CN101951158B - Compensating controller of PWM converter and PWM control circuit - Google Patents

Abstract

The invention relates to a compensating controller of PWM converter, use in a PWM control circuit. The compensating controller includes: the terminal S of an RS trigger receives a square wave generated by an oscillator, the terminal R of the RS trigger receives the output signal of an and gate, and the terminal Q of the trigger is an output terminal; a sawtooth wave after a triangular wave generated by the oscillator is processed by a processor is accumulated with an induced voltage, and the result after accumulation is sent to an overcurrent comparator; the output terminal of the overcurrent comparator is connected with the input terminal of the and gate; the other input terminal of the and gate is connected with the output terminal of a PWM comparator; and the two signals received by the PWM comparator are respectively a feedback network signal and a signal that the triangular wave is superimposed after the induced voltage is subject to and processing.

Description

A kind of compensating controller and pwm control circuit to the PWM transducer

Technical field

The present invention relates to PWM controller technology field, particularly a kind of controller and compensating circuit that PWM transducer peak power output and input voltage relation are compensated.

Background technology

The PWM control technology is widely used in various switch power controllers, in order to provide suitable operating voltage and electric current for different circuit modules.For power supply itself and load are protected, the PWM controller is inner integrated various defencive functions, such as overvoltage protection (OVP), overcurrent protection (OCP), excess temperature is protected (OTP) and is protected etc.The peak power output of transducer when wherein, the overcurrent protection of Cycle by Cycle (OCP) also is used for restriction output overloading and short circuit.

When the PWM converter output current reached the over-current protection point of setting, the PWM controller can cut out output.But because there is certain time-delay in system detecting to flow to close between the output, under identical time delay condition, it is different that different input voltages will cause exporting the turn-off transient inductive current, thereby power output is also different.In addition when system works when continuous mode (CCM), if the cycle is identical with the overcurrent protection flow point, different input voltages also can cause former limit and secondary ON time different.More than two factors all can cause input voltage higher, power output is just larger.May cause damage to power supply itself and load thereof like this, must compensate power output for this reason, it is not changed with input voltage.

Input voltage is detected in compensation method commonly used exactly, then according to certain proportionate relationship over-current protection point is compensated, but this can increase the power consumption of system and the complexity of circuit.

Referring to Fig. 1, this figure is the conventional application circuit of PWM controller.Resistance 107 is connected on the source electrode of power switch pipe 108, is used for controlling former limit peak current, thus the peak power output of control system.Connect an input of pwm chip 100 inner overcurrent comparators in the Vs, and compare with a fixed level Vref, as Vs during greater than Vref, pwm chip (PWM controller) 100 can switch-off power switching tubes 108.

Like this, former limit peak current Ipp can pass through formula (1) and obtains.

$I_{\mathrm{pp}}=\frac{V_{\mathrm{ref}}}{R_S}---\left(1\right)$

Because need one section time-delay td greater than Vref to power switch pipe 108 shutoffs from detecting Vs, in this section time-delay, different line voltage can cause different primary current increment Id.

$I_d=\frac{V_{\mathrm{in}}}{L_P}*t_d---\left(2\right)$

Actual former limit peak current Ip is the function of input voltage:

$I_p=I_{\mathrm{pp}}+I_d=\frac{V_{\mathrm{ref}}}{R_S}+\frac{V_{\mathrm{in}}}{L_P}*t_d---\left(3\right)$

Under discontinuous mode (DCM), system's peak power output also is the function of input voltage, for:

$P=\frac{{I_P}^2*L_P}{2T}---\left(4\right)$

For Ipp is not changed with input voltage, introduce resistance 104 and resistance 105 composition compensating networks in the application system, then:

$V_{\mathrm{ref}}=I_{\mathrm{pp}}*R_S+V_{\mathrm{in}}*\frac{R_{105}}{{\mathrm{<figure-callout\; id="105"\; label="R"\; filenames="HSA00000275441700011.png"\; state="\{\{state\}\}">R</figure-callout>}}_{105}+R_{104}}---\left(5\right)$

$I_{\mathrm{Pp}}=\frac{V_{\mathrm{ref}}}{R_S}-\frac{V_{\mathrm{in}}*R_{105}}{({\mathrm{<figure-callout\; id="105"\; label="R"\; filenames="HSA00000275441700011.png"\; state="\{\{state\}\}">R</figure-callout>}}_{105}+R_{104})*R_S}---\left(6\right)$

$I_P=\frac{V_{\mathrm{ref}}}{R_S}-\frac{V_{\mathrm{in}}*R_{105}}{({\mathrm{<figure-callout\; id="105"\; label="R"\; filenames="HSA00000275441700011.png"\; state="\{\{state\}\}">R</figure-callout>}}_{105}+R_{104})*R_S}+\frac{V_{\mathrm{in}}}{L_P}*t_d---\left(7\right)$

Ip is not changed with Vin, and then two of back will equate, that is:

$\frac{R_{105}}{(R_{105}+R_{104})}=\frac{R_S*t_d}{L_P}---\left(8\right)$

Existing this compensation method meeting brings extra power consumption, consumes at resistance 104 with above the resistance 105.

