LED lighting power supply device and LED lighting device

Abstract

To provide an LED lighting power supply device and an LED lighting device that reduces the loss of a switching element of a constant current converter and noise generated by the same, and can reduce the peak current when switching loads.SOLUTION: On an output LED lighting power supply device that performs dimming and / or color control by using AC or DC as a power source and switching and driving two or more independent LED loads 15, 16 with different voltages of a load terminal connected to an output of one constant current converter 13, the control of the constant current converter is a real-time control in a critical mode operation of turning off a switching element 132 of the constant current converter when the output current of the constant current converter reaches an upper threshold value, and turning it on when the output current becomes zero. Furthermore, the on-time operation speed of a switching element 18 for the LED load 16 is slowed down, thereby suppressing the LED peak current generated when the switching element is turned on.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a power supply device for LED lighting that switches between and drives two or more systems of LED loads, and an LED lighting device in which this power supply device is used. [Background technology]

[0002] 2. Description of the Related Art As an LED lighting device that uses an LED (light emitting diode) as a light source, for example, an LED lighting device that performs color adjustment control by alternately switching and driving two or more systems of LED loads with different color temperatures has been conventionally known (for example, Patent Document 1 and Patent Document 2).

[0003] Incidentally, as a power supply for such an LED lighting device that alternately switches and drives two or more systems of LED loads, a feedback control type power supply is often used to stabilize the current flowing through the LED loads.

[0004] This feedback control type power supply detects the current flowing through the LED load, and when the detected current value decreases, it increases the output of the constant current converter so that the current flowing through the LED load increases, and when the detected current value increases, it decreases the output of the constant current converter so that the current flowing through the LED load decreases.

[0005] However, such feedback type power supply devices have the following problems. That is, the terminal voltages of two or more systems of LED loads that are switched and driven are generally not the same. For example, when switching the drive from an LED load with a low load terminal voltage to an LED load with a high load terminal voltage, if the difference in the load terminal voltages is large, the current to the LED load with the high load terminal voltage will decrease rapidly immediately after switching. For this reason, feedback is applied and the constant current converter is controlled to increase the output rapidly, which may cause a sudden large current to flow through the LED load and cause it to break down.

[0006] In addition, a relatively large-capacity capacitor is generally connected to the output of a constant current converter in order to supply a stable current to the LED load. However, when the drive is switched from an LED load with a high load terminal voltage to an LED load with a low load terminal voltage, a sudden large current (peak current) flows from the capacitor to the LED load with the low load terminal voltage, and because the capacitance of the capacitor is large, this current continues, which can also cause the LED load to fail.

[0007] As described above, conventional feedback-type power supplies had a problem in that if the terminal voltages of two or more systems of LED loads being switched between, there was a risk of the LED loads breaking down due to a sudden peak current during switching.

[0008] These sudden peak currents flow through the LED load as currents that are difficult to control, resulting in problems such as unstable LED load current.

[0009] Furthermore, in order to solve the problems described above, Patent Document 3 proposes an LED lighting power supply device that uses AC or DC as a power source and performs dimming and / or color adjustment by switching and driving two or more independent LED loads with different load terminal voltages connected to the output of a single constant current converter, in which the constant current converter is controlled by real-time control that turns on the switching element of the constant current converter when the output current of the constant current converter falls below a lower threshold and turns off when it exceeds an upper threshold, and in which the capacitance of the capacitor connected to the output end of the constant current converter is 0.1 μF or less, or no capacitor is provided at the output end of the constant current converter. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Patent No. 5141874 [Patent Document 2] JP 2015-95347 A [Patent Document 3] Patent No. 6999100 Summary of the Invention [Problem to be solved by the invention]

[0011] However, in the power supply device described in Patent Document 3, the constant current converter operates in a continuous mode that continuously outputs current, which causes problems such as increased loss in the switching element of the constant current converter and increased noise during switching. Also, although there is no occurrence of a sudden peak current flowing to the load when the load is switched, there is also a problem of increased noise due to peak current that does not damage the LED.

