JP2006244878A - Lighting control device of vehicular lighting fixture - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lighting control device of vehicular lighting fixture performing switching operation depending on a current boundary even if a circuit is simply constituted. <P>SOLUTION: A transistor 20 is turned on and off by output of a switching signal generating circuit 30. When the transistor 20 is turned on, the energy accumulated in a transformer T1 is released to a rectifying-smoothing circuit 14, and when the transistor 20 is turned off, and a non-current period is generated at secondary side of the transistor T1 during the process that a transistor 46 is turned off, and charging voltage of a capacitor C3 is increased, a capacitor C4 is charged in accordance with the length of the non-current period, current flows through a transistor 48 in accordance with the charging voltage, and the charging voltage of the capacitor 3 is increased. When the voltage of the capacitor 3 exceeds a standard voltage 60, the output of a comparator 58 becomes low level, and a cathode of a diode D5 is grounded, the switching signal is reversed from a low-level to a high-level, and an off-period of the switching signal is shortened. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a lighting control device for a vehicular lamp, and more particularly to a lighting control device for a vehicular lamp configured to control lighting of a semiconductor light source including a semiconductor light emitting element.

  2. Description of the Related Art Conventionally, a vehicular lamp using a semiconductor light emitting element such as an LED (Light Emitting Diode) as a light source is known, and this type of vehicular lamp has a lighting control circuit for controlling the lighting of the LED. Has been implemented.

  In configuring the lighting control circuit, for example, as one element of a multi-output switching power supply device, one that controls lighting of an LED using a DC-DC converter has been proposed (see Patent Document 1). This DC-DC converter is connected to a high-frequency forward transformer having three secondary windings, a transistor as a switching element connected in series to the primary winding of the transformer, and each secondary winding of the forward transformer. And a switching control circuit that detects an output voltage of the secondary rectifying and smoothing circuit and outputs a switching pulse having a pulse width corresponding to the detected voltage to the base of the transistor. . In this DC-DC converter, the electromagnetic energy accumulated on the primary side of the transformer is released to each secondary side of the transformer when the transistor is turned on, and the emitted electromagnetic energy is transmitted to each LED via each secondary rectifying and smoothing circuit. To supply.

  In this type of DC-DC converter or switching regulator, an output current or output voltage is fed back, and a switching transistor is on / off controlled so as to keep the output voltage or output current at a specified value. Here, in order to improve the electrical conversion efficiency of this type of DC-DC converter or switching regulator, an attempt is made to set a current boundary in a switching signal (switch pulse) applied to the switching transistor. When a switching signal with a current boundary set is applied to the transistor, the switching transistor can be turned on when electromagnetic energy is no longer supplied to the secondary side of the transformer, and the rectifier diode provided on the secondary side of the transformer The reverse recovery time can be shortened and the power loss can be made almost zero.

  When setting the timing for controlling the on / off operation of the switching transistor, for example, when the output voltage of the rectifier diode connected to the secondary side of the forward transformer reaches a certain set voltage, it is turned off. A method of turning on the switching transistor can be employed.

  On the other hand, as a multi-output switching power supply device, if the transformer has a plurality of rectifying and smoothing circuits on the secondary side, and the coils (choke coils) constituting the smoothing circuit are magnetically coupled to each other, the current boundary is set strictly. Then, when the demagnetization occurs, this demagnetization may not be removed. In addition, when the magnetism occurs, a DC current is generated on the secondary side of the transformer, and a current having a current ratio set by the winding ratio of each coil cannot be passed through each rectifying / smoothing circuit. For this reason, after electromagnetic energy is no longer supplied to the secondary side of the transformer, a 0A period (a period in which current does not flow to the secondary side) is provided in which the current flowing to the secondary side of the transformer is 0A (zero ampere). Attempts have been made to reset (demagnetize) the demagnetization.

Japanese Patent Laid-Open No. 9-331677 (pages 3 to 6, FIG. 1)

  By the way, in order to turn on and off the switching transistor according to the current boundary, a high-speed circuit for immediately turning on the switching transistor that is turned off is necessary. However, if a high-speed circuit is provided, the circuit board becomes large. Or the current consumption of the circuit increases.

  Also, in order to provide the 0A period in accordance with the input / output voltage and the characteristics of each element, it is necessary to consider the inductance value of the coil, the variation of the forward voltage (Vf) of the LED, and the temperature characteristics. However, if the 0A period is set in consideration of the variation in the Vf of the LED in consideration of the variation in the Vf of the LED, the timing for turning on the switching transistor becomes longer for the case where the variation in Vf is small. As the peak current value increases, the electrical efficiency of the DC-DC converter or the switching regulator may decrease and the power loss may increase. In the case of a vehicular lamp, the ambient temperature of the LED varies greatly depending on the arrangement of the LED in the lamp, the travel region of the vehicle, and the travel environment, so that the absolute deviation of Vf is large and a power loss is noticeable.

