Oscillator circuit driven by constant power
By designing a constant power-driven oscillator circuit, using inductor coils and switching units to control current changes, monitor and adjust current, the problem of poor frequency stability of existing oscillator circuits is solved, and the effect of high stability and low power consumption is achieved.
Patent Information
- Application Number
- CN202411964919.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-30
- Publication Date
- 2025-04-29
AI Technical Summary
The frequency stability of existing oscillator circuits is poor and are susceptible to environmental factors such as temperature and humidity, resulting in fluctuations in the oscillation frequency.
A constant power driven oscillator circuit is designed, using an inductor coil, switching unit, sampling module, current monitoring module, time control module and logic processing control output unit. By controlling the charging and power outage of the inductor coil, the current changes are monitored, and the next cycle period is periodically triggered through the time control module to reduce the average power consumption.
The high stability of the oscillator circuit is achieved, frequency fluctuations are avoided, average power consumption is reduced, and overall stability and frequency stability are improved.
Smart Images
Figure CN119906367A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of oscillators, and in particular to an oscillator circuit driven by constant power. Background Art
[0002] The oscillator currently used in inductive sensors uses the coil L as a part of the oscillator. Even if it is not working in a resonant state, it still emits a magnetic field to the outside, and uses the eddy current effect to detect metal objects. The general technology is to build an LC oscillator in the sensor. The commonly used typical structures can be divided into: LC parallel oscillation circuit, capacitor three-point oscillation circuit and transformer feedback oscillation circuit. In these three circuits, the coil L resonates in parallel with the capacitor C to generate a sine wave.
[0003] LC parallel oscillation circuit: The frequency selection network formed by inductance and capacitance, combined with the amplification function of transistors or operational amplifiers, can also achieve self-excited oscillation and generate sinusoidal wave output. Figure 1 As shown; Capacitor three-point oscillation circuit: The three resistors and transistors in the circuit form a common emitter amplifier circuit, and its output signal passes through the resonant network composed of C1, C2, and L1 to achieve frequency selection and phase shift, and the signal is sent back to the input base of the common emitter amplifier circuit to form a closed loop, as shown in the figure. Figure 2 As shown; Transformer feedback oscillation circuit: The transformer equivalent inductance that resonates with C1 includes the primary self-inductance and the primary mutual inductance. The signal is coupled to the secondary side through the transformer and fed back to the base of the transistor at the input end of the amplifier to form a closed loop, as shown in the figure. Figure 3 As shown; the resonant frequencies in the above three typical oscillator circuits are:
[0004] Disadvantages of the existing technology: The main disadvantage of the LC type oscillation circuit is that the frequency stability is not high, because its frequency stability can usually only reach 10 -5, which means that its frequency stability is relatively low and the loss is large. Because the LC parallel network has loss, when the loss is small, the quality factor and resonant frequency will be affected, resulting in a decrease in circuit performance and a poor waveform. Due to loss and instability factors, the waveform generated by the circuit may be poor, often containing high-order harmonics, and various stability problems may be encountered; One of the disadvantages of the capacitor three-point oscillation circuit is that the frequency stability is relatively poor. Since the capacitance value of the capacitor may change due to environmental factors such as temperature and humidity, resulting in fluctuations in the oscillation frequency, in addition, it is difficult to start the capacitor three-point circuit, and the requirements for transistors are high, requiring them to have a large transconductance and a high amplification factor, which to a certain extent increases the difficulty of circuit design and device selection; The disadvantage of the transformer feedback oscillation circuit is that the frequency stability is relatively poor. Since its oscillation frequency depends to a large extent on the parameters of the transformer, and the parameters of the transformer are easily affected by environmental factors such as temperature and humidity, resulting in the oscillation frequency drifting, and the starting conditions are more stringent. It requires precise adjustment of the component parameters in the circuit to meet the starting requirements, which increases the difficulty of circuit design and debugging. Summary of the invention
[0005] In view of the shortcomings of the prior art described above, an object of the present invention is to provide an oscillator circuit with a constant power drive, so as to solve the problem that the frequency stability of the existing oscillation circuit is relatively poor, and the capacitance of the capacitor in the oscillation circuit may change due to environmental factors such as temperature and humidity, thereby causing fluctuations in the oscillation frequency.
