JPH06267669A - Lighting device for incandescent lamp - Google Patents

Abstract

PURPOSE:To reduce loss in electric power when an incandescent lamp is lighted by means of an inverter. CONSTITUTION:Pulsating current obtained through the full wave rectification of a commercial AC power supply by a rectifying circuit Re is transformed into high frequency in electric power by means of an inverter. The output voltage of the rectifying circuit Re is detected by a voltage detection circuit 3, and if pulsating voltage is found to have been less than a specified value, a drive circuit 2 is thereby suspended. Therefore, feeding electricity to an incandescent lamp L is suspended at the trough section of each pulsating voltage wave form. Since the trough section of each pulsating voltage wave form practically does not contribute to the light output of the incandescent lamp L, the suspension of feeding electricity can suppress the useless consumption of electric power.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting device for an incandescent light bulb that lights an incandescent light bulb by converting a pulsating current obtained by rectifying an AC power source into a high frequency alternating current and then supplying the high frequency AC power to the incandescent light bulb.

[0002]

2. Description of the Related Art Conventionally, it has been proposed to use an inverter, which is easier to miniaturize than a transformer, as a means for converting an AC power supply voltage such as a commercial power supply. For example, in the circuit shown in FIG. 21, after the commercial power source AC is full-wave rectified by a rectifier circuit Re such as a diode bridge, the direct current obtained by smoothing with the capacitor C ₂ is input to the inverter 1 to be converted into high frequency alternating current. To do. The inverter 1 is provided with a transformer T ₁ that also serves as a transformer and an insulator in the output part, and after half-wave rectifying the output of the transformer T ₁ with a diode D ₄ , supplies it to an incandescent light bulb L through an inductor L ₂ and a capacitor C _3. The incandescent light bulb L is turned on.

An incandescent lamp L having a rated voltage lower than the power supply voltage of the commercial power supply AC is used, and a step-down transformer is used as the transformer T ₁ . The inverter 1 includes a switch element Q ₁ composed of a MOSFET connected in series to the primary winding of the transformer T ₁ , and this series circuit is connected between the output terminals of the rectifier circuit Re. A series circuit of a capacitor C ₁ and a diode D ₁ is connected in parallel to the primary winding of the transformer T ₁ , and a diode D ₂ and an inductor L are provided in the series circuit of the switch element Q ₁ and the capacitor C _1. The series circuit with ₁ is connected in parallel. Inductor L ₁
Is inserted between the two diodes D _1, D _2, both diodes D _1, D ₂ is the output polarity of the rectifier circuit Re is connected in reverse polarity. This inverter 1 outputs a high frequency wave to the secondary winding of the transformer T ₁ by turning on / off the switch element Q ₁ with a high frequency rectangular wave signal generated from a drive circuit 2 which uses a DC power source Vcc as a power source.

On the other hand, as described above, the series circuit of the diode D ₄ for half-wave rectification, the inductor L ₂ and the capacitor C ₃ is connected to the secondary winding of the transformer T ₂ . The voltage across the capacitor C ₃ is applied to the incandescent bulb L, and the diode D ₃ is connected in parallel to the series circuit of the inductor L ₂ and the capacitor C ₃ . The cathodes of the diode D ₃ are connected to the diode D ₄ .

Next, the operation of the above configuration will be described. Here, the frequency of the rectangular wave signal output from the drive circuit 2 is set sufficiently higher than the frequency of the commercial power supply AC. When the switching element Q ₁ is turned on by the rectangular wave signal output from the drive circuit 2, a current starts to flow through the primary winding of the transformer T ₁ . Since the amount of current flowing through the primary winding of the transformer T ₁ increases with time, the transformer T ₁
A voltage is induced in the secondary winding of the incandescent bulb L through the diode D ₄ and the inductor L ₂ to energize the incandescent bulb L to light up the incandescent bulb L.

On the other hand, when the switching element Q ₁ is turned off by the rectangular wave signal output from the drive circuit 2, the transformer T
_In the primary winding of ₁ , the energy stored in the transformer T ₁ tries to keep the current flowing in the same direction as when the switch element Q ₁ was on, so that the current flows through the capacitor C ₁ and the diode D _1. , Capacitor C
₁ is charged. During this period, the polarity of the voltage induced in the secondary winding of the transformer T ₁ is reversed, so that the diode D ₄ blocks the current from the transformer T ₁ to the incandescent lamp L. On the other hand, the inductor L ₂ and the capacitor C ₃
The energy accumulated in the incandescent light bulb L is emitted through the incandescent light bulb L.
Lights up. That is, electric power can be supplied to the incandescent lamp L regardless of whether the switch element Q ₁ is on or off. Since the unipolar voltage is applied to the incandescent lamp L in this way, the influence of the inductance component of the filament of the incandescent lamp L is greater than that when the bipolar voltage output from the transformer T ₁ is applied to the incandescent lamp L. It will decrease.

The diode D ₂ and the inductor L ₁ are
Switching element Q ₁ is provided to form a discharge path of the capacitor C ₁ when the transition from OFF to ON, then the capacitor C ₁ when the switching element Q ₁ is turned off
Allow the charging current to flow. In the incandescent light bulb lighting device described above, the output of the rectifier circuit Re is smoothed by the capacitor C _2. Therefore, in the valley of the output voltage of the rectifier circuit Re (near the zero cross of the commercial power supply AC), the capacitor C ₂ The current supplied to the rectifier circuit Re is hardly required, and the input voltage waveform and the input current waveform to the rectifier circuit Re are out of phase. That is, the power factor decreases, resulting in a large power loss. Further, the capacitor C ₃ and the inductor L ₂ connected to the secondary side of the transformer T ₂ are also factors that reduce the power factor.

