CN103248246B - Off-line AC-DC (alternating current-direct current) control circuit and switching circuit comprising control circuit - Google Patents

Abstract

The invention relates to the field of off-line alternating current-direct current switching circuits. An off-line AC-DC (alternating current-direct current) control circuit comprises overvoltage detection modules (10,16), current-limiting modules (11,17), pulse width modulation modules (12,18) and a switch control module (13) which is coupled with all the above modules, and is characterized in that the overvoltage detection modules (10,16), the current-limiting modules (11,17), the pulse width modulation modules (12,18) are provided with a common input port (CS) and a current sampling signal and a voltage sampling signal are provided at the common input port (CS) in a time division multiplexing way. The overvoltage detection of the output voltage is carried out during a power tube cut-off period through a time division multiplexing port, the current of a power tube is detected during a power tube breakover period, the two signals are input in a time division way and are not interfered with each other, and therefore whether the output voltage is overvoltage or not can be precisely detected under the premise of not increasing the number of the port, and the overvoltage condition is controlled.

Description

Off-line type AC-DC control circuit and the change-over circuit comprising this control circuit

The application be applicant on March 25th, 2011 submit to, application number is " 201110084811.0 ", name is called the divisional application of the application for a patent for invention of " off-line type AC-DC control circuit and comprise the change-over circuit of this control circuit ".

Technical field

The present invention relates to off-line type AC-DC (AC-DC) translation circuit field, particularly relate to secondary and control output overvoltage detection technique in (Secondary Side Regulation, SSR) inverse-excitation converting circuit.

Background technology

At present, in medium output power off-line type AC-DC translation circuit, it is the most common that secondary controls (SSR) inverse-excitation converting circuit.

Fig. 1 is that typical secondary controls flyback off-line type AC-DC transfer circuit system structure chart.As shown in Figure 1, this translation circuit comprises off-line type AC-DC control circuit 1 and peripheral circuit, and wherein off-line type AC-DC control circuit 1 comprises overvoltage detection module 10, current limliting module 11, PWM comparator 12 and switch control module 13.

See Fig. 1, overvoltage detection module 10 comprises comparator A1, the positive input termination power port vdd terminal mouth of comparator A1, the negative input termination internal reference voltage VREF1 of comparator A1.Current limliting module 11 comprises comparator A2, the positive input termination current sample port CS port of comparator A2, the negative input termination internal reference voltage VREF2 of comparator A1.Pulse-width modulation (PWM) comparator or pulse width modulation module 12 comprise comparator A3, the positive input termination current sample port CS port of comparator A3, the negative input termination feedback port FB port of comparator A1.The input of switch control module 13 is connected to the output of comparator A1-A3, and it exports and is connected to grid driving port GATE.The grid of control circuit 1 drive port VDD to connect the negative pole of outside sustained diode 6 and the positive plate of electric capacity C3.The current sample port CS port of control circuit 1 connects the source electrode of external power pipe M1 and one end of sampling resistor R1.The grid of control circuit 1 drive port GATE to connect the grid of external power pipe M1.

Control in flyback off-line type AC-DC transfer circuit system at above-mentioned secondary, the overvoltage of output voltage Vo detect by detect vdd voltage whether overvoltage indirectly realize, but for identical output voltage, when load is different, vdd voltage has a greater change, so the overvoltage realizing output voltage Vo by detecting vdd voltage detects, overvoltage detection threshold can be very large with load variations.

The secondary shown in Fig. 2 can be adopted to control flyback off-line type AC-DC translation circuit for this reason.In the translation circuit shown in Fig. 2, the overvoltage detection port OVP linking control circuit 1 is held, detect sampled point as overvoltage after the dividing potential drop of the different name end of auxiliary winding N3 by resistance R2/R3.The relation of the auxiliary different name terminal voltage V3 of winding N3 and the different name terminal voltage V2 of vice-side winding N2 is as follows:

$\frac{V3}{V2}=\frac{n3}{n2}---\left(1\right)$

Wherein n3 is the number of turn of auxiliary winding N3, and n2 is the number of turn of vice-side winding N2.

In addition, power tube M1 be in cut-off state and vice-side winding and auxiliary winding afterflow time, the relation of voltage V3 and output voltage Vo is as follows:

$V3=\frac{n3}{n2}(\mathrm{Vo}+V_{\mathrm{FD}5})---\left(2\right)$

Wherein V _fD5for the forward conduction voltage drop of diode D5

Thus, OVP port voltage is:

$\frac{R3}{R2+R3}\·\frac{n3}{n2}(\mathrm{Vo}+V_{\mathrm{FD}5})---\left(3\right)$

Wherein R2 and R3 is respectively the resistance of resistance R2 and R3.

