JPH04137489A - Lamp lighting apparatus - Google Patents

Abstract

PURPOSE:To detect a voltage applied to a lamp with high accuracy and stability by providing a switching element, for converting a DC voltage into a pulse voltage, on the side where potential is higher than that of the lamp. CONSTITUTION:A DC voltage is converted into a pulse voltage, by a switching element 14 which is ON and OFF controlled by means of a control circuit 13, and is applied to a lamp 15. The control circuit feedback-controls switching operation of the switching element 14 so that the effective value of the pulse voltage applied to the lamp 15 may become a set value, and lights the lamp 15 at a set brightness value. Because this switching element 14 is connected to the high potential side of the lamp 15, potentials on both terminals of the lamp are fixed. Therefore, e.g. when a voltage division resistor 16 is connected in parallel to both terminals of the lamp, the voltage applied to the lamp can be simply detected by this voltage division resistor 16 and detection accuracy can be improved.

Description

[Detailed description of the invention] [Object of the invention] (Industrial application field) This invention is a high-speed digital RPC (plain paper copying machine)
The present invention relates to a lamp device suitable for devices that pulse-light an exposure lamp, such as full-color PPC, facsimile, and scanners, and particularly relates to a lamp lighting device that improves the detection accuracy of pulse voltage applied to the lamp.

(Prior Art) As a lamp lighting device for lighting a lamp such as a halogen lamp for exposure of this type, the one shown in FIG. 5 can be considered.

This involves rectifying the AC voltage of a commercial power supply 1 into DC voltage by a rectifier circuit 2, and converting this DC voltage into a unipolar pulse voltage by a switching element 4 such as an FET (field effect transistor), which is controlled on and off by a control circuit 3. Convert and
The voltage is applied to the lamp 5 to light it up.

Further, a similar waveform generator 6 generates a voltage having a waveform similar to the voltage applied to the lamp 5, and this similar waveform voltage is r m
It is converted into an effective value by the s/DC converter 7 and sent to the control circuit 3.
The control circuit 3 compares this effective value voltage with the set voltage, and controls the switching element 4 so as to eliminate the deviation between the two voltages.
is feedback-controlled, and the lamp 5 is turned on at a constant brightness set value.

(Problem to be solved by the invention) However, in such a lamp lighting device, the lamp 5
Since the switching element 4 is connected to the latter stage side, that is, the low potential side, the low potential side of the lamp 5 is not determined while the switching element 4 is OFF, so that the voltage applied to both ends of the lamp 5 is not determined. cannot directly detect the voltage waveform.

Therefore, in this lamp lighting device, a similar waveform generator 5 is provided to generate a waveform similar to the voltage waveform applied to the lamp 5, and to detect the lamp applied voltage in a pseudo manner. An error occurs with respect to the true voltage applied to the lamp due to delays in the control system such as the circuit 3, and this error cannot be ignored in reading devices such as PPCs and facsimiles that require high accuracy.

In addition, since the on/off control signal is directly applied from the control circuit 3 to the switching element 4 so that a pseudo voltage similar to the lamp applied voltage becomes the set value, on/off control is performed.
In addition to the low stability accuracy of the effective value of the voltage applied to the lamp, the primary circuit including the lamp 5 and the secondary circuit including the control circuit 3 are not separated, creating a risk of electric shock etc. in the entire circuit, and connection is difficult.

Furthermore, when the frequency of the pulse voltage applied to the lamp is increased to reduce ripples in the optical output of the lamp 5, there is a problem that the loss of the switching element 3 increases due to the fact that it is not reverse biased.

Therefore, the present invention has been made in consideration of such circumstances, and a first object thereof is to provide a lamp lighting device that can detect the voltage applied to the lamp with high precision and stability.

A second object is to provide a lamp lighting device that electrically separates the primary circuit including the lamp from the secondary circuit including the control circuit, thereby making it easy to connect the secondary circuit to an external interface. There is a particular thing.

[Structure of the invention]

(Means for Solving the Problems) The present invention is configured as follows in order to solve the above problems.

