JP6323200B2 - Vehicle headlamp device and constant voltage supply device - Google Patents

Description

  The present invention relates to a vehicle headlamp device and a constant voltage supply device.

  2. Description of the Related Art Conventionally, in a vehicle headlamp device, a method using a switching circuit such as a DC / DC converter is known as a method for driving a load (see, for example, Patent Document 1). In recent years, a vehicle headlamp device using a light emitting diode (LED) has been proposed because of its high luminous efficiency and excellent design. A driving system using a switching circuit is also used for a vehicle headlamp apparatus using the LED.

  When load disconnection or short circuit occurs, overvoltage and overcurrent occur in the switching circuit. This overvoltage and overcurrent may exceed the rated voltage of the parts constituting the circuit, and may cause damage to the parts. For this reason, the vehicle headlamp apparatus has a function of detecting a load failure. As a failure detection method, for example, there is a method in which a reference voltage as a determination threshold is compared with an output voltage of a switching circuit by a comparator. As a reference voltage input to the comparator, a voltage output from a control unit (IC) having a control function is used.

JP 2005-209580 A

  An input voltage from a power source such as a battery is applied to the switching circuit and also applied to the control unit as power for operating the control unit. Usually, the voltage output from the control unit, that is, the reference voltage is set to maintain a constant value. However, when the input voltage is lower than a certain determination voltage, there is a disadvantage that the reference voltage is also lowered as the input voltage is lowered. Therefore, there is a problem that the reference voltage is deviated from an appropriate value and failure detection cannot be performed accurately.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a vehicle headlamp device and a constant voltage supply device that can maintain a constant supply voltage even when the input voltage is reduced. provide.

  In order to solve such a problem, a first invention includes a load that operates by current, a power conversion unit that steps up and down an input voltage to an output voltage of a predetermined voltage through a switching operation, and outputs the output voltage to the load. A control unit that controls the switching operation to control the output of the load, a failure detection unit that detects a load failure based on a comparison between the output voltage and a reference voltage applied from the control unit, and an input voltage A vehicle headlamp device having a voltage supply unit that applies a supply voltage for operating the control unit to the control unit is provided. Here, the voltage supply unit supplies the voltage based on the voltage generated by the switching operation of the power conversion unit so that the supply voltage maintains the determination voltage when the input voltage is lower than a preset determination voltage. Control the voltage.

  Here, in the first invention, the voltage supply unit includes a first diode to which the voltage generated by the switching operation of the power conversion unit is input to the anode, one end connected to the ground, and the other end to the cathode of the first diode. A first capacitor connected to the transistor, a transistor connecting the collector to the connection point of the first diode and the first capacitor, a resistor connected between the collector base of the transistor, an anode connected to the ground, and a cathode connected to the base of the transistor A zener diode connected to a connection point between the first capacitor and the resistor, a second capacitor having one end connected to the ground and the other end connected to the emitter of the transistor, and an anode connected to a connection point between the second capacitor and the transistor. Two diodes and the cathode of the second diode are connected to the cathode and input to the anode It preferably has a third diode which pressure is input, a.

  The second invention outputs a supply voltage to be applied to a predetermined supply target based on the input voltage, and a power converter that steps up and down the input voltage to an output voltage of a predetermined voltage through a switching operation. And a voltage supply unit. Here, the voltage supply unit supplies the voltage based on the voltage generated by the switching operation of the power conversion unit so that the supply voltage maintains the determination voltage when the input voltage is lower than a preset determination voltage. It is preferable to control the voltage.

  Here, in the second invention, the voltage supply unit includes a first diode to which the voltage generated by the switching operation of the power conversion unit is input to the anode, one end connected to the ground, and the other end to the cathode of the first diode. A first capacitor connected to the transistor, a transistor connecting the collector to the connection point of the first diode and the first capacitor, a resistor connected between the collector base of the transistor, an anode connected to the ground, and a cathode connected to the base of the transistor A zener diode connected to a connection point between the first capacitor and the resistor, a second capacitor having one end connected to the ground and the other end connected to the emitter of the transistor, and an anode connected to a connection point between the second capacitor and the transistor. Two diodes and the cathode of the second diode are connected to the cathode and input to the anode It is preferred to have a third diode which pressure is input, a.

