JP7114378B2 - Power supply device and LED lighting equipment provided with the same - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device and an LED lighting fixture having the same, and more particularly to technology using a switching power supply.

A power supply using a step-down chopper circuit is conventionally known as a DC power supply. This is suitable for the purpose of supplying a voltage lower than the effective voltage of the received AC power, and is used, for example, as a power supply for LED (Light Emitting Diode) lighting fixtures. In a step-down chopper circuit, as disclosed in Patent Document 1, it is known to adopt a synchronous rectification method using a switching element such as a field effect transistor (FET) instead of a diode as a commutation element.

Japanese Patent No. 6253200

The conventional power supply device as described above has the following problems. Such a DC power supply device includes a rectifier circuit using a diode bridge as a front stage of the step-down chopper circuit. The voltage supplied from the rectifier circuit to the step-down chopper circuit is not constant over time, but pulsates according to the frequency of the commercial power supply. Then, while the input voltage of the step-down chopper circuit is lower than the output voltage, current cannot flow from the input side to the output side. There was a back and forth and wasted energy loss.

An object of one embodiment of the present invention is to suppress energy loss in a power supply device using a step-down chopper circuit.

To solve the above problems, a power supply device according to one aspect of the present invention includes a rectifier circuit that rectifies alternating current, a step-down chopper circuit that steps down an input voltage from the rectifier circuit, and a step-down chopper circuit that reduces the input voltage from the step-down chopper. a control unit for stopping the switching operation of the step-down chopper circuit during a period smaller than the output voltage of the circuit, the step-down chopper circuit being connected in series between the high potential side terminal and the low potential side terminal of the input terminal pair. a choke coil and an output capacitor, which are connected in series between a first switching element and a second switching element, a connection portion between the first switching element and the second switching element, and the low potential side terminal; wherein, in the switching operation, when the magnitude of a reverse current obtained by inverting the current flowing through the choke coil reaches a predetermined value or more, the control unit turns off the second switching element, and the predetermined value changes according to the input voltage of the step-down chopper circuit, and the predetermined value changes so as to increase as the input voltage of the step-down chopper circuit increases .

In order to solve the above problems, a power supply device according to another aspect of the present invention includes a rectifier circuit that rectifies an alternating current, a step-down chopper circuit that steps down an input voltage from the rectifier circuit, and a switching circuit for the step-down chopper circuit. a control unit for controlling an operation of the step-down chopper circuit, wherein the step-down chopper circuit includes a first switching element and a second switching element connected in series between a high potential side terminal and a low potential side terminal of a pair of input terminals; a choke coil and an output capacitor connected in series between a connecting portion of the first switching element and the second switching element; and the low-potential side terminal; In operation, the second switching element is turned off when the magnitude of the reverse current obtained by inverting the current flowing through the choke coil reaches a predetermined value or more, and the predetermined value is the step-down chopper circuit of the step-down chopper circuit. It changes so that it increases as the input voltage increases .

According to one aspect of the present invention, useless energy loss can be suppressed in a power supply device using a step-down chopper circuit.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic circuit diagram which shows the LED lighting fixture and power supply device which concern on Embodiment 1 of this invention. It is a time chart which shows operation|movement of the said power supply device. FIG. 4 is a schematic circuit diagram showing an LED lighting fixture and a power supply device according to Embodiment 2 of the present invention; FIG. 7 is a flowchart showing internal control of the power supply device according to Embodiment 2 of the present invention; 4 is a time chart showing switching operations in the power supply device; 9 is a time chart showing switching operations in the power supply device according to Embodiment 3 of the present invention; FIG. 4 is a schematic circuit diagram showing an LED lighting fixture and a power supply device according to Embodiment 4 of the present invention;

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below based on the drawings. However, the material, shape, relative arrangement, processing method, etc. of the configuration described in this embodiment are merely examples, and the scope of the present invention should not be construed as limited by these. Furthermore, the drawings are schematic, and dimensional ratios and shapes differ from the actual ones. Moreover, in each figure and each embodiment, the same reference numerals may be given to the same or corresponding components.

[Embodiment 1]
Embodiment 1 of the present invention will be described with reference to FIGS. 1 and 2. FIG.

