A soft start control circuit for full-bridge drive controller

Abstract

The present invention relates to a soft start control circuit for a full-bridge drive controller, comprising: a soft start capacitor, a capacitor charge and discharge circuit, a second operational amplifier, a first operational amplifier, a current mirror circuit, a pull-up variable resistor group and a ground control switch tube, wherein the capacitor charge and discharge circuit is used to charge and discharge the soft start capacitor, the soft start capacitor is used to provide a soft start voltage signal for the second operational amplifier, the pull-up variable resistor group is used to convert a feedback current signal into a feedback voltage signal, the second operational amplifier A02 and the ground control switch tube M03 are used to unidirectionally couple the soft start voltage signal to the feedback voltage signal, and the first operational amplifier is used to generate a PWM signal according to a ramp signal and the feedback voltage signal. The soft start voltage signal of the present invention is coupled to the feedback voltage signal through the operational amplifier, ensuring that the feedback voltage signal level is always not higher than the soft start voltage signal, and significantly improving the startup stability and efficiency of the system.

Description

Technical Field

[0001] The invention belongs to the technical field of integrated circuits, and in particular relates to a soft start control circuit for a full-bridge drive controller. Background Art

[0002] With the rapid development of power electronics technology, the importance of isolated DCDC converters (also known as DCDC isolation converters) as the core technology of electrical isolation and voltage conversion regulation is self-evident. With its excellent electrical isolation capability and flexible voltage conversion characteristics, isolated DCDC converters have become the preferred solution for high reliability, high safety and low electromagnetic interference requirements in industrial automation, high-end medical equipment, precision communication equipment, and automotive electronics. This type of converter achieves electrical isolation through a high-frequency transformer, which can not only effectively isolate the electrical connection between input and output, but also realize flexible voltage rise and fall, which perfectly meets the needs of complex and changeable circuit systems.

[0003] Figure 1 A typical isolated DCDC full-bridge drive PWM controller circuit structure is demonstrated, which mainly includes the following four main functional modules: 1) Internal power supply module VCCRegulator, which provides a stable internal power supply for the entire chip; 2) Protection enable modules such as external power supply overvoltage protection OVP, undervoltage lockout UVLO, internal power supply undervoltage lockout, etc., detect and ensure that the chip works in a normal state; 3) Digital modules such as oscillators, PWM controllers and logic controllers are used to compare the difference between the actual output voltage and the expected value to generate a PWM signal to control the switching time; 4) Drive module, which is mainly used to amplify the PWM control signal to drive the switch tube to turn off.

[0004] However, at power-on, the initial discharge state of the output capacitor causes the difference between the output voltage and the set value to be the largest, which in turn triggers the PWM controller to output a signal with a maximum duty cycle, causing a significant inrush current problem. This phenomenon not only threatens the safety of the power system itself, but may also affect surrounding electrical components and even cause system failures. Especially in systems that require a power-on reset function, smooth soft start becomes particularly important. To achieve this goal, a variety of soft start strategies have emerged:

[0005] 1) Time-controlled soft start: Through a preset time delay or a gradual time control strategy, the output voltage is gradually increased to make the capacitor charging process smooth, thereby reducing the starting current.

[0006] 2) Current-limited soft start: During the startup process, the input or output current is detected in real time, and the control signal is adjusted through the feedback mechanism to keep the current within a safe range.

[0007] 3) Combined soft start: Combines time control and current limiting strategies, and flexibly adjusts according to specific circumstances to achieve the best soft start effect.

[0008] It is worth noting that, given the diversity of peripheral conditions that the DCDC full-bridge driver PWM control chip can apply, the soft-start circuit must also have a high degree of adaptability and dynamic adjustment capabilities. For example, assuming that under heavy load conditions, the PWM signal enters the feedback signal control after setting the t1 time soft-start control, but under light load conditions, the t1 time soft-start may have entered the set expected voltage and should immediately enter the feedback signal control. This puts higher demands on the soft-start circuit, requiring the PWM control signal to adaptively and dynamically switch between soft-start control and feedback signal control under different load capacitance and load resistance conditions. Summary of the invention

[0009] The present invention provides a soft start control circuit for a full-bridge drive controller, which realizes smooth, adaptive and dynamic switching of a PWM signal between soft start control and feedback signal control, thereby solving the technical problems mentioned in the background technology.

