Low quiescent current start-up circuit

Abstract

The present disclosure relates to low quiescent current start-up circuits. A switch mode power supply includes a bootstrap circuit, a control circuit, and an auxiliary winding coupled to the bootstrap circuit and configured to supply power to the control circuit after start-up of the power supply. The bootstrap circuit is configured to supply power to the control circuit during start-up and includes an isolation circuit to limit current flow between a start-up capacitor and the control circuit until the start-up capacitor is charged to a start-up voltage by a high voltage input. During initial charging of the start-up capacitor, the control circuit is not powered to provide initial functionality of the power supply. Once the start-up capacitor is charged to the start-up voltage, the isolation circuit is activated to allow current flow to power the control circuit during the remainder of start-up until the auxiliary winding is able to power the control circuit.

Description

Background Technology

[0001] Power systems typically incorporate startup circuits—also known as bootstrap circuits—within the power source to provide starting power to the low-voltage control circuitry system required for initial functionality and to allow the entire power supply to start. These startup circuits can be very simple when the low-voltage control circuitry system providing initial functionality is simple, the load is small, and / or it is configured to limit quiescent current draw. However, when the low-voltage control circuitry system draws a large quiescent current or when the control circuitry system becomes more complex under larger loads, these startup circuits can quickly become very complex and costly to implement. Summary of the Invention

[0002] To address the need for more complex low-voltage control circuitry systems, the solution described herein includes a bootstrap circuit (i.e., startup circuit) within a high-voltage switch-mode power supply. The switch-mode power supply includes: a control circuit; an auxiliary winding coupled to the bootstrap circuit and configured to supply power to the control circuit after the power supply has started. The bootstrap circuit is configured to supply power to the control circuit during the startup period and may include: a starting resistor coupled to the high-voltage input; and a starting capacitor coupled in series to the starting resistor and configured to be charged to the startup voltage via the starting resistor at the high-voltage input during the initial charging period. During the initial charging of the starting capacitor, the control circuit is not energized (no current flows to the control circuit), and the power supply does not start. The bootstrap circuit also includes: an output coupled to the control circuit; an auxiliary capacitor coupled to the output; and an isolation circuit coupled between the starting resistor and the output and in parallel with the auxiliary capacitor. The isolation circuit is configured to limit current flow between a) the control circuit and b) the starting resistor and the starting capacitor until the starting capacitor is charged to the startup voltage. After the starting capacitor is charged to the starting voltage, the isolation circuit is configured to activate (i.e., allow current to flow to the auxiliary capacitor and the control circuit).

[0003] Implementation may include one or more of the following features. In some implementations, the starting capacitor and auxiliary capacitor are configured and sized to store sufficient charge during the startup time after initial charging to power the control circuitry.

[0004] In some implementations, the starting resistor may have a resistance value that ensures the initial charging time is less than ten seconds.

[0005] In some implementations, the high-voltage input has a wide operating range, for example, between 200 volts and 1200 volts.

[0006] In some implementations, the isolation circuit is configured to deactivate when the starting capacitor drops below a low-voltage threshold, and the low-voltage threshold is configured to be lower than the voltage of the starting capacitor at the end of the startup time, so that the isolation circuit will not deactivate.

[0007] In some implementations, the isolation circuit may include a voltage-limiting diode connected in parallel with the auxiliary capacitor, which is configured to be activated based on the operating voltage specification of the control circuit to limit the voltage of the starting capacitor.

[0008] In some embodiments, the isolation circuit may include: a diode configured to define a startup voltage; a main switching device coupled between a startup capacitor and the diode and configured to activate when the startup capacitor is charged to the startup voltage; and a transistor configured to generate hysteresis between the startup voltage and a low-voltage threshold. The main switching device may include a bipolar junction transistor (“BJT”). The main switching device may also include a metal-oxide-semiconductor field-effect transistor (“MOSFET”).

[0009] In some implementations, the isolation circuit may include a load switch. The input of the load switch may be coupled to a starting capacitor, and the output of the load switch may be coupled to the output of a bootstrap circuit. The isolation circuit may further include: a first resistor coupled between a fast output discharge port of the load switch and an enable port of the load switch; and a second resistor coupled between the input of the load switch and the enable port of the load switch. The first and second resistors may be configured to define a low-voltage threshold, and the isolation circuit may be configured to deactivate when the starting capacitor voltage is below the low-voltage threshold. The low-voltage threshold may be configured such that the starting capacitor voltage remains above the low-voltage threshold at the end of the startup time.

[0010] In some implementations, the isolation circuit may include a linear regulator. The input of the linear regulator may be coupled to a starting capacitor, and the output of the linear regulator may be coupled to the output of a bootstrap circuit. The isolation circuit may include a first diode coupled between the input of the linear regulator and the enable port of the linear regulator, and the first diode may be configured to limit a startup voltage. The isolation circuit may also include a second diode coupled between the input of the linear regulator and the output of the linear regulator.

[0011] Some implementations include a method for configuring a switch-mode power supply (“SMPS”). This method may include configuring the SMPS to charge a starting capacitor to a threshold charging voltage during an initial charging period. In response to the starting capacitor reaching the threshold charging voltage, the SMPS is configured to activate isolation circuitry to electrically couple the starting capacitor to an auxiliary capacitor and one or more control circuits. The SMPS may also be configured to use the starting capacitor to charge the auxiliary capacitor and to power the control circuitry during the startup period until the auxiliary winding begins to supply power to the bootstrap circuitry (i.e., startup complete).

