A dimming control circuit and a dimming chip thereof

Abstract

The present application provides a dimming control circuit and a dimming chip thereof, wherein the dimming control circuit comprises: a peak control voltage generating unit, a current limiting control unit and a control logic unit; the peak control voltage generating unit is used to sample the load voltage of the load circuit to obtain a voltage compensation signal, generate a compensation voltage according to the voltage compensation signal, and generate a peak control voltage according to the compensation voltage and the load voltage; the current limiting control unit is used to receive the peak control voltage, and send a disconnection drive signal to the control logic unit when the peak control voltage reaches a preset voltage threshold; the control logic unit is used to drive the power control device in the load circuit to disconnect according to the disconnection drive signal, so as to control the peak current of the inductor in the load circuit in each switching cycle, so that the charge transmitted by the inductor in each charging and discharging cycle is not affected by the RLC resonance, thereby making the dimming output current of the load change linearly, thereby eliminating ripple.

Description

Technical Field

[0001] The present application relates to the field of dimming control technology, and in particular to a dimming control circuit and a dimming chip thereof. Background Art

[0002] When the current intelligent dimming circuit uses the discontinuous conduction mode (DCM mode) to dim the load (such as LED) in the load circuit, the power control device in the load circuit is turned on and off. When the power control device is closed, the inductor stores electrical energy and the inductor current gradually increases. After the power control device is disconnected, the inductor releases electrical energy and the inductor current gradually decreases. When the inductor current decreases to 0, since the power control device has not been closed, the load circuit generates RLC resonance.

[0003] RLC resonance will cause the starting value of the inductor current to be inconsistent in different switching cycles, that is, under the same dimming condition, the amount of charge transmitted by the inductor to the load is different in different switching cycles, which causes the load output current to fluctuate in different switching cycles under the same dimming condition, and then cause the load output current to fluctuate nonlinearly during the linear dimming process, resulting in ripple phenomenon. Summary of the invention

[0004] The purpose of the embodiments of the present application is to provide a dimming control circuit and a dimming chip thereof to solve the above-mentioned problems.

[0005] In a first aspect, the present invention provides a dimming control circuit, comprising: a peak control voltage generating unit, a current limiting control unit and a control logic unit; the peak control voltage generating unit is used to sample the load voltage of the load circuit to obtain a voltage compensation signal, generate a compensation voltage according to the voltage compensation signal, and generate a peak control voltage according to the compensation voltage and the load voltage; the current limiting control unit is used to receive the peak control voltage, and send a disconnection drive signal to the control logic unit when the peak control voltage reaches a preset voltage threshold; the control logic unit is used to drive the power control device in the load circuit to disconnect according to the disconnection drive signal.

[0006] In the dimming control circuit designed above, this scheme first generates a compensation voltage based on a voltage compensation signal of a sampled load voltage through a peak control voltage generating unit, and then calculates the load voltage and the compensation voltage to generate a peak control voltage. The current limiting control unit sends a disconnection drive signal when the peak control voltage reaches a preset voltage threshold, so that the control logic unit controls the power control device in the load circuit to disconnect according to the disconnection drive signal, thereby controlling the peak current of the inductor in the load circuit through the compensation voltage in each switching cycle, and then when the starting value of the inductor current changes relative to the previous cycle, the compensation voltage presents the same change, thereby causing the peak current of the inductor to present an opposite change, thereby controlling the charge transmitted by the inductor in the load circuit in each charging and discharging cycle to be not affected by the RLC resonance, and then making the dimming output current of the load present a linear change, thereby eliminating the ripple phenomenon in the dimming process.

[0007] In an optional implementation of the first aspect, the peak control voltage generating unit includes a sampling control circuit and a peak control voltage generating circuit; the input end of the sampling control circuit is used to receive the load voltage, the output end of the sampling control circuit is connected to the input end of the peak control voltage generating circuit, and the output end of the peak control voltage generating circuit is connected to the input end of the current limiting control unit; the sampling control circuit is used to control the peak control voltage generating circuit to sample the load voltage to obtain the voltage compensation signal after the power control device is closed; the peak control voltage generating circuit is used to generate the compensation voltage according to the voltage compensation signal, and generate the peak control voltage according to the compensation voltage and the load voltage.

