CN106300985A - A kind of current equalizing method controlling input current and circuit - Google Patents

Abstract

The invention discloses a current equalization method and circuit for controlling input current, comprising: respectively performing current sampling and power conversion on each of at least two inputs to obtain a feedback input signal of each channel; signal, and output the compensation control signal to the compensation pin COMP of the pulse width modulation PWM controller corresponding to each input. The current sharing method and circuit for controlling the input current disclosed by the invention are used to solve the problem that the prior art cannot guarantee the current sharing dynamic characteristics and higher current sharing precision.

Description

A current sharing method and circuit for controlling input current

technical field

The invention relates to the field of reverse power supply of switching power supplies, in particular to a method and circuit for controlling input current for equalizing current.

Background technique

With the continuous development of communication network technology, while using the communication network to propagate information flow, it can also use the communication network to propagate current and supply power to electrical equipment in the network. For example: use Ethernet to supply power to electronic equipment such as Internet phones, wireless access points, surveillance cameras, and terminal switching equipment in the network; The device is powered. The communication network is used to supply power to the equipment, which solves the problem of difficulty in obtaining power, improves the flexibility of the equipment, reduces the installation complexity and use cost of the equipment itself, and can also use the communication network to remotely control the power supply or power off of the equipment.

With the widespread adoption of communication network power supply technology, the electrical loads in the communication network have higher power consumption requirements. In order to realize a higher power communication network power supply, two or more power supply terminals are usually used to supply power to the same electric load. When the interface control module receives the power supply from the power supply terminal, it first passes through the current sharing module to realize the same current in two or more power supply lines, and then passes through the DC/DC voltage converter (DC/DC, Direct Current/Direct Current) output to the electrical load. Due to the difference in the power supply distance of the power supply end and the loss in the power supply line, there is a problem of large voltage difference between the ports of the interface control module. The voltage regulator (LDO, low dropout regulator) uses linear voltage conversion and series resistors to divide the voltage) to compensate the voltage difference between the input ports to achieve current sharing. However, the voltage compensation range of this method is limited, resulting in poor current sharing effect. , and the greater the pressure difference at the input port, the greater the loss and the lower the efficiency.

In the existing solution, each power supply line corresponds to a DC/DC voltage converter, and current sharing is realized by adjusting the output voltage. FIG. 1 is a schematic structural diagram of a conventional DC/DC converter. As shown in Figure 1, the DC/DC converter includes an input part (Input), a current sampling circuit (Current sense), a power conversion circuit (DC/DC), a feedback circuit (Feedback) and a pulse width modulation control chip (Pulse Width Modulation control, PWM control). Wherein, the input part may include an anti-surge circuit, an anti-reverse circuit, a filter circuit, a slow start circuit, and the like. The current sampling circuit is used to sample the input current cycle by cycle (for example, it is applied to the current-mode control converter) or to sample the current for over-current protection (for example, it is applied to the non-current-mode control converter). In addition, the way to sample the current is usually a resistor or a current transformer. The power conversion circuit may include a power switch tube, a power diode, and a power inductor, and a power transformer is required for an isolation circuit. Feedback circuits can include divider resistors, operational amplifiers, and optocouplers for isolation circuits. The feedback circuit processes the output voltage or current information and transmits it to the PWM control chip. The PWM control chip forms the required duty ratio through the collected information to control the power switching device.

In addition, FIG. 2 is a schematic structural diagram of an existing current sharing method. The content shown in Figure 2 is the parallel connection of multiple structures in Figure 1, and the number of parallel connections can be any natural number above 1. Among them, each circuit needs to add a current processing link (Share process). This link is calculated to form the voltage of the current sharing bus (Share Bus). At the same time, according to its own current and the voltage of the current sharing bus, a signal is formed to control the output voltage. To achieve the effect of equal flow.

However, the dynamic characteristics of the above-mentioned current sharing method cannot be guaranteed, and with the increase of power supply lines and the increase in the number of DC/DC voltage converters, the accuracy of current sharing will decrease.

Contents of the invention

In order to solve the above technical problems, the present invention provides a current sharing method and circuit for controlling input current, which are used to solve the problem that the current sharing dynamic characteristics and high current sharing accuracy cannot be guaranteed in the prior art.

In order to achieve the above-mentioned technical purpose, the present invention provides a current sharing method for controlling the input current, which includes: performing current sampling and power conversion on each of at least two inputs respectively to obtain the feedback input signal of each channel; feedback input signal, and output a compensation control signal to the compensation pin COMP of the pulse width modulation PWM controller corresponding to each input.

