JP2010183729A - Power supply circuit and illumination apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce manufacturing cost, improve power efficiency and improve reliability in a power supply circuit for supplying power to a plurality of load circuits different in drive current. <P>SOLUTION: A series load circuit is a circuit formed by connecting a light-emitting element unit 851 (the first load circuit) and a light-emitting element unit 852 (the second load circuit) in series. A voltage generating circuit 111 generates a voltage to be applied to the series load circuit. A current detecting circuit 112 detects an electric current flowing through the light-emitting element unit 851. A voltage detecting circuit 113 detects voltages generated on both ends of the series load circuit. A control circuit 114 controls the voltage generating circuit 111 so that the electric current detected by the current detecting circuit 112 becomes a predetermined current value within a range where the voltage detected by the voltage detecting circuit 113 is not more than a predetermined voltage value. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a power supply circuit that supplies power to a plurality of load circuits having different drive currents.

When there are multiple loads that should be controlled at constant current, such as LEDs (light emitting diodes), if the drive currents of the multiple loads are the same, connect the multiple loads in series to form a load circuit and connect to the power supply circuit , Flow the same current through multiple loads.
When the drive currents of a plurality of loads are different, the plurality of loads are divided for each drive current, and only a load having the same drive current is connected in series to form a plurality of load circuits, which are connected to different power supply circuits.
The power supply circuit is configured by connecting a resistor in series from a common power supply circuit to limit the drive current supplied to each load, or by feeding back the drive current and using a buck converter for each. A configuration for driving control is known.

JP 2002-244103 A

Conventionally, when driving a plurality of loads having different driving currents, it has been necessary to prepare a configuration in which a common power supply circuit is used to limit current with a resistor, and different constant current driving circuits for each.
A configuration in which a resistor is connected in series to a common power supply circuit is simple in configuration and can reduce the size of the circuit and the manufacturing cost, but has poor power efficiency.
In addition, the configuration using a flyback converter or the like is high in power efficiency, but the configuration is complicated, the circuit becomes large, and the manufacturing cost increases.
The present invention has been made, for example, in order to solve the above-described problems. In a power supply circuit that supplies power to a plurality of load circuits having different drive currents, the manufacturing cost is low, the power efficiency is high, and the reliability is improved. The purpose is to increase the nature.

The power supply circuit according to the present invention is configured to supply power to a first load circuit that operates with a first drive current and a second load circuit that operates with a second drive current larger than the first drive current. In the power supply circuit that supplies
The power supply circuit has a constant current circuit and a current addition circuit,
The constant current circuit includes a voltage generation circuit, a current detection circuit, a voltage detection circuit, and a control circuit, and a series load in which the first load circuit and the second load circuit are electrically connected in series. Supplying the first drive current to the circuit;
The current adding circuit supplies a current having a current value corresponding to a difference between the first driving current and the second driving current to the second load circuit;
The voltage generation circuit generates a voltage to be applied to the series load circuit,
The current detection circuit uses any one of the first load circuit and the second load circuit as a current detection target circuit, detects a current flowing through the current detection target circuit,
The voltage detection circuit has one of the first load circuit, the second load circuit, and the series load circuit as a voltage detection target circuit, and is generated at both ends of the voltage detection target circuit. Detect the voltage,
The control circuit controls the voltage generation circuit so that the current detected by the current detection circuit becomes a predetermined current value within a range where the voltage detected by the voltage detection circuit is equal to or less than a predetermined voltage value. It is characterized by.

According to the power supply circuit of the present invention, the constant current circuit supplies a predetermined current to a series load circuit in which a plurality of load circuits are connected in series, and the current adding circuit is a part of the plurality of load circuits. Supply insufficient current to the load circuit. A constant current circuit that supplies a relatively large current with a high voltage has a circuit configuration with high power efficiency, and a current addition circuit that supplies a relatively small current with a low voltage uses a simple configuration circuit. The manufacturing cost can be reduced while increasing the power efficiency of the power supply circuit that drives a plurality of load circuits having different driving currents.
In addition, the control circuit controls the voltage generation circuit so that the voltage detected by the voltage detection circuit is equal to or lower than a predetermined voltage value, and the drive current detected by the current detection circuit becomes a predetermined current value. . Thereby, the overvoltage output of the power supply circuit can be prevented, the load circuit can be prevented from being destroyed by the overvoltage, and high reliability can be ensured.

FIG. 3 is a block configuration diagram showing a functional block configuration of lighting apparatus 800 in Embodiment 1. FIG. 3 is an electric circuit diagram illustrating a circuit configuration of the power supply circuit 100 according to the first embodiment. FIG. 3 shows a relationship between voltages and currents of respective parts in the first embodiment. FIG. 3 shows a relationship between voltages and currents of respective parts in the first embodiment. FIG. 6 is an electric circuit diagram illustrating a modification of the voltage detection circuit 113 in the first embodiment. The figure which shows the relationship between the voltage of each part at the time of using the voltage detection circuits 113a-113c, and an electric current. FIG. 6 is an electric circuit diagram illustrating another example of the circuit configuration of the power supply circuit 100 according to the first embodiment. FIG. 6 is an electric circuit diagram illustrating still another example of the circuit configuration of the power supply circuit 100 according to the first embodiment. FIG. 6 is an electric circuit diagram illustrating still another example of the circuit configuration of the power supply circuit 100 according to the first embodiment. FIG. 4 is an electric circuit diagram illustrating a circuit configuration of a power supply circuit 100 according to a second embodiment. FIG. 6 is an electric circuit diagram illustrating another example of the circuit configuration of the power supply circuit 100 according to the second embodiment. FIG. 5 is an electric circuit diagram illustrating a circuit configuration of a power supply circuit 100 according to a third embodiment.

Embodiment 1 FIG.
The first embodiment will be described with reference to FIGS.

FIG. 1 is a block configuration diagram showing a functional block configuration of the lighting apparatus 800 in this embodiment.
The illumination device 800 includes a plurality of types of light emitting elements such as white LEDs and red LEDs. The lighting device 800 has high color rendering properties by mixing light emitted from a plurality of types of light emitting elements, and emits light having a desired color temperature such as a light bulb color.
The light emitting elements have different electrical characteristics for each type, for example, different drive current values.

The lighting device 800 includes a plurality of light emitting element units 851 and 852 and a power supply circuit 100.
Each of the light emitting element units 851 and 852 (load circuit, light emitting element series circuit) has a single type of light emitting element. When the light emitting element units 851 and 852 have a plurality of light emitting elements, the light emitting elements are electrically connected in series with each other.

The power supply circuit 100 supplies power for lighting the light emitting element units 851 and 852 to the light emitting element units 851 and 852. The power supply circuit 100 includes a constant current circuit 110 and a current addition circuit 150.
The constant current circuit 110 supplies current to a circuit (hereinafter referred to as “series load circuit”) in which a plurality of light emitting element units 851 and 852 are electrically connected in series.
The current adding circuit supplies a current to some of the light emitting element units 852 and 852.
In this example, the current supplied from the constant current circuit 110 flows to the light emitting element unit 851 (first load circuit), and supplied from the constant current circuit 110 to the light emitting element unit 852 (second load circuit). The combined current and the current supplied from the current adding circuit 150 flow.
The constant current circuit 110 generates a current having a drive current value (hereinafter referred to as “first drive current”) that lights the light emitting element of the light emitting element unit 851 with a desired brightness. The current adding circuit 150 is a current value corresponding to a difference between a drive current value (hereinafter referred to as “second drive current”) that turns on the light emitting element of the light emitting element unit 852 with a desired brightness, and the first drive current. Generates a current of
As a result, the first drive current flows through the light emitting element unit 851, the second drive current flows through the light emitting element unit 852, and the respective light emitting elements are turned on with a desired brightness.

The constant current circuit 110 includes a voltage generation circuit 111, a current detection circuit 112, a voltage detection circuit 113, and a control circuit 114.
The voltage generation circuit 111 generates a voltage to be applied to the series load circuit.
The current detection circuit 112 detects a current flowing through the light emitting element unit 851. Note that the current detection circuit 112 may be configured to detect a current flowing through the light emitting element unit 852 instead of the light emitting element unit 851. Hereinafter, a circuit that is a current detection target of the current detection circuit 112 is referred to as a current detection target circuit.
The voltage detection circuit 113 detects a voltage generated at both ends of the series load circuit. Note that the voltage detection circuit 113 may be configured not to be a series load circuit but to detect a voltage generated at both ends of the light emitting element unit 851 or the light emitting element unit 852. Hereinafter, a circuit that is a target of voltage detection by the voltage detection circuit 113 is referred to as a voltage detection target circuit.
The control circuit 114 controls the voltage generation circuit 111 based on the current detected by the current detection circuit 112 and the voltage detected by the voltage detection circuit 113. Specifically, the control circuit 114 detects the current detected by the current detection circuit 112 within a range where the voltage detected by the voltage detection circuit 113 is equal to or lower than a predetermined voltage value (hereinafter referred to as “maximum voltage value”). Is set to a predetermined current value (hereinafter referred to as “target current value”), and the voltage generated by the voltage generation circuit 111 is adjusted. That is, when the voltage detected by the voltage detection circuit 113 is lower than the maximum voltage value and the current detected by the current detection circuit 112 is less than the target current value, the control circuit 114 increases the voltage generated by the voltage generation circuit 111. To do. Conversely, when the voltage detected by the voltage detection circuit 113 is higher than the maximum voltage value, or when the current detected by the current detection circuit 112 is larger than the target current value, the control circuit 114 generates the voltage generation circuit 111. Reduce the voltage.