[0008] In an optional implementation of the first aspect, the peak control voltage generating circuit includes a compensation voltage operational amplifier, a compensation voltage controlled switch tube, a first resistor, a second resistor and a current mirror, the non-inverting input terminal of the compensation voltage operational amplifier is connected to the output terminal of the sampling control circuit, the output terminal of the compensation voltage comparator is connected to the control terminal of the compensation voltage controlled switch tube, the first end of the compensation voltage controlled switch tube is respectively connected to the first end of the first resistor and the inverting input terminal of the compensation voltage operational amplifier, and the second end of the first resistor is grounded; the second end of the compensation voltage controlled switch tube is respectively connected to the first end of the second resistor and the input terminal of the current limiting control unit through the current mirror, and the second end of the second resistor is used to receive the load voltage.

[0009] In an optional implementation of the first aspect, the sampling control circuit includes a sampling signal generating subcircuit, a sampling controllable switch tube and an energy storage capacitor, the sampling signal generating subcircuit is connected to the control end of the sampling controllable switch tube, the first end of the sampling controllable switch tube is connected to the second end of the second resistor, the second end of the sampling controllable switch tube is respectively connected to the first end of the energy storage capacitor and the non-inverting input end of the compensation voltage operational amplifier, and the second end of the energy storage capacitor is connected to the second end of the first resistor; the sampling signal generating subcircuit is used to generate a sampling signal to control the sampling controllable switch tube to be turned on after the power control device is closed.

[0010] In an optional implementation of the first aspect, the current limiting control unit is further used to receive a dimming signal and adjust the preset voltage threshold according to the dimming signal to adjust the closing time of the power control device and the peak current of the load circuit, thereby achieving dimming.

[0011] In an optional implementation of the first aspect, the current limiting control unit includes a current limiting comparator, and the non-phase input terminal of the current limiting comparator is connected to the output terminal of the peak control voltage generating unit; the inverting input terminal of the current limiting comparator is used to receive a peak threshold signal, and the peak threshold signal is obtained by converting the dimming signal, and the peak threshold signal represents the preset voltage threshold; the output terminal of the current limiting comparator is connected to the control logic unit to send a disconnect drive signal to the control logic unit when the peak control voltage reaches the voltage threshold corresponding to the peak threshold signal.

[0012] In an optional implementation of the first aspect, the current limiting control unit also includes a peak detection control circuit, which is arranged between the positive phase input terminal of the current limiting comparator and the output terminal of the peak control voltage generating unit, and is used to control the conduction state between the positive phase input terminal of the current limiting comparator and the output terminal of the peak control voltage generating unit.

[0013] In an optional implementation of the first aspect, the peak detection control circuit includes a peak detection signal generating subcircuit and a peak detection controllable switch tube, the peak detection signal generating subcircuit is connected to the control end of the peak detection controllable switch tube, the first end of the peak detection controllable switch tube is respectively connected to the output end of the peak control voltage generating unit and the first end of the second resistor, and the second end of the peak detection controllable switch tube is connected to the non-phase input end of the current limiting comparator.

[0014] In an optional implementation of the first aspect, the dimming control circuit also includes a demagnetization detection unit and a load switch cycle control unit; the demagnetization detection unit is used to send a demagnetization completion signal to the load switch cycle control unit when the load current drops from a maximum to 0; the switch cycle control unit is used to send a closing drive signal to the control logic unit according to the demagnetization completion signal; the control logic unit is used to control the power control device to close according to the closing drive signal.

[0015] In an optional implementation manner of the first aspect, the compensation voltage is inversely correlated with a peak current of an inductor of the load circuit.

[0016] In an optional implementation of the first aspect, the control logic unit includes a control logic circuit and a drive circuit, the input end of the control logic circuit is connected to the output end of the current limiting control unit, the output end of the control logic circuit is connected to the input end of the drive circuit, and the output end of the drive circuit is connected to the control end of the power control device.

[0017] In a second aspect, the present invention provides a dimming chip, wherein the dimming chip comprises the dimming control circuit described in any optional implementation manner in the first aspect.