From formula (3), OVP port voltage and Vo linear, accurately can reflecting the whether overvoltage of Vo voltage, therefore can to solve in system shown in Figure 1 overvoltage detection threshold with the shortcoming of load variations by measuring this voltage.But the shortcoming of the translation circuit shown in Fig. 2 is control circuit 1 to be needed to increase extra OVP port for input voltage signal.

Summary of the invention

The present invention is intended to solve above-mentioned shortcoming, provides a kind of off-line type AC-DC control circuit, and it, by the mode of time division multiplexing public port, under the prerequisite not increasing control circuit port, realizes the accurate detection of output voltage overvoltage.

Above-mentioned purpose of the present invention is realized by following technical proposal:

A kind of off-line type AC-DC control circuit, it generates corresponding control signal according to the current sampling signal of input and voltage sampling signal, it is characterized in that, described current sampling signal and described voltage sampling signal provide in a time multiplexed manner on single input port.

Preferably, in above-mentioned off-line type AC-DC control circuit, described off-line type AC-DC control circuit comprises overvoltage detection module, current limliting module, pulse width modulation module and the switch control module be coupled with above-mentioned module, described overvoltage detection module receives described voltage sampling signal through described single input port, described current limliting module and pulse width modulation module receive described current sampling signal through described single input port, comprise sequential further and select module, it comprises the input and at least two outputs that are coupled with described single input port, described sequential selects module alternately to make output described in one of them and described current limliting module and described pulse width modulation module connect and make output described in another and described overvoltage detection module to connect, thus described current sampling signal and described voltage sampling signal are provided.

Preferably, in above-mentioned off-line type AC-DC control circuit, first reference voltage of described voltage sampling signal and setting compares and exports comparative result to described switch control module by described overvoltage detection module, if described voltage sampling signal is greater than described first reference voltage, then described switch control module exports and makes power tube be in the cut-off signals of cut-off state, second reference voltage of described current sampling signal and setting compares and exports comparative result to switch control module by described current limliting module, if described current sampling signal is greater than described second reference voltage, then described switch control module exports and makes power tube be in the cut-off signals of cut-off state, described current sampling signal and the signal inputted from described off-line type AC-DC control circuit outside compare and export comparative result to switch control module by described pulse width modulation module, if described current sampling signal is greater than the signal of described outside input, then described switch control module exports and makes power tube be in the cut-off signals of cut-off state.

Preferably, in above-mentioned off-line type AC-DC control circuit, described off-line type AC-DC control circuit comprises overvoltage detection module, current limliting module, pulse width modulation module and the switch control module be coupled with above-mentioned module, described overvoltage detection module receives described voltage sampling signal through described single input port, described current limliting module and pulse width modulation module receive described current sampling signal through described single input port, wherein, described overvoltage detection module, described current limliting module and described pulse width modulation module comprise the gating circuit being coupled to described switch control module, described gating circuit alternately makes the output signal of the output signal of described overvoltage detection module and described current limliting module and described pulse width modulation module be supplied to described switch control module.

Preferably, in above-mentioned off-line type AC-DC control circuit, the first enable signal is applied by the enable input of the gating circuit at described overvoltage detection module, the output signal of described overvoltage detection module is made to be provided to described switch control module, and apply the second enable signal by the enable input of the gating circuit in described current limliting module and described pulse width modulation module, make the output signal of described current limliting module and described pulse width modulation module be provided to described switch control module, described first and second enable signals are mutual exclusions.

Preferably, in above-mentioned off-line type AC-DC control circuit, first reference voltage of described voltage sampling signal and setting compares and exports comparative result to described switch control module when the enable input of described gating circuit applies the first enable signal by described overvoltage detection module, if described voltage sampling signal is greater than described first reference voltage, then described switch control module exports and makes power tube be in the cut-off signals of cut-off state, second reference voltage of described current sampling signal and setting compares and exports comparative result to switch control module when the enable input of described gating circuit applies the second enable signal by described current limliting module, if described current sampling signal is greater than described second reference voltage, then described switch control module exports and makes power tube be in the cut-off signals of cut-off state, described current sampling signal and the signal inputted from described off-line type AC-DC control circuit outside compare and export comparative result to switch control module when the enable input of described gating circuit applies the second enable signal by described pulse width modulation module, if described current sampling signal is greater than the signal of described outside input, then described switch control module exports and makes power tube be in the cut-off signals of cut-off state.

The present invention is also intended to solve above-mentioned shortcoming, provides a kind of off-line type AC-DC change-over circuit, and it, by the mode of time division multiplexing public port, under the prerequisite not increasing control circuit port, realizes the accurate detection of output voltage overvoltage.

