CN101212184B - Slope compensation method and circuit for power switching circuit - Google Patents
Slope compensation method and circuit for power switching circuit Download PDFInfo
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Abstract
The invention provides a slope compensation circuit of a power conversion circuit used in a control mode of peak current. The power conversion circuit comprises two straightforward converters and a pulse width regulating controller which controls the movement of the two straightforward converters. The slope compensation circuit comprises a first charging loop having a first series resistor formedby parallel connecting two resistors and a capacitor, wherein, two ends of the first series resistor are respectively connected with one end of the capacitor and a DC power, the other end of the capacitor is connected with a feedback input end of output voltage of the pulse width regulating controller; a second charging loop which has a second series resistor formed by parallel connecting two resistors and which is in series with the first series resistor; a discharging loop having a third electronic switch and a fourth electronic switch which are respectively connected with series nodes of the first and second series resistors. Return signals of voltage compensated by the invention can effectively avoid misjudgment due to surges generated when another electronic switch of the power conversion circuit turns on noise coupling, so as to provide DC power with stable output.
Description
Technical Field
The present invention relates to a slope compensation method for a power conversion circuit in a peak current control mode and a circuit thereof, and more particularly, to a power conversion circuit in a peak current control mode in which noise generated by a switch is suppressed by a slope compensation circuit.
Background
At present, a dc-dc converter processes a dc power into a single or multiple dc power with different voltages and outputs the dc power to be used by different circuit units on a circuit board or different electronic devices.
There are many different types of control methods for dc-dc converters, one is a power conversion circuit with peak current control mode, which has the advantage of circuit simplification, but has the disadvantage of poor suppression capability due to noise. Referring to fig. 8, fig. 8 shows a dc-dc converter circuit 50 with a conventional peak current control mode, which includes:
a first and a second forward converters 51, 52, which are composed of at least two sets of high frequency transformers T3, T4 and two main switches Q1, Q2; the primary side of each high-frequency transformer T3, T4 is connected to the corresponding main switch Q1, Q2, the main switch Q1, Q2 is turned on or off to determine whether the primary side current is generated, and the secondary side output end of each high-frequency transformer T3, T4 is the output end of the power conversion circuit 50; and
a pwm controller 53, which includes two pwm output terminals OUT1, OUT2, two output voltage feedback input terminals COMP1, COMP2 and two current feedback input terminals CS1, CS2, wherein the two pwm output terminals OUT1, OUT2 are connected to the control terminals of the main switches Q1, Q2 of the first and second forward converters 51, 52, and the two output voltage feedback input terminals COMP1, COMP2 are coupled to the dc power output terminals of the corresponding forward converters 51, 52 to obtain two voltage feedback signals Verror1, Verror2 corresponding to the two dc power output terminals; the current feedback input terminals CS1 and CS2 obtain current feedback signals corresponding to the current states of the primary sides of the high-frequency transformers T3 and T4.
Referring to fig. 9, fig. 9 shows that when two main switches Q1 and Q2 are respectively driven by pulse width signals with 50% open pulse width, an ideal waveform of the current feedback signals of the two current feedback input terminals CS1 and CS2 is obtained, that is, when the on time of the first electronic switch reaches 50% pulse width time, the voltage value VCS1 corresponding to the feedback current peak value of the first current feedback input terminal CS1 is greater than the voltage value VCOMP1 of the first voltage feedback signal, at this time, the pulse width modulation controller 53 will turn off the first main switch Q1 and control the second main switch Q2 to be turned on, and similarly, when the on time of the second electronic switch Q2 reaches 50% pulse width time, the pulse width modulation controller 53 will compare the voltage value VCS2 corresponding to the current peak value of the feedback current input terminal CS2 with the voltage value VCOMP2 of the current feedback signal, when the voltage VCS2 corresponding to the current peak of the second current sense terminal CS2 is determined to be greater than the current second voltage feedback signal VCOMP1, the second main switch Q2 is turned off and the first main switch Q1 is controlled at the same time, so that the pulse widths of the first and second main switches Q1 and Q2 occupy half of a full pulse width period. As can be seen from the foregoing description, the pwm controller 53 converts the current peak value of the current feedback signal on the primary side of each of the high frequency transformers T3 and T4 into a corresponding voltage value, compares the voltage value with the voltage value of the current feedback signal corresponding to the secondary output voltage of the high frequency transformers T3 and T4, and alternately changes the on/off states of the current first and second main switches Q1 and Q2 once the voltage peak value is greater than the voltage value of the feedback voltage.
