Capacitive voltage dividing circuit system applied to power voltage input control

Abstract

This invention discloses a capacitor voltage divider circuit system for power supply voltage input control, including an AC voltage divider network circuit, an input voltage judgment and identification circuit, and a switching execution logic circuit. The AC voltage divider network circuit is used to divide the input voltage. The input voltage judgment and identification circuit is used to determine whether the input voltage reaches the threshold for voltage division. The switching execution logic circuit is used to select whether to connect the AC voltage divider network circuit to perform voltage division based on the judgment result of the input voltage judgment and identification circuit. This invention enables low line voltage drop and a wide input voltage range, giving the subsequent switching power supply better surge protection and load short-circuit protection.

Description

Technical Field

[0001] This invention relates to the field of power supply voltage control technology, and more specifically to a capacitor voltage divider circuit system applied to power supply voltage input control. Background Technology

[0002] In inverter welding machine control circuits, switching power supplies are increasingly used. In practical applications, customers expect the welding machine to operate in both single-phase AC 220V and single-phase AC 380V power supply modes, with automatic identification and switching. Currently, the industry-standard solution is to increase the withstand voltage of the power switching transistors to 900V or even higher, exceeding 1200V. However, this approach has the following drawbacks in practical applications:

[0003] 1. The improvement in power supply has led to a greater requirement for creepage distance, resulting in a larger PCB area and product size, which is not conducive to installation in confined spaces.

[0004] 2. The design can only use switching power supply chips with external power switching transistors. Chips with built-in power switching transistors cannot be used. Currently, such switching power supply chips on the market are designed for AC220V input, and the on-chip power switching transistors have a voltage rating of around 600V to 750V, which leads to a significant increase in hardware costs.

[0005] 3. The inherent leakage inductance of the switching power supply transformer generates a high peak voltage when the power switching transistor is turned off. An increase in the input voltage will make this peak voltage even higher. In some cases, the peak voltage can even exceed 1500 volts, which can break down the power switching transistor, resulting in a high failure rate.

[0006] 4. When using an existing power frequency transformer to step down AC380V to AC220V under conditions where the generator supply voltage is unstable, there are a series of drawbacks, such as excessive voltage drop of the power frequency transformer, narrow input voltage range, and large size of the power frequency transformer which is not conducive to installation in confined spaces.

[0007] Therefore, there is an urgent need for a power supply voltage input control circuit with low line voltage drop, wide input voltage range, and the ability to enable the subsequent switching power supply to have better surge protection and load short-circuit protection. Summary of the Invention

[0008] The purpose of this invention is to provide a capacitor voltage divider circuit system for power supply voltage input control, in order to solve the problems of large voltage drop and narrow input voltage range of existing power frequency transformers, which result in poor surge protection and load short-circuit protection of the subsequent switching power supply.

[0009] To achieve the above objectives, the technical solution of the present invention is as follows:

[0010] A capacitor voltage divider circuit system for power supply voltage input control includes an AC voltage divider network circuit, an input voltage judgment and identification circuit, and a switching execution logic circuit. The AC voltage divider network circuit is used to divide the input voltage. The input voltage judgment and identification circuit is used to determine whether the input voltage reaches the threshold for voltage division. The switching execution logic circuit is used to select whether to connect the AC voltage divider network circuit to divide the input voltage based on the judgment result of the input voltage judgment and identification circuit.

[0011] Furthermore, as a preferred technical solution, the AC voltage divider network circuit includes a first capacitor C1, a second capacitor C2, and a third capacitor C3. The first capacitor C1 and the second capacitor C2 are connected in parallel and then connected in series with the third capacitor C3. The parallel and series network formed by the first capacitor C1, the second capacitor C2, and the third capacitor C3 is respectively connected to the ACL terminal and the ACN terminal of the external input voltage.

[0012] Furthermore, as a preferred technical solution, the capacitance ratio of the first capacitor C1, the second capacitor C2, and the third capacitor C3 is (2~2.4):1:(2~2.4).

