TWI759690B - Flyback converter with fixed on-time and the control method thereof - Google Patents

Abstract

The invention discloses a flyback converter with a fixed on-time and a control method thereof. When the flyback converter is in the switch-on phase, according to the gate voltage of the gate switch and the input voltage of the flyback converter, the primary side controller of the transformer primary side is used to perform corresponding processing to obtain a second control signals, through which the gate switch is controlled to open, so that the flyback converter enters the switch-off phase; when the flyback converter is in the switch-off phase, the secondary side controller of the transformer secondary sends a first control signal to the primary-side controller according to the output voltage and output current of the secondary side, thereby controlling the gate switch to be turned on, so that the flyback converter enters the switch-on stage. The invention has the beneficial effects of reducing calculation complexity and eliminating the need to set a blanking time, so that the flyback converter can be applied to a scenario with a high switching frequency.

Description

A fixed on-time flyback converter and control method

The present invention relates to the technical field of conversion circuits, and in particular, to a flyback converter with fixed on-time control and a control method.

The flyback converter is a kind of switching power supply. The flyback converter can provide insulation isolation between the input stage and the output stage, so it is widely used in the current switching of alternating current to direct current (AC/DC). in the scene.

The working process of the flyback converter is mainly divided into two stages, that is, the switch-on phase and the switch-off phase.

During the switch-on phase, the primary coil (Primary Coil) on the primary side of the transformer of the flyback converter is directly connected to the input voltage, the current in the primary coil and the magnetic field in the transformer core increase, and energy is stored in the core . At this time, the voltage generated in the secondary coil (Secondary Coil) of the secondary side of the transformer is reversed, so that the diode is in a reverse biased state and cannot be turned on. At this time, voltage and current are supplied to the load from the capacitor on the secondary coil side.

During the switch-off phase, the current in the primary coil is zero and the magnetic field in the core starts to drop. At this time, a forward voltage is induced on the secondary coil, and the diode on the secondary coil side is in a forward biased state. When it is turned on, the turned-on current flows into the capacitor and the load on the secondary coil side, that is, the energy stored in the magnetic core is transferred to the capacitor and the load.

The above two stages are executed cyclically, thus constituting the whole working process of the flyback converter.

In the prior art, the structure of a flyback converter applied in an AC/DC scenario is generally as shown in FIG. 1 , and a primary controller 1 (Primary Controller) is mainly responsible for controlling the turn-on and turn-off of the gate switch. The secondary side controller 2 (Secondary Controller) is mainly responsible for the calculation of the on-time TON and the sending of the on/off command. The primary side controller and the secondary side controller transmit signals through the isolator 3 (Isolator). In the circuit shown in FIG. 1 , the secondary-side controller 2 transmits a switch-on command signal to the primary-side controller 1 through one line, and transmits a switch-off command to the primary-side controller 1 through another line Signal.

Based on the above working process, the control method of the on-time of such a flyback converter has obvious defects: First, since all command calculation and transmission are completed by the secondary-side controller 2, it is difficult for the secondary-side controller 2 to The input voltage and other related information on the primary side are directly detected, which will increase the computational complexity of the secondary side controller 2, and the secondary side controller 2 needs to be connected to the secondary coil through a resistor to detect the input voltage and other related information on the primary side. , but this resistance and the parasitic capacitance of the pin of the secondary-side controller 2 present the effect of RC time delay, which affects the waveform of the detection signal in the synchronous rectifier in the system, thereby delaying the conduction of the synchronous rectifier and reducing the synchronous rectifier. efficiency. US Patent US9577543B2 discloses an isolated converter with a fixed on-time, the converter uses a secondary-side controller to control the on-time of the switch of the entire converter, which also has such defects.

Secondly, since the switching command is sent to the primary side controller 1 after the calculation by the secondary side controller 2, there will inevitably be signal errors in the transmission process, so in this type of flyback converter It is necessary to additionally set the blanking time (Blanking Time) of switch on/off to exclude wrong switching commands caused by transmission errors, which makes this type of flyback converter unsuitable for high switching frequency scenarios. US Patent US9755529B2 discloses a flyback converter, which uses a secondary side controller to control the switching on-time of the entire converter, which also has such defects.

According to the above problems existing in the prior art, a technical solution of a flyback converter with a fixed on-time and a control method is provided, which aims to use a primary-side controller to realize the calculation and control process of the on-time, so as to reduce the computational complexity while reducing the computational complexity. There is no need to set the switch on/off blanking time, making the flyback converter suitable for high switching frequency scenarios.

The above technical solution specifically includes: a fixed on-time flyback converter, one end of the primary coil on the primary side of the transformer of the flyback converter is connected to the input end of the flyback converter, and the other end is connected to a gate switch The drain of the gate switch, a gate of the gate switch is connected to a primary side controller, the gate switch is used as the switch of the flyback converter; one end of the secondary coil on the secondary side of the transformer of the flyback converter The output terminal of the flyback converter is connected through a diode, and the other terminal is connected to the reference ground potential of the primary side. The primary side controller is coupled to the secondary side of the transformer and generates according to the output of the output terminal of the flyback converter. a first control signal; the primary-side controller is connected to the secondary-side controller through an isolator; wherein the primary-side controller includes: a receiving unit, connected to the secondary-side controller through the isolator, and through the isolator Receive the first control signal generated by the secondary side controller, the receiving unit outputs the first control signal as a turn-on trigger signal; the driving unit is coupled to receive the first control signal, and outputs a gate control signal to control the gate The pole switch is turned on; the first control unit receives the gate control signal output by the drive unit, and after a fixed turn-on time, outputs a second control signal coupled to the drive unit as a disconnect start signal to trigger the The drive unit outputs a gate control signal to control the gate switch to be turned off.

Preferably, in the flyback converter, the first input terminal of the first control unit is connected to a first voltage terminal, the second input terminal of the first control unit is connected to the gate of the gate switch, and the first input terminal of the first control unit is connected to the gate of the gate switch. A control unit processes and obtains the second control signal according to the first voltage of the first voltage terminal and the gate voltage of the gate switch, and the first voltage of the first voltage terminal is equal to the input voltage of the input terminal of the flyback converter. proportionally related.

Preferably, in the flyback converter, the primary side controller further includes a trigger, the output end of the first control unit is connected to the zero-setting end of the trigger, and the output end of the receiving unit is connected to the trigger The setting terminal of the trigger, the output terminal of the trigger is connected to the gate of the gate switch through the driving unit; when the receiving unit outputs the first control signal to the setting terminal of the trigger, the driving unit drives the The gate switch is turned on; and when the first control unit outputs the second control signal to the zero-setting terminal of the flip-flop, the drive unit drives the gate switch to turn off; when the gate switch is turned on, the first The control unit processes and outputs the second control signal according to the first voltage; and when the gate switch is turned off, the first control unit does not output the second control signal.

Preferably, the flyback converter, wherein the flyback converter operates in discontinuous mode; the first control unit further comprises: a first amplifying module, the input end of the first amplifying module is connected to the a first voltage terminal, the output terminal of the first amplifying module is connected to a non-inverting input terminal of a first comparator through a first node, and the first amplifying module is used to convert the current flowing through the first amplifying module Or the voltage is amplified by a first predetermined multiple output; the first field effect transistor, the gate of the first field effect transistor is connected to the gate of the gate switch through an inverter, and the drain of the first field effect transistor passes through the The first node is connected to the non-inverting input terminal of the first comparator, and the source of the first field effect transistor is grounded; the first capacitor, one end of the first capacitor is connected to the non-inverting phase of the first comparator through the first node an input terminal, the other terminal is grounded; a first reference terminal, the first reference terminal is connected to the inverting input terminal of the first comparator for providing a first reference voltage; the output terminal of the first comparator is connected to the first reference terminal The output end of the control unit; when the voltage value of the non-inverting input end of the first comparator is greater than the first reference voltage, the output end of the first comparator outputs the second control signal.

Preferably, in the flyback converter, the flyback converter operates in a continuous mode; the first control unit further comprises: a first amplifying module, the input end of the first amplifying module is connected to the first amplifying module a voltage terminal, the output terminal of the first amplifying module is connected to the non-inverting input terminal of a first comparator through a second node, and the first amplifying module is used to convert the current flowing through the first amplifying module or amplifying the voltage and outputting a first predetermined multiple; The first field effect transistor, the gate of the first field effect transistor is connected to the gate of the gate switch through an inverter, and the drain of the first field effect transistor is connected to the first comparator through the second node. a non-inverting input terminal, the source of the first field effect transistor is grounded; a first capacitor, one end of the first capacitor is connected to the non-inverting input terminal of the first comparator through the second node, and the other end is grounded; the first reference terminal, the first reference terminal is connected to the inverting input terminal of the first comparator for providing a first reference voltage; reference module, the input terminal of the reference module is connected to a set voltage terminal with a predetermined voltage value , the output end of the reference module is connected to the non-inverting input end of the first comparator through the second node, the reference module is used for amplifying the voltage input to the reference module and then output; the first comparison The output terminal of the comparator is connected to the output terminal of the first control unit; when the voltage value of the non-inverting input terminal of the first comparator is greater than the first reference voltage, the output terminal of the first comparator outputs the second control signal.

Preferably, in the flyback converter, the voltage setting terminal includes a reference resistor and a setting current terminal, which are respectively connected to the input terminal of the reference module; the reference resistor has a predetermined resistance value, and the setting current terminal There is a predetermined input current; the reference module includes: an amplifier, the input end of the amplifier is used as the input end of the reference module, the output end of the amplifier is connected to the first comparator through the second node, and the amplifier is used for The voltage output from the set voltage terminal is amplified according to a second predetermined multiple and then output.

Preferably, in the flyback converter, the voltage setting terminal includes a reference resistor and a current setting terminal, which are respectively connected to the input terminal of the reference module; A switch is set between the set current terminal and the input terminal of the reference module, and the switch is initially in a closed conduction state. When the input current of the set current terminal is set, the switch is turned off; the reference module further includes: A digital-to-analog converter, the input terminal of the digital-to-analog converter is used as the input terminal of the reference module, after the switch is turned off, the digital-to-analog converter is used to lock the input voltage transmitted by the set current terminal; Amplifier, the amplifier The input end of the amplifier is connected to the output end of the digital-to-analog converter, the output end of the amplifier is connected to the first comparator through the second node, and the amplifier is used to amplify the voltage output by the set voltage end according to a second predetermined multiple output after processing.

Preferably, in the flyback converter, the first voltage terminal is connected to an auxiliary coil through a first resistor, and the auxiliary coil and the primary coil have a predetermined turns ratio, so that the first voltage and the primary coil have a predetermined turns ratio. The input voltage at the input of the flyback converter is proportionally related.

Preferably, in the flyback converter, there is a connection node between the first voltage terminal and the first resistor; the flyback converter further includes a second resistor connected to the connection between the node and ground.

Preferably, in the flyback converter, the first voltage terminal is connected to the input terminal of the flyback converter through a first resistor, so that the first voltage and the input terminal of the flyback converter are The input voltage is proportionally related; there is a connection node between the first voltage terminal and the first resistor; the flyback converter further includes a second resistor, the second resistor is connected between the connection node and the ground terminal .

Preferably, in the flyback converter, wherein the flyback converter can work in discontinuous mode and can also work in continuous mode; then the first control unit further comprises: a first control module, the The input end of the first control module is connected to the first voltage end; the second control module, the input end of the second control module is connected to the first voltage end; the judgment module, the two input ends of the judgment module The output end of the first control module and the output end of the second control module are respectively connected, and the output end of the judgment module is used as the output end of the first control unit; when the first control module or the second control module When the control module outputs a predetermined signal, the judgment module outputs the second control signal.