Above-mentioned purpose of the present invention is realized by following technical proposal:

A kind of off-line type AC-DC change-over circuit, comprising:

Rectifier bridge stack;

The former limit winding be coupled with described rectifier bridge stack;

With the power tube of described former limit winding coupled;

Vice-side winding;

Auxiliary winding;

External sampling module, comprises two inputs respectively with described former limit winding and described auxiliary winding coupled;

And

Off-line type AC-DC control circuit, it generates corresponding control signal according to the current sampling signal of input and voltage sampling signal, described current sampling signal and described voltage sampling signal in a time multiplexed manner, are provided on single input port by described external sampling module.

Preferably, in above-mentioned off-line type AC-DC change-over circuit, in described power tube conduction period, described single input port provides described current sampling signal, and between the described power tube off period and vice-side winding and auxiliary winding afterflow time, described single input port provides voltage sampling signal.

Preferably, in above-mentioned off-line type AC-DC change-over circuit, described external sampling module is by when described power tube conducting, the electric current detecting described former limit winding flows through and obtains described current sampling signal with the pressure drop on the sampling resistor of described former limit windings in series, and described external sampling module, by when described power tube ends, obtains described voltage sampling signal by the voltage of the different name end detecting described auxiliary winding.

Preferably, in above-mentioned off-line type AC-DC change-over circuit, described off-line type AC-DC control circuit comprises overvoltage detection module, current limliting module, pulse width modulation module and the switch control module be coupled with above-mentioned module, described overvoltage detection module receives described voltage sampling signal through described single input port, described current limliting module and pulse width modulation module receive described current sampling signal through described single input port, the grid voltage of described power tube is controlled by described switch control module, comprise sequential further and select module, it comprises the input and at least two outputs that are coupled with described single input port, described sequential selects module alternately to make output described in one of them and described current limliting module and described pulse width modulation module connect and make output described in another and described overvoltage detection module to connect, thus described current sampling signal and described voltage sampling signal are provided.

Preferably, in above-mentioned off-line type AC-DC change-over circuit, described sequential selects module also to comprise control signal input, by the alternately output providing the first control signal to realize described voltage sampling signal and described current sampling signal at this control signal input, the frequency of described first control signal is synchronous with the signal of described power tube.

Preferably, in above-mentioned off-line type AC-DC change-over circuit, first reference voltage of described voltage sampling signal and setting compares and exports comparative result to described switch control module by described overvoltage detection module, if described voltage sampling signal is greater than described first reference voltage, then described switch control module exports and makes power tube be in the cut-off signals of cut-off state, second reference voltage of described current sampling signal and setting compares and exports comparative result to switch control module by described current limliting module, if described current sampling signal is greater than described second reference voltage, then described switch control module exports and makes power tube be in the cut-off signals of cut-off state, described current sampling signal and the signal inputted from described off-line type AC-DC control circuit outside compare and export comparative result to switch control module by described pulse width modulation module, if described current sampling signal is greater than the signal of described outside input, then described switch control module exports and makes power tube be in the cut-off signals of cut-off state.

Preferably, in above-mentioned off-line type AC-DC change-over circuit, described off-line type AC-DC control circuit comprises overvoltage detection module, current limliting module, pulse width modulation module and the switch control module be coupled with above-mentioned module, described overvoltage detection module receives described voltage sampling signal through described single input port, described current limliting module and pulse width modulation module receive described current sampling signal through described single input port, the grid voltage of described power tube is controlled by described switch control module, described overvoltage detection module, described current limliting module and described pulse width modulation module comprise the gating circuit being coupled to described switch control module, described gating circuit alternately makes the output signal of the output signal of described overvoltage detection module and described current limliting module and described pulse width modulation module be supplied to described switch control module.

Preferably, in above-mentioned off-line type AC-DC change-over circuit, the first enable signal is applied by the enable input of the gating circuit at described overvoltage detection module, the output signal of described overvoltage detection module is made to be provided to described switch control module, and apply the second enable signal by the enable input of the gating circuit in described current limliting module and described pulse width modulation module, make the output signal of described current limliting module and described pulse width modulation module be provided to described switch control module, described first and second enable signals are mutual exclusions.

Preferably, in above-mentioned off-line type AC-DC change-over circuit, first reference voltage of described voltage sampling signal and setting compares and exports comparative result to described switch control module when the enable input of described gating circuit applies the first enable signal by described overvoltage detection module, if described voltage sampling signal is greater than described first reference voltage, then described switch control module exports and makes power tube be in the cut-off signals of cut-off state, second reference voltage of described current sampling signal and setting compares and exports comparative result to switch control module when the enable input of described gating circuit applies the second enable signal by described current limliting module, if described current sampling signal is greater than described second reference voltage, then described switch control module exports and makes power tube be in the cut-off signals of cut-off state, described current sampling signal and the signal inputted from described off-line type AC-DC control circuit outside compare and export comparative result to switch control module when the enable input of described gating circuit applies the second enable signal by described pulse width modulation module, if described current sampling signal is greater than the signal of described outside input, then described switch control module exports and makes power tube be in the cut-off signals of cut-off state.

