JP5576748B2 - Discharge lamp lighting device - Google Patents

Description

  The present invention relates to a discharge lamp lighting device for lighting a discharge lamp such as a fluorescent lamp or an HID lamp, and more particularly to an improvement in on / off control of a switching element in a power factor correction circuit or a power conversion circuit.

  Conventionally, as a discharge lamp lighting device, a copper iron type ballast (so-called copper iron ballast) has been used. Ballasts have the role of properly limiting the lamp current, but copper iron ballasts are heavier and larger in size, so in recent years the ballasts have become lighter and smaller. So-called electronic ballasts using electronic components such as switching elements and diodes have been used for the purpose of higher functionality.

An electronic ballast, a so-called electronic ballast, adjusts and controls the power supplied to the discharge lamp La connected to both output terminals of the DC power supply circuit and the DC power supply circuit that receive the AC output of the AC power supply AC and outputs DC. It consists of a power conversion circuit.
Some DC power supply circuits are configured relatively simply by a full-wave rectifier for full-wave rectification of alternating current and a smoothing capacitor connected in parallel to both output terminals thereof. The DC power supply circuit includes a full-wave rectifier and a power factor correction circuit (also called an active filter) that inputs the full-wave rectified output and generates a DC voltage having a constant amplitude with high efficiency. There is also. This power factor correction circuit is provided with a switching element that can be switched on and off at a frequency of several tens of kHz to improve the power factor, and the power factor correction control circuit controls the driving of the switching element.

On the other hand, a step-down chopper type circuit configuration is generally used as the power conversion circuit. The power conversion circuit is provided with a switching element that can be switched on and off at a frequency of 10 kHz to 500 kHz, and the power conversion control circuit controls driving of the switching element. The power conversion control circuit controls the power supplied to the discharge lamp by adjusting the switching frequency or on-duty of the switching element according to the lamp voltage of the discharge lamp.
The power factor correction circuit and the power conversion circuit are provided with an inductor that accumulates magnetic field energy when the switching element is on and releases energy when the switching element is off. Power factor improvement and power conversion are achieved by repeatedly storing and releasing the energy of the inductor by high-frequency on / off switching.

In recent years, the demand for miniaturization of electronic ballasts has increased, and the miniaturization of components has been attempted by increasing circuit efficiency. In order to increase the circuit efficiency of the DC power supply circuit and the power conversion circuit, a control called soft switching is employed as a method for controlling the switching elements incorporated in these circuits (see, for example, Patent Document 1).
Patent Document 1 describes the circuit efficiency when the control of the zero-cross switching mode is executed for the switching element of the power conversion circuit. Zero-cross switching is a control method for switching on and off a switching element at a timing when voltage or current of an inductor or the like becomes zero (this timing is referred to as zero-crossing). If the switching element is switched from OFF to ON at the timing when the current (I _L ) flowing through the inductor becomes substantially zero, the switching loss caused by the relationship between the current (I _L ) and the voltage applied to the switching element can be reduced. .

Japanese Patent No. 3470529 Special table 2009-539220

  What is important in executing the zero-crossing switching mode is to properly detect the timing of switching from off to on, that is, the timing of the end of one cycle of soft switching. In general, a secondary winding added to the choke coil (see FIG. 1 of Patent Document 1) and a current transformer (see FIG. 2 of Patent Document 2) are used to determine the on-timing based on the change in voltage. Was. However, the rise and fall of the signal obtained by the secondary winding and current transformer are slow, and the amplitude of the signal fluctuates depending on the power handled, resulting in inaccurate timing at the end of one cycle. It was.

  Further, in Patent Document 1, a resistor (see reference numeral 28 in FIG. 10 of Patent Document 1) is connected to the output terminal on the ground level side of the DC power supply circuit, and this is used as a detection resistor. A method for detecting the end of one cycle of switching is also described. The voltage of the detection resistor is detected, and the switching element is on / off controlled based on this voltage. In order to detect a signal having a large amplitude, it is necessary to increase the resistance value of the resistor. However, an increase in resistance causes an increase in circuit loss and should be avoided. If it does so, in the detection by the resistor of patent document 1, a signal amplitude cannot be enlarged, but it becomes easy to receive to the influence of noise.

  In particular, since the lamp characteristics of the HID lamp (high pressure discharge lamp) fluctuate drastically, the energy release time of the inductor in each soft switching period changes. Conventional soft switching cannot sufficiently follow the timing of on / off switching to such a change in lamp characteristics, which causes deterioration in circuit efficiency. In order to reduce the circuit loss even when the proper on-timing always changes, it has been required to accurately detect the timing when the current flowing through the inductor becomes zero in real time.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned reasons, and an object of the present invention is to accurately detect the end of one cycle of soft switching in a DC power supply circuit or a power conversion circuit and to detect a circuit caused by an on-timing shift in a zero cross switching mode. Minimize losses. Provides a discharge lamp lighting device that can contribute to the prevention of global warming by improving the circuit efficiency, reducing the power consumption of the discharge lamp lighting device, and reducing the amount of CO2 generated in the power plant There is to do.

