CN210156945U

CN210156945U - Battery charger with digital/analog hybrid controller

Info

Publication number: CN210156945U
Application number: CN201921006121.1U
Authority: CN
Inventors: 陈建宏; 陆宇铨
Original assignee: Simplo Technology Co Ltd
Current assignee: Simplo Technology Co Ltd
Priority date: 2019-07-01
Filing date: 2019-07-01
Publication date: 2020-03-17
Anticipated expiration: 2029-07-01

Abstract

The utility model provides a battery charger with digit analog hybrid controller contains: a digital control circuit and an analog control circuit; the digital control circuit is used for receiving the relevant parameters of constant voltage, constant current charging and the like written by the external electronic device, generating an analog voltage according to the voltage and current feedback signal of the battery and electrically connecting the analog voltage with the input stage of the analog control circuit; the analog control circuit generates a PWM signal to drive the power converter of the rear stage after performing control operation on the input-stage voltage signal, the battery voltage and the current feedback signal. Implement the embodiment of the utility model provides a carry out the bias voltage adjustment of feedback input for the charger can utilize multiple pulse width modulation controller elastically, realizes single-stage voltage and current controller's framework. In addition, the digital control circuit is only used for parameter adjustment and feedback compensation of the charging command, and a high-level digital signal processor is not needed, so that the circuit cost can be effectively reduced.

Description

Battery charger with digital/analog hybrid controller

Technical Field

The present invention relates to a battery charger, and more particularly to a battery charging system having both digital and analog control circuits.

Background

In battery charger applications, the power converter needs to have both constant current and constant voltage output functions. The constant current is usually charged in two stages. Taking the charging of the lithium secondary battery as an example, when the charger detects that the voltage of the battery string is too low and the voltage of a single lithium battery cell is lower than 3V, the charger charges the lithium secondary battery with a constant small current, so as to avoid the problems of overheating and life decay of the battery caused by a high charging current when the battery is over-discharged, which is also called as a Pre-charging mode (Pre-ChargingMode). After the voltage of the lithium battery string is greater than the threshold voltage, the charger converts to a large current to charge the lithium secondary battery pack, which is also called a Fast Charging Mode. In the conventional method, an operational amplifier or an adjustable shunt regulator TL431 is used to form an analog voltage controller and a current controller, and the outputs of the two controllers are connected to a pwm IC through a diode to achieve the above functions. The two controllers adopt a switching mode, and a voltage controller or a current controller is determined by the load condition to control a Pulse width modulation controller. For example, since the output voltage of the charger is approximately equal to the voltage of the lithium secondary battery, when the lithium secondary battery is in a low state, the voltage controller is saturated because the output voltage cannot be controlled at the command voltage, and the output diode is in an open circuit state, and at this time, the Duty cycle of the power conversion stage is determined by the current controller; on the contrary, when the voltage of the lithium secondary battery is close to the command voltage of the constant voltage mode, the voltage controller is recovered from the saturation state, when the output voltage of the voltage controller is lower than the output of the current controller, the output diode of the current controller is open, and the voltage controller determines the duty cycle of the power conversion stage.

Fig. 1 is a partial circuit diagram of a prior art battery charger. Referring to fig. 1, the battery voltage and the charging current signals measured by the sensors are respectively inputted to the analog voltage controller 114 and the analog current controller 116, wherein the voltage command VCMD _ CV and the current command VCMD _ CC may be a hardware generated reference voltage or an adjustable reference voltage generated by the micro-controller through the digital-to-analog converter. The output of the voltage controller 114 and the analog current controller 116 are respectively provided with a diode 112 and a diode 110, and the analog voltage VC after the parallel connection of the diode 112 and the diode 110 is connected to the COMP voltage point of the pwm chip 100; the pwm wafer 100 may be, but is not limited to, a UC3843 wafer; then, the analog voltage VC is connected to the negative input of the comparator 108 through the series diode 104 and the voltage dividing resistor 106 inside the PWM chip 100; finally, the comparison with the sawtooth wave signal VRAMP of the positive input point of the comparator 108 generates the gate driving signal required by the power conversion stage. It should be noted that, in this embodiment, the error amplifier 102 inside the pwm chip 100 is not used, and the feedback stability and the output response of the charger are determined by the analog voltage controller 114 or the analog current controller 116 during the whole charging process. However, the parallel connection of the external controllers through the diodes increases the output signal VC of the controller by a diode forward conduction voltage; at this time, if the designer chooses to use the pwm chip without a compensation bias at the positive input of the comparator or without the serial diode 104 as in the pwm chip 100, the pwm rate will be reduced and the minimum duty cycle will be too high.