However, when the two main switches Q2 are driven by pwm signals with a duty ratio greater than 50%, the peak current mode control is not as ideal as described above. Assuming that the first and second main switches Q1, Q2 are driven by 55% pwm signals, respectively, please refer to fig. 10, when only the first main switch Q1 is driven to be turned on at time t10, theoretically the first main switch Q1 should be turned off when t12 reaches 55% pwm time, but the second main switch Q2 should be driven to be turned on because it reaches first at time t20, which is earlier than time t 12; since the second main switch Q2 is driven to be turned on at the time point T20, so that the current waveform of the first current feedback input terminal CS1 generates a transient surge at the time point T11, and the generation of the transient surge may cause the pwm controller 53 to determine that the voltage peak VCS1 corresponding to the first current feedback signal is higher than the voltage value VCOMP1 of the secondary feedback voltage signal thereof, and further turn off the first main switch Q1, if the first main switch Q1 is turned off as shown by an ideal waveform (marked by a dotted line), the first main switch Q1 is turned off, that is, the first main switch Q1 is not coupled to affect the primary current waveform of the second high frequency transformer T4, and as shown in fig. 11, the output dc power of the first and second high frequency transformers T3, T4 cannot avoid oscillation. Similarly, when the on-time of the second main switch Q2 is close to the 55% pwm time T21, since the first main switch Q1 is driven to turn on by the pwm controller 53 at the time point T13, its turning-on instant will couple and affect the primary side current of the second high frequency transformer T4 that is currently turned on to generate a transient surge, so that the voltage peak VCS2 corresponding to the second current feedback signal is higher than the voltage value VCOMP2 corresponding to the second voltage feedback signal at the time point T21, and the second main switch Q2 is turned off.
As can be seen from the above description, as long as the pwm signals of the first and second electronic switches Q1, Q2 are greater than 50%, the duty cycles of the first and second forward converters 51, 52 overlap each other, and the noise generated when the electronic switches are turned off is coupled to another set of power current waveforms, which affects the determination of turning off the electronic switches by the current peak, and further causes the oscillation phenomenon of the output. Therefore, the dc-dc converter circuit of the current peak current control mode needs to be further improved in design to provide a more stable dc power.
Disclosure of Invention
The present invention provides a slope compensation circuit, the power conversion circuit includes two forward converters and a pwm controller for controlling the operation of the two forward converters, wherein each forward converter includes a high frequency transformer and a first and a second main switches connected in series to a primary side of the high frequency transformer, the slope compensation circuit includes:
a first charging loop, including a first series resistor and a capacitor formed by two resistors connected in series, wherein two ends of the first series resistor are respectively connected with one end of the capacitor and a direct current power supply, and the other end of the capacitor is connected to an output voltage feedback input end of the pulse width modulation controller;
the second charging loop comprises a second series resistor formed by connecting two resistors in series, and the second series resistor is connected with the first series resistor in parallel; and
a discharge loop including a third and a fourth electronic switch, each of the third and fourth electronic switches including two terminals and a control terminal, wherein one terminal of the third and fourth electronic switches is connected to the series node of the first and second series resistors, and the other terminal is grounded; the control end of the third electronic switch is connected to the control end of the first main switch of the first forward converter, and the control end of the fourth electronic switch is connected to the control end of the second main switch of the second forward converter; the third and fourth electronic switches are turned on and off synchronously with the first and second main switches, respectively.
The resistors connected with the capacitor in the first and second series resistors are further connected with a diode in parallel respectively, the anode of each diode is connected to the series node corresponding to the first and second series resistors, and the cathode is connected to the capacitor.
The other end of the capacitor is further connected to a group of output direct current voltage ends of the power conversion circuit through an optical coupler, wherein a light emitting diode end of the optical coupler is connected to the output direct current voltage end, and the photosensitive transistor is connected to the capacitor.
The resistance values of two resistors connected with the capacitor in the first series resistor and the second series resistor are the same, and the resistance values of the other two resistors in the first series resistor and the second series resistor are the same.
The resistance values of two resistors connected with the capacitor in the first series resistor and the second series resistor are the same, and the resistance values of the other two resistors in the first series resistor and the second series resistor are the same.
The present invention also provides a slope compensation circuit for a power conversion circuit in a peak current control mode, the power conversion circuit including two forward converters and a pwm controller for controlling the operation of the two forward converters, wherein each of the forward converters includes a high frequency transformer and first and second main switches connected in series to a primary side of the high frequency transformer, the slope compensation circuit including:
the first charging loop is composed of a first series resistor and a capacitor which are formed by connecting two resistors in series, wherein two ends of the first series resistor are respectively connected with one end of the capacitor and a direct current power supply, and the other end of the capacitor is connected to the output voltage feedback input end of the pulse width modulation controller;
the second charging loop comprises a second series resistor formed by connecting two resistors in series, and the second series resistor is connected with the first series resistor in parallel; and
a discharge loop including a third and a fourth electronic switch, each of the third and fourth electronic switches including two terminals and a control terminal, wherein one terminal of the third and fourth electronic switches is connected to the series node of the first and second series resistors, and the other terminal is grounded; the control ends of the third and fourth electronic switches are respectively connected with a current transformer, and the two current transformers are respectively coupled and connected to the primary sides of the corresponding first and second high-frequency transformers so as to induce current signals of the primary sides of the corresponding high-frequency transformers, so that the third and fourth electronic switches are respectively synchronously opened and closed with the first and second main switches.
The resistors connected with the capacitor in the first and second series resistors are further connected with a diode in parallel respectively, the anode of each diode is connected to the series node corresponding to the first and second series resistors, and the cathode is connected to the capacitor.
The other end of the capacitor is further connected to a group of output direct-current voltage ends of the power conversion circuit through an optical coupler, wherein a light emitting diode end of the optical coupler is connected to the output direct-current voltage end, and the photosensitive transistor is connected to the capacitor.
