Drive control circuit and LED driver

Abstract

The utility model provides a drive control circuit and an LED driver. The driving control circuit is used for controlling the LED driver and comprises a chopping signal control circuit and a driving signal generation circuit. The input end of the chopping signal control circuit is used for being coupled with a dimming signal end, and the output end of the chopping signal control circuit outputs a chopping signal. The driving signal generation circuit comprises a delay control circuit, a brightness judgment circuit and a constant current driving circuit. The first input end of the brightness judgment circuit is coupled with the output end of the chopping signal control circuit, and the second input end of the brightness judgment circuit is coupled with a preset signal end to obtain a preset value. The input end of the delay control circuit is respectively coupled with the output end of the brightness judgment circuit and the output end of the chopping signal control circuit. The input end of the constant current driving circuit is coupled with the output end of the chopping signal control circuit. The drive control circuit and the LED driver provided by the utility model can solve the stroboflash problem and ensure the dimming resolution at the same time.

Description

Technical Field

[0001] This utility model belongs to the field of power electronics, and relates to LED driving technology, particularly to a driving control circuit and an LED driver. Background Technology

[0002] LED lights are widely used in the lighting industry due to their high brightness, low power consumption, and long lifespan. With continuous innovation in LED driver technology, user needs are also constantly evolving, shifting from the initial requirement of high brightness and low efficiency to demands for dimming characteristics and light quality. As part of smart homes, smart lighting allows users to adjust the dimming and color temperature to achieve the desired lighting conditions based on their current needs.

[0003] In LED driver systems, the brightness of LED lights typically needs to be adjustable. At high brightness levels, flicker-free operation or a predetermined flicker threshold is usually required, while at low brightness levels, although flicker-free operation is not mandatory, higher dimming resolution is required. Driver circuits usually adjust the average output current by changing the proportion of the effective driving time to the entire driving cycle, thereby altering the LED light's brightness. For example... Figure 1 In existing technical solutions, a fixed driving frequency is used, with varying duty cycle, i.e., PWM control. A larger duty cycle results in a longer effective driving time, a larger average output current, and higher LED brightness. Conversely, lower LED brightness requires a smaller duty cycle and a narrower effective driving pulse width. To achieve flicker-free operation at high brightness, a relatively high driving frequency is typically required, meaning a shorter PWM period, further reducing the effective driving pulse width. This places high demands on driving speed and limits dimming resolution.

[0004] In view of this, a new structure is needed to solve at least some of the above problems. Utility Model Content

[0005] In view of one or more problems in the prior art, the present invention proposes a drive control circuit and an LED driver.

[0006] According to one aspect of the present invention, a drive control circuit is disclosed, which is used to control an LED driver, the drive control circuit comprising:

[0007] A chopper signal control circuit, whose input is coupled to a dimming signal terminal, and whose output terminal outputs a chopper signal; and

[0008] The drive signal generation circuit includes a delay control circuit, a brightness judgment circuit, and a constant current drive circuit. The first input terminal of the brightness judgment circuit is coupled to a detection signal terminal to receive a detection signal characterizing the brightness of the LED load or the output terminal of a chopper signal control circuit. The second input terminal of the brightness judgment circuit is coupled to a preset signal terminal to obtain a preset value. The input terminal of the delay control circuit is coupled to the output terminal of the brightness judgment circuit and the output terminal of the chopper signal control circuit, respectively. The input terminal of the constant current drive circuit is coupled to the output terminal of the chopper signal control circuit. The drive signal generation circuit generates a drive signal based on the chopper signal to control the power transistor.

[0009] In one embodiment, the first input terminal of the delay control circuit is coupled to the output terminal of the brightness judgment circuit, and the second input terminal of the delay control circuit is coupled to the output terminal of the chopper signal control circuit; the input terminal of the constant current drive circuit is coupled to the output terminal of the delay control circuit, and the constant current drive circuit outputs a drive signal.

[0010] In one embodiment, the input terminal of the constant current driving circuit is coupled to the output terminal of the chopper signal control circuit; the first input terminal of the delay control circuit is coupled to the output terminal of the brightness judgment circuit; the second input terminal of the delay control circuit is coupled to the output terminal of the constant current driving circuit; and the delay control circuit outputs a driving signal.

