A lithium battery BUCK synchronous buck charging anti-reverse boost circuit

Abstract

The embodiment of the present invention discloses a lithium battery BUCK synchronous buck charging anti-reverse boost circuit. The circuit includes a first switch module, a second switch module, an energy storage module, an input capacitor, a PWM drive module and a controller module, a current detection module and a controllable load. The PWM drive module includes a first input terminal electrically connected to the output terminal of the controller module, and an enable input terminal of the PWM drive module is electrically connected to the output terminal of the current detection module, which is used to control whether the second switch module works according to an enable signal; the control terminal of the controllable load is electrically connected to the output terminal of the current detection module, which is used to receive the output signal of the current detection module to control the conduction of the controllable load. The anti-reverse boost module is composed of the current detection module and the controllable load. Compared with the prior art, the embodiment of the present invention improves the problem of reverse boost when the lithium battery BUCK synchronous buck charging current is small, and improves the reliability of the BUCK circuit.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of electronic circuits, and in particular to a lithium battery BUCK synchronous buck charging circuit. Background Art

[0002] With the increase of electronic product functions and consumers' pursuit of higher performance of electronic products, the requirements for power conversion efficiency have become higher, and the use of more energy-saving switching power supplies to replace traditional low-dropout linear regulators (Low Dropout Regulator, LDO) has become the mainstream. The control principle of the switching power supply is to determine the ratio of the required output voltage to the input voltage through the system, and obtain the corresponding pulse width modulation (Pulse Width Modulation, PWM) duty cycle square wave signal. The PWM square wave signal can control the on and off time ratio of the power tube.

[0003] There are many types of switching power supplies. In the prior art, lithium batteries are charged using a BUCK synchronous buck circuit. When a BUCK synchronous buck circuit is used for charging, when the input is disconnected, the lithium battery load will reversely boost VIN through the BUCK synchronous buck path, that is, the reverse boost problem of the BUCK synchronous buck circuit described in the present invention will affect the reliability of the BUCK circuit. Summary of the invention

[0004] The embodiment of the present invention provides a lithium battery BUCK synchronous buck charging anti-reverse boost circuit to improve the reverse boost problem existing in the lithium battery BUCK synchronous buck charging and improve the reliability of the BUCK circuit.

[0005] In a first aspect, an embodiment of the present invention provides an improved circuit of a lithium battery BUCK synchronous buck charging circuit, comprising:

[0006] A first output terminal of a power supply, a second output terminal of a power supply, a first output terminal of a load, and a second output terminal of a load; the second output terminal of the power supply and the second output terminal of the load are both grounded;

[0007] A first switch module, comprising a control end, a first end and a second end, wherein the first end of the first switch module is electrically connected to the first output end of the power supply;

[0008] A second switch module, comprising a control end, a first end, and a second end, wherein the first end of the second switch module is electrically connected to the second end of the first switch module, and the second end of the second switch module is electrically connected to the second output end of the load;

[0009] An energy storage module, wherein the energy storage module is connected in series between the second end of the first switch module and the first output end of the load;

[0010] An output capacitor, the output capacitor is connected in parallel between the first output terminal of the load and the second output terminal of the load;

[0011] An input capacitor connected in parallel between the first output terminal of the power supply and the second output terminal of the power supply;

[0012] a current detection module, comprising a first detection input terminal, a second detection input terminal and an enable output terminal, wherein the first detection input terminal is electrically connected to the first terminal of the first switch module, and the second detection input terminal is electrically connected to the second terminal of the first switch module; the current detection module is used to detect the current flowing through the first switch module, and generate an enable signal when the output current is less than a current comparison threshold;

[0013] The controllable load includes a control terminal, a first terminal and a second terminal, wherein the control terminal is electrically connected to the enable output terminal of the current detection module, the first terminal is electrically connected to the first output terminal of the input power supply, and the second terminal is grounded. When the current detection module outputs an enable signal, a pulse of a fixed time is generated to pull the voltage of the input point, so that the input voltage becomes lower more easily.

