JP6767860B2 - Converter controller and vehicle lighting - Google Patents

Description

The present invention relates to a switching converter.

Vehicle lamps are generally capable of switching between low beam and high beam. The low beam illuminates a nearby vehicle with a predetermined illuminance, and has a light distribution regulation that does not give glare to an oncoming vehicle or a preceding vehicle, and is mainly used when traveling in an urban area. On the other hand, the high beam illuminates a wide area and a distant place in front with a relatively high illuminance, and is mainly used when traveling at high speed on a road where there are few oncoming vehicles or preceding vehicles. Therefore, the high beam is more visible to the driver than the low beam, but has a problem of giving glare to the driver and pedestrian of the vehicle existing in front of the vehicle.

In recent years, ADB (Adaptive Driving Beam) technology has been proposed that dynamically and adaptively controls the light distribution pattern of a high beam based on the surrounding condition of a vehicle. ADB technology reduces glare given to a vehicle or pedestrian by detecting the presence or absence of a preceding vehicle, oncoming vehicle or pedestrian in front of the vehicle and dimming or turning off the area corresponding to the vehicle or pedestrian. It is a thing.

A switching converter is often used to turn on the light source of the vehicle lighting equipment, but in ADB control, it is necessary to turn off the light source and change the amount of light at high speed. Therefore, the present inventor has examined the adoption of hysteresis control (Bang-Bang control) having excellent high-speed response. FIG. 1 is a block diagram of a hysteresis-controlled vehicle lamp device examined by the present inventors. This comparative technique must not be certified as a known technique.

The vehicle lamp 1r includes a light source 10 and a lighting circuit 20r. The light source 10 includes a semiconductor light source such as an LED (light emitting diode) or an LD (laser diode). The lighting circuit 20r includes a switching converter 30r and a converter controller 32r.

The switching converter 30r receives the battery voltage V _BAT (also referred to as the input voltage _VIN ) from the battery 2 via the switch 4, and supplies the drive current I _DRV to the light source 10. For example, the switching converter 30r is a buck converter, and includes an input capacitor C ₁ , a switching transistor M ₁ , a rectifier diode D ₁ , and an inductor L ₁ .

Converter controller 32r is the output current _{I OUT} or the coil current _{I L} of the switching converter is stabilized between the upper threshold _{I UPPER} and lower threshold _{I BOTTOM} defined so as to sandwich the target current _{I REF.} The converter controller 32r includes a current detection circuit 34, a hysteresis comparator 36, and a driver 38. A current detection resistor (hereinafter referred to as a sense resistor) _{RC S} is inserted on the path of the output current I _OUT of the switching converter 30r. A voltage drop proportional to the output current I _OUT occurs in the sense resistor R _CS . Current detection circuit 34, based on the voltage drop across the sense resistor _{R CS} generates a current detection signal _{V CS} that shows the current output current _{I OUT.}

Hysteresis comparator 36 compares the current detection signal _{V CS,} alternating with lower threshold _{V BOTTOM} defining the upper threshold _{V UPPER} and lower threshold _{I BOTTOM} defining the upper threshold _{I UPPER} , A control pulse _SCNT is generated according to the comparison result. The driver 38 drives the switching transistor _{M 1} on the basis of the control pulse _{S CNT.}

International Publication No. 2013/161215

FIG. 2 is an operation waveform diagram of the lighting circuit 20r of FIG. Control pulse S _CNT has a high level period, the switching transistor M ₁ is turned on, the low level of the interval, the switching transistor M ₁ is turned off. When the switching transistor M ₁ is on, V _IN is applied to the left end of the inductor L ₁ and V _OUT is applied to the right end, so that the voltage between both ends is V _IN −V _OUT . Thus the coil current flowing through the inductor _{L 1 I L} (i.e. the driving current _{I DRV) is} increased with a slope of _{(V IN -V OUT) / L} . L is the inductance of the inductor _{L 1.} When the switching transistor _{M 1} is turned off, the left end of the inductor _{L 1} is substantially the ground potential 0V (strictly -V _F), since _{V OUT} is applied to the right end, the voltage across the -V It becomes _OUT . Thus the coil current _{I L} (i.e. the driving current _{I DRV) decreases} at a slope of _{-V OUT} / L.

On-time _{T ON} switching transistors _{M 1,} the off time _{T OFF} the formula (1) is given by (2).
T _ON = ΔI / {(V _IN −V _OUT ) / L}… (1)
T _OFF = ΔI / (V _OUT / L)… (2)
ΔI is the hysteresis width of the coil current _{I L,} that is, the difference between the peak value _{I UPPER} and the bottom value _{I BOTTOM,} the upper threshold _{V UPPER} and lower threshold _{V BOTTOM} as represented by the following formula It is proportional to the difference ΔV.
ΔI = ΔV / R _CS
Therefore, if the input voltage V _IN (that is, the battery voltage V _BAT ) or the output voltage V _OUT fluctuates, the switching cycle T _ON + T _{OFF of} the switching transistor M ₁ , in other words, the switching frequency fluctuates, making it difficult to take measures against electromagnetic noise. ..

