JPH07106082A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To obtain a discharge lamp lighting device, which can lower the burden to be applied to a switching element without flowing a large current to an inverter circuit at the time of starting. CONSTITUTION:Before a capacitor C3 is charged, a transistor Q1 is not turned on, and a transistor Q2 is turned on, and a smoothening capacitor C1 is charged by a closed circuit formed of a full-wave rectifying unit 1, the smoothening capacitor C, a resistor R2, an emitter and a collector of the transistor Q2, and the full-wave rectifying unit. When the smoothening capacitor C1 is charged, the oscillation of the transistor Q1 of an inverter circuit 3 is started, and since electric potential exists in the smoothening capacitor C1 when the inverter circuit 3 is started, application of the peak current to the transistor Q1 can be prevented, and a high current is not flowed to the transistor Q1 at a moment when the transistor Q1 is turned on. The transistor Q1 is switched by an oscillation control means 5, and the inverter circuit 3 generates the high-frequency alternating current to light a fluorescent lamp FL at a high frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting device for rectifying and smoothing the voltage of an AC power source and then converting it into a high frequency by an inverter circuit.

[0002]

2. Description of the Related Art Conventionally, as a discharge lamp lighting device of this type, a structure disclosed in, for example, Japanese Patent Laid-Open No. 2-192695 is known.

In the discharge lamp lighting device disclosed in Japanese Patent Laid-Open No. 2-192695, a transistor as a switching element of a single-stone inverter circuit is formed by rectifying the voltage of a commercial AC power source E by a rectifying circuit and smoothing it by a smoothing circuit. There is known a configuration in which the inductor and the capacitor of the resonance circuit of the inverter circuit are caused to resonate to oscillate at a high frequency to illuminate the discharge lamp and charge the smoothing capacitor provided in the smoothing circuit.

[0004]

However, in the case of the structure described in Japanese Patent Laid-Open No. 192695/1990, when the commercial AC power source is first turned on, no charge is stored in the smoothing capacitor, and the input voltage is reduced. Is applied to the inductor of the resonance circuit, and a high voltage is applied to the switching element based on the impedance of the inductor, so that a large current flows.

In particular, in a section where the voltage of the commercial AC power source is high, the inductance of the resonance circuit rises sharply and the inductor is likely to be saturated.

Further, when the current to the switching element is large, the current when the switching element is turned on becomes large, and the load on the switching element also becomes large, so that it is necessary to use a large capacity switching element.

The present invention has been made in view of the above problems, and does not cause a large current to flow through the inverter circuit even at the time of startup.
In particular, it is an object of the present invention to provide a discharge lamp lighting device that reduces the load on the switching element.

[0008]

According to a first aspect of the present invention, there is provided a discharge lamp lighting device in which an AC power source voltage is rectified by a rectifying circuit, an output of the rectifying circuit is smoothed by a smoothing circuit having a smoothing capacitor, and an inverter circuit is provided. In a discharge lamp lighting device that switches a switching element to light a discharge lamp at a high frequency and charges the smoothing capacitor by the operation of the switching element, a charging circuit that charges the smoothing capacitor before oscillation of the inverter circuit is provided. It is a thing.

In the discharge lamp lighting device according to the second aspect, the voltage of the AC power supply is rectified by the rectifier circuit, the output of the rectifier circuit is smoothed by the smoothing circuit having the smoothing capacitor, and the output is switched by the switching element of the inverter circuit. In a discharge lamp lighting device that lights a discharge lamp at a high frequency and charges the smoothing capacitor by the operation of the switching element, a low voltage that starts the switching element when the AC power supply has a low voltage during oscillation of the inverter circuit. It is equipped with a starting circuit.

[0010]

In the discharge lamp lighting device according to the first aspect, since the switching element of the inverter circuit is activated after the smoothing capacitor is charged by the charging circuit, the current flowing through the switching element can be lowered and the capacity of the switching element can be reduced. Therefore, even when the inverter circuit oscillates, the burden on the components is reduced.

In the discharge lamp lighting device according to the second aspect of the present invention, the low voltage starting circuit activates the switching element when the AC power supply is at a low voltage, so that the current flowing through the switching element can be reduced and the capacity of the switching element can be reduced. The load on the components is reduced even when the inverter circuit oscillates.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the discharge lamp lighting device of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, a commercial AC power source E is connected via a switch SW1 to an input terminal of a full-wave rectifier 1 as a rectifier circuit, and the output terminal of the full-wave rectifier 1 has a high power factor smoothing. Circuit 2 is connected. This smoothing circuit 2
A series circuit of a smoothing capacitor C1 and an impedance element Z1 is connected between the output terminals of the full-wave rectifier 1, and a diode D1 is connected between the impedance element Z1 and the negative electrode of the full-wave rectifier 1.

