Disclosure of Invention
Based on at least one of the above technical problems, the present invention provides an LLC synchronous rectification apparatus, a control method thereof, an electronic device, and a storage medium, which can effectively, quickly, and accurately determine the turn-off time of a secondary MOSFET, and is simple to control and low in cost.
In order to achieve the above object, the present invention provides an LLC synchronous rectification apparatus, including an input terminal, a switch circuit, a resonant network circuit, a transformer, a rectification filter circuit, an output terminal, and a driving apparatus, wherein the driving apparatus includes a driving module, a resonant frequency detection module, an excitation current detection module, and a rectification turn-off module, the driving module is connected to the switch circuit, the driving module outputs a driving signal to drive the switch circuit to turn on, the resonant frequency detection module and the excitation current detection module are respectively connected to the resonant network circuit, the resonant frequency detection module obtains a resonant current of the resonant network circuit and sends the resonant current to the rectification turn-off module, the excitation current detection module obtains an excitation current of the resonant network circuit and sends the excitation current to the rectification turn-off module, and the rectification turn-off module receives the resonance current and the excitation current and monitors the time corresponding to the driving signal when the resonance current is equal to the excitation current in real time.
Furthermore, the rectification filter circuit comprises a rectification circuit and an output capacitor, wherein the rectification circuit is formed by connecting four MOS tubes in a full bridge manner, and the output capacitor is connected in parallel between two opposite MOS tubes in the rectification circuit.
Further, the transformer also comprises a current transformer CT which is connected between the secondary coil of the transformer and the rectifying circuit in series.
Further, the switch circuit comprises a first main switch MOS tube and a second main switch MOS tube, the driving module is respectively connected with a grid electrode of the first main switch MOS tube and a grid electrode of the second main switch MOS tube, the driving module outputs a driving signal to drive the first main switch MOS tube and the second main switch MOS tube to be conducted, and the resonant network circuit is connected with the second main switch MOS tube in parallel.
Further, the resonant network circuit comprises a resonant capacitor, a resonant inductor and an excitation inductor, the resonant capacitor, the resonant inductor and the excitation inductor are sequentially connected in series, and the excitation inductor is connected with two ends of a primary coil of the transformer.
The LLC synchronous rectifying device control method comprises the following steps:
driving a switching tube to be conducted, outputting a driving signal to the switching circuit, and driving the switching tube of the switching circuit to be conducted through the driving signal;
detecting current in real time, and detecting the resonant current and the exciting current of the resonant circuit in real time;
and determining the turn-off time of the synchronous rectification, monitoring the time corresponding to the driving signal when the resonant current is equal to the exciting current in real time, and determining the turn-off time of a rectifying tube in the rectifying and filtering circuit according to the time.
Further, the step of driving the switching tube to be turned on specifically is to output the driving signal to a gate of a first main switching MOS transistor or a gate of a second main switching MOS transistor of the switching circuit, and drive the first main switching MOS transistor or the second main switching MOS transistor to be turned on by the driving signal.
Further, the step of detecting the current in real time specifically detects the resonant current on the resonant inductor in the resonant circuit and the exciting current on the exciting inductor in the resonant circuit in real time.
An electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the processor performing the steps of the LLC synchronous rectification apparatus control method described above.
A computer readable storage medium, having stored thereon a computer program which, when being executed by a processor, carries out the steps of the LLC synchronous rectification apparatus control method described above.
Compared with the prior art, the invention has the advantages that: the invention provides an LLC synchronous rectifying device, which comprises an input end, a switch circuit, a resonant network circuit, a transformer, a rectifying and filtering circuit, an output end and a driving device, wherein the driving device comprises a driving module, a resonant frequency detection module, an exciting current detection module and a rectifying and switching-off module, the driving module is connected with the switch circuit, the driving module outputs a driving signal to drive the switch circuit to be conducted, the resonant frequency detection module and the exciting current detection module are respectively connected with the resonant network circuit, the resonant frequency detection module acquires resonant current of the resonant network circuit, and sends the resonant current to a rectification switch-off module, an exciting current detection module obtains the exciting current of the resonant network circuit, and the rectification turn-off module receives the resonant current and the exciting current and monitors the time of the corresponding driving signal when the resonant current is equal to the exciting current in real time. The method can effectively, quickly and accurately determine the turn-off time of the secondary MOSFET, and has the advantages of simple control and low cost.