Generally, the problem is solved by connecting the output of the external analog controller in series with the input of the error amplifier in the width modulation chip. However, this method will increase the poles and zeros of the feedback system, which causes difficulties in designing the constant current and constant voltage controller of the charger; this problem is particularly significant in applications with wide input voltages and wide output voltages. In addition, the control architecture of the digital signal processor instead of the analog controller and the pulse width modulation chip is flexible and can also solve the above problems. However, in a miniaturized product application, such as a Resonant and quasi-Resonant converter (Resonant and quasi-Resonant converter) with a high switching frequency, a digital signal processor with a higher operation speed is required, which results in an increase in product cost.

SUMMERY OF THE UTILITY MODEL

An object of an embodiment of the present invention is to provide a battery charger with a digital/analog hybrid controller. Therefore, the charger can use the low-level micro-control device and the commercially available pulse width modulation chip to achieve the constant voltage and constant current charging function without using the multi-level analog controller. According to the present novel embodiment, the above-mentioned disadvantages of the prior art can be improved.

According to an embodiment of the present invention, a battery charger with a digital/analog hybrid controller includes a digital control circuit and an analog control circuit. The digital control circuit is used for receiving a relevant charging parameter, a battery current feedback signal and a battery voltage feedback signal and generating a control voltage according to the relevant charging parameter, the battery current feedback signal and the battery voltage feedback signal. The analog control circuit is electrically connected to the digital control circuit for receiving the control voltage, the battery current feedback signal and the battery voltage feedback signal to generate a pulse width modulation signal.

In one embodiment, the digital control circuit further comprises a micro-control device. The micro control device comprises a command generator and a controller, and generates two control voltage signals by the command generator and the controller respectively according to the written related charging parameter, the battery current feedback signal and the battery voltage feedback signal; and generating a mode selection signal according to the written related charging parameter.

In one embodiment, the digital control circuit further comprises a two-to-one multiplexer, wherein the two-to-one multiplexer is used for receiving the two control voltage signals and the mode selection signal generated by the micro-control device, and selecting one of the two control voltage signals to output according to the mode selection signal.

In one embodiment, the digital control circuit further comprises a digital-to-analog converter. The digital-to-analog converter is electrically connected to the output ends of the two-to-one multiplexer, and converts the output digital value into an analog control voltage signal as the control voltage.

In one embodiment, the analog control circuit further includes an adder circuit. The adder circuit is used for receiving the battery current feedback signal and the battery voltage feedback signal, and generates an added voltage signal after adding the battery current feedback signal and the battery voltage feedback signal.

In one embodiment, the analog control circuit further includes a pwm controller, a subtractor circuit, and an impedance. The subtractor circuit is used for receiving the added voltage signal and the control voltage output by the adder circuit, and generating a subtracted analog voltage after subtracting the added voltage signal and the control voltage. The impedor is electrically connected with the subtractor circuit and the pulse width modulation controller respectively. The analog voltage after the subtraction is inputted to the PWM controller through the resistor, so as to generate the PWM signal by using the resistor and the PWM controller.

As described above, an advantage of an embodiment of the present invention is that it can perform bias adjustment of feedback input, so that the charger can flexibly employ various pwm controllers to realize a single-stage voltage and current controller architecture. In addition, the digital control circuit is only used for parameter adjustment and feedback compensation of the charging command, so that a high-order digital signal processor is not needed, and the circuit cost can be effectively reduced.

Drawings

The objects, advantages and novel features of the invention will become apparent from the following detailed description when considered in conjunction with the drawings, in which:

fig. 1 is a partial circuit diagram of a prior art battery charger.