In order to solve the above-mentioned problems, a discharge lamp lighting device according to the present invention supplies full current rectification of an AC voltage to the discharge lamp via an electrolytic capacitor connected in parallel to the discharge lamp. Because
A series circuit of an inductor and a diode that supplies a rectified current after full-wave rectification toward the positive electrode of the electrolytic capacitor, and a connection point of the inductor and the diode and a negative electrode of the electrolytic capacitor are connected to the electrolytic capacitor. Charging means having switching elements connected in parallel and configured to charge the electrolytic capacitor by on-off driving of the switching elements;
Control means for controlling on-off driving of the switching element;
Zero-cross detection means for generating an on-switching timing signal based on the voltage between both terminals of the switching element and sending it to the control means;
Is provided.
The drain side terminal of the switching element is connected to the connection point of the inductor and the diode, the source side terminal of the switching element is connected to the negative electrode of the electrolytic capacitor, and the zero cross detection means It has a CR series circuit of a detection capacitor and a detection resistor connected in parallel to both terminals of the element. When the current flowing through the inductor in the off state becomes zero, the output capacitance between the drain and source of the switching element and the inductor resonate, and the drain voltage of the switching element is reduced. The capacitor for taking out the change portion of the drain voltage, and the voltage of the detection resistor is sent to the control means as an ON switching timing signal .
In the present invention, the detection capacitor is a reactance element, and basically has a characteristic that heat generation such as resistance does not occur. Therefore, although the detection capacitor is responsible for most voltage drop functions from the high drain voltage (for example, several hundred volts) to the input signal (for example, 10 V or less) of the control means, heat generation does not occur, so power loss is small. I'll do it.
In the present invention, the capacitance of the detection capacitor is preferably smaller than the output capacitance between the drain and source of the switching element.

The discharge lamp lighting device according to the present invention includes a rectifier circuit for full-wave rectification of an AC voltage, an electrolytic capacitor connected to both output terminals of the rectifier circuit, and a direct current from the electrolytic capacitor for lighting the discharge lamp. A power conversion circuit that converts and supplies the current, and supplies a lighting current to the discharge lamp based on a direct current from the electrolytic capacitor,
One electrode of a discharge lamp is connected to the positive electrode of the electrolytic capacitor,
The power conversion circuit includes:
A series circuit of an inductor and a switching element connecting the other electrode of the discharge lamp and the negative electrode of the electrolytic capacitor, and a current from the inductor in the off state is routed to the inductor via the discharge lamp. Having a diode connecting both ends of the series circuit, and converting the direct current from the electrolytic capacitor to the lighting current of the discharge lamp by the on-off drive of the switching element,
Control means for controlling on-off driving of the switching element;
And zero-cross detection means for generating an ON switching timing signal based on the voltage between both terminals of the switching element and sending the timing signal to the control means.
The drain side terminal of the switching element is connected to a connection point of the inductor and the diode, and the source side terminal of the switching element is connected to the negative electrode of the electrolytic capacitor. The same means is used.

  In the half-bridge type or full-bridge type power conversion circuit, the zero-cross detection means switches on from a voltage between both terminals of a ground level side switching element having one end connected to the negative electrode side of the electrolytic capacitor. It is preferable to generate a timing signal.

  The specific configuration of the zero-cross detection means preferably includes a CR series circuit of a detection capacitor and a detection resistor connected in parallel to both terminals of the switching element, and the current flowing through the inductor in the off state is zero. When the output capacitance between the drain and the source of the switching element and the inductor resonate at a timing when the drain voltage of the switching element decreases, the detection capacitor detects the change portion of the drain voltage. The voltage of the detection resistor may be taken out and sent to the control means as an ON switching timing signal.

Here, the detection resistor of the zero-cross detection means is constituted by a series connection of a plurality of resistors, and the voltage divided by the plurality of resistors may be sent to the control means as an ON switching timing signal. Good.
The zero-cross detection means has a Zener diode connected in parallel to both terminals of the detection resistor, and the control means uses the voltage of the detection resistor via the Zener diode as an ON switching timing signal. It is preferable to send to.

In the present invention, when the current flowing through the inductor becomes zero when the switching element is in the OFF state, the output capacitance between the drain and source of the switching element and the inductor resonate, and the drain voltage of the switching element rapidly decreases. According to the present invention, since a small-capacitance detection capacitor is connected to both terminals of the switching element, the detection capacitor can extract a change in drain voltage. In addition, since a small-capacitance detection capacitor is connected in parallel to both terminals of the switching element, it is possible to take out the voltage change portion with particular emphasis and to accurately grasp the on-switching timing.
Further, if a zero-cross is detected only by a resistor without using a detection capacitor as the zero-cross detection means, a power loss due to heat generation of the resistor is caused. On the other hand, in the present invention, the detection capacitor is a reactance element, and basically has a characteristic that heat generation such as resistance does not occur. Therefore, although the detection capacitor is responsible for most of the voltage drop functions, power loss can be reduced. For example, it becomes possible to generate an input signal of 10 V or less to the control means with little energy loss from a high voltage of several hundred volts.
Therefore, if the timing of the change of the drain voltage of the switching element taken out by the detection capacitor is used, an ON switching timing signal can be generated accurately. Therefore, if the zero cross detection means of the present invention is used, the end of one cycle of soft switching can be accurately detected in the DC power supply circuit or the power conversion circuit, and the circuit efficiency of the discharge lamp lighting device can be greatly improved. it can.

