TWI400991B - Control circuit with frequency compensation - Google Patents

Description

Control circuit with frequency compensation

The invention provides a control circuit applied to an open loop control system, in particular to a control circuit with frequency compensation which automatically reduces the frequency of the control circuit when the required on-time of the system is less than the minimum on-time.

According to the light-emitting diode, it has become the most important kind of light source in recent years. Because the light-emitting diode has the advantages of high luminous efficiency, long service life, no damage, low power consumption, environmental protection and small volume, etc. Modern energy-saving, very in line with current needs. In the early days, due to the insufficient brightness of the light-emitting diodes, it was often applied to the light of the indicator light and the display panel. However, in recent years, due to the breakthrough of materials and technology, the brightness of the light-emitting diode has been greatly improved. The emergence of white light-emitting diodes, in particular, has led to the replacement of current conventional lighting devices by light-emitting diodes.

When the application of the light-emitting diode is more and more, it is very important to drive the driving circuit of the light-emitting diode, and the driving circuit can appropriately provide the stable power supply of the light-emitting diode, so that the light-emitting diode can be stabilized. In order to reduce the cost and circuit space, many manufacturers integrate the illumination driver circuit into the integrated circuit. The manufacturer can effectively drive the LED for illumination by using an illumination driver circuit. .

However, when the above illumination driving circuit is used, the following problems and defects are indeed to be improved:

The lighting driver circuits on the market cannot be applied to the heavy line and light load conditions, because the on-time required by the circuit is often less than the minimum on-time, thus causing the illumination through The current of an element such as a light-emitting diode is too large to cause the light-emitting diode to burn out.

Therefore, how to solve the above problems and deficiencies in the above-mentioned applications, that is, the inventors of the present invention and those involved in the industry are eager to study the direction of improvement.

Therefore, the inventors of the present invention have collected the relevant materials in view of the above-mentioned shortcomings, and through multi-party evaluation and consideration, and through years of experience accumulated in the industry, through continuous trial and modification, the design of such a system is required. The inventor of the control circuit with frequency compensation is automatically controlled by the control circuit when the on-time is less than the minimum on-time.

The main object of the present invention is to provide a control circuit that can automatically down-convert according to system requirements.

In order to achieve the above object, the control circuit of the present invention includes an oscillator, a first comparator, a second comparator, and a flip-flop. Wherein, the oscillator is capable of periodically generating a setting signal; the first comparator includes a first input terminal for sampling the input current, and a second input terminal for inputting a reference voltage and a DC level voltage summing voltage, And comparing, according to the first input end, the second input end, when the current sample is greater than the sum voltage value, generating a down-converted signal output to the first output end of the oscillator, thereby lowering the oscillator Generating a frequency of the set signal; the second comparator includes a third input terminal for inputting the current sample, a fourth input terminal for inputting the reference voltage, and according to the third input terminal and the fourth input Comparing the end, when the current sampling is greater than the reference voltage, generating a second output end of the reset signal output; the flip-flop includes a setting end, a reset end and an output end, and the setting end can receive the oscillator a set signal generated, and the reset end can receive a reset signal generated by the second output end, and the output end can perform high level and low level according to the set signal and the reset signal Change.

Thereby, when the current sample of the first comparator is greater than the sum voltage of the reference voltage and the DC level voltage, that is, when the required on-time of the system is less than the minimum on-time, the first comparator outputs a down-converted signal. Reduce the frequency of the oscillator to match the frequency required by the circuit, further avoiding the risk of burnout due to excessive system load current.

In order to achieve the above objects and effects, the technical means and the structure of the present invention will be described in detail with reference to the preferred embodiments of the present invention.

