LED power supply system 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] This invention relates to an LED power supply system and a conversion device used therein, which supply power to an LED light irradiation device used for surface inspection and the like. [Background technology]

[0002] Conventionally, as shown in Reference 1, there is a known analog dimming type power supply that supplies a DC drive current to an LED and controls the value of that DC drive current with an analog dimming signal (current command signal in Reference 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 supplies capable of adjusting the brightness of LEDs using a PWM drive signal are also known. This type of power supply is configured to adjust the brightness of LEDs by changing the duty cycle of the PWM drive signal, and the value of the duty cycle (dimming value) is set, for example, by a digital switch; it is, so to speak, a digital dimming type.

[0004] Using the former power supply unit, the LED will light up continuously, while using the latter LED power supply unit, the LED will blink rapidly. Due to these differences in LED lighting behavior, in fields such as surface inspection, the choice between the former and the latter power supply unit may depend on the type of inspection being performed. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2017-135225 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, when the two types of power supplies mentioned above are mixed, the user needs to set the dimming value for each power supply separately. Furthermore, analog dimming type power supplies have the drawback of poor reproducibility.

[0007] The inventors of this invention were the first to focus on the above-mentioned problems and aimed to provide an LED power supply system that, while using the two types of power supply devices, can unify the input interface related to dimming settings, thereby improving usability and dimming reproducibility. [Means for solving the problem]

[0008] In other words, the LED power supply system according to the present invention is A first power supply unit that outputs a PWM lighting drive signal of a predetermined amplitude voltage to an LED light irradiation device to light it up, and can change and set the duty cycle of the PWM lighting drive signal according to the value of the input digital dimming signal, A second power supply unit that supplies a DC lighting drive current to an LED light irradiation device to light it up, and can change the value of the DC lighting drive current according to a set value of an analog dimming signal, The invention is characterized by comprising a conversion device that uses a switching step-down circuit to generate a secondary PWM signal with a reduced 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 unit. [Effects of the Invention]

[0009] With the present invention configured in this way, by setting the digital dimming signal of the first power supply, the dimming value of the analog dimming type second power supply can be set via the conversion device. Therefore, the first power supply can be used as an input interface for setting the dimming value of the second power supply. Consequently, the input interfaces 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 setting the dimming value of the second power supply can be improved in particular.

[0010] Furthermore, directly smoothing the PWM lighting drive signal can lead to increased energy loss and slower response speed due to the capacitance of snubber circuits and other components in the switching elements of the first power supply. However, by reducing the amplitude voltage of the PWM lighting drive signal using a switching-type step-down circuit and then smoothing it, it is possible to suppress energy loss while maintaining a fast response speed.

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

[0012] [Figure 1] A schematic overall circuit diagram of an LED power supply system in one embodiment of the present invention. [Figure 2] A schematic circuit diagram of the conversion device according to the same embodiment. [Modes for carrying out the invention]

[0013] Hereinafter, an embodiment of the LED power supply system according to the present invention will be described with reference to the drawings.

[0014] 1. Overview of the LED power supply system 100 In this embodiment, the LED power supply system 100 supplies current to an LED light irradiation device 200 for surface inspection to light it up, and as shown in Figure 1, it comprises a first power supply device 1, a second power supply device 2, and a converter 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, let me explain the LED light irradiation device 200. As shown in FIG. 1, this LED light irradiation device 200 includes an LED circuit 201 composed of a plurality of LEDs arranged in series or in parallel, and a current limiting resistor 202 connected in series to this LED circuit 201. Also, on its housing panel (not shown), a plus terminal 203 and a minus terminal 204 are provided as external connection terminals. By applying a voltage between these plus terminal 203 and minus terminal 204, a current flows through the LED circuit 201 and the LEDs 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) First Power Supply Device 1 The first power supply device 1 includes a PWM control signal generation 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 for lighting and driving the LED based on this PWM control signal.

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

[0018] Among these external connection terminals, a constant voltage power supply circuit 15 provided inside is connected to the constant voltage output terminal 13 so that a constant voltage V H (here 24V) is output.

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

[0020] More specifically, the PWM control signal generation 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 cycle corresponding to the value of this dimming signal (hereinafter also referred to as the dimming value). The PWM control signal generation circuit 11 here is composed of, for example, a dedicated PWMIC.

