A load switch based isolation circuit

Abstract

This application discloses an isolation circuit based on a load switch, belonging to the field of electrical isolation circuit technology. The isolation circuit includes: directly connecting the power input terminal and the enable terminal of the load switch module through a first resistor. The level of the enable terminal changes synchronously with the level of the power input terminal. This eliminates the need for an external control source to enable or disable the power supply path between the power input and output terminals of the load switch module, thus achieving synchronous triggering of power supply on / off and power level changes. This eliminates the timing obstacles of residual current discharge and rapid voltage drop after power failure in the load circuit, solving the problem of traditional technologies where the inability to synchronously trigger power supply on / off leads to the downstream circuit voltage not quickly returning to zero, thus causing reset abnormalities. This effectively ensures the fast response characteristics of the isolation circuit and can meet the practical application requirements of various electronic circuits for fast isolation circuit response.

Description

Technical Field

[0001] This application relates to the field of electrical isolation circuit technology, and in particular to an isolation circuit based on a load switch. Background Technology

[0002] To achieve electrical isolation between the front-end DC power supply and the back-end load circuit, and to ensure the power supply stability of the load circuit, an isolation circuit is usually configured between the two. By rationally designing the on / off control logic and circuit topology of the isolation circuit, the power supply path can be controlled to switch on and off. This allows for the rapid disconnection of the power supply link to the load circuit when the power supply fails, providing hardware support for solving problems such as reset anomalies and system startup failures caused by slow voltage drop under load.

[0003] However, when designing isolation circuits, traditional technologies typically employ an external control source to drive the load switch enable terminal. This involves configuring external components such as MCU GPIO, dedicated driver chips, or independent control power supplies to transmit level signals to the load switch enable terminal, thereby enabling the power supply path to be turned on and off.

[0004] Traditional technologies rely on external control sources to control the enable level. However, the relay-type triggering of external control sources has delays in software instruction parsing and control signal transmission, making it impossible to achieve synchronous triggering of power supply switching and power level changes. This creates timing obstacles for residual discharge and rapid voltage drop after the load circuit loses power, preventing the voltage of the downstream circuit from returning to zero quickly. Ultimately, this leads to problems such as reset anomalies and system restart failures, making it difficult to meet the practical application requirements of various electronic circuits for rapid response of isolation circuits. Summary of the Invention

[0005] The main objective of this application is to propose an isolation circuit based on a load switch. By directly connecting the power input terminal and the enable terminal of the load switch with a first resistor, synchronous triggering of power supply switching and power level changes is achieved, effectively ensuring the fast response characteristics of the isolation circuit.

[0006] To achieve the above objectives, one aspect of this application proposes an isolation circuit based on a load switch, comprising: a first resistor and a load switch module; the load switch module includes: a power input terminal, a power output terminal, an enable terminal, and a ground terminal; The power input terminal is connected to the output terminal of an external DC power supply; The power output terminal is connected to the load circuit; the grounding terminal is connected to the system ground. One end of the first resistor is connected to the power input terminal, and the other end of the first resistor is connected to the enable terminal; wherein, when the level of the power input terminal changes, the level of the enable terminal changes simultaneously, so as to enable or disable the power supply path between the power input terminal and the power output terminal.

[0007] Furthermore, the load switch module also includes: a control logic unit, a transistor, and a gate drive unit; The input terminal of the control logic unit is connected to the enable terminal; The first output terminal of the control logic unit is connected to the input terminal of the gate driving unit; The output terminal of the gate driving unit is connected to the gate terminal of the transistor; The drain terminal of the transistor is connected to the power input terminal; the source terminal of the transistor is connected to the power output terminal.

[0008] Furthermore, the load switch module also includes: a second resistor; The second output terminal of the control logic unit is connected to the controlled terminal of the second resistor, and the control logic unit is used to control the on / off state of the second resistor; One end of the second resistor is connected to the power output terminal; the other end of the second resistor is connected to the ground terminal; wherein, when the transistor is in the on state, the second resistor is controlled to be disconnected, and when the transistor is in the off state, the second resistor is controlled to be turned on.

[0009] Furthermore, the isolation circuit also includes: a first capacitor; The first terminal of the first capacitor is connected to the power input terminal; The second terminal of the first capacitor is connected to system ground.

[0010] Furthermore, the isolation circuit also includes: a second capacitor; The first terminal of the second capacitor is connected to the power output terminal; The second terminal of the second capacitor is connected to system ground.

