The principle of operation of the electronic starter on the UBA2000T chip. Scheme, description

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
Free library / Electrician

Electronic starters. The principle of operation of the electronic starter on the UBA2000T chip. Encyclopedia of radio electronics and electrical engineering

Free technical library

Encyclopedia of radio electronics and electrical engineering / Ballasts for fluorescent lamps

Comments on the article

Let us consider in more detail an electronic starter implemented on a specialized chip from PHILIPS - UBA2000T. The UBA2000T is an integrated circuit used in electronic starters for fluorescent lamps designed to replace conventional bimetal starters.

The microcircuit controls the preheating of the lamp electrodes and its ignition. The warm-up time of the lamp is strictly defined by using a power frequency divider. When a lamp fails, the circuit automatically shuts off after seven failed ignition attempts, thus preventing the ballast from overheating. In the event of interruptions in the supply voltage, the circuit automatically resets to its original state and ensures that the lamp is re-ignited.

The UBA2000T chip provides the sequence of actions necessary to ignite a fluorescent lamp. Ways to turn on the microcircuit in the lamp power circuit are shown in fig. 3.4, and the functional block diagram of the UBA2000T is shown in fig. 3.5.

The mains voltage is rectified and divided by external resistors R1 and R2 to the required level. When the power is turned on, the buffer capacitor C1 is charged through a resistive divider and an internal switch S1; the voltage across the capacitor is used to power the chip.

As long as the voltage across the buffer capacitor V_cc will not exceed trigger level V_cc (гst), the internal circuits of the microcircuit are initialized. When the supply voltage V_cc reaches the trigger threshold V_cc (gst), and the peak value of VlN becomes greater than FIGN (that is, the mains voltage is near its peak value), the external power switch opens. As a result, the heating current of the lamp electrodes begins to flow through the lamp electrodes, the power switch and the integral current sensor.

Throughout the entire period of time, while the external power switch is closed, the microcircuit is powered by the buffer capacitor C1. Typical voltage waveform at pin 6 (V_cc) is shown in Fig. 3.6.

Rice. 3.4. Ways to turn on the microcircuit in the LL power circuit (click to enlarge)

The principle of operation of the electronic starter on the UBA2000T chip
Rice. 3.5. Function block diagram UBA2000T

The principle of operation of the electronic starter on the UBA2000T chip
Rice. 3.6. Pin 6 voltage (Vcc)

During the warm-up period of the lamp electrodes the capacitor is discharging. The voltage from the current sense resistor is fed to a comparator whose output is used as a clock signal for an internal counter. This counter determines the warm-up time of the lamp electrodes, equal to 1,52 s at a power supply frequency of 50 Hz. Thanks to the use of a counter, the warm-up time is kept very precisely, since it depends only on the frequency of the supply network.

After preheating the lamp electrodes the external power switch opens at the moment when the voltage across the current-measuring resistor corresponds to the flowing current of at least 285 mA. As a result of current interruption in a circuit containing an inductive load, a high-voltage pulse is generated, which ignites the fluorescent lamp.

After successful ignition of the lamp the voltage on it becomes much lower than the mains. As a result, the supply voltage of the microcircuit does not exceed the threshold level necessary for its operation. On fig. 3.6 shows the shape of the microcircuit supply voltage when the lamp is ignited after the second attempt.

While warming up the lamp electrodes the microcircuit is powered by the energy stored in the buffer capacitor, and the supply voltage gradually decreases. If after applying a high-voltage pulse lamp did not ignite, then the external power switch remains closed, and the voltage on the buffer capacitor again rises above the starting level. The external power switch closes again, and the next cycle of warming up and ignition of the lamp begins. On all subsequent ignition attempts, except for the first, the warm-up time is reduced to 0,64 s, since the lamp electrodes have not yet cooled down after previous unsuccessful ignition attempts. An internal counter limits the number of failed ignition attempts to 7. This prevents the lamp from flashing at the end of its life.

