JP2570869Y2 - Lamp lighting device - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a lamp lighting device which can dimming a lamp or the like by pulse width modulation of an applied voltage.

[0002]

2. Description of the Related Art Conventionally, there has been known a lamp lighting device capable of dimming a lamp or the like by pulse width modulation of an applied voltage. As an example, a lamp lighting device using an inverter circuit is known. An example of this is shown in FIG. In the figure, 1 is a DC power supply, 2 is a chopper control unit, 3 is a chopper unit, 4 is an inverter unit, and 5 is a current detection unit.

The chopper control unit 2 includes an oscillator 21, an amplifier circuit 22, and an operational amplifier 2 used as a comparator.
3, composed of resistors 24 and 25, a variable resistor 26 and an NPN transistor 27. The oscillator 21 outputs, for example, a triangular wave signal. The resistors 24 and 25 and the variable resistor 26 are connected in series, and divides the voltage Vrf output from the current detection unit 5 into a voltage Vd.
d is applied to the non-inverting input terminal of the operational amplifier 23 via the amplifier 22. The output voltage V1 of the operational amplifier 23 is applied to the base of the transistor 27, and the emitter of the transistor 27 is grounded.

The chopper section 3 includes a P-channel type field effect transistor (hereinafter referred to as FET) 31 and a resistor 3.
2, 33, diode 34, choke coils 35, 36
And a capacitor 37. The gate of the FET 31 is connected to the collector of the transistor 27 through the resistor 32.
In addition, it is connected to its source and the positive electrode of the DC power supply 1 via a resistor 33, respectively. The negative electrode of the DC power supply 1 is grounded. Further, the drain of the FET 31 is connected to the cathode of the diode 34 and one end of the choke coil 35, and the other end of the choke coil 35 is connected to one end of the choke coil 36 and one end of the capacitor 37. The anode of the diode 34 and the capacitor 3
The other end of 7 is grounded.

[0005] The inverter unit 4 is composed of a known lower circuit. That is, a transformer 41 having a primary winding 411 having an intermediate tap 411c, a secondary winding 412 and a tertiary winding 413, NPN transistors 42 and 43, resistors 44 and 45, and capacitors 46 and 47 It is configured. A capacitor 46 is connected in parallel with the primary winding 411, and a transistor 4 is connected to one end 411a of the primary winding 411.
2 and the collector of the transistor 43 is connected to the other end 411b of the primary winding 411, respectively. The emitters of the transistors 42 and 43 are grounded, and the base of the transistor 42 is connected to the tertiary winding 41.
3 is connected to the other end 413b, and the base of the transistor 43 is connected to one end 413a of the tertiary winding 413.

The intermediate tap 411c of the primary winding 411 is connected to the other end of the choke coil 36, and is connected to the base of the transistor 42 via a resistor 44 and to the base of the transistor 43 via a resistor 45. Each is connected to the base. One end 412a of the secondary winding 412 is connected to one end of the lamp 6 via the capacitor 47 and one output terminal 4a, and the other end 412b is grounded. Further, the other end of the lamp 6 is connected to the other output terminal 4b.

[0007] The current detecting section 5 is composed of a half-wave rectifier circuit comprising a resistor 51, a diode 52 and a capacitor 53. That is, the resistor 51 is connected to the other output terminal 4
b and the anode of the diode 52, and the other end is grounded. Further, the cathode of the diode 52 is grounded via the capacitor 53, and a voltage Vrf corresponding to the value of the current flowing from the cathode of the diode 52 to the lamp 6 is output.

Next, the operation of the lamp lighting device having the above-described configuration will be described. While current is supplied to the transformer 41 via the FET 31 and the choke coils 35 and 36 of the chopper section 3, current flows through the primary winding 411, and when the transistor 42 reaches the saturated region from the unsaturated region, Transistor 42 turns off. As a result, a voltage is generated at one end 413b of the tertiary winding 413 by the back electromotive force so as to turn on the transistor 43, and the transistor 43 is turned on. Thus, while the transistor 43 remains on, the collector current increases linearly up to the saturation region. Here, the transistor 43 is turned off and the transistor 42 is turned on, and this relationship is repeated. As a result, an AC voltage is generated in the secondary winding 412,
The lamp is turned on.

