Circuit and method for generating composite rectangular wave signal

Abstract

The invention relates to a composite rectangular wave signal generation circuit which is composed of two forward feedback self-oscillation unit circuits, the first unit circuit comprises two triodes Q1 and Q3, a resistor R2, a resistor R3, a resistor R7, a resistor R9, a resistor R10, a capacitor C2 and a diode D2, and the second unit circuit comprises two triodes Q2 and Q4, a resistor R1, a resistor R5, a resistor R6, a resistor R11, a resistor R12, a capacitor C1, a diode D1 and a coupling resistor R4. According to the invention, based on a forward feedback mechanism of a crystal triode system, the system enters a self-oscillation state, rectangular wave oscillation signals with different frequencies are generated, and a composite rectangular wave signal can be generated through adjustment of static parameters and coupling. The device is simple in structure, convenient to design, easy to maintain and lower in production and manufacturing cost.

Description

Technical Field

[0001] The present invention relates to the field of circuit technology, and in particular to a circuit and method for generating a composite rectangular wave signal. Background Art

[0002] Rectangular wave signals are ubiquitous in electronic control systems and are widely used, such as load device switching, timing control, light brightness adjustment, motor or stepper motor speed, vector angle control, power, voltage, current control of digital switching power supply systems, data communication, and industrial automation control. The market size is huge. Under the existing technology, rectangular wave signals and the more complex composite rectangular wave signals involved in the present invention are generally implemented using dedicated integrated circuits or MCU programming, which greatly increases the complexity of circuit design and increases the cost and difficulty of production and subsequent maintenance. Summary of the invention

[0003] The object of the present invention is to provide a circuit and method for generating a composite rectangular wave signal.

[0004] In order to solve the above technical problems, the present invention is implemented by the following technical measures: a composite rectangular wave signal generating circuit, characterized in that it is composed of two positive feedback self-excited oscillation unit circuits, wherein:

[0005] Unit circuit 1 includes two NPN transistors Q1 and Q3; one end of the bias resistor R2 is connected to the positive electrode of the DC voltage regulator source V1, and the other end is connected to the base B of Q1 and the collector C of Q3; one end of the bias resistor R3 is connected to the positive electrode of the DC voltage regulator source V1, and the other end is connected to the collector of Q1 and the 1st pin of the coupling resistor R4; one end of the bias resistor R7 is connected to the emitter of Q3 and one end of R10, and the other end is connected to the emitter of Q1 and the positive electrode of the isolation diode D2. One end of the feedback resistor R9 is connected to the base of Q3, and the other end is connected to pin 1 of C2 and one end of resistor R8. One end of the bias resistor R10 is connected to the emitter of Q3 and one end of resistor R7, and the other end is connected to the common reference point 0. One end of the energy storage capacitor C2 is connected to the common reference point 0, and the other end is connected to resistor R8 and one end of resistor R9. One end of the isolation diode D2 is connected to the emitter of Q1 and one end of resistor R7, and the other end is connected to one end of resistor R8.

[0006] Unit circuit 2 includes two PNP-type transistors Q2 and Q4; one end of the current limiting resistor R1 is connected to the positive electrode of the diode D1, and the other end is connected to the pin 1 of C1; one end of the bias resistor R5 is connected to the emitter of Q2 and one end of R6, and the other end is connected to the emitter of Q4 and the negative electrode of the diode D1; one end of the bias resistor R6 is connected to the positive electrode of the DC regulated power supply V2 and the pin 2 of C1, and the other end is connected to the emitter of Q2 and one end of R5; one end of the bias resistor R11 is connected to the collector of Q4, and the other end is connected to the common reference point 0; one end of the positive feedback resistor R12 is connected to the base of Q2, and the other end is connected to the pin 1 of the capacitor C1 and one end of the resistor R1; the pin 2 of the energy storage capacitor C1 is connected to the positive electrode of the DC power supply V2 and one end of the resistor R6, and the other end is connected to the resistors R1 and one end of R12; one end of the isolation diode D1 is connected to the emitter of Q4 and one end of R5, and the other end is connected to one end of R1.

