CN101902126A - Power supply unit for sputter ion pump - Google Patents

Abstract

Disclosed is a power supply device for an ion pump, comprising: a switching element having a first end, a second end and a third end; a sensing element connected to the second end of the switching element; a step-up transformer including a primary and a A secondary winding in which the polarity of the same-named end of the primary winding is opposite to that of the secondary winding and one end of the primary winding is connected to a DC power supply and the other end is connected to the third end of the switching element; the control circuit, based on the The flyback voltage and the voltage on the sensing element generate a switch control signal to be applied to the first end of the switch element, and the switch element is turned on and off under the control of the switch control signal, thereby in the secondary winding of the step-up transformer The output terminal of the transformer generates an output voltage; the rectifier circuit filters the output voltage generated by the output terminal of the secondary winding of the transformer. The power supply device has the advantages of high efficiency, small size and light weight, and its power range meets the power requirements of the sputtering ion pump power supply.

Description

Power supply unit for sputter ion pump

technical field

The present invention relates to a power supply for a sputtering ion pump, in particular to a power supply for a sputtering ion pump based on the principle of a single-ended flyback switching power supply, and a device with functional requirements such as real-time display and interlock protection for the working current and voltage of a vacuum ion pump power supply application field.

Background technique

The sputtering ion pump is the most widely used vacuum pump in the ultra-high vacuum obtaining system. The internal core components are the anode and the cathode. The anode is a thin-walled stainless steel cylinder, and the cathode is two titanium plates placed on both sides of the anode. Therefore, the sputter ion pump is referred to as the titanium pump. When it works, an external permanent magnet provides a magnetic field line parallel to the anode cylinder with a strength of 1000-1500 Gauss, and a 3-7kV DC high voltage is directly applied between the anode and the cathode to generate a Penning discharge, and the gas molecules are ionized to produce Titanium atoms are sputtered out by the ion bombardment of the cathode, and the titanium atoms are deposited on the wall of the anode cylinder and the part of the cathode where the ion bombardment is less, forming a fresh titanium film. The fresh titanium film can absorb polar gas molecules and bury inert gas molecules, so as to achieve gas extraction To achieve the purpose of high vacuum. The 3-7kV DC high voltage required for the ion pump to work is provided by the ion pump power supply, and the size of the generated current is determined by the ion concentration and moving speed of the gas molecules after ionization, that is to say, the size of the ion pump current and the number of gas molecules It is directly proportional, that is, inversely proportional to the degree of vacuum. Therefore, the degree of vacuum in the system can be calculated from the current of the ion pump. When the ion pump is working normally, its current is usually only a few microamperes to tens of microamperes. In extreme cases, the operating current can reach several milliamps. The power of the sputter ion pump power supply is usually tens of watts.

Single-ended flyback switching power supply is an emerging power supply technology, which has the advantages of high efficiency, simple circuit, small size and light weight. The disadvantage is that the power is small, usually 20-100W, so it is mainly used in low-power low-voltage DC power supplies at present. .

The operation of an electron accelerator is inseparable from vacuum technology. The core component of the accelerator tube is a high-vacuum component, and its vacuum is obtained and maintained by an ion pump. During the working process of the accelerator, it is necessary to monitor the vacuum state inside the accelerator tube online. The control system determines the next step of the accelerator working state through the vacuum state information, in case the vacuum degree of the accelerator tube drops, or the ion pump or the ion pump power supply does not work normally. The accelerator system wreaks havoc. This requires the ion pump power supply not only to provide high voltage with stable amplitude during operation, but also to monitor the voltage and current signals in real time, and to send an alarm signal to the superior control system when an abnormality is found. When the accelerator is shut down, it is also necessary for the ion pump to be able to continue to work, to maintain the vacuum state of the accelerating tube, so that the accelerator will have a good vacuum state when it is turned on next time, and it can be put into work immediately, which requires that the ion pump power supply can be uninterrupted for 24 hours work.

