JP5159895B2 - Lighting device for in-vehicle light source - Google Patents

Description

  The present invention relates to a discharge lamp lighting device and an LED lighting device used for a light source of an in-vehicle headlamp.

As a light source for an in-vehicle headlamp (head lamp), a halogen gas is used as a filling gas for a tungsten filament bulb or a discharge lamp without a filament (HID lamp) has been used because of the demand for brightness. The brightness of the discharge lamp is recognized by the driver's preference and is widely used as a light source for a headlamp or the like, but a lighting device is required to light the discharge lamp. Similarly, LEDs that have recently begun to attract attention also require lighting devices.
For this reason, the structure as a light source becomes expensive and complicated as compared with a halogen bulb, and a light source that is always mechanically simple and inexpensive is required.

  In response to the above-mentioned demand, for example, Patent Document 1 discloses a discharge lamp in which a switching element for operating a chopper of a power supply is directly operated by an output signal of a CPU also serving as another control function without using a control IC. A lighting device is disclosed. In this device, an operation table corresponding to a lighting mode prepared in advance is referred to, and a power chopper or an output inverter circuit is directly operated by the output of the CPU to obtain an assumed lighting state. It also describes that the output voltage and output current are fed back to control the chopper and the inverter circuit in order to keep the lighting state appropriately.

JP 2004-355864 A

  In the conventional device represented by Patent Document 1, it is possible to make the lighting state almost assumed by the control using the operation table corresponding to the lighting mode, but the above-described feedback control is necessary, and the lighting state is concerned. Is not expected to always be adequate.

  In addition, when the above-described feedback control of the chopper and inverter circuit is realized by a general analog circuit, a DSP (Digital Signal Processor) level function and calculation speed are required, and the processing speed is low and the CPU is low in calculation speed. Realization by a general-purpose microcomputer equipped with is difficult. Note that Patent Document 1 does not describe any specific method for solving the above-described problem in feedback control.

  The present invention has been made to solve the above-described problems, and operates a rectangular wave that operates a switching element of a DC / DC converter by an output signal of a CPU while performing lighting control for maintaining a lighting state appropriately. On the other hand, an object of the present invention is to obtain a discharge lamp lighting device and an LED lighting device that can be realized by a microcomputer equipped with a CPU having a low processing capability and a low calculation speed.

A discharge lamp lighting device according to the present invention includes a DC / DC converter that boosts an output voltage applied from a DC power source by ON / OFF driving of a switching element, and a DC lamp from the DC / DC converter that converts an AC voltage into an AC voltage. a DC / AC inverter and supplies the output electric Nagaremata applied to the discharge lamp is actually applied should do output voltage Nagaremata value to the discharge lamp with an output voltage comparison processing unit which compares the target value of the output voltage When, in accordance with the operation cycle of the free-running timer, DC / and the rectangular wave output unit for outputting a rectangular wave as a drive signal to the switching element DC converter has, the applied output current or output voltage to the discharge lamp Indeed with feedback to applied should do output voltage Nagaremata is the value output to the comparison processing unit computes the target value of the output voltage, calculates the power to be supplied to the discharge lamp, the calculation of A lighting power control unit for changing the frequency and duty of the drive signal outputted to the DC / DC converter in accordance with the operation result in accordance with the results of power, starts at a predetermined interrupt cycle, free according to the comparison result of the comparison processing unit The lighting power control unit is applied to the light source by changing the setting of the running timer to increase or decrease the duty ratio of the rectangular wave output from the rectangular wave output unit by a predetermined amount. By setting the operation period of the free running timer based on the output voltage, the output current applied to the light source, and the power supply voltage of the DC power supply, the period of the rectangular wave output from the rectangular wave output unit is changed to DC / DC. converter is shall be and characterized by a period or periods of near operates in the critical mode.

  According to the present invention, a rectangular wave for operating the switching element of the DC / DC converter is generated using the free running timer 15 of the CPU, and feedback for realizing PWM (duty) control using this rectangular wave. The processing time is shortened by limiting the arithmetic processing in the interrupt processing to the necessary processing so that the operation is executed and completed in the timer interrupt processing at short intervals (about 10 μs) (within several μs). In this way, while performing the lighting control to keep the lighting state properly, the processing power is low compared with the operation of the rectangular wave that operates the switching element of the DC / DC converter by the output signal of the CPU. There is also an effect that it can be realized by a microcomputer equipped with a slow CPU.

