CN214014114U - Secondary control isolated DC/DC converter circuit topological structure - Google Patents
Secondary control isolated DC/DC converter circuit topological structure Download PDFInfo
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- CN214014114U CN214014114U CN202020896949.5U CN202020896949U CN214014114U CN 214014114 U CN214014114 U CN 214014114U CN 202020896949 U CN202020896949 U CN 202020896949U CN 214014114 U CN214014114 U CN 214014114U
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Abstract
The utility model discloses a secondary control isolated form DC/DC converter circuit topological structure, the main power return circuit based on secondary control isolated form DC/DC converter includes input filter circuit, power conversion circuit, transformer, rectifier circuit, output filter circuit; the device also comprises an output over-voltage and under-voltage protection circuit, a pulse width control circuit, a sampling feedback circuit, an isolation circuit and a primary function circuit; the pulse width control circuit is positioned on the secondary side of the isolated DC/DC converter; the utility model simultaneously places the pulse width control circuit and the sampling feedback circuit on the secondary side of the isolated DC/DC converter, and the primary switch tube driving signal is transmitted to the primary through the pulse width modulator or the digital isolator; the feedback signal of the topological structure does not need to be transmitted through an isolation circuit, is suitable for control modes such as voltage mode control, peak current mode control, ripple-based COT control, V2C control and the like, and can effectively improve the dynamic response speed of the DC/DC converter.
Description
Technical Field
The utility model relates to a switching power supply technical field, concretely relates to secondary control isolated form DC/DC converter circuit topological structure.
Background
With the increase of system functions and loads of modern electronic equipment and the wide application of high-voltage large-current DC/DC converters, higher requirements are put forward on dynamic performances of the DC/DC converter, such as load jump. The utility model discloses/utility model circuit topology's sample feedback circuit and pulse width control circuit all are located isolated form DC/DC converter output side, and the sample is faster with feedback response speed.
The isolated DC/DC converter is used for converting power through a control circuit in a switching power supply, converting input voltage into different output voltages and currents required by an electronic system, and is a power circuit with an input side and an output side isolated from each other. The isolation of the power circuit part is realized by a power transformer, and the isolation of the control circuit part is usually realized by a pulse transformer, a digital isolator, a photoelectric coupler and the like. The current common circuit topology structure usually puts the pulse width control circuit at the primary side, and transmits the secondary feedback signal to the primary pulse width control circuit through a pulse transformer or a photoelectric coupler to realize closed-loop control. The feedback signal needs to be transmitted to the primary stage through the isolation circuit, so that the delay performance is realized, and the dynamic characteristics such as load jump are not facilitated to be improved. Meanwhile, when the synchronous rectification scheme is adopted, the driving signal of the secondary rectifier tube also needs to be transmitted to the secondary side through the pulse transformer, so that the circuit is complex.
The pulse width control circuit of the secondary control isolation type DC/DC converter is arranged on the load side, the sampling feedback error signal can be directly connected to the pulse width control circuit, the driving output of the pulse width control circuit can be directly used for driving the secondary rectifying switch tube, and the driving signal of the primary switch tube is transmitted to the primary side through the pulse transformer or the digital isolator, so that electrical isolation is realized. Compared with a primary control topological structure, the topological structure is more suitable for low-voltage and high-current application occasions adopting a synchronous rectification scheme.
The current common control method of the isolated DC/DC converter mainly comprises a voltage control mode and a peak current control mode, and feedback error signals of the two control modes are transmitted to a primary side through an isolation circuit to realize closed-loop control. In order to improve the dynamic response speed of products, ripple-based COT control, V2C control, and the like are increasingly applied to non-isolated DC/DC converters. The control mode does not need a PI regulator and has simple structure. But an accurate output ripple voltage or an output inductor ripple current is needed as a feedback signal, the signal is difficult to be accurately transmitted to the primary pulse width control circuit through the isolation circuit, and the dynamic response speed of the DC/DC converter is limited due to time delay and the like.
SUMMERY OF THE UTILITY MODEL
The utility model provides a secondary control isolated form DC/DC converter circuit topological structure can solve the technical problem that prior art DC/DC converter's dynamic response is inefficient.
