Terminal protection voltage detection circuit and power supply device

Abstract

A terminal protection voltage detection circuit and a power supply device capable of detecting current of each output terminal and eliminating the risk of burnout. In order to protect a terminal block having a plurality of output terminals in a power supply device, the terminal protection voltage detection circuit has: a current detection unit that detects a plurality of output currents respectively flowing from the power supply device to a plurality of loads via a plurality of output terminals; a first comparator that compares a sum of the plurality of output currents detected with a prescribed first threshold value and outputs a first comparison result signal when the sum of the plurality of output currents is the first threshold value or more; a second comparator that compares a maximum value of the plurality of output currents detected with a prescribed second threshold value and outputs a second comparison result signal when the maximum value is the second threshold value or more; and a current stop unit that stops the power supply device from flowing current at the plurality of output terminals based on the first comparison result signal or the second comparison result signal.

Description

Technical Field

[0001] The present invention relates to a terminal protection voltage detection circuit for protecting multiple terminals of a power supply device, and a power supply device having said terminal protection voltage detection circuit. Background Technology

[0002] Existing power supply devices have terminal blocks with multiple output terminals for connecting multiple loads (see, for example, Patent Document 1). Generally speaking, for example, in the case of a power supply device capable of outputting a large current, it is necessary to increase the size of the terminal block with multiple output terminals according to the output current.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2016-116366

[0004] However, increasing the actual terminal block size in the power supply unit results in thicker wiring, making manufacturing more difficult. Furthermore, even if the wiring is divided according to each load to separate the output current, if a load is short-circuited and damaged, the output current will concentrate at that point, potentially burning out the wiring at the corresponding output terminal.

[0005] In addition, even if the user wants to connect the two wires in parallel, if one wire is not in contact due to misconnection and the output current is concentrated on one wire, the wire may still be burned out. Summary of the Invention

[0006] The purpose of this invention is to solve the above-mentioned problems and provide a terminal protection voltage detection circuit that can detect the current of each output terminal to eliminate the risk of burn-out as described above, as well as a power supply device equipped with the terminal protection voltage detection circuit.

[0007] [Methods used to solve problems]

[0008] One aspect of the present invention provides a voltage detection circuit for terminal protection of a terminal block having multiple output terminals in a power supply device. The voltage detection circuit includes: a current detection unit that detects multiple output currents flowing from the power supply device to multiple loads via the multiple output terminals; a first comparator that compares the sum of the detected multiple output currents with a predetermined first threshold, and outputs a first comparison result signal when the sum of the multiple output currents is greater than or equal to the first threshold; a second comparator that compares the maximum value among the detected multiple output currents with a predetermined second threshold, and outputs a second comparison result signal when the maximum value is greater than or equal to the second threshold; and a current stopping unit that stops the current flowing through the power supply device at the multiple output terminals based on either the first comparison result signal or the second comparison result signal.

[0009] [Invention Effects]

[0010] Therefore, the voltage detection circuit for terminal protection according to the present invention can detect the current of each output terminal and eliminate the risk of burn-out as described above. Attached Figure Description

[0011] Figure 1 This is a block diagram showing a structural example of a power supply device having a terminal protection voltage detection circuit 20 according to an embodiment.

[0012] Label Explanation

[0013] 1: DC power supply; 2: Inverter circuit; 3: Rectifier circuit; 4, 5: Terminal block; 10: PWM control circuit; 20: Voltage detection circuit for terminal protection; 21-24: Differential amplifier; 25: Optocoupler; 31-32: Comparator; 41-44, 51-54: Output terminal; 61-64: Load; C1-C2: Electrolytic capacitor; D1-D22: Diode; D31: Light-emitting diode; L1-L2: Inductor; P1-P12: Connection point; Q1: MOS transistor; Q11: Bipolar transistor; Q31: Optotransistor; Rd, R11-R33: Resistors; R1-R4: Current sensing resistors; TR1: Transformer; VR1-VR2: Variable resistors. Detailed Implementation

[0014] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Furthermore, the same or identical constituent elements will be labeled with the same reference numerals.

