JP4337791B2 - Discharge lamp lighting device - Google Patents

Description

  The present invention relates to a discharge lamp lighting device.

Conventionally, a discharge lamp lighting device as shown in FIG. 7 has been provided (see, for example, Patent Document 1). The discharge lamp lighting device includes a lighting circuit IN that generates electric power for lighting the discharge lamp La using a DC power source E, a starting circuit IG that generates a high voltage required when starting the discharge lamp La, and a discharge lamp La. And a filter circuit FI for reducing conduction noise to the starting circuit IG. A common mode choke L and an across-the-line capacitor C are used for the filter circuit.
JP-A-9-129379

  However, in the above-described conventional configuration, although there is an effect of protecting the starting circuit IG and the lighting circuit IN with respect to the conduction noise generated in the discharge lamp La, it is not very effective for radiation noise from the outside.

  As a method for preventing radiation noise from the outside, a method of covering with a metal shield plate has been conventionally used. However, there is a problem that an increase in size tends to be caused if a high effect is obtained by this method.

  The present invention has been made in view of the above reasons, and an object of the present invention is to provide a discharge lamp lighting device that is resistant to external radiation noise and hardly increases in size.

  The invention of claim 1 includes a DC-DC converter circuit that receives DC power and converts the voltage to output, and an inverter circuit that converts the DC power output from the DC-DC converter circuit to AC power and supplies it to a discharge lamp. A lamp current detection means for detecting a lamp current, a lamp voltage detection means for detecting a lamp voltage, a control circuit for controlling a DC-DC converter circuit, a DC-DC converter circuit, an inverter circuit, and a control circuit. A first detection means for detecting a first electrical variable detected at the first, an electrical variable detected at any of the DC-DC converter circuit, the inverter circuit, and the control circuit, wherein A second detection means for detecting a second electrical variable that is different from the static variable and is affected by the mixed electromagnetic noise, and a variation of the first electrical variable. And a noise detection means for detecting mixing of electromagnetic noise when the variation of the second electrical variable is outside the predetermined second range, and the control circuit includes at least the noise detection means. When the mixing of electromagnetic noise is not detected by the above, the DC-DC converter circuit is controlled based on the lamp current detected by the lamp current detecting means and the lamp voltage detected by the lamp voltage detecting means, and the noise detecting means When mixing of electromagnetic noise is detected, an operation that is less affected by electromagnetic noise than when no mixing of electromagnetic noise is detected by the noise detecting means is performed. Here, the operation that is not easily affected by electromagnetic noise means that a parameter that may be affected by electromagnetic noise is not used for control, or the range of control that uses a parameter that is affected by electromagnetic noise is limited, Or, it is an operation to recover from an abnormal operation that may occur due to the influence of electromagnetic noise.

  According to the present invention, when mixing of electromagnetic noise is detected by the noise detecting means, an operation that is less susceptible to the influence of electromagnetic noise is performed, so that it is also resistant to external radiation noise. In addition, since it is not necessary to add large parts, it is difficult to increase the size.

  According to a second aspect of the present invention, in the first aspect of the invention, the first detecting means detects the power supply voltage input to the DC-DC converter circuit as the first electrical variable, and the second detecting means is the second electric variable. The lamp current is detected as an electrical variable, and the DC-DC converter circuit is composed of a switching converter, and the control circuit is detected by the lamp current detection means when no noise noise is detected by the noise detection means. The duty ratio for turning on and off the switching element of the DC-DC converter circuit is controlled based on the lamp current and the lamp voltage detected by the lamp voltage detecting means, and when the noise detection means detects the mixing of electromagnetic noise, The duty ratio is set to a predetermined constant value.

  According to the present invention, when mixing of electromagnetic noise is detected, the detected value of the lamp current and the lamp voltage is not reflected in the control, so that the control of the DC-DC converter circuit is not greatly mistaken due to the influence of the electromagnetic noise. It is difficult to cause the discharge lamp to go out or an excessive load on the circuit components.

  According to a third aspect of the present invention, in the first aspect of the invention, the first detecting means detects the power supply voltage input to the DC-DC converter circuit as the first electric variable, and the second detecting means is the second electric variable. It is characterized in that an input current to the DC-DC converter circuit is detected as an electrical variable.

