Protection circuit for low ripple LED control device
By introducing a protection circuit into the LED driver circuit, the diode shunts overvoltage and overcurrent, the problem of power MOSFETs is solved, the reliability and durability of the circuit are improved, and the LEDs with lower cost and higher reliability are achieved. control.
Patent Information
- Application Number
- CN201811127608.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2018-09-26
- Publication Date
- 2024-12-31
- Estimated Expiration
- 2038-09-26
AI Technical Summary
In existing LED driver circuits, power MOSFETs are prone to failure due to overheating or other reasons, resulting in low circuit reliability, and the control principle of derippling, destroboscopic circuits is easily affected by external factors, increasing the risk of failure.
A protection circuit for low-ripples LED control device is designed, including deripples, destrobe and flash circuit and protection circuit. The protection circuit adopts a diode series circuit to divert overvoltage and overcurrent through the diode to protect the field effect tube to ensure that the circuit is in Continue to work when the MOSFET fails.
Effectively protects power MOSFETs, improves circuit reliability and durability, allows the use of lower cost and lower parameters MOSFET models, reduces circuit costs, and provides dual insurance functions.
Smart Images
Figure CN108966435B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to an LED control device, and in particular to a protection circuit of a low-ripple LED control device. Background Art
[0002] With the rapid development of LED lighting, the cost requirements for LED drivers are getting lower and lower, and the cost of LED drivers depends on the choice of LED driving solutions. At present, the most commonly used LED driving solution at home and abroad is the single-stage PFC circuit solution, which is a single-stage primary constant current control PSR + power factor correction control PFC. This solution has the characteristics of simple circuit, high constant current accuracy and low cost. However, a disadvantage of the single-stage PFC + PSR solution is that the LED has flicker, that is, there is a fixed frequency flicker when taking pictures with a camera. In order to make up for the disadvantage of flicker in this solution, there is an application of adding a ripple and flash removal circuit, such as the application number 201610795710.7, named a ripple elimination circuit and an LED control circuit using it, that is, this solution is used to remove ripples and flicker.
[0003] The ripple and flicker removal scheme has a significant effect in removing flicker. After installing the flicker removal circuit, the flicker problem is solved, but a new problem arises. The control principle of the ripple removal circuit is to use a power MOSFET in series with the LED light source to control the dynamic resistance of the MOSFET (on) to absorb the current ripple. However, since the MOSFET is in the amplification area and critical conduction state for a long time and has a large current, it is easily affected by external factors, and overcurrent, overvoltage or overheating will occur instantly, causing the MOSFET to fail, especially when the independent LED driver is powered and unloaded, or the load has poor contact or short circuit, or the MOSFET is overheated or static electricity, etc., the defect rate is extremely high and the failure cycle is short. Summary of the invention
[0004] In view of the deficiencies in the prior art, the present invention discloses a protection circuit for a low-ripple LED control device.
[0005] The technical solution adopted by the present invention is as follows:
[0006] A protection circuit for a low-ripple LED control device comprises a ripple and flash removal circuit and a protection circuit; the ripple and flash removal circuit comprises a control chip and a first field effect tube; a gate voltage output port of the control chip is connected to the gate of the first field effect tube; a current sensing input port of the control chip is connected to the first electrode of the first field effect tube; an LED voltage limiting port of the control chip is connected to the second electrode of the first field effect tube; the second electrode of the first field effect tube serves as a negative output terminal of the LED control device; the protection circuit is a diode series circuit; two ends of the diode series circuit are connected in parallel between the first electrode and the second electrode of the first field effect tube.
[0007] Its further technical solution is: it also includes a sixth resistor and a seventh resistor in parallel, the first end of the parallel circuit is connected to the first electrode of the first field effect tube, and the second end of the parallel circuit is grounded; the current ripple control port of the control chip is grounded through the fourth capacitor; the gate voltage output port of the control chip is grounded through the fifth capacitor.
