CN107565954B - Passive shaping circuit - Google Patents
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- CN107565954B CN107565954B CN201610509754.9A CN201610509754A CN107565954B CN 107565954 B CN107565954 B CN 107565954B CN 201610509754 A CN201610509754 A CN 201610509754A CN 107565954 B CN107565954 B CN 107565954B
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Abstract
The invention discloses a passive shaping circuit, which comprises: the triode comprises a first triode, a second triode, a first resistor, a second resistor, a third resistor, a fourth resistor and a fifth resistor, wherein an emitting electrode of the first triode is connected with a negative electrode input end, a collecting electrode of the first triode is connected with a base electrode of the second triode through the first resistor, a base electrode of the first triode is connected with a collecting electrode of the second triode through the second resistor, the base electrode of the first triode is connected with the negative electrode input end through the third resistor, an emitting electrode of the second triode is connected with a positive electrode input end, the base electrode of the second triode is connected with the negative electrode input end through the fourth resistor, the base electrode of the second triode is connected with the positive electrode input end through the fifth resistor, a collecting electrode of the second triode is connected with a positive electrode output end, and the negative electrode input end. The passive shaping circuit can effectively filter differential mode noise carried in signals, has strong anti-interference capability and good stability, does not need external isolation power supply, and has simple structure.
Description
Technical Field
The invention relates to the field of electronic circuits, in particular to a passive shaping circuit.
Background
In an industrial environment, optical coupling isolation is generally used for eliminating the interference of common mode noise to signals, but the optical coupling isolation cannot completely eliminate the interference of differential mode noise to signals.
At present, active shaping circuits are mainly used for eliminating differential mode noise carried in target signals. Although the active shaping circuit can effectively filter the differential mode noise, the method needs to additionally provide an isolating power supply to supply power to the shaping circuit, thereby increasing the complexity of the circuit and increasing the cost of the shaping circuit. In addition, a filtering mode (for example, through an RC filter circuit) can be adopted to eliminate differential mode noise, which can easily filter a useful signal or cannot act on partial interference under the condition that the noise bandwidth is uncertain, and can also have the problem of poor filtering effect under the condition of high noise.
Disclosure of Invention
The invention aims to provide a passive shaping circuit which is simple and can effectively filter differential mode noise.
In order to achieve the above object, the present invention provides a passive shaping circuit including: the circuit comprises a first triode, a second triode, a first resistor, a second resistor, a third resistor, a fourth resistor and a fifth resistor.
Wherein the emitter of the first triode is connected with the negative input end of the passive shaping circuit, the collector of the first triode is connected with the base of the second triode through the first resistor, the base of the first triode is connected with the collector of the second triode through the second resistor, the base electrode of the first triode is connected with the negative electrode input end through the third resistor, the base electrode of the second triode is connected with the negative electrode input end through the fourth resistor, the base electrode of the second triode is connected with the positive input end through the fifth resistor, the emitting electrode of the second triode is connected with the positive input end of the passive shaping circuit, and the collector of the second triode is connected with the positive output end of the passive shaping circuit, and the negative input end of the second triode is connected with the negative output end of the passive shaping circuit.
The first triode, the second triode, the first resistor, the second resistor, the third resistor, the fourth resistor and the fifth resistor are used for determining a rising edge conduction threshold and a falling edge conduction threshold, so that the pulse signal input into the passive shaping circuit is turned off when the pulse signal is converted from a low level to a high level and the voltage is smaller than the rising edge conduction threshold and when the pulse signal is converted from the high level to the low level and the voltage is smaller than the falling edge conduction threshold.
Optionally, the passive shaping circuit further comprises: the collector of the first triode is connected with the cathode of the first diode, the anode of the first diode is connected with the negative input end, the emitter of the second triode is connected with the cathode of the second diode, and the anode of the second diode is connected with the collector of the second triode.
Optionally, the passive shaping circuit further comprises: the base of the third triode is connected with the anode input end through the sixth resistor, the base of the third triode is connected with the cathode input end through the seventh resistor, and the collector of the third triode is connected with the anode output end.
