CN215912260U - Circuit unit and driving circuit - Google Patents

Abstract

The application provides a circuit unit and drive circuit, circuit unit is used for the drive load, includes: an adjustable current source in series with the load; the dimming circuit is electrically connected with the control end of the adjustable current source and controls the current flowing through the adjustable current source; and the output end of the protection circuit is coupled to the control end of the adjustable current source, when the current flowing through the load is zero, the input end of the protection circuit can detect a first signal representing the voltage at two ends of the adjustable current source, and the current of the adjustable current source is controlled to be larger than zero in response to the first signal being larger than a preset threshold value V1. By the arrangement, the problem that the adjustable current source connected with the load in series is easy to damage when the load current is zero can be solved.

Description

Circuit unit and driving circuit

Technical Field

The utility model relates to the technical field of electronic control, in particular to a circuit unit and a driving circuit applied to control an LED array.

Background

The current dimmable LED lighting device needs to adjust the current flowing through the LED to change the light emitting amount of the LED, the device for adjusting the current is a power tube, such as a field effect tube or a triode, the power tube is connected in series with the LED, the change of the output current of the power tube is realized by changing the voltage of a control electrode, and when the current of the LED needs to be adjusted to be approximately zero to turn off the LED, the power tube needs to be correspondingly controlled to be turned off. The LED lighting device is usually powered by a mains grid, and when a lightning surge occurs, a voltage spike occurs in the voltage of the mains grid, which easily causes the power tube to be broken down due to overvoltage. The reason is as follows: on one hand, the voltage drop at two ends of the LED is positively correlated with the current flowing through the LED, when the current of the LED is zero, the power tube connected in series with the LED needs to bear higher voltage, and when the power supply voltage of the LED lighting device has a peak, the power tube is easy to break down; on the other hand, the LED and the power tube connected in series therewith generally need to be electrically connected to a copper foil of a copper-clad aluminum substrate (aluminum substrate for short), an aluminum plate of the aluminum substrate and a metal shell of the LED lighting device are electrically connected to a ground wire of a power supply grid, a parasitic capacitor exists between the aluminum plate and the copper foil, and when a voltage spike occurs between the ground wire and a power supply line, energy leaked from the parasitic capacitor easily causes the power tube to be broken down.

Therefore, a circuit and a method for improving the breakdown of the power tube connected in series with the LED when the LED current is zero are needed.

SUMMERY OF THE UTILITY MODEL

In view of the above technical problems in the prior art, the present application provides a circuit unit for driving a load, comprising: an adjustable current source connected in series with the load, the adjustable current source having at least one control terminal; the dimming circuit is electrically connected with at least one control end and is used for controlling the current flowing through the adjustable current source; and the output end of the protection circuit is coupled to at least one control end, the input end of the protection circuit is used for acquiring a first signal representing the voltage at two ends of the adjustable current source, and the current of the adjustable current source is controlled to be larger than zero in response to the fact that the first signal is larger than a preset threshold value.

Optionally, the adjustable current source includes a first power transistor, a drain of the first power transistor is configured to be connected to a load, a source of the first power transistor is grounded, and the protection circuit is configured to: and controlling the first power tube to operate in a safe working area in response to the first signal being greater than a preset threshold value.

Optionally, the adjustable current source includes a first power transistor, a drain of the first power transistor is configured to be connected to a load, a source of the first power transistor is grounded, and the protection circuit is configured to: and if the first power tube is in a cut-off state, controlling the first power tube to operate in a safe working area in response to the first signal being greater than a preset threshold value.

It should be understood that the grounding of the source of the power transistor includes the direct grounding of the source or the indirect grounding through a current limiting device (such as a resistor), which is not described in detail elsewhere.

Optionally, the protection circuit comprises: a comparison circuit, two input ends of which are respectively configured to receive the first signal and a preset threshold value; the control end of the controllable switch is connected with the output end of the comparison circuit, and the first end of the controllable switch is connected with the control end of the adjustable current source; and the first voltage source is connected with the controllable switch in series, the positive electrode of the first voltage source is connected with the second end of the controllable switch, and the negative electrode of the first voltage source is grounded.

