JPH0534799B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a device for lighting and maintaining a discharge lamp.

Conventional Structure and Problems In recent years, discharge lamp lighting devices have been made smaller, lighter, and more efficient by using semiconductors.

A conventional discharge lamp lighting device will be explained below.

FIG. 3 is a circuit diagram of a conventional discharge lamp lighting device. 1 is an AC power supply, 2 is a rectifier circuit, 3 is an input smoothing capacitor, 4 is a discharge lamp, 5 is an inductance, 6 is a switching transistor, 7
8 is a diode, 8 is an output smoothing capacitor, and 9 is a control circuit that controls on/off of the transistor 6 and conducts/disconnects current between the collector and emitter. 10 is a DC step-down chopper circuit comprising a discharge lamp 4, an inductance 5, a transistor 6, a diode 7, a capacitor 8, and a control circuit 9.

The operation of the conventional example will be explained below. first,
A DC voltage including ripples is rectified by a rectifier circuit 2 and smoothed by a capacitor 3 from an AC power supply 1.
Applied to the DC step-down chopper circuit. When this DC voltage is applied, a current flows from the (+) side terminal of the rectifier circuit to the input smoothing capacitor 8 and the discharge lamp 4 to the inductance 5 to the transistor 6 to the (-) side terminal of the rectifier circuit. This current is the discharge lamp 4
Since it is limited by the inductance 5, it increases linearly. Additionally, energy is stored in the inductance due to this current. Next, at a certain point, the control circuit 9 turns off the transistor 6. Therefore, the energy stored in the inductance 5 is released via the diode 7 and the discharge lamp 4, and a lamp current continues to flow through the discharge lamp 4, keeping it lit. The output smoothing capacitor 8 is limited by the inductance 5, smoothes the variation in the supplied lamp current, and supplies the discharge lamp 4 with current and voltage with less ripple. Therefore, the discharge lamp 4 maintains lighting more stably.

However, in the above configuration, if the ripple of the DC voltage rectified and smoothed by the rectifier circuit 2 and the input smoothing capacitor 3 is large, the discharge lamp 4 will go out. That is, when the value obtained by subtracting the circuit voltage drop from the rectified and smoothed voltage becomes lower than the lamp voltage, the lamp current cannot be supplied, and if this period becomes longer, the discharge lamp 4 will go out. Furthermore, in order to downsize the discharge lamp lighting device, the capacitance of the input smoothing capacitor 3 is as small as possible. Furthermore, it is desirable that there is no such thing. However, if this capacitance is reduced, the ripple of the voltage after rectifying the voltage of the AC power supply 1 will increase,
The minimum value of the output voltage of the rectifier circuit 2 becomes lower.
Therefore, it becomes more likely to disappear, and the capacitor 3
The problem is that it cannot be made smaller.

In addition, to solve this problem, instead of using the DC step-down chopper circuit described above, a large amount of energy is first stored in the inductance without going through the discharge lamp.
Next, there is a method to solve this problem by lighting the discharge lamp using an inverted chopper circuit that can take out the energy of this inductance as a high voltage as a kick voltage and apply it to the discharge lamp. In other words, with this method, even if the output voltage of the rectifier circuit is lower than the lamp voltage, the lamp voltage can be supplied, so
The input smoothing capacitor can be made smaller by increasing the output voltage ripple of the rectifier circuit. However, in this case, there is a problem that circuit efficiency deteriorates.

Purpose of the invention The present invention solves the above-mentioned conventional problems.
An object of the present invention is to provide a discharge lamp lighting device that can stably light a discharge lamp with a small and highly efficient circuit.

