Power supply system for LED and converter

Abstract

To provide an LED power supply system 100 that can share an input interface for dimming settings and improve ease of use and dimming reproducibility while using two types of power supply devices.SOLUTION: A converter 3 is provided which can control a second power supply device of a continuous lighting drive type that can set the luminance of an LED light irradiation device 100 by an analog dimming value by using a PWM lighting drive signal of a first power supply device 1 of a PWM lighting drive type that can set the luminance of the LED light irradiation device 100 by a digital dimming value.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an LED power supply system that supplies power to an LED light irradiation device used for surface inspection and the like, and a conversion device used therein. [Background technology]

[0002] Conventionally, as shown in Cited Document 1, there is known an analog dimming type power supply device that supplies a DC drive current to an LED and controls the value of the DC drive current with an analog dimming signal (a current command signal in Cited Document 1) to adjust the brightness of the LED. The value of this analog dimming signal (dimming value) is set, for example, by turning a knob connected to a variable resistor.

[0003] On the other hand, power supply devices capable of adjusting the brightness of an LED using a PWM drive signal are also known. This type of power supply device is configured to adjust the brightness of an LED by changing the duty ratio of the PWM drive signal, and is a so-called digital dimming type in which the value of the duty ratio (dimming value) is set, for example, by a digital switch.

[0004] If the former power supply is used, the LED will light continuously, and if the latter LED power supply is used, the LED will blink at high speed. Because of the difference in the lighting state of the LED, for example in the field of surface inspection, the former or latter power supply may be used depending on the type of inspection. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-135225 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, when the two types of power supply devices are mixed, the user needs to set the dimming value of each power supply device separately. Also, analog dimming type power supply devices have the disadvantage of poor reproducibility.

[0007] The present inventors were the first to focus on the above-mentioned problem, and attempted to provide an LED power supply system that uses the two types of power supply devices, but can share a common input interface for dimming settings, thereby improving usability and dimming reproducibility. [Means for solving the problem]

[0008] That is, the LED power supply system according to the present invention is a first power supply device that outputs a PWM lighting drive signal of a predetermined amplitude voltage to the LED light irradiation device to light it, and that is capable of changing and setting a duty ratio of the PWM lighting drive signal according to a value of an input digital dimming signal; a second power supply device that supplies a direct current driving current to the LED light irradiation device to light it, and that can change and set a value of the direct current driving current according to a value of a set analog dimming signal; The present invention is characterized in that it includes a conversion device that uses a switching-type step-down circuit to generate a secondary PWM signal that reduces the amplitude voltage of the PWM lighting drive signal, smoothes the secondary PWM signal to generate the analog dimming signal, and outputs the analog dimming signal to the second power supply device. Effect of the Invention

[0009] According to the present invention configured in this manner, by setting a digital dimming signal for the first power supply, the dimming value of the second power supply of an analog dimming type can be set via the conversion device, so that the first power supply can be used as an input interface for setting the dimming value of the second power supply. Therefore, the input interface of the first power supply and the second power supply can be made common, and since the dimming value is set digitally, the reproducibility of the dimming value setting of the second power supply can be improved in particular.

[0010] In addition, if the PWM lighting drive signal is directly smoothed, energy loss will be large and the response speed will be slow due to the capacitance of a snubber circuit, etc., provided in the switching element of the first power supply device. However, the amplitude voltage of the PWM lighting drive signal is reduced using a switching type step-down circuit and then smoothed, so that energy loss can be suppressed while ensuring the response speed.

[0011] Furthermore, since existing power supplies can be used as the first power supply device and the second power supply device, users who already own these power supply devices can easily build this LED power supply system by simply installing the conversion device. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic overall circuit diagram of an LED power supply system according to one embodiment of the present invention; [Diagram 2] FIG. 2 is a schematic circuit diagram of the conversion device according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a power supply system for LEDs according to the present invention will be described with reference to the drawings.

[0014] 1. Overview of LED power supply system 100 The LED power supply system 100 in this embodiment supplies current to an LED light irradiation device 200 for surface inspection to light it up, and as shown in FIG. 1, includes a first power supply device 1, a second power supply device 2, and a conversion device 3 provided between the first power supply device 1 and the second power supply device 2.

