A switching power supply for a dual-drive transformer

Abstract

The present invention provides a switching power supply for a dual-drive transformer, which relates to the technical field of switching power supplies; it includes a voltage input terminal, a transformer assembly, a controller, a high-side switch SW1, a low-side switch SW2, a resistor string, and a voltage output terminal; the transformer assembly is connected to the voltage input terminal, and the transformer assembly includes a first switching transformer L1 and a second switching transformer L2 connected in parallel or in series; the high-side switch SW1 is arranged between the input terminal of the transformer assembly and the controller, and the high-side switch SW1 is controlled to be turned on and off through the controller; the low-side switch SW2 is connected to the output terminal of the transformer assembly, and the low-side switch SW2 is controlled to be turned on and off through the controller; the resistor string is connected between the voltage output terminal and the controller; the beneficial effect of the present invention is that this switching power supply can convert the application of high-frequency transformers and improve the power of the switching power supply.

Description

Technical Field

[0001] The present invention relates to the technical field of switching power supplies, and more specifically, the present invention relates to a switching power supply with a dual-driven transformer. Background Art

[0002] Generally speaking, a switching power supply refers to a power supply that stabilizes the output by controlling the on / off time of a switching element. Since a switching power supply can reduce size and weight while presenting high efficiency, switching power supplies are widely used in electronic devices and apparatuses. A switching power supply includes an inductor (primary side of a high-frequency transformer), a high-side switch (high-frequency signal generation circuit), a low-side switch (secondary side circuit of a high-frequency transformer), and a zero-current sensor (sampling feedback, voltage regulation circuit).

[0003] When it is sensed by the zero-current sensor that the current flowing through the inductor is zero during a boost operation, the switching power supply turns off the high-side switch and operates in discontinuous conduction mode (DCM) to control the negative current flowing through the inductor. However, in a traditional switching power supply, a high-frequency transformer of a certain specification can only be used for a corresponding power supply. If the power exceeds the limit, the temperature of the high-frequency transformer will increase, it will saturate and conduct, damaging the power supply, and the power supply efficiency may also decrease. Summary of the Invention

[0004] In order to overcome the deficiencies of the prior art, the present invention provides a switching power supply with a dual-driven transformer, which can convert the application of the high-frequency transformer and improve the power of the switching power supply.

[0005] The technical solution adopted by the present invention to solve its technical problems is: a switching power supply with a dual-driven transformer, which is improved in that it includes a voltage input terminal, a transformer assembly, a controller, a high-side switch SW1, a low-side switch SW2, a resistor string, and a voltage output terminal;

[0006] The transformer assembly is connected to the voltage input terminal, and the transformer assembly includes a first switching transformer L1 and a second switching transformer L2 connected in parallel or in series;

[0007] The high-side switch SW1 is arranged between the input terminal of the transformer assembly and the controller, and the high-side switch SW1 is controlled to be turned on and off through the controller;

[0008] The low-side switch SW2 is connected to the output terminal of the transformer assembly, and the low-side switch SW2 is controlled to be turned on and off through the controller;

[0009] The resistor string is connected between the voltage output terminal and the controller, and is used to obtain the feedback voltage VFB and transmit the feedback voltage VFB into the controller. The controller obtains the error voltage VER by comparing the feedback voltage VFB with the reference voltage VREF, and controls the on and off of the high-side switch SW1 and the low-side switch SW2 according to the level of the error voltage VER.

[0010] Further, the voltage transformer assembly includes a first switching transformer L1 and a second switching transformer L2 connected in series. After the primary coils of the first switching transformer L1 and the second switching transformer L2 are connected in series, one end thereof is connected to the voltage output terminal;

[0011] The high-side switch SW1 is a field effect transistor Q1, and the low-side switch SW2 is a field effect transistor Q2 and a field effect transistor Q3; the gate of the field effect transistor Q1 is electrically connected to the output terminal of the controller, and the drain of the field effect transistor Q1 is connected to the other end after the primary coils of the first switching transformer L1 and the second switching transformer L2 are connected in series, and the source of the field effect transistor Q1 is electrically connected to the output terminal of the reference voltage VREF;

[0012] The drain of the field effect transistor Q2 is connected to one end of the secondary side of the first switching transformer L1, and the other end of the secondary side of the first switching transformer L1 is grounded; the drain of the field effect transistor Q3 is connected to one end of the secondary side of the second switching transformer L2, and the other end of the secondary side of the second switching transformer L2 is grounded;

[0013] The gates of the field effect transistor Q2 and the field effect transistor Q3 are connected to the controller.

