TWI400004B - Method and device for driving light source - Google Patents

Description

Light source driving method and light source driving device

The present invention relates to a light source driving method and a light source driving device for driving a light emitting element such as a light emitting diode with a pulse signal of a certain period.

In recent years, light sources using light-emitting diodes (LEDs) are becoming more and more widely used. For example, it is used in a backlight of a liquid crystal display device or the like, a car interior lamp or a headlight, an indoor and outdoor lighting device, and the like. The easiest way to adjust the amount of light in such an LED is to adjust the current value flowing through the LED. However, the color characteristics of the LED, because the wavelength will vary depending on the amount of current flowing, and the problem of visible color change can be seen. In order to improve such a problem, in the light amount adjustment control, a Pulse Width Modulation (PWM) method is generally used (Patent Documents 1 and 2).

Further, Patent Document 3 discloses an apparatus for detecting an overcurrent when a low voltage is applied to detect a peak current in a light source load portion to which an LED is connected.

Fig. 8 is a diagram showing the basic circuit configuration of an LED lighting circuit using a conventional PWM method. This LED lighting circuit is configured to include a current limiting resistor R0, a semiconductor switch Q0, and a PWM control circuit. The current limiting resistor R0 is a resistor that limits the current flowing through the LED, and the LEDs are connected in series. One of the series circuits is connected to the power supply line Vcc, and the other side is connected to the ground (GND) via the semiconductor switch Q0. The PWM control circuit is provided with a function of supplying a PWM signal modulated by a PWM method to a gate of the semiconductor switch Q0 to turn the semiconductor switch Q0 on (on).

Further, the driving conditions such as the driving timing of the connected light-emitting elements and the current value to be supplied are stored in the control unit in the form of a table in advance, and are set according to the form.

[Advanced technical literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2006-210835

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2007-4995

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2004-227951

However, when the lighting circuit shown in the above-mentioned Fig. 8 causes the LED to be lit for a long time, the LED itself generates heat due to the power consumed by the LED. As this heat rises, a temperature rise occurs, and a phenomenon that the rated voltage value VF decreases. When the lighting circuit is in such a situation, since the power supply is controlled by the constant voltage, the voltage across the current limiting resistor R0 and the circuit current will rise as the VF decreases, resulting in a change in the luminance of the LED. problem. In addition, the ON resistance of the semiconductor switch Q0 also changes due to the heat generation of the semiconductor switch Q0, resulting in the same problem as the temperature rise of the LED. Further, when the supply voltage fluctuates, there is a case where the fluctuation of the current value is directly changed, which is a cause of fluctuation in the luminance of the LED. In particular, since the VF of the LED which is a semiconductor is made to have a large difference due to manufacturing variations of the lot, it is not easy to maintain a certain luminance while connecting a plurality of LEDs on the load side. Continuous illumination.

Further, although the light-emitting element is generally driven by a pulse formed by turning on/off at a certain period, the pulse is not more precisely pulsed during the on-time of the on/off period of the predetermined period, and further, This pulse is controlled while maintaining the vicinity of the peak current value of the limit value of the driving ability of the light-emitting element.

Accordingly, an object of the present invention is to provide a light source driving method and a light source driving device capable of calculating a peak current value of a connected light emitting element, and defining an on period of the light emitting element based on the peak current value, and during the conducting period The maximum amplitude of the medium pulse is the peak current value, and the duty ratio (duty ratio) of the on period and the off period is made variable, whereby power consumption can be suppressed and high-luminance and stable light emission can be obtained.

