JP4655347B2 - Voltage frequency conversion circuit and lighting device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a voltage frequency conversion circuit and a lighting device that control the on-time and frequency of a high-frequency power supply voltage supplied to a discharge lamp.
[0002]
[Prior art]
Generally, a discharge lamp lighting device has an inverter circuit that applies a high frequency voltage to a discharge lamp by alternately turning on and off a pair of switching elements, converts an AC power supply voltage to DC, and converts the DC voltage to a high frequency voltage. Then, it is applied to the discharge lamp to maintain the lighting. The switching element of the inverter circuit is on / off controlled by a control circuit using an oscillator.
[0003]
FIG. 3 is a circuit diagram showing a configuration example of such a discharge lamp lighting device. The AC voltage supplied from the commercial power supply 1 is rectified by the power supply circuit 2 and then converted to a predetermined voltage DC and applied to the switching elements 3a and 3b. These switching elements 3a and 3b are alternately turned on and off by the drive circuit 4 to switch a predetermined voltage direct current at a high frequency. As a result, a high-frequency current is output from the switching elements 3a and 3b via the coil L to the discharge lamp 5 to which the capacitor C1 is connected in parallel, and the discharge lamp 5 is lit.
[0004]
The load voltage applied to the discharge lamp 5 is divided by resistors R1 and R2, further voltage rectified by a voltage rectifier circuit including capacitors C2 and C3 and diodes D1 and D2, and fed back to the voltage frequency conversion circuit 6. The The voltage frequency conversion circuit 6 changes its oscillation frequency according to the feedback voltage and outputs an oscillation signal to the drive circuit 4. The drive circuit 4 outputs a drive signal synchronized with the frequency of the input oscillation signal to the gates of the switching elements 3a and 3b to switch the switching elements 3a and 3b at a high frequency. Thereby, the voltage frequency conversion circuit 6 adjusts the frequency of the high frequency voltage output from the switching elements 3a and 3b.
[0005]
When the frequency of the high frequency voltage is adjusted by the voltage frequency conversion circuit 6, the frequency is varied by changing the charge / discharge current of a capacitor (not shown), or the frequency is changed by switching the capacitance of the capacitor.
[0006]
[Problems to be solved by the invention]
However, in order to change the charge / discharge current of the capacitor, the circuit configuration becomes complicated. When the frequency is varied by switching the capacitance of the capacitor, a switching capacitor is required.
[0007]
An object of the present invention is to provide a voltage frequency conversion circuit and a lighting apparatus capable of varying the frequency of the high-frequency voltage while the charging and discharging current of the capacitor to be constant with a simple circuit configuration.
[0008]
[Means for Solving the Problems]
A voltage frequency conversion circuit according to a first aspect of the present invention is a resistance voltage dividing circuit that divides a voltage varied by a voltage regulator for varying a frequency of a high frequency voltage by controlling on / off of a switching element to determine an upper limit value and a lower limit value. circuit and; the switching element oN and the voltage adjusted when it becomes the lower limit value to turn off the switching element when the charging voltage of the capacitor flowing discharge current reaches the upper limit value determined by the resistor divider to the capacitor An output circuit for outputting a high-frequency voltage corresponding to a variable voltage of the capacitor, wherein the output circuit outputs a reset signal when the voltage of the capacitor reaches an upper limit value determined by the resistance voltage dividing circuit. A second comparator that outputs a set signal when the voltage of the capacitor reaches a lower limit value determined by the resistance voltage dividing circuit; A first charging / discharging control circuit that starts charging the capacitor when a signal is output and stops charging the capacitor when the reset signal is output; and adjusting the charging current flowing through the capacitor to adjust the charging current. A first direct current power supply that supplies a regulated charging current to a charge / discharge control circuit of 1 to vary a charging characteristic of the capacitor and adjust a duty ratio of an on / off time of the switching element ; A second charge / discharge control circuit that starts discharging the capacitor when output and stops discharging the capacitor when the set signal is output; and adjusts a charging current flowing through the capacitor to adjust the second charge / discharge supplying the adjusted charging current to the discharge control circuit to the discharge characteristics of the capacitor in the variable on-off time of the switching element Dew Characterized by comprising a; and second direct current power source that enables adjusting the I ratio.
