A transistor driving circuit for a transistor-driven switching power supply

Abstract

The application discloses a transistor driving circuit for a transistor driving switching power supply, which comprises a driving control circuit, a turn-on switch and a turn-off switch. The turn-on switch is connected between the base and the collector of the transistor. In a single turn-on period of the transistor, the first driving signal is directly increased to a first amplitude to initially turn on the turn-on switch, then increased from the first amplitude to a second amplitude after a first preset time length, and then directly decreased to an amplitude for turning off the turn-on switch after maintaining the second amplitude for a second preset time length. The sum of the first preset time length and the second preset time length is less than the total time required for the transistor from initial turn-on to complete turn-on and maintaining complete turn-on, and the first preset time length is greater than the time required for the transistor from initial turn-on to complete turn-on. The driving circuit of the application greatly improves the loss of the base current in the transistor driving process, optimizes the EMI characteristics of the transistor, and has a simple circuit structure, and therefore has wide applicability.

Description

Technical Field

[0001] This invention relates to the field of switching power supplies, and more particularly to a transistor driving circuit for a transistor-driven switching power supply. Background Technology

[0002] Existing transistor drive circuits such as Figure 1 As shown, it includes a drive control circuit, a drive current Ib0, a control switch S1, and a switching transistor M2. The drive control circuit controls the states of S1 and M2 through output signals K1 and K2, thereby controlling the opening and closing of the NPN transistor. Figure 2 The waveform diagram shows the transistor driving mode under normal operation. When the transistor is on, K2 controls M2 to be off, and K1 controls S1 to be on. The driving current Ib0 flows from the energy storage capacitor C0 through S1 to the transistor driving pin. At this time, the base-collector junction is reverse biased, and the base-emitter junction is forward biased, so the transistor is on. Because the base current is very large when the transistor is on, the transistor turns on quickly. When the transistor is off, K1 controls S1 to be open, the driving current is 0, K2 controls M2 to be closed, and the transistor Q1 is turned off quickly. Since the transistor driving current is powered by the external energy storage capacitor C0, the Vcc voltage is generally around 12V for normal start-up of capacitive loads, and the transistor amplification factor is generally around 15. Therefore, when the primary current Ipk = 1A, the driving current needs to be 66mA. In the worst case, the transistor duty cycle exceeds 50%, 12V x 66mA * 50% = 396mW, resulting in excessive conduction losses. Taking the SOP8 (junction-to-air θjA = 150℃ / W) package as an example, the driving temperature rise reaches 0.396W x 150℃ / W ≈ 60℃. The chip temperature rise is too high, so the transistor has a large conduction loss and efficiency loss when it is turned on. Therefore, it is necessary to optimize the efficiency loss when the transistor is turned on. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a transistor driving circuit for a transistor-driven switching power supply, which addresses the above-mentioned defects of the prior art, such as large conduction loss and efficiency loss when conducting.

[0004] The technical solution adopted by the present invention to solve its technical problem is as follows: a transistor driving circuit for a transistor-driven switching power supply is constructed, wherein the transistor driving switching power supply is connected in series between the input voltage and ground in the output branch, the output branch includes a transistor, the transistor driving circuit includes a driving control circuit, a conducting switch controlled by a first driving signal sent by the driving control circuit, and a turning-off switch controlled by a second driving signal sent by the driving control circuit, wherein the conducting switch is connected between the base and collector of the transistor, the turning-off switch is connected between the base and emitter of the transistor, the conducting switch is turned on and the turning-off switch is turned off during the conduction cycle of the transistor, and the conducting switch is turned off and the turning-off switch is turned on during the turn-off cycle of the transistor;

[0005] During a single conduction cycle of the transistor, the first drive signal first rises directly to a first amplitude and initially turns on the conduction switch, then increases from the first amplitude to a second amplitude after a first preset time, and then maintains the second amplitude for a second preset time before directly decreasing to an amplitude that turns off the conduction switch, so that the current input to the base of the transistor is a dynamically and smoothly changing drive current.

