CN104022646A - Control system for Cuk-type switching power supply - Google Patents

Abstract

The invention relates to a control system for a Cuk-type switching power supply. On the basis of a single-period control circuit, a III compensating network and a feedback circuit are additionally arranged. An output voltage Vo is divided by the feedback circuit to generate feedback signals VFB. The III compensating network comprises an error amplifier EA, resistors R1, R2 and R3 and capacitors C11, C22 and C33, the in-phase end of the error amplifier EA is connected with the feedback signals VFB, the opposite-phase end of the error amplifier EA is connected with a reference voltage VREF through the resistor R1, the resistor R3 is connected with the capacitor C33 in series to be bridged to the two ends of the resistor R1, the resistor R2 is connected with the capacitor C22 in series to be connected with the capacitor C11 in parallel, and the two ends of the parallel connection part are bridged between the output end and the opposite-phase end of the error amplifier EA. The output of the error amplifier EA is compared with the output of an integral circuit in the single-period control circuit, and the duty ratio generated by comparative results controls connection and disconnection of a power tube in the Cuk-type switching power supply.

Description

A kind of control system of Cuk type Switching Power Supply

Technical field

The present invention relates to DC-DC Switching Power Supply, particularly, in the control system of a kind of Cuk of IC interior (Qiu Ke) type Switching Power Supply, belong to microelectronics technology.

Background technology

The features such as Organic Light Emitting Diode (Organic Light Emitting Diode OLED) has softness, transparent, image quality is clear, energy-conserving and environment-protective, are considered to be the novel planar Display Technique of future generation of tool potentiality.OLED display floater needs a positive voltage and negative supply voltage power supply, thereby the design of negative pressure chip becomes the main flow trend in this field.Cuk circuit input and output voltage direction, has low output voltage current ripples and high efficiency advantage, and meanwhile, Cuk circuit also possesses extraordinary noise resisting ability and antijamming capability, so Cuk type circuit becomes the focus of research gradually.But the power stage of traditional Cuk type circuit structure exists two inductance and electric capacity, small-signal model is comparatively complicated.Existing control circuit (Fig. 1) is to adopt monocycle (One-cycle) control mode, although circuit can unconditional stability, but there is comparatively significantly defect in this control mode: monocycle control is a kind of pulse duration (Pulse Width Modulation PWM) modulator approach of non-linear large-signal, it is not a kind of proper closed-loop control system, control signal is limited to the calibration capability of output voltage, in the time of load variations, output voltage will produce larger variation, the load regulation extreme difference of circuit is (in Fig. 1 when load current saltus step, output voltage produces larger variation).

Summary of the invention

The present invention controlled on the basis of Cuk circuit in the existing monocycle, provided a kind of Cuk type switch converters monocycle in conjunction with III type compensation control system.On the basis of original monocycle control circuit, add III type compensating network and feedback circuit, make loop form a closed-loop control system, by zero limit of compensation power level, thereby make Cuk type switch converters keep stable.

Technical scheme of the present invention is: a kind of control system of Cuk type Switching Power Supply, comprise Cuk type Switching Power Supply and monocycle control circuit two parts, it is characterized in that, on the basis of monocycle control circuit, set up III compensating network and feedback circuit, form closed-loop control system, compare the break-make of power tube in the Duty ratio control Cuk type Switching Power Supply of comparative result generation with the output of integrating circuit in the output of III compensating network and monocycle control circuit;

Cuk type Switching Power Supply comprises first, second two stage power level circuit, wherein:

The first power stage circuit comprises inductance L 1, capacitor C 1 and power tube Sn, one end of inductance L 1 is connected with supply voltage VDD anode, supply voltage VDD negativing ending grounding, the other end of inductance L 1 connects one end of capacitor C 1 and the drain electrode of power tube Sn, the source ground of power tube Sn, the grid of power tube Sn connects the output of drive circuit;

The second power stage circuit comprises inductance L 2, capacitor C 2, sustained diode 1 and load resistance Ro, in the anode of one end of inductance L 2 and sustained diode 1 and the first power stage circuit, the other end of capacitor C 1 is connected, the negativing ending grounding of sustained diode 1, the other end of inductance L 2 connects one end of capacitor C 2 and one end of load resistance Ro and as output voltage V o, the equal ground connection of the other end of the other end of capacitor C 2 and load resistance Ro;

Monocycle control circuit comprises integrating circuit, comparator, rest-set flip-flop and drive circuit, wherein:

Integrating circuit comprises operational amplifier E1, resistance R z, capacitor C and reset switch K, the end of oppisite phase of operational amplifier E1 connects the anode of sustained diode 1 in the second power stage circuit by resistance R z, the in-phase end ground connection of operational amplifier E1, is connected across after capacitor C and reset switch K parallel connection between the end of oppisite phase and output VE1 of operational amplifier E1;

