FI96657C - Electronic ballast for gas discharge pipe - Google Patents

Abstract

An electronic ballast (1) for gas discharge lamps (2), having an input circuit part (10, 11) for producing an intermediate-circuit DC voltage (Uz) from a supply voltage (L1,N), having an oscillator circuit part (4,8,S1,S2), supplied from the intermediate circuit DC voltage (Uz) for generating an alternating signal (uw) which can be supplied to the gas discharge lamp (2), having a bistable switch-off latching circuit part (3) which supplies a switch-off signal (us) in its first and second stable state to the oscillator circuit part (4,8,S1,S2), and hence releases the oscillator circuit part (4,8,S1,S2) or switches it off, a first signal (u1), derived from the alternating signal (uw), driving the switch-off latching circuit part (3) from its first into its second stable state in the event of a predetermined value being exceeded, and generating the switch-off signal (us), is to be designed such that its operating reliability is further improved. This is achieved in that a further signal (u2), derived from the intermediate circuit DC voltage (Uz), produces the switch-off signal (us) when the intermediate circuit DC voltage (Uz) exceeds a predetermined maximum value. <IMAGE>

Description

96657

Electronic ballast for gas discharge pipe

The invention relates to an electronic front switching device (EVG) for gas discharge pipes according to the preamble of claim 1.

Such a device is known, for example, from EP 0 146 683. In the event that the used gas discharge pipe is constantly unable to ignite, i.e. has to be repeatedly ignited without success, the frequency converter is switched off by a bista-switch switching device. This is achieved by short-circuiting the secondary cut-off coil of the impregnation transformer, the primary winding of which is connected to the piping circuit. In the operating mode of the electronic pre-switching device, this saturation transformer generates carrier voltages in the operating mode of the electronic pre-switching device, by means of which two alternating switches of the transistors produce an alternating voltage signal. If the voltage induced in the secondary switching winding rises above the breakdown voltage of the trigger diode, then a thyristor lights up, which short-circuits the switching circuit through two single data diodes. In this way, it is no longer possible to produce other carrier voltages from the saturation transformer to the alternating switching transistors. The inverter is and will now remain in the off state until it is interrupted by disconnecting the electronic front switching device or dismantling the non-ignitable gas discharge tube.

The object of the invention is to form a gas discharge pipe of the type mentioned at the beginning so that its operational reliability is even better.

According to the invention, the task is solved by the features set forth in the characterizing part of claim 1.

The invention takes advantage of the idea that the disconnection mechanism is extended by at least one additional branch which monitors the DC link voltage. The measure according to the invention avoids thermal overloads of sensitive components, for example 96657, for example rectifiers or terminal transistors, which could cause an excessive DC link voltage.

Another advantage of the electronic front switching device according to the invention is the present protection against neutral conductor interference.

A further development form or alternative solution of the solution set out in claim 1 is set out in claim 7. This is based on taking a load current and, when a predetermined maximum value is exceeded, tripping the oscillator switching part.

The invention is explained in more detail below by means of exemplary embodiments. In the drawings: Fig. 1 shows an electronic front switching device according to the invention with either a single output for a gas discharge pipe or two outputs in tandem connection for two gas discharge pipes, Fig. 2 shows a block diagram of an electronic front switching device according to the invention with a single load. Fig. 3 shows a detailed circuit diagram showing a switch variant of the oscillator switching part according to the invention, Fig. 4 shows a cut-hold-switching device according to the invention for disconnecting or closing the oscillator switching part, respectively. 5 shows an example of a power switch according to the invention with a parallel current connection for load current partial input, and Fig. 6 shows a partial circuit diagram of an electronic front switching device according to the invention with two more than 3 96657 voltage signals and disjunctive connection of the overcurrent signal.

Figure 1 shows an electronic front switching device 1 which can be connected to a 220V household network or directly to a DC voltage or a battery, respectively. One or two gas discharge pipes 2 can be connected to this electronic front switching device. The directly heated gas discharge pipe 2 in each case has four connections connected to the electronic pre-switching device 1. In each case, one connection of the two opposite heating coils 22, 23 is connected via an incandescent capacitor (¾).

