CN102055334B - Control circuit and method of buck-boost power converter - Google Patents

Abstract

A control circuit of a buck-boost power converter for providing a control signal to drive a buck-boost power stage to convert an input voltage to an output voltage, the buck-boost power stage comprising an inductor and at least two switches connected to the inductor, the control circuit comprising: the feedback circuit detects the output voltage to generate a feedback signal; the error amplifier is connected with the feedback circuit and amplifies the difference between the feedback signal and a reference voltage to generate an error signal; a dynamic duty cycle generator for generating a first signal according to the detection signal after being activated; and the driving circuit is connected with the error amplifier and the dynamic working period generator and determines the control signal according to the error signal and the first signal. The control circuit and the method of the buck-boost power converter have the advantages of optimizing the switching sequence of the switch, reducing switching loss, improving efficiency and reducing output ripple.

Description

Control circuit and method of buck-boost power converter

technical field

The invention relates to a buck-boost power converter, in particular to a control circuit and method for a buck-boost power converter.

Background technique

1 shows a known synchronous buck-boost power converter 10, which includes a buck-boost power stage 12 and a control circuit 22 that provides signals VA, VB, VC, and VD to switch the voltages in the buck-boost power stage 12, respectively. The switches SWA, SWB, SWC and SWD convert the input voltage Vin to the output voltage Vo. In the control circuit 14, the resistors R1 and R2 divide the output voltage Vo to generate the feedback signal VFB, and the error amplifier 24 amplifies the difference between the feedback signal VFB and the reference voltage Vref to generate the signal VCL to the signal generator 22, and the signal generator 22 provides signals VU, VX and VY, wherein the signal VU is related to the signal VCL, the signals VX and VY are sawtooth wave signals, the comparator 18 compares the signals VU and VX to generate a signal VZ1, and the comparator 20 compares the signals VU and VY to generate a signal VZ2, The logic circuit 16 generates signals VA, VB, VC and VD according to the signals VZ1 and VZ2.

Fig. 2 shows the waveform diagram of the signal in Fig. 1, wherein the waveform 26 is the signal VY, the waveform 28 is the signal VU, the waveform 30 is the signal VX, the waveform 32 is the signal VZ1, the waveform 34 is the signal VZ2, the waveform 36 is the signal VA, and the waveform 38 is signal VB, waveform 40 is signal VC, and waveform 42 is signal VD. 1 and 2, when the signal VX is greater than the signal VU, such as from time t1 to t2, the signal VZ1 is at a low level, as shown in waveforms 28, 30 and 32, when the signal VX is smaller than the signal VU, such as from time t2 to t2 At t5, the signal VZ1 is at a high level. When the signal VY is greater than the signal VU, such as time t0 to t3, the signal VZ2 is low level, as shown in waveforms 26, 28 and 34, when the signal VY is smaller than the signal VU, such as time t3 to t4, the signal VZ2 is Micro Motion bit. Assuming that a cycle of the output voltage Vo is represented by time t1 to t5, during the period from time t1 to t2, the buck-boost power stage 12 is in the first state, at this time the switches SWA and SWC are turned off and the switches SWB and SWD are turned on (turn on), as shown in waveforms 36 to 42. During the time t2 to t3, the buck-boost power stage 12 is in the second state, at this time the switches SWA and SWD are turned on and the switches SWB and SWC are turned off. During time t3 to t4, the buck-boost power stage 12 is in the third state, at this time, the switches SWA and SWC are turned on and the switches SWB and SWD are turned off. During time t4 to t5, the buck-boost power stage 12 returns to the second state. Wherein the second state appears twice in one cycle, if the switching sequence can be changed to arrange the two second states together, the switching loss can be reduced and the performance can be improved. In addition, when the signal VU rises or falls and approaches the peak value of the signal VX or the valley value of the signal VY, the duty cycle of the signal VB or VC will be very short, so the switch SWB or SWC may not be fully turned on (turn on) It turns off again, which has no meaning other than increasing the switching loss.

U.S. Patent No. 7,176,667 also proposes a control circuit for a buck-boost power converter, which uses a pulse width modulation signal that adjusts the pulse width with the output voltage Vo and a signal with a fixed pulse width to determine the switch in the buck-boost mode. The switching of SWA, SWB, SWC and SWD, however, this method of inserting a fixed pulse width signal may cause a discontinuous duty cycle during mode conversion, resulting in a large output ripple.

Therefore, there are various inconveniences and problems mentioned above in the control circuit of the known buck-boost power converter.

Contents of the invention

The object of the present invention is to provide a control circuit and method for a buck-boost power converter.

Another object of the present invention is to provide a control circuit and method for optimizing switching sequence of switches to improve performance.

Another object of the present invention is to provide a control circuit and method for reducing output ripple.

Another object of the present invention is to provide a control circuit and method for accelerating the transient response from the power-saving mode back to normal operation.

