TWI821742B - Apparatus and method for controlling dead time of active clamp flyback converter power supply - Google Patents

Abstract

The present disclosure relates to apparatus and methods for controlling dead time of an active clamp flyback converter power supply. A device for controlling the dead time in an active clamp flyback converter power supply, including: a voltage signal generation module, used to: obtain the dead time of the current pulse width modulation (Pulse Width Modulation, PWM) cycle ; and generate a voltage signal based on the dead time; a reference voltage signal generation module for generating a reference voltage signal based on the preset reference dead time; and a control signal generation module for generating a reference voltage signal based on the voltage signal and the reference voltage signal to generate a control signal, wherein the control signal is used to control the conduction time of the active clamp power MOS field effect transistor in the active clamp flyback converter power supply.

Description

Apparatus and method for controlling dead time of active clamp flyback converter power supply

The present disclosure relates to integrated circuits, and more particularly, to devices and methods for controlling dead time in an Active Clamping Flyback (ACF) converter power supply.

Active clamp flyback converter power supplies can operate at higher switching frequencies. At the system level of the active clamp flyback converter power supply, the power density can be increased by reducing the size of the transformer, achieving Zero Voltage Switch (ZVS), and improving system efficiency. The traditional active clamp flyback converter power supply has a fixed switching frequency, and the entire system can only be designed in continuous conduction mode (Continuous Conduction Mode, CCM) or discontinuous conduction mode (Discontinuous Conduction Mode, DCM). The dead time in a flyback converter power supply will vary with input voltage, output voltage, and output load, resulting in suboptimal system efficiency.

In view of the above-mentioned problems, the present disclosure provides a novel device and method for controlling dead time in an active clamp flyback converter power supply.

According to an aspect of an embodiment of the present disclosure, a method for controlling dead time in an active clamp flyback converter power supply is provided, including: obtaining the dead time of the current pulse width modulation PWM cycle; based on the generate a voltage signal based on the dead time; generate a reference voltage signal based on a preset reference dead time; and generate a control signal based on the voltage signal and the reference voltage signal, wherein the control signal is used to control the Describes the conduction time of the active clamp power MOS field effect transistor in the active clamp flyback converter power supply.

According to another aspect of embodiments of the present disclosure, a method for controlling an active A device for clamping the dead time in a flyback converter power supply, including: a voltage signal generation module for: obtaining the dead time of the current pulse width modulation PWM cycle; and generating a voltage signal based on the dead time ; a reference voltage signal generation module, used to generate a reference voltage signal based on a preset reference dead time; and a control signal generation module, used to generate a control signal based on the voltage signal and the reference voltage signal, wherein , the control signal is used to control the conduction time of the active clamp power MOS field effect transistor in the active clamp flyback converter power supply.

According to yet another aspect of an embodiment of the present disclosure, an active clamp flyback converter power supply is provided, including the device for controlling the dead time in the active clamp flyback converter power supply as described above.

The apparatus and method for controlling the dead time in the active clamp flyback converter power supply according to the embodiments of the present disclosure can control the active clamp power MOS field effect in the active clamp flyback converter power supply. The conduction time of the transistor is used to achieve precise control of the dead time in the active clamp flyback converter power supply, so that the dead time in the active clamp flyback converter power supply does not vary with the input voltage and output voltage. And the output load changes, thereby achieving ZVS, while avoiding energy consumption caused by excessive negative current of the main inductor of the transformer, and improving system efficiency.

T: Transformer

Q _L : Main PWM power MOS field effect transistor

Q _H : Active clamp power MOS field effect transistor

C _clamp : active clamp capacitor

R _sense , Rf: resistance

D1: Secondary side rectifier diode

VD, DEM, CS: terminal

FB: input terminal

GateL: Main PWM drive output terminal (gate drive signal of Q _L )

GateH: Active clamp drive output terminal (gate drive signal of Q _H )