[0012] The method can be implemented in a manner that includes one or more of the following features. In some implementations, the method may include configuring the SMPS to maintain the activation of the isolation circuit after startup time.

[0013] In some implementations, SMPS is configured such that the initial charging time is less than ten seconds.

[0014] In some implementations, the SMPS is configured to deactivate the isolation circuit to electrically isolate the starting capacitor from the auxiliary capacitor and control circuitry when the starting capacitor voltage drops below a low-voltage threshold. The low-voltage threshold is configured such that the starting capacitor voltage remains above the low-voltage threshold at the end of the startup time.

[0015] In some implementations, the isolation circuit may include a load switch. The method may include configuring a switch-mode power supply to use a voltage-limiting diode to limit the voltage of the starting capacitor based on the control circuit load. Attached Figure Description

[0016] Many aspects of this disclosure can be better understood with reference to the following accompanying drawings. Components in the drawings are not necessarily drawn to scale. For the purpose of discussing some embodiments, some components or operations may not be divided into different blocks or may be combined into a single block. Furthermore, in the drawings, the same reference numerals denote corresponding parts throughout several views. Although several embodiments are described in conjunction with these drawings, this disclosure is not limited to the embodiments disclosed herein. The technology can be modified in various ways and alternatives. The disclosure and drawings herein are intended to provide a description of certain embodiments and are intended to cover all alternatives, modifications, and equivalents.

[0017] Figure 1 A simplified schematic diagram of a switch-mode power supply (“SMPS”) according to some embodiments is shown.

[0018] Figure 2 A simplified schematic diagram of an SMPS with additional details of a bootstrap circuit according to some embodiments is shown.

[0019] Figure 3 A simplified schematic diagram showing further details of a bootstrap circuit according to some embodiments is shown.

[0020] Figure 4 A simplified schematic diagram showing further details of a bootstrap circuit according to some embodiments is shown.

[0021] Figure 5 A simplified schematic diagram showing further details of a bootstrap circuit according to some embodiments is shown.

[0022] Figure 6 A simplified schematic diagram showing further details of a bootstrap circuit according to some embodiments is shown.

[0023] Figure 7 A graph showing the voltage and current values ​​during the startup interval of the SMPS according to some embodiments is shown.

[0024] Figure 8 A method for configuring SMPS according to some implementations is shown. Detailed Implementation

[0025] The following description and associated drawings teach the preferred mode of the invention. For the purpose of teaching the principles of the invention, some conventional aspects of the preferred mode may be simplified or omitted. The appended claims define the scope of the invention. Note that some aspects of the preferred mode may not fall within the scope of the invention as defined by the claims. Therefore, those skilled in the art will understand variations from the preferred mode that fall within the scope of the invention. Those skilled in the art will understand that the features described below can be combined in various ways to form multiple variations of the invention. Therefore, the invention is not limited to the specific examples described below, but only by the claims and their equivalents.

[0026] In many systems utilizing high-voltage power supplies, including switch-mode power supplies, both the power supply and the system have a startup period during which inductors and capacitors are charged and the power supply itself is started. During this startup period, the power supply is not fully functional. Furthermore, the power supply contains control circuitry, typically low-voltage, required to start (i.e., initiate) the power supply. The bootstrap circuitry in the power supply typically supplies current directly to the control circuitry from the high-voltage input. After the power supply starts, it can supply power to the control circuitry through one of its own low-voltage supply outputs—referred to herein as the auxiliary circuitry or auxiliary winding.

[0027] In systems with simple control circuitry, typically an integrated chip with a function to limit quiescent current, the bootstrap circuit can be very simple, where a starting resistor (e.g., a resistor string coupled to the high-voltage input) is coupled to a starting capacitor. In such a simple system, the capacitor is charged via the resistor until the voltage reaches the starting threshold. Once the capacitor reaches the starting voltage threshold, it discharges to supply power to the control circuitry, and the voltage level is maintained by balancing the charging current from the high-voltage input via the resistor and the discharging current supplying the control circuitry until the power supply starts. Once the power supply is started, the control circuitry is powered by auxiliary circuitry of the power supply.

[0028] While these simple systems are straightforward, system design becomes more complex when the input voltage range used to start and operate the power supply is wide (e.g., 200 volts to 1400 volts). Additional complexity arises when additional control circuitry is connected to the bootstrap circuitry. For example, additional circuitry may be used when the power supply has functional safety requirements, a wide input / output operating range, multi-pole outputs, silicon carbide (SiC) switches, etc. These additional circuits may draw significant quiescent current. This drawdown increases the power dissipation of the starting resistor, potentially leading to thermal problems that can cause power supply failure (e.g., the power supply fails to start). The resistor must be low enough to supply the control circuitry and reach the threshold voltage across the capacitor, while also being high enough to meet power dissipation derating criteria. If the resistance is too high, the power supply will not power on; if the resistance is too low, the resistor will overheat. To make the circuit thermally viable, a starting resistor must be added, which is space-consuming and more expensive. In some systems, insufficient space and / or cooling requirements may preclude a resistor of the necessary size. Therefore, a simple bootstrap circuit consisting only of resistors or resistor strings and capacitors may not be sufficient to ensure proper startup and function of the power supply.

[0029] To address the aforementioned problems, a bootstrap circuit is described herein, comprising an isolation circuit that isolates the starting resistor and the starting capacitor from the low-voltage control circuit during the initial charging of the starting capacitor. When the starting capacitor is charged, the isolation circuit is activated, and current from the starting capacitor can flow to the control circuit during startup to power the control circuit for power-up. The isolation circuit is configured to remain active in the power supply during normal operation and exhibit hysteresis during startup to ensure sufficient time for the power supply to start up before the isolation circuit is deactivated. Implementation details are provided in the following figures.

