Silicon controlled rectifier circuit
By introducing a freewheeling control circuit into the SCR circuit, the operating state of the freewheeling circuit is automatically controlled according to the conduction angle, which solves the problems of high power consumption and heat generation of the freewheeling circuit, realizes efficient and reliable SCR driving, is compatible with PUSH function, and improves sampling accuracy and overall efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-12
- Publication Date
- 2026-04-21
AI Technical Summary
The freewheeling circuit in existing thyristor drive circuits has high power consumption, serious heat generation, and cannot be automatically turned off, resulting in low overall efficiency and incompatibility with dimming requirements for high input voltage and large conduction angle.
A thyristor circuit is designed, including a freewheeling control circuit. The sampling circuit detects the conduction angle of the thyristor dimmer. When the conduction angle is greater than or less than a certain threshold A, the working state of the freewheeling circuit is automatically controlled to maintain or turn off the freewheeling circuit, thereby reducing unnecessary power consumption and heat generation.
It effectively reduces the heat generation of the freewheeling circuit, reduces power consumption, improves the reliability and compatibility of the circuit, is compatible with the PUSH function, requires no additional auxiliary power supply, and improves sampling accuracy and overall efficiency.
Smart Images
Figure CN224154386U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of LED control, in particular to a thyristor circuit. Background Art
[0002] When we use thyristor dimming, when the load current of the thyristor is lower than the holding current of the thyristor, the thyristor will turn off, and at this time, the lamp will flash. To solve this problem, we usually add a thyristor freewheeling circuit to ensure that the minimum holding current of the thyristor will not be lower. However, the thyristor freewheeling circuit adopted in the existing thyristor drive circuit has high power consumption and large heat generation, reducing the overall efficiency of the drive. Because the existing circuit does not have the function of turning off the freewheeling circuit, when the input voltage is higher, the power consumption of the freewheeling circuit is greater, and the heat generation is also greater; and the existing thyristor freewheeling all adopts a linear constant current circuit. When the conduction angle of the thyristor is larger, the output voltage of the thyristor is also larger, and the power of the linear constant current circuit is also greater, and the heat generation is also greater. Content of the Utility Model
[0003] The purpose of the utility model is to at least solve one of the technical problems existing in the prior art, and provide a thyristor circuit.
[0004] The thyristor circuit according to an embodiment of the utility model includes: a thyristor dimmer Q1, a rectifier circuit, a sampling circuit, a freewheeling control circuit and a freewheeling circuit. The output voltage of the thyristor dimmer Q1 is rectified by the rectifier circuit and then input to the input end of the sampling circuit and the positive end of the freewheeling circuit respectively. The output end of the sampling circuit is electrically connected to the control end of the freewheeling control circuit. The positive end of the freewheeling control circuit is electrically connected to the control end of the freewheeling circuit. The negative end of the freewheeling circuit and the negative end of the freewheeling control circuit are grounded respectively; when the sampling circuit detects that the conduction angle of the thyristor dimmer Q1 ≥ A, the freewheeling control circuit controls the freewheeling circuit not to work, and when the sampling circuit detects that the conduction angle of the thyristor dimmer Q1 < A, the freewheeling control circuit controls the freewheeling circuit to work to maintain the conduction of the thyristor dimmer Q1.
[0005] The thyristor circuit according to the embodiment of the present utility model has at least the following beneficial effects: The circuit can automatically turn off the freewheeling circuit through the freewheeling control circuit. When the sampling circuit detects that the conduction angle of the thyristor dimmer Q1 is ≥ A (at this time, the thyristor load current is not lower than the holding current of the thyristor), the freewheeling control circuit controls the freewheeling circuit not to work. When the sampling circuit detects that the conduction angle of the thyristor dimmer Q1 is < A (at this time, the thyristor load current is lower than the holding current of the thyristor), the freewheeling control circuit controls the freewheeling circuit to work to maintain the conduction of the thyristor dimmer Q1. In the existing circuit, there is no function of turning off the freewheeling circuit. When the input voltage is higher, the power consumption of the freewheeling circuit is greater, and the heat generation is also greater. Therefore, this solution can effectively reduce the heat generation of the freewheeling circuit, reduce power consumption, and improve the reliability of the circuit.