[0011] Furthermore, the isolation circuit also includes a third capacitor; The first terminal of the third capacitor is connected to the power output terminal, and the first terminal of the third capacitor is connected to the first terminal of the second capacitor. The second terminal of the third capacitor is connected to system ground.

[0012] Furthermore, the isolation circuit also includes a noise filtering element; The first end of the noise filtering element is connected to the output end of an external DC power supply. The second end of the noise filtering element is connected to the power input terminal, and the second end of the noise filtering element is also connected to the first end of the first capacitor.

[0013] Furthermore, the isolation circuit also includes a voltage clamping protection unit for limiting the peak voltage at the power output terminal to a preset operating voltage range; One end of the voltage clamping protection unit is connected to the power output terminal; The other end of the voltage clamping protection unit is connected to the system ground.

[0014] Furthermore, the voltage clamping protection unit includes a first diode, a second diode, and a voltage divider circuit; The cathode of the first diode is connected to the power output terminal, and the anode of the first diode is connected to the first terminal of the voltage divider circuit. The anode of the second diode is connected to system ground, and the cathode of the second diode is connected to the power output terminal; The second terminal of the voltage divider circuit is connected to system ground.

[0015] Furthermore, the voltage divider circuit includes a third resistor and a fourth resistor; One end of the third resistor is connected to the anode of the first diode, and the other end of the third resistor is connected to one end of the fourth resistor; the other end of the fourth resistor is connected to system ground.

[0016] The embodiments of this application include at least the following beneficial effects: This application provides an isolation circuit based on a load switch. This scheme directly connects the power input terminal and the enable terminal of the load switch module through a first resistor. The level of the enable terminal changes synchronously with the level of the power input terminal. The power supply path between the power input terminal and the power output terminal of the load switch module can be turned on or off without configuring an external control source. Compared with traditional technologies, this application's design of directly connecting the power input terminal and the enable terminal of the load switch module through a first resistor eliminates the mode of external control source driving the enable terminal, avoiding the intermediate delay in software instruction parsing and control signal transmission. By simultaneously changing the levels at both ends, synchronous triggering of power supply on / off and power level changes is achieved, eliminating the timing obstacles of residual current discharge and rapid voltage drop after the load circuit loses power. This solves the problem in traditional technologies where the inability to synchronously trigger power supply on / off leads to the downstream circuit voltage not returning to zero quickly, thus causing reset abnormalities. It effectively ensures the fast response characteristics of the isolation circuit and can meet the practical application requirements of various electronic circuits for fast isolation circuit response. Attached Figure Description

[0017] Figure 1This is a schematic diagram of the structural connection of an isolation circuit based on a load switch provided in an embodiment of this application; Figure 2 This is a structural connection diagram of a load switch module provided in another embodiment of this application; Figure 3 This is a schematic diagram of the isolation circuit structure provided in another embodiment of this application; Figure 4 This is a schematic diagram of an isolation circuit structure including a voltage clamping protection unit provided in an embodiment of this application. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit the scope of this application. In the following description, when referring to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with those of this application; they are merely examples of a load switch-based isolation circuit consistent with some aspects of the embodiments of this application as detailed in the appended claims.

[0019] In existing technologies, isolation circuits used between DC power supplies and load circuits commonly employ external control sources to drive the load switch enable terminal. This can be achieved through MCU GPIO, dedicated driver chips, or independent control power supply outputs to control the load switch's on / off state. However, external control sources require software instruction parsing and control signal transmission, inevitably resulting in control delays. This prevents synchronized triggering of the load switch's power on / off state with changes in the power input level. Consequently, when the power supply fails, the power supply path cannot be cut off promptly, hindering the discharge of residual current and rapid voltage drop in the load circuit. This prevents the power output voltage from quickly returning to zero, ultimately causing problems such as abnormal chip reset in the load circuit and system restart failures. Furthermore, the additional external control components increase the complexity of the circuit structure.

[0020] In view of this, this application provides an isolation circuit based on a load switch. This solution directly connects the power input terminal and the enable terminal of the load switch module through a first resistor, instead of using the traditional external control source driving method. From the circuit topology, it realizes real-time synchronization between the enable terminal level and the power input terminal level, ensuring that the power supply path can be shut off immediately when the power supply fails. It also eliminates the need for external control devices such as MCU and dedicated driver chips, which not only simplifies the overall structure of the isolation circuit, but also improves the circuit response speed and operational reliability.