[0006] To achieve the above objectives and other related objectives, the present invention provides the following technical solutions:
[0007] An oscillator circuit driven by constant power, comprising: an inductor, a switch unit, a sampling module, a current monitoring module, a time control module and a logic processing control output unit; wherein the inductor is used to detect metal objects; the switch unit comprises a first switch module, a second switch module and a third switch module connected to the inductor, the first switch module and the third switch module are used to control the charging and power-off of the inductor, and the second switch module is used to connect the end of the inductor connected to the first switch module to the ground when the inductor is powered off;
[0008] The sampling module is connected to the third switch module, and the sampling module is used to monitor the current change when the inductor is charged; the current monitoring module is respectively connected to the third switch module and the sampling module, and the current monitoring module is also connected to the time control module, and the current monitoring module is used to detect the current flowing through the coil when the inductor is charged, and control the conduction and cutoff of the time control module according to the detection result; the time control module is connected to the logic processing control output unit, and the logic processing control output unit is respectively connected to the first switch module, the second switch module and the third switch module, and the time control module is used to periodically control the conduction and cutoff of the first switch module, the second switch module and the third switch module through the logic processing control output unit under the control of the current monitoring module.
[0009] In one embodiment of the present invention, the first switch module includes a first field effect transistor, the gate of the first field effect transistor is connected to the logic processing control output unit through a first resistor, the source of the first field effect transistor is connected to a voltage source, and the drain of the first field effect transistor is respectively connected to one end of the inductor coil and the second switch module.
[0010] In one embodiment of the present invention, the second switch module includes a second field effect transistor, the gate of the second field effect transistor is connected to the logic processing control output unit, the gate of the second field effect transistor is also connected to the source of the second field effect transistor through an eighth resistor and grounded, and the drain of the second field effect transistor is respectively connected to the first switch module and one end of the inductor coil.
[0011] In one embodiment of the present invention, the third switch module includes a third field effect transistor, the gate of the third field effect transistor is connected to the logic processing control output unit through a ninth resistor, the drain of the third field effect is connected to the other end of the inductor coil, the other end of the inductor coil is also connected to the external signal processing unit, the source of the third field effect transistor is grounded through the sampling module, and the source of the third field effect transistor is also connected to the current monitoring module.
[0012] In an embodiment of the present invention, the sampling module includes a sampling resistor, one end of the sampling resistor is respectively connected to the third switch module and the current monitoring module, and the other end of the sampling resistor is grounded.
[0013] In one embodiment of the present invention, the current detection module includes a first comparator and a first inverter, the non-inverting input terminal of the first comparator is used to input a reference voltage of 0.6V, the reverse input terminal of the first comparator is connected to the third switch module and the sampling module, the output terminal of the first comparator is connected to the input terminal of the first inverter, the output terminal of the first inverter is connected to the time control module through a twelfth resistor, the power supply terminals of the first comparator and the first inverter are both connected to a voltage source, and the ground terminals of the first comparator and the first inverter are both grounded.
[0014] In one embodiment of the present invention, the time control module includes a fourth field effect transistor and a second capacitor, the gate of the fourth field effect transistor is connected to the current monitoring module through a twelfth resistor, the drain of the fourth field effect transistor is connected to the logic processing control output unit, the drain of the fourth field effect transistor is also connected to the voltage source through an eleventh resistor, the drain of the fourth field effect transistor is also connected to the positive electrode of the second capacitor, and the negative electrode of the second capacitor is connected to the source of the fourth field effect transistor and grounded.
[0015] In one embodiment of the present invention, the logic processing control output unit includes a first logic processing module, a second logic processing module and a third logic processing module that are interconnected. The first logic processing module includes a second comparator. The non-inverting input terminal of the second comparator is used to input a reference voltage of 1V. The inverting input terminal of the second comparator is connected to the time control module. The output terminal of the second comparator is respectively connected to the second logic processing module and the third logic processing module. The power supply terminal of the second comparator is connected to a voltage source, and the ground terminal of the second comparator is grounded.
[0016] In one embodiment of the present invention, the second logic processing module includes a buffer, a third comparator and a first capacitor, the second input end of the buffer is connected to the first logic processing module, the output end of the buffer is connected to the same-direction input end of the third comparator, the reverse input end of the third comparator is used to input a reference voltage of 1V, the output end of the third comparator is connected to the voltage source through a fifth resistor and a fourth resistor, the output end of the third comparator is also connected to the positive electrode of the first capacitor through a fifth resistor, the negative electrode of the first capacitor is connected to the second switch module, the first input end of the buffer and the power supply end and the power supply end of the third comparator are both connected to the voltage source, and the ground ends of the buffer and the third comparator are both grounded.
