CN100391315C - Power supply device and current converter used by same - Google Patents

Abstract

The present invention provides a power supply apparatus which combines a rectifier/filter and a converter circuit with an inverter in order to reduce the volume and improve the power supply efficiency. The power supply device includes: a rectifier/filter, a direct current to direct current (DC-DC) converter, and a direct current to alternating current (DC-AC) inverter. The rectifier/filter is connected to an ac input for converting the input ac power to dc power. The DC-DC converter and the DC-AC converter are mutually supplied in parallel, one end of the DC-DC converter and one end of the DC-AC converter are simultaneously connected to the output end of the rectifier/filter, the DC-DC converter reduces the input DC voltage and converts the reduced voltage into fixed low-voltage DC voltage to be output so as to supply power to a system circuit, and the DC-AC converter converts the input DC voltage into higher-voltage AC voltage to be output so as to supply power to a lamp tube.

Description

Power supply unit and converter used therein

technical field

The present invention relates to a power supply system, in particular to a structure with multi-level input voltage, which combines rectification/filter and converter (converter) lines with converter (inverter), so as to reduce volume and improve power supply efficiency.

Background technique

Today's indoor power supply system is dominated by AC, and most of them are in the range of 90-264V (AC), for example, typically 90-132V (AC) or 180-264V (AC). However, in current liquid crystal displays, in addition to requiring a lower-voltage DC power supply to supply power to the general circuits in the display, such as circuits for controlling image signals, a higher-voltage AC power supply is also required to provide lighting discharge for power supply. Lamp powered. For example, in a notebook computer LCD panel with a single lamp, a power supply of about 7-21V (DC) is required, while in a multi-lamp LCD display, different fixed voltages such as 12 or 15V (DC) are required to supply The display circuit is powered; at the same time, an AC power supply of more than 1,000 volts is required to drive a cold cathode fluorescent lamp (CCFL) that provides a light source. Therefore, a typical power supply system, as shown in Figure 1, must include an input alternating current from the socket, through a rectifier/filter 11, a reverse converter (Fly-Back converter) 12, a converter (DC- ACinverter) 13 and a buck regulator (Buck regulator) 14, supply power to the lamp tube with the required AC power, and supply power to other components of the display system with the required DC power. However, this typical power supply system needs to be converted layer by layer. The current commercially available products are composed of rectifier/filter 11 and reverse converter 12 as an additional adapter (additional adapter), which needs to be connected through connectors and cables. Connected to the inverter 13 and the step-down regulator 14; therefore, the efficiency of the power supply is low, only about 70%, and the cost of parts and assembly is high, and the appearance also occupies a large volume.

Contents of the invention

Therefore, an object of the present invention is to provide a power supply device, which does not need an external adapter, can achieve the purpose of reducing the size and improving the power supply efficiency. The power supply device can be used to provide power to a system including a lamp tube, including: a rectifier/filter, a direct current to direct current (DC-DC) converter and a direct current to alternating current (DC-AC) converter. The rectifier/filter has an input terminal connected to an AC power source for converting the input AC voltage into a DC voltage. The DC-to-DC converter and the DC-to-AC converter supply power in parallel with each other, and one end of the two is connected to the output end of the rectifier/filter at the same time, and the other ends output the power required by the system respectively, wherein the DC to AC converter The DC converter steps down the input DC voltage into a low-voltage DC voltage output to supply power to the system circuits except the lamp tube, and the DC-to-AC converter converts the input DC voltage into AC and boosts the output to Supply power to the lamp.

Accordingly, the power supply device of the present invention can be directly combined with rectifier/filter, converter and inverter, not only can improve the power supply efficiency, but also can choose parts with lower rated power, and because it can be made on the same circuit board, It can also achieve the effect of reducing the volume and reducing the cost of parts and assembly.

Another object of the present invention is to provide a converter for driving a discharge lamp, including: two switches; a driver circuit (driver) for driving the two switches to conduct alternately; a transformer; a sampling circuit , used to obtain the current value of the lamp tube and output a feedback signal, a pulse width modulation (PWM) control circuit, used to control the duty cycle of the drive circuit according to the feedback signal; a voltage detection circuit, used to commutate the current according to the input Outputting a control signal according to the DC voltage of the device, and an impedance adjustment circuit for adjusting the equivalent impedance value according to the control signal.