(Configuration of LED lighting equipment)
FIG. 1 is a schematic diagram showing the circuit configuration of an LED lighting fixture 10 and a power supply device 100 of this embodiment. As shown, LED lighting fixture 10 includes power supply 100 and light source 160 . An input terminal of the power supply device 100 is connected to an AC power supply 90 . AC power supply 90 is normally a general commercial AC power supply. Light source 160 is configured by connecting a plurality of LED elements in series, and is connected to an output terminal of power supply device 100 .

(Configuration of power supply)
As shown in FIG. 1, in the power supply device 100, a rectifier circuit 110, a step-down chopper circuit 120, and a constant current circuit 130 are connected in series from the input side. The output terminal pair of rectifier circuit 110 is connected to the input terminal pair of step-down chopper circuit 120 , and the output terminal pair of step-down chopper circuit 120 is connected to the input terminal pair of constant current circuit 130 .

The rectifier circuit 110 is a circuit that rectifies alternating current using a diode bridge.

In the step-down chopper circuit 120, a first switching element Q1 as a main switching element and a second switching element Q1 as a commutating element are provided between the terminal A1 on the high potential side of the input terminal pair and the terminal A0 on the low potential side. element Q2 is connected in series. Each switching element is composed of a field effect transistor (FET). A drain terminal of the first switching element Q1 is provided on the terminal A1 side, and a source terminal of the first switching element Q1 is provided on the connection portion H side with the second switching element Q2. A drain terminal of the second switching element Q2 is provided on the connection portion H side, and a source terminal of the second switching element Q2 is provided on the terminal A0 side. An input capacitor Ci is connected in parallel between the input terminals A1 and A0.

Furthermore, a choke coil L and an output capacitor Co are connected in series between the connection portion H and the input terminal A0. Both terminals B1 and B0 of the output capacitor Co constitute an output terminal pair of the step-down chopper circuit 120, of which the output terminal B0 is electrically common to the input terminal A0.

The capacitance between the connection H and the input terminal A0 (output terminal B0) is called switching node capacitance Ch. The switching node capacitance Ch may be the sum of the parasitic capacitance of the first switching element Q1 and the parasitic capacitance of the second switching element Q2. Alternatively, the switching node capacitance Ch may be obtained by actually arranging a capacitor and adding its capacitance.

As illustrated, a reverse current detector 143 can be provided between the second switching element Q2 and the input terminal A0 (output terminal B0), but may be omitted in this embodiment. An example of controlling the operation using the reverse current detector 143 will be described later.

Next, the constant current circuit 130 will be explained. The input terminal connected to the output terminal B1 of the step-down chopper circuit 120 is directly connected to the output terminal on the high potential side. The other input terminal is connected to the low potential side output terminal through a linear constant current source 131 using a known circuit configuration. The constant current source 131 is suitable for operating the light source 160 made up of LED elements while maintaining a constant brightness. is inexpensive without being complicated. Therefore, it is suitable for application as a power source for LED lighting fixtures. However, the constant current circuit 130 is not limited to a linear system, and may be a switching system. For example, when the light source 160 has a large number of LED elements connected in series, constant current control can be performed even if the output voltage of the step-down chopper circuit 120 is low by using a step-up chopper type constant current circuit.

Further, an input voltage detection section 141 and an output voltage detection section 142 for detecting the input voltage Vi and the output voltage Vo are provided between the input terminal pair and the output terminal pair of the step-down chopper circuit 120, respectively. Since it is not always necessary to directly detect the voltage between each terminal pair, it is composed of a voltage dividing circuit using resistors.

Also, the power supply device 100 is provided with a control section 150 that controls the switching operation of the step-down chopper circuit 120 . The control unit 150 controls on/off operations of the switching elements Q1 and Q2. In this embodiment, the control section 150 receives an input voltage signal from the input voltage detection section 141 and an output voltage signal from the output voltage detection section 142 and reflects them in its control. Also, the control unit 150 can receive a signal from the reverse current detection unit 143 and appropriately reflect it in the control of the on/off operation of the switching elements Q1 and Q2. The control unit 150 can also exchange signals with the constant current circuit 130 to appropriately manage the operation of the power supply device 100 as a whole.

(Power supply operation)
In order to explain the operation of the power supply device of this embodiment, first, the basic switching operation in the step-down chopper circuit 120 will be briefly explained.

