JPS644320B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a constant input lighting device for a discharge lamp that can control the input current of the discharge lamp to be constant from immediately after the discharge lamp is started until it shifts to the rated lighting state.

discharge lamps, which generally have a high vapor pressure during lighting;
For example, when starting and lighting a mercury lamp or a high-pressure sodium lamp, the impedance of the discharge lamp is extremely low immediately after starting, and the impedance of the discharge lamp increases as the vapor pressure of the discharge lamp increases. , becomes constant in the rated lighting condition. For this reason, if the inductive reactance that limits the tube current of the discharge lamp is constant, a larger tube current will flow through the inductive reactance during the transition from the starting state to the lighting state than during rated lighting. Therefore, the input current from the power source also increases during this starting period, and therefore it is necessary to increase the current capacity of the electric wire.

Conventionally, it is necessary to suppress the input current during the starting period to the same level or lower than that during rated lighting, so a capacitor is connected between the input wires, a large phase-advanced current flows during the starting period, the input current is limited, and the rated A method is known in which this capacitor is disconnected during lighting to realize constant input lighting. However, this method requires a capacitor and its connection switch, and has the disadvantage that the lighting device inevitably becomes larger. On the other hand, in order to eliminate this drawback of increasing the size, an AC control element is connected in series with the inductive reactance, and the conduction angle is controlled according to the phase of the current flowing through the inductive reactance, that is, the phase of the tube current. There is a way to achieve this.

This method utilizes the property that the phase of the tube current advances as the lamp reaches its rated lighting, since the impedance of the discharge lamp increases from just after starting until it reaches its rated lighting. In other words, when the phase of the tube current lags significantly behind the power supply voltage, it is determined that the initial stage of startup is occurring, the conduction phase angle of the AC control element is increased to throttle the tube current, and then as the phase of the tube current progresses, the conduction begins. The phase angle is made smaller. Figure 1 shows the on-phase angle (hereinafter referred to as T) representing the delayed phase angle of tube current I _l with respect to the phase of this power supply voltage V _S and the off-phase angle (hereinafter referred to as ΔT) representing the off period of the AC control element. Indicates the relationship between
FIG. 2 shows an example of such a constant input lighting circuit. The circuit constants are V _S = 200V, C _S = 25μF, L ₁ =
126V/3.3A, L ₂ = 68V/0.375A, C ₀ = 0.22μF,
R ₀ =120Ω. Discharge lamp F was a 400W mercury lamp with a tube voltage of 130V. T-ΔT in this figure 1
The relationship shown in FIG. 2 is the relationship when the input current _IS is constant at 2.3A and is controlled at a constant input.

The operation of the conventional example shown in FIG. 2 will be explained below. FIG. 3 is a waveform diagram of each part of the circuit shown in FIG. 2. Inside the frame is a circuit for generating a reference voltage waveform that is a certain phase ahead of the power supply voltage. A voltage waveform V _R1 shown in FIG. 3b is obtained across the resistor R ₁ . The area within the frame is the tube current phase detection section, and when the tube current commutates, a power supply voltage appears across the triax _Q0 , which is an AC control element, and the pulse transformer T1,
A voltage is developed across the resistor _R2 through the rectifier stack DB1, turning on the transistor _Q1 and turning off the transistor _Q2 , charging the capacitor _C1 through the resistor _R3 . The voltage across capacitor _C1, V _C1 , is shown in Figure 3c.
Shown below. When this voltage is equal to the reference voltage
PUT (Programmable Union Transistor) S ₀ turns on, and transistor Q ₃ turns on at time t ₂ ,
Turns on at t ₅ . At this time, the charge in the capacitor _C2 is discharged through the transistor _Q3 , and a trigger pulse V _T is obtained on the secondary side of the pulse transformer T2 as shown in FIG. 3d. This operation is repeated every half cycle. Therefore, as the tube current phase progresses, the tube operates so that ΔT becomes smaller as shown in FIG. 3c.

However, in such a conventional circuit, the capacitor C ₁ is used to determine the off-phase angle ΔT.
Therefore, if there are variations in the values of the capacitor _C1 and its charging resistor _R3 , the operating point of the circuit will also change and the value of the off-phase angle ΔT with respect to the on-phase angle T will vary. This resulted in a problem that caused a major hindrance to mass production. The present invention has been made to solve these problems of the conventional example, and even if there is variation in the value of the capacitor for determining the magnitude of the off-phase angle ΔT, the off-phase with respect to the on-phase angle T The object of the present invention is to provide a discharge lamp constant input lighting device in which the value of the angle ΔT does not fluctuate.