In this example, the target current value is the first drive current. Further, when the current detection target circuit is the light emitting element unit 852, the target current value is the second drive current.
The maximum voltage value is set based on a maximum value that can be said to be within a normal operation range in consideration of variations in forward voltage in the light emitting element. For example, when the current flowing through the current detection target circuit is smaller than the target current value, the control circuit 114 increases the voltage generated by the voltage generation circuit 111 so as to set the current flowing through the current detection target circuit to the target current value. To do. However, even if the voltage generated by the voltage generation circuit 111 is increased in the case of an abnormality such as when the forward voltage in the light emitting element increases due to a decrease in the ambient temperature or when the light emitting element breaks down, the current detection target Since the current flowing through the circuit does not increase so much, if the voltage generated by the voltage generation circuit 111 is further increased, the light emitting element units 851 and 852 and other circuits may be destroyed. Therefore, when the voltage generated by the voltage generation circuit 111 is increased and the voltage across the voltage detection target circuit reaches the maximum voltage value, the control circuit 114 increases the voltage generated by the voltage generation circuit 111 further. Do not protect the circuit.

FIG. 2 is an electric circuit diagram showing a circuit configuration of the power supply circuit 100 according to this embodiment.
The power supply circuit 100 inputs direct current or pulsating voltage and supplies power to the light emitting element units 851 and 852.

The voltage generation circuit 111 is, for example, a flyback converter. The flyback converter is an isolated switching power supply that performs an on / off operation. The voltage generation circuit 111 includes an input capacitor C11, a switching element Q12, a transformer T60, a rectifier element D13, and a smoothing capacitor C14 (first capacitor).
The input capacitor C11 is electrically connected between the input terminals of the power supply circuit 100. The input capacitor C11 inputs power. The input capacitor C11 removes and smoothes the ripple of the voltage input by the power supply circuit 100, and prevents the switching noise generated in the power supply circuit 100 from leaking to the outside.
Switching element Q12 is, for example, a MOSFET, and opens and closes according to a signal representing an instruction from control circuit 114.
The transformer T60 includes a primary winding L63 and two secondary windings L61 (first winding) and L62 (second winding). Among these, the voltage generation circuit 111 includes the primary winding L63 and the secondary winding L61. The transformer T60 insulates and transmits the primary power to the secondary side.
The primary winding L63 (third winding) is electrically connected between the input terminals of the power supply circuit 100 via the switching element Q12. The switching element Q12 performs switching of the input voltage and accumulates necessary energy in the transformer T60.
The anode terminal of the rectifying element D13 is electrically connected to one end of the secondary winding L61 (first winding). The cathode terminal of the rectifying element D13 is electrically connected to the anode terminal of the smoothing capacitor C14 (first capacitor). The cathode terminal of the smoothing capacitor C14 is electrically connected to the other end of the secondary winding L61. That is, the secondary winding L61, the rectifying element D13, and the smoothing capacitor C14 constitute a closed loop. The rectifying element D13 rectifies the output of the secondary winding L61. The smoothing capacitor C14 smoothes the output of the secondary winding L61 rectified by the rectifying element D13. That is, the current flowing through the secondary winding L61 is rectified by the rectifying element D13 and charges the smoothing capacitor C14.

  The anode side terminal (the anode side terminal of the light emitting element unit 851) of the series load circuit (light emitting element series circuit) is electrically connected to the anode terminal of the smoothing capacitor C14. The cathode side terminal of the series load circuit (the cathode side terminal of the light emitting element unit 852) is electrically connected to the cathode terminal of the smoothing capacitor C14 via the current detection circuit 112. Thereby, the voltage charged in the smoothing capacitor C14 is applied to the series load circuit, and the current for discharging the smoothing capacitor C14 flows through the series load circuit.

The current adding circuit 150 includes a rectifying element D51, a smoothing capacitor C52, and a current limiting resistor R53.
The anode terminal of the rectifying element D51 is electrically connected to one end of the secondary winding L62. The cathode terminal of the rectifying element D51 is electrically connected to the anode terminal of the smoothing capacitor C52. The cathode terminal of the smoothing capacitor C52 is electrically connected to the other end of the secondary winding L62. The number of turns of the secondary winding L62 is smaller than the number of turns of the secondary winding L61. That is, the secondary winding L62, the rectifier element D51, and the smoothing capacitor C52 constitute a closed loop. The rectifying element D51 rectifies the output of the secondary winding L62. The smoothing capacitor C52 smoothes the output of the secondary winding L62 rectified by the rectifying element D51. That is, the current flowing through the secondary winding L62 is rectified by the rectifying element D51 and charges the smoothing capacitor C52.
One end of the current limiting resistor R53 is electrically connected to the anode terminal of the smoothing capacitor C52. The current limiting resistor R53 limits the current flowing into the light emitting element unit 852.

The anode side terminal of the light emitting element unit 852 is electrically connected to the other end of the current limiting resistor R53. The cathode side terminal of the light emitting element unit 852 is electrically connected to the cathode terminal of the smoothing capacitor C52. Thereby, the voltage charged in the smoothing capacitor C52 is applied to the light emitting element unit 852. The current limiting resistor R53 limits the current flowing into the light emitting element unit 852. The current limited by the current limiting resistor R53 flows through the light emitting element unit 852.
Instead of the current limiting resistor R53, for example, a constant current diode may be used to limit the current that discharges the smoothing capacitor C52.

  The voltage detection circuit 113 includes a resistor R31 (voltage / current conversion circuit). One end of the resistor R31 is electrically connected to the anode side terminal (the anode side terminal of the light emitting element unit 851) of the series load circuit. The other end of the resistor R31 is electrically connected to the cathode side terminal (the cathode side terminal of the light emitting element unit 852) of the series load circuit. That is, the resistor R31 is electrically connected in parallel with the series load circuit. As a result, a current proportional to the voltage across the series load circuit (in this case, the series load circuit becomes the “voltage detection target circuit”) flows through the resistor R31. Note that the resistance value of the resistor R31 is sufficiently larger than the equivalent resistance value during normal operation of the series load circuit.

  The current detection circuit 112 has a resistor R21. One end of the resistor R21 is electrically connected to the cathode side terminal of the series load circuit. The other end of the resistor R21 is electrically connected to the cathode terminal of the smoothing capacitor C14. As a result, a current that combines the current flowing through the light emitting element unit 851 (in this case, the light emitting element unit 851 becomes the “current detection target circuit”) and the current flowing through the voltage detection circuit 113 flows through the resistor R21. A voltage proportional thereto is generated across the resistor R21. Note that the resistance value of the resistor R21 is sufficiently smaller than the equivalent resistance value during normal operation of the series load circuit.

The control circuit 114 includes a reference voltage source V41, a differential amplifier A42, a photocoupler PC, and a control IC 145.
The reference voltage source V41 generates a DC voltage having a predetermined voltage value. The differential amplifier A42 is, for example, an operational amplifier. The differential amplifier A42 (error amplifier) performs an operation based on the voltage (current value information) generated in the resistor R21 (current detection resistor) and the reference voltage of the reference voltage source V41, and outputs an output signal to the photocoupler PC. Output. The differential amplifier A42 compares the voltage across the current detection circuit 112 with the voltage of the reference voltage source V41. The power supply of the differential amplifier A42 is taken from the output voltage of the voltage generation circuit 111, for example.
The photocoupler PC transmits a signal while electrically insulating the primary side circuit and the secondary side circuit of the transformer T60. The photocoupler PC insulates the output signal from the differential amplifier A42 (error amplifier) and sends it to the control IC 145.
Control IC 145 generates a signal for opening / closing switching element Q12 based on a signal representing a comparison result by differential amplifier A42 transmitted through photocoupler PC.
Note that the control circuit 114 may be configured using, for example, an analog-digital conversion circuit, a microcomputer, or the like.

When the switching element Q12 is turned on, the voltage across the input capacitor C11 is applied to the primary winding L63, and the current flowing through the primary winding L63 increases. At this time, a reverse voltage is generated in the secondary windings L61 and L62, but no current flows through the secondary windings L61 and L62 due to the action of the rectifying elements D13 and D51. When the switching element Q12 is turned off, the current flowing through the primary winding L63 becomes 0, and the current flows through the secondary windings L61 and L62 in order to maintain the magnetic flux. The rectifying elements D13 and D51 are turned on, a voltage substantially equal to the voltage across the smoothing capacitor C14 is applied to the secondary winding L61, and a voltage approximately equal to the voltage across the smoothing capacitor C52 is applied to the secondary winding L62. Is applied. As a result, the current flowing through the secondary windings L61 and L62 decreases and becomes zero. By repeating this, the energy supplied to the primary winding L63 of the transformer T60 is transmitted to the secondary side, and the secondary winding L61 and the secondary winding L62 are transmitted to the smoothing capacitor C14 and the smoothing capacitor C52. A voltage that is approximately proportional to the turns ratio is charged.
The energy supplied to the primary winding L63 of the transformer T60 increases as the proportion of time during which the switching element Q12 is turned on increases, and the voltage charged in the smoothing capacitors C14 and C52 increases. In this way, the control IC 145 adjusts the voltage charged in the smoothing capacitors C14 and C52 by controlling the ratio of the period during which the switching element Q12 is turned on.

When the voltage output from the current detection circuit 112 is lower than the voltage value of the reference voltage source V41, the control IC 145 increases the ratio of the ON period of the switching element Q12 and increases the voltage charged in the smoothing capacitors C14 and C52. Thereby, the electric current which flows through the light emitting element units 851 and 852 increases.
When the voltage output from the current detection circuit 112 is higher than the voltage value of the reference voltage source V41, the control IC 145 reduces the ratio of the ON period of the switching element Q12 and lowers the voltage charged in the smoothing capacitors C14 and C52. Thereby, the electric current which flows through the light emitting element units 851 and 852 decreases.
In this way, the control circuit 114 adjusts the voltage generated by the voltage generation circuit 111 so that the current flowing through the current detection circuit 112 becomes a predetermined current (target current value).
The output voltage of the voltage generation circuit 111 causes a drive current to flow through the series load circuit (light emitting element units 851 and 852). The control circuit 114 controls the on / off switching ratio of the switching element Q12 of the voltage generation circuit 111 so that the drive current detected by the current detection circuit 112 matches the target current value. As a result, the constant current circuit 110 is a constant current drive circuit that allows a predetermined current (target current value; in this example, the first drive current) to flow through the series load circuit (light emitting element series circuit, light emitting element units 851 and 852). Operate.

