CN101292415B - Device and method for measuring output current from primary side of power converter - Google Patents

Abstract

An apparatus and method thereof for measuring an output current from a primary side of a power converter are provided. A peak detector is designed to sample a peak value of a converted voltage of a primary-side switching current. A zero-current detector detects a discharge-time of a secondary-side switching current through an auxiliary winding of a transformer. An oscillator generates a switching signal for switching the power converter. An integrator generates an integrated signal by integrating the converted voltage of the primary-side switching peak current with the discharge-time. The time constant of the integrator is correlated with the switching period of the switching signal. The integrated signal is thus proportional to the output current of the power converter.

Description

Measurement is from the Apparatus and method for of the output current of primary side of power converter

Technical field

The present invention relates to a kind of power converter, and more particularly relate to a kind of monitoring and control method described power converter.

Background technology

The voltage and current that provides through regulating has been provided various power converters.For the sake of security, off-line power converter must provide electricity to isolate (galvanicisolation) between its primary side and primary side.Be configured at control circuit under the situation of primary side of power converter, will be difficult to measure output current.Therefore, need provide a kind of Apparatus for () and method therefor of measuring output current in the primary side of power converter.Therefore, measured output current can be used for further output current control and/or power converter protection etc.

Summary of the invention

One aspect of the present invention provides a kind of equipment of measuring output current in the primary side of power converter.Described equipment comprises: peak detector, it is taken a sample to changing voltage, wherein said changing voltage is changed and is produced by primary side switch peak value electric current, described primary side switch peak value electric current is the peak value of primary side switch current, and described primary side switch current is that the described primary side from the transformer of described power converter produces; Zero current detector, it is used to detect the discharge time through the primary side switch current of the auxiliary winding of transformer, and wherein said primary side switch current is that the primary side from described transformer produces; Oscillator, it produce to produce pulse signal, is used to switch the switching frequency of this power converter with generation, in order to control the switching of described power converter; And integrator, it is used for by with the changing voltage of primary side switch peak value electric current and carry out integration discharge time and produce integrated signal.In order to obtain the output current of power converter, integrated signal and output current are in direct ratio, because the time constant of integrator is relevant with the switching cycle of switching signal.

Another aspect of the present invention provides a kind of primary side that is used in power converter to measure the method for output current.Described power converter has elementary winding, secondary winding and auxiliary winding.Described method comprises: by peak detector the changing voltage of primary side switch peak value electric current is taken a sample; Detect the discharge time of the primary side switch current of the auxiliary winding that passes through transformer by the zero current detection device; Produce the switching signal that is used to switch this power converter by oscillation device; And by with the changing voltage of primary side switch peak value electric current and carry out integration discharge time and produce integrated signal.

Should be appreciated that above description substantially and hereinafter detailed description all are exemplary, and the of the present invention further explaination to being advocated will be provided.To understand other purpose and advantage by considering subsequently description content and accompanying drawing.

Description of drawings

Fig. 1 illustrates the schematic circuit diagram of power converter according to an embodiment of the invention.

Fig. 2 illustrates the schematic diagram of the various signal waveforms of power converter according to an embodiment of the invention.

Fig. 3 illustrates the schematic circuit diagram of the method for measurement of the output current of power converter according to an embodiment of the invention.

Fig. 4 illustrates the schematic circuit diagram of the oscillator of power converter according to an embodiment of the invention.

Fig. 5 illustrates the schematic circuit diagram of the zero current detector of power converter according to an embodiment of the invention.

Embodiment

Referring to Fig. 1, the schematic circuit diagram of power converter according to an embodiment of the invention is described.Power converter comprises transformer 10, and it has auxiliary winding N _A, elementary winding N _PWith secondary winding N _SOutput voltage V for the regulatory work rate converter _OAnd/or output current I _O, controller 70 produces pwm control signal V _PWMTo switch this transformer 10 by switching transistor 20.Referring to Fig. 2, the schematic diagram of the various signal waveforms of the power converter in the key diagram 1.As pwm control signal V _PWMLevel is upgraded to when high, correspondingly produces primary side switch current I _PPrimary side switch current I _PProvide by following formula,

$I_P=\frac{V_{\mathrm{IN}}}{L_P}\×T_{\mathrm{ON}}---\left(1\right)$

V wherein _INBe the input voltage that is applied to transformer 10, L _PBe the elementary winding N of transformer 10 _PInductance, and T _ONBe pwm control signal V _PWMInterval turn-on time.