Optionally, the protection circuit is configured to: controlling the controllable switch to be closed in response to the first signal being greater than a preset threshold; and controlling the controllable switch to be switched off in response to the first signal being smaller than a preset threshold value.

Optionally, the protection circuit comprises: a comparison circuit, two input ends of which are respectively configured to receive the first signal and a preset threshold value; the adjustable current source further comprises: and the drain electrode and the source electrode of the second power tube are respectively and correspondingly connected with the drain electrode and the source electrode of the first power tube, and the control end of the second power tube is connected with the output end of the comparison circuit.

Optionally, the protection circuit comprises: a comparison circuit, two input ends of which are respectively configured to receive the first signal and a preset threshold value; the adjustable current source further comprises: the drain electrode and the source electrode of the second power tube are respectively and correspondingly connected with the drain electrode and the source electrode of the first power tube, and the control end of the second power tube is connected with the output end of the comparison circuit; the third power tube is connected between the first power tube and the load in series; and the anode of the second voltage source is connected with the control end of the third power tube, and the cathode of the second voltage source is connected with the source electrode of the first power tube.

In order to achieve the above object, the present application provides a driving circuit, which includes the circuit unit and the load described above.

Optionally, the load comprises an LED.

Optionally, the load further comprises a filter capacitor connected in parallel with the LED.

Optionally, the load further comprises a first current source in series with the LED.

The circuit unit that this application provided can be applied to by the load of commercial power supply to when load current is zero, can be when the voltage peak of commercial power appears, through control and load series connection's power tube's electric current in its safe workspace, avoid load current to be zero, the problem that the power tube that input voltage suddenly changes and lead to easily destroys.

Drawings

Fig. 1 is a schematic circuit structure diagram of a circuit unit and a driving circuit provided in an embodiment of the present application;

fig. 2 is a schematic circuit structure diagram of a circuit unit and a driving circuit provided in another embodiment of the present application;

fig. 3 is a schematic circuit structure diagram of a circuit unit and a driving circuit provided in another embodiment of the present application;

FIG. 4 is a schematic circuit diagram of one implementation of a load in an embodiment of the present application;

fig. 5 is a schematic circuit diagram of another implementation of a load in an embodiment of the present application.

Detailed Description

Hereinafter, exemplary embodiments will be described in detail with reference to the accompanying drawings. However, the present application is not limited to the following embodiments, but includes various changes, substitutions, and alterations within the technical scope of the present disclosure. The terms "first," "second," and the like may be used to explain various elements, the number of elements is not limited by such terms. These terms are only used to distinguish one element from another. Thus, an element referred to as a first element in one embodiment may be referred to as a second element in another embodiment. The singular forms "a", "an" and "the" do not exclude the plural forms unless the context requires otherwise. The following description of the embodiments of the present application is provided for illustrative purposes, and other advantages and capabilities of the present application will become apparent to those skilled in the art from the present disclosure.

In the following description, reference is made to the accompanying drawings that describe several embodiments of the application. It is to be understood that other embodiments may be utilized and that mechanical, structural, electrical, and operational changes may be made without departing from the spirit and scope of the present application. The following detailed description is not to be taken in a limiting sense, and the scope of embodiments of the present application is defined only by the claims of the issued patent. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. Spatially relative terms, such as "upper," "lower," "left," "right," "lower," "below," "lower," "above," "upper," and the like, may be used herein to facilitate describing one element or feature's relationship to another element or feature as illustrated in the figures.

Although the terms first, second, etc. may be used herein to describe various elements in some instances, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, the first preset threshold may be referred to as a second preset threshold, and similarly, the second preset threshold may be referred to as a first preset threshold, without departing from the scope of the various described embodiments. The first preset threshold and the preset threshold are both described as one threshold, but they are not the same preset threshold unless the context clearly indicates otherwise. Similar situations also include a first volume and a second volume.

