JP2576174B2 - No-load protection ballast with automatic adjustment function - Google Patents

Description

The present invention relates to a fluorescent lamp, that is, a ballast for a gas discharge tube. In particular, the present invention relates to automatic gain control ballasts for fluorescent lamps. The present invention limits the ballast output voltage and reduces it when the gas discharge tube or fluorescent lamp is electrically disconnected from the entire circuit.

More particularly, the invention belongs to a no-load protection transformer,
The transformer is connected in series with the induction circuit to prevent the generation of a voltage above a predetermined value when the gas discharge tube, that is, the fluorescent lamp is electrically disconnected from the circuit. More particularly, the present invention relates to a ballast, wherein the primary winding of a no-load protection transformer forms a variable inductance, which is inversely proportional to the amount of power applied to the gas discharge tube or fluorescent lamp.

BACKGROUND OF THE INVENTION Gas discharge tubes or ballasts for fluorescent lamps are known in the prior art. However, in some prior art ballasts, removing the gas discharge tube or fluorescent lamp from the ballast circuit causes excessive voltage output to the discharge tube or fluorescent lamp. Such conditions can have a detrimental effect on the working life of special tubes, ie tubes used in special ballasts.

(Summary of the Invention) A no-load protection ballast having an automatic adjustment function is provided with a power supply for operating at least one gas discharge tube with an adjustment current and a limit voltage for maintaining input / output power of the discharge tube at a predetermined value. . The ballast includes a filter circuit connected to a power supply to maintain the smoothed DC, current and voltage signals (1) and suppress the harmonic frequencies generated by the ballast (2). Further, the no-load protection ballast with automatic regulation includes an induction circuit connected to a filter circuit having a tap primary winding with an automatic transformer component forming the frequency of the regulation current. .

(Example) FIG. 1 will be described. FIG. 1 shows a no-load protective ballast 10 with automatic regulation, which is provided with a power supply 12 for operating at least one gas discharge tube 66.
The gas discharge tube 66 is a standard fluorescent lamp and has first and second filaments respectively. A no-load protection ballast 10 with automatic adjustment is provided to maintain the output and input voltage of the gas discharge tube 66 approximately at a predetermined value, which is relatively constant during operation, generally constant, It is also independent of electrical material tolerances between ballasts.

In the overall idea, a no-load protective ballast with automatic regulation is provided to maximize the efficiency of the light output from the gas discharge tube 66 for the power input from the power supply 12. In addition, the no-load protection ballast 10 with automatic regulation provides a light output that is approximately constant, despite the voltage fluctuations due to the output of the gas discharge tube, of the order of ± 3.0%. Tube 66
Responds to the square wave pulse drive current relative to the square wave pulse input voltage.

As shown in the following paragraphs, when the gas discharge tube 66 is electrically disconnected from the circuit, the output voltage of the ballast 10 is limited and substantially reduced.

It is important to adjust and control ballast 10 first, which eliminates the need to tune or preselect transistors with special gains and to reduce manufacturing tolerances and associated manufacturing of electrical components. It provides a relatively constant light output, largely independent.

When the gas discharge tube 66 fails or is physically removed from the circuit, and is electrically disconnected from the circuit, the output voltage is reduced below the normal operating voltage.

Further, the no-load protection ballast 10 having an automatic adjustment function is provided with a frequency control mechanism, and the mechanism includes an inverter transformer.
40 induction characteristics, secondary winding 160 and capacitor of transformer 100
The tank circuit formed by 130 is used and the ballast 10
There is the benefit of operating the camera without cumbersome flickering.

In particular, the operation of the gas discharge tube 66 is maintained at a minimum level for the higher efficiencies provided by the no-load protective ballast 10 with automatic adjustment. It is important for ballast 10 to provide ballast 10 with minimized reliability and to combine minimized electrical components to simplify the ballast and associated circuitry. By connecting the elements in this manner, the effect of improving the reliability of the no-load protection ballast having the automatic adjustment function can be improved, while the gas discharge tube 66
To maximize the operating life of the

The ballast 10 shown in FIG. 1 will be described. Ballast 10 includes
A power supply 12 for the gas discharge tube 66 is provided and includes a filter circuit 11 connected to the power supply 12 for establishing DC and voltage signals and suppressing harmonics generated by the ballast.

