JPH0444400B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an electronic circuit for lighting a discharge lamp, such as a low-pressure mercury vapor discharge lamp, and more particularly to an electronic lighting circuit that operates at a high frequency using a capacitor as a ballast. be.

[Conventional technology]

Since the voltage-current characteristics of a discharge lamp exhibit negative resistance at low frequencies, in order to keep the discharge current stable,
A discharge lamp is lit by connecting an impedance such as resistance, inductance, or capacitance in series with the discharge lamp. This impedance is usually called a ballast or ballast. A resistor is used as a ballast for a DC discharge lamp, but this is inefficient and undesirable because the ballast consumes power approximately equal to the input power of the discharge lamp.

Inductance is mainly used for AC discharge lamps. As the inductance for the commercial frequency, an inductance in which a coil is wound around a laminated core of silicon steel plates called a chiyoke coil is used. Chiyoke coils are well suited to the characteristics of discharge lamps and are nonflammable and safe, but they are heavy and bulky, and consume a considerable amount of electricity. The power loss of a chiyoke coil consists of copper loss and iron loss, and the power loss of a 20W fluorescent lamp ballast reaches 6 to 6 watts. In recent years, power-saving light sources that are interchangeable with light bulbs have been developed and are becoming popular, by attaching light bulb caps to small fluorescent lamps. This light source incorporates a chiyoke coil as a ballast, but this makes the lamp heavy and large.
This is the reason why light bulbs cannot be replaced in many uses. Furthermore, when the life of the lamp reaches its end, the ballast, which is a block of iron and copper, must be discarded together with the lamp, which is not desirable from the standpoint of saving resources.

In addition, by lighting discharge lamps at high frequencies, electronic lighting circuits such as inverters and switching regulators were developed and began to be put into practical use as ballasts with smaller inductance, lighter weight, and lower losses. There is. Although the losses of this type of ballast are reduced compared to the chiyoke coil, they are still not negligible. Such electronic lighting circuits currently suffer from complexity and high cost.

There is also an example of a discharge lamp lighting device that uses a capacitor as a ballast for a commercial frequency AC power source. In this case, it is necessary to increase the capacitance of the capacitor to 10 microfarads or more, which inevitably increases the volume of the ballast. Although electrolytic capacitors are relatively compact, they generate heat and reduce efficiency due to dielectric loss. As a discharge lamp lighting device that uses a capacitor as a ballast and operates at a frequency higher than the commercial frequency, US Patent No.
There is a known example described in No. 3428862. In this known example, two discharge lamps are lit by one capacitor ballast, but since the capacitors are charged and discharged via different discharge lamps, each discharge lamp is lit by one capacitor ballast. However, this method has the disadvantage that there are periods in which the discharge is stopped alternately, resulting in a decrease in luminous efficiency.

[Purpose of the invention]

An object of the present invention is to obtain a small, lightweight, inexpensive, and highly efficient electronic lighting device, and in particular, to find a structure suitable for semiconductor integration in order to reduce the size and weight of the lighting device.

[Summary of the invention]

In order to eliminate inductance from an electronic lighting device for a discharge lamp and configure the electronic lighting device using a capacitor and a semiconductor switch, the power supply, capacitor, and discharge lamp are coupled through a plurality of semiconductor switches, and a control circuit is specified. According to the combination and order of the switching, the open/close state of the semiconductor switch changes in synchronization with the clock pulse, and the capacitor is periodically charged and discharged via the discharge lamp, resulting in an alternating current flowing through the discharge lamp. It turns on the lights.
Therefore, the present invention can be said to be an electronic lighting device using a capacitor as a ballast.

When considering the electric power P supplied to the discharge lamp by the discharge lamp lighting device of the present invention, the following results are obtained. If the power supply voltage is V, the capacitance of the ballast capacitor is C, the number of ballast capacitors connected in parallel is n, and the operating frequency is f, one capacitor is discharged during the previous half cycle. When charging through an electric lamp, 1/2 CV ² of energy is supplied to the discharge lamp, and in the next half cycle, when 1/2 CV ² of energy stored in the capacitor is discharged through the discharge lamp, 1
During the cycle, CV ² of energy is supplied to the discharge lamp. When the number of capacitors connected in parallel is n, the power P supplied to the discharge lamp is given by the following equation.

P=nfCV ^2In practice, when 20 watts of power is supplied by a capacitor ballast from a 100 volt supply at an operating frequency of 50 kilohertz, the capacitance of the capacitor is
0.04 microfarads.