[0006] The sum of the first preset duration and the second preset duration is less than the total time required for the transistor to go from initial conduction to full conduction and to maintain full conduction. The first preset duration is greater than the time required for the transistor to go from initial conduction to full conduction. The second amplitude is the maximum amplitude of the first drive signal, which is limited by the voltage / current of the output branch.

[0007] Preferably, the second preset duration is zero, and the proportion of the first preset duration to the total time is within a fluctuation range centered around 80%.

[0008] Preferably, the first driving signal rises directly from the amplitude that turns off the conduction switch to the first amplitude at the beginning of a single conduction cycle of the transistor, and then smoothly increases from the first amplitude to the second amplitude with a fixed or varying slope, and decreases directly from the second amplitude to the amplitude that turns off the conduction switch before the end of the single conduction cycle.

[0009] The second driving signal is switched directly from the amplitude that turns on the off switch to the amplitude that turns off the off switch at the beginning of a single conduction cycle of the transistor. The amplitude remains unchanged until the end of a single conduction cycle of the transistor, at which point it is switched directly back to the amplitude that turns on the off switch.

[0010] Preferably, the on switch is a MOSFET or a transistor; and / or, the off switch is a transistor or a MOSFET; and / or, a current-limiting resistor or a switching transistor is connected in series between the on switch and the base of the transistor for current limiting.

[0011] Preferably, the transistor-driven switching power supply includes an input circuit and a transformer, the output branch includes the primary side of the transformer, the first end of the primary side of the transformer is connected to the input circuit, the on switch is an NMOS transistor, the drain of the on switch is connected to the collector of the transistor, the source of the on switch is connected to the base of the transistor via a current-limiting resistor, the emitter of the transistor is grounded via a sampling resistor, and the collector of the transistor is connected to the second end of the primary side of the transformer.

[0012] The first driving signal is a voltage signal, and the first amplitude satisfies the following condition:

[0013] V1>Vbe(Q1)+Vth(M1)+Ib1*R0;

[0014] In the above formula, V1 represents the magnitude of the first amplitude, Vbe(Q1) represents the base-emitter voltage of the transistor, Vth(M1) represents the threshold voltage of the turn-on switch, R0 represents the resistance value of the current-limiting resistor, and Ib1 represents the base current when the transistor is initially turned on.

[0015] The second amplitude satisfies the following condition:

[0016] V2>Vbe(Q1)+Vth(M1)+Vs1+Ib2*R0;

[0017] Ib2 = Vs1 / (ka*Rs1);

[0018] In the above formula, V2 represents the magnitude of the second amplitude, Ib2 represents the base current of the transistor when the first driving signal increases to the second amplitude, Vs1 is a fixed voltage value set based on the voltage / current of the output branch, and ka is a constant, which is less than the amplification factor of the transistor.

[0019] Preferably, Ib1 and Ib2 satisfy the following relationship:

[0020] Ib1 = kb * Ib2, 0 < ka < 1;

[0021] kb is a constant, and kb is specifically set according to the model of the transistor.

[0022] Preferably, the shutdown switch is an NMOS transistor, the drain of the shutdown switch is connected to the base of the transistor, and the source of the shutdown switch is grounded or directly connected to the emitter of the transistor.

[0023] Preferably, the number of the conducting switches is multiple, and the multiple conducting switches are connected in parallel; and / or, the number of the shut-off switches is multiple, and the multiple shut-off switches are connected in parallel.