A configuration for solving this problem is shown in FIG.
The configuration of FIG. 22 in which the capacitors C ₂ , C ₃ , the diode D ₃ , and the inductor L ₂ are omitted from the configuration of FIG. In this configuration, since the main element that causes the phase shift between the input voltage waveform and the input current waveform is removed, the power factor can be increased. In this circuit configuration, the inverter 1
The input voltage waveform is a pulsating current waveform obtained by full-wave rectifying the commercial power supply AC, and the electric power is supplied to the incandescent lamp L only when the switch element Q ₁ is turned on. Therefore, the voltage waveform of the voltage across the incandescent lamp L is as shown in FIG.

[0009]

By the way, in the configuration shown in FIG. 22, the power factor is improved as compared with the configuration shown in FIG. 21, but the voltage across the incandescent lamp L changes from the rectifier circuit Re. The output pulsating current voltage waveform has an envelope, and the pulsating current voltage waveform has valleys. Although such a valley portion hardly contributes to the light output of the incandescent light bulb L, the inverter 1 is also operating in the valley portion of the input voltage waveform, so that wasteful power consumption occurs. Become. That is, even though the output current is generated from the drive circuit 2 in the vicinity of the peak portion of the pulsating voltage waveform for turning on / off the switch element Q ₁ , the contribution rate to the light output of the incandescent lamp L is Less and moreover, switching element Q ₁
Is a MOSFET, if the drain-source voltage at the valley portion of the pulsating voltage waveform decreases, the threshold voltage rises due to an increase in MOS capacitance, making it difficult to turn on the switch element Q _{1 and} increasing power consumption. . After all, in the configuration of FIG. 21, there is a problem that the power loss is large due to the low power factor, and in the configuration of FIG. 22, the inverter 1 is operated even during a period that hardly contributes to the light output of the incandescent light bulb L, and thus the power loss is large. There's a problem.

The present invention is intended to solve the above problems, and an object of the present invention is to provide a lighting device for an incandescent light bulb with reduced power loss.

[0011]

In order to achieve the above object, the invention of claim 1 includes an inverter for feeding power to an incandescent light bulb after converting a pulsating current obtained by rectifying an alternating current power source into a high frequency alternating current, and an incandescent light bulb. And a power supply limiting unit that suspends power supply to the incandescent light bulb when the peak value of the voltage applied to both ends is equal to or lower than a predetermined value.

According to a second aspect of the present invention, an inverter that includes a switch element that is turned on and off by a rectangular wave signal and that converts a unipolar power source into a high-frequency alternating current is rectified by half-wave rectification of the high-frequency output. A rectifier that supplies the incandescent light bulb, a voltage detection circuit that detects the voltage across the incandescent light bulb and outputs a detection voltage that is approximately proportional to the effective value of this voltage, and the voltage across the incandescent light bulb based on the voltage detected by the voltage detection circuit. The voltage detection circuit includes a pulse width control circuit that feedback-controls the duty cycle of the rectangular wave signal so that the effective value is kept substantially constant, and the voltage detection circuit incandescently forms a series circuit of the reverse current blocking diode, the first resistor, and the capacitor. A second resistor connected in parallel with either the series circuit of the diode and the first resistor and the capacitor while being connected between both ends of the light bulb A voltage proportional to the voltage across the capacitor is output as the detection voltage, and the geometric mean of the lower limit value and the upper limit value of the duty cycle control range is the ratio of the first resistance to the second resistance. It is characterized in that the resistance values of the first resistance and the second resistance are set so as to be equal to each other.

According to the third aspect of the invention, in the inverter, the input power source is connected to the series circuit of the primary winding of the transformer and the switch element which is turned on / off by the rectangular wave signal, and the high frequency is supplied from the secondary winding of the transformer. It is characterized by outputting alternating current.

[0014]

In the first aspect of the invention, the pulsating current obtained by rectifying the AC power is applied to the incandescent light bulb after being converted into high frequency AC by the inverter, so that there is an element for reducing the power factor in the input to the inverter and the output from the inverter. The power loss is reduced. Moreover, with the above configuration, the waveform of the voltage applied to the incandescent lamp has an envelope curve of the pulsating current waveform corresponding to the input voltage to the inverter, and a valley is generated in the waveform of the applied voltage. When the crest value of the voltage applied to both ends of the light bulb is less than or equal to a predetermined value, it is determined that it is a valley, and the power supply to the incandescent bulb is stopped in the valley that hardly contributes to the light output of the incandescent bulb. It is possible to prevent wasteful power consumption during a period that hardly contributes to the light output of the incandescent light bulb, and consequently suppress power loss.

According to the second aspect of the present invention, the effective value of the voltage applied to the incandescent light bulb is feedback-controlled to be kept substantially constant to obtain a stable light output from the incandescent light bulb. A voltage detection circuit for detecting a voltage is connected to a series circuit of a reverse current blocking diode, a first resistor and a capacitor across the incandescent bulb, and a series circuit of the diode and the first resistor and a capacitor is connected. A second resistor is connected in parallel to either one of the capacitors, and a voltage proportional to the voltage across the capacitor is output as the detection voltage. The duty cycle control of the rectangular wave signal that turns on / off the switch element of the inverter is controlled. The resistance values of the first resistance and the second resistance are set so that the geometric mean of the lower limit value and the upper limit value of the range becomes equal to the ratio of the first resistance and the second resistance. Because they were constant, the control range of the duty cycle can be obtained a detection voltage so as to be substantially proportional to the effective value of the voltage applied to incandescent bulbs. That is, there is almost no excess or deficiency in the duty cycle compensation amount by the feedback control, and the light output can be controlled with high accuracy.