[0021] Figure 1This is a schematic diagram of the structural connection of an isolation circuit based on a load switch according to an embodiment of this application. The isolation circuit based on the load switch includes: a first resistor and a load switch module; the load switch module includes: a power input terminal, a power output terminal, an enable terminal and a ground terminal; The power input terminal is connected to the output terminal of an external DC power supply; The power output terminal is connected to the load circuit; the grounding terminal is connected to the system ground. One end of the first resistor is connected to the power input terminal, and the other end of the first resistor is connected to the enable terminal; wherein, when the level of the power input terminal changes, the level of the enable terminal changes simultaneously, so as to enable or disable the power supply path between the power input terminal and the power output terminal.

[0022] In illustratively, in this embodiment of the invention, when the level of the external DC power supply changes, such as increasing when powered on or decreasing when powered off, the level of the enable terminal can synchronously follow the level change of the power input terminal through the coupling effect of the first resistor. Without any software parsing or signal relay, the power supply path inside the load switch module can be directly controlled to be turned on or off, eliminating the timing delay caused by the control signal transmission in the traditional solution, and realizing the complete synchronous triggering of power supply on / off action and power level change.

[0023] Therefore, the embodiments of the present invention not only ensure that the power supply path can be shut off in time when the power supply fails, thus reducing timing obstacles for the rapid discharge of residual power at the output terminal and the rapid return of voltage to zero, but also eliminate the need for external control devices such as MCU and dedicated driver chips. The isolation circuit consists only of the first resistor and the load switch module, which greatly reduces the number of components, reduces the PCB layout space requirements, and also reduces the material cost of the circuit.

[0024] For example, when a controller system loses power, the external DC power supply level immediately drops. The enable terminal of the load switch module of the present invention is coupled by the first resistor, and its level will drop synchronously with the power input terminal. At this time, the power supply path inside the load switch can be turned off immediately, quickly cutting off the power supply output to the large capacitor load and the main control chip at the back end. This avoids the problem of slow voltage drop caused by continuous power supply input from the root, and clears the timing obstacle for the rapid pull-down of the output voltage.

[0025] The structure of this invention retains the electrical separation function of the input and output of the isolation circuit, and specifically solves the problem of slow voltage drop under large capacitor loads. This allows the supply voltage to drop quickly to below the reset threshold, enabling the chip to achieve normal and correct hardware reset without manual waiting for a long time or relying on forced reset operations or hardware. The device can be quickly restarted, greatly improving the efficiency and power-on reliability of the controller.

[0026] like Figure 2 The diagram shows the internal structure of the load switch module. In some embodiments, the load switch module further includes: a control logic unit, a transistor, and a gate drive unit. The input terminal of the control logic unit is connected to the enable terminal; The first output terminal of the control logic unit is connected to the input terminal of the gate driving unit; The output terminal of the gate driving unit is connected to the gate terminal of the transistor; The drain terminal of the transistor is connected to the power input terminal; the source terminal of the transistor is connected to the power output terminal.

[0027] Furthermore, the load switch module also includes: a second resistor; The second output terminal of the control logic unit is connected to the controlled terminal of the second resistor, and the control logic unit is used to control the on / off state of the second resistor; One end of the second resistor is connected to the power output terminal; the other end of the second resistor is connected to the ground terminal; wherein, when the transistor is in the on state, the second resistor is controlled to be disconnected, and when the transistor is in the off state, the second resistor is controlled to be turned on.

[0028] For illustrative purposes, please refer to Figure 2 The internal structure of the load switch module in this embodiment of the invention further refines the collaborative working mechanism of power supply on / off control and residual power discharge based on the above-mentioned hardware self-synchronization architecture.

[0029] In this embodiment, the load switch module integrates a control logic unit, a gate drive unit, a transistor, and a second resistor R2, forming a dual-path interlocked control architecture for main power supply path control and output residual current discharge. Specifically, the control logic unit acts as the control hub within the module. Its input terminal receives an enable terminal level signal synchronized in real time with the power input terminal, and outputs two complementary control signals synchronously according to the level state. One control signal is sent to the gate drive unit via the first output terminal, where the gate drive unit amplifies the weak current control signal to drive the gate terminal of the transistor, thereby controlling the transistor's conduction and turn-off. The transistor forms the main power supply path from the power input terminal to the power output terminal. The other control signal is sent to the controlled terminal of the second resistor via the second output terminal, specifically controlling the on / off state of the second resistor, so that the second resistor forms a controllable residual current discharge path from the power output terminal to the ground terminal. The control logic unit incorporates interlocking logic to ensure that the transistor and the second resistor are always in opposite operating states. For example, the second resistor is disconnected when the transistor is turned on and turned on when the transistor is turned off, thus preventing the main power supply path and the discharge path from being simultaneously turned on, which could cause a power short circuit or ineffective power loss.