As pwm control signal V _PWMLevel is reduced to when hanging down, and the energy that is stored in the transformer 10 will be delivered to the primary side of transformer 10, and be delivered to the output of power converter via rectifier 40.Primary side switch current I _SCan be expressed as:

$I_S=\frac{(V_O+V_F)}{L_S}\×T_{\mathrm{DS}}---\left(2\right)$

V wherein _OBe the output voltage of power converter, V _FBe the forward drop on the rectifier 40, L _SBe the secondary winding N of transformer 10 _SInductance, and T _DSBe primary side switch current I _SDischarge time.

Simultaneously, at the auxiliary winding N of transformer 10 _AThe place produces a reflected voltage V _AUXThis reflected voltage V _AUXGiven by following formula:

$V_{\mathrm{AUX}}=\frac{T_{\mathrm{NA}}}{T_{\mathrm{NS}}}\×(V_O+V_F)---\left(3\right)$

T wherein _NAAnd T _NSBe respectively auxiliary winding N _AWith secondary winding N _SUmber of turn.

Along with primary side switch current I _SBe reduced to zero, reflected voltage V _AUXReduce beginning.This energy of also pointing out this transformer 10 discharges this moment fully.Therefore, as shown in Figure 2, can be from pwm control signal V _PWMThe drop edge to reflected voltage V _AUXDrop point measure T discharge time in the equation (2) _DS

Referring to Fig. 1, controller 70 has power supply terminal VCC, voltage detection terminal VDET, earth terminal GND, current-sense terminal VS and output terminals VP WM.Output terminals VP WM output pwm control signal V _PWMVoltage detection terminal VDET is connected to auxiliary winding N via resistor 50 _ATo detect this reflected voltage V _AUXReflected voltage V _AUX Further power capacitor 65 is charged to power to controller 70 via rectifier 60.Current-sense resistor 30 is connected to the ground connection reference level from the source electrode of transistor 20, with primary side switch current I _PBe converted to changing voltage V _S

Referring to Fig. 3, illustrate according to one embodiment of the invention and measure this output current I _OSchematic circuit diagram.The changing voltage V of 300 pairs of primary side switch peak values of peak detector electric current _STake a sample.Zero current detector (zero current detection) 100 is through the auxiliary winding N of transformer 10 _ADetect primary side switch current I _ST discharge time _DSOscillator 200 produces high-frequency signal to switch described power converter.Oscillator 200 produces pulse signal PLS to be used for synchronous and to produce pwm control signal V _PWMIntegrator 500 is through designing to pass through the changing voltage V with primary side switch peak value electric current _SWith T discharge time _DSCarry out integration and produce integrated signal V _XThe time constant of integrator 500 is relevant with the switching cycle T of this switching frequency.Therefore, integrated signal V _XOutput current I with power converter _OIn direct ratio.Primary side switch peak value electric current is primary side switch current I _PPeak value.Primary side switch current I _PWith primary side switch current I _SBe respectively the primary side of transformer 10 and the switch current in the primary side.According to the waveform among Fig. 2, the output current I of power converter _OGiven by following formula:

$I_O=I_S\×\frac{T_{\mathrm{DS}}}{2\×T}---\left(4\right)$

The primary side switch current I of transformer 10 _PWith umber of turn decision primary side switch current I _SPrimary side switch current I _SCan be given by following formula,

$I_S=\frac{T_{\mathrm{NP}}}{T_{\mathrm{NS}}}\×I_P---\left(5\right)$

T wherein _NPBe the elementary winding N of transformer 10 _PUmber of turn.

Primary side switch current I _PBe converted to changing voltage V by current-sense resistor 30 _SR _SBe the resistance of current-sense resistor 30.Peak detector 300 passes through changing voltage V _STake a sample and produce peak voltage signal V _SPIntegrated signal V _XCan be expressed as:

$V_X=\frac{V_{\mathrm{SP}}\×T_{\mathrm{DS}}}{T_1}---\left(6\right)$

Notice integrated signal V in equation (4)-(6) _XCan be rewritten as:

$V_X=\frac{2T}{T_1}\×\frac{T_{\mathrm{NS}}}{T_{\mathrm{NP}}}\×R_S\×I_O---\left(7\right)$

T wherein _IIt is the time constant of integrator 500.