The invention of claim 3 is a preferred embodiment of an inverter, wherein an input power source is connected to a series circuit of a primary winding of a transformer and a switch element which is turned on / off by a rectangular wave signal, Since the inverter is configured to output high-frequency alternating current from the secondary winding, the configuration is simple, and in comparison with an inverter that constitutes a self-excited oscillation circuit, a rectangular wave signal that turns a switching element on and off. This has the advantage that it is easy to stop the output and change the effective value of the output voltage only by controlling the above.

[0017]

【Example】

(Embodiment 1) FIG. 1 shows a block diagram of this embodiment. The basic configuration of this embodiment is the same as the conventional configuration shown in FIG. 22, and the operation of the drive circuit 2 for controlling the on / off of the switch element Q ₁ of the inverter 1 is monitored by the output voltage waveform of the rectifier circuit Re. It is different from the conventional configuration in that it is controlled by the voltage detection circuit 3. Further, in FIG. 1, the diode D ₄ is not connected to the secondary winding of the transformer T ₁ . The drive circuit 2 is supplied with power from the power supply circuit P that stabilizes the output voltage of the rectifier circuit Re, and when the voltage value of the pulsating voltage waveform detected by the voltage detection circuit 3 is less than or equal to a predetermined value, the switch element Q ₁
ON / OFF control stops.

FIG. 2 shows an example of a concrete circuit having the configuration of FIG.
become that way. 2, the same components as those of the conventional circuit shown in FIG. 22 are designated by the same reference numerals. In FIG. 2, the diode D ₄ is connected to the secondary winding of the transformer T ₁ . The voltage detection circuit 3 is connected a series circuit of two resistors R _2, R ₃ between the output ends of the rectifier circuit Re, the resistors R _2, R ₃
The cathode of the Zener diode ZD ₂ is connected to the connection point of. The anode of the Zener diode ZD ₂ is connected to the base of a transistor Q ₂ which is a switch element inserted in a power feeding path from the power supply circuit P to the drive circuit 2.

The drive circuit 2 comprises a general purpose timer integrated circuit IC ₁ generally known as 555 and an oscillator constituted by connecting resistors R ₄ and R ₅ and a capacitor C ₆ for determining a time constant. Become. That is, the resistors R ₄ , R ₅ inserted in the charging path to the capacitor C ₆
Of the rectangular wave signal output from the terminal is determined by the series resistance of the capacitor C ₆ and the capacitor C ₆
The off period of the rectangular wave signal output from the terminal is determined by the resistor R ₄ and the capacitor C ₆ that form the discharge path of the.

The power supply circuit P is constructed by connecting a series circuit of a resistor R ₁ and a capacitor C ₄ between the output terminals of a rectifying circuit Re, and connecting a zener diode ZD ₁ in parallel between both ends of the capacitor C _4. . That is, the voltage across the capacitor C ₄ is clipped by the Zener diode ZD ₁ to stabilize the voltage supplied to the drive circuit 2. The capacitor C ₄ is the drive circuit 2
The power factor of the input is hardly affected as long as it has a capacity capable of operating the.

Since the collector-emitter of the transistor Q ₂ is inserted in the power supply path from the power supply circuit P to the drive circuit 2, power is supplied to the drive circuit 2 only while the transistor Q ₂ is on. The drive circuit 2 operates.
That is, the rectangular wave signal generated from the terminal timer integrated circuit IC ₁ only in this period is input to the switch element Q ₁ inverter 1 operates. The transistor Q ₂ turns on when the output voltage of the rectifier circuit Re becomes equal to or higher than a predetermined voltage determined by the Zener voltage of the resistors R ₂ and R ₃ and the Zener diode ZD ₂ . That is, the voltage detection circuit 3 and the transistor Q ₂ cut off the front end portion and the rear end portion of the pulsating voltage waveform, which is the envelope of the rectangular wave signal output from the driving circuit 2, and cut the middle portion of the pulsating voltage waveform. By supplying power to the drive circuit 2 only in the portion corresponding to FIG.
As shown in, the output of the drive circuit 2 is stopped at the valley portion of the pulsating voltage waveform. In this way, the voltage detection circuit 3 and the transistor Q ₂ form a power supply limiting unit.

As described above, in the valley portion of the pulsating voltage waveform, the ON / OFF control by the rectangular wave signal of the switching element Q ₁ of the inverter 1 is stopped and the operation of the inverter 1 is stopped. It is possible to prevent useless power loss from occurring in the valley portion of the waveform. Moreover, since there is no smoothing capacitor that reduces the power factor, this also results in less power loss.

(Second Embodiment) In the first embodiment, the voltage detection circuit 3 is used.
The detection voltage at, that is, the voltage for determining the period during which the transistor Q ₂ is turned on by being compared with the output voltage of the rectifier circuit Re is fixedly set, but in this embodiment, as shown in FIG. One resistor R ₃ used in the voltage detection circuit ₃
It differs from the first embodiment in that a variable resistor VR is used instead of the above.

That is, the period during which the output of the inverter 1 is stopped can be adjusted, so that useless power loss can be prevented, and the power supplied to the incandescent light bulb L is changed by adjusting the variable resistor VR. The light output changes, and dimming becomes possible. Other configurations are similar to those of the first embodiment. (Embodiment 3) In this embodiment, as shown in FIG.
In this configuration, the transistor Q ₂ between the power supply circuit P and the drive circuit 2 is omitted, and instead, the transistor Q ₃ is provided between the power supply terminal and the ground terminal of the timer integrated circuit IC ₁ that configures the drive circuit 2. emitter - a series circuit of a collector and the resistance R _6, are connected the anodes of the Zener diode ZD ₂ to the base of the transistor Q _3.
Further, the emitter of the transistor Q ₄ between the terminal timer integrated circuit IC ₁ and the ground terminal - a collector connected, to connect the base of transistor Q ₄ to a connection point between the collector of the transistor Q ₃ and the resistor R ₆ is there.

