FI68747C - LIGHT RELEASE FOR MEDICAL ELECTRONIC SYSTEMS FOR FORED LAMPS - Google Patents

Description

1 68747

Fluorescent lamp dimmer with electronic ballast. - Ljusreglage för en med el eliskisk anslut-ningsanordning försedd lyslampa.

The invention relates to a light dimmer for a fluorescent lamp with an electronic ballast, which is formed as a control unit separate from the ballast, connected to a mains voltage line supplying the ballast to control the mains voltage supplied to the to control, a comparator connected to the control unit, to the input of which a control voltage and a voltage dependent on the set voltage are connected, a control device for adjusting the control voltage and a starting circuit for connecting the control voltage.

FI patent publications 64487 and 63849 disclose a switching arrangement in which power is supplied to an electronic ballast via a separate mains voltage regulator. With this arrangement, the light level of the lamps can be adjusted within wide limits without interference when using fluorescent lamps with tubes 38 mm thick. Today, the use of so-called thin fluorescent lamps 26 mm thick. The advantage of these thin fluorescent lamps is about 10% lower power consumption compared to a thick tube, with the same amount of light. However, thin fluorescent tubes have not been adjustable by traditional methods of adjusting 38 mm tubes. However, by using a certain type of electronic ballast (cf. FI patent publication 64487), thin fluorescent lamps can also be adjusted over a considerably wide adjustment range. However, the use of an electronic ballast suitable for the use of the controller places the following special requirements on the controller.

1. The power absorbed by the controller load must be kept constant by the controller despite fluctuations in the mains voltage.

2. The maximum output voltage of the controller must be artificially limited.

2 68747 3. When starting the controller, the output voltage of the controller must be changed according to a certain start sequence before the output voltage reaches the value set by the control voltage.

These objects are achieved by a controller according to the invention on the basis of the features set out in the appended claims.

By implementing Objective 1, e.g. the advantage is that when a certain minimum level of illumination is set at which the lamps do not flicker, this set minimum level remains unchanged, and even a decrease in the mains voltage does not cause the lamps to flicker. Correspondingly, for example, the preset lighting level for slide viewing remains constant.

Achieving Objective 2 has the advantage of avoiding over-burning of lamps. The preamplifier of the electronic ballast and the thyristor controller form an oscillation circuit, where the internal DC voltage of the electronic ballast can rise higher than when sinusoidal electricity is supplied directly from the mains. This increase in DC voltage causes the lamps to burn with overvoltage, which shortens the life of both the lamps and the electronic ballast. This can therefore be avoided by achieving Objective 2.

As a combination of the implementation of Objectives 1 and 2, e.g. the fact that a rise in the mains voltage above the nominal value does not lead to an increase in the power consumption of the lamps and a consequent reduction in the life of the lamps.

The implementation of Objective 3 has the advantage that, in the event of an ignition, sufficient voltage can always be guaranteed to ignite the lamps. In addition, by performing the ignition "softly" by first applying a large incandescent current to the cathodes of the lamp, the life of the lamps can be extended as a function of the number of firings.

In the following, an embodiment of the invention will be described in more detail with reference to the accompanying drawing, in which Fig. 1 shows a block diagram of a controller according to the invention and Fig. 2 shows a circuit diagram of a block 10 connected to the block diagram as a novelty.

Figure 3 shows the adjusted voltage curve during start-up.

Figure 4 shows a circuit diagram of blocks 7-10 of the block diagram of Figure 1.

Electrical power for the fluorescent lamps 1 is supplied via electronic ballasts 2. The connection device 2 can be, for example, as described in FI patent publication 64487. One or more fluorescent lamps may be connected to one of the ballasts 2.

Electrical power is supplied to one or more ballasts 2 via a separate mains voltage regulator, the power regulating power stage 5 of which is connected to the mains voltage line. The thyristors in the terminal stage 5 intersect a part of the half-waves of the mains voltage 4 determined by their trigger control, whereby the phase angle-adjusted voltage 3 acts at the output of the controller.

Reference numeral 6 denotes a block containing thyristor trigger control circuits.

