JP4619167B2 - Discharge lamp lighting device - Google Patents

Description

  The present invention relates to a discharge lamp lighting device for lighting a discharge lamp with high frequency power by an inverter.

  Conventionally, a discharge lamp has been provided with a preheating control circuit that controls the current flowing in the filament in the discharge lamp to preheat by preheating and starting the discharge lamp and controlling the current flowing in the filament in the discharge lamp during lighting. An apparatus is disclosed (for example, see Patent Document 1). In this discharge lamp lighting device, the operating frequency of the inverter circuit at the time of preheating the discharge lamp is set in a region that is sufficiently higher than the resonance frequency of the resonance inductor and the resonance capacitor. The voltage applied from the inverter circuit to the discharge lamp is set to a value that is sufficiently lower than the voltage required for starting, so that the discharge lamp is not started.

  In the preheating transformer in this preheating control circuit, a current flows by a high frequency output of the inverter circuit through a capacitor and a bidirectional preheating switch element as a preheating switch element. The preheating is performed by the filament current flowing from the preheating winding of the lamp through the filament current limiting capacitor to the filament of the discharge lamp.

  Then, when a predetermined time has elapsed, the operation state of the inverter circuit becomes the start operation state, and the operation frequency is set to an area where a voltage necessary for starting the discharge lamp can be applied. It comes to light up. As a result, the lamp current flows to the discharge lamp. Immediately after starting the discharge lamp, the preheating switch element is kept on, and the filament current continues to flow through the filament of the discharge lamp. Thereafter, when the discharge lamp is turned on, the preheating switch element is controlled to be turned off.

JP 2001-351790 (page 4, FIG. 1)

  When the discharge lamp is lit, the discharge lamp lighting device turns off the preheating switch element of the preheating control circuit so that the filament current flowing from the preheating winding of the preheating transformer to the filament of the discharge lamp is cut off. It has become. In this case, when the discharge lamp is turned on after the discharge lamp is replaced, it is necessary to preheat and start again, and the objectives of reducing power consumption and shortening time cannot be achieved.

  Further, if the discharge lamp is removed during the preheating / starting state after replacement of the discharge lamp, a loop may be formed in which a current circulates in the preheating control circuit. Then, an overvoltage that does not occur during normal operation is applied to the inverter control circuit that controls the inverter circuit. As a result, there is a problem that a failure occurs in the inverter control circuit.

  The present invention has been made in order to solve the above-described problems, and reduces power consumption and time without complicating the circuit configuration, and releases it during the preheating / starting state after replacing the discharge lamp. An object of the present invention is to provide a discharge lamp lighting device capable of protecting an inverter control integrated circuit even when the electric lamp is removed.

  The discharge lamp lighting device according to the present invention converts an inverter control integrated circuit that outputs an oscillation output signal and a DC voltage into a high-frequency voltage by turning on and off the switching element by the oscillation output signal output from the inverter control integrated circuit. A high-frequency inverter circuit that is supplied to the discharge lamp, a detection resistor that is connected between the switching element and a ground potential and detects a current flowing through the discharge lamp, and the high-frequency inverter circuit performs preheating / starting operation of the discharge lamp. A preheating control circuit that preheats the filament of the discharge lamp by flowing current when it is in a state, and the negative potential side of the preheating control circuit is connected between the switching element and the detection resistor. Features.

  The discharge lamp lighting device according to the present invention includes an inverter control integrated circuit that outputs an oscillation output signal, and a switching element that is turned on / off by the oscillation output signal output from the inverter control integrated circuit to convert a DC voltage into a high-frequency voltage. A high-frequency inverter circuit that is converted into a discharge lamp and supplied to a discharge lamp, a bootstrap circuit including a bootstrap capacitor connected between the inverter control integrated circuit and the high-frequency inverter circuit, and the switching element and a ground potential A detection resistor connected between them for detecting the current flowing in the discharge lamp, and a preheating control circuit for preheating by supplying a current to the filament of the discharge lamp when the high frequency inverter circuit is in a preheating / starting operation state of the discharge lamp A constant voltage element is connected in parallel to the bootstrap capacitor.