Most of the traditional ion pump power supplies can only provide simple high-voltage power supply functions. The mode of obtaining high voltage is usually the traditional linear transformer boost mode. Although the structure is simple, it has large volume and weight, low efficiency and poor stability; Moreover, it lacks the monitoring and alarm functions for voltage and current signals, so it is not suitable for applications in fields such as accelerators that require online monitoring of the vacuum state. In the latest technology, there are also solutions that use switching power supply technology to replace linear transformer boost technology, such as the technology used in the Chinese patent (00112595.8) "Intelligent Sputtering Ion Pump Power Controller", although it also has the monitoring of voltage and current signals And alarm function, but the power supply mode is single, it cannot meet the requirements of 24-hour uninterrupted work when the mains power is cut off, and the latest electronic technology and superior electronic components are not used, the circuit structure is complicated, and the efficiency is not high.

Contents of the invention

The purpose of the present invention is to provide a sputtering ion pump power supply based on the principle of single-end flyback switching power supply, which uses the single-end flyback switching power supply mode to replace the traditional linear power supply mode.

In one aspect of the present invention, a power supply device for an ion pump is provided, comprising: a switching element having a first end, a second end and a third end; a sensing element connected to the second end of the switching element Connection; a step-up transformer, including a primary winding and a secondary winding, where the polarity of the same-named end of the primary winding and the same-named end of the secondary winding are opposite, and one end of the primary winding is connected to the DC power supply, and the other end is connected to the third of the switching element terminal; a control circuit, based on the flyback voltage generated in the primary winding and the voltage on the sensing element, generates a switching control signal to be applied to the first terminal of the switching element, wherein the switching element is controlled by the switching control signal The lower conduction and disconnection generate an output voltage at the output end of the secondary winding of the step-up transformer; the rectification circuit filters the output voltage generated at the output end of the secondary winding of the step-up transformer.

According to an embodiment of the present invention, the control circuit generates the time length for the switch element to be turned on and off based on the relative magnitudes of the feedback voltage generated by dividing the flyback voltage and the voltage on the sensing element.

According to an embodiment of the present invention, the power supply device further includes a discharge circuit for discharging the energy in the primary winding of the step-up transformer when the switching element is turned off.

According to an embodiment of the present invention, the discharge circuit includes: a diode, the anode of which is connected to the third terminal, and the cathode is connected to the same-named terminal of the primary winding through a capacitor; a plurality of multi-position selection switches connected in parallel are connected in parallel with the capacitor; resistor in parallel with the capacitor.

According to an embodiment of the invention, the sensing element is a resistor.

According to an embodiment of the present invention, the rectification circuit includes: a plurality of series connected diodes and a filter capacitor connected in parallel with the series connected diodes.

According to an embodiment of the present invention, the power supply device also includes a voltage monitoring and protection circuit, including: a sampling amplifier circuit, which samples the output voltage, and amplifies the sampled voltage; a voltage adjustment display circuit, which adjusts the sampled voltage to a predetermined multiple; The alarm circuit compares the adjusted voltage with the preset threshold, and when the adjusted voltage exceeds the preset threshold, an alarm is sent to the user.

According to an embodiment of the present invention, the power supply device further includes a current monitoring and protection circuit, including: a sampling amplifier circuit, which samples the output current, and amplifies the sampled current; a current adjustment display circuit, which adjusts the sampled current to a predetermined multiple; The comparison alarm circuit compares the adjusted current with the preset threshold, and when the adjusted current exceeds the preset threshold, an alarm is sent to the user.

According to an embodiment of the present invention, the voltage of the DC power supply is 24 volts.

According to an embodiment of the present invention, the DC power source is a battery pack.

According to an embodiment of the invention, said DC power source is converted from AC power.

The above power supply device has the advantages of high efficiency, small size and light weight.