[0012] The present invention has been made in view of the above technical background, and has an object to provide a power supply device for LED lighting and an LED lighting device that can reduce the loss and generated noise of the switching element of the constant current converter, and can reduce the peak current when the load is switched. [Means for solving the problem]

[0013] The above problems are solved by the following means. (1) A power supply device for LED lighting that uses AC or DC as a power source and performs dimming and / or color adjustment by switching and driving two or more independent LED loads with different load terminal voltages connected to the output of a single constant current converter. The constant current converter is controlled in real time in a critical mode of operation, in which the switching element of the constant current converter is turned off when the output current of the constant current converter reaches an upper threshold value and turned on when the output current disappears, and the on operating speed of the switching element that switches the LED load is slowed down to suppress the LED peak current that occurs when the switching element is on. This power supply device for LED lighting is characterized in that (2) A power supply device for LED lighting that uses AC or DC as a power source and performs dimming and / or color adjustment by switching and driving two or more independent LED loads with different load terminal voltages connected to the output of a single constant current converter, The constant current converter is controlled in real time in a discontinuous mode, in which the switching element of the constant current converter is turned off when the output current of the constant current converter reaches an upper threshold value, and turned on when a predetermined time has elapsed, including the time when the output current is zero, and the on operating speed of the switching element that switches the LED load is slowed down to suppress the LED peak current that occurs when the switching element is on. (3) A power supply device for LED lighting that uses AC or DC as a power source and performs dimming and / or color adjustment by switching and driving two or more independent LED loads with different load terminal voltages connected to the output of a single constant current converter, The control of the constant current converter is a combination of real-time control of critical mode operation in which the switching element of the constant current converter is turned off when the output current of the constant current converter reaches an upper threshold and turned on when the output current disappears, and real-time control of discontinuous mode operation in which the switching element of the constant current converter is turned off when the output current of the constant current converter reaches an upper threshold and turned on when a predetermined time has passed, including the time when the output current is zero, and the on operating speed of the switching element that switches the LED load is slowed down to suppress the LED peak current that occurs when it is on. (4) A power supply device for LED lighting as described in any one of paragraphs 1 to 3 above, in which the capacitance of the capacitor connected to the output terminal of the constant current converter is 4.7 μF or less, or no capacitor is provided at the output terminal of the constant current converter. (5) An LED lighting device equipped with the power supply device for LED lighting described in any one of the preceding paragraphs 1 to 3. (6) An LED lighting device as described in the preceding paragraph 5, in which the capacitance of a capacitor connected to the output end of the constant current converter is 4.7 μF or less, or no capacitor is provided at the output end of the constant current converter. Effect of the Invention

[0014] According to the present invention, in an output LED lighting power supply device that uses AC or DC as a power source and performs dimming and / or color adjustment by switching and driving two or more independent LED loads with different load terminal voltages connected to an output smoothing capacitor of one constant current converter, the constant current converter is controlled by real-time control of critical mode operation in which the switching element of the constant current converter is turned off when the output current of the constant current converter reaches an upper threshold and turned on when the output current disappears, real-time control of discontinuous mode operation in which the switching element of the constant current converter is turned off when the output current of the constant current converter reaches an upper threshold and turned on when a predetermined time including the time when the output current is zero has elapsed, or real-time control of critical mode operation and discontinuous mode operation in combination, so that current does not flow constantly through the switching element of the constant current converter. This reduces the loss of the switching element and reduces the heat dissipation from the switching element of the constant current converter, which simplifies the heat dissipation structure of the constant current converter, and allows the constant current converter to be made smaller and less costly. Moreover, noise generation during switching of the switching element of the constant current converter can be suppressed.

[0015] In addition, by slowing down the on-operation speed of the switching element that switches the LED load, the LED peak current that occurs when the element is on is reduced, which not only prevents damage to the LED load but also suppresses noise caused by the peak current. [Brief description of the drawings]