In this configuration, the power supply to the drive circuit 2 is not stopped in a certain period including the valley portion of the pulsating voltage waveform output from the rectifier circuit Re, but the transistor Q ₄ is turned on and driven during this period. Circuit 2 to switch element Q ₁
However, the rectangular wave signal is not input. That is, when the output voltage of the rectifier circuit Re becomes equal to or lower than the predetermined voltage set by the resistors R ₂ , R ₃ and the Zener diode ZD ₂ , the transistor Q ₃ turns off and the transistor Q ₄ turns on. As a result, the terminal and the ground terminal are short-circuited, and the rectangular wave signal is not input to the switch element Q ₁ . If the output voltage of the rectifier circuit Re exceeds a predetermined voltage, the transistor Q ₃ turns on,
The transistor Q ₄ is turned off, and the switch element Q ₁ is on / off controlled. Other configurations are similar to those of the first embodiment.

In each of the above embodiments, a general-purpose timer integrated circuit is used in the drive circuit 2. However, an oscillator that generates a rectangular wave signal such as an integrated circuit that constitutes a control circuit of a switching power supply or an astable multivibrator is used. The drive circuit 2 may be of any type as long as it can be configured. (Embodiment 4) In the present embodiment, the switching element Q of the inverter 1 is set so that the voltage applied to the incandescent lamp L is kept substantially constant.
_The pulse width of 1 is controlled according to the voltage across the incandescent lamp L. That is, as shown in FIG. 6, the voltage detection circuit 4 for detecting the voltage applied to the incandescent light bulb L is connected between both ends of the incandescent light bulb L, and the detection voltage by the voltage detection circuit 4 is input to the error amplifier 5. , A difference from a reference voltage preset as a reference value of the voltage applied to the incandescent light bulb L is detected. The output of the error amplifier 5 is input to the pulse width control circuit 6 via the insulating photocoupler PC, and the switch element Q ₁ is turned on / off in the direction of reducing the error of the voltage applied to the incandescent lamp L with respect to the reference voltage. The duty cycle of the rectangular wave signal to be controlled is set. Thus, according to the voltage applied to the incandescent lamp L, the switching element Q ₁
Since the feedback control is performed so as to adjust the ON period of, the voltage applied to the incandescent lamp L is kept substantially constant.

By the way, in the voltage detecting circuit 4, a series circuit of a diode D ₁₁ , a resistor R _11, and a capacitor C ₁₁ is connected between both ends of the incandescent light bulb L, and a series circuit of the diode D ₁₁ and the resistor R ₁₁ is connected. It has a configuration in which R ₁₂ is connected in parallel and is configured to output the voltage across the capacitor C ₁₁ as a detection voltage. The resistors R ₁₁ and R ₁₂ are set according to the duty cycle control range of the pulse width control circuit 6. The duty cycle is the ratio of the ON period to the period of one cycle of the rectangular wave signal, and when the lower limit value of the duty cycle control range is set to A and the upper limit value is set to B, the values of the resistors R ₁₁ and R ₁₂ are: It is set so as to satisfy the relationship of R ₁₁ / R ₁₂ ≈ (AB) ^1/2 . By satisfying such a relationship, even if the peak value of the voltage applied to the incandescent lamp L fluctuates according to the pulsating current waveform as shown in FIG. 7A, the detection output from the voltage detection circuit 4 is detected. The voltage becomes substantially proportional to the effective value of the voltage applied to the incandescent lamp L as shown in FIG. 7B, and the voltage applied to the incandescent lamp L can be accurately compensated within the control range of the duty cycle. it can.

The reason why the compensation accuracy of the applied voltage is improved by satisfying the above conditions will be described. The detection voltage of the voltage detection circuit 4 is the voltage across the capacitor C ₁₁ ,
It becomes stable when the charging current and the discharging current to the capacitor C ₁₁ become equal. Therefore, assuming that the peak value of the input voltage to the voltage detection circuit 4 is Em, the voltage across the capacitor C ₁₁ is Vc, and the duty cycle is D, the charging current and the discharging current to the capacitor C ₁₁ are equal. Equation 1 holds.

[0029]

[Equation 1]

However, in Equation 1, the forward voltage of the diode D ₁₁ , the resistance of the incandescent lamp L, and the current flowing into the error amplifier 5 are sufficiently small and are omitted. By solving the equation 1 for the voltage Vc across the capacitor C _11, the following equation 2 is obtained.

[0031]

[Equation 2]

In Expression 2, Em√D is the effective value of the voltage applied to the incandescent light bulb L. If the value of the portion excluding the effective value is a constant, the detected voltage output from the voltage detection circuit 4 is the effective value. Will be proportional to. Further, since the peak value Em of the input to the voltage detection circuit 4 is not included in the portion excluding the effective value, the detected voltage is proportional to the effective value even if the input voltage changes.

Actually, in the equation 2, the part excluding the effective value includes √D, and the duty cycle D varies depending on the voltage applied to the incandescent lamp L, so that it is not a constant. It is possible to make the value approximately constant within the range of usage conditions. Therefore, if the conditions of the resistors R ₁₁ and R ₁₂ are set so that the value of the part excluding the effective value in the equation 2 becomes equal in the lower limit value A and the upper limit value B of the duty cycle under the use condition, the following equation 3 (1)
It is understood that the relation of the equation is established, and as a result, the relation of the equation (2) of Formula 3 may be satisfied.