For realizing the above object, technical solution of the present invention is:

A control circuit of a buck-boost power converter, which is used to provide a control signal to drive a buck-boost power stage to convert an input voltage into an output voltage. The buck-boost power stage includes an inductor and at least two switch connections The inductance is characterized in that the control circuit includes:

A feedback circuit, detecting the output voltage to generate a feedback signal;

The error amplifier is connected to the feedback circuit, and amplifies the difference between the feedback signal and a reference voltage to generate an error signal;

a dynamic duty cycle generator, which generates a first signal according to the detection signal after being activated; and

The drive circuit is connected to the error amplifier and the dynamic duty cycle generator, and determines the control signal according to the error signal and the first signal.

The control circuit of the buck-boost power converter of the present invention can also be further realized by adopting the following technical measures.

In the aforementioned control circuit, the detection signal is related to at least one of the input voltage, the output voltage, the inductor current passing through the inductor, and the variation of the output voltage.

The aforementioned control circuit, wherein the dynamic duty cycle generator provides a compensation signal according to the detection signal.

The aforementioned control circuit, wherein the dynamic duty cycle generator includes:

an analog-to-digital converter that converts the detection signal into a compensation signal; and

A digital-to-analog converter is connected to the analog-to-digital converter to convert the compensation signal into the first signal.

The aforementioned control circuit further includes a duty cycle compensator connected to the error amplifier and the dynamic duty cycle generator, and compensates the error signal according to the compensation signal.

The aforementioned control circuit, wherein the duty cycle compensator includes:

a voltage divider circuit, which divides the error signal according to the compensation signal to generate a first voltage;

a voltage-to-current converter connected to the voltage dividing circuit to convert the first voltage into a current;

The resistor is connected between the error amplifier and the voltage-to-current converter, and generates a second voltage for adjusting the error signal in response to the current.

The aforementioned control circuit, wherein the drive circuit includes:

The first comparator is connected to the error amplifier, and compares the error signal with a sawtooth signal to generate a first comparison signal;

The second comparator is connected to the dynamic duty cycle generator, and compares the first signal and the sawtooth signal to generate a second comparison signal; and

The logic circuit is connected to the first comparator and the second comparator, and generates the control signal according to the first and second comparison signals.

The aforementioned control circuit further includes a mode selector connected to the dynamic duty cycle generator to generate an enable signal according to the detection signal to activate the dynamic duty cycle generator.

The aforementioned control circuit further includes a mode selector connected to the dynamic duty cycle generator to generate an enable signal according to the error signal to activate the dynamic duty cycle generator.

The aforementioned control circuit further includes a clamp detector connected to the error amplifier, and clamps the level of the error signal according to the second detection signal, the second detection signal is related to at least one of the input voltage, the output voltage and the inductor current a related.

A control method for a buck-boost power converter, which is used to provide a control signal to drive a buck-boost power stage to convert an input voltage into an output voltage. The buck-boost power stage includes an inductor and at least two switch connections Described inductance, it is characterized in that described control method comprises the following steps:

(A) detecting the output voltage to generate a feedback signal;

(B) amplifying the difference between the feedback signal and a reference voltage to generate an error signal;

(C) determining the first signal according to the detection signal;

(D) triggering the first signal according to an enabling signal; and

(E) determining the control signal according to the error signal and the first signal.

In the aforementioned control method, wherein the detection signal is related to at least one of the input voltage, the output voltage, the inductor current passing through the inductor, and the variation of the output voltage.

The aforementioned control method, which further includes

providing a compensation signal based on the detection signal; and

The error signal is compensated according to the compensation signal.

The aforementioned control method, wherein said step C comprises:

converting the detection signal into the compensation signal; and

converting the compensation signal into the first signal.

The aforementioned control method, wherein the step of compensating the error signal according to the compensation signal comprises:

dividing the error signal according to the compensation signal to generate a first voltage;

converting the first voltage to a current to a resistor to generate a second voltage; and

The error signal is adjusted by the second voltage.

The aforementioned control method, wherein said step E includes:

comparing the error signal with a sawtooth signal to generate a first comparison signal;

comparing the first signal and the sawtooth signal to generate a second comparison signal; and

The control signal is generated according to the first and second comparison signals.

The aforementioned control method further includes generating the enable signal according to the detection signal.

The aforementioned control method further includes generating the enabling signal according to the error signal.

The aforementioned control method further includes clamping the level of the error signal according to a second detection signal, and the second detection signal is related to at least one of the input voltage, the output voltage and the inductor current.

A control circuit of a buck-boost power converter, which is used to provide a control signal to drive a buck-boost power stage to convert an input voltage into an output voltage. The buck-boost power stage includes an inductor and at least two switch connections The inductance is characterized in that the control circuit includes:

A feedback circuit, detecting the output voltage to generate a feedback signal;

The error amplifier is connected to the feedback circuit, and amplifies the difference between the feedback signal and a reference voltage to generate a first error signal;

The duty cycle compensator is connected to the error amplifier, and compensates the first error signal according to the compensation signal to generate a second error signal;

a duty cycle generator connected to the duty cycle compensator and generating a first signal after being activated; and

The driving circuit is connected to the duty cycle compensator and the duty cycle generator, and determines the control signal according to the second error signal and the first signal.