Especially in in-vehicle devices, since the power supply voltage _VBAT, that is, the input voltage of the switching converter is expected to fluctuate greatly, noise countermeasures are costly. It is possible to monitor the input voltage V _IN and the output voltage V _OUT and correct the frequency based on them, but it is not possible to correct the variation in inductance and the temperature fluctuation.

The present invention has been made in view of the above problems, and one of the exemplary objects of the embodiment is to provide a lighting circuit having improved stability of switching frequency.

One aspect of the present invention relates to a converter controller that controls a switching converter that supplies power to a light source. The converter controller alternately compares the current detection signal according to the drive current generated by the switching converter with the upper threshold and the lower threshold, and generates a control pulse according to the comparison result, and a hysteresis comparator and a control pulse. The driver that drives the switching transistor of the switching converter according to the above, the frequency detection circuit that generates the frequency detection signal indicating the frequency of the control pulse, and the upper side so that the frequency detection signal approaches the reference value based on the target frequency of the control pulse. When the hysteresis width adjustment circuit that changes the potential difference between the threshold value and the lower threshold value and the fluctuation of the load voltage between both ends of the light source are detected or predicted, the frequency of the control pulse temporarily approaches the target frequency. It includes a feed-forward circuit that acts on a frequency feedback loop formed by a frequency detection circuit and a hysteresis width adjustment circuit.

According to this aspect, the switching frequency can be stabilized to the target frequency regardless of variations in input voltage, output voltage, and inductance. When the output voltage fluctuates sharply (transient fluctuation), the feedforward circuit can change the operating point of the frequency feedback loop faster than the response speed of the frequency feedback loop, and can suppress the fluctuation of the switching frequency.

The extent to which the feedforward circuit acts on the frequency feedback loop may depend on the fluctuation range of the load voltage. The "degree of action on the frequency feedback loop" may include, for example, at least one of the change width (feedforward amount) of the operating point of the frequency feedback loop, the change speed, and the time for changing the operating point (action time).

The polarity with which the feedforward circuit acts on the frequency feedback loop may depend on the voltage range of the load voltage.
As a result, the operating point of the frequency feedback loop can be appropriately changed in a wide range of load voltages.

When the feedforward circuit detects or predicts the fluctuation of the load voltage, the feedforward circuit may change the signal according to the error between the frequency detection signal and the reference value.

The feedforward circuit may change the reference value when it detects or predicts the fluctuation of the load voltage.

The feedforward circuit may change the frequency detection signal when it detects or predicts fluctuations in the load voltage.

The hysteresis width adjustment circuit includes an error signal generation circuit that generates a frequency error signal according to the error between the frequency detection signal and the reference value, and an upper voltage and a lower voltage that generate an upper voltage and a lower voltage according to the frequency error signal. It may include a voltage source that changes the potential difference of the side voltage. The hysteresis comparator may include a selector that receives the upper voltage and the lower voltage and selects one according to the control pulse, and a first comparator that compares the current detection signal with the threshold voltage according to the output of the selector. Good.

The fluctuation of the load voltage may be based on the measured value.

The light source may include a plurality of light emitting elements connected in series. At least one bypass switch may be connected in parallel with the corresponding one of each of the plurality of light emitting elements. Fluctuations in voltage across the light source may be detected based on control commands to at least one bypass switch. As a result, the operating point of the frequency feedback loop can be changed with a small response delay.

Another aspect of the present invention relates to vehicle lamps. The vehicle lamp includes a light source, a switching converter that supplies electric power to the light source, and any of the above-mentioned converter controllers that control the switching converter.

It should be noted that any combination of the above components and those in which the components and expressions of the present invention are mutually replaced between methods, devices, systems and the like are also effective as aspects of the present invention.

Furthermore, the description of this item (means for solving the problem) does not explain all the essential features of the present invention, and therefore subcombinations of these features described may also be the present invention. ..

According to certain aspects of the invention, the switching frequency can be stabilized.