Accordingly, when the input voltage of the converter of the present invention is relatively high, the relationship curve between frequency and impedance can be changed through the adjustment of the impedance adjustment circuit, so that the operating frequency of the converter will not be increased by the input voltage. significant changes due to the impact. Therefore, the service life of the lamp tube can be ensured, and the problem of temperature rise of parts caused by the skin effect of the wire due to high frequency can be avoided, and the conversion loss can be effectively reduced.

Description of drawings

In order to make the above-mentioned and other purposes, features, and advantages of the present invention more obvious, a preferred embodiment is listed below, together with the accompanying drawings, and described in detail as follows, wherein:

Figure 1 shows a typical power supply system block diagram;

Fig. 2 represents a block diagram of a power supply device of the present invention;

Figure 3 shows a block diagram of the converter of Figure 2 according to the present invention;

Fig. 4 shows two impedance-frequency relation curves produced when the impedance adjustment circuit of Fig. 3 switches impedance; and

Fig. 5 is a circuit diagram showing an embodiment of Fig. 3 according to the present invention;

Fig. 6 represents the second embodiment of the impedance adjusting circuit in Fig. 5;

Figure 7 shows a third embodiment of the impedance adjustment circuit in Figure 5; and

FIG. 8 shows a fourth embodiment of the impedance adjustment circuit in FIG. 5 .

Explanation of symbols: 11, 21: rectifier/filter; 12, 22: converter; 13, 23: inverter; 14: buck regulator; 30: pulse width modulation control circuit 31: upper driver 32: lower driver 33: Switch 34: Impedance adjustment circuit 36: Voltage detection circuit 37: Light tube 38: Sampling circuit

Detailed ways

Similar functional elements in the following description use the same number.

Referring to FIG. 2 , it is a block diagram of a power supply device of the present invention. In FIG. 2 , the power supply device includes: a rectifier/filter 21 , a direct current (DC-DC) converter 22 and a direct current (DC-AC) converter 23 . As shown in Figure 2, an input end of this rectification/filter 21 is connected to an external AC power supply, for inputting AC voltage (for example, general room electricity is 90-132V (AC) or 180-264V (AC)) Convert to a DC voltage output (for example, the voltage value at point M in the figure is 120-190V or 250-380V (DC)). The DC-to-DC converter 22 and the DC-to-AC converter 23 are different from a typical three-level power supply system, and are connected in parallel to the output end of the rectifier/filter so as to shorten the input AC voltage to the required output voltage between stages and increase its power efficiency to about 80%. That is, the power supply efficiency of this structure is increased by about 10% compared with the typical power supply system. Wherein, the DC-to-DC converter 22 steps down the input high-voltage DC voltage into a fixed low-voltage DC voltage output, so as to supply power to parts and circuits in the system except the lamp tube, and the DC-to-AC converter 23 converts the input The DC voltage is converted into a higher voltage AC output for driving the lamp. For example, the fixed voltage of 12V (direct current) and/or 5V (direct current) provided by the converter 22 can be used by other circuits of the liquid crystal display, etc., and can even be used by a personal computer system. A multi-volt AC voltage is used to drive a CCFL. Wherein, the inverter part is further described in detail as follows.

Referring to FIG. 3 , it is a block diagram of the inverter 23 in FIG. 2 . In Fig. 3, the inverter 23 can be used to drive the lamp tube 37, which includes: a switch 33 (including a first switch M1 and a second switch M2), an upper drive circuit (HSD, high side driver) 31, a lower A drive circuit (LSD, low side driver) 32, a transformer T3, an impedance adjustment circuit (34, a voltage detection circuit 36, a sampling circuit 38 and a pulse width modulation (PWM) control circuit 30.