[0007] The coupling resistor R4 is used for signal coupling transmission between two unit circuits, one end of which is connected to the collector C of Q1 and one end of the resistor R3, and the other end is connected to the collector of Q2 and the base of Q4.

[0008] Compared with the prior art, the advantages of the present invention are: the present invention is based on the positive feedback mechanism of the crystal triode system, so that the system enters a self-excited oscillation state, generates rectangular wave oscillation signals of different frequencies, the frequency of which can be adjusted by static bias parameters, and then generates a composite rectangular wave signal after coupling. It has a simple structure, convenient design, easy maintenance, and lower production and manufacturing costs, which solves the technical problems of complex design, difficult maintenance, and high production and manufacturing costs caused by the use of dedicated integrated circuits or programmable MCUs for composite rectangular wave signals in the prior art.

[0009] The present invention also provides a method for generating a composite rectangular wave signal, comprising a composite rectangular wave signal generating circuit as described in claim 1, characterized in that: when initially powered on, since the voltage across the capacitor cannot change suddenly; the potential of pin 1 of unit circuit C2 is 0V, the NPN-type crystal triode Q3 has no saturated conduction condition and is in a cut-off state, and the NPN-type crystal triode Q1 obtains a saturated conduction condition under the action of the bias resistor R2 and is in a conducting state, and its collector C outputs a low level containing a voltage offset; the current flowing through the NPN-type crystal triode Q1 forms each emitter bias voltage after passing through the bias resistors R7 and R10; the other current slowly charges the capacitor C2 after passing through the isolation diode D2 and the current limiting resistor R8; when the voltage of pin 1 is greater than the emitter bias voltage of the NPN-type crystal triode Q3, the ... collector C outputs a low level containing a voltage offset; the collector C outputs a low level containing a voltage offset; the collector C outputs a low level containing a voltage offset; the collector C outputs a low level containing a voltage offset; the collector C outputs a low level containing a voltage offset; the collector C outputs When the sum of the set voltage, the emitter PN junction turn-on voltage and the R9 conduction voltage drop is reached, the NPN transistor Q3 changes from the cut-off state to the saturated conduction state, and the NPN transistor Q1 changes from the saturated conduction state to the cut-off state, and its collector C outputs a 12V high level; the capacitor C2 changes to a slow discharge state, maintaining the saturated conduction state of the NPN transistor Q3 until the next charging cycle starts; when charging, the collector C of the NPN transistor Q1 outputs a low level containing a voltage offset, and the 1 foot of C2 and both ends of the feedback resistor R9 are low levels; when discharging, the collector C of the NPN transistor Q1 outputs a 12V high level, and the 1 foot of C2 and both ends of the feedback resistor R9 are high levels, so the system is a positive feedback, forming a self-excited oscillation, and continuously outputting a low-frequency rectangular wave signal.

[0010] Unit circuit 2, when the coupling signal is high level, the positive feedback mechanism is destroyed, and self-excited oscillation cannot be generated. The collector C of the PNP transistor Q4 only outputs a low level; when the coupling signal is low level, the PNP transistor Q4 obtains the saturation conduction condition, and the working state changes from cut-off to saturation conduction, and its collector C outputs a high level, and the amplitude is the bias voltage generated by the collector resistor R11; the current flowing into the PNP transistor Q4 flows into Q4 through the DC regulated power supply V2, bias resistors R5 and R6, forming each emitter bias voltage; the other route is the DC regulated power supply V2, RC circuit 2, and isolation diode D1 input; during the saturation conduction period of the PNP transistor Q4, the capacitor C1 is slowly charged, and the potential of its 1 foot slowly becomes lower. When the voltage is lower than that of the PNP transistor When the sum of the emitter bias voltage of the body transistor Q2, the emitter PN junction turn-on voltage and the conduction voltage drop of R12 is reached, the PNP transistor Q2 changes from the cut-off state to the saturated conduction state, and the PNP transistor Q4 changes from the saturated conduction state to the cut-off state, and its collector C outputs a low level, and the capacitor C1 changes to a slow discharge state, maintaining the saturated conduction state of the PNP transistor Q2 until the next charging cycle starts; when charging, the collector C of the PNP transistor Q4 outputs a high level, and the 1st pin of C1 and both ends of the feedback resistor R12 are high levels; when discharging, the collector C of the PNP transistor Q4 outputs a low level, and the 1st pin of C1 and both ends of the feedback resistor R12 are low levels. At this time, the system is in positive feedback, forming a self-excited oscillation, and continuously outputting a high-frequency rectangular wave signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their description are used to explain the present invention and do not constitute improper limitations on the present invention.

