TWM586483U - Battery charger with digital analog hybrid controller - Google Patents

Abstract

A battery charger with a digital analog hybrid controller includes: a digital control circuit and an analog control circuit; wherein the digital control circuit is used to receive constant voltage and constant current charging parameters written by an external electronic device, And according to the voltage and current feedback signals of the battery, an analog voltage is generated, which is electrically connected to the input stage of the analog control circuit; the analog control circuit uses the voltage signal of its input stage, the battery voltage and current feedback signal to perform control operations After that, a pulse width modulation signal is generated to drive the subsequent power converter.

Description

Battery charger with digital analog hybrid controller

This creation is about a battery charger, especially a battery charging system with both digital and analog control circuits.

In battery charger applications, the power converter needs to have both constant current and constant voltage output functions. Among them, the constant current is usually charged in two stages. Taking lithium secondary battery charging as an example, when the charger detects that the battery string voltage is too low and the voltage of a single lithium battery cell is lower than 3V, the charger charges the lithium secondary battery pack with a constant low current to avoid overdischarging the battery. At this time, the high charging current causes the battery to overheat and reduce the life. This mode is also called Pre-Charging Mode. After the lithium battery string voltage is greater than the threshold voltage, the charger converts to a large current to charge the lithium secondary battery pack. This mode is also called Fast Charging Mode. At present, the traditional method is to use an operational amplifier or an adjustable parallel regulator TL431 to form an analog voltage controller and a current controller. The output of the two controllers is then connected to the pulse width modulation IC through the diode to achieve the above functions. Among them, the two controllers adopt a switching method, and the voltage controller or the current controller determines the pulse wave according to the load conditions. A width modulation chip (Pulse width modulation controller) controls. For example, because the output voltage of the charger is approximately equal to the voltage of the lithium secondary battery, when the lithium secondary battery is at a low level, the voltage controller saturates because it cannot control the output to the command voltage, and its output diode is In the open state, the current controller determines the duty cycle of the power conversion stage. On the contrary, when the voltage of the lithium secondary battery approaches the command voltage in the constant voltage mode, the voltage controller recovers from the saturation state. When the output voltage is lower than the output of the current controller, the output diode of the current controller shows an open circuit. At this time, the voltage controller determines the duty cycle of the power conversion stage.

FIG. 1 is a partial circuit diagram of a battery charger in the related art. Please refer to Figure 1. The battery voltage and charging current signals measured by the sensor are input to the analog voltage controller 114 and the analog current controller 116 respectively. Among them, the voltage command VCMD_CV and the current command VCMD_CC can be a hard The reference voltage generated by the body, or the adjustable reference voltage generated by the micro control device through a digital analog converter. The output of the voltage controller 114 and the analog current controller 116 are each provided with a diode 112 and a diode 110. The analog voltage VC after the diode 112 and the diode 110 are connected in parallel is connected to the pulse width modulation chip. COMP pin of 100; among them, the pulse width modulation chip 100 may be, but is not limited to, a UC3843 chip; then, the analog voltage VC is connected via the series diode 104 and the voltage dividing resistor 106 inside the pulse width modulation chip 100. The negative input of the comparator 108; finally, compared with the sawtooth wave signal VRAMP of the positive input pin of the comparator 108, a gate driving signal required for the power conversion stage is generated. It is worth noting that the error amplifier 102 inside the PWM chip 100 is not used in this embodiment. During the entire charging process, the feedback stability and output response of the charger are controlled by the analog voltage controller 114 or the analog current. Device 116. However, the method of connecting the external controller in parallel through the diode causes the controller output signal VC to add a diode forward Turn-on voltage; at this time, if the pulse width modulation chip selected by the designer is not configured with a compensation bias at the positive input of the comparator, or if there is no series diode 104 such as the pulse width modulation chip 100, a pulse wave will be generated Decreased width modulation rate and high minimum duty cycle.

Generally speaking, the output of the external analog controller is connected in series with the input of the error amplifier in the width modulation chip to solve the above problem. However, this method will increase the poles and zeros of the feedback system, causing difficulties in the design of the constant current and constant voltage controllers of the charger; this problem is particularly obvious in the application of wide input voltage and wide output voltage. In addition, the use of a digital signal processor instead of the control structure of the analog controller and the pulse width modulation chip is a flexible method that can also solve the above problems. However, in the application of miniaturized products, such as Resonant and quasi-resonant converters with high switching frequency, it is necessary to use digital signal processors with higher computing speeds, resulting in increased product costs. .