[0015] (The inventor's perspective)

[0016] As described above, in existing power supply devices that have terminal blocks with multiple output terminals for connecting multiple loads, for example, in the case of a power supply device capable of outputting a large current, it is necessary to increase the size of the terminal block with multiple output terminals according to the output current. However, if the actual terminal block in the power supply device is increased, the wiring becomes thicker, and manufacturing becomes difficult. In addition, even if the wiring is divided according to each load in order to divide the output current, if a load is short-circuited and damaged, the output current will concentrate at that point, and the wiring of the corresponding output terminal may be burned out, so it is necessary to prevent this situation.

[0017] Therefore, the inventors have developed a structure that monitors overcurrent at each output terminal to ensure that the current at each output terminal does not exceed the rated value. Specifically, the structure is configured such that after amplifying the output current of each output terminal through each differential amplifier, current control for protection of each terminal and current control for the sum of currents are performed simultaneously. This allows for current control of each output terminal without significantly affecting the mounting area.

[0018] (Implementation Method)

[0019] Figure 1 This is a block diagram showing a structural example of a power supply device having a terminal protection voltage detection circuit 20 according to an embodiment.

[0020] exist Figure 1 In this embodiment, the power supply device is configured to include: a DC power supply 1, a smoothing electrolytic capacitor C1, an inverter circuit 2, a rectifier circuit 3, a smoothing electrolytic capacitor C2, a resistor Rd, a PWM control circuit 10, a terminal block 4 with four output terminals 41 to 44, a terminal block 5 with four output terminals 51 to 54, current sensing resistors R1 to R4, and a terminal protection voltage detection circuit 20. The inverter circuit 2 includes a MOS transistor Q1 and an inductor L1, and the rectifier circuit 3 includes two diodes D1 and D2, forming a single-phase full-wave rectifier circuit. Here, the inductors L1 and L2 form a transformer TR1 electromagnetically coupled with a coupling degree k.

[0021] The PWM control circuit 10 is the drive control circuit for the inverter circuit 2. Based on the feedback control signal FB from the terminal protection voltage detection circuit 20, it generates a PWM gate signal (drive control signal) with a predetermined period, which is applied to the gate of the MOS transistor Q1 via resistor Rd. Thus, the inverter circuit 2 controls the switching of the DC voltage from the DC power supply 1, thereby generating an AC voltage and outputting it to the rectifier circuit 3. The PWM control circuit 10 generates the PWM gate signal based on a low-level feedback control signal FB and stops generating the PWM gate signal based on a high-level feedback control signal FB. The rectifier circuit 3 converts the input AC voltage into a DC voltage and outputs it to the loads 61-64 via current detection resistors R1-R4 (negative side only) and the output terminals (41, 51; 42, 52; 43, 53; 44, 54) of terminal blocks 4 and 5.

[0022] The terminal protection voltage detection circuit 20 is configured to have:

[0023] (1) Differential amplifier 21, which has a feedback resistor R21, an output resistor R11 and an output diode D11;

[0024] (2) Differential amplifier 22, which has a feedback resistor R22, an output resistor R12 and an output diode D12;

[0025] (3) Differential amplifier 23, which has a feedback resistor R23, an output resistor R13 and an output diode D13;

[0026] (4) Differential amplifier 24, which has a feedback resistor R24, an output resistor R14 and an output diode D14;

[0027] (5) Resistor R15;

[0028] (6) Voltage divider resistors R31 and R32;

[0029] (7) Variable resistors VR1 and VR2;

[0030] (8) Output resistance R33;

[0031] (9) Comparators 31 and 32;

[0032] (10) Output diodes D21 and D22;

[0033] (11) Bipolar transistor Q11; and

[0034] (12) An optocoupler 25 having a light-emitting diode D31 and a phototransistor Q31.

[0035] Differential amplifiers 21-24 are so-called operational amplifiers that amplify and output the voltage difference obtained by subtracting the voltage applied to the inverting input terminal from the voltage applied to the non-inverting input terminal.

[0036] A voltage across the current sensing resistor R11 is applied to the inverting input terminal of differential amplifier 21 (this voltage is proportional to the output current I1 flowing through the output terminal 51 or the load 61). A feedback resistor R21 is connected between the inverting input terminal and the output terminal of differential amplifier 21. The output voltage V1 of differential amplifier 21 is output to the non-inverting input terminal of comparator 31 via resistor R11 and connection point P1, and is output to the non-inverting input terminal of comparator 32 via output diode D11 and connection point P2.