Preferably, in the flyback converter, the first control module includes: a first amplification module, the input end of the first amplification module is connected to the first voltage end, and the output of the first amplification module The terminal is connected to the non-inverting input terminal of a first comparator through a first node, and the first amplifying module is used to amplify the current or voltage flowing through the first amplifying module by a first predetermined multiple and output; the first field effect transistor, the gate of the first FET is connected to the gate of the gate switch through an inverter, and the drain of the first FET is connected to the non-inverting input of the first comparator through the first node terminal, the source of the first FET is grounded; a first capacitor, one end of the first capacitor is connected to the non-inverting input terminal of the first comparator through the first node, and the other terminal is grounded; the first reference terminal, the The first reference terminal is connected to the inverting input terminal of the first comparator for providing a first reference voltage; the output terminal of the first comparator is connected to the input terminal of the judging module; When the voltage value of the non-inverting input terminal of the first comparator is greater than the first reference voltage, the output terminal of the first comparator outputs the predetermined signal.

Preferably, in the flyback converter, the second control module includes: a second amplification module, the input end of the second amplification module is connected to the first voltage end, and the output of the second amplification module The terminal is connected to the non-inverting input terminal of a second comparator through a second node, and the second amplifying module is used to amplify the current or voltage flowing through the second amplifying module by a third predetermined multiple and output; the second field effect transistor, the gate of the second FET is connected to the gate of the gate switch through an inverter, and the drain of the second FET is connected to the non-inverting input of the second comparator through the second node terminal, the source of the second FET is grounded; the second capacitor, one end of the second capacitor is connected to the non-inverting input terminal of the second comparator through the second node, and the other end is grounded; the second reference terminal, the The second reference terminal is connected to the inverting input terminal of the second comparator for providing a second reference voltage; the reference module, the input terminal of the reference module is connected to a set voltage terminal with a predetermined voltage value, the reference The output end of the module is connected to the non-inverting input end of the second comparator through the second node, and the reference module is used for amplifying and outputting the voltage input to the reference module; the output of the second comparator The terminal is connected to the input terminal of the judging module; when the voltage value of the non-inverting input terminal of the second comparator is greater than the second reference voltage, the output terminal of the second comparator outputs the predetermined signal.

Preferably, in the flyback converter, the voltage setting terminal includes a reference resistor and a setting current terminal, which are respectively connected to the input terminal of the reference module; the reference resistor has a predetermined resistance value, and the setting current terminal has a predetermined input current; The reference module includes: an amplifier, the input end of the amplifier is used as the input end of the reference module, the output end of the amplifier is connected to the second comparator through the second node, and the amplifier is used for pairing according to a second predetermined multiple The voltage output from the set voltage terminal is amplified and output.

Preferably, in the flyback converter, the voltage setting terminal includes a reference resistor and a setting current terminal, which are respectively connected to the input terminal of the reference module; the setting current terminal and the input terminal of the reference module A switch is set between them, and the switch is initially in a closed conduction state. When the input current of the set current terminal is set, the switch is turned off; the reference module further includes: a digital-to-analog converter, an input terminal of the digital-to-analog converter As the input terminal of the reference module, after the switch is turned off, the digital-to-analog converter is used to lock the input voltage transmitted by the set current terminal; the amplifier, the input terminal of the amplifier is connected to the output terminal of the digital-to-analog converter, The output end of the amplifier is connected to the second comparator through the second node, and the amplifier is used for amplifying the voltage output by the set voltage end according to a second predetermined multiple and then outputting the output.

Preferably, in the flyback converter, the first voltage terminal is connected to an auxiliary coil through a first resistor, and the auxiliary coil and the primary coil have a predetermined turns ratio, so that the first voltage and the primary coil have a predetermined turns ratio. The input voltage of the input terminal of the flyback converter is proportionally related; the first voltage terminal is also connected to an auxiliary coil through a third resistor, and the auxiliary coil and the primary coil have a predetermined turns ratio, so that the first voltage The voltage is proportional to the input voltage at the input of the flyback converter.

Preferably, in the flyback converter, between the first voltage terminal and the first resistor has a first connection node; the flyback converter also includes a second resistor, the second resistor is connected between the first connection node and the ground terminal; there is a connection between the first voltage terminal and the third resistor a second connection node; the flyback converter further includes a fourth resistor connected between the second connection node and the ground terminal.

Preferably, in the flyback converter, the first voltage terminal is connected to the input terminal of the flyback converter through a first resistor, so that the first voltage and the input terminal of the flyback converter are The input voltage is proportionally related; there is a first connection node between the first voltage terminal and the first resistor; the flyback converter further includes a second resistor, the second resistor is connected between the first connection node and the between the ground terminals; the first voltage terminal is also connected to the input terminal of the flyback converter through a third resistor, so that the first voltage is proportional to the input voltage of the input terminal of the flyback converter; There is a second connection node between the first voltage terminal and the third resistor; the flyback converter further includes a fourth resistor connected between the second connection node and the ground terminal.

Preferably, in the flyback converter, the secondary side controller further comprises: a second control unit, the first input end of the second control unit is used to detect the output voltage of the secondary coil, the second control unit The second input end of the control unit is used to detect the output current of the secondary coil, and the second control unit is used to process and output the first control signal according to the output voltage and output current of the secondary coil; a transmission unit, the input end of the transmission unit is connected to the output end of the second control unit, the output end of the transmission unit is connected to the isolator, the transmission unit is used for the first control signal output by the second control unit to pass through the The isolator sends to the receiving unit in the primary side controller.

A control method for a fixed on-time of a flyback converter, which is applied to the above flyback converter; the control method comprises: the secondary side controller detects the output loop of the secondary coil and generates a first control signal, the secondary-side controller sends the first control signal to the receiving unit through the isolator, the receiving unit sends the first control signal to the set terminal of the flip-flop, the driving unit according to the flip-flop The output signal drives the gate switch to be turned on; when the gate switch is turned on, the first control unit obtains the second control signal according to the first voltage of the first voltage terminal and the gate voltage of the gate switch It is sent to the zero-setting terminal of the flip-flop, and the driving unit drives the gate switch to turn off according to the signal output by the flip-flop; the control method is executed cyclically, so as to control the operating state of the flyback converter with a fixed on-time .

The beneficial effects of the above technical solutions are:

1) The primary-side controller is used to perform the calculation and control process of the on-time of the flyback converter, which is convenient to obtain relevant information such as input voltage, reduces the computational complexity, and reduces the amount of time between the primary-side controller and the secondary-side controller. The transmission line connection will not affect the detection of the synchronous rectifier in the system.

2) The primary side controller is used to perform the calculation and control process of the on-time of the flyback converter, and there is no need to worry about the problem of wrong switching commands caused by transmission errors, so there is no need to use the system in the system. Setting the switch on/off blanking time makes the flyback converter suitable for high switching frequency scenarios.

1: Primary side controller 1

2: Secondary side controller

3: Isolator

A1: Control unit

A2: Receiving unit

A3: Drive unit

A4: Trigger

B1: Second control unit

B2: Transmission unit

FB: the first input terminal

CSP: the second input

A: Primary side controller

B: Secondary side controller

C: The output terminal is connected to the isolator

E: Judgment module

P: Primary coil

S: Secondary coil

AUX: auxiliary coil

D1: The first node

D2: second node

COM1: first comparator

COM2: Second comparator

Mirror 1: The first amplification module

C1: first capacitor

C2: second capacitor

R1: first resistor

R2: Second resistor

R3: the third resistor

R4: Fourth resistor

Ref1: The first reference terminal

Ref2: set current terminal

Ref3: The second reference terminal

R _SET : Reference resistance

V _AUX : first voltage

V _IN : Input voltage

VDD: External voltage

I _DMAG : Demagnetization current

TON_END: The second control signal

gm: amplifier

V _RSET : Input voltage

I _SET : Input current

V _{REF_ON2} : the first reference voltage

DAC: Digital to Analog Converter

Converter 1: The first amplification module

Converter 2: The second amplification module

Q1: The first FET

Q2: Second FET

S1: switch

GATE: gate control signal

1 is a schematic circuit diagram of a flyback converter in the prior art; FIG. 2 is an overall circuit block diagram of a flyback converter in the present invention; Schematic circuit diagram of the converter; Figures 5-6 are schematic circuit diagrams of a flyback converter in Embodiment 2 of the present invention; Figure 7 is a schematic circuit diagram of a flyback converter in Embodiment 3 of the present invention; Figure 8 -9 is the circuit diagram of the flyback converter in the fourth embodiment of the present invention; FIG. 10 is the circuit diagram of the flyback converter in the fifth embodiment of the present invention; FIG. 11 is the sixth embodiment of the present invention. , a schematic circuit diagram of a flyback converter; Figures 12-13 are schematic circuit diagrams of a flyback converter in Embodiment 7 of the present invention; Figure 14 is a circuit diagram of a flyback converter in Embodiment 8 of the present invention Schematic diagram; Figures 15-16 are schematic circuit diagrams of a flyback converter in Embodiment 9 of the present invention; Figure 17 is a schematic circuit diagram of a flyback converter in Embodiment 10 of the present invention; In the eleventh embodiment, a schematic diagram of a control method of a flyback converter.

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention. not all examples. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

It should be noted that the embodiments of the present invention and the features of the embodiments may be combined with each other under the condition of no conflict.

The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but it is not intended to limit the present invention.

In the present invention, based on the above problems existing in the prior art, a flyback converter with a fixed on-time is provided. The general circuit frame of the flyback converter is shown in FIG. 2 . One end of the primary coil P on the primary side of the transformer is connected to the input end V _IN of the flyback converter, and the other end is grounded through a gate switch G. A gate of the gate switch is connected to the output terminal of a primary side controller A, receives the gate control signal (GATE) output by the primary side controller A, and controls the gate switch G as the on-and-off of the flyback converter switch. disconnect. One end of the secondary coil S on the secondary side of the transformer of the flyback converter is directly or via a diode connected to the output end _VO of the flyback converter, and the other end is connected to the reference ground potential of the primary side. The primary side controller B is coupled to the secondary side to obtain the output information of the flyback converter and generate a first control signal. The primary side controller A includes a first control unit A1, a receiving unit A2 and a driving unit A3. An input end of the receiving unit A2 is connected to the secondary side controller B through an isolator C, and receives the first control signal sent by the secondary side controller B through the isolator C; an output end of the receiving unit A2 outputs the first control signal. The control signal is coupled to the drive unit A3 as a trigger-on signal (Trigger-on) to trigger the drive unit A3 to output a gate control signal to control the gate switch G to be turned on. The first control unit A1 of the primary side controller A simultaneously receives the gate turn-on signal output by the drive unit A3, and after a fixed turn-on time T _ON , outputs a second control signal and is coupled to the drive unit A3 as an off-state signal. Turn on the trigger signal (Trigger-off) to trigger the drive unit A3 to output the gate control signal to control the gate switch G to be turned off.

Further, as shown in FIGS. 3 , 5 , 9 , 12 and 15 , the primary side controller A includes: a first control unit A1 , the first input terminal of the first control unit A1 is connected to a first voltage terminal, the first control unit A1 The second input terminal of a control unit A1 is connected to the gate control signal GATE of the gate switch G, and the output terminal of the first control unit A1 is connected to the zero-setting terminal R of a flip-flop A4. Based on the above connection relationship, the first control unit A1 processes the first voltage input from the first voltage terminal and the gate voltage of the gate switch to obtain a second control signal and outputs it to the zero-setting terminal R of the flip-flop A4. The first voltage The first voltage of the terminal is proportional to the input voltage V _IN of the input terminal of the flyback converter; the receiving unit A2, the receiving unit A2 is connected between the isolator C and the set terminal S of the flip-flop A4, for connecting the first The control signal is output to the set terminal S of the flip-flop A4; the output terminal Q of the flip-flop A4 is connected to the gate of the gate switch G through a driving unit A3; when the receiving unit A2 outputs the first output to the set terminal S of the flip-flop A4 When a control signal is applied, the driving unit A3 drives the gate switch G to conduct, thereby driving the flyback converter to enter the switch-on state; and when the first control unit A1 outputs the second control signal to the zero-setting terminal R of the flip-flop A4 , the driving unit A3 drives the gate switch G to be turned off, thereby driving the flyback converter to enter the switch-off stage; and: when the gate switch G is turned on, the first control unit A1 obtains and outputs the second voltage according to the first voltage processing. control signal; and when the gate switch G is turned off, the first control unit A1 does not output the second control signal.

