CN202978709U - Switching power supply and adaptive multi-mode control circuit thereof - Google Patents

Abstract

The utility model relates to the technical field of switching power supplies, and provides a switching power supply and an adaptive multi-mode control circuit thereof. The adaptive multi-mode control circuit is used for the switching power supply; secondary demagnetizing time and auxiliary winding voltage of a transformer T1 are detected, output voltage of the switching power supply is detected according to output voltage of an output stage rectifying filter circuit or the auxiliary winding voltage of the transformer T1, conducted current of a switching tube Q1 is sampled, and then driving pulse signals are output correspondingly according to detecting results and sample results so as to control the working state of the switching tube Q1. Thus, the adaptive multi-mode control circuit is capable of switching control mode stably, working states of the switching power supply can be changed stably, and system average efficiency is improved.

Description

A kind of Switching Power Supply and adaptive multi-mode control circuit thereof

Technical field

The utility model belongs to the switch power technology field, relates in particular to a kind of Switching Power Supply and adaptive multi-mode control circuit thereof.

Background technology

In field of switch power, the control mode of Switching Power Supply is varied, mainly is divided into pulse width modulation (PWM, Pulse Width Modulation), pulse frequency modulated (PFM, Pulse FrequencyModulation) and quasi-resonance control (QR, Quasi-Resonant).Wherein, pulse width modulation control method is in the situation that the constant purpose of exporting to reach constant voltage by output feedback signal by-pass cock duty ratio of the output frequency of control circuit.In the situation that the pulse frequency modulated control mode is constant by the maintenance ON time or the shut-in time is constant, change the output frequency of control circuit by output feedback signal, and then reach the purpose of constant voltage output; Quasi-resonance control is opened with control switch by no-voltage point or the zero-current point at sense switch two ends, and turn-offs by the output feedback signal control switch, thereby reaches the purpose of constant voltage output.

Above-mentioned three kinds of control modes respectively have pluses and minuses, and for PWM, its advantage is that control mode is simple, output ripple is little, and system's efficient when heavy duty is high, and can enter continuous conduction mode (CCM, Continuous Conduction Mode), system cost is lower; Its shortcoming is that the efficient of system when underload is lower.For PFM, when its advantage is system's underload, efficient is higher; Its shortcoming is the control mode relative complex, and output ripple is larger, and system cost is higher; For QR, its advantage is to have used the soft switch technique control switch to open (ZVS at no-voltage point, Zero Voltage Switch) or in zero-current point open (ZCS, Zero Currency Switch), can effectively reduce switching loss, improve system effectiveness, and it is tested by electromagnetic interference (EMI, Electromagnetic Interference) than being easier to; Its shortcoming is in wide input voltage range, the switching frequency excursion is very large, can make the cost of transformer increase, and consider the problem of EMI due to needs, switching frequency can't be too high, and this can seriously limit again the application of QR in the wide input voltage range system.

Consider the characteristics of above-mentioned three kinds of control modes, existing switch power supply system mixes use to above-mentioned three kinds of control modes usually, PWM/PFM control mode more commonly, it adopts pwm pattern in system in the heavy duty situation, switch to the PFM control model in system under light load condition, can learn from other's strong points to offset one's weaknesses between PWM and these two kinds of control models of PFM like this.Also have in addition the QR/PFM control mode, it adopts the QR control model in the heavy duty situation in system, adopt the PFM control model under light load condition in system.

in sum, adopt the switch power supply system of composite mode control mode for the switch power supply system of single control mode, its performance can increase, but existing multi-mode control circuit is to adopt dead load point switching mode to carry out control mode switch, namely set one or more POL switching thresholds, just switching controls pattern when reaching certain POL switching threshold, and system easily causes circuit concussion and unstable in the dead load point carries out the process of control mode switch, and system's average efficiency of reduction switch power supply system, and then affect the performance of Switching Power Supply.

The utility model content

The purpose of this utility model is to provide a kind of adaptive multi-mode control circuit of Switching Power Supply, is intended to solve multi-mode control circuit in existing switch power supply system and causes circuit concussion and unstable and make the problem of the average efficiency reduction of switch power supply system when the dead load switching point carries out control mode switch.

The utility model is to realize like this, a kind of adaptive multi-mode control circuit of Switching Power Supply, with the starting resistance R1 of Switching Power Supply, be connected in the secondary of transformer T1 and rise the dividing potential drop sampling action resistance R 2 and resistance R 3, switching tube Q1, detect the sampling resistor R of the On current of described switching tube Q1 _CSAnd the connection of output stage current rectifying and wave filtering circuit, the output of described switching tube Q1 and described sampling resistor R _CSFirst end connect, described sampling resistor R _CSThe second end ground connection, described adaptive multi-mode control circuit comprises:

Module, output feedback module, feedback processing modules, the first oscillator, the first comparator, logic processing module and switch drive module are selected in demagnetization detection module, valley point voltage detection module, signal output;

The input of described demagnetization detection module connects the common contact of described resistance R 2 and described resistance R 3, power end is connected with the second end of described resistance R 1, earth terminal ground connection, whether the secondary that described demagnetization detection module judge described transformer T1 according to the sampled voltage of described resistance R 2 and the common contact of described resistance R 3 the demagnetization end, and correspondingly exports the demagnetization detection signal according to judged result;

the first input end of described valley point voltage detection module connects the common contact of described resistance R 2 and described resistance R 3, the second input connects the output of described logic processing module, power end connects the second end of described resistance R 1, earth terminal ground connection, the drive pulse signal that described valley point voltage detection module is exported according to sampled voltage and the described logic processing module of the common contact of described resistance R 2 and described resistance R 3 judges whether the voltage of the auxiliary winding of described transformer T1 is minimum value between the switching tube Q1 off period, and correspondingly export the valley detection signal according to judged result,

Described signal output selects the first input end of module to connect the second end of described resistance R 1, control end be connected input and connect respectively the output of described demagnetization detection module and the output of described valley point voltage detection module, described signal output selects module to select the corresponding level signal of selecting of output according to described demagnetization detection signal, and described selection level signal is high level signal or described valley point voltage detection signal;

The input of described output feedback module connects the output of described output stage current rectifying and wave filtering circuit, output is connected with the input of described feedback processing modules, the first earth terminal ground connection, the second ground connection termination output, described output feedback module is exported feedback voltage to the input of described feedback processing modules according to the variation of the output voltage of described output stage current rectifying and wave filtering circuit;

The power end of described feedback processing modules connects the second end of described resistance R 1, earth terminal ground connection, described feedback processing modules produces a reference voltage to described the first comparator and described the first oscillator according to described feedback voltage, and controls the output clock variation of described the first oscillator;

The power end of described the first oscillator connects the second end of described resistance R 1, earth terminal ground connection, input connects the output of described feedback processing modules, and described the first oscillator produces corresponding clock signal according to the described reference voltage of described feedback processing modules output;

The positive power source terminal of described the first comparator, in-phase input end and inverting input connect respectively the output of the second end of described resistance R 1, described switching tube Q1 and the output of described feedback processing modules, negative power end ground connection, the described reference voltage that the sampled voltage that described the first comparator will obtain from the output of described switching tube Q1 and described feedback processing modules produce compares, and according to comparative result output pulse width modulation signal correspondingly;

The power end of described logic processing module connects the second end of described resistance R 1, the output that first input end, the second input and the 3rd input are selected the output of module, described oscillator with the output of described signal respectively be connected the output of the first comparator and be connected, earth terminal ground connection, described logic processing module carries out exporting corresponding drive pulse signal after logical process to described selection level signal, described clock signal and described pulse-width signal;

The power end of described switch drive module and input connect respectively the second end of described resistance R 1 and the output of described logic processing module, output is connected with the control end of described switching tube Q1, earth terminal ground connection, described switch drive module carries out exporting after driving force strengthens processing to described drive pulse signal, and then drive described switching tube Q1 according to the duty ratio work of described drive pulse signal, so that Switching Power Supply enters corresponding mode of operation.

Another purpose of the present utility model also is to provide a kind of Switching Power Supply, and it comprises current rectifying and wave filtering circuit, starting resistance R1, capacitor C 1, diode D1, resistance R 2, resistance R 3, transformer T1, switching tube Q1, sampling resistor R _CS, output stage current rectifying and wave filtering circuit and above-mentioned adaptive multi-mode control circuit.

