Constant-current discharge circuit and electronic equipment
By designing a constant current discharge circuit in a Buck-like power converter, using MOS tubes and transistors to achieve accurate discharge of the output capacitor, the sudden current problem caused by the failure of capacitor discharge in time is solved, and the power efficiency and device protection are improved.
Patent Information
- Application Number
- CN202421789611.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-26
- Publication Date
- 2025-06-17
- Estimated Expiration
- 2034-07-26
AI Technical Summary
During the soft start process of Buck-like power converters, the capacitor at the output end is not discharged in time, causing energy to flow from the output end to the input end, resulting in a large sudden current, which may damage the synchronous rectifier tube. The prior art solves this problem by accessing resistors as dead load between the positive and negative poles of the output terminal, but this increases standby power consumption and reduces power efficiency.
A constant current discharge circuit is designed to realize precise discharge control of the output capacitor through the first MOS tube and the first transistor. This circuit adjusts the discharge rate according to the level signal sent by the upper computer to achieve a more accurate and controllable capacitor discharge process.
This circuit enables accurate discharge of capacitors without increasing standby power consumption and reducing power efficiency, avoiding damage to the synchronous rectifier tube, and providing more reliable device protection.
Smart Images
Figure CN222996436U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the field of electronic technology, in particular to a constant-current discharging circuit and an electronic device. Background Art
[0002] The Buck type power converter is a common step-down DC-DC power converter (hereinafter referred to as the power supply), which is used to reduce the input voltage to a lower output voltage. Generally, it consists of a power switch tube, an inductor element, a capacitor, a diode and other devices. During the soft start process of the power supply, if the capacitor at the output end fails to complete discharging in time, the output capacitor will discharge reversely through the inductor and the synchronous rectifier tube composed of the power switch tube or the diode, resulting in energy flowing from the output end to the input end and generating a large mutation current. When the synchronous rectifier tube is in the cut-off state during the discharging process, due to the fact that the current of the inductor cannot mutate, the generated mutation current will charge the junction capacitance between the source and drain (DS) of the synchronous rectifier tube. Since this junction capacitance is generally very small, a relatively high voltage will be generated between the source and drain (DS) junctions, thus causing the synchronous rectifier tube to be broken down and damaged.
[0003] In order to enable the capacitor at the output end of the power supply to discharge in time, in the prior art, a resistor is mostly connected between the positive and negative poles of the output end of the power supply as a dead load. See Figure 1 , Figure 1 which is a schematic connection diagram of a discharging protection circuit of a common Buck type power converter in the prior art. After the power supply stops outputting, the capacitor at the power supply output end is discharged through the connected resistor to ensure that the voltage across the capacitor is 0 when starting up next time. However, when the dead load is connected to the power supply, even if the dead load has no actual power consumption requirement, the power supply still needs to provide energy to maintain the stability of the load. This will cause the power supply to consume extra energy in the working state and the non-working state, increasing the standby power consumption. And in the case of connecting the dead load, the power supply needs to continuously provide energy to meet the constant load demand, which may lead to a reduction in the efficiency of the power supply during operation. Further, the power supply needs to continuously provide energy to maintain the stability of the load. If the power supply overheats, it may cause performance degradation or even damage to the device. Therefore, better heat dissipation is also required to dissipate the excess heat. During the operation of the power supply, the dead load will always have current flowing through it and be in a heating environment, which is likely to accelerate the aging of the resistor and cause the load to fail. Summary of the Utility Model
[0004] The utility model aims to provide a constant-current discharging circuit and an electronic device to solve the above technical problems and improve the accuracy and efficiency of capacitor discharging during the soft start process of the power supply.