[0017] In one embodiment of the present invention, the third logic processing module includes a second inverter and a fourth comparator, the input end of the second inverter is connected to the first logic processing module, the output end of the second inverter is connected to the same-direction input end of the fourth comparator, the reverse input end of the fourth comparator is used to input a reference voltage of 1V, the output end of the fourth comparator is connected to the third switch module through a ninth resistor, the power supply ends of the second inverter and the fourth comparator are both connected to a voltage source, and the ground ends of the second inverter and the fourth comparator are both grounded.
[0018] As described above, the constant power driven oscillator circuit of the present invention has the following beneficial effects:
[0019] The inductor coil in the present invention is used to detect metal objects, the first switch module and the third switch module are used to control the charging and power-off of the inductor coil, and the second switch module is used to connect the end of the inductor coil connected to the first switch module to the ground when the inductor coil is powered off, so that the inductor current can be quickly cleared, avoiding the influence on metal detection during subsequent charging; the sampling module is used to monitor the current change when the inductor coil is charged, and the current monitoring module is used to detect the current flowing through the coil when the inductor coil is charged. The coil current is calculated by the voltage on the sampling resistor in the sampling module, and then the set trigger current value is compared with the current on the sampling resistor, and the time control module is controlled according to the comparison result; the time control module can periodically trigger the next cycle, so as to reduce the oscillator. Average power consumption; the logic processing control output unit is used to receive the control signal sent by the time control module, and perform level conversion, logic switching, and comparator output control on the control signal, so that the first switch module, the second switch module, and the third switch module can be in the on and off state; therefore, the inductor coil in the present invention is always controlled to be charged to a fixed inductance energy, the coil current is quickly eliminated, a high-voltage signal is induced, the signal decays and tends to a steady state, this process can be predicted, and the influence of coil consistency differences is ignored; and since there is no resonant capacitor involved, the influence of temperature on capacitance does not exist; and the influence of temperature on the coil does not change the way of storing energy with a fixed inductance energy, the factor of temperature change is ignored, and the oscillator signal is always stable, so the overall stability of the oscillator circuit is relatively high. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 Shown is a schematic diagram of a conventional LC type parallel oscillation circuit;
[0021] Figure 2 Shown is a schematic diagram of an existing capacitor three-point oscillation circuit;
[0022] Figure 3 Shown is a schematic diagram of a conventional transformer feedback oscillation circuit;
[0023] Figure 4 Shown is an overall structural block diagram of an oscillator circuit with constant power drive disclosed in an embodiment of the present invention;
[0024] Figure 5 Shown is an overall circuit schematic diagram of an oscillator circuit with constant power drive disclosed in an embodiment of the present invention;
[0025] Figure 6 Shown is a schematic diagram of signals of various important nodes in two cycles of an oscillator circuit driven by a constant power according to an embodiment of the present invention;
[0026] Figure 7 It is a schematic diagram showing the influence of the distance of metal on the signal at point B of the inductor coil in the constant power driven oscillator circuit disclosed in the embodiment of the present invention. DETAILED DESCRIPTION
[0027] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.
[0028] See also Figure 4 , the present invention provides an oscillator circuit with constant power drive, comprising: an inductor coil L, a first switch module K1, a second switch module K2, a third switch module K3, a sampling module R, a current monitoring module, a time control module and a logic processing control output unit;
[0029] Among them, one end of the inductor L is connected to the voltage source through the first switch module K1, one end of the inductor L is also connected to the second switch module K2, the other end of the inductor L is connected to the external signal processing unit, and the other end of the inductor L is also connected to the sampling module R through the third switch module K3;
[0030] It should be noted that the inductor L is used to detect the approach of metal, and different metals have different characteristic effects on the inductor L, which are manifested in signal S7. The external signal processing unit is used to calculate the charging time t and the overall area of the signal; when the first switch module K1 and the third switch module K3 are closed and the second switch module K2 is disconnected, the inductor L is charged and the current passes through the sampling module R; when the first switch module K1 and the third switch module K3 are disconnected and the second switch module K2 is closed, point A of the coil L is pulled down to the reference ground; the sampling module R is used to monitor the current change when the inductor L is charged; the current monitoring module is used to detect the current flowing through the coil when the inductor L is charged, determine the voltage on the sampling module R, calculate the current of the inductor L, and compare the trigger current value set by the internal circuit with the current on the sampling module R to output the control signal S4; time control module: the internal circuit periodically triggers the next cycle to reduce the average power consumption of the oscillator and output the control signal S6; the logic processing control output unit is used to receive the S6 signal, perform level conversion, logic switching, comparator output control, and provide signals S1, S2, and S3.