The purpose of an embodiment of the present invention is to provide a battery charger with a digital analog hybrid controller. In this way, the charger can use a low-order micro-control device and a commercially available pulse width modulation chip to achieve constant voltage and constant current charging functions without using a multi-stage analog controller architecture. According to an embodiment of the present invention, the disadvantages of the conventional technology 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 A related charging parameter signal, a battery current feedback signal and a battery voltage feedback signal, and a control voltage is generated according to the related charging parameter signal, the battery current feedback signal and the battery voltage feedback signal. The analog control circuit is electrically connected to the digital control circuit, and is used 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 includes a micro control device. The micro control device includes a command generator and a controller, and according to the related charging parameters, the battery current feedback signal, and the battery voltage feedback signal, the command generator and the controller are used, Two types of control voltage signals are generated respectively; and a mode selection signal is generated according to the related charging parameters written.

In an embodiment, the digital control circuit further includes a two-to-one multiplexer for receiving the two control voltage signals and the mode selection signal generated by the micro-control device, according to the mode. The selection signal outputs one of the two control voltage signals.

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

In an embodiment, the analog control circuit further includes an adder circuit. The adder circuit is used to receive the battery current feedback signal and the battery voltage feedback signal, which feedback the battery current After the signal and the battery voltage feedback signal are added, a voltage signal after the addition is generated.

In an embodiment, the analog control circuit further includes a pulse width modulation controller, a subtractor circuit, and an resistor. The subtractor circuit is used to receive the voltage signal after the addition and the control voltage output by the adder circuit, and perform a subtraction operation on the voltage signal after the addition and the control voltage to generate an analog voltage after the subtraction. The resistor is electrically connected to the subtractor circuit and the pulse width modulation controller, respectively. After the subtraction operation, the analog voltage is input to the pulse width modulation controller through the resistor, so as to generate the pulse width modulation signal by using the resistor and the pulse width modulation controller.

As mentioned above, the advantage of an embodiment of the present invention is that the bias of the feedback input can be adjusted, so that the charger can flexibly use a variety of pulse width modulation controllers to implement a single-stage voltage and current controller architecture. In addition, the digital control circuit is only used for charging command parameter adjustment and feedback compensation, so it does not need to use a high-order digital signal processor, which can effectively reduce the circuit cost.

10‧‧‧DC voltage source

100‧‧‧Pulse Width Modulation Chip

102‧‧‧Error Amplifier

104‧‧‧series diode

106‧‧‧ Voltage Divider

108‧‧‧ Comparator

110‧‧‧diode

112‧‧‧diode

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

300‧‧‧ Adder Circuit

302‧‧‧Subtractor

304‧‧‧ Impedance

306‧‧‧Pulse Width Modulation Controller

30602‧‧‧Error Amplifier

30604‧‧‧ Comparator

40‧‧‧electronic device

502‧‧‧ Analog Digital Converter

504‧‧‧Micro-control device

50402‧‧‧Memory

50404‧‧‧Command generator

50406‧‧‧Controller

506‧‧‧Two-to-One Multiplexer

508‧‧‧ Digital Analog Converter

FIG. 1 is a partial circuit diagram of a battery charger in the related art.

FIG. 2 is a block diagram of a battery charger with a digital 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 an 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.

The following is a detailed description of the preferred embodiments of the present invention. However, the illustrations and text descriptions of the embodiments are for disclosure only and do not limit the scope of application of the present invention.

Please refer to FIG. 2. FIG. 2 is a block diagram of an embodiment of a new type of battery charger with a digital analog hybrid controller. The new battery charger 20 with a digital analog hybrid controller is based on the charging voltage and charging current parameters written by the electronic device 40, and converts the DC voltage source 10 into a demand voltage and provides it to the load 30. Among them, the DC voltage The source 10 may be an externally inputted DC voltage, or an externally inputted AC voltage, a DC voltage generated by an internal AC-to-DC converter via a charger. It can be understood that the digital-analog hybrid control method described in the present invention can also be applied to other fields, so the load 30 may be, for example, but not limited to, a lithium secondary battery module. The battery charger 20 having a digital 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 relevant charging parameter 20202 written by the external electronic device 40, the second input is a battery current feedback signal V1, and the third input is a battery voltage feedback signal V2; The battery current feedback signal V1 and the battery voltage feedback signal V2 are from the output of the current sensor and the voltage sensor. The current sensor can be a Hall effect transducers, a A current transformer or a resistor-configured amplifier circuit; and a voltage sensor can be a resistor-divider network or a resistor-divider network configured with an isolation amplifier. Circuit; since the current and voltage sensing method is well known to those having ordinary knowledge in the art, details are not repeated here. The digital control circuit 202 generates a control voltage VC according to the three input signals, and is electrically connected to the analog control circuit 204. The analog control circuit 204 receives the control voltage VC, the battery current feedback signal V1, and the battery voltage feedback signal V2 at the same time, and outputs a pulse width modulation signal PWM to drive the power converter 206. The power converter 206 transmits the pulse width The modulation signal PWM converts the DC voltage source 10 into a demand voltage to charge the load 30.