In addition, the power range of the power supply device according to the embodiment is 20-100W, which just meets the power requirements of the sputtering ion pump power supply, and can be directly powered by a 24V low-voltage power supply (such as a battery), so that the sputtering ion pump can still be used when the mains power fails. 24 hours non-stop work.

In the vacuum ion pump power supply device of the embodiment of the present invention, the output high voltage is continuously adjustable from 3kV to 7kV.

The vacuum ion pump power supply device of the embodiment of the present invention also includes a complete online monitoring and status alarm protection function of the ion pump and power supply, including real-time monitoring and display of voltage and current, and an interlock protection device when the current and voltage are abnormal. When the working state of the power supply or the vacuum state of the equipment is abnormal, the fault can be reported to the superior control system through the contacts of the relay, so as to meet the needs of some specific equipment such as accelerators for current and voltage monitoring and interlock protection of the vacuum system. Require.

Description of drawings

The above-mentioned and other purposes, features and advantages of the present invention will be made clearer by illustrating preferred embodiments of the present invention in conjunction with the accompanying drawings below, wherein:

Figure 1 is a simple new vacuum ion pump power supply unit.

Fig. 2 is a schematic diagram of the functional structure of a signal monitoring and protection circuit.

Fig. 3 is a specific structure of a sputtering ion pump power supply with voltage and current signal monitoring and protection functions.

Figure 4 is a specific structure of a voltage monitoring and alarm circuit.

Figure 5 is a specific structure of a current monitoring and alarm circuit.

Detailed ways

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. In the following description, details and functions unnecessary to the present invention are omitted in order to prevent confusing understanding of the present invention.

As shown in Figure 1, a simple sputtering ion pump power supply device based on the principle of single-ended flyback switching power supply consists of 24V power supply 1, control circuit 2, high-frequency switch 3, protection circuit 4, high-frequency step-up transformer 5 and rectifier Circuit 6 is composed. The control circuit controls the on-off of the high-frequency switch. The fast on-off of the high-frequency switch allows the high-voltage step-up transformer to work in the single-ended flyback mode to generate high-voltage pulses. The rectifier circuit shapes the high-voltage pulses into a DC high-voltage output of 3kV~7kV. Supply sputter ion pump.

Fig. 2 shows a specific implementation circuit of the simple sputtering ion pump power supply device based on the principle of single-ended flyback switching power supply described in Fig. 1 .

The high-frequency step-up transformer 5 is composed of T1. T1 is a ferrite core, the transformation ratio is not lower than 1:10, the withstand voltage of the primary coil is not less than 500V, the withstand voltage of the secondary coil is not less than 7kV, and the input and output are isolated from each other. high frequency transformer.

The rectifier circuit 6 is composed of high-voltage rectifier diodes VD1, VD2, VD3, VD4 and high-voltage energy storage capacitor C1 connected in series. Using multiple diodes in series is to improve their overall withstand voltage capability and make their overall reverse breakdown after series connection The voltage is not less than 7kV, and the withstand voltage of the high-voltage energy storage capacitor is not less than 7kV.

High-frequency switch 3 is made of high-power transistor, as field effect tube (MOSFET tube), selects the 20N60 type field effect tube of maximum current 20A withstand voltage 600V in the embodiment of the present invention, also can select the field effect tube of other models for use, as long as withstand The transformation ratio product of voltage and transformer T1 is not less than 7kV.

The protection circuit 4 is composed of a low-resistance and small-power resistor R1, the resistance of which is usually 0.1-0.2 ohms. When the high-frequency switch is turned on, the current flows through the primary winding of the transformer T1 and the field effect transistor VT1 through the resistor R1. A voltage not higher than 1V is formed at the upper end; if the voltage reaches 1V, after the voltage is sent to the control circuit, the control circuit will turn off the high-frequency switch to protect the circuit.

