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

Abstract

The utility model discloses a voltage-controlled pulse duty ratio circuit based on the 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 utility model relates to a kind of design of voltage-controlled pulse duty cycle circuit, if voltage-controlled U i Voltage is properly set, and circuit component parameter is proper, then within the range of smaller U i Variation, duty cycle regulation can reach about 1:1000, but the entire circuit is very simple. BACKGROUND

[0002] PWM generally refers to pulse width modulation, i.e. duty cycle modulation, and the commonly used PWM circuit is essentially a square wave period certain and duty cycle adjustable circuit. Its basic working principle is to compare a frequency certain sawtooth wave signal with a direct current control voltage, and when the direct current control voltage changes, the output pulse duty cycle will change accordingly.

[0003] Since the oscillation frequency of the multivibrator composed of NE555 timer is less affected by 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 and the difference between the charging path and the discharge path of the timing circuit, the duty cycle of the output pulse signal can be adjusted by directly changing the resistance-capacitance time constant τ=RC of the charging and discharging circuit, such as by changing the resistance value or the capacitance value.

[0004] Strictly speaking, this is not what we need, i.e. the requirement of controlling the pulse output duty cycle by a direct current voltage. Therefore, based on the 555 time base circuit, some direct current voltage controlled pulse duty cycle circuits can also be designed. The commonly used method in the industry is as follows: the 555 time base circuit first forms a non-steady multivibrator with peripheral resistance and capacitance elements, compares a direct current control voltage with a sawtooth wave signal generated during the charging and discharging process, and the pulse waveform duty cycle of the comparator output can be adjusted within a large range.

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

[0006] The 555 time base circuit 5 pin (CO) is actually the positive input terminal of the internal operational amplifier used for comparison. In general applications, this pin is usually connected to ground through a 0.01 μF capacitor to filter out interference.

[0007] When the reverse voltage is lower than the reverse breakdown voltage, the reverse leakage current of the zener diode is very 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 in a large range, the voltage change across the zener diode is quite small. Conversely, the same is true. A very small change in reverse voltage ΔU ZIf the reverse breakdown characteristic of the Zener diode is applied to the charging circuit and the discharging circuit of the 555-based multivibrator, and the Zener diode is made to work in the reverse breakdown region no matter the charging voltage or the discharging voltage, a large reverse breakdown current change Δi can be caused.

[0008] At the same time, a direct current U i is connected to the 5-pin (CO terminal) of the 555 time base circuit, then the two threshold voltages of the 555 circuit will change with U i , the TL pin is short-circuited with the TH pin, an oscillation capacitor is designed between the short-circuit point and the ground, and a charging circuit and a discharging circuit are connected in parallel between the short-circuit point and the output (3-pin, U O ) of the 555 time base circuit, based on the above-mentioned characteristic of the Zener diode, the charging and discharging circuits are controlled by a reverse Zener diode, so the Zener diode here does not function as voltage stabilization, but as controlled reverse breakdown current.

[0009] Based on the external direct current U i of the 5-pin of the 555 circuit, the two threshold voltages of the time base circuit will change, if U i voltage changes within a certain range, the Zener diode constituting the charging and discharging circuits can work in the reverse breakdown region, then when U i voltage increases, the charging current will significantly decrease, and the discharging current will significantly increase; on the contrary, when U i voltage decreases, the charging current will significantly increase, and the discharging current will significantly decrease.

[0010] Due to the effect of the direct current U i , the duty cycle of the pulse wave signal at the 3-pin output of the 555 circuit will change, realizing the preset of voltage-controlled pulse duty cycle, if U i voltage is set properly and the circuit component parameters are proper, then within a small U i change range, the duty cycle adjustment can reach about 1:1000, but the entire circuit is very simple. The utility model discloses

[0011] The utility model discloses want to solve the technical problem to provide a kind of structure more simple, cost more cheap, use more reliable's voltage-controlled pulse duty cycle circuit design technology.