[0030] Figure 1A simplified schematic diagram of power supply 100 is shown. Power supply 100 may be a switch-mode power supply (“SMPS”). The SMPS may be direct current (“DC”) to DC. In some embodiments, the power supply is a high-voltage power supply. Power supply 100 provides power to system 110. System 110 may be any system that uses power, for example, in an industrial automation environment. System 110 may be a standard motor driver, a programmable logic controller, or any other machine or system that uses a low-voltage power supply. For example, power supply 100 may be a high-voltage DC to low-voltage DC SMPS, and system 110 may be a standard motor driver control system.

[0031] Power supply 100 includes a bootstrap circuit 105, a load 115, and an auxiliary winding 120. The bootstrap circuit 105 can be used to power the load 115 during the startup of power supply 100. After startup, the auxiliary winding 120, which can be at the low-voltage output of power supply 100, can be used to power the load 115 during normal operation of power supply 100.

[0032] Details of the bootstrap circuit 105 Figures 2 to 7 The following describes the load 115 in further detail. The load 115 may include any circuitry system used for power supply startup and operation, including, for example, control circuitry, gate circuitry, and any other loads that may be incorporated into power supply 100. Other loads may include, for example, a linear regulator, a charge pump, a limiting Zener diode, functional safety circuitry, etc.

[0033] The starting current flowing through the starting resistor in the bootstrap circuit 105 (in Figures 2 to 7 (As shown in more detail below) can be evaluated as the voltage connected at the threshold voltage when the gate is closed at V. 辅助 The sum of the static currents of all loads at the point and the operating current i OP Flow begins. Therefore, the maximum quiescent current is equal to i. L1 +i L2 +i L3 For a conventional bootstrap circuit (consisting of a starting resistor and a starting capacitor), the value of the starting resistor depends on the maximum quiescent current; otherwise, power supply 100 may not start. The resistance value must be low enough to adequately supply the load 115 and reach the threshold voltage across the starting capacitor, and also high enough to meet power dissipation derating criteria. If the starting resistor is too high, power supply 100 will not power on. If the starting resistor is too low, the resistor will overheat. Therefore, the solution implemented in bootstrap circuit 105 is to include an isolation circuit to isolate the starting resistor from the load 115, so that the quiescent current drawn by the load 115 is zero or very limited. Figures 2 to 7 Describe this situation in more detail.

[0034] Figure 2A simplified schematic diagram showing more details of the bootstrap circuit 105 in the power supply 100 is provided. Note that components with the same reference numerals between the figures may be the same or substantially the same components and may be used in various embodiments of the power supply 100 having different specific circuit implementations as described with respect to each figure. The bootstrap circuit 105 includes a starting resistor 210, a starting capacitor 215, an isolation circuit 205, and an auxiliary capacitor 220. The isolation circuit 205 isolates the starting resistor 210 and the starting capacitor 215 from the auxiliary capacitor 220 and the load 115. The leakage current of the isolation circuit 205 is configured to be minimal or zero, resulting in a very low quiescent current drawn by the isolation circuit 205, which becomes i L0 Instead of i L1 +i L2 +i L3 The isolation circuit 205, which limits quiescent current, allows the starting capacitor 215 to charge to a sufficiently high voltage, such that the stored energy is high enough to power the load 115 during power supply 100 startup, until the auxiliary winding 120 provides sufficient current to charge the starting capacitor 215 and the auxiliary capacitor 220 to power the load 115 during normal operation of power supply 100. The low quiescent current draw also allows for a very high resistance in the starting resistor 210. This high resistance value of the starting resistor 210 ensures that the power dissipation of the starting resistor is limited, making it easy to meet thermal requirements (e.g., limiting the risk of overheating). Furthermore, since the starting resistor 210 and the starting capacitor 215 are isolated from the rest of the power supply control circuitry, the high-voltage input is primarily used to charge the starting capacitor 215 until it reaches the threshold starting voltage.

[0035] The isolation circuit 205 is configured to have a minimum leakage current i L0 and minimum i SIn and i SOut The isolation circuit 205 remains highly impedance until the voltage across the starting capacitor 215 reaches the starting voltage threshold. Once the starting capacitor 215 reaches the starting voltage threshold, the isolation circuit 205 activates, and i SIn and i SOut They should be equal because when the isolation circuit 205 is activated, it begins to operate as a short circuit between its input and output, for example, or as a constant output voltage source if a linear regulator is used in the isolation circuit 205. The isolation circuit 205 is also configured such that when the voltage of the starting capacitor 215 drops to a low-voltage threshold, the isolation circuit 205 deactivates and returns to having very high impedance inputs and outputs, thus isolating the starting resistor 210 and the starting capacitor 215 from the load 115 and the auxiliary capacitor 220.

[0036] Figure 3 A simplified schematic diagram depicting an implementation of isolation circuit 300 is shown. Isolation circuit 300 includes a main switching device 305, a threshold diode 310, resistors 315, 320, 330 and 335, and a hysteresis device 325. The bootstrap circuit also includes an optional limiting diode 340.