Please refer to FIG. 3, which is a partial circuit diagram of an embodiment of the analog control circuit of the present invention. As shown in FIG. 3, the analog control circuit 204 includes an adder circuit 300, a subtracter circuit 302, an impedance 304, and a pulse width modulation controller 306. First, the battery current feedback signal V1 and the battery voltage feedback signal V2 are input to the adder circuit 300. The adder circuit 300 adds the battery current feedback signal V1 and the battery voltage feedback signal V2 to generate an addition operation. Voltage signal. The output of the adder circuit 300 is electrically connected to the subtractor circuit 302. The subtractor circuit 302 subtracts the voltage signal after the addition operation and the control voltage VC to generate an analog voltage after the subtraction operation. The analog voltage after the subtraction operation is then input to the pulse width modulation controller 306 via the resistor 304. Amplifier 30602; 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 subsequent power converter. It is worth noting that the analog control circuit of the new type only includes a group of feedback compensators composed of an impedance 304 and an error amplifier 30602. Compared with the prior art, the external voltage is set by a diode. The embodiment in which the output of the current controller is connected to the output of the error amplifier can effectively solve the problems of reduced pulse width modulation rate and excessively high minimum duty cycle. In addition, due to the constant current and constant power during charging The voltage mode is determined by the control voltage VC. The control voltage is continuous and differentiable, so it can improve the transient response adjustment problem of the voltage controller and the current controller in the prior art.

Please refer to FIG. 4. FIG. 4 is a schematic diagram of an analog command curve of an embodiment of the analog control circuit of the present invention. Here, this embodiment designs the current command in the fast charging mode and the voltage command in the constant voltage mode at the maximum values of the battery current feedback signal V1 and the battery voltage feedback signal V2. As shown in Figure 4, when the battery voltage is lower than the pre-charge termination voltage VPRE, the charger operates in the pre-charge mode and charges the battery at a constant current at 10% of the standard charge current IPRE. The calculation of the voltage VC is as follows: V _C = V ₂ -V _REF + V ₁

When the battery voltage rises to the pre-charge termination voltage VPRE, the charger enters the fast charging mode and uses the fast charging current ICC to charge the battery at a constant current. Because the fast charging current command is the internal reference of the pulse width modulation controller 306 The voltage VREF, so the control voltage VC in this mode only needs to deduct the battery feedback voltage signal V2, the formula is as follows: V _C = V ₂

Similarly, since the constant voltage charging command is the reference voltage VREF inside the pulse width modulation controller 306, when the battery voltage reaches the constant voltage VCV, the charger enters the constant voltage charging mode operation. At this time, the control voltage VC only needs to be After deducting the battery feedback current signal V1, the formula is as follows: V _C = V ₁

The above three formulas can be used to draw the control voltage VC curve during charging as shown in Figure 4. Among them, the charger changes from the pre-charge mode to the fast-charge mode as a step-by-step current change. In fact, the mode switching is usually The ramp command is used to reduce the impact of the transient response on the system. In addition, the subtractor 302 shown in Figure 3 includes a low-pass filter, which can adjust the output of the subtractor 302 to a continuous Differential signals. Therefore, the design of the feedback compensator composed of the resistor 304 and error amplifier 30602 has no transient response problem. The poles and zeros are adjusted for output current ripple and voltage ripple.

