JP4869722B2 - Oscillation frequency control device and discharge lamp lighting device - Google Patents

Description

  The present invention relates to a technique for controlling the oscillation frequency switching timing of an inverter circuit, for example.

Conventionally, a dedicated control IC or the like has been used for frequency control of the inverter circuit. In recent years, with a reduction in the price of a microcomputer (hereinafter referred to as a microcomputer), a microcomputer that controls the oscillation frequency of an inverter circuit by a microcomputer is becoming mainstream in order to configure a circuit at a low cost.
Japanese Patent Application Laid-Open No. 2004-355864 describes control of an inverter circuit by a microcomputer.
JP 2004-355864 A

When the oscillation frequency of the inverter circuit is controlled using a microcomputer, the timing for switching the oscillation frequency is not controlled. There is a problem that the circuit balance is lost due to the timing of switching the oscillation frequency, leading to failure of the components.
For example, an object of the present invention is to prevent the circuit balance from being lost by controlling the timing for switching the oscillation frequency.

An oscillation frequency control device according to the present invention is, for example, an oscillation frequency that controls an oscillation frequency of the inverter circuit by applying a rectangular wave voltage to an inverter circuit that is connected to a load circuit and converts a direct current into a high frequency current. In the control device,
The oscillation frequency designating unit for designating the oscillation frequency, and when the oscillation frequency designating unit changes the specification of the oscillation frequency, calculate the period during which the current flowing through the inverter circuit is in a predetermined direction, and the oscillation frequency after the change The timing determination unit determines the output timing for outputting the rectangular wave voltage to be generated by the inverter circuit as the calculated period, and the timing determination unit determines the rectangular wave voltage for the inverter circuit to generate the changed oscillation frequency. And a rectangular wave voltage output unit for outputting at the output timing.

  According to the oscillation frequency control device of the present invention, the period in which the current flowing through the inverter circuit is in a predetermined direction is calculated, and the output timing for outputting the rectangular wave voltage that causes the inverter circuit to generate the changed oscillation frequency is calculated. Determined as the period. For this reason, the circuit balance is not lost by switching the oscillation frequency.

First, the hardware of the oscillation frequency control apparatus 100 according to the embodiment will be described with reference to FIG. FIG. 1 is a diagram illustrating a hardware configuration of an oscillation frequency control apparatus 100 according to the embodiment.
In FIG. 1, an oscillation frequency control apparatus 100 includes a CPU 911 (central processing unit, processor) that executes a program. The CPU 911 is a processing device 980. The CPU 911 is connected to the ROM 913, the RAM 914, and the voltage generator 917 via the bus 912, and controls these hardware devices.

The ROM 913 stores, for example, software and programs. The oscillation frequency control unit 110 described later may be software, a program, or the like, for example. When the oscillation frequency control unit 110 is software, a program, or the like, the ROM 913 may store the oscillation frequency control unit 110. For example, the CPU 911 reads the oscillation frequency control unit 110 stored in the ROM 913 and executes processing.
The voltage generator 917 generates a pulse voltage (rectangular wave voltage) to the inverter circuit via the connection line 20.

Embodiment 1 FIG.
Next, the first embodiment will be described. In the first embodiment, an oscillation frequency control apparatus 100 that controls the oscillation frequency by calculating a period in which the current flowing through the inverter circuit is in a predetermined direction will be described.

First, a circuit of a general discharge lamp lighting device when the oscillation frequency is controlled by the microcomputer 11 will be described with reference to FIG. FIG. 2 is a circuit block diagram of a general discharge lamp lighting device when controlled by the microcomputer 11. The discharge lamp lighting device includes a rectifying circuit unit 1, an active filter circuit unit 2, an inverter circuit unit 3, a load circuit unit 4, a drive circuit unit 5, and a microcomputer 11. The inverter circuit unit 3 includes an FET (switching element) 6 and an FET 7. The load circuit unit 4 includes an inductor 8, a capacitor 9, and a lamp 10. The lamp 10 is removable, and the discharge lamp lighting device may not be provided. The drive circuit unit 5 includes a transistor 12, a transistor 13, a primary side inductor 14, a secondary side inductor 15, and a secondary side inductor 16.
The circuit of the discharge lamp lighting device shown in FIG. 2 is configured to drive the inverter circuit unit 3 with a pulse voltage generated by the microcomputer 11. That is, the transistor 12 and the transistor 13 are controlled via the connection line 20 by the pulse voltage generated by the microcomputer 11. Then, a voltage is alternately generated in the secondary inductor 15 and the secondary inductor 16 through the primary inductor 14. Then, the switching element 6 and the switching element 7 are switched to generate a high frequency. Therefore, the operation frequency of the inverter circuit unit 3 and the operation at the time of frequency switching follow the change in the pulse voltage generated by the microcomputer 11.