FIG. 2 is a block diagram of a battery charger with a digital-to-analog hybrid controller according to an embodiment of the present invention.

FIG. 3 is a partial circuit diagram of an analog control circuit according to an embodiment of the present invention.

FIG. 4 is a schematic diagram of an analog command curve of the analog control circuit according to an embodiment of the present invention.

FIG. 5 is a block diagram of a digital control circuit according to an embodiment of the present invention.

Reference numerals:

10: DC voltage source

100: pulse width modulation chip

102: error amplifier

104: series diode

106: voltage dividing resistor

108: comparator with a comparator circuit

110: diode with a high-voltage source

112: diode with a high-voltage source

114: voltage controller

116: analog current controller

20: battery charger

202: digital control circuit

20202: related charging parameters

204: analog control circuit

206: power converter

30: load(s)

300: adder circuit

302: subtracter

304: impedance device

306: pulse width modulation controller

30602: error amplifier

30604: comparator with a comparator circuit

40: electronic device

502: analog-to-digital converter

504: micro-control device

50402: memory device

50404: command generator

50406: controller

506: two-to-one multiplexer

508: digital-to-analog converter

Detailed Description

The following detailed description of the preferred embodiments of the present invention is provided for illustrative purposes only, and is not intended to limit the scope of the present invention.

Referring to fig. 2 of the drawings, a schematic diagram of a display device,FIG. 2 is a block diagram of a battery charger with a digital/analog hybrid controller according to an embodiment of the present invention. The novel battery charger 20 with digital/analog hybrid controller converts the dc voltage source 10 into a required voltage according to the charging voltage and charging current parameters written by the electronic device 40 and provides the required voltage to the load 30; the dc voltage source 10 may be an externally directly input dc voltage, or an externally input ac voltage, a dc voltage generated by an internal ac-dc converter of the charger. It is understood that the digital/analog hybrid control method described in the present invention can also be applied to other fields, so the load 30 can be, for example, but not limited to, a lithium secondary battery module. The battery charger 20 with a digital to analog hybrid controller includes a digital control circuit 202, an analog control circuit 204 and a power converter 206. The first input of the digital control circuit 202 is the related charging parameter 20202 written by the external electronic device 40, and the second input is a battery current feedback signal V₁The third input is a battery voltage feedback signal V₂(ii) a Wherein, the battery current feedback signal V₁And a battery voltage feedback signal V₂Is the output from the Current sensor and the voltage sensor, the Current sensor can be a Hall effect sensor (Hall effect transducers), a Current transformer (Current transformer) or a circuit of a resistance configuration amplifier; the voltage sensor may be a resistor voltage divider network, or a resistor voltage divider network configured with a detection circuit of an Isolation amplifier (Isolation amplifier); since the current and voltage sensing methods are well known to those skilled in the art, the details thereof are not repeated herein. The digital control circuit 202 generates a control voltage V according to the three input signals_CElectrically connected to the analog control circuit 204. The analog control circuit 204 receives the control voltage V at the same time_CBattery current feedback signal V₁And a battery voltage feedback signal V₂Outputting a PWM signal to drive the power converter 206; the power converter 206 converts the dc voltage source 10 into a required voltage to charge the load 30 through the PWM signal PWM.

