JPH0580191U - Lamp lighting device - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a lamp lighting device that prevents the occurrence of beats. [Structure] The charging / discharging voltage of the capacitors Ca, Cb of the oscillation circuit 71 that repeatedly oscillates by repeatedly charging / discharging the capacitors Ca, Cb corresponds to the voltage of the intermediate tap 411c of the primary winding 411 of the transformer 41 of the inverter unit 4. The voltage Vb is superposed to make the oscillation cycle of the oscillation circuit 71 equal to the operation cycle of the inverter section 4 to synchronize them. Further, the chopper drive circuit 72 drives the chopper unit 3 based on the comparison result of the triangular wave voltage Vosc and the voltage Vd ′ output from the oscillation circuit 71, and the inverter unit 4 is energized. [Effect] Since no beat is generated, audible noise is not generated, and even when it is combined with another host device, malfunction of the host device does not occur.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an improvement of a lamp lighting device capable of dimming a lamp or the like by applying pulse width modulation to an applied voltage.

[0002]

[Prior Art]

 Conventionally, a lamp lighting device capable of dimming a lamp or the like by pulse-width-modulating an applied voltage has been known, and an example 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, an operational amplifier 23 used as a comparator, resistors 24 and 25, a variable resistor 26 and an NPN type transistor 27. A triangular wave signal is output, and this voltage V osc is applied to the inverting input terminal of the operational amplifier 23. The resistors 24 and 25 and the variable resistor 26 are connected in series, and divide the voltage Vrf output from the current detector 5 into a voltage Vd. This voltage Vd is non-inverted by the operational amplifier 23 via the amplifier 22. Applied to the input terminal. 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 unit 3 is composed of a P-channel type field effect transistor (hereinafter referred to as FET) 31, resistors 32 and 33, a diode 34, choke coils 35 and 36, and a capacitor 37, and the gate of the FET 31 is It is connected to the collector of the transistor 27 through the resistor 32, and its source and the positive electrode of the DC power supply 1 through the resistor 33. Further, the negative electrode of the DC power supply 1 is grounded. Furthermore, 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 other end of the capacitor 37 are grounded.

The inverter unit 4 is composed of a well-known Royer circuit. That is, a transformer 41 including a primary winding 411 having an intermediate tap 411c, a secondary winding 412 and a tertiary winding 413, NPN type transistors 42 and 43, resistors 44 and 45, capacitors 46, It is composed of 47. A capacitor 46 is connected in parallel with the primary winding 411, one end side 411a of the primary winding 411 is connected to the collector of the transistor 42, and the other end side 411b of the primary winding 411 is connected to the collector of the transistor 43. ing. Further, the emitters of the transistors 42 and 43 are grounded, the base of the transistor 42 is at the other end side 413b of the tertiary winding 413, and the base of the transistor 43 is at the one end side of the tertiary winding 413. Connected to 413a respectively.

The center 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 the transistor 43 via a resistor 45. Connected to the base of each. Further, 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.

The current detector 5 is composed of a half-wave rectification circuit including a resistor 51, a diode 52 and a capacitor 53. That is, the resistor 51 is connected to the other output terminal 4b 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 through the lamp 6 is output from the cathode of the diode 52.

Next, the operation of the lamp lighting device configured as described above will be described. While the current is supplied to the transformer 41 via the FET 31 and the choke coils 35 and 36 of the chopper unit 3, when the current flows through the primary winding 411 and the transistor 42 reaches the saturation region from the unsaturated region, The transistor 42 turns off. As a result, the counter electromotive force generates a voltage in the direction of turning on the transistor 43 on the one end side 413b of the tertiary winding 413, and the transistor 43 turns on. As a result, the collector current linearly increases to the saturation region while the transistor 43 remains on. Here, this time, 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 is turned on.

Further, the current flowing through the secondary winding 412 is detected by the current detection circuit 5 and is converted into the voltage Vrf. The voltage Vrf is divided by the resistors 24 and 25 and the variable resistor 26 and converted into the voltage Vd. The values of the resistors 24 and 25 and the variable resistor 26 are set so that the value of the voltage Vd becomes a value between the maximum value and the minimum value of the output voltage Vosc of the oscillator 21 at the input terminal of the operational amplifier 23. 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, 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, so that the resistance value of the variable resistor 26 is changed. The brightness of the lamp can be adjusted by changing the pulse width of the output signal of the operational amplifier 23.

