Secondary side self-adaptive driving control circuit and control method thereof

Abstract

The invention discloses a secondary side self-adaptive driving control circuit and a control method thereof, and the circuit comprises an input voltage sampling module which is used for obtaining a power input voltage; the output voltage sampling module is used for acquiring the output voltage of the converter; the controller module is used for determining the conduction time of a synchronous follow current tube according to the input voltage signal and the output voltage signal, generating a synchronous follow current driving signal and outputting the synchronous follow current driving signal; and the staggered active clamping forward main circuit module is used for receiving the synchronous freewheeling driving signal and controlling the conduction of the synchronous freewheeling tube according to the synchronous freewheeling driving signal. According to the invention, the discontinuous working mode and the continuous working mode of the interleaved active clamping forward converter can be discriminated. The synchronous freewheeling tube can work in an intermittent working mode and a continuous working mode, and the problems of reliability reduction and even machine explosion caused by backflow of the freewheeling tube are solved. And the light-load working efficiency of the staggered active clamping forward converter is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of DC-DC isolation converters, and in particular to a secondary side adaptive drive control circuit and a control method thereof. Background Art

[0002] DC switching power supplies are widely used as power supplies for various electronic devices and electrical equipment, and have developed rapidly in recent years. As the integration of electronic devices continues to increase, their functions become more and more powerful, but their size becomes smaller and smaller, there is an urgent need for new power supplies with small size, light weight, high efficiency and good performance, which provides a strong impetus for the development of switching power supply technology.

[0003] In order to improve the power density of the power supply, high transmission efficiency is very important. In order to reduce the rectification loss of the secondary side switch tube, a dedicated power MOSFET with extremely low on-resistance is used to replace the Schottky diode, which can greatly improve the efficiency of the power supply. The freewheeling tube in the existing interleaved active clamp forward scheme uses a power MOSFET to replace the Schottky diode, which is generally called a synchronous freewheeling tube. When the converter works in the continuous working mode, the use of the synchronous freewheeling tube improves the efficiency of the converter; when the converter works in the discontinuous working mode, the use of the synchronous freewheeling tube brings disadvantages: when the converter works in the discontinuous state, the synchronous freewheeling tube will provide a reverse path for the current, resulting in a decrease in circuit reliability and even causing the machine to explode.

[0004] The traditional solution is to sample the secondary output current, set a suitable threshold to determine when the converter is operating in the discontinuous working mode, turn off the synchronous freewheeling tube drive, and use the body diode of the synchronous freewheeling tube for freewheeling.

[0005] This method can prevent the synchronous freewheeling tube from providing a reverse path for the current and improve the reliability of the converter. The disadvantage is that the forward voltage drop of the body diode is higher than the conduction voltage drop, which reduces the efficiency in the discontinuous working mode. Summary of the invention

[0006] The purpose of the present invention is to provide a secondary side adaptive drive control circuit and a control method thereof, which aims to solve the problem of reduced converter reliability or even machine explosion due to freewheeling tube backflow in the intermittent working mode of the interleaved active clamped forward converter, and at the same time improve the output efficiency in the intermittent working mode.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] In a first aspect, an embodiment of the present invention provides a secondary side adaptive drive control circuit, the secondary side adaptive drive control circuit comprising:

[0009] An input voltage sampling module is used to obtain the power supply input voltage;

[0010] An output voltage sampling module is used to obtain the output voltage of the converter;

[0011] A controller module, used to determine the conduction time of the synchronous freewheeling tube according to the input voltage signal and the output voltage signal, generate a synchronous freewheeling drive signal and output it;

[0012] The staggered active clamp forward main circuit module is used to receive and control the conduction of the synchronous freewheeling tube according to the synchronous freewheeling drive signal.

[0013] Further, the staggered active clamped forward main circuit module includes a first active clamped forward circuit, a second active clamped forward circuit, an input capacitor, a synchronous freewheeling tube, an output inductor and an output capacitor. The positive output end of the first active clamped forward circuit and the positive output end of the second active clamped forward circuit are both connected to the drain of the synchronous freewheeling tube, the negative output end of the first active clamped forward circuit and the negative output end of the second active clamped forward circuit are both connected to the source of the synchronous freewheeling tube, the gate of the synchronous freewheeling tube is connected to the synchronous freewheeling drive signal, the drain of the synchronous freewheeling tube is connected to the drain of the output capacitor through the output inductor, the source of the synchronous freewheeling tube is connected to the source of the output capacitor, the drain of the output capacitor is connected to the input end of the output voltage sampling module, the input end of the first active clamped forward circuit is connected to the first end of the input capacitor, and the second end of the input capacitor is connected to the reference ground.

