JP3121378B2 - Power converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a first switching circuit for generating a DC power supply from an AC power supply, and a power supply to a load using the DC power supply supplied from the first switching circuit as a power supply. The present invention relates to a power conversion device including two switching circuits.

[0002]

2. Description of the Related Art As a power converter, a first switching circuit for producing a DC power supply from an AC power supply,
And a second switching circuit that uses a DC power supply supplied from the switching circuit as a power supply to generate power to be supplied to a load. An example of this type of power converter is shown in FIG.

[0003] This power conversion device is used as a discharge lamp lighting device for lighting a discharge lamp La at a high frequency. In this discharge lamp lighting device, the first switching circuit is composed of a diode bridge DB and a step-up chopper 1, the second switching circuit is composed of an inverter 2, and an AC power supply supplied via a power switch SW is a diode. The DC power obtained by full-wave rectification by the bridge DB is boosted by the boost chopper 1, and the boosted output is converted into high-frequency power by the inverter 2 and supplied to the discharge lamp La, and the discharge lamp La is lit at high frequency.

The boost chopper 1 is composed of an inductance element L ₁ , a diode D ₁ , a transistor Q ₁ and a capacitor C ₁ , and boosts a rectified output by switching the transistor Q ₁ . Further, specifically, the energy stored in the on period of the transistor Q ₁ in the inductance element L ₁ to be switched,
Charge is supplied to the capacitor C ₁ through the diode D ₁ when the off-transistor Q ₂ together with the output of the diode bridge DB, and generating a boosted output across the capacitor C _1.

The inverter 2 has transistors Q ₂ and Q ₃ connected in series to the output of the step-up chopper 1 and has a so-called half-bridge configuration in which a discharge lamp La is connected to both ends of the transistor Q ₂ together with a resonance circuit. on the discharge lamp La and the transistor current feedback transformer CT which is inserted in series with the load circuit comprising the resonant circuit Q _2, Q ₃ transistor Q ₂ by feeding back the current to, Q ₃ alternately turned off and the discharge lamp La Is a self-excited type that supplies high-frequency power to the

Here, the transistor Q_Two, Q_ThreeTo
Diodes D for flywheel in anti-parallel_Two, D_Three
Is connected. Also, the load circuit is
Capacitor C_ThreeThrough the transistor Q_TwoConnected to both ends of
And the resonance circuit is a capacitor C _Four, C_FiveAnd inductance
Element L_TwoIt consists of. The filler of the discharge lamp La
Capacitor C connected to the non-power supply side of the_FiveIs the discharge
Also has a function for preheating the filament of the lamp La
Combine. Furthermore, the current feedback transformer CT has a secondary winding
n_Two, N_ThreeBase resistance R_Two, R
_ThreeThrough the transistor Q_Two, Q_ThreeThe current is fed back to.

In this type of inverter 2, when power is turned on,
A starting circuit is provided to reliably start the inverter 2.
This starting circuit is connected to a resistor R₁, Capacitor C_Two,
Bidirectional trigger element Q such as diac_FourComposed of
Yes, the output of the step-up chopper 1₁Charged via
Capacitor C_TwoIs the bidirectional trigger element Q
_FourWhen the breakover voltage of
Moth element Q_FourIs turned on, and the transistor Q_ThreeTo base
Supply of current, first the transistor Q _ThreeOn
To start the inverter 2.

The switching control of the transistor Q ₁ of the step-up chopper 1 is performed by the control circuit 3. This control circuit 3
Is supplied from a power supply circuit 6 composed of capacitors C ₆ and C ₉ , a transformer T ₃ , a diode D ₆ and a resistor R ₈ . That is, the fluctuation component of the potential at the connection point between the transistors Q ₂ and Q ₃ is extracted by the transformer T ₃ and the DC cut capacitor C ₉ connected in series to the primary winding of the transformer T _3. The variation component is represented by a diode D ₆ and a resistor R
It has created a supply of the control circuit 3 ₈ and rectifying and smoothing by a capacitor C _6.

Here, since the power supply circuit 6 generates the power supply by the oscillating operation of the inverter 2, the power supply is supplied to the control circuit 3 from the power supply circuit 6 after the inverter 2 starts operating. become. Thus, the transistor Q ₁ is switched Sarezu of the power-on initial boost chopper 1, the boost chopper 1 is the period simply functions as a current limiting element.

