Dimming circuit

Abstract

The utility model relates to the technical field of dimming power supplies, and discloses a dimming circuit, which comprises a control circuit, a dimming signal receiving circuit, a rectifying circuit, a DC / DC circuit and an overcurrent detection circuit. The control circuit is used for outputting dimming driving signals according to dimming control voltage, the input end of the dimming signal receiving circuit is connected with dimming signals, and the output end of the dimming signal receiving circuit is connected with the control circuit. The input end of the rectifying circuit is connected with a mains supply, the input end of the DC / DC circuit is connected with the output end of the rectifying circuit, the control end of the DC / DC circuit is connected with the output end of the control circuit, the output end of the DC / DC circuit is connected with a light source, a protection triode is arranged between the grid electrode of each driving MOS tube and the ground, and the collector electrode of the protection triode is connected with the grid electrode of the corresponding driving MOS tube. The emitter of the protection triode is grounded; the input end of the over-current detection circuit is connected with the output end of the DC / DC circuit, and the output end of the over-current detection circuit is connected with the gate pole of the protection triode. According to the dimming circuit, the MOS tube in the DC / DC circuit is protected during short circuit, and the dimming circuit can be automatically recovered after abnormities are eliminated.

Description

Technical Field

[0001] The utility model relates to the technical field of dimming power supplies, in particular to a dimming circuit. Background Art

[0002] As people's living standards continue to improve, LED light sources are increasingly becoming the preferred choice for indoor and outdoor lighting. LED light sources can be adjusted in brightness and color temperature using dimming circuits to meet diverse lighting needs. Existing dimming circuits often disconnect the dimming circuit from the mains when a short circuit is detected, protecting the light source. However, the MOS transistors in the DC / DC circuit within the dimming circuit may still be damaged by the high current during a short circuit, making it impossible to protect the high-power MOS transistors in the dimming circuit. Furthermore, short-circuit protection achieved by disconnecting the mains requires restarting the dimming circuit to recover, and does not automatically recover. Utility Model Content

[0003] In order to overcome the deficiencies of the prior art, the present invention aims to provide a dimming circuit that can promptly lower the gate voltage of a MOS tube in a DC / DC circuit when a short circuit occurs, thereby preventing the MOS tube from being broken down by a large current.

[0004] To solve the above-mentioned problem, the technical solution adopted by the present invention is as follows: a dimming circuit, comprising: a control circuit, configured to output a dimming drive signal according to a dimming control voltage; a dimming signal receiving circuit, having an input end connected to the dimming signal and an output end connected to the control circuit, configured to receive an external dimming signal and convert the dimming signal into a dimming control voltage recognizable by the control circuit; a rectifier circuit, having an input end connected to the mains power supply and configured to convert alternating current (AC) into direct current (DC); a DC / DC circuit, having an input end connected to the output end of the rectifier circuit, a control end connected to the output end of the control circuit, and an output end connected to a light source, configured to convert the DC output of the rectifier circuit into DC matching the dimming drive signal, wherein a protection transistor is provided between the gate of each driving MOS transistor and ground, the collector of the protection transistor being connected to the gate of the corresponding driving MOS transistor, and the emitter of the protection transistor being grounded; and an overcurrent detection circuit, having an input end connected to the output end of the DC / DC circuit and an output end connected to the gate of the protection transistor, configured to sample the current output from the DC / DC circuit to the light source.

[0005] Compared to the prior art, the present invention has the following beneficial effects: by disposing a protection transistor between the gate and ground of each driver MOS transistor in the DC / DC circuit, and detecting whether a short circuit exists through an overcurrent detection circuit, when the overcurrent circuit detects an excessive short-circuit current, the protection transistor turns on, thereby grounding the gate of the driver MOS transistor, thereby preventing the driver MOS transistor from breaking down during a short circuit. Furthermore, when the short circuit is eliminated, the voltage output by the overcurrent detection circuit to the gate of the protection transistor returns to normal, and the dimming drive signal output by the control circuit to the gate of the driver MOS transistor is not pulled low, allowing the control circuit to resume control of the driver MOS transistor. After the short-circuit protection is triggered, normal power supply to the light source can be automatically restored after the short circuit fault is removed, without restarting the entire dimming circuit.