As mentioned above, once the lamp power is applied and the power supply voltage and operating frequency are determined, the total capacitance of the capacitor as a ballast is determined, and the size of the capacitor is approximately determined. The capacitance of the capacitor can be reduced in inverse proportion to the operating frequency if the lamp power is kept constant. Therefore, by increasing the frequency, it is possible to downsize the ballast. Also, by changing the operating frequency, the lamp power can be varied while keeping the power supply voltage and ballast capacity constant. That is, dimming is possible by switching the operating frequency. Furthermore, when the brightness of the discharge lamp changes due to fluctuations in the power supply voltage, it is relatively easy to control the operation frequency so that a constant light output is obtained by changing the operating frequency according to the change in the power supply voltage.

The gist of the present invention is to include a DC power supply 101, a first semiconductor switch 111 having one end connected in series to the DC power supply 101, and a first semiconductor switch 111 having one end connected in series to the other end of the first semiconductor switch 111. a capacitor 105 provided at one end side of a discharge tube constituting a discharge lamp 103 connected in series to the other end of the capacitor 105;
A preheating current is passed until immediately before the start of discharge of the discharge lamp 103, and a discharge current is passed after the discharge of the discharge lamp 103 starts. a semiconductor switch 114;
The preheating current is provided at the other end of the discharge tube constituting the discharge lamp 103 which is connected in series to the other end of the second semiconductor switch 114, and the preheating current is applied immediately before the discharge of the discharge lamp 103 starts. After the discharge of the discharge lamp 103 starts, a second electrode b for passing the discharge current and a third semiconductor switch 112, one end of which is connected in series to the second electrode b, are connected. A ground potential is applied to the connection point between the second electrode b and the third semiconductor switch 112, and the other end of the third semiconductor switch 112 is connected to the other end of the first semiconductor switch 111. One end of the fourth semiconductor switch 113 is connected in series to the DC power supply 101, the other end of the fourth semiconductor switch 113 is connected in series to one end of the diode, and the other end of the fourth semiconductor switch 113 is connected in series to one end of the diode. is connected in series to the one end of the second semiconductor switch 114, and the diode is connected from the other end of the fourth semiconductor switch 113 to the second
The first semiconductor switch 114 is connected to be electrically conductive only to the one end side of the semiconductor switch 114, and while the second semiconductor switch 114 is always kept in a conductive state during preheating of the discharge lamp 103, the first semiconductor switch 1
The operation of making only the third semiconductor switch 11 conductive and the operation of making only the third semiconductor switch 112 conductive are repeated alternately, and when the discharge lamp 103 starts discharging, the fourth semiconductor switch
operating only the semiconductor switch 113 and the third semiconductor switch 112 to be conductive;
Subsequently, the first semiconductor switch 111
The discharge lamp 10 is operated so as to conduct only the discharge lamp 10.
3. After the start of the discharge, the operation of turning on only the first semiconductor switch 111 and the operation of turning on only the third semiconductor switch 112 are alternately repeated. It's in the device.