The configuration of the present invention will be described below with reference to illustrated embodiments. Figures 4a and 4b show circuit diagrams of an embodiment of the invention. First, in FIG. 4a, 1 is a zero-cross detection circuit that detects the zero-crossing point of the power supply voltage.The AC power supply voltage _Vs is full-wave rectified by the rectifier stack DB2, and the transistor _Q4 is connected through the resistors _R4 and _R5 . Although it is always on,
It is turned off only when the AC power supply voltage _Vs becomes zero, and the collector of the transistor _Q4 is set to the H level to generate a zero-cross detection signal as shown in FIG. 5b. Next, 2 is a commutation phase detection circuit, and when the tube current of the discharge lamp F is commutated and the AC control element Q ₀ is turned off, the AC control element Q ₀ is turned off.
Since the power supply voltage appears at both ends of the voltage, the pulse transformer T1 detects the sudden voltage change, and full-wave rectification is performed by the rectifier stack DB1 to turn on the transistor _Q1 , thereby lowering the collector potential of the transistor _Q1 to the L level. Drop it into the knot circuit
By taking the negative logic at _N1 , a commutation detection pulse as shown in FIG. 5d is output. Furthermore, 3 is a trigger pulse generation circuit for the AC control element _Q0 , and when the base potential of the transistor _Q3 reaches the H level, the electric charge stored in the capacitor _C2 is passed between the collector and emitter of the transistor _Q3 . By discharging, a trigger pulse is generated on the secondary side of the pulse transformer T2 to turn on the AC control element _Q0 .

A timing control circuit 4 as shown in FIG. 4b is connected to frame A in FIG. 4a. In the figure, reference numeral 5 denotes a Miller integration circuit, which is comprised of an amplifier circuit 6 with a sufficiently large degree of amplification, a capacitor C and a resistor R that determine an integration time constant.
Reference numerals 7 and 8 designate changeover switches, which are controlled by switch control circuits 9 ₁ and 9 ₂ to connect a positive power source 10 or a negative power source 11 to the input side of the Miller integrating circuit 5 as appropriate. When the zero-crossing detection circuit 1 generates a zero-crossing signal as shown in FIG. 5b at time _t0 , the changeover switch 7 is turned on as shown in FIG. Connected to 5. Therefore, the output voltage of the Miller integration circuit 5 is as shown in FIG.
As shown in , it increases almost linearly. Next, the time
When the commutation phase detection signal shown in FIG. 5d is output from the commutation phase detection circuit 2 at _t1 , the changeover switch 7 is turned off and the changeover switch 8 is turned on. As a result, the negative power supply 11 is connected to the Miller integrating circuit 5 instead of the positive power supply 10, so that the output voltage of the Miller integrating circuit 5 decreases almost linearly as shown in FIG. 5f. However,
The output voltage of the Miller integrating circuit 5 is compared with the ground potential (that is, 0 volts) by the comparator 12, and when the output voltage of the Miller integrating circuit 5 becomes 0 volts, the output of the comparator 12 is as shown in FIG. It becomes H level as shown in . As a result, the trigger pulse generating circuit 3 outputs _a trigger pulse as shown in FIG. This detection output closes the changeover switch 8 and stops applying the voltage V ₂ of the negative power supply 11 to the Miller integrating circuit 5. Since the same operation is repeated thereafter, the off-phase angle ΔT of the AC control element Q ₀ increases almost proportionally as the on-phase angle T increases. By the way, since the circuit of the present invention also uses a capacitor C and a resistor R in the Miller integrating circuit 5,
If there are variations in the values of these circuit elements, the rate of rise and fall of the terminal voltage of the capacitor C will also change. However, in the present invention, as shown in FIG. 6, when the time constant of the circuit element is small, instead of the terminal voltage Vc of the capacitor C rising rapidly, the terminal voltage Vc also falls rapidly. When the time constant of the circuit element is large, instead of the terminal voltage Vc of the capacitor C rising slowly, the terminal voltage Vc also falls slowly. Therefore, even if there are variations in the values of the circuit elements, those variations are canceled out during the charging and discharging process of the capacitor C, and the relationship between the on-phase angle T and the off-phase angle ΔT is exclusively determined by the voltage V ₁ of the positive power supply 10 and the negative power supply 10. 11 voltage V ₂
If this voltage ratio is set to k=V ₁ /V ₂ , then the relationship ΔT=kT holds true. In other words, even if the voltage values V ₁ and V ₂ themselves vary slightly, if the voltage ratio k = V ₁ /V ₂ is constant, the relationship between the on-phase angle T and the off-phase angle ΔT satisfies the proportional equation ΔT = kT. I will do it.
Since the voltage ratio k can be set relatively precisely compared to the capacitance value of the capacitor C, variations in characteristics from design values can be suppressed even during mass production.