[0006] The additional aspects and advantages of the present utility model will be partially given in the following description, partially become obvious from the following description, or be understood through the practice of the present utility model. BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The following further describes the specific embodiments of the present utility model with reference to the drawings;
[0008] Figure 1 is the schematic diagram of the thyristor circuit. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0009] This part will describe the specific embodiments of the present utility model in detail. The preferred embodiments of the present utility model are shown in the drawings. The role of the drawings is to supplement the description in the text part of the specification, enabling people to intuitively and vividly understand each technical feature and the overall technical solution of the present utility model, but it cannot be understood as a limitation on the protection scope of the present utility model.
[0010] In the description of the present utility model, it should be understood that for the orientation description, such as the orientation or positional relationship indicated by up, down, front, back, left, right, etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present utility model.
[0011] In the description of the present utility model, the meaning of several is one or more, the meaning of multiple is two or more, greater than, less than, exceeding, etc. are understood as not including the present number, above, below, within, etc. are understood as including the present number. If there is a description of first and second, it is only for the purpose of distinguishing technical features and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features or the sequence relationship of the indicated technical features.
[0012] Reference Figure 1 For a thyristor circuit of the present utility model, it includes: a thyristor dimmer Q1, a rectifier circuit 10, a sampling circuit 20, a freewheeling control circuit 30, and a freewheeling circuit 40. The output voltage of the thyristor dimmer Q1 is rectified by the rectifier circuit 10 and then input to the input terminal of the sampling circuit 20 and the positive terminal of the freewheeling circuit 40 respectively. The output terminal of the sampling circuit 20 is electrically connected to the control terminal of the freewheeling control circuit 30. The positive terminal of the freewheeling control circuit 30 is electrically connected to the control terminal of the freewheeling circuit 40. The negative terminal of the freewheeling circuit 40 and the negative terminal of the freewheeling control circuit 30 are grounded respectively; when the sampling circuit 20 detects that the conduction angle of the thyristor dimmer Q1 ≥ A, the freewheeling control circuit 30 controls the freewheeling circuit 40 not to work, and when the sampling circuit 20 detects that the conduction angle of the thyristor dimmer Q1 < A, the freewheeling control circuit 30 controls the freewheeling circuit 40 to work to maintain the conduction of the thyristor dimmer Q1. The value of A is related to the holding current of the thyristor dimmer. Assuming that when the conduction angle of the thyristor dimmer is 20%, the corresponding load power just maintains the minimum holding current of the thyristor, at this time A = 20%. The specific advantages of this circuit are: through the freewheeling control circuit 30, this circuit can automatically turn off the freewheeling circuit 40. When the sampling circuit 20 detects that the conduction angle of the thyristor dimmer Q1 ≥ A (at this time the thyristor load current is not lower than the holding current of the thyristor), the freewheeling control circuit 30 controls the freewheeling circuit 40 not to work, and when the sampling circuit 20 detects that the conduction angle of the thyristor dimmer Q1 < A (at this time the thyristor load current is lower than the holding current of the thyristor), the freewheeling control circuit 30 controls the freewheeling circuit 40 to work to maintain the conduction of the thyristor dimmer Q1. However, the existing circuit does not have the function of turning off the freewheeling circuit. When the input voltage is higher, the power consumption of the freewheeling circuit is greater and the heat generation is also greater. Therefore, this solution can effectively reduce the heat generation of the freewheeling circuit 40, reduce the power consumption, and improve the reliability of the circuit.