The operation of the discharge lamp lighting device will be briefly described below. First, at the time of power-on, the transistor to Q ₁ boost chopper 1 is not switched, FIGS. 7 (a) a diode bridge the commercial power source AC shown in DB
At the charged capacitor C ₁ to a peak value of an output obtained by full-wave rectified (V _ACP), the voltage across the capacitor C ₁ (V _ACP) is supplied as a power supply to the inverter 2. The inverter 2 is activated by the activation circuit by the supply of the power, and starts an oscillation operation in which the transistors Q ₂ and Q ₃ are alternately turned on and off. At this time, the voltage applied to the discharge lamp La is lower than the starting voltage of the discharge lamp La because the boosting chopper 1 is not performing the boosting operation, and the filament preheating is performed without lighting the discharge lamp La. Is performed.

As described above, when the inverter 2 starts oscillating, the output voltage of the power supply circuit 6 for generating the power supply of the control circuit 3 from the fluctuation component at the connection point of the transistors Q ₂ and Q ₃ is shown in FIG. It rises as shown in, and the control circuit 3 after the time t ₂ elapses starts operating. That is, the transistor Q ₁ is being switched by the output of the control circuit 3. Therefore, a boosted voltage (V _DC ) is generated across the capacitor C ₁ as shown in FIG. 7A, and the output voltage of the inverter 2 becomes a high voltage as shown in FIG. Lights up. When the discharge lamp La is turned on, the lamp voltage V _La decreases.
_{The La} waveform is as shown in FIG.

That is, in the case of the above-described discharge lamp lighting device,
By obtaining the power of the control circuit 3 of the step-up chopper 1 from the inverter 2, the discharge lamp La is preheated during the period when the step-up chopper 1 is not operating, and the discharge lamp La is operated after the step-up chopper 1 operates.
Is turned on.

[0013]

However, the above-described discharge lamp lighting device has a problem in the following cases. That is, when the preheating and the start lighting of the discharge lamp La are controlled by the boost chopper 1 as described above, the inverter 2 needs to have a small output so as not to start the lighting of the discharge lamp La during the preheating period. The output of the chopper 1 must be relatively high. Therefore, there is no degree of freedom in setting the output of the boost chopper 1 and the inverter 2, and it is necessary that both the boost chopper 1 and the inverter 2 are configured with high tolerance of circuit elements.

Further, the discharge lamp lighting device has the following problem. In the discharge lamp lighting device, the discharge lamp L
The output voltage of the boost chopper 1 required to start the
_When the output voltage of the step-up chopper 1 necessary to obtain a desired output from the discharge lamp La is set to _VDCL, and when _VDCL > _VDCS , normal lighting after starting the discharge lamp La is performed. at the output of the step-up chopper 1 it is sufficient to raise the V _DCL.

However, V_DCL<V_DCSIf, boost
Once the output of chopper 1 is V_DCSAnd then V_DCLTo
I need to lower it. For this reason, a higher power than during normal lighting
When the pressure starts, the transistor Q of the boost chopper 1₁And a
Transistor Q of inverter 2 _Two, Q_ThreeMark on circuit elements such as
In addition, the stress on the circuit element at the time of starting increases.
Therefore, a circuit with a high withstand voltage of an unnecessary level during normal lighting
Devices need to be used to reduce start-up stress
Occurs.

Incidentally, the above problem has basically occurred because the output voltage of the step-up chopper 1 needs to be increased. Therefore, a method for suppressing the output voltage of the boost chopper 1 is considered below. In order to suppress the output voltage of the boosting chopper 1 in this manner, even when the boosting chopper 1 is inactive, the inverter 2 discharges the discharge lamp La.
May be applied so that a voltage that can be turned on is applied.

However, in this case, the discharge lamp La is turned on at the same time when the power is turned on, so that it is impossible to sufficiently preheat the filament of the discharge lamp La before starting, thereby adversely affecting the life of the discharge lamp La. As a method of solving this point, the output of the inverter 2 is limited from the time of turning on the power until the start of the discharge lamp La, and the discharge lamp La need not be turned on.

In order to explain this method in detail, FIG.
Consider using the specific circuit shown in FIG. The discharge lamp shown in FIG.
In the lighting device, the boost chopper 1 has the same configuration as the circuit in FIG.
The inverter 2 has a half-bridge structure as in the circuit of FIG.
But the transistor Q _Two, Q_ThreeControl circuit 4
The difference is that it is a so-called separately excited type that turns on and off with
Furthermore, the respective controls of the step-up chopper 1 and the inverter 2
Control power supply V for control circuits 3 and 4_ccAnd the resistance R₄₁, Zenadai
Aether ZD₄₁, Capacitor C₄₁Power supply circuit 6
Has formed.

As shown in FIG. 9, the operation of the step-up chopper 1 and the inverter 2 is started at the same time as the power is turned on as shown in FIG. 9, and the output of the inverter 2 is limited from the time the power is turned on until the discharge lamp La is started. The control circuit 4 is operated so that La does not light. In this case, since the output of the inverter 2 is limited so as not to light the discharge lamp La from the time when the power is turned on to the time when the discharge lamp La is started, the boost chopper 1 is connected to the power supply as shown in the circuit of FIG. It is not necessary to make it inoperative during the period from the time of turning on to the time of starting the discharge lamp La.