The utility model also provides the adaptive multi-mode control circuit of another kind of Switching Power Supply, are connected with resistance R with the starting resistance R1 of Switching Power Supply, the resistance R 2 that is connected in the secondary of transformer T1 and plays the dividing potential drop sampling action, switching tube Q1, the sampling resistor Rcs and the output stage current rectifying and wave filtering circuit that detect the On current of described switching tube Q1 be connected, the output of described switching tube Q1 and described sampling resistor R _CSFirst end connect, described sampling resistor R _CSThe second end ground connection, described adaptive multi-mode control circuit comprises:

Module, feedback processing modules, the second oscillator, the second comparator, logic processing module and switch drive module are selected in demagnetization detection module, valley point voltage detection module, signal output;

The input of described demagnetization detection module connects the common contact of described resistance R 2 and described resistance R 3, power end is connected with the second end of described resistance R 1, earth terminal ground connection, whether the secondary that described demagnetization detection module judge described transformer T1 according to the sampled voltage of described resistance R 2 and the common contact of described resistance R 3 the demagnetization end, and correspondingly exports the demagnetization detection signal according to judged result;

the first input end of described valley point voltage detection module connects the common contact of described resistance R 2 and described resistance R 3, the second input connects the output of described logic processing module, power end connects the second end of described resistance R 1, earth terminal ground connection, the drive pulse signal that described valley point voltage detection module is exported according to sampled voltage and the described logic processing module of the common contact of described resistance R 2 and described resistance R 3 judges whether the voltage of the auxiliary winding of described transformer T1 is minimum value between the described switching tube Q1 off period, and correspondingly export the valley detection signal according to judged result,

Described signal output selects the first input end of module to connect the second end of described resistance R 1, control end be connected input and connect respectively the output of described demagnetization detection module and the output of described valley point voltage detection module, described signal output selects module to select the corresponding level signal of selecting of output according to described demagnetization detection signal, and described selection level signal is high level signal or described valley point voltage detection signal;

The power end of described feedback processing modules connects the second end of described resistance R 1, input is connected with the common contact of described resistance R 3 with described resistance R 2, earth terminal ground connection, described feedback processing modules detects according to the sampled voltage of described resistance R 2 and the common contact of described resistance R 3 output voltage to described output stage current rectifying and wave filtering circuit, and follows testing result and correspondingly export feedback voltage;

The input of described the second oscillator connects the output of described feedback processing modules, and described the second oscillator is according to the corresponding clock signal of described feedback voltage output;

The positive power source terminal of described the second comparator, in-phase input end and inverting input connect respectively the output of the second end of described resistance R 1, described switching tube Q1 and the output of described feedback processing modules, negative power end ground connection, described the second comparator compares with described feedback voltage with from the sampled voltage that the output of described switching tube Q1 obtains, and according to comparative result output pulse width modulation signal correspondingly;

The power end of described logic processing module connects the second end of described resistance R 1, the output that first input end, the second input and the 3rd input are selected the output of module, described the second oscillator with the output of described signal respectively be connected the output of the second comparator and be connected, earth terminal ground connection, described logic processing module carries out exporting corresponding drive pulse signal after logical process to described selection level signal, described clock signal and described pulse-width signal;

The power end of described switch drive module and input connect respectively the second end of described resistance R 1 and the output of described logic processing module, output is connected with the control end of described switching tube Q1, earth terminal ground connection, described switch drive module carries out exporting after driving force strengthens processing to described drive pulse signal, and then drive described switching tube Q1 according to the duty ratio work of described drive pulse signal, so that Switching Power Supply enters corresponding mode of operation.

Another purpose of the present utility model also is to provide another kind of Switching Power Supply, and it comprises current rectifying and wave filtering circuit, starting resistance R1, capacitor C 1, diode D1, resistance R 2, resistance R 3, transformer T1, switching tube Q1, sampling resistor R _CS, output stage current rectifying and wave filtering circuit and above-mentioned adaptive multi-mode control circuit.

the utility model is by adopting described adaptive multi-mode control circuit in Switching Power Supply, detect by secondary erasing time and auxiliary winding voltage to transformer T1, and detect according to the auxiliary winding voltage of the output voltage of output stage current rectifying and wave filtering circuit or the transformer T1 output voltage to Switching Power Supply, and to the On current of switching tube Q1 sample (namely the output end voltage of switching tube Q1 being sampled), then correspondingly export the operating state of drive pulse signal control switch pipe Q1 according to testing result and On current sampled result, and then to make described adaptive multi-mode control circuit can stablize the switching controls pattern (be PWM, PFM or QR), and stably conversion mode of operation of Switching Power Supply, improved system's average efficiency, thereby solved multi-mode control circuit in existing switch power supply system and caused circuit concussion and unstable and make the problem of the average efficiency reduction of switch power supply system when the dead load switching point carries out control mode switch.

Description of drawings

Fig. 1 is the modular structure figure of the adaptive multi-mode control circuit of the Switching Power Supply that provides of the utility model the first embodiment;

Fig. 2 is the exemplary circuit structure chart of the adaptive multi-mode control circuit of the Switching Power Supply that provides of the utility model the first embodiment;

Fig. 3 is the structural representation of the related adaptive multi-mode control chip of the utility model the first embodiment;

Fig. 4 is the related signal waveforms of operation principle of the adaptive multi-mode control circuit of the Switching Power Supply that provides of the utility model the first embodiment;

Fig. 5 is the modular structure figure of the adaptive multi-mode control circuit of the Switching Power Supply that provides of the utility model the second embodiment;

Fig. 6 is the exemplary circuit structure chart of the adaptive multi-mode control circuit of the Switching Power Supply that provides of the utility model the second embodiment;

Fig. 7 is the structural representation of the related adaptive multi-mode control chip of the utility model the second embodiment;

Fig. 8 is the related signal waveforms of operation principle of the adaptive multi-mode control circuit of the Switching Power Supply that provides of the utility model the second embodiment.

Embodiment

In order to make the purpose of this utility model, technical scheme and advantage clearer, below in conjunction with drawings and Examples, the utility model is further elaborated.Should be appreciated that specific embodiment described herein only in order to explaining the utility model, and be not used in restriction the utility model.

the utility model embodiment is by adopting the adaptive multi-mode control circuit in Switching Power Supply, detect by secondary erasing time and auxiliary winding voltage to transformer T1, and detect according to the auxiliary winding voltage of the output voltage of output stage current rectifying and wave filtering circuit or the transformer T1 output voltage to Switching Power Supply, and to the On current of switching tube Q1 sample (namely the output end voltage of switching tube Q1 being sampled), then correspondingly export the operating state of drive pulse signal control switch pipe Q1 according to testing result and On current sampled result, and then to make the adaptive multi-mode control circuit can stablize the switching controls pattern (be PWM, PFM or QR), and stably conversion mode of operation of Switching Power Supply, improved system's average efficiency.

The adaptive multi-mode control circuit of the Switching Power Supply that the utility model embodiment is provided below in conjunction with specific embodiment is elaborated:

Embodiment one:

Fig. 1 shows the modular structure of the adaptive multi-mode control circuit of the Switching Power Supply that the utility model the first embodiment provides, and for convenience of explanation, only shows the part relevant to the utility model, and details are as follows:

The Switching Power Supply that the present embodiment provides comprises current rectifying and wave filtering circuit 100, starting resistance R1, capacitor C 1, diode D1, resistance R 2, resistance R 3, transformer T1, switching tube Q1, sampling resistor Rcs, output stage current rectifying and wave filtering circuit 200 and adaptive multi-mode control circuit 300.Wherein, 100 couples of input AC electricity Vac of current rectifying and wave filtering circuit carry out rectifying and wave-filtering to be processed, and it comprises rectifier bridge BD and filter capacitor C2; Switching tube Q1 is the NMOS pipe, and the grid of NMOS pipe, drain electrode and source electrode are respectively control end, input and the output of switching tube Q1; The output DC of 200 couples of transformer T1 of output stage current rectifying and wave filtering circuit carries out rectifying and wave-filtering to be processed, and it comprises rectifier diode D2 and filter capacitor C3.In addition, Switching Power Supply also comprises adaptive multi-mode control circuit 300.