It is a whole circuit block diagram of the discharge lamp lighting device of this invention. It is a circuit diagram at the time of applying the zero cross detection circuit concerning this invention to a power factor improvement circuit. It is a block diagram of a zero cross detection circuit. It is a figure which shows the signal waveform in the principal part of the zero cross detection circuit shown in FIG. It is a circuit diagram at the time of applying the zero cross detection circuit concerning this invention to a full bridge type inverter circuit.

Preferred embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows a configuration diagram of a discharge lamp lighting device according to the present invention.
In the figure, the discharge lamp lighting device is composed of a DC power supply circuit 7 and a power conversion circuit 3. The DC power supply circuit 7 performs processing for generating DC power for stable supply to the power conversion circuit 3 from the AC power supply AC. The power conversion circuit 3 performs a process of converting DC power from the DC power supply circuit 7 into lamp power of a discharge lamp. The discharge lamp lighting device supplies a predetermined lighting current to the discharge lamp connected to both output ends of the power conversion circuit 3.

The DC power supply circuit 7 and the power conversion circuit 3 are each incorporated with a high-frequency switching element and are controlled to be turned on and off by soft switching. The present invention can provide a detection circuit that accurately detects the end of one cycle of soft switching, that is, the timing of switching from an off state to an on state, using circuit technology.
Here, a case will be described in which the switching element of the DC power supply circuit 7 is controlled by soft switching in the first embodiment, and a case in which the switching element of the power conversion circuit 3 is controlled by soft switching in the second embodiment. .

First Embodiment FIG. 2 shows a circuit configuration of a discharge lamp lighting device according to this embodiment.
<Overall configuration of discharge lamp lighting device>
In the figure, the discharge lamp lighting device full-wave rectifies the full-wave rectified AC power supplied from the commercial power supply AC, and converts the output of the full-wave rectifier 2 to a constant voltage and increases the power factor. The power factor improvement circuit 8, the power conversion circuit 3 that converts the DC power output from the power factor improvement circuit 8 into lamp power and supplies it to the discharge lamp La, and the end of one cycle of soft switching in the power factor improvement circuit 8 A zero-cross detection circuit 12 for detecting, and a power factor correction control circuit 1 for performing on / off control of the high-frequency switching element Q1 incorporated in the power factor correction circuit 8 are provided.

The zero-cross detection circuit 12 receives the voltage of the switching element Q ₁ and sends the output voltage of the detection circuit 12 to the power factor correction control circuit 1. The power factor correction control circuit 1 discriminates an optimum on timing from the output voltage of the detection circuit 12 and sends an on / off switching signal to the switching element Q ₁ of the power factor correction circuit 8.

  The full-wave rectifier 2 is configured by a full-wave rectifier diode bridge, and is connected to both ends of the commercial AC power supply AC that is a low-frequency (for example, 50 Hz) power supply.

The power factor correction circuit 8 is connected to the subsequent stage of the full-wave rectifier 2 and is also called an active smoothing filter. The power factor correction circuit 8, a full-wave rectifier one output terminal of the second inductor end to the (+ voltage output terminal in the drawing) is connected L ₁ and _(choke coil), and the other end of the inductor L ₁ (in the figure - voltage output terminal) the other output terminal of the full-wave rectifier 2 and the high frequency switching element Q ₁ which drain and source are connected between, as a high-frequency component passing diverted filter with the switching of the switching element Q ₁ A smoothing capacitor C ₁ , a commutation diode D ₁ having an anode connected to a connection point between the inductor L ₁ and the switching element Q ₁ , a cathode of the commutation diode D ₁ , and a negative voltage output of the full-wave rectifier 2. and a electrolytic capacitor C ₂ connected between an end.

The power factor correction circuit 8, the alternating current input to the full-wave rectifying circuit 2 is shaped into a sine wave without distortion, the amplitude constant stabilized direct current generated by the high efficiency, the electrolytic capacitor C ₂ Charge electrostatic energy. The inductor L ₁ , the high-frequency switching element Q ₁ , and the commutation diode D ₁ incorporated in the power factor correction circuit 8 constitute a charging circuit 9 that charges the electrolytic capacitor C ₂ with energy. Electrolytic capacitor C ₂ supplies a lighting current to the discharge lamp La which is connected via a power conversion circuit 3 between both terminals of the capacitor.

In other words, the charging circuit 9, the series circuit of the inductor L ₁ and the diode D ₁ supplies a rectified current after full-wave rectification toward the positive electrode of the electrolytic capacitor C _2, and, between the inductors L ₁ and the diode D ₁ having a switching element Q ₁ which connects the connecting point between the anode of the electrolytic capacitor C _2. The switching element Q ₁ is said to be connected in parallel to the diode D ₁ and the electrolytic capacitor C _2.