Structure of the Invention The present invention includes a power supply whose output voltage has a constant polarity, a first diode connected in the forward direction to one end of the output end of the power supply, and an output end of the first diode connected in series to the one end. a discharge lamp, an inductance having the other end of the discharge lamp connected in series to one end thereof, and a first a second diode connected to supply a current in the same direction as the current flowing through the first diode from a connection point between the switch element with the control terminal and the inductance to the discharge lamp; , a voltage detection circuit that detects either the output voltage of the power supply or the difference voltage therebetween when the output voltage is higher than the voltage across the discharge lamp; and conduction when the output of the voltage detection circuit is lower than a predetermined value; A second diode having one end connected to the connection point between the discharge lamp and the inductance in a direction in which a current is supplied in the same direction as the current flowing through the inductance by the first diode, and the other end connected to the output end of the power source. and a current supply means having a switch element with a control terminal,
In the discharge lamp lighting device, the first switch element with a control terminal is made conductive at least at the time of starting, and has a control means for controlling on/off. As a result, the voltage detection circuit detects a drop in the output voltage of the power supply from the difference between the output voltage or the lamp voltage, and the current supply means supplies current to the inductance, thereby eliminating the possibility of the discharge lamp turning off. can be made compact, lightweight, and highly efficient.

DESCRIPTION OF EMBODIMENTS FIG. 1 shows a circuit diagram of a discharge lamp lighting device according to a first embodiment of the present invention. In FIG. 1, 11 is an AC power supply, 12 is a rectifier circuit, 1
3 is an input smoothing capacitor, 14 is a rectifier and smoothing circuit consisting of a rectifier circuit 12 and a capacitor 13, 15 is a first diode, 16 is a discharge lamp, 17 is an output smoothing capacitor, 18 is an inductance, and 19 is a first control terminal with A switching transistor which is a switching element, 20 is a second diode, 2
1 is a current detection circuit, 22 is a starting resistor, 23 is a current detection resistor, 24 is a cut-off transistor, 2
5 is a base current limiting resistor, 26 is a secondary coil with inductance 18, 27 is a diode, 28 is a current detection circuit 21, resistors 22, 23, 25, secondary coil 26, diode 27, transistor 24
a control circuit 29 consisting of a discharge lamp 16, a capacitor 17, an inductance 18, a transistor 19, and a chopper circuit 30 consisting of a control circuit 28;
31 is a diode, 32 is a base current supply resistor, 33 and 34 are voltage detection resistors, 35 is a transistor, and 36 is a voltage composed of resistors 33, 34 and transistor 35. The detection circuit 37 is a current supply means consisting of a transistor 30, a diode 31, a resistor 32, and a voltage detection circuit 36.

The operation of the discharge lamp lighting device of this embodiment configured as described above will be described below. When the AC power supply 11 is turned on before starting the discharge lamp, a DC voltage containing ripples rectified and smoothed by the rectification and smoothing circuit 14 is generated between the output terminals a and b of the rectification and smoothing circuit 14 . When voltage is generated at terminal a, terminal a,
The output voltage V _IN of the rectifying and smoothing circuit is applied to the voltage dividing resistors 33 and 34 connected in parallel between b. At this time, since the discharge lamp 16 is not lit, almost no current flows, so that V _IN is close to the peak value of the AC power supply, and the ripple is small. In this state, the voltage generated across the resistor 34 of the voltage dividing resistors 33 and 34 turns on the transistor 35. Therefore, the base voltage of the transistor 30 connected to the collector of the transistor 35 becomes a low voltage level, and the transistor 30 is turned off. Therefore, no current flows through the current supply means 37. Therefore, V _IN is applied to the chopper circuit 29 from the terminal a via the first diode 15.

In the chopper circuit 29, resistor 2 is connected by V _IN.
The base current of the first transistor 19 is supplied through the transistor 2. Therefore, the first transistor 19
is on and V _IN is applied to capacitor 17 and discharge lamp 16 and inductance 18 . At this _time , diode 15→
A current flows from the capacitor 17 to the inductance 18 to the first transistor 19 to the current detection resistor 23 to the terminal b, charging the capacitor 17 and applying this charging voltage to the discharge lamp 16. This voltage starts the discharge lamp 16 (or it may be started by adding another starter). When the discharge lamp 16 is turned on, it is passed from the diode 15 to the discharge lamp 16, from the inductance 18 to the first transistor 19, and the current detection resistor 23 to the terminal b.
Current flows to. This current flows through the discharge lamp 16,
It increases linearly, limited by the inductance 18. At this time, this current generates a substantially constant voltage in the secondary coil 26 of the inductance 18, and this voltage sufficiently supplies the base current to the first transistor 19 via the resistor 25.
The first transistor 19 remains on.
Therefore, the discharge lamp 16, the inductance 18,
The current flowing through transistor 19 continues to increase. When this current flows through the current detection resistor 23, the voltage generated across the resistor 23 also increases. When this voltage reaches a predetermined value set by the current detection circuit 21, the transistor 24 is turned on. When the transistor 24 is turned on, B and E of the first transistor 19 are short-circuited, and the first transistor 19 is turned off. Therefore, the energy stored in the inductance 18 due to the current flowing through the inductance 18 is released from the second diode 20 via the discharge lamp 16. At this time, the current emitted from the inductance 18 decreases linearly. The current from the inductance 18 to the discharge lamp 16 decreases, but is compensated for by the charge stored in the capacitor 17 when the first transistor 19 is on, increasing the lamp voltage during the on-off periods of the transistor 19. is a nearly constant voltage with some ripple.