[0024] The transistor driving circuit for a transistor-driven switching power supply of the present invention has the following beneficial effects: A conduction switch is connected between the base and collector of the transistor. Based on the above circuit design, the control signal of the conduction switch within a single conduction cycle of the transistor is optimized. The control signal of the conduction switch is not fixed, but a first driving signal that dynamically changes within the conduction cycle. Specifically, within a single conduction cycle of the transistor, the first driving signal first rises directly to a first amplitude to turn on the conduction switch, then increases from the first amplitude to a second amplitude after a first preset time, maintains the second amplitude for a second preset time, and then directly decreases to the amplitude that turns off the conduction switch. This ensures that the current input to the base of the transistor is a dynamic driving current. Moreover, the sum of the first preset time and the second preset time is less than the total time required for the transistor to go from initial conduction to full conduction and to maintain full conduction. The first preset time is greater than the time required for the transistor to go from initial conduction to full conduction, that is, before the transistor is fully conducted, the dynamic driving current is still... The dynamic drive current is relatively small, and it has not yet reached its maximum value (the maximum value is limited by the voltage / current of the output branch where the transistor is located). After the transistor is fully turned on, the dynamic drive current slowly increases to its maximum value, and it drops from its maximum value before the transistor is fully turned off. Therefore, this invention not only reduces the turn-on loss of the transistor at the moment of turn-on, but also has better efficiency characteristics in both the zero-voltage switching mode and the valley conduction mode of the transistor. Moreover, it can turn off earlier and use the turn-off delay to reduce power loss. In addition, the smooth change of the base current of the transistor drives the transistor, which can also improve EMI during the conduction process, as reflected in the smaller overshoot of the sampling resistor connected in series with the transistor when the transistor is turned on. Moreover, the entire circuit structure is simpler than the traditional circuit, occupies less area, and is easier to package. In summary, the drive circuit of this invention greatly improves the base current loss during transistor drive and optimizes the EMI characteristics of the transistor. Moreover, the entire circuit structure is simpler, thus having wide applicability. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort:

[0026] Figure 1 This is a schematic diagram of an existing transistor drive circuit;

[0027] Figure 2 The waveform diagram shows the existing transistor driving method when it is working normally.

[0028] Figure 3 This is a schematic diagram of a transistor driving circuit according to an embodiment of the present invention;

[0029] Figure 4 This is a waveform diagram of the driving method in an embodiment of the present invention when it is working normally. Detailed Implementation

[0030] To address the shortcomings of existing transistor driver circuits, such as significant conduction losses and efficiency degradation during turn-on, this invention designs a transistor driver circuit for driving transistor-driven switching power supplies. (Refer to...) Figure 3 The present invention connects a turn-on switch M1 between the base and collector of transistor Q1, and a turn-off switch M2 between the base and emitter of transistor Q1. During the conduction cycle of transistor Q1, the turn-on switch M1 is on and the turn-off switch M2 is off; during the turn-off cycle of transistor Q1, the turn-on switch M1 is off and the turn-off switch M2 is on. Based on the above circuit design, we have also optimized the operation of the entire circuit during a single conduction cycle of the transistor. The main optimization is that during a single conduction cycle of the transistor, the control signal of the turn-on switch that controls the conduction of the transistor is not fixed, but a first driving signal that dynamically changes during the conduction cycle. Specifically, within a single conduction cycle of the transistor, the first drive signal first rises directly to a first amplitude to initially turn on the conduction switch, then spends a first preset time increasing from the first amplitude to a second amplitude, and then maintains the second amplitude for a second preset time before directly decreasing to the amplitude that turns off the conduction switch M1. This ensures that the current input to the transistor base is a dynamic drive current. The sum of the first preset time and the second preset time is less than the total time required for the transistor Q1 to go from initial conduction to full conduction and to maintain full conduction. The first preset time is greater than the time required for the transistor Q1 to go from initial conduction to full conduction. That is, before the transistor is fully turned on, the dynamic drive current is still relatively small and has not yet reached its maximum value (the maximum value is limited by the voltage / current of the output branch where the transistor is located). Moreover, after the transistor is fully turned on, the dynamic drive current also slowly increases to its maximum value. Therefore, this invention not only reduces the turn-on loss at the moment of transistor conduction, but also in the transistor zero-voltage switching mode ( Figure 4 (mid-T1 time period) and valley conduction mode ( Figure 4Both the T2 time period and the current distribution exhibit superior efficiency characteristics. Furthermore, the current drops from its maximum value before the transistor fully turns off, allowing for earlier turn-off and reducing power loss through turn-off delay. The smooth change in the transistor's base current also improves EMI during conduction, resulting in a smaller overshoot in the sampling resistor connected in series with the transistor when it turns on. Moreover, the overall circuit structure is simpler, occupies less area, and is easier to package compared to traditional circuits. In summary, the driving circuit of this invention significantly improves base current loss during transistor driving, optimizes transistor EMI characteristics, and has a simpler overall circuit structure, thus possessing broad applicability.

