Utility model content
Technical problem to be solved in the utility model is to overcome the shortcomings of existing for above-mentioned prior art, and proposes one
That plants three-phase and four-line intelligent electric meter falls zero line detection circuit, it is possible to increase detection efficiency, and reduces testing cost.
The utility model proposes a kind of zero line detection circuit that falls of three-phase and four-line intelligent electric meter, bag for above-mentioned technical problem
Include:Voltage detecting circuit, for carrying out voltage division processing to input voltage, when zero line is normal, its output is in setting range;
Threshold voltage comparator, for the output of the voltage detecting circuit to be compared with setting thresholding;Threshold voltage is set, for setting
The fixed setting thresholding;Follower, voltage follow treatment is carried out for the output to the comparator;And signal amplification circuit, use
Treatment is amplified in the output to the follower.
In certain embodiments, the voltage detecting circuit is made up of multiple resistance, wherein, a part of resistance is serially connected,
And constitute a resistor voltage divider circuit with another part resistance.
In certain embodiments, the threshold voltage comparator realizes that the follower is by another by an operational amplifier
Operational amplifier realizes that the two operational amplifiers are located in same chip.
In certain embodiments, the threshold voltage sets and is made up of voltage-stabiliser tube and multiple resistance;Wherein, the voltage-stabiliser tube is selected
Voltage stabilizing triode, these resistance select 1% high-precision resistance.
In certain embodiments, the signal amplification circuit has level conversion function, and it is mainly made up of a triode;
The triode uses the front stage circuits of the direct current supply of the first level, the signal amplification circuit to be supplied using the direct current of second electrical level
Electricity, the second electrical level is more than first level.
In certain embodiments, first level is+3.3V, and the second electrical level is+13V.
In certain embodiments, the setting range is+5V to+12V, and this sets thresholding as+5V.
In certain embodiments, also include:Pi type filter, its string is located at output and thresholding of the voltage detecting circuit
Between the input of voltage comparator.
In certain embodiments, the pi type filter is made up of two filter capacitors and a current-limiting resistance, wherein, with this
The filter capacitor that the output of voltage detecting circuit is connected is used to filter high-frequency clutter, with the threshold voltage comparator
Another connected filter capacitor of input is used to filter low-frequency clutter.
The utility model also proposes a kind of three-phase and four-line intelligent electric meter for above-mentioned technical problem, including falls as described above
Zero line detection circuit.
Compared with prior art, three-phase and four-line intelligent electric meter of the present utility model falls zero line detection circuit, by ingenious
Ground voltage detecting circuit, threshold voltage comparator, threshold voltage are set, follower and signal amplification circuit are constituted, can
Detection efficiency is improved, and reduces testing cost.
Specific embodiment
Below in conjunction with the accompanying drawing of this specification, further elaboration is given to preferred embodiment of the present utility model.
Referring to Fig. 1, Fig. 1 is the block diagram that zero line detects circuit embodiments that falls of three-phase and four-line intelligent electric meter of the present utility model
Illustrate.Fall zero line detection circuit 10 the utility model proposes a kind of three-phase and four-line intelligent electric meter, it is generally comprised:Voltage detecting
Circuit 1, pi type filter 2, threshold voltage comparator 3, threshold voltage setting 4, follower 5 and signal amplification circuit 6.
The voltage of input is the High Level DC Voltage after three-phase voltage rectification, the voltage after three-phase voltage rectification is detected
After value, voltage division processing is carried out by the voltage detecting circuit 1, (+5V to+12V, there is zero line to one low dc voltage scope of output
On the premise of access).
The pi type filter 2 is used to carry out necessary filtering process to the output of the voltage detecting circuit 1.
The voltage detection signal that the threshold voltage comparator 3 is used to export the pi type filter 2 is set with the threshold voltage
The 4 setting thresholdings for providing are compared.After comparative result carries out voltage follow treatment by the follower 5, the signal is given to amplify electricity
Road 6 is amplified, and the signal after amplification can be sent to microprocessor and carry out subsequent treatment, for example:Alarm.
Zero line detection circuit 10 is fallen using this, zero line break and the artificial stealing feelings pulled out can be exactly detected whether
Condition, it is ensured that the reliability of three-phase and four-line intelligent electric meter onsite application.
Referring to Fig. 2, Fig. 2 is the electrical schematic diagram for falling zero line detection circuit of three-phase and four-line intelligent electric meter of the present utility model.
This falls the relatively simple, practicality of zero line detection circuit 10, and cost is relatively low;Also, influenceed small by factors such as environment temperatures, work is steady
It is fixed.
