Overvoltage detection circuit

Abstract

This overvoltage detection circuit has: a bus-bar voltage detection circuit (7); a first delay circuit (29) that delays bus-bar voltage by a first delay time; a comparator (28a) that compares the delayed bus-bar voltage with a first cutoff threshold value and outputs the obtained first comparison result; a power supply voltage detection circuit (32); a second delay circuit (31) that delays power supply voltage by a second delay time; another comparator (30a) that compares the delayed power supply voltage with a second cutoff threshold value and outputs the obtained second comparison result; and a relay (4) that switches, on the basis of the first comparison result and the second comparison result, between on and off of power receiving of an outdoor unit (3) from an AC power supply (50). The first delay time is longer than the second delay time. The first cutoff threshold value is lower than the second cutoff threshold value.

Description

[Technical field]

[0001] The present disclosure relates to an overvoltage detection circuit for protecting a power supply circuit from a surge voltage. [Background technology]

[0002] Conventionally, an overvoltage detection circuit for protecting a circuit against abrupt fluctuations in a power supply voltage has been known. Patent Document 1 discloses a configuration having a first comparison circuit for high-speed response and a second comparison circuit for low-speed response, in which the set voltage is lowered for frequencies lower than the response limit frequency and the set voltage is raised for frequencies higher than the response limit frequency. Patent Document 1 also discloses a configuration in which the overvoltage detection circuit has time response characteristics, and the set voltage is lowered for long operating times and raised for short operating times. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2003-52120 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the conventional technology, comparison is performed only on the DC voltage on the bus voltage side, and therefore, since overvoltage detection is performed on the DC voltage after rectification by the rectifier, the detection sensitivity of overvoltage protection is poor for surge voltages, which are steep overvoltages superimposed on the power supply voltage, and there are problems such as delayed protection.

[0005] The present disclosure has been made in consideration of the above, and aims to provide an overvoltage detection circuit for protecting a power supply circuit from a surge voltage, which is a steep overvoltage superimposed on a power supply voltage, and a long-term increase in the power supply voltage in areas where the power supply voltage is unstable. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, the overvoltage detection circuit of the present disclosure includes a busbar voltage detection circuit that detects a busbar voltage, a first delay circuit that delays the busbar voltage detected by the busbar voltage detection circuit by a first delay time, a first comparison unit that outputs a first comparison result obtained by comparing the busbar voltage delayed by the first delay circuit with a first cut-off threshold, a power supply voltage detection circuit that detects a power supply voltage, a second delay circuit that delays the power supply voltage detected by the power supply voltage detection circuit by a second delay time, a second comparison unit that outputs a second comparison result obtained by comparing the power supply voltage delayed by the second delay circuit with a second cut-off threshold, and a relay that switches on and off the reception of power from the AC power supply to an outdoor unit based on the first comparison result output from the first comparison unit and the second comparison result output from the second comparison unit. The first comparator outputs a first comparison result indicating low when the bus voltage is equal to or higher than a first cutoff threshold. The second comparator outputs a second comparison result indicating low when the power supply voltage is equal to or higher than a second cutoff threshold. The relay turns off the reception of power from the AC power supply to the outdoor unit when the first comparator outputs the first comparison result indicating low or when the second comparator outputs the second comparison result indicating low. The first delay time is longer than the second delay time, and the first shut-off threshold is lower than the second shut-off threshold. Effect of the Invention