In this case, a method of controlling the output of the inverter 2 and
Therefore, from the time when the power is turned on to the time when the discharge lamp La is started,
The period (period indicated by ta to tb in FIG. 9) is a transistor.
TA Q _Two, Q_ThreeThe switching frequency of the resonant circuit
Higher than the wave number, thereby applying to the discharge lamp La
Is lower than the starting voltage of the discharge lamp La.
To By doing so, the discharge lamp La is supplied during this period.
The filament of the discharge lamp La is preheated by the supplied power.
By setting this period appropriately, the filament
Can be sufficiently preheated.

When the discharge lamp La is started and lit, the switching frequency of the transistors Q ₂ and Q ₃ is brought closer to the resonance frequency (natural oscillation frequency) of the resonance circuit from the time point tb in FIG. And the discharge lamp La is started and lit. In addition,
In FIG. 9, the starting point of the discharge lamp La is indicated by a point in time tc. Thereafter, the output of the inverter 2 is adjusted to obtain a desired output from the discharge lamp La.

As a method of reducing the voltage applied to the discharge lamp La, for example, a method of controlling the ON periods of the transistors Q ₂ and Q ₃ proposed in Japanese Patent Application Laid-Open No. 61-271792 is adopted. You can also. According to this method, the output of the boost chopper 1 can be made lower than in the case of the circuit of FIG. In addition, since the step-up chopper 1 is operated from the time when the power is turned on, the voltage supplied to the inverter 2 does not become higher when the discharge lamp La is started than when it is normally lit. Therefore, it is not necessary to select the withstand voltage of the circuit element of the inverter 2 based on the voltage applied to the inverter 2 at the time of starting.

However, in this method, the circuit shown in FIG.
Can also lower the output voltage of the boost chopper 1,
Since the boost chopper 1 is in operation during the preheating period,
When a high voltage is applied to the inverter 2,
Transistor Q of inverter 2 _Two, Q_ThreeStrikes that join
Less. That is, the preheating period as in this method
Operating the boost chopper 1 during operation is a fundamental improvement
This is not a solution. Therefore, the preheating period of the discharge lamp La
It is preferable that the boost chopper 1 is stopped during operation
I can say that.

Therefore, as a further improved method, as shown in FIG.
b, the boost chopper 1 is deactivated, and the boost chopper 1 and the inverter 2 are both soft-started (the output is gradually increased) during the period from tb to tc, so that the voltage applied to the discharge lamp La is gradually increased. And discharge lamp La
May be started.

In this case, since the step-up chopper 1 is not operated during the period from ta to tb, as described with reference to FIG.
The stress on the circuit elements of the inverter 2 during the preheating period a does not increase. However, in this case, there are the following problems. That is, when operated as described above, during the period from tb to tc, the boost chopper 1 is in a transient state in which the boost operation starts to increase the output voltage to the target set value, and the inverter 2 applies the voltage to the discharge lamp La. to have voltage transients increases the further discharge lamp La is the state equivalent impedance when preheating to start lighting was infinite transients rapidly changing the R _LA.
Note that R _LA has a relatively low impedance.

That is, according to the above-described method, the step-up chopper 1, the inverter 2, and the load (the resonance circuit and the discharge lamp La)
Are in a transient state, and during this period, the amount of change in the resonance current flowing through the inverter 2 is large and the voltage supplied to the inverter 2 changes, so that the transistors Q ₂ and Q ₃
And the amount of change in current and voltage at For this reason, it is difficult to control the stable operation of the transistors Q ₂ and Q ₃ at the time of starting, and it is difficult to smoothly change the light output of the discharge lamp La. In addition, there is a problem that the stress of the transistors Q ₂ and Q ₃ increases due to the influence of the transient current and the like.

On the other hand, with regard boost chopper 1, the load fluctuation becomes large in the transient period, in order to follow this, it is necessary to increase the current flowing into the transistor Q _1, the stress of the transistor Q ₁ is increased Problem. The present invention has been made in view of the above points, and an object of the present invention is to provide a power conversion device capable of stabilizing the operation state of a load at the time of starting and having less stress on circuit elements. Is to do.

[0028]

According to the present invention, in order to achieve the above object, a first method for producing a DC power supply from an AC power supply is provided.
And a second switching circuit that uses the DC power supplied from the first switching circuit as a power supply and generates power to be supplied to the load. Each of the second switching circuits is provided, and the second switching circuit is operated in a state where the output is limited to a small value. After a desired time, the second switching circuit is set to an operation state in which a desired output can be obtained. After the operation state of the first switching circuit is stabilized, the operation of the first switching circuit is started.