[0015] 2. Overview of the LED light irradiation device 200 First, the LED light irradiation device 200 will be described. 1, this LED light irradiation device 200 includes an LED circuit 201 consisting of a plurality of LEDs arranged in series or parallel, and a current limiting resistor 202 connected in series to this LED circuit 201. In addition, a positive terminal 203 and a negative terminal 204 are provided on the housing panel (not shown) as external connection terminals, and the LED light irradiation device 200 is configured such that, by applying a voltage between the positive terminal 203 and the negative terminal 204, a current flows through the LED circuit 201, causing the LED to emit light. 3. Configuration of each part of the LED power supply system 100 Next, each device constituting the LED power supply system 100 will be described.

[0016] (1) 1st power supply device 1 The first power supply device 1 includes a PWM control signal generating circuit 11 that generates a PWM control signal based on an input digital dimming signal, and a drive circuit 12 that outputs a PWM lighting drive signal that drives the LED to light based on the PWM control signal.

[0017] Furthermore, a constant voltage output terminal 13 and a PWM output terminal 14 are provided on the housing panel (not shown) as external connection terminals.

[0018] Of these external connection terminals, the constant voltage output terminal 13 is connected to a constant voltage power supply circuit 15 provided inside to supply a constant voltage V H (Here, 24V) is configured to be output.

[0019] On the other hand, the drive circuit 12 is connected to the PWM output terminal 14, and the negative terminal 204 of the LED light irradiation device 200 is connected to this PWM output terminal 14, so that the PWM lighting drive signal is generated and output.

[0020] More specifically, the PWM control signal generating circuit 11 receives a dimming signal input as a digital value from a digital switch or an external computer, and generates a PWM control signal with a duty ratio according to the value of the dimming signal (hereinafter also referred to as a dimming value). The PWM control signal generating circuit 11 here is composed of, for example, a dedicated PWM IC.

[0021] The drive circuit 12 is mainly composed of, for example, an N-type MOSFET 121. The gate of this MOSFET 121 is connected to the output terminal of the PWM control signal generation circuit 11, its drain is connected to the PWM output terminal 14, and its source is connected to ground.

[0022] The drive circuit 12 is also provided with a snubber circuit including a capacitor 122 for absorbing a transient high voltage that occurs when the MOSFET 121 is switched on and off.

[0023] Thus, by connecting the constant voltage output terminal 13 of the first power supply device 1 configured as above to the positive terminal 203 of the LED light irradiation device 200 and the PWM output terminal 14 of the first power supply device 1 to the negative terminal 204 of the LED light irradiation device 200 by a cable, a current flows in the LED circuit 201 due to a PWM lighting drive signal having a duty ratio corresponding to the set dimming value, and the LED light irradiation device 200 lights up at a brightness according to the dimming value.

[0024] In addition, the first power supply device 1 of this embodiment is provided with multiple circuits (two circuits) of units each consisting of the PWM control signal generating circuit 11, the drive circuit 12, the constant voltage output terminal 13 and the PWM output terminal 14, and is configured to be able to independently drive the LED light irradiation devices 200 in PWM lighting mode for the number of units.

[0025] (2)Second power supply device 2 The second power supply device 2 includes a current drive circuit 21 that supplies a DC lighting drive current to the LED circuit 201, the DC lighting drive current being proportional to the value indicated by the input analog dimming signal (hereinafter also referred to as the analog dimming value).

[0026] Further, on the housing panel (not shown), a dimming signal input terminal 22 to which the analog dimming signal is input from outside, a constant voltage input terminal 23, a constant voltage output terminal 24, and a current output terminal 25 are provided as external connection terminals.

[0027] Among these external connection terminals, the constant voltage output terminal 24 and the constant voltage input terminal 23 are internally connected, and the constant voltage V H (here, 24 V) is configured to be output from constant voltage output terminal 24. Note that a constant voltage power supply circuit may be provided inside and the voltage output from constant voltage output terminal 24. In this case, constant voltage input terminal 23 is not necessary.

[0028] The current drive circuit 21 is connected to the current output terminal 25 so that the DC lighting drive current flows through the current output terminal 25 .

[0029] More specifically, the current drive circuit 21 includes an N-type transistor 211, a current detection resistor element 212, and a differential amplifier element (op-amp) 213. The value of the detected current detected by the current detection resistor element 212 connected to the emitter of the transistor 211 is compared with the analog dimming value by the op-amp 213, and FB control is performed so that the collector current of the transistor 211 flowing via the current output terminal 25, i.e., the DC lighting drive current, becomes a value corresponding to the analog dimming value so that the difference between the detected current and the analog dimming value becomes small.

