A kind of cascade type buck-boost converter control circuit and control method thereof
Technical field
The present invention relates to a kind of buck DC converter, relate in particular to a kind of control circuit of buck DC converter, belong to converters control technology field, especially belong to the charging and the discharge converter technique field of energy storage battery in the non-green energy resource electricity generation systems such as wind energy and solar energy that are incorporated into the power networks.
Background technology
The step-down/up type DC converter usually is used for charge in batteries or discharge conversion etc., in recent years, more obtains extensive studies, development and application in generating of green energy resources such as solar energy and fuel cell and transformation system.
Traditional single switching tube buck-boost converter comprises topologys such as Buck-Boost, Cuk, Sepic, Zeta, and is big or efficient is low or input-output reason such as altogether not owing to stresses of parts, is restricted in a lot of its application of occasion.Traditional B oost converter and the cascade of Buck converter can be constructed two kinds of new buck-boost converters, H bridge buck-boost converter as shown in Figure 1 and the cascade type buck-boost converter shown in Fig. 2 main circuit topology.
The more buck-boost converter control method of former studies is primarily aimed at H bridge buck-boost converter shown in Figure 1, as No. the 6166527th, United States Patent (USP), Chinese patent 101212173A number, and it is less for the prime booster converter with the control method research of the buck-boost converter of the direct cascade formation of back level buck converter, the control method of actual two kinds of converters is similar, some control methods of buck-boost converter shown in Figure 1 can directly apply to the tandem type buck-boost converter, as No. the 6166527th, United States Patent (USP), the control method of announcing in Chinese patent 101212173A number, all be to adopt two triangular carriers stacks and the mode that adopts a voltage error amplifier on these control method principles, but the Control Parameter of a voltage error amplifier can not be applicable to the two-stage circuit of tandem type buck-boost converter simultaneously, thereby can cause the converter instability.Document " Rae-Young Kim; Jih-Sheng Lai; A Seamless Mode Transfer Maximum Power Point Tracking Controller ForThermoelectric Generator Applications; IEEE Transactions on Power Electronics; 2008; vol.23, page (s): 2310-2318 " in studied digital control method when the tandem type buck-boost converter is applied to the thermoelectric cell occasion; its digital control method pays attention to realizing the universal control method of MPPT maximum power point tracking controller rather than research tandem type buck-boost converter; and digitial controller cost height, and control is complicated.
H bridge buck-boost converter often need be at the bigger LC low pass filter of the extra setting of input because the input and output side electric current is the rectangular pulse form.Boost-Buck cascade connection type converter is because the filter action of input/output terminal inductance, and the input and output current pulsation is very little, therefore, and in many instances, particularly high-power applications more has superiority.
Summary of the invention
The technical problem to be solved in the present invention is control circuit and the control method thereof that proposes a kind of cascade type buck-boost converter.
Cascade type buck-boost converter control circuit of the present invention, its structure comprises: output voltage sampling circuit, first error amplifier, second error amplifier, circuit for generating triangular wave, comparator circuit, drive circuit and voltage setting circuit, wherein: output voltage sampling circuit comprises first divider resistance and second divider resistance, one end of first divider resistance connects the positive pole of cascade type buck-boost converter circuit output voltage, the other end connects the inverting input of first error amplifier and second error amplifier and an end of second divider resistance, the other end ground connection of second divider resistance respectively; First error amplifier all is connected reference voltage with the in-phase input end of second error amplifier; Comparator circuit comprises first comparator, second comparator, first inverter and second inverter, the output of first error amplifier connects the in-phase input end of first comparator, first control signal of first comparator output is as the control voltage of first power switch pipe and connect the input of drive circuit, the output of first comparator connects the input of first inverter, second control signal of first inverter output is as the control voltage of second power switch pipe and connect the input of drive circuit, the output of second error amplifier connects the in-phase input end of second comparator, the 3rd control signal of second comparator output is as the control voltage of the 3rd power switch pipe and connect the input of drive circuit, the output of second comparator connects the input of second inverter, the 4th control signal of second inverter output is as the control voltage of the 4th power switch pipe and connect the input of drive circuit, and the inverting input of first comparator and the inverting input of second comparator all are connected the output of circuit for generating triangular wave; Driving voltage, the driving voltage of second power switch pipe, the driving voltage of the 3rd power switch pipe and the driving voltage of the 4th power switch pipe of the corresponding output of drive circuit first power switch pipe; The voltage setting circuit comprises first diode, second diode, first resistance, second resistance and electric capacity, the anode of first diode connects the output of first comparator, the negative electrode of first diode connects an end of first resistance, the other end of first resistance connects an end of electric capacity, an end of second resistance and the anode of second diode respectively, the other end of electric capacity connects the other end and the ground connection of second resistance, and the negative electrode of second diode connects the output of second error amplifier.
