A synchronous rectification control circuit based on current detection

Abstract

The present invention discloses a synchronous rectification control circuit based on current detection, belonging to the field of power supply technology. It includes connecting a current transformer CT in series to the synchronous rectification side, sampling the current on the synchronous rectification side by the CT, obtaining a current zero-crossing detection signal through a zero-crossing detection circuit, and outputting the current zero-crossing detection signal to a control circuit. The control circuit is controlled by the current zero-crossing detection signal to obtain an output synchronous rectifier control signal, solving the technical problem of high-precision and high-speed control of the synchronous rectifier. The present invention utilizes the characteristic that the current is flowing in the multi-winding side of the CT is synchronous with the conduction of the diodes in the bridge rectifier to achieve the control of the synchronous rectifier, and uses the voltage drop of the diodes to achieve high-speed flipping, realizing high-precision high-speed control, and the circuit is simple and the cost is relatively low. The present invention has a wide range of applications and can automatically form a dead zone according to the voltage drop of the diodes to prevent through conduction.

Description

Technical Field

[0001] The present invention belongs to the technical field of power supplies and relates to a synchronous rectification control circuit based on current detection. Background Art

[0002] Currently, synchronous rectification technology is widely used in various high-efficiency power supply applications. It is crucial for improving efficiency and reducing losses, especially in the field of high-current applications. However, the control of synchronous rectification is relatively complex, and it is prone to reliability risks while achieving high efficiency.

[0003] Defects and deficiencies of the prior art:

[0004] The main control method of the prior art is to control the corresponding synchronous rectifier tube based on the timing of the primary switching tube. For this control method to be implemented, precise sampling of the primary timing is required. Generally, a digital signal processor is needed for signal processing and sending it to the synchronous rectification side. The design is complex and an isolated drive circuit is required, resulting in a high cost.

[0005] In the prior art, there is also synchronous rectification control based on the voltage drop across the DS terminal of the synchronous rectifier tube. This control method requires relatively accurate sampling of the voltage drop across the DS terminal and also requires a filter circuit to process the interference generated at the DS terminal of the synchronous rectifier tube. Additionally, in this implementation method, the parasitic parameters generated by the circuit board layout will interfere with the control, and a compensation circuit is needed to offset this influence. The circuit design is complex, the requirements for circuit board layout are high, and the cost is also high. Summary of the Invention

[0006] The purpose of the present invention is to provide a synchronous rectification control circuit based on current detection, which solves the technical problem of high-precision and high-speed control of the synchronous rectifier tube.

[0007] To achieve the above purpose, the present invention adopts the following technical solutions:

[0008] A synchronous rectification control circuit based on current detection includes a current transformer CT connected in series to the synchronous rectification side. The CT samples the current on the synchronous rectification side, and a zero-crossing detection circuit obtains a current zero-crossing detection signal and outputs the current zero-crossing detection signal to a control circuit. The control circuit is controlled by the current zero-crossing detection signal to obtain an output synchronous rectifier tube control signal.

[0009] According to an embodiment of the present invention, the synchronous rectification side includes a transformer T and an IGBT drive bridge circuit. The input end of the IGBT drive bridge circuit is connected to the secondary side of the transformer T, the primary side of the transformer T is connected to an external power supply, and a capacitor C1 is a filter capacitor at the output end of the IGBT drive bridge circuit. The current transformer CT is arranged on the secondary side of the transformer T and is used to sample the current on the secondary side of the transformer T.

[0010] According to an embodiment of the present invention, the zero-crossing detection circuit includes diode D1, diode D2, diode D3, diode D4, resistor R1, diode D5, diode D6, resistor R2, resistor R3, resistor R4, resistor R5, triode Q1 and triode Q2. The positive electrode of diode D1 is connected to the positive output terminal of the current transformer CT and the negative electrode of diode D2. The positive electrode of diode D2 is connected to the ground wire. The positive electrode of diode D4 is connected to the ground wire and the negative electrode is connected to the negative output terminal of the current transformer CT. The positive electrode of diode D3 is connected to the negative output terminal of the current transformer CT and the negative electrode is connected to the negative electrode of diode D1. The negative electrode of diode D3 is connected to the ground wire through resistor R1;

[0011] The negative electrode of diode D5 is connected to the positive output terminal of the current transformer CT and the positive electrode is connected to the base of triode Q1. The emitter of triode Q1 is connected to the ground wire and the collector is connected to the positive electrode of power supply VCC through resistor R3. The negative electrode of power supply VCC is connected to the ground wire. The base of triode Q1 is connected to the positive electrode of the power supply VCC through resistor R2;

[0012] The collector of triode Q1 outputs voltage Vo1;

[0013] The negative electrode of diode D6 is connected to the negative output terminal of the current transformer CT and the positive electrode is connected to the base of triode Q2. The emitter of triode Q2 is connected to the ground wire and the collector is connected to the positive electrode of power supply VCC through resistor R5. The base of triode Q2 is connected to the positive electrode of power supply VCC through resistor R4. The collector of triode Q2 outputs voltage Vo2.

