Power converter control unit including branch switch

Abstract

To provide a controller for a power converter.SOLUTION: In a power converter 100, a first controller 132 is a first controller for the power converter, and includes a driver, a supply terminal, a branch switch 152, and a branch control unit. The driver provides a drive signal to turn ON and turn OFF a power switch 114. The power switch includes a first switch 116 and a second switch 118 coupled in a cascode configuration. The supply terminal is coupled to a bypass capacitor 144 that provides operating power to the first controller. The bypass capacitor has a bypass voltage VBP142. The branch switch is coupled to an intermediate node A117 between the first switch and the second switch.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure generally relates to power converters, and more particularly to control devices for power converters. [Background technology]

[0002] Electronic devices use power to operate. Due to their high efficiency, small size, and light weight, switching power converters are commonly used to power many modern electronic devices. Conventional wall sockets provide high-voltage alternating current. In a switching power converter, a high-voltage alternating current (AC) input is converted through an energy transfer element to provide a appropriately regulated direct current (DC) output. The control unit of a switching power converter typically provides output regulation by detecting one or more signals representing one or more output quantities and by controlling the output in a closed loop. During operation, switches are used to provide the desired output by changing the duty cycle (typically the ratio of the switch's on period to the total switching period), changing the switching frequency, or changing the number of pulses per unit time of the switch in a switching power converter.

[0003] A power converter generally includes one or more control devices that detect and regulate the output of the power converter. These control devices generally require a regulated or unregulated voltage source to power the control device's circuit components. Bypass capacitors coupled to the control device may provide operating power to the control device's circuitry. [Overview of the project]

[0004] Non-limiting and non-exclusive embodiments of the present invention will be described with reference to the following figures. Similar reference numerals in different figures indicate the same parts unless otherwise specified. [Brief explanation of the drawing]

[0005] [Figure 1] Figure 1 is a schematic diagram of an exemplary isolated power converter, which includes a control device comprising a branch switch and a branch control unit, according to an embodiment of the present disclosure. [Figure 2] Figure 2 is a timing diagram showing exemplary waveforms of a power converter and control device, including the branch switch and branch control unit shown in Figure 1, according to an embodiment of the present disclosure. [Figure 3] Figure 3 is a functional block diagram of another exemplary control device according to an embodiment of the present disclosure, which includes a branch switch, a branch control unit, and a current diversion regulator. [Figure 4A] Figure 4A is a timing diagram showing exemplary waveforms of a control device, including the branch switch, branch control unit, and shunt regulator shown in Figure 3, when the power converter operates in discontinuous conduction mode (DCM), according to an embodiment of the present disclosure. [Figure 4B] Figure 4B is a timing diagram showing exemplary waveforms of a control device, including the branch switch, branch control unit, and shunt regulator shown in Figure 3, when the power converter operates in continuous conduction mode (CCM), according to an embodiment of the present disclosure. [Figure 5A] Figure 5A is a schematic diagram of a further exemplary control device according to an embodiment of the present disclosure, which includes a branch switch, a branch control unit, and a current shunt regulator. [Figure 5B] Figure 5B is a timing diagram showing exemplary waveforms of a control device, including the branch switch, branch control unit, and current shunt regulator shown in Figure 5A, according to an embodiment of the present disclosure. [Figure 6] Figure 6 is a timing diagram showing an example of the bypass voltage of a bypass capacitor and a branch control signal according to an embodiment of the present disclosure. [Figure 7] Figure 7 is a schematic diagram of another exemplary isolated power converter, which includes a control device including a branch switch and a branch control unit, according to an embodiment of the present disclosure. [Modes for carrying out the invention]

[0006] In the drawings, corresponding reference numerals indicate corresponding components across multiple figures. Those skilled in the art will understand that elements in the figures are drawn to be concise and clear, and not necessarily to a constant scale. For example, the dimensions of some elements in the figures may be exaggerated compared to others to make the various embodiments of the invention easier to understand. Furthermore, common but well-understood elements that are useful or necessary in commercially viable embodiments are often omitted so as not to obscure the drawings of these various embodiments of the invention.

[0007] The following description includes many specific details to help you fully understand the present invention. However, it will be apparent to those skilled in the art that these specific details are not necessarily used to carry out the present invention. For example, well-known materials or methods are not described in detail to avoid complicating the understanding of the present invention.

[0008] In this specification, any reference to “one embodiment,” “an embodiment,” “an example,” or “an example” means that a particular feature, structure, or characteristic described in relation to an embodiment or example is included in at least one embodiment of the present invention. Therefore, the use of expressions such as “one embodiment,” “an embodiment,” “an example,” or “an example” in various places in this specification does not necessarily relate to the same embodiment or example. Furthermore, a particular feature, structure, or characteristic may be combined in any suitable combination and / or partial combination in one or more embodiments or examples. A particular feature, structure, or characteristic may be included in an integrated circuit, electronic circuit, coupled logic circuit, or other suitable component that provides the function described. In addition, it should be understood that the drawings provided with this specification are intended for those skilled in the art and that the drawings are not necessarily drawn to a fixed scale.

[0009] A power converter generally includes one or more control devices that detect and regulate the output of the power converter. These control devices generally require a regulated or unregulated voltage source to power the control device's circuit components. A bypass capacitor is an example of a voltage source that can be coupled to a control device that can provide operating power to the control device's circuit. Bypass capacitors are generally regulated to provide sufficient operating power for the control device.

[0010] An isolated power converter may include a primary control unit, also called a first control unit or input control unit, and a secondary control unit, also called a second control unit or output control unit, which are galvanically isolated from each other by energy transfer elements (e.g., coupling inductors, transformers, etc.). In other words, the DC voltage applied between the input and output sides of the power converter generates a current that is substantially zero.

[0011] The primary control unit is configured to control a power switch on the primary side of an isolated power converter to control the transfer of energy from the primary winding of the energy transfer element to the secondary winding of the energy transfer element. The secondary control unit is coupled to a circuit component on the secondary side of the isolated power converter. It should be understood that the primary side may also be called the input side, while the secondary side may also be called the output side. The secondary control unit may be further configured to control a secondary switch coupled to the secondary winding of the energy transfer element, such as a transistor used as a synchronous rectifier for the power converter. However, the primary and secondary control units are galvanically isolated from each other, and the secondary control unit may transmit signals to the primary control unit that control how the primary control unit switches the power switch to transfer energy to the secondary side.

[0012] Generally, both the primary and secondary sides of a power converter include bypass capacitors that provide operating power to the primary or secondary control circuitry, respectively. Bypass capacitors for primary control circuits are generally coupled to the auxiliary (or bias) windings of energy transfer elements such as transformers or coupled inductors, and the bypass capacitors are charged from the auxiliary windings. The bypass voltage across the bypass capacitors is generally regulated to a level sufficient to operate the primary control circuitry. For example, the bypass voltage may be regulated to substantially 5 volts (V).

[0013] As described above, the primary control unit is configured to control a power switch on the primary side of an isolated power converter in order to control the transfer of energy between the input and output of the power converter. In one example, the power switch may be a cascode switch (or hybrid switch). A cascode switch (or hybrid switch) may include a first switch and a second switch. The first switch is generally a normally-on device, while the second cascode switch is generally a normally-off device. A cascode switch includes three terminals: source, gate, and drain. In one example, the normally-on device (e.g., the first switch) may be a high-voltage GaN transistor, while the normally-off device (e.g., the second switch) may be a low-voltage MOSFET. The source and gate of the normally-off device (e.g., MOSFET) are used as the source and gate of the cascode switch, while the drain of the normally-on device (e.g., GaN transistor) is used as the drain of the cascode switch. The source of the normally-on device (e.g., GaN transistor) is coupled to the drain of the normally-off device (e.g., MOSFET). Normally-off devices (e.g., MOSFETs) are generally used to switch normally-on devices (e.g., GaN transistors) on and off. An off (or open) switch cannot conduct current, while an on (or closed) switch can conduct current. The node between a normally-off device and a normally-on device may be called an intermediate node.

[0014] Embodiments of the present invention include a power switch in a cascode configuration and a bypass capacitor coupled to an intermediate node between a first switch and a second switch of the cascode power switch. The power switch is controlled so that at least a portion of the current conducted by the first switch is redirected to the bypass capacitor and used to charge the bypass capacitor. In other words, the power switch is controlled so that at least a portion of the current conducted by the first switch is used to regulate the bypass voltage across the bypass capacitor. In a further embodiment, the second switch may be used to further control the amount of current redirected to charge the bypass capacitor. In other words, the second switch may be used to further control the amount of current redirected from the first switch to the bypass capacitor. As described above, the bypass capacitor provides operating power.

[0015] In embodiments of the present invention, the control device includes a branch switch and a branch control unit. In one example, the branch switch is coupled between an intermediate node of a cascode power switch and a bypass capacitor for the control device. The branch control unit is configured to control the on and off switching of the branch switch. In an embodiment, when the bypass capacitor voltage drops below a bypass reference, the branch control unit switches the branch switch on. The current conducted by the first switch is redirected to the branch switch and conducted by the branch switch to charge the bypass capacitor. In other words, the branch switch is controlled so that the current conducted by the first switch is used to regulate the bypass voltage of the bypass capacitor.

[0016] In another embodiment, the control device further includes a shunt regulator that controls the amount of current conducted by a branch switch. Thus, a portion of the current conducted by the first switch is redirected and conducted by the branch switch to charge a bypass capacitor. A second switch of the power cascode switch is controlled to shunt the remaining current conducted by the first switch, and thus controls the amount of current conducted by the branch switch. The bypass capacitor provides operating power for the control device.

[0017] Figure 1 shows a power converter 100 according to an embodiment of the present disclosure, which includes a first control device 132 (e.g., a primary control device) including a branch switch 152 and a branch control unit 150. The shown power converter 100 further includes a clamp circuit 104, an energy transfer element T1 106, an input winding 108 of the energy transfer element T1 106, an output winding 110 of the energy transfer element T1 106, an auxiliary winding 112 of the energy transfer element T1 106, a power switch S1 114, an input return path 111, an output rectifier S2 122, an output capacitor CO 124, an output return path 127, an output detection circuit 129, a second control device 134 (e.g., a secondary control device), a first control device 132 (e.g., a primary control device), a bypass capacitor 144 (e.g., a power capacitor for the first control device 132), and a diode D1 146. A communication link 136 between the second control unit 134 and the first control unit 123 is further shown. The power switch S1 114 is shown as a cascode switch (or hybrid switch) including a first switch 116 and a second switch 118, and includes an intermediate node A117 between the first switch 116 and the second switch 118. The first control unit 132 is shown as including a main control unit 148, a branch control unit 150, a branch switch 152, a diode D2 154, a comparator 156, and a driver 158.

[0018] Figure 1 shows the input voltage V IN 102. Drain current I D 119. Second switch current I1120, output voltage V O 128. Output current IO 125, output power U O 126, feedback signal FB130, request signal REQ133, second drive signal SR135, primary drive signal DR138, current detection signal ISNS140, bypass voltage V BP 142, on signal ON160, off signal OFF162, bypass adjustment signal BP_REG163, main on signal MAIN_ON164, branch drive signal BR165, reference REF167 (e.g., a bypass reference), and branch current I BR 168 is further shown.

[0019] In the illustrated example, power converter 100 is shown as including a flyback topology, but it should be understood that other known topologies and configurations of power converters may also benefit from the teachings of the present disclosure. Furthermore, the input side of power converter 100 is galvanically isolated from the output side 100 of the power converter, such that input return path 111 is galvanically isolated from output return path 127. Since the input side and the output side of power converter 100 are galvanically isolated, there is no direct current (DC) path across the insulation barrier of energy transfer element T1 106, no direct current (DC) path between input winding 108 and output winding 110, no direct current (DC) path between auxiliary winding 112 and output winding 110, and no direct current (DC) path between input return path 111 and output return path 127.

[0020] Power converter 100 provides output power from an unregulated input voltage V IN 102 to a load 128. In one embodiment, input voltage V IN 102 is a rectified and filtered AC line voltage. In another embodiment, input voltage V IN 102 is a DC input voltage. Input voltage V IN102 is coupled to the energy transfer element 106. In some examples, the energy transfer element 106 may be a coupled inductor, transformer, or inductor. The energy transfer element 106 is shown as having three windings, namely, an input winding 108 (also called the primary winding), an output winding 110 (also called the secondary winding), and an auxiliary winding 112 (also called the bias winding or tertiary winding). However, the energy transfer element 106 may have more than three windings. The input winding 108 of the energy transfer element is further coupled to a power switch S1 114, which is further coupled to the input return path 111. A clamp circuit 104 is coupled across the input winding 108. The clamp circuit 104 limits the maximum voltage in the power switch S1 114.