[0037] A voltage across the current sensing resistor R12 is applied to the non-inverting input terminal of differential amplifier 22 (this voltage is proportional to the output current I2 flowing through output terminal 52 or load 62). A feedback resistor R22 is connected between the inverting input terminal and the output terminal of differential amplifier 22. The output voltage V2 of differential amplifier 22 is output to the non-inverting input terminal of comparator 31 via resistor R12 and connection point P1, and is output to the non-inverting input terminal of comparator 32 via output diode D12 and connection point P2.

[0038] A voltage across the current sensing resistor R13 is applied to the non-inverting input terminal of differential amplifier 23 (this voltage is proportional to the output current I3 flowing through output terminal 53 or load 63). A feedback resistor R23 is connected between the inverting input terminal and the output terminal of differential amplifier 23. The output voltage V3 of differential amplifier 23 is output to the non-inverting input terminal of comparator 31 via resistor R13 and connection point P1, and is output to the non-inverting input terminal of comparator 32 via output diode D13 and connection point P2.

[0039] A voltage across the current sensing resistor R14 is applied to the non-inverting input terminal of differential amplifier 24 (this voltage is proportional to the output current I4 flowing through output terminal 54 or load 64). A feedback resistor R24 ​​is connected between the inverting input terminal and the output terminal of differential amplifier 24. The output voltage V4 of differential amplifier 24 is output to the non-inverting input terminal of comparator 31 via resistor R14 and connection point P1, and is output to the non-inverting input terminal of comparator 32 via output diode D14 and connection point P2.

[0040] Here, connection point P1 is connected to the negative power supply voltage -VCC via resistor R15. The positive power supply voltage +VCC is grounded via voltage divider resistor R31 and variable resistor VR1, and also via voltage divider resistor R32 and variable resistor VR2. Additionally, the positive power supply voltage +VCC is connected to the anode of the light-emitting diode D31 of optocoupler 25 via resistor R33, and the cathode of light-emitting diode D31 is grounded via the collector and emitter of bipolar transistor Q11.

[0041] The voltage V11th at the connection point P11 of the voltage divider resistor R31 and the variable resistor VR1 is set, for example, by adjusting the variable resistor VR1 to correspond to the rated current of the overall current of the output terminals 51-54. This voltage is applied as the first threshold voltage V11 to the inverting input terminal of the comparator 31. Similarly, the voltage V12th at the connection point P12 of the voltage divider resistor R32 and the variable resistor VR2 is set, for example, by adjusting the variable resistor VR2 to correspond to the rated current of each current in the output terminals 51-54. This voltage is applied as the second threshold voltage V12 to the inverting input terminal of the comparator 32.

[0042] Here, the voltage V11 at connection point P1 corresponds to the sum of the currents flowing through output terminals 51 to 54 (the overall current). Similarly, the voltage V12 at connection point P2 corresponds to the maximum value of the currents flowing through output terminals 51 to 54.

[0043] Comparator 31 applies a high-level comparison result signal SC1 to the base of bipolar transistor Q11 via diode D21 when V11 ≥ V11th, and applies a low-level comparison result signal SC1 to the base of bipolar transistor Q11 via diode D21 when V11 < V11th. Similarly, comparator 32 applies a high-level comparison result signal SC2 to the base of bipolar transistor Q11 via diode D22 when V12 ≥ V12th, and applies a low-level comparison result signal SC2 to the base of bipolar transistor Q11 via diode D22 when V12 < V12th.

[0044] Here, the current sensing resistors R1 to R4 (which may also include differential amplifiers 21 to 24) are examples of the current sensing section, and the comparators 31 and 32 are examples of the comparators.

[0045] When either the comparison result signals SC1 or SC2 are high, the bipolar transistor Q11 is turned on, causing the light-emitting diode D31 to emit light. The emitted light is incident on the phototransistor Q31, outputting a high-level feedback control signal FB to the PWM control circuit 10. Conversely, when both comparison result signals SC1 and SC2 are low, the bipolar transistor Q11 is turned off, causing the light-emitting diode D31 to turn off, and outputting a low-level feedback control signal FB from the optocoupler 25 to the PWM control circuit 10.