[0012] In the attached picture:

[0013] Figure 1 The schematic diagram of the circuit of the present invention.

[0014] Figure 2 It is a rectangular wave signal of an independently working unit circuit VQ1:C described in the present invention.

[0015] Figure 3 It is the rectangular wave signal of VQ2:C of the second independent working unit circuit described in the present invention.

[0016] Figure 4 It is the rectangular wave signal of VQ4:C of the second independent working unit circuit described in the present invention.

[0017] Figure 5 It is the composite rectangular wave signal of the coupled working VQ2:C described in the present invention.

[0018] Figure 6 It is the composite rectangular wave signal of the coupled working VQ4:C described in the present invention. DETAILED DESCRIPTION

[0019] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0020] Example 1

[0021] Please refer to Figure 1-6 The present embodiment provides a composite rectangular wave signal generating circuit, which is composed of two positive feedback self-excited oscillation unit circuits, wherein:

[0022] Unit circuit 1 includes two NPN transistors Q1 and Q3; one end of the bias resistor R2 is connected to the positive electrode of the DC voltage regulator source V1, and the other end is connected to the base B of Q1 and the collector C of Q3; one end of the bias resistor R3 is connected to the positive electrode of the DC voltage regulator source V1, and the other end is connected to the collector of Q1 and pin 1 of the coupling resistor R4; one end of the bias resistor R7 is connected to the emitter of Q3 and one end of R10, and the other end is connected to the emitter of Q1 and the positive electrode of the isolation diode D2. One end of the forward feedback resistor R9 is connected to the base of Q3, and the other end is connected to pin 1 of C2 and one end of resistor R8. One end of the bias resistor R10 is connected to the emitter of Q3 and one end of resistor R7, and the other end is connected to the common reference point 0. One end of the energy storage capacitor C2 is connected to the common reference point 0, and the other end is connected to resistor R8 and one end of resistor R9. One end of the isolation diode D2 is connected to the emitter of Q1 and one end of resistor R7, and the other end is connected to one end of resistor R8.

[0023] Unit circuit 2 includes two PNP-type transistors Q2 and Q4; one end of the current limiting resistor R1 is connected to the positive electrode of the diode D1, and the other end is connected to the pin 1 of C1; one end of the bias resistor R5 is connected to the emitter of Q2 and one end of R6, and the other end is connected to the emitter of Q4 and the negative electrode of the diode D1; one end of the bias resistor R6 is connected to the positive electrode of the DC regulated power supply V2 and the pin 2 of C1, and the other end is connected to the emitter of Q2 and one end of R5; one end of the bias resistor R11 is connected to the collector of Q4, and the other end is connected to the common reference point 0; one end of the positive feedback resistor R12 is connected to the base of Q2, and the other end is connected to the pin 1 of the capacitor C1 and one end of the resistor R1; the pin 2 of the energy storage capacitor C1 is connected to the positive electrode of the DC power supply V2 and one end of the resistor R6, and the other end is connected to the resistors R1 and one end of R12; one end of the isolation diode D1 is connected to the emitter of Q4 and one end of R5, and the other end is connected to one end of R1.

[0024] The coupling resistor R4 is used for signal coupling transmission between two unit circuits, one end of which is connected to the collector C of Q1 and one end of the resistor R3, and the other end is connected to the collector of Q2 and the base of Q4.

[0025] The connection relationship between the discrete components is shown in Figure 1 (Circuit schematic diagram), the functions of the main components are described as follows:

[0026] V1 DC 12V DC regulated voltage source, energy supply device for unit circuit 1, provides stable electrical energy for unit circuit 1.