Also, as used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context indicates otherwise. It will be further understood that the terms "comprises," "comprising," "includes" and/or "including," when used in this specification, specify the presence of stated features, steps, operations, elements, components, items, species, and/or groups, but do not preclude the presence, or addition of one or more other features, steps, operations, elements, components, species, and/or groups thereof. The terms "or" and/or "as used herein are to be construed as inclusive or meaning any one or any combination. Thus, "A, B or C" or "A, B and/or C" means "any of the following: a; b; c; a and B; a and C; b and C; A. b and C ". An exception to this definition will occur only when a combination of elements, functions, steps or operations are inherently mutually exclusive in some way.

The present embodiment provides a circuit unit 10, as shown in fig. 1, for driving a load 1 supplied with power from a power supply 02, including: the adjustable current source 2 is connected with the load 1 in series and used for controlling the current of the load 1; the dimming circuit 3 is electrically connected with the control end of the adjustable current source 2 and is used for controlling the current flowing through the adjustable current source 2; and the output end of the protection circuit 4 is coupled to the control end of the adjustable current source 2, the input end of the protection circuit detects the voltage of the anode of the power supply 02, the voltage can be used as a first signal for representing the voltage at two ends of the adjustable current source, and the current of the adjustable current source 2 is controlled to be larger than zero in response to the first signal being larger than a preset threshold value.

So set up, can realize when power supply 02's output voltage appears the voltage peak (arouses by the thunderbolt surge usually), through the current control with adjustable current source 2 for being greater than zero, pass through the return circuit with surge energy and release to avoid adjustable current source 2 to damage because of both ends voltage is too big.

Optionally, the first signal indicative of the voltage across the adjustable current source may also be taken from the load and/or the adjustable current source. For example, in some embodiments, the input terminal of the protection circuit 4 may also be coupled to the load 1 and/or the adjustable current source 2, and the preset threshold is set adaptively to enable the adjustable current source to discharge the surge energy in response to the peak voltage.

Optionally, the adjustable current source 2 includes a first power transistor Q1, a drain of the first power transistor Q1 is configured for connection with the load 1, a source of the first power transistor Q1 is grounded, and the protection circuit 4 is configured to: in response to the first signal being greater than the preset threshold, the current and voltage of the first power transistor Q1 are controlled not to exceed the safe operating area of the first power transistor Q1, or the first power transistor Q1 is operated in the safe operating area.

Optionally, the input of the protection circuit 4 may also detect the voltage of the adjustable current source 2 to obtain a first signal indicative of the occurrence of surge energy in the series branch. In the present embodiment, the current and the voltage of the first power transistor Q1 are controlled to be not more than the safe operating area of the first power transistor Q1, or the first power transistor Q1 is operated in the safe operating area, so that the protection of the first power transistor Q1 is implemented.

It should be noted that, in this embodiment, the specific implementation manner of "enabling the first power transistor Q1 to operate in the safe operating area" includes: no matter the dimming circuit 3 controls the first power tube Q1 to operate in a high-current, low-current or even off state, once the protection circuit 4 detects the occurrence of surge energy, the protection circuit 4 controls the first power tube Q1 to be turned on and operate in a safe working area. That is, the on-current of the adjustable current source 2 is controlled so that the first power transistor Q1 operates in the safe operating region. For example, in response to the occurrence of a surge, if the adjustable current source 2 is in a high-current operation state, the protection circuit 4 can control the current of the adjustable current source 2 to decrease so as to prevent the power of the first power transistor Q1 from exceeding the safe operation area, whereas in response to the occurrence of a surge, if the adjustable current source 2 is in a low-current operation state or a cut-off state, the protection circuit 4 can control the current of the controllable current source 2 to increase so as to prevent the voltage across the adjustable current source 2 from exceeding the safe operation area.