[0046] The operation of the power supply device having the terminal protection voltage detection circuit 20 configured as described above will be explained below.

[0047] The output currents I1 to I4 of the power supply device flow from the output terminals 41 to 44 of the positive terminal block 4 back to the output terminals 51 to 54 of the negative terminal block 5 via loads 61 to 64. Here, the current I1 flowing through output terminal 51 flows through resistor R1, and the voltage across resistor R1 is amplified by differential amplifier 21 to become voltage V1. Similarly, the current I2 flowing through output terminal 52 flows through resistor R2, and the voltage across resistor R2 is amplified by differential amplifier 22 to become voltage V2. Furthermore, the current I3 flowing through output terminal 53 flows through resistor R3, and the voltage across resistor R3 is amplified by differential amplifier 23 to become voltage V3. Finally, the current I4 flowing through output terminal 54 flows through resistor R4, and the voltage across resistor R4 is amplified by differential amplifier 24 to become voltage V4.

[0048] Generally speaking, the output terminals 41-44 and 51-54 of terminal blocks 4 and 5 are of the same shape, and are therefore set as follows, for example.

[0049] R1 = R2 = R3 = R4

[0050] R11 = R12 = R13 = R14

[0051] (Case 1) When a current exceeding the rated current (corresponding to the second threshold voltage V12th) flows through any one of the output terminals 41 to 44 (when the maximum value of each current flowing through output terminals 41 to 44 exceeds the rated current).

[0052] (1) V1≥V12th or

[0053] (2) V2 ≥ V12th or

[0054] (3) V3 ≥ V12th or

[0055] (4) V4≧V12th

[0056] The comparison result signal SC2 becomes high. At this time, the photodiode D31 of the optocoupler 25 is lit, generating a high-level feedback control signal FB, which causes the PWM control circuit 10 to stop generating the PWM gate signal.

[0057] (Scenario 2) When the output current of the entire power supply exceeds its rated current (corresponding to the first threshold voltage V11th),

[0058] (1) The current flowing through the output resistor R11 is V1 / R11.

[0059] (2) The current flowing through the output resistor R12 is V1 / R12.

[0060] (3) The current flowing through the output resistor R13 is V1 / R13.

[0061] (4) The current flowing through the output resistor R14 is V1 / R14.

[0062] Since the synthesized current is greater than the current value of -VCC / R15 flowing out from the negative power supply voltage -VCC, the comparison result signal SC1 becomes high. At this time, the photodiode D31 of the optocoupler 25 is lit, generating a high-level feedback control signal FB, which stops the PWM control circuit 10 from generating the PWM gate signal.

[0063] In cases 1 or 2 above, when the current of the entire power supply exceeds the rated current (first threshold current), or when the current of any of the output terminals exceeds the rated current (second threshold current), a high-level feedback control signal FB is generated, causing the PWM control circuit 10 to stop generating the PWM gate signal. This prevents the output terminals 41-44, 51-54 of terminal blocks 4 and 5, or their wiring, from being damaged by burnout, and prevents overcurrent from flowing through the power supply.

[0064] As explained above, according to this embodiment, when wiring is performed from multiple output terminals to carry a large current, it is possible to prevent load damage and current concentration at the output terminals when the terminals are not in contact, thereby eliminating the risk of output terminal and wiring burnout.

[0065] (Modified Example)

[0066] In the above embodiments, the PWM control circuit 10 generates a PWM gate signal based on the feedback control signal FB to drive and control the inverter circuit 2. However, the present invention is not limited to this. The inverter circuit 2 can also be driven and controlled by other drive control circuits such as FM control circuits that use FM gate signals to control the frequency.

[0067] In the above embodiments, a terminal block 4 having four output terminals 41 to 44 and a terminal block 5 having four output terminals 51 to 54 are provided. However, the present invention is not limited to this and multiple terminal blocks may also be used.

[0068] In the above embodiments, the current sensing resistors R1 to R4 are inserted into the negative side of the output terminal, but the present invention is not limited to this and can also be inserted into the positive side of the output terminal.

[0069] In the above embodiments, the inverter circuit 2 is composed of a circuit that converts DC voltage to AC voltage, but the present invention is not limited to this, and may also be composed of a circuit that converts DC power to AC power.