Can find integrated signal V _XOutput current I with power converter _OIn direct ratio, shown in equation (7).

Further referring to Fig. 3, peak detector 300 comprises comparator 71, and it has the positive input that is connected to current-sense terminal VS.Changing voltage V _SValue and primary side switch current I _PValue in direct ratio.Capacitor 91 is used to keep changing voltage V _SPeak value.Therefore, on capacitor 91, obtain peak voltage signal V _SPThe negative input of comparator 71 is connected to capacitor 91.Apply constant current source 73 so that capacitor 91 is charged.Switch 75 is connected between constant current source 73 and the capacitor 91.Switch 75 comes on/off by the output of comparator 71.Transistor 84 is connected in parallel so that capacitor 91 is discharged with capacitor 91.

Integrator 500 comprises switch 76, and it is used for the peak voltage signal V of self-capacitance device 91 in the future _SPPeriodically be sampled to capacitor 92.Operational amplifier 72, resistor 90 and transistor 80 form first voltage-to-current converter, and it produces programmable current I in response to the voltage on the capacitor 92 ₈₀The positive input of operational amplifier 72 is connected to capacitor 92.The negative input of operational amplifier 72 is connected to resistor 90.Transistor 81 and transistor 82 form current mirror.Current mirror is from programmable current I ₈₀Mirror one programmable charge current I ₈₂The drain and gate of transistor 81 is connected to the drain electrode of transistor 80.This programmable charge current I is exported in the drain electrode of transistor 82 ₈₂Switch 78 is connected between the drain electrode and capacitor 95 of transistor 82.Switch 78 is only at T discharge time _DSCycle during connect.Transistor 85 is connected in parallel so that capacitor 95 is discharged with capacitor 95.Switch 79 be used for the voltage cycle on the capacitor 95 be sampled to output capacitor 96.Therefore, on output capacitor 96, obtain integrated signal V _XThe time constant of resistor 90 and capacitor 95 decision integrators 500.

Referring to Fig. 4, the oscillator 200 of power converter according to an embodiment of the invention is described.Operational amplifier 201, resistor 210 and transistor 250 form second voltage-to-current converter.Second voltage-to-current converter is in response to a reference voltage V _REFAnd produce a reference current I ₂₅₀A plurality of transistors (for example, 251,252,253,254 and 255) form current mirror, are used in response to this reference current I ₂₅₀And generation oscillator charging current I ₂₅₃With oscillator discharge current I ₂₅₅The drain electrode of transistor 253 produces oscillator charging current I ₂₅₃Oscillator discharge current I ₂₅₅Flow through the drain electrode of transistor 253.Switch 230 is connected between the drain electrode and capacitor 215 of transistor 253.Switch 231 is connected between the drain electrode and capacitor 215 of transistor 255.Comparator 205 has the positive input that is connected to capacitor 215.Comparator 205 output pulse signal PLS.Pulse signal PLS decision switching frequency and on/off switch 76 and switch 79, as shown in Figure 3.The first terminal of switch 232 is supplied with high threshold voltage V _HThe first terminal of switch 233 is supplied with low threshold voltage V _LSecond terminal of switch 232 and second terminal of switch 233 all are connected to the negative input of comparator 205.The input of inverter 260 is connected to the output of comparator 205 to produce rp pulse signal/PLS.This switch 231 of pulse signal PLS on/off and switch 233.This switch 230 of rp pulse signal/PLS on/off and switch 232.Inverter 261,262,263 and 264 is connected in series.The input of inverter 261 is supplied with pulse signal PLS.Produce a clear signal CLR with door 270.Import the output that is connected to inverter 264 with first of door 270.Import the output that is connected to inverter 261 with second of door 270.This clear signal CLR on/off transistor 84 and transistor 85.The resistance R of resistor 210 ₂₁₀Capacitor C with capacitor 215 ₂₁₅The switching cycle T of decision switching frequency,