  According to a fourth aspect of the present invention, in the first aspect of the invention, the control circuit controls the DC-DC converter circuit based on a predetermined value when the noise detection means detects mixing of electromagnetic noise. It is characterized by.

  According to the present invention, when mixing of electromagnetic noise is detected, the detected value of the lamp current and lamp voltage is not reflected in the control of the DC-DC converter circuit, so that the control of the DC-DC converter circuit is greatly increased due to the influence of electromagnetic noise. Since there is no mistake, it is difficult to cause the discharge lamp to go out or an excessive load is applied to the circuit components.

  According to a fifth aspect of the present invention, in the first aspect of the invention, when the control circuit detects that electromagnetic noise is mixed by the noise detecting means, the control circuit is based on the lamp current and the lamp voltage detected in the past. The circuit is controlled.

  According to the present invention, since the detected value of the lamp current and the lamp voltage when the mixing of electromagnetic noise is detected is not reflected in the control of the DC-DC converter circuit, the control of the DC-DC converter circuit is controlled by the influence of the electromagnetic noise. Because there is no big mistake, it is hard to cause the discharge lamp to go out or an excessive load on the circuit components.

  According to a sixth aspect of the present invention, in the first aspect of the present invention, the DC-DC converter circuit comprises a switching converter, and the control circuit controls a duty ratio for turning on / off the switching element of the DC-DC converter circuit. When the electromagnetic noise contamination is detected by the noise detection means, the range in which the duty ratio can be taken is narrower than when the electromagnetic noise contamination is not detected by the noise detection means.

  According to the present invention, when mixing of electromagnetic noise is detected, the duty ratio range is limited. Therefore, even if the duty ratio is erroneously controlled due to the influence of electromagnetic noise, the duty ratio is too large. Since the value is not too small, it is difficult to cause the discharge lamp to turn off and an excessive load is applied to the circuit components.

  The present invention provides noise detection for detecting mixing of electromagnetic noise when the variation of the first electrical variable is smaller than a predetermined first threshold and the variation of the second electrical variable is larger than a predetermined second threshold. And the control circuit operates less susceptible to electromagnetic noise when the noise detection means detects that the electromagnetic noise is mixed than when the noise detection means does not detect the electromagnetic noise. Also, it is strong against external radiation noise. In addition, since it is not necessary to add large parts, it is difficult to increase the size.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  The present embodiment is an in-vehicle discharge lamp lighting device used for lighting a discharge lamp La such as a high-intensity discharge lamp that serves as a headlight of an automobile (not shown), as shown in FIG. A DC-DC converter circuit 1 that boosts the output of a DC power source E such as a vehicle-mounted battery, and a rectangular-wave AC power having a low frequency by inverting the polarity of the DC power output by the DC-DC converter circuit 1 The inverter circuit 2 that converts the voltage into the discharge lamp La and supplies it to the discharge lamp La, the booster circuit 3 that further boosts the output of the DC-DC converter circuit 1 when the discharge lamp La is started, and the output of the booster circuit 3 It has an igniter circuit 4 for generating a high voltage for starting, and a control circuit 5 for controlling the DC-DC converter circuit 1 and the inverter circuit 2 respectively.

  More specifically, the DC-DC converter circuit 1 includes a switching element Q1 that is on / off controlled by the control circuit 5, a flyback transformer T1 in which a primary winding is connected in series to the switching element Q1 and a DC power source E, This is a so-called flyback converter circuit comprising a diode D1 connected between both ends of the secondary winding of the flyback transformer T1 and a series circuit of a smoothing capacitor C1. Since this circuit is well known, a detailed description of its operation is omitted. In addition, a capacitor C 0 is connected to the DC power source E in parallel with the DC-DC converter circuit 1. Switching element Q1 is driven by converter drive circuit 6 controlled by control circuit 5.

