JP2009219275A - Diode-bridge deficiency detection circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem, wherein a conventional power supply circuit cannot detect the deficiency of a diode bridge, and an abnormal DC voltage is applied to an apparatus, when the diode bridge has deficiency and there is a possibility that a nonconformity is generated in the connected apparatus. <P>SOLUTION: The diode-bridge deficiency detection circuit is provided with: first and second resistance elements R1 and R2, connected respectively between input terminals 21, 22 and output terminals 24, 25 of the diode bridge 20; first-fourth detecting diodes D1-D4; and first and second photocouplers Q1 and Q2. A deficiency determining section 60 detects deficiency of the diode bridge 20, based on a state detection signal 55a from a signal output terminal 55 which corresponds to the opening and closing of first and second light-receiving elements 51 and 52 of the first and second photocouplers Q1 and Q2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a diode bridge loss detection circuit, and in particular, by adding a circuit composed of a resistance element, a diode, and a photocoupler between the input and output of the diode bridge, the loss of the diode bridge can be detected. The present invention relates to a novel improvement for more reliably protecting a device connected to a power supply circuit.

  Conventionally, as a power supply circuit that converts an AC voltage into a DC voltage, for example, a circuit described in Patent Document 1 below is used. FIG. 7 is a circuit diagram showing a power supply circuit using a conventional diode bridge. In the figure, the AC voltage source 10 includes first and second output lines 11 and 12 and a fuse 14 provided in the first and second output lines 11 and 12. The first and second output lines 11 and 12 are connected to input terminals 21 and 22 of a diode bridge 20 composed of four diodes. A plurality of smoothing capacitors are connected to the output terminals 24 and 25 of the diode bridge 20. 30 is provided. That is, the AC voltage from the AC voltage source 10 is full-wave rectified by the diode bridge 20, and the full-wave rectified voltage is smoothed by the smoothing capacitor 30, thereby converting the AC voltage into a DC voltage.

JP-A-9-322540

  In the power supply circuit using the conventional diode bridge as described above, the defect of the diode bridge 20, that is, the failure of the diode included in the diode bridge 20 cannot be detected, and an abnormality occurs when the defect of the diode bridge 20 occurs. A large DC voltage is supplied to the device, which may cause a malfunction of the device.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to detect a diode bridge deficiency and to detect a diode bridge deficiency, and to more reliably protect a device connected to a power supply circuit. Is to provide.

A diode bridge deficiency detection circuit according to the present invention is provided in a power supply circuit that performs full-wave rectification of an AC voltage from an AC voltage source using a diode bridge and smoothes the voltage subjected to full-wave rectification using a smoothing capacitor. A diode bridge defect detection circuit for detecting a defect, wherein the first light-emitting element of the first photocoupler has a first input terminal connected between a plus-side output terminal of the diode bridge and the smoothing capacitor; A first resistance element connected to a first output terminal of one light emitting element, and connected between the first resistance element and a first output line of the AC voltage source, and the first output from the first resistance element The first resistance element is connected between the first detection diode whose forward direction is the forward direction, the first resistance element, and the second output line of the AC voltage source. And a second photocoupler having a second input terminal connected between the negative output terminal of the diode bridge and the smoothing capacitor. Two light-emitting elements, a second resistance element connected to a second output terminal of the second light-emitting element, connected between the second resistance element and the second output line of the AC voltage source, A direction from the second output line to the second resistance element is connected between the third detection diode having a forward direction, the second resistance element and the first output line of the AC voltage source; A fourth detection diode having a forward direction from the output line toward the second resistance element, a constant voltage source, a third resistance element, a first light receiving element of the first photocoupler, and a second photocoupler of the second photocoupler. Two light receiving elements are connected in series A defect state output unit; and a defect determination unit connected to a signal output terminal of the defect state output unit, wherein the first and second light receiving elements are first and second resistors of the first and second resistance elements, respectively. When the voltage across the two ends exceeds a preset threshold value, it is electrically opened or closed, and the defect determining unit is connected to the signal output terminal corresponding to the opening and closing of the first and second light receiving elements. The loss of the diode bridge is detected based on the state detection signal.
In addition, the deficiency determination unit counts a time during which at least one of the first and second both-end voltages does not exceed the threshold based on the state detection signal, and the first and second both-end voltages Counts the number of times at least one of which has not exceeded the threshold for a predetermined time, and detects that the diode bridge is defective when the counted number reaches a preset number. To do.
The AC voltage source is a three-phase AC power supply further having a third output line, and is connected between the first resistance element and a third output line of the AC voltage source. A fifth detection diode whose forward direction is directed to the third output line is connected between the second resistance element and the third output line of the AC voltage source, and is connected to the third output line from the third output line. And a sixth detection diode whose forward direction is toward the two-resistance element.
Further, the loss determination unit counts the number of times that at least one of the first and second both-end voltages has not exceeded the threshold based on the state detection signal, and the counted number is preset. When the number of times is reached, it is detected that the diode bridge is defective.