The resistance values of two resistors connected with the capacitor in the first series resistor and the second series resistor are the same, and the resistance values of the other two resistors in the first series resistor and the second series resistor are the same.
The resistance values of two resistors connected with the capacitor in the first series resistor and the second series resistor are the same, and the resistance values of the other two resistors in the first series resistor and the second series resistor are the same.
The present invention further provides a slope compensation circuit for a power conversion circuit in a peak current control mode, the power conversion circuit comprising two forward converters and a pwm controller for controlling the operation of the two forward converters, wherein each of the forward converters comprises a high frequency transformer and first and second main switches connected in series to a primary side of the high frequency transformer, the slope compensation circuit comprising:
the first charging loop comprises a first series resistor and a capacitor which are formed by connecting two resistors in series, wherein two ends of the first series resistor are respectively connected with one end of the capacitor and a direct current power supply, and the other end of the capacitor is connected to the output voltage feedback input end of the pulse width modulation controller;
the second charging loop comprises a second series resistor formed by connecting two resistors in series, and the second series resistor is connected with the first series resistor in parallel; and
a discharge loop including a first diode and a second diode, wherein the anode of the first diode is connected to the second series resistor series node, and the cathode of the first diode is connected to the second main switch control end; the anode of the second diode is connected to the first series resistor series node, and the cathode of the second diode is connected to the control end of the first main switch.
The resistors connected with the capacitor in the first and second series resistors are further connected with a diode in parallel respectively, the anode of each diode is connected to the series node corresponding to the first and second series resistors, and the cathode is connected to the capacitor.
The other end of the capacitor is further connected to a group of output direct current voltage ends of the power conversion circuit through an optical coupler, wherein a light emitting diode end of the optical coupler is connected to the output direct current voltage end, and the photosensitive transistor is connected to the capacitor.
The resistance values of two resistors connected with the capacitor in the first series resistor and the second series resistor are the same, and the resistance values of the other two resistors in the first series resistor and the second series resistor are the same.
The resistance values of two resistors connected with the capacitor in the first series resistor and the second series resistor are the same, and the resistance values of the other two resistors in the first series resistor and the second series resistor are the same.
The present invention further provides a slope compensation circuit for a power conversion circuit in a peak current control mode, the power conversion circuit comprising two forward converters and a pwm controller for controlling the operation of the two forward converters, wherein each of the forward converters comprises a high frequency transformer and first and second main switches connected in series to a primary side of the high frequency transformer, the slope compensation circuit comprising:
the first charging loop is composed of a first series resistor and a capacitor which are formed by connecting two resistors in series, wherein two ends of the first series resistor are respectively connected with one end of the capacitor and a direct current power supply, and the other end of the capacitor is connected to the output voltage feedback input end of the pulse width modulation controller;
the second charging loop comprises a second series resistor formed by connecting two resistors in series, and the second series resistor is connected with the first series resistor in parallel; and
and a discharge loop including a first diode and a second diode, wherein the anode of the first diode is connected to the second series resistor series node, the anode of the second diode is connected to the first series resistor series node, the cathodes of the first diode and the second diode are respectively connected to a second and a first current transformer, and the second and the first current transformers are respectively coupled and connected in series to the corresponding second and the first high-frequency transformer primary sides. The first and second diodes are turned on and off synchronously with the second and first main switches, respectively, by inducing a current signal corresponding to the primary side of the high frequency transformer.
The resistors connected with the capacitor in the first and second series resistors are further connected with a diode in parallel respectively, the anode of each diode is connected to the series node corresponding to the first and second series resistors, and the cathode is connected to the capacitor.
The other end of the capacitor is further connected to a group of output direct current voltage ends of the power conversion circuit through an optical coupler, wherein a light emitting diode end of the optical coupler is connected to the output direct current voltage end, and the photosensitive transistor is connected to the capacitor.
The resistance values of two resistors connected with the capacitor in the first series resistor and the second series resistor are the same, and the resistance values of the other two resistors in the first series resistor and the second series resistor are the same.
The resistance values of two resistors connected with the capacitor in the first series resistor and the second series resistor are the same, and the resistance values of the other two resistors in the first series resistor and the second series resistor are the same.
The invention further provides a slope compensation method for a power conversion circuit in a peak current control mode, wherein the power conversion circuit comprises two forward converters and a pulse width modulation controller for controlling the action of the two forward converters, wherein each forward converter respectively comprises a high-frequency transformer and a first main switch and a second main switch which are connected in series with the primary side of the high-frequency transformer; the slope compensation method comprises the following steps:
obtaining a synchronization signal with the first and second main switch driving signals;
generating a set of triangular wave signals, wherein the rising time of the triangular wave signals is determined by the first main switch driving signal and the second main switch driving signal; and
the triangular wave signal is added into a direct current voltage feedback signal which corresponds to the output of the power conversion circuit and is used for comparing current peak values to form a triangular wave direct current voltage feedback signal, the voltage level of the triangular wave direct current voltage feedback signal is higher than that of the direct current voltage feedback signal, the triangular wave direct current voltage feedback signal is input into the output voltage feedback input end of the pulse width modulation controller, the pulse width modulation controller is enabled to carry out peak value comparison by the triangular wave direct current voltage feedback signal and the corresponding voltage values of the primary side current signals of the first high-frequency transformer and the second high-frequency transformer, and driving signals of the first main switch and the second main switch are determined.