$P_R=\frac{{V_{\mathrm{IN}}}^2}{{\mathrm{<figure-callout\; id="104"\; label="R"\; filenames="HSA00000275441700011.png"\; state="\{\{state\}\}">R</figure-callout>}}_{104}+R_{105}}---\left(9\right)$

Increase again simultaneously the complexity of chip exterior circuit and taken the PCB area.

Summary of the invention

The technical problem to be solved in the present invention provides a kind of controller and compensating circuit that utilizes triangular wave that PWM transducer peak power output and input voltage relation are compensated.

The present invention proposes a kind of compensating controller to the PWM transducer, is used for pwm control circuit; Described compensating controller comprises:

The S termination of rest-set flip-flop is received the square wave that oscillator produces, and the R termination of rest-set flip-flop is received the output signal with door, and the Q end of trigger is output;

Sawtooth waveforms and induced voltage after the treated device of the triangular wave that described oscillator produces is processed are cumulative, and cumulative rear result sends to the overcurrent comparator; The output of described overcurrent comparator links to each other with the input of door with described; Described sawtooth waveforms reduces with the increase of power switch pipe ON time in the described pwm control circuit;

Describedly link to each other with the output of PWM comparator with another input of door;

The two paths of signals that described PWM comparator receives is respectively the feedback network signal, and the signal after induced voltage and the stack of processing Vee formation ripple.

Preferably, described sawtooth waveforms and induced voltage superpose, and determine the over-current protection point of described overcurrent comparator.

Preferably, the square wave trailing edge power ratio control switching tube conducting that described oscillator produces, the over-current protection point that described power switch pipe turn-offs is by signal deciding described and door.

Preferably, described processor converts the difference of described triangular wave and a reference level to first electric current, and obtaining an amplitude by current mirror is K the second electric current doubly, and described the first electric current and the second electric current are sawtooth waveforms.

Preferably, the stack of described sawtooth waveforms and induced voltage is specially by resistance the signal of described the second electric current is superimposed upon on the current sensing signal.

The invention also discloses a kind of pwm control circuit, described control circuit comprises the compensating controller of described PWM transducer.

The relative prior art of the present invention has following technique effect:

Because the described compensating controller to the PWM transducer of the embodiment of the invention, because the input voltage of the pwm control circuit of using is higher, during the power switch pipe conducting of pwm control circuit, the transformer primary side inductive current rate of rise of pwm control circuit is larger, so ON time ton is less.By the sawtooth waveforms that reduces with the increase of ON time (also claiming oblique wave) that superposes to induced voltage.Like this, ON time was less when input voltage was higher, and the amount that superposes on the induced voltage is just larger, and the value of induced voltage is just less, and namely input voltage is higher, and the transformer primary side peak current is less.By selecting suitable compensation slope and bucking voltage can offset the error current that brings owing to time-delay, so that under different input voltages, transformer primary side true peak electric current is all identical, thereby the peak power output of pwm control circuit equates.

Description of drawings

In order to be illustrated more clearly in the embodiment of the invention or technical scheme of the prior art, the below will do to introduce simply to the accompanying drawing of required use in embodiment or the description of the Prior Art, apparently, accompanying drawing in the following describes only is some embodiments of the present invention, for those of ordinary skills, under the prerequisite of not paying creative work, can also obtain according to these accompanying drawings other accompanying drawing.

Fig. 1 is the conventional application circuit of PWM controller;

Fig. 2 is the circuit diagram of the pwm control circuit used of the described compensating controller to the PWM transducer of the embodiment of the invention;

Fig. 3 is the waveform correlation figure of the described circuit of Fig. 2;

Fig. 4 is the realization circuit diagram of the described processor of the embodiment of the invention and adder.

Embodiment

The technical problem to be solved in the present invention provides a kind of controller and pwm control circuit that utilizes triangular wave that PWM transducer peak power output and input voltage relation are compensated.