[0018] In the dimming chip designed above, since the dimming chip includes the dimming control circuit of any optional implementation in the first aspect, the dimming chip can ensure that the charge transmitted by the inductor in the load circuit in each charging and discharging cycle is not affected by the RLC resonance, thereby making the dimming output current of the load show a linear change, thereby eliminating the ripple phenomenon in the dimming process. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 A first structural schematic diagram of a dimming control circuit provided in an embodiment of the present application;

[0021] Figure 2 A schematic diagram of the signal timing in the dimming control circuit provided in an embodiment of the present application;

[0022] Figure 3 A second structural schematic diagram of the dimming control circuit provided in an embodiment of the present application;

[0023] Figure 4A third structural schematic diagram of the dimming control circuit provided in an embodiment of the present application;

[0024] Figure 5 A fourth structural schematic diagram of the dimming control circuit provided in an embodiment of the present application;

[0025] Figure 6 A fifth structural diagram of the dimming control circuit provided in an embodiment of the present application;

[0026] Figure 7 A schematic diagram of the structure of the dimming chip provided in an embodiment of the present application.

[0027] Icons: 1-dimming chip; 4-load circuit; 41-load working circuit; 42-power control device; 43-load detection circuit; 10-peak control voltage generating unit; 101-sampling control circuit; 102-peak control voltage generating circuit; 1011-sampling signal generating subcircuit; 20-current limiting control unit; 201-peak detection control circuit; 2011-peak detection signal generating subcircuit; 30-control logic unit; 301-control logic circuit; 302-drive Circuit; 40-demagnetization detection unit; 50-load switch cycle control unit; LED-light-emitting diode; L-inductor; C-capacitor; C1-energy storage capacitor; Q1-diode; Rcs-resistor; R1-first resistor; R2-second resistor; M0-MOS tube; M1-compensation voltage controllable switch tube; M2-sampling controllable switch tube; M3-peak detection controllable switch tube; L1-compensation voltage operational amplifier; L2-current limiting comparator; P1-current mirror; A1-signal conversion unit. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application.

[0029] First embodiment

[0030] The embodiment of the present application provides a dimming control circuit, which is used to dim a load circuit, wherein the load circuit can be as follows Figure 1 The load circuit 4 shown in FIG. 4 includes a load working circuit 41, a power control device 42 and a load detection circuit 43 connected in sequence. Specifically, the load working circuit 41 may include a light emitting diode LED, an inductor L, a capacitor C and a diode Q1. The power control device 42 may be as follows: Figure 1 The MOS tube M0 shown in the figure, the load detection circuit 43 can be as follows Figure 1The resistor Rcs shown, the positive electrode of the LED is respectively connected to the cathode of the diode Q1, the first end of the capacitor C and the power supply, the negative electrode of the LED is respectively connected to the second end of the capacitor C and the first end of the inductor L, the second end of the inductor L is connected to the anode of the diode Q1, the anode of the diode Q1 is also connected to the drain of the MOS tube M0, and the source of the MOS tube M0 is grounded through the resistor Rcs.

[0031] Based on the load circuit 4 of the above structure, the dimming circuit designed in the present application dims the LED in the load working circuit 41. It should be noted that the load circuit 4 described above is only a specific implementation structure of the current load circuit, and the dimming circuit designed in the present application can perform dimming control on any load circuit currently working in the DCM mode.

[0032] The dimming circuit designed in this application can make the charge transmitted by the inductor L in the load circuit in each charge and discharge cycle not be affected by the RLC resonance, so that the dimming output current of the load changes linearly, thereby eliminating the ripple. Figure 1 As shown, the designed dimming control circuit includes: a peak control voltage generating unit 10 , a current limiting control unit 20 and a control logic unit 30 .

[0033] The input end of the peak control voltage generating unit 10 is used to sample the load voltage Vcs to obtain the voltage compensation signal Vc. The output end of the peak control voltage generating unit 10 is connected to the input end of the current limiting control unit 20. The output end of the current limiting control unit 20 is connected to the input end of the control logic unit 30. The output end of the control logic unit 30 is connected to the control end of the power control device 42. Figure 1 The gate of the MOS tube M0 is connected. Based on the design of the aforementioned load circuit 4, the input end of the peak control voltage generating unit 10 and the input end of the current limiting control unit 20 can be connected to the source of the MOS tube M0, so as to sample the load voltage Vcs.