As shown in FIG. 3 , the upper driving circuit 31 and the lower driving circuit 32 are respectively connected to the control input terminals of the first switch M1 and the second switch M2 for driving the two switches M1 and M2 to be turned on alternately according to the driving frequency. Therefore, the DC power input from the terminal Vin (ie equivalent to the DC voltage fed from the node M in FIG. 2 ) can be converted into an AC square wave and fed to the primary side of the transformer T3 through the switching action of the switches M1 and M2. Then, through the step-up and filtering of the transformer T3, a sine wave AC power of about 1,000 volts is output to drive the fluorescent tube 37 connected to the secondary side of the transformer T3. The sampling circuit 38 is connected to one end of the lamp tube 37 for detecting the current flowing through the lamp tube 37 and outputting a feedback signal to the pulse width modulation control circuit 30 . The PWM control circuit 30 can control the duty cycle of the upper driving circuit 31 and the lower driving circuit 32 according to the feedback signal, so as to adjust the brightness of the lamp 37 . The impedance adjustment circuit 34 is connected between the primary side of the transformer T3 and the voltage detection circuit 36 . The voltage detection circuit 36 can compare the DC voltage value Vin input to the converter with a preset reference voltage value Vref, and control the switching of the impedance adjustment circuit 34 according to the comparison result, that is, change the impedance value of the impedance adjustment circuit 34 , to change the equivalent impedance value observed from the transformer T3 primary side.

In the above circuit of FIG. 3 , the pulse width modulation control circuit 30 can also be replaced by other circuits with similar effects. For example, a frequency modulation control circuit can be used to control the switching frequency of the upper driving circuit 31 and the lower driving circuit 32 according to the feedback signal, and the purpose of adjusting the brightness of the lamp tube 37 can also be achieved.

Referring to FIG. 4 , FIG. 4 is a graph showing the impedance-frequency relationship generated when the impedance adjustment circuit in FIG. 3 switches impedance. As shown in Figure 4, when the power supply device shown in Figure 2 of the present invention uses an input power supply of 90-132V (AC), that is, the voltage detection circuit 36 detects that Vin is about 120-190V (DC) after being converted into a DC voltage , the impedance adjustment circuit 34 can be controlled to switch the operation of the converter 23 to the impedance Z ₁ . At this time, the operating frequency is in the range of f ₁ to f ₃ (frequency f ₁ corresponds to 120V (DC) input voltage; frequency f ₃ corresponds to 190V (DC) input voltage). When the power supply device shown in FIG. 2 of the present invention adopts an input power supply of 180-264V (AC), that is, when the voltage detection circuit 36 detects that Vin is about 250-380V (DC) after being converted into a DC voltage, the impedance adjustment can be controlled. circuit 34 so that the operation of the inverter 23 is switched to impedance Z ₂ , at this time, the operating frequency is in the range of f ₂ ~ f ₄ (frequency f ₂ corresponds to 250V (DC) input voltage; frequency f ₄ corresponds to 380V ( DC) input voltage). Therefore, generally speaking, the operating frequency of the inverter of the present invention is in the range of f ₁ -f ₄ , actually in the range of about 50 kHz to 65 kHz. Compared with it, the known converter does not have the function of impedance switching because the voltage detection circuit 36 and the impedance adjustment circuit 34 are not provided. Therefore, when the power supply device adopts an input power supply of 180-264V (AC), the operating frequency will be at a low level. In the range of f ₅ ~ f ₆ (frequency f ₅ corresponds to 250V (DC) input voltage; and frequency f ₆ corresponds to 380V (DC) input voltage), obviously, the operating frequency range will become larger. That is, when the input voltage is high, the inverter may operate and switch at a high frequency of 80 kHz, which easily causes skin phenomenon. Therefore, the converter circuit provided by the present invention can control the impedance-frequency relationship curve to switch from impedance Z ₁ to impedance Z ₂ when the input voltage is high, so that the converter operates at a relatively low frequency, effectively improving The generation of skin effect. In addition, since the range of frequency variation is narrowed, the life of the lamp tube can be extended. Furthermore, the switching frequency of the switch 33 is reduced, reducing the temperature rise of the parts, thereby reducing losses and improving its efficiency. The input voltage range of 120 to 380V (direct current) is only for illustration, not for limitation, and those skilled in the art can design the required input voltage range according to actual needs. In addition, the voltage detection circuit 36 can also be modified appropriately to detect the external AC power source shown in FIG. 2 , and output a control signal to the impedance adjustment circuit 34 according to its voltage value.