[0034]

[Equation 3]

For example, the lower limit value A of the duty cycle
= 0.2, upper limit value = 0.4, peak value Em of input voltage to the voltage detection circuit 4 = 30 V, and resistance R ₁₁ = 1 kΩ, resistance R ₁₂ ≈3.54 kΩ. The duty cycle, the detected voltage, the effective value of the input voltage under this condition,
Table 1 and FIG. 8 show the relationship between the average values of the input voltage.

[0036]

[Table 1]

As is clear from FIG. 8, the detected voltage is substantially proportional to the effective value of the voltage across the incandescent lamp L in the duty cycle range of 0.2 to 0.4. 8 shows the average value of the voltage across the incandescent lamp L. Here, as in the comparative example shown in FIG. 9, after the secondary side output of the transformer T ₁ is half-wave rectified by the diode D ₄ , it is passed through a circuit including an inductor L ₂ , a capacitor C ₃ , and a diode D _3. While supplying power to the incandescent bulb L,
Comparison will be made with a configuration in which a series circuit of a resistor R ₁₃ and a capacitor C ₁₃ is connected between both ends of the incandescent light bulb L and a voltage detection circuit 4a for extracting the voltage across the capacitor C ₁₃ as a detection voltage is provided. In the circuit configuration of the comparative example shown in FIG. 9, the inverter 1
When the switch element Q ₁ is turned on, electric power is supplied to the incandescent lamp L through the diode D _4, and when the switch element Q ₁ is turned off, the electric charge of the capacitor C ₃ is discharged and the incandescent lamp L is discharged.
To supply power to. As a result, a voltage having a waveform as shown in FIG. 10A is applied to the incandescent light bulb L. On the other hand, the voltage detection circuit 4a outputs the voltage applied to the incandescent light bulb L after being smoothed by the resistor R ₁₃ and the capacitor C _13, and thus the detected voltage is the voltage applied to the incandescent light bulb L as shown in FIG. 10B. The average value of

Since the voltage to the incandescent lamp L has a waveform as shown in FIG. 10 (a), the effective value of the voltage applied to the incandescent lamp L,
When the peak value of the applied voltage is Em, the average values are Em (1/2) ^1/2 and Em (2 / π), respectively, and the waveform ratio (= effective value / average value) is 1.11. Become. That is,
Since the average value is proportional to the effective value, even if the output voltage on the secondary side of the transformer T ₁ fluctuates due to fluctuations in the power supply voltage or the duty cycle fluctuates, the detected voltage accurately reflects the effective value. You will be able to compensate.
Therefore, even with such a circuit configuration, the voltage applied to the incandescent lamp L can be kept substantially constant as in the case of this embodiment, but the transformer T ₁ has a constant waveform ratio of 2%.
Inductor L ₂ , capacitor C ₃ , diode D on the next side
_{Since 3} is used, there is a problem that the loss in this part becomes large and the efficiency becomes low. On the other hand, in the circuit configuration of the present embodiment, the loss is small and the efficiency is high because the secondary side of the transformer T ₂ does not have the element that causes the loss as in the comparative example. After all, the circuit configuration of the present embodiment has a small power loss and can accurately compensate the voltage applied to the incandescent lamp L. In addition, about the structure which attached | subjected the same code | symbol as Example 1, it operates similarly to Example 1.

FIG. 11 shows a specific circuit having the configuration of this embodiment. As the pulse width control circuit 6, M51 manufactured by Mitsubishi Electric
I am using 996. The pulse width control circuit 6 has a resistor R
₆ , the Zener diode ZD ₃ and the transistor Q ₅ are used to stabilize the output of the rectifier circuit Re, and the capacitor C ₆ smoothes the output to supply power. The basic operation is as described above. In the concrete circuit shown in FIG. 11, parts for coping with unsteady operations such as starting and parts for stably operating the circuit are added. Is there.

(Embodiment 5) In this embodiment, a commercial power supply AC having two kinds of high and low voltages of about 100 V and about 200 V is adapted. That is, the voltage detection circuit 4 is provided with voltage switching means corresponding to the voltage of the commercial power supply AC. Explaining the voltage detection circuit 4 in detail, as shown in FIG. 12, a series circuit of a diode D ₁₁ , a resistor R ₁₁ , and a capacitor C ₁₁ is connected between both ends of the incandescent light bulb L,
In addition, the resistor R ₁₂ is connected to the series circuit of the diode D ₁₁ and the resistor R _11.
Is similar to that of the fourth embodiment, and a series circuit of the diode D ₂₁ and the capacitor C ₂₁ is connected to the incandescent light bulb L.
The voltage across the capacitor C ₂₁ is divided by two resistors R ₂₁ and R ₂₂ and then input to the bases of two transistors Q ₂₁ and Q ₂₂ that are connected in a complementary manner. The collector of the npn-type transistor Q ₂₁ is connected to the connection point between the diode D ₁₁ and the resistor R ₁₁ via the resistor R ₂₃ , and the resistor R ₂₄ is connected between the emitter and collector of the pnp-type transistor Q _22. Further, a series circuit of a resistor R ₂₃ and a resistor R ₂₄ is connected in parallel with the capacitor C ₁₁ . The voltage detected by the voltage detection circuit 4 is output as the voltage across the resistor R ₂₅ .

