Control device, lighting device, and lighting fixture for vehicle

Abstract

To implement switching of a plurality of power sources and flowing-round prevention in the switching at low cost and with a low loss.SOLUTION: A control device comprises: a first power supply input path from a first power supply input terminal to a load; a second power supply input path from a second power supply input terminal to the load; a first reverse connection protection circuit which is provided in the first power supply input path and blocks a flow of current in a reverse connection of a DC power source; a second reverse connection protection circuit which is provided in the second power supply input path and composed of a switching element which blocks a flow of current in the reverse connection of the DC power source; an activation circuit which is connected to the second power supply input terminal and performs control for turning on the switching element by supplying a power supply voltage from the DC power source from the second power supply input terminal; a current detection circuit which detects the current flowing through the first power supply input path; and a cutoff circuit which turns off the switching element based on the detection current of the current detection circuit and switches a power supply input path to the load from the second power supply input path to the first power supply input path.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a control device, a lighting device, and a vehicle lamp. [Background technology]

[0002] By inserting a diode or ideal diode IC into each power supply line to switch between the two power supplies that supply power to the load, it is possible to switch between the power supplies and prevent leakage from one power supply line to the other.

[0003] For example, Patent Document 1 discloses a vehicle lamp that receives power from a battery and emits light, in which a switch and a reverse polarity protection diode for turning on / off the daytime running lamps (DRL), and a switch and a reverse polarity protection diode for turning on / off the position lamps (Po), are connected in parallel to each other in the power supply path between the battery and the vehicle lamp, thereby controlling the state of power supply to the vehicle lamp. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-225043 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when using diodes, although they are inexpensive, they have large losses. In particular, when diodes handle large currents, heat generation and current consumption increase in proportion to the current, making a heat dissipation structure necessary. Furthermore, as losses increase, it becomes necessary to select a package with high allowable loss, which increases the board area and component costs. Furthermore, when using ideal diode ICs, losses are smaller than diodes, but they are expensive.

[0006] The present invention has been made in view of the above, and an object of the present invention is to realize switching between a plurality of power sources and preventing sneak current during switching at low cost and with low loss. [Means for solving the problem]

[0007] The control device according to the present invention includes a first power supply input path from a first power supply input terminal to a load, a second power supply input path from a second power supply input terminal to the load, a first reverse polarity protection circuit provided in the first power supply input path and preventing current from flowing when a DC power supply is connected in reverse, a second reverse polarity protection circuit provided in the second power supply input path and consisting of a switching element that prevents current from flowing when the DC power supply is connected in reverse, a start-up circuit connected to the second power supply input terminal and controlling the switching element to be turned on when a power supply voltage is supplied from the DC power supply through the second power supply input terminal, a current detection circuit that detects the current flowing in the first power supply input path, and a shut-off circuit that turns off the switching element based on the current detected by the current detection circuit, thereby switching the power supply input path to the load from the second power supply input path to the first power supply input path. [Effects of the Invention]

[0008] According to the present invention, by using a switching element with low loss as a reverse connection protection circuit and providing a shutoff circuit that turns off the switching element based on the current detected by the current detection circuit and switches the power supply input path to the load, it is possible to switch between multiple power sources and prevent sneak current during switching at low cost and with low loss. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a block diagram showing a configuration of a vehicle lamp according to an embodiment of the present invention; [Figure 2]10A and 10B are waveform diagrams of a DRL input voltage input from a DRL input terminal, a DRL input current input from a DRL input terminal, a PO input voltage input from a PO input terminal, a PO input current input from a PO input terminal, a detected current detected by a current detection circuit, and a current consumption in a vehicle lamp according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A vehicle lamp according to an embodiment of the present invention will now be described with reference to the accompanying drawings. In the drawings, the same or equivalent parts are designated by the same reference numerals.

[0011] FIG. 1 is a block diagram showing the configuration of a vehicle lamp 1. The vehicle lamp 1 includes a light source 2 and a lighting control device 3 that controls the lighting of the light source 2. The vehicle lamp 1 is illuminated by receiving power from a battery 4 as a DC power source. The vehicle lamp 1 has lighting functions for multiple purposes, in this case a DRL lighting mode in which it functions as a daytime running lamp (DRL) and a PO lighting mode in which it functions as a position lamp (PO), which are switched between the two modes depending on whether a switch SW connected between the battery 4 and the lighting control device 3 is turned on or off. Daytime running lamps are designed to be approximately 10 to 20 times brighter than position lamps, and a larger current is supplied to the light source 2 than for position lamps.