[0034] The dimming control circuit designed above is as follows: Figure 2 As shown in the timing diagram, when the power control device 42, i.e., the MOS tube M0, is closed, the inductor current on the inductor L gradually increases, and the voltage across the resistor Rcs, i.e., the load voltage Vcs, also gradually increases. The peak control voltage generating unit 10 can sample the load voltage Vcs after the power control device 42 is closed to obtain a voltage compensation signal Vc, and then generate a compensation voltage Vn according to the sampled voltage compensation signal Vc, and generate a peak control voltage Vm according to the compensation voltage Vn and the load voltage Vcs, and then transmit the generated peak control voltage Vm to the current limiting control unit 20.

[0035] like Figure 2As shown in the timing diagram, the peak control voltage generating unit 10 can sample the load voltage Vcs at a fixed time after the power control device 42 is closed to obtain the voltage compensation signal Vc, thereby generating the compensation voltage Vn as shown in the timing diagram according to the voltage compensation signal Vc, wherein the fixed time can be any time period Tn between the closing and the opening of the power control device 42, for example, the time period Tn can be a time period starting from the moment the power control device 42 is closed to the end of the preset time length, or a time period starting from any moment after the power control device 42 is closed to the end of the preset time length, and the fixed time sampling time is short so that the voltage compensation signal Vc is a fixed value in the current sampling.

[0036] The current limiting control unit 20 is connected to the output end of the peak control voltage generating unit 10, and the current limiting control unit 20 receives the peak control voltage Vm, and after the peak control voltage Vm reaches a preset voltage threshold Vref, the current limiting control unit 20 sends a disconnect drive signal DK to the control logic unit 30.

[0037] The control logic unit 30 controls the power control device 42, i.e., the MOS tube M0, to disconnect according to the disconnection drive signal DK. Since the inductor current gradually increases after the power control device 42 is closed, when the control logic unit 30 controls the power control device 42 to disconnect, the inductor current presents a maximum value and then gradually decreases.

[0038] from Figure 2 It can be seen from the timing diagram that when ripples are generated in different switching cycles, the starting values ​​of the inductor current are different, so that the starting values ​​of the corresponding load voltage Vcs are also different. The peak control voltage generating unit 10 in the present application scheme samples the load voltage Vcs at a fixed time in each switching cycle to obtain the voltage compensation signal Vc. When the starting value of the load voltage Vcs is different, the voltage compensation signal Vc obtained by the peak control voltage generating unit 10 at the fixed time is also different, so that the compensation voltage Vn generated by the peak control voltage generating unit 10 based on the voltage compensation signal Vc is also different, and then when the starting value of the load voltage Vcs is different, the peak control voltage Vm transmitted to the current limiting control unit 20 is different.

[0039] Since the present solution controls the power control device 42 to be disconnected when the peak control voltage Vm reaches the preset voltage threshold Vref, and the peak control voltage Vm is generated by calculating the compensation voltage Vn and the load voltage Vcs, the following formula can be obtained:

[0040] Vref=Vm=Vn+Vcs=Vn+I pk *Rcs;

[0041] From the above formula, it can be concluded that when the power control device is disconnected, the maximum inductor current is:

[0042]

[0043] From the above formula, Vref is the preset voltage threshold, which is a fixed value, and Rcs is also a fixed value. Therefore, the maximum value of the inductor current I pk It is inversely correlated with the compensation voltage Vn.