[0006] The above-mentioned dimming circuit, the dimming signal receiving circuit includes a three-in-one dimming circuit and a thyristor dimming circuit, the input end of the three-in-one dimming circuit is connected to a 0-10V dimming signal, a PWM dimming signal or a 100K resistor dimming signal, the input end of the thyristor dimming circuit is electrically connected to the thyristor dimming signal, and the output end of the three-in-one dimming circuit and the output end of the thyristor dimming circuit are respectively connected to two independent input ends of the control circuit.

[0007] In the dimming circuit described above, the rectifier circuit includes an EMI rectifier circuit and a PFC power control circuit. The input end of the EMI rectifier circuit is connected to the mains, the output end of the EMI rectifier circuit is connected to the input end of the PFC power control circuit, and the output end of the PFC control circuit is connected to the input end of the DC / DC circuit.

[0008] In the dimming circuit described above, the PFC power control circuit includes a PFC control chip and its peripheral circuits, as well as a PFC power control circuit. The input end of the PFC power control circuit is connected to the input end of the EMI rectifier circuit, the control pin of the PFC control chip is connected to the control end of the PFC power control circuit, and the output end of the PFC power control circuit is connected to the feedback pin of the PFC control chip and the input end of the DC / DC circuit.

[0009] In the dimming circuit described above, the rectifier circuit further includes a startup auxiliary power supply circuit, a primary auxiliary power supply circuit, and a secondary auxiliary power supply circuit. The input end of the startup auxiliary power supply circuit is connected to the output end of the EMI rectifier circuit, the output end of the startup auxiliary power supply circuit is connected to the input end of the primary auxiliary power supply circuit, and the input end of the secondary auxiliary power supply circuit is connected to the output end of the DC / DC circuit. The startup auxiliary power supply circuit is used to assist in standby startup, the primary auxiliary power supply circuit is used to power various control chips in the circuit, and the secondary auxiliary power supply circuit is used to power various active components in the circuit.

[0010] In the dimming circuit described above, the startup auxiliary power supply circuit includes a power management chip and its peripheral circuits.

[0011] In the dimming circuit described above, both the primary auxiliary power supply circuit and the secondary auxiliary power supply circuit include power transistors and peripheral circuits thereof.

[0012] In the above-mentioned dimming circuit, the rectifier circuit also includes a dimming power supply circuit, the input end of the dimming power supply circuit is connected to the output end of the secondary auxiliary power supply circuit, and the dimming power supply circuit is used to provide a reference voltage.

[0013] The dimming circuit mentioned above, the dimming power supply circuit includes at least one voltage stabilizing chip and its peripheral circuits.

[0014] The above-mentioned dimming circuit, the DC / DC circuit includes a power control chip and its peripheral circuits and a DC / DC power circuit, the input end of the DC / DC power circuit is connected to the output end of the rectifier circuit, the output end of the DC / DC power circuit is connected to the light source, the input end of the DC / DC power circuit is connected to the control pin of the power control chip, and the control end of the DC / DC power circuit is connected to the output end of the control circuit.

[0015] The present invention will be described in further detail below with reference to the accompanying drawings and specific implementation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a functional block diagram of a dimming circuit according to an embodiment of the present utility model;

[0017] Figure 2 This is a schematic diagram of a DC / DC power circuit according to an embodiment of the present invention;

[0018] Figure 3 A schematic diagram of a control circuit according to an embodiment of the present invention;

[0019] Figure 4 This is a schematic diagram of a three-in-one dimming circuit according to an embodiment of the present invention;

[0020] Figure 5 This is a schematic diagram of a thyristor dimming circuit according to an embodiment of the present invention;

[0021] Figure 6 This is a schematic diagram of an EMI rectifier circuit according to an embodiment of the present invention;

[0022] Figure 7 This is a schematic diagram of the peripheral circuit of the PFC control chip according to an embodiment of the present utility model;

[0023] Figure 8 This is a schematic diagram of a PFC power control circuit according to an embodiment of the present utility model;

[0024] Figure 9 This is a schematic diagram of a startup auxiliary power supply circuit according to an embodiment of the present utility model;

[0025] Figure 10 This is a schematic diagram of a primary auxiliary power supply circuit according to an embodiment of the present invention;

[0026] Figure 11 This is a schematic diagram of a secondary auxiliary power supply circuit according to an embodiment of the present invention;

