CN102364858B - Constant-current switching power supply controller capable of controlling through primary side and method - Google Patents

Abstract

The invention discloses a constant current switching power supply controller and method for primary side control. The constant current switching power supply controller includes: a sampling and holding module, a secondary diode conduction time detection circuit, a multiplier module, an average current loop, a sawtooth wave generation module, a comparison module, a timing trigger, a driving pulse generation module and a drive module. The controller of the present invention does not need an optocoupler and a secondary side feedback circuit, and only needs to detect the peak value of the primary side current to realize output constant current control, so the real-time performance is good, the control loop is easy to stabilize, and the circuit dynamic performance is good. For occasions with power factor requirements, due to the use of constant frequency constant on-time control, no multiplier is required, the structure is simple, and high power factor of the input current within the full input range can be achieved. In addition, because the circuit works at a fixed frequency, it is easier to pass through the electromagnetic Compatible marking; further, the controller can be integrated into a single chip.

Description

A primary-side controlled constant current switching power supply controller and method

technical field

The invention belongs to the technical field of switching power supplies, and relates to a primary side controlled constant current switching power supply controller and a method.

Background technique

At present, many isolated power supplies such as mobile phone chargers and high-power LED drivers usually require the circuit to have the function of outputting constant current due to application requirements; IEC1000-3-2, etc., the above-mentioned isolated power supply must also have the power factor correction (PFC) function. Figure 1 shows a commonly used single-stage power factor correction scheme: by detecting the output current on the secondary side of the transformer, the power factor correction is performed on the secondary side. After constant current control, it is fed back to the primary side PFC control circuit through the optocoupler. The existing technical scheme shown in FIG. 1 increases the complexity of the circuit due to the existence of the secondary current sampling circuit and the optocoupler. Furthermore, due to the aging problem of the optocoupler, the stability and service life of the circuit are affected to a certain extent.

The solution to the above problems is to adopt a control scheme with both primary side constant current control and power factor correction functions, that is, without secondary side current sampling and optocoupler components, and directly obtain output current information on the primary side of the isolation transformer to control Realize output constant current, and realize high power factor at the same time, as shown in Figure 2. At present, there are already some control chips on the market that can realize the above output constant current and PFC functions, such as ICL8001G from Infineon, MP4020 from MPS, LinkSwitch-PH series from PI, etc. However, these chips all adopt frequency conversion control mode (current critical intermittent mode), so the circuit frequency fluctuation range is relatively large, and it is difficult to pass the electromagnetic compatibility standard;

In addition, when the above chip is applied to the flyback circuit, the input current is:

${\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; avg</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; pk</span>}}\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\frac{\mathrm{<span\; class="notranslate">\; k</span>}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; ac</span>}}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}^{<span\; class="notranslate">\; \&prime;</span>}\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&omega;t</span>}}{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; ac</span>}}\mathrm{<span\; class="notranslate">\; sin</span>}\mathrm{<span\; class="notranslate">\; \&omega;t</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

为输出电压折算到变压器原边之后的电压，k为电流电压对应系数，D为占空比，为导通时间与开关周期的比值；半个工频周期内的归一化的输出电流波形如图3所示，其中s＝V_o’/V_ac，可以看到随着s变小，即输入电压幅值增大，输入电流的波形失真越厉害，功率因数越低。in

It is the voltage after converting the output voltage to the primary side of the transformer, k is the corresponding coefficient of current and voltage, D is the duty cycle, and is the ratio of the conduction time to the switching period; the normalized output current waveform in half a power frequency cycle is as follows As shown in Figure 3, where s=V _o '/V _ac , it can be seen that as s becomes smaller, that is, the amplitude of the input voltage increases, the waveform distortion of the input current is more severe, and the power factor is lower.

Contents of the invention

The purpose of the present invention is to overcome the defects in the above-mentioned prior art, and propose a constant current switching power supply controller and method for primary side control, which has a simple structure and can realize constant output current only by detecting the peak value of the primary side current. Current control can also achieve a higher power factor in the full voltage input range; in addition, the circuit operating frequency is constant, so it is easier to pass the electromagnetic compatibility standard; the invention can also be used for low-power power supplies with no power factor requirements for DC input, Realize output constant current function.