[0009]
In the present invention and the following inventions, the meanings of terms are as follows unless otherwise specified. The voltage frequency conversion circuit determines the frequency and on-time of the high-frequency voltage applied to the discharge lamp. The resistance voltage dividing circuit provides two threshold values, an upper limit value and a lower limit value, and the voltage to be compared is applied to the capacitor of the output circuit. The frequency and the on-time are determined by flowing a charge / discharge current in a constant current circuit.
[0010]
The voltage regulator variably outputs an input voltage, for example, a resistance voltage dividing circuit that varies an input voltage proportional to a load voltage of a discharge lamp and divides the variable input voltage with a voltage dividing resistor. Apply to. The resistance voltage dividing circuit divides the variable input voltage and outputs an upper limit value and a lower limit value. That is, the resistance voltage dividing circuit determines the upper limit value and the lower limit value according to the variable input voltage.
[0011]
The output circuit includes a capacitor that repeatedly charges and discharges, and outputs a high-frequency voltage that turns on when the charging voltage of the capacitor reaches an upper limit value determined by the resistance voltage dividing circuit and turns off when the capacitor voltage reaches the lower limit value.
[0012]
As a result, the frequency and on-time of the high-frequency voltage applied to the discharge lamp are made variable by merely changing the input voltage with the voltage regulator while keeping the charge / discharge current of the capacitor constant.
[0014]
The output circuit includes a first comparator that compares the upper limit value from the resistance voltage dividing circuit and the charging voltage of the capacitor, and a second comparator that compares the lower limit value from the resistance voltage dividing circuit and the charging voltage of the capacitor. It has two comparators.
[0015]
The first comparator outputs a reset signal when the capacitor voltage reaches an upper limit value determined by the resistance voltage dividing circuit, and the second comparator outputs a reset signal when the capacitor voltage reaches a lower limit value determined by the resistance voltage dividing circuit. A set signal is output.
[0016]
The first charge / discharge control circuit and the second charge / discharge control circuit adjust and control the charge / discharge current of the capacitor, and the first charge / discharge control circuit is a charge adjusted by the first DC current power supply. The current is caused to flow through the capacitor, and the second charge / discharge control circuit causes the discharge current adjusted by the second direct current power source to flow through the capacitor.
[0017]
The first charge / discharge control circuit starts charging the capacitor when the set signal is output from the first comparator, and stops charging the capacitor when the reset signal is output from the second comparator. . On the other hand, the second charge / discharge control circuit starts discharging the capacitor when the reset signal is output from the first comparator, and stops discharging the capacitor when the set signal is output from the second comparator. . As a result, the capacitor is repeatedly charged and discharged.
[0018]
According to a second aspect of the present invention, there is provided a lighting device according to the first aspect, the voltage frequency conversion circuit according to the first aspect; one or a plurality of switching elements that are turned on and off based on a high frequency voltage from the voltage frequency conversion circuit when a DC power supply voltage is applied; It is characterized by comprising;
[0019]
Switching elements, Ru is on-off controlled by the on-off signal of the variable frequency and on-time from the voltage frequency conversion circuit of claim 1.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below. FIG. 1 is a circuit configuration diagram of a voltage frequency conversion circuit according to an embodiment of the present invention.
[0021]
A voltage V proportional to the load voltage of the discharge lamp is input to the voltage regulator 7, and the input voltage V is adjusted and varied by the voltage regulator 7. The voltage adjusted by the voltage regulator 7 is input to the resistance voltage dividing circuit via the operational amplifier 8. The resistance voltage dividing circuit includes resistors R3 to R5, and an upper limit value H and a lower limit value L are obtained. The upper limit value H is input to the first comparator 9 of the output circuit, and the lower limit value L is input to the second comparator 10 of the output circuit.
