JPH0536485A - Discharge lamp lighting apparatus - Google Patents

Abstract

PURPOSE:To achieve high power efficiency of a lighting apparatus by sending current with similar waveform as the waveform of input voltage. CONSTITUTION:A commercial electric power source V is rectified by a rectifying device 2 and made into pulse flow. The pulse flow is sent in a step-up type converter composed of a choke coil 11, a switching device 12, a resistor 13 for current detection, a diode 14, a filter capacitor 3, and resistors 15, 16 for output voltage detection. At that time, in the case that the switching frequency by an IC for current mode switching control is sufficiently high as compared with the frequency of the commercial electric power source V, current corresponding to the voltage applied to run instantly to the device 12. The current running in the device 12 is converted into voltage by a resistor 13, sent in a controller 17, and by controlling the device 12 properly by the controller 17, current with similar waveform to the waveform of the input voltage is made to run. Consequently, with a simple circuit structure, high power efficiency of an apparatus is achieved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting device for a high-intensity discharge lamp such as a metal halide lamp, which is capable of lighting a high frequency wave or a rectangular wave using an inverter, and more particularly to improvement of a rectifying circuit thereof.

[0002]

2. Description of the Related Art In recent years, high-intensity discharge lamps such as metal halide lamps have begun to spread as various light sources. Lighting devices for such discharge lamps are also used in conventional phase-advancing ballasts such as leakage transformers and main capacitors. From a method of lighting a lamp using an iron ballast to a method using a high frequency inverter,
Furthermore, the rectangular wave lighting system using an inverter is being reduced in size and weight.

FIG. 8 is a diagram showing an example of the configuration of a conventional rectangular wave lighting system lighting device, where 1 is a commercial power supply, 2 is a rectifying element, and 3 is a rectifying device.
Is a smoothing capacitor, 4 is a step-down chopper circuit for power control, 5 is a full-bridge inverter, 6
Is a starting pulse transformer, 7 is a bidirectional two-terminal semiconductor switching element (SSS) connected between output terminals of the full-bridge inverter 5 via a resistor 8, and 9 is an intermediate tap of the starting pulse transformer 6. And a capacitor connected between the connection points of the semiconductor switching element 7 and the resistor 8, and the starting pulse transformer 6, the semiconductor switching element 7, the resistor 8 and the capacitor 9 constitute a starting circuit. .. Reference numeral 10 is a metal halide lamp connected to the output terminal of the full-bridge inverter 5 via the starting circuit.

In the lighting device thus constructed, the commercial power source 1 is rectified by the rectifying element 2 and input to the full-bridge type inverter 5 via the smoothing capacitor 3 and the chopper circuit 4. Then, by the operation of the inverter 5, a rectangular wave alternating voltage is applied to the metal halide lamp 10 through the starting circuit. When a rectangular wave alternating voltage is applied to the starting circuit, the capacitor 9 starts charging, and when the charging voltage exceeds the breakover voltage of the semiconductor switching element 7, the semiconductor switching element 7 is turned on,
The discharge current of the capacitor 9 suddenly flows into the pulse transformer 6 via the semiconductor switching element 7. As a result, a high-voltage pulse is generated in the pulse transformer 6 and applied to the metal halide lamp 10, the lamp 10 is started, and rectangular wave lighting is performed. In this rectangular wave lighting method, since a rectangular wave is applied, flicker of the lamp is reduced and good lighting is performed.

[0005]

By the way, as mentioned above,
Rectification circuit used in a discharge lamp lighting device of a rectangular wave type
In the road, the AC input from the commercial power source 1 is rectified.
It is converted to pulsating flow by the child 2, and the smoothing capacitor 3
Although the number of pulls is reduced to make it direct current, at that time, the input voltage V
₁Is the output voltage V₀Higher very short periods (commercial power
The smoothing capacitor 3 is charged only for 3 to 10 msec.
Input current I that is several times to several tens times that of the steady state ₁Flows.

Therefore, the following problems occur. That is, the apparent current is large and the power factor is poor compared to active power,
Further, since the current flowing through the smoothing capacitor is large, a capacitor having a large capacity is required, which causes a problem that a large inrush current is generated. In addition, there are problems in that a large number of harmonics are generated, other devices are affected, and the stability is poor with respect to input voltage fluctuations and load fluctuations.