Compared with prior art, tool has the following advantages in the present invention:

By time division multiplexing port, output voltage overvoltage detection is carried out between the power tube off period, and at power tube conduction period detection power tube current, two kinds of signals input in a time division manner, be independent of each other, therefore can detect output voltage whether overvoltage exactly under the prerequisite not increasing port, and overpressure situation is controlled.

From following detailed description by reference to the accompanying drawings, above and other objects of the present invention and advantage will be made more completely clear.

Accompanying drawing explanation

Fig. 1 is a kind of schematic diagram of typical off-line type AC-DC change-over circuit.

Fig. 2 is the schematic diagram of another kind of typical off-line type AC-DC change-over circuit.

Fig. 3 is the schematic diagram of the off-line type AC-DC change-over circuit according to one embodiment of the invention.

Fig. 4 is the schematic diagram of the off-line type AC-DC change-over circuit according to another embodiment of the present invention.

Fig. 5 is the schematic diagram of the off-line type AC-DC change-over circuit also having an embodiment according to the present invention.

Fig. 6 is the schematic diagram of the off-line type AC-DC change-over circuit also having an embodiment according to the present invention.

Fig. 7 is a kind of example circuit diagram of sequential selection circuit shown in Fig. 3 and 4.

Fig. 8 shows the oscillogram of each coherent signal of the AC-DC of off-line type shown in Fig. 3 and 4 change-over circuit under continuous conduction mode.

Fig. 9 shows the oscillogram of each coherent signal of the AC-DC of off-line type shown in Fig. 3 and 4 change-over circuit under discontinuous conduction mode.

Figure 10 shows the oscillogram of each coherent signal of the AC-DC of off-line type shown in Fig. 5 and 6 change-over circuit under continuous conduction mode.

Figure 11 shows the oscillogram of the AC-DC of off-line type shown in Fig. 5 and 6 change-over circuit each coherent signal under discontinuous conduction mode.

Figure 12 is the schematic diagram of the off-line type AC-DC change-over circuit also having an embodiment according to the present invention.

Figure 13 is the schematic diagram of the off-line type AC-DC change-over circuit also having an embodiment according to the present invention.

Embodiment

Below by the specific embodiment of the present invention being described with reference to the drawings to set forth the present invention.But it is to be appreciated that these embodiments are only exemplary, restriction be there is no for spirit of the present invention and protection range.

In this manual, " coupling " one word to should be understood to be included between two unit the situation directly transmitting energy or signal, or indirectly transmit the situation of energy or signal through one or more Unit the 3rd, and alleged signal includes but not limited to the signal of the form of electricity, light and magnetic existence here.In addition, " comprise " and the term of " comprising " and so on represents except having the unit and step that have in the specification and in the claims directly and clearly state, technical scheme of the present invention does not get rid of the situation had not by other unit of directly or clearly stating and step yet.Moreover the such as term of " first " and " second " and so on does not represent order in time, space, size etc. of unit or numerical value and is only be used as to distinguish each unit or numerical value.

Below in conjunction with accompanying drawing, content of the present invention is further illustrated.

Fig. 3 is the schematic diagram of the off-line type AC-DC change-over circuit according to one embodiment of the invention.

As shown in Figure 3, this off-line type AC-DC change-over circuit comprises: rectifier bridge stack (being made up of diode D1, diode D2, diode D3, diode D4) and filter capacitor C1, former limit winding N1, power tube M1 and sampling resistor R1, vice-side winding N2 and filter circuit (being made up of afterflow diode D5 and filter capacitor C2), auxiliary winding N3 and filter circuit (being made up of sustained diode 6 and filter capacitor C3), output voltage feedback circuit and off-line type AC-DC control circuit 1.

See Fig. 3, off-line type AC-DC control circuit 1 comprises time division multiplexing port CS, this time division multiplexing port inputs former limit winding current sampled signal in the power tube M1 conduction period of off-line type AC-DC change-over circuit, between the power tube M1 off period, input the output voltage sampled signal of AC-DC translation circuit, realize time division multiplexing port thus and time-division sampling is carried out to the former limit winding current of AC-DC translation circuit and output voltage.

In the present embodiment, being coupled of the output of time division multiplexing port CS and the external sampling module 14 of off-line type AC-DC change-over circuit, the current sampling signal of the former limit winding N1 of the first input end input off-line type AC-DC change-over circuit of this external sampling module 14, the output voltage sampled signal of the second input input off-line type AC-DC change-over circuit of external sampling module 14.Specifically, when the M1 conducting of external power pipe, the electric current of former limit winding N1 flows through the sampling resistor R1 with former limit windings in series, the current sampling signal of former limit winding N1 can be obtained by the pressure drop on measuring resistance R1, when external power pipe M1 ends, output voltage sampled signal can be obtained by the different name terminal voltage V3 of the auxiliary winding N3 measuring off-line type AC-DC change-over circuit.

