CN201435677Y - Flyback switch power supply - Google Patents

Abstract

The utility model discloses a flyback switch power supply which comprises a pulse modulation controller and a transformer, wherein a synonym end of a primary winding of the transformer is connected with a collector of a switching tube, an emitter of the switching tube is grounded, and a base of the switching tube is connected with an output end of the pulse modulation controller. Furthermore, thepulse modulation controller is used for sampling the voltage Vin of the primary line of the transformer, calculating the turn-on time of the switching tube according to the sampling result and outputting a control signal through the output end according to the calculated turn-on time to control the switching tube to be turned on or off. The flyback switch power supply can ensure the efficiency thereof.

Description

A kind of reverse exciting switching voltage regulator

Technical field

The utility model relates to switch power technology, relates in particular to a kind of reverse exciting switching voltage regulator.

Background technology

In the prior art, the system topological figure of reverse exciting switching voltage regulator as shown in Figure 1.As seen from Figure 1, pulse modulation controller 101 limits the size of former limit inductance peak current by the pressure drop on the detection primary current detection resistance 103.When switching tube 102 conductings, inductive current increases gradually and flows through described primary current and detects resistance 103, produce voltage Vcs, pulse modulation controller 101 is sampled to voltage Vcs by the pin that connects voltage Vcs, after voltage Vcs is higher than a certain threshold voltage, pulse modulation controller 101 on-off switching tubes 102, thereby the purpose that reaches restriction former limit inductance peak current (here, emphasis describes in the circuit how to control former limit inductance peak current by detecting primary current, and other function comprises that the sampling of feedback signal and supply power mode etc. do not describe at this).Described pulse modulation controller can be pulse width modulation (PWM) controller or pulse frequency modulated (PFM) controller.

Below, specifically describe in the prior art by detecting circuit structure and the principle that primary current limits former limit inductance peak current by traditional former limit control PFM reverse exciting switching voltage regulator shown in Figure 2.As shown in Figure 2, the Vout that positive voltage on the auxiliary winding 106 is followed the secondary winding changes, the value of negative voltage reflection input line voltage, wherein, the branch pressure voltage Vfb of first resistance 109 and second resistance 110 is by behind the voltage error controller (VEC) 134, produce asserts signal, the control signal of trigger 133 outputs is opened switching tube 102 by drive circuit (DRV) 135, former limit inductive current flows through current sense resistor 103, and comparator 108 compares the reference voltage V ref that pressure drop Vcs and inner setting are good on the resistance 103, after the time-delay through lead-edge-blanking circuit (LEB) 25, produce reset signal input trigger 133, make trigger 133 output control signals, this control signal is by DRV135 on-off switching tube 102, at this moment, power transfer is to the secondary winding, below, the switch motion of switching tube repeats, and does not give unnecessary details here.

Wherein, during switching tube 102 conductings, following relation is arranged:

$\frac{V_{\mathrm{in}}}{L_P}\&times;T_{\mathrm{on}}{\&times;\mathrm{<figure-callout\; id="103"\; label="R"\; filenames="Y2009201561570015H1.png,Y2009201561570015H2.png"\; state="\{\{state\}\}">R</figure-callout>}}_{103}=V_{\mathrm{CS}}=V_{\mathrm{ref}}---\left(1\right)$

By above formula, because internal reference voltage Vref fixes, when line voltage Vin and former limit inductance L p were fixed value, the ON time Ton of the switching tube 102 on former limit was fixed value.Because there is transmission delay Td the inside of PFM controller 201, system capacity is output as:

$P_{\mathrm{IN}}=\frac{1}{2}\&times;L_P\&times;\frac{V_{\mathrm{in}}^2}{L_P^2}\&times;{(T_{\mathrm{on}}+T_d)}^2\&times;f_{\mathrm{SW}}=\frac{1}{2}\&times;f_{\mathrm{SW}}\&times;\frac{V_{\mathrm{in}}^2}{L_P}\&times;{(T_{\mathrm{on}}+T_d)}^2---\left(2\right)$

When line voltage not simultaneously, through identical Td duration, the switching tube 102 actual inductive current value I constantly that turn-off _PKCan be different, make the maximal input of reverse exciting switching voltage regulator can not keep constant, when promptly former sideline voltage Vin increased, the input power of reverse exciting switching voltage regulator increased, and when line voltage Vin reduced, input power reduced, and this will bring the design risk to switching tube.