The switching element Q ₁ has a drain side terminal of the switching element Q ₁ connected to an intermediate point between the inductor L ₁ and the diode D ₁ , and a source side of the switching element Q ₁ connected to a ground line to which a negative electrode terminal of the electrolytic capacitor C ₂ is connected. Connect the terminals. The switching element _{Q 1} using the enhancement type N-channel MOSFET. When the gate voltage drive current is supplied from the power factor improvement control circuit 1 to the gate of the switching element Q ₁ is generated, the drain - current flows between the source. This state of the ON state of the switching element Q _1. On the other hand, a state where no drive current is supplied to the gate and no drain current flows is called an off state.

Incidentally, smoothing capacitor C ₁ is also used for returning the partial smoothing and the current generated in the inductor L ₁ when off the switching element to Q ₁ rectified current from the full-wave rectifying circuit 2 to the inductor L _1.

Zero-cross detection circuit 12 for capturing the voltage between the two terminals of the switching element Q _1, the two locations inputs 1a, is connected to 1b. One input terminal 1a is provided from the connection point between the inductor L ₁ and the diode D ₁ until the drain of the switching element Q _1, the other input terminal 1b is of the full-wave rectifier 2 - from the voltage output terminal It is provided on an extended ground level power line.

The power factor improvement control circuit 1 controls the ON period of the high frequency switching switching element Q ₁ in accordance with the output voltage of the electrolytic capacitor C ₂ of the power factor correction circuit (step-up chopper circuit) 8 output side, the output Feedback control is performed so that the voltage becomes a constant value. At the same time, the control circuit 1 detects the full-wave rectified voltage based on the monitoring of the amplitude level of the full-wave rectified voltage of the full-wave rectifier 2 (the detected voltage at the + voltage output terminal of the rectifier) and the current level flowing through the ground level. by controlling the oN period of the switching element Q ₁ in accordance with the amplitude level, and also controls the power factor correction to match the phase of the input AC voltage input AC current. As a result, the power factor correction circuit 8 converts the full-wave rectified voltage into a stabilized DC voltage with a high power factor. The switching frequency of the switching element _{Q 1} is usually several tens kHz.

Next, the operation of the power factor correction circuit 8 will be described.
In the on-state switching element Q _1, the potential of the midpoint of the inductor L ₁ and the diode D ₁ is the ground level (zero), and the voltage between the terminals of the inductor L ₁ becomes equal to the DC voltage after rectification. Then, the energy of the magnetic field in the inductor L ₁ is accumulated, the current flowing through the inductor L ₁ is increased. Direct current from the full-wave rectifier 2 flows from the inductor L ₁ through the switching element Q ₁ to the ground line. In other words, in the on-state switching element Q _1, so that the diode D ₁ and the electrolytic capacitor C ₂ is bypassed.

In the off state of the switching element Q _1, the potential of the midpoint of the inductor L ₁ and the diode D ₁ is equal to the electrolytic capacitor C ₂ of the voltage (> DC voltage after rectification). Then, the energy of the magnetic field from the inductor L ₁ is discharged, the current flowing through the inductor L ₁ is gradually decreased. Current from the inductor _{L 1} passes through the diode _{D 1} to charge the electrolytic capacitor _{C 2,} back through the smoothing capacitor _{C 1} to the inductor _{L 1.}

<Zero cross detection circuit>
Hereinafter, the zero-cross detection circuit 12 that enables soft switching with high circuit efficiency characteristic of the present invention will be described.
The zero cross detection circuit 12 is a circuit that accurately detects the end of one cycle of soft switching so that the generation of a stabilized DC voltage with a high power factor by the power factor correction circuit 1 can be executed with high circuit efficiency. As shown in FIG. 2, one set of input terminals 1 a and 1 b of the zero cross detection circuit 12 are connected to both terminals of the switching element, and one set of output terminals 2 a and 2 b are connected to the power factor correction control circuit 1. .

FIG. 3 shows a detailed circuit configuration of the zero cross detection circuit 12.
In the figure, the zero-cross detection circuit 12 has an input terminal 1a, a CR series circuit 10 connected in parallel between 1b, and a zener diode ZD ₁ connected in parallel with the resistance component of the CR series circuit 10 It has an output terminal 2a to the terminals of the Zener diode ZD _1, 2b are provided.

The CR series circuit 10 has a capacitance component and a resistance component connected in series. Relatively small end of the detection capacitor C ₁₁ is a capacitance component (positive charge side), whereby the input terminal 1a, the other end of the detection capacitor C ₁₁ (negative charge side) and for the two detection between the output terminals 1b A resistance component that is a series connection of resistors R ₂ and R ₁ is connected. One end of the detection resistor R ₂ connected to the other end of the detecting capacitor C ₁₁ and the terminal 3a, an intermediate point between the detection resistor R _2, R ₁ and terminal 3b, is connected to the output terminal 1b the other end of the detection resistor R ₁ and the terminal 3c.
Zener diode ZD ₁ is both terminals 3b of the detection resistor _{R 1,} is connected in parallel to 3c.
An input voltage V ₁ to the zero cross detection circuit 12 is a voltage between the drain of the switching element Q ₁ of the power factor correction circuit 8 and the ground. The voltage generated in the resistance components (R ₂ , R ₁ ) when this input voltage V ₁ is applied to the CR series circuit 10 is divided by the two detection resistors R ₂ , R ₁ , and the Zener diode ZD ₁ becomes the output voltage.