[0031] See also Figure 5 The first switch module K1 includes a first field effect transistor, the second switch module K2 includes a second field effect transistor, and the third switch module K3 includes a third field effect transistor. The first field effect transistor Q1, the second field effect transistor Q2, and the third field effect transistor Q3 are taken as examples for explanation;
[0032] The second pin of the first field effect transistor Q1 is connected to the logic processing control output unit through the first resistor R1, the third pin of the first field effect transistor Q1 is connected to the voltage source, and the first pin of the first field effect transistor Q1 is respectively connected to one end of the inductor L and the second switch module K2; the second pin of the second field effect transistor Q2 is connected to the logic processing control output unit, the second pin of the second field effect transistor Q2 is also connected to the third pin of the second field effect transistor through the eighth resistor R8 and grounded, and the first pin of the second field effect transistor Q2 is respectively connected to the first switch module K1 and one end of the inductor L; the second pin of the third field effect transistor Q3 is connected to the logic processing control output unit through the ninth resistor R9, the first pin of the third field effect Q3 is connected to the other end of the inductor L, and the other end of the inductor L is also connected to the external signal processing unit, the third pin of the third field effect transistor Q3 is grounded through the sampling module R, and the third pin of the third field effect transistor Q3 is also connected to the current monitoring module;
[0033] It should be noted that the first field effect transistor Q1 controls the high side conduction, and the third field effect transistor Q3 controls the low side conduction; the gate input of pin 2 of the second field effect transistor Q2 forms a differential circuit through the eighth resistor R8 and the first capacitor C1, the third comparator U2A in the second logic processing module outputs a low side signal, the second field effect transistor Q2 remains cut off, the third comparator U2A in the second logic processing module outputs a high side signal, and the second field effect transistor Q2 is turned on, thereby bypassing the potential at point A on the inductor coil L to the ground, so that the inductor current can be quickly cleared, because the inductor coil L will generate a magnetic field during charging, and the metal can be detected through the magnetic field. The metal to be measured generates an eddy current field under the influence of the magnetic field. When the inductor coil L is powered off, the eddy current field will in turn affect the inductor coil L, and the generated voltage will affect subsequent detection, so it is necessary to quickly clear the inductor current by grounding the second field effect transistor Q2.
[0034] See also Figure 5 The sampling module R includes a sampling resistor, and the sampling resistor R10 is selected as an example for explanation below; one end of the sampling resistor R10 is connected to the third switch module K3 and the current monitoring module respectively, and the other end of the sampling resistor R10 is grounded; wherein, the sampling resistor R10 is used to monitor the current change when the inductor coil L is charged. Since the inductor has the characteristic of hindering the current change, the current continues to increase until the inductor coil L presents a resistive state, and the current in the charging saturation coil is the largest. This process is controlled here, and the current of the inductor coil L is terminated at a certain moment before the charging saturation.
[0035] See also Figure 5 The current detection module includes a first comparator and a first inverter. The first comparator U6 and the first inverter U5 are taken as examples for explanation.
[0036] The third pin of the first comparator U6 is used to input a reference voltage of 0.6V, the fourth pin of the first comparator U6 is connected to the third switch module K3 and the sampling module R, the first pin of the first comparator U6 is connected to the second pin of the first inverter U5, the fourth pin of the first inverter U5 is connected to the time control module through the twelfth resistor R12, the fifth pin of the first comparator U6 and the fifth pin of the first inverter U5 are both connected to the voltage source, the second pin of the first comparator U6 and the third pin of the first inverter U5 are both grounded; it should be noted that the first comparator U6 is a current sampling comparison circuit, IN+ of the first comparator U6 is set to a voltage of 0.6V, the voltage on the sampling resistor R10 is input to IN- of the first comparator U6, the charging current of the inductor L is limited to 20mA, V R =30Ω*20mA=0.6V, which is greater than 20mA, and the first comparator U6 outputs a low level; the first inverter U5 is a NOT gate, which is used to logically invert the input level signal.
[0037] See also Figure 5 The time control module includes a fourth field effect transistor and a second capacitor. The fourth field effect transistor Q4 and the second capacitor C2 are taken as examples for explanation below.