[0013] In some embodiments, the freewheeling control circuit 30 includes a diode D3 and a switching transistor U3. The positive terminal of diode D3 is electrically connected to the control terminal of the freewheeling circuit 40, and the negative terminal of diode D3 is electrically connected to the positive terminal of switching transistor U3. The negative terminal of switching transistor U3 is grounded. The freewheeling circuit 40 includes a switching transistor Q2 (which may be a MOSFET), a switching transistor Q3 (which may be a transistor), and a resistor R12. The positive terminal of switching transistor Q2 is electrically connected to the output terminal of the rectifier circuit 10 via a series resistor. The control terminal of switching transistor Q2 is electrically connected to the positive terminals of diode D3 and switching transistor Q3, respectively. The negative terminal of switching transistor Q2 is electrically connected to the positive terminal of resistor R12 and the control terminal of switching transistor Q3, respectively. The negative terminals of resistor R12 and switching transistor Q3 are grounded. The sampling circuit 20 includes resistors R6 and R11. One end of resistor R6 is electrically connected to the output terminal of rectifier circuit 10, and the other end of resistor R6 and one end of resistor R11 are electrically connected to the control terminal of switch U3, respectively. The other end of resistor R11 is grounded. When the conduction angle of the SCR dimmer Q1 is at its maximum, the corresponding load power is also at its maximum. When the conduction angle of the SCR dimmer Q1 is at its minimum, the corresponding load power is also at its minimum. Assuming that the conduction angle of the SCR dimmer Q1 is 20%, the corresponding load power is just enough to maintain the minimum holding current of the SCR. Then we set the voltage across resistor R11 in the voltage detection circuit to be approximately greater than the reference voltage of the switching transistor U3. In this way, when the conduction angle of the SCR dimmer Q1 is greater than 20%, the voltage across resistor R11 will be greater than the reference voltage of the switching transistor U3, and the switching transistor U3 will start to conduct. Through diode D3, the gate voltage of MOSFET Q2 is pulled down, MOSFET Q2 is turned off, and the freewheeling circuit 40 does not work. At this time, since the load power is greater than the minimum holding current of the SCR dimmer Q1, the SCR dimmer Q1 and the load circuit work normally, the freewheeling circuit 40 does not work, reducing losses, reducing heat generation, and improving the overall efficiency of the drive. When the conduction angle of the SCR dimmer Q1 is less than 20%, the output voltage of the SCR dimmer Q1 decreases. The voltage across the voltage divider resistor R11 is lower than the reference voltage of the switching transistor U3, causing U3 to turn off and restoring gate control of the MOSFET Q2. The freewheeling circuit 40 then maintains the conduction of the SCR dimmer Q1, ensuring its normal operation under low load. Simultaneously, the high accuracy of the reference voltage of the switching transistor U3 significantly improves the compatibility and consistency of dimming.
[0014] In some embodiments, a voltage clamping circuit 50 is also included. The voltage clamping circuit 50 includes a resistor R5 and a diode D6. One end of the resistor R5 is electrically connected to the output terminal of the rectifier circuit 10, and the other end of the resistor R5 is electrically connected to the negative terminal of the diode D6, the positive terminal of the freewheeling control circuit 30, and the control terminal of the freewheeling circuit 40, respectively. The positive terminal of the diode D6 is grounded. The diode D6 is a Zener diode, and its Zener voltage is generally set to be less than about 80% of the gate voltage of the MOSFET Q2, ensuring that the voltage will not exceed the gate voltage of the MOSFET Q2 at any time.
[0015] In some embodiments, the system further includes a voltage regulator circuit 60, a drive circuit 70, and a zero-crossing detection circuit 80. The input terminal of the voltage regulator circuit 60 is electrically connected to the output terminal of the rectifier circuit 10, and the output terminal of the voltage regulator circuit 60 is electrically connected to the drive circuit 70. The input terminal of the zero-crossing detection circuit 80 is electrically connected to the input terminal of the voltage regulator circuit 60, and the output terminal of the zero-crossing detection circuit 80 is electrically connected to the control terminal of the drive circuit 70. The voltage regulator circuit 60 includes diodes D1 and D2, and capacitor C2. The positive terminal of diode D1 is electrically connected to the output terminal of the rectifier circuit 10, and the negative terminal of diode D1 is electrically connected to the negative terminal of diode D2, one end of capacitor C2, and the input terminal of the drive circuit 70. The positive terminal of diode D2 and the other end of capacitor C2 are grounded. The zero-crossing detection circuit 80 includes a diode D4, a capacitor C4, and a switching transistor U2. The negative terminal of diode D4, one end of capacitor C4, and the control terminal of switching transistor U2 are electrically connected to the input terminal of the voltage regulator circuit 60. The positive terminal of switching transistor U2 is electrically connected to the driving circuit 70. The positive terminal of diode D4, the other end of capacitor C4, and the negative terminal of switching transistor U2 are grounded. The driving circuit 70 includes an optocoupler U1, a resistor R1, and a resistor R8. One input terminal of optocoupler U1 is electrically connected to the output terminal of the voltage regulator circuit 60, and the other input terminal of optocoupler U1 is electrically connected to the positive terminal of switching transistor U2. The voltage regulator is typically set around 5V. Since the optocoupler U1 has very low power consumption, a properly configured capacitor C2 will provide a stable 5V voltage. Regardless of whether the SCR dimmer's conduction angle is less than 20% or at its maximum conduction angle, theoretically, as long as the SCR dimmer's output voltage is greater than 5V, capacitor C2 will provide a stable 5V voltage, supplying power to the optocoupler U1. No additional auxiliary power supply is required. Furthermore, this circuit module is independent and does not require grounding from the main power supply circuit, significantly reducing interference from the main circuit and improving sampling and control accuracy. In contrast, existing SCR freewheeling circuits require auxiliary power, thus this application effectively reduces costs.
