JPH07142180A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To improve the input power factor and suppress the increase of the switching loss and the power loss of a control circuit. CONSTITUTION:A chopper circuit 1 outputs the DC boosted from the output of a rectifier DB to drive an inverter circuit IV, and a discharge lamp La is lighted by the high-frequency power outputted from the inverter circuit IV. The switching element Q1 of the chopper circuit 1 is turned on or off by a control circuit 2. The control circuit 2 is provided with the first control circuit 2a changing the operating frequency of the switching element Q1 in response to the input/output of the chopper circuit 1 and the second control circuit 2b turning the switching element Q1 on or off with the constant operating frequency. A selecting circuit 3 operates the switching element Q1 with the first control circuit 2a when the power consumption of a load circuit Z is large and operates the switching element Q1 with the second control circuit 2b when the power consumption of the load circuit Z is small.

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 in which a chopper circuit is provided in front of an inverter circuit for supplying alternating electric power to a discharge lamp.

[0002]

2. Description of the Related Art Conventionally, a discharge lamp lighting device has been widely used in which a DC input obtained by rectifying an AC voltage of a commercial power source and smoothed by a smoothing capacitor is converted into high frequency power by an inverter circuit and supplied to a discharge lamp. In this type of discharge lamp lighting device, the reason why the commercial power supply is smoothed after being rectified is that when the discharge lamp is used as a load, the envelope of the supplied high-frequency current fluctuates in the AC cycle of the commercial power supply and becomes the discharge lamp. This is to substantially eliminate the occurrence of the re-strike phenomenon, which improves the luminous efficiency of the discharge lamp and prevents the flicker of the light output from the discharge lamp.

However, when the commercial power source is rectified and smoothed, the current flowing from the commercial power source to the smoothing capacitor flows only near the peak value of the AC voltage, and a peak having a pause period for each half cycle of the AC voltage of the commercial power source. Since the current has a high value, the input power factor is poor, and many high-order harmonic current components are included in the basic waveform of the AC voltage, so that other equipment connected to the same AC distribution system There is a problem of adverse effects such as mixing of harmonic noise.

As a configuration for solving the above problems, increasing the input power factor, reducing the harmonic components, and supplying a DC voltage with little fluctuation to the inverter circuit, the following is conceivable. ing. That is, as shown in FIG. 7, a direct current obtained by full-wave rectifying the commercial power supply AC by a rectifier DB such as a diode bridge is input to the chopper circuit 1, and the output of the chopper circuit 1 is supplied to an inverter circuit and a discharge lamp. It is supplied to the load circuit Z including. A filter circuit NF for blocking high frequencies is inserted between the commercial power source AC and the rectifier DB. The chopper circuit 1 includes an inductor L ₁ and an FE connected between output terminals of the rectifier DB.
A series circuit of switching elements Q ₁ made of T, consisting of a series circuit of the diode D ₁ and capacitor C ₁ for smoothing for parallel connected reverse blocking of the switching element Q _1. The switching element Q ₁ is turned on and off by the control circuit 2 to be described later, the energy stored in inductor L ₁ during the ON period of the switching element Q ₁ is being added to the DC input is in the OFF period of the switching element Q ₁ diode D It is supplied to the output side through ₁ . Therefore, the voltage across the capacitor C ₁ will rise above the input voltage, and the chopper circuit 1 will boost the DC input. The voltage across the capacitor C ₁ is determined according to the duty ratio of the switching element Q ₁ .

Two resistors R ₁ and R ₂ connected in series are connected between both ends of the capacitor C ₁ , and a capacitor C ₂ is connected in parallel to the resistor R ₂ . The connection point between the resistors R ₁ and R ₂ becomes the input of the control circuit 2, and the control circuit 2 is based on the potential at the connection point between the resistors R ₁ and R ₂ so that the output voltage Vo is kept substantially constant. Control the Deuch ratio of the switching element Q ₁ . The control circuit 2 includes a control integrated circuit (e.g., Sharp Corporation IR3M02) the IC ₁ as a main configuration, the integrated circuit IC ₁ resistor R ₉ to R _14, capacitors C
₄ and C ₅ are externally attached. Here, the integrated circuit IC ₁ is configured to output a rectangular wave having a constant frequency determined by the resistor R ₉ and the capacitor C ₄ from the 8th and 11th terminals. Further, resistors R _{4 to} R ₈ and transistors Q _{2 to} Q ₄ are provided to give the output of the integrated circuit IC ₁ to the switching element Q _1, and the commercial power source is rectified through the filter circuit NF to supply power to the control circuit 2. A diode D ₂ for limiting current, a resistor R _{3 for current} limiting, and a capacitor C ₃ for smoothing are provided. Here, the positive electrode side of the capacitor C ₃ is connected to the input side of the rectifier DB through a diode D ₂ and the resistor R _3, the negative electrode side of the capacitor C ₃ is a rectifier D
It is connected to the negative output terminal of B.

