JPH0261114B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a half-cycle lighting device for lighting a high-pressure vapor discharge lamp having a lamp voltage approximately equal to the power supply voltage using a switching circuit.
Among these, the present invention relates to loss reduction in a lighting device in which a switching circuit is connected to an intermediate tap of a choke coil used as a ballast.

[Background of the invention]

The half-cycle lighting method, which aims to reduce the size, weight, and power consumption of discharge lamp lighting devices, uses a chiyoke coil without boosting the voltage using a transformer when the lamp voltage of the lamp being lit is close to the power supply voltage. This is a method of lighting using a switching circuit.
In this type of lighting device, the switching circuit is usually connected in parallel with the lamp, but since high voltage pulses are applied to the switching circuit when starting and lighting the lamp, the switching circuit has a high withstand voltage of around 1,000 volts. Constructed using switch elements. Therefore, the cost of the lighting device becomes extremely high, which is a drawback in terms of product quality.

As a conventional example for reducing the voltage applied to the switching circuit, there is a discharge lamp lighting device described in Japanese Patent Application Laid-Open No. 132566/1983. The circuit configuration of this conventional example is shown in FIG. The operation of this voltage is to turn on the switch element 7 once every half cycle during a certain period in the first half of each half cycle of the AC power supply 1, and during this on period, the voltage on the AC power supply 1 side is increased from the intermediate tap of the inductance 2. Energy is stored in the winding 4, and the stored energy is superimposed on the AC power supply 1 and applied to the discharge lamp 3 while the switch element 7 is off, thereby lighting the discharge lamp 3 steadily.

In this operation, the ignition pulse for starting and lighting the lamp 3 is generated across the choke coil 2, but this voltage is divided into the turns ratio of the winding 4 and the winding 5, and the ignition pulse is generated across the switching circuit terminals A, B. In between, the voltage of the winding 4 is superimposed on the voltage of the AC power supply 1. Therefore, the voltage between terminals A and B is
The smaller the ratio of the winding 4, the lower the voltage.

By the way, in order for the lighting circuit shown in FIG. 1 to operate normally, the turn-on trigger signal of the switch element 7 must be set at the time when the lamp current or input current becomes 0 or when the voltage value of the power supply 1 reaches a predetermined value. Occurs when the time is detected. These methods have no problem when the lamp voltage is close to constant, such as in a fluorescent lamp. However, in the case of high-pressure vapor discharge lamps such as metal halide lamps and high-pressure sodium lamps, most of the lamps are short-circuited in the initial stage of lighting, which causes trouble in the circuit operation of the switch element 7.

FIG. 4 shows current and voltage waveforms at the initial stage of lighting of the high-pressure steam discharge lamp. This figure shows the operating waveforms with the switching circuit removed. As is clear from this figure, at time t ₂ when the input current I ₁ is 0 (this time t ₂ coincides with the time when the lamp current becomes 0), there is a voltage of V _{t 2} between terminals A and B of the switching circuit. This means that this is occurring. On the other hand, a connecting capacitor 13' is connected between the terminals A and B for stabilizing distributed capacitance or switching characteristics. Therefore, when the switch element 7 is turned on at time _t2 , a discharge current of the connection capacitor 13' flows,
This causes a loss in the switch element 7, resulting in heat generation and
This may even cause destruction. Also, the lamp current I ₁
The phase at time _t2 when 0 becomes 0 changes gradually as the lamp impedance increases, so the power supply voltage
The same problem occurs when detecting V ₁ and triggering the switch element 7.

[Purpose of the invention]

Therefore, the object of the present invention is to provide a low cost and
An object of the present invention is to provide a highly reliable half-cycle lighting device for a high-pressure steam discharge lamp.

[Summary of the invention]

In order to achieve the above object, in the present invention,
In the lighting device configured as described above, the switching circuit is configured to turn on when the voltage across the switching circuit is approximately zero, and turn off when the current flowing through the switching circuit reaches a predetermined value. It is characterized by a lighting device that operates every half cycle.

