SU869081A1 - Device for power supply of luminescent lamp with unipolar pulses - Google Patents

Description

(54) DEVICE FOR POWER SUPPLY OF LUMINESCENT LAMPS WITH UNIPOLAR PULSES

one

The invention relates to electrical engineering and can be used in lighting installations with fluorescent lamps.

A device for supplying fluorescent lamps is known, comprising a bridge rectifier, a rectifier output capacitor, a transistor switch in a rectified current circuit connected in series with a fluorescent lamp and a choke, the lamp and the choke being shunted by a diode, the transistor controlling It comes from a separate Y pulse generator.

The drawbacks of the device are its complexity, low energy performance and lack of reliability. The complexity of the device is associated with the presence in the power circuit of a throttle and a diode shunting the choke and the lamp, as well as the fact that the pulse generator providing the key pulse mode of operation of the power transistor contains several additional transistors and other elements.

Low energy performance. due to losses in active resistance of drossel. If the power supply of the device comes from an unstabilized AC mains, then in order to limit the current to the AC circuit, an additional ballast in the form of a resistor or droplets is inserted in front of the 10 straightener, which creates additional losses in the device. With an inductive ballast choke, the power factor at the device input is lagging, and the device is a consumer of reactive power from the network. This, in turn, increases the power losses in the network or requires co

