Driver circuit for GaN switch-mode power converter

Abstract

The driver circuit is for driving a GaN power commutation switch in a switch-mode power converter. A sensing component is connected to the GaN switch to sense a parameter such as a peak current of the power commutation. An energy storage component provides a certain turn-on voltage between the gate and source of the GaN switch. Charging and discharging of the energy storage component are regulated and sensing is disabled at a time synchronized with the charging and discharging functions of the energy storage component. The voltage across the sensing component is prevented from reducing the generated gate-source drive voltage of the GaN switch.

Description

Technical Field

[0001] The present invention relates to a switch-mode power converter, and more particularly, to a switch-mode power converter having a GaN power commutation switch.

Background Art

[0002] Switch-mode power converters are widely used.

[0003] Conventional switch-mode power converters use a MOSFET power commutation switch to control the commutation between the energy storage mode of an energy storage component (generally an inductor) and the flyback / freewheeling mode in which energy is released from the energy storage component to the output load. The switching, such as the duty cycle of the power commutation switch in the energy storage mode and the flyback mode, controls the energy transfer rate between the input and the output, and the circuit can be, for example, a boost converter, a buck converter, a buck-boost converter or a flyback converter. More advanced circuits can be, for example, LLC, LCC, Cuk, SEPIC, or BiFRED converters. The general principle is the same, which is energy storage and freewheeling.

[0004] Generally, a sense resistor is connected in series with the MOSFET power commutation switch to supply a current sensing feedback signal. The gate driver of the MOSFET power commutation switch has a voltage higher than the threshold voltage Vth (such as about 3.5V) of the MOSFET power commutation switch, for example, 12V or 15V, so that the voltage drop through the sense resistor does not affect the circuit operation.

[0005] The gate driver can be directly connected to the ground without considering the influence of the voltage in the sense resistor.

[0006] There is a demand for GaN transistors, such as GaN HEMTs, as power commutation switches for switch-mode power supplies in high-power applications. These transistors have high breakdown voltage, low parasitic capacitance, and low turn-on resistance (and therefore efficient operation). The advantages of GaN transistors also include the ability to switch at higher frequencies, which reduces the size of the energy storage components and thus minimizes the overall size of the switch-mode power converter.

[0007] However, the turn-on threshold voltage of these transistors is much closer to zero, around 1.5V, and also close to the typical gate drive voltage of around 6V. The influence of the voltage in the current sense resistor on the gate drive signal of a GaN transistor cannot be ignored; otherwise, it can lead to oscillation or linear operation or high drain-source on-resistance, which can harm the power commutation switch. In short, the gate-source drive voltage for a GaN switch must be precise and stable, unlike the gate-source drive voltage for a MOSFET, which has a larger tolerance.

[0008] Figure 1 shows an example of a known circuit for driving a GaN power commutation switch in a switch-mode power converter to address these problems.

[0009] This example shows a boost converter comprising an energy storage inductor L1, a power commutation GaN switch M1, and a current sensing resistor RCS in series between the drain of the GaN switch and ground. An input capacitor C3 is located between the positive input and ground. The node between the inductor L1 and the power commutation switch M1 is connected to a load LED via a freewheeling diode D1, and an output capacitor C1 is located in parallel with the load.

[0010] The supply voltage VCC is obtained from the high-voltage side of the power commutation switch M1 and stored in capacitor C3. This is used to supply power to the first low-dropout regulator LDO1, which powers the control unit MCU. This power is stored in capacitor C5. The control unit MCU receives the voltage across the sense resistor RCS as a current sense feedback signal CS, which is used by the controller to determine the switching time of the power commutation switch M1.

[0011] The supply voltage VCC is also used to supply a second 6V low-dropout regulator LDO2, which supplies the gate drive signal stored in capacitor C4 to the power commutation switch. The gate drive signal is optionally supplied via a gate driver circuit GDr, such as a push-pull transistor bridge.

[0012] Capacitor C4 stores the gate-source drive voltage of the power commutator switch M1 (not the voltage from gate to ground).