In the above configuration, the feedback control is performed so that the voltage across the resistor R ₂₅ becomes substantially constant,
The voltage across the resistor R ₂₅ becomes substantially constant, and the voltage across the capacitor C ₁₁ becomes substantially constant. On the other hand, capacitor C
₂₁ will change in proportion to the power supply voltage.
Therefore, the relationship between the voltage V ₂₂ across the resistor R ₂₂ and the voltage Vc across the capacitor C ₁₁ is V ₂₂ <Vc for a commercial power supply AC with a low voltage (around 100 V), and a commercial power supply with a high voltage (around 200 V). Resistors R ₂₁ and R ₂₂ are set so that V ₂₂ > Vc for AC. Thus, the resistance R ₂₁ ,
If R ₂₂ is set, the transistor Q ₂₂ is turned on when the commercial power source AC of low voltage is turned on, the both ends of the resistor R ₂₄ are short-circuited, and the detection voltage output from the voltage detection circuit 4 is the both ends of the capacitor C ₁₁ . Become a voltage. In addition, high-voltage commercial power supply AC
Then, the transistor Q ₂₂ is turned off, and the detection voltage output from the voltage detection circuit 4 becomes a voltage obtained by dividing the voltage across the capacitor C ₁₁ by the resistors R ₂₄ and R ₂₅ . In this way, when the voltage of the commercial power supply AC becomes high, the detection voltage is lowered, so that the commercial power supply AC of different voltage can be dealt with.

In the case of a low-voltage commercial power supply AC, since V ₂₂ <Vc and the transistor Q ₂₁ is off, the resistor R ₂₃ does not affect the detection voltage, and the resistors R ₁₁ , R _{12 are} not affected.
Is set so as to satisfy the equation (2) of Expression 3, it is possible to accurately compensate when the lower limit value of the duty cycle control range is A and the upper limit value is B. On the other hand, in the case of the high-voltage commercial power supply AC, V ₂₂ > Vc and the transistor Q ₂₁ is turned on. Therefore, the resistor R ₂₃ is connected in parallel with the resistor R ₁₁ . Therefore, the resistance R
The ratio of the combined resistance of ₁₁ and the resistance R ₂₃ to the resistance R ₁₂ may be set to be the geometric mean of the lower limit value and the upper limit value of the duty cycle control range. For example, if the lower limit value of the duty cycle control range is A ′ and the upper limit value is B ′, then {R ₁₁ · R ₂₃ / (R ₁₁ + R ₂₃ )} / R ₁₂ = (A ′ ·
B ') ^1/2 , the resistors R ₁₁ , R ₁₂ , and R ₂₃ may be selected.

As described above, the duty cycle control range and the detection voltage are switched according to the voltage of the commercial power supply AC. Therefore, when the voltage of the commercial power supply AC is switched,
The detected voltage in the duty cycle control range is shown in FIG.
As shown in, the voltage can be set so as to be approximately proportional to the effective value. The curve in FIG. 13 shows the voltage across the capacitor C ₁₁ for the high-voltage commercial power supply AC, the curve for the high-voltage commercial power supply AC, the curve for the low-voltage commercial power supply AC, and the curve for the incandescent bulb L. It shows the effective value of the voltage across.
Other configurations are the same as those in the fourth embodiment.

(Embodiment 6) In this embodiment, as shown in FIG. 14, three kinds of voltages set so as to be substantially proportional to the effective value of the voltage applied to the incandescent light bulb L for the control ranges having different duty cycles. Detection circuit 4 ₁ , 4 ₂ , 4 ₃
The provided, which is constituted so as to input to the error amplifier 5 to detect the voltage of each voltage detection circuit 4 _1, 4 _2, 4 ₃ via the diode _{D 21, D 22, D 23} . In the configuration of the fourth embodiment, the detection voltage is substantially proportional to the effective value of the voltage applied to the incandescent light bulb L, that is, the control range of the duty cycle is limited, and if the control range is widened, the detection voltage is increased. This means that the interval in which is not proportional to the effective value increases. Therefore, in the present embodiment, a plurality of voltage detection circuits 4 ₁ ,
By providing 4 ₂ and 4 _{3 and} setting each of the voltage detection circuits 4 ₁ , 4 ₂ and 4 ₃ so as to correspond to the range of different duty cycles, the detection voltage is approximately proportional to the effective value over a wide range. I am trying to do it.

The voltage detecting circuits 4 ₁ , 4 ₂ and 4 ₃ are basically the same in configuration as the voltage detecting circuit 4 of the fourth embodiment, and respectively include a diode D ₁₁ and resistors R ₁₁ and R ₁₂ . , The diodes D ₁₁₁ , D ₁₁₂ corresponding to the capacitor C ₁₁ ,
D ₁₁₃ and resistors R ₁₁₁ , R ₁₂₁ , R ₁₁₂ , R ₁₂₂ , R
₁₁₃ , R ₁₂₃ and capacitors C ₁₁₁ , C ₁₁₂ , C ₁₁₃ are provided. Further, in the voltage detection circuits 4 ₂ and 4 ₃ , a series circuit of two resistors R ₁₆₂ , R ₁₇₂ , R ₁₆₃ , and R _{173 forms} a capacitor C ₁₁₂ , so as to divide the voltage across the capacitors C ₁₁₂ and C ₁₁₃ . It is connected between both ends of C ₁₁₃ . However, the voltage detecting circuit 4 _1, 4 _2, 4 _3, as shown in FIG. 15, so that the control range of the duty cycle is _{A 1 ~B 1, A 2 ~B} 2, A 3 ~B 3 respectively To the resistors R ₁₁₁ , R ₁₂₁ , R ₁₁₂ , R ₁₂₂ , R ₁₁₃ , R
₁₂₃ is set, and the error amplifier 5 has a diode D.
By passing through ₂₁ , D ₂₂ , and D ₂₃ , each voltage detection circuit 4
_{Since the} highest detection voltage ~ among ₁ , 4, ₂ and 4 ₃ is input, even if the duty cycle changes over a wide range as a result, the effective value of the voltage applied to the incandescent lamp L is almost the same. The proportional detection voltage can be input to the error amplifier 5. Therefore, even if the control range of the duty cycle is set to a wide range, the voltage applied to the incandescent light bulb L can be accurately compensated. Other configurations are the same as those in the fourth embodiment.