  The present invention has been made in view of the above-described problems of the prior art, and an object thereof is to execute a switching operation according to a current boundary even with a simple circuit configuration.

  In order to achieve the above object, in the lighting control device for a vehicle lamp according to claim 1, the input voltage from the power source is converted into electromagnetic energy according to the on / off operation of the switching element connected to the primary side of the transformer, and A switching regulator that emits to the secondary side of the transformer, an energy propagation means that rectifies and smooths electromagnetic energy emitted from the switching regulator, and propagates it to the semiconductor light source, and a light source current detection means that detects the current of the semiconductor light source A switching signal generating means for generating a switching signal based on the detected current of the light source current detecting means, and turning on and off the switching element according to the generated switching signal, and responding to the switching signal generated by the switching signal generating means. The switching signal Switching state defining means for generating and outputting a defined value for defining the switching frequency of the switching signal or the off time of the switching signal, and no current that no longer flows on the secondary side of the transformer during the off operation of the switching element A non-current period detecting means for detecting a period and reflecting the detection result on a specified value of the switching state defining means; a reference value relating to a switching frequency of the switching signal or an off time of the switching signal; and a switching state defining means Switching signal control means for controlling a switching signal generated by the switching signal generating means according to the comparison result, and the switching signal control means is defined by the generation of the switching state defining means. Value is the reference value When the deviation occurs, the switching frequency of the switching signal generated by the switching signal generating unit or the OFF time of the switching signal is controlled to approach the reference value according to the non-current period detected by the non-current period detecting unit. The configuration is as follows.

  (Operation) In the process in which the light emission energy is supplied from the switching regulator to the semiconductor light source, a switching signal is generated based on the current of the semiconductor light source, and the on / off operation of the switching element is controlled according to the generated switching signal. At this time, in response to the switching signal, a defined value for defining the switching frequency or off time of the switching signal is generated, and no current flows to the secondary side of the transformer when the switching element is turned off. A period (0A period) is detected, and the detection result is reflected in the specified value. For example, if the detection result of the no-current period is reflected in the specified value for specifying the off-time of the switching signal, the specified value for specifying the off-time increases as the non-current period becomes longer. Then, the specified value reflecting the no-current period is compared with the reference value, and when the specified value deviates from the reference value, the control for switching the switching signal switching frequency or the off time to the reference value according to the no-current period. For example, the switching frequency of the switching signal is high or the off time (off period) of the switching signal is short. As a result, when the no-current period becomes longer and the specified value for specifying the off time becomes larger than the reference value, a switching signal for shortening the off time of the switching signal is generated. As described above, when the no-current period becomes longer, the switching signal OFF time is shortened and control close to the current boundary is performed. Therefore, when setting the current boundary, a high-speed circuit for turning on the switching element at high speed The switching element can be switched according to the current boundary even with a simple circuit configuration, and the current consumption can be reduced.

  In the lighting control device for a vehicle lamp according to claim 2, the input voltage from the power source is converted into electromagnetic energy and released to the secondary side of the transformer in accordance with the on / off operation of the switching element connected to the primary side of the transformer. A switching regulator, a plurality of energy propagation means for rectifying and smoothing electromagnetic energy emitted from the switching regulator and respectively propagating to different semiconductor light sources, and detecting a current from any of the plurality of semiconductor light sources By generating light source current detecting means, a switching signal generating means for generating a switching signal based on the detected current of the light source current detecting means, and turning on and off the switching element in accordance with the generated switching signal, and generation of the switching signal generating means In response to the switching signal Switching state defining means for generating and outputting a defined value for defining a switching frequency of the switching signal or an off time of the switching signal, and a plurality of energy on the secondary side of the transformer when the switching element is turned off A non-current period detecting means for detecting a non-current period in which no current flows in at least one of the propagation means and reflecting the detection result in a specified value generated by the switching state defining means; and a switching frequency of the switching signal Or a switching signal control means for comparing a reference value related to an off time of the switching signal with a specified value of the switching state defining means, and controlling a switching signal generated by the switching signal generating means according to the comparison result, Multiple energy transmissions The means includes secondary coils that are magnetically coupled to each other, the light emission energy having a current ratio corresponding to the winding ratio of the secondary coil is propagated to each semiconductor light source, and the switching signal control means includes The switching frequency of the switching signal generated by the switching signal generating means according to the no-current period detected by the no-current period detecting means when the specified value generated by the switching state defining means deviates from the reference value or The switching signal is controlled so that the OFF time of the switching signal approaches the reference value.

