CN111351979A - Overcurrent detection circuit, overcurrent protection device, circuit board and air conditioner - Google Patents
Overcurrent detection circuit, overcurrent protection device, circuit board and air conditioner Download PDFInfo
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- CN111351979A CN111351979A CN202010307725.0A CN202010307725A CN111351979A CN 111351979 A CN111351979 A CN 111351979A CN 202010307725 A CN202010307725 A CN 202010307725A CN 111351979 A CN111351979 A CN 111351979A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/165—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
- F24F11/00—Control or safety arrangements
- F24F11/62—Control or safety arrangements characterised by the type of control or by internal processing, e.g. using fuzzy logic, adaptive control or estimation of values
- F24F11/63—Electronic processing
- F24F11/64—Electronic processing using pre-stored data
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
- F24F11/00—Control or safety arrangements
- F24F11/88—Electrical aspects, e.g. circuits
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/08—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current
Abstract
The invention discloses an overcurrent detection circuit, an overcurrent protection device, a circuit board and an air conditioner, wherein the overcurrent detection circuit comprises a sampling circuit, a first voltage regulating circuit, a second voltage regulating circuit and a comparison circuit, the comparison circuit comprises a first comparator and a second comparator, the first voltage regulating output end is connected with the in-phase input end of the first comparator, the sampling output end is connected with the reverse-phase input end of the first comparator, the second voltage regulating output end is connected with the reverse-phase input end of the second comparator, the sampling output end is connected with the in-phase input end of the second comparator, and the output ends of the first comparator and the second comparator are both connected to a controller to output comparison results; the sampling voltage is respectively compared with the first reference voltage and the second reference voltage through the comparison circuit, whether the sampling voltage exceeds an overcurrent threshold value is detected, and the first reference voltage and the second reference voltage can be adjusted according to signals of the controller, so that the circuit is suitable for different circuit scenes.
Description
Technical Field
The invention relates to the technical field of electronic circuits, in particular to an overcurrent detection circuit, an overcurrent protection device, a circuit board and an air conditioner.
Background
The overcurrent protection circuit is widely applied to various electric devices and is used for protecting working circuits in the electric devices. When the current at the detection position is suddenly increased, the overcurrent protection circuit can be triggered to stop the operation of the working circuit, so that the damage of components in the circuit is prevented, and the protection effect is achieved.
At present, an overcurrent protection circuit samples a direct-current electric signal and cannot sample a circuit before rectification, for example, in electric equipment with a PFC circuit, the overcurrent protection circuit can only be arranged at the rear-stage output of the PFC circuit, and if the PFC circuit is interfered and the output is abnormal, the overcurrent protection circuit cannot protect components in the PFC circuit, so that the electric equipment cannot work; in addition, for the condition that the frequency conversion electric equipment switches the circuit in the working process, the current overcurrent protection circuit cannot adjust the overcurrent threshold value of the current overcurrent protection circuit, and has certain limitation; therefore, the current overcurrent protection circuit needs to be designed for different electric devices, and is time-consuming and labor-consuming.
Disclosure of Invention
The present invention is directed to solving at least one of the problems of the prior art. Therefore, the invention provides an overcurrent detection circuit, an overcurrent protection device, a circuit board and an air conditioner, which can sample direct current or alternating current voltage and output an overcurrent protection signal, can adjust the overcurrent threshold value of the circuit board according to a control signal, and are suitable for different circuit scenes.
According to an embodiment of the first aspect of the invention, the overcurrent detection circuit comprises:
the sampling circuit comprises a sampling output end for outputting sampling voltage;
the first voltage regulating circuit comprises a first voltage regulating receiving terminal and a first voltage regulating output terminal, wherein the first voltage regulating receiving terminal is used for receiving a first voltage regulating signal sent by the controller, and the first voltage regulating output terminal is used for outputting a first reference voltage based on the first voltage regulating signal;
the second voltage regulating circuit comprises a second voltage regulating receiving end and a second voltage regulating output end, the second voltage regulating receiving end is used for receiving a second voltage regulating signal sent by the controller, and the second voltage regulating output end is used for outputting a second reference voltage based on the second voltage regulating signal;
the comparison circuit comprises a first comparator and a second comparator, wherein the first voltage regulating output end is connected with the non-inverting input end of the first comparator, the sampling output end is connected with the inverting input end of the first comparator, the second voltage regulating output end is connected with the inverting input end of the second comparator, the sampling output end is connected with the non-inverting input end of the second comparator, and the output end of the first comparator and the output end of the second comparator are both connected to the controller to output a comparison result.