[0021] As shown in Figure 1, the power switch S1 114 is a cascode switch comprising a first switch 116 and a second switch 118. The first switch 116 is generally a normally-on device, while the second switch 118 is generally a normally-off device. The cascode power switch S1 114 includes three terminals: source, gate, and drain. In one example, the normally-on device (e.g., the first switch 116) may be a high-voltage transistor, while the normally-off device (e.g., the second switch 118) may be a low-voltage transistor. In one example, the high-voltage transistor used for the first switch 116 may be rated at approximately 750 volts (V), while the low-voltage transistor used for the second switch 118 may be rated at between 25V and 30V. The source and gate of the second switch 118 (e.g., a normally-off device) are used as the source and gate of the cascode power switch 114, while the drain of the first switch 116 (e.g., a normally-on device) is used as the drain of the cascode power switch 114. In one example, the source of the first transistor 116 (e.g., a normally-on device) is coupled to the drain of the second transistor 118 (e.g., a normally-off device). The gate of the first transistor 116 is shown coupled to the source of the second transistor 118, which is coupled to the input return 111. It should be understood that the gate of the first transistor 116 may also be directly coupled to the input return 111. An intermediate node A117 is shown as the coupling between the source of the first transistor 116 and the drain of the second transistor 118. The second transistor 118 is generally used to switch the first transistor 116 (normally-on device) on and off. In one example, the first switch 116 may be a transistor, such as a gallium nitride (GaN)-based transistor or a silicon carbide (SiC)-based transistor.The second switch 118 may be a transistor such as a metal-oxide-semiconductor field-effect transistor (MOSFET), a bipolar junction transistor (BJT), or an insulated-gate bipolar transistor (IGBT). In one example, the current 116 conducted by the first switch is the drain current I. D While the current 119 is represented by 119, the current 118 conducted by the second switch is denoted as the second switch current I1120.

[0022] The output winding 110 is coupled to the output rectifier S2 122, which is exemplified as a transistor used as a synchronous rectifier. However, the output rectifier may be exemplified as a diode. The output capacitor CO124 is shown coupled to the output rectifier S2 122 and the output return 127. The power converter 100 has an output quantity U O The circuit further includes a circuit to adjust 126, and the output amount U O 126 is an example where the output voltage V O 128. Output current I O 125, or a combination of the two. The output detection circuit 129 provides the second control device 134 with a feedback signal FB130 representing the output of the power converter 100, in order to measure the output amount U O It is configured to detect 126.

[0023] The second control unit 134 is configured to output a request signal REQ133 in response to a feedback signal FB130. In another example, the second control unit 134 is configured to transmit the feedback signal FB130 to the first control unit 132. As an example of the request signal REQ133, it represents a request to switch the power switch S1 114 on. The request signal REQ133 may include a request event generated in response to the feedback signal FB130. In one exemplary operation, the second control unit 134 is configured to compare the feedback signal FB130 with an adjustment criterion. In response to the comparison, the second control unit 134 may output a request event in the request signal REQ133 to request the first control unit 132 to switch the power switch S1 114 on. The request signal REQ133 may be a square pulse waveform that pulses to a logic high and rapidly returns to a logic low. The logic high pulse may be called the request event. In other embodiments, while still benefiting from the teachings of this disclosure, it will be understood that the request signal REQ133 may be an analog, continuously fluctuating signal rather than a pulsed waveform.

[0024] The second control unit 134 and the first control unit 123 may communicate via a communication link 136. In the example shown, the second control unit 134 is coupled to the secondary side of the power converter 100 and references the output return path 127, while the first control unit 123 is coupled to the primary side of the power converter 100 and references the input return path 111. In some embodiments, the first control unit 132 and the second control unit 134 are galvanically isolated from each other, and the communication link 136 provides galvanic isolation using inductive coupling (such as a transformer or coupling inductor, optocoupler), capacitive coupling, or other devices that maintain isolation. However, it should be understood that in some embodiments, the second control unit 134 is not galvanically isolated from the first control unit 123. In one example, the communication link 136 may be inductively coupled from lead frames supporting the first control unit 123 and / or the second control unit 134.

[0025] In one example, the first control device 132 and the second control device 134 may be formed as part of an integrated circuit manufactured as either a hybrid integrated circuit or a monolithic integrated circuit. In one example, the power switch S1 114 may be integrated into a single integrated circuit package that includes the first control device 132 and the second control device 134. In addition, in one example, the first control device 132 and the second control device 134 may be formed as separate integrated circuits. The power switch S1 114 may be integrated into the same integrated circuit as the first control device 132, or it may be formed into its own integrated circuit. In particular, the first switch 116 of the power switch S1 114 may be integrated into its own integrated circuit, while the second switch 118 of the power switch S1 114 may be integrated into the same integrated circuit as the first control device 132. Furthermore, it should be understood that both the first control device 132 and the second control device 134 and the power switch S1 114 do not need to be included in a single package, and may be implemented in separate control device packages or in a combination of combined / different packages.

[0026] The first control device 132 controls the drain current I of the power switch S1 114. D The first control device 132 is coupled to receive a current detection signal ISNS140 representing 119, and to receive a request signal REQ133 or a feedback signal FB130 via the communication link 136, and outputs a primary drive signal DR138. The first control device 132 provides the primary drive signal DR138 to the power switch S1 114 to control various switching parameters of the power switch S1 114 in order to control the transfer of energy from the input to the output of the power converter 100 through the energy transfer element 106. An example of such a parameter is the switching frequency f SW (or switching period T) SWThis includes changing the duty cycle, on-period and off-period, or the number of pulses per unit time of the power switch S1 114. In addition, the power switch S1 114 can be controlled to have a fixed switching frequency or a variable switching frequency.

[0027] In one embodiment, the first control unit 132 outputs a primary drive signal DR138 to control the conduction of the power switch S1 114. In particular, the first control unit 132 outputs a primary drive signal DR138 to control the conduction of the second switch 118. In one example, the first control unit 132 outputs a primary drive signal DR138 to switch the power switch S1 114 on in response to a request event in a request signal REQ133 or in response to information provided by a feedback signal FB130. In another example, the first control unit 132 outputs a primary drive signal DR138 to switch the power switch S1 114 on in response to a drain current I provided by a current detection signal ISNS140. D When 119 reaches the current limit, it outputs a primary drive signal DR138 to switch power switch S1 114 off. It should be understood that other control methods may be used.

[0028] The energy transfer element T1 106 includes an auxiliary winding 112 referenced to the input return path 111. The auxiliary winding 112 is shown coupled to diode D1 146 and bypass capacitor 144. For the power converter 100 shown in Figure 1, the bypass voltage V of the bypass capacitor 144 is shown. BP 131 can be derived from the voltage across the auxiliary winding 112. The bypass capacitor 144 is coupled to the first control device 132 to provide operating power for the circuit of the first control device 132.

[0029] Bypass voltage V BP 131 is the drain current I of the power switch S1 114, which is redirected from the first switch 116 to the bypass capacitor 144. D It may be derived from 119. In this embodiment, drain current ID Total or drain current I D A portion of 119 is redirected to the bypass capacitor 144. As explained in relation to this figure, the branch switch 152 is directed to charge the bypass capacitor 144 with drain current I D 119 (for example, the current conducted by the first switch 116) is controlled to change direction. In another embodiment described in relation to Figure 3, the branch switch is controlled to charge the bypass capacitor 144 with drain current I D By reversing the direction of part of 119, the second switch 118 is reversed to charge the bypass capacitor 144, and the drain current I D It is used to control part of the 119 system.

[0030] Comparator 156 is coupled to bypass capacitor 144, and the bypass voltage V is at its inverting input. BP 142 is received. Comparator 156 further receives reference REF167, also called bypass reference, at its non-inverting input. The output of comparator 156 is denoted as bypass adjustment signal BP_REG163. In one example, reference REF167 is bypass voltage V BP Represents the desired adjusted value relative to 142. Comparator 156 is used for bypass voltage V BP Compare 142 to the reference REF167. As shown, the bypass adjustment signal BP_REG163 is the bypass voltage V BP If 142 is less than the reference REF167, it is a logical high value, and the bypass voltage V BP If 142 is greater than the reference REF167, it is a logic low value. In other words, the asserted bypass adjustment signal BP_REG163 is the bypass voltage V BP This indicates that 142 has fallen below the reference REF167 (e.g., a logical high). It should be understood that comparator 156 may further utilize hysteresis.

[0031] In the embodiment shown, the bypass voltage V BP When 142 is less than the reference REF167, the drain current I DThe branch switch 152 is controlled to redirect 119 to the bypass capacitor 144. In another embodiment, the bypass voltage V BP When 142 is less than the reference REF167, the drain current I D The branch switch 152 is controlled to redirect a portion of 119. In other words, the bypass voltage V BP When 142 is less than the reference REF167, branch switch 152 is switched ON. Furthermore, drain current I D The first control device 132 is configured to control the power switch S1 114 such that at least a portion of 119 is used to charge the bypass capacitor 144.

[0032] The first control device 132 is shown to include a main control unit 148, a branch control unit 150, a branch switch 152, a diode D2 154, a comparator 156, and a driver 158. The main control unit 148 is configured to receive a request signal REQ 133 or a feedback signal FB 130 and a current detection signal ISNS 140, and outputs an ON signal ON 160 and an OFF signal OFF 162. In one example, both the ON signal ON 160 and the OFF signal OFF 162 are square pulse waveforms with variable durations of logic high and logic low sections. The ON signal ON 160 represents controlling power switch S1 114 to ON, while the OFF signal OFF 162 represents controlling power switch S1 114 to OFF. A logic high value for the ON signal ON 160 (e.g., asserted) corresponds to switching power switch S1 114 to ON, and in particular to switching the second switch 118 to ON. Similarly, a logic high value for the (e.g., asserted) off signal OFF162 corresponds to switching power switch S1 114 off, and in particular, represents switching the second switch 118 off. It should be understood that the off signal OFF162 is an inverted version of the on signal ON160.

[0033] The main control unit 148 determines to switch the power switch S1 114 to ON in response to a request signal REQ133 or a feedback signal FB130. During operation, the main control unit 148 determines to switch the power switch S1 114, in particular the second switch 118, to ON in response to a request event in the request signal REQ133. In another example, the main control unit 148 determines to switch the power switch S1 114, in particular the second switch 118, to ON in response to a feedback signal FB130 indicating that the output of the power converter 100 has decreased to a state where it is not properly regulated. During operation, the ON signal ON160 is asserted and the OFF signal OFF162 is deasserted.

[0034] The main control unit 148 further controls the drain current I D In response to the current detection signal ISNS140 indicating that 119 has reached the current limit value ILIM, it is determined to switch the power switch S1 114 to the OFF position. It should be understood that other control schemes may be implemented by the main control unit 148 to control the transfer of energy from the input side to the output side of the power converter 100. To switch the power switch S1 114 to the OFF position, the OFF signal OFF162 is asserted, while the ON signal ON160 is deasserted.

[0035] The branch control unit 150 is configured to receive the ON signal ON160 and the bypass adjustment signal BP_REG163, and outputs the branch drive signal BR165 and the main ON signal MAIN_ON164. The branch drive signal BR165 is a control signal for switching the branch switch 152 on and off, and in one example, is a square pulse waveform with a variable duration between the logic high section and the logic low section. The logic high section represents an asserted signal for switching the branch switch 152 on, while the logic low section represents an unasserted signal for switching the branch switch 152 off. The main ON signal MAIN_ON164 is a control signal for switching the power switch S1 114, in particular the second switch 118, on and off, and is further a square pulse waveform with a variable duration between the logic high section and the logic low section. The logic high section represents the asserted signal for switching the second switch 118 on, while the logic low section represents the deasserted signal for switching the second switch 118 off. If the branch control unit does not control the branch switch 152 to turn on (for example, the branch drive signal BR165 is not asserted), the main ON signal MAIN_ON164 substantially follows the ON signal ON160.

[0036] The branch switch 152 and diode D2 154 are shown coupled between the bypass capacitor 144 and the intermediate node A117 of the power switch S1 114. Branch current I BR 168 is the current conducted by the branch switch 152. In the example shown, one end of the branch switch 152 is coupled to the intermediate node A117 of the power switch S1 114, while the other end is coupled to the anode of diode D2 154. The cathode of diode D2 154 is coupled to the bypass capacitor 144. Diode D2 is used to prevent current from flowing from the bypass capacitor 144 to the power switch S1 114. However, it should be understood that other configurations of the branch switch 152 and diode D2 154 may be used. As shown, the branch current IBR The sum of 168 and the second switch current I1120 is effectively the drain current I D It is 119, or mathematically, I D =I BR +I1 That is the case.