[0031] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Typical embodiments of the invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to make the disclosure of the present invention more thorough and complete. It should be understood that the embodiments of the present invention and the specific features thereof are detailed descriptions of the technical solutions of this application, and not limitations thereof. Where there is no conflict, the embodiments of the present invention and the technical features thereof can be combined with each other.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0033] The terms "first," "second," and other ordinal terms used in this specification are used to describe various constituent elements, but these constituent elements are not limited by these terms. The purpose of using these terms is solely to distinguish one constituent element from others. For example, without departing from the scope of the invention, a first constituent element may be named a second constituent element, and similarly, a second constituent element may be named a first constituent element. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. The term "connected" or "linked" as used in this invention includes not only directly connecting two entities but also indirectly connecting them through other entities that have beneficial improvement effects.

[0034] refer to Figure 3In this embodiment, the transistor driving circuit is applied to a transistor-driven switching power supply. The transistor-driven switching power supply includes an input circuit, a transformer T, and an output circuit. The input circuit provides an input voltage (primarily AC, but DC can also be used). The circuit between the input voltage and ground is defined as the output branch; for example, transistor Q1 and the primary winding of transformer T both belong to the output branch structure. The first end of the primary winding of transformer T is connected to the input circuit, and the second end of the primary winding of transformer T is connected to transistor Q1, which is periodically turned on and off. The two ends of the secondary winding of transformer T are connected to the output circuit. During the conduction period of transistor Q1, the primary winding stores energy; during the turn-off period of transistor Q1, the primary winding converts energy to the secondary winding.

[0035] The transistor driving circuit in this embodiment includes a driving control circuit 1, a turn-on switch M1 controlled by a first driving signal K1 sent by the driving control circuit 1, and a turn-off switch M2 controlled by a second driving signal K2 sent by the driving control circuit 1. The turn-on switch M1 is connected between the base and collector of the transistor Q1 (the connection between the turn-on switch M1 and the collector of the transistor Q1 can be direct or indirect). The turn-off switch M2 is connected between the base and emitter of the transistor Q1 (the connection between the turn-off switch M2 and the emitter of the transistor Q1 can be direct or indirect). During the conduction cycle of the transistor Q1, the turn-on switch M1 is on and the turn-off switch M2 is off. During the turn-off cycle of the transistor Q1, the turn-on switch M1 is off and the turn-off switch M2 is on. The driving control circuit 1 controls the switching of the transistor Q1 by controlling the switching states of the turn-on switch M1 and the turn-off switch M2.

[0036] This invention improves the circuit by modifying the current during the turn-on process of transistor Q1. This improvement is mainly achieved by controlling the waveform of the first driving signal K1 of the switching switch M1 during a single conduction cycle of transistor Q1. It should be noted that the waveform of the first driving signal K1 during a single turn-off cycle of transistor Q1 is not limited, as long as it can turn off the switching switch M1. Similarly, the waveforms of the second driving signal K2 during the turn-off and turn-on cycles of transistor Q1 are not limited, as long as they can drive the transistor Q1 to turn off and turn on during a single turn-on cycle.