  The converter drive circuit 6 has an AND circuit 61 having an output terminal connected to the gate of the switching element Q1 and one input terminal connected to the control circuit 5, and a Q terminal connected to the other input terminal of the AND circuit 61 and an S terminal. Is connected to the control circuit 5, the negative input terminal is connected to the control circuit 5, the output terminal is connected to the R terminal of the SR flip-flop circuit 62, and the DC power supply E to DC A voltage generation unit 64 that inputs a voltage corresponding to the input current IP to the DC converter circuit 1 to the positive input terminal of the comparator 63;

  The control circuit 5 includes a converter drive unit 51 that inputs a common drive signal to the S terminal of the SR flip-flop circuit 62 and the AND circuit 61. The drive signal is, for example, a rectangular wave having a constant frequency. In addition, the control circuit 5 includes a control signal output unit 52 that inputs a control signal to be described later to the negative input terminal of the comparator 63.

  Here, since a sawtooth wave having a frequency corresponding to the drive signal is input to the positive input terminal of the comparator 63, the switching element Q1 corresponds to the voltage of the control signal input to the negative input terminal of the comparator 63. It is turned on / off at a specified duty ratio. That is, the DC-DC converter circuit 1 is PWM (Pulse-Width Modulation) controlled by the control circuit 5.

  The inverter circuit 2 is a well-known full bridge circuit in which two series circuits of two switching elements Q2 to Q5 are connected in parallel between the output terminals of the DC-DC converter circuit 1. The switching elements Q2 to Q5 are turned on or off at the same time by the inverter drive circuit 7 and the switching elements Q2 to Q5 connected in series are alternately turned on and off at a low frequency. To be driven. Thereby, low frequency rectangular wave alternating current power is output from the connection point of switching elements Q2-Q5 connected in series. The output terminal of the inverter circuit 2 is connected to the discharge lamp La via the common mode choke L and the igniter circuit 4. The frequency of the output of the inverter drive circuit 7, that is, the frequency of the output of the inverter circuit 2 is controlled by an inverter control unit 53 provided in the control circuit 5. The control circuit 5 is composed of, for example, a microcomputer, and the control circuit 5, the converter drive circuit 6, and the inverter drive circuit 7 are housed in a common container (not shown) as a drive / control block CB.

  The booster circuit 3 includes a so-called Cockcroft-Walton circuit composed of four capacitors C2 to C5 and four diodes D2 to D5, and resistors R1, R2 are connected to the DC-DC converter circuit 1 and the igniter circuit 4, respectively. Connected through.

  The igniter circuit 4 includes a capacitor C6 having one end connected to the output terminal of the booster circuit 3 and the other end grounded, a transformer T2 having a secondary winding connected between the inverter circuit 2 and the discharge lamp La, And a spark gap SG connected between both ends of the capacitor C6 via a primary winding of T2.

  Next, the operation of the present invention will be described in detail with reference to the flowchart of FIG.

  When the power is turned on (S1), the capacitor C0 connected between both ends of the DC power supply E is charged. Here, the control circuit 5 includes a voltage across the capacitor C0 (hereinafter referred to as “power supply voltage”) V1 and a voltage across the smoothing capacitor C1 of the DC-DC converter circuit 1 (hereinafter referred to as “lamp voltage”). The voltages corresponding to V2 and the current flowing through the input terminal of the inverter circuit 2 (hereinafter referred to as “lamp current”) I2 are the power supply voltage input circuit 81, the lamp voltage input circuit 82, and the lamp current input, respectively. Input from the circuit 83. The control circuit 5 includes a power supply voltage detection unit 54, a lamp voltage detection unit 55, and a lamp current detection unit 56 that A / D convert voltages according to the input power supply voltage V1, lamp voltage V2, and lamp current I2, respectively. The converter drive unit 51 starts outputting a drive signal when the power supply voltage V1 falls within a predetermined startable range (for example, 9 V or more) after the power is turned on, whereby the DC-DC converter circuit 1 outputs DC power. To start. The control signal output unit 52 starts outputting a control signal based on the lamp voltage V2 and the lamp current I2.

