Fluorescent lamp electronic ballast based on half-bridge driver IR2153

Keywords: Electronic ballast; Power factor correction; Preheat filament; Restart

Introduction

It is an indisputable fact that the luminous efficiency of fluorescent lamp is better than that of incandescent lamp. For this reason, in the past 20 years, electronic ballast has been rapidly popularized and developed all over the world. Semiconductor manufacturers have introduced many driving circuits for electronic ballast. The electronic ballast introduced in this paper is based on IR2153 driver developed by IR company and MC33262 power factor controller of Motorola company. It is a simple structure and low cost. High reliability solutions.

Introduction of 1 self-exciting half-bridge driver IR2153

IR2153 is an improved VMOS and IGBT grid driver based on IR2155 and IR2151. It integrates a high voltage half-bridge driver and a front-end oscillator similar to a 555 time-based circuit on an 8-foot chip, making it a more functional and easier-to-use power-driven IC chip. As shown in Fig. 1, a foot CT with protective shut-off function can stop the driver output with a low voltage signal. In addition, the width of the output pulse remains equal, and once the Vcc rises to the undervoltage locking threshold, the driver can start to vibrate at a more stable frequency. By reducing the peak di/dt of the grid driver and increasing the lag voltage to 1V of the undervoltage blocking threshold, the noise resistance of the circuit has been substantially improved, and the overall anti-noise protection of the pins of the circuit has also been improved.


530)this.width=530" border="0">
Click here to view all news pictures

2 power factor correction circuit

MC33262 is an active power factor corrector. It is especially suitable for pre-converter in electronic ballast and offline switching power supply. As shown in Figure 2, many control functions are integrated in MC33262: A startup timer is set to facilitate the use of the circuit alone. A quadrant multiplier is used to achieve a power factor close to 1. Zero current detection can ensure that the circuit works in critical conduction mode. The fast start circuit improves the starting characteristics of the circuit. There is also a pre-calibrated reference voltage source, a transconductance error amplifier and a current detection comparator. The totem column output structure is ideal for driving power MOS transistors. In addition, MC33262 also integrates many protection functions, such as over voltage comparator, which can reduce the out-of-control output voltage caused by no load. The multiplier output embedding limits the peak switching current. Drive output high bit insert to protect MOS tube grid. There are also input undervoltage blocking circuit with lag characteristics, continuous current limiting characteristics, and RS lock for single pulse measurement.
3 Circuit working principle

Detailed schematic diagram of electronic ballast is shown in Figure 3, which can be divided into EMI filter, bridge rectifier, power factor control, half-bridge inverter, lamp resonance, start-up and protection circuit, etc.

3.1 Input EMI Filter Circuit

In addition to the over current and over voltage protection circuit consisting of F1A fuse and RVP1 varistor, the input circuit of electronic ballast is mainly EMI filter. This is a typical two-stage composite low-pass filter circuit. The CP1-CP4 filter capacitance is used to filter out the signal of serial mode interference. One end of C1 and C2 is connected to the ground as a midpoint, and the other end is grounded together to effectively suppress the common mode interference. LP1 and LP2 are common mode choke coils to filter the common mode interference. The two coils are wound around the ferrite magnetic ring with low loss and high magnetic conductivity, respectively. When the current passes through, The magnetic fields on the two coils will be strengthened each other. The inductance of LP1 and LP2 is related to the rated current of the EMI filter. The resonant frequency of the filter should be much lower than that of the ballast.

Click here to view all news pictures

530)this.width=530" border="0">
3.2 Frequency Conversion Control Circuit

We know that fluorescent lamps need to be preheated before they can be ignited to work properly. In these three states, the inverter works in frequency conversion mode. First, preheat the filament at a relatively high frequency so that the cathode reaches the temperature of the emitted electrons. Then the frequency decreases rapidly, and when the series resonant frequency is reached, the resonant high voltage generated causes the lamp to break down and light up instantly; Stable on working frequency. The oscillation frequency of IR2153 can be determined by Formula (1) and the series resonance frequency by Formula (2).

530)this.width=530" border="0">
Click here to view all news pictures

Frequency control can be achieved by changing the effective CT capacitance of IR2153. Therefore, frequency control can be achieved by switching the connection between two oscillating capacitors through the conduction and cutoff of a NPN triode QN1. Figure 3 After power-on, QN1 is not conductive until capacitor CC14 is fully charged. The oscillation frequency is determined by series connection of capacitor CC18 and CC19. When capacitor CC14 is fully charged, DC18 conducts, QN1 conducts and capacitor CC19 does not work. Frequency is determined by direct grounding of capacitor CC18.

