CN201171243Y - Converter with Variable Resonant Gain - Google Patents

Abstract

The utility model relates to a but transverter of variable resonance gain, this transverter includes a pulse width modulation unit, a change over switch unit, a resonance unit, a transformer and a frequency control unit, this change over switch unit obtains a direct current power, this pulse width modulation unit then produces a duty cycle signal drive this change over switch unit and converts this direct current power into a pulse power, this resonance unit changes this pulse power into a drive power and supplies this transformer to convert into an output power, a serial communication port, this resonance unit forms a starting voltage gain and a working voltage gain respectively when a starting frequency and a frequency of operation that is higher than this starting frequency, wherein this starting voltage gain is greater than this working voltage gain, in order to produce the output power of higher voltage in order to start this banks of lamps smoothly through great starting voltage gain, improve promptly that known transverter adjustment output voltage amplitude is limited and frequency of operation is difficult to adjust output simultaneously and reach this banks of operation The drawback of switching to zero voltage.

Description

Converter with Variable Resonant Gain

technical field

The utility model relates to a converter with variable resonance gain, which is applied to the converter for driving lamp tubes and adjusting the driving voltage by changing the resonance frequency.

Background technique

The most important components of liquid crystal displays that are becoming more and more popular today are polarizers and backlight modules. The backlight module must generate uniform light, and then produce colorful images through the dialysis of different colors of light generated by the polarizer. In order to make the backlight module To achieve the effect of generating uniform light, the backlight module must have a plurality of long-life lamps and an inverter that provides the output power of the lamps, and adjust the output power of the inverters to adjust the output power of the lamps. Brightness; and the known inverter structure as shown in Figure 1, including a power source 1, a dimming signal source 6, a pulse width modulation unit 3, a switching unit 2, a resonant unit 4, a transformer 5 And a feedback unit 7, the power source 1 provides a DC power, the pulse width modulation unit 3 generates a duty cycle signal to drive the switching unit 2, and the switching of the DC power through the switching unit 2 will be Form a pulse power, the resonance unit 4 obtains the pulse power and converts it into a drive power through resonance, and converts the drive power by the transformer 5 to output an output power to drive a lamp group 9, and the dimming signal source 6 Generate a dimming signal for the pulse width modulation unit 3 to adjust the duty cycle of the duty cycle signal to control the size of the output power, and the feedback unit 7 captures a feedback signal on the secondary side of the transformer 5 The signal is sent to the pulse width modulation unit 3 to provide the effect of feedback and voltage stabilization, wherein the most basic known converter determines the size of the output power by controlling the duty cycle of the duty cycle signal; Most of known utility models use resonant circuits as converters for driving backlight modules, all of which use LC resonant circuits. For the most basic equivalent circuit of general LC resonant circuits, please refer to Figure 2-1, where R _Lamp is the equivalent impedance of a lamp, V _d (t) is the input voltage, Ls is the resonant inductance, Cp is the resonant capacitor, and the input voltage is a pulse power of a certain voltage, V _λ is the voltage at both ends of the lamp, The input voltage and the output voltage are calculated as follows:

$\frac{v_{\mathrm{\λ}}\left(\mathrm{j\ω}\right)}{v_d\left(\mathrm{j\ω}\right)}=\frac{R_{\mathrm{lamp}}//\frac{1}{\mathrm{j\ω}{C}_p}}{\mathrm{j\ω}{L}_{\mathrm{the\; s}}+(R_{\mathrm{lamp}}//\frac{1}{\mathrm{j\ω}{C}_p})}$ ...(1-1) formula

Available after finishing

$\begin{array}{c}\frac{v_{\mathrm{\&lambda;}}\left(\mathrm{j\&omega;}\right)}{v_d\left(\mathrm{j\&omega;}\right)}=\frac{\frac{{\mathrm{<figure-callout\; id="1"\; label="R\; lamp"\; filenames="Y20082000369600131.png,Y20082000369600142.png"\; state="\{\{state\}\}">R</figure-callout>}}_{\mathrm{lamp}}}{1+\mathrm{j\&omega;}{C}_p}}{\mathrm{j\&omega;}{L}_{\mathrm{the\; s}}+\frac{{\mathrm{<figure-callout\; id="1"\; label="R\; lamp"\; filenames="Y20082000369600131.png,Y20082000369600142.png"\; state="\{\{state\}\}">R</figure-callout>}}_{\mathrm{lamp}}}{1+\mathrm{j\&omega;}{C}_p}}\\ =\frac{R_{\mathrm{lamp}}}{\left(\mathrm{j\&omega;}{L}_{\mathrm{the\; s}}{R}_{\mathrm{lamp}}\right)\left(\mathrm{j\&omega;}{C}_p\right)+\mathrm{j\&omega;}{L}_{\mathrm{the\; s}}+R_{\mathrm{lamp}}}\end{array}$ .....(1-2) formula

In order to simplify the above calculation formula, another parameter is defined as follows:

$Q=\frac{R_{\mathrm{lamp}}}{\sqrt{\frac{L_{\mathrm{the\; s}}}{C_p}}}$ .....(1-3) formula

where Q is defined as the series resonance quality factor.