[0014] Further, the first active clamp forward circuit includes a first active clamp tube, a first clamp capacitor, a first main pipe, a first synchronous rectifier tube and a first transformer, the drain of the first active clamp tube is connected to the same-name end of the primary winding of the first transformer through the first clamp capacitor, the source of the first active clamp tube is respectively connected to the drain of the first main pipe and the opposite-name end of the primary winding of the first transformer, the same-name end of the secondary winding of the first transformer is connected to the drain of the synchronous freewheeling tube, the opposite-name end of the secondary winding of the first transformer is connected to the drain of the first synchronous rectifier tube, the source of the first synchronous sorting tube is connected to the source of the synchronous freewheeling tube, the gate of the first active clamp tube, the gate of the first main pipe and the gate of the first synchronous rectifier tube are respectively connected to corresponding drive signals, and the same-name ends of the primary winding of the first transformer are respectively connected to the first end of the first capacitor and the input end of the input voltage sampling module.

[0015] Further, the second active clamp forward circuit includes a second active clamp tube, a second clamp capacitor, a second main tube, a second synchronous rectifier tube and a second transformer, the drain of the second active clamp tube is connected to the same-name end of the primary winding of the second transformer through the second clamp capacitor, the source of the second active clamp tube is respectively connected to the drain of the second main tube and the opposite-name end of the primary winding of the second transformer, the same-name end of the secondary winding of the second transformer is connected to the drain of the synchronous freewheeling tube, the opposite-name end of the secondary winding of the second transformer is connected to the drain of the second synchronous rectifier tube, the source of the second synchronous sorting tube is connected to the source of the synchronous freewheeling tube, the gate of the second active clamp tube, the gate of the second main tube and the gate of the second synchronous rectifier tube are respectively connected to corresponding drive signals, and the same-name ends of the primary winding of the second transformer are respectively connected to the first end of the first capacitor and the input end of the input voltage sampling module.

[0016] In a second aspect, the present invention provides a control method applied to the secondary side adaptive drive control circuit described in the first aspect, comprising the following steps:

[0017] Get the power input voltage;

[0018] Obtaining converter output voltage;

[0019] Determine the conduction time of the synchronous freewheeling tube according to the input voltage signal and the output voltage signal, generate and output a synchronous freewheeling driving signal;

[0020] Receive and control the conduction of the synchronous freewheeling tube according to the synchronous freewheeling driving signal.

[0021] Further, the method of determining the conduction time of the synchronous freewheeling tube according to the input voltage signal and the output voltage signal, generating and outputting the synchronous freewheeling drive signal specifically includes:

[0022] Determine the on-time of the continuous working mode and the on-time of the discontinuous working mode according to the input voltage signal and the output voltage signal;

[0023] Determine the current working mode according to the on-time of the continuous working mode and the on-time of the intermittent working mode;

[0024] According to the working mode, the conduction time is determined, and then the synchronous freewheeling driving signal is generated and output.

[0025] Furthermore, the calculation formula for the on-time of the continuous working mode is:

[0026] t2' = T / 2 - t1;

[0027] Wherein, t2' is the conduction time of the continuous working mode, T is the working cycle of the converter, and t1 is the conduction time of the first main pipe or the second main pipe.

[0028] Furthermore, the calculation formula for the on-time of the intermittent working mode is:

[0029] t2=(Vin / n*t1 / Vo-t1) / 2;

[0030] Wherein, t2 is the conduction time of the intermittent working mode, Vin is the power input voltage, Vo is the converter output voltage, n is the turns ratio of the first transformer or the second transformer, and t1 is the conduction time of the first main tube or the second main tube.

[0031] Further, the current working mode is determined according to the on-time of the continuous working mode and the on-time of the intermittent working mode, specifically:

[0032] The intermittent working mode on time is less than the continuous working mode on time, and the current working mode is determined to be the intermittent working mode;

[0033] The on-time of the intermittent working mode is greater than or equal to the on-time of the continuous working mode, and it is determined that the current working mode is the continuous working mode.