Optionally, the passive shaping circuit further comprises: the base electrode of the third triode is connected with the anode of the third diode, the cathode of the third diode is connected with the collector electrode of the second triode, the collector electrode of the third triode is connected with the anode of the fourth diode, and the cathode of the fourth diode is connected with the collector electrode of the second triode.
Optionally, the passive shaping circuit further comprises: the first diode, the second diode, the third triode, the sixth resistor, the seventh resistor, the third diode and the fourth diode.
Wherein, the collector of the first triode is connected with the cathode of the first diode, the anode of the first diode is connected with the negative input end, the emitter of the second triode is connected with the cathode of the second diode, the anode of the second diode is connected with the collector of the second triode, the emitter of the third triode is connected with the collector of the second triode, the collector of the third triode is connected with the positive output end, the base of the third triode is connected with the anode of the third diode, the cathode of the third diode is connected with the collector of the second triode, the collector of the third triode is connected with the anode of the fourth diode, the cathode of the fourth diode is connected with the collector of the second triode, the base of the third triode is connected with the positive input end through the sixth resistor, and the base electrode of the third triode is connected with the negative electrode input end through the seventh resistor.
Determining the rising edge conduction threshold and the falling edge conduction threshold according to the following equations:
VT1<VTL；
wherein, VTHFor the rising edge conduction threshold, VbeQ2Is the conduction voltage drop, V, of the second triodeTLFor the falling edge conduction threshold, VceQ1Is the voltage value between the collector and emitter of the first triode, VT1For the voltage value, V, of the collector of the second triode during the conversion of the input signal from high level to low levelbeQ1Is the conduction voltage drop, R, of the first triode1Is the resistance value of the first resistor, R2Is the resistance value of the second resistor, R3Is the resistance value of the third resistor, R4Is the resistance value of the fourth resistor, R5Is the resistance value of the fifth resistor, R6Is the resistance value of the sixth resistor, R7Is a resistance value of the seventh resistor, VT3Is the base voltage value, V, of the third triodeTAIs the voltage value, V, of said pulse signaljis the voltage value beta of the third triode when working in the amplifying region1is the amplification factor of the first triode, beta2Is the amplification factor, V, of the second trioded3Is the voltage value of the third diode, Vbe2Is the voltage value between the base and the emitter of the second triode, VbeQ3Is the conduction voltage drop of the third triode.
Optionally, the passive shaping circuit further comprises a load resistor connected between the positive output terminal and the negative output terminal.
Through the technical scheme, the rising edge conduction threshold and the falling edge conduction threshold can be set by changing device parameters in the passive shaping circuit, so that the pulse signal flowing through the passive shaping circuit is switched from low level to high level when the voltage is smaller than the rising edge conduction threshold, and is switched from high level to low level when the voltage is smaller than the falling edge conduction threshold. Like this, the differential mode noise that can filter effectively and carry in the pulse signal, and the interference killing feature is strong, and stability is good, and simultaneously, this passive shaping circuit simple structure need not external isolation power and provides the electric energy.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
fig. 1 is a circuit diagram of a passive shaping circuit provided in accordance with an embodiment of the present invention;
fig. 2 is a circuit diagram of a passive shaping circuit provided in accordance with another embodiment of the present invention;
FIG. 3 is a circuit diagram of a passive shaping circuit provided in accordance with yet another embodiment of the present invention;
FIG. 4 is a circuit diagram of a passive shaping circuit provided in accordance with yet another embodiment of the present invention;
FIG. 5 is a circuit diagram of a passive shaping circuit provided in accordance with yet another embodiment of the present invention;
FIG. 6 is a circuit diagram of a passive shaping circuit provided in accordance with yet another embodiment of the present invention; and
fig. 7a and 7b are time domain waveform diagrams of the input/output of a passive shaping circuit provided under an embodiment of the present invention.
Detailed Description
The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.
Fig. 1 is a circuit diagram of a passive shaping circuit provided in accordance with an embodiment of the present invention. As shown in fig. 1, the passive shaping circuit may include a first transistor Q1, a second transistor Q2, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, and a fifth resistor R5.
