Signal isolation type metal oxide semiconductor field effect transistor (MOSFET) driving circuit and dimming circuit

Abstract

The utility model relates to the technical field of electronic circuits, and specifically discloses a signal isolation type MOSFET drive circuit and a dimming circuit. The signal isolation type MOSFET driving circuit comprises a first driving signal input end, a second driving signal input end, a first photoelectric coupler, a second photoelectric coupler and a first MOS tube, the first driving signal input end is connected with the positive electrode input end of the first photoelectric coupler, and the second driving signal input end is connected with the negative electrode input end of the second photoelectric coupler. The cathode input end of the first photoelectric coupler and the second driving signal input end are both connected with the anode input end of a second photoelectric coupler, and the cathode input end of the second photoelectric coupler is grounded; the direct-current power supply is connected with the first output end of the first photoelectric coupler, the second output end of the first photoelectric coupler and the grid electrode of the first MOS tube are both connected with the first output end of the second photoelectric coupler, and the second output end of the second photoelectric coupler and the source electrode of the first MOS tube are both grounded. According to the utility model, the MOSFET can be controlled to be switched off at any time point, and the stability of the system is improved.

Description

Technical Field

[0001] This utility model relates to the field of electronic circuit technology, and in particular to a signal isolation type MOSFET driving circuit and a dimming circuit. Background Technology

[0002] Existing MOSFET drive circuits generally use a PWM signal to turn the MOSFET on or off. To improve the signal's anti-interference capability, an optocoupler is often connected in series between the PWM signal input terminal and the MOSFET gate.

[0003] Figure 1 That is, a similar driving circuit is provided, in Figure 1 In this circuit, the gate voltage of the MOSFET is provided by VCC, and the PWM signal input to the PWM1 port controls the MOSFET to turn on or off. However, the high and low levels of the PWM signal are fixed within a single cycle and cannot be stopped or changed. If a system anomaly is detected within a single cycle and the switching state of the MOSFET needs to be changed, the MOSFET can only turn on or off according to the inherent law of the PWM signal and cannot be controlled. This may lead to system damage or even a safety accident. Utility Model Content

[0004] This invention provides a signal-isolated MOSFET driving circuit and a dimming circuit, which can control the MOSFET to disconnect at any time, increasing the controllability of the process and improving the stability of the system.

[0005] To solve the above problems, the present invention adopts the following technical solution:

[0006] According to a first aspect of the present invention, an embodiment of the present invention provides a signal-isolated MOSFET driving circuit, including a first driving signal input terminal, a second driving signal input terminal, a first optocoupler, a second optocoupler, and a first MOSFET. The first driving signal input terminal is connected to the positive input terminal of the first optocoupler, and the negative input terminal of the first optocoupler and the second driving signal input terminal are both connected to the positive input terminal of the second optocoupler. The negative input terminal of the second optocoupler is grounded. A DC power supply is connected to the first output terminal of the first optocoupler, and the second output terminal of the first optocoupler and the gate of the first MOSFET are both connected to the first output terminal of the second optocoupler. The second output terminal of the second optocoupler and the source of the first MOSFET are both grounded.

[0007] In some embodiments, the first drive signal input terminal is used to input a first PWM signal, and the second drive signal input terminal is used to input a second PWM signal. The first PWM signal and the second PWM signal have the same frequency, and at any given time, the level states of the first PWM signal and the second PWM signal are opposite.

[0008] In some embodiments, a fourth resistor is connected in series between the first drive signal input terminal and the positive input terminal of the first optocoupler, and a first resistor is connected in series between the second drive signal input terminal and the positive input terminal of the second optocoupler.

[0009] In some embodiments, a second resistor and a third resistor are further included, wherein the third resistor is connected in series between the DC power supply and the first output terminal of the first optocoupler, and the first output terminal and the second output terminal of the second optocoupler are respectively connected to the two ends of the second resistor.

[0010] In some embodiments, the first MOS transistor is an N-channel MOS transistor.

[0011] According to a second aspect of the present invention, an embodiment of the present invention provides a dimming circuit, including a main control module, a power supply module, a light-emitting device, and a signal-isolated MOSFET driving circuit as described in any of the first aspects above; the first driving signal input terminal and the second driving signal input terminal are both connected to the main control module; the power supply module is used to output DC power, and the power supply module is connected to the main control module and the first output terminal of the first optocoupler respectively; the power supply module, the light-emitting device, and the drain of the first MOSFET are connected in sequence.

[0012] In some embodiments, the power supply module includes mains power, a rectifier module, a transformer, a second MOSFET, and a switch control module. The mains power is connected to the input terminal of the rectifier module, the positive output terminal of the rectifier module is connected to one end of the main winding of the transformer, the other end of the main winding of the transformer is connected to the drain of the second MOSFET, the source of the second MOSFET is grounded, and the switch control module is connected to the gate of the second MOSFET. The positive output terminal of the primary winding of the transformer is the output terminal of the power supply module.