Primary-side controlled constant current switching power supply controllers include:

Sample and hold module, the input terminal of the sample and hold module receives the output signal CS from the primary side current sampling network of the switching power supply main circuit, and its output terminal is connected to an input terminal of the multiplier module, and the described sample and hold module is used for Sample and hold the primary current sampling signal in each switching cycle, and extract the peak value of the primary current sampling signal;

The secondary diode conduction time detection circuit, the secondary diode conduction time detection circuit detects the time interval during which the secondary diode has current according to the signal TD received from the main circuit, and detects the time interval during which the secondary diode has current The time interval signal is sent to the multiplier module;

A multiplier module, after the multiplier module receives the signals of the sample-and-hold module and the conduction time detection circuit of the secondary side diode, an output value is proportional to the output signal of the sample-and-hold module, and the duty cycle and period are all related to the secondary The output signal of the side diode conduction time detection circuit is the same as the rectangular pulse signal, and the average value of the output signal is proportional to the average value of the secondary side diode current signal;

The average current loop, the average current loop receives the output signal from the multiplier module, the output terminal of the average current loop is connected to an input terminal of the comparison module, and the average current loop is used to average the output signal of the multiplier module Compare with the voltage reference inside the average current loop and amplify the error between the two;

A sawtooth wave generation module, the input terminal of the sawtooth wave generation module is connected to the output end of the drive pulse generation module, the sawtooth wave generation module generates a sawtooth wave during the conduction period of the primary switch tube of the main circuit of the switching power supply, and the primary side switch tube During shutdown, the sawtooth wave generating module outputs low level;

Comparison module, the input of the comparison module receives the output signal of the sawtooth wave generation module and the output signal of the average current loop respectively, the comparison module compares the output signal of the sawtooth wave generation module and the output signal of the average current loop, when the sawtooth When the output signal of the wave generation module rises to be equal to the output signal of the average current loop, the output signal of the comparison module flips from low level to high level, and when the output signal of the sawtooth wave generation module drops below the output signal of the average current loop When , the output signal of the comparison module flips from high level to low level;

A timing trigger, the timing trigger is used to generate a clock signal with a fixed frequency, which is output to the driving pulse generation module;

A driving pulse generating module, the driving pulse generating module is used to generate a pulse signal according to the signal output by the comparison module and the clock signal output by the timing trigger;

When the comparison module produces a low-level to high-level reversal, the pulse signal of the driving pulse generation module is reset from high level to low level; when the clock signal output by the timing trigger is reversed from low level to high level , the pulse signal of the driving pulse generating module is set from low level to high level; repeating and beginning to generate a pulse sequence;

A driving module, the driving module is used to enhance the ability of the driving pulse generating module to drive the primary switching tube.

The input signal of the secondary diode conduction time detection circuit comes from a signal that can reflect the secondary diode conduction time in the circuit, such as:

The signal TD received by the secondary diode conduction time detection circuit from the main circuit is received from a winding Na (auxiliary winding) of the main circuit transformer.

The signal TD received from the main circuit by the conduction time detection circuit of the secondary diode is received from the drain of the primary switch tube of the main circuit through the DC blocking/voltage dividing circuit.

The signal TD received by the secondary diode conduction time detection circuit from the main circuit is from the secondary winding of the current transformer CT in the secondary winding Ns circuit of the main circuit. The cathode is received by one end of the resistor Rc.

The multiplier module may be a multiplier or an equivalent circuit capable of realizing the same function.

The average current loop includes input resistance, voltage reference, compensation network and operational amplifier.

Further, the average current loop voltage reference may be a DC voltage reference, and when the main circuit input of the switching power supply is an AC source, the average current loop voltage reference may also be a sine half-wave reference with a fixed amplitude.

Wherein, the switching power supply main circuit works in discontinuous current mode (DCM) or critical discontinuous mode (BCM).

Wherein, the operational amplifier of the average current loop can be a voltage type or a current type (transconductance type).

Further, the compensation network of the average current loop may be a pure integral link, or a proportional integral link, or a proportional integral derivative link.

Wherein, the driving module is a push-pull structure (totem pole structure) composed of two bipolar transistors or metal oxide semiconductor field effect transistors.

Control method of the present invention is:

(1) Through the design of the main circuit of the switching power supply, the main circuit of the switching power supply works in an intermittent or critical intermittent state;

(2) sample and hold the primary switching current sampling signal of the main circuit of the switching power supply, extract the primary current sampling peak value of the main circuit; detect the conduction time of the secondary side diode simultaneously, and compare the primary current sampling peak value of the main circuit with The conduction time of the secondary diodes is multiplied to simulate a current waveform proportional to the output secondary diode current;

(3) Through the average current loop control, the average value of the signal simulated in step (2) is kept constant, thereby realizing the constant output current.

(4) produce sawtooth wave while carrying out above-mentioned steps; When sawtooth wave rises to be equal to the output signal amplitude of average current loop described in step (3), obtain the turn-off trigger signal of the primary switch tube of main circuit

(5) While carrying out the above steps, use a timing trigger to obtain a fixed working frequency of the switching tube of the switching power supply, and use the timing trigger to generate a trigger signal to turn on the primary side switching tube.

