Power supply unit that supplies drive current to LED load devices

Abstract

To make it possible to accurately determine a short-circuit abnormality and an open-circuit abnormality in a power supply device regardless of the presence or absence of a short-circuit protection function of an LED load device.SOLUTION: A power supply(100) includes a detection signal input terminal (130) for inputting an overcurrent detection signal generated by an overcurrent protection function when an LED load device has an overcurrent protection function, and a diagnosis unit (120) that detects an index indicating the magnitude of a drive current, determines that the LED load device is normal when the index is within a range determined by a first reference value and a second reference value larger than the first reference value, determines that a short circuit has occurred in the LED load device when the index is greater than the second reference value, or when the voltage at the detection signal input terminal is greater than a third reference value, otherwise, determines that an open failure has occurred in the LED load device.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a power supply device that supplies a drive current to an LED load device. [Background technology]

[0002] A power supply device that supplies a drive current to an LED load device that emits LED light is known. FIG. 10(a) shows a conventional LED load device 200 and a power supply device that supplies a drive current I LED 1 is a diagram illustrating an example of the configuration of a power supply device 400 that supplies

[0003] In the example shown in the figure, the LED load device 200 includes an LED group 210 and an LED driver 220. The LED driver 220 switches on and off a switching element to control a driving current I LED Control.

[0004] The power supply device 400 includes an intelligent power device (IPD) 410 and a microprocessor unit (MPU) 420. The IPD 410 controls V out The driving current I from the terminal to the LED load device LED The IPD410 has a current detection terminal IS, which detects the drive current I LED The detected current I IS is output from the current detection terminal IS.

[0005] The MPU420 detects the detected current I, which is converted to a voltage by a resistor R. IS The value of is taken from the AD1 terminal and the resulting drive current I LED Based on the magnitude of I, an abnormality determination is made for the LED load device 200. LED If the magnitude of I is within a predetermined range, it is determined that the LED load device 200 is normal. LED If the magnitude of I is smaller than a predetermined range, it is determined that an open circuit abnormality has occurred in the LED load device 200. LEDIf the magnitude of the voltage is greater than a predetermined range, it is determined that a short circuit abnormality has occurred in the LED load device 200. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 09-015104 Summary of the Invention [Problem to be solved by the invention]

[0007] Incidentally, there are cases where the LED load device itself has a short-circuit protection function. FIG. 10(b) shows an LED load device 230 having a short-circuit protection function and a driving current I LED 1 is a diagram illustrating an example of the configuration of a power supply device 400 that supplies

[0008] In the example shown in the figure, the LED load device 230 has a drive current I LED The cutoff switch 250 is normally in a conductive state, being in a conductive state when the gate terminal is at a low level and in a non-conductive state when the gate terminal is at a high level.

[0009] When the LED driver 240 detects a short circuit abnormality in the LED load device 230, it outputs an overcurrent detection signal. Specifically, the PGate terminal connected to the gate terminal of the cutoff switch 250 is switched from low level to high level. This overcurrent detection signal switches the cutoff switch 250 to a non-conductive state, and the drive current I LED is blocked.

[0010] When a short circuit occurs in the LED load device 230 having a short circuit protection function, the LED load device 230 itself detects the short circuit and reduces the drive current I LED On the other hand, the drive current I LED When the power supply 400 is cut off, the power supply 400 erroneously determines that an open circuit abnormality has occurred in the LED load device 200.

[0011] In order to enhance the versatility of the power supply device 400, it is desirable that the power supply device 400 be able to accurately determine abnormalities not only when connected to an LED load device 200 that does not have a short-circuit protection function, but also when connected to an LED load device 230 that has a short-circuit protection function.

