JP2018183008A - Voltage output device and power supply system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a voltage output device and power supply system having the same, configured so that an average of voltages output through a switch is not limited.SOLUTION: A voltage output device 2 is configured so that an input voltage input into an input terminal of a booster circuit 21 varies. The booster circuit 21 boosts an input voltage to a voltage which is not less than an upper-limit value of a variation range of the input voltage and outputs the boosted voltage through an output switch 22. A switching part 24 alternately repeats switching to turning on and off of the output switch 22.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a voltage output device and a power supply system.

  As a power supply system mounted on a vehicle, there is a power supply system in which a battery outputs a voltage to a light emitting diode. In this power supply system, the cathode of the light emitting diode is grounded via a resistor, and the voltage output from the battery is applied to the anode of the light emitting diode.

  It is assumed that the battery also supplies power to the starter. In this case, a large current is supplied from the battery to the starter while the starter is operating. In the battery, current is output from the battery main body via an internal resistance. Therefore, when the current output from the battery is large, the width of the voltage drop generated by the internal resistance is large. Thus, while the starter is operating, the output voltage of the battery is low. When the starter has stopped operating, the amount of voltage drop caused by the internal resistance is small because the current output from the battery is small, and the output voltage of the battery is high.

  The light emitting diode functions as a lamp, or an alarm for notifying various information, and the intensity of light sensed by a person corresponds to the average value of the intensity of light emitted from the light emitting diode. The average value of the light intensity emitted by the light emitting diode is larger as the average value of the current flowing through the light emitting diode is larger. The average value of the current flowing to the light emitting diode is larger as the average value of the voltage applied to the anode of the light emitting diode is higher. Therefore, the intensity of light sensed by a person is larger as the average value of the voltage applied to the anode of the light emitting diode, ie, the higher the output voltage of the battery.

  Since the output voltage of the battery differs depending on whether or not the starter is operating, the intensity of light sensed by a person differs depending on whether or not the starter is operating. For this reason, when the starter operates or when the starter stops operating, the light emitted from the light emitting diode flickers.

  Patent Document 1 discloses a technique for outputting a voltage through a switch. In this technique, switching on and off of the switch is alternately repeated, and the duty related to the on and off of the switch is adjusted to adjust the average value of the voltage output through the switch. The duty related to the on and off of the switch is a ratio of the period in which the switch is on during a certain period.

  By using the technology described in Patent Document 1, it is possible to configure a power supply system in which the flicker of the light emitted from the light emitting diode is prevented. Specifically, a switch is provided between the battery and the anode of the light emitting diode, and switching on and off of the switch is alternately repeated. By adjusting the duty of turning on and off the switch, the average value of the voltage applied to the anode of the light emitting diode can be kept constant.

  It is assumed that while the starter is operating, the output voltage of the battery is 9V, and while the starter is not operating, the output voltage of the battery is 12V. In this case, when the output voltage of the battery is 9 V, the duty related to the on and off of the switch is adjusted to 100%, and when the output voltage of the battery is 12 V, the duty related to the on and off of the switch is 75% Adjust to As described above, when the duty related to the on and off of the switch is adjusted, the average value of the voltage applied to the light emitting diode is always maintained at 9 V, so that the flicker of the light emitted from the light emitting diode is prevented.

JP 2003-338396 A

  However, in the power supply system configured using the technology described in Patent Document 1, the average value of the voltage output through the switch is limited to the lower limit value or less of the voltage input to the switch. For this reason, the average value of the light intensity emitted by the light emitting diode is the average value of the light intensity emitted by the light emitting diode when the average value of the voltage applied to the anode of the light emitting diode is the lower limit of the voltage input to the switch. Limited to less than or equal to the value. As a result, the power supply system configured using the technology described in Patent Document 1 has a problem that the average value of the light intensity emitted by the light emitting diode is small.

