Voltage-controlled pulse duty ratio circuit based on reverse breakdown characteristic of voltage stabilizing diode

Abstract

The invention discloses a voltage-controlled pulse duty ratio circuit based on a reverse breakdown characteristic of a voltage stabilizing diode, which is characterized in that an input direct current control voltage Ui is connected with a pin 5 of an NE555 circuit, a pin 7 of the NE555 circuit is connected with a working ground, a power supply Vcc circuit is simultaneously connected with a pin 4 and a pin 8 of the NE555 circuit, and the power supply Vcc circuit is connected with the working ground. A third pin of the NE555 circuit is connected with a working ground through a forward switching diode D1, a reverse voltage stabilizing diode D2, a divider resistor R1 and an oscillation capacitor C1 in sequence, the third pin of the NE555 circuit is connected with the working ground through a reverse switching diode D4, a forward voltage stabilizing diode D3, a divider resistor R2 and the oscillation capacitor C1 in sequence, and a connection point of the divider resistor R1 and the divider resistor R2 is connected with a second pin and a sixth pin of the NE555 circuit. And a pin 3 of the NE555 circuit outputs an oscillation signal Uo controlled by direct current voltage.

Description

Technical Field

[0001] The present invention relates to the design of a voltage-controlled pulse duty cycle circuit. If the voltage-controlled U i voltage is set appropriately and the parameters of the circuit components are appropriate, then within a relatively small range of U i variation, the duty cycle adjustment can reach about 1:1000, but the entire circuit is very simple. Background Art

[0002] PWM generally refers to pulse width modulation, that is, duty cycle modulation. A common PWM circuit is essentially a circuit with a fixed square wave period and an adjustable duty cycle. Its basic working principle is to compare a sawtooth wave signal with a fixed frequency with a DC control voltage. When the DC control voltage changes, the output pulse duty cycle changes accordingly.

[0003] Since the oscillation frequency of the multivibrator composed of the NE555 timer is less affected by the power supply voltage and external temperature changes, in the absence of a dedicated PWM circuit, based on the two threshold voltages (1 / 3Vcc and 2 / 3Vcc) of the 555 timing circuit being different, and the charging path and discharging path of the timing circuit being different, the duty cycle of the output pulse signal can be adjusted by directly changing the RC time constant τ = RC of the charging and discharging circuits, such as by changing the resistance value or capacitance value.

[0004] Strictly speaking, this is not the requirement of controlling the pulse output duty cycle by a DC voltage that we need. Then, based on the 555 time-base circuit, some DC voltage-controlled pulse duty cycle circuits can also be designed. The commonly used method in the industry is: the 555 time-base circuit first forms an astable multivibrator with peripheral resistive and capacitive elements, and compares a DC control voltage with the sawtooth wave signal generated during the charging and discharging process. The duty cycle of the pulse waveform output by the comparator can be adjusted within a large range.

[0005] However, the common DC voltage-controlled pulse duty cycle circuit structures based on the NE555 are relatively complex, with a large number of components used, resulting in a high cost and a low cost performance.

[0006] Pin 5 (CO) of the 555 time-base circuit is actually the positive input terminal of the operational amplifier used for internal comparison. In a typical application, this pin is usually grounded through a 0.01 μF capacitor to filter out interference.

[0007] When the reverse voltage of a zener diode is lower than the reverse breakdown voltage, the reverse leakage current is extremely small. However, when the reverse voltage approaches the critical value of the reverse breakdown voltage, the reverse current suddenly increases, and the reverse breakdown curve is relatively steep. After that, although the current changes within a large range, the change in the voltage across the zener diode is quite small; vice versa, a very small change in the reverse voltage ΔU ZIt can cause a large change Δi in the reverse breakdown current. If this reverse breakdown characteristic of the zener diode is applied to the charging circuit and the discharging circuit of the 555-based multivibrator, and both the charging voltage and the discharging voltage are made to operate the zener diode in the reverse breakdown region.