The over-current detection circuit according to the embodiment of the first aspect of the invention has at least the following beneficial effects: the sampling circuit samples and outputs sampling voltage, the sampling voltage is respectively compared with first reference voltage and second reference voltage through a first comparator and a second comparator, and whether the sampling voltage exceeds an overcurrent threshold value is detected; when the sampling voltage is the alternating-current voltage, the first comparator compares the positive voltage of the alternating-current sampling voltage, the second comparator compares the negative voltage of the alternating-current sampling voltage, and when the sampling voltage is the direct-current voltage, the first comparator directly compares the sampling voltage with the alternating-current sampling voltage; in addition, the first reference voltage and the second reference voltage can be adjusted according to signals of the controller, and the over-current detection circuit can adaptively change an over-current threshold value under the condition that part of variable-frequency electric equipment switches circuits in the working process; therefore, the over-current detection circuit is suitable for different circuit scenes.
According to some embodiments of the first aspect of the present invention, the first voltage regulating circuit comprises a first switching device and a first oscillating circuit, the first switching device comprises a first terminal connected to a direct current source, a second terminal connected to a reference ground, and a third terminal for controlled switching of the first switching device, the first oscillating circuit is connected in parallel with the first switching device, and a voltage output terminal of the first oscillating circuit is connected to the first voltage regulating output terminal.
According to some embodiments of the first aspect of the present invention, the first voltage regulating circuit further comprises a first voltage follower, and the voltage output terminal of the first oscillating circuit is connected to the first voltage regulating output terminal through the first voltage follower.
According to some embodiments of the first aspect of the present invention, the second voltage regulating circuit comprises a second switching device and a second oscillating circuit, the second switching device comprises a second terminal connected to the dc source, a second terminal connected to the reference ground, and a third terminal for controlled switching of the second switching device, the second oscillating circuit is connected in parallel with the second switching device, and a voltage output terminal of the second oscillating circuit is connected to the second voltage regulating output terminal.
According to some embodiments of the first aspect of the present invention, the second voltage regulating circuit further comprises a second voltage follower, and the voltage output terminal of the second oscillating circuit is connected to the second voltage regulating output terminal through the second voltage follower.
According to some embodiments of the first aspect of the present invention, the first voltage regulation signal and the second voltage regulation signal are PWM signals.
According to some embodiments of the first aspect of the present invention, the first reference voltage is greater than the second reference voltage.
According to some embodiments of the first aspect of the present invention, the comparison circuit further comprises a ninth resistor, a tenth resistor, and a constant voltage port for adjusting a voltage of the sampling output terminal, the sampling output terminal is connected to the inverting input terminal of the first comparator and the non-inverting input terminal of the second comparator through the ninth resistor, and the constant voltage port is connected to the inverting input terminal of the first comparator and the non-inverting input terminal of the second comparator through the tenth resistor.
According to some embodiments of the first aspect of the present invention, the sampling circuit further comprises at least one sampling input for acquiring the electrical signal.
According to some embodiments of the first aspect of the present invention, the sampling circuit further includes a sampling operational amplifier, the first sampling end is connected to a non-inverting input end of the sampling operational amplifier, the second sampling end is connected to an inverting input end of the sampling operational amplifier, and an output end of the sampling operational amplifier is connected to the sampling output end.
The overcurrent protection device according to the second aspect of the invention includes a controller, a PFC circuit, and the overcurrent detection circuit according to any one of the first aspect of the invention, the controller outputting a PWM signal to the PFC circuit to control an operating state of the PFC circuit, the sampling circuit connecting an ac input of the PFC circuit to sample an electrical signal and output an ac sampled voltage, and the controller maintaining or stopping the operation of the PFC circuit according to a comparison result output by the comparison circuit.
The overcurrent protection device according to the embodiment of the second aspect of the invention has at least the following beneficial effects: the over-current detection circuit is applied to the PFC circuit and samples an alternating-current input signal of the PFC circuit, meanwhile, a comparison result of the over-current detection circuit is sent to the controller, the controller controls the working state of the PFC circuit according to the comparison result, and when the PFC circuit is interfered, the current at the alternating-current input end is suddenly increased.
A wiring board according to an embodiment of the third aspect of the present invention comprises the overcurrent detection circuit according to any one of the embodiments of the first aspect of the present invention;
alternatively, the first and second electrodes may be,
the overcurrent protection device comprises the overcurrent protection device according to the embodiment of the second aspect of the invention.
The circuit board according to the embodiment of the third aspect of the invention has at least the following beneficial effects: the overcurrent detection circuit or the overcurrent protection device comprising the overcurrent detection circuit is integrated on a circuit board, so that the overcurrent protection device can be conveniently installed on different electric equipment; when the sampling voltage is the alternating-current voltage, the first comparator compares the positive voltage of the alternating-current sampling voltage, the second comparator compares the negative voltage of the alternating-current sampling voltage, and when the sampling voltage is the direct-current voltage, the first comparator directly compares the sampling voltage with the alternating-current sampling voltage; in addition, the first reference voltage and the second reference voltage can be adjusted according to signals of the controller, and the over-current detection circuit can adaptively change an over-current threshold value under the condition that part of variable-frequency electric equipment switches circuits in the working process; therefore, the over-current detection circuit is suitable for different circuit scenes.