For this reason, must add extra circuit design, lead-in voltage compensation resistor network, resistance 123 and 124 as shown in Figure 2, PFM controller 201 keeps identical peak inductor current value in full voltage range, make maximal input constant in full voltage range.

Main loss on the resistance 103 is:

${\mathrm{<figure-callout\; id="103"\; label="P"\; filenames="Y2009201561570015H1.png,Y2009201561570015H2.png"\; state="\{\{state\}\}">P</figure-callout>}}_{103}=\frac{1}{3}{\&times;\mathrm{<figure-callout\; id="103"\; label="R"\; filenames="Y2009201561570015H1.png,Y2009201561570015H2.png"\; state="\{\{state\}\}">R</figure-callout>}}_{103}\&times;{\left(I_{\mathrm{PK}}\right)}^2\&times;T_{\mathrm{on}}\&times;f_{\mathrm{SW}}---\left(3\right)$

Special line voltage compensation resistor network (resistance 123 and resistance 124) and the current sense resistor of introducing (resistance 103) all brought a certain proportion of power consumption, reduced the efficient of reverse exciting switching voltage regulator.

As shown in Figure 3 be operated in reverse exciting switching voltage regulator under the PWM pattern, its ON time is to detect pressure drop on the resistance 103 and the error signal of electric resistance partial pressure voltage Vfb relatively obtains by primary current, that is:

$\frac{V_{\mathrm{in}}}{L_P}\&times;T_{\mathrm{on}}\&times;{\mathrm{<figure-callout\; id="103"\; label="R"\; filenames="Y2009201561570015H1.png,Y2009201561570015H2.png"\; state="\{\{state\}\}">R</figure-callout>}}_{103}=V_{\mathrm{CS}}=(V_{\mathrm{fb}}-V_{\mathrm{ref}})\&times;\mathrm{EA}---\left(4\right)$

The reverse exciting switching voltage regulator maximal input is:

$P_{\mathrm{IN}}=\frac{1}{2}{\&times;L}_P\&times;\frac{V_{\mathrm{in}}^2}{L_P^2}\&times;{(T_{\mathrm{on}}+T_d)}^2\&times;f_{\mathrm{SW}}=\frac{1}{2}\&times;f_{\mathrm{SW}}\&times;\frac{V_{\mathrm{in}}^2}{L_P}\&times;{(T_{\mathrm{on}}+T_d)}^2---\left(5\right)$

Similar with anti-energizing switch voltage shown in Figure 2, in the reverse exciting switching voltage regulator shown in Figure 3, also need to add extra circuit design, lead-in voltage compensation resistor network (resistance 123 and 124), PWM controller 301 keeps identical peak inductor current value in full voltage range, make maximal input constant in full voltage range.

In the above-mentioned reverse exciting switching voltage regulator, in switching tube 102 turn on process, current sense resistor 103 itself can produce power consumption, and the pressure drop meeting on the current sense resistor 103 simultaneously reduces the efficient of switching tube 102, thereby reduces the efficient of reverse exciting switching voltage regulator.Secondly, PWM controller 301 must be established a dedicated pin Vcs with the voltage on the sample rate current detection resistance 103, and, need the LEB circuit mask switch pipe conducting spine noise of moment.In addition, need extra specialized circuitry, for example described resistance 123 and 124 when realizing the line voltage compensation function.

To sum up, line voltage compensation resistor network and the current sense resistor introduced in the reverse exciting switching voltage regulator have all brought a certain proportion of power consumption, have reduced the efficient of reverse exciting switching voltage regulator.

The utility model content

In view of this, the technical problems to be solved in the utility model is, a kind of reverse exciting switching voltage regulator is provided, and can improve the efficient of reverse exciting switching voltage regulator.

For this reason, the utility model embodiment adopts following technical scheme:

The embodiment of the invention provides a kind of reverse exciting switching voltage regulator, comprises pulse modulation controller and transformer; Wherein,

The different name end of the former limit of transformer winding links to each other with the collector electrode of switching tube, the grounded emitter of described switching tube, and the base stage of switching tube links to each other with the output of pulse modulation controller; And,

Described pulse modulation controller is used for: the former sideline voltage Vin to transformer samples, calculate the ON time of described switching tube according to the result of described sampling, according to the described ON time that calculates, export control signal with conducting of control switch pipe or shutoff by output.