Compared with Fig. 1 and 2, the off-line type AC-DC control circuit 1 of the present embodiment also comprises overvoltage detection module 10, current limliting module 11, PWM comparator 12 and switch control module 13.But difference is that also comprising sequential selects module 15, and it comprises the input and at least two outputs that are coupled with time division multiplexing port CS.Under the control of the first control signal, sequential selects module 15 that the signals revivification being input to time division multiplexing port CS is become the first signal and secondary signal, wherein the first signal is output voltage sampled signal, it is provided to overvoltage detection module 10, and secondary signal former limit winding current sampled signal, it is provided to current limliting module 11 and PWM comparator 12, and here, the frequency of the first control signal is synchronous with the signal of power tube M1.

Fig. 4 is the schematic diagram of the off-line type AC-DC change-over circuit according to another embodiment of the present invention.

Compared with the off-line type AC-DC change-over circuit shown in Fig. 3, external sampling selects module 14 to comprise: first input end, and it connects the source electrode of external power pipe M1 and one end of resistance R1; Second input, it connects the different name end of auxiliary winding N3; Output, it connects the time division multiplexing port CS of off-line type AC-DC control circuit 1; Diode D7 and some resistance, wherein diode D7 positive pole connects the different name end of auxiliary winding N3, one end of diode D7 negative pole connecting resistance R5, some resistance comprises resistance R5 and R4, the negative pole of the one terminating diode D7 of resistance R5, another termination time division multiplexing port CS of resistance R5 and one end of resistance R4, one end of other end connecting resistance R1 of resistance R4 and the source electrode of power tube M1.

Fig. 7 is a kind of example circuit diagram of sequential selection circuit shown in Fig. 3 and 4.

Select in module 15 in the sequential shown in Fig. 7, when the first control signal is high level, controls transfer door 153 conducting, it is the first signal that the signal exported by time division multiplexing port CS exports; When the first control signal is low level, controls transfer door 154 conducting, the first signal is zero level.On the other hand, when the first control signal is input to trailing edge detection module 151, at the trailing edge of the first control signal, trailing edge detection module 151 exports a high level narrow pulse signal; When this high level narrow pulse signal is high level, controls transfer door 156 conducting, the signal of multiplexing port CS exports as secondary signal; When this high level narrow pulse signal is low level, controls transfer door 157 conducting, secondary signal is zero level.

Fig. 8 shows the oscillogram of each coherent signal of the AC-DC of off-line type shown in Fig. 3 and 4 change-over circuit under continuous conduction mode.Fig. 9 shows the oscillogram of each coherent signal of the AC-DC of off-line type shown in Fig. 3 and 4 change-over circuit under discontinuous conduction mode.

As shown in Figure 8, Figure 9, be between high period in power tube M1 signal, first signal is identical with the voltage VR1 waveform on sampling resistor R1, and within a period of time that power tube M1 signal trailing edge starts, secondary signal is identical with the positive voltage part of auxiliary winding different name end V3 waveform.

In the embodiment shown in Fig. 3 and 4, first reference voltage V REF1 of the first signal that sequential selects module 15 to export by overvoltage detection module 10 and setting compares and exports comparative result to switch control module 13, when the first signal is greater than the first reference voltage V REF1 of setting, represent output voltage overvoltage, switch control module 13, according to the cut-off signals of comparative result power output pipe M1 on port GATE, makes power tube M1 be in cut-off state.On the other hand, the secondary signal that sequential selects module to export by current limliting module 11 compares with the second reference voltage V REF2 set and exports comparative result to switch control module 13, when secondary signal is greater than the second reference voltage V REF2 of setting, represent former limit winding current overcurrent, switch control module 13, according to the cut-off signals of comparative result power output pipe on port GATE, makes power tube M1 be in cut-off state.

The output voltage error signal of the same AC-DC translation circuit being received from port FB of secondary signal that sequential selects module 15 to export by PWM comparator 12 compares and exports comparative result to switch control module 13, when secondary signal is higher than output voltage error signal, switch control module 13, according to the cut-off signals of comparative result power output pipe M1, makes power M1 pipe be in cut-off state.

The concrete operation principle of translation circuit shown in Fig. 3 and 4 is as follows:

The current rectifying and wave filtering circuit be made up of auxiliary winding N3 and the diode D5, the electric capacity C2 that are connected with N3 different name end provides the off-line type AC-DC vdd voltage of control circuit.Pass between the different name end V3 voltage of auxiliary group of winding N3 and the different name terminal voltage V2 of vice-side winding N2 is:

$\frac{V3}{V2}=\frac{n3}{n2}---\left(1\right)$

Wherein, n3 is the number of turn of auxiliary winding N3, and n2 is the number of turn of vice-side winding N2.