  (Operation) In the process in which light emission energy is supplied from the switching regulator to each semiconductor light source via each energy propagation means, a switching signal is generated based on the current of one of the semiconductor light sources, and switching is performed according to the generated switching signal. The on / off operation of the signal is controlled. At this time, in response to the switching signal, a specified value for specifying the switching frequency or the off time of the switching signal is generated, and current is applied to one of the secondary sides of the transformer when the switching element is turned off. A no-current period (0A period) in which the flow has stopped is detected, and the detection result is reflected in the specified value. For example, if the detection result of the no-current period is reflected in the specified value for specifying the off-time of the switching signal, the specified value for specifying the off-time increases as the non-current period becomes longer. Then, the specified value reflecting the no-current period is compared with the reference value, and when the specified value deviates from the reference value, the control for switching the switching signal switching frequency or the off time to the reference value according to the no-current period. For example, the switching frequency of the switching signal is high or the off time (off period) of the switching signal is short. As a result, when the no-current period becomes longer and the specified value for specifying the off time becomes larger than the reference value, a switching signal for shortening the off time of the switching signal is generated. As described above, when the no-current period becomes longer, the switching signal OFF time is shortened and control close to the current boundary is performed. Therefore, when setting the current boundary, a high-speed circuit for turning on the switching element at high speed The switching element can be switched according to the current boundary even with a simple circuit configuration, and the current consumption can be reduced.

  The lighting control device for a vehicle lamp according to claim 3 is the lighting control device for a lighting device for a vehicle according to claim 1 or 2, wherein the switching signal control means is a non-current based on detection by the non-current period detection means. The control is performed on the switching signal generated by the switching signal generating means on condition that the period is maintained for a predetermined time.

  (Operation) When controlling the switching frequency or the off time of the switching signal, the switching signal is controlled on condition that the non-current period is maintained for a predetermined time. Demagnetization), and the peak current value can be reduced to improve electrical efficiency.

  As is clear from the above description, according to the lighting control device for a vehicle lamp according to claim 1, the switching element can be switched according to the current boundary even with a simple circuit configuration, and the current consumption can be reduced and Cost can be reduced.

  According to the lighting control device for a vehicle lamp according to claim 2, the switching element can be switched in accordance with the current boundary even with a simple circuit configuration at a plurality of outputs, thereby reducing current consumption and cost. Is possible.

  According to the third aspect, it is possible to improve the electric efficiency by reducing the peak current value.

  Next, embodiments of the present invention will be described according to examples. FIG. 1 is a circuit configuration diagram showing the overall configuration of a lighting control apparatus for a vehicle lamp according to a first embodiment of the present invention, FIG. 2 is a circuit configuration diagram showing a specific configuration of the apparatus shown in FIG. Fig. 4 is a circuit configuration diagram of a switching signal generation circuit, Fig. 4 is a circuit configuration diagram of an off-time defining circuit and a comparison circuit, Fig. 5 is a circuit configuration diagram showing a first embodiment of a no-current period detection circuit, and Fig. 6 FIG. 7 is a waveform diagram for explaining the relationship between the switching signal and the cathode common voltage, and FIG. 8 is a vehicle showing a second embodiment of the present invention. FIG. 9 is a circuit configuration diagram showing a second embodiment of a no-current period detection circuit, and FIG. 10 is a lighting control for a vehicle lamp showing a third embodiment of the present invention. FIG. 11 is a circuit configuration diagram of the apparatus, and FIG. A waveform diagram for explaining the relation between the voltage of the common cathode, FIG. 12 is a circuit diagram showing a third embodiment of the currentless period detection circuit.

  In these drawings, a lighting control device 10 for a vehicular lamp, as shown in FIG. 1, includes a forward switching regulator 12, a rectifying / smoothing circuit 14, and a control circuit as an element of the vehicular lamp (light emitting device). The LED 18 is connected to the output side of the rectifying / smoothing circuit 14 as a semiconductor light source composed of a semiconductor light emitting element. LED18 can be comprised as a light source of various vehicle lamps, such as a headlamp, a stop & tail lamp, a fog lamp, and a turn signal lamp. The LEDs 18 may be a plurality of LEDs connected in series with each other, or a plurality of LEDs connected in series as a light source block and a plurality of light source blocks connected in parallel.

  The forward switching regulator 12 includes a capacitor C1, a transformer (forward transformer) T1, and an NMOS transistor 20. One end of the transformer T1 is connected to the input terminal 22, and the other end is connected to the NMOS transistor 20. Are connected to the input terminal 24. The input terminal 22 is connected to the plus terminal of the vehicle battery (DC power supply), and the input terminal 24 is connected to the minus terminal of the vehicle battery and grounded. The NMOS transistor 20 has a drain connected to the primary side of the transformer T1, a source grounded, a gate connected to the control circuit 16, and an on / off operation in response to a switching signal (pulse signal) output from the control circuit 16. It is supposed to be. When the NMOS transistor 20 is turned on / off, the input voltage from the vehicle battery is converted into electromagnetic energy in accordance with the on / off operation of the NMOS transistor 20, and is discharged to the rectifying / smoothing circuit 14 from the secondary side of the transformer T1. Yes. In this case, since the transformer T1 is configured as a forward type high frequency transformer, the electromagnetic energy is released to the secondary side when the NMOS transistor 20 is turned on.