  The series load circuit (light emitting element series circuit) is formed by connecting a plurality of light emitting element units 851 and 852 in series. The first light emitting element unit 851 has a main light emission output. The second light emitting element unit 852 has a secondary light emission output. In the light emitting element unit 851, for example, four white light emitting diodes are connected in series. Since the light emitting element unit 852 is a slave, the light emission output may be small. For example, one red light emitting diode is used. In order to obtain a necessary light output, for example, a driving current (first driving current) of 350 mA is supplied to the white light emitting diode, and a driving current (second driving current) of 400 mA is supplied to the red light emitting diode, for example. Shed. That is, the current for driving the light emitting element unit 852 (second driving current) is 50 mA larger than the current for driving the light emitting element unit 851 (first driving current).

The current (first drive current) generated by the constant current circuit 110 is charged from the secondary winding L61 (first winding) through the rectifier element D13 to charge the smoothing capacitor C14. It flows through a loop that passes through the light emitting element unit 851, the light emitting element unit 852, and the current detection circuit 112.
The current generated by the current adding circuit 150 is charged from the secondary winding L62 through the rectifying element D51 to charge the smoothing capacitor C52, and then flows from the smoothing capacitor C52 through a loop passing through the light emitting element unit 852. 851 and the current detection circuit 112 do not pass.
Therefore, the current (first driving current) generated by the constant current circuit 110 flows through the light emitting element unit 851, and the current (first driving current) generated by the constant current circuit 110 flows through the light emitting element unit 852. And the current generated by the current adding circuit 150 (difference between the second drive current and the first drive current; a current that is insufficient when the first drive current is passed through the light emitting element unit 852). (Second drive current) flows. Further, the current (first drive current) generated by the constant current circuit 110 flows through the current detection circuit 112.
For example, if the constant current circuit 110 supplies a current of 350 mA and the current addition circuit 150 supplies a current of 50 mA, the current (first drive current) flowing through the light emitting element unit 851 becomes 350 mA, and the light emitting element unit 852 The current flowing through (second drive current) is 400 mA.
Here, the current flowing through the voltage detection circuit 113 and the power supply current of the differential amplifier A42 that takes power from the output of the constant current circuit 110 are assumed to be sufficiently smaller than the current flowing through the light emitting element unit 851, and are ignored. Yes.

FIG. 3 is a diagram showing the relationship between the voltage and current of each part in this embodiment.
The horizontal axis represents the voltage across the series load circuit and the current detection circuit 112. The vertical axis represents the current flowing through the series load circuit and voltage detection circuit 113 and the voltage detection circuit 113. A curve 511 shows the voltage-current characteristic of the series load circuit. A straight line 512 shows the voltage-current characteristic of the current detection circuit 112. Straight 513 _(and the _{I g1} to the reference, the downward direction is a positive) voltage-current characteristic of the voltage detection circuit 113 shows a.
The control circuit 114 adjusts the voltage generated by the voltage generation circuit 111 so that the voltage across the current detection circuit 112 matches the reference voltage value _VREF . That is, the control circuit 114 adjusts the voltage generated by the voltage generation circuit 111 so that the current detected by the current detection circuit 112 matches the current value _Ig1 .
The current detected by the current detection circuit 112 is the sum of the current I ₁ flowing through the light emitting element unit 851 and the current I _Vd flowing through the voltage detection circuit 113. When the voltage generated by the voltage generation circuit 111 is lower than the voltage value V _{S at} the intersection of the curve 511 and the straight line 513, the current detected by the current detection circuit 112 is less than the current value _{Ig 1.} The voltage generated by the circuit 111 is increased. Further, when the voltage of the voltage generating circuit 111 generates higher than the voltage value V _S, since the current the current detection circuit 112 detects that more than the current value I _g1, the control circuit 114, a voltage that the voltage generating circuit 111 generates make low. As a result of such control, the voltage generation circuit 111 generates a voltage having the voltage value V _S.

In the case where the light emitting element unit 851 breaks down and no current flows through the light emitting element unit 851, the current detected by the current detection circuit 112 is only the current I _Vd flowing through the voltage detection circuit 113. Since the current detected by the current detection circuit 112 is less than the current value _Ig1 , the control circuit 114 increases the voltage generated by the voltage generation circuit 111. When the voltage generated by the voltage generation circuit 111 reaches the voltage value V _MAX at the intersection of the straight line 513 and the voltage axis, the current detected by the current detection circuit 112 matches the current value _Ig1 . The voltage generation circuit 111 is stable in a state where a voltage having a voltage value V _MAX is generated.

  Further, when the forward voltage of the light emitting element increases due to a decrease in the ambient temperature of the light emitting element unit 851, the curve 511 moves to the right in the drawing. Then, the intersection of the curve 511 and the straight line 513 moves along the straight line 513 in the lower right direction in the figure. As a result, a smaller current flows through the light emitting element unit 851 than during normal operation. Thereby, an increase in power consumption in the light emitting element unit 851 due to an increase in forward voltage can be suppressed.

In addition, no matter what the voltage-current characteristic curve of the series load circuit becomes due to an unexpected failure or the like, the voltage generated by the voltage generation circuit 111 is controlled to a voltage value V _MAX or less.

FIG. 4 is a diagram showing the relationship between the voltage and current of each part in this embodiment.
The horizontal axis indicates the voltage across the light emitting element unit 852 and the current limiting resistor R53. The vertical axis indicates the current flowing through the light emitting element unit 852 and the current limiting resistor R53. A curve 521 represents voltage-current characteristics of the light emitting element unit 852. A straight line 522 represents the voltage-current characteristic of the current limiting resistor R53 (the left direction is positive with respect to V _C2 and I ₁ ).

When the control circuit 114 adjusts the voltage generated by the voltage generation circuit 111 to match the voltage value V _S , the smoothing capacitor C52 is charged with a voltage value V _C2 that is substantially proportional to the voltage value V _S. The
Current flowing through the light emitting unit 852 includes a current I ₁ flowing through the light emitting unit 851, a total current and the current I ₂ for discharging the smoothing capacitor C52. Voltage across the smoothing capacitor C52 is a voltage across _{V 2} of the light emitting unit 852, is pressed and the voltage across _{V r} of the current limiting resistor R53 bisection. Therefore, the current limiting resistor R53, the current value current flow [Delta] I, the light emitting unit 852, a current of a current value I ₁ and the current value I ₂ which is the sum of the current value [Delta] flows.

The variation of the forward voltage of the light emitting device unit 851, when the voltage value V _S varies, since the voltage value V _C2 fluctuates, the current value ΔI is varied. Further, when the curve 521 changes due to the change in the forward voltage of the light emitting element unit 852, the intersection of the curve 521 and the straight line 522 changes, and the current value ΔI changes.
For example, the light emitting element unit 851 is formed by connecting three white light emitting diodes each having a forward voltage of 3.7 V in series, and the light emitting element unit 852 emits red light having a forward voltage of 3.1 V. In the case of one diode, the voltage value V _S is 14.2V. If the number of turns of the secondary winding L62 is half the number of turns of the secondary winding L61, the voltage across the smoothing capacitor C52 becomes 7.0 V, which is about half the voltage across the smoothing capacitor C14, and the current limiting resistor R53 Is about 118Ω, the current value ΔI is about 50 mA.

If the resistance value of the current limiting resistor R53 to some extent large, the inclination of the straight line 522 is small, a small variation in the current value ΔI according to variation of the variation and the curve 521 of voltage V _C2, a current value ΔI is substantially constant.

In any case, the voltage value V _S of the voltage generated by the voltage generation circuit 111 is equal to or lower than the voltage value V _MAX . As a result, the voltage V _C2 charged in the smoothing capacitor C52 becomes equal to or lower than a predetermined voltage value, so that the current value ΔI of the current flowing through the current limiting resistor R53 becomes equal to or lower than the predetermined current value. Accordingly, an excessive current does not flow through the light emitting element unit 852.

  FIG. 5 is an electric circuit diagram showing a modification of the voltage detection circuit 113 in this embodiment. Modified examples 113a to 113c of the voltage detection circuit are circuits connected as a voltage-current conversion circuit instead of the resistor R31.

  The voltage detection circuit 113a is a circuit in which a constant voltage diode Z32 such as a Zener diode and a resistor R33 are electrically connected in series. When the voltage across the voltage detection target circuit is lower than the breakdown voltage value of the constant voltage diode Z32, no current flows, and when the voltage across the voltage detection target circuit exceeds the breakdown voltage value of the constant voltage diode Z32, the constant voltage diode Z32 Is turned on, and a current proportional to the difference between the voltage across the voltage detection target circuit and the breakdown voltage of the constant voltage diode Z32 flows.

  The voltage detection circuit 113b has two resistors R34 and R35 and a switching element Q36. The switching element Q36 is, for example, a bipolar transistor, and a resistor R34 is electrically connected between the collector terminal and the base terminal, and a resistor R35 is electrically connected between the base terminal and the emitter terminal. The resistors R34 and R35 have a sufficiently large resistance value. When the resistors R34 and R35 divide the voltage across the voltage detection target circuit and the voltage generated across the resistor R35 exceeds the base-emitter forward voltage value of the switching device Q36, the switching device Q36 is turned on.