_IM : Inductor magnetizing current of transformer

V _D : Drain voltage signal of Q _L

Vin: input voltage

N*V _out : voltage on C _clamp

V _th :threshold voltage

Td, Td_det: dead time

Td_ref: preset reference dead time

Vtd_det: voltage signal

Vth_ref: reference voltage signal

Cf: capacitance

GateH off: control signal

Comp: voltage signal at the output of the error amplifier

Vout: the output voltage of the active clamp flyback converter power supply

900: Device for controlling dead time in active clamp flyback converter power supplies

910: Voltage signal generation module

920: Reference voltage signal generation module

930: Control signal generation module

1010, 1020, 1030, 1040: steps

S1: Charging switch generated by Vref_ref signal

S2: Sampling switch for Vref_ref signal generation

S3: Charging switch generated by Vtd_det signal

S4: Sampling switch for Vtd_det signal generation

C1: Charging capacitor generated by Vref_ref signal

C2: Sampling capacitor generated by Vref_ref signal

C3: Charging capacitor generated by Vtd_det signal

C4: Sampling capacitor generated by Vtd_det signal

GM: Transconductance Amplifier (OTA)

Cloop: loop compensation capacitor

The present disclosure can be better understood from the following description of specific embodiments of the present disclosure in conjunction with the drawings, in which: Figure 1 shows a schematic structural diagram of a traditional active clamp flyback converter power supply; Figure 2 shows The structural schematic diagram of the ACF controller of the active clamp flyback converter power supply of Figure 1; Figure 3 shows the waveform schematic diagram of some signals of the active clamp flyback converter power supply of Figure 1; Figure 4 shows the waveform diagram according to A schematic structural diagram of the self-adjusting dead time control loop module in the ACF controller of the active clamp flyback converter power supply according to an embodiment of the present disclosure; Figure 5 shows an active clamp flyback converter power supply according to an embodiment of the present disclosure. The self-adjusting dead time in the ACF controller of the source clamp flyback converter power supply controls the output voltage of the error amplifier in the loop module. schematic diagrams of currents and input voltages; Figures 6-7 show part of the signals during the adjustment process of the dead time in the active clamp flyback converter power supply from too large to a steady state according to one embodiment of the present disclosure. Waveform schematic diagram; Figure 8 shows a schematic structural diagram of the self-adjusting dead time control loop module in the ACF controller of the active clamp flyback converter power supply according to an embodiment of the present disclosure; Figure 9 shows A schematic structural diagram of a device for controlling dead time in an active clamp flyback converter power supply according to an embodiment of the present disclosure; and FIG. 10 shows a device for controlling an active clamp flyback converter power supply according to an embodiment of the present disclosure. Flow diagram of a method for clamping dead time in a flyback converter power supply.

Features and exemplary embodiments of various aspects of the present disclosure will be described in detail below with reference to the drawings. Example implementations can be implemented in various forms and should not be construed as limited to the implementations set forth herein; rather, these implementations are provided so that this disclosure will be thorough and complete, and to fully convey the concepts of example implementations to those skilled in the art. technical staff. In the drawings, the size of areas and components may be exaggerated for clarity. Furthermore, in the drawings, the same drawing symbols represent the same or similar structures, and thus their detailed descriptions will be omitted.

Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to provide a thorough understanding of embodiments of the present disclosure. However, those skilled in the art will appreciate that the technical solutions of the present disclosure may be practiced without one or more of the specific details, or other methods, components, materials, etc. may be employed. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring the main technical ideas of the disclosure.

As mentioned before, in order to solve the problem that the dead time in the power supply of the traditional active clamp flyback converter changes with the input voltage, output voltage and output load, a method for controlling the active clamp flyback converter is proposed. Apparatus and method for dead time in power supplies.

Figure 1 shows the structural schematic diagram of a traditional active clamp flyback converter power supply. As shown in Figure 1, the traditional active clamp flyback converter power supply can include a transformer T, a main pulse width modulation (PWM) power MOS field effect transistor Q _L , and an active clamp power MOS field effect transistor. Q _H , active clamping capacitor C _clamp , ACF controller, resistor R _sense , secondary side rectifier diode D1, charging capacitor C1 generated by Vref_ref signal, error amplifier and optocoupler on the secondary side.