Also, at this time, a voltage with a polarity opposite to that when the first transistor is on appears in the secondary winding 26 of the inductance 18, and a voltage with a polarity opposite to that when the first transistor is on appears, and
A current flows through the diode 27 connected in antiparallel between BE and E of the first transistor 19 to keep the first transistor 19 off.

When the energy in the inductance 18 is released, the secondary coil 26 of the inductance 18
The reverse voltage that had been generated disappears, and the base current of the first transistor 19 is again supplied from the terminal a via the resistor 22, and the first transistor 19 is turned on again. When the first transistor 19 is turned on, current flows from the terminal a to the terminal b via the first diode 15, the capacitor 17, the discharge lamp 16, the inductance 18, the first transistor 19, and the current detection resistor 23. Then, repeat the above operation.

In such a lighting state, the output power from the rectifying and smoothing circuit 14 is the lamp power and the loss of the lighting circuit. In this case, the output power from the rectifier smoothing circuit 14 becomes larger than that before starting the discharge lamp 16, so the output voltage V _IN of the rectifier smoothing circuit 14 is
The rectification ripple of the AC power supply increases. That is, the minimum value of the voltage at V _IN will be lower.
Here, the detection level V _INT of the voltage detection circuit 36 that detects V _IN is defined as V _{IN peok} > V _INT ≧ (lamp voltage V _la ) + (voltage drop due to circuit loss) (However, the lamp voltage V _la is approximately Assuming that V _IN > V _INT , in the voltage detection circuit 36, the voltage across the resistor 34 becomes a voltage that turns on the transistor 35, and the transistor 35 is on, and the voltage from the terminal a to the resistor 32 is a voltage that turns on the transistor 35. The base voltage of the second transistor 30 is set to a low voltage level to prevent the base current from flowing. Therefore, transistor 3
0 is off, and the current supply means 37 does not operate, so it continues the lighting operation of the discharge lamp. That is, the chopper circuit 29 operates as a step-down chopper circuit, and in this case, the circuit efficiency is very high.

Next, when V _IN ≦V _INT , the voltage generated across the resistor 34 in the voltage detection circuit 36 becomes lower than the base voltage that turns the transistor 35 on. Therefore, the transistor 35 is turned off. Therefore, the base current is supplied to the second transistor 30 from the terminal a via the resistor 32. Therefore, the second transistor 30 is conductive, and from the terminal a to the C-E of the second transistor 30.
Inductance 1 is applied via diode 31 between
8. First transistor 19, current detection resistor 2
Current flows from 3 to terminal b. At this time, the function of the first control circuit 28 is the same as in the case of V _IN >V _INT . Therefore, this current increases linearly,
When a predetermined level is reached, the first transistor 1
9 is off.

In this operation, the only thing that limits the current is primarily the inductance 18, which does not pass through the discharge lamp 16 and therefore increases rapidly.
At this time, the discharge lamp has an output smoothing capacitor 1
The current is only supplied by the charge accumulated in the discharge lamp 7, but this period is short and the discharge lamp 1
6 will never go away.

When the first transistor 19 is turned off, the energy stored in the inductance 18 charges the capacitor 17 via the diode 20 and is released as a lamp current. At this time,
The current is limited by the inductance 18 and the discharge lamp 16 and decreases linearly when V _IN > V _INT
The same is true for . When the energy of the inductance 18 is released, the first transistor 19 is turned on again, and current flows from the current supply means 37 to the terminal b via the inductance 18, the first transistor 19, and the resistor 23. , repeat the above operation. At this time, the chopper circuit 29
will operate as an inverted chopper circuit. Therefore, even if V _IN ≦V _INT , current continues to be supplied to the discharge lamp, and the discharge lamp can maintain lighting.