[0038] The second pin of the fourth field effect transistor Q4 is connected to the current monitoring module through the twelfth resistor R12, the first pin of the fourth field effect transistor Q4 is connected to the logic processing control output unit, the first pin of the fourth field effect transistor Q4 is also connected to the voltage source through the eleventh resistor R11, the first pin of the fourth field effect transistor Q4 is also connected to the positive electrode of the second capacitor C2, the negative electrode of the second capacitor C2 is connected to the third pin of the fourth field effect transistor Q4 and grounded; it should be noted that, when the fourth field effect transistor Q4 is turned on, the voltage on the second capacitor C2 is cleared to 0; when the fourth field effect transistor Q4 is turned off, the eleventh resistor R11 charges the second capacitor C2, the voltage on the second capacitor C2 is greater than 1V, and the second comparator U3 below outputs a low level.
[0039] See also Figure 5 , the logic processing control output unit includes a first logic processing module, a second logic processing module and a third logic processing module which are connected to each other, the first logic processing module includes a second comparator, the second logic processing module includes a buffer, a third comparator and a first capacitor, the third logic processing module includes a second inverter and a fourth comparator, and the second comparator U3, the buffer U1, the third comparator U2A, the first capacitor C1, the second inverter U4 and the fourth comparator U2B are selected as examples for explanation;
[0040] The third pin of the second comparator U3 is used to input a reference voltage of 1V, the fourth pin of the second comparator U3 is connected to the time control module, the first pin of the second comparator U3 is connected to the second logic processing module and the third logic processing module respectively, the fifth pin of the second comparator U3 is connected to the voltage source, and the second pin of the second comparator U3 is grounded;
[0041] The second pin of the buffer U1 is connected to the first logic processing module, the fourth pin of the buffer U1 is connected to the third pin of the third comparator U2A, the second pin of the third comparator U2A is used to input a reference voltage of 1V, the first pin of the third comparator U2A is connected to the first switch module K1 through the first resistor R1, the first pin of the third comparator U2A is also connected to the voltage source through the fifth resistor R5 and the fourth resistor R4, the first pin of the third comparator U2A is also connected to the positive electrode of the first capacitor C1 through the fifth resistor R5, the negative electrode of the first capacitor C1 is connected to the second switch module K2, the first pin and the fifth pin of the buffer U1 and the eighth pin of the third comparator U2A are all connected to the voltage source, and the third pin of the buffer U1 and the fourth pin of the third comparator U2A are both grounded;
[0042] The second pin of the second inverter U4 is connected to the first logic processing module, the fourth pin of the second inverter U4 is connected to the fifth pin of the fourth comparator U2B, the sixth pin of the fourth comparator U2B is used to input a reference voltage of 1V, the seventh pin of the fourth comparator U2B is connected to the third switch module K3 through the ninth resistor R9, the fifth pin of the second inverter U4 and the eighth pin of the fourth comparator U2B are both connected to the voltage source, and the third pin of the second inverter U4 and the fourth pin of the fourth comparator U2B are both grounded;
[0043] It should be noted that the logic gate circuit: the second inverter U4 is also a NOT gate, which is used to logically invert the input level signal. The buffer U1 is an AND gate, which cooperates with the signal synchronization made by the second inverter U4 and gives the logic signal to the comparator U2 (the third comparator U2A and the fourth comparator U2B) at the same time; the comparator circuit: the comparator U2 is used for level conversion, which converts the low-voltage signal output by the logic gate circuit buffer U1 and the second inverter U4 into a high-voltage signal output. The second comparator U3 is a hysteresis comparator for signal inversion, receives the S6 signal, and the output is stable; please refer to the key signal position Figure 6 .
[0044] See also Figure 5 , further comprising a voltage bias module, the voltage bias module comprising a first voltage zener diode, a second voltage zener diode and other circuit components, and the first voltage zener diode D1 and the second voltage zener diode D2 are selected as examples for explanation below;
[0045] The first voltage-stabilizing diode D1 is connected in parallel with the sixth resistor R6, the cathode of the first voltage-stabilizing diode D1 is connected to the voltage source through the second resistor R2, the anode of the first voltage-stabilizing diode D1 is grounded, the second voltage-stabilizing diode D2 is connected in parallel with the seventh resistor R7, the cathode of the second voltage-stabilizing diode D2 is connected to the voltage source through the third resistor R3, and the anode of the second voltage-stabilizing diode D2 is grounded; it should be noted that the voltage bias module is provided with a bias voltage of 2.5V by resistors R2, R3, R6, and R7, which acts on both ends of the inductor L, so as to make the voltage at both ends of the coil stable and not easily interfered with and introduced noise when the first field-effect transistor Q1, the second field-effect transistor Q2, and the third field-effect transistor Q3 are all cut off.