Further, the PWM controller is a current-mode PWM controller with independent COMP or equivalent COMP.

Further, performing current sampling and power conversion on each of the at least two inputs respectively to obtain the feedback input signal of each includes: respectively sampling the peak current or the average of each of the at least two inputs cycle by cycle The value current is obtained to obtain the sampling current output signal of each channel; after the power conversion is performed on the sampling current output signal of each channel respectively, the feedback input signal of each channel is obtained.

Further, after performing current sampling and power conversion on each of the at least two inputs, and obtaining the feedback input signal of each input, it also includes: outputting the sampled current output signal obtained after performing current sampling on each input to Each input corresponds to the current sampling input pin of the PWM controller.

Further, according to the feedback input signals of each channel, outputting the compensation control signal to the COMP of the PWM controller corresponding to the input of each channel includes: sampling the feedback input signals of each channel to obtain a sampling signal, and the The sampled signal is proportional, supplemented or isolated to obtain a compensation control signal; the compensation control signal is output to the COMP of the PWM controller corresponding to each input.

The present invention also provides a current equalizing circuit for controlling input current, including: a feedback circuit, at least two current sampling circuits, at least two power conversion circuits and at least two PWM controllers, the current sampling circuit, the power The number of conversion circuits and PWM controllers corresponds to the number of inputs, and each input is connected to a corresponding current sampling circuit and a power conversion circuit, and each current sampling circuit is connected to a corresponding power conversion circuit and a PWM controller. , the outputs of all power conversion circuits are connected to the feedback circuit, and the outputs of the feedback circuit are connected to COMP of all PWM controllers.

Further, the PWM controller is a current-mode PWM controller with independent COMP or equivalent COMP.

Further, the current sampling circuit is used for sampling the peak current or average current corresponding to each input on a cycle-by-cycle basis.

Further, the current sampling circuit is configured to output a sampled current output signal obtained after performing current sampling corresponding to each input to a current sampling input pin of a corresponding PWM controller.

Further, the feedback circuit is configured to sample the feedback input signals of each channel to obtain a sampled signal, and perform proportional, supplementary or isolated processing on the sampled signal to obtain a compensation control signal.

In the present invention, current sampling and power conversion are performed on each of the at least two inputs to obtain the feedback input signal of each channel; according to the feedback input signal of each channel, the compensation control signal is output to the corresponding PWM of each channel. Compensation pin COMP of the controller. In this way, there is no need to use a current sharing bus, no need to achieve current sharing through the existing method of adjusting the output voltage, and directly adjust the input current of each cycle, reducing the current sharing link, thereby ensuring dynamic characteristics and high current sharing accuracy. Moreover, the accuracy of current sharing will not decrease due to the increase in the number of parallel input channels. At the same time, the number of components used is reduced and the cost is reduced.

Description of drawings

FIG. 1 is a schematic structural diagram of an existing DC/DC converter;

FIG. 2 is a schematic diagram of an existing current sharing method;

3 is a schematic diagram of a current sharing circuit for controlling input current provided by an embodiment of the present invention;

4 is a schematic diagram of a current sharing circuit for controlling input current provided by a specific embodiment of the present invention;

FIG. 5 is a schematic diagram of a current mode control chip applied to an embodiment of the present invention.

detailed description

The embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. It should be understood that the embodiments described below are only used to illustrate and explain the present invention, and are not intended to limit the present invention.

An embodiment of the present invention provides a current sharing method for controlling an input current, including the following steps:

Step 11: Perform current sampling and power conversion on each of the at least two inputs to obtain a feedback input signal for each.

Step 12: According to the feedback input signals of each channel, output a compensation control signal to the compensation pin COMP of the PWM controller corresponding to each input channel.

Wherein, the PWM controller is a current-mode PWM controller with an independent COMP or an equivalent COMP.

Here, performing current sampling and power conversion on each of the at least two inputs respectively, and obtaining the feedback input signal of each includes: respectively sampling the peak current or the average current of each of the at least two inputs cycle by cycle , to obtain the sampling current output signal of each channel; after performing power conversion on the sampling current output signal of each channel respectively, the feedback input signal of each channel is obtained.

Here, current sampling and power conversion are respectively performed on each of the at least two inputs, and after the feedback input signal of each is obtained, the method further includes: outputting the sampled current output signal obtained after performing current sampling on each input to Each input corresponds to the current sampling input pin of the PWM controller.