[0016] [Figure 1] 1 is a circuit diagram of an LED lighting device according to an embodiment of the present invention. [Diagram 2] 2 is a waveform diagram for explaining the critical mode operation of the constant current converter in the LED lighting device of FIG. 1. [Diagram 3] 1. FIG. 4 is a waveform diagram for explaining the drive switching operation of two systems of LED loads when the constant current converter operates in a critical mode in the LED lighting device of FIG. [Figure 4]2 is a waveform diagram for explaining the discontinuous mode operation of the constant current converter in the LED lighting device of FIG. 1. [Diagram 5] 1. FIG. 4 is a waveform diagram for explaining the drive switching operation of two systems of LED loads when the constant current converter operates in discontinuous mode in the LED lighting device of FIG. [Figure 6] 1 is a circuit diagram showing an example of an operation speed adjustment circuit that slows down the ON operation speed of a switching element that switches an LED load, thereby suppressing an LED peak current that occurs when the element is ON. [Figure 7] 7 is a waveform diagram of an input signal and an output signal of the operation speed adjustment circuit in the case where the operation speed adjustment circuit in FIG. 6 is mounted, and of a current flowing through a first LED load and a second LED load when a load is switched. [Figure 8] FIG. 13 is a circuit diagram showing another example of the operation speed adjustment circuit. [Figure 9] FIG. 13 is a circuit diagram showing yet another example of the operation speed adjustment circuit. [Figure 10] 10 is a waveform diagram of input and output signals of the operation speed adjustment circuit when the operation speed adjustment circuit of FIG. 9 is mounted and the load is switched. [Figure 11] FIG. 4 is a circuit diagram of an LED lighting device according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0018] Fig. 1 is a circuit diagram showing the configuration of an LED lighting device 1 equipped with an LED power supply device according to an embodiment of the present invention. This LED lighting device 1 includes a rectifier circuit 11, a smoothing capacitor 12 connected to the output of the rectifier circuit 11, a constant current converter 13 connected to the output of the smoothing capacitor 12, a capacitor (corresponding to an output smoothing capacitor) 14 connected to the output end of the constant current converter 13, first and second LED loads 15 and 16, first and second load switching units 17 and 18, a load switching and dimming control unit 19, etc. Furthermore, an operation speed adjustment circuit 20 is connected between the second load switching unit 18 and the load switching and dimming control unit 19.

[0019] The rectifier circuit 11 is a circuit that performs full-wave rectification on the AC input from the AC power source 2, and the smoothing circuit 12 serves to smooth the input voltage after full-wave rectification by the rectifier circuit 11.

[0020] The constant current converter 13 is a converter that operates to output a constant current, and in this embodiment specifically includes a real-time control unit 131, a switching element 132 consisting of a MOSFET whose drain terminal is connected to the positive terminal of the smoothing capacitor 12, a resistor 133 whose one end is connected to the source terminal of the switching element 132, an impedance element 134 connected to the other end of the resistor 133, and a diode 135 connected between the negative terminal of the smoothing capacitor 12 and the source terminal of the switching element 132 with its cathode side facing the source terminal of the switching element 132.

[0021] A gate signal is input from the real time control unit 131 to the gate of the switching element 132 . When this gate signal is input, the switching element 132 turns on and the power charged in the smoothing capacitor 12 is supplied to the output side of the switching element 132 .

[0022] Resistor 133 detects the output current of constant current converter 13. In other words, real-time control unit 131 constantly monitors the voltage across resistor 133, which is determined by the output current value and resistance value, and outputs a gate signal from real-time control unit 131 to switching element 132 at a predetermined timing, turning on switching element 132. When the monitored voltage exceeds an upper limit threshold, the gate signal from real-time control unit 131 to switching element 132 disappears, and switching element 132 turns off. In other words, real-time control is performed.

[0023] In this embodiment, the timing at which a gate signal is output from the real-time control unit 131 to the switching element 132 to turn on the switching element 132 is set to the timing at which the constant current converter 13 operates in either the critical mode operation or the discontinuous mode operation, or in a combination of both.

[0024] The critical mode operation is an operation in which the switching element 132 is turned off at timings T12 and T14 when the output current A of the constant current converter 13 exceeds the upper threshold A1, and turned on at timings T11 and T13 when the output current A disappears (becomes zero), as shown in Figures 2(A) and 2(B). The discontinuous mode operation is an operation in which the switching element 132 is turned off at timings T22 and T25 when the output current A of the constant current converter 13 exceeds the upper threshold A1, and turned on at timings T24 and T27 when a predetermined time has elapsed after the switching off, including the time when the output current is zero (timings T23 to T24 and T26 to T27 in Figure 4).