Further, the current flowing through the secondary winding 412 is detected by the current detection circuit 5 and converted into a voltage Vrf. This voltage Vrf is divided by the resistors 24 and 25 and the variable resistor 26 and is converted into a voltage Vd. As for the value of the voltage Vd, the values of the resistors 24 and 25 and the variable resistor 26 are set so that the value at the input terminal of the operational amplifier 23 is between the maximum value and the minimum value of the output voltage Vosc of the oscillator 21. Further, the value of the variable resistor 26 is set to a value at which a sufficient dimming effect can be obtained. As a result, the current is supplied to the transformer 41 via the FET 31 only while the low-level signal is being output from the operational amplifier 23 to the transistor 27. Therefore, the resistance of the variable resistor 26 is changed to change the operational amplifier. The brightness of the lamp can be adjusted by changing the pulse width of the output signal of the lamp 23.

[0010]

However, in the conventional lamp lighting device described above, since the oscillation frequency of the oscillator 21 and the operating frequency of the inverter unit 4 are different,
Beats of these frequencies occur. Since this beat occurs over many orders and includes a plurality of frequency components, it generates audible noise or, when used for lighting a backlight of a liquid crystal display, interference with the frame frequency of the liquid crystal display. Causes screen beats, flicker, etc. Furthermore, when combined with other higher-level devices, there is a problem that interference with the natural frequency of the higher-level device causes a malfunction or the like of the higher-level device.

It is also conceivable to set the oscillation frequency of the oscillator 21 and the operating frequency of the inverter unit 4 to a frequency that does not affect the host device.
Each of these is accompanied by fluctuations due to the ambient temperature, drift over time, etc., and the beat spectrum changes due to these fluctuations, so that setting these frequencies is difficult.

Further, as a lighting frequency of a lamp, a backlight or the like, a frequency of about 30 to 60 KHz is often used. It is conceivable to set a higher order, but in this case, there is a problem that the overall efficiency is reduced.

In view of the above problems, an object of the present invention is to provide a lamp lighting device which prevents generation of a beat.

[0014]

According to the present invention, a transformer having a primary winding having an intermediate tap and a secondary winding is provided. First and second switch elements respectively connected to both ends, switching control means for alternately switching on and off states of the first and second switch elements, and on / off of voltage application to the intermediate tap And a oscillating means having a charge / discharge circuit, for repeating charge / discharge of the charge / discharge circuit based on the charge voltage of the charge / discharge circuit, and outputting a substantially triangular wave based on the charge voltage. A voltage control means for comparing the voltage of the triangular wave with a predetermined control voltage and controlling the on / off state of the third switch element based on the comparison result. Propose a potential detection means for detecting a potential of up, the lamp lighting device provided with a voltage superimposing unit for superimposing a predetermined voltage corresponding to the detection result of said potential detection means to the charging voltage of the charging and discharging circuit.

According to a second aspect of the present invention, there is provided a transformer having a primary winding having an intermediate tap and a secondary winding, and a first and a second connected corresponding to both ends of the primary winding, respectively. , A switching control means for alternately switching on / off states of the first and second switch elements, a third switch element for switching on / off of voltage application to the intermediate tap, and a charge / discharge circuit. Repeating the charging and discharging of the charging and discharging circuit based on the charging voltage of the charging and discharging circuit, and an oscillating means for outputting a substantially triangular wave based on the charging voltage, and comparing the voltage of the triangular wave with a predetermined control voltage, A voltage control means for controlling the on / off state of the third switch element based on the comparison result; a potential detection means for detecting a potential at both ends of the primary winding; The predetermined voltage corresponding to the detection result to propose a lamp lighting device provided with a voltage superimposing means for superimposing the charging voltage of the charging and discharging circuit.