[0046] Specifically, the first field effect transistor Q1 and the third field effect transistor Q3 are turned on to charge the inductor coil L, and the charging current passes through the tenth resistor R10. The voltage on the tenth resistor R10 is greater than 0.6V, and the current monitoring module is triggered to switch the state to start turning off the first field effect transistor Q1 and the third field effect transistor Q3; the first field effect transistor Q1 and the third field effect transistor Q3 are turned off, and the second field effect transistor Q2 is synchronously triggered to be pulled down to 0V by the rising and falling edge signal of the comparator U2_1 pin through the differential circuit. The opening time of the second field effect transistor Q2 depends on the parameters of the resistor and capacitor, and the falling edge signal of the third comparator U2A_1 pin is not affected; point A of the inductor coil L is pulled down to 0V for a short time, and a high-voltage signal is induced at point B, which is infinite in theory. In order not to damage the device, the first voltage-stabilizing diode D1 and the second voltage-stabilizing diode D2 select TVS tube clamping protection;
[0047] Analyze the influence of the distance of metal on the signal at point B, as follows: Figure 7 As shown: when iron material approaches, the charging time t of the inductor L will be lengthened. Under the same voltage, the larger the inductance value, the longer the charging time required. The closer the iron is, the longer the time t is. The calculated length of t can be used to detect the distance. When stainless steel material approaches, the time t of feature 1 and the voltage curve of feature 2 do not change significantly, which shows that it is insensitive to stainless steel. This reflects that stainless steel only affects the attenuation slope of the induced high-voltage signal. The rapid decline in the slope in the actual circuit is difficult to detect. When copper and aluminum materials are close, the process change of the voltage described by feature 2 tends to a stable state of 2.5V is affected by the metal. The closer the metal is, the voltage changes in a dotted voltage path. When iron is close, it is not obvious. This feature can be used to distinguish metal materials. Therefore, it can be seen that when detecting different metal materials, different feature effects are reflected, and the difference between iron and copper and aluminum can be distinguished. The characteristic of being insensitive to stainless steel is conducive to the application of the oscillator being enclosed in a stainless steel shell, which provides more solid protection without affecting the detection of other metals.
[0048] More specifically, the working process of the oscillator circuit is:
[0049] For the current monitoring module, the most efficient way to monitor the current is to collect and compare the voltage. When S1 is at a low level, the first switch module K1 is turned on. When S3 is at a high level, the third switch module K3 is turned on. When S2 is at a low level, the second switch module K2 is not turned on. With 7.5V power supply, the current passes through the first switch module K1, flows through the inductor coil L, passes through the third switch module K3, flows through the tenth resistor R10 to PGND's 0V. The inductance characteristic of the coil L is to hinder the current change, so the coil current rises slowly, that is, it slowly increases from 0mA, and flows through the third switch module K3. The currents on the tenth resistor R10 are the same; the voltage V on the tenth resistor R10 is R10*I, and the resistance value of R10 is 30Ω. If the coil current rises to 20mA, the voltage on the tenth resistor R10 is 0.6V; the first comparator U6_4 introduces the voltage on the tenth resistor R10 and compares it with the 0.6V reference voltage set by the first comparator U6_3. If the voltage on the tenth resistor R10 is greater than 0.6V, the first comparator U6_1 outputs a low level, otherwise it outputs a high level, which is connected to the logic reverse output S4 of the first inverter U5;
[0050] For the time control module, when S4 is at a low level, the fourth field effect tube Q4 is not turned on, and the eleventh resistor R11 charges the second capacitor C2. The eleventh resistor R11 is 30KΩ, and the second capacitor C2 is 30nF. Therefore, it takes about 600us for the second capacitor C2 to charge to 1V. When S4 is at a high level, the fourth field effect tube Q4 is turned on, and the charging voltage of the previous cycle on the second capacitor C2 is quickly released to 0V. The signal of S6 rises from 0V to 1V (required 600us). During this period, the second comparator U3 outputs a high level, and the first switch module K1 and the third switch module K3 are turned off through the logic processing control unit. The current on the tenth resistor R10 is 0mA, and the voltage on the tenth resistor R10 is 0V. The first comparator U6 outputs a high level, and the first inverter U5 reversely outputs a low level. When S4 is at a low level, the fourth field effect tube Q4 is not turned on, waiting for the voltage on the second capacitor C2 to be charged to greater than 1V, and the second comparator U3 outputs a low level. The first switch module K1 and the third switch module K3 are controlled to be turned on through the logic processing control unit, and the inductor L and the tenth resistor R10 start to generate and increase current. Since the coil current is limited to 0—>20mA change, this period of time is completed within about 50us, that is, the voltage of the tenth resistor R10 reaches greater than 0.6V, the first comparator U6 outputs a low level, the first inverter U5 outputs a high level, S4 is a high level, and the next cycle begins; through the above description, it can be seen that the time when the inductor L is energized is much shorter than the time when it is not energized (50us is much shorter than 600us), so the inductor L is in an intermittent working state, and the average power consumption is reduced;