  The present invention has been made in view of such circumstances, and an object of the present invention is a voltage output device in which the average value of voltages output via switches is not limited, and a power supply system including the voltage output device. It is to provide.

  In a voltage output device according to one aspect of the present invention, a booster circuit that boosts a fluctuating input voltage to a voltage equal to or higher than an upper limit value of a fluctuation range of the input voltage, a switch, and switching the switch on and off And a switching unit that repeats alternately, and the booster circuit outputs a boosted voltage via the switch.

  A power supply system according to an aspect of the present invention includes the voltage output device described above and a light emitting diode to which a voltage output from the voltage output device is applied.

  According to the above aspect, the average value of the voltage output through the switch is not limited.

It is a block diagram which shows the principal part structure of the power supply system in this embodiment. It is explanatory drawing of operation | movement of a voltage output device. It is a circuit diagram of a booster circuit. It is explanatory drawing of operation | movement of a comparator.

Description of the embodiment of the present invention
First, the embodiments of the present invention will be listed and described. At least a part of the embodiments described below may be arbitrarily combined.

(1) A voltage output device according to one aspect of the present invention includes a booster circuit that boosts a fluctuating input voltage to a voltage that is equal to or higher than an upper limit value of the fluctuation range of the input voltage; a switch; And a switching unit that alternately switches to the switching unit, and the booster circuit outputs a boosted voltage via the switch.

  In the above aspect, the booster circuit boosts the input voltage to a voltage equal to or higher than the upper limit value of the variation range of the input voltage, and outputs the boosted voltage via the switch. For this reason, it is possible to adjust the average value of the voltage output via the switch to a voltage higher than the lower limit value of the fluctuation range of the input voltage by alternately repeating switching on and off of the switch . As a result, the average value of the voltage output through the switch is not limited to the lower limit value or less of the fluctuation range of the input voltage.

(2) In the voltage output device according to one aspect of the present invention, the booster circuit boosts the input voltage to a predetermined target voltage which is equal to or higher than the upper limit value.

  In the above aspect, the booster circuit outputs a constant target voltage. Therefore, when the average value of the voltage output through the switch is fixed to a constant value, it is not necessary to change the duty related to the on and off of the switch.

(3) A power supply system according to an aspect of the present invention includes the voltage output device described above and a light emitting diode to which the voltage output from the voltage output device is applied.

  In the above aspect, the voltage output from the voltage output device is applied to the light emitting diode, and the light emitting diode emits light.

Details of the Embodiment of the Present Invention
A specific example of a power supply system according to an embodiment of the present invention will be described below with reference to the drawings. The present invention is not limited to these exemplifications, but is shown by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

  FIG. 1 is a block diagram showing an essential configuration of a power supply system 1 in the present embodiment. The power supply system 1 is preferably mounted on a vehicle, and has a voltage output device 2, a generator 31, a battery 32, a starter 33 and LED units 41 and 42. The voltage output device 2 includes a booster circuit 21, an output switch 22, a signal output unit 23, and a switching unit 24.

  One end of the generator 31 and the starter 33 and the positive electrode of the battery 32 are connected to the input end of the booster circuit 21 of the voltage output device 2. The other ends of the generator 31 and the starter 33 and the negative electrode of the battery 32 are grounded. The output end of the booster circuit 21 is connected to one end of the output switch 22. The other end of the output switch 22 is connected to one end of the LED units 41 and 42. The other ends of the LED units 41 and 42 are grounded. In the voltage output device 2, the signal output unit 23 is connected to the switching unit 24.

The LED unit 41 includes a diode D1, a light emitting diode E1 and a resistor R1, which are connected in series. Specifically, the cathode of the diode D1 is connected to the anode of the light emitting diode E1, and the cathode of the light emitting diode E1 is connected to one end of the resistor R1. The anode of the diode D1 is connected to the other end of the output switch 22, and the other end of the resistor R1 is grounded.
The connection order is not limited to the order of the diode D1, the light emitting diode E1, and the resistor R1 because the diode D1, the light emitting diode E1, and the resistor R1 may be connected in series.