Considered more generally, the self-regulating no-load ballast 10 includes an inductive circuit 15, which is electrically connected to a filter circuit 11 and the magnitude of the pulse drive current established by the switching network 13. To establish.

As described in detail in the following paragraph, the inductive circuit includes a no-load protection circuit 99, which generates a voltage in the gas discharge tube 66 according to the pulse drive current, and the gas discharge tube 66 is not electrically connected to the ballast. In some cases, the output voltage is maintained at a predetermined value. The induction circuit 15 is connected to the adjustment control circuit 17 to maintain the gain value of the switching network 13 at a predetermined level. In this way, the filter circuit 11 is connected to the power
Maintain smooth current and voltage signals (1) and suppress harmonics generated by the ballast 10.

The induction circuit 15 is provided with a base drive winding 48 for generating a switching signal. The switching network 13 generates a pulse drive current responsive to the switching signal generated in the base drive winding 48.

More specifically, the no-load protection circuit 99 is connected to the filter circuit 11 and is provided with a secondary winding 160 to generate a tuned high voltage output to the gas discharge tube 66 responsive to the regulated drive current.

FIG. 1 will be further described. The power supply 12 supplies power to the no-load protection ballast 10 with automatic regulation.
In the embodiment of FIG. 1, the power supply 12 may be an AC power supply, the standard voltage of which is, for example, 120, 240, 270 [V], and the power receiving standard voltage is generated at about 50.0 or 60.0 [Hz].

In broad general belief, power supply 12 may be a DC power supply, which eliminates basic circuitry and filter elements in a manner well known in the prior art to provide self-adjusting no-load protection. It is added to the ballast 10 from inside and outside.

For illustrative purposes, in the following paragraphs, the power supply 12 is shown as a 210-240 volt, 50 Hz AC power supply and will be used in the description of the embodiments.

The power of the ballast 10 is supplied by a power supply 12 via a switch 14, which may be a standard switch element such as, for example, a single pole, single throw switch mechanism. Power is supplied from switch element 14 through choke 32 and harmonic filter capacitor 28. Harmonic filter capacitor 28
Are connected in parallel to the power supply 12, so that the high-frequency component fed back from the ballast 10 to the power supply is short-circuited. The choke element 32 is connected in series with the power supply 12 and the rectifier circuit 16, and the rectifier circuit 16 performs full-wave rectification of the power supply AC voltage.

The rectifier circuit 16 may be a full-wave bridge circuit and a standard one well known in the prior art. In the embodiment shown, the full-wave bridge circuit 16 is formed by diode elements 18, 20, 22, and 24;
The AC voltage of the power supply 12 is rectified as required. Diode elements 18, 20, 22 and 24 may be one of a number of standard diode elements, and in one example of a self-adjusting no-load protection ballast, diode elements 18, 20, 22 and 24 are ,
Has the standard specification of IN4005. Rectification in the full-wave bridge circuit produces a pulsating DC voltage signal, which passes through output 26, which is connected to shunt capacitor 34 of filter network 11.

The filter network 11 filters the input and output of the voltage from the rectifier circuit 16 and is electrically connected to the bridge circuit 16 by an input 19 and an output 16. Rectifier bridge circuit 16
Is connected to a return path 64, which is a return path for supplying DC at both ends of the bridge circuit 16, and supplies a DC power input to the shunt capacitor 34 of the filter network 11.

The smoothing filter section of the filter network 11 includes a choke element 32 and a shunt capacitor. The choke element 32 is connected on the primary side to the power supply 12 and on the secondary side to the rectifier circuit 16 via the input. A shunt capacitor 34 is connected via output 26 in parallel with the output of rectifier circuit 16. Shunt capacitor 34
Is connected to the rectifier circuit 16 via the output terminal 26 on the primary side, and to the DC return path 64 on the opposite side.