A first switching circuit for generating a DC power supply from an AC power supply and a second switching circuit for generating power to be supplied to a load using the DC power supplied from the first switching circuit as a power supply. The first and second switching circuits each include a control circuit for controlling the driving of the switching element. The first switching circuit is operated in a state where the output is limited to a small value, and the first switching circuit is operated after a desired time. Is started, and after the operation state of the first switching circuit is stabilized, the second switching circuit is brought into an operation state in which a desired output can be obtained, and the same object as in the above case can be achieved.

[0030]

According to the present invention, the output of the second switching circuit is fixed and the output of the first switching circuit is fixed by making the output of both the first and second switching circuits variable as described above. It is not necessary to set the output voltage of the first switching circuit high as in the case of operating the load as desired, so that the tolerance of the circuit elements of the first and second switching circuits can be reduced,
In addition, when either operation of both switching circuits is stable, the other switching circuit performs a desired operation, thereby operating both switching circuits stably and forming a circuit element by overlapping transient operations. In addition, the stress can be prevented from increasing, and the load can be operated stably.

[0031]

【Example】

(Embodiment 1) FIGS. 1 to 3 show an embodiment of the present invention.
As shown in FIG. 1, the basic configuration of the power converter of this embodiment is an AC power supply AC supplied through a power switch SW.
A first switching circuit A for creating a DC power supply from
A second switching circuit B for generating power to be supplied to the load 5 using a DC power supply supplied from the first switching circuit A as a power supply. And second switching circuits A and B, respectively. In this embodiment, a power converter used as a discharge lamp lighting device is also taken as an example. As shown in FIG. 2, a first switching circuit A is a diode bridge DB as a rectifier circuit and a booster chopper 1. And the second switching circuit B
Is constituted by the inverter 2.

Each of the control circuits 3 and 4 is operated at the following timing. That is, as shown in FIG. 3, first, the inverter 2 is operated in a state where the output is limited to a small value.
After a desired time, the inverter 2 is set to an operation state in which a desired output is obtained, and after the operation state of the inverter 2 is stabilized, the operation of the boost chopper 1 is started. Hereinafter, a specific configuration of the discharge lamp lighting device of the present embodiment that achieves the above operation will be described. In the following description, the same components as those of the conventional circuit are denoted by the same reference numerals, and description thereof will be omitted.
Only the features of the present embodiment will be described.

The step-up chopper 1 includes an inductance element L
₁ , a diode D ₁ , an FET Q ₁ and a capacitor C ₁ . However, in the case of the embodiment using a transformer primary winding n ₁₁ as an inductance element L _1, FE
The difference from the above case is that TQ ₁ is used as a switching element. The inverter 2 has a so-called half-bridge configuration.
₂ is turned on and off in a self-excited manner, and the transistor Q ₃
Is different from the above-described case in that the control circuit 4 is a so-called self-excited separately-excited type in which the control circuit 4 controls the on and off in a separately excited manner. Incidentally, on the transistor Q ₂ with self-excited, to turn off, are using a current feedback transformer CT. Further, the transistor Q _2, Q ₃ is Yes insert the emitter resistor R _22, R ₂₃ respectively series, thereby stabilizing the switching operation at these emitter resistors R _22, R _23.

The control circuit 3 of the step-up chopper 1 includes a switching regulator IC (for example, a T
DA4814A). Hereinafter, the configuration of the control circuit 3 will be described based on the terminal description of the IC 31. The third terminal of the IC 31 is a power terminal. Here, the power source of the control circuit 3 is the inverter 2
Operate. Specifically, the power supply circuit of the control circuit 3 is composed of capacitors C ₁₁ and C ₁₃ and diodes D ₁₁ and D ₁₂ .
A variable component is extracted from a connection point of the diodes D ₂ and D ₃ by a capacitor C ₁₁ , and rectified and smoothed by a diode D ₁₂ and a capacitor C ₁₃ to create a drive power source for the control circuit 3. The diode D ₁₁ is for the potential of the connection point of the diodes D _2, D ₃ is to discharge the charges of the capacitor C ₁₁ during a low level.

The 14th terminal of the IC 31 is connected to the FET Q ₁
Terminal for taking on timing of
During the steady operation voltage induced in the secondary winding n ₁₂ of the transformer constituting the inductance element L ₁ is inputted through a resistor R _31, the on-timing of the FETs Q ₁ according to the current flowing in the inductance element L ₁ Control. By the way, in the IC 31, when the FET Q ₁ is switching, in the steady state, the FET Q ₁ is detected from the induced voltage of the secondary winding n _12.
1 can control the on-timing,
Q ₁ is can not control the on-timing in response to the secondary winding n ₁₂ until first turned on.