[0013] Further, as a preferred technical solution, the input voltage judgment and recognition circuit includes a third diode D3, a transient suppression diode DR1, a fifth resistor R5, an optocoupler U1, a fourth capacitor C4, a third resistor R3, and a fourth resistor R4. The anode of the third diode D3 is connected to the ACL terminal of the external input voltage. The third diode D3, the transient suppression diode DR1, the fifth resistor R5, and the fourth capacitor C4 are connected in series. The photodiode inside the optocoupler U1 is connected in parallel with the fourth capacitor C4. The cathode of the photodiode is connected to the ACN terminal of the external input voltage. The collector of the phototransistor inside the optocoupler U1 is connected to a 24V DC voltage. The emitter of the phototransistor is connected to the third resistor R3 and the fourth resistor R4, respectively.

[0014] Furthermore, as a preferred technical solution, the switching execution logic circuit includes a unidirectional thyristor VT1, a first resistor R1, a second diode D2, a seventh diode D7, a Zener diode DZ1, a first electrolytic capacitor E1, a field-effect transistor Q1, a relay JK1, and a thermistor PTC. The 16P unidirectional thyristor VT1 has its gate connected to the third resistor R3, its positive terminal connected to the cathode of the second diode D2, its anode connected to the gate of the field-effect transistor Q1, its source grounded, its drain connected to one end of the relay JK1, and its other end connected to a 24V DC voltage. One end of the first resistor R1 is connected to a 24V DC voltage, and its other end is connected to the gate of the field-effect transistor Q1. The seventh diode D7 is connected in parallel across the first resistor R1, and its cathode is connected to a 24V DC voltage. The anode of the Zener diode DZ1 is grounded, and its cathode is connected to the gate of the field-effect transistor Q1. The first electrolytic capacitor E1 is connected in parallel with the Zener diode DZ1, and its negative terminal is grounded. The thermistor PTC16P is connected in series with the contacts of the relay JK1 and then in parallel across the second capacitor C2.

[0015] Furthermore, as a preferred technical solution, it also includes a first light-emitting diode LED1, a second resistor R2, a second light-emitting diode LED2, and a tenth resistor R10. The first light-emitting diode LED1 is connected in series with the second resistor R2, and the second resistor R2 is connected to the cathode of the seventh diode D7. The cathode of the first light-emitting diode LED1 is connected to the cathode of the second diode D2. The anode of the second light-emitting diode LED2 is connected to a 24V DC voltage. The cathode of the second light-emitting diode LED2 is connected to one end of the tenth resistor R10, and the other end of the tenth resistor R10 is connected to the drain of the field-effect transistor Q1.

[0016] Furthermore, as a preferred technical solution, it also includes a ninth resistor R9, which is connected in parallel across the two ends of the second capacitor C2.

[0017] Furthermore, as a preferred technical solution, it also includes a rectifier bridge B1, a varistor VR1, and a second electrolytic capacitor E2. The rectifier bridge B1 is connected in parallel across the two ends of the third capacitor C3. The positive terminal of the second electrolytic capacitor E2 is connected to the DC output terminal of the rectifier bridge B1, and the negative terminal of the second electrolytic capacitor E2 is grounded. The varistor VR1 is connected in parallel across the two ends of the second electrolytic capacitor E2.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] (1) Compared with traditional power frequency transformers, especially in the case of unstable generator power supply voltage, the voltage drop of the line is smaller than that of power frequency transformers. At the same time, compared with power frequency transformers, the present invention does not require the use of external power switching transistors in the switching power supply chip, which is lower in cost.

[0020] (2) This invention greatly expands the input voltage range of the subsequent switching power supply, which can range from AC70V to AC550V. At the same time, due to the high resistance design of the input line, the subsequent switching power supply has better surge protection and load short-circuit protection, which greatly improves the life and reliability of the switching power supply.