Wherein, also comprise:

First resistance is connected with second resistance, and the end that first resistance is not connected with second resistance links to each other with the end of the same name of the former limit of transformer winding or links to each other the end ground connection that second resistance does not link to each other with first resistance with the different name end of the auxiliary winding of transformer;

The end that second resistance links to each other with first resistance links to each other with the input of described pulse modulation controller.

Described pulse modulation controller is a pulse frequency modulated PFM controller, in this pulse modulation controller,

The first input end of ON time calculator links to each other with the input of pulse modulation controller by line voltage detecting circuit LVD; Second input of ON time calculator links to each other with first reference voltage that presets, and the 3rd input links to each other with the output of trigger, and output links to each other with the reset terminal of described trigger; The voltage that the ON time calculator is used for receiving according to first, second, third input calculates the ON time of switching tube, and this ON time is sent to trigger;

The set end of described trigger links to each other with the input of pulse modulation controller by voltage error controller VEC, and output links to each other with the output of pulse modulation controller by drive circuit DRV.

Described pulse modulation controller is the pulse width modulation (PWM) controller, in this pulse modulation controller,

The in-phase input end of error amplifier connects second reference voltage that presets, and inverting input links to each other with the input of pulse modulation controller by sampling hold circuit S/H, and output links to each other with second input of ON time calculator;

The first input end of ON time calculator links to each other with the input of pulse modulation controller by LVD, and the 3rd input links to each other with the output of comparator, and output links to each other with the reset terminal of comparator; The voltage that the ON time calculator is used for receiving according to first, second, third input calculates the ON time of switching tube, and this ON time is sent to trigger;

The set end of trigger links to each other with internal oscillator OSC, and output is connected with the output of pulse modulation controller by DRV.

In the described ON time calculator,

First input end is connected with the voltage input end of Voltage-controlled Current Source, and described Voltage-controlled Current Source also is connected the end ground connection that electric capacity is not connected with Voltage-controlled Current Source with voltage VCC end and electric capacity;

The end that electric capacity links to each other with Voltage-controlled Current Source is connected the in-phase input end of comparator;

First switching tube source electrode and the drain electrode in-phase input end of ground connection and comparator respectively, grid links to each other with the 3rd input of ON time calculator by inverter;

The inverting input of comparator links to each other with second input of ON time calculator; Output links to each other with the input of ON time calculator.

Described voltage VCC end links to each other with the end of the same name of the former limit of described transformer winding by the 3rd resistance.

Described voltage VCC end passes through capacity earth, and links to each other by the different name end of diode and the auxiliary winding of transformer.

Technique effect for technique scheme is analyzed as follows:

In the described reverse exciting switching voltage regulator in the utility model, the emitter of switching tube is no longer by current sense resistor ground connection, but direct ground connection, and the pulse modulation controller detects former sideline voltage Vin according to the described electric resistance partial pressure voltage Vfb that gets access to, or directly detect former sideline voltage Vin from the end of the same name of the former limit of transformer winding, according to the ON time of the former sideline voltage Vin compute switch pipe that obtains; Thereby the reverse exciting switching voltage regulator in the utility model has omitted current sense resistor of the prior art, simultaneously, also omitted the line voltage compensation resistor network, thereby eliminated because the power loss that described current sense resistor and line voltage compensation resistor network bring, improved the efficient of reverse exciting switching voltage regulator.

Description of drawings

Fig. 1 is a prior art reverse exciting switching voltage regulator topological structure schematic diagram;

Fig. 2 is the reverse exciting switching voltage regulator structural representation under the prior art PFM pattern;

Fig. 3 is the reverse exciting switching voltage regulator structural representation under the prior art PWM pattern;

Fig. 4 is the reverse exciting switching voltage regulator structural representation under the utility model embodiment PFM pattern;

Fig. 5 is the reverse exciting switching voltage regulator structural representation under the utility model embodiment PWM pattern;

Fig. 6 is the implementation structure schematic diagram of the utility model ON time calculator.