The first switching element Q1, which is the main switching element in the step-down chopper circuit 120, is on/off controlled with a duty aimed at a predetermined output voltage Vo that is lower than the input voltage Vi. While the first switching element Q1 is on (on period T1), the second switching element Q2 is off, magnetic energy is accumulated in the choke coil L by the input voltage Vi, the choke coil current Ic increases, and the output Charge is accumulated in the capacitor Co.

Next, after the first switching element Q1 is turned off, the second switching element Q2 is turned on. While the second switching element Q2 is on (on period T2), the choke coil current Ic flows through the second switching element Q2. Since the voltage with respect to the input terminal A0 (output terminal B0) of the connection point H becomes 0, the magnetic energy of the choke coil L is released and the choke coil current Ic decreases. If this state continues, the choke coil current Ic is reversed.

Next, the second switching element Q2 is turned off and the first switching element Q1 is turned on to return to the initial operation. Since the input side is short-circuited when both switching elements are turned on at the same time, a first dead time D1 is provided as a period from when the second switching element Q2 is turned off to when the first switching element Q1 is turned on. A second dead time D2 is provided as a period from when the first switching element Q1 is turned off until when the second switching element Q2 is turned on.

In this embodiment, which is a power supply device for an LED lighting fixture, the switching frequency, which is the reciprocal of one cycle of the switching operation, is about 20 to 100 kHz, typically about 50 kHz.

Next, the operation of the power supply device 100 of this embodiment will be described with reference to the time chart of FIG. 2 showing the switching operation.

(a) of FIG. 2 shows the power supply voltage Vs supplied from the AC power supply 90, which is a sinusoidal alternating current. Its frequency is typically 50-60 Hz.

FIG. 2B shows the input voltage Vi to the step-down chopper circuit 120, which is based on the waveform obtained by full-wave rectifying the power supply voltage Vs by the rectifier circuit 110. FIG. The input voltage Vi has a periodic waveform with a frequency twice as high as the power supply frequency. FIG. 2(b) also shows the output voltage Vo of the step-down chopper circuit 120. FIG. This is a DC voltage and is constant over time. Also, its value is set to a value smaller than the effective value of the voltage Vs supplied from the AC power supply 90 . During the period when the full-wave rectified waveform of the power supply voltage Vs is smaller than Vo, a current flows from the output capacitor Co, and the input voltage Vi is changed. It becomes a voltage slightly lower than the output voltage Vo. Note that the rectifier circuit 110 does not smooth the full-wave rectified waveform. This is because if a smoothing capacitor is provided, the power factor of the power supply device 100 is lowered, the harmonic current is increased, and the efficiency is further deteriorated.

Thus, there is a period during which the input voltage Vi is lower than the output voltage Vo within one cycle of the power supply voltage Vs. In the power supply device 100 of this embodiment, the switching operation is stopped during that period. (c) of FIG. 2 shows the period W during which the switching operation is performed and the period H during which the switching operation is stopped.

The operation of power supply device 100 is realized as follows. The control unit 150 receives the input voltage signal from the input voltage detection unit 141 and the output voltage signal from the output voltage detection unit 142, and determines the magnitude relationship between the input voltage Vi and the output voltage Vo. As an example, the control section 150 may have an A/D converter and may be configured to be able to evaluate the A/D converted input voltage Vi and output voltage Vo. When the input voltage Vi is lower than the output voltage Vo, the controller 150 turns off both the switching elements Q1 and Q2 to stop the switching operation (stop period H). Otherwise, each switching element is controlled to perform the switching operation described above (implementation period W).

More preferably, the control unit 150 controls the ratio of the period during which the first switching element Q1 is turned on according to the fluctuation of the input voltage Vi so that the output voltage Vo becomes a desired constant value during the period W during which the switching operation is performed. (on-duty).

(effect)
In the power supply device of the prior art, no countermeasures were taken against the possibility that the input voltage Vi of the step-down chopper circuit becomes lower than the output voltage Vo during the period during which the switching operation was continued even during this period. . However, the choke coil current Ic immediately reverses when the second switching element Q2 is turned on during this period, and the reverse current becomes large. After that, when Q2 is turned off, a large reverse current maintained by the choke coil L flows back to the input side through the first switching element Q1, causing the input voltage Vi to become higher than the output voltage Vo. Then, step-down chopper circuit 120 becomes capable of step-down chopper operation, and current flows from the input side to the output side. Such an exchange causes the charge of the output capacitor Co to reciprocate between the input side and the output side of the step-down chopper circuit 120, causing energy loss.