An air conditioner according to a fourth aspect embodiment of the present invention includes the wiring board according to the third aspect embodiment of the present invention.
According to the air conditioner of the fourth aspect of the invention, at least the following advantages are achieved: the over-current detection circuit is applied to the air conditioner, and can adaptively adjust the over-current threshold value according to the condition that the air conditioner switches the working circuit in the working process, so as to adapt to different working frequencies of the air conditioner.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
fig. 1 is a circuit diagram of a sampling circuit and a PFC circuit of an over-current detection circuit according to an embodiment of the present invention;
fig. 2 is a circuit diagram of a first voltage regulating circuit and a second voltage regulating circuit of the over-current detection circuit according to an embodiment of the present invention;
fig. 3 is a circuit diagram of a comparison circuit of the over-current detection circuit according to an embodiment of the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.
In the description of the present invention, the meaning of a plurality of means is one or more, the meaning of a plurality of means is two or more, and larger, smaller, larger, etc. are understood as excluding the number, and larger, smaller, inner, etc. are understood as including the number. If the first and second are described for the purpose of distinguishing technical features, they are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of the technical features indicated.
In the description of the present invention, unless otherwise explicitly limited, terms such as arrangement, installation, connection and the like should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above terms in the present invention in combination with the specific contents of the technical solutions.
The current overcurrent protection circuit judges whether the circuit of a sampling object has overcurrent or not based on direct current sampling and comparing the direct current voltage obtained by sampling with a reference voltage, but the circuit cannot be suitable for different electric equipment; the current overcurrent protection circuit needs to be designed independently aiming at different electric equipment, a large amount of time is spent on design and debugging, the production period of the electric equipment is prolonged, the cost is increased, and the development of a new product is not facilitated; therefore, the current overcurrent protection circuit still needs to be improved.
Based on the over-current detection circuit, the over-current protection device, the circuit board and the air conditioner, on one hand, the over-current detection circuit can be connected into a direct current or alternating current circuit for sampling, on the other hand, on the premise that circuit components are not replaced, a control signal is sent out through the controller to change reference voltage, and the over-current threshold value of the circuit is adjusted, so that the over-current detection circuit can be suitable for different circuit scenes.
The embodiments of the present invention will be further explained with reference to the drawings.
Referring to fig. 1 to 3, an over-current detection circuit provided in a first aspect of an embodiment of the present invention includes:
a sampling circuit 100 including a sampling output terminal for outputting a sampling voltage;
the first voltage regulating circuit 200 comprises a first voltage regulating receiving terminal and a first voltage regulating output terminal, wherein the first voltage regulating receiving terminal is used for receiving a first voltage regulating signal sent by the controller 400, and the first voltage regulating output terminal is used for outputting a first reference voltage VrefA based on the first voltage regulating signal;
the second voltage regulating circuit 300 includes a second voltage regulating receiving terminal and a second voltage regulating output terminal, the second voltage regulating receiving terminal is configured to receive a second voltage regulating signal sent by the controller 400, and the second voltage regulating output terminal is configured to output a second reference voltage VrefB based on the second voltage regulating signal;
the comparison circuit comprises a first comparator U3 and a second comparator U4, wherein the first voltage regulating output end is connected with a non-inverting input end of the first comparator U3, the sampling output end is connected with an inverting input end of the first comparator U3, the second voltage regulating output end is connected with an inverting input end of the second comparator U4, the sampling output end is connected with a non-inverting input end of the second comparator U4, and the output end of the first comparator U3 and the output end of the second comparator U4 are both connected to a controller 400 to output a comparison result.
The comparison circuit in this embodiment is provided with a first comparator U3 and a second comparator U4, and can be adapted to the situation that the sampling output end outputs an alternating voltage, and since the alternating voltage outputs a negative voltage in a negative half period and cannot be directly input into the comparator, a constant voltage port V0 is provided to pull up the voltage at the sampling output end, so that the voltage input to the inverting input end of the first comparator U3 and the non-inverting input end of the second comparator U4 is greater than 0, and the first comparator U3 and the second comparator U4 can perform comparison of positive voltages. Specifically, referring to fig. 3, the comparison circuit further includes a ninth resistor R9, a tenth resistor R10, and a constant voltage port V0 for adjusting a voltage of a sampling output terminal, the sampling output terminal is connected to an inverting input terminal of the first comparator U3 and a non-inverting input terminal of the second comparator U4 through the ninth resistor R9, and the constant voltage port V0 is connected to the inverting input terminal of the first comparator U3 and the non-inverting input terminal of the second comparator U4 through the tenth resistor R10. According to circuit analysis, the resistance value of the ninth resistor R9 and the resistance value of the tenth resistor R10 influence the voltage values input to the inverting input terminal of the first comparator U3 and the non-inverting input terminal of the second comparator U4, for example, when the resistance values of the ninth resistor R9 and the tenth resistor R10 are equal, the value of the P-point voltage is equal to half of the sum of the voltage of the constant voltage port V0 and the voltage of the sampling output terminal.