With the above configuration, the voltage across the capacitor C ₃ is supplied to the control circuit 2. The terminals 8 and 11 which are the output terminals of the integrated circuit IC ₁ are
Two resistors R connected in series between both ends of the capacitor C _3.
Control circuit 2 by connecting to the connection point of ₇ and R ₈
Is connected to the output section of. Therefore, the integrated circuit IC
_When the output of ₁ is H level, the connecting point between the emitters of the _two transistors Q ₂ and Q ₃ which are connected complementarily is L
And the switching element Q ₁ is turned off,
When the output of the integrated circuit IC ₁ is L level, the switching element Q ₁ is turned on.

Next, the operations of the chopper circuit 1 and the control circuit 2 will be described. 8A shows the current flowing through the inductor L ₁ , and FIG. 8B shows the voltage across the switching element Q ₁ . When the switching element Q ₁ is turned on at time t ₁ , the current flowing through the inductor L ₁ gradually increases,
When the switching element Q ₁ is turned off at time t ₂ , the inductor L ₁ releases the stored energy and the current gradually decreases. In this way the inductor L ₁
When the current flowing through the switch becomes 0 at time t ₃ , as shown by the broken line in FIG. 9, the switching element Q ₁ and the diode D
_The electric charge accumulated in the capacitance components C ₆ and C ₇ of ₁ is released, and the reverse current i ₁ flows through the inductor L ₁ . Therefore, the resonance current flows through the capacitance component C ₅ of the rectifier DB. That is, FIG. 8 (a)
A current waveform such as between time t ₃ and time t ₄ at is generated.

Accordingly, since the current flowing through the inductor L ₁ becomes 0 at time t _3, at time t ₄ when the rest period to the switching element Q ₁ is turned on again is long, many harmonic in the input current waveform Wave components will be included.
As described above, the switching element Q ₁ is turned on.
Since the OFF cycle is kept constant, when the input voltage waveform to the rectifier DB is a sine wave, the stored energy in the inductor L ₁ is large near the peak value of the input voltage, and the time t ₃ and the time t. _Although the current quiescent period between ₄ becomes short, the energy stored in the inductor L ₁ is small and the current quiescent period becomes long during the period when the input voltage is low. That is,
As shown in FIG. 10, there is a problem that the input current is large in the vicinity of the peak value of the input voltage, and the input current is significantly reduced in the low input voltage period, and the harmonic component increases in the low input voltage period. The problem arises.

To solve such a problem, a configuration as shown in FIG. 11 can be considered. In this configuration, the operating frequency for turning on / off the switching element Q ₁ is variable, and the on-duty is substantially constant (changes within a range in which the output voltage of the chopper circuit 1 is kept constant). The control circuit 2 includes a general-purpose integrated circuit IC ₂ for a switching regulator (for example, MC34246 manufactured by Motorola).
And the inductor L ₁ has a secondary winding. In the control circuit 2, the current flowing through the inductor L ₁ is detected to become 0 on the basis of the induced voltage e ₂ of the secondary winding of the inductor L _1, it is of turns on the switching element Q _1.