[0014] A controller module, the controller module comprising a PWM output terminal for obtaining a PWM control signal according to an input-output voltage ratio;

[0015] The PWM driving module comprises a first input terminal, an enable input terminal, a first output terminal and a second output terminal, wherein the first input terminal is electrically connected to the PWM output terminal of the controller module; the enable input terminal is electrically connected to the enable output terminal of the current detection module; the first output terminal is electrically connected to the control terminal of the first switch module; the second output terminal is electrically connected to the control terminal of the second switch module; the PWM driving module is used to generate a PWM driving signal according to the enable signal and the PWM control signal to control the opening and closing of the first switch module and the second switch module.

[0016] Optionally, the current detection module includes:

[0017] A current mirror amplifier, wherein the first input end of the current mirror amplifier serves as the first detection input end of the current detection module, and the second input end of the current mirror amplifier serves as the second detection input end of the current detection module;

[0018] a first resistor, wherein a first end of the first resistor is electrically connected to an output end of the current mirror amplifier;

[0019] a second resistor, a first end of the second resistor being electrically connected to an output end of the current mirror amplifier;

[0020] a first capacitor, a first end of the first capacitor being electrically connected to a second end of the second circuit;

[0021] The first capacitor and the second resistor form an RC filter circuit for averaging the output current of the current mirror amplifier;

[0022] A comparator, wherein a first input terminal of the comparator is used to access a reference signal, a second input terminal of the comparator is electrically connected to a second end of the second resistor, and an output terminal of the comparator serves as an enable output terminal of the current detection module;

[0023] Optionally, the PWM driving module includes:

[0024] A first NAND gate, comprising a first input terminal, a second input terminal, a third input terminal and an output terminal, wherein the first input terminal of the first NAND gate is electrically connected to the enable input terminal, and the second input terminal of the first NAND gate is electrically connected to the output terminal of the controller module;

[0025] A second NAND gate, comprising a first input terminal, a second input terminal and an output terminal, wherein the first input terminal of the second NAND gate is electrically connected to the output terminal of the controller module;

[0026] A first inverter, wherein an input terminal of the first inverter is electrically connected to an output terminal of the first NAND gate;

[0027] A second inverter, wherein an input end of the second inverter is electrically connected to an output end of the first inverter, and an output end of the second inverter serves as a second output end of the PWM driving module;

[0028] a third inverter, wherein an input terminal of the third inverter is electrically connected to an output terminal of the second NAND gate;

[0029] a fourth inverter, wherein the input end of the fourth inverter is electrically connected to the output end of the third inverter; and the output end of the fourth inverter serves as the first output end of the PWM driving module;

[0030] a fifth inverter, wherein an input terminal of the fifth inverter is electrically connected to an output terminal of the first inverter; and an output terminal of the fifth inverter is electrically connected to a second input terminal of the second NAND gate;

[0031] A sixth inverter, wherein an input terminal of the sixth inverter is electrically connected to an output terminal of the fourth inverter, and an output terminal of the sixth inverter is electrically connected to a third input terminal of the first NAND gate.

[0032] Optionally, the energy storage module includes an inductor, and the inductor is connected in series between the second end of the first switch module and the first power supply output end.

[0033] Optionally, the energy storage module includes an inductor, and the inductor is connected in series between the second end of the first switch module and the first output end of the load.

[0034] Optionally, an output capacitor is connected in parallel between the first output terminal of the load and the second output terminal of the load.

[0035] Optionally, the first switch module includes a first power tube, a gate of the first power tube serves as a control end of the first switch module, a first electrode of the first power tube serves as a first end of the first switch module, and a second electrode of the first power tube serves as a second end of the first switch module;

[0036] Optionally, the second switch module includes a second power tube, the gate of the second power tube serves as the control end of the second switch module, the first pole of the second power tube serves as the first end of the second switch module, and the second pole of the second power tube serves as the second end of the second switch module.

[0037] Optionally, the first power tube is a P-type power tube, the first electrode of the first power tube is a source electrode, and the second electrode of the first power tube is a drain electrode. However, the first power tube is not limited to the P-type, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

[0038] The second power tube is an N-type power tube, the first electrode of the second power tube is a drain, and the second electrode of the second power tube is a source.

