CN112630512B - FF bus undervoltage indicating circuit - Google Patents
FF bus undervoltage indicating circuit Download PDFInfo
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- CN112630512B CN112630512B CN202011430510.4A CN202011430510A CN112630512B CN 112630512 B CN112630512 B CN 112630512B CN 202011430510 A CN202011430510 A CN 202011430510A CN 112630512 B CN112630512 B CN 112630512B
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- 230000000087 stabilizing effect Effects 0.000 claims abstract description 8
- 230000005611 electricity Effects 0.000 claims abstract description 4
- 238000001514 detection method Methods 0.000 claims description 12
- 239000003990 capacitor Substances 0.000 claims description 4
- 238000004891 communication Methods 0.000 description 11
- 230000008859 change Effects 0.000 description 8
- 238000010586 diagram Methods 0.000 description 5
- 230000008878 coupling Effects 0.000 description 3
- 238000010168 coupling process Methods 0.000 description 3
- 238000005859 coupling reaction Methods 0.000 description 3
- 230000006978 adaptation Effects 0.000 description 2
- 230000008033 biological extinction Effects 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000001012 protector Effects 0.000 description 2
- 230000003321 amplification Effects 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
Classifications
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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
- G01R19/16566—Circuits and arrangements for comparing voltage or current with one or several thresholds and for indicating the result not covered by subgroups G01R19/16504, G01R19/16528, G01R19/16533
- G01R19/16576—Circuits and arrangements for comparing voltage or current with one or several thresholds and for indicating the result not covered by subgroups G01R19/16504, G01R19/16528, G01R19/16533 comparing DC or AC voltage with one threshold
-
- 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
- G01R19/16504—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values characterised by the components employed
-
- 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
- G01R19/16504—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values characterised by the components employed
- G01R19/16523—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values characterised by the components employed using diodes, e.g. Zener diodes
Abstract
The invention provides a novel FF bus undervoltage indicating circuit which comprises a voltage detecting unit, an indicating lamp unit and a constant current unit, wherein the indicating lamp unit at least comprises an LED and a bypass voltage stabilizing tube D1 connected in parallel with the LED, the constant current unit is used for being coupled with a bus power supply end to take electricity and providing a constant current power supply for the indicating lamp unit, and the voltage detecting unit is coupled with the bus power supply end and is coupled between an LED cathode and a power supply ground and used for controlling the on-off of a circuit between the LED cathode and the power supply ground based on detected bus voltage. The FF bus undervoltage indicating circuit keeps the circuit to continue constant current while undervoltage is turned off, does not interfere the bus, and has lower cost compared with the circuit in the prior art.
Description
Technical Field
The invention relates to the technical field of FF bus communication, in particular to an FF bus undervoltage indicating circuit.
Background
When the FF bus network reaches the vicinity of the instrument, a junction box is used for accessing a plurality of instruments to the bus, a branch protector is arranged in the junction box, and the bus overvoltage and undervoltage are required to be indicated on the branch protector, so that the maintenance and the investigation are convenient. The indicator lights are on in the FF bus 9-32V operating voltage range, otherwise off (the actual minimum nominal voltage for the different devices may be higher). Overvoltage extinction is generally realized by directly switching off a total power supply by an overvoltage shutoff circuit, but under-voltage extinction needs an additional circuit.
As shown in fig. 1, in the prior art, a low-voltage protection threshold point is set by matching R1 and R2 voltage dividing resistors with a voltage reference at the high end side of U1, when the voltage is higher than a threshold value, U1 is conducted, then the base electrode of Q1 is pulled high to be conducted, and the right constant current lighting circuit works to light an LED lamp. The constant current lighting circuit is characterized in that the Q1 is conducted, so that the Q2 base electrode is pulled down to be conducted through the R5, when the voltage drop generated by the current on the R6 reaches the threshold value of the reference U2, the U2 is conducted, so that the Q2 base electrode is pulled up to enter the linear region, and finally, the current flowing through the R6 is constant, namely, the current of the LED is basically constant. When the voltage is below the threshold, U1 is not on, Q1 is off, vbe of Q2 is 0V off, and the lamp is turned off. However, with such a circuit, when the voltage fluctuates around the threshold, the constant current circuit is in an unstable region, and the current is large and small, thereby causing serious bus signal interference and failure in communication.