[0021] (3) Compared with power frequency transformers, the present invention is smaller in size and lighter in weight, making it easier to install in confined spaces. Attached Figure Description

[0022] Figure 1 This is a block diagram of the components of the present invention;

[0023] Figure 2 This is a schematic diagram of the circuit structure of the present invention;

[0024] Figure 3 This is a schematic diagram showing the electrical connection between the structure of the present invention and the switching power supply. Detailed Implementation

[0025] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the invention.

[0026] It should be noted that in the description of this invention, the terms "first," "second," etc., are used only for distinguishing descriptions and should not be construed as indicating or implying relative importance; the term "connected" refers to electrical or signal connections between components, and those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0027] Example

[0028] like Figure 1As shown in this embodiment, a capacitor voltage divider circuit system for power supply voltage input control includes an AC voltage divider network circuit, an input voltage judgment and identification circuit, and a switching execution logic circuit. The AC voltage divider network circuit is used to divide the input voltage. The input voltage judgment and identification circuit is used to determine whether the input voltage reaches the threshold for voltage division. The switching execution logic circuit is used to select whether to connect the AC voltage divider network circuit to divide the input voltage based on the judgment result of the input voltage judgment and identification circuit. Specifically, when an external 220V or 380V AC voltage is input, the input voltage judgment and identification circuit determines whether the input voltage is 220V AC voltage or 380V AC voltage. If the input voltage is 220V AC voltage, there is no need to connect the AC voltage divider network circuit; the 220V AC voltage is directly used as the input voltage of the subsequent circuit. If the input voltage is 380V AC voltage, the AC voltage divider network circuit is connected to divide the 380V AC voltage to obtain 220V AC voltage, which is then used as the input voltage of the subsequent circuit.

[0029] The implementation process of this invention and its advantages over existing technical solutions will be explained below with reference to a specific circuit structure:

[0030] like Figure 2 As shown, the AC voltage divider network circuit of this embodiment includes a first capacitor C1, a second capacitor C2, and a third capacitor C3. The first capacitor C1 and the second capacitor C2 are connected in parallel and then connected in series with the third capacitor C3. The parallel and series network formed by the first capacitor C1, the second capacitor C2, and the third capacitor C3 is respectively connected to the ACL terminal and the ACN terminal of the external input voltage. The AC 220V or 380V voltage is input from the ACL terminal and the CAN terminal.

[0031] Preferably, in this embodiment, the capacitance ratio of the first capacitor C1, the second capacitor C2, and the third capacitor C3 is (2-2.4):1:(2-2.4).

[0032] Preferably, the input voltage judgment and recognition circuit of this embodiment includes a third diode D3, a transient suppression diode DR1, a fifth resistor R5, an optocoupler U1, a fourth capacitor C4, a third resistor R3, and a fourth resistor R4. The anode of the third diode D is connected to the ACL terminal of the external input voltage. The third diode D3, the transient suppression diode DR1, the fifth resistor R5, and the fourth capacitor C4 are connected in series. The photodiode inside the optocoupler U1 is connected in parallel with the fourth capacitor C4. The cathode of the photodiode is connected to the ACN terminal of the external input voltage. The collector of the phototransistor inside the optocoupler U1 is connected to a 24V DC voltage. The emitter of the phototransistor is connected to the third resistor R3 and the fourth resistor R4, respectively.

[0033] Preferably, the switching execution logic circuit in this embodiment includes a unidirectional thyristor VT1, a first resistor R1, a second diode D2, a seventh diode D7, a Zener diode DZ1, a first electrolytic capacitor E1, a field-effect transistor Q1, a relay JK1, and a thermistor PTC. The gate of a 16P PTC unidirectional thyristor VT1 is connected to the third resistor R3. The positive terminal of the unidirectional thyristor VT1 is connected to the cathode of the second diode D2. The anode of the second diode is connected to the gate of the field-effect transistor Q1. The source of the field-effect transistor Q1 is grounded. The drain of the field-effect transistor Q1 is connected to one end of the relay JK1. The other end of the relay JK1 is connected to a 24V DC voltage. One end of the first resistor R1 is connected to a 24V DC voltage. The other end of the first resistor R1 is connected to the gate of the field-effect transistor Q1. The seventh diode D7 is connected in parallel across the first resistor R1, and the cathode of the seventh diode D7 is connected to a 24V DC voltage. The anode of the Zener diode DZ1 is grounded, and the cathode of the Zener diode DZ1 is connected to the gate of the field-effect transistor Q1. The first electrolytic capacitor E1 is connected in parallel with the Zener diode DZ1, and the cathode of the first electrolytic capacitor E1 is grounded. The 16P PTC thermistor is connected in series with the contacts of the relay JK1 and then in parallel across the second capacitor C2.