[0044] Since the compensation voltage Vn is obtained based on the sampled voltage compensation signal Vc, and the compensation voltage Vn is positively correlated with the voltage compensation signal Vc, on this basis, combined with the above formula and the timing diagram, it can be concluded that when the initial value of the inductor current decreases relative to the previous switching cycle, the sampled voltage compensation signal Vc decreases, so that the generated compensation voltage Vn and the peak control voltage Vm decrease, thereby extending the time for the peak control voltage Vm to reach the preset voltage threshold Vref, that is, delaying the time for controlling the power control device 42 to be disconnected, which causes the inductor current peak value I pk Increase, so that the amount of charge transmitted by the inductor in each switching cycle is not affected by the RLC resonance (that is, S0=S1-S2=S3+S4 in the timing diagram, where S represents the amount of charge transmitted by the inductor in the switching cycle); similarly, when the starting value of the inductor current increases relative to the previous switching cycle, the sampled voltage compensation signal Vc increases, so that the generated compensation voltage Vn and the peak control voltage Vm increase, thereby shortening the time for the peak control voltage Vm to reach the preset voltage threshold Vref, which promotes the inductor current peak value I pk The RLC resonance of the inductor is reduced, so that the amount of charge transmitted by the inductor in each switching cycle is not affected by the RLC resonance, thereby causing the dimming output current of the load to change linearly, thereby eliminating the ripple phenomenon introduced by the RLC resonance during the dimming process.

[0045] In the dimming control circuit designed above, the present scheme first generates a compensation voltage Vn by a voltage compensation signal Vc obtained by a peak control voltage generating unit 10 based on a sampled load voltage Vcs, and then calculates the load voltage Vcs and the compensation voltage Vn to generate a peak control voltage Vm. The current limiting control unit 20 sends a disconnection drive signal DK when the peak control voltage Vm reaches a preset voltage threshold value Vref, so that the control logic unit 30 controls the power control device 42 in the load circuit 4 to disconnect according to the disconnection drive signal DK, thereby controlling the peak current of the inductor L in the load circuit 4 according to the compensation voltage Vn in each switching cycle, so that when the starting value of the inductor current changes relative to the previous cycle, the compensation voltage presents the same change, thereby causing the peak current of the inductor to present an opposite change, thereby controlling the charge transmitted by the inductor in the load circuit in each charging and discharging cycle to be not affected by the RLC resonance, thereby causing the dimming output current of the load to present a linear change, thereby eliminating the ripple phenomenon in the dimming process.

[0046] As a possible implementation, the peak control voltage generating unit 10 can implement the aforementioned functions of sampling the load voltage Vcs at a fixed time to obtain the voltage compensation signal Vc and generate the compensation voltage Vn and the peak control voltage Vm through the following specific structure.

[0047] like Figure 3 As shown, the peak control voltage generating unit 10 includes: a sampling control circuit 101 and a peak control voltage generating circuit 102. The sampling control circuit 101 controls the peak control voltage generating circuit 102 to sample the load voltage Vcs at the fixed time mentioned above to obtain a voltage compensation signal Vc. The peak control voltage generating circuit 102 can generate a compensation voltage Vn according to the sampled voltage compensation signal Vc, and generate a peak control voltage Vm according to the compensation voltage Vn and the load voltage Vcs.

[0048] The sampling control circuit 101 includes a sampling signal generating subcircuit 1011, a sampling controllable switch tube M2 and an energy storage capacitor C1. The peak control voltage generating circuit 102 includes a compensation voltage operational amplifier L1, a compensation voltage controllable switch tube M1, a first resistor R1, a second resistor R2 and a current mirror P1.

[0049] The sampling signal generating subcircuit 1011 is connected to the control end of the sampling controllable switch tube M2. The first end of the sampling controllable switch tube M2 is used to receive the load voltage Vcs. The second end of the sampling controllable switch tube M2 is respectively connected to the non-inverting input end of the compensation voltage operational amplifier L1 and the first section of the energy storage capacitor C1. The output end of the compensation voltage operational amplifier L1 is connected to the control end of the compensation voltage controllable switch tube M1. The first end of the compensation voltage controllable switch tube M1 is respectively connected to the first end of the first resistor R1 and the inverting input end of the compensation voltage operational amplifier L1. The second end of the first resistor R1 is connected to the second end of the energy storage capacitor C1 and is grounded. The second end of the compensation voltage controllable switch tube M1 is respectively connected to the first end of the second resistor R2 and the input end of the current limiting control unit 20 through the current mirror P1. The second end of the second resistor R2 receives the load voltage Vcs. For the convenience of example, Figure 3 The compensation voltage controllable switch tube M1 and the sampling controllable switch tube M2 are exemplified as PMOS tubes. In practical applications, they can also be NMOS tubes or other forms of switch tubes, such as insulated gate bipolar transistors (IGBT).