[0010] The technical solution of the present invention is as follows: A soft start control circuit for a full-bridge drive controller, characterized in that it includes:

[0011] A soft start capacitor, a capacitor charging and discharging circuit, a second operational amplifier A02, a first operational amplifier A01, a current mirror circuit, a pull-up variable resistor group and a ground control switch tube M03;

[0012] The soft start capacitor is respectively connected to the capacitor charging and discharging circuit and the negative input terminal of the second operational amplifier A02, the positive input terminal of the second operational amplifier A02 is respectively connected to the negative input terminal of the first operational amplifier A01, the drain of the ground control switch tube M03, the output terminal of the current mirror circuit and the negative terminal of the pull-up variable resistor group, the output terminal of the second operational amplifier A02 is connected to the gate of the ground control switch tube M03, the source of the ground control switch tube M03 is connected to the signal ground, the input terminal of the current mirror circuit is connected to the feedback current signal, the positive terminal of the pull-up variable resistor group is connected to the power supply, and the positive input terminal of the first operational amplifier A01 is connected to the ramp signal;

[0013] The capacitor charge and discharge circuit is used to charge and discharge the soft start capacitor, the soft start capacitor is used to provide a soft start voltage signal for the second operational amplifier A02, the current mirror circuit is used to replicate the feedback current signal, the pull-up variable resistor group is used to convert the feedback current signal into a feedback voltage signal, the second operational amplifier A02 and the ground control switch tube M03 are used to unidirectionally couple the soft start voltage signal to the feedback voltage signal, and the first operational amplifier A01 is used to generate a PWM signal according to the ramp signal and the feedback voltage signal.

[0014] Further, when the feedback voltage signal is greater than the soft start voltage signal, the second operational amplifier A02 outputs a high level, and the ground control switch tube M03 is turned on to discharge the feedback voltage signal until the feedback voltage signal is equal to the soft start voltage signal;

[0015] When the feedback voltage signal is less than the soft start voltage signal, the second operational amplifier A02 outputs a low level, the ground control switch tube M03 is turned off, and the feedback voltage signal remains unchanged.

[0016] Furthermore, the capacitor charging and discharging circuit includes: a first MOS tube M01 and a second MOS tube M02, wherein the drain of the first MOS tube M01 is connected to a soft-start capacitor, the source is connected to a reference current, and the gate is connected to a soft-start control signal;

[0017] The source of the second MOS transistor M02 is connected to the signal ground, the drain is connected to the soft start capacitor, and the gate is connected to the soft start control signal;

[0018] The soft start control signal is provided by a full-bridge drive controller.

[0019] Further, the second operational amplifier A02 includes: a tenth MOS tube M10, a thirteenth MOS tube M13, a fourteenth MOS tube M14, a fifteenth MOS tube M15 and a sixteenth MOS tube M16, the gate of the tenth MOS tube M10 is connected to a reference current, the source of the tenth MOS tube M10 is connected to a power supply, the drain of the tenth MOS tube M10 is connected to the source of the fifteenth MOS tube M15 and the source of the sixteenth MOS tube M16, the gate of the fifteenth MOS tube M15 is connected to the output end of the current mirror circuit, the drain of the fifteenth MOS tube M15 is connected to the drain and gate of the thirteenth MOS tube M13, the source of the thirteenth MOS tube M13 is connected to a signal ground, the gate of the sixteenth MOS tube M16 is connected to a soft start capacitor, the drain of the sixteenth MOS tube M16 is connected to the drain of the fourteenth MOS tube M14, the gate of the fourteenth MOS tube M14 is connected to the gate of the thirteenth MOS tube M13, and the source of the fourteenth MOS tube M14 is connected to the signal ground.

