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Electronic ballasts. A simple electronic ballast based on the IR2153 chip. Encyclopedia of radio electronics and electrical engineering

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

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Consider a simple electronic ballast circuit based on the IR2153 (IR2151) microcircuit, shown in fig. 3.14. Main parameters of IR2153 are as follows:

• the maximum voltage at the VB terminal relative to the common wire is 600 V;
• supply voltage (V_cc) - 15 V;
• consumption current (I_cc) - 5 mA;
• maximum control current I_o -+100 mA / -210 mA;
• switch-on time (t_op) - 80 ns;
• turn-off time (t_off) - 40 ns;
• switching pause (delay) -1,2 µs.

Rice. 3.14. Structural diagram of the IC IR2153 (click to enlarge)

Schematic diagram of the electronic ballast, made on the basis of IR2153, is shown in fig. 3.15.

IR2153 is a high power insulated gate field effect transistor (MOSFET) driver with an internal oscillator. It is an exact copy of the generator used in the 555 series timer, the domestic analogue is KR1006VI1. Operates directly from the DC bus through the quenching resistor R1.

Internal voltage regulation prevents overvoltage V_cc greater than 15,6 V. Undervoltage blocking blocks both gate control outputs VT1 and VT2 when voltage V_cc below 9 V.

DA1 has two control outputs:

• lower 5 to control VT2;
• the upper 7 output for controlling VT1, "floating", since the pulse shaper for controlling the field-effect transistor VT1 is powered by a floating power source, which is formed by the elements VD2, C7).

Rice. 3.15. Schematic diagram of an electronic ballast based on IR2153 (click to enlarge)

When managing power keys (VT1, VT2), the IR2151 chip provides a switching delay of 1,2 µs to prevent the situation when transistors VT1 and VT2 are simultaneously open and through current flows through them, which instantly disables both transistors.

This ballast is designed to power one or two lamps with a power of 40 (36) W (lamp current - 0,43 A) from an alternating current network of 220 V 50 Hz. When using two lamps of 40 W, it is necessary to add the elements marked with a dotted line (EL2, L3, C11, RK3). It should be noted that for stable operation, the values ​​​​of the elements in parallel branches must be equal (L3, C11 \u2d L10, CXNUMX), and the length of the wires supplied to the lamps must be the same.

Council. When using one driver for two lamps, it is preferable to use frequency heating of the electrodes (without posistors). This method will be discussed below (when describing the electronic ballast on the IR53HD420 chip).

When using lamps of a different power (18-30 W), the values ​​\u2b\u1,8bof L1,5 \u60d 80-2 mH should be changed (respectively); when using lamps with a power of 1-0,85 W - L2 \uXNUMXd XNUMX-XNUMX mH, and RXNUMX - from the condition F_г ~F_б (the formulas for calculating these frequencies are given below).

Mains voltage 220 V is supplied to network filter (EMC filter) formed by elements C1, L1, C2, C3. The need for its use is due to the fact that key converters are sources of electromagnetic radio frequency interference, which network wires radiate into the surrounding space like antennas.

The current Russian and foreign standards regulate the levels of radio interference generated by these devices. Good results are obtained by two-section LC filters and screening of the entire structure.

At the input of the mains filter, a traditional unit for protecting against mains overvoltages and impulse noise is included, including a varistor RU1 and a fuse FU1. Thermistor RK1 with a negative temperature coefficient (NTC) limits the input current surge caused by the charge of the capacitive filter C4 at the input of the inverter when the electronic ballast is connected to the network.

Further, the mains voltage is rectified by the diode bridge VD1 and smoothed out by capacitors C4. The R1C5 chain feeds the DAI - IR2153 chip. The frequency of the internal oscillator FT of the microcircuit is set by the elements R2 = 15 kOhm; C6 \u1d XNUMX nF in accordance with the formula

The resonant frequency of the ballast circuit F6 is set by the elements L2 = 1,24 mH; C10 = 10 nF according to formula

To ensure good resonance, the following condition is required: the frequency of the internal generator should be approximately equal to the resonant frequency of the ballast circuit, i.e. Fg ~ Fb.