[0027] Figure 12 This is a schematic diagram of a dimming power supply circuit according to an embodiment of the present utility model;

[0028] Figure 13 This is a schematic diagram of the peripheral circuit of the power control chip according to an embodiment of the present utility model. DETAILED DESCRIPTION

[0029] The embodiments of the present invention are described in detail below. Figure 1An embodiment of the present invention provides a dimming circuit, comprising a control circuit, a dimming signal receiving circuit, a rectifier circuit, a DC / DC circuit, and an overcurrent detection circuit. The control circuit is configured to output a dimming drive signal to the DC / DC circuit based on a dimming control voltage. The dimming signal receiving circuit has an input connected to the dimming signal and an output connected to the control circuit. The circuit is configured to receive an external dimming signal, convert the dimming signal into a dimming control voltage recognizable by the control circuit, and then output the dimming control voltage to the control circuit. The rectifier circuit has an input connected to the mains power supply and an output connected to the input of the DC / DC circuit, configured to convert alternating current (AC) into direct current (DC). The output of the DC / DC circuit is connected to an LED light source, configured to convert the DC output from the rectifier circuit into DC that matches the dimming drive signal and transmit it to the light source, thereby matching the brightness of the LED light source with the dimming signal. A protection transistor is provided between the gate of each MOS driver transistor in the DC / DC circuit and ground. The collector of the protection transistor is connected to the gate of the corresponding MOS driver transistor, and the emitter of the protection transistor is grounded. The input end of the overcurrent detection circuit is connected to the output end of the DC / DC circuit, and the output end is connected to the gate of the protection transistor. It is used to sample the current output from the DC / DC circuit to the LED light source, and output the sampling result to the gate of the protection transistor to control the on and off of the protection transistor.

[0030] In the dimming circuit described above, when the overcurrent detection circuit detects that the current output by the DC / DC circuit is excessive, indicating a short circuit between the DC / DC circuit and the LED light source, the voltage output by the overcurrent detection circuit to the gate of the protection transistor causes the protection transistor to conduct, grounding the gate of the corresponding driver MOS transistor. This causes the dimming drive signal output by the control circuit to the gate of the driver MOS transistor to be pulled low, thereby shutting off the driver MOS transistor. This prevents the driver MOS transistor from being damaged by the high current breakdown caused by the short circuit, thereby protecting the driver MOS transistor. When the short circuit fault is eliminated, the voltage output by the overcurrent detection circuit to the gate of the protection transistor decreases, shutting off the protection transistor. The dimming drive signal output by the control circuit to the gate of the driver MOS transistor will not be pulled low, allowing the control circuit to resume control of the driver MOS transistor, and thus automatically restoring power to the LED light source without restarting the entire dimming circuit.

[0031] Reference Figure 3 In this embodiment, the control circuit includes a single-chip microcomputer U4 and its peripheral circuits, and the single-chip microcomputer adopts a single-chip microcomputer of the STM32 series. Figure 4 and Figure 5In order to make the dimming circuit adapt to a variety of different dimming signals and enhance the applicability of the dimming circuit, in this embodiment, the dimming signal receiving circuit includes a three-in-one dimming circuit and a thyristor dimming circuit. The input end of the three-in-one dimming circuit is connected to the 0-10V dimming signal, the PWM dimming signal or the 100K resistor dimming signal, and the output end is connected to the 7th pin of the single-chip microcomputer U4. The input end of the thyristor dimming circuit is connected to the thyristor dimming signal, and the output end is connected to the 9th pin of the single-chip microcomputer U4. The specific structures of the three-in-one dimming circuit and the thyristor dimming circuit are common knowledge in this field and are not described in detail here. Figure 4 and Figure 5 In this embodiment, the three-in-one dimming circuit uses transformer T3 as the isolation between the dimming signal and the output dimming control voltage, so that the output of the three-in-one dimming circuit is not limited by the optocoupler, further improving the applicability of the dimming circuit.

