CN104821726A - Electron beam welding machine power supply high-voltage voltage stabilization method and method employing micro ripper Cuk type converter - Google Patents

Abstract

The invention discloses a method and device for stabilizing the high voltage of an electron beam welding power supply using a microripple Cuk type converter, which comprises the following steps: 1) after boosting, rectifying and filtering the three-phase AC power supply, a high voltage voltage is obtained; 2) The high-voltage voltage passes through the DC converter to control the on-off duty ratio to adjust the output voltage; 3) The output voltage passes through the PID and PWM circuits to control the duty ratio of the power device, and the output voltage can be adjusted; 4) In the output capacitor The required voltage is obtained everywhere, including boost rectification filter circuit, uk main circuit, control circuit, output circuit; the Cuk circuit is introduced into the switching power supply circuit, and the two inductances of the Cuk circuit are coupled by the nature of the coupled inductance, and the distribution is reasonable The coupling degree of the inductance greatly reduces the circuit ripple, adding a feed-forward circuit makes the fluctuations generated at the input end directly adjusted from the input end, making the control and adjustment speed of the entire power system higher and more stable, and the structure is simple, easy to control, and low cost. low.

Description

Method and device for high voltage stabilization of electron beam welding machine power supply using micro-ripple Cuk converter

technical field

The invention relates to a high-voltage switching power supply device, in particular to a high-voltage stabilizing method and device for an electron beam welding machine power supply using a micro-ripple Cuk type converter.

Background technique

Electron Beam Welding (EBW for short) high-voltage stable power supply is mainly used to provide acceleration voltage for the electron gun, and its performance directly determines the electron beam welding process and welding quality. Its power supply has high efficiency. High energy density. A series of advantages such as wide voltage regulation range have been used more and more widely, but due to its inherent high ripple output voltage, its application range is limited. However, the switching power supply will inevitably produce ripples due to its own structure. Capacitive filtering of high-voltage voltage requires a certain capacitance, but under high-voltage conditions, only small-capacity capacitors can be selected, because the capacitor current of the converter has a large peak current, so it may still be There will be a possibility of capacitor failure. The other is that the frequency of switching devices in high-voltage switching power supplies also has many restrictions, because on the one hand, considering that increasing the switching frequency requires reducing the size of inductors, capacitors, and transformers, this can reduce harmonic content; on the other hand , If the switching frequency is too high, it will cause a large switching loss, which will reduce the efficiency of the converter. Therefore, the output ripple has become a key issue in the switching power supply.

In the prior art, it is one of the commonly used methods to filter output ripple by filtering method. The filter includes active and passive filters. The filter is realized by connecting several resistors and capacitors in parallel or in series in the output circuit. This method Ripple frequency characteristics must be obtained through detailed and rigorous calculations, so as to select accurate resistance and capacitance values. Once the capacitors and resistors fail or the resistance and capacitance calculations are inaccurate, new ripples and noise may be mixed in. , On the contrary, the output ripple is increased. This method is suitable for low-power switching power supplies. There are different losses in high-current and high-power switching power supplies, and the size of the switching power supply will also increase accordingly.

Since one of the main factors of switching power supply ripple is the switching on and off of the switching tube, it is possible to design a circuit for absorbing switching spikes in the switching tube, but this method is suitable for topological structures with external switches. For some built-in integrated The integrated module of the switching tube is powerless, and this method requires precise and complicated calculations, and the operability is poor.

The high-frequency ripple technology is added to the DC power supply side to reduce the ripple of the switching power supply by adding a high-frequency ripple processing unit on the DC power supply side, but this solution requires additional control loops and complex auxiliary circuits, and the price is relatively high, and The entire switching power supply system is composed of discrete components, which has the disadvantages of poor integration and low power density.

In the impulse control technology, the impulse control technology based on the equivalent principle of impulse is proposed, such as the single-cycle control technology, and it is applied to the DC switching power supply to eliminate the output low-frequency ripple of the DC switching power supply. At the same time, BUCK (step-down conversion The simulation research of the circuit shows that the output low-frequency ripple is only theoretically less than 5mV, which is not completely eliminated, which limits the frequency and output voltage of the high-voltage switching power supply, and its application range is limited.

The problem of output ripple of high-voltage switching power supply has always been a technical problem in high-power high-voltage regulated power supply. At the same time, in the traditional voltage control mode, no matter where the interference occurs inside the circuit, it must be regulated through the feedback circuit. However, the speed of adjustment is affected, and any position change in the system must be transmitted to the output terminal, and the system can make corresponding adjustments after feedback, so the dynamic response characteristics of the system are relatively poor.

Contents of the invention

The object of the present invention is to address the deficiencies in the prior art, and provide a method and device for stabilizing the high voltage of the electron beam welding machine power supply using a micro-ripple Cuk type converter. The method has low requirements on the input voltage and outputs smooth DC Voltage, small output pulsation, adjustable output current pulsation ripple size, minimize output current pulsation ripple, simple operation, no need for a lot of complicated calculations and derivations; the device is small in size, high in transmission efficiency, and resistant to grid interference Strong capability, low power switch loss.