In our case, this rule is fulfilled. Elements VD2, C7 form floating (bootstrap) power supply pulse shaper control field effect transistor .VT1. Elements R5, C9 - damping circuit (snubber), which prevents snapping (operation of a parasitic thyristor in the CMOS driver structure) of the output stages of the microcircuit. R3, R4 - limiting gate resistors, limit the induced currents and also protect the output stages of the microcircuit from snapping. It is not recommended to increase (within large limits) the resistance of these resistors, since this can lead to spontaneous opening of power transistors.

Construction and details. The mains filter inductor L1 is wound on a K32x20x6 M2000NM ferrite ring with a two-core network wire until the window is completely filled. It is possible to replace the choke from the PFP power supply of a TV, VCR, computer.

Good noise suppression results are provided by specialized EPCOS filters: B8414-D-B30; B8410-B-A14.

To make a gap it is necessary to lay gaskets of non-magnetic material (non-foil fiberglass or getinax) of appropriate thickness between the mating surfaces of the halves of the magnetic circuit and fasten with epoxy glue.

The value of the inductance of the inductor (with a constant number of turns) depends on the value of the non-magnetic gap. With a decrease in the gap, the inductance increases, with an increase, it decreases. Reducing the gap is not recommended, because this leads to saturation of the core.

When the core is saturated, its relative magnetic permeability decreases sharply, which entails a proportional decrease in inductance. The decrease in inductance causes an accelerated increase in current through the inductor and its heating. The current passing through the LL also increases, which negatively affects its service life. The rapidly increasing current through the inductor also causes shock current overloads of power switches VT1, VT2, increased ohmic losses in the switches, their overheating and premature failure.

Winding L2 - 143 turns of PEV-2 wire with a diameter of 0,25 mm. Interlayer insulation - varnished cloth. Winding - turn to turn. The main dimensions of W-shaped corec (consist of two identical W-shaped cores) of soft magnetic ferrites (according to GOST 18614-79) are given in Table. 3.2.

Table 3.2. Main dimensions of W-shaped cores

Transistors VT1, VT2 - IRF720, high power insulated gate field effect transistors. MOSFET is a Metal Oxide Semiconductor Field Effect Transistor; in the domestic version, MOSFETs are field-effect transistors of the metal-oxide-semiconductor structure.

Consider their parameters:

• DC drain current (I_D) - 3,3 A;
• surge current drain (I_DM)-13 A;
• maximum drain-source voltage (V_DS) - 400 V;
• maximum power dissipation (P_D) - 50 W;
• operating temperature range (Tj) - from -55 to +150 °С;
• open resistance -1,8 Ohm;
• total gate charge (Q_G) - 20 nC;
• input capacitance (C_ISS) - 410 pF.

When choosing and replacing transistors (comparison in table 3.3) for electronic ballasts it should be rememberedthat today the number of firms producing field-effect transistors is quite large (IR, STMicro, Toshiba, Fairchild, Infineon, etc.). The range of transistors is constantly expanding, more advanced ones with improved characteristics appear. Parameters to pay special attention to:

• direct current drain (ID);
• maximum drain-source voltage (VDS);
• open resistance, RDS(on);
• total gate charge (QG);
• CISS input capacitance.

Possible replacement transistors for electronic ballast: IRF730, IRF820, IRFBC30A (International Rectifier); STP4NC50, STP4NB50, STP6NC50, STP6NB50 (STMicroelectronics); field-effect transistors from Infineon (infineon.com) series LightMos, CoolMOS, SPD03N60C3, ILD03E60, STP03NK60Z; PHX3N50E from PHILIPS, etc.

The transistors are mounted on small plate heatsinks. The length of the conductors between the driver outputs 5, 7, the resistors in the gate circuits R3, R4 and the gates of the field-effect transistors must be minimal.

Table 3.3. Comparison table with the parameters of some transistors for electronic ballasts

Rice. 3.16. The main dimensions of the core (to table. 3.2)

Diode bridge VD1 - imported RS207; permissible forward current 2 A; reverse voltage 1000 V. Can be replaced by four diodes with the appropriate parameters.

