Drive device and its control method

Abstract

This invention provides a driving device and its control method. The driving device is used to drive a power switch. The driving device includes a power supply, a first bridge arm coupled to the power supply, a second bridge arm coupled in parallel to the first bridge arm, and a resonant inductor. The first bridge arm includes a first switch and a second switch connected to a first midpoint. The second bridge arm includes a first semiconductor device and a second semiconductor device connected to a second midpoint. The resonant inductor is coupled between the first midpoint and the second midpoint. The control method includes: turning on the first switch for a first time period to charge the gate of the power switch; and, in response to the current of the resonant inductor dropping to a first threshold, turning on the first switch again for a second time period to make the potential of the first midpoint equal to the potential of the second midpoint. Compared with conventional technical solutions, this invention can effectively reduce driving losses and suppress oscillations.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and in particular to a drive device and its control method. Background Technology

[0002] Based on the technical development requirements of SST (Solid State Transformer) power units, the need for higher frequency switching was proposed to achieve goals such as high efficiency and high power density. Increasing the switching frequency is an effective way to achieve high power density. At higher frequencies, fewer turns can be used to reduce the size and losses of the transformer windings, leaving more space for insulation.

[0003] In high-frequency power converters, the drive losses of the power switches increase linearly with increasing frequency. Under light loads, the proportion of drive losses to total losses increases, making the drive loss problem more pronounced. As the frequency increases further, the percentage of drive losses to total losses gradually becomes unacceptable, thus necessitating efforts to reduce the gate drive losses of the power switches.

[0004] Traditional solutions typically use push-pull circuits for power output, which mainly control the power switching transistors by controlling their gate voltage. Figure 1 The topology of a traditional push-pull circuit is shown. When switch S1 is on and switch S2 is off, the power supply V... DD Through the switching transistor S1 and the external gate resistor R g-ex and internal resistance R g-in The gate capacitance C of the power switch Q gs As charging progresses, the gate voltage rises, turning on the power switch Q. When switch S2 is on and switch S1 is off, the gate capacitance C... gs Through the internal resistor R g-in Gate external resistor R g-ex And the switching transistor S2 discharges to the power supply V. EE The gate voltage drops, thus turning off the power switch Q. The driving loss in this traditional method is:

[0005] P gating =Q g ×V gs ×f s

[0006] Among them, Q g It is the gate charge of the power switch Q, V gs It is the voltage between the gate (G) and source (S) of the power switch Q, f s It is the switching frequency of the power switch Q.

[0007] As can be seen from the above formula, under this traditional driving method, the driving loss P gating With switching frequency f s Proportional. With the switching frequency f s The increase in driving loss P gating It will increase significantly.

[0008] The basic technical features of this traditional scheme are as follows: (1) a push-pull circuit is used for power output; (2) the switching speed of the switching transistor Q is determined by the external gate drive resistor R. g-ex To control. However, this traditional solution has the following disadvantages: (1) the drive loss is high and proportional to the switching frequency. High frequency will lead to a sharp increase in loss; (2) under light load, the proportion of drive loss to system loss will increase.

[0009] Existing technologies also propose a lossless driving scheme, which adds a resonant inductor L to the push-pull output. r And diodes D1 and D2, their topology and operating mode are as follows Figure 2A and Figure 2B As shown.

[0010] At time t0, switch S1 is turned on, and power supply V... DD Through the switching transistor S1 and the resonant inductor L r and internal resistance R g-in The gate capacitance C of the switching transistor Q gs As charging progresses, the gate voltage rises, and the power switch Q begins to conduct.

[0011] At time t1, the gate voltage increases to VDD, power switch Q is stably turned on, switch S1 is turned off, diode D1 is turned on, and the resonant inductor current freewheels through diode D1 and the body diode of switch S2 (switching states are as follows). Figure 2C (As shown), until the current is zero, the energy is fed back to the power source, reducing losses.

[0012] During the time intervals from t1 to t3, the state of the switching transistors remains unchanged, that is, the power switching transistor Q is stably turned on, while the switching transistors S1 and S2 remain turned off.

[0013] At time t3, switch S2 is turned on, and gate capacitor C... gs Through the internal resistor R g-in Resonant inductor L r And the switching transistor S2 discharges to the power supply V. EE As the gate voltage drops, the power switch Q begins to turn off.

[0014] At time t4, the gate voltage drops to VEE, the power switch Q is completely turned off, the switch S2 is turned off, the diode D2 is turned on, and the resonant inductor current freewheels through the body diode of the diode D2 and the switch S1 until the current is zero, and the energy is fed back to the power supply to reduce losses.

[0015] However, this lossless driving scheme has the following problem: at time t2, the resonant inductor current decreases to 0, and due to the different potentials (V) at nodes a and b... a ≈V EE V b ≈V DD A voltage difference can cause the resonant inductor current to reverse, leading to oscillations with the parasitic capacitances of switching transistors S1 and S2, and diodes D1 and D2. Figure 3A As shown, it is equivalent to an LC oscillating circuit, and the equivalent circuit is as follows. Figure 3B As shown. This oscillation causes a drop in the drive voltage. For some switching transistors that require a drive voltage of +15V / -5V, the voltage may drop from -5V to around 0V during turn-off, making reliable turn-off impossible and potentially leading to false triggering. Furthermore, the drop in drive voltage also increases the on-resistance of the power switching transistor. For example... Figure 3C , Figure 3D As shown, when the driving voltage drops from 15V to 13V, the on-resistance increases from 45mΩ to 70mΩ. Under the same current, the conduction loss will increase, thereby reducing the system efficiency.

[0016] The basic technical features of this lossless driving scheme are as follows: (1) Diode freewheeling resonant inductor L r The current and energy are fed back to the power source to reduce losses; (2) Resonant inductor L r Used to control the switching speed; (3) Switching transistors S1 / S2 at voltage V gs (4) Partial losses in the drive circuit and switching frequency f s It is irrelevant, so the loss is further reduced at high frequencies. However, this lossless drive scheme has the following disadvantages: (1) There is oscillation when the switch is activated, the gate voltage will drop, there is a risk of false triggering, and the gate reliability is reduced; (2) The gate voltage affects the on-resistance, and the drop in gate voltage will lead to an increase in on-resistance and a significant increase in on-loss.

[0017] Therefore, there is a need to provide a lossless driving solution that can suppress oscillations. Summary of the Invention

[0018] The purpose of this invention is to provide a driving device and its control method, which can solve one or more defects of the prior art.

