A dimming power supply
The short-circuit protection mechanism triggered by the voltage sampling circuit solves the problem of mistaken triggering of existing dimming power supplies under high input surge current conditions, and achieves fast response and sensitive protection, avoiding the damage to the power control tube and afterglow problems.
Patent Information
- Application Number
- CN202411171079.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-26
- Publication Date
- 2024-12-27
- Estimated Expiration
- 2044-08-26
AI Technical Summary
Existing dimming power supplies are prone to fail to output normally due to falsely triggering short circuit protection under lamp loads with high input surge current, and reducing the response speed of the protection circuit will increase the risk of power device damage.
The voltage sampling circuit triggers the short circuit protection through the voltage sampling circuit, and directly inputs to the control end of the first switching device through the voltage sampling circuit, so that it closes and pulls the driving signal low or cuts off the gate of the power control tube to avoid mistriggering, and passes through the second switch. The device disconnects the load from the common ground to prevent loop formation.
It realizes fast and sensitive short-circuit protection under high input surge current conditions, avoiding breakdown damage to the power control tube, and avoiding the afterglow problem after the short-circuit protection is accidentally triggered.
Smart Images
Figure CN118695451B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of power supplies, and in particular to a dimming power supply. Background Art
[0002] Existing dimming power supplies generally adjust the power output to achieve the purpose of dimming or color adjustment by controlling the switching frequency of the power MOS tube connected in series at the output end. When the output is short-circuited, the power MOS tube may be broken down and damaged due to the excessive power output instantaneously or continuously during the short circuit. Therefore, in order to avoid the above phenomenon, the dimming power supplies currently on the market are equipped with a short-circuit protection circuit to protect the power device from being damaged when a short circuit occurs.
[0003] At present, the short-circuit protection scheme on the market is to trigger the short-circuit protection by connecting a sampling resistor in series at the output end and collecting the output current. However, this protection method is only applicable to resistive load lamps or lamps with low input surge current. When connected to capacitive or inductive load lamps with high input surge current, it is very easy to mistakenly trigger the short-circuit protection due to the instantaneous surge current, resulting in the power supply being unable to output normally. If the current sampling time is increased or the reaction speed of the protection circuit is reduced in order to avoid the above problems, the risk of damage to the power device will increase. For this reason, it is necessary to design a dimming power supply suitable for lamp loads with high input surge current. Summary of the invention
[0004] In order to overcome the deficiencies of the prior art, the present invention aims to provide a dimming power supply which can avoid the problem that the short-circuit protection is easily falsely triggered by the surge current when a lamp load with a high input surge current is connected without reducing the sensitivity of the short-circuit protection.
[0005] To solve the above problems, the technical solution adopted by the present invention is as follows: a dimming power supply, comprising: a power supply circuit, an output end of which is connected to a load; a power control tube, which is connected in series between the power supply circuit and the negative electrode of the load; a control circuit, an input end of which is connected to the output end of the power supply circuit; a drive circuit, an input end of which is connected to the output end of the control circuit, and an output end of which is connected to the gate of the power control tube; a short-circuit protection circuit, comprising a voltage sampling circuit and a first switching device, the input end of the voltage sampling circuit is connected to the negative electrode of the load, the output end of the voltage sampling circuit is connected to the control end of the first switching device, the first switching device pulls down or cuts off the signal input to the gate of the power control tube when it is turned on, a second switching device is connected in series in the voltage sampling circuit, the control end of the second switching device is connected to the gate of the power control tube, and the second switching device is turned off when the power control tube is turned off.
[0006] Compared with the prior art, the beneficial effect of the present invention is that the output voltage is collected by the voltage sampling circuit to trigger the short-circuit protection, which will not be affected by the surge current of the power supply output, so that when the lamp load with high input surge current is connected, it will not be falsely triggered by the high surge current at the moment of power-on and cannot output normally. When a short circuit occurs between the positive and negative poles of the power supply output, the voltage output by the power supply circuit will be directly input to the control end of the first switch device through the voltage sampling circuit, so that the first switch device is closed, thereby immediately pulling down or cutting off the signal output by the drive circuit to the gate of the power control tube, so that the power control tube is turned off, thereby avoiding the power control tube from being broken down and damaged during a short circuit, and the short-circuit protection reacts quickly and sensitively. After the power control tube is turned off, the second switch device is also turned off, thereby disconnecting the connection between the load and the common ground, so as to avoid the power supply circuit and the lamp load forming a loop through the voltage sampling circuit when the power control tube is turned off, so that the lamp produces afterglow.