The beneficial effect of the present invention is that: the constant current switching power supply controller and method of the primary side control of the present invention can realize the output constant current control only by detecting the peak value of the primary side current without optocoupler and secondary side feedback circuit, so real-time The control loop is easy to be stable, the dynamic performance of the circuit is better, and the structure is simpler; furthermore, due to the use of constant frequency and constant on-time control, the high power factor of the input current in the full input range can be achieved, and it is easier to pass the electromagnetic Compatibility standard, in addition the controller can be integrated as a single chip.

Description of drawings

Fig. 1 is a block diagram of a conventional secondary side constant current flyback circuit;

Fig. 2 is a block diagram of the flyback circuit of primary side constant current control;

Fig. 3 is the input current calculation waveform of the flyback circuit adopting frequency conversion control (critical conduction mode);

Fig. 4 block diagram of the controller circuit of the present invention;

FIG. 5(a) is a schematic circuit diagram of a first specific embodiment of the current sampling module 100 in the present invention;

FIG. 5(b) is a working waveform diagram of the circuit of the first specific embodiment of the current sampling module 100 in the present invention;

Fig. 6 (a) is the circuit schematic diagram of the second specific embodiment of the current sampling module 100 in the present invention;

Fig. 6 (b) is the working waveform diagram of the circuit of the second specific embodiment of the current sampling module 100 in the present invention;

Fig. 7 (a) is the circuit diagram of the first specific embodiment of the present invention;

Fig. 7 (b) is the working waveform diagram of the circuit of the first specific embodiment of the present invention;

Fig. 8 (a) is the circuit schematic diagram of the second specific embodiment of the present invention;

Fig. 8 (b) is the working waveform diagram of the circuit of the second specific embodiment of the present invention;

9 is a schematic circuit diagram of a third embodiment of the present invention;

FIG. 10 is a schematic circuit diagram of an embodiment of several modules in the present invention;

Fig. 11 is a schematic circuit diagram of a specific embodiment of the present invention applied to a DC-DC conversion circuit without power factor requirements;

Fig. 12 is a working waveform diagram of Fig. 11 embodiment;

FIG. 13 is a schematic circuit diagram of a specific embodiment of the present invention applied to an AC-DC conversion circuit with power factor requirements;

Fig. 14 is the working waveform diagram of Fig. 13 embodiment;

FIG. 15 is a schematic diagram of the present invention applied to a non-isolated buck-boost circuit.

Detailed ways

The content of the present invention will be described in detail below in conjunction with the block diagram of the present invention and the schematic diagrams of specific embodiments.

As shown in Figure 4, the constant current switching power supply controller controlled by the primary side includes:

Sample and hold module 100, the input terminal of described sample and hold module 100 receives the output signal CS from the primary side current sampling network 005 of switching power supply main circuit, and its output terminal is connected to an input terminal of secondary side current analog module 300, described The sampling and holding module 100 is used to sample and hold the sampling signal of the primary current i _pri in each switching cycle, and extract the peak value of the sampling signal of the primary current i _pri ;

The secondary diode conduction time detection circuit 200, the secondary diode conduction time detection circuit 200 detects the time interval during which the secondary diode has current according to the signal TD received from the main circuit of the switching power supply, and detects the secondary diode conduction time interval. The time interval signal when the side diode has current is sent to the multiplier module 300;

The multiplier module 300, after the multiplier module 300 receives the signal of the sampling and holding module 100 and the secondary diode conduction time detection circuit 200, outputs a value proportional to the output signal of the sampling and holding module, and the duty ratio and a rectangular pulse signal with the same period as the output signal of the secondary diode conduction time detection circuit, and the average value of the output signal is proportional to the average value of the secondary diode current signal;

Average current loop 400, described average current loop 400 comprises input resistance Rf, compensation network, voltage reference Vref, the output of multiplier module 300 receives the negative terminal input of the operational amplifier Uf in average current loop 400 through resistance Rf, operation The positive terminal input of the amplifier Uf is connected to the voltage reference Vref; since the average current loop 400 itself has a switching cycle average value filtering effect, the input signal of the negative terminal of the operational amplifier of the average current loop 400 is the output signal of the multiplier module 300, and the switching cycle ripple is filtered After the average value; this signal is compared with the voltage reference Vref, the error between the two is amplified by the compensation network and the operational amplifier, and the output terminal of the average current loop 400 is connected to an input terminal of the comparison module 600;

The sawtooth wave generation module 500, the input terminal of the sawtooth wave generation module is connected to the output end of the drive pulse generation module, the sawtooth wave generation module 500 generates a sawtooth wave during the conduction period of the primary switching tube of the main circuit of the switching power supply. When the side switch tube is turned off, the sawtooth wave generating module 500 outputs a low level;