Shunt capacitor 34 and choke element 32 act in combination to average the 100 Hz pulsating DC voltage provided by full-wave bridge circuit 16. In addition, this combination keeps the current flow at an average value and does not cause unacceptable leading or lagging power factors. When large capacitors or inductances are used as stand-alone filter devices for smoothing pulsating DC voltages, harmful leads and lags occur.

If the choke element 32 is not incorporated into the self-adjusting no-load protective ballast 10 for illustration,
When the shunt capacitor 34 starts to charge, a surge current in each cycle and an increasing current generally referred to flow. By incorporating a choke element, the inductance stores energy during each half cycle and provides a current for initial charging of the shunt capacitor 34, which provides a smooth, average current.

In this embodiment, the choke element is about 2.0
With the inductance of [H] and the resistance of less than 40.0 [Ω], the shunt capacitor 34 is generally available at 100.0 [μF], 25
0.0 [V] electrolytic capacitor.

Filter network 11 is a harmonic filter capacitor
28, the harmonic filter capacitor 28, combined with the choke element 32, attenuates the harmonic frequency generated by the induction circuit 15, the harmonic filter capacitor 28 is tuned in combination with the choke element 32,
At least the first 5 generated from the DC power supply of ballast 10
It is significant to attenuate the amplitude of the two harmonic frequencies. This type of filter typically attenuates many primary five harmonic frequencies, the harmonic frequencies.

In this embodiment, the harmonic filter capacitor
Reference numeral 28 denotes a 1.5-μF, 400.0-V mylar-type capacitor, and a bridge circuit 16 through a power supply 12 and a choke element 32.
And are connected in parallel.

A no-load protection circuit 99 is connected between the filter network 11 and the inductive circuit 15. No-load protection circuit 99 is transformer 100
Including a primary winding 125 and a pair of filament excitation windings 140
And 150 of course comprise a tuned high voltage output secondary winding 160. Tuning high voltage output secondary winding 160 to tuning capacitor 130
Are connected in parallel to each other to form a tank circuit and generate an output voltage in the gas discharge tube 66. Filament excitation winding 150 and 1
40 is connected to filaments 70 and 68 of gas discharge tube 66, respectively.

In this embodiment, the no-load protection circuit 99 includes the transformer 10
It consists of a core material of ferrite composition consisting of 0, and has a primary winding 125 consisting of 29 turns and a tuned high voltage output secondary winding consisting of 50 turns specified by Ferroxcube 2616. And each of the filament excitation windings 140 and 150, each of which consists of one turn. Transformer 100 has a magnetic core with linear magnetic properties and is not saturated. The tuning capacitor 130 is 10 (n
F] is a capacitor.

Automatic adjustment control circuit 17 has no-load protection circuit 99 and induction circuit 15
Connect between The automatic adjustment control circuit
4, including toroid transformer 56 and shunt resistor 51. Shunt resistance 5
1 is connected in parallel with the primary winding 55 of the toroidal transformer 56.
In addition to connecting the primary winding 55 of the toroid transformer 56 in parallel with the shunt resistor 51, it is connected on the primary side to the return path 64 and on the secondary side to the base coupling capacitor 54 of the transistor 72. A base coupling capacitor 54 is connected at one end to the primary winding 55 of the toroidal transformer and is connected at an opposite end to the base drive winding 48 of the inductive circuit 15.

Here, the shunt resistance 51 is about 200 [Ω]. The toroid transformer 56 has a ferrite core material composition and is designated Ferroxcube designation 3B7-266T125 or 3B7.
-266CT125, comprising a 12-turn primary winding with line 28 and a 1-turn secondary wire 57 formed by a DC power input or a filter output 36 passing through the toroid core axis. The base coupling capacitor is 0.22 [μF], 100
[V] Mylar type capacitor.

The series combination of the primary winding 55 of the toroid transformer 56 and the base coupling capacitor 54 provides a return path for the base drive signal of the switching network 13 following the no-load protection ballast 10 having an automatic adjustment function that causes an oscillating state. Provided.

Furthermore, the self-regulating no-load protection ballast 10 includes a switching network 13 and is feedback-coupled to the inductive circuit 15 to form a pulsating current. As shown in the following paragraph, the switching network 13 is provided with an adjustment mechanism to maintain the power output of the gas discharge tube 66 at a predetermined value and then at a constant value.