[0013] The problem with this circuit is that the supply voltage VCC is referenced to ground, while the 6V regulator LDO2 supplies ground to the GaN driver circuit GDr, which is connected to the source of the GaN power commutation switch. These two power supplies use different grounds. [Overview of the Initiative] [Problems that the invention aims to solve]

[0014] In the circuit shown in Figure 1, the gate-source voltage of the power rectifier switch M1 is still affected by the current sensing resistor RCS because the regulator LDO2 is connected to ground via the current sensing resistor RCS. When the power commutator switch M1 is on and the current sensing resistor RCS is sensing the power supply current, a voltage spike across the current sensing resistor RCS can result in a drop in the voltage across capacitor C4, and therefore in the gate-source voltage of the GaN switch M1, which is the voltage when it is turned on. This can prevent the GaN switch M1 from turning on or cause oscillation. In particular, the regulator LD01 is affected by the voltage across RCS due to its relatively low response speed, and because a small voltage drop through the regulator LD01 is desirable (for better efficiency). Therefore, the voltage across capacitor C4 may not be very stable. When C4 is charged or discharged, the current flowing through C4 also flows through the sensing resistor RCS, affecting the sensing voltage in RCS, which in turn can affect the feedback control loop.

[0015] Therefore, there is a need for improved driver circuits to drive GaN power transistors in switch-mode power converters.

[0016] US20160181929A1 and Linear Technology's "LT8312 Boost Controller with Power Factor Correction" disclose signal blanking in a sensing resistor for a period of time after the switch is turned on. EP0514064A2 discloses a circuit for controlling the timing of a switch, in which turning the switch on triggers the discharge of a capacitor in an RC timing circuit, and the switch is turned off when the capacitor discharges below a certain threshold. [Means for solving the problem]

[0017] The present invention is defined by the claims.

[0018] The sensing component of a switch-mode power supply is essential to control loops such as current control loops. However, the concept of the present invention is to store the energy required to switch on the power commutation switch of a switch-mode power converter in an energy storage component, and to control the charging and / or discharging of the energy storage component without being affected by the sensing component, so that the power commutation switch can be stably switched on. In addition, the feedback sensing function is not affected. The charging and discharging of the energy storage component is coordinated in timing synchronized with the decoupling of the sensing path. This decoupling may be electrical or logical (i.e., performed based on feedback control timing). In short, an example of the present invention selectively omits the function of the sensing component at the moment when the energy required to switch on the power commutation switch is being coordinated. This choice is not obvious from the prior art in which the sensing component always senses the power supply current and affects the coordination of the energy required to switch on the power commutation switch in the switch-mode power supply.

[0019] According to an example of one aspect of the present invention, a driver circuit for driving a power commutation GaN switch of a switch-mode power converter, wherein the power converter has, in power commutation, an energy storage phase when the GaN switch is closed and a freewheeling phase when the GaN switch is open, and the driver circuit A sensing component that can be connected to the GaN switch and is adapted to detect the power commutation parameters, comprising a sensing component in the sensing path, An energy storage component for supplying a specific turn-on voltage between the gate and source of the GaN switch, For the purpose of feedback control, the GaN switch has a control circuit connected to it to control the switching of the GaN switch and to adjust the charging and discharging of the energy storage component according to the detected parameters of the power commutation, A driver circuit is provided which is adapted to adjust the charging of the energy storage component via the sensing component so that the control unit does not use the signal (CS) in the sensing component for feedback control purposes at that time, and / or adjust the discharge of energy stored in the energy storage component so that the sensing component is supplied with the certain turn-on voltage to the GaN switch so that the GaN switch is turned on without the sensing component by decoupling the sensing component from sensing the parameter of the power commutation.

[0020] This driver circuit prevents the voltage drop through the sensing component from affecting the energy storage component for switching the GaN switch on, and therefore, the desired turn-on voltage (e.g., 6V) is supplied.

[0021] Decoupling the detection path from detecting the parameters of the power commutation means that, at the time of regulating the charging / discharging of the energy stored in the energy storage component, the detection component is not performing its function of detecting the parameters of the power commutation.

[0022] In the examples described in more detail below, the charging current of the energy storage component may still flow through the detection component, but in that case, the detection component is not detecting the parameters of the power transfer. Thus, the term "decoupling" may not only be physical or electrical decoupling, but may also be logical decoupling in the sense that the detection component still exists but is not detecting the parameters. For example, the charging or discharging current may flow through the detection component even when the detection path is decoupled, but the signal being detected (e.g., voltage) is not interpreted as a feedback parameter, and the voltage drop in the detection component ultimately does not affect the voltage of the energy storage component.