Disclosure of Invention
The technical problem solved by the invention is to provide a novel FF bus undervoltage indicating circuit, which keeps the circuit to continue constant current while the undervoltage is turned off, does not interfere the bus, and has lower cost compared with the circuit in the prior art.
In order to solve the problems, the invention adopts the following technical scheme:
The utility model provides a FF bus undervoltage indicating circuit, includes voltage detection unit, pilot lamp unit and constant current unit, the pilot lamp unit includes LED and the parallelly connected bypass steady voltage tube D1 of LED at least, the constant current unit is used for coupling bus power supply end to get the electricity and provide constant current power supply for the pilot lamp unit, voltage detection unit coupling bus power supply end to coupling is between LED negative pole and power ground, is used for controlling the break-make of the circuit between negative pole of LED and the power ground based on the bus voltage of detection.
In one embodiment, the voltage detection unit at least includes voltage dividing resistors R7 and R8 coupled in series between the bus power supply terminal and the power supply ground, and a reference chip U1 coupled between the LED cathode and the power supply ground, wherein a voltage reference terminal of the reference chip U1 is coupled between the resistors R7 and R8.
In another illustrated embodiment, the voltage detection unit includes at least voltage dividing resistors R251 and R256 coupled in series between a bus power supply terminal and a power supply ground, and a comparator U7; the INA+ pin of the comparator U7 is coupled between the resistors R251 and R256, the OUTB pin is coupled to the LED cathode, the VDD pin is coupled to the bus power terminal via the resistor R245, and is coupled to the power ground via the capacitor C100 and the zener diode D29 in parallel, and the GND pin is coupled to the power ground.
In an embodiment, the constant current unit is a constant current diode.
In another illustrated embodiment, the constant current unit includes PNP transistors Q1 and Q2, and resistors R9 and R10; one end of the emitter of the triode Q2 and one end of the resistor R9 are coupled with a bus power supply end, the other end of the resistor R9 is coupled with the base of the triode Q2 and the emitter of the triode Q1, the collector of the triode Q2 is coupled with the base of the triode Q1 and is coupled with the power supply ground through the resistor R10, and the collector of the triode Q1 is coupled with the anode of the LED.
Compared with the prior art, the FF bus undervoltage indicating circuit has the following advantages:
1) By arranging the bypass voltage stabilizing tube D1, when the indication LED is turned on or off due to voltage change, the current in the indication loop is not changed, so that the state change of the indication circuit does not interfere with bus communication, the lowest voltage of the bus communication can be consistent with the lower limit of the lowest working voltage of the instrument, the working voltage limit of the bus is widened, and the communication voltage range of the bus is maximized.
2) The reference chip U1 used is a low-end side reference, which is more versatile and cheaper than a high-end side reference. Meanwhile, the constant current circuit adopts a triode to limit current, and the cost is further reduced.
Drawings
Fig. 1 is a schematic circuit diagram of a conventional FF bus under-voltage indication circuit.
FIG. 2 is a schematic circuit diagram of an FF bus undervoltage indication circuit according to a first embodiment of the present invention.
FIG. 3 is a schematic circuit diagram of an FF bus undervoltage indication circuit according to a second embodiment of the present invention.
FIG. 4 is a schematic circuit diagram of an FF bus undervoltage indication circuit according to a third embodiment of the present invention.
Detailed Description
For a further understanding of the present invention, preferred embodiments of the invention are described below in conjunction with the examples, but it should be understood that these descriptions are merely intended to illustrate further features and advantages of the invention, and are not limiting of the claims of the invention.
Fig. 1 is a schematic circuit diagram of a conventional FF bus under-voltage indication circuit. The low-voltage protection threshold point is set by matching R1 and R2 voltage dividing resistors with a high-side voltage reference U1, when the voltage is higher than the threshold value, U1 is conducted, then the base electrode of Q1 is pulled high to be conducted, and the right-side constant-current lighting circuit works to light an LED lamp. The constant current lighting circuit is characterized in that the Q1 is conducted, so that the Q2 base electrode is pulled down to be conducted through the R5, when the voltage drop generated by the current on the R6 reaches the threshold value of the reference U2, the U2 is conducted, so that the Q2 base electrode is pulled up to enter the linear region, and finally, the current flowing through the R6 is constant, namely, the current of the LED is basically constant. When the voltage is below the threshold, U1 is not on, Q1 is off, vbe of Q2 is 0V off, and the lamp is turned off. However, with such a circuit, a constant current state cannot be maintained due to the change of the operating point of the constant current circuit in the vicinity of the undervoltage turn-off threshold, resulting in abrupt current change of the lighting circuit, resulting in abrupt bus impedance change, and affecting communication. That is, the existing circuit can only work normally when the threshold value is above. The bus signal amplitude is (+/-) (0.75-1) V during single terminal communication, and the lowest voltage is pulled to 8V when 9V is supplied, and the bus signal is interfered by the lighting circuit. The minimum working voltage of the instrument is often lower than 9V required by the bus, and the bus fails in advance due to lighting when the instrument can work, so that the application of the bus is not facilitated.