[0037] The main switching device 305 may be a transistor. In some embodiments, the main switching device 305 may be a bipolar junction transistor (“BJT”), and in some embodiments, it may be a high-gain BJT. The main switching device 305 is configured to remain off (non-conductive) when the voltage of the starting capacitor 215 is lower than the Zener voltage of the threshold diode 310. The threshold diode 310 may be a Zener diode that determines the starting voltage threshold based on the Zener voltage of the threshold diode 310. Once the starting capacitor reaches the Zener voltage (i.e., the starting voltage threshold), the main switching device 305 is activated, and current flows between the input and output of the isolation circuit 300. At the input, the current is i. SIn And at the output terminal, the current is i SOut , such as regarding Figure 2 As described, current flow will charge auxiliary capacitor 220. Once the voltage of auxiliary capacitor 220 reaches a lower voltage threshold (i.e., the voltage at which isolation circuit 300 is deactivated), hysteresis device 325 will conduct and saturate main switching device 305. Hysteresis device 325 may be a transistor, and more specifically a BJT. When main switching device 305 is saturated, main switching device 305 charges auxiliary capacitor 220 to a voltage based on the ratio of the capacitance of auxiliary capacitor 220 to that of starting capacitor 215 and the voltage of starting capacitor 215. As auxiliary capacitor 220 is charged, load 115 will pull down the voltage of auxiliary capacitor 220 until the voltage of starting capacitor 215 drops below the low voltage threshold or auxiliary winding 120 begins to supply current to starting capacitor 215 and therefore auxiliary capacitor 220. Therefore, the capacitance values ​​of auxiliary capacitor 220 and starting capacitor 215 should be selected to ensure they store sufficient energy so that auxiliary winding 120 begins charging starting capacitor 215 and thus auxiliary capacitor 220 before the voltage of starting capacitor 215 drops below a low-voltage threshold. If starting capacitor 215 drops below a low-voltage threshold before auxiliary winding 120 begins charging starting capacitor 215 and auxiliary capacitor 220, isolation circuit 300 will deactivate, thereby isolating starting capacitor 215 and starting resistor 210, and power supply 100 will not start. Resistors 315, 320, 330, and 335 can be selected such that i refThe current should be as low as possible. The limiting diode 340 is optional and ensures that the voltage across the starting capacitor 215 is limited if the load 115 does not draw sufficient current. (Regarding...) Figure 7 The described graph 700 provides a description of the intervals experienced by the isolation circuit and the associated current and voltage values.

[0038] Figure 4 A simplified schematic diagram illustrating the implementation of isolation circuit 400 is shown. Isolation circuit 400 includes a main switching device 405, a threshold diode 410, resistors 415, 425 and 430, and a hysteresis device 420.

[0039] The main switching device 405 may be a transistor. In some embodiments, the main switching device 405 may be a metal-oxide-semiconductor field-effect transistor (“MOSFET”). The main switching device 405 is configured to remain off (non-conductive) when the voltage of the start-up capacitor 215 is lower than the Zener voltage of the threshold diode 410 plus the threshold voltage of the main switching device 405 (e.g., the MOSFET threshold voltage). The threshold diode 410 may be a Zener diode, and the main switching device may be a MOSFET, such that the start-up voltage is determined based on the Zener voltage of the threshold diode 410 plus the MOSFET threshold voltage of the main switching device 405. Once the start-up capacitor reaches the start-up voltage threshold, the main switching device 405 is activated and current flows between the input and output of the isolation circuit 400. At the input, the current is i. SIn And at the output terminal, the current is i SOut , such as regarding Figure 2As described, current flow will charge auxiliary capacitor 220. Once the voltage of auxiliary capacitor 220 reaches a lower voltage threshold (i.e., the voltage at which isolation circuit 400 is deactivated), hysteresis device 420 will conduct and fully turn on main switching device 405. Hysteresis device 420 may be a transistor, and more specifically, a MOSFET. When main switching device 405 is fully turned on, it charges auxiliary capacitor 220 to a voltage based on the ratio of the capacitance of auxiliary capacitor 220 to that of starting capacitor 215 and the voltage of starting capacitor 215. As auxiliary capacitor 220 is charged, load 115 will pull down the voltage of auxiliary capacitor 220 until the voltage of starting capacitor 215 drops below the low voltage threshold or auxiliary winding 120 begins to supply current to starting capacitor 215 and thus auxiliary capacitor 220. Therefore, the capacitance values ​​of auxiliary capacitor 220 and starting capacitor 215 should be selected to ensure they store sufficient energy so that auxiliary winding 120 begins charging starting capacitor 215 and thus auxiliary capacitor 220 before the voltage of starting capacitor 215 drops below a low-voltage threshold. If starting capacitor 215 drops below a low-voltage threshold before auxiliary winding 120 begins charging starting capacitor 215 and thus auxiliary capacitor 220, isolation circuit 400 will be deactivated, thereby isolating starting capacitor 215 and starting resistor 210, and power supply 100 will not start. Resistors 415, 425, and 430 can be selected such that i ref Keep the current as low as possible. Regarding Figure 7 The described graph 700 provides a description of the intervals experienced by the isolation circuit and the associated current and voltage values.

[0040] Figure 5 A simplified schematic diagram depicting an implementation of isolation circuit 500 is shown. Isolation circuit 500 includes a main switching device 505 and resistors 510 and 515.