The UBA2000T chip contains built-in current protection circuits. When the current through the sensor resistor exceeds the protection threshold (I_PROT), the power switch is closed, and the microcircuit goes into rest mode. Switching the supply voltage off and on again resets the protection circuits. The state diagram of the microcircuit during the ignition of the lamp is shown in fig. 3.7.

The principle of operation of the electronic starter on the UBA2000T chip
Rice. 3.7. State diagram of the UBA2000Te chip during lamp ignition

Source of power. When the supply voltage is applied to the microcircuit, the buffer capacitance is charged and the internal current source is allowed to work. The internal supply voltage of the microcircuit is stabilized and does not depend on the voltage on the buffer capacitor. The built-in zener diode limits the voltage at pin 6 (V_cc) at the Vcc (sl) level.

Voltage comparators. Comparators monitor the voltage on the buffer capacitor and allow the operation of the internal circuits of the microcircuit when the supply voltage reaches the starting level - V_cc (sl). It takes a certain period of time t to initially charge the capacitor_this (See Figure 3.6). This time depends on the value of the capacitor C1, the current consumption of the microcircuit and the resistance of the external divider at the input V_in (R1IIR2). After the capacitor C1 is charged and provided that the mains voltage is close to its maximum value, a current pulse is generated that opens the external power switch.

If the supply voltage drops to a level indicating the absence of mains voltage, the internal circuits of the microcircuit are reset, and it becomes ready to warm up and start the lamp when the mains voltage is turned on again.

Trigger. The state of the internal trigger reflects the state of the external power switch. The process of setting the trigger is determined by the state of the voltage comparators, the counter of the number of ignitions and the rest mode of the microcircuit. The trigger reset is controlled by the timer, current sensor and current protection circuits.

current sensor. The current sensor controls the moment when the power switch is turned off and generates clock pulses to control the internal counters of the microcircuit (Fig. 3.8).

The principle of operation of the electronic starter on the UBA2000T chip
Rice. 3.8. Clock generation

For proper operation, the heating current of the lamp electrodes must be within the allowable range of I_PR. Due to some hysteresis, individual peaks of the electrode heating current do not affect the state of the counter. In addition, the current sensor circuits carry out additional low-frequency filtering of the signal, which eliminates the influence of short current pulses on the warm-up time of the lamp electrodes.

Front sensor. The front sensor ensures the closing of the external power switch on the falling edge of the rectified heating current.

Counter. When a clock signal is applied to the counter with a doubled mains frequency, the counter sets the duration of the first warm-up of the lamp electrodes and, if necessary, the duration of the next six warm-ups.

Warm-up time control circuit. Depending on the state of the counter of the number of runs, a large (t_PRF = 1,25 s) or small (t_PRN = 0,64 s) warm-up time.

Run counter. The number of starts is counted by a separate counter. After seven unsuccessful start attempts, the microcircuit is transferred to a rest state. At rest, the current drawn increases, so that the buffer capacitor discharges quickly when the starter is disconnected from the power source. This provides an automatic starter reset when hot-swapping a defective bulb.

Current protection circuits. If the current through the measuring resistor exceeds the threshold value I_PROT, the external power key closes. During the first few periods of the open state of the power key (blocking time t_D) the operation of current protection circuits is prohibited. Due to this, transient processes when opening the key do not lead to the operation of the current protection circuits. If the current exceeds the threshold value, the power switch is turned off, and the microcircuit is transferred to the rest state, preventing the subsequent opening of the key. The microcircuit can be brought out of this state only by turning off the supply voltage.

output buffer. The output buffer is designed to control an external thyristor with a low input current or a powerful field-effect transistor. In the process of turning on the microcircuit, its output is maintained at a low level, which prevents the power switch from opening.

Power switch on thyristor. As already mentioned, UBA2000T can work together with a high-voltage thyristor TN22 (Fig. 3.9). It is a high quality single-ended thyristor manufactured by high voltage pnpn diffusion planar technology. The manufacturer is STMicroelectronics (st.com). The thyristor is produced in IPAK (TO-251), DPAK (TO-252) plastic cases and is intended for use in electronic starting devices for fluorescent lamps.