Here, according to the feedback input signals of each channel, outputting the compensation control signal to the COMP of the PWM controller corresponding to the input of each channel includes: sampling the feedback input signals of the various channels to obtain a sampling signal, and the sampling signal A compensation control signal is obtained after performing proportional, supplementary or isolation processing; outputting the compensation control signal to the COMP of the PWM controller corresponding to each input.

FIG. 3 is a schematic diagram of a current sharing circuit for controlling input current provided by an embodiment of the present invention. As shown in Figure 3, the current sharing circuit for controlling the input current provided by the embodiment of the present invention includes a feedback circuit (Feedback), at least two current sampling circuits (Current sense 1, Current sense 2, Current sense N), at least two Power conversion circuits (DC/DC 1, DC/DC 2, DC/DC N) and at least two PWM controllers (PWM control 1, PWM control 2, PWM controlN). Wherein, the number of current sampling circuits, power conversion circuits and PWM controllers corresponds to the number of inputs (Input 1, Input 2, Input N), and each input is connected to a corresponding current sampling circuit and a power conversion circuit, and Each current sampling circuit is respectively connected to a corresponding power conversion circuit and a PWM controller. Outputs of all power conversion circuits are connected to feedback circuits, and outputs of feedback circuits are connected to COMP of all PWM controllers.

As shown in Figure 3, the input Input 1 is connected to the current sampling circuit Current sense 1 and the power conversion circuit DC/DC 1, and the current sampling circuit Current sense 1 is connected to the power conversion circuit DC/DC 1 and the PWM controller PWM control 1; input Input 2 Connect the current sampling circuit Current sense 2 and the power conversion circuit DC/DC 2, the current sampling circuit Current sense 2 is connected to the power conversion circuit DC/DC 2 and the PWM controller PWM control 2; input Input N is connected to the current sampling circuit Current sense N and the power The conversion circuit DC/DC N and the current sampling circuit Current sense N are connected to the power conversion circuit DC/DC N and the PWM controller PWM control N. The output of the power conversion circuit (including DC/DC 1, DC/DC 2, DC/DC N) is connected to the feedback circuit Feedback, and the output of the feedback circuit Feedback is connected to the PWM controller (including PWM control 1, PWMcontrol 2, PWM control N ) COMP.

As shown in Figure 3, each input has an independent PWM controller, an independent current sampling circuit and an independent power conversion circuit. The output of each input after passing through the current sampling circuit and the power conversion circuit is connected in parallel and provided to the feedback circuit, and the output of the feedback circuit is simultaneously sent to the COMP of each PWM controller.

Wherein, the PWM controller is a current-mode PWM controller with an independent COMP (for example, a current-mode PWM control chip UC3842), or a current-mode PWM controller with an equivalent COMP. The power conversion circuit includes power tubes, capacitors, and inductors, or may include transformers, diodes, and the like.

Wherein, the feedback circuit is used for sampling the feedback input signals of each channel to obtain a sampling signal, and performing proportional, supplementary or isolation processing on the sampling signal to obtain a compensation control signal. Specifically, the output (compensation control signal) of the feedback circuit is sent to the COMP of each PWM controller at the same time, and this compensation control signal can be delivered directly; Actuation capability, or scaling up or down, etc.

Wherein, the current sampling circuit is used to output the sampling current output signal obtained after performing current sampling corresponding to each input to the current sampling input pin (CurrentSense Input pin) of the corresponding PWM controller. Specifically, the current sampling method can be resistance sampling or current transformer sampling. In addition, the peak current can be sampled cycle by cycle, or the average current can be sampled to improve the accuracy of current sharing, or other processing methods can be used.

FIG. 4 is a schematic diagram of a current sharing circuit for controlling input current provided by a specific embodiment of the present invention. As shown in Figure 4, this embodiment uses two independent inputs. Among them, the main power topology adopts an isolated flyback conversion circuit. The PWM controller is UC3842 controller, the current sampling is obtained through resistance sampling, and the feedback circuit is realized by parallel voltage regulator integrated circuit TL431 and isolated optocoupler.

In this embodiment, two independent inputs share one feedback signal and send it to COMP of each PWM controller.

FIG. 5 is a schematic diagram of a current mode control chip applied to an embodiment of the present invention. Here, the PWM controller adopts, for example, a current mode control chip as shown in FIG. 5 .

