JP2835666B2 - Power supply for incandescent lamp - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply for lighting an incandescent lamp such as a halogen lamp or the like having a low voltage and a high power. More specifically, the invention rectifies an AC power and supplies power to the incandescent lamp through an inverter circuit. The present invention relates to a power supply device for an incandescent lamp having the configuration described below.

[0002]

2. Description of the Related Art The life of a low-voltage halogen lamp used in an OHP or a slide screen varies greatly depending on the lamp terminal voltage. Is required. Conventionally, a power supply device for an incandescent lamp having such a function is provided with an inverter circuit that operates by receiving full-wave rectification of an AC power supply and operating the inverter circuit using a half-wave cycle using an AC phase. There is known a device provided with a phase control circuit that turns on and off within the circuit (for example, Japanese Patent Application Laid-Open No. 64-59797).
In such a device, since the inverter circuit is used, the size of the step-down transformer can be reduced.

[0003]

However, in such a power supply device, the voltage applied to the halogen lamp is suppressed to 24 volts ± 0.2 to 0.3 volts when the commercial power supply changes from 90 to 130 volts. For such a high demand, the stabilization of the lamp terminal voltage is still insufficient, and the lamp life cannot be sufficiently extended.
For example, in the circuit disclosed in the above publication, the effective value of the voltage supplied to the inverter circuit is compared with the divided voltage of the AC power supply, and the thyristor is turned on at a predetermined phase to perform voltage control. However, since the voltage on the input side of the inverter circuit is controlled, it has been considered that the voltage actually applied to the lamp may not be constant.

Further, it is naturally conceivable to use the power supply circuit in an environment temperature range of about 5 ° C. to 40 ° C. In an actual circuit, the voltage supplied to the incandescent lamp in response to such a temperature change is considered. There was a problem that it fluctuated greatly. Therefore, the problem of stabilizing the voltage applied to the incandescent lamp must be able to sufficiently cope with the two problems of the fluctuation of the ambient temperature as well as the fluctuation of the commercial power supply.

[0005] The incandescent lamp power supply of the present invention has been made to solve the above problems and stabilize the voltage supplied to the incandescent lamp with high accuracy, and has the following configuration.

[0006]

According to the first aspect of the present invention, there is provided a power supply device for an incandescent lamp according to the present invention, comprising: an OHP, a slide projector, and the like.
A low-voltage, high-power incandescent lamp power supply device for lighting a high-power incandescent lamp used as a light source of an optical device, a rectifier circuit for full-wave rectification of an AC power supply, and power supplied from the rectifier circuit,
An inverter circuit that converts the voltage to a high frequency using a switching element and supplies the incandescent lamp to the incandescent lamp via a high-frequency transformer; And a voltage detection circuit that detects by comparing the output voltage from the reference voltage and, using the waveform of the AC power supply, for each half-wave of the power supply,
A phase control circuit for starting and / or ending the operation of the inverter circuit at a phase for canceling the detected voltage level; and generating a DC voltage from the AC power supply and stabilizing the DC voltage with respect to an environmental temperature. In addition, there is provided a stabilized power supply circuit for a phase control circuit that supplies the DC voltage to the phase control circuit for generating a reference voltage of the voltage detection circuit .

Here, in order to further enhance the accuracy of the voltage control, it is preferable to provide a stabilizing circuit for stabilizing a DC voltage supplied as a circuit power to the voltage detecting circuit.

[0008]

The power supply device for an incandescent lamp according to the first aspect of the present invention configured as described above, changes the level of the voltage applied to the incandescent lamp with respect to the output voltage from the secondary winding of the high-frequency transformer and the environmental temperature.
DC voltage, which is detected by comparing with a stabilized reference voltage,
In the supplied phase control circuit, the operation of the inverter circuit is started and / or stopped at a phase that cancels the level of the detected voltage. The inverter circuit converts power supplied from the rectifier circuit into high frequency using a switching element, and supplies the high frequency to the incandescent lamp via a high frequency transformer.

[0009] Therefore, the voltage detection circuit is not suitable for OHP or sliding.
The level of the voltage supplied to the incandescent lamp as a light source of an optical device such as a de projector can be accurately detected without being affected by the environmental temperature, the level of the voltage applied to incandescent lamp
It becomes possible to very precisely detected. Further, since the voltage supplied to the phase control circuit is also stabilized with respect to the environmental temperature, the output of the inverter circuit does not fluctuate with respect to the environmental temperature as a result, and the voltage applied to the incandescent lamp is It is also stabilized against changes in environmental temperature. The environmental temperature is not limited to the outside air temperature of the device, but also means the temperature on the electric circuit board of the device of the present invention. Claim 2
As described in, if the stabilization circuit also stabilizes the DC voltage supplied to the voltage detection circuit as circuit power,
The accuracy of controlling the voltage applied to the incandescent lamp is further improved.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to further clarify the structure and operation of the present invention described above, preferred embodiments of the present invention will be described below. FIG. 1 is a circuit diagram of a halogen lamp lighting device according to one embodiment of the present invention.