The sampling circuit 100 in this embodiment may sample a dc line or an ac line, the sampling circuit 100 further includes at least one sampling input terminal, configured to obtain an electrical signal, if the number of the sampling input terminals is one, the sampling input terminal may be connected to a voltage-dividing dc circuit to obtain a dc voltage, or the sampling input terminal may be connected to an ac circuit to obtain an ac current or an ac voltage, if the number of the sampling input terminals is two, the sampling input terminals are respectively a first sampling terminal and a second sampling terminal, at this time, the sampling circuit 100 further includes a sampling op amp U5, the first sampling terminal is connected to a non-inverting input terminal of the sampling op amp U5, the second sampling terminal is connected to an inverting input terminal of the sampling op amp U5, an output terminal of the sampling op amp U5 is connected to the sampling output terminal, and a characteristic that a voltage drop exists between two ends of the sampling resistor R0 is utilized, the first and second sampling terminals provide different voltage inputs to the sample op-amp U5. Obviously, the case that the number of sampling input end is two can also be sampled direct current circuit or alternating current circuit, when sampling direct current circuit, only first sampling end is connected to direct current circuit, the second sampling end is unsettled, sampling fortune is put ware U5 and is equivalent to a voltage follower this moment, output direct current voltage, when sampling alternating current circuit, first sampling end, second sampling end and sampling resistance R0 all insert on same alternating current circuit, thereby obtain two different voltages at two inputs of sampling fortune ware U5, therefore sampling circuit 100 can be to sampling direct current circuit or alternating current circuit, have the commonality.
The sampling operational amplifier U5 can be a differential operational amplifier, which can linearly scale down the voltage, reduce the common-mode signal interference, improve the accuracy of the sampling voltage, and realize the accurate control.
In an embodiment, referring to fig. 1, the non-inverting input terminal of the sampling and operational amplifier U5 is connected in series with an eleventh resistor R11, the inverting input terminal is connected in series with a twelfth resistor R12, the sampling and operational amplifier U5 further includes a thirteenth resistor R13 and a fourteenth resistor R14, wherein one end of the thirteenth resistor R13 is connected to a connection point of the eleventh resistor R11 and the non-inverting input terminal of the sampling and operational amplifier U5, the other end of the thirteenth resistor R13 is connected to the reference ground, one end of the fourteenth resistor R14 is connected to a connection point of the twelfth resistor R12 and the inverting input terminal of the sampling and operational amplifier U5, and the other end of the fourteenth resistor R14 is connected to the output terminal of the sampling and operational amplifier U5. By adjusting the resistance values of the eleventh resistor R11, the twelfth resistor R12, the thirteenth resistor R13 and the fourteenth resistor R14, the output voltage of the sampling operational amplifier U5 can be adjusted, so that the voltage output amplitude of the sampling output end is adjusted, and the voltage output amplitude is matched with the voltage of the constant voltage port V0 conveniently.
In an embodiment, referring to fig. 2, the first voltage regulating circuit 200 includes a first switching device Q1 and a first oscillating circuit, the first switching device Q1 includes a first terminal connected to a dc source, a second terminal connected to a ground reference, and a third terminal for controlled switching of the first switching device Q1, the first oscillating circuit is connected in parallel with the first switching device Q1, and a voltage output terminal of the first oscillating circuit is connected to the first voltage regulating output terminal. The second voltage regulating circuit 300 comprises a second switching device Q2 and a second oscillating circuit, the second switching device Q2 comprises a second end connected with a direct current source, a second end connected with a reference ground and a third end used for being controlled to open and close the second switching device Q2, the third end is connected with a second voltage regulating receiving end, the second oscillating circuit is connected with the second switching device Q2 in parallel, and the voltage output end of the second oscillating circuit is connected with the second voltage regulating output end.