[0012] Therefore, an object of the present invention is to provide a power supply device that supplies drive current to an LED load device, capable of accurately determining whether an LED load device has a short-circuit or open-circuit abnormality, regardless of whether the LED load device has a short-circuit protection function or not. [Means for solving the problem]

[0013] In order to solve the above problem, one embodiment of the present invention provides a power supply device that supplies a drive current to an LED load device, and includes: a detection signal input terminal for inputting an overcurrent detection signal generated by the overcurrent protection function when the LED load device has the overcurrent protection function; and a diagnostic unit that detects an index indicating the magnitude of the drive current, and determines that the LED load device is normal if the index is within a range determined by a first reference value and a second reference value that is greater than the first reference value; otherwise, if the index is greater than the second reference value or if the voltage of the detection signal input terminal is greater than a third reference value, determines that a short-circuit abnormality has occurred in the LED load device; and otherwise, determines that an open-circuit abnormality has occurred in the LED load device. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a diagram illustrating a configuration of a power supply device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram illustrating the operation of a buffer circuit. [Figure 3] FIG. 2 is a diagram illustrating a configuration example of a buffer circuit. [Figure 4] FIG. 10 is a diagram showing a case where an LED load device without a short-circuit protection function is connected. [Figure 5]FIG. 10 is a diagram showing the terminal voltages for each state of an LED load device that does not have a short-circuit protection function. [Figure 6] FIG. 10 is a diagram showing a case where an LED load device having a short-circuit protection function is connected. [Figure 7] FIG. 10 is a diagram showing the terminal voltage for each state of an LED load device having a short-circuit protection function. [Figure 8] FIG. 10 is a flowchart showing a procedure for determining an abnormality in a power supply device. [Figure 9] FIG. 10 is a flowchart showing another example of the procedure for determining an abnormality in the power supply device. [Figure 10] FIG. 1 is a diagram illustrating an example of the configuration of a conventional power supply device and an LED load device. DETAILED DESCRIPTION OF THE INVENTION

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described in detail with reference to the accompanying drawings. Fig. 1 is a diagram showing the configuration of a power supply device 100 according to this embodiment.

[0016] As shown in the figure, the power supply device 100 includes an IPD (intelligent power device) 110, an MPU (micro-processor unit) 120, a detection signal input terminal 130, and a buffer circuit 140. The IPD 110 controls V out The driving current I from the terminal to the LED load device LED The LED load device may be an LED load device 200 that does not have a short-circuit protection function, or an LED load device 230 that has a short-circuit protection function. The IPD 110 also has a current detection terminal IS, and a drive current I LED The detected current I IS is output from the current detection terminal IS.

[0017] The MPU120 detects the detected current I, which is converted to a voltage by the resistor R. IS The value of is taken from the AD1 terminal and used as an index to determine the drive current I LEDThe MPU 120 also has an I / O terminal and determines whether the output of the buffer circuit 140 is at L2 (low level) or H2 (high level).

[0018] As will be described later, the MPU 120 controls the drive current I LED This function functions as a diagnostic unit that determines whether the LED load device to which the power is supplied has a short circuit or an open circuit. This determination is made accurately regardless of whether the LED load device has a short circuit protection function or not.

[0019] When the current supply target is an LED load device 230 having a short-circuit protection function, the detection signal input terminal 130 is connected to the PGate terminal of the LED driver 240. That is, the detection signal input terminal 130 inputs an overcurrent detection signal that is output when the LED load device 230 detects a short-circuit abnormality. On the other hand, when the current supply target is an LED load device 200 without a short-circuit protection function, the detection signal input terminal 130 is in an open state. Alternatively, the detection signal input terminal 130 may be grounded.

[0020] 2, the buffer circuit 140 outputs a voltage level based on the voltage level of the detection signal input terminal 130 to the I / O terminal of the MPU 120. In this diagram, L1 is the low level of the PGate terminal of the LED driver 240, and H1 is the high level of the PGate terminal. Also, L2 is the low level of the I / O terminal of the MPU 120, and H1 is the high level of the I / O terminal.

[0021] That is, when the detection signal input terminal 130 is at a high level, the buffer circuit 140 outputs a high level, and when the detection signal input terminal 130 is at a low level, the buffer circuit 140 outputs a low level. At this time, level shifting is performed to adjust the threshold value as necessary. When the detection signal input terminal 130 is open or grounded, the input is essentially at a low level, so the buffer circuit 140 outputs L2, which is the low level of the I / O terminal.