Embodiment

Anti-sharp power supply comprises former limit control mode and secondary control mode, when being operated in the PFM pattern, because former limit peak inductive current I _PLBe set to fixed value, and $I_{\mathrm{PL}}=\frac{V_{\mathrm{in}}}{L_P}\&times;T_{\mathrm{on}},$ So V _In* T _On=I _PL* L _P=CONST1.And this moment, the effect of current sense resistor 103 only is the former limit inductance peak current I of restriction _PLMaximum.Therefore, under the PFM pattern, the principle of the utility model compute switch pipe ON time is: the ON time Ton according to the value control switch pipe 102 of detected line voltage Vin makes $T_{\mathrm{on}}=\frac{\mathrm{CONST}1}{V_{\mathrm{in}}},$ Promptly equal the mode of constant, can realize restriction former limit inductance peak current by the product of control switch ON time Ton and line voltage Vin.Wherein, CONST1 is a constant, and its value equals the product of the designed former limit maximum induction current value of former limit inductance value and reverse exciting switching voltage regulator, CONST1=L _P* I _PL

In addition, when reverse exciting switching voltage regulator is operated in PWM, the error amount of feedback signal Vfb limits the size of former limit peak inductive current by the ON time of control switch pipe 102, thereby adjust the power output of load end, that is: the product of the ON time of switching tube 102 and line voltage only is subjected to the control of feedback signal.Therefore, the principle of the utility model compute switch pipe ON time is: the ON time Ton according to value and the feedback signal Vfb of detected line voltage Vin determines switching tube 102 makes $T_{\mathrm{on}}=\frac{(V_{\mathrm{fb}}-V_{\mathrm{ref}})\&times;\mathrm{EA}}{V_{\mathrm{in}}}\&times;\mathrm{CONST}2,$ Promptly be proportional to the mode of the error amount of feedback signal Vfb, realize control former limit inductance peak current by the product of control switch pipe ON time Ton and line voltage Vin.Wherein CONST2 is a constant, and its value equals the ratio of the designed primary current detection resistance value of former limit inductance value and system, $\mathrm{CONST}2=\frac{L_P}{R_{103}}.$

Below, be described with reference to the accompanying drawings the realization of the utility model reverse exciting switching voltage regulator.

Fig. 4 is a kind of reverse exciting switching voltage regulator structural representation of the utility model embodiment, and this reverse exciting switching voltage regulator works under the PFM pattern.As shown in Figure 4, mainly comprise PFM controller 401 and transformer in this reverse exciting switching voltage regulator; Wherein,

The different name end of the former limit of transformer winding 104 links to each other with the collector electrode of switching tube 102, the grounded emitter of described switching tube 102, and the base stage of switching tube 102 links to each other with the output OUT of PFM controller; And, described PFM controller is used for: obtain electric resistance partial pressure voltage, according to the former sideline of described electric resistance partial pressure voltage detecting voltage, and then calculate the ON time of described switching tube, according to the described ON time that calculates, by output output control signal control switch pipe conducting or shutoff.

Concrete, as shown in Figure 4, first resistance 109 is connected with second resistance 110, and the end that first resistance 109 is not connected with second resistance 110 links to each other the end ground connection that second resistance 110 does not link to each other with first resistance 109 with the different name end of the auxiliary winding 106 of transformer; The end that second resistance 110 links to each other with first resistance 109 links to each other with the input IN of described PFM controller.

Wherein, in circuit structure shown in Figure 4, the end that first resistance 109 does not link to each other with second resistance 110 can also not link to each other with the different name end of the auxiliary winding 106 of transformer, and links to each other with the end of the same name of the former limit of transformer winding 104.

As shown in Figure 4, the concrete structure of described PFM controller inside is:

The first input end A of ON time calculator 132 links to each other with the input IN of PFM controller by LVD131; The second input B of ON time calculator 132 links to each other with the first reference voltage V ref1 that presets, the 3rd input C of ON time calculator 132 links to each other with the output Q of trigger 133, and the output of ON time calculator 132 links to each other with the reset terminal R of described trigger 133; ON time calculator 132 is used for the ON time Ton of the voltage signal compute switch pipe 102 that receives according to first, second, third input, and this ON time Ton is sent to trigger 133;

The set end S of described trigger 133 links to each other with the input IN of PFM controller by VEC134, and output Q links to each other with the output OUT of PFM controller by DRV135.