[0034] In this embodiment, the AC 220V or 380V voltage is input from the ACL terminal and the ACN terminal, and after passing through the first capacitor C1 and the second capacitor C2 in parallel, it is connected in series with the third capacitor C3 to divide the voltage. The equivalent capacitive reactance of the capacitors divides the AC 380V voltage. The voltage division formula can be calculated by the following approximate simple formula:

[0035] First, select a 2.2uF / 400V first capacitor C1, a 1uF / 400V second capacitor C2, and a 2.2uF / 400V third capacitor C3. Since 1uF capacitance is approximately equal to 3000 ohms capacitive reactance, the parallel capacitance of C1 and C2 is 3.2uF, and its capacitive reactance is 3000 ÷ 3.2 ≈ 937.5 ohms. The capacitive reactance of C3 is 3000 ÷ 2.2 ≈ 1363.6 ohms. After voltage division... Figure 2 The AC voltage between points A and B is approximately 225 volts (AC voltage) 380 ÷ (937.5 + 1363.6) × 1363.6. The inventor has verified this voltage multiple times and it matches the calculated result.

[0036] II. Calculate the load-carrying capacity of the current provided by the circuit.

[0037] First, calculate the current that the parallel capacitance of C1 and C2 can provide to the load when the input voltage is 380V. Then, calculate the current that a 4.7uF capacitance can provide under full-wave rectification using the formula:

[0038] I(AV)=0.89×V÷Zc=0.89×380×2×π×f×C

[0039] =0.89×380×2×3.14×50×C≈0.499 Amperes (499mA) Current

[0040] Calculate the current shunted by C3. After voltage division, the voltage across C3 is AC225 volts. Then:

[0041] I(AV) = 0.89 × 225 × 2 × 3.14 × 50 × C = 0.0628 amperes (63 mA)

[0042] 499(mA) - 63(mA) = 436(mA). After deducting the current shunted by C3, this circuit can provide 436(mA) of current to the downstream load. The output power of the downstream load switching power supply is approximately 40W, with two output voltages: one 15V and the other 24V. Calculate the required current on the primary high-voltage side of the switching power supply, based on the 24V output.

[0043] 40W ÷ 225V = 0.177A (177mA), 436 (mA) is greater than 177 (mA), therefore, it can meet the load requirements.

[0044] In this embodiment, the presence of the first resistor R1 and the first electrolytic capacitor E1 provides the circuit with a detection time when the input power is turned on. The logic is that the input is assumed to be AC380V at the moment of power-on. The field-effect transistor Q1 waits for the potential of the first electrolytic capacitor E1 to charge to the threshold. During the waiting process, the voltage judgment circuit completes the judgment and identification in advance. If the input voltage is greater than AC270V, it is determined to be AC380V. The unidirectional thyristor VT1 is turned on, pulling the potential on the first electrolytic capacitor E1 low. The field-effect transistor Q1 cannot be turned on, and the AC voltage divider network circuit enters the working state. When the input voltage is detected to be lower than AC270V, the unidirectional thyristor VT1 will not be turned on. The field-effect transistor Q1 waits for about 1 second. The potential on the first electrolytic capacitor E1 charges to the threshold of the field-effect transistor Q1. The field-effect transistor Q1 is turned on, the relay JK1 is closed, the first capacitor C1 and the second capacitor C2 are short-circuited, and the voltage divider capacitor network of the first capacitor C1 and the second capacitor C2 is cut off.