The voltage detection circuit 113c includes a differential amplifier A37 and a resistor R38 in addition to the voltage detection circuit 113b. The positive input terminal of the differential amplifier A37 is electrically connected to the connection point between the resistors R34 and R35, the negative input terminal of the differential amplifier A37 is electrically connected to the reference voltage _Vref, and the output terminal of the differential amplifier A37. Are electrically connected to the base terminal of the switching element Q36. The resistor R38 is electrically connected to the collector terminal of the switching element Q36 and limits the current that flows when the switching element Q36 is turned on. When the potential at the connection point between the resistor R34 and the resistor R35 exceeds the reference voltage _Vref , the switching element Q36 is turned on and a current flows through the resistor R38.

FIG. 6 is a diagram illustrating the relationship between the voltage and current of each unit when the voltage detection circuits 113a to 113c are used.
A curve 514 shows voltage-current characteristics of the voltage detection circuits 113a to 113c.
When any of the voltage detection circuits 113a to 113c is used as the voltage detection circuit 113, the curve 514 has substantially the same shape. When the voltage at both ends is lower than the threshold value _VTH , almost no current flows, and the voltage at both ends is the threshold value. higher than V _TH, the current flows substantially proportional to the difference between the voltage value and the threshold value V _TH of the voltage across.
When the voltage detection circuit 113a is used, the threshold value V _TH is substantially equal to the breakdown voltage value of the constant voltage diode Z32. The on-current is limited by the resistance value of the resistor R33.
When the voltage detection circuit 113b is used, the threshold V _TH is a voltage value obtained by multiplying the base-emitter forward voltage value of the switching element Q36 by (R ₄ + R ₅ ) / R ₅ (where R ₄ is the resistance R 34 Resistance value R ₅ is substantially equal to the resistance value of the resistance R 35. The on-current is limited by the resistance value of the resistor R34 and the amplification factor of the switching element Q36.
When the voltage detection circuit 113c is used, the threshold value V _TH is a voltage value at which the voltage divided by the resistors R34 and R35 becomes equal to the reference voltage _Vref . The on-current is limited by the resistor R38.

In any case, when the series load circuit (calling element series circuit) is operating normally, the current _IVd hardly flows, so that the power consumption can be suppressed. Further, the maximum voltage value V _MAX when an abnormality occurs in the series load circuit can be lowered.
The voltage-current conversion circuit is not limited to the resistor R31 and the voltage detection circuits 113a to 113c described above, and may have other configurations.

  FIG. 7 is an electric circuit diagram showing another example of the circuit configuration of the power supply circuit 100 in this embodiment.

The voltage generation circuit 111 is, for example, a forward converter. The voltage generation circuit 111 includes an input capacitor C11, a switching element Q12, a primary winding L63, a secondary winding L61, a rectifying element D13, a rectifying element D15, a coil L16, and a smoothing capacitor C14. The anode terminal of the rectifying element D13 is electrically connected to one end of the secondary winding L61. The anode terminal of the rectifying element D15 is electrically connected to the other end of the secondary winding L61. The cathode terminals of the rectifying elements D13 and D15 are both electrically connected to one end of the coil L16. The other end of the coil L16 is electrically connected to the anode terminal of the smoothing capacitor C14.
When the switching element Q12 is turned on, the voltage across the input capacitor C11 is applied to the primary winding L63, and a voltage is generated across the secondary windings L61 and L62. The rectifier element D13 is turned on, a current flows through the secondary winding L61, and the smoothing capacitor C14 is charged via the coil L16. The current flowing through the secondary winding L61 hardly changes due to the action of the coil L16. Further, the rectifying element D51 is turned off, and no current flows through the secondary winding L62. Due to the energy supplied to the primary winding L63, the current flowing through the primary winding L63 increases.
When the switching element Q12 is turned off, the current flowing through the primary winding L63 becomes zero. Due to the action of the coil L16, the current flowing through the secondary winding L61 does not increase suddenly, and in order to maintain the magnetic flux in the transformer T60, the current flows through the secondary winding L62, the rectifying element D51 is turned on, The smoothing capacitor C52 is charged. A voltage substantially equal to the voltage across the smoothing capacitor C52 is applied to both ends of the secondary winding L62, and a reverse voltage is generated across the secondary winding L61. The rectifying element D13 is turned off and the current flowing through the coil L16 is maintained, so that the rectifying element D15 is turned on and charging of the smoothing capacitor C14 is continued.
By repeating this, energy is transmitted from the primary side of the transformer T60 to the secondary side.

  Thus, the voltage generation circuit 111 is not limited to the flyback converter, and may be a forward converter or another method.

  Similarly, the current adding circuit 150 may be a forward method or another method.

In this example, the current output from the current adding circuit 150 is configured to pass not only through the light emitting element unit 852 but also through the current detection circuit 112. Thus, the current detection circuit 112 uses the light emitting element unit 852 as a current detection target circuit, and detects a current obtained by combining the current flowing through the light emitting element unit 852 and the current flowing through the voltage detection circuit 113.
In such a configuration, the control circuit 114 generates the voltage generated by the voltage generation circuit 111 based on the current detected by the current detection circuit 112 so that the current flowing through the light emitting element unit 852 has a predetermined current value. adjust. Since the current value ΔI of the current generated by the current adding circuit 150 is substantially constant, the light emitting element unit 851 receives the current value ΔI of the current generated by the current adding circuit 150 from the current value of the current flowing through the light emitting element unit 852. The current of the subtracted current value flows.
Accordingly, even with such a configuration, the currents flowing through the light emitting element unit 851 and the light emitting element unit 852 can be set to desired values.

FIG. 8 is an electric circuit diagram showing still another example of the circuit configuration of the power supply circuit 100 according to this embodiment.
In this example, the voltage detection circuit 113 is electrically connected in parallel to the light emitting element unit 852 instead of the series load circuit. That is, the voltage detection circuit 113 detects the voltage across the light emitting element unit 852 using the light emitting element unit 852 as a voltage detection target circuit.
Thereby, when an abnormality occurs in the light emitting element unit 852, it is possible to prevent an overvoltage from occurring in the light emitting element unit 852.

FIG. 9 is an electric circuit diagram showing still another example of the circuit configuration of the power supply circuit 100 according to this embodiment.
In this example, the connection order of the light emitting element unit 851 and the light emitting element unit 852 is reversed. The voltage detection circuit 113 is electrically connected in parallel to the light emitting element unit 851. That is, the voltage detection circuit 113 detects the voltage across the light emitting element unit 851 using the light emitting element unit 851 as a voltage detection target circuit.
Accordingly, when an abnormality occurs in the light emitting element unit 851, it is possible to prevent an overvoltage from occurring in the light emitting element unit 851.

The power supply circuit 100 in this embodiment includes a first load circuit (light emitting element unit 851) that operates with a first drive current, and a second load circuit that operates with a second drive current larger than the first drive current. Power is supplied to the load circuit (light emitting element unit 852).
The power supply circuit 100 includes a constant current circuit 110 and a current addition circuit 150.
The constant current circuit 110 includes a voltage generation circuit 111, a current detection circuit 112, a voltage detection circuit 113, and a control circuit 114, and the first load circuit and the second load circuit are connected in series. The first drive current is supplied to the electrically connected series load circuit.
The current adding circuit 150 supplies a current having a current value corresponding to a difference between the first drive current and the second drive current to the second load circuit.
The voltage generation circuit 111 generates a voltage to be applied to the series load circuit.
The current detection circuit 112 uses any one of the first load circuit and the second load circuit as a current detection target circuit, and detects a current flowing through the current detection target circuit.
The voltage detection circuit 113 has one of the first load circuit, the second load circuit, and the series load circuit as a voltage detection target circuit, and is generated at both ends of the voltage detection target circuit. The voltage to be detected is detected.
The control circuit 114 is configured so that the current detected by the current detection circuit 112 becomes a predetermined current value within a range where the voltage detected by the voltage detection circuit 113 is equal to or less than a predetermined voltage value (maximum voltage value). The voltage generation circuit 111 is controlled.

According to the power supply circuit 100 in this embodiment, a constant current circuit is provided for a series load circuit (light emitting element series circuit) in which a plurality of load circuits (light emitting element units 851 and 852) having different driving currents are electrically connected in series. For some load circuits (light emitting element units 852) 110 supply the first drive current and flow a second drive current larger than the first drive current, the current adding circuit 150 includes the second drive current A current corresponding to the difference between the drive current and the first drive current is supplied. In addition, since the current adding circuit 150 has a small current value to be supplied and can be realized with a relatively simple and inexpensive configuration, the current adding circuit 150 itself consumes less power.
Since the power supply circuit 100 can simultaneously supply power to a plurality of load circuits (light emitting element units) having different drive currents, a plurality of constant current drive circuits as in the prior art or a plurality of power supply circuits from a single power supply circuit can be used. Unlike the configuration in which current is limited by a resistor in the load circuit, the number of parts can be reduced, the manufacturing cost can be reduced, the reliability can be improved, and the power efficiency can be improved.
When an abnormality occurs in the first load circuit or the second load circuit, the voltage detection circuit 113 detects the voltage across the voltage detection target circuit, and the control circuit 114 is set so that the detected voltage is equal to or lower than a predetermined voltage value. Controls the voltage generation circuit 111, so that the occurrence of overvoltage can be prevented and the reliability of the power supply circuit 100 and the load circuit can be increased.

In the power supply circuit 100 in this embodiment, the voltage detection circuit 113 includes a voltage-current conversion circuit (resistor R31) electrically connected in parallel with the voltage detection target circuit.
The current detection circuit 112 detects a current that is the sum of the current flowing through the voltage-current conversion circuit and the current flowing through the current detection target circuit.