As shown in the figure, this halogen lamp lighting device receives a commercial 100 volt alternating current, receives the output of a diode stack D1 for full-wave rectification of the alternating current, and converts it to a direct current of 24 volts. Power supply circuit 10, inverter circuit 12 that incorporates a high-frequency oscillation circuit, performs high-frequency oscillation, and performs full-wave rectification and phase-controls the output of diode stack D1, and inverter circuit 12
And a detection circuit 14 for detecting a variation in the voltage applied to the halogen lamp L1 by using the output voltage of the secondary winding of the high-frequency transformer T1 to step down the output of the high-frequency halogen lamp L1. ing. Details of each circuit will be described.

The power supply circuit 10 includes a smoothing capacitor C
1, a three-terminal regulator IC1 that inputs a stabilized power supply (output voltage of about 35 volts) simply constituted by a resistor R1 and a zener diode D4. A resistor R7 for stabilization and a Zener diode D7 are connected.
The voltage highly stabilized by the Zener voltage of the Zener diode D7 serves as the power supply of the operational amplifier IC2 in the detection circuit 14 and the power supply of the reference voltage Vref generated by the variable resistor VR. The output of the three-terminal regulator IC1 is directly connected to the inverter circuit 1
2 is connected to the emitter terminal of the transistor Q3. Since the variation of the Zener voltage with respect to the temperature cannot be ignored in the Zener diode D4, a voltage stabilized by the three-terminal regulator IC1 is supplied to the transistor Q3 in addition to the Zener diode D4, thereby controlling the inverter circuit 12 in a manner described later. The phase is minimally affected by temperature.

The inverter circuit 12 includes a transformer T2, two transistors Q1, Q2, and two capacitors C2,
And a trigger diode D3 interposed between a base terminal of the transistor Q2 and a collector terminal of the transistor Q3, and a collector-emitter current of the transistor Q3. And a diode D2 for discharging the electric charge of the capacitor C1.

The transistors Q1 and Q2 have their collectors and emitters connected in series between a power supply line and a ground line, which are the outputs of the diode stack D1, and further have capacitors C2 and C2 connected in series. C
3 is connected in parallel to this. The winding A of the transformer T2 is interposed between the base and the emitter of the transistor Q1, and the winding B is also interposed between the base and the emitter of the transistor Q2. Transistor Q1
Is connected to the collector of the transistor Q2.
Connected to one terminal of the winding C of the transformer T2,
The other terminal of the winding C is the primary winding A of the high-frequency transformer T1.
Is connected to the connection point between the capacitors C2 and C3.

Transformer T2, transistors Q1, Q2
The above-described circuit including the capacitors C1 and C2 and the primary winding A of the high-frequency transformer T1 provides an oscillation start condition (transistor Q2 ON) once the power supply voltage is equal to or higher than a predetermined voltage. Oscillates at 20 to 30 KHz. Moreover, for this oscillation circuit, the full-wave rectified output of the diode stack D1 is the power supply voltage as it is, so that if oscillation continues, the high-frequency transformer T
As shown in FIG. 2 (A), the voltage applied to the halogen lamp L1 via
The waveform has a high frequency component of about 20 KHz superimposed on z). The voltage applied to the halogen lamp L1 actually has a form in which phase control is further added as shown in FIG. 2B, but the function of the phase control performed by the transistor Q3 and the like is as follows. Details will be described after the description of the configuration and operation of the detection circuit 14.

The secondary winding B of the high-frequency transformer T1 has a terminal P
The secondary winding C of the high-frequency transformer T1 is connected to the detection circuit 14 via the terminals P5 and P6.
The secondary winding C is provided to detect a change in the voltage applied to the halogen lamp L1.

An AC output of about 10 volts is obtained from the secondary winding C.
5. Smoothing by resistors R3 and R4 and capacitor C5, and a zener diode D having a zener voltage of 6 volts
6. The voltage is almost converted to a DC voltage by a large-capacity electrolytic capacitor C6. This DC voltage is a voltage proportional to the magnitude of the output voltage of the secondary winding C of the high-frequency transformer T1.