Specifically, based on the above description, the working principle of the flyback converter in the present invention is as follows: when the flyback converter is in the switch-on phase, the primary coil P is directly connected to the loop of the input voltage, and the primary coil The current in P and the magnetic field in the transformer core increase, in the core store energy. At this time, the voltage generated in the secondary coil S is reversed, so that the diode on the side of the secondary coil S is in a reverse biased state and cannot be turned on. At this time, the voltage and current are supplied to the load from the capacitor on the S side of the secondary coil.

At this time, the first control unit A1 can obtain the first voltage from the first voltage terminal and the gate voltage from the gate switch G, so it can output the second control signal (high level after a period of time T _ON processing through the circuit) signal) to the zero-setting terminal R of the flip-flop A4, so that the output terminal Q of the flip-flop A4 outputs a low-level signal, and the gate voltage of the gate switch G is controlled to be pulled down through the driving unit A3, so that the gate switch G is off, thus entering the switch off phase of the flyback converter.

When the flyback converter is in the switch-off phase, the current flowing through the gate switch G is zero and the magnetic field in the core starts to drop. At this time, a forward voltage is induced on the secondary coil S, the diode on the secondary coil S side is in a forward biased state and is turned on, and the conductive current flows into the capacitor and the load on the secondary coil S side, that is, the storage in the magnetic core. The energy is transferred to the capacitor and the load.

At this time, the first control unit A1 cannot obtain the first voltage from the first voltage terminal and the gate voltage from the gate switch G, so no circuit processing is performed. And because the diode on the secondary coil S side is turned on, the secondary side controller B can receive the signal and send it to the receiving unit A2 in the primary side controller A through the isolator C, and the receiving unit A2 outputs the first control signal ( high-level signal) to the set terminal S of the flip-flop A4, so that the output terminal Q of the flip-flop A4 outputs a high-level signal, and the gate voltage of the gate switch G is controlled by the driving unit A3 to be pulled up, thereby making the gate The switch G is turned on, thereby entering the switch-on turn-on phase of the flyback converter.

The above-mentioned two stages are cycled and repeated, thereby constituting the working process of the flyback converter in the present invention.

In the technical solution of the present invention, since the controller on the primary side is used to realize the conduction of the gate switch Through time calculation and control, relevant information such as the input voltage of the primary side can be easily obtained, so the computational complexity is greatly reduced, and the detection of the synchronous rectifier in the system will not be affected. In addition, the calculation process of the on-time is placed on the primary side, avoiding the process of calculating and transmitting instructions on the secondary side to the primary side. The secondary side controller only needs to transmit the signal when the switch is on to the primary side controller. This not only saves a transmission line, but also avoids transmission errors, and does not need to set the blanking time of the switch on/off in the system, so that the flyback converter in the present invention can be applied to the scene of high switching frequency , extending the applicable range of the flyback converter.

Several specific implementations of the flyback converter in the technical solution of the present invention are described in detail below.

Example 1:

In this embodiment, as shown in FIG. 3 , the flyback converter operates in a discontinuous conduction mode (Discontinuous Conduction Mode, DCM); then as shown in FIG. 4 , the first control unit A1 further includes: a first amplifier module, the input end of the first amplifying module is connected to the first voltage end, the output end of the first amplifying module is connected to the non-inverting input end of a first comparator COM1 through a first node D1, the first amplifying module Mirror1 It is used to amplify the current flowing through the first amplifying module Mirror1 by a first predetermined multiple K before outputting.

The first field effect transistor Q1, the gate of the first field effect transistor Q1 is connected to the gate of the gate switch through an inverter, and the drain electrode of the first field effect transistor Q1 is connected to the first comparator COM1 through the first node D1. The non-inverting input terminal, the source of the first field effect transistor Q1 is grounded; the first capacitor C1, one end of the first capacitor C1 is connected to the non-inverting input terminal of the first comparator COM1 through the first node D1, and the other end is grounded; the first reference terminal Ref1, the first reference terminal Ref1 is connected to the inverting input terminal of the first comparator COM1 for providing a first reference voltage; the output terminal of the first comparator COM1 is connected to the output terminal of the first control unit A1; When the voltage value of the non-inverting input terminal of the first comparator COM1 is greater than the first reference voltage, the output terminal of the first comparator outputs the second control signal.

In this embodiment, the first voltage terminal is connected to an auxiliary coil AUX through a first resistor R1, and the auxiliary coil AUX and the primary coil P have a predetermined turns ratio, so that the first voltage V _AUX is converted to the flyback type is proportionally related to the input voltage VIN at the input of the device.

In this embodiment, the above-mentioned first amplifying module is actually a current mirror Mirror1 , and the current mirror Mirror1 amplifies the input current by a first predetermined multiple K and outputs it. The current mirror Mirror1 is also connected to an external voltage VDD, which is not repeated here.

Specifically, in this embodiment, when the flyback converter is in the switch-on phase, the first amplifying module Mirror1 receives the demagnetizing current (I _DMAG ) transmitted through the first voltage terminal, and the current is assisted by an auxiliary The current sense pins of the windings are detected. Then the first amplifying module Mirror1 amplifies the demagnetizing current by a first predetermined multiple K(K*I _DMAG ) and outputs it to the non-inverting input terminal of the first comparator COM1. The first predetermined multiple K is a fixed value, which is The possible value range can be [0.001, 0.1], preferably 0.01.

Correspondingly, the above-mentioned first reference terminal Ref1 continues to input a first reference voltage to the inverting input terminal of the first comparator COM1, and the possible value range of the first reference voltage is [0.1V, 5V], preferably can be 2V.

Then the first comparator COM1 continuously compares the signals input from the non-inverting input terminal and the inverting input terminal. When the input signal of the non-inverting input terminal is higher than the first reference voltage of the inverting input terminal, the first comparator COM1 The output terminal of COM1 outputs a high level signal as the second control signal (TON_END).

In other words, based on the circuit configuration and signal processing process of the first control unit A1, the switch-on time (TON) of the entire flyback converter is determined by K times the demagnetization current (K*I _DMAG ), the capacitance of the first capacitor C1 value and the first reference voltage, the derivation process is as follows:

I is K times the demagnetization current (K*I _DMAG ); C is the capacitance value of the first capacitor C1; V _{REF_ON} is the voltage value of the first reference voltage; T _ON is the switch on time of the flyback converter.

It can be derived from the above formula (1): I˙T _ON =C˙V _{REF_ON} ; (2)

Since the capacitance value C of the first capacitor C1 and the voltage value V _{REF_ON} of the first reference voltage are both fixed values, the right side of the equation is a fixed value, which means that the left side of the equation is also a fixed value. The demagnetizing current of K times is obtained according to VIN, and K is a fixed value, so V _IN ˙T _ON is also a fixed value.

While in DCM mode, the switching frequency of the gate switch of the flyback converter can be obtained by:

Among them, _fs is used to represent the switching frequency of the gate switch; _Lm is used to represent the inductance of the primary coil; _PO is used to represent the output power of the secondary side, which is related to the input voltage VIN of the primary side; based on _VIN ˙T _ON is fixed, the on-time of the gate switch is fixed in terms of the change of the input voltage VIN, which means that the on-time of the flyback converter is fixed.

Further, in this embodiment, the resistance value of the first resistor R1 can be determined by the following formula:

Among them, _NA is used to represent the number of turns of the auxiliary winding AUX; NP is used to represent the number of turns of the primary coil _P ; the derivation process of the above formula (4) is as follows: First, according to the above formula (3), the switch on time T _ON can be processed by the following formula:

The theoretical switch on-time T _{ON_Design} is expressed by the following formula:

Among them, gain is used to represent the theoretical gain value.

According to the above formulas (5) and (6), it can be derived (assuming T _{ON=TON_Design} ):

At the same time, the gain value gain can be expressed as:

Then, the above formula (4) can be obtained by combining the above formulas (7) and (8), thereby determining the resistance value of the first resistor R1.

Optionally, in this embodiment, as shown in FIG. 4, there is a connection node DR between the first voltage terminal and the first resistor _R1 ; then the flyback converter further includes a second resistor R2, The second resistor R2 is connected between the connection node DR and the ground. The above-mentioned second resistor R2 can be selectively configured according to the actual situation, and details are not repeated here.

Embodiment 2:

In this embodiment, as shown in FIG. 5 , the flyback converter works in the DCM mode; as shown in FIG. 6 , the first control unit A1 further includes: a first amplifying module Converter1 , a first amplifying module The input terminal of Converter1 is connected to the first voltage terminal (at the same time, the first amplifier module Converter1 is also connected to an external voltage VDD, which will not be repeated here), and the output terminal of the first amplifier module Converter1 is connected to a first voltage terminal through a first node D1. A non-inverting input terminal of the comparator COM1, the first amplifying module Converter1 is used to amplify the input voltage by a first predetermined multiple K before outputting; the first field effect transistor Q1, the gate of the first field effect transistor Q1 passes through a The inverter is connected to the gate of the gate switch, the drain of the first field effect transistor Q1 is connected to the non-inverting input terminal of the first comparator COM1 through the first node D1, and the source of the first field effect transistor Q1 is grounded; Capacitor C1, one end of the first capacitor C1 is connected to the non-inverting input end of the first comparator COM1 through the first node D1, and the other end is grounded; the first reference terminal Ref1, the first reference terminal Ref1 is connected to the inverting input terminal of the first comparator COM1 for providing a first reference voltage; the output terminal of the first comparator COM1 is connected to the output terminal of the first control unit A1; When the voltage value of the non-inverting input terminal of the first comparator COM1 is greater than the first reference voltage, the output terminal of the first comparator outputs the second control signal.

The first voltage terminal is connected to the input terminal of the flyback converter through a first resistor R1, so that the first voltage is proportional to the input voltage V _IN of the input terminal of the flyback converter; the first voltage terminal and the first There is a connection node DR between the resistors _R1 ; the flyback converter further includes a second resistor R2, and the second resistor _R2 is connected between the connection node DR and the ground terminal.

The difference between this embodiment and the first embodiment is that:

1) The first voltage generated by the first voltage terminal is no longer a voltage proportional to the input voltage V _IN generated by the auxiliary winding, but directly detects the input voltage V _IN , thereby obtaining a proportional relationship to the input voltage V _IN . the first voltage V _DET .

2) The first amplifying module in this embodiment is no longer a current mirror, but a voltage-to-current module Converter1, which converts the first voltage V _DET into a first predetermined multiple K and outputs it.

3) The first predetermined multiple K in this embodiment can be expressed as:

Wherein, I _OUTPUT represents the output current of the first amplifying module; V _INPUT represents the input voltage of the first amplifying module.

Further, the value range of the above-mentioned first predetermined multiple K may be [0.1 μA/V, 100 μA/V], preferably 2 μA/V.

4) The second resistor R2 in this embodiment is a necessary circuit component, and the resistance relationship between the first resistor R1 and the second resistor R2 can be determined by the following formula:

Among them, gain is used to represent the theoretical gain value; C is used to represent the resistance value of the first capacitor C1; V _{REF_ON} is used to represent the voltage value of the first reference voltage; f _s is used to represent the switching frequency of the gate switch; L _m is used to represent the inductance of the primary coil; _PO is used to represent the output power of the secondary side; R1 is used to represent the resistance value of the first resistor; R2 is used to represent the resistance value of the second resistor; K is used to represent the first resistance value The calculation formula of the preset magnification is as shown in the above formula (9).

The derivation process of the above formula (10) is similar to the above formulas (5)-(8), and will not be repeated here.

Embodiment three:

In this embodiment, the flyback converter operates in a continuous mode (Continuous Conduction Mode, CCM), and its general circuit block diagram is still as shown in FIG. 3 .

