JPH02114496A - Discharge lamp lighting apparatus - Google Patents

Abstract

PURPOSE:To flow sufficient electric current for starting and carry out stable starting by adding a serial circuit of a resistor and Zener diode in a feedback circuit of a computing amplifier of a switching circuit to control the pulse amplitude of a tension descending type chopper circuit. CONSTITUTION:A current detecting device R1 inserted between a free wheel diode D in an output part of a tension descending type chopper circuit 2 and a filter capacitor C2 and a switching circuit 12 to control the pulse amplitude of a tension descending type chopper circuit 2 containing a computing amplifier to put in a detection output of the current detecting device R1 are installed. The computing amplifier 22 has a feedback circuit composed of serial circuit of first resistor R3 and a Zener diode ZD and a parallel circuit of a second resistor R7 and alters the amplification factor of the computing amplifier 22 responding to the current of a lamp, and controls the pulse amplitude of a chopper circuit 2. At the time of starting of a discharge lamp 5, the amplification factor of the computing amplifier 22 decreases and the pulse amplitude of the tension descending type chopper circuit 2 is controlled to become high, and as a result, sufficient electric current for starting flows and starting is carried out stably.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to a high-intensity discharge lamp, such as a metal halide lamp, in which the discharge lamp is lit by controlling the current with a step-down chopper circuit inputting a DC output. This invention relates to improvements in lighting devices.

[Conventional technology]

In recent years, high-intensity discharge lamps such as metal halide lamps have become popular, and lighting devices for such discharge lamps also include phase-advanced ballasts consisting of a leakage transformer T and a main capacitor C, as shown in FIG. From the method of lighting the lamp L using a steel type ballast to the method using high frequency inverters H and I as shown in FIG. 7, efforts are being made to make the lamp smaller and lighter.

However, in a lighting device using such a high frequency inverter, there is a problem that when a current in a certain frequency range is supplied, an acoustic resonance phenomenon occurs, causing the arc to go out and becoming unstable.

Conventionally, in order to eliminate instability caused by such an acoustic resonance phenomenon, a rectangular wave lighting system as shown in FIG. 8, for example, has been proposed. In other words, in Fig. 8, 1 is the commercial power supply, D
1 is a rectifying element, C1 is a smoothing capacitor, 2 is a step-down chopper circuit, a switching transistor Q, and a freewheel diode D! , a DC reactor L1, a smoothing capacitor C2, and a constant current feedback circuit 3 that drives and controls the switching transistor Q. R3 is a current detection element that inputs a detection output to the constant current feedback circuit 3, and 4 is a full bridge inverter consisting of switching transistors Qt, Qx, Qa, and Qs.

In the lighting device configured in this way, the commercial power supply l is rectified by the rectifier element, and its DC output is input to the step-down chopper circuit 2, where constant current control is performed.
The output of the chopper circuit 2 is a full bridge type inverter 4.
is input. By the operation of the inverter 4, a rectangular wave alternating voltage is applied to the lamp 5, and rectangular wave lighting is performed.

In this rectangular wave lighting, since a rectangular wave is applied, it is said that the lamp can be lit well with less flickering.

[Problem to be solved by the invention]

However, in the discharge lamp lighting device proposed above, constant current control is performed in the step-down type Chirotsuba circuit, so
Even when starting a lamp, only the current that is stable can flow through the lamp. However, when lighting a discharge lamp for fishing on a boat, when starting the lamp, a current that is about 1.2 to 2.5 times the stable current is required, and therefore the current is stable. If you start the lamp with a current of 100 mph, it may take a long time to start, or the lamp may not start due to unstable discharge.

In order to improve this point, as shown in Fig. 9, a relay R7 using a timer circuit 6 is provided, and the relay R9 is operated only for a predetermined lamp starting time, and the relay contact ``,'' causes the current detection element R5 to be activated. The configuration is such that a resistor R1 is inserted in parallel, and thereby the input signal to the constant current feedback circuit 3 is changed at the time of starting, and the output current of the chopper circuit 2 is adjusted to be large, and after the lamp is lit, the current is stabilized. Measures are being taken to control the return.

However, when such measures are taken, although the lamp starts, it takes a long time to reach stable lighting, and constant current control is performed when the lamp is stable, so changes in lamp voltage directly affect lamp power. Therefore, it is not possible to prevent variations in lamp voltage due to variations in lamp manufacturing, or excessive input due to increases in lamp voltage at the end of the lamp's life, and furthermore, circuit reliability is deteriorated due to wear of relay contacts. Defects arise.