[0037] During operation, bypass voltage V BP When the bypass adjustment signal BP_REG163 indicates that 142 has fallen below the reference REF167, the branch control unit 150 outputs a branch drive signal BR165 to switch the branch switch 152 on. Bypass voltage V BP If the bypass adjustment signal BP_REG163 indicates that 142 has not dropped below the reference REF167, the branch switch 152 is not switched on, and the main ON signal MAIN_ON164 is effectively the ON signal ON160.

[0038] Bypass voltage V BP When the bypass adjustment signal BP_REG163 indicates that 142 has fallen below the reference REF167, the branch control unit 150 synchronizes the ON signal with the ON signal to switch the branch switch 152 to ON. As further shown in relation to Figure 2, the bypass voltage V BP If 142 drops below reference REF167 during the switching cycle of power switch S1 114, branch switch 152 is switched ON at the start of the next (or subsequent) switching cycle. In one embodiment, as long as the ON signal ON160 is asserted, or the bypass voltage V BP The branch switch 152 is switched ON until 142 reaches the reference REF167. Drain current I D When 119 reaches the current limit, the ON signal ON160 may be deasserted, and therefore the drain current I D 119 until the current limit is reached, or the bypass voltage V BPThe branch switch 152 remains ON until 142 reaches the reference REF167. In another embodiment, the branch switch 152 may switch ON for a fixed time period. Furthermore, if the branch switch 152 switches OFF before the ON signal ON160 is deasserted, the main ON signal MAIN_ON164 is asserted and then follows the ON signal ON160 to switch the power switch S1 114 ON. When the ON signal ON160 is deasserted, the main ON signal MAIN_ON164 is deasserted. In the example shown in Figure 1, when the branch switch 152 is conducting, the branch current I BR 168 is the drain current I D It is practically equal to 119.

[0039] The driver 158 is configured to receive the branch drive signal BR165, the main ON signal MAIN_ON158, and the OFF signal OFF162, and outputs a primary drive signal DR138 to control the conduction of the power switch S1 114. In particular, the primary drive signal DR138 controls the conduction of the second switch 118 of the cascode power switch S1 114. For example, the driver 158 can control the conduction and amount of current conducted by the second switch 118. When operating, in response to the asserted branch drive signal BR165, the driver 158 outputs the primary drive signal DR138 so that the second switch 118 is OFF, i.e., does not conduct. When the main ON signal MAIN_ON164 is asserted, the driver 158 outputs the primary drive signal DR138 so that the second switch 118 is ON, i.e., conducts. When the OFF signal OFF162 is asserted, the driver 158 outputs the primary drive signal DR138 so that the second switch 118 is off, i.e., not conducts. In the example shown, when the second switch 118 is conduction, the second switch current I1120 is substantially the drain current I D The number is 119.

[0040] Therefore, the first control device 132 controls at least a portion of the current conducted by the first switch 116 (for example, the drain current I DUsing at least a portion of 119, the bypass capacitor 144 that provides operating power to the first control device 132 is charged. In the example shown in Figure 1, the branch switch 152 is switched on to charge the bypass capacitor 144 with drain current I D Direct the entire 119. In other words, when the branch switch 152 is switched on, the branch current I BR 168 is drain current I D This is substantially equivalent to 119. Furthermore, energy savings are possible because the power switch S1 114 is a cascode device that includes a normally-on transistor (first switch 116) and a normally-off transistor (second switch 118). Conventional solutions have used normally-off transistors, such as bipolar junction transistors (BJTs), as power switches. A normally-off transistor (e.g., a BJT) would require a higher voltage power supply to maintain the normally-off transistor in a conducted state, or alternatively, its base-emitter capacitance (or gate-source capacitance) would be pre-charged to allow all energy to flow through the branch switch to the bypass capacitor. In addition, in the case of a BJT, an on-switching transistor and an off-switching transistor would be further used. However, since the power switch S1 114 is a cascode device that includes normally-on and normally-off devices, neither a higher voltage output voltage source nor pre-charging of the gate-source capacitance or base-emitter capacitance is required.

[0041] Figure 2 shows the bypass voltage V for the power converter 100 in Figure 1. BP 142. Drain current I DFigure 200 shows exemplary waveforms of the request signal REQ133, the ON signal ON160, the OFF signal OFF162, the main ON signal MAIN_ON163, the branch drive signal BR165, and the primary drive signal DR138. It should be understood that the similarly named and numbered elements combine and function as described above. For the waveforms in Figure 2, the first control device 132 switches the power switch S1 114 or the branch switch 152 to ON when the request event in the request signal REQ133 is received, and the drain current I D When 119 reaches the current limit value ILIM221, the power switch S1 114 is switched off. The first control device 132 detects the bypass voltage V BP In response to 142, the branch switch 152 is switched to ON.

[0042] At time t1, a request event (e.g., a pulse) is received by request signal REQ133, and the ON signal ON160 is asserted to switch power switch S1 114 to ON. At time t1, the bypass voltage V BP Since 142 is substantially equal to the reference REF167, the main ON signal MAIN_ON164 substantially follows the ON signal ON160, and the primary drive signal DR138 is provided to switch the power switch S1 114 ON. As shown, the primary drive signal DR138 is the ON voltage V, which is the voltage for switching the device used for the second switch 118 ON. ON The transition is to 268, and therefore the second switch current I1120 conducted by the second switch 118 is determined by the component coupled to the second switch 118. Furthermore, the branch drive signal BR165 is not asserted, and the branch switch 152 is not conducting.

[0043] Between time point t1 and time point t3, the drain current I D 119 is input voltage V IN It increases at a rate proportional to 102 divided by the inductance of the input winding 108. Furthermore, the power converter 100 has a drain current I DAs shown in 119, it is operating in discontinuous conduction mode (DCM). Since the branch switch 152 is not conducting, the second switch current I1120 is the drain current I D Substantially equal to 119, branch current I BR 168 is practically zero. At time t3, the drain current I D When 119 reaches the current limit value ILIM221, the first control device 132 switches the power switch S1 114 to OFF. Consequently, the ON signal ON160 and the main ON signal MAIN_ON164 are deasserted (transition to a logic low value), and the OFF signal OFF162 is asserted (transition to a logic high value). The primary drive signal DR138 is off voltage V OFF Transitions to 269, off voltage V OFF 269 ​​is the voltage across the device used for the second switch 118 so that the second switch 118 and the power switch S1 114 cannot conduct current (for example, when switched off). After the second switch 118 is turned off, the drain current I D 119 decreases to zero.

[0044] However, at time t2, the bypass voltage V BP 142 drops below the reference REF167. At time t4, during the next switching cycle of power switch S1 114, branch switch 152 is switched on to charge bypass capacitor 144, and the bypass voltage V BP 142 rises. After time t2, until branch switch 152 is switched on at time t4, the bypass voltage V BP 142 continues to decline.

[0045] At time t4, another request event is received in request signal REQ133, and the bypass voltage V BP142 is less than reference REF167. The main control unit 148 asserts the on-signal ON160, de-asserts the off-signal OFF162, and the branch control unit 150 asserts the branch drive signal BR165. Since the branch drive signal BR165 is asserted, the main on-signal MAIN_ON164 does not follow the on-signal ON160, the main on-signal MAIN_ON164 remains de-asserted, and the primary drive signal DR138 remains at the off-voltage V OFF 269. The branch switch 152 is switched on (e.g., conducts current), and the second switch 118 is prevented from conducting current (e.g., is switched off). Drain current I D 119 increases, the branch switch 152 conducts all of the drain current I D 119 to charge the bypass capacitor 144, and the bypass voltage V BP 142 rises. In other words, the branch current I BR 168 is substantially equal to the drain current I D 119, while the second switch current I1120 is substantially zero.

[0046] At time t5, the drain current I D 119 reaches the current limit value ILIM221, the main control unit 148 de-asserts the on-signal ON160 and asserts the off-signal OFF162. The branch control unit 150 de-asserts the branch drive signal BR165 to switch the branch switch 152 off. Furthermore, the off-signal OFF162 is received by the driver 158, and the primary drive signal DR138 remains at the off-voltage V to prevent the second switch 118 from conducting OFF 269, and the drain current I D 119 decreases to zero. However, as shown, the bypass voltage V BP 142 is still less than reference REF167, and the bypass voltage V BP 142 decreases between time t5 and time t6.

[0047] At time t6, another request event is received in the request signal REQ133, the main control unit 148 asserts the on signal ON160 and deasserts the off signal OFF162. The bypass voltage V BP 142 is still less than the reference REF167, therefore the branch control unit 150 asserts the branch drive signal BR165 to turn on the branch switch 152, and the main on signal MAIN_ON remains deasserted to prevent the second switch 118 from being turned on. The branch switch 152 conducts the drain current I D 119 to charge the bypass capacitor 144, and the bypass voltage V BP 142 rises. Between time t6 and time t7, the branch current I BR 168 is substantially equal to the drain current I D 119, while the second switch current I1120 is substantially zero.

[0048] As shown in Figure 2, before the drain current I D 119 reaches the current limit value ILIM221 at time t8, the bypass voltage V BP 142 reaches the reference REF167 at time t7. At time t7, the branch control unit 150 deasserts the branch drive signal BR165 to prevent the branch switch 152 from conducting, and asserts the main on signal MAIN_ON164 to turn on the second switch 118. In other words, the branch control unit 150 allows the main on signal MAIN_ON164 to follow the on signal ON160. The driver 158 receives the asserted main on signal MAIN_ON164, and transitions the primary drive signal DR138 to the on voltage V ON 268 to turn on the second switch 118, therefore, the second switch 118 conducts the drain current I D 119. Between time t7 and time t8, the second switch current I1120 is substantially equal to the drain current I D 119, and the branch current I BR 168 is substantially zero.

[0049] At time t8, the drain current I D When 119 reaches the current limit value ILIM221, the main control unit 148 deasserts the ON signal ON160 and asserts the OFF signal OFF162. Furthermore, the OFF signal OFF162 is received by the driver 158, and the primary drive signal DR138 is prevented from being conducted by the second switch 118 by the off voltage V OFF Transition to 269, drain current I D 119 decreases to zero.

[0050] At time t9, the request event is received by the request signal REQ133, and the main control unit 148 asserts the ON signal ON160 and deasserts the OFF signal OFF162. At time t9, the bypass voltage V BP Since 142 is substantially equal to the reference REF167, the main ON signal MAIN_ON164 substantially follows the ON signal ON160, and the branch drive signal BR165 remains in the deasserted state. Driver 158 turns the primary drive signal DR138 to the ON voltage V ON The switch transitions to 268, and therefore the second switch 118 drains current I D 119 can be transmitted. 10 In this case, the drain current I D When 119 reaches the current limit value ILIM221, the main control unit 148 deasserts the ON signal ON160 and asserts the OFF signal OFF162 to switch the second switch 118 off. The primary drive signal DR138 is then subjected to an off voltage V to prevent the second switch 118 from conducting. OFF Transition to 269, drain current I D 119 decreases to zero.

[0051] Figure 3 shows another embodiment of the first control unit 332, including a main control unit 148, a branch control unit 150, a branch switch 152, a diode D2 154, a comparator 156, a driver 358, and a shunt regulator 349. Figure 3 further shows a power switch S1 114, including a first switch 116 and a second switch 118, a bypass capacitor 144, a diode D1 146, and an auxiliary winding 112. The power switch S1 114, the bypass capacitor 144, the diode D1 146, and the auxiliary winding 112 are included to provide context for the first control unit 332 related to Figure 1. Drain current I D 119, Second switch current I1120, Feedback / request signal FB / REQ130 / 133, Primary drive signal DR138, Current detection signal ISNS140, Bypass voltage V BP 142, ON signal ON 160, OFF signal OFF 152, Bypass adjustment signal BP_REG 163, Main ON signal MAIN_ON 164, Branch drive signal BR 165, Reference REF 167, Branch current I BR 168, and the shunt regulator output 372 are further shown in Figure 3. It should be understood that the first control device 332 may be used in conjunction with the power converter 100 shown in Figure 1.