[0008] At the same time, a DC voltage U i is connected to pin 5 (CO terminal) of the 555 timer circuit. Then the two threshold voltages of the 555 circuit will change with the value of U i . Short-circuit pin TL and pin TH, design an oscillation capacitor between the short-circuit point and the ground, and at the same time, in parallel with a charging circuit and a discharging circuit between the short-circuit point and the output terminal (pin 3, U O ) of the 555 timer circuit. Based on the above characteristics of the zener diode, both the charging and discharging circuits are controlled by a reverse zener diode for the charging and discharging currents. Therefore, the function of the zener diode here is not to regulate voltage, but to have its reverse breakdown current controlled.

[0009] Based on the externally connected DC voltage U i connected to pin 5 of the 555 circuit, the two threshold voltages of the timer circuit will change. If the U i voltage changes within a certain appropriate range, it can exactly make the zener diodes constituting the charging and discharging circuits operate in the reverse breakdown region. Then when the U i voltage increases, the charging current will decrease significantly, and the discharging current will increase significantly; conversely, when the U i voltage decreases, the charging current will increase significantly, and the discharging current will decrease significantly.

[0010] Due to the action of the DC voltage U i , finally the duty cycle of the pulse wave signal at the output terminal (pin 3) of the 555 circuit will change, achieving the preset of voltage-controlled pulse duty cycle. If the U i voltage is set appropriately and the circuit component parameters are appropriate, then within a relatively small range of change of U i , the duty cycle adjustment can reach about 1:1000, but the whole circuit is very simple. Summary of the Invention

[0011] The technical problem to be solved by the present invention is to provide a design technology of a voltage-controlled pulse duty cycle circuit with a simpler structure, lower cost, and more reliable use.

[0012] To achieve the above object, the present invention provides a voltage-controlled pulse duty cycle circuit based on the reverse breakdown characteristic of a zener diode, which includes a power supply Vcc circuit, a time base circuit, an oscillation capacitor, an oscillation capacitor charging circuit, an oscillation capacitor discharging circuit, an input DC control voltage, an oscillation signal output voltage, and a working ground; the time base circuit is composed of an NE555 circuit, the input DC control voltage Ui is connected to the 5th pin of the NE555 circuit, the 7th pin of the NE555 circuit is connected to the working ground, the power supply Vcc circuit is simultaneously connected to the 4th pin and the 8th pin of the NE555 circuit, the oscillation capacitor charging circuit is composed of a switching diode D1, a zener diode D2, and a voltage-dividing resistor R1, the oscillation capacitor discharging circuit is composed of a voltage-dividing resistor R2, a zener diode D3, and a switching diode D4, the 3rd pin of the NE555 circuit is sequentially connected to the working ground through a forward switching diode D1, a reverse zener diode D2, a voltage-dividing resistor R1, and the oscillation capacitor C1, the 3rd pin of the NE555 circuit is sequentially connected to the working ground through a reverse switching diode D4, a forward zener diode D3, a voltage-dividing resistor R2, and the oscillation capacitor C1, the connection point of the voltage-dividing resistor R1 and the voltage-dividing resistor R2 is connected to the 2nd pin and the 6th pin of the NE555 circuit, and the 3rd pin of the NE555 circuit outputs the oscillation signal output voltage Uo.

[0013] For the oscillation capacitor charging circuit, the parameters of the switching diode D1, the zener diode D2, and the voltage-dividing resistor R1 are all related to the power supply Vcc circuit. Different power supply Vcc voltage values correspond to different parameters of the switching diode D1, the zener diode D2, and the voltage-dividing resistor R1. When the power supply Vcc is 15V, the reverse voltage of the switching diode D1 only needs to be greater than 25V, the regulated voltage value of the zener diode D2 is 6V, and the resistance value of the voltage-dividing resistor R1 is taken as 240Ω.

[0014] For the oscillation capacitor discharging circuit, the parameters of the switching diode D4, the zener diode D3, and the voltage-dividing resistor R2 are all related to the power supply Vcc circuit. Different power supply Vcc voltage values correspond to different parameters of the switching diode D4, the zener diode D3, and the voltage-dividing resistor R2. When the power supply Vcc is 15V, the reverse voltage of the switching diode D2 only needs to be greater than 25V, the regulated voltage value of the zener diode D3 is 2V, and the resistance value of the voltage-dividing resistor R2 is taken as 240Ω.