The present invention was made in order to solve the above-mentioned problems in the conventional discharge lamp lighting device, and it stabilizes the discharge of the lamp at the time of starting, shortens the starting time, and sets a predetermined value for the increase in lamp voltage. It is an object of the present invention to provide a discharge lamp lighting device that prevents overpowering.

[Means and operations for solving the problem] In order to solve the above problems, the present invention provides a discharge lamp lighting device equipped with a step-down chopper circuit that inputs direct current to control current. A current detection element inserted between the freewheel diode and the smoothing capacitor in the output section,
a switching circuit for controlling the pulse width of the step-down chopper circuit incorporating an operational amplifier that inputs the detection output of the current detection element; the operational amplifier includes a series circuit of a first resistor and a Zener diode; It has a feedback circuit consisting of a parallel circuit of resistors, and is configured to change the amplification factor of the operational amplifier in response to the lamp current and control the pulse width of the thixobar circuit.

In the discharge lamp lighting device configured in this way, when starting the discharge lamp, four Zener diodes in the feedback circuit of the operational amplifier are connected to control the amplification factor of the operational amplifier to decrease and the pulse width of the step-down chopper circuit to increase. is,
Stable starting is achieved by supplying sufficient current for starting. In addition, near stability, the Zener diode in the feedback circuit becomes non-conducting, increasing the amplification factor, and controlling the pulse width of the pressure-type chipper circuit to be small, to prevent overpowering as the lamp voltage increases. is supplied with adequate power.

〔Example〕

Next, an example will be described. FIG. 1 is a circuit configuration diagram showing an embodiment of a discharge lamp lighting device according to the present invention, and the same components as those of the conventional example shown in FIG. 8 are designated by the same reference numerals.

The step-down chopper circuit 2 according to the present invention inputs the switching transistor Q1, the freewheel diode Dt, the DC reactor Ll+smoothing capacitor Ct, the driving circuit 11 of the switching transistor Ql, and the detection output of the current detection element R1 to the driving circuit 11. It is composed of a switching circuit 12 that sends out a control signal 4B. 1
3 is a secondary voltage detection circuit that detects the output voltage of the step-down chopper circuit 2, and compares the divided voltage of the series circuit of the resistor R1°R1 connected to the output terminal of the chopper circuit 2 and the resistor Rs with a predetermined value. It consists of a voltage detection section 14. 15 is a timer circuit, 16 is an OR circuit, and the output signal of the voltage detection circuit 13 and the output signal of the timer circuit 15 are manually input. 17 is full pre-Fuji type inverter 4
The switching transistors Q2゜Q, ,Q,
, a flip-flop circuit for driving Qs,
Control is controlled by switching between monostable and astable depending on the output of the OR circuit 16, and 18 is a starting circuit connected to the output end of the inverter 4, which also controls the O
Operation and non-operation are controlled depending on the output state of the R circuit 16. Note that C1 is a capacitor for bypassing the high voltage pulse generated from the starting circuit 18.

FIG. 2 is a diagram showing a detailed circuit configuration of the switching circuit 12 in the step-down chopper circuit 2. As shown in FIG.

In FIG. 2, 21 is an oscillator of a triangular reference wave, and a resistor R4 and a capacitor C4 determine the oscillation frequency of the reference wave generated by the oscillator 21. 22 is an operational amplifier, R
S is a drift compensation resistor of the amplifier 22, R& is an input resistor, and the detection output of the current detection element R1 is input to the operational amplifier 22 via these resistors R* and Rh. And between the output terminals of the 22 operational amplifiers, a feedback circuit is connected in parallel with a resistor Rq, a series circuit of a resistor R1 and a Zener diode ZD, and a series circuit of a resistor R9 and a capacitor C1 for phase compensation. . 23 is a comparator that compares and amplifies the reference voltage from the operational amplifier 22 and the triangular wave from the oscillator 21, and the output of the comparator 23 is sent to the drive circuit 1 of the chopper circuit 2.
1 is entered.

Next, the operation of the discharge lamp lighting device configured as described above will be described mainly with respect to the parts that are different from the conventional example. First, the 8th
Similar to the conventional lighting device shown in the figure, the commercial power supply l is rectified by a rectifying element, and its DC output is input to a step-down chopper circuit 2 to perform current control.
The output is input to a full bridge inverter 4. Then, the lamp 5 is started and lit by the operation of the inverter 4 and the starting circuit 18.