In order to achieve the above purpose, the utility model adopts the following technical scheme:
the main power loop of the secondary control isolation type DC/DC converter comprises an input filter circuit, a power conversion circuit, a transformer, a rectifying circuit and an output filter circuit;
the device also comprises an output over-voltage and under-voltage protection circuit, a pulse width control circuit, a sampling feedback circuit, an isolation circuit and a primary function circuit;
the pulse width control circuit is positioned on the secondary side of the isolation DC/DC converter;
the output of the input filter circuit is connected with the power conversion circuit, the output of the power conversion circuit is connected with the input end of the transformer, the output of the transformer is connected with the input end of the rectifying circuit, the output of the rectifying circuit is connected with the input end of the output filter circuit, the output of the output filter circuit is connected with the input end of the sampling feedback circuit, and the output end of the sampling feedback circuit is connected with the input end of the pulse width control circuit and the input end of the isolation circuit;
meanwhile, the output end of the pulse width control circuit is connected with the input end of the rectifying circuit and the input end of the isolating circuit, the output end of the isolating circuit is connected with the input end of the power conversion circuit, the output end of the output over-voltage and under-voltage protection circuit is connected with the input end of the primary function circuit, and the output end of the primary function circuit is connected with the input end of the input isolating circuit.
Further, the main power loop of the secondary control isolation type DC/DC converter comprises a primary input filter inductor L1, an input filter capacitor C1, a switching tube V1, a primary current sampling transformer L2, a transformer T1, a secondary synchronous rectifier tube V2, a secondary synchronous follow current tube V3, an output energy storage filter inductor L3 and an output filter capacitor C2;
wherein,
one end of an input filter inductor L1 is connected with an input voltage source Vin, and the other end of the input filter inductor L1 is connected with an input filter capacitor C1 to form an input primary filter circuit;
one end of an input filter capacitor C1 is connected with a sampling winding at one end of a current transformer L2, the other end of the input filter capacitor C1 is connected with a drain electrode of a power switch tube V1, the other end of the current transformer L2 is connected with a primary winding of a transformer T1, the other end of the primary winding of the transformer T1 is connected with a drain electrode of a switch tube V1, the drain electrode of the switch tube V1 is connected with one end of the primary winding of the transformer, a source stage is connected with one end of an input filter capacitor, a gate stage is connected with one end of an isolation circuit, and the switch tube V1 forms a power conversion circuit;
a secondary winding of a transformer T1 is connected with a drain of a synchronous rectifier tube V2, a source of the synchronous rectifier tube V2 is connected with a source of a follow current switch tube V3, the synchronous rectifier tube V2 and a gate of the follow current switch tube V3 are respectively connected with a pulse width control output of a pulse width control circuit, the source is connected with one end of an output filter capacitor C2, the other end of the secondary winding of the transformer is connected with a drain of the follow current tube V3 and is connected with one end of the output filter capacitor C2, and the synchronous rectifier tube V2 and the follow current switch tube V3 jointly form a rectification circuit;
one end of an output filter inductor L3 is connected with one end of the secondary winding of the transformer and the drain electrode of the follow current switch tube V3, and the other end of the output filter inductor L3 is connected with an output filter capacitor C2 to form an output filter circuit (5).
Furthermore, the sampling feedback circuit comprises a resistor R1, one end of which is connected to the output voltage Vo, the other end of which is connected to the resistor R2, the other end of the resistor R2 is connected to a secondary reference ground to form an output voltage sampling circuit, one end of the resistor R2 is connected to the inverting input terminal of the operational amplifier N1, the inverting input terminal of the operational amplifier N1 is connected to one ends of capacitors C3 and C2, one end of the resistor R4 is connected to a capacitor C3, the other end of the resistor R4 is connected to the output terminals of the capacitors C2 and the operational amplifier, one end of the resistor R3 is connected to the output voltage Vo, the other end of the resistor R68525 is connected to a capacitor C1, one end of a capacitor C1 is connected to the inverting input terminal of the operational amplifier N1, the non-inverting input terminal of the operational amplifier N1 is connected to a reference voltage, and the resistors R3, R4, capacitors C1, C2, C3 and the operational amplifier N1 form a negative feedback compensation circuit;
the pulse width control circuit adopts a comparator N2, the output of the operational amplifier N1 is connected with the non-inverting input end of a comparator N2, the inverting input end of the comparator N2 is connected with a sawtooth wave signal Vramp, and the output PWM control signal of the comparator N2 is connected with the grid electrode of a switch tube V1 through an isolation circuit 9.
