JP6278238B2 - Light emitting load driving device and vehicle light emitting device - Google Patents

Description

The present invention relates to a light emitting load driving device that drives, for example, an LED (light emitting diode) and the like, and a vehicle light emitting device including the same.

FIG. 4 is a circuit diagram showing a configuration of a light emitting load driving device and a vehicle light emitting device described in Patent Document 1. The vehicle light emitting device includes a light emitting load driving device 1a and a plurality of light emitting loads D1, D2, D3,. The light emitting load driving device 1a includes a plurality of switching elements M1, M2, M3,..., Mn connected in parallel to the light emitting loads D1, D2, D3. , M2, M3,..., Mn are individually provided with a gate drive unit 10a that drives the pulse width modulation (PWM). The plurality of light emitting loads D1, D2, D3,..., Dn are connected in series between both ends of the constant current source IDD. The gate driver 10a outputs a driving signal that repeats high level and low level to the gate terminals of the plurality of switching elements M1, M2, M3,..., Mn, and a plurality of light emitting loads D1, D2, D3. Adjust the brightness of Dn.

JP2013-84635A

FIG. 5 is a timing chart showing the operation of the drive device for the light emitting load described in Patent Document 1. Waveforms M1 to Mn indicate operations of the first to nth switching elements M1 to Mn. A waveform VDD indicates a voltage applied between the positive terminal T + and the negative terminal T− of the constant current source IDD. A waveform IDD indicates a current flowing between the positive terminal T + and the negative terminal T− of the constant current source IDD. At time t0 and time t2, when the switching elements simultaneously change from the off state to the on state (simultaneous turn-on), the load of the constant current source IDD is rapidly reduced, thereby generating an overshoot current _IO . Further, at time t1 and time t3, transition to the OFF state from the switching elements are simultaneously turned on (co off), the by the load of the constant current source IDD increases rapidly, undershoot current I _U occurs.

These overshoots and undershoots of currents may cause adverse effects such as generation of unnecessary electromagnetic radiation noise on the system, load short detection error or load open error detection by the constant current source IDD, and should be suppressed as much as possible. . The present invention provides a light emitting load driving device and a vehicle light emitting device capable of suppressing adverse effects such as generation of unnecessary electromagnetic radiation noise on the system, load short detection error or load open error detection by the constant current source IDD.

According to one aspect of the present invention, a driving device for a light emitting load includes a first switching element, a second switching element, and a gate driving unit, and the first light emitting load and the second light emitting element are connected in series to each other. When the first switching element is in an on state, the first switching element bypasses a current flowing through the first light emitting load, and the second switching element is turned on. When in a state, the current flowing through the second light emitting load is bypassed, the first light emitting load and the second light emitting load are connected in series between both ends of a constant current source, and the gate driver is The first switching element and the second switching element are driven based on a control signal input from a light emission control unit to individually determine the light emission luminances of the first light emission load and the second light emission load. Of generating a drive signal, by detecting the control signal which lead to at least one of simultaneous turn-on and the simultaneous turning off of said first switching element and the second switching element, the first switching element and the second It is characterized in that at least one of an overshoot current and an undershoot current of a current supplied from the constant current source caused by simultaneous turn-on or simultaneous turn-off of the two switching elements is reduced.

ADVANTAGE OF THE INVENTION According to this invention, the drive device of the light emission load and vehicle light-emitting device which can suppress the bad influence of generation | occurrence | production of unnecessary electromagnetic radiation noise on a system, load short circuit false detection by the constant current source IDD, or load open false detection can be provided.

It is a circuit diagram which shows the structure of the drive device of the light emission load which concerns on embodiment of this invention, and the light-emitting device for vehicles. It is a circuit diagram which shows the structure of the drive device of the light emission load which concerns on embodiment of this invention. It is a timing chart which shows operation | movement of the drive device of the light emission load which concerns on embodiment of this invention. It is a circuit diagram which shows the structure of the drive device of the light emission load described in patent document 1, and the light-emitting device for vehicles. 10 is a timing chart showing the operation of the light emitting load driving device described in Patent Document 1.

Next, an embodiment of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic. Further, the embodiments described below exemplify apparatuses and methods for embodying the technical idea of the present invention, and the embodiments of the present invention have the following structure and arrangement of components. It is not something specific. The embodiment of the present invention can be variously modified within the scope of the claims.