According to the diode bridge loss detection circuit of the present invention, the loss of the diode bridge can be detected by adding a circuit composed of a resistance element, a diode, and a photocoupler between the input and output of the diode bridge. Equipment connected to the circuit can be protected more reliably.
In addition, the deficiency determination unit counts a time during which at least one of the first and second both-end voltages does not exceed the threshold based on the state detection signal, and the first and second both-end voltages Counting the number of times that at least one of the states in which the threshold does not exceed the predetermined time has continued for a predetermined time, and detecting that a defect has occurred in the diode bridge when the counted number reaches a predetermined number of times, It is possible to more reliably detect the occurrence of the loss of the diode bridge, and it is possible to more reliably protect the device connected to the power supply circuit.
Further, a fifth detection diode having a forward direction from the first resistance element to the third output line is connected between the first resistance element and the third output line of the AC voltage source, and Since a sixth detection diode having a forward direction from the third output line to the second resistance element is connected between the second resistance element and the third output line of the AC voltage source, three-phase AC Occurrence of defects can also be detected more reliably in the diode bridge for power supply.
Further, the loss determination unit counts the number of times that at least one of the first and second both-end voltages has not exceeded the threshold based on the state detection signal, and the counted number is preset. Since the occurrence of a defect in the diode bridge is detected when the number of times is reached, the occurrence of the defect can be detected more reliably in the diode bridge for a three-phase AC power supply.

The best mode for carrying out the present invention will be described below with reference to the drawings.
Embodiment 1 FIG.
FIG. 1 is a circuit diagram showing a diode bridge loss detection circuit according to Embodiment 1 of the present invention. The same or equivalent parts as those of the conventional circuit (see FIG. 7) will be described using the same reference numerals. In the figure, the AC voltage source 10 includes first and second output lines 11 and 12 and a fuse 14 provided in the first and second output lines 11 and 12. The first and second output lines 11 and 12 are connected to input terminals 21 and 22 of a diode bridge 20 composed of four diodes, and positive and negative output terminals 24 and 25 of the diode bridge 20 are connected to the input terminals 21 and 22, respectively. A plurality of smoothing capacitors 30 are provided. That is, the AC voltage from the AC voltage source 10 is full-wave rectified by the diode bridge 20, and the full-wave rectified voltage is smoothed by the smoothing capacitor 30, thereby converting the AC voltage into a DC voltage.