Therefore, the IC 31 has the FET Q₁The most
It is necessary to start up to turn it on first. This origin
Movement is diode D_Two, D_ThreeResistance at the connection point
R₁₉, R ₂₀By applying the voltage to the 14th terminal
I'm going. In this way, the IC 31 is activated in this way.
After the IC 31 starts operating, the resistance R₁₉, R₂₀
When the starting voltage is applied to the terminal No. 14 via
May cause operation. So the transistor
Q_{twenty one}, Q_{twenty two}, Resistance R₃₀~ R₃₃, Capacitor C₁₅And die
Aether D₁₄Is provided.

[0037] The start-stop circuit, when the control power V _cc to the control circuit 4 of the inverter 2 is supplied, the capacitor C ₁₅
There is charged via the resistor R _31, thereby the transistor Q ₂₂ is turned on, the transistor Q ₂₁ is turned off, start from the starting circuit is in a state according to the IC 31. And I
C31 to boot rests with FETs Q ₁ is turned on, charges the capacitor C ₁₅ through the diode D ₁₄ is discharged. In this case, the transistor Q ₂₂ is turned off, the transistor Q ₂₁ is turned on is controlled so as not to apply starting from the starting circuit to the IC 31. Here, if sufficiently large time constant of the resistor R ₃₁ and capacitor C ₁₅ to the switching speed of FETs Q _1, the period in which the FETs Q ₁ is switched, the coercive transistor Q ₂₁ is in the ON state As a result, it is possible to prevent the activation circuit from being activated by the activation circuit.

The second terminal of the IC 31 is an output terminal, and a resistor R
_14, on the FETs Q ₁ through R _15, off controls. I
12 Pin and 13 Pin of C31 is a terminal corresponding to the output and the inverting input of an operational amplifier with a built-in IC 31, by a divided voltage of the resistors R _17, R ₁₈ is negatively fed back via a resistor R ₂₆ IC 31 Functions to control the output voltage of the boost chopper 1 to a desired constant state.

The input to the twelfth terminal of the IC 31 is
Voltage when the boost chopper 2 starts operating.
And then gradually reduce the
In this case, the soft start operation of the power source 2 is performed. This soft star
The gate circuit is a transistor Q _{twenty three}, Capacitor C₁₆, Die
Aether D₁₄, D₁₅And resistance R_{twenty one}And so on. this
In the soft start circuit, the operation of the boost chopper 1
Time the start of operation (non-operating period of boost chopper 1)
When the output of the timer circuit is obtained, the transistor Q_{twenty three}But
Turns off. This transistor Q_{twenty three}At the off point
Capacitor C ₁₆The control power supply V_ccIs charged to the voltage of
Therefore, the output voltage is supplied to the boost chopper 1 by the IC 31.
Control to reduce output as in the case of high pressure
The output of the boost chopper 1 is controlled to be small immediately after startup
Is done. And the capacitor C ₁₆The charging voltage of the resistor R_{twenty one}
Output from the step-up chopper 1
A so-called soft start control that rises every time is performed.

The other terminals of the IC 31 will be briefly described. Terminal 11 receives the input voltage divided by the resistors R ₁₁ and R ₁₂ , and synchronizes the input voltage with the FET.
To Q ₁ on a terminal for performing off control. Also,
Pin 4 is a terminal for detecting current flowing from the voltage across the resistor R ₁₆ which is inserted in series with the FETs Q ₁ to FETs Q _1, for example, is used to detect the abnormal state of the step-up chopper 1. Further, the first terminal is a ground terminal.

Next, the control circuit 4 of the inverter 2 will be described below. The control circuit 4 includes a monostable multivibrator configured using a general-purpose timer IC (for example, μPC1555 manufactured by NEC). The monostable multivibrator, a period determined by the time constant of the resistor R ₅₁ and capacitor C _17, the output becomes high level.

[0042] Then, a trigger circuit to trigger on the monostable multivibrator, resistors R _52, R _53, are constituted by an inverter gate I _1, I ₂ and a capacitor C _18. That is, in this trigger circuit, the diodes D ₂ , D
The potential of the _third connection point detected by the resistors R _52, R _53, the output of the inverter gate I ₁ the potential of the resistor R _52, R ₅₃ becomes high level when the drops to negative potential of approximately diode bridge DB Is converted into a differential waveform through the capacitor _C18, and a trigger pulse is input to the trigger terminal (second terminal) of the IC 41. That is, the transistor Q ₂ is turned off, the negative electrode of the off current flows through the diode D ₃ in energy stored in the inductance element L ₂ at the time, the diode D _2, D ₃ of approximately the diode bridge DB is the potential of the connection point The timing at which the potential drops to the potential of the above is detected.