FIG. 1 is a circuit diagram showing a configuration of a light emitting load driving device and a vehicle light emitting device according to an embodiment of the present invention. The light emitting device for a vehicle according to the embodiment of the present invention includes a light emitting load driving device 1, a first light emitting load D1, and a second light emitting load D2. The light emitting load driving device 1 according to the present embodiment includes a first switching element M1, a second switching element M2, and a gate driving unit 10. The first switching element M1 bypasses the current flowing through the first light emitting load D1 when in the on state. The second switching element M2 bypasses the current flowing through the second light emitting load D2 when in the on state. The gate driver 10 reduces at least one of the first overshoot current caused by the simultaneous turn-on or simultaneous turn-off of the switching element M1 and the second switching element M2 I _O and undershoot current I _U.

The vehicle light emitting device includes a light emitting load driving device 1 and a plurality of light emitting loads D1, D2,..., Dn. The vehicle light emitting device is connected to the light emission control unit 2. The light emitting loads D1, D2,..., Dn are, for example, LEDs. The light emitting loads D1, D2,..., Dn are connected in series between the positive terminal T + and the negative terminal T− of the constant current source IDD. The vehicle light-emitting device generates a direct current supplied from the constant current source IDD based on the control signals S _C1 , S _C2 ..., S _Cn output from the light emission control unit 2 and emits light loads D1, D2. Supply to Dn.

The light emitting load driving device 1 includes a plurality of switching elements M1, M2,..., Mn and a gate driving unit 10. The light emitting load driving device 1 is configured as, for example, a single semiconductor integrated circuit. The light emitting load driving device 1 is connected to the light emitting loads D1, D2,..., Dn, the light emission control unit 2, and the constant current source IDD. Drive device 1 of the light-emitting load, the control signals _{S C1, S} C2 ··· output from the light emission control unit _2, based on the _{S Cn,} to adjust the brightness of the light emission load D1, D2 ···, Dn. The light emission control unit 2 is configured by a digital circuit using an ASIC, FPGA, or the like, a microcomputer, or the like. The light emission control unit 2 outputs pulse-like control signals S _C1 , S _C2 ..., S _Cn in order to individually determine the light emission luminances of the light emission loads D1, D2 _,.

The plurality of switching elements M1, M2,..., Mn are, for example, MOSFETs. The switching elements M1, M2,..., Mn are connected in series between the positive terminal T + and the negative terminal T− of the constant current source IDD. Each of the switching elements M1, M2,..., Mn is connected in parallel to each of the light emitting loads D1, D2,. When the switching elements M1, M2,..., Mn are in the OFF state, the direct current supplied from the constant current source IDD flows through the light emitting loads D1, D2,. Each of the switching elements M1, M2,..., Mn bypasses the current flowing through each of the light emitting loads D1, D2,.

The gate drive unit 10 according to the present embodiment includes a phase shift unit 11 and a plurality of signal output units 12-1, 12-2, ... 12-n. The gate driving unit 10 repeats the high level and the low level based on the control signals S _C1 , S _C2 , S _Cn output from the light emission control unit 2, and the pulsed driving signals S ₁ , S _2. , _Sn are generated. Driving signals _{S 1,} S 2 · · ·, the ratio of high level and a low level of _{S n} (Duty), the control signals _{S C1,} S C2 · · _·, are modulated on the basis of the _{S Cn.} Driving signals _{S 1, S 2 ···, S} n is the signal output unit 12-1, 12-2, via the · · · 12-n, the switching element M1, M2 · · ·, to the gate terminal of the Mn Is output. The gate driver 10 individually drives the switching elements M1, M2,..., Mn by PWM (Pulse Width Modulation). For example, a first driving signal S ₁ is at a high level, the first switching element M1 is turned on, the light emission load is turned off. When the first driving signal S ₁ is at the low level, the first switching element M1 is turned off, the light emission load is light. The gate driver 10, a control signal _{S C1,} S C2 · · _·, by controlling the time period and the off state of the on-state of each switching element in response to _{S Cn,} the light emission load D1, D2 · · ·, Adjust the brightness of Dn.

The phase shift unit 11 is connected to the light emission control unit 2 and the signal output units 12-1, 12-2,. The phase shifter 11 detects control signals S _C1 , S _C2 ..., S _Cn that cause the switching elements M1, M2,..., Mn to cause at least one of simultaneous turn-on and simultaneous turn-off. Here, the simultaneous turn-on and the simultaneous turn-off mean that all the switching elements simultaneously transition from the off state to the on state, and that all the switching elements simultaneously transition from the on state to the off state. For example, when the phase shift unit 11 detects the control signals S _C1 , S _C2 , S _Cn that cause simultaneous turn-on, the rising timing of the _first drive signal S ₁ based on the first control signal S _C1 as a reference, delaying the rise timing of the other control signals, and outputs driving signals _{S 1,} S 2 · · ·, a _{S n} to the signal output unit 12-1,12-2 ··· 12-n. When the phase shift unit 11 detects the control signals S _C1 , S _C2 ..., S _Cn that cause simultaneous turn-off, the phase shift unit 11 determines the falling timing of the _first drive signal S ₁ based on the first control signal S _C1. As a reference, the fall timing of other control signals is delayed.