[0020] Further, the current mirror circuit includes: a fourth MOS tube M4, a fifth MOS tube M5, a sixth MOS tube M6 and a seventh MOS tube M7;

[0021] The drain of the fourth MOS tube M4 is connected to its gate, the feedback current signal and the gate of the sixth MOS tube M6, the source of the fourth MOS tube M4 is connected to the drain and the gate of the fifth MOS tube M5 and the gate of the seventh MOS tube M7, the source of the fifth MOS tube M5 is connected to the signal ground, the source of the seventh MOS tube M7 is connected to the signal ground, the drain of the seventh MOS tube M7 is connected to the source of the sixth MOS tube M6, and the drain of the sixth MOS tube M6 is connected to the negative input terminal of the first operational amplifier A01.

[0022] Furthermore, the first operational amplifier A01 comprises:

[0023] An eleventh MOS tube M11, a seventeenth MOS tube M17, an eighteenth MOS tube M18, a nineteenth MOS tube M19, a twentieth MOS tube M20, a twelfth MOS tube M12, and a twenty-first MOS tube M21;

[0024] The source of the eleventh MOS tube M11 is connected to the power supply, the gate of the eleventh MOS tube M11 is connected to the reference current, the drain of the eleventh MOS tube M11 is connected to the drain of the seventeenth MOS tube M17 and the drain of the eighteenth MOS tube M18, the gate of the seventeenth MOS tube M17 is connected to the output end of the current mirror circuit, the gate of the seventeenth MOS tube M17 is connected to the drain and the gate of the nineteenth MOS tube M19 and the gate of the twentieth MOS tube M20, the source of the nineteenth MOS tube M19 is connected to the signal ground, the source of the twentieth MOS tube M20 is connected to the signal ground, the drain of the twentieth MOS tube M20 is connected to the drain of the eighteenth MOS tube M18 and the gate of the twenty-first MOS tube M21, the source of the twelfth MOS tube M12 is connected to the power supply, the gate of the twelfth MOS tube M12 is connected to the reference current, the drain of the twelfth MOS tube M12 is connected to the drain of the twenty-first MOS tube M21, and the source of the twenty-first MOS tube M21 is connected to the signal ground.

[0025] Further, the pull-up variable resistor group includes: a first resistor R01, a second resistor R02, a third resistor R03, a first resistor switch R04, and a second resistor switch R05. The first resistor R01, the second resistor R02, and the third resistor R03 are connected in series with each other, one end of the first resistor R01 away from the second resistor R02 is connected to the power supply, and one end of the third resistor R03 away from the second resistor R02 is connected to the negative input end of the first operational amplifier A01. The first resistor switch R04 is connected in parallel to both ends of the second resistor R02, and the second resistor switch R05 is connected in parallel to both ends of the third resistor R03. The first resistor switch R04 is used to control the connection and disconnection of the second resistor R02, and the second resistor switch R05 is used to control the connection and disconnection of the third resistor R03.

[0026] Furthermore, the first resistance switch R04 and the second resistance switch R05 are both fuse resistors.

[0027] Furthermore, it also includes a reference current mirror, which is connected to the reference current and the power supply, and is used to provide bias current for the second operational amplifier A02 and the first operational amplifier A01.

[0028] Further, the reference current mirror includes an eighth MOS tube M08 and a ninth MOS tube M09, the source of the eighth MOS tube M08 is connected to the power supply, the drain of the eighth MOS tube M08 is connected to its gate, the reference current and the gate of the ninth MOS tube M09, the source of the ninth MOS tube M09 is connected to the power supply, and the drain is connected to the capacitor charging and discharging circuit.

[0029] Beneficial effects of the present invention: The soft-start voltage signal of the present invention is coupled to the feedback voltage signal through a unidirectional operational transconductance amplifier, ensuring that the feedback voltage signal level is always no higher than the soft-start voltage signal, thereby realizing smooth and adaptive dynamic switching of the PWM control signal between soft-start control and feedback signal control, significantly improving the startup stability and efficiency of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a typical isolated DC / DC full-bridge drive PWM controller circuit structure.

[0031] Figure 2 It is a circuit structure diagram of a soft start control circuit for a full-bridge drive controller according to the present invention.

[0032] Figure 3 4 is a circuit diagram of an embodiment of a soft start control circuit for a full-bridge drive controller according to the present invention.