[0034] The beneficial effects of the present invention are:

[0035] 1. The present invention realizes the discrimination between the interleaved active clamp forward converter's discontinuous working mode and the continuous working mode.

[0036] 2. The synchronous freewheeling tube of the present invention can operate in an intermittent working mode and a continuous working mode, and the problem of reduced reliability or even machine explosion caused by the backflow of the freewheeling tube will not occur.

[0037] 3. The present invention improves the light-load operating efficiency of the interleaved active clamp forward converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a principle block diagram of a secondary side adaptive drive control circuit of the present invention;

[0039] Figure 2 A driving timing diagram of an interleaved active clamping forward main circuit module of a secondary side adaptive driving control circuit of the present invention;

[0040] Figure 3 It is a schematic diagram of an output voltage sampling module in a specific embodiment of a secondary side adaptive drive control circuit of the present invention;

[0041] Figure 4It is a schematic diagram of an input voltage sampling module in a specific embodiment of a secondary side adaptive drive control circuit of the present invention;

[0042] Figure 5 It is a schematic diagram of a controller module in a specific embodiment of a secondary side adaptive drive control circuit of the present invention. DETAILED DESCRIPTION

[0043] The present invention is described in detail below in conjunction with the embodiments and the accompanying drawings to help those skilled in the art better understand the inventive concept of the present invention. However, the protection scope of the claims of the present invention is not limited to the following embodiments. For those skilled in the art, all other embodiments obtained without creative work without departing from the inventive concept of the present invention belong to the protection scope of the present invention. When introducing the embodiments, only the key modules of the present invention are described in detail.

[0044] refer to Figure 1 to Figure 5 , an embodiment of the present invention provides a secondary side adaptive drive control circuit, the secondary side adaptive drive control circuit comprising:

[0045] An input voltage sampling module 100 is used to obtain a power supply input voltage;

[0046] An output voltage sampling module 200 is used to obtain the output voltage of the converter;

[0047] The controller module 300 is used to determine the conduction time of the synchronous freewheeling tube S4 according to the input voltage signal and the output voltage signal, generate and output the synchronous freewheeling driving signal;

[0048] The interleaved active clamp forward main circuit module 400 is used to receive and control the conduction of the synchronous freewheeling transistor S4 according to the synchronous freewheeling driving signal.

[0049] In this embodiment, the input voltage sampling module 100 converts the input voltage signal Vin of the primary side into a signal Vin_sense that can be received by the controller module 300 to obtain the power input voltage; the output voltage sampling module 200 converts the output voltage signal Vo of the secondary side into a signal Vo_sense that can be received by the controller module 300 to obtain the converter output voltage;

[0050] The controller module 300 calculates and outputs 7 PWM drive signals, one of which is a synchronous freewheeling drive signal. The timing of each PWM drive signal is as follows: Figure 2 As shown;

[0051] In the figure, S1 is the timing waveform of the first active clamping tube S1, S2 is the timing waveform of the first main pipe S2, S3 is the timing waveform of the first synchronous rectifier tube S3, S4 is the timing waveform of the synchronous freewheeling tube S4 in the intermittent working mode, S4' is the timing waveform of the synchronous freewheeling tube S4 in the continuous working mode, S5 is the timing waveform of the second active clamping tube S5, S6 is the timing waveform of the second main pipe S6, S7 is the timing waveform of the second synchronous rectifier tube S7, Ilo is the output inductor Lo current waveform in the intermittent working mode, and Ilo' is the output inductor Lo current waveform in the continuous working mode.

[0052] In one embodiment, the staggered active clamped forward main circuit module 400 includes a first active clamped forward circuit 401, a second active clamped forward circuit 402, an input capacitor C1, a synchronous freewheeling tube S4, an output inductor Lo and an output capacitor C4. The positive output end of the first active clamped forward circuit 401 and the positive output end of the second active clamped forward circuit 402 are both connected to the drain of the synchronous freewheeling tube S4, the negative output end of the first active clamped forward circuit 401 and the negative output end of the second active clamped forward circuit 402 are both connected to the source of the synchronous freewheeling tube S4, the gate of the synchronous freewheeling tube S4 is connected to the synchronous freewheeling drive signal, the drain of the synchronous freewheeling tube S4 is connected to the drain of the output capacitor C4 through the output inductor Lo, the source of the synchronous freewheeling tube S4 is connected to the source of the output capacitor C4, and the drain of the output capacitor C4 is connected to the input end of the output voltage sampling module 200.