[0037] Specifically, combined Figure 4During a single conduction cycle of the transistor Q1, the first drive signal K1 first instantaneously rises directly to the first amplitude V1 and turns on the conduction switch M1. Then, after a first preset duration, it increases from the first amplitude V1 to the second amplitude V2. After maintaining the second amplitude V2 for a second preset duration (the second preset duration is zero in this embodiment), it directly decreases to the amplitude that turns off the conduction switch M1, so that the current input to the base of the transistor Q1 is a dynamically and smoothly changing drive current. The first preset duration is less than the time for the transistor Q1 to go from initial conduction to full conduction. The second amplitude V2 is the maximum amplitude of the first drive signal K1 set by the voltage / current of the output branch (i.e., the voltage / current of the primary side of the transformer T).

[0038] Wherein, the sum of the first preset duration and the second preset duration is less than the total time required for transistor Q1 to go from initial conduction to full conduction and maintain full conduction, and the first preset duration is greater than the time required for transistor Q1 to go from initial conduction to full conduction. In this embodiment, it is preferable that the second preset duration is zero, and the proportion of the first preset duration to the total time is within a fluctuation range centered on 80% (the fluctuation range can be set by the user, for example, 78%-82%), that is, the smooth growth process of the first drive signal K1 lasts for about 80% of the transistor's conduction cycle, specifically: refer to Figure 4 The first driving signal K1 rises directly from the amplitude (e.g., 0) that turns off the conducting switch M1 to the first amplitude V1 at the beginning of a single conduction cycle of the transistor Q1. Then, it smoothly increases from the first amplitude V1 to the second amplitude V2 with a fixed or varying slope, and decreases directly from the second amplitude V2 to the amplitude that turns off the conducting switch M1 before the end of the single conduction cycle.

[0039] In contrast, the second drive signal K2 changes synchronously with the change of a single conduction cycle of transistor Q1: at the beginning of a single conduction cycle of transistor Q1, the second drive signal K2 directly switches from the amplitude that turns on the off switch M2 to the amplitude that turns off the off switch M2, and then the amplitude remains unchanged until the end of a single conduction cycle of transistor Q1, when it directly switches back to the amplitude that turns on the off switch M2.

[0040] The turn-on switch M1 can be a MOS transistor or a bipolar transistor. If a bipolar transistor is used, the first drive signal K1 is a current signal. In this embodiment, the turn-on switch M1 is preferably an NMOS transistor. The waveform of the first drive signal K1 is the same as the waveform of the gate voltage Vg of the turn-on switch M1.

[0041] In this embodiment, the off switch M2 is a transistor or a MOSFET; preferably, it is an NMOS transistor. The on switch M1 can be directly connected to the base of the transistor Q1. Preferably, a current-limiting resistor R0 or a switching transistor can be connected in series between the on switch M1 and the base of the transistor Q1 for current limiting; in this embodiment, a current-limiting resistor R0 is connected in series.

[0042] Specifically, the drain of the on switch M1 is connected to the collector of the transistor Q1, the source of the on switch M1 is connected to the base of the transistor Q1 via a current-limiting resistor R0, the emitter of the transistor Q1 is grounded via a sampling resistor Rs, the collector of the transistor Q1 is connected to the primary side of the transformer T, the drain of the off switch M2 is connected to the base of the transistor Q1, and the source of the off switch M2 is grounded (equivalent to indirectly connecting to the emitter of the transistor Q1). Of course, in other embodiments, the source of the off switch M2 can also be directly connected to the emitter of the transistor Q1.

