阅读说明：本技术 一种电压电流控制模式自动切换电路及方法 (Voltage and current control mode automatic switching circuit and method ) 是由 范喆 张宏科 于 2020-06-19 设计创作，主要内容包括：本发明公开了一种电压电流控制模式自动切换电路及方法包括电流互感器L1、三极管Q1和芯片U1；电阻R8第二端和电容C1第二端之间连接有电阻R6,电容C1第二端和电阻R9第二端之间连接有电阻R5,电容C1的第二端通过电阻R3连接芯片U1的RAMP,电容C3的第二端连接芯片U1的CT,三极管Q1的发射极通过电阻R2连接芯片U1的RAMP；三极管Q1的集电极连接芯片U1的Vref；三极管Q1的基极连接芯片U1的CT,且三极管Q1的基极通过电阻R1连接芯片U1的RAMP引脚,电阻R1阻值至少为电阻R2阻值的5倍。使电路具备电流型控制与电压型控制的综合优点,使电源的性能得到了大幅度的提升。(The invention discloses a voltage and current control mode automatic switching circuit and a method, wherein the circuit comprises a current transformer L1, a triode Q1 and a chip U1; a resistor R6 is connected between the second end of the resistor R8 and the second end of the capacitor C1, a resistor R5 is connected between the second end of the capacitor C1 and the second end of the resistor R9, the second end of the capacitor C1 is connected with a RAMP of the chip U1 through the resistor R3, the second end of the capacitor C3 is connected with a CT of the chip U1, and an emitter of the triode Q1 is connected with the RAMP of the chip U1 through the resistor R2; the collector of the triode Q1 is connected with the Vref of the chip U1; the base of the triode Q1 is connected with the CT of the chip U1, the base of the triode Q1 is connected with the RAMP pin of the chip U1 through a resistor R1, and the resistance value of the resistor R1 is at least 5 times that of the resistor R2. The circuit has the comprehensive advantages of current mode control and voltage mode control, and the performance of the power supply is greatly improved.)

1. A voltage and current control mode automatic switching circuit is characterized by comprising a current transformer L1, a triode Q1 and a chip U1;

the chip U1 adopts a current type pwm control chip, a first output end of the current transformer L1 is sequentially connected with a resistor R8, a capacitor C1, a capacitor C3 and a capacitor C4, first ends of a resistor R9, a resistor R10 and a resistor R11 are grounded, a second output end of a current transformer L1 is sequentially connected with second ends of a resistor R8, a capacitor C1 and a resistor R9, a resistor R6 is connected between a second end of a resistor R8 and a second end of a capacitor C1, a resistor R5 is connected between a second end of a capacitor C1 and a second end of a resistor R9, a second end of a capacitor C1 is connected with a RAMP pin of a chip U1 through a resistor R3, a second end of a capacitor C3 is connected with a CT pin of a chip U1, a second end of the capacitor C4 is connected with a Vref pin of the chip U4, a second end of the resistor R4 is connected with an SD pin of the chip U4, a second end of the resistor R4 is connected with an RT pin of the chip U4, a second end of the resistor R4 is connected with a GND pin of;

an emitter of the triode Q1 is connected with a RAMP pin of the chip U1 through a resistor R2; the collector of the triode Q1 is connected with the Vref pin of the chip U1; the base of the triode Q1 is connected with the CT pin of the chip U1, the base of the triode Q1 is connected with the RAMP pin of the chip U1 through a resistor R1, and the resistance value of the resistor R1 is at least 5 times that of the resistor R2.

2. The automatic switching circuit of claim 1, wherein a first terminal of a resistor R7 is connected between the first output terminal of the current transformer L1 and the first terminal of the resistor R8, and a second terminal of a resistor R7 is connected between the second output terminal of the current transformer L1 and the second terminal of the resistor R8.

3. The automatic switching circuit of claim 2, wherein the second terminal of the resistor R7 is connected to the anode of a diode V1, and the cathode of the diode V1 is connected to the second terminal of the resistor R8.

4. The automatic switching circuit of claim 1, wherein a first terminal of a resistor R4 is connected between a first terminal of a resistor R11 and ground, and a second terminal of a resistor R4 is connected to an SS pin of a chip U1.

5. The automatic switching circuit of claim 1, wherein the second terminal of the resistor R11 is connected to ground through a capacitor C2.