3.3 Preheating Control Circuit

After power-on, before DC18 is not powered on, QN1 cuts off, IR2153 starts to vibrate at preheating frequency, QN2 does not cut off, VCC provides bias current to MO4 grid via RC22 to make it powered on, CO33 and LO6 start to vibrate, filament transformer works, preheating starts; Subsequently, when the CC14 voltage rises and DC18 is turned on, QN1 is turned on, causing IR2153 to oscillate at its normal operating frequency. At the same time, current through RC21 makes QN2 turn on, MO4 grid potential goes to zero, MO4 is turned off, and preheating ends.
3.4 Protection self-lock and restart circuit

The protection circuit protects the abnormal phenomena that occur during the use of the ballast. Generally, the principle of amplitude detection protection is used. The ballast has more protection functions. There are five kinds of protection, among which the lamp overvoltage protection introduced from RC36 is used. Under-voltage protection of lamp introduced from RC37; There are four types of power high voltage protection introduced from DC19 and low voltage protection introduced from QP6 and RC15, which are assembled to the grid of MOS tube MC5. When no protection occurs, MC5 is not conductive, and foot CT is provided with partial voltage by IR2153, which can get about 8V voltage and work normally. When any of the four types of protection occurs, MC5 conducts, OP7 conducts due to the grounding of the base potential, RC33 lowers the foot CT voltage, IR2153 stops oscillating, and the half-bridge circuit is closed. Even if the protection is withdrawn, the high potential of foot CT cannot be restored due to the interlock between MC5 and OP7. Only when the power failure is restarted, the ballast can resume operation.

530)this.width=530" border="0">

Click here to view all news pictures

The filament protection introduced from DC20 is different from the other four types of protection. It does not protect interlock function, so it can be restarted. When filament is burned out or the lamp is detached, QN3, QN4, QN5 are turned on. QN3 is used to prohibit protection and interlock circuit. QN4 receives footCT, stops IR2153, QN5 discharges capacitance CC14, and is ready for restart. Once the new lamp is installed, QN3, QN4, QN5 immediately cuts off, and the start-up process restarts preheating, restarting Ignition and stable operation.
3.5 Power VCC Circuit

The IC power supply in this ballast is mainly designed to reduce power consumption. When the circuit is first started, it is first lowered by DC high voltage via Ziner tube DC4 and DC5, and then by RC14 and DC7 regulator. Due to the small power consumption start-up characteristic of IR2153, the circuit is guaranteed to start normally. After the IR2153 vibration is started, the secondary of choke transformer LO4 is rectified by double voltage, and the power supply to IR2153 is supplied by DC8 and RC23 one way. The other one supplies power to MC33262 power factor controller via DPF2 and RPF4. When the circuit is protected, the half-bridge circuit stops working, the LO4 secondary stops providing voltage, and the power supply of IR2153 is changed to micro-power consumption. Obviously, after the IR2153 stops vibration, MC33262 stops working due to power loss, which is another protection for the power factor controller.

530)this.width=530" border="0">
Click here to view all news pictures

4 Test results

Figure 4 shows the lamp voltage and filament current waveform measured by this ballast connected with OSRAM-FQ highlight T5 lamp. The power is 54W. The instrument used is a remote HB5A ballast comprehensive parameter tester.
5 Conclusion

Modern electronic ballast is a broad knowledge and difficult technology. The circuit board needs to input 220V AC voltage, output 300V DC high voltage after full wave rectification, and then boost energy storage inductance through power factor corrector, which can reach 400V. If the components are not selected properly or carefully debugged in the design, the power tube will be burned out. The design of protection circuit in this scheme greatly reduces the chance of abnormal tube burning. In addition, the restart circuit and the harmonic circuit in this circuit can be used to drive the double lamp with a slight change, for which the author will write a separate description.

Information Source: Power Technology Application Wang Suoxhong

Reference:

[1].IR2135 Datasheethttp://www.dzsc.com/datasheet/IR2135_406781.html.
[2].IR2153datasheethttp://www.dzsc.com/datasheet/IR2153_406799.html.
[3].MC33262 Datasheethttp://www.dzsc.com/datasheet/MC33262_1068717.html.
[4].IR2155 Datasheethttp://www.dzsc.com/datasheet/IR2155_406810.html.
[5].IR2151datasheethttp://www.dzsc.com/datasheet/IR2151_406797.html.
[6].DC20 Datasheethttp://www.dzsc.com/datasheet/DC20_1134676.html.