[0022]
In addition to the first comparator 9 and the second comparator 10, the output circuit is a flip-flop that operates by a capacitor Ct that repeatedly charges and discharges, a reset signal from the first comparator 9, and a set signal from the second comparator 10. 11. A first charging / discharging control circuit 13 for flowing the charging current adjusted by the first DC current power supply 12 to the capacitor Ct, and a second charging current adjusted by the second DC current power supply 14 for flowing the capacitor Ct. The charging / discharging control circuit 15 includes a charging current supply circuit 16 that supplies a charging current from a control power source to the capacitor Ct.
[0023]
This output circuit outputs a high frequency voltage by charging / discharging the capacitor Ct by supplying a charging / discharging current to the capacitor Ct, and is turned off when the charging voltage of the capacitor Ct reaches the upper limit value H determined by the resistance voltage dividing circuit. The high-frequency voltage V0 that is turned on when the lower limit is reached is output.
[0024]
FIG. 2 is a characteristic diagram showing the operation of the voltage frequency conversion circuit. FIG. 2A is a characteristic diagram of the capacitor voltage Ct and the output voltage V0 when the charging current and the discharging current are the same.
[0025]
The capacitor Ct starts charging when the input voltage reaches the lower limit L and turns on the output voltage V0 (t1). That is, when the second comparator 10 outputs a set signal, the first charge / discharge control circuit 13 turns on the charging current supply circuit 16 and charges the capacitor Ct. While the capacitor Ct is being charged, the output voltage V0 is on.
[0026]
When the voltage of the capacitor Ct rises to the upper limit value H by charging the capacitor Ct (t2), the first comparator 9 operates and outputs a reset signal. As a result, the first charge / discharge control circuit 13 turns off the charge current supply circuit 16 to stop charging the capacitor Ct, and the second charge / discharge control circuit 15 starts discharging the capacitor Ct. During the discharge of the capacitor Ct, the output voltage V0 is off.
[0027]
Then, when the voltage of the capacitor Ct reaches the lower limit value L, the second comparator operates and outputs a set signal. As a result, the capacitor Ct starts charging and turns on the output voltage V0 (t3). Thereafter, the output voltage V0 is repeatedly turned on and off by the charging and discharging of the capacitor Ct to generate a high frequency voltage.
[0028]
FIG. 2B shows an upper limit value H ′ and a lower limit value lower than the upper limit value H and the lower limit value L of FIG. 2A by lowering the input voltage applied to the resistance voltage dividing circuit by the voltage adjustment circuit 7. FIG. 6 is a characteristic diagram of a capacitor voltage Ct and an output voltage V0 when L ′.
[0029]
As shown in FIG. 2B, when the input voltage applied to the resistance voltage dividing circuit is lowered, the frequency of the output voltage V0 increases even if the charge / discharge characteristics of the capacitor Ct are the same. That is, since the width between the upper limit value H ′ and the lower limit value L ′ is smaller than the width between the upper limit value H and the lower limit value L in FIG. 2A, the voltage of the capacitor Ct becomes faster when the capacitor Ct is charged. The voltage of the capacitor Ct quickly reaches the lower limit L ′ at the time of discharge. Therefore, the charge / discharge cycle of the capacitor Ct is shortened, and the output voltage V0 becomes a high-frequency voltage having a higher frequency even if the charge / discharge characteristics of the capacitor Ct are the same.
[0030]
FIG. 2C is a characteristic diagram of the capacitor voltage Ct and the output voltage V0 when the input voltage applied to the resistance voltage dividing circuit remains constant and the discharge current characteristic is slow.
[0031]
As shown in FIG. 2C, when the input voltage applied to the resistance voltage dividing circuit and the charging current characteristic of the capacitor Ct are the same as those in FIG. 1A, and the discharge current characteristic of the capacitor Ct is made slow. The off time of the output voltage V0 becomes longer. Conversely, if the charging current characteristic of the capacitor Ct is made slow, the ON time of the output voltage V0 becomes longer.
Thereby, the duty ratio of the on / off time can be adjusted.
[0032]
The charging current characteristic is made variable by adjusting the first DC current source 13, and the discharging characteristic is made variable by adjusting the second DC current power source 14.