[0007] The overvoltage detection circuit according to the present disclosure has the advantage of being able to protect a power supply circuit from a surge voltage, which is a steep overvoltage superimposed on the power supply voltage, and from a long-term increase in the power supply voltage in areas where the power supply voltage is unstable. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing a configuration of an air conditioner according to a first embodiment. [Diagram 2] A circuit diagram showing details of a power supply overvoltage detection circuit, a bus overvoltage detection circuit, a relay control unit, and a relay control circuit included in the air conditioner according to the first embodiment. [Diagram 3] Time chart of the power supply voltage waveform and relay control signal that rises over a long period of time [Figure 4] Waveform of steep surge voltage in power supply system and time chart of relay control signal [Diagram 5] 1 is a flowchart showing the procedure of an operation performed by an air conditioner according to a first embodiment. [Figure 6]FIG. 13 is a diagram showing a configuration of an overvoltage detection circuit according to a second embodiment; [Figure 7] FIG. 1 is a diagram showing a processor in a case where a part or the whole of a control unit included in an outdoor unit of an air conditioner according to a first embodiment is realized by a processor. [Figure 8] FIG. 1 is a diagram showing a processing circuit in the case where a part or all of a control unit included in an outdoor unit of an air conditioner according to a first embodiment is realized by the processing circuit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An overvoltage detection circuit according to an embodiment will be described in detail below with reference to the drawings.

[0010] Embodiment 1 FIG. 1 is a diagram showing the configuration of an air conditioner 1 according to a first embodiment. The air conditioner 1 has an overvoltage detection circuit, which will be described in detail later. The air conditioner 1 has an indoor unit 2 and an outdoor unit 3. The indoor unit 2 has a terminal block 21, a converter circuit 22, a smoothing capacitor 23, a bus voltage detection circuit 24, an indoor unit control circuit 25, a relay 26, and a serial communication circuit 27. The indoor unit control circuit 25 controls the fan of the indoor unit 2 and processes signals from a remote controller and the like, and also communicates with the outdoor unit 3. The fan and remote controller are not shown in FIG. 1.

[0011] One end of the relay 26 is connected to an AC power supply 50. The other end of the relay 26 is connected to a serial communication circuit 27. The relay 26 switches between supplying power to the outdoor unit 3 and serial communication in accordance with the energized state of the coil, based on a control signal from the indoor unit control circuit 25. An AC power supply 50 that supplies power to the air conditioner 1 is also shown in FIG. 1. The AC power supply 50 applies a power supply voltage to the air conditioner 1.

[0012] The outdoor unit 3 has a terminal block 20, a relay 4, a converter circuit 5, a smoothing capacitor 6, a bus voltage detection circuit 7, an inverter circuit 8, a compressor 9, a relay 10, a serial communication circuit 11, a bus overvoltage detection circuit 14, a power supply overvoltage detection circuit 12, a control unit 15, a relay control circuit 13, and a current detection circuit 19.

[0013] The terminal block 20 is connected to a converter circuit 5 of the outdoor unit 3 via a relay 4. The terminal block 20 is also connected to an AC power source 50 in parallel with the indoor unit 2.

[0014] The relay 4 is configured as a so-called A-contact relay. One end of the relay 4 is connected to an AC power source 50 via a terminal block 20. The other end of the relay 4 is connected to a converter circuit 5.

[0015] The converter circuit 5 has a rectifier circuit 51 and a power factor correction circuit 52, and converts AC to DC. The rectifier circuit 51 is, for example, a diode bridge circuit. The power factor correction circuit 52 is, for example, a boost chopper circuit. The converter circuit 5 is connected to a smoothing capacitor 6.

[0016] The control unit 15 has a converter control unit 16 for controlling the power factor correction circuit 52, a relay control unit 17 for controlling the on / off of the relay 4 based on a value from a bus voltage detection circuit 7 that detects the bus voltage, and an inverter control unit 18 for controlling the inverter circuit 8 based on a command from the serial communication circuit 11 of the outdoor unit 3 and a value from a current detection circuit 19. The control unit 15 has a function of outputting a switching determination signal regarding the on / off switching determination of the relay control circuit 13 based on the bus voltage detected by the bus voltage detection circuit 7. The control unit 15 further has a function of detecting the on / off state of the relay control circuit 13.

[0017] The relay 10 is configured as a so-called C-contact relay. When the coil of the relay 10 is not energized, the relay 10 is connected to the AC power supply 50 via the indoor unit 2. When the coil of the relay 10 is energized by a control signal from the control unit 15, the relay 10 is connected to the serial communication circuit 11, and thus the serial communication circuit 11 can communicate with the serial communication circuit 27 of the indoor unit 2.