  The rectifying / smoothing circuit 14 includes diodes D1 and D2, a coil L1, and a capacitor C2. The anode side of the diode D1 is connected to one end side of the secondary side of the transformer T1, and the anode side of the diode D2 is The transformer T1 is connected to the other end of the secondary side and is grounded. The cathodes of the diodes D1 and D2 are connected to each other as a cathode common, and are connected to one end of the coil L1. The other end side of the coil L1 is connected to one end side of the capacitor C2 and connected to the output terminal 26, and the other end side of the capacitor C2 is grounded and connected to the output terminal 28 via the resistor R1. . Both ends of the LED 18 are connected to the output terminals 26 and 28, respectively.

  The diodes D1 and D2, the coil L1, and the capacitor C2 in the rectifying / smoothing circuit 14 are configured as energy propagation means for propagating the electromagnetic energy emitted from the secondary side of the transformer T1 to the LED 18 as light emission energy. The diodes D1 and D2 Is configured as rectifying means for rectifying the current output from the secondary side of the transformer T1, and the coil L1 and the capacitor C2 are configured as smoothing means for smoothing the rectified current.

  The resistor R1 is configured as light source current detection means for detecting a current supplied to the LED 18 from the secondary side of the transformer T1, that is, a current flowing through the LED 18, and a voltage generated at both ends of the resistor R1 is input to the control circuit 16. It has become so.

  As shown in FIGS. 2 to 5, the control circuit 16 includes a switching signal generation circuit 30, an off time defining circuit 32, a no-current period detection circuit 34, and a comparison circuit 36. As shown in FIGS. 2 and 3, the switching signal generation circuit 30 includes an error amplifier 38, an operational amplifier 40, reference voltages 42 and 44, diodes D5 and D6, resistors R12, R13, R14, R15, as switching signal generation means. R16 and a capacitor C5 are provided.

  The error amplifier 38 takes in a voltage generated at both ends of the resistor R1 from the output terminal 28, and outputs a voltage corresponding to a deviation between this voltage and the reference voltage 44 to the negative input terminal of the operational amplifier 40 and the capacitor C5 via the resistor R15. It is like that.

  The operational amplifier 40 is configured as an operational amplifier having hysteresis characteristics. The negative input terminal is connected to the connection point between the resistor R15 and the capacitor C5, and is connected to the comparison circuit 36 via the resistor R16 and the diode D5. Are connected to the output terminal via a resistor R12 and a diode D6. Further, the operational amplifier 40 has a positive input terminal connected to the reference voltage 42 via the resistor R14 and is connected to the output terminal via the resistor R13.

  The operational amplifier 40 compares the voltage of the positive input terminal with the voltage of the capacitor C5 (voltage of the negative input terminal) in the process of charging the capacitor C5 by the output voltage of the error amplifier 38, and FIG. As shown in (b), during the amplifier output High period (when the voltage of the positive input terminal of the operational amplifier 40 is higher than that during the amplifier output Low period), the voltage of the capacitor C5 is the voltage of the positive input terminal ( A high level signal is output until the voltage reaches the voltage (shown by a broken line), and when the voltage of the capacitor C5 reaches the voltage of the positive input terminal, a low level signal is output as the amplifier output low period. It has become. When the output of the operational amplifier 40 becomes low level, the voltage at the positive input terminal of the operational amplifier 40 also decreases, and the charge of the capacitor C5 is discharged through the resistor R12 and the diode D6. Further, as shown in FIG. 6D, the electric charge of the capacitor C5 is discharged through the resistor R16 and the diode D5 even when the output of the comparison circuit 36 becomes low level and the diode D5 becomes conductive. In the course of these discharges, when the voltage of the capacitor C5 becomes the voltage of the positive input terminal of the operational amplifier 40 (a voltage lower than that during the amplifier output High period), the output of the operational amplifier 40 is inverted from the low level to the high level. . When the capacitor C5 is repeatedly charged and discharged, a high-level or low-level switching signal is output from the operational amplifier 40 according to the voltage of the capacitor C5. In this case, when the current flowing through the LED 18 is smaller than the rated current, the output voltage of the error amplifier 40 is lowered, so that charging of the capacitor C5 is delayed, and the ON time of the switching signal is lengthened (frequency is lowered). On the contrary, when the current flowing through the LED 18 is larger than the rated current, the output voltage of the error amplifier 40 becomes high, so that the capacitor C5 is quickly charged, and the ON time of the switching signal is shortened (frequency is increased). That is, the switching signal generation circuit 30 generates a switching signal (PFM: Pulse Frequency Modulation) based on the voltage (current of the LED 18) generated across the resistor R1, and turns on the NMOS transistor 20 according to the generated switching signal. At the same time, the generated switching signal is output to the off-time defining circuit 32. In this case, the ON time of the switching signal is defined by the charging time for the capacitor C5.