FIG. 2 shows a schematic structural diagram of the ACF controller of the active clamp flyback converter power supply of FIG. 1 . As shown in Figure 2, the ACF controller of the active clamp flyback converter power supply in Figure 1 can include the VD terminal, the DEM terminal, the CS terminal, the FB input terminal, the main PWM drive output terminal GateL, and the active clamp driver Output terminal GateH. The ACF controller can include a VD falling edge detection module, a peak current control module, a self-adjusting dead time control loop module, a main PWM drive module, and an active clamp drive module.

FIG. 3 shows a schematic waveform diagram of some signals of the active clamp flyback converter power supply of FIG. 1 . Specifically, Figure 3 respectively shows the gate drive signal GateL of the main PWM power MOS field effect transistor Q _L , the gate drive signal GateH of the active clamp power MOS field effect transistor Q _H , and the inductance of the transformer. Schematic diagram of the waveforms of the magnetic current _IM and the drain voltage signal V _D of the main PWM power MOS field effect transistor Q _L.

As shown in Figure 3, at time T0, the main PWM power MOS field effect transistor Q _L is turned on, the input voltage Vin is applied to both ends of the inductor of the transformer, and the inductor magnetizing current _IM of the transformer rises linearly. At time T1, the main PWM power MOS field effect transistor Q _L is turned off, and after a short fixed delay, the active clamping power MOS field effect transistor Q _H is turned on. When the active clamp power MOS field effect transistor Q _H is turned on, the inductor magnetizing current _IM of the transformer decreases linearly, the secondary rectifier diode D1 is turned on, and the secondary side of the transformer charges the charging capacitor C1 generated by the Vref_ref signal. When the inductor magnetizing current _IM of the transformer drops to zero, all the energy stored in the inductor of the transformer is released, and the secondary rectifier diode D1 is naturally disconnected. At this time, the active clamp power MOS field effect transistor Q _H is in the on state, the main inductor of the transformer resonates with the active clamp capacitor C _clamp , and the voltage N*V _out on the active clamp capacitor C _clamp is added in reverse. At both ends of the inductor of the transformer, the inductor magnetizing current _IM of the transformer drops to zero and continues to increase linearly in the reverse direction. At time T2, the active clamping power MOS field effect transistor _QH is disconnected, the main inductance of the transformer resonates with the parasitic capacitance at the VD end, the parasitic capacitance is discharged, and the voltage _VD drops. When the voltage V _D drops to the set threshold voltage V _th , the main PWM power MOS field effect transistor Q _L is turned on, where the voltage V _D drops to the set threshold voltage V _th and is in contact with the main PWM power MOS field effect transistor. The delay time between Q _L turn-on is fixed and very small. The time from when the active clamping power MOS field effect transistor Q _H is turned off to when the voltage V _D drops to reach the set threshold voltage V _th is the dead time Td, that is, T3-T2. Increasing the conduction time of the active clamp power MOS field effect transistor Q _H can reduce the dead time, and decreasing the conduction time of the active clamp power MOS field effect transistor Q _H can increase the dead time.

FIG. 4 shows a schematic structural diagram of a self-adjusting dead time control loop module in an ACF controller of an active clamp flyback converter power supply according to an embodiment of the present disclosure. As shown in Figure 4, the self-adjusting dead time control loop module in the ACF controller of the active clamp flyback converter power supply according to one embodiment of the present disclosure adjusts the dead time detected in each PWM cycle. Td_det, and the internally preset reference dead time Td_ref are used as inputs. The dead time Td_det detected in each PWM cycle is converted into a voltage signal Vtd_det, and the preset reference dead time Td_ref is converted into a reference voltage signal Vth_ref. The resistor Rf and the capacitor Cf form a low-pass filter to filter the voltage signal Vtd_det. The filtered voltage signal Vtd_det and the reference voltage signal Vth_ref are input to the error amplifier of the GM structure, and the generated output signal is input to the comparator together with the triangular wave signal with a fixed slope generated by the slope generator to generate a control signal GateH off, the control signal GateH off is used to control to turn off the active clamping power MOS field effect transistor Q _H.

