Control circuit and method applied to current-adjustable constant-current power supply

Abstract

The invention relates to the technical field of constant-current power supply control, in particular to a control circuit applied to a current-adjustable constant-current power supply, which comprises a constant-current module power supply, a single-channel operational amplifier, a high-side comparator, a sampling resistor and a pulse width modulator, and is characterized in that the constant-current module power supply is used for supplying power; the input end of the high-side comparator is connected with the two ends of the sampling resistor respectively, the output end of the high-side comparator is connected with the input end of the single-channel operational amplifier, the output end and the reverse input end of the single-channel operational amplifier are connected with a TRIM1 port and a TRIM2 port respectively, and the resistor is connected between the TRIM1 port and the TRIM2 port in parallel. The output end of the operational amplifier is connected with the signal receiving end of the pulse width modulator, and the output current of the constant-current module power supply is controlled to be kept constant by adjusting the duty ratio of the pulse of the pulse width modulator. The circuit is stable in constant-current regulation performance, can be used in an input-output common-ground mode, and can be used in an output-parallel mode; the adjustable constant current function is realized by changing the amplification factor of the operational amplifier, and the adjustable range of the constant current is wider.

Description

Technical Field

[0001] The present invention relates to the technical field of constant current power supply control, and specifically to a control circuit applied to a current adjustable constant current power supply. Background Art

[0002] A constant current power supply is a controllable power supply that stably outputs current, and its output current is independent of the change of its resistive load. It is mostly used in LED lighting systems, power supply for precision electronic equipment, communication base stations, data transmission equipment, etc. At present, a constant current circuit with high power, small size, and high efficiency has been realized in DC / DC constant current sources, and non-domestic chips have achieved constant current integrated circuits, which perform constant current control through internal integration. However, it is impossible to split and control the constant current signal, and the controllability is poor.

[0003] There are generally two common constant current control circuits. One is a circuit that uses a sampling resistor to collect the high-side current (as shown in Figure 1 ), and realizes constant current control by means of output floating ground step-down. However, due to the too large voltage fluctuation of the output ground, it cannot be used in common ground with the input ground, and has great limitations. The other is a circuit that uses a sampling resistor to sample from the output ground wire to achieve constant current (as shown in Figure 2 ), and its disadvantage is still that it cannot realize common ground use of input and output, and its ground wire is easily interfered, with poor stability. When multiple modules are used in parallel, sampling chaos is likely to occur, and the constant current effect cannot be achieved. Summary of the Invention

[0004] Aiming at the problem that the existing constant current chips cannot realize input and output common ground use, the present invention provides a control circuit applied to a current adjustable constant current power supply.

[0005] The present invention is realized through the following technical solutions: A control circuit applied to a current adjustable constant current power supply includes a positive line current sampling circuit, a sampling resistor, and a pulse width modulator. The positive line current sampling circuit includes a constant current module power supply, a single-channel operational amplifier, and a high-side comparator. The constant current module power supply is used to supply power to the high-side comparator and the single-channel operational amplifier. The input terminals of the high-side comparator are respectively connected to both ends of the sampling resistor, the output terminal of the high-side comparator is connected to the input terminal of the single-channel operational amplifier, the output terminal and the inverting input terminal of the single-channel operational amplifier are respectively connected to the TRIM1 port and the TRIM2 port, and a magnifying resistor is connected in parallel between the TRIM1 port and the TRIM2 port. The output terminal of the single-channel operational amplifier is connected to the signal receiving terminal of the pulse width modulator.

[0006] Preferably, the Vcc of the constant current module power supply is powered by 12V.

[0007] Preferably, the constant current module, the high-side comparator, and the single-channel operational amplifier form a positive line current sampling circuit.

[0008] Preferably, the output terminal of the single-channel operational amplifier is connected to the signal receiving end of the pulse width modulator through the feedback pin FB of the pulse width modulator.

[0009] Preferably, a P-channel MOS transistor is also connected to the positive output line of the constant current module power supply.

[0010] Preferably, the pulse width modulator outputs a PWM square wave signal.

[0011] A control method for a control circuit applied to a current-adjustable constant current power supply includes the following steps: S1. Use the positive line current sampling circuit to collect the voltages across the resistors, denoted as U1 and U2; S2. Then use the high-side comparator to feedback the voltage difference across the resistors to obtain the voltage difference; S3. The voltage difference is feedback to the pulse width modulator after being adjustable amplified by the operational amplifier of the single-channel operational amplifier; S4. The pulse width modulator outputs a constant current.