The LED unit 42 includes a diode D2, two light emitting diodes E2 and E2, and a resistor R2, which are also connected in series. Specifically, the cathode of the diode D2 is connected to the anode of one light emitting diode E2, and the cathode of one light emitting diode E2 is connected to the anode of the other light emitting diode E2. The cathode of the other light emitting diode E2 is connected to one end of the resistor R2. The anode of the diode D2 is connected to the other end of the output switch 22, and the other end of the resistor R2 is grounded.
The connection order is not limited to the order of the diode D2, the light emitting diodes E2 and E2, and the resistor R2 as long as the diode D2, the two light emitting diodes E2 and E2, and the resistor R2 may be connected in series.

  The generator 31 interlocks with an engine (not shown) of the vehicle to generate AC power, and rectifies the generated AC power into DC power. The generator 31 outputs a DC generated voltage Vg related to the rectified DC power to the input end of the booster circuit 21 and the positive electrode of the battery 32.

  When the generator 31 generates alternating current power, the generator 31 outputs the generated voltage Vg to the input end of the booster circuit 21, and the battery 32 does not output a voltage. Therefore, when the generator 31 generates alternating current power, the input voltage input to the input terminal of the booster circuit 21 is the generated voltage Vg. Further, when the generator 31 generates alternating current power, the generated voltage Vg is applied to the positive electrode of the battery 32, and the battery 32 is charged.

  The starter 33 is a motor for starting an engine (not shown) of the vehicle. When the engine has stopped operating, the generator 31 has also stopped operating. For this reason, the starter 33 operates in a state in which the generator 31 has stopped operating. Electric power is supplied to the starter 33 from the battery 32.

  When the generator 31 and the starter 33 stop operating, the battery 32 outputs the first battery voltage Vb1 to the input end of the booster circuit 21. In the case where the generator 31 has stopped operating, when the starter 33 is operating, the battery 32 outputs the second battery voltage Vb2 to the input end of the booster circuit 21. Each of the first battery voltage Vb1 and the second battery voltage Vb2 is lower than the generated voltage Vg.

  In the battery 32, a current is output from a battery main body (not shown) through an internal resistance (not shown), and a voltage drop occurs in the internal resistance. When the starter 33 is not operating, no current flows from the battery 32 to the starter 33, so the value of the current flowing through the internal resistance is small, and the width of the voltage drop caused by the internal resistance is small. When the starter 33 is in operation, a large current flows from the battery 32 to the starter 33, and the voltage drop produced by the internal resistance is wide. Therefore, the first battery voltage Vb1 is higher than the second battery voltage Vb2.

  As described above, one of the generated voltage Vg, the first battery voltage Vb1, and the second battery voltage Vb2 is input to the input terminal of the booster circuit 21, and the input voltage input to the input terminal of the booster circuit 21 fluctuates. .

  The booster circuit 21 boosts the input voltage to a constant target voltage Vm that is equal to or higher than the generated voltage Vg, and outputs the boosted voltage to the LED units 41 and 42 via the output switch 22.

  The signal output unit 23 outputs a first PWM (Pulse Width Modulation) signal configured by the high level voltage and the low level voltage to the switching unit 24. In the first PWM signal, switching from low level voltage to high level voltage or switching from high level voltage to low level voltage is performed periodically. The duty ratio of the duty of the first PWM signal, that is, the period in which the voltage indicated by the first PWM signal is high level voltage in one cycle is fixed. The unit of duty is a percentage.

  When the voltage indicated by the first PWM signal is switched from the low level voltage to the high level voltage, the switching unit 24 switches the output switch 22 from off to on and changes the voltage indicated by the first PWM signal from the high level voltage to the low level voltage. When switched, the output switch 22 is switched from on to off. The switching unit 24 alternately repeats switching on and off of the output switch 22 in accordance with the voltage indicated by the first PWM signal.