Next, FIGS. 7a and 7b show circuit diagrams of an embodiment of the combined invention. In this combined invention, a positive current source 13 and a negative current source 14 are used in place of the above-mentioned positive power source 10 and negative power source 11, and a charging/discharging capacitor 15 is used in place of the Miller integrating circuit 5. be. In FIG. 7a, 1 is a zero-crossing detection circuit for detecting the zero-crossing point of the power supply voltage, and outputs a zero-crossing detection pulse as shown in FIG. 5b. Further, 2 is a commutation phase detection circuit, which outputs a commutation detection pulse as shown in FIG. 5d when the AC control element _Q0 is turned on or turned off. Furthermore, 3 is a trigger pulse generation circuit, and a comparator 12
When the output rises to H level as shown in Fig. 5g, Fig. 5h for AC control element _Q0 .
It sends out a trigger pulse as shown in the figure below. Next, in FIG. 7b, 7 and 8 are changeover switches, which, like the changeover switches 7 and 8 in FIG. 4b, are turned on at the timings shown in FIGS. 5c and 5e. When the changeover switch 7 is turned on, a charging current flows from the voltage source V _CC to the capacitor 15 via the positive current source 13, and the terminal voltage of the capacitor 15 becomes approximately linear as shown in FIG. 5f. to rise. Next, when the AC control element _Q0 is turned off at time _t1 , a commutation detection pulse is output from the commutation phase detection circuit 2, and the changeover switch 7 is turned off, as shown in FIG. 5d. The changeover switch 8 is turned on. As a result, the charge in the capacitor 15 is discharged by the current _I2 of the negative current source 14, so that the terminal voltage thereof falls almost linearly as shown in FIG. 5f. By the way, the terminal voltage of this capacitor 15 is compared with the ground potential (that is, 0 volts) by the comparator 12.
When the terminal voltage of the capacitor 15 drops to 0 volts, the output of the comparator 12 rises to the H level as shown in FIG. A trigger pulse is output. When the AC control element _Q0 is turned on, a detection pulse is outputted from the commutation phase detection circuit 2 as shown in FIG. 5d, and the changeover switch 8 is turned off. By the way, since the ratio between the charging time and the discharging time of the capacitor 15 is determined by the ratio of the currents I ₁ and I ₂ flowing through the positive and negative current sources 13 and 14, the ON phase angle T and the OFF phase angle of the AC control element Q ₀ are The ratio to the phase angle ΔT does not change even if the value of the capacitor 15 varies, and is determined only by the ratio between the charging current I ₁ and the discharging current I ₂ . In order to keep the ratio of charging current I ₁ and discharging current I ₂ constant, a constant current circuit as shown in FIG. 8 may be used, in which terminal 16 is connected to voltage source V _CC and terminal 17 18 may be connected to the capacitor 15 via the changeover switches 7 and 8, respectively.

As described above, in the present invention, a voltage integration circuit is provided that integrates the output voltages of the first power supply and the second power supply, which have opposite polarities to each other, and the first power supply is connected to the voltage integration circuit when zero crossing of the AC power supply voltage is detected. Then, when the AC control element is detected to be off, the second power supply is switched and connected to the voltage integration circuit, and the AC control element is turned on when the output of the voltage integration circuit returns to the voltage value before connecting the first power supply. Since the configuration is configured, calculate the ratio of the on-phase angle T from the zero-crossing point of the AC power supply voltage until the AC control element turns off, and the off-phase angle ΔT from when the AC control element turns off until it turns on again to the first power supply. It can be determined by the ratio of the voltage value with the second power supply, and even if there is a slight variation in the integration characteristics of the voltage integration circuit, the variation will be reduced to the proportional relationship between the on-phase angle T and the off-phase angle ΔT. This does not occur and has the advantage that characteristics as designed can be obtained. In addition, in the combined invention, a capacitor is provided that is charged and discharged by the output currents of the first current source and the second current source whose current directions are opposite to each other, and when the zero cross of the AC power supply voltage is detected, the first current source is The second current source is connected to the capacitor when the AC control element is detected to be off, and the AC control element is turned on when the terminal voltage of the capacitor returns to the voltage value before connecting the first current source. Therefore, the ratio of the on-phase angle T to the off-phase angle ΔT is different from that of the first current source and the second current source.
It can be determined by the ratio of current to the current source. Therefore, even if a capacitor with a large variation in capacitance value is used, as long as the current ratio is constant, the on phase angle T and the off phase angle ΔT can be determined. This has the advantage that the ratio can be kept constant, and that highly accurate constant input lighting of the discharge lamp can be performed using an inexpensive capacitor whose capacitance value is not guaranteed.