[0052] Figure 3 shares many similarities with the first control device 132 described in relation to Figure 1, and it should be understood that similarly named and numbered elements combine and function as already described with reference to Figures 1 and 2. However, at least one difference is the addition of a shunt regulator 349 with a shunt regulator output 372, and how the driver 358 responds to the shunt regulator output 372. Furthermore, the branch control unit 150 is further configured to receive an off signal OFF 162 from the main control unit 148 and to determine whether the branch switch 152 should be switched on, a bypass voltage V during the off period of the power switch S1 114 is set. BPIt determines whether 142 has fallen below the reference REF167. However, it should be understood that the branch control unit 150 may use the inverted ON signal ON160 instead of the OFF signal OFF162.

[0053] In the embodiment shown, the first control device 332 controls the branch current I conducted by the branch switch 152. BR The amount of 168 is controlled. Furthermore, the first control device 332 controls the magnitude of the second switch current I1120 conducted by the second switch 118, thereby controlling the branch current I conducted by the branch switch 152. BR It controls the quantity of 168. In other words, the first control device 332 controls the branch current I BR The second switch 118 is used to adjust 168. Thus, the first control device 332 draws a drain current I to charge the bypass capacitor 144. D Determine how much of 119 is redirected by the branch switch 152. The remaining drain current I that is not used to charge the bypass capacitor 144. D 119 is conducted by the second switch 118.

[0054] The physical size of the branch switch is the branch current I that the branch switch 152 conducts. BR This is partially determined by the maximum amount of 168 and the duration for which the branch switch 152 conducts the maximum current. For example, when the branch switch 152 conducts the drain current I D In order to conduct the entire 119, the physical size of the branch switch 152 is similar to that of the second switch 118. Depending on the package used to house the first control device 332 and the second switch 118, if the size of the branch switch 152 is similar to that of the second switch 118, there may not be enough space to house both the second switch 118 and the branch switch 152. Therefore, the physical size of the branch switch 152 is such that the branch current I BR It can be controlled by adjusting 168 to be below the branch current threshold. Branch current I BRAdjust the drain current I to 168 below the branch current threshold. D If the second switch 118 is controlled to divert a portion of 119, a smaller branch switch 152 may be used.

[0055] In the embodiment shown in Figure 3, the bypass voltage V is applied before the start of the switching cycle. BP If 142 is less than the reference REF167, the branch control unit 150 outputs a branch drive signal BR165 to switch the branch switch 152 on during the switching cycle. In one embodiment, the bypass voltage V BP The branch switch 152 remains ON until 142 rises above the reference REF167 or until the OFF signal OFF162 is asserted. In another embodiment described with reference to Figures 5A and 5B, the branch switch 152 switches ON for a fixed time length or until the OFF signal OFF162 is asserted. When the branch control unit 150 receives the OFF signal OFF162 and the OFF signal OFF162 is asserted, the bypass voltage V BP If 142 is less than the reference REF167, it may be decided to switch branch switch 152 to ON for the next switching cycle. Alternatively, branch control unit 150 may use the ON signal ON160, and when the ON signal ON160 is not asserted, bypass voltage V BP If 142 is less than the reference REF167, it may be decided to switch branch switch 152 to ON for the next switching cycle. In one example, drain current I D When 119 reaches the current limit, the OFF signal OFF162 is asserted (or the ON signal ON160 is deasserted) and remains asserted until the next request event is received in the request signal REQ133. When the OFF signal OFF162 is asserted, the power switch S1 114 and the branch switch 152 are switched off to prevent conduction.

[0056] The shunt regulator 349 receives the branch drive signal BR165 from the branch control unit 150, and the branch current I BR It is configured to detect 168. The shunt regulator 349 outputs the shunt regulator output 372 to the driver 358. When operating, when the branch drive signal BR165 indicates that the branch switch 152 is on (for example, or conducted), the shunt regulator 349 controls the branch current I BR It detects 168. Furthermore, the shunt regulator 349 controls the branch current I BR When 168 reaches the branch current threshold, it detects and outputs the shunt regulator output 372. Together with the driver 358, the branch current I BR 168 is prevented from exceeding the branch current threshold. In one example, the shunt regulator output 372 may be a voltage regulated by the shunt regulator 349 to determine the level of the primary drive signal DR138. In one example, the shunt regulator 349 functions similarly to a linear amplifier.

[0057] The driver 358 is configured to receive the main ON signal MAIN_ON164, the branch drive signal BR165, and the shunt regulator output 372. The main ON signal MAIN_ON164 represents switching the second switch 118 on to be fully ON. In response to the asserted main ON signal MAIN_ON164, the driver 358 turns the second switch 118 fully ON (e.g., ON voltage V ON The drive signal DR138 is output to a level such that ). In other words, the current conducted by the second switch 118 is determined by an external component coupled to the second switch 118.

[0058] The branch drive signal BR165 represents conduction through the branch switch 152. In response to the asserted branch drive signal BR165, the driver 358 controls the value of the second switch current I1120 conducted by the second switch 118, thereby controlling the branch current I BR The level of the primary drive signal DR138 is determined in response to the shunt regulator output 372, which represents 168.

[0059] The driver 358 changes the level of the primary drive signal DR138 to control the conduction of the second switch 118 in response to the shunt regulator output 372 while the branch switch 152 is on (e.g., conducting). BR The sum of 168 and the second switch current I1120 is effectively the drain current I D 119, that is, mathematically, I D =I BR It is +I1. In the example shown, the second switch 118 is a voltage-controlled device shown as a MOSFET, and the primary drive signal DR138 is a voltage signal. The driver 358 changes the voltage level of the primary drive signal DR138 to control the value of the second switch current I1120 conducted by the second switch 118. The voltage level of the primary drive signal DR138 may be selected such that the value of the second switch current I1120 is determined by the gate-source voltage of the second switch 118. In one example, the voltage level of the primary drive signal DR138 may be selected such that the second switch 118 operates in linear mode.

[0060] In another embodiment, the driver 358 is configured to receive the main ON signal MAIN_ON164 and the shunt regulator output 372, but not the branch drive signal BR165. The main ON signal MAIN_ON164 indicates that the second switch 118 should be turned on to fully switch the second switch 118 on, or to turn the second switch 118 on in response to the shunt regulator output 372. Thus, the main ON signal MAIN_ON164 can be asserted to fully switch the second switch 118 on when the branch switch 152 cannot be turned on. Furthermore, to control the value of the second switch current I1120, and the branch current I when the branch switch 152 is on BRIn order to adjust 168 below the branch current threshold, the main ON signal MAIN_ON164 may be asserted so that the driver 358 determines the level of the primary drive signal DR138 in response to the shunt regulator output 372.

[0061] Therefore, the shunt regulator 349 and driver 358 are conducted by the second switch 118 (e.g., the second switch current I1120) and the drain current I D By controlling the amount of 119, the branch current I BR Adjust the value of 168 to be below the branch current threshold. In other words, the shunt regulator 349 and driver 358 use the drain current I used to charge the bypass capacitor 144. D Quantity 119 (for example, branch current I BR Adjust 168). Drain current I D The remainder of 119 is conducted by the second switch 118 as a second current I1120.

[0062] Furthermore, when the power converter 100 is operating in discontinuous conduction mode (DCM) or continuous conduction mode (CCM), the first control device 332 may change the operation of the branch switch 152 and the second switch 118. During DCM, when the power switch S1 114 or the branch switch 152 is switched on, the switch current I D 119 is zero. In CCM, when power switch S1 114 or branch switch 152 is switched ON, switch current I D 119 is not practically zero.

[0063] During DCM operation, when a switching cycle is requested (e.g., when the ON signal ON160 is asserted), the bypass voltage V BP If 142 is less than the reference REF167, the branch drive signal BR165 controls the branch switch 152 to turn on (e.g., conduction state). The shunt regulator 349 and driver 358 control the extent to which the second switch 118 conducts the second switch current I1120, thereby controlling the branch current I BRAdjust 168.

[0064] However, in CCM, when the power switch S1 114 is switched on, the drain current I D 119 is not zero. Therefore, when the power switch S1 114 or the branch switch 152 is switched on, a large current spike may occur. This large current spike may damage the branch switch 152. The drain current I of the branch switch 152 D The physical size of the branch switch 152 can be similar to that of the second switch 118 so that it can conduct the entire branch current I. BR It can be used by adjusting 168. In CCM operation, the second switch 118 is switched on at the start of the switching cycle so as to conduct a large current spike before switching the branch switch 152 on. After a given time length, the branch current I BR The shunt switch 152 is then switched on so that 168 charges the bypass capacitor 144. The shunt regulator 349 and driver 358 control the extent to which the second switch 118 conducts the second switch current I1120, thereby controlling the shunt current I BR Adjust 168. Therefore, the second switch 118 is used to protect the branch switch 152.

[0065] Figure 4A is a timing diagram 400 showing an exemplary waveform of the first control device 332 in Figure 3 when the power converter 100 is operating in discontinuous conduction mode (DCM). Bypass voltage V BP 142, Request signal REQ133, Drain current I D 119. Branch current I BRFigure 168 shows the second current I1120, the ON signal ON160, the OFF signal OFF162, the voltage at node A117, the main ON signal MAIN_ON164, the branch drive signal BR165, and the primary drive signal DR138. Similar to Figure 2, the primary drive signal DR138 is shown as a voltage signal, and the voltage level of the primary drive signal DR138 controls the value of the second switch current I1120. It should be understood that the similarly named and numbered elements combine and function as described above.

[0066] In the example shown, comparator 156 uses hysteresis, and the upper reference REF+167a and lower reference REF-167b shown in Figures 4A and 4B represent the hysteresis threshold relative to the reference REF167. The bypass adjustment signal BP_REG163 is the bypass voltage V BP When 142 drops below the lower reference REF-167b, it transitions to a logic high value, and the bypass voltage V BP When 142 exceeds the upper reference REF+167a, it transitions to a logic low value. In other words, the bypass voltage V BP When 142 falls below the lower reference REF-167b, the first control device 332 may decide to switch on the branch switch 152 to charge the bypass capacitor 144. Bypass voltage V BP When 142 exceeds the upper reference REF+167a, the control device 332 may further decide to switch the branch switch 152 to the OFF position.

[0067] time t 11 From point t 13 Between and at point t 20 The part before this represents the normal switching cycle of power switch S1 114, in which the second switch 118 is fully switched on and energy is delivered from the input to the output of power converter 100. However, at point t 13 From point t 16 between, and at point t 16 From point t 20The switching cycles in between represent charging cycles, during which the branch switch 152 is switched on to charge the bypass capacitor 144. During these cycles, the branch current I BR 168 Branch current threshold I BRTH A second switch 118 is used to adjust it to less than 490. However, at point t 16 From point t 20 It must be understood that the switching cycle in between transitions from a charging cycle to a normal switching cycle.

[0068] time t 11 In this configuration, a request event (e.g., a pulse) is received by the request signal REQ133, and the main control unit 148 asserts the ON signal ON160 and deasserts the OFF signal OFF162. When a request event is received, the bypass voltage V BP 142 is higher than the lower reference REF-167b, and therefore the branch switch 152 cannot be switched on to charge the bypass capacitor 144. The branch control unit 150 asserts the main ON signal MAIN_ON164 so that the main ON signal MAIN_ON164 substantially follows the ON signal ON160. The branch drive signal BR165 is also not asserted by the branch control unit 150, at time t 11 and time t 12 The branch current I between is virtually zero. BR As shown in 168, the branch switch 152 does not conduct electricity.

[0069] As the main ON signal MAIN_ON164 is asserted, the primary drive signal DR138 provided by driver 358 is effectively turned ON at voltage V ON The on-voltage becomes 268, V ON 268 is drain current I D 119 and the second current I1120 are the voltages required to switch the second switch 118 on, as determined by the components coupled to the power switch S1 104. Therefore, at time t 11 and time t 12Between these two states, the second switch 118 is fully turned on, and the voltage at node A117 becomes a small value close to zero. In one example, the voltage at node A117 when the second switch 118 is fully turned on may be substantially 100mV. The second switch 118 is in a conducted state, and the second current I1120 is the drain current I D It is practically equal to 119.

[0070] time t 12 In this case, the drain current I D 119 reaches the current limit value ILIM221, and the power switch S1 114 is switched off. Both the ON signal ON160 and the main ON signal MAIN_ON164 are deasserted, and the OFF signal OFF162 is asserted. Driver 358 turns the drive signal DR138 off voltage V OFF Transition to 269, off voltage V OFF 269 ​​is such that the second switch 118 cannot conduct current, and the drain current I D This is the voltage value at which both 119 and the second current I1120 decrease to zero. This occurs when the power switch S1 114 is off. 12 and time t 13 Between these two points, the voltage at node A117 is such that the first switch 116 is in the cutoff state and does not conduct current, and the threshold voltage of the first switch 116 is V TH116 This is a high value, exceeding 491.