The present invention has been made to solve the above-mentioned problems in the rectifier circuit of the conventional discharge lamp lighting device, and a current having a waveform similar to the input voltage waveform is input to obtain a high power factor. It is an object of the present invention to provide a discharge lamp lighting device having a rectifier circuit in which the harmonic content rate is drastically reduced during use and stability is improved against variations in input voltage and variations in load.

[0008]

In order to solve the above problems, the present invention rectifies an input AC voltage by a rectifying circuit composed of a rectifying element and a smoothing capacitor, inputs the rectified voltage to an inverter, and outputs the output of the inverter. In a discharge lamp lighting device for connecting a discharge lamp to an end to perform high frequency or rectangular wave lighting, a series circuit of a choke coil and a diode connected in series between a rectifying element of the rectifying circuit and a smoothing capacitor, and the diode. , A series circuit of a switching element connected in parallel to the smoothing capacitor and a current detection resistor of the switching element, a means for adding a bias component and a triangular wave component to the current detection value of the switching element, and an output of the adding means. Is input and a control signal is output to the switching element when the input value reaches a predetermined value. And it constitutes provided a sufficiently high current mode switching control circuit than the frequency.

In the rectifier circuit of the discharge lamp lighting device configured as described above, the duty ratio of the switching element is controlled according to the magnitude of the input voltage, and a current having a waveform similar to the input voltage waveform is input. This solves the problem of the conventional discharge lamp lighting device having the rectifier circuit.

[0010]

EXAMPLES Before explaining the examples, the principle of the present invention will be described. In the present invention, in order to input a current having a waveform similar to the input voltage waveform, a boost converter having a configuration as shown in FIG. 1 is used. In FIG. 1, 2 is a rectifying element, 3 is a smoothing capacitor, 11 is a choke coil,
12 is a FET switching element, 13 is a current detection resistor, 14
Is a diode, 15 and 16 are resistors for detecting output voltage, and 17 is a controller, which detects a current flowing through the switching element 12 and outputs a control signal for the switching element 12. In the rectifier circuit using such a boost converter, the controller 17 appropriately controls the switching element 12 so that the current i having a waveform similar to the waveform of the input voltage v flows as shown in FIG. ..

As a control method of the switching element 12 for flowing a current similar to such an input voltage waveform, a method of flowing a current in a triangular wave as shown in FIG. 3A and a method of FIG. 3B. ), There is a method of passing the current in a trapezoidal shape. The method shown in FIG. 3A in which a current flows in a triangular waveform has the advantage of high efficiency because no current flows through the diode 14 during the reverse recovery period, but the peak value of the current is large, so a noise filter is used. Has the drawback of becoming large. On the other hand, the trapezoidal method shown in FIG. 3B is less efficient than the triangular wave method.
Since the peak value of the current can be reduced, there is an advantage that the noise filter can be small. The present invention employs a trapezoidal method in which a noise filter can be small in size so that a circuit can be configured at low cost, and configures a controller using a general-purpose current mode switching control IC.

Next, the control of the switching element by the controller when a trapezoidal wave current is passed will be described based on the basic circuit of the boost converter shown in FIG. In FIG. 4A, the current I _L flowing through the choke coil 11 changes as shown in FIG. 4B.
That is, when the switching element 12 is ON, the current I _L
The rising side of is represented by V ₁ / L (V ₁ : input voltage, L: choke coil inductance), and its slope is proportional to the input voltage V ₁ . Meanwhile, when the switching element 12 is turned OFF, but the energy accumulated in the choke coil 11 flows into the smoothing capacitor 3 via the diode 14, the slope of the current I _L at that time, (V ₀ -V ₁ ) / L
(V ₀ : output voltage).

That is, the controller 17 causes the current I flowing through the switching element 12 detected by the current detection resistor 13 to flow.
Control to keep _Tr constant, that is, controller
When the constant current threshold I _P 17, the higher the input voltages V ₁ inclined V ₁ / L increases, becomes time is ON of the switching element 12 (Duty) is short, the duty ratio decreases.