[0016] Furthermore, when the pulsating DC voltage exceeds the reference voltage of switching transistor U2 (typically 2.5V), U2 conducts, and optocoupler U1 conducts, resulting in a high-level output signal from the secondary winding of U1. When the thyristor dimmer Q1 is in phase-cut mode, it does not conduct, so there is no output voltage. At this point, the voltage is lower than the reference voltage of U2, causing U2 to turn off, which in turn turns off optocoupler U1. The secondary signal output of the optocoupler is pulled low by resistor R8. Because the reference voltage of U2 is highly accurate, zero-crossing detection is effectively achieved. The filtering effect of capacitor C4 significantly improves the circuit's anti-interference capability. This circuit cleverly achieves precise zero-crossing sampling through U2. Existing circuits control optocoupler conduction via a resistor-divided voltage divider, resulting in large sampling errors and sampling delays. Sampling is impossible in regions where the voltage divider is lower than the transistor's control voltage, which can range from tens of volts. This is why existing thyristors cannot achieve high-precision consistency.
[0017] This cleverly utilizes the fact that the switching transistor U2 has only two states, on and off, to sample the conduction angle of the SCR dimmer into a precise digital signal for subsequent control. Even better, when the SCR dimmer is not connected to the circuit input, the rectified output is a complete and continuous half-sine wave. By appropriately selecting the value of capacitor C4 to ensure it is greater than the reference voltage of switching transistor U2 throughout the entire pulsation cycle, switching transistor U2 is in the on state for the entire cycle, as is optocoupler U1, and its secondary winding. The signal output remains high, allowing subsequent circuits to control the LED's brightness and color temperature by reading the duration of this high-level signal. This also makes the circuit input compatible with the PUSH function.
[0018] Even better, when the circuit input is not connected to a thyristor dimmer, the rectified output is a complete and continuous sine half-wave. At this time, the voltage across resistor R11 will be greater than the base voltage of switch U3 for 80% of the time period, and switch U3 will start to conduct. Through diode D3, the gate voltage of MOSFET Q2 is pulled down, MOSFET Q2 is turned off, and freewheeling circuit 40 does not work, reducing heat generation. Freewheeling circuit 40 only works for the remaining 20% of the time period. Since the voltage is in a relatively low range during this 20% period, the power consumption of freewheeling circuit 40 is very low and the heat generation is also small. Therefore, it is well compatible with both the functions of thyristor dimmer Q1 and push.
[0019] When a PUSH signal is input, the PUSH switch is turned on, and the rectifier circuit 10 outputs a complete half-wave sine wave signal. The zero-crossing detection circuit 80 then ensures that the optocoupler U1 remains on throughout the entire sine wave cycle, resulting in a high-level output signal. The subsequent circuit can detect the duration of the high-level signal to implement PUSH-related functions, a function that existing circuits cannot achieve.
[0020] This circuit features a simple structure, effectively reducing power consumption and heat generation, and minimizing the size of power components. This reduces costs while improving the overall system efficiency and reliability. Furthermore, the circuit is compatible with push functionality, eliminating the need for an additional push sampling circuit, achieving accurate detection, and improving dimming compatibility and consistency. It also operates as an independent module, facilitating modular design and ensuring excellent compatibility with conventional products.
[0021] It will be readily understood by those skilled in the art that the above preferred methods can be freely combined and superimposed without conflict.
[0022] The above are merely preferred embodiments of this utility model and do not limit the patent scope of this utility model. Any equivalent structural transformations made based on the inventive concept of this utility model and the contents of this utility model specification and drawings, or direct or indirect applications in other related technical fields, are included within the patent protection scope of this utility model.