<Zero cross detection method>
The zero cross indicates a timing at which the current value or voltage value causing the switching loss becomes exactly zero. Based on signal waveform diagrams generated in the detection circuit, a zero cross detection method will be described.
FIG. 4 shows a signal waveform of a main part in the zero-cross detection circuit 12.
Fig (A) shows a state of the switching element _{Q 1,}
FIG (B) shows a change in inductor current _{I L.}
FIG. 4C shows the waveform of the voltage (V ₁ ) between both terminals of the switching element Q ₁ .
FIG (D) are based on the input end 1b of the ground side, of the detection capacitor side terminal 3a of the detection resistor R ₂ potential, i.e., the series circuit of the detection resistor R _1, R ₂ It is a waveform of a both-ends voltage.
FIG. 4E shows the waveform of the voltage (V ₂ ) between both terminals of the Zener diode ZD ₁ .

Depending on and off driving of the switching element Q _1, between the two terminals of the voltage (V ₁₎ the figure zero volts (ON state) and the voltage equal to the voltage value of the electrolytic capacitor C ₂ as shown in (C) (off-state) Are shown alternately. If the input voltage V ₁ is applied to the CR series circuit 10 of the zero-crossing detection circuit 12, that is, as a reference (ground level) input terminal 1b, the potential of the input terminal 1a is assumed to be V _1, the detection capacitor C only the change component of the input signal V ₁ by ₁₁ detecting resistor R _1, is transmitted to the series circuit of the R _2, detecting capacitor C ₁₁ and the detection resistor R ₂ relative to the ground level (input 1b) The potential V _{3a at} the midpoint (terminal 3a) is a bipolar signal as shown in FIG.
The potential V _{3a at} the midpoint between the detection capacitor C ₁₁ and the detection resistor R ₂ is _divided by the detection resistors R ₁ and R ₂ , and the divided potential is detected by the detection resistors R ₂ and R ₂ . ₁ appears at the midpoint (terminal 3b). In this mid-point (pin 3b) potential will through the Zener diode ZD ₁ connected in parallel to both ends of the detecting resistor R ₁ Output voltage (V _2).

<On state>
This will be described with reference to FIGS.
In the ON state of the switching element, the rectified voltage is applied to the inductor L, and magnetic field energy is accumulated in the inductor L. During this time, the inductor current (I _L ) increases as shown in FIG.
In the on state, the voltage between the terminals V ₁ of the switching element Q ₁ is zero volts (FIG. C), the potential V _3a at the terminal 3a indicates a negative polarity (FIG D). Although this negative voltage component is divided by the detection resistors R ₂ and R ₁ , the forward direction of the Zener diode ZD ₁ coincides with the direction from the terminal 3c to the terminal 3b. Diode ZD ₁ indicates zero volts. Therefore, the output voltage _{V 2} denotes the zero voltage (Fig E).

<Off state>
In the off state of the switching device, the energy of the magnetic field from the inductor L is discharged to charge the electrolytic capacitor C _2. During this time, the inductor current (I _L ) decreases as shown in FIG.
In the off state, the voltage V ₁ between the terminals of the switching element Q ₁ is equal to the voltage of the electrolytic capacitor C ₂ , and shows 200 V, for example (FIG. C). Since the voltages _{V 1} is applied to the CR series circuit of the zero-crossing detection circuit 12, the potential _{V 3a} at the terminal 3a on the turn-off is reversed to the positive electrode, for example a 100 V.

A voltage V ₁ between terminals of the switching element Q ₁ of 200 V is applied to the CR series circuit 10 and accumulates electric charges in its capacitance component. That is, flows from the input end 1a positive charges to the detection capacitor _{C 11.} The rate of accumulation of charges to the detection capacitor C ₁₁ is dependent by the time constant determined by the capacitance value and the resistance value of the CR series circuit. Here, the capacitance value and the resistance value are set so that the time constant is sufficiently longer than the discharge time of the inductor L. Accordingly, the potential V _{3a at the} terminal 3a decreases with the passage of time (D in the figure). Further, the positive voltage component at the terminal 3a is divided by the detection resistors R ₂ and R ₁ , but each resistance value is set so that the Zener voltage is smaller than the divided value. The voltage at the terminal 3b is cut by the Zener voltage. Therefore, the output voltage V ₂ denotes the Zener voltage value (FIG E).