The output of this monostable multivibrator
Buffer B₁Through a totem pole connected transformer
Jista Q₃₁, Q₃₂Drive circuit consisting of
When the output of the multivibrator is high,
Transistor Q₃₁Is turned on, and the transistor Q_ThreeNibe
Supply current to turn on. Even with this inverter 2,
A starting circuit is required to actually start the
The circuit, transistor Q₃₃, Diac, etc.
Riga element Q₃₄, Capacitor C₁₉, Diode D_{twenty one}And
Anti-R₅₄, R₅₅It consists of. In this startup circuit,
Inductance element L of chopper 1₁Output voltage
Capacitor C₁₉Is charged, and the trigger element Q₃₄The breako
The transistor Q₃₃To the monostable
By triggering the multi vibrator,
Jista Q _ThreeAnd turn on the inverter 2
It is like that. Once activated, the
Star Q_ThreeAs long as the switch operates normally,
Do D_{twenty one}And resistance R₅₅The capacitor C₁₉Charge
Riga element Q₃₄Never reach the breakover voltage of
It has become.

Power for the control circuit 4 is supplied from a power supply circuit 6 comprising a resistor R ₄₁ , a zener diode ZD ₄₁ and a capacitor C ₄₁ . By the way, in the control circuit 4, the control power supply V _cc supplied from the power supply circuit 6 is used.
An operation control circuit of the control circuit 4 is provided in order to operate when the voltage is sufficiently stabilized. The operation control circuit includes an operational amplifier OP _1, the Zener diode ZD _51, diode D _22, are constituted by the capacitor C ₂₁ and resistor R ₅₆ to R _58. That constitutes the comparator operational amplifier OP _1, until control power V _cc reaches a voltage determined by the Zener diode ZD _51, the output of the comparator becomes a low level by the delay action of the capacitor C _21, IC 41
The IC 41 is kept in a non-operating state by lowering the reset terminal (No. 4 terminal) to a low level. Then, the output of the comparator becomes a high level when the voltage of the control power supply V _cc is steady, IC 41 is operable.

In addition, the control circuit 4 has a preheat
Timer circuit that measures time and the output of this timer circuit
Shorten the high-level period of the monostable multivibrator accordingly.
Control to keep the voltage applied to the discharge lamp La low.
And a preheating control circuit. Where the timer circuit
Is an operational amplifier OP_Two, Capacitor C_{twenty two}, Diode D _{twenty three}
And resistance R₆₁~ R₆₄The operational amplifier OP_Two
The output of the comparator constituted by using the resistor R₆₁And
Capacitor C_{twenty two}Low level for the time determined by the time constant of
You. The preheating control circuit includes the transistor Q₃₅, Capacitor C
₂₀, Diode D_{twenty four}And resistance R₆₅, R₆₆Consists of
While the output of the Ima circuit is low level, the transistor
Q₃₅Is turned on, the resistance R₅₁In another route
Capacitor C₁₇To charge the capacitor C₁₇of
Make charging faster. Therefore, monostable multivibrator
The period during which the output of the
Star Q_ThreeBecomes shorter. Therefore, inverter 2
The voltage applied to the discharge lamp La from below is below the starting voltage.
As a result, the discharge lamp La is preheated.

Incidentally, the monostable multi
Set the period during which the vibrator output goes high
In the time constant circuit, the resistance R₅₁Through the capacitor C
₁Output capacitor C₁₇Is charging. This is
Transient during preheating against voltage fluctuations of the AC power supply
Star Q_ThreeThis is for properly controlling the on-period. Toes
When the voltage of the AC power supply AC rises,
Sensor C₁₇Charging current of the transistor Q_Threeof
The ON period is shortened, the amount of preheating is reduced,
When the voltage of the source AC is low, the operation is the reverse of the above.
As a result, the amount of preheating increases, and the voltage of the AC power supply AC changes.
Transistor Q when preheating against motion _ThreeOn period
Can be properly controlled.

Incidentally, the timer circuit for counting the preheating time has a common configuration, and a timer circuit for counting the time when the operation of the step-up chopper 1 is started is provided. Wherein the timer circuit is also used as the capacitor C _22, a diode D ₂₃ and the resistor R ₆₁ to R ₆₄ and timer for preheating, capacitor C
It is used comparator and an operational amplifier OP ₃ for comparing the divided voltage across voltage ₂₂ and the resistor R ₆₁ to R _64. Since the reference voltage of the comparator of the timer circuit is higher than that of the timer circuit for preheating,
The period during which the output is at the high level is delayed by a certain time.

[0048] By connecting the output of the timer circuit through the diode D ₂₆ to Pin 14 of the IC 31, the boost chopper 1 are to avoid work during time limit operation period. Further, connected to the base of the transistor Q ₂₃ of the soft start circuit through the diode D ₂₅ the output of the timer circuit, by turning on the transistor Q _23, to be soft start at startup to charge the capacitor C ₁₆ Prepare.

