JPH0367318B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a discharge lamp lighting device for lighting a saturated vapor pressure discharge lamp.

Figure 1 shows a basic discharge lamp lighting system in which a saturated vapor pressure discharge lamp 2, such as a high-pressure sodium lamp, is controlled in phase by a bidirectional three-terminal thyristor (hereinafter referred to as thyristor) _Q1 , which is a phase control element. The circuit configuration of the device is shown. In the figure, L ₁ is the main current-limiting inductance, and L ₂ is the high-impedance auxiliary inductance for preventing the power from disappearing. Reference numeral 3 denotes a phase control circuit for controlling the phase of the thyristor _Q1 , and this phase control circuit 3 has conventionally been provided with a circuit configuration as shown in FIG. By the way, the saturated vapor pressure type discharge lamp 2 has low impedance at the time of starting and is almost in a short-circuit state, so in the circuit shown in FIG. 1, the lamp voltage V _la − shown in _FIG . By delaying the conduction phase angle θ of thyristor _Q1 as in the relationship of phase angle θ,
It is necessary to suppress the current. (Point in Figure 3). This conduction phase angle θ represents the electrical angle seen from the beginning of the voltage Vs of the AC power source 1 at the time of conduction of the thyristor _Q1 . As the discharge lamp 2 warms up, the impedance of the discharge lamp 2 increases, the lamp voltage V _la increases, and the conduction phase angle θ changes from point to point in FIG.
Gradually, after the discharge lamp 2 transitions to steady lighting, the relationship between current and voltage statically shows a positive characteristic in a saturated vapor pressure discharge lamp, so
When the lamp voltage is to increase, the conduction phase angle θ must be delayed, and when the voltage is to be decreased, the conduction phase angle θ must be controlled to be advanced. In other words, a saturated vapor pressure discharge lamp 2
In phase control, as shown in FIG. 3, there are two modes: ◯ mode from startup to steady lighting, and ◯ low mode which shows positive characteristics until steady lighting is reached.

Next, the operation of the conventional circuit will be explained based on FIGS. 1 to 3. First, by turning on the AC power supply 1,
AC power supply 1 voltage is applied to the terminal of phase control circuit 3.
V _S is applied, the voltage is stepped down by a step-down transformer T, full-wave rectified by a diode bridge DB ₁ , the rectified output is clipped to a Zener voltage by a Zener diode ZD ₁ , and the clipped voltage is used as a power source to connect a resistor.
Charging of capacitor C ₁ begins with a time constant determined by the values of R ₂ and capacitor C ₁ . On the other hand, the voltage across the discharge lamp 2 applied to the terminals of the phase control circuit 3
V _la is divided by resistors Ra and Rb, and the voltage across resistor Ra is rectified by diode bridge DB _{2 and} then
Along with charging capacitor C ₂ through R ₅ ,
Capacitor C ₃ begins to be charged from capacitor C ₂ via resistor R ₉ and diode D ₄ . This capacitor C ₃ is also simultaneously charged with a current flowing through resistor R ₈ . When the voltage across capacitor _C3 reaches the breakover voltage V _B0 of silicon bilateral switch (SBS) _Q6 , _SBSQ6 becomes conductive and transistor _Q3 also becomes conductive. Therefore, the charge in the capacitor C ₁ is discharged in the closed circuit of the diode D ₇ , transistors Q ₃ and Q ₄ , and the primary winding of the pulse transformer PT, and a pulse is generated on the secondary side of the pulse transformer PT. , this pulse is passed from the terminal to the thyristor Q ₁ through the resistor R ₆ and the diode D ₃
conduction. Immediately after starting discharge lamp 2, the lamp voltage
Since V _la is small, the voltage across capacitor C ₂ V _c2 is also small, and therefore the voltage across capacitor C ₂ to capacitor C ₃
The amount of charge to is small and the voltage across capacitor _C3 is
Reaching the breakover voltage V _B0 of SBSQ ₆ is dominated by the time constants of resistor R ₈ and capacitor C ₃ .
Note that during the above operation, the transistor Q ₄ is in a non-conductive state only when the AC power supply 1 voltage V _S is V _S ≈0. This is because the smoothed DC current from capacitor C ₂ flows through SBSQ ₆ and SBSQ ₆ does not turn off, so transistor Q ₄ is connected to AC power supply 1.
is synchronized with the zero cross point of SBSQ ₆
This is to forcibly make it non-conductive. Also
SBSQ ₇ is in a non-conducting state because the voltage V _c2 across capacitor C ₂ is small, transistor Q ₅ is non-conducting, programmable union transistor (hereinafter abbreviated as PUT) Q ₂ is non-conducting, and transistor Q ₅ is non-conducting. The above state continues until conduction occurs. When the lamp voltage V _la increases due to the warm-up of the discharge lamp 2, the voltage V c2 across the capacitor C ₂ increases, and the voltage V _c2 across the capacitor C ₃ increases.
As the amount of charge increases gradually, the conduction phase of thyristor _Q1 becomes faster (advances). This is the curve shown by ○Imode.