Therefore, as shown in FIG. 5, this current threshold value I _P is set high when the duty ratio is small, that is, when the input voltage V ₁ is high, and conversely when the duty ratio is large, that is, the input voltage V ₁ is The input current I _L proportional to the input voltage V ₁ can be obtained by setting the triangular waveform so that it becomes lower when it is low. That is, as described above, since the positive slope of the current I _L is determined by V ₁ / L, the higher the input voltage V ₁ , the larger the slope, the larger the current threshold I _P , and the larger the current I _L. On the other hand, the negative slope of the current I _L is (V ₀ −V ₁ ).
Since it is determined by / L, when the input voltage V ₁ is high, the slope becomes smaller. And each change amount (slope x time)
Are converged so as to be equal to each other, so that the overall level is increased, and accordingly, a large current flows when the input voltage is high. On the other hand, when the input voltage is low, the current I _L ′ becomes small.
Flows.

As described above, the current threshold value I _{P of the} controller
By setting, the current similar to the input voltage waveform can be input. However, in the present invention, in order to simplify the operation of the comparator in the controller, the current threshold I _P of the controller 17 is set as described below.
Is set to a constant value, a rising triangle wave is added to the current detection value of the switching element 12 for each cycle of switching control, and the result is input to the controller 17, so that the current threshold value of the controller 17 becomes the input voltage value. An operation equivalent to changing the value is performed. In this case, the current waveform I _sens input to the controller 17 is
When the input voltage is high, the solid line is shown in FIG. 6A, and when the input voltage is low, the solid line is shown in FIG. 6B. That is, when the switching element 12 is ON, the sum of the current I _L or I _L ′ and the triangular wave is input, and when the switching element 12 is OFF, only the triangular wave is input.

Next, specific examples of the present invention will be described. FIG. 7 is a circuit configuration diagram showing a rectifier circuit portion of an embodiment of a discharge lamp lighting device according to the present invention, and the same or corresponding members as those of the basic circuit configuration shown in FIG. The description is omitted. In FIG. 7, 21 is an operational amplifier, the detection output of the detection resistor 13 for the current flowing through the switching element 12 is input to one of its input terminals via the input resistors 22 and 23, and the other input terminal is The voltage-divided output of the bias adjusting resistors 24 and 25 is input via the input resistor 26, and the bias current is subtracted from the voltage obtained by converting the detection current flowing through the switching element 12 by the resistor 13 and output. Has been done. 27 is a feedback resistor of the operational amplifier 21.

28 is an IC for current mode switching control
In, for example, Motorola of UC3842A / 43A is used, the reference voltage terminal R _ef is connected to the bias adjustment resistor 24, 25, also one end connected to the resistor 29 for a time constant circuit for setting the switching frequency The other end of the resistor 29 is connected to the R _T / C _T terminal of the IC 28, and a capacitor 30 for the time constant circuit is also connected to the R _T / C _T terminal. 31 is a buffer transistor, the collector is the reference voltage terminal _Ref , and the base is the connection point of the time constant circuit resistor 29 and the capacitor R _T / C
_The emitter is connected to the _T terminal through the mixing resistor 32.
It is connected to the current detection terminal I _sens of C28, and the output terminal of the operational amplifier 21 is also connected to the current detection terminal I _sens of the IC 28 via the mixing resistor 33. Further, the divided voltage output of the output voltage detecting resistors 15 and 16 is passed through the filter 34 to the IC.
28 is connected to the voltage feedback terminal V _IN, and the output terminal OUT of the IC 28 is connected to the gate of the switching element 12 so that the switching element 12 is turned on and off.

Next, the operation of the rectifier circuit thus configured will be described. First, the commercial power supply 1 is rectified by the rectifying element 2 and made into a pulsating flow. And this pulsating current is choke coil 1
1, a switching element 12, a current detection resistor 13, a diode 14, a smoothing capacitor 3, and output voltage detection resistors 15 and 16 are input to the boost converter. At this time, if the switching frequency by the current mode switching control IC 28 is sufficiently higher than the input frequency of the commercial power supply 1 (for example, 60 KHz), a current corresponding to the instantaneous value of the input voltage is supplied to the switching element 12. Flowing.