Fig. 2 shows a block diagram of the electronic front switching device according to Fig. 1. The mains input voltage is supplied via a rectifier 10 and possibly a subsequently connected large setting controller (especially in battery operation). Its output signal is fed through a smoothing device 11 provided with a smoothing capacitor (intermediate circuit capacitor) Cg, which provides a DC link voltage Uz. The DC link voltage Uz is supplied to an inverter 4, which makes available at its output connections an alternating signal uw for at least one gas discharge pipe 2. On the other hand, a voltage proportional to the output-AC voltage of the inverter 4 is supplied to the cut-off-switching device • u! and, on the other hand, with respect to the DC link voltage Uz: a zero voltage uz · It receives its distribution or holding current resistance R14 via the series connection and the second heating coil 22 from the positive output terminal + of the inverter 4 or rectifier 10. The winding voltage of the cut-off holding part 3 is thus cut off when the gas discharge tube 2 is removed from its holder. The switching device 3 produces a cut-off or · "* release signal, respectively, by means of which the reversing device 4 can be switched on or off, respectively.

This cut-off signal ug is produced by the OR connection of both measured signals uz and u ^, possibly after rectification and smoothing.

4 96657

Figure 3 shows a detailed wiring diagram of an OR interface together with other functional groups of components. The DC link capacitor Cz has already been shown above. In the load circuit arranged between the positive output terminal + and the series connection consisting of two power switches S1 and S2, in addition to the conventional gas discharge tube 2 equipped with the incandescent capacitor Cjj, there is further a series circuit of oscillation circuit inductance Lq and oscillation circuit capacitance Cq. Furthermore, a saturation converter Ö with a primary winding n1 and a secondary winding n2, n2 'can be connected in series with the load circuit. This acts (as an oscillator switching device 8) to produce the carrier voltage signals of the power switches S1 and S2. The series connection of the power semiconductors S1 and S2 connects the positive output terminal + to the negative output terminal -. Both of these connections correspond to the positive and negative connections of the equalization capacitor Cz of the equalization device 11.

The AC voltage between the oscillation circuit capacitance Co and the second connection of the second heating coil 23 is now taken from the load circuit or measured, respectively. This is guaranteed by a series connection formed of the capacitor Ci, the first resistor Rz and the second resistor R3 with respect to the negative output connection. There is a first signal U] _ between the resistors Rz and R3 with respect to the negative output terminal. The first diode is connected to this point: ***. Dz anode, the cathode of which is connected via a resistor Rg ne- • · ·. ·. ·. to the negative output terminal. A capacitance Cg can be connected in parallel with the resistor Rg.

the intermediate circuit capacitor Cz is bypassed by a series connection consisting of a third resistor R4 and a fourth resistor R5. This voltage divider provides a second signal uz proportional to the DC link voltage Uz in parallel with the fourth resistor R5. The anode of the second diode D4 is connected to the connection point between the resistors R4 and R5, its cathode is connected like the cathode of the diode D2 to the resistor Rg. The resistor Rg thus always has a higher voltage than the voltages ui or U2 ·

In order to better separate the signals u1 and U2 to be connected with respect to the diodes D2 or D4, respectively, one resistor Riq, R13 can still be connected in series.

The voltage signal generated in the resistor Rg and then in the capacitor Cg connected in parallel with respect to the negative distribution connection is now fed to the cut-off-stop switching device 3. It is shown in more detail in Fig. 4.

Fig. 4 shows, as an alternative to the disjunctive connection formed as diode-transistor logic shown in Fig. 3, an OR gate to which three signals u1, U2 and U3 can be fed. The first signal U2 and the second signal U2 correspond to the load voltage-derived and rectified signal u1 according to Fig. 3 and the second signal U2 · derived from the DC link voltage and echo ratio. Both are connected to a resistor Rg. The third signal U3 shown here can alternatively be connected either via the OR gate 6 or directly to the cut-off-switching device. It is a load current-dependent cut-off signal.