  According to the power supply circuit 100 in this embodiment, the current detection circuit 112 detects the current that is the sum of the current flowing through the voltage-current conversion circuit and the current flowing through the current detection target circuit. The voltage generation circuit 111 may be controlled based only on the current detected by the circuit 112, the configuration of the control circuit 114 can be simplified, and the manufacturing cost of the power supply circuit 100 can be reduced.

  In the power supply circuit 100 in this embodiment, the voltage-current conversion circuit is, for example, a resistor R31. According to this configuration, since the circuit configuration is relatively simple, the manufacturing cost of the power supply circuit 100 can be reduced.

Alternatively, the voltage-current conversion circuit is a series circuit of a resistor R33 and a constant voltage diode Z32. According to this configuration, power consumption during normal operation can be suppressed, and the maximum voltage value V _MAX can be lowered.

Alternatively, the voltage-current conversion circuit includes a transistor (switching element Q36), a first resistor R34 electrically connected between the collector terminal and the base terminal of the transistor, and a base terminal and an emitter terminal of the transistor. And a second resistor R35 electrically connected to the circuit. According to this configuration, power consumption during normal operation can be suppressed, the maximum voltage value V _MAX can be lowered, and the threshold value V _TH can be designed relatively freely.

  In the power supply circuit 100 according to this embodiment, the control circuit 114 increases the voltage generated by the voltage generation circuit 111 when the current detected by the current detection circuit 112 is smaller than a predetermined current value, and the current When the current detected by the detection circuit 112 is larger than a predetermined current value, the voltage generated by the voltage generation circuit 111 is lowered.

  According to the power supply circuit 100 in this embodiment, since the current detection circuit 112 detects the current including the current flowing through the voltage detection circuit 113, the control circuit 114 is based on the current detected by the current detection circuit 112. By controlling the voltage generation circuit 111, the voltage detected by the voltage detection circuit 113 can be set to a predetermined voltage value or less.

The power supply circuit 100 in this embodiment further includes a transformer T60.
The transformer T60 has a first winding (secondary winding L61) and a second winding (secondary winding L62).
The voltage generation circuit 111 obtains energy from the current flowing through the first winding, and generates a voltage to be applied to the series load circuit.
The current adding circuit 150 obtains energy from the current flowing through the second winding, and generates a current to be supplied to the second load circuit (light emitting element unit 852).

  According to the power supply circuit 100 in this embodiment, since the voltage generation circuit 111 and the current addition circuit 150 obtain energy from one transformer T60 and generate voltage and current, the number of components of the power supply circuit 100 is reduced. be able to.

In the power supply circuit 100 according to this embodiment, the voltage generation circuit 111 has a first capacitor (smoothing capacitor C14), and applies a voltage generated across the first capacitor to the series load circuit. To do.
The first capacitor is charged by a current flowing through the first winding (secondary winding L61).

  According to the power supply circuit 100 in this embodiment, since the first capacitor is charged by the current flowing through the first winding, the adjustment of the charging voltage is easy.

In the power supply circuit 100 according to this embodiment, the current adding circuit 150 includes a second capacitor (smoothing capacitor C52) and a current limiting circuit (current limiting resistor R53), and discharges the second capacitor. Current is supplied to the second load circuit (light emitting element unit 852).
The second capacitor is charged by a current flowing through the second winding (secondary winding L62).
The current limiting circuit limits a current for discharging the second capacitor.

According to the power supply circuit 100 in this embodiment, the current addition circuit 150 is configured to provide a current (second drive current) that is insufficient with respect to the second drive current required by the second load circuit (light emitting element unit 852). Only the difference between the first drive current and the first drive current), and the output voltage and output current may be small. Therefore, even if the current adding circuit 150 has a relatively simple configuration, the power of the power supply circuit 100 as a whole The efficiency will not be significantly reduced.
The power supply circuit 100 can be composed of a single constant current circuit and a simple circuit that supplies insufficient current, and can drive a plurality of load circuits having different drive currents without reducing power efficiency. The number of points can be reduced, the circuit can be downsized, and the reliability can be improved.

In the power supply circuit 100 in this embodiment, the transformer T60 further includes a third winding (primary winding L63).
The control circuit 114 adjusts the voltage generated by the voltage generation circuit 111 by adjusting the power (energy) supplied to the third winding.

  According to the power supply circuit 100 in this embodiment, power is supplied to the primary side of the transformer T60 and energy is extracted from the secondary side, so that the primary side circuit and the secondary side circuit are electrically insulated. Therefore, even when the voltage generated by the voltage generation circuit 111 is a high voltage, safety can be improved.

The lighting device 800 in this embodiment includes the power supply circuit 100, a first light emitting element unit 851, and a second light emitting element unit 852.
The first light emitting element unit 851 has one or a plurality of first light emitting elements electrically connected in series, and is electrically connected to the power supply circuit 100 as the first load circuit.
The first light emitting element emits light by the first driving current.
The second light emitting element unit 852 has one or a plurality of second light emitting elements electrically connected in series, and is electrically connected to the power supply circuit 100 as the second load circuit.
The second light emitting element emits light by the second driving current.

  According to lighting apparatus 800 in this embodiment, since a plurality of types of light emitting elements having different driving currents are combined, light having a high color rendering property and a desired color temperature can be emitted.

The lighting device 800 described above includes a light emitting element series circuit (series load circuit) and a power supply circuit 100.
The light emitting element series circuit includes first and second light emitting element units 851 and 852 connected in series. The first light emitting element unit 851 has one or a plurality of first light emitting elements connected in series. The second light emitting element unit 852 has one drive current larger than that of the first light emitting element or a plurality of second light emitting elements connected in series.
The power supply circuit 100 includes a transformer T60, a current detection circuit 112, a voltage detection circuit 113, a current limiting circuit (current limiting resistor R53), and a control circuit 114.
The transformer T60 includes a primary winding L63, a first output winding (secondary winding L61) for supplying the first driving current, and a current (first driving) that is insufficient with respect to the second driving current. A second output winding (secondary winding L62) for supplying a difference from the current.
The light emitting element series circuit is connected to the first output winding of the transformer T60, and the first light emitting element unit 851 is driven by a first drive current supplied from the first output winding. The
The second light emitting element unit 852 is connected to the second output winding of the transformer T60 and supplied with an additional current from the second output winding, and the additional current is supplied to the first drive current. It is driven by the second drive current added with the current.
The current detection circuit 112 detects the first or second drive current.
The voltage detection circuit 113 detects all or a part of voltage value information applied to the light emitting element units 851 and 852 and transmits the voltage value information to the control circuit 114.
The current limiting circuit is connected to the second output winding of the transformer T60 and limits the additional current to the second light emitting element unit.
The control circuit 114 performs control to suppress an increase in drive current flowing to the light emitting element units 851 and 852 based on the current value information transmitted from the current detection circuit 112, and the voltage value transmitted from the voltage detection circuit 113. Control is performed to suppress an increase in voltage applied to the light emitting element units 851 and 852 based on the information, and the first or second drive current is controlled based on the first or second drive current.

A light emitting element unit 851 and a light emitting element unit 852 that requires more current are connected in series to the first winding (secondary winding L61), and a predetermined current (first driving current) is detected by the current detection resistor R21. ) And the control circuit 114 controls the switching time ratio of the MOSFET (switching element Q12), and the constant current control of the light emitting element series circuit (the circuit in which the two light emitting element units 851 and 852 are connected in series) is performed. To drive. In addition, the light emitting element unit 852 has a current (second driving current and first driving current) that is insufficient with respect to a current necessary for obtaining a desired light emission output from the second winding (secondary winding L62). And the second driving current is used for driving.
As a result, the lighting apparatus 800 uses a power supply circuit configured by one constant current driving circuit (constant current circuit 110) and a simple circuit (current addition circuit 150) that supplies insufficient current. Unlike a configuration in which a plurality of constant current driving circuits are used, or a current is limited to a plurality of light emitting element units from a single power supply circuit by a resistor, a plurality of driving currents having different driving currents are reduced without reducing power efficiency. The light emitting element unit can be driven simultaneously, the number of parts can be reduced, the circuit can be downsized, and the reliability can be improved.
In addition, even if the ambient temperature of the light emitting diode decreases and the forward voltage increases, the constant current drive circuit has a function to suppress the increase in output voltage. Can be prevented.

The lighting device 800 described above uses a combination of a plurality of types of light-emitting elements (for example, pure white light-emitting diodes and red or green light-emitting diodes) having different driving currents, so that the light bulb color (light source color), that is, pure Light having a desired color temperature slightly lower than white can be emitted.
A plurality of light emitting elements are divided for each drive current, and a plurality of load circuits are configured by connecting in series each light emitting element of the same type having the same drive current.

  In the case of a configuration in which a power supply circuit is connected for each of a plurality of load circuits, the efficiency of the power supply circuit is reduced if an inexpensive resistor or a circuit using control characteristics of an active region of a semiconductor is used as the power supply circuit. In addition, if a relatively efficient switch mode control circuit, for example, a DC / DC converter such as a flyback converter, is used as the power supply circuit, the manufacturing cost increases and the reliability decreases as the number of components increases. Become.

  On the other hand, in the lighting device 800 described above, the constant current circuit 110 supplies current to a circuit in which a plurality of load circuits are all connected in series, and the current addition circuit 150 is one of the plurality of load circuits. Supply a shortage of current to the load circuit. Compared with the constant current circuit 110, the current adding circuit 150 has a lower voltage and less current to supply. The constant current circuit 110 uses an insulating power supply circuit system such as a flyback converter to increase electrical efficiency. By using a relatively simple and inexpensive circuit for the current adding circuit 150, the manufacturing cost is reduced and the reliability is increased.