This characteristic configuration of the present invention makes it possible to eliminate inrush current from the parallel connection capacitance to the switching circuit at turn-on during the entire lighting period from the initial lighting stage to steady lighting. the result,
The loss of the switching circuit is reduced, and the configuration of the switching circuit is also simplified. In other words, the present invention makes it possible to provide a low-cost and highly reliable lighting device for high-pressure steam discharge lamps every half cycle.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 2 shows the circuit configuration of the switching circuit portion of the half-cycle lighting device for a high-pressure steam discharge lamp according to the present invention. This switching circuit is used by connecting the C and D terminals to the C and D terminals in FIG. 1 in place of the transistor 7. In the figure, a switch element 7 uses a transistor, but other switch elements such as a power MOSFET or a gate turn-off SCR may also be used. Reference numeral 11 denotes a voltage sensitive switch such as an SBS, which is a switch element that turns on when a voltage of about 8V is applied across it, for example. 12 is an avalanche diode for protecting the transistor 7.

Next, the operation of this switching circuit will be explained with reference to the voltage and current waveforms shown in FIGS. 5A and 6B and FIGS. 6A and 6B. When the AC power supply 1 shown in FIG. 1 is turned on, the voltage is applied to the winding 4 of the
The signal is full-wave rectified by the full-wave rectifier 6, and is generated between terminals C and D in FIG. At this point, the voltage sensitive switch 11 is in the off state, so the transistor 7 is turned on through the resistor 10, and the connection between the C and D terminals is in the on state, and the winding 4 of the choke coil 2 is turned on.
A progressively increasing current flows through. As a result, the voltage of the resistor 9 gradually increases, and the base terminal voltage of the transistor 7 increases accordingly. When the current reaches a predetermined value, the voltage sensitive switch 11 is turned on, and the base current of the transistor 7 is no longer supplied. Therefore, the transistor 7 is turned off, and the terminals C and D are turned off. As a result, a pulse voltage is generated between the A and B terminals, and this voltage is stepped up to a value determined by the turns ratio of the choke coil 2 and is applied to the lamp 3 to start it.

As a result, the impedance of the lamp 3 decreases, and a current having a value close to the short-circuit current across the lamp flows. The waveforms of various parts in this state are shown in Figure 5 A and B. Figure A shows the input voltage V ₁ and the voltage V _AB between A and B terminals.
The figure (b) shows the input current _I1 and the switching current _IAB flowing between the A and B terminals, respectively. In this state, it is possible to continue lighting even if the switching circuit does not work, but the switching circuit continues to operate. That is, the voltage sensitive switch 11 continues to be in the on state after the previous cutoff operation. Then, at time t ₁ , the voltage V _AB between the A and B terminals becomes 0,
Since the current flowing through the voltage sensitive switch 11 becomes less than the holding current value, the voltage sensitive switch 11 is turned off. As a result, the continuously applied voltage drives the transistor 7 through the resistor 10 and turns it on. Since the voltage V _AB between the A and B terminals immediately before this time t ₁ is approximately 0, the discharge current of the connected capacitor 13' does not flow through the transistor (switch) 7 in a pulsed manner. And time t ₁ - _{t 2}
During this period, the switching current I _AB flows in a triangular waveform, but the input current I ₁ is a reverse current flowing during this period, and the switching current I _AB is superimposed, resulting in a discontinuous waveform. Then, a pulse is generated at time _t2 , but this is unnecessary. Then, the polarity of the input current _I1 is reversed at time _t3 , the switching circuit operates from time _t4 to time _t5 , and the above operation is repeated, gradually increasing the arc temperature of the lamp 3, The voltage continues to rise. In this state, the lamp current has a waveform obtained by subtracting the switching current _IAB component from the input current _I1 , and flows throughout the entire period without any rest period.

Waveforms in a state where the arc temperature of the lamp 3 rises and the discharge voltage becomes high are shown in FIGS. 6A and 6B. Figure A shows the power supply voltage _V1 and the terminal A of the switching circuit.
The waveform of the voltage between B and V _AB is shown. Figure B shows the input current.
The waveform of I ₁ and the current I _AB flowing between terminals A and B of the switching circuit is shown. At time t ₁ with the waveform of input current I ₁
~ t ₃ , times t ₄ ~ _{t 6} , and so on become lamp current.
Even during the period from time _t3 to _t4 , time _t6 to _t7 ,...
Depending on the ratio of the number of turns of the lamp 3, the voltage across the lamp 3 may rise above its discharge voltage, and a discharge current may flow.

