JPH04303596A - Electric discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To prevent abnormal oscillation by controlling an oscillation output of an oscillation transistor in a small quantity even when power source voltage drops. CONSTITUTION:Resistances 91, 92 are connected in parallel referring to a power source, and the cathode of a Zener diode 94 is connected to the contact of the resistance, and the anode thereof is connected to the base of a transistor 94. The emitter of the transistor 94 is connected to the ground side, and a collector is connected to an end of a base bias resistance 71 through a resistance 95. When a power source voltage is rated, the diode 93 and the transistor 94 are turned on, and the resistance 95 is connected in parallel to the resistance 77. Hereupon, if power source voltage much drops, the diode 93 and the transistor 94 are off, and resustantly, a transistor 63 is off, and the resistance value of FET 56 is very much greatly set, and the oscillation output of a transistor 50 is controlled to a small quantity. It is thereby possible to eliminate flickering of a lamp.

Description

[Detailed description of the invention]

[Object of the invention]

0002

[Industrial Application Field] The present invention relates to a discharge lamp lighting device.
In particular, the present invention relates to a discharge lamp lighting device that prevents abnormal oscillation from occurring in a single-voltage resonance inverter circuit.

0003

2. Description of the Related Art Generally, all-electronic ballasts have become popular as a lighting method for fluorescent lamps.

In such a lighting device for a fluorescent lamp, the secondary winding of a high-frequency oscillation transformer used as a high-frequency oscillation means functions as a ballast, and the oscillation frequency is, for example, several tens of thousands.
Because the frequency is as high as kHz, a sufficient discharge stabilization effect can be obtained even with a very small transformer.Furthermore, since a high frequency voltage is applied between the fluorescent lamp electrodes, the luminous efficiency is high and the discharge sustaining ability is high, eliminating light that causes flickering. It has the excellent advantage of less pulsation.

Among high-frequency lighting devices for fluorescent lamps, the single-voltage resonance inverter circuit has the simplest circuit configuration and is capable of output control.

FIG. 2 shows an example of a conventional single-voltage resonant inverter circuit. This circuit shows a circuit configuration in which constant oscillation voltage and high voltage functions for starting a fluorescent lamp are added to the basic circuit configuration of a single-voltage resonant inverter circuit.

In FIG. 2, 1 is a DC power supply, and a high frequency inverter is connected to this power supply 1. The high-frequency inverter is a one-stone self-excited voltage resonance type, in which a resonant capacitor 3 is connected in parallel to the primary winding 2a of the high-frequency transformer 2, an oscillation transistor 4 is connected to the other end of the primary winding 2a, and the high-frequency transformer Both ends of the secondary winding 2b of the transformer 2 are connected to electrodes at both ends of the fluorescent lamp 5, a starting capacitor 6 is connected between each electrode, and the transformer 2 further comprises the secondary winding of the transformer 2 and the fluorescent lamp 5. Current transformer 7 for positive feedback to the lamp circuit
and one end of its secondary winding is connected to the base of the oscillation transistor 4. A transistor 4 is connected between the other end of the secondary winding of the transformer 7 and the emitter of the oscillation transistor 4.
Capacitors 8, 9 and MOSF are used to control the on-time of
ET10 is connected, and a diode 11 and a resistor 1 for controlling the on-time are connected between the base and emitter of the transistor 4.
2 is connected.

In the above configuration, MOSFET 10 functions as a variable resistance element, and a drive voltage is supplied to its gate. By changing the drive voltage, if the resistance value of the FET 10 is increased, the feedback voltage to the base of the oscillation transistor 4 will be reduced and the switching on time will be shortened, and if the resistance value is decreased, the feedback voltage to the transistor 4 will be reduced. can be controlled so that the on-time of switching increases. A diode 13 and a capacitor 14 are connected between the collector and emitter of the oscillation transistor 4.
A peak voltage detection circuit 15 is provided, and this detected voltage is appropriately divided by a voltage dividing circuit 16, and then compared and amplified with a reference voltage source 18 by an error amplifier 17, and the comparison output is used to drive the MOSFET 10. drive 15 like this
By providing a closed loop control system consisting of the transistors 18 and 10, 4, the peak value of the resonant voltage generated between the terminals of the transistor 4 can be made constant. As a result, output fluctuations can be compensated for minute power supply voltage fluctuations.