[0013] In some embodiments, the transformer further includes a first voltage regulator module, and the transformer also has a second stage winding, wherein the positive output terminal of the second stage winding of the transformer, the first voltage regulator module, and the main control module are connected in sequence.

[0014] In some embodiments, a second voltage regulator module is further included, wherein the power supply module, the second voltage regulator module and the first output terminal of the first optocoupler are connected in sequence.

[0015] This invention has at least the following beneficial effects: The first drive signal input terminal of this invention can input a PWM signal to control the first MOSFET to turn on or off. If, within a single cycle, a system abnormality is detected and it is necessary to change the switching state of the first MOSFET, the second drive signal input terminal can immediately input a signal with a level opposite to that of the PWM signal, thereby controlling the first MOSFET to change its switching state. This allows the first MOSFET to be turned off at any point in time, increasing the controllability of the process, preventing safety accidents, and improving the stability of the system. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of a MOSFET driving circuit in the prior art;

[0017] Figure 2 This is a schematic diagram of the structure of a signal isolation type MOSFET driving circuit according to an embodiment of the present invention;

[0018] Figure 3 This is a schematic diagram of the waveforms of the first PWM signal and the second PWM signal according to an embodiment of the present invention;

[0019] Figure 4 This is a schematic diagram of the circuit module structure of a dimming circuit according to an embodiment of the present invention;

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

[0021] The attached figures are labeled as follows:

[0022] Main control module 100, power supply module 200. Detailed Implementation

[0023] This invention provides the following description with reference to the accompanying drawings to aid in a comprehensive understanding of the various embodiments of the invention as defined by the claims and their equivalents. The description includes various specific details to aid understanding, but these details should be considered exemplary only. Therefore, those skilled in the art will recognize that various changes and modifications can be made to the various embodiments described herein without departing from the scope and spirit of the invention.

[0024] In the description of this utility model, the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0025] It should be understood that when one element (e.g., the first element) is “connected” to another element (e.g., the second element), the element may be directly connected to the other element, or there may be an intervening element (e.g., the third element) between the element and the other element.

[0026] An embodiment of this utility model provides a signal-isolated MOSFET driving circuit, such as... Figure 2 As shown, the device includes a first drive signal input terminal PWM1, a second drive signal input terminal PWM2, a first optocoupler U1, a second optocoupler U2, and a first MOSFET Q1. The first drive signal input terminal is connected to the positive input terminal of the first optocoupler. The negative input terminal of the first optocoupler and the second drive signal input terminal are both connected to the positive input terminal of the second optocoupler. The negative input terminal of the second optocoupler is grounded. The first drive signal input terminal can input a PWM signal, and the second drive signal input terminal can input other control signals in real time.

[0027] A DC power supply is connected to the first output terminal of the first optocoupler. This DC power supply can be provided by a power module, specifically 3.3V, 5V, or other DC voltage signals as needed by the circuit. The second output terminal of the first optocoupler and the gate of the first MOSFET are both connected to the first output terminal of the second optocoupler. The second output terminal of the second optocoupler and the source of the first MOSFET are both grounded. Both the first output terminals of the first and second optocouplers are the collectors of the internal phototransistors. Figure 2 The four pins in the diagram, the second output terminal of the first optocoupler and the second output terminal of the second optocoupler are both emitters of the internal phototransistor, i.e. Figure 2 Pin 3 in the middle.

[0028] As is well known, MOSFETs include N-channel MOSFETs and P-channel MOSFETs. The first MOSFET in this embodiment can also be an N-channel MOSFET or a P-channel MOSFET. For ease of explanation, we will take an N-channel MOSFET as an example.

[0029] When Q1 needs to be temporarily turned off, a high-level signal is only required at the second drive signal input terminal. The gate voltage of the first MOSFET is pulled low. At this time, Q1 is in the off state regardless of whether there is a signal input at the first drive signal input terminal, thus achieving a protection function without delay.

[0030] Therefore, in this embodiment, the first drive signal input terminal can input a PWM signal to control the first MOSFET to turn on or off. If a system abnormality is detected within a single cycle and it is necessary to change the switching state of the first MOSFET, the second drive signal input terminal can immediately input a signal with the opposite level of the PWM signal to control the first MOSFET to change its switching state. This allows the first MOSFET to be turned off at any point in time, increasing the controllability of the process, preventing safety accidents, and improving the stability of the system.