In order to solve the problems, the invention provides a novel FF bus undervoltage indicating circuit which comprises a voltage detecting unit, an indicating lamp unit and a constant current unit. The indicator lamp unit at least comprises an LED and a bypass voltage stabilizing tube D1 connected in parallel with the LED, and the bypass voltage stabilizing tube D1 is used for providing a follow current channel for current generated by the second circuit when the LED is extinguished; the constant current unit is used for being coupled with the bus power supply end to take electricity and providing a constant current power supply for the indicator lamp unit to light up, the voltage detection unit is coupled with the bus power supply end and is coupled between the LED cathode and the power supply ground, and the voltage detection unit is used for controlling the on-off of a circuit between the LED cathode and the power supply ground based on the detected bus voltage.
According to the scheme, the bypass voltage stabilizing tube D1 ensures that the lighting current cannot change due to the lamp switch, the lighting circuit cannot interfere bus communication, the lowest voltage of the bus communication can be consistent with the lowest working voltage lower limit of the instrument, and the communication voltage range of the bus is maximized. The scheme of the invention is further described below with reference to specific examples.
Example 1
As shown in fig. 2, in the embodiment shown in the present disclosure, the indicator light unit includes at least a light emitting indicator LED and a bypass regulator D1 connected in parallel with the LED. The voltage detection unit at least comprises voltage dividing resistors R7 and R8 coupled in series between the bus power supply terminal and the power supply ground, and a reference chip U1 coupled between the LED cathode and the power supply ground, wherein a voltage reference terminal of the reference chip U1 is coupled between the resistors R7 and R8. The constant current unit adopts a constant current pipe D33 which is coupled with a bus power supply end VCC to obtain power and provide a constant current power supply for the LED.
The working principle of the circuit is as follows: the threshold voltage for turning off the lamp is set through the voltage dividing resistors R7 and R8, when the threshold voltage is exceeded, the U1 works, the LED has low impedance to the ground, at the moment, because the voltage drop of the LED and the U1 is far smaller than the working voltage of the voltage stabilizing tube D1, the current flows through a series circuit formed by the LED and the U1, the D1 does not flow through the current, and the LED is lighted. In this process, the current in the lighting circuit will not change due to the lamp switch, so the whole lighting circuit will not interfere with the bus communication.
In one embodiment, U1 is model number TI LMV431. Generally, the temperature drift and other performances of the device affect the accuracy of the threshold point, but the application in the embodiment has low requirement on the threshold range, so that other domestic TL431 can be selected, and compared with a high-end side reference, the TL431 is more general and cheaper.
Example 2
As shown in fig. 3, in the present embodiment, the circuit configuration of the indicator lamp unit and the voltage detection unit 201 is similar to that in embodiment 1, and the constant current unit 202 is replaced with a high-side constant current circuit composed of transistors, which includes PNP transistors Q1 and Q2, and resistors R9 and R10; one end of the emitter of the triode Q2 and one end of the resistor R9 are coupled with a bus power supply end, the other end of the resistor R9 is coupled with the base of the triode Q2 and the emitter of the triode Q1, the collector of the triode Q2 is coupled with the base of the triode Q1 and is coupled with the power supply ground through the resistor R10, and the collector of the triode Q1 is coupled with the anode of the LED.
The working principle of the constant current circuit is as follows: after power-on, the base electrode of Q1 is pulled down by R10, so that Q1 is conducted, at the moment, the base electrode of Q2 is pulled down by Q1 to be conducted, the voltage of R10 is increased to enable Q1 to enter an amplifying region from a switching state, and then the voltage of the base electrode of Q2 is increased to enter the amplifying region to enable the voltage of R10 to be low, so that negative feedback is formed. When the current flowing through the Q1 is overlarge in a steady state, the voltage drop on the R9 is larger than the Vbe of the Q2, the conduction capacity of the Q2 is increased, so that the voltage of the R10 is increased, the Vbe voltage of the Q1 is reduced, the amplification capacity is weakened, and the current flowing through the R9 is reduced; when the current flowing through R9 is too small, the current flowing through Q1 is Veb/R3 of Q2 finally, and constant current is formed.