  A first input terminal 41a of the first light emitting element 41 of the first photocoupler Q1 is connected between the plus side output terminal 24 of the diode bridge 20 and the smoothing capacitor 30, and the first light emitting element 41 is connected. A first resistance element R1 is connected to the first output terminal 41b. Between the first resistance element R1 and the first output line 11, a first detection diode D1 having a forward direction from the first resistance element R1 toward the first output line 11 is provided. Between the first resistance element R1 and the second output line 12, a second detection diode D2 having a forward direction from the first resistance element R1 toward the second output line 12 is provided. Yes. As will be described later, a circuit constituted by the first light emitting element 41, the first resistance element R1, the first detection diode D1, and the second detection diode D2 includes an input terminal 21 and 22 and a positive output terminal 24. This is a circuit for detecting an open failure of two diodes of the diode bridge 20 provided between the two. Between the first output terminal 41b and the smoothing capacitor 30, an output-side diode 80 whose forward direction from the first output terminal 41b to the smoothing capacitor 30 is provided is provided.

  A second input terminal 42a of the second light emitting element 42 of the second photocoupler Q2 is connected between the negative output terminal 25 of the diode bridge 20 and the smoothing capacitor 30, and the second light emitting element 42 is connected. A second resistance element R2 is connected to the second output terminal 42b. A third detection diode D3 having a forward direction from the second output line 12 to the second resistance element R2 is connected between the second resistance element R2 and the second output line 12. A fourth detection diode D4 having a forward direction from the first output line 11 to the second resistance element R2 is connected between the second resistance element R2 and the first output line 11. ing. As will be described later, a circuit constituted by the second light emitting element 42, the second resistance element R2, the third detection diode D3, and the fourth detection diode D4 includes an input terminal 21 and a negative output terminal 25, This is a circuit for detecting an open failure of two diodes of the diode bridge 20 provided between the two.

  The first and second photocouplers Q1 and Q2 are applied with a forward voltage on the light emitting states of the first and second light emitting elements 41 and 42, that is, whether or not the first and second light emitting elements 41 and 42 are forwarded. First and second light receiving elements 51 and 52 that are electrically opened and closed in accordance with the above are provided. These first and second light receiving elements 51 and 52 constitute a part of the defect state output unit 50. That is, the constant voltage source 53, the third resistance element R3, the first light receiving element 51, and the second light receiving element 52 are connected to each other in series to form the defect state output unit 50. The output end of the second light receiving element 52 is connected to the ground 54.

  A signal output terminal 55 is provided between the third resistance element R 3 and the first light receiving element 51, and the first and second light receiving elements 51 and 52 are opened from the signal output terminal 55. And the state detection signal 55a according to closing is output. The signal output terminal 55 is connected to a defect determination unit 60 constituted by a microcomputer or the like. The defect determination unit 60 detects the defect of the diode bridge 20 based on the state detection signal 55a.

  Next, FIG. 2 is an explanatory diagram showing a current flowing in the circuit when the diode bridge 20 of FIG. 1 is normal, and FIG. 3 is a timing chart in the circuit of FIG. Note that FIG. 2 is a diagram in which currents A1, A2, B1, and B2 are added to FIG. 1, and a part of the reference numerals in FIG. 1 is omitted to avoid complication. In FIG. 2, currents A1 and B1 indicate currents that flow when the potential of the first output line 11 is higher than the potential of the second output line 12, and currents A2 and B2 indicate the second output line. 12 shows a current that flows when the potential of 12 is higher than the potential of the first output line 11. That is, currents A1 and B1 flow when the amplitude of power supply input 70 in FIG. 3 is positive, and currents A2 and B2 flow when the amplitude of power supply input 70 is negative. At this time, the first and second both-end voltages 71 and 72 of the first and second resistance elements R1 and R2 have waveforms obtained by full-wave rectification of the power input 70 as shown in FIG.

  The first and second light receiving elements 51 and 52 are closed (ON) when the first and second both-end voltages 71 and 72 are equal to or higher than a preset threshold, and the first and second light receiving elements 51 and 52 are closed. It is opened (OFF) when both-end voltages 71 and 72 are less than the threshold value. The state detection signal 55a becomes Hi level (the voltage of the constant voltage source 53, that is, 5V) when at least one of the first and second light receiving elements 51 and 52 is opened, and the first and second light receiving elements 51 , 52 becomes Lo level (0 V) when both are closed.