It is a block diagram of the lamp fixture for a vehicle of hysteresis control examined by the present inventors. It is an operation waveform diagram of the lighting circuit of FIG. It is a circuit diagram of the vehicle lighting equipment which concerns on embodiment. It is a circuit diagram of the converter controller which concerns on one Example. It is a circuit diagram which shows the structural example of a hysteresis comparator. It is a figure which shows the relationship between the output voltage V _OUT of a switching converter, and the switching frequency f _SW . It is a circuit diagram which shows the structural example of the feedforward circuit. It is an operation waveform diagram of the feedforward circuit of FIG. It is a circuit diagram which shows the structural example of the feedforward circuit. It is an operation waveform diagram of the feedforward circuit of FIG. It is a perspective view of the lamp unit provided with the vehicle lamp of FIG.

Hereinafter, the present invention will be described with reference to the drawings based on preferred embodiments. The same or equivalent components, members, and processes shown in the drawings shall be designated by the same reference numerals, and redundant description will be omitted as appropriate. Further, the embodiment is not limited to the invention but is an example, and all the features and combinations thereof described in the embodiment are not necessarily essential to the invention.

In the present specification, the "state in which the member A is connected to the member B" means that the member A and the member B are physically directly connected, and the member A and the member B are electrically connected to each other. It also includes the case of being indirectly connected via other members, which does not substantially affect the connection state, or does not impair the functions and effects performed by the combination thereof.

Similarly, "a state in which the member C is provided between the member A and the member B" means that the member A and the member C, or the member B and the member C are directly connected, and their electricity. It also includes the case of being indirectly connected via other members, which does not substantially affect the connection state, or does not impair the functions and effects performed by the combination thereof.

Further, in the present specification, the reference numerals attached to electric signals such as voltage signals and current signals, or circuit elements such as resistors and capacitors have their respective voltage values, current values, resistance values and capacitance values as required. It shall be represented.

The vertical and horizontal axes of the waveform charts and time charts referred to in the present specification are appropriately enlarged or reduced for ease of understanding, and each waveform shown is also simplified for ease of understanding. Or exaggerated or emphasized.

FIG. 3 is a circuit diagram of the vehicle lamp 100 according to the embodiment. The vehicle lamp 100 includes a light source 102 and a lighting circuit 200. For example, the light source 102 includes a plurality of light emitting elements 104_1 to 104_N connected in series. The light emitting element 104 is, for example, an LED, and the light source 102 is also referred to as an LED bar or an LED string. The light emitting element 104 may be an LD or an organic EL element. For example, each of the plurality of light emitting elements 104_1 to 104_N irradiates different regions via an optical system (not shown).

The lighting circuit 200 supplies a drive current _IDRV to the light source 102 to emit light, and controls each of the plurality of light emitting elements 104 to be turned on and off individually. The lighting circuit 200 receives a control command S _PTN instructing a light distribution pattern from a processor (ECU: Electronic Control Unit) (not shown), and turns on and off a plurality of light emitting elements 104 according to the control command S _PTN. Control.

The lighting circuit 200 includes a boost converter 202, a switching converter 210, a bypass circuit 220, and a converter controller 300.
The boost converter 202 boosts the voltage V _BAT from a battery (not shown) to generate a DC voltage V _IN stabilized at a predetermined voltage level. When a forward voltage at the time of lighting of the light emitting element 104 and _{V F,} the target value of the DC voltage _{V IN is} defined such that _V IN> V _F × N. If the number N of the light emitting element 104 is _{small, V} BAT> _{V F} × N is satisfied, the step-up converter 202 can be omitted.

The switching converter 210 is a buck converter including a switching transistor M ₁ , a rectifier diode D ₁ , and an inductor L ₁ . The switching converter 210 is controlled by the converter controller 300 to step down the DC voltage _VIN and generate a regulated output current I _OUT to a predetermined target amount I _REF . The output current I _OUT is supplied to the light source 102 as a drive current I _DRV .

The bypass circuit 220 individually controls the on and off of each of the plurality of light emitting elements 104_1 to 104_N. The bypass circuit 220 includes a plurality of bypass switches 222_1 to 222_N and a bypass controller 224. Each bypass switch 222_i (i = 1, 2, ... N) is connected in parallel with the corresponding one of the plurality of light emitting elements 104_1 to 104_N. The bypass controller 224 controls on / off of each of the plurality of bypass switches 222_1 to 222_N based on a command signal _SPTN from a microcomputer (not shown) or the like.

When the bypass switch 222_i is off, the output current I _OUT (drive current I _DRV ) generated by the switching converter 210 flows to the corresponding light emitting element 104_i, and thus the light emitting element 104_i is lit. When the bypass switch 222_i is on, the drive current I _DRV bypasses the corresponding light emitting element 104_i and flows to the bypass switch 222_i, so that the light emitting element 104_i is turned off.

The number of light emitting elements 104 that are lit, in other words, the number of bypass switches 222 that are off is K (0 ≦ K ≦ N). At this time, the load voltage V _LOAD is
_{V LOAD} = K × V _F
Will be. That is, when the light distribution pattern is changed and the number K of the light emitting elements 104 to be lit changes, the load voltage V _LOAD changes.