[0071] time t 13 In this case, the request event is received by the request signal REQ133, the ON signal ON160 is asserted, and the OFF signal OFF162 is deasserted. In addition, the bypass voltage V BP 142 is less than the lower reference REF-167b, and therefore the drain current I D At least a portion of 119 is used to charge the bypass capacitor 144. Bypass voltage V BP Since 142 has dropped below the lower reference REF-167b, the branch control unit 150 does not assert the main ON signal MAIN_ON164, but instead switches the branch switch 152 ON to turn on the branch current IBR To conduct 168, the branch drive signal BR165 is asserted. The primary drive signal DR138 is off voltage V to prevent the second switch S1 118 from conducting. OFF It remains at 269. 13 In this case, the voltage at node 117 is higher than the input return path 111 (shown as 0V in Figures 4A and 4B), and the threshold V of the first switch 116 is higher. TH116 It will drop to below 491.

[0072] time t 13 and time t 14 Between them, the branch current I BR 168 is the branch current threshold I BRTH It is less than 490. Therefore, the primary drive signal DR138 is off voltage V OFF The current remains at 269, and the second switch 118 does not conduct. Branch current I BR 168 is effectively drain current I D The value is 119, and the second current I1120 is effectively zero.

[0073] However, at point t 14 In this case, branch current I BR 168 is the branch current threshold I BRTH As time t reaches 490, the shunt regulator 349 provides the shunt regulator output 372 so that the driver 358 controls the second switch 118 to turn on and controls the amount of current (e.g., second current I1120) conducted by the second switch 118. 14 In this configuration, the current conducted by the second switch 118 (e.g., the second current I1120) depends on the value of the gate voltage of the second switch 118 (e.g., the primary drive signal DR138), such that the primary drive signal DR138 is the threshold voltage of the second switch 118. TH118 It transitions to a value higher than 492. Therefore, the shunt current regulator 349 has a branch current threshold I BRTH 490, or branch current threshold I BRTH Branch current I less than 490 BR 168 can be adjusted.

[0074] time t 14 and time t 15 Between, branch current I BR 168 is the branch current threshold I BRTH The shunt regulator 349 and driver 358 control the conduction of the second switch 118 so that it remains at 490. The remaining drain current I is not redirected to the bypass capacitor 144 by the branch switch 152. D Current 119 is conducted by the second switch 118 as a second current I1120. The second current I1120 and the branch current I BR The sum with 168 is effectively the drain current I D It must be understood that the number is 119. 14 and time t 15 Between them, bypass voltage V BP 142 rose above the lower reference REF-167b, but did not reach the upper reference REF+167a. Therefore, the bypass voltage V BP Until 142 reaches the upper reference REF+167a, the output of comparator 156 (e.g., bypass adjustment signal BP_REG163) remains unchanged, and branch switch 152 remains ON to charge bypass capacitor 144.

[0075] time t 15 In this case, the drain current I D When 119 reaches the current limit value ILIM221, the power switch S1 114 is switched off. The ON signal ON160 is deasserted, and the OFF signal OFF162 is asserted. The driver turns the drive signal DR138 off voltage V OFF The transition is made to 269, and the voltage at node A117 is the threshold V of the first switch 116. TH116 The value becomes higher than the given value. Therefore, neither the first switch 116 nor the second switch 118 conducts, and the drain current I D 119, second current I1120, and branch current I BR The value decreases from 168 to zero. Bypass voltage V BP 142 is, at time t 15 Prior to this, the upper criterion REF+167a was not reached.

[0076] time t 16 In this case, a request event is received, and the bypass voltage V BP 142 is less than the upper threshold REF+167a. Therefore, the drain current I D A portion of 119 is used to charge the bypass capacitor 144. The ON signal ON 160 is asserted, and the OFF signal OFF 162 is deasserted. The branch control unit 150 does not assert the main ON signal MAIN_ON 164, and the branch current I BR The branch drive signal BR165 is asserted to switch branch switch 152 to ON in order to conduct 168. The primary drive signal DR138 is off voltage V to prevent the second switch S1 118 from conducting. OFF It remains at 269. The voltage at node 117 is higher than the input return path 111 (shown as 0V in Figures 4A and 4B), and the threshold V of the first switch 116 is higher. TH116 The value will drop to less than 491.

[0077] time t 13 and time t 14 Similar to the duration between, time t 16 and time t 17 Between, branch current I BR 168 is the branch current threshold I BRTH It is less than 490. Therefore, the second switch 118 cannot be switched on to conduct current, and the branch current I BR 168 is effectively drain current I D The value is 119, and the second current I1120 is effectively zero.

[0078] time t 17 In this case, branch current I BR 168 is the branch current threshold I BRTH Upon reaching 490, the shunt regulator 349 and driver 358 control the second switch 118 to turn on. Furthermore, the amount of current conducted by the second switch 118 (e.g., the second current I1120) is determined by the detected branch current I BR It depends on 168. As shown, at time t 17In this configuration, the current conducted by the second switch 118 (e.g., the second current I1120) depends on the value of the gate voltage of the second switch 118 (e.g., the primary drive signal DR138), such that the primary drive signal DR138 is the threshold voltage of the second switch 118. TH118 It transitions to a value higher than 492.

[0079] time t 17 and time t 18 Between, branch current I BR 168 is the branch current threshold I BRTH To keep the current at 490, the shunt regulator 349 and driver 358 control the conduction of the second switch 118. The remaining drain current I is not used by the branch switch 152 to charge the bypass capacitor 144. D Current 119 is conducted by the second switch 118 as a second current I1120. The second current I1120 and the branch current I BR The sum with 168 is effectively the drain current I D It must be understood that the number to call is 119.

[0080] time t 18 In this case, the drain current I D Before 119 reaches the current limit value ILIM221, the bypass voltage V BP 142 reaches the upper reference REF+167a. The ON signal ON160 is still asserted, and the branch control unit 150 deasserts the branch drive signal BR165 to switch the branch switch 152 off, and asserts the main ON signal MAIN_ON164 to fully switch the second switch 118 on. The cycle returns to the normal switching cycle and the second switch 118 drains current I D Conducts the entire 119. Or, to put it another way, the second current I1120 is essentially the drain current I D It is 119. The voltage at node A117 is the threshold V of the first switch 116. TH116 When the value drops to well below 491, the primary drive signal DR138 is on voltage V ON It will rise to 268.

[0081] time t 19 In this case, the drain current I D When 119 reaches the current limit value ILIM221, the power switch S1 114 is switched to OFF. The main control unit 148 deasserts the ON signal ON160 and asserts the OFF signal 162. The main ON signal MAIN_ON164 is further deasserted, and the OFF signal OFF162 is deasserted. The driver 358 turns the drive signal DR138 off voltage V OFF The transition is made to 269, and the voltage at node A117 is the threshold V of the first switch 116. TH116 The value becomes high, exceeding 491. Therefore, neither the first switch 116 nor the second switch 118 conducts, and the drain current I D 119, second current I1120, and branch current I BR 168 decreases to zero. 20 The power switch S1 114 remains off until another request event is received in request signal REQ133.

[0082] Figure 4B is a timing diagram 401 showing an exemplary waveform of the first control device 332 in Figure 3 when the power converter 100 is operating in continuous conduction mode (CCM). Bypass voltage V BP 142, Request signal REQ133, Drain current I D 119. Branch current I BR Figures 168, 168, 168, 168, 168, 168, 168, 168, 17, 18, 19, 1

[0083] time t 22 From point t 23 During and at point t 31The following represents the normal switching cycle of power switch S1 114, in which the second switch 118 is fully switched on and energy is delivered from the input to the output of power converter 100. However, at point t 24 From point t 27 During and at point t 27 From point t 31 The switching cycle between these represents a charging cycle, during which the branch switch 152 is switched on to charge the bypass capacitor 144. During these cycles, the second switch 118 switches the branch current I BR 168 Branch current threshold I BRTH Further adjustments are made to keep it below 490. The charging cycle is bypass voltage V BP It begins when 142 drops below the lower reference REF-167b, bypass voltage V BP The process terminates when 142 reaches the upper limit REF+167a.

[0084] Time point t related to Figure 4A 11 From point t 13 between, and at point t 22 Similar to the normal switching cycle described above, at time t 22 and time t 31 In this case, when a request event (e.g., a pulse) is received in the request signal REQ133, the bypass voltage V BP When 142 is higher than the lower reference REF-167b or has reached the upper reference REF+167a, the branch switch 152 cannot be switched on to charge the bypass capacitor 144. The main control unit 148 asserts the ON signal ON160 and deasserts the OFF signal OFF162. The branch control unit 150 asserts the main ON signal MAIN_ON164, and the main ON signal MAIN_ON164 substantially follows the ON signal ON160. The branch drive signal BR165 is also not asserted by the branch control unit 150, at time t 22 and time t 23 Between and t 31 Beyond that point, the branch current I is virtually zero. BRAs shown in 168, the branch switch 152 does not conduct electricity.

[0085] The primary drive signal DR138 is ON voltage V ON Substantially equal to 268, with an on-voltage V ON 268 is drain current I D 119 and the second current I1120 are the voltages required to switch the second switch 118 on, determined by the components coupled to the power switch S1 104. Therefore, at time t 22 From point t 23 During and at point t 31 At this point, the second switch 118 is fully turned on, and the voltage at node A117 is a small value close to zero. For example, the voltage at node A117 when the second switch 118 is fully turned on may be substantially 100mV. When the second switch 118 is fully turned on and conducting, the second current I1120 is the drain current I D It is substantially equal to 119. As shown, the drain current I D 119 is not virtually zero at the start of the switching cycle, indicating CCM operation. 22 and time t 31 When the power switch S1 114 is switched on, a current spike is observed.

[0086] time t 23 and time t 32 In this case, the drain current I D When 119 reaches the current limit value ILIM221, the power switch S1 114 is switched off. Both the ON signal ON160 and the main ON signal MAIN_ON164 are deasserted, and the OFF signal OFF162 is asserted. The driver turns the drive signal DR138 off voltage V OFF Transition to 269, off voltage V OFF 269 ​​is such that the second switch 118 cannot conduct current, and the drain current I D This is the voltage value at which currents 119 and the second current I1120 decrease to zero. 23and time t 24 Between these points, when power switch S1 114 is off, the voltage at node A117 is such that the voltage at node A117 is below the threshold V of the first switch 116, so that the first switch 116 is in a cutoff state and does not conduct current. TH116 This will be a high value, exceeding 491.

[0087] time t 24 At this point, the request event is received by the request signal REQ133, and the main control unit 148 asserts the ON signal ON160 and deasserts the OFF signal 162. However, at time t 24 In this case, the bypass voltage V BP 142 is less than the lower reference REF-167b, and by switching branch switch 152 to ON, the drain current I D A portion of 119 is used to charge the bypass capacitor 144. However, in CCM operation, the second switch 118 conducts the CCM current spike observed at the start of the switching cycle, at time t 24 and time t 25 It is temporarily switched to completely ON between these two points. The branch control unit 150 asserts the main ON signal MAIN_ON164, but at point t 25 Do not assert the branch drive signal BR165 until the primary drive signal DR138 is on voltage V. ON The transition to 268 occurs, the voltage at node A117 becomes a small value close to zero, the second switch 118 turns completely on, and the drain current I D Conducting 119 (for example, the second current I1120 is effectively the drain current I) D (It is 119).

[0088] time t 25 In this configuration, the branch control unit 150 asserts the branch drive signal BR165 and deasserts the main ON signal MAIN_ON164 to switch the branch switch 152 ON. The driver 358 sets the threshold V of the second switch 118 such that the current conducted by the second switch 118 (e.g., the second current I1120) depends on the value of the gate voltage of the second switch 118 (e.g., the primary drive signal DR138). TH118The primary drive signal DR138 is transitioned to a value higher than 492. As shown, the voltage at node A117 is the threshold V of the first switch 116. TH116 The value transitions to a value less than 491. (Time point t) 24 and time t 25 It must be understood that the duration between these two points may be fixed or variable.