As described above, in the first PWM signal, switching from the low level voltage to the high level voltage or switching from the high level voltage to the low level voltage is periodically performed. Therefore, the switching unit 24 periodically switches the output switch 22 from off to on or switches the output switch 22 from on to off. The duty relating to the on and off of the output switch 22, that is, the ratio of the period in which the output switch 22 is on in one cycle occupies substantially the duty of the first PWM signal. Therefore, the duty relating to the on and off of the output switch 22 is also fixed.
The output switch 22 is configured by an FET (Field Effect Transistor), a bipolar transistor, or the like.

  The voltage output from the voltage output device 2 through the output switch 22 is applied to the light emitting diode E1 through the diode D1 in the LED unit 41. When the voltage output device 2 outputs a voltage through the output switch 22, a current flows in the order of the diode D1, the light emitting diode E1, and the resistor R1, and the light emitting diode E1 emits light. The light emitting diode E1 functions as an illuminating lamp or an alarm that notifies various information.

  As the average value of the voltage output through the output switch 22 is higher, the average value of the current flowing through the light emitting diode E1 is larger. Also, the larger the average value of the current flowing to the light emitting diode E1, the larger the average value of the light intensity emitted by the light emitting diode E1, that is, the light intensity sensed by a person. Thus, the higher the average value of the voltage output via the output switch 22, the greater the intensity of light perceived by a person.

  Similarly, the voltage output by the voltage output device 2 through the output switch 22 is applied to the light emitting diodes E2 and E2 in the LED unit 42 through the diode D2. When the voltage output device 2 outputs a voltage through the output switch 22, a current flows in the order of the diode D2, the two light emitting diodes E2 and E2, and the resistor R2, and the light emitting diodes E2 and E2 emit light. The light emitting diode E2 also functions as a lamp or a notification tool for notifying various information.

  As the average value of the voltage output through the output switch 22 is higher, the average value of the current flowing through the light emitting diode E2 is larger. Also, the larger the average value of the current flowing to the light emitting diode E2, the larger the average value of the light intensity emitted by the light emitting diode E2, that is, the light intensity sensed by a person. Thus, the higher the average value of the voltage output via the output switch 22, the greater the intensity of light perceived by a person.

  FIG. 2 is an explanatory diagram of the operation of the voltage output device 2. FIG. 2 shows the transition of the input voltage input to the input terminal of the booster circuit 21, the transition of the boosted voltage boosted by the booster circuit 21, and the transition of the output voltage output via the output switch 22. ing. For each transition, time is shown on the horizontal axis and voltage is shown on the vertical axis.

  As shown in FIG. 2, when the generator 31 and the starter 33 stop operating, the first battery voltage Vb1 is input to the input terminal of the booster circuit 21. When the starter 33 is operating, the second battery voltage Vb2 is input to the input terminal of the booster circuit 21. When the generator 31 is operating, that is, when the generator 31 generates alternating current power, the generated voltage Vg is input to the input terminal of the booster circuit 21. As described above, the input voltage input to the input end of the booster circuit 21 fluctuates in accordance with the operating conditions of the generator 31 and the starter 33. The lower limit value of the variation range of the input voltage is the second battery voltage Vb2, and the upper limit value of the variation range of the input voltage is the generated voltage Vg.

  The booster circuit 21 boosts the input voltage to a constant target voltage Vm which is equal to or higher than the generated voltage Vg. When the generator 31 and the starter 33 have stopped operating, the booster circuit 21 boosts the first battery voltage Vb1 to the target voltage Vm. When the starter 33 is operating, the booster circuit 21 boosts the second battery voltage Vb2 to the target voltage Vm. When the generator 31 is operating, the generated voltage Vg is boosted to the target voltage Vm. The booster circuit 21 appropriately adjusts the boosting width so that the boosted voltage becomes the target voltage Vm.