[0016]

According to the first aspect of the present invention, a voltage is applied to the intermediate tap of the primary winding via the third switch element, and the on / off states of the first and second switch elements are alternately controlled by the switching control means. And an AC voltage is generated in the secondary winding of the transformer. The oscillating means repeats charging and discharging of the charging and discharging circuit based on the charging voltage of the charging and discharging circuit, and outputs a substantially triangular wave based on the charging voltage. The voltage control means compares the voltage of the triangular wave with the control voltage, and controls the on / off state of the third switch element based on the comparison result. A time voltage is applied. Further, the potential of the intermediate tap is detected by potential detecting means, and a predetermined voltage corresponding to the potential is superimposed on the charging voltage of the charge / discharge circuit by voltage superimposing means. Thus, the charge / discharge cycle of the charge / discharge circuit coincides with the switching cycle of the first and second switch elements by the switching control unit.

According to the second aspect, a voltage is applied to the intermediate tap of the primary winding via the third switch element,
The on / off state of the first and second switch elements is alternately switched by the switching control means, and an AC voltage is generated in the secondary winding of the transformer. The oscillating means repeats charging and discharging of the charging and discharging circuit based on the charging voltage of the charging and discharging circuit, and outputs a substantially triangular wave based on the charging voltage. The voltage control means compares the voltage of the triangular wave with the control voltage, and controls the on / off state of the third switch element based on the comparison result. A time voltage is applied. Further, a potential at both ends of the primary winding is detected by a potential detecting means, and a predetermined voltage corresponding to the potential is superimposed on a charging voltage of the charge / discharge circuit by a voltage superimposing means. Thus, the charge / discharge cycle of the charge / discharge circuit coincides with the switching cycle of the first and second switch elements by the switching control unit.

[0018]

FIG. 1 is a block diagram showing a first embodiment of the present invention. In the figure, the same components as those of the above-described conventional example are denoted by the same reference numerals, and description thereof will be omitted. Further, the difference between the conventional example and the first embodiment is that a chopper control unit 7 that operates in synchronization with the oscillation frequency of the inverter unit 4 is provided instead of the chopper control unit 2.

That is, the chopper control unit 7 includes the oscillation circuit 71
And a chopper drive circuit 72. The oscillation circuit 71 includes an operational amplifier OP1, resistors Ra to Rf, capacitors Ca and Cb, and a diode D1, and the non-inverting input terminal of the operational amplifier OP1 is grounded via a resistor Re and also via a resistor Rd. A predetermined constant voltage Vcc is applied. The inverting input terminal is grounded via capacitors Ca and Cb connected in series, and is connected to its output terminal via a resistor Ra. Further, the output terminal of the operational amplifier OP1 is connected to its non-inverting input terminal via a resistor Rc, and the resistor Rb
The voltage Vcc is applied via the.

A connection point Pa between the capacitor Ca and the capacitor Cb is connected to the node a of the diode D1, and the primary winding 411 of the transformer 41 is connected via a resistor Rf.
Are connected to the intermediate tap 411c of the.

The chopper drive circuit 72 includes an operational amplifier OP
2. NPN transistor Tr1 amplifier A, resistor R
1 and R2 and a variable resistor VR. The inverting input terminal of the operational amplifier OP2 is connected to the inverting input terminal of the operational amplifier OP1. The output terminal of the operational amplifier OP2 is connected to the base of the transistor Tr1, the emitter of the transistor Tr1 is grounded, and the collector is connected to the gate of the FET 31 via the resistor 32 of the chopper 3. Further, the resistors R1 and R2 and the variable resistor VR are connected in series, and the voltage Vrf output from the current detection unit 5 is divided into a voltage Vd, and this voltage Vd
Is the operational amplifier OP2 as the voltage Vd 'via the amplifier A.
Is applied to the non-inverting input terminal.

Next, the operation of the first embodiment having the above configuration will be described with reference to the waveform diagram shown in FIG. The transistor 31 and the choke coils 35 and 36 of the chopper section 3
While the current is being supplied to the transformer 41 via the circuit, the current flows through the primary winding 411, and when the transistor 42 reaches the saturation region from the unsaturated region, the transistor 42 is turned off. As a result, a voltage is generated at one end 413b of the tertiary winding 413 by the back electromotive force so as to turn on the transistor 43, and the transistor 43 is turned on. Thus, while the transistor 43 remains on, the collector current increases linearly up to the saturation region. Here, the transistor 43 is turned off and the transistor 42 is turned on, and this relationship is repeated. As a result, an AC voltage is generated in the secondary winding 412, and the lamp 6 is turned on.