[0023] Embodiments of the present invention prevent the voltage across both ends of the detection component from reducing the gate-source drive voltage generated by the GaN switch. The energy storage component such as a capacitor can store the desired gate-source drive voltage so that, for example, the desired gate-source drive voltage can be applied between the gate and the source. On the other hand, this example of the present invention also prevents the charging / discharging of the energy storage component from affecting the detection path.

[0024] Instead of a passive energy storage component that stores the gate-source voltage (similar to the prior art), the charging and discharging of the energy storage component are adjusted by the control circuit. This enables, for example, control of the timing of the charging and discharging currents such that no voltage spikes occur in the detection component when detection is being performed.

[0025] The parameter being detected is, for example, the current flowing, such as the peak current in the energy storage phase.

[0026] The detection component is, for example, a detection resistor connected between the source of the GaN switch and the ground.

[0027] In some examples, the driver circuit further includes a control loop, preferably a feedback control loop, adapted to use the parameter detected by the sensing component. This embodiment clearly indicates that the sensing path is, to those skilled in the art, usually essential and indispensable for the control loop. Therefore, decoupling the sensing path to handle the energy storage component is not obvious to those skilled in the art.

[0028] In one example of the present invention, the control circuit may be adapted to adjust the discharge of energy stored in the energy storage component so that the GaN switch is turned on while the detection path including the detection component is being decoupled.

[0029] In other words, the adjustment of the energy storage component to turn on the GaN switch occurs at a different time than the detection function of the detection path, which includes the detection component. Therefore, the detection path can be disabled when the detection function is not required. Thus, the energy storage component can fully supply voltage to the GaN switch to reliably turn it on, and the energy storage component does not affect the detection function of the detection component.

[0030] The detection path may be disabled by providing that the detection component is short-circuited, or the detection path may be disabled because the detection function is not performed while the GaN switch is turned on, even if the detection component still functions later after the GaN switch has been stably turned on.

[0031] The control circuit may be adapted to (re)connect the sensing path such that, after the GaN switch is turned on, the sensing component is adapted to detect an amount related to the charge energy in the energy storage phase of the power commutation. At that moment, the voltage requirements across the gate and source of the GaN switch for maintaining the GaN switch are relaxed, and any voltage fluctuations due to any voltage spikes in the sensing component no longer prevent the GaN switch from turning on.

[0032] Therefore, the detection component can be disabled until the energy storage phase begins.

[0033] The driver circuit may have a voltage regulator for supplying energy from the energy storage component to the control circuit, the voltage regulator being adapted to output a certain turn-on voltage and coupled to the gate drive terminal and ground. Therefore, since the LDO regulator and the GaN switch are co-grounded (because the detection path is decoupled), a single LDO regulator is required in the circuit to supply a stable turn-on voltage.

[0034] The gate drive terminal may be connected to the gate of the GaN switch, or to a gate driver, in which case the gate driver applies a drive voltage to the gate. A gate driver, such as a push-pull transistor bridge or half-bridge, may be further provided to turn on the GaN switch, but this is optional.

[0035] In the first set of the example, a short-circuit switch is provided to short-circuit the sensing component, the energy storage component is supplied by a supply voltage and connected to ground, and the control circuit is The energy storage component is discharged via the voltage regulator to supply the turn-on voltage across the gate and source of the GaN switch to turn on the GaN switch while the sensing component is temporarily short-circuited using the short-circuit switch, The voltage regulator is adapted to use a voltage in the energy storage component so as to terminate the short circuit in the sensing component after the GaN switch has been fully turned on, keep the GaN switch on, and enable the sensing component to sense the parameters of the energy storage phase.

[0036] In the first set of this example, the voltage supplied by the energy storage component does not flow into the sensing component but is sent (discharged) to the gate of the GaN switch (and therefore to the gate-source junction). Therefore, the current through the GaN switch does not flow through the sensing component and does not change the potential of the source of the GaN switch, thus ensuring that switching can be reliably performed at a low voltage in the energy storage component. The discharge current of the energy storage component also does not flow through the sensing component and therefore does not affect current sensing.

[0037] In that case, the discharge of the energy storage component may occur at the start of the energy storage phase, at which point the detection component is short-circuited. The short-circuiting of the detection component avoids the effects of voltage spikes caused in the detection component by the power supply current passing through the GaN switch.

[0038] The energy storage component may be coupled to the gate of the GaN switch via a low-dropout regulator acting as a voltage regulator. In this case, the driver circuit may further include a gate driver circuit at the output of the low-dropout regulator, and the low-dropout regulator and the gate driver circuit are connected to ground.