Optionally, the protection circuit 4 includes: a comparison circuit 41, two input terminals being respectively configured to receive the first signal and a preset threshold, wherein the preset threshold may be provided by the second voltage source V2; a controllable switch S1, a control end of which is connected to the output end of the comparison circuit 41, and a first end of which is connected to the control end of the adjustable current source 2; and a first voltage source V1 connected in series with the controllable switch S1, the positive terminal of which is connected to the second terminal of the controllable switch S1, and the negative terminal of which is grounded.

Alternatively, the comparison circuit 41 may be implemented as a comparator CMP1 having an inverting input configured to input the preset threshold and a non-inverting input configured to receive the first signal.

Optionally, the protection circuit 4 is configured to: in response to the first signal being greater than the preset threshold, controlling the controllable switch S1 to close; in response to the first signal being less than the preset threshold, the controllable switch S1 is controlled to open.

In this embodiment, whether a peak voltage occurs in a power supply path of the power supply 02 (or an output end thereof, or a series branch formed by the load 1 and the adjustable current source 2) is determined according to a comparison result of the first signal and the preset threshold, if the first signal is greater than the preset threshold, it is determined that the peak voltage occurs, at this time, the controllable switch S1 is controlled to be closed, and the first power tube Q1 is controlled to be turned on by the first voltage source V1 and the current of the first power tube Q1 is limited in a safe working area thereof, so as to protect the first power tube Q1.

Alternatively, in another embodiment, a circuit unit 20 is provided, as shown in fig. 2, an adjustable current source 2 having a first control terminal and a second control terminal, connected in series with a load 1 for controlling the current of the load 1; the dimming circuit 3 is electrically connected with the first control end of the adjustable current source 2 and is used for controlling the current flowing through the adjustable current source 2; and a protection circuit 4, an output end of which is coupled to the control end of the adjustable current source 2.

The adjustable current source 2 includes: a first power transistor Q1, a drain of the first power transistor Q1 is configured to be connected to the load 1, a source of the first power transistor Q1 is grounded, and a gate (i.e., a first control terminal of the adjustable current source 2) is connected to the output terminal of the dimming circuit 3; and a drain and a source of the second power transistor Q2 are respectively and correspondingly connected with a drain and a source of the first power transistor Q1, the protection circuit 4 includes a comparison circuit 41, and an output terminal of the comparison circuit 41 is coupled to the control terminal of the adjustable current source 2.

It differs from the circuit unit 10 shown in fig. 1 in that:

the adjustable current source 2 further comprises: the drain and the source of the second power transistor Q2 are respectively connected to the drain and the source of the first power transistor Q1, and the output terminal of the comparison circuit 41 is connected to the control terminal of the second power transistor Q2 (i.e., the second control terminal of the adjustable current source 2).

In this embodiment, when the first power transistor Q1 is turned off, the comparison circuit 41 outputs a high level in response to the occurrence of a spike voltage, and controls the current of the second power transistor Q2 to be limited within the range of the safe operating area thereof, so as to protect the first power transistor Q1 and the second power transistor Q2.

Optionally, in another embodiment, a circuit unit 30 is shown, as shown in fig. 3, which differs from the circuit unit 20 shown in fig. 2 in that the adjustable current source 2 further comprises: the source of the third power transistor Q3 is connected to the drain of the first power transistor Q1, the drain thereof is connected to the load 1, the gate thereof is connected to the positive terminal of the third voltage source V3, and the negative terminal of the third voltage source V3 is connected to the source of the first power transistor Q1.

In this embodiment, in response to the occurrence of the spike voltage, the second power transistor Q2 is turned on, and the source voltage of the third power transistor Q3 is pulled low, so that the voltage difference between the gate voltage and the source voltage of the third power transistor Q3 is increased to be enough to turn on the third power transistor Q3, and further, the current of the second power transistor Q2 is configured to make the second power transistor Q2 and the third power transistor Q3 operate in the respective safe operating areas.

In this embodiment, only the third power transistor Q3 needs to be implemented as a high voltage power transistor, and both the first power transistor Q1 and the second power transistor Q2 need to be implemented as low voltage power transistors, compared to the circuit unit 20 shown in fig. 2, in which both the first power transistor Q1 and the second power transistor Q2 need to be implemented as high voltage power transistors, the manufacturing cost of the circuit unit 30 is low.