<Discharge of charge accumulated in detection capacitor>
When the energy release of the magnetic field of the inductor L ₁ is completed, the inductor current I _L becomes zero. Between the inductor L ₁ and the electrolytic capacitor C ₂ and a diode D _1, because the charge of the electrolytic capacitor C ₂ is never flow back, the inductor current I _L is zero, the drain of the switching element Q ₁ - between the source the resonance occurs between the output capacitance and the inductor L _1, the input voltages V ₁ becomes substantially zero potential rapidly decreases (FIG C). Then, the drain of the accumulated in the detecting capacitor C ₁₁ electrostatic energy (charge) the switching element Q ₁ - through the output capacitance between the source, further terminal 3c from the terminal 1b, the detecting resistor R _1, R ₂ a pass in order, return to the switching element Q _1. As a result, a negative voltage is generated at the terminal 3a as shown in FIG. This negative voltage is divided by the detection resistors R ₂ and R _{1 and} should also generate a negative voltage at the terminal 3b, but is short-circuited by the forward conduction of the Zener diode ZD ₁ to generate an output voltage V ₂ indicates zero volts. Note that the output capacitance, the switching element to Q ₁ off state, its drain - shows the capacitance existing between the source terminal.

It present invention characteristic of the inductor current I _L roughly the timing becomes zero at the same time, by the operation of the zero-crossing detection circuit 12 is that the output voltage V ₂ decreases rapidly to zero volts. Change in the signal waveform of such zero-cross detection circuit 12, i.e. when the inductor current becomes zero, by utilizing the change of the signal waveform of the output signal V ₂ of the zero-cross detection circuit 12 is reduced to zero volts instantaneously, the inductor current It is possible to accurately detect the timing of zero crossing when becomes zero.

The power factor improvement control circuit 1, the change in the output voltage of the zero-cross detection circuit 12 (V _2), the inductor current I _L can detect timing just become zero, turn the switching element Q ₁ based on the information Turn on to start the next switching period.

According to the present embodiment, steep rise, and, falling signal source from (input voltage V _1), detecting resistor R ₁ and emphasizes capacitive coupling (detection capacitor C ₁₁ and the change _component, R _Since the voltage signals of the detection resistors R ₁ and R ₂ are taken out as the output voltage V ₂ by connecting the serial connection of ₂ in parallel with the switching element), the timing of zero crossing in soft switching can be accurately performed Can be detected.
Further, when varying the lamp characteristics are vigorous as HID lamps, the energy release time of the inductor L ₁ in each cycle of the soft switching is changed, according to the present embodiment, flows through the inductor L ₁ Since the timing when the current becomes zero can be accurately detected in real time, deterioration of circuit efficiency can be avoided.

The negative voltage component is cut by the forward voltage of the Zener diode ZD _1, since a positive voltage component is cut by the Zener voltage, the midpoint potential in (terminal 3b) safe 10V below the voltage value for the control circuit Will be converted to.

Further, without using the detecting capacitor C ₁₁ to the zero-crossing detection circuit 12, when trying to detect a zero-cross in only resistors, causing power loss due to heat generation of the resistor. Detection capacitor C ₁₁ having a small capacity for use in the present invention, on the other hand is a reactance element, basically, have the property of heat generation does not occur, such as resistance. Therefore, the detection capacitor C _11, despite the charge of the voltage drop of the majority, it is possible to reduce the loss of power. For example, it becomes possible to generate an input signal (10 V or less) to the control circuit with little energy loss from a high voltage of several hundred volts.
Depending on the difference in the component constants and switching frequency of the switching circuit, a signal delay circuit may be added after the zero cross detection circuit of the present invention to adjust the timing of zero volt switching.

Second Embodiment FIG. 5 shows a circuit configuration of a discharge lamp lighting device according to the present embodiment.
In the figure, the discharge lamp lighting device generates a DC power from an AC power supplied from a commercial power source AC, and a process of converting the DC power from the DC power circuit 7 into the lamp power of the discharge lamp. ON / OFF control of a plurality of high-frequency switching elements Q _{2 to} Q ₅ incorporated in the power conversion circuit 3, a zero cross detection circuit 12 that detects the end of one cycle of soft switching in the power conversion circuit 3, And a full-bridge type power conversion control circuit 11 for performing

The zero-cross detection circuit 12, a source to the ground line of the plurality of switching elements Q ₂ to Q ₅ is connected, the voltage of the switching element Q ₅ to perform high-frequency switching is input. The output voltage of the detection circuit 12 is sent to the power conversion control circuit 11, and the power conversion control circuit 11 identifies the optimum on-timing from the output voltage and sends a switching signal to each of the switching elements Q _{2 to} Q _{5 of} the power conversion circuit 3. To send.