The invention according to claim 1 of the present application (hereinafter referred to as the first invention) includes a switching element that converts a DC voltage into a pulse voltage, a lamp that is lit by applying this pulse voltage, and a switching element that converts a DC voltage into a pulse voltage. and a control circuit that controls the switching operation of the switching element so that the effective value of the pulse voltage becomes a set value, and the switching element is provided on a higher potential side than the lamp.

Further, the invention according to claim 2 of the present application (hereinafter referred to as the second invention) is characterized in that the control circuit of the first invention is electrically connected to the switching element via a transformer.

Further, the invention according to claim 3 of the present application (hereinafter referred to as the third invention) converts the detected current from the detection circuit for detecting the voltage applied to the lamp of the first invention into an effective value, and A converter comprising a driven effective value converter and a current-voltage converter that converts an effective value current from the effective value converter into an effective value voltage and supplies it to the control circuit, and a plurality of constant voltage elements. The converter is characterized by having a power supply circuit that connects in series to generate three potentials, high, medium and low, and applies these three potentials to the converter with an intermediate potential as an apparent zero potential.

In addition, the invention according to claim 4 of the present application (hereinafter referred to as the fourth invention) converts the detected current from the detection circuit for detecting the voltage applied to the lamp into an effective value by converting the transformer of the second invention into a negative voltage. It is characterized in that it is configured to apply a negative voltage to a converter driven by.

(effect) <First invention> The commercial power supply voltage is rectified into a DC voltage by a rectifier circuit.

Furthermore, this DC voltage is converted into a pulse voltage by the switching operation of a switching element that is controlled on and off by a control circuit, and is applied to the lamp, thereby lighting the lamp.

Further, the control circuit feedback-controls the switching operation of the switching element so that the effective value of the pulse voltage applied to both ends of the lamp becomes the set value, and lights the lamp at a constant brightness of the set value.

Since the switching element is connected to the high potential side of the lamp, the potential across the lamp is fixed even while the switching element is off.

For this purpose, for example, by connecting a voltage dividing resistor in parallel to both ends of the lamp, the voltage applied to the lamp can be directly and easily detected from this voltage dividing resistor. can be increased.

<Second invention> The control circuit in the first invention is electrically connected to the switching element via the transformer, and since the control circuit is not directly connected to the switching element, the primary circuit including the lamp and the control circuit The secondary circuit including the secondary circuit can be electrically isolated, and the connection between the secondary circuit and an external interface can be simplified.

Furthermore, since the control circuit controls the switching operation of the switching element via the transformer, even when the frequency of the voltage applied to the lamp is increased to reduce optical ripple in the lamp, a reverse bias is applied to the switching element. Loss of switching elements can be reduced.

<Third invention> The commercial power supply voltage is rectified into a DC voltage by a rectifier circuit.

Furthermore, this DC voltage is converted into a pulse voltage by a switching element that is controlled on and off by a control circuit, and is applied to the lamp, thereby lighting the lamp.

The current supplied to the lamp is detected by a detection circuit and then converted into an effective value current by an effective value converter of a converter.

Further, this effective value current is converted into an effective value voltage by a current-voltage converter and then applied to a control circuit.

The control circuit compares this lamp applied voltage detection value with a set value, and provides an on/off control signal to the switching element to eliminate the deviation between the two voltages to control its switching operation,
Feedback control is performed so that the lamp is lit at a constant brightness set value.

On the other hand, a power supply circuit connects multiple constant voltage elements in series to generate three potentials, high, medium and low, and when applying these three potentials to the converter, the intermediate potential is used as an apparent zero potential to the converter. Give and drive. Therefore, there is no need to provide a separate negative power supply for driving the converter, and the circuit configuration can be simplified and the size and weight can be reduced accordingly.

<Fourth invention> Since a negative voltage is applied to the converter from the transformer in the second invention, there is no need to provide a separate negative voltage power supply for driving the converter, and the circuit configuration is simplified and reduced in size and weight. It is possible to aim for

(Example) Examples of the first to fourth inventions of the present application will be described below based on FIGS. 1 to 4.

