JP3518230B2 - Lighting device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting device,
In particular, the present invention relates to an active converter that reduces harmonic components of an input current to improve efficiency of the device.

[0002]

2. Description of the Related Art In a conventional lighting device for lighting, an alternating current is converted into a direct current by a rectifying circuit composed of a diode bridge, and then a direct current voltage in which a voltage ripple is suppressed is converted by a smoothing capacitor. This direct current voltage is converted into a high frequency alternating current by a resonance type inverter circuit, and this voltage is applied to a discharge tube to light an illumination lamp.

In recent years, regulations on harmonics of power supply current have been enforced, and lighting lighting devices having an active converter for suppressing harmonics have been reported. One of them is disclosed in JP-A-8-64376. This conventional example
This is a configuration called a one-converter system in which an active filter circuit that suppresses harmonics and a resonant inverter circuit that supplies high-frequency power to a discharge tube also serve as a power switching element. The active filter circuit includes a resonance unit having a capacitor and an inductor, and stores a voltage proportional to an AC voltage in the resonance capacitor according to the operation of turning on and off the two power switching elements alternately, and then stores the voltage. The operation of transferring the charge to the smoothing capacitor is repeated. When the current flowing from the AC power supply to the active converter is passed through the filter, the input current has a sinusoidal waveform synchronized with the AC voltage.

The resonant inverter circuit has two capacitors and an inductor connected in series, and a discharge tube is connected in parallel to one of the capacitors. The control method changes the drive frequencies of the two power switching elements of the inverter according to the voltage of the smoothing capacitor. This is because at no load or at a light load, the energy consumed by the resonant inverter circuit decreases with respect to the energy input from the active filter circuit, and the voltage of the smoothing capacitor rises. In order to prevent such a state, the ratio of the drive frequency of the power switching element of the inverter to the resonance frequency of the active filter circuit is 1/2.
It is set to be larger and smaller than 1.

[0005]

In the lighting device having the above-described structure, the resonance current of the active filter circuit has a waveform in which the phase advances from the output voltage of the inverter. In the case of the lead phase, as one cycle of operation, the resonance current switches from positive to negative during the ON period of one switching element, and the current flows through the antiparallel diode. Next, when the other switching element is turned on, a reverse voltage is suddenly applied to the anti-parallel diode that was previously supplying the forward current. As a result, electrons and holes accumulated in the diode (hereinafter referred to as residual carriers) are discharged, and a reverse current (hereinafter referred to as reverse recovery current) flows in the diode from the cathode to the anode. This current flows through the other switching element and becomes a through current for the inverter. In a normal discharge lamp lighting device, the switching frequency is 50 kHz to 100 kHz, and the loss due to shoot-through current is small, but when operating a resonance type inverter of several MHz near the resonance point, the frequency is high when the lead phase occurs, so the loss is high. Becomes a factor that determines the thermal operating limit.

An object of the present invention is to have a lighting operation frequency of several MH.
An object of the present invention is to provide a lighting device for lighting that reduces the loss of the switching element even when z is high and suppresses the harmonic component of the input current during the entire period of the AC power supply.

[0007]

To solve the above-mentioned problems, an AC voltage is applied to a first resonance means provided with a lighting tube together with an inductance and a capacitance according to a switching operation of a semiconductor element connected to a smoothing capacitor. In the lighting device, the second resonance means is provided between the rectifying means for rectifying the input AC voltage and the semiconductor element, and the current is input from the rectifying means according to the switching operation of the semiconductor element, Energy corresponding to is supplied to the smoothing capacitor via the second resonance means,
This can be achieved by setting the resonance frequency of the second resonance means lower than the resonance frequency of the first resonance means and setting the switching frequency of the semiconductor element higher than the resonance frequency of the first resonance means. .

[0008]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing a first embodiment of the present invention. In FIG. 1, a power source obtained by rectifying an AC power source AC with a rectifier circuit DB configured by a diode bridge is passed through an AC filter including inductors L1 and C1 connected in series, and a resonant active converter circuit 1 is provided. After the smoothing, the inverter circuit 2 supplies high-frequency power to the discharge tube to perform high-frequency lighting.