[0027] The Q1 unit circuit is an NPN transistor, which works in saturated conduction and cutoff states. When initially powered on, it is first saturated and turned on, and provides power for the subsequent RC circuit. Further, the emitter E bias voltage of Q1 and Q3 is generated through resistors R7 and R10. The collector C bias voltage of Q1 is generated through resistor R3, and when the system continues to operate, a low-frequency rectangular wave signal containing a voltage offset is output at the collector C, such as Figure 2 As shown in the circuit connection relationship, the collector C is connected to one end of the resistors R3 and R4, the base B is connected to the collector C of the NPN transistor Q3 and one end of the resistor R2, and the emitter E is connected to the resistor R7 and one end of the diode D2.

[0028] The Q3 unit circuit is an NPN transistor, which works in saturation conduction and cutoff states. When the potential of C2's 1 pin is greater than the sum of the current limiting voltage drop of R9, the Q3 emitter junction turn-on voltage and the emitter E bias voltage, it is saturated and turned on, otherwise it is cut off. Its circuit connection relationship is that the collector C is connected to the Q1 base B and one end of the resistor R2, the base B is connected to one end of the current limiting resistor R9, and the emitter E is connected to one end of the resistors R7 and R10.

[0029] R2 unit circuit is a bias resistor between the base B of Q1 and the collector C of Q3, which is used to generate bias voltages for the base B of Q1 and the collector C of Q3. Its circuit connection relationship is that one end is connected to the positive electrode of the DC voltage regulator source V1 and one end of the resistor R3, and the other end is connected to the base B of Q1 and the collector C of Q3.

[0030] R3 unit circuit is a bias resistor for the collector C of Q1. It is used to generate a bias voltage for the collector C of Q1. Its circuit connection relationship is that one end is connected to the positive electrode of the DC voltage regulator V1 and one end of the resistor R2, and the other end is connected to the collector C of Q1 and the 1st pin of the coupling resistor R4.

[0031] R4 is a coupling resistor between unit circuit 1 and unit circuit 2, used for signal coupling transmission between the two unit circuits. Its circuit connection relationship is that one end is connected to the collector C of Q1 and one end of the resistor R3, and the other end is connected to the collector C of Q2 and the base B of Q4.

[0032] R7 unit circuit is a Q1 emitter E bias resistor, which is connected in series with R10 to generate a bias voltage for Q1 emitter E. Its circuit connection relationship is that one end is connected to Q3 emitter E and one end of R10, and the other end is connected to Q1 emitter E and the positive electrode of the isolation diode D2.

[0033] R8 is a current limiting resistor in the RC circuit 1 in the unit circuit 1, which is used to adjust the charging current of the capacitor C2 and further adjust the charging time of the capacitor C2. Its circuit connection relationship is that one end is connected to the cathode of the isolation diode D2, and the other end is connected to the 1st pin of C2 and one end of the resistor R9.

[0034] R9 is a self-oscillating positive feedback resistor in the unit circuit, and is also the base B resistor of Q3. It is used to limit the discharge speed of capacitor C2 and improve the frequency response of the circuit. Its circuit connection relationship is that one end is connected to the base B of Q3, and the other end is connected to the 1st pin of C2 and one end of resistor R8.

[0035] R10 unit circuit is the emitter E bias resistor of Q3. It is used to generate the emitter E bias voltage of Q3 and increase the emitter E bias voltage of Q1. Its circuit connection relationship is that one end is connected to the emitter E of Q3 and one end of the resistor R7, and the other end is connected to the common reference point 0.

[0036] The energy storage capacitor in the RC circuit of the C2 unit circuit is charged when Q1 is saturated and Q3 is turned off, and discharged when Q3 is saturated and Q1 is turned off. Its circuit connection relationship is that one end is connected to the common reference point 0, and the other end is connected to one end of the resistor R8 and the resistor R9.