29 in the network of additional compensated devices,

The reliability of a known device is low, due to the fact that a voltage close to the amplitude of the alternating voltage of the network is applied to the transistor 3 of the power circuit during its closed state. When used as an additional ballast in an alternating current circuit of the drossel, the voltage at the output of the rectifier may be even higher (double the magnitude of the amplitude of the alternating voltage of the network). When a diode that shunts a lamp and a choke fails, the voltage across the transistor at the time of its locking due to the emf of self-induction of the throttle can be significantly (several times) higher than the operating voltage of the transistor. An additional source for supplying the generator of control pulses with a transistor switch than (the power circuit transistor) and the generator itself contains many elements, which further reduces the reliability of the device. The closest to the proposed technical solution is a device containing a rectifying bridge, the input connected via a ballast capacitor to the terminals for connection to the AC network, and the output connected to the capacitor of the smoothing filter, with a terminal for connecting the fluorescent lamp and the emitter of the pp -n transistor, the collector of which is connected to the water to connect the lamp, and the base through a transistor amplifier connected to the output of the multivibrator. A separate rectifier transformer and a smoothing capacitor are provided for powering the multivibrator and amplifier. The disadvantage of this device is its great complexity and low reliability. The purpose of the invention is to increase the reliability of the device. This goal is achieved by providing a device for supplying a fluorescent lamp with unipolar pulses, containing a rectifying bridge connected by an input through a ballast capacitor to the terminals for connection to an AC network, and an output connected to a smoothing filter capacitor, with one of the terminals for connecting a fluorescent lamp and with an emitter of a pnp transistor, equipped with a pulse transformer, a capacitor, a voltage divider with two feedback resistors and another capacitor, and A voltage input is connected between the emitter of the pnp transistor output to connect the fluorescent lamp, parallel connected to the voltage divider are connected in series a capacitor and the primary winding of a pulse transformer, the secondary winding of which is the specified two resistors and the other capacitor connected to the base n p-p- n a transistor whose collector is connected to the output of the voltage divider. The drawing shows a diagram of the proposed device. The luminescent lamp 1 is connected by points 2 and 3 of its different electrodes through a transistor 4 to the output points 5 and 6 of a bridge rectifier formed by diodes 7-10, whose input is connected to the AC network 14 by points 11 and 12 through a capacitor 13. At the output of the rectifier 7-10, a capacitor 15 is installed, which serves to smooth the output voltage. The other ends 16 and 17 of the electrodes of the lamp 1 are connected to the starter 18 of the glow discharge. Capacitor-, 19 is connected through the primary winding 20 of a pulse transformer 21 s ce; a material from a hysteresis loop. The end of the winding 20 and the beginning of the secondary winding 22 of the same transformer 21 are connected to the emitter of the transistor 4, and the end of the winding 22 is connected through series-connected feedback resistors 23 and 24 to the base of the transistor 4. A feedback capacitor 25 is connected in parallel with the resistor 23. Resistors 26 and 27 form a voltage divider. The device works as follows. Before connecting the device to the network 14, the circuit is in a non-operating state, the currents and voltages on all elements are zero. When the voltage of the si 14 is turned on through the capacitor 13, the rectifier 7-10 begins to flow the charge current of the capacitor 15, since the capacitance of the capacitor 15 is much greater than the capacitance of the capacitor 13, the voltage on the capacitor 15 increases in steps along the network half-periods. With a small voltage at the output of the rectifier (on the capacitor 15), only 5 flows through the lamp 1 and the starter 18, the leakage current between the electrodes and the current of the initiating discharge, and the voltage across the transistor 4, is shunted by a high-resistance resistor 27 is almost zero. Starter 18 and lamp 1 are selected so that the glow discharge develops in the starter 18 by the applied voltage than in the lamp 1. The appearance of the current of the glow discharge of the starter 18 increases the voltage on the transistor 4 and can create conditions for the generation of transistor 4 control pulses from the positive feedback circuit. The collector circuit of transistor 4 includes a relatively small resistance formed by the resistance between the points and the ends of electrodes 2-16 and 3-17 of lamp 1 and resistor 26. As a result, a large voltage is applied to the emitter-collector junction of transistor 4 and a regenerative process occurs. As the voltage across the transistor increases, a current begins to flow through the capacitor 19 and the winding 20, and a positive potential is applied to the beginning of the winding 20. The polarity of the voltage induced on the secondary winding 22 of the transformer 21 is such that its positive pole is applied to the emitter, and negative to the base of transistor 4. The capacitor 25 increases the steepness of the leading front applied to the base voltage transistor i of the blocking transistor 4 and thereby contributing to a further increase in the voltage on the transistor 4. If the voltage build-up on the transistor 4 stops, then the current through the capacitor 19 disappears and the voltage on the windings of the transforms disappears. The driver 21 and the base circuit of the transistor 4 are already applied to the locking voltage, and the residual voltage of the capacitor 25 created during the flow of current in the base in the previous time interval. This voltage turns out to be unlocking for transistor 4. As a result, its resistance decreases slightly and the voltage across the transistor decreases. A current is generated through the capacitor 19 of such a direction that a negative voltage is applied to the winding 20 in negative polarity at its beginning. On the secondary winding 22, EMF is also induced in the negative field at its beginning. This EMF turns out to be unlocking for transistor 4, which causes a further process of unlocking transistor 4. Capacitor 25 increases the slope of the leading edge of the voltage unlocking transistor 4. Unlock voltage is generated as long as the capacitor 9 is charged, or the core of the transformer 21 does not occur. In both these cases, the unpicked voltage induced on the winding 22 decreases, and the base voltage of the capacitor 25 applied in the preceding the time interval. The process of locking transistor 4 develops, accompanied by an increase in the voltage across it. The locked state of the transistor 4 is maintained until the charge of the capacitor 19 ends or the core of the transformer 21 is struck, after which the transition of the transistor 4 from the locked to the open state occurs again. The use of a capacitor 25 and a core with a rectangular hysteresis loop in transformer 21 provides a sharp fracture from locked: the state of transistor 4 to the open state and the reverse transition, which makes it possible to reduce the switching losses in transistor 4 to the smallest possible value. The same goal of reducing switching losses in the transistor 4 is the choice of the feedback depth due to the corresponding value of the transformer ratio 21. The reverse connection also allows for. A stable generation in the wider range is changed. The load resistance in the collector circuit of transistor 4 and the network voltage is changed. This solution simplifies the device, since it does not require additional power sources. Thus, when the voltage across the transistor appears, a stable key mode occurs that alternates between open and closed states of transistor 4 with a duty cycle and frequency depending on the ftameters of the elements of the feedback circuit. Each time the transistor 4 is locked, its current is reduced to a very small value. To prevent the lamp from turning off, parallel

Claims (1)

Claim A device for supplying a fluorescent lamp with unipolar pulses, containing a rectifier bridge connected to the terminals via an input through a ballast capacitor for connection to an alternating current network, and output ₅ connected to a smoothing filter capacitor, with one of the terminals for connecting a fluorescent lamp and an emitter -n transistor, characterized in that, 10, in order to increase the reliability of the device, it is equipped with a pulse transformer, capacitor, voltage divider, two resistors and another capacitor m, the divider _15, the voltage input is connected between the emitter of the n-p-n transistor and a terminal for connection of a fluorescent lamp, parallel voltage divider connected in series coupled ₂₀ nye capacitor and the primary winding of the pulse transformer secondary winding is through these two resistors and the other capacitor is connected to the base of the pnp transistor, the _25th collector of which is connected to the output of the voltage divider.