Comparison module 600, the comparison module 600 includes a comparator Uc, the negative terminal input of the comparator Uc is connected to the output of the average current loop 400, the positive terminal input of the comparator Uc is connected to the output of the sawtooth wave generation module 500; the comparison module 600 generates a sawtooth wave The output signal of the module 500 is compared with the output signal of the average current loop 400. When the output signal of the sawtooth wave generation module 500 rises to be equal to the output signal of the average current loop 400, the output of the comparison module 600 is turned from low level to high level. Level, when the output signal of the sawtooth wave generation module drops below the output signal of the average current loop, the output signal of the comparison module flips from high level to low level;

Timing flip-flop 700, the timing flip-flop 700 is used to generate a clock signal, output to the drive pulse generation module 800;

The driving pulse generating module 800, the driving pulse generating module 800 is used to generate a pulse signal according to the signal output by the comparison module 600 and the clock signal output by the timing flip-flop 700; when the comparison module 600 generates a low level to a high level When turning over, the pulse signal of the driving pulse generating module 800 is reset from high level to low level; Set from low level to high level; repeat and start, generate pulse sequence;

The driving module 900 , the driving module 900 is used to enhance the ability of the driving pulse generating module 800 to drive the primary switch tube 004 .

VDD is the power supply end of the detection control circuit 008, which is connected to the external power supply of the main circuit.

GND is the ground terminal of the detection control circuit 008, through which the internal ground of the detection control circuit is connected with the ground of the main circuit.

Fig. 5(a) is a schematic circuit diagram of the first specific embodiment of the sampling and holding module 100 in the present invention, and the circuit sampling module 100 adopts a Chinese patent (publication number: CN 101615432). Fig. 5 (b) is the operating waveform diagram of the first specific embodiment circuit of the current sampling module 100 in the present invention, wherein Va is the input signal of the peak sampling and holding circuit, and Vb is the output signal of the peak sampling and holding circuit; the sampling and holding module The circuit shown in Figure 6(a) can also be used, in which one end of the sampling switch Sa is connected to the input signal Va, the other end is connected to one end of the capacitor Ca and the positive input end of the operational amplifier Ua, the control end of Sa is connected to the control signal Vg, and the capacitor The other end of Ca is grounded, the negative input terminal of the operational amplifier is connected to the output terminal, and the output signal is represented by Vb, and the operational amplifier constitutes a forward follower; the working waveform of the sample-and-hold circuit shown in Figure 6(a) is shown in Figure 6(b) shown.

The secondary diode conduction time detection circuit 200 is mainly used to detect the time interval during which current flows in the secondary diode. According to the different ways in which the secondary diode conduction time detection circuit 200 receives the signal TD from the main circuit, it can be Take the following three options:

Option 1: Realize the secondary diode conduction time detection circuit 200 by detecting the positive voltage of the auxiliary winding of the main circuit transformer, that is, the secondary diode conduction time detection circuit 200 receives the signal TD from the main circuit from one of the main circuit transformers. Winding Na (auxiliary winding) receives. As shown in Figure 7(a), the main waveform is shown in Figure 7(b). Among them, the transformer auxiliary winding terminal with the same name is connected to the primary ground, the terminal with the different name is connected to the input terminal of the positive level detection circuit, the output terminal of the positive level detection circuit is connected to the input terminal of the delay link, and the output of the delay link is used as the secondary side diode conduction time detection The output of the circuit 200; when the secondary diode conducts and flows current i _sec , the auxiliary winding voltage Vaux is at a high level, and by detecting the high level time interval of the auxiliary winding, it can be indirectly detected that the secondary diode has current flowing time interval; considering that there is a certain amount of advance between the _isec zero-crossing point and the auxiliary winding voltage Vaux zero-crossing point in the actual circuit, a delay link is introduced after the positive level detection circuit in the realization circuit of Figure 7 (a) to compensate; Another method is to increase the reference level of the positive level detection circuit to reduce the detection error of the secondary diode conduction time; the positive level detection circuit in Fig. towards the voltage realization.

Solution 2: Realize the secondary diode conduction time detection circuit 200 by detecting the source-drain voltage waveform V _Qds of the main circuit switch tube 004, that is, the secondary diode conduction time detection circuit 200 receives the signal from the main circuit TD is received from the drain of the primary switching tube of the main circuit through the DC blocking/dividing circuit 010 . As shown in Figure 8(a), the main waveform is shown in Figure 8(b). where i _sec is the secondary side diode current, V _{in_dc} is the input power supply voltage; after the source-drain voltage V _Qds of the switch tube 004 is blocked and divided by the DC blocking/dividing circuit 010, the detection signal V _TD is obtained, The high level obtained after the differential comparison by the comparator Ub roughly corresponds to the time interval of the current flowing through the secondary side diode. Also consider that there is a certain advance between the i _sec zero-crossing point and the high-level zero-crossing point output by the comparator Ub in the actual circuit. Amount, Figure 8 (a) implements a delay link after the comparator Ub in the implementation circuit for compensation.