[0022] The buffer circuit 140 can be realized, for example, by a known non-inverting level shift circuit in which two transistors (Tr1, Tr2) are connected as shown in FIG. 3. Here, the high level of the I / O terminal is 5V, and the low level is 0V. In the example shown in this figure, when the detection signal input terminal 130 is H1, Tr1 is conductive, Tr2 is also conductive, and the output of the buffer circuit 140 is H2 of 5V. Also, when the detection signal input terminal 130 is L1, open, or grounded, Tr1 is non-conductive, Tr2 is also non-conductive, and the output of the buffer circuit 140 is L2 of 0V. However, the configuration of the buffer circuit 140 is not limited to the example shown in this figure.

[0023] Next, the operation of the power supply device 100 of this embodiment will be described. First, the case where the power supply device 100 is connected to an LED load device 200 that does not have a short-circuit protection function will be described. Figure 4 shows the case where the power supply device 100 is connected to an LED load device 200 that does not have a short-circuit protection function. In the example shown in this figure, the detection signal input terminal 130 is open.

[0024] 5 shows the AD1 input voltage and the I / O input voltage for each state of the LED load device 200. Because the detection signal input terminal 130 is open, the I / O input voltage is constant at low level L2 regardless of the state of the LED load device 200.

[0025] Drive current I LED The AD1 input voltage corresponding to the magnitude of the drive current I is the same as that of the conventional power supply device 400. In other words, when the LED load device 200 is normal, the value falls within the normal range determined by the first reference value and the second reference value (>first reference value). When an open circuit abnormality occurs in the LED load device 200, the drive current I LED As a result, the AD1 input voltage becomes smaller than the first reference value. LED As a result, the AD1 input voltage becomes greater than the second reference value.

[0026] Next, a case where the power supply device 100 is connected to an LED load device 230 having a short-circuit protection function will be described. Fig. 6 shows a case where the power supply device 100 is connected to an LED load device 230 having a short-circuit protection function. As shown in this figure, the PGate terminal of the LED driver 240 is connected to the detection signal input terminal 130.

[0027] 7 shows the AD1 input voltage and the I / O input voltage for each state of the LED load device 230. LED The AD1 input voltage corresponding to the magnitude of is the same as when the conventional power supply device 400 is connected to the LED load device 230 having a short circuit protection function.

[0028] That is, when the LED load device 230 is normal, the value falls within the normal range determined by the first reference value and the second reference value (>first reference value). When an open circuit abnormality occurs in the LED load device 230, the drive current I LED As a result, the AD1 input voltage becomes smaller than the first reference value. LED As a result of this, the AD1 input voltage becomes smaller than the first reference value. Therefore, it is not possible to distinguish between an open circuit and a short circuit based on the AD1 input voltage alone.

[0029] The I / O input voltage corresponding to the overcurrent detection signal of the LED driver 240 becomes high level H2 only when a short circuit abnormality occurs in the LED load device 230, and becomes low level L2 in other cases.

[0030] As can be seen from Figures 5 and 7, regardless of whether the short circuit protection function is present or not, if the AD1 input voltage is within the normal range, the LED load device can be determined to be normal.

[0031] When the AD1 input voltage is greater than the second reference value, it is only the "short circuit abnormality" in Figure 5, so it can be determined that a short circuit abnormality has occurred in the LED load device. Also, when the I / O input voltage is at high level H2, it is only the "short circuit abnormality" in Figure 7, so it can be determined that a short circuit abnormality has occurred in the LED load device.

[0032] Other abnormal conditions (when the AD1 input voltage is not within the normal range) are limited to when the AD1 input voltage is smaller than the first reference value and the I / O input voltage is at low level L2, and it can be determined that an open circuit abnormality has occurred in the LED load device.

[0033] From the above, the MPU 120 of the power supply device 100 controls the drive current I LED This makes it possible to accurately determine whether there is a short circuit or an open circuit in the LED load device (200, 230) that supplies the power.

[0034] First, it is determined whether the AD1 input voltage is within a normal range defined by a first reference value and a second reference value (S101). If the AD1 input voltage is within the normal range (S101: Yes), it is determined that the LED load device is normal (S102).