  According to the present invention, in a scene where the input voltage is lower than the determination voltage, the supply voltage is controlled based on the voltage generated by the switching operation of the power converter, and the supply voltage can be maintained at the determination voltage. it can. For this reason, the supply voltage can be maintained at a constant voltage value regardless of the decrease in the input voltage.

Explanatory drawing which shows typically the structure of the vehicle headlamp apparatus Explanatory diagram schematically showing the configuration of the voltage supply unit Explanatory diagram showing transition of voltage waveform Explanatory diagram showing the concept of load failure detection

  FIG. 1 is an explanatory diagram schematically showing the configuration of a vehicle headlamp device according to the present embodiment. A vehicle headlamp device is a lighting device applied to a headlamp of a vehicle such as an automobile, and forms a predetermined light distribution pattern in front of the vehicle. The vehicular headlamp apparatus is mainly configured by a load 1, a DC / DC converter 2, a control unit 3, and a voltage supply unit 4. Electric power is supplied to the vehicle headlamp device from a power source such as a battery (not shown) mounted on the vehicle.

  The load 1 is connected to the output terminal of the DC / DC converter 2 and is operated by a current supplied from the DC / DC converter 2. For example, the load 1 is composed of a plurality of light emitting diodes (LEDs) connected in series with each other.

  The DC / DC converter 2 is a power conversion unit that steps up and down (converts) the input voltage Vin to an output voltage Vout of a predetermined voltage and outputs it to the load 1 through a switching operation. An input voltage Vin is applied to a pair of input terminals to which a power source such as a battery (not shown) is connected. One input terminal corresponds to the positive side of the power supply, and the other input terminal corresponds to the ground side. A load 1 is connected to the pair of output terminals, and an output voltage Vout is applied to the load 1. One output terminal corresponds to the positive side of the power supply, and the other output terminal corresponds to the ground side.

  The DC / DC converter 2 is, for example, a step-up / step-down chopper circuit, and mainly includes inductors L1 and L2, a switching element FET such as a MOSFET, a diode D11, and capacitors C11, C21, C22, C31, and C32.

  The capacitor C11 has one terminal connected to the positive input terminal and the other terminal connected to the ground input terminal. The inductor L1 has one terminal connected to the connection point between the positive input terminal and the capacitor C11, and the other terminal connected to the anode of the diode D11 via a pair of capacitors C21 and C22 connected in series. . The cathode of this diode D1 is connected to the positive output terminal. Each of the capacitors C31 and C32 has one terminal connected to the positive output terminal and the other terminal connected to the ground output terminal. These capacitors C31 and C32 are positioned closer to the output terminal than the diode D1. The switching element FET has a drain connected to a connection point between the inductor L1 and the capacitor C21, and a source connected to the ground side. The gate of the switching element FET is connected to the control unit 3. The inductor L2 has one terminal connected to the connection point between the diode D11 and the capacitor C22, and the other terminal connected to the ground side.

  In the DC / DC converter 2, the connection point between the capacitor C <b> 11 and the positive input terminal is connected to the voltage supply unit 4. As a result, the input voltage Vin is applied to the voltage supply unit 4. The connection point between the inductor L1 and the capacitor C21 is connected to the voltage supply unit 4. Thereby, the voltage Va generated by the switching operation of the DC / DC converter 2 is applied to the voltage supply unit 4.

  The control unit 3 has a function of controlling the vehicle headlamp device. A supply voltage Vic is applied to the control unit 3 from the voltage supply unit 4 in order to obtain power for operation.

  As a first function, the control unit 3 controls the gate voltage of the switching element FET to perform the switching operation of the switching element FET. Then, the control unit 3 controls the output of the load 1 through the switching operation of the DC / DC converter 2.

  The control unit 3 receives an output voltage from a comparator COMP as a failure detection unit of the load 1. A reference voltage obtained by dividing the output voltage Vout of the DC / DC converter 2 by the resistors R11 and R12 is input to the comparator COMP, and the reference voltage Vcc output from the control unit 3 is divided by the resistors R21 and R22. The pressed voltage is input. The comparator COMP compares two input voltages, and the output is switched depending on which voltage is larger. That is, the comparator COMP compares the two input voltages, determines whether the load 1 is faulty or not, and notifies the control unit 3 of the result as a difference in output voltage. And the control part 3 judges whether the output current to the load 1 is continued or stopped based on the output voltage from the comparator COMP.