The control circuit 2 is composed of a current-controlled PWM (pulse width modulation) circuit and an energy discharge circuit. The current-controlled PWM circuit used in the embodiment of the present invention is based on the UC3842 chip and its typical application circuit. The on-off frequency, the length of each on-on time, and the off-conditions when the current is too large are controlled. The UC3842 chip is a single-ended output current-controlled pulse width modulator chip produced by Unitrode. Using this chip to form a current-controlled PWM circuit has the advantages of a small number of pins, simple peripheral circuits, good frequency response characteristics, high operating frequency, and over-current Full-featured advantages such as limiting, overvoltage protection, and undervoltage lockout.

Diode VD5, multi-position selector switch K1, series voltage regulator tube VZ1, resistor R2, and capacitor C2 form an energy discharge circuit. When the high-frequency switch is turned off, the energy of the primary winding of transformer T1 is discharged through this circuit. The working voltage V of Zener tube VZ1 is the voltage on the primary winding when the primary winding of transformer T1 performs energy discharge. At this time, the secondary winding of transformer T1 obtains high voltage Vo through flyback. The following relationship is formed among them: Vo=V×n, and the voltage regulator tube VZ1 connected with different working voltages can be selected through the multi-position selection switch K1, so that different output high voltages of the sputtering ion pump power supply can be obtained. At the same time, in order to protect the high-frequency switch VT1, the working voltage of the voltage regulator VZ1 is lower than the withstand voltage of the field effect tube. In this circuit, the working voltages of the series voltage regulator VZ1 are 150V, 250V, and 350V respectively. The transformation ratio n of the transformer is 20, and the highest output voltage of the sputtering ion pump power supply is 3kV, 5kV, and 7kV adjustable. In the highest voltage range, to continuously adjust the output voltage of the sputtering ion pump power supply, you can adjust the potentiometer RP1 to change the reference voltage of the pin (2) of the UC3842 chip, thereby changing the output voltage of the sputtering ion pump power supply.

The so-called single-ended in this circuit means that the magnetic core of the high-frequency step-up transformer T1 only works on one side of the hysteresis loop. The so-called flyback means that the terminals of the high-frequency step-up transformer T1 are connected according to the method shown in FIG. 2 , and the terminal (1) and the terminal (3) form a terminal with the same name. When the high-frequency switch is turned on, the induced voltage of the primary winding of the high-frequency step-up transformer T1 is (1) positive (2) negative, and the rectifier diodes VD1-VD4 connected to the secondary winding are in a cut-off state, storing energy in the primary winding. When the switch tube VT1 is turned off, the energy stored in the primary winding of the transformer T1 generates a flyback voltage (1) negative (2) positive, which is coupled to the secondary winding (3) negative (4) positive, and the rectifier diodes VD1～VD4 conduct Through the pass, the energy of the primary winding is flyback to the secondary winding, filtered by rectifier diodes VD1~VD4 and capacitor C1, and then output to the titanium pump (load).

The working principle of the whole circuit is:

The 24V power supply provides the driving power higher than 16V to pin (7) of the UC3842 chip, that is, the power supply terminal, through the voltage stabilizing circuit formed by the resistor R4, the Zener diode ZT2, and the capacitor C3. Resistor R9 and capacitor C6 constitute an oscillating circuit connected to pin (4) of the UC3842 chip to generate a sawtooth wave of the required frequency, that is, the oscillation frequency of the resistor R9 and capacitor C6 determines the final output pulse frequency of the UC3842 chip. Resistor R3 and potentiometer RP1 form a voltage-dividing sampling circuit for the flyback voltage of the primary winding of transformer T1, which is sent to pin (2) of the UC3842 chip as a voltage reference, that is, the voltage feedback input terminal, and pin (1) of the UC3842 chip is (2) The output compensation end of the pin is connected to the (2) pin through the parallel resistance R5 and the capacitor C4. Resistor R8 introduces the current feedback signal from the upper end of the protection circuit resistor R1 to pin (3) of the UC3842 chip, which is the current detection input end. The current feedback signal introduced from pin (3) and the voltage feedback signal introduced from pin (2) are converted and compared in the UC3842 chip to generate a PWM (pulse width modulation) wave, which is output from pin (6) (ie the output terminal). Signal to control the on-off of the field effect transistor VT1. The relative size of the current feedback signal and the voltage feedback signal determines the pulse width of the PWM (Pulse Width Modulation) wave, that is to say, they determine the length of each conduction time of the high-frequency switch. The more, the wider the PWM pulse, the longer the VT1 conduction time; the closer the current feedback signal is to the voltage feedback signal, the smaller the difference, the narrower the PWM pulse, and the shorter the VT1 conduction time. At the same time, the current detection input terminal is set with a 1V current clamp. When the current on the protection circuit is too large and the voltage on the resistor R1 exceeds 1V (that is, the level of pin 3 is greater than 1V), the PWM pulse will be turned off to achieve current limiting. purpose of protection.