According to an embodiment of the present disclosure, the ACF controller of the active clamp flyback converter power supply uses a self-adjusting dead time control loop module as shown in Figure 4 to construct a control loop to adjust the active clamp. The conduction time of the power MOS field effect transistor Q _H is precisely controlled to accurately control the dead time to achieve the set time. By using the self-adjusting dead time control loop module as shown in Figure 4 to control the dead time in the active clamp flyback converter power supply, the actual dead time in steady state can be infinitely close to the set threshold. , so that the dead time can be controlled very accurately, and the dead time will not change with the input voltage, output voltage and output load, which can simplify the system design. Since the dead time can be precisely controlled at the most ideal value, ZVS can be achieved while avoiding energy consumption caused by excessive negative current in the main inductor of the transformer, thereby improving the efficiency of the system.

5 shows a schematic diagram of the output current and input voltage of the error amplifier in the self-adjusting dead time control loop module in the ACF controller of the active clamp flyback converter power supply according to one embodiment of the present disclosure. . As shown in Figures 4 and 5, the reverse input terminal voltage of the GM structure error amplifier is the reference voltage signal Vth_ref. In the case where the non-inverting input voltage of the error amplifier of the GM structure changes linearly between Vth_L1 and Vth_H1, it corresponds to a smaller Gm value. In the case where the non-inverting input voltage of the error amplifier in the GM structure changes between Vth_L2 and Vth_L1 or between Vth_H1 and Vth_H2, it corresponds to a larger Gm value and at the same time limits the maximum current amplitude at the output end. Gm is designed to have such a Gm value with segmented changes, which can not only take into account the loop bandwidth in the steady state, but also speed up the loop response during dynamic switching.

6-7 show schematic waveform diagrams of some signals during the adjustment process of the dead time in the active clamp flyback converter power supply from too large to a steady state according to one embodiment of the present disclosure. Specifically, FIGS. 6-7 illustrate the use of a self-adjusting dead time control loop module in an ACF controller of an active clamp flyback converter power supply according to one embodiment of the present disclosure to change the dead time from A schematic diagram of the waveforms of some signals during the adjustment process from excessive adjustment to steady state. Initially, the detected dead time is greater than the preset reference dead time, so the voltage Vtd_det signal input to the non-inverting input terminal of the error amplifier of the GM structure is also greater than the reference input to the inverting input terminal of the error amplifier of the GM structure. The voltage signal Vth_ref causes the output signal (voltage Comp) at the output end of the GM structure error amplifier to slowly increase, which in turn increases the conduction time of the active clamping power MOS field effect transistor Q _H , and the negative direction of the inductance of the transformer. The amplitude of the current increases, that is, the amplitude of the discharge current to the VD terminal increases after the active clamp power MOS field effect transistor Q _H is disconnected. Therefore, the absolute value of the falling slope of VD increases, that is, the falling speed is faster, thus making Dead time is reduced.

8 shows a schematic structural diagram of a self-adjusting dead time control loop module in an ACF controller of an active clamp flyback converter power supply according to an embodiment of the present disclosure. When the output voltage Vout of the active clamp flyback converter power supply is different, for example, when the output voltage Vout changes between 3V and 20V, since the decreasing slope of the inductor current of the transformer is inversely proportional to the voltage N*Vout, the lower the output voltage , the longer the conduction time of the active clamp power MOS field effect transistor Q _H. Due to the very high parameter requirements for the range of the output signal (voltage Comp) at the output end of the GM structure error amplifier and the slope of the triangular wave signal generated by the slope generator, it is difficult to take into account changes in the output voltage level and changes in different output loads. , that is, the output voltage has a great influence on the bandwidth of the control loop of the self-adjusting dead time control loop module. As shown in Figure 8, the self-adjusting dead time control loop module in the ACF controller of the active clamp flyback converter power supply according to one embodiment of the present disclosure samples the output voltage through the transformer winding, based on the sampled The output voltage is used to adjust the slope of the triangular wave signal generated by the ramp generator. The slope of the triangular wave signal generated by the ramp generator is set to be proportional to the output voltage, thereby reducing the effect of the output voltage on the self-adjusting dead time control. The influence of the control loop of the loop module.