The switching network 13 is provided with a transistor 72, which is connected by feedback to the bias or trigger control winding 48 of the inverter transformer 40. This connection causes switching of the current signal in response to the bias signal.
The bias control winding 48 of the inverter transformer 40 will be described.
The current entering the primary side of the bias control winding 48 passes through the winding 48 to the base 78 of the transistor 72. Transistor 72 has a base 78, a collector 74, and an emitter 76, respectively.
Consists of

The no-load protection ballast with automatic adjustment function is designed to supply a constant visible light as well as the power input of the gas discharge tube, and this supply is equivalent to the current gain of the transistor 72 used in the ballast 10. Irrespective of this, this is done by keeping the current of the collector 74 constant.

Light output should not fluctuate more than ± 3%, while ballast
The current gain of the transistor 72 used in 10 is 10 to
It has been determined that it can vary drastically between 60. stabilizer
Although 10 operates a single gas discharge tube 66, as shown in the embodiment, although a general description is provided here, it is also possible to operate two gas discharge tubes. This is because in such a case, the transistor current gains do not necessarily have to be matched in pairs.

The positive voltage provided to the base 78 by the resistor 53 ensures a small but sufficient starting current flow through the base 78, thereby initiating the conduction of the transistor 72.
1 [MΩ] has been used for the resistor 53.

When the transistor 72 is conducting or "on", current from the power supply 12 flows through the choke 32, the bridge circuit 16 and the primary winding of the transformer 100 to the DC output 36. The DC output 36 is connected to the primary winding 42 of the inverter transformer 40 and passes through the core axis of the toroidal transformer. Such current passes through the first portion 46 of the primary winding 42 to the tap line 25, which connects the tap line 25 to the collector 74 of the switching transistor 72.

Current flows from collector 74 to emitter via transistor 72
It flows to 76 and flows from the emitter 76 to the return path 64. The increase in collector current formed by switching transistor 72 includes the voltage on bias control winding 48, connecting the bias control winding to base 78 of transistor 72. Base current flows from base 78 to emitter at transistor 72
It flows to 76 and from the emitter 76 to the return path 64.

Once the circuit is formed, current will flow and the toroid transformer 56
Through the primary winding 55 and the base coupling capacitor 54.
Due to the series combination of the above elements, a pulse is generated at the base, and after a lapse of a predetermined period, the switching transistor 72 is driven from the "on" state to the "off" state.

The pulse driving the switching transistor 72 controls the "on" time interval between the operating frequencies of the anti-load protection ballast with automatic adjustment. At the end of this pulse, transistor 72 is turned "off" and the differentiated pulse via capacitor 54 provides a negative signal to base 78, which is limited in its magnitude by diode 38. The energy stored in the inverter transformer 40 is released from the primary winding 42 to the capacitor 62, and the return path 64
To

At the same time, the collector current passes through the primary winding 125 of the transformer 100, inducing a voltage on the secondary winding of each transformer 100. The voltage induced in the filament excitation windings 140 and 150 causes a current flow through the respective filaments 68 and 70 of the gas discharge tube 66.

The voltage induced in the tuned high voltage output secondary winding 160 is applied to the tuned capacitor 130 and the gas discharge tube 66. The voltage induced at this point in the cycle is sufficient to sustain a discharge in gas discharge tube 66, but not enough to initiate the discharge itself.

To reiterate, first, the transistor 72 is turned on by a small current flowing from the output terminal 36 to the base 78 of the transistor 72 through the resistor 53 and the base drive winding 48. As a result, the primary winding 42
A current flows toward the return path 64 via the first part 46, the line 25, the collector 74 and the emitter 76.

As described above, the magnetic field of the ferrite core of the transformer 40 has a magnetic induction on the hysteresis from zero to a predetermined value B.
And this circuit operates in a range where the characteristics are linear. The change in the magnetic field induces a voltage in the windings of the core of the transformer 40, which voltage is proportional to the number of turns of the special winding. The winding is connected to increase the positive voltage applied to the base 78, and the voltage applied to the base 78 causes the collector 7
4, increasing the current flow of the loop consisting of the emitter 76 and all the elements connected in series with it,
It reaches a maximum value determined by the impedance at 46 and the voltage level at output 36.