[0039] Therefore, the gate driver circuit can reference ground even though the sensing component is on a path to ground, because the sensing component is short-circuited when the GaN switch is turned on.

[0040] Since the time the GaN switch is turned on is very short compared to the entire energy storage phase, the sensing component is switched back to perform the sensing function, and during that time the voltage of the energy storage component is sufficient to keep the GaN switch on, since the voltage requirements for keeping the GaN switch on are far less stringent (not required to be as precise and stable) than the voltage requirements for turning the GaN switch on.

[0041] In the second set of the example, the control unit is: In the charging phase, the signal in the detection component is used for feedback control purposes. The control circuit is configured to charge the energy storage component via the sensing component during the freewheeling phase, in which case the control unit does not use the signal (CS) from the sensing component for feedback control purposes.

[0042] In the second set of examples, the energy storage component is not referenced to ground in this case. Instead, the energy storage component is charged to a sufficient level during the freewheeling phase so that the voltage drop through the sensing component does not affect the turn-on of the GaN switch, and a sufficient voltage is directly applied between the gate and the source. However, separate power supplies are not required despite the different ground references in different parts of the circuit. During the freewheeling phase, since this is a different time from the sensing time, the sensing component does not operate to sense the commutation parameter.

[0043] In the dedicated capacitor for the gate-source voltage, charging may occur at any point in the freewheeling phase, because at this time there is no power commutation to be detected by the sensing component, and such power commutation does not affect the charging of this capacitor.

[0044] The control circuit is adapted, for example, to charge the energy storage component from the supply voltage (VCC) via the sensing component during the freewheeling phase, when the control unit does not use the signal (CS) in the sensing component for feedback control purposes. Decoupling the sensing path means that the sensing path is logically open because the power switch is open during the freewheeling phase.

[0045] The charging is performed through the sensing component. However, the sensing path is decoupled during this process. Since the sensing component is typically a low-impedance component, the energy storage component can be charged to a sufficiently accurate voltage in time during the freewheeling phase.

[0046] The supply voltage may be coupled to the energy storage component via a voltage regulator, the voltage regulator being adapted to output a certain turn-on voltage, and the control circuit being adapted to charge the voltage of the energy storage component up to the output voltage of the voltage regulator.

[0047] The voltage regulator may be connected to ground, the negative terminal (cathode) of the energy storage component may be coupled to ground via the sensing component, and the positive terminal (anode) of the energy storage component may be coupled to the gate of the GaN switch. In this example, the voltage regulator charges the energy storage component to the turn-on voltage during the freewheeling phase.

[0048] The coupling with the gate may be via a gate driver circuit. In that case, the ground terminal of the gate driver circuit may be connected to the source of the GaN switch.

[0049] The present invention Power communication component, GaN switch and Freewheeling diode and A power converter having the above-described driver circuit for driving the GaN switch is also provided.

[0050] The power transmission component, the GaN switch, and the detection component are arranged in series between the power input and ground and are adapted to define the detection path.

[0051] Any converter topology can be used, as long as it includes a series connection of the power commutation switch and the sensing component (with or without a series load), and examples of the present invention can overcome interference between the energy storage component and the sensing component for turning on the GaN switch in those topologies. The power converter may have, for example, a boost converter, a buck converter, a buck boost converter, or a flyback converter.

[0052] These and other aspects of the present invention will be described and clarified with reference to the following examples. [Brief explanation of the drawing]

[0053] For a better understanding of the present invention and to more clearly illustrate how it can be carried out, the accompanying drawings are referenced here, as merely one example. [Figure 1] An example of a known circuit for driving an GaN power commutation switch in a switch-mode power converter is shown. [Figure 2] This shows the first example of a boost converter architecture. [Figure 3] The operating waveform of the circuit in Figure 2 is shown. [Figure 4] Figure 2 shows the same circuit technique applied to a buck converter architecture. [Figure 5] This shows a second example of a boost converter architecture. [Figure 6] The operating waveform of the circuit in Figure 5 is shown. [Figure 7] Figure 5 shows the same circuit technique applied to a buck converter architecture. [Modes for carrying out the invention]

[0054] The present invention will be described with reference to the figures.

[0055] The detailed descriptions and specific examples illustrate the apparatus, systems, and methods, but are for illustrative purposes only and should not be used to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, systems, and methods of the invention will be better understood from the following description, the appended claims, and the appended drawings. The figures are for illustrative purposes only and are not drawn to scale. Throughout the figures, the same reference numerals are used to indicate the same or similar parts.