On the other hand, in the power supply device 100 of the present embodiment, each switching element is not turned on while the input voltage Vi is lower than the output voltage Vo, and no such energy loss occurs. Therefore, an efficient power supply device and LED lighting fixture can be realized.

(preferred configuration)
As a preferred configuration of the power supply device 100, the control unit 150 acquires from the constant current circuit 130 a signal regarding the voltage Vc that the constant current source 131 bears, and adjusts the target value of the output voltage Vo of the step-down chopper circuit 120. Things are mentioned. This is because the driving voltage of the light source 160 changes according to the number of LED elements connected in series. Assuming that the output voltage Vo of the step-down chopper circuit 120 is fixed, the voltage Vc borne by the constant current source 131 changes when the driving voltage of the light source 160 is changed. If the voltage Vc is too high, energy is wasted in the constant current source 131. Conversely, if the voltage Vc is too low, the constant current operation cannot be maintained. Therefore, it is preferable that the control unit 150 adjusts the output voltage Vo so that the voltage Vc borne by the constant current source 131 becomes the minimum required for constant current operation and performs feedback control.

Another preferred configuration is that the constant current value maintained by the constant current source 131 can be changed according to an instruction from the control unit 150 . Thereby, the brightness of the light source 160 can be adjusted, and a preferable configuration for the LED lighting fixture 10 can be obtained.

The preferred configuration as described above can be similarly applied to other embodiments.

[Embodiment 2]
Embodiment 2 of the present invention will be described with reference to FIGS. 3 to 5. FIG.

FIG. 3 shows the circuit configurations of the LED lighting fixture 20 and the power supply device 200 of Embodiment 2. As shown in FIG. In this embodiment, the circuit configuration is the same as that of the first embodiment except that the reverse current detector 143 is always provided. Thus, the reverse current detection unit 143 monitors the reverse current Ir, and further controls the operation accordingly, which is different from the first embodiment. Also, in FIG. 3, the parasitic diodes of the respective switching elements Q1 and Q2 are shown for explanation, but they are not different from FIG. 1 in terms of circuit configuration.

(Power supply operation)
FIG. 4 is a flowchart showing the internal operation of the power supply device 200 of this embodiment. This diagram shows one cycle of the switching operation performed by the control unit 150 by controlling the switching elements Q1 and Q2. The initial states of the switching elements Q1 and Q2 are both turned off.

The control unit 150 receives signals from the input voltage detection unit 141 and the output voltage detection unit 142, and compares the magnitudes of the input voltage Vi and the output voltage Vo of the step-down chopper circuit 120 at that time (S1). If the input voltage Vi is lower than the output voltage Vo (YES in S1), the switching elements Q1 and Q2 are not operated and the series of flow ends while they are in the OFF state. If the input voltage Vi is not lower than the output voltage Vo (NO in S1), the first switching element Q1 is turned on (S2). The control unit 150 determines the ON period T1 according to the magnitude of the input voltage Vi detected by the input voltage detection unit 141 so that the average value of the choke coil current Ic increases according to the input voltage Vi. This is for improving the power factor. After the on period T1 has elapsed, the first switching element Q1 is turned off (S3).

After the second dead time D2 has elapsed since the first switching element Q1 was turned off, the second switching element Q2 is turned on (S4). Next, the control section 150 receives a signal about the reverse current Ir flowing through the second switching element Q2 from the reverse current detecting section 143 connected to the second switching element Q2. When the second switching element Q2 is on (ON period T2), the magnitude of the current flowing through the second switching element Q2 is equal to the choke coil current Ic, but a reverse current Ir is defined as a current in the opposite direction. As described above, when the second switching element Q2 is turned on, the choke coil current Ic decreases over time and reverses at a certain point (Ic<0). During this time, the controller 150 continues to compare the reverse current Ir with a predetermined threshold It (>0) (S5). When the magnitude of the reverse current Ir exceeds the threshold It (Ir>It), the second switching element Q2 is turned off (S6).