$T=\frac{{\mathrm{<figure-callout\; id="215"\; label="C"\; filenames="185996DEST\_PATH\_HA20180221200580051519101E00012.png"\; state="\{\{state\}\}">C</figure-callout>}}_{215}\&times;V_{\mathrm{OSC}}}{V_{\mathrm{REF}}/{\mathrm{<figure-callout\; id="210"\; label="R"\; filenames="185996DEST\_PATH\_HA20180221200580051519101E00012.png"\; state="\{\{state\}\}">R</figure-callout>}}_{210}}={\mathrm{<figure-callout\; id="210"\; label="R"\; filenames="185996DEST\_PATH\_HA20180221200580051519101E00012.png"\; state="\{\{state\}\}">R</figure-callout>}}_{210}\&times;{\mathrm{<figure-callout\; id="215"\; label="C"\; filenames="185996DEST\_PATH\_HA20180221200580051519101E00012.png"\; state="\{\{state\}\}">C</figure-callout>}}_{215}\&times;\frac{V_{\mathrm{OSC}}}{V_{\mathrm{REF}}}---\left(8\right)$

V wherein _OSC=V _H-V _L

Referring to Fig. 5, the zero current detector 100 of power converter according to an embodiment of the invention is described.The delay circuit of zero current detector 100 comprise inverter 150, transistor 122, constant current source 120, capacitor 121 and with door 155.The input of delay circuit is supplied with pwm control signal V _PWMDelay circuit is at pwm control signal V _PWMThe drop edge a kind of propagation delay time is provided.The electric capacity of the electric current of constant current source 120 and capacitor 121 determines this propagation delay time.Inverter 151, inverter 152, transistor 125, constant current source 123, capacitor 124 and form single triggering signal generator with door 156 are used to produce voltage sampling signal SMP.The input of single triggering signal generator is connected to the output of delay circuit, and the output of described delay circuit also is the output with door 155.The pulse duration of the electric capacity decision voltage sampling signal SMP of the electric current of constant current source 123 and capacitor 124.

Operational amplifier 101 is operable to buffer amplifier.The negative input and output of operational amplifier 101 link together.The positive input of operational amplifier 101 is the inputs that are connected to the buffer amplifier of voltage detection terminal VDET.Voltage detection terminal VDET is connected to the auxiliary winding N of transformer 10 via resistor 50 _A, to detect this reflected voltage V _AUXSwitch 109 is connected between the output and capacitor 112 of buffer amplifier.This switch 109 of voltage sampling signal SMP on/off.Therefore, this reflected voltage V _AUXBe sampled as voltage V _DETVoltage V _DETTo remain in the capacitor 112.Comparator 105 is used to detect this reflected voltage V _AUXAttenuation, wherein the positive input of comparator 105 is connected to capacitor 112.A kind of reference threshold voltage source 106 is coupling between the output of the negative input of comparator 105 and buffer amplifier, to be provided for detecting this reflected voltage V _AUXThe threshold value of attenuation.Therefore, in case the attenuation of reflected voltage surpasses the voltage of this reference threshold voltage source 106, comparator 105 will be exported a kind of logic high signal.The input of inverter 115 is supplied with pwm control signal V _PWMThe input of inverter 116 is supplied with voltage sampling signal SMP.Has first input of the output that is connected to comparator 105 with door 119.Set-reset flip-floop 117 and set-reset flip-floop 118 have setting input and the high-level reset input that triggers the rising edge respectively.The setting input of set-reset flip-floop 118 is connected to the output of inverter 116.The input of reseting of set-reset flip-floop 118 is supplied with pwm control signal V _PWMThe output of set-reset flip-floop 118 is connected to second input with door 119.Set-reset flip-floop 117 is used to produce discharge time signal S _DSThe setting input of set-reset flip-floop 117 is connected to the output of inverter 115.The output that is connected to door 119 is imported in reseting of set-reset flip-floop 117.Discharge time signal S _DSThis switch 78 of on/off, wherein discharge time signal S _DSPulse duration and primary side switch current I _ST discharge time _DSRelevant.