[0041] The main switching device 505 can be a load switch. As depicted, this is not a conventional configuration for a load switch, but is implemented as an isolation circuit 500 exhibiting the desired hysteresis behavior of the bootstrap circuit 105. The main switching device 505 can be an integrated circuit load switch including an enable input 530, an open-collector fast discharge output 535, a voltage input 520, and a voltage output 525. When the enable input 530 is low and the starting capacitor 215 is below the starting voltage threshold, the impedances of the voltage input 520 and voltage output 525 are very high. The starting voltage threshold is determined based on resistors 510 and 515. When the enable input 530 reaches a predefined threshold such that the voltage input 520 is at the starting voltage threshold (i.e., the starting capacitor 215 reaches the starting voltage threshold), the voltage input 520 is short-circuited to the voltage output 525, thereby activating the isolation circuit 500, and the discharge output 535 becomes high-impedance. Resistors 510 and 515 are configured to set a low-voltage threshold and create a hysteresis between the startup voltage and the low-voltage threshold. When the main switching device 505 is activated, it charges the auxiliary capacitor 220 to a voltage based on the ratio of the capacitances of the auxiliary capacitor 220 and the startup capacitor 215 and the voltage of the startup capacitor 215. While the auxiliary capacitor 220 is charging, the load 115 pulls down the voltage of the auxiliary capacitor 220 until the voltage of the startup capacitor 215 drops below the low-voltage threshold or the auxiliary winding 120 begins to supply current to the startup capacitor 215 and thus the auxiliary capacitor 220. Therefore, the capacitance values ​​of the auxiliary capacitor 220 and the startup capacitor 215 should be selected to ensure that they store sufficient energy so that the auxiliary winding 120 begins to charge the startup capacitor 215 and thus the auxiliary capacitor 220 before the voltage of the startup capacitor 215 drops below the low-voltage threshold. If the starting capacitor 215 drops below the low-voltage threshold before the auxiliary winding 120 begins charging the starting capacitor 215 and thus the auxiliary capacitor 220, the isolation circuit 500 will deactivate, thereby isolating the starting capacitor 215 and the starting resistor 210, and the power supply 100 will not start. Regarding Figure 7 The described graph 700 provides a description of the intervals experienced by the isolation circuit and the associated current and voltage values.

[0042] Figure 6 A simplified schematic diagram depicting an implementation of isolation circuit 600 is shown. Isolation circuit 600 includes a main switching device 605, a threshold diode 630, a hysteresis diode 625, a resistor 640, and a capacitor 635.

[0043] The main switching device 605 can be a linear regulator. As depicted, this is not a conventional configuration for a linear regulator, but is implemented as an isolation circuit 600 exhibiting the desired hysteresis behavior of the bootstrap circuit 105. The main switching device 605 can be an integrated circuit linear regulator including an enable input 620, a voltage input 610, and a voltage output 615. When the enable input 620 is low and the starting capacitor 215 is below the starting voltage, the impedance at the voltage input is very high. A threshold diode 630 determines the starting voltage. When the voltage at the starting capacitor 215 rises to the starting voltage, the threshold diode 630 conducts and pulls the enable input high, thereby activating the isolation circuit 600. When active, the voltage output 615 will rise and remain at a predefined or user-set voltage for regulation, depending on the linear regulator implementation. The voltage output 615 will also pull the enable input 620 higher via a hysteresis diode 625 to facilitate hysteresis. If the voltage of the starting capacitor 215 drops below the low-voltage threshold, the linear regulator will deactivate and stop conducting. When the main switching device 605 is activated, it charges the auxiliary capacitor 220 to the regulated output voltage of the linear regulator or a voltage based on the ratio of the capacitance of the auxiliary capacitor 220 to that of the starting capacitor 215, whichever is lower. In other words, the output voltage is based on the capacitance ratio, and the auxiliary capacitor is charged to that voltage, as long as this voltage is lower than the regulated output voltage of the linear regulator. If this voltage is higher than the regulated output voltage of the linear regulator, the linear regulator will maintain a constant regulated output voltage, charging the auxiliary capacitor to the regulated output voltage until the input (i.e., the starting capacitor voltage) drops below the input regulated voltage of the linear regulator, which in turn causes the ratio-based output voltage to drop below the regulated output voltage. When auxiliary capacitor 220 is charged, load 115 pulls down the voltage of auxiliary capacitor 220 until the voltage of starting capacitor 215 drops below the low-voltage threshold or auxiliary winding 120 begins to supply current to starting capacitor 215 and thus auxiliary capacitor 220. Therefore, the capacitance values ​​of auxiliary capacitor 220 and starting capacitor 215 should be selected to ensure they store sufficient energy so that auxiliary winding 120 begins to charge starting capacitor 215 and thus auxiliary capacitor 220 before the voltage of starting capacitor 215 drops below the low-voltage threshold. If starting capacitor 215 drops below the low-voltage threshold before auxiliary winding 120 begins to charge starting capacitor 215 and thus auxiliary capacitor 220, isolation circuit 600 will deactivate, thereby isolating starting capacitor 215 and starting resistor 210, and power supply 100 will not start. Regarding Figure 7 The described graph 700 provides a description of the intervals experienced by the isolation circuit and the associated current and voltage values.

[0044] In each of the embodiments of isolation circuits 300, 400, 500, and 600, the isolation circuit remains active and conductive during normal operation of the power supply 100. Maintaining the activity of the isolation circuit during normal operation of the power supply 100 avoids the need for additional circuitry to remove the bootstrap circuitry or isolation circuitry from the active circuitry of the power supply 100.

[0045] Figure 7 A graph 700 depicts the voltage and current behavior of the components described in bootstrap circuit 105. The graph is divided into six intervals. In the first interval, the starting capacitor is charged from the high-voltage input terminal via the starting resistor, and the isolation circuit is not yet activated because the starting capacitor has not yet reached the starting voltage. In the second interval, the starting voltage is reached, and the auxiliary capacitor is charged. In the third interval, the control circuit and other integrated circuits (e.g., load 115) begin to start up. In the fourth interval, the power supply begins to switch, causing the power supply output to begin to rise. During this fourth interval, the auxiliary winding is charging. In the fifth interval, the auxiliary winding begins to supply the auxiliary circuit and rises until it reaches its rated voltage (e.g., 15 volts) to supply the low-voltage circuit (e.g., load 115). In the sixth interval, the power supply is in normal operation, startup is complete, and the auxiliary winding is at its rated voltage and used to supply power to the control circuit load.