Furthermore, it waits for the first dead time D1 until the first switching element Q1 is turned on next time. (S7).

Thus, one unit of the switching operation, which is the flow shown in FIG. 4, is completed. The power supply device 200 repeatedly executes this unit operation.

FIG. 5 shows the input voltage Vi, the choke coil current Ic, and the ON/OFF control states of the switching elements Q1 and Q2 in the switching operation as described above, in a very small part of the cycle of the voltage waveform of the AC power supply 90. is a diagram showing the time range of . As described in the basic operation above, the choke coil current Ic increases and decreases within one cycle of the switching operation. In this embodiment, the threshold It of the reverse current Ir is constant. When the choke coil current Ic is reversed during the ON period T2 and its magnitude Ir exceeds the threshold value It (Ir>It), the second switching element Q2 is turned off and the choke coil current Ic increases again.

(effect)
In this embodiment, similarly to the first embodiment, by stopping the switching operation when the input voltage Vi is lower than the output voltage Vo, an efficient power supply device and LED lighting fixture can be realized.

Furthermore, by detecting the reverse current Ir and performing control, the following effects can be obtained.

A typical step-down chopper circuit may operate in a current continuous mode in which the second switching element Q2 is turned off while the choke coil current Ic is not reversed. On the other hand, in the present embodiment, the second switching element Q2 is turned off when the magnitude of the reverse current Ir exceeds the predetermined threshold value It. As a result, in the power supply device 200 of the present embodiment, noise can be reduced and efficiency can be improved.

In the circuit configuration diagram of FIG. 3, the parasitic diodes of the switching elements Q1 and Q2 are shown, and the destination of the choke coil current Ic during the period of the first dead time D1 is also indicated by arrows. When the second switching element Q2 is turned off and the first dead time D1 is entered, the choke coil current Ic tries to continue to flow for a while just before the end of the ON period T2. When the choke coil current Ic does not reverse as in the current continuous mode operation of a general step-down chopper circuit, the parasitic diode of the second switching element Q2 becomes forward, and current flows through it (dotted arrow Ia in the figure). Since the parasitic diode of the first switching element Q1 is in the opposite direction to the choke coil current Ic, no current flows to the first switching element Q1 side. Then, the first dead time D1 ends, and the power supply is turned off until the parasitic diode of the forward-biased second switching element Q2 turns off (recovery operation) when the first switching element Q1 is turned on. Both of the switching elements Q1 and Q2 are almost short-circuited and a large current flows, causing noise and a decrease in efficiency.

On the other hand, as in the power supply device 200 of the present embodiment, when the choke coil current Ic reverses and then enters the first dead time D1, the parasitic diode of the first switching element Q1 becomes forward, and current flows through it. (solid line Ib in the figure). Since the parasitic diode of the second switching element Q2 is in the opposite direction to the choke coil current Ic, no current flows through the second switching element Q2. Since the parasitic diode of the second switching element Q2 is already turned off when the first dead time D1 ends, the power supply is not short-circuited, the above noise is not generated, and the efficiency is prevented from being lowered. .

In addition, a general step-down chopper circuit may operate in a discontinuous current mode in which the second switching element Q2 is turned off while the choke coil current Ic is inverted. However, even in this case, the inversion of the choke coil current Ic is not detected to determine when to turn off the second switching element Q2, and the second switching element Q2 is turned off for a predetermined period of time. do. In the conventional power supply device, no consideration is given to the fluctuation of the input voltage Vi of the step-down chopper circuit due to pulsation and the fluctuation of the output voltage Vo due to the load. If the ON/OFF of the switching element is controlled at a constant time when the input/output voltage fluctuates, the value of the reverse current Ir, which is the reverse of the choke coil current Ic, may become too large or too small. Then, if the reverse current Ir is excessively large, wasteful exchange of current occurs between the input side and the output side of the step-down chopper circuit 120, leading to a decrease in efficiency and noise. If the reverse current Ir is too small, the switching node capacitance Ch cannot be charged, and an excessive voltage is applied to the first switching element Q1 when the first switching element Q1 is turned on, resulting in reduced efficiency and noise. It also becomes.