  When the generated voltage Vg matches the target voltage Vm, when the generator 31 is operating, the booster circuit 21 does not perform boosting, and uses the generated voltage Vg as the target voltage Vm as it is, the output switch 22. Output through

  When the output switch 22 is on, a voltage is output to the LED units 41 and 42, and the output voltage output through the output switch 22 substantially matches the target voltage Vm. When the output switch 22 is off, the output of the voltage to the LED units 41 and 42 is stopped, and the output voltage is zero V. As described above, the switching unit 24 alternately switches the output switch 22 on and off.

  When a duty relating to on and off of the output switch 22 is described as D, an average value Va of voltages output via the output switch 22 is expressed by (Vm · D / 100). “·” Represents a product. In the example of FIG. 2, since the duty D is (100/2/3), the average value Va is (Vm / 2/3). As described above, the duty D is fixed, and the average value Va of the voltage output through the output switch 22 is higher than the second battery voltage Vb2 and lower than the generated voltage Vg, ie, the input voltage Is adjusted to a voltage within the fluctuation range of Since target voltage Vm and duty D are fixed, average value Va is constant.

  FIG. 3 is a circuit diagram of the booster circuit 21. As shown in FIG. The booster circuit 21 includes a booster switch 51, a switching unit 52, a comparator 53, a differential amplifier 54, a triangular wave generator 55, capacitors C1 and C2, a diode D3, an inductor L1 and resistors R1 and R2. The comparator 53 and the differential amplifier 54 each have a plus terminal, a minus terminal, and an output terminal.

  One end of the capacitor C 1 and the inductor L 1 is connected to one end of the generator 31 and the starter 33 and the positive electrode of the battery 32. The other end of the capacitor C1 is grounded. The other end of the inductor L1 is connected to one end of the boost switch 51 and the anode of the diode D3. The other end of the boost switch 51 is grounded. The cathode of the diode D3 is connected to one end of the output switch 22, the capacitor C2 and the resistor R1. The other end of the resistor R1 is connected to one end of the resistor R2. The other end of the resistor R2 is grounded.

  The switching unit 52 is connected to the output terminal of the comparator 53. The output terminal of the differential amplifier 54 is connected to the positive terminal of the comparator 53. A triangular wave generator 55 is connected to the negative terminal of the comparator 53. A constant reference voltage Vr is applied to the positive terminal of the differential amplifier 54. The negative terminal of the differential amplifier 54 is connected to a connection node between the resistors R1 and R2.

The input voltage input to the input terminal of the booster circuit 21 is smoothed by the capacitor C1. The switching unit 52 alternately repeats switching on and off of the boost switch 51. As a result, the input voltage smoothed by the capacitor C1 is boosted. The booster switch 51 is also configured by an FET or a bipolar transistor. Hereinafter, boosting of the input voltage will be described.
The switching unit 52 periodically switches the boost switch 51 from off to on or switches the boost switch 51 from on to off, and adjusts the duty related to the on and off of the boost switch 51. This duty is also a ratio occupied by a period in which the boost switch 51 is on in one cycle.

  When the boost switch 51 is on, current flows in the order of the inductor L 1 and the boost switch 51. The value of the current flowing through the inductor L1 rises with a constant slope as time passes. While the boost switch 51 is on, energy is stored in the inductor L1. When the boost switch 51 is on, zero V is output through the diode D3.

  When the boost switch 51 is switched from on to off, current flows in the order of the inductor L1 and the diode D3, and the value of the current flowing in the inductor L1 decreases. When the boost switch 51 is off, the value of the current flowing through the inductor L1 decreases at a constant slope as time passes.

  While the boost switch 51 is off, the inductor L1 outputs a voltage higher than the input voltage applied across the capacitor C1 through the diode D3. While the boost switch 51 is off, the inductor L1 outputs a constant voltage. The difference between the voltage output from the inductor L1 and the input voltage increases as the absolute value of the slope of the current value decreasing with the passage of time increases.