It is a circuit diagram which shows the structure of the discharge lamp lighting device by Embodiment 1 of this invention. It is a figure which shows the functional block implement | achieved by CPU in FIG. 4 is a flowchart showing a flow of main routine processing according to the first embodiment. 6 is a flowchart showing a flow of interrupt routine processing according to the first embodiment. 4 is a flowchart showing a flow of a free running routine process according to the first embodiment. 3 is a diagram illustrating an operation mode of the DC / DC converter according to Embodiment 1. FIG. It is a circuit diagram which shows the level shifter and buffer in FIG. It is a circuit diagram which shows the structure of the discharge lamp lighting device by Embodiment 2 of this invention.

Hereinafter, in order to explain the present invention in more detail, modes for carrying out the present invention will be described with reference to the accompanying drawings.
Embodiment 1 FIG.
1 is a circuit diagram showing a configuration of a discharge lamp lighting device according to Embodiment 1 of the present invention. In FIG. 1, a discharge lamp lighting device 1 includes a DC / DC converter 3 that boosts a DC voltage from a DC power supply 2, a DC / AC inverter 4 that converts an output voltage of the DC / DC converter 3 into a rectangular wave AC, and an HID valve. (Discharge lamp) An igniter 5 for starting discharge, a CPU 8 for controlling the DC / DC converter 3 and the DC / AC inverter 4, comparators 9a and 9b, a D / A converter 10, a level shifter 11, and a buffer 12 are provided.

  The DC / DC converter 3 includes a flyback transformer 3a, a switching element Qa composed of a MOS field effect transistor, rectifying diodes D1 and D2, and a smoothing capacitor C2. In this DC / DC converter 3, the switching element Qa is switching-controlled by an output signal from the CPU 8 input via the level shifter 11 and the buffer 12, so that magnetic energy is stored in and discharged from the flyback transformer 3 a. The voltage generated by the back transformer 3a is rectified by the rectifying diodes D1 and D2, and smoothed by the smoothing capacitors C1 and C2, thereby generating a DC voltage.

  The DC / AC inverter 4 includes switching elements Q1 to Q4 using MOS field effect transistors and an H / B (H bridge) driver 4a. In the DC / AC inverter 4, the switching elements Q1 to Q4 are connected in an H shape and constitute an H bridge type inverter. In this configuration, switching elements Q1 and Q3 output a high potential, and switching elements Q2 and Q4 output a low potential. The H / B driver 4a drives the switching elements Q1 to Q4 according to the output signal from the CPU 8.

  The igniter 5 is a circuit that applies a high voltage pulse for starting (igniter pulse) to the output voltage of the DC / AC inverter 4 and applies it to the HID valve 6. A transformer 5b and a capacitor C3 for storing discharge start energy are provided. Note that one end of the capacitor C3 is connected to the flyback transformer 3a via the resistor R1, and one end of the gap switch 5a is also connected. The other end of the capacitor C3 is connected to an H bridge composed of switching elements Q1 to Q4 and a pulse transformer 5b. When an igniter pulse is applied to the HID bulb 6, the gas filled therein breaks down and starts discharging.

  The control unit 7 includes a CPU 8 and controls driving of the switching element Qa of the DC / DC converter 3 and the H / B driver 4a. The CPU 8 feeds back each control program for controlling the DC / DC converter 3 and the DC / AC inverter 4 and at least the output voltage Vo applied to the HID valve 6, so that the HID valve 6 is appropriately turned on. A rectangular wave is continuously output to the switching element Qa of the DC / DC converter 3 regardless of the progress of the lighting power control (lighting power control) program that gives the power (rectangular wave output). A program and a program for periodically increasing or reducing the on-duty of the continuous rectangular wave by a predetermined amount according to the output values of the comparators 9a and 9b (interrupt processing) are executed.

  The comparator (comparison processing unit, second comparator) 9a is a value of the output voltage Vo applied to the HID valve 6 and an analog value (target voltage value) of the voltage to be applied to the HID valve 6 calculated by the CPU 8. Are compared, and a digital signal (high level or low level) corresponding to the result is output. The output voltage Vo is supplied to the comparator 9a and the control unit 7 from a path connected to a connection point of resistors R2 and R3 connected in series between the output paths of the DC / DC converter 3. In the control unit 7, the output voltage Vo is converted into a digital value by an A / D converter in the CPU and taken into the CPU 8. The supply path of the output voltage Vo and the A / D converter constitute an output voltage detector.

  The comparator (comparison processing unit, first comparator) 9b is a value of the output current Io energized to the HID valve 6 and an analog value (target current value) of the current to be energized to the HID valve 6 calculated by the CPU 8. Are compared, and a digital signal (high level or low level) corresponding to the result is output. The output current Io is input to the comparator 9b through a path passing through a current detection resistor R4 provided between the DC / DC converter 3 and the DC / AC inverter 4. This current detection resistor R4 and its supply path constitute an output current detection unit. The outputs of the comparators 9a and 9b are unified by wired OR connection.