FIG. 5 is a circuit diagram of an embodiment of FIG. 3 according to the present invention. In FIG. 5 , the PWM control circuit 30 can be implemented using any known technology, so it is only shown as a block diagram. As shown in Figure 5, in order to improve the drive capability of the PWM 2 signal, in the upper drive circuit 31, switches Q14 and Q18 are set, and their alternate switching actions can generate a square wave, which is then generated through a capacitor C56 and an isolated drive transformer T4. A signal to drive switch M1. This signal is then passed through circuits such as the switch Q13, the resistor R44, the resistor R77, the resistor R88, and the capacitor C8 to accelerate the switching action of the switch M1. The lower drive circuit 32 includes circuits such as a switch Q19, a resistor R95, and a diode D3, which can accelerate the switching action of the switch M2. The switch 33 includes the above-mentioned first and second switches M1 and M2, which are respectively driven by the upper drive circuit 31 and the lower drive circuit 32, so as to be alternately conducted according to a frequency, and the input DC voltage Vin is converted into a square wave and output to the The primary side of the transformer T3 is then boosted by the transformer T3 and filtered to become an AC sine wave, which is used to drive the lamp 37 connected to the secondary side of the transformer. A capacitor C35 is connected in parallel to the secondary side of the transformer T3 to adjust the resonance curve. In addition, the capacitor C67 is connected in series with the lamp tube 37 to reduce the influence of the characteristics of the liquid crystal panel on the lamp tube. The feedback circuit 38 is connected to the other end of the lamp tube 37, which includes a pair of half-wave rectifier diodes D5 and D8 for rectifying the AC signal into a positive half-wave signal, and a sampling resistor R100 for convecting the current through the lamp. The current value of the tube 37 is sampled and converted into a voltage feedback signal FB and output to the pulse width modulation control circuit 30 . The circuit 30 outputs the output signals PWM 2 and PWM 1 according to the feedback signal, which are respectively used to control the duty cycle of the upper driving circuit 31 and the lower driving circuit 32, so as to adjust the brightness of the lamp tube 37.

The voltage detection circuit 36 has two input terminals for inputting the input voltage Vin of the converter and a preset reference voltage Vref respectively. Circuit 36 mainly comprises a comparator OP, the non-inverting input of which is fed with voltage Vin and the inverting input of which is fed with voltage Vref. The impedance adjustment circuit 34 mainly includes a first capacitor C97 and a second capacitor C52 connected in parallel, the connection point of the first capacitor and the second capacitor is connected to the primary side of the transformer, and the second capacitor C52 is connected in series with a control switch Q15, and the control switch Q15 It has a control input terminal connected to the output terminal of the voltage detection circuit 36 . Therefore, when the voltage Vin is higher than the preset reference voltage Vref, the comparator OP will output a high voltage to turn on a switch Q17 connected to its output terminal, thereby outputting a control signal to the switch Q15 of the impedance adjustment circuit 34 to enable its on. In this case, the equivalent impedance of the impedance adjustment circuit 34 is the parallel equivalent impedance of the capacitor C97 and the capacitor C52, which is equivalent to the situation of the curve Z2 in FIG. 4 . Relatively, if the voltage Vin is lower than the preset reference voltage Vref, the switch Q15 will not be turned on, and the equivalent impedance of the impedance adjustment circuit 34 is the impedance of the capacitor C97, which is equivalent to the situation of the curve Z1 in FIG. 4 . Therefore, the purpose of switching the frequency-impedance relationship curve can be achieved, so that the operating frequency of the inverter only changes within a small bandwidth.

Preferably, the voltage detection circuit 36 further includes a hysteresis circuit, mainly composed of a switch Q39 and a resistor R22k, which is used to adjust the switching threshold of the control switch Q15. For example, if the circuit of the present invention is designed to switch the frequency-impedance relationship curve when the external AC voltage input in the power supply device in Fig. Make the switch Q15 malfunction. After the hysteresis circuit is set, the signal sent to the switch Q15 can be reliably switched to avoid malfunctions. For example, when the voltage rises, the switch Q15 must exceed 160V (AC), and the switch Q15 must be turned on when the voltage rises. In the case of voltage drop, it must be lower than 140V (AC) to make the switch non-conductive.

This embodiment is only for illustration rather than limitation, and other modifications are also possible. For example, as shown in FIG. 6 , the impedance adjustment circuit 34 can be a first inductor L61 and a second inductor L62 connected in series, and the second inductor L62 is connected in parallel with the control switch Q15 . In addition, the above-mentioned two series connected inductors L61 and L62 in FIG. 6 can be transformed into an inductor L7 connected in parallel with the primary coil of the transformer T3, and the switch Q15 is connected in series with the inductor L7 to form a circuit as shown in FIG. 7 . In addition, the switch Q15 can also be directly connected to one of the primary side coils of the transformer T3, so that the turn-on or non-conduction of the switch Q15 can be used to change the number of turns of the primary side coil of the transformer T3, thereby changing the equivalent impedance value , as shown in Figure 8.