6. The automatic switching circuit of claim 1 wherein the type of the chip U1 is UC 1825.

7. A voltage and current control mode automatic switching method based on the circuit of any one of claims 1 to 6 is characterized in that a current transformer L1 weights a power-on current signal and a CT signal transmitted by a resistor R1 to a RAMP pin of a chip U1 at the moment of circuit starting, a power-on instantaneous triode Q1 cannot work due to the fact that the voltage transmitted by the resistor R3 is high, the CT signal weights current information at the resistor R1 and the resistor R3, and the circuit is in a voltage control mode at the moment; when the circuit works in a steady state, the function of the transistor Q1 and the resistor R2 replacing the resistor R1 and the current information reflected by the resistor R3 are weighted, and the circuit is in a current control mode.

Technical Field

The invention belongs to the field of circuit control, and relates to a voltage and current control mode automatic switching circuit and method.

Background

The control method using the analog circuit at the present stage can be divided into a voltage control type and a current control type, and both the two schemes have respective advantages and disadvantages. The current type control has the greatest advantage that the circuit can be protected instantly when overcurrent occurs, but the output duty ratio is usually larger at the moment of electrification, so that output overshoot is caused, and the adjustment is difficult; voltage mode control is relatively simple and easy to debug, but the speed of protection is slow when an input over-current occurs.

Disclosure of Invention

The present invention is directed to overcome the above drawbacks of the prior art, and provides a circuit and a method for automatically switching between voltage and current control modes, so that the circuit has the integrated advantages of current control and voltage control, and the performance of the power supply is greatly improved.

In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose:

a voltage and current control mode automatic switching circuit comprises a current transformer L1, a triode Q1 and a chip U1;

the chip U1 adopts a current type pwm control chip, a first output end of the current transformer L1 is sequentially connected with a resistor R8, a capacitor C1, a capacitor C3 and a capacitor C4, first ends of a resistor R9, a resistor R10 and a resistor R11 are grounded, a second output end of a current transformer L1 is sequentially connected with second ends of a resistor R8, a capacitor C1 and a resistor R9, a resistor R6 is connected between a second end of a resistor R8 and a second end of a capacitor C1, a resistor R5 is connected between a second end of a capacitor C1 and a second end of a resistor R9, a second end of a capacitor C1 is connected with a RAMP pin of a chip U1 through a resistor R3, a second end of a capacitor C3 is connected with a CT pin of a chip U1, a second end of the capacitor C4 is connected with a Vref pin of the chip U4, a second end of the resistor R4 is connected with an SD pin of the chip U4, a second end of the resistor R4 is connected with an RT pin of the chip U4, a second end of the resistor R4 is connected with a GND pin of;

an emitter of the triode Q1 is connected with a RAMP pin of the chip U1 through a resistor R2; the collector of the triode Q1 is connected with the Vref pin of the chip U1; the base of the triode Q1 is connected with the CT pin of the chip U1, the base of the triode Q1 is connected with the RAMP pin of the chip U1 through a resistor R1, and the resistance value of the resistor R1 is at least 5 times that of the resistor R2.

Preferably, a first end of the resistor R7 is connected between the first output end of the current transformer L1 and the first end of the resistor R8, and a second end of the resistor R7 is connected between the second output end of the current transformer L1 and the second end of the resistor R8.

Further, a second terminal of the resistor R7 is connected to an anode of a diode V1, and a cathode of the diode V1 is connected to a second terminal of the resistor R8.

Preferably, a first end of the resistor R4 is connected between a first end of the resistor R11 and ground, and a second end of the resistor R4 is connected to an SS pin of the chip U1.

Preferably, the second terminal of the resistor R11 is connected to ground through a capacitor C2.

Preferably, the chip U1 has the model UC 1825.

A voltage and current control mode automatic switching method based on any one of the circuits is characterized in that a current transformer L1 weights an electrified current signal and a CT signal transmitted through a resistor R1 at the moment of circuit starting and sends the electrified current signal and the CT signal to a RAMP pin of a chip U1, a transistor Q1 cannot work due to the fact that voltage sent from the resistor R3 is high, the CT signal is weighted through a resistor R1 and current information at a resistor R3, and the circuit is in a voltage control mode at the moment; when the circuit works in a steady state, the function of the transistor Q1 and the resistor R2 replacing the resistor R1 and the current information reflected by the resistor R3 are weighted, and the circuit is in a current control mode.