The synchronization signal is obtained from the first and second master switch driving terminals.
The synchronous signal is obtained from the first and second main switch driving signals by a current transformer coupled to the primary sides of the two high-frequency transformers.
Compared with the prior art, the invention has the following beneficial effects:
the third and fourth electronic switches of the slope compensation circuit are synchronously opened and closed with the first and second main switches, so that the rising time of triangular waves generated by charging and discharging of the capacitor can be the same as the conduction time of primary side currents of the first and second high-frequency transformers; in addition, the capacitor is connected to the output voltage feedback input end of the PWM controller, so that the voltage feedback signal originally input to the output voltage feedback input end can be compensated to be a triangular voltage feedback signal with a higher level than the DC voltage feedback signal; therefore, when the pulse width modulation controller outputs more than 50% pulse width modulation signals to the two main switches, the defect that the electronic switch of the existing high-frequency transformer is closed in advance due to the sudden wave of the conducting current signal of the high-frequency transformer can be effectively avoided.
Drawings
FIG. 1 is a detailed circuit diagram of a power conversion circuit applied to a peak current control mode according to the present invention;
FIGS. 2A to 2C are equivalent circuits of the voltage feedback terminal and the voltage feedback signal source of the PWM controller according to the first preferred embodiment of the present invention;
FIGS. 3A-3F are graphs of voltage and current waveforms at the input and output terminals of the PWM controller of FIG. 1 according to the present invention;
FIGS. 4A-4B are graphs comparing the voltage waveforms corresponding to the high-level triangular-wave voltage feedback signal wave and the first on-current of the first high-frequency transformer according to the present invention;
FIG. 5 is a circuit diagram of a triangular wave generating unit according to a second preferred embodiment of the present invention;
FIG. 6 is a circuit diagram of a triangular wave generating unit according to a third preferred embodiment of the present invention;
FIG. 7 is a circuit diagram of a triangular wave generating unit according to a fourth preferred embodiment of the present invention;
FIG. 8 is a circuit diagram of an existing peak current control mode power conversion circuit;
FIG. 9 is a current waveform diagram of two current feedback input terminals under the condition that the PWM controller in FIG. 8 outputs a 50% PWM signal;
FIG. 10 is a current waveform diagram of two current feedback input terminals under the condition that the PWM controller in FIG. 8 outputs a 55% PWM signal;
fig. 11 is a graph of the voltage waveform at the output of the power supply of fig. 8.
Wherein,
10 power conversion circuit 11 first forward converter
12 second forward converter 13 PWM controller
21. 21a, 21b, 21c slope compensation circuit
22 first series resistance 23 second series resistance
24 capacitor 25 third electronic switch
26 fourth electronic switch 27 forward diode
28 first current transformer 29 second current transformer
30 first diode 31 second diode
50 DC converting circuit 51 forward converter
Pulse width modulation controller for 52-way converter 53
Detailed Description
The invention provides a slope compensation method and a slope compensation circuit, which aims to effectively eliminate the defect of oscillation of an output direct-current power supply caused by switching noise of opening and closing of an electronic switch, help a direct-current-to-direct-current conversion circuit adopting a current peak control mode and output a stable direct-current power supply.
The invention carries out slope compensation aiming at the direct current voltage feedback signal originally input to the output voltage feedback input end of the pulse wave modulator, so that when the compensated triangular wave direct current voltage feedback signal is compared with the conducting current signal in the subsequent voltage magnitude, the condition that the electronic switch of the prior high-frequency transformer is closed by the surge on the conducting current signal in advance can be effectively avoided.
The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.
As shown in fig. 1, fig. 1 shows a slope compensation circuit 21a of a power conversion circuit 10 for peak current control mode according to the present invention, wherein in order to effectively reduce the use of high-efficiency and large-sized transformers, the power conversion circuit connects the outputs of a first and a second forward converters 11, 12 in parallel, and provides only one set of input dc power OUT, and the first and the second forward converters 11, 12 are controlled by a pwm controller 13, which respectively comprises:
a first or second high frequency transformer T1, T2 having a primary side connected to an input DC power supply; and
a first or second main switch Q4, Q6 connected in series with the primary side of the high frequency transformer T1, T2, and the on/off of the first or second main switch Q4, Q6 determines whether the high frequency transformer T1, T2 is current conducting.
Further, the pwm controller 13 includes:
two pwm output terminals OUT1, OUT2 connected to the control terminals of the first and second main switches Q4, Q6 of the corresponding first and second forward converters 11, 12, respectively;
two output voltage feedback input terminals COMP1 and COMP2 coupled to the dc power output terminals of the corresponding first or second forward converters 11 and 12, respectively, for obtaining a set of output voltage feedback signals; and
the two current feedback input terminals CS1 and CS2 respectively obtain the on-current signals of the primary sides of the first and second high frequency transformers T1 and T2.