Between the power tube M1 off period, vice-side winding and auxiliary winding afterflow, the pass of V3 and output voltage Vo is:

$V3=\frac{n3}{n2}(\mathrm{Vo}+V_{\mathrm{FD}5})---\left(2\right)$

Wherein, V _fD5for the forward conduction voltage drop of diode D5;

The relation of the voltage Vcs that time division multiplexing port CS holds and output voltage Vo is as follows:

$\mathrm{Vcs}=(V3-V_{\mathrm{FD}7})\·\frac{R4+R1}{R5+R4+R1}=[\frac{n3}{n2}(\mathrm{Vo}+V_{\mathrm{FD}5})-V_{\mathrm{FD}7}]\·\frac{R4+R1}{R5+R4+R1}--\left(4\right)$

Wherein, V _fD7for the forward conduction voltage drop of diode D7.

Because resistance R1 is former limit winding current sampling resistor, resistance is very little compared with resistance R4, resistance R5, so above formula is reduced to:

$\mathrm{Vcs}=[\frac{n3}{n2}\mathrm{Vo}+\frac{V_{\mathrm{FD}5}-n2\·V_{\mathrm{FD}7}}{n2}]\·\frac{R4}{R5+R4}---\left(5\right)$

Visible, Vcs and output voltage Vo is linear.Now, the signals revivification of multiplexing port CS is become output voltage sampled signal and outputs to overvoltage detection module 10 by time-sequence control module 15, by comparing Vcs voltage and internal reference voltage VREF1, realizes output voltage overvoltage measuring ability.

When power tube M1 conducting, former limit winding flows through electric current, and the voltage that former limit winding current flows through resistance R1 generation is VR1, and vice-side winding different name end is negative voltage, and diode D7 oppositely ends, and time division multiplexing port CS no current flows into, and therefore Vcs voltage equals VR1.Now, the signals revivification of multiplexing port CS is become the sampled signal of former limit winding and outputs to current limliting module 11 and PWM comparator 12 by time-sequence control module 15, realizes former limit winding current sampling functions.

Fig. 5 is the schematic diagram of the off-line type AC-DC change-over circuit also having an embodiment according to the present invention.Fig. 6 is the schematic diagram of the off-line type AC-DC change-over circuit also having an embodiment according to the present invention.

As compared to the off-line type AC-DC change-over circuit shown in Fig. 3 with 4, difference is, overvoltage detection module 16, current limliting module 17 and pulse width modulation module 18 comprise gating circuit NA1, NA2, NA3 respectively, wherein, gating circuit N1 is coupling between comparator A1 and switch control module 13, gating circuit N2 is coupling between comparator A2 and switch control module 13, and gating circuit N3 is coupling between comparator A3 and switch control module 13.When power tube M1 conducting, gating circuit NA2, NA3 make the output signal of current limliting module 17 and pulse width modulation module 18 export switch control module 13 to, and when power tube M1 ends, gating circuit NA1 makes the output signal of overvoltage detection module 16 be supplied to switch control module 13.

The first reference voltage V REF1 of the voltage of time division multiplexing port CS with setting compares by overvoltage detection module 16, when the voltage of time-division multiplexing port CS is greater than the first reference voltage V REF1 of setting and when the first enable signal is effective, represent that the comparative result of the output voltage overvoltage of off-line type AC-DC change-over circuit is sent to switch control module 13, and switch control module 13 cut-off signals of power output pipe M1 on port GATE thus, make power tube M1 be in cut-off state.

The second reference voltage V REF2 of the voltage of time division multiplexing port CS with setting compares by current limliting module 17, when the voltage of time-division multiplexing port CS is greater than the second reference voltage V REF2 of setting and when the second enable signal is effective, represent that the comparative result of the former limit winding current overcurrent of off-line type AC-DC change-over circuit is sent to switch control module 13, and switch control module 13 cut-off signals of power output pipe M1 on port GATE thus, make power tube M1 be in cut-off state.

The output voltage error signal of the voltage of time division multiplexing port CS with off-line type AC-DC change-over circuit compares by PWM comparator A3, when time-division multiplexing port CS voltage higher than off-line type AC-DC change-over circuit output voltage error signal and when the second enable signal is effective, pulse width modulation module 18 exports excitation signal to switch control module 13, and switch control module 13 cut-off signals of power output pipe M1 on port GATE thus, make power tube M1 be in cut-off state.

In the embodiment shown in Fig. 5 and 6, the waveform of the first enable signal is identical with the waveform of the grid control signal of power tube M1, and the second enable signal is a high level burst pulse, produces at the trailing edge of the grid control signal of power tube M1.

Between the power switch M1 off period, as previously mentioned, Vcs and output voltage Vo is linear.Now, when the first signal is greater than the first reference voltage of setting, represents output voltage overvoltage, realize output voltage overvoltage measuring ability.At power switch M1 turn on period, as previously mentioned, Vcs voltage equals VR1.