  The generation of the control signal in the control circuit 5 will be described in detail. The control circuit 5 divides the reference power by the storage unit 57 in which the reference power corresponding to the power to be output by the DC-DC converter circuit 1 is stored, and the lamp voltage V2 output by the lamp voltage detection unit 53, and the reference current. And a second calculator 59 that calculates a control value that is the difference between the reference current and the lamp current I2 detected by the lamp current detector 54. The control signal output unit 52 generates a control signal by D / A converting the control value output from the second calculation unit 59 and inputs the control signal to the negative input terminal of the comparator 63 of the converter drive circuit 6. As described above, the duty ratio at which the converter drive circuit 6 turns on and off the switching element Q1 of the DC-DC converter circuit 1 is controlled so that the output power of the DC-DC converter circuit 1 has a magnitude corresponding to the reference power.

  Further, at the time of start-up, the first calculation unit 58 starts counting the timer with the start of the operation of the converter driving unit 51, and gradually increases the reference power to be used according to the timer counting. As a result, the output of the DC-DC converter circuit 1 is controlled so as to gradually increase in accordance with the count of the timer until the lamp voltage V2 becomes constant (for example, 400 V), and then is maintained constant. The output voltage of the DC-DC converter circuit 1 is further boosted (for example, to 800 V) by the booster circuit 3. When the capacitor C6 is charged by the output voltage of the booster circuit 3 and the voltage across the capacitor C6 eventually reaches the discharge start voltage of the spark gap SG, a high voltage is induced in the secondary winding of the transformer T2, and this voltage The discharge lamp La is started (S2).

  In the control circuit 5, for example, the start of the discharge lamp La is detected based on the lamp voltage V2 being lower than a predetermined threshold value, and the inverter control unit 53 starts the operation of the inverter drive circuit 7, and the discharge lamp La is turned on. Start supplying AC power to maintain the power.

  After starting the discharge lamp La, the abnormality detection unit 50 of the control circuit 5 first compares the lamp voltage V2 with a predetermined extinction threshold value Va (for example, 220V) (S3), and extinguishes if the lamp voltage V2 is greater than the extinction threshold value Va. For example, the output of the drive signal of the converter drive unit 51 is stopped and the switching element Q1 of the DC-DC converter circuit 1 is turned off to stop the output of the DC-DC converter circuit 1 (S4). . If the lamp voltage V2 is equal to or less than the extinction threshold value Va in step S3, the abnormality detection unit 50 determines that the extinction has not occurred, and then the power supply voltage V1 is within a predetermined lighting possible range Vb ≦ V1 ≦ Vc. It is determined whether or not (S5). The lower limit Vb of the lightable range is 6 V, for example, and the upper limit Vc of the lightable range is 20 V, for example. As a result, if the power supply voltage V1 is outside the lighting range, the output of the DC-DC converter circuit 1 is also stopped (S4).

  Then, if the power supply voltage V1 is within the lighting-enabled range in step S5, the abnormality detecting unit 50 next detects the fluctuation value ΔA of the first electrical variable A periodically detected within a predetermined first range A1 ≦ It is determined whether or not ΔA ≦ A2 (S6). The first electric variable A is, for example, the power supply voltage V1, and the fluctuation value ΔA is a difference between the first electric variable A detected most recently and the first electric variable A detected before that. The first range is, for example, -1V to 1V.

  In step S6, if the variation value ΔA of the first electrical variable is outside the first range, the first computation unit 58 and the second computation unit 59, as already described, use the lamp voltage V2 and the lamp current I2. Based on the above, a control value is calculated (S7). Next, the control signal output unit 52 inputs a control signal having a voltage corresponding to the control value to the comparator 63 of the converter drive circuit 6 (S8), and returns to step S3.

  In step S6, if the variation value ΔA of the first electrical variable is within the first range, the abnormality detecting unit 50 determines that the variation value ΔB of the second electrical variable B that is periodically detected is a predetermined value. In the second range, it is determined whether B1 ≦ ΔB ≦ B2 (S9). The second electric variable B is, for example, the lamp current I2, and the fluctuation value ΔB is the difference between the second electric variable B detected most recently and the second electric variable B detected before that. The second range is, for example, -20% to 20% with respect to the lamp current I2 to be maintained. If the variation value ΔB of the second electrical variable B is within a predetermined second range B1 ≦ ΔB ≦ B2, the process also proceeds to step S7.