The sampling resistor R of the On current of the resistance R 2 of the starting resistance R1 of adaptive multi-mode control circuit 300 and Switching Power Supply, the auxiliary winding that is connected in transformer T1 and a dividing potential drop sampling action and resistance R 3, switching tube Q1, sense switch pipe Q1 _CSAnd the connection of output stage current rectifying and wave filtering circuit, the output of switching tube Q1 and sampling resistor R _CSFirst end connect, sampling resistor R _CSThe second end ground connection, adaptive multi-mode control circuit 300 comprises:

Module 303, output feedback module 304, feedback processing modules 305, the first oscillator OSC1, the first comparator U1, logic processing module 306 and switch drive module 307 are selected in demagnetization detection module 301, valley point voltage detection module 302, signal output.

The input contact resistance R2 of demagnetization detection module 301 and the common contact of resistance R 3, power end is connected with the second end of resistance R 1, earth terminal ground connection, whether the secondary that demagnetization detection module 301 judge transformer T1 according to the sampled voltage of resistance R 2 and the common contact of resistance R 3 the demagnetization end, and correspondingly exports the demagnetization detection signal according to judged result.

The first input end of valley point voltage detection module 302 connects the common contact of described resistance R 2 and described resistance R 3, the second input connects the output of logic processing module 306, the second end of power end contact resistance R1, earth terminal ground connection, the drive pulse signal that valley point voltage detection module 302 is exported according to sampled voltage and the logic processing module 306 of the common contact of resistance R 2 and resistance R 3 judges whether the voltage of the auxiliary winding of transformer T1 is minimum value between the switching tube Q1 off period, and correspondingly exports the valley detection signal according to judged result.

The second end of the first input end connecting resistance R1 of module 303 is selected in signal output, control end be connected input and connect respectively the output of demagnetization detection module 301 and the output of valley point voltage detection module 302, signal output selects module 303 to select the corresponding level signal of selecting of output according to described demagnetization detection signal, and this selection level signal is high level signal or described valley point voltage detection signal.

The input of output feedback module 304 connects the output of output stage current rectifying and wave filtering circuit 200, output is connected with the input of feedback processing modules 305, the first earth terminal ground connection, the second ground connection termination output, output feedback module 304 is exported feedback voltage to the input of feedback processing modules 305 according to the variation of the output voltage of output stage current rectifying and wave filtering circuit 200.The second end of the power end contact resistance R1 of feedback processing modules 305, earth terminal ground connection, the feedback voltage of exporting according to output feedback module 304 produces reference voltage to the first a comparator U1 and the first oscillator OSC1, and controls the output clock variation of the first oscillator OSC1.

The second end of the power end connecting resistance R1 of the first oscillator OSC1, earth terminal ground connection, input connects the output of feedback processing modules 305, and the first oscillator OSC1 produces corresponding clock signal according to the reference voltage of feedback processing modules 305 outputs.

The positive power source terminal of the first comparator U1, in-phase input end and inverting input connect respectively the output of the second end of described resistance R 1, described switching tube Q1 and the output of feedback processing modules 305, negative power end ground connection, the reference voltage that the sampled voltage that the first comparator U1 will obtain from the output of switching tube Q1 and feedback processing modules 305 produces compares, and according to comparative result output pulse width modulation signal correspondingly.

The second end of the power end contact resistance R1 of logic processing module 306, first input end, the second input and the 3rd input respectively with signal output select module 303 output, oscillator OSC1 output be connected the output of comparator U1 and be connected, earth terminal ground connection, logic processing module 306 pairs of described selection level signals, described clock signal and described pulse-width signals carry out exporting corresponding drive pulse signal after logical process.

The second end of the power end of switch drive module 307 and input difference contact resistance R1 and the output of logic processing module 306, output is connected with the control end of switching tube Q1, earth terminal ground connection, the drive pulse signal that 307 pairs of logic processing module 306 of switch drive module are exported carries out exporting after driving force strengthens processing, and then driving switch pipe Q1 is according to the duty ratio work of this drive pulse signal, so that Switching Power Supply enters corresponding mode of operation.

Fig. 2 illustrates the exemplary circuit structure of adaptive multi-mode control circuit shown in Figure 1, for convenience of explanation, only shows the part relevant to the utility model, and details are as follows:

Demagnetization detection module 301 comprises:

The 3rd comparator U3, the first reference voltage source 3011, PMOS pipe Q2, NMOS pipe Q3, the first current source I1, capacitor C 4 and the first Schmidt trigger S1;

the in-phase input end of the 3rd comparator U3, positive power source terminal and negative power end are respectively the input of demagnetization detection module 301, power end and earth terminal, the output of the first reference voltage source 3011 connects the inverting input of the 3rd comparator U3, the grid of the grid of PMOS pipe Q2 and NMOS pipe Q3 is connected to the output of the 3rd comparator U3 altogether, the source electrode of PMOS pipe Q2 connects the positive power source terminal of the 3rd comparator U3, the drain electrode of the drain electrode of NMOS pipe Q3 and PMOS pipe Q2 and the first end of capacitor C 4 are connected to the input of the first Schmidt trigger S1 altogether, the source electrode of NMOS pipe Q3 connects the input of the first current source I1, the second end of the output of the first current source I1 and capacitor C 4 and the negative power end of the first Schmidt trigger S1 are connected to the negative power end of the 3rd comparator U3 altogether, the positive power source terminal of the first Schmidt trigger S1 connects the positive power source terminal of the 3rd comparator U3, the output of the first Schmidt trigger S1 is the output of demagnetization detection module 301.Wherein, the first reference voltage source 3011 is generating circuit from reference voltage of commonly using, and the reference voltage of its output is 50mV.Wherein PMOS pipe Q2, NMOS pipe Q3, the first current source I1, capacitor C 4 and the first Schmidt trigger S1 form filter circuit 3012.

Valley point voltage detection module 302 comprises:

The 4th comparator U4, the second reference voltage source 3021, the first inverter U5, the first delay circuit 3022 and first and door U6;

the inverting input of the 4th comparator U4, positive power source terminal and negative power end are respectively the first input end of valley point voltage detection module 302, power end and earth terminal, the output of the second reference voltage source 3021 connects the in-phase input end of the 4th comparator U4, the input of the first inverter U5 is the second input of valley point voltage detection module 302, the output of the first inverter U5 connects the input of the first delay circuit 3022, first with the first input end 1 of door U6 be connected input 2 and be connected respectively the output of the 4th comparator U4 and the output of the first delay circuit 3022, first with the door U6 output 5 be the output of valley point voltage detection module 302, the positive power source terminal of the first inverter U5 and first and the positive power source terminal 3 of door U6 be connected to altogether the positive power source terminal of the 4th comparator U4, the negative power end of the first inverter U5 and first and the negative power end 4 of door U6 be connected to altogether the negative power end of the 4th comparator U4.Wherein, the second reference voltage source 3021 is generating circuit from reference voltage of commonly using, and the reference voltage of its output is 50mV; The first delay circuit 3022 can be made of odd number delayer or even number delayer.

Signal output selects module 303 to comprise NMOS pipe Q4 and PMOS pipe Q5, the source electrode of the drain electrode of NMOS pipe Q4 and PMOS pipe Q5 is respectively first input end and the second input that module 303 is selected in signal output, the common contact of the grid of the grid of NMOS pipe Q4 and PMOS pipe Q5 is exported the control end of selecting module 303 as signal, the common contact of the drain electrode of the source electrode of NMOS pipe Q4 and PMOS pipe Q5 is as the output of signal output selection module 303.

Output feedback module 304 comprises:

Resistance R 4, optocoupler U7, capacitor C 5, resistance R 5, resistance R 6 and 431 a reference source TL;

the first end of resistance R 4 is the input of output feedback module 304, the second end of resistance R 4 connects the anode of the light-emitting diode of optocoupler U7, the negative electrode of the first end of capacitor C 5 and 431 a reference source TL is connected to the negative electrode of the light-emitting diode of optocoupler U7 altogether, the collector and emitter of the phototriode of optocoupler U7 is respectively output and first earth terminal of output feedback module 304, the second end of capacitor C 5 and the first end of resistance R 5 are connected to the first end of resistance R 4 altogether, the second end of resistance R 5 and the first end of resistance R 6 are connected to the adjustment utmost point of 431 a reference source TL altogether, the common contact of the second end of resistance R 6 and the anode of 431 a reference source TL is as the second earth terminal of output feedback module 304.

Feedback processing modules 305 comprises:

The second current source I2, diode D3, resistance R 7 and resistance R 8;

The input of the second current source I2 is the power end of feedback processing modules 305, the output of the second current source I2 connects the anode of diode D3, the anode of diode D3 is the input of feedback processing modules 305, the first end of resistance R 7 connects the negative electrode of diode D3, the common contact of the second end of resistance R 7 and the first end of resistance R 8 is as the output of feedback processing modules, and the second end of resistance R 8 is the earth terminal of feedback processing modules 305.