[0032] Reference Figures 6 to 8 In this embodiment, to further improve the reliability of the dimming circuit and enhance the quality of the power output to the LED light source, the rectifier circuit includes an EMI rectifier circuit and a PFC control circuit. These circuits reduce noise in the output power and correct distortion in the output current waveform, resulting in more stable lighting from the LED light source. In this embodiment, the PFC control circuit utilizes an active PFC circuit, including a PFC control chip U2, its peripheral circuits, and a PFC power control circuit. The input of the EMI rectifier circuit is connected to the mains power supply, while the output is connected to the input of the PFC power control circuit. PFC control chip U2 utilizes a power factor correction chip, model NCP1654. The output of the PFC power control circuit is connected to the input of the DC / DC circuit and to pin 6 of the PFC control chip U2 via resistors R205 and R206. Pin 8 of the PFC control chip is connected to the gate of MOSFET Q212 in the PFC power control circuit. By controlling the on / off state of MOSFET Q212, the power factor of the output power is adjusted.

[0033] Reference Figures 9 to 12 In this embodiment, in order to assist the startup of the PFC control circuit and the DC / DC circuit when power is turned on, and to provide the operating voltage and the reference voltage for logic judgment for each control chip and each active component in the dimming circuit, the rectifier circuit also includes a startup auxiliary power supply circuit, a primary auxiliary power supply circuit, a secondary auxiliary power supply circuit and a dimming power supply circuit. Figure 9 The startup auxiliary power supply circuit includes the power management chip U3 and its peripheral circuits. The power management chip U3 adopts the power management chip model VIPER12A. Pins 5-8 are connected to the output of the PFC power control circuit, and pins 1-2 are connected to the input of the primary auxiliary power supply circuit. Figure 10 and Figure 11 The primary auxiliary power supply circuit and the secondary auxiliary power supply circuit both include a power transistor and its peripheral circuits. By adjusting the parameters of the components in the peripheral circuits, the voltage output by the circuit is adjusted. The collector of the power transistor Q202 of the primary auxiliary power supply circuit is connected to the 5-8 pins of the power management chip U3, and the emitter transmits the operating voltage to some control chips, mainly the control chip in the PFC control circuit, through the diode D205 and the resistor R218. The collector of the power transistor Q203 of the secondary auxiliary power supply circuit is connected to the positive pole of the DC / DC circuit output, and the emitter supplies power to the active components in some circuits and the dimming power supply circuit. Figure 12 In this embodiment, the dimming power supply circuit includes two voltage regulator chips, U1 and U2. Voltage regulator chip U1 uses a 78L33 model, while voltage regulator chip U2 uses a 78L09 model. The input pin of voltage regulator chip U2 is connected to the output of the secondary auxiliary power supply circuit, converting the output power of the secondary auxiliary power supply circuit into a stable 9V voltage. The input pin of voltage regulator chip U1 is connected to the output pin of voltage regulator chip U2, converting the stable 9V voltage into a stable 3.3V voltage. The dimming power supply circuit provides 9V and 3.3V reference voltages for the entire dimming circuit, which serve as the basis for some logical judgments within the circuit.

[0034] Reference Figure 2 and Figure 13 In this embodiment, the DC / DC circuit includes a power control chip U6, its peripheral circuits, and a DC / DC power circuit. The power control chip U6 is model L6599AD. The gates of the two driver MOS transistors Q207 and Q9 in the DC / DC power circuit are connected to the control pin of the microcontroller U4 and are grounded through protection transistors Q206 and Q8, respectively. The gates of protection transistors Q206 and Q8 are connected to the I o_sesen signal output by the overcurrent detection circuit. The overcurrent detection circuit can be a sampling resistor connected between the DC / DC circuit and the LED light source, or a comparator circuit composed of an operational amplifier. The specific structure of this circuit is common knowledge in the art and will not be described in detail here.

[0035] It should be noted that in the description of the present invention, if there are any descriptions of directions, such as up, down, front, back, left, right, etc., the directions or positional relationships indicated are all based on the directions or positional relationships shown in the accompanying 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 direction, be constructed or operated in a specific direction, and cannot be understood as a limitation on the present invention.

[0036] In the description of this utility model, "several" means one or more, "more" means two or more, "greater than," "less than," and "exceed" are understood to exclude the number itself, while "above," "below," and "within" are understood to include the number itself. If there are descriptions of "first," "second," and so on, these are used solely to distinguish technical features and are not to be construed as indicating or implying relative importance, or implicitly specifying the number of the indicated technical features, or implicitly specifying the order of the indicated technical features.

[0037] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, and connecting 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.