The hysteresis control (Bang-Bang control) type converter controller 300 stabilizes the output current I _OUT (coil current _IL ) of the switching converter 210 in the vicinity of the target current I _REF . More specifically converter controller 300, the output current _{I OUT} or the coil current _{I L} of the switching converter 210, between the upper threshold _{I UPPER} and lower threshold _{I BOTTOM} defined so as to sandwich the target current _{I REF} Stabilize.

The converter controller 300 includes a current detection circuit 302, a driver 304, a frequency detection circuit 306, a hysteresis comparator 310, a hysteresis width adjustment circuit 340, and a feedforward circuit 360.

Current detecting circuit 302 generates an output current _{I OUT} or the coil current _{I L} corresponding current detection signal _{V CS} switching converter 210 is produced. Current detecting circuit 302 includes a path current sense resistor arranged on the detection target current, may generate a current detection signal V _CS that corresponds to the voltage drop across the current sense resistor. Alternatively, the current detection circuit 302 may be another type of current sensor such as transcurrent.

Hysteresis comparator 310, a current detection signal _{V CS,} compared alternately with two threshold values _{V UPPER} and _{V BOTTOM} defining two current threshold _{I UPPER} and _{I BOTTOM,} control pulses S in accordance with the comparison result Generate _CNT . Control pulse _{S CNT,} when the current detection signal _{V CS} reaches the upper threshold _{V UPPER} changes to the first level (for example low level), the current detection signal _{V CS} reaches the lower threshold _{V BOTTOM} first It changes to 2 levels (for example, high level).

The driver 304 drives the switching transistor of the switching converter 210 in response to the control pulse _SCNT .

Frequency detecting circuit 306 generates a frequency detection signal _{V F_DET} illustrating frequency (switching _{frequency) f SW} of the control pulses _{S CNT.} The signal format of the frequency detection signal V _{f_DET} is not limited, and may be an analog signal or a digital signal. Alternatively, the frequency detection signal V _{f_DET} may be a lamp signal and its amplitude may represent a frequency, or may be a pulse signal and its duty ratio (on time) may represent a frequency.

The hysteresis width adjustment circuit 340 sets the potential difference between the upper threshold value V _UPPER and the lower threshold value V _BOTTOM so that the frequency detection signal V _{f_DET} approaches the reference value V _{f_REF} based on the target frequency f _REF of the control pulse S _CNT. The hysteresis width ΔV is changed.

The hysteresis comparator 310, the frequency detection circuit 306, and the hysteresis width adjustment circuit 340 form a feedback loop (frequency feedback loop) 308 that stabilizes the switching frequency _fSW . By this feedback loop, when the switching frequency f _SW becomes higher than the target frequency f _REF , the hysteresis width ΔV becomes larger and feedback is applied in the direction in which the switching frequency f _SW becomes lower, and conversely, the switching frequency f _SW becomes higher than the target frequency f _REF . When it becomes low, the hysteresis width ΔV becomes small, and feedback is applied in the direction in which the switching frequency _fSW increases.

Feed-forward circuit 360 detects or predicts a variation of the voltage (load _{voltage) V LOAD} across the light source 102, the control pulse _S temporarily frequencies such that the frequency _{f SW} approaches rapidly to the target frequency _{f REF} of the _CNT It acts on the feedback loop 308. Specifically, the feedforward circuit 360 forcibly changes the operating point of the frequency feedback loop toward a new operating point corresponding to the changed load voltage V _LOAD .

The above is the basic configuration of the lighting circuit 200. The present invention extends to various devices and circuits grasped as the block diagram and circuit diagram of FIG. 3 or derived from the above description, and is not limited to a specific configuration. Hereinafter, more specific configuration examples and modification examples will be described not for narrowing the scope of the present invention but for helping the understanding of the essence of the invention and the circuit operation and clarifying them.

FIG. 4 is a circuit diagram of the converter controller 300 according to the embodiment. The hysteresis width adjusting circuit 340 includes an error amplifier 342. The error amplifier 342 generates a hysteresis width setting signal V _HYS corresponding to an error between the frequency detection signal V _{f_DET} and the reference value V _{f_REF} .

The hysteresis comparator 310 generates a threshold generation circuit 312 and a comparator 314. The threshold generation circuit 312 generates an upper threshold V _UPPER and a lower threshold V _BOTTOM , and outputs one according to the level of the control pulse _SCNT . The comparator 314, a current detection signal _{V CS,} threshold generator circuit 312 is compared with the upper threshold _{V UPPER} and lower threshold _{V BOTTOM} alternately outputs, it outputs a control pulse _{S CNT.}

In the threshold value generation circuit 312, the average value of the upper threshold value V _UPPER and the lower threshold value V _BOTTOM corresponds to the reference voltage V _REF , and the difference ΔV = V _UPPER −V _BOTTOM between them is the hysteresis width. It is configured to respond to the setting signal _VHYS . In the present embodiment, the hysteresis width ΔV has a negative correlation with the hysteresis width setting signal _VHYS .