[0053] The first active clamp forward circuit 401 includes a first active clamp tube S1, a first clamp capacitor C2, a first main tube S2, a first synchronous rectifier tube S3 and a first transformer T1. The drain of the first active clamp tube S1 is connected to the same-name end of the primary winding of the first transformer T1 through the first clamp capacitor C2. The source of the first active clamp tube S1 is respectively connected to the drain of the first main tube S2 and the opposite-name end of the primary winding of the first transformer T1. The same-name end of the secondary winding of the first transformer T1 is connected to the drain of the synchronous freewheeling tube S4. The first transformer T1 The opposite-name end of the secondary winding is connected to the drain of the first synchronous rectifier S3, the source of the first synchronous sorting tube is connected to the source of the synchronous freewheeling tube S4, the gate of the first active clamping tube S1, the gate of the first main tube S2 and the gate of the first synchronous rectifier S3 are respectively connected to the corresponding drive signals, the same-name end of the primary winding of the first transformer T1 is respectively connected to the first end of the input capacitor C1 and the input end of the input voltage sampling module, the input end of the first active clamping forward circuit is connected to the first end of the input capacitor, and the second end of the input capacitor is connected to the reference ground.

[0054] The second active clamp forward circuit 402 includes a second active clamp tube S5, a second clamp capacitor C3, a second main pipe S6, a second synchronous rectifier tube S7 and a second transformer T2. The drain of the second active clamp tube S5 is connected to the same-name end of the primary winding of the second transformer T2 through the second clamp capacitor C3. The source of the second active clamp tube S5 is respectively connected to the drain of the second main pipe S6 and the opposite-name end of the primary winding of the second transformer T2. The same-name end of the secondary winding of the second transformer T2 is connected to the drain of the synchronous freewheeling tube S4. The opposite-name end of the secondary winding of the second transformer T2 is connected to the drain of the second synchronous rectifier tube S7. The source of the second synchronous sorting tube is connected to the source of the synchronous freewheeling tube S4. The gate of the second active clamp tube S5, the gate of the second main pipe S6 and the gate of the second synchronous rectifier tube S7 are respectively connected to corresponding drive signals. The same-name end of the primary winding of the second transformer T2 is respectively connected to the first end of the input capacitor C1 and the input end of the input voltage sampling module.

[0055] In this embodiment, in the intermittent working mode, the first main pipe S2 and the first synchronous rectifier S3 are turned on, and the output inductor Lo current Ilo increases; after the first main pipe S2 and the first synchronous rectifier S3 are turned off, the output inductor Lo current Ilo decreases to 0. When the second main pipe S6 and the second synchronous rectifier S7 are just turned on, the output inductor Lo current Ilo is equal to 0. The second main pipe S6 and the second synchronous rectifier S7 are turned on, and the output inductor Lo current Ilo increases; the second main pipe S6 and the second synchronous rectifier S7 are turned off, and the output inductor Lo current Ilo decreases to 0. When the first main pipe S2 and the first synchronous rectifier S3 are just turned on, the output inductor Lo current Ilo is equal to 0.

[0056] In the continuous working mode, the first main pipe S2 and the first synchronous rectifier S3 are turned on, and the output inductor Lo current Ilo' increases; after the first main pipe S2 and the first synchronous rectifier S3 are turned off, the output inductor Lo current Ilo' decreases. When the second main pipe S6 and the second synchronous rectifier S7 are just turned on, the output inductor Lo current Ilo' ≥ 0. The second main pipe S6 and the second synchronous rectifier S7 are turned on, and the output inductor Lo current Ilo' increases; the second main pipe S6 and the second synchronous rectifier S7 are turned off, and the output inductor Lo current Ilo' decreases. When the first main pipe S2 and the first synchronous rectifier S3 are just turned on, the output inductor Lo current Ilo' ≥ 0.

[0057] In one embodiment, the present invention provides a control method applied to a secondary side adaptive drive control circuit, comprising the following steps:

[0058] S100, obtaining a power input voltage;

[0059] S200, obtaining a converter output voltage;

[0060] S300. Determine the conduction time of the synchronous freewheeling diode S4 based on the input voltage signal and the output voltage signal, generate a synchronous freewheeling drive signal, and output it.