[Embodiments of the invention]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a first example of a discharge lamp lighting device according to the present invention.
In this figure, a is a circuit diagram when one discharge lamp, which is a fluorescent lamp, is lit using one capacitor ballast, b is a block diagram showing the control circuit of the above circuit, and c is a diagram showing an example of the above circuit. FIG. 3 is a waveform diagram showing the operation of the above circuit. The discharge lamp lighting device shown in FIG. It performs all of the preheating, application of starting voltage, and steady lighting operations. In the figure, 101 is a direct current or rectified power source, 102 is a control circuit for controlling opening of the switch, and 111 to 114 are switches made of semiconductors, such as bipolar transistors. The control circuit 102 includes an oscillator 1102 and a delay circuit 1, as shown in the block diagram of FIG.
022, a timer 1023, and a gate circuit 1024, and an oscillator 1021 generates a 50 kHz clock pulse having a voltage waveform shown in A in the waveform diagram of FIG. 1C. The clock pulse is sent to the delay circuit 10.
At step 22, the clock pulses are transformed into two-phase clock pulses shown in FIG. Since there is no on-overlapping period between these two sets of clock pulses, 2 in Figure 1a.
semiconductor switches 111,1 connected in series
12, 113, and 114 are conductive at the same time, and a large overcurrent does not flow from the power supply 101. The timer 1023 is composed of a monostable multivibrator, a shift register, etc., and determines the time to preheat electrodes a and b at startup, and the time for each semiconductor switch 111 after that.
The timing of the opening/closing operations of ~114 is determined. The gate circuit 1024 provides signals from the timer 1023 to the semiconductor switches 111 to 114 in order to control the respective semiconductor switches.
Outputs a signal with the waveform shown below. In the above figure, H is the waveform of the current flowing through the electrodes a and b when preheating the discharge lamp 103, and R in the figure is the lamp current waveform of the discharge lamp 103. In order to start the discharge lamp 103, a voltage with a waveform of G is applied to the semiconductor switch 114 to make it conductive, and a voltage of a waveform of G is applied to the semiconductor switch 113 and the semiconductor switch 111 is kept open.
and 112 are alternately opened and closed by applying voltages of waveforms D and E, respectively. semiconductor switch 1
When 11 is conductive and 112 is open, the current flows through the power supply 101 - semiconductor switch 111 - capacitor 10
5-electrode a-semiconductor switch 114-electrode b, semiconductor switch 111 is opened, and 112
conducts, current flows from capacitor 105 - semiconductor switch 112 - electrode b - semiconductor switch 1
14-Since it flows like electrode a, the discharge lamp 103
An alternating current flows through electrodes a and b, respectively, to preheat them. In FIG. 1c, the period during which these electrodes a and b are heated, _t1 is 0.1 to 1 second. In the next period, semiconductor switches 111 and 114 are opened, 112 and 113 are made conductive, and current flows from power supply 101 in the order of semiconductor switch 113 - electrode a - capacitor 105 - semiconductor switch 112, and capacitor 105 is turned on in the reverse order. After charging to the polarity, semiconductor switches 112, 113, 114 are opened and closed.
When only 11 is made conductive, a starting voltage equal to the sum of the voltage charged in the capacitor 105 and the power supply voltage, that is, approximately twice the power supply voltage, is applied to the discharge lamp 103, and the discharge lamp 103 starts discharging. Next, a steady lighting operation is started with the semiconductor switches 113 and 114 open, and the semiconductor switches 111 and 112 are alternately opened and closed. Semiconductor switch 111 conducts 112
When is open, the current flowing from the power source 101 flows from electrode a to b within the discharge lamp 103 via semiconductor switch 111 and capacitor 105, and when semiconductor switch 111 is open and 112 is conductive,
The charge accumulated in the capacitor 105 flows from the electrode b to the electrode a of the discharge lamp 103 via the semiconductor switch 112. This state is repeated and the discharge lamp 10
An alternating current flows between electrodes a and b in Figure 1, and
The lighting state shown at _t3 is maintained.

FIG. 2 is a diagram showing a reference example of the present invention, which is a discharge lamp lighting device in which one discharge lamp is lit using two capacitor ballasts. In this reference example, by using two capacitors 205 and 206, the starting voltage applied to the discharge lamp 203 can be increased to three times the power supply voltage. In FIG. 2, 201 is a direct current or rectified power source, 202 is a control circuit that instructs the opening/closing operation of semiconductor switches, and 211--
218 is a semiconductor switch, and 221 and 222 are diodes that prevent reverse current flow. To start the discharge lamp 203, the semiconductor switch 217 is made conductive, the semiconductor switch 218 is opened, and the other semiconductor switches are turned on to the first group 211, 214, 216 and the second group 212, 2.
13 and 215, and voltages having signal waveforms shown in D and E of FIG. 1C are applied from the control circuit 202 to the semiconductor switches of the first group and the second group,
The semiconductor switches of the first group and the second group are alternately turned on and off. When the first group of semiconductor switches conducts in the first half cycle, current flows from the power supply 201 to the semiconductor switch 211 - capacitor 205 - electrode a of the discharge lamp 203 - semiconductor switch 217 - electrode b of the discharge lamp 203 - semiconductor switch 216. flows, and when the second group of semiconductor switches conducts in the second half cycle, the power is supplied from the power supply 201 to the semiconductor switch 212 - capacitor 206 - electrode B - semiconductor switch 217 - electrode a - semiconductor switch 215.
Current flows to. On the other hand, the electric charge accumulated in the capacitor 205 causes a current to flow through the semiconductor switch 213-
Diode 211-electrode b-semiconductor switch 21
7 - Flows to electrode a. When the first group of semiconductor switches conducts in the next half cycle, the electric charge accumulated in the capacitor 206 together with the current of the first half cycle is transferred to the semiconductor switch 214 - the diode 222.
- Electrode a - Semiconductor switch 217 - Flows through electrode b. In this way, the electrodes a of the discharge lamp 203,
An alternating current flows through b, and both electrodes a and b are preheated. If the semiconductor switches 211, 213, 214, and 215 are made conductive and the semiconductor switches 212, 216, 217, and 218 are opened in a state where electrodes a and b are sufficiently preheated, the power will flow from the power supply 201 through the semiconductor switch 211 to the capacitor 205 and the semiconductor switch 215. A current flows to charge the capacitor 205, and a current flows from the semiconductor switch 211 to the semiconductor switch 213-diode 221-capacitor 206-semiconductor switch 214-diode 222-semiconductor switch 215, charging the capacitor 206 to the opposite polarity. do. After this charge has been sufficiently charged to reach the power supply voltage, the semiconductor switch 21
2 and 218 are made conductive by applying a voltage with the signal waveform shown in Fig. 1c, and when the other semiconductor switches are opened by applying a voltage with the signal waveform shown in Fig. 1c, the discharge occurs. A voltage three times the power supply voltage obtained by adding the power supply voltage to the voltage stored in the capacitor 205 and the voltage stored in the capacitor 206 is applied to the lamp 203, and the discharge lamp 203 starts discharging. After that, with the semiconductor switches 217 and 218 open,
If the first group and the second group of semiconductor switches are alternately turned on and off, when the first group is turned on in the first cycle, the power supply 201 is connected to the semiconductor switch 211 - capacitor 205 - electrode a - electrode b
- When current flows through semiconductor switch 216 and the second group becomes conductive in the next half cycle, current flows from power supply 201 to semiconductor switch 212 - capacitor 206 - electrode B - electrode A - semiconductor switch 215, and in the first half cycle The electric charge charged in the capacitor 205 flows as a current between the semiconductor switch 213, the diode 221, the electrode b, and the electrode a. Similarly, when the next first group becomes conductive, the electric charge charged in the capacitor 206 in the next half cycle is transferred as a current to the semiconductor switch 214 - diode 222 - electrode a - electrode b, together with the current when the first group becomes conductive. This is repeated to cause an alternating current to flow through the discharge lamp 203 and keep it lit.