FIG. 9 shows a schematic structural diagram of a device for controlling dead time in an active clamp flyback converter power supply according to an embodiment of the present disclosure. As shown in FIG. 9 , an apparatus 900 for controlling dead time in an active clamp flyback converter power supply according to an embodiment of the present disclosure may include a voltage signal generation module 910 and a reference voltage signal generation module 920 and a control signal generation module 930.

The voltage signal generation module 910 may be used to obtain the dead time of the current PWM cycle, and generate a voltage signal based on the obtained dead time. The reference voltage signal generation module 920 may be used to generate a reference voltage signal based on a preset reference dead time. The control signal generation module 930 may be used to generate a control signal based on the voltage signal generated by the voltage signal generation module 910 and the reference voltage signal generated by the reference voltage signal generation module 920, wherein the control signal may be used for Controls the conduction time of the active clamp power MOS field effect transistor in the active clamp flyback converter power supply.

In an example embodiment, the apparatus 900 for controlling dead time in an active clamp flyback converter power supply according to an embodiment of the present disclosure may further include a filter module (not shown). The filter module can be used to filter the voltage generated by the voltage signal generation module 910 The voltage signal is filtered to generate a filtered voltage signal. The control signal generation module 930 may be used to generate a control signal based on the filtered voltage signal and the reference voltage signal.

In an example embodiment, the control signal generation module 930 may include an output signal generation sub-module, a triangular wave signal generation sub-module, and a control signal generation sub-module. The output signal generation sub-module can be used to generate an output signal based on the voltage signal and the reference voltage signal, the triangular wave signal generation sub-module can be used to generate a triangular wave signal, and the control signal generation sub-module can be used to generate a sub-module based on the output signal. The control signal is generated by combining the generated output signal and the triangular wave signal generated by the triangular wave signal generation sub-module. In an example embodiment, the triangle wave signal generation sub-module may be used to generate a triangle wave signal based on the output voltage of the active clamp flyback converter power supply. In another example embodiment, the triangle wave signal may have a fixed slope.

10 illustrates a flow diagram of a method for controlling dead time in an active clamp flyback converter power supply according to one embodiment of the present disclosure. As shown in Figure 10, in step 1010, the dead time of the current PWM cycle can be obtained. In step 1020, a voltage signal may be generated based on the dead time. In step 1030, a reference voltage signal may be generated based on a preset reference dead time. In step 1040, a control signal may be generated based on the voltage signal and the reference voltage signal, wherein the control signal is used to control the conduction time of the active clamp power MOS field effect transistor in the active clamp flyback converter power supply.

In an example embodiment, the method for controlling dead time in an active clamp flyback converter power supply according to an embodiment of the present disclosure may further include: filtering the voltage signal generated in step 1010 to generate The filtered voltage signal, wherein generating the control signal based on the voltage signal and the reference voltage signal in step 1040 may include: generating the control signal based on the filtered voltage signal and the reference voltage signal.

In an example embodiment, generating the control signal based on the voltage signal and the reference voltage signal in step 1040 may include: generating an output signal based on the voltage signal and the reference voltage signal, generating a triangular wave signal, and generating based on the output signal and the triangular wave signal. control signal. In an example embodiment, generating the triangular wave signal includes: based on an active clamp flyback transform The output voltage of the device power supply is used to generate a triangular wave signal. In another example embodiment, the triangle wave signal has a fixed slope.

The apparatus and method for controlling dead time in an active clamp flyback converter power supply according to embodiments of the present disclosure described in conjunction with FIGS. 9 and 10 may refer to the disclosure as described in detail above in conjunction with other figures. For the sake of brevity, certain details will not be repeated. It can be understood that the function blocks and method steps shown in the above-mentioned structure and flow diagrams can be implemented as hardware, software, firmware or a combination thereof.