[0030] By connecting the constant voltage output terminal 24 of the second power supply 2 configured as above to the positive terminal 203 of the LED light irradiation device 200 and connecting the current output terminal 25 of the second power supply 2 to the negative terminal 204 of the LED light irradiation device 200 by cables, a DC lighting drive current flows through the LED circuit 201, and the LED light irradiation device 200 lights up at a brightness corresponding to the analog dimming value.

[0031] (3) Converter 3 As shown in FIG. 2, the conversion device 3 includes a secondary PWM signal generating circuit 32 that generates a secondary PWM signal by lowering the voltage when the PWM lighting drive signal is ON, i.e., the output voltage from the constant voltage power supply circuit 15, using a DC-DC converter 31, which is a switching type step-down circuit, and an analog dimming signal generating circuit 33 that smoothes the secondary PWM signal to generate and output the analog dimming signal.

[0032] Further, on the housing panel (not shown), a constant voltage input terminal 34, a constant voltage output terminal 35 internally connected thereto, a PWM input terminal 36, and an analog dimming signal output terminal 37 are provided as external connection terminals.

[0033] Of these external connection terminals, the constant voltage input terminal 34 is connected to the constant voltage output terminal 13 of the first power supply device 1 by a cable, and the PWM input terminal 36 is connected to the PWM output terminal 14 of the first power supply device 1. In addition, the analog dimming signal output terminal 37 is connected to the dimming signal input terminal 22 of the second power supply device 2 by a cable, and the constant voltage output terminal 35 is connected to the constant voltage input terminal 23 of the second power supply device 2 by a cable.

[0034] The DC-DC converter 31 is connected to the constant voltage power supply circuit 15 of the first power supply device 1 via the constant voltage input terminal 13, and the output voltage V H A second constant voltage (e.g. 3V) V L Output.

[0035] The secondary PWM signal generating circuit 32 includes a signal generating resistive element 321 having one end to which the second constant voltage is applied and the other end connected to the MOSFET 121 of the first power supply device 1 via an external connection terminal or a cable.

[0036] With this configuration, the ON voltage at the other end of the signal generating resistor element 321 is equal to the second constant voltage V L Therefore, the secondary PWM signal having an OFF voltage of approximately 0V is generated.

[0037] The analog dimming signal generating circuit 33 converts the secondary PWM signal into an optical PWM signal, and further converts the optical PWM signal into an arbitrary amplitude voltage (here, V H ) and a voltage generating resistor element 332, an RC smoothing circuit 333 that smoothes the intermediate PWM signal output from the photocoupler 331, and an impedance conversion circuit 334 that performs impedance conversion on the output signal of the RC smoothing circuit 333 to generate the analog dimming signal, and the emitter of a transistor that constitutes the impedance conversion circuit is connected to the analog dimming signal output terminal 37.

[0038] With this configuration, the maximum voltage from the analog dimming signal output terminal 37 is V H The analog dimming signal is output. 4. Connection and operation of the LED power supply system 100 In the LED power supply system 100 of this embodiment, as shown in FIG. 1, one unit of the first power supply device 1 is connected to one LED light irradiation device 200 by cable, and when a digital dimming value is input to the PWM signal generating circuit 11 belonging to that unit, the LED light irradiation device 200 is PWM-lit with a duty ratio corresponding to the dimming value.

[0039] The other unit of the first power supply device 1 is connected to the other LED light irradiation device 200 via a cable via the conversion device 3 and the second power supply device 2. When a digital dimming value is input to the PWM signal generating circuit 11 belonging to that unit, this digital dimming value is converted to an analog dimming value by the conversion device 3 and input to the second power supply device 2. The LED light irradiation device 200 is then continuously lit by a DC drive current corresponding to the dimming value.

[0040] 5.Effects According to such an LED power supply system 100, the following effects can be obtained.

[0041] Since the dimming can be controlled using the dimming value digitally set in the first power supply device 1 of the digital dimming type in contrast to the second power supply device 2 of the analog dimming type, the input interface for setting the dimming value can be standardized, improving usability.