Solution 3: Realize the secondary diode conduction time detection circuit 200 by directly detecting the secondary diode current, that is, the secondary diode conduction time detection circuit receives the signal TD from the main circuit from the secondary winding of the main circuit The secondary winding of the current transformer CT in the Ns circuit is connected to the anode of the diode Dc with the same name, and the cathode of the diode Dc is connected to one end of the resistor Rc to receive. As shown in Figure 9, the terminal with the same name of the primary winding of the current transformer CT is connected to the negative terminal of the output capacitor, the terminal with the same name of the primary winding of the current transformer CT is connected to the terminal with the same name of the secondary winding of the transformer, and the secondary winding of the current transformer CT is The end of the same name of the diode Dc is connected to the anode of the diode Dc, the cathode of the diode Dc is connected to one end of the resistance Rc and the positive input end of the comparator Ub, the opposite end of the secondary winding of the current transformer CT and the other end of the resistance Rc are grounded, and the end of the comparator Ub The negative input terminal is grounded, and the output terminal of the comparator is used as the output of the secondary diode conduction time detection circuit 200 .

当控制端电平为高电平，开关Sc导通，将电容器Cs两端电压保持为零；当控制端电平为高电平，开关Sc关断，直流电流源IDC给电容器Cs充电，产生锯齿波信号。当锯齿波产生模块500产生的锯齿波信号触及到平均电流环400的输出电平，比较模块600的输出电平从低电平翻转为高电平。锯齿波产生模块500产生的锯齿波信号斜率固定，锯齿波信号的宽度对应着原边开关管004的导通时间，因此对于特定的平均电流环400的输出电平幅值，原边开关管004的导通时间恒定。在有功率因数要求的应用时，当原边开关管004的导通时间恒定，原边开关管004的电流波形包络线跟随反激电路的输入信号为与正弦半波信号，从而实现高功率因数。The sawtooth wave generation module 500 includes a DC current source IDC, a capacitor Cs and a switch Sc, as shown in Figure 10; wherein the DC current source IDC can be obtained by known techniques; the input terminal of the DC current source IDC is connected to the DC voltage source VDD, and the output terminal is connected to One end of the capacitor Cs is connected to one end of the switch Sc as the output end of the sawtooth wave generation module 500, the other end of the capacitor Cs is connected to the other end of the switch Sc and then grounded, and the control end of the switch Sc is connected to the inverting output end of the drive generation module 800

When the level of the control terminal is high, the switch Sc is turned on, and the voltage across the capacitor Cs is kept at zero; when the level of the control terminal is high, the switch Sc is turned off, and the DC current source IDC charges the capacitor Cs, generating sawtooth signal. When the sawtooth wave signal generated by the sawtooth wave generation module 500 reaches the output level of the average current loop 400, the output level of the comparison module 600 is turned from low level to high level. The slope of the sawtooth wave signal generated by the sawtooth wave generation module 500 is fixed, and the width of the sawtooth wave signal corresponds to the conduction time of the primary side switch tube 004. Therefore, for a specific output level amplitude of the average current loop 400, the primary side switch tube 004 The on-time is constant. In applications with power factor requirements, when the conduction time of the primary switch tube 004 is constant, the current waveform envelope of the primary switch tube 004 follows the input signal of the flyback circuit and is a half-sine wave signal, thereby achieving high power factor.

The timing flip-flop 700 generates a narrow pulse with a fixed frequency, and the pulse frequency determines the operating frequency of the circuit. The specific implementation circuit of the timing flip-flop 700 belongs to the known technology.

The driving pulse generation module 800 can be realized by RS flip-flop, as shown in FIG. During flat reversal, the output signal of the drive pulse generation module 800 is reset from high level to low level; The low level is set to the high level, and this cycle repeats to generate an output pulse sequence.

The output of the driving pulse generating module 800 is sent to the gate of the flyback LED driver primary switch Q1 through the driving module 900 , and the specific implementation circuit of the driving pulse generating module 800 belongs to the known technology.

Fig. 11 is a circuit schematic diagram of a specific embodiment of the present invention applied to a DC-DC conversion circuit, wherein the input power of the main circuit adopts a DC power supply Vdc, the transformer adopts a three-winding structure, that is, an auxiliary winding Taux is added, and the sample and hold module 100 Using the circuit shown in FIG. 5( a ), the scheme of the secondary diode current detection module 200 is the same as that shown in FIG. 7 .