[0018] Fig. 2 is a circuit diagram showing details of the power supply overvoltage detection circuit 12, bus bar overvoltage detection circuit 14, relay control unit 17, and relay control circuit 13 that the air conditioner 1 according to embodiment 1 has. More specifically, Fig. 2 shows the configuration of the overvoltage detection circuit according to embodiment 1. Fig. 2 also shows components other than the power supply overvoltage detection circuit 12, bus bar overvoltage detection circuit 14, relay control unit 17, and relay control circuit 13 out of all the components that the outdoor unit 3 of the air conditioner 1 has. Fig. 2 also shows an AC power supply 50.

[0019] The power supply overvoltage detection circuit 12 includes an overvoltage detection section 30, which is a second comparison section, a second delay circuit 31, and a power supply voltage detection circuit 32 that detects the power supply voltage. The overvoltage detection section 30 includes a comparator 30a, resistors R8, R9, and R10, and a capacitor C4. The resistors R8 and R9 are connected in series between a comparator power supply voltage 30b and a ground potential, and divide the voltage of the comparator power supply voltage 30b and apply it to the comparator 30a. The capacitor C4 is connected between the comparator power supply voltage 30b and the ground potential as a bypass capacitor. The output of the comparator 30a is connected to a pull-up voltage 30c via a resistor R10, and is connected to the relay control circuit 13.

[0020] The second delay circuit 31 constitutes an integrating circuit having a resistor R7 and a capacitor C3. An output node of the second delay circuit 31 is connected to a comparator 30a of the overvoltage detection unit 30, and an input node of the second delay circuit 31 is connected to a power supply voltage detection circuit 32. The second delay circuit 31 delays the power supply voltage detected by the power supply voltage detection circuit 32 by a second delay time. The overvoltage detection unit 30 compares the power supply voltage delayed by the second delay circuit 31 with a second cutoff threshold and outputs a second comparison result obtained.

[0021] The power supply voltage detection circuit 32 includes resistors R5, R6, and R15, and diodes D1 and D2. One end of the resistor R5 is connected to the relay 4 and the converter circuit 5, and the other end of the resistor R5 is connected to the anode of the diode D1. One end of the resistor R6 is connected to the AC power supply 50, and the other end of the resistor R6 is connected to the anode of the diode D2. The cathode of the diode D1 is connected to the cathode of the diode D2. The cathode of the diode D1 and the cathode of the diode D2 are connected to one end of the resistor R15 and are connected to the second delay circuit 31. The other end of the resistor R15 is connected to the ground potential.

[0022] The bus overvoltage detection circuit 14 has an overvoltage detection unit 28, which is a first comparison unit, and a first delay circuit 29. The overvoltage detection unit 28 has a comparator 28a, resistors R2, R3, and R4, and a capacitor C2. The resistors R2 and R3 are connected in series between a comparator power supply voltage 28b and a ground potential, and divide the voltage of the comparator power supply voltage 28b and apply it to the comparator 28a. The capacitor C2 is connected between the comparator power supply voltage 28b and the ground potential as a bypass capacitor. The output of the comparator 28a is connected to a pull-up voltage 28c via a resistor R4.

[0023] The first delay circuit 29 constitutes an integrating circuit having a resistor R1 and a capacitor C1. The capacitance value of the capacitor C1 is greater than the capacitance value of the capacitor C3 of the second delay circuit 31. The output node of the first delay circuit 29 is connected to the comparator 28a, and the input node of the first delay circuit 29 is connected to the bus voltage detection circuit 7. The first delay circuit 29 delays the bus voltage detected by the bus voltage detection circuit 7 by a first delay time. The overvoltage detection unit 28 compares the bus voltage delayed by the first delay circuit 29 with a first cutoff threshold value and outputs a first comparison result. The relay 4 switches on and off the power reception of the outdoor unit 3 from the AC power source 50 based on the first comparison result output from the overvoltage detection unit 28 and the second comparison result output from the overvoltage detection unit 30.