[0070] In the above embodiments, the rectifier circuit 3 is composed of a circuit that converts AC voltage to DC voltage, but the present invention is not limited to this, and may also be composed of a circuit that converts AC power to DC power.

[0071] In the above embodiments, the inverter circuit 2 is configured to use a MOS transistor Q1 as a switching element, but the present invention is not limited thereto, and may also be configured to use a switching element such as a thyristor.

[0072] [Industry availability]

[0073] As detailed above, the voltage detection circuit for terminal protection according to the present invention can detect the current of each output terminal and eliminate the risk of burn-out as described above.

Claims

1. A voltage detection circuit for terminal protection, used to protect a terminal block with multiple output terminals in a power supply device, wherein, The voltage detection circuit for terminal protection has the following features: The current detection unit detects multiple output currents flowing from the power supply device to multiple loads via multiple output terminals, and converts the detected multiple output currents into multiple voltage values. A first comparator compares the voltage value of a first connection point, which corresponds to the sum of multiple currents flowing through the plurality of output terminals, with a predetermined first threshold, and outputs a first comparison result signal when the voltage value of the first connection point is above the first threshold. The second comparator compares the voltage value of the second connection point, which corresponds to the maximum value of a plurality of currents flowing through the plurality of output terminals, with a predetermined second threshold, and outputs a second comparison result signal when the voltage value of the second connection point is above the second threshold. as well as The current-stopping unit, based on the first comparison result signal or the second comparison result signal, stops the power supply device from flowing current through the plurality of output terminals. The current detection unit includes multiple differential amplifiers, which amplify the detected multiple output currents after converting them into multiple voltage values. The output terminals of the plurality of differential amplifiers are respectively connected to the first connection point via their respective output resistors, and the voltage at the first connection point is output to the first comparator. Each output terminal of the plurality of differential amplifiers is connected to the second connection point via a respective output diode, and the voltage of the second connection point is output to the second comparator.

2. The voltage detection circuit for terminal protection according to claim 1, wherein, The first threshold is the voltage value corresponding to the rated current value of the entire terminal block. The second threshold is a voltage value corresponding to the rated current value of each of the plurality of output terminals.

3. A power supply device having a voltage detection circuit for terminal protection, wherein, The voltage detection circuit for terminal protection is used to protect the terminal block with multiple output terminals in the power supply device. The voltage detection circuit for terminal protection has the following features: The current detection unit detects multiple output currents flowing from the power supply device to multiple loads via multiple output terminals, and converts the detected multiple output currents into multiple voltage values. A first comparator compares the voltage value of a first connection point, which corresponds to the sum of multiple currents flowing through the plurality of output terminals, with a predetermined first threshold, and outputs a first comparison result signal when the voltage value of the first connection point is above the first threshold. The second comparator compares the voltage value of the second connection point, which corresponds to the maximum value of a plurality of currents flowing through the plurality of output terminals, with a predetermined second threshold, and outputs a second comparison result signal when the voltage value of the second connection point is above the second threshold. as well as The current-stopping unit, based on the first comparison result signal or the second comparison result signal, stops the power supply device from flowing current through the plurality of output terminals. The current detection unit includes multiple differential amplifiers, which amplify the detected multiple output currents after converting them into multiple voltage values. The output terminals of the plurality of differential amplifiers are respectively connected to the first connection point via their respective output resistors, and the voltage at the first connection point is output to the first comparator. The output terminals of the plurality of differential amplifiers are respectively connected to the second connection point via their respective output diodes, and the voltage at the second connection point is output to the second comparator. The power supply device has: Inverter circuits convert direct current (DC) power to alternating current (AC); and A rectifier circuit that converts AC power from the inverter circuit into DC power. The current stopping unit stops the operation of the inverter circuit.

4. The power supply device according to claim 3, wherein, The inverter circuit has the following characteristics: Switching elements that perform switching control on the DC power to convert it into AC power; and The drive control circuit generates drive control signals and outputs them to the switching elements. The current stopping unit causes the drive control circuit to stop generating drive control signals.

5. The power supply device according to claim 4, wherein, The drive control signal is a PWM gate signal or an FM gate signal.

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