An inverter circuit 3 is connected to the smoothing circuit 2. The inverter circuit 3 includes a parallel circuit of a resonance capacitor C2 and an inductor L1 and a collector and an emitter of a transistor Q1 as a switching element in series. It is connected.

Further, a smoothing circuit 2 and a charging circuit 4 connected to the base of the transistor Q1 are connected to the output terminal of the full-wave rectifier 1. In this charging circuit 4, the time constant circuit of the resistor R1 and the capacitor C3 is connected between the output terminals of the full-wave rectifier 1, and the base of the transistor Q2 is connected to the connection point of the resistor R1 and the capacitor C3. The emitter of Q2 is connected to the connection point of the smoothing capacitor C1 and the impedance element Z1 via the resistor R2, and is also connected to the base of the transistor Q1 via the resistor R3. Further, the separately-excited or self-excited oscillation control means 5 is connected to the base of the transistor Q1.

In addition, the filaments FL1 and FL2 of the fluorescent lamp FL as a discharge lamp are connected in parallel to the inductor L1 of the inverter circuit 3 via the choke coil L2, and the filaments FL1 and FL2 are used for starting. Capacitor C4 is connected.

Next, the operation of the embodiment shown in FIG. 1 will be described with reference to FIG.
It will be described with reference to the waveform charts shown in FIGS.

First, when the switch SW1 is closed, electric power is supplied from the commercial AC power source E to the full-wave rectifier 1, and after full-wave rectification by the full-wave rectifier 1, the charging circuit 4 and the smoothing circuit 2
Supply power to. Until the capacitor C3 is charged, the base current is not supplied to the transistor Q1 and the transistor Q1 does not turn on. Therefore, the full-wave rectifier 1,
Smoothing capacitor C1, impedance element Z1, diode
In the closed circuit of D1, the collector and emitter of the transistor Q1, and the full-wave rectifier 1, the smoothing capacitor C1 is not charged.

During the period when the transistor Q1 is not turned on, the base current of the transistor Q2 flows because the capacitor C3 is not charged, so the transistor Q2 is turned on and the full-wave rectifier 1, the smoothing capacitor C1, the resistor R2, Transistor Q2 emitter, collector and full-wave rectifier 1
The smoothing capacitor C1 is charged in the closed circuit. Then, while the transistor Q2 is on, the resistor R1, the capacitor C3,
It may be set by the smoothing capacitor C1 and the resistor R2.
After the inverter circuit 3 operates, the output waveform of the full-wave rectifier 1 is as shown in FIG. 2, though it depends on the values of the smoothing capacitor C1 and the impedance element Z1 to achieve high efficiency. Then, after the smoothing capacitor C1 has been charged once, a portion having a voltage higher than the charge level is applied to the impedance element Z1.

When the smoothing capacitor C1 is charged in this way, the transistor Q1 of the inverter circuit 3 starts oscillating after the smoothing capacitor C1 is charged as shown in FIG. 3, so that the inverter circuit 3 is activated. Sometimes
Since the potential exists in the smoothing capacitor C1, it is possible to prevent the peak current as shown in FIG. 4 from being applied to the transistor Q1, and a high current does not flow in the transistor Q1 at the moment when the transistor Q1 is turned on.

Then, the oscillation control means 5 switches the transistor Q1, the inverter circuit 3 generates a high frequency alternating current, and the fluorescent lamp FL is lit at a high frequency.

Further, since a large current does not flow in the impedance element Z1 even if an inductance element is used as the impedance element Z1, it is not saturated, so that the inductance element can be downsized.

Furthermore, since the charging circuit 4 is charged only at the time of starting, the resistance loss becomes 0 in normal use, the loss does not increase, and the heat generation is extremely short, so there is no problem.

According to the discharge lamp lighting device shown in FIG.
After the smoothing capacitor C1 of the smoothing circuit 2 is charged, the transistor Q1 of the inverter circuit 3 starts oscillating,
Even when the transistor Q1 is turned on when the commercial AC power source E has a high voltage, the voltage applied to the impedance element Z1 of the smoothing circuit 2 is reduced and a high current is prevented from flowing to the transistor Q1 when the inverter circuit 3 is started. it can.