[0031] In some embodiments, the first drive signal input terminal is used to input a first PWM signal, and the second drive signal input terminal is used to input a second PWM signal. The first PWM signal and the second PWM signal have the same frequency, and at any given time, their level states are opposite. This provides the signal output under normal operating conditions, ensuring the normal switching of the first MOSFET.

[0032] by Figure 3 For example, the sum of the duty cycles of the first PWM signal (PWM1) and the second PWM signal (PWM2) can be 1. When PWM1 is high and PWM2 is low, PIN1 and PIN2 of U1 are turned on, and PIN1 and PIN2 of U2 are turned off. Therefore, PIN4 and PIN3 of U1 are turned on, and PIN4 and PIN3 of U2 are not turned on. The gate voltage of Q1 is high. When the gate voltage Vgs2 reaches the turn-on threshold of Q1, Q1 is turned on; otherwise, it is not turned on. When PWM1 is low and PWM2 is high, PIN1 and PIN2 of U1 are turned off, and PIN1 and PIN2 of U2 are turned on. Therefore, PIN4 and PIN3 of U1 are not turned on, and PIN4 and PIN3 of U2 are turned on. The gate voltage of Q1 is low, which is lower than the turn-on threshold of Q1, so Q1 is turned off.

[0033] Suppose that an anomaly is detected in the system at 0.3ms and Q1 needs to be temporarily disconnected, simply inputting a high level to the second drive signal input terminal will disconnect Q1. At this time, Q1 will be in the disconnected state regardless of whether there is a signal input to the first drive signal input terminal.

[0034] In some embodiments, such as Figure 2 As shown, a fourth resistor R4 is connected in series between the first drive signal input terminal and the positive input terminal of the first optocoupler, and a first resistor R1 is connected in series between the second drive signal input terminal and the positive input terminal of the second optocoupler. Both the first resistor R1 and the fourth resistor R4 serve to limit current in order to prevent the light-emitting components inside the first and second optocouplers from being damaged due to excessive current.

[0035] In some embodiments, such as Figure 2As shown, the signal-isolated MOSFET driving circuit of this embodiment also includes a second resistor R2 and a third resistor R3. The third resistor R3 is connected in series between the DC power supply VCC and the first output terminal of the first optocoupler. The first and second output terminals of the second optocoupler are respectively connected to the two ends of the second resistor R2. The second resistor R2 and the third resistor R3 form a voltage divider circuit. When the voltage of VCC is too high, the voltage across the second resistor R2 is made to reach the turn-on voltage of Q1 through the voltage divider, thus avoiding damage to Q1 due to excessive voltage and ensuring safe use.

[0036] In some embodiments, the first MOSFET is an N-channel MOSFET, and its specific operation is illustrated in the above embodiments by way of example, and will not be repeated here. Of course, the first MOSFET can also be a P-channel MOSFET.

[0037] An embodiment of this utility model also provides a dimming circuit, such as Figure 4 As shown, it includes a main control module 100, a power supply module 200, a light-emitting device LED, and a signal-isolated MOSFET driving circuit of any of the above embodiments. For a detailed description of the signal-isolated MOSFET driving circuit, please refer to the above embodiments, which will not be repeated here.

[0038] The first drive signal input terminal and the second drive signal input terminal are both connected to the main control module 100; the power supply module 200 is used to output DC power, and the power supply module 200 is connected to the main control module 100 and the first output terminal of the first optocoupler respectively; the power supply module 200, the light-emitting device LED and the drain of the first MOS transistor Q1 are connected in sequence.

[0039] The power module 200 provides operating voltage to the main control module 100 and the light-emitting device LED. The main control module 100 outputs a PWM signal to the first drive signal input terminal to control the first MOSFET Q1 to turn on or off. When the first MOSFET Q1 is turned on, the light-emitting device LED emits light. When the first MOSFET Q1 is turned off, the light-emitting device LED turns off. The brightness can be adjusted arbitrarily by changing the duty cycle of the PWM wave.

[0040] When the system malfunctions, the main control module 100 outputs a high-level signal to the second drive signal input terminal, and the gate voltage of the first MOSFET is pulled low. At this time, regardless of whether there is a signal input at the first drive signal input terminal, Q1 is in the off state, and the light-emitting device LED is turned off, thus avoiding damage to the light-emitting device due to system malfunction.

[0041] In some embodiments, such as Figure 5As shown, the power supply module includes mains power, a rectifier module, a transformer T1B, a second MOSFET Q2, and a switch control module U3. The mains power is connected to the input terminal of the rectifier module, which rectifies the mains power to output a DC signal. The positive output terminal of the rectifier module is connected to one end of the main winding of the transformer, and the other end of the main winding of the transformer is connected to the drain of the second MOSFET. The source of the second MOSFET is grounded, and the switch control module is connected to the gate of the second MOSFET. The positive output terminal of the primary winding of the transformer is the output terminal of the power supply module.