As shown in Figure 10 and Figure 11, wherein Figure 10 is the oscillogram of each coherent signal under continuous conduction mode to the waveform of each coherent signal of the off-line type AC-DC change-over circuit shown in Fig. 5,6, and Figure 11 is the oscillogram of each coherent signal under discontinuous conduction mode.

Figure 12 is the schematic diagram of the off-line type AC-DC change-over circuit also having an embodiment according to the present invention.Figure 13 is the schematic diagram of the off-line type AC-DC change-over circuit also having an embodiment according to the present invention.

As compared to the embodiment shown in Fig. 3 with 5, difference is, current limliting module 17 and pulse width modulation module 18 are integrated and form current limliting and pulse width modulation module 19 or 20, namely adopt comparator A7 or A8 with three inputs to replace comparator A2 and A3 of previous embodiment.

In the embodiment shown in fig. 12, sequential selects the output signal of module 15 optionally to be exported to the comparator A7 of the comparator A1 of overvoltage detection module 10 and current limliting and pulse width modulation module 19, and the output voltage error signal of the second reference voltage V REF2 and off-line type AC-DC change-over circuit is also transfused to comparator A7.First reference voltage V REF1 of the first signal that sequential selects module 15 to export by overvoltage detection module 10 and setting compares and exports comparative result to switch control module 13, when the first signal is greater than the first reference voltage V REF1 of setting, represent output voltage overvoltage, switch control module 13, according to the cut-off signals of comparative result power output pipe M1 on port GATE, makes power tube M1 be in cut-off state.On the other hand, second reference voltage V REF2 of the secondary signal that sequential selects module to export by current limliting and pulse width modulation module 19 and setting and the output voltage error signal of AC-DC translation circuit compare and export comparative result to switch control module 13, when secondary signal is greater than the second reference voltage V REF2 of setting or when secondary signal is greater than output voltage error signal, switch control module 13, according to the cut-off signals of comparative result power output pipe on port GATE, makes power tube M1 be in cut-off state.

In the embodiment shown in fig. 13, overvoltage detection module 16 and current limliting and pulse width modulation module 20 comprise gating circuit NA1 and NA2 respectively, wherein, gating circuit N1 is coupling between comparator A1 and switch control module 13, and gating circuit N2 is coupling between comparator A8 and switch control module 13.When power tube M1 conducting, gating circuit NA2 makes the output signal of current limliting and pulse width modulation module 20 export switch control module 13 to, and when power tube M1 ends, gating circuit NA1 makes the output signal of overvoltage detection module 16 be supplied to switch control module 13.

The first reference voltage V REF1 of the voltage of time division multiplexing port CS with setting compares by overvoltage detection module 16, when the voltage of time-division multiplexing port CS is greater than the first reference voltage V REF1 of setting and when the first enable signal is effective, represent that the comparative result of the output voltage overvoltage of off-line type AC-DC change-over circuit is sent to switch control module 13, and switch control module 13 cut-off signals of power output pipe M1 on port GATE thus, make power tube M1 be in cut-off state.

The voltage of time division multiplexing port CS compares with the second reference voltage V REF2 of setting and the output voltage error signal of AC-DC translation circuit by current limliting and pulse width modulation module 20, when the voltage of time-division multiplexing port CS is greater than the second reference voltage V REF2 of setting or when being greater than output voltage error signal when the voltage of time-division multiplexing port CS, and when the second enable signal is effective, comparative result is sent to switch control module 13, and switch control module 13 cut-off signals of power output pipe M1 on port GATE thus, make power tube M1 be in cut-off state.

It is understood that above-described embodiment is just to explanation of the present invention, instead of limitation of the present invention, any innovation and creation do not exceeded in spirit of the present invention, include but not limited to that control principle time division multiplexing CS port of the present invention being realized overvoltage detection is applied to the fields such as other Switching Power Supply, sequential is selected to the amendment of the implementation of module, to the amendment of the implementation of outside sampling module, to the change of the local structure of circuit, to the type of components and parts or the replacement of model, and the replacement of other unsubstantialities or amendment, all fall within scope.

Claims (7)

1. an off-line type AC-DC control circuit, it generates corresponding control signal according to the current sampling signal of input and voltage sampling signal, it is characterized in that, described current sampling signal and described voltage sampling signal provide in a time multiplexed manner on single input port (CS), wherein, described off-line type AC-DC control circuit comprises overvoltage detection module (10), current limliting module (11), pulse width modulation module (12) and with described overvoltage detection module (10), described current limliting module (11), the switch control module (13) that described pulse width modulation module (12) is coupled and sequential select module (15), described sequential selects module to comprise the input and at least two outputs that are coupled with described single input port (CS), described sequential selects module (15) alternately to make output described in one of them and described current limliting module (11) and described pulse width modulation module (12) connect and make output described in another and described overvoltage detection module (10) to connect, thus provide described current sampling signal through described single input port (CS) alternately to described current limliting module (11) and pulse width modulation module (12), and provide described voltage sampling signal through described single input port (CS) to described overvoltage detection module (10).