As mentioned above, the feedforward circuit 360 acts on the frequency feedback loop 308. Although feed forward destination node is not particularly limited, for example, it is possible to select the output node N ₁ of the hysteresis width adjusting circuit 340. When the feedforward circuit 360 detects the fluctuation of the load voltage V _LOAD , the feedforward circuit 360 temporarily forcibly changes the signal corresponding to the error between the frequency detection signal V _{f_DET} and the reference value V _{f_REF} , that is, the hysteresis width setting signal V _HYS .

FIG. 5 is a circuit diagram showing a configuration example of the hysteresis comparator 310.
The operational amplifier 320, the transistor M ₁₁ , and the resistors R ₁₁ and R ₁₂ generate two voltages, V _H and _VL . When R ₁₁ = R ₁₂ ,
V _H = V _REF- V _HYS x R ₁₁ / R ₁₂ = V _REF- V _HYS
VL = V _HYS
Is established. The average value of the two voltages (V _H + _VL ) / 2 = V _REF / 2, which corresponds to the reference voltage V _REF . The difference (hysteresis width) ΔV between the two voltages is ΔV = V _H− V _L = V _REF -2V _HYS , and has a negative correlation with the hysteresis width setting signal V _HYS .

The selector 322 receives two voltages V _H and _VL , and selects one according to the control pulse _SCNT . The output voltage of the selector 322 and the reference voltage V _REF are combined by the resistor networks R _21- R ₂₃ . The non-inverting input terminal of the comparator 314, in response to the control pulse _{S CNT,} the threshold voltage _V UPPER varying _{binary, V BOTTOM} are generated.

The operation of the feedforward circuit 360 will be described. FIG. 6 is a diagram showing the relationship between the output voltage V _OUT of the switching converter and the switching frequency f _SW . The switching frequency f _SW is given by the equation (3).
f _SW = 1 / (T _ON + T _OFF )… (3)
By substituting the equations (1) and (2) for T _ON and T _OFF of the equation (3), the equation (4) is obtained.
f _SW = {V _OUT − (V _OUT ² / V _IN )} / L × ΔI… (4)
That is, the switching frequency f _SW is represented by a convex quadratic function having V _OUT = V _IN / 2 as the apex. The output voltage V _OUT is nothing but the load voltage V _LOAD .

That is, the direction in which the switching frequency _fSW changes when the output voltage V _OUT fluctuates in a range higher than a certain threshold voltage (for example, V _IN / 2) and when it fluctuates in a range lower than the threshold voltage. Is in the opposite direction. Therefore, when the output voltage V _OUT can take both a region higher and a region lower than the threshold value V _IN / 2, the polarity that the feed forward circuit 360 acts on the hysteresis width adjusting circuit 340 is the load voltage V _LOAD (V). It changes according to the voltage range of _OUT ).

The operation of the feedforward circuit 360 can be divided into the following four cases.
(I) When the load voltage V _LOAD increases in the range of V _LOAD <V _IN / 2, in this case, the switching frequency f _SW rises sharply, and on the contrary, the switching frequency f _SW decreases. That is, feedforward may be applied so that the hysteresis width ΔV increases. Therefore, the hysteresis width setting signal _VHYS may be lowered.

(Ii) When the load voltage V _LOAD decreases in the range of V _LOAD <V _IN / 2, in this case, the switching frequency f _SW drops sharply, so that the switching frequency f _SW rises on the contrary. That is, feedforward may be applied so that the hysteresis width ΔV decreases. Therefore, the hysteresis width setting signal _VHYS may be increased.

(Iii) When the load voltage V _LOAD increases in the range of V _IN / 2 <V _{LOAD In} this case, the switching frequency f _SW drops sharply, so that the switching frequency f _SW rises on the contrary. That is, feedforward may be applied so that the hysteresis width ΔV decreases. Therefore, the hysteresis width setting signal _VHYS may be increased.

(Iv) When the load voltage V _LOAD decreases in the range of V _IN / 2 <V _{LOAD In} this case, the switching frequency f _SW rises sharply, so that the switching frequency f _SW decreases on the contrary. That is, feedforward may be applied so that the hysteresis width ΔV increases. Therefore, the hysteresis width setting signal _VHYS may be lowered.