Please refer to FIG. 5, which 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. Among them, the micro-control device 504 contains A memory 50402, a command generator 50404, and a controller 50406. First, the relevant charging parameters 20202 are written into the memory 50402 inside the micro-control device 504 through a digital communication interface. The relevant charging parameters 20202 have different precharge mode boundary voltages, precharge mode currents, fast charge mode currents, Voltage mode voltage, charging cut-off current, input signal selection conditions of two-to-one multiplexer 506, and controller gain and other parameters. The battery current feedback signal V1 and the battery voltage feedback signal V2 pass through the analog-to-digital converter 502 to convert the analog voltage into a digital signal and input it to the micro-control device 504, and provide it to the command generator 50404 and control in the micro-control device 504.器 50406. The command generator 50404 and the controller 50406 calculate the feedback signal and the charging command in the memory 50402, and generate respective digital output signals as two control voltage signals, which are electrically connected to the external two-to-one multiplexer 506 . Then two to one more The multiplexer 506 selects one of the two input signals for the two control voltage signals according to the conditions in the memory 50402, and the output of the two-to-one multiplexer 506 is electrically connected to the digital analog converter 508. Finally, the digital analog converter 508 converts the digital signal into an analog control voltage signal, which is used as the control voltage VC to control the subsequent analog control circuit 204.

As described in the new content, the digital control circuit can be operated in open-loop mode or closed-loop mode according to the charging requirements of different batteries. The open loop is the mode in which the control generator VC generates the control voltage VC. The calculation method of the control voltage VC is as described previously, so the details are not repeated; and when the charger chooses to operate in the closed loop mode, the charger feedback The compensation will be executed by the controller 50406 instead. Please refer to FIG. 3 and FIG. 5 at the same time. In order to eliminate the feedback compensation of the analog control circuit 204 and the influence of the internal reference voltage VREF of the error amplifier 30602 on the output, the output expression of the digital control circuit 202 is as follows: V _C = V ₁ + V ₂ -V _REF + △ V

Among them, ΔV is the operation output value of the controller 50406. For example, when the charger operates in the constant voltage mode, the controller 50406 subtracts the constant voltage value in the memory 50402 from the value of the battery voltage feedback signal V2 converted by the analog-to-digital converter 502. The input of the error value may be, for example, but not limited to, a proportional-integral controller. It is worth noting that in order to simplify the design, the proportional-integral controller is usually connected in series with an additional compensator. This compensator adopts the design rule of pole-zero cancellation to offset the internal resistor of the analog controller 204. Pole and zero generated by 304 and error amplifier 30602.

In addition, the analog-to-digital converter 502, the microcontroller 504, and the two-to-one converter shown in FIG. The circuit architectures of the multiplexer 506 and the digital-to-analog converter 508 are only examples, and are not intended to limit the present invention. After reading the above disclosure, those with ordinary knowledge in the art should understand that the functions of the analog-to-digital converter 502 and the two-to-one multiplexer 506 can also be integrated into the microcontroller 504; and, the two-to-one multiplexer The output of the converter 506 can also be a PWM signal, and the function of the digital analog converter 508 can be realized by a low-cost RC low-pass filter.

In addition, the circuit architecture of the adder circuit 300, the subtracter circuit 302, the impedance 304, and the pulse width modulation controller 306 in FIG. 3 is only an example, and is not a limitation of the present invention. After reading the above disclosure, those with ordinary knowledge in the field should understand that the circuit architecture has the greatest design flexibility. That is, by adjusting the control voltage VC, the compensator inside the circuit can be used for constant voltage or fixed voltage. Current control; however, if digital and analog mixed control is adopted, that is, constant current mode control is performed by analog control circuit 204, constant voltage mode control is performed by digital control circuit 202, or constant voltage mode control is performed by analog control circuit 204, The digital control circuit 202 executes a constant current mode control strategy; at this time, only one of the battery current feedback signal V1 and the battery voltage feedback signal V2 needs to be input to the analog control circuit 204, so that the adder circuit 300 can be omitted. Or, the digital control circuit generates an inverted control voltage VC signal, and the adder circuit 300 is designed as an adder with three sets of inputs, so that the subtractor circuit 302 can be omitted; these design changes should belong to the present New category.

Briefly explain the benefits of this new model. In this new type of battery charger with a digital analog hybrid controller, the digital control circuit can operate in two modes, of which the open loop mode can be controlled by the control voltage generated by it and the feedback compensation in the analog circuit. Charger to complete the pre-charging mode in the entire charging process Type, fast charging mode and constant voltage charging mode; and, according to different battery charging requirements, the digital control circuit can freely switch to the closed loop mode, and the loop compensation of the charger is transferred to the digital controller. Therefore, the new type battery charger with digital analog hybrid controller has high design flexibility and low cost performance.