The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical solutions of the present invention more clearly understood and to implement them in accordance with the contents of the description, the following detailed description is given with reference to the preferred embodiments of the present invention and the accompanying drawings. The detailed description of the present invention is given in detail by the following examples and the accompanying drawings.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
An LLC synchronous rectification apparatus, as shown in fig. 1-2, comprises an input terminal, a switch circuit, a resonant network circuit, a transformer, a rectification filter circuit, an output terminal, and a driving device, wherein the driving device comprises a driving module, a resonant frequency detection module, an exciting current detection module, and a rectification turn-off module, the driving module is connected with the switch circuit, the driving module outputs a driving signal to drive the switch circuit to be turned on, the resonant frequency detection module and the exciting current detection module are respectively connected with the resonant network circuit, the resonant frequency detection module obtains the resonant current of the resonant network circuit, and sends the resonant current to a rectification switch-off module, an exciting current detection module obtains the exciting current of the resonant network circuit, and the rectification turn-off module receives the resonant current and the exciting current and monitors the time of the corresponding driving signal when the resonant current is equal to the exciting current in real time.
As shown in fig. 2, preferably, the rectifying and filtering circuit includes a rectifying circuit formed by connecting four MOS transistors in full bridge and an output capacitor, and the output capacitor is connected in parallel between two opposite MOS transistors in the rectifying circuit. In fig. 2, the output capacitor of the rectifying circuit is Cout, which is formed by full-bridge connection of MOS transistors S1, S2, S3, and S4. When outputting low-voltage large current, because the forward conduction voltage drop of the secondary diode of the LLC resonant converter is increased, the rectification loss occupies a great proportion of the total loss, which is not beneficial to the improvement of efficiency.
In an embodiment, it is preferable that a current transformer CT is further included, and the current transformer CT is connected in series between the secondary winding of the transformer T1 and the rectifying circuit in fig. 2.
In an embodiment, preferably, the switching circuit includes a first main switching MOS and a second main switching MOS, the first main switching MOS is Q1 in fig. 2, the second main switching MOS is Q2, the driving module is respectively connected to the gate of the first main switching MOS Q1 and the gate of the second main switching MOS Q2, the driving module outputs a driving signal PWM _ Q1 to drive the first main switching MOS Q1 to be turned on, the driving module outputs a driving signal PWM _ Q2 to drive the second main switching MOS Q2 to be turned on, the resonant network circuit is connected in parallel to the second main switching MOS, and Cin is an input capacitor.
In an embodiment, preferably, in fig. 2, the resonant network circuit includes a resonant capacitor Cr, a resonant inductor Lr, and an excitation inductor Lm, where the resonant capacitor Cr, the resonant inductor Lr, and the excitation inductor Lm are sequentially connected in series, and the excitation inductor Lm is connected to two ends of the primary winding of the transformer T1.