[0015] The value range of the voltage of the input DC control voltage Ui is related to the selection of the parameters of the switching diode D1, the switching diode D2, the zener diode D2, the zener diode D3, the voltage-dividing resistor R1, and the voltage-dividing resistor R2. Description of the Drawings

[0016] Appendix Figure 1 Appendix Figure 2 Appendix Figure 3 Appendix Figure 4 AppendixFigure 5 It is used to provide further understanding of the present invention and constitutes a part of this application. Attached Figure 1 is the working principle of pulse width modulation; Attached Figure 2 is the schematic diagram of a pulse width adjustable positive and negative polarity current square wave modulator; Attached Figure 3 is a waveform shaping circuit composed of CMOS inverters; Attached Figure 4 is the internal circuit diagram of the 555 timer; Attached Figure 5 is the function table diagram of the 555 timer. Specific embodiments

[0017] The embodiments of the present invention will be further described below in conjunction with the accompanying drawings.

[0018] Traditional 555-based circuit for voltage-controlled pulse duty cycle First, briefly introduce the traditional voltage-controlled pulse duty cycle circuit, understand its working principle, illustrate its advantages, and prove its deficiencies, so as to reflect the advantages of our design: novel working principle, simple structure, low cost, and high cost performance.

[0019] In automatic control systems, there are some occasions where it is necessary to use voltage changes to control the duty cycle of a pulse wave, such as Figure 1 shown.

[0020] The circuit mainly consists of a timer chip IC1 of model NE555 and an astable multivibrator composed of resistor R1, timing capacitor C1, and transistor T1. The charging circuit is power supply V CC → resistor R1 → transistor T1 (saturated conduction) → capacitor C1, and the discharge circuit consists of capacitor C1 → the internal discharge tube T of 555 → the working ground.

[0021] Among them, transistor T1, diodes D1, and D2 constitute a constant current source circuit. T1 serves as the charging constant current source of timing capacitor C1, making the sawtooth wave curve of the charging process of C1 have good linearity. The operational amplifier IC2 is used as a comparator. Since the inverting input terminal of IC2, that is, the low and high threshold voltages of IC1, vary between 1 / 3Vcc and 2 / 3Vcc respectively, and the control voltage Ui is connected to the non-inverting input terminal of operational amplifier IC2, when the range of the control voltage Ui also varies between 1 / 3Vcc and 2 / 3Vcc, the duty cycle of the pulse waveform output by IC2 can be adjusted within a range approximately from 0 to 100%.

[0022] For example, when the Ui voltage is equal to 2 / 3U cc , the pulse duty cycle output by IC2 is the highest at 100%; when the Ui voltage is equal to 1 / 3U cc , the pulse duty cycle output by IC2 is the lowest at 0, that is, the closer it is to 2 / 3U cc , the higher the duty cycle, the closer it is to 1 / 3Ucc , the lower the duty cycle.

[0023] The advantage of this duty cycle adjustment circuit is that the pulse frequency can remain unchanged while the output pulse duty cycle changes; the disadvantage is that the circuit uses two integrated circuits, which is slightly complicated, but the working principle is easy to understand and it is a relatively mature solution.

[0024] Voltage-controlled pulse duty cycle circuit based on reverse breakdown characteristics of Zener diode A voltage regulator diode is also called a Zener diode. A voltage regulator diode is a single PN junction diode used to stabilize voltage. This diode is a semiconductor device that has a very high resistance until the reverse breakdown voltage. In the reverse breakdown region, the reverse resistance is reduced to a very small value.

[0025] Therefore, when the reverse voltage of the Zener diode is lower than the reverse breakdown voltage, the reverse leakage current is extremely small. However, when the reverse voltage approaches the critical value of the reverse voltage, the reverse current suddenly increases, which is called breakdown. The voltage regulator diode must meet the working conditions of the Zener diode to stabilize the voltage. Its reverse breakdown curve is as follows: Figure 2 shown.

[0026] exist Figure 2 In the figure, we can see that the actual voltage regulation value U Z It changes with the working current, but the change is relatively small. That is, although the current changes in a large range, the voltage across the diode is basically stable near the breakdown voltage, thus realizing the voltage stabilization function of the diode.