The aforementioned control circuit, wherein the duty cycle compensator includes:

a voltage dividing circuit, which divides the first error signal according to the compensation signal to generate a first voltage;

a voltage-to-current converter connected to the voltage dividing circuit to convert the first voltage into a current; and

The resistor is connected between the error amplifier and the voltage-to-current converter, and a second voltage generated in response to the current is subtracted from the first error signal to generate the second error signal.

The aforementioned control circuit, wherein the duty cycle generator provides the dynamic first signal according to the detection signal, the detection signal is related to the input voltage, the output voltage, the inductor current passing through the inductor, and the output voltage At least one of the deltas is correlated.

The aforementioned control circuit, wherein the duty cycle generator generates the compensation signal according to the detection signal.

The aforementioned control circuit, wherein the duty cycle generator includes:

an analog-to-digital converter converting the detection signal into the compensation signal; and

A digital-to-analog converter is connected to the analog-to-digital converter to convert the compensation signal into the first signal.

The aforementioned control circuit, wherein the duty cycle generator provides a fixed first signal.

The aforementioned control circuit, wherein the drive circuit includes:

The first comparator is connected to the duty cycle compensator, and compares the second error signal with a sawtooth signal to generate a first comparison signal;

The second comparator is connected to the duty cycle generator, and compares the first signal and the sawtooth signal to generate a second comparison signal; and

The logic circuit is connected to the first comparator and the second comparator, and generates the control signal according to the first and second comparison signals.

The aforementioned control circuit further includes a mode selector connected to the duty cycle generator, and generates an enable signal to start the duty cycle generator according to the detection signal, and the detection signal is related to the input voltage, the output voltage, and the At least one of the inductor current of the inductor and the variation of the output voltage is related.

The aforementioned control circuit further includes a mode selector connected to the duty cycle generator for generating an enable signal according to the error signal to activate the duty cycle generator.

The aforementioned control circuit further includes a clamping detector connected to the error amplifier, clamping the level of the first error signal according to the detection signal, the detection signal and the input voltage, the output voltage and the inductance passing through the inductor At least one of the currents is relevant.

A control method for a buck-boost power converter, which is used to provide a control signal to drive a buck-boost power stage to convert an input voltage into an output voltage. The buck-boost power stage includes an inductor and at least two switch connections Described inductance, it is characterized in that described control method comprises the following steps:

(A) detecting the output voltage to generate a feedback signal;

(B) amplifying the difference between the feedback signal and a reference voltage to generate a first error signal;

(C) compensating the first error signal to generate a second error signal;

(D) triggering the first signal according to the enabling signal; and

(E) determining the control signal according to the second error signal and the first signal.

The aforementioned control method, wherein the step C includes determining a compensation signal for compensating the first error signal according to the detection signal, the detection signal is related to the input voltage, the output voltage, the inductor current passing through the inductor, and the output At least one of the variations in voltage is correlated.

The aforementioned control method, wherein said step C comprises:

dividing the first error signal according to the compensation signal to generate a first voltage;

converting the first voltage to a current to a resistor to generate a second voltage; and

Subtracting the second voltage from the first error signal produces the second error signal.

The aforementioned control method further includes providing the dynamic first signal according to the detection signal.

The aforementioned control method, wherein the step of providing the dynamic first signal according to the detection signal comprises:

converting the detection signal into said compensation signal; and

converting the compensation signal into the first signal.

The aforementioned control method further includes providing a fixed first signal.

The aforementioned control method, wherein said step E includes:

comparing the second error signal with a sawtooth signal to generate a first comparison signal;

comparing the first signal and the sawtooth signal to generate a second comparison signal; and

The control signal is generated according to the first and second comparison signals.

The aforementioned control method further includes generating the enable signal according to a detection signal related to at least one of the input voltage, the output voltage, the inductor current passing through the inductor, and the variation of the output voltage .

The aforementioned control method further includes generating the enabling signal according to the error signal.

The aforementioned control method further includes clamping the level of the first error signal according to a detection signal related to at least one of the input voltage, the output voltage, and the inductor current passing through the inductor.

A control circuit of a buck-boost power converter, which is used to provide a control signal to drive a buck-boost power stage to convert an input voltage into an output voltage. The buck-boost power stage includes an inductor and at least two switch connections The inductance is characterized in that the control circuit includes:

A feedback circuit, detecting the output voltage to generate a feedback signal;

The error amplifier is connected to the feedback circuit, and amplifies the difference between the feedback signal and a reference voltage to generate an error signal;

A clamping detector is connected to the error amplifier, and clamps the level of the error signal according to the detection signal; and

The drive circuit is connected to the error amplifier, and determines the control signal according to the error signal and a first signal.

In the aforementioned control circuit, wherein the detection signal is related to at least one of the input voltage, the output voltage, and the inductor current passing through the inductor.

The aforementioned control circuit, which further includes a dynamic duty cycle generator to generate the first signal according to the second detection signal, the second detection signal is related to the variation of the input voltage, output voltage, inductor current and the output voltage At least one of them is relevant.

In the aforementioned control circuit, the dynamic duty cycle generator further includes providing a compensation signal according to the second detection signal.

The aforementioned control circuit, wherein the dynamic duty cycle generator includes:

an analog-to-digital converter converting the second detection signal into a compensation signal; and

A digital-to-analog converter is connected to the analog-to-digital converter to convert the compensation signal into the first signal.