  The absolute value of the slope of the current value decreasing with time when the boost switch 51 is off is larger as the energy stored in the inductor L1 is larger, that is, the longer the period in which the boost switch is on is longer. Therefore, the voltage that the inductor L1 outputs while the boost switch 51 is off is higher as the duty related to the on and off of the boost switch 51 is larger.

  When the boost switch 51 is switched from off to on, a current flows in the order of the inductor L1 and the boost switch 51, and the value of the current flowing in the inductor L1 rises again with the passage of time. While the boost switch 51 is on, zero V is output through the diode D3 as described above.

  The capacitor C2 smoothes the voltage output from the diode D3, and the voltage smoothed by the capacitor C2 is output to the output switch 22. The voltage smoothed by the capacitor C2 is a boosted voltage boosted by the booster circuit 21. The boosted voltage is also higher as the duty relating to on and off of the boost switch 51 is larger. The boosted voltage is higher than the input voltage smoothed by the capacitor C1.

  The resistors R1 and R2 divide the boosted voltage and output the divided voltage divided to the negative terminal of the differential amplifier 54. When the resistance values of the resistors R1 and R2 are described as r1 and r2, respectively, the divided voltage is represented by the product of the boosted voltage and (r2 / (r1 + r2)). Each of the resistance values r1 and r2 is constant. Therefore, the voltage output from the resistors R1 and R2 is proportional to the boosted voltage, and is higher as the boosted voltage is higher.

  The differential amplifier 54 is a so-called error amplifier, and outputs a voltage corresponding to the difference between the reference voltage Vr and the divided voltage divided by the resistors R1 and R2 to the plus terminal of the comparator 53 as the threshold voltage Vth. Do. Specifically, the threshold voltage Vth is higher as the voltage calculated by subtracting the divided voltage from the reference voltage Vr is higher.

  The triangular wave generator 55 outputs a triangular wave. The comparator 53 outputs a second PWM signal according to the relationship between the triangular wave output from the triangular wave generator 55 and the voltage output from the differential amplifier 54.

  FIG. 4 is an explanatory view of the operation of the comparator 53. As shown in FIG. FIG. 4 shows the waveform of the triangular wave output from the triangular wave generator 55 and the waveform of the second PWM signal. With respect to the waveforms of the triangular wave and the second PWM signal, voltages are shown on the vertical axis and time is shown on the horizontal axis. In FIG. 4, the high level voltage is indicated by "H" and the low level voltage is indicated by "L".

  In the triangular wave output by the comparator 53, as shown in FIG. 4, a gradual voltage rise and a rapid voltage drop are periodically repeated. The triangular wave output from the comparator 53 is a so-called sawtooth wave. While the threshold voltage Vth is equal to or higher than the voltage of the triangular wave, the second PWM signal indicates a high level voltage, and while the threshold voltage Vth is less than the voltage of the triangular wave, the second PWM signal indicates a low level voltage.

  The duty of the second PWM signal output from the comparator 53 is larger as the threshold Vth is higher and smaller as the threshold voltage Vth is lower. The duty of the second PWM signal is also a ratio occupied by a period in which the second PWM signal indicates a high level voltage in one cycle.

  When the voltage indicated by the second PWM signal is switched from the low level voltage to the high level voltage, the switching unit 52 switches the boost switch 51 from off to on. When the voltage indicated by the second PWM signal is switched from the high level voltage to the low level voltage, the switching unit 52 switches the boost switch 51 from on to off. The duty of the second PWM signal substantially matches the duty related to the on and off of the boost switch 51. Therefore, the boosted voltage is higher as the duty of the second PWM signal is larger.