[0030] In this embodiment of the invention, through the unified scheduling of the control logic unit, the main power supply path and the discharge path are strictly mutually exclusive. When the power supply is normal, the discharge branch is disconnected and no additional power consumption is generated; when the power is turned off, the discharge branch is turned on, without relying on the external discharge circuit, thus ensuring the safety and reliability of residual power discharge.

[0031] In this embodiment of the invention, in response to the large capacitive load characteristics commonly found in integrated chip controllers, the second resistor is automatically turned on to form a ground discharge circuit while the main power supply path is turned off. This directly and quickly releases the residual charge of the output capacitor, load circuit and chip pins to the system ground, thus accelerating the output voltage drop from the discharge mechanism.

[0032] The coupling effect of the first resistor solves the problem of asynchronous switching action and power loss and control delay. In this embodiment, the internal structure of the load switch module further solves the problem of residual power having nowhere to be discharged and voltage tailing after shutdown. The two work together to achieve full-process acceleration from power cut-off to voltage zeroing. No PMU (Power Management Unit) is required to monitor it or wait manually. The chip can naturally and reliably complete the reset.

[0033] Furthermore, in this embodiment of the invention, the control logic, driver, power switch and bleed resistor are integrated inside the load switch module, which eliminates the need for additional bleed circuits or timing control circuits in the external environment, further simplifying the circuit layout, reducing the number of components and cost, while improving the circuit's anti-interference capability and signal integrity.

[0034] like Figure 3 The schematic diagram of the specific structure of the isolation circuit shown may include, in some embodiments, a first capacitor. The first terminal of the first capacitor is connected to the power input terminal; The second terminal of the first capacitor is connected to system ground.

[0035] The isolation circuit further includes: a second capacitor; The first terminal of the second capacitor is connected to the power output terminal; The second terminal of the second capacitor is connected to system ground.

[0036] The isolation circuit also includes: a third capacitor; The first terminal of the third capacitor is connected to the power output terminal, and the first terminal of the third capacitor is connected to the first terminal of the second capacitor. The second terminal of the third capacitor is connected to system ground.

[0037] The isolation circuit also includes: a noise filtering element; The first end of the noise filtering element is connected to the output end of an external DC power supply. The second end of the noise filtering element is connected to the power input terminal, and the second end of the noise filtering element is also connected to the first end of the first capacitor.

[0038] like Figure 3 As shown, in the load switch module, the power input terminal is the VIN pin, the ground terminal is the GND pin, the enable terminal is the ON pin, and the power output terminal is the VOUT pin; furthermore, the first resistor is R1, the first capacitor is C1, the second capacitor is C2, and the third capacitor is C3.

[0039] In this embodiment of the invention, the following series connection relationship exists: The output terminal of the external DC power supply is connected in series with the first terminal of the noise filtering element, the second terminal of the noise filtering element is connected in series with the power input terminal VIN, the transistor inside the load switch module is connected in series between the power input terminal VIN and the power output terminal VOUT, the power output terminal VOUT is connected in series with the load circuit at the back end, and the load circuit is connected in series with the system ground, forming a complete DC power supply main circuit. The power input terminal VIN of the load switch module is connected in series with one end of the first resistor R1, and the other end of the first resistor R1 is connected in series with the enable terminal ON of the load switch module, forming a hardware synchronous self-driving path. The grounding terminal GND of the load switch module and the grounding terminal of each capacitor are connected in series with the system ground to ensure the integrity of the common ground loop of the entire circuit.

[0040] Furthermore, the following parallel connection relationships also exist: The two ends of the first capacitor C1 are connected in parallel between the power input terminal VIN of the load switch module and the system ground, and at the same time, they are connected in parallel with the second end of the noise filter element and one end of the first resistor R1 to form a common node, thus forming a parallel branch on the input side. The second capacitor C2 and the third capacitor C3 are connected in parallel. The two are then connected in parallel between the power output terminal VOUT of the load switch module and the system ground, and at the same time, they form a parallel relationship with the load circuit, thus forming a parallel branch on the output side. Indicatively, inside the load switch module, the second resistor R2 is connected in parallel between the power output terminal VOUT and the ground terminal GND, forming a residual current discharge branch, thus creating a discharge parallel branch.

