JPH04315796A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To improve a power factor with a simple circuit constitution in a discharge lamp lighting device using an inverter circuit of a half-bridge type or a full-bridge type. CONSTITUTION:In a discharge lamp lighting device, in which a half-bridge type inverter circuit 35 is connected, via a first choke coil 34, to an output terminal of a full-wave rectifying diode bridge 32 and a discharge lamp 42 is connected to an output terminal of the inverter circuit, a switching transistor 37 in the inverter circuit 35 is connected, via a diode 33 and the first choke coil 34, to the output terminal of the diode bridge circuit. A closed circuit is formed of the series circuit of the first choke coil 34, a diode 48, and DC dividing capacitors 38 and 39 in the inverter 35 having a smoothing function.

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 using a half-bridge or full-bridge inverter circuit.

0002

2. Description of the Related Art Conventionally, there has been known a discharge lamp lighting device using, for example, a half-bridge type inverter circuit, as shown in FIG. In this system, an AC power source 1 is full-wave rectified by a full-wave rectifier circuit 2 consisting of a diode bridge, and the pulsating voltage outputted from the rectifier circuit is supplied to a smoothing capacitor 4 via a choke coil 3 for smoothing. The output of the smoothing capacitor 4 is then supplied to a half-bridge inverter circuit 5.

This inverter circuit 5 includes a series circuit of a pair of switching transistors 6 and 7, a series circuit of a pair of DC dividing capacitors 8 and 9, a feedback diode 10 connected in parallel to each transistor 6 and 7, respectively. 11, an oscillation transformer 12, and starting resistors 13 and 14 for starting each transistor 6 and 7. That is, the primary winding 12p of the oscillation transformer 12 is connected to the connection point of each transistor 6, 7 and the connection point of each capacitor 8, 9, and the feedback windings 12b1, 12b2 attached to the oscillation transformer 12 are connected to each other.
The transistors 6 and 7 are switched and driven by the voltages generated in the respective transistors.

[0004]The secondary winding 12s of the oscillation transformer 12
A discharge lamp 16 is connected to the discharge lamp 16 via a choke coil 15.

[0005] In such a discharge lamp lighting device, since the smoothing capacitor 4 is used to obtain a DC voltage, there is a problem in that the input power factor is poor.

In order to improve this, as shown in FIG. 6, a switching transistor 17 is installed between the full-wave rectifier circuit 2 and the smoothing capacitor 4, a switch control circuit 18 for controlling switching of this transistor 17, a choke coil 19, and a diode 20. A discharge lamp lighting device is known in which a chopper circuit 21 is connected to improve the power factor.

However, this discharge lamp lighting device requires a separate chopper circuit 21, which makes the circuit configuration complicated and expensive.

[0008]

[Problems to be Solved by the Invention] As described above, a discharge lamp lighting device using a conventional half-bridge type inverter circuit has a poor power factor, and a device designed to improve the power factor has a complicated circuit configuration. There was also the problem that it was expensive.

Therefore, the present invention provides a discharge lamp lighting device that uses a half-bridge type or full-bridge type inverter circuit and can improve the power factor with a simple circuit configuration, thereby reducing costs. This is what we are trying to provide.

0010

[Means for solving the problem] The invention corresponding to claim 1 is:
A half-bridge type or full-bridge type having a series circuit of at least one pair of switching transistors connected to an AC power supply via a full-wave rectifier circuit and a choke coil, and a series circuit of a pair of DC dividing capacitors with a smoothing function. An inverter circuit, a discharge lamp connected to the output terminal of this inverter circuit, and the energy stored in a choke coil when one switching transistor in each switching transistor is turned off is fed back to a series circuit of a pair of DC dividing capacitors. A feedback circuit is provided.

The invention corresponding to claim 2 uses a pair of DC dividing capacitors without a smoothing function, and instead connects a smoothing capacitor in parallel to a series circuit of the pair of DC dividing capacitors.

0012

[Operation] In the present invention having such a structure, high frequency power is supplied to the discharge lamp by the switching operation of the switching transistor of the inverter circuit, and lighting is maintained. When one switching transistor turns off, the energy stored in the choke coil is fed back to the series circuit of a pair of DC dividing capacitors and superimposed on the input power supply voltage. This increases the voltage supplied to the inverter circuit. That is, a boost chopper circuit is formed by the feedback circuit.

[0013]

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

As shown in FIG. 1, an input terminal of a full-wave rectifier diode bridge circuit 32 is connected to an AC power source 31. A half-bridge type inverter circuit 35 is connected to the output terminal of the diode bridge circuit 32 via a diode 33 and a first choke coil 34.

The inverter circuit 35 includes a pair of NPN
A series circuit of type switching transistors 36 and 37 and a pair of DC dividing capacitors 38 and 39 having a smoothing function.
series circuits are connected in parallel to each other, and the connection point of each of the transistors 36 and 37 is connected to one end of one filament electrode 42a of the discharge lamp 42 through the winding 40a of the transformer 40 and the second choke coil 41 in series. Connected. Further, the connection point of each of the DC split capacitors 38 and 39 is connected to one end of the other filament electrode 42b of the discharge lamp 42.