The boosted voltage boosted by the booster circuit 21 temporarily fluctuates when the input voltage input to the input terminal of the booster circuit 21 fluctuates, and returns immediately to the target voltage Vm.
When the boosted voltage rises, the divided voltage obtained by dividing the resistors R1 and R2 also rises, so the voltage calculated by subtracting the divided voltage from the reference voltage Vr decreases. As a result, the threshold voltage Vth decreases and the duty of the second PWM signal decreases. As a result, the boosted voltage decreases and the divided voltage also decreases.

  When the boosted voltage decreases, the divided voltage also decreases, and the voltage calculated by subtracting the divided voltage from the reference voltage Vr increases. Therefore, the threshold voltage Vth rises, and the duty of the second PWM signal rises. As a result, the boosted voltage rises and the divided voltage also rises.

  The duty of the second PWM signal is adjusted such that the divided voltage becomes the reference voltage Vr, that is, the boosted voltage becomes a voltage represented by the product of the reference voltage Vr and ((r1 + r2) / r2). Ru. The target voltage Vm substantially matches the product of the reference voltage Vr and ((r1 + r2) / r2).

  As described above, when the input voltage input to the input terminal of the booster circuit 21 fluctuates, the boosted voltage boosted by the booster circuit 21 also fluctuates. Thereafter, in the booster circuit 21, the duty of the second PWM signal, that is, the boosted width is adjusted according to the input voltage inputted to the input terminal of the booster circuit 21, and the boosted voltage immediately returns to the target voltage Vm.

  Using a booster circuit in which the comparator 53, the differential amplifier 54 and the triangular wave generator 55 are replaced with a microcomputer (hereinafter referred to as a microcomputer) and a filter in the booster circuit 21 as a booster circuit for boosting the input voltage to the target voltage Vm. it can. When this booster circuit is used, the filter removes noise from the voltage divided by the resistors R1 and R2, and the microcomputer converts the analog value of the voltage from which the noise is removed by the filter into a digital value and converts it. A second PWM signal is generated based on the digital value.

  Thus, when the second PWM signal is generated, the processing of the microcomputer is slow, and a delay occurs in the filter. Therefore, for the booster circuit including a microcomputer and a filter, if the input voltage input to the input terminal of the booster circuit changes rapidly and the boosted voltage fluctuates rapidly, the boosted voltage fluctuates before reaching the target voltage Vm. It takes a long time to return.

  The average value of the voltage output via the output switch 22 fluctuates from the average value Va as the boosted voltage rapidly changes. If the time from when the boosted voltage fluctuates to when it returns to the target voltage Vm is long, the average value of the voltage output through the output switch 22 gradually returns to the average value Va. As a result, the light emitted from the light emitting diodes E1, E2, E2 flickers.

  On the other hand, in the booster circuit 21, the aforementioned microcomputer and filter are not used. Therefore, even when the input voltage input to the input terminal of the booster circuit changes rapidly and the boosted voltage fluctuates rapidly, the boosted voltage immediately returns to the target voltage Vm. For this reason, the light emitted from the light emitting diodes E1, E2 and E2 does not flicker.

  In the voltage output device 2 configured as described above, as described above, the booster circuit 21 boosts the input voltage to the target voltage Vm that is equal to or higher than the upper limit value of the fluctuation range of the input voltage. Therefore, by adjusting the duty relating to the on and off of the output switch 22, the average value Va of the voltage output via the output switch 22 is the lower limit value of the fluctuation range of the input voltage, that is, the second battery voltage Vb2. It can be adjusted to a higher average value. As a result, the average value Va is not limited to the lower limit value or less of the fluctuation range of the input voltage.

  Therefore, the average value of the voltages to be applied to the LED units 41 and 42 is determined by the specifications of the LED units 41 and 42, and the average value determined by the specifications is the input voltage input to the input terminal of the booster circuit 21. It is assumed that the voltage is higher than the lower limit value of the fluctuation range. Even in this case, the voltage output device 2 can adjust the average value Va of the voltages output via the output switch 22 to an average value determined by the specification. As a result, the light emitting diodes E1 and E2 of the LED units 41 and 42 emit light of appropriate intensity. The average values of the voltages to be applied to the LED units 41 and 42 are the same or substantially the same.