[0014] According to an embodiment of the present invention, the IGBT drive bridge circuit is composed of IGBT tube Q1, IGBT tube Q2, IGBT tube Q3, IGBT tube Q4 and capacitor C1. IGBT tube Q1, IGBT tube Q2, IGBT tube Q3 and IGBT tube Q4 form a full-bridge drive circuit. The G pole of IGBT tube Q1 is connected to an external control signal and the S pole is connected to pin 1 of the secondary side of the transformer T;

[0015] The G pole of IGBT tube Q2 is connected to an external control signal and the D pole is connected to pin 1 of the secondary side of the transformer T;

[0016] The G pole of IGBT tube Q3 is connected to an external control signal and the S pole is connected to pin 2 of the secondary side of the transformer T;

[0017] The G pole of IGBT tube Q4 is connected to an external control signal and the D pole is connected to pin 2 of the secondary side of the transformer T;

[0018] The S poles of IGBT tube Q2 and IGBT tube Q4 are connected to form a first output terminal;

[0019] The D pole of the IGBT tube Q1 and the D pole of the IGBT tube Q3 are connected to form a second output terminal;

[0020] The first output terminal and the second output terminal form the output terminal of the IGBT drive bridge circuit.

[0021] According to an embodiment of the present invention, the diode D1, the diode D2, the diode D3, and the diode D4 form a bridge rectifier.

[0022] According to an embodiment of the present invention, the voltage Vo1 and the voltage Vo2 are complementary drive voltages.

[0023] According to an embodiment of the present invention, the synchronous rectification side is a full-bridge drive circuit or a half-bridge drive circuit.

[0024] According to an embodiment of the present invention, the transformer T is a transformer with a center tap.

[0025] Advantages of the present invention:

[0026] A synchronous rectification control circuit based on current detection according to the present invention solves the technical problem of high-precision and high-speed control of synchronous rectifier tubes. The present invention utilizes the characteristic that the current is flowing in the CT multi-winding side is synchronized with the conduction of the diodes in the bridge rectifier to control the synchronous rectifier tubes, and utilizes the voltage drop of the diodes to achieve high-speed flipping, realizing high-precision high-speed control, and the circuit is simple and the cost is relatively low. The present invention has wide applications and can automatically form a dead zone according to the voltage drop of the diodes to prevent through conduction. Description of the drawings

[0027] Figure 1 Is the circuit diagram of Embodiment 1;

[0028] Figure 2 Is the current flow diagram when the current ip in the CT few-turn side changes from negative to positive and passes through zero in Embodiment 1;

[0029] Figure 3 Is the current flow diagram when the current ip in the CT large-current side changes from positive to negative and passes through zero in Embodiment 1;

[0030] Figure 4 Is the circuit diagram of the synchronous rectification side in Embodiment 1;

[0031] Figure 5 Is the circuit diagram of the synchronous rectification side in Embodiment 2;

[0032] Figure 6 Is the circuit diagram of the synchronous rectification side in Embodiment 3;

[0033] Figure 7 This is the voltage waveform diagram of the present invention. Detailed implementation manners

[0034] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with 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, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. Embodiment

[0035] As Figures 1 - 4 shown, a synchronous rectification control circuit based on current detection includes connecting a current transformer CT in series to the synchronous rectification side. The CT samples the current on the synchronous rectification side, and obtains a current zero-crossing detection signal through a zero-crossing detection circuit, and outputs the current zero-crossing detection signal to a control circuit. The control circuit is controlled by the current zero-crossing detection signal to obtain an output synchronous rectifier control signal.

[0036] The control circuit is an external controller, and the external controller is an ARM controller or an FPGA controller.