[0033] Figure 4 It is a signal schematic diagram of the soft start control circuit for the full-bridge drive controller of the present invention during the soft start process under heavy load and light load conditions. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. The described embodiment is only a part of the embodiment of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work should fall within the scope of protection of the present invention.

[0035] In an embodiment of the present invention, Figure 2 1 is a circuit diagram provided according to the specific structure of a soft start control circuit for a full-bridge drive controller of the present invention, such as Figure 2 As shown, the present invention specifically includes: a soft start capacitor, a capacitor charging and discharging circuit, a second operational amplifier A02, a first operational amplifier A01, a current mirror circuit, a pull-up variable resistor group and a ground control switch tube M03.

[0036] The soft start capacitor is respectively connected to the capacitor charging and discharging circuit and the negative input terminal of the second operational amplifier A02, the positive input terminal of the second operational amplifier A02 is respectively connected to the negative input terminal of the first operational amplifier A01, the drain of the ground control switch tube M03, the output terminal of the current mirror circuit and the negative terminal of the pull-up variable resistor group, the output terminal of the second operational amplifier A02 is connected to the gate of the ground control switch tube M03, the source of the ground control switch tube M03 is connected to the signal ground, the input terminal of the current mirror circuit is connected to the feedback current signal IFB, the positive terminal of the pull-up variable resistor group is connected to the power supply, and the positive input terminal of the first operational amplifier A01 is connected to the ramp signal RAMP.

[0037] like Figure 2 As shown, Figure 2 An external soft-start capacitor is connected to the SS pin of the circuit, which is not shown in the figure. A programmable soft-start is formed by the external capacitor, and the duration of the soft-start is adjusted by adjusting the capacitance of the soft-start capacitor. The capacitor charge-discharge circuit is used to charge and discharge the soft-start capacitor.

[0038] The soft-start capacitor is used to provide a soft-start voltage signal for the second operational amplifier A02, the feedback current signal IFB is formed by coupling the output voltage of the isolated DC / DC converter circuit of the full-bridge drive controller through an isolated optical coupler, the current mirror circuit is used to replicate the feedback current signal IFB, and the pull-up variable resistor group is used to convert the feedback current signal IFB into a feedback voltage signal. The feedback current signal IFB is inversely proportional to the feedback voltage signal, and the larger the feedback current, the smaller the feedback voltage signal.

[0039] The second operational amplifier A02 and the ground control switch tube M03 are used to unidirectionally couple the soft start voltage signal to the feedback voltage signal. Specifically, when the feedback voltage signal is greater than the soft start voltage signal, the second operational amplifier A02 outputs a high level, and the ground control switch tube M03 is turned on to discharge the feedback voltage signal until the feedback voltage signal is equal to the soft start voltage signal.

[0040] When the feedback voltage signal is less than the soft start voltage signal, the second operational amplifier A02 outputs a low level, the ground control switch tube M03 is turned off, and the feedback voltage signal remains unchanged.

[0041] In this process, the coupling process of the soft start voltage signal of the soft start capacitor externally connected to the SS pin to the feedback voltage signal is unidirectional, and the voltage value of the feedback voltage signal will not be higher than the voltage value of the soft start external capacitor voltage signal.

[0042] The first operational amplifier A01 is used to generate a PWM signal according to the ramp signal RAMP and a feedback voltage signal.

[0043] During the entire startup process, the duty cycle of the PWM signal is first adjusted through soft-start control. As the capacitor charging and discharging circuit charges the soft-start capacitor, the soft-start voltage signal continues to rise, and the duty cycle of the PWM signal continues to increase. At this time, the feedback voltage signal is completely controlled by the soft-start voltage signal. When the voltage value of the PWM signal is getting closer and closer to the set value, the feedback current signal IFB is getting larger and larger. At this time, the feedback voltage signal is lower than the soft-start voltage signal, and the PWM signal is converted from soft-start control to feedback signal control.