The technical scheme that realizes the object of the present invention:

A method for stabilizing the high-voltage voltage of an electron beam welding machine power supply using a micro-ripple Cuk type converter, comprising the steps of:

1) After the three-phase AC power supply is boosted, rectified and filtered, a high voltage voltage is obtained;

2) The high-voltage voltage passes through the DC converter, and the output voltage is adjusted by controlling the on-off duty cycle of the switching device;

3) The output voltage is fed back through the voltage outer loop and current inner loop of the Proportional-Integral-Differential Controller (PID), and compared with the set value, and the error voltage obtained by comparison is used as the control signal through Pulse Width Modulation (PWM) circuit can adjust the output voltage by controlling the duty cycle of the power device;

4) Obtain a high-voltage regulated output voltage with minimal ripple at the output capacitor.

In step 2), the DC converter is a Cuk circuit:

The Cuk circuit includes an input inductor L ₁ and an output inductor L ₂ , and the two inductors L ₁ and L ₂ are coupled to each other. When the switch tube V _T is turned on, the current in the inductor L ₁ increases linearly, and the capacitor C ₁ passes through V _T Form a discharge circuit with L ₂ , the diode V _D is in the reverse bias state, the mutual inductance coefficient between the inductance L ₁ and L ₂ is M, the following formula can be derived

$\left\{\begin{array}{c}{u}_i=L_1{\mathrm{di}}_1/\mathrm{dt}+{\mathrm{Mdi}}_2/\mathrm{dt}\\ u_i=L_2{\mathrm{di}}_2/\mathrm{dt}+{\mathrm{Mdi}}_1/\mathrm{dt}\end{array}\right.---\left(1\right)$

Where U _i is the input voltage of the Cuk circuit, di ₁ /dt is the current change rate of the input inductor L ₁ , di ₂ /dt is the current change rate of the output inductor L ₂ , and M is the mutual inductance coefficient.

From formula (1) can get $\left\{\begin{array}{c}\frac{{\mathrm{di}}_1}{\mathrm{dt}}=\frac{u_i(1-m/L_2)}{L_1(1-m^2/L_1{L}_2)}\\ \frac{{\mathrm{di}}_2}{\mathrm{dt}}=\frac{u_i(1-m/L_1)}{L_2(1-m^2/L_1{L}_2)}\end{array}\right.---\left(2\right)$

Where U _i is the input voltage of the Cuk circuit, di ₁ /dt is the current change rate of the input inductor L ₁ , di ₂ /dt is the current change rate of the output inductor L ₂ , and M is the mutual inductance coefficient.

make

$\begin{array}{cc}{L}_{1\mathrm{eq}}=\frac{L_1(1-m/\left(L_1{L}_2\right))}{1-m/L_2},& L_{2\mathrm{eq}}=\frac{L_2(1-m/\left(L_1{L}_2\right))}{1-m/L_1}\end{array}$

Then formula (2) can be simplified as

$\left\{\begin{array}{c}{\mathrm{di}}_1/\mathrm{dt}=u_i/L_{1\mathrm{eq}}\\ {\mathrm{di}}_2/\mathrm{dt}=u_i/L_{2\mathrm{eq}}\end{array}\right.---\left(3\right)$

Where U _i is the input voltage of the Cuk circuit, M is the mutual inductance coefficient, di ₁ /dt is the current change rate of the input inductance L ₁ , and di ₂ /dt is the current change rate of the output inductance L ₂ .

Obviously, increasing the value of L _1eq and L _2eq can reduce the ripple current in L ₁ or L ₂ . If L ₁ = L ₂ = M is satisfied in the circuit, the input ripple current and output ripple current in the Cuk circuit can be reduced to zero at this time, but due to the design and processing of magnetic devices, the component coupling coefficient K is always less than 1.

In order to analyze the influence of K on the circuit ripple, the coil turn ratio of L ₁ and L ₂ can be set Then the expressions of L _1eq and L _2eq become

$\left\{\begin{array}{c}{L}_{1\mathrm{eq}}=L_1(1-K^2)/(1-\mathrm{nK})\\ L_{2\mathrm{eq}}=L_2(1-K^2)/(1-K/\mathrm{no})\end{array}\right.---\left(4\right)$

where K is the coupling coefficient of the component.

It can be known from formula (4) that when nK= ₁ , the input ripple current of L1 is zero ripple current, and when K=n, the output ripple current of L2 is micro _- ripple or even zero-ripple current requirement, Make the input and output current smooth.