[0037] Preferably, the synchronous rectification side includes a transformer T (the Main Transformer in the figure is the main transformer), an IGBT drive bridge circuit. The input end of the IGBT drive bridge circuit is connected to the secondary side of the transformer T, the primary side of the transformer T is connected to an external power supply, and the capacitor C1 is a filter capacitor at the output end of the IGBT drive bridge circuit. The current transformer CT is disposed on the secondary side of the transformer T for sampling the current on the secondary side of the transformer T.

[0038] Preferably, the zero-crossing detection circuit includes diodes D1, D2, D3, D4, resistor R1, diode D5, D6, resistors R2, R3, R4, R5, transistor Q1 and transistor Q2. The positive electrode of diode D1 is connected to the positive output terminal of the current transformer CT and the negative electrode of diode D2. The positive electrode of diode D2 is connected to the ground wire. The positive electrode of diode D4 is connected to the ground wire and the negative electrode is connected to the negative output terminal of the current transformer CT. The positive electrode of diode D3 is connected to the negative output terminal of the current transformer CT and the negative electrode is connected to the negative electrode of diode D1. The negative electrode of diode D3 is connected to the ground wire through resistor R1;

[0039] The negative electrode of the diode D5 is connected to the positive output terminal of the current transformer CT, and the positive electrode is connected to the base of the triode Q1. The emitter of the triode Q1 is connected to the ground wire, and the collector is connected to the positive electrode of the power supply VCC through the resistor R3. The negative electrode of the power supply VCC is connected to the ground wire. The base of the triode Q1 is connected to the positive electrode of the power supply VCC through the resistor R2;

[0040] The collector of the triode Q1 outputs the voltage Vo1;

[0041] The negative electrode of the diode D6 is connected to the negative output terminal of the current transformer CT, and the positive electrode is connected to the base of the triode Q2. The emitter of the triode Q2 is connected to the ground wire, and the collector is connected to the positive electrode of the power supply VCC through the resistor R5. The base of the triode Q2 is connected to the positive electrode of the power supply VCC through the resistor R4. The collector of the triode Q2 outputs the voltage Vo2.

[0042] Preferably, the IGBT drive bridge circuit consists of IGBT tubes Q1, Q2, Q3, Q4 and a capacitor C1. The IGBT tubes Q1, Q2, Q3 and Q4 form a full-bridge drive circuit. The G pole of the IGBT tube Q1 is connected to an external control signal, and the S pole is connected to pin 1 of the secondary side of the transformer T;

[0043] The G pole of the IGBT tube Q2 is connected to an external control signal, and the D pole is connected to pin 1 of the secondary side of the transformer T;

[0044] The G pole of the IGBT tube Q3 is connected to an external control signal, and the S pole is connected to pin 2 of the secondary side of the transformer T;

[0045] The G pole of the IGBT tube Q4 is connected to an external control signal, and the D pole is connected to pin 2 of the secondary side of the transformer T;

[0046] The S poles of the IGBT tube Q2 and the IGBT tube Q4 are connected to form a first output terminal;

[0047] The D poles of the IGBT tube Q1 and the IGBT tube Q3 are connected to form a second output terminal;

[0048] The first output terminal and the second output terminal form the output terminal of the IGBT drive bridge circuit.

[0049] Preferably, the diodes D1, D2, D3 and D4 form a bridge rectifier.

[0050] Preferably, the voltages Vo1 and Vo2 are complementary drive voltages.

[0051] Preferably, the synchronous rectification side is a full-bridge drive circuit or a half-bridge drive circuit.

[0052] Preferably, the transformer T is a transformer with a center tap.

[0053] In this embodiment, the current transformer CT changes the current ip on the large-current side to a smaller current is through the turn ratio of the transformer, and then detects the current.

[0054] When the current ip on the few-turn side of the current transformer CT crosses zero from negative to positive, the current signal is sampled in the current transformer CT along Figure 2 When flowing through the loop shown, that is, input from the positive pole of the diode D1, flowing through the resistor R1 to the negative output terminal of the current transformer CT, at this time the diode D6 conducts, the triode Q2 turns off, the voltage Vo2 outputs a high level, and at this time the diode D2 turns off, the diode D5 turns off, the triode Q1 conducts, and the voltage Vo1 outputs a low level. In this way, two complementary drive signals are output by two circuits, that is, the voltage Vo2 and the voltage Vo1 are complementary.

[0055] When the current ip on the large-current side of the current transformer CT crosses zero from positive to negative, the current signal is sampled in the current transformer CT along Figure 3 When flowing through the loop shown, the diode D6 turns off, the triode Q1 conducts, the voltage Vo2 outputs a low level, and at this time the diode D2 turns on, the diode D5 turns on, the triode Q1 turns off, and the voltage Vo1 outputs a high level. In this way, the two output signals are inverted, and due to the voltage drop when the diode conducts, a dead zone of two complementary signals is naturally formed. If a drive bridge circuit is used, it can prevent through conduction.