[0008] Its further technical solution is: the model of the control chip is JW1221A; the fourth pin of the control chip is connected to the gate of the first field effect tube; the fifth pin of the control chip is connected to the source of the first field effect tube; the sixth pin of the control chip is connected to the drain of the first field effect tube through the fifth resistor; the third pin of the control chip is grounded through the fourth capacitor; and the fourth pin of the control chip is grounded through the fifth capacitor.
[0009] Its further technical solution is: the protection circuit includes a second diode, a third diode and a fourth diode connected in series; the positive terminal of the protection circuit is connected to the second pole of the field effect tube; the negative terminal of the protection circuit is connected to the first pole of the field effect tube.
[0010] A further technical solution is: the on-voltage of the protection circuit is 2.7V to 3.3V.
[0011] A further technical solution is: the first electrode is a source, and the second electrode is a drain; or the first electrode is a drain, and the second electrode is a source.
[0012] Its further technical solution is: it also includes a power supply circuit; the first output end of the power supply circuit is used as the positive output end of the LED control device; the second output end of the power supply circuit is used as the power supply end of the control chip.
[0013] Its further technical solution is: the power supply circuit is a unipolar primary constant current control circuit; the unipolar primary constant current control circuit includes a PWM generating chip; the PWM generating port of the PWM generating chip is connected to the gate of the second field effect tube; the source of the second field effect tube is grounded through a first resistor; the drain of the second field effect tube is connected to the primary side of the isolation circuit; the secondary side of the isolation circuit is connected to the output rectifier circuit; the output end of the output rectifier circuit serves as the positive output end of the LED control device.
[0014] The beneficial effects of the present invention are as follows:
[0015] When a power factor control circuit is used in an LED driving circuit, the control MOSFET is prone to failure. The present invention can protect the power MOSFET in the circuit from failure and improve the circuit reliability. When the power MOSFET fails or opens due to overheating or other reasons, the protection circuit is turned on, providing a double insurance function for the entire circuit. After using this circuit, the power MOSFET can be selected with a lower withstand voltage value or a lower electrical parameter model, and the circuit cost is lower and more reliable. The circuit of the present invention is simple, does not take up space and has low cost. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 It is a schematic diagram of the circuit structure of the present invention. DETAILED DESCRIPTION
[0017] The specific implementation of this embodiment is described below with reference to the accompanying drawings.
[0018] Figure 1 FIG. 2 is a schematic diagram of the circuit structure of the present invention. Figure 1 As shown, the protection circuit of the low ripple LED control device of the present invention includes a power supply circuit for providing power to the LED control device, a ripple and flash removal circuit, and a protection circuit.
[0019] The external voltage source is input to the input end of the power supply circuit. The first output end of the power supply circuit is used as the positive output end of the LED control device, connected to the positive pole of the LED light string. The second output end of the power supply circuit is used as the power supply end of the ripple and flash removal circuit.
[0020] In this embodiment, the power supply circuit is a single-stage primary constant current control circuit. The power supply circuit may also use other constant current circuits, which are not specifically limited.
[0021] The unipolar primary constant current control circuit includes a PWM generating chip IC2, the PWM generating port of the PWM generating chip IC2 is connected to the gate of the second field effect transistor Q2, the source of the second field effect transistor Q2 is grounded through the first resistor R1, and the drain of the second field effect transistor Q2 is connected to the primary side of the isolation circuit. The secondary side of the isolation circuit is connected to the output rectifier circuit. The output rectifier circuit is used to absorb the fluctuation of the output voltage to make the output voltage more stable. Other circuit structures of the power supply circuit
[0022] In the output rectifier circuit, a second resistor R2 and a first capacitor C1 are connected in series. The two ends of the first diode D1 are connected in parallel to the two ends of this series circuit. The first end of the second capacitor C2 is connected to the negative terminal of the first diode D1, and the second end of the second capacitor C2 is grounded. The first end of the third resistor R3 is connected to the negative terminal of the first diode D1, and the second end of the third resistor R3 is grounded. The first end of the fourth resistor R4 is connected to the negative terminal of the first diode D1. The first end of the fourth resistor R4 serves as the first output end of the power supply circuit, that is, the positive output end of the LED control device, and is connected to the positive pole of the LED light string. The second end of the fourth resistor R4 serves as the second output end of the power supply circuit, that is, the power supply end of the ripple and flash removal circuit.