[0007] In the dimming power supply mentioned above, the first switch device is connected in series between the input end of the driving circuit and the common ground, or the first switch device is connected in series between the output end of the driving circuit and the common ground.
[0008] In the above-mentioned dimming power supply, the driving circuit includes a PWM signal amplifying circuit and a driving control tube, the input end of the PWM signal amplifying circuit is connected to the output end of the control circuit, the output end of the PWM signal amplifying circuit is connected to the gate of the power control tube through the source and drain of the driving control tube, the gate of the driving control tube is connected to the working voltage, and the gate of the driving control tube is connected to the common ground through the first switching device.
[0009] In the above-mentioned dimming power supply, the voltage sampling circuit includes multiple voltage-dividing resistors, one end of the voltage-dividing resistor R4 is connected to the negative electrode of the load, the other end of the voltage-dividing resistor R4 is connected to the drain of the second switching device, the source of the second switching device is grounded through the voltage-dividing resistor R2, the gate of the first switching device is connected to the end of the voltage-dividing resistor R2 facing away from the common ground, the source of the first switching device is connected to the common ground, and the drain of the first switching device is connected to the input end of the drive circuit, the output end of the drive circuit or the gate of the drive control tube.
[0010] In the dimming power supply mentioned above, the control end of the second switch device is connected to the gate of the power control tube through an elimination control circuit.
[0011] In the dimming power supply mentioned above, the elimination control circuit includes a plurality of resistors, the gate of the power control tube is connected to the control end of the second switch device through a resistor R5, and the control end of the second switch device is connected to a common ground through a resistor R6.
[0012] In the dimming power supply mentioned above, the elimination control circuit includes a plurality of resistors and transistors, the control end of the second switch device is connected to the common ground through the resistor R6, the control end of the second switch device is connected to the working voltage through the resistor R5, the collector and emitter of the transistor Q4 and the resistor R7, the end of the resistor R7 facing away from the working voltage is connected to the gate of the transistor Q4 through the resistor R8, the gate of the transistor Q4 is connected to the common ground through the drain and source of the MOS tube Q5, the gate of the MOS tube Q5 is connected to the gate of the power control tube through the resistor R10, and the end of the resistor R10 facing away from the power control tube is connected to the common ground through the resistor R9.
[0013] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Figure 1 FIG. 4 is a principle block diagram of a dimming power supply according to a first embodiment of the present invention.
[0015] Figure 2 FIG. 4 is a circuit diagram of a dimming power supply according to a first embodiment of the present invention.
[0016] Figure 3 FIG. 4 is a circuit diagram of a dimming power supply according to a second embodiment of the present invention.
[0017] Figure 4 FIG. 4 is a circuit diagram of a dimming power supply according to a third embodiment of the present invention. DETAILED DESCRIPTION
[0018] The embodiments of the present invention are described in detail below. Figure 1An embodiment of the present invention provides a dimming power supply, including a power supply circuit, a power control tube Q3, a control circuit, a drive circuit and a short-circuit protection circuit. The input end of the power supply circuit is connected to the input voltage, the output end is connected to the lamp load, and the power control tube Q3 is connected in series between the output end of the power supply circuit and the negative pole of the lamp load. The power supply circuit can be an AC / DC circuit or a DC / DC circuit, which converts the input mains power into direct current and an operating voltage, or converts the input direct current into an operating voltage to drive the load and the control circuit, the drive circuit, etc. to work. The control circuit is used to generate a control signal of the power control tube Q3 according to the dimming control signal, and the drive circuit is used to convert the control signal into a drive signal for driving the power control tube Q3 to operate, so as to control the switching frequency of the power control tube Q3 and adjust the electric power output to the load. The short-circuit protection circuit includes a voltage sampling circuit and a first switch device. The control end of the first switch device is connected to the negative pole of the load through the voltage sampling circuit. The voltage sampling circuit converts the voltage after the load voltage division into an electrical signal to drive the first switch device to operate. When a short circuit occurs between the positive and negative poles of the power supply, the voltage output by the power supply circuit to the load is directly applied to the voltage sampling circuit, so that the voltage output by the voltage sampling circuit to the control end of the first switch device increases, which is higher than the threshold voltage required for the operation of the first switch device, so that the first switch device operates, and the signal output by the drive circuit to the gate of the power control tube Q3 is pulled down or cut off, so that the power control tube Q3 is turned off, and the power control tube Q3 is prevented from being broken down and burned by the high-power current when the power control tube Q3 is short-circuited. A second switch device is connected in series in the voltage sampling circuit, and the control end of the second switch device is connected to the gate of the power control tube Q3, and is turned on or off synchronously with the power control tube Q3. When the power control tube Q3 is turned off, the voltage sampling circuit is isolated from the load to avoid the power supply circuit and the load being connected to the common ground through the voltage sampling circuit to form a loop, resulting in afterglow of the lamp load.