When the pulse output by the UC3842 chip (pin 6) is at a high level, VT1 is turned on, and VT1 is turned on, then the current flows from the 24V power supply through the primary winding of the transformer T1, and goes to the ground through the high-frequency switch VT1 and the protection circuit R1. At this time, the transformer The rectifier diode on the secondary winding of T1 is equivalent to reverse connection, the secondary winding has no output, and the primary winding stores energy. The current feedback signal is obtained from the protection circuit R1 and sent to pin (3) of the UC3842 chip (current detection input terminal). When the pulse output by the UC3842 chip (pin 6) changes from high level to low level, VT1 is cut off, and the energy stored in the primary winding of transformer T1 is discharged through the energy discharge circuit, forming a reverse voltage of 350V on the primary winding. The primary winding forms a high voltage of about 7kV through the flyback, which is applied to the load (sputtering ion pump) through the rectifier diodes VD1, VD2, VD3, VD4 and filter capacitor C1. At the same time, the voltage dividing sampling circuit composed of the resistor R3 and the potentiometer RP1 will reflect The signal of the flyback voltage of the primary winding of the transformer T1 is sent to the voltage feedback input terminal (2) pin of the UC3842 chip, and the signal is converted and compared with the previously input current feedback signal inside the UC3842 chip to control the width of the next output pulse of the UC3842 chip. By adjusting the length of the next turn-on time of the field effect transistor VT1 and changing the amount of energy stored in the transformer T1 when it works next time, the output power is adjusted to achieve the purpose of stabilizing the output voltage. Since the working frequency of the whole circuit is very high, up to 500kHz, the actual output working voltage of the sputtering ion pump power supply according to the embodiment of the present invention is very stable and the ripple is very small.

Figure 3 shows the structure of a sputtering ion pump power supply with voltage and current monitoring and protection functions based on Figure 1. It consists of 24V power supply 1, control circuit 2, high-frequency switch 3, protection circuit 4, high-frequency booster In addition to the voltage transformer 5 and the rectification circuit 6, it also includes an AC220V to 24V circuit 7, a 24V to ±12V circuit 8, a voltage monitoring and alarm circuit 9, and a current monitoring and alarm circuit 10.

The AC220V to 24V circuit 7 converts the 220V AC power of the mains into 24V DC power, which meets the requirement that the single-ended flyback switching power supply can only be converted based on DC power. The single-ended flyback sputtering ion pump power supply with AC220V to 24V circuit 7 can directly use AC220V mains power as the power supply, and at the same time connect the output end of the AC220V to 24V circuit 7 in parallel with a 24V battery, then when there is mains power, AC220V supplies power for the single-ended flyback sputtering ion pump and at the same time charges the battery. Excited sputtering ion pump power supply works 24 hours a day.

The AC220V to 24V circuit 7 has multiple implementation methods. The traditional method is to first convert AC220V to AC20V through a transformer, and then use a rectifier bridge to rectify, 24V regulator tube to stabilize the voltage, and capacitor filter to realize 24V DC. Since the current low-voltage power module technology is very mature, the embodiment of the present invention directly adopts the mature power module RS308 on the market, inputs AC220V, directly outputs 24V, and realizes AC220V to 24V circuit 7 .