Similarly, the above derivation formula can be used to calculate the current change rate di ₁ /dtdi ₂ /dt of L ₁ and L ₂ when the switch tube V _T is turned off and the diode V _D is turned on:

$\left\{\begin{array}{c}{\mathrm{di}}_1/\mathrm{dt}=-u_0/L_{1\mathrm{eq}}\\ {\mathrm{di}}_2/\mathrm{dt}={-u}_0/L_{2\mathrm{eq}}\end{array}\right.---\left(5\right)$

$\begin{array}{cc}{L}_{1\mathrm{eq}}=\frac{L_1(1-m/\left(L_1{L}_2\right))}{1-m/L_2}& L_{2\mathrm{eq}}=\frac{L_2(1-m/\left(L_1{L}_2\right))}{1-m/L_1}\end{array}$

M is the mutual inductance coefficient, U _o is the output voltage of the Cuk circuit.

Regardless of whether the switch tube V _D is on and the diode V _D is off or the switch tube V _T is off and the diode V _D is on, the current change rate di ₁ for L ₁ , L ₂ , K and L ₁ and L ₂ The relationship between /dt and di ₂ /dt can be based on the formula

(4) Perform calculations to realize the micro-ripple requirements of the Cuk circuit.

In step 2), a reverse conduction diode is also introduced, and a diode is connected in parallel next to the switch tube of the Cuk circuit to protect the triode and prevent reverse breakdown.

In step 3), the output voltage first goes through sampling, starting, over-current and over-voltage protection, over-temperature protection and noise filter circuits to detect changes in the output voltage; the PID control circuit consists of three parts: the current inner loop and the voltage outer loop and the overvoltage Three parts of flow protection;

The output voltage _Uo gets the actual output value through the sampling circuit. This voltage can be used as the actual value of the PID regulator and compared with the set value to correct the deviation. The output control signal of the PID control circuit is sent to the PWM circuit to adjust the pulse width. It also constitutes a conventional voltage feedback, that is, the voltage outer loop.

In the Cuk circuit, the emitter of the switch tube V _T is connected to the Hall current sensor T _A , and the Hall current sensor T _A will transfer the current signal I _s to the output and convert it into a voltage signal output according to the size of the measured current and select an appropriate transformation ratio In the PID control circuit, it is compared with the set value and corrected. Once the voltage is detected to deviate from the set value, the current detection comparator will reset the PWM latch, and the gate drive signal will adjust the output pulse of the power switch tube. Before the output sampling voltage error occurs, the pulse output of the PWM circuit will have a regulating effect. What the feedforward compensation circuit detects is the disturbance itself. As long as there is a change in the mains grid voltage, it will immediately detect and compensate synchronously. In this way, the transient voltage error can be minimized to form an inner loop of current feedback.

These two feedbacks are finally converted into control signals and sent to the PWM circuit, forming a double closed-loop structure of voltage and current to achieve the effect of compensating and stabilizing the output.

Excessive surge current affects the normal operation of the circuit system and causes a great impact on circuits and devices. Therefore, a current limiting device must be designed to limit it. In the present invention, the Hall current sensor is used for overcurrent detection, and its working principle is: when the current value detected by the Hall current sensor at the load output terminal is greater than the set value, the output signal forces the PWM signal to be 0, thereby turning off the switch The element stops the current from rising. This method is accurate in current limiting, can effectively prevent short circuits, and is easy to implement over-current protection.

The PWM circuit generates a control signal through the error amplifier, which acts on the PWM comparator, and compares it with the sawtooth wave with a fixed amplitude generated by the internal oscillator of the control chip to generate a PWM signal. After the PWM signal is processed by the clock pulse Generate a PWM signal with an adjustable duty ratio that is finally used to control the power switch tube, so the realization of the automatic adjustment of the PWM circuit is completely realized by the feedback, that is, the error amplifier. When the load current decreases or the DC input voltage increases , will cause an increase in the output voltage. At this time, the feedback voltage of the system increases and the control signal decreases, which narrows the output pulse width and reduces the output voltage.

The high-voltage regulated output voltage in step 4) provides an accelerating electric field for the electrons escaping from the cathode filament of the loaded electron gun.

A high-voltage stabilizing device for an electron beam welding machine power supply using a micro-ripple Cuk type converter, including a boost rectification filter circuit, a Cuk main circuit, a control circuit, and an output circuit;

The function of the step-up rectification filter circuit is to obtain a smooth high-voltage voltage, and the step-up rectification filter circuit is composed of a three-phase transformer step-up circuit and a rectification filter circuit;

The function of the Cuk main circuit is to perform power conversion and voltage regulation, and also to suppress the current ripple. The Cuk main circuit includes an input inductance and an output inductance. Diode, power switch triode and reverse conduction diode, the input inductance is connected to the common end of the input capacitor, power switch triode and reverse conduction diode, one end of the output inductance is connected to the common end of the input capacitor and the output diode, and the other end is connected to the output capacitor connection, the output capacitor is the input terminal of the output circuit, the gate of the power switch transistor is the control input terminal, and the emitter of the power switch transistor is the current feedback terminal;