[0037] The D2 unit circuit is an isolation diode, which uses its unidirectional conductivity to isolate the charging and discharging loops of the RC circuit to prevent the discharge current from flowing in the reverse direction. Its circuit connection relationship is that one end is connected to the emitter E of Q1 and one end of the resistor R7, and the other end is connected to one end of the resistor R8.

[0038] V2 DC 12V DC regulated voltage source, energy provider for unit circuit 2, provides stable electrical energy for unit circuit 2.

[0039] The Q2 unit circuit is a PNP transistor that works in saturated conduction and cutoff states. When the capacitor C1 is discharged, its emitter junction voltage VEB is greater than the emitter junction turn-on voltage, and it is saturated conduction. When the capacitor C1 is charged, it is cut off. Its circuit connection relationship is that the collector C is connected to the base B of Q4 and one end of the resistor R4, the base B is connected to one end of the current limiting resistor R12, and the emitter E is connected to one end of the resistors R5 and R6.

[0040] The second PNP transistor in the Q4 unit circuit works in saturation conduction and cut-off states. When it is saturated conduction, its collector C outputs a high-frequency rectangular wave signal, and stops outputting when it is cut off. At the same time, the RC circuit 2 is closed when Q4 is saturated conduction, and C1 is charged; when it is cut off, C1 is discharged, and the cycle repeats. Its circuit connection relationship is that the collector C is connected to one end of the resistor R11, the base B is connected to the collector C of Q2 and the 2nd pin of the resistor R4, and the emitter E is connected to the cathode of the diode D1 and one end of R5.

[0041] The RC circuit 2 charging current limiting resistor in the R1 unit circuit 2 is used to adjust the charging current of the capacitor C1 and further adjust the charging time of the capacitor C1. Its circuit connection relationship is that one end is connected to the positive electrode of the diode D1, and the other end is connected to the 1st pin of C1.

[0042] R5 is the bias resistor on the emitter E of Q4 and the bias resistor on the emitter E of Q2 in the second unit circuit. During the saturation conduction period of Q4, it changes the bias voltage of the emitter E of the two PNP transistors together with R6 and R11. Its circuit connection relationship is that one end is connected to the emitter E of Q2 and one end of R6, and the other end is connected to the emitter E of Q4 and the negative electrode of the diode D1.

[0043] R6 is the bias resistor on the emitter E of Q2 in the second unit circuit. During the saturation conduction period of Q4, it changes the bias voltage of the emitter E of Q2 together with R5 and R11. Its circuit connection relationship is that one end is connected to the positive pole of the DC regulated power supply V2 and the 2nd foot of C1, and the other end is connected to the emitter E of Q2 and one end of R5.

[0044] R11 is a Q4 collector C bias resistor in the second unit circuit, which is used to generate a collector C bias voltage. Its circuit connection relationship is that one end is connected to the collector C of Q4, and the other end is connected to the common reference point 0.

[0045] R12 is the positive feedback resistor of the self-oscillation unit circuit 2, and is also the base B resistor of Q2. It is used to limit the discharge speed of capacitor C1 and improve the frequency response of the circuit. Its circuit connection relationship is that one end is connected to the base B of Q2, and the other end is connected to the 1st pin of capacitor C1 and one end of resistor R1.

[0046] The energy storage capacitor of RC circuit 2 in C1 unit circuit 2 is charged when Q4 is saturated and Q2 is turned off, and discharged when Q2 is saturated and Q4 is turned off. Its circuit connection relationship is that pin 2 is connected to the positive electrode of DC power supply V2 and one end of resistor R6, and the other end is connected to one end of resistors R1 and R12.

[0047] The D1 unit circuit 2 isolation diode uses its unidirectional conductivity to isolate the RC circuit 2 charging and discharging loop to prevent the discharge current from flowing in the reverse direction. Its circuit connection relationship is that one end is connected to the emitter E of Q4 and one end of R5, and the other end is connected to one end of R1.

[0048] Working principle:

[0049] Two self-excited oscillation circuits based on positive feedback of transistors are used to generate rectangular wave signals with different frequencies, different voltage offsets and different amplitudes according to corresponding bias parameters, and finally output the composite rectangular wave signal with a voltage offset of 0 at the collector C of the PNP transistor Q4.