On the other hand, when starting the fluorescent lamp 5, a high oscillation voltage is required. For this reason, a circuit is provided to apply the high voltage necessary for starting the fluorescent lamp to the fluorescent lamp. Specifically, as shown in FIG. 2, the lamp voltage at both ends of the fluorescent lamp 5 is supplied to the light emitting part 24a of the photocoupler 24 through a voltage dividing circuit 19, a rectifying and smoothing circuit 20, and further through a delay circuit 21 using a capacitor. The delay circuit 21 is composed of a capacitor for charging the lamp voltage and a switch transistor that is turned on during the charging process, and the light emitting part 24a of the photocoupler 24 starts to emit light while the switch transistor is on. ing. Light emitting part 24a
The optical signal from the photocoupler 24 is supplied to the reference voltage source 18 through the light receiving section 24b of the photocoupler 24, and the voltage value of the reference voltage source 18 is controlled to be lowered. As a result, the output level of the error amplifier 17 increases, the resistance value of the FET 10 decreases, and the oscillation output of the oscillation transistor 4 increases. As a result, a high voltage necessary for starting is applied to the fluorescent lamp 5 for a certain period of time, and the fluorescent lamp 5 is started. After starting, since the capacitor in the delay circuit 21 has completed charging, the transistor connected to the capacitor is turned off, and as a result, the light emitting section 24a of the photocoupler 24 is turned off. When the photocoupler 24 is turned off, the voltage value of the reference voltage source 18 increases and the output of the error amplifier 17 decreases, so that the FE
The resistance value of T10 increases, and the oscillation output of the oscillation transistor 4 decreases to a value necessary to maintain normal operation.

FIG. 3 shows an example of the configuration of the peak voltage detection circuit 15, voltage dividing circuit 16, and error amplifier 17 in FIG.

In FIG. 3, the peak voltage detection circuit 15 is composed of a diode 13, a resistor 25, and a capacitor 14, and a peak detection value obtained at the connection point between the resistor 25 and the capacitor 14 is input to the base of a switch transistor 17. ing. The emitter of the transistor 17 is connected to the resistors 26, 27,
The collector is connected to the positive side of the power source 1 via resistors 29 and 30, and the collector is connected to the negative side of the power source 1 via resistors 29 and 30. Then, the connection point of the resistors 29 and 30 is connected to the MOSFE.
Connected to the gate of T10. On the other hand, transistor 1
The base of 7 is connected to the negative side of power supply 1 via bias resistors 31, 32, and 33.
The light receiving portion 24b of the photocoupler is connected between the connection point of the power source 1 and the negative terminal of the power source 1.

In the inverter circuit configured as described above, the circuit provided for stabilizing the oscillation voltage of the transistor 4 (see FIG. 3) is such that when the oscillation voltage of the transistor 4 slightly fluctuates, the voltage When the peak detection voltage of the peak voltage detection circuit 15 decreases due to the drop, the transistor 17 turns on and collector current flows, and as a result, the gate voltage of the variable resistance element (MOSFET) 10 increases and the resistance value of 10 increases. decreases, FET 10 turns on, and the oscillation output of transistor 4 increases. Therefore, the oscillation output is controlled to be constant.

By the way, when the power supply voltage fluctuates greatly and decreases, the oscillation output of the transistor 4 operates to increase, but at this time abnormal oscillation occurs, causing the lamp to flicker. Abnormal oscillation when the power supply voltage drops in this way appears as flickering in the lamp, so it is necessary to reduce the oscillation output.
No measures had been taken.

Furthermore, as shown in FIG. 3 above, in a photocoupler used to generate high voltage when starting a fluorescent lamp, both ends of the light receiving section 24b of the photocoupler are connected in parallel to both ends of a bias resistor 33. Therefore, after the capacitor in the delay circuit 21 in FIG. 2 completes charging (that is, when the steady state is reached), the charging voltage is discharged due to fluctuations in the power supply voltage, etc., and current flows to the light emitting part 24a of the photocoupler. As a result, the light-receiving section 24b of the photocoupler malfunctions or its operation slightly fluctuates, and the resistance value of the on-time control FET 10 fluctuates, causing an abnormality in the oscillation waveform of the transistor 4. Such waveform abnormalities become a factor that deteriorates luminous efficiency.

[0015]

[Problem to be solved by the invention] As mentioned above, conventionally,
When the power supply voltage decreases or the light receiving section of the photocoupler malfunctions, abnormal oscillation occurs, causing the lamp to flicker and the luminous efficiency to decrease.