[0010]

[Problems to be solved by the device]

 However, in the above-described conventional lamp lighting device, since the oscillation frequency of the oscillator 21 and the operating frequency of the inverter unit 4 are different, beats of these frequencies occur. This beat is generated over a number of times and contains multiple frequency components, so it may cause audible noise, or may cause interference with the frame frequency of the liquid crystal display when used for lighting the backlight of the liquid crystal display. Causes screen beats, flickers, etc. Furthermore, when combined with other higher-level devices, there is a problem that interference with the natural frequency of the higher-level device may cause malfunction 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 frequencies that do not affect the higher-level device, but these frequencies individually vary due to ambient temperature, drift over time, and the like. As a result, the beat spectrum due to these changes, and it is difficult to set these frequencies.

Further, as a lighting frequency of a lamp, a backlight, etc., a frequency of about 30 to 60 KHz is often used. As a countermeasure against the audible noise described above, the lighting frequency is set to 300 to 600 KHz, and a beat component of the audible frequency is set. May be set to 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 that prevents the occurrence of beats.

[0014]

[Means for Solving the Problems]

 In order to achieve the above object, the present invention provides a transformer having a primary winding and a secondary winding each having an intermediate tap, and correspondingly connected to both ends of the primary winding. A first and a second switch element, a switching control means for alternately switching the on and off states of the first and the second switch element, and a third switch element for switching on and off of voltage application to the intermediate tap. And an oscillating means that has a charging / discharging circuit, repeats charging / discharging of the charging / discharging circuit based on the charging voltage of the charging / discharging circuit, and outputs a substantially triangular wave based on the charging voltage, and a voltage of the triangular wave. In a lamp lighting device including a voltage control unit that compares a predetermined control voltage and a voltage control unit that controls the on / off state of the third switch element based on the comparison result, a voltage that detects the potential of the intermediate tap. Proposes a detecting means, 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, a transformer having a primary winding and a secondary winding having an intermediate tap, and first and second transformers respectively connected to both ends of the primary winding. The switching element, the switching control means for alternately switching the on / off states of the first and second switching elements, the third switching element for switching on / off of the voltage application to the intermediate tap, and the charge / discharge circuit. Comparing the voltage of the triangular wave and a predetermined control voltage with an oscillating means for repeating charging / discharging of the charging / discharging circuit based on the charging voltage of the charging / discharging circuit and outputting a substantially triangular wave based on the charging voltage In the lamp lighting device, which includes a voltage control unit that controls the on / off state of the third switch element based on the comparison result, a potential detection unit that detects a potential at both ends of the primary winding. There is proposed a lamp lighting device provided with voltage superimposing means for superimposing a predetermined voltage corresponding to the detection result of the potential detecting means on the charging voltage of the charging / discharging circuit.

[0016]

[Action]

 According to claim 1 of the present invention, a voltage is applied to the intermediate tap of the primary winding through the third switch element, and the on / off states of the first and second switch elements are alternately switched by the switching control means. It is switched and an AC voltage is generated in the secondary winding of the transformer. Further, the oscillating means repeats charging / discharging of the charging / discharging circuit based on the charging voltage of the charging / 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, and the intermediate wave has the triangular wave. The voltage is applied for a predetermined time in the cycle. Further, the potential of the intermediate tap is detected by the potential detecting means, and a predetermined voltage corresponding to the potential is superimposed on the charging voltage of the charge / discharge circuit by the voltage superimposing means. As a result, the charging / discharging cycle of the charging / discharging circuit coincides with the switching cycle of the first and second switch elements by the switching control means.

Further, according to claim 2, 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 switched by the switching control means. It is switched and an alternating voltage is generated in the secondary winding of the transformer. Further, the oscillating means repeats charging / discharging of the charging / discharging circuit based on the charging voltage of the charging / 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, controls the on / off state of the third switch element based on the comparison result, and controls the intermediate tap at the cycle of the triangular wave. The voltage is applied for a predetermined time. Further, the potential across the primary winding is detected by the potential detecting means, and a predetermined voltage corresponding to the potential is superimposed on the charging voltage of the charge / discharge circuit by the voltage superimposing means. As a result, the charging / discharging cycle of the charging / discharging circuit described above coincides with the switching cycle of the first and second switch elements by the switching control means.