:. * The output signal us 'of the OR circuit 6, which corresponds to the signal us' in the resistor Rg of the band Rg according to Fig. 3, is applied via a low-voltage circuit to the slide 7 (trigger diode). The low-pass filter optionally consists of a series connection of a resistor Rio and Cu or a parallel connection of a capacitance Cu and a resistor Rn. The trigger diode 7 connected to the capacitance Cu controls the gate connection of the thyristor 5. It determines the threshold voltage with which the response threshold of the cut-hold device 3 can be adjusted. This response threshold is predetermined according to the amplitude, but it can nevertheless be delayed in time by means of a low-pass switching, so that an arbitrary amplitude can be adjusted on the one hand and an arbitrary response rate on the other hand can be determined. The amplitude is adjusted by the divider ratio R4 / R5 or the divider ratio R10 / R11. The time delay can be adjusted with either capacitor C6 or capacitor Cu ·

Different response rates and response amplitudes can be provided for different cut-off signals u1, U2 or U3. Here, for example, the connection of the current-dependent signal U3 via a series connection formed of a diode D12 and a resistor R12 directly to the gate terminal of the thyristor 5 (forming a bistable disconnecting element) is shown. Different threshold voltages thus provide different response amplitudes.

The anode circuit of the thyristor 5 further has a holding current generating resistor R14 connected from its second terminal via the first heating coil 22 of the gas discharge lamp 2 to the positive terminal of the intermediate circuit capacitor Cj and the second terminal of which is connected to the anode of the thyristor 5. This connection point between the arresting current resistor R14 and the anode of the thyristor 5 is fed to the oscillator 8 to cut off its oscillation or to suppress the carrier voltages of the semiconductor switches S1 and / or S2. This can be done either by short-circuiting one of the n2 'multiple secondary windings n2, n2' of the equalizer U (self-oscillating inverter) to be connected to the load circuit or in a separate, non-load current '; ·; la in a controlled oscillator (free-oscillating inverter * · ’·” rectifier) by blocking the base control signals of the power semiconductors S1 and / or S2.

Fig. 5 shows a detailed circuit diagram of a second power semiconductor S1 or S2, respectively, which is controlled either directly from the oscillator 8 or via a saturation converter U provided with a primary winding n1 and a plurality of secondary windings n2, n2 '. For example, the power semiconductor S2 has a series connection consisting of a power transistor and an emitter resistor Rg. Its base potential of 966657 is produced via one secondary winding n2 of the saturation converter ϋ via a series connection of a small choke and a diode depending on the load current. In the resistor Rg, a voltage U3 proportional to the load current can now be measured with respect to the negative connection of the circuit capacitor Cz. It can optionally be supplied via a disjunctively connecting OR gate 6, via a switching device corresponding to the switching device R2, R3 and D2 according to Fig. 3, or via a separate input of the diode D12 and the resistor R12 in series and the trip-hold switching device 3.

Fig. 6 shows a partial circuit diagram of the electronic front switching device according to Fig. 1 with a single gas discharge tube 2 loaded. It is provided with the components of the rectifier 10, the intermediate capacitor Cz, the power switches S1, S2, the oscillator 8 and the holding circuit R14 already shown. A mains interference suppression filter with a capacitor Cx is connected in front of the rectifier 10. With respect to the capacitor Cz, a series connection formed of a resistor R4 and a resistor R5 is connected in parallel.

In the middle output between these two resistors, the DC link-dependent signal U2, as shown, is connected to the capacitor Cg via a series connection formed by the diode D4 and the additional resistor R13 • with respect to the negative connection of the DC link capacitor Cz. You- • . the alternating voltage component connected from the load circuit via the capacitor Ci is automatically connected to the same capacitor Cg via the second disjunctive connection branch of the series resistor R2 and the additional resistor R1g. The voltage us' in this capacitor Cg controls the resistor R15 connected in parallel with the resistor R15, R16, R17 to the distribution terminal and the resistor 8 connected in parallel with the resistor R15.

A lattice circuit connected in parallel with R17.

