Power supply device for light emitting diode and operation method thereof

Abstract

A power supply for light emitting diodes (LEDs) and an operating method thereof, wherein the operating method comprises the following operations: controlling an output voltage to be a first voltage through a control circuit; detecting a load current through a detection circuit; when the load current is greater than zero, maintaining the output voltage to be the first voltage through a constant voltage control circuit, and when the load current is equal to zero, changing the output voltage from the first voltage to a second voltage through the control circuit, wherein the second voltage is greater than the first voltage.

Description

Technical Field

[0001] The present disclosure relates to a power supply device for light emitting diodes and an operating method thereof, and more particularly to a power supply device capable of corresponding to two output voltages and an operating method thereof. Background Art

[0002] Compared to T12HO fluorescent tubes, LED tubes save nearly 70% of energy, so in the application of advertising light boxes, LED tubes quickly replace T12HO fluorescent tubes as the light source of advertising light boxes. LED tubes can be mainly divided into two types: 12V system and 24V system, so the corresponding LED sign power supply is also divided into two series: 12V constant voltage output and 24V constant voltage output.

[0003] 12V and 24V power supplies for LED signs are mainstream products on the market. Lighting construction manufacturers must prepare stocks of power supplies with two output voltages to meet the inconsistency of 12V and 24V LED light source systems. Traditionally, two drivers are required to correspond to 12V and 24V LEDs, causing inconvenience to manufacturers in inventory. Summary of the invention

[0004] A method for operating a power supply for light emitting diodes includes the following operations: controlling an output voltage to a first voltage through a control circuit; detecting a load current through a detection circuit; when the load current is greater than zero, maintaining the output voltage to the first voltage through a constant voltage control circuit, and when the load current is equal to zero, changing the output voltage from the first voltage to a second voltage through the control circuit, wherein the second voltage is greater than the first voltage.

[0005] A method for operating a power supply for light emitting diodes includes the following operations: controlling an output voltage to a first voltage through a control circuit; detecting a load current through a detection circuit; when the load current is equal to zero, changing the output voltage from the first voltage to a second voltage through the control circuit, the second voltage being greater than the first voltage; when the output voltage changes from the first voltage to the second voltage, detecting the load current, and when the load current is equal to zero, maintaining the output voltage at the second voltage through a constant voltage control circuit.

[0006] A power supply for light emitting diodes comprises a constant voltage control circuit, a detection circuit and a control circuit. The constant voltage control circuit is used to control the output voltage of the power supply to be a first voltage or a second voltage, wherein the second voltage is greater than the first voltage. The detection circuit is used to detect the load current. The control circuit is used to control the constant voltage control circuit to change the output voltage to the first voltage or the second voltage according to the load current, wherein when the output voltage is the first voltage and the load current is greater than zero, the constant voltage control circuit maintains the output voltage at the first voltage, and when the load current is equal to zero, the control circuit changes the output voltage from the first voltage to the second voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 A functional block diagram of a power supply according to an embodiment of the present disclosure is shown.

[0008] Figure 2 A flow chart showing an operating method according to an embodiment of the present disclosure.

[0009] Figure 3 A flow chart showing an operating method according to an embodiment of the present disclosure.

[0010] Figure 4 FIG. 1 shows a timing diagram of output voltage and load current according to an embodiment of the present disclosure.

[0011] Figure 5 FIG. 1 shows a timing diagram of output voltage and load current according to an embodiment of the present disclosure.

[0012] Figure 6 FIG. 1 shows a timing diagram of output voltage and load current according to an embodiment of the present disclosure.

[0013] Figure 7 FIG. 1 shows a timing diagram of output voltage and load current according to an embodiment of the present disclosure.

[0014] Figure 8 FIG. 1 shows a timing diagram of output voltage and load current according to an embodiment of the present disclosure.

