JPH01213994A - Electric discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To hold the lamp current constant at a desired value by providing pulse width modulation means in a feedback control system and outputting a PWM signal to a semiconductor switching device in response to the result of comparison for controlling it. CONSTITUTION:The desired value of a lamp Current flowing through an electric discharge lamp 2 is set by a reference power supply 10. On the other hand, during the operation of the circuit, a switching ripple current, accompanied by the charging and discharging of a capacitor C, corresponding to the lamp current is continually detected via a detecting winding 5a by a detecting circuit 5b, and the detected current value is supplied to the input of an error amplifier 7. If there is a difference between the detected current value and the desired value, an error signal is produced from the output of the error amplifier 7, and a pulse width modulation(PWM) signal is produced from the output of a pulse width modulator 8 for correcting the error so that the switching duty ratio of the switching transistor Q3 or Q4 is automatically controlled. The lamp current is thus held constant at a desired value.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a discharge lamp lighting device suitable for lighting a discharge lamp, particularly a high-intensity discharge lamp.

Conventional technology Generally speaking, the main function of a discharge lamp lighting device is "current limiting".
In other words, from a different perspective, it can be said to be the exchange of reactive power.

Handling reactive power requires temporary energy storage means.

In this regard, conventional discharge lamp lighting devices of this type connect an AC power supply, a discharge lamp, a phase control circuit, and an inductance element for energy storage in series, and conduct current through the inductance element using the phase control circuit. The current flowing through the discharge lamp is converted into a direct current, and the current value flowing through the discharge lamp is controlled via this inductance element, so that the discharge lamp is supplied with a current that is close to a rectangular wave and has a controlled average current value. This is known from Japanese Patent Application Laid-Open No. 57-72296.

In other words, flicker is reduced by bringing the current supplied to the discharge lamp closer to a rectangular wave, and the discharge lamp is dimmed by controlling the lamp current (average value).

However, in a discharge lamp lighting device, in order to reduce flicker, it is necessary to make the inductor as an inductance element larger, and it is necessary to make the inductor as an inductance element larger. are contradictory.

Therefore, in order to satisfy these conflicting demands, the present applicant proposed a device in which the inductance element is composed of a simulated inductor.
It has been proposed as Publication No.-181491.

Problems to be Solved by the Invention According to the publication, it is stated that the lamp current can be made constant by detecting the lamp current and controlling the phase of the firing angle α of the thyristor. However, when attempting to maintain the lamp current at a certain target value, there is no specific description of how to control the lamp current in accordance with the target value.

Means for Solving the Problems In a discharge lamp lighting device comprising an AC power source, a discharge lamp, and a simulated inductor circuit or simulated capacitor circuit including a main capacitor and a semiconductor switching element, the lamp current flowing through the discharge lamp a detection means for detecting a current corresponding to the current value, and a feedback control system for controlling the semiconductor switching element so that the current value detected by the detection means matches a target value;
A pulse width modulation means is provided in this feedback control system.

A current corresponding to the active lamp current is always detected by the detection means, for example as a switching ripple current of the main capacitor. The detected current value is compared with a target value in a feedback control system, and feedback control is performed to match the target value.

At this time, since a pulse width modulation means is provided in the feedback control system, by outputting a PWM signal according to the comparison result to the semiconductor switching element and controlling it, the lamp current value is kept constant as the target value. maintained at the value.

Example An embodiment of the present invention will be described based on the drawings.

First, an AC power source 1, a discharge lamp 2, and a simulated inductor circuit (slow-phase current-limiting circuit) 3 are connected in series. This simulated inductor circuit 3
has the property of flowing a slow-phase current with respect to the applied AC voltage from the AC power supply 1, and has a main capacitor C as an energy storage means and a semiconductor connected in a bridge to control charging and discharging of the capacitor C. A single choke-like high-frequency smoothing device is connected between the connection midpoint of the four transistors Q1 to Q4 as switching elements, the four rectifying diodes D1 to D4, and the transistor Q3゜Q and the discharge lamp 2. (inductance). Here, the transistors Q1 to Q4 are individually controlled in operation by a drive circuit 4 to be turned on and off.