  In step S9, if the variation value ΔB of the second electrical variable B is outside the second range, the abnormality detection unit 50 determines that electromagnetic noise has been mixed, and determines a control value for the second calculation unit 58. Is set to a predetermined constant value (S10), and the process proceeds to step S8. As a result, the control circuit 5 outputs a control signal indicating a constant duty ratio to the converter drive circuit 6. That is, the control circuit 5 is also a noise detection unit. That is, mixing of electromagnetic noise is detected based on the large variation of the second electrical variable B even though the variation of the first electrical variable A is small, and when the mixing of the electromagnetic noise is detected, the lamp The control based on the current I2 and the lamp voltage V2 is not performed.

  According to the above configuration, even if the detected values of the lamp current I2 and the lamp voltage V2 are affected by electromagnetic noise, they are not reflected in the control. Therefore, the control of the DC-DC converter circuit 1 may be greatly mistaken due to the influence of electromagnetic noise. Therefore, it is difficult for the discharge lamp La to disappear or an excessive load is applied to the circuit components. Since the above effect is exhibited regardless of the type of electromagnetic noise, it is strong against external radiation noise. Moreover, since it is not necessary to add particularly large parts, it is difficult to increase the size.

  The first electrical variable A is not limited to the power supply voltage V1 as long as it is an electrical variable detected anywhere in the discharge lamp lighting device. For example, the lamp voltage V2 may be used. The second electrical variable B is different from the first electrical variable B among the electrical variables detected anywhere in the discharge lamp lighting device and is affected by electromagnetic noise. For example, the lamp voltage V2 or a reference voltage used in a general microcomputer may be used instead of the lamp current I2. Alternatively, as shown in FIG. 3, an input current input circuit 84 that outputs a voltage corresponding to the input current I2 to the DC-DC converter circuit 1 is provided in the drive / control block CB, and the control circuit 5 includes an input current input circuit. An input current detection unit 5a for A / D converting the output of 84 and inputting the output to the abnormality detection unit 50 may be provided, and the input current I2 may be used as the second electrical variable B.

  When the lamp voltage V2 is used as the first electrical variable A, the first range is, for example, −5% to 5% with respect to the lamp voltage V2 to be maintained. When the lamp voltage V2 is used as the second electrical variable B, the second range is set to, for example, -20% to 20% with respect to the lamp voltage to be maintained. Further, when the reference voltage or input current I2 is used as the second electrical variable B, the second range is, for example, −5% to 5% with respect to the normal reference voltage or input current I2.

  In addition, as an operation when mixing of electromagnetic noise is detected, instead of making the control value directly constant by an instruction to the second calculation unit 59, the lamp current I2 and the lamp voltage are set as in step S11 of FIG. The control value may be constant by using fixed values If and Vf as V2.

  Further, instead of using a constant value as the control value, the lamp current I2, and the lamp voltage V2, the first calculation unit 58 and the second calculation unit 59 hold the lamp current I2 and the lamp voltage V2 used every step S7. When electromagnetic noise contamination is detected, the lamp current I2 and the lamp voltage V2 detected before the electromagnetic noise contamination is detected (for example, once before) according to an instruction from the abnormality detection unit 50 are used. Also good.

  Alternatively, instead of making the control value constant, the electromagnetic noise is set after setting a control value range narrower than the range that the control value can take when electromagnetic noise contamination is not detected, as in step S12 of FIG. The control value is calculated in the same manner as when no contamination is detected, and when the obtained control value exceeds the upper limit value of the control value range, the control value is obtained as the upper limit value of the control value range. When the control value falls below the lower limit value of the control value range, the control value may be the lower limit value of the control value range. If this configuration is adopted, even if the error of the lamp current I2 and the lamp voltage V2 is increased due to electromagnetic noise, the control value does not become an extremely large value or a small value. It is hard to happen that it disappears or an excessive load is applied to circuit components.