Further, by connecting the resistor R31 (voltage detection circuit 113) in parallel with the series load circuit, an increase in the output voltage of the constant current circuit 110 is suppressed.
In general, a light emitting diode has a characteristic that the forward voltage increases as the ambient temperature decreases. In addition, the light emitting diode has a characteristic that the forward voltage increases as the forward current increases. Therefore, an increase in the forward current leads to an increase in the forward voltage of the entire light emitting element units 851 and 852.
For example, when the ambient temperature of the light emitting element units 851 and 852 decreases and the forward voltage of the light emitting elements increases, the current (first drive current) flowing through the light emitting element units 851 and 852 decreases. Since the current detected by the current detection circuit 112 is less than a predetermined current value, the control circuit 114 increases the voltage generated by the voltage generation circuit 111. As the voltage generated by the voltage generation circuit 111 increases, the current (first drive current) flowing through the light emitting element series circuit (series load circuit) increases and the current flowing through the resistor R31 (voltage detection circuit 113) also increases.
When the current detected by the current detection circuit 112 reaches a predetermined current value, the current flowing through the light emitting element series circuit (first drive current) is reduced by an increase in the current flowing through the resistor R31. An increase in the current flowing through (first drive current) is suppressed.
In addition, since the voltage generated by the voltage generation circuit 111 is stabilized at a low voltage value by the increase in the current flowing through the light emitting element series circuit (first drive current), the output voltage of the voltage generation circuit 111 increases. Is also suppressed.
That is, the resistor R31 has a function of suppressing an increase in voltage applied to the light emitting element units 851 and 852 (an increase in output voltage) against a forward voltage increase of the light emitting element units 851 and 852 due to a decrease in ambient temperature.
Thereby, the constant current circuit 110 functions as one constant current drive circuit that performs control for suppressing an increase in output voltage and current feedback control.

  According to the illuminating device 800 described above, a constant current driving DC / DC converter is individually provided on the secondary side of the insulated constant voltage driving circuit even when driving light emitting diodes having different required currents. There is no need to provide. With a configuration of one constant current driving circuit (constant current circuit 110) having a function of suppressing voltage rise and a simple circuit (current adding circuit 150), a plurality of types of light emitting diodes having different driving currents are driven, The light output required for each can be obtained.

  Since the current adding circuit 150 has a low output voltage and a small output current, even if it is realized with a very simple configuration in which the output current is limited by the current limiting resistor R53 without performing feedback control or the like, power efficiency is not so much. There is no reduction, and the benefits of reducing manufacturing costs and improving reliability by reducing the number of parts are greater.

  In a configuration in which a plurality of light emitting element units are connected in parallel, a plurality of constant current driving DC / DC converters are not provided, but the output is separated from the output of one DC / DC converter using a current limiting resistor. A configuration is also conceivable in which a current is supplied to some of the light emitting element units. In this configuration, the voltage across the current limiting resistor R53 increases, so that the power loss in the current limiting resistor R53 increases and the electrical efficiency decreases. To do.

On the other hand, the lighting device 800 described above obtains energy from the secondary winding L62 having a smaller number of turns than the secondary winding L61 and charges the smoothing capacitor C52, so that the voltage across the smoothing capacitor C52 is smooth. It becomes lower than the voltage across the capacitor C14. Therefore, the voltage across the current limiting resistor R53 is low, the power loss in the current limiting resistor R53 is small, and the electrical efficiency is high.
Note that the ratio of the number of turns of the secondary winding L62 to the number of turns of the secondary winding L61 is equal to or greater than the ratio of the voltage across the light emitting element unit 852 to the voltage across the series load circuit.

  The light emitting elements of the light emitting element units 851 and 852 are not limited to white light emitting diodes and red light emitting diodes, and may be light emitting diodes of other colors or other types of light emitting elements such as organic EL elements. Further, the number of light emitting elements constituting one light emitting element unit may be an arbitrary number, and the number of light emitting element units may be an arbitrary number of 2 or more. In that case, one current adding circuit 150 may be provided for each light emitting element unit having a different driving current value, or the output is separated from one current adding circuit 150 using a current limiting resistor. Also good. Further, the connection order of the plurality of light emitting element units may be any order.

The control circuit 114 may be configured using an integrator, an analog multiplier, an IC, a microcomputer, or the like instead of the differential amplifier A42.
The voltage detection circuit 113 is not limited to the example described above, and may have other configurations. The voltage detection circuit 113 only needs to have a characteristic in which the flowing current increases as the voltage at both ends increases. However, the voltage detection circuit 113 has a characteristic that when the voltage at both ends is lower than a predetermined voltage value, the flowing current is small, and when the voltage at both ends exceeds the predetermined voltage value, the flowing current suddenly increases. preferable.
As described above, the voltage detection circuit 113 is connected in parallel with the voltage detection target circuit. The voltage detection target circuit is not limited to the series load circuit, and may be any one light emitting element unit, or may be all or a part of three or more light emitting element units.
Further, instead of the rectifier elements D13 and D51, a switching element such as a MOSFET may be provided, and a synchronous rectification type rectifier circuit that actively controls switching of the switching element in synchronization with opening and closing of the switching element Q12 may be used. Good.

In addition, although it is difficult to configure a small-capacity, high-efficiency constant-current driving DC / DC converter for a light-emitting output that is a slave of a small output such as the second load circuit (light-emitting element unit 852), The described power supply circuit 100 has a simple configuration, improves electric efficiency, and can contribute to energy saving.
In particular, the number of light emitting elements (light emitting diodes for obtaining main light emitting output) constituting the light emitting element unit 851 is large, and the number of light emitting elements (light emitting diodes for obtaining subordinate light emitting output) constituting the light emitting element unit 852 is large. When the amount is small, the electric efficiency is further improved.
In addition, the electric noise is reduced by reducing the number of constant current driving DC / DC converters that perform the switching operation.
Further, by connecting the resistor R31 as the voltage detection circuit 113, when the ambient temperature of the light emitting element unit decreases and the forward voltage of the light emitting element unit increases, the voltage applied to the light emitting element unit increases (output voltage). Rise). Accordingly, it is possible to prevent the forward current of the light emitting element unit from increasing due to the increase in the applied voltage and further increasing the forward voltage of the light emitting element unit. In addition, by suppressing a change in the current value of the light emitting element, a change in luminance of the light emitting element can be suppressed and the brightness can be kept constant. Also, an unexpected increase in output power can be prevented. For example, when the forward voltage of the light emitting element is increased due to aging of the light emitting element or an increase in impedance due to a failure of the light emitting element, the same increase suppressing effect can be obtained.
Further, by suppressing an increase in the voltage applied to the light emitting element unit, it is possible to prevent the current and voltage of the series load circuit (light emitting element series circuit) from becoming more than necessary, and to improve the reliability as the lighting device. In addition, since the voltage applied to the light emitting element can be prevented from becoming more than necessary, the light emitting element can be prevented from being damaged.
When the resistance value of the resistor R31 is relatively small, and the light emitting element fails in the open mode, an operation such as constant voltage control by the resistor R31 and the current detection resistor R21 is performed, and an overvoltage can be prevented.
In addition, by performing constant current control that has a function of suppressing an increase in the output voltage, immediately after the light emitting element is turned on or when the temperature is low and the forward voltage is large, the increase in the output voltage of the drive circuit is suppressed. When the directional voltage decreases, it is possible to perform a constant current drive control with a desired current value.
In addition, by performing such constant current control, when the forward voltage of the light emitting element is large, it is possible to prevent excessive power consumption and overloading the drive circuit, and to improve the reliability of the drive circuit and the light emitting element unit. To improve.

In the illuminating device 800 described above, the voltage detection circuit 113 performs the control IC 145 only when the voltage applied to the light emitting element units 851 and 852 reaches or exceeds a predetermined voltage value (threshold value V _TH ). Transmit voltage value information to
For example, the voltage detection circuit 113 has a breakdown effect in which a current flows when a certain voltage or more is applied. The voltage detection circuit 113 is, for example, a series circuit of a Zener diode (constant voltage diode Z32) and a resistor R33. A Zener diode having a breakdown voltage higher than the total value of forward voltages of the light emitting elements of the light emitting element unit 851 is used.
Thus, when the voltage across the voltage detection target circuit is lower than a predetermined voltage value (breakdown voltage), no current flows through the resistor R33, and no power loss occurs in the resistor R33.
When the voltage between both ends of the voltage detection target circuit exceeds a predetermined voltage value (breakdown voltage), a current flows through the resistor R33, and an increase in voltage is suppressed.
Note that the voltage detection circuit 113 may be one using another semiconductor element or another configuration as long as it has similar voltage-current characteristics.

According to the lighting device 800 described above, only when the output voltage of the constant current circuit 110 exceeds a certain voltage (the breakdown voltage of the Zener diode), a current flows through the resistor R33, and the voltage applied to the light emitting element increases. Suppress.
When the output voltage of the constant current circuit 110 does not reach a constant voltage, no current flows through the resistor R33, so that it is possible to reduce power loss during normal times.

Embodiment 2. FIG.
The second embodiment will be described with reference to FIGS.
In addition, about the part which is common in Embodiment 1, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  FIG. 10 is an electric circuit diagram showing a circuit configuration of the power supply circuit 100 in this embodiment.

The voltage generation circuit 111 is, for example, a step-down chopper circuit. The voltage generation circuit 111 includes an input capacitor C11, a switching element Q12, a rectifier element D13, a primary winding L64 of a transformer T60, and a smoothing capacitor C14.
Switching element Q12 is, for example, a MOSFET, and opens and closes according to a signal representing an instruction from control circuit 114. One end of the switching element Q12 is electrically connected to the anode side terminal of the input capacitor C11. The other end of the switching element Q12 is electrically connected to one end of the primary winding L64 and the cathode terminal of the rectifying element D13. The other end of the primary winding L64 is electrically connected to the anode terminal of the smoothing capacitor C14. The anode terminal of the rectifying element D13 is electrically connected to the cathode terminal of the input capacitor C11 and the cathode terminal of the smoothing capacitor C14.