  The D / A converter 10 converts the voltage (target voltage) to be applied to the HID valve 6 and the current (target current) to be applied to the HID valve 6 calculated by the CPU 8 from a digital value to an analog value, thereby comparing the comparator 9a. , 9b, respectively. The level shifter 11 and the buffer 12 serving as level shift means convert the output rectangular wave of the CPU 8 into a rectangular wave having a voltage necessary for driving the switching element Qa.

  FIG. 2 is a diagram showing functional blocks realized by the CPU in FIG. The lighting power control unit 14 inputs the output voltage Vo and the power supply voltage Vi applied to the HID valve 6 converted into digital values by the A / D converter 13, and based on these values, the DC / DC converter 3. Is driven to control the power for lighting to light the HID bulb 6, and the H / B driver 4a is driven to control the output of the DC / AC inverter 4.

  Further, the rectangular wave output unit 16 is not affected by the progress of the control operation of the lighting power control unit 14 and is used for PWM (Pulse Width Modulation) according to the count cycle of a free running timer (hereinafter abbreviated as FRT) 15. Are continuously generated and output to the level shifter 11. The interrupt processing unit 17 starts at a predetermined period set in the interrupt timer 17a, and sets the FRT 15 according to the output values of the comparators 9a and 9b without hindering the progress of the control operation of the lighting power control unit 14. By changing, the on-duty of the continuous rectangular wave output from the rectangular wave output unit 16 is enlarged or reduced by a predetermined amount.

  The mode table 18 is table data in which the power supply voltage Vi at each timing during the lighting operation, the output voltage Vo applied to the HID bulb 6, and the appropriate frequency (cycle) of the FRT 15 corresponding to the output current Io are registered. Here, the appropriate frequency of the FRT 15 is a frequency at which the transformer 3a of the DC / DC converter 3 operates in a critical mode, which will be described later with reference to FIG. 6, by a rectangular wave output by the rectangular wave output unit 16 at the frequency. . The lighting power control unit 14 refers to the mode table 18 and changes the frequency of the FRT 15 in the operation control of the DC / DC converter 3.

  The lighting power control unit 14, the rectangular wave output unit 16, the interrupt processing unit 17, and the like are block representations of a lighting control program according to the gist of the present invention executed by the CPU 8.

  Here, the lighting power control unit 14 causes the CPU 8 to execute a main routine processing program (main program) for controlling the DC / DC converter 3 and the DC / AC inverter 4 among the lighting control programs. Realized. The interrupt processing unit 17 is realized by the CPU 8 executing an interrupt routine program (interrupt program) for performing feedback control by timer interrupt among the lighting control programs. Further, the rectangular wave output unit 16 is a CPU 8 which is a free-running routine program (self-running program) that outputs a rectangular wave according to the count cycle of the FRT 15 without being affected by the progress of the main routine process among the lighting control programs. Is realized by executing.

Next, the operation will be described.
3 is a flowchart showing the flow of the main routine process according to the first embodiment, FIG. 4 is a flowchart showing the flow of the interrupt routine process according to the first embodiment, and FIG. 5 is a free flowchart according to the first embodiment. It is a flowchart which shows the flow of a running routine process. When the CPU 8 executes the lighting control program, the lighting power control unit 14 executes the main routine processing shown in FIG. 3, and the rectangular wave output unit 16 frees the free routine shown in FIG. 5 according to the count cycle of the FRT 15. The running routine process is executed, and the interrupt processing unit 17 executes the interrupt routine process shown in FIG. 4 at a predetermined cycle of the interrupt timer 17a.

  The lighting power control unit 14 inputs the power supply voltage Vi (step ST1) and the output voltage Vo applied to the HID valve 6 (step ST2) as a main routine process of the lighting operation of the HID bulb 6. The output power value and the output current value are calculated (step ST3, step ST4). Next, the lighting power control unit 14 calculates a current value to be output from the output power calculated in step ST3 / the output voltage Vo fed back in step ST2, and outputs the current value to the D / A converter 10 (step ST5). ).

  The current value to be output calculated by the lighting power control unit 14 is converted into an analog signal by the D / A converter 10 and then input to the comparator 9b. The digital signal from the CPU 8 may be a serial output by PWM or a parallel output by ladder resistance.