[0038] 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 replacements made by technicians in this field on the basis of the present invention fall within the scope of protection required by the present invention.

Claims

1. A dimming circuit, characterized in that: include: A control circuit, used for outputting a dimming drive signal according to a dimming control voltage; A dimming signal receiving circuit, the input end of which is connected to the dimming signal, the output end of which is connected to the control circuit, and is used to receive an external dimming signal and convert the dimming signal into a dimming control voltage that can be recognized by the control circuit; A rectifier circuit, the input end of which is connected to the mains, is used to convert alternating current into direct current; A DC / DC circuit, wherein the input end is connected to the output end of the rectifier circuit, the control end is connected to the output end of the control circuit, and the output end is connected to the light source, and is used to convert the direct current output by the rectifier circuit into direct current matching the dimming drive signal, wherein a protection transistor is arranged between the gate of each driving MOS tube and the ground, the collector of the protection transistor is connected to the gate of the corresponding driving MOS tube, and the emitter of the protection transistor is grounded; An overcurrent detection circuit, whose input end is connected to the output end of the DC / DC circuit and whose output end is connected to the gate of the protection transistor, is used for sampling the current output from the DC / DC circuit to the light source.

2. The dimming circuit according to claim 1, characterized in that: The dimming signal receiving circuit includes a three-in-one dimming circuit and a thyristor dimming circuit. The input end of the three-in-one dimming circuit is connected to a 0-10V dimming signal, a PWM dimming signal or a 100K resistor dimming signal. The input end of the thyristor dimming circuit is electrically connected to the thyristor dimming signal. The output end of the three-in-one dimming circuit and the output end of the thyristor dimming circuit are respectively connected to two independent input ends of the control circuit.

3. The dimming circuit according to claim 1, characterized in that: The rectifier circuit includes an EMI rectifier circuit and a PFC control circuit, the input end of the EMI rectifier circuit is connected to the mains, the output end of the EMI rectifier circuit is connected to the input end of the PFC control circuit, and the output end of the PFC control circuit is connected to the input end of the DC / DC circuit.

4. The dimming circuit according to claim 3, characterized in that: The PFC control circuit includes a PFC control chip and its peripheral circuits, and a PFC power control circuit, wherein the input end of the PFC power control circuit is connected to the input end of the EMI rectifier circuit, the control pin of the PFC control chip is connected to the control end of the PFC power control circuit, and the output end of the PFC power control circuit is connected to the feedback pin of the PFC control chip and the input end of the DC / DC circuit.

5. The dimming circuit according to claim 3, characterized in that: The rectifier circuit also includes a startup auxiliary power supply circuit, a primary auxiliary power supply circuit and a secondary auxiliary power supply circuit. The input end of the startup auxiliary power supply circuit is connected to the output end of the EMI rectifier circuit, the output end of the startup auxiliary power supply circuit is connected to the input end of the primary auxiliary power supply circuit, the input end of the secondary auxiliary power supply circuit is connected to the output end of the DC / DC circuit, the startup auxiliary power supply circuit is used to assist standby startup, the primary auxiliary power supply circuit is used to power each control chip in the circuit, and the secondary auxiliary power supply circuit is used to power each active component in the circuit.

6. The dimming circuit according to claim 5, characterized in that: The startup auxiliary power supply circuit includes a power management chip and its peripheral circuits.

7. The dimming circuit according to claim 5, characterized in that: The primary auxiliary power supply circuit and the secondary auxiliary power supply circuit both include power transistors and peripheral circuits thereof.

8. The dimming circuit according to claim 5, characterized in that: The rectifier circuit also includes a dimming power supply circuit, an input end of the dimming power supply circuit is connected to the output end of the secondary auxiliary power supply circuit, and the dimming power supply circuit is used to provide a reference voltage.

9. The dimming circuit according to claim 8, characterized in that: The dimming power supply circuit includes at least one voltage stabilizing chip and its peripheral circuits.

10. The dimming circuit according to claim 1, characterized in that: The DC / DC circuit includes a power control chip and its peripheral circuits and a DC / DC power circuit, the input end of the DC / DC power circuit is connected to the output end of the rectifier circuit, the output end of the DC / DC power circuit is connected to the light source, the input end of the DC / DC power circuit is connected to the control pin of the power control chip, and the control end of the DC / DC power circuit is connected to the output end of the control circuit.

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