[0019] To achieve the above objectives, according to an embodiment of the present invention, the present invention provides a control method for a driving device, the driving device being used to drive a power switch, wherein the driving device includes a power supply, a first bridge arm coupled to the power supply, a second bridge arm coupled in parallel to the first bridge arm, and a resonant inductor, the first bridge arm including a first switch and a second switch connected to a first midpoint, the second bridge arm including a first semiconductor device and a second semiconductor device connected to a second midpoint, and the resonant inductor being coupled between the first midpoint and the second midpoint, the control method including: turning on the first switch for a first time period to charge the gate of the power switch by the power supply; and, in response to the current of the resonant inductor dropping to a first threshold, turning on the first switch again for a second time period to make the potential of the first midpoint equal to the potential of the second midpoint.

[0020] In one embodiment of the present invention, the control method further includes: turning on the second switch for a third time period to discharge the gate of the power switch; and turning on the second switch again for a fourth time period in response to the current of the resonant inductor rising to a second threshold to make the potential of the first midpoint equal to the potential of the second midpoint.

[0021] In one embodiment of the present invention, the power supply includes a first power supply and a second power supply, the first power supply being coupled to a first switch and the second power supply being coupled to a second switch; wherein, during a second time period, the potential of the first midpoint is clamped to the voltage of the first power supply by the first switch, and the potential of the second midpoint is equal to the voltage of the first power supply; during a fourth time period, the potential of the first midpoint is clamped to the voltage of the second power supply by the second switch, and the potential of the second midpoint is equal to the voltage of the second power supply.

[0022] In one embodiment of the present invention, the first switch is turned on again when the current in the resonant inductor drops to zero, and the second switch is turned on again when the current in the resonant inductor rises to zero.

[0023] In one embodiment of the present invention, the first switch is turned on again before the second switch is turned on, and the second switch is turned on again before the first switch is turned on in the next switching cycle.

[0024] In one embodiment of the present invention, the control method further includes: calculating the time t when the current of the resonant inductor drops to the first threshold according to the first inductor current formula. α1 The moment t when the current in the resonant inductor drops to zero is calculated according to the second inductor current formula. β1The time t for turning on the second switch is calculated based on the duty cycle and switching frequency of the power switch. μ1 The internal timer's timing is equal to time t. α1 When [time], the first switch is turned on again; the internal timer counts for [t]. β1 , t μ1 At a certain moment in the second time period, the first switch is turned off, and the second time period ends.

[0025] In one embodiment of the present invention, the control method further includes: calculating the time t when the current of the resonant inductor rises to the second threshold according to the third inductor current formula. α2 The moment t when the current in the resonant inductor rises to zero is calculated according to the fourth inductor current formula. β2 Determine the start time t0 of the next switching cycle; the internal timer counts down to time t. α2 When [time], the second switch is turned on again; the internal timer counts for [t]. β2 At a certain moment in t0), the second switch is turned off, and the fourth time period ends.

[0026] In one embodiment of the present invention, the control method further includes: sampling the current of the resonant inductor through a sampling unit and inputting the sampled value into a control unit; comparing the sampled value with a first threshold through the control unit, and when the sampled value is equal to the first threshold, turning on the first switch again; comparing the sampled value with zero through the control unit, and when the sampled value is equal to zero, turning off the first switch, and ending the second time period.

[0027] In one embodiment of the present invention, the control method further includes: sampling the current of the resonant inductor through a sampling unit and inputting the sampled value into a control unit; comparing the sampled value with a first threshold through the control unit, and when the sampled value is equal to the first threshold, reactivating the first switch; comparing the sampled value with zero through the control unit, and when the sampled value is equal to zero, recording the time t of the internal timer at this time. β1 The control unit obtains the on-time t of the second switch. μ1 When the internal timer counts to (t) β1 , t μ1 At a certain moment in the second time period, the first switch is turned off, and the second time period ends.

[0028] In one embodiment of the present invention, the control method further includes: sampling the current of the resonant inductor through a sampling unit and inputting the sampled value into a control unit; comparing the sampled value with a second threshold through the control unit, and when the sampled value is equal to the second threshold, turning on the second switch again; comparing the sampled value with zero through the control unit, and when the sampled value is equal to zero, turning off the second switch, and the fourth time period ends.

[0029] In one embodiment of the present invention, the control method further includes: sampling the current of the resonant inductor through a sampling unit and inputting the sampled value into a control unit; comparing the sampled value with a second threshold through the control unit, and reactivating the second switch when the sampled value equals the second threshold; and comparing the sampled value with zero through the control unit, and recording the time t of the internal timer when the sampled value equals zero. β2 The control unit obtains the start time t0 of the next switching cycle, and the internal timer counts down to (t...). β2 At a certain moment in t0), the second switch is turned off, and the fourth time period ends.

[0030] In one embodiment of the present invention, the value range of the first threshold is (0, 1A], and the value range of the second threshold is [-1A, 0].

[0031] To achieve the above objectives, according to another embodiment of the present invention, a driving device is provided for driving a power switch, wherein the driving device includes: a power supply; a first bridge arm coupled to the power supply, the first bridge arm including a first switch and a second switch connected at a first midpoint; a second bridge arm coupled in parallel to the first bridge arm, the second bridge arm including a first semiconductor device and a second semiconductor device connected at a second midpoint; and a resonant inductor coupled between the first midpoint and the second midpoint; wherein the first switch is controlled to be turned on for a first time period to charge the gate of the power switch by the power supply; in response to the current of the resonant inductor dropping to a first threshold, the first switch is controlled to be turned on again for a second time period to make the potential of the first midpoint equal to the potential of the second midpoint.

[0032] In another embodiment of the invention, the second switch is controlled to be turned on for a third time period to discharge the gate of the power switch; in response to the current of the resonant inductor rising to a second threshold, the second switch is controlled to be turned on again for a fourth time period to make the potential of the first midpoint equal to the potential of the second midpoint.

[0033] In another embodiment of the present invention, the power supply includes a first power supply and a second power supply, the first power supply being coupled to the first switch and the second power supply being coupled to the second switch; wherein, during the second time period, the potential of the first midpoint is clamped to the voltage of the first power supply by the first switch, and the potential of the second midpoint is equal to the voltage of the first power supply; during the fourth time period, the potential of the first midpoint is clamped to the voltage of the second power supply by the second switch, and the potential of the second midpoint is equal to the voltage of the second power supply.

[0034] In another embodiment of the invention, the first switch is turned on again when the current in the resonant inductor drops to zero, and the second switch is turned on again when the current in the resonant inductor rises to zero.

[0035] In another embodiment of the present invention, the first switch is turned on again before the second switch is turned on, and the second switch is turned on again before the first switch is turned on in the next switching cycle.

[0036] In another embodiment of the present invention, the driving device further includes a control unit electrically connected to the first switch and the second switch, the control unit being configured to perform: calculating the time t when the current of the resonant inductor drops to the first threshold according to the first inductor current formula. α1 The moment t when the current in the resonant inductor drops to zero is calculated according to the second inductor current formula. β1 The time t for turning on the second switch is calculated based on the duty cycle and switching frequency of the power switch. μ1 The internal timer's timing is equal to time t. α1 When [time], the first switch is turned on again; the internal timer counts for [t]. β1 , t μ1 At a certain moment in the second time period, the first switch is turned off, and the second time period ends.