Diode VD2 class ultra-fast (superfast) - reverse voltage of at least 400 V; permissible direct direct current - 1 A; reverse recovery time - 35 ns. Fits 11DF4, BYV26B/C/D, HER156, HER157, HER105-HER108, HER205-HER208, SF18, SF28, SF106-SF109, BYT1-600. This diode should be located as close to the chip as possible.

Chip DAI - IR2153, it is interchangeable with IR2152, IR2151, IR2153D, IR21531, IR2154, IR2155, L6569, MC2151, MPIC2151. When using the IR2153D, the VD2 diode is not required, since it is installed inside the microcircuit.

Resistors R1-R5 - OMLT or MLT.

Capacitors C1-C3 - K73-17 for 630 V; C4 - electrolytic (imported) for a rated voltage of at least 350 V; C5 - electrolytic for 25 V; C6 - ceramic for 50 V; C7 - ceramic or K73-17 for a voltage of at least 60 V; C8, C9 - K73-17 for 400 V; SU - polypropylene K78-2 for 1600 6.

Varistor RU1 from EPCOS - S14K275, S20K275, replace with TVR (FNR) 14431, TVR (FNR) 20431 or domestic CH2-1a-430 V.

Thermistor (thermistor) RK1 with a negative temperature coefficient (NTC - Negative Temperature Coefficient) - SCK 105 (10 Ohm, 5 A) or EPCOS - B57234-S10-M, B57364-S100-M.

The thermistor can be replaced with a 4,7 ohm wirewound resistor with a power of 3-5 watts.

The RK2 posistor is a PTC thermistor (Positive Temperature Coefficient) with a positive temperature coefficient. The developers of IR2153 recommend using a posistor from Vishay Cera-Mite - 307C1260. His Main settings:

• nominal resistance at +25 °С - 850 Ohm;
• instantaneous (maximum allowable) rms voltage applied to the posistor when the lamp is ignited - 520 V;
• constant (maximum allowable) rms voltage applied to the posistor during normal lamp operation, -175 V;
• maximum allowable switching current (translating the posistor into a high-resistance state) -190 mA;
• the diameter of the posistor is 7 mm.

A possible replacement for the RK2 posistor is EPCOS pulsed posistors (the number of switching cycles is 50000-100000): B59339-A1801-P20, B59339-A1501-P20, B59320-J120-A20, B59339-A1321-P20.

Posistors with the necessary parameters in an amount sufficient for eight electronic ballasts can be made from the widely used ST15-2-220 thesistor from the demagnetization system of the ZUSCT TV. After disassembling the plastic case, two "tablets" are removed. With a diamond file, two notches are made crosswise on each, as shown in fig. 3.17, and break it into four pieces along the cuts.

Council. It is very difficult to solder leads to the metallized surfaces of a posistor made in this way. Therefore, as shown in Fig. 3.18, make a rectangular hole in the printed circuit board (pos. 3) and clamp the "tablet" fragment (pos. 1) between the elastic contacts (pos. 2) soldered to the printed conductors. By selecting the size of the fragment, you can achieve the desired duration of the lamp warm-up.

Rice. 3.17. "Tablet" posistor with notches

Rice. 3.18. Mounting a homemade posistor on the board

Council. If the fluorescent lamp is supposed to be used in the infrequent on-off mode, then the posistor can be excluded.

Setting. The spread of the parameters of the elements C6, L2, SU may require adjustment of the driver frequency. The equality of the frequency of the master oscillator of the IR2153 microcircuit to the resonant frequency of the L2C10 circuit is easiest to achieve by selecting the frequency-setting resistor R2. To do this, it is convenient to temporarily replace it with a pair of series-connected resistors: constant (10-12 kOhm) and trimmer (10-15 kOhm). The criterion for the correct setting is reliable start-up (ignition) and stable burning of the lamp.

The ballast is assembled on a printed circuit board made of foil fiberglass and placed in an aluminum shielding casing. The printed circuit board and arrangement of elements is shown in fig. 3.19.

Rice. 3.19. Printed circuit board and layout of elements

Author: Koryakin-Chernyak S.L.

See other articles Section Ballasts for fluorescent lamps.

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