[0005] In a first aspect, the present application provides a constant-current discharge circuit applicable to a Buck-type power converter, where the Buck-type power converter includes a first inductor and a first capacitor; the constant-current discharge circuit includes: a first resistor, a second resistor, a third resistor, a first MOS transistor, and a first triode;
[0006] A first end of the first resistor is connected to a first end of the first inductor and a first end of the first capacitor;
[0007] A second end of the first resistor is connected to a source electrode of the first MOS transistor;
[0008] A gate electrode of the first MOS transistor is connected to a first end of the second resistor and a collector of the first triode;
[0009] A second end of the second resistor is connected to a host computer; wherein, the host computer is configured to send a level signal to the first MOS transistor;
[0010] A drain electrode of the first MOS transistor is connected to a first end of the third resistor and a base of the first triode;
[0011] A second end of the third resistor and an emitter of the first triode are connected to a second end of the first capacitor.
[0012] In the above solution, precise discharge control of the output capacitor is achieved through the first MOS transistor and the first triode. Compared with a simple resistive dead load, it can adjust the discharge rate according to the level signal sent by the host computer, thereby realizing a more precise and controllable capacitor discharge process. The host computer can control the gate voltage of the first MOS transistor in real time, thereby adjusting the discharge current, enabling the capacitor to discharge more quickly when needed, or maintaining a constant discharge characteristic when the load changes. This optimized dynamic response performance is not possessed by traditional dead loads. Moreover, the power supply does not need to provide energy for the constant-current discharge current to maintain the stability of the circuit, will not generate additional standby power consumption, and will not reduce the power supply efficiency. The constant-current discharge circuit only discharges the capacitor when the power supply is in the off state or before soft start, and will not affect the device during the working state of the power supply. The constant-current discharge circuit can provide more reliable device protection.
[0013] In one implementation, the constant-current discharge circuit further includes a second capacitor, specifically:
[0014] A first end of the second capacitor is connected to a gate electrode of the first MOS transistor and a first end of the second resistor;
[0015] A second end of the second capacitor is connected to an emitter of the first triode, a second end of the third resistor, and a second end of the first capacitor.
[0016] In one implementation, the first MOS transistor is an NMOS transistor, and the first triode is an NPN transistor.
[0017] In one implementation, the constant current discharge circuit further includes an output voltage detection module, specifically:
[0018] The output voltage detection module includes a fourth resistor, a fifth resistor, and a differential amplifier;
[0019] The first end of the fourth resistor is connected to the first end of the first capacitor;
[0020] The first end of the fifth resistor is connected to the second end of the first capacitor;
[0021] The second end of the fourth resistor is connected to the negative input terminal of the differential amplifier;
[0022] The second end of the fifth resistor is connected to the positive input terminal of the differential amplifier;
[0023] The output terminal of the differential amplifier is connected to the host computer.
[0024] In one implementation, the output voltage detection module further includes a sixth resistor, a seventh resistor, a third capacitor, a fourth capacitor, a fifth capacitor, and a sixth capacitor, specifically:
[0025] The first end of the sixth resistor and the first end of the third capacitor are connected to the negative input terminal of the differential amplifier;
[0026] The second end of the sixth resistor and the second end of the third capacitor are connected to the output terminal of the differential amplifier;
[0027] The first end of the fourth capacitor is connected to the negative input terminal of the differential amplifier, the first end of the third capacitor, and the first end of the fourth resistor;
[0028] The second end of the fourth capacitor is connected to the negative input terminal of the differential amplifier, the first end of the sixth capacitor, and the first end of the seventh resistor;
[0029] The first end of the fifth capacitor is connected to the positive input terminal of the differential amplifier;
[0030] The second end of the fourth capacitor, the second end of the fifth capacitor, the second end of the sixth capacitor, the second end of the seventh resistor, and the output terminal of the differential amplifier are grounded.
[0031] In a second aspect, the present application further provides an electronic device, including the constant current discharge circuit as described above. Description of the Drawings
[0032] Figure 1 It is a schematic diagram of the connection relationship of a discharge protection circuit of a Buck - type power converter commonly used in the prior art;
[0033] Figure 2 It is a schematic diagram of the connection relationship of a constant - current discharge circuit provided in an embodiment of the present invention;
[0034] Figure 3 It is a schematic diagram of the connection relationship of an output voltage detection module provided in an embodiment of the present invention. Specific embodiments
[0035] Next, with reference to the drawings and embodiments, the specific embodiments of the present invention will be further described in detail. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.