In order to solve the above problems, the light source driving method of the present invention includes the steps of: supplying current to a light source load side connected to the light emitting element while detecting current, and detecting a rated voltage value; calculating an absolute absolute value of the light emitting element from the rated voltage value a maximum rated current value, and calculating a peak current value that can flow through the light-emitting element within a range that does not exceed the absolute maximum rated current value; and in order to regulate the conduction period of the light-emitting element according to the peak current value, a first drive pulse formed by a first on/off cycle that is set to be variable during a period of the period of the off period; and a further switching in the on period of the first drive pulse The maximum amplitude of the pulse is the peak current value, and the second drive pulse formed by the second on/off cycle in which the duty ratio of the on period and the off period is set to be variable; and the second drive A current driven by the pulse is applied to the load side of the light source to cause the light emitting element to continuously emit light.

Further, the light source driving device of the present invention includes: a light source load portion that connects the light emitting element; and a load capacity detecting portion that detects a rated voltage value of the light emitting element by a current supplied to the light source load portion; and a signal processing control portion according to Calculating a rated current value for causing the light-emitting element to be stably driven by the rated voltage value detected by the load capacity detecting unit, and calculating an absolute maximum rated current value unique to the light-emitting element from the rated current value, and not exceeding the absolute value Calculating and setting a peak current value that can flow through the light-emitting element within a range of a maximum rated current value; and a constant current pulse driving unit that performs pulse width modulation based on the peak current value to generate conduction by the predetermined light-emitting element The first driving pulse of the square formed by the first on/off cycle of the period, and by further switching during the on period of the first driving pulse, the maximum amplitude of the pulse is made to be the peak current value. Moreover, the duty cycle ratio during the on period and the off period is set to be the second on/off which is variable. The second period of the driving pulse is formed; the driving current of the second driving pulse is applied to the light source side of the load, whereby the continuous light emission driving the light emitting element and the light source connected to the load portion.

According to the light source driving method of the present invention, by initially detecting the rated voltage value of the light source load side to which the light emitting element is connected, and calculating the absolute maximum rated current value inherent to the light emitting element from the rated voltage value, the steady state state can be obtained. The peak current value of the light-emitting characteristics of the light-emitting element is maximized and set. Further, based on the peak current value, the maximum amplitude of the pulse is set to the peak current value by performing the switching in the on-period from the first driving pulse of the predetermined period of the light-emitting element, and the on-period is The duty ratio of the duty cycle is set to a variable second drive pulse, and a current driven by the second drive pulse is applied to the light source load side, whereby the light-emitting element is stably and continuously driven to emit light, and the whole can be achieved. Reduced power consumption.

Further, the light source driving device according to the present invention has means for detecting the load capacity of the light-emitting element connected to the load side of the light source in advance, and can generate a signal processing control unit to calculate the load capacity from the load capacity in accordance with the driving ability of the light-emitting element. The peak current value directly drives the drive pulse of the light-emitting element. Thereby, it is possible to reduce the amount of heat generation and power consumption while maintaining the driving ability of the light-emitting element at a certain level.

Hereinafter, embodiments of the light source driving method and the light source driving device of the present invention will be described in detail based on the drawings. Fig. 1 is a schematic flow chart showing a method of driving a light source according to the present invention, and Fig. 2 is a view showing an overall configuration of a light source driving device 10 of the present invention. As shown in FIG. 1, the light source driving method of the present invention detects the rated voltage value VF of a single or a plurality of light-emitting elements (LEDs) 17 connected to the light source load portion 12 when the power source is turned on (step-1). ). At the time of this detection, the light source load unit 12 is configured to measure the voltage applied between the light source load portion 12 and the electrode terminal 16 while gradually increasing the detection current from a small value. The detection current is obtained by reading a voltage value when the voltage between the electrode terminals 16 is stabilized in a state of being positioned, and obtaining a rated voltage value VF from the reading result.

Next, the CPU 18 in the signal processing control unit 15 calculates the rated current value IF required for driving the LED 17 in the steady state from the rated voltage value VF detected in the step-1. Further, the absolute maximum rated current value (IPmax) which can be circulated without destroying the LED 17 is calculated from the rated current value (IF) (step-2). The rated current value (IF) and the absolute maximum rated current value (IPmax) are calculated based on a calculation formula stored in advance in the memory of the CPU 18, and the peak current value required to actually drive the LED 17 with high efficiency is set from the calculation result. IP (IF ≦ IP < IPmax) (Step-3).