Therefore, a detection means 5 is provided for detecting the switching ripple current of the main capacitor C as a current corresponding to the lamp current flowing through the discharge lamp 2. This detecting means 5 consists of a detecting winding 5a provided on the wiring to the main capacitor C and a detecting circuit 5b. Also, depending on the current value detected by the detection means 5, the transistors Q1 to Q
A feedback control system 6 is provided to control the operation and status of the . This feedback control system 6 consists of an error amplifier 7, a pulse width modulation circuit 8, and a switching circuit 9. Here, the target value of the lamp current is input to the error amplifier 7 from the variable voltage reference power supply 10 as a reference voltage, and the detected current value (voltage conversion value) output from the detection circuit 6b is inputted as a reference voltage. ) is compared with a reference voltage.

In such a configuration, basically, when the voltage of the AC power source 1 is positive, only the transistor Q is switched at a frequency higher than the AC power frequency in a certain phase to charge the main capacitor C and store energy. Let's do it. This charging operation is performed like a step-up switching power supply circuit. Next, at a predetermined phase in which the AC power source is also positive, the transistor Q2 is turned on, and the switching operation of the transistor Q is continued to discharge the energy stored in the main capacitor C. In other words, it operates as a step-down switching power supply circuit. When the power supply voltage is negative, exactly the same operation is performed using transistors Q, , Q.

In this way, the simulated inductor circuit 3 performs the function of transmitting and receiving energy to continue a current like a normal inductor, and the discharge lamp 2 is lit. Further, since the single choke L only has to function to smooth high-frequency switching ripple, a small one with low inductance is sufficient. Also, the main capacitor C is
Considering the case where the same reactive power is handled, it is possible to significantly reduce the size by using an inductor.

In such an operation, the target value of the lamp current to be passed through the discharge lamp 2 is set by the base tUt source 10. On the other hand, regarding the circuit in operation, a switching ripple current accompanying charging/discharging of the main capacitor C corresponding to the lamp current flows through the detection circuit 5 through the detection winding 5a.
b, and the detected current value is always detected by the error amplifier 7.
is input. And if there is a deviation from the target value,
An error signal is output from the error amplifier 7, a pulse width modulated PWM signal is output from the pulse width modulator 8 to correct the error, and the switching duty ratio of the switching transistor Q3 or Q4 is automatically controlled. . Such operations are performed until the detected current value matches the target value. In this way, the lamp current is maintained at a constant value, which is the target value, by feedback control accompanied by PWM signal generation.

Further, when controlling the PWM I11, the lamp current becomes a rectangular wave by switching the polarity in synchronization with the power supply voltage. At this time, since there is no rest period, the breast factor is minimized, the lamp efficiency is increased, and therefore the lamp life is also extended. In addition, in these operations, the response of the feedback control system 6 is set to be sufficiently fast compared to the power supply frequency. Furthermore, in this embodiment, the target value of the lamp current can be set externally by variable operation of the reference power source 10, so it can be applied to constant power control, dimming control, remote control control, etc. as necessary. It is also easy.

Note that in this embodiment, the simulated inductor circuit 3
However, for example, a simulated capacitor circuit (phase-advanced current limiting circuit) having the property of flowing a phase-advanced current with respect to the applied AC power source in the same circuit configuration may be similarly applied.

Effects of the Invention As described above, the present invention utilizes a simulated inductor circuit or a simulated capacitor circuit to reduce flicker and reduce the size and weight of the device. PW value control
This can be done easily and reliably using feedback control with M control, and since PWM control is used, the lamp current can be reliably turned into a square wave by switching the polarity in synchronization with the power supply, making it more effective in reducing flicker. It is possible.

[Brief explanation of the drawing]

The drawing is a circuit diagram showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... AC power supply, 2... Discharge lamp, 3... Simulated inductor circuit, 5... Detection means, 6...
Feed pack control system, 8... pulse width modulation means, C
...Main capacitors, Q1 to Q4...For semiconductor switching elements Application Person Toshiba Electric Materials Corporation

Claims (1)

[Claims] In a discharge lamp lighting device comprising an AC power supply, a discharge lamp, and a simulated inductor circuit or simulated capacitor circuit including a main capacitor and a semiconductor switching element, detection for detecting a current corresponding to a lamp current flowing through the discharge lamp. and a feedback control system for controlling the semiconductor switching element so that the current value detected by the detection means matches the target value,
A discharge lamp lighting device characterized in that a pulse width modulation means is provided in this feedback control system.