The main technical characteristics of the thyristor TN22:

avalanche breakdown voltage Vbr - 1200-1500 V;
hold-open current 1N, not less than -175 mA;
control current is not more than -1,5 mA.

The principle of operation of the electronic starter on the UBA2000T chip
Rice. 3.9. Scheme and appearance of the thyristor TN22

Maximum values of parameters and modes TN22:

the repeating value of the voltage in the closed state (at the temperature of the crystal T_j\u110d XNUMX ° С) V_DRM- 400 V;
rms value of the open thyristor current (at a conduction angle of 180° and case temperature T_C = 95 °C) I_T (rms) - 2 A;
the average value of the current of an open thyristor (at a conduction angle of 180° and a case temperature T_C = 95 °C) I_T (av) -1,8 A;
non-repeating peak current of an open thyristor (at the initial junction temperature T_j = 25 °C):
at t_P = 8,3 ms - 22 A;
at t_P= 10 ms - 20 A;
limit value I2t at t_P = 10 ms - 2 A2-s;
critical rate of current rise in the open state (at I_G = 5 mA and dI_G/dt = 70 mA/µs) - 50 A/µs;
operating temperature of the crystal T_j - -40...+110 °C;
storage temperature T_STG 40...+150 °C.

A typical example of using a microcircuit in conjunction with a thyristor with a small input current (type TN22) used as an external power switch is shown in fig. 3.4, a. In this case, the resistive input voltage divider is connected not to a common wire, but to the control electrode of the external switch. Since the voltage on the control electrode of the key is small, this does not lead to a noticeable change in the division factor.

Output buffer amplifier generates a current pulse required to open the external key TH1. This current pulse is synchronized with the voltage at pin 4 (V_IN). The power switch opens when the voltage V_IN reaches level V_IGN. In this case, the current through the divider R1 and R2 is an integral part of the current required to open the key. If necessary, the current pulse is repeated every half cycle of mains voltage. When it is required to close the foreign key, the output buffer is able to supply the large current flow required to close the key reliably.

Sometimes it is necessary to limit the pulsed current flowing when the key is opened due to the discharge of the noise suppressing capacitor C2. To do this, a resistor R3 can be connected in series with the capacitor.

Power key on a field effect transistor. A typical scheme for using the UBA2000T chip in conjunction with a power field-effect transistor switch is shown in fig. 3.4, b. In this case, the resistive divider is connected to the common wire. The output buffer of the microcircuit works similarly to the previous case. The output current pulse charges the gate of the field-effect transistor. As a result, the transistor opens.

To hold the transistor in a conductive state, a high-resistance resistor is used, connected between the gate of the transistor and buffer capacitor C1. The need for this resistor is due to the fact that the output current is pulsed, not continuous. It should be notedthat the use of a resistor leads to an increase in the discharge current of the buffer capacitance C1.

The internal zener diode limits the voltage at the output of the microcircuit, and, consequently, at the gate of the field-effect transistor, at a level of approximately 6,8 V.

Both applications require the use of a power switch with breakdown voltage V_(BR)AC or V_(BR)DSexceeding the ignition voltage of the fluorescent lamp.

In table. 3.1 are given limit values of UBA2000T chip parameters.

Table 3.1. Limit values of UBA2000T chip parameters

The principle of operation of the electronic starter on the UBA2000T chip

Notes to the table.

1. The output is connected to an internal zener diode with a breakdown voltage of about 6,8 V.

2. The output is connected to an internal zener diode with a breakdown voltage of 130-230 V. The current through the output must be limited to 10 mA.

3. Impulse value with a pulse duration of 2 ms.

Author: Koryakin-Chernyak S.L.