Please refer to fig. 3, fig. 3 is the bookAn embodiment of the novel analog control circuit is a partial circuit diagram. As shown in FIG. 3, the analog control circuit 204 includes an adder circuit 300, a subtractor circuit 302, an impedance 304, and a PWM controller 306. First, a battery current feedback signal V₁And a battery voltage feedback signal V₂The voltage is inputted to the adder circuit 300, and the adder circuit 300 feeds back the battery current feedback signal V₁And a battery voltage feedback signal V₂After the addition operation, an added voltage signal is generated. The output of adder circuit 300 is electrically connected to subtractor circuit 302. The subtractor circuit 302 adds the added voltage signal to the control voltage V_CAfter subtraction, a subtracted analog voltage is generated, and the subtracted analog voltage is inputted to the error amplifier 30602 inside the PWM controller 306 through the resistor 304; finally, the output of the error amplifier 30602 is electrically connected to the comparator 30604, and after comparing with the sawtooth wave signal VRAMP, a pulse width modulation signal PWM is generated to modulate the post-stage power converter. It should be noted that the analog control circuit of the present invention only includes a Feedback compensator (Feedback compensator) composed of the resistor 304 and the error amplifier 30602, which can effectively solve the problems of the decrease of the pwm rate and the over-high minimum duty cycle compared to the prior art embodiment in which the output of the external voltage and current controller is connected in parallel to the output of the error amplifier by a diode. In addition, the constant current and constant voltage mode in the charging process is controlled by the control voltage V_CThe control voltage is determined to be continuous and differentiable, thereby improving the transient response adjustment problem at the switching moment of the voltage controller and the current controller in the prior art.

Referring to fig. 4, fig. 4 is a schematic diagram of an analog command curve according to an embodiment of the analog control circuit of the present invention. In this embodiment, the current command in the fast charge mode and the voltage command in the constant voltage mode are designed in the battery current feedback signal V₁And a battery voltage feedback signal V₂Is measured. As shown in FIG. 4, when the battery voltage is lower than the precharge end voltage VPRE, the charger operates in the precharge mode at 10%The battery is charged with constant current by the Standard charge current (IPRE), and the control voltage V is obtained_CIs calculated as follows:

V_C＝V₂-V_REF+V₁

when the voltage of the battery rises to the pre-charging termination voltage VPRE, the charger enters a quick charging mode and charges the battery with constant current by using quick charging current ICC; the control voltage V in this mode is due to the fast charge current command, i.e., the reference voltage VREF within the PWM controller 306_COnly need to deduct the battery feedback voltage signal V₂The formula is as follows:

V_C＝V₂

similarly, due to the constant voltage charging command, i.e., the reference voltage VREF within the PWM controller 306, when the battery voltage reaches the constant voltage VCV, the charger enters the constant voltage charging mode of operation, wherein the control voltage V is controlled_COnly need to deduct the battery feedback current signal V₁The formula is as follows:

V_C＝V₁

from the above three equations, the control voltage V in the charging process shown in FIG. 4 can be plotted_CA curve; the charger is changed from a pre-charging mode to a rapid charging mode, namely one-step current change, and actually, the mode switching usually adopts a ramp command to reduce the influence of transient response on the system; in addition, the subtractor 302 shown in fig. 3 includes a low-pass filter, which can adjust the output of the subtractor 302 to a continuously differentiable signal, so that the feedback compensator composed of the resistor 304 and the error amplifier 30602 is designed without the transient response problem, and the poles and zeros are adjusted for the output current ripple and the voltage ripple.

Referring to fig. 5, fig. 5 is a block diagram of an embodiment of the digital control circuit of the present invention. As shown in FIG. 5, the digital control circuit 202 includes an analog-to-digital converter 502, a micro-control device 504, a two-to-one multiplexer 506, and a digital-to-analog converter 508; wherein the micro-control device 504 internal packageIncludes a memory 50402, a command generator 50404, and a controller 50406. First, the related charging parameters 20202 are written into the memory 50402 of the micro-controller 504 through the digital communication interface, and the related charging parameters 20202 have different parameters such as the boundary voltage of the pre-charge mode, the pre-charge mode current, the fast charge mode current, the constant voltage mode voltage, the charge cut-off current, the input signal selection condition of the two-to-one multiplexer 506, and the controller gain according to the specific battery. Battery current feedback signal V₁And a battery voltage feedback signal V₂The analog voltage is converted into a digital signal by the analog-to-digital converter 502 and input to the micro-control device 504, and provided to the command generator 50404 and the controller 50406 inside the micro-control device 504. The command generator 50404 and the controller 50406 calculate the feedback signal and the charging command in the memory 50402, and then generate respective digital output signals as two control voltage signals, which are electrically connected to the external two-to-one multiplexer 506. Then, the two-to-one multiplexer 506 selects one of the two input signals as the two control voltage signals according to the condition in the memory 50402, and the output terminal of the two-to-one multiplexer 506 is electrically connected to the digital-to-analog converter 508. Finally, the DAC 508 converts the digital signal into an analog control voltage signal as the control voltage V_CThe latter stage analog control circuit 204 is controlled.