Logic processing module 306 comprise second with door U8 and rest-set flip-flop TRIG, second is respectively first input end, the second input, power end and the earth terminal of logic processing module 306 with first input end 1, the second input 2, positive power source terminal 3 and the negative power end 4 of door U8, second is connected the first input end S of rest-set flip-flop TRIG, the 3rd input and output that the second input R of rest-set flip-flop TRIG and output Q are respectively logic processing module 306 with the output 5 of door U8.Wherein, the basic rest-set flip-flop that formed by basic NOR gate of rest-set flip-flop TRIG.

Switch drive module 307 comprises the 3rd inverter U9 and the 4th inverter U10, the input of the 3rd inverter U9, positive power source terminal and negative power end are respectively input, power end and the earth terminal of switch drive module 307, the output of the 3rd inverter U9 connects the input of the 4th inverter U10, the positive power source terminal of the 4th inverter U10 and negative power end connect respectively positive power source terminal and the negative power end of the 3rd inverter U9, and the output of the 4th inverter U10 is the output of switch drive module 307.

in actual application, in order to improve the integrated level of circuit, as shown in Figure 3, demagnetization detection module 301, valley point voltage detection module 302, module 303 is selected in signal output, feedback processing modules 305, the first oscillator OSC1, the first comparator U1, logic processing module 306 and switch drive module 307 can be integrated into an adaptive multi-mode control chip, the power end of the power end of demagnetization detection module 301 and valley point voltage detection module 302, the first input end of module 303 is selected in signal output, the power end of feedback processing modules 305, the power end of the first oscillator OSC1, the positive power source terminal of the first comparator U1, the common contact of the power end of the power end of logic processing module 306 and switch drive module 307 is as the power end VDD of adaptive multi-mode control chip, the common contact of the first input end of the input of demagnetization detection module 301 and valley point voltage detection module 302 is as the secondary test side DEM of adaptive multi-mode control chip, the input of feedback processing modules 305 is simultaneously also as the feedback end FB of adaptive multi-mode control chip, the in-phase input end of the first comparator U1 is as the On current sampling end CS of adaptive multi-mode control chip, the output of switch drive module 307 is as the switch control end GATE of adaptive multi-mode control chip, the earth terminal of the earth terminal of demagnetization detection module 301 and valley point voltage detection module 302, the earth terminal of feedback processing modules 305, the earth terminal of the first oscillator OSC1, the negative power end of the first comparator U1, the common contact of the earth terminal of the earth terminal of logic processing module 306 and switch drive module 307 is as the earth terminal GND of adaptive multi-mode control chip.

Below in conjunction with operation principle, above-mentioned adaptive multi-mode control circuit 300 is described further:

When the output loading of Switching Power Supply was heavier, the first oscillator OSC1 can export a clock signal with fixed frequency.The 4th comparator U4 of valley point voltage detection module 302 compares rear output comparison signal to the first and door U6 by resistance R 2 and the sampled voltage of the common contact of resistance R 3 and the output voltage of the second reference voltage source 3021, the output signal of logic processing module 306 is carried out anti-phase processing and the first delay circuit 3022 by the first phase inverter U5 and is carried out input first and a door U6 after delay process, first with door U6 to the output signal of described comparison signal and the logic processing module after anti-phase delay process 306 carry out with logical process after resulting output signal as the output signal (being the valley detection signal) of valley point voltage detection module 302.

When the rising edge (or being set as trailing edge) of clock signal arrives, if it is low level (secondary (auxiliary winding signal is the equal proportion convergent-divergent of secondary secondary winding signal) the demagnetization end of transformer T1 namely being detected) after filter circuit 3012 that the sampled voltage of the common contact of resistance R 2 and resistance R 3 and the output voltage of the first reference voltage source 3011 compare the level of rear output, the first Schmidt trigger S1 in demagnetization detection module 301 can output low level make NMOS manage Q4 shutoff and PMOS pipe Q5 conducting; Wait for the minimum value (also referred to as secondary no-voltage point) in secondary secondary winding voltage that valley point voltage detection module 302 detects transformer T1 is between the switching tube Q1 off period, namely first manage Q5 to logic processing module 306 with door U6 output high level by PMOS, and open by switch drive module 307 control switch pipe Q1 conductings.Along with switching tube Q1 conducting is opened, On current increases, the source voltage of switching tube Q1 can increase gradually, when reaching the output end voltage of feedback processing modules 305, relatively export high level signal through the first comparator U1, make the output level upset of rest-set flip-flop TRIG be low level, this low level is closed cut-off through switch drive module 307 control switch pipe Q1.At this moment, adaptive multi-mode control circuit 300 enters the QR control model, and Switching Power Supply is operated in critical conduction mode (BCM, BoundaryConduction Mode) or discontinuous conduction mode (DCM, Discontinuous Conduction Mode), also claim discontinuous mode.

when if the rising edge of clock signal (or being set as trailing edge) arrives, resistance R 2 is high level (the also not demagnetization end of secondary of transformer T1 namely being detected) with the sampled voltage of the common contact of resistance R 3 and the level of relatively exporting of the first reference voltage source 3011 after filter circuit 3012, the first Schmidt trigger S1 in demagnetization detection module 301 can export high level and make NMOS pipe Q4 conducting and PMOS pipe Q5 shutoff, signal output this moment selects module 303 directly to manage Q4 output high level to logic processing module 306 by NMOS, and open by switch drive module 307 control switch pipe Q1 conductings.Along with switching tube Q1 conducting is opened, On current increases, the source voltage of switching tube Q1 can increase gradually, when reaching the output end voltage of feedback processing modules 305, relatively export high level signal through the first comparator U1, this high level signal makes the output level upset of rest-set flip-flop TRIG be low level, and this low level is closed cut-off through switch drive module 307 control switch pipe Q1.At this moment, adaptive multi-mode control circuit 300 enters pwm pattern, and Switching Power Supply enters continuous conduction mode (CCM).

When Switching Power Supply is operated in discontinuous conduction mode or critical conduction mode, the ON time T of switching tube Q1 _onBe shown below:

$T_{\mathrm{on}}=\frac{L_P\×I_{\mathrm{PK}}}{\mathrm{Vin}}---\left(1\right)$

The secondary erasing time T of transformer T1 _DBe shown below:

$T_D=\frac{L_S\·N\·I_{\mathrm{PK}}}{\mathrm{Vout}}---\left(2\right)$

Wherein, L _PAnd L _SBe respectively the inductance value on former limit (being armature winding) of transformer T1 and the inductance value of secondary (being secondary winding), N is the turn ratio of the former limit of transformer T1 and secondary, I _PKBe the former limit peak current (that is to say the conducting peak current of switching tube Q1) of transformer T1, Vin and Vout are respectively input voltage and the output voltage of transformer T1.

By relational expression (1) and (2) as can be known, when the system parameters of Switching Power Supply keeps one regularly, the inductance value of transformer T1, turn ratio etc. remain unchanged, the ON time T of switching tube Q1 _onOnly by the former limit peak current I of transformer T1 _PKDetermine secondary erasing time T with the ratio of input voltage vin _DOnly by former limit peak current I _PKDetermine with output voltage V out.And former limit peak current I _PKDetect output voltage V out by output feedback module 304, and the collector electrode of the phototriode by optocoupler U7 makes, and the anode voltage FB of diode D3 and Vout's change in the opposite direction to regulate former limit peak current I _PK, namely output voltage V out increases, the anode voltage of diode D3 (being feedback voltage) V _FBReduce former limit peak current I _PKReduce.

Hence one can see that, when Switching Power Supply is operated in above-mentioned discontinuous conduction mode, the control model of adaptive multi-mode control circuit 300 is the QR control model at this moment, by the unlatching of the secondary zero voltage signal co-controlling switching tube Q1 of the clock signal of the first oscillator OSC1 output and transformer T1 (with respect to switch periods, the time difference of the rising edge of clock signal and secondary zero voltage signal is less), the approximate clock frequency that is equal to the first oscillator OSC1 of switching frequency.If output loading is constant, input voltage vin reduces, and ON time Ton increases, and this moment, output voltage temporarily remained unchanged, feedback voltage V because output loading does not change _FBConstant, former limit peak current I _PKRemain unchanged, therefore secondary erasing time T _DConstant; Switch periods T=T due to switching tube Q1 this moment _on+ T _offApproximate be equal to the clock cycle of the first oscillator OSC1 and remain unchanged, ON time Ton increase can cause turn-off time T _offReduce, work as T _offBe reduced to and T _DWhen equating, Switching Power Supply enters critical conduction mode, and meanwhile, adaptive multi-mode control circuit 300 still is in the QR control model; When input voltage vin continues to reduce and make T _on+ T _DDuring T (when the rising edge of clock signal or trailing edge arrived, the demagnetization not yet of transformer T1 finished), adaptive multi-mode control circuit 300 enters pwm pattern, Switching Power Supply also enters continuous conduction mode simultaneously.