[0039] The embodiment of the present invention sets a current detection module. When the current detection module detects that the average value of the output current is less than the current comparison threshold, it generates an enable signal. The enable signal acts on the PWM drive module, and can output a control signal at the second output end of the PWM drive module to control the second switch module to close. The enable signal generated by the current detection module is processed into a pulse signal in the controllable load to control the load to pull the input current. In this way, when the input power is disconnected and the current is less than the comparison threshold, the second switch module is closed, the BUCK synchronous buck circuit has no reverse boost path, and the energy storage module has only forward energy and no reverse energy during operation. At the same time, due to the effect of the controllable load, the input voltage is pulled lower, so that the BUCK buck system is closed, thereby solving the problem of reverse boost of the BUCK circuit and improving the reliability of the BUCK circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a schematic diagram of an existing lithium battery BUCK synchronous buck charging circuit;

[0041] Figure 2This is a waveform diagram of the existing lithium battery BUCK when the input is disconnected during synchronous buck charging;

[0042] Figure 3 A schematic diagram of a circuit for an existing lithium battery BUCK synchronous buck charging and anti-reverse boost mode;

[0043] Figure 4 Schematic diagram of the second circuit for the existing lithium battery BUCK synchronous buck charging and reverse boost prevention method

[0044] Figure 5 The waveform diagram of the working process of the existing lithium battery BUCK synchronous buck charging anti-reverse boost mode 1 and mode 2;

[0045] Figure 6 A circuit diagram of a current detection module provided by an embodiment of the present invention;

[0046] Figure 7 A waveform diagram of the working process of a lithium battery BUCK synchronous buck charging anti-reverse boost circuit provided in an embodiment of the present invention;

[0047] Figure 8 An equivalent circuit diagram of a lithium battery BUCK synchronous buck charging anti-reverse boost circuit operating at low current provided by an embodiment of the present invention

[0048] Fig. 9 A circuit diagram of a current detection module provided by an embodiment of the present invention;

[0049] Fig.10 A circuit diagram of a controlled load provided by an embodiment of the present invention;

[0050] Fig.11 A circuit diagram of a PWM drive module provided by an embodiment of the present invention; DETAILED DESCRIPTION

[0051] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0052] As mentioned in the background technology, when the existing lithium battery BUCK is synchronously buck-charged, when the input power of the BUCK circuit is reduced to a certain voltage value, the energy of the load will boost the input end through the BUCK synchronous buck path, causing the lithium battery to reversely boost the input end. The inventors have found that the cause of this problem is as follows.

[0053] Analyze the situation when the input is disconnected during the synchronous buck charging process of the lithium battery BUCK. Figure 1 This is a schematic diagram of an existing lithium battery BUCK synchronous buck charging circuit. Figure 1 , the output of the BUCK circuit is connected to the lithium battery load V BAT , the lithium battery load V BAT It can be a load with a battery, such as a mobile phone.

[0054] Figure 2 This is a waveform diagram of the working process of an existing lithium battery BUCK synchronous buck charging circuit when the input is disconnected. Figure 2 , the working process of the BUCK circuit is as follows:

[0055] During the time period from 0 to t1, the BUCK circuit is in normal working state, and the input voltage V IN remains unchanged, the duty ratio of the control signal HS of the first switch module 110 and the control signal LS of the second switch module 120 remains unchanged, and the output voltage V O remains unchanged, and the average current I flowing through the energy storage module 130 O The value remains unchanged, and the average current I flowing through the first switch module 110 IN The size remains unchanged.

[0056] The lithium battery BUCK synchronous buck charging is the working waveform when the input power is disconnected by 150, see Figure 2 Specifically, at time t1, the input power supply 150 is disconnected, and due to the input capacitor C IN The BUCK synchronous buck circuit continues to work, and the input voltage V IN The duty cycle of the control signal HS of the first switch module 110 gradually increases, the duty cycle of the control signal LS of the second switch module 120 gradually decreases, and the energy storage time of the energy storage module 130 gradually increases, thereby maintaining the average value I of the current flowing through the energy storage module 130. O The input IIN remains unchanged, and the output energy is the same, but the output voltage is reduced, so V IN Output current I IN Increase.