In this case, the voltage V _AB between the A and B terminals decreases to nearly 0 at time t ₃ before the previous half cycle of discharge ends. As a result, the current of the voltage sensitive switch (SBS) 11 flowing through the resistor 10 decreases below the holding current, and the voltage sensitive switch 11 is turned off. Since the voltage of the power supply voltage V ₁ at this point is not 0, the base of the transistor 7 is immediately driven through the resistor 10, and the terminals A and B are immediately turned on. As a result, the switching circuit current _IAB flows as shown by the broken line during the period from time _t3 to _{time t4} . Then, at time _t4 when the switching current _IAB reaches a predetermined current value, the base end potential of the transistor 7 reaches the breakover voltage of the voltage sensitive switch 11, the voltage sensitive switch 11 is turned on, and the base current of the transistor 7 increases. becomes 0,
The A and B terminals are in an off state. So, time t ₄
, a high voltage pulse is generated, the lamp 3 is re-ignited, and the lamp 3 continues to receive an input current I ₁ from time t ₄ to _{t 6}
The same current flows. Then, at time _t6 , the voltage V _AB between the A and B terminals decreases, causing the voltage sensitive switch 1 to
1 is turned off, and as a result, the terminals A and B are turned on, and the above operation is repeated again. By repeating this operation, steady lighting is performed.

In this operation, the discharge voltage of the lamp 3 is
Since it becomes equal to the value of the power supply voltage V ₁ , the phase at time t ₃ has moved to just before the input current I ₁ becomes 0, and the pulse generation phase definitely matches the inversion phase of the lamp discharge polarity. The normal operation is to turn on the light every half cycle. Further, in this case as well, since the transistor 7 is turned off when the voltage V _AB between the A and B terminals is 0, a rush current due to the discharge of the connected capacitor 13' does not flow, and normal operation is performed.

The transition process from the low impedance state of the lamp 3 shown in FIGS. 5A and 5B to the high impedance state of the lamp 3 shown in FIGS. 6A and 6B is an operation in which the input current _I1 gradually shifts. Therefore, as the impedance of the lamp 3 increases, the cut-off time of the switching current I _AB moves to a time after the half-cycle of the input current I ₁ has finished flowing, and this becomes a restriking pulse, so that the lamp returns to a steady state. Lamp 3 does not go out during the transition process.

FIG. 3 shows the configuration of a switching circuit portion in another embodiment of the present invention. In this configuration, in order to make it possible to generate a voltage of several hundred to several thousand volts necessary for starting the lamp 3, the switch element is further connected in series with the transistor 71 and an SCR 72. Of course, the transistor 71 and the SCR 72 may be other switch elements such as a power MOSFET. In order to ensure the operation of this switching circuit, a capacitor 13 was connected between the A and B terminals. Reference numerals 121 and 122 are avalanche diodes for protecting the transistor 71 and the SCR 72, and a circuit consisting of a diode 14, a capacitor 15, a diode 16, and a resistor 17 is provided to limit the current cutoff operation to once in each half cycle. This is a circuit with a

Since the lighting operation of this switching circuit is almost the same as that shown in FIG. 2, only the main points will be described. When the voltage between the A and B terminals approaches 0, the voltage sensitive switch 11 turns off, and then the transistor 71 and SCR 72 are triggered through the resistors 101 and 102 to turn on, and the A and B terminals are turned on. Then, when the switching current I _AB reaches a predetermined value, the voltage sensitive switch 11 is turned on and the transistor 71 is turned off. Therefore, the switching current _IAB is commutated to the capacitor 13, and this voltage gradually increases. During this time, the cathode current in SCR72 is 0.
Therefore, a gate turn-off trigger current flows from the gate of the SCR 72 through the resistor 102 and then the voltage sensitive switch 11. As a result, the SCR 72 is turned off during the period from when the transistor 71 is turned off until the voltage across it reaches the avalanche voltage of the avalanche diode 121. This completes the turn-off operation between the A and B terminals, but in order for the SCR72 to turn off reliably, the voltage value between the A and B terminals must be equal to or higher than the avalanche voltage of the avalanche diode 121 within the turn-off recovery time of the SCR72. It is necessary to set the capacitance value of the capacitor 13 so that this does not occur. In this case, the inrush winding caused by the discharge of the capacitor 13 during turn-on becomes a particularly serious problem.