The aforementioned control circuit further includes a duty cycle compensator connected to the error amplifier and the dynamic duty cycle generator, and compensates the error signal according to the compensation signal.

The aforementioned control circuit, wherein the duty cycle compensator includes:

a voltage divider circuit, which divides the error signal according to the compensation signal to generate a first voltage;

a voltage-to-current converter connected to the voltage dividing circuit to convert the first voltage into a current; and

The resistor is connected between the error amplifier and the voltage-to-current converter, and generates a second voltage to adjust the error signal in response to the current.

The aforementioned control circuit further includes a mode selector connected to the dynamic duty cycle generator to generate an enable signal according to the second detection signal to activate the dynamic duty cycle generator.

The aforementioned control circuit further includes a mode selector connected to the dynamic duty cycle generator to generate an enable signal according to the error signal to activate the dynamic duty cycle generator.

The aforementioned control circuit, wherein the drive circuit includes:

The first comparator is connected to the error amplifier, and compares the error signal with a sawtooth signal to generate a first comparison signal;

a second comparator, comparing the first signal and the sawtooth signal to generate a second comparison signal; and

The logic circuit is connected to the first comparator and the second comparator, and generates the control signal according to the first and second comparison signals.

A control method for a buck-boost power converter, which is used to provide a control signal to drive a buck-boost power stage to convert an input voltage into an output voltage. The buck-boost power stage includes an inductor and at least two switch connections Described inductance, it is characterized in that described control method comprises the following steps:

(A) detecting the output voltage to generate a feedback signal;

(B) amplifying the difference between the feedback signal and a reference voltage to generate an error signal;

(C) clamping the level of the error signal according to the detection signal; and

(D) determining the control signal according to the error signal and a first signal.

In the aforementioned control method, wherein the detection signal is related to at least one of the input voltage, the output voltage, and the inductor current passing through the inductor.

The aforementioned control method further includes determining the first signal according to a second detection signal, and the second detection signal is related to at least one of the input voltage, output voltage, inductor current, and variation of the output voltage.

The aforementioned control method further includes providing a compensation signal to compensate the error signal according to the second detection signal.

The aforementioned control method, wherein the step of determining the first signal includes:

converting the second detection signal into a compensation signal; and

converting the compensation signal into the first signal.

The aforementioned control method, wherein the step of compensating the error signal comprises:

dividing the error signal according to the compensation signal to generate a first voltage;

converting the first voltage to a current to generate a second voltage for a resistor; and

The error signal is adjusted according to the second voltage.

The aforementioned control method further includes generating an enabling signal to trigger the first signal according to the second detection signal.

The aforementioned control method further includes generating an enabling signal to trigger the first signal according to the error signal.

The aforementioned control method, wherein said step D comprises:

comparing the error signal with a sawtooth signal to generate a first comparison signal;

comparing the first signal and the sawtooth signal to generate a second comparison signal; and

The control signal is generated according to the first and second comparison signals.

A control circuit of a buck-boost power converter, which is used to provide a control signal to drive a buck-boost power stage to convert an input voltage into an output voltage. The buck-boost power stage includes an inductor and at least two switch connections The inductance is characterized in that the control circuit includes:

A feedback circuit, detecting the output voltage to generate a feedback signal;

The error amplifier is connected to the feedback circuit, and amplifies the difference between the feedback signal and a reference voltage to generate a first error signal;

A clamping detector is connected to the error amplifier, and clamps the level of the first error signal according to the first detection signal;

The duty cycle compensator is connected to the error amplifier, and compensates the first error signal according to the compensation signal to generate a second error signal;

The dynamic duty cycle generator is connected to the duty cycle compensator, and generates a first signal according to the second detection signal after being activated;

a mode selector connected to the dynamic duty cycle generator, providing an enable signal to start the dynamic duty cycle generator; and

The driving circuit is connected to the duty cycle compensator and the dynamic duty cycle generator, and determines the control signal according to the second error signal and the first signal.

In the aforementioned control circuit, wherein the first detection signal is related to at least one of the input voltage, the output voltage, and the inductor current passing through the inductor.

In the aforementioned control circuit, wherein the second detection signal is related to at least one of the input voltage, the output voltage, the inductor current, and the variation of the output voltage.

The aforementioned control circuit, wherein the duty cycle compensator includes:

a voltage dividing circuit, which divides the first error signal according to the compensation signal to generate a first voltage;

a voltage-to-current converter connected to the voltage dividing circuit to convert the first voltage into a current;

The resistor is connected between the error amplifier and the voltage-to-current converter, generates a second voltage corresponding to the current and subtracts the first error signal to generate the second error signal.

The aforementioned control circuit, wherein the dynamic duty cycle generator provides the compensation signal to the duty cycle compensator according to the second detection signal.

The aforementioned control circuit, wherein the dynamic duty cycle generator includes:

an analog-to-digital converter converting the second detection signal into the compensation signal; and

A digital-to-analog converter is connected to the analog-to-digital converter to convert the compensation signal into the first signal.

In the aforementioned control circuit, wherein the mode selector generates the enable signal according to the second detection signal.