[0037] In another embodiment of the invention, the driving device further includes a control unit electrically connected to the first switch and the second switch, the control unit being configured to perform: calculating the time t when the current of the resonant inductor rises to the second threshold according to the third inductor current formula. α2 The moment t when the current in the resonant inductor rises to zero is calculated according to the fourth inductor current formula. β2 Determine the start time t0 of the next switching cycle; the internal timer counts down to time t. α2 When [time], the second switch is turned on again; the internal timer counts for [t]. β2 At a certain moment in t0), the second switch is turned off, and the fourth time period ends.

[0038] In another embodiment of the present invention, the driving device further includes a sampling unit and a control unit, wherein the sampling unit is electrically connected to the resonant inductor, and the control unit is electrically connected to the first switch and the second switch, wherein: the sampling unit samples the current of the resonant inductor and inputs the sampled value into the control unit; the control unit compares the sampled value with a first threshold, and when the sampled value is equal to the first threshold, the control unit turns the first switch back on; the control unit compares the sampled value with zero, and when the sampled value is equal to zero, the control unit turns off the first switch, and the second time period ends.

[0039] In another embodiment of the present invention, the driving device further includes a sampling unit and a control unit, wherein the sampling unit is electrically connected to the resonant inductor, and the control unit is electrically connected to the first switch and the second switch, wherein: the sampling unit samples the current of the resonant inductor and inputs the sampled value to the control unit; the control unit compares the sampled value with a first threshold, and when the sampled value equals the first threshold, the control unit re-opens the first switch; the control unit compares the sampled value with zero, and when the sampled value equals zero, the control unit records the time t of the internal timer at this time. β1 The control unit obtains the on-time t of the second switch. μ1 When the internal timer counts to (t) β1 , t μ1 At a certain moment in the second time cycle, the control unit turns off the first switch, and the second time cycle ends.

[0040] In another embodiment of the present invention, the driving device further includes a sampling unit and a control unit, wherein the sampling unit is electrically connected to the resonant inductor, and the control unit is electrically connected to the first switch and the second switch, wherein: the sampling unit samples the current of the resonant inductor and inputs the sampled value into the control unit; the control unit compares the sampled value with a second threshold, and when the sampled value is equal to the second threshold, the control unit turns the second switch on again; the control unit compares the sampled value with zero, and when the sampled value is equal to zero, the control unit turns off the second switch, and the fourth time period ends.

[0041] In another embodiment of the present invention, the driving device further includes a sampling unit and a control unit, wherein the sampling unit is electrically connected to the resonant inductor, and the control unit is electrically connected to the first switch and the second switch, wherein: the sampling unit samples the current of the resonant inductor and inputs the sampled value to the control unit; the control unit compares the sampled value with a second threshold, and when the sampled value equals the second threshold, the control unit turns the second switch back on; the control unit compares the sampled value with zero, and when the sampled value equals zero, the control unit records the time t of the internal timer at this time. β2 The control unit obtains the start time t0 of the next switching cycle, and the internal timer counts down to (t...). β2 At a certain moment in t0), the control unit turns off the second switch, and the fourth time cycle ends.

[0042] This invention achieves the purpose of suppressing oscillations by changing the modulation method without adding any components to the existing lossless drive circuit.

[0043] Compared with existing technologies, the present invention reduces drive losses and improves reliability.

[0044] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0045] The above and other features and advantages of the present invention will become more apparent from a detailed description of exemplary embodiments thereof with reference to the accompanying drawings.

[0046] Figure 1 The topology of a traditional push-pull circuit is shown.

[0047] Figure 2A The topology of an existing lossless drive scheme is shown;

[0048] Figure 2B The operating waveforms of the existing lossless drive scheme are shown;

[0049] Figure 2C The switching state of the existing lossless drive scheme at time t1 is shown;

[0050] Figure 3A The circuit structure of the existing lossless drive scheme is shown to generate oscillations at time t2 due to the parasitic capacitances of the resonant inductor, switches S1 and S2, and diodes D1 and D2.

[0051] Figure 3B It shows Figure 3AThe circuit structure is equivalent to the equivalent circuit of an LC oscillating circuit.

[0052] Figure 3C A schematic diagram is shown illustrating how existing lossless drive schemes cause a drop in drive voltage when oscillations occur;

[0053] Figure 3D A schematic diagram is shown illustrating the change in on-resistance caused by oscillation in existing lossless drive schemes;

[0054] Figure 4A The circuit topology of a first preferred embodiment of the driving device of the present invention is shown;

[0055] Figure 4B It shows Figure 4A The working waveform of the drive device;

[0056] Figure 4C The circuit state of the driving device of the present invention is shown in which, at time t2, in response to the resonant inductor current dropping to a first threshold, the first switch of the first bridge arm is turned on again for a second time period so that the potential of the first midpoint a is equal to the potential of the second midpoint b.

[0057] Figure 4D It shows Figure 4C The circuit structure is equivalent to the equivalent circuit of an LC oscillating circuit.

[0058] Figure 5 The control method of the drive device of the present invention is shown;

[0059] Figure 6 It shows Figure 4A The working waveform of another specific embodiment of the driving device;

[0060] Figure 7 It shows Figure 4A The operating waveform of another specific embodiment of the driving device;

[0061] Figure 8A The circuit topology of a second preferred embodiment of the driving device of the present invention is shown;

[0062] Figure 8B It shows Figure 8A The working waveform of the drive device;

[0063] Figure 9 The comparison of losses between the conventional scheme and the scheme of the present invention is shown at different frequencies;

[0064] Figure 10A The V measured by the existing lossless drive scheme is shown. gs Waveform;

[0065] Figure 10BThe V measured by the present invention is shown. gs Waveform. Detailed Implementation

[0066] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, they are provided so that the invention will be thorough and complete, and the concept of the exemplary embodiments will be fully conveyed to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and therefore their detailed description will be omitted.

[0067] In describing the elements / components / etc. described and / or illustrated herein, the terms “a,” “an,” “the,” “the,” and “at least one” are used to indicate the presence of one or more elements / components / etc. The terms “comprising,” “including,” and “having” are used to indicate an open-ended inclusion and to mean that additional elements / components / etc. may exist in addition to those listed. Relative terms, such as “upper” or “lower,” may be used in the embodiments to describe the relative relationship of one component of the icon to another component. It is understood that if the device of the icon is flipped so that it is upside down, the component described as being on the “upper” side will become the component on the “lower” side. Furthermore, the terms “first,” “second,” etc., in the claims are used only as illustrative marks and are not intended to limit the number of objects to which they apply.