The active converter circuit 1 and the inverter circuit 2 are two powers connected in a half bridge structure.
Also serves as MOSFETs Q1 and Q2. Q1 and Q2 are power
A MOSFET, which has a drain terminal for inputting a current, a source terminal for outputting a current, and a gate terminal to which a control voltage is applied or removed, and a control voltage is applied to or removed from the gate terminal to cause a drain-source connection. Pass or shut off the flowing current. The MOSFET has a diode built in antiparallel in the direction from the source terminal to the drain terminal, and can conduct electricity in both directions. Hereinafter, the diode included in Q1 will be referred to as QD1 and the diode included in Q2 will be referred to as QD2.

In the active converter circuit 1, diodes D1 and D2 are connected in series in the forward direction between the contact between the inductor L1 of the AC filter and the capacitor C1 and the high potential side of the smoothing capacitor C2. Further, a resonance circuit in which a capacitor C3 and an inductor L2 are connected in series is inserted between the contacts of D1 and D2 and the contacts of Q1 and Q2 connected in a half bridge structure.

The inverter circuit 2 includes a power MOSFET Q1 connected in a half-bridge structure between the positive and negative electrodes of a DC power supply.
A series resonance circuit including Q2 is connected to the drain-source of Q2 in which an inductor L3 and a resonance capacitor C4 are connected in series. The discharge tube is a resonance capacitor C.
4 are connected in parallel. The inductors L4 and L5 are feedback windings provided in the inductor L3. The inductor L4 is connected in parallel with the capacitor C5 so that the inductor L4 is connected between the base and the emitter of the power MOSFET Q1.
6 is connected in parallel and is connected between the base and emitter of Q2. Each of the power MOSFETs Q1 and Q2 is turned on / off by feeding back the high frequency current flowing in the inductor L3 through the inductors L4 and L5 and performing self-oscillation.

The active converter circuit 1 and the inverter circuit 2 each include a resonance circuit, and the relationship between each resonance frequency and the switching frequency and the relationship between both resonance frequencies will be described with reference to FIG. First, the relationship between the resonance frequency and the switching frequency will be described. First,
When the resonance frequency determined by the capacitor C3 and the inductor L2 of the active converter circuit 1 is fa, the switching frequency f is higher than fa. Further, when the resonance frequency determined by the resonance inductor L3 and the resonance capacitor C4 of the inverter circuit 2 is fo, the switching frequency f is set to be higher than fo. The switching frequency is set higher than any of the resonance frequencies, and it is configured to operate in the delay phase.

Next, the frequency relationship between the active converter circuit 1 and the inverter circuit 2 will be described. As described above, according to the present invention, both the active converter and the inverter circuit are configured to have a delay phase. However, in the inverter circuit, the power MOSFETs Q1 and Q2 are connected to the inductor L3.
Since it is turned on and off by the resonance current flowing through, the operating point is close to the resonance point. The closer the operating point is to the resonance point, the smaller the impedance of the resonance circuit becomes, and the higher voltage required to maintain the lighting of the discharge tube can be obtained.

On the other hand, in the active converter circuit, the voltage at the connection point between the resonance capacitor C3 and the inductor L2 changes greatly as the operating point approaches the resonance point, as in the inverter circuit. Since the input current flowing from the AC power supply AC charges the smoothing capacitor C2 according to the voltage change at the connection point, setting the operating point near the resonance point may result in excessive charging. When the voltage of the smoothing capacitor C2 rises, a high voltage is applied to the power MOSFETs Q1 and Q2, causing destruction of the element. Furthermore, if the voltage at the connection point fluctuates significantly in the positive and negative directions, the capacitors and inductors used in the resonance circuit become high breakdown voltage parts, resulting in high cost. Therefore, the resonance frequency fa of the active converter circuit is configured to be lower than the resonance frequency fo of the inverter circuit.
Since the charging current of the smoothing capacitor is determined by the impedance of the resonance circuit, it is set by the resonance capacitor C3 and the inductor L2 that determine the resonance frequency fa.

Next, the operation of the above configuration will be described with reference to FIGS.
Will be explained. In FIG. 3A, the power MOSFET
When Q2 is turned on, the active converter circuit 1
Rectifier circuit from AC power supply AC, AC filter, diode D1, capacitor C3, inductor L2, power MOSFET
Q2, a resonance current flows through the path of the AC filter. Since the relation between the resonance frequency fa of the active converter circuit 1 and the switching frequency f is fa <f, the current flowing through L2 continues to flow from L2 to Q2 until the power MOSFET Q2 is turned off. In the inverter circuit 2, a path including the resonance capacitor C4, the discharge tube, the inductor L3, and the power MOSFET Q2 is formed, and a resonance current flows in the load resonance circuit. The current flowing through L3 has a resonance frequency fo of the inverter circuit 2 and a switching frequency f of fo <f.
Therefore, the current continues to flow from L3 to Q2 until the power MOSFET Q2 is turned off.