[0061] S400. Receive and control the conduction of the synchronous freewheeling diode S4 according to the synchronous freewheeling drive signal.

[0062] In one embodiment, step S300 determines the conduction time of the synchronous freewheeling diode S4 based on the input voltage signal and the output voltage signal, generates a synchronous freewheeling drive signal, and outputs it, specifically including:

[0063] S310. Determine the continuous operation mode conduction time and the discontinuous operation mode conduction time based on the input voltage signal and the output voltage signal.

[0064] S320. Determine the current operation mode according to the continuous operation mode conduction time and the discontinuous operation mode conduction time.

[0065] S330. Determine the conduction time according to the operation mode, and then generate a synchronous freewheeling drive signal and output it.

[0066] In this embodiment, the calculation of the conduction time of the synchronous freewheeling diode S4 is divided into two cases: discontinuous operation mode and continuous operation mode.

[0067] In the discontinuous operation mode, the first main transistor S2 and the first synchronous rectifier diode S3 conduct, and the current Ilo of the output inductor Lo increases; after the first main transistor S2 and the first synchronous rectifier diode S3 turn off, the current Ilo of the output inductor Lo decreases to 0. When the second main transistor S6 and the second synchronous rectifier diode S7 just conduct, the current Ilo of the output inductor Lo is equal to 0. The second main transistor S6 and the second synchronous rectifier diode S7 conduct, and the current Ilo of the output inductor Lo increases; the second main transistor S6 and the second synchronous rectifier diode S7 turn off, and the current Ilo of the output inductor Lo decreases to 0. When the first main transistor S2 and the first synchronous rectifier diode S3 just conduct, the current Ilo of the output inductor Lo is equal to 0.

[0068] In the discontinuous operation mode, the current of the output inductor Lo will drop to 0. Therefore, the synchronous freewheeling diode S4 needs to turn off during the conduction period of the first synchronous rectifier diode S3 and the second synchronous rectifier diode S7 and during the period when the current Ilo of the output inductor Lo is equal to 0. That is, the conduction time of the synchronous freewheeling diode S4 is t2 = (Vin / n * t1 / Vo - t1) / 2; where t2 < t2’, Vin is the power input voltage, Vo is the converter output voltage, n is the turn ratio of the first transformer T1 and the second transformer T2, and t1 is the conduction time of the first main transistor S2 and the second main transistor S6.

[0069] In the discontinuous operation mode, the conduction time t2 = (Vin / n * t1 / Vo - t1) / 2, and the derivation of t2 < t2' is as follows: For the first transformer T1, assume that when the first main switch S2 just conducts, the current of the output inductor Lo just drops to 0. At this time, the volt-second balance gives Vin / n * t1 = Vo * toff. Here, toff is the time when the first main switch S2 is off in one operating cycle. Since both the first transformer T1 and the second transformer T2 need to satisfy the volt-second balance for the circuit to work properly, during this toff period, it includes the time of two freewheeling periods and the time when the second main switch S6 conducts once, that is, toff = t2 * 2 + t1. Substituting it into Vin / n * t1 = Vo * toff, we get Vin / n * t1 = Vo * (t2 * 2 + t1). After transformation, we can obtain t2 = (Vin / n * t1 / Vo - t1) / 2. Previously, it was assumed that when the first main switch S2 just conducts, the current of the output inductor Lo just drops to 0, so the calculated t2 does not include the time when it remains 0. The assumption can hold only when the preconditions are met. Therefore, the condition t2 < t2' is required. The same result applies to the second transformer T2.

[0070] In the continuous operation mode, the first main switch S2 and the first synchronous rectifier S3 conduct, and the current Ilo' of the output inductor Lo increases; after the first main switch S2 and the first synchronous rectifier S3 turn off, the current Ilo' of the output inductor Lo decreases. When the second main switch S6 and the second synchronous rectifier S7 just conduct, the current Ilo' of the output inductor Lo ≥ 0. When the second main switch S6 and the second synchronous rectifier S7 conduct, the current Ilo' of the output inductor Lo increases; when the second main switch S6 and the second synchronous rectifier S7 turn off, the current Ilo' of the output inductor Lo decreases. When the first main switch S2 and the first synchronous rectifier S3 just conduct, the current Ilo' of the output inductor Lo ≥ 0.