[0050] In the peak control voltage generating circuit 102 designed above, the sampling signal generating sub-circuit 1011 sends a sampling signal to the sampling controllable switch tube M2 at a fixed time to control the sampling controllable switch tube M2 to be turned on, so that the non-phase input terminal of the compensation voltage operational amplifier L1 receives the load voltage Vcs for a fixed time, thereby obtaining a voltage compensation signal Vc, wherein the fixed time can be the moment when the power control device is closed or any moment between the closing and the opening of the power control device.

[0051] The compensation voltage operational amplifier L1 clamps the voltage compensation signal Vc sampled at the non-phase input terminal to the first terminal of the compensation voltage controllable switch tube M1, so that a current I0 is formed in the first resistor R1 and the compensation voltage controllable switch tube M1 branch, and the current I0 = Vc / R1.

[0052] The current I0 is transmitted to the current mirror P1. Assuming that the current mirror ratio of the current mirror P1 is K, the current mirror outputs a compensation current I1=K*I0=K*Vc / R1. The compensation current I1 is transmitted to the second resistor R2, and a compensation voltage Vn is formed on the second resistor R2. The second end of the second resistor R2 receives the load voltage Vcs, so that the first end of the second resistor R2 outputs a peak control voltage Vm generated by combining the compensation voltage Vn and the load voltage Vcs.

[0053] As a possible implementation, the current limiting control unit 20 may also receive a peak threshold signal, which is obtained by converting the dimming signal. Specifically, Figure 3 , Figure 4 , Figure 5 or Figure 6 As shown, the dimming control circuit also includes a signal conversion unit A1, the input end of the signal conversion unit A1 receives the dimming signal, the output end of the signal conversion unit A1 is connected to the current limiting control unit 20, and the signal conversion unit A1 converts the dimming signal into a peak threshold signal and transmits it to the current limiting control unit 20. The peak threshold signal can represent the preset voltage threshold Vref, so that the peak threshold signal can be changed by changing the dimming signal to change the preset voltage threshold. By changing the preset voltage threshold, the closing time of the power control device 42 and the peak current of the inductor L can be adjusted, thereby achieving dimming.

[0054] The current limiting control unit 20 can realize the aforementioned function of generating the disconnection driving signal through the following specific structure, such as Figure 4 As shown, the current limiting control unit 20 includes a current limiting comparator L2, the non-phase input terminal of the current limiting comparator L2 is connected to the first end of the second resistor R2, thereby receiving the peak control voltage Vm transmitted by the first end of the second resistor R2; the inverting input terminal of the current limiting comparator L2 is used to receive the peak threshold signal, specifically, the inverting input terminal of the current limiting comparator L2 is connected to the output terminal of the signal conversion unit A1, thereby receiving the peak threshold signal output by the signal conversion unit A1; the output terminal of the current limiting comparator L2 is connected to the control logic unit 30.

[0055] When the peak control voltage Vm received at the positive input terminal of the current limiting comparator L2 reaches the preset voltage threshold Vref represented by the peak threshold signal received at the inverting input terminal, the current limiting comparator L2 outputs a disconnection drive signal DK, so that the control logic unit 30 controls the power control device 42 to disconnect according to the disconnection drive signal DK.

[0056] As a possible implementation, Figure 5 As shown, the current limiting control unit 20 may also include a peak detection control circuit 201, which includes a peak detection signal generating sub-circuit 2011 and a peak detection controllable switch tube M3, the peak detection signal generating sub-circuit 2011 is connected to the control end of the peak detection controllable switch tube M3, the first end of the peak detection controllable switch tube M3 is connected to the first end of the second resistor R2, and the second end of the peak detection controllable switch tube M3 is connected to the non-phase input end of the current limiting comparator L2.