[0050] When the coupling is disconnected, that is, when the R4 pin 1 is disconnected from the Q1 collector C and connected to the common reference point 0, the two unit circuits can work independently and generate self-excited oscillation. Among them, the unit circuit 1 can output a low-frequency rectangular wave signal with an offset of VQ1:C and an amplitude of VR3 at the Q1 collector C, such as Figure 2 As shown. Unit circuit 2 can generate a high-frequency rectangular wave signal with a voltage offset of VQ2:C and an amplitude of VQ2:E-VQ2:C at the collector C of Q2, as shown Figure 3 As shown; at the same time, the output voltage offset at the reverse pole of Q4 collector C is 0, and the amplitude is a high-frequency rectangular wave of VQ4:C, as shown Figure 4 shown.

[0051] After direct coupling, the circuit diagram is as follows: Figure 1 As shown. Under the interaction of the two unit circuits, that is, when the collector C of unit circuit Q1 outputs a high-level signal with an offset of VQ1:C, the saturated conduction condition of Q2 in unit circuit 2 is broken and it turns to the cut-off state, and its collector C stops generating a high-frequency rectangular wave signal with a voltage offset of VQ2:C; when the collector C of unit circuit Q1 outputs a low-level signal with an offset of VQ1:C, Q2 in unit circuit 2 obtains a saturated conduction condition, and its collector C generates a high-frequency rectangular wave signal with a voltage offset of VQ2:C, and further obtains a composite rectangular wave signal for controlling the PNP transistor Q4, whose offset is VQ2:C and the maximum amplitude is 12v-VQ2:C, as shown Figure 5 Finally, the collector C of the PNP transistor Q4 outputs a composite rectangular wave signal with a voltage offset of 0 according to the present invention, as shown in FIG. Figure 6 As shown, it can be used for subsequent drive control of various loads.

[0052] The present invention also provides a method for generating a composite rectangular wave signal:

[0053] At the initial power-on, the voltage across the capacitor cannot change suddenly. Unit circuit 1, the potential of pin 1 of C2 is 0V, the NPN transistor Q3 has no saturated conduction condition and is in the cut-off state. Under the action of bias resistor R2, the NPN transistor Q1 obtains the saturated conduction condition and is in the conduction state, and its collector C outputs a low level containing a voltage offset. The current flowing through the NPN transistor Q1 forms the emitter bias voltage after passing through the bias resistors R7 and R10; the other current slowly charges the capacitor C2 after passing through the isolation diode D2 and the current limiting resistor R8. When the voltage of pin 1 is greater than the sum of the emitter bias voltage of the NPN transistor Q3, the emitter PN junction turn-on voltage and the conduction voltage drop of R9, the NPN transistor Q3 changes from the cut-off state to the saturated conduction state, and the NPN transistor Q1 changes from the saturated conduction state to the cut-off state, and its collector C outputs a 12V high level. Capacitor C2 turns to a slow discharge state, maintaining the saturated conduction state of NPN transistor Q3 until the next charging cycle starts. When charging, the collector C of NPN transistor Q1 outputs a low level with a voltage offset, and both pin 1 of C2 and both ends of the feedback resistor R9 are low levels; when discharging, the collector C of NPN transistor Q1 outputs a 12V high level, and both pin 1 of C2 and both ends of the feedback resistor R9 are high levels, so the system is positive feedback, forming a self-excited oscillation, and continuously outputting a low-frequency rectangular wave signal.