As shown in FIG. 6, the fluctuation range of the switching frequency depends on the fluctuation amount of the load voltage V _LOAD . Therefore, it is preferable that the degree to which the feedforward circuit 360 acts on the hysteresis width adjusting circuit 340, that is, the amount of forced change (feedforward amount) of the hysteresis width setting signal _VHYS depends on the fluctuation range of the load voltage V _LOAD .

FIG. 7 is a circuit diagram showing a configuration example of the feedforward circuit 360. The amplifier 362 generates a detection signal V _DET according to the load voltage V _LOAD . The comparator 364 compares the detection signal V _DET with the threshold value V _TH and generates a range determination signal S ₁₁ indicating whether the load voltage V _LOAD is higher or lower than V _IN / 2. The non-inverting amplifier 366 and the inverting amplifier 368 each amplify the detection signal V _DET . The selector 370 receives the output voltages V ₁₂ and V ₁₃ of the non-inverting amplifier 366 and the inverting amplifier 368, respectively, and selects one of them according to the output S _{11 of the} comparator 364.

The output voltage V ₁₄ of the selector 370 is superimposed on the output node N ₁ of the hysteresis width adjusting circuit 340 via the capacitor C4. Capacitor C4 acts as a high-pass filter or differentiator.

FIG. 8 is an operation waveform diagram of the feedforward circuit 360 of FIG.
When the detection voltage V _DET is lower than the threshold value V _TH (V _OUT <V _IN / 2), the range determination signal S ₁₁ is at a high level and the output of the inverting amplifier 368 is selected. When the load voltage V _LOAD rises sharply, the switching frequency f _{SW tends} to rise. At this time, the output V _FF of the feedforward circuit 360 becomes negative, the hysteresis width setting signal _VHYS decreases, and the hysteresis width increases. As a result, the switching frequency f _SW drops rapidly. 8 for comparison, the case without feedforward, gradual change of the hysteresis width setting signal V _HYS and the switching frequency f _SW based on the response speed of the frequency feedback loop is shown by a dashed line.

When the load voltage V _LOAD decreases at V _OUT <V _IN / 2, the output V _FF of the feedforward circuit 360 becomes positive, the hysteresis width setting signal V _HYS increases, and the hysteresis width decreases. As a result, the switching frequency f _SW rises rapidly.

When the detection voltage V _DET is higher than the threshold value V _TH (V _IN / 2 <V _OUT ), the range determination signal S ₁₁ is low level and the output of the non-inverting amplifier 366 is selected. When the load voltage V _LOAD rises, the output V _FF of the feedforward circuit 360 becomes positive, the hysteresis width setting signal V _HYS rises, and the hysteresis width decreases. As a result, the switching frequency f _SW rises rapidly. On the contrary, when the load voltage V _LOAD decreases, the output V _FF of the feedforward circuit 360 becomes negative, the hysteresis width setting signal V _HYS decreases, and the hysteresis width increases. As a result, the switching frequency f _SW drops rapidly.

According to this feedforward circuit 360, the above-mentioned operations (i) to (iv) can be realized. In particular, by making the feedforward amount proportional to the fluctuation range of the load voltage V _LOAD , complicated calculations are not required, and it can be configured by a combination of an amplifier and a selector.

Return to FIG. Feedforward target node by the feed-forward circuit 360 may be an input node N ₂ of the hysteresis width adjusting circuit 340. That is, the feedforward circuit 360 may change the frequency detection signal V _{f_DET} when it detects the fluctuation of the load voltage V _LOAD . When acting on the input node N _2, the polarity of the feed-forward may be reverse to the node N _1. When the feedforward circuit 360 of FIG. 7 is used, the control logic of the selector 370 may be replaced.

The feedforward target node by the feed-forward circuit 360 may be a reference node N ₃ of the hysteresis width adjusting circuit 340. That is, the feedforward circuit 360 may change the reference value V _{f_REF when} it detects the fluctuation of the load voltage V _LOAD . In addition, the feedforward circuit 360 may change the voltage or current of the intermediate node of the error amplifier 342, or may act on the intermediate node of the frequency detection circuit 306.

In the description so far, the feedforward circuit 360 directly monitors the voltage of the load voltage V _LOAD , but this is not the case. As described above, the load voltage V _LOAD is proportional to the number K of the light emitting elements 104 in the lit state. Therefore, by monitoring the control command _SPTN of the light distribution pattern, it is possible to predict the fluctuation of the load voltage V _LOAD .