FIG. 1 is an electric circuit diagram of an embodiment of the first invention of the present application, and in the figure, a lamp lighting device 10 includes a commercial power supply 11, a rectifier circuit 12 that rectifies the commercial power supply voltage into a DC voltage, and a control circuit 13. A switching element 14 whose switching operation is controlled, and a lamp 1 such as a halogen lamp for exposure.
5 are sequentially electrically connected in this order, and the lamp 15 is lit in pulses in a dimmable manner.

The switching element 14 is composed of an FET (field effect transistor) or the like, and has its drain connected to the rectifier circuit 12, its gate connected to the control circuit 13, and its source connected to the lamp 15.
Before lamp 15, high potential (high potential)
A switching element 14 is connected to the side.

The control circuit 13 controls the switching element 14 at a duty ratio (
The pulse voltage is converted into a pulse voltage by performing on/off control in synchronization with the commercial power supply 11 (pulse width/pulse repetition period).

In other words, the control circuit 13 converts the DC voltage from the rectifier circuit 12 into
It converts into a unipolar pulse voltage with a duty ratio corresponding to the brightness setting value and applies it to the lamp 15 to turn it on. By appropriately controlling the duty ratio of the pulse voltage, the brightness of the lamp 15 can be adjusted. It is meant to be controlled.

When the lamp 15 is turned on, it exposes an object such as a copying machine document (not shown) to light, and the exposed image is electrically read by a high-speed digital reading element (C0D (charge coupled device)), and the read image signal is read. For example, it is designed to write on a photosensitive drum or the like.

A voltage dividing resistor 16 is connected in parallel to both ends of the lamp 15, the voltage applied to the lamp 15 is detected by the voltage dividing resistor 16, and this detected voltage is converted to an rms/DC converter (for example, New Japan Radio Co., Ltd. NJM4200) 17 (manufactured by NJM4200) 17 converts the voltage into an effective value voltage and supplies it to the control circuit 13.

The control circuit 13 compares the effective value of the DC voltage from the RMS7' DC converter 17 with the reference voltage of the set value, determines the deviation, and controls the switching element 14 to eliminate the deviation. By controlling the operation, the duty ratio of the pulse voltage on the output side of the switching element 14 is feedback-controlled.

Next, the operation of this embodiment will be explained.

The AC voltage of the commercial power supply 11 is rectified into a DC voltage by the rectifier circuit 12, and this DC voltage is converted into a DC voltage by the switching operation of the switching element 14 controlled by the control circuit 13.
It is converted into a unipolar pulse voltage with a duty ratio corresponding to the brightness setting value.

Further, this pulse voltage is applied to the lamp 15, and the lamp 15 is turned on at a brightness constant to the set value.

The applied pulse voltage of this lamp 15 is directly detected by a voltage dividing resistor 16 and then converted to an rms/DC converter 17.
It is converted into an effective value of DC voltage and given to the control circuit 13.

The control circuit 13 compares the effective value of this DC voltage with the set external reference voltage, determines the duty ratio of the pulse voltage that eliminates the deviation between the two, and sends an on/off signal to the switching element 14 according to this duty ratio. and control its switching operation.

Therefore, a pulse voltage having a duty ratio that cancels out fluctuations in the power supply voltage is outputted to the output side of the switching element 14 and applied to the lamp 15.

As a result, the lamp 15 is always lit at a constant brightness setting regardless of voltage fluctuations of the commercial power supply 11.

Since the switching element 14 is connected to the high potential side of the lamp 15, the potential across the lamp 15 can be fixed even while the switching element 14 is OFF, so the voltage applied to the lamp can be easily and Direct detection is possible, and the circuit configuration can be simplified.

In addition, since the voltage applied to the lamp can be directly detected, the detection accuracy can be increased, and since the detection accuracy is high, the control circuit 1
3, the control accuracy can be improved.

Furthermore, by increasing the frequency of the pulses applied to the lamp 15, the optical ripple of the lamp 15 can be reduced to approximately the same level as DC lighting.

