CN201171243Y - Current changer with variable resonance gain - Google Patents

Abstract

The utility model relates to a variable syntony gain current changer which comprises a pulse-width modulation unit, a switch unit, a syntony unit, a transformer and a frequency control unit. The switch gains direct current power, the pulse-width modulation unit generates a working period signal to drive the switch unit to convert the direct current power into pulse power, and the syntony unit converts the pulse power into electric driving power which is converted into output electric power by the transformer. The variable syntony gain current changer is characterized in that the syntony unit respectively forms a starting voltage gain and a working voltage gain at the starting frequency and the working frequency which is higher than the starting frequency; wherein, the starting voltage gain is larger than the working voltages gain so that the larger starting voltage gain generates higher voltage of output electric power to smoothly start a lighting tube group, namely, the defects that the regulation of the output voltage range of the present current changer is limited and the working frequency is hard to simultaneously regulate the output and achieve zero-voltage switching are improved.

Description

The converter of variable resonance gain

Technical field

The utility model relates to a kind of converter of variable resonance gain, is applied to drive fluorescent tube and utilizes the converter that changes resonance frequency and adjust driving voltage.

Background technology

The topmost element of constantly popularizing of LCD is polaroid and backlight module now, this module backlight must produce uniform light, dialysis by polaroid generation light different colours forms colorful picture again, in order to allow this module backlight be reached the effect that produces uniform light, this module backlight must possess a plurality of converters that long-life fluorescent tube and provides the fluorescent tube output power that have, and utilizes the output power size of adjusting this converter to adjust the brightness of this fluorescent tube; And known converter framework as shown in Figure 1, comprise a power source 1, one dim signal source 6, one pulse-width modulation unit 3, one switches switch element 2, one resonant element 4, one transformer 5 and a back coupling unit 7, this power source 1 provides a direct current electric power, this pulse-width modulation unit 3 produces a working period signal and drives this diverter switch unit 2, and the switched conductive of this this diverter switch unit 2 of direct current power process will form a pulse electric power, this resonant element 4 is obtained this pulse electric power and is a driving electric and exports an output power by this transformer 5 these driving electric of conversion and drive a light tube group 9 by harmonic conversion, and produce a dim signal by this dim signal source 6 and adjust the size of the responsibility cycle (duty cycle) of these working period signal with the control output power for this pulse-width modulation unit 3, this back coupling unit 7 captures a feedback signal in the secondary side of this transformer 5 and delivers to this pulse-width modulation unit 3 and feedback the effect of voltage stabilizing to provide, wherein, the most basic known converters utilization responsibility cycle (duty cycle) of controlling this working period signal decides the size of this output power; The converter that exhausted major part utilized resonant circuit to be used as driving module backlight during known practical was novel all utilizes LC formula resonant circuit, and the most basic equivalent electric circuit of general LC formula resonant circuit sees also Fig. 2-1, wherein R _LampBe the equiva lent impedance of a fluorescent tube, V _d(t) be input voltage, Ls is a resonant inductance, and Cp is a resonant capacitance, and this input voltage is the pulse electric power of certain voltage, V _λBe the voltage of this lamp tube ends, being calculated as follows of this input voltage and this output voltage:

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

Can get after the arrangement

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

For simplifying the aforementioned calculation formula, defined parameters is as follows in addition:

$Q=\frac{R_{\mathrm{lamp}}}{\sqrt{\frac{L_s}{C_p}}}$ ... .. (1-3) formula

Wherein Q is defined as the series resonance quality factor.

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

Z wherein _OThe characteristic impedance of resonant circuit for this reason.

(1-3) formula of utilization is with (1-4) formula can be as follows with the simplification of (1-2) formula:

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

And the transfer function gain curve of this LC formula resonant circuit sees also Fig. 2-2; Known LC formula resonant circuit all with fixed pattern work frequently, forms fixing voltage gain, adjusts the brightness of this light tube group 9 by the responsibility cycle (duty cycle) of these pulse-width modulation unit 3 these working period signal of change; Utilize " the many fluorescent tubes parallel driver circuit and the current-sharing control method thereof of LCD " of the previous utility model of LC formula resonant circuit such as TaiWan, China patent certificate I290707 number, in Fig. 3 of this previous patent, a visible resonant inductance of the primary side of its transformer T1 (Lr) and a resonant capacitance (Cr), and utilize this resonant inductance (Lr) and this resonant capacitance (Cr) to produce the string ripple to pass through this transformer T 1 power conversion; Yet above-mentioned converter is controlled the brightness meeting and is produced following defective by changing this working period signal:

1. the responsibility cycle (duty cycle) of adjusting working period signal can cause the diverter switch unit of this converter can't be stabilized in the operating state of zero voltage switching (zero voltage switching), produces extra loss.

2. be subject to the component pressure of this diverter switch unit, the responsibility cycle of this working period signal has its restriction than the adjusting range of (duty ratio).

Therefore, the converter that drives module backlight still need improve above-mentioned defective.