[0012] To achieve the above object, the utility model provides a kind of pressure-controlled pulse duty cycle circuit based on the reverse breakdown characteristic of stabilizing diode, it includes power supply Vcc circuit, time base circuit, oscillation capacitor, oscillation capacitor charging circuit, oscillation capacitor discharging circuit, input DC control voltage, oscillation signal output voltage, work ground;Time base circuit is formed by NE555 circuit, the 5 feet of input DC control voltage Ui is connected NE555 circuit, the 7 feet of NE555 circuit is connected work ground, the 4 feet and the 8 feet of power supply Vcc circuit are simultaneously connected NE555 circuit, the oscillation capacitor charging circuit is formed by switch diode D1, stabilizing diode D2, voltage dividing resistor R1, the oscillation capacitor discharging circuit is formed by voltage dividing resistor R2, stabilizing diode D3, switch diode D4, the 3 feet of NE555 circuit is connected work ground in turn by forward switch diode D1, reverse stabilizing diode D2, voltage dividing resistor R1, the oscillation capacitor C1, the 3 feet of NE555 circuit is connected work ground in turn by reverse switch diode D4, forward stabilizing diode D3, voltage dividing resistor R2, the oscillation capacitor C1, the connecting point of voltage dividing resistor R1 and voltage dividing resistor R2 is connected the 2 feet and the 6 feet of NE555 circuit, and the 3 feet of NE555 circuit exports the oscillation signal output voltage Uo.

[0013] The oscillation capacitor charging circuit, the parameter of switch diode D1, the parameter of stabilizing diode D2, the parameter of voltage dividing resistor R1 are all related to the power supply Vcc circuit, different power supply Vcc voltage value corresponds to different parameter of switch diode D1, the parameter of stabilizing diode D2, the parameter of voltage dividing resistor R1, power supply Vcc is 15V, switch diode D1 reverse voltage is greater than 25V, stabilizing diode D2 voltage is 6V, voltage dividing resistor R1 resistance is 240Ω.

[0014] The oscillation capacitor discharging circuit, the parameter of switch diode D4, the parameter of stabilizing diode D3, the parameter of voltage dividing resistor R2 are all related to the power supply Vcc circuit, different power supply Vcc voltage value corresponds to different parameter of switch diode D4, the parameter of stabilizing diode D3, the parameter of voltage dividing resistor R2, power supply Vcc is 15V, switch diode D2 reverse voltage is greater than 25V, stabilizing diode D3 voltage is 2V, voltage dividing resistor R2 resistance is 240Ω.

[0015] The voltage value of the input DC control voltage Ui is related to the selection of the parameters of switch diode D1, switch diode D2, stabilizing diode D2, stabilizing diode D3, voltage dividing resistor R1 and voltage dividing resistor R2.

[0016] The time base circuit, the 1 feet of NE555 circuit is connected work ground. BRIEF DESCRIPTION OF DRAWINGS

[0017] ATTACHFigure 1 , attached Figure 2 , attached Figure 3 , attached Figure 4 , attached Figure 5 to provide further understanding of the present application, form a part of this application, attached Figure 1 is the working principle of pulse width modulation; attached Figure 2 is the schematic diagram of the positive and negative polarity current square wave modulator with adjustable pulse width; attached Figure 3 is the waveform shaping circuit composed of CMOS inverters; attached Figure 4 is the internal circuit diagram of 555 timer; attached Figure 5 is the function table diagram of 555 timer. DETAILED DESCRIPTION

[0018] The embodiments of the present application are further described below in conjunction with the drawings.

[0019] Conventional voltage-controlled pulse duty cycle circuit based on 555 circuit

[0020] First, the conventional voltage-controlled pulse duty cycle circuit is simply introduced, the working principle is understood, the advantages are explained, and the shortcomings are proved, so that the advantages of our design are embodied: novel working principle, simple structure, low cost, and high performance-price ratio.

[0021] In the automatic control system, the change of voltage is needed to control the duty cycle of the pulse wave in some occasions, such as Figure 1 as shown.