[0057] The peak detection control circuit 201 designed as above is used to control the conduction state between the positive phase input terminal of the current limiting comparator L2 and the second resistor R2. When conduction is required, the peak detection signal generating sub-circuit 2011 sends a conduction signal to the control terminal of the peak detection controllable switch tube M3, thereby controlling the peak detection controllable switch tube M3 to be turned on, thereby causing the line between the positive phase input terminal of the current limiting comparator L2 and the first end of the second resistor R2 to be turned on, so that the positive phase input terminal of the current limiting comparator L2 receives the peak control voltage Vm.

[0058] As a specific implementation method, when the power control device 42 is just closed, the load voltage Vcs is prone to fluctuate. On this basis, this scheme can control the conduction of the line between the positive input terminal of the current limiting comparator L2 and the first end of the second resistor R2 through the peak detection control circuit 201 after a preset time length after the power control device 42 is closed.

[0059] In an optional implementation of this embodiment, if Figure 6 As shown, the dimming control circuit also includes a demagnetization detection unit 40 and a load switch cycle control unit 50. The control logic unit 30 includes a control logic circuit 301 and a drive circuit 302. The demagnetization detection unit 40 sends a demagnetization completion signal to the load switch cycle control unit 50 when the load current drops from a maximum to 0. The load switch cycle control unit 50 sends a closing drive signal to the control logic circuit 301 according to the demagnetization completion signal, so that the control logic circuit 301 controls the drive circuit 302 to drive the power control device to close according to the closing drive signal. Among them, it should be noted here that the demagnetization detection unit 40, the load switch cycle control unit 50, the control logic circuit 301 and the drive circuit 302 can adopt any existing implementation method. The demagnetization detection unit 40 and the load switch cycle control unit 50 combined with the control logic unit 30 can be controlled by the existing control logic of the closing time point to control the closing time point of the power control device 42. The scheme of the present application is mainly to control the disconnection time point of the power control device to control the peak value of the inductor current, thereby achieving that the charge transmitted by the inductor in each charging and discharging cycle is not affected by the RLC resonance, so that the dimming output current of the load changes linearly, thereby eliminating the ripple.

[0060] Second embodiment

[0061] The present application provides a dimming chip, such as Figure 7 As shown, the dimming chip 1 includes the dimming control circuit described in any optional implementation manner in the first embodiment.

[0062] In the dimming chip 1 of the above-mentioned design, since the dimming chip 1 includes the dimming control circuit in the first embodiment, the dimming chip 1 can make the charge transmitted by the inductor L in the load circuit 4 in each charging and discharging cycle not be affected by the RLC resonance, so that the dimming output current of the load changes linearly, thereby eliminating the ripple phenomenon in the dimming process.

[0063] In the embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are merely schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some communication interfaces, and the indirect coupling or communication connection of the devices or units can be electrical, mechanical or other forms.

[0064] In addition, the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0065] Furthermore, the functional modules in the various embodiments of the present application may be integrated together to form an independent part, or each module may exist separately, or two or more modules may be integrated to form an independent part.

[0066] In this document, relational terms such as first and second, etc. are used merely to distinguish one entity or operation from another entity or operation, but do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0067] The above description is only an embodiment of the present application and is not intended to limit the protection scope of the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A dimming control circuit, characterized in that: include: A peak control voltage generating unit (10), a current limiting control unit (20) and a control logic unit (30); The peak control voltage generating unit (10) is used to sample the load voltage of the load circuit to obtain a voltage compensation signal, generate a compensation voltage according to the voltage compensation signal, and generate a peak control voltage according to the compensation voltage and the load voltage, wherein the peak control voltage is the sum of the compensation voltage and the load voltage; The current limiting control unit (20) is used to receive the peak control voltage and send a disconnection drive signal to the control logic unit (30) when the peak control voltage reaches a preset voltage threshold; The control logic unit (30) is used to drive the power control device in the load circuit to disconnect according to the disconnection drive signal; The current limiting control unit (20) is further used to receive a dimming signal and adjust the preset voltage threshold according to the dimming signal to adjust the closing time of the power control device and the peak current of the load circuit, thereby achieving dimming; The current limiting control unit (20) comprises a current limiting comparator (L2), and a positive phase input terminal of the current limiting comparator (L2) is connected to an output terminal of the peak control voltage generating unit (10); The inverting input terminal of the current limiting comparator (L2) is used to receive a peak threshold signal, the peak threshold signal is obtained by converting the dimming signal, and the peak threshold signal represents the preset voltage threshold; The output end of the current limiting comparator (L2) is connected to the control logic unit (30) so as to send a disconnection drive signal to the control logic unit (30) when the peak control voltage reaches a voltage threshold corresponding to the peak threshold signal.