Further, the impedance element Z1 of the smoothing circuit 2
Since the current flowing through is also small, even when an inductor element is used, saturation can be prevented even with a small inductor element.

Next, a discharge lamp lighting device of another embodiment is shown in FIG.
Will be described with reference to.

As shown in FIG. 5, the commercial AC power source E is connected via a switch SW11 to the input terminal of a full-wave rectifier 11 as a rectifier circuit. The output terminal of the full-wave rectifier 11 has a high power factor smoothing circuit. 12 are connected. In this smoothing circuit 12, a series circuit of a smoothing capacitor C11, an inductor L11, and a diode D11 is connected between the output terminals of the full-wave rectifier 11, and between the inductor L11 and the diode D11,
Diode D12 is connected.

An inverter circuit 13 is connected to the smoothing circuit 12, and the inverter circuit 13 includes a parallel circuit of a resonance capacitor C12 and an inductor L12, and a collector and an emitter of a transistor Q11 as a switching element in series. It is connected.

Further, a smoothing circuit 12 and a low voltage starting circuit 14 connected to the base of the transistor Q11 are connected to the output terminal of the full-wave rectifier 11. This low voltage starter circuit
14 is a resistor R11 and a resistor between the output terminals of the full-wave rectifier 11.
A series circuit of R12 is connected and these resistors R11 and
The base of the transistor Q12 is connected to the connection point of R12. The collector of the transistor Q12 is a resistor
It is connected to the positive electrode of the full-wave rectifier 11 via R13, and the emitter is connected to the negative electrode of the full-wave rectifier 11. In addition, the collector of transistor Q12 is connected to diode D13 and resistor R14.
It is connected to the base of transistor Q11 via a series circuit. The transistor Q12 is a smoothing capacitor.
It is set to operate at the threshold value S shown in FIG. 6 which is lower than the voltage of C11.

A self-excited oscillation control means 15 is connected between the base and emitter of the transistor Q11.
Then, the oscillation control means 15 includes a resistor R15 and a diode D14 between the emitter and collector of the transistor Q11.
And the series circuit of the output winding CT11b of the current transformer CT11 in which the capacitor C13 and the input winding CT11a are connected to the inductor L12 are connected in parallel.

Further, the inductor L1 of the inverter circuit 13
Filaments FL1 and FL2 of the fluorescent lamp FL in parallel with 1 via the input winding CT11a and the choke coil L13.
And a starting capacitor C14 is connected between these filaments FL1 and FL2.

Next, the operation of the embodiment shown in FIG.
It will be described with reference to the waveform charts shown in FIGS.

First, when the switch SW11 is closed, electric power is supplied from the commercial AC power source E to the full-wave rectifier 11, and after full-wave rectification by the full-wave rectifier 11, the low-voltage starting circuit 14 and the smoothing circuit 12 are supplied with electric power. To supply. Then, the base current is supplied to the base of the transistor Q11 via the resistor R13, the diode D13 and the resistor R14 to turn on the transistor Q11, and the full-wave rectifier 11, smoothing capacitor C11, inductor
L11, diode D12, collector of transistor Q11,
In the closed circuit of the emitter and full-wave rectifier 11, the smoothing capacitor
Charge C11.

Further, the transistor Q11 is turned on, and
When charging the smoothing capacitor C11, as shown in FIG. 6, when the output voltage from the full-wave rectifier 11 is equal to or higher than the threshold value S, the voltage set by the resistors R11 and R12 turns on the transistor Q12. Since the base current is supplied to the transistor Q12 to turn on the transistor Q12 and the base current of the transistor Q11 is bypassed, the transistor Q11 does not turn on and the smoothing capacitor C11 is not charged.

On the other hand, when the output voltage from the full-wave rectifier 11 is equal to or lower than the threshold value S, the voltage set by the resistors R11 and R12 is set to turn off the transistor Q12. A current is supplied to turn on transistor Q11, and full-wave rectifier 11, smoothing capacitor C11, inductor L11, diode D12, collector, emitter and full-wave rectifier of transistor Q11 11
The closed circuit is formed and the smoothing capacitor C11 is charged.

Then, when the transistor Q11 is turned on when the output voltage from the full-wave rectifier 11 is low, the charging current of the smoothing capacitor C11 becomes the output voltage of the full-wave rectifier 11 as shown in FIG. Correspondingly, the transistor Q11 turns on when the output voltage of the full-wave rectifier 11 is low, and the oscillation of the transistor Q11 of the inverter circuit 13 starts. Therefore, the voltage applied to the smoothing circuit 12 is reduced and the peak as shown in FIG. You can prevent the current from flowing to the transistor Q11,
At the moment when the transistor Q11 turns on, a high current does not flow in the transistor Q11.