[0051] For the logic processing control output unit, the pin signal of the fourth field effect transistor Q4_1 is the S6 signal, which is provided to the 4th pin of the second comparator U3 and compared with the 1V_REF reference voltage 1V. The second comparator U3 outputs a level of 0V or 3.3V, which is synchronously provided to the buffer U1 and the second inverter U4; the buffer U1 and the second inverter U4 output 1 signal U1_Y and U4_Y respectively, depending on the device properties. The buffer U1 is an "AND" gate, and U4 is an inverter. U1_Y and U4_Y are synchronous and completely reversed; the second comparator U3 outputs a logic high level (3.3V), which is given to the buffer U1_B and U1_A (which have been pulled to a high level of 3.3V) for logic "AND" processing, then U1_Y outputs a high level, otherwise the buffer U1_B inputs a low level and performs a logic "AND" with U1_A, and outputs a low level. The function of the buffer U1 It is a unidirectional output; the output of the second comparator U3 is given to the second inverter U4_A. Because U4 is an inverter, U4_Y outputs an inverse signal of U4_A; the third comparator U2A and the fourth comparator U2B are both level converters, the device power supply voltage is 7.5V, the U2A / B comparator outputs a logic high level of 7.5V, and a logic low level of 0V. The U2A / B input signal comes from the previous level buffer U1 and the second inverter U4. The buffer U1 and the second inverter U4 are both powered by 3.3V, so the function of U2A / B is to convert the input 0V / 3.3V level into a 0V / 7.5V level; the third comparator U2A_1 pin outputs the S1 signal, the fourth comparator U2B_7 pin outputs the S3 signal, the third comparator U2A_1 pin signal is branched, and the S2 signal is obtained through integration of the first capacitor C1 and the eighth resistor R8.
[0052] In summary, the charging and discharging process of the inductor coil L in the present invention is affected by the different materials of the metal being measured and the distance, resulting in different signal characteristics; and the present invention can monitor the change of the current flowing through the inductor coil L during the energy storage process of the inductor coil L, so that the periodic charging power of the inductor coil L is constant, so the inductor coil L is always controlled to be charged to a fixed inductance energy; and the present invention pulls point A of the inductor coil L down to the reference ground through the second switch module K2, which can quickly eliminate the coil current, induce a high-voltage signal, and the signal attenuates and tends to a steady state. This process can be predicted, and the influence of coil consistency differences is ignored; and since the present invention does not involve the resonant capacitor, the influence of temperature on the capacitor does not exist, and the influence of temperature on the coil does not change the way of storing energy with a fixed inductance, so the overall stability of the oscillator circuit is relatively high, wherein the overall stability of the oscillator circuit is relatively high, and the energy / power stability of the externally emitted magnetic field is relatively high, and since there is no resonant capacitor involved, the frequency stability of the oscillator circuit is also relatively high.
[0053] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. All equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical ideas disclosed by the present invention shall still be covered by the claims of the present invention.
Claims
1. A constant power driven oscillator circuit, characterized in that: include: Inductor coil, switch unit, sampling module, current monitoring module, time control module and logic processing control output unit; The inductor is used to detect metal objects; the switch unit includes a first switch module, a second switch module and a third switch module connected to the inductor, the first switch module and the third switch module are used to control the charging and power-off of the inductor, and the second switch module is used to connect the end of the inductor connected to the first switch module to the ground when the inductor is powered off; The sampling module is connected to the third switch module, and the sampling module is used to monitor the current change when the inductor is charged; the current monitoring module is connected to the third switch module and the sampling module respectively, and the current monitoring module is also connected to the time control module, and the current monitoring module is used to detect the current flowing through the coil when the inductor is charged, and control the conduction and cutoff of the time control module according to the detection result; The time control module is connected to the logic processing control output unit, and the logic processing control output unit is respectively connected to the first switch module, the second switch module and the third switch module. The time control module is used to periodically control the conduction and cutoff of the first switch module, the second switch module and the third switch module through the logic processing control output unit under the control of the current monitoring module.