The signal output units 12-1, 12-2,..., 12-n are connected to the phase shift unit 11 and the switching elements M1, M2,. Signal output unit 12-1 and 12-2 · · ·, 12-n, when the driving signal _{S 1,} S 2 · · ·, the _{S n} of high level, on the switching elements M1, M2 · · ·, the Mn Control to the state. Signal output unit 12-1 and 12-2 · · ·, 12-n, the drive signals _{S 1,} S 2 · · ·, when _{S n} is low, the switching elements M1, M2 · · ·, off Mn Control to the state.

FIG. 2 is a circuit diagram showing a configuration of the light emitting load driving device according to the embodiment of the present invention. The light emitting load driving device 10 includes a first charging unit 13-1 connected to the first signal output unit 12-1. The first signal output unit 12-1 includes a first switch SW1, a second switch SW2, and an inverting circuit INV. The first switch SW1 is based on a first driving signal S _1, it opens and closes between the first gate terminal and the first charging portion 13-1 of the switching element M1. The second switch SW1 is based on a first inverted signal of the driving signal S ₁ output from the inverting circuit INV, to open and close both ends of the parasitic capacitance C2 of the first switching element M1.

The potential of the source terminal of the first switching element M1 varies depending on the operation of other switching elements. Under such circumstances, the first charging unit 13-1 stabilizes driving of the first switching element M1 by the first signal output unit 12-1. The first charging unit 13-1 includes a current source ICC, first and second diodes Di1, Di2, a Zener diode ZDi, a first capacitor C1, and a driving unit DRV. The current source ICC is connected to one end of the first capacitor C1 via the first diode Di1. One end of the first capacitor C1 is connected to the signal output unit 12 via the second diode Di2. The other end of the first capacitor is connected to the output end of the drive unit DRV. The bidirectional Zener diode ZDi, which is a protection element, is connected in parallel with the first capacitor. Driver DRV, the driving signals _{S 1,} S 2 · · ·, independent of _{S n,} and outputs the drive pulse _{S D} repeating the high and low levels of several hundred kHz. When the drive pulse _SD is at a low level, electric charge is accumulated in the first capacitor C1 by the current source ICC. When the drive pulse _SD is at a high level, the potential at the other end of the first capacitor C1 is raised.

In the first signal output unit 12-1, when the first switch SW1 is turned on, the charge accumulated in the first capacitor C1 moves to the second capacitor C2 via the second diode Di2. As the potential across the second capacitor C2 rises, the first switching element M1 is turned on. When the second switch SW2 is turned on, the charge of the second capacitor C2 is discharged, and the first switching element M1 is turned off. The charging unit is provided for each of the plurality of signal output units.

FIG. 3 is a timing chart showing the operation of the light emitting load driving device according to the embodiment of the present invention. A waveform M1 shows the operation of the first switching element M1. A waveform M2 shows the operation of the second switching element M2. A waveform Mn indicates the operation of the n-th switching element Mn. A waveform VDD indicates a voltage applied between the positive terminal T + and the negative terminal T− of the constant current source IDD. A waveform IDD indicates a current flowing between the positive terminal T + and the negative terminal T− of the constant current source IDD.

When the control signals S _C1 , S _C2 ..., S _Cn that turn on the plurality of switching elements M1, M2... Mn at the same time are output from the light emission controller 2 to the gate driver 10 at time t01. The operation of each unit will be described. At time t01, the phase shift unit 11, the first driving signals _{S 1} is output to the first signal output unit 12-1, to turn on the first switching element M1. At this time, the phase shift unit 11 delays the _{second to} nth drive signals S ₂ , S ₃ ..., _Sn with respect to the first drive signal S ₁ . For example, the t02, the phase shift unit 11, a second driving signal _{S 2} is output to the second signal output unit 12-2, thereby turning on the second switching device M2. At time T0n, the phase shift unit 11, a drive signal _{S n} of the n outputs the signal output unit 12-n of the n, thereby turning on the switching element Mn of the n. From time t0n to time t11, all the switching elements are maintained in the on state.