As for the input end of the slope compensation circuit 21a of the present invention coupled to a set of dc power output ends, since the present embodiment is applied to a power conversion circuit of a single set of output dc power, the output end of the slope compensation circuit of the present embodiment is coupled to two output voltage feedback input ends COMP1 and COMP2 of the pwm controller 13, so as to input a triangular wave dc voltage feedback signal with a higher level than the original dc voltage feedback signal to the two output voltage feedback input ends COMP1 and COMP2 of the pwm controller 13 simultaneously with the dc voltage feedback signal.
As shown in fig. 2C, the slope compensation circuit 21a includes:
a first charging loop, which includes a first series resistor 22 and a capacitor 24 formed by connecting two resistors R63 and R66 in series, wherein two ends of the first series resistor 22 are respectively connected to one end of the capacitor 24 and a first dc power supply + V1, and the other end of the capacitor 24 is connected to an output voltage feedback input terminal COMP1 and COMP2 of the pwm controller 13;
a second charging loop, which includes a second series resistor 23 formed by two resistors R68 and R67 connected in series, wherein the second series resistor 23 is connected in parallel with the first series resistor 22; and
a discharge circuit including a third and a fourth electronic switch 25, 26 respectively connected to the series nodes of the first and the second series resistors 22, 23; wherein the control terminal of the third electronic switch 25 is connected to the control terminal of the first forward converter first main switch Q4, and the control terminal of the fourth electronic switch 26 is connected to the control terminal of the second forward converter second main switch Q6; therefore, the third and fourth electronic switches 25, 26 are turned on and off synchronously with the first and second main switches Q4, Q6, respectively.
The following further describes the manner of generating the triangular wave DC voltage feedback signal with high DC level in the embodiment of the triangular wave generating unit 21a of the slope compensation circuit:
referring to fig. 1 and fig. 2A to 2C, since the output end of the slope compensation circuit 21a is connected to the output voltage feedback input ends COMP1 and COMP2 of the pwm controller 13, and the output voltage feedback input ends COMP1 and COMP2 are connected to a second dc voltage source V2 through an internal resistor RIN, and the voltage of the second dc voltage source V is lower than that of the first dc voltage source V, the equivalent circuit is as shown in the circuits of fig. 2A to 2C, and for convenience of description, the phototransistor of the photo-coupler M4 is assumed to be a current source IO.
As shown in fig. 3A to 3F, when the pwm controller 13 outputs a pulse width signal from T10 to T12 to the first main switch Q4, the first main switch Q4 is turned on, so that the first high frequency transformer T1 has a conducting current induced by the first current transformer T3; at the same time, the third switch 25 of the present invention is also turned on, and the second main switch Q6 and the fourth electronic switches Q6, Q1626 are turned off; since the voltage of the first voltage source V1 is higher than that of the second voltage source V2, and the third electronic switch 25 short-circuits the series node of the first charging loop, the first voltage source V1 charges the capacitor through the second charging loop, as shown in fig. 2A, and the potentials of VCOMP1 and VCOMP2 rise; referring to fig. 2B, when the pwm controller 13 controls the second electronic main switch Q6 to turn on at time t11 to t12, i.e. the third and fourth electronic switches 25 and 26 are turned on simultaneously during this period, the capacitor 24 fully charged during the previous period starts to discharge to ground through the turned-on third and fourth electronic switches 25 and 26, and the voltage levels of VCOMP1 and VCOMP2 decrease; as shown in fig. 4A to 4B, when the capacitor 24 discharges for a certain period of time, the voltage value VCS1 corresponding to the current peak of the on-current signal of the first high-frequency transformer T1 is crossed, and the frequency width modulation controller 13 immediately controls the first main switch Q4 and the third electronic switch 25 to turn off; as shown in fig. 2C and fig. 3A to fig. 3F, the pwm controller 13 only continues to control the second main switch Q6 and the fourth electronic switch Q6, 26 to be turned on, and the capacitor 24 is also charged through the first charging loop, and the pwm controller 13 further controls the capacitor 24 to be discharged when the first main switch Q4 and the third electronic switch 25 are turned on, so that the triangular wave voltage feedback signals VCOMP1 and VCOMP2 are decreased until meeting the voltage value VCS2 corresponding to the current peak of the on-current signal of the second high frequency transformer T2, and the pwm controller 13 turns off the second main switch Q6 and the fourth electronic switch 26, and thus the operation is cycled.
As shown in fig. 4A and 4B, the slope compensation circuit of the present invention actually performs slope compensation on the output dc voltage of the power conversion circuit, so that the original dc output voltage feedback signal is compensated to become a triangular wave voltage feedback signal VCOMP, (VCOMP 2) with a higher voltage level than the original output voltage feedback signal, it can effectively avoid the voltage surge generated by the conduction of the high frequency transformer from turning off the two main switches Q4, Q6 early, and can be correctly closed when the originally predetermined pulse width of the first and second main switches Q4, Q6 is reached, without turning off the first and second switches Q4, Q6 early, the rising slope and falling slope of the triangular wave voltage feedback signal at high level can be changed by the resistance and capacitance of the first and second loops; in another preferred embodiment, the resistors R63 and R66 are R68 and R67, respectively, to make the charging and discharging characteristics of the two current loops consistent.