The emitter of the first triode Q1 is connected with the negative input end IN-of the passive shaping circuit, the collector of the first triode Q1 is connected with the base of the second triode Q2 through a first resistor R1, the base of the first triode Q1 is connected with the collector of the second triode Q2 through a second resistor R2, the base of the first triode Q1 is connected with the negative input end IN-through a third resistor R3, the base of the second triode Q2 is connected with the negative input end IN-through a fourth resistor R4, the base of the second triode Q2 is connected with the positive input end IN + through a fifth resistor R5, the emitter of the second triode Q2 is connected with the positive input end IN + of the passive shaping circuit, the collector of the second triode Q2 is connected with the positive output end OUT + of the passive shaping circuit, and the negative input end IN-is connected with the negative output end OUT-of the passive shaping circuit.
The first triode Q1, the second triode Q2, the first resistor R1, the second resistor R2, the third resistor R3, the fourth resistor R4 and the fifth resistor R5 are used for determining a rising edge conduction threshold and a falling edge conduction threshold, so that the pulse signal input into the passive shaping circuit is turned off when the pulse signal is converted from a low level to a high level and the voltage is less than the rising edge conduction threshold and when the pulse signal is converted from the high level to the low level and the voltage is less than the falling edge conduction threshold.
As shown in fig. 1, the first transistor Q1 may be an NPN transistor, and the second transistor Q2 may be a PNP transistor, for example. When a pulse signal flows in, in the process of starting the circuit, the pulse signal is converted from a low level to a high level, the second resistor R2 and the third resistor R3 are connected in series, a forward voltage difference can be generated between the collector and the base of the first triode Q1, the emitter junction of the first triode Q1 is enabled to be positively biased, and the first triode Q1 works in an amplifying region. Meanwhile, the current output by the collector of the first triode Q1 can influence the base voltage value of the second triode Q2 through the first resistor R1, when the voltage value of the pulse signal continues to rise, the first triode Q1 can enter a saturation region to work, the current output by the collector does not change along with the change of the voltage value of the pulse signal any more, at this time, the current output by the collector of the first triode Q1 clamps the base voltage value of the second triode Q2 at a fixed value through the first resistor R1, when the voltage value of the pulse signal is not greater than the fixed value, the second triode Q2 enters a cut-off region to work, and the base and the collector are disconnected, so the passive shaping circuit provided by the invention has no signal output, namely, the voltage value is close to 0V; the voltage value of the pulse signal continuously rises, when the voltage value is larger than the base voltage value of the second triode Q2, the second triode Q2 also enters a saturation region to work, at the moment, the passive shaping circuit provided by the invention outputs the pulse signal, and the fixed value is the conduction threshold value of the rising edge of the pulse signal.
When the pulse signal starts to switch from high level to low level, the first transistor Q1 works in saturation region, the collector current is not affected by the change of the pulse signal, the first transistor Q1 affects the base voltage value of the second transistor Q2 via the first resistor R1, when the voltage value of the pulse signal continues to drop, the first transistor Q1 cannot continue to work in saturation region, the base voltage value of the second transistor Q2 affected by the first resistor R1 is no longer a fixed value, the fourth resistor R4 and the fifth resistor R5 are connected in series, so that when the first transistor Q1 does not work in saturation region, the voltage difference can be generated between the emitter and the base of the second transistor Q2, the voltage difference is greater than the conducting voltage drop of the second transistor Q2, the second transistor Q2 is conducted, the emitter voltage value of the second transistor Q2 is less than the base voltage value, the second transistor Q2 can work in cut-off region reliably, it should be understood that the present invention is not limited to the specific type of the second transistor Q2, wherein the turn-on voltage drop of the second transistor Q2 may be, for example, 0.7V, so that the critical voltage value of the second transistor Q2 from the saturation region to the cut-off region is the falling edge turn-on threshold of the pulse input signal. When the pulse signal is converted from a high level to a low level and the voltage value of the pulse signal is greater than the conduction threshold value of the falling edge, the second triode Q2 is in a saturated state, the passive shaping circuit is conducted, and the pulse signal is output; when the voltage value of the pulse signal is smaller than the falling edge conducting threshold value, the second triode Q2 enters a cut-off region to work, and no signal is output, namely the voltage value is close to 0V.