Next, a square light-emission period signal (first drive pulse) P1 (steps 4 and 3) for driving the LEDs 17 to be pulse-driven is generated based on the peak current value IP set in step-3. The first drive pulse P1 is composed of a continuous first on/off cycle T1 in which the CPU 18 performs pulse width modulation, and is a period during which the current is continuously repeated (on-period) and during which the current does not flow (off) During the break). For example, the first on/off period T1 is set to be about 200 Hz, the duty cycle ratio is 1 with respect to the on period, and the off period is 9. The aforementioned T1 is appropriately set in accordance with the driving ability of the LED 17.

The first drive pulse P1 is a square light-emitting drive signal formed by a second on/off cycle T2 in which a period of a current flowing is interrupted by a high-speed switching during a first on-period. (second drive pulse) P2 (step-5). The second on/off period T2 is set to about 300 kHz under the condition of T1 described above, and the duty ratio is the same as that of the first drive pulse P1, and is 1 for the on period and 9 for the off period. Similarly to the first drive pulse P1, the second drive pulse P2 sets the maximum amplitude and duty cycle ratio of the pulse based on the peak current value IP set by the drive capability such as the type and number of the LEDs 17. The current driven by the second drive pulse P2 is applied to the light source load side, whereby the LED 17 is driven to emit light (step -6). Further, as shown in FIG. 4, the second drive pulse P2 is a triangular-wavelength light-emission drive waveform W2 that is repeatedly charged and discharged in the second on/off cycle T2 via the RC integration circuit 27. Further, from the pulse formed by the light-emission drive waveform W2, a current generated by the triangular-wave-shaped illumination period waveform W1 which is repeatedly charged and discharged in the first on/off period T1 is output. In this manner, by applying the current generated by the illumination period waveform W1 having the peak current value IP to the maximum amplitude width to the LED 17 connected to the light source load side 12, power consumption can be suppressed, and the LED 17 can be continuously stabilized with high efficiency. The light is driven in the state.

Fig. 2 is a view showing an example of the configuration of a light source driving device for realizing the above-described light source driving method. The light source driving device 10 is configured to include a constant current pulse driving unit 13, a load capacity detecting unit 14, and a signal processing control unit 15 between the power supply source 11 and the light source load unit 12. The power supply source 11 has any of an AC global input, a DC input, and a battery input, and is a constant voltage source of the constant current pulse driving unit 13. The light source load portion 12 includes a pair of electrode terminals 16, and a single or a plurality of LEDs 17 are connected between the electrode terminals 16. The signal processing control unit 15 includes a CPU 18, and the CPU 18 stores therein a voltage value (VF), a rated current value (IF), and an absolute maximum rated current value of the LED 17 from a voltage value applied between the electrode terminals 16. (IPmax) and the calculation formula for the peak current value (IP) that is most suitable for driving.

The detection current setting unit 29 is provided in the signal processing control unit 15 to supply a detection current for detecting the load capacity (w) of the light source load unit 12 from the power supply source 11 while controlling. In order to change the current supplied from the power supply source 11 stepwise, the detection current setting unit 29 has, for example, a power (w) in which an LED corresponding to a minimum from 1 mA to 10 mA is set in advance. And a conversion form based on the rated voltage value of this power. When the light source driving device 10 is activated, the voltage conversion value is gradually increased from the lower current value to the light source load portion 12 in accordance with the conversion form, and the voltage value at the time when the LED 17 is illuminated is sequentially detected, and the voltage value is read. The standard power (w) of the aforementioned LED 17 is detected at a stable time. Based on the detected power value, the rated voltage value (VF) required to continuously illuminate the LED 17 is set.