  As shown in FIGS. 2 and 4, the off-time specifying circuit 32 generates a specified value for specifying the off-time of the switching signal or the switching frequency of the switching signal in response to the switching signal generated by the output of the operational amplifier 40. As an element of the switching state defining means to be output to the comparison circuit 36, resistors R2, R3, R4, a capacitor C3, an NPN transistor 46, and PNP transistors 48, 50 are provided. One end of the resistor R2 is an NMOS transistor. 20 gates and the output side of the operational amplifier 40 are connected.

  The NPN transistor 46 takes in the switching signal from the output of the operational amplifier 40 through the resistor R2, and is turned on when the level of the switching signal becomes high, forming a discharge circuit that discharges the charge charged in the capacitor C3. When the level of the switching signal is inverted from the high level to the low level, the switching signal is turned off to cut off the discharge circuit of the capacitor C3. One end side of the capacitor C3 is connected to the comparison circuit 36 and to the collector of the PNP transistor 50. The PNP transistor 50 and the PNP transistor 48 constitute a current mirror circuit. The emitters of the PNP transistors 48 and 50 are connected to the DC power supply 52, respectively, and the collector of the PNP transistor 48 is connected to the resistor R4. That is, the same current as the current flowing through the PNP transistor 48 flows through the capacitor C3 due to the action of the current mirror circuit, and the same current as the current flowing through the PNP transistor 48 flows into the capacitor C3. The charge corresponding to the specified value for specifying the OFF time of the switching signal is accumulated.

  In this case, in the present embodiment, a large value is used as the resistance value of the resistor R4 in order to store a predetermined value of charge corresponding to an off time longer than the off time to be set in the capacitor C3. The current flowing through the transistor 48 is made variable by reflecting the output of the non-current period detection circuit 34, and the charging time (charging voltage) of the capacitor C3 is adjusted.

  For example, the current flowing through the PNP transistor 48 is increased as the non-current period (0A period) in which current does not flow to the secondary side of the transformer T1 becomes longer, and the charging time until the capacitor C3 is fully charged is increased. The OFF time (OFF period) of the switching signal is shortened (switching frequency is increased).

  Specifically, the no-current period detection circuit 34 for adjusting the current flowing through the PNP transistor 48 includes resistors R5, R6, R7, R8, as no-current period detection means, as shown in FIGS. R9, R10, R11, diodes D3, D4, Zener diode ZD1, capacitor C4, PNP transistor 54, and NPN transistor 56, and one end of the resistor R5 is connected to the gate of the NMOS transistor 20 and the output side of the operational amplifier 40. The anode side of the diode D3 is connected to the cathode common of the diodes D1 and D2, and the collector of the NPN transistor 56 is connected to one end side of the resistor R4.

  The no-current period detection circuit 34 takes in the switching signal (gate voltage) output from the operational amplifier 40 to the gate of the NMOS transistor 20 and the cathode common voltage of the diodes D1 and D2, and the gate voltage of the NMOS transistor 20 is shown in FIG. In the process in which the voltage of the cathode common of the diodes D1 and D2 changes with a waveform as shown in FIG. 7B, the level of the switching signal applied to the gate of the NMOS transistor 20 changes. When in the high level, the PNP transistor 54 is in an off state. Furthermore, since the NMOS transistor 20 is turned off from the timing t1 to the timing t2 when the level of the switching signal is inverted from the high level to the low level, the energy accumulated in the coil L1 is transferred to the diode on the secondary side of the transformer T1. The voltage of the cathode common of the diodes D1 and D2 flows through D2, and becomes -Vf (forward voltage of the diode D2), and the PNP transistor 54 is maintained in the OFF state. Thereafter, at timing t2, no current flows on the secondary side of the transformer T1, and a no-current period (0A period) occurs, and the cathode common voltages of the diodes D1 and D2 resonate around the output voltage. Thereafter, the voltage of the cathode common of the diodes D1 and D2 is increased by the energy released from the secondary side of the transformer T1 when the level of the switching signal is inverted from the low level to the high level at the timing t3. .

  In the non-current period from timing t2 to timing t3, the emitter voltage of the PNP transistor 54 becomes higher than the base voltage, so that the PNP transistor 54 is turned on and electric charge is accumulated in the capacitor C4. As shown in FIG. 6E, the voltage of the capacitor C4 sequentially increases every time a no-current period occurs. Then, the transistor 56 is turned on by the voltage generated across the capacitor C4, and the current flowing through the PNP transistor 48 increases. In this case, the longer the non-current period, the higher the voltage charged in the capacitor C4 and the larger the current flowing through the PNP transistor 48. Conversely, if the no-current period is shortened, the voltage charged in the capacitor C4 approaches 0V and the current flowing through the PNP transistor 48 also decreases.