[0068] like Figure 4A As shown, the present invention provides a driving device 100, which can be used to drive a power switch Q, the power switch Q may have, for example, a gate G, a source S, and a drain D. The driving device 100 may include a power supply (e.g., a first power supply V). DD Second power supply V EE ), first bridge arm 10, second bridge arm 20 and resonant inductor L r The first bridge arm 10 is coupled to the power supply and includes a first switch S1 and a second switch S2 connected at the first midpoint a. For example, the first power supply V... DD Coupled to the first switch S1, the second power supply V EE It can be coupled to the second switch S2. The second bridge arm 20 is coupled in parallel to the first bridge arm 10, including a first semiconductor device and a second semiconductor device, such as diodes D1 and D2, connected at the second midpoint b. The resonant inductor L r It is coupled between the first midpoint a and the second midpoint b. Figure 4A It can also include only the first power supply V. DD The second switch S2 is grounded.

[0069] Combination Figure 4BIn this invention, the first switch S1 is controlled to be turned on for a first time period, so that the power supply (first power supply V) DD ) is the gate capacitance C of the power switch Q. gs Charging. Responding to the resonant inductor L r When the current drops to a first threshold, the first switch S1 is controlled to turn on again for a second time period, so that the potential of the first midpoint a is equal to the potential of the second midpoint b. For example, during the second time period, the potential of the first midpoint a can be clamped to the first power supply V by the first switch S1. DD The voltage VDD, and the potential at the second midpoint b is equal to that of the first power source V. DD The voltage VDD. It should be noted that "equal to" or "clamped to" in this embodiment is not an absolute equality, and a certain degree of error is allowed.

[0070] Furthermore, in this invention, the second switch S2 is controlled to be on for a third time period, so that the gate capacitance C of the power switch Q... gs Discharge. In response to the resonant inductor L r When the current rises to the second threshold, the second switch S2 is controlled to turn on again for a fourth time period, so that the potential of the first midpoint a is equal to the potential of the second midpoint b. For example, during the fourth time period, the potential of the first midpoint a is clamped to the second power supply V by the second switch S2. EE The voltage VEE, and the potential at the second midpoint b is equal to that of the second power source V. EE The voltage VEE. It should be noted that "equal to" or "clamped to" in this embodiment is not an absolute equality, and a certain degree of error is allowed.

[0071] like Figures 4A-4D As shown, the specific control method for the drive power switch Q by the drive device 100 of the present invention is as follows:

[0072] At time t0, the upper switch of the first bridge arm 10 (i.e., the first switch S1) is turned on, and the inductor current i Lr The inductor current i flows into the gate G of the power switch Q. Lr As the voltage increases, the gate voltage V of the power switch Q also increases. gs Increase, and power switch Q turns on;

[0073] At time t1, the gate voltage V of power switch Q gs Increased to VDD, power switch Q is stably turned on, turning off the first switch S1 of the first bridge arm 10, and the upper transistor (i.e., diode D1) of the second bridge arm 20 is turned on, and the inductor current i Lr Freewheeling occurs through the body diode of diode D1 and switching transistor S2;

[0074] At time t2, the inductor current i Lr When the value is about to drop to 0 (e.g., drop to the first threshold), the first switch S1 of the first bridge arm 10 is turned on again. Figure 4C The circuit state at this time is shown, with the inductor current freewheeling through the first switch S1 and diode D1; at this time, the resonant inductor L... r The voltages at the first midpoint a and the second midpoint b are Va≈VDD and Vb≈VDD, respectively. The resonant network has no resonant source and does not oscillate. The equivalent circuit at this time is as follows: Figure 4D As shown;

[0075] At time t3, the inductor current i Lr The value drops to 0, and the first switch S1 of the first bridge arm 10 is turned off before the power switch Q is activated (i.e., the second switch is turned on at time t4).

[0076] The turn-off process of power switch Q corresponds to this:

[0077] At time t4, the lower switch of the first bridge arm 10 (i.e., the second switch S2) is turned on, and the inductor current i Lr The gate G of the power switch Q flows out with the inductor current i Lr The decrease in voltage reduces the gate voltage V of the power switch Q. gs Decrease, and power switch Q turns off;

[0078] At time t5, the gate voltage V of power switch Q gs When VEE decreases to a minimum, power switch Q stably turns off, turning off the second switch S2 of the first bridge arm 10. The lower transistor (i.e., diode D2) of the second bridge arm 20 turns on, and the inductor current i... Lr Freewheeling occurs through diode D2 and the body diode of switching transistor S1;

[0079] At time t6, the inductor current i Lr When the current is about to rise to 0 (e.g., rise to the first threshold), the second switch S2 of the first bridge arm 10 is turned on again. At this time, the inductor current freewheels through the second switch S2 and the diode D2, and the resonant inductor L... r The voltages at the first midpoint a and the second midpoint b at both ends are Va≈VEE and Vb≈VEE, respectively. The resonant network has no resonant source and does not oscillate.

[0080] At time t7, the inductor current i Lr The value rises to 0, and the second switch S2 of the first bridge arm 10 is turned off before the power switch Q is activated (i.e., the first switch S1 is turned on in the next switching cycle).

[0081] like Figure 5 As shown, the control method of the drive device of the present invention mainly includes:

[0082] Step S51: Turn on the first switch S1 for the first time period, so that the power supply (first power supply V) is activated. DD The gate G of the power switch Q is charged.

[0083] Step S52: Response to resonant inductor L r When the current drops to the first threshold, the first switch S1 is turned on again for the second time period, so that the potential of the first midpoint a is equal to the potential of the second midpoint b.

[0084] Preferably, the control method of the drive device of the present invention may further include:

[0085] Step S53: Turn on the second switch S2 for the third time period to discharge the gate G of the power switch Q.

[0086] Step S54: Response to resonant inductor L r The current rises to the second threshold, and the second switch S2 is turned on again for the fourth time period, so that the potential of the first midpoint a is equal to the potential of the second midpoint b.

[0087] In this embodiment, the driving device 100 of the present invention is based on the resonant inductor L r When the current is about to decrease to 0, the first switch S1 of the first bridge arm is turned on for the second time; and, in the resonant inductor L r When the current is 0, the first switch S1, which is turned on again, is turned off before the driven power switch Q operates again. The driving device 100 of the present invention operates based on the resonant inductor L... r When the current is about to rise to 0, the second switch S2 of the first bridge arm is turned on for the second time; and, in the resonant inductor L r When the current is 0, the second switch S2, which is turned on again, is turned off before the driven power switch Q operates again, that is, before the first switch S1 is turned on in the next cycle.