[0024] The outdoor unit 3 further has resistors R11 and R12. The relay control unit 17 is connected to the bus voltage detection circuit 7 to read the value of the bus voltage, and is connected to the relay control circuit 13 via the resistor R11 to read the relay control state. The relay control unit 17 is also connected to the relay control circuit 13 via the resistor R12 to open and close the relay 4 by software control.

[0025] The relay control circuit 13 is a circuit that switches on and off the reception of power from the AC power supply 50, and includes a transistor Q1 and resistors R13 and R14. The transistor Q1 is a driving transistor that drives the relay 4 based on the first comparison result output from the overvoltage detection unit 28, the second comparison result output from the overvoltage detection unit 30, and the switching determination signal output from the control unit 15. The output of the overvoltage detection unit 28, the output of the overvoltage detection unit 30, and the output of the relay control unit 17 are connected to the base terminal of the transistor Q1.

[0026] The resistor R13 is connected to the base of the transistor Q1, and the resistor R14 is connected between the base and emitter of the transistor Q1. The outdoor unit 3 further has a diode D3. One end of the diode D3 is connected to the relay control circuit 13, and the other end of the diode D3 is connected to the control unit 15. The coil portion 4a of the relay 4 is connected in parallel with the diode D3. That is, one end of the coil portion 4a is connected to the control unit 15, and the other end of the coil portion 4a is connected to the collector of the transistor Q1.

[0027] The overvoltage detection circuit of embodiment 1 is composed of a bus voltage detection circuit 7, a first delay circuit 29, a comparator 28a, a power supply voltage detection circuit 32, a second delay circuit 31, a comparator 30a, and a relay 4.

[0028] Next, the operation of the air conditioner 1 according to the first embodiment will be described. When the air conditioner 1 is operating normally, the relay 26 is turned off under control of the indoor unit control circuit 25 of the indoor unit 2. The relay 10 of the outdoor unit 3 is connected to the serial communication circuit 11 by a control signal from the control unit 15. The relay 4 is turned on under control of the relay control circuit 13, so that the converter circuit 5 is directly powered by the AC power source 50.

[0029] Fig. 3 is a time chart of the waveform of the power supply voltage that rises over a long period of time and the relay control signal. Fig. 3 shows how the relay control state, the relay control signal of the power supply overvoltage detection circuit 12, the bus overvoltage detection circuit 14, and the relay control unit 17, and the power supply voltage change over time. For example, as shown in Fig. 3, when the amplitude of the power supply voltage rises by ΔVa for a long period of time with respect to the rated value Vtyp, the output voltage of the bus voltage detection circuit 7 rises. The rise in the output voltage is delayed by the first delay circuit 29 of the bus overvoltage detection circuit 14, but when the output voltage exceeds the potential of the midpoint of the resistors R2 and R3 connected in series, the output of the comparator 28a becomes Low and the potential becomes the ground potential, so that the transistor Q1 of the relay control circuit 13 turns off and the relay 4 is cut off, thereby protecting the circuit downstream of the relay 4 from the overvoltage.

[0030] FIG. 4 is a time chart of the waveform of a steep surge voltage in the power supply system and a relay control signal. FIG. 4 shows how the relay control state, the relay control signal of the power supply overvoltage detection circuit 12, the busbar overvoltage detection circuit 14, and the relay control unit 17, and the power supply voltage change over time. As shown in FIG. 4, for example, when a steep surge voltage ΔVb is superimposed on the rated Vtyp of the amplitude value of the power supply voltage, the voltage detected by the power supply voltage detection circuit 32 of the power supply overvoltage detection circuit 12 rises steeply. The steep voltage rise is delayed by the second delay circuit 31, but when the voltage exceeds the potential of the midpoint of the resistors R8 and R9 connected in series, the output of the comparator 30a becomes Low and the potential becomes the ground potential, so that the transistor Q1 of the relay control circuit 13 turns off and the relay 4 is cut off, thereby protecting the circuit downstream of the relay 4 from the overvoltage.