[0014] Further, the models of the field effect transistor Q1, the field effect transistor Q2, and the field effect transistor Q3 are 20N60.

[0015] Further, a resistor R2 and a capacitor C2 connected in series are provided between the source and the drain of the field effect transistor Q2, and a resistor R3 and a capacitor C3 connected in series are provided between the source and the drain of the field effect transistor Q3.

[0016] Further, a resistor R1, a capacitor C1, and a diode D3 are further provided between the drain of the field effect transistor Q1 and the positive pole of the voltage input terminal. After the resistor R1 and the capacitor C1 are connected in parallel, one end thereof is connected to the positive pole of the voltage input terminal, and the other end is connected to the negative pole of the diode D3, and the positive pole of the diode D3 is connected to the drain of the field effect transistor Q1.

[0017] Further, the resistor string includes an optocoupler U2, a three-terminal voltage regulator U3, a resistor R4, a resistor R5, a resistor R7, a resistor R8, and a capacitor C20;

[0018] The resistor R4 is arranged between the positive pole of the input end of the optocoupler U2 and the positive pole of the voltage input end. The anode of the three-terminal voltage regulator U3 is connected to the negative pole of the voltage input end, and the cathode of the three-terminal voltage regulator U3 is connected to the negative pole of the input end of the optocoupler U2. The capacitor C20 and the resistor R7 are connected in series between the cathode and the reference pole of the three-terminal voltage regulator U3. The resistor R5 and the resistor R8 are connected in series between the positive pole and the negative pole of the voltage input end, and the cathode of the three-terminal voltage regulator U3 is connected to the common end point between the resistor R5 and the resistor R8.

[0019] The positive pole of the output end of the optocoupler U2 is connected to the controller, and the negative pole of the output end of the optocoupler U2 is grounded.

[0020] Further, a resistor R6 is connected between the positive pole and the negative pole of the input end of the optocoupler U2.

[0021] Further, the model of the optocoupler U2 is BPC-817C_DIP_4, and the model of the three-terminal voltage regulator U3 is TL431.

[0022] Further, a capacitor CE1 is arranged between the positive terminal port VIN and the ground terminal GND of the voltage input end.

[0023] Further, the switching power supply of the dual-drive transformer further includes an output capacitor CE2, and this output capacitor CE2 is connected between the positive output port VOUT+ and the negative output port VOUT- of the voltage output end.

[0024] The beneficial effects of the present invention are as follows: It can prevent negative current from flowing to the switching diode, thereby improving the power efficiency while protecting the switching element. In addition, the switching power supply can prevent LC resonance generated by the inductor and the parasitic capacitor, thereby improving the EMI characteristics. Description of the Drawings

[0025] Figure 1 It is a principle block diagram of a switching power supply of a dual-drive transformer of the present invention.

[0026] Figure 2 It is a specific embodiment diagram of a switching power supply of a dual-drive transformer of the present invention.

[0027] Figure 3 It is a waveform diagram of the CS1 switching signal in the present invention.

[0028] Figure 4 It is a voltage waveform diagram after passing through the transformer assembly in the present invention. Detailed Embodiment

[0029] The present invention will be further described below in conjunction with the drawings and embodiments.

[0030] The concept, specific structure and technical effects of the present invention will be clearly and completely described below in conjunction with the embodiments and the drawings, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative efforts all fall within the scope of protection of the present invention. In addition, all connection / connection relationships involved in the patent do not simply refer to the direct connection of components, but refer to the composition of a better connection structure by adding or reducing connection accessories according to specific implementation situations. Each technical feature in the present invention can be interactively combined without mutual contradiction and conflict.