The operation of the circuit shown in FIG. 11 will be described below.
In the chopper circuit 1, so that the output voltage is kept constant,
The input voltage is divided by resistors R ₁₅ and R ₁₆ to obtain the first detection voltage V
_11, and the second detection voltage V ₁₂ obtained by dividing the output voltage by the resistors R ₁ and R ₂ is input to the error amplifier 21.
The error voltage V ₁₂ ′ proportional to the difference between the reference voltage generated by the reference voltage generator 29 and the second detection voltage V ₁₂ is multiplied by the first detection voltage V ₁₁ by the multiplier 22, and the switching element Q ₁ The third detection voltage V ₁₃ which is the voltage across the resistor R ₁₇ connected in series with the switching element Q ₁ and the output voltage of the multiplier 22 are compared in the comparator 23 in order to detect the current flowing in the switching element Q ₁ . The output of the comparator 23 is the RS latch 24.
When the output of the RS latch 24 becomes L level, the switching element Q ₁ is turned off through the output circuit 25. That is, the target value of the peak value of the current flowing through the switching element Q ₁ is determined by the output of the multiplier 22, and when the passing current of the switching element Q ₁ detected by the voltage across the resistor R ₁₇ reaches the target value, the desired energy is reached. Turns off the switching element Q ₁ as if it were stored in the inductor L ₁ .

On the other hand, the RS latch 24 has an inductor L ₁
Is set by inputting the output of the zero-point detector 26, which detects the time when the induced voltage e ₂ to the secondary winding becomes approximately 0 V, through the delay circuit 27 to bring the output to the H level. That is, when the stored energy of the inductor L ₁ becomes almost 0 after the switching element Q ₁ is turned off, the switching element Q ₁ is turned on again. The timer circuit 28 is provided to ensure the operation of the RS latch 24.

By the above-described operation, the ON period of the switching element Q ₁ is adjusted so that the stored energy of the inductor L ₁ becomes almost constant regardless of the input voltage, and the current idle period hardly occurs. Since the off period of the switching element Q ₁ is controlled, the peak value of the current flowing through the switching element Q ₁ is on a sine wave that substantially matches the input voltage waveform. Moreover, the output voltage V of the chopper circuit 1 which is the input voltage of the load circuit Z
It is possible to keep o almost constant.

[0013]

As described above, FIG.
Although the input power factor is improved by the configuration of 1,
The following problems occur. That is, in the configuration of FIG. 11, the ON period of the switching element Q ₁ is set so that the energy stored in the inductor L ₁ is substantially constant, and the switching element Q ₁ is set so that there is almost no rest period of the current flowing in the inductor L ₁ . Since the off period of Q ₁ is set,
Not only the input voltage but also the amount of power consumption in the load circuit Z connected to the output of the chopper circuit 1 changes the ON period and the OFF period of the switching element Q ₁ , and eventually the consumption in the load circuit Z is changed. The operating frequency will vary depending on the power. Therefore, when the power consumption in the load circuit Z is small, the operating frequency becomes high and the switching element Q
There arises a problem that the switching loss in ₁ increases and the power consumption in the control circuit 2 also increases.

For example, assuming that the power consumption in the load circuit Z is P and the operating frequency at this time is f, the power consumption is reduced to P '(P>P'), at which time the operating frequency becomes It is assumed to have changed to f '. Current flowing through the switching element Q ₁ in the ON period Suinngu element Q _1,
That current i _p flowing through the inductor L _1, when the effective value of the commercial power source voltage and _{V RMS, i p = {2} (√2) P / V RMS} sinθ ( However, 0 <θ <π) envelope line of Considering the case of θ = π / 2, since i _p = 2 (√2) P / _VRMS , the input voltage is Vi, the ON period of the switching element Q ₁ is t _ON , and the OFF period is t _ON . _{When OFF} and the inductance of the inductor L ₁ is L, the following equation holds. Vi · t _ON / L = (Vo-Vi) t _OFF / L = 2 (√
2) P / V _RMS ∴t _ON = 2 (√2) P · L / Vi · V _RMS t _OFF = 2 (√2) P · L / (Vo-Vi) · V _RMS Operating frequency f is 1 / Since (t _ON + t _OFF ), f = 1 / {2 (√2) P · L / Vi · V _RMS +2 (√
2) P · L / (Vo−Vi) · V _RMS } = V _RMS Vi (Vo−Vi) / 2 (√2) P · L · Vo holds, and similarly, when the operating frequency becomes f ′. , F ′ = _VRMS Vi (Vo-Vi) / 2 (√2) P ′ · L
・ Vo is established. Now, if P '= P / 4, then f' = 4f, and if the power consumption is reduced, the operating frequency is increased. In short, P · f = V _RMS Vi (Vo-Vi) / 2 (√2) L · V
Since o 2 is constant on the right side, it can be seen that the power consumption P and the operating frequency f are in inverse proportion.