[0027] Based on the above principles, see Figure 2 , if the reverse voltage is less than U A When the reverse current of the diode is very small, the reverse voltage is equal to U A When the diode breaks down, the reverse breakdown current is I Zmin ; Reverse voltage is equal to U B When the reverse breakdown current is I Zmax , U A -U B =ΔU Z , I Zmax -I Zmin =Δi.

[0028] It can be proved from the figure that a very small reverse voltage change ΔU Z It can cause a larger reverse breakdown current change Δi if the reverse breakdown characteristic of the Zener diode is applied to the charging circuit and discharge circuit of the 555-based multivibrator, and the Zener diode is made to work in the reverse breakdown region regardless of the charging voltage or the discharging voltage.

[0029] Meanwhile, a change in the externally applied DC voltage Ui can cause the zener diode to vary within the reverse breakdown region, i.e., ΔU Z range. Then, the charging and discharging currents of the multivibrator will both change. If the change in the DC voltage Ui can make the direction of change of the charging current opposite to that of the discharging current, then the duty cycle of the output pulse of the multivibrator will change.

[0030] Based on the above description that a very small ΔU Z can cause a large Δi, this circuit can achieve a large duty cycle adjustment with a small change in Ui, but the oscillation frequency may change simultaneously.

[0031] It can be seen that this voltage-controlled pulse duty cycle circuit based on the reverse breakdown characteristic of the zener diode is not only simple in circuit but also very sensitive to voltage control compared with the above-mentioned traditional 555 multivibrator-based voltage-controlled pulse duty cycle circuit.

[0032] The electrical principle of this voltage-controlled duty cycle circuit is as Figure 3 shown. In addition to the NE555 timer circuit, the circuit only uses 7 simple peripheral components, two voltage-dividing resistors, two zener diodes, two switching diodes, and one oscillating capacitor. The circuit has the advantages of high voltage control sensitivity and a large duty cycle adjustment range.

[0033] It can be seen that this voltage-controlled duty cycle circuit includes a power supply Vcc circuit, a 555 timer circuit, an oscillating capacitor charging circuit, an oscillating capacitor discharging circuit, an input DC control voltage, an oscillating signal output voltage, and a working ground.

[0034] NE555 timing circuit Figure 3 The core component of the circuit is the 555 timer circuit. The 555 circuit is low-cost and reliable in performance. It includes two voltage comparators, three equal-value series resistors, an RS flip-flop, a discharge tube T, and a power output stage inside. It provides two reference voltages 1 / 3U CC and 2 / 3U CC . Its internal voltage standard uses three 5K resistors, so it is named the 555 circuit, as Figure 4 .

[0035] The 555 circuit only needs to be externally connected with a few resistors and capacitors to implement pulse generation and transformation circuits such as multivibrators, monostable flip-flops, and Schmitt triggers. This is the most commonly used function of the 555 circuit. The function of the 555 timer is as Figure 5 shown.

[0036] Pin 5 (CO) of the 555 timer circuit is actually the non-inverting input terminal of the operational amplifier used for internal comparison. Through the internal voltage-dividing resistors, the voltage at this pin is two-thirds of the power supply voltage. After adding a 0.01 μF capacitor, due to the charging and discharging characteristics of the capacitor, the voltage change caused by the instantaneous high or low interference signal applied to this place will slow down. It can also be said that the instantaneous interference is absorbed, and the signal obtained at this pin can be made more stable. To put it simply, it is to filter out interference. This is a common usage of the 555 timer circuit, that is, pin 5 is grounded through a capacitor.

[0037] Voltage-controlled Pulse Duty Cycle Circuit Structure and Working Principle Based on the Reverse Breakdown Characteristic of Zener Diodes The 555 timer circuit has two threshold voltages. The first threshold voltage is 1 / 3Vcc: when the input voltage at the TL terminal drops to 1 / 3Vcc and then decreases by an infinitesimal value, the output state of the 555 circuit will change. Usually, it changes from low level to high level. This characteristic enables the 555 circuit to respond to the falling edge of the input voltage, which is called the falling-edge threshold voltage, denoted by V N2— =1 / 3Vcc, where N2- represents the inverting input terminal of the internal comparator N2 of the 555 timer circuit. See Figure 4 .