The power conversion circuit 3 is a full bridge type inverter circuit. The power conversion circuit 3 includes a series circuit of switching elements Q ₂ and Q ₃ connected in parallel to both output terminals of the DC power supply circuit 7, and a high-frequency switching circuit connected in parallel to both output terminals of the DC power supply circuit 7. a series circuit of elements _Q 4, _{Q 5,} and the diode _D 2 to D ₅ that is connected in the opposite direction to the direction of and current of each element _Q 2 to Q ₅ in parallel to the respective switching elements _Q 2 to Q ₅ a series circuit of the switching element Q _2, a connection point of the series circuit of Q ₃ and the high frequency switching element Q _4, Q the discharge lamp connected between the connection point of the series circuit of ₅ La and the inductor L _2, the discharge lamp A capacitor C ₄ for bypassing a high-frequency component due to high-frequency switching of the switching elements Q ₄ and Q ₅ from a current flowing in the discharge lamp La connected in parallel to La; A current detection resistor R ₃ for detecting an input current to the power conversion circuit 3 and a small-capacitance capacitor C ₃ for bypassing a high frequency component for preventing a high frequency current from flowing through the resistor R _3. I have. The switching element Q ₅ is a switching element on the ground level side, one end of which is connected to the negative electrode side of the DC power supply circuit 7.

When MOSFETs are used as the switching elements Q _{2 to} Q ₅ , parasitic diodes built in the MOSFETs are used for the reverse current carrying diodes D _{2 to} D _5. do not have to.

Each of the switching elements Q _{2 to} Q ₅ is in a state in which the switching element Q ₂ is turned on, the Q ₅ is high-frequency switched, and the switching elements Q ₃ and Q ₄ are turned off by the control signal from the power conversion control circuit 11. The state in which Q ₂ and Q ₅ are off, the switching element Q ₃ is on, and Q ₄ is high-frequency switched alternately repeats at low frequencies (several tens to several hundreds of Hz).

The switching element Q ₂ is on, in a period in which Q ₅ is high-frequency switching, when the switching element Q _5, a DC current from the DC power supply circuit 7, the switching element Q ₂ → discharge lamp La → inductor L ₂ → flows in the order of the switching elements Q ₅ to the negative electrode terminal of the DC power supply circuit 7, the energy of the magnetic field is stored in the inductor L _1. Then, when the off of the switching element Q _5, energy stored in the inductor L ₂ is released, the current flows through a path of the inductor L ₂ → diode D ₄ → the switching element Q ₂ → discharge lamp La → inductor L _2.

On the other hand, the switching element Q ₃ is turned on, in a period in which Q ₄ is a high-frequency switching, when the switching element Q _4, direct current from the DC power supply circuit 7, the switching element Q ₄ → inductor L ₂ → release flows to the negative electrode terminal of the lamp La → switching element Q DC power supply circuit 7 in ₃ of the order, the energy of the magnetic field is stored in the inductor L _1. Then, when the off of the switching element Q _4, the energy stored in the inductor L ₂ is released, the current flows through a path of the inductor L ₂ → discharge lamp La → switching element Q ₃ → the diode D ₅ → inductor L _2.

The power conversion circuit 3 of the present embodiment that performs such an operation can be said to be a full-bridge type power conversion circuit having the following circuit as a basic configuration. That is, the electrolytic capacitor C ₂ of the DC power supply circuit 3 to the positive electrode, the discharge lamp one of the electrodes is connected to La, the electric power conversion circuit as a basic configuration, the discharge lamp La and the other electrode and the electrolytic capacitor C ₂ of a series circuit of an inductor L ₂ and the switching element Q ₅ connecting the negative electrode _(or Q _4), for routing current from the inductor L ₂ in the inductor L ₂ through the discharge lamp La in the off state, and the discharge lamp La And a diode D ₄ (or D ₅ ) connecting both ends of the series circuit of the inductor L ₂ . Then, to convert the direct current from the electrolytic capacitor C ₂ to the lighting current of the discharge lamp La in off driving of the switching element Q _{5 (or} Q _4).

The zero cross detection circuit 12 in the present embodiment has the same configuration as that of the previous embodiment. As shown in FIG. 5, a pair of input terminals 1a of the zero-crossing detection circuit 12, 1b are connected to both terminals of the switching element Q _5.
In a mode in which the switching element Q ₅ is turned on and off at a high frequency, similar to the embodiment described above, the current in the inductor L ₂ is at the same time a timing substantially becomes zero, the operation of the zero-crossing detection circuit 12, the output voltage V ₂ is zero volts Since it rapidly decreases, it is possible to accurately detect the timing of zero crossing when the inductor current becomes zero.

The switching element Q ₄ is in the mode to turn on and off at a high frequency, the current in inductor L ₂ is substantially the timing becomes zero at the same time, by the operation of the zero-crossing detection circuit 12, the output voltage V ₂ increases rapidly from zero to the Zener voltage. The change in the output voltage V _2, the timing of the zero crossing of the inductor current becomes zero can be accurately detected.

  In the present embodiment, the full bridge type power conversion circuit 3 has been described. However, the discharge lamp lighting device of the present invention can be similarly applied to a herb bridge type power conversion circuit. The present invention is also applied to a power conversion circuit in which a step-down chopper circuit using one switching element and a polarity inversion circuit using four switching elements are combined to supply a lighting current alternating to a discharge lamp. An electric lighting device can be applied.