[0054] Unit circuit 2, when the coupling signal is at a high level, the forward feedback mechanism is destroyed, and self-excited oscillation cannot be generated. The collector C of the PNP transistor Q4 only outputs a low level. When the coupling signal is at a low level, the PNP transistor Q4 obtains a saturated conduction condition, and the working state changes from cutoff to saturated conduction. Its collector C outputs a high level, and the amplitude is the bias voltage generated by the collector resistor R11. The current flowing into the PNP transistor Q4 flows into Q4 through the DC regulated power supply V2, bias resistors R5 and R6, forming the bias voltage of each emitter; the other route is the DC regulated power supply V2, RC circuit 2, and isolation diode D1 input. During the saturation conduction period of the PNP transistor Q4, the capacitor C1 is charged slowly, and the potential of its pin 1 slowly decreases. When the voltage is lower than the sum of the emitter bias voltage of the PNP transistor Q2, the emitter PN junction turn-on voltage and the conduction voltage drop of R12, the PNP transistor Q2 changes from the cut-off state to the saturation conduction state, and the PNP transistor Q4 changes from the saturation conduction state to the cut-off state. Its collector C outputs a low level, and the capacitor C1 changes to a slow discharge state, maintaining the saturation conduction state of the PNP transistor Q2 until the next charging cycle starts. When charging, the collector C of the PNP transistor Q4 outputs a high level, and the pin 1 of C1 and both ends of the feedback resistor R12 are high levels; when discharging, the collector C of the PNP transistor Q4 outputs a low level, and the pin 1 of C1 and both ends of the feedback resistor R12 are low levels. At this time, the system is positive feedback, forming a self-excited oscillation, and continuously outputting a high-frequency rectangular wave signal.

[0055] In summary, when the unit circuit 1 is self-oscillating, it will output a low-frequency rectangular wave signal containing a voltage offset. When the low level of the low-frequency rectangular wave signal is coupled to the unit circuit 2, the unit circuit 2 has a positive feedback condition, generates self-oscillation, and outputs a high-frequency rectangular wave signal with a voltage offset of 0 at the collector C of the PNP-type transistor Q4; when the high level of the low-frequency rectangular wave signal is coupled to the unit circuit 2, the positive feedback condition of the unit circuit 2 is destroyed, no self-oscillation is generated, and the collector C of the PNP-type transistor Q4 outputs a low level with a voltage offset of 0. Finally, the composite rectangular wave signal of the present invention is formed.

[0056] Compared with the prior art, the invention has the following beneficial effects:

[0057] Through the coupling and interaction of self-excited oscillation units of different frequencies, various types of composite rectangular wave signals can be easily realized. It has a simple structure, convenient design, easy maintenance, lower production cost, and is composed of general discrete components, so it has higher economic value.

[0058] In the description of the present invention, it should be noted that the terms "vertical", "up", "down", "horizontal", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0059] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0060] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A composite rectangular wave signal generating circuit, characterized in that: It is composed of two positive feedback self-excited oscillation unit circuits, where: Unit circuit 1 includes two NPN transistors Q1 and Q3; one end of the bias resistor R2 is connected to the positive electrode of the DC voltage regulator source V1, and the other end is connected to the base B of Q1 and the collector C of Q3; one end of the bias resistor R3 is connected to the positive electrode of the DC voltage regulator source V1, and the other end is connected to the collector of Q1 and pin 1 of the coupling resistor R4; one end of the bias resistor R7 is connected to the emitter of Q3 and one end of R10, and the other end is connected to the emitter of Q1 and the positive electrode of the isolation diode D2. One end of the forward feedback resistor R9 is connected to the base of Q3, and the other end is connected to pin 1 of C2 and one end of the resistor R8. One end of the bias resistor R10 is connected to the emitter of Q3 and one end of the resistor R7, and the other end is connected to the common reference point 0. One end of the energy storage capacitor C2 is connected to the common reference point 0, and the other end is connected to the resistor R8 and one end of the resistor R9. One end of the isolation diode D2 is connected to the emitter of Q1 and one end of the resistor R7, and the other end is connected to one end of the resistor R8. Unit circuit 2 includes two PNP-type transistors Q2 and Q4; one end of the current limiting resistor R1 is connected to the positive electrode of the diode D1, and the other end is connected to the pin 1 of C1; one end of the bias resistor R5 is connected to the emitter of Q2 and one end of R6, and the other end is connected to the emitter of Q4 and the negative electrode of the diode D1; one end of the bias resistor R6 is connected to the positive electrode of the DC regulated power supply V2 and the pin 2 of C1, and the other end is connected to the emitter of Q2 and one end of R5; one end of the bias resistor R11 is connected to the collector of Q4, and the other end is connected to the common reference point 0; one end of the positive feedback resistor R12 is connected to the base of Q2, and the other end is connected to the pin 1 of the capacitor C1 and one end of the resistor R1; the pin 2 of the energy storage capacitor C1 is connected to the positive electrode of the DC power supply V2 and one end of the resistor R6, and the other end is connected to one end of the resistors R1 and R12; one end of the isolation diode D1 is connected to the emitter of Q4 and one end of R5, and the other end is connected to one end of R1; The coupling resistor R4 is used for signal coupling transmission between two unit circuits, one end of which is connected to the collector C of Q1 and one end of the resistor R3, and the other end is connected to the collector of Q2 and the base of Q4.