In one embodiment, DIR _ CT is set as the current direction of the current transformer CT, which specifies that the current flows from left to right to be high level, and vice versa to be low level, and PWM _ S1 is the driving signal of the MOS transistor S1. As shown in FIG. 3, the level at point A is the AND and negation of PWM _ Q1 and DIR _ CT; the level of the point B is a signal value of the point A and the RS trigger acted by the PWM _ Q1 together; the level of the point C is the phase OR between B and DIR _ CT; the level of the point D is a signal value of the RS trigger acted by the PWM _ Q1 and the C together; the E point level is the AND of PWM _ Q1 and DIR _ CT; the PWM _ S1 levels are D AND E. The primary MOS tube is a first main switch MOS tube Q1 and a second main switch MOS tube Q2 in the switch circuit, and the secondary MOS tubes are MOS tubes S1, S2, S3 and S4 in the rectifier circuit. When the primary MOS transistor Q1 is turned off, that is, PWM _ Q1 is 0, and the level of point a is 0; b point level is 1; the C point level is 1; the D point level is 1; the E point level is 0; the PWM _ S1 is equal to 0, and the secondary MOS transistors S1, S2, S3, and S4 are all turned off; when the primary MOS transistor Q1 is turned on, that is, PWM _ Q1 is 1, the current flows from the positive electrode of the power supply to the MOS transistors Q1, Cr, Lr, the primary side and the secondary side of the transformer in sequence to induce a positive-negative current, and the current flows from the upper end of the secondary side to CT, the MOS transistors S1, Cout, S4 and the lower end of the secondary side, and the current direction through CT is from left to right, that is, DIR _ CT is 1, and the level at point a is 0 according to the logic of fig. 3; the B point level is 0; the C point level is 1; the level of the point D keeps the last state, namely 1; e point level is 1; PWM _ S1 is equal to 1, i.e. MOS transistor S1, S4 is turned on; as the switching frequency fs is less than the resonant frequency fr, as shown in fig. 4, that is, before the time t2 when the MOS transistor Q1 is turned off, there is a resonant current ir equal to the excitation current im, at this time, the primary side current of the transformer is zero, and energy cannot be transferred to the back end, the current on the secondary MOS transistor is zero, PWM-Q1 is equal to 1, and DIR _ CT is equal to 0, and according to the logic of fig. 3, the level at the point a is equal to 1; b point level keeps last state as 0; the C point level is 0; d point level is 0; the E point level is 0; PWM _ S1 is 0, i.e. MOS transistor S1, S4 is turned off; however, oscillation occurs due to the node capacitance and the degaussing capacitance, and after oscillation, DIR _ CT is 1, at this time, the level of the point a is 0, and the level of the point B is 0; the C point level is 1, and the D point level keeps the last state to be 0; PWM _ S1 is equal to 0, i.e. MOS transistor S1, S4 is turned off. Therefore, as long as the resonant current is equal to the excitation current, the MOS transistors S1 and S4 are not turned on regardless of how the secondary current oscillates; therefore, the rectification turn-off module monitors the time of the corresponding driving signal when the resonant current is equal to the exciting current in real time, and the time is the turn-off time of the secondary MOSFET.
In one embodiment, DIR _ CT is set as the current direction of the current transformer CT, which specifies that the current flows from left to right to be high level, and vice versa to be low level, and PWM _ S3 is the driving signal of the MOS transistor S3. The logic similar to that of the driving MOS transistor Q1 is that the A point level is that the phase of PWM _ Q2 is inverted by the phase of DIR _ CT; the level of the point B is a signal value of the point A and the RS trigger acted by the PWM _ Q2 together; the level of the point C is the phase OR between B and DIR _ CT; the level of the point D is a signal value of the RS trigger acted by the PWM _ Q2 and the C together; the E point level is the AND of PWM _ Q2 and DIR _ CT; the PWM _ S2 levels are D AND E. The primary MOS tube is a first main switch MOS tube Q1 and a second main switch MOS tube Q2 in the switch circuit, and the secondary MOS tubes are MOS tubes S1, S2, S3 and S4 in the rectifier circuit. When the primary MOS transistor Q2 is turned off, that is, PWM _ Q2 is 0, and the level of point a is 0; b point level is 1; the C point level is 1; the D point level is 1; the E point level is 0; the PWM _ S1 is equal to 0, and the secondary MOS transistors S1, S2, S3, and S4 are all turned off; when the primary MOS transistor Q2 is turned on, that is, PWM _ Q2 is 1, the current flows sequentially to the MOS transistor Q2, the primary side of the transformer, Lr, Cr, and the secondary side to induce currents of up, down, and up, and positive, the current flows from the lower end of the secondary side to the upper ends of the MOS transistors S3, Cout, S2, CT, and