As shown in FIG. 7 , the first control unit A1 further includes: a first amplifying module, the input end of the first amplifying module is connected to the first voltage end, and the output end of the first amplifying module passes through a second node D2 It is connected to the non-inverting input terminal of a first comparator COM1, and the first amplifying module is used to amplify the current flowing through the first amplifying module by a first predetermined multiple K before outputting. In this embodiment, the first amplifying module The group is realized by the current mirror Mirror1; the first field effect transistor Q1, the gate of the first field effect transistor Q1 is connected to the gate of the gate switch through an inverter, and the drain of the first field effect transistor Q1 is connected through the second node. The non-inverting input terminal of the first comparator, the source of the first field effect transistor Q1 is grounded; the first capacitor C1, one end of the first capacitor C1 is connected to the non-inverting input terminal of the first comparator COM1 through the second node D2, and the other One end is grounded; the first reference terminal Ref1, the first reference terminal Ref1 is connected to the inverting input terminal of the first comparator COM1 for providing a first reference voltage; the reference module, the input terminal of the reference module is connected to a predetermined The set voltage terminal of the voltage value, the output terminal of the reference module is connected to the non-inverting input terminal of the first comparator COM1 through the second node D2, and the reference module is used for amplifying and outputting the voltage input to the reference module; The output terminal of a comparator COM1 is connected to the output terminal of the first control unit A1; when the voltage value of the non-inverting input terminal of the first comparator COM1 is greater than the first reference voltage, the output terminal of the first comparator outputs a second control signal.

The first voltage terminal is connected to an auxiliary coil AUX through a first resistor R1, and there is a predetermined turns ratio between the auxiliary coil AUX and the primary coil P, so that the first voltage V _AUX is connected to the input of the input end of the flyback converter. The voltage V _IN is proportionally related.

There is a connection node DR between the first voltage terminal and the first resistor _R1 ; the flyback converter further includes a second resistor R2, and the second resistor _R2 is connected between the connection node DR and the ground terminal.

The first amplifying module in this embodiment can also be a current mirror Mirror1 . The structure, working mode and setting of the first predetermined multiple K of the current mirror Mirror1 can be referred to in Embodiment 1, which will not be repeated here.

In this embodiment, the first voltage terminal also detects the winding voltage of the auxiliary coil and obtains a first voltage V _AUX proportional to the input voltage V _IN of the flyback converter. The first voltage terminal is connected to the auxiliary coil and the first resistor R1 The connection relationship with the second resistor R2 is the same as that of the first embodiment, which is not repeated here.

In this embodiment, the resistance range of the first resistor R1 may be 50kΩ-2MΩ.

Optionally, the second resistor R2 can be selectively configured according to the actual situation, and details are not repeated here.

Further, in this embodiment, as shown in FIG. 7 , the above-mentioned voltage setting terminal includes a reference resistor R _SET and a setting current terminal Ref2, which are respectively connected to the input terminals of the reference module; the reference resistor R _SET has a predetermined value. The resistance value, the set current terminal Ref2 has a predetermined input current I _SET ; then the above-mentioned reference module includes: an amplifier gm, the input terminal of the amplifier gm is used as the input terminal of the reference module, and the output terminal of the amplifier is connected through the second node D2. A comparator COM1 and an amplifier gm are used for amplifying the voltage output by the set voltage terminal according to a second predetermined multiple M and then outputting the output.

Specifically, in this embodiment, on the basis of the above-mentioned first embodiment, a reference module and a voltage setting terminal are added. The voltage setting terminal obtains a reference input voltage V _RSET by setting the input currents I _SET and R _SET , and after processing by the amplifier gm, it is amplified by a second predetermined multiple M times to form M ˙ I _SET and output to participate in the comparison.

The value range of the second predetermined multiple M may be [0.1 μA/V, 100 μA/V], preferably 1 μA/V.

The value range of the reference voltage V _RSET output by the above-mentioned set voltage terminal may be [0.1V, 5V], preferably 0.65V.

The resistance value of the reference resistor R _SET can be in the range of 0Ω-10kΩ.

Then the input signal of the non-inverting input terminal of the first comparator COM1 is determined by K˙I _DMAG , M˙V R _SET , the capacitance value C of the first capacitor C1 and the reference voltage VREF_ON, and its working principle is the same as the above-mentioned embodiment, that is, : When the flyback converter is in the switch-on phase, the first control unit A1 starts to work. When the input signal of the non-inverting input terminal of the first comparator COM1 is greater than the reference voltage V _{REF_ON} of the inverting input terminal, the output terminal of the first comparator COM1 outputs a second control signal (high level signal) to control the gate switch G off, the flyback converter enters the switch off phase.

Embodiment 4:

In this embodiment, the flyback converter operates in the CCM mode, and its overall circuit block diagram is shown in FIG. 3 .

As shown in FIG. 8 , the first control unit A1 in this embodiment includes: a first amplifying module, the input end of the first amplifying module is connected to the first voltage end, and the output end of the first amplifying module is connected through a The second node D2 is connected to a non-inverting input terminal of a first comparator COM1. The first amplifying module is used to amplify the current flowing through the first amplifying module by a first predetermined multiple and output. In this embodiment, the first amplifying module The group is realized by the current mirror Mirror1; the first field effect transistor Q1, the gate of the first field effect transistor Q1 is connected to the gate of the gate switch through an inverter, and the drain of the first field effect transistor Q1 passes through the second node D2 Connect to the non-inverting input terminal of the first comparator COM1, and the source of the first field effect transistor Q1 is grounded; The first capacitor C1, one end of the first capacitor C1 is connected to the non-inverting input end of the first comparator COM1 through the second node D2, and the other end is grounded; the first reference end Ref1, the first reference end is connected to the inverse of the first comparator COM1. The phase input terminal is used to provide a first reference voltage; for the reference module, the input terminal of the reference module is connected to a set voltage terminal with a predetermined voltage value, and the output terminal of the reference module is connected to the first comparator through the second node D2 The non-inverting input terminal of the comparator COM1, the reference module is used to amplify and output the voltage input to the reference module; the output terminal of the first comparator COM1 is connected to the output terminal of the first control unit A1; when the first comparator When the voltage value of the non-inverting input terminal of COM1 is greater than the first reference voltage VREF_ON, the output terminal of the first comparator COM1 outputs the second control signal.

The set voltage terminal includes a reference resistor R _SET and a set current terminal Ref2, which are respectively connected to the input terminal of the reference module; a switch S1 is set between the set current terminal Ref2 and the input terminal of the reference module, and the switch S1 is initially closed In the on state, when the input current of the set current terminal Ref2 is set, the switch S1 is turned off; the reference module further includes: a digital-to-analog converter DAC, and the input end of the digital-to-analog converter DAC is used as the input end of the reference module. After the switch S1 is turned on, the digital-to-analog converter is used to lock the input voltage V _RSET transmitted by the set current terminal Ref2; the amplifier gm, the input end of the amplifier gm is connected to the output end of the digital-to-analog converter DAC, and the output end of the amplifier gm passes through the second node D2 is connected to the first comparator COM1, and the amplifier gm is used for amplifying the voltage V _RSET output by the set voltage terminal according to a second predetermined multiple M and then outputting it.

The first voltage terminal is connected to an auxiliary coil AUX through a first resistor R1. The auxiliary coil AUX and the primary coil P have a predetermined turns ratio, so that the first voltage is equal to the input voltage V _IN of the input terminal of the flyback converter. proportionally related.

There is a connection node DR between the first voltage terminal and the first resistor _R1 ; the flyback converter further includes a second resistor R2, and the second resistor _R2 is connected between the connection node DR and the ground terminal.

The only difference between this embodiment and the third embodiment is that a switch S1 is set at the voltage setting terminal. In this way, the set voltage terminal can be locked during the actual system operation. The specific principle is as follows: firstly, the conduction switch S1 is closed, and the input current I _SET is set at the set current terminal Ref2 . After the setting is completed, the switch S1 is turned off, and the corresponding input voltage is latched in the digital-to-analog converter DAC. The advantage of this is that since the input voltage V _RSET can be latched in the digital-to-analog converter DAC, it is no longer necessary to draw out an additional pin to set the reference resistor R _SET , _which can be directly connected to the original in the system. existing pins (such as the case shown in Figure 9).

In this embodiment, the remaining circuit structures and operating principles are the same as those in the third embodiment, and will not be repeated here.

Embodiment 5:

In this embodiment, the flyback converter operates in the CCM mode, and its overall circuit block diagram is shown in FIG. 5 .

As shown in FIG. 10 , the first control unit further includes: a first amplifying module Converter1, the input end of the first amplifying module Converter1 is connected to the first voltage end, and the output end of the first amplifying module Converter1 is connected through a first The two nodes D2 are connected to the non-inverting input terminal of a first comparator COM1, and the first amplifying module Converter1 is used to amplify the input voltage by a first predetermined multiple K and output it; the first field effect transistor Q1, the first field effect transistor Q1 The gate of the first FET is connected to the gate of the gate switch through an inverter, the drain of the first FET Q1 is connected to the non-inverting input terminal of the first comparator through the second node D2, and the source of the first FET Q1 Ground; the first capacitor C1, one end of the first capacitor C1 is connected to the non-inverting input end of the first comparator COM1 through the second node D2, and the other end is grounded; the first reference end Ref1, the first reference end Ref1 is connected to the first comparator The inverting input terminal of COM1 is used to provide a first reference voltage V _{REF_ON} ; for the reference module, the input terminal of the reference module is connected to a set voltage terminal with a predetermined voltage value, and the output terminal of the reference module passes through the second node D2 is connected to the non-inverting input terminal of the first comparator COM1, and the reference module is used for amplifying and outputting according to the voltage input to the reference module; the output terminal of the first comparator COM1 is connected to the output terminal of the first control unit A1; When the voltage value of the non-inverting input terminal of the first comparator COM1 is greater than the first reference voltage VREF_ON, the output terminal of the first comparator COM1 outputs the second control signal.

The voltage setting terminal includes a reference resistor R _SET and a setting current terminal Ref2, which are respectively connected to the input terminal of the reference module; the reference resistor R _SET has a predetermined resistance value, and the setting current terminal Ref2 has a predetermined input current I _SET ; the reference The module includes: an amplifier gm, the input terminal of the amplifier gm is used as the input terminal of the reference module, the output terminal of the amplifier gm is connected to the first comparator COM1 through the second node D2, and the amplifier gm is used for setting according to a second predetermined multiple M. The voltage V _RSET output from the voltage terminal is amplified and output.

The first voltage terminal is connected to the input terminal of the flyback converter through a first resistor R1, so that the first voltage is proportional to the input voltage VIN of the input terminal of the flyback converter; the first voltage terminal and the first resistor There is a connection node DR between _R1 ; the flyback converter further includes a second resistor R2, and the second resistor R2 is connected between the connection node DR and the ground terminal.

The difference between this embodiment and the third embodiment above is that the first voltage terminal in this embodiment no longer provides the auxiliary winding voltage V _AUX from the auxiliary coil AUX, but directly detects the input voltage V _IN of the primary side to obtain the same voltage as the input voltage. VIN is proportional to the related first voltage, and the second resistor R2 in this embodiment is a mandatory resistor. Moreover, the first amplifying module in this embodiment is implemented by a voltage-to-current module Converter1.

In other words, the circuit structure of the first control unit A1 in this embodiment can be obtained by combining the structural setting of the first voltage terminal in the second embodiment with the remaining structural settings in the third embodiment. Therefore, in this embodiment, the resistance values of the first resistor R1 and the second resistor R2 can be determined by the above formula (10).

The first predetermined multiple K can be determined by the above formula (9), and its value range can be [0.1 μA/V, 100 μA/V], preferably 2 μA/V.

The resistance value of the reference resistor R _SET is the same as that in the third embodiment.

The second predetermined multiple M is the same as that in the above-mentioned third embodiment, and its value range may be [0.1 μA/V, 100 μA/V], preferably 1 μA/V.

The operation principle of the above-mentioned first control unit A1 is implemented with reference to the above-mentioned Embodiment 2 and Embodiment 3, and details are not described herein again.

Embodiment 6:

In this embodiment, the flyback converter works in the CCM mode, and its overall circuit block diagram is as follows shown in Figure 5.