Further, the current flowing through the secondary winding 412 is detected by the current detection circuit 5 and converted into a voltage Vrf. This voltage Vrf is divided by the resistors R1 and R2 and the variable resistor VR, and is converted into a voltage Vd. The value of the voltage Vd 'obtained by amplifying the voltage Vd is determined by the operational amplifier OP
The resistors R1 and R2 are connected so that the output voltage Vosc of the oscillation circuit 71 becomes a value between the maximum value and the minimum value at the input terminal of the oscillation circuit 71.
And the value of the variable resistor VR are set, and the value of the variable resistor VR is set to a value at which a sufficient dimming effect is obtained. Thus, the operational amplifier OP2 outputs the transistor T
FE only while the low-level voltage is being output to r1
Since current is supplied to the transformer 41 via T31, the brightness of the lamp 6 can be adjusted by changing the resistance value of the variable resistor VR and changing the pulse width of the output signal of the operational amplifier OP2. .

On the other hand, the oscillation circuit 71 has the above-described configuration, and the charging and discharging cycle of the capacitors Ca and Cb in the known astable multivibrator circuit is corrected by the voltage Va of the intermediate tap 411c of the primary winding 411 of the transformer 41. Have been. As a result, the voltage Vosc having a substantially triangular waveform is output from the oscillation circuit 71, and the cycle of the voltage Vosc is equal to the oscillation cycle of the inverter unit 4 and is synchronized. That is, when the lamp lighting device is activated,
The oscillating circuit 71 performs self-excited oscillation, and obtains a time constant based on the resistance value of the resistor Ra and the capacitance of the capacitors Ca and Cb.
The charging and discharging of the capacitors Ca and Cb are repeated, and the voltage Vos
The chopper unit 3 is driven by the chopper drive circuit 72 based on c and the voltage Vd ′, and the inverter unit 4 is energized. Thereby, the inverter unit 4 operates and the lamp 6 is turned on.

When the inverter unit 4 starts operating, the intermediate tap 411c of the primary winding 411 of the transformer 41 has
A voltage Va having a pulsating waveform synchronized with the oscillation cycle is generated.
This voltage Va is clamped by the diode D1,
The peak value is converted to a voltage Vb equal to or lower than the forward voltage VF of the diode D1. This voltage Vb wave is integrated by the capacitor Cb and is superimposed on the charging and discharging of the capacitors Ca and Cb. The cycle of this charging and discharging is equal to the operation cycle of the inverter unit 4 and is synchronized.

Therefore, according to the present embodiment, the operating frequency of the inverter unit 4 is equal to the operating frequency of the chopper unit 3,
Because they are synchronized, they do not generate beats of these frequencies, so they do not generate audible noise as in the past, and even when used for lighting the backlight of the liquid crystal display. In addition, screen beats, flicker, and the like due to interference with the frame frequency of the liquid crystal display do not occur. Furthermore, even when combined with another higher-level device, a malfunction of the higher-level device does not occur. Further, as the lighting frequency of the lamp 6, an efficient frequency of about 30 to 60 KHz can be used.

Next, a second embodiment of the present invention will be described.
FIG. 4 is a configuration diagram showing the second embodiment. In the figure,
The same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted. In addition, the first embodiment and the second embodiment
The difference from this embodiment is that the voltage Vosc in the chopper control unit 7 is changed to both ends 411a, 411b of the primary winding 411 of the transformer 41.
Is synchronized with the voltage equal to the oscillation frequency of the inverter unit 4 by the voltage of (1).

That is, the connection point Pa between the capacitor Ca and the capacitor Cb of the oscillation circuit 71 is connected to one end 411a of the primary winding 411 of the transformer 41 via the resistor Rg, and via the resistor Rh. It is connected to the other end 411b of the primary winding 411. Here, the resistance values of the resistor Rg and the resistor Rh are set to be equal.

According to the above configuration, as shown in FIG.
The voltages VA and VB at one end 411a and the other end 411b of the primary winding 411
Are pulsating waveforms whose phases are shifted from each other by 180 degrees, and the voltage Vb obtained by synthesizing these via resistors Rg and Rh is the same as that of the first embodiment.