According to the above description of the embodiment of the invention and referring to Fig. 3～5, integrated signal V _XBe and primary side switch current I _SOutput current I with power converter _ORelevant.Therefore, equation (7) can be rewritten as:

$V_X=m\&times;\frac{T_{\mathrm{NS}}}{T_{\mathrm{NP}}}\&times;R_S\&times;I_O---\left(9\right)$

Wherein m is a constant, and it can be determined by following formula:

$m=\frac{2\&times;{\mathrm{<figure-callout\; id="210"\; label="R"\; filenames="185996DEST\_PATH\_HA20180221200580051519101E00012.png"\; state="\{\{state\}\}">R</figure-callout>}}_{210}\&times;C_{215}}{R_{90}\&times;C_{95}}\&times;\frac{V_{\mathrm{OSC}}}{V_{\mathrm{REF}}}---\left(10\right)$

The resistance R of the resistor 90 among Fig. 3 ₉₀Resistance R with resistor 210 among Fig. 4 ₂₁₀Relevant.The capacitor C of the capacitor 95 among Fig. 3 ₉₅Capacitor C with capacitor 215 among Fig. 4 ₂₁₅Relevant.Therefore, integrated signal V _XOutput current I with power converter _OIn direct ratio.

Be understood by those skilled in the art that, can do not depart from the scope of the present invention or the situation of spirit under structure of the present invention is made various modifications and variations.In view of above content, if modifications and variations of the present invention are dropped in the scope of appended claims and equivalent thereof, then described modifications and variations are contained in the present invention.

Claims (17)

1. equipment that is used for measuring output current from the primary side of power converter, it comprises:

Peak detector, it is taken a sample to changing voltage, wherein said changing voltage is changed and is produced by primary side switch peak value electric current, described primary side switch peak value electric current is the peak value of primary side switch current, and described primary side switch current is that the described primary side from the transformer of described power converter produces;

Zero current detector, it detects discharge time of primary side switch current by the auxiliary winding of described transformer, and wherein said primary side switch current is that the primary side from described transformer produces; And

Integrator, it is used for by with the described changing voltage of described primary side switch peak value electric current and carry out integration described discharge time and produce integrated signal.

2. equipment according to claim 1, it further comprises oscillator, described oscillator produces pulse signal, to control the switching of described power converter.

3. equipment according to claim 1 is characterized in that, the described output current of described integrated signal and described power converter is in direct ratio.

4. equipment according to claim 1 is characterized in that, described peak detector comprises:

First comparator, it has positive input, and described positive input is coupled to current-sense terminal to transmit described changing voltage;

First capacitor, it is used to keep the peak value of described changing voltage, and described first capacitor is coupled in the negative input of wherein said first comparator;

First constant current source, it is used for described first capacitor is charged;

First switch, it is coupling between described first constant current source and described first capacitor, and wherein said first switch comes on/off by the output of described first comparator; And

The first transistor, itself and the described first capacitor parallel coupled are used for described first capacitor is discharged.

5. equipment according to claim 4 is characterized in that described current-sense terminal receives described changing voltage.

6. equipment according to claim 4 is characterized in that, the value of the value of described changing voltage and described primary side switch current is in direct ratio.

7. equipment according to claim 4 is characterized in that, described integrator comprises:

Second capacitor;

Second switch, its be used for the voltage cycle on described first capacitor be sampled to described second capacitor;

First voltage-to-current converter, it produces programmable current in response to the voltage on described second capacitor;

Current mirror, it produces programmable charge current in response to described programmable current, and wherein said current mirror is formed by the 3rd transistor and the 4th transistor;

The 3rd capacitor;

The 3rd switch, it is coupling between described the 4th transistor drain and described the 3rd capacitor, wherein produces described programmable charge current via the described the 4th transistorized described drain electrode;

Transistor seconds, itself and described the 3rd capacitor parallel coupled are used for described the 3rd capacitor is discharged;

Output capacitor; And

The 4th switch, its be used for the voltage cycle on described the 3rd capacitor be sampled to described output capacitor, wherein on described output capacitor, obtain described integrated signal.

8. equipment according to claim 7 is characterized in that, described first voltage-to-current converter comprises:

First resistor;

The 5th transistor; And

Operational amplifier, the positive input of wherein said operational amplifier are connected to described second capacitor, and the negative input of described operational amplifier is connected to described first resistor.