[0041] like Figure 3 As shown, V3.3 is actually a 3.3V DC power input, which determines whether the load switch works and is also the object that the noise filtering element needs to protect.

[0042] To illustrate, when powered on: V3.3 = 3.3V, at which point the load switch is activated to power the load circuit of the downstream chip.

[0043] When power is lost: V3.3 = 0V. At this time, the load switch is turned off, and then a fast reset is triggered.

[0044] Optionally, the noise filtering element in this embodiment can be a ferrite bead, model CBM160808U121T; Optionally, the load switch module in this embodiment can be a low on-resistance load switch with fast output discharge function, model TPS22915B / TPS22914.

[0045] Optionally, in this embodiment, the first capacitor C1 and the second capacitor C2 are both tantalum capacitors with a specification of 4.7μF / 6.3V; the third capacitor C3 is a multilayer ceramic capacitor (MLCC) with a specification of 100nF / 16V and a precision of 10%.

[0046] The noise filtering element is connected in series between the external DC power supply and the input terminal VIN of the load switching power supply. When it is working, it presents extremely low impedance to DC signals and does not affect the normal power supply transmission. The noise filtering element presents high impedance to high-frequency electromagnetic interference and power supply ripple, which can block high-frequency noise introduced by the front-end power supply, and at the same time suppress interference generated by the operation of the back-end circuit from flowing back to the front-end power supply, thereby improving the electromagnetic compatibility performance of the circuit.

[0047] For the transistors inside the load switch module, as the main power supply path switching device, they are turned on and off under the control of the gate drive unit, controlling the on and off of the power supply path, and realizing electrical isolation and power supply switching between the power input terminal and the output terminal.

[0048] The second resistor R2 inside the load switch module acts as a controllable discharge device. It is synchronously turned on when the transistor is turned off, providing a discharge loop to ground for the output capacitor and load circuit, thus accelerating the output voltage drop.

[0049] The first capacitor C1 serves as an input filter capacitor. It is connected in parallel between the power input terminal VIN and the system ground. Its main functions are: to perform low-frequency filtering on the power input terminal, suppress power-on surges and low-frequency power ripple, and stabilize the operating level of the VIN pin; together with noise filtering components, the two can form an LC filter network to improve the purity of the input power supply, avoid enable terminal jitter caused by input level fluctuations, and ensure stable and reliable load switch on / off control.

[0050] The second capacitor C2 can be used as a large-capacity energy storage capacitor for the output. The second capacitor C2 is connected in parallel between the power output terminal VOUT and the system ground. Its main functions are: to undertake the functions of energy storage and voltage regulation on the output side, to charge and discharge quickly when the load current changes suddenly, to avoid a large drop in output voltage, and to ensure the stable operation of the load circuit; as a large-capacitance energy storage device, it is suitable for large-capacitance load scenarios such as integrated chip controllers, and at the same time, it works with the internal discharge resistor to quickly release charge when power is lost.

[0051] The third capacitor C3 serves as an output high-frequency decoupling capacitor. It is connected in parallel with the second capacitor C2. Its main functions are to compensate for the poor high-frequency characteristics of large-capacity capacitors, absorb high-frequency noise, voltage spikes and electromagnetic interference on the output side, provide high-frequency decoupling for the load chip, ensure the signal integrity of high-speed devices such as the star flash chip, and avoid communication errors and abnormal operation.

[0052] This invention employs a combined filtering design using a ferrite bead and a first capacitor C1 on the input side, and a second capacitor C2 and a third capacitor C3 on the output side. While maintaining the electrical isolation and anti-interference capabilities of the isolation circuit, it specifically addresses the issues of slow voltage drop, abnormal chip reset, and prolonged restart delays during power loss in scenarios with large capacitor loads, such as controllers with integrated star-flash chips. The overall design of this invention eliminates the need for an external control chip, reduces the number of components, and features a simple layout. It ensures stable power supply and noise suppression while achieving power on / off synchronization with power level and rapid discharge and reset after power loss, thus balancing circuit reliability, electromagnetic compatibility performance, and the need for rapid restart.

[0053] The following are examples of specific implementation scenarios of the present invention: First, during the system's power-on process, after the external 3.3V DC power supply is powered on, the DC signal passes sequentially through the noise filtering element and the VIN pin of the load switch module; one path is synchronously coupled to the ON pin through the first resistor R1, causing the enable terminal level to rise synchronously, controlling the internal transistor to conduct and opening the main power supply path; the other path charges the first capacitor C1 to stabilize the input level.