[0036] The terms "first" and "second" etc. in the specification, claims and drawings of this application are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non - exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally further includes steps or units not listed, or optionally further includes other steps or units inherent to these processes, methods, products or devices.
[0037] Referring to "embodiment" herein means that the specific features, structures or characteristics described in connection with the embodiment can be included in at least one embodiment of this application. The phrase appears in various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.
[0038] Embodiment 1
[0039] Refer to Figure 2 , Figure 2 It is a schematic diagram of the connection relationship of a constant - current discharge circuit provided in an embodiment of the present invention. The constant - current discharge circuit provided in the embodiment of the present invention is applicable to a Buck - type power converter, and the Buck - type power converter includes a first inductor L1 and a first capacitor C1; the constant - current discharge circuit includes: a first resistor R1, a second resistor R2, a third resistor R3, a first MOS transistor Q3 and a first triode Q4;
[0040] The first end of the first resistor R1 is connected to the first end of the first inductor L1 and the first end of the first capacitor C1;
[0041] The second terminal of the first resistor R1 is connected to the source of the first MOS transistor Q3;
[0042] The gate of the first MOS transistor Q3 is connected to the first terminal of the second resistor R2 and the collector of the first triode Q4;
[0043] The second terminal of the second resistor R2 is connected to the host computer (not shown in the figure); wherein, the host computer is used to send a level signal to the first MOS transistor Q3;
[0044] The drain of the first MOS transistor Q3 is connected to the first terminal of the third resistor R3 and the base of the first triode Q4;
[0045] The second terminal of the third resistor R3 and the emitter of the first triode Q4 are connected to the second terminal of the first capacitor C1.
[0046] In the embodiment of the present invention, the circuit structure of a conventional Buck type power converter in the art is used for illustration. This Buck type power converter uses four MOSFETs to replace diodes as rectifiers. It should be noted that this Buck type power converter is only used for illustration and does not limit the application scenario of a constant current discharge circuit provided by the embodiment of the present invention. The embodiment of the present invention constructs a constant current discharge circuit through the first resistor, the second resistor, the third resistor, the first MOS transistor and the first triode to replace the discharge scheme in the prior art that uses a discharge resistor as a dead load to be connected to the power supply. Among them, the host computer refers to an electronic device or computer software corresponding to the lower computer (such as a sensor, an actuator or a controller). Usually, the host computer is used to monitor, control, configure and manage the work of the lower computer. It can communicate with the lower computer through a network or a data bus, collect the data collected by the sensors of the lower computer, and send control commands or configuration information to the lower computer. In the embodiment of the present invention, the level signal sent by the host computer is used to switch the on / off state of the first MOS transistor, so as to control whether the constant current discharge circuit discharges. That is, it acts as a discharge switch, and the magnitude of the discharge current is determined by the resistance value of the third resistor R3 and the voltage between the base and the emitter of the first triode Q4. In the embodiment of the present invention, when the power supply is in a state before soft start or other states that turn off the power supply, the host computer sends a high level signal to the first MOS transistor Q3 through the second resistor R2 to turn on the first MOS transistor Q3. At this time, the electric energy in the first capacitor C1 quickly discharges through the first resistor R1, the first MOS transistor Q3 and the third resistor R3. The third resistor R3 and the first triode Q4 form a current limiting circuit to avoid damage to the first resistor R1 and the third resistor R3 caused by excessive flowing current. When the power supply enters the soft start state, the host computer sends a low level signal to the first MOS transistor Q3 through the second resistor R2 to turn off the first MOS transistor Q3.
[0047] In one embodiment, the first MOS transistor Q3 is an NMOS transistor, and the first triode Q4 is an NPN transistor.