9. equipment according to claim 2 is characterized in that, described oscillator comprises:

Second voltage-to-current converter, it produces reference current by changing a reference voltage, and wherein said second voltage-to-current converter is formed by vibration operational amplifier, oscillation resistance device and oscillistor;

The first oscillating current mirror, it produces the vibration charging current, and the wherein said first oscillating current mirror is formed by first oscillistor, second oscillistor and the 3rd oscillistor;

The second oscillating current mirror, it produces the oscillating discharge electric current, and the wherein said second oscillating current mirror is formed by the 4th oscillistor and the 5th oscillistor;

Oscillating capacitor;

First oscillation switch, it is coupling between the drain electrode and described oscillating capacitor of described the 3rd oscillistor;

Second oscillation switch, it is coupling between the drain electrode of described oscillating capacitor and described the 5th oscillistor;

The vibration comparator, it produces pulse signal, the on/off state that described pulse signal is used for determining the switching frequency of the described power converter of switching and is used to control described second oscillation switch;

The 3rd oscillation switch, it has the first terminal that is supplied with high threshold voltage and is coupled to second terminal of the negative input of described vibration comparator;

The 4th oscillation switch, it has the first terminal that is supplied with low threshold voltage and is coupled to second terminal of the described negative input of described vibration comparator, and wherein said the 4th oscillation switch is controlled by described pulse signal;

The vibration inverter, the input that it has the output of being coupled to described vibration comparator is used to produce the rp pulse signal;

Coupled in series first inverter, second inverter, the 3rd inverter and the 4th inverter successively, the input of wherein said first inverter is supplied with the described pulse signal of described vibration comparator; And

With door, it produces a clear signal, wherein said output of being coupled to described the 4th inverter with first input of door, described output of being coupled to described first inverter, and the on/off state of described clear signal control the first transistor and transistor seconds with second input of door.

10. equipment according to claim 9, it is characterized in that, the described pulse signal of described vibration comparator is controlled the on/off state of described second oscillation switch and described the 4th oscillation switch, and described first oscillation switch of described rp pulse signal controlling of described vibration inverter and the on/off state of described the 3rd oscillation switch.

11. equipment according to claim 1 is characterized in that, described zero current detector comprises:

Delay circuit, it has the first zero current detection inverter, the first zero current detection transistor, the first zero current detection constant current source, the first zero current detection capacitor and first zero current detection and door, the input of wherein said delay circuit is supplied with pwm control signal, wherein said pwm control signal is used for switching described transformer via the power transistor of the primary side of described power converter, wherein said delay circuit provides propagation delay at the drop edge of described pwm control signal, and the time interval of wherein said propagation delay is by the electric capacity decision of the electric current and the described first zero current detection capacitor of the described first zero current detection constant current source;

Single triggering signal generator, it has the second zero current detection inverter, the 3rd zero current detection inverter, the second zero current detection transistor, the second zero current detection constant current source, the second zero current detection capacitor and second zero current detection and door, wherein said single triggering signal generator produces voltage sampling signal, the output of described delay circuit is coupled in the input of wherein said single triggering signal generator, and the pulse duration of wherein said voltage sampling signal is by the electric capacity decision of the electric current and the described second zero current detection capacitor of the described second zero current detection constant current source;

The zero current detection operational amplifier, it serves as buffer amplifier, voltage detection terminal is coupled in the input of wherein said zero current detection operational amplifier, and wherein said voltage detection terminal is coupled to the described auxiliary winding of described transformer via the zero current detection resistor;

The sampling capacitor device;

Sampling switch, it is coupling between the output and described sampling capacitor device of described zero current detection operational amplifier, and wherein said voltage sampling signal is controlled the on/off state of described sampling switch;

Zero current detection comparator, the positive input of wherein said zero current detection comparator are coupled to described sampling capacitor device;

The reference threshold voltage source, it is coupling between the described output of the negative input of described zero current detection comparator and described zero current detection operational amplifier;

The 4th zero current detection inverter, it has the input that is supplied with described pwm control signal;

The 5th zero current detection inverter, it has the input that is supplied with described voltage sampling signal;

Zero current detection and door, it has first input of the output of being coupled to described zero current detection comparator;

First set-reset flip-floop, it has setting input and the high-level reset input that triggers the rising edge, wherein said first set-reset flip-floop is used to produce discharge time signal, the output that described the 4th zero current detection inverter is coupled in the described setting input of wherein said first set-reset flip-floop, described the reseting of described first set-reset flip-floop imported the output of being coupled to described zero current detection and door, described discharge time signal is controlled the on/off state of the 3rd switch, and the pulse duration of described discharge time signal is relevant with the discharge time of described primary side switch current; And

Second set-reset flip-floop, it has setting input and the high-level reset input that triggers the rising edge, the output that described the 5th zero current detection inverter is coupled in the described setting input of wherein said second set-reset flip-floop, described second set-reset flip-floop described reseted input and is supplied with described pwm control signal, and second input of described zero current detection and door is coupled in the output of described second set-reset flip-floop.