[0044] In one embodiment of the present invention, the capacitor charging and discharging circuit includes: a first MOS tube M01 and a second MOS tube M02, wherein the drain of the first MOS tube M01 is connected to the soft start capacitor, and the source is connected to the reference current. I Bias The gate is connected to the soft start control signal. The first MOS tube M01 controls the charging of the soft start capacitor. When the soft start control signal is at a low level, the first MOS tube M01 is turned on, and the soft start capacitor is charged by the reference current.

[0045] The source of the second MOS transistor M02 is connected to the signal ground, the drain is connected to the soft start capacitor, and the gate is connected to the soft start control signal V ctrl The second MOS tube M02 is used to control the discharge of the soft start capacitor, and its function is to clear the voltage of the soft start capacitor in a timely and effective manner. V ctrl Turn on when high.

[0046] The soft start control signal V ctrl Provided by the full-bridge driver controller. Soft start control signal V ctrl When the level is high, the second MOS tube M02 is turned on and the first MOS tube M01 is turned off. When the level is low, the first MOS tube M01 is turned on and the second MOS tube M02 is turned off. During soft start, the soft start control signal V ctrl When the soft start is turned off, the soft start control signal V ctrl is high level.

[0047] In one embodiment of the present invention, Figure 3As shown, the second operational amplifier A02 includes: a tenth MOS tube M10, a thirteenth MOS tube M13, a fourteenth MOS tube M14, a fifteenth MOS tube M15 and a sixteenth MOS tube M16, the gate of the tenth MOS tube M10 is connected to a reference current, the source of the tenth MOS tube M10 is connected to a power supply, the drain of the tenth MOS tube M10 is connected to the source of the fifteenth MOS tube M15 and the source of the sixteenth MOS tube M16, the gate of the fifteenth MOS tube M15 is connected to the output end of the current mirror circuit, the drain of the fifteenth MOS tube M15 is connected to the drain and gate of the thirteenth MOS tube M13, the source of the thirteenth MOS tube M13 is connected to a signal ground, the gate of the sixteenth MOS tube M16 is connected to a soft start capacitor, the drain of the sixteenth MOS tube M16 is connected to the drain of the fourteenth MOS tube M14, the gate of the fourteenth MOS tube M14 is connected to the gate of the thirteenth MOS tube M13, and the source of the fourteenth MOS tube M14 is connected to the signal ground.

[0048] The tenth MOS tube M10, the thirteenth MOS tube M13, the fourteenth MOS tube M14, the fifteenth MOS tube M15 and the sixteenth MOS tube M16 constitute a five-tube operational amplifier unit, whose output terminal is connected to the gate of the n-type MOS tube grounding control switch tube M03.

[0049] In one embodiment of the present invention, the current mirror circuit includes: a fourth MOS transistor M4, a fifth MOS transistor M5, a sixth MOS transistor M6 and a seventh MOS transistor M7.

[0050] The drain of the fourth MOS tube M4 is connected to its gate, the feedback current signal IFB and the gate of the sixth MOS tube M6, the source of the fourth MOS tube M4 is connected to the drain and the gate of the fifth MOS tube M5 and the gate of the seventh MOS tube M7, the source of the fifth MOS tube M5 is connected to the signal ground, the source of the seventh MOS tube M7 is connected to the signal ground, the drain of the seventh MOS tube M7 is connected to the source of the sixth MOS tube M6, and the drain of the sixth MOS tube M6 is connected to the negative input terminal of the first operational amplifier A01.

[0051] The fourth MOS tube M4 , the fifth MOS tube M5 , the sixth MOS tube M6 and the seventh MOS tube M7 form a cascode current mirror structure to accurately mirror the feedback current signal IFB into the circuit.

[0052] In one embodiment of the present invention, the first operational amplifier A01 includes an eleventh MOS tube M11, a seventeenth MOS tube M17, an eighteenth MOS tube M18, a nineteenth MOS tube M19, a twentieth MOS tube M20, a twelfth MOS tube M12, and a twenty-first MOS tube M21.