The first switching device Q1 and the second switching device Q2 of the present embodiment have a function of controlled on and off, the voltage regulation device can be selected from switching devices such as a triode, an MOS tube and the like, in order to realize voltage regulation, the first voltage regulation signal and the second voltage regulation signal are both PWM signals, by outputting the first reference voltage VrefA and the second reference voltage VrefB through the first oscillation circuit and the second oscillation circuit, it is apparent that the duty ratios of the first voltage regulation signal and the second voltage regulation signal are controlled, the magnitudes of the first reference voltage VrefA and the second reference voltage VrefB may be changed, for example, the dc source is 3V, then at a duty cycle of 0, the first reference voltage VrefA and the second reference voltage VrefB are both 3V, when the duty ratio is 1, the first reference voltage VrefA and the second reference voltage VrefB are both 0, and when the duty ratio is between 0 and 1, the first reference voltage VrefA and the second reference voltage VrefB are between 3V and 0. It is noted that, since the comparison circuit is to compare the positive voltage and the negative voltage, the first reference voltage VrefA is larger than the second reference voltage VrefB, that is, the PWM waveform of the first voltage regulation signal is different from the PWM waveform of the second voltage regulation signal.
The first oscillation circuit and the second oscillation circuit have various embodiments, for example, the first oscillation circuit includes a first resistor R1 and a first capacitor C1, a first end of a first switching device Q1, a first resistor R1, a first capacitor C1 and a reference ground are sequentially connected, a connection point between the first resistor R1 and the first capacitor C1 is connected to a first voltage regulation output terminal, the second oscillation circuit includes a second resistor R2 and a second capacitor C2, a second end of a second switching device Q2, a second resistor R2, a second capacitor C2 and the reference ground are sequentially connected, and a connection point between the second resistor R2 and the second capacitor C2 is connected to the second voltage regulation output terminal; for another example, the first oscillation circuit and the second oscillation circuit adopt LC circuits, and the voltage regulation function may also be realized based on the PWM signal, which is not described herein again.
Although the first voltage regulating circuit 200 and the second voltage regulating circuit 300 of the above embodiment adopt the same circuit connection manner, they are independently arranged, that is, when the first voltage regulating circuit 200 adopts the above circuit structure, the second voltage regulating circuit 300 can adopt different circuit structures for voltage regulation, for example, the second voltage regulating circuit 300 can adopt an electronic digital rheostat for voltage regulation, a plurality of resistors are connected in series inside the electronic digital rheostat, a switch is led out at a connection point between the two resistors, and the total resistance value on a series branch can be adjusted by opening and closing the switches, thereby realizing voltage regulation; similarly, in the case that the second voltage regulating circuit 300 adopts the above circuit structure, the first voltage regulating circuit 200 may adopt different circuit structures for voltage regulation; the voltage regulation is realized in many ways, which are not listed here. It can be understood that the reference voltage can be continuously adjusted by adopting the PWM signal for voltage regulation, and compared with a step-by-step adjustable voltage regulation mode, the precision of the overcurrent detection circuit can be improved.
Based on the above embodiment, referring to fig. 2, the first voltage regulating circuit 200 further includes a first voltage follower U1, and a connection point of the first resistor R1 and the first capacitor C1 is connected to the first voltage regulating output terminal through the first voltage follower U1. The second voltage regulating circuit 300 further comprises a second voltage follower U2, and a connection point of the second resistor R2 and the second capacitor C2 is connected to the second voltage regulating output terminal through the second voltage follower U2. Since the PWM signals for voltage regulation in the first voltage regulating circuit 200 and the second voltage regulating circuit 300 are irrelevant to the circuit of the protection object, in order to isolate signal interference, a voltage follower is used for isolation, and output values of the first reference voltage VrefA and the second reference voltage VrefB are stabilized at the same time.
The following explains the working mode of the over-current detection circuit under the dc sampling by taking the sampling voltage as the dc voltage as an example: the voltage of the sampling output end is direct-current voltage, namely Vout is always greater than 0, then the sampling output end is simultaneously added to the inverting input end of the first comparator U3 through a ninth resistor R9 and a constant-voltage port V0 through a tenth resistor R10, because the constant-voltage port V0 is constant-voltage, the voltage of a point P is positively correlated with the voltage of the sampling input end, a first voltage-regulating signal is set to regulate a first reference voltage VrefA, and the first reference voltage VrefA is not higher than the highest voltage allowed by the point P in a normal working state; when the circuit of the protection object is in a normal working state, the voltage of the inverting input end of the first comparator U3 is not higher than the voltage of the non-inverting input end, therefore, the first comparator U3 outputs a high level, the controller 400 judges that the circuit works normally when receiving a high level signal, when the circuit of the protection object is abnormal, the voltage of the inverting input end of the first comparator U3 is higher than the voltage of the non-inverting input end, the first comparator U3 outputs a low level, and the controller 400 judges that the circuit is abnormal through the low level and makes a protection action.