The purpose of an embodiment of the present invention is to provide a battery charger with a digital analog hybrid controller. In this way, the charger can use a low-order micro-control device and a commercially available pulse width modulation chip to achieve constant voltage and constant current charging functions without using a multi-stage analog controller architecture. According to an embodiment of the present invention, the disadvantages of the conventional technology 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; wherein the digital control circuit is used to receive a constant voltage and Constant current charging and other related parameters, and based on the battery voltage and current feedback signals, generate an analog voltage, which is electrically connected to the input stage of the analog control circuit; the analog control circuit uses the voltage signal of its input stage, the battery voltage and After the current feedback signal is used for control calculation, a pulse width modulation signal is generated to drive the power converter in the subsequent stage.

In addition, in the new battery charger with a digital analog hybrid controller, the analog control circuit includes an operational amplifier circuit and a pulse width modulation controller. The function of the operational amplifier circuit is to calculate the battery voltage, battery current feedback signal and a specific control voltage. Through the adjustment of this control voltage, the pre-charge mode, fast charge mode, Voltage charging mode and Float charging mode.

In addition, in the new type of battery charger with a digital analog hybrid controller, the digital control circuit has two control modes, namely an open-loop control mode and a closed-loop control mode. In the open-loop control mode, the digital control circuit uses its internal command generator to calculate the battery voltage and current feedback signals with the charging command. The calculation result is then used by a digital analog converter to generate a control voltage. The control circuit performs constant voltage or constant current control. In the closed-loop control mode, the digital control circuit uses its internal controller to subtract the battery voltage and current feedback signals from the charging command, and generates an error signal to be input into the internal circuit. A feedback compensator. The output of the feedback compensator then generates a control voltage through a digital analog converter to perform constant voltage or constant current control on the subsequent analog control circuit.

As described above, the advantage disclosed by the new model is that the bias adjustment of the feedback input through the operational amplifier circuit allows the charger to flexibly use a variety of pulse width modulation controllers to implement a single-stage voltage and current controller architecture. . In addition, the digital control circuit is only used for charging command parameter adjustment and feedback compensation, so it does not need to use a high-order digital signal processor, which can effectively reduce the circuit cost.

Claims (6)

A battery charger with a digital analog hybrid controller includes a digital control circuit for receiving a related charging parameter signal, a battery current feedback signal and a battery voltage feedback signal, and according to the related charging parameter. A signal, the battery current feedback signal and the battery voltage feedback signal generate a control voltage; and an analog control circuit, which is electrically connected to the digital control circuit to receive the control voltage and the battery current feedback signal And the battery voltage feedback signal to generate a pulse width modulation signal. The battery charger with a digital analog hybrid controller as described in item 1 of the scope of patent application, wherein the digital control circuit further includes: a micro-control device, including a command generator and a controller, and written according to The related charging parameters, the battery current feedback signal, and the battery voltage feedback signal, respectively, generate two kinds of control voltage signals through the command generator and the controller; and, according to the related charging written The parameter generates a mode selection signal. The battery charger with a digital analog hybrid controller as described in item 2 of the scope of the patent application, wherein the digital control circuit further includes a one-to-two multiplexer for receiving the two types generated by the micro-control device. The control voltage signal and the mode selection signal are output according to the mode selection signal. The battery charger with a digital analog hybrid controller as described in item 3 of the scope of patent application, wherein the digital control circuit further includes: a digital analog converter, which is electrically connected to the output end of the two-to-one multiplexer. Connected to convert the digital value of the output into an analog control voltage signal as the control voltage. The battery charger with a digital analog hybrid controller as described in item 1 of the scope of the patent application, wherein the analog control circuit further includes: an adder circuit for receiving the battery current feedback signal and the battery voltage feedback Signal, which adds the battery current feedback signal and the battery voltage feedback signal to generate an addition voltage signal. The battery charger with a digital analog hybrid controller as described in item 5 of the scope of the patent application, wherein the analog control circuit further includes: a pulse width modulation controller; and a subtractor circuit for receiving the adder. The voltage signal after the addition and the control voltage output by the circuit, and after the subtraction operation is performed on the voltage signal after the addition and the control voltage, an analog voltage after the subtraction is generated; and a resistor, which is electrically connected to the subtraction respectively And the pulse width modulation controller, wherein the analog voltage after the subtraction operation is input to the pulse width modulation controller through the resistor, so as to use the resistor and the pulse width modulation controller. The pulse width modulation signal is generated.