As described above, according to this embodiment, the voltage detection circuit 36 for detecting V _IN is provided _, and the current is caused to flow through the current supply means 37 when V _IN ≦V _INT . Even when the rectification ripple temporarily drops to zero potential as in half-wave rectification or full-wave rectification, the discharge lamp voltage can be maintained by making the capacity of the output smoothing capacitor 17 sufficiently large as described above. The discharge lamp 16 can be stably and safely kept lit without going out from the start. In addition, since it can maintain stable lighting even when there are large fluctuations in the AC power supply voltage, the range of use and safety can be expanded, especially for HID lamps that are difficult to restart. Furthermore, since the ripple of V _IN can be increased, the capacitance of the input smoothing capacitor 13 can be reduced, and the discharge lamp lighting device can be made smaller and cheaper. Furthermore, if V _IN > V _INT ,
Since the chopper circuit 29 operates as a step-down chopper circuit, circuit efficiency can be improved.

A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a circuit diagram of a discharge lamp lighting device showing a second embodiment of the present invention. In the same figure, 1
1 to 32 have the same structure as that shown in FIG.

What differs from the configuration in FIG. 1 is a voltage detection circuit 46 consisting of voltage dividing resistors 43 and 44 and a transistor 45, one end of which is connected between the diode 31 and the inductance 18 and the other end connected to terminal b.
47 is a current supply means including this voltage detection circuit.

The operation of the second embodiment of the discharge lamp lighting device constructed as described above will be described below.
Before starting the discharge lamp, when the AC power supply 11 is turned on, the DC voltage including ripples rectified and smoothed by the rectification and smoothing circuit 14 is output to the output terminal a of the rectification and smoothing circuit 14.
The process is the same as in the first embodiment until it occurs during interval b.

In the second embodiment, when a voltage is generated at terminal a, since the discharge lamp 16 is not lit yet, a current flows from the diode 15 through the capacitor 17, the inductance 18, the first transistor 19, and the resistor 23 to the terminal b. As a result, the capacitor 17 attempts to be charged up to the rectifier and smoothing circuit output voltage V _IN . When the capacitor 17 is charged, its voltage will be applied to the current supply means 47, so that the base current of the second transistor 30 is supplied via the resistor 32. At this time, voltage dividing resistor 4
3 and 44, the voltage of the inductance 18 and the first transistor 19, that is, almost no voltage is applied. Therefore, the transistor 45 whose base voltage is the voltage of the resistor 44 is turned off, and the base potential of the second transistor 30 is at a high voltage level, so the second transistor 30 is turned on. Therefore, a current limited by the inductance 18 flows from the terminal a to the second transistor 30 → diode 31 → inductance 18 → first transistor 19 → current detection resistor 23 → terminal b, and increases linearly. When this current reaches a predetermined value, the control circuit 28 turns off the first transistor 19 in the same manner as in the first embodiment. When the first transistor 19 is turned off,
The energy stored in the inductance 18 is applied to the capacitor 17 and the discharge lamp 16 via the second diode 20, but since the discharge lamp 16 is not lit, this energy becomes a high voltage across the inductance 18 as a so-called kick voltage. appears. This high voltage will be applied to the capacitor 17 and the discharge lamp 16 via the diode 20. Therefore, a high voltage is stored in the capacitor, and even after the peak voltage of the inductance 18 has decreased, the high DC voltage continues to be applied to the discharge lamp, blocked by the diodes 20 and 15. At this time, the kick voltage of the inductance 18, that is, the stored energy is released through the leakage current of each part and the secondary coil 26, and decreases. Then, the first transistor is turned on again and the above operation is repeated. When the discharge lamp 16 breaks down, lamp current flows. When the discharge lamp 16 starts, the voltage dividing resistors 43 and 44 of the voltage detection circuit 46 have (V _IN −
A voltage of V _la ) is applied. Immediately after starting, V _la rapidly decreases, and therefore (V _IN −V _la ) rapidly increases. Therefore, the voltage generated across the resistor 44 rises rapidly, turning on the transistor 45. When the transistor 45 is turned on, the base voltage of the second transistor 30 becomes a low voltage level and turned off.