Compared with the prior art, the invention has the following beneficial effects:

according to the circuit, the resistor R1 is arranged, and after a signal sent by the CT pin of the chip U1 is weighted and sent to the RAMP pin, the situation of large duty ratio output by PWM at the moment of power-on can be greatly reduced, the function of the resistor R1 can be replaced by the triode Q1 and the resistor R2 to serve as a new voltage weight network to weight current information reflected by the resistor R3, so that the effect of replacing the resistor R1 when a circuit works in a steady state is ensured, the automatic switching of a voltage control mode and a current control mode of the circuit is realized, and the performance of a power supply is greatly improved.

According to the method, at the moment of starting the circuit, the CT signal is weighted through the current information at the resistor R1 and the resistor R3, when the circuit works in a steady state, the triode Q1 and the resistor R2 can replace the function of the resistor R1 to serve as a new voltage weight network to weight the current information reflected by the resistor R3, so that the effect of the resistor R1 can be replaced when the circuit works in the steady state, the voltage control mode and the current control mode of the circuit are automatically switched, and the performance of a power supply is greatly improved.

Drawings

FIG. 1 is a circuit diagram of the present invention.

Detailed Description

The invention is described in further detail below with reference to the accompanying drawings:

as shown in fig. 1, the voltage-current control mode automatic switching circuit according to the present invention includes a current transformer L1, a transistor Q1, and a chip U1.

The chip U1 adopts a current mode pwm control chip, and the model of the chip U1 is UC 1825.

A first output end of a current transformer L1 is sequentially connected with first ends of a resistor R7, a resistor R8, a capacitor C1, a capacitor C3, a capacitor C4, a resistor R9, a resistor R10 and a resistor R11 and is grounded, a second output end of a current transformer L1 is sequentially connected with second ends of the resistor R7, the resistor R8, the capacitor C1 and the resistor R9, a second end of the resistor R7 is connected with an anode of a diode V1, and a cathode of the diode V1 is connected with a second end of the resistor R8; a resistor R6 is connected between the second end of the resistor R8 and the second end of the capacitor C1, a resistor R5 is connected between the second end of the capacitor C1 and the second end of the resistor R9, the second end of the capacitor C1 is connected to a RAMP pin of the chip U1 through a resistor R3, the second end of the capacitor C3 is connected to a CT pin of the chip U1, the second end of the capacitor C4 is connected to a Vref pin of the chip U1, the second end of the resistor R9 is connected to an SD pin of the chip U1, the second end of the resistor R10 is connected to an RT pin of the chip U1, the second end of the resistor R11 is connected to a CLK pin of the chip U1, the second end of the resistor R11 is grounded through a capacitor C2, the first end of the resistor R11 is connected to ground, the second end of the resistor R11 is connected to an SS pin of the chip U11, and the GND.

The resistor R1 is a weight resistor controlled by a power-on instant response voltage type; the resistor R3 is a weight resistor which reflects the received current signal; when the circuit enters into steady-state operation, the resistor R2 and the transistor Q1 take over the R1 to become a weight network.

When the circuit is used, the current transformer L1 weights the electrified current signal and the CT signal transmitted by the resistor R1 to the RAMP pin of the chip U1 at the moment of circuit starting, the CT signal is sent by the CT pin of the chip U1, if the resistor R1 does not exist, the electrified current signal can directly influence the output of PWM, the output duty ratio is instantly opened to the maximum, and the situation that the PWM outputs a larger duty ratio at the moment of electrification can be greatly reduced after the resistor R1 is added and the signal of the CT is weighted to the RAMP pin. The optimal power-on operating point is found by adjusting the size of the weighted resistor R1 and the resistor R3. The transistor Q1 cannot operate due to the high voltage from the resistor R3, so the CT signal can be directly weighted by the current information from the resistor R1 and the resistor R3. The resistor R1 is a weighted resistor for voltage control mode, and the resistor R3 is a weighted resistor for current control. When the circuit works in a steady state, the triode Q1 and the resistor R2 take the function of replacing the weight resistor R1 as a new voltage weight network to weight the current information reflected by the resistor R3. The value of the resistor R2 is more than 5 times smaller than that of the resistor R1, so that the effect of the resistor R1 can be replaced when the circuit works in a steady state.

The circuit has a simple structure, is convenient to debug, and can quickly determine weight parameters by testing the relation between the electrified waveform and the weight resistors of the resistor R1 and the resistor R3; compared with the conventional current mode control or voltage mode control circuit, the circuit has fewer added devices and high cost performance. The output constant current value can be realized by adjusting the proportional relation of the differential resistors; the circuit can realize the automatic switching between the voltage control mode and the current control mode of the circuit, so that the performance of the power supply is greatly improved.

The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.