[0089] time t 25 and time t 26 Between, branch current I BR 168 is the branch current threshold I BRTH If it is less than 490, or the branch current threshold I BRTH It has reached a state of 490. The shunt regulator 349 controls the branch current I BR 168 is the branch current threshold I BRTH 490, or branch current threshold I BRTH To control the amount of current conducted by the second switch 118 (e.g., the second current I1120) so that it remains below 490, the driver 358 is provided with a shunt regulator output 372. The remaining drain current I that is not conducted by the branch switch 152 to charge the bypass capacitor 144 D Current 119 is conducted by the second switch 118 as a second current I1120. The second current I1120 and the branch current I BR The sum with 168 is effectively the drain current I D It must be understood that it is 119. During this switching cycle, the bypass voltage V BP Although 142 is rising above the lower reference REF-167b, it has not reached the upper reference REF+167a, and the output of comparator 156 (e.g., bypass adjustment signal BP_REG163) does not change state.

[0090] time t 26 In this case, the drain current I DWhen 119 reaches the current limit value ILIM221, the power switch S1 114 is switched off. Both the ON signal ON160 and the main ON signal MAIN_ON164 are deasserted, and the OFF signal OFF162 is asserted. The driver turns the drive signal DR138 off at the off voltage V OFF The transition is made to 269, and the voltage at node A117 is the threshold V of the first switch 116. TH116 The value becomes high, exceeding 491. Therefore, neither the first switch 116 nor the second switch 118 conducts, and the drain current I D 119, second current I1120, and branch current I BR 168 decreases to zero. As branch switch 152 is off, the bypass voltage V BP 142 decreases.

[0091] time t 27 In this configuration, the request event is received by the request signal REQ133, and the main control unit 148 asserts the ON signal ON160 and deasserts the OFF signal 162. Bypass voltage V BP 142 is time t 27 The upper threshold is less than REF+167a, and the drain current I D A portion of 119 is used to charge the bypass capacitor 144. As described above, the second switch 118 is switched at time t to conduct the CCM current spike observed at the start of the switching cycle. 27 and time t 28 It is temporarily switched to completely ON between these two points. The branch control unit 150 asserts the main ON signal MAIN_ON164, and at point t 28 Do not assert the branch drive signal BR165 until the primary drive signal DR138 is on voltage V. ON The transition to 268 occurs, the voltage at node A117 becomes a small value close to zero, the second switch 118 turns completely on, and the drain current I D 119 conducts, and therefore the second current I1120 is substantially the drain current I D The number is 119.

[0092] time t28 In this configuration, the branch control unit 150 controls the branch current I BR The branch drive signal BR165 is asserted to switch branch switch 152 ON in order to conduct 168, and the main ON signal MAIN_ON164 is deasserted. The driver 358 sets the threshold V of the second switch 118 such that the current conducted by the second switch 118 (e.g., second current I1120) depends on the value of the gate voltage of the second switch 118 (e.g., primary drive signal DR138). TH118 The primary drive signal DR138 is transitioned to a value higher than 492. As shown, the voltage at node A117 is the threshold V of the first switch 116. TH116 It transitions to a value slightly below 491. Time t 27 and time t 28 It must be understood that the duration between these two points may be fixed or variable.

[0093] time t 28 and time t 29 Between, branch current I BR 168 is the branch current threshold I BRTH It is controlled to less than 490. During this period, the branch current I BR 168 is the branch current threshold I BRTH 490, or branch current threshold I BRTH To control the amount of current conducted by the second switch 118 (e.g., second current I1120) so that it remains below 490, the shunt regulator 349 provides the shunt regulator output 372 to the driver 358. The remaining drain current I that is not conducted by the branch switch 152 charges the bypass capacitor 144. D Current 119 is conducted as a second current I1120 by the second switch 118.

[0094] time t 29 In this case, the drain current I D Before 119 reaches the current limit value ILIM221, the bypass voltage V BPWhen 142 reaches the upper reference REF+167a, the branch control unit 150 deasserts the branch drive signal BR165 to switch branch switch 152 off. The ON signal ON160 is still asserted, and then the branch control unit 150 asserts the main ON signal MAIN_ON164 to fully switch the second switch 118 on. The voltage at node A117 is the threshold V of the first switch 116. TH116 When the value drops to a value well below 491, the primary drive signal DR138 turns on voltage V ON It rises to 268. The cycle returns to the normal switching cycle, and the second switch 118 drains current I D Conducting the entire 119, the second current I1120 is substantially the drain current I D The result is 119.

[0095] time t 30 In this case, the drain current I D When 119 reaches the current limit value ILIM221, the power switch S1 114 is switched to OFF. Both the ON signal ON160 and the main ON signal MAIN_ON164 are deasserted, and the OFF signal OFF162 is asserted. The primary drive signal DR138 is set to the OFF voltage V OFF The transition is to 269, and the voltage at node A117 is the threshold V of the first switch 116. TH116 The value becomes high, exceeding 491. Therefore, neither the first switch 116 nor the second switch 118 conducts, and the drain current I D 119, second current I1120, and branch current I BR 168 decreases to zero. 31 The power switch S1 114 remains off until another request event is received in request signal REQ133.

[0096] Figure 5A shows another embodiment of the first control unit 532, including a branch control unit 550, a branch switch 152, a diode D2 154, a comparator 156, a driver 558, and a shunt regulator 349. A power switch S1 114, including a first switch 116 and a second switch 118, and a bypass capacitor 144 are shown to provide context for the first control unit 532 related to Figure 1. Drain current I D 119, Second switch current I1120, Primary drive signal DR138, Bypass voltage V BP 142, ON signal ON 160, OFF signal OFF 152, Bypass adjustment signal BP_REG 163, Main ON signal MAIN_ON 164, Branch drive signal BR 165, Reference REF 167, Branch current I BR 168 and the shunt regulator output 372 are further shown in Figure 5A. It should be understood that the first control device 532 may be used with the power converter 100 shown in Figure 1. Although the main control unit is not shown in Figure 5A, it should be understood that the first control device 532 further includes a main control unit to provide an ON signal ON 160 and an OFF signal OFF 162.

[0097] Figure 5A shows exemplary embodiments of the branch control unit 550 and the driver 558. The branch control unit 550 is shown as including AND gate 574, latch 575, AND gate 576, capacitor C1 581, resistor R1 582, inverter 577, inverter 578, AND gate 579, and AND gate 580. The driver 558 is shown as including switches 585, 586, and 587, and resistor R3 588. In the example shown, diode 589 is shown coupled between the shunt regulator 349 and the driver 558 to indicate the direction of the shunt regulator output 372. It should be understood that diode 589 may be optional.

[0098] Figure 5A shares many similarities with the first control device 132 described in relation to Figure 1, and it should be understood that similarly named and numbered elements combine and function as already described with reference to Figures 1 and 2. However, at least one difference is the addition of a shunt regulator 349 with a shunt regulator output 372, and how the driver 558 responds to the shunt regulator output 372. Similar to the first control device 332 described in relation to Figure 3, the first control device 532 has a branch current threshold I BRTH to, or branch current threshold I BRTH Branch current I is less than BR Adjust 168.

[0099] Figure 5A shares many similarities with the first control device 332 related to Figure 3, and it should be understood that similarly named and numbered elements combine and function as already described in relation to Figures 3, 4A, and 4B. However, at least one difference is that the branch switch 152 is switched on for part of the on-period of the power switch S1 114 in order to charge the bypass capacitor 144. The bypass voltage V BP If 142 is less than the reference REF167, the branch control unit 550 decides to switch branch switch 152 on for a period T1 at the beginning of the ON period of power switch S1 114. During period T1, the shunt regulator 349 and driver 558 control the second current I1120 conducted by the second switch 118, thereby controlling the branch current I BR 168 Branch current threshold I BRTH Adjust to less than. After period T1 has elapsed, the switching cycle returns to the normal switching cycle, the branch control unit 550 controls the branch switch 152 to turn off, and the driver 558 controls the drain current I D To conduct the entire 119, the second switch 118 is controlled to be fully ON.

[0100] The branch control unit 550, as indicated by the off signal OFF162 (or alternatively the inverted on signal ON160) and the bypass adjustment signal BP_REG163, applies a bypass voltage V during the off period of the power switch S1 114. BP The branch control unit 550 then determines whether 142 has fallen below the reference REF167. D Determine whether the branch switch 152 must be switched on so that a portion of 119 is used to charge the bypass capacitor 144. The AND gate 574 is shown coupled to the comparator 156 and receives the bypass adjustment signal BP_REG 163 and the off signal OFF 162. Alternatively, the AND gate 574 may receive the inverted on signal ON 160 instead of the off signal OFF 162.

[0101] Latch 575 is coupled to AND gate 574. As shown, the output of AND gate 574 is received at the S input of latch 575. The reset input of latch 575 is coupled to capacitor C2 583 and resistor R2 584. AND gate 576 is coupled to the Q output of latch 575 to receive the ON signal ON160. The output of AND gate 576 is coupled to capacitance C1 581, which in turn is coupled to resistor R1 582 and inverter 577. Capacitor C1 581 and resistor R1 582 are coupled together as a monostable multivibrator to provide a pulse with duration T1.

[0102] Inverter 577 is coupled to inverter 578 and AND gate 580. Both AND gates 579 and 580 are coupled to receive the ON signal ON160. Furthermore, AND gate 579 is coupled to receive the output of inverter 578, and AND gate 580 is coupled to receive the output of inverter 577. The output of AND gate 579 is the branch drive signal BR165, and the output of AND gate 580 is the main ON signal MAIN_ON164.

[0103] During operation, bypass voltage V BP If 142 is less than the reference REF167, the bypass adjustment signal BP_REG163 is logically high. During the off period of power switch S1 114, the off signal OFF162 is logically high (e.g., asserted). During the off period of power switch S1 114, the bypass voltage V BP If the bypass adjustment signal BP_REG163 indicates that 142 is less than the reference REF167, the output of the AND gate 574 becomes logic high, the latch 575 is set, and the Q output becomes logic high. The ON signal ON160 becomes logic high (e.g., asserted) at the start of the next switching cycle of the power switch S1 114. Bypass voltage V BP The output of AND gate 576 is logic high because the Q output is high due to 142 being less than the reference REF167 in the previous switching cycle. In other words, with the rising edge of the ON signal ON160, the output of AND gate 576 transitions to a logic high value. Capacitor C1 581 and resistor R1 582 are coupled together as a monostable multivibrator. When the output of AND gate 576 transitions to a logic high value (e.g., on the rising edge), capacitor C1 581 and resistor R1 582 provide a pulse with a duration substantially equal to the period T1.

[0104] Inverter 577 provides an inverted pulse to AND gate 580 for a period T1, and inverter 578 provides a pulse to AND gate 579 for a period T1. When the ON signal ON160 is first asserted, AND gate 579 provides a logic high (e.g., asserted) value for branch drive signal BR165, and branch switch 152 is switched ON for a period T1. In other words, branch drive signal BR165 is logic high for a period substantially equal to the period T1.

[0105] Since inverter 577 provides the AND gate 580 with an inverted pulse for period T1, when the ON signal ON160 is first asserted, the main ON signal MAIN_ON164 is logic low (e.g., unasserted) for the duration of period T1. At the end of period T1, the pulses provided by capacitor C1 581 and resistor R1 582 transition to a logic low value, the branch drive signal BR165 is unasserted (e.g., logic low), and the branch switch 152 is switched off. After period T1, the output of inverter 577 becomes logic high, and therefore, after period T1 has elapsed, the main ON signal MAIN_ON164 transitions to a logic high value (e.g., asserted) and remains asserted to switch the second switch S1 118 on until the ON signal ON160 is unasserted. Capacitor C2 583 and resistor R2 584 provide edge triggers to reset latch 575.

[0106] The bypass adjustment signal BP_REG163 remains in a logic low state, and the bypass voltage V BP If 142 is greater than the reference REF167, then latch 575 is not set, the Q output of latch 575 is logic low, AND gate 576 is logic low, inverter 577 is logic high, and inverter 578 is logic low. Therefore, when the ON signal ON160 is logic high (e.g. asserted), the branch drive signal BR165 remains logic low (e.g. deasserted), and the main ON signal MAIN_ON164 becomes logic high (e.g. asserted).

[0107] Driver 558 is illustrated as including switches 585, 586, and 587, and resistor R3 588. Diode 589 is shown coupled between shunt regulator 349 and driver 558 to indicate the direction of the shunt regulator output 372. However, it should be understood that diode 589 is optional. As shown, switch 585 is connected to the gate and on voltage V of the second switch 118 ONIt is coupled to 268 and controlled by the main ON signal MAIN_ON164. When in operation, switch 585 is coupled to the gate of the second switch 118 as a pull-up switch to drive the second switch 118 fully ON. When the main ON signal MAIN_ON164 is asserted, switch 585 is closed and the primary drive signal DR138 (e.g., the gate voltage of the second switch 118) is effectively turned ON voltage V ON It becomes 268. As mentioned above, the second switch 118 is turned on completely, and the drain current I D To conduct 119, the on-voltage V ON A value of 268 could be selected.