See other articles Section Ballasts for fluorescent lamps.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Alcohol content of warm beer 07.05.2024

Beer, as one of the most common alcoholic drinks, has its own unique taste, which can change depending on the temperature of consumption. A new study by an international team of scientists has found that beer temperature has a significant impact on the perception of alcoholic taste. The study, led by materials scientist Lei Jiang, found that at different temperatures, ethanol and water molecules form different types of clusters, which affects the perception of alcoholic taste. At low temperatures, more pyramid-like clusters form, which reduces the pungency of the "ethanol" taste and makes the drink taste less alcoholic. On the contrary, as the temperature increases, the clusters become more chain-like, resulting in a more pronounced alcoholic taste. This explains why the taste of some alcoholic drinks, such as baijiu, can change depending on temperature. The data obtained opens up new prospects for beverage manufacturers, ... >>

Major risk factor for gambling addiction 07.05.2024

Computer games are becoming an increasingly popular form of entertainment among teenagers, but the associated risk of gaming addiction remains a significant problem. American scientists conducted a study to determine the main factors contributing to this addiction and offer recommendations for its prevention. Over the course of six years, 385 teenagers were followed to find out what factors may predispose them to gambling addiction. The results showed that 90% of study participants were not at risk of addiction, while 10% became gambling addicts. It turned out that the key factor in the onset of gambling addiction is a low level of prosocial behavior. Teenagers with a low level of prosocial behavior do not show interest in the help and support of others, which can lead to a loss of contact with the real world and a deepening dependence on virtual reality offered by computer games. Based on these results, scientists ... >>

Traffic noise delays the growth of chicks 06.05.2024

The sounds that surround us in modern cities are becoming increasingly piercing. However, few people think about how this noise affects the animal world, especially such delicate creatures as chicks that have not yet hatched from their eggs. Recent research is shedding light on this issue, indicating serious consequences for their development and survival. Scientists have found that exposure of zebra diamondback chicks to traffic noise can cause serious disruption to their development. Experiments have shown that noise pollution can significantly delay their hatching, and those chicks that do emerge face a number of health-promoting problems. The researchers also found that the negative effects of noise pollution extend into the adult birds. Reduced chances of reproduction and decreased fertility indicate the long-term effects that traffic noise has on wildlife. The study results highlight the need ... >>

Random news from the Archive

EU and South Korea to develop 5G network 19.06.2014

The website of the European Commission published a message about a key agreement with South Korea to jointly develop next-generation cellular networks.

The parties intend to cooperate in research and development of specifications, as well as in the "harmonization" of the use of the radio frequency spectrum, which should ensure compatibility on a global scale.

Ahead is the signing of a memorandum of understanding between the European alliance 5G Infrastructure Association, which includes Alcatel-Lucent, Atos, Deutsche Telekom, Ericsson, Nokia, Orange, Telecom Italia, Telenor and Telefonica, and the South Korean association 5G Forum.

For now, the partners will need to "deepen the discussion" on the future of networks, including 5G and cloud computing, and define the objectives of a joint research project that will begin in 2016.

Last December, the European Commission launched the Public-Private Partnership on 5G, planning an investment of 700 million euros over the next seven years. European business intends to allocate at least 5 billion euros for the creation of 3G networks.

A 5G connection will allow you to download a 60-minute video in HD quality in 6 seconds.

Other interesting news:

▪ A new way of light propagation in glass

▪ Pessimism Gene

▪ Increasing the life of ultracold molecules

▪ Acer Extensa EX2510 and EX2509 laptops

▪ Lenovo Legion R7000P and R9000P gaming laptops

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ site section Chargers, accumulators, batteries. Article selection

▪ article On one word of honor. Popular expression

▪ article Which languages don't distinguish between blue and green? Detailed answer

▪ article Juniper red. Legends, cultivation, methods of application

▪ article Amplifier for self-powered stereo telephones. Encyclopedia of radio electronics and electrical engineering

▪ article Liquid crystal indicators. Encyclopedia of radio electronics and electrical engineering

Leave your comment on this article:

All languages of this page

Home page | Library | Articles | Website map | Site Reviews