[0042] In this embodiment, the power supply module is a switching power supply. The switching control module outputs a PWM signal to the gate of the second MOSFET and controls the output voltage of the transformer by changing the duty cycle.

[0043] In some embodiments, the dimming circuit further includes a first voltage regulator module U4, and the transformer also has a second secondary winding T1A. The positive output terminal of the transformer's second secondary winding, the first voltage regulator module, and the main control module are connected in sequence. Power is supplied to the main control module through the second secondary winding.

[0044] The first voltage regulator module can use a conventional voltage regulator chip or other voltage regulator circuit.

[0045] In some embodiments, the main control module 100 may include a microcontroller chip, a DSP signal and a programmable logic control chip, such as the GQ-MLM8 chip.

[0046] The switch control module may also include a microcontroller chip, DSP signal and programmable logic control chip, such as the IW3627 chip.

[0047] In some embodiments, the dimming circuit further includes a second voltage regulator module U5, with the power supply module, the second voltage regulator module, and the first output terminal of the first optocoupler connected sequentially. The second voltage regulator module can stably output a 5V DC voltage to ensure the normal operation of Q1.

[0048] The second voltage regulator module can use conventional voltage regulator chips or other voltage regulator circuits.

[0049] The terms and words used in the foregoing description and claims are not limited to their literal meaning, but are merely used by the applicant to enable a clear and consistent understanding of the present invention. Therefore, those skilled in the art should understand that the foregoing description of various embodiments of the present invention is for illustrative purposes only, and not intended to limit the present invention as defined by the appended claims and their equivalents.

Claims

1. A signal-isolated MOSFET driving circuit, characterized in that: The device includes a first drive signal input terminal, a second drive signal input terminal, a first optocoupler, a second optocoupler, and a first MOSFET. The first drive signal input terminal is connected to the positive input terminal of the first optocoupler. The negative input terminal of the first optocoupler and the second drive signal input terminal are both connected to the positive input terminal of the second optocoupler. The negative input terminal of the second optocoupler is grounded. A DC power supply is connected to the first output terminal of the first optocoupler. The second output terminal of the first optocoupler and the gate of the first MOSFET are both connected to the first output terminal of the second optocoupler. The second output terminal of the second optocoupler and the source of the first MOSFET are both grounded.

2. The signal-isolated MOSFET driving circuit according to claim 1, characterized in that: The first drive signal input terminal is used to input a first PWM signal, and the second drive signal input terminal is used to input a second PWM signal. The first PWM signal and the second PWM signal have the same frequency, and at any time, the level states of the first PWM signal and the second PWM signal are opposite.

3. The signal-isolated MOSFET driving circuit according to claim 1, characterized in that: A fourth resistor is connected in series between the first drive signal input terminal and the positive input terminal of the first optocoupler, and a first resistor is connected in series between the second drive signal input terminal and the positive input terminal of the second optocoupler.

4. The signal-isolated MOSFET driving circuit according to claim 1, characterized in that: It also includes a second resistor and a third resistor, wherein the third resistor is connected in series between the DC power supply and the first output terminal of the first optocoupler, and the first and second output terminals of the second optocoupler are respectively connected to the two ends of the second resistor.

5. The signal-isolated MOSFET driving circuit according to claim 1, characterized in that: The first MOSFET is an N-channel MOSFET.

6. A dimming circuit, characterized in that: It includes a main control module, a power supply module, a light-emitting device, and a signal-isolated MOSFET driving circuit as described in any one of claims 1-5; the first driving signal input terminal and the second driving signal input terminal are both connected to the main control module; the power supply module is used to output DC power, and the power supply module is connected to the main control module and the first output terminal of the first optocoupler respectively; the power supply module, the light-emitting device, and the drain of the first MOSFET are connected in sequence.

7. The dimming circuit according to claim 6, characterized in that: The power supply module includes mains power, a rectifier module, a transformer, a second MOSFET, and a switch control module. The mains power is connected to the input terminal of the rectifier module. The positive output terminal of the rectifier module is connected to one end of the main winding of the transformer. The other end of the main winding of the transformer is connected to the drain of the second MOSFET. The source of the second MOSFET is grounded. The switch control module is connected to the gate of the second MOSFET. The positive output terminal of the primary winding of the transformer is the output terminal of the power supply module.

8. The dimming circuit according to claim 7, characterized in that: It also includes a first voltage regulator module, and the transformer also has a second stage winding. The positive output terminal of the second stage winding of the transformer, the first voltage regulator module and the main control module are connected in sequence.

9. The dimming circuit according to any one of claims 6-8, characterized in that: It also includes a second voltage regulator module, and the power supply module, the second voltage regulator module and the first output terminal of the first optocoupler are connected in sequence.

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