[0056] As Figure 7 is the voltage waveform diagram of the present invention. It can be seen from the figure that the voltages Vo1 and Vo2 are complementary in time sequence. Embodiment

[0057] The difference between Embodiment 2 and Embodiment 1 is that:

[0058] As Figure 5 shown, the synchronous rectification side includes IGBT tubes Q5, Q6 and capacitor C2. The D pole of IGBT tube Q5 is connected to pin 1 of the secondary side of transformer T, the S pole is connected to the S pole of IGBT tube Q6, the D pole of IGBT tube Q6 is connected to pin 2 of the secondary side of transformer T, pin 3 of transformer T, that is, the center tap is connected to the positive pole of capacitor C3, and the negative pole of capacitor C3 is connected to pin 2 of the secondary side of transformer T;

[0059] The current transformer CT is provided at the 1st pin of the secondary side of the transformer T, and is used to collect the current of the 1st pin of the secondary side of the transformer T.

[0060] In Embodiment 2, the circuit structure and principle of the zero-crossing detection circuit are the same as those in Embodiment 1. Embodiment

[0061] As Figure 6 shown, the difference between Embodiment 3 and Embodiment 1 is that the synchronous rectification side includes IGBT tubes Q5, Q6 and capacitor C2. The D pole of IGBT tube Q5 is connected to the 1st pin of the secondary side of the transformer T, and the S pole is connected to the S pole of IGBT tube Q6. The D pole of IGBT tube Q6 is connected to the 2nd pin of the secondary side of the transformer T. The 3rd pin of the transformer T, that is, the center tap, is connected to the positive pole of capacitor C3, and the negative pole of capacitor C3 is connected to the 2nd pin of the secondary side of the transformer T.

[0062] The current transformer CT is provided at the 3rd pin of the secondary side of the transformer T, and is used to collect the current of the 3rd pin of the secondary side of the transformer T, that is, to collect the current signal of the center tap of the transformer T.

[0063] In Embodiment 3, the circuit structure and principle of the zero-crossing detection circuit are the same as those in Embodiment 1.

[0064] A synchronous rectification control circuit based on current detection according to the present invention solves the technical problem of high-precision and high-speed control of synchronous rectifier tubes. The present invention utilizes the characteristic that the current is flowing in the multi-winding side of CT is synchronous with the conduction of the diodes in the bridge rectifier to realize the control of the synchronous rectifier tubes, and utilizes the voltage drop of the diodes to realize high-speed flipping, achieving high-precision high-speed control, and the circuit is simple and the cost is relatively low. The present invention has wide applications and can automatically form a dead zone according to the voltage drop of the diodes to prevent through conduction.

[0065] Any process or method description described in the present invention can be understood as representing a module, segment or part of code including one or more executable instructions for implementing a customized logic function or process, and the scope of the preferred embodiments of the present invention includes additional implementations, where the functions can be executed in a substantially simultaneous manner or in the reverse order according to the involved functions, rather than in the order shown or discussed, which should be understood by those skilled in the technical field to which the embodiments of the present invention belong.

[0066] The logic and / or steps described in this invention, for example, can be considered as a defined sequence list of executable instructions for implementing logical functions, and can be specifically implemented in any computer-readable medium for use by an instruction execution system, apparatus, or device (such as a computer-based system, a system including a processor, or other systems that can fetch and execute instructions from the instruction execution system, apparatus, or device), or in combination with these instruction execution systems, apparatuses, or devices. For the purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate, or transport a program for use by or in combination with an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include the following: an electrical connection portion with one or more wirings (electronic device), a portable computer diskette (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disc read-only memory (CDROM). Additionally, the computer-readable medium can even be paper or other suitable media on which the program can be printed, because the program can be obtained electronically, for example, by optically scanning the paper or other media, followed by editing, interpretation, or other appropriate processing as necessary, and then stored in a computer memory.

[0067] It should be understood that various parts of the present invention can be implemented by hardware, software, firmware, or a combination thereof. In the above-described embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, any one or a combination of the following techniques well-known in the art can be used: discrete logic circuits having logic gate circuits for implementing logical functions on data signals, application-specific integrated circuits having appropriate combinational logic gate circuits, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0068] Those of ordinary skill in the art of this technology can understand that all or part of the steps carried by the methods of the above-described embodiments can be completed by instructing relevant hardware through a program, and the program can be stored in a computer-readable storage medium. When the program is executed, it includes one or a combination of the steps of the method embodiments.