Referring to fig. 5, fig. 5 shows a second preferred embodiment of the slope compensation circuit 21b of the present invention, which is similar to the first preferred embodiment in most circuit designs, but the resistors R66 and R67 connected between the first and second series resistors and the capacitor 24 are further connected in parallel with a forward diode D1 and D2 to adjust the RC charging and discharging time.
Referring to fig. 6, fig. 6 shows a third preferred embodiment of the slope compensation circuit 21c of the present invention, most of the circuit designs are the same as the first preferred embodiment, and the control terminals (gates) of the third and fourth electronic switches 25 and 26 of the present embodiment pass through a current sensor, such as: the current transformer is coupled to the primary side of the corresponding first and second high frequency transformers T1, T2 to obtain the primary side conduction current signals of the high frequency transformers T1, T2, which are synchronized with the driving signals for turning on the first and second main switches Q4, Q6, so that the third and fourth electronic switches 25, 26 can be turned on.
Referring to fig. 7, fig. 7 shows a slope compensation circuit 21d according to a fourth preferred embodiment of the present invention, which has a circuit design similar to that of the first preferred embodiment, but the third and fourth electronic switches 25 and 26 are replaced by first and second diodes 30 and 31, wherein the anode of the first diode 30 is connected to the series node of the series resistor 23 of the first and second charging loops, and the cathode thereof is connected to the control terminal of the second main switch Q6 or to a current transformer serially connected to the primary side of the second high frequency transformer T2; similarly, the anode of the second diode 31 is connected to the series node of the series resistor 22 of the second charging loop, and the cathode thereof can be connected to the control terminal of the first main switch Q4, or connected to another current transformer connected in series to the primary side of the first high-frequency transformer T1.
The electronic switch can be a transistor such as a MOSFET or a BJT.
In the embodiments, the slope compensation method of the present invention includes:
obtaining a synchronization signal with the first and second main switch driving signals;
generating a set of triangular wave signals, wherein the rising time of the triangular wave signals is determined by the first main switch driving signal and the second main switch driving signal; and
the triangular wave signal is added to a voltage feedback signal corresponding to one of the output DC voltage feedback signals of the power conversion circuit and used for comparing the current peak value to form a triangular wave DC voltage feedback signal with a higher level than the DC voltage feedback signal, the triangular wave DC voltage feedback signal is input to the output voltage feedback input end of the pulse width modulator, so that the pulse width modulation controller performs peak value comparison by using the triangular wave DC voltage feedback signal and the voltage values corresponding to the primary side current signals of the first and second high-frequency transformers to determine the driving signals of the first and second main switches.
In summary, the present invention performs slope compensation on the output dc voltage feedback signal, so that when the triangular-wave dc voltage feedback signal with high dc level is compared with the conducting current signal in the subsequent voltage magnitude, the surge on the conducting current signal can be effectively avoided, and the electronic switch of the present high-frequency transformer is turned off in advance; therefore, the slope compensation method can effectively reduce the defect of unstable oscillation of the output direct-current power supply caused by the conduction noise of the alternately conducting electronic switch.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be construed as the protection scope of the present invention.
Claims (23)
1. A slope compensation circuit for a power conversion circuit in a peak current control mode, the power conversion circuit comprising two forward converters and a PWM controller for controlling the operation of the two forward converters, wherein each of the forward converters comprises a high frequency transformer and first and second main switches connected in series to a primary side of the high frequency transformer, the slope compensation circuit comprising:
a first charging loop, including a first series resistor and a capacitor formed by two resistors connected in series, wherein two ends of the first series resistor are respectively connected with one end of the capacitor and a direct current power supply, and the other end of the capacitor is connected to an output voltage feedback input end of the pulse width modulation controller;
the second charging loop comprises a second series resistor formed by connecting two resistors in series, and the second series resistor is connected with the first series resistor in parallel; and
a discharge loop including a third and a fourth electronic switch, each of the third and fourth electronic switches including two terminals and a control terminal, wherein one terminal of the third and fourth electronic switches is connected to the series node of the first and second series resistors, and the other terminal is grounded; the control end of the third electronic switch is connected to the control end of the first main switch of the first forward converter, and the control end of the fourth electronic switch is connected to the control end of the second main switch of the second forward converter; the third and fourth electronic switches are turned on and off synchronously with the first and second main switches, respectively.
2. The slope compensation circuit of claim 1, wherein the resistor of the first and second series resistors connected to the capacitor is further connected in parallel with a diode, respectively, the anode of each diode being connected to the series node corresponding to the first and second series resistors, and the cathode of each diode being connected to the capacitor.
3. The slope compensation circuit of claim 1 or2, wherein the other end of the capacitor is further connected to a set of output dc voltage terminals of the power conversion circuit through an optocoupler, wherein a light emitting diode terminal of the optocoupler is connected to the output dc voltage terminals and the phototransistor is connected to the capacitor.
4. The slope compensation circuit according to claim 1 or2, wherein two resistors connected to the capacitor in the first series resistor and the second series resistor have the same resistance value, and the other two resistors in the first series resistor and the second series resistor have the same resistance value.
