CN204205946U - Switch converter and control circuit thereof - Google Patents

Abstract

The utility model discloses a switch converter and control circuit thereof. The control circuit includes a slope compensation circuit and a slope adjustment circuit that provide a slope compensation signal and a slope adjustment signal, respectively. The amplitude of the sum signal obtained by superposing the slope compensation signal and the slope adjustment signal does not change along with the change of the duty ratio of the switching converter, so that the stability of the system is improved.

Description

Switch converters and control circuit thereof

Technical field

The utility model relates to electronic circuit, particularly relates to switch converters and control circuit thereof.

Background technology

Control in (COT) switch converters, as output voltage V at constant on-time _oUTwhen changing, switching frequency can along with output voltage V _oUTchange and change.In order at output voltage V _oUTduring change, maintained switch frequency is constant, and in switch converters, the accurate constant on-time of normal employing controls (PCOT) circuit.

Fig. 1 illustrates existing PCOT switch converters 100, comprises turn-on time generation circuit 101, comparison circuit 102, logical circuit 103, switching circuit 104, slope compensation circuit 105 and feedback circuit 106.

In the PCOT switch converters 100 shown in Fig. 1, the ON time T of the main switch M1 determined by turn-on time generation circuit 101 _oNfor:

$T_{\mathrm{ON}}=\frac{C_{\mathrm{TON}}\×R_{\mathrm{FREQ}}\×V_{\mathrm{REF}1}}{V_{\mathrm{IN}}}---\left(1\right)$

The amplitude V of the slope compensation signal produced by slope compensation circuit 105 _{sLOPE (PP)}for:

$V_{\mathrm{SLOPE}\left(\mathrm{pp}\right)}=\frac{(V_{\mathrm{IN}}-V_{\mathrm{OUT}})\×T_{\mathrm{ON}}}{R_C\×C_C}---\left(2\right)$

Formula (1) is substituted in formula (2), can obtain:

$V_{\mathrm{SLOPE}\left(\mathrm{pp}\right)}=\frac{(V_{\mathrm{IN}}-V_{\mathrm{OUT}})\×C_{\mathrm{TON}}\×R_{\mathrm{FREQ}}\×V_{\mathrm{REF}1}}{R_C\×C_C\×V_{\mathrm{IN}}}=\frac{C_{\mathrm{TON}}\×R_{\mathrm{FREQ}}\×V_{\mathrm{REF}1}\×(1-D)}{R_C\×C_C}---\left(3\right)$

From formula (3), in the PCOT switch converters 100 shown in Fig. 1, the amplitude V of slope compensation signal _{sLOPE (PP)}relevant with the duty ratio D of switch converters 100, duty ratio D is larger, the amplitude V of slope compensation signal _{sLOPE (PP)}less.If the amplitude V of slope compensation signal _{sLOPE (PP)}too small, then circuit is easily unstable.

Utility model content

For problems of the prior art, the purpose of this utility model is to provide a kind of can make switch converters that system is more stable and control circuit thereof.

According to a kind of control circuit for switch converters of the utility model embodiment, this switch converters comprises switching circuit, switching circuit comprises main switch, continued flow component and has the inductor of first end and the second end, and switching circuit receives input voltage and input voltage is converted to output voltage; This control circuit comprises: turn-on time generation circuit, produces ON time control signal; Slope compensation circuit, produce slope compensation signal, wherein, the amplitude of slope compensation signal and 1 is directly proportional to the difference of the duty ratio of main switch; Slope Circuit tuning, produces slope adjustment signal, and wherein, the slope adjustment amplitude of signal and the duty ratio of main switch are directly proportional; Comparison circuit, there is first input end, the second input and output, wherein, that first input end receiving feedback signals and slope compensation signal and slope adjust signal and be worth, second input receives reference signal, and what feedback signal and slope compensation signal and slope were adjusted signal by comparison circuit to compare with reference signal with value and produce comparison signal at output; And logical circuit, there is first input end, the second input and output, wherein, first input end receives ON time control signal, second input receives comparison signal, and logical circuit produces control signal to control conducting and the shutoff of main switch and continued flow component based on ON time control signal and comparison signal.

