JPS5854479B2 - Discharge lamp lighting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for lighting a discharge lamp, and more particularly, a method for applying a high voltage for restriking to the discharge lamp separately from the power supply voltage, for example, at each cycle of an AC power supply at least during lighting of the discharge lamp. This invention relates to a discharge lamp lighting method.

Conventionally, for the purpose of downsizing the current limiting choke for lighting discharge lamps such as fluorescent lamps, the discharge lamp is lit by superimposing AC power supply voltage and pulse voltage at the first start, and then It has been proposed and realized that the lighting is maintained using the power supply voltage I.

In such a conventional system, the maximum value E of the power supply voltage e
Naturally, m is determined by σ in order to provide the re-ignition voltage ERst (a voltage that allows lighting to be maintained even if the voltage applied to the discharge lamp drops to a certain level after the initial start). Therefore, it is selected to be larger than this re-ignition voltage EFLst (Em>ERst).

In this conventional lighting method, this re-ignition voltage ER3t is large compared to the tube voltage of the discharge lamp, and the maximum value Em of the power supply voltage e must also become large accordingly.

Therefore, the ballast that shares the difference between the power supply voltage Em and the discharge lamp tube voltage ■Tm is also large-sized.

That is, as long as the effect of the starter is limited to simply supplying the initial starting voltage, there is a limit to miniaturization.

Therefore, the main object of the present invention is to provide a different method for lighting a discharge lamp, which allows the current limiting device to be extremely miniaturized.

To summarize, the present invention provides a lighting method for applying a high voltage as restriking energy to a discharge lamp at least during each half cycle of an AC power source during each half cycle of the discharge lamp. A method for lighting a discharge lamp in which the maximum value vRm of the high voltage V during lighting is made larger than the restriking voltage ER8t, and the maximum value Em of the power supply voltage e is made smaller than the restriking voltage El(,st). It is.

The above objects and other objects and features of the invention will become more apparent from the following detailed description with reference to the drawings.

FIG. 1 is an electrical circuit diagram showing one embodiment of the present invention.

In the drawing, AC is an alternating current power source, and a series circuit of a current limiting choke CH as an example of a current limiting device and a discharge lamp FL is connected.

A secondary winding W20 is wound around the current limiting choke CH, one end of the secondary winding W20 is connected to one end A of the filament f of the discharge lamp FL, and the other end is connected to the booster circuit R. There is.

The booster circuit R is a circuit in which an intermittent oscillation capacitor C1 is connected in series to an oscillating circuit voltage formed by connecting a series circuit of a thyristor S and a bouncing booster inductor L, and a capacitor C in parallel. is connected to one end of the secondary winding W20 mentioned above, and the other end is connected to the discharge lamp FL.
is connected to one end of the filament f'.

PRH is an electronic filament preheating circuit that is driven to conduct by the oscillation output of the booster circuit R and preheats the filaments f and f' of the discharge lamp FL, and includes a thyristor Sp, a high frequency blocking inductor NL that blocks the oscillation output, and is connected in series between the two filaments l-f, f' of the discharge lamp FL.

As long as the booster circuit R performs high-frequency oscillation operation, it may be replaced with one using a gated silice such as a triac, or even a high voltage generation circuit using an inverter.

Next, the operation of the above configuration will be explained.

First, when the power supply AC is connected, the power supply voltage e is applied to the discharge lamp FL via the current limiting choke CH, and the power supply voltage e is also applied to the booster circuit R via the secondary winding W20 of the current limiting choke CH. be done.

In the booster circuit R, the power supply voltage e is applied to the thyristor S via the intermittent oscillation capacitor C1, and the oscillating circuit pressure starts an oscillation operation to cause the thyristor S to break over.

This oscillation operation would continue without the intermittent oscillation capacitor C1, but because of the intermittent oscillation capacitor C1, it oscillates intermittently every half cycle during the rising portion of the power supply voltage e.

Now, considering a half cycle of the power supply voltage e, when the oscillation circuit R' starts the oscillation operation as described above, the intermittent oscillation capacitor C1 is charged to a polarity that cancels out the power supply voltage e.

Therefore, when the terminal voltage vc1 increases and the voltage difference from the power supply voltage e becomes less than the breakover voltage VBO of the thyristor S, the thyristor S remains in the off state and the oscillating circuit R' stops oscillating. be stopped.

Therefore, during the subsequent period in this half cycle, the terminal voltage vcl of the intermittent oscillation capacitor C1 remains at a constant value, and the oscillation circuit R' stops oscillating.

However, when the power supply voltage e changes to the next half cycle, the power supply voltage e becomes a voltage with the opposite polarity to the voltage of the previous half cycle, so this voltage and the intermittent oscillation capacitor C1 are charged in the previous half cycle. A voltage summed with the terminal voltage Vcl is applied to the oscillating circuit R', and the sum voltage causes the thyristor S to break over and start oscillating.