[0025] The on / off timing and frequency of the switching element 132 by the real time control unit 131 are also controlled by a dimming signal from the load switching and dimming control unit 19. In other words, when adjusting the light intensity (brightness) of the first and second LED loads 15, 16, the load switching and dimming control unit 19 sends a dimming signal according to an instruction from the user to the real time control unit 131, and the real time control unit 131 controls the on / off of the switching element 132 according to this dimming signal, and further adjusts the light intensity of the LED loads 15, 16 by changing the upper limit threshold value that is compared with the voltage across the resistor 133, if necessary.

[0026] The impedance element 134 stabilizes the current output from the constant current converter 13 and supplied to the LED loads 15 and 16. The diode 135 is an element for forming a discharge circuit for the energy held by the impedance element 134 when the switching element 132 is off.

[0027] Capacitor 14 connected to the output end of constant current converter 13 serves to suppress and smooth the pulsation of the output current of constant current converter 13 and to supply a stable current to LED loads 15 and 16 .

[0028] The first and second LED loads 15, 16 are both connected in parallel to the capacitor 14. These LED loads 15, 16 have different color temperatures and each is composed of one LED or a series connection of multiple LEDs. The load terminal voltages of the LED loads 15, 16 are different due to the number of LEDs included in each load, variations in characteristics, etc., and in this embodiment, the load terminal voltage of the first LED load 15 is higher than the load terminal voltage of the second LED load 16.

[0029] The first load switching unit 17 and the second load switching unit 18 are each composed of a switching element such as a MOSFET, the first load switching unit 17 being connected between the cathode side of the first LED load 15 and the negative terminal of the capacitor 14, and the second load switching unit 18 being connected between the cathode side of the second LED load 16 and the negative terminal of the capacitor 14. Therefore, when the load switching units 17 and 18 are turned on, the circuits of the LED loads 15 and 16 are closed and a current flows through the LED loads 15 and 16, causing the LED loads 15 and 16 to emit light. Conversely, when the load switching units 17 and 18 are turned off, the LED loads 15 and 16 are opened and no current flows through the LED loads 15 and 16.

[0030] The on / off of each of the load switching units 17, 18 is controlled by a gate signal, which is a drive switching signal, from the load switching / dimming control unit 19. In this embodiment, the load switching / dimming control unit 19 alternately outputs drive switching signals to each of the load switching units 17, 18, thereby alternately switching and driving the first and second LED loads 15, 16. Also, by adjusting the on time (duty ratio) of each of the load switching units 17, 18, the light emission time of each of the LED loads 15, 16 can be changed, allowing color adjustment.

[0031] As described above, the load switching / dimming control unit 19 performs dimming control by outputting a dimming signal to the real time control unit 131, and also performs light emission / color adjustment control by outputting a drive switching signal to each of the load switching units 17, 18. The dimming / color adjustment settings and changes are made based on instructions from the user. The user operates a dial knob, a remote control, etc. to give instructions to the load switching / dimming control unit 19 to set or change the dimming / color adjustment.

[0032] The operation speed adjustment circuit 20 plays a role in suppressing the peak current of the second LED load 16 generated when the MOSFET serving as the driving switching element constituting the second load switching unit 18 is turned on by slowing down the operation speed. This will be described later.

[0033] Next, a basic operation of the LED lighting device 1 shown in FIG. 1 will be described.

[0034] When the constant current converter 13 is controlled to operate in the critical mode, as shown in FIG. 2B, when the switching element 132 is turned on at timing T11 by a gate signal from the real-time control unit 131, a current A flows from the smoothing capacitor 12 to the load side via the switching element 132, the resistor 133, and the impedance element 134. The current A gradually increases linearly as shown in FIG. 2A. The increase in the current A increases the voltage difference between both ends of the resistor 133, and when the voltage difference reaches an upper limit threshold, the real-time control unit 131 turns off the switching element 132 at timing T12 as shown in FIG. 2B. Then, the current A gradually decreases linearly as shown in FIG. 2A. The decrease in the current A reduces the voltage difference between both ends of the resistor 133, and when the voltage difference becomes zero, in other words, the current A disappears, the real-time control unit 131 turns on the switching element 132 again at timing T13. Then, the current A starts to rise again, and this process is repeated thereafter. 2A, the current A repeatedly increases and decreases in a triangular wave shape between a lower limit value of zero and an upper limit value A1 as the switching element 132 is turned on and off. The frequency f1 of the increase and decrease of the current A (the on / off frequency of the switching element 132) is preferably set to several tens of kHz to several hundreds of kHz.