[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] Furthermore, the drive circuit 12 is provided with a snubber circuit that includes a capacitor 122 to absorb the transient high voltage generated when the MOSFET 121 is switched ON / OFF.

[0023] However, by connecting the constant voltage output terminal 13 of the first power supply unit 1 with this configuration to the positive terminal 203 of the LED light illuminator 200, and the PWM output terminal 14 of the first power supply unit 1 to the negative terminal 204 of the LED light illuminator 200, a current flows through the LED circuit 201 due to a PWM lighting drive signal with a duty cycle corresponding to the set dimming value, and the LED light illuminator 200 lights up with a brightness corresponding to the dimming value.

[0024] In this embodiment, the first power supply unit 1 is provided with multiple circuits (2 circuits) of units consisting of the PWM control signal generation circuit 11, drive circuit 12, constant voltage output terminal 13, and PWM output terminal 14, and is configured to independently drive the LED light illumination devices 200 for each unit using PWM.

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

[0026] Furthermore, the housing panel (not shown) is provided with external connection terminals including a dimming signal input terminal 22, a constant voltage input terminal 23, a constant voltage output terminal 24, and a current output terminal 25, to which the analog dimming signal is input from an external source.

[0027] Of these external connection terminals, the constant voltage output terminal 24 and the constant voltage input terminal 23 are internally connected, and a constant voltage V is input to the constant voltage input terminal 23. H The device is configured to output a constant voltage (24V in this case) from the constant voltage output terminal 24. Alternatively, a constant voltage power supply circuit may be provided internally, and its voltage may be output from the constant voltage output terminal 24. In this case, the constant voltage input terminal 23 is not required.

[0028] The current output terminal 25 is connected to the current drive circuit 21, and the DC lighting drive current is configured to flow through the current output terminal 25.

[0029] More specifically, the current drive circuit 21 comprises an N-type transistor 211, a current sensing resistor 212, and a differential amplifier (operational amplifier) ​​213. The operational amplifier 213 compares the value of the detected current, detected by the current sensing resistor 212 connected to the emitter of the transistor 211, with the analog dimming value. The operational amplifier then performs feedback control so that the collector current of the transistor 211 flowing through the current output terminal 25, i.e., the DC lighting drive current, becomes a value corresponding to the analog dimming value, thereby minimizing the difference between the two values.

[0030] However, by connecting the constant voltage output terminal 24 of the second power supply unit 2 with this configuration to the positive terminal 203 of the LED light illuminator 200, and the current output terminal 25 of the second power supply unit 2 to the negative terminal 204 of the LED light illuminator 200, a DC lighting drive current flows through the LED circuit 201, causing the LED light illuminator 200 to light up at a brightness corresponding to the analog dimming value.

[0031] (3) Conversion device 3 As shown in Figure 2, the conversion device 3 includes a secondary PWM signal generation circuit 32 that generates a secondary PWM signal by lowering the voltage when the PWM lighting drive signal is ON, that is, 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 generation circuit 33 that smooths this secondary PWM signal to generate and output the analog dimming signal.

[0032] Furthermore, the enclosure panel (not shown) is provided with external connection terminals including a constant voltage input terminal 34 and a constant voltage output terminal 35 internally connected thereto, as well as a PWM input terminal 36 and an analog dimming signal output terminal 37.

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

[0034] However, the DC-DC converter 31 is connected to the constant voltage power supply circuit 15 of the first power supply unit 1 via the constant voltage input terminal 13, and the output voltage V of the first power supply unit 1 H A second constant voltage (e.g., 3V) V obtained by dropping the voltage using a switching method. L Outputs.

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

[0036] With this configuration, the ON voltage at the other end of the signal generating resistor element 321 is the second constant voltage V L This generates the aforementioned secondary PWM signal with an OFF voltage of approximately 0V.

[0037] The analog dimming signal generation circuit 33 converts the secondary PWM signal into an optical PWM signal, and further converts this optical PWM signal into an arbitrary amplitude voltage (here, V H The system comprises a photocoupler 331 and a voltage generating resistor element 332 that convert the signal to an intermediate PWM signal, an RC smoothing circuit 333 that smooths the intermediate PWM signal output from the photocoupler 331, and an impedance conversion circuit 334 that impedance-converts the output signal of the RC smoothing circuit 333 to generate the analog dimming signal, wherein the emitter of the transistor constituting 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 aforementioned 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 Figure 1, one unit of the first power supply device 1 is connected by cable to one LED light illuminator 200, and when a digital dimming value is input to the PWM signal generation circuit 11 belonging to that unit, the LED light illuminator 200 is PWM lit with a duty cycle corresponding to that dimming value.