[0088] It should be noted that, for the sake of convenience, Figure 4A The arrows in the diagram indicate the direction of the inductor current; when they are in the same direction, the inductor current is positive, and when they are in opposite directions, the inductor current is negative, thus obtaining... Figure 4B Schematic curve of inductor current i Lr Of course, this invention is not limited to this, and the direction of the inductor current can be set according to actual needs.

[0089] The advantages of this embodiment are: using a resonant inductor instead of a resistor, some energy is fed back to the power supply through the resonant inductor, reducing the loss of the drive circuit and maintaining its advantages in high-frequency applications; based on the lossless drive circuit, without adding components, the purpose of suppressing oscillation can be achieved by changing the modulation method, ensuring reliable turn-on and turn-off of the power switch and preventing false triggering.

[0090] In this invention, within one switching cycle of the power switch Q, the driving square waves driving the first switch S1 and the second switch S2 are respectively outputting a high level in the first time cycle, a high level in the second time cycle, a high level in the third time cycle, and a high level in the fourth time cycle, and outputting a low level for the rest of the time. Therefore, as long as the start and end times of the time period corresponding to the high level are calculated, the driving square waves of switches S1 and S2 can be obtained.

[0091] (Method 1) The wave generation time is obtained through mathematical calculation, and the controller (including but not limited to DSP / MCU / FPGA, etc.) sends out a driving square wave, which corresponds to a high or low level. Please refer to [link / reference]. Figure 4B The time intervals t0 to t8 correspond to one switching cycle T of the power switch. Within each switching cycle, the operation and waveforms of the power switch Q, the switching transistors S1 and S2 are exactly the same. Therefore, it is sufficient to describe the working condition within one switching cycle T.

[0092] The duration of the first time period can be set according to the selection of the switching transistor Q and the desired switching speed (i.e., turn-on speed). In other words, the length of the first time period, or time t1, can be set by the designer or user according to their needs. Time t0 is the start time of the switching cycle, which can be considered zero for ease of understanding or description. The controller outputs a high level at time t0 to control the first switch S1 to turn on, and outputs a high level at the end of time t1 to control the first switch S1 to turn off. A driving square wave within the first time period can be generated using methods such as a timer or carrier comparison.

[0093] At the end of the first time period, the resonant inductor L r The current in the circuit can be obtained from the following expression:

[0094]

[0095] Among them, after the power switch Q is determined, the power supply voltages VDD and VEE, and the resistance R are... g-in Capacitor C gs and inductor L r The selection and design have been completed, and the circuit parameters are fixed. In Formula 1, VDD, VEE, and L... r R g-in and C gs All parameters are fixed circuit parameters, and t1 is a known quantity. By substituting the relevant parameters into calculation formula one, the current i flowing through the resonant inductor at time t1 can be manually calculated by the designer. Lr (t1), or the known parameters in Formula 1 can be input and saved to the corresponding memory for use by the corresponding calculation program, and the current i flowing through the resonant inductor at time t1 can be obtained through the calculation program. Lr(t1). Furthermore, α and β can be calculated using the following expressions:

[0096]

[0097] Before the start of the second time period, the resonant inductor L r The current in the circuit can be obtained from the following expression:

[0098]

[0099] The first or second threshold can be set by the designer or user according to their needs. The values ​​of the first and second thresholds are generally close to zero; for example, the first threshold ranges from 0.1A to 1A, and the second threshold ranges from -1A to -0.1A. The absolute values ​​of the first and second thresholds can be equal or unequal. Based on the circuit parameters and the first threshold (at which point the current flowing through the resonant inductor is equal to the first threshold), the time t2 when the current through the resonant inductor equals the first threshold is calculated using Formula 1 and Formula 2. Where i Lr (t2) equals the first threshold, i Lr (t1) Calculated using Formula 1, VDD, VEE, L r t1 is a fixed parameter of the circuit and t1 is a known quantity.

[0100] Starting from time t2, the current in the resonant inductor gradually decreases to 0, starting from the first threshold voltage and flowing through the upper diode (i.e., diode D1) of the second bridge arm and the first switch S1. The resonant inductor current during this stage can be approximated by the following expression:

[0101]

[0102] Among them, V dson This is the on-state voltage drop of the first switch S1, which is small and negligible. V d This is the forward voltage drop of diode D1. The zero-crossing time t3 of the resonant inductor current is calculated using Formula 3, at which point the resonant inductor current i... Lr (t3) equals zero, V dson V d and L r For device parameters, t2 is calculated using Formula 2. The switching period T and duty cycle D of the power switch Q are known. The start time t4 of the third time period is calculated based on the switching period T and duty cycle D, where t4 = DT. After calculating t2, t3, and t4, the controller starts outputting a high level at time t2 to control the first switch S1 to turn on again. At time t3 or any time between t3 and t4, the controller outputs a high level to control the first switch S1 to turn off again. A driving square wave for the second time period can be generated using a timer or carrier comparison method.

[0103] The third and fourth time periods are similar to the first and second time periods in terms of wave generation and calculation methods, differing only slightly in their calculation formulas. The duration of the third time period can be set according to the selection of the switching transistor Q and the desired switching speed (i.e., turn-off speed). In other words, the length and time t5 of the third time period can be set by the designer or user. The controller starts outputting a high level at time t4 to control the second switch S2 to turn on, and ends at time t5 to control the second switch S2 to turn off. A driving square wave within the third time period can be generated using methods such as a timer or carrier comparison.

[0104] At the end of the third time period, i.e., at time t5, the resonant inductor L r The current in the circuit can be obtained from the following expression:

[0105]

[0106] Before the start of the fourth time period, the resonant inductor L r The current in the circuit can be obtained from the following expression:

[0107]

[0108] Based on the circuit parameters and the second threshold (at which point the inductor current equals the second threshold), time t6 is calculated using formulas four and five.

[0109] Starting from time t6, the current in the resonant inductor gradually increases from the second threshold voltage level through the lower diode of the second bridge arm (i.e., diode D2) and the second switch S2, until it reaches zero. The resonant inductor current during this stage can be approximated by the following expression:

[0110]

[0111] Among them, V dson This is the on-state voltage drop of switch S2, which is small and negligible. V d It is the forward voltage drop of diode D2.

[0112] The zero-crossing time t7 of the resonant inductor current is calculated using Formula 6, at which point the resonant inductor current is zero. After calculating t6, t7, and t8, the controller starts outputting a high-level signal at time t6 to re-enable switch S2. At t7 or any time between t7 and t8, the high-level signal ends, turning off switch S2. A driving square wave for the fourth time period can be generated using a timer or carrier comparison method. Here, time t8 is the end of the current switching cycle and the start of the next switching cycle.