Furthermore, the sampling feedback circuit comprises a resistor R1, one end of which is connected with the output voltage Vo, the other end of which is connected with a resistor R2, the other end of the resistor R2 is connected with a secondary reference ground to form an output voltage sampling circuit, one end of the resistor R2 is connected with the inverting input end of an operational amplifier N1, the inverting input end of the operational amplifier N1 is connected with one ends of capacitors C1 and C2, one end of the resistor R3 is connected with a capacitor C2, the other end of the resistor R3 is connected with the capacitor C1 and the output end of the operational amplifier, the non-inverting input end of the operational amplifier N1 is connected with a reference voltage, and the resistor R3, the capacitors C1 and C2 and the operational amplifier N1 form a type II negative feedback compensation circuit;
one end of the resistor R4 is connected with the secondary reference ground, the other end of the resistor R4 is connected with the current sampling signal Vi, one end of the diode D1 is connected with the current sampling signal Vi, the other end of the diode D1 is connected with one end of the resistor R5, one ends of the resistor R6 and the capacitor C3 are connected with the resistor R4, and the other ends of the resistor R5 are connected with the resistor R5; the resistors R4, R5 and R6, the diode D1 and the capacitor C3 jointly form a current sampling filter circuit;
the output of the operational amplifier N1 is connected with the inverting input end of a comparator N2, the non-inverting input end of a comparator N2 is connected with one end of a capacitor C3, the output of the comparator N2 is connected with the reset end of a trigger N3, the set end of a trigger N3 is connected with a clock signal, and the output of the trigger N3 is connected with the grid electrode of a switch tube V1 through an isolation circuit 9; the comparator N2 and the flip-flop N3 constitute a pulse width control circuit.
Further, the sampling feedback circuit comprises a resistor R1, one end of which is connected to the output voltage Vo, the other end of which is connected to the resistor R2, the other end of the resistor R2 is connected to the secondary reference ground, so as to form an output voltage sampling circuit, one end of the resistor R2 is connected to the inverting input terminal of the comparator N2, the inverting input terminal of the comparator N2 is connected to one end of the capacitor C2, the other end of the capacitor C2 is connected to one end of the capacitor C1 and one end of the resistor R3, the other end of the resistor R3 is connected to one end of the output filter inductor L, the other end of the capacitor C1 is connected to the other end of the output filter inductor L, the non-inverting input terminal of the comparator N2 is connected to the reference voltage Vref, and the resistor R3, the capacitor C1, the capacitor C2 and the comparator N2 form a feedback compensation circuit;
the output end of the comparator N2 is connected with the set end of the trigger N3, the reset end of the trigger N3 is connected with the output end of the on-timer, and the output of the trigger N3 is connected with the grid of the switch tube V1 through an isolation circuit; the flip-flop N3 and the on-timer constitute a pulse width control circuit.
Further, the circuit comprises a control conduction timer circuit, wherein the circuit comprises a constant current source I1 positively correlated with the input power supply voltage, a capacitor C1, a conduction timer switch tube V1 and a comparator N4;
one end of a capacitor C1 is connected with the non-inverting input end of a comparator N4, the inverting input end of a comparator N4 is threshold voltage VTon, and the gate of a timer switch tube V1 is conducted and controlled by a trigger N3;
when the sampling voltage is reduced to the reference voltage Vref, the trigger N3 is set, the on-timer switch V1 is disconnected at the moment, the constant current source I1 charges the capacitor C1, when the voltage of the non-inverting input end of the comparator N4 is charged and is increased to the threshold voltage VTon, the trigger N3 is reset, the output voltage is reduced, the on-timer switch V1 is closed, and the capacitor voltage VC1 is reduced to 0; when the sampling voltage drops to the reference voltage, the next switching period is entered.
According to the above technical scheme, the utility model discloses a secondary control isolated form DC/DC converter circuit topological structure, with input direct current voltage transmit input filter circuit and input under-voltage protection circuit simultaneously, when input voltage is in the operating voltage within range that sets up, elementary function circuit work, give pulse width control circuit and sample feedback circuit power supply through isolating circuit, pulse width control circuit output drive signal makes power conversion circuit and rectifier circuit work, rectifier circuit's output is through output filter circuit output direct current voltage. The sampling feedback circuit samples the output voltage and compares with the reference to form a feedback signal to input a pulse width control signal to realize closed-loop control.
The topological structure of the utility model places the pulse width control circuit and the sampling feedback circuit at the load (secondary) side of the isolated DC/DC converter, and the primary switch tube driving signal is transmitted to the primary through the pulse width modulator or the digital isolator; the feedback signal of the topological structure does not need to be transmitted through an isolation circuit, is suitable for control modes such as voltage mode control, peak current mode control, ripple-based COT control, V2C control and the like, and can effectively improve the dynamic response speed of the DC/DC converter.
Drawings
FIG. 1 is a block diagram of a secondary control isolated DC/DC converter topology according to the present invention;
fig. 2 is a main power circuit block diagram (taking Forward topology as an example) of the secondary control isolated DC/DC converter of the present invention;
FIG. 3 is a schematic diagram of the sampling feedback circuit and the pulse width control circuit of the present invention;
FIG. 3(a) is a schematic circuit diagram of a sampling feedback circuit and a pulse width control circuit when voltage-type feedback is adopted; FIG. 3(b) is a schematic circuit diagram of a current mode time sampling feedback circuit and a pulse width control circuit; FIG. 3(c) is a schematic circuit diagram of a sampling feedback circuit and a pulse width control circuit using a COT (constant on time control) control based on ripple feedback;
fig. 4 is a schematic diagram of the on-timer circuit based on ripple feedback COT control of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention.