When the switching element Q12 is turned on, a voltage corresponding to the difference between the voltage across the input capacitor C11 and the voltage across the smoothing capacitor C14 is applied across the primary winding L64. If the voltage across the input capacitor C11 is larger, the current flowing through the primary winding L64 increases and charges the smoothing capacitor C14. A reverse voltage is generated in the secondary winding L62, and no current flows due to the function of the rectifying element D51.
When the switching element Q12 is turned off, the rectifying element D13 is turned on in order to maintain the magnetic flux, the current continues to flow through the primary winding L64, and the smoothing capacitor C14 continues to be charged. A voltage substantially equal to the voltage across the smoothing capacitor C14 is applied across the primary winding L64. The polarity of the voltage across the secondary winding L62 is reversed, the rectifying element D51 is turned on, a current flows through the secondary winding L62, and the smoothing capacitor C52 is charged.
By repeating this, a part of the energy supplied to the primary winding L64 of the transformer T60 is transmitted to the secondary winding L62.

The voltage detection circuit 113 is electrically connected in parallel with a voltage detection target circuit (in this figure, it is a series load circuit but may be a light emitting element unit 851 or a light emitting element unit 852). The voltage at both ends is detected and converted into a current flowing through the voltage detection circuit 113.
The current detection circuit 112 combines the current flowing through the current detection target circuit (in this figure, the light emitting element unit 851 but may be the light emitting element unit 852) and the current flowing through the voltage detection circuit 113. A current is detected and converted into a voltage across the current detection circuit 112.
The control circuit 114 compares the voltage across the current detection circuit 112 with a predetermined reference voltage value V41, and controls the voltage generation circuit 111 so that the voltage across the current detection circuit 112 matches the reference voltage value V41. Specifically, the voltage charged to the smoothing capacitor C14 is adjusted by adjusting the length of the period during which the switching element Q12 is turned on and the period for opening and closing the switching element Q12.

  When an abnormality occurs in the light emitting element unit 851 or the light emitting element unit 852 and the flowing current decreases, the control circuit 114 increases the voltage generated by the voltage generation circuit 111, but the current flowing through the voltage detection circuit 113 increases. For this reason, the voltage across the current detection circuit 112 rises, and the control circuit 114 does not set the voltage generated by the voltage generation circuit 111 to a predetermined maximum voltage value or more. Thereby, destruction of the power supply circuit 100 and the light emitting element units 851 and 852 due to overvoltage can be prevented, and reliability can be improved.

  FIG. 11 is an electric circuit diagram showing another example of the circuit configuration of the power supply circuit 100 in this embodiment.

The voltage generation circuit 111 is, for example, a boost chopper circuit. The voltage generation circuit 111 includes an input capacitor C11, a primary winding L64 of a transformer T60, a switching element Q12, a rectifier element D13, and a smoothing capacitor C14.
Switching element Q12 is, for example, a MOSFET, and opens and closes according to a signal representing an instruction from control circuit 114. One end of the switching element Q12 is electrically connected to one end of the primary winding L64. The other end of the switching element Q12 is electrically connected to the cathode terminal of the input capacitor C11 and the cathode terminal of the smoothing capacitor C14. The other end of the primary winding L64 is electrically connected to the anode terminal of the input capacitor C11. The anode terminal of the rectifying element D13 is electrically connected to the connection point between the primary winding L64 and the switching element Q12. The cathode terminal of the rectifying element D13 is electrically connected to the anode terminal of the smoothing capacitor C14.

When the switching element Q12 is turned on, a voltage substantially equal to the voltage across the input capacitor C11 is applied to both ends of the primary winding L64, and the current flowing through the primary winding L64 increases. At this time, a reverse voltage is generated in the secondary winding L62, and no current flows through the secondary winding L62 due to the function of the rectifying element D51.
When the switching element Q12 is turned off, the rectifying element D13 is turned on to maintain the magnetic flux, and the current continues to flow through the primary winding L64, thereby charging the smoothing capacitor C14. A voltage corresponding to the difference between the voltage across the smoothing capacitor C14 and the voltage across the input capacitor C11 is applied across the primary winding L64. If the voltage across the smoothing capacitor C14 is larger, the current flowing through the primary winding L64 decreases. The polarity of the voltage across the secondary winding L62 is reversed, the rectifying element D51 is turned on, a current flows through the secondary winding L62, and the smoothing capacitor C52 is charged.
By repeating this, a part of the energy supplied to the primary winding L64 of the transformer T60 is transmitted to the secondary winding L62.

As described above, the voltage generation circuit 111 replaces the choke coil in the power supply circuit method such as the step-down chopper circuit and the step-up chopper circuit with the transformer T60 instead of the insulation type power supply circuit method such as the flyback converter and the forward converter. It may be a configuration.
The current adding circuit 150 obtains energy from the secondary winding L62 of the transformer T60, charges the smoothing capacitor C52, and generates a current to be supplied to the light emitting element unit 852.

  In the power supply circuit 100 in this embodiment, the control circuit 114 generates the voltage generation circuit 111 by adjusting the power (energy) supplied to the first winding (primary winding L64). Adjust the voltage.

  According to the power supply circuit 100 in this embodiment, even when the voltage generation circuit 111 is a power supply circuit system such as a step-down chopper circuit or a step-up chopper circuit, the current addition circuit 150 is generated by energy divided using the transformer T60. Can generate the current supplied to the second load circuit. Even in such a configuration, as in the first embodiment, the voltage detection circuit 113 detects the voltage across the voltage detection target circuit, and the control circuit is configured so that the voltage detected by the voltage detection circuit 113 is equal to or lower than a predetermined voltage value. Since 114 controls the voltage generation circuit 111, the occurrence of overvoltage can be prevented, and the reliability of the power supply circuit 100 and the load circuit can be increased.

Embodiment 3 FIG.
Embodiment 3 will be described with reference to FIG.
FIG. 12 is an electric circuit diagram showing an example of the circuit configuration of the power supply circuit 100 in this embodiment.
In addition, about the part which is common in Embodiment 1, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  The current detection circuit 112 generates a voltage proportional to the current flowing through the light emitting element unit 851 that is a current detection target circuit. The current detection circuit 112 includes, for example, a resistor R21. The resistor R21 is electrically connected in series with the series load circuit. The current detection circuit 112 outputs a voltage generated at both ends of the resistor R21 as a current detection voltage. The resistance value of the resistor R21 is sufficiently smaller than the equivalent resistance value when the series load circuit is operating normally.

  The voltage detection circuit 113 generates a voltage proportional to the voltage across the series load circuit that is a voltage detection target circuit. The voltage detection circuit 113 includes, for example, two resistors R34 and R35. One end of the resistor R34 is electrically connected to the anode side terminal of the light emitting element unit 851. The other end of the resistor R34 is electrically connected to one end of the resistor R35. The other end of the resistor R35 is electrically connected to the negative output terminal of the voltage generation circuit 111. The voltage detection circuit 113 outputs the voltage generated at both ends of the resistor R35 as a voltage detection voltage. The sum of the resistance values of the two resistors R34 and R35 is sufficiently larger than the equivalent resistance value when the series load circuit is operating normally.

The control circuit 114 includes two reference voltage sources V41 and V46, two differential amplifiers A42 and A47, two rectifier elements D43 and D48, a photocoupler PC, and a control IC 145.
The differential amplifier A42 compares the current detection voltage output from the current detection circuit 112 with the voltage value of the reference voltage source V41. The differential amplifier A47 compares the voltage detection voltage output from the voltage detection circuit 113 with the voltage value of the reference voltage source V46. When the voltage value of the reference voltage source V41 is equal to the voltage value of the reference voltage source V46, the reference voltage source V46 is not provided, and the differential amplifier A47 uses the voltage detection voltage output from the voltage detection circuit 113. The voltage value of the reference voltage source V41 may be compared.
The two rectifying elements D43 and D48 connect the outputs of the two differential amplifiers A42 and A47 by wired OR.
Thus, either the current detection voltage output from the current detection circuit 112 is higher than the voltage value of the reference voltage source V41, or the voltage detection voltage output from the voltage detection circuit 113 is higher than the voltage value of the reference voltage source V46. In this case, the photocoupler PC is turned on, the photocoupler PC is turned off when the current detection voltage is lower than the voltage value of the reference voltage source V41 and the current detection voltage is lower than the voltage value of the reference voltage source V46. become.
The control IC 145 opens and closes the switching element Q12 based on the signal transmitted through the photocoupler PC, and adjusts the voltage generated by the voltage generation circuit 111. The control IC 145 reduces the voltage generated by the voltage generation circuit 111 by shortening the period during which the switching element Q12 is turned on, for example, when the photocoupler PC is on, and switches the switching element Q12 when the photocoupler PC is off. The voltage generated by the voltage generation circuit 111 is increased by, for example, extending the period during which the voltage is turned on.
That is, the control circuit 114 generates the voltage generation circuit 111 when the current detected by the current detection circuit 112 is less than a predetermined current value and the voltage detected by the voltage detection circuit 113 is lower than the predetermined voltage value. The voltage generated by the voltage generation circuit 111 when the voltage is increased and the current detected by the current detection circuit 112 is greater than a predetermined current value and when the voltage detected by the voltage detection circuit 113 is higher than the predetermined voltage value Lower.

  When an abnormality occurs in the light emitting element unit 851 or the light emitting element unit 852 and the flowing current decreases, the control circuit 114 increases the voltage generated by the voltage generation circuit 111, but the voltage detected by the voltage detection circuit 113 is Therefore, the control circuit 114 does not set the voltage generated by the voltage generation circuit 111 to be equal to or higher than a predetermined maximum voltage value. Thereby, destruction of the power supply circuit 100 and the light emitting element units 851 and 852 due to overvoltage can be prevented, and reliability can be improved.