[0012] The light source 2 is a light-emitting string composed of light-emitting elements 21 and 22 connected in series, and the light-emitting elements are LEDs (Light Emitting Diodes). The number of light-emitting elements constituting the light source 2 is not limited to this, and may be one, or a string composed of three or more light-emitting elements, and the number of light-emitting elements constituting the light source can be set appropriately. Here, each light-emitting element is assumed to be the same and has the same forward voltage, but for example, a combination of light-emitting elements with different emission colors may also be used.

[0013] The lighting control device 3 includes a diode reverse connection protection circuit 31 which is a first reverse connection protection circuit using a diode, a FET reverse connection protection circuit 32 which is a second reverse connection protection circuit using a field effect transistor (FET), a FET start-up circuit 33 which is a start-up circuit that turns on the FET to enable the FET reverse connection protection circuit 32, a current detection circuit 34, and a FET shut-off circuit 35 which is a shut-off circuit that turns off the FET to disable the FET reverse connection protection circuit 32.

[0014] The diode reverse connection protection circuit 31 is provided in the PO input path, which is the first power supply input path between the PO input terminal 5, which is the first power supply input terminal to which the drive voltage for lighting the PO is input from the battery 4, and the light source 2. This circuit is intended to prevent current from flowing in the opposite direction to normal operation through the light source 2 when the battery 4 is accidentally reverse-connected. The diode reverse connection protection circuit 31 is formed by a diode 311, with the anode of the diode 311 connected to the PO input terminal 5 and the cathode connected to the light source 2. The diode 311 is used as the reverse connection protection circuit because the current required to light the PO is smaller than the current required to light the DRL, so the loss due to the use of the diode 311 is small, and diodes are inexpensive. Note that the diode reverse connection protection circuit 31 may be replaced by a reverse connection protection circuit using a FET.

[0015] The FET reverse connection protection circuit 32 is provided in the DRL input path, which is a second power supply input path between the light source 2 and the DRL input terminal 6, which is a second power supply input terminal to which a drive voltage for lighting the DRL is input from the battery 4 via the switch SW. The FET reverse connection protection circuit 32 prevents current from flowing in the direction opposite to that in normal operation through the light source 2 when the battery 4 is accidentally reverse-connected. The FET reverse connection protection circuit 32 is formed by a field-effect transistor (FET) 321, which is a switching element. The FET 321 is a p-channel MOS FET, and its drain is connected to the DRL input terminal 6 and its source is connected to the light source 2. The gate is grounded via a resistor 331 and a transistor 332 in the FET start-up circuit 33. When the transistor 332 in the FET start-up circuit 33 is turned on and the gate becomes negative in potential relative to the source, the FET 321 is turned on. A reverse polarity protection circuit using a diode generates heat due to the voltage drop across the diode, but a reverse polarity protection circuit using a FET has lower losses than a diode because the FET's on-resistance is low, and is also less expensive than an ideal diode IC. As mentioned above, the current required to light the DRL is greater than the current required to light the PO, so a FET is used in this reverse polarity protection circuit.

[0016] A PO drive voltage is applied to the PO input terminal 5 from the battery 4, and a PO drive current for lighting the PO is supplied to the light source 2 by a resistor 341 connected on the PO input path via a diode reverse connection protection circuit 31. Meanwhile, a switch SW is provided between the DRL input terminal 6 and the battery 4. When the switch SW is turned on, a DRL drive current for lighting the DRL is supplied to the light source 2. Therefore, when the switch SW is turned on, the DRL is switched on in priority to the PO.

[0017] The FET start-up circuit 33 is a control circuit for controlling the on / off of the FET 321 in the FET reverse connection protection circuit 32. The FET start-up circuit 33 includes a resistor 331 connected to the gate of the FET 321 and a transistor 332. The collector of the transistor 332 is connected to the resistor 331, and the emitter is grounded. The base of the transistor 332 is connected to the DRL input terminal 6 via a resistor 333. When the switch SW is turned on and a DRL drive voltage is applied from the battery 4 to the DRL input terminal 6, a current flows to the base of the transistor 332, turning the transistor 332 on. When the transistor 332 is turned on, the gate of the FET 321 in the FET reverse connection protection circuit 32 becomes a negative potential relative to the source of the FET 321, turning the FET 321 on. That is, when the switch SW is turned on and a DRL drive voltage is applied from the battery 4 to the DRL input terminal 6, the FET start-up circuit 33 controls the FET in the FET reverse connection protection circuit 32 to the on state.

[0018] The current detection circuit 34 detects the PO input current flowing from the PO input terminal 5 to the light source 2. The current detection circuit 34 includes resistors 341, 342, and 343, and a transistor 344. Resistors 342 and 343 are connected in parallel to resistor 341, and the base of transistor 344 is connected to the junction between resistors 342 and 343. The emitter of transistor 344 is connected to resistors 341 and 342, and the collector is connected to the FET shutoff circuit 35. At the junction between resistors 342 and 343, the voltage drop due to the PO input current is divided, and the divided voltage is applied to the base of transistor 344. When an overcurrent occurs in the PO drive current, the potential difference across resistor 342 increases, and the base voltage of transistor 344, connected to the junction, increases, turning on transistor 344. As a result, an overcurrent is detected, and the detected current is input to the FET shutoff circuit 35 from the connection point between the resistors 341 and 342.