  The Zener diode ZD1 clamps the cathode common voltage of the diodes D1 and D2 so that the value of the cathode common voltage of the diodes D1 and D2 does not affect the charging voltage of the capacitor C4. Further, the charging resistor used for charging the capacitor C4, for example, the resistance value of the resistor R7 is reduced, and the non-current period is shortened as the discharging resistance used for discharging, for example, the resistance value of the resistor R11 is increased. In the opposite case, the no-current period becomes longer.

  On the other hand, as shown in FIGS. 2 and 4, the comparison circuit 36 includes a comparator 58 as a switching signal control unit, and the negative input terminal of the comparator 58 is connected to one end of the capacitor C3 and the NPN transistor 46. The reference voltage 60 corresponding to the reference value relating to the OFF time of the switching signal is input to the positive input terminal, the output side is connected to the cathode of the diode D5, and the anode side of the diode D5 is connected via the resistor R16. It is connected to the negative input terminal of the operational amplifier 40.

  As shown in FIGS. 6C and 6D, the comparator 58 compares the voltage across the capacitor C3 (the voltage corresponding to the specified value for specifying the OFF time of the switching signal) with the reference voltage 60, When the voltage at both ends of the capacitor C3 is lower than the reference voltage 60, a high level signal is output. When the voltage at both ends of the capacitor C3 exceeds the reference voltage 60, it is determined that the specified value has deviated from the reference value. Is output. When the output of the comparator 58 becomes low level, the diode D5 becomes conductive, the negative input terminal of the operational amplifier 40 is forcibly grounded through the resistor R16 and the diode D5, and the charge of the capacitor C5 is discharged. That is, when the specified value for specifying the OFF time of the switching signal deviates from the reference value, the diode D5 is turned on to forcibly ground the negative input terminal of the operational amplifier 40 and the output of the operational amplifier 40 from the low level. The time to invert to high level is advanced.

  Specifically, as shown in FIG. 6B, during the amplifier output Low period, when the charge of the capacitor C5 is discharged through the resistor R12 and the diode D6, the output of the comparator 58 becomes low level. When the negative input terminal of the operational amplifier 40 is instantaneously grounded, the charge of the capacitor C5 is rapidly discharged through the resistor R16 and the diode D5, so that the voltage of the negative input terminal of the operational amplifier 40 becomes equal to the voltage of the positive input terminal. Time is getting faster. As a result, the off time (off period) of the switching signal is shortened, the no-current period is shortened, and the off time (off period) of the switching signal can be made closer to the current boundary. Note that when the OFF time of the switching signal is shortened under the constant duty control, the switching frequency of the switching signal increases.

  In this case, the no-current period can be set to be kept for a predetermined time by the value of the charge / discharge time constant in the no-current period detection circuit 34. That is, when the switching signal level shifts from the low level to the high level, when the no-current period is reached, the NMOS transistor 20 is immediately turned on as the current boundary, or the no-current period is set to 0. In this case, a non-current period is provided for a predetermined time, and the NMOS transistor 20 can be turned on after the predetermined time has elapsed.

  In the present embodiment, the NMOS transistor 20 is turned on / off according to the switching signal generated in the switching signal generation circuit 30, and the electromagnetic energy accumulated in the switching regulator 12 is converted into the secondary of the transformer T1 when the NMOS transistor 20 is turned on. When the level of the switching signal is reversed from the high level (on time) to the low level (off time) in the process of emitting the LED 18 and turning on the LED 18, charging of the capacitor C3 is started and the switching signal is turned off. When there is a non-current period on the secondary side of the transformer T1 during the time (off period), the capacitor C4 is charged according to the length of the non-current period, and the charging voltage charged in the capacitor C4 is set. Therefore, the current flowing through the PNP transistor 48 is increased. When the charge voltage of the capacitor C3 reaches the specified value earlier, and when the charge voltage of the capacitor C3 exceeds the reference voltage 60, the negative input terminal of the operational amplifier 40 is instantaneously grounded, and the level of the switching signal is changed from low level to high level. Since the switching signal is forcibly inverted to shorten the OFF time (OFF period) of the switching signal (ie, the switching signal switching frequency is increased), a high-speed circuit for quickly turning on the NMOS transistor 20 is not used. Even with a simple circuit configuration, the NMOS transistor 20 can be switched according to the current boundary, so that current consumption can be reduced and costs can be reduced.

  In addition, since a high-speed circuit for turning on the NMOS transistor 20 at high speed is not required, the control circuit 16 can be constituted by a general-purpose IC, and the cost can be reduced.

  Next, a second embodiment of the present invention will be described with reference to FIG. In this embodiment, a rectification / smoothing circuit 62 is provided as a multi-output circuit on the output side of the switching regulator 12 in addition to the rectification / smoothing circuit 14, and the transformer T1, the rectification / smoothing circuit 14, and the non-current are provided. The structure of the period detection circuit 34 is the same as that of FIG.