[0033]
Thus, the voltage frequency conversion circuit adjusts the frequency of the high frequency voltage applied to the discharge lamp by adjusting the input voltage to the resistance voltage dividing circuit, and sets the duty ratio of the on / off time of the high frequency voltage applied to the discharge lamp to the first value. The adjustment is performed by adjusting the first DC current power source 12 and the second DC current source 14. As a result, a high-frequency voltage having a desired frequency and on-time can be obtained.
[0034]
This voltage frequency conversion circuit is applied to the discharge lamp lighting device shown in FIG. 3 as an example. That is, the voltage frequency conversion circuit of the present invention applied to the discharge lamp lighting circuit controls on / off of the switching elements 3a, 3b with an on / off signal having a variable frequency and an on time. As a result, a high frequency voltage is applied to the discharge lamp, and the discharge lamp can be controlled to light at a desired frequency and on time.
[0035]
【The invention's effect】
As described above, according to the present invention, the voltage frequency conversion circuit applies the input voltage to the discharge lamp only by changing the input voltage with the voltage regulator while keeping the charge / discharge current of the capacitor constant. The frequency and on-time of the high frequency voltage can be varied. Further, the duty ratio of the on / off time of the high-frequency voltage can be made variable by changing the charge / discharge characteristics of the capacitor. Therefore, a wide dynamic range can be taken.
[0036]
Further, the discharge lamp lighting device having this voltage frequency conversion circuit can appropriately control lighting of the discharge lamp.
[Brief description of the drawings]
FIG. 1 is a circuit configuration diagram of a voltage frequency conversion circuit according to an embodiment of the present invention.
FIG. 2 is a characteristic diagram showing the operation of the voltage frequency conversion circuit 6 according to the embodiment of the present invention.
FIG. 3 is a circuit configuration diagram of a discharge lamp lighting device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Commercial power supply, 2 ... Power supply circuit, 3 ... Switching element, 4 ... Drive circuit, 5 ... Discharge lamp, 6 ... Voltage frequency conversion circuit, 7 ... Voltage adjustment circuit, 8 ... Operational amplifier, 9 ... 1st comparator, 10 DESCRIPTION OF SYMBOLS 2nd comparator, 11 ... Flip-flop, 12 ... 1st direct current power supply, 13 ... 1st charging / discharging control circuit, 14 ... 2nd direct current power supply, 15 ... 2nd charging / discharging control circuit, 16 ... Charging current supply circuit

Claims (2)

A resistance voltage dividing circuit that divides the voltage varied by a voltage regulator for varying the frequency of the high-frequency voltage by controlling on / off of the switching element to determine an upper limit value and a lower limit value;
When a charging / discharging current flows through the capacitor and the charging voltage of the capacitor reaches an upper limit value determined by the resistance voltage dividing circuit, the switching element is turned off, and when the charging voltage reaches the lower limit value, the switching element is turned on and the voltage regulator is variable. An output circuit that outputs a high-frequency voltage corresponding to the voltage;
The output circuit includes a first comparator that outputs a reset signal when a voltage of the capacitor reaches an upper limit value determined by the resistance voltage dividing circuit;
A second comparator that outputs a set signal when the voltage of the capacitor reaches a lower limit value determined by the resistance voltage dividing circuit;
A first charge / discharge control circuit that starts charging the capacitor when the set signal is output and stops charging the capacitor when the reset signal is output;
The charging current flowing through the capacitor is adjusted, the adjusted charging current is supplied to the first charge / discharge control circuit, the charging characteristic of the capacitor is made variable, and the duty ratio of the on / off time of the switching element can be adjusted . A first direct current power supply;
A second charge / discharge control circuit that starts discharging the capacitor when the reset signal is output and stops discharging the capacitor when the set signal is output;
By adjusting the charging current flowing through the capacitor and supplying the adjusted charging current to the second charge / discharge control circuit, the discharge characteristics of the capacitor can be varied to adjust the duty ratio of the on / off time of the switching element. A second direct current power supply;
A voltage frequency conversion circuit comprising: Lighting apparatus comprising the; voltage frequency conversion circuit according to claim 1; and one or a plurality of switching elements to be turned on and off based on the high-frequency voltage from the DC power supply voltage is applied the voltage frequency conversion circuit .

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