[0019] The dimming power supply of the embodiment of the present invention directly uses a voltage sampling circuit to collect the voltage value of the voltage output from the power supply circuit to the load after the voltage is divided by the load to detect whether the power supply output is short-circuited, thereby avoiding the problem that the current sampling method used in the traditional solution is easily triggered by a large surge current, and ensuring that the dimming power supply can output normally when driving a capacitive or inductive lamp load that is prone to generate a high input surge current. When the power output is short-circuited, the voltage output by the power supply circuit will be directly loaded on the voltage sampling circuit, so that the output of the voltage sampling circuit will quickly rise to above the threshold value of the first switch device, and the first switch device will be driven to pull down or cut off the control signal output by the drive circuit to the power control tube Q3, so that the power control tube Q3 is quickly turned off, and the short-circuit protection response speed is fast. The dimming power supply of the embodiment of the present invention can avoid the short-circuit protection from being falsely triggered by the surge current without affecting the corresponding sensitivity of the short-circuit protection, and at the same time, by connecting the second switch device in series in the voltage sampling circuit, the afterglow problem after the short-circuit protection is triggered introduced by the additional voltage sampling circuit is solved.
[0020] It can be understood that the voltage sampling circuit can be a voltage conversion circuit such as a voltage divider circuit or a voltage stabilizing circuit, and the first switch device can control the power control tube Q3 to be turned off in the event of a short circuit by lowering or cutting off the control signal input from the control circuit to the drive circuit, or directly lowering or cutting off the drive signal output by the drive circuit. The first switch device and the second switch device can be controllable semiconductor elements such as triodes and MOS tubes. The specific structure of the short-circuit protection circuit needs to be determined according to the power range of the actual power supply circuit and the load, as well as the type of the selected first switch device and the second switch device. The control circuit preferably uses a PWM control signal to control the conduction and shutdown of the power control tube Q3, and the drive circuit is a corresponding PWM signal amplification circuit.
[0021] Example 1: Reference Figure 2In this embodiment, both the first switch device and the second switch device are NMOS tubes, and the voltage sampling circuit is a voltage dividing circuit composed of voltage dividing resistors R2 and R4. One end of the voltage dividing resistor R4 is connected to the negative electrode of the load, and the other end is connected to the drain of the second switch device Q2. The source of the second switch device Q2 is connected to the common ground through the voltage dividing resistor R2. The voltage dividing resistor R4 also serves as a voltage dividing resistor in the voltage sampling circuit and also as a current limiting resistor of the second switch device Q2. The drain of the first switch device Q1 is connected to the input end of the PWM signal amplifier circuit, the source is connected to the common ground, and the gate is connected to the end of the voltage dividing resistor R2 facing away from the common ground. The gate of the second switch device Q2 is connected to the output end of the PWM signal amplifier circuit through a resistor R5, and is connected to the common ground through a resistor R6. When the dimming power supply is working normally, the driving signal output by the PWM signal amplifier circuit is converted by the elimination control circuit composed of resistors R5 and R6 into a driving voltage that drives the conduction of the second switch device Q2, so that the voltage output by the power supply circuit can flow into the voltage sampling circuit through the load. When the power output is short-circuited, the voltage output by the power circuit is directly input into the voltage sampling circuit, so that the voltage input to the gate of the first switch device Q1 after being divided by the voltage-dividing resistor R4, the second switch device Q2 and the voltage-dividing resistor R2 is increased, and is higher than the voltage between the gate and the source of the first switch device Q1 and higher than its conduction threshold, so that the first switch device Q1 is turned on, so that the PWM control signal output by the control circuit to the PWM signal amplification circuit is pulled down to a low level, so that the PWM signal amplification circuit outputs a low level, so that the power control tube Q3 is turned off, forming a short-circuit protection for the power control tube Q3. At the same time, because the driving signal output by the PWM signal amplification circuit becomes a low level, the voltage between the gate and the source of the second switch device Q2 is reduced to below its conduction threshold, and the second switch device Q2 is turned off, thereby cutting off the connection between the load and the common ground through the voltage sampling circuit, preventing the load from connecting to the common ground through the voltage sampling circuit after the power control tube Q3 is turned off to form a loop, thereby preventing the lamp load from generating afterglow after the short-circuit protection is triggered.