As described above, when the power consumption of the load circuit Z and the operating frequency of the chopper circuit 1 are in inverse proportion to each other, the fluctuation of the power consumption of the load circuit Z causes a switching loss or a switching loss in the switching element Q _1. The problem arises that the power loss in the control circuit 2 increases. The present invention is intended to solve the above-mentioned problems, and it is possible to apply a substantially constant DC voltage to a load circuit with a high input power factor, while switching due to fluctuations in power consumption in the load circuit. An object of the present invention is to provide a discharge lamp lighting device that suppresses a change in operating frequency of an element and suppresses an increase in switching loss and power loss in a control circuit.

[0016]

According to a first aspect of the present invention, a switching element interrupts a direct current input to store energy in an inductor, and the stored energy of the inductor is discharged through a diode. A load circuit consisting of an inverter circuit that converts the output to alternating power and a discharge lamp that lights up with the output of the inverter circuit, and the operating frequency that turns the switching element on and off based on the current flowing in the inductor and the operating state of the load circuit A first control circuit for
A second control circuit for turning on / off the switching element at a constant operating frequency, and a selection circuit for selecting one of the first control circuit and the second control circuit to operate the switching element are provided. .

According to a second aspect of the invention, in the first aspect of the invention, the selection circuit selects the first control circuit when the power consumption in the load circuit exceeds a predetermined value, and the power consumption is less than or equal to the predetermined value. Is selected, the second control circuit is selected. According to a third aspect of the invention, in the first aspect of the invention, the discharge lamp includes a filament, and the selection circuit selects the first control circuit when the discharge lamp is lit and the second control circuit when the discharge lamp is preheated. It is characterized by selecting.

A fourth aspect of the present invention is characterized in that, in the first or second aspect of the invention, the inverter circuit includes a dimming control section for varying the power supplied to the discharge lamp. According to a fifth aspect of the present invention, in the first aspect of the invention, the inverter circuit includes a dimming control unit that receives a dimming signal from the outside to change the power supplied to the discharge lamp, and the selection circuit includes the discharge lamp. The first control circuit is selected when the light output of is above a predetermined level, and the second control circuit is selected when the light output of the discharge lamp is below a predetermined level.

The invention of claim 6 is characterized in that, in the invention of claim 5, the selection circuit selects one of the first control circuit and the second control circuit by a dimming signal.

[0020]

According to the first aspect of the present invention, the first control circuit for varying the operating frequency of the switching element of the chopper circuit based on the current flowing through the inductor and the operating state of the load circuit, and the switching element performing a constant operation. A second control circuit for turning on / off at a frequency is provided, and one of the first control circuit and the second control circuit is selected by the selection circuit to operate the switching element. When the distortion of the input current waveform becomes a problem, the operating frequency of the switching element is made variable to suppress the decrease of the input power factor. The distortion of the input current waveform does not become a problem but the switching loss of the switching element increases. If this becomes a problem, the operating frequency of the switching element can be fixed to suppress an increase in loss.

According to the second aspect of the invention, the first control circuit and the second control circuit are selected according to the power consumption of the load circuit, so that the power consumption of the load circuit is relatively large. When the input current waveform is distorted and the power factor drops significantly, the operating frequency is made variable by the first control circuit,
It suppresses the decrease of the input power factor. In addition, when the power consumption in the load circuit is relatively small and the input power waveform does not have much influence even if the input current waveform is slightly distorted, the operating frequency is fixed by selecting the second control circuit.
The switching loss in the switching element and the power loss in the control circuit are suppressed.

According to the third aspect of the present invention, it is an embodiment in which the load circuit includes a discharge lamp having a filament, and when the discharge lamp is lit and the power consumption in the load circuit is large. This suppresses a decrease in the input power factor and suppresses switching loss and the like when the discharge lamp is preheated and the power consumption in the load circuit is small. According to the structure of claim 4, the inverter circuit provided in the load circuit enables the dimming control by adjusting the power supplied to the discharge lamp. Therefore, when the light output of the discharge lamp is large, the load circuit consumes less power. The first control circuit is selected so as to suppress the decrease in the input power factor due to the increase in the power, and when the light output of the discharge lamp is low, the power consumption of the load circuit is reduced and the power loss such as the switching loss is suppressed. It is.