  The rectifying / smoothing circuit 62 includes diodes D7 and D8, a coil L2, and a capacitor C6. One end of the capacitor C6 is connected to the output terminal 64, and the other end side of the capacitor C6 is grounded and has a resistance. The LED 18 is connected to the output terminal 66 via the R 17, and the output terminals 64, 66 are connected to the LED 18. Similarly to the resistor R1, the resistor R17 detects a current flowing through the LED 18 as a light source current detection unit. In this embodiment, the output terminal 66 is connected to the error amplifier 38.

  As shown in FIGS. 8 and 9, the no-current period detection circuit 34 includes diodes D9 and D10 instead of the diode D3 shown in FIG. 2, and also includes a resistor R18 and a reference voltage 68. The cathode side of D9 is connected to the cathode common of diodes D1 and D2, the cathode side of diode D10 is connected to the cathode common of diodes D7 and D8, and the anode sides of diodes D9 and D10 are connected to resistors R10 and R18, respectively. One end of the resistor R18 is connected to the reference voltage 68.

  In the present embodiment, when the non-current period in which the current on the secondary side of the transformer T1 is non-current occurs in the rectifying / smoothing circuits 14 and 62 in the OFF period of the switching signal, that is, the logic of the diodes D9 and D10. Since the current from the reference voltage 68 flows to the capacitor C4 through the PNP transistor 54 on the condition of the product and the charging current of the capacitor C3 increases, there is no current period in the rectifying / smoothing circuits 14 and 62. When it occurs, the OFF time (OFF period) of the switching signal can be shortened.

  In this embodiment, the coil L1 and the coil L2 are magnetically coupled to each other, and a current having a current ratio corresponding to the winding ratio between the coil L1 and the coil L2 is supplied to the rectifying / smoothing circuit 14 and the rectifying / smoothing circuit 62. Since each current flows, the current flowing through each of the rectifying / smoothing circuits 14 and 62 can be arbitrarily set according to the winding ratio of the coils L1 and L2.

  When the coil L1 and the coil L2 are magnetically coupled to each other, there may be a case where the magnetization is deviated during the OFF period of the switching signal. However, in this embodiment, the non-current period is set to be kept for a predetermined time by the value of the charge / discharge time constant in the non-current period detection circuit 34.

  That is, when the switching signal level shifts from the low level to the high level, when the no-current period is reached, the NMOS transistor 20 is immediately turned on as the current boundary, or the no-current period is set to 0. In this predetermined time, a demagnetization occurring on the secondary side of the transformer T1 is naturally demagnetized (reset), and then the NMOS transistor 20 is turned on. Yes.

  Therefore, according to the present embodiment, even if a demagnetization occurs in the process of switching the switching signal from OFF to ON, a predetermined time is provided as a non-current period. It is possible to reduce the peak current value and improve the electric efficiency.

  In this embodiment, the charging current is made to flow through the capacitor C4 under the condition of the logical product of the diodes D9 and D10. However, the diodes D9 and D10 are reversed, and the cathode common of the diodes D1 and D2 or the diode D7. If the configuration connected to the cathode common of D8 is adopted, the charging current can be supplied to the capacitor C4 when a non-current period occurs in one of the rectifying / smoothing circuits 14, 62. In this case, since the capacitor C4 is charged under the condition of the logical sum of the diodes D9 and D10, the capacitor C4 is charged when the no-current period occurs in the rectifying / smoothing circuit 14, 62, whichever is earlier. Will be.

  In each of the embodiments described above, the case where a positive output voltage is generated on the secondary side of the transformer T1 when the NMOS transistor 20 is turned on has been described. However, the present invention relates to the secondary of the transformer T1 when the NMOS transistor 20 is turned on. It can also be applied to a type that outputs a negative voltage on the side.

  For example, a configuration as shown in FIG. 10 can be adopted as a multi-output type that generates a negative output voltage when the NMOS transistor 20 is turned on. In this case, the output side of the rectifying / smoothing circuit 14 is connected to the output terminal 26 via the resistor R1, and the output side of the rectifying / smoothing circuit 62 is connected to the output terminal 64 via the resistor R17. Are each grounded. In order to detect the current supplied from the rectifying / smoothing circuit 62 to the LED 18, the voltage at the connection point between the capacitor C 6 and the resistor R 17 is input to the control circuit 16. In this case, as shown in FIG. 11, when a non-current period (0A period) occurs in the OFF period of the switching signal, the voltage of the cathode common resonates around 0 V, and the voltage accompanying this resonance is the length of the no-current period. The voltage corresponding to the voltage is input to the control circuit 16. In this case, as shown in FIG. 12, in order to prevent the emitter voltage of the PNP transistor 54 of the no-current detection circuit 34 from decreasing negatively, a diode D11 is connected between the emitter of the PNP transistor 54 and GND. By providing, the PNP transistor 54 can be protected.