[0031] After the relay 4 is turned off, power supply to the converter circuit 5 of the outdoor unit 3 is cut off and the bus voltage gradually drops. The smoothing capacitor 6 discharges, the bus voltage falls below a predetermined voltage, and the outdoor unit 3 stops functioning. The smoothing capacitor 6 is a bus capacitor.

[0032] At this time, by setting the delay time used by the second delay circuit 31 of the power supply overvoltage detection circuit 12 shorter than the delay time used by the first delay circuit 29 of the busbar overvoltage detection circuit 14 and the cutoff threshold value used by the overvoltage detection unit 30 of the power supply overvoltage detection circuit 12 higher than the cutoff threshold value used by the overvoltage detection unit 28 of the busbar overvoltage detection circuit 14, the converter circuit 5, which is a power supply circuit, can be protected from an overvoltage surge superimposed on the power supply voltage. More specifically, the electronic circuit can be protected from a long-term rise in the power supply voltage that approaches the withstand voltage rating of the circuit components and a rise in the busbar voltage. This makes it possible to reduce the cost of components because it is not necessary to use components with a higher voltage rating than necessary in the electronic circuit of the outdoor unit 3. Therefore, in the first embodiment, the delay time used by the second delay circuit 31 is set shorter than the delay time used by the first delay circuit 29, and the cutoff threshold value used by the overvoltage detection unit 30 is set higher than the cutoff threshold value used by the overvoltage detection unit 28.

[0033] Fig. 5 is a flowchart showing the procedure of the operation performed by the air conditioner 1 according to the first embodiment. Fig. 5 shows the procedure of the operation from detection of an overvoltage to recovery in the first embodiment. The bus voltage detection circuit 7 detects the bus voltage (S1), and the bus overvoltage detection circuit 14 determines whether the bus voltage detected by the bus voltage detection circuit 7 is equal to or higher than the threshold value of the bus overvoltage detection circuit 14 (S2). If the bus overvoltage detection circuit 14 determines that the bus voltage is lower than the threshold value (No in S2), the operation of step S2 is performed, and then the operation of step S1 is performed.

[0034] The relay control unit 17 determines whether or not the bus voltage detected by the bus voltage detection circuit 7 is equal to or higher than the overvoltage protection threshold of the relay control unit 17 (S3). If the relay control unit 17 determines that the bus voltage is lower than the overvoltage protection threshold (No in S3), the operation of step S3 is performed, and then the operation of step S1 is performed.

[0035] The power supply voltage detection circuit 32 detects the power supply voltage (S4), and the power supply overvoltage detection circuit 12 determines whether or not the power supply voltage detected by the power supply voltage detection circuit 32 is equal to or higher than the threshold of the power supply overvoltage detection circuit 12 (S5). If the power supply overvoltage detection circuit 12 determines that the power supply voltage is lower than the threshold (No in S5), the operation of step S5 is performed, and then the operation of step S4 is performed.

[0036] When the bus voltage detected by the bus voltage detection circuit 7 is determined by the bus overvoltage detection circuit 14 to be equal to or higher than the threshold of the bus overvoltage detection circuit 14 (Yes in S2), the comparator 28a outputs a signal indicating Low (S6). When the relay control unit 17 determines that the bus voltage detected by the bus voltage detection circuit 7 is equal to or higher than the overvoltage protection threshold of the relay control unit 17 (Yes in S3), it outputs a signal indicating Low (S7). When the power supply overvoltage detection circuit 12 determines that the power supply voltage detected by the power supply voltage detection circuit 32 is equal to or higher than the threshold of the power supply overvoltage detection circuit 12 (Yes in S5), the comparator 30a outputs a signal indicating Low (S8). After the operation of step S6, step S7 or step S8 is performed, the operation of step S9 is performed.

[0037] In step S9, the relay 4 is turned off. That is, if any of the bus overvoltage detection circuit 14, the relay control unit 17, and the power supply overvoltage detection circuit 12 detects an overvoltage (Yes in S2, S3, S5), the relay 4 is turned off (S9). The relay control unit 17 checks the control state of the relay 4 via the resistor R11, detects that a Low signal has been output from any of the overvoltage protection circuits among the bus overvoltage detection circuit 14, the relay control unit 17, and the power supply overvoltage detection circuit 12 (S6, S7, S8), and outputs a Low signal to maintain the state in which the relay 4 is off (S9). The power supply to the outdoor unit 3 is cut off, and the outdoor unit 3 stops (S10).