(Embodiment 7) In the present embodiment, as shown in FIG. 16, in order to detect the voltage applied to the incandescent lamp L, a voltage detecting winding is added to the transformer T ₁ and the voltage detecting winding is added. The induced voltage of the line is input to the voltage detection circuit 4. The output of the voltage detection winding is half-wave rectified by the diode D ₅ , smoothed by the resistor R ₇ and the capacitor C ₇ , and the pulse width control circuit 6 is fed from both ends of the capacitor C ₇ .

In the voltage detection circuit 4, a series circuit of a diode D ₁₁ , a resistor R ₁₁ and a capacitor C ₁₁ is connected across the voltage detection winding of the transformer T ₂ , and a resistor R ₁₂ is connected to the capacitor C ₁₁ . The capacitor C ₁₁ has a configuration of being connected in parallel.
Is configured to be output as a detection voltage. Further, the input side of a current mirror circuit composed of a pair of transistors Q ₁₁ and Q ₁₂ is connected to both ends of the capacitor C ₁₁ via a resistor R _15, and the output of the current mirror circuit is input to the pulse width control circuit 6. . In this configuration, since the incandescent light bulb L is insulated by the transformer T ₁ , an insulating photocoupler is unnecessary.

The detection voltage Vc of the voltage detection circuit 4 having the configuration shown in FIG.

[0049]

[Equation 4]

In order to be able to regard the portion of the equation 4 excluding the effective value Em√D as a substantially constant value in the adjustment range of the duty cycle, the lower limit value and the upper limit value of the duty cycle are the same except the effective value. When the condition is obtained, the equation (2) of the equation 3 is obtained, and it is understood that the present embodiment operates in the same manner as the fourth embodiment. Other configurations and operations are similar to those of the fourth embodiment.

[0051] By the way, the resistor R ₁₁ as shown in FIG. 17,
In the comparative example having a voltage detection circuit 4b is omitted R _12, the detection voltage is a voltage across the capacitor C ₁₁ is substantially proportional to that the variation of the corresponding supply voltage to the peak value of the voltage applied to incandescent lamp L However, the detected voltage does not follow the variation of the duty cycle. Therefore, when the power supply voltage changes, the duty cycle changes more than necessary, which causes a problem of excessive compensation. In the present embodiment, as described above, the detected voltage which is the output of the voltage detection circuit 4 is substantially proportional to the effective value of the induced voltage to the voltage detection winding of the transformer T _2. It can be prevented.

(Application Example) In each of the above-described embodiments, the output of the rectifier circuit Re is directly input to the inverter 1 to generate the incandescent light bulb L.
The envelope of the voltage applied to the rectifier circuit Re has a pulsating voltage waveform that is the output of the rectifier circuit Re, but as an application example of the configuration in which the voltage applied to the incandescent lamp L is feedback-controlled,
FIG. 18 shows an example in which the output of 1 is smoothed and then input to the inverter 1.

That is, as compared with the fourth embodiment, a choke input type smoothing circuit 7 including an inductor L ₈ and a capacitor C ₈ is connected to the output of the rectifying circuit Re, and the output of the smoothing circuit 7 is input to the inverter 1. The difference is. In this configuration, since the input voltage to the inverter 1 is a direct current having a substantially constant voltage, the envelope of the voltage applied to the incandescent light bulb L becomes a substantially straight line. Except for this point, the application example of FIG. 18 operates similarly to the fourth embodiment, and by setting the resistances R ₁₁ and R ₁₂ to the condition shown in equation (2), the duty cycle It is possible to accurately compensate in the control range. Other configurations are the same as those in the fourth embodiment.

By the way, in the comparative example including the voltage detection circuit 4c in which the diode D ₁₁ and the resistor R ₁₂ are omitted as shown in FIG. 19, the detection voltage which is the voltage across the capacitor C ₁₁ is the same as that of the fourth embodiment. Similarly, the average value of the voltage applied to the incandescent light bulb L is obtained. Here, in the comparative example of FIG. 19, the capacitor C ₃ or the like for supplying power to the incandescent bulb L is not provided during the off period of the switch element Q ₁ , so the voltage applied to the incandescent bulb L is as shown in FIG. It becomes a rectangular wave. Therefore, the voltage across the capacitor C ₁₁ has a substantially constant value as shown in FIG. In this case, the effective value and the average value of the applied voltage to the incandescent light bulb L are expressed as follows: Em is the peak voltage of the applied voltage and D is the duty cycle.
They are Em√D and Em · D, respectively. Therefore, the form factor is (1 / D) ^1/2 , and the form factor includes the duty cycle D. As a result, when the duty cycle D changes due to the operation of the pulse width control circuit 6, the detected voltage is not proportional to the effective value, and there is a problem that sufficient compensation cannot be performed. In the application example shown in FIG. 18, this point is improved, and the feedback control can be performed accurately.