The utility model content

In view of the defective of above-mentioned converter, primary and foremost purpose of the present utility model promptly is to provide a kind of converter that improves its resonance manner, thereby reaches the characteristic with bigger dimming scope and zero voltage switching.

Via as can be known above, for achieving the above object, the utility model is a kind of converter of variable resonance gain, this converter comprises the pulse-width modulation unit, the diverter switch unit, resonant element, transformer, frequency control unit and back coupling unit, direct current power is obtained from power source in this diverter switch unit, this pulse-width modulation unit then produces working period signal and drives this diverter switch unit this direct current power is converted to pulse electric power, and this resonant element changes this pulse electric power into driving electric and is converted to output power for this transformer, connect the light tube group of establishing to drive this converter, it is characterized in that, this pulse electric power this resonant element when starting frequency and be higher than the operating frequency of this startups frequency forms the starting resistor gain respectively and operating voltage gains, wherein this starting resistor gain is greater than this operating voltage gain, to produce the output power of high voltage with this light tube group of smooth startup by big starting resistor gain, and can make this resonant element produce different voltage gains by the frequency of controlling this pulse electric power, moreover, the frequency that cooperates this pulse-width modulation unit by using of characteristic of this resonant element to change this working period signal reaches the frequency of adjusting this pulse electric power, this frequency control unit can determine reference voltage signal by obtaining dim signal and obtaining feedback signal from this back coupling unit, this pulse-width modulation unit determines the frequency of this working period signal according to this reference voltage signal, and then make this pulse electric power have the operating frequency that starts frequency and be higher than this startup frequency, reach the effect of adjusting this light tube group brightness.

In sum, the utility model utilization changes the pattern of this resonant element, utilizes its resonance characteristic and reaches and provide different gains when starting this light tube group or the work of this light tube group and can start easily and operate as normal, also reaches the effect of zero voltage switching.

Description of drawings

Fig. 1 is the converter Organization Chart of known drive fluorescent tube.

Fig. 2-1 is the known resonant element Organization Chart of the converter of Fig. 1.

Fig. 2-2 is the transfer function gain curve figure of Fig. 2-1.

Fig. 3 is circuit framework figure of the present utility model.

Fig. 4 is the transfer function gain curve figure of Fig. 3.

Embodiment

Relevant detailed description of the present utility model and technology contents, existing conjunction with figs. is described as follows:

See also Fig. 3, this figure is depicted as the Organization Chart of the converter of this variable resonance gain, this converter has a pulse-width modulation unit 3, one switches switch element 2, one resonant element 4, one transformer 5, an one back coupling unit 7 and a frequency control unit 8, this pulse-width modulation unit 3 produces a working period signal and drives this diverter switch unit 2, a direct current electric power is obtained from a power source 1 in this diverter switch unit 2, and be subjected to the driving of this working period signal and this direct current power be converted to a pulse electric power to deliver to this resonant element 4, this resonant element 4 is converted to a driving electric with this pulse electric power and delivers to this transformer 5 and is converted to an output power to drive this light tube group 9, this frequency control unit 8 then connects a dim signal source 6 and should feedback unit 7, this back coupling unit 7 captures a feedback signal from these transformer 5 secondary sides, 6 in this dim signal source provides a dim signal, 8 of this frequency control units produce a reference frequency signal according to this dim signal and this feedback signal, supply this pulse-width modulation unit 3 to adjust the frequency of this working period signal, and then adjust the frequency of this pulse electric power according to this reference frequency signal; Wherein this resonant element 4 has the characteristic of resonance, and this resonant element 4 of frequency influence that makes this pulse electric power is changed the voltage gain of these driving electric, and this pulse electric power is when a startup frequency and is higher than the operating frequency of this startup frequency, this resonant element 4 forms respectively starting resistor gain that should start frequency and this operating frequency and operating voltage gain, wherein this starting resistor gain gains to provide higher voltage to start this light tube group 9 greater than this operating voltage, reach the circuit such as the resonant element among Fig. 34 of this characteristic, this resonant element 4 comprises one first resonant inductance (L _r) 42,1 second resonant inductance (L _m) 43 and one resonant capacitance (C _s) 41, wherein this first resonant inductance 42 and this resonant capacitance 41 are connected with the first siding ring of this transformer 5, and this second resonant inductance 43 is connected in the two ends of this first siding ring, and this first resonant inductance 42 is looked into formation form in parallel from this first siding ring with this second resonant inductance 43; The transfer function of above-mentioned resonant element 4 is derived as follows:

$A=\frac{L_r}{L_m}$

This is this first resonant inductance (L _r) 42 with this second resonant inductance (L _m) 43 ratio .... (2-1 formula)

L＝L _r+L _m

This is the series connection equivalent inductance of this resonant element 4 .... (2-2 formula)

${\mathrm{\&omega;}}_o=\frac{1}{\sqrt{{\mathrm{LC}}_s}}$

This is a resonance frequency .... (2-3 formula)