[0022] The circuit mainly consists of a time base chip of IC1 type NE555 and a non-stable 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 is composed of capacitor C1 → discharge tube T inside 555 → working ground.

[0023] Among them, transistor T1, diodes D1 and D2 constitute a constant current source circuit, T1 acts as a constant current source for charging timing capacitor C1, so that the sawtooth curve of the charging process of C1 has good linearity, 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~2 / 3Vcc, the control voltage Ui is connected to the non-inverting input terminal of operational amplifier IC2, so when the range of control voltage Ui also varies between 1 / 3Vcc~2 / 3Vcc, the duty cycle of the pulse waveform output by IC2 can be adjusted in the range of approximately 0~100%.

[0024] For example, when Ui voltage is equal to 2 / 3U ccWhen Ui voltage equals 1 / 3 U, IC2 output pulse duty cycle is lowest 0, i.e. the closer to 2 / 3 U cc , the higher the duty cycle, the closer to 1 / 3 U cc , the lower the duty cycle. cc

[0025] The advantage of this duty cycle adjusting 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 complex, but the working principle is easy to understand, and it belongs to a mature scheme.

[0026] Voltage-controlled pulse duty cycle circuit based on reverse breakdown characteristics of zener diode

[0027] Zener diode, also known as Zener diode, is a single PN junction diode used for voltage stabilization. This diode is a semiconductor device with very high resistance until the reverse breakdown voltage, and in the reverse breakdown region, the reverse resistance decreases to a very small value.

[0028] Therefore, when the reverse voltage is lower than the reverse breakdown voltage, the reverse leakage current is extremely small, but when the reverse voltage approaches the critical value of the reverse voltage, the reverse current suddenly increases, which is called breakdown. To stabilize the voltage, the working conditions of the zener diode must be met, and its reverse breakdown curve is as shown in Figure 2 .

[0029] In Figure 2 , it can be seen that the actual zener voltage U Z changes with the working current, but the change is relatively small, i.e. although the current changes in a large range, the voltage across the diode is basically stable near the breakdown voltage, thereby realizing the voltage stabilization function of the diode.

[0030] Based on the above principle, referring to Figure 2 , if the reverse voltage is less than U A , the reverse current of the diode is very small; when the reverse voltage equals U A , the diode breaks down, and the reverse breakdown current is I Zmin ; when the reverse voltage equals U B , the reverse breakdown current is I Zmax , U A -U B =ΔU Z , I Zmax -I Zmin =Δi.

[0031] As can be seen from the figure, a small change in reverse voltage ΔU Z ​If the reverse breakdown characteristic of the Zener diode is applied to the charging circuit and the discharging circuit of the 555-based multivibrator, and the Zener diode is operated in the reverse breakdown region regardless of the charging voltage or the discharging voltage, a large reverse breakdown current change Δi can be caused.

[0032] At the same time, a change in an applied DC voltage Ui can cause the Zener diode to change in the reverse breakdown region, i.e., ΔU Z The charging and discharging currents of the multivibrator will change, and if the change in the DC voltage Ui is in the opposite direction to the change in the charging current, the duty cycle of the output pulse of the multivibrator will change.

[0033] Based on the above extremely small ΔU Z The description of a large Δi that can be caused by a small change in Ui to achieve a large duty cycle adjustment, but the oscillation frequency can change at the same time.

[0034] It can be seen that, compared with the above-mentioned traditional voltage-controlled pulse duty cycle circuit based on the 555 multivibrator, the 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 in voltage control.

[0035] The electrical principle of the voltage-controlled duty cycle circuit is shown in Figure 3 In addition to the NE555 time base circuit, the circuit only uses seven simple peripheral elements, two voltage dividing resistors, two Zener diodes, two switching diodes, and an oscillation capacitor. The circuit has the advantages of high voltage control sensitivity and large duty cycle adjustment range.

[0036] It can be seen that the voltage-controlled duty cycle circuit includes a power supply Vcc circuit, a 555 time base circuit, an oscillation capacitor charging circuit, an oscillation capacitor discharging circuit, an input DC control voltage, an oscillation signal output voltage, and a working ground.