The function of the control circuit is to generate a control signal by comparing the actual voltage and current value with the set value voltage through the feedback of the double closed loop to control the duty cycle of the power device through the PWM circuit, so as to achieve the function of stabilizing the welding beam current. The control circuit Including PWM circuit, PID control circuit, two Hall current sensor circuits. In the control circuit, the PWM circuit is connected with the PID control circuit, the PID control circuit is connected with two Hall current sensor circuits, the output terminal of the PWM circuit is the output terminal of the control circuit, and the input terminal of the PID control circuit is the input terminal of the control circuit , the output terminals of the two Hall current sensor circuits are the current input terminal and the overcurrent protection terminal of the control circuit respectively, and the PID control circuit is connected with the set value circuit at the same time;

The output circuit is composed of an overcurrent protection resistor, a choke inductor, a freewheel diode, and a load variable resistor. The overcurrent protection resistor is connected in series with the freewheel diode and the choke inductor, and the choke inductor is connected in parallel with the freewheel diode. The input end of the protection resistor is the input end of the output circuit;

The output end of the boost rectification filter circuit is connected to the input end of the Cuk main circuit, the control input end of the Cuk main circuit is connected to the output end of the control circuit, the output end of the Cuk main circuit is connected to the input end of the output circuit, and the control The input end of the circuit is connected with the output end of the output circuit;

Beneficial effect of the present invention, this method obtains the requirement that realizes the micro-ripple in the switching power supply after two coupling inductors are carried out simple coupling operation, adopts double closed-loop circuit theory in the control link, has introduced the link of current feedback, to The output voltage has a feed-forward adjustment function, which improves the dynamic response of the system. When the current in the system changes, the duty cycle and the PID circuit can be adjusted quickly. The inductor current directly follows the change of the error voltage, and the output voltage can be controlled. The ring also makes it easy for switching power converters to realize parallel operation, which is conducive to the realization of Cuk circuit design, the system output current ripple is small, has strong operability, and the system control adjustment speed is higher and more stable, which has high market application value;

This device introduces a Cuk converter circuit into the switching power supply module circuit, and both the input and output links of the circuit contain inductive elements, so the input and output ripples are low, and there is no single limit such as buck-boost, and the main circuit of Cuk The topological structure requires very few components, and the design of the drive circuit is simple. Compared with the DC power supply side, the high-frequency ripple technology is a circuit structure that can use the least components to obtain ideal power conversion characteristics. The Cuk circuit achieves zero The calculation of the circuit parameters of the ripple is also some basic calculations, and there is no huge special calculation method, so it is simple and easy to implement compared with the switching spike circuit design scheme, and has a simple structure, easy control, and low cost.

Description of drawings

Fig. 1 is the electrical schematic diagram of the high-voltage regulated switching power supply of the present invention in the embodiment.

Detailed ways

The content of the present invention will be further elaborated below in conjunction with the accompanying drawings and embodiments, but the present invention is not limited thereto.

Example:

A method for stabilizing the high-voltage voltage of an electron beam welding machine power supply using a micro-ripple Cuk type converter, comprising the steps of:

1) After the three-phase AC power supply is boosted, rectified and filtered, a high voltage voltage is obtained;

2) The high-voltage voltage passes through the DC converter, and the output voltage is adjusted by controlling the on-off duty cycle of the switching device;

3) The output voltage is fed back through the voltage outer loop and current inner loop of the Proportional-Integral-Differential Controller (PID for short), and compared with the set value, the voltage of the error obtained by comparison (whether it is correct to write ) After a pulse width modulation (Pulse Width Modulation, PWM for short) circuit, the output voltage can be adjusted by controlling the duty cycle of the power device;

4) Obtain a high-voltage regulated output voltage with minimal ripple at the output capacitor.

In step 2), the DC converter is a Cuk circuit:

The Cuk circuit includes an input inductor L ₁ and an output inductor L ₂ , and the two inductors L ₁ and L ₂ are coupled to each other. When the switch tube V _T is turned on, the current in the inductor L ₁ increases linearly, and the capacitor C ₁ passes through V _T Form a discharge circuit with L ₂ , at this time the diode V _D is in the reverse bias state, the mutual inductance coefficient between the inductance L ₁ and L ₂ is M, the following formula can be derived

$\left\{\begin{array}{c}{u}_i=L_1{\mathrm{di}}_1/\mathrm{dt}+{\mathrm{Mdi}}_2/\mathrm{dt}\\ u_i=L_2{\mathrm{di}}_2/\mathrm{dt}+{\mathrm{Mdi}}_1/\mathrm{dt}\end{array}\right.---\left(1\right)$

Where U _i is the input voltage of the Cuk circuit, di ₁ /dt is the current change rate of the input inductor L ₁ , di ₂ /dt is the current change rate of the output inductor L ₂ , and M is the mutual inductance coefficient.