[0038] Since power supply to the converter circuit 22 of the indoor unit 2 continues, after a predetermined time has elapsed since the outdoor unit 3 was stopped, the bus voltage detection circuit 24 determines whether the bus voltage is at a normal value (S11). If the bus voltage detection circuit 24 determines that the bus voltage is not at a normal value (No in S11), it performs the operation of step S11. If the bus voltage detection circuit 24 determines that the bus voltage is at a normal value (Yes in S11), the relay 26 is turned on (S12). This starts power supply to the converter circuit 5 of the outdoor unit 3. In other words, the bus voltage is supplied to the outdoor unit 3 (S13).

[0039] After charging of the smoothing capacitor 6, which is the bus capacitor, is completed and the control unit 15 is able to confirm that the bus voltage is at a normal value, the relay 26 is turned off again (S14). The relay 10 is turned on (S15), and a state in which serial communication can be performed is established. Thereafter, the relay control unit 17 outputs an on signal to the relay control circuit 13, which turns the relay 4 on (S16), and the state of the air conditioner 1 transitions to a state in which it operates normally.

[0040] As described above, the delay time used by the second delay circuit 31 of the power supply overvoltage detection circuit 12 is set shorter than the delay time used by the first delay circuit 29 of the busbar overvoltage detection circuit 14, and the cutoff threshold value used by the overvoltage detection unit 30 of the power supply overvoltage detection circuit 12 is set higher than the cutoff threshold value used by the overvoltage detection unit 28 of the busbar overvoltage detection circuit 14, so that the converter circuit 5 can be protected from an overvoltage surge superimposed on the power supply voltage. In addition, the electronic circuit can be protected from a long-term rise in the power supply voltage that approaches the withstand voltage rating of the circuit components, and from a rise in the busbar voltage. This eliminates the need to use components with a higher voltage rating than necessary for the electronic circuit of the outdoor unit 3, so that the cost of components can be reduced. That is, the overvoltage detection circuit according to the first embodiment can protect the power supply circuit from a surge voltage, which is a steep overvoltage superimposed on the power supply voltage, and a long-term rise in the power supply voltage in an area where the power supply voltage is unstable.

[0041] Embodiment 2 The overvoltage detection circuit according to the first embodiment is provided with one each of power supply overvoltage detection circuit 12 and busbar overvoltage detection circuit 14, and protects an electronic circuit from a surge voltage on the power supply system side using power supply overvoltage detection circuit 12 and busbar overvoltage detection circuit 14. FIG. 6 is a diagram showing the configuration of an overvoltage detection circuit according to the second embodiment. As shown in FIG. 6, the overvoltage detection circuit according to the second embodiment has a busbar voltage detection circuit 7, a power supply overvoltage detection circuit 12, n busbar overvoltage detection circuits 14, and a relay 4. n is an integer equal to or greater than 2.

[0042] In the second embodiment, the delay time used by the second delay circuit 31 of the power supply overvoltage detection circuit 12 is t[ac], and the cutoff threshold used by the overvoltage detection unit 30 of the power supply overvoltage detection circuit 12 is Vth[ac]. The delay time used by the first delay circuit 29 of the n-th busbar overvoltage detection circuit 14 among the n busbar overvoltage detection circuits 14 is t[n], and the cutoff threshold used by the overvoltage detection unit 28 of the n-th busbar overvoltage detection circuit 14 is Vth[n]. The delay time used by the first delay circuit 29 of each of the n busbar overvoltage detection circuits 14 is different from the delay time used by the first delay circuit 29 of the other busbar overvoltage detection circuits 14. The cutoff threshold used by the overvoltage detection unit 28 of each of the n busbar overvoltage detection circuits 14 is different from the cutoff threshold used by the overvoltage detection unit 28 of the other busbar overvoltage detection circuits 14.