Equally, in the situation that input voltage vin is constant, if the output loading of Switching Power Supply increases, output voltage V out reduces, feedback voltage V _FBIncrease former limit peak current I _PKIncrease, ON time Ton increases, secondary erasing time T _DIncrease, also T can occur _on+ T _DThe situation of T, adaptive multi-mode control circuit 300 enters the PWM pattern, and Switching Power Supply enters continuous conduction mode.

When input voltage vin and output loading change simultaneously, equally can be by with upper type, the control model of adaptive multi-mode control circuit 300 being regulated, and this adjustment process is to be undertaken by the system load situation of real-time sense switch power supply, do not need to arrange the dead load mode switch points, system's adjustment is more flexible.

When output loading is reduced to certain limit, feedback voltage V _FBThe clock signal frequency of controlling the first oscillator OSC1 is reduced, by the concrete condition that detects output loading, adaptive multi-mode control circuit 300 is carried out control model and regulate.Due to the duty ratio lower (for example fully loaded half) of this moment, former limit peak current I _PKAlso smaller, ON time T _onWith secondary erasing time T _DLess all, and switch periods T has increased, therefore T〉T _on+ T _DSwitching Power Supply can be operated in discontinuous conduction mode, the mixing control model that in fact adaptive multi-mode control circuit 300 was in PFM and QR and deposited this moment, the switching frequency of PFM control model assurance switching tube Q1 is adjusted with the variation of output loading, the QR control model guarantees that the each conducting unlatching of switching tube Q1 is all the secondary no-voltage point moment at transformer T1, so just can reduce the switching loss of switching tube Q1.Switching Power Supply is in this operating state, and adaptive multi-mode control circuit 300 changes the ON time T of switching tube Q1 by the variation of the secondary detection output loading of transformer T1 _onWith switch periods T, realize the output of Switching Power Supply constant voltage, and improved the system effectiveness of Switching Power Supply.

When output loading continues to be reduced to very low scope (as fully loaded 5%), by anode voltage (the being feedback voltage) V of 304 couples of diode D3 of output feedback module _FBControl, adaptive multi-mode control circuit 300 control switch pipe Q1 are so that Switching Power Supply enters burst mode, work as feedback voltage V that is: _FBWhen being reduced to certain value, closing switch pipe Q1 is along with the consumption of Switching Power Supply output energy, feedback voltage V _FBCan again increase, when it reached certain value, control switch pipe Q1 realized high-frequency break-make again, made the system power dissipation of Switching Power Supply be reduced to minimum value.

The sampled voltage V of adaptive multi-mode control circuit 300 related resistance R 2 and common contact of resistance R 3 in above-mentioned different control model _DEM, switching tube Q1 source voltage V _CS, the pulse signal S that exports of the clock signal C LOCK that exports of the first oscillator OSC1 and switch drive module 307 _GATEOscillogram as shown in Figure 4.

The present embodiment also provides a kind of Switching Power Supply, and it comprises current rectifying and wave filtering circuit 100, starting resistance R1, capacitor C 1, diode D1, resistance R 2, resistance R 3, transformer T1, switching tube Q1, sampling resistor R _CS, output stage current rectifying and wave filtering circuit 200 and above-mentioned adaptive multi-mode control circuit 300.

Embodiment two:

Fig. 5 shows the modular structure of the adaptive multi-mode control circuit of the Switching Power Supply that the utility model the second embodiment provides, and for convenience of explanation, only shows the part relevant to the utility model, and details are as follows:

Related the same of the Switching Power Supply that the present embodiment provides and the utility model the first embodiment comprises current rectifying and wave filtering circuit 100, starting resistance R1, capacitor C 1, diode D1, resistance R 2, resistance R 3, transformer T1, switching tube Q1, sampling resistor Rcs, output stage current rectifying and wave filtering circuit 200 and adaptive multi-mode control circuit 300 equally.Wherein, 100 couples of input AC electricity Vac of current rectifying and wave filtering circuit carry out rectifying and wave-filtering to be processed, and it comprises rectifier bridge BD and filter capacitor C2; Switching tube Q1 is the NMOS pipe, and the grid of NMOS pipe, drain electrode and source electrode are respectively control end, input and the output of switching tube Q1; The output DC of 200 couples of transformer T1 of output stage current rectifying and wave filtering circuit carries out rectifying and wave-filtering to be processed, and it comprises rectifier diode D2 and filter capacitor C3.In addition, Switching Power Supply also comprises adaptive multi-mode control circuit 400.

The sampling resistor R of the On current of the resistance R 2 of the starting resistance R1 of adaptive multi-mode control circuit 400 and Switching Power Supply, the secondary that is connected in transformer T1 and a dividing potential drop sampling action and resistance R 3, switching tube Q1, sense switch pipe Q1 _CSAnd the connection of output stage current rectifying and wave filtering circuit, the output of switching tube Q1 and sampling resistor R _CSFirst end connect, sampling resistor R _CSThe second end ground connection, adaptive multi-mode control circuit 400 comprises:

Module 403, feedback processing modules 404, the second oscillator OSC2, the second comparator U2, logic processing module 405 and switch drive module 406 are selected in demagnetization detection module 401, valley point voltage detection module 402, signal output;

The input contact resistance R2 of demagnetization detection module 401 and the common contact of described resistance R 3, power end is connected with the second end of resistance R 1, earth terminal ground connection, whether the secondary that demagnetization detection module 401 judge transformer T1 according to the sampled voltage of resistance R 2 and the common contact of resistance R 3 the demagnetization end, and correspondingly exports the demagnetization detection signal according to judged result;

The first input end contact resistance R2 of valley point voltage detection module 402 and the common contact of resistance R 3, the second input connects the output of logic processing module 405, the second end of power end contact resistance R1, earth terminal ground connection, the drive pulse signal that valley point voltage detection module 402 is exported according to sampled voltage and the logic processing module 405 of the common contact of resistance R 2 and resistance R 3 judges whether the voltage of the auxiliary winding of transformer T1 is minimum value between the switching tube Q1 off period, and correspondingly exports the valley detection signal according to judged result;

The second end of the first input end connecting resistance R1 of module 403 is selected in signal output, control end be connected input and connect respectively the output of demagnetization detection module 401 and the output of valley point voltage detection module 402, signal output selects module 403 to select the corresponding level signal of selecting of output according to described demagnetization detection signal, and this selection level signal is high level signal or described valley point voltage detection signal;

The second end of the power end contact resistance R1 of feedback processing modules 404, input is connected with the common contact of resistance R 3 with resistance R 2, earth terminal ground connection, feedback processing modules 404 detects according to the sampled voltage of resistance R 2 and the common contact of resistance R 3 output voltage to output stage current rectifying and wave filtering circuit 200, and follows testing result and correspondingly export feedback voltage;

The second end of the power end contact resistance R1 of the second oscillator OSC2, earth terminal ground connection, input connects the output of feedback processing modules 404, and the second oscillator OSC2 is according to the corresponding clock signal of described feedback voltage output;

The positive power source terminal of the second comparator U2, in-phase input end and inverting input be the second end, the output of switching tube Q1 and the output of feedback processing modules 404 of contact resistance R1 respectively, negative power end ground connection, the second comparator U2 compares to described feedback voltage with from the sampled voltage that the output of switching tube Q1 obtains, and according to comparative result output pulse width modulation signal correspondingly;

The second end of the power end contact resistance R1 of logic processing module 405, first input end, the second input and the 3rd input respectively with signal output select module 403 output, the second oscillator OSC2 output be connected the output of comparator U2 and be connected, earth terminal ground connection, logic processing module 405 pairs of described selection level signals, described clock signal and described pulse-width signals carry out exporting corresponding drive pulse signal after logical process;

The second end of the power end of switch drive module 406 and input difference contact resistance R1 and the output of logic processing module 405, output is connected with the control end of switching tube Q1, earth terminal ground connection, the drive pulse signal that 406 pairs of logic processing module 405 of switch drive module are exported carries out exporting after driving force strengthens processing, and then driving switch pipe Q1 is according to the duty ratio work of this drive pulse signal, so that Switching Power Supply enters corresponding mode of operation.