From formula (1) can get $\left\{\begin{array}{c}\frac{{\mathrm{di}}_1}{\mathrm{dt}}=\frac{u_i(1-m/L_2)}{L_1(1-m^2/L_1{L}_2)}\\ \frac{{\mathrm{di}}_2}{\mathrm{dt}}=\frac{u_i(1-m/L_1)}{L_2(1-m^2/L_1{L}_2)}\end{array}\right.---\left(2\right)$

Where U _i is the input voltage of the Cuk circuit, di ₁ /dt is the current change rate of the input inductor L ₁ , di ₂ /dt is the current change rate of the output inductor L ₂ , and M is the mutual inductance coefficient.

make

$\begin{array}{cc}{L}_{1\mathrm{eq}}=\frac{L_1(1-m/\left(L_1{L}_2\right))}{1-m/L_2},& L_{2\mathrm{eq}}=\frac{L_2(1-m/\left(L_1{L}_2\right))}{1-m/L_1}\end{array}$

Then formula (2) can be simplified as

$\left\{\begin{array}{c}{\mathrm{di}}_1/\mathrm{dt}=u_i/L_{1\mathrm{eq}}\\ {\mathrm{di}}_2/\mathrm{dt}=u_i/L_{2\mathrm{eq}}\end{array}\right\}---\left(3\right)$

Where U _i is the input voltage of the Cuk circuit, M is the mutual inductance coefficient, di ₁ /dt is the current change rate of the input inductance L ₁ , and di ₂ /dt is the current change rate of the output inductance L ₂ .

Obviously, increasing the value of L _1eq and L _2eq can reduce the ripple current in L ₁ or L ₂ . If L ₁ = L ₂ = M is satisfied in the circuit, the input ripple current and output ripple current in the Cuk circuit can be reduced to zero at this time, but due to the design and processing of magnetic devices, the component coupling coefficient K is always less than 1.

In order to analyze the influence of K on the circuit ripple, the coil turn ratio of L ₁ and L ₂ can be set Then the expressions of L _1eq and L _2eq become

$\left\{\begin{array}{c}{L}_{1\mathrm{eq}}=L_1(1-K^2)/(1-\mathrm{nK})\\ L_{2\mathrm{eq}}=L_2(1-K^2)/(1-K/\mathrm{no})\end{array}\right\}---\left(4\right)$

where K is the coupling coefficient of the component.

It can be known from formula (4) that when nK= ₁ , the input ripple current of L1 is zero ripple current, and when K=n, the output ripple current of L2 is micro _- ripple or even zero-ripple current requirement, Make the input and output current smooth.

Similarly, the above derivation formula can be used to obtain the current change rate di ₁ /dt of L ₁ and L ₂ when the switch tube V _T is turned off and the diode V _D is turned on

Calculation formula of di ₂ /dt:

$\left\{\begin{array}{c}{\mathrm{di}}_1/\mathrm{dt}=-u_0/L_{1\mathrm{eq}}\\ {\mathrm{di}}_2/\mathrm{dt}={-u}_0/L_{2\mathrm{eq}}\end{array}\right.---\left(5\right)$

$\begin{array}{cc}{L}_{1\mathrm{eq}}=\frac{L_1(1-m/\left(L_1{L}_2\right))}{1-m/L_2}& L_{2\mathrm{eq}}=\frac{L_2(1-m/\left(L_1{L}_2\right))}{1-m/L_1}\end{array}$

M is the mutual inductance coefficient, U _o is the output voltage of the Cuk circuit.

Whether the switch tube V _T is on and the diode V _D is off or the switch tube V _T is off and the diode V _D is on, the current change rate di ₁ for L ₁ , L ₂ , K and L ₁ and L ₂ The relationship between /dt and di ₂ /dt can be calculated according to the formula (4) to realize the micro-ripple requirement of the Cuk circuit.

In step 2), a reverse conduction diode V _R is connected in parallel next to the power switch tube of the Cuk circuit to protect the power switch tube V _T and prevent reverse breakdown.

In step 3), the output voltage first goes through sampling, starting, over-current and over-voltage protection, over-temperature protection and noise filter circuits to detect changes in the output voltage; the PID control feedback circuit consists of three parts: current inner loop, voltage outer loop and overvoltage Three parts of flow protection;

In the Cuk circuit, the emitter of the power switch tube V _T is connected to the Hall current sensor T _A , and the Hall current sensor T _A will transfer the current signal I _s to the output and convert it into a voltage signal according to the magnitude of the measured current and select an appropriate transformation ratio The output is compared with the set value in the PID control circuit and corrected. Once the voltage deviation from the set value is detected, the current detection comparator will reset the PWM latch, and the gate drive signal will adjust the output pulse of the power switch tube. , before the output sampling voltage error occurs, the pulse output of the PWM circuit will have a regulating effect. What the feedforward compensation circuit detects is the disturbance itself. As long as there is a change in the mains grid voltage, it will immediately detect and compensate synchronously. , so that the transient voltage error can be minimized to form an inner current feedback loop.

These two feedbacks are finally converted into control signals and sent to the PWM circuit, forming a double closed-loop structure of voltage and current to achieve the effect of compensating and stabilizing the output.