The peak current value IP based on the aforementioned rated voltage value VF is obtained by multiplying the absolute maximum rated current value (IPmax) by a predetermined coefficient k. The coefficient k is used to define the amount of luminescence. For example, if it is set to 0.9, high-intensity luminescence in the vicinity of IPmax can be obtained. The coefficient k can be arbitrarily set as long as it does not exceed a range of 1 (0 < k < 1), and the amount of light emitted by the LED can be adjusted by setting. In addition, the setting of the coefficient k can be set by a device such as a variable resistor, a trimmer or a DIP switch connected to an external terminal (CONT) of the light source driving device 10. External settings.

In addition, in the method of setting the peak current value IP, the rated current value reference form (VF-IF form) and the absolute maximum rated current value reference form (IF-IPmax form) may be first stored in the memory of the CPU 18, and It is calculated by the program processing based on the reference form. In the VF-IF form, the rated voltage value VF and the rated current value IF based on the power value detected by the LED 17 connected to the light source load portion 12 are set, and in the IF-IPmax form, the setting is as described above. The absolute maximum rated current value IPmax corresponding to the rated current value IF.

Here, the rated voltage value VF is a voltage value at which the LED 17 connected to the light source load unit 12 can be made to emit light with a certain degree of brightness in a stable state, and the rated current value IF is a value that flows through the LED 17 at this time. In addition, the absolute maximum rated current value IPmax is the maximum allowable value for the operation of the LED 17 under certain conditions. If it exceeds this value, the component is destroyed. Therefore, it is defined as a value that does not exceed even in a short period of time. On the other hand, the peak current value IP in the present invention refers to the range of the above rated current value IF and not exceeding the absolute maximum rated current value IPmax (IF≦IP<IPmax), and the pulse drive control is performed in such a manner as to maintain the range. . Further, the rated voltage value VF and the rated current value IF vary depending on the number of the LEDs 17 and the connection form or the brightness to be set.

In the light source driving device 10 of the present invention, the signal processing control unit 15 and the constant current pulse driving unit 13 control the peak current value IP within a range satisfying the relationship of IF ≦ IP < IPmax, and the peak current value IP is made. It is constructed by switching in a predetermined duty cycle ratio.

As shown in FIG. 2, the constant current pulse drive unit 13 includes a constant current control unit 21, a first switching element Q1, a current detecting element R1, and a second switching element Q2. The constant current control unit 21 is controlled such that the current value I1 flowing through the light source load unit 12 is constantly monitored and supplied constantly. The constant current control unit 21 includes a buck-boost converter (not shown), and increases or decreases the current level from the power supply source 11 to fill the current value I1 flowing through the LED 17 connected to the light source load unit 12. Increase or decrease. Thereby, a certain current level is maintained. The first switching element Q1 is configured to generate a first driving pulse P1 composed of the first on/off cycle T1, and the current increased or decreased by the buck-boost converter at a predetermined timing via the first driving circuit 23. The signal is switched, thereby setting the ratio of the on-time to the off-period (duration ratio). The first on/off period T1 is controlled to be about 200 Hz. Further, although the duty ratio is controlled such that the LED 17 has a rated luminance, by setting the on period to about 50% or less, the amount of heat generation and power consumption can be reduced. In the present embodiment, the duty cycle ratio is also set such that the on period is 10% and the off period is 90%.

The current detecting element R1 is connected in series to the input side of the light source loading unit 12 for detecting a current value flowing through the current detecting element R1 and feeding back to the constant current control unit 21. The second switching element Q2 is for generating the second driving pulse P2 composed of the second on/off period T2, and can operate during the period in which the first switching element Q1 is turned on. The second switching element Q2 is switched at a high speed based on the switching control signal SW from the signal processing control unit 15 via the second drive circuit 24. With this switch, the second on/off period T2 is controlled to 300 kHz, the duty cycle ratio is 10% during the on period, and the off period is 90%.