Next, the switching element 6 included in the inverter circuit unit 3 when switching the oscillation frequency, the drain-source (DS) current of the switching element 7, and the DS voltage of the switching element 7 will be described with reference to FIGS. 3 and 4 are diagrams showing the switching element 6 included in the inverter circuit unit 3 when switching the oscillation frequency, the DS current of the switching element 7, and the DS voltage of the switching element 7. FIG. In particular, FIG. 3 is a diagram showing a case where switching of the oscillation frequency is normally connected, and FIG. 4 is a diagram showing a case where switching of the oscillation frequency is not normally connected.
As shown in FIG. 3, when the oscillation frequency is controlled by the microcomputer 11, there is a period in which the pulse voltage stops for several tens of μs when the frequency of the output pulse voltage of the microcomputer 11 is changed. This is the time for setting the next pulse voltage inside the microcomputer 11. This time varies depending on the clock used and the processing capability of the microcomputer 11. In general, the cheaper the microcomputer 11, the smaller the clock that can be used and the lower the processing capability, so that the period during which the pulse voltage is stopped becomes longer. When the stop period of the pulse voltage is very short, the stop of the pulse voltage can be ignored. However, in general, the output stop time of the pulse voltage of the microcomputer 11 is about 30 μs. In general, the inverter operates at 50 kHz or the like. When operating at 50 kHz, one period is 20 μs. Therefore, when the microcomputer 11 stops outputting the pulse voltage, a pulse voltage stop period of one cycle or more occurs. Further, the pulse voltage stop period varies randomly depending on the processing state inside the microcomputer 11 at that time unless otherwise specified. Therefore, the output stop of the pulse voltage cannot be ignored.
3 and 4 show a case where the DS voltage of the switching element 7 enters the pulse voltage stop period when the LOW state is reached. That is, this is a case where the switching element 7 enters the pulse voltage stop period while the switching element 7 is on, and the switching element 7 remains on (the switching element 6 remains off). In this case, in the circuit block diagram shown in FIG. 2, a current flows in a closed loop that passes through the switching element 7, the inductor 8, the capacitor 9, and the coupling capacitor. In addition, the DS current of the switching element 7 oscillates at the resonance frequency of the series resonance circuit including the inductor 8, the capacitor 9, and the coupling capacitor of the load circuit.
In FIG. 3, the oscillation of the pulse voltage from the microcomputer 11 is started again with the DS current of the switching element 7 swinging positive. In the state where the DS current of the switching element 7 is swinging positively, when the DS voltage of the switching element 7 becomes HI, oscillation is continued with a normal waveform.
In FIG. 4, the oscillation of the pulse voltage from the microcomputer 11 is started again in a state where the DS current of the switching element 7 is negatively swinging. When the DS voltage of the switching element 7 becomes HI while the DS current of the switching element 7 is negatively oscillated, oscillation does not continue with a normal waveform. This is because the switching element 6 is turned on while a forward current is flowing through the parasitic diode inside the switching element 7, so that a short-circuit current is applied to the switching element 6 and the switching element 7 during the reverse recovery time of the parasitic diode. Flows. That is, in the state where the DS current of the switching element 7 swings negatively, in the switching element 7, a current flows from the source to the drain. Then, when the switching element 6 is turned on, a short circuit current flows from the drain to the source during the reverse recovery time of the parasitic diode. In addition, the phase of the DS current of the switching element 6 changes and the circuit that operates in the delayed phase operates in the advanced phase, so that the circuit balance is lost.

  FIG. 5 is a diagram showing a waveform of the DS current flowing through the switching element 7 during the pulse voltage stop period. As described above, when the oscillation of the pulse voltage from the microcomputer 11 is started again in a state where the DS current flowing through the switching element 7 is swinging positive, and the DS voltage of the switching element 7 becomes HI, a normal waveform is displayed. Oscillation continues. In the pulse voltage stop state (period when the DS voltage of the switching element 7 is LOW), the DS current of the switching element 7 is the resonance frequency f0 of the series resonance circuit including the inductor 8, the capacitor 9, and the coupling capacitor of the load circuit. Vibrate. Assuming that the period of the resonance frequency f0 is T, the timing t at which the pulse voltage is generated again from the microcomputer 11 and oscillation is continued with a normal waveform as described above is the period during which the DS current of the switching element 7 is positively swinging. It is. That is, as shown in FIG. 5, the timing t is T / 4 <t <3T / 4, 5T / 4 <t <7T / 4, 9T / 4 <t <11T / 4,. To summarize this condition, the timing t at which the pulse voltage is generated again when the frequency is switched is from the moment when the pulse voltage is stopped (from the moment when the DS voltage of the switching element 7 becomes LOW), (2n− 1) It is a period satisfying the condition of xT / 4 ≦ t ≦ (2n + 1) × T / 4 (n = 1, 3, 5, 7, 9,...). When the frequency is switched during this period, the circuit can be stably operated by generating the pulse voltage again.