The operation of this embodiment will be described below. First,
When the power is turned on, the power is supplied from the power supply circuit 6 to the control circuit 4 and the start / stop circuit of the control circuit 3. At this time, the operation of the control circuit 4 is stopped by the operation of the operation control circuit of the control circuit 4 until the voltage supplied from the power supply circuit 6 is stabilized. This state is shown at t _{0 to} ta in FIG.

[0050] Then, the monostable by the activation circuit voltage supplied from the power supply circuit 6 to the control circuit 4 is stable after the operation is supplied with power from the output side of the inductance element L ₁ of the step-up chopper 1 is stopped The multivibrator starts up. Therefore, the transistor Q ₃ is fixed time turned on, the inverter 2 starts oscillation operation. However, the ON time of the transistor Q _{3 at} this time is controlled by the operation of the preheating control circuit, so that the ON period of the transistor Q ₃ is controlled to be short, and the output of the inverter 2 is suppressed to a small value. At this time, the discharge lamp La
Is controlled to be lower than the starting voltage, and the discharge lamp L
a is preheated without starting lighting. This pre-heating state is shown at ta to tb in FIG.

[0051] Then, when the counting operation of the timer circuit for counting of the preheating time is completed, the transistor Q ₃₅ is turned off by the output of the timer circuit becomes high level, reducing the output of the inverter 2 by the preheating control circuit The suppression control is released. However, during this time the charge stored in the capacitor C ₂₀ of the preheating control circuit is present in the charge as a power supply, a capacitor C and resistor R ₅₁ by another route
Since ₁₇ is charged, gradually ON time of the transistor Q ₃ becomes longer over time. As described above, when the output of the inverter 2 increases (shown at tb to tc in FIG. 4),
Eventually, the output voltage applied to the discharge lamp La of the inverter 2 reaches the starting voltage, and the discharge lamp La is turned on at time tc.

Thereafter, the resistance R₅₁And capacitor C₁₇time
Transistor Q with ON period determined by constant_ThreeIs turned on,
Transistor Q_Two, Q_ThreeIs turned on and off alternately
State. In this way, the inverter 2 operates stably.
In this case, the operation stop period of the step-up chopper 1 is
The timed operation of the timer circuit that measures the time ends, and the boost chopper
Becomes operable. And the transistor Q_TwoNo
Diode D_Two, D _ThreeVoltage at the connection point
Sensor C₁Voltage (diode bridge DB
Peak voltage of output voltage (V_ACP)), IC
31 is activated by the activation circuit, and the boost chopper 1
Start the boost operation. However, in this case, soft start
The output of the boost chopper 1 gradually increases due to the operation of the circuit,
Eventually, the output stabilizes at a constant voltage.

Thereafter, power is supplied from the inverter 2 to the discharge lamp La using the boost output of the boost chopper 1 as a power source, and the discharge lamp La is lit and held in a state where the light output is constant.
As described above, in this embodiment, first, the inverter 2 is operated in a state where the output is limited to a small value, the inverter 2 is set to an operation state in which a desired output can be obtained after a desired time, and after the operation state of the inverter 2 is stabilized, Step-up chopper 1
Is started, there is no overlap in the period during which the transient operation is performed between the boost chopper 1 and the inverter 2, the boost chopper 1 and the inverter 2 can be operated stably, and the light of the discharge lamp La Since the output can be changed stably and the step-up chopper 1 and the inverter 2 can be operated stably, an increase in stress on the circuit element can be prevented. The inverter 2 is connected to the discharge lamp L
Since the output can be limited at the time of preheating of a, it is not necessary to set the output voltage of the boost chopper 1 to be high, and thus the stress on the circuit elements can be reduced by operating the boost chopper 1 and the inverter 2 stably. The tolerance of the circuit elements of the boost chopper 1 and the inverter 2 can be reduced.

(Embodiment 2) FIGS. 4 and 5 show another embodiment of the present invention. In the present embodiment, as shown in FIG. 5, first, the inverter 2 is operated in a state in which the output is limited so as to preheat the discharge lamp La, and after a desired time, the inverter 2 is brought into a state in which the inverter 2 preheats the discharge lamp La. At a certain time, the step-up chopper 1 is started, and when the output of the step-up chopper 1 becomes stable, the inverter 2 is soft-started to discharge the discharge lamp La.
To start lighting.