[0046] Check the voltage of the starting capacitor (C) STARTIn the first interval, the starting capacitor voltage rises until it reaches the starting voltage. Once the starting capacitor reaches the starting voltage, the second interval begins, and the auxiliary capacitor is charging, which pulls down the starting capacitor voltage. In the third interval, the auxiliary capacitor has been charged, and the load begins to pull down the auxiliary capacitor, so the starting capacitor voltage is also pulled down to continue charging the auxiliary capacitor. However, the control circuit has not yet activated the SMPS switch. In the fourth interval, the SMPS switch has activated, but the auxiliary winding is still charging and is below the starting capacitor voltage. Therefore, the auxiliary winding has not yet charged the starting capacitor, and therefore has not charged the auxiliary capacitor either, so the auxiliary capacitor continues to draw from the starting capacitor, further reducing the starting capacitor voltage. At the beginning of the fifth interval, the auxiliary winding voltage reaches the starting capacitor voltage. During the fifth interval, the auxiliary winding charges the starting capacitor and therefore the auxiliary capacitor until the starting capacitor and the auxiliary winding reach a rated voltage above the low-voltage threshold (e.g., 15 volts). Therefore, the starting capacitor is charged back to its rated operating voltage (e.g., 15 volts). Although the starting voltage and rated operating voltage are equal in this example, they may be different values ​​in some implementations. During the sixth interval, the starting capacitor remains at its rated voltage because it is supplied by the auxiliary winding. The low-voltage threshold is determined by the operating voltage specification of the control circuit. The starting voltage threshold, starting capacitor, and auxiliary capacitor should be selected such that the starting capacitor voltage does not drop above the low-voltage threshold before the auxiliary winding reaches the starting capacitor voltage and begins charging the starting capacitor, and thus the auxiliary capacitor, to supply the control circuit. If the starting capacitor drops below the low-voltage threshold during one of the first four intervals, the isolation circuit will deactivate, and the power supply will fail to start.

[0047] Check Figure 6 The auxiliary capacitor voltage (C) in the implementation with a linear regulator described in the figure AUXIn the voltage-linear regulator, during the first interval, the auxiliary capacitor voltage is zero because the isolation circuit blocks current from the auxiliary capacitor, so it is not charged to a certain voltage. In the second interval, the auxiliary capacitor voltage increases because the isolation circuit is activated and the starting capacitor charges the auxiliary capacitor. During the third interval, the load powered by the bootstrap circuit draws voltage from the auxiliary capacitor, but the auxiliary capacitor retains its charge from the starting capacitor, and the voltage at the auxiliary capacitor remains stable because the isolation circuit includes the linear regulator. This behavior continues into the fourth interval, but both experience a voltage drop as the starting capacitor voltage drops to the level of the auxiliary capacitor. During the fifth interval, the auxiliary winding rises to charge the starting capacitor and therefore the auxiliary capacitor, so the auxiliary capacitor voltage increases to the regulated voltage level of the linear regulator and remains at the regulated voltage level during normal operation in the sixth interval.

[0048] Check each one in Figures 3 to 5 The auxiliary capacitor voltage (C) in the implementation described above, in addition to the implementation with a linear regulator, is... AUX (Voltage - other implementations) During the first interval, the auxiliary capacitor voltage is zero because the isolation circuit blocks current from the auxiliary capacitor, so it is not charged to a certain voltage. In the second interval, the auxiliary capacitor voltage increases because the isolation circuit is activated and the starting capacitor charges the auxiliary capacitor. During the third interval, the load powered by the bootstrap circuit during startup draws voltage from the auxiliary capacitor, which tracks the decrease in the starting capacitor voltage. This behavior continues during the fourth interval. During the fifth interval, the auxiliary winding rises to a sufficiently high voltage to charge the starting capacitor and thus the auxiliary capacitor, so the auxiliary capacitor voltage increases to the rated voltage level and remains at the rated voltage level during normal operation in the sixth interval.

[0049] View in Figure 6 The control circuit operating current (i) in the implementation of the linear regulator described in the figure SOut The current-linear regulator operates as follows: In the first interval, the current is zero. In the second interval, the current rises slightly as the auxiliary capacitor charges. In the third interval, the current increases further as the load begins to start. In the fourth interval, the power switch has been activated, and... Sout Current due to operating current i OP And a jump occurs. The operating current is... Figure 1 and Figure 2As shown, this is the current leaving the gate circuit in load 115, which switches the power supply to a switch-mode power supply. In some embodiments, the switch-mode power supply may be a high-voltage DC-to-DC power supply that supplies power to the low-voltage driver. Near the end of the fourth interval, as the auxiliary capacitor charge drops below the regulation level of the linear regulator, the current decreases accordingly until the start of the fifth interval. In the fifth interval, the auxiliary winding reaches the starting capacitor voltage and begins to power the control circuit, charging the starting capacitor and the auxiliary capacitor, and the current begins to rise again. Once the auxiliary winding reaches its rated voltage and the starting capacitor and the auxiliary capacitor are fully charged, I... SOut The current is then increased to the normal operating level and maintained at that level. During the sixth interval of normal operation, the current draw remains constant.