$Z_o={\mathrm{\&omega;}}_{o}L=\frac{1}{{\mathrm{\&omega;}}_o{C}_s}=\sqrt{\frac{L}{C_s}}$

This is the characteristic impedance of this resonant element 4 .... (2-4 formula)

$Q={\mathrm{\&omega;}}_o{C}_s{R}_{\mathrm{lamp}}=\frac{R_{\mathrm{lamp}}}{{\mathrm{\&omega;}}_{o}L}=\frac{R_{\mathrm{lamp}}}{Z_o}$

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

$\frac{v_l\left(\mathrm{j\&omega;}\right)}{v_d\left(\mathrm{j\&omega;}\right)}=\frac{1}{(1+A)[1-{\left(\frac{{\mathrm{\&omega;}}_o}{\mathrm{\&omega;}}\right)}^2]+j\frac{1}{Q}(\frac{\mathrm{\&omega;}}{{\mathrm{\&omega;}}_o}\frac{\mathrm{<figure-callout\; id="1"\; label="A"\; filenames="Y20082000369600131.png,Y20082000369600142.png"\; state="\{\{state\}\}">A</figure-callout>}}{1+A}-\frac{{\mathrm{\&omega;}}_o}{\mathrm{\&omega;}})}$

This is the transfer function of this resonant element 4 .... (2-6 formula)

$\left|\frac{v_l\left(\mathrm{j\&omega;}\right)}{v_d\left(\mathrm{j\&omega;}\right)}\right|=\frac{1}{\sqrt{{(1+A)}^2{[1-{\left(\frac{{\mathrm{\&omega;}}_o}{\mathrm{\&omega;}}\right)}^2]}^2+\frac{1}{Q^2}{(\frac{\mathrm{\&omega;}}{{\mathrm{\&omega;}}_o}\frac{\mathrm{<figure-callout\; id="1"\; label="A"\; filenames="Y20082000369600131.png,Y20082000369600142.png"\; state="\{\{state\}\}">A</figure-callout>}}{1+A}-\frac{{\mathrm{\&omega;}}_o}{\mathrm{\&omega;}})}^2}}$

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

When this converter desire started this light tube group 9, this light tube group 9 had higher equivalent resistance (R just as open circuit when first startup _Lamp), and no current flows in this resonant element 4 when this converter is not started working, can make this moment this pulse-width modulation unit 3 produce the working period signal of default startup frequency, this resonant element 4 is started in this startup frequency, thereby have starting the starting resistor gain of frequency, therefore this resonant element 4 can have the higher voltage gain and start this light tube group 9 smoothly, and this light tube group 9 will have the secondary side of current flowing in this transformer 5 after starting, make this back coupling unit 7 be obtained this feedback signal and deliver to this pulse-width modulation unit 3 and make it work in the preset working frequency, 4 of this resonant elements produce corresponding operating voltage gain according to the operating frequency of this pulse electric power; As shown in Figure 4, this light tube group 9 this resonant element 4 when starting works in this starting resistor gain point P1, then work in the higher operating voltage gain point P2 of frequency after these light tube group 9 operate as normal, therefore, this resonant element 4 can be when this light tube group 9 starts and provides different voltage gain values so that start this light tube group 9 during operate as normal, and this resonant element 4 can provide corresponding voltage gain according to the frequency of this pulse electric power after these light tube group 9 operate as normal, reaches the effect of these light tube group 9 brightness of control; And the utilization of above-mentioned enforcement circuit is adjusted the measured value of this resonant element 4 these output powers of control and is seen also 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 value table

Wherein Pin is the power of this converter of input, and Fs be the frequency of this resonant element 4 work, in table the 1st be listed as the 6th list apparent as can be known, when the operating frequency of this resonant element 4 can produce higher light tube electric voltage (V in lower frequency _Lamp), higher light tube electric voltage (V _Lamp) help starting this light tube group 9, and its equivalent resistance (R after these light tube group 9 operate as normal _Lamp) descend, frequency can rise to higher operating frequency, and the voltage gain of this resonant element 4 then diminishes with the change of frequency and makes light tube electric voltage (V _Lamp) descend, can confirm that by the measured value shown in the table 1 this resonant element 4 utilizes the circuit framework of this first resonant inductance 42, this second resonant inductance 43 and this resonant capacitance 41 can change the voltage of its output power by the Control work frequency, reaches the effect of adjusting these light tube group 9 brightness.

Above-mentioned this first resonant inductance 42 is different with the sensibility reciprocal of this second resonant inductance 43, and two resonant inductance sensibility reciprocals of this resonant element 4 compare less than 10: 1 to guarantee that this resonant element 4 has above-mentioned resonance characteristic; Though the utility model discloses as above with preferred embodiment; right its is not in order to limit the utility model; any those skilled in the art; in not breaking away from spirit and scope of the present utility model; and a little change and the retouching done; all should be covered by in the utility model, therefore protection range of the present utility model is as the criterion when looking the claim person of defining.

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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