The operation principle of reverse exciting switching voltage regulator shown in Figure 4 is: the voltage that VEC134 detects PFM controller input IN produces asserts signal, sends to trigger 133; Trigger 133 output Q output control signal V3, by DRV135 switching tube 102 is opened, simultaneously, control signal V3 control ON time calculator 132 beginnings of trigger 133 outputs are according to the ON time Ton of the voltage V1 compute switch pipe 102 of reference voltage V ref1 that presets and LVD output, and ON time calculator 132 this moment produces reset signal according to the ON time that Vref1 and V1 calculate, trigger 133 output control signal V3 are turn-offed switching tube 102, simultaneously, V3 control ON time calculator 132 is prepared for the calculating of ON time Ton next time.Wherein, the voltage V1 of LVD output one is proportional to the value of former sideline voltage.

Work as the maximal input difference that line voltage difference causes system for compensation, LVD131 can do compensation to charging current I according to detected Vin value, thereby saves the line voltage compensation network that uses in the conventional method, repeats no more here.

In reverse exciting switching voltage regulator shown in Figure 4, saved described current sense resistor 103 of the prior art, simplified the line voltage compensation network, eliminate the loss of resistance, thereby improved the efficient of reverse exciting switching voltage regulator.The peripheral Pin pin of PFM controller reduces, and has simplified the periphery circuit design of PFM controller, and has saved the lead-edge-blanking circuit of PFM controller inside, thereby improved the reliability of reverse exciting switching voltage regulator.

Be illustrated in figure 5 as another kind of reverse exciting switching voltage regulator implementation structure figure, as shown in Figure 5, identical among the annexation between PWM controller and the transformer and Fig. 4, the main distinction is: the structural change in the PWM controller, as shown in Figure 5, in the described PWM controller,

The in-phase input end of error amplifier 136 connects the second reference voltage V ref2 that presets, and inverting input links to each other with the input IN of PWM controller by sampling hold circuit (S/H) 137, and output links to each other with the second input B of ON time calculator 132;

The first input end A of ON time calculator 132 links to each other with the input IN of PWM controller by LVD131, and the 3rd input C links to each other with the output Q of comparator 133, and output links to each other with the reset terminal R of comparator 133; ON time calculator 132 is used for the ON time Ton of the voltage signal compute switch pipe that receives according to first, second, third input, and this ON time Ton is sent to trigger 133;

The set end S of trigger 133 links to each other with internal oscillator (OSC) 138, and output Q is connected with the output OUT of PWM controller by DRV135.

The operation principle of anti-energizing switch circuit shown in Figure 5 is mainly: the PWM controller obtains branch pressure voltage Vfb by input IN, this voltage Vfb is through the inverting input of error originated from input amplifier 136 behind the S/H137, the second reference voltage V ref2 that the in-phase input end input of error amplifier 136 is preset, error amplifier 136 is exported its error amount V2 in view of the above and is given ON time calculator 132; OSC138 produces asserts signal and sends to trigger 133, and the control signal V3 of trigger 133 outputs opens switching tube 102 by DRV135; Simultaneously, described control signal V3 control ON time calculator 132 calculates ON time Ton, ON time calculator 132 is by the ON time Ton of the magnitude of voltage V1 compute switch pipe 102 of described error amount V2 and LVD131 input, the reset terminal of input trigger 133, trigger 133 output control signal V3 are turn-offed switching tube 102, simultaneously, control ON time calculator 132 is prepared for the calculating of ON time Ton next time.Wherein, the voltage V1 of LVD output one is proportional to the value of former sideline voltage.

Work as the maximal input difference that line voltage difference causes system for compensation, LVD131 can do compensation to charging current I according to detected Vin value, thereby saves the line voltage compensation network that uses in the prior art.

Save described current sense resistor 103 of the prior art and line voltage compensation network in the reverse exciting switching voltage regulator under the PWM pattern shown in Figure 5, eliminated the loss of resistance, thereby improved the efficient of reverse exciting switching voltage regulator.The peripheral Pin pin of PWM controller reduces, and has simplified the periphery circuit design of PWM controller, and has saved the lead-edge-blanking circuit in the PWM controller, has improved the reliability of reverse exciting switching voltage regulator.

Switching tube described in Fig. 4 and the reverse exciting switching voltage regulator shown in Figure 5 102 is an example with the triode, but described switching tube 102 is not limited to triode, also can be for metal-oxide-semiconductor etc.