However, at the same time as the oscillation, the terminal voltage cI of the intermittent oscillation capacitor C1 rapidly reverses its polarity and is charged again in a direction that cancels out the power supply voltage e, and eventually the oscillation of the oscillation circuit R is stopped.

Therefore, the oscillating circuit R' oscillates only during the rapid inversion period of the intermittent oscillation capacitor C1, and only during that period, current flows from the power supply AC to the oscillating circuit R' through the intermittent oscillating capacitor C1.

This operation is repeated in each subsequent half cycle.

FIG. 2A is a voltage and current waveform diagram of each part showing this state, where e is the power supply voltage and Vc is the intermittent oscillation capacitor C1.
This shows the terminal voltage of
c1 flows, and a high-frequency, high-voltage oscillation output vR is generated at both ends of the booster circuit R during this period.

The oscillation output VR is the primary winding WIO of the current limiting choke CH.
and is divided by the secondary winding W20, and the divided voltage by the primary winding W10 is superimposed on the power supply voltage e with the opposite polarity and applied to the discharge lamp FL and the filament preheating circuit PRH.

Then, in the filament preheating circuit PRH, the voltage is applied to the thyristor Sp via the high-frequency block inductor NL, and the thyristor Sp receives the sudden voltage change effect (
In other words, the conduction is driven by the dv/dt effect).

Therefore, at the rear end of the intermittent oscillation phase, the current from the power supply AC flows through the filament f, thyristor Sp1, and inductor NL.
, flows through filament f′, filament) f, f
' begins to preheat.

The thyristor Sp is driven into conduction every time the oscillation output vR of the booster circuit R is applied to the preheating circuit PRH, and during periods f and f' when the thyristor Sp is conductive, a current flows from the power supply AC to perform preheating. .

In this way, the filaments t-f and f' are heated to the next level, and when the voltage required to start the discharge lamp FL drops to Est, the discharge lamp FL is started by being triggered by the oscillation output R from the booster circuit R.

When the discharge lamp FL is turned on, most of the intermittent oscillation force flows into the conductive discharge lamp F'L, and the remaining force is absorbed by the high-frequency block inductor NL, and further increases the breakover voltage of the thyristor Sp. By setting VBO sufficiently higher than the peak value vTp of the tube voltage, the thyristor Sp becomes non-conductive.

Note that if the breakover voltage of the thyristor Sp is very high, the high frequency blocking inductor NL may be omitted depending on the case.

However, such thyristors are currently uncommon and expensive.

Therefore, after lighting, the discharge lamp FL is re-ignited by the oscillation output vR every half cycle of the power supply AC while the preheating of the filaments f and f' is stopped. It is kept lit by e (second
(See Figure B).

It goes without saying that the preheating circuit PRH in FIG. 1 may be replaced with an electrode preheating circuit using a filament transformer.

FIG. 3 shows waveforms of various parts observed as a result of experiments using the circuit of FIG. 1, with high frequency components ignored.

In this figure, the tube voltage vT becomes a rectangular wave having a pause period due to an intermittent oscillation period, as shown in FIG. 3B.

Therefore, the effective value vT of the tube voltage VT exhibits a value of about 90 to 95 in the conventional lighting system.

The discharge lamp FL is forcibly reignited by the oscillation output VR at the rising edge of each half cycle.

That is, at each re-ignition, the high-voltage oscillation output VR is applied to the discharge lamp FL to prevent ions from disappearing, and the intermittent current ic1 flowing through the booster circuit R flows through the secondary winding W20. , the corresponding terminal voltage of the secondary winding W20 applies a rapidly increasing low frequency voltage to the discharge lamp FL through coupling with the primary winding WIO.

The rising phase of the tube current iT remains constant regardless of fluctuations in the power supply voltage e, and therefore the rate of fluctuation of the tube current in the lighting system of this embodiment is good regardless of the decrease in stable impedance.

In this case, the discharge lamp FL has a restriking voltage ER due to glow discharge.
Without st, it immediately shifts to arc discharge upon re-ignition.

Note that this method also has advantageous characteristics regarding the fluctuation rate of VA (volt-ampere) of the ballast.

In other words, the tube voltage maintains a constant value against power supply voltage fluctuations,
Therefore, the voltage difference between the power supply voltage and the tube voltage, that is, the fluctuation rate of the ballast terminal voltage is much smaller than in the case of the conventional system having a tube voltage with a drooping characteristic.

Next, the tube current iT flowing from the power supply AC to the discharge lamp FL mainly flows during a period other than the oscillation period (t2
~1+).