Now, if the resistance values of resistors R ₁₀ and R ₁₅ are set so that SBSQ ₇ becomes conductive when the lamp voltage V _la rises to the vicinity of steady lighting (point), SBSQ ₇ ,
When transistors Q ₅ and PUTQ ₂ become conductive, the following operation occurs. i.e. SBSQ ₇
When conducts, transistor Q ₅ conducts and the charging of capacitor C ₃ from capacitor C ₂ stops,
The conduction phase in SBSQ ₆ moves from point to point in Figure 3, becoming almost the same phase (point) as immediately after starting discharge lamp 2, and the above operation switches from ○I mode to ○R mode, as follows. An action is taken. In other words, as the lamp voltage V _la increases, the gate voltage of PUTQ ₂ increases, so
The conduction time of PUTQ ₂ becomes earlier. Now, in the configuration of FIG. 1 which requires two phase control modes ○a and ○b, a mode switching circuit is required, and furthermore, the circuit configuration for achieving this function is complicated. At the same time, depending on the switching timing, there may be times when thyristor Q ₁ does not conduct, or the conduction phase angle θ may change significantly, and the discharge lamp 2 may flicker or cause other problems when switching modes.
There was a problem that it caused unstable operation.

The present invention has been made in view of the above-mentioned drawbacks, and its purpose is to enable a smooth transition from starting to steady lighting of a discharge lamp;
Further, it is an object of the present invention to provide a discharge lamp lighting device which has a simple circuit configuration and allows easy selection of circuit constants in circuit design.

The present invention will be explained in detail below with reference to Examples.