[0011] In one embodiment, the brightness determination circuit includes a duty cycle comparison circuit. The first input terminal of the duty cycle comparison circuit is coupled to the output terminal of the chopper signal control circuit, and the second input terminal of the duty cycle comparison circuit is coupled to a preset signal terminal to obtain a preset value.

[0012] In one embodiment, when the brightness of the LED load is higher than a preset value, the drive control circuit uses a fixed frequency to adjust the duty cycle of the chopping signal; and when the brightness of the LED load is lower than a preset value but greater than zero, the drive control circuit uses a fixed on-time to reduce the frequency of the chopping signal.

[0013] In one embodiment, the drive signal generation circuit further includes a rising edge acquisition circuit and / or a falling edge acquisition circuit; the input terminal of the rising edge acquisition circuit is coupled to the output terminal of the chopper signal control circuit, and the output terminal of the rising edge acquisition circuit is coupled to the input terminal of the delay control circuit; the input terminal of the falling edge acquisition circuit is coupled to the output terminal of the chopper signal control circuit, and the output terminal of the falling edge acquisition circuit is coupled to the input terminal of the delay control circuit.

[0014] In one embodiment, the drive control circuit further includes a power transistor, the control terminal of which is coupled to the output terminal of the constant current drive circuit.

[0015] In one embodiment, the delay control circuit controls the length of the delay time based on the output signal of the brightness judgment circuit.

[0016] According to another aspect of the present invention, an LED driver is disclosed, the LED driver comprising the drive control circuit as described in any of the preceding claims.

[0017] In one embodiment, the LED driver further includes an LED load coupled to a power transistor, and a drive control circuit is used to control the operating state of the power transistor.

[0018] This invention discloses a drive control circuit and an LED driver. The drive control circuit controls the LED driver and includes a chopper signal control circuit and a drive signal generation circuit. The input terminal of the chopper signal control circuit is coupled to a dimming signal terminal, and the output terminal of the chopper signal control circuit outputs a chopper signal. The drive signal generation circuit includes a delay control circuit, a brightness judgment circuit, and a constant current drive circuit. The first input terminal of the brightness judgment circuit is coupled to the output terminal of the chopper signal control circuit, and the second input terminal of the brightness judgment circuit is coupled to a preset signal terminal to obtain a preset value. The input terminal of the delay control circuit is coupled to both the output terminal of the brightness judgment circuit and the output terminal of the chopper signal control circuit. The input terminal of the constant current drive circuit is coupled to the output terminal of the chopper signal control circuit. The drive signal generation circuit generates a drive signal based on the chopper signal to control the power transistor. This invention provides a drive control circuit and an LED driver that can solve the flicker problem while ensuring dimming resolution. Attached Figure Description

[0019] The accompanying drawings are provided to further illustrate the present invention and, together with the description, serve to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings:

[0020] Figure 1 A schematic diagram of the signal waveform of a prior art LED driver is shown;

[0021] Figure 2 A schematic diagram of the signal waveform of an LED driver according to an embodiment of the present invention is shown;

[0022] Figure 3 A schematic diagram of the circuit structure of an LED driving control circuit according to an embodiment of the present invention is shown;

[0023] Figure 4 A schematic diagram of the signal waveform of an LED driver according to another embodiment of the present invention is shown;

[0024] Figure 5 A schematic diagram of the signal waveform of an LED driver according to another embodiment of the present invention is shown. Detailed Implementation

[0025] To further understand this utility model, preferred embodiments of this utility model are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of this utility model, and not for limiting the scope of the claims of this utility model.

[0026] The description in this section pertains to only a few typical embodiments, and this utility model is not limited to the scope of the embodiments described. Combinations of different embodiments, substitution of some technical features in different embodiments, and substitution of the same or similar prior art with some technical features in the embodiments are also within the scope of the description and protection of this utility model.

[0027] The terms "coupled" or "connected" in this specification include both direct and indirect connections. An indirect connection is a connection made through an intermediate medium, such as a connection through an electrically conductive medium like a conductor, which may contain parasitic inductance or capacitance. It can also be a connection through intermediate circuits or components described in the embodiments of this specification. Indirect connections may also include connections through other active or passive devices that achieve the same or similar functions, such as connections through switches, signal amplification circuits, follower circuits, or other circuits or components. "Multiple" or "more" indicates two or more. Furthermore, in this invention, terms such as "first" and "second" are primarily used to distinguish one technical feature from another, and do not necessarily require or imply any actual relationship or order between these technical features.