In the aforementioned control circuit, wherein the mode selector generates the enabling signal device according to the first error signal.

The aforementioned control circuit, wherein the drive circuit includes:

The first comparator is connected to the duty cycle compensator, and compares the second error signal with a sawtooth signal to generate a first comparison signal;

The second comparator is connected to the dynamic duty cycle generator, and compares the first signal and the sawtooth signal to generate a second comparison signal; and

The logic circuit is connected to the first comparator and the second comparator, and generates the control signal according to the first and second comparison signals.

A control method for a buck-boost power converter, which is used to provide a control signal to drive a buck-boost power stage to convert an input voltage into an output voltage. The buck-boost power stage includes an inductor and at least two switch connections Described inductance, it is characterized in that described control method comprises the following steps:

(A) detecting the output voltage to generate a feedback signal;

(B) amplifying the difference between the feedback signal and a reference voltage to generate a first error signal;

(C) clamping the level of the first error signal according to the first detection signal;

(D) triggering a first signal according to the enabling signal;

(E) determining the first signal according to the second detection signal;

(F) compensating the first error signal to generate a second error signal; and

(G) determining the control signal according to the second error signal and the first signal.

In the aforementioned control method, wherein the first detection signal is related to at least one of the input voltage, the output voltage, and the inductor current passing through the inductor.

In the aforementioned control method, wherein the second detection signal is related to at least one of the input voltage, output voltage, inductor current, and variation of the output voltage.

In the aforementioned control method, the step D includes generating the enable signal according to the second detection signal.

In the aforementioned control method, the step D includes generating the enable signal according to the first error signal.

In the aforementioned control method, the step F includes determining a compensation signal to compensate the first error signal according to the second detection signal.

The aforementioned control method, wherein said step E includes:

converting the second detection signal into the compensation signal; and

The compensation signal is converted into an analog first signal.

The aforementioned control method, wherein said step F further includes:

dividing the first error signal according to the compensation signal to generate a first voltage;

converting the first voltage to a current to a resistor to generate a second voltage; and

Subtracting the second voltage from the first error signal produces the second error signal.

The aforementioned control method, wherein said step G includes:

comparing the second error signal with a sawtooth signal to generate a first comparison signal;

comparing the first signal and the sawtooth signal to generate a second comparison signal; and

The control signal is generated according to the first and second comparison signals.

After adopting the above technical solution, the control circuit and method of the buck-boost power converter of the present invention have the following advantages:

1. Optimize the switch switching sequence, reduce switching loss and improve performance.

2. Reduce output ripple.

Description of drawings

FIG. 1 is a schematic diagram of a known synchronous buck-boost power converter;

Fig. 2 is the oscillogram of signal among Fig. 1;

Fig. 3 is a schematic diagram of an embodiment of the present invention;

FIG. 4 is a schematic diagram of the current path of the buck-boost power stage in the buck mode in FIG. 3;

FIG. 5 is a schematic diagram of the current path of the buck-boost power stage in the buck-boost mode in FIG. 3;

FIG. 6 is a schematic diagram of the current path of the buck-boost power stage in the boost mode in FIG. 3;

Fig. 7 is the oscillogram of signal among Fig. 3;

Fig. 8 is the waveform diagram of signal in Fig. 3;

Fig. 9 is a waveform diagram of the signal in Fig. 3;

Figure 10 is a schematic diagram of an embodiment of the duty cycle compensator in Figure 3; and

FIG. 11 is a schematic diagram of an embodiment of the logic circuit, the dynamic duty cycle generator and the mode selector in FIG. 3 .

In the figure, 10, buck-boost power converter 12, buck-boost power stage 14, control circuit 16, logic circuit 18, comparator 20, comparator 22, signal generator 24, error amplifier 26, signal VY Waveform 28, waveform 30 of signal VU, waveform 32 of signal VX, waveform 34 of signal VZ1, waveform 36 of signal VZ2, waveform 38 of signal VA, waveform 40 of signal VB, waveform 42 of signal VC, waveform 50 of signal VD , buck-boost power converter 52, buck-boost power stage 54, control circuit 55, drive circuit 56, logic circuit 58, comparator 60, comparator 62, duty cycle compensator 64, dynamic duty cycle generator 66 , pulse omission mode clamp detector 68, mode selector 70, error amplifier 72, feedback circuit 74, buck charging path 76, buck discharging path 78, boost charging path 80, buck charging or boost discharging path 82 , step-down discharge path 84, boost discharge path 86, boost charge path 90, signal Vcomp' waveform 92, sawtooth wave signal Vramp waveform 94, first signal Di waveform 96, inductor current IL waveform 100, signal The waveform 102 of Vcomp', the waveform 104 of the sawtooth signal Vramp, the waveform 106 of the first signal Di, the waveform 110 of the inductor current IL, the waveform 112 of the signal Vcomp', the waveform 114 of the sawtooth signal Vramp, and the waveform of the first signal Di 116, the waveform 118 of the inductor current IL, the average current 120 of the inductor current IL, the buffer 122, the voltage divider circuit 124, the buffer 126, the voltage-current converter 130, the sawtooth wave generator 132, the analog-to-digital converter 134, the digital-to-analog Converter 138, comparator 140, inverter 142, NAND gate 144, inverter.