[0048] In one embodiment, the constant current discharge circuit further includes a second capacitor, specifically: the first end of the second capacitor C2 is connected to the gate of the first MOS transistor Q3 and the first end of the second resistor R2; the second end of the second capacitor C2 is connected to the emitter of the first triode Q4, the second end of the third resistor R3, and the second end of the first capacitor C1.
[0049] Connecting a second resistor at the gate of the first MOS transistor Q3 and the collector of the first triode Q4 can limit the current between the gate and the collector, which is crucial for controlling the constant current discharge process. It ensures that the current change of the first capacitor C1 during charging and discharging is controlled, helping to maintain a constant discharge characteristic. Through the combination of the second resistor R2 and the second capacitor C2, an RC circuit can be formed. The time constant of this RC circuit determines the charging and discharging speed of the capacitor, thereby affecting the time response characteristic of the entire constant current discharge process.
[0050] As an optimized solution of the embodiment of the present invention, in order to prevent more serious damage caused by the failure of the constant current discharge circuit, a constant current discharge circuit provided by the embodiment of the present invention further includes an output voltage detection module. See Figure 3 , Figure 3 which is a schematic diagram of the connection relationship of an output voltage detection module provided in an embodiment of the present invention. In one embodiment, the constant current discharge circuit further includes an output voltage detection module, specifically: the output voltage detection module includes a fourth resistor R5, a fifth resistor R6, and a differential amplifier IC1; the first end of the fourth resistor R5 is connected to the first end of the first capacitor C1, that is, connected to the negative output terminal of the power supply; the first end of the fifth resistor R6 is connected to the second end of the first capacitor C1, that is, connected to the positive output terminal of the power supply; the second end of the fourth resistor R5 is connected to the negative input terminal of the differential amplifier IC1; the second end of the fifth resistor R6 is connected to the positive input terminal of the differential amplifier IC1; the output terminal of the differential amplifier IC1 is connected to the upper computer.
[0051] In the embodiment of the present invention, the output current of the power supply is detected by means of differential sampling. The output terminal of the differential sampler IC1 is connected to the upper computer, and the upper computer analyzes and discriminates the output voltage of the power supply. If the output voltage is higher than the preset voltage of soft start (preferably, generally 2V), the startup is prohibited.
[0052] In one embodiment, the output voltage detection module further includes a sixth resistor R4, a seventh resistor R7, a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, and a sixth capacitor C6, specifically: the first end of the sixth resistor R4 and the first end of the third capacitor C3 are connected to the negative input terminal of the differential amplifier IC1; the second end of the sixth resistor R4 and the second end of the third capacitor C3 are connected to the output terminal of the differential amplifier IC1; the first end of the fourth capacitor C4 is connected to the negative input terminal of the differential amplifier IC1, the first end of the third capacitor C3, and the first end of the fourth resistor R5; the second end of the fourth capacitor C4 is connected to the negative input terminal of the differential amplifier IC1, the first end of the sixth capacitor C6, and the first end of the seventh resistor R7; the first end of the fifth capacitor C5 is connected to the positive input terminal of the differential amplifier IC1; the second end of the fourth capacitor C4, the second end of the fifth capacitor C5, the second end of the sixth capacitor C6, the second end of the seventh resistor R7, and the output terminal of the differential amplifier IC1 are grounded.
[0053] In the embodiment of the present invention, a resistor is provided at the input terminal of the differential amplifier to match the input impedance of the input port of the differential amplifier, which can ensure the best signal transmission between the signal source and the amplifier. Further, a capacitor is provided to form an RC filter with the resistor, which is used to control the frequency response characteristics of the input signal, can effectively reduce the input impedance, and improve the matching between the signal source and the amplifier.
[0054] Further, as another optimization solution of the embodiment of the present invention, an electronic device is further provided, including the constant current discharge circuit as described above.