As shown in FIG. 11 , the first control unit further includes: a first amplifying module Converter1, the input end of the first amplifying module Converter1 is connected to the first voltage end, and the output end of the first amplifying module is connected through a second The node D2 is connected to a non-inverting input terminal of a first comparator COM1, and the first amplifying module Converter1 is used to amplify the input voltage by a first predetermined multiple K and output it; the first field effect transistor Q1, the first field effect transistor Q1 The gate is connected to the gate of the gate switch through an inverter, the drain of the first field effect transistor Q1 is connected to the non-inverting input terminal of the first comparator through the second node D2, and the source of the first field effect transistor Q1 is grounded ; The first capacitor C1, one end of the first capacitor C1 is connected to the non-inverting input end of the first comparator COM1 through the second node D2, and the other end is grounded; the first reference end Ref1, the first reference end Ref1 is connected to the first comparator COM1 The inverting input terminal of the reference module is used to provide a first reference voltage V _{REF_ON} ; for the reference module, the input terminal of the reference module is connected to a set voltage terminal with a predetermined voltage value, and the output terminal of the reference module passes through the second node D2 It is connected to the non-inverting input terminal of the first comparator COM1, and the reference module is used for amplifying and outputting according to the voltage input to the reference module; the output terminal of the first comparator COM1 is connected to the output terminal of the first control unit A1; when When the voltage value of the non-inverting input terminal of the first comparator COM1 is greater than the first reference voltage V _{REF_ON} , the output terminal of the first comparator COM1 outputs the second control signal.

The setting voltage terminal includes a reference resistor R _SET and a setting current terminal Ref2, which are respectively connected to the input terminal of the reference module; a switch S1 is set between the setting current terminal Ref2 and the input terminal of the reference module, and the switch S1 is initially closed In the on state, when the input current I _SET of the set current terminal Ref2 is set, the switch S1 is turned off; the reference module further includes: a digital-to-analog converter DAC, and the input end of the digital-to-analog converter DAC is used as the input end of the reference module , after disconnecting the switch S1, the digital-to-analog converter DAC is used to lock the input voltage V _RSET transmitted by the set current terminal Ref2; the amplifier gm, the input end of the amplifier gm is connected to the output end of the digital-to-analog converter DAC, and the output of the amplifier gm The terminal is connected to the first comparator COM1 through the second node D2, and the amplifier gm is used for amplifying the voltage V _RSET output by the set voltage terminal according to a second predetermined multiple M and then outputting it.

The first voltage terminal is connected to the input terminal of the flyback converter through a first resistor R1, so that the first voltage is proportional to the input voltage VIN of the input terminal of the flyback converter; the first voltage terminal and the first resistor There is a connection node DR between _R1 ; the flyback converter further includes a second resistor R2, and the second resistor _R2 is connected between the connection node DR and the ground terminal.

The difference between this embodiment and the fourth embodiment above is that the first voltage terminal in this embodiment no longer provides the auxiliary winding voltage V _AUX from the auxiliary coil AUX, but directly detects the input voltage V _IN of the primary side to obtain the same voltage as the input voltage. V _IN is proportional to the related first voltage, and the second resistor R2 in this embodiment is a mandatory resistor. Moreover, the first amplifying module in this embodiment is implemented by a voltage-to-current module Converter1.

In other words, the circuit structure of the first control unit A1 in this embodiment can be obtained by combining the structural setting of the first voltage terminal in the second embodiment with the remaining structural settings in the third embodiment. Therefore, in this embodiment, the resistance values of the first resistor R1 and the second resistor R2 can be determined by the above formula (10).

The first predetermined multiple K can be determined by the above formula (9), and its value range can be [0.1 μA/V, 100 μA/V], preferably 2 μA/V.

The resistance value of the reference resistor R _SET is the same as that in the third embodiment.

The second predetermined multiple M is the same as that in the above-mentioned third embodiment, and its value range may be [0.1 μA/V, 100 μA/V], preferably 1 μA/V.

The operation principle of the above-mentioned first control unit A1 is implemented with reference to the above-mentioned Embodiment 2 and Embodiment 4, and details are not described herein again.

The above-mentioned Embodiments 1 to 6 specifically describe the circuit structure and the working principle of the flyback converter in the DCM mode and the CCM mode, respectively. Specifically, Embodiments 1 to 2 describe the circuit structure and working principle of the flyback converter in DCM mode, and Embodiments 3 to 6 describe the circuit structure and working principle of the flyback converter in CCM mode .

The circuit structure and working principle when the flyback converter can support the DCM mode and the CCM mode at the same time are described below with reference to the above-mentioned first to sixth embodiments.

Embodiment 7:

In this embodiment, the flyback converter can work in DCM mode as well as in CCM mode, that is, the flyback converter supports both DCM mode and CCM mode, and its circuit block diagram is shown in Figure 12 .

As shown in FIG. 13 , the above-mentioned first control unit A1 specifically includes: a first control module, the input end of the first control module is connected to the first voltage end; a second control module, the input of the second control module The terminal is connected to the first voltage terminal; the judgment module E, the two input terminals of the judgment module E are respectively connected to the output of the first control module terminal and the output terminal of the second control module, the output terminal of the judgment module E is used as the output terminal of the first control unit; when the first control module or the second control module outputs a predetermined signal, it is judged that the output terminal of the module E is output the second control signal.

Further, the above-mentioned first control module includes: a first amplification module, the input terminal of the first amplification module is connected to the first voltage terminal, and the output terminal of the first amplification module is connected to a first comparator through a first node D1 The non-inverting input terminal of the device COM1, the first amplifying module is used to amplify the current flowing through the first amplifying module by a first predetermined multiple K1 and output; the first field effect transistor Q1, the gate of the first field effect transistor Q1 The gate of the gate switch G is connected through an inverter, the drain of the first field effect transistor Q1 is connected to the non-inverting input terminal of the first comparator COM1 through the first node D1, and the source of the first field effect transistor Q1 is grounded ; The first capacitor C1, one end of the first capacitor C1 is connected to the non-inverting input end of the first comparator COM1 through the first node D1, and the other end is grounded; the first reference end Ref1, the first reference end Ref1 is connected to the first comparator COM1 The inverting input terminal of the first comparator COM1 is used to provide a first reference voltage V _{REF_ON1} ; the output terminal of the first comparator COM1 is connected to the input terminal of the judgment module; when the voltage value of the non-inverting input terminal of the first comparator COM1 is greater than the first reference voltage When the voltage VREF_ON1 is used, the output terminal of the first comparator COM1 outputs a predetermined signal (high level signal).

The second control module includes: a second amplification module, the input terminal of the second amplification module is connected to the first voltage terminal, and the output terminal of the second amplification module is connected to the positive terminal of a second comparator COM2 through a second node D2 Phase input terminal, the second amplifying module is used to amplify the current flowing through the second amplifying module by a third predetermined multiple K2 and output; the second field effect transistor Q2, the gate of the second field effect transistor Q2 is reversed through a reverse The second FET Q2 is connected to the non-inverting input terminal of the second comparator COM2 through the second node D2, and the source of the second FET Q2 is grounded; the second capacitor C2, one end of the second capacitor C2 is connected to the non-inverting input end of the second comparator COM2 through the second node D2, and the other end is grounded; the second reference end Ref3, the second reference end is connected to the inverting input end of the second comparator COM2 , used to provide a second reference voltage V _{REF_ON2} ; reference module, the input end of the reference module is connected to a set voltage end provided with a predetermined voltage value, and the output end of the reference module is connected to the second comparator through the second node D2 The non-inverting input terminal of COM2, the reference module is used to amplify and output the voltage input to the reference module; the output terminal of the second comparator COM2 is connected to the input terminal of the judgment module; when the positive phase of the second comparator COM2 When the voltage value of the phase input terminal is greater than the second reference voltage V _{REF_ON2} , the output terminal of the second comparator COM2 outputs a predetermined signal.

The voltage setting terminal includes a reference resistor RSET and a setting current terminal Ref2, which are respectively connected to the input terminals of the reference module; the reference resistor _RSET has a predetermined resistance value, and the setting current terminal Ref2 has a predetermined input current _ISET ; the reference module has a predetermined resistance value. The group includes: the amplifier gm, the input terminal of the amplifier gm is used as the input terminal of the reference module, the output terminal of the amplifier gm is connected to the second comparator COM2 through the second node D2, and the amplifier gm is used to set the voltage according to a second predetermined multiple M The voltage output from the terminal is amplified and output.

The first voltage terminal is connected to an auxiliary coil AUX through a first resistor R1, and the auxiliary coil AUX It has a predetermined turns ratio with the primary coil P, so that the input voltage of the first voltage terminal is proportional to the input voltage of the input terminal of the flyback converter; the first voltage terminal is also connected to the above auxiliary through a third resistor R3 The coil AUX, the auxiliary coil AUX and the primary coil P have a predetermined turns ratio, so that the voltage input at the first voltage terminal is proportional to the input voltage at the input terminal of the flyback converter.

There is a first connection node DR1 between the first voltage terminal and the first resistor _R1 ; the flyback converter further includes a second resistor R2, the second resistor R2 is connected between the first connection node _DR1 and the ground terminal There is a second connection node DR2 between the first voltage terminal and the third resistor _R3 ; the flyback converter also includes a fourth resistor R4, the fourth resistor R4 is connected between the second connection node _DR2 and the ground terminal between.

Specifically, in this embodiment, the above-mentioned first amplifying module is implemented by using a current mirror Mirror1, and the first predetermined multiple K1 of the current mirror Mirror1 magnification can be set to a fixed value. Likewise, the above-mentioned second amplifying module is implemented by using the current mirror Mirror2, and the third predetermined multiple K2 of the current mirror Mirror2 magnification can be set to a fixed value. The value ranges of the above K1 and K2 can both be [0.001, 0.1], preferably 0.01.

In this embodiment, the resistance value of the first resistor R1 can be determined by the above formula (4), where K is replaced by K1, C is used to represent the capacitance value of the first capacitor C1, and V _{REF_ON} is replaced by V _{REF_ON1} . The second resistor R2 is an optional setting solution, and its resistance value is not limited.

In this embodiment, the resistance value of the third resistor R3 is the same as that in the above-mentioned third embodiment, and the fourth resistor R4 is an optional setting scheme, and its resistance value is not limited.

In this embodiment, the value of the above-mentioned second predetermined multiple M is the same as that in the above-mentioned third embodiment, Its value range can be [0.1 μA/V, 100 μA/V], preferably 1 μA/V.

In this embodiment, the value range of V _RSET of the above-mentioned voltage setting terminal may be [0.1V, 5V], preferably 0.65V.

The resistance value of the above-mentioned reference resistor R _SET is the same as that in the above-mentioned third embodiment.

The above judgment module E is actually an OR gate circuit module. When one of the two input ends of the OR gate circuit module inputs a high-level signal, the output end of the OR gate circuit module outputs a second control signal (high level signal). The structure of the OR-gate circuit module can be implemented by using an existing OR-gate circuit, which will not be repeated here.

In this embodiment, for the first control module, when the flyback converter enters the switch-on phase, the first amplifying module Mirror1 obtains the demagnetizing current I _DMAG1 according to the voltage V _AUX of the detection auxiliary coil AUX. After being amplified by K1 times, K1*I _DMAG1 is formed and sent to the non-inverting input terminal of the first comparator COM1. Meanwhile, the inverting input terminal of the first comparator COM1 is connected to the first reference terminal Ref1 to input the first reference voltage V _{REF_ON1} . If the input signal of the non-inverting input terminal of the first comparator COM1 is greater than the input signal of the inverting input terminal thereof, the first comparator COM1 outputs a predetermined signal, that is, a high-level signal.

For the second control module, when the flyback converter enters the switch-on state, the second amplifying module Mirror2 amplifies the demagnetizing current I _DMAG2 obtained by detecting the voltage V _AUX of the auxiliary coil AUX by a factor of K2 and then forms K2 *I _DMAG2 is sent to the non-inverting input terminal of the second comparator COM2, while the reference module gm amplifies the set voltage V _RSET from the set voltage terminal by M times to form M*V _RSET and sends it to the positive phase of the second comparator COM2 phase input. The inverting input terminal of the second comparator COM2 is connected to the second reference terminal Ref3 to input the first reference voltage V _{REF_ON2} . If the input signal of the non-inverting input terminal of the second comparator COM2 is greater than the input signal of the inverting input terminal thereof, the second comparator COM2 outputs a predetermined signal, that is, a high-level signal.