Therefore, in view of the above problems, the present invention has been developed to prevent abnormal oscillation even when the power supply voltage decreases.
Another object of the present invention is to provide a discharge lamp lighting device that can obtain a normal oscillation waveform even if the light receiving section of the photocoupler malfunctions.

[Configuration of the invention]

[0018]

[Means for Solving the Problems] A discharge lamp lighting device according to the present invention as set forth in claim 1 includes: a transistor inverter that switches a voltage from a DC power source and converts it into an AC voltage using a transformer and a first transistor; A lamp circuit that lights a discharge lamp using AC output from this inverter;
A transformer is provided in the lamp circuit to provide positive feedback to the first transistor to cause the first transistor to self-oscillate, and a feedback circuit is provided in the feedback circuit to control the on-time of the first transistor. The peak value of the oscillation voltage generated between the terminals of the variable resistance element and the first transistor is detected, and the output obtained by turning off and on the second transistor depending on the magnitude of this detected voltage is used to control the variable resistance element. A first control circuit that drives the element and controls the oscillation voltage to be constant, and a third transistor that switches the value of the base bias resistance of the second transistor of the first control circuit. By turning off and on the third transistor according to voltage fluctuations of the DC power supply, the variable resistance element is driven in a direction to turn off when the power supply voltage drops below a predetermined value, and the oscillation output of the first transistor is generated. The present invention is characterized in that it includes a second control circuit that lowers the temperature.

The discharge lamp lighting device according to the present invention according to claim 2 includes a transistor inverter that switches a voltage from a DC power source and converts it into an AC voltage using a transformer and a first transistor, and an AC output from the inverter. a lamp circuit for lighting a discharge lamp; a feedback circuit for providing positive feedback to the first transistor by providing a transformer in the lamp circuit to cause the first transistor to self-oscillate; and a feedback circuit provided in the feedback circuit. detecting a peak value of an oscillation voltage generated between a variable resistance element for controlling an on-time of the first transistor and a terminal of the first transistor;
The variable resistance element is driven by the output obtained by turning off and on the second transistor depending on the magnitude of the detected voltage,
a first control circuit that controls the oscillation voltage to be constant;
means connected in parallel to the discharge lamp, which turns on a third transistor while gradually charging a capacitor at the same time as starting the discharge lamp, turns on a light emitting part of a photocoupler for a certain period of time, and generates an optical signal; The base of the second transistor of the first control circuit is sometimes provided with a photocoupler light receiving section that receives an optical signal from the photocoupler light emitting section.
A parallel circuit of a capacitor and a resistor is connected between the base and emitter of the fourth transistor, and one end of the parallel circuit is connected to the photocoupler through the resistor to receive light from the photocoupler. By connecting the fourth transistor to the circuit and turning on the fourth transistor with the voltage charged in the capacitor of the parallel circuit at the time of starting, the variable resistance element is driven in the direction of turning on, and the oscillation output of the first transistor is turned on. This is characterized by comprising a second control circuit for raising the height.

[0020]

According to the invention as set forth in claim 1, even if the power supply voltage fluctuates and drops significantly, abnormal oscillation does not occur and flickering of the lamp can be prevented.

Further, according to the second aspect of the invention, even if the light receiving section of the photocoupler malfunctions, a normal oscillation waveform can be obtained, and a decrease in luminous efficiency can be prevented.

[0022]

[Example] An example will be described with reference to the drawings. FIG. 1 is a circuit diagram showing a discharge lamp lighting device according to an embodiment of the present invention.

In FIG. 1, 41 is a commercial AC power supply, 42
is a power rectifier circuit, and capacitors 43 and 44 and diodes 45 to 4 are connected to both ends of the output terminal of this power rectifier circuit 42.
A smoothing rectifier circuit consisting of 7 is connected. A high frequency inverter is connected to this smoothing rectifier circuit. The high-frequency inverter is a single-stone self-excited voltage resonance type, and a resonant capacitor 49 is connected to the primary winding 48a of the high-frequency transformer 48.
are connected in parallel, the oscillation transistor 50 is connected to the other end of the primary winding 48a, and the secondary winding 48 of the high frequency transformer 48
Both ends of b are connected to the electrodes at both ends of the fluorescent lamp 51, a starting capacitor 52 is connected between each electrode, a current transformer 53 for positive feedback is connected to the lamp circuit, and the secondary winding is One end is connected to the base of the oscillation transistor 50. Capacitors 54 and 55 and a MOSFET 56 are connected between the other end of the secondary winding of the transformer 53 and the emitter of the oscillation transistor 50 for controlling the on-time of the transistor 50.
A diode 57 and a resistor 58 for controlling on-time are connected between the base and emitter of the transistor 50. The MOSFET 56 functions as a variable resistance element, and a drive voltage is supplied to its gate. The resistance value of the FET 56 can be controlled by the drive voltage.