[0050] Check each one in Figures 3 to 5 The control circuit operating current (i) in the implementation described above, besides the implementation with a linear regulator, is... SOut (Current - other implementations), during the first interval, the current is zero. During the second interval, the current rises slightly as the auxiliary capacitor charges. During the third interval, the current rises further as the load begins to start. In the fourth interval, the power switch has been activated, the power supply output rises, and i Sout Current due to operating current i OP And a jump occurs. The operating current is... Figure 1 and Figure 2 As shown, this is the current leaving the gate circuit in load 115, which switches the power supply to a switch-mode power supply. In some embodiments, the switch-mode power supply may be a high-voltage DC-to-DC power supply that supplies power to the low-voltage driver. During the fourth interval, as the charge of the starting capacitor and auxiliary capacitor decreases, the operating current decreases accordingly until the fifth interval when the auxiliary winding reaches the starting capacitor voltage and begins to charge it, thus supplying power to the load. Once the auxiliary capacitor is charged during the sixth interval of normal operation, the operating current increases to the operating level and remains at that level.

[0051] Figure 8 A method 800 for configuring a power supply bootstrap circuit is shown. This method may include configuring in Figures 3 to 6Any bootstrap circuit described herein. At step 805, the bootstrap circuit is configured to charge the starting capacitor to a threshold starting voltage during the initial charging time. For example, during a first interval (i.e., the initial charging time) as depicted in graph 700, a high-voltage input is used to charge the starting capacitor 215 via the starting resistor 210. At step 810, the bootstrap circuit is configured to activate an isolation circuit to electrically couple the starting capacitor to an auxiliary capacitor and one or more control circuits. For example, isolation circuits 205, 300, 400, 500, or 600 are activated to allow current flow between the starting capacitor 215 and the auxiliary capacitor 220 and the load 115. At step 815, the bootstrap circuit is configured to charge the auxiliary capacitor using the starting capacitor during the startup time. For example, starting capacitor 215 charges auxiliary capacitor 220 during intervals two, three, and four as depicted in graph 700, until auxiliary winding 120 reaches its rated voltage to begin charging starting capacitor 215 and auxiliary capacitor 220 to power load 115. At step 820, the starting capacitor powers the control circuitry until the auxiliary winding charges the auxiliary capacitor. For example, starting capacitor 215 provides current to charge auxiliary capacitor 220 and power load 115 until auxiliary winding 120 reaches a sufficiently high voltage to charge auxiliary capacitor 220, after which auxiliary winding 120 powers load 115.

[0052] Unless the context explicitly requires otherwise, throughout the specification and claims, the words “comprising,” “including,” etc., should be interpreted as encompassing, not exclusive or exhaustive; that is, they should be interpreted as “including, but not limited to.” As used herein, the terms “connection,” “coupled,” or any variation thereof refer to any direct or indirect connection or coupling between two or more elements; the coupling or connection between elements can be physical, logical, or a combination thereof. Furthermore, when used in this application, the words “in this document,” “above,” “below,” and similar terms refer to the entire application and not any particular part of it. Where the context permits, singular or plural terms used in the above specific embodiments may also include either the plural or the singular, respectively. When referring to a list of two or more items, the word “or” encompasses all of the following interpretations: any one item in the list, all items in the list, and any combination of items in the list.

[0053] The phrases "in some embodiments," "according to some embodiments," "in the illustrated embodiments," "in other embodiments," etc., generally refer to a specific feature, structure, or characteristic that follows the phrase being included in at least one implementation of the present technology, or that may be included in more than one implementation. Furthermore, such phrases do not necessarily refer to the same or different embodiments.

[0054] The specific embodiments of this technology described above are not intended to be exhaustive or to limit the technology to the exact forms disclosed herein. While specific examples of the technology have been described above for illustrative purposes, various equivalent modifications are possible within the scope of this technology, as will be recognized by those skilled in the art. For example, although processes or blocks are presented in a given order, alternative implementations may execute routines with steps in a different order, or employ a system with blocks, and some processes or blocks may be deleted, moved, added, subdivided, combined, and / or modified to provide alternatives or sub-combinations. Each of these processes or blocks can be implemented in a variety of different ways. Furthermore, although processes or blocks are sometimes shown as being executed serially, these processes or blocks may instead be executed or implemented in parallel, or may be executed at different times. Moreover, any specific figures mentioned herein are merely examples: alternative implementations may employ different values ​​or ranges.

[0055] The teachings of the techniques provided herein can be applied to other systems, not necessarily those described above. For example, although the technique is described in a driver, any component with a DC bus can implement the solution described above. Elements and actions from the various examples described above can be combined to provide other implementations of the technique. Some alternative implementations of the technique may include not only additional elements to those implementations described above, but may also include fewer elements.

[0056] Based on the specific embodiments described above, these and other modifications can be made to the technology. While the above description illustrates certain examples of the technology and describes the envisioned best mode, the technology can be practiced in many ways, no matter how detailed it appears in the text. The details of the system may vary considerably in its specific implementation, but are still covered by the technology disclosed herein. As noted above, specific terms used in describing certain features or aspects of the technology should not be construed as implying that the term is redefined herein to limit it to any particular characteristic, feature, or aspect of the technology associated with the term. Generally, the terms used in the appended claims should not be construed as limiting the technology to the specific examples disclosed in the specification, unless these terms are expressly defined in the foregoing detailed embodiments section. Therefore, the actual scope of this technology includes not only the disclosed examples but also all equivalent ways of practicing or implementing the technology according to the claims.

