lamp tubes. The brightness is uniform, the picture is realistic, and the three-dimensional effect is strong. It can reduce the energy waste caused by the use of most ballasts, reduce the maintenance cost of ballasts and lamp failures, and improve the service life of itself.

Description of drawings

Fig. 1 is a schematic diagram of the utility model

Figure 2 is the EMI filter circuit diagram

Figure 3 is a power factor compensation circuit diagram

Figure 4 is a ballast control circuit/inverter boost/protection circuit diagram

Detailed ways

Below in conjunction with accompanying drawing, the utility model is further described.

As shown in Figure 1, the electronic ballast for fluorescent lamps with external electrodes is composed of EMI filter circuit, rectification/power factor compensation circuit, ballast controller, inverter/boost circuit, and protection circuit. The 220V AC input voltage passes through The EMI filter circuit removes EMI (Electro Magnetic Interference) electromagnetic interference and RFI (Radio Frequency Interference) high-frequency interference, and then rectifies the rectification circuit and corrects the power factor by the power factor compensation circuit. The output of the variable/boost circuit is a high-frequency voltage to drive parallel-connected external electrode fluorescent lamps.

The EMI filter circuit is shown in Figure 2. This circuit consists of capacitors C1, C2, C3, C4, C5, and inductor L1 to form a double Π-type EMI filter. Using differential mode-common mode can effectively suppress EMI electromagnetic interference and RFI high-frequency interference. The two windings of the inductor L1 are symmetrically wound on the same magnetic core, and the inductance values on both sides are the same, forming two sets of mutually symmetrical Π-type EMI filters with the capacitors C4 and C5. Since the windings of L1 are wound on the same The magnetic fields generated by the magnetic materials on the magnetic core compensate each other. For asymmetric interference signals, the magnetic fields generated by the two coils strengthen each other, and the inductance appearing on the outer layer increases, and the symmetrical interference information is suppressed. Similarly, for the interference signal between the live wire and the ground wire, it is attenuated by the filter composed of C1, L1, and C5 and then introduced into the earth; for the interference signal between the neutral wire and the ground wire, it is attenuated by the filter composed of capacitors C2, L1, and C5 Then import into the earth.

The design of this circuit presents high impedance to common-mode interference signals and low impedance to differential-mode signals and power supply current, which can greatly attenuate current noise signals in the power supply. In fact, the design of this circuit is also a low-pass filter. Since the L1 inductance blocks the flow of radio frequency, it can also effectively suppress the interference of radio frequency signals. The EMI filter adopted by the utility model can effectively suppress the electromagnetic interference from the power grid, and at the same time attenuate the electromagnetic interference generated by the electronic ballast itself, which can ensure that the power grid is not polluted.

The power compensation circuit is shown in Figure 3. The utility model adopts the active power factor correction special chip L6561 produced by ST Company, which can conveniently form an APFC power supply with wide voltage input (AC85V-265V) and low harmonic content; it can directly drive the MOS tube, and integrates various protection Function; due to the high level of integration, it greatly reduces the components required to form the system, reduces losses and improves efficiency. Its principle is to convert the input alternating current into direct current after being rectified by the rectifier bridge as the input of the boost circuit; the capacitor C6 is used to filter out the high-frequency part of the inductor current and reduce the harmonic content of the input current; the resistors R4 and R5 form a resistor divider The voltage network is used to determine the waveform and phase of the input voltage. The capacitor C7 and the resistor R6 form an RC filter to remove the high-frequency interference signal of the No. 3 pin; the inductor L2 has a secondary winding, which passes through the resistor on the one hand. R8 transmits the inductor current zero-crossing signal to pin 5 of the chip, and on the other hand, it is used as the power supply for the chip to work normally; the chip drive signal is connected to the gate of the MOS tube through the resistor R9, and R11 is used to prevent the drive signal of the MOS tube Oscillation; resistors R12~R17 are connected in parallel as inductor current detection resistors to sample the rising edge of the inductor current (MOS tube current). One end of the resistor is connected to the system ground, and the other end is connected to the source of the MOS tube and No. 4 of the chip at the same time. pin; resistors R18~R22 form a resistor divider network to form a negative feedback loop for the output voltage; capacitor C10 is connected between pins 1 and 2 of the chip to form a compensation network for the voltage loop; resistor R7, capacitor C9, The diode D1, the voltage regulator tube D2 and the secondary side of the boost inductor L2 together constitute the power supply of the chip, wherein the resistor R6 is connected between the capacitor C7 and the pin 8 of the chip to provide the startup voltage of the chip when the system is powered on. The APFC circuit designed by using this chip can ensure that the output voltage is stable at 400V when the voltage is input (85VAC-265VAC, the power factor of the power supply system is increased to above 0.97, and the total harmonic content is lower than 5%, which provides power for the inverter of the ballast. A quality power supply.