Fig. 6 has provided a kind of implementation structure of ON time calculator, as shown in Figure 5:

The first input end A of ON time calculator 132 is connected with the voltage input end of Voltage-controlled Current Source 1321, another input of Voltage-controlled Current Source 1321 is connected with voltage VCC end, the output of Voltage-controlled Current Source 1321 is connected with electric capacity 1322, the end ground connection that electric capacity 1322 is not connected with Voltage-controlled Current Source 1321;

The end that electric capacity 1322 links to each other with Voltage-controlled Current Source 1321 is connected the in-phase input end of comparator 1323, the in-phase input end of the source electrode of first switching tube 1324 and drain electrode difference ground connection and comparator 1323;

The grid of first switching tube 1324 links to each other with the 3rd input C of ON time calculator 132 by inverter 1325;

The inverting input of comparator 1323 links to each other with the second input B of ON time calculator 132, and output links to each other with the input of ON time calculator 132.

In addition, as shown in Figure 4 and Figure 5, described voltage VCC end links to each other with the end of the same name of the former limit of described transformer winding 104 by the 3rd resistance 121.When winding was assisted in existence, described voltage VCC end passed through capacitor C 1 ground connection, and assists the different name end of winding 106 to link to each other by diode 111 and transformer.

In the ON time calculator shown in Figure 6, the input of calculator is connected with the output of LVD, and LVD131 detects the size of input line voltage Vin from the input IN of pulse modulation controller, and produces V ₁=K * V _In, K is a constant.Voltage V1 is an input signal of ON time calculator 132, and Voltage-controlled Current Source 1321 is by voltage V1 control, and the charging current value of electric capacity 1322 is directly proportional with voltage V1.When the voltage on the electric capacity 1322 surpassed the input voltage V2 of the second input B, comparator 1323 can make output signal Ton upset immediately, thus on-off switching tube 102.And the initial moment of electric capacity 1322 chargings is subjected to the 3rd input signal V3 signal controlling, the V3 signal is a logic control signal, output signal for trigger 133, the Continuity signal of V3 and switching tube 102 is synchronous, when being switching tube 102 beginning conductings, V3 turn-offs first switching tube 1324 by inverter 1325, and current source 1321 is begun synchronously to electric capacity 1322 chargings.And after switching tube 102 was turned off, 1324 electric charges that can discharge immediately on the electric capacity 1322 of first switching tube were for next time charging begins to prepare.Therefore the ON time Ton of switching tube 102 is exactly that the charging of electric capacity 1322 is carved into the moment that the output switching activity of comparator 1323 turn-offs switching tube 102 when initial.

The setting charging current is I, and the capacitance of electric capacity 1322 is C, then I=G * V ₁=G * K * V _In, G is the gain of Voltage-controlled Current Source 1321.In charging interval, the maximum voltage signal that obtains on the electric capacity 1322 is: ${\mathrm{<figure-callout\; id="1322"\; label="V"\; filenames="Y2009201561570017H2.png"\; state="\{\{state\}\}">V</figure-callout>}}_{1322}=T_{\mathrm{on}}\&times;\frac{1}{C}\&times;I=\frac{1}{C}\&times;T_{\mathrm{on}}\&times;G\&times;K\&times;V_{\mathrm{in}}=V_2.$

Can derive ON time: $T_{\mathrm{on}}=\frac{V_2\&times;C}{G\&times;K\&times;V_{\mathrm{in}}}$

Can find out that from formula for the reverse exciting switching voltage regulator that adopts the PFM pattern, as shown in Figure 4, the product of Ton and Vin is a constant.The input signal of second input is illustrated in figure 4 as the reference voltage V ref1 that presets, as long as choose the value of suitable reference voltage V ref1, COEFFICIENT K, gain G and capacitor C, just can realize $\frac{V_2\&times;C}{G\&times;K}=\mathrm{CONST}1=L_P\&times;I_{\mathrm{PL}}.$

For the reverse exciting switching voltage regulator that adopts the PWM pattern, as shown in Figure 5.The input voltage V2 of second input of ON time calculator 132 becomes the error signal (V of feedback signal Vfb _Fb-V _Ref) * EA as long as select the suitable COEFFICIENT K and the value of gain G and capacitor C, just can realize

$\frac{C}{G\&times;K}=\mathrm{CONST}2=\frac{{\mathrm{<figure-callout\; id="103"\; label="L\; P\; R"\; filenames="Y2009201561570015H1.png,Y2009201561570015H2.png"\; state="\{\{state\}\}">L</figure-callout>}}_P}{R_{}}.$

The structure of carrying out the inductance peak current control of former limit in the reverse exciting switching voltage regulator structure of Fig. 4～shown in Figure 5 is applicable to that also the secondary of band optocoupler detects reverse exciting switching voltage regulator.