According to a kind of switch converters of the utility model embodiment, comprise switching circuit and control circuit.This switching circuit comprises main switch, continued flow component and has the inductor of first end and the second end, and this switching circuit receives input voltage and input voltage is converted to output voltage.This control circuit comprises: turn-on time generation circuit, produces ON time control signal; Slope compensation circuit, produce slope compensation signal, wherein, the amplitude of slope compensation signal and 1 is directly proportional to the difference of the duty ratio of main switch; Slope Circuit tuning, produces slope adjustment signal, and wherein, the slope adjustment amplitude of signal and the duty ratio of main switch are directly proportional; Comparison circuit, there is first input end, the second input and output, wherein, that first input end receiving feedback signals and slope compensation signal and slope adjust signal and be worth, second input receives reference signal, and what feedback signal and slope compensation signal and slope were adjusted signal by comparison circuit to compare with reference signal with value and produce comparison signal at output; And logical circuit, there is first input end, the second input and output, wherein, first input end receives ON time control signal, second input receives comparison signal, and logical circuit produces control signal to control conducting and the shutoff of main switch and continued flow component based on ON time control signal and comparison signal.

In embodiment of the present utility model, slope compensation signal is adjusted comparing with reference signal together with feedback signal with value of signal with slope by switch converters and control circuit thereof, slope compensation signal and slope adjust can not changing along with the change of main switch duty ratio with value of signal, and therefore system is more stable.

Accompanying drawing explanation

Fig. 1 illustrates existing PCOT switch converters 100;

Fig. 2 illustrates the switch converters 200 according to the utility model embodiment;

Fig. 3 A illustrates an embodiment of current source circuit shown in Fig. 2;

Fig. 3 B and 3C illustrates equivalent electric circuit 30B and 30C of current source circuit 30A shown in Fig. 3 A;

Fig. 4 illustrates the switch converters 400 according to the utility model embodiment.

Embodiment

To specific embodiment of the utility model be described in detail below, it should be noted that the embodiments described herein is only for illustrating, is not limited to the utility model.In the following description, in order to provide thorough understanding of the present utility model, a large amount of specific detail has been set forth.But, those of ordinary skill in the art be it is evident that: these specific detail need not be adopted to carry out the utility model.In other instances, in order to avoid obscuring the utility model, do not specifically describe known circuit or material.

In whole specification, " embodiment ", " embodiment ", " example " or mentioning of " example " are meaned: the special characteristic, structure or the characteristic that describe in conjunction with this embodiment or example are comprised at least one embodiment of the utility model.Therefore, the phrase " in one embodiment " occurred in each place of whole specification, " in an embodiment ", " example " or " example " differ to establish a capital and refer to same embodiment or example.In addition, can with any combination suitably and or sub-portfolio by specific feature, structure or property combination in one or more embodiment or example.In addition, it should be understood by one skilled in the art that the diagram provided at this is all for illustrative purposes, and diagram is not necessarily drawn in proportion.Should be appreciated that when claim " element " " be connected to " or " coupling " to another element time, it can be directly connected or coupled to another element or can there is intermediary element.On the contrary, when claim element " be directly connected to " or " being directly coupled to " another element time, there is not intermediary element.Identical Reference numeral indicates identical element.Term "and/or" used herein comprises any and all combinations of one or more relevant project listed.

Fig. 2 illustrates the switch converters 200 according to the utility model embodiment.Switch converters 200 comprises switching circuit 204, feedback circuit 207 and control circuit.Wherein, control circuit comprises turn-on time generation circuit 201, comparison circuit 202, logical circuit 203, slope compensation circuit 205 and slope Circuit tuning 206.