[0043] The delay time and the cutoff threshold satisfy the following relationship: Delay time: t[ac] <t[n]<t[n-1]、···、t[2]<t[1] Cut-off threshold: Vth[ac]>Vth[n]>Vth[n-1], ... Vth[2]>Vth[1]

[0044] As described above, the overvoltage detection circuit according to the second embodiment has a plurality of bus overvoltage detection circuits 14 that use different delay times and cutoff thresholds, and therefore can protect the circuit from the occurrence of a plurality of overvoltages.

[0045] Fig. 7 is a diagram showing a processor 91 in the case where a part or all of the control unit 15 included in the outdoor unit 3 of the air conditioner 1 according to embodiment 1 is realized by the processor 91. In other words, a part or all of the functions of the control unit 15 may be realized by the processor 91 that executes a program stored in a memory 92. The processor 91 is a CPU (Central Processing Unit), a processing system, an arithmetic system, a microprocessor, or a DSP (Digital Signal Processor). The memory 92 is also shown in Fig. 7.

[0046] When some or all of the functions of control unit 15 are realized by processor 91, the functions are realized by processor 91 and software, firmware, or a combination of software and firmware. The software or firmware is written as a program and stored in memory 92. Processor 91 realizes some or all of the functions of control unit 15 by reading and executing the program stored in memory 92.

[0047] When some or all of the functions of the control unit 15 are realized by the processor 91, the outdoor unit 3 has a memory 92 for storing a program that results in some or all of the steps executed by the control unit 15 being executed. It can also be said that the program stored in the memory 92 causes a computer to execute at least some of the procedures or methods executed by the control unit 15.

[0048] The memory 92 may be, for example, a non-volatile or volatile semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable Read Only Memory), an EEPROM (registered trademark) (Electrically Erasable Programmable Read-Only Memory), a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, or a DVD (Digital Versatile Disk).

[0049] 8 is a diagram showing a processing circuit 93 in a case where a part or all of the control unit 15 included in the outdoor unit 3 of the air conditioner 1 according to embodiment 1 is realized by the processing circuit 93. In other words, a part or all of the control unit 15 may be realized by the processing circuit 93.

[0050] The processing circuit 93 is dedicated hardware, and may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof.

[0051] A part of the control unit 15 may be realized by dedicated hardware separate from the rest of the control unit 15.

[0052] Some of the functions of the control unit 15 may be realized by software or firmware, and the remaining functions may be realized by dedicated hardware. In this way, the functions of the control unit 15 can be realized by hardware, software, firmware, or a combination of these.

[0053] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or the embodiments may be combined with each other. Also, parts of the configurations may be omitted or modified without departing from the spirit of the invention. [Explanation of symbols]

[0054] 1 air conditioner, 2 indoor unit, 3 outdoor unit, 4, 10, 26 relay, 4a coil section, 5 converter circuit, 6 smoothing capacitor, 7 bus voltage detection circuit, 8 inverter circuit, 9 compressor, 11 serial communication circuit, 12 power supply overvoltage detection circuit, 13 relay control circuit, 14 bus overvoltage detection circuit, 15 control section, 16 converter control section, 17 relay control section, 18 inverter control section, 19 current detection circuit, 20, 21 terminal block, 22 converter circuit, 23 smoothing capacitor, 24 bus voltage detection circuit, 25 indoor unit control circuit, 27 serial communication circuit, 28 overvoltage detection section, 28a, 30a comparator, 28b comparator power supply voltage, 28c pull-up voltage, 29 first delay circuit, 30 overvoltage detection section, 30b comparator power supply voltage, 30c pull-up voltage, 31 second delay circuit, 32 Power supply voltage detection circuit, 50 AC power supply, 51 rectifier circuit, 52 power factor correction circuit, 91 processor, 92 memory, 93 processing circuit, C1, C2, C3, C4 capacitors, D1, D2, D3 diodes, Q1 transistor, R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R15 resistors.