By the way, in the present invention, when the lamp is started, the detection output v1 of the current detection element R1 becomes large because the starting current is large. Therefore, this detection output V.

operational amplifier 220 of the switching circuit 12 into which
The input/output difference increases, which causes the Zener diode ZD of the feedback circuit to become conductive. As a result, the amplification factor α of the operational amplifier 22 is approximately expressed by the following equation +11.

R, +R.

This amplification factor α is determined by the following equation (2
) can be kept lower than the amplification factor α'.

As a result, as shown in FIG. 3(a), the operational amplifier 2
The output reference voltage B of No. 2 is lower than the value B1 when the amplification factor is α. The output reference voltage B1 or B2 of the operational amplifier 22 is compared with the triangular wave A of the oscillator 21 shown in FIG. 3(a) in the comparator 23, and the comparison output waveform C1 or C2 shown in FIG. 3(b) is obtained. can get. This comparison output C is input to the drive circuit 11 of the step-down chopper circuit 2, and a drive pulse having the same pulse width t1 or t2 shown in FIG. 3(b) is applied to the switching transistor QI of the step-down chopper circuit 2. Drive controlled.

Since the pulse width t1 when the amplification factor of the operational amplifier 22 is α is wider than the pulse width t2 when the amplification factor is α', a large starting current is caused to flow at the time of starting.

After the lamp is started, the lamp voltage increases, the detection output V of the current detection element R3 decreases, and the output reference voltage B of the operational amplifier 22 decreases, but the predetermined value before reaching the rated lamp voltage decreases. After reaching the voltage, the Zener voltage of the Zener diode ZD is set to the input/output potential difference of the operational amplifier 22 at that time so that the Zener diode ZD of the feedback circuit of the operational amplifier 22 is cut off.

As a result, when the predetermined lamp voltage is reached, from then on the operational amplifier 22 becomes an amplifier with an amplification factor α', and while the predetermined lamp voltage is reached, the amplification factor is analog-based due to the nonlinear characteristics of the Zener diode ZD. To increase.

Therefore, the rainbow curve showing the relationship between lamp voltage and lamp power is, as shown in FIG. The characteristic curve changes continuously across points P and Q due to the nonlinear characteristics of the Zener diode ZD, resulting in a characteristic as shown by the solid line. It has a constant function to prevent overpowering due to a rise in lamp voltage.

As described above, a means for supplying a lamp starting current with a value sufficient for starting can be obtained by simply adding a series circuit of a resistor and a Zener diode to the feedback circuit of the operational amplifier in the switching circuit of the step-down chopper circuit. , and by appropriately selecting these values, the lamp current at startup can be freely set, and it is possible to prevent overpowering as the lamp voltage increases.

By the way, when starting the lamp, a starting pulse is applied to the lamp 5 via the starting circuit 18, but at this time, noise enters the flip-flop circuit 17 that drives the full-bridge inverter 4, making it likely to malfunction.

In order to solve this problem, in the present invention, when starting the lamp, the flip-flop circuit 17 operates in a monostable state, and the full-bridge inverter 4 is operated in a fixed direction, for example, the switching transistor Q z .

Q is turned on and DC is supplied to light it up. 6 Then, when the lamp starts and the voltage detected by the voltage detection circuit 13 exceeds a predetermined value, the detection control signal is passed through the OR circuit 16 to the flip-flop circuit 17. is added to the starting circuit 18, stopping the starting circuit 18 and switching the operation of the flip-flop circuit 17 to an unstable state, which causes the
The full bridge inverter 4 is driven so as to apply a 00 Hz rectangular wave to the balance wheel 5.

As a result, the malfunction of the flip-flop circuit 17 will not cause short-circuit accidents of the transistors of the full-fledged circuit 4, and the lamp can be started stably. Further, as described above, the starting circuit 18 is stopped after starting by the detection control signal from the voltage detection circuit 13, and the generation of unnecessary starting pulses is prevented. Even if the lamp does not start, the starting circuit 18 is stopped by the output signal of the timer circuit 15 when the set time of the timer circuit 15 is reached, thereby preventing the pulse generation time from becoming excessive. There is.

That is, the starting circuit 18 is stopped by the control signal from the voltage detection circuit 13 or the signal from the timer circuit 15, whichever is earlier.