[0018]

【Example】

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

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

The connection point Pa between the capacitors Ca and Cb is connected to the node a of the diode D1 and is also connected to the intermediate tap 411c of the primary winding 411 of the transformer 41 via the resistor Rf. There is.

The chopper drive circuit 72 is composed of an operational amplifier OP2, an NPN type transistor Tr1 amplifier A, resistors R1 and R2, and a variable resistor VR, and the inverting input terminal of the operational amplifier OP2 is an inverting input terminal of the operational amplifier OP1. It is connected to the terminal. 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 unit 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. This voltage Vd is converted into a voltage Vd 'via the amplifier A. It is applied to the non-inverting input terminal of the operational amplifier OP2.

Next, the operation of the first embodiment having the above configuration will be described based on the waveform diagram shown in FIG. While current is being supplied to the transformer 41 through the transistor 31 and the choke coils 35 and 36 of the chopper unit 3, when current flows through the primary winding 411 and the transistor 42 reaches the saturation region from the unsaturated region. , The transistor 42 turns off. As a result, the counter electromotive force causes a voltage in the direction of turning on the transistor 43 on the one end side 413b of the tertiary winding 413, and the transistor 43 turns on. As a result, the collector current of the transistor 43 increases linearly to the saturation region while the transistor 43 remains on. Here, the transistor 43 is turned off and the transistor 42 is turned on this time, 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 converted into the voltage Vrf when detected by the current detection circuit 5. The voltage Vrf is divided by the resistors R1 and R2 and the variable resistor VR and converted into the voltage Vd. The value of the voltage Vd ′ obtained by amplifying the voltage Vd is set to a value between the maximum value and the minimum value of the output voltage Vosc of the oscillation circuit 71 at the input terminal of the operational amplifier OP2, and the resistors R1 and R2 and the variable resistors are set. The value of the resistor VR is set, and further, the value of the variable resistor VR is set to a value that can obtain a sufficient dimming effect. As a result, current is supplied to the transformer 41 via the FET 31 only while the low level voltage is being output from the operational amplifier OP2 to the transistor Tr1. Therefore, the resistance value of the variable resistor VR is changed to change the operational amplifier. The brightness of the lamp 6 can be adjusted by changing the pulse width of the output signal of OP2.

On the other hand, the oscillating circuit 71 has the above-described configuration, and the charging / discharging cycle of the capacitors Ca and Cb in the well-known astable multivibrator circuit is determined by the voltage Va of the intermediate tap 411c of the primary winding 41 1 of the transformer 41. Have been corrected by. As a result, the oscillating circuit 71 outputs a voltage Vosc having a substantially triangular waveform, and the period of this voltage Vosc is equal to the oscillation period of the inverter section 4 and is synchronized. That is, when the lamp lighting device is started, the oscillation circuit 71 performs self-excited oscillation, and the capacitors Ca and Cb are repeatedly charged and discharged by the time constant based on the resistance value of the resistor Ra and the capacitances of the capacitors Ca and Cb. Then, the chopper drive circuit 72 drives the chopper unit 3 based on the voltage Vosc and the voltage Vd ′, and the inverter unit 4 is energized. As a result, the inverter unit 4 operates and the lamp 6 is turned on.

When the inverter unit 4 starts operating, a pulsating-wave-shaped voltage Va synchronized with the oscillation cycle is generated at the intermediate tap 411c of the primary winding 411 of the transformer 41. This voltage Va is clamped by the diode D1 and converted into a voltage Vb whose peak value is equal to or lower than the forward voltage VF of the diode D1. This voltage Vb wave is integrated by the capacitor Cb and superposed on the charging / discharging of the capacitors Ca and Cb, and the cycle of this charging / discharging is equal to the operating cycle of the inverter section 4 and synchronized.