  Next, the lighting power control unit 14 sets the cycle (frequency) and resolution of the FRT 15 (steps ST6 and ST7). Here, an appropriate period (frequency) (1 to 10 μs) is set in the FRT 15 with respect to the operating frequency that changes depending on the specifications of the transformer 3 a constituting the DC / DC converter 3 and the lighting state of the HID bulb 6.

  For example, regarding the specifications of the transformer 3a and the frequency of the FRT 15, if the inductance of the transformer winding is large (when a large size transformer can be used), a low operating frequency with good efficiency is selected, and if the inductance is small (the transformer is When it is necessary to reduce the size, a high operating frequency that does not saturate the core of the transformer 3a is selected.

  In addition, regarding the lighting state of the HID bulb 6 and the frequency of the FRT 15, if high power (for example, 75 W) is output immediately after lighting, the HID bulb 6 is operated in a continuous mode, which will be described later with reference to FIG. When the rated power (for example, 35 W) is output, the operation is performed at a frequency at which a critical mode described later with reference to FIG.

  The FRT 15 counts up with the above setting contents, and the rectangular wave output unit 16 continuously generates rectangular waves and outputs them to the level shifter 11 according to the counting cycle (step ST1b in FIG. 5). As a result, the switching element Qa is controlled to be switched by the drive signal based on the rectangular wave generated by the rectangular wave output unit 16 via the level shifter 11 and the buffer 12, and the DC / DC converter 3 is operated.

  In this way, the lighting power control unit 14 takes a relatively long time during the main routine process to change the period and resolution of the rectangular wave output from the rectangular wave output unit 16 according to the change in the lighting state of the HID valve 6. To change. Thereby, even an inexpensive CPU with a low clock frequency can execute the processing.

  In addition, the lighting power control unit 14 outputs an H / B drive signal to the H / B driver 4a to drive the switching elements Q1 to Q4 of the DC / AC inverter 4, thereby switching the output of the DC / AC inverter 4. (Step ST8). Then, it returns to step ST1 again and the operation mentioned above is repeated.

On the other hand, separately from the main routine processing, the interrupt processing shown in FIG. 4 is executed by the interrupt processing unit 17 at a predetermined cycle set in the interrupt timer 17a.
In order for the CPU 8 to perform feedback control similar to that of the DC / DC converter 3 using an analog circuit, it is necessary to frequently perform feedback. More specifically, a short cycle (for example, about 10 μs) is set in the interrupt timer 17a and the processing time used by the lighting power control unit 14 is left during this short timer interrupt cycle. Must be completed in a short time. A CPU with a low clock frequency can execute only a few instructions within the interrupt routine processing time, assuming that the timer interrupt processing time is about several μs.

  Therefore, in the first embodiment, in order to reduce the processing time in the interrupt routine, the number of instructions to be executed is limited as shown in FIG. Is performed.

  When the interrupt routine is activated, the interrupt processing unit 17 determines the comparison result between the output current Io or the output voltage Vo and the target value according to the output level (high level or low level) of the comparators 9a and 9b (step ST1a). . If the output current Io or the output voltage Vo is larger than the value to be output, the interrupt processing unit 17 determines that the on-duty of the rectangular wave output by the rectangular wave output unit 16 is a predetermined minimum from the setting value of the immediately preceding FRT 15. It is determined whether the value is equal to or less than the value (step ST2a).

  In step ST2a, when the on-duty of the rectangular wave is equal to or smaller than the predetermined minimum value (YES), the interrupt processing unit 17 ends the interrupt processing of this cycle. Further, when the on-duty of the rectangular wave is not equal to or less than the above minimum value (NO), the interrupt processing unit 17 performs setting to reduce (decrement) the on-duty of the rectangular wave output from the rectangular wave output unit 16 by a predetermined value. The process returns to the main routine process (return) (step ST3a).

  In step ST1a, if the output current Io or the output voltage Vo is smaller than the value to be output, the interrupt processing unit 17 starts the rectangular wave output by the rectangular wave output unit 16 from the set value of the previous FRT 15. It is determined whether or not the on-duty is equal to or greater than a predetermined maximum value (step ST4a).

  If the on-duty of the rectangular wave is greater than or equal to the predetermined maximum value (YES), the interrupt processing unit 17 completes the interrupt processing of this cycle and returns to the main routine processing (return). If the on-duty of the rectangular wave is not equal to or greater than the maximum value (NO), the interrupt processing unit 17 performs setting to increase (increment) the on-duty of the rectangular wave output from the rectangular wave output unit 16 by a predetermined value. Returning to the main routine processing (return) (step ST5a).