Control method based on above-mentioned cascade type buck-boost converter control circuit is: first divider resistance in the output voltage sampling circuit and second divider resistance obtain feedback voltage by output voltage being carried out the dividing potential drop sampling, first error amplifier and second error amplifier are according to the corresponding respectively output first control voltage of the error between feedback voltage and the reference voltage and the second control voltage, and feedback voltage is directly proportional with output voltage; First control signal that the first control voltage and triangle wave voltage relatively obtain and second control signal are controlled first power switch pipe and the action of second power switch pipe by drive circuit: when first controls voltage greater than triangle wave voltage, first control signal is a positive voltage, second control signal is zero, the first power switch pipe conducting, second power switch pipe turn-offs, when first controls voltage less than triangle wave voltage, first control signal is zero, second control signal is a positive voltage, first power switch pipe turn-offs, the second power switch pipe conducting, the complementary conducting of first power switch pipe and second power switch pipe; First control signal is by the voltage setting circuit set second control voltage; The 3rd control signal that the second control voltage and triangle wave voltage relatively obtain and the 4th control signal are controlled the 3rd power switch pipe and the action of the 4th power switch pipe by drive circuit: when second controls voltage greater than triangle wave voltage, the 3rd control signal is a positive voltage, the 4th control signal is zero, the 3rd power switch pipe conducting, the 4th power switch pipe turn-offs, when second controls voltage less than triangle wave voltage, the 3rd control signal is zero, the 4th control signal is a positive voltage, the 3rd power switch pipe turn-offs, the 4th power switch pipe conducting, the complementary conducting of the 3rd power switch pipe and the 4th power switch pipe.
Circuit of the present invention is realized simple, only need one road triangular signal to control the two-stage circuit of buck-boost converter, two error amplifiers have been realized the decoupling zero control of two-stage circuit, can according to boost mode and decompression mode Control Parameter be set respectively, have only two power switch pipe actions in each switch periods at most, the conversion efficiency height.
Description of drawings
Fig. 1 is a H bridge buck-boost converter main circuit diagram in the background technology.
Fig. 2 is cascade type buck-boost converter and the control circuit schematic diagram thereof that the embodiment of the invention relates to, number in the figure title: 10-cascade type buck-boost converter main circuit topology; The 101-boost converter circuit; The 102-decompression converter circuit; 20-cascade type buck-boost converter control circuit; 201,202 be respectively first and second error amplifiers; The 206-output voltage sampling circuit; The 207-comparator circuit; 209,210 be respectively first and second comparators; 211,212 be respectively first and second inverters; 205-voltage setting circuit.
Fig. 3 is the groundwork waveform of cascade type buck-boost converter when working in boost mode.
Fig. 4 is the groundwork waveform of cascade type buck-boost converter when working in decompression mode.
Among Fig. 3 and Fig. 4: V
TriminMinimum value for triangle wave voltage; V
TrimaxMaximum for triangle wave voltage.
Fig. 5 is the buck-boost converter of the using control circuit of the present invention stable state experimental waveform when working in boost mode.
Fig. 6 is the buck-boost converter of the using control circuit of the present invention stable state experimental waveform when working in decompression mode.
Embodiment
As shown in Figure 2, the cascade type buck-boost converter and the control circuit schematic diagram thereof that relate to of the embodiment of the invention.