In the preferred embodiment of the present invention shown in FIG. 5 , the switch 33 adopts a half-bridge structure. However, the switch 33 can also adopt a full-bridge or push-pull structure. The switches M1 and M2 can use MOS field effect transistors or any other kind of transistors. The driving circuits 31 and 32 are also only illustrative examples, and other forms of design can be adopted depending on actual circuit needs. In addition, although the impedance adjustment circuit 34 is shown as being connected to the primary side of the transformer T3, it can also be connected to the secondary side of the transformer T3, that is, the impedance adjustment circuit 34 in FIG. 5 is changed to be connected to the capacitor C35 and Between the ground terminals, the effect of frequency-impedance relationship curve switching can also be achieved.

Although the present invention has been disclosed as above with a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can make modifications and changes without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection of the invention shall prevail as defined by the appended claims.

Claims (30)

1. a supply unit is used to provide power supply to comprise the system of fluorescent tube, comprising:

One rectification/filter, it has an input, is connected to an external ac power source, is used for converting this input ac voltage to direct voltage, and has an output, to export this direct voltage;

Flow to direct current (DC-DC) transducer, the output that it is connected to this rectification/filter is used for converting this direct voltage step-down to a fixedly direct voltage output, to power to the system except that this fluorescent tube always; And

Flow to exchange (DC-AC) converter, its and this direct current is used for that this direct voltage is converted to an alternating voltage and exports to the parallel output that is connected to this rectification/filter of direct current transducer always, with to this lamp tube power supply,

Wherein, this direct current further comprises to alternating-current converter:

Two switches, it respectively has a control input end;

One drive circuit is electrically connected to the control input end of these two switches, is used to drive this two switch alternate conduction;

One transformer, its primary side are electrically connected to this two switches, and secondary side is electrically connected to this fluorescent tube;

One sample circuit is electrically connected to this fluorescent tube, is used for detecting flowing through this lamp tube current value and exporting a feedback signal;

One modulation control circuit is electrically connected to this sample circuit and this drive circuit, is used for controlling this drive circuit according to this feedback signal;

One voltage detecting circuit, it has an input, is used for the voltage swing according to this input, exports a control signal; And

One impedance adjustment circuit is electrically connected to this voltage detecting circuit and this transformer, is used for adjusting its equivalent impedance according to this control signal.

2. supply unit as claimed in claim 1, wherein, this system is a LCD.

3. supply unit as claimed in claim 1, wherein, this system is a personal computer.

4. supply unit as claimed in claim 1, wherein, this system is a portable computer.

5. supply unit as claimed in claim 1, wherein, the voltage range of this external ac power source is in about 90 in the voltage range of 270V.

6. supply unit as claimed in claim 1, wherein, the input of this voltage detecting circuit is electrically connected to the output of this rectification/filter.

7. supply unit as claimed in claim 1, wherein, the input of this voltage detecting circuit is electrically connected to this external ac power source.

8. supply unit as claimed in claim 1, wherein, this transformer is a step-up transformer.

9. supply unit as claimed in claim 1, wherein, the operational frequency range of this converter is to be in about 50KHz in the frequency range of 65KHz.

10. supply unit as claimed in claim 1, wherein, this impedance adjustment circuit is the primary side that is electrically connected to this transformer.

11. supply unit as claimed in claim 1, wherein, this impedance adjustment circuit is electrically connected to the secondary side of this transformer.

12. supply unit as claimed in claim 1, wherein, this modulation control circuit is to be a control circuit for pulse-width modulation, is used for controlling according to this feedback signal the duty cycle of this drive circuit.

13. supply unit as claimed in claim 1, wherein, this modulation control circuit is to be a frequency modulation(FM) control circuit, is used for controlling according to this feedback signal the switching frequency of this drive circuit.