  The voltage supply unit 4 receives the input voltage Vin and outputs a supply voltage Vic applied to the control unit 3. Further, the voltage supply unit 4 is generated by the switching operation of the DC / DC converter 2 so that the supply voltage Vic maintains the determination voltage Vth when the input voltage Vin is lower than the predetermined determination voltage Vth. The output voltage of the supply voltage Vic is controlled by using the input voltage as input.

  FIG. 2 is an explanatory diagram schematically showing the configuration of the voltage supply unit 4. The voltage supply unit 4 includes diodes D1, D2, and D3, capacitors C1 and C2, a resistor R, a transistor Tr, and a Zener diode ZD.

  The voltage Va generated in the DC / DC converter 2 is input to the anode of the diode D1 (first diode). The capacitor C1 has one end connected to the ground and the other end connected to the cathode of the diode D1 (first capacitor). In the transistor Tr, a resistor R is connected between the collector base and a connection point between the collector and the resistor R and a connection point between the diode D1 and the capacitor C1 are connected to each other. The Zener diode ZD has an anode connected to the ground and a cathode connected to a connection point between the base of the transistor Tr and the resistor R. The capacitor C2 has one end connected to the ground and the other end connected to the emitter of the transistor Tr (second capacitor). The diode D2 has an anode connected to the connection point between the capacitor C2 and the transistor Tr, and a cathode connected to the cathode of the diode D3. The input voltage Vin is input to the anode of the diode D3 (third diode). The connection point between the cathodes of the diodes D2 and D3 is connected to the control unit 3, whereby the supply voltage Vic is applied to the control unit 3.

  Hereinafter, the operation of the voltage supply unit 4 according to the present embodiment will be described with reference to FIG. Here, FIG. 3 is an explanatory diagram showing the transition of the voltage waveform. In this figure, (a) shows the transition of the voltage Va, (b) shows the transition of the voltage Vb, (c) shows the transition of the input voltage Vin, and (d) shows the transition of the supply voltage Vic.

  Here, the voltage Va is a voltage generated by the switching operation of the DC / DC converter 2, and the voltage Vb is a voltage at a connection point between the diode D1 and the capacitor C1 (see FIG. 2). The voltage Vc is a voltage at the connection point between the resistor R and the Zener diode ZD, and the voltage Vd is a voltage at the connection point between the cathodes of the diodes D2 and D3 (see FIG. 2).

  In the circuit shown in FIG. 2, the voltage Vc is fixed to the Zener voltage of the Zener diode ZD. By selecting the Zener voltage of the Zener diode ZD, it is possible to determine the determination voltage Vth, that is, what voltage is to be output as a constant voltage as the supply voltage Vic.

  First, when the input voltage Vin is equal to or higher than the voltage Vc, the relationship that the input voltage Vin is larger than the voltage Vd and the voltage Vd is larger than the voltage Vc is established. In this case, the voltage supply unit 4 does not substantially function, and the supply voltage Vic depends on the input voltage Vin. The diode D2 is set from the viewpoint that the input voltage Vin does not go to the transistor Tr side.

  Next, consider the case where the input voltage Vin is lower than the voltage Vc. First, as shown in FIG. 3A, a predetermined voltage is periodically generated in the voltage Va by the switching operation of the switching element FET. That is, 0V (period (a)) and a predetermined voltage (period (b)) appear repeatedly in the voltage Va. The predetermined voltage corresponding to the period (b) can be considered as a voltage (Vin + Vout) obtained by adding the input voltage Vin and the output voltage Vout.

  When the voltage Va is periodically switched, no current flows in this circuit during the period (a). For this reason, the capacitor C1 charges the capacitor C1 corresponding to the period (b) and discharges the capacitor C corresponding to the period (a) so that a current flows.