[0045] In this embodiment, the function of the seventh diode D7 is to quickly discharge the charge on the first electrolytic capacitor E1 when the power is turned off, so as to reset it to zero and make the field-effect transistor Q1 have a delayed conduction function when it is turned on again.

[0046] In this embodiment, the introduction of a thermistor PTC 16P into the circuit structure serves two purposes: first, it prevents the first capacitor C1 and the second capacitor C2 from discharging and causing the JK1 contacts to arc and stick together when the relay JK1 contacts are closed; second, when the AC 220V input is applied, the closing of the relay JK1 contacts increases the impedance of the input line, improving the line's surge protection capability. Simultaneously, it can provide approximately 2 amps of current to the downstream load. In the event of a severe short circuit in the downstream load, the thermistor PTC 16P heats up significantly, rapidly increasing its resistance to a high-resistance state, thus protecting the downstream load circuit components.

[0047] The working principle of this invention is as follows: When the input power supply is detected to be AC380V, the AC380V is half-wave rectified by the third diode D3 and applied to the transient suppression diode DR1. DR1 is turned on, and the current is limited by the fifth resistor R5 and applied to the first pin of optocoupler U1, flowing to the CAN terminal through the internal photodiode. Optocoupler U1 is turned on. At this time, the DC24V voltage at the fourth pin of the optocoupler flows out through the emitter of the internal phototransistor and is applied to the four resistors R4. This voltage is then applied to the gate of the unidirectional thyristor VT1 through the third resistor R3, turning on and locking VT1. The second diode D2 pulls the gate potential of the field-effect transistor Q1 down to near 0 volts, causing Q1 to turn off. The coil of relay JK1 is de-energized and the contacts open. The input AC 380 volts can only be divided to AC 225 volts through the series-parallel network composed of the first capacitor C1, the second capacitor C2, and the third capacitor C3. This achieves the step-down of the 380V AC voltage to 225V before inputting it into the subsequent circuit, without the need for a dedicated power frequency transformer. This reduces costs and also makes the device smaller, lighter, and easier to install in confined spaces.

[0048] It should be noted that, theoretically, an AC voltage divider network circuit can divide the input voltage to AC220 volts. However, due to limitations in capacitor capacitance specifications, achieving a precise AC220 volt level is not easy. Firstly, the mains voltage fluctuates, typically by more than 5 volts. Therefore, this invention is designed to divide the input voltage to AC225 volts. In fact, this 5-volt range is perfectly adequate for a switching power supply, as its mains input voltage range is AC70V to AC270V.

[0049] When the input power supply is detected to be AC220V, optocoupler U1 does not operate. Due to the presence of the first resistor R1 and the first electrolytic capacitor E1, the gate potential of the field-effect transistor Q1 rises linearly according to the integral time constant. After a certain delay, the contacts of relay JK1 close, shorting the parallel network of the first capacitor C1 and the second capacitor C2. This allows the input power supply to form a loop from the ACL terminal through the thermistor PTC 16P and the contacts of relay JK1 to point A, ensuring the load-carrying capacity of the subsequent switching power supply when the input voltage is low. At this time, the third capacitor C3 only acts as an X capacitor in the circuit.

[0050] In this embodiment, even when the AC input voltage is as high as 500 volts, the voltage across the third capacitor C3 (between points A and B) will not exceed AC280V according to the voltage division ratio, and there is a 470V varistor after the rectifier bridge for overvoltage protection.

[0051] It should be noted that the present invention has significant advantages when applied to the switching power supply of a three-phase frequency converter. The relay can be eliminated, and only an AC voltage divider network circuit is used. The three voltage divider capacitors (first capacitor C1, second capacitor C2, and third capacitor C3) can be replaced with high-voltage surface-mount non-polarized capacitors. As a result, the cost of the subsequent switching power supply can be significantly reduced. At the same time, the area occupied by the switching power supply on the PCB can be greatly reduced, and the reliability is further improved.