As described in the disclosure, the digital control circuit can be selected to operate in an open loop mode or a closed loop mode according to the charging requirements of different batteries. The open loop is the control voltage V generated by the command generator 50404_COf the control voltage V_CThe calculation method is as described above, and thus details are not repeated; when the charger selects to operate in the closed loop mode, feedback compensation of the charger is performed by the controller 50406. Referring to fig. 3 and fig. 5, in order to eliminate the influence of the feedback compensation of the analog control circuit 204 and the reference voltage VREF inside the error amplifier 30602 on the output, the output of the digital control circuit 202 is expressed as follows:

V_C＝V₁+V₂-V_REF+ΔV

where Δ V is the operational output value of the controller 50406. For example, when the charger is operating in the constant voltage mode, the controller 50406 compares the constant voltage value in the memory 50402 with the battery voltage feedback signal V converted by the ADC 502₂The values are subtracted and the subtracted error value input to the internal portion may be, for example and without limitation, a proportional-integral controller. It is noted that, for simplicity of design, the pi controller is usually connected in series with an additional compensator, which adopts a Pole-zero cancellation (Pole-zero cancellation) design rule to cancel the poles and zeros generated by the resistor 304 and the error amplifier 30602 inside the analog controller 204.

In addition, the circuit architecture of the analog-to-digital converter 502, the micro-control device 504, the two-to-one multiplexer 506 and the digital-to-analog converter 508 shown in fig. 5 is only an example and is not meant to limit the present invention. After reading the above disclosure, it should be understood that the functions of the adc 502 and the two-to-one multiplexer 506 can be integrated into the micro-controller 504; also, the output of the two-to-one multiplexer 506 can be a PWM signal, and the low-cost RC low-pass filter can realize the function of the DAC 508.

In addition, the circuit architecture of the adder circuit 300, the subtractor circuit 302, the resistor 304, and the pwm controller 306 in fig. 3 is only an example and not intended to limit the present invention. After reading the above disclosure, those skilled in the art will appreciate that the circuit architecture has the greatest design flexibility, i.e., via the control voltage V_CThe adjustment can use the compensator in the circuit to control the constant voltage or the constant current; however, if a mixed control manner of digital and analog is adopted, i.e. the analog control circuit 204 performs constant current mode control, the digital control circuit 202 performs constant voltage mode control, or the analog control circuit 204 performs constant voltage mode control, and the digital control circuit 202 performs constant current mode control; at this time, only the battery current feedback signal V is needed₁And a battery voltage feedback signal V₂An input is selected to the analog control circuit 204, so that the adder circuit 300 can be omitted. Alternatively, the digital control circuit generates an inverted control voltage V_CThe adder circuit 300 is designed as an adder with three inputs, thus eliminating the subtractor circuit 302; these design variations described above are intended to fall within the scope of the present invention.

Briefly explaining the benefits of the present invention, in the battery charger with the digital analog hybrid controller, the digital control circuit can operate in two modes, wherein the control voltage generated by the open-loop mode can cooperate with the feedback compensator in the analog circuit to complete the pre-charge mode, the fast charge mode and the constant voltage charge mode in the whole charging process; and, according to different battery charging requirements, the digital control circuit can be freely switched to a closed loop mode, and the loop compensation of the charger is executed by the digital controller. Therefore, the novel battery charger with the digital-analog hybrid controller has high design flexibility and low cost performance.

An object of an embodiment of the present invention is to provide a battery charger with a digital/analog hybrid controller. Therefore, the charger can use the low-level micro-control device and the commercially available pulse width modulation chip to achieve the constant voltage and constant current charging function without using the multi-level analog controller. According to the present novel embodiment, the above-mentioned disadvantages of the prior art can be improved,

according to an embodiment of the present invention, a battery charger with a digital/analog hybrid controller comprises: a digital control circuit and an analog control circuit; the digital control circuit is used for receiving the relevant parameters of constant voltage, constant current charging and the like written by the external electronic device, generating an analog voltage according to the voltage and current feedback signal of the battery and electrically connecting the analog voltage with the input stage of the analog control circuit; the analog control circuit generates a PWM signal to drive the power converter of the rear stage after performing control operation on the input-stage voltage signal, the battery voltage and the current feedback signal.