  Alternatively, as shown in step S13 of FIG. 6, the disappearance may be detected when mixing of electromagnetic noise is detected. In this case, when the determination method of extinction when mixing of electromagnetic noise is detected is the same as in step S3, the extinction threshold value Vd used is set lower than the extinction threshold value Va in step S3, and more than in step S3. Ensure disappearance is detected with high accuracy. When the extinction is detected in step S13, for example, the process returns to step S2 to start the discharge lamp La again. That is, it recovers from the disappearance caused by the influence of electromagnetic noise. At the time of extinction due to the life of the discharge lamp La, restarting may cause an excessive load on the circuit components. On the other hand, when the extinction occurs due to an abnormal value of the control signal due to electromagnetic noise The discharge lamp La may be turned on, and if it is an on-vehicle headlamp, it can be said that it is safer to turn it on as much as possible as in the above configuration.

  4 to 6 are the same as those shown in FIG. 2 except for the above-described portions, and thus description of common parts is omitted.

It is a circuit diagram showing an embodiment of the present invention. It is a flowchart which shows operation | movement same as the above. It is a circuit diagram which shows another form same as the above. It is a flowchart which shows operation | movement of another form same as the above. It is a flowchart which shows operation | movement of another form same as the above. It is a flowchart which shows operation | movement of another form same as the above. It is a block diagram which shows a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 DC-DC converter circuit 2 Inverter circuit 5 Control circuit La Discharge lamp

Claims (6)

A DC-DC converter circuit which receives DC power and converts the voltage to output;
An inverter circuit that converts the DC power output from the DC-DC converter circuit into AC power and supplies the AC power to the discharge lamp;
Lamp current detecting means for detecting lamp current; lamp voltage detecting means for detecting lamp voltage;
A control circuit for controlling the DC-DC converter circuit;
One of a first detection means for detecting a first electrical variable detected in any of the DC-DC converter circuit, the inverter circuit, and the control circuit, and the DC-DC converter circuit, the inverter circuit, and the control circuit. A second detection means for detecting a second electrical variable that is different from the first electrical variable and is affected by the mixed electromagnetic noise, detected in step (b).
Noise detecting means for detecting mixing of electromagnetic noise when the variation of the first electrical variable is within a predetermined first range and the variation of the second electrical variable is outside the predetermined second range; Prepared,
The control circuit is a DC-DC converter circuit based on the lamp current detected by the lamp current detecting means and the lamp voltage detected by the lamp voltage detecting means, at least when mixing of electromagnetic noise is not detected by the noise detecting means. When the electromagnetic noise contamination is detected by the noise detection means, the operation is less affected by the electromagnetic noise than when the electromagnetic noise contamination is not detected by the noise detection means. Discharge lamp lighting device. The first detection means detects the power supply voltage input to the DC-DC converter circuit as the first electrical variable,
The second detection means detects the lamp current as a second electrical variable,
The DC-DC converter circuit consists of a switching converter,
When the noise detection means does not detect mixing of electromagnetic noise, the control circuit is configured to detect the DC-DC converter circuit based on the lamp current detected by the lamp current detection means and the lamp voltage detected by the lamp voltage detection means. Control the duty ratio to turn on and off the switching element,
2. The discharge lamp lighting device according to claim 1, wherein when the noise detection means detects mixing of electromagnetic noise, the duty ratio is set to a predetermined value. The first detection means detects the power supply voltage input to the DC-DC converter circuit as the first electrical variable,
2. The discharge lamp lighting device according to claim 1, wherein the second detection means detects an input current to the DC-DC converter circuit as the second electrical variable.   2. The discharge lamp lighting device according to claim 1, wherein the control circuit controls the DC-DC converter circuit based on a predetermined value when mixing of electromagnetic noise is detected by the noise detecting means.   2. The control circuit according to claim 1, wherein the control circuit controls the DC-DC converter circuit based on the lamp current and the lamp voltage detected in the past when mixing of electromagnetic noise is detected by the noise detecting means. Discharge lamp lighting device. The DC-DC converter circuit consists of a switching converter,
The control circuit controls the duty ratio for turning on and off the switching element of the DC-DC converter circuit,
2. The range that the duty ratio can take is narrower when electromagnetic noise contamination is detected by the noise detection means than when electromagnetic noise contamination is not detected by the noise detection means. The discharge lamp lighting device described.

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