[0019] The FET shutoff circuit 35 is a circuit that shuts off the operation of the FET reverse connection protection circuit 32 that has been turned on by the FET start-up circuit 33. Based on the detection of an overcurrent from the current detection circuit 34, the FET start-up circuit 33 controls the FET 321 in the FET reverse connection protection circuit 32 to change from an on state to an off state, thereby disabling the operation of the FET reverse connection protection circuit 32. The FET shutoff circuit 35 includes a resistor 351 and a transistor 352. One end of the resistor 351 is connected to the collector of the transistor 344 of the current detection circuit 34, and the other end is connected to the base of the transistor 352. The collector of the transistor 352 is connected to the base of the transistor 332 of the FET start-up circuit 33 via a resistor 333, and the emitter is grounded. When the current detection circuit 34 detects an overcurrent, the transistor 344 of the current detection circuit 34 is turned on, and a detection signal is input to the base of the transistor 352 via the resistor 351. In response to the input of the detection signal, transistor 352 is turned on, the base of transistor 332 of FET starter circuit 33 is grounded, and transistor 332 is turned off. By turning transistor 332 off, the potential difference between the gate and source of FET 321 decreases, blocking the source and drain and turning FET 321 off. This shuts off FET reverse connection protection circuit 32. An LED driver may be provided between point A, which is the connection point between the DRL input path and the PO input path, and light source 2.

[0020] Next, the operation of the lighting control device 3 when switching from a PO lighting mode that turns on the PO to a DRL lighting mode that turns on the DRL, and the operation of the lighting control device 3 when switching from the DRL lighting mode to the PO lighting mode will be described.

[0021] Figure 2 shows waveform diagrams of the DRL input voltage input from the DRL input terminal, the DRL input current input from the DRL input terminal, the PO input voltage input from the PO input terminal, the PO input current input from the PO input terminal, the detected current detected by the current detection circuit, and the current consumption during the above operation.

[0022] 2, the period from 0 ms to 50 ms shows a waveform diagram in which the vehicle lamp 1 is in the PO lighting mode. In the PO lighting mode, the power supply voltage of the battery 4 is supplied as the PO input voltage, and a first current, which is the current required to light the PO, flows as the PO input current and is supplied to the light source 2. At this time, the switch SW is in the off state, and both the DRL input voltage and the DRL input current are zero.

[0023] At 50 ms, switch SW is turned on, switching from PO lighting mode to DRL lighting mode. Turning switch SW on connects DRL input terminal 6 to battery 4, and the DRL input voltage input from the DRL input terminal rises rapidly to the power supply voltage of battery 4. This activates FET start-up circuit 33, causing current to flow to the base of transistor 332 via resistor 333, turning on transistor 332. Turning on transistor 332 places the gate of FET 321 at a negative potential relative to the source of FET 321 in FET reverse connection protection circuit 32, turning on FET 321, and enabling FET reverse connection protection circuit 32. Activating FET reverse connection protection circuit 32 brings the DRL input path into a conductive state, causing a DRL input current to flow rapidly from DRL input terminal 6 to light source 2, reaching the second current value required to turn on the DRL. When a large DRL input current flows from the DRL input path, no current flows in the PO input path, and the PO input current becomes zero. This switches from PO lighting mode to DRL lighting mode.

[0024] Next, we will explain the operation when switching from DRL lighting mode to PO lighting mode. In Figure 2, at 150 ms, switch SW is turned off and switching from DRL lighting mode to PO lighting mode is performed. When switch SW is turned off, the DRL input terminal 6 is disconnected from the battery 4 and the supply of power supply voltage to the battery 4 is cut off.

[0025] However, even if the supply of power voltage from the DRL input terminal 6 is interrupted, the FET 321 remains on immediately after the interruption, and the FET reverse connection protection circuit 32 remains enabled. Therefore, a sneak current flows from Point A, the connection point between the DRL input path and the PO input path, toward the DRL input path. Due to the sneak current, the PO input current rises rapidly from zero, exceeding the current value in PO lighting mode, to a current value that satisfies the DRL lighting conditions. The sneak current flows from Point B, the connection point between the DRL input path and the input path to the base of transistor 332 in the FET starter circuit 33, to the base of transistor 332, thereby maintaining transistor 332 in an on state. This allows the FET starter circuit 33 to maintain the FET reverse connection protection circuit 32 enabled, and the sneak current continues. If the sneak current continues, it can cause inconvenience, such as an inability to switch to PO lighting mode.