[0108] Switch 586 is the gate and off voltage V of the second switch 118. OFF It is coupled to 269. Switch 586 is controlled by the OFF signal OFF162. When operating, switch 586 is coupled to the gate of the second switch 118 as a pull-down switch to drive the second switch 118 completely off. When the OFF signal OFF162 is asserted, switch 585 is closed and the primary drive signal DR138 (e.g., the gate voltage of the second switch 118) is effectively the off voltage V OFF The value becomes 269. Off-voltage V OFF A value of 269 may be selected so that current cannot be conducted, causing the second switch 118 to be completely turned off.

[0109] Resistor 588 and switch 587 are shown coupled between the gate of the second switch 118 and the input return path 111. As shown, switch 587 is controlled by the branch drive signal BR165. The shunt regulator output 372 is coupled through diode 589 to resistor R3 588 and the gate of the second switch 118. When operating, if the branch drive signal BR165 is asserted, both branch switch 152 and switch 587 are turned on. The level of the primary drive signal DR138 (e.g., the gate voltage of the second switch 118) is determined by the shunt regulator 349. The shunt regulator 349 controls the branch current IBR When 168 is detected and the branch drive signal BR165 indicates that the branch switch 152 is ON (for example, or conducting), the shunt regulator output 372 is provided. Furthermore, the shunt regulator 349 provides the branch current I BR 168 is the branch current threshold I BRTH When it reaches the target, the branch current I is detected. BR 168 is the branch current threshold I BRTH To prevent exceeding this value, the shunt regulator output 372 is changed. As shown, the shunt regulator output 372 can be a voltage value determined by the shunt regulator 349. The shunt regulator output 372 is used as the value of the primary drive signal DR138 (e.g., the gate voltage of the second switch 118), and the second switch 118 controls the conduction of the second current I1120, thereby controlling the branch current I BR 168 is the branch current threshold I BRTH It will be adjusted to less than.

[0110] Figure 5B is a timing diagram 500 showing exemplary waveforms of the first control device 532 in Figure 5A. The exemplary waveforms are representative of a power converter 100 operating in discontinuous conduction mode (DCM). Bypass voltage V BP 142, Request signal REQ133, Drain current I D 119. Branch current I BR Figure 5B shows the second current I1120, the ON signal ON160, the OFF signal OFF162, the voltage at node A117, the main ON signal MAIN_ON164, the branch drive signal BR165, and the primary drive signal DR138. In the example shown, comparator 156 has hysteresis, and the upper reference REF+167a and lower reference REF-167b shown in Figure 5B represent the hysteresis threshold relative to reference REF167. The bypass adjustment signal BP_REG163 is the bypass voltage V BP When 142 drops below the lower reference REF-167b, the logic is high, and the bypass voltage V BPThe logic is low when 142 reaches the upper reference REF+167a. As with the other diagrams, the primary drive signal DR138 is a voltage signal, and the voltage value of the primary drive signal DR138 controls the value of the second switch current I1120 conducted by the second switch 118. It should be understood that the similarly named and numbered elements combine and function as described above.

[0111] time t 32 From point t 34 The switching cycle between these two points represents the normal switching cycle of power switch S1 114, during which the second switch 118 is fully switched on and energy is delivered from the input to the output of power converter 100. However, at point t 34 From point t 38 During, at point t 38 From point t 42 During, and, 42 The subsequent switching cycles represent charging cycles, during which the branch switch 152 is switched on to charge the bypass capacitor 144. During these cycles, the second switch 118 switches the branch current I BR 168 Branch current threshold I BRTH It is used to adjust to less than 590. Compared to other timing diagrams, at least one difference shown in timing diagram 500 is that during the charging cycle, the branch switch 152 is switched on for a period T1570 of each charging cycle in order to charge the bypass capacitor 144. For the remainder of the charging cycle, it returns to a normal switching cycle after period T1570.

[0112] time t 32 In this configuration, a request event (pulse) is received by the request signal REQ133, and the main control unit 148 asserts the ON signal ON160 and deasserts the OFF signal OFF162. Furthermore, the bypass voltage V BP 142 is higher than the lower reference REF-167b, and the branch switch 152 drains current I to charge the bypass capacitor 144.D It cannot be switched on to change the direction of part of 119. The branch control unit 150 asserts the main ON signal MAIN_ON164 so that the main ON signal MAIN_ON164 substantially follows the ON signal ON160. The branch drive signal BR165 is also not asserted by the branch control unit 150, at time t 32 and time t 33 The branch current I between is virtually zero. BR As shown in 168, the branch switch 152 does not conduct electricity.

[0113] time t 32 and time t 33 Between these two points, the primary drive signal DR138 is effectively on voltage V ON The value is 268, and the on-voltage is V ON 268 is drain current I D 119 and the second current I1120 are the voltages required to switch the second switch 118 on, as determined by the components coupled to the power switch S1 104. Thus, when the second switch 118 is fully on, the voltage at node A117 is a small value close to zero. For example, when the second switch 118 is fully on, the voltage at node A117 may be substantially 100mV. When the second switch 118 is conducting, the second current I1120 is the drain current I D It is practically equal to 119.

[0114] time t 33 In this case, the drain current I D When 119 reaches the current limit value ILIM221, the power switch S1 114 is switched to OFF. The OFF signal OFF162 is asserted, and both the ON signal ON160 and the main ON signal MAIN_ON164 are deasserted. The drive signal DR138 is set to the OFF voltage V OFF Transitions to 269, off voltage V OFF 269 ​​is such that the second switch 118 cannot conduct current, and the drain current I D119 and the second current I1 120 decreases to zero. At time point t when the power switch S1 114 is off 33 and time point t 34 and between the two, the voltage at node A117 is equal to the threshold V of the first switch 116, such that the first switch 116 is in a cut-off state and does not conduct current TH116 reaches a high value exceeding 591.

[0115] At time point t 34 , a request event is received in the request signal REQ133, the on signal ON160 is asserted, and the off signal 162 is deasserted. Bypass voltage V BP 142 is lower than the lower reference REF-167b, drain current I D part of 119 is used to charge the bypass capacitor 144. At time point t 34 in order to turn on the branch switch 152 over a period T1570 shown as the duration between time point t36 and the foregoing time point t, the branch control unit 550 asserts the branch drive signal BR165. As shown, the bypass voltage V BP 142 starts to increase. To prevent the second switch S1 118 from conducting, the primary drive signal DR138 remains at the off voltage V OFF 269, but the voltage at node 117 is higher than the input return path 111 (shown as 0V in FIG. 5A) but lower than the threshold V of the first switch 116 TH116 drops to a value less than 591.

[0116] At time point t 34 and time point t 35 and between the two, the branch current I BR 168 is lower than the branch current threshold I BRTH 590. Therefore, the shunt regulator 349 does not change the primary drive signal DR138, and the second switch 118 does not conduct. The branch current I BR 168 is substantially equal to the drain current I D 119, and the second current I1 120 is substantially zero.

[0117] At time point t35 In the above, the branch current I BR 168 reaches the branch current threshold I BRTH 590, the shunt regulator 349 provides the shunt regulator output 372 such that the driver 558 controls the second switch 118 to turn on, and controls the amount of current conducted by the second switch 118 (e.g., the second current I1120). As shown, the primary drive signal DR138 transitions to a value higher than the threshold V TH118 592 of the second switch 118, such that the current conducted by the second switch 118 (e.g., the second current I1120) depends on the gate voltage of the second switch 118 (e.g., the primary drive signal DR138). Accordingly, the shunt regulator 349 regulates the branch current I BR 168.

[0118] Between time point t 35 and time point t 36 , the shunt regulator 349 and the driver 358 control the conduction of the second switch 118 such that the branch current I BR 168 remains at the branch current threshold I BRTH 590. The remaining drain current I BR 119 that is not conducted by the branch switch 152 as the branch current I D 168 is conducted by the second switch 118 as the second current I1120. Between time point t 35 and time point t 36 , the bypass voltage V BP 142 rises above the lower reference REF-167b, but has not reached the upper reference REF+167a.

[0119] At time point t 36At this point, period T1570 ends. It should be understood that the duration of period T1570 can be determined by the capacitor C1 581 and resistor R1 582 shown in Figure 5A. The branch control unit 550 deasserts the branch drive signal BR165 and asserts the main ON signal MAIN_ON164 to substantially follow the ON signal ON160. As the voltage at node A117 drops to a value close to zero, the primary drive signal DR138 turns ON to voltage V ON The transition is to 268. The second switch 118 is fully turned on, and the branch switch 152 is switched off. Time t 36 From point t 37 During the period, branch current I BR 168 is practically zero, and the second current I1120 is practically the drain current I D It is 119. After the branch switch 152 is switched off, the bypass voltage V BP 142 begins to decrease.

[0120] time t 37 In this case, the drain current I D When 119 reaches the current limit value ILIM221, the power switch S1 114 is switched to OFF. The ON signal ON160 is deasserted, and the OFF signal OFF162 is asserted. The drive signal DR138 is set to the OFF voltage V OFF The transition is to 269, and the voltage at node A117 is the threshold V of the first switch 116. TH116 The value becomes high, exceeding 591. Therefore, neither the first switch 116 nor the second switch 118 conducts, and the drain current I D Currents 119 and the second current I1120 decrease to zero. 38 In this case, another request event is received in request signal REQ133, and the bypass voltage V BP 142 is below the upper threshold REF+167a and the lower threshold REF-167b. Time t 38 From point t 42 The cycle shown between points t 34 From point t 38It must be understood that this is similar to the cycle already described during this period. The branch drive signal BR165 is asserted to switch the branch switch 152 on over the period T1570 in order to charge the bypass capacitor 144. During the period T1570, the branch current I BR 168 controls the branch current threshold I by controlling the second current I1120. BRTH It is adjusted to less than 590. After period T1570, branch switch 152 is switched off, and second switch 118 is switched completely on, drain current I D The second switch 118 drains the current I until 119 reaches the current limit value ILIM221 and the power switch S1 114 is switched off. D Conduction of voltage 119. During this switching cycle, bypass voltage V BP 142 does not reach the upper threshold REF+167a.

[0121] time t 42 In this case, another request event is received in request signal REQ133, and the bypass voltage V BP 142 is less than the upper threshold REF+167a. Time t 42 For a switching period starting from t, time t 44 Bypass voltage V BP 142 reaches the threshold REF+167. Therefore, at time t 44 In this state, the cycle returns to the normal switching cycle, the main ON signal MAIN_ON164 is asserted, and the drain current I D The second switch 118 is fully switched on to conduct 119.

[0122] Figure 6 shows an exemplary bypass voltage V BPThe timing diagram 600 shows the timing of 142 and the branch drive signal BR165. It should be understood that the similarly named and numbered elements are coupled and function as described above. In one embodiment, the branch switch 152 may be switched on over a fixed number of consecutive switching cycles. In a further embodiment, the branch switch 152 may not be switched on over more than a fixed number of consecutive switching cycles. In the example shown in Figure 6, the branch switch 152 is switched on over three consecutive switching cycles. As shown, the bypass voltage V BP When 142 reaches the lower reference REF-167b, the charging cycle may begin, and the branch drive signal BR165 switches branch switch 152 to ON. Bypass voltage V BP When 142 reaches the upper reference REF+167a, the charging cycle is stopped. Bypass voltage V BP When 142 reaches the lower reference REF-167b, the branch drive signal BR165 pulses to a logic high to switch branch switch 152 on.

[0123] In one example, the branch switch 152 is switched on for a period T1 as described with reference to Figures 5A and 5B, but the branch switch 152 may also be switched on as described with reference to Figures 1, 2, 3, 4A, and 4B. When the branch switch 152 is on, the bypass voltage V BP 142 is rising. When branch switch 152 is off, bypass voltage V BP 142 is decreasing. As shown in timing diagram 600, the branch drive signal BR165 turns on branch switch 152 over three consecutive switching cycles, bypass voltage V BP 142 reached the upper reference REF+167a. Bypass voltage V BPPeriod T1 may be selected such that it takes three consecutive switching cycles for 142 to reach the upper reference REF+167a from the lower reference REF-167b. However, it should be understood that a different number of consecutive switching cycles may be used.