[0055]

According to the first aspect of the present invention, the pulsating current obtained by rectifying the AC power source is applied to the incandescent light bulb after being converted into high frequency AC by the inverter, so that the power factor is reduced in the input to the inverter and the output from the inverter. The advantage is that there are no elements and power loss is small. Moreover, with the above configuration, the waveform of the voltage applied to the incandescent light bulb will have an envelope of the pulsating current waveform corresponding to the input voltage to the inverter, which causes a valley in the waveform of the applied voltage.
If the crest value of the voltage applied to both ends of the incandescent lamp is below a predetermined value, it is determined that it is a valley part, and the power supply to the incandescent lamp is stopped in the valley part that hardly contributes to the light output of the incandescent lamp. Thus, it is possible to prevent wasteful power consumption during a period that hardly contributes to the light output of the incandescent light bulb, and consequently suppress power loss.

According to the second aspect of the present invention, the effective value of the voltage applied to the incandescent light bulb is feedback-controlled to be kept substantially constant to obtain a stable light output from the incandescent light bulb. A voltage detection circuit for detecting a voltage is connected to a series circuit of a reverse current blocking diode, a first resistor and a capacitor across the incandescent bulb, and a series circuit of the diode and the first resistor and a capacitor is connected. A second resistor is connected in parallel to either one of the capacitors, and a voltage proportional to the voltage across the capacitor is output as the detection voltage. The duty cycle control of the rectangular wave signal that turns on / off the switch element of the inverter is controlled. The resistance values of the first resistance and the second resistance are set so that the geometric mean of the lower limit value and the upper limit value of the range becomes equal to the ratio of the first resistance and the second resistance. Because it was constant, so that it is possible to obtain the detected voltage so as to be substantially proportional to the effective value of the voltage applied to incandescent lamps in the control range of the duty cycle. That is, there is almost no excess or deficiency in the compensation amount of the duty cycle by the feedback control, and there is an advantage that the light output can be accurately controlled.

According to the third aspect of the invention, the input power source is connected to the series circuit of the primary winding of the transformer and the switch element which is turned on / off by the rectangular wave signal, and the high frequency AC is output from the secondary winding of the transformer. Since the inverter is configured so that the configuration is simple, and in comparison with the inverter that configures the self-excited oscillation circuit, the output can be stopped only by controlling the rectangular wave signal that turns the switch element on and off. ,
It has an advantage that it is easy to change the effective value of the output voltage.

[Brief description of drawings]

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

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

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

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

FIG. 5 is a circuit diagram showing a third embodiment.

FIG. 6 is a schematic circuit diagram showing a fourth embodiment.

FIG. 7 is an operation explanatory diagram of the fourth embodiment.

FIG. 8 is an operation explanatory diagram of the fourth embodiment.

FIG. 9 is a schematic circuit diagram showing a comparative example with respect to the fourth embodiment.

FIG. 10 is an operation explanatory diagram of a comparative example with respect to the fourth embodiment.

FIG. 11 is a specific circuit diagram of the fourth embodiment.

FIG. 12 is a circuit diagram showing a fifth embodiment.

FIG. 13 is an operation explanatory diagram of the fifth embodiment.

FIG. 14 is a circuit diagram showing a sixth embodiment.

FIG. 15 is an operation explanatory diagram of the sixth embodiment.

FIG. 16 is an explanatory diagram of the operation of the seventh embodiment.

FIG. 17 is a schematic circuit diagram showing a comparative example with respect to the seventh embodiment.

FIG. 18 is a circuit diagram showing an application example.

FIG. 19 is a schematic circuit diagram showing a comparative example with respect to an application example.

FIG. 20 is an operation explanatory diagram of a comparative example with respect to an application example.

FIG. 21 is a circuit diagram showing a conventional example.

FIG. 22 is a circuit diagram showing another conventional example.

23 is an explanatory diagram of the operation of the conventional example shown in FIG.

[Explanation of symbols]

1 inverter 2 drive circuit 3 voltage detection circuit 4 voltage detection circuit 5 error amplifier 6 pulse width control circuit AC commercial power supply C ₁₁ capacitor D ₄ diode D ₁₁ diode L incandescent bulb Q ₁ switch element Q ₂ transistor R ₁₁ resistance R ₁₂ resistance Re Rectifier circuit T ₁ transformer

Claims (3)

[Claims] 1. An inverter for supplying electric power to an incandescent light bulb after converting a pulsating current obtained by rectifying an AC power supply into a high frequency AC, and an incandescent light bulb when a peak value of a voltage applied to both ends of the incandescent light bulb is a predetermined value or less. An incandescent light bulb lighting device, comprising: a power supply limiting unit that suspends power supply to the light source. 2. An inverter that includes a switch element that is turned on and off by a rectangular wave signal and that converts a unipolar power source into a high-frequency alternating current, and a high-frequency output that is output from the inverter is half-wave rectified and supplied to an incandescent light bulb. A rectifier, a voltage detection circuit that detects the voltage across the incandescent bulb and outputs a detection voltage that is approximately proportional to the effective value of this voltage, and the effective value of the voltage across the incandescent bulb is approximately constant based on the voltage detected by the voltage detection circuit. And a pulse width control circuit for feedback-controlling the duty cycle of the rectangular wave signal so that the voltage detection circuit includes a series circuit of a reverse current blocking diode, a first resistor and a capacitor across the incandescent lamp. In addition to being connected, a series circuit of a diode and a first resistor and a second resistor that is connected in parallel to either one of the capacitors are provided. A voltage proportional to the voltage between both ends is output as the detection voltage, and the geometric mean of the lower limit value and the upper limit value of the control range of the duty cycle is equal to the ratio of the first resistance and the second resistance. First resistance and second
A lighting device for an incandescent light bulb, characterized in that the resistance value of the resistance is set. 3. The inverter connects an input power supply to a series circuit of a primary winding of a transformer and a switch element that is turned on / off by a rectangular wave signal, and outputs a high frequency alternating current from the secondary winding of the transformer. The lighting device for an incandescent light bulb according to claim 1 or 2, characterized in that.