Detailed ways

The present invention will be further described below in conjunction with embodiment and accompanying drawing.

Please refer to FIG. 3 , which shows a schematic diagram of an embodiment of the present invention. As shown in the figure, in the buck-boost power converter 50, the control circuit 54 provides control signals VA, VB, VC and VD to switch the switches SWA, SWB, and SWC and SWD are used to convert the input voltage Vin to the output voltage Vo. In the control circuit 54, the feedback circuit 72 detects the output voltage Vo to generate a feedback signal VFB, the error amplifier 70 amplifies the difference between the feedback signal VFB and the reference voltage VREF to generate an error signal Vcomp, and the pulse omission mode clamps the detector 66 clamps the level of the error signal Vcomp according to the detection signal S1, wherein the detection signal S1 is related to at least one of the input voltage Vin, the output voltage Vo and the inductor current IL, and the mode selector 68 generates a signal S3 according to the detection signal S2 to the logic The circuit 56 and the enabling signal EN enable the dynamic duty cycle generator 64, wherein the detection signal S2 is related to at least one of the input voltage Vin, the output voltage Vo, the inductor current IL, and the variation of the output voltage. In other embodiments, the mode The selector 68 can also use the error signal Vcomp to generate the signals S3 and EN, the dynamic duty cycle generator 64 determines the dynamic first signal Di and the compensation signal DDC according to the detection signal S2, and the duty cycle compensator 62 compensates the error signal according to the compensation signal DDC Vcomp generates an error signal Vcomp', and the driving circuit 55 generates control signals VA, VB, VC, and VD according to the sawtooth signal Vramp, the error signal Vcomp', the first signal Di, and the signal S3. The driving circuit 55 includes a comparator 58 comparing the signal Vcomp' and the sawtooth signal Vramp to generate a comparison signal S4, the comparator 60 comparing the sawtooth signal Vramp and the first signal Di to generate a comparison signal S5, and the logic circuit 56 according to the signals S3, S4 and S5 Determine the control signals VA, VB, VC and VD.

FIG. 4 shows the current path of the buck-boost power stage 52 in the buck mode. In the buck mode, the switch SWC is kept closed (turn off) and the switch SWD is kept open (tunr on). When the switch SWA is turned on and the switch SWB A buck charge path 74 is formed when switched off, and a buck discharge path 76 is formed when switch SWA is closed and switch SWB is opened. 5 shows the current path of the buck-boost power stage 52 in the buck-boost mode. In the buck-boost mode, when the switches SWA and SWC are turned on and the switches SWB and SWD are turned off, a boost charging path 78 is formed. When the switch SWA When SWD is open and switches SWB and SWC are closed, a buck charge or boost discharge path 80 is formed, and when switches SWB and SWD are opened and switches SWA and SWC are closed, a buck discharge path 82 is formed. FIG. 6 shows the current path of the buck-boost power stage 52 in the boost mode. In the boost mode, the switch SWA is kept open and the switch SWB is kept closed. When the switch SWC is opened and the switch SWD is closed, a boost charging path 86 is formed. , the boost discharge path 84 is formed when the switch SWC is closed and the switch SWD is opened.

7 shows the waveform diagram of the signal in FIG. 3, wherein the waveform 90 is the error signal Vcomp', the waveform 92 is the sawtooth signal Vramp, the waveform 94 is the first signal Di, and the waveform 96 is the inductor current IL passing through the inductor L. Referring to FIG. 3 and FIG. 7, in the step-down mode, the dynamic duty cycle generator 64 is closed, so the first signal Di is zero, so the switch SWC remains closed and the switch SWD remains open, and the error signal Vcomp' and the sawtooth signal Vramp are Control the switching of switches SWA and SWB to control the rise and fall of the inductor current IL, as shown in waveforms 90, 92 and 96, during the step-down charging period D2', such as time t6 to t7, the switch SWA is turned on and the switch SWB is turned off. The inductor current IL increases, and during the step-down discharge cycle D3', such as time t7 to t8, the switch SWA is turned off and the switch SWB is turned on, so the inductor current IL decreases. When entering the buck-boost mode from the buck mode, as shown at time t8, the mode selector 68 sends the enable signal EN to enable the dynamic duty cycle generator 64, so the first signal Di is not zero, as shown in the waveform 94 , so the boost charging cycle D1 is generated, such as time t8 to t9, since the first signal Di changes with the detection signal S2, the boost charging cycle D1 also changes with the signal S2, in order to avoid the large output ripple, the dynamic duty cycle generator 64 sends a compensation signal DDC to the duty cycle compensator 62 so that the error signal Vcomp' decreases with the rise of the first signal Di, as shown in waveforms 90 and 94, so the step-down charging cycle is formed by D2' is reduced to D2 and the step-down discharge cycle is increased from D3' to D3, so that the start level and end level of the inductor current IL in each cycle are the same, as shown in time t8 and t11, so large output ripple can be avoided Wave. From the waveform 96 in Figure 7, it can be seen that the time t8 to t11 can be regarded as a cycle, wherein the time t8 to t9 is the boost charging state, the time t9 to t10 is the step-down charging state, and the time t10 to t11 is the step-down discharging state. The same state does not appear repeatedly in each cycle, in other words, the control circuit 54 of the present invention optimizes the switching sequence of the switches SWA, SWB, SWC and SWD, thereby reducing switching losses. In this embodiment, although only the operation when entering the buck-boost mode from the buck mode is described, those skilled in the art can easily deduce the operation when entering the buck-boost mode from the boost mode from this embodiment, so No more details here.