[0053] The source of the eleventh MOS tube M11 is connected to the power supply, the gate of the eleventh MOS tube M11 is connected to the reference current, the drain of the eleventh MOS tube M11 is connected to the drain of the seventeenth MOS tube M17 and the drain of the eighteenth MOS tube M18, the gate of the seventeenth MOS tube M17 is connected to the output end of the current mirror circuit, the gate of the seventeenth MOS tube M17 is connected to the drain and the gate of the nineteenth MOS tube M19 and the gate of the twentieth MOS tube M20, the source of the nineteenth MOS tube M19 is connected to the signal ground, the source of the twentieth MOS tube M20 is connected to the signal ground, the drain of the twentieth MOS tube M20 is connected to the drain of the eighteenth MOS tube M18 and the gate of the twenty-first MOS tube M21, the source of the twelfth MOS tube M12 is connected to the power supply, the gate of the twelfth MOS tube M12 is connected to the reference current, the drain of the twelfth MOS tube M12 is connected to the drain of the twenty-first MOS tube M21, and the source of the twenty-first MOS tube M21 is connected to the signal ground.

[0054] The eleventh MOS tube M11, the seventeenth MOS tube M17, the eighteenth MOS tube M18, the nineteenth MOS tube M19, the twentieth MOS tube M20, the twelfth MOS tube M12 and the twenty-first MOS tube M21 constitute a first operational amplifier circuit A01, which is used to compare the ramp signal RAMP and the coupled feedback voltage signal and output a driving PWM signal.

[0055] It should be noted that the first operational amplifier A01 and the second operational amplifier A02 are common operational amplifiers. Figure 3 In the figure, it is in the form of a 5-tube op amp and a two-stage op amp, but other topologies of operational amplifiers can also be used, such as cascode or folded.

[0056] In one embodiment of the present invention, the pull-up variable resistor group includes: a first resistor R01, a second resistor R02, a third resistor R03, a first resistor switch R04, and a second resistor switch R05. The first resistor R01, the second resistor R02, and the third resistor R03 are connected in series with each other. An end of the first resistor R01 away from the second resistor R02 is connected to a power supply. An end of the third resistor R03 away from the second resistor R02 is connected to a negative input end of a first operational amplifier A01. The first resistor switch R04 is connected in parallel to both ends of the second resistor R02. The second resistor switch R05 is connected in parallel to both ends of the third resistor R03. The first resistor switch R04 is used to control the connection and disconnection of the second resistor R02. The second resistor switch R05 is used to control the connection and disconnection of the third resistor R03.

[0057] The positive terminals of the first resistor R01, the second resistor R02, the third resistor R03, the first resistor switch R04, and the second resistor switch R05 in the pull-up variable resistor group are connected to the power supply VCC, and the negative terminal is connected to the drain of the sixth MOS tube M06, whose function is to convert the feedback current signal IFB into a feedback voltage signal, and then the feedback voltage signal is coupled to the soft start control signal. In order to accurately convert the feedback current signal IFB into a feedback voltage signal, the pull-up variable resistor group has a trimming function, and the first resistor switch R04 and the second resistor switch R05 determine whether the second resistor R02 and the third resistor R03 are connected to the loop. Among them, the first resistor R01, the second resistor R02, and the third resistor R03 are conventional resistors. The first resistor switch R04 and the second resistor switch R05 are both fuse resistors.

[0058] In one embodiment of the present invention, a reference current mirror is further included, the reference current mirror is connected to the reference current and the power supply, and is used to provide bias current for the second operational amplifier A02 and the first operational amplifier A01. The reference current mirror includes an eighth MOS tube M08 and a ninth MOS tube M09, the source of the eighth MOS tube M08 is connected to the power supply, the drain of the eighth MOS tube M08 is connected to its gate, the reference current and the gate of the ninth MOS tube M09, the source of the ninth MOS tube M09 is connected to the power supply, and the drain is connected to the capacitor charging and discharging circuit.

[0059] The reference current mirror formed by the eighth MOS tube M08 and the ninth MOS tube M09 mainly converts the reference current I bias The eighth MOS tube M08 provides a stable bias current to the soft start module. Meanwhile, the reference current mirror controls the tenth MOS tube M10, the eleventh MOS tube M11 and the twelfth MOS tube M12 to provide a stable current source to the second operational amplifier A02 and the first operational amplifier A01.