Fig. 6 illustrates the exemplary circuit structure of adaptive multi-mode control circuit shown in Figure 5, for convenience of explanation, only shows the part relevant to the utility model, and details are as follows:

Because demagnetization detection module 401, valley point voltage detection module 402, signal output that the present embodiment provides select the internal structure of module 403, logic processing module 405 and switch drive module 406 to select module 303, logic processing module 306 and switch drive module 307 identical with demagnetization detection module 301, valley point voltage detection module 302, signal output that the utility model the first embodiment provides respectively, therefore repeat no more.

In the present embodiment, feedback processing modules 404 comprises:

The 5th comparator U11, the 3rd reference voltage source 4041, PMOS pipe Q6, NMOS pipe Q7, the 3rd current source I3, capacitor C 6, the second Schmidt trigger S2, the second delay circuit 4042, the 3rd are managed Q8, capacitor C 7, error amplifier U14, reference voltage source 4043 and capacitor C 8 with door U13, NMOS;

the common contact of the source electrode of the in-phase input end of the 5th comparator U11 and NMOS pipe Q8 is as the input of feedback processing modules 404, the positive power source terminal of the 5th comparator U11 and negative power end are respectively power end and the earth terminal of feedback processing modules 404, the output of the 3rd reference voltage source 4041 connects the inverting input of the 5th comparator U11, the grid of the grid of PMOS pipe Q6 and NMOS pipe Q7 is connected to the output of the 5th comparator U11 altogether, the source electrode of NMOS pipe Q7 connects the input of the 3rd current source I3, the source electrode of PMOS pipe Q6 and the output of the 3rd current source I3 connect respectively positive power source terminal and the negative power end of the 5th comparator U11, the drain electrode of the drain electrode of PMOS pipe Q6 and NMOS pipe Q7 is connected to the input of the second Schmidt trigger S2 altogether, capacitor C 6 is connected between the negative power end of the input of the second Schmidt trigger S2 and the 5th comparator U11, the positive power source terminal of the second Schmidt trigger S2 and negative power end connect respectively positive power source terminal and the negative power end of the 5th comparator U11, the input of the second delay circuit 4042 and the 3rd is connected to the output of the second Schmidt trigger S2 altogether with the second input 2 of door U13, the 3rd is connected the output of the second delay circuit 4042 with the first input end 1 of door U13, the 3rd is connected with the positive power source terminal 3 of door U13 positive power source terminal and the negative power end that is connected respectively the 5th comparator U11 with negative power end, the grid of NMOS pipe Q8 and be connected connects respectively the 3rd and the output 5 of a U13 and the in-phase input end of error amplifier U14, the in-phase input end of the first termination error amplifier U14 of capacitor C 7, the positive power source terminal of positive supply termination the 5th comparator U11 of error amplifier U14, the second end of capacitor C 7 and the negative power end of error amplifier U14 are connected to the negative power end of the 5th comparator U11 altogether, the output of reference voltage source 4043 connects the inverting input of error amplifier U14, the output of error amplifier U14 is the output of feedback processing modules 404, capacitor C 8 is connected between the negative power end of the output of error amplifier U14 and the 5th comparator U11.

in actual application, in order to improve the integrated level of circuit, as shown in Figure 7, demagnetization detection module 401, valley point voltage detection module 402, module 403 is selected in signal output, feedback processing modules 404, the second oscillator OSC2, the second comparator U2, logic processing module 405 and switch drive module 406 can be integrated into an adaptive multi-mode control chip, the power end of the power end of demagnetization detection module 401 and valley point voltage detection module 402, the first input end of module 403 is selected in signal output, the power end of feedback processing modules 404, the positive power source terminal of the second comparator U2, the common contact of the power end of the power end of logic processing module 405 and switch drive module 406 is as the power end VDD of adaptive multi-mode control chip, the common contact of the input of the first input end of the input of demagnetization detection module 401 and valley point voltage detection module 402 and feedback processing modules 404 is as the secondary test side DEM of adaptive multi-mode control chip, the in-phase input end of the second comparator U2 is as the current sample end CS of adaptive multi-mode control chip, the output of switch drive module 406 is as the switch control end GATE of adaptive multi-mode control chip, the earth terminal of the earth terminal of demagnetization detection module 401 and valley point voltage detection module 402, the earth terminal of feedback processing modules 404, the earth terminal of the second oscillator OSC2, the negative power end of the second comparator U2, the common contact of the earth terminal of the earth terminal of logic processing module 405 and switch drive module 406 is as the earth terminal GND of adaptive multi-mode control chip.

Below in conjunction with operation principle, above-mentioned adaptive multi-mode control circuit 400 is described further: when the output loading of Switching Power Supply was heavier, the second oscillator OSC2 can export a clock signal with fixed frequency.The 4th comparator U4 of valley point voltage detection module 402 compares rear output comparison signal to the first and door U6 by resistance R 2 and the sampled voltage of the common contact of resistance R 3 and the output voltage of the second reference voltage source 3021, the output signal of logic processing module 405 is carried out anti-phase processing and the first delay circuit 3022 by the first phase inverter U5 and is carried out input first and a door U6 after delay process, first with door U6 to the output signal of described comparison signal and the logic processing module after anti-phase delay process 405 carry out with logical process after resulting output signal as the output signal (being the valley detection signal) of valley point voltage detection module 402.

When the rising edge (or being set as trailing edge) of clock signal arrives, if resistance R 2 is low level (secondary (auxiliary winding signal and secondary secondary winding signal change in proportion) the demagnetization end of transformer T1 namely being detected) after filter circuit with the sampled voltage of the common contact of resistance R 3 and the level of relatively exporting of the first reference voltage source 3011, the first Schmidt trigger S1 in demagnetization detection module 401 can output low level make NMOS manage Q4 shutoff and PMOS pipe Q5 conducting; Wait for that valley point voltage detection module 402 detects the secondary no-voltage point of transformer T1, namely first manage Q5 to logic processing module 405 with door U6 output high level by PMOS, and open by the 406 control switch pipe Q1 conductings of switch drive mould.Along with switching tube Q1 conducting is opened, On current increases, the source voltage of switching tube Q1 can increase gradually, when reaching the output end voltage of feedback processing modules 404, relatively export high level signal through the second comparator U2, the output switching activity that makes rest-set flip-flop TRIG is low level, and this low level is closed cut-off through switch drive module 406 control switch pipe Q1.At this moment, adaptive multi-mode control circuit 400 enters the QR control model, and Switching Power Supply is operated in critical conduction mode (BCM, Boundary Conduction Mode) or discontinuous conduction mode (DCM, Discontinuous Conduction Mode).

when if the rising edge of clock signal (or being set as trailing edge) arrives, resistance R 2 is high level (the also not demagnetization end of secondary of transformer T1 namely being detected) with the sampled voltage of the common contact of resistance R 3 and the level of relatively exporting of the first reference voltage source 3011 after filter circuit 3012, the first Schmidt trigger S1 in demagnetization detection module 401 can export high level and make NMOS pipe Q4 conducting and PMOS pipe Q5 shutoff, signal output this moment selects module 403 directly to manage Q4 output high level to logic processing module 405 by NMOS, and by the switch drive mould, 406 control switch pipe Q1 conductings are opened.Along with switching tube Q1 conducting is opened, On current increases, the source voltage of switching tube Q1 can increase gradually, when reaching the output end voltage of feedback processing modules 404, relatively export high level signal through the second comparator U2, make the output level upset of rest-set flip-flop TRIG be low level, this low level is closed cut-off through switch drive module 406 control switch pipe Q1.At this moment, adaptive multi-mode control circuit 400 enters pwm pattern, and Switching Power Supply enters continuous conduction mode (CCM).