[0052] Because of the capacitive reactance of the first capacitor C1 and the second capacitor C2, when the DC circuit of the subsequent switching power supply is short-circuited, the input short-circuit current will be limited to less than 500 mA, thereby ensuring that the subsequent circuit will not be damaged. At the same time, it also has the effect of suppressing the peak voltage generated by the surge current.

[0053] Additionally, it should be noted that, with the voltage division ratio of the AC voltage divider network circuit remaining unchanged, increasing the capacitance of the first capacitor C1, the second capacitor C2, and the third capacitor C3 proportionally can increase the input current and improve the load-carrying capacity.

[0054] To more intuitively determine whether the input voltage is AC220V or AC380V, this invention also includes a first light-emitting diode LED1, a second resistor R2, a second light-emitting diode LED2, and a tenth resistor R10. The first light-emitting diode LED1 is connected in series with the second resistor R2, and the second resistor R2 is connected to the cathode of the seventh diode D7. The cathode of the first light-emitting diode LED1 is connected to the cathode of the second diode D2. The anode of the second light-emitting diode LED2 is connected to a 24V DC voltage. The cathode of the second light-emitting diode LED2 is connected to one end of the tenth resistor R10, and the other end of the tenth resistor R10 is connected to the drain of the field-effect transistor Q1. When the input power is AC220V, the first electrolytic capacitor E1 charges to the threshold of the field-effect transistor Q1 (3.4V in about 1 second) according to the integral time constant, turning on the field-effect transistor Q1. At this time, the second light-emitting diode LED2 is simultaneously turned on and lit, while the first light-emitting diode LED1 is off. When the input power is AC380V, the unidirectional thyristor VT1 is turned on, preventing the first electrolytic capacitor E1 from charging. The field-effect transistor Q1 is turned off, and the first light-emitting diode LED1 lights up. At the same time, the start enable signal of the relay JK1 is disabled, and the second light-emitting diode LED2 is turned off. Of course, to better distinguish between the first light-emitting diode LED1 and the second light-emitting diode LED2, it can be selected that the first light-emitting diode LED1 is red and the second light-emitting diode LED2 is green. That is, when the red light is on, it indicates that the input is AC380V, and when the green light is on, it indicates that the input is AC220V.

[0055] To enhance circuit safety, this implementation also includes a ninth resistor R9, which is connected in parallel across the second capacitor C2. When the input voltage is AC380V, since the relay JK1 circuit is open, residual voltage remains on the first capacitor C1 and the second capacitor C2 after the power is turned off. Accidental contact with this circuit could cause injury. However, by introducing the ninth resistor R9, R9 can discharge the voltage on the first capacitor C1 and the second capacitor C2 within a few hundred milliseconds, and the residual voltage on the third capacitor C3 will also be quickly consumed by the downstream load, thus effectively improving circuit safety.

[0056] To enhance the protection of downstream circuits and components, this embodiment also includes a rectifier bridge B1, a varistor VR1, and a second electrolytic capacitor E2. The rectifier bridge B1 is connected in parallel across the two ends of the third capacitor C3. The positive terminal of the second electrolytic capacitor E2 is connected to the DC output terminal of the rectifier bridge B1, and the negative terminal of the second electrolytic capacitor E2 is grounded. The varistor VR1 is connected in parallel across the two ends of the second electrolytic capacitor E2. In the circuit, the varistor VR1 plays a good role in voltage limiting in the DC bus, protecting the second electrolytic capacitor E2 (with a withstand voltage of DC 450 volts). When the DC bus voltage exceeds DC 470 volts (the input AC voltage exceeds 550 volts), the varistor VR1 avalanche conducts, clamping the DC bus voltage. The thermistor PTC 16P in the switching execution logic circuit will also quickly switch to a high-impedance state due to the huge current increase, limiting the current of the input circuit. This effectively protects the downstream components, giving the downstream switching power supply better surge resistance and load short-circuit resistance, greatly improving the life and reliability of the switching power supply.