  In this way, output comparison results, comparison of rectangular wave on-duty and minimum / maximum values, reduction of rectangular-wave on-duty, realized by simple comparison processing or FRT15 setting value change, or By setting the instruction to execute enlargement, even a CPU with a low clock frequency can complete the interrupt routine in a processing time of about several μs. Therefore, the operation of the interrupt processing unit 17 can be performed without interfering with the processing performed by the lighting power control unit 14.

  It should be noted that an excessively large or small on-duty of the rectangular wave may cause the DC / DC converter 3 to operate abnormally. In particular, an excessive on-duty (for example, an on-duty of 100%) has little timing for discharging the magnetic energy stored in the transformer 3a, causing the core of the transformer 3a to reach magnetic saturation, and an excessive primary current is applied. For this reason, there is a risk of applying stress to the constituent elements and leading to destruction.

  Therefore, as described above, the on-duty of the rectangular wave is compared with the minimum value or the maximum value, so that the on-duty of the excessive or too small rectangular wave is not set. Thus, an inexpensive CPU having a low clock frequency can be used for lighting control of the discharge lamp lighting device 1 while avoiding abnormal operation of the DC / DC converter 3.

  In step ST1a, before the HID bulb 6 is turned on (before breakdown), the comparator 9a feeds back the output voltage Vo and compares it with the target value, whereby the maximum output voltage in the no-load state (for example, , 400V constant voltage). Further, after lighting (after breakdown), the comparator 9b feeds back the output current Io and compares it with the target value, so that the output power required for lighting the HID valve 6 in the above procedure (for example, The constant current is controlled from 75 W immediately after lighting to 35 W of steady lighting.

  As shown in FIG. 1, since the outputs of the comparators 9a and 9b are unified by wired OR connection, the number of comparison processes in the input of the CPU 8 and the interrupt routine is reduced, and the discharge lamp lighting device 1 is turned on. An inexpensive CPU having a low clock frequency can be used for the control.

  FIG. 6 is a diagram illustrating an operation mode of the DC / DC converter according to the first embodiment. In the continuous mode shown in FIG. 6A, the energy accumulated as the primary current flowing through the transformer 3a during the ON period of the switching element Qa in the drive signal (rectangular wave from the CPU 8) is all converted into the secondary current during the OFF period. This mode is a state in which magnetic energy is stored inside the transformer 3a without being emitted.

  In the critical mode shown in FIG. 6B, the energy accumulated in the transformer 3a as the primary current during the ON period of the switching element Qa is all released as the secondary current during the OFF period, and the accumulated energy and the energy released. And a mode in which there is no period during which no current flows on either the primary side or the secondary side. In the discontinuous mode shown in FIG. 6 (c), the magnetic energy accumulated in the transformer 3a as the primary current is released as the secondary current during the OFF period of the switching element Qa, and then the switching element Qa is turned on. This is a mode in which a period during which no current flows as indicated by reference symbol A occurs.

  In step ST6 of the main routine process shown in FIG. 3, the lighting power control unit 14 refers to the mode table 18 when the high power (for example, 75 W) is output immediately after the HID bulb 6 is turned on. A low frequency for operating the DC / DC converter 3 in the continuous mode is selected as the operating frequency of the FRT 15 corresponding to the power supply voltage Vi, the output voltage Vo, or the output current Io at the timing, and the cycle of the FRT 15 is set. In addition, when the rated power (for example, 35 W) is output when the HID bulb 6 is stably lit, the frequency (period) at which the DC / DC converter 3 is operated in the critical mode with reference to the mode table 18 or the vicinity thereof. The period of FRT15 used as a period is set.

  In addition, in the main routine process, the lighting power control unit 14 uses the transformer 3a of the DC / DC converter 3 in the critical mode (to be described later) in order to increase the operation efficiency of the DC / DC converter 3. Calculate the appropriate frequency (cycle) of the rectangular wave using the power supply voltage Vi, output voltage Vo or output current Io at the timing, and switch the cycle of the FRT 15 to the appropriate frequency (cycle) of the calculation result as appropriate. The converter 3 may be operated.

  In this way, the response to the critical operating frequency that varies depending on the fluctuation of the power supply voltage and the lighting state of the HID bulb 6 is controlled by controlling the discharge lamp lighting device 1 by processing over a relatively long time in the main routine processing. An inexpensive CPU with a low clock frequency can be used.

  Further, when the responsiveness of the DC / DC converter 3 is made variable in accordance with the lighting state of the HID bulb 6, the lighting power control unit 14 determines that the FRT 15 corresponding to the on-duty resolution in step ST7 of the main routine processing. The count resolution is changed, and the on-duty resolution of the rectangular wave generated by the rectangular wave output unit 16 is changed to an appropriate amount. With this operation, the range of on-duty expansion or reduction operated by one interrupt process can be changed, and the responsiveness of the DC / DC converter 3 can be changed.