[0028] One embodiment of this utility model discloses a drive control circuit, combined with... Figure 2 When the brightness of the LED load is higher than the preset value (i.e., high brightness state), the drive control circuit uses a fixed frequency to adjust the duty cycle of the chopping signal. When the brightness of the LED load is lower than the preset value but greater than zero (i.e., low brightness state), the drive control circuit uses a fixed on-time to reduce the frequency of the chopping signal, thereby ensuring an effective drive pulse width and improving dimming resolution.

[0029] In one embodiment, a drive control circuit is disclosed. The drive control circuit is used to control an LED driver, such as... Figure 3As shown, the drive control circuit includes a chopper signal control circuit 10 and a drive signal generation circuit 20. The input terminal of the chopper signal control circuit 10 is coupled to a dimming signal terminal, and the output terminal of the chopper signal control circuit outputs a chopper signal PWM. The dimming signal terminal provides a dimming signal, which is used to control the brightness of the LED load. The drive signal generation circuit 20 includes a brightness judgment circuit 21, a delay control circuit 22, and a constant current drive circuit 23. The first input terminal of the brightness judgment circuit 21 is coupled to the output terminal of the chopper signal control circuit 10, and the second input terminal of the brightness judgment circuit 21 is coupled to a preset signal terminal to obtain a preset value. The brightness judgment circuit 21 determines whether the brightness of the LED load is in a high-brightness state or a low-brightness state based on the chopper signal PWM and the preset value. In another embodiment, the brightness judgment circuit 21 includes a duty cycle comparison circuit, the first input terminal of which is coupled to the output terminal of the chopper signal control circuit, and the second input terminal of which is coupled to the preset signal terminal to obtain the preset value. The duty cycle comparison circuit determines whether the drive control circuit is in a high-brightness or low-brightness state by comparing the duty cycle of the PWM chopper signal with a preset value. The drive signal generation circuit generates a drive signal based on a delay of the PWM chopper signal when the duty cycle is lower than the preset value. This drive signal is used to control the power transistor.

[0030] In another embodiment, the first input terminal of the brightness determination circuit is coupled to the detection signal terminal to receive a detection signal characterizing the brightness of the LED load, and the second input terminal of the brightness determination circuit is coupled to the preset signal terminal to obtain a preset value. The brightness determination circuit determines whether the drive control circuit is in a high brightness state or a low brightness state by comparing the detection signal and the preset value.

[0031] In one embodiment, such as Figure 3 As shown, the first input terminal of the delay control circuit 22 is coupled to the output terminal of the brightness judgment circuit 21, and the second input terminal of the delay control circuit 22 is coupled to the output terminal of the chopper signal control circuit. Combined with... Figure 4 In one embodiment, when the drive control circuit determines that the brightness is low, it controls the LED load current to gradually increase (e.g., starting at time t1) after a preset delay at the rising edge of the chopper signal PWM (e.g., time t0); and controls the LED load current to gradually decrease (e.g., starting at time t4) after a preset delay at the falling edge of the chopper signal PWM (e.g., time t3). In another embodiment, when the drive control circuit determines that the brightness is low, it controls the LED load current to gradually increase after a preset delay at the rising edge of the chopper signal PWM. In yet another embodiment, when the drive control circuit determines that the brightness is low, it controls the LED load current to gradually decrease after a preset delay at the falling edge of the chopper signal PWM. Figure 3As shown, in one embodiment, the input terminal of the constant current drive circuit 23 is coupled to the output terminal of the delay control circuit 22. The drive signal generation circuit is used to generate a drive signal based on the delay signal generated by the delay control circuit 22 to control the operating state of the power transistor. In one embodiment, the delay control circuit can control the length of the delay time based on the output signal of the brightness judgment circuit.

[0032] In another embodiment, the drive control circuit includes a chopper signal control circuit and a drive signal generation circuit. The input terminal of the chopper signal control circuit is used to couple to the dimming signal terminal, and the output terminal of the chopper signal control circuit outputs a chopper signal PWM.