[0023] In this embodiment, the model of the PWM generation chip IC2 is CL1100, and the second pin of the PWM generation chip IC2 is connected to the gate of the second field effect transistor Q2. Other chips with similar functions may also be used.
[0024] The ripple and flash removal circuit includes a control chip IC1 and a field effect transistor Q1 , and the second output end of the power supply circuit is connected to the power supply end Vin of the control chip IC1 .
[0025] The gate voltage output port VG of the control chip IC1 is connected to the gate of the first field effect transistor Q1. The current sensing input port VS of the control chip IC1 is connected to the first electrode of the first field effect transistor Q1. The LED voltage limiting port VLMT of the control chip IC1 is connected to the second electrode of the first field effect transistor Q1. The second electrode of the first field effect transistor Q1 serves as the negative output terminal of the LED control device.
[0026] The control chip IC1 also has some auxiliary circuits for ensuring the normal function of the chip. The auxiliary circuit includes a sixth resistor R6 and a seventh resistor R7 connected in parallel. The first end of the parallel circuit is connected to the first pole of the first field effect tube Q1, and the second end of the parallel circuit is grounded. The current ripple control port VC of the control chip IC is grounded through the fourth capacitor C4. The gate voltage output port VG of the control chip IC1 is grounded through the fifth capacitor C5. The second pole of the first field effect tube Q1 is connected to the LED voltage limit pin VLMT of the control chip IC1 through the fifth resistor R5.
[0027] The second electrode of the first field effect transistor Q1 serves as the negative electrode output terminal of the LED control device and is connected to the negative electrode of the LED light string.
[0028] The first electrode mentioned above is the source electrode, and the second electrode is the drain electrode, or the first electrode is the drain electrode, and the second electrode is the source electrode.
[0029] Specifically, in this embodiment, the model of the control chip IC1 is JW1221A. The second output end of the power supply circuit is connected to the first pin of the control chip IC1. The fourth pin of the control chip IC1 is connected to the gate of the first field effect transistor Q1, and the fifth pin of the control chip IC1 is connected to the source of the first field effect transistor Q1. The sixth pin of the control chip IC1 is connected to the drain of the first field effect transistor Q1 through the fifth resistor R5. The third pin of the control chip IC1 is grounded through the fourth capacitor C4. The fourth pin of the control chip IC1 is grounded through the fifth capacitor C5.
[0030] The protection circuit is a diode series circuit, and two ends of the diode series circuit are connected in parallel between the source and the drain of the first field effect transistor Q1.
[0031] Specifically, the protection circuit includes a second diode D2, a third diode D3 and a fourth diode D4 connected in series. The positive terminal of the protection circuit is connected to the drain of the field effect transistor Q1, and the negative terminal of the protection circuit is connected to the source of the field effect transistor Q1.
[0032] The second diode D2, the third diode D3 and the fourth diode D4 are all common diodes, and their forward conduction voltages are all about 1V. After the second diode D2, the third diode D3 and the fourth diode D4 are connected in series, the conduction voltage is about 2.7V to 3.3V, generally 3V. That is, the conduction voltage of the protection circuit is 2.7V to 3.3V, generally 3V.
[0033] The voltage between the source and drain of the first field effect transistor Q1 has a peak voltage below 2.7V during normal operation. At this time, the second diode D2, the third diode D3 and the fourth diode D4 have no operating current and have no effect on the operation of the first field effect transistor Q1.