Fig. 12 is the working waveform diagram of Fig. 11 embodiment, wherein, v ₄₀₀ is the output waveform of average current loop 400, v ₆₀₀ is the output waveform of sawtooth wave generation module 600, v ₇₀₀ is the output waveform of timing flip-flop 700, i _pri is the current waveform of the primary switch tube of the flyback circuit. i _sec is the diode flow waveform on the secondary side of the flyback circuit, V _{GS_Q1} and V _{GS_sa} are the driving waveform of the switch tube 004 of the flyback circuit and the control terminal waveform of the switch Sa respectively, v ₁₀₀ is the output waveform of the sample and hold module 100, and v _Taux is The voltage waveform of the auxiliary winding of the transformer, v ₃₀₀ is the output waveform of the multiplier module 300 .

Fig. 13 is the circuit schematic diagram of a specific embodiment of the present invention applied to the AC-DC conversion circuit with power factor requirements, wherein, the main circuit input power adopts the AC power supply Vac (001), and the output of Vac is connected to the two rectifier bridges B1 Input, the positive output of the rectifier bridge B1 is connected to one end of the capacitor Cin, the same-named end of the transformer 003, and one end of the absorption network 002, the negative output of the rectifier bridge B1 and the other end of the capacitor Cin are connected to the primary ground, and Cin is a small-capacity non-polar Capacitor, other parts of the main circuit and the implementation circuit of the controller module are the same as those in the embodiment shown in FIG. 11 .

FIG. 14 is a working waveform diagram of the embodiment in FIG. 13 , where v ₂₀₀ is the output waveform of the secondary diode current detection module 200 . Assuming that the number of turns of the primary winding of the main circuit transformer is Np, the number of turns of the secondary side is Ns, and the sampling coefficient of the primary circuit is K ₁ , it can be known from Figure 12 and Figure 14:

${\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; V</span>}}}_{\mathrm{<span\; class="notranslate">\; 300</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\frac{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}}{\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; I</span>}}}_{\mathrm{<span\; class="notranslate">\; sec</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\frac{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

送入平均电流环300，与设定的基准Vref进行比较，即可间接调节输出平均电流，从而实现输出电流恒流。由于平均电流环自身具有滤波功能，只要将v₃₀₀送入平均电流环400，即可在平均电流环400的运算放大器输入端获得v₃₀₀的平均值也可以在乘法器模块300的输出和平均电流环300增加一级滤波电路，但对电路功能基本没有影响。That is, the average value of the output v ₃₀₀ of the multiplier module 300 is proportional to the output current average value I _o ; as can be seen from equation (2), as long as the

Sending it into the average current loop 300 and comparing it with the set reference Vref can indirectly adjust the output average current, thereby realizing a constant output current. Since the average current loop itself has a filtering function, as long as v ₃₀₀ is fed into the average current loop 400, the average value of v ₃₀₀ can be obtained at the input terminal of the operational amplifier of the average current loop 400 It is also possible to add a filter circuit to the output of the multiplier module 300 and the average current loop 300 , but this basically has no effect on the circuit function.

For the application of the present invention to an AC-DC converter circuit with power factor requirements, it is assumed that the input voltage is U _in sin(ωt), so the average value of the input current can be obtained:

${\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}<span\; class="notranslate">\; =</span>{\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; i</span>}}}_{\mathrm{<span\; class="notranslate">\; the\; price</span>}}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span>}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; on</span>}}<span\; class="notranslate">\; \&CenterDot;</span>\frac{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; on</span>}}}{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; on</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; sin</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; |</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

Among them, Lm is the excitation inductance of the transformer, Ton is the conduction time of the switch tube, and T is the switching period. For a certain input voltage, due to the constant conduction time Ton of the switch tube and the constant switching period T, the AC incoming line voltage is completely proportional to the input voltage wave, thereby achieving a high power factor.

The present invention can be applied to isolated output, and can also be applied to non-isolated output. FIG. 15 is a schematic diagram of the present invention applied to a non-isolated buck-boost circuit; wherein, the specific implementation of each module can refer to the specific embodiments shown in FIGS. 7 to 10 .

The specific modules included in the present invention, such as the current sampling and holding circuit 100, the secondary diode conduction time detection module 200, the multiplier module 300, etc., can be implemented by those skilled in the art without violating its spirit. Or through various combinations to form different specific embodiments, which will not be described in detail here.

No matter how detailed the above description is, there are still many ways to implement the present invention, and what is described in the specification is only a specific implementation example of the present invention. All equivalent changes or modifications made according to the spirit of the present invention shall fall within the protection scope of the present invention.