As shown in fig. 1, the utility model discloses a secondary control isolated form DC/DC converter includes input filter circuit 1, power conversion circuit 2, transformer 3, rectifier circuit 4, output filter circuit 5, output cross undervoltage protection circuit 6, be located the secondary pulse width control circuit 7 of isolation DC/DC converter, sample feedback circuit 8, isolating circuit 9, elementary functional circuit 10.
The output of the input filter circuit 1 is connected with the power conversion circuit 2, the output of the power conversion circuit 2 is connected with the input end of the transformer 3, the output of the transformer 3 is connected with the input end of the rectification circuit 4, the output of the rectification circuit 4 is connected with the input end of the output filter circuit 5, the output of the output filter circuit 5 is connected with the input end of the sampling feedback circuit 8, the output end of the sampling feedback circuit 8 is connected with the input end of the pulse width control circuit 7 and the input end of the isolation circuit 9, the output end of the pulse width control circuit 7 is connected with the input end of the rectification circuit 4 and the input end of the isolation circuit 8, the output end of the isolation circuit 9 is connected with the input end of the power conversion circuit 2, the output end of the primary function circuit 6 is connected with the input end of the primary function circuit 10, and the output end of the primary function circuit 10 is connected with the input end of the output isolation circuit 9.
The working principle is as follows:
the embodiment of the utility model provides a transmit input DC voltage simultaneously input filter circuit 1 and input under-voltage protection circuit, when input voltage was in the operating voltage within range that sets up, elementary function circuit work, give pulse width control circuit 7 and the power supply of sample feedback circuit 8 through isolating circuit 9, pulse width control circuit 7 output drive signal makes power conversion circuit 2 and rectifier circuit 4 work, rectifier circuit 4's output is through output filter circuit 5 output DC voltage. The sampling feedback circuit 8 samples the output voltage and compares the output voltage with a reference to form a feedback signal to be input into the pulse width control signal 7 to realize closed-loop control.
The utility model discloses set up pulse width control circuit at isolated form DC/DC converter's level to because pulse width control circuit 7 lies in same one side with sample feedback circuit 8, the sample feedback circuit among this topological structure can adopt voltage type feedback control mode, current type feedback control mode, based on multiple control modes such as COT (invariable on-time control) control of ripple feedback.
As shown in fig. 2, taking Forward topology Forward as an example, the main power circuit of the secondary control isolated DC/DC converter includes a primary input filter inductor L1, an input filter capacitor C1, a switching tube V1, a primary current sampling transformer L2, a transformer T1, a secondary synchronous rectifier tube V2, a secondary synchronous follow current tube V3, an output energy storage filter inductor L3, and an output filter capacitor C2.
As shown in fig. 2, taking Forward topology as an example, an input filter inductor L1 of the secondary control isolated DC/DC converter has one end connected to an input voltage source Vin and the other end connected to an input filter capacitor C1 to form an input said primary filter circuit 1, one end of an input filter capacitor C1 is connected to a sampling winding at one end of a current transformer L2, the other end is connected to a drain of a power switch tube V1, the other end of the current transformer L2 is connected to a primary winding of a transformer T1, the other end of the primary winding of the transformer T1 is connected to a drain of a switch tube V1, a drain of a switch tube V1 is connected to one end of the primary winding of the transformer, a source is connected to one end of the input filter capacitor, a gate is connected to one end of an isolation circuit, the switch tube V1 forms a power conversion circuit 2, a secondary winding of the transformer T1 is connected to a drain of a synchronous rectifier V2, a source of the synchronous rectifier tube V2 is connected to a source of a freewheeling switch tube V3, the synchronous rectifier tube V2 and the follow current switch tube V3 are respectively connected with the pulse width control output of the pulse width control circuit, the source stage is connected with one end of an output filter capacitor C2, the other end of the secondary winding of the transformer is connected with the drain electrode of the follow current tube V3 and is connected with one end of the output filter capacitor C2, the synchronous rectifier tube V2 and the follow current switch tube V3 jointly form a rectifier circuit 4, one end of an output filter inductor L3 is connected with one end of the secondary winding of the transformer and the drain electrode of the follow current switch tube V3, and the other end of the output filter inductor L3 is connected with an output filter capacitor C2, so that an output filter circuit 5 is jointly formed. The main power topology of the secondary control isolation type DC/DC converter is also suitable for the isolation type converter topologies such as a Flyback topology, a Push-Pull topology, a Half-Bridge topology, a Full-Bridge topology and the like.