The current flowing through the switching element 12 is converted into a voltage by the current detection resistor 13 and input to one end of the operational amplifier 21. At the other end of the operational amplifier 21, the divided voltage output of the bias adjusting resistors 24 and 25 to which the reference voltage of the IC 28 is applied is input as a bias component, and is subtracted from the detected current conversion voltage. The output of the operational amplifier 21 is added to the triangular wave obtained through the buffer transistor 31 through the mixing resistors 32 and 33, respectively, and input to the IC 28.

The IC 28 sends a control signal for turning off the switching element 12 when the added output reaches a predetermined value (threshold current I _P ). This control signal is output according to the magnitude of the pulsating flow rectified in each switching cycle. That is, when the voltage value of the pulsating current is low, as shown in FIG.
Since the slope of the current _IL 'is small as shown in (B) of
The switching element 12 is turned off in the state where many triangular wave components are added, that is, in the late stage when many triangular wave components are added, and when the voltage value of the pulsating current is high, the current I as shown in FIG. _Since the slope of _L is large, the switching element 12 is controlled to be turned off in a state where the triangular wave component is not added so much, that is, at an early stage when the triangular wave component is added little. This allows a current similar to the input voltage waveform to flow.

The divided output voltage of the voltage detecting resistors 15 and 16 is input to the voltage feedback terminal of the IC 28 through the filter 34, and ON / OFF control of the switching element 12 is performed so that the output voltage becomes a predetermined value. The output voltage is being stabilized.

Further, since the operational amplifier is used in the control portion and the rating can be changed by adjusting the resistance such as the input resistance and the mixing resistance, it can be easily applied to the discharge lamp lighting devices of various ratings.

In the above embodiments, the present invention is applied to the discharge lamp lighting device for performing rectangular wave lighting, but the present invention is of course also applied to a high frequency lighting type discharge lamp lighting device using a rectifier circuit. It is possible.

[0024]

As described above on the basis of the embodiments,
According to the present invention, with a simple configuration using a general-purpose current mode switching control circuit, the duty ratio of the switching element is controlled according to the magnitude of the input voltage, and a current having a waveform similar to the input voltage waveform is input. The power factor can be increased.

[Brief description of drawings]

FIG. 1 is a basic circuit configuration diagram for explaining the principle of the present invention.

FIG. 2 is a diagram showing an input voltage waveform and an input current waveform.

FIG. 3 is an explanatory diagram showing a control method of a switching element for causing a current having a similar input voltage waveform to flow.

FIG. 4 is a diagram showing a basic circuit of a boost converter and changes in its input current.

FIG. 5 is a diagram showing a relationship between a current threshold value and an input voltage.

FIG. 6 is a diagram showing a relationship with a current threshold value when a triangular wave is added to a detected value of a switching element current and input to a controller.

FIG. 7 is a circuit configuration diagram showing a rectifier circuit portion of a specific embodiment of the present invention.

FIG. 8 is a diagram showing a configuration example of a conventional rectangular-wave lighting type discharge lamp lighting device.

[Explanation of symbols]

 1 Commercial power supply 2 Rectifier element 3 Smoothing capacitor 11 Choke coil 12 Switching element 13 Current detection resistor 14 Diode 15, 16 Output voltage detection resistor 17 Controller 21 Operational amplifier 24, 25 Bias adjustment resistor 28 Current mode switching control IC 31 Transistor for buffer 34 Filter

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H05B 41/24 J 7913-3K

Claims (1)

Claim: What is claimed is: 1. An input AC voltage is rectified by a rectifying circuit composed of a rectifying element and a smoothing capacitor and input to an inverter,
In a discharge lamp lighting device for connecting a discharge lamp to an output terminal of the inverter to perform high frequency or rectangular wave lighting, a series circuit of a choke coil and a diode connected in series between a rectifying element of the rectifying circuit and a smoothing capacitor. A series circuit of a switching element connected in parallel with the diode and the smoothing capacitor and a current detection resistor of the switching element; a means for adding a bias component and a triangular wave component to the current detection value of the switching device; And a current mode switching control circuit having a switching frequency that is sufficiently higher than an input AC voltage frequency and that outputs a control signal to the switching element when the output of the adding means is input and the input value reaches a predetermined value. A discharge lamp lighting device characterized in that a current having a waveform similar to the input AC voltage waveform is input to the circuit. .