[0035] 3(C)(D), the first load switching unit 17 is turned on and the second load switching unit 18 is turned off at timing T15, and the first load switching unit 17 is turned off and the second load switching unit 18 is turned on at timing T16, and thereafter, this switching is repeated as shown at timings T17 to 19. The switching frequency is set to about 1 kHz.

[0036] When the first load switching unit 17 is turned on and the second load switching unit 18 is turned off, the load current 1 flows through the first LED load 15, and the load current 2 that was flowing through the second LED load 16 becomes zero, as shown in Figures 3(A) and (B). When the first load switching unit 17 is switched off and the second load switching unit 18 is switched on, the load current 1 that was flowing through the first LED load 15 becomes zero, and the load current 2 flows through the second LED load 16. The load currents 1 and 2 repeatedly increase and decrease in a triangular wave shape in response to the output current A in the critical operation mode of the constant current converter 13.

[0037] However, since an operation speed adjustment circuit 20 is installed between the second load switching unit 18 and the load switching / dimming control unit 19, the signal applied to the second load switching unit 18 shown in FIG. 3(D) has a blunt rise, as will be described later.

[0038] When the constant current converter 13 is controlled to operate in discontinuous mode, as shown in FIG. 4B, when the switching element 132 is turned on at timing T21 by a gate signal from the real-time control unit 131, a current A flows from the smoothing capacitor 12 to the load side through the switching element 132, the resistor 133, and the impedance element 134. The current A gradually increases linearly as shown in FIG. 4A. The increase in the current A increases the voltage difference between both ends of the resistor 133, and when the voltage difference reaches an upper limit threshold, the real-time control unit 131 turns off the switching element 132 at timing T22 as shown in FIG. 4B. Then, the current A gradually decreases linearly as shown in FIG. 4A, and eventually becomes zero at timing T23. After the zero period of the current A continues for a while, and at timing T24 when a predetermined time has elapsed after the switching element 132 is turned off, the real-time control unit 131 turns on the switching element 132 again. Then, the current A starts to rise again, and this process is repeated thereafter. 4A, the waveform of current A is in a state where a triangular wave with a lower limit of zero and an upper limit of A1 is intermittently generated as the switching element 132 is turned on and off. In this case, too, the frequency f1 of the increase and decrease of current A (the on / off frequency of switching element 132) is preferably set to several tens of kHz to several hundreds of kHz.

[0039] 5(C)(D), the first load switching unit 17 is turned on and the second load switching unit 18 is turned off at timing T31, and the first load switching unit 17 is turned off and the second load switching unit 18 is turned on at timing T32, and thereafter, this switching is repeated as shown at timings T33 to T35. The switching frequency is set to about 1 kHz.

[0040] When the first load switching unit 17 is turned on and the second load switching unit 18 is turned off, the load current 1 flows through the first LED load 15, and the load current 2 that was flowing through the second LED load 16 becomes zero, as shown in Figures 5(A) and (B). When the first load switching unit 17 is switched off and the second load switching unit 18 is switched on, the load current 1 that was flowing through the first LED load 15 becomes zero, and the load current 2 flows through the second LED load 16. The load currents 1 and 2 correspond to the output current A in the critical operation mode of the constant current converter 13, and become repeated intermittent triangular waves.

[0041] However, since an operation speed adjustment circuit 20 is installed between the second load switching unit 18 and the load switching / dimming control unit 19, the signal applied to the second load switching unit 18 shown in Figure 5 (D) has a blunt rise, as will be described later.

[0042] As disclosed in Patent Document 3, Japanese Patent No. 6999100, when the constant current converter 13 operates in a continuous mode, the switching element 132 is turned on while the output current A of the constant current converter 13 is flowing, resulting in large losses and easily generating noise. In contrast, in the critical mode operation of this embodiment, the switching element 132 is turned on when the output current A of the constant current converter 13 becomes zero, so that the output current A does not flow when the switching element 132 is on (at timings T11 and T13), reducing losses and noise.