As shown in fig. 3(a), the circuit schematic diagram of the sampling feedback circuit and the pulse width control circuit when the voltage type feedback is adopted includes a pulse width control circuit 7 and a sampling feedback circuit 8. Specifically, one end of a resistor R1 is connected with the output voltage Vo, the other end of the resistor R1 is connected with a resistor R2, the other end of the resistor R2 is connected with a secondary reference ground to form an output voltage sampling circuit, one end of a resistor R2 is connected with the inverting input end of an operational amplifier N1, the inverting input end of the operational amplifier N1 is connected with one ends of capacitors C3 and C2, one end of a resistor R4 is connected with a capacitor C3, the other end of the resistor R4 is connected with a capacitor C2 and the output end of the operational amplifier, one end of a resistor R3 is connected with the output voltage Vo, the other end of the resistor R6725 is connected with a capacitor C1, one end of a capacitor C1 is connected with the inverting input end of an operational amplifier N1, the non-inverting input end of the operational amplifier N1 is connected with a reference voltage, and the resistors R3, R4, C1, C2 and C3 and the operational amplifier N1 form a III type negative feedback compensation circuit.
The output of the operational amplifier N1 is connected to the non-inverting input terminal of the comparator N2, the inverting input terminal of the comparator N2 is connected to the sawtooth wave signal Vramp, and the output PWM control signal of the comparator N2 is connected to the gate of the switching tube V1 through the isolation circuit 9. The resistors R1 and R2 realize the divided sampling of the output voltage, and the divided sampling is compared with the reference voltage Vref. The resistor R3, the R4 capacitor C1, the C2, the C3 and the operational amplifier N1 form a III-type compensation unit, and 1 main pole, 2 common poles and 2 zeros are generated to compensate a double pole and a high-frequency zero generated by a voltage type control main power circuit link. An error signal output by the operational amplifier N1 is compared with a sawtooth wave voltage Vramp through a comparator N2 to generate a power switch tube pulse width control signal, so that the closed-loop control of the DC/DC converter is realized.
As shown in fig. 3(b), the circuit schematic diagram of the sampling feedback circuit and the pulse width control circuit in the current mode control includes a pulse width control circuit 7 and a sampling feedback circuit 8. One end of a resistor R1 is connected with the output voltage Vo, the other end of the resistor R1 is connected with a resistor R2, the other end of a resistor R2 is connected with a secondary reference ground to form an output voltage sampling circuit, one end of a resistor R2 is connected with the inverting input end of an operational amplifier N1, the inverting input end of the operational amplifier N1 is connected with one ends of capacitors C1 and C2, one end of a resistor R3 is connected with a capacitor C2, the other end of the resistor R2 is connected with the capacitor C1 and the output end of the operational amplifier, the non-inverting input end of the operational amplifier N1 is connected with a reference voltage, and the resistor R3, the capacitors C1 and C2 and the operational amplifier N1 form a type II negative feedback compensation circuit. One end of the resistor R4 is connected with the secondary reference ground, the other end of the resistor R4 is connected with the current sampling signal Vi, one end of the diode D1 is connected with the current sampling signal Vi, the other end of the diode D1 is connected with one end of the resistor R5, one ends of the resistor R6 and the capacitor C3 are connected with the resistor R4, and the other ends of the resistor R5 are connected with each other. The resistors R4, R5 and R6, the diode D1 and the capacitor C3 jointly form a current sampling filter circuit.
The output of the operational amplifier N1 is connected with the inverting input end of the comparator N2, the non-inverting input end of the comparator N2 is connected with one end of the capacitor C3, the output of the comparator N2 is connected with the reset end of the flip-flop N3, the set end of the flip-flop N3 is connected with a clock signal, and the output of the flip-flop N3 is connected with the grid of the switch tube V1 through the isolation circuit 9. The resistors R1 and R2 realize the voltage division sampling of the output voltage, and the voltage division sampling is compared with the reference voltage Vref to form a voltage feedback loop. The resistor R3, the capacitors C1 and C2 and the operational amplifier N1 form a II-type compensation unit, and 1 main pole, 1 common pole and 1 zero point are generated to compensate an RC load pole generated by a current type control main power circuit link. A current sampling signal Vi is sent to a non-inverting input end of a comparator N2 through ramp signals rectified and filtered by resistors R4, R5, R6, a diode D1 and a capacitor C3, an inverting input end of the comparator N2 is connected with an error signal output by an operational amplifier N1, an output end of the comparator is connected with a reset end R of a trigger N3, a set end S of a trigger N3 is connected with a clock signal, a pulse width control signal of a power switch tube is generated, and closed-loop control of the DC/DC converter is achieved. The type iii compensation unit shown in fig. 3(a) is also applicable to a circuit employing current mode control.