[0038] The second threshold voltage is 2 / 3Vcc: corresponding to the first threshold voltage, when the input voltage rises to 2 / 3Vcc and then increases by an infinitesimal value, the output state will also change. Usually, it changes from high level to low level. This change allows the 555 circuit to perform specific operations when the input voltage rises, which is called the rising-edge threshold voltage, denoted by V N1+ =2 / 3Vcc, where N1+ represents the non-inverting input terminal of the internal comparator N1 of the 555 timer circuit.

[0039] Figure 4 In, that is to say, as long as the voltage at the inverting input terminal of comparator N1 increases to V N1+ and then increases by an infinitesimal value, the output of comparator N1 will reverse to the low level "0", and the output Uo of 555 will become the low level "0". Similarly, as long as the voltage at the non-inverting input terminal of comparator N2 drops to V N2-- and then decreases by an infinitesimal value, the output of comparator N2 will reverse to the low level "0", and the output Uo of 555 will become the high level "1".

[0040] Suppose a DC voltage U i is connected to pin 5 of the 555 timer circuit, then the two threshold voltages (V N1+ 、V N2- ) of the 555 circuit will change with the change of the U i value. For example, if Ui = 5V, then V N1+=5V, V N2-- =2.5V, Will Figure 3 The TL terminal and TH terminal of the NE555 are short-circuited, and the short-circuit point is connected to the working ground through the oscillation capacitor C1. O ), and a capacitor C1 charging circuit and a capacitor C1 discharging circuit are connected in parallel. The charging circuit is composed of a switching diode D1, a voltage-stabilizing diode D2, and a voltage-dividing resistor R1, and the discharging circuit is composed of a voltage-dividing resistor R2, a voltage-stabilizing diode D3, and a switching diode D4. Figure 3 As shown, when the output terminal Uo is at a high level, the current charges the capacitor C1 through the D1, D2, and R1 branches; when the output terminal is at a low level, the current discharges the capacitor C1 through the D3, D4, and R2 branches.

[0041] Figure 3 In the example, it is assumed that the output voltage Uo is high level, because the external DC voltage U i Will change the two threshold voltages V of the timing circuit N1+ and V N2— , if U i When the voltage changes within a certain appropriate range, the voltage-stabilizing diode constituting the charge and discharge circuit can operate in the reverse breakdown region ΔU. Z , then when U i When the voltage increases slightly, due to the corresponding threshold voltage V N1+ and V N2— The voltage at the TH terminal (V N1+ voltage) will also increase. Similarly, the TL terminal voltage (V N2— The voltage) will also increase, which also means that the cut-off charging potential of capacitor C1 will also increase, causing the Zener diode D2 to be cut off, and the charging current will decrease rapidly. The charging time of C1 will be extended, and the output Uo voltage will be high level "1" time will be extended until the Uo voltage becomes "0".

[0042] Similarly, a slight increase in the control voltage Ui increases the initial discharge potential of C1. Based on the reverse breakdown characteristics of the Zener diode: a very small reverse voltage change ΔU Z It can cause a larger reverse breakdown current change Δi. The increased C1 potential increases the voltage drop relative to the "0" level of the output voltage Uo, and the reverse breakdown current of the Zener diode D3 suddenly increases, which suddenly shortens the discharge time of C1 and the "0" level time of the output voltage Uo, until the Uo voltage becomes "1".

[0043] The above shows that a slight increase in the control voltage Ui greatly increases the duty cycle of the output voltage Uo.

[0044] Conversely, when U i slightly decreases in voltage, it causes V N1+ and V N2— to decrease in voltage. This also reduces the cut-off charging potential of capacitor C1, shortens the charging time of C1, and shortens the time that the output Uo voltage is at "1"; controlling the slight decrease of Ui is still based on the reverse breakdown characteristic of the zener diode: a very small reverse voltage change ΔU Z can cause a relatively large change in the reverse breakdown current Δi. The reverse breakdown current of zener diode D3 suddenly decreases, and the discharge time suddenly becomes longer. The "0" level time of the output voltage Uo becomes much longer, indicating that the slight decrease of the control voltage Ui greatly reduces the duty cycle of the output voltage Uo.