[0035] If the AD1 input voltage is not within the normal range (S101: No), it is determined whether the AD1 input voltage is greater than a second reference value (S103). If the AD1 input voltage is greater than the second reference value (S103: Yes), it is determined that a short circuit abnormality has occurred in the LED load device (S104).

[0036] If the AD1 input voltage is not greater than the second reference value (S103: No), that is, if the AD1 input voltage is smaller than the first reference value, it is determined whether the I / O input voltage is at a high level (S105). For example, if the I / O input voltage is greater than a predetermined third reference value corresponding to the threshold values ​​of H2 and L2, it can be determined to be at a high level, and if it is smaller than the third reference value, it can be determined to be at a low level.

[0037] If the I / O input voltage is at a high level (S105: Yes), it is determined that a short circuit abnormality has occurred in the LED load device (S106).On the other hand, if the I / O input voltage is at a low level (S105: No), it is determined that an open circuit abnormality has occurred in the LED load device (S107).

[0038] Alternatively, the procedure shown in the flow chart of Figure 9 can be used to reduce the drive current I LED It is possible to accurately determine whether there is a short circuit or an open circuit in the LED load device (200, 230) that supplies the power. The normal range of the AD1 input voltage and the high level of the I / O input voltage are the same as those in the flow chart of FIG.

[0039] First, it is determined whether the AD1 input voltage is within the normal range (S201). If the AD1 input voltage is within the normal range (S201: Yes), it is determined that the LED load device is normal (S202).

[0040] If the AD1 input voltage is not within the normal range (S201: No), it is determined whether the I / O input voltage is at a high level (S203). If the I / O input voltage is at a high level (S203: Yes), it is determined that a short circuit abnormality has occurred in the LED load device (S204).

[0041] If the I / O input voltage is not at a high level (S203: No), it is determined whether it is greater than the normal range (S205). If the AD1 input voltage is greater than the normal range (S205: Yes), it is determined that a short circuit abnormality has occurred in the LED load device (S206).

[0042] If the AD1 input voltage is not higher than the normal range (S205: No), that is, if the AD1 input voltage is lower than the normal range, it is determined that an open circuit abnormality has occurred in the LED load device (S207).

[0043] As described above, power supply device 100 of this embodiment includes detection signal input terminal 130 for inputting an overcurrent detection signal generated by the overcurrent protection function when the LED load device has the overcurrent protection function, and the input level of detection signal input terminal 130 is received via buffer circuit 140 to determine whether the LED load device has an abnormality. If the LED load device does not have the overcurrent protection function, buffer circuit 140 constantly outputs a low level, allowing power supply device 100 to identify the state of the LED load device based on the magnitude of the drive current supplied and the output of the buffer circuit. Therefore, power supply device 100 of this embodiment can accurately determine whether the LED load device has a short-circuit or open-circuit abnormality, regardless of whether the LED load device has a short-circuit protection function. [Explanation of symbols]

[0044] 100 Power supply 110 IPD 120 MPU 130 Detection signal input terminal 140 Buffer Circuit 200 LED load device 210 LED group 220 LED driver 230 LED load device 240 LED driver 250 Cut-off switch

Claims

1. A power supply device that supplies a drive current to an LED load device, a detection signal input terminal for inputting an overcurrent detection signal generated by the overcurrent protection function when the LED load device has the overcurrent protection function; Detecting an index indicating the magnitude of the drive current; determining that the LED load device is normal when the index is within a range determined by a first reference value and a second reference value greater than the first reference value; If the index is greater than a second reference value, it is determined that a short circuit abnormality has occurred in the LED load device; When the index is smaller than a second reference value and the overcurrent detection signal is input to the detection signal input terminal, it is determined that a short circuit abnormality has occurred in the LED load device; and a diagnostic unit that determines that an open circuit abnormality has occurred in the LED load device when the index is smaller than a first reference value and the overcurrent detection signal is not input to the detection signal input terminal.

2. 2. The power supply device according to claim 1, a buffer circuit is provided between the detection signal input terminal and the diagnostic unit; The buffer circuit is composed of a level shift circuit.

3. 3. The power supply device according to claim 1 or 2, The detection signal input terminal is open or grounded when the LED load device does not have an overcurrent protection function.

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