The constant current pulse driving unit 13 is provided with a charge and discharge circuit 30 composed of an inductor (coil) L1 and capacitors C1 and C2 on the output side connected to the electrode terminal 16 of the light source supporting unit 12. In the charge and discharge circuit 30, the current flowing through the LEDs 17 is also charged to the capacitor C2 every time the first switching element Q1 and the second switching element Q2 are turned on. Further, during the period in which the first switching element Q1 and the second switching element Q2 are turned off, the electric charge charged in the capacitor C2 is discharged, and a current is caused to flow through the LED 17. Thereby, not only during the respective on periods of the switches of the first switching element Q1 and the second switching element Q2, the LED 17 can be continuously supplied with a constant amount of current even during the off period. Therefore, although the driving current is an intermittent square wave pulse, the LED 17 continuously flows a constant current, so that the luminance can be maintained constant and the power consumption can be reduced. Further, the coil L1 and the capacitor C1 are provided to smooth the peak current value IP flowing through the LED 17 due to the conduction of the second switching element Q2.

As shown in FIG. 2, the load capacity detecting unit 14 includes a current detecting element R2, an RC integrating circuit 27, and a differential amplifier 28. The current detecting element R2 detects a current flowing through the LED 17 by the switching of the second switching element Q2 by using a high-precision shunt resistance. In the RC integrating circuit 27, the detected current detected by the current detecting element R2 is integrated by the on/off period of the second switching element Q2. The differential amplifier 28 amplifies the difference between the signal integrated by the RC integrating circuit 27 and the reference voltage source 32, and outputs the amplified detection voltage V1. This detection voltage V1 is sent to the signal processing control unit 15.

Fig. 5 is a configuration example of the case where the protection circuit 31 is provided in the above-described charge and discharge circuit 30. The protection circuit 31 is composed of a limiting resistor R4 for limiting the charging current to the capacitor C2 and a rectifying element (diode) D1 for bypassing the discharging current, thereby preventing the light source load portion. The electrode terminal 16 of 12 flows a current when the LED 17 is connected in a state where the electrode is open and the main power source of the light source driving device 10 is turned on. According to the protection circuit 31, in the on period of the second drive pulse P2 generated by the switching of the second switching element Q2, the smoothing of the peak current value IP by the capacitor C1 and the coil L1 is started simultaneously with the capacitor C2. The charge is made while the LED 17 is lit. At this time, the limiting resistor R4 has a function of preventing the current from entering the capacitor C2 and limiting the charging current. When the shift to the second drive pulse P2 is turned off, the charge charged in the capacitor C2 is discharged to the light source load portion 12 via the diode D1, and the LED 17 is turned on.

Next, the driving operation sequence of the above-described light source driving device 10 will be described based on Figs. 2 to 6 . After the LEDs 17 are connected between the electrode terminals 16 of the light source load portion 12, the main power source is turned on to turn on. By the conduction of the main power source, the CPU 18 in the signal processing control unit 15 is reset, and the switch control signal output from the CPU 18 is turned ON. The second switching element Q2 in the constant current pulse driving unit 13 is turned off by the ON of the switching control signal. Here, the PWM signal is output from the CPU, and the first switching element Q1 is turned on via the constant current control unit 21, and the ON state is held until the detection current of the current detecting element R1 becomes 1 mA. Further, when the current detecting element R1 detects 1 mA, the PWM control is locked, and the voltage detecting unit 26 reads the voltage value between the electrode terminals 16 of the light source supporting portion 12. From the voltage value detected here, the driving power of the LED 17 connected to the light source supporting portion 12 is divided. In the CPU 18, the rated voltage value VF, the rated current value IF, and the absolute maximum rated current value IPmax are calculated from the stored calculation formula, and the optimum peak current value IP is set therefrom. In addition, the peak current value IP can also be converted from the VF-IF form and the IF-IPmax form that can be stored in the CPU 18 as described above. In the range where the peak current value IP satisfies the relationship IF ≦ IP < IPmax as described above, in particular, by maintaining the state close to IPmax, the brightness can be maximized while being illuminated in a stable state.