Specifically, the current-type control chip compares the sampled current value with a certain reference value through a comparator according to the sampled current (such as obtained through pin 3 (5)) in each control cycle. When the reference value is greater than the current sampled value , the duty cycle is effectively turned on; when the current sampling value is greater than the reference value, the comparator operates, the duty cycle is turned off, and then the cycle ends, and the next switching cycle is ready. Wherein, the reference value for comparison with the current sampling value is obtained through signal processing of COMP (that is, pin pin1 (1)). In UC3842, the voltage of the COMP pin passes through two diodes first, and then it is divided by a resistance of 2R to 1R. In other words, the output voltage is controlled through COMP, and the input current is controlled through the Current Sense Input pin (pin3(5)). When all parallel circuits share one COMP, each parallel circuit will adjust its output voltage to the same value. In addition, each current adopts the input of its own Current Sense Input pin, so each cycle regulates its own current. Since the voltage reference is a common one, even if the input voltage of each channel is different, the regulated current value is the same. Among them, in order to improve the precision of adjusting the current, the sampling current can be sent to the CurrentSense Input pin after the average value processing. In this regard, by using a capacitor, the average value of the current can be easily obtained. Each conversion circuit can be set to the same switching frequency, so that the input current of each switching cycle is the same, and the input current of the whole period is also the same. Wherein, the input current of the whole period is equal to the input current of each switching cycle multiplied by the switching frequency.

To sum up, the present invention realizes current sharing with better dynamic characteristics by controlling the input current cycle by cycle, and there is no problem of oscillation due to current loop adjustment. In addition, because there is no current-sharing busbar and a common feedback circuit, this current-sharing method saves a lot of components and achieves the beneficial effect of saving volume and reducing cost. Moreover, because there is no current sharing bus, the current sharing accuracy of this current sharing method will not be reduced due to the increase in the number of channels.

The basic principles and main features of the present invention and the advantages of the present invention have been shown and described above. The present invention is not limited by the above-mentioned embodiments, and what described in the above-mentioned embodiments and the description only illustrates the principle of the present invention, and without departing from the spirit and scope of the present invention, the present invention also has various changes and improvements, these changes All modifications and improvements are within the scope of the claimed invention.

Claims (10)

1. A current sharing method for controlling input current, characterized in that, comprising: performing current sampling and power conversion on each of the at least two inputs respectively to obtain a feedback input signal of each; According to the feedback input signals of each channel, a compensation control signal is output to the compensation pin COMP of the pulse width modulation PWM controller corresponding to each input channel. 2. The method according to claim 1, wherein the PWM controller is a current-mode PWM controller with independent COMP or equivalent COMP. 3. The method according to claim 1, wherein the step of performing current sampling and power conversion on each of the at least two inputs respectively to obtain a feedback input signal of each comprises: Sampling the peak current or average current for each of the at least two inputs, respectively, cycle by cycle, to obtain a sampled current output signal for each; After performing power conversion on the sampling current output signal of each channel respectively, the feedback input signal of each channel is obtained. 4. The method according to claim 1, characterized in that, performing current sampling and power conversion on each of the at least two inputs respectively, and after obtaining the feedback input signals of each, further comprising: outputting each Input the sampling current output signal obtained after current sampling to the current sampling input pin of the PWM controller corresponding to each input. 5. The method according to claim 1, characterized in that, according to the feedback input signals of each path, outputting the compensation control signal to the COMP of the PWM controller corresponding to the input of each path comprises: The feedback input signal is sampled to obtain a sampling signal, and the sampling signal is proportional, supplemented or isolated to obtain a compensation control signal; the compensation control signal is output to the COMP of the PWM controller corresponding to each input. 6. A current sharing circuit for controlling input current, characterized in that it comprises: A feedback circuit, at least two current sampling circuits, at least two power conversion circuits, and at least two PWM controllers, the number of the current sampling circuits, the power conversion circuits, and the PWM controllers corresponds to the number of input channels, Each input is connected to a corresponding current sampling circuit and a power conversion circuit, each current sampling circuit is respectively connected to a corresponding power conversion circuit and a PWM controller, and the outputs of all power conversion circuits are connected to the feedback circuit. The output of the feedback circuit is connected to COMP of all PWM controllers. 7. The circuit according to claim 6, wherein the PWM controller is a current-mode PWM controller with independent COMP or equivalent COMP. 8. The circuit according to claim 6, wherein the current sampling circuit is configured to sample the peak current or average current corresponding to each input on a cycle-by-cycle basis. 9. The circuit according to claim 6, characterized in that: the current sampling circuit is used to output the sampling current output signal obtained after performing current sampling corresponding to each input to the current sampling input pin of the corresponding PWM controller . 10. The circuit according to claim 6, wherein the feedback circuit is configured to sample the feedback input signals of each channel to obtain a sampled signal, and perform proportional, supplementary or isolated processing on the sampled signal Get the compensation control signal.