When the current in the path of the collector 74 and the emitter 76 stops increasing, the magnetic induction reaches a predetermined value B, which drops sharply and induces a voltage of the opposite polarity at the base drive winding 48. The current flowing through the collector 74 and the emitter 76 is blocked by the reversal of the polarity.

At this time, the induced voltage becomes large, typically equal to the sum of the inductance times the time derivative of the current.

Total inductance is transformer primary winding 125, part 1 4
6. The sum of the inductance of the second part 44 of the primary winding and twice the mutual inductance between FIG. 46 and the second part 44, and is a half of the square root of the sum of the inductance and the capacity of the capacitor 62. A discharge with a discharge frequency equal to 1 occurs.

The discharge current is considered as a sine curve and depends on the reciprocal of the discharge frequency, which is the "off" time and the "on"
This is the time it takes to release one half of the energy stored over a period of time, the sum of the inductance times the square of the current.

When the magnetic induction drops abruptly, the current direction is made opposite to that of the corresponding part of the sine wave.

The instantaneous voltage and current are large enough to induce either a positive or negative initial voltage at winding 160.

The magnitude of the voltage across winding 160 of transformer 100 depends on the mutual inductance between primary winding 125 and winding 160
Is multiplied by the current passing through and twice the discharge frequency.

The electromotive forces on windings 125 and 160 of transformer 100 are in phase opposition and, like winding 160, the currents in 140 and 150 reverse the flux changes in primary winding 125.

This has the effect of reducing the impedance of the primary winding, causing a larger current to flow through the loop that induces the electromotive force.

Thus, when a current flows through any of the secondary windings, the current of the primary winding 125 increases. When the discharge tube 66 is disconnected from the circuit, no current flows through the windings 140, 150 or 160, the impedance of the primary winding increases, and the primary winding 125, the first part 4
The current of the circuit loop including 6 and transistor 72 is reduced.

Further, a switching diode 38 is provided in the switching network 13, and this diode 13 is connected to a transistor.
Connected in parallel with the base-emitter junction of 72, the polarity of the switching diode 38 is provided so that a negative voltage does not damage the transistor 72. Switching diode 38
May be a commercially available type IN4005, which is connected such that its polarity is opposite to the polarity formed by the base-emitter junction of transistor 72.

The primary winding of the inverter transformer 40 is connected to the automatic transformer configuration by a tap winding, and the voltage induced in the primary winding second part is added in series to increase the voltage of the primary winding first part.

Capacitor 62 is connected in series with primary winding 42 to apply the total voltage across primary winding 42 to capacitor 62. As shown, the capacitor 62 is connected to the inverter transformer 40 on the primary side.
To the primary winding 42 and further to the return path 64 on the secondary side. In the description of this embodiment, the capacitor 62 is 3.5 (nF), 1.0 (k
V] Mylar capacitor to release the energy stored in inverter transformer 40 during transistor 72 "on" cycle during transistor 72 "off" cycle.

The primary winding of the no-load protection transformer 100 is one of the series combination elements through which the transistor 72 collector current flows. The magnitude of the current in each of these elements is the same, and the maximum value of the current is equal to the DC power supply voltage at the output terminal 36, and this voltage is divided by the sum of the series impedance of the current path.

The impedance of the primary winding 125 of the transformer 100 is a function of the impedance reflected from the winding itself and the secondary winding.

When the tuned high voltage output secondary winding 160 is loaded, the impedance produced in the primary winding is at a minimum. The reflected impedance of the filament excitation windings 140 and 150 is negligible. This is because each winding consists of only one turn. Assuming that the dc supply voltage at the output 36 is at a design value, minimizing the impedance of the primary winding 125 will result in a maximum collector current.

When the gas discharge tube 66 is no longer connected to the ballast 10, the resulting reflected impedance of the tuned high voltage secondary winding at the primary winding 125 will be very high. As the impedance in series with primary winding 125 increases, the collector current decreases proportionally. In this manner, the energy stored in transformer 100 is similarly proportionally reduced, and the resulting voltage across the output of winding 160 is similarly reduced.