The above detailed description of embodiments of the invention is not intended to be exhaustive or to limit the invention to the precise forms described above. While specific embodiments of, and examples for, the invention were described above for illustrative purposes, various equivalent modifications are possible within the scope of the invention, those skilled in the relevant art will recognize.

While the above description describes particular embodiments of the invention and describes the best mode contemplated, no matter how detailed the foregoing description appears, the invention can be practiced in many ways. The details of the above-described circuit structure and its control manner may vary considerably in its implementation details, yet it is still included in the invention disclosed herein.

As above, it should be noted that specific terms used in describing certain features or solutions of the present invention should not be used to indicate that the terms are redefined here to limit some specific features, features or aspects of the present invention to which the terms are related. plan. In conclusion, the terms used in the following claims should not be construed to limit the invention to the particular embodiments disclosed in the specification, unless the above detailed description expressly defines those terms. Accordingly, the true scope of the invention encompasses not only the disclosed embodiments but also the appended claims.

Claims (15)

1. the constant current switch power-supply controller of electric of former limit control is characterized in that comprising:

Sampling keeps module; Described sampling keeps the input of module to receive the output signal CS from the primary current sampling network of Switching Power Supply main circuit; An input of its output termination multiplication module; Described sampling keeps module to be used in each switch periods maintenances of sampling of primary current sampled signal, the peak value of the sampled signal of extraction primary current;

Secondary diode current flow time detection circuit; Described secondary diode current flow time detection circuit is according to receiving the signal TD from main circuit; Detecting the secondary diode has the time interval of electric current, and will detect the secondary diode and have the time interval signal of electric current to send to multiplication module;

Multiplication module; Described multiplication module receives sampling and keeps after the signal of module and secondary diode current flow time detection circuit; Exporting an amplitude keeps the output signal of module proportional with sampling; Duty ratio and cycle all with the identical rectangular pulse signal of output signal of secondary diode current flow time detection circuit, the output signal averaging and the secondary diode current signal averaging of this multiplication module are proportional;

The average current ring; Described average current articulating is received the output signal from multiplication module; An input of the output termination comparison module of average current ring, described average current ring are used for the inner voltage reference of the output signal averaging of multiplication module and average current ring is compared and error between the two is amplified;

The sawtooth waveforms generation module; The output of the input termination driving pulse generation module of described sawtooth waveforms generation module; The sawtooth waveforms generation module is switching tube conduction period generation sawtooth waveforms on the former limit of Switching Power Supply main circuit, the switching tube blocking interval on former limit, sawtooth waveforms generation module output low level;

Comparison module; The input of described comparison module receives the output signal of sawtooth waveforms generation module and the output signal of average electric current loop respectively; This comparison module compares the output signal of sawtooth waveforms generation module and the output signal of average electric current loop; When the output signal of sawtooth waveforms generation module rises to when equating with the output signal of average current ring; For high level, when the output signal of sawtooth waveforms generation module dropped to the output signal that is lower than the average current ring, comparison module output signal was low level from the high level upset to comparison module output signal from the low level upset;

Clocked flip-flop, described clocked flip-flop is used to produce the clock signal of fixed-frequency, outputs to the driving pulse generation module;

The driving pulse generation module; Two inputs of described driving pulse generation module connect the output of comparison module and the output of clocked flip-flop respectively, and the driving pulse generation module produces pulse signal according to the signal of comparison module output and the clock signal of clocked flip-flop output; When low level of comparison module generation arrived the upset of high level, the pulse signal of driving pulse generation module reset to low level by high level; When the clock signal of clocked flip-flop output was high level by the low level upset, the pulse signal of driving pulse generation module was set to high level by low level; Go round and begin again, produce pulse train;

Driver module, the input of described driver module connects the output of driving pulse generation module, is used to strengthen the ability of the former limit of the driving switching tube of said driving pulse generation module.

2. controller according to claim 1 is characterized in that it is that auxiliary winding from the main circuit transformer receives that described secondary diode current flow time detection circuit receives signal TD from main circuit.

3. controller according to claim 1 is characterized in that it is that drain electrode from the former limit switching tube of main circuit is through receiving at a distance from straight/bleeder circuit that described secondary diode current flow time detection circuit receives signal TD from main circuit.

4. controller according to claim 1; It is characterized in that described average current ring comprises input resistance, voltage reference, compensating network and operational amplifier; The negative terminal input that the output of multiplication module is received the operational amplifier in the average current ring through resistance R _ f, the input of operational amplifier Uf anode meets voltage reference Vref.