Next, the function of the oscillation frequency control apparatus 100 according to the first embodiment will be described with reference to FIG. FIG. 6 is a functional block diagram illustrating functions of the oscillation frequency control apparatus 100 according to the first embodiment.
The oscillation frequency control device 100 controls the oscillation frequency of the inverter circuit by applying a pulse voltage to the inverter circuit. Here, the inverter circuit is a circuit that is connected to a load circuit and converts a direct current into a high-frequency current. The oscillation frequency control device 100 includes an oscillation frequency control unit 110, a processing device 980, and a storage device 984. The oscillation frequency control unit 110 includes an oscillation frequency designation unit 120, a timing determination unit 130, and a rectangular wave voltage output unit 140.
The oscillation frequency designation unit 120 designates the oscillation frequency of the inverter circuit.
The timing determination unit 130 calculates a period in which the current flowing through the inverter circuit is in a predetermined direction when the oscillation frequency specification unit 120 changes the specification of the oscillation frequency, and generates a pulse for causing the inverter circuit to generate the changed oscillation frequency. The output timing for outputting the voltage is determined as the calculated period. For example, the timing determination unit 130 calculates a period during which current flows from the drain to the source of the switching element included in the inverter circuit, and calculates an output timing for outputting a pulse voltage that causes the inverter circuit to generate the changed oscillation frequency. You may decide. That is, for example, the timing determination unit 130 may determine a period during which the DS current of the switching element 7 of the inverter circuit unit 3 shown in FIG. 2 flows in the positive direction as the output timing for outputting the pulse voltage. In addition, the timing determination unit 130 sets the output timing t at which the pulse voltage for causing the inverter circuit to generate the changed oscillation frequency is output based on the period T of the resonance frequency of the load circuit starting from the output stop of the pulse voltage (2n −1) × T / 4 ≦ t ≦ (2n + 1) × T / 4 (n: arbitrary odd number) may be calculated and determined.
The rectangular wave voltage output unit 140 outputs a pulse voltage. The rectangular wave voltage output unit 140 outputs a pulse voltage that causes the inverter circuit to generate the changed oscillation frequency at the output timing determined by the timing determination unit 130. The rectangular wave voltage output unit 140 outputs a pulse voltage to the connection line 20 via, for example, the voltage generator 917 shown in FIG.

Next, an operation flow of the oscillation frequency control apparatus 100 according to the first embodiment will be described with reference to FIG. FIG. 7 is a flowchart of an oscillation frequency control process (an oscillation frequency control method, an oscillation frequency control program) that is an operation of the oscillation frequency control apparatus 100 according to the first embodiment.
First, in the oscillation frequency designation step (S101), the oscillation frequency designation unit 120 designates the oscillation frequency of the inverter circuit. When the oscillation frequency is changed (designated), the pulse voltage stops for a predetermined time. For example, in FIG. 2, the DS current of the switching element 7 of the inverter circuit unit 3 oscillates at the resonance frequency of the series resonance circuit including the inductor 8, the capacitor 9, and the coupling capacitor of the load circuit.
Next, in the timing determination step (S102), the timing determination unit 130 calculates a period in which the current flowing through the inverter circuit is in a predetermined direction, and outputs a pulse voltage that causes the inverter circuit to generate the changed oscillation frequency. The output timing is determined as the calculated period.
In the rectangular wave voltage output step (S103), the rectangular wave voltage output unit 140 outputs a pulse voltage that causes the inverter circuit to generate the changed oscillation frequency at the output timing determined by the timing determination unit 130.

  In the above, the case where the switching element 7 enters the pulse voltage stop period in the LOW state in the circuit block diagram shown in FIG. 2 has been described. However, the present invention is not limited to this, and the switching element 6 may enter the pulse voltage stop period when the switching element 6 is in the LOW state. Also in this case, the timing for outputting the pulse voltage can be determined in the same manner as described above.