Turn-on time generation circuit 201 produces ON time control signal COT, with the ON time of control switch circuit 204 breaker in middle pipe.Turn-on time generation circuit 201 comprises resistor R _fREQ, capacitor C _tON, switch S _tONand comparator CMP1.Resistor R _fREQhave first end and the second end, its first end receives input voltage V _iN.Capacitor C _tONhave first end and the second end, its first end is coupled to resistor R _fREQthe second end, its second end be connected to reference to ground.Switch S _tONhave first end, the second end and control end, its first end is coupled to resistor R _fREQthe second end, its second end be connected to reference to ground.Comparator CMP1 has first input end, the second input and output, and its first input end is coupled to capacitor C _tONfirst end with receiving condenser C _tONon voltage, its second termination receive reference signal V _rEF1.Comparator CMP1 is by capacitor C _tONon voltage and reference signal V _rEF1compare, and produce ON time control signal COT at its output.It will be understood by those of skill in the art that turn-on time generation circuit 201 shown in Fig. 2 is just exemplary, in other embodiments, turn-on time generation circuit can adopt other suitable topological structure.

Switching circuit 204 adopts synchronous buck structure, comprises main switch M1, continued flow switch pipe M2, inductor L and capacitor C _oUT.Switching circuit 204 passes through conducting and the shutoff of main switch M1 and continued flow switch pipe M2, by input voltage V _iNbe converted to output voltage V _oUT.One end of main switch M1 receives input voltage V _iN, the other end is coupled to one end of continued flow switch pipe M2.The other end ground connection of continued flow switch pipe M2.Inductor L has first end and the second end, and its first end is coupled to the common port of main switch M1 and continued flow switch pipe M2.Capacitor C _oUTbe coupled between second end of inductor L and ground.Capacitor C _oUTthe voltage at two ends is output voltage V _oUT.

In one embodiment, main switch M1 in switching circuit 204 and continued flow switch pipe M2 can be any controllable semiconductor switch device, such as mos field effect transistor (MOSFET), igbt (IGBT) etc.In another embodiment, continued flow switch pipe M2 can be replaced by other continued flow component, as diode.In yet another embodiment, switching circuit 204 can adopt other suitable topological structure, such as buck-boost converters etc.

Slope compensation circuit 205 comprises compensating resistor R _cwith compensation condenser C _c.Particularly, compensating resistor R _chave first end and the second end, its first end is coupled to the first end of inductor L.Compensation condenser C _chave first end and the second end, its first end is coupled to compensating resistor R _cthe second end, its second end is coupled to second end of inductor L.Compensating resistor R _cwith electronic compensating container C _ccommon port be the output of slope compensation circuit 205, slope compensation signal V is provided _sLOPE.The amplitude V of this slope compensation signal _{sLOPE (PP)}as shown in formula (3).

Those skilled in the art is to be understood that, slope compensation circuit 205 shown in Fig. 2 is just exemplary, in other embodiments, slope compensation circuit can adopt other suitable topological structure, as utilized the slope compensation topological structure of digital circuit, or utilize that current source constructs, signal can be produced with circuit topological structure of the electric current that simulated inductor L flows through etc.

Slope Circuit tuning 206 comprises current source circuit and slope compensation circuit C _c.This current source circuit is coupled to compensation condenser C _cfirst end with to compensation condenser C _ccarry out discharge and recharge, thus at compensation condenser C _cfirst end produce slope adjustment signal V _aDJ.When main switch M1 conducting, current source circuit to compensation condenser CC fan-in size is electric current.When the M2 conducting of continued flow switch pipe, current source circuit is from compensation condenser C _cfan-out size is electric current.More specifically, in circuit shown in Fig. 2, current source circuit comprises filling current source (current source) CS1, draws current source (current sink) CS2 and switch S ₁.Fill with current source CS1 and be coupled to compensation condenser C _cfirst end with to compensation condenser C _cfan-in size is electric current I ₁.Draw current source CS2 and switch S ₁compensation condenser C is coupled to after being connected in series _cfirst end, with in switch S ₁from compensation condenser C during conducting _cmiddle fan-out size is electric current I ₂, wherein, switch S ₁with the synchronous turn-on and turn-off of continued flow switch pipe M2.