[0060] In the embodiment of the present invention, the signal schematic diagram of the soft start circuit under the output heavy load and light load conditions is as follows: Figure 4 Under heavy load conditions, the soft start voltage (SS pin) continues to rise, the PWM signal duty cycle also continues to rise, and the output voltage V out It shows a quadratic function growth. When the soft start time T1 is set to end, the soft start voltage (SS pin) reaches the maximum, and the PWM signal V PWM Output at maximum duty cycle, at this time the output V out Grows in linear order.

[0061] Under light load conditions, as the soft-start voltage (SS pin) continues to rise, the output voltage V out It shows a quadratic function growth, which quickly approaches the set output voltage value V out_set At this time, the feedback signal control mode is entered, and the PWM signal V PWM The duty cycle changes to decrease. When V out Reach output voltage value V out_set When the PWM signal V PWM Also stable at a fixed duty cycle.

[0062] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A soft start control circuit for a full-bridge drive controller, characterized in that: include: A soft start capacitor, a capacitor charging and discharging circuit, a second operational amplifier A02, a first operational amplifier A01, a current mirror circuit, a pull-up variable resistor group and a ground control switch tube M03; The soft start capacitor is respectively connected to the capacitor charging and discharging circuit and the negative input end of the second operational amplifier A02, the positive input end of the second operational amplifier A02 is respectively connected to the negative input end of the first operational amplifier A01, the drain of the ground control switch tube M03, the output end of the current mirror circuit and the negative end of the pull-up variable resistor group, the output end of the second operational amplifier A02 is connected to the gate of the ground control switch tube M03, the source of the ground control switch tube M03 is connected to the signal ground, the input end of the current mirror circuit is connected to the feedback current signal, the feedback current signal is formed by the output voltage of the isolated DC / DC converter circuit of the full-bridge drive controller through the isolated optical coupler, the positive end of the pull-up variable resistor group is connected to the power supply, and the positive input end of the first operational amplifier A01 is connected to the ramp signal; The capacitor charge and discharge circuit is used to charge and discharge the soft start capacitor, the soft start capacitor is used to provide a soft start voltage signal for the second operational amplifier A02, the current mirror circuit is used to replicate the feedback current signal, the pull-up variable resistor group is used to convert the feedback current signal into a feedback voltage signal, the second operational amplifier A02 and the ground control switch tube M03 are used to unidirectionally couple the soft start voltage signal to the feedback voltage signal, and the first operational amplifier A01 is used to generate a PWM signal according to the ramp signal and the feedback voltage signal; When the feedback voltage signal is greater than the soft start voltage signal, the second operational amplifier A02 outputs a high level, and the ground control switch tube M03 is turned on to discharge the feedback voltage signal until the feedback voltage signal is equal to the soft start voltage signal; When the feedback voltage signal is less than the soft start voltage signal, the second operational amplifier A02 outputs a low level, the ground control switch tube M03 is turned off, and the feedback voltage signal remains unchanged.

2. The soft start control circuit for a full-bridge driver controller according to claim 1, characterized in that: The capacitor charging and discharging circuit comprises: a first MOS tube M01 and a second MOS tube M02, wherein the drain of the first MOS tube M01 is connected to one end of the soft-start capacitor, the source is connected to the reference current, and the gate is connected to the soft-start control signal; The source of the second MOS transistor M02 is connected to the signal ground, the drain is connected to one end of the soft-start capacitor, and the gate is connected to the soft-start control signal; The soft start control signal is provided by a full-bridge drive controller.

3. The soft start control circuit for a full-bridge driver controller according to claim 1, characterized in that: The second operational amplifier A02 includes: a tenth MOS tube M10, a thirteenth MOS tube M13, a fourteenth MOS tube M14, a fifteenth MOS tube M15 and a sixteenth MOS tube M16, the gate of the tenth MOS tube M10 is connected to a reference current, the source of the tenth MOS tube M10 is connected to a power supply, the drain of the tenth MOS tube M10 is connected to the source of the fifteenth MOS tube M15 and the source of the sixteenth MOS tube M16, the gate of the fifteenth MOS tube M15 is connected to the output end of the current mirror circuit, the drain of the fifteenth MOS tube M15 is connected to the drain and gate of the thirteenth MOS tube M13, the source of the thirteenth MOS tube M13 is connected to a signal ground, the gate of the sixteenth MOS tube M16 is connected to one end of a soft start capacitor, the drain of the sixteenth MOS tube M16 is connected to the drain of the fourteenth MOS tube M14, the gate of the fourteenth MOS tube M14 is connected to the gate of the thirteenth MOS tube M13, and the source of the fourteenth MOS tube M14 is connected to the signal ground.