[0054] After the power supply path is turned on, the voltage is transmitted to the VOUT pin to charge the second capacitor C2 and the third capacitor C3, and to power the load circuit at the back end; C2 maintains the output voltage stability, and C3 suppresses high-frequency noise to ensure that the chip starts up and works normally without power-on jitter or reset abnormalities.

[0055] Next, during the noise suppression process during normal operation, the high-frequency noise introduced by the front-end power supply is blocked by the noise filtering element, and the residual low-frequency ripple is bypassed to ground by C1; the high-frequency interference generated when the back-end load circuit is working is quickly absorbed and discharged by C3, and the low-frequency ripple is smoothly filtered out by C2, realizing bidirectional noise suppression, ensuring clean power supply and stable communication, and preventing interference crashes and signal packet loss problems.

[0056] Finally, during the rapid power-down reset process after a system power failure, the VIN pin level drops instantaneously after the external DC power supply fails. Coupled by R1, the ON pin level is synchronously pulled low, the internal transistor of the load switch is instantly turned off, and the main power supply path is immediately cut off without any control delay. Simultaneously, the internal second resistor conducts synchronously, and the residual charge on the VOUT pin, C2, C3, and the back-end load circuit flows rapidly to system ground through the discharge circuit. The output voltage drops below the chip reset threshold within a short time. At this point, the chip in the back-end load circuit completes a normal hardware reset, eliminating the need for manual shutdown or forced reset by other control devices. The device can be immediately powered on again, significantly improving operational reliability.

[0057] like Figure 4 The diagram shows an isolation circuit structure including a voltage clamping protection unit. In some embodiments, the isolation circuit further includes a voltage clamping protection unit for limiting the peak voltage at the power supply output terminal to a preset operating voltage range. One end of the voltage clamping protection unit is connected to the power output terminal; The other end of the voltage clamping protection unit is connected to the system ground.

[0058] Furthermore, the voltage clamping protection unit includes a first diode, a second diode, and a voltage divider circuit; The cathode of the first diode is connected to the power output terminal, and the anode of the first diode is connected to the first terminal of the voltage divider circuit. The anode of the second diode is connected to system ground, and the cathode of the second diode is connected to the power output terminal; The second terminal of the voltage divider circuit is connected to system ground.

[0059] Furthermore, the voltage divider circuit includes a third resistor and a fourth resistor; One end of the third resistor is connected to the anode of the first diode, and the other end of the third resistor is connected to one end of the fourth resistor; the other end of the fourth resistor is connected to system ground.

[0060] As an illustration, in some applications such as controllers integrating stroboscopic chips, the backend load, such as the stroboscopic chip or a large capacitor array, may generate positive voltage spikes higher than the normal 3.3V during sudden load changes, switching actions, or electromagnetic interference. For example, it may momentarily surge to 4V-5V, or experience negative voltage spikes below 0.0V. If these voltage spikes are not controlled, they can damage the transistors inside the load switching module, the power supply pins of the backend stroboscopic chip, or cause capacitors to overheat and fail, severely reducing the lifespan of the equipment.

[0061] To address the aforementioned issues, this invention provides a voltage clamping protection unit that clamps the voltage at the VOUT terminal within a safe range, such as limiting it to below 4V, to prevent overvoltage or undervoltage spikes from damaging the circuit.

[0062] like Figure 4 As shown, in this embodiment of the invention, a bidirectional clamping network is formed by the first diode D1 and the second diode D2. This network can absorb both positive and negative surges, providing more comprehensive protection than a unidirectional clamping circuit and significantly improving the reliability of the isolation circuit in complex electromagnetic environments.

[0063] Specifically, the voltage clamping protection unit consists of a first diode D1, a second diode D2, a third resistor R3, and a fourth resistor R4. Its working principle can be analyzed in three states: For normal operating conditions (cutoff state): When the voltage at the power output terminal VOUT stabilizes at a preset value (e.g., 3.3V), the cathode of the second diode D2 is connected to a high level (3.3V), and the anode is grounded, placing it in a reverse cutoff state (non-conducting). The cathode of the first diode D1 is connected to a high level (3.3V), and the anode is connected to a voltage divider circuit, placing it in a reverse cutoff state (non-conducting). At this time, the voltage clamping protection unit consumes almost no current and does not affect normal power transmission or power quality. The current mainly flows to the load circuit.