  For example, when the on-duty resolution is “128” per cycle, the increase / decrease value “1” of the duty corresponds to the increase / decrease value of “2” when the on-duty resolution is “256” per cycle. Therefore, even if the increase / decrease value is fixed to “1”, if the on-duty resolution is set coarsely, the increase / decrease value when the output of the DC / DC converter 3 is quickly changed can be greatly changed. On the other hand, when fine output control of the DC / DC converter 3 is required, it can be dealt with by finely setting the on-duty resolution.

  Therefore, in steps ST3a and ST5a of the interrupt processing shown in FIG. 4, when the interrupt processing unit 17 increases or reduces the on-duty of the rectangular wave by a predetermined amount, the responsiveness of the DC / DC converter 3 is set to the interrupt processing. There is no need to consider it, and the increase / decrease value can be fixed to “1”. Thereby, the calculation load of the interrupt routine can be reduced, and even a CPU with a low clock frequency can cope with it.

  Note that the process of expanding or reducing the on-duty of the rectangular wave by a predetermined amount requires a step of setting the predetermined amount and a plurality of steps of adding the set predetermined amount. If “1” is “1”, it can be handled by one step of increment or decrement. For example, by changing the input clock and the maximum count value as a pair, the input clock of the FRT 15 is set to a low speed in a state where the lighting state of the HID bulb 6 immediately after lighting is severe without changing the cycle of the FRT 15. By making the count maximum value small, the output of the DC / DC converter 3 is made to respond quickly, and at the time of steady steady lighting, the input clock of the FRT 15 is made high-speed and slow by increasing the count maximum value. Can respond.

  Further, when the gate voltage for driving the switching element Qa of the DC / DC converter 3 is higher than the power supply voltage of the CPU 8, it is necessary to convert the output signal (rectangular wave) from the CPU 8 into the gate voltage. In the first embodiment, by providing a level shifter 11 and a buffer 12 with a simple configuration, a continuous rectangular wave output from the rectangular wave output unit 16 is converted into a gate voltage.

  FIG. 7 is a circuit diagram showing the level shifter and the buffer shown in FIG. In FIG. 7, a case where the gate voltage of the switching element Qa is about 10V and the power supply voltage of the CPU 8 is 5V is taken as an example. As shown in FIG. 7, the continuous rectangular wave output from the rectangular wave output unit 16 of the CPU 8 passes through an output path via the inverter 19 and an output path not via the inverter 19, thereby generating the rectangular wave. And a pair of inverted rectangular waves are output.

  The level shifter 11 includes a level shift transistor 20. The level shift transistor 20 is connected to the output terminal of the inverter 19 and the base terminal via the resistor Ra, and the rectangular wave output path not via the inverter 19 described above. An emitter terminal is connected, and a collector terminal is connected to a power source (10 V) via a resistor Rb. The buffer 12 includes a pair of transistors 21 and 22 in which emitter terminals and base terminals are connected to each other.

  The transistor 21 has a collector terminal connected to the power supply (10 V), and the collector terminal of the transistor 22 is grounded. The connection point between the emitter terminals of the transistors 21 and 22 is connected to the gate terminal of the switching element Qa of the DC / DC converter 3, and the connection point between the base terminals is connected to the collector terminal of the level shift transistor 20. It is connected to the connection point with the resistor Rb.

  In the rectangular wave output unit 16 of the CPU 8, a rectangular wave having a power supply voltage of 5V, a low level of 0V, and a high level of 5V is output to the level shifter 11 together with the inverted rectangular wave. In the level shifter 11, when the level shift transistor 20 is turned on, the base voltage is set to the high level and the emitter voltage is set to the low level. Further, when the level shift transistor 20 is turned off, the base voltage is set to a low level and the emitter voltage is set to a high level to reverse bias the base terminal so that carriers are rapidly extinguished to shorten the off time. .

  In the buffer 12, a rectangular wave corresponding to the on / off of the level shift transistor 20 is current-amplified by the pair of transistors 21 and 22 and supplied to the gate terminal of the switching element Qa. As a result, the switching element Qa is driven by a driving rectangular wave (low level is 0 V, high level is 10 V) having a sufficient current capacity synchronized with a rectangular wave (low level is 0 V, high level is 5 V) output from the CPU 8. Is driven.