Through the technical scheme, the rising edge conduction threshold and the falling edge conduction threshold can be set by changing device parameters in the passive shaping circuit, so that the pulse signal flowing through the passive shaping circuit is switched from low level to high level when the voltage is smaller than the rising edge conduction threshold, and is switched from high level to low level when the voltage is smaller than the falling edge conduction threshold. Like this, the differential mode noise that can filter effectively and carry in the pulse signal, and the interference killing feature is strong, and stability is good, and simultaneously, this passive shaping circuit simple structure need not external isolation power and provides the electric energy.
Fig. 2 is a circuit diagram of a passive shaping circuit provided in accordance with another embodiment of the present invention. As shown in fig. 2, on the basis of fig. 1, the passive shaping circuit may further include a first diode D1 and a second diode D2.
The collector of the first triode Q1 is connected with the cathode of the first diode D1, the anode of the first diode D1 is connected with the negative input end IN-, the emitter of the second triode Q2 is connected with the cathode of the second diode D2, and the anode of the second diode D2 is connected with the collector of the second triode Q2.
Since the circuit may generate a reverse large voltage several times as much as the input voltage at the moment of starting or stopping, in order to avoid the breakdown of the transistors by the reverse large voltage, a first diode D1 may be connected between the emitter and collector of the first transistor Q1, and a second diode D2 may be connected between the emitter and collector of the second transistor Q2 to provide a loop for the reverse current to protect the transistors. In addition, the passive shaping circuit provided by the invention does not limit the specific types of the first diode D1 and the second diode D2, and diodes with a unidirectional conduction function all belong to the protection scope of the invention.
Fig. 3 is a circuit diagram of a passive shaping circuit provided in accordance with yet another embodiment of the present invention. As shown in fig. 3, on the basis of fig. 1, the passive shaping circuit may further include: a third transistor Q3, a sixth resistor R6, and a seventh resistor R7. An emitter of the third triode Q3 is connected with a collector of the second triode Q2, a base of the third triode Q3 is connected with the positive input terminal IN + via a sixth resistor R6, a base of the third triode Q3 is connected with the negative output terminal OUT-via a seventh resistor R7, and a collector of the third triode Q3 is connected with the positive output terminal OUT +.
When the pulse signal is switched between high and low levels near the conducting threshold of the rising edge, the noise carried in the pulse signal may cause the first transistor Q1 and the second transistor Q2 to enter the linear amplification region, thereby generating switching glitches which are not beneficial to the shaping effect. The sixth resistor R6 and the seventh resistor R7 are connected in series to divide voltage, and the base voltage of the third transistor Q3 can be set by setting the resistance value of the sixth resistor R6 and the resistance value of the seventh resistor R7, so that the voltage value of the shaping signal output by the collector of the second transistor Q2 is greater than the base voltage of the third transistor Q3, and the third transistor Q3 is turned on; when the voltage value of the shaped signal output by the collector of the second triode Q2 is smaller than the base voltage value of the third triode Q3, the third triode Q3 can be reliably cut off. In the passive shaping circuit provided in this embodiment, the glitch in the output signal in the foregoing embodiment can be filtered out, and thus the shaping effect is improved.
Fig. 4 is a circuit diagram of a passive shaping circuit provided in accordance with yet another embodiment of the present invention. As shown in fig. 4, on the basis of fig. 3, the passive shaping circuit may further include a third diode D3 and a fourth diode D4. The base of the third triode Q3 is connected to the anode of the third diode D3, the cathode of the third diode D3 is connected to the collector of the second triode Q2, the collector of the third triode Q3 is connected to the anode of the fourth diode D4, and the cathode of the fourth diode D4 is connected to the collector of the second triode Q2.
Therefore, the third diode D3 is provided to make the second transistor Q2 and the third transistor Q3 not conduct under normal conditions, so as to avoid mutual interference, and the fourth diode D4 is provided to provide a conducting loop for reverse current in order to protect the third transistor Q3. Similarly, the present invention does not limit the specific types of the third diode D3 and the fourth diode D4, and any diode capable of realizing unidirectional conduction is within the protection scope of the present invention.