$Z_o={\mathrm{\&omega;}}_o{L}_{\mathrm{the\; s}}=\frac{1}{{\mathrm{\&omega;}}_o{C}_p}=\sqrt{\frac{L_{\mathrm{the\; s}}}{C_p}}$ .....(1-4) formula

Where Z _O is the characteristic impedance of this resonant circuit.

Using formula (1-3) and formula (1-4), formula (1-2) can be simplified as follows:

$\frac{v_{\mathrm{\&lambda;}}\left(\mathrm{j\&omega;}\right)}{v_d\left(\mathrm{j\&omega;}\right)}=\frac{1}{1-{\left(\frac{\mathrm{\&omega;}}{{\mathrm{\&omega;}}_o}\right)}^2+j\frac{1}{Q}\left(\frac{\mathrm{\&omega;}}{{\mathrm{\&omega;}}_o}\right)}$ ...(1-5) formula

And the gain curve of the transfer function of the LC resonant circuit is shown in Figure 2-2; the known LC resonant circuits all work in the fixed frequency mode to form a fixed voltage gain, and the duty cycle is changed through the pulse width modulation unit 3 The duty cycle (duty cycle) of signal adjusts the brightness of this lamp tube group 9; Utilize the previous utility model of LC type resonant circuit as China Taiwan patent certificate No. I290707 "multi-lamp parallel drive circuit of liquid crystal display and its Control method", in Figure 3 of the previous patent, a resonant inductance (Lr) and a resonant capacitor (Cr) can be seen on the primary side of the transformer T1, and the resonant inductance (Lr) and the resonant capacitor (Cr) are used to generate A sine wave is used to convert power through the transformer T1; however, the above inverter to control brightness by changing the duty cycle signal has the following drawbacks:

1. Adjusting the duty cycle of the duty cycle signal will cause the switching unit of the converter to be unable to stabilize in the zero voltage switching (zero voltage switching) working state, resulting in additional losses.

2. Due to the withstand voltage of the switch unit, the adjustment range of the duty ratio of the duty cycle signal is limited.

Therefore, the inverter for driving the backlight module still needs to improve the above defects.

Utility model content

In view of the above-mentioned defects of the inverter, the primary purpose of the present invention is to provide an inverter with an improved resonance mode, so as to achieve the characteristics of a larger dimming range and zero-voltage switching.

It can be seen from the above that in order to achieve the above purpose, the utility model is a variable resonance gain converter, which includes a pulse width modulation unit, a switch unit, a resonance unit, a transformer, a frequency control unit and a feedback unit, the switching unit obtains DC power from the power source, the pulse width modulation unit generates a duty cycle signal to drive the switching unit to convert the DC power into pulse power, and the resonance unit converts the pulse power into driving power The transformer is converted into output power to drive the lamp group connected to the inverter, and the characteristic is that the resonance unit respectively forms a starting voltage gain when the pulse power is at the starting frequency and an operating frequency higher than the starting frequency And the working voltage gain, wherein the starting voltage gain is greater than the working voltage gain, so as to generate a higher voltage output power through a larger starting voltage gain to start the lamp group smoothly, and the resonance can be made by controlling the frequency of the pulse power The unit generates different voltage gains. Moreover, the pulse width modulation unit adjusts the frequency of the pulse power by changing the frequency of the duty cycle signal in accordance with the characteristics of the resonance unit. The frequency control unit can obtain the dimming signal and automatically The feedback unit obtains the feedback signal to determine the reference voltage signal, and the pulse width modulation unit determines the frequency of the duty cycle signal according to the reference voltage signal, so that the pulse power has a starting frequency and a working frequency higher than the starting frequency , to achieve the effect of adjusting the brightness of the lamp group.

To sum up, the utility model uses changing the type of the resonant unit, and utilizes its resonant characteristics to achieve starting the lamp group or providing different gains when the lamp group is working, so that it can be easily started and work normally, and also achieve zero voltage The effect of switching.

Description of drawings

FIG. 1 is a structure diagram of a conventional inverter for driving a lamp.

FIG. 2-1 is a structural diagram of a known resonant unit of the converter of FIG. 1 .