  As described above, according to the first embodiment, a rectangular wave that operates as shown in FIGS. 1 and 2 and operates the switching element Qa of the DC / DC converter 3 is generated using the free running timer 15 of the CPU 8. Generate and execute feedback operation to realize PWM (duty) control using this rectangular wave within a short time (about 10 μs) timer interrupt processing (within several μs) and complete an interrupt. The processing time is shortened by limiting the arithmetic processing in the processing to the necessary processing. In this way, while performing the lighting control to keep the lighting state properly, the processing power is low compared with the operation of the rectangular wave that operates the switching element of the DC / DC converter by the output signal of the CPU. It can also be realized by a microcomputer equipped with a slow CPU.

  As shown in the first embodiment, the simplified program for the discharge lamp lighting device can be used because the characteristics of the discharge lamp as a connected load are generally uniformized by the standard. The discharge lamp lighting control is a one-way control from the state before lighting to stable lighting through breakdown, and there is no sudden state change or reverse state transition, so complicated control is omitted Because it can.

Embodiment 2. FIG.
FIG. 8 is a circuit diagram showing a configuration of a discharge lamp lighting device according to Embodiment 2 of the present invention. 8A, the DC / DC converter 3A is configured by connecting in parallel a DC / DC converter circuit composed of a switching element Qa1 and a transformer 3a1, and a DC / DC converter circuit composed of a switching element Qa2 and a transformer 3a2. The voltages generated by the transformers 3a1 and 3a2 are rectified by rectifying diodes D1 and D2, and smoothed by a smoothing capacitor C4 to generate a DC voltage.

  The CPU 8 includes a rectangular wave output unit (not shown) that outputs continuous rectangular waves according to the count cycle of the two systems of FRT, and the rectangular waves from these rectangular wave output units are level shifters 11a and 11b and a buffer 12a. , 12b are converted into driving rectangular waves (indicated by (A) and (B) in FIGS. 8A and 8B) and then output to the gate terminals of the switching elements Qa1 and Qa2.

  In the configuration described above, the rectangular waves from the respective rectangular wave output units of the CPU 8 have their output phases shifted as shown in FIG. By doing so, the power burdened by each DC / DC converter circuit is reduced, and the components of each DC / DC converter circuit can be made small and small capacity. Further, by shifting the operation phase of each DC / DC converter circuit, ripples in the power supply current and output current can be reduced, and the filter components can be made small and small capacity.

  As described above, according to the second embodiment, in the configuration shown in FIG. 8, the rectangular waves are output so that the output phases of the rectangular wave output units by the two systems of FRTs are shifted from each other, and two systems of DC / Since the operation of the DC converter circuit is controlled, a DC / DC converter 3A having a small ripple and noise (without protruding and using large parts) and each element can be configured.

  In the second embodiment, two DC / DC converter circuits are connected in parallel and drive control is performed with rectangular waves by two systems of FRTs. However, three or more DC / DC converter circuits and rectangular waves are used. You may comprise by an output part.

Embodiment 3 FIG.
Of the configuration of the discharge lamp lighting device described in the first embodiment with reference to FIG. Is boosted by the DC / DC converter 3 and applied to the LED to light it, whereby an LED lighting device can be configured. In this configuration, when the CPU 8 executes the lighting control program, the lighting power control unit 14 controls the DC / DC converter 3 in the main routine process shown in FIG. 3 in the first embodiment. The interrupt processing unit 17 performs feedback control based on the timer interrupt shown in FIG. 4 in the first embodiment, and the rectangular wave output unit 16 uses the FRT 15 shown in FIG. 5 in the first embodiment. A rectangular wave is output according to the count cycle.

  In the LED lighting control, the main function is to feed back the output current and supply a constant current to the LED. As in the lighting control of the discharge lamp, the lighting power is obtained by the output voltage and the output current, and the DC / DC Operating the converter is a preliminary function in preparation for abnormal situations.

  As described above, according to the third embodiment, even if the load to be connected is an LED, the characteristics of the LED are almost uniform according to the standard, and the lighting control of the LED only causes stable lighting. Since this is a control and there is no sudden state change, complicated control can be omitted. Thereby, it is possible to apply the structure shown in the said Embodiment 1, 2 to a LED lighting device. Therefore, as in the first and second embodiments, an inexpensive CPU with a low clock frequency can be used for controlling the LED lighting device.

  In the present invention, any constituent element of the embodiment can be modified or any constituent element of the embodiment can be omitted within the scope of the invention.