12. the method from the primary side measurement output current of power converter, described power converter has elementary winding, secondary winding and auxiliary winding, said method comprising the steps of:

Detect the peak value of changing voltage, wherein said changing voltage is changed and is produced by the primary side switch current;

The auxiliary winding of the transformer by described power converter detects the discharge time of primary side switch current;

With the described peak value of the described changing voltage of described primary side switch current and carry out integration described discharge time and produce integrated signal;

Obtain described output current with the directly proportional described power converter of described integrated signal.

13. method according to claim 12, it further may further comprise the steps:

Produce the switching signal that is used to switch described power converter with oscillation method, wherein said oscillation method comprises the switching signal that is used to switch described power converter by the oscillation device generation;

Obtain the switching cycle of described switching signal;

Wherein said oscillation device comprises:

Voltage-to-current converter, it produces reference current by changing a reference voltage, and wherein said voltage-to-current converter is formed by vibration operational amplifier, oscillation resistance device and oscillistor;

The first oscillating current mirror, it produces the vibration charging current, and the wherein said first oscillating current mirror is formed by first oscillistor, second oscillistor and the 3rd oscillistor;

The second oscillating current mirror, it produces the oscillating discharge electric current, and the wherein said second oscillating current mirror is formed by the 4th oscillistor and the 5th oscillistor;

Oscillating capacitor;

First oscillation switch, it is coupling between the drain electrode and described oscillating capacitor of described the 3rd oscillistor;

Second oscillation switch, it is coupling between the drain electrode of described oscillating capacitor and described the 5th oscillistor;

The vibration comparator, it produces pulse signal, the on/off state that described pulse signal is used for determining described switching frequency and is used to control described second oscillation switch;

The 3rd oscillation switch, it has the first terminal that is supplied with high threshold voltage and is coupled to second terminal of the negative input of described vibration comparator;

The 4th oscillation switch, it has the first terminal that is supplied with low threshold voltage and is coupled to second terminal of the described negative input of described vibration comparator, and wherein said the 4th oscillation switch is controlled by described pulse signal;

The vibration inverter, the input that it has the output of being coupled to described vibration comparator is used to produce the rp pulse signal;

Coupled in series first inverter, second inverter, the 3rd inverter and the 4th inverter successively, the input of wherein said first inverter is supplied with the described pulse signal of described vibration comparator; And

With door, it produces a clear signal, wherein said output of being coupled to described the 4th inverter with first input of door, described output of being coupled to described first inverter, and the on/off state of described clear signal control the first transistor and transistor seconds with second input of door;

The resistance R of wherein said oscillation resistance device and the capacitor C of described oscillating capacitor determine described switching cycle, when described switching cycle is represented with T as shown in the formula:

$T=R\&times;C\&times;\frac{V_{\mathrm{OSC}}}{V_{\mathrm{REF}}},$

V wherein _OSC=V _H-V _L, V _REFBe expressed as described reference voltage, V _HBe expressed as described high threshold voltage, V _LBe expressed as described low threshold voltage.

14. method according to claim 12 is characterized in that, described integrated signal is the function of time constant and switching cycle.

15. method according to claim 12 is characterized in that, the step of the peak value of described detection changing voltage comprises: by peak detector described changing voltage is taken a sample.

16. method according to claim 12 is characterized in that, the described step that detected described discharge time comprises: the discharge time of detecting the primary side switch current of the described auxiliary winding that passes through described transformer by the zero current detection device.

17. method according to claim 12 is characterized in that, the described step that described changing voltage is carried out integration comprises: by integrator with described changing voltage and carry out integration described discharge time and produce described integrated signal.

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