Therefore, slope adjustment signal V _aDJamplitude V _{aDJ (PP)}for:

$V_{\mathrm{ADJ}\left(\mathrm{pp}\right)}=\frac{V_{\mathrm{OUT}}\×T_{\mathrm{ON}}}{R_C\×C_C}=\frac{V_{\mathrm{OUT}}\×C_{\mathrm{TON}}\×R_{\mathrm{FREQ}}\×V_{\mathrm{REF}1}}{R_C\×C_C\×V_{\mathrm{IN}}}=\frac{C_{\mathrm{TON}}\×R_{\mathrm{FREQ}}\×V_{\mathrm{REF}1}\×D}{R_C\×C_C}---\left(4\right)$

It will be understood by those of skill in the art that the Circuit tuning of slope shown in Fig. 2 206 is just exemplary, in other embodiments, slope Circuit tuning can adopt other topological structure that is suitable, that can produce the signal that amplitude is directly proportional to the duty ratio of upper switching tube.

From formula (3) and formula (4), by slope compensation signal and slope adjustment signal superimposed obtained with value signal V _sLOPE1amplitude V _{sLOPE1 (PP)}for:

$V_{\mathrm{SLOPE}1\left(\mathrm{pp}\right)}=V_{\mathrm{SLOPE}\left(\mathrm{pp}\right)}+V_{\mathrm{ADJ}\left(\mathrm{pp}\right)}=\frac{C_{\mathrm{TON}}\×R_{\mathrm{FREQ}}\×V_{\mathrm{REF}1}}{R_C\×C_C}---\left(5\right)$

From formula (5), at resistor R _fREQ, R _cwith capacitor C _tON, C _cand reference signal V _rEF1under selected condition, and value signal V _sLOPE1amplitude V _{sLOPE1 (PP)}be a steady state value, can not change along with the change of the duty ratio of switch converters 200, therefore system is more stable.

Feedback circuit 207 comprises the resitstance voltage divider be connected in series by resistor R1 and R2, and it is coupled between the output of switching circuit 204 and reference ground.Feedback circuit 207 is based on the output voltage V of switching circuit 204 output _oUT, at the common port output feedback signal V of resistor R1 and R2 _fB.

Comparison circuit 202 has first input end, the second input and output, and wherein, first input end is coupled to the output of feedback circuit 207, slope compensation circuit 205 and slope Circuit tuning 206 with receiving feedback signals V _fB, slope compensation signal V _sLOPEwith slope adjustment signal V _aDJwith value V _sLOPE1, the second input receives reference signal V _rEF2, comparison circuit 202 is by feedback signal V _fB, slope compensation signal V _sLOPEwith slope adjustment signal V _aDJwith value V _sLOPE1with reference signal V _rEF2compare, and produce comparison signal SET at output.

Logical circuit 203 has first input end and the second input, wherein, first input end is coupled to turn-on time generation circuit 201 to receive ON time control signal COT, second input is coupled to comparison circuit 202 to receive comparison signal SET, logical circuit 203 produces control signal Q and Q ' according to ON time control signal COT and comparison signal SET, with the conducting of main switch M1 in control switch circuit 204 and continued flow switch pipe M2 and shutoff and turn-on time generation circuit 201 breaker in middle S _tONconducting and shutoff.

Under switch converters 200 shown in Fig. 2 is operated in continuous operation mode (CCM).If under switch converters 200 is operated in discontinuous conduction mode (DCM), be then coupled to compensation condenser C after filling current source CS1 and switch can being connected in series _cfirst end, this switch turns off when main switch M1 and continued flow switch pipe M2 all turns off, all the other time conductings.