  The discharge lamp lighting device according to the present invention converts an inverter control integrated circuit that outputs an oscillation output signal and a DC voltage into a high-frequency voltage by turning on and off the switching element by the oscillation output signal output from the inverter control integrated circuit. A high-frequency inverter circuit that is supplied to the discharge lamp, a detection resistor that is connected between the switching element and a ground potential and detects a current flowing through the discharge lamp, and the high-frequency inverter circuit performs preheating / starting operation of the discharge lamp. A preheating control circuit that preheats by flowing current to the filament of the discharge lamp when in a state, and the negative potential side of the preheating control circuit is connected between the switching element and the detection resistor, Reduces power consumption and time without complicating the circuit configuration, and even if the discharge lamp is removed during preheating / starting after the discharge lamp is replaced. It can be protected over motor control integrated circuits.

  The discharge lamp lighting device according to the present invention includes an inverter control integrated circuit that outputs an oscillation output signal, and a switching element that is turned on / off by the oscillation output signal output from the inverter control integrated circuit to convert a DC voltage into a high-frequency voltage. A high-frequency inverter circuit that is converted into a discharge lamp and supplied to a discharge lamp, a bootstrap circuit including a bootstrap capacitor connected between the inverter control integrated circuit and the high-frequency inverter circuit, and the switching element and a ground potential A detection resistor connected between them for detecting the current flowing in the discharge lamp, and a preheating control circuit for preheating by supplying a current to the filament of the discharge lamp when the high frequency inverter circuit is in a preheating / starting operation state of the discharge lamp Since the constant voltage element is connected in parallel to the bootstrap capacitor, the circuit configuration is complicated. It is possible to shorten the reduction and time of the power consumption, the discharge lamp during preheat-start state after replacement of the discharge lamp to protect the inverter control IC be detached without.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Embodiment 1 FIG.
FIG. 1 is a circuit diagram showing a circuit configuration of a discharge lamp lighting device 50 according to Embodiment 1 of the present invention. The discharge lamp lighting device 50 includes a high-frequency inverter circuit 1 that converts a DC voltage from a DC power source (including a power source obtained by rectifying and smoothing a commercial power source) E into a high-frequency voltage, an inverter control integrated circuit IC2, and an output of the high-frequency inverter circuit 1. The load circuit 2 limits the lamp current of the discharge lamp L connected between the ends, and the preheating control circuit 3 controls the preheating / starting of the discharge lamp L.

  The high-frequency inverter circuit 1 includes a MOSFET Q4 and a MOSFET Q5 that are switching elements that perform switching. MOSFET Q4 has a drain connected to a DC voltage power source, a source connected to the drain of MOSFET Q5, and a gate connected to the HVG terminal of inverter control integrated circuit IC2. The source of the MOSFET Q5 is grounded via the detection resistor R3, and the gate is connected to the LVG terminal of the inverter control integrated circuit IC2.

  The inverter control integrated circuit IC2 controls the MOSFET Q4 and the MOSFET Q5 of the high frequency inverter circuit 1. That is, an oscillation output signal that is an on / off control signal of the MOSFET Q4 is output from an HVG (high side output) terminal, and an oscillation output signal that is an on / off control signal of the MOSFET Q5 is output from an LVG (low side output) terminal, The MOSFET Q4 and the MOSFET Q5 are on / off controlled alternately.

  Further, the inverter control integrated circuit IC2 has a Vboot terminal, an OUT terminal, an OPin− terminal, and a GND terminal. The Vboot terminal functions as an output bootstrap terminal, and is a terminal for operating a high-side drive circuit (not shown). The OUT terminal functions as a high-side reference terminal and determines the reference potential of the high-side drive circuit. The OPin− terminal functions as a sense amplifier inverting input terminal, and is used here as an abnormality detection terminal. The GND terminal is an abbreviation for the ground terminal, and means grounding. The bootstrap circuit 5 is configured by connecting a capacitor C76 between the Vboot terminal and the OUT terminal.