[0113] In one embodiment of the present invention, the driving device 100 may further include a control unit (not shown) electrically connected to the first switch S1 and the second switch S2. The control unit is used to perform:

[0114] Calculate the resonant inductance L according to the first inductor current formula (e.g., formula two). r The current drops to the first threshold at time t α1 ,For example Figure 4B At time t2;

[0115] The resonant inductance L is calculated according to the second inductor current formula (e.g., formula three). r The moment t when the current drops to zero β1 ,For example Figure 4B At time t3;

[0116] Based on the duty cycle of power switch Q and the switching frequency f s Calculate the time t when the second switch S2 is turned on. μ1 ,For example Figure 4B At time t4;

[0117] The internal timer counts down to time t. α1 When this happens, the first switch S1 is turned on again;

[0118] The internal timer counts as [t] β1 , t μ1 At a certain moment in the second time period, the first switch S1 is turned off, and the second time period ends.

[0119] In another embodiment of the invention, the control unit may further be used to perform:

[0120] The resonant inductance L is calculated according to the third inductor current formula (e.g., formula five). r The time t when the current rises to the second threshold α2 ,For example Figure 4B The time t6 in the middle;

[0121] The resonant inductance L is calculated according to the fourth inductor current formula (e.g., formula six). r The moment t when the current rises to zero β2 ,For example Figure 4B The time t7 in the equation; determines the start time of the next switching cycle or the end time of the current switching cycle, for example... Figure 4B The time t8 in the middle;

[0122] The internal timer counts down to time t. α2 At that time, the second switch S2 is turned on again;

[0123] The internal timer counts as [t] β2 At a certain moment in t8), the second switch S2 is turned off, and the fourth time period ends.

[0124] (Method 2) Using a sensor to sample the resonant inductor L r The current is sampled and input to the controller. The controller compares the sampled value with the first threshold or the second threshold to determine the time point to send the driving square wave again.

[0125] In one embodiment of the present invention, the driving device 100 may further include a sampling unit (not shown) and a control unit (not shown), wherein the sampling unit may be connected to the resonant inductor L. r Electrically connected, the control unit is electrically connected to the first switch S1 and the second switch S2. The resonant inductor L is sampled through the sampling unit. r The current is measured and the sampled value is input to the control unit. The control unit compares the sampled value with the first threshold. When the sampled value equals the first threshold, the control unit turns the first switch S1 back on. The control unit compares the sampled value with zero. When the sampled value equals zero, the control unit turns off the first switch S1, and the second time period ends. Alternatively, the control unit compares the sampled value with zero. When the sampled value equals zero, the control unit records the time t of the internal timer at this time. β1 The control unit obtains the on-time t of the second switch S2. μ1 When the internal timer counts to (t) β1 , t μ1 At a certain moment in the second time cycle, the control unit turns off the first switch S1, and the second time cycle ends.

[0126] In another embodiment of the present invention, the current of the resonant inductor is sampled by the sampling unit, and the sampled value is input to the control unit; the control unit compares the sampled value with the second threshold, and when the sampled value equals the second threshold, the control unit turns on the second switch S2 again; the control unit compares the sampled value with zero, and when the sampled value equals zero, the control unit turns off the second switch S2, and the fourth time period ends. Alternatively, the control unit compares the sampled value with zero, and when the sampled value equals zero, the control unit records the time t of the internal timer at this time. β2 The control unit obtains the start time t0 of the next switching cycle, and the internal timer counts down to (t...). β2 At a certain moment in t8), the control unit turns off the second switch S2, and the fourth time cycle ends.

[0127] Figure 6 The present invention is shown as follows Figure 4A The diagram shows the operating waveform of another specific embodiment of the drive device 100. In this embodiment, the first switch S1 is turned on again at the resonant inductor L. r The second switch S2 is turned off when the current drops to zero and is turned on again when the current in the resonant inductor L... r It turns off when the current rises to zero. In the resonant inductor L... r current i Lr When the current is about to decrease to 0, generally less than 1A, the first switch S1 is turned on for the second time; at the resonant inductor L r current i Lr When the value is zero, the first switch S1, which was turned on again, turns off. At the resonant inductor L... r current i Lr When the current is about to increase to 0, and is generally greater than -1A, the second switch S2 is turned on for the second time; at the resonant inductor L r current i Lr When the current is zero, the second switch S2, which is turned on again, is turned off. In this embodiment, the first switch S1 / second switch S2 is turned off at the zero-crossing point of the resonant inductor current. At this time, the second and fourth time periods are relatively small. Figure 6 The high level in the second and fourth time periods shown corresponds to a narrow pulse. By using the modulation method in this embodiment, the first switch S1 / second switch S2 that is turned on again is turned off as early as possible, which can cut off the inherent leakage current path of the gate G of the power switch Q and further reduce the conduction loss of the drive circuit.

[0128] In this embodiment, the driving device 100 can sample the resonant inductor L through the sampling unit. r The current is sampled and the sampled value is input to the control unit; the control unit compares the sampled value with a first threshold (e.g., 1A), and when the sampled value is equal to the first threshold, the control unit turns on the first switch S1 again; the control unit compares the sampled value with zero, and when the sampled value is equal to zero, the control unit turns off the first switch S1, and the second time cycle ends.

[0129] In this embodiment, the driving device 100 can further sample the resonant inductor L through the sampling unit. r The current is sampled and the sampled value is input to the control unit; the control unit compares the sampled value with a second threshold (e.g., -1A), and when the sampled value is equal to the second threshold, the control unit turns on the second switch S2 again; the control unit compares the sampled value with zero, and when the sampled value is equal to zero, the control unit turns off the second switch S2, and the fourth time cycle ends.

[0130] like Figure 7 As shown, the present invention is illustrated as follows. Figure 4A The operating waveforms of another specific embodiment of the drive device 100 are shown. In this embodiment, the first switch S1, which is turned on again, is turned off before the second switch S2 is turned on, and the second switch S2, which is turned on again, is turned off before the first switch S1 is turned on in the next switching cycle. In the resonant inductor L... r current i Lr When the voltage is about to decrease to 0, typically less than 1A, the first switch S1 is turned on for the second time. During the driving voltage maintenance phase, the first switch S1 remains on until the second switch S2 operates. In the resonant inductor L... r current i Lr When the voltage is about to increase to 0, typically greater than -1A, the second switch S2 is turned on for the second time. During the drive voltage maintenance phase, the second switch S2 remains on until the first switch S1 operates. In the second and fourth time cycles, the gate G of the power switch Q is connected to the power supply V with extremely low internal resistance. DD / V EE The gate G is a low-impedance connection. In this embodiment, the gate G of the power switch Q is connected to the power supply, and the gate G has high stability and strong anti-crosstalk capability.