It can be understood that, since the dc sampling only needs to sample a single voltage point in the dc line, the sampling circuit 100 can only access the circuit with one sampling input terminal, and the second comparator U4 in the comparator circuit does not need to perform the comparison, the second comparator U4 can be bypassed, or the second reference voltage VrefB is lowered to maintain the output high level of the second comparator U4.
The working mode of the over-current detection circuit under the dc sampling is described below by taking the sampling voltage as the ac voltage as an example: the sampling resistor R0 is connected in series in an alternating current line, the first sampling end and the second sampling end are respectively connected to two ends of the sampling resistor R0, at this time, the output end of the sampling operational amplifier U5 outputs positive voltage and negative voltage following the period of the alternating current, namely, in the positive half period of the alternating current, the sampling operational amplifier U5 outputs positive voltage, in the negative half period of the alternating current, the sampling operational amplifier U5 outputs negative voltage, taking the resistance values of the ninth resistor R9 and the tenth resistor R10 as an example, in order to make the P point voltage be greater than 0, the voltage value of the constant voltage port V0 is greater than the minimum value of the negative voltage of the sampling output end, for example, the constant voltage port V0 is a 3V constant voltage source, the resistance around the sampling operational amplifier U5 is adjusted, the minimum value of the negative voltage of the sampling output end is greater than-3V, meanwhile, the first reference voltage Vrefa is set to be greater than the second reference voltage, and the first reference voltage is slightly greater than the maximum value of the P point voltage, the second reference voltage VrefB is slightly smaller than the minimum value of the P-point voltage of the circuit for protecting the object in the normal operation state, when the circuit for protecting the object is in the normal operation state, the P-point voltage is lower than the first reference voltage VrefA and higher than the second reference voltage VrefB in the positive half period of the alternating current, the first comparator U3 and the second comparator U4 both output a high level, and in the negative half period of the alternating current, similarly, the P-point voltage is lower than the first reference voltage VrefA and higher than the second reference voltage VrefB, the first comparator U3 and the second comparator U4 both output a high level, and at this time, the controller 400 determines that the circuit is operating normally when receiving a high level signal; when the circuit of the protection object is abnormal, the voltage at the point P is higher than the first reference voltage VrefA in the positive half period of the alternating current, the first comparator U3 outputs a low level, or the voltage at the point P is lower than the second reference voltage VrefB in the negative half period of the alternating current, the second comparator U4 outputs a low level, and the controller 400 judges the circuit is abnormal by the low level and performs a protection action.
The overcurrent detection circuit provided by the embodiment of the invention can be applied no matter whether the sampled voltage is direct current voltage or alternating current voltage; on the other hand, since the first reference voltage VrefA and the second reference voltage VrefB can both change the voltage value by voltage regulation on the premise of not replacing components, the voltage value has good adaptability to the situation that the overcurrent threshold value changes due to the switching of the circuit in the frequency conversion equipment, for example, when the circuit in the frequency conversion equipment is switched, the controller 400 obtains the circuit corresponding to the switched circuit, and changes the first voltage regulation signal and the second voltage regulation signal according to the preset overcurrent threshold value of the switched circuit, so that the first reference voltage VrefA and the second reference voltage VrefB change to adapt to the switched circuit. Therefore, the over-current detection circuit is suitable for different circuit scenes.
A second aspect of the embodiments of the present invention provides an overcurrent protection apparatus, including a controller 400, a PFC circuit 500 and an overcurrent detection circuit as in any one of the first aspects, where the controller 400 outputs a PWM signal to the PFC circuit 500 to control an operating state of the PFC circuit 500, the sampling circuit 100 is connected to an ac input of the PFC circuit 500 to sample an electrical signal and output an ac sampled voltage, and the controller 400 maintains or stops the PFC circuit 500 according to a comparison result output by the comparison circuit.
The PFC circuit 500 in this embodiment is a vienna rectification circuit, the pre-stage input is an ac input, wherein the PFC circuit 500 includes a PFC signal input terminal connected to the controller 400, the PFC signal input terminal is used to control on/off of the third switching tube Q3 and the fourth switching tube Q4, and the controller 400 can stop the operation of the PFC circuit 500 by stopping the PWM signal output, thereby preventing the PFC circuit 500 from being damaged by overcurrent; wherein, the sampling resistor R0 is arranged before the PFC circuit 500 for sampling before rectification, in this embodiment, the sampling resistor R0 is connected in series to the live wire, according to the voltage drop relationship between the two ends of the sampling resistor R0, the sampling operational amplifier U5 outputs a positive voltage in the positive half cycle of the ac power and outputs a negative voltage in the negative half cycle of the ac power, the controller 400 is set to receive a low level signal and determine that an overcurrent occurs in the circuit, according to the content of the overcurrent determination on the ac voltage in the first aspect of the embodiment, when the PFC circuit 500 operates normally, the controller 400 receives a high level output by the comparison circuit, the controller 400 keeps outputting a PWM signal to the PFC circuit 500, when the PFC circuit 500 is abnormal, for example, the current of the first inductor rises suddenly, the controller 400 receives a low level output by the comparison circuit, the controller 400 performs a wave-sealing operation to disconnect the PWM signal to the PFC circuit 500, preventing the PFC circuit 500 from being damaged.