Excessive surge current affects the normal operation of the circuit system and causes a great impact on circuits and devices. Therefore, a current limiting device must be designed to limit it. In this design, the Hall current sensor T _B is used for overcurrent detection. Its working principle is: when the current value detected by the Hall current sensor at the output terminal of the load is greater than the set value, the output signal forces the PWM signal to be 0, thereby turning off Turning off the switching element stops the current from rising. This method is accurate in current limiting, can effectively prevent short circuits, and is easy to implement over-current protection.

The PWM circuit generates a control signal through the error amplifier, which acts on the PWM comparator, and compares it with the sawtooth wave with a fixed amplitude generated by the internal oscillator of the control chip to generate a PWM signal. After the PWM signal is processed by the clock pulse Generate a PWM signal with an adjustable duty ratio that is finally used to control the power switch tube, so the realization of the automatic adjustment of the PWM circuit is completely realized by the feedback, that is, the error amplifier. When the load current decreases or the DC input voltage increases , will cause an increase in the output voltage. At this time, the feedback voltage of the system increases and the control signal decreases, which narrows the output pulse width and reduces the output voltage.

The high-voltage regulated output voltage in step 4) provides an accelerating electric field for the electrons escaping from the cathode filament of the loaded electron gun.

As shown in Figure 1, the electron beam welding machine power supply high-voltage regulator using a micro-ripple Cuk converter includes a step-up rectification filter circuit 1, a Cuk main circuit 2, a control circuit 3, and an output circuit 4;

The function of the step-up rectification filter circuit 1 is to obtain a smooth high-voltage voltage, and the step-up rectification filter circuit 1 is composed of a three-phase transformer step-up circuit and a rectification filter circuit;

The function of the Cuk main circuit 2 is to perform power conversion and voltage regulation, and also to suppress the current ripple. The Cuk main circuit ₂ includes an input inductance L1 and _an output inductance L2, and the inductances have a coupling relationship. Input capacitor C ₁ and output capacitor C ₂ , output diode V _D and reverse conduction diode VR and power switch transistor V _T , input inductor _{L 1} and input capacitor C ₁ and power switch transistor V _T , reverse conduction diode V _R common _One end of the output inductor L2 is connected to the common end of the input capacitor _C1 and the output diode _VD , and the other end is connected to the output capacitor C2. _The output capacitor _C2 is the input end of the output circuit, and the power switch transistor The gate of V _T is the control input terminal, and the emitter of the power switch transistor V _T is the current feedback terminal;

The function of the control circuit 3 is to generate a control signal by comparing the actual voltage and current value with the set value voltage through the feedback of the double closed loop to control the duty ratio of the power device through the PWM circuit, so as to achieve the effect of stabilizing the welding beam current and controlling Circuit 3 includes a PWM circuit, a PID control circuit, Hall current sensors _TA and _TB , the PWM circuit in the control circuit 3 is connected to the PID control circuit, and the PID control circuit is connected to the output terminal I _s of the Hall current sensor _TA and the Hall The output terminal I _o of the current sensor T _B is connected, the PID control circuit is connected with the setting value circuit, the output terminal of the PWM circuit is the output terminal of the control circuit 3, and the input terminal of the PID control circuit is the input terminal of the control circuit 3, The output terminal of the Hall current sensor circuit T _A is the current input terminal of the control circuit 3, and the output terminal of the Hall current sensor circuit T _B is the overcurrent protection terminal of the control circuit 3;

The output circuit 4 _is composed of an overcurrent protection resistor _Rx , a _choke inductance _Lx , a _freewheeling diode _Vx , and a load variable resistor. connected in series, the choke inductance L _x is connected in parallel with the freewheeling diode V _x , and the input terminal of the overcurrent protection resistor R _x is the input terminal of the output circuit 4;

The output end of the boost rectification filter circuit 1 is connected to the input end of the Cuk main circuit 2, the control input end of the Cuk main circuit 2 is connected to the output end of the control circuit 3, the output end of the Cuk main circuit 2 is connected to the output end of the output circuit 4 The input terminals are connected, and the input terminal of the control circuit 3 is connected with the output terminal of the output circuit 4 .

The working principle of the control circuit 3 is as follows:

The PID control circuit is composed of three parts: the output voltage is obtained by the sampling circuit to obtain the actual output value, and this voltage can be used as the actual value and set value of the PID regulator for correction, and finally the output control signal of the PID control circuit is sent to the PWM circuit for adjustment Pulse width, which also constitutes conventional voltage feedback, the voltage outer loop.

In the Cuk main circuit 2, the source of the power switch transistor V _T is connected in series with the Hall current sensor T _A , and the Hall current sensor T _A will convert the current signal into a voltage signal and output it to the PID control according to the magnitude of the measured current and select an appropriate transformation ratio Comparing and correcting the set value in the circuit, once the deviation from the set value is detected, the current detection comparator will reset the PWM latch, the gate drive signal will adjust the output pulse of the power switch tube, and the output sampling Before the voltage error occurs, the pulse output of the PWM circuit will have a regulating effect. What the feedforward compensation circuit detects is the disturbance itself. As long as there is a change in the mains grid voltage, it will immediately detect and compensate synchronously, so that Minimize the transient voltage error and form the inner loop of current feedback.