[0037] The NE555 timing circuit

[0038] Figure 3 The core element of the circuit is the 555 timer circuit. The 555 circuit is low in cost and reliable in performance. It includes two voltage comparators, three equivalent 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 555 circuit, as Figure 4 .

[0039] 555 circuit only need to external resistance, capacitance, can realize multi-resonant oscillator, monostable trigger and Schmidt trigger pulse generation and transformation circuit, this is the most commonly used function of 555 circuit, 555 timer functions as shown in Figure 5 .

[0040] 555 time base circuit 5 feet (CO) is actually the internal use for comparison of the positive input of operational amplifier, through the internal voltage dividing resistor, the voltage of this foot is two-thirds of the supply voltage, plus a 0.01 μF capacitor, due to the influence of the charging and discharging characteristics of the capacitor, the voltage changes caused by the instantaneous or high or low interference signal added to this place will slow down, it can also be said to absorb the instantaneous interference, can make the signal more stable, in a word, it is to filter out the interference. This is the common use of 555 time base circuit, that is, 5 feet through the capacitor to ground.

[0041] Voltage control pulse duty cycle circuit structure and working principle based on reverse breakdown characteristics of zener diode

[0042] 555 time base circuit has two threshold voltages, the first threshold voltage is 1 / 3Vcc: when the TL end input voltage decreases to 1 / 3Vcc and decreases infinitely small, the output state of 555 circuit will change, usually from low to high, this feature makes 555 circuit can respond to the falling edge of the input voltage, called falling edge threshold voltage, expressed as V N2— =1 / 3Vcc, where N2- represents the inverting input of comparator N2 inside 555 time base circuit, see Figure 4 .

[0043] The second threshold voltage is 2 / 3Vcc: corresponding to the first threshold voltage, when the input voltage rises to 2 / 3Vcc and increases infinitely small, the output state will also change, usually from high to low, this change allows 555 circuit to perform specific operations when the input voltage rises, called rising edge threshold voltage, expressed as V N1+ =2 / 3Vcc, where N1+ represents the non-inverting input of comparator N1 inside 555 time base circuit.

[0044] Figure 4 In other words, as long as the voltage of the inverting input of comparator N1 increases to V N1+ and increases infinitely small, the output of comparator N1 will be inverted to low "0", and the output Uo of 555 will become low "0". Similarly, as long as the voltage of the non-inverting input of comparator N2 decreases to V N2-- and decreases infinitely small, the output of comparator N2 will be inverted to low "0", and the output Uo of 555 will become high "1".

[0045] 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 value of U i , for example, if Ui=5V, then V N1+ =5V, V N2-- =2.5V,

[0046] The TL end of U Figure 3 is shorted to the TH end, the shorting point is connected to the working ground through the oscillation capacitor C1, between the shorting point and the output end (pin 3, U O ) of the NE555 timer circuit, a charging circuit and a discharging circuit are connected in parallel, the charging circuit is composed of switch diode D1, voltage stabilizing diode D2, and voltage dividing resistor R1, the discharging circuit is composed of voltage dividing resistor R2, voltage stabilizing diode D3, and switch diode D4, as shown in Figure 3 , when the output end Uo is at high level, current charges capacitor C1 through D1, D2, and R1 branches; when the output end is at low level, current discharges capacitor C1 through D3, D4, and R2 branches.

[0047] Figure 3 In the above, assuming that the output voltage Uo is at high level, since the external DC voltage U i connected to pin 5 of the 555 circuit will change the two threshold voltages V N1+ and V N2— of the timer circuit, if the U i voltage changes within a certain appropriate range, it can just make the voltage stabilizing diodes that constitute the charging and discharging circuits work in the reverse breakdown region ΔU Z , then when the U i voltage slightly increases, since the corresponding threshold voltages V N1+ and V N2— both increase, the TH end voltage (i.e. V N1+ voltage) at which the comparator N1 output reverses to "0" will also increase, and by the same token, the TL end voltage (V N2— voltage) at which the comparator N2 output reverses to "0" will also increase, which also indicates that the cutoff charging potential of capacitor C1 will also rise, making voltage stabilizing diode D2 tend to be cut off, the charging current of C1 rapidly decreases, the charging time of C1 is prolonged, and the time for the output Uo voltage to be at high level "1" is prolonged, until the Uo voltage becomes "0".