Claims
1. A silicon controlled rectifier circuit, characterized by, Comprising: A thyristor dimmer Q1, a rectifier circuit (10), a sampling circuit (20), a freewheeling control circuit (30), and a freewheeling circuit (40). The output voltage of the thyristor dimmer Q1 is rectified by the rectifier circuit (10) and then input to the input terminal of the sampling circuit (20) and the positive terminal of the freewheeling circuit (40) respectively. The output terminal of the sampling circuit (20) is electrically connected to the control terminal of the freewheeling control circuit (30). The positive terminal of the freewheeling control circuit (30) is electrically connected to the control terminal of the freewheeling circuit (40). The negative terminal of the freewheeling circuit (40) and the negative terminal of the freewheeling control circuit (30) are grounded respectively. When the sampling circuit (20) detects that the conduction angle of the thyristor dimmer Q1 ≥ A, the freewheeling control circuit (30) controls the freewheeling circuit (40) not to work. When the sampling circuit (20) detects that the conduction angle of the thyristor dimmer Q1 < A, the freewheeling control circuit (30) controls the freewheeling circuit (40) to work to maintain the conduction of the thyristor dimmer Q1.
2. The thyristor circuit of claim 1, wherein: The freewheeling control circuit (30) includes a diode D3 and a switching tube U3. The positive terminal of the diode D3 is electrically connected to the control terminal of the freewheeling circuit (40). The negative terminal of the diode D3 is electrically connected to the positive terminal of the switching tube U3. The negative terminal of the switching tube U3 is grounded.
3. The thyristor circuit according to claim 2, characterized in that: The sampling circuit (20) includes a resistor R6 and a resistor R11. One end of the resistor R6 is electrically connected to the output terminal of the rectifier circuit (10). The other end of the resistor R6 and one end of the resistor R11 are respectively electrically connected to the control terminal of the switching tube U3. The other end of the resistor R11 is grounded.
4. The thyristor circuit of claim 1, wherein: It further includes a voltage clamping circuit (50). The voltage clamping circuit (50) includes a resistor R5 and a diode D6. One end of the resistor R5 is electrically connected to the output terminal of the rectifier circuit (10). The other end of the resistor R5 is respectively electrically connected to the negative terminal of the diode D6, the positive terminal of the freewheeling control circuit (30), and the control terminal of the freewheeling circuit (40). The positive terminal of the diode D6 is grounded.
5. The thyristor circuit of claim 1, wherein: It further includes a voltage stabilizing circuit (60) and a driving circuit (70). The input terminal of the voltage stabilizing circuit (60) is electrically connected to the output terminal of the rectifier circuit (10). The output terminal of the voltage stabilizing circuit (60) is electrically connected to the driving circuit (70).
6. The thyristor circuit of claim 5, wherein: It further includes a zero-crossing detection circuit (80). The input terminal of the zero-crossing detection circuit (80) is electrically connected to the input terminal of the voltage stabilizing circuit (60). The output terminal of the zero-crossing detection circuit (80) is electrically connected to the control terminal of the driving circuit (70).
7. The thyristor circuit of claim 6, wherein: The voltage stabilizing circuit (60) includes a diode D1, a diode D2, and a capacitor C2. The positive terminal of the diode D1 is electrically connected to the output terminal of the rectifier circuit (10). The negative terminal of the diode D1 is respectively electrically connected to the negative terminal of the diode D2, one end of the capacitor C2, and the input terminal of the driving circuit (70). The positive terminal of the diode D2 and the other end of the capacitor C2 are grounded respectively.
8. The thyristor circuit of claim 6, wherein: The zero-crossing detection circuit (80) includes a diode D4, a capacitor C4, and a switch U2. The negative terminal of the diode D4, one end of the capacitor C4, and the control terminal of the switch U2 are electrically connected to the input terminal of the voltage regulator circuit (60), and the positive terminal of the switch U2 is electrically connected to the driving circuit (70). The positive terminal of the diode D4, the other end of the capacitor C4, and the negative terminal of the switch U2 are grounded.
9. The thyristor circuit of claim 8, wherein: The driving circuit (70) includes an optocoupler U1, a resistor R1 and a resistor R8. One input terminal of the optocoupler U1 is electrically connected to the output terminal of the voltage regulator circuit (60), and the other input terminal of the optocoupler U1 is electrically connected to the positive terminal of the switching transistor U2.