The circuits shown in the above embodiments can be configured in various ways using semiconductor elements, one example of which is shown in FIG. FIG. 3 is a diagram illustrating a method of constructing a pair of two series-connected semiconductor switches, which is often used in FIG. 1a of the above embodiment. Since the power supply voltage or a voltage approximately twice that voltage is applied to each semiconductor switch, a withstand voltage of several hundred volts is required, but since the control circuit is composed of logic circuits, it is desirable to operate at a low voltage. The circuit shown in FIG. 3a is an example constructed of a photocoupler 7151 and a transistor 7152. An example of realizing a similar circuit using a directly connected circuit of transistors is the circuit shown in FIG. 3b, in which the semiconductor switch 715
3 is coupled to a control circuit by amplifying transistors 7154 and 7155. These circuits are suitable for constructing the present invention as an integrated circuit or a hybrid integrated circuit. It is also possible to construct the semiconductor switch using a field effect transistor, a silicon controlled rectifier, or the like.

〔Effect of the invention〕

As mentioned above, the discharge lamp lighting device of the present invention does not use an inductance, and is composed of a capacitor as a ballast, a semiconductor switch, and a control circuit that instructs the opening/closing operation of the semiconductor switch. Since the size of the discharge lamp is inversely proportional to the operating frequency, it is possible to significantly reduce the size and weight of the discharge lamp lighting device by lighting the discharge lamp at a high frequency and integrating the semiconductor switch into a silicon chip and miniaturizing it as an integrated or hybrid integrated circuit. can do. The chiyoke palast required to light a 20W fluorescent lamp at a conventional commercial frequency has a small volume.
It was 100 cubic centimeters and weighed 400 grams, but the equivalent discharge lamp lighting device of the present invention weighs 50
It operates at kilohertz and can have a volume of less than 10 cubic centimeters and a weight of less than 50 grams. Therefore, by providing the discharge lamp lighting device of the present invention in the base of the small fluorescent lamp, it is possible to reduce the size and weight of the fluorescent lamp.
Compared to inverters and switching regulators that are composed of individual parts and include a ferrite transformer as an inductance, this discharge lamp lighting device has a significantly simpler configuration, is smaller and lighter, and reduces manufacturing costs. , Since the operation of the circuit is simple, it is easy to analyze and design. In addition, the power loss of the capacitor ballast is negligibly small, and the transistor, which is an active element, also operates as a switch, so power loss is minimized and the efficiency is extremely high. While the power loss of a high frequency inverter with the same rated output is 3 to 4 watts, the power loss of the present discharge lamp lighting device is 2 watts. Since the power loss is small in this way, the temperature rise of the circuit components is low and reliability is high. Furthermore, since the power supplied to the discharge lamp from the present discharge lamp lighting device is approximately proportional to the operating frequency, the lamp power can be changed, that is, dimming can be performed by switching the operating frequency. In addition, since the operation at startup is determined by the sequence of the control circuit, including instant lighting,
For example, by storing an appropriate sequence in the control circuit, programs that are difficult to implement with other lighting methods, such as measures for discharging lamps that have reached the end of their lifespan or protective measures in the event of an abnormality, can be executed. Furthermore, since the power supply, switch, and discharge lamp are connected in series through a capacitor, the capacitor often shares the entire voltage even in the event of an abnormality, providing excellent safety. Conventional chiyoke coils require 50 to 50% of the lamp voltage to light a discharge lamp.
Although a 100% increase in power supply voltage is required, this discharge lamp lighting device can be lit with a low power supply voltage that is 25 to 30% higher than the lamp voltage because the voltage shared by the capacitor ballast is low. Furthermore, since the lamp voltage can be increased with a constant power supply voltage, efficiency can be increased.