When Switching Power Supply is operated in discontinuous conduction mode or critical conduction mode, the ON time T of switching tube Q1 _onBe shown below:

$T_{\mathrm{on}}=\frac{L_P\×I_{\mathrm{PK}}}{\mathrm{Vin}}---\left(3\right)$

The secondary erasing time T of transformer T1 _DBe shown below:

$T_D=\frac{L_s\·N\·I_{\mathrm{PK}}}{\mathrm{Vout}}---\left(4\right)$

Wherein, L _PAnd L _SBe respectively the inductance value on former limit (being armature winding) of transformer T1 and the inductance value of secondary (being secondary winding), N is the turn ratio of the former limit of transformer T1 and secondary, I _PKBe the former limit peak current (that is to say the On current of switching tube Q1) of transformer T1, Vin and Vout are respectively input voltage and the output voltage of transformer T1.

By relational expression (3) and (4) as can be known, when the system parameters of Switching Power Supply keeps one regularly, the parameters such as the inductance value of transformer T1, turn ratio remain unchanged, the ON time T of switching tube Q1 _onOnly by the former limit peak current I of transformer T1 _PKDetermine secondary erasing time T with the ratio of input voltage vin _DOnly by former limit peak current I _PKDetermine with output voltage V out.And feedback processing modules 404 is by the sampled voltage V of resistance R 2 with the common contact of resistance R 3 _DEMDetect output voltage V out, and export corresponding feedback voltage to the second oscillator OSC2 and the second comparator U2 according to the variation of output voltage V out, then by logic processing module 405 and switch drive module 406 output drive pulse signal S _GATEControl switch pipe Q1 is to regulate former limit peak current I _PK, when output voltage V out increases, former limit peak current I _PKCan reduce because of the control of switching tube Q1, otherwise, when output voltage V out reduces, former limit peak current I _PKCan correspondingly increase.

Hence one can see that, suppose that Switching Power Supply is operated in above-mentioned discontinuous conduction mode, this moment, adaptive multi-mode control circuit 400 control models were the QR control model, by the unlatching of the secondary zero voltage signal co-controlling switching tube Q1 of the clock signal of the second oscillator OSC2 output and transformer T1, the approximate clock frequency that is equal to the second oscillator OSC2 of switching frequency.If output loading is constant, input voltage vin reduces, and ON time Ton increases, and this moment, output voltage temporarily remained unchanged, feedback voltage V because output loading does not change _FB(being the output voltage of error amplifier U14) is constant, former limit peak current I _PKRemain unchanged, therefore secondary erasing time T _DConstant; Switch periods T=T due to switching tube Q1 this moment _on+ T _offApproximate be equal to the clock cycle of the second oscillator OSC2 and remain unchanged, ON time Ton increase can cause turn-off time T _offReduce, work as T _offBe reduced to and T _DWhen equating, Switching Power Supply enters critical conduction mode, and meanwhile, adaptive multi-mode control circuit 400 still is in the QR control model; When input voltage vin continues to reduce and make T _on+ T _DDuring T (when the rising edge of clock signal or trailing edge arrived, the demagnetization not yet of transformer T1 finished), adaptive multi-mode control circuit 400 enters pwm pattern, Switching Power Supply also enters continuous conduction mode simultaneously.

Equally, in the situation that input voltage vin is constant, if the output loading of Switching Power Supply increases the weight of, output voltage V out reduces, feedback voltage V _FBIncrease former limit peak current I _PKIncrease, ON time Ton increases, secondary erasing time T _DIncrease, also T can occur _on+ T _DThe situation of T, adaptive multi-mode control circuit 400 enters the PWM pattern, and Switching Power Supply enters continuous conduction mode.

When input voltage vin and output loading change simultaneously, equally can be by with upper type, the control model of adaptive multi-mode control circuit 400 being regulated, and this adjustment process is that the loading condition by real-time sense switch power supply carries out, do not need to arrange the dead load switching point, system's adjustment is more flexible.

When output loading is reduced to certain limit, the feedback voltage V of exporting of error amplifier U14 _FBTo control the second oscillator OSC2 and carry out frequency reducing, the frequency of clock signal C LOCK reduces, and by the concrete condition that detects output loading, adaptive multi-mode control circuit 400 is carried out control model and regulates.Due to the load of this moment low weight (for example fully loaded half), former limit peak current I _PKAlso smaller, ON time T _onWith secondary erasing time T _DLess all, and switch periods T has increased, therefore T〉T _on+ T _DSwitching Power Supply can be operated in discontinuous conduction mode, the mixing control model that in fact adaptive multi-mode control circuit 400 was in PFM and QR and deposited this moment, the switching frequency of PFM control model assurance switching tube Q1 is adjusted with the variation of output loading, the QR control model guarantees that it is all that output voltage at its output is zero (being secondary no-voltage point) constantly that the each conducting of switching tube Q1 is opened, and so just can reduce the switching loss of switching tube Q1.Switching Power Supply is in this operating state, and adaptive multi-mode control circuit 400 changes the ON time T of switching tube Q1 by the variation of the secondary detection output loading of transformer T1 _onWith switch periods T, realize the output of Switching Power Supply constant voltage, and improved the system effectiveness of Switching Power Supply.

When output loading continues to be reduced to very low scope (as fully loaded 5%), by feedback processing modules 404 according to the sampled voltage V of resistance R 2 with the common contact of resistance R 3 _DEMOut detects to output voltage V, and adaptive multi-mode control circuit 400 correspondingly control switch pipe Q1 so that Switching Power Supply enters burst mode, that is: is worked as feedback voltage V _FBWhen being reduced to certain value, closing switch pipe Q1 is along with the consumption of Switching Power Supply output energy, feedback voltage V _FBVoltage can increase again, and when it reached certain value, control switch pipe Q1 realized high-frequency break-make again, makes the system power dissipation of Switching Power Supply be reduced to minimum value.

The sampled voltage V of adaptive multi-mode control circuit 400 related resistance R 2 and common contact of resistance R 3 in above-mentioned different control model _DEM, switching tube Q1 output voltage V _CS, the drive pulse signal S that exports of the clock signal C LOCK that exports of the second oscillator OSC2 and switch drive module 406 _GATE) oscillogram as shown in Figure 8.

The present embodiment also provides a kind of Switching Power Supply, and it comprises current rectifying and wave filtering circuit 100, starting resistance R1, capacitor C 1, diode D1, resistance R 2, resistance R 3, transformer T1, switching tube Q1, sampling resistor Rcs, output stage current rectifying and wave filtering circuit 200 and above-mentioned adaptive multi-mode control circuit 400.

the utility model embodiment is by adopting the adaptive multi-mode control circuit in Switching Power Supply, detect by secondary erasing time and auxiliary winding voltage to transformer T1, and detect according to the auxiliary winding voltage of the output voltage of output stage current rectifying and wave filtering circuit or the transformer T1 output voltage to Switching Power Supply, and to the On current of switching tube Q1 sample (namely the output end voltage of switching tube Q1 being sampled), then correspondingly export the operating state of drive pulse signal control switch pipe Q1 according to testing result and On current sampled result, and then to make the adaptive multi-mode control circuit can stablize the switching controls pattern (be PWM, PFM or QR), and stably conversion mode of operation of Switching Power Supply, improved system's average efficiency, thereby solved multi-mode control circuit in existing switch power supply system and caused circuit concussion and unstable and make the problem of the average efficiency reduction of switch power supply system when the dead load switching point carries out control mode switch.

The above is only preferred embodiment of the present utility model; not in order to limit the utility model; all any modifications of doing within spirit of the present utility model and principle, be equal to and replace and improvement etc., within all should being included in protection range of the present utility model.