[0064] For forward overvoltage protection (power-on surge / spike): When the voltage at the VOUT terminal suddenly rises and exceeds the sum of the preset voltage and the diode forward voltage drop, for example, exceeding 3.3V + 0.7V = 4V, the second diode D2 is forward-biased (at this time, the cathode voltage is higher than the anode voltage). After D2 is turned on, it clamps the voltage at VOUT within a safe threshold of approximately 4V. Excess energy is discharged to ground through D2, protecting the downstream chips from being damaged by high voltage.

[0065] For negative spike protection (negative pulses generated by power failure / electrostatic discharge), when the voltage at the VOUT terminal suddenly drops below 0V, such as -1V or -2V, or due to negative voltage generated by electrostatic discharge, the potential of VOUT is lower than ground (GND). The first diode D1 is forward-biased and conducts. At this time, the anode potential is higher than the cathode potential, and the current flows from ground to VOUT. After D1 conducts, it limits the voltage at the VOUT terminal, preventing the negative voltage from penetrating further into the circuit and protecting the load switching module and the input stage of the downstream load.

[0066] Furthermore, when both D1 and D2 are off, the voltage signal at the VOUT terminal is transmitted to the voltage divider node through the third resistor R3 and the fourth resistor R4. The voltage at this node is: V sample =V OUT × The external monitoring circuit can calculate the actual VOUT output voltage by reading the voltage value after voltage division, thus realizing real-time monitoring of the power supply status.

[0067] For example, an embodiment of the present invention can be applied to an on-board controller with an integrated starlight chip, the power rail being 3.3V: At the moment of vehicle startup, during the positive surge protection phase, the power system experiences a violent surge when the engine ignites, causing the 3.3V power supply to instantly spike to 5V or even higher. At this point, the voltage surge reaches the VOUT terminal, exceeding the 4V threshold, and D2 instantly conducts. This keeps the voltage below 4V and allows energy to drain to ground, ensuring the power supply pins of the StarSpark chip remain intact. Without the conduction of D2 and the energy diversion, the chip might burn out instantly.

[0068] In summary, the load switch-based isolation circuit described in this invention, through the coordinated design of hardware self-synchronization drive, integrated discharge control, multi-stage filtering and voltage regulation, and bidirectional voltage clamping protection, achieves the following outstanding technical effects: This invention does not require external control sources such as MCUs or dedicated driver chips. Instead, it directly connects the load switching power supply input terminal to the enable terminal through a first resistor. The enable terminal level can completely follow the power input terminal level and change synchronously. There is no timing delay due to software parsing or signal transmission. When the power supply fails, the power supply path can be instantly shut off, avoiding the problem of slow output voltage drop caused by continuous power supply input, thus laying the timing foundation for rapid power-down reset.

[0069] This invention can combine the interlock design of the controllable discharge resistor inside the load switch module to simultaneously open the discharge circuit when the main power supply path is turned off. This can quickly release the residual charge on the output capacitor, chip pins and load circuit, so that the output voltage drops below the chip reset threshold in a short time and remains there for a sufficient period of time. This ensures that the main control devices such as the Star Flash chip can complete the normal hardware reset without relying on forced reset hardware. The device can be powered on immediately, which greatly improves the efficiency and power-on reliability.

[0070] This invention integrates control logic, power switch, gate drive, and bleed resistor into the load switch module, eliminating the need for additional external control circuits, independent bleed circuits, and timing control circuits. The entire module consists of only a few passive components and an integrated load switch, effectively reducing the number of components, lowering PCB layout space requirements and material costs, while improving circuit integration and assembly reliability.

[0071] This invention employs a combined filtering design, consisting of an input-side ferrite bead paired with a first capacitor (C1) and an output-side large-capacity energy storage capacitor (C2) paired with a high-frequency decoupling capacitor (C3). This design achieves bidirectional noise isolation across the entire frequency band, from low to high frequencies. It can filter out ripple and interference introduced by the front-end power supply and suppress high-frequency spikes generated by the back-end chip, ensuring power supply purity and preventing bit errors, packet loss, and system crashes in high-speed communication. This significantly improves the electromagnetic compatibility performance of the circuit.

[0072] This invention uses a bidirectional clamping network formed by a first diode and a second diode to limit both positive overvoltage spikes and negative electrostatic discharge pulses at the output end to a safe operating voltage range. This prevents transient voltages from damaging the load switch, the power supply pins of the main control chip, or causing capacitor failure. It is suitable for complex electromagnetic environments such as automotive and industrial applications, and extends the service life of the equipment.