  In the multi-output type, since the current is passed through the capacitor C4 under the condition of the logical product of the diodes D9 and D10, the switching signal OFF period is shortened. Even when the timing of entering the no-current period differs for each LED 18, it is possible to prevent a deviation in the current ratio of the current flowing through each output circuit of the transformer T1.

It is a circuit block diagram which shows the whole structure of the lighting control apparatus of the vehicle lamp which shows 1st Example of this invention. It is a circuit block diagram which shows the specific structure of the apparatus shown in FIG. It is a circuit block diagram of a switching signal generation circuit. It is a circuit block diagram of an off time prescription circuit and a comparison circuit. It is a circuit block diagram which shows 1st Example of a no-current period detection circuit. It is a wave form diagram for demonstrating operation | movement of an operational amplifier and a comparator. It is a wave form diagram for demonstrating the relationship between a switching signal and the voltage of a cathode common. It is a circuit block diagram of the lighting control apparatus of the vehicle lamp which shows 2nd Example of this invention. It is a circuit block diagram which shows 2nd Example of a no-current period detection circuit. It is a circuit block diagram of the lighting control apparatus of the vehicle lamp which shows 3rd Example of this invention. It is a wave form diagram for demonstrating the relationship between the switching signal in 3rd Example, and the voltage of a cathode common. It is a circuit block diagram which shows 3rd Example of a no-current period detection circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Lighting control apparatus of vehicle lamp 12 Switching regulator 14 Rectification / smoothing circuit 16 Control circuit 18 LED
DESCRIPTION OF SYMBOLS 30 Switching signal generation circuit 32 Off time regulation circuit 34 No-current period detection circuit 36 Comparison circuit 38 Error amplifier 40 Operational amplifier 58 Comparator

Claims (3)

  A switching regulator that converts the input voltage from the power source into electromagnetic energy according to the on / off operation of the switching element connected to the primary side of the transformer and releases it to the secondary side of the transformer, and rectifies the electromagnetic energy emitted from the switching regulator And an energy propagation means for smoothly propagating to the semiconductor light source, a light source current detection means for detecting the current of the semiconductor light source, and a switching signal generated based on the detection current of the light source current detection means. Switching signal generating means for turning on and off the switching element in accordance with the switching signal generating means, and a rule for defining a switching frequency of the switching signal or an off time of the switching signal in response to the switching signal generated by the switching signal generating means. A switching state defining means for generating and outputting a value, and a no-current period in which no current flows to the secondary side of the transformer when the switching element is turned off. The detection result is defined by the switching state defining means. A non-current period detecting means to be reflected in the value, a reference value relating to a switching frequency of the switching signal or an OFF time of the switching signal and a specified value generated by the switching state defining means, and comparing the switching signal according to the comparison result Switching signal control means for controlling a switching signal generated by the generating means, wherein the switching signal control means detects the no-current period when a specified value generated by the switching state specifying means deviates from the reference value. Depending on the no-current period detected by the means. Generating lighting controller for a vehicle lamp off time of the switching frequency or the switching signal is obtained by controlled so as to approach the reference value of the Sutchingu signal by the etching signal generating means.   A switching regulator that converts the input voltage from the power source into electromagnetic energy according to the on / off operation of the switching element connected to the primary side of the transformer and releases it to the secondary side of the transformer, and rectifies the electromagnetic energy emitted from the switching regulator And a plurality of energy propagation means that propagates to a plurality of different semiconductor light sources, respectively, a light source current detection means that detects any one of the plurality of semiconductor light sources, and a detection current of the light source current detection means Switching signal generation means for generating a switching signal based on the switching signal, and switching the switching element on and off according to the generated switching signal, and in response to the switching signal generated by the switching signal generation means, the switching frequency of the switching signal or The switching state defining means for generating and outputting a prescribed value for defining the off time of the switching signal, and at least one of a plurality of energy propagation means on the secondary side of the transformer when the switching element is turned off A non-current period detecting means for detecting a non-current period in which no current flows and reflecting the detection result on a specified value generated by the switching state defining means; and a switching frequency of the switching signal or an off time of the switching signal A switching signal control unit that compares a reference value with a specified value of the switching state defining unit and controls a switching signal generated by the switching signal generating unit according to the comparison result; and the plurality of energy propagation units are mutually connected Having a magnetically coupled secondary coil; The light emission energy having a current ratio corresponding to the winding ratio of the secondary coil is propagated to each of the semiconductor light sources, and the switching signal control means has a prescribed value generated from the switching state defining means from the reference value. When the deviation occurs, the switching frequency of the switching signal generated by the switching signal generation unit or the OFF time of the switching signal is controlled to approach the reference value according to the non-current period detected by the non-current period detection unit. A lighting control device for a vehicular lamp.   3. The lighting control device for a vehicular lamp according to claim 1 or 2, wherein the switching signal control means is provided on the condition that a non-current period detected by the non-current period detection means is maintained for a predetermined time. A lighting control device for a vehicular lamp characterized by performing control on a switching signal generated by a generating means.

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