  According to the oscillation frequency control device 100 according to the first embodiment, by calculating the timing at which the timing determination unit 130 outputs the pulse voltage, it is possible to continue oscillation with a normal waveform even when the oscillation frequency is switched. It is. Therefore, by providing the discharge lamp lighting device with the oscillation frequency control device 100 according to the first embodiment, even when the oscillation frequency is switched, the circuit balance is not lost and the possibility of causing a component failure is reduced.

That is, the oscillation frequency control apparatus 100 according to the first embodiment includes a DC power source obtained by boosting or stepping down a commercial power source, an inverter circuit that converts DC supplied from the DC power source into a high-frequency current, A pulse voltage for generating from the microcomputer 11 a choke coil connected to the inverter circuit, a discharge lamp, a discharge lamp load circuit comprising a starting capacitor and a coupling capacitor connected in parallel to the discharge lamp, and an oscillation frequency control of the inverter circuit. In the discharge lamp device controlled by
When the oscillation frequency is changed, the timing t at which the pulse voltage of the frequency after the change is stopped after the pulse voltage of the frequency before the change is stopped is defined as (2n− 1) It is characterized in that it is performed at the timing of * T / 4≤t≤ (2n + 1) * T / 4 (n = 1, 3, 5, 7, 9,...).

Embodiment 2. FIG.
Next, a second embodiment will be described. In the second embodiment, an oscillation frequency control apparatus 100 that detects the current flowing through the inverter circuit unit 3 and controls the oscillation frequency will be described.

First, the circuit of the discharge lamp lighting device according to the second embodiment will be described with reference to FIG. FIG. 8 is a circuit block diagram of the discharge lamp lighting device according to the second embodiment. The difference between the circuit block diagram shown in FIG. 8 and the circuit block diagram shown in FIG. 2 is that the voltage waveform generated in the current detection resistor 17 connected in series with the switching element 7 is fed back to the microcomputer 11. . A circuit block including the current detection resistor 17 is a current detection resistor unit 18.
FIG. 9 is a diagram illustrating the relationship between the switching element 6 included in the inverter circuit unit 3 at the time of switching the oscillation frequency, the DS current of the switching element 7, the DS voltage of the switching element 7, and the voltage across the current detection resistor 17. is there. As shown in FIG. 9, a voltage waveform synchronized with the DS current of the switching element 7 is generated at both ends of the current detection resistor 17. Therefore, the microcomputer 11 detects the timing at which the voltage of the current detection resistor 17 becomes positive during the pulse voltage stop period. The pulse voltage is generated again in synchronization with the detected predetermined timing. Thereby, the pulse voltage generation timing can be determined regardless of the resonance frequency of the load circuit.

Next, functions of the oscillation frequency control apparatus 100 according to the second embodiment will be described with reference to FIG. FIG. 10 is a functional block diagram illustrating functions of the oscillation frequency control apparatus 100 according to the second embodiment.
The difference between the function of the oscillation frequency control device 100 according to the first embodiment shown in FIG. 6 and the function of the oscillation frequency control device 100 according to the second embodiment shown in FIG. 10 is different from the function of the oscillation frequency control device 100 according to the second embodiment. 100 includes the current detection unit 150.
The current detection unit 150 detects the current of the inverter circuit. That is, the current detection unit 150 detects, for example, a current generated in the current detection resistor 17 illustrated in FIG. Therefore, when the oscillation frequency designation unit 120 changes the designation of the oscillation frequency, the timing determination unit 130 outputs a pulse voltage that causes the inverter circuit to generate the changed oscillation frequency based on the current detected by the current detection unit 150. Determine the output timing. In particular, the timing determination unit 130 determines to provide an output timing for outputting a pulse voltage within a period in which the current detected by the current detection unit 150 is positive. Then, the rectangular wave voltage output unit 140 outputs a pulse voltage that causes the inverter circuit to generate the changed oscillation frequency at the output timing determined by the timing determination unit 130.

Next, an operation flow of the oscillation frequency control apparatus 100 according to the second embodiment will be described with reference to FIG. FIG. 11 is a flowchart of an oscillation frequency control process (oscillation frequency control method, oscillation frequency control program) that is an operation of the oscillation frequency control apparatus 100 according to the second embodiment.
A different part from the operation of the oscillation frequency control apparatus 100 according to the first embodiment will be described based on FIG.
(S201) is the same as (S101).
Next, in the current detection step (S202), the current detection unit 150 detects the current of the inverter circuit.
Next, in the timing determination step (S203), the timing determination unit 130 determines an output timing for outputting a pulse voltage that causes the inverter circuit to generate the changed oscillation frequency based on the current detected by the current detection unit 150.
(S204) is the same as (S103).