Fig. 5 is a circuit diagram of a passive shaping circuit provided in accordance with yet another embodiment of the present invention. As shown in fig. 5, on the basis of fig. 1, the passive shaping circuit may further include a first diode D1, a second diode D2, a third transistor Q3, a sixth resistor R6, a seventh resistor R7, a third diode D3, and a fourth diode D4.
The collector of the first triode Q1 is connected with the cathode of the first diode D1, the anode of the first diode D1 is connected with the negative input terminal IN-, the emitter of the second triode Q2 is connected with the cathode of the second diode D2, the anode of the second diode D2 is connected with the collector of the second triode Q2, the emitter of the third triode Q3 is connected with the collector of the second triode Q2, the collector of the third triode Q3 is connected with the positive output terminal OUT +, the base of the third triode Q3 is connected with the anode of the third diode D3, the cathode of the third diode D3 is connected with the collector of the second triode Q6329, the collector of the third triode Q3 is connected with the anode of the fourth diode D4, the cathode of the fourth diode D4 is connected with the collector of the second triode Q2, the base of the third triode Q3 is connected with the positive input terminal IN + via a sixth resistor R6, and the base of the third triode Q3 is connected with the negative input terminal IN via a seventh resistor R7-7.
The rising edge conduction threshold and the falling edge conduction threshold are determined according to the following equations:
VT1<VTL；
wherein, VTHFor rising edge conduction threshold, VbeQ2Is the conduction voltage drop, V, of the second transistor Q2TLFor falling edge conduction threshold, VceQ1Is the voltage value between the collector and emitter of the first transistor Q1, VT1For the voltage value, V, of the collector of the second transistor Q2 during the transition of the input signal from high level to low levelbeQ1Is the conduction voltage drop, R, of the first transistor Q11Is the resistance value of the first resistor R1, R2Is the resistance value of the second resistor R2, R3Is the resistance value of the third resistor R34Is the resistance value of the fourth resistor R45Is the resistance value of a fifth resistor R56Is the resistance value of the sixth resistor R67Is the resistance value, V, of the seventh resistor R7T3Is the base voltage value, V, of the third transistor Q3TAIs the voltage value of the pulse signal, Vjβ represents the voltage value of the third transistor Q3 when operating in the amplifying region1is the amplification factor, beta, of the first transistor Q12Is the amplification factor, V, of the second transistor Q2d3Is the voltage value, V, of the third diode D3be2Is the voltage value between the base and the emitter of the second triode Q2, VbeQ3Is the conduction voltage drop of the third transistor Q3.
As shown in fig. 5, the fourth resistor R4 and the fifth resistor R5 are connected in series to divide the voltage, when the second transistor Q2 is in a critical state of entering a saturation region, its emitter junction is biased positively, the voltage across the fifth resistor R5 is the conduction voltage drop of the second transistor Q2, and the voltage value of the pulse signal at this time can be represented as:
when the voltage value of the pulse signal is larger than the voltage value, the pulse signal is conducted, so that the rising edge of the pulse signal conducts the threshold value VTHCan be expressed as:
the pulse signal is switched on when the voltage value of the pulse signal is larger than the rising edge conducting threshold value in the process of switching from the low level to the high level, and is switched off otherwise.