  The bootstrap circuit 5 is a circuit type that operates a high-side drive circuit (high-side driver) (not shown) with the voltage charged by the capacitor C76. That is, the capacitor C76 is charged while the MOSFET Q5 is turned on, and the voltage is input to the high-side drive circuit via the OUT terminal. In the bootstrap circuit 5, the gate of the MOSFET Q4 is boosted as the output voltage rises, and the high level is raised to the power supply voltage.

  Therefore, when the bootstrap circuit 5 is used, the gate voltage of the MOSFET Q4 becomes high, and the charging speed is increased. The capacitor C76 functions as a bootstrap capacitor and is connected to the inverter control integrated circuit IC2 and the high frequency inverter circuit 1.

  The preheating control circuit 3 includes a capacitor C80, a preheating transformer T3-1, and a MOSFET Q6 that is a switching element connected in series. Further, the preheating control circuit 3 is provided with a preheating control integrated circuit IC3 that controls on / off of the MOSFET Q6. Note that the preheat control integrated circuit IC3 controls the MOSFET Q6 to be turned off after a predetermined time (several seconds) has elapsed since the discharge lamp L was turned on. Even if the MOSFET Q6 is controlled to be off, a current flows through the capacitor 81. Further, the preheating control circuit 3 includes a preheating transformer T3-2 connected in series with the capacitor C2 and a preheating transformer T3-3 connected in series with the capacitor C3.

  The source of the MOSFET Q6 constituting the preheating control circuit 3 is connected to the source of the MOSFET Q5 without being grounded. That is, since the negative potential side of the preheating control circuit 3 is connected between the MOSFET Q5 and the detection resistor R3, the current passing through the MOSFET Q6 is circulated to the high frequency inverter circuit 1 without being grounded. (Arrow C). The current that has passed through the MOSFET Q6 also flows through the resistor R4 to the OPin-terminal of the inverter control integrated circuit IC2. Based on this current, the inverter control integrated circuit IC2 can detect an abnormality occurring in the load circuit 2 or the preheating control circuit 3.

  The load circuit 2 is connected between the output terminals of the high-frequency inverter circuit 1, and includes a ballast choke T2, a discharge lamp L connected in series to the ballast choke T2, and a resonance ( Starting) and a capacitor C1. The ballast choke T2 generally functions as a resonance inductor. The discharge lamp L may be a hot cathode discharge lamp. The resonance (starting) capacitor C1 limits the voltage applied to the discharge lamp L by utilizing the resonance characteristics with the ballast choke T2. The load circuit 2 includes a capacitor C10 and a capacitor C11. Thereby, even if the discharge lamp L is removed, an electric current flows.

  Next, the discharge lamp L lighting processing operation of the discharge lamp lighting device 50 will be described. First, when the DC power source E is turned on, a voltage is applied to the inverter control integrated circuit IC2 via the bootstrap circuit 5. When this voltage rises and reaches the operating voltage of the inverter control integrated circuit IC2, the inverter control integrated circuit IC2 starts oscillating. Due to this oscillation, a high frequency voltage is applied from the HVG terminal of the inverter control integrated circuit IC2 to the gate of the MOSFET Q4 and the MOSFET Q4 is turned on. Next, a high frequency voltage is applied from the LVG terminal to the gate of the MOSFET Q5 and the MOSFET Q5 is turned on. Is done.

  That is, the inverter control integrated circuit IC2 controls the MOSFET Q4 and the MOSFET Q5 alternately on and off so that the high frequency inverter circuit 1 oscillates at a high frequency. Then, LC series resonance occurs in the ballast choke T2 and the resonance (starting) capacitor C1. Due to this resonance, a resonance high voltage is generated in the resonance (starting) capacitor C1, and the discharge lamp L is lit by this resonance high voltage.