FIG. 2 shows a lamp lighting device 2 including the second and fourth inventions.
FIG. 3 is a detailed circuit diagram of FIG. 2, and this lamp lighting device 20 includes the control circuit 13 and switching element 14 of the lamp lighting device 10 shown in FIG.
A drive transformer 21 is interposed between the lamp 1 and
The main feature is that the primary circuit including the control circuit 5 and the secondary circuit including the control circuit 13 are separated.

The drive transformer 21 connects the A and B terminals on the secondary side to the a and b terminals of the switching element 14, respectively, and applies an on/off control signal from the control circuit 13 to the switching element 14 via the drive transformer 21, thereby controlling the switching element 14. It is designed to control movement.

In addition, the drive transformer 21 connects its C and D terminals to rsm.
/effective value converter 17 of DC converter 17. c, d of a
The effective value converter 17a is connected to a terminal and is driven by applying a negative voltage to the effective value converter 17a, which is driven by a negative voltage.

The effective value converter 17a receives a current proportional to the lamp current divided into the voltage dividing resistor 16 and converts it into an effective value, and is driven by a negative voltage.

Further, the current-voltage converter 17b converts the effective value current converted by the effective value converter 17a into an effective value voltage, and this effective value voltage is compared with the voltage that is the set value of the Zener diode 22, When there is a deviation, the deviation voltage is applied to the photocoupler light emitting section 23a to emit light, and this light emission is received by the photocoupler light receiving section 23b of the secondary circuit.

The control circuit 13 applies an on/off control signal to the switching element 14 via the drive transformer 21 so that the amount of light received by the photocoupler light receiving section 23b is zero, that is, the deviation between the lamp applied voltage and its detected voltage is eliminated, and the lamp applied voltage is changed. The switching operation of the switching element 14 is controlled so that the effective value of the switching element 14 becomes the set value.

Next, the operation of this embodiment will be explained.

22. If the power supply voltage of the commercial power source 11 fluctuates and increases, the power supplied to the lamp 15 will also increase and the amount of light emitted by the lamp 15 will also increase.

Then, since the lamp applied voltage also rises, rm s / D from the partial voltage resistor 16 to which this lamp applied voltage is applied.
The detected current detected by the effective value converter 17a of the C converter 17 also increases, and the effective value current that is converted into an effective value here also increases.

For this reason, the output voltage of the current-voltage conversion section 17b that converts this effective value current into an effective value voltage also increases, so the current flowing through the photocoupler light emitting section 23a increases and the amount of light emitted by it increases.

For this reason, the amount of light received by the photocoupler light receiving section 23b of the secondary circuit that receives the light emitted from the photocoupler light emitting section 23a increases, so the control circuit 13 sets a duty ratio (pulse width/pulse repetition An on/off control signal for causing the switching element 14 to output a pulse voltage with a period of 100% is applied to the switching element 14 via the drive transformer 21 to control its switching operation.

As a result, the power supplied to the lamp 15 is always controlled to be constant at the set value, and the lamp 15 can always be lit at a brightness constant at the set value, regardless of fluctuations in the power supply voltage of the commercial power source 11.

Furthermore, even if the power supply voltage of the commercial power source 11 drops, the control circuit 13 controls the switching operation of the switching element 14 to offset the drop, so that the lamp 15 is lit at a constant brightness of the set value.

Therefore, according to this embodiment, the brightness of the lamp 15 can always be controlled to a constant set value regardless of the presence or absence of voltage fluctuations in the commercial power supply 11.

Further, the control circuit 13 and the switching element 14 are electrically connected via the drive transformer 21, and the primary circuit including the lamp 15 and the secondary circuit including the control circuit 13 are connected to the photocoupler light emitting section 23a and the photocoupler light receiving section 23a. Part 23
Since the primary circuit including the lamp 15 and the secondary circuit including the control circuit 13 are separated in an electrically insulated state by ing.

Further, from the drive transformer 21 to the effective value converter 17a
Since a negative voltage is applied to the effective value converter 7a, a negative voltage power supply dedicated to the effective value converter 7a can be omitted, and the cost can be reduced by '.