The 24V to ±12V circuit 8 converts DC 24V into DC positive 12V and negative 12V, and serves as the power supply for the voltage monitoring and alarm circuit 9 and the current monitoring and alarm circuit 10 of the two low-voltage control circuits of the sputtering ion pump power supply. The 24V to ±12V circuit 8 also has multiple implementations. In the embodiment of the present invention, the mature power module HNM5-24D12 on the market is also used to input 24V to directly obtain two outputs of ±12V to realize the 24V to ±12V circuit 8 .

The voltage monitoring and alarm circuit 9 monitors and displays the output voltage of the sputtering ion pump power supply in real time. At the same time, when the output voltage is lower than the alarm value set by the user due to a power failure or a short circuit of the load, the relay contacts are turned on and off to The superior control system sends out an alarm signal.

Figure 4 shows the specific structure of a voltage monitoring and alarm circuit. It includes three parts: sampling amplifier circuit 91, voltage adjustment display circuit 92, and comparison alarm circuit 93. Its working principle is: resistors R21 and R22 complete the sampling of the output voltage of the sputtering ion pump, and diodes VD21 and VD22 perform voltage limiting protection. , the comparator N21 and the resistors R23, R24, R25 amplify and output the voltage sampling signal so as to provide it to the voltage adjustment display circuit 92 and the comparison alarm circuit 93. Comparator N23, resistors R27, R28 and variable potentiometer RP22 constitute a voltage adjustment display circuit 92, which adjusts the sampling voltage to an appropriate multiple and displays it through the low-voltage voltmeter head PV. For example, in this circuit, the output voltage of the sputtering ion pump power supply is 3-7kV, and the sampling voltage obtained from the voltage-dividing sampling resistor is 1.2-2.8V, and the comparator N21 amplifies it to 2.4-5.6V. By adjusting RP2, N23 The output is 3-7V, which corresponds to one-thousandth of the output voltage of the sputtering ion pump power supply, which can be displayed by a 10V DC voltage meter, and each 1V of the meter actually represents 1kV. Comparator N22, resistor R26, adjustable potentiometer RP21, diode VD23, and relay K21 form a voltage comparison alarm circuit. The user sets the protection threshold through the adjustable potentiometer RP21 for the normal output voltage of the sputtering ion pump power supply. Circuit 91 reflects that the output signal of the output voltage of the sputtering ion pump power supply is lower than the protection threshold, then the comparator N22 outputs +12V high level so that the wire package of the relay K21 has no current, the contact of the relay K21 is disconnected, and the upper control system The alarm signal A is disconnected, forming a failure alarm of "the output voltage of the sputtering ion pump power supply is too low".

The current monitoring and alarm circuit 10 monitors and displays the working current of the load (sputtering ion pump) in real time. The on-off of the contact sends an alarm signal to the superior control system.

Figure 5 shows the specific structure of a current monitoring and alarm circuit. It includes three parts: sampling amplifier circuit 101, current display circuit 102, and comparison alarm circuit 103. Its working principle is: current display circuit 102 is composed of microampere ammeter PA, diodes VD31, VD32, and capacitor C31. On the circuit of the ion pump current, the PA meter directly displays the magnitude of the current in real time, the diodes VD31 and VD32 form a voltage limiting protection for the meter PA, and the capacitor C31 acts as a filter. In the sampling amplifier circuit 101, the sampling resistor R31 is connected in series on the current circuit of the sputtering ion pump. When the current flows through the resistor R31, a negative voltage signal is obtained at the upper end of the R31, which is sent to the comparator N31, resistors R32, R33, and R34. The amplifying circuit performs signal amplification and outputs to the comparison alarm circuit 103, diodes VD33 and VD34 perform voltage limiting protection on the sampling signal, and capacitor C32 performs filtering on the sampling signal. The comparison alarm circuit 103 is composed of a comparator N32, a resistor R35, an adjustable potentiometer RP31, a diode VD35, and a relay K31. The user can set the normal vacuum state and working current of the sputtering ion pump through the adjustable potentiometer RP31. Protection threshold, when the output signal of the sampling amplifier circuit 102 reflecting the working current of the sputtering ion pump is lower than the protection threshold (that is, after the sampling signal is amplified, it is more negative voltage than the protection threshold), then the comparator outputs +12V high voltage Make the wire pack of relay K21 have no current, the contact of relay K21 is disconnected, and the alarm signal C of the superior control system is disconnected, forming a fault alarm of "excessive sputtering ion pump current".