Then, when the first control module or the second control module outputs the predetermined signal, the judgment module E outputs the second control signal to drive the gate switch G off, and the flyback converter enters the switch off stage.

Embodiment 8:

In this embodiment, the flyback converter can work in DCM mode as well as in CCM mode, that is, the flyback converter supports both DCM mode and CCM mode, and its circuit block diagram is shown in Figure 12 .

As shown in FIG. 14, the above-mentioned first control unit A1 specifically includes: a first control module, the input terminal of the first control module is connected to the first voltage terminal; a second control module, the input terminal of the second control module The terminal is connected to the first voltage terminal; the judgment module E, the two input ends of the judgment module E are respectively connected to the output end of the first control module and the output end of the second control module, and the output end of the judgment module E is used as the first control module. An output end of the control unit; when the first control module or the second control module outputs a predetermined signal, the judgment module E outputs the second control signal.

The first control module includes: a first amplifying module, the input end of the first amplifying module is connected to the first voltage end, and the output end of the first amplifying module is connected to a positive terminal of a first comparator COM1 through a first node D1. At the phase input end, the first amplifying module is used to amplify the input current I _{DMAG1 by} a first predetermined multiple K1 and output, the first amplifying module can be realized by using a current mirror Mirror1; the first field effect transistor Q1, the first field effect transistor The gate of Q1 is connected to the gate of the gate switch G through an inverter, the drain of the first field effect transistor Q1 is connected to the non-inverting input terminal of the first comparator COM1 through the first node D1, and the first field effect transistor Q1 The source is grounded; the first capacitor C1, one end of the first capacitor C1 is connected to the non-inverting input end of the first comparator COM1 through the first node D1, and the other end is grounded; the first reference end Ref1, the first reference end is connected to the first The inverting input terminal of the comparator COM1 is used to provide a first reference voltage V _{REF_ON1} ; the output terminal of the first comparator COM1 is connected to the input terminal of the judgment module E; when the voltage value of the non-inverting input terminal of the first comparator COM1 When greater than the first reference voltage V _{REF_ON1} , the output terminal of the first comparator COM1 outputs a predetermined signal.

The second control module includes: a second amplification module, the input terminal of the second amplification module is connected to the first voltage terminal, and the output terminal of the second amplification module is connected to the positive terminal of a second comparator COM2 through a second node D2 Phase input terminal, the second amplifying module is used to amplify the input current I _{DMAG2 by} a third predetermined multiple K2 and output, the second amplifying module can be realized by the current mirror Mirror2; the second field effect transistor Q2, the second field effect transistor Q2 The gate of the gate is connected to the gate of the gate switch G through an inverter, and the drain of the second field effect transistor Q2 is connected to the non-inverting input terminal of the second comparator COM2 through the second node D2. The source is grounded; the second capacitor C2, one end of the second capacitor C2 is connected to the non-inverting input end of the second comparator COM2 through the second node D2, and the other end is grounded; the second reference end Ref3, the second reference end Ref3 is connected to the second The inverting input end of the comparator COM2 is used to provide a second reference voltage V _{REF_ON2} ; the reference module, the input end of the reference module is connected to a set voltage end provided with a predetermined voltage value, and the output end of the reference module passes through the The two nodes D2 are connected to the non-inverting input terminal of the second comparator COM2, and the reference module is used for amplifying and outputting the voltage input to the reference module; the output terminal of the second comparator COM2 is connected to the input terminal of the judgment module E ; When the voltage value of the non-inverting input terminal of the second comparator COM2 is greater than the second reference voltage V _{REF_ON2} , the output terminal of the second comparator COM2 outputs a predetermined signal.

The set voltage terminal includes a reference resistor R _SET and a set current terminal Ref2, which are respectively connected to the input terminal of the reference module; a switch S1 is set between the set current terminal Ref2 and the input terminal of the reference module R _SET , and the switch S1 is initially In the closed conduction state, when the input current I _SET of the set current terminal Ref2 is set, the switch is turned off; the reference module further includes: a digital-to-analog converter DAC, and the input end of the digital-to-analog converter DAC is used as the input end of the reference module , after disconnecting the switch S1, the digital-to-analog converter DAC is used to lock the input voltage V _RSET transmitted by the set current terminal Ref2; the amplifier gm, the input end of the amplifier gm is connected to the output end of the digital-to-analog converter DAC, and the output of the amplifier gm The terminal is connected to the second comparator COM2 through the second node D2, and the amplifier gm is used for amplifying the voltage V _RSET output by the set voltage terminal according to a second predetermined multiple M and then outputting it.

The first voltage terminal is connected to an auxiliary coil AUX through a first resistor R1, and the auxiliary coil AUX and the primary coil P have a predetermined turns ratio, so that the voltage input from the first voltage terminal is equal to the input terminal of the flyback converter. The voltage is proportional and related; the first voltage terminal is also connected to an auxiliary coil AUX through a third resistor R3, and the auxiliary coil AUX and the primary coil P have a predetermined turns ratio, so that the voltage input from the first voltage terminal is related to the flyback type. The input voltage at the input of the converter is proportionally related.

There is a first connection node DR1 between the first voltage terminal and the first resistor _R1 ; the flyback converter further includes a second resistor R2, the second resistor R2 is connected between the first connection node _DR1 and the ground terminal There is a second connection node DR2 between the first voltage terminal and the third resistor _R3 ; the flyback converter also includes a fourth resistor R4, the fourth resistor R4 is connected between the second connection node _DR2 and the ground terminal between.

The only difference between this embodiment and the seventh embodiment is that a switch S1 is set at the voltage setting terminal, and the switch S1 is turned off after the current I _SET is set at the setting current terminal Ref2, so that the digital-to-analog converter DAC can lock the input voltage V _RSET . For details of this process, reference may be made to the foregoing Embodiment 4 and Embodiment 6, and details are not described herein again.

For other operating principles in this embodiment, reference may be made to Embodiment 7, and details are not described herein again.

Embodiment 9:

In this embodiment, the flyback converter can work in DCM mode as well as in CCM mode, that is, the flyback converter supports both DCM mode and CCM mode, and its circuit block diagram is shown in Figure 15 .

In this embodiment, as shown in FIG. 16 , the above-mentioned first control unit A1 specifically includes: a first control module, the input end of the first control module is connected to the first voltage end; The input end of the control module is connected to the first voltage end; for judging module E, the two input ends of judging module E are respectively connected to the output end of the first control module and the output end of the second control module, and judging module E The output terminal of E is used as the output terminal of the first control unit; when the first control module or the second control module outputs a predetermined signal, the judgment module E outputs the first control signal.

The first control module includes: a first amplifying module Converter1, an input end of the first amplifying module Converter1 is connected to a first voltage end, an output end of the first amplifying module Converter1 is connected to a first comparator through a first node D1 The non-inverting input terminal of the first amplifying module Converter1 is used to amplify the input voltage by a first predetermined multiple K1 and output. In this embodiment, the first amplifying module is realized by the first voltage-to-current module Converter1, and the determination method of K1 Can refer to the above formula (9), the value range can be [0.1μA/V, 100μA/V], preferably 2μA/V; the first field effect transistor Q1, the gate of the first field effect transistor Q1 passes through An inverter is connected to the gate of the gate switch, the drain of the first field effect transistor Q1 is connected to the non-inverting input terminal of the first comparator COM1 through the first node D1, and the source of the first field effect transistor Q1 is grounded; A capacitor C1, one end of the first capacitor C1 is connected to the non-inverting input end of the first comparator COM1 through the first node D1, and the other end is grounded; the first reference end Ref1, the first reference end Ref1 is connected to the inverting input end of the first comparator COM1 The phase input terminal is used to provide a first reference voltage V _{REF_ON1} ; the output terminal of the first comparator COM1 is connected to the input terminal of the judgment module E; when the voltage value of the non-phase input terminal of the first comparator COM1 is greater than the first reference voltage When V _{REF_ON1} , the output terminal of the first comparator COM1 outputs a predetermined signal.

The second control module includes: a second amplification module Converter2, the input terminal of the second amplification module Converter2 is connected to the first voltage terminal, and the output terminal of the second amplification module Converter2 is connected to a second comparator through a second node D2 The non-inverting input terminal of COM2, the second amplifying module Converter2 is used to amplify the input voltage by a third predetermined multiple K2 and output, the determination method of K2 can refer to the above formula (9), and its value range can be [0.1μA/V ,100μA/V], preferably 2μA/V; the second field effect transistor Q2, the gate of the second field effect transistor Q2 is connected to the gate of the gate switch through an inverter, and the gate of the second field effect transistor Q2 The drain is connected to the non-inverting input terminal of the second comparator COM2 through the second node D2, and the source of the second field effect transistor Q2 is grounded; the second capacitor C2, one end of the second capacitor C2 is connected to the second comparator through the second node D2 The non-inverting input terminal of the comparator COM2, the other terminal is grounded; the second reference terminal Ref3, the second reference terminal Ref3 is connected to the inverting input terminal of the second comparator COM2, for providing a second reference voltage V _{REF_ON2} ; the reference module, The input terminal of the reference module is connected to a set voltage terminal with a predetermined voltage value, and the output terminal of the reference module is connected to the non-inverting input terminal of the second comparator COM2 through the second node D2. The voltage of the module is amplified and output; the output end of the second comparator COM2 is connected to the input end of the judgment module E; when the voltage value of the non-inverting input end of the second comparator COM2 is greater than the second reference voltage V _{REF_ON2} , the first The output terminals of the two comparators output a predetermined signal.

The voltage setting terminal includes a reference resistor R _SET and a setting current terminal Ref2, which are respectively connected to the input terminal of the reference module; the reference resistor R _SET has a predetermined resistance value, and the setting current terminal Ref2 has a predetermined input current I _SET ; the reference The module includes: an amplifier gm, the input terminal of the amplifier gm is used as the input terminal of the reference module, the output terminal of the amplifier gm is connected to the second comparator COM2 through the second node D2, and the amplifier gm is used for setting according to a second predetermined multiple M. The voltage V _RSET output from the voltage terminal is amplified and output.

The first voltage terminal is connected to the input terminal of the flyback converter through a first resistor R1, so that the input voltage of the first voltage terminal is proportional to the input voltage V _IN of the input terminal of the flyback converter; the first voltage There is a first connection node DR1 between the terminal and the first resistor _R1 ; the flyback converter also includes a second resistor R2, the second resistor R2 is connected between the first connection node DR1 and the ground terminal; the first voltage The terminal is also connected to the input terminal of the flyback converter through a third resistor R3, so that the voltage input by the first voltage terminal is proportional to the input voltage V _IN of the input terminal of the flyback converter; the first voltage terminal and There is a second connection node DR2 between the third resistors _R3 ; the flyback converter further includes a fourth resistor R4, and the fourth resistor R4 is connected between the second connection node _DR2 and the ground.

Specifically, the difference between this embodiment and the above-mentioned seventh embodiment is:

1) The input voltage generated by the first voltage terminal is no longer a voltage proportional to the input voltage VIN generated by the auxiliary winding AUX, but directly detects the input voltage VIN, thereby obtaining a voltage V _DET1 proportional to the input voltage VIN and V _DET2 .

2) The first amplifying module and the second amplifying module in this embodiment are no longer current mirrors, but voltage-to-current modules Converter1 and Converter2, which convert the voltage VDET into a current K˙ of a first predetermined multiple K V _DET .

3) The first predetermined multiple K1 and the third predetermined multiple K2 in this embodiment can be determined by using the above formula (9) (K1 and K2 are used instead of K).

4) The second resistor R2 in this embodiment is a necessary circuit component, and the resistance relationship between the first resistor R1 and the second resistor R2 can be determined by the above formula (10). C represents the capacitance value of the first capacitor C1, V _{REF_ON1} is used instead of V _{REF_ON} , and K1 is used instead of K.