[0043] In this embodiment, since the on switch M1 is preferably an NMOS transistor, the first drive signal K1 is a voltage signal. The first amplitude V1 and the second amplitude V2 satisfy the following conditions:

[0044] V1>Vbe(Q1)+Vth(M1)+Ib1*R0;

[0045] V2>Vbe(Q1)+Vth(M1)+Vs1+Ib2*R0;

[0046] Ib1 = kb * Ib2, 0 < ka < 1;

[0047] Ib2 = Vs1 / (ka*Rs1);

[0048] In the above formula, V1 represents the magnitude of the first amplitude V1, VbeQ1 represents the base-emitter voltage of the transistor Q1, Vth(M1) represents the threshold voltage of the turn-on switch M1, R0 represents the resistance value of the current-limiting resistor R0, and Ib1 represents the base current of the transistor Q1 when it is initially turned on. V2 represents the magnitude of the second amplitude V2, Ib2 represents the base current of the transistor Q1 when the first drive signal K1 increases to the second amplitude V2, Vs1 is a fixed voltage value set based on the voltage / current of the output branch, ka is a constant, ka is less than the amplification factor of the transistor Q1, the amplification factor of the transistor Q1 is 15, and ka is 10 in this embodiment. kb is a constant, and kb is specifically set according to the model of the transistor Q1, for example, kb is 1 / 3 in this embodiment.

[0049] Combination Figure 3, 4 The working principle of this embodiment is as follows:

[0050] First, the main working principle of the entire circuit is explained: When transistor Q1 is turned on, the second drive signal K2 controls the turn-off switch M2 to turn off, and the first drive signal K1 controls the turn-on switch M1 to turn on. The gate voltage of the turn-on switch M1 is Vg. The base current Ib of transistor Q1 flows from the collector through the turn-on switch M1 and the current-limiting resistor R0 to the base of transistor Q1. The base emitter is forward biased, and the collector is reverse biased. Through the multiplication and amplification of transistor Q1, current flows through the collector Rs. When transistor Q1 is turned off, the first drive signal K1 controls the turn-on switch M1 to open, and the second drive signal K2 controls the turn-off switch M2 to turn on. The drive current Ib is 0, and the base charge of transistor Q1 is quickly discharged to ground through the turn-off switch M2. Transistor Q1 is quickly turned off. At this time, the collector voltage of transistor Q1 will rise rapidly, and the peak current on the primary inductor will be transferred to the secondary inductor through the transformer T, thus switching to the output circuit.

[0051] Secondly, the working principle of transistor Q1 during a single conduction cycle is explained in detail: When transistor Q1 is turned on, the second drive signal K2 controls the turn-off switch M2 to turn off, and the first drive signal K1 controls the gate voltage Vg of the turn-on switch M1. The drive current Ib flows into the base of transistor Q1, the base-collector electrode of the transistor is forward biased, the base-emitter electrode is forward biased, and transistor Q1 is turned on. When it starts to conduct, the base current of transistor Q1 is Ib1 = (Vg - Vth - Vbe) / R0. Vg rises to V1 instantaneously, and then the voltage Vg rises slowly. The base current Ib of transistor Q1 also rises slowly. During the conduction period of transistor Q1, through the multiplication amplification of transistor Q1, the current of the primary inductance of transformer T will increase at a fixed slope. The collector-emitter current flows through Rs, and the voltage Vs of Rs also increases accordingly. During the slow rise of Vg, transistor Q1 is fully turned on, and Vg and Ib continue to rise slowly until the voltage Vs reaches the set value Vs1 (the voltage Vs can be sent to the comparator in the drive control circuit 1 for comparison, thereby feedback control of transistor Q1 to achieve the maximum value of Vs to Vs1, which is also the control principle of switching power supply). At this time, Vg reaches V2 (because the drive signal K1, or the slow growth rate of Vg, is preset, so that when Vs reaches Vs1, Vg, or K1, exactly reaches V2, at which point transistor Q1...). The base current of transistor Q1 has increased from the initial Ib1 to Ib2. Ib1 is generally preferably set to about 1 / 3 of Ib2; for example, in this embodiment, Ib2 is 50mA and Ib1 is approximately 17mA. Since the collector voltage of transistor Q1 is close to 0.7V during conduction, the Ibase loss during conduction at a duty cycle of 50% is approximately 0.7*(Ib1+Ib2) / 2*50% = 12mW, which is far less than the loss during conduction of Q1 at a duty cycle of 50% in existing transistors. Furthermore, compared to… Figure 2 , 4 It can be seen that the present invention has a great improvement in suppressing the initial spike of Vs, and has a great promoting effect on improving system EMI.