[0055] The embodiment of the present invention provides a constant current discharge circuit, which realizes precise discharge control of the output capacitor through the first MOS transistor and the first triode. Compared with a simple resistor dead load, it can adjust the discharge rate according to the level signal sent by the host computer, so as to realize a more accurate and controllable capacitor discharge process. The host computer can control the gate voltage of the first MOS transistor in real time, so as to adjust the discharge current, so that the capacitor can discharge more quickly when needed, or maintain a constant discharge characteristic when the load changes. This dynamic response performance optimization is not available in traditional dead loads. And the power supply does not need to provide energy for the constant current discharge current to maintain the stability of the circuit, will not generate additional standby power consumption, and will not reduce the power supply efficiency. The constant current discharge circuit only discharges the capacitor when the power supply is in the off state or before soft start, and will not affect the device when the power supply is in the working state. The constant current discharge circuit can provide more reliable device protection.
[0056] The above are only the preferred embodiments of the present utility model. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present utility model, several improvements and substitutions can be made, and these improvements and substitutions should also be regarded as the protection scope of the present utility model.
Claims
1. A constant current discharge circuit, characterized in that: Applicable to a Buck type power converter, the Buck type power converter comprises a first inductor and a first capacitor; the constant current discharge circuit comprises: a first resistor, a second resistor, a third resistor, a first MOS tube and a first transistor; The first end of the first resistor is connected to the first end of the first inductor and the first end of the first capacitor; The second end of the first resistor is connected to the source of the first MOS tube; The gate of the first MOS tube is connected to the first end of the second resistor and the collector of the first transistor; The second end of the second resistor is connected to a host computer; wherein the host computer is used to send a level signal to the first MOS tube; The drain of the first MOS tube is connected to the first end of the third resistor and the base of the first transistor; The second end of the third resistor and the emitter of the first transistor are connected to the second end of the first capacitor.
2. A constant current discharge circuit according to claim 1, characterized in that: The constant current discharge circuit further includes a second capacitor, specifically: A first end of the second capacitor is connected to the gate of the first MOS transistor and a first end of the second resistor; The second end of the second capacitor is connected to the emitter of the first transistor, the second end of the third resistor, and the second end of the first capacitor.
3. A constant current discharge circuit according to claim 1, characterized in that: The first MOS tube is an NMOS tube, and the first transistor is an NPN tube.
4. A constant current discharge circuit according to claim 1, characterized in that: The constant current discharge circuit also includes an output voltage detection module, specifically: The output voltage detection module includes a fourth resistor, a fifth resistor and a differential amplifier; The first end of the fourth resistor is connected to the first end of the first capacitor; The first end of the fifth resistor is connected to the second end of the first capacitor; The second end of the fourth resistor is connected to the negative input terminal of the differential amplifier; The second end of the fifth resistor is connected to the positive input end of the differential amplifier; The output end of the differential amplifier is connected to the host computer.
5. A constant current discharge circuit according to claim 4, characterized in that: The output voltage detection module further includes a sixth resistor, a seventh resistor, a third capacitor, a fourth capacitor, a fifth capacitor and a sixth capacitor, specifically: The first end of the sixth resistor and the first end of the third capacitor are connected to the negative input terminal of the differential amplifier; The second end of the sixth resistor and the second end of the third capacitor are connected to the output end of the differential amplifier; The first end of the fourth capacitor is connected to the negative input end of the differential amplifier, the first end of the third capacitor, and the first end of the fourth resistor; The second end of the fourth capacitor is connected to the negative input end of the differential amplifier, the first end of the sixth capacitor, and the first end of the seventh resistor; The first end of the fifth capacitor is connected to the positive input end of the differential amplifier; The second end of the fourth capacitor, the second end of the fifth capacitor, the second end of the sixth capacitor, the second end of the seventh resistor and the output end of the differential amplifier are grounded.
6. An electronic device, characterized in that: It comprises a constant current discharge circuit as described in any one of claims 1 to 5.