[0033] The drive signal generation circuit includes a brightness judgment circuit, a constant current drive circuit, and a delay control circuit. The first input terminal of the brightness judgment circuit is coupled to the output terminal of the chopper signal control circuit, and the second input terminal is coupled to a preset signal terminal to obtain a preset value. The brightness judgment circuit determines whether the LED load's brightness is in a high-brightness or low-brightness state based on the chopper signal PWM and the preset value. The input terminal of the constant current drive circuit is coupled to the output terminal of the chopper signal control circuit, such as... Figure 5 As shown, the constant current drive circuit generates a pre-drive signal Gate_pre that can be used to drive the power transistor. The first input of the delay control circuit is coupled to the output of the brightness judgment circuit, the second input of the delay control circuit is coupled to the output of the constant current drive circuit, and the output of the delay control circuit is used to couple to the power transistor to control its operating state. The output of the delay control circuit outputs the drive signal Gate. The drive signal generation circuit generates the drive signal Gate based on the chopping signal to control the power transistor.

[0034] In one embodiment, the drive signal generation circuit further includes a rising edge acquisition circuit and a falling edge acquisition circuit. The input terminal of the rising edge acquisition circuit is coupled to the output terminal of the chopper signal control circuit, and the output terminal of the rising edge acquisition circuit is coupled to the input terminal of the delay control circuit. The input terminal of the falling edge acquisition circuit is coupled to the output terminal of the chopper signal control circuit, and the output terminal of the falling edge acquisition circuit is coupled to the input terminal of the delay control circuit. In another embodiment, the drive signal generation circuit further includes a rising edge acquisition circuit, the input terminal of which is coupled to the output terminal of the chopper signal control circuit, and the output terminal of which is coupled to the input terminal of the delay control circuit. In yet another embodiment, the drive signal generation circuit further includes a falling edge acquisition circuit, the input terminal of which is coupled to the output terminal of the chopper signal control circuit, and the output terminal of the falling edge acquisition circuit is coupled to the input terminal of the delay control circuit.

[0035] In one embodiment of this utility model, combined with Figure 4It can be seen that T is the driving pulse width, t0-t1 is the delay from the rising edge of the chopper signal PWM to the generation of LED load current output, t1-t2 is the rise time of LED load current, t3-t4 is the delay from the falling edge of the chopper signal PWM to the LED load current starting to decrease, and t4-t5 is the fall time of LED load current.

[0036] according to Figure 4 Analysis shows that, assuming the difference between the additional output current during the load current decrease phase (t3-t5) and the reduced output current during the rise phase (t0-t2) is δI, after frequency reduction by a factor of K, excluding the current change caused by the decrease in grayscale itself, the additional current decrease due to the difference between the drive signal and the current signal is K*δI. This value affects the linearity of the output current during frequency reduction and may even affect the monotonicity of the dimming process. This invention innovatively inserts a settable delay into the t0-t1 and t3-t4 phases to control the linearity change after frequency reduction caused by the drive process. Through compensation, it effectively solves the problem of poor dimming linearity caused by frequency reduction. Combined with... Figure 4-5 If the chopper signal PWM directly controls the power transistor after frequency reduction by a factor of K, the LED load current will decrease by K*δI due to the delay of the drive circuit itself. This invention improves the dimming performance after frequency reduction by adding a delay control circuit to the drive circuit, so that the additional current change caused by frequency reduction can be compensated by the delay control circuit.

[0037] In one embodiment, the drive control circuit further includes a power transistor, the control terminal of which is coupled to the output terminal of the constant current drive circuit, and the power transistor is connected in series with the LED load. The drive control circuit generates a drive signal to control the operating state of the power transistor. In another embodiment, the power transistor is externally located in the drive control circuit, and the output terminal of the drive control circuit is coupled to the control terminal of the power transistor. The power transistor can be one of the following transistors: a metal-oxide-semiconductor field-effect transistor (MOSFET), a junction field-effect transistor (JFET), and an insulated-gate bipolar transistor (IGBT).

[0038] One embodiment of this utility model also discloses an LED driver, which includes the drive control circuit as described in any of the preceding embodiments. In one embodiment, the LED driver further includes an LED load coupled to a power transistor, and the drive control circuit is used to control the operating state of the power transistor, thereby controlling the brightness of the LED load.

[0039] Those skilled in the art should know that the logic controls such as "high level" and "low level", "set" and "reset", "AND gate" and "OR gate", "non-inverting input" and "inverting input" in the logic control involved in the specification or drawings can be interchanged or changed, and the same function or purpose as the above embodiment can be achieved by adjusting the subsequent logic control.