In order to be illustrated more clearly in the principle of the embodiment of the invention or technical scheme of the prior art, be specifically described below in conjunction with Fig. 1.

Referring to Fig. 2, this figure is the circuit diagram of the pwm control circuit used of the described compensating controller to the PWM transducer of the embodiment of the invention.

The described compensating controller 200 to the PWM transducer of the embodiment of the invention is used for pwm control circuit.

Input voltage vin is the VCC end power supply of compensating controller 200 behind resistance 101.The electric current of the secondary winding of transformer 109 provides input voltage by diode 110 rectifications and the backward load of capacitor filtering.

Described compensating controller to the PWM transducer comprises rest-set flip-flop 114, oscillator 116, processor 118 and overcurrent comparator 125, and PWM comparator 126.

The S termination of rest-set flip-flop 114 is received the square wave that oscillator 116 produces, the R end of rest-set flip-flop 114 and the output signal of door 119, and the Q end of rest-set flip-flop 114 is the OUT end of the described compensating controller of output termination.The signal of the Q end output of rest-set flip-flop 114 is used for power ratio control switching tube 108.

Sawtooth waveforms 121 after the triangular wave 117 treated devices 118 that described oscillator 116 produces are processed is cumulative with induced voltage Vs, and the result sends to overcurrent comparator 125 after adding up.This stack is to realize by adder 122.The output of described overcurrent comparator 125 links to each other with described input with door 119; Described sawtooth waveforms 121 reduces with the increase of power switch pipe 108 ON time in the described pwm control circuit.

Describedly link to each other with the output of PWM comparator 126 with another input of door 119.

The two paths of signals that described PWM comparator 126 receives is respectively the feedback network signal of optocoupler 112 outputs, and the signal after signal superposes after induced voltage Vs and 124 processing of triangular wave 117 process oblique wave compensation processors.This stack is to realize by adder 123.

Because the described compensating controller 200 to the PWM transducer of the embodiment of the invention, because the input voltage vin of the pwm control circuit of using is higher, the transformer 109 former limit inductive current rates of rise of pwm control circuit are larger, so ON time ton is less.By giving an induced voltage Vs stack sawtooth waveforms 121 that reduces with the increase of ON time ton (also claiming oblique wave).Like this, ON time ton was less when input voltage was higher, and the amount of the upper stack of induced voltage Vs is just larger, and the value of induced voltage Vs is just less, and namely input voltage is higher, and 109 former limit peak current Ipp1 are less for transformer.Can offset because the error current Id that time-delay td brings by selecting suitable compensation slope and bucking voltage, so that under different input voltages, 109 former limit true peak electric current I pp are identical for transformer, thereby the peak power output of pwm control circuit equates.

For the ease of those skilled in the art's understanding, describe below in conjunction with concrete waveform.

Referring to Fig. 3, this figure is the waveform correlation figure of the described circuit of Fig. 2.

115 is the square wave CLK oscillogram that vibrator 116 produces among the figure; 117 is the oscillogram of the triangular wave SAW of vibrator 116 generations; 130 is that the Q end of rest-set flip-flop 114 is the oscillogram of output output signal; 121 is the oscillogram of the sawtooth waveforms after triangular wave 117 treated devices 118 are processed; 128 is the overcurrent protection comparative level oscillogram after adder 122 is processed; 131,132 time waveform figures for difference corresponding input voltage V1, V2; 129,130 is respectively the schematic diagram of the induced voltage Vs pressure drop of primary current on resistance 107 of correspondence under different input voltage V1 and V2.

Be superimposed upon on the induced voltage VS by the sawtooth waveforms 121 of processing rear generation by triangular wave 117, to determine the over-current protection point of overcurrent comparator 125.

In trailing edge power ratio control switching tube 108 conductings of square wave CLK115, and determine that the over-current protection point of power switch pipe shutoff 108 is determined by waveform 128.ON time ton1 and ton2 are respectively ON time corresponding to input voltage V1 and V2 (V1＞V2).When input voltage is larger, ON time ton is less, and corresponding current-limiting points is also lower to be Vpp1＜Vpp2, thereby offsets the error Id that is brought by time-delay td.The current-limiting points of setting is:

$I_{\mathrm{Pp}1}=\frac{V_{\mathrm{pp}1}}{R_S}=\frac{V_{\mathrm{ref}}-V_1}{R_S}---\left(10\right)$

$I_{\mathrm{Pp}2}=\frac{V_{\mathrm{pp}2}}{R_S}=\frac{V_{\mathrm{ref}}-V_2}{R_S}---\left(11\right)$

After considering time-delay td, actual current-limiting points is:

$I_{P1}=\frac{V_{\mathrm{ref}}-V_1}{R_S}+\frac{V_{\mathrm{in}1}}{L_P}*t_d---\left(12\right)$

$I_{P2}=\frac{V_{\mathrm{ref}}-V_2}{R_S}+\frac{V_{\mathrm{in}2}}{L_P}*t_d---\left(13\right)$

Formula (13) Lp is the inductance of transformer 109.