Referring to the first and second figures, which are schematic diagrams of the first and second embodiments of the preferred embodiment of the present invention, it will be apparent from the drawings that the present invention can be applied to the illumination driving circuit 1. The illumination driving circuit 1 includes a light emitting diode 14, a capacitor 15, an inductor 16, a diode 17, a power transistor 18 and a resistor 19, wherein the power transistor 18 is used as a switch in the circuit, and the power is used. The two ends of the transistor 18 are respectively connected to a control circuit 2, which is an output end 63 and a current sampling end 11, respectively, and the control circuit 2 includes (from the second figure):

Oscillator 3, the oscillator 3 can periodically generate a setting signal 31; a first comparator 4, the first comparator 4 is configured to generate a down-converted signal 44 to reduce the frequency of the oscillator 3, and the first comparator 4 includes a first input terminal 41, the first input terminal 41 is for inputting the current sample 11; a second input terminal 42 is for summing the input reference voltage 12 and the DC level voltage 13 which is generated in the control circuit 2, and The DC level voltage 13 can be between 0.1 volts and 10 volts, typically 0.25 volts according to material properties; the first output 43 can be based on the first input 41 and the second input 42 In comparison, when the current sample 11 is greater than the sum voltage, a down-converted signal 44 is generated and output to the oscillator 3, thereby reducing the frequency at which the oscillator 3 generates the set signal 31.

a second comparator 5, the second comparator 5 includes: a third input terminal 51 for inputting the current sample 11; a fourth input terminal 52, the fourth input terminal 52 is inputtable The second output terminal 53 is compared with the fourth input terminal 52 according to the third input terminal 51. When the current sample 11 is greater than the reference voltage 12, a voltage is generated. The reset signal 54 is output.

The flip-flop 6 can be an RS flip-flop 6 , and the flip-flop 6 includes a set end 61 , a reset end 62 and an output end 63 , and the set end 61 can receive the oscillator 3 The reset signal 62 can receive the reset signal 54 generated by the second output end 53, and the output end 63 can be based on the set signal 31 and the weight The signal 54 is switched between a high level and a low level.

With the above structure and composition design, the operation of the present invention will be described as follows. Please refer to the first, second, third and fourth figures at the same time, which is a preferred embodiment of the present invention. FIG. 1 and FIG. 2 are schematic diagrams 3 and 4, as is clear from the figure, when the control circuit 2 of the present invention is applied to the illumination driving circuit 1 and is actuated, since the inductor 16 is charged first, the illumination is made. The driving circuit 1 is inductive, further causing the power transistor 18 used as a switch to be turned on (ON), and the oscillator 3, that is, the periodic generating setting signal 31 is outputted to the setting end 61 of the flip-flop 6, whereby The output 63 of the flip-flop 6 is switched to a high level output.

Moreover, since the power transistor 18 is in an on state, the current sample 11 is gradually increased due to the charging of the inductor 16. When the current sample 11 is greater than the reference voltage 12, the second comparator 5 generates a reset signal 54. The output, whereby the flip-flop 6 is switched to a low level output.

When the current sampling 11 continues to increase and is greater than the sum voltage of the reference voltage 12 and the DC level voltage 13, the required conduction time for the illumination driving circuit 1 is less than the minimum conduction time, the first comparison. The device 4 outputs a down-converted signal 44 to the oscillator 3, thereby reducing the frequency at which the oscillator 3 generates the set signal 31, so that the on-time required for the illumination driving circuit 1 is greater than the minimum on-time, by the present invention The control circuit 2 can make the illumination driving circuit 1 equally applicable to the heavy line and light load conditions, and prevent the illumination element such as the light-emitting diode 14 from being burnt due to excessive current flow, further Increasing the application range of the module of the illumination driving circuit 1 can also be used as a protection mechanism for extreme system conditions.

Furthermore, as can be seen from the fourth figure, since the on-time required by the system is less than the minimum on-time, the load current 7 is continuously increased. If this situation continues to occur, the load current 7 will be too large to burn the load. In the invention, the first comparator 4 generates a down-converted signal 44 to be output to the oscillator 3 to reduce the frequency at which the oscillator 3 generates the set signal 31, further reducing the system original period 71 to the adjustment period 72, and achieving automatic frequency compensation. Practical and progressive.

Therefore, the control circuit with frequency compensation of the present invention is a key to improving the technical application of the prior art. Lie in:

The first comparator 4 is additionally connected to the oscillator 3, and when the current sampling 11 of the illumination driving circuit 1 is increased and greater than the sum of the reference voltage 12 and the DC level voltage 13, this is the case. The required on-time of the illumination driving circuit 1 is less than the minimum on-time, and the first comparator 4 generates a down-converted signal 44 to be output to the oscillator 3, thereby reducing the frequency at which the oscillator 3 generates the set signal 31. In order to make the illumination circuit 1 require a conduction time greater than the minimum on-time.