  Next, the discharge lamp L pre-heat treatment operation of the discharge lamp lighting device 50 will be described. Preheating is performed before the discharge lamp L is turned on, and enables the discharge lamp L to be turned on quickly and in a short time. In the preheating control circuit 3, the operating frequency of the high-frequency inverter circuit 1 during preheating is set to a region sufficiently higher than the resonance frequency of the ballast choke T2 and the resonance (starting) capacitor C1. Since the voltage applied from the high frequency inverter circuit 1 to the discharge lamp L is set to a value sufficiently lower than the voltage required for starting, even if the discharge lamp lighting device 50 starts operating, The discharge lamp L is not turned on.

  That is, during preheating, the MOSFET Q6 is turned on by the preheating control integrated circuit IC3, and a current flows to the preheating transformer T3-1 by the high frequency output of the high frequency inverter circuit 1 through the capacitor C80, so that the preheating transformer T3. -2 and the preheating transformer T3-3 also generate a voltage, and the current flows to the filament (not shown) of the discharge lamp L via the filament current limiting capacitors C2 and C3 so that the preheating is performed. .

  During the lighting of the discharge lamp L, the DC voltage is input to the OPin− terminal. This voltage is set to a value lower than the operating voltage of the OPin− terminal, and the inverter control integrated circuit IC2 can continue normal oscillation. On the other hand, at this time, a high-frequency voltage (positive voltage) is generated in the detection resistor R3. Further, the preheating control integrated circuit IC3 of the preheating control circuit 3 controls the MOSFET Q6 to be turned off when a predetermined time elapses after the discharge lamp L is turned on.

  By the way, if the source of the MOSFET Q6 of the preheating control circuit 3 is grounded, the current flowing through the preheating control circuit 3 when the discharge lamp L is removed flows through the GND, the detection resistor R3, the MOSFET Q5, and again the preheating control circuit 3 It will form a loop to return to. That is, a negative voltage is generated in the detection resistor R3 with respect to GND. Under such a state, when the MOSFET Q5 is turned on, a negative voltage is also generated at the OUT terminal of the inverter control integrated circuit IC2 with respect to GND.

  As a result, the voltage generated at the OUT terminal and the detection resistor R3 is relatively increased. That is, a voltage (overvoltage) that is relatively larger than a voltage difference set in advance between the HVG terminal and the OUT terminal. In that case, the overvoltage is also applied between the OUT terminal and the Vboot terminal, and the Vboot terminal and the inverter control integrated circuit IC2 may break down.

  Therefore, the discharge lamp lighting device 50 according to the present invention can be lit quickly without applying a starting voltage more than necessary to the discharge lamp L even after replacement of the discharge lamp L without having a complicated circuit configuration. Even if the discharge lamp L is removed during preheating / starting of the discharge lamp L, the source of the MOSFET Q6 is not grounded to GND, so that an overvoltage is applied to the Vboot terminal and the inverter control integrated circuit IC2. There is nothing. In the present embodiment, the inverter control integrated circuit IC2 and the preheating control integrated circuit IC3 are shown separately as an example, but the inverter control integrated circuit IC2 has the function of the preheating control integrated circuit IC3. You may comprise as one.

Embodiment 2. FIG.
FIG. 2 is a circuit diagram showing a circuit configuration of a discharge lamp lighting device 50a according to Embodiment 2 of the present invention. Components common to the first embodiment shown in FIG. 1 are denoted by the same reference numerals and description thereof is omitted. The discharge lamp lighting device 50a is configured to connect a constant voltage diode (Zener diode) DZ171 that is a constant voltage element in parallel with a capacitor C76 that functions as a bootstrap capacitor. The constant voltage diode DZ171 allows a current to flow when a predetermined voltage is reached.