Next, at time t11, control signals S _C1 , S _C2 ..., S _Cn that simultaneously turn off the plurality of switching elements M1, M2... Mn are output from the light emission control unit 2 to the gate driving unit 10. For these cases, the operation of each unit will be described. In time t11, the phase shift unit 11, the first driving signals _{S 1} is output to the first signal output unit 12-1, thereby turning off the first switching element M1. Next, at t12, the phase shift unit 11, a second driving signal _{S 2} is output to the second signal output unit 12-2, thereby turning off the second switching device M2. After that, at time t1n, the phase shift unit 11 outputs the nth drive signal _Sn to the nth signal output unit 12-n to turn off the nth switching element Mn. The voltage VDD rises and falls in a step-like manner when each switching element is turned on and turned off.

The light emitting load driving device 1a described in Patent Document 1 has suddenly reduced or increased the load of the constant current source IDD due to simultaneous turn-on or simultaneous turn-off of a plurality of switching elements. However, the light emitting load driving device 1 and the gate driving unit 10 include the phase shift unit 11 and suppress at least one of the simultaneous turn-on and the simultaneous turn-off of the first switching element M1 and the second switching element M2. The load fluctuation of the current source IDD can be reduced, and at least one of the overshoot current and the undershoot current can be reduced.

The driving device 1, a gate driver 10 of the light-emitting load, the driving signals S _1, S ₂ · · ·, charging unit to increase the operating potential of the signal output unit 12 according to the drive pulse S _D, which is independent from S _n 13 is provided. Therefore, like the light emitting load driving device 1a described in Patent Document 1, it is possible to reduce restrictions on turning on and off the plurality of switching elements M1, M2,.

Drive device 1, a gate driver 10 of the light emission load, instead of the phase shifter 11, the driving signal S ₂ of the second to _n, S ₃ · · ·, the rise time and the fall time of the S _n first ramp creating unit to extend the drive signals S ₁ of it may be provided with a. Even when all of the plurality of switching elements M1, M2,..., Mn are turned on or turned off at the same time, the load fluctuation of the constant current source IDD can be reduced by reducing the speed.

As mentioned above, although this invention was described by embodiment, it should not be understood that the description and drawing which form a part of this indication limit this invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art. That is, it goes without saying that the present invention includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description. For example, the light emitting load driving device 1 may include a plurality of switching elements M1, M2,..., Mn formed of individual devices and a gate driving unit 10 formed of a semiconductor integrated circuit. The light emitting load driving device 1 may include at least one of the light emission control unit 2 and the constant current source IDD. Moreover, each of the plurality of light emitting loads D1, D2,..., Dn may be configured by a plurality of LEDs.

DESCRIPTION OF SYMBOLS 1 Light emission load drive device 2 Light emission control part 10 Gate drive part 11 Phase shift part 12 Signal output part 13 Charging part D1 1st light emission load D2 2nd light emission load Dn nth light emission load M1 1st switching element M2 Second switching element Mn nth switching element IDD constant current source

Claims (7)

A driving device for a light emitting load that includes a first switching element, a second switching element, and a gate driving unit, and that drives the first light emitting load and the second light emitting load connected in series with each other,
When the first switching element is in an on state, the first switching element bypasses a current flowing through the first light emitting load;
When the second switching element is in an on state, the second switching element bypasses a current flowing through the second light emitting load;
The first light emitting load and the second light emitting load are connected in series between both ends of a constant current source,
The gate driving unit is configured to control the first switching element and the second switching element based on a control signal input from a light emission control unit to individually determine light emission luminances of the first light emission load and the second light emission load. Generating a drive signal for driving the switching element;
Detecting the control signal that causes at least one of simultaneous turn-on and simultaneous turn-off of the first switching element and the second switching element;
At least one of an overshoot current and an undershoot current of a current supplied from the constant current source, which is caused by simultaneous turn-on or simultaneous turn-off of the first switching element and the second switching element, is reduced. Drive device for light emitting load. 2. The light emitting load driving device according to claim 1 , wherein the gate driving unit turns on both the first switching element and the second switching element. 3. 2. The light emitting load driving device according to claim 1 , wherein the gate driving unit suppresses at least one of simultaneous turn-on and simultaneous turn-off of the first switching element and the second switching element. The gate driving unit delays at least one of an on timing and an off timing of a switching element connected to a negative terminal side of the constant current source among the first switching element and the second switching element. The drive device of the light emission load described in claim 3 . 2. The driving of a light emitting load according to claim 1 , wherein the gate driver reduces at least one of a turn-on speed and a turn-off speed of at least one of the first switching element and the second switching element. apparatus. The gate driving unit reduces at least one of a turn-on speed and a turn-off speed of a switching element connected to a negative terminal side of the constant current source among the first switching element and the second switching element. The light emitting load driving device according to claim 5 , wherein the driving device is a light emitting load. A drive device 1 of the light-emitting load that is described in any one of claims 1 to 6, wherein the first light emitting load, and the second light-emitting load, the vehicle emitting device characterized by comprising a.

Images