[0042] Since the dimming value is set digitally, the reproducibility of the dimming value setting of the second power supply device 2 in particular can be improved.

[0043] The amplitude voltage of the PWM lighting drive signal is reduced and smoothed using the switching type DC-DC converter 31, so that it is possible to suppress energy loss while ensuring the response speed.

[0044] Since existing power supply devices can be used as the first power supply device 1 and the second power supply device 2, users who already own these power supply devices 1 and 2 can easily construct this LED power supply system 100 by simply installing the conversion device 3.

[0045] The converter 3 converts the secondary PWM signal into an intermediate PWM signal of any amplitude voltage via a photocoupler, and smoothes this to generate an analog dimming signal, so that the maximum value of the analog dimming signal can be set arbitrarily and it can be used with various analog dimming type power supply devices.

[0046] 6. Other embodiments The present invention is not limited to the above-described embodiment.

[0047] In the above embodiment, in the conversion device 3, the maximum voltage of the analog dimming signal is the output voltage V H However, it is not limited to this.

[0048] In addition, the photocoupler 331 is provided in the conversion device 3, but is not necessarily required. For example, L This makes it possible to eliminate the need for the photocoupler 331.

[0049] Furthermore, in the conversion device 3, as shown in FIG. 2, the constant voltage input terminal 34 and the constant voltage output terminal 35 are directly connected, but a filter circuit or the like for smoothing ripples generated during PWM conversion may be added here, or a DC-DC converter may be provided between these terminals to make the voltage output from the constant voltage output terminal, i.e., the voltage applied to the second power supply device, different from the voltage input to the constant voltage input terminal.

[0050] In the above embodiment, since the second power supply device 2 does not have a constant voltage power supply circuit, power is supplied from the constant voltage power supply circuit 15 of the first power supply device 1 via a cable. However, if the second power supply device has a constant voltage power supply circuit, power supply from the first power supply device is not necessary, and the cable for that purpose is also not required.

[0051] In the above embodiment, a plurality of units are provided in the first power supply device 1, but a single unit may be provided. In this case, when the LED light irradiation device is driven by DC, the converter and the second power supply device are connected by a cable, and when the LED light irradiation device is driven by PWM, the converter and the second power supply device are directly connected by a cable.

[0052] The second power supply device may be built into the LED light irradiation device.

[0053] Needless to say, various modifications can be made to the circuit configuration and the like without departing from the spirit of the present invention. [Explanation of symbols]

[0054] 100···LED Power Supply System 200...LED light irradiation device 1...1st power supply 2...Second power supply 3. Conversion device 31 DC-DC converter (step-down circuit)

Claims

1. a first power supply device that outputs a PWM lighting drive signal of a predetermined amplitude voltage to the LED light irradiation device to light it, and that is capable of changing and setting a duty ratio of the PWM lighting drive signal according to a value of an input digital dimming signal; a second power supply device that supplies a direct current driving current to the LED light irradiation device to light it, and that is capable of changing and setting a value of the direct current driving current according to a value of a set analog dimming signal; A power supply system for an LED, comprising: a conversion device that uses a switching-type step-down circuit to generate a secondary PWM signal that reduces the amplitude voltage of the PWM lighting drive signal, smooths the secondary PWM signal to generate the analog dimming signal, and outputs the analog dimming signal to the second power supply device.

2. 2. The LED power supply system according to claim 1, wherein the conversion device converts the secondary PWM signal into an intermediate PWM signal of an arbitrary amplitude voltage via a photocoupler, and smoothes the intermediate PWM signal to generate the analog dimming signal.

3. A conversion device is provided between a first power supply device that outputs a PWM lighting drive signal of a predetermined amplitude voltage to an LED light irradiation device to light the device and is capable of changing and setting a duty ratio of the PWM lighting drive signal depending on a value of an input digital dimming signal, and a second power supply device that supplies a DC lighting drive current to the LED light irradiation device to light the device and is capable of changing and setting a value of the DC lighting drive current depending on a value of a set analog dimming signal, a secondary PWM signal generating circuit that generates a secondary PWM signal having a reduced amplitude voltage of the PWM lighting drive signal by using a switching type step-down circuit; and an analog dimming signal generating circuit that smoothes the secondary PWM signal to generate the analog dimming signal and outputs the analog dimming signal to the second power supply device.

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