5. The slope compensation circuit of claim 3, wherein two of the first and second series resistors connected to the capacitor have the same resistance value, and the other two of the first and second series resistors have the same resistance value.
6. A slope compensation circuit for a power conversion circuit in a peak current control mode, the power conversion circuit comprising two forward converters and a PWM controller for controlling the operation of the two forward converters, wherein each of the forward converters comprises a high frequency transformer and first and second main switches connected in series to a primary side of the high frequency transformer, the slope compensation circuit comprising:
the first charging loop is composed of a first series resistor and a capacitor which are formed by connecting two resistors in series, wherein two ends of the first series resistor are respectively connected with one end of the capacitor and a direct current power supply, and the other end of the capacitor is connected to the output voltage feedback input end of the pulse width modulation controller;
the second charging loop comprises a second series resistor formed by connecting two resistors in series, and the second series resistor is connected with the first series resistor in parallel; and
a discharge loop including a third and a fourth electronic switch, each of the third and fourth electronic switches including two terminals and a control terminal, wherein one terminal of the third and fourth electronic switches is connected to the series node of the first and second series resistors, and the other terminal is grounded; the control ends of the third and fourth electronic switches are respectively connected with a current transformer, and the two current transformers are respectively coupled and connected to the primary sides of the corresponding first and second high-frequency transformers so as to induce current signals of the primary sides of the corresponding high-frequency transformers, so that the third and fourth electronic switches are respectively synchronously opened and closed with the first and second main switches.
7. The slope compensation circuit of claim 6, wherein the resistor of the first and second series resistors connected to the capacitor is further connected in parallel with a diode, respectively, the anode of each diode being connected to the series node corresponding to the first and second series resistors, and the cathode of each diode being connected to the capacitor.
8. The slope compensation circuit of claim 5 or 6, wherein the other end of the capacitor is further connected to a set of output dc voltage terminals of the power conversion circuit through an optocoupler, wherein a light emitting diode terminal of the optocoupler is connected to the output dc voltage terminals and the phototransistor is connected to the capacitor.
9. The slope compensation circuit according to claim 5 or 6, wherein two resistors connected to the capacitor in the first series resistor and the second series resistor have the same resistance value, and the other two resistors in the first series resistor and the second series resistor have the same resistance value.
10. The slope compensation circuit of claim 7, wherein two of the first and second series resistors connected to the capacitor have the same resistance value, and the other two of the first and second series resistors have the same resistance value.
11. A slope compensation circuit for a power conversion circuit in a peak current control mode, the power conversion circuit comprising two forward converters and a PWM controller for controlling the operation of the two forward converters, wherein each of the forward converters comprises a high frequency transformer and first and second main switches connected in series to a primary side of the high frequency transformer, the slope compensation circuit comprising:
the first charging loop comprises a first series resistor and a capacitor which are formed by connecting two resistors in series, wherein two ends of the first series resistor are respectively connected with one end of the capacitor and a direct current power supply, and the other end of the capacitor is connected to the output voltage feedback input end of the pulse width modulation controller;
the second charging loop comprises a second series resistor formed by connecting two resistors in series, and the second series resistor is connected with the first series resistor in parallel; and
a discharge loop including a first diode and a second diode, wherein the anode of the first diode is connected to the second series resistor series node, and the cathode of the first diode is connected to the second main switch control end; the anode of the second diode is connected to the first series resistor series node, and the cathode of the second diode is connected to the control end of the first main switch.
12. The slope compensation circuit of claim 11, wherein the resistor of the first and second series resistors connected to the capacitor is further connected in parallel with a diode, respectively, the anode of each diode being connected to the series node corresponding to the first and second series resistors, and the cathode of each diode being connected to the capacitor.
13. The slope compensation circuit of claim 11 or 12, wherein the other end of the capacitor is further connected to a set of output dc voltage terminals of the power conversion circuit through an optocoupler, wherein a light emitting diode terminal of the optocoupler is connected to the output dc voltage terminals and the phototransistor is connected to the capacitor.
14. The slope compensation circuit according to claim 11 or 12, wherein two resistors connected to the capacitor in the first series resistor and the second series resistor have the same resistance value, and the other two resistors in the first series resistor and the second series resistor have the same resistance value.
15. The slope compensation circuit of claim 13, wherein two of the first and second series resistors connected to the capacitor have the same resistance value, and the other two of the first and second series resistors have the same resistance value.
16. A slope compensation circuit for a power conversion circuit in a peak current control mode, the power conversion circuit comprising two forward converters and a PWM controller for controlling the operation of the two forward converters, wherein each of the forward converters comprises a high frequency transformer and first and second main switches connected in series to a primary side of the high frequency transformer, the slope compensation circuit comprising:
the first charging loop is composed of a first series resistor and a capacitor which are formed by connecting two resistors in series, wherein two ends of the first series resistor are respectively connected with one end of the capacitor and a direct current power supply, and the other end of the capacitor is connected to the output voltage feedback input end of the pulse width modulation controller;
the second charging loop comprises a second series resistor formed by connecting two resistors in series, and the second series resistor is connected with the first series resistor in parallel; and
and the discharge loop comprises a first diode and a second diode, wherein the anode of the first diode is connected to the series node of the second series resistor, the anode of the second diode is connected to the series node of the first series resistor, the cathodes of the first diode and the second diode are respectively connected with a second and a first current transformer, and the second and the first current transformers are respectively coupled and connected in series to the primary sides of the corresponding second and first high-frequency transformers so as to induce a current signal corresponding to the primary side of the high-frequency transformer and enable the first and the second diodes to be respectively synchronously opened and closed with the second and the first main switches.