The in-phase end of comparator connects the output VE1 of operational amplifier E1 in integrating circuit;

The reset terminal R of rest-set flip-flop connects the output of comparator, and the set end S of rest-set flip-flop connects clock signal, and the output Q of rest-set flip-flop connects the input of drive circuit, the non-end of output of rest-set flip-flop connect the control end of reset switch K in integrating circuit;

Feedback circuit comprises two identical series resistance R, and the non-series connection end of two resistance R connects respectively the anode of output voltage V o and supply voltage VDD, the series connection end dividing potential drop output feedback signal VFB of two resistance R;

III compensating network comprises error amplifier EA, resistance R 1, R2, R3 and capacitor C 11, C22, C33, the in-phase end of error amplifier EA connects the feedback signal VFB of feedback circuit output, the end of oppisite phase of error amplifier EA connects reference voltage V REF by resistance R 1, resistance R 3 is connected across the two ends of resistance R 1 after connecting with capacitor C 33, the non-series connection end of capacitor C 33 connects the end of oppisite phase of error amplifier EA, the non-series connection end of resistance R 3 connects reference voltage V REF, resistance R 2 is connected with capacitor C 22, the non-series connection end of capacitor C 33 connects one end of capacitor C 11 and the output VEA of error amplifier EA, the non-series connection end of resistance R 2 connects the other end of capacitor C 11 and the end of oppisite phase of error amplifier EA, the output VEA of error amplifier EA connects the end of oppisite phase of comparator as the output that connects III compensating network.

Advantage of the present invention and remarkable result:

1) the invention provides closed-loop control system in a kind of sheet of fully realizing in Cuk integrated circuit, this system is on the basis of prior art monocycle control circuit, to set up III type compensating network and feedback circuit realization, power tube conducting in the time that each clock starts, now output voltage declines, in the output of III type compensating network and monocycle control circuit, the output of integrating circuit compares the duty ratio of generation by the shutoff of power tube, ensure that Cuk loop can steady operation, strengthened the load regulation of circuit.

2) remove to compensate a pair of conjugate pole of two stage power level circuit in monocycle control circuit by zero limit of III type compensating network, make Cuk type Switching Power Supply produce stable duty ratio and output voltage.

3) first order of power stage and the second level are separated, the disturbance of the first order is not exerted an influence to the second level.

Brief description of the drawings

Fig. 1 is the Cuk type circuit of controlling traditional monocycle;

Fig. 2 is Cuk circuit control system of the present invention;

Fig. 3 is the present invention while normally working, Cuk circuit each point work wave.

Embodiment

Referring to Fig. 2, compared with prior art Fig. 1, increase the III type compensating network and two feedback circuits that same resistance R is in series that comprise that error amplifier EA, resistance R 1, R2, R3 and capacitor C 11, C22, C33 form, for zero limit of compensation loop, kept the stable of loop.Control section is by integrating circuit of the prior art, comparator, rest-set flip-flop, drive circuit add that III type compensating circuit and feedback circuit form, the output VEA of III type compensating network connects the end of oppisite phase of comparator in prior art, in the integrating circuit being connected with the in-phase end of comparator, the output VE1 of operational amplifier E1 compares, the output of comparator connects the R end of rest-set flip-flop, be reset terminal, be used for producing duty cycle signals, carry out the break-make of power ratio control pipe Sn by drive circuit.

The specific works process of circuit is as follows: in the time that the rising edge of clock arrives, the output Q set of rest-set flip-flop is " 1 ", now power tube Sn closure, K switch disconnects, the voltage that integrator gathers diode D1 forward end starts integration, its output linearity rises, when crossing with the output VEA of III type compensator, comparator reverses, K switch closure, and integrator resets, in this metal-oxide-semiconductor Sn disconnection simultaneously, until next rising edge clock arrives, and so forth, circuit produces stable duty ratio and output voltage.