  Therefore, even if the source of the MOSFET Q6 of the preheating control circuit 3 is grounded to GND, an overvoltage between the HVG terminal and the OUT terminal generated due to the negative voltage generated in the detection resistor R3 is not applied to the Vboot terminal. become. That is, failure of the Vboot terminal and the inverter control integrated circuit IC2 can be prevented. With such a configuration, even if a negative voltage is generated in the detection resistor R3, no overvoltage is applied to the Vboot terminal of the inverter control integrated circuit IC2.

  In other words, it is only necessary to add the constant voltage diode DZ171, and without complicating the circuit configuration, after the replacement of the discharge lamp L, it is possible to quickly turn on the discharge lamp L after the replacement without applying more than necessary. At the same time, it is possible to prevent a failure occurring in the inverter control integrated circuit IC2.

  In the embodiment, the case where the switching element is a MOSFET has been described as an example. However, the present invention is not limited to this, and may be a switching element such as an FET or an IGBT. In the embodiment, the case where the constant voltage (zener) diode DZ171 is provided in the bootstrap circuit 5 has been described as an example. However, the present invention is not limited to this, and a varistor or the like may be used. In the present embodiment, the inverter control integrated circuit IC2 and the preheating control integrated circuit IC3 are shown separately as an example, but the inverter control integrated circuit IC2 has the function of the preheating control integrated circuit IC3. You may comprise as one.

1 is a circuit diagram illustrating a circuit configuration of a discharge lamp lighting device according to Embodiment 1. FIG. 5 is a circuit diagram showing a circuit configuration of a discharge lamp lighting device according to Embodiment 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 High frequency inverter circuit, 2 Load circuit, 3 Preheating control circuit, 5 Bootstrap part, 50 Discharge lamp lighting device, 50a Discharge lamp lighting device, IC2 Inverter control integrated circuit, IC3 Preheating control integrated circuit, Q4 MOSFET, Q5 MOSFET, Q6 MOSFET, C1 resonance (starting) capacitor, C2 filament current limiting capacitor, C3 filament current limiting capacitor, C10 capacitor, C11 capacitor, C76 bootstrap capacitor, C80 preheating capacitor, T2 ballast choke, T3-1 preheating transformer , T3-2 preheating transformer, T3-3 preheating transformer, R3 detection resistance, R4 resistance, E DC power supply, L discharge lamp, DZ171 constant voltage (zener) diode.

Claims (3)

An inverter control integrated circuit for outputting an oscillation output signal;
A high-frequency inverter circuit that turns on and off a switching element with an oscillation output signal output from the inverter control integrated circuit, converts a DC voltage into a high-frequency voltage, and supplies it to a discharge lamp;
A detection resistor connected between the switching element and a ground potential to detect a current flowing in the discharge lamp;
A preheating control circuit for preheating by supplying a current to the filament of the discharge lamp when the high frequency inverter circuit is in a preheating / starting operation state of the discharge lamp,
The negative potential side of the preheating control circuit is
The discharge lamp lighting device is connected between the switching element and the detection resistor. An inverter control integrated circuit for outputting an oscillation output signal;
A high-frequency inverter circuit that turns on and off a switching element with an oscillation output signal output from the inverter control integrated circuit, converts a DC voltage into a high-frequency voltage, and supplies it to a discharge lamp;
A bootstrap circuit comprising a bootstrap capacitor connected between the inverter control integrated circuit and the high-frequency inverter circuit;
A detection resistor connected between the switching element and a ground potential to detect a current flowing in the discharge lamp;
A preheating control circuit for preheating by supplying a current to the filament of the discharge lamp when the high frequency inverter circuit is in a preheating / starting operation state of the discharge lamp,
A discharge lamp lighting device comprising a constant voltage element connected in parallel to the bootstrap capacitor. The discharge lamp lighting device according to claim 2, wherein the constant voltage element is a Zener diode.

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