When the pulse signal starts to switch from a high level to a low level, the first triode Q1 switches from a saturation region to a cut-off region, and in a critical state, the current between the emitter and the collector of the first triode Q1 is small, the voltage value of the base of the second triode Q2 can be regarded as the voltage value corresponding to the first resistor R1 and the fourth resistor R4 which are connected in parallel and then connected in series with the fifth resistor R5, and the voltage value V of the base of the second triode Q2 is obtained by utilizing the connection relationship between the second triode Q2 and the first resistor R1, the fourth resistor R4 and the fifth resistor R5eQ2Can be expressed as:
at the moment, the voltage value V between the emitter and the base of the second triode Q2be2Can be controlled by the voltage value V between the emitter and the collector of the first triode Q1ceQ1And the connection relationship of the circuit is expressed as:
in order to operate the second transistor Q2 in the saturation region, the voltage value of the pulse signal needs to satisfy the following conditions: is greater than the voltage value V of the base of the second triode Q2eQ2And the voltage value V between the emitter and the base of the second triode Q2be2And, therefore, the falling edge of the pulse signal turns on the threshold VTLCan be expressed as:
in addition, the pulse signal continues to drop, in order to prevent the second triode Q2 from entering the amplification region to work, the collector junction thereof needs to be reversely biased, a reverse voltage difference is generated between the base electrode and the collector electrode, and the voltage value V of the collector electrode of the second triode Q2 is obtained according to the circuit connection relationT1Can be expressed as:
avoiding the collector voltage value V of the second triode Q2 needed by the work of entering the amplifying regionT1Less than VTL。
As shown in FIG. 5, the sixth resistor R6 is connected in series with the seventh resistor R7 to provide a base voltage value for the third transistor Q3, and the base voltage value V of the third transistor Q3 is determined according to the circuit connection relationshipT3Can be expressed as:
illustratively, the third transistor Q3 is a PNP transistor, and the third transistor Q3 operates in saturation, so that the emitter junction of the third transistor Q3 is biased forward, and the voltage value of the shaped signal output by the collector of the second transistor Q3 should be greater than the voltage value of the base of the third transistor Q3. Therefore, the base voltage value V of the third triode Q3T3Namely the shaping threshold value of the passive shaping circuit for filtering the switch burr. Wherein, VTAIs the voltage value of the pulse signal.
In one embodiment, the resistance of the sixth resistor R6 may be set to be equal to the resistance of the seventh resistor R7, so that the base voltage V of the third transistor Q3T3Can be that
If the voltage value of the shaped signal output by the collector of the second triode Q3 is larger than that of the shaped signal output by the collector of the second triode Q3
The third transistor Q3 operates in the saturation region; if the voltage value of the shaped signal output by the collector of the second triode Q2 is less than
The third transistor Q3 operates in the cut-off region.
In addition, when the pulse signal is converted from low level to high level, the third triode Q3 is prevented from entering the amplification region to work, and the voltage value of the shaped signal output by the collector of the second triode Q2 is required to be larger than the voltage value V of the third triode Q3 working in the amplification regionj. The voltage value of the shaped signal output by the collector of the second triode Q2 is the voltage value V of the emitter of the third triode Q3e3The emitter voltage value V of the third triode Q3e3The voltage value V of the base electrode of the third triode Q3 can be usedb3Voltage drop V in connection with itbeQ3Is expressed as a sum of. Therefore, the voltage value V of the emitter of the third triode Q3e3Can be expressed as:
to avoid the third transistor Q3 from entering the amplification region when the pulse signal is converted from low level to high level, it should satisfy:
according to the circuit connection relation, the conduction voltage drop V of the first triode Q1beQ1Can be expressed as:
voltage value V between emitter and collector of second triode Q2ecQ2Can be expressed as: vecQ2＝VTA-VjThe current value I between the base and the emitter of the first triode Q1beQ1Can be expressed as：
Current value I of base electrode of second triode Q2bQ2Can be expressed as:
according to the characteristics of the triode, the current value I between the collector and the emitter of the first triode Q1ceQ1Can be expressed as: i isceQ1＝β1IbeQ1The current value I between the emitter and the collector of the second triode Q2ecQ2Can be expressed as: i isecQ2＝β2IbQ2. Wherein, IceQ1Is the current value between the collector and emitter of the first transistor Q1, IecQ2Is the current value between the emitter and collector of the second triode Q2, Vbe2Is the voltage value between the base and the emitter of the second triode Q2. The third triode Q3 works in the voltage value V of the amplifying region by the connection relationship between the circuitsjCan be expressed as:
therefore, according to the requirements of different pulse signals, the rising edge conduction threshold value and the falling edge conduction threshold value of the pulse input signal and the shaping threshold value for filtering switch burrs can be flexibly set by selecting the type of the triode and the resistance value of each resistor, so that the passive shaping circuit provided by the invention can be suitable for different pulse signals.
Fig. 6 is a circuit diagram of a passive shaping circuit provided in accordance with yet another embodiment of the present invention. As shown in fig. 6, based on fig. 5, the passive shaping circuit may further include a load resistor R8, and the load resistor R8 is connected between the positive output terminal OUT + and the negative output terminal OUT-. The voltage value of the output signal of the passive shaping circuit can be more stable by increasing the load resistor R8.