[0043] In addition, the output current A does not flow during the on-time (timings T21 and T23) in the discontinuous mode operation, so that the loss can be reduced and the noise can be reduced. In the discontinuous mode in real-time control, the on-timing cannot be determined by the current value, and the off-period of the switching element 132 (for example, T23 to T24 and T26 to T27 in FIG. 4) must be fixed. In this case, attention must be paid to the influence of load fluctuations and input fluctuations. In addition, if the LED load current is dimmed to a small value only in the critical mode operation, there is a concern that the oscillation frequency f1 will increase and the loss of the switching element 132 will increase. For this reason, for example, the critical mode operation and the discontinuous mode operation may be used together when the LED load current is dimmed to a small value, and the critical mode operation may be used otherwise. The critical mode operation and the discontinuous mode operation may be used together not only when the LED load current is dimmed to a small value.

[0044] In this embodiment, as described above, the load terminal voltage of the first LED load 15 is greater than the load terminal voltage of the second LED load 16. Therefore, when the first load switching unit 17 switches from on to off and the second load switching unit 18 switches from off to on, and the load switches from the first LED load 15 to the second LED load 16, the terminal voltage of the load drops suddenly. Depending on the timing of the switching, the charge of the capacitor 14 may suddenly flow to the second LED load 16 due to the difference in terminal voltage. If the capacity of the capacitor 14 is large, a sudden peak current will flow to the second LED load 16, leading to a failure of the second LED load 16. If the capacity of the capacitor 14 is reduced, the magnitude of the peak current can also be reduced, but the absorption performance of noise generated in the circuit will decrease.

[0045] In this embodiment, in order to reduce the peak value of the peak current that suddenly flows from the capacitor 14 to the second LED load 16 when the load is switched from the first LED load 15 to the second LED load 16, as described above, the operation speed adjustment circuit 20 is connected between the second load switching unit 18 and the load switching / dimming control unit 19.

[0046] An example of the operation speed adjustment circuit 20 is shown in Fig. 6. As shown in Fig. 6, the operation speed adjustment circuit 20 includes two resistors 201 and 202 connected in series to the gate of the second load switching unit 18, and further includes a diode 203 connected in parallel to the resistor 201. The anode of the diode 203 is connected to the connection point of the resistors 201 and 202. In addition, a parasitic capacitance 184 exists between the gate and source of the second load switching unit 18.

[0047] When switching from the first LED load 15 to the second LED load 16, an input signal Vin, which is a pulsed drive signal as shown in Fig. 7(D) is applied from the load switching / dimming control unit 19 to the input of the operation speed adjustment circuit 20 in Fig. 6. Resistors 201 and 202 are connected to the gate of the second load switching unit 18, and a parasitic capacitance 184 exists between the gate and source. Therefore, if the resistance values ​​of the resistors 201 and 202 are Ra and Rb, respectively, and the value of the parasitic capacitance 184 is Ca, the gate signal, which is the output signal Vout of the operation speed adjustment circuit 20, gradually rises with a time constant of (Ra+Rb)×Ca, as shown in Fig. 6(C).

[0048] In this way, by blunting the gate signal when the second load switching unit 18 is on, the speed at which the second load switching unit 18 turns on is slowed down, so that as shown in the waveform of the load current 2 flowing through the second LED load 16 in Fig. 7(B), the load current 2 starts to flow gradually when the load is on (solid line I2) and then settles to the current value I3 of the constant current converter 13. This makes it possible to suppress the peak current (dashed line I1) of the second LED load 16 that occurs when the load is on. The load current 1 flowing through the first LED load 15 is not affected, as shown in Fig. 7(A).

[0049] Furthermore, when the second load switching unit 18 is off, discharge occurs with a time constant of Rb×Ca. However, by setting Ra>>Rb, the gate signal can be made dull only when the second load switching unit 18 is on.

[0050] 8 shows another example of the operation speed adjustment circuit 20. In this example, the operation speed adjustment circuit 20 includes one resistor 211 and a diode 212 connected in series to the gate of the second load switching unit 18, and further includes a resistor 213 connected in parallel to the resistor 211 and the diode 212. The diode 212 is connected such that its anode is on the resistor 211 side and its cathode is on the gate side of the second load switching unit 18. In addition, a parasitic capacitance 184 exists between the gate and source of the second load switching unit 18.