[0031] Referring to Figure 1 As shown, the present invention discloses a switching power supply of a dual-drive transformer. The switching power supply includes a voltage input terminal 10, a transformer assembly 20, a controller 30, a high-side switch SW1, a low-side switch SW2, a resistor string 40 and a voltage output terminal 50; wherein, the transformer assembly 20 is connected to the voltage input terminal 10, and the transformer assembly 20 includes a first switching transformer L1 and a second switching transformer L2 connected in series; in another embodiment, the first switching transformer L1 and the second switching transformer L2 are connected in parallel, which does not affect the normal operation of the switching power supply of the present invention.

[0032] Combined with Figure 1 As shown, the high-side switch SW1 is arranged between the input end of the transformer assembly 20 and the controller 30, and the on-off control of the high-side switch SW1 is realized through the controller 30; the low-side switch SW2 is connected to the output end of the transformer assembly 20, and the on-off control of the low-side switch SW2 is realized through the controller 30; the resistor string 40 is connected between the voltage output terminal 50 and the controller 30, and is used to obtain the feedback voltage VFB and transmit the feedback voltage VFB into the controller 30. The controller 30 obtains the error voltage VER by comparing the feedback voltage VFB with the reference voltage VREF, and controls the on-off of the high-side switch SW1 and the low-side switch SW2 according to the level of the error voltage VER.

[0033] In the above embodiments, the secondary inductance of the first switching transformer L1 is configured to form a first circuit path between the voltage transformer assembly 20 and the output voltage terminal, and the secondary inductance of the second switching transformer L2 is configured to form a second circuit path between the voltage transformer assembly 20 and the output voltage terminal; by detecting the current in the first circuit path, when the detected current is greater than or equal to a negative current of a preset value, an overcurrent protection signal is generated by the controller 30; at the same time, the controller 30 activates the discontinuous conduction mode (DCM) when generating the overcurrent protection signal, and in response to the activated DCM, disconnects the high-side switch SW1 and turns on the low-side switch SW2.

[0034] Therefore, in this embodiment, when the current detected by the controller 30 is greater than or equal to a negative current of a preset value, the switching power supply can disconnect the high-side switch SW1 and perform control to keep the low-side switch SW2 in the on state until the inductor assembly reaches the zero-current position; thus, the switching power supply can prevent the negative current from flowing through the switching diode, improve the power efficiency, and protect the switching element. In addition, when the DCM is activated, the switching power supply can electrically connect the two terminals of the inductor assembly, prevent the negative current from flowing to the switching diode, thereby improving the power efficiency and protecting the switching element. In addition, the switching power supply can prevent the LC resonance generated by the inductor and the parasitic capacitor, thereby improving the EMI characteristics.

[0035] Refer to Figure 2 As shown, for a switching power supply with a dual-drive transformer according to the present invention, a specific embodiment is proposed. In this embodiment, the voltage transformer assembly 20 includes a first switching transformer L1 and a second switching transformer L2 connected in series. After the primary coils of the first switching transformer L1 and the second switching transformer L2 are connected in series, one end thereof is connected to the voltage output terminal 50; in addition, a capacitor CE1 is provided between the positive terminal VIN and the ground terminal GND of the voltage input terminal 10.

[0036] In this embodiment, the high-side switch SW1 is a field effect transistor Q1, and the low-side switches SW2 are a field effect transistor Q2 and a field effect transistor Q3; it should be noted that the field effect transistors Q1, Q2, and Q3 are N-channel field effect transistors; in this embodiment, the models of the field effect transistors Q1, Q2, and Q3 are 20N60. In another specific embodiment, the field effect transistors Q1, Q2, and Q3 can also be P-channel field effect transistors.