Therefore, the primary winding 125 of the no-load protection transformer 100 functions as a variable impedance, which is inversely proportional to the load on the secondary winding 160 of the transformer 100. Since the impedance of the primary winding 125 is all inductive, there is little heat dissipation generated by the primary winding 125, which affects ballast efficiency or component life.

No.1 no-load protection ballast with automatic adjustment function
The figure will be described. When the ballast 10 is in the oscillating state and the transistor 72 is in the “on” state, the collector current, which is the driving current of the ballast 10, flows from the power supply 12 through the filter network 11 including the rectifier circuit 16 and the output terminal 26. Transformer 100
Flows through the primary winding 125 to the output terminal 36. The DC power output 36 passes through the axis of the toroidal transformer 56 and is connected to one end of the primary winding 42 of the inverter transformer 40.

The drive current passes through the first portion 46 of the primary winding 42 and flows to the tap line 25, where it connects the tap line 25 to the collector 74 of the switching transistor 72. Transistor 72
Is in the "on" state, causing current to flow from collector 74 to emitter 76 back to the power return path via line 64. Since this current has the property of increasing, a voltage is induced in the bias control winding 48, and the winding direction of the bias control winding 48 is changed so that a voltage is generated at the base 78 of the transistor 72. Positive for emitter 76, about
It is required to keep the transistor 72 in the "on" state at 0.7 V or more, and the voltage generated by the bias control winding 48 reinforces the "on" condition of the transistor 72.

The collector current increases linearly until it reaches a maximum. The maximum value is a function of the supply voltage and the impedance of the collector circuit. Thus, when the collector current flows through the first part 46 of the primary winding 42 during the transistor "on" state, a magnetic flux is created in the core of the inverter transformer 40 and Induces voltage, reinforces the "on" condition, and supplies base drive current. When the same drive current passes through the primary winding 125 of the transformer 100, it creates a magnetic flux in the transformer core and induces a voltage in all of the secondary windings of the no-load protection transformer 100.

The induced voltage at 140 and 150 of the secondary winding is a gas discharge tube
The heater current is supplied to each of the 66 filters 68 and 70.

The induced voltage of the tuned high voltage output secondary winding 160 is connected to the tuning capacitor 130 and the gas discharge tube 66 to generate a visible light output from the gas discharge tube 66.

The induced voltage in the second part 44 of the primary winding 42 of the single-turn inverter transformer 40 is a capacitor during the corresponding period of the cycle.
Just charge 62.

Turning the transistor 72 to the "off" state causes the first part of the inverter transformer primary winding 42 and the no-load protection transformer 100
Of the collector current passing through the primary winding 125 rapidly disappears. The rapid change in collector current re-induces the voltage in the second part 46 of the inverter transformer primary winding 42 and the secondary windings 150, 140 and 160 of the transformer 100 as well as in the secondary winding 48.

As is known from old music theory, the voltage polarity induced by the rapid disappearance of the collector current depends on the transformer 40 and the transformer.
100 is intended to maintain the original current direction of each primary winding 46 and 125. Due to the direction of current flow in windings 46 and 48 as indicated by dot 77, the bias control winding 48 of inverter transformer 40 reverses polarity as described above when collector current is flowing. Thus, a negative signal is generated at the base 78 for the emitter 76, turning the transistor 72 "off".

It is important to maintain the relatively uniform gain of the transistors used in the no-load protective ballasts with self-tuning so that the light output is consistent from one particular unit to another. It may be within the range of about ± 3%.

However, due to normal manufacturing techniques known in the industry, the gain of transistor 72 may vary between 10.0 and 50.0 or more. Thus, automatic adjustment control requires manual adjustment of the gain control element, i.e., the device must be within a small tolerance to obtain a constant light output from one ballast to another. Is an advantage that must be selected in advance.