[0026] Therefore, to eliminate this sneak current and enable swift switching from DRL lighting mode to PO lighting mode, current detection circuit 34 and FET shutoff circuit 35 are provided. When an overcurrent that satisfies the DRL lighting conditions occurs in the PO input current, the potential difference across resistor 342 of current detection circuit 34 increases, and the base voltage of transistor 344 connected to this connection point increases, turning on transistor 344. This detects an overcurrent, and a detected current flows from the connection point of resistors 341 and 342 to FET shutoff circuit 35.

[0027] The detection current is input to the base of transistor 352 in FET shutoff circuit 35, turning transistor 352 on. The collector of transistor 352 is connected to the base of transistor 332 in FET start-up circuit 33 via resistor 333, and the emitter of transistor 352 is grounded. Therefore, turning transistor 352 on grounds the base of transistor 332 and cuts off the supply of sneak current to the base. With the sneak current no longer being supplied to the base, transistor 332 is turned off, reducing the potential difference between the gate and source of FET 321 in FET reverse connection protection circuit 32, cutting off the source-drain connection and turning FET 321 off. This disables the function of FET reverse connection protection circuit 32 and stops the sneak current from flowing into the DRL input path.

[0028] When the sneak current stops, the DRL input voltage drops to zero, and the DRL input current also drops to zero. Furthermore, because the sneak current stops, the PO input current supplied from the PO input terminal 5 does not flow into the DRL input path at point A, but flows toward light source 2 as the drive current for light source 2, and the PO input current changes to the current value required to light the PO. Furthermore, as the PO input current drops from the current value that satisfies the DRL lighting conditions to the current value required to light the PO, transistor 344 of the current detection circuit 34 turns off, and the detected current changes to zero. As a result, the system switches from DRL lighting mode to PO lighting mode, and power is supplied from the PO input path to light the PO.

[0029] In the above embodiment, FETs are used as switching elements, but the present invention is not limited to this and bipolar transistors and insulated gate transistors may also be used.

[0030] Furthermore, in the above embodiment, the description has been given of a vehicle lamp, but the present invention is not limited to this and can also be used as a lighting device for other purposes, such as amusement equipment, etc. Furthermore, the present invention is not limited to lighting devices and can be applied to circuit devices that have multiple power supply input paths and drive loads other than a shared light source, or to circuit devices that drive a single shared control circuit.

[0031] Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to the above-described embodiments, but includes the scope of the invention described in the claims and its equivalents. [Explanation of symbols]

[0032] 1...vehicle lamp, 2...light source, 3...lighting control device, 4...battery, 5...PO input terminal, 6...DRL input terminal, 21, 22...light emitting element, 31...diode reverse connection protection circuit, 32...FET reverse connection protection circuit, 33...FET start circuit, 34...current detection circuit, 35...FET shutoff circuit, 311...diode, 321...FET, 331, 333, 341, 342, 343, 351...resistor, 332, 344, 352...transistor, SW...switch

Claims

1. a first power supply input path from the first power supply input terminal to the load; a second power input path from a second power input terminal to the load; a first reverse connection protection circuit provided in the first power supply input path and configured to prevent current from flowing when the DC power supply is reverse-connected; a second reverse connection protection circuit provided in the second power supply input path and including a switching element that prevents current from flowing when the DC power supply is reverse connected; a start-up circuit connected to the second power supply input terminal, the start-up circuit controlling the switching element to be turned on when a power supply voltage is supplied from the DC power supply through the second power supply input terminal; a current detection circuit that detects a current flowing through the first power supply input path; a cutoff circuit that switches the power supply input path to the load from the second power supply input path to the first power supply input path by turning off the switching element based on the current detected by the current detection circuit, Control device.

2. The switching element is an FET. The control device according to claim 1 .

3. the first power supply input terminal is always connected to the DC power supply; the second power supply input terminal is selectively connected to the DC power supply; the first power supply input path supplies a first current to the load; the second power supply input path supplies a second current greater than a first current to the load, and when the second power supply input terminal is connected to the DC power supply, the power supply input path to the load is switched to the second power supply input path in preference to the first power supply input path; The control device according to claim 1 or 2.

4. the first reverse connection protection circuit is a diode. The control device according to claim 3 .

5. the load is a light source, and the lighting mode is controlled by switching the power supply input path; The control device according to claim 1 .

6. The lighting modes are a PO lighting mode in which a driving current is supplied through the first power supply input path to function as a position lamp, and a DRL lighting mode in which a driving current is supplied through the second power supply input path to function as a daytime running lamp. The control device according to claim 5 .

7. A lighting device comprising the control device according to claim 5 or 6 and the light source.

8. A vehicle lamp constructed using the lighting device according to claim 7.

Images