[0037] Further, continue to refer to Figure 2As shown, specific descriptions are made regarding its connection relationships. The gate of the field effect transistor Q1 is electrically connected to the output terminal of the controller 30. The drain of the field effect transistor Q1 is connected to the other end after the primary coils of the first switching transformer L1 and the second switching transformer L2 are connected in series. The source of the field effect transistor Q1 is electrically connected to the output terminal of the reference voltage VREF. A resistor R15 is also provided between the source of the field effect transistor Q1 and the ground terminal. The drain of the field effect transistor Q2 is connected to one end of the secondary side of the first switching transformer L1, and the other end of the secondary side of the first switching transformer L1 is grounded. The drain of the field effect transistor Q3 is connected to one end of the secondary side of the second switching transformer L2, and the other end of the secondary side of the second switching transformer L2 is grounded. The gates of the field effect transistor Q2 and the field effect transistor Q3 are connected to the controller 30.

[0038] In addition, a resistor R1, a capacitor C1, and a diode D3 are also provided between the drain of the field effect transistor Q1 and the positive pole of the voltage input terminal 10. After the resistor R1 and the capacitor C1 are connected in parallel, one end thereof is connected to the positive pole of the voltage input terminal 10, and the other end is connected to the negative pole of the diode D3. The positive pole of the diode D3 is connected to the drain of the field effect transistor Q1. A series-connected resistor R2 and capacitor C2 are provided between the source and the drain of the field effect transistor Q2. A series-connected resistor R3 and capacitor C3 are provided between the source and the drain of the field effect transistor Q3.

[0039] In the above embodiment, the switching power supply of the dual-drive transformer further includes an output capacitor CE2, and this output capacitor CE2 is connected between the positive output port VOUT+ and the negative output port VOUT- of the voltage output terminal 50. The output capacitor CE2 is charged through the circuit path formed between the voltage transformer assembly 20 and the output voltage terminal V0UT when the high-side switch SW1 is turned on, and discharges through the output voltage terminal VOUT when the high-side switch SW1 is turned off. The switching power supply boosts the input voltage VIN through the current path formed by the on / off of the low-side switch SW2 and the high-side switch SW1 to generate the output voltage VOUT. Through the current path formed by the on / off of the low-side switch SW2 and the high-side switch SW1, the current flowing through the voltage transformer assembly 20 linearly increases or decreases.

[0040] For example, when the low-side switch SW2 is turned on and the high-side switch SW1 is turned off, a circuit path is formed between the input voltage terminal VIN and the ground voltage terminal, and the current of the inductor component increases linearly. On the other hand, when the low-side switch SW2 is turned off and the high-side switch SW1 is turned on, a circuit path is formed between the input voltage terminal VIN and the output voltage terminal VOUT, and the current of the inductor component decreases linearly. In this way, the low-side switch SW2 and the high-side switch SW1 are alternately turned on / off, and the input voltage VIN is boosted to the output voltage VOUT through the current path formed by the on / off of the low-side switch SW2 and the high-side switch SW1.

[0041] The voltage of the two terminals of the high-side switch SW1 is sensed by a negative current sensor, and the negative current is sensed by using the voltage difference between the terminals; when the current of the transformer component 20 is sensed as a negative current greater than or equal to a preset value, the negative current sensor generates a negative overcurrent protection signal N-OCP. When the controller 30 receives the negative overcurrent protection signal N-OCP, the controller 30 activates the DCM; in response to the DCM, the controller 30 turns off the high-side switch SW1 and turns on the low-side switch SW2.

[0042] At this time, the controller 30 can be configured to perform control to keep the low-side switch SW2 in the on state from the time point when the DCM is activated to the time point when the current of the transformer component 20 is determined to be close to zero. For example, the controller 30 can determine the off time of the low-side switch SW2 by timing a preset time from the time point when the negative overcurrent protection signal N-OCP is generated, or turn off the low-side switch SW2 at the time point when the current of the transformer component 20 reaches zero.

[0043] The controller 30 provides a control signal CS1 to control the on / off of the high-side switch SW1, and provides a control signal CS2 to control the on / off of the low-side switch SW2. Refer to Figure 3 As shown, it is the waveform diagram of the CS1 switch signal. Refer to Figure 4 As shown, it is the voltage waveform diagram after passing through the transformer component.