[0057] like Figure 3 As shown, after the rectifier bridge B1, varistor VR1, and the second electrolytic capacitor E2, there is a common switching power supply circuit. U2 is a switching power supply IC chip (THT2205A), a highly integrated switching power supply IC chip with overvoltage, overcurrent, undervoltage, and overheat protection functions. It requires very few external auxiliary components, has excellent electrical performance, a minimum startup voltage of AC 70V, and operates in frequency modulation mode. Therefore, it can still output at full load under the lowest voltage input conditions. It has a built-in 1.5A / 750V MOS power transistor. When it detects that the transistor current exceeds 1.5A, the PWM pulse shuts off the output, entering overcurrent protection mode; when it detects that the power transistor drain spike voltage exceeds 700V, it enters overvoltage protection mode; when it detects that the chip temperature exceeds 150 degrees Celsius, it enters overheat protection mode; and when it detects that the input voltage is lower than AC 68V, it enters undervoltage protection mode.

[0058] It should be noted that, although not all of the components involved in this embodiment, such as the first capacitor C1, the second capacitor C2, the third capacitor C3, the third diode D3, the transient suppression diode DR1, the fifth resistor R5, the optocoupler U1, the fourth capacitor C4, the third resistor R3, the fourth resistor R4, the unidirectional thyristor VT1, the first resistor R1, the second diode D2, the seventh diode D7, the Zener diode DZ1, the first electrolytic capacitor E1, the field-effect transistor Q1, the relay JK1, the thermistor PTC 16P, the first light-emitting diode LED1, the second resistor R2, the second light-emitting diode LED2, the ninth resistor R9, the tenth resistor R10, the rectifier bridge B1, the varistor VR1, and the second electrolytic capacitor E2, are given specific models or sizes. However, given the circuit structure and technical effects of this invention, selecting appropriate models or sizes of components is easily achievable for those skilled in the art. Furthermore, to better illustrate this invention, Figure 2 , Figure 3 The document provides the model numbers or sizes of the components. For example, the preferred choice for the field-effect transistor Q1 is the 2N7002, and the preferred choice for the optocoupler is the PC817. Other components are not listed here; please refer to the relevant documentation for details. Figure 2 , Figure 3 .

[0059] By employing the above-described structure, the present invention has the following beneficial effects:

[0060] Compared to traditional power frequency transformers, this invention has a smaller line voltage drop, especially under conditions where the generator supply voltage is unstable. At the same time, the cost of this invention is significantly lower than that of power frequency transformers. Compared to power frequency transformers, this invention is smaller in size and lighter in weight, making it more suitable for installation in confined spaces.

[0061] This invention greatly expands the input voltage range of the subsequent switching power supply, which can range from AC70V to AC550V. At the same time, due to the high-impedance design of the input line, the subsequent switching power supply has better surge protection and load short-circuit protection, which greatly improves the lifespan and reliability of the switching power supply.