the secondary side, the current direction through CT is from right to left, that is, DIR _ CT is 0, and the level at point a is obtained as 0; the B point level is 0; the C point level is 1; the level of the point D keeps the last state, namely 1; e point level is 1; PWM _ S3 is equal to 1, i.e. MOS transistor S3, S2 is turned on; as the switching frequency fs is less than the resonant frequency fr, as shown in fig. 4, that is, before the time t5 when the MOS transistor Q2 is turned off, there exists a resonant current ir equal to the excitation current im, ir is identified by a solid line, im is identified by a dashed line, at this time, the primary side current of the transformer is zero, energy cannot be transferred to the rear end, the current on the secondary MOS transistor is zero, PWM-Q1 is 1, DIR _ CT is 0, and the level at the point a is 1; b point level keeps last state as 0; the C point level is 0; d point level is 0; the E point level is 0; PWM _ S3 is 0, i.e. MOS transistor S3, S2 is turned off; however, oscillation occurs due to the node capacitance and the degaussing capacitance, and after oscillation, DIR _ CT is 1, at this time, the level of the point a is 0, and the level of the point B is 0; the C point level is 1, and the D point level keeps the last state to be 0; PWM _ S3 is equal to 0, i.e. MOS transistor S3, S2 is turned off. Therefore, as long as the resonant current is equal to the excitation current, the MOS transistors S3 and S2 are not turned on regardless of how the secondary current oscillates; therefore, the rectification turn-off module monitors the time of the corresponding driving signal when the resonant current is equal to the exciting current in real time, and the time is the turn-off time of the secondary MOSFET.
The control method of the LLC synchronous rectifying device, as shown in FIG. 5, comprises the following steps:
the driving switch tube is conducted, a driving signal is output to the switch circuit, and the switch tube of the switch circuit is driven to be conducted through the driving signal;
detecting current in real time, and detecting the resonant current and the exciting current of the resonant circuit in real time;
and determining the turn-off time of the synchronous rectification, monitoring the time of the corresponding driving signal when the resonant current is equal to the exciting current in real time, and determining the turn-off time of a rectifier tube in the rectification filter circuit according to the time.
In an embodiment, preferably, the step of driving the switching transistor to be turned on is to output a driving signal to a gate of a first main switching MOS transistor or a gate of a second main switching MOS transistor of the switching circuit, and drive the first main switching MOS transistor or the second main switching MOS transistor to be turned on by the driving signal.
In an embodiment, preferably, the step of detecting the current in real time specifically detects the resonant current on the resonant inductor in the resonant circuit and the exciting current on the exciting inductor in the resonant circuit in real time.
An electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the processor performing the steps of the LLC synchronous rectification apparatus control method described above.
A computer readable storage medium having stored thereon a computer program which, when being executed by a processor, carries out the steps of the LLC synchronous rectification apparatus control method described above.
The invention provides an LLC synchronous rectifying device, which comprises an input end, a switch circuit, a resonant network circuit, a transformer, a rectifying and filtering circuit, an output end and a driving device, wherein the driving device comprises a driving module, a resonant frequency detection module, an exciting current detection module and a rectifying and switching-off module, the driving module is connected with the switch circuit, the driving module outputs a driving signal to drive the switch circuit to be conducted, the resonant frequency detection module and the exciting current detection module are respectively connected with the resonant network circuit, the resonant frequency detection module acquires resonant current of the resonant network circuit, and sends the resonant current to a rectification switch-off module, an exciting current detection module obtains the exciting current of the resonant network circuit, and the rectification turn-off module receives the resonant current and the exciting current and monitors the time of the corresponding driving signal when the resonant current is equal to the exciting current in real time. The method can effectively, quickly and accurately determine the turn-off time of the secondary MOSFET, and has the advantages of simple control and low cost.
The technical features of the above embodiments can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above examples only show some embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.