[0051] The waveforms of the drive signal (input signal) Vin input to the operation speed adjustment circuit 20 in Fig. 8, the gate signal Vout output from the operation speed adjustment circuit 20, and the load currents 1 and 2 are almost the same as those shown in Fig. 7(A) to (D). That is, when switching from the first LED load 15 to the second LED load 16, a pulse-shaped input signal Vin as shown in Fig. 7(D) is applied from the load switching / dimming control unit 19 to the input of the operation speed adjustment circuit 20. Since a resistor 211 and a diode 212 are connected to the gate of the second load switching unit 18 and a parasitic capacitance 184 exists between the gate and source, if the resistance value of the resistor 211 is Ra and the value of the parasitic capacitance 184 is Ca, the gate signal, which is the output signal Vout of the operation speed adjustment circuit 20, gradually rises with a time constant of Ra x Ca as shown in Fig. 7(D).

[0052] In this way, by blunting the gate signal when the second load switching unit 18 is on, the operating speed of the second load switching unit 18 to turn on is slowed down, so that as shown in the waveform of the load current 2 flowing through the second LED load 16 in Fig. 7(B), the load current 2 starts to flow gradually when on (solid line I2) and then settles to the current value I3 of the constant current converter 13. This makes it possible to suppress the peak current (dashed line I1) of the second LED load 16 that occurs when on.

[0053] Furthermore, if the resistance value of resistor 213 is Rb, when second load switching unit 18 is off, it discharges with a time constant of Rb×Ca. However, by setting Rb to a small value, it is possible to dull the gate signal only when it is on.

[0054] Another example of the operation speed adjustment circuit 20 is shown in Fig. 9. In this example, the operation speed adjustment circuit 20 includes a resistor 221 and a capacitor 222 connected in series between the output of the load switching / dimming control section 19 and the source of the second load switching section 18, and further includes an operational amplifier 223 and a diode 224 connected in parallel with the resistor 221. The inverting input terminal of the operational amplifier 223 is connected to the output terminal of the operational amplifier 223, the output terminal of the operational amplifier 223 is connected to the gate of the second load switching section 18, and the non-inverting input terminal of the operational amplifier 223 is connected to the connection point of the resistor 221 and the capacitor 222. The diode 224 plays a role of quickly discharging the charge of the capacitor 222 when the second load switching section 18 is switched from on to off, and is connected with its anode on the capacitor 222 side.

[0055] When switching from the first LED load 15 to the second LED load 16, a pulsed drive signal is output from the load switching and dimming control unit 19, and this drive signal is applied to the series circuit of the resistor 221 and the capacitor 222. As a result, the voltage at the connection point between the resistor 221 and the capacitor 222, in other words, the input signal Vin applied to the non-inverting input terminal of the operational amplifier 223, gradually rises with the time constant of the resistor 221 and the capacitor 222, as shown in Fig. 10(B). Therefore, the gate signal Vout output from the operational amplifier 223 also gradually rises, as shown in Fig. 10(A).

[0056] In this way, by blunting the gate signal when the second load switching unit 18 is on, the ON operation speed of the second load switching unit 18 is slowed down, so that the load current 2 flowing through the second LED load 16 starts to flow gradually and thereafter settles to the current value of the constant current converter 13, similar to the case of the operation speed adjustment circuit 20 shown in Figures 6 and 8. Therefore, the peak current of the second LED load 16 generated when the second LED load 16 is on can be suppressed.

[0057] As is clear from the above explanation, the operating speed adjustment circuit 20 slows down the ON operating speed of the switching element of the second load switching unit 18, thereby suppressing the peak value of the peak current I1 flowing through the second LED load 16 when the load is switched, thereby preventing the second LED load 16 from breaking down due to an unexpected peak current, or reducing instability in the operation of the second LED load 16. Moreover, since the peak value of the peak current I1 can be suppressed regardless of the capacitance of the capacitor 14, a capacitor with a relatively large capacity can be used for the capacitor 14, resulting in excellent performance in absorbing noise generated in the circuit.