Fig. 7a and 7b are time domain waveform diagrams of the input/output of a passive shaping circuit provided under an embodiment of the present invention. The gray portion of the sine wave shown in fig. 7a is a portion where the pulse signal is not output after passing through the passive shaping circuit. The waveform in fig. 7b is a waveform diagram of the pulse signal output after passing through the passive shaping circuit. The horizontal axis represents time t in milliseconds (ms), and the vertical axis represents the voltage value of the pulse signal in volts (V). The input signal adopts a mode of increasing noise by sine wave superposition, the whole sine wave represents a pulse signal input into the passive shaping circuit, and black parts represent output signals of the passive shaping circuit. The passive shaping circuit is conducted when the pulse signal is converted from low level to high level and the voltage value of the pulse signal is greater than the rising edge conduction threshold value; when the pulse signal is converted from high level to low level and the voltage value of the pulse signal is smaller than the falling edge conduction threshold value, the signal is not output. Therefore, when the voltage value is close to the low level and is not negative voltage, the voltage of the output signal is stable and is not influenced by large noise, and differential mode noise carried in the pulse signal can be effectively filtered. For the optical coupler input, the optical coupler input is sensitive to voltage change at a low level and is not influenced by noise at a high level.
The preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications can be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.
It should be noted that the various features described in the above embodiments may be combined in any suitable manner without departing from the scope of the invention. The invention is not described in detail in order to avoid unnecessary repetition.
In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.
Claims (6)
1. A passive shaping circuit, comprising: a first triode Q1, a second triode Q2, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4 and a fifth resistor R5,
wherein an emitter of the first transistor Q1 is connected to a negative input terminal of the passive shaping circuit, a collector of the first transistor Q1 is connected to a base of the second transistor Q2 via the first resistor R1, a base of the first transistor Q1 is connected to a collector of the second transistor Q2 via the second resistor R2, a base of the first transistor Q1 is connected to the negative input terminal via the third resistor R3, a base of the second transistor Q2 is connected to the negative input terminal via the fourth resistor R4, a base of the second transistor Q2 is connected to a positive input terminal of the passive shaping circuit via the fifth resistor R5, an emitter of the second transistor Q2 is connected to the positive input terminal of the passive shaping circuit, and a collector of the second transistor Q2 is connected to the positive output terminal of the passive shaping circuit, the negative input end is connected with the negative output end of the passive shaping circuit,
the first triode Q1, the second triode Q2, the first resistor R1, the second resistor R2, the third resistor R3, the fourth resistor R4 and the fifth resistor R5 are used for determining a rising edge conduction threshold and a falling edge conduction threshold, so that the pulse signal input into the passive shaping circuit is turned off when the pulse signal is converted from a low level to a high level and the voltage is less than the rising edge conduction threshold and when the pulse signal is converted from the high level to the low level and the voltage is less than the falling edge conduction threshold.
2. The passive shaping circuit of claim 1, further comprising: a first diode D1 and a second diode D2,
the collector of the first triode Q1 is connected to the cathode of the first diode D1, the anode of the first diode D1 is connected to the negative input terminal, the emitter of the second triode Q2 is connected to the cathode of the second diode D2, and the anode of the second diode D2 is connected to the collector of the second triode Q2.
3. The passive shaping circuit of claim 1, further comprising: a third transistor Q3, a sixth resistor R6, and a seventh resistor R7, wherein an emitter of the third transistor Q3 is connected to a collector of the second transistor Q2, a base of the third transistor Q3 is connected to the positive input terminal via the sixth resistor R6, a base of the third transistor Q3 is connected to the negative output terminal via the seventh resistor R7, and a collector of the third transistor Q3 is connected to the positive output terminal.
4. The passive shaping circuit of claim 3, further comprising: a third diode D3 and a fourth diode D4, wherein the base of the third transistor Q3 is connected to the anode of the third diode D3, the cathode of the third diode D3 is connected to the collector of the second transistor Q2, the collector of the third transistor Q3 is connected to the anode of the fourth diode D4, and the cathode of the fourth diode D4 is connected to the collector of the second transistor Q2.