[0071] In the continuous operation mode, the current of the output inductor Lo is not 0. Therefore, the synchronous freewheeling diode S4 needs to turn off during the conduction of the first synchronous rectifier S3 and the second synchronous rectifier S7, that is, the conduction time of the synchronous freewheeling diode S4 is t2' = T / 2 - t1; where T is the operating cycle of the converter, and t1 is the conduction time of the first main switch S2 and the second main switch S6.

[0072] Then, based on the calculated continuous conduction time t2’ = T / 2 - t1 and discontinuous conduction time t2 = (Vin / n * t1 / Vo - t1) / 2, where t2 < t2’. It can be determined whether the converter operates in the discontinuous mode from the limiting conditions. If the discontinuous conduction time is less than the continuous conduction time, it is determined that the current operating mode is the discontinuous mode; if the discontinuous conduction time is greater than or equal to the continuous conduction time, it is determined that the current operating mode is the continuous mode. That is, when the calculated value of (Vin / n * t1 / Vo - t1) / 2 is less than t2’, it is the discontinuous mode, otherwise it is the continuous mode.

[0073] The specific embodiments of the present invention are as follows:

[0074] Figure 1 It is a schematic diagram of the principle of the secondary-side adaptive drive control circuit of the present invention, which includes an output voltage sampling module 200, an input voltage sampling module 100, a controller module 300, and an interleaved active-clamp forward main circuit module 400.

[0075] The output voltage sampling module 200 includes resistors R3 and R4.

[0076] The connection method is as follows: The output voltage Vo is connected to the upper end of resistor R3, the lower end of resistor R4 is connected to the secondary-side ground, and the lower end of resistor R3 and the upper end of resistor R4 are connected together and used as Vo_sense output.

[0077] The input voltage sampling module 100 includes resistors R1, R2, and an isolation operational amplifier U1.

[0078] The connection method is as follows: The input voltage Vin is connected to the upper end of resistor R1, the lower end of resistor R2 is connected to the primary-side ground, the lower end of resistor R1, the upper end of resistor R2, and the IN terminal of the isolation operational amplifier are connected together. The GND1 terminal of the isolation operational amplifier U1 is connected to the primary-side ground, the GND2 terminal is connected to the secondary-side ground, and the OUT terminal is used as Vin_sense output.

[0079] The controller module 300 includes output voltage comparison, conduction time calculation, PWM modulation, isolation drive output, and drive output.

[0080] The connection method is that the output of the comparison between Vo_sense and Vo_ref, Vin_sense is connected to the conduction time calculation, the output after the conduction time calculation is connected to the PWM modulation, the output after the PWM modulation is connected to the primary-side drives S1, S2, S5, S6 through the isolation drive output, and the secondary-side drives S3, S7, S4 are connected to the drive output.

[0081] The connection relationship of the interleaved active-clamp forward main circuit module 400 is described separately for the primary-side connection relationship and the secondary-side connection relationship;

[0082] The connection relationship between the primary sides of the first transformer T1 and the second transformer T2 is as follows: the upper end of the input filter capacitor C1 is connected to the positive electrode of the power supply V1, the input end of the input voltage sampling module 100, the upper end of the first transformer T1, the upper end of the second transformer T2, the upper end of the first clamp capacitor C2, and the upper end of the second clamp capacitor C3; the lower end of the input filter capacitor C1, the source of the first main pipe S2, the source of the second main pipe S6, and the lower end of the power supply V1 are connected to the primary ground; the lower end of the first clamp capacitor C2 is connected to the first clamp The drain of the first clamping tube S1 is connected; the source of the first clamping tube S1 and the lower end of the first transformer T1 are connected to the drain of the first main pipe S2; the lower end of the second clamping capacitor C3 is connected to the drain of the second clamping tube S5; the source of the second clamping tube S5 and the lower end of the second transformer T2 are connected to the drain of the second main pipe S6; the gate of the first clamping tube S1, the gate of the first main pipe S2, the gate of the second clamping tube S5, and the gate of the second main pipe S6 are connected to the output terminals S1, S2, S5, and S6 of the controller module 300.