FIG. 4 is a block diagram showing the basic configuration of the phase control circuit 3 used in the discharge lamp lighting device of the present invention.
The terminal is the terminal connected to the gate circuit of the thyristor Q, and the terminal is the terminal connected to both ends of the discharge lamp 2. In the figure, 5 is a lamp voltage detection circuit that detects the lamp voltage V _la of the discharge lamp 2. It's hot,
This lamp voltage detection circuit 5 controls the charging of the capacitor _C1 of the trigger means 6 consisting of a timer circuit and a trigger circuit in the above-mentioned ○mode, and the lamp voltage An output proportional to the lamp voltage V _la of the detection circuit 5 changes the threshold level of the voltage comparator 9 via a resistor R ₃ to control the firing phase of the thyristor Q ₁ . In other words, when the output voltage of the lamp voltage detection circuit 5 becomes higher than the voltage V _R4 obtained by dividing the power supply voltage +V ₁ by the resistors R ₁₆ and R ₄ , control in the ○ mode is better than in the ○ mode due to the operation of the starting control circuit 8. It will make you stronger. Note that 4 is a power supply circuit. Next, the operation of the present invention will be explained in detail using the phase control circuit 3 of the embodiment shown in FIG. In the circuit shown in FIG. 5, in the case of the ○ mode shown in _{FIG .} Charge the capacitor _C2 through. As the voltage rises due to this charging of capacitor C ₂ , current flows through the circuit including resistor R ₁₇ , diode D ₈ , capacitor C ₁ , and diode D ₂ to charge capacitor C ₁ . During this operation, the capacitor _C5 is charged with the power supply voltage of the power supply circuit 4 + _V1 via the diode _D9 to a voltage determined by the Zener voltage of the Zener diode _ZD1 , and the voltage of this capacitor _C5 is connected to the resistor _R16 . , _R4 . The voltage across this resistor R ₄ is connected to the capacitor until it reaches the point in Figure 3.
By setting the voltage to be higher than the voltage of C ₂ , the gate voltage of PUTQ ₂ , which constitutes the voltage comparator 9, does not change in ○ mode, and the voltage of PUTQ 2 does not change with only a change in the voltage V _c1 of capacitor C _{1 .} The conduction phase _{of the capacitor C1 is determined, so the voltage V c1 of} the capacitor C1 is the resistance
When the voltage across R ₄ exceeds the voltage V _R4 , PUTQ ₂ turns on and the discharge current of capacitor C 1 is generated in the closed circuit of capacitor C ₁ , PUTQ ₂ , the primary winding of pulse transformer PT, and capacitor _{C 1} flows, pulse transformer
A pulse is generated at the secondary output of PT, and a pulse for ignition of thyristor _Q1 is generated at the terminal via resistor _R6 and diode _D3 , making thyristor _Q1 conductive. When near the point in Figure 3, the resistance
Since the voltage V _c2 of capacitor C ₂ is set to be higher than the voltage V _R4 of R ₄ , capacitor C ₂ ,
Capacitor C ₁ through resistor R ₁₇ , diode D ₈
The voltage across resistor R4 _{, V R4 ,} increases more than the charging speed of R4 increases.
As the voltage V _c2 of the capacitor C ₂ increases, the conduction phase of PUTQ ₂ is delayed. In other words, it becomes the ◯ lo mode in Fig. 3. This transition from ○mode to ○romode is caused by the voltage of capacitor _C2 V _c2
Since it can be determined based on the relationship between the voltage V R4 of the resistor _R4 and the voltage V _R4 of the resistor R4, there is no need to change the switching mode as in the conventional case.

○When transitioning to low mode, the voltage across discharge lamp 2
The voltage across capacitor C ₂ changes according to the fluctuation of V _la , and from capacitor C ₂ to diode D ₁ and resistor R ₃
The voltage V _R4 of the resistor R ₄ through which current flows changes accordingly, changing the gate voltage of PUTQ ₂ of the voltage comparator 9. That is, the lamp voltage V _la
When increases (decreases), the gate voltage of PUTQ ₂ increases (decreases), the conduction phase of PUTQ ₂ lags (advances), and as a result the conduction phase angle θ of thyristor Q ₁ lags (advances), the lamp current The thyristor _Q1 performs phase control in a direction to limit (increase) the power, thereby keeping the power supplied to the discharge lamp 2 almost constant.

FIG. 6 shows a phase control circuit 3 of another embodiment of the present invention.
In this example, an IC timer 7 such as μPC1555 (manufactured by NEC Corporation) is used as the timer circuit of the trigger means 6 and the voltage comparator, and in this example, the lamp voltage V _la is Resistance Ra,
The voltage obtained by dividing the voltage by Rb is connected to the diode block.
The rectified output is rectified by DB ₂ , and the capacitor C ₂ is charged through the resistor R _5. The voltage V c2 across the capacitor C ₂ is connected to the terminal where the voltage V _c2 controls the threshold level of the timer IC 7, and the resistor R ₁₇ and diode D. ₈
The voltage V c1 is applied to the threshold terminal and compared with the voltage V _c1 applied to the threshold terminal. When the voltage level of the trigger terminal exceeds a certain level and the voltage level of the threshold terminal exceeds the voltage level of the control terminal, the timer IC 7 sets the output terminal to "L" level, sets the threshold terminal to "L" level, and switches the trigger terminal to "L" level. When the voltage level of the AC power source 1 falls to a predetermined level, the output terminal is set to the "H" level. In the illustrated circuit, when the voltage V _S of the AC power supply 1 exceeds a predetermined level, the resistors R ₁₈ and R ₁₉ of the power supply circuit 4 The timer IC 7 can be controlled by the divided voltage. At this time, the capacitor C ₁ is charged via the starting control circuit 8 including the diode D ₁ and the resistor R ₃ . Since the detection circuit 5 detects the no-load voltage and its output is almost constant until starting, the voltage at the control terminal to which the output voltage of the detection circuit 5 is applied remains almost constant until starting. , timer
The threshold level of IC7 is set constant,
After starting and lighting, the output voltage of the detection circuit 5 changes according to the lamp voltage V _la , so the timer IC 7
The voltage at the control terminal also changes, and the same operation as in the case of the circuit of FIG. 5 is performed. That is, in this embodiment, the diode D ₁ and the resistor R ₃ constitute the starting control circuit 8, and the timer IC 7 serves both as a timer circuit and a voltage comparator. Further, the terminal of the timer IC 7 is a power supply terminal, a ground terminal, and a reset terminal, and this reset terminal is connected to the power supply when reset is not necessary to prevent malfunction.