[0012] Preferably, the output current accuracy is controlled by adjusting the duty cycle of the pulse width modulator pulses.

[0013] A system including the control circuit applied to a current-adjustable constant current power supply described above.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The control method of the present invention applied to a current-adjustable constant current power supply uses a comparator to collect the output positive line current, converts the current signal into a voltage signal, feeds it back to the circuit through adjustable amplification by an operational amplifier, and then controls the output current accuracy by adjusting the duty cycle of the pulse width modulator pulses. By adjusting the output sampling resistor or the operational amplifier amplification resistor, the output current is controlled to reach the set value, and the constant current circuit is PWM-constant-current controlled by adding an MOS transistor.

[0015] By adding this constant current feedback circuit to the output terminal of the power supply module, the present invention can achieve constant current output of the module according to requirements (the output current does not change due to load changes), and its sampling on the positive line can achieve output common ground use and multi-module parallel use, and is mainly applied to the constant current circuit control of an adjustable constant current power supply, ultimately achieving constant output current and linearly adjustable output current.

[0016] Furthermore, the output current is made PWM-adjustable by adding an MOS transistor to regulate the output loop. Description of the Drawings

[0017] Figure 1 is a certain domestic constant current source circuit in the prior art; Figure 2 is a ground wire sampling circuit in the prior art; Figure 3 is the schematic diagram of the use of a certain LED light adjustment system in the embodiment of the present invention; Figure 4 is the schematic diagram of the positive line current sampling circuit of the present invention; Figure 5 is the schematic diagram of the PWM constant current regulation part of the present invention. Specific embodiments

[0018] The following further elaborates on the present invention in conjunction with specific embodiments, which is an explanation rather than a limitation of the present invention.

[0019] The present invention discloses a control circuit applied to a current-adjustable constant current power supply, including a constant current module power supply, a single-channel operational amplifier, a high-side comparator, a sampling resistor, and a pulse width modulator. The Vcc of the constant current module power supply is powered by 12V and is used to supply power to the high-side comparator and the single-channel operational amplifier. The input terminals of the high-side comparator are respectively connected to both ends of the sampling resistor, the output terminal of the high-side comparator is connected to the input terminal of the single-channel operational amplifier, the output terminal and the inverting input terminal of the single-channel operational amplifier are respectively connected to the TRIM1 port and the TRIM2 port, and a resistor is connected in parallel between the TRIM1 port and the TRIM2 port to adjust the amplification factor of the operational amplifier. The output terminal of the operational amplifier is connected to the signal receiving terminal of the pulse width modulator, and the output current of the constant current module power supply is controlled to remain constant by adjusting the duty cycle of the pulse of the pulse width modulator.

[0020] Among them, the output terminal of the single-channel operational amplifier is connected to the signal receiving terminal of the pulse width modulator through the feedback pin FB of the pulse width modulator. A P-channel MOS transistor is also connected to the positive output line of the constant current module power supply. The pulse width modulator outputs a PWM square wave signal.

[0021] The present invention has a three-stage architecture of high-side comparator + operational amplifier adjustable gain + PWM dynamic modulation. Among them, the high-side comparator samples the current of the output positive line, the operational amplifier performs adjustable signal feedback, and the output current accuracy is controlled by adjusting the duty cycle of the pulse of the pulse width modulator, achieving breakthroughs in terms of current accuracy, dynamic response, and topology scalability, and adapting to high-end scenarios such as LED lighting and laser driver.

[0022] Taking a certain LED light adjustment system as an example, referring to Figure 3 , the control method of a control circuit applied to a current-adjustable constant current power supply of the present invention is as follows: S1, using the positive line current sampling circuit to collect the voltages at both ends of the resistor, denoted as U1 and U2; S2, then using the high-side comparator to feedback the voltage difference between both ends of the resistor to obtain the voltage difference; S3. The voltage difference is fed back to the pulse width modulator after being adjusted and amplified by the operational amplifier of a single-channel operational amplifier. S4. The pulse width modulator outputs a constant current.