8 shows a waveform diagram of the signal in FIG. 3, wherein the waveform 100 is the error signal Vcomp', the waveform 102 is the sawtooth signal Vramp, the waveform 104 is the first signal Di, and the waveform 106 is the inductor current IL passing through the inductor L. In the current power converters, there are power-saving modes to save energy, such as pulse skipping mode (Pulse Skipping Mode; PSM), when the traditional buck-boost power converter returns from power-saving mode to buck-boost mode , it must first enter the buck mode, and then wait for the error signal Vcomp to rise from zero to a critical value before entering the buck-boost mode, and it may take several cycles for the error signal Vcomp to rise from zero to the critical value. Referring to Fig. 8, when the buck-boost power converter 50 of the present invention is to return to the buck-boost mode from the power-saving mode, it returns to the buck mode from the power-saving mode in the first cycle, because the pulse omission mode The clamp detector 66 can dynamically clamp the level of the error signal Vcomp according to the detection signal S1, so the error signal Vcomp does not need to rise slowly from zero, and the dynamic duty cycle generator 64 is turned off in the step-down mode, so the error signal Vcomp'=Vcomp , that is to say, the error signal Vcomp' is clamped at a level close to the critical value, as shown in the waveform 100, so in the second cycle, the buck-boost power converter 50 immediately enters the buck-boost mode from the buck mode mode, and the transient response ends at the third cycle. In other words, the pulse omission mode clamp detector 66 in the control circuit 54 can speed up the transient response from the power saving mode back to the buck-boost mode.

9 shows a waveform diagram of the signal in FIG. 3, wherein waveform 110 is the error signal Vcomp', waveform 112 is the sawtooth signal Vramp, waveform 114 is the first signal Di, waveform 116 is the inductor current IL passing through the inductor L, and waveform 118 is The average current of the inductor current IL. In the buck-boost mode, when the first signal Di rises, as shown in waveform 114, the boost charging cycle D1 increases, so the average current of the inductor current IL rises, as shown in waveform 118, and the dynamic duty cycle generator 64 will output the compensation signal DDC to the duty cycle compensator 62 to reduce the error signal Vcomp′, as shown by the waveform 110 . When the first signal Di changes, the average current of the inductor current IL will change accordingly, so the control circuit 54 does not need to use the error signal Vcomp to adjust the inductor current IL.

FIG. 10 shows an embodiment of the duty cycle compensator 62 in FIG. 3, wherein the error signal Vcomp from the error amplifier 70 is sent to the voltage divider circuit 122 and the resistor R3 through the buffers 120 and 124 respectively, and is composed of multiple resistors RD1-RDN and multiple resistors. A voltage divider circuit 122 composed of switches SW1-SWN divides the voltage error signal Vcomp to generate a voltage Vd. The multiple switches SW1-SWN are controlled by the compensation signal DDC from the dynamic duty cycle generator 64, and the voltage-to-current converter 126 converts the voltage to Vd. Vd is converted into a current Id, and the current Id generates a voltage VR3 through the resistor R3, and the error signal Vcomp' is obtained by subtracting the voltage VR3 from the error signal Vcomp.

FIG. 11 shows an embodiment of logic circuit 56 , dynamic duty cycle generator 64 and mode selector 68 in FIG. 3 . In FIG. 11, the sawtooth wave generator 130 composed of the switch M2, the current source Ich and the capacitor C provides the sawtooth wave signal Vramp. The logic circuit 56 includes inverters 140 and 144 and a NAND gate 142. In the logic circuit 56, the signal S4 from the comparator 58 is used as the control signal VB, and the inverter 140 inverts the control signal VB to generate the control signal VA. The NAND gate 142 generates a signal VD according to the signals S3 and S5 , and the inverter 144 inverts the signal VD to generate a signal VC. The dynamic duty cycle generator 64 includes an analog-to-digital converter 132 and a digital-to-analog converter 134. In the dynamic duty-cycle generator 64, after the signal S2 is converted into a digital compensation signal DDC by the analog-to-digital converter 132, the digital-to-analog converter 134 Then the compensation signal DDC is converted into an analog first signal Di. The mode selector 68 includes a comparator 138 to compare the detection signal S2 and the threshold value VTH to generate a signal S3. The threshold value VTH is used to judge whether to switch the power converter 50 to the buck-boost mode, wherein the threshold value VTH can be a fixed value or determined by The variation of the inductor current IL or the output voltage Vo is determined. The dynamic threshold VTH can improve the efficiency of the power converter 50 and the ripple of the output voltage Vo, and can also speed up the load or power transient response. Under the condition that the critical value VTH changes with the inductor current IL, when the load is heavy and the inductor current is large, the critical value VTH is increased to make the buck-boost power converter 50 work in the buck-boost mode, and the charging and discharging are relatively fast at this time. , so that excessive ripple can be avoided. In the case that the critical value VTH changes with the change of the output voltage Vo, when the change of the output voltage Vo increases, the critical value VTH increases, so the working area of the buck-boost mode is increased, and the inductor current IL is easy to charge Easy to release, it can reduce the ripple of the output voltage Vo.