[0045] The above discussion also proves that although the DC control voltage Ui is added to pin 5, the multivibrator process is similar to traditional applications, as described below.

[0046] The high level at the output terminal 3 of IC1 charges the oscillating capacitor C1 through the charging circuit. The voltage of C1 gradually rises to the rising edge threshold voltage V N1+ and then rises by an infinitesimal value. The Uo voltage at pin 3 of IC1 reverses to the low level "0"; when the output at pin 3 is low, the voltage of the oscillating capacitor C1 (at this time U C1 = V N1+ ) discharges to the "0" at the output terminal 3 through the discharge circuit. The voltage of C1 gradually decreases. When the voltage of C1 decreases to the falling edge threshold voltage V N2— and then decreases by an infinitesimal value, pin 3 of IC1 flips back to the high level "1" again. At this time U C1 = V N2— , and the oscillating capacitor will be charged again.

[0047] The above process repeats. Due to the small effect of the DC control voltage U i , the duty cycle of the pulse wave signal at the output terminal 3 of the 555 circuit will ultimately change greatly, achieving the preset of voltage-controlled pulse duty cycle. If the DC control U i voltage is set appropriately and the circuit component parameters are appropriate, then within a relatively small U i change range, the duty cycle adjustment can reach about 1:1000.

[0048] Therefore, the function of the zener diode here is not to regulate voltage, but to control the reverse breakdown current.

[0049] Summary The above working process can be simply summarized as follows. When the output terminal of the 555 timer circuit is at a high level, the current charges the capacitor C1 through the D1, D2, and R1 branch. When the output terminal is at a low level, the current discharges the capacitor C1 through the D3, D4, and R2 branch. If the control voltage Ui at the 5th pin increases, the charging potential of the capacitor C1 will also increase, causing the zener diode D2 to tend to cut off, the average charging current to decrease rapidly, and the charging time to extend. During discharge, since the voltage on the capacitor C1 is relatively high and the reverse breakdown current of the zener diode D4 is relatively large, the discharge time becomes shorter. Conversely, when Ui decreases, the charging potential of C1 also decreases, the average charging current increases rapidly, the charging time becomes shorter, and during discharge, since the voltage on the capacitor C1 is relatively low and the average reverse breakdown current of the zener diode D4 decreases, the discharge time becomes longer. Finally, a small change in the control voltage Ui results in a large change in the duty cycle of the output voltage Uo.

[0050] Debugging and Precautions The circuit structure of this design is very simple, but the selection of component parameters and the debugging process require carefulness. When the power supply voltage Vcc is 15V, the parameters of each component used in this circuit are as Figure 3 shown. D1 and D2 are switching diodes, and the reverse voltage greater than 25V is sufficient. The zener voltage of the zener diode D2 in the charging circuit is 6V, the zener voltage of the zener diode D3 in the discharging circuit is 2V, and the voltage-dividing resistors R1 and R2 are both taken as 240Ω.

[0051] If the values of the voltage-dividing resistors R1 and R2 are larger, the control sensitivity will be lower, and the frequency of the multivibrator circuit composed of the 555 circuit will decrease; if the values are smaller, the control sensitivity will increase, and the oscillation frequency will also increase. However, if the resistance values are too small, unexpected oscillations will also occur.

[0052] The capacitor C1 is selected as a 0.01uF polyester capacitor. If the component parameters of the circuit are accurate, when the control voltage Ui at the 5th pin varies between 6V and 7V, the duty cycle can reach more than 1:1000.

[0053] Compared with the traditional voltage-controlled duty cycle circuit introduced above, this design has a simpler structure and higher cost performance. The disadvantage is that the debugging is slightly more troublesome. Regarding the selection of the resistance values of the resistors R1 and R2, it is recommended to first use a 1K potentiometer for debugging. Within the complete control range of the Ui voltage, the operation of the zener diodes D2 and D4 can be included in the reverse breakdown region, so as to achieve voltage control of the pulse width in the full range.