The above only is a preferred implementation of the present utility model; should be pointed out that for those skilled in the art, under the prerequisite that does not break away from the utility model principle; can also make some improvements and modifications, these improvements and modifications also should be considered as protection range of the present utility model.

Claims (7)

1, a kind of reverse exciting switching voltage regulator is characterized in that, comprises pulse modulation controller and transformer; Wherein,

The different name end of the former limit of transformer winding links to each other with the collector electrode of switching tube, the grounded emitter of described switching tube, and the base stage of switching tube links to each other with the output of pulse modulation controller; And,

Described pulse modulation controller is used for: the former sideline voltage Vin to transformer samples, calculate the ON time of described switching tube according to the result of described sampling, according to the described ON time that calculates, export control signal with conducting of control switch pipe or shutoff by output.

2, reverse exciting switching voltage regulator according to claim 1 is characterized in that, also comprises:

First resistance is connected with second resistance, and the end that first resistance is not connected with second resistance links to each other with the end of the same name of the former limit of transformer winding or links to each other the end ground connection that second resistance does not link to each other with first resistance with the different name end of the auxiliary winding of transformer;

The end that second resistance links to each other with first resistance links to each other with the input of described pulse modulation controller.

3, reverse exciting switching voltage regulator according to claim 2 is characterized in that, described pulse modulation controller is a pulse frequency modulated PFM controller, in this pulse modulation controller,

The first input end of ON time calculator links to each other with the input of pulse modulation controller by line voltage detecting circuit LVD; Second input of ON time calculator links to each other with first reference voltage that presets, and the 3rd input links to each other with the output of trigger, and output links to each other with the reset terminal of described trigger; The voltage that the ON time calculator is used for receiving according to first, second, third input calculates the ON time of switching tube, and this ON time is sent to trigger;

The set end of described trigger links to each other with the input of pulse modulation controller by voltage error controller VEC, and output links to each other with the output of pulse modulation controller by drive circuit DRV.

4, reverse exciting switching voltage regulator according to claim 2 is characterized in that, described pulse modulation controller is the pulse width modulation (PWM) controller, in this pulse modulation controller,

The in-phase input end of error amplifier connects second reference voltage that presets, and inverting input links to each other with the input of pulse modulation controller by sampling hold circuit S/H, and output links to each other with second input of ON time calculator;

The first input end of ON time calculator links to each other with the input of pulse modulation controller by LVD, and the 3rd input links to each other with the output of comparator, and output links to each other with the reset terminal of comparator; The voltage that the ON time calculator is used for receiving according to first, second, third input calculates the ON time of switching tube, and this ON time is sent to trigger;

The set end of trigger links to each other with internal oscillator OSC, and output is connected with the output of pulse modulation controller by DRV.

5, according to claim 3 or 4 described reverse exciting switching voltage regulators, it is characterized in that, in the described ON time calculator,

First input end is connected with the voltage input end of Voltage-controlled Current Source, and described Voltage-controlled Current Source also is connected the end ground connection that electric capacity is not connected with Voltage-controlled Current Source with voltage VCC end and electric capacity;

The end that electric capacity links to each other with Voltage-controlled Current Source is connected the in-phase input end of comparator;

First switching tube source electrode and the drain electrode in-phase input end of ground connection and comparator respectively, grid links to each other with the 3rd input of ON time calculator by inverter;

The inverting input of comparator links to each other with second input of ON time calculator; Output links to each other with the input of ON time calculator.

6, reverse exciting switching voltage regulator according to claim 5 is characterized in that, described voltage VCC end links to each other with the end of the same name of the former limit of described transformer winding by the 3rd resistance.

7, reverse exciting switching voltage regulator according to claim 6 is characterized in that, described voltage VCC end passes through capacity earth, and links to each other by the different name end of diode and the auxiliary winding of transformer.

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