[0052] It should be noted that, depending on the model of transistor Q1, the number of the on switches M1 and the number of the off switches M2 can both be multiple, with multiple on switches M1 connected in parallel and multiple off switches M2 connected in parallel. Transistor Q1 can be a unipolar transistor or a multipolar transistor.

[0053] In summary, the transistor driving circuit of the transistor-driven switching power supply of the present invention has the following beneficial effects: a conduction switch is connected between the base and collector of the transistor. Based on the above circuit design, the control signal of the conduction switch during a single conduction cycle of the transistor is optimized. During a single conduction cycle of the transistor, the control signal of the conduction switch that controls the transistor to conduct is not fixed, but a first driving signal that dynamically changes during the conduction cycle. Specifically, within a single conduction cycle of the transistor, the first drive signal first rises directly to a first amplitude to initially turn on the conduction switch, then spends a first preset time increasing from the first amplitude to a second amplitude, and then maintains the second amplitude for a second preset time before directly decreasing to the amplitude that turns off the conduction switch M1. This ensures that the current input to the transistor base is a dynamic drive current. The sum of the first preset time and the second preset time is less than the total time required for the transistor Q1 to go from initial conduction to full conduction and to maintain full conduction. The first preset time is greater than the time required for the transistor Q1 to go from initial conduction to full conduction. That is, before the transistor is fully turned on, the dynamic drive current is still relatively small and has not yet reached its maximum value (the maximum value is limited by the voltage / current of the output branch where the transistor is located). Moreover, after the transistor is fully turned on, the dynamic drive current also slowly increases to its maximum value. Therefore, this invention not only reduces the turn-on loss at the moment of transistor conduction, but also in the transistor zero-voltage switching mode ( Figure 4 (mid-T1 time period) and valley conduction mode ( Figure 4 Both the T2 time period and the current distribution exhibit superior efficiency characteristics. Furthermore, the current drops from its maximum value before the transistor fully turns off, allowing for earlier turn-off and reducing power loss through turn-off delay. The smooth change in the transistor's base current also improves EMI during conduction, resulting in a smaller overshoot in the sampling resistor connected in series with the transistor when it turns on. Moreover, the overall circuit structure is simpler, occupies less area, and is easier to package compared to traditional circuits. In summary, the driving circuit of this invention significantly improves base current loss during transistor driving, optimizes transistor EMI characteristics, and has a simpler overall circuit structure, thus possessing broad applicability.

[0054] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A transistor driving circuit for a transistor-driven switching power supply, the transistor-driven switching power supply including an output branch connected in series between an input voltage and ground, the output branch including a transistor (Q1), characterized in that, The transistor driving circuit includes a driving control circuit (1), a turn-on switch (M1) controlled by a first driving signal (K1) sent by the driving control circuit (1), and a turn-off switch (M2) controlled by a second driving signal (K2) sent by the driving control circuit (1). The turn-on switch (M1) is connected between the base and collector of the transistor (Q1), and the turn-off switch (M2) is connected between the base and emitter of the transistor (Q1). During the conduction cycle of the transistor (Q1), the turn-on switch (M1) is open and the turn-off switch (M2) is off. During the turn-off cycle of the transistor (Q1), the turn-on switch (M1) is off and the turn-off switch (M2) is on. During a single conduction cycle of the transistor (Q1), the first drive signal (K1) first rises directly to a first amplitude V1 and initially turns on the conduction switch (M1), then increases from the first amplitude V1 to a second amplitude V2 over a first preset time, and then maintains the second amplitude V2 for a second preset time before directly decreasing to an amplitude that turns off the conduction switch (M1), so that the current input to the base of the transistor (Q1) is a dynamically and smoothly changing drive current; The sum of the first preset duration and the second preset duration is less than the total time required for the transistor (Q1) to go from initial conduction to full conduction and to maintain full conduction. The first preset duration is greater than the time required for the transistor (Q1) to go from initial conduction to full conduction. The second amplitude V2 is the maximum amplitude of the first drive signal (K1) set by the voltage and current of the output branch. The first drive signal (K1) rises directly from the amplitude that turns off the conduction switch (M1) to the first amplitude V1 at the beginning of a single conduction cycle of the transistor (Q1), and then increases smoothly from the first amplitude V1 to the second amplitude V2 with a fixed or varying slope, and decreases directly from the second amplitude V2 to the amplitude that turns off the conduction switch (M1) before the end of the single conduction cycle.