Figure 2-2 is a graph of the transfer function gain curve of Figure 2-1.

Fig. 3 is a circuit structure diagram of the utility model.

FIG. 4 is a gain curve diagram of the conversion function of FIG. 3 .

Detailed ways

Relevant detailed description and technical content of the present utility model, now cooperate accompanying drawing to illustrate as follows:

Please refer to Fig. 3, which shows the structural diagram of the converter with variable resonance gain, the converter has a pulse width modulation unit 3, a switch unit 2, a resonance unit 4, a transformer 5, A feedback unit 7 and a frequency control unit 8, the pulse width modulation unit 3 generates a duty cycle signal to drive the switching unit 2, the switching unit 2 obtains a DC power from a power source 1, and receives the working The driving of the periodic signal converts the DC power into a pulse power and sends it to the resonance unit 4, and the resonance unit 4 converts the pulse power into a driving power and sends it to the transformer 5 to convert it into an output power to drive the lamp. Group 9, and the frequency control unit 8 is connected to a dimming signal source 6 and the feedback unit 7, the feedback unit 7 extracts a feedback signal from the secondary side of the transformer 5, and the dimming signal source 6 Provide a dimming signal, the frequency control unit 8 generates a reference frequency signal according to the dimming signal and the feedback signal, for the pulse width modulation unit 3 to adjust the frequency of the duty cycle signal according to the reference frequency signal, and then Adjust the frequency of the pulse power; wherein the resonant unit 4 has resonance characteristics, so that the frequency of the pulse power affects the voltage gain of the resonant unit 4 to convert the driving power, and the pulse power is at a starting frequency and a higher than the When the operating frequency of the starting frequency, the resonant unit 4 respectively forms a starting voltage gain and a working voltage gain corresponding to the starting frequency and the working frequency, wherein the starting voltage gain is greater than the working voltage gain to provide a higher voltage to start the The lamp group 9, the circuit to achieve this characteristic is shown in the resonant unit 4 in Fig. 3, the resonant unit 4 includes a first resonant inductance (L _r ) 42, a second resonant inductance (L _m ) 43 and a resonant capacitor ( C _s ) 41, wherein the first resonant inductance 42 and the resonant capacitor 41 are connected in series with the primary side coil of the transformer 5, and the second resonant inductance 43 is connected to both ends of the primary side coil, so that the first resonant inductance 42 and the second resonant inductance 43 are viewed from the primary side coil to form a parallel form; the transfer function of the above-mentioned resonant unit 4 is derived as follows:

$\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}}$

This is the ratio of the first resonant inductance (L _r ) 42 to the second resonant inductance (L _m ) 43....(Equation 2-1)

L=L _r +L _m

This is the series equivalent inductance of the resonant unit 4...(2-2 formula)

${\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\sqrt{{\mathrm{<span\; class="notranslate">\; LC</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}}$

This is the resonant frequency....(2-3 type)

${\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}\mathrm{<span\; class="notranslate">\; L</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}<span\; class="notranslate">\; =</span>\sqrt{\frac{\mathrm{<span\; class="notranslate">\; L</span>}}{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}}$

This is the characteristic impedance of the resonance unit 4... (2-4 formula)

$\mathrm{<span\; class="notranslate">\; Q</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; lamp</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; lamp</span>}}}{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; lamp</span>}}}{{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}$

This is the series resonance quality factor....(2-5 formula)

$\frac{{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j</span>}\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; Q</span>}}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}\frac{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="A"\; filenames="Y20082000369600131.png,Y20082000369600142.png"\; state="\{\{state\}\}">A</figure-callout></span>}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}<span\; class="notranslate">\; )</span>}$

This is the transfer function of the resonance unit 4... (2-6 formula)

$<span\; class="notranslate">\; |</span>\frac{{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; l</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\sqrt{{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; A</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ]</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; Q</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}\frac{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="A"\; filenames="Y20082000369600131.png,Y20082000369600142.png"\; state="\{\{state\}\}">A</figure-callout></span>}}{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}$

This is the gain value of (2-6 formula)....(2-7 formula)