The collector of the oscillation transistor 50 is provided with a circuit for controlling the oscillation voltage of the transistor to be constant. A diode 59, a resistor 60, and a capacitor 61 are connected between the collector and emitter of the oscillation transistor 50.
A peak voltage detection circuit 62 is provided, and the peak voltage value obtained at the connection point between the resistor 60 and the capacitor 61 is inputted to the base of the switching transistor 63. The emitter of transistor 63 is resistor 64, 65, 66
The collector is connected to the positive side of the power rectifier circuit 42 through resistors 67 and 68, and the collector is connected to the negative side of the power rectifier circuit 42 through resistors 67 and 68. The connection point between the resistors 67 and 68 is connected to the gate of the MOSFET 56. On the other hand, the base of the transistor 63 is connected to a bias resistor 69,
It is connected to the negative side of the power rectifier circuit 42 via 70 and 71. The resistor 70 is composed of a variable resistor,
By adjusting this, the bias value of the transistor 63 can be varied and the on-time of the transistor 50 can be adjusted.

On the other hand, a circuit is provided between the electrodes of the fluorescent lamp 51 to generate a high voltage when starting the lamp. The lamp voltage across the fluorescent lamp 51 is connected to the capacitor 7.
After dividing with a voltage divider circuit of 2.73, diodes 74,7
5, a rectifying and smoothing circuit consisting of a capacitor 76 and a resistor 77, and further leading to the base of a switching transistor 81 through a delay circuit consisting of a capacitor 78 and a resistor 79. A diode is connected between the base and emitter of the transistor 81 to prevent the capacitor 78 from charging in the opposite direction.
A parallel circuit of a capacitor 82, a resistor 83, and a photocoupler light emitting section 85 is connected to the collector side. In the light emitting section 85, when the capacitor 78 gradually charges after the power is turned on when starting the lamp, base current is supplied to the transistor 81 during the charging process, and the transistor 81 is supplied with base current.
1 is turned on, and at this time, the phototransistor constituting the light emitting section 85 is also turned on, and the transistor 81 has the light emitting section 85.
Electric current flows through it and it emits light. This light emission continues for a certain period of time until charging of the capacitor 78 is completed.

The optical signal from the light emitting section 85 is input to the light receiving section 86 of the photocoupler. One end of this light receiving section 86 is connected to the positive side of the power rectifier circuit 42 via resistors 65 and 66, and the other end is connected to the base of a transistor 90 via a resistor 87. A capacitor 88 and a resistor 89 are connected in parallel between the emitters, and the collector-emitter path of the transistor 90 is connected in parallel to both ends of the resistor 71.

When an optical signal enters the light receiving section 86 and turns it on, current flows through the resistor 87 and connects the capacitor 8.
8 and a resistor 89 in parallel. At this time, the voltage generated across resistor 89 is applied to the base of transistor 90, turning transistor 90 on. As a result, the base resistance of the transistor 63 decreases, and the transistor 63
is turned on, and the voltage generated in the resistor 86 operates to turn on the FET 56, lengthening the on time of the oscillation transistor 50, increasing the oscillation output, and lighting the fluorescent lamp 51. When the fluorescent lamp 51 is on, the capacitor 7
Since the transistor 8 completes charging, no base current is supplied to the transistor 81, so the transistor 81 is turned off, and therefore the photocoupler light emitting section 85 is turned off. Then, the light receiving section 86 is also turned off, the transistors 90 and 63 are also turned off, the resistance value of the FET 56 is increased, and the oscillation output of the transistor 50 is set to a low output necessary to maintain stable lighting. In this embodiment, the charge in the capacitor 78 is then discharged and flows into the photocoupler light-emitting section 85, so that even if the light-emitting section 85 accidentally emits light instantaneously, the light will cause the light-receiving section to The current instantaneously flowing through capacitor 86 is absorbed by capacitor 88 and does not reach the point where transistor 90 is turned on. Therefore, the lighting state is kept stable and no abnormal oscillation waveform is generated in the transistor 50.