Therefore, according to the present embodiment, the operating frequency of the inverter unit 4 and the operating frequency of the chopper unit 3 are equal and synchronized with each other, so that beats of these frequencies are not generated. It does not generate audible noise as in the past, and when used for lighting the backlight of a liquid crystal display, it causes screen beats, flicker, etc. due to interference with the frame frequency of the liquid crystal display. There is no. Furthermore, even when combined with other higher-level devices, malfunction of the higher-level devices will 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 block diagram showing the second embodiment. In the figure, the same components as those in the first embodiment described above are designated by the same reference numerals and the description thereof will be omitted. Further, the difference between the first embodiment and the second embodiment is that the voltage Vosc in the chopper control unit 7 is oscillated by the inverter unit 4 by the voltage at both ends 411a and 411b of the primary winding 411 of the transformer 41. It is equal to the frequency and has been synchronized.

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

According to the above-described configuration, as shown in FIG. 5, the waveforms of the voltages VA and VB at the one end 411a and the other end 411b of the primary winding 411 are 180 ° out of phase with each other. Thus, the voltage Vb obtained by combining these via the resistors Rg and Rh is the same as in the first embodiment.

Therefore, as in the first embodiment, the operating frequency of the inverter unit 4 and the operating frequency of the chopper unit 3 are equal and synchronized in the second embodiment as well. Since it does not generate the beat of audible noise, it does not generate audible noise as in the past, and even when it is used for lighting the backlight of the liquid crystal display, it does not interfere with the frame frequency of the liquid crystal display. Does not cause screen beats or flicker. Furthermore, even when combined with other higher-level devices, malfunction of the higher-level devices 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]

[Effect of the device]

 As described above, according to claims 1 and 2 of the present invention, the charging / discharging cycle of the charging / discharging circuit coincides with the switching cycle of the first and second switch elements by the switching control means. Since the switching cycle of the first and second switching elements and the switching cycle of the on / off state of the third switching element are equal and synchronized, beats can be generated between them as in the conventional case. No audible noise is generated, and even when it is used for lighting the backlight of a liquid crystal display, it does not cause screen beats, flicker, etc. due to interference with the frame frequency of the liquid crystal display. Furthermore, even when combined with other higher-level devices, malfunction of the higher-level devices does not occur. In addition, as a lighting frequency of the lamp, it is possible to use a highly efficient frequency of about 30 to 60 KHz, which is a very excellent effect.

[Brief description of drawings]

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

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

FIG. 3 is a waveform diagram illustrating 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 diagram for explaining the operation of the second embodiment of the present invention.

[Explanation of symbols]

1 ... DC power supply, 3 ... chopper part, 31 ... FET, 32,
33 ... Resistor, 34 ... Diode, 35, 36 ... Choke coil, 37 ... Capacitor, 4 ... Inverter section, 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)

[Scope of utility model registration request] 1. A transformer having a primary winding having an intermediate tap and a secondary winding, and first and second switching elements connected corresponding to both ends of the primary winding, respectively. The charging / discharging circuit includes a switching control unit that alternately switches ON and OFF states of the first and second switching elements, a third switching element that switches ON / OFF of voltage application to the intermediate tap, and a charging / discharging circuit. The charging / discharging circuit repeats charging / discharging based on the charging voltage, and an oscillating means for outputting a substantially triangular wave based on the charging voltage is compared with the voltage of the triangular wave and a predetermined control voltage, and based on the comparison result. And a voltage control means for controlling the on / off state of the third switch element, in a lamp lighting device, a potential detection means for detecting the 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, and first and second switching elements connected corresponding to both ends of the primary winding, respectively. The charging / discharging circuit includes a switching control unit that alternately switches ON and OFF states of the first and second switching elements, a third switching element that switches ON / OFF of voltage application to the intermediate tap, and a charging / discharging circuit. The charging / discharging circuit repeats charging / discharging based on the charging voltage, and an oscillating means for outputting a substantially triangular wave based on the charging voltage is compared with the voltage of the triangular wave and a predetermined control voltage, and based on the comparison result. And a voltage control means for controlling the on / off state of the third switch element, in a lamp lighting device, a potential detection means for detecting a potential at both ends of the primary winding, and a detection result of the potential detection means. 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.