The transformer 40 has a pair of feedback windings 40b1 and 40b2 attached to a winding 40a, and the feedback winding 40b1 is connected between the base and emitter of the transistor 36 via a resistor 43, and the feedback winding 40b1 is connected between the base and emitter of the transistor 36 through a resistor 43. Winding wire 40b2
is connected between the base and emitter of the transistor 37 via a resistor 44.

Feedback diodes 45 and 46 are connected in parallel to each of the transistors 36 and 37, respectively, with their cathodes facing the collectors of the transistors.

The diode 33 has its anode connected to the positive side of the output terminal of the diode bridge circuit 32, and its cathode connected to each of the transistors 36,
It is connected to 37 connection points. Further, one end of the first choke coil 34 is connected to the negative electrode side of the output terminal of the diode bridge circuit 32, and the other end is connected to the emitter of the switching transistor 37.

Each filament electrode 42 of the discharge lamp 42
A starting capacitor 47 is connected between the other ends of a and 42b.

One end of the first choke coil 34 is also connected to the collector of the switching transistor 36 and the DC dividing capacitor 3 via a diode 48 in the forward direction.
It is connected to the connection point with one end of 8.

In this embodiment having such a configuration, when the AC power supply 31 is turned on, the diode bridge circuit 32
A full-wave rectified waveform is supplied to an inverter circuit 35 via a diode 33 and a first choke coil 34.

Now, when the transistor 37 is turned on, a chopping current flows from the positive side to the negative side of the output terminal of the diode bridge circuit 32 via the diode 33, the transistor 37, and the first choke coil 34. As a result, electromagnetic energy is stored in the first choke coil 34.

Also, a pair of DC dividing capacitors 38, 39
The input power supply voltage is applied through the diode 33 and the feedback diode 45, and the voltage is applied to the capacitors 38 and 39.
It is divided into

When the transistor 37 is turned off, the first
The electromagnetic energy stored in the choke coil 34 is released to the DC split capacitors 38, 39 through the closed circuit of the diode 48, the DC split capacitors 38, 39, and the first choke coil 34. As a result, the electromagnetic energy from the first choke coil 34 is superimposed on the input power supply voltage applied to the DC dividing capacitors 38 and 39, and the voltage across the series circuit of the DC dividing capacitors 38 and 39 is boosted. That is, the series closed loop circuit consisting of the first choke coil 34, the diode 48, and the DC dividing capacitors 38 and 39 functions as a boost chopper circuit.

Next, when the transistor 36 is turned on, the inverter circuit 35 operates in oscillation using the DC dividing capacitors 38 and 39 as power sources.

When the inverter circuit 35 operates in oscillation and the transistor 37 is turned on, a combined current of the chopping current from the diode bridge circuit 32 and the current generated by the inverter operation flows through the transistor 37.

In this way, the DC dividing capacitors 38, 39
On the other hand, since the boost chopper function superimposes the electromagnetic energy from the first choke coil 34 to boost the voltage, the power factor is improved and the power source can be boosted. It is also possible to reduce harmonics. Furthermore, the step-up chopper function is achieved by a simple circuit consisting of the first choke coil 34, the diode 48, and the transistor 37, and the transistor 37 also serves as the switching transistor of the inverter circuit 35, so the configuration can be simplified and costs can be reduced. can be achieved.

In this embodiment, the pair of DC split capacitors 38 and 39 are provided with a smoothing function, but the present invention is not limited to this, and the pair of DC split capacitors 3
8 and 39 are capacitors without a smoothing function, and instead, a pair of DC split capacitors 38 and 3 are used as shown by the dotted line in the figure.
A smoothing capacitor 49 may be connected in parallel to the 9 series circuits.

Next, another embodiment of the present invention will be described with reference to the drawings. Note that the same parts as in the above embodiment are given the same reference numerals and detailed explanations will be omitted.

In the configuration shown in FIG. 2, a first choke coil 34 is inserted in series between the positive side of the output terminal of the diode bridge circuit 32 and the anode of the diode 33, and the diode 48 is omitted. .

Even in this case, when the transistor 37 is turned on, a chopping current flows from the positive side to the negative side of the output terminal of the diode bridge circuit 32 via the first choke coil 34, the diode 33, and the transistor 37, and the first Electromagnetic energy is stored in the choke coil 34.

When the transistor 37 is turned off, the first
The electromagnetic energy stored in the choke coil 34 is transferred to the diodes 33, 45, DC dividing capacitors 38, 39,
A closed circuit formed by the diode of the diode bridge circuit 32 and the first choke coil 34 discharges the current to the DC dividing capacitors 38 and 39. As a result, the electromagnetic energy from the first choke coil 34 is superimposed on the input power supply voltage applied to the DC dividing capacitors 38 and 39, and the voltage across the series circuit of the DC dividing capacitors 38 and 39 is boosted.