14. a converter is used to drive a discharge lamp, this converter comprises:

Two switches, it respectively has a control input end;

One drive circuit is electrically connected to the control input end of these two switches, is used to drive this two switch alternate conduction;

One transformer, its primary side are electrically connected to this two switches, and secondary side is electrically connected to this fluorescent tube;

One sample circuit is electrically connected to this fluorescent tube, is used for detecting flowing through this lamp tube current value and exporting a feedback signal;

One modulation control circuit is electrically connected to this sample circuit and this drive circuit, is used for controlling this drive circuit according to this feedback signal;

One voltage detecting circuit is used for the voltage swing according to this converter of input, exports a control signal; And

One impedance adjustment circuit is electrically connected to this voltage detecting circuit and this transformer, is used for adjusting its equivalent impedance according to this control signal.

15. converter as claimed in claim 14, wherein, this transformer is a step-up transformer.

16. converter as claimed in claim 14, wherein, the operational frequency range of this converter is to be in about 50KHz in the frequency range of 65KHz.

17. converter as claimed in claim 14, wherein, this impedance adjustment circuit is electrically connected to the primary side of this transformer.

18. converter as claimed in claim 14, wherein, this impedance adjustment circuit is electrically connected to the secondary side of this transformer.

19. converter as claimed in claim 14, wherein, these two switches are to be the MOS field-effect transistor.

20. converter as claimed in claim 14, wherein, this impedance adjustment circuit is to comprise a control switch, it has a control input end, be electrically connected to this voltage detecting circuit, control this control switch conducting or not conducting according to this control signal, to adjust the equivalent impedance of this impedance adjustment circuit.

21. converter as claimed in claim 14, wherein, this modulation control circuit is to be a control circuit for pulse-width modulation, is used for controlling according to this feedback signal the duty cycle of this drive circuit.

22. converter as claimed in claim 14, wherein, this modulation control circuit is to be a frequency modulation(FM) control circuit, is used for controlling according to this feedback signal the switching frequency of this drive circuit.

23. a converter is used to drive a discharge lamp, this converter comprises:

Two switching transistors, it respectively has a control input end;

One drive circuit is electrically connected to the control input end of these two switching transistors, is used to drive these two switching transistors by the driving frequency alternate conduction;

One transformer, it has first siding ring and second siding ring, and this first siding ring is electrically connected to this two switching transistors, and this second siding ring is electrically connected to this fluorescent tube;

One sample circuit, it comprises a sample resistance, is connected in series in this fluorescent tube, is used for detecting flowing through this lamp tube current value and exporting a feedback signal;

One modulation control circuit is electrically connected to this sample circuit and this drive circuit, is used for controlling this drive circuit according to this feedback signal, to regulate the brightness of this fluorescent tube;

One voltage detecting circuit, it comprises a comparator, and an input of this comparator is electrically connected to the input voltage of this converter, and another input is electrically connected to a predefined reference voltage, be used for exporting a control signal according to the input voltage of this converter and the comparative result of this reference voltage; And

One impedance adjustment circuit, the one end is electrically connected to this transformer, the other end is electrically connected to this voltage detecting circuit via the control input end of a control switch, controls this control switch conducting or not conducting according to this control signal, to adjust the equivalent impedance of this impedance adjustment circuit.

24. converter as claimed in claim 23, wherein, an end of this impedance adjustment circuit is electrically connected to the first siding ring of this transformer.

25. converter as claimed in claim 23, wherein, an end of this impedance adjustment circuit is electrically connected to the second siding ring of this transformer.

26. converter as claimed in claim 23, wherein, this impedance adjustment circuit comprises first capacitor and second capacitor in parallel, and the tie point of this first and second capacitor is electrically connected to the first siding ring of this transformer, and this second capacitors in series connects this control switch.

27. converter as claimed in claim 23, wherein, this impedance adjustment circuit comprises first inductor and second inductor of series connection, and an end of this first inductor is electrically connected to the first siding ring of this transformer, this second inductor this control switch that is connected in parallel.

28. converter as claimed in claim 23, wherein, this voltage detecting circuit also comprises a lagging circuit, is used to adjust the threshold value that this control switch switches.

29. converter as claimed in claim 23, wherein, this impedance adjustment circuit comprises first inductor, and the one end is electrically connected to the first siding ring of this transformer, and is connected in series with this control switch.

30. converter as claimed in claim 23, wherein, this control switch of this impedance adjustment circuit is connected in the first siding ring of this transformer, to change equivalent impedance by the number of turns that changes this first siding ring.

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