[0022] In this embodiment, the junction capacitance of the power control tube Q3 is greater than the sum of the junction capacitances of the first switch device Q1 and the second switch device Q2, so that the conduction time of the power control tube Q3 is longer than the sum of the conduction time of the second switch device Q2 and the first switch device Q1, so that after the second switch device Q2 is turned off, the first switch device Q1 is turned off, and the PWM signal amplification circuit outputs normally again. If the power output short circuit is not eliminated, the first switch device Q1 will also be turned on after the first switch device Q2 is turned on, so that the power control tube Q3 is turned off again. Since the conduction time of the power control tube Q3 is longer than the sum of the conduction time of the first switch device Q1 and the second switch device Q2, when the power output short circuit is not eliminated, the power control tube Q3 will switch continuously, and will be turned off when it is not fully turned on during each opening process, so as to avoid damage to the power control tube Q3. When the power output short circuit is eliminated, the dimming power supply will automatically resume normal operation.
[0023] Example 2: Reference Figure 3 In some embodiments, the driving signal output by the PWM signal amplifying circuit cannot directly drive the power control tube Q3, and the output end of the PWM signal amplifying circuit needs to be connected to the power control tube Q3 through the driving control tube Q4. The gate of the driving control tube Q4 is connected to the working voltage through the resistor R7, and is connected to the drain of the first switch device Q1. The source of the driving control tube Q4 is connected to the gate of the power control tube Q3, and the drain is connected to the output end of the PWM signal amplifying circuit. During normal operation, the first switch device Q1 is turned off, and the driving control tube Q4 is turned on under the drive of the working voltage. The driving signal output by the PWM signal amplifying circuit can be output to the gates of the power control tube Q3 and the second switch device Q2, so that the two are turned on; when the power output is short-circuited, the first switch device Q1 is turned on, so that the gate of the driving control tube Q4 is connected to the common ground and turned off, thereby turning off the power control tube Q3 and the second switch device Q2, protecting the power control tube Q3 and eliminating the afterglow. In this embodiment, in order to keep the power control tube Q3 turned off or repeatedly turned off when not fully turned on when short-circuited, the turn-on time of the drive control tube Q4 needs to be greater than the sum of the turn-on times of the first switch device Q1 and the second switch device Q2, or the turn-on time of the power control tube Q3 needs to be greater than the sum of the turn-on times of the first switch device Q1, the second switch device Q2 and the drive control tube Q4.
[0024] Example 3: Reference Figure 4In some embodiments, the driving signal output by the PWM signal amplifying circuit cannot directly drive the second switch device Q2 to turn on. In addition to the resistors R5 and R6, the elimination control circuit of the second switch device Q2 also includes a transistor Q4 and a MOS transistor Q5. The gate of the MOS transistor Q5 is connected to the output end of the PWM signal amplifying circuit through a resistor R10, and is connected to the common ground through a resistor R9, the source is grounded, and the drain is connected to the gate of the transistor Q4. The emitter of the transistor Q4 is connected to the working voltage through a resistor R7, the collector is connected to the gate of the second switch device Q2 through a resistor R5, and the resistor R8 is connected in parallel between the gate and the emitter of the transistor Q4. The gate of the second switch device Q2 is connected to the common ground through a resistor R6. During normal operation, the driving signal output by the PWM signal amplifying circuit drives the MOS tube Q5 to turn on, so that the triode Q4 is turned on, and the working voltage is input to the gate of the second switch device Q2 after being divided by the resistors R5, R6 and R7, so that the second switch device Q2 is turned on; when a short circuit occurs in the power output, the first switch device Q1 is turned off, so that the PWM signal amplifying circuit outputs a low level, the MOS tube Q5 and the triode Q4 are disconnected, so that the gate voltage of the second switch device Q2 is reduced, so that the second switch device Q2 is turned off, thereby eliminating the afterglow of the lamp load after the short circuit protection is triggered.