[0056] The present invention provides a driver circuit for driving a GaN power commutation switch in a switch-mode power converter. A sensing component is connected to the GaN switch to sense parameters such as the peak current of power commutation. An energy storage component supplies a specific turn-on voltage between the gate and source of the GaN switch. The charging and / or discharging of the energy storage component is regulated to specific times, and the sensing is deactivated at a timing synchronized with the charging and / or discharging of the energy storage component. The voltage across the sensing component is prevented from reducing the voltage in the energy storage component, thereby reducing the gate-source drive voltage generated by the GaN switch. The charging and discharging of the energy storage component is also prevented from affecting the sensing of the sensing component.

[0057] Figure 2 shows a boost converter architecture employing the first example of the driver circuit of the present invention.

[0058] Figure 2 shows the same inductor L1, freewheeling diode D1, output storage capacitor C1, power commutation GaN switch M1, sensing component RCS, input capacitor C2, and load LED as in the circuit of Figure 1. Similar to the example in Figure 1, the sensing component is a sensing resistor RCS connected between the source and ground GND of the GaN switch.

[0059] The power converter has an energy storage phase when the GaN switch M1 is closed. At this time, current flows from the input through inductor L1 and GaN switch M1 to ground. Energy is stored in the inductor, and the load LED is supplied by output capacitor C1. The freewheeling phase occurs when the GaN switch M1 is open. The energy stored in the input and inductor L1 is supplied to the load (and output capacitor C1).

[0060] The control circuit 20 is connected to the gate G of the GaN switch M1 not only to control the switching of the GaN switch M1, but also to adjust the charging and discharging of the energy storage component, namely capacitor C3. Capacitor C3 functions as an energy storage component that stores the supply voltage VCC and discharges to supply a specific turn-on voltage between the gate and source of the GaN switch.

[0061] This circuit has a single regulator 22 for supplying energy from the energy storage component C3 to the control circuit 20. The voltage regulator 22 is adapted to output a specific turn-on voltage and is coupled to the gate drive terminal and ground GND. In this example, the gate drive terminal is an input to a gate driver circuit 24 (GDr), in which case the gate driver circuit 24 (GDr) is connected to the gate G. The gate driver circuit 24 is a well-known circuit, such as a half-bridge circuit, for facilitating control at the gate G. It should be noted that the gate driver circuit 24 is optional, and most importantly, a precise and stable turn-on voltage, such as 6V in some examples (depending on the specific GaN switch design), needs to be supplied to the gate source of the GaN switch.

[0062] The regulator 22 may be, for example, a low-dropout regulator 22, and the gate driver circuit 24 is connected to ground GND. Therefore, in this circuit, there is only one ground reference.

[0063] In this example, decoupling of the detection path involves using a short-circuit switch M2 in parallel with the detection component RCS to short-circuit the detection component. The short-circuit switch may be a low-voltage MOSFET.

[0064] The controller 20 discharges the energy storage component C3 via the voltage regulator 22 to supply a turn-on voltage across the gate and source of the GaN switch to turn on the GaN switch M1. At this time, the sensing component RCS is temporarily short-circuited using the short-circuit switch M2. At this moment, the energy storage component C3, the LDO 22, and the source of the GaN switch M1 are all connected to common ground (RCS is short-circuited), so the LDO 22 can accurately and stably supply a 6V voltage to the gate and source of the GaN switch M1, and thus the GaN switch M1 can be turned on without interference.

[0065] The short-circuit function is terminated after the GaN switch M1 is fully turned on. The sensing path is then (re)connected. The voltage across the energy storage component C3 keeps the GaN switch M1 on via the voltage regulator 22 (the GaN switch is voltage-driven, unlike the current-driven BJT transistor), allowing the sensing component RCS to continue sensing the parameters of the energy storage phase. Thus, the sensed parameters can be used as a feedback sensing signal.

[0066] Therefore, in this example, during the turn-on of the GaN switch, the energy stored in the energy storage component C3 is discharged to turn on the GaN switch. During this time, the detection path, including the detection component, is decoupled.

[0067] This circuit has a stable voltage reference VCC stored in capacitor C3 connected to a common ground. It is used to generate a precise GaN drive voltage such as 6V. The charging of C3 does not need to be timed with the charging or freewheeling phase of the converter.