A third aspect of the embodiments of the present invention provides a circuit board, including the overcurrent detection circuit according to the first aspect of the embodiments, or including the overcurrent protection device according to the second aspect of the embodiments. The overcurrent detection circuit or the overcurrent protection device comprising the overcurrent detection circuit is integrated on a circuit board, so that the overcurrent protection device can be conveniently installed on different electric equipment, a sampling circuit 100 in the overcurrent detection circuit samples and outputs sampling voltage, the sampling voltage is respectively compared with a first reference voltage VrefA and a second reference voltage VrefB through a first comparator U3 and a second comparator U4, and whether the sampling voltage exceeds an overcurrent threshold value is detected; when the sampling voltage is an alternating current voltage, the first comparator U3 compares the positive voltage of the alternating current sampling voltage, the second comparator U4 compares the negative voltage of the alternating current sampling voltage, and when the sampling voltage is a direct current voltage, the first comparator U3 directly compares the sampling voltage; in addition, the first reference voltage VrefA and the second reference voltage VrefB can be adjusted according to signals of the controller 400, and the over-current detection circuit can adaptively change an over-current threshold value for the condition that part of the variable-frequency electric equipment switches circuits in the working process; therefore, the over-current detection circuit is suitable for different circuit scenes.
A fourth aspect of the embodiments of the present invention provides an air conditioner, including the circuit board of the third aspect. The over-current detection circuit is applied to the air conditioner, and can adaptively adjust the over-current threshold value according to the condition that the air conditioner switches the working circuit in the working process, so as to adapt to different working frequencies of the air conditioner.
While the preferred embodiments of the present invention have been described in detail, it will be understood by those skilled in the art that the foregoing and various other changes, omissions and deviations in the form and detail thereof may be made without departing from the scope of this invention.
Claims (13)
1. An over-current detection circuit, comprising:
the sampling circuit comprises a sampling output end for outputting sampling voltage;
the first voltage regulating circuit comprises a first voltage regulating receiving terminal and a first voltage regulating output terminal, wherein the first voltage regulating receiving terminal is used for receiving a first voltage regulating signal sent by the controller, and the first voltage regulating output terminal is used for outputting a first reference voltage based on the first voltage regulating signal;
the second voltage regulating circuit comprises a second voltage regulating receiving end and a second voltage regulating output end, the second voltage regulating receiving end is used for receiving a second voltage regulating signal sent by the controller, and the second voltage regulating output end is used for outputting a second reference voltage based on the second voltage regulating signal;
the comparison circuit comprises a first comparator and a second comparator, wherein the first voltage regulating output end is connected with the non-inverting input end of the first comparator, the sampling output end is connected with the inverting input end of the first comparator, the second voltage regulating output end is connected with the inverting input end of the second comparator, the sampling output end is connected with the non-inverting input end of the second comparator, and the output end of the first comparator and the output end of the second comparator are both connected to the controller to output a comparison result.
2. The overcurrent detection circuit as recited in claim 1, wherein the first voltage regulation circuit comprises a first switching device and a first oscillating circuit, the first switching device comprises a first terminal connected to a dc source, a second terminal connected to a reference ground, and a third terminal for controlled switching of the first switching device, the first oscillating circuit is connected in parallel with the first switching device, and a voltage output terminal of the first oscillating circuit is connected to the first voltage regulation output terminal.
3. The over-current detection circuit of claim 2, wherein the first voltage regulator circuit further comprises a first voltage follower, and wherein the voltage output of the first oscillator circuit is coupled to the first voltage regulator output via the first voltage follower.
4. The overcurrent detection circuit as recited in claim 1 or 2, wherein the second voltage regulation circuit comprises a second switching device and a second oscillating circuit, the second switching device comprises a second terminal connected with a direct current source, a second terminal connected with a reference ground and a third terminal for controlled switching on and off of the second switching device, the second oscillating circuit is connected with the second switching device in parallel, and a voltage output terminal of the second oscillating circuit is connected with the second voltage regulation output terminal.
5. The over-current detection circuit of claim 4, wherein the second voltage regulator circuit further comprises a second voltage follower, and wherein the voltage output of the second oscillating circuit is coupled to the second voltage regulator output via the second voltage follower.
6. The over-current detection circuit of claim 1, wherein the first and second voltage regulation signals are PWM signals.
7. The over-current detection circuit according to claim 1, wherein the first reference voltage is greater than the second reference voltage.