[0048] By the same token, the slight increase of the control voltage Ui makes the initial potential of C1 discharging also rise, based on the reverse breakdown characteristics of the voltage stabilizing diode: a small change ΔU Z in the reverse voltage.The slight increase of the control voltage Ui can cause a large reverse breakdown current change Δi, the "0" level voltage drop of the output voltage Uo increases, the reverse breakdown current of the voltage regulator D3 increases suddenly, the discharge time of C1 becomes shorter, and the "0" level time of the output voltage Uo becomes shorter until the Uo voltage becomes "1".

[0049] The above shows that the slight increase of the control voltage Ui greatly increases the duty cycle of the output voltage Uo.

[0050] Conversely, when U i slightly decreases, V N1+ and V N2— drop, and the cutoff charging potential of the capacitor C1 also decreases, the charging time of C1 becomes shorter, and the "1" level time of the output voltage Uo becomes shorter; the slight decrease of the control Ui still based on the reverse breakdown characteristics of the voltage regulator diode: a small reverse voltage change ΔU Z can cause a large reverse breakdown current change Δi, the reverse breakdown current of the voltage regulator D3 decreases suddenly, the discharge time becomes longer, and the "0" level time of the output voltage Uo greatly becomes longer, which shows that the slight decrease of the control voltage Ui greatly reduces the duty cycle of the output voltage Uo.

[0051] The above discussion also proves that although the 5-pin adds a direct current control voltage Ui, the multi-resonance process is similar to the traditional application, which is described as follows.

[0052] The high level of the output 3-pin of IC1 charges the oscillation capacitor C1 through the charging circuit, and the C1 voltage gradually rises to the rising threshold voltage V N1+ , and then rises by an infinitesimal value, the 3-pin Uo voltage of IC1 reverses to the low level "0"; when the 3-pin outputs the low level, the voltage of the oscillation capacitor C1 (at this time U C1 = V N1+ ) discharges to the "0" of the output 3-pin through the discharging circuit, and the C1 voltage gradually decreases, and when the C1 voltage decreases to the falling threshold voltage V N2— , and then decreases by an infinitesimal value, the 3-pin of IC1 reverses to the high level "1" again, at this time U C1 = V N2— , and the oscillation capacitor will be charged again.

[0053] The above process circulates back and forth, and due to the slight effect of the direct current control voltage U i , the duty cycle of the pulse signal of the output 3-pin of the 555 circuit will greatly change, the preset of the voltage control pulse duty cycle is realized, and if the direct current control U i voltage is properly set and the circuit component parameters are proper, then within a small U i change range, the duty cycle adjustment can reach about 1:1000.

[0054] Therefore, the function of the voltage stabilizer here is not to stabilize voltage, but to control the reverse breakdown current.

[0055] Summary

[0056] The above working process can be simply summarized as follows: when the output end of the 555 time base circuit is at high level, the current charges the capacitor C1 through the D1, D2 and R1 branches; when the output end is at low level, the current discharges the capacitor C1 through the D3, D4 and R2 branches. If the control voltage Ui at the 5 pin increases, the charging potential of the capacitor C1 also increases, so that the average charging current decreases rapidly, and the charging time is prolonged. During the discharging, because the voltage on the capacitor C1 is relatively high, the reverse breakdown current of the voltage stabilizer D4 is relatively large, so that the discharging time is shortened. Conversely, if Ui decreases, the charging potential of the capacitor C1 also decreases, so that the average charging current increases rapidly, and the charging time is shortened. During the discharging, because the voltage on the capacitor C1 is relatively low, the average reverse breakdown current of the voltage stabilizer D4 decreases, so that the discharging time is prolonged. Ultimately, a small change in the control voltage Ui leads to a large duty cycle change of the output voltage Uo.