As described above, the rated voltage value VF can be set from the power consumption of the LED 17 by the stepwise application of the detection current from the minute value to the light source load portion 12. The following describes a specific example of using this detection method. First, the load capacity detecting unit 14 detects a voltage value when a minute current of about 1 mA supplied from the constant current pulse driving unit 13 flows through the LED 17 connected to the light source load unit 12, and sets the driving value based on the voltage value. Current. Here, in order to set appropriate driving conditions according to the type and number of LEDs connected to the light source load unit 12, first, the power consumption of the connected LEDs belonging to the load capacity is detected, and the driving current is set to match the power consumption. . As described above, since the power consumption of the LED is performed while gradually increasing the detection current from a small value, the LED 17 is not subjected to unnecessary load, and detection can be performed with high precision. From the power consumption detected here, the signal processing control unit 15 calculates an appropriate rated current value IF and peak current value IP. Furthermore, after determining these driving conditions, switching is controlled by pulse driving by constant current. The time to shift to this pulse drive control is a few microseconds after the main power supply is turned on, so the standby time is not recognized.

When the signal processing control unit 15 switches to the pulse drive control, the second switching element Q2 is turned on/off at a predetermined timing based on the peak current value IP and the switch control signal SW calculated by the signal processing control unit 15. Broken. By the switch, a current generated by the light-emission drive waveform W2 is applied to the light source load portion 12, and the light-emission drive waveform W2 is driven by the second drive at a higher speed in the first drive pulse P1 that determines the light-emitting period of the LED 17. Pulse P2 is generated. The illuminating drive waveform W2 is a triangular wave in which RC integration is performed on the basis of periodically repeating the pulse wave during the on period and the off period, thereby suppressing the overall power consumption and heat generation, and at the same time maintaining the illuminance at a higher level. The LED is driven continuously.

Fig. 7 is a diagram for comparing power consumption and heat generation when the LED of the driving method of the present invention is driven by the conventional driving method and the driving method of the present invention. Here, (a) is a conventional driving method, and (b) is a driving method of the present invention. This comparison was carried out under ambient conditions of an input voltage of AC 100 V, a temperature of 25.0 ° C, and a humidity of 43.5%. In addition, the luminance of the light is also set to the same condition. As shown in (a), in the conventional driving method, power consumption of 1.62 (W) is generated when a constant current (Irms = 0.45 A) and a constant current of VF = 3.6 V are continuously flowed, and the LED device at that time is used. The heat generated is about 115 °C. In order to achieve the same luminance as that of (a), in the case of driving with a constant current pulse, as shown in (b), the pulse peak current (IP = 2.8 A), VF = 4 V, and ON operation are set. Cycle ratio = 0.1. The power consumption at this time is 1.12 (W), and the heat generated by the LED is about 60 °C.

As can be seen from the experimental results of the above-mentioned Fig. 7, according to the LED driving method of the present invention, the power ratio can be reduced to about 69% as compared with the conventional method, and the amount of heat generation can be suppressed to about half.

Further, the LED 17 controls the width (duty cycle ratio) at which the first switching element Q1 and the second switching element Q2 in the constant current pulse driving unit 13 are turned on by the external control signal (CONT), or adjusts the RC integral. The RC time constant of the circuit 27 and the capacitance of the capacitor in the charge and discharge circuit 30 can be adjusted to adjust the amount of light emitted, the brightness of the light, and the like.

In summary, according to the light source driving method and the light source driving device of the present invention, the pulse signal of the on/off change of the peak current value IP is switched at a high speed instead of continuously supplying and connecting the load side of the light source to the load side of the light source. LED lighting control is performed by a constant current corresponding to the characteristics or the number of LEDs. Therefore, it is possible to achieve an advantageous effect of reducing the heat generation and the power consumption caused by the heat generation while maintaining the light emission level of the LED in a certain state.