  According to the oscillation frequency control device 100 according to the second embodiment, even when the oscillation frequency is switched by the timing determination unit 130 determining the output timing of the pulse voltage based on the current detected by the current detection unit 150, It is possible to continue oscillation with a normal waveform. Therefore, by providing the discharge lamp lighting device with the oscillation frequency control device 100 according to the first embodiment, even when the oscillation frequency is switched, the circuit balance is not lost and the possibility of causing a component failure is reduced.

That is, the oscillation frequency control apparatus 100 according to the second embodiment includes a DC power source obtained by boosting or stepping down a commercial power source, an inverter circuit that converts DC supplied from the DC power source into a high-frequency current, A pulse voltage for generating from the microcomputer 11 a choke coil connected to the inverter circuit, a discharge lamp, a discharge lamp load circuit comprising a starting capacitor and a coupling capacitor connected in parallel to the discharge lamp, and an oscillation frequency control of the inverter circuit. In the discharge lamp device controlled by
When the oscillation frequency is changed, the timing for generating the pulse voltage having the changed frequency from the pulse voltage having the changed frequency is determined by detecting the current of the inverter circuit.

The figure which shows the hardware constitutions of the oscillation frequency control apparatus 100 in embodiment. The circuit block diagram of the general discharge lamp lighting device in the case of controlling with the microcomputer 11. FIG. The figure which shows the case where switching of an oscillation frequency is connected normally. The figure which shows the case where switching of an oscillation frequency is not connected normally. The figure which shows the waveform of DS electric current which flows into the switching element 7 in a pulse voltage stop period. FIG. 3 is a functional block diagram showing functions of the oscillation frequency control device 100 according to the first embodiment. 3 is a flowchart showing an oscillation frequency control process (an oscillation frequency control method, an oscillation frequency control program) that is an operation of the oscillation frequency control apparatus 100 according to the first embodiment. FIG. 4 is a circuit block diagram of a discharge lamp lighting device according to a second embodiment. The figure which shows the relationship between the switching element 6 with which the inverter circuit part 3 is provided at the time of oscillation frequency switching, the DS current of the switching element 7, the DS voltage of the switching element 7, and the voltage of the both ends of the current detection resistor 17. FIG. FIG. 3 is a functional block diagram illustrating functions of the oscillation frequency control device 100 according to the second embodiment. 9 is a flowchart showing an oscillation frequency control process (an oscillation frequency control method and an oscillation frequency control program) that is an operation of the oscillation frequency control apparatus 100 according to the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rectification circuit part, 2 Active filter circuit part, 3 Inverter circuit part, 4 Load circuit part, 5 Drive circuit part, 6 Switching element, 7 Switching element, 8 Inductor, 9 Capacitor, 10 Lamp, 11 Microcomputer, 12 Transistor, 13 Transistor, 14 Primary side inductor, 15 Secondary side inductor, 16 Secondary side inductor, 17 Current detection resistor, 18 Current detection resistor unit, 100 Oscillation frequency control device, 110 Oscillation frequency control unit, 120 Oscillation frequency designation unit, 130 Timing determination unit, 140 rectangular wave voltage output unit, 150 current detection unit, 911 CPU, 912 bus, 913 ROM, 914 RAM, 917 voltage generator, 980 processing device, 984 storage device.

Claims (2)

In the oscillation frequency control device that controls the oscillation frequency of the inverter circuit by applying a rectangular wave voltage to the inverter circuit that is connected to the load circuit and converts a direct current into a high frequency current.
An oscillation frequency designating unit for designating the oscillation frequency;
When the oscillation frequency designation unit changes the designation of the oscillation frequency, the period T of the resonance frequency of the load circuit starting from the time when the output of the rectangular wave voltage that causes the inverter circuit to generate the oscillation frequency before the change is stopped A timing determination unit that determines, as an output timing, a period t calculated by (2n−1) × T / 4 ≦ t ≦ (2n + 1) × T / 4 (n: any odd number) ,
Oscillation frequency control device in which the oscillation frequency after the change, characterized in that it comprises a square wave voltage output unit to start the output timing of the output of the rectangular wave voltage to be generated in the inverter circuit to determine the above timing determination section. An oscillation frequency control device according to claim 1 ;
An inverter circuit that oscillates based on the output of the oscillation frequency control device, converts the direct current into a high frequency current, and supplies the high frequency current to a lamp that is used for lighting;
A discharge lamp lighting device comprising:

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