These two feedbacks are respectively added to the non-inverting end and the inverting end of the internal comparator of the PWM circuit to form a double closed loop to achieve the effect of compensating the output.

Excessive surge current affects the normal operation of the circuit system and causes a great impact on the circuit and devices. Therefore, a current limiting device must be designed to limit it. In this design, the Hall current sensor T _B is used for overcurrent detection. Its working principle is: when the current value detected by the Hall current sensor at the output terminal of the load is greater than the set value, the output signal forces the PWM signal to be 0, thereby turning off Turning off the switching element stops the current from rising. This method is accurate in current limiting, can effectively prevent short circuits, and is easy to implement over-current protection.

The PWM circuit generates a control signal through the error amplifier, which acts on the PWM comparator, and compares it with the sawtooth wave with a fixed amplitude generated by the internal oscillator of the control chip to generate a PWM signal. After the action, a PWM signal with an adjustable duty ratio that is finally used to control the power switch tube is generated. Therefore, the realization of the automatic adjustment of the PWM circuit is completely realized by the feedback, that is, the error amplifier. When the load current decreases or the DC input voltage increases When it is high, it will cause the output voltage to increase. At this time, the feedback voltage of the system increases and the control signal decreases, which makes the output pulse width narrow and the output voltage decreases.

The content not described in detail in this specification, such as the transformer boosting circuit, rectification and filtering circuit, PID controller circuit, Hall current sensor circuit and PWM circuit in the embodiments, belongs to the prior art known to those skilled in the art.

Claims (6)