In the above embodiment, the present invention is applied to a discharge lamp lighting device using an AC-AC converter, but it may also be configured to directly input to a step-down chipper circuit using a DC power supply. As shown in FIG. 5, the present invention can be similarly applied to a discharge lamp lighting device using a DC-DC converter that lights with DC output without using a full-bridge inverter, and the same effects and effects can be obtained. is obtained.

〔Effect of the invention〕

As described above based on the embodiments, according to the present invention, the feedback circuit of the operational amplifier constituting the switching circuit that controls the pulse width of the step-down chopper circuit includes:
With a simple configuration that adds a series circuit of a resistor and a Zener diode, when starting a discharge lamp, the amplification factor of the operational amplifier is suppressed and the pulse width is controlled to be large, allowing sufficient current to flow for starting and stabilizing the lamp. Appropriate power can be supplied to start the lamp and increase the operational amplification factor near the stable state to prevent overpower from occurring as the lamp voltage increases.

Furthermore, since no relays are used, reliability is improved and a large economical effect can be obtained.

In addition, in the case of a device using a full-bridge type inverter, by configuring the flip-flop circuit that drives the full-bridge type inverter to be in a monostable state when starting the lamp, it is possible to prevent the flip-flop circuit from causing noise in the starting circuit when starting the lamp. Malfunctions can be prevented. Furthermore, by configuring the starting circuit to stop after lighting the lamp or after a certain period of time, it is possible to prevent unnecessary energy consumption and provide a highly reliable discharge lamp lighting device.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a discharge lamp lighting device according to the present invention, FIG. 2 is a circuit diagram showing a switching circuit of a step-down chipper circuit, and FIGS. B) is a signal waveform diagram for explaining the operation, FIG. 4 is a diagram showing the relationship between lamp voltage and lamp power, and FIG. 5 is a circuit configuration diagram showing another embodiment of the present invention. Fig. 6 shows a discharge lamp lighting device using a conventional steel type ballast, Fig. 7 shows a discharge lamp lighting device using a conventional high frequency inverter, and Fig. 8 shows a conventional low frequency inverter. FIG. 9 is a diagram showing an example of the circuit configuration of a discharge lamp lighting device for square wave lighting, and FIG. 9 is a circuit configuration diagram showing an example of an improvement of the discharge lamp lighting device of FIG. In the figure, 2 is a step-down chipper circuit, 4 is a full-bridge inverter, 5 is a discharge lamp, 11 is a drive circuit, 12 is a switching circuit, 13 is a voltage detection circuit, 15 is a timer circuit, 18 is a starting circuit, and 21 is a An oscillator, 23 indicates a comparator.

Claims (1)

[Scope of Claims] 1. In a discharge lamp lighting device equipped with a step-down chopper circuit that performs current control by inputting direct current, the device is inserted between a freewheel diode and a smoothing capacitor at the output section of the step-down chopper circuit. and a switching circuit that controls the pulse width of the step-down chopper circuit that includes a built-in operational amplifier that inputs the detection output of the current sensing element, and the operational amplifier has a first resistor and a Zener diode. The radiation source is characterized in that it has a feedback circuit consisting of a series circuit and a parallel circuit of a second resistor, and is configured to change the amplification factor of the operational amplifier in response to the lamp current and control the pulse width of the chopper circuit. Electric light lighting device. 2. A full-bridge inverter is provided to input the output of the step-down chopper circuit, a discharge lamp and a lamp starting circuit are connected to the output terminal of the full-bridge inverter, and the lamp starting circuit is operated for a predetermined period of time at the time of starting. In addition, the flip-flop circuit driving the full-bridge inverter is operated in a monostable state, the lamp starting circuit is stopped at the same time the lamp is turned on, and the flip-flop circuit is operated in an astable state. The discharge lamp lighting device according to claim 1. 3. The discharge lamp lighting device according to claim 2, further comprising a circuit that outputs a stop signal for the lamp starting circuit based on the DC voltage at the output end of the step-down chopper circuit or the full-bridge inverter. 4. A lamp starting circuit is connected to the output end of the step-down chopper circuit together with the discharge lamp, and a circuit is provided for outputting a stop signal for the lamp starting circuit based on the voltage at the output end of the step-down chopper circuit. The discharge lamp lighting device according to claim 1. 5. A timer circuit is provided that outputs a signal to stop the lamp starting circuit if the lamp is not lit within a predetermined time, and at least one of the output signal from the timer circuit and the starting circuit stop signal is used. 5. The discharge lamp lighting device according to claim 3, wherein the discharge lamp lighting device is configured to stop the lamp starting circuit.