Claims

1. A bus voltage detection circuit for detecting a bus voltage; a first delay circuit that delays the bus voltage detected by the bus voltage detection circuit by a first delay time; a first comparator that compares the bus voltage delayed by the first delay circuit with a first shutoff threshold and outputs a first comparison result; a power supply voltage detection circuit for detecting a power supply voltage; a second delay circuit that delays the power supply voltage detected by the power supply voltage detection circuit by a second delay time; a second comparison unit that compares the power supply voltage delayed by the second delay circuit with a second cutoff threshold and outputs a second comparison result; a relay that switches on and off the reception of power from an AC power source to the outdoor unit based on the first comparison result output from the first comparison unit and the second comparison result output from the second comparison unit, the first comparator outputs the first comparison result indicating low when the bus voltage is equal to or higher than the first shutoff threshold; the second comparator outputs the second comparison result indicating low when the power supply voltage is equal to or higher than the second cut-off threshold; the relay turns off the reception of power from the AC power supply to the outdoor unit when the first comparison unit outputs the first comparison result indicating the low level, or when the second comparison unit outputs the second comparison result indicating the low level, the first delay time is longer than the second delay time; The first cut-off threshold is lower than the second cut-off threshold. Overvoltage detection circuit.

2. the first delay circuit includes a first resistor and a first capacitor; the second delay circuit includes a second resistor and a second capacitor; The capacitance value of the first capacitor is greater than the capacitance value of the second capacitor.

2. The overvoltage detection circuit according to claim 1.

3. a relay control circuit that switches on and off the reception of power from the AC power source; a control unit that outputs a switching determination signal regarding a switching determination of ON / OFF of the relay control circuit based on the bus voltage detected by the bus voltage detection circuit, The relay control circuit has a driving transistor that drives the relay based on the first comparison result, the second comparison result, and the switching determination signal.

3. The overvoltage detection circuit according to claim 1 or 2.

4. The control unit has a function of detecting an on / off state of the relay control circuit, The output of the first comparison unit, the output of the second comparison unit, and the output of the control unit are connected to a base terminal of the driving transistor.

4. The overvoltage detection circuit according to claim 3.

5. n bus overvoltage detection circuits; a power supply voltage detection circuit for detecting a power supply voltage; a second delay circuit that delays the power supply voltage detected by the power supply voltage detection circuit by a predetermined delay time; a second comparison unit that compares the power supply voltage delayed by the second delay circuit with a second cutoff threshold and outputs a second comparison result; A relay. n is an integer of 2 or more, Each of the n bus overvoltage detection circuits A bus voltage detection circuit for detecting a bus voltage; a first delay circuit that delays the bus voltage detected by the bus voltage detection circuit by a predetermined delay time; a first comparison unit that compares the bus voltage delayed by the first delay circuit with a first cutoff threshold and outputs a first comparison result; the relay switches on and off reception of power from an AC power source to the outdoor unit based on the first comparison result output from the first comparison unit and the second comparison result output from the second comparison unit included in each of the n bus overvoltage detection circuits, the first comparator outputs the first comparison result indicating low when the bus voltage is equal to or higher than the first shutoff threshold; the second comparator outputs the second comparison result indicating low when the power supply voltage is equal to or higher than the second cut-off threshold; the relay turns off the reception of power from the AC power supply to the outdoor unit when the first comparison unit outputs the first comparison result indicating the low level, or when the second comparison unit outputs the second comparison result indicating the low level, a delay time used by the second delay circuit is defined as t[ac], a cutoff threshold used by the second comparison unit is defined as Vth[ac], a delay time used by the first delay circuit included in an n-th bus overvoltage detection circuit among the n bus overvoltage detection circuits is defined as t[n], and a cutoff threshold used by the first comparison unit included in an n-th bus overvoltage detection circuit among the n bus overvoltage detection circuits is defined as Vth[n], The delay time is t[ac]<t[n]<t[n-1],..., t[2]<t[1] Fulfilling the relationship, The cutoff threshold is Vth[ac]>Vth[n]>Vth[n-1],...Vth[2]>Vth[1] Satisfying the relationship Overvoltage detection circuit.

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