8. The over-current detection circuit according to claim 1, wherein the comparison circuit further comprises a ninth resistor, a tenth resistor, and a constant voltage port for adjusting a voltage of the sampling output terminal, the sampling output terminal is connected to the inverting input terminal of the first comparator and the non-inverting input terminal of the second comparator through the ninth resistor, and the constant voltage port is connected to the inverting input terminal of the first comparator and the non-inverting input terminal of the second comparator through the tenth resistor.
9. The over-current detection circuit of claim 1, wherein the sampling circuit further comprises at least one sampling input for obtaining an electrical signal.
10. The over-current detection circuit according to claim 9, wherein the number of the sampling input terminals is two, and the sampling input terminals are a first sampling terminal and a second sampling terminal respectively, a sampling resistor is connected between the first sampling terminal and the second sampling terminal, the sampling resistor is connected in series to an ac line, the sampling circuit further comprises a sampling operational amplifier, the first sampling terminal is connected to a non-inverting input terminal of the sampling operational amplifier, the second sampling terminal is connected to an inverting input terminal of the sampling operational amplifier, and an output terminal of the sampling operational amplifier is connected to the sampling output terminal.
11. The over-current protection device is characterized by comprising a controller, a PFC circuit and the over-current detection circuit as claimed in any one of claims 1 to 10, wherein the controller outputs a PWM signal to the PFC circuit to control the working state of the PFC circuit, the sampling circuit is connected with an alternating current input of the PFC circuit to sample an electric signal and output an alternating current sampling voltage, and the controller maintains or stops the PFC circuit to work according to a comparison result output by the comparison circuit.
12. A wiring board comprising the overcurrent detection circuit according to any one of claims 1 to 10;
alternatively, the first and second electrodes may be,
comprising an overcurrent protection arrangement as set forth in claim 11.
13. An air conditioner characterized by comprising the wiring board according to claim 12.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010307725.0A CN111351979A (en) | 2020-04-17 | 2020-04-17 | Overcurrent detection circuit, overcurrent protection device, circuit board and air conditioner |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010307725.0A CN111351979A (en) | 2020-04-17 | 2020-04-17 | Overcurrent detection circuit, overcurrent protection device, circuit board and air conditioner |
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| CN111351979A true CN111351979A (en) | 2020-06-30 |
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| CN202010307725.0A Pending CN111351979A (en) | 2020-04-17 | 2020-04-17 | Overcurrent detection circuit, overcurrent protection device, circuit board and air conditioner |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113189468A (en) * | 2021-05-13 | 2021-07-30 | 中国工程物理研究院电子工程研究所 | Health state on-line monitoring circuit and system of power device |
| CN113252969A (en) * | 2021-04-15 | 2021-08-13 | 厦门华联电子股份有限公司 | Double-limit adjustable overcurrent detection circuit and overcurrent detection device |
| CN113983664A (en) * | 2021-10-29 | 2022-01-28 | 北京小米移动软件有限公司 | Air conditioner, control method thereof, and computer-readable storage medium |
| CN114963346A (en) * | 2022-05-06 | 2022-08-30 | 宁波奥克斯电气股份有限公司 | Totem-pole circuit, air conditioner external unit and air conditioner |
| WO2023218598A1 (en) * | 2022-05-12 | 2023-11-16 | ファナック株式会社 | Voltage monitoring circuit and voltage monitoring method |
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2020
- 2020-04-17 CN CN202010307725.0A patent/CN111351979A/en active Pending
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113252969A (en) * | 2021-04-15 | 2021-08-13 | 厦门华联电子股份有限公司 | Double-limit adjustable overcurrent detection circuit and overcurrent detection device |
| CN113252969B (en) * | 2021-04-15 | 2023-12-15 | 厦门华联电子股份有限公司 | Double-limit adjustable overcurrent detection circuit and overcurrent detection device |
| CN113189468A (en) * | 2021-05-13 | 2021-07-30 | 中国工程物理研究院电子工程研究所 | Health state on-line monitoring circuit and system of power device |
| CN113983664A (en) * | 2021-10-29 | 2022-01-28 | 北京小米移动软件有限公司 | Air conditioner, control method thereof, and computer-readable storage medium |
| CN114963346A (en) * | 2022-05-06 | 2022-08-30 | 宁波奥克斯电气股份有限公司 | Totem-pole circuit, air conditioner external unit and air conditioner |
| CN114963346B (en) * | 2022-05-06 | 2023-08-25 | 宁波奥克斯电气股份有限公司 | Totem pole circuit, air conditioner external unit and air conditioner |
| WO2023218598A1 (en) * | 2022-05-12 | 2023-11-16 | ファナック株式会社 | Voltage monitoring circuit and voltage monitoring method |
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