The ballast controller, inverter/boost circuit, and protection circuit are shown in Figure 4. In the inverter design of the utility model, the chip IR21571 specially used for electronic ballasts produced by IR Company is used in the inverter design. The integrated oscillation frequency of this chip is programmable , Over-current detection threshold voltage programming, DC voltage detection, under-voltage shutdown circuit, half-bridge current sensing and protection circuit, lamp failure detection and protection circuit, automatic restart, over-temperature detection and shutdown, control logic, high-voltage level shifting Control circuits such as bit registers and high/low gate drivers.

The principle is to divide the power factor compensation output voltage of the pre-stage through R23, R24 and R25 to supply power to the IR21571 chip, and the pins 2, 3, 4, 5, 6, and 7 of the chip and the peripheral resistance-capacitance components form the control electronics. Circuits for starting, preheating, ignition and operating status of the ballast. Pins 11 and 16 of the chip are low-end and high-end gate output driving signals, which are used to drive the half-bridge field effect transistors Q2 and Q3 to switch on in turn. Pin 1 of the chip has a DC bus voltage sensing function. When the port voltage is lower than 5.1V, the chip stops working, so that the half-bridge power FET is cut off, and the fluorescent lamp is automatically extinguished for protection. The voltage and current signals sampled by the lamp head are fed back to pins 9 and 10 of the chip. When the lamp head has no-load, short circuit, or ignition failure failures, the drive signal of the power field effect tube is cut off to automatically extinguish the fluorescent lamp for protection.

Claims (4)

1. The electronic ballast for fluorescent lamps with external electrodes is composed of EMI filter circuit, rectifier circuit, power factor compensation circuit, ballast controller, inverter/boost circuit, and protection circuit. It is characterized in that: 220V AC input voltage EMI electromagnetic interference and RFI high-frequency interference are removed by the EMI filter circuit, and then the power factor is corrected by the rectifier circuit and the power factor compensation circuit. Under the control of the ballast controller, the output is high frequency through the inverter/boost circuit. The voltage drives external electrode fluorescent tubes connected in parallel. 2. The electronic ballast for fluorescent lamps with external electrodes as claimed in claim 1, characterized in that: in the EMI filter circuit, capacitors C4, C5 and inductor L1 form a double Π-type filter circuit, wherein the two inductors of inductor L1 The two windings are symmetrically wound on the same magnetic core, and the inductance values on both sides are the same, forming two sets of mutually symmetrical Π-type EMI filters with capacitors C4 and C5. 3. The electronic ballast for fluorescent lamps with external electrodes as claimed in claim 1, characterized in that: the power factor compensation circuit adopts an active power factor correction dedicated chip L6561, the AC input is rectified by a rectifier bridge, and then passed through a capacitor C6 High-frequency filtering becomes DC input, which is connected to pin 3 of the chip through resistor R4 and R5. Capacitor C7 and resistor R6 form an RC filter. On the one hand, the secondary winding of inductor L2 transmits the inductor current zero-crossing signal to On the other hand, pin 5 of the chip is used as the power supply for the chip to work normally; the drive signal of the chip is output from pin 7 and connected to the gate of the MOS tube through resistor R9, and grounded through R11 at the same time, and resistors R12~R17 are connected in parallel. One end of the resistor is connected to the system ground, and the other end is connected to the source of the MOS tube and pin 4 of the chip at the same time; resistors R18~R22 form a resistor divider network to form a negative feedback loop of the output voltage; capacitor C10 is connected to chip 1, Between the No. 2 pins, it is used to form the compensation network of the voltage loop; the resistor R7, the capacitor C9, the diode D1, the voltage regulator tube D2 and the secondary side of the inductor L2 together constitute the chip power supply, wherein the resistor R6 is connected to the capacitor C7 and Between pin 8 of the chip, the startup voltage of the chip is provided when the system is powered on. 4. The electronic ballast for fluorescent lamps with external electrodes as claimed in claim 1, characterized in that: the ballast controller, inverter/boost circuit, and protection circuit use a dedicated chip IR21571, and the power factor compensation circuit The output voltage is divided by R23, R24 and R25 to supply power to the IR21571 chip. Pins 2, 3, 4, 5, 6, and 7 of the chip and the peripheral resistance-capacitance components are respectively composed of control electronic ballast start-up, preheating, In the circuit of ignition and running state, pins 11 and 16 of the chip are low-end and high-end gate output drive signals, which are used to drive the half-bridge field effect transistors Q2 and Q3 to switch on in turn, and pin 1 of the chip detects the DC bus Voltage, when the port voltage is lower than 5.1V, the chip stops working, so that the half-bridge power FET is cut off, and the voltage and current signals sampled from the lamp head are fed back to pins 9 and 10 of the chip.

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