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

[0040] 5. Effects The following effects can be achieved with such an LED power supply system 100.

[0041] Since the second power supply unit 2, which is an analog dimming type, can be dimmed using the dimming value digitally set by the first power supply unit 1, the input interface for setting the dimming value can be standardized, improving ease of use.

[0042] Since the dimming value is set digitally, the reproducibility of the dimming value setting, especially for the second power supply unit 2, can be improved.

[0043] The amplitude voltage of the PWM lighting drive signal is reduced using a switching-type DC-DC converter 31 and then smoothed, thereby ensuring a fast response while suppressing energy loss.

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

[0045] The conversion device 3 converts the secondary PWM signal into an intermediate PWM signal of an arbitrary amplitude voltage via a photocoupler, smooths it, and generates an analog dimming signal. This allows the maximum value of the analog dimming signal to be set arbitrarily, and enables compatibility with various types of analog dimming power supplies.

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

[0047] In the above-described embodiment, in the conversion device 3, the maximum voltage of the analog dimming signal was set to the output voltage V of the constant voltage power supply circuit 15, but it is not limited thereto. H Moreover, in the conversion device 3, the photocoupler 331 was provided, but it is not necessarily required. For example, by setting the maximum voltage of the analog dimming signal to the second constant voltage V, the photocoupler 331 can be made unnecessary.

[0048] Furthermore, in the conversion device 3, as shown in FIG. 2, the constant voltage input terminal 34 and the constant voltage output terminal 35 were directly connected, but a filter circuit or the like for smoothing ripples generated during PWM conversion may be added thereto, or a DC-DC converter may be provided between these terminals so as to make the voltage output from the constant voltage output terminal, that is, the voltage applied to the second power supply device, different from the voltage input to the constant voltage input terminal. L In the above-described 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 unnecessary, and the cable therefor is also unnecessary.

[0049] In the above-described embodiment, a plurality of units were provided in the first power supply device 1, but one unit may be used. In this case, when the LED light irradiation device is driven by direct current, the conversion device and the second power supply device are connected by a cable, and when the LED light irradiation device is driven by PWM, it is directly connected by a cable.

[0050] Also, the second power supply device may be built in the LED light irradiation device.

[0051]

[0052]

[0053] ​​Furthermore, it goes without saying that the present invention can be modified in various ways, including circuit configurations, without departing from its spirit. [Explanation of Symbols]

[0054] 100...Power supply system for LEDs 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 unit that outputs a PWM lighting drive signal of a predetermined amplitude voltage to an LED light irradiation device to light it up, and can change and set the duty cycle of the PWM lighting drive signal according to the value of the input digital dimming signal, A second power supply unit that supplies a DC lighting drive current to an LED light irradiation device to light it up, and can change the value of the DC lighting drive current according to a set value of an analog dimming signal, An LED power supply system characterized by comprising a conversion device that generates a secondary PWM signal by reducing the amplitude voltage of the PWM lighting drive signal using a switching step-down circuit, generates the analog dimming signal by smoothing the secondary PWM signal, and outputs the analog dimming signal to the second power supply device.

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 smooths this intermediate PWM signal to generate the analog dimming signal.

3. A conversion device interposed between a first power supply unit that outputs a PWM lighting drive signal of a predetermined amplitude voltage to an LED light irradiation device to light it up and can change the duty cycle of the PWM lighting drive signal according to the value of an input digital dimming signal, and a second power supply unit that supplies a DC lighting drive current to the LED light irradiation device to light it up and can change the value of the DC lighting drive current according to a set value of an analog dimming signal, A secondary PWM signal generation circuit that generates a secondary PWM signal with a reduced amplitude voltage of the PWM lighting drive signal using a switching step-down circuit, A conversion device characterized by comprising an analog dimming signal generation circuit that smooths the secondary PWM signal to generate the analog dimming signal and outputs it to the second power supply unit.

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