In addition, the analog control circuit of the novel battery charger with the digital analog hybrid controller comprises an operational amplifier circuit and a pulse width modulation controller. The operational amplifier circuit has the effect of operating the voltage of the battery, the battery current feedback signal and a specific control voltage, and can realize the pre-charging mode, the quick charging mode, the constant voltage charging mode and the floating charging mode (Float chargingmode) required by a common charger through the adjustment of the control voltage.

In addition, the novel battery charger with the digital analog hybrid controller has two control modes, namely an open loop control mode and a closed loop control mode, in the digital control circuit. In the open loop control mode, the digital control circuit calculates the battery voltage and current feedback signal with the charging command through its internal command generator, and the calculation result is used to generate a control voltage through the digital-to-analog converter for performing constant voltage or constant current control on the post-stage analog control circuit; in the closed loop control mode, the digital control circuit subtracts the battery voltage and the current Feedback signal from the charging command through its internal controller to generate an error signal, and inputs the error signal to its internal Feedback compensator (Feedback compensator), and the output of the Feedback compensator generates a control voltage through the digital analog converter to perform constant voltage or constant current control on the post-stage analog control circuit.

As described above, the present invention is advantageous in that the operational amplifier circuit is used to adjust the bias voltage of the feedback input, so that the charger can flexibly employ various pwm controllers to realize the architecture of the single-stage voltage and current controller. In addition, the digital control circuit is only used for parameter adjustment and feedback compensation of the charging command, so that a high-order digital signal processor is not needed, and the circuit cost can be effectively reduced.

Claims

1. A battery charger having a digital to analog hybrid controller, comprising:

a digital control circuit for receiving a related charging parameter, a battery current feedback signal and a battery voltage feedback signal and generating a control voltage according to the related charging parameter, the battery current feedback signal and the battery voltage feedback signal; and

an analog control circuit electrically connected to the digital control circuit for receiving the control voltage, the battery current feedback signal and the battery voltage feedback signal to generate a pulse width modulation signal.

2. The battery charger with digital to analog hybrid controller as claimed in claim 1, wherein the digital control circuit further comprises:

a micro-control device, which comprises a command generator and a controller, and generates two control voltage signals by the command generator and the controller respectively according to the written related charging parameter, the battery current feedback signal and the battery voltage feedback signal; and generating a mode selection signal according to the written related charging parameter.

3. The battery charger with digital to analog hybrid controller as claimed in claim 2, wherein the digital control circuit further comprises:

and the two-to-one multiplexer is used for receiving the two control voltage signals and the mode selection signal generated by the micro control device and selecting one of the two control voltage signals to output according to the mode selection signal.

4. The battery charger with digital to analog hybrid controller as claimed in claim 3, wherein the digital control circuit further comprises:

a digital analog converter electrically connected to the output ends of the two-to-one multiplexer for converting the output digital value into an analog control voltage signal as the control voltage.

5. A battery charger having a digital to analog hybrid controller as defined in claim 1, wherein the analog control circuit further comprises:

an adder circuit for receiving the battery current feedback signal and the battery voltage feedback signal, and adding the battery current feedback signal and the battery voltage feedback signal to generate an added voltage signal.

6. The battery charger with digital analog hybrid controller according to claim 5, wherein the analog control circuit further comprises:

a pulse width modulation controller;

a subtractor circuit for receiving the added voltage signal and the control voltage output by the adder circuit, and subtracting the added voltage signal and the control voltage to generate a subtracted analog voltage; and

an impedance device electrically connected to the subtractor circuit and the PWM controller,

wherein, the analog voltage after the subtraction is inputted to the PWM controller through the resistor, so as to generate the PWM signal by using the resistor and the PWM controller.