  Further, since the target voltage Vm is a constant value, when fixing the average value Va to a constant value, it is not necessary to change the duty relating to the on and off of the output switch 22. Therefore, the signal output unit 23 can be easily configured.

  The boosted voltage boosted by the booster circuit 21 may be equal to or higher than the upper limit value of the fluctuation range of the input voltage, so the target voltage Vm may not be set. In this case, the signal output unit 23 adjusts the duty of the second PWM signal, that is, the duty relating to the on and off of the output switch 22 according to the boosted voltage. Thus, even when the voltage output device 2 is configured, the average value Va is not limited to the lower limit value or less of the fluctuation range of the input voltage, and the average value Va is determined according to the specification. Can be adjusted.

  In addition, the LED unit 41 may have a drive switch connected in series to the diode D1, the light emitting diode E1, and the resistor R1. When emitting light to the light emitting diode E1, the drive switch is switched on, a current is supplied to the light emitting diode E1, and when emitting light is stopped to the light emitting diode E1, the drive switch is switched off, to the light emitting diode E1. Stop the current supply.

  Similarly, the LED unit 42 may have a drive switch connected in series to the diode D2, the two light emitting diodes E2 and E2, and the resistor R2. When emitting light to the light emitting diodes E2 and E2, the drive switch is switched on, current is supplied to the light emitting diodes E2 and E2, and when the light emitting diodes E2 and E2 are stopped emitting light, the drive switch is switched off , The current supply to the light emitting diode E2 is stopped.

  Furthermore, the number of light emitting diodes E1 included in the LED unit 41 is not limited to one, and may be two or more. Similarly, the number of light emitting diodes E2 included in the LED unit 42 is not limited to two, and may be one or three or more. Furthermore, the number of LED units connected to the voltage output device 2 is not limited to two, and may be one or three or more. When the number of LED units is three or more, these are connected in parallel.

  Further, the booster circuit 21 may be any circuit that can boost the input voltage. Therefore, a second boost switch may be used instead of the diode D3. One end of the second boost switch is connected to one end of the boost switch 51, and the other end of the second boost switch is connected to one end of the capacitor C2. The booster switch 51 and the second booster switch are complementarily switched on or off. That is, when the boost switch 51 is switched on, the second boost switch is switched off, and when the boost switch 51 is switched off, the second boost switch is switched on. Thus, the booster circuit 21 having the second booster switch functions in the same manner as the booster circuit 21 having the diode D3.

  Furthermore, the waveform output from the triangular wave generator 55 is not limited to the sawtooth wave, and may be, for example, a triangular wave that periodically repeats a gradual rise in voltage and a gradual fall in voltage.

  The disclosed embodiments are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is indicated not by the meaning described above but by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

DESCRIPTION OF SYMBOLS 1 Power supply system 2 Voltage output apparatus 21 Boost circuit 22 Output switch 23 Signal output part 24, 52 Switching part 31 Generator 32 Battery 33 Starter 41, 42 LED unit 51 Boost switch 53 Comparator 54 Differential amplifier 55 Triangular wave generator C1, C2 Capacitor D1, D2, D3 Diode E1, E2 Light Emitting Diode L1 Inductor R1, R2 Resistance

Claims (3)

A booster circuit for boosting a fluctuating input voltage to a voltage equal to or higher than the upper limit value of the fluctuation range of the input voltage;
With the switch
And a switching unit that alternately switches on and off of the switch.
A voltage output device for outputting the boosted voltage via the switch; The voltage output device according to claim 1, wherein the booster circuit boosts the input voltage to a constant target voltage which is equal to or higher than the upper limit value. A voltage output device according to claim 1 or 2;
And a light emitting diode to which a voltage output from the voltage output device is applied.

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