[0015] Description of reference numerals:

[0016] 100: Power supply

[0017] 110: Constant voltage control circuit

[0018] 120: Detection circuit

[0019] 130: Control circuit

[0020] 140: Constant current control circuit

[0021] 150: Rectifier circuit

[0022] 160: Transformer circuit

[0023] 180: Load

[0024] 200, 300: Operation method

[0025] Vo: output voltage

[0026] Io: load current

[0027] S210, S220, S230, S240, S310, S320, S330, S340: Steps

[0028] t0, t1, t2, t3, t4, t5, t6, T: time DETAILED DESCRIPTION

[0029] The words "including", "having" and the like used in this article are open-ended terms, meaning "including but not limited to". In addition, "and / or" used in this article includes any one or more items in the relevant enumerated items and all combinations thereof.

[0030] In this document, when an element is referred to as being "connected" or "coupled", it may refer to being "electrically connected" or "electrically coupled". "Connected" or "coupled" may also be used to indicate that two or more elements cooperate or interact with each other. In addition, although the terms "first" and "second" are used in this document to describe different elements, the terms are only used to distinguish between elements or operations described by the same technical terms. Unless the context clearly indicates otherwise, the terms do not specifically refer to or imply an order or sequence, nor are they used to limit this disclosure document.

[0031] Please refer to Figure 1 , Figure 1 FIG. 1 is a functional block diagram of a power supply 100 according to an embodiment of the present disclosure. The power supply 100 includes a constant voltage control circuit 110, a detection circuit 120, a control circuit 130, a constant current control circuit 140, a rectifier circuit 150, and a voltage transformation circuit 160. The power supply 100 is used to provide an output voltage Vo to a load 180. In this embodiment, the load 180 may be a 12V / 60W LED and a 24V / 60W LED.

[0032] The constant voltage control circuit 110 is used to control the output voltage Vo of the power supply 100 to be a first voltage or a second voltage, and the second voltage is greater than the first voltage. In this embodiment, the first voltage can be 12V and the second voltage can be 24V. The detection circuit 120 is used to detect the load current Io. In one embodiment, the detection circuit 120 can be a resistor, which converts the load current Io into a load voltage and transmits it to the control circuit 130.

[0033] The control circuit 130 is used to control the constant voltage control circuit 110 to change the output voltage Vo to a first voltage or a second voltage according to the load current Io. When the output voltage Vo is the first voltage and the load current Io is greater than zero, the constant voltage control circuit 110 maintains the output voltage Vo at the first voltage. When the load current Io is zero, the control circuit 130 changes the output voltage Vo from the first voltage to the second voltage.

[0034] In one embodiment, the constant voltage control circuit 110 may be a comparison circuit or other circuits having a comparison signal function, for comparing the magnitude of the output voltage Vo. When the power supply 100 is intended to output a first voltage, and the output voltage Vo is greater than or less than the first voltage (i.e., the output voltage Vo is not equal to the first voltage), the constant voltage control circuit 110 will compare the output voltage Vo with a reference voltage, and control the output voltage Vo to be at the same potential as the reference voltage. The reference voltage may be provided by the control circuit 130, for example, if the control circuit 130 provides a reference voltage of 12V, the constant voltage control circuit 110 may control the output voltage Vo to be 12V.

[0035] The constant current control circuit 140 is used to control the load current Io to prevent the load current Io from being greater than the rated current and causing damage to the appliance. For example, when the load 180 is a 12V / 60W LED, the rated current of the load 180 is 5A, and when the load 180 is a 24V / 60W LED, the rated current of the load 180 is 2.5A.

[0036] The rectifier circuit 150 is used to convert the AC power input to the power supply 100 into a DC power. In this embodiment, the rectifier circuit 150 can be a full-wave rectifier circuit. The transformer circuit 160 is used to convert the DC power into an output voltage Vo required by the load 180, such as 12V and 24V. In this embodiment, the transformer circuit 160 can be a flyback converter, a boost converter, or other transformer circuits that have the function of converting a DC voltage into another DC voltage.