[0057] At time t2, the duty cycle of the control signal HS of the first switch module 110 reaches the maximum, and the duty cycle of the control signal LS of the second switch module 120 reaches the minimum. MIN_ON , which is the minimum duty cycle. IN The current flowing through the first switch module 110 also gradually decreases. The average value I of the current flowing through the energy storage module 130 O Gradually decrease.

[0058] At time t3, the average value of the current flowing through the energy storage module 130 is I AVEThe BUCK synchronous buck circuit composed of the first switch module 110 and the second switch module 120 continuously operates in the minimum duty cycle state. The opening time of the first switch module 110 and the second switch module 120 is fixed. According to the volt-second balance theory, the input voltage V IN However, the instantaneous value of the current flowing through the energy storage module 130 is not always equal to zero. The output voltage is constant, and the input voltage V IN The voltage value is determined according to the ratio of the conduction time of the first switch module 110 and the second switch module 120, resulting in reverse boost. Figure 2 Middle curve 11.

[0059] From the above analysis, it can be seen that when the lithium battery BUCK synchronous buck charging circuit is charging, the input power supply is disconnected by 150, and the load V BAT The input voltage will be boosted through the BUCK synchronous buck path, thus affecting the reliability of the BUCK synchronous circuit.

[0060] Existing lithium battery BUCK synchronous buck anti-reverse boost method 1:

[0061] like Figure 3 As shown, a diode 170 is added to the power path based on the BUCK synchronous buck circuit, the first end 171 of the diode 170 is electrically connected to the first output end 101 of the power supply, and the first end 172 of the anti-reverse circuit 170 is electrically connected to the first input end 112 of the first switch module 110. Figure 3 , see the working process Figure 5 At time t3, the energy storage module 230 also has reverse energy, but due to the presence of the diode 170, the energy on the energy storage module 230 cannot be transferred back to the input. Figure 5 As shown in curve 10, the input voltage cannot be maintained, which will eventually shut down the BUCK synchronous buck path.

[0062] Disadvantages of method 1:

[0063] 1. The addition of the anti-reverse module 170 on the power path, that is, the current output by the power supply will pass through the anti-reverse module, causing relatively large power loss and affecting efficiency conversion.

[0064] 2. In terms of device selection, a high-power Schottky diode is required, which increases the cost of circuit implementation.

[0065] 3. Because there is reverse energy that is not transmitted back to the input, it will accumulate at the negative end of the diode, and the voltage will be higher. The process requirements for the first switch module and the second switch module are higher.

[0066] 4. It is not convenient to integrate the power diode into the chip.

[0067] Now lithium battery BUCK synchronous buck charging anti-reverse boost circuit method 2:

[0068] See also Figure 4 , the load 180 is connected in parallel at both ends of the input power supply 150, and the input is always pulled with a fixed capacity. When the output capacity of the power supply is small, there is enough capacity to pull the input down to ensure that when there is no power supply 150, the input end will be forced to be pulled down, and the BUCK synchronous buck will not work.

[0069] Disadvantages of method 2:

[0070] 1. According to different loads, different power supplies need to set different dummy loads to meet their requirements.

[0071] The application is rather cumbersome.

[0072] 2. The addition of dummy load consumes energy at the input end at any time, which directly affects the conversion efficiency.

[0073] In view of this, an embodiment of the present invention provides a lithium battery BUCK synchronous buck charging anti-reverse boost circuit. Figure 6 A schematic diagram of a lithium battery BUCK synchronous buck and reverse boost circuit provided by an embodiment of the present invention. Figure 6 The lithium battery BUCK synchronous buck charging circuit includes: an input power supply 280, a first power supply output terminal 201, a second power supply output terminal 202, a first load output terminal 203 and a second load output terminal 204; the second load output terminal 204 and the second power supply output terminal 202 are both grounded. The BUCK synchronous buck circuit also includes a first switch module 210, a second switch module 220, an energy storage module 230, an input capacitor C IN , a controller module 250, a current detection module 260, a controllable load 270 and a PWM drive module 240. The first switch module 210 includes a control terminal 211, a first terminal 212 and a second terminal 213, the first terminal 212 and the second terminal 213 respectively input / output a signal DCP and a signal DCN; the first terminal 212 of the first switch module 210 is electrically connected to the first output terminal 201 of the power supply; the second switch module 220 includes a control terminal 221, a first terminal 222 and a second terminal 223, the first terminal 222 of the second switch module 220 is electrically connected to the second terminal 213 of the first switch module 210, and the second terminal 223 of the second switch module 220 is electrically connected to the second output terminal 204 of the load; the energy storage module 230 is connected in series between the second terminal 213 of the first switch module 210 and the first output terminal 203 of the load; the input capacitor C INThe current detection module 260 is connected in parallel between the first output terminal 201 of the power supply and the second output terminal 202 of the power supply; the current detection module 260 includes a first detection input terminal 261, a second detection input terminal 262 and an enable output terminal 263, the first detection input terminal 261 is electrically connected to the first terminal 212 of the first switch module 210, and the second detection input terminal 262 is electrically connected to the second terminal 213 of the first switch module 210; the current detection module 260 is used to detect the output current flowing through the first switch module 210, and when the output current is less than the current comparison threshold, generate an enable signal ENLS; the output terminal 251 of the controller module 250 is used to generate a voltage that meets the system voltage requirement PWM control signal; the PWM driving module 240 includes a PWM input terminal 241, an enable input terminal 242, a first output terminal 243 and a second output terminal 244, the PWM input terminal 241 is electrically connected to the output terminal 251 of the controller module 250; the enable input terminal 242 is electrically connected to the enable output terminal 263 of the current detection module 260; the first output terminal 243 is electrically connected to the control terminal 211 of the first switch module 210; the second output terminal 244 is electrically connected to the control terminal 221 of the second switch module 220; the PWM driving module 240 is used to generate a control signal according to the enable signal to control the second switch module 220 to be closed.

[0074] Considering that the current provided by the BUCK synchronous buck power supply may be limited, it is necessary to reasonably set the current comparison threshold I TH Optionally, the output current of the first switch module 210 is non-DC, but the current comparison threshold I TH is the average current comparison threshold, and accordingly, the detected output current should be the output average current. IN The average current I IN The current detection module 260 is used to detect the current flowing through the first switch module 210 to determine whether the current is too small.

[0075] Figure 7 This is a waveform diagram of the working process of disconnecting the power supply of a lithium battery BUCK synchronous buck charging circuit provided by an embodiment of the present invention. Figure 7 , the working process of the BUCK circuit is as follows:

[0076] In the time period from 0 to t1, if Figure 7 As shown, the lithium battery BUCK synchronous buck charging circuit is in normal working state, and the input voltage V IN The duty cycle of the control signal HS of the first switch module 210 and the duty cycle of the control signal LS of the second switch module 220 remain unchanged, and the average current I flowing through the energy storage module 230 remains unchanged. O unchanged, the output voltage V OAt the same time, the current detection module 260 detects the current flowing through the first terminal 212 and the second terminal 213 of the first switch module 210, thereby detecting the output current I IN , put I IN Compare with current threshold I TH Make a comparison. Because I IN >I TH , the signal ENLS output by the current detection module 260 is not an enable signal.

[0077] At time t1, the first output terminal 201 of the BUCK circuit is disconnected. IN The BUCK circuit continues to work, but the input capacitor C IN The charge release makes the input voltage V IN Therefore, after time point t1, see Figure 7 , input voltage V IN The duty cycle of the control signal HS of the first switch module 210 gradually increases, and the duty cycle of the control signal LS of the second switch module 220 gradually decreases, that is, the current I flowing through the energy storage module 230 L The duty cycle of the energy storage module 230 gradually increases, and the average value I O Maintain, while the input voltage is decreasing, at this time the current released by the input capacitor will increase. That is, it is detected that the current I flowing through the first switch module 210 IN will increase, and the output current I flowing through the first switch module 210 detected IN Compare with current threshold I TH Make a comparison. IN >I TH , the signal ENLS output by the current detection module 260 is a non-enable signal.