As shown in fig. 3(c), a schematic circuit diagram of a sampling feedback circuit and a pulse width control circuit when ripple feedback COT (constant on time control) control is adopted includes a pulse width control circuit 7 and a sampling feedback circuit 8. Specifically, one end of a resistor R1 is connected with the output voltage Vo, the other end of the resistor R1 is connected with a resistor R2, the other end of a resistor R2 is connected with a secondary reference ground to form an output voltage sampling circuit, one end of the resistor R2 is connected with an inverting input end of a comparator N2, the inverting input end of the comparator N2 is connected with one end of a capacitor C2, the other end of the capacitor C2 is connected with a capacitor C1 and a resistor R3, the other end of the resistor R3 is connected with one end of an output filter inductor L, the other end of the output filter inductor L is connected with one end of a capacitor C1, a non-inverting input end of the comparator N2 is connected with a reference voltage, and the resistor R3, the capacitors C1 and C2 and the comparator N1 form a feedback compensation circuit together.
The output end of the comparator N2 is connected with the set end of the trigger N3, the reset end of the trigger N3 is connected with the output end of the turn-on timer, and the output end of the trigger N3 is connected with the grid electrode of the switch tube V1 through the isolation circuit 9. The resistors R1 and R2 realize the divided sampling of the output voltage, and the divided sampling is compared with the reference voltage Vref. The sampling voltage is compared with the reference voltage Vref, when the sampling voltage is lower than the reference voltage Vref, the comparator outputs high level, the trigger N3 is set, the output voltage rises, after the fixed time Ton is conducted, the timer is conducted to reset the trigger, the output voltage begins to drop, and the closed-loop control of the output voltage is realized. The capacitors C1, C2 and the resistor R3 are current harmonic compensation circuits and are used for compensating subharmonic oscillation phenomena possibly caused by using ceramic capacitors. Compared with voltage type control and current type control, the control circuit has the advantages of no need of a PI regulator, simple structure, quick dynamic response and the like.
COT control is a variable frequency control method, and the switching frequency of COT control is affected by various factors, especially the input voltage. In practical use, if the switching frequency variation range is too large, the design of the output filter is difficult, and the system EMI problem is caused. The constant frequency COT control mode can be realized by introducing signals such as input voltage, load current and the like to adjust the conduction time or introducing an additional phase-locked loop.
As shown in fig. 4, the ripple feedback COT based on control on the timer circuit is composed of a constant current source I1 positively correlated with the input power supply voltage, a capacitor C1, a on-timer switching tube V1, and a comparator N4. One end of the capacitor C1 is connected with the non-inverting input end of the comparator N4, and the inverting input end of the comparator N4 is provided with a threshold voltage VTonThe gate of the on-timer switch V1 is controlled by the flip-flop N3 in fig. 3 (c). When the sampled voltage drops to the reference voltage, the flip-flop N3 in fig. 3(C) is set, the on-timer switch V1 is turned off, the constant current source I1 charges the capacitor C1, and when the voltage at the non-inverting input of the comparator N4 rises to the threshold voltage VTonWhen the trigger N3 is reset, the output voltage drops, the on-timer switch V1 is closed, and the capacitor voltage V is reducedC1Down to 0; when the sampling voltage drops to the reference voltage, the next switching period is entered.
The scaling factor K1 of the controlled current source is:
the working cycle of the converter is as follows:
it can be seen from equation (2) that, because of introducing input voltage feedforward into the turn-on timer, the influence of the input voltage on the converter operating frequency in equation (5) is eliminated, and the converter switching frequency is ensured to be stable in the input voltage range.
To sum up, the utility model discloses a this topological structure's feedback signal need not to pass through the isolation circuit transmission, is applicable to control mode such as voltage mode control, peak current mode control, COT control based on the ripple, V2C control, can effectively promote the dynamic response speed of DC/DC converter.
The above embodiments are only used to illustrate the technical solution of the present invention, and not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the present invention in its corresponding aspects.