[0068] The sensing resistor RCS is bypassed (short-circuited) for each turn-on time of the GaN switch, during which time the source of the GaN switch M1 is coupled to common ground. Thus, the source of the GaN switch M1 and capacitor C3 are connected to common ground. The voltage across C3 can accurately turn on the GaN switch M1 via the LDO22 without damage from overvoltage driving conditions and without driving it with an insufficient undervoltage to fully turn on the GaN switch M1.

[0069] The short-circuit function also prevents the voltage spike caused in the sensing resistor by the power supply current passing through the GaN switch M1 when the GaN switch M1 is turned on from affecting the 6V voltage across the gate and ground (and therefore the source).

[0070] The sensing path can be recombined after the turn-on transient period has completely elapsed. The sensing resistor can then be used to detect the peak current signal for controlling the converter circuit in the conventional manner. There is still sufficient time for the input current to reach the peak current detected by the sensing resistor, and therefore the current control of the switch-mode power supply remains unaffected.

[0071] When resistor RCS is reconnected to the circuit, the gate-source voltage Vgs changes slightly, and more specifically, is reduced by the voltage across RCS. However, since GaN switch M1 is already fully turned on, this changed voltage Vgs does not significantly affect the state of GaN switch M1, nor does it turn off GaN switch M1, nor does it cause GaN switch M1 to oscillate.

[0072] Figure 3 shows the operating waveform of the circuit.

[0073] The top plot shows the inductor current I L1 The second plot shows the gate voltage V of the power commutation GaN switch M1. M1GThe third plot shows the gate voltage V of the short-circuit switch M2. M2G This shows the voltage V across the current sensing resistor. The bottom plot shows the voltage V across the current sensing resistor. RCS This demonstrates that the turn-on process of the GaN switch M1 is unaffected by voltage spikes at the source, as M2 is turned on so that the source is connected to ground. Peak current sensing for circuit loop control is also unaffected, as a valid signal reflecting the peak current still exists. Therefore, the driver circuit can ensure the operation of the power commutation switch with a single power supply without affecting the current sensing function used by the feedback control loop.

[0074] Figure 2 shows a boost converter architecture. Figure 4 shows the same circuit technique applied to a buck converter architecture.

[0075] The same components are given the same names. The short-circuit switch M2, as before, is a low-voltage MOSFET that is turned on before the power commutation switch M1 is turned on and turned off after the turn-on transient period of the GaN switch M1 has ended.

[0076] In a buck converter topology, when the power commutation GaN switch M1 is turned on, the input sequentially supplies current to the load LED, output capacitor C1, and inductor L1. When the GaN switch M1 is turned off, inductor L1 sequentially supplies current to the load LED, output capacitor, and inductor L1 through the freewheeling diode D2.

[0077] Figure 5 shows the application of the second circuit method to a boost converter architecture.

[0078] Figure 5 shows the same inductor L1, freewheeling diode D1, output storage capacitor C1, power commutation GaN switch M1, sensing component RCS, input capacitor C2, and load LED as in the circuit of Figure 1. Similar to the example in Figure 1, the sensing component is a sensing resistor RCS connected between the source and ground GND of the GaN switch.

[0079] The power converter has an energy storage phase when the GaN switch M1 is closed. At this time, current flows from the input through inductor L1 and GaN switch M1 to ground. Energy is stored in the inductor, and the load LED is supplied by output capacitor C1. The freewheeling phase occurs when the GaN switch M1 is open. The energy stored in inductor L1 is supplied to the load (and output capacitor C1).

[0080] This circuit has a separate energy storage component C4 for storing the gate-source voltage of the power commutation switch M1. The energy storage component C4 is connected between the gate and source of the GaN switch M1.

[0081] The control circuit 20 controls the switching of the GaN switch M1, but as before, it is also connected to the gate G of the GaN switch M1 to adjust the charging and discharging of the energy storage component, namely the capacitor C4. The charging of the energy storage component C4 occurs during the freewheeling phase, which is when the detection path is decoupled.

[0082] In this case, as before, the circuit has a single regulator 22 with a voltage source VCC as its input. The voltage regulator 22 is connected to ground, and the negative terminal of the energy storage component C4 is coupled to the same ground via a sensing component. The output of the regulator 22 is stored in a capacitor C5 connected to ground. The anode of the energy storage component C4 is coupled to the gate of the GaN switch.

[0083] A switch SW is in series between the output of regulator 22 and the anode (positive terminal) of capacitor C4. Capacitor C4 is charged through this switch SW and through the sensing component RCS. During the freewheeling phase, the sensing path is decoupled.