Similarly, the fourth resistor in this embodiment is a necessary circuit component, and the resistance relationship between the third resistor R3 and the fourth resistor R4 can be determined by the above formula (10), in this case, in formula (10) C represents the capacitance value of the first capacitor C2, V _{REF_ON2} is used instead of V _{REF_ON} , and K2 is used instead of K.

In this embodiment, the remaining operation principles and structural settings of the above-mentioned first control unit A1 can be performed with reference to the above-mentioned seventh embodiment, which will not be repeated here.

Embodiment ten:

In this embodiment, the flyback converter can work in DCM mode as well as in CCM mode, that is, the flyback converter supports both DCM mode and CCM mode, and its circuit block diagram is shown in Figure 15 .

As shown in FIG. 17, the above-mentioned first control unit A1 specifically includes: a first control module, the input end of the first control module is connected to the first voltage end; a second control module, the input of the second control module The terminal is connected to the first voltage terminal; the judgment module E, the two input ends of the judgment module E are respectively connected to the output end of the first control module and the output end of the second control module, and the output end of the judgment module is used as the first control module. The output end of the control unit; when the first control module or the second control module outputs a predetermined signal, the judgment module outputs the first control signal.

The first control module includes: a first control module, the input end of the first control module is connected to the first voltage end; the second control module, the input end of the second control module is connected to the first voltage end; the judgment module E, the two input ends of the judgment module E are respectively connected to the output end of the first control module and the output end of the second control module, and the output end of the judgment module E is used as the output end of the first control unit; When the first control module or the second control module outputs a predetermined signal, the judgment module E outputs the first control signal.

The first control module includes: a first amplifying module Converter1, an input end of the first amplifying module Converter1 is connected to a first voltage end, an output end of the first amplifying module Converter1 is connected to a first comparator through a first node D1 The non-inverting input terminal of the first amplifying module Converter1 is used to amplify the input voltage by a first predetermined multiple K1 and output. In this embodiment, the first amplifying module is realized by the first voltage-to-current module Converter1, and the determination method of K1 Can refer to the above formula (9), the value range can be [0.1μA/V, 100μA/V], preferably 2μA/V; the first field effect transistor Q1, the gate of the first field effect transistor Q1 passes through An inverter is connected to the gate of the gate switch, the drain of the first field effect transistor Q1 is connected to the non-inverting input terminal of the first comparator COM1 through the first node D1, and the source of the first field effect transistor Q1 is grounded; A capacitor C1, one end of the first capacitor C1 is connected to the non-inverting input end of the first comparator COM1 through the first node D1, and the other end is grounded; the first reference end Ref1, the first reference end Ref1 is connected to the inverting input end of the first comparator COM1 The phase input terminal is used to provide a first reference voltage V _{REF_ON1} ; the output terminal of the first comparator COM1 is connected to the input terminal of the judgment module E; when the voltage value of the non-phase input terminal of the first comparator COM1 is greater than the first reference voltage When V _{REF_ON1} , the output terminal of the first comparator COM1 outputs a predetermined signal.

The second control module includes: a second amplification module Converter2, the input terminal of the second amplification module Converter2 is connected to the first voltage terminal, and the output terminal of the second amplification module Converter2 is connected to a second comparator through a second node D2 The non-inverting input terminal of COM2, the second amplifying module Converter2 is used to amplify the input voltage by a third predetermined multiple K2 and output, the determination method of K2 can refer to the above formula (9), and its value range can be [0.1μA/V ,100μA/V], preferably 2μA/V; the second field effect transistor Q2, the gate of the second field effect transistor Q2 is connected to the gate of the gate switch through an inverter, and the gate of the second field effect transistor Q2 The drain is connected to the non-inverting input terminal of the second comparator COM2 through the second node D2, and the source of the second field effect transistor Q2 is grounded; the second capacitor C2, one end of the second capacitor C2 is connected to the second comparator through the second node D2 The non-inverting input terminal of the comparator COM2, the other terminal is grounded; the second reference terminal Ref3, the second reference terminal Ref3 is connected to the inverting input terminal of the second comparator COM2, for providing a second reference voltage V _{REF_ON2} ; the reference module, The input terminal of the reference module is connected to a set voltage terminal with a predetermined voltage value, and the output terminal of the reference module is connected to the non-inverting input terminal of the second comparator COM2 through the second node D2. The voltage of the module is amplified and output; the output end of the second comparator COM2 is connected to the input end of the judgment module E; when the voltage value of the non-inverting input end of the second comparator COM2 is greater than the second reference voltage V _{REF_ON2} , the first The output terminals of the two comparators output a predetermined signal.

The set voltage terminal includes a reference resistor R _SET and a set current terminal Ref2, which are respectively connected to the input terminal of the reference module; a switch S1 is set between the set current terminal Ref2 and the input terminal of the reference module, and the switch S1 is initially closed In the conduction state, when the input current I _SET of the set current terminal Ref2 is set, the switch S1 is turned off; the reference module further includes: a digital-to-analog converter DAC, the input end of the digital-to-analog converter is used as the input end of the reference module, and the reference module further includes: After the switch S1 is turned off, the digital-to-analog converter DAC is used to lock the input voltage V _RSET transmitted by the set current terminal Ref2; the input terminal of the amplifier gm is connected to the output terminal of the digital-to-analog converter DAC, and the output terminal of the amplifier gm passes through The second node D2 is connected to the second comparator COM2, and the amplifier gm is used for amplifying the voltage V _RSET output by the setting voltage terminal according to a second predetermined multiple M and then outputting it.

The first voltage terminal is connected to the input terminal of the flyback converter through a first resistor R1, so that the voltage of the first voltage terminal is proportional to the input voltage V _IN of the input terminal of the flyback converter; the first voltage terminal and the There is a first connection node DR1 between the first resistors _R1 ; the flyback converter further includes a second resistor R2, the second resistor R2 is connected between the first connection node _DR1 and the ground terminal; the first voltage terminal It is also connected to the input terminal of the flyback converter through a third resistor R3, so that the voltage of the first voltage terminal is proportional to the input voltage V _IN of the input terminal of the flyback converter; the first voltage terminal and the third resistor There is a second connection node DR2 between _R3 ; the flyback converter further includes a fourth resistor R4, and the fourth resistor R4 is connected between the second connection node _DR2 and the ground terminal.

The difference between this embodiment and the above-mentioned ninth embodiment is only that a switch S1 is set at the voltage setting terminal, and the switch S1 is turned off after the current I _SET is set at the setting current terminal Ref2, so that the digital-to-analog converter DAC can be locked Input voltage _VRSET . For details of this process, reference may be made to the foregoing Embodiment 4 and Embodiment 6, and details are not described herein again.

For other operating principles in this embodiment, reference may be made to Embodiment 9, which will not be repeated here.

Except for the primary-side controller A described by taking the above-mentioned first to tenth embodiments as examples In addition, the secondary side controller B in the flyback converter in the present invention is specifically shown in FIGS. 3 , 5 , 9 , 12 and 15 , and includes: a second control unit B1 , a The first input terminal FB is used to detect the output voltage of the secondary coil, the second input terminal CSP of the second control unit B1 is used to detect the output current of the secondary coil, and the second control unit B1 is used to detect the output voltage of the secondary coil according to the output voltage of the secondary coil. and output current processing to obtain the first control signal and output; transmission unit B2, the input end of the transmission unit B2 is connected to the output end of the second control unit B1, the output end of the transmission unit B2 is connected to the isolator C, and the transmission unit B2 is used to The first control signal output by the second control unit B1 is sent to the receiving unit A2 in the primary side controller through the isolator C.

Specifically, in the present invention, when the flyback converter is in the switch-off phase, the diode on the secondary side is turned on, and at this time, the second control unit B1 can detect through its first input terminal FB and second input terminal CSP. Get the output voltage and output current from the secondary side. Then the second control unit B1 outputs a first control signal to the transmission unit B2 according to the detected output voltage and output current, and the transmission unit B2 sends the first control signal to the receiving unit in the primary side controller A through the isolator C A2, for the driving unit A3 on the primary side to turn on the gate switch G, so that the flyback converter enters the switch-on phase.

To sum up, in the technical solution of the present invention, the primary side controller is used to perform the calculation and control process of the on-time of the flyback converter, which facilitates the acquisition of relevant information such as the input voltage, reduces the computational complexity, and reduces the number of Transmission line connections between secondary-side controllers also do not affect the detection of synchronous rectifiers in the system. At the same time, the primary-side controller is used to perform the calculation and control process of the on-time of the flyback converter, and there is no need to worry about the problem of transmission error, so there is no need to set the blanking time of switch on/off in the system, so that the flyback The converter can be used in high switching frequency scenarios. Therefore, the flyback converter in the present invention has better electrical performance than the related structures in the prior art. road performance.

In a preferred embodiment of the present invention, based on the flyback converter described above, a control method for a flyback converter is also provided, as shown in FIG. 18 , including: when the flyback converter is in a When the switch is off, the secondary side controller B detects the output loop of the secondary coil S and generates a first control signal (high level signal), and the secondary side controller B sends the first control signal through the isolator C To the receiving unit A2, the receiving unit A2 sends the first control signal as a trigger signal (Trigger-on) to the set terminal S of the flip-flop A4, and the driving unit A3 outputs the signal (high power) according to the output terminal Q of the flip-flop A4. A flat signal) drives the gate switch to conduct, thus entering the switch-on phase of the flyback converter.

After the gate switch is turned on, the first control unit A1 processes and obtains the second control signal (high level signal) according to the first voltage of the first voltage terminal and the gate voltage GATE of the gate switch G as the disconnection trigger signal (Trigger -off) and sent to the zero-setting terminal R of the flip-flop A4, the drive unit A3 drives the gate switch G to disconnect according to the signal output by the output terminal Q of the flip-flop A4, thereby entering the switch-off stage of the flyback converter; The above-described control method is performed cyclically (switch-on phases and switch-off phases alternate), so as to control the operating state of the flyback converter with a fixed on-time.

In the above description of the present invention and FIG. 18, for ease of understanding, the flyback converter is in the switch-off phase as the starting point of the entire control method. In the actual operation process, the above control method is a cyclic execution process. , the starting point is only when the system is initialized and starts running, not during any switch-off phase or switch-on phase.

The above are only preferred embodiments of the present invention, and are not intended to limit the embodiments and protection scope of the present invention. Those skilled in the art should be able to realize that any application of the description of the present invention The solutions obtained by the equivalent replacements and obvious changes made to the contents of the drawings and drawings shall be included in the protection scope of the present invention.