Fig. 2 cascade type buck-boost converter main circuit topology 10 comprises DC power supply V
In, four power switch pipe Q
1, Q
2, Q
3And Q
4, two inductance L
1And L
2, two filter capacitor C
1And C
2, resistance R
o, wherein: DC power supply V
InThe anodal inductance L that connects
1An end, inductance L
1The other end connect power switch pipe Q respectively
1Drain electrode and power switch pipe Q
2Source electrode, power switch pipe Q
2Drain electrode connect filter capacitor C respectively
1An end and power switch pipe Q
3Drain electrode, power switch pipe Q
3Source electrode connect inductance L respectively
2An end and power switch pipe Q
4Drain electrode, inductance L
2The other end connect filter capacitor C respectively
2An end and resistance R
oAn end, power switch pipe Q
1Source electrode, filter capacitor C
1The other end, power switch pipe Q
4Source electrode, filter capacitor C
2The other end and resistance R
oThe other end all connect DC power supply V
ThNegative pole.101 is boost converter circuit among the figure, the 102nd, and decompression converter circuit.In this circuit, power switch pipe all adopts N type metal oxide semiconductor field-effect transistor (N-MOSFET), and inductance adopts the coiling of magnetic core magnetic core, and filter capacitor adopts multi-layer ceramic capacitance (MLCC).
The control circuit 20 of Fig. 2 cascade type buck-boost converter comprises output voltage sampling circuit 206, first error amplifier 201, second error amplifier 202, circuit for generating triangular wave 203, comparator circuit 207, drive circuit 208 and voltage setting circuit 205, and wherein: output voltage sampling circuit 206 comprises the first divider resistance R
23With the second divider resistance R
24, the first divider resistance R
23An end connect cascade type buck-boost converter circuit output voltage V
oPositive pole, the other end connects the inverting input and the second divider resistance R of first error amplifier 201 and second error amplifier 202 respectively
24An end, the second divider resistance R
24Other end ground connection; First error amplifier 201 all is connected reference voltage V with the in-phase input end of second error amplifier 202
Ref Comparator circuit 207 comprises first comparator 209, second comparator 210, first inverter 211 and second inverter 212, the output of first error amplifier 201 connects the in-phase input end of first comparator 209, the first control signal V of first comparator, 209 outputs
Cd1As the first power switch pipe Q
1Control voltage and connect the input of drive circuit 208, the output of first comparator 209 connects the input of first inverter 211, the second control signal V of first inverter, 211 outputs
Cd2As the second power switch pipe Q
2Control voltage and connect the input of drive circuit 208, the output of second error amplifier 202 connects the in-phase input end of second comparator 210, the 3rd control signal V of second comparator, 210 outputs
Cd3As the 3rd power switch pipe Q
3Control voltage and connect the input of drive circuit 208, the output of second comparator 210 connects the input of second inverter 212, the 4th control signal V of second inverter, 212 outputs
Cd4As the 4th power switch pipe Q
4Control voltage and connect the input of drive circuit 208, the inverting input of first comparator 209 and the inverting input of second comparator 210 all are connected the output of circuit for generating triangular wave 203; The drive circuit 208 corresponding output first power switch pipe Q
1Driving voltage V
D1, the second power switch pipe Q
2Driving voltage V
D2, the 3rd power switch pipe Q
3Driving voltage V
D3With the 4th power switch pipe Q
4Driving voltage V
D4 Voltage setting circuit 205 comprises the first diode D
21, the second diode D
22, first resistance R
21, second resistance R
22And capacitor C
21, the first diode D
21Anode connect the output of first comparator 209, the first diode D
21Negative electrode connect first resistance R
21An end, first resistance R
21The other end connect capacitor C respectively
21An end, second resistance R
22An end and the second diode D
22Anode, capacitor C
21The other end connect second resistance R
22The other end and ground connection, the second diode D
22Negative electrode connect the output of second error amplifier 202.
The key of this control circuit is voltage setting circuit 205, the first diode D in the voltage setting circuit 205
21With first resistance R
21Effect be to prevent capacitor C
21On voltage to the first control signal V
Cd1Exert an influence the first control signal V
Cd1For having the pwm voltage signal of certain amplitude, the second diode D
22With second resistance R
22Effect be to work as capacitor C
21On voltage be reduced to less than the second control voltage V
C2The time, prevent that this voltage is to the second control voltage V
C2Exert an influence.