4. The soft start control circuit for a full-bridge driver controller according to claim 1, characterized in that: The current mirror circuit includes: a fourth MOS tube M4, a fifth MOS tube M5, a sixth MOS tube M6 and a seventh MOS tube M7; The drain of the fourth MOS tube M4 is connected to its gate, the feedback current signal and the gate of the sixth MOS tube M6, the source of the fourth MOS tube M4 is connected to the drain and the gate of the fifth MOS tube M5 and the gate of the seventh MOS tube M7, the source of the fifth MOS tube M5 is connected to the signal ground, the source of the seventh MOS tube M7 is connected to the signal ground, the drain of the seventh MOS tube M7 is connected to the source of the sixth MOS tube M6, and the drain of the sixth MOS tube M6 is connected to the negative input terminal of the first operational amplifier A01.

5. The soft start control circuit for a full-bridge driver controller according to claim 1, characterized in that: The first operational amplifier A01 comprises: An eleventh MOS tube M11, a seventeenth MOS tube M17, an eighteenth MOS tube M18, a nineteenth MOS tube M19, a twentieth MOS tube M20, a twelfth MOS tube M12, and a twenty-first MOS tube M21; The source of the eleventh MOS tube M11 is connected to the power supply, the gate of the eleventh MOS tube M11 is connected to the reference current, the drain of the eleventh MOS tube M11 is connected to the source of the seventeenth MOS tube M17 and the source of the eighteenth MOS tube M18, the gate of the seventeenth MOS tube M17 is connected to the output end of the current mirror circuit, the drain of the seventeenth MOS tube M17 is connected to the drain and the gate of the nineteenth MOS tube M19 and the gate of the twentieth MOS tube M20, the source of the nineteenth MOS tube M19 is connected to the signal ground, the source of the twentieth MOS tube M20 is connected to the signal ground, the drain of the twentieth MOS tube M20 is connected to the drain of the eighteenth MOS tube M18 and the gate of the twenty-first MOS tube M21, the source of the twelfth MOS tube M12 is connected to the power supply, the gate of the twelfth MOS tube M12 is connected to the reference current, the drain of the twelfth MOS tube M12 is connected to the drain of the twenty-first MOS tube M21, and the source of the twenty-first MOS tube M21 is connected to the signal ground.

6. The soft start control circuit for a full-bridge driver controller according to claim 1, characterized in that: The pull-up variable resistor group includes: a first resistor R01, a second resistor R02, a third resistor R03, a first fuse resistor R04, and a second fuse resistor R05. The first resistor R01, the second resistor R02, and the third resistor R03 are connected in series with each other. The end of the first resistor R01 away from the second resistor R02 is connected to a power supply. The end of the third resistor R03 away from the second resistor R02 is connected to the negative input end of the first operational amplifier A01. The first fuse resistor R04 is connected in parallel at both ends of the second resistor R02. The second fuse resistor R05 is connected in parallel at both ends of the third resistor R03.

7. The soft start control circuit for a full-bridge driver controller according to claim 1, characterized in that: It also includes a reference current mirror, which is connected to a reference current and a power supply and is used to provide a bias current for the second operational amplifier A02 and the first operational amplifier A01.

8. The soft start control circuit for a full-bridge driver controller according to claim 7, characterized in that: The reference current mirror includes an eighth MOS tube M08 and a ninth MOS tube M09, wherein the source of the eighth MOS tube M08 is connected to the power supply, the drain of the eighth MOS tube M08 is connected to its gate, the reference current and the gate of the ninth MOS tube M09, the source of the ninth MOS tube M09 is connected to the power supply, and the drain is connected to the capacitor charging and discharging circuit.

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