Next, when the power MOSFET Q2 is turned off,
In the active converter circuit 1, the energy stored in the inductor L2 is Q
It is discharged through the path of the anti-parallel diode QD1 of 1 and the smoothing capacitor C2. During this period, the counter electromotive force of L2 is added to the input voltage to charge the smoothing capacitor C2. on the other hand,
In the inverter circuit 2, the energy stored in the inductance L3 is released through a path including a diode QD1, a smoothing capacitor C2, a resonance capacitor C4, and a discharge tube.

Next, referring to FIG. 3B, the power MOSF
When ETQ1 turns on, the active converter circuit 1
Capacitor C3, diode D2, switching element Q
1, the resonance current flows through the path of the inductor L2.
Since the current flowing through L2 is fa <f, the power MOSF
Flow continues from L2 to C3 until ETQ1 turns off. Here, the diode D1 provided between the AC filter and the diode D2 blocks a current flowing from the smoothing capacitor C2 to the AC filter via the power MOSFET Q1, the inductor L2 and the capacitor C3. The inverter circuit 2 includes a power MOSF from the smoothing capacitor C2.
ETQ1, resonance inductor L3, resonance capacitor C4
A path including the discharge tube and the smoothing capacitor C2 is formed, a resonance current flows, and power is supplied to the discharge tube. Due to the relationship fo <f, the current flowing through L3 continues to flow from L3 toward the discharge tube until the power MOSFET Q1 is turned off.

After that, when the power MOSFET Q1 is turned off, in the active converter circuit 1, the energy stored in the inductor L2 is stored in the capacitor C3, the diode D2, the smoothing capacitor C2, and the diode QD2 as shown by the broken line in FIG. It is released by the route. this period,
As described above, the counter electromotive force of L2 is added to the input voltage to charge the smoothing capacitor C2. Where diode D
No. 1 prevents the energy stored in L2 from being discharged to the AC filter side through the capacitor C3 and blocking the charging of the smoothing capacitor C2. On the other hand, in the inverter circuit 2, the energy stored in the inductor L3 is
Resonance capacitor C4 and discharge tube, diode QD2
Is released by the route.

As described above, the power MOSFETs Q1 and Q2 are alternately turned on and off at a high frequency, a current flows through the resonance capacitor C3 during the on period, and a smoothing capacitor C during the off period.
By causing the current to charge 2 to flow, it is possible to cause the input current to flow during the entire period of the AC power supply AC, as shown in FIG. AC high-frequency current that flows in response to switching
By passing it through a filter, the input current has a waveform close to a sine wave, and harmonic components can be suppressed.

FIG. 5 is a circuit diagram showing a second embodiment of the present invention. In FIG. 5, the inverter circuit 2 is similar to that of FIG. 1, but the active converter circuit 1 has a circuit configuration in which the diode D1 provided in FIG. 1 is also used as the diode of the rectifier circuit DB. An AC filter composed of an inductor L1 and a capacitor C1 is connected to both ends of an AC power source AC, and contacts of L1 and C1 and a smoothing capacitor C are connected.
The rectifier circuit DB formed of a diode bridge and the diode D2 are connected between the high potential side of the diode 2 and the high potential side of the diode 2. The diode of the rectifier circuit DB provided between the AC filter and the diode D2 is such that the smoothing capacitor C2 moves to the power MOSFET Q1 and the inductor L when the power MOSFET Q1 is turned on.
2. Blocks the current flowing to the AC filter via the capacitor C3. Further, when Q1 is turned off, the energy stored in L2 is discharged through the path of the AC filter and diode QD2 via the capacitor C3, and the smoothing capacitor C2
It prevents the charging of the battery from being blocked.