In terms of the characteristics of the LED, since the forward rated voltage value VF tends to decrease due to the temperature rise, if the output voltage from the conventional constant current source is constant, the current flowing through the load portion of the light source increases. Moreover, the aforementioned rated voltage value VF is further reduced. However, as described above, by the constant current pulse driving section intermittently switching the energization time of the LED, the effect of lowering the temperature rise can be obtained, and at the same time, suppression can be obtained. The effect of changes in VF.

The load capacity detecting unit 14 of the value VF can instantaneously obtain the peak current value IP and the absolute maximum rated current value IPmax from the calculation formula or the VF-IF form and the IF-IPmax form provided in the CPU 18 in the signal processing control unit 15, the peak value. The current value IP and the absolute maximum rated current value IPmax correspond to the characteristics and the number of the LEDs 17 connected to the light source load unit 12 while the main power source is turned on. Therefore, it is not necessary to calculate the load capacity connected to the light source load unit 12 in advance, and if the required LEDs 17 are connected to the light source load portion 12, the LEDs 17 can be more appropriately and efficiently driven to emit light.

One of the LEDs 17 connected to the light source load unit 12 may be driven, and when a plurality of LEDs are connected, they may be mixed in series or in parallel or in series and in parallel. Further, in the present embodiment, the LED is driven, but the LED is not limited to the LED, and the inductive load of various motors, solenoid valve coils, actuators, etc., which can be driven by the pulsed constant current signal, is also Can be used as a drive object.

10. . . Light source driving device

11. . . Power supply

12. . . Light source load

13. . . Constant current pulse drive

14. . . Load capacity detection unit

15. . . Signal processing control unit

16. . . Electrode terminal

17. . . led

18. . . CPU

twenty one. . . Constant current control unit

twenty three. . . First drive circuit

twenty four. . . Second drive circuit

26. . . Voltage detection unit

27. . . RC integration circuit

28. . . Differential amplifier

29. . . Detection current setting unit

30. . . Charge and discharge circuit

31. . . protect the circuit

32. . . Reference voltage source

C1, C2. . . Capacitor

D1. . . Dipole

I1. . . Current value

IF. . . Rated current value

IP. . . Peak current value

IPmax. . . Absolute maximum current rating

k. . . coefficient

L1. . . Coil

P1. . . First drive pulse

P2. . . Second drive pulse

Q0. . . Semiconductor switch

Q1. . . First switching element

Q2. . . Second switching element

R0. . . Current limiting resistor

R1, R2. . . Current detecting element

R4. . . Limiting resistor

SW. . . Switch control signal

T1. . . 1st on/off cycle

T2. . . 2nd on/off cycle

V1. . . Detection voltage

Vcc. . . power cable

VF. . . Rated voltage

W1. . . Illumination period waveform

W2. . . Illuminated drive waveform

Fig. 1 is a schematic flow chart showing a method of driving a light source of the present invention.

Fig. 2 is a block diagram of a light source driving device of the present invention.

Fig. 3 is a driving timing chart of the above-described light source driving device.

Fig. 4 is an output waveform diagram of the above-described light source driving device.

Fig. 5 is a circuit diagram of a charge and discharge circuit constituting a part of the above-described light source driving device.

Fig. 6 is a timing chart of each part according to the above detailed flowchart.

Fig. 7 is a graph comparing the power consumption and the amount of heat generated when the LED is illuminated.

Fig. 8 is a circuit diagram showing the basic configuration of a conventional LED driving device.