5. like the said controller of claim 4, it is characterized in that said average current loop voltag benchmark can be the direct voltage benchmark, average current loop voltag benchmark also can be the fixing half-sinusoid benchmark of amplitude when the Switching Power Supply main circuit is input as alternating current source.

6. controller according to claim 1, the operational amplifier that it is characterized in that described average current ring can be voltage-type or current mode.

7. controller according to claim 1, the compensating network that it is characterized in that said average current ring is pure integral element, proportional integral link, perhaps a kind of in the PID link.

8. the constant current switch power supply of former limit control comprises main circuit and controller, and said main circuit is isolated form or non-isolation type topology, comprises the input rectifying bridge, and switching tube, primary current sampling network is characterized in that said controller comprises:

Sampling keeps module; Described sampling keeps the input of module to receive the output signal CS from the primary current sampling network of Switching Power Supply main circuit; An input of its output termination multiplication module; Described sampling keeps module to be used in each switch periods maintenances of sampling of primary current sampled signal, the peak value of the sampled signal of extraction primary current;

Secondary diode current flow time detection circuit; Described secondary diode current flow time detection circuit is according to receiving the signal TD from main circuit; Detecting the secondary diode has the time interval of electric current, and will detect the secondary diode and have the time interval signal of electric current to send to multiplication module;

Multiplication module; Described multiplication module receives sampling and keeps after the signal of module and secondary diode current flow time detection circuit; Exporting an amplitude keeps the output signal of module proportional with sampling; Duty ratio and cycle all with the identical rectangular pulse signal of output signal of secondary diode current flow time detection circuit, the output signal averaging and the secondary diode current signal averaging of this multiplication module are proportional;

The average current ring; Described average current articulating is received the output signal from multiplication module; An input of the output termination comparison module of average current ring, described average current ring are used for the inner voltage reference of the output signal averaging of multiplication module and average current ring is compared and error between the two is amplified;

The sawtooth waveforms generation module; The output of the said driving pulse generation module of input termination of described sawtooth waveforms generation module; The sawtooth waveforms generation module is switching tube conduction period generation sawtooth waveforms on the former limit of Switching Power Supply main circuit; The switching tube blocking interval on former limit, sawtooth waveforms generation module output low level;

Comparison module; The input of described comparison module receives the output signal of sawtooth waveforms generation module and the output signal of average electric current loop respectively; This comparison module compares the output signal of sawtooth waveforms generation module and the output signal of average electric current loop; When the output signal of sawtooth waveforms generation module rises to when equating with the output signal of average current ring; For high level, when the output signal of sawtooth waveforms generation module dropped to the output signal that is lower than the average current ring, comparison module output signal was low level from the high level upset to comparison module output signal from the low level upset;

Clocked flip-flop, described clocked flip-flop is used to produce the clock signal of fixed-frequency, outputs to the driving pulse generation module;

Driving pulse generation module, described driving pulse generation module are used for producing pulse signal according to the clock signal of the signal of comparison module output and clocked flip-flop output;

When low level of comparison module generation arrived the upset of high level, the pulse signal of driving pulse generation module reset to low level by high level; When the clock signal of clocked flip-flop output was high level by the low level upset, the pulse signal of driving pulse generation module was set to high level by low level; Go round and begin again, produce pulse train;

Driver module, described driver module are used to strengthen the ability of the former limit of the driving switching tube of said driving pulse generation module.

9. like the said Switching Power Supply of claim 8, it is characterized in that it is that auxiliary winding from the main circuit transformer receives that said secondary diode current flow time detection circuit receives signal TD from main circuit.

10. like the said Switching Power Supply of claim 8, it is characterized in that it is that drain electrode from the former limit switching tube of main circuit is through receiving at a distance from straight/bleeder circuit that described secondary diode current flow time detection circuit receives signal TD from main circuit.

11. like the said Switching Power Supply of claim 8; It is characterized in that described average current ring comprises input resistance, voltage reference, compensating network and operational amplifier; The negative terminal input that the output of multiplication module is received the operational amplifier in the average current ring through resistance R _ f, the input of operational amplifier Uf anode meets voltage reference Vref.

12. like the said Switching Power Supply of claim 8, it is characterized in that said average current loop voltag benchmark can be the direct voltage benchmark, average current loop voltag benchmark also can be the fixing half-sinusoid benchmark of amplitude when the Switching Power Supply main circuit is input as alternating current source.

13. like the said Switching Power Supply of claim 8, the operational amplifier that it is characterized in that described average current ring can be voltage-type or current mode.

14. like the said Switching Power Supply of claim 8, the compensating network that it is characterized in that said average current ring is pure integral element, proportional integral link, perhaps a kind of in the PID link.

15. be operated in discontinuous current or critical discontinuous mode like the said Switching Power Supply main circuit of claim 8.

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