[0057] To reduce the number of claims, certain aspects of the technology are presented below in certain claim forms, but the applicant has considered all aspects of the technology in any number of claim forms. For example, although only one aspect of the technology is described as a computer-readable medium claim, other aspects may also be implemented as computer-readable medium claims, or in other forms, such as as a means plus function claim. Any claim intended to be treated under 35 U.S.SC §112(f) will begin with the phrase “means for…”, but the use of the term “for” in any other context is not intended to invoke treatment under 35 U.S.SC §112(f). Therefore, the applicant reserves the right to seek appended claims after the filing of this application, in order to seek such appended claim forms in this application or a continuing application.

Claims

1. A switch-mode power supply, comprising: One or more control circuits; An auxiliary winding, coupled to a bootstrap circuit and configured to supply power to one or more control circuits after the startup period of the switch-mode power supply; as well as The bootstrap circuit is configured to supply power to the one or more control circuits during the startup period of the switch-mode power supply, the bootstrap circuit comprising: A starting resistor coupled to the high-voltage input terminal; A starting capacitor, which is connected in series to the starting resistor and is configured to be charged to the starting voltage via the high voltage input terminal during the initial charging period of the startup period; Coupled to the output of one or more control circuits; An auxiliary capacitor coupled in parallel with the isolation circuit to the output terminal; and The isolation circuit coupled between the starting resistor and the output terminal, wherein the isolation circuit includes: A diode configured to limit the start-up voltage; A main switching device, coupled between the starting capacitor and the diode, is configured to be inactive to limit current flow between A) the one or more control circuits and B) the starting resistor and the starting capacitor until the starting capacitor is charged to the starting voltage, and is configured to be activated when the starting capacitor is charged to the starting voltage, thereby charging the auxiliary capacitor; and A transistor configured to generate a hysteresis between the starting voltage and the low-voltage threshold of the starting capacitor, wherein when the auxiliary capacitor reaches the voltage at which the isolation circuit is deactivated, the transistor turns on the main switching device and saturates the main switching device so that the main switching device further charges the auxiliary capacitor.

2. The switched mode power supply of claim 1, wherein, The starting capacitor and the auxiliary capacitor are configured to store sufficient charge during the startup period following the initial charging period to power the one or more control circuits.

3. The switched mode power supply of claim 1, wherein, The starting resistor includes a resistance value configured such that the initial charging time period is less than ten seconds.

4. The switched mode power supply of claim 1, wherein, The voltage at the high-voltage input terminal is between 200 volts and 1200 volts.

5. The switched mode power supply of claim 1, wherein, The isolation circuit is configured to deactivate when the voltage of the starting capacitor is lower than the low-voltage threshold, and the low-voltage threshold is lower than the voltage of the starting capacitor at the end of the startup period.

6. The switched mode power supply of claim 1, wherein, The isolation circuit also includes a voltage-limiting diode connected in parallel with the auxiliary capacitor, the voltage-limiting diode being configured to activate based on the operating voltage specifications of the one or more control circuits to limit the voltage of the starting capacitor.

7. The switched mode power supply of claim 1, wherein, The main switching device includes a bipolar junction transistor (BJT).

8. The switched mode power supply of claim 1, wherein, The main switching device includes a metal-oxide-semiconductor field-effect transistor (MOSFET).

9. A method comprising configuring a switch-mode power supply to: During the initial charging time, the bootstrap circuit's starting capacitor is charged to the threshold charging voltage; During the initial charging time, an isolated circuit using the bootstrap circuit is used to limit the static current pulled by all components that are loads on the start capacitor, wherein, The component includes one or more control circuits; In response to the voltage of the starting capacitor reaching the threshold charging voltage, the isolation circuit is activated to electrically couple the starting capacitor to the auxiliary capacitor of the bootstrap circuit and the component, and to allow current flow from the starting capacitor to the auxiliary capacitor and the component, wherein the isolation circuit includes: A diode configured to limit the start-up voltage; A main switching device, coupled between the starting capacitor and the diode, and remaining inactive to limit current flow between A) the one or more control circuits and B) the starting resistor and the starting capacitor until the starting capacitor is charged to the starting voltage. When the starting capacitor is charged to the starting voltage, the main switching device is activated, thereby charging the auxiliary capacitor during the startup time; and A transistor that produces a hysteresis between the start-up voltage and the low-voltage threshold of the start-up capacitor, wherein when the auxiliary capacitor reaches the deactivation voltage of the isolation circuit, the transistor turns on the main switching device and saturates the main switching device to further charge the auxiliary capacitor; and The starting capacitor is used to power one or more control circuits until the auxiliary winding begins to provide power to the bootstrap circuit.

10. The method of claim 9, further comprising configuring the switch-mode power supply to maintain the activation of the isolation circuit after the startup time.

11. The method of claim 9, further comprising configuring the switch-mode power supply such that the initial charging time is less than ten seconds.

12. The method of claim 9, further comprising configuring the switch-mode power supply to: deactivate the isolation circuit to electrically isolate the starting capacitor from the auxiliary capacitor and the one or more control circuits when the voltage of the starting capacitor drops below the low-voltage threshold.

13. The method according to claim 12, wherein, The low-voltage threshold is lower than the voltage of the starting capacitor at the end of the startup time.

14. The method of claim 9, further comprising configuring the switch-mode power supply to use a voltage-limiting diode to limit the voltage of the starting capacitor based on the load of the one or more control circuits.

15. The method according to claim 9, wherein, The input voltage used to charge the starting capacitor is between 200 volts and 1200 volts.

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