[0062] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A capacitor voltage divider circuit system for power supply voltage input control, characterized in that, It includes an AC voltage divider network circuit, an input voltage judgment and identification circuit, and a switching execution logic circuit. The AC voltage divider network circuit is used to perform voltage divider processing on the input voltage. The input voltage judgment and identification circuit is used to determine whether the input voltage reaches the threshold that requires voltage divider processing. The switching execution logic circuit is used to select whether to connect the AC voltage divider network circuit to perform voltage divider processing on the input voltage based on the judgment result of the input voltage judgment and identification circuit. The AC voltage divider network circuit includes a first capacitor C1, a second capacitor C2, and a third capacitor C3. The first capacitor C1 and the second capacitor C2 are connected in parallel and then connected in series with the third capacitor C3. The parallel and series network formed by the first capacitor C1, the second capacitor C2, and the third capacitor C3 is respectively connected to the ACL terminal and the ACN terminal of the external input voltage. The input voltage determination and recognition circuit includes a third resistor R3 and a fourth resistor R4; The switching execution logic circuit includes a unidirectional thyristor VT1, a first resistor R1, a second diode D2, a seventh diode D7, a Zener diode DZ1, a first electrolytic capacitor E1, a field-effect transistor Q1, a relay JK1, and a 16P thermistor PTC. The gate of the unidirectional thyristor VT1 is connected to one end of a third resistor R3, and the other end of the third resistor R3 is connected to a fourth resistor R4. The positive terminal of the unidirectional thyristor VT1 is connected to the cathode of the second diode D2, and the negative terminal of the unidirectional thyristor VT1 is grounded. The anode of the second diode is connected to the gate of the field-effect transistor Q1, the source of the field-effect transistor Q1 is grounded, and the drain of the field-effect transistor Q1 is connected to one end of the relay JK1. The other end of the relay JK1 is connected to a 24V DC voltage. One end of the first resistor R1 is connected to a 24V DC voltage. The first resistor R1 is connected to the grid of the field-effect transistor Q1. The seventh diode D7 is connected in parallel across the first resistor R1, and the cathode of the seventh diode D7 is connected to a 24V DC voltage. The anode of the seventh diode D7 is connected to the anode of the second diode D2. The anode of the Zener diode DZ1 is grounded, and the cathode of the Zener diode DZ1 is connected to the grid of the field-effect transistor Q1. The first electrolytic capacitor E1 is connected in parallel with the Zener diode DZ1, and the cathode of the first electrolytic capacitor E1 is grounded. The thermistor PTC 16P is connected in series with the contacts of the relay JK1 and then in parallel across the second capacitor C2.

2. The capacitor voltage divider circuit system for power supply voltage input control according to claim 1, characterized in that, The capacitance ratio of the first capacitor C1, the second capacitor C2, and the third capacitor C3 is (2~2.4):1:(2~2.4).

3. A capacitor voltage divider circuit system for power supply voltage input control according to claim 1, characterized in that, The input voltage judgment and recognition circuit also includes a third diode D3, a transient suppression diode DR1, a fifth resistor R5, an optocoupler U1, and a fourth capacitor C4. The anode of the third diode D3 is connected to the ACL terminal of the external input voltage. The third diode D3, the transient suppression diode DR1, the fifth resistor R5, and the fourth capacitor C4 are connected in series. The photodiode inside the optocoupler U1 is connected in parallel with the fourth capacitor C4. The cathode of the photodiode is connected to the ACN terminal of the external input voltage. The collector of the phototransistor inside the optocoupler U1 is connected to a 24V DC voltage. The emitter of the phototransistor is connected to the third resistor R3 and the fourth resistor R4, respectively.

4. A capacitor voltage divider circuit system for power supply voltage input control according to claim 3, characterized in that, It also includes a first light-emitting diode LED1, a second resistor R2, a second light-emitting diode LED2, and a tenth resistor R10. The first light-emitting diode LED1 is connected in series with the second resistor R2, and the second resistor R2 is connected to the cathode of the seventh diode D7. The cathode of the first light-emitting diode LED1 is connected to the cathode of the second diode D2. The anode of the second light-emitting diode LED2 is connected to a 24V DC voltage. The cathode of the second light-emitting diode LED2 is connected to one end of the tenth resistor R10, and the other end of the tenth resistor R10 is connected to the drain of the field-effect transistor Q1.

5. A capacitor voltage divider circuit system for power supply voltage input control according to claim 4, characterized in that, It also includes a ninth resistor R9, which is connected in parallel across the second capacitor C2.

6. A capacitor voltage divider circuit system for power supply voltage input control according to any one of claims 2-5, characterized in that, It also includes a rectifier bridge B1, a varistor VR1, and a second electrolytic capacitor E2. The rectifier bridge B1 is connected in parallel across the two ends of the third capacitor C3. The positive terminal of the second electrolytic capacitor E2 is connected to the DC output terminal of the rectifier bridge B1, and the negative terminal of the second electrolytic capacitor E2 is grounded. The varistor VR1 is connected in parallel across the two ends of the second electrolytic capacitor E2.

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