For this purpose, in the concrete circuit, the timer circuit for measuring the preheating time and the timer circuit for measuring the period during which the operation of the step-up chopper 1 is stopped are different from each other, and the operation stop period of the step-up chopper 1 is measured. The timer has a shorter time limit. For this reason, when the output of the inverter 2 is in a state of preheating the discharge lamp La, the operation of the boost chopper 1 is started, and then, when the operation of the boost chopper 1 is stabilized, the output voltage of the inverter 2 is reduced. L
The reference voltages of the comparators constituting the respective timer circuits in FIG. 4 are set so that a is increased to a voltage for starting lighting. Incidentally, this setting is performed by selecting the constant of resistor R ₆₂ '~R _64'.

[0056] In the case of this embodiment to insert the volume VR ₁ in series with resistor R ₅₁ to set the ON period of the transistor Q ₃ of the monostable multivibrator, there the ON period as adjustable. By the way, in the above description, the second
Although the switching circuit described above is a full-bridge configuration inverter, the present invention can be applied to a case where a full-bridge configuration inverter or a single-type inverter is used, and the load is other than a discharge lamp. Needless to say, the present invention basically includes the first and second switching circuits, and any control of the operation timing of the first and second switching circuits as described above is included in the present invention.

[0057]

As described above, the present invention provides a first switching circuit for generating a DC power supply from an AC power supply,
And a second switching circuit for generating power to be supplied to the load by using a DC power supply supplied from the switching circuit as a power supply, and the first and second switching circuits each include a control circuit for controlling the driving of the switching element. First, the second switching circuit is operated in a state where the output is limited to a small value, and after a desired time, the second switching circuit is set to an operation state in which a desired output is obtained, and the operation state of the second switching circuit is stabilized. After that, the operation of the first switching circuit is started.
The output of the second switching circuit is fixed, and the output of the first switching circuit can be operated as desired by the output of the first switching circuit. By eliminating the need to set a high voltage, the tolerance of the circuit elements of the first and second switching circuits can be reduced,
In addition, when either operation of both switching circuits is stable, the other switching circuit performs a desired operation, thereby operating both switching circuits stably and forming a circuit element by overlapping transient operations. Can be prevented from increasing, and the load can be operated stably.

A first switching circuit for producing a DC power supply from an AC power supply and a second switching circuit for producing power supplied to a load using the DC power supplied from the first switching circuit as a power supply. The first and second switching circuits each include a control circuit for controlling the driving of the switching element. The first switching circuit is operated in a state where the output is limited to a small value, and the first switching circuit is operated after a desired time. Is started, and after the operation state of the first switching circuit is stabilized, the second switching circuit is brought into an operation state in which a desired output can be obtained, and the same object as in the above case can be achieved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic circuit configuration of an embodiment of the present invention.

FIG. 2 is a specific circuit diagram of the above.

FIG. 3 is an operation explanatory diagram of the above.

FIG. 4 is a specific circuit diagram showing another embodiment.

FIG. 5 is an operation explanatory view of the above.

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

FIG. 7 is an operation explanatory view of the above.

FIG. 8 is a circuit diagram of another conventional example.

FIG. 9 is an operation explanatory view of the above.

FIG. 10 is an explanatory diagram of the operation when the operation control is different from the case of FIG. 9;

[Explanation of symbols]

 A first switching circuit B second switching circuit 3, 4 control circuit 5 load AC AC power supply

Continued on the front page (72) Inventor Yukio Yamanaka 1048 Kadoma, Kadoma, Osaka Pref. Matsushita Electric Works, Ltd. (72) Inventor Narunoyo Ohara 3-6-1, Shintaka, Yodogawa-ku, Osaka Meiji National Industrial Co., Ltd. (56) References JP-A-3-141597 (JP, A) JP-A-1-248969 (JP, A) JP-A-1-298692 (JP, A) JP-A-62-77860 (JP, A) Kaihei 3-27,000 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) H05B 41/282 H02M 7/48

Claims (2)

(57) [Claims] 1. A first switching circuit for generating a DC power supply from an AC power supply, and a second switching circuit for generating power supplied to a load using a DC power supply supplied from the first switching circuit as a power supply. The first and second switching circuits are provided with control circuits for controlling the driving of the switching elements, respectively. First, the second switching circuit is operated in a state where the output is limited to a small value, and after a desired time, the second switching circuit is operated. In a power conversion device, wherein the operation state of the second switching circuit is stabilized and the operation of the first switching circuit is started after the operation state of the second switching circuit is stabilized. 2. A first switching circuit for generating a DC power supply from an AC power supply, and a second switching circuit for generating power supplied to a load using the DC power supplied from the first switching circuit as a power supply. The first and second switching circuits each include a control circuit for controlling the driving of the switching element. The first switching circuit is operated in a state where the output is limited to a small value, and the first switching circuit is operated after a desired time. 2. The power converter according to claim 1, wherein the operation is started, and after the operation state of the first switching circuit is stabilized, the second switching circuit is brought into an operation state in which a desired output is obtained.