Then, the current is returned by the current transformer CT11 to switch the transistor Q11 by the oscillation control means 15, and the inverter circuit 13 generates high frequency alternating current to light the fluorescent lamp FL at high frequency.

Further, even when the smoothing capacitor C11 is not charged, the inductor L11 is not applied with twice the peak voltage shown in FIG. Since no current flows and there is no saturation, miniaturization can be achieved.

Further, since the charging circuit 4 is charged only at the time of starting, the resistance loss becomes 0 in normal use, the loss does not increase, and the heat generation is extremely short, so there is no problem.

Also, when the base circuits of the transistors Q1 and Q11 have a capacitive impedance, oscillation occurs when the inverter circuits 3 and 13 are started, and the transistors Q1 and Q11
Since a large base current flows in Q11, conventionally, for protection of transistors Q1 and Q11, for example, the resonance circuit of inductor L1 and capacitor C2, or inductor L1
A snubber circuit was connected in parallel with the resonant circuit of 2 and capacitor C12, but a large current does not flow between the collector and emitter of transistors Q1 and Q11, so a snubber circuit is not necessary in this case as well. become.

All the inverter circuits 3 and 13 are 1
The same effect can be obtained not only with the stone type but also with two or more types.

[0042]

According to the discharge lamp lighting device of the first aspect, since the switching element of the inverter circuit is activated after the smoothing capacitor is charged by the charging circuit, the current flowing through the switching element can be lowered, and the switching element Since the capacitance can be reduced, the burden on the components can be reduced even when the inverter circuit oscillates.

According to the discharge lamp lighting device of the second aspect,
The low-voltage starter circuit activates the switching element when the AC power supply is at a low voltage, so the current flowing through the switching element can be reduced and the capacity of the switching element can be reduced. Can be reduced.

[Brief description of drawings]

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

FIG. 2 is a voltage waveform diagram showing the charging voltage of the smoothing capacitor C1.

FIG. 3 is a waveform diagram showing an operation when the transistor Q1 is oscillated after charging the smoothing capacitor C1. (A) Output voltage of full-wave rectifier 1 (b) Charging current of smoothing capacitor C1

FIG. 4 is a waveform diagram showing the operation when the transistor Q1 is oscillated before the smoothing capacitor C1 is charged. (A) Output voltage of full-wave rectifier 1 (b) Charging current of smoothing capacitor C1

FIG. 5 is a circuit diagram showing a discharge lamp lighting device of another embodiment of the same as above.

FIG. 6 is a voltage waveform diagram showing the threshold value of the operation of the same transistor Q12.

FIG. 7 is a waveform diagram showing an operation when the transistor Q11 is oscillated in a state where the voltage of the full-wave rectifier 11 is low. (A) Output voltage of full-wave rectifier 11 (b) Charging current of smoothing capacitor C11

FIG. 8 is a waveform diagram showing an operation when the transistor Q11 is oscillated in a state where the full-wave rectifier 11 has a high voltage. (A) Output voltage of full-wave rectifier 11 (b) Charging current of smoothing capacitor C11

[Explanation of symbols]

 1,11 Full wave rectifier as rectifier circuit 2,12 Smoothing circuit 3,13 Inverter circuit 4 Charging circuit 14 Low voltage starting circuit C1, C11 Smoothing capacitor E Commercial AC power supply FL Fluorescent lamp as discharge lamp Q1, Q11 As switching element Transistor

Claims (2)

[Claims] 1. A rectifier circuit rectifies the voltage of an AC power source, an output of this rectifier circuit is smoothed by a smoothing circuit having a smoothing capacitor, and switching is performed by a switching element of an inverter circuit to turn on a discharge lamp at a high frequency.
A discharge lamp lighting device that charges the smoothing capacitor by the operation of the switching element, comprising a charging circuit that charges the smoothing capacitor before oscillation of the inverter circuit. 2. An AC power supply voltage is rectified by a rectifier circuit, an output of the rectifier circuit is smoothed by a smoothing circuit having a smoothing capacitor, and switching is performed by a switching element of an inverter circuit to light a discharge lamp at a high frequency.
In a discharge lamp lighting device that charges the smoothing capacitor by the operation of the switching element, a low voltage starting circuit that starts the switching element when the AC power supply has a low voltage when the inverter circuit oscillates is provided. Discharge lamp lighting device.