[0044] When a negative current greater than or equal to a preset value is sensed, when the switching power supply with the above configuration can generate a negative overcurrent protection signal N-OCP, the switching power supply can turn off the high-side switch SW1 and maintain the on state of the low-side switch SW2 until the current of the transformer component 20 is determined to be close to zero. Therefore, the switching power supply can prevent the negative current from flowing to the diode of the switch, thereby improving the power efficiency while protecting the switching element.

[0045] In addition, the positive current sensor senses the positive current by using the voltage difference between the two terminals of the low-side switch SW2. When a positive current greater than or equal to a preset value is sensed, the positive current sensor can generate a positive over-current protection signal P-OCP. When the positive over-current protection signal P-OCP is received, the controller 30 can generate control signals CS1 and CS2 for controlling the high-side switch SW1 and the low-side switch SW2. For example, when the positive over-current protection signal P-COP is generated, the controller 30 can turn off the low-side switch SW2 and turn on the high-side switch SW1.

[0046] Regarding the resistor string 40, as shown Figure 2 In this embodiment, the resistor string 40 includes an optocoupler U2, a three-terminal voltage regulator U3, a resistor R4, a resistor R5, a resistor R7, a resistor R8, and a capacitor C20. The resistor R4 is disposed between the positive pole of the input terminal of the optocoupler U2 and the positive pole of the voltage input terminal 10. The anode of the three-terminal voltage regulator U3 is connected to the negative pole of the voltage input terminal 10, and the cathode of the three-terminal voltage regulator U3 is connected to the negative pole of the input terminal of the optocoupler U2. The capacitor C20 and the resistor R7 are connected in series between the cathode and the reference pole of the three-terminal voltage regulator U3. The resistor R5 and the resistor R8 are connected in series between the positive pole and the negative pole of the voltage input terminal 10, and the cathode of the three-terminal voltage regulator U3 is connected to the common terminal between the resistor R5 and the resistor R8. The positive pole of the output terminal of the optocoupler U2 is connected to the controller 30, and the negative pole of the output terminal of the optocoupler U2 is grounded. A resistor R6 is connected between the positive pole and the negative pole of the input terminal of the optocoupler U2. In this embodiment, the model of the optocoupler U2 is BPC-817C_DIP_4, and the model of the three-terminal voltage regulator U3 is TL431.

[0047] In the above embodiment, the resistor string 40 outputs a feedback voltage VFB obtained by dividing the output voltage VOUT, and amplifies the difference between the reference voltage VREF and the feedback voltage VFB by an operational amplifier, and outputs an error voltage VER. The controller 30 controls the on / off of the high-side switch SW1 according to the level of the error voltage VER. For example, when the error voltage VER is lower than the preset voltage, the controller 30 turns on the high-side switch SW1 and turns off the low-side switch SW2. On the other hand, when the error voltage VER is higher than the preset voltage, the controller 30 turns off the high-side switch SW1 and turns on the low-side switch SW2.

[0048] In discontinuous conduction mode (CCM), the controller 30 controls the turning on / off of the high-side switch SW1 and the low-side switch SW2 according to the level of the error voltage VER. In DCM, regardless of the error voltage VER, the controller 30 turns off the high-side switch SW1 and maintains the on-state of the low-side switch SW2 from the time point when DCM is activated to the time point when the inductor component current is determined to be close to zero.

[0049] The above has specifically described the preferred embodiments of the present invention, but the present invention is not limited to the described embodiments. Those skilled in the art can also make various equivalent deformations or substitutions without departing from the spirit of the present invention, and these equivalent deformations or substitutions are all included within the scope defined by the claims of this application.