It should be noted that Fig. 2, Fig. 4, and Fig. 5 are a specific implementation circuit of various functional modules in the embodiment of the present invention. The layout changes of components in the circuit, signal changes in similar products, and the addition of a small amount of resistance/capacitance devices, etc., can all realize the functions described in the embodiments of the present invention without substantially changing the original circuit, which is common to electronic circuit engineers. Known.

So far the invention has been described with reference to the preferred embodiments. It should be understood that various other changes, substitutions and additions can be made by those skilled in the art without departing from the spirit and scope of the present invention. Accordingly, the scope of the present invention is not limited to the specific embodiments described above, but should be defined by the appended claims.

Claims (11)

1. A power supply device for an ion pump, comprising: a switching element having a first terminal, a second terminal and a third terminal; a sensing element connected to the second end of the switching element; a step-up transformer comprising a primary winding and a secondary winding, wherein the dotted end of the primary winding is opposite in polarity to the dotted end of the secondary winding, and one end of the primary winding is connected to a DC source and the other end is connected to a third end of the switching element; A control circuit, based on the flyback voltage generated in the primary winding and the voltage on the sensing element, generates a switching control signal to be applied to the first terminal of the switching element, wherein the switching element conducts under the control of the switching control signal on and off, thereby producing an output voltage at the output of the secondary winding of the step-up transformer; The rectification circuit filters the output voltage generated by the output terminal of the secondary winding of the step-up transformer. 2. The power supply device as claimed in claim 1, wherein the control circuit generates the switching element on and off based on the relative magnitude of the feedback voltage generated by dividing the flyback voltage and the voltage on the sensing element. length of time on. 3. The power supply device as claimed in claim 2, further comprising a bleeder circuit for bleedering energy in the primary winding of the step-up transformer when the switching element is turned off. 4. The power supply device of claim 3, wherein the bleeder circuit comprises: a diode with the anode connected to the third terminal and the cathode connected via a capacitor to the terminal of the same name of the primary winding; a plurality of parallel multi-position selector switches connected in parallel with the capacitor; resistor in parallel with the capacitor. 5. The power supply device of claim 2, the sensing element is a resistor. 6. The power supply device according to claim 1, wherein the rectification circuit comprises: A plurality of series connected diodes and a filter capacitor connected in parallel with the series connected diodes. 7. The power supply device of claim 2, further comprising a voltage monitoring and protection circuit comprising: The sampling amplifier circuit samples the output voltage and amplifies the sampled voltage; The voltage adjustment display circuit adjusts the sampling voltage to a predetermined multiple, The comparison alarm circuit compares the adjusted voltage with the preset threshold, and when the adjusted voltage exceeds the preset threshold, an alarm is sent to the user. 8. The power supply device of claim 2, further comprising a current monitoring and protection circuit comprising: The sampling amplifier circuit samples the output current and amplifies the sampling current; The current adjustment display circuit adjusts the sampling current to a predetermined multiple; The comparison alarm circuit compares the adjusted current with the preset threshold, and when the adjusted current exceeds the preset threshold, an alarm is sent to the user. 9. The power supply device according to claim 1, the voltage of the DC power supply is 24 volts. 10. The power supply device of claim 9, said DC power supply being a battery pack. 11. The power supply device of claim 9, said DC power source being converted from AC power.

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