Therefore, the apparatus and method for controlling the dead time in the active clamp flyback converter power supply according to the embodiments of the present disclosure can control the active clamp power MOS in the active clamp flyback converter power supply. The conduction time of the field effect transistor is used to achieve precise control of the dead time in the active clamp flyback converter power supply, so that the dead time in the active clamp flyback converter power supply does not vary with the input voltage, The output voltage and output load change, thereby achieving ZVS, while avoiding energy consumption caused by excessive negative current of the main inductor of the transformer, and improving system efficiency.

The present disclosure may be implemented in other specific forms without departing from its spirit and essential characteristics. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the disclosure being defined by the appended claims rather than the foregoing description, and the meanings and equivalents falling within the claims are All changes within the scope are therefore included in the scope of the present disclosure.

Rf: resistance

Td_det: dead time

Td_ref: preset reference dead time

Vtd_det: voltage signal

Vth_ref: reference voltage signal

Cf: capacitance

GateH off: control signal

Comp: voltage signal at the output of the error amplifier

S1: Charging switch generated by Vref_ref signal

S2: Sampling switch for Vref_ref signal generation

S3: Charging switch generated by Vtd_det signal

S4: Sampling switch for Vtd_det signal generation

C1: Charging capacitor generated by Vref_ref signal

C2: Sampling capacitor generated by Vref_ref signal

C3: Charging capacitor generated by Vtd_det signal

C4: Sampling capacitor generated by Vtd_det signal

GM: Transconductance Amplifier (OTA)

Cloop: loop compensation capacitor

Claims (11)

A method for controlling dead time in an active clamp flyback converter power supply, including: obtaining the dead time of the current pulse width modulation PWM cycle; generating a voltage signal based on the dead time; a preset reference dead time to generate a reference voltage signal; and generate a control signal based on the voltage signal and the reference voltage signal, wherein the control signal is used to control the active clamp flyback converter power supply The conduction time of the active clamp power MOS field effect transistor. The method of claim 1, further comprising: filtering the voltage signal to generate a filtered voltage signal, wherein generating the control signal based on the voltage signal and the reference voltage signal includes: based on the The filtered voltage signal and the reference voltage signal are used to generate the control signal. The method of claim 1, wherein generating the control signal based on the voltage signal and the reference voltage signal includes: generating an output signal based on the voltage signal and the reference voltage signal; generating a triangular wave signal; and generating the control signal based on the output signal and the triangular wave signal. The method of claim 3, wherein the generating a triangular wave signal includes generating the triangular wave signal based on an output voltage of the active clamp flyback converter power supply. The method of claim 3, wherein the triangular wave signal has a fixed slope. A device for controlling the dead time in an active clamp flyback converter power supply, including: a voltage signal generation module for: obtaining the dead time of the current pulse width modulation PWM cycle; and based on the The dead time is used to generate a voltage signal; a reference voltage signal generation module is used to generate a reference voltage signal based on the preset reference dead time; and a control signal generation module is used to generate a reference voltage signal based on the voltage signal and the reference Voltage signal afterlife into a control signal, wherein the control signal is used to control the conduction time of the active clamp power MOS field effect transistor in the active clamp flyback converter power supply. The device according to claim 6, further comprising: a filtering module, configured to filter the voltage signal to generate a filtered voltage signal, wherein the control signal generating module is configured to: based on the filtered voltage signal and the reference voltage signal to generate the control signal. The device of claim 6, wherein the control signal generation module includes: an output signal generation sub-module for generating an output signal based on the voltage signal and the reference voltage signal; a triangular wave signal generation sub-module A group for generating a triangular wave signal; and a control signal generation sub-module for generating the control signal based on the output signal and the triangular wave signal. The device of claim 8, wherein the triangle wave signal generating sub-module is configured to generate the triangle wave signal based on the output voltage of the active clamp flyback converter power supply. The device of claim 8, wherein the triangular wave signal has a fixed slope. An active clamp flyback converter power supply includes the device for controlling the dead time in the active clamp flyback converter power supply as described in any one of claims 6 to 10.

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