Normally, the pulse voltage generated by the turn-off operation oscillates, and when this backswing crosses the 0 point, the voltage sensitive switch 11 is turned off, and the A and B terminals are turned on again to perform a current cutoff operation. A circuit consisting of a diode 14, a capacitor 15, a diode 16, and a resistor 17 is a circuit for preventing this re-operation. That is, the voltage generated by the resistor 9 just before the transistor 71 is turned off is transferred to the capacitor 1 through the diode 14.
It is charged to 5. And the transistor 71,
After the SCR 72 is turned off, the discharge current of the capacitor 13 flows through the voltage sensitive switch 11 through the diode 16 and the resistor 17 for a while, and the current of the voltage sensitive switch 11 is maintained at the holding current value or higher even when the above-mentioned backswing occurs. Thereby, multiple cut-off operations can be reliably prevented. Furthermore, by connecting the capacitor 5, the voltage generated across the resistor 9 when a rush current flows during turn-on is absorbed by the diode 14, thereby ensuring that malfunctions such as turning off the terminals A and B due to the turn-on of the voltage sensitive switch 11 immediately after turn-on are ensured. can be prevented. The configuration of this circuit part is also effective for general discharge lamps such as fluorescent lamps, and the same effect can be obtained even when terminals A and B in Fig. 3 are connected to both ends of a general discharge lamp. , it is clear from the above operation description.

〔Effect of the invention〕

According to the present invention, in a half-cycle lighting device for lighting a high-pressure steam discharge lamp via a choke coil using an intermediate tap, the switching circuit connected between the intermediate tap and the end of the AC power supply on the non-tidal coil side is reset, and The subsequent turn-on operation is performed by detecting the voltage across both ends of the lamp, so that the parallel capacitance at turn-on of the switching circuit is Since inrush current due to discharge can be eliminated, highly reliable switching circuit operation can be expected. In particular, the switching circuit required for steady operation of a high-pressure steam discharge lamp requires an interruption current on the order of amperes, and the loss caused by this operation is quite large. Therefore, it is particularly important from the viewpoint of reliability to prevent inrush current from the parallel capacitor and to keep the loss of the switch element small. Also, this configuration is very simple,
The disadvantage that discharge lamp lighting circuits using semiconductor circuits are more expensive than conventional leaky transformer type circuits can be solved at once.

[Brief explanation of drawings]

FIG. 1 is a basic configuration diagram of a conventional half-cycle lighting device for a discharge lamp, and FIGS. 2 and 3 are circuit configuration diagrams of a switching circuit portion of a half-cycle lighting device for a high-pressure steam discharge lamp according to the present invention, respectively. Figure 4 is a voltage and current waveform diagram at the initial stage of lighting in the lighting device shown in Figure 1, Figure 5 A and B are voltage and current waveform diagrams at the time of starting in the lighting device shown in Figure 2, and Figure 6 I. , B are voltage and current waveform diagrams during steady lighting in the lighting device shown in FIG. 2, respectively. DESCRIPTION OF SYMBOLS 1...AC power supply, 2...Choice coil with intermediate tap consisting of windings 4 and 5, 3...High pressure steam discharge lamp, 6...Full wave rectifier, 7, 71, 72...Semiconductor switch element with control pole, 11... Voltage sensitive switch, 12, 121, 122... Avalanche diode, 8, 14, 16... Diode, 1
3, 13', 15... Capacitor, 10, 101,
102, 9, 17...Resistance.

Claims (1)

[Claims] 1. An AC power supply, a chiyoke coil, and a high-pressure steam discharge lamp having a discharge voltage value around the voltage value of the AC power supply are connected in series, and an intermediate tap provided on the chiyoke coil is connected between the end of the non-chyoke coil of the AC power supply. Turns on once every half cycle of the lighting cycle.
It is formed by connecting a switching circuit that performs an OFF operation, and turns on when the voltage across the switching circuit is approximately zero, and turns off when the current flowing through the switching circuit reaches a predetermined value. A half-cycle lighting device for a high-pressure steam discharge lamp, characterized in that the switching circuit described above is configured.