[0033] Therefore, in this embodiment as well, the same effects as in the previous embodiment can be obtained.

In the circuit shown in FIG. 3, the positive electrode side of the output terminal of the diode bridge circuit 32 is connected to the first choke coil 34.
and the collector of the switching transistor 36 of the inverter circuit 35 via the diode 33, and the negative electrode side is connected to the connection point of the switching transistors 36 and 37, and the diode 48 is connected to the series circuit of the DC dividing capacitors 38 and 39. are connected in parallel via a first choke coil 34 and a diode 33.

Even in this case, when the transistor 36 is turned on, a chopping current flows from the positive side to the negative side of the output terminal of the diode bridge circuit 32 via the first choke coil 34, the diode 33, and the transistor 36, and the first Electromagnetic energy is stored in the choke coil 34.

When the transistor 36 is turned off, the first
The electromagnetic energy stored in the choke coil 34 is released to the DC split capacitors 38, 39 through a closed circuit including the diode 33, the DC split capacitors 38, 39, the diode 48, and the first choke coil 34. As a result, the electromagnetic energy from the first choke coil 34 is superimposed on the input power supply voltage applied to the DC dividing capacitors 38 and 39, and the voltage across the series circuit of the DC dividing capacitors 38 and 39 is boosted.

[0037] Therefore, the same effects as in the previous embodiment can be obtained in this embodiment as well.

In the circuit shown in FIG. 4, the positive side of the output terminal of the diode bridge circuit 32 is connected to the collector of the switching transistor 36 of the inverter circuit 35 via the diode 33, and the negative side is connected to the first choke coil 34. Through the switching transistors 36, 37
, and the diode 48 is omitted.

Even in this case, when the transistor 36 is turned on, a chopping current flows from the positive side to the negative side of the output terminal of the diode bridge circuit 32 via the diode 33, the transistor 36, and the first choke coil 34. Electromagnetic energy is stored in the choke coil 34.

When the transistor 36 is turned off, the first
The electromagnetic energy stored in the choke coil 34 is transferred to the diode of the diode bridge circuit 32, the diode 3.
3, DC split capacitors 38, 39, diode 46,
A closed circuit formed by the first choke coil 34 discharges the current to the DC dividing capacitors 38 and 39. As a result, the electromagnetic energy from the first choke coil 34 is superimposed on the input power supply voltage applied to the DC dividing capacitors 38 and 39, and the voltage across the series circuit of the DC dividing capacitors 38 and 39 is boosted.

[0041] Therefore, in this embodiment as well, the same effects as in the previous embodiment can be obtained.

Although each of the above embodiments uses a half-bridge type inverter circuit, the invention is not necessarily limited to this, and similar effects can be obtained even if a full-bridge type inverter circuit is used. It is something that can be done.

[0043]

Effects of the Invention As detailed above, according to the present invention, it is possible to improve the power factor with a simple circuit configuration in an inverter circuit using a half-bridge type or full-bridge type, thereby reducing costs. Accordingly, it is possible to provide a discharge lamp lighting device that can also achieve the following.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention.

FIG. 2 is a circuit diagram showing another embodiment of the present invention.

FIG. 3 is a circuit diagram showing another embodiment of the present invention.

FIG. 4 is a circuit diagram showing another embodiment of the present invention.

FIG. 5 is a circuit diagram showing a conventional example.

FIG. 6 is a circuit diagram showing a conventional example.

[Explanation of symbols]

31... AC power supply, 32... Full wave rectifier diode bridge circuit, 34... First choke coil, 35... Half bridge type inverter circuit, 36, 37... Switching transistor, 38, 39... DC split capacitor, 42... Discharge lamp , 48...diode.

Claims (2)

[Claims] 1. A half-bridge type comprising a series circuit of at least one pair of switching transistors connected to an AC power source via a full-wave rectifier circuit and a choke coil, and a series circuit of a pair of DC dividing capacitors having a smoothing function. Alternatively, a full-bridge inverter circuit, a discharge lamp connected to the output terminal of the inverter circuit, and the energy stored in the choke coil when one of the switching transistors is turned off is transferred to the pair of DC currents. A discharge lamp lighting device characterized by providing a feedback circuit for feeding back to a series circuit of split capacitors. 2. A half-bridge type or full-bridge type battery having a series circuit of at least one pair of switching transistors and a series circuit of a pair of DC dividing capacitors connected to an AC power source via a full-wave rectifier circuit and a choke coil. an inverter circuit, a smoothing capacitor connected in parallel to the series circuit of the pair of DC dividing capacitors, a discharge lamp connected to the output terminal of the inverter circuit, and an OFF operation of one of the switching transistors. A discharge lamp lighting device characterized in that a feedback circuit is provided for feeding back energy stored in the choke coil to the smoothing capacitor.