[0084] In this case, decoupling is a logic function. While the charging current is flowing, a voltage still exists across the sensing component RCS, but the control unit does not use the signal CS for feedback control purposes at this time. In an RC circuit charged by a DC voltage, capacitor C4 will eventually charge to the DC voltage if there is sufficient time. Because the sensing component is very small, the time it takes to charge capacitor C4 to the 6V level in normal operation (capacitor C4 still has a residual voltage after the last turn-on operation) is very short.

[0085] The gate driver 24 controls the operation of the switch SW. In particular, inversion of the gate drive signal can be used to control the switch SW. In this manner, the energy storage component C4 is charged when the main switch is off during the freewheeling phase. Therefore, the charging of the energy storage component C4 does not affect the sensing function of the RCS, which only occurs during the charging phase of the boost converter. The energy storage component C4 is fully charged to 6V in a stable state. After that, there is no charging current and therefore no voltage drop through the RCS.

[0086] Since the energy storage component C4 is already coupled between the gate and source, it is discharged to stably turn on the main switch. When the GaN switch is on, switch SW is off, and therefore, during this time, the energy storage component C4 supplies energy to drive the power commutation switch for this period, directly with reference to the source of switch M1, not to the common ground. The power supply current from the input through the sense resistor does not affect the voltage across the gate and source of the GaN switch, and similarly, voltage spikes in the sense resistor do not affect the voltage, which is supplied independently by capacitor C4.

[0087] Figure 6 shows the operating waveform of the circuit.

[0088] The top plot shows the inductor current I L1 The second plot shows the gate voltage V of the GaN switch M1. M1G The third plot shows the enable signal EN for the series switch SW. The bottom plot shows the voltage V across the current sensing resistor. RCS This indicates that.

[0089] The turn-on process of the GaN switch M1 is, in this case as well, unaffected by voltage spikes. In particular, when the main switch is turned on by coupling the energy storage component C4 that drives the GaN between the gate and source of the power commutation GaN switch M1, the effect of voltage spikes in the sensing resistor RCS on the gate-source voltage is avoided, in this case as well, as before.

[0090] Peak current sensing for circuit loop control is also unaffected in this case, as before, because a valid signal reflecting the peak current still exists. Therefore, the driver circuit can ensure the operation of the power commutation switch with a single power supply without affecting the current sensing function for the control loop.

[0091] Regulator 22 charges the series connection between the energy storage component C4 and the sensing component RCS. Ultimately, the entire output voltage of the regulator, for example 6V, is stored in capacitor C4. In this manner, the circuit eliminates the need for two regulators, even though controller 20 is referenced to ground.

[0092] Figure 5 shows a boost converter architecture. Figure 7 shows the same circuit technique applied to a buck converter topology.

[0093] The same components are given the same names. The circuit operates in the same way as the circuit in Figure 4, but it operates using the second method as explained with reference to Figure 5.

[0094] As described above, the present invention can be used in any topology having a GaN power commutation switch cascaded with a current sensing resistor, such as a boost or buck converter. Those skilled in the art will understand that the present invention can also be used in other topologies, such as buck boost or flyback converters, or other types of converters, to solve the problem of sensing components interfering with the charging / discharging of energy storage components for supplying turn-on voltage to a power switch.

[0095] The present invention may be used, for example, within an LED driver.

[0096] A person skilled in the art will be able to understand and achieve, in carrying out the claimed invention, variations to the disclosed examples by studying the drawings, specification and appended claims. In the claims, the word “has” does not exclude other elements or steps, and singular nouns do not exclude plural nouns.

[0097] The mere fact that certain means are mentioned in different dependent claims does not mean that combinations of these means cannot be used to one's advantage.

[0098] Note that when the term "adapted to..." is used in the claims or specification, it is intended to be equivalent to the term "configured to...".

[0099] No reference numeral in the claims should be construed as limiting the scope.