A1: Control unit

A2: Receiving unit

A3: Drive unit

B1: Second control unit

B2: Transmission unit

FB: the first input terminal

CSP: the second input

A: Primary side controller

B: Secondary side controller

C: The output terminal is connected to the isolator

P: Primary coil

S: Secondary coil

GATE: gate control signal

Claims (20)

A flyback converter with fixed on-time, wherein one end of the primary coil on the primary side of the transformer of the flyback converter is connected to the input end of the flyback converter, and the other end is connected to the drain of a gate switch, the A gate of the gate switch is connected to a primary side controller, and the gate switch is used as the switch of the flyback converter; one end of the secondary coil on the secondary side of the transformer of the flyback converter is connected through a diode The output end of the flyback converter is connected, and the other end is connected to the reference ground potential of the primary side. The primary side controller is coupled to the secondary side of the transformer and generates a first one according to the output of the output end of the flyback converter control signal; the primary side controller is connected with the secondary side controller through an isolator; wherein, the primary side controller includes: a receiving unit, connected with the secondary side controller through the isolator, and through the isolation The receiver receives the first control signal generated by the secondary side controller, and the receiving unit outputs the first control signal as a turn-on trigger signal; a driving unit is coupled to receive the first control signal, and outputs a gate control signal to control The gate switch is turned on; a first control unit receives the gate control signal output by the drive unit, and after a fixed turn-on time, outputs a second control signal coupled to the drive unit as a disconnect trigger signal, Trigger the drive unit to output a gate control signal to control the gate switch to turn off. The flyback converter as described in claim 1, wherein the first input terminal of the first control unit is connected to a first voltage terminal, and the second input terminal of the first control unit is connected to the gate switch gate, the first control unit according to the first voltage of the first voltage terminal and the gate switch The gate voltage is processed to obtain the second control signal, and the first voltage of the first voltage terminal is proportional to the input voltage of the input terminal of the flyback converter. The flyback converter as described in claim 2, wherein the primary side controller further comprises a flip-flop, the output terminal of the first control unit is connected to the zero-setting terminal of the flip-flop, and the output terminal of the receiving unit is connected to the zero-setting terminal of the flip-flop. The terminal is connected to the set terminal of the trigger, and the output terminal of the trigger is connected to the gate of the gate switch through the drive unit; when the receiving unit outputs the first control signal to the set terminal of the trigger, The driving unit drives the gate switch to turn on; and when the first control unit outputs the second control signal to the zero-setting terminal of the flip-flop, the driving unit drives the gate switch to turn off; when the gate switch turns on When , the first control unit obtains and outputs the second control signal according to the first voltage; and when the gate switch is turned off, the first control unit does not output the second control signal. The flyback converter as described in claim 3, wherein the flyback converter operates in a discontinuous mode; the first control unit further comprises: a first amplifying module, the first amplifying module The input terminal of the amplifier is connected to the first voltage terminal, the output terminal of the first amplifier module is connected to the non-inverting input terminal of a first comparator through a first node, and the first amplifier module is used to The current or voltage of the amplifying module is amplified by a first predetermined multiple and output; the first field effect transistor, the gate of the first field effect transistor is connected to the gate of the gate switch through an inverter, the first field effect transistor The drain electrode is connected to the non-inverting input terminal of the first comparator through the first node, and the source electrode of the first field effect transistor is grounded; a first capacitor, one end of the first capacitor is connected to the non-inverting input end of the first comparator through the first node, and the other end is grounded; a first reference end, the first reference end is connected to the inverting phase of the first comparator The input terminal is used to provide a first reference voltage; the output terminal of the first comparator is connected to the output terminal of the first control unit; when the voltage value of the non-inverting input terminal of the first comparator is greater than the first reference voltage , the output end of the first comparator outputs the second control signal. The flyback converter according to claim 3, wherein the flyback converter operates in a continuous mode; the first control unit further comprises: a first amplifying module, wherein the first amplifying module has a The input terminal is connected to the first voltage terminal, the output terminal of the first amplifier module is connected to the non-inverting input terminal of a first comparator through a second node, and the first amplifier module is used to The current of the module is amplified by a first predetermined multiple and output; the first field effect transistor, the gate of the first field effect transistor is connected to the gate of the gate switch through an inverter, and the drain of the first field effect transistor The non-inverting input terminal of the first comparator is connected through the second node, and the source of the first field effect transistor is grounded; the first capacitor, one end of the first capacitor is connected to the first comparator through the second node. a non-inverting input terminal, the other terminal is grounded; a first reference terminal, the first reference terminal is connected to the inverting input terminal of the first comparator for providing a first reference voltage; a reference module, the input of the reference module The terminal is connected to a set voltage terminal with a predetermined voltage value, the output terminal of the reference module is connected to the non-inverting input terminal of the first comparator through the second node, and the reference module is used for inputting to the reference module according to the input terminal. The voltage is amplified and output; The output end of the first comparator is connected to the output end of the first control unit; when the voltage value of the non-inverting input end of the first comparator is greater than the first reference voltage, the output end of the first comparator outputs the first Two control signals. The flyback converter as described in claim 5, wherein the voltage setting terminal comprises a reference resistor and a setting current terminal, which are respectively connected to the input terminal of the reference module; the reference resistor has a predetermined resistance value , the set current terminal has a predetermined input current; the reference module includes: an amplifier, the input terminal of the amplifier is used as the input terminal of the reference module, and the output terminal of the amplifier is connected to the first comparator through the second node , the amplifier is used for amplifying the voltage output by the set voltage terminal according to a second predetermined multiple and then outputting the output. The flyback converter as described in claim 5, wherein the voltage setting terminal includes a reference resistor and a setting current terminal, which are respectively connected to the input terminal of the reference module; A switch is set between the input terminals of the module, and the switch is initially in a closed state. When the input current of the set current terminal is set, the switch is turned off; the reference module further includes: a digital-to-analog converter, the digital-to-analog converter The input terminal of the amplifier is used as the input terminal of the reference module. After the switch is turned off, the digital-analog converter is used to lock the input voltage transmitted by the set current terminal; the amplifier, the input terminal of the amplifier is connected to the digital-analog converter. The output end of the amplifier is connected to the first comparator through the second node, and the amplifier is used for amplifying the voltage output by the set voltage end according to a second predetermined multiple and then outputting it. The flyback converter as described in claim 4 or claim 5, wherein the first voltage terminal is connected to an auxiliary coil through a first resistor, and the auxiliary coil and the primary coil have a predetermined A turns ratio is determined so that the first voltage is proportional to the input voltage at the input of the flyback converter. The flyback converter as described in claim 8, wherein there is a connection node between the first voltage terminal and the first resistor; the flyback converter further comprises a second resistor, the second resistor A resistor is connected between the connection node and ground. The flyback converter as described in claim 4 or item 5, wherein the first voltage terminal is connected to the input terminal of the flyback converter through a first resistor, so that the first voltage and the The input voltage of the input terminal of the flyback converter is proportionally related; there is a connection node between the first voltage terminal and the first resistor; the flyback converter further includes a second resistor connected to the second resistor between the connection node and ground. The flyback converter as described in claim 3, wherein the flyback converter can work in discontinuous mode or continuous mode; the first control unit further comprises: a first control unit module, the input end of the first control module is connected to the first voltage end; the second control module, the input end of the second control module is connected to the first voltage end; the judgment module, the The two input ends are respectively connected to the output end of the first control module and the output end of the second control module, and the output end of the judgment module is used as the output end of the first control unit; when the first control module Or when the second control module outputs a predetermined signal, the judgment module outputs the second control signal. The flyback converter as described in claim 11, wherein the first control module comprises: a first amplifying module, an input end of the first amplifying module is connected to the first voltage end, the first The output end of the amplifying module is connected to the non-inverting input end of a first comparator through a first node, and the first amplifying module is used for amplifying the current flowing through the first amplifying module to a first predetermined multiple output; the first A field effect transistor, the gate of the first field effect transistor is connected to the gate of the gate switch through an inverter, and the drain of the first field effect transistor is connected to the positive pole of the first comparator through the first node a phase input terminal, the source of the first field effect transistor is grounded; a first capacitor, one end of the first capacitor is connected to the non-inverting input terminal of the first comparator through the first node, and the other terminal is grounded; a first reference terminal , the first reference terminal is connected to the inverting input terminal of the first comparator for providing a first reference voltage; the output terminal of the first comparator is connected to the input terminal of the judgment module; when the first comparator When the voltage value of the non-inverting input terminal of the first comparator is greater than the first reference voltage, the output terminal of the first comparator outputs the predetermined signal. The flyback converter as claimed in claim 11, wherein the second control module comprises: a second amplifying module, the input end of the second amplifying module is connected to the first voltage end, the second amplifying module The output end of the amplifying module is connected to the non-inverting input end of a second comparator through a second node, and the second amplifying module is used to amplify the current flowing through the second amplifying module by a third predetermined multiple and output; The second field effect transistor, the gate of the second field effect transistor is connected to the gate of the gate switch through an inverter, and the drain of the second field effect transistor is connected to the second comparator through the second node. non-inverting input, The source of the second field effect transistor is grounded; the second capacitor, one end of the second capacitor is connected to the non-inverting input end of the second comparator through the second node, and the other end is grounded; the second reference end, the second The reference terminal is connected to the inverting input terminal of the second comparator for providing a second reference voltage; the reference module, the input terminal of the reference module is connected to a set voltage terminal with a predetermined voltage value, the reference module The output terminal of the second comparator is connected to the non-inverting input terminal of the second comparator through the second node, and the reference module is used for amplifying the output according to the voltage input to the reference module; the output terminal of the second comparator is connected to The input terminal of the judging module; when the voltage value of the non-inverting input terminal of the second comparator is greater than the second reference voltage, the output terminal of the second comparator outputs the predetermined signal. The flyback converter as described in claim 13, wherein the voltage setting terminal comprises a reference resistor and a setting current terminal, which are respectively connected to the input terminals of the reference module; the reference resistor has a predetermined resistance value , the set current terminal has a predetermined input current; the reference module includes: an amplifier, the input terminal of the amplifier is used as the input terminal of the reference module, and the output terminal of the amplifier is connected to the second comparator through the second node , the amplifier is used for amplifying the voltage output by the set voltage terminal according to a second predetermined multiple and then outputting the output. The flyback converter as described in claim 13, wherein the voltage setting terminal includes a reference resistor and a setting current terminal, which are respectively connected to the input terminal of the reference module; the setting current terminal and the reference A switch is set between the input terminals of the module, the switch is initially closed, and the switch is turned off after the input current of the set current terminal is set; The reference module further includes: a digital-to-analog converter, the input terminal of the digital-to-analog converter is used as the input terminal of the reference module, and after the switch is turned off, the digital-to-analog converter is used to lock the set current terminal. Input voltage; amplifier, the input end of the amplifier is connected to the output end of the digital-to-analog converter, the output end of the amplifier is connected to the second comparator through the second node, the amplifier is used for setting the setting according to a second predetermined multiple The voltage output from the voltage terminal is amplified and output. The flyback converter of claim 11, wherein the first voltage terminal is connected to an auxiliary coil through a first resistor, and the auxiliary coil and the primary coil have a predetermined turns ratio, so that the The first voltage is proportional to the input voltage of the input terminal of the flyback converter; the first voltage terminal is also connected to an auxiliary coil through a third resistor, and the auxiliary coil and the primary coil have a predetermined turns ratio, so that the first voltage is proportional to the input voltage at the input of the flyback converter. The flyback converter of claim 16, wherein there is a first connection node between the first voltage terminal and the first resistor; the flyback converter further comprises a second resistor, the The second resistor is connected between the first connection node and the ground terminal; there is a second connection node between the first voltage terminal and the third resistor; the flyback converter further includes a fourth resistor, the first Four resistors are connected between the second connection node and the ground terminal. The flyback converter as described in claim 11, wherein the first voltage terminal is connected to the input terminal of the flyback converter through a first resistor, so that the first voltage is connected to the flyback converter The input voltage at the input of the converter is proportionally related; There is a first connection node between the first voltage terminal and the first resistor; the flyback converter further includes a second resistor connected between the first connection node and the ground terminal; the The first voltage terminal is also connected to the input terminal of the flyback converter through a third resistor, so that the first voltage is proportional to the input voltage of the input terminal of the flyback converter; the first voltage terminal and the There is a second connection node between the third resistors; the flyback converter further includes a fourth resistor connected between the second connection node and the ground. The flyback converter as described in claim 3, wherein the secondary side controller further comprises: a second control unit, the first input of the second control unit is used to detect the output of the secondary coil voltage, the second input end of the second control unit is used to detect the output current of the secondary coil, and the second control unit is used to process and output the first control signal according to the output voltage and output current of the secondary coil ; a transmission unit, the input end of the transmission unit is connected to the output end of the second control unit, the output end of the transmission unit is connected to the isolator, the transmission unit is used for the first control signal output by the second control unit to pass through The isolator sends to the receiving unit in the primary side controller. A control method for a fixed on-time of a flyback converter, which is applied to the flyback converter as described in any one of the claims 1 to 19, wherein the control method includes: the secondary The side controller generates a first control signal according to the output of the output terminal of the flyback converter, and the secondary side controller sends the first control signal to the receiving unit through the isolator for The receiving unit outputs the first control signal as the turn-on trigger signal, and the drive unit outputs a gate control signal according to the first control signal to control the gate switch to turn on; when the gate switch is turned on, after a fixed turn-on After time, the first control unit outputs a second control signal as a disconnect trigger signal, and the drive unit controls the gate switch to disconnect according to the second control signal. The operating state of the flyback converter.

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