[0058] However, because there is a limit to suppressing the peak current due to the mirror effect of the second load switching unit 18, experiments have shown that the capacitance of the capacitor 14 should be 4.7 μF or less. Although the noise absorption performance generated in the circuit deteriorates, it is not necessary to provide the capacitor 14. In this case, it is still possible to prevent the second LED load 16 from breaking down due to the peak current.

[0059] The operation speed adjustment circuit 20 is not limited to the configurations shown in Figures 6, 8, and 9, and may be a circuit of another configuration as long as it is a circuit that can slow down the ON operation speed of the second load switching unit 18, which is a switching element, and suppress the LED peak current that occurs when the second load switching unit 18 is on.

[0060] In the above embodiment, the operation speed adjustment circuit 20 is operated only for the second load switching unit 18, but as shown in Fig. 11, an operation speed adjustment circuit may also be provided between the load switching / dimming control unit 19 and the first load switching unit 17 to slow down the ON operation speed for both the first load switching unit 17 and the second load switching unit 18. With this configuration, if the terminal voltage of the first LED load 15 becomes smaller due to a failure or the like of the second LED load 16, a sudden peak current flows through the first LED load 15 when the first LED load 15 is switched on, which can cause a failure or the like, and this can be prevented.

[0061] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. For example, the power source of the LED lighting power supply device 1 has been described as an AC power supply 2, but the power supply device may obtain a constant current from a DC power supply and supply it to the first and second LED loads 15 and 16.

[0062] Also, although the LED loads having different load voltages are two systems, the first and second LED loads 15 and 16, three or more systems may be used. [Explanation of symbols]

[0063] 1 LED lighting device 2 AC power supply 11 Rectifier circuit 12 Smoothing capacitor 13 Constant current converter 131 Real-time control section 132 Switching element 133 Resistance 134 Impedance Element 135 Diode 14 Capacitor 15 First LED Load 16 Second LED Load 17 First load switching section 18 Second load switching section 19 Load switching and dimming control unit 20 Operating speed adjustment circuit 184 Stray Capacitance 201, 202, 211, 212, 221 Resistors 203, 212 Diodes 222 Capacitor 223 Operational Amplifier

Claims

1. A power supply device for LED lighting that uses AC or DC as a power source and performs dimming and / or color adjustment by switching and driving two or more independent systems of LED loads with different load terminal voltages connected to the output of a single constant current converter, The constant current converter is controlled in real time in a critical mode operation in which a switching element of the constant current converter is turned off when the output current of the constant current converter reaches an upper limit threshold and turned on when the output current disappears, and the on operating speed of the switching element that switches the LED load is slowed down to suppress the LED peak current generated when the switching element is on.

2. A power supply device for LED lighting that uses AC or DC as a power source and performs dimming and / or color adjustment by switching and driving two or more independent systems of LED loads with different load terminal voltages connected to the output of a single constant current converter, The constant current converter is controlled in real time in a discontinuous mode, in which a switching element of the constant current converter is turned off when the output current of the constant current converter reaches an upper limit threshold and turned on when a predetermined time has elapsed, including a time when the output current is zero, and the switching element is turned on at a slower speed to suppress the LED peak current generated when the switching element is on.

3. A power supply device for LED lighting that uses AC or DC as a power source and performs dimming and / or color adjustment by switching and driving two or more independent systems of LED loads with different load terminal voltages connected to the output of a single constant current converter, The control of the constant current converter is a combination of real-time control of critical mode operation in which the switching element of the constant current converter is turned off when the output current of the constant current converter reaches an upper threshold and turned on when the output current is zero, and real-time control of discontinuous mode operation in which the switching element of the constant current converter is turned off when the output current of the constant current converter reaches an upper threshold and turned on when a predetermined time has elapsed, including the time when the output current is zero, and the on operating speed of the switching element that switches the LED load is slowed down to suppress the LED peak current that occurs when it is on.

4. 4. The power supply device for LED lighting according to claim 1, wherein the capacitance of a capacitor connected to the output terminal of the constant current converter is set to 4.7 μF or less, or no capacitor is provided at the output terminal of the constant current converter.

5. An LED lighting device comprising the power supply device for LED lighting according to any one of claims 1 to 3.

6. 6. The LED lighting device according to claim 5, wherein the capacitance of a capacitor connected to the output end of the constant current converter is set to 4.7 μF or less, or no capacitor is provided at the output end of the constant current converter.

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