  The capacitance of the capacitor C1 is set so that the transistor Tr operates normally even during the period (a). Specifically, the capacitor C1 is set so that the voltage Vb is equal to or higher than the voltage Vc. The diode D1 is set from the viewpoint of preventing the current from the capacitor C1 from flowing toward the drain of the switching element FET on the DC / DC converter 2 side.

  When the input voltage Vin is lower than the voltage Vc, the relationship that the voltage Vc is larger than the input voltage Vin and the input voltage Vin is larger than the voltage Vd is established. In this case, the base-emitter voltage of the transistor Tr is secured, and the transistor Tr is turned on. As a result, a voltage obtained by subtracting the base-emitter voltage of the transistor Tr from the voltage Vc is secured as the voltage Vd. That is, the relationship that the voltage Vc is larger than the voltage Vd and the voltage Vd is larger than the input voltage Vin is established. Thus, the supply voltage Vic is guaranteed by the constant voltage Vd (= determination voltage Vth).

  FIG. 4 is an explanatory diagram showing the concept of load 1 failure detection. In the figure, (a) shows the transition of the output voltage Vout, (b) shows the relationship between the output voltage Vout and the normal reference voltage Vcc, and (c) shows the output voltage Vout and the lowered reference voltage Vcc. The relationship is shown.

  When the input voltage Vin for the DC / DC converter 2 is turned on, the output voltage Vout applied to the load 1 changes at a substantially constant value. At this time, when a failure of the load 1 such as disconnection occurs, the output voltage Vout increases as shown in FIG.

  Therefore, as shown in FIG. 6B, failure detection can be performed by comparing the reference voltage Vcc set to a voltage value for detecting an abnormal increase in the output voltage Vout with the output voltage Vout. it can. That is, when the output voltage Vout is equal to or higher than the reference voltage Vcc, it is determined that the load 1 has failed. When the output voltage Vout is lower than the reference voltage Vcc, it is determined that the load 1 has not failed. be able to. In the circuit configuration described above, the reference voltage obtained by dividing the output voltage Vout and the voltage obtained by dividing the reference voltage Vcc are compared by the comparator COMP.

  By the way, although the control part 3 comprised by IC etc. operate | moves by applying the input voltage Vin, the input voltage Vin may fall due to power supply states, such as a battery remaining charge. When the input voltage Vin falls below a predetermined voltage, the reference voltage Vcc output from the control unit 3 also falls accordingly. In this case, as shown in FIG. 6C, a deviation occurs in the reference voltage Vcc serving as a failure detection determination threshold value, and it is difficult to appropriately execute the failure detection.

  In that respect, the vehicle headlamp device of the present embodiment includes a load 1 that operates by current, and a DC / DC converter 2 that steps up and down the input voltage Vin to a predetermined output voltage Vout and outputs it to the load 1 through a switching operation. (Power conversion unit), the control unit 3 that controls the switching operation of the DC / DC converter 2 to control the output of the load 1, and the comparison between the output voltage Vout and the reference voltage Vcc applied from the control unit 3 A comparator COMP (failure detection unit) that detects a failure of the load 1 based on the voltage supply unit 4 that applies a supply voltage Vic for operating the control unit 3 to the control unit 3 based on the input voltage Vin; have. The voltage supply unit 4 is generated by the switching operation of the DC / DC converter 2 so that the supply voltage Vic maintains the determination voltage Vth when the input voltage Vin is lower than the predetermined determination voltage Vth. The supply voltage Vic is controlled based on the voltage Va.

  According to this configuration, in a scene where the input voltage Vin is lower than the determination voltage Vth, the supply voltage Vic is controlled based on the voltage Va, and the supply voltage Vic can be maintained at the determination voltage Vth. For this reason, the supply voltage Vic can be maintained at a constant voltage value regardless of the decrease in the input voltage Vin. As a result, the supply voltage Vic does not decrease to a voltage that causes a decrease in the reference voltage Vcc, and the reference voltage Vcc is also maintained constant. As a result, it is possible to accurately detect the failure of the load 1 regardless of fluctuations in the input voltage Vin.