In other embodiments, a fixed duty cycle generator providing a fixed signal may be used instead of the dynamic duty cycle generator 64 .

The above embodiments are only for illustrating the present invention, rather than limiting the present invention. Those skilled in the relevant technical field can also make various transformations or changes without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions should also belong to the category of the present invention and should be defined by each claim.

Claims (17)

1. A control circuit for a buck-boost power converter, used to provide a control signal to drive a buck-boost power stage to convert an input voltage into an output voltage, and the buck-boost power stage includes an inductor and at least two switches Connect the inductor, characterized in that the control circuit includes: A feedback circuit, detecting the output voltage to generate a feedback signal; The error amplifier is connected to the feedback circuit, and amplifies the difference between the feedback signal and a reference voltage to generate an error signal; A clamping detector is connected to the error amplifier, and clamps the level of the error signal according to a first detection signal, the first detection signal is related to at least one of the input voltage, the output voltage, and the inductor current passing through the inductor; as well as The drive circuit is connected to the error amplifier, and determines the control signal according to the error signal and a first signal. 2. The control circuit according to claim 1, further comprising a dynamic duty cycle generator generating the first signal according to a second detection signal, the second detection signal is related to the input voltage, output voltage, At least one of an inductor current passing through the inductor and a variation of the output voltage is related. 3. The control circuit as claimed in claim 2, wherein the dynamic duty cycle generator further comprises providing a compensation signal according to the second detection signal. 4. The control circuit according to claim 3, wherein the dynamic duty cycle generator comprises: an analog-to-digital converter converting the second detection signal into the compensation signal; and A digital-to-analog converter is connected to the analog-to-digital converter to convert the compensation signal into the first signal. 5. The control circuit according to claim 3, further comprising a duty cycle compensator connected to the error amplifier and the dynamic duty cycle generator to compensate the error signal according to the compensation signal. 6. The control circuit according to claim 5, wherein the duty cycle compensator comprises: a voltage divider circuit, which divides the error signal according to the compensation signal to generate a first voltage; a voltage-to-current converter connected to the voltage dividing circuit to convert the first voltage into a first current; and The resistor is connected between the error amplifier and the voltage-to-current converter, and generates a second voltage to adjust the error signal in response to the first current. 7. The control circuit according to claim 2, further comprising a mode selector connected to the dynamic duty cycle generator to generate an enable signal according to the second detection signal to activate the dynamic duty cycle generator. 8. The control circuit according to claim 2, further comprising a mode selector connected to the dynamic duty cycle generator to generate an enable signal according to the error signal to activate the dynamic duty cycle generator. 9. The control circuit according to claim 1, wherein the drive circuit comprises: The first comparator is connected to the error amplifier, and compares the error signal with a sawtooth signal to generate a first comparison signal; a second comparator, comparing the first signal and the sawtooth signal to generate a second comparison signal; and The logic circuit is connected to the first comparator and the second comparator, and generates the control signal according to the first and second comparison signals. 10. A control method for a buck-boost power converter, which is used to provide a control signal to drive a buck-boost power stage to convert an input voltage into an output voltage, and the buck-boost power stage includes an inductor and at least two switches Connecting the inductance, characterized in that the control method comprises the following steps: (A) detecting the output voltage to generate a feedback signal; (B) amplifying the difference between the feedback signal and a reference voltage to generate an error signal; (C) clamping the level of the error signal according to a first detection signal related to at least one of the input voltage, the output voltage, and the inductor current through the inductor; and (D) determining the control signal according to the error signal and a first signal. 11. The control method according to claim 10, further comprising determining the first signal according to a second detection signal, the second detection signal is related to the input voltage, the output voltage, the At least one of the inductor current and the variation of the output voltage is related. 12. The control method according to claim 11, further comprising providing a compensation signal according to the second detection signal to compensate the error signal. 13. The control method according to claim 12, wherein the step of determining the first signal comprises: converting the second detection signal into the compensation signal; and converting the compensation signal into the first signal. 14. The control method according to claim 12, wherein the step of compensating the error signal comprises: dividing the error signal according to the compensation signal to generate a first voltage; converting the first voltage to a current to generate a second voltage for a resistor; and The error signal is adjusted according to the second voltage. 15. The control method according to claim 11, further comprising generating an enabling signal to trigger the first signal according to the second detection signal. 16. The control method according to claim 10, further comprising generating an enabling signal to trigger the first signal according to the error signal. 17. The control method according to claim 10, wherein said step D comprises: comparing the error signal with a sawtooth signal to generate a first comparison signal; comparing the first signal and the sawtooth signal to generate a second comparison signal; and The control signal is generated according to the first and second comparison signals.