1. a method for stabilizing the high voltage voltage of an electron beam welding machine power supply that adopts a micro-ripple Cuk formula converter, is characterized in that, comprises the steps: 1) After the three-phase AC power supply is boosted, rectified and filtered, a high voltage voltage is obtained; 2) The high-voltage voltage passes through the DC converter, and the output voltage is adjusted by controlling the on-off duty cycle of the switching device; 3) The output voltage is fed back through the voltage outer loop, current inner loop and overcurrent protection of the Proportional-Integral-Differential Controller (Proportional-Integral-Differential Controller, referred to as PID), and compared with the set value, the error obtained by comparison The voltage is used as a control signal through a Pulse Width Modulation (PWM) circuit, and the output voltage can be adjusted by controlling the duty cycle of the power device; 4) Obtain a high-voltage regulated output voltage with minimal ripple at the output capacitor. 2. The method according to claim 1, characterized in that, in step 2), the DC converter is a Cuk circuit: The Cuk circuit includes an input inductor L ₁ and an output inductor L ₂ , and the two inductors L ₁ and L ₂ are coupled to each other. When the switch tube V _T is turned on, the current in the inductor L ₁ increases linearly, and the capacitor C ₁ passes through V _T Form a discharge circuit with L ₂ , the diode V _D is in the reverse bias state, the mutual inductance coefficient between the inductance L ₁ and L ₂ is M, the following formula can be derived Where U _i is the input voltage of the Cuk circuit, di ₁ /dt is the current change rate of the input inductance L ₁ , di ₂ /dt is the current change rate of the output inductance L ₂ , and M is the mutual inductance coefficient; From formula (1) can get Where U _i is the input voltage of the Cuk circuit, di ₁ /dt is the current change rate of the input inductance L ₁ , di ₂ /dt is the current change rate of the output inductance L ₂ , and M is the mutual inductance coefficient; make Then formula (2) can be simplified as Where U _i is the input voltage of the Cuk circuit, M is the mutual inductance coefficient, di ₁ /dt is the current change rate of the input inductance L ₁ , di ₂ /dt is the current change rate of the output inductance L ₂ ; Obviously, increasing the value of L _1eq and L _2eq can reduce the ripple current in L ₁ or L ₂ , if the circuit satisfies L ₁ =L ₂ =M, then the input ripple current and output ripple in the Cuk circuit The wave current can be reduced to zero, but due to the design and processing of magnetic devices, the component coupling coefficient K is always less than 1; In order to analyze the influence of K on the circuit ripple, the coil turn ratio of L ₁ and L ₂ can be set Then the expressions of L _1eq and L _2eq become where K is the coupling coefficient of the component; It can be known from formula (4) that when nK= ₁ , the input ripple current of L1 is zero ripple current, and when K=n, the output ripple current of L2 is micro _- ripple or even zero-ripple current requirement, Make the input and output current smooth; Similarly, the above derivation formula can be used to calculate the current change rate di ₁ /dt di ₂ /dt of L ₁ and L ₂ when the switch tube V _T is turned off and the diode V _D is turned on: M is the mutual inductance coefficient, U _o is the output voltage of the Cuk circuit; Regardless of whether the switch tube V _D is on and the diode V _D is off or the switch tube V _T is off and the diode V _D is on, the current change rate di ₁ for L ₁ , L ₂ , K and L ₁ and L ₂ The relationship between /dt and di ₂ /dt can be calculated according to the formula (4) to realize the micro-ripple requirement of the Cuk circuit; In step 2), a reverse conduction diode is also introduced, and a reverse conduction diode is connected in parallel next to the power switch tube of the Cuk circuit to protect the power switch tube and prevent reverse breakdown. 3. The method according to claim 1, characterized in that, in step 3), the output voltage first passes through sampling, starting, overcurrent and overvoltage protection, overtemperature protection and noise filter circuits to detect output voltage changes; PID control feedback The circuit consists of three parts: current inner loop, voltage outer loop and overcurrent protection; The output voltage gets the actual output value through the sampling circuit. This voltage can be used as the actual value of the PID regulator and compared with the set value to correct the deviation. The output control signal of the PID control circuit is sent to the PWM circuit to adjust the pulse width, which also constitutes Conventional voltage feedback, that is, the voltage outer loop; The emitter of the switch tube in the Cuk circuit is connected to the Hall current sensor, and the Hall current sensor will select the appropriate transformation ratio according to the measured current to transfer the current signal to the output and convert it into a voltage signal to be output to the PID control circuit and set The fixed value is compared and corrected. Once the voltage is detected to deviate from the set value, the current detection comparator will reset the PWM latch, and the gate drive signal will adjust the output pulse of the power switch tube. Before the output sampling voltage error occurs , the pulse output of the PWM circuit will have a regulating effect. What the feedforward compensation circuit detects is the disturbance itself. As long as there is a change in the mains grid voltage, it will immediately detect and compensate synchronously, so that the transient voltage can be reduced. The error is minimized to form a current feedback inner loop; These two feedbacks are finally converted into control signals and sent to the PWM circuit, forming a double closed-loop structure of voltage and current to achieve the effect of compensating and stabilizing the output; Excessive surge current affects the normal operation of the circuit system and causes a great impact on the circuit and devices. Therefore, a current limiting device must be designed to limit it. In the present invention, a Hall current sensor is used for overcurrent detection. Its working principle It is: when the current value detected by the Hall current sensor at the output terminal of the load is greater than the set value, the output signal forces the PWM signal to be 0, thereby turning off the switching element so that the current does not rise again. This method is accurate in current limiting and can effectively prevent Short circuit, easy to implement over-current protection; The PWM circuit generates a control signal through the error amplifier, which acts on the PWM comparator, and compares it with the sawtooth wave with a fixed amplitude generated by the internal oscillator of the control chip to generate a PWM signal. After the PWM signal is processed by the clock pulse Generate a PWM signal with an adjustable duty ratio that is finally used to control the power switch tube, so the realization of the automatic adjustment of the PWM circuit is completely realized by the feedback, that is, the error amplifier. When the load current decreases or the DC input voltage increases , will cause an increase in the output voltage. At this time, the feedback voltage of the system increases and the control signal decreases, which narrows the output pulse width and reduces the output voltage. 4. An electron beam welder power supply high-voltage regulator using a micro-ripple Cuk formula converter, characterized in that it comprises a step-up rectification filter circuit, a Cuk main circuit, a control circuit, and an output circuit; The function of the step-up rectification filter circuit is to obtain a smooth high voltage; The function of the Cuk main circuit is to perform power conversion and voltage regulation, and also to suppress current pulsation and ripple; The function of the control circuit is to generate a control signal by comparing the actual voltage and current value with the set value voltage through the feedback of the double closed loop to control the duty ratio of the power device through the PWM circuit, so as to achieve the effect of stabilizing the welding beam; The output end of the boost rectification filter circuit is connected to the input of the Cuk main circuit, the control input end of the Cuk main circuit is connected to the output end of the control circuit, the control input end of the Cuk main circuit is connected to the output end of the control circuit, and the Cuk main circuit is connected to the output end of the control circuit. The output terminal of the main circuit is connected with the input terminal of the output circuit, and the input terminal of the control circuit is connected with the output terminal of the output circuit. 5. The device according to claim 4, wherein the Cuk main circuit comprises an input inductor and an output inductor, mutual coupling between the inductors, an input capacitor and an output capacitor, an output diode, a power switch transistor and a reverse conduction diode, The input inductance is connected to the common end of the input capacitor, the power switch transistor and the reverse conduction diode, one end of the output inductance is connected to the common end of the output diode of the input capacitor, and the other end is connected to the output capacitor, and the output capacitor is the output end of the output circuit. The gate of the power switch transistor is a control input terminal, and the emitter of the power switch transistor is a current feedback terminal. 6. The device according to claim 4, wherein the control circuit comprises a PWM circuit, a PID control circuit, and two Hall current sensor circuits, the PWM circuit is connected with the PID control circuit in the control circuit, and the PID control circuit The circuit is connected with two Hall current sensor circuits, the output end of the PWM circuit is the output end of the control circuit, the input end of the PID control circuit is the input end of the control circuit, and the output ends of the two Hall current sensor circuits are respectively The current input terminal and the overcurrent protection terminal of the control circuit, and the PID control circuit is connected with the setting value circuit at the same time.