  Further, in the present embodiment, the voltage supply unit 4 includes a diode D1 (first diode) in which the voltage Va generated by the switching operation of the DC / DC converter 2 is input to the anode, one end connected to the ground, and the other end The capacitor C1 (first capacitor) connected to the cathode of the diode D1, the transistor Tr connecting the collector to the connection point between the diode D1 and the capacitor C1, the resistor R connected between the collector base of the transistor Tr, and the anode being grounded A Zener diode ZD whose cathode is connected to the connection point between the base of the transistor Tr and the resistor R, and a capacitor C2 (second capacitor) whose one end is connected to the ground and the other end is connected to the emitter of the transistor Tr. The connection point between the capacitor C2 and the transistor Tr is on the anode. A diode connection D2 (second diode), the cathode of the diode D2 to the cathode has a diode D3 to the input voltage Vin to the anode is inputted (third diode) with connecting.

  According to this configuration, in a scene where the input voltage Vin is lower than the determination voltage Vth, the supply voltage Vic can be maintained at the determination voltage Vth based on the voltage Va. As a result, the supply voltage Vic does not decrease to a voltage that causes a decrease in the reference voltage Vcc, and the reference voltage Vcc is also maintained constant. As a result, it is possible to accurately detect the failure of the load 1 regardless of fluctuations in the input voltage Vin.

  As mentioned above, although the vehicle headlamp apparatus concerning embodiment of this invention was demonstrated, it is said that this invention is not limited to embodiment mentioned above, A various deformation | transformation is possible within the scope of the invention. Not too long. Moreover, the constant voltage supply apparatus which consists of an electric power conversion part and a voltage supply part as shown to embodiment mentioned above functions as a part of this invention.

DESCRIPTION OF SYMBOLS 1 Load 2 DC / DC converter 3 Control part 4 Voltage supply part D1 Diode D2 Diode D3 Diode C1 Capacitor C2 Capacitor R Resistance ZD Zener diode Tr Transistor

Claims (4)

A load that operates with current,
A power converter that steps up and down an input voltage to an output voltage of a predetermined voltage and outputs it to the load through a switching operation;
A control unit that controls a switching operation of the power conversion unit and performs output control of the load;
A failure detection unit that detects a failure of the load based on a comparison between the output voltage and a reference voltage applied from the control unit;
A voltage supply unit that applies a supply voltage for operating the control unit to the control unit based on the input voltage;
The voltage supply unit is based on a voltage generated by a switching operation of the power conversion unit so that the supply voltage maintains the determination voltage when the input voltage is lower than a predetermined determination voltage. And controlling the supply voltage. The voltage supply unit
A first diode to which a voltage generated by a switching operation of the power converter is input to the anode;
A first capacitor having one end connected to ground and the other end connected to the cathode of the first diode;
A transistor connecting a collector to a connection point between the first diode and the first capacitor;
A resistor connected between the collector base of the transistor;
A Zener diode having an anode connected to ground and a cathode connected to a connection point between the base of the transistor and the resistor;
A second capacitor having one end connected to ground and the other end connected to the emitter of the transistor;
A second diode connected to an anode at a connection point between the second capacitor and the transistor;
A third diode connected to the cathode of the second diode and having the input voltage input to the anode;
The vehicle headlamp device according to claim 1, comprising: A power converter that steps up and down the input voltage to a predetermined output voltage through a switching operation; and
A voltage supply unit that outputs a supply voltage to be applied to a predetermined supply target based on the input voltage, and
The voltage supply unit is based on a voltage generated by a switching operation of the power conversion unit so that the supply voltage maintains the determination voltage when the input voltage is lower than a predetermined determination voltage. And controlling the supply voltage. The voltage supply unit
A first diode to which a voltage generated by a switching operation of the power converter is input to the anode;
A first capacitor having one end connected to ground and the other end connected to the cathode of the first diode;
A transistor connecting a collector to a connection point between the first diode and the first capacitor;
A resistor connected between the collector base of the transistor;
A Zener diode having an anode connected to ground and a cathode connected to a connection point between the base of the transistor and the resistor;
A second capacitor having one end connected to ground and the other end connected to the emitter of the transistor;
A second diode connected to an anode at a connection point between the second capacitor and the transistor;
A third diode connected to the cathode of the second diode and having the input voltage input to the anode;
The constant voltage supply device according to claim 3, comprising: