CN1293480A - Control device and method for changing charging current with system load - Google Patents

Abstract

A control device and method for changing charging current with system load is disclosed, so as to accelerate the charging speed of battery in starting-up state. First, a resistance connected in series to a system load is used to detect a variation in load current and convert the detected variation into a load voltage. Then, the voltage adjustment circuit is used to adjust the magnitude of the detected load voltage. The adjusted load voltage is superposed on the input end of the PWM generating circuit, and then a pulse width modulation signal with corresponding pulse width is utilized. The conducting state on the charging path is controlled, so as to adjust the charging current actually sent to the rechargeable battery, thereby achieving the purpose of accelerating charging.

Description

Control device and method for changing charging current with system load

The present invention relates to a charging control circuit and control method, especially for rechargeable batteries used in electronic devices (such as notebook computers, etc.), which can dynamically adjust the actual charging current according to the current consumed by the actual system load The size of the battery can be used to speed up the charging speed of the rechargeable battery when the system load becomes smaller.

General notebook computers (notebooks) and various portable electronic computer devices mostly use batteries as the main source of power supply to meet the requirements of the portable (protable) feature. Due to the limitation of the size of the battery, most of them have a certain effective power supply time, but for users who operate such equipment for a long time, the limited power supply time limits the freedom of operation of the user. Therefore, for portable products, prolonging the power supply time is a very important issue.

The current method of extending the power supply time is mainly to use rechargeable batteries to achieve. For example, the types of batteries commonly used in general notebook computers are mostly so-called secondary batteries, that is, batteries with rechargeable characteristics, such as nickel metal hydride batteries, lithium batteries, and the like. However, since a general battery pack can only maintain a power supply time of several hours, the notebook computer still has to be operated with general commercial power in some cases. In addition, in order to facilitate the operation convenience of general users, a charging circuit is added to the notebook computer at the same time, so that charging can be performed without removing the rechargeable battery pack.

At present, most of the charging circuits attached to notebook computers use a fixed current charging method. That is, the charging circuit will charge the rechargeable battery with a fixed current. According to the characteristics of general rechargeable batteries, the charging current will determine its charging time. In other words, when the charging current is larger, the required charging time will be shorter; when the charging current is smaller, the required charging time will be longer. . According to the above, the following phenomenon occurs in the charging circuit of the conventional notebook computer.

When the notebook computer is turned off, that is, when the system does not need to consume power, the charging circuit can use the maximum charging current for charging, so the fastest charging speed can be achieved. On the other hand, when the notebook computer is turned on, since the system load needs to consume power, it must be charged with a small charging current, which will delay the charging speed. The problem is that even if the system load becomes smaller during operation, since the charging circuit supplies the charging current in a fixed manner, it will still be charged with a small charging current. The reduced system load may occur when the notebook computer is in a suspend mode (suspend or standby), or when some devices of the notebook computer are turned off. So, even though the system load is only consuming a fairly low amount of power, it doesn't speed up the charge while it's being charged at the same time. Obviously, this doesn't make full use of all the power provided by the AC adapter (ACadaptor).

Therefore, the main purpose of the present invention is to provide a control device and control method for changing the charging current according to the system load, which can detect the change of the system load at any time and adjust the supplied charging current accordingly, so as to accelerate the charging when starting up speed.

According to the above purpose, the present invention provides a control device for changing the charging current according to the system load, which is used to control the charging current of the rechargeable battery from the power supply. The load current flowing through the system load is converted into a corresponding load voltage; a voltage conversion circuit is coupled to the current sensing element and generates a control voltage according to the load voltage; and a charging current adjustment circuit is placed in the power supply to the rechargeable battery The charging path is coupled to the voltage conversion circuit, which adjusts the charging current sent by the power supply to the rechargeable battery according to the control voltage. The above resistance and voltage conversion circuit can be regarded as a load current detection circuit.

Wherein, the charging current adjustment circuit includes: a pulse width modulation circuit, which generates a corresponding pulse width modulation signal according to the control voltage, and the pulse width of the pulse width modulation signal corresponds to the load current of the system load; and a switch element, coupled to In the pulse width modulation circuit and placed in the charging path of the power supply to the rechargeable battery, it adjusts the switch state of the charging path according to the pulse width of the pulse width modulation signal, so as to adjust the charging current.

In addition, the control method for changing the charging current according to the system load of the present invention includes the following steps. Firstly, the load current flowing through the system load is converted into a load voltage by using the current sensing element connected in series with the system load. Then, adjust the load voltage to generate a control signal. Finally, according to the control signal, the conduction state of the charging path is controlled, so as to change the magnitude of the charging current according to the system load. In the step of controlling the state of the charging path, first generate a pulse width modulation signal with a corresponding pulse width according to the control signal, and then control the charging path by using the corresponding pulse width of the pulse width modulation signal through the switching element placed in the charging path. The conduction state is used to adjust the charging current sent by the power supply to the rechargeable battery.

The charging control circuit and method disclosed in the present invention can determine the actually sent charging current according to the load status of the system when the system (such as a notebook computer) is turned on. In this way, even if the system load becomes smaller (that is, the power consumption is lower) when the system is turned on, a larger charging current can still be provided to the rechargeable battery to accelerate the charging speed.

In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and understandable, a preferred embodiment is specifically cited below, and in conjunction with the accompanying drawings, the detailed description is as follows:

FIG. 1 shows a detailed circuit diagram of a charging control circuit for changing the charging current according to the system load in an embodiment of the present invention.

Fig. 2 shows a flow chart of the charging control method in the embodiment of the present invention.

Explanation of the numbers in the accompanying drawings:

1～system load; 2～PWM generation circuit; 3～5V voltage regulator; R1-R9～resistor; D1-D4～diode; OP1～operational amplifier; C1～capacitor; BATT～rechargeable battery; V1～load voltage; V2 ~ Control voltage.

FIG. 1 shows a detailed circuit diagram of a charging control circuit for changing the charging current according to the system load in an embodiment of the present invention. In the figure, VIN represents an external DC power supply, such as the DC power supplied to the notebook computer by the AC mains after being processed by the AC-DC converter (ACadapter). Reference numeral 1 denotes a system load, that is, electronic components and devices inside a general notebook computer. BATT stands for rechargeable battery pack. The rechargeable battery pack BATT and the system load 1 are connected in parallel, and are charged and powered by an external DC power supply VIN through a charging (power supply) circuit.

As shown in the figure, components such as capacitor C1, inductor L1, and diode D4 are placed on the charging (power supply) path to provide functions such as removing high-frequency components of the power supply and preventing EMI interference. Diodes D1, D2 and D3 are used to control the charging and power supply paths of the external DC power supply VIN to the rechargeable battery resistance BATT and the system load 1 . For example, when the rechargeable battery pack BATT is not fully charged, the external voltage of the rechargeable battery pack BATT will be low, so both diodes D1 and D3 will be turned on, and at this time, the external DC power supply VIN will be charged through the diode D1. The battery pack BATT is charging, while supplying power to the system load 1 through the diode D3. At this time, the diode D2 is reverse-biased and presents a non-conductive state. When the rechargeable battery pack BATT is fully charged, the diode D1 is turned off to cut off the charging path, and the external DC power supply VIN continues to supply power to the system load 1 through the diode D3. The diode D2 is turned on after the external DC power supply VIN is cut off, so that the rechargeable battery pack BATT continues to supply power to the system load 1 . In addition, the 5V voltage regulator 3 converts the external DC power supply VIN (generally 12V) into a 5V voltage, which is used to provide power for the operational amplifier OP1 (described later). In addition, the resistor network (including resistors R2, R3, R4, R5, R6) is used to generate a reference voltage, which is sent to the PWM generating circuit 2 (described later) to provide constant current feedback for the rechargeable battery pack BATT.

The charging control circuit of this embodiment is mainly composed of the following components: resistor R7, voltage adjustment circuit (including resistors R8, R9 and operational amplifier OP1), PWM (pulsewidth modulation, pulse width modulation) generating circuit 2, and switching elements ( including resistor R1 and transistor Q1).

The resistor R7 is used as a current sensing element, which is connected in series with the system load 1 , that is, coupled between the system load 1 and the ground terminal. The load current passing through the system load 1 will flow through the resistor R7, thereby converting into a corresponding load voltage V1. The inverting terminal (inverting terminal) and non-inverting terminal (non-inverting terminal) of the operational amplifier OP1 are coupled to both ends of the resistor R7, and the load voltage V1 (control signal) is adjusted according to the resistance ratio of the resistors R8 and R9, and then it is Superimposed on the reference voltage generated by the resistor network (R2-R6), a control voltage V2 (determined by the reference voltage, load voltage V1 and the resistance ratio of resistors R8 and R9) is generated and sent to the PWM generating circuit. The PWM generating circuit 2 generates a pulse width modulation signal according to the control voltage V2 (or the control signal), the pulse width of which corresponds to the value of the control voltage. Finally, the pulse width modulation signal is sent to the base of the transistor Q1, so that the charging path is intermittently turned on and off, so as to adjust the magnitude of the sent charging current.

The following details how this circuit adjusts the charging current sent to the rechargeable battery pack BATT according to the system load. First, assume that the system load 1 is in a high load state (normal state), at this time the load voltage V1 is a stable value, and after being adjusted by the operational amplifier OP1 and resistors R8 and R9, it is superimposed on the reference voltage as the control voltage V2 . The PWM generation circuit 2 generates a pulse width modulation signal with a predetermined pulse width according to the control voltage V2, so as to control the switching state of the transistor Q1. At this time, the power supply and charging system is in a stable state, that is, the system load 1 consumes a large current, and the rechargeable battery pack BATT is charged with a relatively low charging current.

When the system load 1 decreases, that is, when the load current decreases, the current flowing through the resistor R7 will also decrease at this time, so that the load voltage V1 decreases. After the adjustment of the operational amplifier OP1 and the resistors R8 and R9, a control signal with a lower voltage value will be superimposed on the reference voltage (at this time, the reference voltage will also change to maintain the constant current characteristics of the rechargeable battery pack BATT, also That is, the variation of the reference voltage corresponds to the variation of the load current of the system load 1, so its description will be omitted in the following description). Therefore, the PWM generating circuit 2 changes the pulse width of the output PWM signal corresponding to the load voltage V1. Finally, the change of the pulse width will increase the conduction time of the charging path, that is, more current flows from the external DC power supply VIN. Since the system load 1 only consumes the required current, most of the current (charging current) will flow to the rechargeable battery pack BATT to accelerate its charging speed, thereby achieving the purpose of the present invention.

In this embodiment, the resistor R7 and the voltage conversion circuit (including the operational amplifier OP1, resistors R8, R9) can also be implemented by other load current detection circuits. In addition, the PWM generating circuit 2 and the switching elements (including the transistor Q1 and the resistor R1) can also be implemented by other charging current adjustment circuits, so the circuit structure shown in FIG. 1 is not intended to limit the present invention.

FIG. 2 is a flow chart of the charging control method corresponding to the embodiment of the present invention. As shown in the figure, firstly, the variation of the load current is detected by using a resistor connected in series with the system load (resistor R7 shown in FIG. 1 ) (S1). Then the detected load voltage (or current) is adjusted to be applicable to the PWM modulator (S2). Then the adjusted load voltage (current) is superimposed on the input terminal of the PWM generating circuit (S3). Finally, the charging current actually sent to the rechargeable battery is adjusted by using the PWM signal and the switching action of the transistor on the charging path (S4). In this way, the required purpose of the present invention can be achieved.

Although the present invention is disclosed as above with a preferred embodiment, it is not intended to limit the present invention. Those skilled in the art can also make many changes and modifications without departing from the spirit and scope of the present invention. Therefore, protection of the present invention The scope is defined by the appended claims.

Claims (19)

1. A control device for changing the charging current according to the system load, used to control the charging current of a power supply to a rechargeable battery, comprising: A current sensing element, connected in series with the system load, is used to convert the load current flowing through a system load into a load voltage; a voltage conversion circuit, coupled to the current sensing element, for receiving the load voltage and generating a control signal; and A charging current adjustment circuit is placed in the charging path of the power supply to the rechargeable battery and coupled to the voltage conversion circuit, which adjusts the charging current sent by the power supply to the rechargeable battery according to the control signal. 2. The control device according to claim 1, wherein the charging current adjustment circuit comprises: a pulse width modulation circuit, which generates a corresponding pulse width modulation signal according to the control signal, the pulse width of the pulse width modulation signal corresponds to the load current of the system load; and A switch element is coupled to the pulse width modulation circuit and placed in the charging path of the power supply to the rechargeable battery. It adjusts the switching state of the charging path according to the pulse width of the pulse width modulation signal, so as to adjust the charging current. 3. The control device as claimed in claim 2, wherein the switching element is a transistor, the base of which receives the PWM signal, and the collector and emitter of which are respectively coupled to the rechargeable battery and the power supply. 4. The control device according to claim 1, wherein the rechargeable battery is connected in parallel with the system load. 5. The control device according to claim 4, wherein the charging current adjustment circuit comprises: a pulse width modulation circuit, which generates a corresponding pulse width modulation signal according to the control signal, the pulse width of the pulse width modulation signal corresponds to the load current of the system load; and A switch element is coupled to the pulse width modulation circuit and placed in the charging path of the power supply to the rechargeable battery. It adjusts the switching state of the charging path according to the pulse width of the pulse width modulation signal, so as to adjust the charging current. 6. The control device as claimed in claim 5, wherein the switch element is a transistor, the base of which receives the PWM signal, and the collector and emitter of which are respectively coupled to the rechargeable battery and the power supply. 7. The control device as claimed in claim 1, wherein the current sensing element is a resistor. 8. The control device according to claim 1, wherein the voltage conversion circuit is composed of an operational amplifier. 9. A control device for changing the charging current according to the system load, used to control the charging current of a power supply to a rechargeable battery, comprising: a load current detection circuit, used to detect the load current flowing through a system load, and generate a corresponding control signal; and A charging current adjustment circuit is placed in the charging path of the power supply to the rechargeable battery and coupled to the load current detection circuit, which adjusts the charging current sent by the power supply to the rechargeable battery according to the control signal. 10. The control device according to claim 9, wherein the charging current adjustment circuit comprises: a pulse width modulation circuit, which generates a corresponding pulse width modulation signal according to the control signal, the pulse width of the pulse width modulation signal corresponds to the load current of the system load; and A switch element is coupled to the pulse width modulation circuit and placed in the charging path of the power supply to the rechargeable battery. It adjusts the switching state of the charging path according to the pulse width of the pulse width modulation signal, so as to adjust the charging current. 11. The control device according to claim 10, wherein the switching element is a transistor, the base of which receives the PWM signal, and the collector and emitter of which are respectively coupled to the rechargeable battery and the power supply. 12. The control device according to claim 9, wherein the rechargeable battery is connected in parallel with the system load. 13. The control device according to claim 12, wherein the charging current adjustment circuit comprises: a pulse width modulation circuit, which generates a corresponding pulse width modulation signal according to the control signal, the pulse width of the pulse width modulation signal corresponds to the load current of the system load; and A switch element is coupled to the pulse width modulation circuit and placed in the charging path of the power supply to the rechargeable battery. It adjusts the switching state of the charging path according to the pulse width of the pulse width modulation signal, so as to adjust the charging current. 14. The control device according to claim 13, wherein the switching element is a transistor, the base of which receives the PWM signal, and the collector and emitter of which are respectively coupled to the rechargeable battery and the power supply. 15. A control device that changes the charging current with the system load, used to control the charging current of a power supply to a rechargeable battery, the system load is connected in parallel with the rechargeable battery, and the system load and the rechargeable battery are coupled to the rechargeable battery through a charging path power supply, which includes: A resistor, coupled between the system load and the ground terminal, is used to convert the load current flowing through the system load, and generate a corresponding load voltage at the two ends of the resistor; An operational amplifier circuit, the inverting terminal and the non-inverting terminal of which are respectively coupled to the two terminals of the resistor, for receiving the load voltage and generating a control signal; A pulse width modulation circuit, coupled to the operational amplifier circuit, generates a corresponding pulse width modulation signal according to the control voltage, the pulse width of the pulse width modulation signal corresponds to the load current of the system load; and A switch element, coupled to the pulse width modulation circuit and placed in the charging path, adjusts the switching state of the charging path according to the pulse width of the pulse width modulation signal, so as to adjust the part of the charging current. 16. The control device as claimed in claim 15, wherein the switching element is a transistor, the base of which receives the PWM signal, and the collector and emitter of which are respectively coupled to the rechargeable battery and the power supply. 17. A control method for changing the charging current with the system load, used to control the charging current of a power supply to a rechargeable battery, the system load is connected in parallel with the rechargeable battery, and the system load and the rechargeable battery are coupled to the rechargeable battery through a charging path power supply, the control method includes the following steps: converting a load current flowing through the system load into a load voltage by using a current sensing element connected in series with the system load; adjust the load voltage to generate a control signal; and According to the control signal, the conduction state of the charging path is controlled, so as to change the magnitude of the charging current with the system load. 18. The control method according to claim 17, wherein the step of controlling the conduction state of the charging path comprises: generating a pulse width modulated signal with a corresponding pulse width according to the control signal; and By means of the switching element placed in the charging path, the conduction state of the charging path is controlled by using the corresponding pulse width of the pulse width modulation signal, so as to adjust the charging current sent by the power supply to the rechargeable battery. 19. The control method according to claim 18, wherein the switch element is a transistor, the base of which receives the PWM signal, and the collector and emitter of which are respectively coupled to the rechargeable battery and the power supply.

Images