According to the fifth aspect of the present invention, when the discharge circuit is dimming-controlled by the inverter circuit provided in the load circuit, a threshold value is set for the level of the light output and the first control circuit and the second control circuit are set. One of and is selected, and has the same function as in claim 4. According to the configuration of claim 6, since one of the first control circuit and the second control circuit is selected by the dimming signal for controlling the light output of the discharge lamp, the same function as in claim 4 is provided. In this regard, the structure is simplified because no means for detecting the state of the load circuit is required.

[0024]

【Example】

(Embodiment 1) In this embodiment, as shown in FIG. 1, a filter circuit NF is connected to a commercial power supply AC as in the configuration shown in FIG.
The rectifier DB is connected through the rectifier DB, and the direct current (pulsating current) output from the rectifier DB is boosted by the chopper circuit 1 and then supplied to the load circuit Z. That is,
Those having the same configuration as the conventional configuration shown in FIG. 6 except for a control circuit 2 described later are denoted by the same reference numerals. The load circuit Z includes an inverter circuit IV that converts a DC input into high frequency power, and a discharge lamp L that is turned on by being supplied with the output of the inverter circuit IV.
a and. The control circuit 2 for turning on and off the switching element to Q ₁ chopper circuit 1 includes a first control circuit 2a the operating frequency is configured similarly to the control circuit of FIG. 11 is variable, the operating frequency is fixed Figure 7
Second control circuit 2b configured in the same manner as the above control circuit, and one of the control circuits 2a and 2b is selected by the selection circuit 3.
Is selectively applied to the switching element Q ₁ . The selection circuit 3 is controlled by a current detector 4 which detects a current flowing at a connection point between the chopper circuit 1 and the load circuit Z, and when the current detected by the current detector 4 exceeds a prescribed threshold value (that is, , When the power consumption of the load circuit Z exceeds a predetermined value), the first control circuit 2a
And the second control circuit 2b is selected when the detected current is less than or equal to the threshold value.

By adopting the above configuration, by selecting the first control circuit 2a whose operating frequency changes according to the input voltage during the period when the power consumption in the load circuit Z is large, the fluctuation of the input voltage can be prevented. Regardless of this, the energy stored in the inductor L ₁ is made substantially constant and the inductor L ₁
The increase of the current quiescent period is restricted to suppress the distortion of the input current waveform, thereby suppressing the decrease of the input power factor. In addition, the second control circuit 2b is selected because the operating frequency is substantially constant regardless of the input voltage while the power consumption of the load circuit Z is small.
In b, by setting the operating frequency according to the power consumption in the load circuit Z, the switching loss in the switching element Q ₁ and the consumption in the second control circuit 2b can be reduced without significantly reducing the input power factor. The increase in power can be suppressed.

(Embodiment 2) In this embodiment, as shown in FIG. 2, a current detector 4 is inserted between an inverter circuit IV in a load circuit Z and a discharge lamp La. The power consumption in the load circuit Z is detected based on the current flowing from the discharge lamp La to the discharge lamp La. Other configurations and operations are similar to those of the first embodiment.

(Embodiment 3) In this embodiment, as shown in FIG. 3, a discharge lamp La having filaments f ₁ and f ₂ is used, and a discharge lamp La is formed by an inverter circuit IV.
An example is shown in which the filaments f ₁ and f ₂ are preheated before starting the above. That facilitates the discharge lamp start at La having filament f _1, f _2, also for the purpose of long life, after preheated by flowing a small current to the filament f _1, f ₂ for a predetermined time period, transition to a lighting state It is generally done.

In the inverter circuit IV shown in FIG. 3, a series circuit of two switching elements Q ₅ and Q ₆ each formed of a transistor is connected between input terminals, and one switching element Q ₅ has a capacitor C ₈ for cutting a direct current. And the discharge lamp La and the primary winding of the current transformer T are connected in parallel,
The self-excited half-bridge type inverter circuit IV is configured such that the two secondary windings provided in the current transformer T apply a bias to the switching elements Q ₅ and Q ₆ . A condenser C ₉ is connected between the ends of the filaments f ₁ and f ₂ of the discharge lamp La. Diodes D ₅ and D ₆ are connected in antiparallel to the switching elements Q ₅ and Q ₆ , respectively, and a starting circuit S is connected to the base of the switching element Q ₆ .