FIG. 4 shows an embodiment ζ of the first invention shown in FIG.

An electrification circuit 30, which serves as a power source for the RMS/DC converter 17 in the main circuit, is provided in the primary circuit including the lamp 15, and this power supply circuit 30 includes, for example, a Zener diode which is a constant voltage element 31. 31a.

A series circuit in which 31b and 31c are connected in series is connected to lamp 1.
5 in parallel to generate two potentials, high, medium, and low, and convert these three potentials into r m s / DC'1 converter 1
7, the intermediate potential is set as the apparent zero potential, and the voltage below this zero potential is given as the 5 potential. In particular, the negative potential is given to the effective value converter 17a driven by a negative voltage. It is something.

Therefore, according to this embodiment, the expensive and heavy drive transformer 21 shown in FIGS. 2 and 3, for example, can be omitted, making it possible to reduce the size and weight of the device and the cost.

〔Effect of the invention〕

As explained above, in the first invention, since the switching element is provided on the higher potential side than the lamp, the potential at both ends of the lamp is fixed even during the OFF period of the switching element. The voltage applied to the lamp can be detected directly and easily.

Furthermore, since the voltage applied to the lamp can be directly detected, the detection accuracy can be improved.

In the second invention, since the control circuit in the first invention is electrically connected to the switching element via the transformer, the secondary circuit including the control circuit can be easily electrically separated from the primary circuit including the lamp. This makes it possible to simplify the connection with the external interface to the secondary circuit.

Furthermore, in the third invention, the primary circuit including the lamp in the first invention is provided with a power supply circuit that applies a negative potential to the effective value converter driven by a negative voltage. There is no need to separately provide a negative voltage power supply, and costs can be reduced accordingly.

Furthermore, in the fourth invention, the transformer of the second invention is configured to apply a negative voltage to the converter driven by the negative voltage, so there is no need to provide a separate negative voltage power supply exclusively for the converter. , the cost can be reduced accordingly.

[Brief explanation of the drawing]

Fig. 1 is an electrical circuit diagram of an embodiment of the first invention of the present application;
The figure is an electric circuit diagram of an embodiment including the second and fourth inventions of the present application, 3Im is a detailed circuit diagram of Fig. 2, and Fig. 4 is an electric circuit diagram of an embodiment of the third invention of the present application. FIG. 5 is an electric circuit diagram of an example of a lamp lighting device including a similar waveform generating section that generates a voltage having a similar waveform to the voltage applied to the lamp. 10.20... Lamp lighting device, 11... Commercial power supply, 12... Rectifier circuit, 13... Control circuit, 14...
・Switching element, 15...Lamp, 16...Voltage dividing resistor, 17...rms/DC converter, 1
7a... Effective value conversion section, 17b... Current voltage conversion section, 21... Drive transformer, 23a... Photocoupler light emitting section, 23b... Photocoupler light receiving section.

Claims (1)

[Claims] 1. A switching element that converts a DC voltage into a pulse voltage, a lamp that is lit by applying this pulse voltage, and an effective value of the pulse voltage applied to both ends of the lamp as a set value. 1. A lamp lighting device comprising: a control circuit for controlling a switching operation of said switching element, said switching element being provided on a higher potential side than said lamp. 2. The lamp lighting device according to claim 1, wherein the control circuit is electrically connected to the switching element via a transformer. 3. Converting the detected current from the detection circuit that detects the voltage applied to the lamp into an effective value, and converting the effective value converter driven by a negative voltage and the effective value current from this effective value converter into an effective value voltage. A converter equipped with a current-voltage converter that supplies the control circuit to the control circuit, and a plurality of constant voltage elements are connected in series to generate three potentials of high, medium and low. 2. The lamp lighting device according to claim 1, further comprising a power supply circuit that applies a zero potential to said converter. 4. The transformer is configured to convert a detected current from a detection circuit that detects the voltage applied to the lamp into an effective value and to apply a negative voltage to a converter driven by the negative voltage. The lamp lighting device according to claim 2.