Fig. 3 A illustrates an embodiment of current source circuit shown in Fig. 2.As shown in Figure 3A, current source circuit 30A comprises current mirror 301,302 and 303, and the switching tube in each current mirror is to having identical parameters.Current mirror 301 receives output voltage V _oUT, from current mirror operation principle, at the output of current mirror 301, the electric current I provided by switching tube MP1 and MP2 _mP1and I _mP2be in current mirror 302, switching tube MN1 and switch S ₁series connection, switch S ₁suspension control signal Q ' controls, i.e. switch S ₁oN time be (1-D) T, the turn-off time is D × T.Therefore, (1-D) I is had _mN2=(1-D) I _mN3=I _mP1, so, at the output of current mirror 302, the electric current I provided by switching tube MN2 and MN3 _mN2and I _mN3be in current mirror 303, switching tube MP3 and switch S ₂be connected in series, switch S ₂suspension control signal Q controls.Current mirror 303 received current I _mN3as input, therefore, the electric current provided by switching tube MP3 is

Current source circuit 30A shown in Fig. 3 A can be equivalent to equivalent electric circuit 30B shown in Fig. 3 B.Due to switch S ₂suspension control signal Q controls, and switch S ₁by controlling with the control signal Q ' of control signal Q complementation, therefore, circuit 30B can be equivalent to 30C further.From current source equivalent electric circuit 30C, current source circuit 30A is the current source circuit shown in Fig. 2.

Fig. 4 illustrates the switch converters 400 according to the utility model embodiment.Switch converters 400 comprises switching circuit 404, feedback circuit 407 and control circuit.Wherein, control circuit comprises turn-on time generation circuit 401, comparison circuit 402, logical circuit 403, slope compensation circuit 405 and slope Circuit tuning 406.

Turn-on time generation circuit 401 produces ON time control signal COT, with the ON time of control switch circuit 404 breaker in middle pipe.Feedback circuit 407 receives output voltage V _oUT, and generation represents output voltage V _oUTfeedback signal V _fB.

Slope compensation circuit 405 produces slope compensation signal V _sLOPE, slope compensation signal V _sLOPEamplitude V _{sLOPE (PP)}be directly proportional with 1-D, there is scale factor K, namely

V _SLOPE(PP)＝K×(1-D) (6)

Wherein, D represents the conducting duty ratio of main switch in switching circuit 404.

Slope Circuit tuning 406 produces slope adjustment signal V _aDJ, slope adjustment signal V _aDJamplitude V _{aDJ (PP)}be directly proportional with D, its scale factor is also K, namely

V _ADJ(PP)＝K×D (7)

Slope compensation signal V _sLOPEwith slope adjustment signal V _aDJwith value for V _sLOPE1, its amplitude V _{sLOPE1 (PP)}for:

V _SLOPE1(PP)＝K×(1-D)+K×D＝K (8)

From formula (8), because scale factor K is a steady state value, slope compensation signal V _sLOPEsignal V is adjusted with slope _aDJsuperimposed with value signal V _sLOPE1amplitude V _{sLOPE1 (PP)}have nothing to do with the duty ratio D of switching circuit, therefore system is more stable.

Comparison circuit 402 receiving feedback signals V _fB, and value signal V _sLOPE1, and by signal V _sLOPE1with feedback signal V _fBwith value with reference signal V _rEF2compare, produce comparison signal SET.

Logical circuit 403 receives ON time control signal COT and comparison signal SET, and produces control signal CTRL based on ON time control signal COT and comparison signal SET.Switching circuit 404 receives input voltage V _iN, and according to control signal CTRL by input voltage V _iNbe converted into output voltage V _oUT.

Although exemplary embodiment describe the utility model with reference to several, should be appreciated that term used illustrates and exemplary and nonrestrictive term.Specifically can implement in a variety of forms due to the utility model and not depart from spirit or the essence of utility model, so be to be understood that, above-described embodiment is not limited to any aforesaid details, and explain widely in the spirit and scope that should limit in claim of enclosing, therefore fall into whole change in claim or its equivalent scope and remodeling and all should be claim of enclosing and contained.