2. off-line type AC-DC control circuit as claimed in claim 1, wherein, first reference voltage (VREF1) of described voltage sampling signal and setting compares and comparative result is exported to described switch control module (13) by described overvoltage detection module (10), if described voltage sampling signal is greater than described first reference voltage (VREF1), then described switch control module (13) exports and makes power tube (M1) be in the cut-off signals of cut-off state, second reference voltage (VREF2) of described current sampling signal and setting compares and comparative result is exported to switch control module (13) by described current limliting module (11), if described current sampling signal is greater than described second reference voltage (VREF2), then described switch control module (13) exports and makes power tube (M1) be in the cut-off signals of cut-off state, described current sampling signal and the signal inputted from described off-line type AC-DC control circuit outside compare and comparative result are exported to switch control module (13) by described pulse width modulation module (12), if described current sampling signal is greater than the signal of described outside input, then described switch control module (13) exports and makes power tube (M1) be in the cut-off signals of cut-off state.

3. an off-line type AC-DC change-over circuit, comprising:

Rectifier bridge stack (D1, D2, D3, D4);

Former limit winding (N1) be coupled with described rectifier bridge stack (D1, D2, D3, D4);

The power tube (M1) be coupled with described former limit winding (N1);

Vice-side winding (N2);

Auxiliary winding (N3);

External sampling module (14); And

Off-line type AC-DC control circuit (1), it is characterized in that generating corresponding control signal according to the current sampling signal inputted and voltage sampling signal, described current sampling signal and described voltage sampling signal are in a time multiplexed manner, thered is provided on single input port (CS) by described external sampling module (14)

Wherein, described off-line type AC-DC control circuit comprises overvoltage detection module (10), current limliting module (11), pulse width modulation module (12) and with described overvoltage detection module (10), described current limliting module (11), the switch control module (13) that described pulse width modulation module (12) is coupled and sequential select module (15), described sequential selects module to comprise the input and at least two outputs that are coupled with described single input port (CS), described sequential selects module (15) alternately to make output described in one of them and described current limliting module (11) and described pulse width modulation module (12) connect and make output described in another and described overvoltage detection module (10) to connect, thus provide described current sampling signal through described single input port (CS) to described current limliting module (11) and pulse width modulation module (12), and provide described voltage sampling signal through described single input port (CS) to described overvoltage detection module (10), the grid voltage of described power tube (M1) is controlled by described switch control module (13).

4. off-line type AC-DC change-over circuit as claimed in claim 3, wherein, in described power tube (M1) conduction period, described single input port (CS) provides described current sampling signal, and described power tube (M1) between the off period and vice-side winding and auxiliary winding afterflow time, described single input port (CS) provides voltage sampling signal.

5. off-line type AC-DC change-over circuit as claimed in claim 4, wherein, described external sampling module (14) is by when described power tube (M1) conducting, the pressure drop that the electric current detecting described former limit winding (N1) flows through on the sampling resistor (R1) of connecting with described former limit winding (N1) obtains described current sampling signal, and described external sampling module (14), by when described power tube (M1) ends, obtains described voltage sampling signal by the voltage of the different name end detecting described auxiliary winding (N3).

6. off-line type AC-DC change-over circuit as claimed in claim 4, wherein, described sequential selects module (15) also to comprise control signal input, by the alternately output providing the first control signal to realize described voltage sampling signal and described current sampling signal at this control signal input, the frequency of described first control signal is synchronous with the signal of described power tube (M1).

7. off-line type AC-DC change-over circuit as claimed in claim 4, wherein, first reference voltage (VREF1) of described voltage sampling signal and setting compares and comparative result is exported to described switch control module (13) by described overvoltage detection module (10), if described voltage sampling signal is greater than described first reference voltage (VREF1), then described switch control module (13) exports and makes power tube (M1) be in the cut-off signals of cut-off state, second reference voltage (VREF2) of described current sampling signal and setting compares and comparative result is exported to switch control module (13) by described current limliting module (11), if described current sampling signal is greater than described second reference voltage (VREF2), then described switch control module (13) exports and makes power tube (M1) be in the cut-off signals of cut-off state, described current sampling signal and the signal inputted from described off-line type AC-DC control circuit outside compare and comparative result are exported to switch control module (13) by described pulse width modulation module (12), if described current sampling signal is greater than the signal of described outside input, then described switch control module (13) exports and makes power tube (M1) be in the cut-off signals of cut-off state.