In this embodiment, by providing the reverse current detection unit 143, the choke coil current Ic is reversed, and after detecting that the reverse current Ir reaches a predetermined value, the second switching element Q2 is turned off. You can keep the status quo. Therefore, even when the input voltage Vi to the step-down chopper circuit 120 fluctuates, it is possible to realize a power supply device and an LED lighting fixture with reduced noise and reduced energy loss.

[Embodiment 3]
A third embodiment of the present invention will be described with reference to FIG.

The circuit configurations of the LED lighting fixture and the power supply device of this embodiment are the same as those of Embodiment 2 shown in FIG. However, in this embodiment, the setting of the threshold value It is different from that in the second embodiment.

FIG. 6 shows a time chart of the switching operation of the power supply device of this embodiment. The difference from the power supply device 200 of the second embodiment shown in FIG. 5 is that the reverse current threshold It is not constant but varies according to the input voltage Vi. In the power supply device of this embodiment, when the input voltage Vi is small, the threshold It is small.

When the choke coil current Ic is inverted in the ON period T2, the switching node capacitance Ch is charged from the output capacitor Co. This charge is returned to the power supply side through the parasitic diode of the first switching element Q1 during the subsequent first dead time D1. At this time, if the input voltage Vi is small, the amount of returned charge increases. However, this is an exchange of charge between the input side (input capacitor Ci, etc.) and the output side (output capacitor Co, etc.) of the step-down chopper circuit 120, and in reality, charge transfer is performed without loss. Since it does not exist, it is repeated at every switching operation, resulting in energy loss. In the present embodiment, the threshold value It is increased according to the magnitude of the input voltage Vi. Therefore, when the input voltage Vi is small, less charge is accumulated in the switching node capacitance Ch. Therefore, the electric charge is not excessively returned, and the efficiency of the power supply device is further improved as compared with the case where the threshold value It is constant.

Therefore, according to the present embodiment, it is possible to realize a power supply device and an LED lighting fixture in which energy loss is further suppressed.

[Embodiment 4]
Embodiment 4 of the present invention will be described based on FIG.

In the circuit configuration of the LED lighting fixture 40 and the power supply device 400 of the present embodiment, a signal related to the input voltage Vi output by the input voltage detection unit 141 and a signal related to the output voltage Vo output by the output voltage detection unit 142 are compared with a comparator. 171, and a signal indicating the magnitude relationship between the input voltage Vi and the output voltage Vo is input to the control unit 450, which is different from the other embodiments. A comparator 172 compares a voltage corresponding to the reverse current Ir output by the reverse current detection unit 143 and a voltage proportional to the input voltage Vi output by the input voltage detection unit 141, and the magnitude of the reverse current Ir is , a signal indicating whether or not a predetermined value (threshold value It) proportional to the input voltage Vi is exceeded is input to the control unit 450, which is also different from the other embodiments. Based on these signals, the control unit 450 controls the switching elements Q1 and Q2 to perform the same operation as in the third embodiment. With such a configuration, the LED lighting fixture 40 and the power supply device 400 of this embodiment can also obtain the same effect as in the case of the third embodiment.

〔summary〕
A power supply device 100, 200, or 400 according to aspect 1 of the present invention includes a rectifier circuit 110 that rectifies an alternating current, a step-down chopper circuit 120 that steps down an input voltage from the rectifier circuit 110, and a step-down chopper circuit in which the input voltage and controllers 150 and 450 for stopping the switching operation of the step-down chopper circuit 120 during a period when the output voltage of the step-down chopper circuit 120 is smaller than the output voltage of the step-down chopper circuit 120 .

According to the above configuration, energy loss can be suppressed even if the input voltage of the step-down chopper circuit pulsates.

The power supply device 200 or 400 according to aspect 2 of the present invention is the first power supply device in which the step-down chopper circuit 120 is connected in series between the high potential side terminal and the low potential side terminal of the input terminal pair in the above aspect 1. a switching element, a second switching element, a connection portion between the first switching element and the second switching element, and a choke coil and an output capacitor connected in series between the low-potential side terminal; The control units 150 and 450 are configured to turn off the second switching element when the magnitude of the reverse current obtained by reversing the current flowing through the choke coil in the switching operation exceeds a predetermined value. good too.

According to the above configuration, energy loss can be further suppressed and noise generation can be prevented.