This DC voltage is divided by the voltage dividing resistors R5 and R6 and input to the positive input terminal + of the operational amplifier IC2. The operational amplifier IC2 is configured with a feedback resistor R8 as a non-inverting amplifier. The output voltage of the variable resistor VR for zero adjustment is input to the negative input terminal-. The output of the operational amplifier IC2 is connected to the transistor Q3 of the inverter circuit 12 via the resistor R2.
Is connected to the base terminal. Since the operational amplifier IC2 is configured as a non-inverting amplifier, the resistor R
5, the voltage divided by R6, that is, the high-frequency transformer T
As the output voltage of the secondary winding C increases, the base voltage of the transistor Q3 increases, the potential difference between the base and the emitter decreases, and the collector current of the transistor Q3 decreases. That is, as the secondary voltage of the high-frequency transformer T1 becomes higher, the charging of the capacitor C1 by the collector current of the transistor Q3 is performed more slowly.

FIG. 2C shows a temporal change in the voltage across the capacitor C1. Charged by the collector current of the transistor Q3, the voltage across the capacitor C1 rises with time, and eventually becomes the turn-on voltage Vtr of the trigger diode D3. At this time, the trigger diode D3 is
The transistor C2 becomes conductive, and the charge of the capacitor C1 flows into the base of the transistor Q2 via the trigger diode D3. As a result, the transistor Q2 is turned on, and a current flows between the capacitor C2, the primary winding A of the high-frequency transformer T1, the winding C of the transformer T2, and the collector and emitter of the transistor Q2.

When a current flows through the winding C of the transformer T2, a forward electromotive force is generated in the winding B between the base and the emitter of the transistor Q2.
Remains on until the transformer T2 is saturated even after the current flowing through the trigger diode D3 is lost. Eventually, the transformer T2 saturates and the transistor Q
2 is turned off, the current flowing through the winding C sharply decreases, so that the transistor Q1 is connected to the winding A of the transformer T2.
Generates a forward electromotive force between the base and the emitter of
As a result, the transistor Q1 is turned on. When the transistor Q1 is turned on, current starts to flow through the collector-emitter of the transistor Q1, the winding C of the transformer T2, the primary winding A of the high-frequency transformer T1, and the capacitor C3.

This current through winding C causes an electromotive force in winding A and transistor Q1 remains on until transformer T2 saturates. Eventually, transformer T
2 saturates and the transistor Q1 is turned off, the current flowing through the winding C sharply decreases.
Generates an electromotive force in the winding B. Thus, the transistor Q2 is turned on again. By repeating the above operation, the transistors Q1 and Q2 are turned on and off alternately to generate high-frequency oscillation, and a current flows in the primary winding A of the high-frequency transformer T1 in an alternating direction. Halogen lamp L1 connected to secondary winding B of T1
To which a high frequency superimposed voltage (see FIG. 2A) is applied.

Since the power supply voltage supplied to the oscillation circuit formed by the transistors Q1, Q2 and the like is not smoothed, the power supply voltage becomes zero volts every half cycle of AC. At this time, regardless of the on state of the transistors Q1 and Q2, no current flows through the transformer T2, so that both the transistors Q1 and Q2 are turned on and the oscillation stops. Note that once the trigger diode D3 is turned on and oscillation starts, the charge of the capacitor C1 continues to be discharged through the diode D2 during that cycle (１ ／ cycle of AC). The capacitor C1 is in a completely discharged state, and as shown in FIG. 2C, the voltage across the capacitor C1 starts to rise again from zero volt.

In this halogen lamp lighting device, consider the case where the voltage of the commercial alternating current fluctuates. For example, assume that the power supply voltage fluctuates and rises from a normal voltage. At this time, the output voltage of the secondary winding of the high-frequency transformer T1 also increases. However, the increase in the voltage is immediately detected by the detection circuit 14, and the output voltage of the operational amplifier IC2 also increases. As a result, the impedance between the emitter and the collector of the transistor Q3 increases, and the current for charging the capacitor C1 decreases. That is, the rise of the voltage across the capacitor C1 becomes gentle, and the trigger voltage V of the trigger diode D3 is increased.
The time T required to exceed tr becomes longer. Therefore, 1
The oscillation start phase in the / 2 cycle becomes large,
As a result, the rise in the power supply voltage is canceled. When the power supply voltage decreases, the output voltage of the operational amplifier IC2 decreases, and the reverse process occurs. As a result, the voltage applied to the halogen lamp L1 is stabilized with respect to the fluctuation of the power supply voltage.