Oscillation period 'l-'2) y (14 to i5) is power supply A
A current 'cs flows from C to the booster circuit R1.

The figure shows the current waveform of this current 'ct.

This current flows through both the primary winding W10 and the secondary winding W20, which are coupled to the magnetizing property of the current limiting choke CH, and generally has an excitation effect depending on the turns ratio between the primary winding WIO and the secondary winding W20. can be controlled.

The tube voltage vT, the tube current iT, the current ic to the booster circuit R
1 and the waveform of the power supply voltage e, the voltage-current product (vcH-4) of the current limiting choke CH and the stored energy S are calculated, resulting in the waveforms shown in E and F in the figure.

Figure E shows the voltage/current product of the current limiting choke CH due to the difference between the oscillation output VR, the power supply voltage e, and the tube voltage vT.

The energy SI due to the current ic1 is (S+=ft'(,
5-vR) Kic, dt).

K is a constant depending on the turn ratio of the primary and secondary windings WIO and W20.

The energy ft3 energy 82 accumulated during the period (tz to ts) where the power supply voltage e is higher than the tube voltage vT is (S2 = (e VT ) 1Td
t) is given by 2.

Conversely, the tube voltage VT is higher than the power supply voltage e during the period (t
a to 11) release the stored energy, and the total released energy S3 is given by (S s = J'''(e vT)3 iTdt).

As a result, the energy level stored inside the current limiting choke CH increases or decreases as shown in FIG. 3F.

In the case of the waveform shown in Figure 3, S r + 82 = S
The relationship s holds true.

Next, the reason for the miniaturization in the every-cycle lighting method will be explained based on the waveform shown in FIG. 3.

However, for the sake of simplicity, it is assumed that the initial value of the tube current iT at time t2 is zero, and the part of the energy accumulated by the intermittent oscillation capacitor C11 is ignored.

In such a case, the tube current iT can be calculated as follows.

However, L is the inductance of the current limiting choke CH, the power supply voltage e=Emsinθ, θ=ωt, and the amplitude of the tube voltage VT is v
Let Tm be the period in which the tube current iT appears, 9), :5il
The period is θ=π+ψ2 from 1vTm/Em.

The above formula is 0.1/2. If calculations are made for the cases of l/J2 and Em J3/2, it will be seen that iT decreases sharply as the ratio of vTm and Em increases.

For example, if vTm/Em=J3/2, vTm/Em
= J1/2, iT becomes 1/7.

Therefore, the inductance L of the current limiting choke CH required to obtain the rated iT is 1/7.

This means that the terminal voltage vcH of the current-limiting choke CH can be drastically reduced, the impedance of the current-limiting choke CH can be reduced accordingly, and the size of the current-limiting choke CH can be reduced accordingly.

In order to explain the effect of this invention, FIG. 4 shows the case where FL40 or FLR40 is used as the discharge lamp FL.
FIG. 3 is a diagram showing the relationship between voltages at various parts.

In FIG. 4, the horizontal axis represents the high voltage applied every half cycle during starting and lighting, that is, the high voltage output VR.
The application period (oscillation amplitude in FIG. 2A) [ms] is plotted, and the starting voltage and restriking voltage [v] of the discharge lamp are plotted on the vertical axis.

Here, since the starting voltage of a discharge lamp is unstable and changes depending on the filament preheating power in a hot cathode type discharge lamp, and to make it easier to understand the effect in the case of a cold cathode type electric lamp, the line A indicates the initial starting voltage Est when the filament is not preheated, and line B indicates the restriking voltage E□,
Indicates t.

Further, the line C2"C indicates the maximum value vRJT1. of the high voltage output VR.
vRm' is the line, and D' is the maximum value Em of the power supply voltage e.
, indicates Err/.

Furthermore, line E shows the initial starting voltage when the filament is preheated at 4W, and lines F and Fv are the maximum value v of high voltage output vB.
Rm.

vRm' is shown.

However, if the filament is preheated, the filament temperature will rise as time passes after the start of filament preheating, and when the filament temperature reaches a predetermined value, an end glow will occur between both ends of the filament, which is the first time the filament is heated. Since the starting voltage decreases, the initial starting voltage after the decrease is shown.

To put it simply, what this figure shows is that although it is possible to start the discharge lamp for the first time using a conventional single pulse with an extremely narrow time width, it is difficult to reduce the restriking voltage. In particular, when the restriking voltage is related to the power supply voltage, in order to reduce the power supply voltage to the level of the tube voltage,
This means that it is necessary to continue applying high voltage for a considerable period of time.

\That is, in this invention, it goes without saying that VRm > Est is set at the time of initial startup using the method described above, but in particular, when the lamp is turned on, it is set to Vl (, m > El (St), and Em It is characterized in that the voltages of each part are set so that < E RS t.