The voltage detecting circuit 1 is specifically made up of resistance R1, R2, R3, R4 and R5.Wherein, resistance R1, R2, R3 and R4 phases
Mutually series connection, and a resistor voltage divider circuit is constituted with resistance R5, for carrying out partial pressure to input voltage HV.Signal TP208 is this
The output of voltage detecting circuit 1.
The pi type filter 2 is specifically made up of filter capacitor C1, current-limiting resistance R6 and filter capacitor C2.Wherein, filter capacitor
C1 selects capacitance high, the patch capacitor of high withstand voltage, for filtering high-frequency clutter.Filter capacitor C2 is from low capacitance, low resistance to
The patch capacitor of pressure, for filtering low-frequency clutter.Current-limiting resistance R6 is used to prevent the voltage after sampling excessive, burns rear class
Circuit.
The threshold voltage comparator 3 is specifically realized by an operational amplifier in chip U1.
The threshold voltage sets 4 and is specifically made up of voltage-stabiliser tube U2 and resistance R7, R8, R9 and R10.
The follower 5 is specifically realized by another operational amplifier in chip U1.
In the present embodiment, chip U1 is the circuit of dual operational amplifier.Voltage-stabiliser tube U2 is a voltage stabilizing triode,
By this voltage stabilizing triode, through resistance R7, R8, R9 and R10 partial pressure, very stable comparison voltage can be obtained(Set door
Limit).Specifically, resistance R7, R8, R9 and R10 uses 1% high-precision resistance, to obtain accurate threshold voltage 5V.
The follower 5 is connected with the output end of the threshold voltage comparator 3.Because the follower 5 is voltage follower, it is possible to understand that:
Its input resistance is intended to infinitely great, output resistance and is intended to 0, can reach an effect for impedance matching, can make prime
The voltage of circuit is not influenceed by the voltage of late-class circuit.
The signal amplification circuit 6 is specifically made up of NPN type triode Q1 and resistance R11, R12 and R13.The follower 5
Output is input to the base stage of triode Q1 by resistance R11 current limlitings.If the output voltage of follower 5 is height, triode Q1
Cut-off, the output signal NU_MS for falling zero line detection circuit 10 is low level;If the output voltage of follower 5 is low, three poles
Pipe Q2 is turned on, and the output signal NU_MS for falling zero line detection circuit 10 is high level.
The operation principle for falling zero line detection circuit 10 is generally comprised:When the zero line of three-phase and four-line intelligent electric meter is in normally
During state, after the voltage detecting circuit 1 carries out voltage division processing to input voltage HV, obtain a magnitude of voltage higher (+5V to+
12V), the magnitude of voltage sets the setting thresholding of the 4+5V for providing more than the threshold voltage, and at this moment the threshold voltage comparator 3 is defeated
It is high level to go out, and the follower 5 is output as high level, triode Q1 cut-offs, and this falls the output letter of zero line detection circuit 10
Number NU_MS is low level.
Conversely, when the zero line of three-phase and four-line intelligent electric meter is in abnormal condition, 1 pair of input electricity of the voltage detecting circuit
After pressure HV carries out voltage division processing, a relatively low magnitude of voltage (less than+5V) is obtained, the magnitude of voltage sets 4 less than the threshold voltage
There is provided+5V setting thresholding, at this moment the threshold voltage comparator 3 be output as low level, the follower 5 is output as low electricity
It is flat, triode Q1 conductings, the output signal NU_MS for falling zero line detection circuit 10 is high level.
It is noted that in the present embodiment, triode Q1 has level conversion function.Triode Q1 uses+
3.3V powers so that the output signal NU_MS for falling zero line detection circuit 10 be powered with+3.3V it is adaptable, i.e.,:It is high
Close to+3.3V, low level is close to 0V for level.And in the front stage circuits of the signal amplification circuit 6, powered using+13V,
The setting range that detection voltage TP208 during by zero line normal condition is maintained at+5V to+12V can be so well adapted for
Application.
Compared with prior art, three-phase and four-line intelligent electric meter of the present utility model falls zero line detection circuit 10, by skilful
4, follower 5 and the structure of signal amplification circuit 6 are set with voltage detecting circuit 1, threshold voltage comparator 3, threshold voltage wonderfully
Into, it is possible to increase detection efficiency, and reduce testing cost.
The above is only preferred embodiment of the present utility model, is not intended to limit embodiment of the present utility model,
Those of ordinary skill in the art can very easily carry out corresponding accommodation according to central scope of the present utility model and spirit
Or modification, therefore protection domain of the present utility model should be defined by the protection domain required by claims.