[0069] In addition, each functional unit in various embodiments of the present invention may be integrated into a processing module, may exist physically separately for each unit, or two or more units may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. When the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0070] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A synchronous rectification control circuit based on current detection, characterized in that: It includes connecting a current transformer CT in series to the synchronous rectification side, sampling the current on the synchronous rectification side by the CT, obtaining a current zero-crossing detection signal through a zero-crossing detection circuit, and outputting the current zero-crossing detection signal to a control circuit, and controlling the control circuit by the current zero-crossing detection signal to obtain an output synchronous rectifier control signal; The synchronous rectification side includes a transformer T and an IGBT drive bridge circuit. The input end of the IGBT drive bridge circuit is connected to the secondary side of the transformer T, the primary side of the transformer T is connected to an external power supply, and the capacitor C1 is a filter capacitor at the output end of the IGBT drive bridge circuit. The current transformer CT is arranged on the secondary side of the transformer T and is used to sample the current on the secondary side of the transformer T; The zero-crossing detection circuit includes diodes D1, D2, D3, D4, resistor R1, diode D5, diode D6, resistor R2, resistor R3, resistor R4, resistor R5, transistor Q1 and transistor Q2. The positive electrode of diode D1 is connected to the positive output end of the current transformer CT and the negative electrode of diode D2. The positive electrode of diode D2 is connected to the ground wire. The positive electrode of diode D4 is connected to the ground wire and the negative electrode is connected to the negative output end of the current transformer CT. The positive electrode of diode D3 is connected to the negative output end of the current transformer CT and the negative electrode is connected to the negative electrode of diode D1. The negative electrode of diode D3 is connected to the ground wire through resistor R1; The negative electrode of diode D5 is connected to the positive output end of the current transformer CT, the positive electrode is connected to the base of transistor Q1. The emitter of transistor Q1 is connected to the ground wire, the collector is connected to the positive electrode of power supply VCC through resistor R3. The negative electrode of power supply VCC is connected to the ground wire. The base of transistor Q1 is connected to the positive electrode of power supply VCC through resistor R2; The voltage Vo1 is output at the collector of transistor Q1; The negative electrode of diode D6 is connected to the negative output end of the current transformer CT, the positive electrode is connected to the base of transistor Q2. The emitter of transistor Q2 is connected to the ground wire, the collector is connected to the positive electrode of power supply VCC through resistor R5. The base of transistor Q2 is connected to the positive electrode of power supply VCC through resistor R4. The voltage Vo2 is output at the collector of transistor Q2.

2. The synchronous rectification control circuit based on current detection according to claim 1, wherein: The IGBT drive bridge circuit consists of IGBT tubes Q1, Q2, Q3, Q4 and capacitor C1. IGBT tubes Q1, Q2, Q3 and Q4 form a full-bridge drive circuit. The G pole of IGBT tube Q1 is connected to an external control signal, and the S pole is connected to pin 1 of the secondary side of the transformer T; The G pole of IGBT tube Q2 is connected to an external control signal, and the D pole is connected to pin 1 of the secondary side of the transformer T; The G pole of IGBT tube Q3 is connected to an external control signal, and the S pole is connected to pin 2 of the secondary side of the transformer T; The G pole of IGBT tube Q4 is connected to an external control signal, and the D pole is connected to pin 2 of the secondary side of the transformer T; The S poles of IGBT tube Q2 and IGBT tube Q4 are connected to form a first output end; The D pole of the IGBT Q1 and the D pole of the IGBT Q3 are connected to form a second output terminal; The first output terminal and the second output terminal form the output terminals of the IGBT drive bridge circuit.

3. The synchronous rectification control circuit based on current detection according to claim 1, characterized in that: The diode D1, the diode D2, the diode D3, and the diode D4 form a bridge rectifier.

4. The synchronous rectification control circuit based on current detection according to claim 1, wherein: The voltage Vo1 and the voltage Vo2 are complementary drive voltages.

5. A synchronous rectification control circuit based on current detection according to claim 1, characterized in that: The synchronous rectification side is a full-bridge drive circuit or a half-bridge drive circuit.

6. The synchronous rectification control circuit based on current detection according to claim 1, wherein: The transformer T is a transformer with a center tap.

Images