5. The passive shaping circuit of claim 1, further comprising: a first diode D1, a second diode D2, a third triode Q3, a sixth resistor R6, a seventh resistor R7, a third diode D3, and a fourth diode D4,
wherein a collector of the first transistor Q1 is connected to a cathode of the first diode D1, an anode of the first diode D1 is connected to the negative input terminal, an emitter of the second transistor Q2 is connected to a cathode of the second diode D2, an anode of the second diode D2 is connected to a collector of the second transistor Q2, an emitter of the third transistor Q3 is connected to a collector of the second transistor Q2, a collector of the third transistor Q3 is connected to the positive output terminal, a base of the third transistor Q3 is connected to an anode of the third diode D3, a cathode of the third diode D3 is connected to a collector of the second transistor Q2, a collector of the third transistor Q3 is connected to an anode of the fourth diode D4, and a cathode of the fourth diode D4 is connected to a collector of the second transistor Q2, the base of the third transistor Q3 is connected to the positive input terminal via the sixth resistor R6, the base of the third transistor Q3 is connected to the negative input terminal via the seventh resistor R7,
determining the rising edge conduction threshold and the falling edge conduction threshold according to the following equations:
VT1<VTL；
wherein, VTHFor the rising edge conduction threshold, VbeQ2Is the conduction voltage drop, V, of the second transistor Q2TLFor the falling edge conduction threshold, VceQ1Is the voltage value between the collector and the emitter of the first triode Q1, VT1Is the voltage value, V, of the collector of the second triode Q2 during the transition from high level to low level of the input signalbeQ1Is the conduction voltage drop, R, of the first transistor Q11Is the resistance value of the first resistor R1, R2Is the resistance value of the second resistor R2, R3Is the resistance value of the third resistor R3, R4Is the resistance value of the fourth resistor R4, R5Is the resistance value of the fifth resistor R56Is the resistance value of the sixth resistor R67Is the resistance value, V, of the seventh resistor R7T3Is the base voltage value, V, of the third transistor Q3TAIs the voltage value, V, of said pulse signaljis the voltage value, beta, of the third triode Q3 when operating in the amplifying region1is the amplification factor, beta, of the first transistor Q12Is the amplification factor, V, of the second transistor Q2d3Is the voltage value, V, of the third diode D3be2Is the voltage value between the base electrode and the emitter electrode of the second triode Q2, VbeQ3Is the conduction voltage drop of the third transistor Q3.
6. The passive shaping circuit of claim 5, further comprising a load resistor R8, the load resistor R8 being connected between the positive output terminal and the negative output terminal.
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Citations (4)
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| US4161703A (en) * | 1977-03-22 | 1979-07-17 | Licentia Patent-Verwaltungs-G.M.B.H. | Schmitt trigger square wave oscillator |
| CN201467542U (en) * | 2009-06-16 | 2010-05-12 | 深圳市垅运照明电器有限公司 | Direct current (DC) electronic ballast and half-bridge inverter LC series-resonance circuit thereof |
| CN101867214A (en) * | 2010-06-24 | 2010-10-20 | 深圳市瑞必达电源有限公司 | Charging circuit and charger |
| CN102769453A (en) * | 2012-06-30 | 2012-11-07 | 东南大学 | High-voltage side gate drive circuit capable of resisting noise interference |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4161703A (en) * | 1977-03-22 | 1979-07-17 | Licentia Patent-Verwaltungs-G.M.B.H. | Schmitt trigger square wave oscillator |
| CN201467542U (en) * | 2009-06-16 | 2010-05-12 | 深圳市垅运照明电器有限公司 | Direct current (DC) electronic ballast and half-bridge inverter LC series-resonance circuit thereof |
| CN101867214A (en) * | 2010-06-24 | 2010-10-20 | 深圳市瑞必达电源有限公司 | Charging circuit and charger |
| CN102769453A (en) * | 2012-06-30 | 2012-11-07 | 东南大学 | High-voltage side gate drive circuit capable of resisting noise interference |
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