The potentiometer in the control device 9 controls the control voltage Uc, which is controlled by the starter circuit 8 and connected to the adder unit 7. On the other hand, the adjusted voltage 3 is fed back to the controller via a circuit 10 simulating the electronic ballast 2. The voltage obtained from the simulator circuit 10 and the control voltage Uc are summed as opposite signs. If the control voltage Uc is sufficiently high than the absolute value of the voltage obtained from the simulator circuit 10, the adder unit 7 controls the trigger control unit 6 of the thyristors so that the thyristors in the terminal unit 5 half-waves. When the control voltage Uc remains constant, the thyristors are controlled so that they emit such a large part of the mains voltage half-waves that the control voltage U, minus the differential voltage corresponding to the equilibrium state,

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and the absolute value of the voltage obtained from the simulator circuit 10 is equal.

Figure 2 shows in more detail the simulator circuit 10 of the electronic ballast. It is separated from the main circuit by means of a transformer 11. The formation circuit of the choke 12, the capacitor 13, the rectifier 14 and the electrolyte capacitor 15 corresponds in connection to the preamplifier of the electronic ballast. Resistor 16 is a ballast for the ballast. The components 12 to 15 simulating the ballast respond to the regulated voltage 3 in exactly the same way as the ballasts 2 themselves, so that such a simulating scale model can most accurately obtain information on the DC voltage inside the electronic ballast 2. Another advantage of the simulating scale model is that if one of the adjustable electronic ballasts 2 is damaged and causes a change in the voltage level of the other ballasts 2, information is immediately obtained from which the output voltage of the controller is automatically directed in the right direction.

In addition, the invention provides a starting voltage circuit in the starting circuit 8, which connects the control voltage U set by the control device 9 to the comparator only after

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the constant start voltage U, which causes an illumination level of about 10%, has been applied for a certain time. Figure 3 shows the voltage 3 adjusted on the vertical axis and the time on the horizontal axis. The mains voltage is switched on at time tQ and after a waiting time tQ - the starting voltage Ug for a certain time t1 - t2 is applied, at which the cathode annealing of the lamps takes place at a light level of about 10%. In the time interval t2 ~, the set voltage is set to the state according to the control voltage U, whereby a high control voltage c 5 68747 leads to a voltage level "a" and a low control voltage to a voltage level wb ".

The starting circuit 8 shown in Fig. 4 operates in such a way that when the mains voltage is switched on, the capacitor C 3 is empty, which causes the transistor T to go into a conductive state. When the transistor conducts, the voltage U does not affect the operational amplifier IC 1 and thus the output of the operational amplifier IC 2 also remains low. However, so that the voltage applied to the adder unit 7 is not zero, a voltage is passed through the diode D3, which is set to correspond to a light level of 10%. When C 3 is sufficiently charged, the transistor T ceases to conduct and the current flow through the diode D 3 also stops. In this case, the control voltage Uc can affect the output of the operational amplifier IC 2, which is set to Uc. Correspondingly, the output voltage of the entire controller changes towards the value of the output voltage corresponding to Uc.

Claims (3)

6,68747 A light regulator for a fluorescent lamp (1) provided with an electronic ballast (2), formed as a control unit separate from the ballast, connected to a mains voltage line supplying the ballast to control the mains voltage (4) supplied with the ballast, (6) for controlling power control components, an adder (7) connected to the control unit (6), the input of which is connected to a control voltage (Uc) and a voltage dependent on the regulated voltage (3), a control device (9) for adjusting the control voltage (Uc) and a starting circuit (8) ) for connecting a control voltage (U), characterized in that a voltage dependent on the regulated voltage (3) is connected to the comparator (7) via a circuit (10) simulating the electronic ballast (2). A dimmer according to claim 1, characterized by a starting circuit (8) connected between the control device (9) and the comparator (7) and provided with a starting voltage circuit which switches the control voltage set by the control device (9) to the comparator (7) only after a constant The voltage causing the% illumination level has been active for a certain time (t ^ - t2). Light dimmer according to Claim 1, characterized in that the circuit (10) simulating the electronic ballast is connected to the output voltage (3) of the dimmer by means of a isolating transformer (11).