A power supply device 200 or 400 according to aspect 3 of the present invention includes a rectifier circuit 110 that rectifies alternating current, a step-down chopper circuit 120 that steps down the input voltage from the rectifier circuit 110, and a switching operation of the step-down chopper circuit 120. The step-down chopper circuit 120 includes a first switching element and a second switching element connected in series between the high potential side terminal and the low potential side terminal of the input terminal pair, It has a choke coil and an output capacitor connected in series between the connecting portion of the first switching element and the second switching element, and the low potential side terminal, and the control units 150 and 450 control the step-down In the switching operation of the chopper circuit 120, the second switching element is turned off when the magnitude of the reverse current obtained by reversing the current flowing through the choke coil exceeds a predetermined value.

According to the above configuration, even if the input voltage of the step-down chopper circuit pulsates, energy loss can be suppressed and noise generation can be prevented.

A power supply device 400 according to aspect 4 of the present invention, in aspect 2 or 3, may have a configuration in which the predetermined value changes according to the input voltage of the step-down chopper circuit 120 .

According to said structure, an energy loss can be suppressed further.

The power supply device 200 or 400 according to aspect 5 of the present invention may further include a reverse current detection unit 143 that detects the magnitude of the reverse current in the above-described aspects 2 to 4.

According to the above configuration, it is possible to appropriately detect the magnitude of the reverse current.

A power supply device 100, 200, or 400 according to aspect 6 of the present invention is, in aspects 1 to 5 above, further provided with a constant current circuit 130 having a linear constant current source 131 for supplying a constant current to the load of the step-down chopper circuit 120. It's okay to be there.

According to the above configuration, it is possible to stably operate the light source composed of the LED elements.

LED lighting fixtures 10, 20, and 40 according to aspect 7 of the present invention include the power supply device 100, 200, and 400 according to any one of aspects 1 to 6, and the power supply device 100, 200, and 400 drives an LED. may be provided.

According to said structure, an energy loss can be suppressed.

The present invention is not limited to the above-described embodiments, but can be modified in various ways within the scope of the claims, and can be obtained by appropriately combining technical means disclosed in different embodiments. is also included in the technical scope of the present invention. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment.

Reference Signs List 10, 20, 40 LED lighting equipment 100, 200, 400 power supply device 110 rectifier circuit 120 step-down chopper circuit 130 constant current circuit 131 linear constant current source 141 input voltage detector 142 output voltage detector 143 reverse current detector 150, 450 Control unit 160 Light source 171, 172 Comparator

Claims (5)

a rectifier circuit that rectifies alternating current;
a step-down chopper circuit that steps down the input voltage from the rectifier circuit;
a control unit that stops the switching operation of the step-down chopper circuit during a period in which the input voltage is lower than the output voltage of the step-down chopper circuit ,
The step-down chopper circuit is
a first switching element and a second switching element connected in series between the high potential side terminal and the low potential side terminal of the input terminal pair;
a choke coil and an output capacitor connected in series between the connecting portion of the first switching element and the second switching element, and the low potential side terminal;
The control unit
In the switching operation,
turning off the second switching element when the magnitude of the reverse current obtained by reversing the current flowing through the choke coil reaches or exceeds a predetermined value;
A power supply device , wherein the predetermined value increases as the input voltage of the step-down chopper circuit increases . a rectifier circuit that rectifies alternating current;
a step-down chopper circuit that steps down the input voltage from the rectifier circuit;
A control unit that controls the switching operation of the step-down chopper circuit,
The step-down chopper circuit is
a first switching element and a second switching element connected in series between the high potential side terminal and the low potential side terminal of the input terminal pair;
a choke coil and an output capacitor connected in series between the connecting portion of the first switching element and the second switching element, and the low potential side terminal;
The control unit
In the switching operation of the step-down chopper circuit,
turning off the second switching element when the magnitude of the reverse current obtained by reversing the current flowing through the choke coil reaches or exceeds a predetermined value ;
The power supply device , wherein the predetermined value increases as the input voltage of the step-down chopper circuit increases . 3. The power supply device according to claim 1, further comprising a reverse current detector that detects the magnitude of said reverse current. 4. The power supply device according to claim 1 , further comprising a constant current circuit having a linear constant current source for supplying a constant current to the load of said step-down chopper circuit. A power supply device according to any one of claims 1 to 4 ,
An LED lighting fixture, wherein an LED is driven by the power supply device.

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