[0037] Please refer to Figure 2 , Figure 2 A flowchart of an operating method 200 according to an embodiment of the present disclosure is shown. Figure 2 The operation method 200 shown is easy to understand. Please also refer to Figure 1 The operation method 200 includes step S210, step S220, step S230 and step S240. Referring to step S210, the control circuit 130 controls the constant voltage control circuit 110 to control the output voltage Vo to a first voltage, such as 12V. Referring to step S220, the detection circuit 120 detects the load current Io of the load 180. When the load current Io is not equal to zero (for example, when the load current Io is greater than zero), step S230 is executed. When the load current Io is equal to zero, step S240 is executed.

[0038] Step S230, the output voltage Vo is maintained at a first voltage by the constant voltage control circuit 110. Step S240, the output voltage Vo is changed from the first voltage to a second voltage by the control circuit 130, and the second voltage is greater than the first voltage. For example, the second voltage may be 24V.

[0039] In the above steps, since the power supply 100 does not know in advance whether the load 180 is a 12V LED lamp or a 24V LED lamp, if the current load 180 is a 12V LED lamp, when the power supply 100 supplies the output voltage Vo as the first voltage 12V, the load current Io is greater than zero, that is, there will be a load current Io. The control circuit 130 in the power supply 100 detects the load current Io through the detection circuit 120 and learns that the current load 180 is a 12V LED lamp. This means that the load 180 is consistent with the output voltage Vo, and the output voltage Vo is maintained at the first voltage 12V, which is the operation of step S230.

[0040] When the output voltage Vo of the power supply 100 is the first voltage 12V, the load 180 is a 24V LED lamp. At this time, the load current Io is equal to zero, that is, there is no load current Io. The control circuit 130 in the power supply 100 cannot detect the load current Io through the detection circuit 120, and it is known that the current load 180 is a 24V LED lamp. Then, the output voltage Vo is changed from the first voltage 12V to the second voltage 24V through the control circuit 130, which is the operation of step S240.

[0041] In one embodiment, the operation method 200 further includes the step of detecting the load current Io when the output voltage Vo changes from the first voltage to the second voltage, and when the load current Io is greater than zero, maintaining the output voltage Vo at the second voltage through the constant voltage control circuit 110. When the output voltage Vo of the power supply 100 is the second voltage 24V, when the load current Io is greater than zero, it indicates that the load 180 is a 24V LED lamp, and thus the output voltage Vo is maintained at the second voltage 24V.

[0042] Please refer to Figure 3 , Figure 3 A flowchart of an operating method 300 according to an embodiment of the present disclosure is shown. Figure 3 The operation method 300 shown is easy to understand. Please also refer to Figure 1 The operation method 300 includes step S210, step S220, step S230, step S240, step S310, step S320, step S330 and step S340.

[0043] Figure 3 Steps S210 to S240 shown in FIG. Figure 2The steps S210 to S240 of the operation method 200 are the same and will not be described again. After step S230, step S310 is executed to detect whether the load current Io is equal to zero. When the load current Io is not equal to zero, it means that the load 180 is a 12V LED lamp, and then the process returns to step S230 to maintain the output voltage Vo at the first voltage 12V. When the load current Io is equal to zero, it means that the load 180 is not a 12V LED lamp, and step S240 is executed to control the output voltage Vo to the second voltage 24V.

[0044] Next, in step S320, it is detected whether the load current Io is equal to zero. If it is not equal to zero, it means that the load 180 is a 24V LED lamp, then the process returns to step S240 to continuously control the output voltage Vo to be the second voltage 24V.

[0045] If the load current Io is equal to zero in step S320, it means that the power supply 100 is currently in an unloaded state, that is, there is no load 180. Then, step S330 is executed to maintain the output voltage Vo at the second voltage 24V. Then, step S340 is executed to detect whether the load current Io is equal to zero. If it is equal to zero, the process returns to step S330 to continue to maintain the output voltage Vo at the second voltage 24V. If the load current Io is not equal to zero, step S210 is executed to control the output voltage Vo to the first voltage 12V.

[0046] Please refer to Figure 4 , Figure 4 The output voltage Vo and load current Io timing diagram according to an embodiment of the present disclosure is shown. In general, if the power supply 100 is connected to a load 180 of a 12V LED lamp, and the power supply 100 is started with the output voltage Vo as the first voltage 12V, after starting, the power supply 100 detects the load current Io and maintains a 12V constant voltage output.