[0057] Debugging and matters needing attention

[0058] The circuit structure of the design is very simple, but the selection of component parameters and the debugging process need to be careful. When the power supply voltage Vcc is 15V, the parameters of each component used in the circuit are as shown in the table. Figure 3 D1 and D2 are switching diodes, and the reverse voltage is greater than 25V. The voltage stabilizing diode D2 of the charging circuit has a voltage stabilizing value of 6V, the voltage stabilizing diode D3 of the discharging circuit has a voltage stabilizing value of 2V, and the voltage dividing resistors R1 and R2 are both 240Ω.

[0059] If the voltage dividing resistors R1 and R2 have larger values, the control sensitivity will be lower, and the frequency of the multi-vibrator composed of the 555 circuit will be reduced. If the values are smaller, the control sensitivity will be higher, and the oscillation frequency will also be increased. However, if the resistance values are too small, unexpected oscillation will also be caused.

[0060] The capacitor C1 is a 0.01uF polyester capacitor. If the component parameters of the circuit are accurate, when the control voltage Ui at the 5 pin changes between 6V and 7V, the duty cycle can reach more than 1:1000.

[0061] Compared with the traditional voltage-controlled duty cycle circuit introduced above, the structure of the design is simpler, and the cost performance is higher. The disadvantage is that the debugging is slightly troublesome. For the selection of the resistance values of the resistors R1 and R2, it is recommended to use a 1K potentiometer to replace the resistors for debugging. Within the complete control range of the voltage Ui, the operation of the voltage stabilizing diodes D2 and D4 can be included in the reverse breakdown region, so as to realize voltage control pulse width in the full range.

[0062] The first innovation point is based on the reverse breakdown characteristic of the voltage stabilizing diode: a small reverse voltage change ΔU Z Can cause a large reverse breakdown current change Δi, the change of current will result in the change of charging or discharging time, finally affect the duty cycle; the second innovation point 555 time base circuit 5 feet (CO) special application, DC control voltage Ui acts on the 5 feet, so as to change the two threshold voltage of 555 time base circuit, finally change the reverse voltage of voltage stabilizing diode, further change the charging and discharging current, the duty cycle changes.

[0063] The above examples are only used to illustrate but not to limit the technical scheme of the utility model, although the utility model is described in detail with reference to the above examples, those skilled in the art should understand; still can modify or equivalent replace to the utility model, without any modification or partial replacement, which should be covered in the scope of the claims of the utility model, which does not depart from the spirit and scope of the utility model.

Claims

1. A voltage controlled pulse duty cycle circuit based on the reverse breakdown characteristics of a zener diode, characterized by, The voltage-controlled pulse duty cycle circuit 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 pin 5 of the NE555 circuit, pin 7 of the NE555 circuit is connected to the working ground, the power supply Vcc circuit is connected to pin 4 and pin 8 of the NE555 circuit at the same time, the oscillation capacitor charging circuit is composed of a switching diode D1, a voltage stabilizing diode D2, and a voltage dividing resistor R1, the oscillation capacitor discharging circuit is composed of a voltage dividing resistor R2, a voltage stabilizing diode D3, and a switching diode D4, pin 3 of the NE555 circuit is connected to the working ground in sequence through the forward switching diode D1, the reverse voltage stabilizing diode D2, the voltage dividing resistor R1, and the oscillation capacitor C1, pin 3 of the NE555 circuit is connected to the working ground in sequence through the reverse switching diode D4, the forward voltage stabilizing diode D3, the 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 pin 2 and pin 6 of the NE555 circuit, and the oscillation signal output voltage Uo is output from pin 3 of the NE555 circuit.

2. The voltage-controlled pulse duty cycle circuit based on the reverse breakdown characteristic of a zener diode according to claim 1, characterized in that: The time base circuit, pin 1 of the NE555 circuit is connected to the working ground.

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