2. A method for generating a composite rectangular wave signal, comprising a composite rectangular wave signal generating circuit as described in right 1, characterized in that: When the power is initially turned on, the voltage across the capacitor cannot change suddenly; the potential of pin 1 of unit circuit C2 is 0V, the NPN transistor Q3 has no saturation conduction condition and is in the cut-off state. Under the action of bias resistor R2, the NPN transistor Q1 obtains the saturation conduction condition and is in the on state, and its collector C outputs a low level containing a voltage offset; the current flowing through the NPN transistor Q1 forms the emitter bias voltage after passing through bias resistors R7 and R10; the other current passes through the isolation diode D2 and the current limiting resistor R8 to slowly charge the capacitor C2; when the voltage of pin 1 is greater than the sum of the emitter bias voltage of the NPN transistor Q3, the emitter PN junction turn-on voltage and the conduction voltage drop of R9 , the NPN transistor Q3 changes from the cut-off state to the saturated conduction state, the NPN transistor Q1 changes from the saturated conduction state to the cut-off state, and its collector C outputs a 12V high level; the capacitor C2 changes to a slow discharge state, maintaining the saturated conduction state of the NPN transistor Q3 until the next charging cycle starts; when charging, the collector C of the NPN transistor Q1 outputs a low level containing a voltage offset, and the 1 foot of C2 and both ends of the feedback resistor R9 are low levels; when discharging, the collector C of the NPN transistor Q1 outputs a 12V high level, and the 1 foot of C2 and both ends of the feedback resistor R9 are high levels, so the system is a positive feedback, forming a self-excited oscillation, and continuously outputting a low-frequency rectangular wave signal; Unit circuit 2, when the coupling signal is high level, the positive feedback mechanism is destroyed, and self-excited oscillation cannot be generated. The collector C of the PNP transistor Q4 only outputs a low level; when the coupling signal is low level, the PNP transistor Q4 obtains the saturation conduction condition, and the working state changes from cut-off to saturation conduction, and its collector C outputs a high level, and the amplitude is the bias voltage generated by the collector resistor R11; the current flowing into the PNP transistor Q4 flows into Q4 through the DC regulated power supply V2, bias resistors R5 and R6, forming each emitter bias voltage; the other route is the DC regulated power supply V2, RC circuit 2, and isolation diode D1 input; during the saturation conduction period of the PNP transistor Q4, the capacitor C1 is slowly charged, and the potential of its 1 foot slowly becomes lower. When the voltage is lower than that of the PNP transistor When the sum of the emitter bias voltage of the body transistor Q2, the emitter PN junction turn-on voltage and the conduction voltage drop of R12 is reached, the PNP transistor Q2 changes from the cut-off state to the saturated conduction state, and the PNP transistor Q4 changes from the saturated conduction state to the cut-off state, and its collector C outputs a low level, and the capacitor C1 changes to a slow discharge state, maintaining the saturated conduction state of the PNP transistor Q2 until the next charging cycle starts; when charging, the collector C of the PNP transistor Q4 outputs a high level, and the 1st pin of C1 and both ends of the feedback resistor R12 are high levels; when discharging, the collector C of the PNP transistor Q4 outputs a low level, and the 1st pin of C1 and both ends of the feedback resistor R12 are low levels. At this time, the system is in positive feedback, forming a self-excited oscillation, and continuously outputting a high-frequency rectangular wave signal.

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