[0047] Please refer to Figure 5 , Figure 5 The timing diagram of the output voltage Vo and the load current Io according to an embodiment of the present disclosure is shown. In general, if the power supply 100 is connected to a load 180 of a 24V LED lamp, and the power supply 100 is started with the output voltage Vo as the first voltage 12V, after starting, the power supply 100 detects no load current Io between time t1 and t2, and then automatically increases the output voltage Vo to the second voltage 24V. After the output voltage Vo is adjusted to 24V, the second voltage 24V constant voltage output is maintained after the load current Io is detected.

[0048] In one embodiment, the power supply 100 can be designed to switch the output voltage Vo after a delay according to actual conditions and needs. For example, in order to avoid dangerous situations caused by too frequent voltage switching of the power supply 100, when the power supply 100 detects no-load current Io between time t1 and t2 after startup, the output voltage Vo is increased to the second voltage 24V after a delay. For example, the power supply 100 is designed to switch the voltage for 2 seconds. When the power supply 100 performs the operation of increasing the output voltage Vo to the second voltage 24V, the output voltage Vo is increased to the second voltage 24V after a delay of 2 seconds.

[0049] Please refer to Figure 6 , Figure 6 The timing diagram of the output voltage Vo and the load current Io according to an embodiment of the present disclosure is shown. Under no-load conditions, if there is no load 180 when the power supply 100 is started, and the power supply 100 is started with the output voltage Vo as the first voltage 12V, after starting, the power supply 100 detects the no-load current Io between time t1 and time t2, and automatically increases the output voltage Vo to the second voltage 24V. After the output voltage Vo is adjusted to the second voltage 24V, the no-load current Io is still detected between time t2 and time t3, and the power supply 100 maintains the second voltage 24V constant voltage output. In one embodiment, the power supply 100 can be designed to switch the output voltage Vo after a delay of a period of time according to actual conditions and needs.

[0050] Please refer to Figure 7 , Figure 7 The output voltage Vo and load current Io timing diagram according to an embodiment of the present disclosure is shown. Under no-load conditions, a 12V LED lamp is connected as a load 180. Between time t3 and time t4, the power supply 100 continuously outputs the second voltage 24V under no-load conditions. At this time, if the load current Io is detected, the output voltage Vo is immediately adjusted from the second voltage 24V to the first voltage 12V output. When the power supply 100 detects the load current Io, it indicates that the output voltage Vo is consistent with the load 180, so the power supply 100 maintains the first voltage 12V constant voltage output.

[0051] Please refer to Figure 8 , Figure 8The timing diagram of the output voltage Vo and the load current Io according to an embodiment of the present disclosure is shown. Under no-load conditions, a 24V LED lamp is connected as the load 180. Between time t3 and time t4, the power supply 100 continuously outputs the second voltage 24V under no-load conditions. If the load current Io is detected, the output voltage Vo is immediately adjusted from the second voltage 24V to the first voltage 12V. When the power supply 100 detects no load current Io between time t4 and time t5, it indicates that the current output voltage Vo does not match the load 180, and then the output voltage Vo is increased to the second voltage 24V. After the output voltage Vo is adjusted to the second voltage 24V, the load current Io is detected, indicating that the output voltage Vo matches the load 180, so the power supply 100 maintains the second voltage 24V constant voltage output. In one embodiment, the power supply 100 can be designed to switch the output voltage Vo after a delay of a period of time according to actual conditions and needs.

[0052] When more LED lamps are connected in parallel to the load 180, the total resistance will be smaller. According to Ohm's law, in the same conductor, the current passing through the conductor is proportional to the voltage across the conductor and inversely proportional to the resistance of the conductor. Therefore, the load current Io will become larger. When the load current Io exceeds the rated current, it will cause a dangerous situation of electrical appliance burning. In order to avoid this situation, when the load current Io is greater than the rated current, the power supply 100 will be controlled by the constant current control circuit 110 to control the output voltage Vo. For example, the rated specification of the power supply 100 is 12V / 60W, and the LED lamp is 12V / 1W. When more than 60 LED lamps are connected in parallel, the power supply 100 will be controlled by the constant current control circuit 110 to control the output voltage Vo so that the load current Io does not exceed the rated current 5A.