[0131] Figure 8A The circuit topology of a second preferred embodiment of the driving device of the present invention is shown. Figure 8B It shows Figure 8A The operating waveform of the drive device. Figure 8A In the illustrated embodiment, MOSFETs S3 / S4 are used instead of Figure 4A Diodes D1 / D2 in the illustrated embodiment. In the resonant inductor L... r At time t1 when freewheeling begins, MOSFET S3 is turned on, and MOSFET S3 is turned off just before the second switch S2 is about to turn on; at the resonant inductor L r At time t5, when freewheeling begins, MOSFET S4 is turned on, and it is turned off just before the first switch S1 is about to turn on. During freewheeling, current flows through MOSFETs S3 / S4, which operate in synchronous rectification mode. During the drive voltage sustaining phase, MOSFETs S3 / S4 remain on, and the gate G of power switch Q is connected to the low-resistance power supply V through MOSFETs S3 / S4. DD / V EE This is a low-impedance connection. In this embodiment, MOSFETs S3 / S4 operate in synchronous rectification mode, which further reduces the conduction loss of the drive circuit. Moreover, the gate G of the power switch Q is directly connected to the power supply without an inductor, further improving stability and enhancing crosstalk immunity.

[0132] Compared with existing traditional solutions and lossless driving solutions, the present invention has the following advantages:

[0133] Compared to traditional solutions, the driving loss of the present invention is reduced:

[0134] (1) Using a resonant inductor instead of a driving resistor, the resonant inductor feeds some energy back to the power supply, reducing the loss of the driving circuit.

[0135] (2) Some losses in the circuit are independent of frequency, with a more pronounced advantage at high frequencies. The comparison of losses between the traditional scheme and the scheme of this invention at different frequencies is as follows: Figure 9 As shown, the driving loss of the present invention can be reduced to about half that of the traditional solution.

[0136] Compared to existing lossless driving solutions, the overall losses of the driving circuit and power switch in this invention are reduced, and the reliability is improved.

[0137] (1) By turning on the switch of the half-bridge arm again, the excitation source of the resonant circuit is eliminated, and the generation of oscillation is suppressed.

[0138] (2) The driving voltage is oscillating and maintains a stable set voltage during the switching process, ensuring the gate reliability of the power switch;

[0139] (3) The driving voltage is a set voltage, which can maintain a small on-resistance of the power switch and further control the conduction loss.

[0140] like Figure 10A As shown, the V measured by the existing lossless drive scheme is illustrated. gs Waveform, by Figure 10A It is evident that the existing lossless drive solutions exhibit voltage oscillations, such as drops of 3V or 5V. The normal drive voltage is approximately 18V / -5V, which drops to 15V / 0V after the voltage drop. Figure 10B As shown, the V measured by the present invention is illustrated. gs Waveform, by Figure 10B As can be seen, the present invention effectively suppresses the generation of oscillations, and the driving voltage is basically maintained at around 18V / -5V.

[0141] Exemplary embodiments of the present invention have been specifically illustrated and described above. It should be understood that the present invention is not limited to the disclosed embodiments; rather, the present invention is intended to cover various modifications and equivalent arrangements contained within the spirit and scope of the appended claims.

Claims

1. A control method for a driving device, the driving device being used to drive a power switch, characterized in that, The driving device includes a power supply, a first bridge arm coupled to the power supply, a second bridge arm coupled in parallel to the first bridge arm, and a resonant inductor. The first bridge arm includes a first switch and a second switch connected to a first midpoint. The second bridge arm includes a first semiconductor device and a second semiconductor device connected to a second midpoint. The resonant inductor is coupled between the first midpoint and the second midpoint. The power supply includes a first power supply and a second power supply. The first power supply is coupled to the first switch, and the second power supply is coupled to the second switch. The control method includes: The first switch is turned on for a first time period to charge the gate of the power switch by the power supply. When the gate voltage of the power switch increases to the voltage of the first power supply, the first switch is turned off. In response to the current of the resonant inductor dropping to a first threshold, the first switch is turned on again for a second time period, so that the potential of the first midpoint is equal to the potential of the second midpoint, and the first threshold is greater than zero.

2. The control method according to claim 1, characterized in that, Also includes: The second switch is turned on for a third time period to allow the gate of the power switch to discharge; In response to the current of the resonant inductor rising to the second threshold, the second switch is turned on again for a fourth time period so that the potential of the first midpoint is equal to the potential of the second midpoint.

3. The control method according to claim 2, characterized in that, During the second time period, the potential of the first midpoint is clamped to the voltage of the first power supply by the first switch, and the potential of the second midpoint is equal to the voltage of the first power supply. During the fourth time period, the potential of the first midpoint is clamped to the voltage of the second power supply by the second switch, and the potential of the second midpoint is equal to the voltage of the second power supply.

4. The control method according to claim 2, characterized in that, The first switch is turned off when the current in the resonant inductor drops to zero, and the second switch is turned off when the current in the resonant inductor rises to zero.

5. The control method according to claim 2, characterized in that, The first switch is turned off before the second switch is turned on, and the second switch is turned off before the first switch is turned on in the next switching cycle.

6. The control method according to any one of claims 1-5, characterized in that, The control method further includes: The time t when the current of the resonant inductor drops to the first threshold is calculated according to the first inductor current formula. α1 ; The moment t when the current of the resonant inductor drops to zero is calculated according to the second inductor current formula. β1 ; The time t for turning on the second switch is calculated based on the duty cycle and switching frequency of the power switch. μ1 ; The internal timer counts down to time t. α1 Then, turn the first switch on again; The internal timer counts as [t] β1 , t μ1 At a certain moment in the second time period, the first switch is turned off, and the second time period ends.

7. The control method according to any one of claims 2-5, characterized in that, The control method further includes: The moment t when the current of the resonant inductor rises to the second threshold is calculated according to the third inductor current formula. α2 ; The moment t when the current of the resonant inductor rises to zero is calculated according to the fourth inductor current formula. β2 ; Determine the start time t0 of the next switching cycle; The internal timer counts down to time t. α2 Then, turn on the second switch again; The internal timer counts as [t] β2 At a certain moment in t0), the second switch is turned off, and the fourth time period ends.

8. The control method according to any one of claims 1-4, characterized in that, The control method further includes: The current of the resonant inductor is sampled by a sampling unit, and the sampled value is input into a control unit; The control unit compares the sampled value with the first threshold, and when the sampled value is equal to the first threshold, the first switch is turned on again. The control unit compares the sampled value with zero. When the sampled value equals zero, the first switch is turned off, and the second time period ends.

9. The control method according to any one of claims 1-5, characterized in that, The control method further includes: The current of the resonant inductor is sampled by a sampling unit, and the sampled value is input into a control unit; The control unit compares the sampled value with the first threshold, and when the sampled value is equal to the first threshold, the first switch is turned on again. The control unit compares the sampled value with zero, and when the sampled value equals zero, records the time t of the internal timer. β1 ; The control unit obtains the on-time t of the second switch. μ1 When the internal timer counts to (t) β1 , t μ1 At a certain moment in the second time period, the first switch is turned off, and the second time period ends.