[0023] In the control method of a control circuit for a current-adjustable constant current power supply according to the present invention, first, the voltage across a resistor is collected through a positive line current sampling circuit, and then the voltage difference across the resistor is fed back through a high-side comparator. The obtained voltage value is adjusted and amplified by an operational amplifier and then fed back to the circuit reference pin FB. Inside the circuit, the output current accuracy is controlled by adjusting the duty cycle of the pulses of the pulse width modulator. By adjusting the amplification factor of the operational amplifier, linearly adjustable output current can be achieved.

[0024] The schematic diagram of the positive line current sampling part is as Figure 4 shown. A sampling resistor is placed on the positive output line of the LED constant current power supply module. Vcc is powered by 12V and is used to supply power to the high-side comparator and the single-channel operational amplifier. FB is the reference pin of the internal pulse width modulator and is fed back to the inside of the circuit to adjust the duty cycle of the pulses of the pulse width modulator to control the constant output current of the power supply module. TRIM1 and TRIM2 are constant current adjustable terminals. By connecting a resistor in parallel between the two ends of the TRIM1 port and the TRIM2 port, the amplification factor of the operational amplifier is adjusted to control the constant output current.

[0025] The circuit structure of the present invention is simple and the constant current regulation is stable; it can be used with the input and output grounded and can be used in parallel for output; controllable constant current is achieved through operational amplifier amplification, and the controllable constant current range is wider. The comparator is used to collect the positive output line current, convert the current signal into a voltage signal, and feed it back to the circuit through adjustable amplification by the operational amplifier. Then, the output current accuracy is controlled by adjusting the duty cycle of the pulses of the pulse width modulator. Adding this constant current feedback circuit to the output end of the power supply module can enable the module to output a constant current according to requirements (the output current does not change due to load changes), and since it samples on the positive line, it can be used with the input and output grounded and can be used in parallel for output.

[0026] Referring to Figure 5 shown, a P-channel MOS tube is added to the positive output line of the power supply of the control LED constant current module. PWM is a square wave signal, and a triode is controlled to turn on and off the gate of the MOS tube to achieve PWM constant current control of the module.

[0027] The above are only the preferred embodiments of the present invention and are not used to limit the technical solutions of the present invention in any way. Those skilled in the art should understand that without departing from the spirit and principles of the present invention, several simple modifications and substitutions can be made to the technical solutions, and these modifications and substitutions also fall within the protection scope covered by the claims.

Claims

1. A control circuit for a current-adjustable constant current power supply, characterized in that: The invention comprises a positive line current sampling circuit, a sampling resistor and a pulse width modulator. The positive line current sampling circuit comprises a constant current module power supply, a single-channel operational amplifier and a high-side comparator. The constant current module power supply is used to supply power to the high-side comparator and the single-channel operational amplifier. The input end of the high-side comparator is respectively connected to the two ends of the sampling resistor, the output end of the high-side comparator is connected to the input end of the single-channel operational amplifier, the output end and the reverse input end of the single-channel operational amplifier are respectively connected to the TRIM1 port and the TRIM2 port, and an amplifying resistor is connected in parallel between the TRIM1 port and the TRIM2 port. The output end of the single-channel operational amplifier is connected to the signal receiving end of the pulse width modulator.

2. The control circuit for a current-adjustable constant current power supply according to claim 1, characterized in that: The Vcc of the constant current module power supply is powered by 12V.

3. The control circuit for a current-adjustable constant current power supply according to claim 1, characterized in that: The output end of the single-channel operational amplifier is connected to the signal receiving end of the pulse width modulator through the feedback pin FB of the pulse width modulator.

4. The control circuit for a current-adjustable constant current power supply according to claim 1, characterized in that: A P-channel MOS tube is also connected to the output positive line of the constant current module power supply.

5. The control circuit for a current-adjustable constant current power supply according to claim 1, characterized in that: The pulse width modulator outputs a PWM square wave signal.

6. A control method for a control circuit of a current-adjustable constant current power supply as claimed in any one of claims 1 to 5, characterized in that: The following steps are involved: S1, uses the positive line current sampling circuit to collect the voltage across the resistor, recorded as U1 and U2; S2, then uses the high-side comparator to feed back the voltage difference across the resistor to obtain the voltage difference; S3, the voltage difference is adjustedly amplified by the single-channel operational amplifier and then fed back to the pulse width modulator; S4, the pulse width modulator outputs a constant current.

7. The control method according to claim 6, characterized in that: The output current accuracy is controlled by adjusting the duty cycle of the PWM pulses.

8. A system comprising a control circuit for a current-adjustable constant-current power supply according to any one of claims 1 to 5.

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