Claims

1. A switching power supply for a dual-drive transformer, characterized in that, It includes a voltage input terminal, a transformer component, a controller, a high-side switch SW1, a low-side switch SW2, a resistor string, and a voltage output terminal; The transformer component is connected to the voltage input terminal; The high-side switch SW1 is arranged between the input terminal of the transformer component and the controller, and the on / off control of the high-side switch SW1 is realized through the controller; The low-side switch SW2 is connected to the output terminal of the transformer component, and the on / off control of the low-side switch SW2 is realized through the controller; The resistor string is connected between the voltage output terminal and the controller, and is used to obtain a feedback voltage VFB and transmit the feedback voltage VFB into the controller. The controller obtains an error voltage VER by comparing the feedback voltage VFB with a reference voltage VREF, and controls the on / off of the high-side switch SW1 and the low-side switch SW2 according to the level of the error voltage VER; The transformer component includes a first switching transformer L1 and a second switching transformer L2 connected in series. After the primary coils of the first switching transformer L1 and the second switching transformer L2 are connected in series, one end of them is connected to the voltage output terminal; The high-side switch SW1 is a field effect transistor Q1, and the low-side switch SW2 is a field effect transistor Q2 and a field effect transistor Q3; the gate of the field effect transistor Q1 is electrically connected to the output terminal of the controller, the drain of the field effect transistor Q1 is connected to the other end after the primary coils of the first switching transformer L1 and the second switching transformer L2 are connected in series, and the source of the field effect transistor Q1 is electrically connected to the output terminal of the reference voltage VREF; The drain of the field effect transistor Q2 is connected to one end of the secondary side of the first switching transformer L1, and the other end of the secondary side of the first switching transformer L1 is grounded; the drain of the field effect transistor Q3 is connected to one end of the secondary side of the second switching transformer L2, and the other end of the secondary side of the second switching transformer L2 is grounded; The gates of the field effect transistor Q2 and the field effect transistor Q3 are connected to the controller.

2. The switching power supply of a dual-drive transformer according to claim 1, wherein The models of the field effect transistor Q1, the field effect transistor Q2, and the field effect transistor Q3 are 20N60.

3. The switching power supply of a dual-drive transformer according to claim 1, wherein A resistor R2 and a capacitor C2 connected in series are arranged between the source and the drain of the field effect transistor Q2, and a resistor R3 and a capacitor C3 connected in series are arranged between the source and the drain of the field effect transistor Q3.

4. The switching power supply of a dual-drive transformer according to claim 1, wherein A resistor R1, a capacitor C1, and a diode D3 are also arranged between the drain of the field effect transistor Q1 and the positive pole of the voltage input terminal. After the resistor R1 and the capacitor C1 are connected in parallel, one end of them is connected to the positive pole of the voltage input terminal, and the other end is connected to the negative pole of the diode D3. The positive pole of the diode D3 is connected to the drain of the field effect transistor Q1.

5. The switching power supply of a dual-drive transformer according to claim 1, wherein, The resistor string includes an optocoupler U2, a three-terminal voltage regulator U3, a resistor R4, a resistor R5, a resistor R7, a resistor R8, and a capacitor C20; The resistor R4 is arranged between the positive electrode of the input end of the optocoupler U2 and the positive electrode of the voltage input end. The anode of the three-terminal voltage regulator U3 is connected to the negative electrode of the voltage input end, and the cathode of the three-terminal voltage regulator U3 is connected to the negative electrode of the input end of the optocoupler U2. The capacitor C20 and the resistor R7 are connected in series between the cathode and the reference electrode of the three-terminal voltage regulator U3. The resistor R5 and the resistor R8 are connected in series between the positive electrode and the negative electrode of the voltage input end, and the cathode of the three-terminal voltage regulator U3 is connected to the common end point between the resistor R5 and the resistor R8. The positive electrode of the output end of the optocoupler U2 is connected to the controller, and the negative electrode of the output end of the optocoupler U2 is grounded.

6. The switching power supply of a dual-drive transformer according to claim 5, characterized in that, A resistor R6 is connected between the positive electrode and the negative electrode of the input end of the optocoupler U2.

7. The switching power supply of a dual-drive transformer according to claim 5, characterized in that, The model of the optocoupler U2 is BPC-817C_DIP_4, and the model of the three-terminal voltage regulator U3 is TL431.

8. The switching power supply of a dual-drive transformer according to claim 1, wherein A capacitor CE1 is arranged between the positive terminal port VIN and the ground terminal GND of the voltage input end.

9. The switching power supply of a dual-drive transformer according to claim 1, wherein, The switching power supply of the dual-drive transformer further includes an output capacitor CE2, and the output capacitor CE2 is connected between the positive output port VOUT+ and the negative output port VOUT- of the voltage output end.

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