Claims (8)

1. the control circuit for switch converters, switch converters comprises switching circuit, switching circuit comprises main switch, continued flow component and has the inductor of first end and the second end, switching circuit receives input voltage and input voltage is converted to output voltage, it is characterized in that, control circuit comprises:

Turn-on time generation circuit, produces ON time control signal;

Slope compensation circuit, produce slope compensation signal, wherein, the amplitude of slope compensation signal and 1 is directly proportional to the difference of the duty ratio of main switch;

Slope Circuit tuning, produces slope adjustment signal, and wherein, the slope adjustment amplitude of signal and the duty ratio of main switch are directly proportional;

Comparison circuit, there is first input end, the second input and output, wherein, that first input end receiving feedback signals and slope compensation signal and slope adjust signal and be worth, second input receives reference signal, and what feedback signal and slope compensation signal and slope were adjusted signal by comparison circuit to compare with reference signal with value and produce comparison signal at output; And

Logical circuit, there is first input end, the second input and output, wherein, first input end receives ON time control signal, second input receives comparison signal, and logical circuit produces control signal to control conducting and the shutoff of main switch and continued flow component based on ON time control signal and comparison signal.

2. control circuit as claimed in claim 1, it is characterized in that, the amplitude of slope compensation signal is identical with the scale factor that the duty ratio of amplitude and main switch that the scale factor that the difference of the duty ratio of main switch is directly proportional and slope adjust signal is directly proportional with 1.

3. control circuit as claimed in claim 1, it is characterized in that, slope compensation circuit comprises:

Compensating resistor, have first end and the second end, described first end is coupled to the first end of inductor; And

Compensation condenser, has first end and the second end, and described first end is coupled to the second end of compensating resistor and exports slope compensation signal, and described second end is coupled to the second end of inductor.

4. control circuit as claimed in claim 1, it is characterized in that, slope Circuit tuning comprises:

Fill with current source, be coupled to compensation condenser with to compensation condenser fan-in electric current;

Draw current source, be coupled to compensation condenser with from compensation condenser fan-out electric current; And

Switch, is connected in series with drawing current source, and the conducting when continued flow component conducting;

Wherein, fill with current source fan-in electric current and draw the electric current of current source fan-out to flow through capacitance voltage that compensation condenser produces is slope adjustment signal.

5. control circuit as claimed in claim 1, it is characterized in that, slope Circuit tuning comprises:

First current mirroring circuit, has input and output, and described input receives output voltage, and produces the reference current relevant with output voltage, and described output provides the first electric current of fan-in compensation condenser according to the reference current of input;

Second current mirroring circuit, has input and output, comprises the switch with input coupled in series, and described input receives the first electric current, and provides the second electric current of fan-out compensation condenser at output; And

3rd current mirroring circuit, has input and output, and comprise the switch with described output coupled in series, described input receives the second electric current, and described output provides the 3rd electric current of fan-in compensation condenser;

Wherein, the first current mirroring circuit, the second current mirroring circuit and the 3rd current mirroring circuit act on the capacitance voltage that compensation condenser produces is slope adjustment signal.

6. control circuit as claimed in claim 1, it is characterized in that, turn-on time generation circuit comprises:

Resistor, has first end and the second end, and described first end receives input voltage;

Capacitor, has first end and the second end, and described first end is coupled to the second end of resistor, and described second end is connected to reference to ground;

Switch, has first end, the second end and output, and described first end is coupled to the second end of resistor, and described second end is connected to ground, and described control end is coupled to logical circuit with reception control signal; And

Comparator, there is first input end, the second input and output, described first input end is coupled to the first end of capacitor with the voltage on receiving condenser, described second input receives reference signal, and the voltage on capacitor and reference signal compare and produces comparison signal at described output by comparator.

7. a switch converters, is characterized in that, switch converters comprises:

Switching circuit, comprise main switch, continued flow component and have the inductor of first end and the second end, switching circuit receives input voltage and input voltage is converted to output voltage; And

Control circuit according to any one of claim 1 to 6.

8. switch converters as claimed in claim 7, it is characterized in that, main switch has first end, the second end and control end, and described first end receives input voltage, described second end is coupled to the first end of inductor, and described control end is coupled to logical circuit with reception control signal; Continued flow component has first end and the second end, and described first end is coupled to the first end of inductor, and described second end is connected to ground; Switching circuit also comprises capacitor, has first end and the second end, and described first end is coupled to the second end of inductor and provides output voltage, and described second end is connected to ground.