Claims (6)
1. A secondary control isolation type DC/DC converter circuit topological structure is based on a main power loop of a secondary control isolation type DC/DC converter, and the main power loop of the secondary control isolation type DC/DC converter comprises an input filter circuit (1), a power conversion circuit (2), a transformer (3), a rectification circuit (4) and an output filter circuit (5);
the method is characterized in that: the circuit also comprises an output over-voltage and under-voltage protection circuit (6), a pulse width control circuit (7), a sampling feedback circuit (8), an isolation circuit (9) and a primary functional circuit (10);
the pulse width control circuit (7) is positioned on the secondary side of the isolation DC/DC converter;
the output of the input filter circuit (1) is connected with the power conversion circuit (2), the output of the power conversion circuit (2) is connected with the input end of the transformer (3), the output of the transformer (3) is connected with the input end of the rectifying circuit (4), the output of the rectifying circuit (4) is connected with the input end of the output filter circuit (5), the output of the output filter circuit (5) is connected with the input end of the sampling feedback circuit (8), and the output end of the sampling feedback circuit (8) is connected with the input end of the pulse width control circuit (7) and the input end of the isolating circuit (9);
meanwhile, the output end of the pulse width control circuit (7) is connected with the input end of the rectifying circuit (4) and the input end of the isolating circuit (9), the output end of the isolating circuit (9) is connected with the input end of the power conversion circuit (2), the output end of the output over-voltage and under-voltage protection circuit (6) is connected with the input end of the primary function circuit (10), and the output end of the primary function circuit (10) is connected with the input end of the input isolating circuit (9).
2. The secondary control isolated DC/DC converter circuit topology of claim 1, wherein: the main power loop of the secondary control isolation type DC/DC converter comprises a primary input filter inductor L1, an input filter capacitor C1, a switch tube V1, a primary current sampling transformer L2, a transformer T1, a secondary synchronous rectifier tube V2, a secondary synchronous follow current tube V3, an output energy storage filter inductor L3 and an output filter capacitor C2;
wherein,
one end of an input filter inductor L1 is connected with an input voltage source Vin, and the other end of the input filter inductor L1 is connected with an input filter capacitor C1 to form an input filter circuit (1);
one end of an input filter capacitor C1 is connected with a sampling winding at one end of a current transformer L2, the other end of the input filter capacitor C1 is connected with a drain electrode of a power switch tube V1, the other end of the current transformer L2 is connected with a primary winding of a transformer T1, the other end of the primary winding of the transformer T1 is connected with a drain electrode of a switch tube V1, the drain electrode of the switch tube V1 is connected with one end of the primary winding of the transformer, a source stage is connected with one end of an input filter capacitor, a gate stage is connected with one end of an isolation circuit, and the switch tube V1 forms a power conversion circuit (2);
a secondary winding of a transformer T1 is connected with a drain of a synchronous rectifier tube V2, a source of the synchronous rectifier tube V2 is connected with a source of a follow current switch tube V3, the synchronous rectifier tube V2 and a gate of the follow current switch tube V3 are respectively connected with a pulse width control output of a pulse width control circuit, the source is connected with one end of an output filter capacitor C2, the other end of the secondary winding of the transformer is connected with a drain of the follow current tube V3 and is connected with one end of the output filter capacitor C2, and the synchronous rectifier tube V2 and the follow current switch tube V3 jointly form a rectifier circuit (4);
one end of an output filter inductor L3 is connected with one end of the secondary winding of the transformer and the drain electrode of the follow current switch tube V3, and the other end of the output filter inductor L3 is connected with an output filter capacitor C2 to form an output filter circuit (5).
3. The secondary control isolated DC/DC converter circuit topology of claim 1, wherein: the sampling feedback circuit (8) comprises a resistor R1, one end of the resistor R1 is connected with the output voltage Vo, the other end of the resistor R2 is connected with a secondary reference ground to form an output voltage sampling circuit, one end of a resistor R2 is connected with the inverting input end of an operational amplifier N1, the inverting input end of the operational amplifier N1 is connected with one ends of capacitors C3 and C2, one end of a resistor R4 is connected with a capacitor C3, the other end of the resistor R4 is connected with a capacitor C2 and the output end of the operational amplifier, one end of a resistor R3 is connected with the output voltage Vo, the other end of the resistor R3 is connected with a capacitor C1, one end of the capacitor C1 is connected with the inverting input end of an operational amplifier N1, the non-inverting input end of the operational amplifier N1 is connected with a reference voltage, and the resistors R3, R4, capacitors C1, C2 and C3 and an operational amplifier N1 form a negative feedback type compensation circuit;
the pulse width control circuit (7) adopts a comparator N2, the output of the operational amplifier N1 is connected with the non-inverting input end of a comparator N2, the inverting input end of the comparator N2 is connected with a sawtooth wave signal Vramp, and the output PWM control signal of the comparator N2 is connected with the grid electrode of a switch tube V1 through an isolation circuit (9).