[0054] There are two innovation points in this design. The first innovation point is based on the reverse breakdown characteristic of the zener diode: a very small reverse voltage change ΔU ZIt can cause a large change Δi in the reverse breakdown current. The change in current will lead to a change in the charging or discharging time, ultimately affecting the duty cycle. The second innovative point is the special application of the 5th pin (CO) of the 555 timer circuit. The DC control voltage Ui acts on the 5th pin, thereby changing the two threshold voltages of the 555 timer circuit, ultimately changing the reverse voltage of the zener diode, further changing the charging and discharging currents, and the duty cycle changes.

[0055] The above embodiments are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that; still modifications or equivalent replacements can be made to the present invention, and any modification or partial replacement without departing from the spirit and scope of the present invention shall be covered by the scope of the claims of the present invention.

Claims

1. A voltage-controlled pulse duty cycle circuit based on the reverse breakdown characteristic of a zener diode, characterized in that The voltage-controlled pulse duty cycle circuit includes a power supply Vcc circuit, a time-base circuit, an oscillating capacitor, an oscillating capacitor charging circuit, an oscillating capacitor discharging circuit, an input DC control voltage, an oscillating signal output voltage, and a working ground; the time-base circuit is composed of an NE555 circuit. The input DC control voltage Ui is connected to the 5th pin of the NE555 circuit. The 7th pin of the NE555 circuit is connected to the working ground, and the 1st pin of the NE555 circuit is connected to the working ground. The power supply Vcc circuit is simultaneously connected to the 4th pin and the 8th pin of the NE555 circuit. The oscillating capacitor charging circuit is composed of a switching diode D1, a voltage-regulating diode D2, and a voltage-dividing resistor R1. The oscillating capacitor discharging circuit is composed of a voltage-dividing resistor R2, a voltage-regulating diode D3, and a switching diode D4. The 3rd pin of the NE555 circuit is sequentially connected to the working ground through the forward switching diode D1, the reverse voltage-regulating diode D2, the voltage-dividing resistor R1, and the oscillating capacitor C1. The 3rd pin of the NE555 circuit is sequentially connected to the working ground through the reverse switching diode D4, the forward voltage-regulating diode D3, the voltage-dividing resistor R2, and the oscillating capacitor C1. The connection point of the voltage-dividing resistor R1 and the voltage-dividing resistor R2 is connected to the 2nd pin and the 6th pin of the NE555 circuit. The 3rd pin of the NE555 circuit outputs the oscillating signal output voltage Uo.

2. The voltage-controlled pulse duty cycle circuit based on the reverse breakdown characteristic of a zener diode according to claim 1, wherein: For the oscillating capacitor charging circuit, the parameters of the switching diode D1, the voltage-regulating diode D2, and the voltage-dividing resistor R1 are all related to the power supply Vcc circuit. Different power supply Vcc voltage values correspond to different parameters of the switching diode D1, the voltage-regulating diode D2, and the voltage-dividing resistor R1. When the power supply Vcc is 15V, the reverse voltage of the switching diode D1 should be greater than 25V, the regulated voltage value of the voltage-regulating diode D2 is 6V, and the resistance value of the voltage-dividing resistor R1 is taken as 240Ω.

3. The voltage-controlled pulse duty cycle circuit based on the reverse breakdown characteristic of a zener diode according to claim 1, wherein: For the oscillating capacitor discharging circuit, the parameters of the switching diode D4, the voltage-regulating diode D3, and the voltage-dividing resistor R2 are all related to the power supply Vcc circuit. Different power supply Vcc voltage values correspond to different parameters of the switching diode D4, the voltage-regulating diode D3, and the voltage-dividing resistor R2. When the power supply Vcc is 15V, the reverse voltage of the switching diode D2 should be greater than 25V, the regulated voltage value of the voltage-regulating diode D3 is 2V, and the resistance value of the voltage-dividing resistor R2 is taken as 240Ω.

4. A voltage-controlled pulse duty cycle circuit based on the reverse breakdown characteristic of a zener diode according to claim 1, characterized in that: The value range of the voltage of the input DC control voltage Ui is related to the selection of the parameters of the switching diode D1, the switching diode D2, the voltage-regulating diode D2, the voltage-regulating diode D3, the voltage-dividing resistor R1, and the voltage-dividing resistor R2.

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