Optionally, the load 1 comprises an LED.

Optionally, as shown in fig. 4, the load 1 further includes a filter capacitor C1 connected in parallel with the LED for suppressing current ripple of the LED and reducing light emission stroboscopic.

Optionally, as shown in fig. 5, the load 1 further includes a ripple removing circuit, for example, a current source I1 is connected in series to the LED, so as to further eliminate the current ripple of the LED and reduce the light emission strobe. The above embodiments are merely illustrative of the principles and utilities of the present application and are not intended to limit the application. Any person skilled in the art can modify or change the above-described embodiments without departing from the spirit and scope of the present application. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical concepts disclosed in the present application shall be covered by the claims of the present application.

Claims (10)

1. A circuit unit for driving a load, comprising:

an adjustable current source in series with the load, the adjustable current source having at least one control terminal;

a dimming circuit electrically connected to the at least one control terminal for controlling the current flowing through the adjustable current source; and

and the output end of the protection circuit is coupled to the at least one control end, the input end of the protection circuit is used for acquiring a first signal representing the voltage at two ends of the adjustable current source, and the current of the adjustable current source is controlled to be larger than zero in response to the fact that the first signal is larger than a preset threshold value.

2. The circuit unit of claim 1, wherein the adjustable current source comprises a first power tube, a drain of the first power tube configured for connection to the load, a source of the first power tube connected to ground, the protection circuit configured to: and controlling the first power tube to operate in a safe working area in response to the first signal being greater than a preset threshold value.

3. The circuit unit of claim 1, wherein the adjustable current source comprises a first power tube, a drain of the first power tube configured for connection to the load, a source of the first power tube connected to ground, the protection circuit configured to:

and if the first power tube is in a cut-off state, responding to the fact that the first signal is larger than a preset threshold value, and controlling the first power tube to operate in a safe working area.

4. The circuit cell of any of claims 1-3, wherein the protection circuit comprises:

a comparison circuit, two input terminals respectively configured to receive the first signal and the preset threshold value;

the control end of the controllable switch is connected with the output end of the comparison circuit, and the first end of the controllable switch is connected with the control end of the adjustable current source; and

the first voltage source is connected with the controllable switch in series, the positive electrode of the first voltage source is connected with the second end of the controllable switch, and the negative electrode of the first voltage source is grounded;

the protection circuit is configured to:

controlling the controllable switch to close in response to the first signal being greater than the preset threshold;

and controlling the controllable switch to be switched off in response to the first signal being smaller than the preset threshold value.

5. The circuit cell of claim 2, wherein the protection circuit comprises:

a comparison circuit, two input terminals respectively configured to receive the first signal and the preset threshold value;

the adjustable current source further comprises: and the drain electrode and the source electrode of the second power tube are respectively and correspondingly connected with the drain electrode and the source electrode of the first power tube, and the control end of the second power tube is connected with the output end of the comparison circuit.

6. The circuit cell of claim 2, wherein the protection circuit comprises:

a comparison circuit, two input terminals respectively configured to receive the first signal and the preset threshold value;

the adjustable current source further comprises: the drain electrode and the source electrode of the second power tube are respectively and correspondingly connected with the drain electrode and the source electrode of the first power tube, and the control end of the second power tube is connected with the output end of the comparison circuit;

the third power tube is connected between the first power tube and the load in series; and

and the anode of the second voltage source is connected with the control end of the third power tube, and the cathode of the second voltage source is connected with the source electrode of the first power tube.

7. A driver circuit comprising the circuit unit according to any one of claims 1 to 6 and the load.

8. The drive circuit of claim 7, wherein the load comprises an LED.

9. The drive circuit of claim 8 wherein the load further comprises a filter capacitor in parallel with the LED.

10. The driver circuit of claim 9, wherein the load further comprises a first current source in series with the LED.

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