FIG. 6 shows a fluorescent lamp lighting device to which the present invention is applied. Although the circuit configuration is almost the same as that of FIG. 1, in the inverter circuit 2, the drain-source of Q2 is
The inductor L3 and the resonance capacitors C7 and C8 are connected in series, and the discharge tube is provided in parallel with the resonance capacitor C8. The operation is as described above, and there is a similar effect in suppressing the harmonics of the input current. An ordinary fluorescent lamp discharges between two electrodes having a filament, and at the end of its life, emission from one or both electrodes disappears and the fluorescent lamp has a high resistance. In such a state, the energy consumed by the inverter circuit decreases with respect to the input energy, and therefore the voltage of the smoothing capacitor C2 may increase in the conventional circuit. Here, the resonance frequency fo of the inverter circuit becomes higher than that during normal lighting due to the combined capacitance of the capacitors C7 and C8 and the inductor L3, and the switching frequency f becomes higher. On the other hand, since the resonance frequency fa on the active converter side is constant, the impedance of the resonance circuit increases and the input current flowing from the AC power supply AC decreases as the switching frequency f increases. Therefore, the charging current of the smoothing capacitor C2 decreases,
Overcharge can be suppressed.

[0022]

According to the present invention, an active converter circuit provided to suppress harmonics of an input current and an inverter circuit for supplying high frequency power to a discharge tube are provided. Since the switching frequency which is lower than the resonance frequency and which turns the switching element on and off is set higher than the resonance frequency of the inverter circuit, all the resonance circuits always operate in the lag phase and the loss of the switching element can be reduced. . Further, there is an effect that it is possible to suppress overcharging of the smoothing capacitor. Further, the switching elements are alternately turned on and off at high frequency, and the input current is changed to AC power supply A.
Since it can be flowed during the entire period of C, it is possible to suppress harmonics.

[Brief description of drawings]

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

FIG. 2 shows the relationship between the resonance frequency and the switching frequency in the embodiment shown in FIG.

FIG. 3 is an explanatory diagram of an operation mode of the embodiment of FIG.

FIG. 4 is a waveform of an AC power supply voltage and an input current of the embodiment of FIG.

FIG. 5 is a circuit diagram showing a second embodiment of the present invention.

FIG. 6 is a configuration of a fluorescent lamp lighting device using the present invention.

[Explanation of symbols] 1 ... Active converter circuit, 2 ... Inverter circuit,
AC ... AC power supply, DB ... Rectifier circuit, Q1, Q2 ... Power
MOSFET, D1, D2, QD1, QD2 ... Diode, C
1 to C8 ... Capacitors, L1 to L5 ... Inductors.

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-8-64376 (JP, A) JP-A-2-174566 (JP, A) JP-A-5-54987 (JP, A) JP-A-2- 202365 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) H05B 41/24

Claims (5)

(57) [Claims] 1. A lighting device for applying an AC voltage to a first resonance means having a lighting tube together with an inductance and a capacitance according to a switching operation of a semiconductor element connected to a smoothing capacitor, wherein an AC input voltage is applied. Second resonance means is provided between the rectification means for rectifying the voltage and the semiconductor element, a current is input from the rectification means in accordance with the switching operation of the semiconductor element, and energy corresponding to the current is applied to the second resonance element. Is supplied to the smoothing capacitor via the resonance means, the resonance frequency of the second resonance means is lower than the resonance frequency of the first resonance means, and the switching frequency of the semiconductor element is set to the first resonance frequency. The lighting device is set to be higher than the resonance frequency of the resonance means. 2. A lighting device for applying an AC voltage to a first resonance means having a lighting tube together with an inductance and a capacitance according to a switching operation of a semiconductor element connected to a smoothing capacitor, said first lighting device comprising: Drive circuit means for turning on / off the semiconductor element in synchronization with a current flowing through the resonance element, and second resonance means between the rectifying means for rectifying an input AC voltage and the semiconductor element. in accordance with a switching operation of the device, enter the current from said rectifying means, with the energy corresponding to said current through said second resonator means for feeding to the smoothing capacitor, the second co
The resonance frequency of the vibration means is the resonance frequency of the first resonance means.
Lower than the switching frequency of the semiconductor device
Set the number higher than the resonance frequency of the first resonance means.
Lighting apparatus characterized by that. 3. The lighting device according to claim 1, wherein a filter means and a diode are provided between the rectifying means and the second resonance means, and the diode has a direction in which a current flows in the second resonance means. Is a forward direction. 4. The lighting device according to claim 3, wherein the second resonance means provides a reactor and a capacitor between the cathode terminal of the diode and the semiconductor element, and connects the cathode terminal of the diode to the smoothing capacitor. A lighting device comprising a second diode whose forward direction is a forward direction. 5. The lighting device according to claim 4, wherein the semiconductor element is an inverter circuit connected to a half bridge between the positive and negative electrodes of the smoothing capacitor, and the first element is provided at a midpoint of the inverter circuit. , And a second resonance means are connected to the lighting device.