Furthermore, the application time of the high voltage output VR, that is, the time width in FIG. The constants of each component are determined so as to utilize the area (the downwardly diagonal shaded area to the right of T1 in FIG. 4).

By doing this, it is possible to reduce the power supply voltage Em by half compared to the conventional system and make it match the tube voltage.

In particular, for 1.1 ms when the restriking voltage ERst becomes almost constant
By using the above region (the cross-hatched region to the right of T2 in FIG. 4), the maximum value VRm of the high voltage output vB can be determined by the line C2? In addition, the maximum value Err/ of the power supply voltage can be further reduced as shown in a line, Em-vTm becomes a minimum, and the voltage shared by the current limiting choke CH that should share the difference becomes small.

Therefore, assuming a certain excitation current, this current-limiting choke CH can be made most compact, and the above-mentioned requirement can be realized.

In the above embodiment, the high voltage generated by the high voltage output generating means is a high frequency high voltage. However, as long as the time width is limited as described above, the pulse height It is also possible to use voltage.

In this case, the pulsed high voltage may be a repeated series of pulses or a single pulse.

That is, the greatest advantage of this lighting method is that the terminal voltage VOH of the current limiting choke CH, that is, the stored energy, can be reduced to about 1/10 as described above.

Due to this Q, power loss can be expected to be reduced to about 1/10, and the overall efficiency of the circuit system can be expected to improve by about 25%, and the efficiency of the lamp itself can be doubled as the current/voltage utilization rate. This can be improved by

Furthermore, in this lighting system, the phase difference between the power supply voltage e and the tube current iT is smaller than in the conventional lighting system, so a power factor correction capacitor is not required or the capacitance can be made extremely small.

Furthermore, as mentioned above, the ability to reduce the maximum value vRn (of the high voltage VB) as shown by lines C' and F' means that the components of the booster circuit R and the oscillating circuit R' can be made small and inexpensive with low withstand voltage. This means that it can be constructed with components, and at the same time this high voltage V
There is also an advantage in interlayer insulation treatment for the current limiting choke CH to which R is applied.

[Brief explanation of the drawing]

FIG. 1 is an electrical circuit diagram showing one embodiment of the present invention. FIG. 2 shows voltage and current waveform diagrams of various parts of the device shown in FIG. 1. Figure 3 shows the voltage and current of the main parts of the device shown in Figure 1.
FIG. 3 is a diagram of energy changes and accumulated energy waveforms. FIG. 4 is a graph showing the relationship between voltages at various parts of the present invention. In the figure, AC is a low-frequency alternating current power supply, and CH is a current limiter (
(current limiting choke), FL is a discharge lamp, f and f' are filaments, R is an intermittent oscillation circuit (step-up circuit) which is a means of generating high voltage output, C1 is a capacitor for intermittent oscillation, R' is an oscillation circuit, and Est is an oscillation circuit. The initial starting voltage, ER8t is the restriking voltage, V
RJntVl(, rn' is the maximum value of the high voltage required for restriking, Em, Em' is the maximum value of the power supply voltage.

Claims (1)

[Claims] 1. A low-frequency AC power supply, a current limiting device, a discharge lamp to which the low-frequency AC power supply voltage is applied via the current limiting device, and a discharge lamp energized by the low-frequency AC power supply to and a high-voltage output generating means that generates a high-voltage output intermittently every cycle, the low-frequency AC power supply voltage and the specified high-voltage output at least when the discharge lamp is re-ignited every half cycle of the low-frequency AC power supply. In the discharge lamp lighting method, the discharge lamp is re-ignited by applying a high voltage generated by the generating means in a superimposed manner to the discharge lamp, and the remaining period of each half cycle after the re-ignition is maintained by only the low-frequency AC power supply voltage. , the maximum value of the low frequency AC power supply voltage is set lower than the restriking voltage of the discharge lamp, and the maximum value of the high voltage during lighting of the discharge lamp is set larger than the restriking voltage, The time width of each half cycle of the high voltage generated by the high voltage output generating means is set in a region where the rate of change of the restriking voltage characteristic curve with respect to the time width of the high voltage is small. How to turn on lights. 2. The discharge lamp lighting method according to claim 1, wherein the high voltage generated by the high voltage output generating means is a high frequency high voltage. 3. The discharge lamp lighting method according to claim 1, wherein the high voltage generated by the high voltage output generating means is a pulsed high voltage. 4. The discharge lamp lighting method according to any one of claims 1 to 3, wherein the time width of the high voltage generated by the high voltage output generating means is 0.5 ms or more. 5. The discharge lamp lighting method according to claim 4, wherein the time width of the high voltage generated by the high voltage output generating means is 1.1 ms or more.