FIG. 9 is a circuit diagram showing a configuration example of the feedforward circuit 360.
The microcontroller 380 is a part of the bypass controller 224 and receives the control command _SPTN instructing the light distribution pattern. The microcontroller 380 generates a first signal S ₂₁ indicating the amount of change ΔK of the number of lights K of the light source, and a second signal S ₂₂ indicating whether the number of lights K increases or decreases. For example, the first signal S ₂₁ includes a number of pulse trains proportional to the amount of change ΔK. The second signal S ₂₂ is a binary digital signal that takes a low level when the number of lights increases and a high level when the number of lights decreases. The first logic gate 382 is an EXOR (exclusive OR) gate, and generates a third signal S ₂₃ indicating the exclusive OR of the first signal S ₂₁ and the second signal S ₂₂ . When the number of lights increases, the third signal S ₂₃ is the same as the pulse train of the first signal S ₂₁ , and when the number of lights decreases, the third signal S ₂₃ is an inverted signal of the pulse train of the first signal S _21. It becomes.

The second logic gate 384 is an EXOR (exclusive OR) gate, and generates a fourth signal S ₂₄ indicating the exclusive OR of the third signal S ₂₃ and the range determination signal S ₁₁ . When the range determination signal S ₁₁ is at low level, the fourth signal S ₂₄ is the same as the third signal S ₂₃ , and when the range determination signal S ₁₁ is at high level, the fourth signal S ₂₄ is the third signal S. It becomes the inverted signal of ₂₃ .

The fourth signal S ₂₄ is superimposed on the output node N ₁ of the hysteresis width adjusting circuit 340 via the capacitor C4. The superimposition destination of the fourth signal S ₂₄ may be changed to other than the output node N ₁ , and if the logical values of the range determination signal S ₁₁ and the second signal S ₂₂ are changed so that the polarity of feedforward becomes correct. Good.

FIG. 10 is an operation waveform diagram of the feedforward circuit 360 of FIG. In the figure, (i) to (iv) correspond to the operations of (i) to (iv) of the feedforward circuit 360 described above. According to the feedforward circuit 360 of FIG. 9, the feedforward amount is changed based on the change amount ΔV of the lighting number K, and is based on the change direction (increase / decrease) of the lighting number K and the range of the load voltage V _LOAD. Therefore, the polarity of feedforward can be changed.

(Use)
Finally, the use of the vehicle lamp 100 will be described. FIG. 11 is a perspective view of a lamp unit (lamp assembly) 500 including the vehicle lamp 100 of FIG. The lamp unit 500 includes a transparent cover 502, a high beam unit 504, a low beam unit 506, and a housing 508. The vehicle lamp 100 described above can be used, for example, in the high beam unit 504. The plurality of light emitting elements 104 are arranged in a row in the horizontal direction, for example, so as to irradiate different regions. Then, in the traveling state of the vehicle, the area to be irradiated is adaptively selected by the controller on the vehicle side, for example, the ECU (electronic control unit). Data indicating an area to be irradiated is input to the vehicle lamp 100, and the vehicle lamp 100 lights the light emitting element 104 corresponding to the designated region.

The present invention has been described above based on the embodiments. This embodiment is an example, and it will be understood by those skilled in the art that various modifications are possible for each of these components and combinations of each processing process, and that such modifications are also within the scope of the present invention. is there. Hereinafter, such a modification will be described.

(First modification)
In FIG. 7, the feedforward amount V _FF by the feedforward circuit 360 is changed in proportion to the fluctuation range of the load voltage V _LOAD , but this is not the case. As shown in FIG. 6, since the switching frequency f _SW changes according to the quadratic function with respect to the load voltage V _LOAD , even if the feedforward amount V _FF is changed according to the quadratic function of the load voltage V _LOAD. Good. As a result, the fluctuation amount of the switching frequency can be further reduced.

On the contrary, from the viewpoint of simplification of control, the feedforward amount may be fixed regardless of the fluctuation range of the load voltage V _LOAD .

(Second modification)
A function equivalent to that of the feedforward circuit 360 of FIG. 7 may be implemented by digital signal processing by a microcontroller.

(Third modification example)
In the feedforward circuit 360 of FIG. 9, the functions of the amplifier 362 and the comparator 364 can be implemented in the microcontroller 380. For example, the load voltage V _LOAD may be taken into the microcontroller 380 as a digital value by using an A / D converter, and the range of the load voltage V _LOAD may be determined. Further, the function of the first logic gate 382 may be implemented inside the microcontroller 380.

(Fourth modification)
In the embodiment, the case where the load voltage V _LOAD operates in both the range higher than the threshold value V _IN / 2 and the range lower than the threshold value V _IN / 2 has been described, but this is not the case. The present invention is also valid for applications that operate only in the range V _LOAD > V _IN / 2, or only in the range V _LOAD <V _IN / 2, in which case the feedforward polarity switching is not required. Specifically, the processing of the comparator 364 and the selector 370 of FIG. 7 becomes unnecessary, and one of the amplifiers 366 and 368 can be omitted.