Claims (9)

1. the adaptive multi-mode control circuit of a Switching Power Supply, are connected with resistance R with the starting resistance R1 of Switching Power Supply, the resistance R 2 that is connected in the auxiliary winding of transformer T1 and plays the dividing potential drop sampling action, switching tube Q1, the sampling resistor Rcs and the output stage current rectifying and wave filtering circuit that detect the On current of described switching tube Q1 be connected, the output of described switching tube Q1 and described sampling resistor R _CSFirst end connect, described sampling resistor R _CSThe second end ground connection, it is characterized in that, described adaptive multi-mode control circuit comprises:

Module, output feedback module, feedback processing modules, the first oscillator, the first comparator, logic processing module and switch drive module are selected in demagnetization detection module, valley point voltage detection module, signal output;

The input of described demagnetization detection module connects the common contact of described resistance R 2 and described resistance R 3, power end is connected with the second end of described resistance R 1, earth terminal ground connection, whether the secondary that described demagnetization detection module judge described transformer T1 according to the sampled voltage of described resistance R 2 and the common contact of described resistance R 3 the demagnetization end, and correspondingly exports the demagnetization detection signal according to judged result;

the first input end of described valley point voltage detection module connects the common contact of described resistance R 2 and described resistance R 3, the second input connects the output of described logic processing module, power end connects the second end of described resistance R 1, earth terminal ground connection, the drive pulse signal that described valley point voltage detection module is exported according to sampled voltage and the described logic processing module of the common contact of described resistance R 2 and described resistance R 3 judges whether the voltage of the auxiliary winding of described transformer T1 is minimum value between the switching tube Q1 off period, and correspondingly export the valley detection signal according to judged result,

Described signal output selects the first input end of module to connect the second end of described resistance R 1, control end be connected input and connect respectively the output of described demagnetization detection module and the output of described valley point voltage detection module, described signal output selects module to select the corresponding level signal of selecting of output according to described demagnetization detection signal, and described selection level signal is high level signal or described valley point voltage detection signal;

The input of described output feedback module connects the output of described output stage current rectifying and wave filtering circuit, output is connected with the input of described feedback processing modules, the first earth terminal ground connection, the second ground connection termination output, described output feedback module is exported feedback voltage to the input of described feedback processing modules according to the variation of the output voltage of described output stage current rectifying and wave filtering circuit;

The power end of described feedback processing modules connects the second end of described resistance R 1, earth terminal ground connection, described feedback processing modules produces a reference voltage to described the first comparator and described the first oscillator according to described feedback voltage, and controls the output clock variation of described the first oscillator;

The power end of described the first oscillator connects the second end of described resistance R 1, earth terminal ground connection, input connects the output of described feedback processing modules, and described the first oscillator produces corresponding clock signal according to the described reference voltage of described feedback processing modules output;

The positive power source terminal of described the first comparator, in-phase input end and inverting input connect respectively the output of the second end of described resistance R 1, described switching tube Q1 and the output of described feedback processing modules, negative power end ground connection, the described reference voltage that the sampled voltage that described the first comparator will obtain from the output of described switching tube Q1 and described feedback processing modules produce compares, and according to comparative result output pulse width modulation signal correspondingly;

The power end of described logic processing module connects the second end of described resistance R 1, the output that first input end, the second input and the 3rd input are selected the output of module, described oscillator with the output of described signal respectively be connected the output of the first comparator and be connected, earth terminal ground connection, described logic processing module carries out exporting corresponding drive pulse signal after logical process to described selection level signal, described clock signal and described pulse-width signal;

The power end of described switch drive module and input connect respectively the second end of described resistance R 1 and the output of described logic processing module, output is connected with the control end of described switching tube Q1, earth terminal ground connection, described switch drive module carries out exporting after driving force strengthens processing to described drive pulse signal, and then drive described switching tube Q1 according to the duty ratio work of described drive pulse signal, so that Switching Power Supply enters corresponding mode of operation.

2. adaptive multi-mode control circuit as claimed in claim 1, is characterized in that, described demagnetization detection module comprises:

The 3rd comparator, the first reference voltage source, PMOS pipe Q2, NMOS pipe Q3, the first current source, capacitor C 4 and the first Schmidt trigger;

the in-phase input end of described the 3rd comparator, positive power source terminal and negative power end are respectively the input of described demagnetization detection module, power end and earth terminal, the output of described the first reference voltage source connects the inverting input of described the 3rd comparator, the grid of the grid of described PMOS pipe Q2 and described NMOS pipe Q3 is connected to the output of described the 3rd comparator altogether, the source electrode of described PMOS pipe Q2 connects the positive power source terminal of described the 3rd comparator, the drain electrode of the drain electrode of described NMOS pipe Q3 and described PMOS pipe Q2 and the first end of described capacitor C 4 are connected to the input of described the first Schmidt trigger altogether, the source electrode of described NMOS pipe Q3 connects the input of described the first current source, the second end of the output of described the first current source and described capacitor C 4 and the negative power end of described the first Schmidt trigger are connected to the negative power end of described the 3rd comparator altogether, the positive power source terminal of described the first Schmidt trigger connects the positive power source terminal of described the 3rd comparator, the output of described the first Schmidt trigger is the output of described demagnetization detection module.

3. adaptive multi-mode control circuit as claimed in claim 1, is characterized in that, described valley point voltage detection module comprises:

The 4th comparator, the second reference voltage source, the first inverter, the first delay circuit and first and door;

the inverting input of described the 4th comparator, positive power source terminal and negative power end are respectively the first input end of described valley point voltage detection module, power end and earth terminal, the output of described the second reference voltage source connects the in-phase input end of described the 4th comparator, the input of described the first inverter is the second input of described valley point voltage detection module, the output of described the first inverter connects the input of described the first delay circuit, described first with the first input end of door be connected input and be connected respectively the output of described the 4th comparator and the output of described the first delay circuit, described first with the door output be the output of described valley point voltage detection module, the positive power source terminal of described the first inverter and described first is connected to the positive power source terminal of described the 4th comparator altogether with the positive power source terminal of door, the negative power end of described the first inverter and described first is connected to the negative power end of described the 4th comparator altogether with the negative power end of door.

4. adaptive multi-mode control circuit as claimed in claim 1, it is characterized in that, described signal output selects module to comprise NMOS pipe Q4 and PMOS pipe Q5, the source electrode of the drain electrode of described NMOS pipe Q4 and described PMOS pipe Q5 is respectively first input end and the second input that module is selected in described signal output, the common contact of the grid of the grid of described NMOS pipe Q4 and described PMOS pipe Q5 is selected the control end of module as described signal output, the common contact of the drain electrode of the source electrode of described NMOS pipe Q4 and described PMOS pipe Q5 is selected the output of module as described signal output.

5. adaptive multi-mode control circuit as claimed in claim 1, is characterized in that, described output feedback module comprises:

Resistance R 4, optocoupler U7, capacitor C 5, resistance R 5, resistance R 6 and 431 a reference sources;

the first end of described resistance R 4 is the input of described output feedback module, the second end of described resistance R 4 connects the anode of the light-emitting diode of described optocoupler U7, the negative electrode of the first end of described capacitor C 5 and described 431 a reference sources is connected to the negative electrode of the light-emitting diode of described optocoupler U7 altogether, the collector and emitter of the phototriode of described optocoupler U7 is respectively feedback end and first earth terminal of described output feedback module, the second end of described capacitor C 5 and the first end of described resistance R 5 are connected to the first end of described resistance R 4 altogether, the second end of described resistance R 5 and the first end of described resistance R 6 are connected to the adjustment utmost point of described 431 a reference sources altogether, the common contact of the second end of described resistance R 6 and the anode of described 431 a reference sources is as the second earth terminal of described output feedback module.

6. adaptive multi-mode control circuit as claimed in claim 1, is characterized in that, described feedback processing modules comprises:

The second current source, diode D3, resistance R 7 and resistance R 8;

The input of described the second current source is the power end of described feedback processing modules, the output of described the second current source connects the anode of described diode D3, the anode of described diode D3 is the input of described feedback processing modules, the first end of described resistance R 7 connects the negative electrode of described diode D3, the common contact of the second end of described resistance R 7 and the first end of described resistance R 8 is as the output of described feedback processing modules, and the second end of described resistance R 8 is the earth terminal of described feedback processing modules.

7. adaptive multi-mode control circuit as claimed in claim 1, it is characterized in that, described logic processing module comprise second with the door and rest-set flip-flop, described second is respectively first input end, the second input, power end and the earth terminal of described logic processing module with first input end, the second input, positive power source terminal and the negative power end of door, described second is connected the first input end of described rest-set flip-flop with the output of door, the second input of described rest-set flip-flop and output are respectively the 3rd input and the output of described logic processing module.

8. adaptive multi-mode control circuit as claimed in claim 1, it is characterized in that, described switch drive module comprises the 3rd inverter and the 4th inverter, the input of described the 3rd inverter, positive power source terminal and negative power end are respectively the input of described switch drive module, power end and earth terminal, the output of described the 3rd inverter connects the input of described the 4th inverter, the positive power source terminal of described the 4th inverter and negative power end connect respectively positive power source terminal and the negative power end of described the 3rd inverter, the output of described the 4th inverter is the output of described switch drive module.

9. a Switching Power Supply, is characterized in that, described Switching Power Supply comprises current rectifying and wave filtering circuit, starting resistance R1, capacitor C 1, diode D1, resistance R 2, resistance R 3, transformer T1, switching tube Q1, sampling resistor R _CS, output stage current rectifying and wave filtering circuit and adaptive multi-mode control circuit as described in claim 1 to 9 any one.

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