Furthermore, in this embodiment, when the power supply voltage fluctuates greatly and changes in the direction of decreasing, the transistor 50
A circuit is provided to prevent the oscillation output from increasing and causing an abnormal oscillation state. That is, the rectified DC voltage obtained at the connection point between the diode 47 and the capacitor 44 is used as a power source, two resistors 91 and 92 are connected in parallel to this power source, and the cathode of a Zener diode 93 is connected to the connection point. The anode is connected to the base of a transistor 94, the emitter of 94 is connected to the ground side, and the collector is connected to one end of the base bias resistor 71 via a resistor 95. In this circuit, when the power supply voltage of the DC power supply is in the rated state, the Zener diode 93 is on, the transistor 94 is on, and a resistor 95 is connected in parallel to the bias resistor 71. There is. Here, when the power supply voltage decreases significantly, the Zener diode 93 and the transistor 94 are turned off, and as a result,
Transistor 63 is turned off, the resistance value of FET 56 is set to a very large value, and the oscillation output of transistor 50 is suppressed to a small value. That is, when the power supply voltage decreases significantly, the oscillation output of the transistor 50 is suppressed, so that abnormal oscillation does not occur and the lamp does not flicker.

[0029]

[Effects of the Invention] As described above, according to the present invention, even if the power supply voltage drops significantly or the photocoupler's light receiving section malfunctions, an abnormal oscillation waveform will not occur.
This eliminates flickering in the lamp and reduction in luminous efficiency.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a discharge lamp lighting device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a conventional discharge lamp lighting device.

FIG. 3 is a circuit diagram showing the main circuit of FIG. 2;

[Explanation of symbols]

42...Power rectifier circuit 48...Transformer 49, 54, 55, 61, 78...Capacitor 50, 6
3,81,90,94...Transistor 51...Fluorescent lamp 56...Variable resistance element (FET) 85,86...Photocoupler

Claims (2)

[Claims] Claim 1: Using a transformer and a first transistor,
a transistor inverter that switches voltage from a DC power source and converts it into AC voltage; a lamp circuit that lights a discharge lamp with AC output from the inverter; and a transformer provided in the lamp circuit to connect the first transistor to the transistor inverter. a feedback circuit that performs positive feedback to cause the first transistor to self-oscillate; a variable resistance element provided in the feedback circuit to control the on-time of the first transistor; and a terminal of the first transistor. A first control device that detects the peak value of the generated oscillation voltage, turns off and turns on the second transistor depending on the magnitude of the detected voltage, and drives the variable resistance element with the obtained output to control the oscillation voltage to be constant. and a third transistor for switching the value of the base bias resistance of the second transistor of the first control circuit, the third transistor being turned off and off in response to voltage fluctuations of the DC power supply. and a second control circuit that turns on the variable resistance element to turn off the variable resistance element when the power supply voltage drops below a predetermined value, thereby reducing the oscillation output of the first transistor. discharge lamp lighting device. [Claim 2] Using a transformer and a first transistor,
a transistor inverter that switches voltage from a DC power source and converts it into AC voltage; a lamp circuit that lights a discharge lamp with AC output from the inverter; and a transformer provided in the lamp circuit to connect the first transistor to the transistor inverter. a feedback circuit that performs positive feedback to cause the first transistor to self-oscillate; a variable resistance element provided in the feedback circuit to control the on-time of the first transistor; and a terminal of the first transistor. A first control device that detects the peak value of the generated oscillation voltage, turns off and turns on the second transistor depending on the magnitude of the detected voltage, and drives the variable resistance element with the obtained output to control the oscillation voltage to be constant. The control circuit is connected in parallel to the discharge lamp, and when the discharge lamp is started, the capacitor is gradually charged while the third transistor is turned on, and the light emitting part of the photocoupler is turned on for a certain period of time to generate an optical signal. and a fourth transistor that includes a photocoupler light receiving section that receives an optical signal from the photocoupler light emitting section during startup, and that switches the value of the base bias resistance of the second transistor of the first control circuit. A parallel circuit of a capacitor and a resistor is connected between the base and emitter of the fourth transistor, one end of the parallel circuit is connected to the photocoupler light receiving section via the resistor, and the parallel circuit is connected at the time of startup. a second control circuit that drives the variable resistance element in the direction of turning on by turning on the fourth transistor with a voltage charged in the capacitor, thereby increasing the oscillation output of the first transistor. A discharge lamp lighting device characterized by: