RU2186468C2 - Gas-discharge lamp starting device - Google Patents

Abstract

FIELD: electrical engineering; starting gas- discharge lamps. SUBSTANCE: starting device has glow-discharge starter connected in series with current-limiting resistor in the form of posistor which is connected in series with resistor. Total resistance of posistor and resistor is determined. EFFECT: enhanced reliability of starting device. 2 dwg

Description

 The invention relates to electrical engineering and can be used to ignite discharge lamps.

 Known igniter device (Russian patent 2120705 CL. H 05 B 41/18, 10.20.1998), containing a glow discharge starter, a resistance connected in series with it, as a posistor.

 However, in the process of ignition of the lamp at an amplitude value of voltage of 300 V, the resistance of the "cold" posistor decreases significantly compared to its nominal value specified by the manufacturer, which leads to an unacceptable increase in current.

 The technical effect is to increase the reliability of the ignition device.

где R_∂ - суммарное сопротивление позистора и резистора;
U_c - действующее напряжение сети;
J₀ - ток удержания стартера;
U_м - амплитуда зажигающего импульса;
R - сопротивление разрядного промежутка стартера;
L - индуктивность дросселя;
С - емкость, включенная параллельно лампе.The essence of the invention lies in the fact that in an ignition device for gas discharge lamps containing a glow discharge starter, a current-limiting resistance in the form of a posistor is connected in series with it, where the latter is connected in series with a resistor under the following condition:

where R _∂ is the total resistance of the posistor and resistor;
U _c - the effective voltage of the network;
J ₀ - holding current of the starter;
U _m is the amplitude of the ignition pulse;
R is the resistance of the discharge gap of the starter;
L is the inductance of the inductor;
C is the capacity connected in parallel with the lamp.

 In FIG. 1 shows the proposed ignition device, including a glow discharge starter 1, a posistor 2 and a resistor 3 connected in series with it.

 The ignition device operates as follows.

 When the ignition device is switched on in the network parallel to the discharge lamp and sequentially with a throttle (not shown), a glow discharge occurs in the starter of the glow discharge 1. This leads to heating of the bimetal and shorts the starter of the glow discharge 1. The discharge in the starter of the glow discharge 1 stops and, as soon as the bimetal it cools, the current is interrupted, which causes a voltage pulse to appear between the electrodes of the discharge lamp. With a sufficient pulse amplitude, an arc discharge is established in the lamp with a voltage drop less than the ignition voltage of the glow discharge starter 1. Due to the specific heat capacity, the posistor 2 does not have time to significantly change its temperature during the contact time of the glow discharge starter 1, and the short circuit current is limited by the resistance of the active resistor 3 and the resistance of the cold posistor 2.

 In an emergency, with a faulty lamp, after several contacts of the glow discharge starter 1, the posistor 2 heats up, and its resistance increases hundreds of times compared with the "cold" state. The glow discharge current flowing through the starter of the glow discharge 1 is insufficient for its contact, which protects the inductor from possible breakdown by high-voltage pulses, and the ignition device from overheating.

 Below is the rationale for choosing the value of the total resistance of the posistor and resistor specified in the essence of the invention.

 It is known (V.V. Pasynkov, L.K. Chirkin, A.D. Shinkov Semiconductor devices, M., Higher School 1981) that the resistance of a posistor at a constant temperature depends on the voltage applied to it - an increase in voltage decreases the resistance value . Figure 2 shows the current-voltage characteristic (CVC) of the "cold" posistor (dependence 1), here also shows the CVC of the resistance 390 Ohms (dependence 2).

It is seen that at a voltage of 100 V, the differential resistance of the posistor decreases to OM units, thereby one resistor connected in series with the starter weakly limits the current through the starter at the moment of its closure at a voltage value greater than 100 V. To eliminate this drawback, it is necessary to sequentially with the posistor include an additional resistor, such that the total resistance of the resistor and the resistor R _{∂ is} selected based on the following considerations:
a) the resistor must provide a current in the circuit, with the starter closed, not more than the holding current J ₀ .

,
где U_c - сетевое напряжение.Indeed, if a current greater than J ₀ flows through the bimetallic starter plate, the heat generated will not allow the plate to cool and break the contact. The value of J ₀ depends on the design of the starter and for individual instances of starters may be less than 2.5 A. Therefore, the condition

,
where U _c is the mains voltage.