Wherein ton1 and ton2 are respectively ON time corresponding to input voltage V1 and V2 (V1＞V2).

Connect an input of the inner overcurrent comparator 125 of compensating controller 200 (chip) in the induced voltage Vs, and compare with a fixed level Vref-saw1, as Vs during greater than Vref-saw1, compensating controller 200 can switch-off power switching tubes 108.

Wherein

Corresponding 129 these oblique lines.

Wherein,

Corresponding 130 these oblique lines.

The actual current peak current will equate namely under two input voltages;

I _P1＝I _P2＝I _p (14)

$\frac{V_{\mathrm{in}1}-V_{\mathrm{in}2}}{L_p}*t_d=\frac{V_1-V_2}{R_S}---\left(15\right)$

$t_{\mathrm{on}1}=\frac{(V_{\mathrm{ref}}-V_1)*L_P}{R_S*V_{\mathrm{in}1}}---\left(16\right)$

$t_{\mathrm{on}2}=\frac{(V_{\mathrm{ref}}-V_2)*L_P}{R_S*V_{\mathrm{in}2}}---\left(17\right)$

Then have:

$t_{\mathrm{on}2}-t_{\mathrm{on}1}=\frac{(V_{\mathrm{in}1}-V_{\mathrm{in}2})*I_P*L_P}{V_{\mathrm{in}1}*V_{\mathrm{in}2}}---\left(18\right)$

$V_1-V_2=\frac{(V_{\mathrm{in}1}-V_{\mathrm{in}2})*t_D*R_S}{L_P}---\left(19\right)$

Divided by formula (18), the slope that can get sawtooth waveforms 121 is by formula (19)

$k_{\mathrm{SAW}1}=\frac{V_1-V_2}{t_{\mathrm{on}1}-t_{\mathrm{on}2}}=-\frac{V_{\mathrm{in}1}*V_{\mathrm{in}2}*t_d*R_S}{{L_P}^2*I_P}---\left(20\right)$

Referring to Fig. 4, this figure is the realization circuit diagram of the described processor of the embodiment of the invention and adder.

Processor 118 is by converting the difference of triangular wave 117saw and a reference level Vref 1 to electric current I 150, in the K electric current I 151 doubly that to obtain an amplitude by the current mirror that is comprised of metal-oxide-semiconductor 150 and metal-oxide-semiconductor 151 be I150, by resistance 147 this signal is superimposed upon on the current sensing signal Vs again, thereby realization is to processing and the superposition function of triangular wave.

Pressure reduction by 148 and 149 two nodes among Fig. 4 can get:

V _{be_133}+V _{be_141}＝V _{be_134}+V _{be_142}＝V ₁₄₈-V ₁₄₉(21)

Current formula according to the NPN pipe has:

$\frac{K*T}{q}\ln \frac{I_{135}}{I_S}+\frac{K*T}{q}\ln \frac{I_{137}}{I_S}=\frac{K*T}{q}\ln \frac{I_{136}}{I_S}+\frac{K*T}{q}\ln \frac{I_{138}}{I_S}---\left(22\right)$

I ₁₃₅*I ₁₃₇＝I ₁₃₆*I ₁₃₈(23)

$\frac{I_{135}}{I_{136}}=\frac{I_{138}}{I_{137}}---\left(24\right)$

Formula (23) and formula (24) processed obtain:

$\frac{I_{135}+I_{136}}{I_{136}}=\frac{I_{138}+I_{137}}{I_{137}}---\left(25\right)$

$\frac{I_{135}-I_{136}}{I_{136}}=\frac{I_{138}-I_{137}}{I_{137}}---\left(26\right)$

Had by 148 and 149 node current formula again:

I ₁₃₅+I ₁₃₆＝I ₁₄₅(27)

I ₁₃₇+I ₁₃₈＝I ₁₄₆(28)

Got by formula (25), formula (26), formula (27), formula (28):

$I_{150}=I_{138}-I_{137}=\frac{I_{138}+I_{137}}{I_{136}+I_{135}}*(I_{135}-I_{136})=\frac{I_{146}}{I_{145}}*(I_{135}-I_{136})---\left(29\right)$