Claims (10)

A lighting device for an in-vehicle light source having a DC / DC converter that boosts an output voltage applied from a DC power source by ON / OFF driving of a switching element, and a control unit,
Said control unit is applied output voltage Nagaremata to the light source actual value and applied should do output voltage Nagaremata to the light source of the output voltage and the comparison processing unit which compares the target value of the output voltage,
Together with the feedback of the actual value applied should do output voltage Nagaremata to the light source of the light source to the applied output current or output voltage calculates a target value of the output voltage, and outputs it to the comparison processing unit, arithmetic A lighting power control unit that changes the frequency and duty of the drive signal output to the DC / DC converter according to the result;
A rectangular wave output unit that outputs a rectangular wave serving as a drive signal to the switching element of the DC / DC converter according to the operation cycle of the free running timer;
Starts at a predetermined interrupt cycle, and changes the set value of the free running timer according to the comparison result of the comparison processing unit, thereby expanding or reducing the duty ratio of the rectangular wave output from the rectangular wave output unit by a predetermined amount a interrupt processing unit for,
The lighting power control unit sets an operation cycle of the free running timer based on an output voltage applied to the light source, an output current applied to the light source, and a power supply voltage of the DC power supply. A lighting device for an in- vehicle light source , characterized in that a period of a rectangular wave output from the rectangular wave output unit is a period in which the DC / DC converter operates in a critical mode or a period in the vicinity thereof . Comparison processing unit includes a first comparator for the actual value of the output current applied to the light source and the target value of the light source applied should do the output current to compares, the applied output voltage to the light source A second comparator for comparing the actual value with the actual value of the output voltage to be applied to the light source;
The lighting device for an in-vehicle light source according to claim 1, wherein the output from the first and second comparators to the interrupt processing unit is one output by OR connection.   The lighting device for an in-vehicle light source according to claim 1, further comprising a D / A converter for converting an output from the lighting power control unit to the comparison processing unit from a digital value to an analog value.   The lighting device for an in-vehicle light source according to claim 1, wherein the interrupt processing unit enlarges or reduces the duty ratio of the rectangular wave output from the rectangular wave output unit within a predetermined range.   2. The lighting device for an on-vehicle light source according to claim 1, wherein the lighting power control unit changes the duty resolution of the rectangular wave output from the rectangular wave output unit by setting an operation cycle of the free running timer. The control unit includes level shift means having a transistor,
The rectangular wave output unit outputs the switching element drive signal rectangular wave and its inverted rectangular wave,
The rectangular wave is output to the emitter terminal of the level shift transistor, the inverted rectangular wave is output to the base terminal of the level shift transistor, and the level-shifted switching element drive signal is output in synchronization with the rectangular wave. The lighting device for an in-vehicle light source according to claim 1. A plurality of DC / DC converters each having a switching element; and a plurality of rectangular wave output units that individually output rectangular waves serving as drive signals to the plurality of switching elements,
The on-vehicle light source lighting device according to claim 1, wherein the plurality of rectangular wave output units output rectangular waves whose output phases are shifted from each other to the switching elements of the plurality of DC / DC converters.   The on-vehicle light source lighting device according to claim 1, wherein the on-vehicle light source is an LED. The in-vehicle light source is a discharge lamp,
The lighting device for an in-vehicle light source according to claim 1, further comprising a DC / AC inverter that converts a DC voltage from the DC / DC converter into an AC voltage and supplies the AC voltage to the discharge lamp.   A lighting device for an in-vehicle light source having a DC / DC converter that boosts an output voltage applied from a DC power source by ON / OFF driving of a switching element, and a control unit,
  In the control unit, a comparison processing unit that compares the actual value of the output current or output voltage applied to the light source and the target value of the output current or output voltage to be applied to the light source,
  The actual value of the output current or output voltage applied to the light source is fed back to calculate the target value of the output current or output voltage to be applied to the light source, output to the comparison processing unit, and according to the calculation result A lighting power control unit that changes the frequency and duty of the drive signal output to the DC / DC converter;
  A rectangular wave output unit that outputs a rectangular wave serving as a drive signal to the switching element of the DC / DC converter according to the operation cycle of the free running timer;
  Starts at a predetermined interrupt cycle, and changes the set value of the free running timer according to the comparison result of the comparison processing unit, thereby expanding or reducing the duty ratio of the rectangular wave output from the rectangular wave output unit by a predetermined amount An interrupt processing unit to
  Comprising a level shift means having a transistor;
  The rectangular wave output unit outputs a rectangular wave for switching element drive signal and its inverted rectangular wave, outputs the rectangular wave to the emitter terminal of the level shift transistor, and inverts the base wave of the level shift transistor to the base terminal An in-vehicle light source lighting device that outputs a rectangular wave and outputs a level-shifted switching element driving signal in synchronization with the rectangular wave.

Images