[0025] It should be noted that in the description of the present invention, if there are any orientation descriptions, such as up, down, front, back, left, right, etc., the orientations or positional relationships indicated are all based on the orientations or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed or operated in a specific orientation, and cannot be understood as a limitation on the present invention.
[0026] In the description of the present invention, "several" means one or more, "more" means two or more, "greater than", "less than", "exceed" etc. are understood to exclude the number itself, and "above", "below", "within" etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used to distinguish the technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.
[0027] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.
[0028] The above-mentioned embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.
Claims
1. A dimming power supply, characterized in that: include: A power supply circuit, wherein the output end is connected to a load; A power control tube is connected in series between the power supply circuit and the negative electrode of the load, the source of the power control tube is directly grounded, and the drain of the power control tube is connected to the negative electrode of the load; A control circuit, an input end of which is connected to an output end of the power supply circuit; A driving circuit, wherein the input end is connected to the output end of the control circuit, and the output end is connected to the gate of the power control tube; A short circuit protection circuit comprises a voltage sampling circuit and a first switch device, wherein the input end of the voltage sampling circuit is connected to the negative electrode of the load, the input end of the voltage sampling circuit is directly connected to the drain of the power control tube, the output end of the voltage sampling circuit is connected to the control end of the first switch device, the first switch device pulls down or cuts off the signal input to the gate of the power control tube when it is turned on, a second switch device is connected in series in the voltage sampling circuit, the control end of the second switch device is connected to the gate of the power control tube, and the second switch device is turned off when the power control tube is turned off; The voltage sampling circuit also includes a plurality of voltage-dividing resistors, one end of the voltage-dividing resistor R4 is connected to the negative electrode of the load, the other end of the voltage-dividing resistor R4 is connected to the drain of the second switch device, the source of the second switch device is grounded through the voltage-dividing resistor R2, the gate of the first switch device is connected to the end of the voltage-dividing resistor R2 facing away from the common ground, the source of the first switch device is connected to the common ground, and the drain of the first switch device is connected to the input end of the drive circuit, the output end of the drive circuit or the gate of the drive control tube of the drive circuit; The first switch device is connected in series between the input end of the drive circuit and the common ground, or the first switch device is connected in series between the output end of the drive circuit and the common ground.
2. The dimming power supply according to claim 1, characterized in that: The driving circuit includes a PWM signal amplifying circuit and a driving control tube, the input end of the PWM signal amplifying circuit is connected to the output end of the control circuit, the output end of the PWM signal amplifying circuit is connected to the gate of the power control tube through the source and drain of the driving control tube, the gate of the driving control tube is connected to the working voltage, and the gate of the driving control tube is connected to the common ground through the first switching device.
3. The dimming power supply according to claim 1, characterized in that: The control end of the second switch device is connected to the gate of the power control tube through an elimination control circuit.
4. The dimming power supply according to claim 3, characterized in that: The elimination control circuit includes a plurality of resistors. The gate of the power control tube is connected to the control end of the second switch device through a resistor R5. The control end of the second switch device is connected to a common ground through a resistor R6.
5. The dimming power supply according to claim 3, characterized in that: The elimination control circuit includes a plurality of resistors and transistors. The control end of the second switch device is connected to the common ground through a resistor R6. The control end of the second switch device is connected to the working voltage through a resistor R5, the collector and emitter of a transistor Q4, and a resistor R7. An end of the resistor R7 facing away from the working voltage is connected to the gate of the transistor Q4 through a resistor R8. The gate of the transistor Q4 is connected to the common ground through the drain and source of the MOS tube Q5. The gate of the MOS tube Q5 is connected to the gate of the power control tube through a resistor R10. An end of the resistor R10 facing away from the power control tube is connected to the common ground through a resistor R9.