Therefore, as in the first embodiment, also in the second embodiment, the operating frequency of the inverter unit 4 and the operating frequency of the chopper unit 3 are equal and synchronized, so that beats of these frequencies are used. No audible noise as in the past, and even when used to turn on the backlight of a liquid crystal display, the screen beat caused by interference with the frame frequency of the liquid crystal display. No flicker or the like is caused. Furthermore, even when combined with another higher-level device, a malfunction of the higher-level device does not occur. Further, as the lighting frequency of the lamp 6, an efficient frequency of about 30 to 60 KHz can be used.

[0031]

[Effects of the Invention] As described above, claims 1 and 2 of the present invention
According to 2, the charge / discharge cycle of the charge / discharge circuit coincides with the change cycle of the first and second switch elements by the change control means, and thus the change cycle of the first and second switch elements. And the switching period of the on / off state of the third switch element is equal to and synchronized with each other, so that a beat is not generated between them as in the related art, and no audible noise is generated.
Also, even when used for turning on the backlight of the liquid crystal display, there is no occurrence of screen beat, flicker or the like due to interference with the frame frequency of the liquid crystal display. Furthermore, even when combined with another higher-level device, a malfunction of the higher-level device does not occur. In addition, as the lighting frequency of the lamp, an efficient 3
This has an extraordinarily excellent effect that a frequency of about 0 to 60 KHz can be used.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a conventional example.

FIG. 3 is a waveform chart for explaining the operation of the first embodiment of the present invention;

FIG. 4 is a block diagram showing a second embodiment of the present invention.

FIG. 5 is a waveform chart for explaining the operation of the second embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... DC power supply, 3 ... Chopper part, 31 ... FET, 32,
33 ... resistor, 34 ... diode, 35, 36 ... choke coil, 37 ... capacitor, 4 ... inverter part, 41
... Transformers, 42, 43 ... Transistors, 44, 45 ... Resistors, 46, 47 ... Capacitors, 5 ... Current detectors, 6 ...
Lamp, 7 ... Chopper control unit, 71 ... Oscillation circuit, 72 ...
Chopper drive circuit, OP1, OP2 ... operational amplifier, Ra
~ Rh: resistor, Ca, Cb: capacitor, D1: diode, Tr1: transistor, A: amplifier, R1, R
2 ... resistor, VR ... variable resistor.

Claims (2)

(57) [Scope of request for utility model registration] A transformer having a primary winding having an intermediate tap and a secondary winding, first and second switch elements respectively connected to both ends of the primary winding, A switching control unit that alternately switches on and off states of the first and second switch elements, a third switch element that switches on and off of voltage application to the intermediate tap, and a charge / discharge circuit; The charge / discharge circuit of the charge / discharge circuit is repeated based on the charge voltage, and an oscillating unit that outputs a substantially triangular wave based on the charge voltage is compared with a voltage of the triangle wave and a predetermined control voltage, and based on the comparison result, A voltage control means for controlling an on / off state of the third switch element, a potential detection means for detecting a potential of the intermediate tap, and a detection result of the potential detection means. A predetermined voltage response provided a voltage superimposing means for superimposing the charging voltage of the charging and discharging circuit, a lamp lighting device, characterized in that. 2. A transformer having a primary winding having an intermediate tap and a secondary winding, first and second switch elements respectively connected to both ends of the primary winding, A switching control unit that alternately switches on and off states of the first and second switch elements, a third switch element that switches on and off of voltage application to the intermediate tap, and a charge / discharge circuit; The charge / discharge circuit of the charge / discharge circuit is repeated based on the charge voltage, and an oscillating unit that outputs a substantially triangular wave based on the charge voltage is compared with a voltage of the triangle wave and a predetermined control voltage, and based on the comparison result, A voltage control means for controlling the on / off state of the third switch element; a potential detection means for detecting a potential at both ends of the primary winding; Corresponding a predetermined voltage is provided and a voltage superimposing means for superimposing the charging voltage of the charging and discharging circuit, it lamp lighting device according to claim to.