[0083] The connection relationship between the secondary sides of the first transformer T1 and the second transformer T2 is as follows: the upper end of the first transformer T1, the upper end of the second transformer T2, and the drain of the synchronous freewheeling tube S4 are connected to the input end of the output inductor Lo; the lower end of the first transformer T1 is connected to the drain of the first synchronous rectifier S3; the lower end of the second transformer T2 is connected to the drain of the second synchronous rectifier S7; the source of the first synchronous rectifier S3, the source of the second synchronous rectifier S7, the source of the synchronous freewheeling tube S4, the lower end of the output capacitor C4, and the lower end of the load resistor Ro are connected to the secondary ground; the output end of the output inductor Lo, the upper end of the output capacitor C4, and the input end of the output voltage sampling module 200 are connected to the upper end of the load resistor Ro; the gate of the first synchronous rectifier S3, the gate of the second synchronous rectifier S7, and the gate of the synchronous freewheeling tube S4 are connected to the output ends S3, S4, and S7 of the controller module 300.

[0084] Specific working principle of the embodiment:

[0085] Step 1: Input voltage Vin is input into input voltage sampling module 100, divided by resistors R1 and R2, and then transmitted to controller module 300 as Vin_sense signal through isolation amplifier U1 to participate in the calculation of conduction time of synchronous freewheeling tube S4.

[0086] Step 2: The output voltage Vo is input to the output voltage sampling module 200, and after voltage division by resistors R3 and R4, it is output as the Vo_sense signal to the controller module 300 for comparison with Vo_ref;

[0087] Step 3: The Vo_sense signal is compared with the expected output voltage Vo_ref in the controller module 300 and then output to the on-time calculation. The on-time of each switch tube except the synchronous rectifier tube is calculated, and the on-time required by the synchronous freewheeling tube S4 and the on-time in the continuous working mode are obtained in conjunction with the Vin_sense signal.

[0088] If the required on-time calculated in step 4 is less than the on-time in the continuous working mode, it is determined that the converter is working in the discontinuous working mode, and the on-time of the synchronous freewheeling tube S4 is the required on-time calculated; otherwise, the converter is working in the continuous working mode, and the on-time of the synchronous freewheeling tube S4 is the on-time in the continuous mode.

[0089] In step 5, the conduction time of all tubes will enter the PWM modulation module for conversion to generate corresponding PWM signals, which are used to control the PWM signals of the primary tubes and input them into the isolated drive output to obtain the drive signals S1, S2, S5, and S6 of the primary tubes; and are used to control the PWM signals of the secondary tubes and input them into the drive output to obtain the drive signals S3, S4, and S7 of the secondary tubes; all drive signals are finally output to the interleaved active clamp forward main circuit module 400 to control the operation of the main circuit and achieve the effect of the present invention.

[0090] According to the above contents of the present invention, by using common technical knowledge and customary means in the field, without departing from the above basic technical ideas of the present invention, the specific implementation circuit in the present invention may also be modified, replaced or changed in other various forms, all of which fall within the scope of protection of the present invention.

Claims

1. A secondary side adaptive drive control circuit, characterized in that: The secondary side adaptive drive control circuit comprises: An input voltage sampling module is used to obtain the power supply input voltage; An output voltage sampling module is used to obtain the output voltage of the converter; A controller module, used to determine the conduction time of the synchronous freewheeling tube according to the input voltage signal and the output voltage signal, generate a synchronous freewheeling drive signal and output it; The staggered active clamp forward main circuit module is used to receive and control the conduction of the synchronous freewheeling tube according to the synchronous freewheeling drive signal.

2. The secondary side adaptive drive control circuit according to claim 1, characterized in that: The staggered active clamp forward main circuit module includes a first active clamp forward circuit, a second active clamp forward circuit, an input capacitor, a synchronous freewheeling tube, an output inductor and an output capacitor. The positive output end of the first active clamp forward circuit and the positive output end of the second active clamp forward circuit are both connected to the drain of the synchronous freewheeling tube, the negative output end of the first active clamp forward circuit and the negative output end of the second active clamp forward circuit are both connected to the source of the synchronous freewheeling tube, and the gate of the synchronous freewheeling tube is connected to the synchronous freewheeling drive signal. , the drain of the synchronous freewheeling tube is connected to the drain of the output capacitor through the output inductor, the source of the synchronous freewheeling tube is connected to the source of the output capacitor, the drain of the output capacitor is connected to the input end of the output voltage sampling module, the input end of the first active clamping forward circuit and the input end of the second active clamping forward circuit are both connected to the input end of the input voltage sampling module, the input end of the first active clamping forward circuit is connected to the first end of the input capacitor, and the second end of the input capacitor is connected to the reference ground.