2. The transistor driving circuit according to claim 1, characterized in that, The second preset duration is zero, and the proportion of the first preset duration to the total time is within a fluctuation range centered around 80%.

3. The transistor driving circuit according to claim 1 or 2, characterized in that, The second drive signal (K2) at the beginning of a single conduction cycle of the transistor (Q1) directly switches from the amplitude that turns on the off switch (M2) to the amplitude that turns off the off switch (M2). The amplitude remains unchanged until the end of a single conduction cycle of the transistor (Q1), at which point it directly switches back to the amplitude that turns on the off switch (M2).

4. The transistor driving circuit according to claim 1, characterized in that, The on switch (M1) is a MOSFET or a transistor; and / or, the off switch (M2) is a transistor or a MOSFET; and / or, a current-limiting resistor (R0) or a switching transistor is connected in series between the on switch (M1) and the base of the transistor (Q1) for current limiting.

5. The transistor driving circuit according to claim 1, characterized in that, The on switch (M1) is an NMOS transistor. The drain of the on switch (M1) is connected to the collector of the transistor (Q1). The source of the on switch (M1) is connected to the base of the transistor (Q1) via a current-limiting resistor (R0). The emitter of the transistor (Q1) is grounded via a sampling resistor (Rs).

6. The transistor driving circuit according to claim 5, characterized in that, The first driving signal (K1) is a voltage signal, and the first amplitude V1 satisfies the following conditions: V1>Vbe(Q1)+Vth(M1)+Ib1*R0; In the above formula, V1 represents the magnitude of the first amplitude, Vbe (Q1) represents the base-emitter voltage of the transistor (Q1), Vth (M1) represents the threshold voltage of the turn-on switch (M1), R0 represents the resistance value of the current-limiting resistor (R0), and Ib1 represents the base current of the transistor (Q1) when it is initially turned on.

7. The transistor driving circuit according to claim 6, characterized in that, The second amplitude V2 satisfies the following condition: V2>Vbe(Q1)+Vth(M1)+Vs1+Ib2*R0; Ib2 = Vs1 / (ka * Rs); In the above formula, V2 represents the magnitude of the second amplitude, Ib2 represents the base current of the transistor (Q1) when the first driving signal (K1) increases to the second amplitude V2, Vs1 is a fixed voltage value set based on the voltage and current of the output branch, ka is a constant, and ka is less than the amplification factor of the transistor (Q1).

8. The transistor driving circuit according to claim 7, characterized in that, Ib1 and Ib2 satisfy the following relationship: Ib1 = kb * Ib2, 0 < kb < 1; kb is a constant, and kb is specifically set according to the model of the transistor (Q1).

9. The transistor driving circuit according to claim 5, characterized in that, The off switch (M2) is an NMOS transistor. The drain of the off switch (M2) is connected to the base of the transistor (Q1), and the source of the off switch (M2) is grounded or directly connected to the emitter of the transistor (Q1).

10. The transistor driving circuit according to claim 1, characterized in that, The number of the conducting switches (M1) is multiple, and the multiple conducting switches (M1) are connected in parallel; and / or, the number of the shut-off switches (M2) is multiple, and the multiple shut-off switches (M2) are connected in parallel.

Images