In the inverter circuit IV, when the switching element Q ₆ is turned on by the starting circuit S, a current flows through a path of capacitor C ₈ -discharge lamp La (-capacitor C ₉ ) -current transformer T-switching element Q _6. At this time, the switching element Q ₅ is kept off. Thereafter, the switching element Q ₆ the current flowing through the current transformer T decreases off, the switching element Q ₅ is turned on, the capacitor C ₈ - that - (capacitor C ₉₎ - switching element Q ₅ current transformer T- discharge lamp La An electric current flows through the path, and an electric current in the opposite direction to the previous one flows to the discharge lamp La. When the current flowing through the current transformer T decreases in time, the switching element Q ₆ is turned on again, and the above-described operation is repeated to perform the well-known operation of applying alternating power to the discharge lamp La.

By the way, in order to light the discharge lamp La after preheating it as described above, one of the two current transformers T is turned on.
A preheat control circuit 5 is connected to the next winding, and the preheat control circuit 5 controls so as to shorten the ON period of the switching element Q ₆ and reduce the output of the inverter circuit IV during preheating (actual application). 63-259794). Next, the configuration of the preheat control circuit 5 will be described together with the operation. The preheat control circuit 5 half-wave rectifies the induced voltage to the secondary winding of the current transformer T with the diode D ₄ , stabilizes it with the Zener diode ZD ₁ , and smoothes it with the capacitor C ₁₁ to obtain a power supply. A series circuit of two resistors R _21, R ₂₂ is across capacitor C _11, a series circuit of a resistor R ₂₃ and capacitor C ₁₂ is connected, two resistors R _21, R ₂₂
The preheat timer circuit 6 is configured so that the comparator CP ₁ compares the potential at the connection point of the resistor R ₂₃ and the potential at the connection point of the resistor R ₂₃ and the capacitor C ₁₂ . That is, the potential at the connection point between the resistors R ₂₁ and R ₂₂ is used as the reference potential, and the output of the comparator CP ₁ is kept at the L level to perform the timed operation until the terminal voltage of the capacitor C ₁₂ reaches the reference potential. When is finished, the output of the comparator CP ₁ becomes H level.

The preheating control circuit 5 includes a switching element Q.
Also provided is a switching element Q _{7 which} is turned off by the output of the secondary winding of the current transformer T while ₆ is on,
The switching element Q ₇ capacitor C ₁₀ are connected in parallel, so that the capacitor C ₁₀ is charged switching element Q ₇ via a a resistor R ₂₀ is off. The terminal voltage of the capacitor C ₁₀ is input to the non-inverting input terminal of the comparator CP _2, is compared with the output of the preheating timer circuit 6 is input to the inverting input terminal of the comparator CP _2. Therefore, during the timed operation of the preheat timer circuit 6, the output of the comparator CP ₂ becomes H level or L level according to the terminal voltage of the capacitor C ₁₀ , and when the timed operation of the preheat timer circuit 6 ends, the output of the comparator CP ₂ becomes It is maintained at the L level regardless of the terminal voltage of the capacitor C ₁₀ . The comparator CP ₂ is a switching element Q ₆
It controls the switching element Q ₈ connected between the base and the emitter of the switching element, and the switching element Q ₆ is forcibly turned off when the output of the comparator CP ₂ becomes H level.

By the above operation, the ON period of the switching element Q ₆ is limited according to the charging / discharging of the capacitor C ₁₀ during the timed operation of the preheat timer circuit 6, so that the output power of the inverter circuit IV is small. As a result, the filaments f ₁ and f ₂ are turned on without turning on the discharge lamp La.
Can be preheated. In addition, the preheat timer circuit 6
When the timed operation of is finished, the switching element Q ₈ is kept off, the ON period of the switching element Q ₆ becomes long, and the inverter circuit IV supplies the electric power necessary for lighting the discharge lamp La. The discharge lamp L
a starts.