2. The constant power driven oscillator circuit according to claim 1, characterized in that: The first switch module includes a first field effect transistor, a gate of the first field effect transistor is connected to the logic processing control output unit through a first resistor, a source of the first field effect transistor is connected to a voltage source, and a drain of the first field effect transistor is respectively connected to one end of the inductor coil and the second switch module.
3. The constant power driven oscillator circuit according to claim 1, characterized in that: The second switch module includes a second field effect transistor, the gate of the second field effect transistor is connected to the logic processing control output unit, the gate of the second field effect transistor is also connected to the source of the second field effect transistor through an eighth resistor and grounded, and the drain of the second field effect transistor is respectively connected to the first switch module and one end of the inductor coil.
4. The constant power driven oscillator circuit according to claim 1, characterized in that: The third switch module includes a third field effect transistor, the gate of the third field effect transistor is connected to the logic processing control output unit through a ninth resistor, the drain of the third field effect is connected to the other end of the inductor coil, the other end of the inductor coil is also connected to the external signal processing unit, the source of the third field effect transistor is grounded through the sampling module, and the source of the third field effect transistor is also connected to the current monitoring module.
5. The constant power driven oscillator circuit according to claim 1, characterized in that: The sampling module comprises a sampling resistor, one end of which is connected to the third switch module and the current monitoring module respectively, and the other end of which is grounded.
6. The constant power driven oscillator circuit according to claim 1, characterized in that: The current detection module includes a first comparator and a first inverter, the non-inverting input terminal of the first comparator is used to input a reference voltage of 0.6V, the reverse input terminal of the first comparator is connected to the third switch module and the sampling module, the output terminal of the first comparator is connected to the input terminal of the first inverter, the output terminal of the first inverter is connected to the time control module through a twelfth resistor, the power supply terminals of the first comparator and the first inverter are both connected to a voltage source, and the ground terminals of the first comparator and the first inverter are both grounded.
7. The constant power driven oscillator circuit according to claim 1, characterized in that: The time control module includes a fourth field effect transistor and a second capacitor, the gate of the fourth field effect transistor is connected to the current monitoring module through a twelfth resistor, the drain of the fourth field effect transistor is connected to the logic processing control output unit, the drain of the fourth field effect transistor is also connected to the voltage source through an eleventh resistor, the drain of the fourth field effect transistor is also connected to the positive electrode of the second capacitor, and the negative electrode of the second capacitor is connected to the source of the fourth field effect transistor and grounded.
8. The constant power driven oscillator circuit according to claim 1, characterized in that: The logic processing control output unit includes a first logic processing module, a second logic processing module and a third logic processing module which are interconnected. The first logic processing module includes a second comparator. The non-inverting input terminal of the second comparator is used to input a reference voltage of 1V. The inverting input terminal of the second comparator is connected to the time control module. The output terminal of the second comparator is respectively connected to the second logic processing module and the third logic processing module. The power supply terminal of the second comparator is connected to a voltage source. The ground terminal of the second comparator is grounded.
9. The constant power driven oscillator circuit according to claim 8, characterized in that: The second logic processing module includes a buffer, a third comparator and a first capacitor. The second input end of the buffer is connected to the first logic processing module, the output end of the buffer is connected to the same-direction input end of the third comparator, the inverse input end of the third comparator is used to input a reference voltage of 1V, the output end of the third comparator is connected to the voltage source through a fifth resistor and a fourth resistor, the output end of the third comparator is also connected to the positive electrode of the first capacitor through a fifth resistor, the negative electrode of the first capacitor is connected to the second switch module, the first input end of the buffer and the power supply end and the power supply end of the third comparator are both connected to the voltage source, and the ground ends of the buffer and the third comparator are both grounded.
10. The constant power driven oscillator circuit according to claim 8, characterized in that: The third logic processing module includes a second inverter and a fourth comparator, the input end of the second inverter is connected to the first logic processing module, the output end of the second inverter is connected to the same-direction input end of the fourth comparator, the inverting input end of the fourth comparator is used to input a reference voltage of 1V, the output end of the fourth comparator is connected to the third switch module through a ninth resistor, the power supply ends of the second inverter and the fourth comparator are both connected to a voltage source, and the ground ends of the second inverter and the fourth comparator are both grounded.