Therefore, the current supply means 47 stops operating immediately after starting. Therefore, the chopper circuit 2
9 performs the same operation as the step-down chopper circuit in the case of V _IN >V _INT in the first embodiment. after that,
When the lamp voltage increases and a stable lighting state is achieved, the current supply means 47 is turned on and off according to the voltage value (V _IN >V _la ) applied to the voltage dividing resistors 43 and 44 .
In other words, the detection level V _T = (V _IN > V _la ) _T is V _T
≧ (voltage drop due to circuit loss).

That is, when V _IN >V _la >V _T , the transistor 45 is on and the second transistor is kept off, so the current supply means 47 is off, and the chopper circuit 29 operates as a step-down chopper circuit.

The next case is when the power supply rectification ripple is large and V _IN becomes low, or when V _la temporarily rises suddenly for some reason.

When V _IN -V _la ≦V _T , the transistor 45 is turned off, so the second transistor 30 remains on, and current flows through the current supply means 47. At this time, the chopper circuit 29 is connected to the V _IN of the first embodiment.
As in the case of ≦V _INT , the discharge lamp 16 operates as an inverted chopper circuit, and the discharge lamp 16 maintains stable lighting.

As described above, according to this embodiment, the voltage detection circuit is connected to the inductance 18 and the first transistor 1.
9 in parallel, even when the ripple of V _IN is large, the voltage (V _IN - V _la ) is detected, so the discharge lamp 16 can be lit stably without turning off more efficiently, and the input smoothing capacitor 13 can be It can be made smaller and cheaper by reducing the capacitance. Furthermore, even when the voltage fluctuations and sudden changes of the AC power supply are large, and when the lamp voltage has large variations, fluctuations, and sudden changes, the lamp can be stably lit without turning off. Furthermore, by using the step-down chopper for a longer period of time, the efficiency is even better than in the first embodiment. In addition, in the case of this embodiment, it can also function as a starter, and a lamp with a high starting voltage can be easily and easily used.
With an inexpensive configuration, everything from starting to lighting can be done smoothly. Note that in the first embodiment,
In _the second embodiment, (V _IN
-V _la ), however, V _IN and V _la may be detected respectively and the voltages may be compared to control the second transistor. In this case, more detailed control from starting to lighting can be performed.

Further, in the first embodiment, V _IN is detected, but it goes without saying that the same effect can be obtained by detecting the voltage of the AC power source and controlling the second transistor.

Further, in the second embodiment, the voltage detection circuit 4
6 was provided in parallel with the inductance and the first transistor 19, but similar results can be obtained even if only the voltage of the inductance 18 is detected, and furthermore,
The voltage generated in the secondary coil 26 of the inductance 18 is also the voltage of the inductance 18, that is,
Since it is a voltage proportional to (V _IN −V _la ), the same operation can be performed even if this voltage is detected, and it can also be used as a low voltage signal, making the configuration inexpensive and easy. .

Further, in the first and second embodiments, the voltage detection circuits 36 and 46 were designed to detect instantaneous values, but they are designed to detect average values and operate the entire circuit with a little margin. Also good. Although transistors are used as the second switch elements for the current supply means 37 and 47, other devices may be used as long as they can turn on and off the current according to the control signal, such as triacs, GTOs, thyristors, and other devices. However, in the case of a thyristor, etc., the current flowing through the current supply means is turned on and off in a very short period of time by the first transistor 19, so a commutation circuit is not necessary, and only a circuit to turn it on is required, which is inexpensive. Can be configured. Further, although the current supply means is connected to the terminal a, it may be connected to a battery or other power source as long as it can supply current. In this case, it is very effective during power outages.