The above-described operation preheats and starts the discharge lamp La, and the preheat timer circuit 6 defines the preheat time. Here, since the power consumption of the load circuit Z during preheating is smaller than that during lighting, in the present embodiment, the second control circuit 2b is selected during preheating and the first control circuit 2a is selected during lighting. The selection circuit 3 is switched so as to select. That is, whether or not preheating is being performed can be known from the output state of the preheating timer circuit 6, so that the selection circuit 3 is switched by the output of the comparator CP ₁ . Since other configurations are the same as those in the first embodiment, the description thereof will be omitted.

(Fourth Embodiment) In this embodiment, in the circuit configuration of the third embodiment, the control circuit 2 shown in FIG. 11 is used not only as the first control circuit 2a but also as the second control circuit 2b. It was done like this. That is, as shown in FIG. 4, the difference from the third embodiment is that the second control circuit 2b
Instead of separately providing, the state where the input to the zero-point detector 26 provided in the first control circuit 2a is obtained from the secondary winding of the inductor L ₁ and the switching elements Q ₅ and Q _{6 of the} inverter circuit IV. The state obtained from the connection point with
This is the point selected by. That is, the voltage across the switching element Q ₆ is a rectangular wave voltage having a constant frequency, and is input to the OR circuit OR through the resistor R ₂₄ . The induced voltage e _{2 of the} secondary winding of the inductor L ₁ is applied to the OR circuit OR.
Is also input, and when the output of the OR circuit OR is selected by the selection circuit OR, the logical sum of the rectangular wave voltage of the constant period and the induced voltage e ₂ of the secondary winding of the inductor L ₁ is detected as a zero point. Will be input to the container 26. Other configurations are similar to those of the third embodiment.

In the above structure, the voltage across the switching element Q ₆ is a rectangular wave having a constant period as shown in FIG. 5A, and the waveform of the current passing through the inductor L ₁ is shown in FIG. 5B.
Then, the induced voltage e ₂ of the secondary winding of the inductor L ₁ is as shown in FIG. 5 (c). That is, the input voltage to the zero point detector 26 is as shown by the broken line in FIG. 5C, and the OFF period of the switching element Q ₁ is extended as compared with the case where no rectangular wave is input. Here, the voltage across the switching element Q ₆ of the inverter circuit IV is used in order to obtain the rectangular wave voltage of a constant cycle, but a means for generating the rectangular wave voltage may be provided separately.

(Embodiment 5) In the present embodiment, the first control circuit 2a can be used also as the second control circuit 2b as in the case of the fourth embodiment, and as shown in FIG. In the selection circuit 3, a state in which the induced voltage e ₂ of the secondary winding of the inductor L ₁ is input to the zero point detector 26 and an astable multivibrator (μPC manufactured by NEC Corporation) separately provided.
A state in which a rectangular wave voltage having a constant period from 7) configured by using an integrated circuit such as 1555) is input to the zero point detector 26 is selected. The selection circuit 3 is controlled by the output of the current detector 4 inserted between the chopper circuit 1 and the load circuit Z. Therefore, the load circuit Z
When the supply current to the load point Z exceeds the specified threshold value, the induced voltage e ₂ of the inductor L ₁ is applied to the zero-point detector 26, the operating frequency of the switching element Q ₁ becomes variable, and the supply current to the load circuit Z becomes the threshold value. In the following case, the rectangular wave voltage from the astable multivibrator 7 is input to the zero point detector 26 and the operating frequency of the switching element Q ₁ is kept constant.

Here, as the inverter circuit IV, the discharge lamp La is fed with power through the resonance circuit, and the operating frequency of the inverter circuit IV is made variable so that the resonance current is adjusted to control the power supplied to the discharge lamp La. Is used (for example, Japanese Patent Application No. 1-24980).
(See No. 3), a discharge lamp La configured to be capable of dimming control from an arc discharge region to a glow discharge region is used. However, the discharge lamp L is driven by the inverter circuit IV.
If a is dimming-controlled, the current supplied to the load circuit Z changes, and the operation of the chopper circuit 1 can be switched according to the dimming level. Other configurations are the same as those in the fourth embodiment.

(Embodiment 6) In the fifth embodiment, the dimming level is determined by monitoring the current supplied to the load circuit Z capable of dimming control. In this embodiment, the dimming control is performed. At this time, the dimming signal externally applied to the inverter circuit IV is used to control the switching of the selection circuit 3. That is, since the power consumption in the load circuit Z is determined according to the dimming level, and the dimming level is determined by the dimming signal, the selection circuit 3 is switch-controlled based on this dimming signal. However, the point is that the selection circuit 3 is substantially switched based on the power consumption of the load circuit Z.