4. The secondary control isolated DC/DC converter circuit topology of claim 1, wherein:
the sampling feedback circuit (8) comprises a resistor R1, wherein one end of the resistor R1 is connected with the output voltage Vo, the other end of the resistor R2 is connected with the secondary reference ground to form an output voltage sampling circuit, one end of a resistor R2 is connected with the inverting input end of an operational amplifier N1, the inverting input end of the operational amplifier N1 is connected with one ends of capacitors C1 and C2, one end of a resistor R3 is connected with a capacitor C2, the other end of the resistor R3 is connected with a capacitor C1 and the output end of the operational amplifier, the non-inverting input end of the operational amplifier N1 is connected with the reference voltage, and the resistor R3, the capacitors C1 and C2 and the operational amplifier N1 form a II-type negative feedback compensation circuit;
one end of the resistor R4 is connected with the secondary reference ground, the other end of the resistor R4 is connected with the current sampling signal Vi, one end of the diode D1 is connected with the current sampling signal Vi, the other end of the diode D1 is connected with one end of the resistor R5, one ends of the resistor R6 and the capacitor C3 are connected with the resistor R4, and the other ends of the resistor R5 are connected with the resistor R5; the resistors R4, R5 and R6, the diode D1 and the capacitor C3 jointly form a current sampling filter circuit;
the output of the operational amplifier N1 is connected with the inverting input end of a comparator N2, the non-inverting input end of a comparator N2 is connected with one end of a capacitor C3, the output of the comparator N2 is connected with the reset end of a trigger N3, the set end of a trigger N3 is connected with a clock signal, and the output of the trigger N3 is connected with the grid electrode of a switch tube V1 through an isolation circuit (9); the comparator N2 and the flip-flop N3 constitute a pulse width control circuit (7).
5. The secondary control isolated DC/DC converter circuit topology of claim 1, wherein:
the sampling feedback circuit (8) comprises a resistor R1, one end of the resistor R1 is connected with the output voltage Vo, the other end of the resistor R2 is connected with the other end of the resistor R2, and the other end of the resistor R2 is connected with a secondary reference ground to form an output voltage sampling circuit;
one end of a resistor R2 is connected with an inverting input end of a comparator N2, the inverting input end of a comparator N2 is connected with one end of a capacitor C2, the other end of the capacitor C2 is connected with one ends of a capacitor C1 and a resistor R3, the other end of a resistor R3 is connected with one end of an output filter inductor L, the other end of the capacitor C1 is connected with the other end of the output filter inductor L, the non-inverting input end of the comparator N2 is connected with a reference voltage Vref, and the resistor R3, the capacitors C1 and C2 and the comparator N2 form a feedback compensation circuit;
the output end of the comparator N2 is connected with the set end of the trigger N3, the reset end of the trigger N3 is connected with the output end of the on-timer, and the output of the trigger N3 is connected with the grid of the switch tube V1 through an isolation circuit; the flip-flop N3 and the on-timer constitute a pulse width control circuit.
6. The secondary control isolated DC/DC converter circuit topology of claim 5, wherein:
the circuit also comprises a control conduction timer circuit, wherein the circuit comprises a constant current source I1 positively correlated with the input power supply voltage, a capacitor C1, a conduction timer switch tube V1 and a comparator N4;
one end of a capacitor C1 is connected with the non-inverting input end of a comparator N4, the inverting input end of a comparator N4 is threshold voltage VTon, and the gate of a timer switch tube V1 is conducted and controlled by a trigger N3;
when the sampling voltage is reduced to the reference voltage Vref, the trigger N3 is set, the on-timer switch V1 is disconnected at the moment, the constant current source I1 charges the capacitor C1, when the voltage of the non-inverting input end of the comparator N2 is charged and is increased to the threshold voltage VTon, the trigger N3 is reset, the output voltage is reduced, the on-timer switch V1 is closed, and the capacitor voltage VC1 is reduced to 0; when the sampling voltage drops to the reference voltage, the next switching period is entered.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111917300A (en) * | 2020-09-17 | 2020-11-10 | 中国电子科技集团公司第四十三研究所 | Secondary control isolated DC/DC converter circuit topological structure |
| CN114553011A (en) * | 2022-04-24 | 2022-05-27 | 深圳英集芯科技股份有限公司 | Flyback power supply and charger |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111917300A (en) * | 2020-09-17 | 2020-11-10 | 中国电子科技集团公司第四十三研究所 | Secondary control isolated DC/DC converter circuit topological structure |
| CN111917300B (en) * | 2020-09-17 | 2024-10-01 | 中国电子科技集团公司第四十三研究所 | Secondary control isolation type DC/DC converter circuit topology structure |
| CN114553011A (en) * | 2022-04-24 | 2022-05-27 | 深圳英集芯科技股份有限公司 | Flyback power supply and charger |
| WO2023207588A1 (en) * | 2022-04-24 | 2023-11-02 | 深圳英集芯科技股份有限公司 | Flyback power supply and charger |
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