[0034] When the driver causes overvoltage between the source and drain of the first field effect transistor Q1 or short-circuit overcurrent at the power output end at the moment of startup or due to external influences, the protection circuit composed of the second diode D2, the third diode D3 and the fourth diode D4 connected in series and connected between the source and drain of the first field effect transistor Q1 can play the role of current shunting and overvoltage limiting, thereby protecting the first field effect transistor Q1 from failure due to overcurrent or overvoltage.
[0035] The above description is an explanation of the present invention, not a limitation of the present invention. The scope of the present invention is defined in the claims. The present invention may be modified in any form without violating the basic structure of the present invention.
Claims
1. A protection circuit for a low ripple LED control device, characterized in that: It comprises a ripple and flash removal circuit and a protection circuit; the ripple and flash removal circuit comprises a control chip (IC1) and a first field effect tube (Q1); the gate voltage output port (VG) of the control chip (IC1) is connected to the gate of the first field effect tube (Q1); the current sensing input port (VS) of the control chip (IC1) is connected to the first pole of the first field effect tube (Q1); the LED voltage limiting port (VLMT) of the control chip (IC1) is connected to the second pole of the first field effect tube (Q1); the second pole of the first field effect tube (Q1) serves as the negative output terminal of the LED control device; the protection circuit is a diode series circuit; the two ends of the diode series circuit are connected in parallel between the first pole and the second pole of the first field effect tube (Q1); The protection circuit comprises a second diode (D2), a third diode (D3) and a fourth diode (D4) which are connected in series; the positive terminal of the protection circuit is connected to the second electrode of the field effect tube (Q1); and the negative terminal of the protection circuit is connected to the first electrode of the field effect tube (Q1); It also includes a power supply circuit; the first output end of the power supply circuit serves as the positive output end of the LED control device; and the second output end of the power supply circuit serves as the power supply end of the control chip (IC1).
2. The protection circuit of the low ripple LED control device according to claim 1, characterized in that: It also includes a sixth resistor (R6) and a seventh resistor (R7) connected in parallel, wherein the first end of the parallel circuit is connected to the first electrode of the first field effect tube (Q1), and the second end of the parallel circuit is grounded; the current ripple control port (VC) of the control chip (IC1) is grounded through a fourth capacitor (C4); and the gate voltage output port (VG) of the control chip (IC1) is grounded through a fifth capacitor (C5).
3. The protection circuit of the low ripple LED control device according to claim 2, characterized in that: The model of the control chip (IC1) is JW1221A; the fourth pin of the control chip (IC1) is connected to the gate of the first field effect tube (Q1); the fifth pin of the control chip (IC1) is connected to the source of the first field effect tube (Q1); the sixth pin of the control chip (IC1) is connected to the drain of the first field effect tube (Q1) through a fifth resistor (R5); the third pin of the control chip (IC1) is grounded through a fourth capacitor (C4); and the fourth pin of the control chip (IC1) is grounded through a fifth capacitor (C5).
4. The protection circuit of the low ripple LED control device according to claim 1, characterized in that: The on-state voltage of the protection circuit is 2.7V~3.3V.
5. The protection circuit of the low ripple LED control device according to any one of claims 1, 2 and 4, characterized in that: The first electrode is a source and the second electrode is a drain; or the first electrode is a drain and the second electrode is a source.
6. The protection circuit of the low ripple LED control device according to claim 1, characterized in that: The power supply circuit is a single-stage primary constant current control circuit; the single-stage primary constant current control circuit comprises a PWM generation chip (IC2); the PWM generation port of the PWM generation chip (IC2) is connected to the gate of the second field effect tube (Q2); the source of the second field effect tube (Q2) is grounded through a first resistor (R1); the drain of the second field effect tube (Q2) is connected to the primary side of the isolation circuit; The secondary side of the isolation circuit is connected to the output rectifier circuit; the output end of the output rectifier circuit serves as the positive output end of the LED control device.