For example, if the dimming signal is a rectangular wave with a constant frequency and indicates the dimming level by changing the duty ratio, the selection circuit 3 detects the duty ratio to perform switching control or a rectangular wave. Switching control can be performed by digital-analog converting a wave and judging the level of the analog signal. Other configurations are similar to those of the fifth embodiment.

[0040]

As described above, according to the present invention, the first control circuit for varying the operating frequency of the switching element of the chopper circuit based on the current flowing in the inductor and the operating state of the load circuit, and the switching element are kept constant. A second control circuit that turns on and off at the operating frequency is provided, and one of the first control circuit and the second control circuit is selected by the selection circuit to operate the switching element. When the distortion of the current waveform becomes a problem, the operating frequency of the switching element is made variable to suppress the decrease of the input power factor, and the distortion of the input current waveform does not become a problem, but the switching loss of the switching element increases. When the above problem occurs, there is an effect that the operating frequency of the switching element can be fixed and an increase in loss can be suppressed. That is, while maintaining a high input power factor as a whole, there is an advantage that power consumption due to switching loss or the like can be suppressed at the time of low power consumption and wasteful power consumption can be suppressed.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment.

FIG. 2 is a circuit diagram showing a second embodiment.

FIG. 3 is a circuit diagram showing a third embodiment.

FIG. 4 is a circuit diagram showing a fourth embodiment.

FIG. 5 is an operation explanatory diagram of the fourth embodiment.

FIG. 6 is a circuit diagram showing a fifth embodiment.

FIG. 7 is a circuit diagram showing a conventional example.

FIG. 8 is an operation explanatory diagram of a conventional example.

FIG. 9 is an operation explanatory diagram of a conventional example.

FIG. 10 is an operation explanatory diagram of a conventional example.

FIG. 11 is a circuit diagram showing another conventional example.

[Explanation of symbols]

1 Chopper Circuit 2 Control Circuit 2a First Control Circuit 2b Second Control Circuit 3 Selection Circuit 4 Current Detector AC Commercial Power Supply C ₁ Capacitor D ₁ Diode IV Inverter Circuit L ₁ Inductor La Discharge Lamp Q ₁ Switching Element Z Load Circuit

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masahiro Yamanaka 1048, Kadoma, Kadoma-shi, Osaka Matsushita Electric Works Co., Ltd.

Claims (6)

[Claims] 1. A chopper circuit for storing energy in an inductor by intermittently connecting a DC input with a switching element and discharging the stored energy of the inductor through a diode, and an inverter circuit and an inverter for converting the output of the chopper circuit into alternating electric power. A load circuit including a discharge lamp that is turned on by the output of the circuit; a first control circuit that changes an operating frequency for turning on / off the switching element based on a current flowing through the inductor and an operating state of the load circuit; Discharge lamp lighting comprising a second control circuit for turning on / off at a constant operating frequency, and a selection circuit for selecting one of the first control circuit and the second control circuit to operate a switching element apparatus. 2. The selecting circuit selects the first control circuit when the power consumption in the load circuit exceeds a predetermined value, and selects the second control circuit when the power consumption is less than the predetermined value. The discharge lamp lighting device according to claim 1. 3. The discharge lamp comprises a filament, and the selection circuit selects the first control circuit when the discharge lamp is turned on, and selects the second control circuit when the discharge lamp is preheated. The discharge lamp lighting device according to 1. 4. The discharge lamp lighting device according to claim 1, wherein the inverter circuit includes a dimming control unit that varies the power supplied to the discharge lamp. 5. The inverter circuit includes a dimming control unit that receives a dimming signal from the outside to vary the power supplied to the discharge lamp, and the selection circuit includes a light output of the discharge lamp exceeding a predetermined level. 2. The discharge lamp lighting device according to claim 1, wherein the first control circuit is selected when the discharge lamp is on, and the second control circuit is selected when the light output of the discharge lamp is below a predetermined level. 6. The discharge lamp lighting device according to claim 5, wherein the selection circuit selects one of the first control circuit and the second control circuit according to the dimming signal.