When the inverter is about to start the lamp group 9, the lamp group 9 is like an open circuit at the initial start-up and has a high equivalent resistance (R _lamp ), and when the inverter does not start to work, the resonance There is no current flowing in the unit 4. At this time, the pulse width modulation unit 3 can be made to generate a duty cycle signal of a preset start-up frequency, so that the resonant unit 4 starts at the start-up frequency, thus having a start-up voltage gain corresponding to the start-up frequency Therefore, the resonant unit 4 can have a higher voltage gain to start the lamp group 9 smoothly, and after the lamp group 9 is started, a current will flow through the secondary side of the transformer 5, so that the feedback unit 7 can The feedback signal is obtained and sent to the pulse width modulation unit 3 to make it work at a preset operating frequency, and the resonance unit 4 generates a corresponding operating voltage gain according to the operating frequency of the pulse power; as shown in Figure 4, The resonant unit 4 works at the starting voltage gain point P1 when the lamp group 9 is started, and works at the operating voltage gain point P2 with a higher frequency after the lamp group 9 works normally. Therefore, the resonant unit 4 can Different voltage gain values are provided when the lamp group 9 starts and works normally so as to start the lamp group 9, and after the lamp group 9 works normally, the resonant unit 4 can provide a corresponding frequency according to the pulse power frequency. voltage gain to achieve the effect of controlling the brightness of the lamp group 9; and the above-mentioned implementation circuit controls the output power by adjusting the resonant unit 4, please refer to Table 1.

Item Pin(W) R _{lamp (KΩ)} Fs(KHz) V _lamp(V) simulate 1 21.6 32.45 67.57 1210 2 46 22.35 62.5 1370 3 62.5 19.07 60.98 1470 4 78 16.77 58.82 1570 5 91 15.6 57.14 1700 6 108 14.84 55.86 1840

Table 1 is the utility model measured numerical table

Among them, Pin is the power input to the converter, and Fs is the operating frequency of the resonant unit 4. It can be clearly seen from the first column to the sixth column in the table that when the operating frequency of the resonant unit 4 is lower than the frequency, it can produce The higher lamp voltage (V _lamp ), the higher lamp voltage (V _lamp ) is beneficial to start the lamp group 9, and the equivalent resistance (R _lamp ) of the lamp group 9 decreases after the normal operation, and the frequency It can be raised to a higher operating frequency, and the voltage gain of the resonant unit 4 becomes smaller as the frequency changes, causing the lamp voltage (V _lamp ) to drop. The measured values shown in Table 1 can confirm that the resonant unit 4 utilizes The circuit structure of the first resonant inductor 42 , the second resonant inductor 43 and the resonant capacitor 41 can change the voltage of the output power by controlling the operating frequency, so as to achieve the effect of adjusting the brightness of the lamp group 9 .

The inductances of the first resonant inductance 42 and the second resonant inductance 43 are different, and the inductance ratio of the two resonant inductances of the resonant unit 4 is less than 10:1 to ensure that the resonant unit 4 has the above-mentioned resonant characteristics; although this The utility model has been disclosed as above with preferred embodiments, but it is not intended to limit the utility model, any modifications and modifications made by those skilled in the art without departing from the spirit and scope of the utility model shall be covered. In the present utility model, therefore, the protection scope of the present utility model should be defined by the claims.

Claims (4)

1. the converter of a variable resonance gain, described converter comprises pulse-width modulation unit (3), diverter switch unit (2), resonant element (4) and transformer (5), described converter connects power source (1) and obtains direct current power, generation working period signal in described pulse-width modulation unit (3) drives described diverter switch unit (2) described direct current power is converted to pulse electric power, and described resonant element (4) is converted to driving electric with described pulse electric power and is converted to output power for described transformer (5), connect the light tube group (9) of establishing to drive described converter, be it is characterized in that:

Described pulse electric power is when starting frequency and being higher than the operating frequency of described startup frequency, described resonant element (4) produces corresponding starting resistor gain and the operating voltage gain that starts frequency and described operating frequency respectively, and wherein said starting resistor gains greater than described operating voltage gain to start described light tube group (9).

2. the converter of variable resonance gain according to claim 1, it is characterized in that, described resonant element (4) comprises first resonant inductance (42), second resonant inductance (43) and resonant capacitance (41), wherein said first resonant inductance (42) and described resonant capacitance (41) are connected with the first siding ring of described transformer (5), and described second resonant inductance (43) is connected in the two ends of described first siding ring, and described first resonant inductance (42) is looked into formation form in parallel from described first siding ring with described second resonant inductance (43).

3. the converter of variable resonance gain according to claim 2 is characterized in that, described first resonant inductance (42) is different with the sensibility reciprocal of described second resonant inductance (43).

4. the converter of variable resonance gain according to claim 1, it is characterized in that, described converter also comprises back coupling unit (7), dim signal source (6) and frequency control unit (8), wherein said dim signal source (6) produces dim signal, feedback signal is obtained from described transformer (5) secondary side in described back coupling unit (7), and described frequency control unit (8) is then adjusted the frequency of described working period signal for described pulse-width modulation unit (3) according to described dim signal and described feedback signal decision reference frequency signal.

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