With the control circuit 2 of the present invention, the illumination driving circuit 1 can be similarly applied to a heavy line and a light load, and the current is prevented from being excessively burned to cause the light-emitting diode 14 to be burnt.

However, the above description is only for the preferred embodiment of the present invention, and thus the scope of the present invention is not limited thereto, so that the simple modification and equivalent structural changes that are made by using the specification and the contents of the present invention should be the same. It is included in the scope of the patent of the present invention and is combined with Chen Ming.

In summary, the frequency compensation control circuit of the present invention can achieve its efficacy and purpose when used, so the invention is an invention with excellent practicability, and is an application requirement for the invention patent, and is proposed according to law. To apply, I hope that the trial committee will grant the invention as soon as possible to protect the inventor's hard work. If there is any doubt in the audit committee, please do not hesitate to give instructions, the inventor will try his best to cooperate and feel polite.

1‧‧‧Lighting drive circuit

11‧‧‧current sampling

12‧‧‧Reference voltage

13‧‧‧DC level voltage

14‧‧‧Lighting diode

15‧‧‧ Capacitance

16‧‧‧Inductance

17‧‧‧ diode

18‧‧‧Power transistor

19‧‧‧resistance

2‧‧‧Control circuit

3‧‧‧Oscillator

31‧‧‧Set signal

4‧‧‧First comparator

41‧‧‧ first input

42‧‧‧second input

43‧‧‧ first output

44‧‧‧down signal

5‧‧‧Second comparator

51‧‧‧ third input

52‧‧‧ fourth input

53‧‧‧second output

54‧‧‧Reset signal

6‧‧‧Fracture

61‧‧‧Setting end

62‧‧‧Reset end

63‧‧‧ Output

7‧‧‧Load current

71‧‧‧ original cycle

72‧‧‧ adjustment cycle

The first figure is a first embodiment of a preferred embodiment of the invention.

The second figure is a second embodiment of the preferred embodiment of the present invention.

The third figure is a schematic diagram 1 of the operation of the preferred embodiment of the present invention.

The fourth figure is a schematic diagram 2 of the action of the preferred embodiment of the present invention.

11‧‧‧current sampling

12‧‧‧Reference voltage

13‧‧‧DC level voltage

2‧‧‧Control circuit

3‧‧‧Oscillator

31‧‧‧Set signal

4‧‧‧First comparator

41‧‧‧ first input

42‧‧‧second input

43‧‧‧ first output

44‧‧‧down signal

5‧‧‧Second comparator

51‧‧‧ third input

52‧‧‧ fourth input

53‧‧‧second output

54‧‧‧Reset signal

6‧‧‧Fracture

61‧‧‧Setting end

62‧‧‧Reset end

63‧‧‧ Output

Claims (3)

A control circuit with frequency compensation is applicable to an open loop control system, the control circuit includes: an oscillator that periodically generates a set signal; and a first comparator, including: a first An input terminal is configured to input a current sampling; a second input terminal is configured to input a sum of a reference voltage and a DC current level voltage; a first output end coupled to the oscillator is Comparing the first input end and the second input end, when the current sampling is greater than the sum voltage value, generating a down-converted signal output to the oscillator, thereby reducing a frequency at which the oscillator generates the setting signal; The second comparator includes: a third input terminal for inputting the current sampling; a fourth input terminal for inputting the reference voltage; and a second output terminal for selecting the third input terminal according to the third input terminal Comparing with the fourth input end, when the current sampling is greater than the reference voltage, a reset signal output is generated; a flip-flop includes a setting end, a reset end and an output end, wherein the setting The oscillator is coupled to the oscillator to receive a setting signal generated by the oscillator, and the reset terminal is coupled to the second comparator to receive a reset signal generated by the second output terminal, where the output terminal can be Switching between the high level and the low level is performed according to the setting signal and the reset signal. A control circuit with frequency compensation as described in claim 1 wherein the DC level voltage can be between 0.1 volts and 10 volts. A control circuit with frequency compensation as described in claim 1 wherein the flip-flop is an RS flip-flop.