  When all the diodes are normal as shown in FIG. 2, the time during which at least one of the first and second both-end voltages 71 and 72 does not exceed the threshold (the time during which the state detection signal 55a becomes Hi level) is The time when both of the first and second both-end voltages 71 and 72 exceed the threshold is shorter than the time when the state detection signal 55a is at the Lo level.

  Next, FIG. 4 is an explanatory diagram showing a current when a defect occurs in the diode bridge 20 of FIG. 3, and FIG. 5 is a timing chart in the circuit of FIG. In FIG. 4, the diode of the diode bridge 20 through which the current A2 flows has an open failure. That is, as shown in FIG. 5, the first both-end voltage 71 of the first resistance element R1 has a half-end rectified waveform. At this time, the first light receiving element 51 is opened (OFF) in a period corresponding to the current A2. Therefore, in the period corresponding to the current A2, the state detection signal 55a is also at the Hi level.

  Accordingly, when a defect occurs in the diode bridge 20 as shown in FIG. 4, at least one of the first and second both-end voltages 71 and 72 is compared with a case where all the diodes are normal (in the case of FIG. 3). Is longer than the threshold value. The loss determination unit 60 counts the time during which at least one of the first and second both-end voltages 71 and 72 does not exceed the threshold, using a known clock signal and the state detection signal 55a. Further, the deficiency determination unit 60 counts the number of times that the time during which at least one of the first and second both-end voltages 71 and 72 does not exceed the threshold continues for a predetermined time, and the counted number is set to the predetermined number. When it reaches, it is detected that the diode bridge 20 is defective.

Embodiment 2. FIG.
FIG. 6 is a circuit diagram showing a diode bridge loss detection circuit according to the second embodiment of the present invention. Although the circuit used for the single-phase AC power supply is shown in Embodiment 1, the present invention can also be applied to a three-phase AC power supply as shown in FIG. Note that portions that are the same as or equivalent to those in the first embodiment are described using the same reference numerals.
The AC voltage source 10 is provided with a third output line 13 connected to the diode bridge 20. Between the first resistance element R1 and the third output line 13, a fifth detection diode D5 having a forward direction from the first resistance element R1 toward the third output line 13 is connected. . Further, a sixth detection diode D6 having a forward direction from the third output line 13 toward the second resistance element R2 is connected between the second resistance element R2 and the third output line 13. ing.

  A full-wave rectified three-phase AC voltage is applied to the first and second resistance elements R1 and R2. That is, in the first embodiment, there is a state where at least one of the first and second both-end voltages 71 and 72 does not exceed the threshold value (see FIG. 3). If there is no defect in the diode bridge 20, the first and second terminal voltages 71 and 72 always exceed the threshold value. The deficiency determination unit 60 counts the number of times that at least one of the first and second both-end voltages 71 and 72 has not exceeded the threshold based on the state detection signal 55a. When the set number of times is reached, it is detected that the diode bridge 20 is defective. Other configurations are the same as those in the first embodiment.

1 is a circuit diagram showing a diode bridge loss detection circuit according to a first embodiment of the present invention. FIG. It is explanatory drawing which shows the electric current which flows into a circuit, when the diode bridge of FIG. 1 is normal. 3 is a timing chart in the circuit of FIG. It is explanatory drawing which shows the electric current when a defect | deletion arises in the diode bridge of FIG. 5 is a timing chart in the circuit of FIG. It is a circuit diagram which shows the diode bridge defect | deletion detection circuit by Embodiment 2 of this invention. It is a circuit diagram which shows the power supply circuit using the conventional diode bridge.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 AC voltage source 11-13 1st-3rd output line 20 Diode bridge 24 Positive side output terminal 25 Negative side output terminal 30 Smoothing capacitor 41, 42 1st and 2nd light emitting element 41a, 42a 1st and 2nd input terminal 41b, 42b First and second output terminals 50 Missing state output unit 51, 52 First and second light receiving elements 53 Constant voltage source 54 Ground 55 Signal output terminal 55a State detection signal 60 Defect determining unit 71, 72 First and second 2 Voltage across terminals D1 to D6 Detection diodes Q1 and Q2 First and second photocouplers R1 to R3 First to third resistance elements