An embodiment in which the zero cross detection circuit 12 is used in a power factor correction circuit will be described.
Using the zero cross detection circuit shown in FIG. 3, the characteristic values of the respective elements were set as follows.
Detection capacitor C ₁₁ : 100 pF,
Resistor R ₁ : 10 kΩ,
Resistor R ₂ : 51 kΩ,
Zener diode ZD ₁ : 4.3V
As a result, the circuit efficiency of the power factor correction circuit can be improved from 93% to 95%, compared with the conventional method of detecting a signal by adding a secondary winding to the choke coil.
Similarly, in the embodiment in which the zero cross detection circuit is used for the power conversion circuit, the circuit efficiency of the power conversion circuit is 90% to 93% compared to the conventional method of detecting a signal using a current transformer. Could be improved.

  The present invention can be applied to lighting devices for high pressure discharge lamps including xenon lamps in addition to HID lamps such as mercury lamps, metal halide lamps, and high pressure sodium lamps. It can also be applied to a lighting device for a low pressure discharge lamp such as a fluorescent lamp.

1 power factor improvement control circuit 2 full-wave rectifier 3 power conversion circuit 7 the DC power supply circuit 11 a power conversion control circuit 12 zero-crossing detecting circuit AC AC power La discharge lamp ZD ₁ Zener diode _L 1, _{L 2} inductor _{C 1, C} 3, C ₄ smoothing capacitor C ₂ electrolytic capacitor C ₁₁ detection capacitor

Claims (5)

In a discharge lamp lighting device that rectifies an AC voltage in full wave and supplies a lighting current to the discharge lamp via an electrolytic capacitor connected in parallel to the discharge lamp.
A series circuit of an inductor and a diode that supplies a rectified current after full-wave rectification toward the positive electrode of the electrolytic capacitor, and a connection point of the inductor and the diode and a negative electrode of the electrolytic capacitor are connected to the electrolytic capacitor. Charging means having switching elements connected in parallel and configured to charge the electrolytic capacitor by on-off driving of the switching elements;
Control means for controlling on-off driving of the switching element;
Zero cross detection means that generates an ON switching timing signal based on a voltage between both terminals of the switching element and sends the timing signal to the control means,
The drain side terminal of the switching element is connected to the connection point of the inductor and the diode, and the source side terminal of the switching element is connected to the negative electrode of the electrolytic capacitor,
The zero-cross detection means has a CR series circuit of a detection capacitor and a detection resistor connected in parallel to both terminals of the switching element,
When the current flowing through the inductor in the off state becomes zero, the output capacitance between the drain and source of the switching element and the inductor resonate, and the drain voltage of the switching element decreases.
The discharge lamp lighting device according to claim 1, wherein the detection capacitor takes out the change portion of the drain voltage, and the voltage of the detection resistor is sent to the control means as an ON switching timing signal . A rectifier circuit for full-wave rectification of an AC voltage, an electrolytic capacitor connected to both output terminals of the rectifier circuit, and a power converter circuit for converting a DC current from the electrolytic capacitor into a lighting current for a discharge lamp and supplying the converted current In the discharge lamp lighting device provided,
One electrode of a discharge lamp is connected to the positive electrode of the electrolytic capacitor,
The power conversion circuit includes:
A series circuit of an inductor and a switching element connecting the other electrode of the discharge lamp and the negative electrode of the electrolytic capacitor, and a current from the inductor in the off state is routed to the inductor via the discharge lamp. Having a diode connecting both ends of the series circuit, and converting the direct current from the electrolytic capacitor to the lighting current of the discharge lamp by the on-off drive of the switching element,
Control means for controlling on-off driving of the switching element;
Zero cross detection means that generates an ON switching timing signal based on a voltage between both terminals of the switching element and sends the timing signal to the control means,
The drain side terminal of the switching element is connected to the connection point of the inductor and the diode, and the source side terminal of the switching element is connected to the negative electrode of the electrolytic capacitor,
The zero-cross detection means has a CR series circuit of a detection capacitor and a detection resistor connected in parallel to both terminals of the switching element,
When the current flowing through the inductor in the off state becomes zero, the output capacitance between the drain and source of the switching element and the inductor resonate, and the drain voltage of the switching element decreases.
The discharge lamp lighting device according to claim 1, wherein the detection capacitor takes out the change portion of the drain voltage, and the voltage of the detection resistor is sent to the control means as an ON switching timing signal . In the discharge lamp lighting device according to claim 2,
The power conversion circuit is configured to perform a switching operation in a half-bridge method or a full-bridge method,
The discharge lamp lighting device, wherein the zero-cross detection means generates an ON switching timing signal from a voltage between both terminals of a ground level side switching element having one end connected to the negative electrode side of the electrolytic capacitor. In the discharge lamp lighting device according to any one of claims 1 to 3 ,
The detection resistor of the zero-cross detection means is constituted by a series connection of a plurality of resistors, and sends the voltage divided by the plurality of resistors to the control means as an ON switching timing signal. Discharge lamp lighting device. In the discharge lamp lighting device according to any one of claims 1 to 4 ,
The zero-cross detection means has a Zener diode connected in parallel to both terminals of the detection resistor, and the voltage of the detection resistor is passed through the Zener diode to the control means as an ON switching timing signal. A discharge lamp lighting device characterized by being sent.

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