17. The slope compensation circuit of claim 16, wherein the resistor of the first and second series resistors connected to the capacitor is further connected in parallel with a diode, respectively, the anode of each diode being connected to the series node corresponding to the first and second series resistors, and the cathode of each diode being connected to the capacitor.
18. The slope compensation circuit of claim 16 or 17, wherein the other end of the capacitor is further connected to a set of output dc voltage terminals of the power conversion circuit through an optocoupler, wherein a light emitting diode terminal of the optocoupler is connected to the output dc voltage terminals and the phototransistor is connected to the capacitor.
19. The slope compensation circuit according to claim 16 or 17, wherein two resistors connected to the capacitor in the first series resistor and the second series resistor have the same resistance value, and the other two resistors in the first series resistor and the second series resistor have the same resistance value.
20. The slope compensation circuit of claim 18, wherein two of the first and second series resistors connected to the capacitor have the same resistance value, and the other two of the first and second series resistors have the same resistance value.
21. A slope compensation method for a power conversion circuit in a peak current control mode comprises two forward converters and a pulse width modulation controller for controlling the operation of the two forward converters, wherein each forward converter comprises a high-frequency transformer and a first main switch and a second main switch which are connected in series with the primary side of the high-frequency transformer; the slope compensation method comprises the following steps:
obtaining a synchronization signal with the first and second main switch driving signals;
generating a set of triangular wave signals, wherein the rising time of the triangular wave signals is determined by the first main switch driving signal and the second main switch driving signal; and
the triangular wave signal is added into a direct current voltage feedback signal which corresponds to the output of the power conversion circuit and is used for comparing current peak values to form a triangular wave direct current voltage feedback signal, the voltage level of the triangular wave direct current voltage feedback signal is higher than that of the direct current voltage feedback signal, the triangular wave direct current voltage feedback signal is input into the output voltage feedback input end of the pulse width modulation controller, the pulse width modulation controller is enabled to carry out peak value comparison by the triangular wave direct current voltage feedback signal and the corresponding voltage values of the primary side current signals of the first high-frequency transformer and the second high-frequency transformer, and driving signals of the first main switch and the second main switch are determined.
22. The slope compensation method of claim 21, wherein the synchronization signals are derived from the first and second master switch drivers.
23. The slope compensation method of claim 21, wherein the synchronization signals are derived from the first and second main switch driving signals by a current transformer coupled to the primary sides of two high frequency transformers.
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| Application Number | Priority Date | Filing Date | Title |
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| CN2007101597221A CN101212184B (en) | 2007-12-21 | 2007-12-21 | Slope compensation method and circuit for power switching circuit |
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| CN2007101597221A CN101212184B (en) | 2007-12-21 | 2007-12-21 | Slope compensation method and circuit for power switching circuit |
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| CN101212184A CN101212184A (en) | 2008-07-02 |
| CN101212184B true CN101212184B (en) | 2010-06-09 |
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| CN2007101597221A Expired - Fee Related CN101212184B (en) | 2007-12-21 | 2007-12-21 | Slope compensation method and circuit for power switching circuit |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US9608606B2 (en) | 2015-08-27 | 2017-03-28 | Amazing Microelectronic Corp. | Slope control circuit |
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| CN112285519B (en) * | 2020-10-26 | 2022-06-24 | 中国科学院上海微***与信息技术研究所 | Method for measuring series resistance and ideal factor in diode gating array |
| CN113204290B (en) * | 2021-04-19 | 2022-12-30 | 深圳天德钰科技股份有限公司 | Signal compensation circuit, touch control circuit and display device |
| CN115395775A (en) * | 2022-09-30 | 2022-11-25 | 苏州英威腾电力电子有限公司 | Slope compensation circuit and PWM modulation circuit |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4689730A (en) * | 1985-04-05 | 1987-08-25 | Victor Company Of Japan, Ltd. | Flyback transformer circuit with a noise cancelling circuit |
| CN1447507A (en) * | 2003-04-08 | 2003-10-08 | 毛灿豪 | Switching power supply |
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- 2007-12-21 CN CN2007101597221A patent/CN101212184B/en not_active Expired - Fee Related
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4689730A (en) * | 1985-04-05 | 1987-08-25 | Victor Company Of Japan, Ltd. | Flyback transformer circuit with a noise cancelling circuit |
| CN1447507A (en) * | 2003-04-08 | 2003-10-08 | 毛灿豪 | Switching power supply |
Non-Patent Citations (1)
| Title |
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| JP平7-231653A 1995.08.29 |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9608606B2 (en) | 2015-08-27 | 2017-03-28 | Amazing Microelectronic Corp. | Slope control circuit |
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