2. The dimming control circuit according to claim 1, characterized in that: The peak control voltage generating unit (10) comprises a sampling control circuit (101) and a peak control voltage generating circuit (102), wherein the input end of the sampling control circuit (101) is used to receive the load voltage, the output end of the sampling control circuit (101) is connected to the input end of the peak control voltage generating circuit (102), and the output end of the peak control voltage generating circuit (102) is connected to the input end of the current limiting control unit (20); The sampling control circuit (101) is used to control the peak control voltage generation circuit (102) to sample the load voltage to obtain the voltage compensation signal after the power control device is closed; The peak control voltage generating circuit (102) is used to generate the compensation voltage according to the voltage compensation signal, and to generate the peak control voltage according to the compensation voltage and the load voltage.

3. The dimming control circuit according to claim 2, characterized in that: The peak control voltage generating circuit (102) comprises a compensation voltage operational amplifier (L1), a compensation voltage controllable switch tube (M1), a first resistor (R1), a second resistor (R2) and a current mirror (P1); the non-phase input end of the compensation voltage operational amplifier (L1) is connected to the output end of the sampling control circuit (101); the output end of the compensation voltage operational amplifier (L1) is connected to the control end of the compensation voltage controllable switch tube (M1); the first end of the compensation voltage controllable switch tube (M1) is respectively connected to the first end of the first resistor (R1) and the inverting input end of the compensation voltage operational amplifier (L1); and the second end of the first resistor (R1) is grounded; The second end of the compensation voltage controllable switch tube (M1) is respectively connected to the first end of the second resistor (R2) and the input end of the current limiting control unit (20) through the current mirror (P1), and the second end of the second resistor (R2) is used to receive the load voltage.

4. The dimming control circuit according to claim 3, characterized in that: The sampling control circuit (101) comprises a sampling signal generating subcircuit (1011), a sampling controllable switch tube (M2) and an energy storage capacitor (C1); the sampling signal generating subcircuit (1011) is connected to the control end of the sampling controllable switch tube (M2); the first end of the sampling controllable switch tube (M2) is connected to the second end of the second resistor (R2); the second end of the sampling controllable switch tube (M2) is respectively connected to the first end of the energy storage capacitor (C1) and the non-phase input end of the compensation voltage operational amplifier (L1); and the second end of the energy storage capacitor (C1) is connected to the second end of the first resistor (R1); The sampling signal generating subcircuit (1011) is used to generate a sampling signal to control the sampling controllable switch tube (M2) to turn on after the power control device is closed.

5. The dimming control circuit according to claim 1, characterized in that: The current limiting control unit (20) further comprises a peak detection control circuit (201), which is arranged between the positive phase input terminal of the current limiting comparator (L2) and the output terminal of the peak control voltage generating unit (10) and is used to control the conduction state between the positive phase input terminal of the current limiting comparator (L2) and the output terminal of the peak control voltage generating unit (10).

6. The dimming control circuit according to claim 1, characterized in that: The dimming control circuit also includes a demagnetization detection unit (40) and a load switch cycle control unit (50); The demagnetization detection unit (40) is used to send a demagnetization completion signal to the load switch cycle control unit (50) when the load current drops from a maximum value to 0; The load switch cycle control unit (50) is used to send a closing drive signal to the control logic unit (30) according to the demagnetization completion signal; The control logic unit (30) is used to control the power control device to close according to the closing drive signal.

7. The dimming control circuit according to claim 1, characterized in that: The compensation voltage is inversely correlated with the peak current of the inductor of the load circuit.

8. A dimming chip, characterized in that: The dimming chip includes the dimming control circuit according to any one of claims 1 to 7.

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