[0040] The description and application of this utility model herein are illustrative and not intended to limit the scope of the utility model to the above embodiments. The effects or advantages described in the specification may not be apparent in actual experimental examples due to uncertainties in specific conditions or parameters or other factors, and such descriptions are not intended to limit the scope of the utility model. Variations and modifications to the embodiments disclosed herein are possible, and various substitutions and equivalent components of the embodiments are well known to those skilled in the art. It should be clear to those skilled in the art that this utility model can be implemented in other forms, structures, arrangements, proportions, and with other components, materials, and parts without departing from the spirit or essential characteristics of the utility model. Other variations and modifications can be made to the embodiments disclosed herein without departing from the scope and spirit of the utility model.

Claims

1. A drive control circuit for controlling an LED driver, characterized in that, The drive control circuit includes: A chopper signal control circuit, whose input is coupled to a dimming signal terminal, and whose output terminal outputs a chopper signal; and The drive signal generation circuit includes a delay control circuit, a brightness judgment circuit, and a constant current drive circuit. The first input terminal of the brightness judgment circuit is coupled to a detection signal terminal to receive a detection signal characterizing the brightness of the LED load or the output terminal of a chopper signal control circuit. The second input terminal of the brightness judgment circuit is coupled to a preset signal terminal to obtain a preset value. The input terminal of the delay control circuit is coupled to the output terminal of the brightness judgment circuit and the output terminal of the chopper signal control circuit, respectively. The input terminal of the constant current drive circuit is coupled to the output terminal of the chopper signal control circuit. The drive signal generation circuit generates a drive signal based on the chopper signal to control the power transistor.

2. The drive control circuit as described in claim 1, characterized in that, The first input terminal of the delay control circuit is coupled to the output terminal of the brightness judgment circuit, and the second input terminal of the delay control circuit is coupled to the output terminal of the chopper signal control circuit; the input terminal of the constant current drive circuit is coupled to the output terminal of the delay control circuit, and the constant current drive circuit outputs a drive signal.

3. The drive control circuit as described in claim 1, characterized in that, The input terminal of the constant current driving circuit is coupled to the output terminal of the chopper signal control circuit; the first input terminal of the delay control circuit is coupled to the output terminal of the brightness judgment circuit, the second input terminal of the delay control circuit is coupled to the output terminal of the constant current driving circuit, and the delay control circuit outputs a driving signal.

4. The drive control circuit as described in claim 1, characterized in that, The brightness judgment circuit includes a duty cycle comparison circuit. The first input terminal of the duty cycle comparison circuit is coupled to the output terminal of the chopper signal control circuit, and the second input terminal of the duty cycle comparison circuit is coupled to a preset signal terminal to obtain a preset value.

5. The drive control circuit as described in claim 1, characterized in that, When the brightness of the LED load is higher than a preset value, the drive control circuit uses a fixed frequency to adjust the duty cycle of the chopping signal; and when the brightness of the LED load is lower than a preset value but greater than zero, the drive control circuit uses a fixed on-time to reduce the frequency of the chopping signal.

6. The drive control circuit as described in claim 1, characterized in that, The drive signal generation circuit further includes a rising edge acquisition circuit and / or a falling edge acquisition circuit; the input terminal of the rising edge acquisition circuit is coupled to the output terminal of the chopper signal control circuit, and the output terminal of the rising edge acquisition circuit is coupled to the input terminal of the delay control circuit; the input terminal of the falling edge acquisition circuit is coupled to the output terminal of the chopper signal control circuit, and the output terminal of the falling edge acquisition circuit is coupled to the input terminal of the delay control circuit.

7. The drive control circuit as described in claim 1, characterized in that, The drive control circuit also includes a power transistor, the control terminal of which is coupled to the output terminal of the constant current drive circuit.

8. The drive control circuit as described in claim 1, characterized in that, The delay control circuit controls the length of the delay time based on the output signal of the brightness judgment circuit.

9. An LED driver, characterized in that, The LED driver includes the drive control circuit as described in any one of claims 1-8.

10. The LED driver as claimed in claim 9, characterized in that, The LED driver also includes an LED load, which is coupled to a power transistor, and a drive control circuit is used to control the operating state of the power transistor.

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