The self-regulating no-load protection ballast 10 utilizes a variable inductance that allows the base current to pass and forms a toroid core with 12 turns of winding. The output end 36 passes through the axis of the toroid core 27 and passes the collector current of the transistor 72. The direction in which the current passes through the two windings is such that each magnetic field is additive in the toroid core 27 of the toroid transformer 56.

Therefore, the inductance in the primary winding 55 of the toroidal transformer 56 is a function of the base and collector currents times the turns ratio and permeability of the core.

Actually, the fluctuation of the inductance of the secondary winding 57 of the toroid transformer 56 may be ignored. The secondary winding is formed from only one turn and the winding 57 inductance is connected relatively low in series with the inductance of the first part of the primary winding 42. The inductance of the secondary winding 57 is meaningless when compared to the inductance of the first part of the primary winding 42, which has a large absolute value.

No-load ballast with automatic adjustment of switching 72
To ensure oscillation within 10, bias control winding 48 is specifically designed to provide sufficient voltage to turn transistor 72 on at the lowest gain. One may expect such a transistor 72 to be available from the ballast manufacturer. Thus, the transistor 72 is turned on and reaches saturation, and the base voltage to the emitter is the voltage required to bring the transistor 72 into saturation, and it is certain that it will be at least 0.7 [V]. is there.

Regardless of the gain of transistor 72 used in a no-load protection ballast with automatic regulation, the collector voltage and the collector circuit impedance are the same, so that the same collector current is used even if the transistor is used with a gain of 10.0 to 50.0. Flows. Therefore, since the base current is a function of the collector current divided by the gain of transistor 72, if transistors 72 with different gain values are used and work properly with self-regulating no-load protection ballast 10, If so, the base current must change. When the base current changes, the elements of the base circuit need to change the impedance value, acting on the automatic adjustment circuit 17 and the primary winding of the toroid transformer 56.

To achieve self-adjustment, the design of the toroidal transformer 56 uses transistors with the maximum expected gain to reach the maximum permeability of the core 27. Similarly, the inductance of the primary winding 55 of the toroidal transformer 56 is therefore maximized and the minimum current passes through the base circuit of the transistor 72.

The impedance of a winding with a core is related to the number of windings and the current as well as the reciprocal of the magnetic path length of the core. The operating point may be adjusted by changing the size of the toroid or by inserting a parallel resistor 51 in parallel with the toroid primary winding 55 for adjusting the corresponding exciting magnetic field. A value of about 200 [Ω] has been used for the parallel resistor 51.

Thus, the primary winding of the toroidal transformer 56 is at its maximum value of inductance, and its impedance is much greater than the impedance of the base coupling capacitor 54, and thus is a controlling factor in limiting the current to the base 78 of the transistor 72. When the transistor 72 has the maximum gain value, almost no current is required. For example, if the gain of the transistor 72 is 50.0, the base current is equal to the collector current.
It becomes 1/50.

However, the voltage induced in the base drive winding 48 is
The transistor has been designed to be "on" at low gain. Therefore, it dissipates in excess energy in the base circuit of transistor 72. The primary winding 55 of the toroid transformer 56 stores excess energy. The impedance of this primary winding 55 is primarily inductive and resistive, with little dissipation in generating heat and excess released when transistor 72 is in the "off" state. Provide efficient devices for dissipating energy.

Conversely, if a low-gain transistor is used in the self-adjusting no-load protection ballast 10, the base current will need to increase significantly, and the permeability of the core of the toroid transformer 56 will increase with the high-gain transistor. Moving to a lower value below that measured at, the inductance is smaller than for the higher gain transistor. Thus, the series impedance is reduced,
A larger base current is allowed to flow to compensate for the low gain transistor 72 used in ballast 10.

In addition, a tuned no-load protection transformer 10 is used for the induction circuit.
15 connected in series to prevent the generation of a voltage higher than a predetermined value when the gas discharge tube 66 is electrically disconnected from the circuit. The primary winding 125 of the tuned no-load protection transformer 100 forms a variable inductance, which is inversely proportional to the amount of power applied to the gas discharge tube 66.