Claims

1. A driver circuit for driving a power commutation GaN switch of a switch-mode power converter, wherein the switch-mode power converter has, in power commutation, an energy storage phase when the power commutation GaN switch is closed and a freewheeling phase when the power commutation GaN switch is open, and the driver circuit drives the power commutation GaN switch. A detection component that is connectable to the power commutation GaN switch and adapted to detect the parameters of the power commutation, the detection component being located in the detection path and having a detection resistor, An energy storage component for supplying a specific turn-on voltage between the gate and source of the power commutation GaN switch, The power commutation GaN switch has a control circuit that can be connected to the power commutation GaN switch for the purpose of controlling the switching of the power commutation GaN switch according to the detected parameters of the power commutation for the purpose of feedback control, and for charging and discharging the energy storage components, The control circuit is adapted to charge the energy storage component via the sensing component so that a certain turn-on voltage is obtained between the gate and the source of the power commutation GaN switch when the control circuit is not using the signal in the sensing component for feedback control purposes, or A driver circuit adapted such that the energy storage component is connectable between the gate and ground of the power commutation GaN switch, the sensing component is connectable to the source and ground of the power commutation GaN switch, and the control circuit discharges the energy stored in the energy storage component and simultaneously bypasses the sensing component so as to supply the power commutation GaN switch with a certain turn-on voltage to turn on the power commutation GaN switch.

2. The driver circuit according to claim 1, further comprising a control loop that uses the parameter detected by the detection component.

3. The control circuit, In the energy storage phase, the signal in the detection component is used for feedback control purposes. The system is adapted so that the signal in the sensing component is not used for feedback control purposes throughout the freewheeling phase. The driver circuit according to claim 1 or 2, wherein the energy storage component is coupled to the gate and source of the power commutation GaN switch, and the control circuit is adapted to charge the energy storage component via the sensing component during the freewheeling phase.

4. The driver circuit according to claim 3, wherein the control circuit is adapted to charge the energy storage component from the supply voltage via the sensing component during the freewheeling phase in which the control circuit does not use the signal in the sensing component for feedback control purposes.

5. The driver circuit according to claim 4, wherein the supply voltage is coupled to the energy storage component via a voltage regulator, the voltage regulator is adapted to output a certain turn-on voltage, and the control circuit is adapted to charge the voltage of the energy storage component up to the output voltage of the voltage regulator.

6. The driver circuit according to claim 5, wherein the voltage regulator is connected to ground, the cathode of the energy storage component is coupled to ground via the sensing component, and the anode of the energy storage component is coupled to the gate of the power commutation GaN switch.

7. The driver circuit according to claim 1 or 2, wherein the control circuit is adapted to bypass the sensing component by short-circuiting the sensing component while the power commutation GaN switch is turned on, such that the voltage of the energy storage component between the gate and ground of the power commutation GaN switch is applied between the gate and source of the power commutation GaN switch without being partially taken up by the sensing component.

8. The driver circuit according to claim 7, wherein the control circuit is adapted so as not to bypass the sensing component so that the sensing component is adapted to detect an amount related to the charge energy in the energy storage phase of the power commutation after the power commutation GaN switch is turned on.

9. The driver circuit according to claim 7, wherein the driver circuit has a voltage regulator for supplying from the energy storage component to the control circuit, the voltage regulator is adapted to output a certain turn-on voltage and is coupled to a gate drive terminal and ground.

10. The control circuit has a short-circuit switch for short-circuiting the detection component, the energy storage component is supplied by a supply voltage and connected to ground, and the control circuit is The energy storage component is discharged via the voltage regulator to supply the turn-on voltage across the gate and source of the power commutation GaN switch to turn on the power commutation GaN switch while the sensing component is temporarily short-circuited using the short-circuit switch, The driver circuit according to claim 9, which is adapted to terminate the short circuit of the sensing component after the power commutation GaN switch has been fully turned on, to keep the power commutation GaN switch on, and to use the voltage in the energy storage component via the voltage regulator to enable the sensing component to sense the parameter of the energy storage phase.

11. The driver circuit according to claim 10, wherein the energy storage component is coupled to the gate of the power commutation GaN switch via a low-dropout regulator acting as a voltage regulator.

12. The driver circuit according to claim 11, further comprising a gate driver circuit at the output of the low dropout regulator, wherein the low dropout regulator and the gate driver circuit are connected to ground.

13. Power transmission components and Power commutation GaN switch, Freewheeling diode and A switch-mode power converter having a driver circuit according to any one of claims 1 to 12 for driving the power commutation GaN switch.

14. The switch-mode power converter according to claim 13, wherein the power transmission component, the power commutation GaN switch, and the detection component are arranged in series between the power input and ground and are adapted to define the detection path.

15. A switch-mode power converter according to claim 13 or 14, comprising a boost converter, a buck converter, a buck boost converter, or a flyback converter.

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