3. The secondary side adaptive drive control circuit according to claim 2, characterized in that: The first active clamp forward circuit includes a first active clamp tube, a first clamp capacitor, a first main pipe, a first synchronous rectifier tube and a first transformer. The drain of the first active clamp tube is connected to the same-name end of the primary winding of the first transformer through the first clamp capacitor. The source of the first active clamp tube is respectively connected to the drain of the first main pipe and the opposite-name end of the primary winding of the first transformer. The same-name end of the secondary winding of the first transformer is connected to the drain of the synchronous freewheeling tube. The opposite-name end of the secondary winding of the first transformer is connected to the drain of the first synchronous rectifier tube. The source of the first synchronous sorting tube is connected to the source of the synchronous freewheeling tube. The gate of the first active clamp tube, the gate of the first main pipe and the gate of the first synchronous rectifier tube are respectively connected to corresponding drive signals. The same-name end of the primary winding of the first transformer is respectively connected to the first end of the first capacitor and the input end of the input voltage sampling module.

4. The secondary side adaptive drive control circuit according to claim 2, characterized in that: The second active clamp forward circuit includes a second active clamp tube, a second clamp capacitor, a second main tube, a second synchronous rectifier tube and a second transformer. The drain of the second active clamp tube is connected to the same-name end of the primary winding of the second transformer through the second clamp capacitor. The source of the second active clamp tube is respectively connected to the drain of the second main tube and the opposite-name end of the primary winding of the second transformer. The same-name end of the secondary winding of the second transformer is connected to the drain of the synchronous freewheeling tube. The opposite-name end of the secondary winding of the second transformer is connected to the drain of the second synchronous rectifier tube. The source of the second synchronous sorting tube is connected to the source of the synchronous freewheeling tube. The gate of the second active clamp tube, the gate of the second main tube and the gate of the second synchronous rectifier tube are respectively connected to corresponding drive signals. The same-name ends of the primary winding of the second transformer are respectively connected to the first end of the input capacitor and the input end of the input voltage sampling module.

5. A control method applied to the secondary side adaptive drive control circuit according to any one of claims 1 to 4, characterized in that: The following steps are involved: Get the power input voltage; Obtaining converter output voltage; Determine the conduction time of the synchronous freewheeling tube according to the input voltage signal and the output voltage signal, generate and output a synchronous freewheeling driving signal; Receive and control the conduction of the synchronous freewheeling tube according to the synchronous freewheeling driving signal.

6. The control method according to claim 5, characterized in that: The method of determining the conduction time of the synchronous freewheeling tube according to the input voltage signal and the output voltage signal, generating and outputting a synchronous freewheeling driving signal specifically includes: Determine the on-time of the continuous working mode and the on-time of the discontinuous working mode according to the input voltage signal and the output voltage signal; Determine the current working mode according to the on-time of the continuous working mode and the on-time of the intermittent working mode; According to the working mode, the conduction time is determined, and then the synchronous freewheeling driving signal is generated and output.

7. The control method according to claim 6, characterized in that: The calculation formula of the on-time of the continuous working mode is: t2' = T / 2 - t1; Wherein, t2' is the conduction time of the continuous working mode, T is the working cycle of the converter, and t1 is the conduction time of the first main pipe or the second main pipe.

8. The control method according to claim 6, characterized in that: The calculation formula for the on-time of the discontinuous working mode is: t2=(Vin / n*t1 / Vo-t1) / 2; Wherein, t2 is the conduction time of the intermittent working mode, Vin is the power input voltage, Vo is the converter output voltage, n is the turns ratio of the first transformer or the second transformer, and t1 is the conduction time of the first main tube or the second main tube.

9. The control method according to claim 6, characterized in that: The determining of the current working mode according to the on-time of the continuous working mode and the on-time of the intermittent working mode is specifically: The intermittent working mode on time is less than the continuous working mode on time, and the current working mode is determined to be the intermittent working mode; The on-time of the intermittent working mode is greater than or equal to the on-time of the continuous working mode, and it is determined that the current working mode is the continuous working mode.

Images