[0053] In summary, the power supply determines the current load condition by detecting the presence or absence of load current, and then controls the output voltage to the first voltage or the second voltage, so that the power supply can automatically respond to loads with different rated voltages without having to prepare different power supplies or transformers for different loads, thereby solving the troubles and hassles in use.

[0054] In addition, when users use a large number of loads at the same time, the power supply can also control the output voltage in real time according to the changes in the load, thereby controlling the load current not to exceed the rated current, avoiding the dangerous situation of circuit burning or electrical damage caused by the simultaneous use of a large number of electrical appliances.

Claims

1. A method for operating a power supply for light emitting diodes, for automatically responding to loads of different rated voltages, and judging the current load condition by detecting the presence or absence of a load current, and switching an output voltage between a first voltage and a second voltage, wherein the second voltage is greater than the first voltage, comprising: By a control circuit, the output voltage is controlled to be the first voltage, where the first voltage is the rated voltage of a load; Detecting the load current through a detection circuit; When the load current is equal to zero, the output voltage is changed from the first voltage to the second voltage through the control circuit, and the second voltage is a rated voltage of another load; and After the output voltage changes from the first voltage to the second voltage, the load current is detected. When the load current is equal to zero, the output voltage is maintained at the second voltage through a constant voltage control circuit. Under no-load conditions, when the output voltage is maintained at the second voltage, the load current is detected, and when the load current is greater than zero, the output voltage is changed from the second voltage to the first voltage through the control circuit.

2. The operating method according to claim 1, further comprising: When the output voltage changes from the second voltage to the first voltage, the load current is detected, and when the load current is greater than zero, the output voltage is maintained at the first voltage through the constant voltage control circuit.

3. The operating method according to claim 1, further comprising: When the output voltage changes from the second voltage to the first voltage, the load current is detected, and when the load current is equal to zero, the output voltage is changed from the first voltage to the second voltage through the control circuit.

4. A power supply for light emitting diodes, for automatically responding to loads of different rated voltages, and judging the current load condition by detecting the presence or absence of a load current, and switching an output voltage between a first voltage and a second voltage, wherein the second voltage is greater than the first voltage, comprising: a constant voltage control circuit for controlling the output voltage of the power supply to be the first voltage or the second voltage, the first voltage being the rated voltage of one load and the second voltage being the rated voltage of another load; a detection circuit for detecting the load current; as well as a control circuit, for controlling the constant voltage control circuit to change the output voltage to the first voltage or the second voltage according to the load current, When the output voltage is the first voltage and the load current is greater than zero, the constant voltage control circuit maintains the output voltage at the first voltage; when the load current is equal to zero, the control circuit changes the output voltage from the first voltage to the second voltage; after the output voltage changes from the first voltage to the second voltage, the detection circuit detects the load current; when the load current is equal to zero, the constant voltage control circuit maintains the output voltage at the second voltage; under no-load conditions, when the output voltage is maintained at the second voltage, the detection circuit detects the load current; when the load current is greater than zero, the control circuit changes the output voltage from the second voltage to the first voltage.

5. The power supply as claimed in claim 4, wherein when the output voltage changes from the second voltage to the first voltage, the detection circuit detects the load current, and when the load current is greater than zero, the constant voltage control circuit maintains the output voltage at the first voltage.

6. The power supply as claimed in claim 4, wherein when the output voltage changes from the second voltage to the first voltage, the detection circuit detects the load current, and when the load current is equal to zero, the control circuit changes the output voltage from the first voltage to the second voltage.

7. The power supply as claimed in claim 4, further comprising: A constant current control circuit is used to control the output voltage according to the load current so that the load current is not greater than a rated current.

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