The variable impedance of the primary winding 125 is
It is a function of the reflection impedance of 60. The impedance is the number of turns of the winding 160, the capacity of the tuning capacitor 130,
It is a function of the current path of the secondary winding 160, which is the magnetic path length of the core of the transformer 100 and the load current of the gas discharge tube 66. in this way,
The change in load current when the gas discharge tube is no longer present in the circuit results in the impedance of the winding 160 and the primary winding 1
Reflected to 25 impedance.

By generating a variable inductance whose impedance is inversely proportional to the load current, the limiting voltage may be generated by controlling the collector current according to the load condition.

[Brief description of the drawings]

FIG. 1 is a schematic view of a no-load protection ballast having an automatic adjustment function. 10: ballast, 11: filter circuit, 12: power supply, 13: switching network, 15: induction circuit, 16: rectifier circuit, 40: inverter transformer, 56: toroid transformer, 64: return path, 66: gas discharge Tube, 68, 70: filament, 72: transistor, 100: transformer.

Claims (10)

(57) [Claims] 1. A ballast having a power supply for operating at least one gas discharge tube at a controlled current and a limited voltage, and for maintaining input and output power of the gas discharge tube at a predetermined value, (A) a filter device connected to the power supply; (1) a filter device for maintaining a smooth DC voltage signal; (2) a harmonic device for suppressing a harmonic frequency generated by the ballast; An induction device provided with a tapped primary winding in an automatic transformer configuration for forming a controlled current magnitude; and (c) a switching device feedback-coupled to the induction device for establishing the controlled current. The induction device has a trigger control winding for generating a control current, the induction device generates a voltage applied to the gas discharge tube according to the controlled current, and the gas discharge tube is stable. From the vessel A switching device including a no-load protection device for maintaining the voltage at a predetermined value when disconnected, the switching device including a regulating device for maintaining the power output of the gas discharge tube at a predetermined value and a substantially constant value; The adjusting device comprises: (1) a primary winding coupled in series with the trigger control winding and the switching device to adjust the control current; and (2) a tapped primary winding of the inductive device and the filter device. A self-adjusting no-load protection ballast having a toroidal transformer having a secondary winding coupled in series and feeding back to the primary winding. 2. The non-load protection device includes a primary winding coupled in series with the tapped primary winding of the filter device and the induction device, and a transformer having a plurality of secondary windings.
2. The self-adjusting no-load protection of claim 1, wherein the primary winding forms a variable inductance to reduce the controlled current when the gas discharge tube is disconnected from the ballast. stabilizer. 3. The plurality of secondary windings includes a tuned high voltage output secondary winding and a pair of filament excitation windings, each filament excitation winding coupled to a corresponding filament of a gas discharge tube. Item 2. A no-load protection ballast having an automatic adjustment function according to item 2. 4. The tuned high voltage secondary winding is connected in parallel to both a tuned capacitor and the gas discharge tube, and the tuned high voltage secondary winding generates the limited voltage at the input of the gas discharge tube. 4. The self-regulating function according to claim 3, wherein the limiting voltage decreases in accordance with a decrease in the controlled current when the gas discharge tube is disconnected from the ballast. Load protection ballast. 5. The ballast of claim 4, wherein the transformer includes a magnetic core ferrite material for generating the voltage input of the gas discharge tube. 6. The switching device of claim 1, wherein said switching device includes a transistor device for circulating said controlled current, said transistor device including a base, an emitter connected to a collector and a power supply. No load protection ballast with automatic adjustment function. 7. The self-adjusting function according to claim 6, wherein the secondary winding of the toroidal transformer is connected in series to the tapped primary winding of the inductive device and the emitter of the transistor device. No-load protection ballast with 8. The no-load protection ballast of claim 6, wherein the regulator is connected in series with the inductive device and the transistor device. 9. A toroidal transformer is provided with a predetermined variable inductance for adjusting the power output of said gas discharge tube.
9. The no-load protection ballast of claim 8, wherein the toroidal transformer includes a primary winding and a secondary winding of the toroidal transformer. 10. The system of claim 1, wherein the regulator has a base coupling capacitor connected to a primary winding of the toroidal transformer and a trigger control winding of the inductive device to block a DC component signal of the current. Item 7. A no-load protection ballast having an automatic adjustment function according to item 7.