10. . . Light source driving device

11. . . Power supply

12. . . Light source load

13. . . Constant current pulse drive

14. . . Load capacity detection unit

15. . . Signal processing control unit

16. . . Electrode terminal

17. . . led

18. . . CPU

twenty one. . . Constant current control unit

twenty three. . . First drive circuit

twenty four. . . Second drive circuit

26. . . Voltage detection unit

27. . . RC integration circuit

28. . . Differential amplifier

29. . . Detection current setting unit

30. . . Charge and discharge circuit

32. . . Reference voltage source

C1, C2. . . Capacitor

I1. . . Current value

IF. . . Rated current value

IP. . . Peak current value

IPmax. . . Absolute maximum current rating

k. . . coefficient

L1. . . Coil

P1. . . First drive pulse

P2. . . Second drive pulse

Q1. . . First switching element

Q2. . . Second switching element

R1, R2. . . Current detecting element

SW. . . Switch control signal

V1. . . Detection voltage

VF. . . Rated voltage

Claims (8)

A light source driving method comprising the steps of: supplying a control current to a light source load side connected to a light emitting element and detecting a rated voltage value; calculating an absolute maximum rated current value inherent to the light emitting element from the rated voltage value, and not Calculating a peak current value that can flow through the light-emitting element within a range that exceeds the absolute maximum rated current value; and, in order to define an on-period of the light-emitting element based on the peak current value, a duty cycle by the on-period and the off-period is generated The first drive pulse formed by the first on/off cycle that is variable; the switching is further performed during the on period of the first drive pulse, and the maximum amplitude of the pulse is the peak current. And a second drive pulse formed by setting a duty cycle ratio between the on period and the off period to a second on/off cycle; and applying a current driven by the second drive pulse to the foregoing On the light source load side, the light emitting element is continuously driven to emit light. The light source driving method according to claim 1, wherein the second driving pulse is charged and discharged by the first on/off cycle after integrating the second driving pulse in the second on/off cycle. A current is applied to the aforementioned light source load side. The method of driving a light source according to the first aspect of the invention, wherein the peak current value is a reference value of a rated voltage value which is automatically supplied to the load side of the light source by gradually increasing a current from a small value stepwise. The rated current value for causing the light-emitting element to be stably driven is calculated from the rated voltage value, and is set based on a conversion form that has been associated with the rated current value. A light source driving device comprising: a light source load portion connected to a light emitting element; and a load capacity detecting portion that detects a rated voltage value of the light emitting element by a current supplied to the light source load portion; and a signal processing control portion according to the load Calculating a rated current value detected by the capacity detecting unit, calculating a rated current value for stably driving the light emitting element, and calculating an absolute maximum rated current value inherent to the light emitting element from the rated current value, and not exceeding the absolute maximum rated current Calculating and setting a peak current value that can flow through the light-emitting element within a range of values; and a constant current pulse driving unit that performs pulse width modulation based on the peak current value to generate a conduction period by specifying the light-emitting element a first driving pulse of a square formed by the on/off cycle, and by further switching during the on period of the first driving pulse, generating a maximum amplitude of the pulse as the peak current value, and turning on The duty cycle during the period and the off period is set to the second on/off cycle that is set to be variable. To the second driving pulse; by the driving current of the second driving pulse is applied to the load side of the light source, the light emitting element and the light source connected to the continuous light emission driving unit load. The light source driving device of claim 4, wherein the signal processing control unit includes a detection current setting unit that detects the current of the load capacity of the light-emitting element from a small value stepwise. The gradual increase is automatically supplied to the light source load portion. The light source driving device according to claim 4, wherein the constant current pulse driving unit includes a charging and discharging circuit including a capacitor and an inductor on an output side connected to the light source supporting portion, and has a maximum amplitude of a pulse Charging is performed during the on period of the first drive pulse and the second drive pulse driven by the peak current value, and is discharged during the off period, whereby a current driven by the pulse signal formed by the charge and discharge is applied to the light source. Load side. The light source driving device of claim 6, wherein the charging and discharging circuit is provided with a limiting resistor for blocking or limiting a charging current to the capacitor, and a rectifying the charging current toward the light source load portion. A protection circuit formed by a polar body. The light source driving device of claim 4, wherein a plurality of light emitting elements are connected to the light source load portion.