According to the halogen lamp lighting device of the present embodiment described above, the voltage applied to the halogen lamp L1 is accurately detected by using the secondary winding C of the high frequency transformer T1, and this is started to oscillate. Since the phase is reflected, the voltage applied to the halogen lamp L1 can be accurately stabilized with respect to the fluctuation of the power supply voltage. In addition, the starting phase of the phase control is determined by the collector current flowing through the transistor Q3. However, since the voltage supplied to the emitter of the transistor Q3 is stabilized by the three-terminal regulator IC1 having excellent temperature characteristics, The starting phase of the inverter does not fluctuate greatly with temperature. In the present embodiment, the fluctuation of the voltage applied to the halogen lamp L1 in the range of 130 volts from the commercial power supply and the ambient temperature of 5 ° C. to 40 ° C. is 24 volts ±
It was able to hold down to 0.2 volts.

The variable resistor VR is an operational amplifier IC
Since it has the function of adjusting the operating point No. 2, by adjusting this, it is possible to easily adjust the voltage applied to the halogen lamp L1. Therefore, according to the halogen lamp lighting device of the present embodiment, the halogen lamp L1
Without applying an excessively high voltage, and the life thereof can be extended. In addition, even when the power supply voltage decreases, there is no shortage of light quantity. Therefore, the halogen lamp lighting device of the present embodiment is extremely useful as a device for lighting a light source of an OHP or a slide screen.

The embodiments of the present invention have been described above.
The present invention is not limited to such embodiments. For example, a configuration in which a commercial AC is half-wave rectified and supplied to an inverter circuit, a configuration using an oscillation circuit other than a half bridge, and a timer IC based on the output of the detection circuit 14 It is needless to say that the present invention can be implemented in various modes without departing from the gist of the present invention, such as a configuration in which phase control is performed by varying the operation time.

[0027]

According to the power supply device for an incandescent lamp according to the first aspect of the present invention, an optical device such as an OHP or a slide projector is used.
By comparing the level of the voltage applied to incandescent lamps such as halogen lamps used as the light source of the equipment, by comparing the output voltage from the secondary winding of the high-frequency transformer with a reference voltage stabilized against the environmental temperature. Accurate detection and reflection of this in the start phase and / or end phase of oscillation, and since the voltage supplied to the phase control circuit is also stabilized with respect to the ambient temperature, fluctuations in power supply voltage and ambient temperature In contrast, the voltage applied to the incandescent lamp can be accurately stabilized. Therefore, according to the present invention, the life of the incandescent lamp can be extended without applying an excessive voltage to the incandescent lamp even when the power supply voltage increases. In addition, even when the power supply voltage decreases, there is no shortage of light quantity. Therefore,
In particular, the same power supply unit that turns on the light source of optical equipment such as OHP and slide projectors
To be installed near the light source
The application of the present invention to a power supply for an incandescent lamp whose temperature changes over a wide range is extremely useful. Further, according to the incandescent lamp power supply device of the second aspect of the present invention, since the voltage detection circuit is provided with the stabilization circuit for stabilizing the DC voltage supplied as the circuit power, the accuracy of the voltage control can be further improved. It has excellent effects.

[Brief description of the drawings]

FIG. 1 is a diagram showing an incandescent lamp power supply device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing waveforms of respective parts of the inverter circuit.

[Explanation of symbols]

 Reference Signs List 10 power supply circuit 12 inverter circuit 14 detection circuit D3 trigger diode IC1 three-terminal regulator IC2 operational amplifier L1 halogen lamp Q1 transistor Q2 transistor Q3 transistor T1 high-frequency transformer T2 transformer VR variable resistor

Claims (2)

(57) [Claims] 1. Optical equipment such as OHP and slide projector
An incandescent lamp power supply device for lighting a low-voltage, high-power incandescent lamp used as a light source for a light source, comprising: a rectifier circuit for full-wave rectification of an AC power supply; and a switching element for supplying power supplied from the rectifier circuit. An inverter circuit that converts the voltage to a high frequency and supplies the incandescent lamp to the incandescent lamp via a high frequency transformer. A voltage detection circuit that detects by comparing with a reference voltage, and using the waveform of the AC power supply, starts the operation of the inverter circuit at a phase that cancels the detected voltage level for each half-wave of the power supply. And / or a phase control circuit for terminating; generating a DC voltage from the AC power supply, stabilizing the DC voltage with respect to an environmental temperature, and converting the DC voltage to the voltage
Incandescent lamp power supply device and a phase control circuit for stabilizing power supply circuit for supplying the previous SL phase control circuit for the generation of the reference voltage of the detection circuit. 2. A stabilizing circuit for stabilizing a DC voltage supplied as a circuit power to the voltage detecting circuit.
The power supply for an incandescent lamp as described above.