[Brief explanation of drawings]

Figures 1a and b are explanatory diagrams of the operation of the conventional example, Figure 2 is the overall circuit diagram of the same as the above, Figures 3a to d are diagrams showing voltage and current waveforms of each part of the same as the above, and Figures 4a and b are the main circuit diagrams of the conventional example. A circuit diagram of an embodiment of the invention, FIGS. 5a to 5h are diagrams showing voltage and current waveforms of each part of the same as above, FIG. 6 is an explanatory diagram of the operation of the same as above, and FIGS. 7a and b are an embodiment of the combined invention FIG. 8 is a circuit diagram showing an example of a current source used in the same. 1 is a zero cross detection circuit, 2 is a commutation phase detection circuit, 3 is a trigger pulse detection circuit, 5 is a Miller integration circuit, 7 and 8 are changeover switches, 10 is a positive power supply, 1
1 is a negative power supply, 12 is a comparator, 13 is a positive current source, 1
4 is a negative current source, and 15 is a capacitor.

Claims (1)

[Claims] 1. A zero-cross detection circuit that connects an AC control element, a current limiting inductance, and a discharge lamp in series to an AC power supply, and detects the zero-cross point of the AC power supply voltage, and a converter that detects the on-off point of the AC control element. A current phase detection circuit is provided, and the off-phase angle ΔT from when the AC control element is turned off until it is turned on again is determined according to the on-phase angle T from the zero-cross point of the AC power supply voltage until the AC control element is turned off. In a discharge lamp constant input lighting device that is equipped with a control circuit that controls the linear approximation formula ΔT=kT so that the proportionality constant k is positive, the voltage value is set so that the proportionality constant k=V ₁ /V ₂ A first power supply of V ₁ , a second power supply of voltage value V ₂ with the opposite polarity to the first power supply, a voltage integration circuit that integrates the output voltages of the first power supply and the second power supply, and an output of the voltage integration circuit. A comparator circuit that turns on the AC control element when the AC control element becomes the reference potential, connects the first power supply to the voltage integration circuit when detecting the zero cross of the AC power supply voltage, and integrates the voltage of the second power supply when the AC control element is detected to be off. The control circuit is connected to the circuit and disconnects the second power supply from the voltage integration circuit using the output of the commutation phase detection circuit when the output of the voltage integration circuit becomes the reference potential and the AC control element is turned on. A discharge lamp constant input lighting device characterized by comprising: 2 An AC control element, a current limiting inductance, and a discharge lamp are connected in series to an AC power source, and a zero-cross detection circuit that detects the zero-cross point of the AC power supply voltage and a commutation phase detection circuit that detects the on-off point of the AC control element are provided. According to the on-phase angle T from the zero-cross point of the AC power supply voltage until the AC control element turns off, the off-phase angle ΔT from when the AC control element turns off until it turns on again is determined by a linear approximation formula ΔT=kT In a discharge lamp constant input lighting device comprising a control circuit that controls the proportionality constant k to be positive, the first current having a current value I ₁ set so that the proportionality constant k = I ₁ /I ₂ a second current source whose current direction is opposite to that of the first current source and whose current value is _I2 ;
A capacitor that is charged and discharged by the output current of the current source and the second current source, a comparator circuit that turns on the AC control element when the terminal voltage of the capacitor reaches the reference potential, and a first current that is charged and discharged when the zero cross of the AC power supply voltage is detected. The second current source is connected to the capacitor when the AC control element is detected to be off, and the commutation phase detection circuit is connected when the terminal voltage of the capacitor becomes the reference potential and the AC control element is turned on. A constant input lighting device for a discharge lamp, characterized in that the control circuit is constituted by a changeover switch that disconnects the second current source from the capacitor at the output.