By adopting the circuit, the constant current can be more accurate and stable, so that the stability of the whole circuit is enhanced. Meanwhile, the constant current circuit adopts a triode to limit current, and the cost is further reduced.
Example 3
As shown in fig. 4, in the present embodiment, the circuit configuration of the indicator light unit and the constant current unit is similar to that in embodiment 2, and the voltage detection unit employs an integrated chip circuit including voltage dividing resistors R251 and R256 coupled in series between the bus power supply terminal and the power supply ground, and a comparator U7; the INA+ pin of the comparator U7 is coupled between the resistors R251 and R256 and grounded via the capacitor C99; the OUTB pin is coupled to the LED cathode, the VDD pin is coupled to the bus power terminal VCC via a resistor R245, and is coupled to the power ground via a capacitor C100 and a zener diode D29, and the GND pin is coupled to the power ground. In this embodiment, the comparator U7 is of the type TPS3700DDCR.
By adopting the circuit, the voltage is more accurate, and the circuit is suitable for occasions with higher requirements on the voltage.
By adopting the scheme in the embodiment, the operating voltage of the lighting constant current can be reduced to below 7V, the light-off threshold point can be designed randomly, the bus impedance characteristic can not change when the light-off prompt is carried out, and the lowest operating voltage depends on a bus instrument and an interface card.
The above description of the embodiments is only for aiding in the understanding of the method of the present invention and its core ideas. It should be noted that it will be apparent to those skilled in the art that various modifications and adaptations of the invention can be made without departing from the principles of the invention and these modifications and adaptations are intended to be within the scope of the invention as defined in the following claims.
Claims (1)
1. The FF bus undervoltage indicating circuit is characterized by comprising a voltage detecting unit, an indicating lamp unit and a constant current unit, wherein the indicating lamp unit comprises an LED and a bypass voltage stabilizing tube D1 connected in parallel with the LED, the constant current unit is used for being coupled with a bus power supply end to take electricity and providing a constant current power supply for the indicating lamp unit, the voltage detecting unit is coupled with the bus power supply end and is coupled between an LED cathode and a power supply ground, the voltage detecting unit is used for controlling the on-off of a circuit between the LED cathode and the power supply ground based on detected bus voltage, and the bypass voltage stabilizing tube D1 is used for providing a follow current channel when the LED is extinguished;
The voltage detection unit comprises voltage dividing resistors R7 and R8 which are coupled in series between a bus power supply end and power supply ground, and a reference chip U1 which is coupled between an LED cathode and the power supply ground, wherein a voltage reference end of the reference chip U1 is coupled between the voltage dividing resistors R7 and R8;
or the voltage detection unit comprises divider resistors R251 and R256 which are coupled in series between a bus power supply terminal and power supply ground, and a comparator U7; the INA+ pin of the comparator U7 is coupled between the voltage dividing resistors R251 and R256, the OUTB pin is coupled with the LED cathode, the VDD pin is coupled with the bus power supply end through the resistor R245, and is coupled with the power supply ground through the capacitor C100 and the zener diode D29 which are connected in parallel, and the GND pin is coupled with the power supply ground;
The constant current unit is a constant current diode;
Or the constant current unit comprises PNP triodes Q1 and Q2 and resistors R9 and R10; one end of the emitter of the triode Q2 and one end of the resistor R9 are coupled with a bus power supply end, the other end of the resistor R9 is coupled with the base of the triode Q2 and the emitter of the triode Q1, the collector of the triode Q2 is coupled with the base of the triode Q1 and is coupled with the power supply ground through the resistor R10, and the collector of the triode Q1 is coupled with the anode of the LED.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011430510.4A CN112630512B (en) | 2020-12-07 | 2020-12-07 | FF bus undervoltage indicating circuit |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202011430510.4A CN112630512B (en) | 2020-12-07 | 2020-12-07 | FF bus undervoltage indicating circuit |
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| CN112630512A CN112630512A (en) | 2021-04-09 |
| CN112630512B true CN112630512B (en) | 2024-05-03 |
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| CN202011430510.4A Active CN112630512B (en) | 2020-12-07 | 2020-12-07 | FF bus undervoltage indicating circuit |
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