10. The control method according to any one of claims 2-4, characterized in that, The control method further includes: The current of the resonant inductor is sampled by a sampling unit, and the sampled value is input into a control unit; The control unit compares the sampled value with the second threshold, and when the sampled value equals the second threshold, the second switch is turned on again. The control unit compares the sampled value with zero. When the sampled value equals zero, the second switch is turned off, and the fourth time period ends.

11. The control method according to any one of claims 2-5, characterized in that, The control method further includes: The current of the resonant inductor is sampled by a sampling unit, and the sampled value is input into a control unit; The control unit compares the sampled value with the second threshold, and when the sampled value equals the second threshold, the second switch is turned on again. The control unit compares the sampled value with zero, and when the sampled value equals zero, records the time t of the internal timer. β2 ; The control unit obtains the start time t0 of the next switching cycle, and the internal timer counts down to (t... β2 At a certain moment in t0), the second switch is turned off, and the fourth time period ends.

12. The control method according to claim 2, characterized in that, The first threshold ranges from (0, 1A], and the second threshold ranges from [-1A, 0].

13. A driving device for driving a power switch, characterized in that, The driving device includes: Power supply, including a first power supply and a second power supply; A first bridge arm is coupled to the power supply. The first bridge arm includes a first switch and a second switch connected to a first midpoint. The first power supply is coupled to the first switch, and the second power supply is coupled to the second switch. The second bridge arm is coupled in parallel to the first bridge arm, and the second bridge arm includes a first semiconductor device and a second semiconductor device connected at the second midpoint; and A resonant inductor is coupled between the first midpoint and the second midpoint; Wherein, the first switch is controlled to be turned on for a first time period so that the power supply charges the gate of the power switch; when the gate voltage of the power switch increases to the voltage of the first power supply, the first switch is turned off; in response to the current of the resonant inductor dropping to a first threshold, the first switch is controlled to be turned on again for a second time period so that the potential of the first midpoint is equal to the potential of the second midpoint, and the first threshold is greater than zero.

14. The driving device according to claim 13, characterized in that, The second switch is controlled to be turned on for a third time period to discharge the gate of the power switch; in response to the current of the resonant inductor rising to a second threshold, the second switch is controlled to be turned on again for a fourth time period to make the potential of the first midpoint equal to the potential of the second midpoint.

15. The driving device according to claim 14, characterized in that, During the second time period, the potential of the first midpoint is clamped to the voltage of the first power supply by the first switch, and the potential of the second midpoint is equal to the voltage of the first power supply. During the fourth time period, the potential of the first midpoint is clamped to the voltage of the second power supply by the second switch, and the potential of the second midpoint is equal to the voltage of the second power supply.

16. The driving device according to claim 14, characterized in that, The first switch is turned off when the current in the resonant inductor drops to zero, and the second switch is turned off when the inductor current rises to zero.

17. The driving device according to claim 14, characterized in that, The first switch is turned off before the second switch is turned on, and the second switch is turned off before the first switch is turned on in the next switching cycle.

18. The driving device according to any one of claims 13-17, characterized in that, It also includes a control unit electrically connected to the first switch and the second switch, the control unit being used to perform: The time t when the current of the resonant inductor drops to the first threshold is calculated according to the first inductor current formula. α1 ; The moment t when the current of the resonant inductor drops to zero is calculated according to the second inductor current formula. β1 ; The time t for turning on the second switch is calculated based on the duty cycle and switching frequency of the power switch. μ1 ; The internal timer counts down to time t. α1 Then, turn the first switch on again; The internal timer counts as [t] β1 , t μ1 At a certain moment in the second time period, the first switch is turned off, and the second time period ends.

19. The driving device according to any one of claims 14-17, characterized in that, It also includes a control unit electrically connected to the first switch and the second switch, the control unit being used to perform: The moment t when the current of the resonant inductor rises to the second threshold is calculated according to the third inductor current formula. α2 ; The moment t when the current of the resonant inductor rises to zero is calculated according to the fourth inductor current formula. β2 ; Determine the start time t0 of the next switching cycle; The internal timer counts down to time t. α2 Then, turn on the second switch again; The internal timer counts as [t] β2 At a certain moment in t0), the second switch is turned off, and the fourth time period ends.

20. The driving device according to any one of claims 13-16, characterized in that, It also includes a sampling unit and a control unit, wherein the sampling unit is electrically connected to the resonant inductor, and the control unit is electrically connected to the first switch and the second switch, wherein: The sampling unit samples the current of the resonant inductor and inputs the sampled value into the control unit; The control unit compares the sampled value with the first threshold. When the sampled value equals the first threshold, the control unit turns the first switch back on. The control unit compares the sampled value with zero. When the sampled value equals zero, the control unit turns off the first switch, and the second time period ends.

21. The driving device according to any one of claims 13-17, characterized in that, It also includes a sampling unit and a control unit, wherein the sampling unit is electrically connected to the resonant inductor, and the control unit is electrically connected to the first switch and the second switch, wherein: The sampling unit samples the current of the resonant inductor and inputs the sampled value into the control unit; The control unit compares the sampled value with the first threshold. When the sampled value equals the first threshold, the control unit turns the first switch back on. The control unit compares the sampled value with zero. When the sampled value equals zero, the control unit records the time t of the internal timer at that moment. β1 ; The control unit obtains the on-time t of the second switch. μ1 When the internal timer counts to (t) β1 , t μ1 At a certain moment in the second time cycle, the control unit turns off the first switch, and the second time cycle ends.

22. The driving device according to any one of claims 14-16, characterized in that, It also includes a sampling unit and a control unit, wherein the sampling unit is electrically connected to the resonant inductor, and the control unit is electrically connected to the first switch and the second switch, wherein: The sampling unit samples the current of the resonant inductor and inputs the sampled value into the control unit; The control unit compares the sampled value with the second threshold. When the sampled value equals the second threshold, the control unit turns the second switch back on. The control unit compares the sampled value with zero. When the sampled value is equal to zero, the control unit turns off the second switch, and the fourth time period ends.

23. The driving device according to any one of claims 14-17, characterized in that, It also includes a sampling unit and a control unit, wherein the sampling unit is electrically connected to the resonant inductor, and the control unit is electrically connected to the first switch and the second switch, wherein: The sampling unit samples the current of the resonant inductor and inputs the sampled value into the control unit; The control unit compares the sampled value with the second threshold. When the sampled value equals the second threshold, the control unit turns the second switch back on. The control unit compares the sampled value with zero. When the sampled value equals zero, the control unit records the time t of the internal timer at that moment. β2 ; The control unit obtains the start time t0 of the next switching cycle, and the internal timer counts down to (t... β2 At a certain moment in t0), the control unit turns off the second switch, and the fourth time cycle ends.

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