The control method of described cascade type buck-boost converter control circuit is: the first divider resistance R in the output voltage sampling circuit 206
23With the second divider resistance R
24By to output voltage V
oCarry out the dividing potential drop sampling and obtain feedback voltage V
Fb, first error amplifier 201 and second error amplifier 202 are according to feedback voltage V
FbWith reference voltage V
RefBetween the respectively corresponding output first control voltage V of error
C1With the second control voltage V
C2, feedback voltage V
FbWith output voltage V
oBe directly proportional; The first control voltage V
C1With triangle wave voltage V
TriThe first control signal V that relatively obtains
Cd1With the second control signal V
Cd2By the drive circuit 208 controls first power switch pipe Q
1With the second power switch pipe Q
2Action: as the first control voltage V
C1Greater than triangle wave voltage V
TriThe time, the first control signal V
Cd1Be positive voltage, the second control signal V
Cd2Be zero, the first power switch pipe Q
1Conducting, the second power switch pipe Q
2Turn-off, as the first control voltage V
C1Less than triangle wave voltage V
TriThe time, the first control signal V
Cd1Be zero, the second control signal V
Cd2Be positive voltage, the first power switch pipe Q
1Turn-off the second power switch pipe Q
2Conducting, the first power switch pipe Q
1With the second power switch pipe Q
2Complementary conducting; The first control signal V
Cd1By the voltage setting circuit 205 set second control voltage V
C2The second control voltage V
C2With triangle wave voltage V
TriThe 3rd control signal V that relatively obtains
Cd3With the 4th control signal V
Cd4By drive circuit 208 controls the 3rd power switch pipe Q
3With the 4th power switch pipe Q
4Action: as the second control voltage V
C2Greater than triangle wave voltage V
TriThe time, the 3rd control signal V
Cd3Be positive voltage, the 4th control signal V
Cd4Be zero, the 3rd power switch pipe Q
3Conducting, the 4th power switch pipe Q
4Turn-off, as the second control voltage V
C2Less than triangle wave voltage V
TriThe time, the 3rd control signal V
Cd3Be zero, the 4th control signal V
Cd4Be positive voltage, the 3rd power switch pipe Q
3Turn-off the 4th power switch pipe Q
4Conducting, the 3rd power switch pipe Q
3With the 4th power switch pipe Q
4Complementary conducting.
The input of described voltage setting circuit 205 is except connecting as the first power switch pipe Q
1The first control signal V of control voltage
Cd1Can also connect the first power switch pipe Q outward
1Driving voltage V
D1, first resistance R
21With first resistance R
21The position can exchange.
The concrete operation principle of control circuit of the present invention is as follows:
As DC power supply V
InVoltage is less than output voltage V
oThe time, the first control voltage V of first voltage error amplifier, 201 outputs
C1Greater than triangle wave voltage V
TriMinimum value, thereby control the first power switch pipe Q
1With the second power switch pipe Q
2Action, the first control signal V
Cd1Mean value in a switch periods makes the second control voltage V greater than zero by voltage setting circuit 205
C2Minimum value in a switch periods is more than or equal to triangle wave voltage V
TriMaximum, thereby control the 3rd power switch pipe Q
3Conducting always, the 4th power switch pipe Q
4Turn-off, converter works in boost mode always, under this pattern, and 201 regulating actions of first error amplifier and second error amplifier 202 does not play regulating action; As DC power supply V
InVoltage is greater than or equal to output voltage V
oThe time, the first control voltage V of first error amplifier, 201 outputs
C1Less than triangle wave voltage V
TriMinimum value, the first control signal V
Cd1All the time equal zero, thereby control the first power switch pipe Q
1Turn-off the second power switch pipe Q always
2Conducting always, voltage setting circuit 205 is inoperative, to the second control voltage V
C2Not influence, the second control voltage V of second error amplifier, 202 outputs
C2Smaller or equal to triangle wave voltage V
TriMaximum, the second control voltage V
C2With triangle wave voltage V
TriThe 3rd control signal V that relatively obtains
Cd3With the 4th control signal V
Cd4Control the 3rd power switch pipe Q respectively
3With the 4th power switch pipe Q
4Action, converter works in decompression mode, under this pattern, 202 regulating actions of second error amplifier and first error amplifier 201 does not play regulating action.