Fig. 6 shows a further variation in which the load current-dependent signal U3 is generated by a measuring resistor Rgh connected to the negative distribution line of the electronic front switching device 8 96657 between the switch S1 and the negative distribution connection. It is supplied directly to the gate circuit of the thyristor by a series connection formed of a diode D3 and a resistor R 1g. To adjust the threshold voltage, several diodes must be connected in series instead of one diode D3.

The above-mentioned switching device provides a safe mode of operation, long operation at a high intermediate circuit voltage Uz and thus avoids high thermal loads on the transistors S1, S2, possibly by means of a time-delayed cut-off. The response threshold for this overvoltage cut-off operation is adjusted according to the following table. In this case, it operates on mains voltages above 280 Veff.

network Voltage in Cx Voltage in Cz ueff_ ^ s_ueff_ ^ s_Ueff

230 V 340 V 264 V 420 V 377 V

280 V 400 V 322 V 420 V 337 V

__________________________________________ threshold

320 V 460 V 369 V 600 V 403 V

350 V 540 V 404 V 620 V 429 V

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Claims (9)

An electronic ballast device (1) for gas discharge lamps (2), comprising an input coupling part (10, 11) for generating an intermediate circuit voltage (U2) from a distribution voltage (Lu N), an oscillator coupling part supplied by the intermediate circuit voltage (U2) (4, 8, S1, S2) for generating a switch signal (u ") which can be input to the gas discharge lamp (2), a bistable switch-arresting coupling part (3) which in its first and second stable states supplies a switching signal (u3) to the oscillator coupling part (4, 8, S1, S2) and thus releasing and disengaging respectively the oscillator coupling part (4, 8, S1, S2), a first signal (ux) derived from the switch signal (u ") exceeding a predetermined controlling the switch-arresting coupling part (3) from its first to its second stable state and generating the switch signal (u3), characterized in that a second signal (u2) derived from the intermediate circuit voltage (U2) generates the switching signal (u2), where the intermediate circuit DC voltage (U,) exceeds a predetermined maximum value, and that means are provided by which desired response rates can be determined in advance for respective signals (ulf u,). Electronic ballast device according to claim 1, characterized in that the second signal (u2) is formed by the intermediate circuit direct voltage (U1) via a voltage divider (R4, R5). • I · · · · · · · Electronic ballast device according to claim 1 • 30 or 2, characterized in that the first signal • · · · (uj) and the second signal (u2) can be measured in an OR • switching device (6), whose output signal (u3 ') can be measured in the switch-arresting coupling part (3) for generating the switching signal (u3) of the oscillator coupling part (4, 8, SI, 3. S2). 13 96657 Electronic ballast device according to claim 3, characterized in that the OR-switching device (6) is designed as an integrated OR-coupling or as a resistive diode logic with discrete components (Rs, D4, R2, D2, 190) and switches the arresting coupling member (3) has a thyristor (5). Electronic ballast device according to any one of claims 2-4, characterized in that the maximum value 10 of the intermediate circuit direct voltage (Uz) is adjustable by means of the partial ratio of the voltage divider (R4 / R5) and a threshold voltage (overvoltage voltage) of in particular a diac or a trigger diode (7). Electronic ballast device according to any of the preceding claims, characterized in that the first and / or the second signal (ux, u2) is delayed / a via a low-pass circuit. Electronic ballast device according to claim 1, or only according to the preamble of claim 1, characterized in that an auxiliary signal (U3) derived from a load current flowing through the gas discharge lamp generates the switch signal (us), where the load current exceeds a maximum pre-limiting current. An electronic ballast device according to claim 7, characterized in that the auxiliary signal (U3) is generated by the current alternator in the lamp circuit or as one with a Current •: But comparable measurement signal in the emitter resistor (RE) to the oscillator power transistor (S2) of the lator coupling part (3) or by means of a resistor in the negative dividing line of the ballast device. Electronic ballast device according to claim 7 or 8, characterized in that the first (uj and second (u2) signal and the additional signal (u3) are input through an OR switching device and the switching arrangement coupling part (3) in the oscillator switching part (4 , 8, SI, S2) as alternate refractive signals (us) 5 • # · • · «• · • · · · · 1: ·« I • · t * · · • · · · · · · · · · «· · • · · * · · 11