[0073] This invention achieves rapid switching, rapid discharge, noise suppression, and voltage protection while retaining the electrical separation function of the isolation circuit input and output. It can effectively block interference and crosstalk between upstream and downstream circuits and the conduction of faults, thereby improving the overall operational safety of the system.

[0074] The internal control logic unit of the load switch module of the present invention can realize strict mutual exclusion control between the main power supply path and the discharge path. When the power supply is normal, the discharge circuit is disconnected and there is no additional power loss; when the power is lost and the discharge occurs, the power supply path is completely shut off, there is no risk of power short circuit, the circuit is stable and reliable, and it is suitable for long-term continuous operation scenarios.

[0075] The preferred embodiments of the present application have been described above with reference to the accompanying drawings, but this does not limit the scope of the claims of the present application. Any modifications, equivalent substitutions, and improvements made by those skilled in the art without departing from the scope and substance of the embodiments of the present application shall be within the scope of the claims of the present application.

Claims

1. A load switch based isolation circuit, characterized by, include: First resistor and load switch module; The load switch module includes: a power input terminal, a power output terminal, an enable terminal, and a ground terminal; The power input terminal is connected to the output terminal of an external DC power supply; The power output terminal is connected to the load circuit; the grounding terminal is connected to the system ground. One end of the first resistor is connected to the power input terminal, and the other end of the first resistor is connected to the enable terminal; wherein, when the level of the power input terminal changes, the level of the enable terminal changes simultaneously, so as to enable or disable the power supply path between the power input terminal and the power output terminal.

2. The isolation circuit based on a load switch according to claim 1, characterized in that, The load switch module further includes: a control logic unit, a transistor, and a gate drive unit; The input terminal of the control logic unit is connected to the enable terminal; The first output terminal of the control logic unit is connected to the input terminal of the gate driving unit; The output terminal of the gate driving unit is connected to the gate terminal of the transistor; The drain terminal of the transistor is connected to the power input terminal; the source terminal of the transistor is connected to the power output terminal.

3. A load switch based isolation circuit according to claim 2, wherein, The load switch module further includes: a second resistor; The second output terminal of the control logic unit is connected to the controlled terminal of the second resistor, and the control logic unit is used to control the on / off state of the second resistor; One end of the second resistor is connected to the power output terminal; the other end of the second resistor is connected to the ground terminal; wherein, when the transistor is in the on state, the second resistor is controlled to be disconnected, and when the transistor is in the off state, the second resistor is controlled to be turned on.

4. The load switch based isolation circuit of claim 1, wherein, The isolation circuit further includes: a first capacitor; The first terminal of the first capacitor is connected to the power input terminal; The second terminal of the first capacitor is connected to system ground.

5. A load switch based isolation circuit according to claim 4, wherein, The isolation circuit further includes: a second capacitor; The first terminal of the second capacitor is connected to the power output terminal; The second terminal of the second capacitor is connected to system ground.

6. A load switch based isolation circuit according to claim 5, wherein, The isolation circuit also includes: a third capacitor; The first terminal of the third capacitor is connected to the power output terminal, and the first terminal of the third capacitor is connected to the first terminal of the second capacitor. The second terminal of the third capacitor is connected to system ground.

7. The load switch based isolation circuit of claim 4, wherein, The isolation circuit also includes: a noise filtering element; The first end of the noise filtering element is connected to the output end of an external DC power supply. The second end of the noise filtering element is connected to the power input terminal, and the second end of the noise filtering element is also connected to the first end of the first capacitor.

8. The load switch based isolation circuit of claim 1, wherein, The isolation circuit further includes a voltage clamping protection unit for limiting the peak voltage at the power output terminal to a preset operating voltage range; One end of the voltage clamping protection unit is connected to the power output terminal; The other end of the voltage clamping protection unit is connected to the system ground.

9. A load switch based isolation circuit according to claim 8, wherein, The voltage clamping protection unit includes a first diode, a second diode, and a voltage divider circuit; The cathode of the first diode is connected to the power output terminal, and the anode of the first diode is connected to the first terminal of the voltage divider circuit. The anode of the second diode is connected to system ground, and the cathode of the second diode is connected to the power output terminal; The second terminal of the voltage divider circuit is connected to system ground.

10. A load switch based isolation circuit according to claim 9, wherein, The voltage divider circuit includes a third resistor and a fourth resistor; One end of the third resistor is connected to the anode of the first diode, and the other end of the third resistor is connected to one end of the fourth resistor; the other end of the fourth resistor is connected to system ground.

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