$V_{\mathrm{comp}}=k*I_{150}*(R_{147}+R_S)=k*\frac{I_{146}}{I_{145}}*(I_{135}-I_{136})*(R_{147}+R_S)---\left(30\right)$

In addition, because the Vbe approximately equal of transistor 133 and 134, then its E pole tension also equates, then has:

V _saw+V _gs+I ₁₃₅*R＝V _ref1+V _gs+I ₁₃₆*R (31)

$I_{135}-I_{136}=\frac{V_{\mathrm{ref}1}-V_{\mathrm{saw}}}{R}---\left(32\right)$

Thereby obtain:

$V_{\mathrm{comp}}=k*\frac{I_{146}}{I_{145}}*\frac{(V_{\mathrm{ref}1}-V_{\mathrm{saw}})}{R}*(R_{147}+R_S)---\left(33\right)$

$V_{\mathrm{saw}}=\frac{V_{p\_p}}{T}*t---\left(34\right)$

V _{P_p}Be the voltage magnitude of triangular wave, T is triangular wave/clk cycle, then V _CompSlope be

$K_{\mathrm{Vcomp}}=-k*\frac{I_{146}}{I_{145}}*\frac{V_{p\_p}}{T}*\frac{(R_{147}+R_S)}{R}$

In input voltage range (Vin1, the Vin2) scope of being concerned about, so that k _SAW1=K _VcompCan be so that input voltage when being Vin1 and Vin2, transformer primary side true peak electric current equates, thus the peak power output of system equates.

The present invention also provides a kind of pwm control circuit, and described control circuit can comprise the compensating controller of previously described any PWM transducer.

More than diffused resistor voltage coefficient provided by the present invention is extracted and the method and system of Building of Simulation Model, be described in detail, used specific case herein principle of the present invention and execution mode are set forth, the explanation of above embodiment just is used for helping to understand method of the present invention and core concept thereof; Simultaneously, for one of ordinary skill in the art, according to thought of the present invention, all will change in specific embodiments and applications, in sum, this description should not be construed as limitation of the present invention.

Claims (6)

1. the compensating controller of a PWM transducer is characterized in that, is used for pwm control circuit; Described compensating controller comprises:

The S termination of rest-set flip-flop is received the square wave that oscillator produces, and the R termination of rest-set flip-flop is received the output signal with door, and the Q end of trigger is output; The output of rest-set flip-flop connects the output of compensating controller, and the output of compensating controller connects the control end of power switch pipe in the described PWM transducer, and the signal of the output output of rest-set flip-flop is used for controlling the turn-on and turn-off of described power switch pipe;

Sawtooth waveforms and induced voltage after the treated device of the triangular wave that described oscillator produces is processed are cumulative, and cumulative rear result sends to an input of overcurrent comparator; Another input of described overcurrent comparator connects the overcurrent reference voltage; The output of described overcurrent comparator links to each other with the input of door with described; Described sawtooth waveforms reduces with the increase of described power switch pipe ON time; Described induced voltage is the voltage on the inductive reactance Rs, and the first end of described power switch pipe is by described inductive reactance Rs ground connection, the Same Name of Ends of the former limit winding of the second end connection transformer of described power switch pipe;

Describedly link to each other with the output of PWM comparator with another input of door;

The two paths of signals that described PWM comparator receives is respectively the feedback network signal, and the signal after induced voltage and the signal stack of described triangular wave after the oblique wave compensation processor is processed.

2. the compensating controller of PWM transducer according to claim 1 is characterized in that, described sawtooth waveforms and induced voltage are cumulative, determines the over-current protection point of described overcurrent comparator.

3. the compensating controller of PWM transducer according to claim 1 is characterized in that, the square wave trailing edge power ratio control switching tube conducting that described oscillator produces, and the over-current protection point that described power switch pipe turn-offs is determined by described output signal with door.

4. the compensating controller of PWM transducer according to claim 1, it is characterized in that, described processor converts the difference of described triangular wave and a reference level to first electric current, obtaining an amplitude by current mirror is described the first electric current K the second electric current doubly, and described the first electric current and the second electric current are sawtooth waveforms.

5. the compensating controller of PWM transducer according to claim 4 is characterized in that, cumulative being specially by resistance of described sawtooth waveforms and induced voltage is accumulated in the signal of described the second electric current on the induced voltage.

6. pwm control circuit, described control circuit comprises the compensating controller of the arbitrary described PWM transducer of claim 1 to 5.

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