обеспечивает зарядку емкости включенной параллельно зажигаемой лампе, W_c= cU_м ², U_м - амплитуда зажигающего импульса и протекание тока аномального тлеющего разряда через стартер при действии зажигающего импульса. При этом в стартере выделяется энергия в тепловом виде Q=U_м ²•t/R, (R - сопротивления разрядного промежутка стартера во время действия импульса; t - время действия импульса). Учитывая, что t - время нарастания импульса в LRC контуре (каковым и является стартерная схема зажигания лампы) в момент разрыва контакта стартера составляет

где Т - период свободных колебаний - можно с достаточной точностью определить

Баланс энергии запишем

Если емкостью С является только паразитная емкость (величина рядка 100 пФ), то членом

в уравнении (1) можно пренебречь.b) on the other hand, it is impossible to increase R _∂ (more than a certain value), in this case the energy stored in the magnetic field of the inductor with inductance L will be small when the starter is in contact. This energy

provides charging of the capacitance to a parallel-switched lamp, W _c = cU _m ² , U _m is the amplitude of the ignition pulse and the flow of the abnormal glow discharge current through the starter under the action of the ignition pulse. In this case, heat energy is released in the starter Q = U _m ² • t / R, (R is the resistance of the discharge gap of the starter during the pulse; t is the pulse duration). Given that t is the pulse rise time in the LRC circuit (which is the starter ignition circuit of the lamp) at the time of breaking the starter contact,

where T is the period of free oscillations - it can be determined with sufficient accuracy

We write the energy balance

If the capacitance C is only parasitic capacitance (the value of the row is 100 pF), then the term

in equation (1) can be neglected.

To achieve an amplitude of the ignition pulse greater than U _{m, the} current J _k must be such that the left side of equality (1) is greater than the right.

где U_a - амплитудное значение сетевого напряжения (~300 В). Компромиссом между двумя пунктами а и б является условие

Например, для U_c=220 В, J₀=2,5А, U_м=300 В, R=10⁴ Ом, 0,1 Гн<L<1 Гн и С= 100 пФ имеем 88 Ом<R_∂<1800 Ом.
Диапазон изменений индуктивностей определяется диапазоном мощностей используемых ламп и может быть шире приведенного. Уменьшение индуктивности будет приводит к сужению диапазона возможных значений сопротивлений R_∂.
Следует отметить, что в предложенном устройстве сопротивление позистора в диапазоне температур 20-60^oС имеет величину менее 300 Ом.Given that J _к = U _a / R _∂ after transformations, we obtain

where U _a is the amplitude value of the mains voltage (~ 300 V). The compromise between two points a and b is the condition

For example, for U _c = 220 V, J ₀ = 2.5 A, U _m = 300 V, R = 10 ⁴ Ohms, 0.1 H <L <1 H and C = 100 pF, we have 88 Ohm <R _∂ <1800 Ohm.
The range of changes in inductances is determined by the power range of the lamps used and may be wider than the above. A decrease in inductance will lead to a narrowing of the range of possible values of the resistances R _∂ .
It should be noted that in the proposed device, the resistance of the posistor in the temperature range of 20-60 ^o C has a value of less than 300 Ohms.

 The proposed device can improve the reliability of ignition of discharge lamps, because the presence in the ignition device of a series-connected resistor and a posistor allows a wider range of adjustment of the device shutdown time and the use of cheaper low-impedance resistors (cold resistance less than 300 Ohms) with sufficient heat capacity, providing due to the use of an active resistor effective limitation even in the presence of a resistor with low heat capacity (i.e. with low weight and, accordingly, low cost), which is impossible to provide with one posistor.

We performed a functional check of the device at R _∂ = 450 Ohms. At the same time, the device steadily ignited the DNAT-400 lamp. We used a TRP-3-62 Ohm posistor and an MLT-2390 Ohm resistor in series.

Claims (1)

The ignition device for a gas discharge lamp connected in series with the inductor, containing a glow discharge starter, a current-limiting resistance in the form of a posistor connected in series with it, characterized in that the posistor is connected in series with a resistor, and the total resistance of the resistor and resistor is determined from the condition

where R _∂ is the total resistance of the posistor and resistor;
U _c - the effective voltage of the network;
I ₀ - holding current of the starter;
U _a - the amplitude value of the network voltage;
U _m is the amplitude of the ignition pulse;
R is the resistance of the discharge intermediate starter;
L is the inductance of the inductor;
C is the capacity connected in parallel with the lamp.

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