As described above, the present invention comprises an electronic lighting circuit for a discharge lamp using a capacitor, a semiconductor switch, and a control circuit for instructing the opening/closing operation of the semiconductor switch, thereby reducing the size and weight of the discharge lamp lighting device.
Through integration, it has many remarkable effects such as cost reduction, improved efficiency, improved reliability, low voltage lighting, dimming, instant lighting, and improved safety.

Although the above embodiments have been described with respect to fluorescent lamps, the present invention can also be implemented with respect to other discharge lamps.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a first embodiment of a discharge lamp lighting device according to the present invention, and a is a circuit diagram when one discharge lamp is lit using one capacitor ballast;
b is a block diagram showing the contents of the control circuit 102 of the above circuit; c is a waveform diagram showing the operation of the above circuit;
The figure shows a reference example of the present invention, and is a circuit diagram when one discharge lamp is lit using two capacitor ballasts. Figure 3 is a diagram showing an example of the configuration of a circuit using semiconductor elements. Here, a is an example of a circuit connected by a photo coupler, and b is an example of a directly connected circuit of transistors. 101,201...power supply, 103,203...
Discharge lamp, 105, 205, 206,... Capacitor ballast, 111-114, 211-218...
Semiconductor switch, a, b... electrode, c... auxiliary electrode.

Claims (1)

[Claims] 1. A DC power supply 101, a first semiconductor switch 111 whose one end is connected in series to the DC power supply 101, and whose one end is connected in series to the other end of the first semiconductor switch 111. capacitor 10
5 and one end of the discharge tube constituting the discharge lamp 103 connected in series to the other end of the capacitor 105, and a preheating current is applied until just before the discharge of the discharge lamp 103 starts;
After the discharge of the discharge lamp 103 starts, a first electrode a for passing a discharge current and a second semiconductor switch 1 connected in series to the first electrode a are connected to one end of the first electrode a.
14 and the other end of the discharge tube constituting the discharge lamp 103 connected in series to the other end of the second semiconductor switch 114, and immediately before the discharge of the discharge lamp 103 starts. A second electrode b for passing the preheating current and passing the discharge current after the start of discharge of the discharge lamp 103, and a third semiconductor switch, one end of which is connected in series to the second electrode b. 112, a ground potential is applied to the connection point between the second electrode b and the third semiconductor switch 112, and the third semiconductor switch 11
The other end of the fourth semiconductor switch 113 is connected in series to the other end of the first semiconductor switch 111, and one end of the fourth semiconductor switch 113 is connected in series to the DC power supply 101. one end of the diode is connected in series to one end of the diode, the other end of the diode is connected in series to the one end of the second semiconductor switch 114, and the diode is connected from the other end of the fourth semiconductor switch 113 to the The discharge lamp 103 is electrically connected only to the one end side of the second semiconductor switch 114.
When preheating, the second semiconductor switch 114
The operation of only conducting the first semiconductor switch 111 and the operation of conducting only the third semiconductor switch 112 are alternately repeated while maintaining the switch 111 in a conductive state at all times, and when the discharge lamp 103 starts discharging, the fourth semiconductor switch operating only the semiconductor switch 113 and the third semiconductor switch 112 to conduct, and subsequently operating only the first semiconductor switch 111 to conduct,
After the discharge starts in the discharge lamp 103, the operation of turning on only the first semiconductor switch 111 and the operation of turning on only the third semiconductor switch 112 are alternately repeated. Discharge lamp lighting device.