Claims (4)

An AC voltage from the AC voltage source (10) is full-wave rectified by a diode bridge (20), and the full-wave rectified voltage is smoothed by a smoothing capacitor (30). The diode bridge (20) A diode bridge deficiency detection circuit for detecting deficiency in
The first light emitting element (41) of the first photocoupler (Q1) in which the first input terminal (41a) is connected between the plus side output terminal (24) of the diode bridge (20) and the smoothing capacitor (30). )When,
A first resistance element (R1) connected to a first output terminal (41b) of the first light emitting element (41);
Connected between the first resistance element (R1) and the first output line (11) of the AC voltage source (10), and directed from the first resistance element (R1) to the first output line (11). A first detection diode (D1) having a forward direction;
Connected between the first resistance element (R1) and the second output line (12) of the AC voltage source (10), and directed from the first resistance element (R1) to the second output line (12). A second detection diode (D2) having a forward direction,
The second light emitting element (42) of the second photocoupler (Q2) in which the second input terminal (42a) is connected between the negative output terminal (25) of the diode bridge (20) and the smoothing capacitor (30). )When,
A second resistance element (R2) connected to a second output terminal (42b) of the second light emitting element (42);
Connected between the second resistance element (R2) and the second output line (12) of the AC voltage source (10), from the second output line (12) to the second resistance element (R2). A third detection diode (D3) whose forward direction is the forward direction;
Connected between the second resistance element (R2) and the first output line (11) of the AC voltage source (10), and from the first output line (11) to the second resistance element (R2). A fourth detection diode (D4) whose forward direction is the forward direction;
A constant voltage source (53), a third resistance element (R3), a first light receiving element (51) of the first photocoupler (Q1), and a second light receiving element (52) of the second photocoupler (Q2). A missing state output section (50) connected in series with each other;
A defect determination unit (60) connected to the signal output terminal (55) of the defect state output unit (50),
In the first and second light receiving elements (51, 52), the first and second terminal voltages (71, 72) of the first and second resistance elements (R1, R2) have exceeded a preset threshold value. When opened or closed electrically,
The defect determination unit (60) is configured to detect the diode based on a state detection signal (55a) from the signal output terminal (55) according to opening and closing of the first and second light receiving elements (51, 52). A diode bridge deficiency detection circuit characterized by detecting a deficiency in the bridge (20).   The loss determination unit (60) counts the time during which at least one of the first and second both-end voltages (71, 72) does not exceed the threshold based on the state detection signal (55a), When the number of times that the time during which at least one of the first and second both-end voltages (71, 72) does not exceed the threshold continues for a predetermined time is counted and the counted number reaches a preset number 2. The diode bridge deficiency detection circuit according to claim 1, wherein a deficiency is detected in the diode bridge (20). The AC voltage source (10) is a three-phase AC power source further having a third output line (13),
Connected between the first resistance element (R1) and the third output line (13) of the AC voltage source (10), from the first resistance element (R1) to the third output line (13). A fifth detection diode (D5) whose forward direction is the forward direction;
Connected between the second resistance element (R2) and the third output line (13) of the AC voltage source (10), and from the third output line (13) to the second resistance element (R2). The diode bridge defect detection circuit according to claim 1, further comprising: a sixth detection diode (D6) whose forward direction is a forward direction.   The loss determination unit (60) counts the number of times that at least one of the first and second both-end voltages (71, 72) does not exceed the threshold based on the state detection signal (55a). 4. The diode bridge deficiency detection circuit according to claim 3, wherein deficiency is detected in the diode bridge (20) when the counted number reaches a preset number.

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