  Further, even when the current detection circuit 112 or the differential amplifier A42 fails and the current flowing through the current detection target circuit cannot be detected correctly, the control circuit 114 increases the voltage generated by the voltage generation circuit 111. If the voltage detection circuit 113 and the differential amplifier A47 are operating normally because the voltage detected by the voltage detection circuit 113 is high, the control circuit 114 sets the voltage generated by the voltage generation circuit 111 to a predetermined maximum voltage. Do not exceed the value. Thereby, destruction of the power supply circuit 100 and the light emitting element units 851 and 852 due to overvoltage can be prevented, and reliability can be improved.

In the power supply circuit 100 in this embodiment, the voltage detection circuit 113 generates a voltage proportional to the voltage generated at both ends of the voltage detection target circuit (series load circuit), and outputs the generated voltage as a voltage detection voltage. To do.
The current detection circuit 112 detects a current flowing through the current detection target circuit (light emitting element unit 851), and outputs a voltage proportional to the detected current as a current detection voltage.
The control circuit 114 adjusts the voltage generated by the voltage generation circuit 111 based on the voltage detection voltage output from the voltage detection circuit 113 and the current detection voltage output from the current detection circuit 112.

  According to the power supply circuit 100 in this embodiment, the control circuit 114 inputs the voltage detected by the voltage detection circuit 113 and the current detected by the current detection circuit 112 independently, and the voltage generation circuit 111 generates the voltage. Since the voltage to be adjusted is adjusted, even if any one of the systems breaks down, the power supply circuit 100 and the light emitting element units 851 and 852 due to overvoltage can be prevented and reliability can be improved.

  In the power supply circuit 100 according to this embodiment, the control circuit 114 is configured such that the voltage detection voltage output from the voltage detection circuit 113 is smaller than a predetermined first reference voltage value and the current output from the current detection circuit 112. When the detection voltage is smaller than a predetermined second reference voltage value, the voltage generated by the voltage generation circuit 111 is increased, and the voltage detection voltage output by the voltage detection circuit 113 is higher than the predetermined first reference voltage value. If it is larger, and if the current detection voltage output from the current detection circuit 112 is greater than a predetermined second reference voltage value, the voltage generated by the voltage generation circuit 111 is lowered.

  According to the power supply circuit 100 in this embodiment, control is performed so that the current detected by the current detection circuit 112 becomes a predetermined current value within a range where the voltage detected by the voltage detection circuit 113 is equal to or lower than the predetermined voltage value. Since the circuit 114 controls the voltage generation circuit 111, destruction of the power supply circuit 100 and the light emitting element units 851 and 852 due to overvoltage can be prevented and reliability can be improved.

In the lighting device 800 described above, the control circuit 114 is configured such that the voltage value information applied to the light emitting element units 851 and 852 transmitted by the voltage detection circuit 113 exceeds the predetermined voltage value information. Only when this is done, control is performed to suppress an increase in voltage applied to the light emitting element units 851 and 852.
For example, the control circuit 114 includes a differential amplifier A47 (error amplifier) that is different from the differential amplifier A42 (error amplifier), and is different from the applied voltage of the light emitting element unit serving as voltage value information and the reference voltage source V41. A predetermined constant voltage from the reference voltage source V46 is input and calculated. Thereby, when it reaches more than the voltage value information determined in advance, it is possible to control to suppress the increase of the output voltage.
Instead of providing the reference voltage source V46, voltage value information corresponding to a predetermined voltage may be prepared inside or around the control circuit.

According to the lighting device 800 described above, the power loss in the voltage detection circuit 113 is small, and the electrical efficiency is high.
Further, even if the circuit configuration of the voltage detection circuit 113 is simple and the output voltage is a high voltage, an expensive component such as a Zener diode having a high breakdown voltage is unnecessary, and thus the manufacturing cost of the light emitting device is low. Become.
Further, even when an abnormality occurs in the differential amplifier A42, since the increase in the output voltage is suppressed by the differential amplifier A47 or the like, the safety is high.

  100 power supply circuit, 110 constant current circuit, 111 voltage generation circuit, 112 current detection circuit, 113 voltage detection circuit, 114 control circuit, 145 control IC, 150 current addition circuit, 511, 514, 521 curve, 512, 513, 522 straight line , 800 Lighting device, 851, 852 Light emitting element unit, A37, A42, A47 Differential amplifier, C11 input capacitor, C14, C52 smoothing capacitor, D13, D15, D43, D48, D51 Rectifier, L16 coil, L61, L62 Secondary winding, L63, L64 Primary winding, PC photocoupler, Q12, Q36 switching element, R21, R31, R33, R34, R35, R38 resistance, R53 current limiting resistance, T60 transformer, V41, V46 Reference voltage source, Z32 Constant voltage diode .

Claims (12)

In a power supply circuit that supplies power to a first load circuit that operates with a first drive current and a second load circuit that operates with a second drive current larger than the first drive current,
The power supply circuit has a constant current circuit and a current addition circuit,
The constant current circuit includes a voltage generation circuit, a current detection circuit, a voltage detection circuit, and a control circuit, and a series load in which the first load circuit and the second load circuit are electrically connected in series. Supplying the first drive current to the circuit;
The current adding circuit supplies a current having a current value corresponding to a difference between the first driving current and the second driving current to the second load circuit;
The voltage generation circuit generates a voltage to be applied to the series load circuit,
The current detection circuit uses any one of the first load circuit and the second load circuit as a current detection target circuit, detects a current flowing through the current detection target circuit,
The voltage detection circuit has one of the first load circuit, the second load circuit, and the series load circuit as a voltage detection target circuit, and is generated at both ends of the voltage detection target circuit. Detect the voltage,
The control circuit controls the voltage generation circuit so that the current detected by the current detection circuit becomes a predetermined current value within a range where the voltage detected by the voltage detection circuit is equal to or less than a predetermined voltage value. A power circuit characterized by. The voltage detection circuit has a voltage-current conversion circuit electrically connected in parallel with the voltage detection target circuit,
2. The power supply circuit according to claim 1, wherein the current detection circuit detects a current obtained by combining a current flowing through the voltage-current conversion circuit and a current flowing through the current detection target circuit. The voltage-current converter circuit is
Resistance,
A series circuit of a resistor and a constant voltage diode;
A circuit comprising a transistor, a first resistor electrically connected between the collector terminal and the base terminal of the transistor, and a second resistor electrically connected between the base terminal and the emitter terminal of the transistor; The power supply circuit according to claim 2, wherein the power supply circuit is any one of the above.   The control circuit increases the voltage generated by the voltage generation circuit when the current detected by the current detection circuit is smaller than a predetermined current value, and the current detected by the current detection circuit is larger than the predetermined current value. 4. The power supply circuit according to claim 2, wherein the voltage generated by the voltage generation circuit is lowered. The voltage detection circuit generates a voltage proportional to the voltage generated at both ends of the voltage detection target circuit, outputs the generated voltage as a voltage detection voltage,
The current detection circuit detects a current flowing through the current detection target circuit, and outputs a voltage proportional to the detected current as a current detection voltage.
The control circuit adjusts a voltage generated by the voltage generation circuit based on a voltage detection voltage output from the voltage detection circuit and a current detection voltage output from the current detection circuit. The power supply circuit according to 1.   In the control circuit, the voltage detection voltage output from the voltage detection circuit is smaller than a predetermined first reference voltage value, and the current detection voltage output from the current detection circuit is smaller than a predetermined second reference voltage value. In the case where the voltage generated by the voltage generation circuit is increased and the voltage detection voltage output by the voltage detection circuit is greater than a predetermined first reference voltage value, and the current detection voltage output by the current detection circuit 6. The power supply circuit according to claim 5, wherein the voltage generated by the voltage generation circuit is lowered when the voltage is larger than a predetermined second reference voltage value. 7. The power supply circuit further includes a transformer,
The transformer has a first winding and a second winding,
The voltage generation circuit obtains energy from the current flowing through the first winding, generates a voltage to be applied to the series load circuit,
7. The current adding circuit according to claim 1, wherein the current adding circuit generates energy to be supplied to the second load circuit by obtaining energy from the current flowing through the second winding. The power circuit according to the above. The voltage generation circuit has a first capacitor, applies a voltage generated across the first capacitor to the series load circuit,
The power supply circuit according to claim 7, wherein the first capacitor is charged by a current flowing through the first winding. The current adding circuit has a second capacitor and a current limiting circuit, and supplies a current for discharging the second capacitor to the second load circuit,
The second capacitor is charged by a current flowing through the second winding,
9. The power supply circuit according to claim 7, wherein the current limiting circuit limits a current for discharging the second capacitor. The transformer further includes a third winding,
The said control circuit adjusts the voltage which the said voltage generation circuit produces | generates by adjusting the electric power supplied to a said 3rd coil | winding, The Claim 7 thru | or 9 characterized by the above-mentioned. Power supply circuit.   The said control circuit adjusts the voltage which the said voltage generation circuit produces | generates by adjusting the electric power supplied to a said 1st coil | winding, The Claim 7 thru | or 9 characterized by the above-mentioned. Power supply circuit. A power supply circuit according to any one of claims 1 to 11, a first light emitting element unit, and a second light emitting element unit,
The first light emitting element unit has one or a plurality of first light emitting elements electrically connected in series, and is electrically connected to the power supply circuit as the first load circuit,
The first light emitting element emits light by the first driving current,
The second light emitting element unit has one or a plurality of second light emitting elements electrically connected in series, and is electrically connected to the power supply circuit as the second load circuit,
The lighting device according to claim 2, wherein the second light emitting element emits light by the second driving current.

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