(Fifth modification)
As the light source 102, a semiconductor light source such as LD (laser diode) or organic EL (electroluminescence) may be used in addition to the LED.

(6th modification)
In the embodiment, the fluctuation of the load voltage V _LOAD with the bypass control method has been described, but the factor of the fluctuation of the load voltage V _LOAD is not particularly limited.

(7th modification)
In the lamp unit 500 of FIG. 11, the case where the vehicle lamp 100 is used for the high beam unit 504 has been described, but instead of or in addition, the architecture of the vehicle lamp 100 may be used for the low beam unit 506.

(8th modification)
The switching converter 210 may be a boost converter, a buck-boost converter, a converter using a transformer, or another converter such as a Cuk converter. Further, a switching converter having a negative voltage output may be used.

Although the present invention has been described using specific terms and phrases based on the embodiments, the embodiments merely indicate the principles and applications of the present invention, and the embodiments are defined in the claims. Many modifications and arrangement changes are permitted without departing from the ideas of the present invention.

100 ... Vehicle lighting equipment, 102 ... Light source, 104 ... Light emitting element, 200 ... Lighting circuit, 202 ... Boost converter, 210 ... Switching converter, 220 ... Bypass circuit, 222 ... Bypass switch, 224 ... Bypass controller, 300 ... Converter controller, 302 ... current detection circuit, 304 ... driver, 306 ... frequency detection circuit, 308 ... frequency feedback loop, 310 ... hysteresis comparator, 312 ... threshold generation circuit, 314 ... comparator, 320 ... operational amplifier, 322 ... selector, 340 ... hysteresis Width adjustment circuit, 342 ... error amplifier, 360 ... feed forward circuit, 362 ... amplifier, 364 ... comparator, 366 ... non-inverting amplifier, 368 ... inverting amplifier, 370 ... selector, 380 ... microcontroller, 382 ... first logic gate, 384 ... Second logic gate.

Claims (10)

A converter controller that controls a switching converter that supplies power to a light source.
A hysteresis comparator that alternately compares the current detection signal corresponding to the drive current generated by the switching converter with the upper threshold value and the lower threshold value and generates a control pulse according to the comparison result.
A driver that drives the switching transistor of the switching converter in response to the control pulse,
A frequency detection circuit that generates a frequency detection signal indicating the frequency of the control pulse, and
A hysteresis width adjusting circuit that changes the potential difference between the upper threshold value and the lower threshold value so that the frequency detection signal approaches a reference value based on the target frequency of the control pulse.
When the fluctuation of the load voltage between both ends of the light source is detected or predicted, the frequency feedback formed by the frequency detection circuit and the hysteresis width adjustment circuit is temporarily formed so that the frequency of the control pulse rapidly approaches the target frequency. The feed forward circuit that acts on the loop and
A converter controller characterized by being equipped with. The converter controller according to claim 1, wherein the degree to which the feedforward circuit acts on the frequency feedback loop depends on the fluctuation range of the load voltage. The converter controller according to claim 1 or 2, wherein the polarity of the feedforward circuit acting on the frequency feedback loop depends on the voltage range of the load voltage. The invention according to any one of claims 1 to 3, wherein the feed-forward circuit changes a signal according to an error between the frequency detection signal and the reference value when the fluctuation of the load voltage is detected or predicted. Converter controller. The converter controller according to any one of claims 1 to 3, wherein the feedforward circuit changes the frequency detection signal when the fluctuation of the load voltage is detected or predicted. The converter controller according to any one of claims 1 to 3, wherein the feedforward circuit changes the reference value when the fluctuation of the load voltage is detected or predicted. The hysteresis width adjusting circuit is
An error signal generation circuit that generates a frequency error signal according to the error between the frequency detection signal and the reference value,
A voltage source that generates an upper voltage and a lower voltage and changes the potential difference between the upper voltage and the lower voltage according to the frequency error signal.
Including
The hysteresis comparator is
A selector that receives the upper voltage and the lower voltage and selects one according to the control pulse.
A first comparator that compares the current detection signal with the threshold voltage corresponding to the output of the selector,
The converter controller according to any one of claims 1 to 6, wherein the converter controller comprises. The converter controller according to any one of claims 1 to 7, wherein the fluctuation of the load voltage is based on an actually measured value. The light source includes a plurality of light emitting elements connected in series.
At least one bypass switch is connected in parallel with the corresponding one of the plurality of light emitting elements.
The converter controller according to any one of claims 1 to 7, wherein the fluctuation of the load voltage is detected based on a control command to the at least one bypass switch. Light source and
A switching converter that supplies power to the light source,
The converter controller according to any one of claims 1 to 9, which controls the switching converter.
A vehicle lamp characterized by being equipped with.

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