The monocycle control loop being made up of integrator circuit and comparator circuit separates the first order of power stage and the second level, and the disturbance of the first order is not exerted an influence to the second level.Like this, only have L2 from VEA to the transfer function of output voltage V o, the impact of the conjugate pole that C2 causes, its small-signal transfer function is as follows:

$\frac{v_0}{v_{\mathrm{EA}}}=\frac{\mathrm{VDD}+\left|\mathrm{Vo}\right|}{L2\·C2\·s^2+L/R_0\·s+1}---\left(1\right)$

Wherein s represents that time domain arrives the Laplace transform of complex frequency domain.From formula (1), can find out and have a pair of conjugate pole to be positioned at frequency filtering place.Now, remove a pair of conjugate pole of compensation power level by traditional III type compensating network, its expression formula is as follows:

$\frac{v_{\mathrm{EA}}}{v_{\mathrm{FB}}}=\frac{K{(\frac{s}{w_z}+1)}^2}{s{(\frac{s}{w_p}+1)}^2}---\left(2\right)$

Wherein $K=\frac{1}{R1(C1+C2)},$ $w_z=\frac{1}{C2\·R2}=\frac{1}{C3(R1+R3)},$ $w_p=\frac{1}{R3\·C3}=\frac{C1+C2}{R2\·C1\·C2}.$ Remove the conjugate pole of compensation power level zero point with two, two limits are mended at high frequency treatment, suppress high-frequency noise.Compensate a low-frequency pole, make to pass through o'clock at 1/10 switching frequency place, obtain enough phase margins simultaneously.

The oscillogram of Cuk circuit each point when Fig. 3 has shown normal work, can see that circuit produces stable duty ratio and output voltage.

Feature and the content of this patent disclose as above, but those skilled in the art may make all replacement and amendments that does not deviate from invention spirit based on explanation of the present invention.Therefore, protection scope of the present invention should be not limited to above-mentioned embodiment, and should comprise the various substitutions and modifications of the present invention that do not deviate from, and is contained by claims.

Claims (1)

1. the control system of a Cuk type Switching Power Supply, comprise Cuk type Switching Power Supply and monocycle control circuit two parts, it is characterized in that, on the basis of monocycle control circuit, set up III compensating network and feedback circuit, form closed-loop control system, compare the break-make of power tube in the Duty ratio control Cuk type Switching Power Supply of comparative result generation with the output of integrating circuit in the output of III compensating network and monocycle control circuit;

Cuk type Switching Power Supply comprises first, second two stage power level circuit, wherein:

The first power stage circuit comprises inductance L 1, capacitor C 1 and power tube Sn, one end of inductance L 1 is connected with supply voltage VDD anode, supply voltage VDD negativing ending grounding, the other end of inductance L 1 connects one end of capacitor C 1 and the drain electrode of power tube Sn, the source ground of power tube Sn, the grid of power tube Sn connects the output of drive circuit;

The second power stage circuit comprises inductance L 2, capacitor C 2, sustained diode 1 and load resistance Ro, in the anode of one end of inductance L 2 and sustained diode 1 and the first power stage circuit, the other end of capacitor C 1 is connected, the negativing ending grounding of sustained diode 1, the other end of inductance L 2 connects one end of capacitor C 2 and one end of load resistance Ro and as output voltage V o, the equal ground connection of the other end of the other end of capacitor C 2 and load resistance Ro;

Monocycle control circuit comprises integrating circuit, comparator, rest-set flip-flop and drive circuit, wherein:

Integrating circuit comprises operational amplifier E1, resistance R z, capacitor C and reset switch K, the end of oppisite phase of operational amplifier E1 connects the anode of sustained diode 1 in the second power stage circuit by resistance R z, the in-phase end ground connection of operational amplifier E1, is connected across after capacitor C and reset switch K parallel connection between the end of oppisite phase and output VE1 of operational amplifier E1;

The in-phase end of comparator connects the output VE1 of operational amplifier E1 in integrating circuit;

The reset terminal R of rest-set flip-flop connects the output of comparator, and the set end S of rest-set flip-flop connects clock signal, and the output Q of rest-set flip-flop connects the input of drive circuit, the non-end of output of rest-set flip-flop connect the control end of reset switch K in integrating circuit;

Feedback circuit comprises two identical series resistance R, and the non-series connection end of two resistance R connects respectively the anode of output voltage V o and supply voltage VDD, the series connection end dividing potential drop output feedback signal VFB of two resistance R;

III compensating network comprises error amplifier EA, resistance R 1, R2, R3 and capacitor C 11, C22, C33, the in-phase end of error amplifier EA connects the feedback signal VFB of feedback circuit output, the end of oppisite phase of error amplifier EA connects reference voltage V REF by resistance R 1, resistance R 3 is connected across the two ends of resistance R 1 after connecting with capacitor C 33, the non-series connection end of capacitor C 33 connects the end of oppisite phase of error amplifier EA, the non-series connection end of resistance R 3 connects reference voltage V REF, resistance R 2 is connected with capacitor C 22, the non-series connection end of capacitor C 33 connects one end of capacitor C 11 and the output VEA of error amplifier EA, the non-series connection end of resistance R 2 connects the other end of capacitor C 11 and the end of oppisite phase of error amplifier EA, the output VEA of error amplifier EA connects the end of oppisite phase of comparator as the output that connects III compensating network.