In addition, the chopper circuit 29 is of a self-excited type in which a secondary coil is provided in the inductance to detect the instantaneous current and perform oscillation operation, but it may be a self-excited type of other type or a separately excited type. Needless to say. Further, although the diode 20 is connected to the discharge lamp 16, a diode may be further provided on the power source side of the diode 15 and connected in the middle thereof. Further, although the capacitor 17 is provided, it may be omitted as long as the discharge lamp 16 does not go out.
Conversely, if the capacitance of the capacitor 17 is large, the capacitor 13 may be omitted. Further, the rectifier circuit 14 may be full wave, half wave, or n times voltage. In addition, as a power source with a constant output voltage polarity, we used a rectified and smoothed AC power source, but a general DC power source may also be used. You can get stable lighting without any problems. Also, the stabilizing capacitor can be made smaller. Further, the discharge lamp may be a preheated discharge lamp or a low-pressure discharge lamp, and is particularly effective for high-pressure discharge lamps.
Moreover, it may have an auxiliary electrode.

Effects of the Invention The discharge lamp lighting device of the present invention is capable of stably and efficiently lighting the discharge lamp even when fluctuations in the power supply or the discharge lamp become large by providing a current supply means including a voltage detection circuit.
The discharge lamp lighting device can be made smaller.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of the first embodiment of the present invention;
The figure is a circuit diagram of a second embodiment of the present invention, and FIG. 3 is a circuit diagram of a conventional example. 11... AC power supply, 12... Rectifier circuit, 13...
...Input smoothing capacitor, 15...First diode, 16...Second diode, 17...Output smoothing capacitor, 18...Inductance, 19...
...First transistor, 28... Control circuit, 30
... second transistor, 36, 46 ... voltage detection circuit, 37, 47 ... current supply means.

Claims (1)

[Claims] 1. A power source whose output voltage has a constant polarity, a first diode connected in a forward direction to one end of the output end of the power source, and an output end of the first diode connected in series to the one end. an inductance with the other end of the discharge lamp connected in series with one end of the inductance, and an inductance with the other end of the inductance connected in series with one end of the inductance, and the other end of the inductance with the other end connected to the other end of the output end of the power source. a second switch element connected to supply a current in the same direction as the current flowing through the first diode from a connection point between the switch element with a control terminal and the inductance to the discharge lamp; a diode, a voltage detection circuit that detects the output voltage of the power supply, and conducts when the output of the voltage detection circuit is lower than a predetermined value;
A second diode having one end connected to a connection point between the discharge lamp and the inductance in a direction in which a current is supplied in the same direction as the current flowing through the inductance by the first diode, and the other end connected to the output end of the power source. a current supply means having a switch element with a control terminal, wherein the first switch element with a control terminal is made conductive at least at the time of starting and has a control means for controlling on/off. 2. a power supply whose output voltage has a constant polarity, a first diode connected in a forward direction to one end of the output end of the power supply, and a discharge lamp having the output end of the first diode connected in series to one end thereof; an inductance having the other end of the discharge lamp connected in series to one end thereof; and a switch with a first control terminal having the other end of the inductance connected in series to the one end and the other end connected to the other end of the output end of the power source. a second diode connected to supply a current in the same direction as the current flowing through the first diode from a connection point between the switch element with a control terminal and the inductance to the discharge lamp; a voltage detection circuit that detects a difference voltage between an output voltage and a voltage across the discharge lamp; and a voltage detection circuit that is electrically connected when the output of the voltage detection circuit is lower than a predetermined value, and a voltage detection circuit that connects the discharge lamp and the inductance with the first current supply means having a switch element with a second control terminal, one end of which is connected to supply current in the same direction as the current flowing through the inductance through a diode, and the other end of which is connected to the output end of the power source; A discharge lamp lighting device, wherein the first switch element with a control terminal is made conductive at least at the time of starting and has a control means for controlling on/off. 3. A patent characterized in that the voltage detection circuit detects the voltage across a series circuit of an inductance and a switch element with a first control terminal when detecting the voltage difference between the output voltage of the power source and the voltage across the discharge lamp. A discharge lamp lighting device according to claim 2. 4. The discharge lamp lighting device according to claim 2, wherein the voltage detection circuit detects the voltage across the inductance when detecting the voltage difference between the output voltage of the power source and the voltage across the discharge lamp. . 5. When the inductance has a secondary coil and the voltage detection circuit detects a voltage difference between the output voltage of the power source and the voltage across the discharge lamp, the voltage detection circuit detects the voltage across the secondary coil of the inductance. A discharge lamp lighting device according to claim 2.