The present invention includes a detection circuit that outputs as a detection output a voltage obtained by rectifying and smoothing a voltage proportional to the voltage across both ends of a discharge lamp, a power supply circuit that generates a constant DC voltage, and a power supply circuit that connects the output of this power supply circuit with a backflow prevention element. A capacitor is charged with the output of the detection circuit, and a pulse generation phase for ignition of the AC phase control element is set by comparing the voltage of the capacitor with a threshold level, and the threshold level is set externally. It has a trigger means that is freely variable according to the input voltage, and a phase control circuit that supplies the detection output of the detection circuit to the trigger means as the external input voltage, so there is no need for a switching element as in the conventional case, and the circuit configuration can be simplified. It is simple, and it is easy to select the circuit constants due to the circuit design. Furthermore, since there is no switching of switching elements, there are no cycles in which the phase control element does not turn on, and the conduction phase does not change suddenly, which reduces the flickering and extinguishing phenomena of the discharge lamp. Furthermore, the switching point between the mode from starting to steady lighting and the steady lighting mode can be easily set in correspondence with the threshold level of the trigger means.

[Brief explanation of drawings]

Figure 1 is a circuit configuration diagram of a basic discharge lamp lighting device, Figure 2 is a specific circuit diagram of a conventional phase control circuit, and Figure 3 shows the lamp voltage of the same discharge lamp and the phase conduction of the phase control element. 4 is a circuit configuration diagram of a phase control circuit according to the present invention, FIG. 5 is a specific circuit diagram of a phase control circuit according to an embodiment of the present invention, and FIG. 6 is a diagram illustrating the relationship with phase angle. 1 is a specific circuit diagram of the phase control circuit of the embodiment, 1 is an AC power supply, 2 is a discharge lamp, 3 is a phase control circuit, 4 is a power supply circuit, 5 is a detection circuit, 6
is the trigger means, L ₁ is the main current limiting inductance,
L ₂ is an auxiliary inductance, and Q ₁ is a bidirectional three-terminal thyristor.

Claims (1)

[Claims] 1 Connect a series circuit of an AC phase control element, a main current-limiting inductance, and a saturated vapor pressure discharge lamp to the AC power source, and connect an auxiliary inductance in parallel to the AC phase control element, and connect the AC phase control element to the AC power source. In a discharge lamp lighting device having a phase control circuit that supplies a constant input to the discharge lamp by controlling the phase of the discharge lamp, a voltage obtained by rectifying and smoothing a voltage proportional to the voltage across the discharge lamp is detected and output. a detection circuit that outputs a constant DC voltage, a power supply circuit that generates a constant DC voltage, a capacitor that is charged by the output of the power supply circuit and the output of the detection circuit via a backflow prevention element, and a voltage that Trigger means for setting the pulse generation phase for ignition of the AC phase control element in comparison with the jord level, and for making the threshold level variable by an external input voltage; A discharge lamp lighting device comprising: the phase control circuit which applies an output to the trigger means as the external input voltage.