[0124] Figure 7 shows an exemplary isolated power converter 700, which includes a first control device 132 comprising a branch switch 152 and a branch control unit 150. It should be understood that power converter 700 shares many similarities with power converter 100 in Figure 1, and that similarly named and numbered elements combine and function as described above. However, at least one difference is that power converter 700 does not include the auxiliary winding 112 and diode D1 146. Thus, the bypass voltage V of bypass capacitor 144 BP 142 is generated by the first control device 132. However, although the first control device 132 is shown in Figure 1, it should be understood that embodiments of the first control device described in relation to Figures 3, 4A, 4B, 5A, and 5B may be used in conjunction with the power converter 700.

[0125] The above description of examples relating to the present invention, including matters described in the abstract, is not intended to be exhaustive or to be a limitation to the disclosed forms themselves. While specific embodiments and examples of the present invention are described herein for illustrative purposes only, various equivalent modifications are possible without departing from the broader spirit and scope of the invention. Indeed, it is understood that specific and exemplary voltages, currents, frequencies, output range values, times, etc., are presented for illustrative purposes, and that other values ​​may be used in other embodiments and examples as taught by the present invention.

[0126] Although the present invention is defined in the claims, it should be understood that the present invention may be defined by the following alternative examples.

[0127] Example 1. A first control device for a power converter, the first control device comprising: a driver configured to provide drive signals for switching a power switch on and off in order to control energy delivery between the input and output of the power converter, wherein the power switch includes a first switch and a second switch coupled in a cascode configuration, the first switch being a normally-on device and the second switch being a normally-off device; a power terminal coupled to a bypass capacitor that provides operating power to the first control device, the bypass capacitor having a bypass voltage; a branch switch coupled to a node between the first switch and the second switch; and a branch control unit configured to receive an adjustment signal representing the result of comparing the bypass voltage to a bypass reference, wherein the branch control unit is configured to switch the branch switch on when the bypass voltage is less than the bypass reference in order to redirect at least a portion of the drain current of the power switch from the node to the bypass capacitor.

[0128] Example 2. The first control device according to Example 1, configured to switch a second switch on and off in order to control the driver switching the power switch on and off.

[0129] Example 3. The first control device according to Example 1 or Example 2, wherein the branch control unit is configured to switch the branch switch ON simultaneously with the switching cycle of the power switch.

[0130] Example 4. The first control device according to any one of Examples 1 to 3, wherein the branch control unit is configured to switch a branch switch to the ON position for a fixed period of time.

[0131] Example 5. The first control device according to any one of Examples 1 to 4, wherein the branch control unit is configured to switch off the branch switch when the bypass voltage reaches a bypass reference or when the drain current of the power switch reaches a current limit.

[0132] Example 6. The first control device according to any one of Examples 1 to 5, wherein the driver is configured to switch on a second switch when the branch switch is off and the drain current is less than a current limit.

[0133] Example 7. The first control device according to any one of Examples 1 to 6, wherein the driver is configured to switch off a second switch when a branch switch is switched on and the branch switch conducts the drain current of the power switch from the node to the bypass capacitor.

[0134] Example 8. The first control device according to any one of Examples 1 to 7, further comprising a shunt regulator configured to detect a branch current conducted by a branch switch and to adjust it to a branch current threshold, wherein the shunt regulator and driver adjust the branch current by controlling a second current conducted by a second switch, the branch current being substantially the portion of the drain current redirected from the node to a bypass capacitor, and the second current being the remainder of the drain current.

[0135] Example 9. The first control device according to any one of Examples 1 to 8, wherein a shunt regulator is configured to provide a shunt output voltage to a driver, the driver determines the gate voltage of a second switch in response to the shunt output voltage, and a second current conducted through the second switch in response to the gate voltage of the second switch.

[0136] Example 10. When the power converter operates in continuous conduction mode, the driver switches on the second switch before the branch control unit switches on the branch switch. The first control device as described in any one of Examples 1 to 9.

[0137] Example 11. The first control device according to any one of Examples 1 to 10, wherein the branch switch is switched on over a fixed number of consecutive switching cycles.

[0138] Example 12. A first control device for a power converter, the first control device comprising: a power switch, wherein the power switch comprises a first switch and a second switch coupled in a cascode configuration, the first switch is a normally-on device, and the second switch is a normally-off device; a branch switch coupled to a node between the first switch and the second switch, the branch switch being further coupled to a bypass capacitor; a driver configured to provide a drive signal for controlling switching on and switching off of the power switch to control energy delivery between an input side and an output side of the power converter, the driver being configured to switch on and switch off the second switch to control the switching on and switching off of the power switch; a main control unit configured to receive a request signal indicating to switch on the power switch, wherein the main control unit determines whether the power switch must be on or must be off; a comparator coupled to receive a bypass reference and a bypass voltage of the bypass capacitor; and a branch control unit coupled to the comparator and the main control unit, wherein the branch control unit is configured to switch on the branch switch when the bypass voltage is lower than the bypass reference and the main control unit determines to switch on the power switch, and a branch current conducted by the branch switch is at least a part of a drain current conducted by the first switch.

[0139] Example 13. The first control device according to Example 12, wherein the branch control unit is configured to switch on the branch switch for a fixed period.

[0140] Example 14. The first control device according to Example 12 or Example 13, wherein the branch control unit is configured to switch off the branch switch when the bypass voltage reaches a bypass reference or when the main control unit determines that it should switch off the power switch.

[0141] Example 15. The first control device according to any one of Examples 12 to 14, wherein the driver is configured to switch on a second switch when the branch switch is off and the main control unit determines to switch the power switch on.

[0142] 16. The first control device according to any one of Examples 12 to 15, wherein the driver is configured to switch off a second switch when a branch switch is switched on, and the branch current is substantially the drain current conducted by the first switch.

[0143] 17. The first control device according to any one of Examples 12 to 16, further comprising a shunt regulator coupled to a branch control unit and a driver, wherein the shunt regulator is configured to detect and adjust the branch current to be less than a branch current threshold, and the driver controls a second current conducted by a second switch in response to the shunt regulator.

[0144] Example 18. The first control device according to any one of Examples 12 to 17, wherein a shunt regulator is configured to provide a shunt output voltage to a driver, the driver determines the gate voltage of a second switch in response to the shunt output voltage, and a second current in response to the gate voltage of the second switch.

[0145] Example 19. The first control device according to any one of Examples 12 to 18, wherein when the power converter is operating in continuous conduction mode, the driver switches on the second switch before the branch control unit switches on the branch switch.

[0146] Example 20. A first control device according to any one of Examples 12 to 19, wherein the first control device is coupled to the input of a power converter, a request signal is received from a second control device coupled to the output of the power converter, and the request signal is received through a magnetic communication link between the first control device and the second control device.

[0147] Example 21. The first control device according to any one of Examples 12 to 20, wherein a bypass capacitor is coupled to provide operating power to the first control device.

Claims

1. A first control device for a power converter, comprising a power switch for transferring energy between the input and output of the power converter, wherein the power switch comprises a first switch and a second switch coupled in a cascode configuration, the first switch being a normally-on device, the second switch being a normally-off device, and the first control device, A driver configured to provide drive signals for switching the power switch on and off in order to control energy delivery between the input and output of the power converter, wherein the driver is configured to switch a second switch on and off in order to control the switching of the power switch on and off, A power supply terminal configured to be coupled to a bypass capacitor that provides operating power to the first control device, wherein the bypass capacitor has a bypass voltage and a power supply terminal, A branch switch configured to be connected to the node between the first switch and the second switch, A branch control unit configured to receive an adjustment signal representing the result of comparing the bypass voltage with respect to a bypass reference, wherein the branch control unit is configured to switch on the branch switch simultaneously with the switching cycle of the power switch when the bypass voltage is less than the bypass reference, in order to redirect at least a portion of the drain current of the power switch from the node to the bypass capacitor, A shunt regulator configured to detect a branch current conducted by the branch switch and to adjust the branch current to a branch current threshold, wherein the shunt regulator and the driver adjust the branch current by controlling a second current conducted by the second switch, wherein the branch current is substantially a portion of the drain current redirected from the node to the bypass capacitor, and the second current is the remainder of the drain current, A first control device comprising:

2. The branch control unit is configured to switch the branch switch ON simultaneously with the switching cycle of the power switch, The first control device according to claim 1.

3. The branch control unit is configured to switch off the branch switch when the bypass voltage reaches the bypass reference or when the drain current of the power switch reaches the current limit value. The first control device according to claim 2.

4. The driver is configured to switch the second switch to the ON position when the branch switch is OFF and the drain current is less than the current limit value, The first control device according to claim 3.

5. When the branch switch is switched on and the branch switch conducts the drain current of the power switch from the node to the bypass capacitor, the driver is configured to switch the second switch off. The first control device according to claim 2.

6. The current shunt regulator is configured to provide the driver with a shunt output voltage. The driver is configured to determine the gate voltage of the second switch in response to the shunt output voltage, The second current conducted by the second switch is in response to the gate voltage of the second switch. The first control device according to claim 1.

7. When the power converter operates in continuous conduction mode, the driver is configured to switch on the second switch before the branch control unit switches on the branch switch. The first control device according to claim 1.

8. The aforementioned branch switch is switched on over a fixed number of consecutive switching cycles. The first control device according to claim 1.

9. A power converter, wherein the power converter is The first control device according to any one of claims 1 to 8, A power switch for controlling energy delivery between the input and output of the power converter, wherein the power switch includes a first switch which is a normally-on device and a second switch which is a normally-off device, coupled in a cascode configuration. The bypass capacitor is coupled to the first control device to provide operating power, A power converter equipped with [a specific feature].

10. The branch switch is physically smaller than the second switch. The power converter according to claim 9.

11. The first switch is a GaN-based transistor or a silicon carbide-based transistor. The power converter according to claim 9.

12. The first control device is coupled and configured to generate the bypass voltage of the bypass capacitor, The power converter according to claim 9.

13. A first control device for a power converter having an input side and an output side, wherein the first control device comprises: A power switch comprising a first switch and a second switch coupled in a cascode configuration, wherein the first switch is a normally-on device and the second switch is a normally-off device, A branch switch coupled to the node between the first switch and the second switch, wherein the branch switch is further configured to be coupled to a bypass capacitor, A driver configured to provide drive signals for controlling the switching on and off of the power switch in order to control energy delivery between the input and output sides of the power converter, wherein the driver is configured to switch on and off a second switch in order to control the switching on and off of the power switch, A main control unit configured to receive a request signal indicating that the power switch should be turned on, wherein the main control unit determines whether the power switch must be on or off. A comparator configured to be coupled to receive a bypass reference and the bypass voltage of the bypass capacitor, A branch control unit coupled to the comparator and the main control unit, wherein the branch control unit is configured to switch on the branch switch simultaneously with the switching cycle of the power switch when the bypass voltage is less than the bypass reference and the main control unit determines to switch on the power switch, and the branch current conducted by the branch switch is at least a portion of the drain current conducted by the first switch, A shunt regulator coupled to the branch control unit and the driver, wherein the shunt regulator is configured to detect the branch current and to adjust the branch current to less than a branch current threshold, and the driver controls a second current conducted by the second switch in response to the shunt regulator, A first control device comprising:

14. The branch control unit is configured to switch the branch switch to the ON position for a fixed period of time. The first control device according to claim 13.

15. The branch control unit is configured to switch off the branch switch when the bypass voltage reaches the bypass reference or when the main control unit determines that the power switch should be switched off. The first control device according to claim 13.

16. When the branch switch is off, and the main control unit determines to turn on the power switch, the driver is configured to turn on the second switch. The first control device according to claim 13.

17. The driver is configured to switch the second switch to the off position when the branch switch is switched on, and the branch current is substantially the drain current conducted by the first switch. The first control device according to claim 13.

18. The current shunt regulator is configured to provide the driver with a shunt output voltage. The driver determines the gate voltage of the second switch in response to the shunt output voltage. The second current is in response to the gate voltage of the second switch. The first control device according to claim 13.

19. When the power converter operates in continuous conduction mode, the driver switches the second switch on before the branch control unit switches the branch switch on. The first control device according to claim 13.

20. The first control device is coupled to the input of the power converter, The request signal is received from a second control device coupled to the output of the power converter. The request signal is received through a magnetic communication link between the first control device and the second control device. The first control device according to claim 13.

21. The branch switch is physically smaller than the second switch. The first control device according to claim 13.

22. The first switch is a GaN-based transistor or a silicon carbide-based transistor. The first control device according to claim 13.

23. The first control device according to any one of claims 13 to 22, The bypass capacitor is coupled to the first control device so as to provide operating power to the first control device, A system equipped with these features.

24. The first control device is coupled and configured to generate the bypass voltage of the bypass capacitor, The system according to claim 23.

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