[0078] t2 time point, see Figure 7 , the duty cycle of the control signal HS of the first switch module 210 reaches the maximum, and the duty cycle of the control signal LS of the second switch module 220 reaches the minimum. At this time, the voltage on the input capacitor continues to decrease. Therefore, in the time period t2 to t3, see Figure 7 , the average value of the average current flowing through the first switch module 210 is I IN The current I flowing through the first switch module 210 detected by the current detection module 250 is gradually reduced. IN Compare with current threshold I TH Make a comparison. Because I IN >I TH , the signal ENLS output by the current detection module 260 is a non-enable signal.

[0079] t3 time point, see Figure 7 , the current detection module 260 detects the output average current I IN drops to the current comparison threshold, I IN TH The signal ENLS output by the current detection module 260 is an enable signal. The PWM driving module 240 generates a control signal LS according to the enable signal to control the second switch module 220 to be turned off.

[0080] For example, Figure 8 As shown, due to I IN TH The generated ENLS is enabled, and the circuit works in asynchronous mode. A fixed time and fixed capacity load is generated in the controllable load 270 to strongly pull V IN , making it easier to get rid of possible reverse boost, see Figure 7 Middle control line 17, input voltage V IN As shown in curve 11. The second switch module 220 remains closed, and the energy stored in the energy storage module 230 when the first switch module 210 is turned on will be continuously circulated through the parasitic diode D in the second switch module 220, and no reverse energy is stored in the energy storage module 230, and the energy at the output end will not be sent to the input. This working state is maintained until the input voltage V IN If the voltage drops below the system's required operating voltage, the system shuts down.

[0081] In summary, the embodiment of the present invention sets the average current comparison threshold I TH , the current detection module 250 detects the average current I flowing through the first switch module 210 IN Less than the average current comparison threshold I TH When the second switch module 220 is turned on, an enable signal is generated, which acts on the PWM drive module 240 and the controllable load module 270, and a control signal can be output at the second output terminal 244 of the PWM drive module 240 to control the second switch module 220 to be turned off. If the second switch module 220 is not turned on, the energy storage module 230 cannot reversely store energy, and the load cannot boost VIN by borrowing the path of the BUCK synchronous buck circuit; at the same time, the controllable load 270 can pull the input VIN with a fixed capacity for a fixed time. IN , so that it can quickly release the input capacitor C IN The charge on the battery is reduced more easily and quickly, making it easier to shut down the buck system. The reverse boost problem of the lithium battery buck synchronous buck charging circuit is solved, thereby improving the reliability of the buck circuit.

[0082] Fig. 9 A circuit diagram of a current detection module provided by an embodiment of the present invention. Fig. 9 ​​In one embodiment of the present invention, optionally, the current detection module 260 includes: a current mirror amplifier OTA, a first resistor R1, a comparator COMP, and an RC filter circuit composed of a second resistor R2 and a first capacitor C1. The first input end of the current mirror amplifier OTA serves as the first detection input end of the current detection module 260, and the second input end of the current mirror amplifier OTA serves as the second detection input end of the current detection module 260; the first end of the first resistor R1 is electrically connected to the output end of the current mirror amplifier OTA; the first input end of the comparator COMP is used to access the reference signal VREF, and the second input end of the comparator COMP is electrically connected to the second end of the second resistor R2; the first end of the first capacitor C1 is electrically connected to the second end of the second resistor R2; the second resistor R2 and the first capacitor C1 form an RC filter circuit for averaging the output current of the current mirror amplifier OTA as I IN The output terminal of the comparator COMP serves as the enable output terminal of the current detection module 260.

[0083] Exemplarily, the working principle of the current detection module 260 is that when the first switch module 210 is turned on, the current mirror amplifier OTA samples the forward current (flowing in from the first end 212 of the module 210 and flowing out from the second end 213) flowing through the first switch module 210. The first switch module 210 is on the input path, and the current flowing through the first switch module 210 is equal to I IN Output current. The OTA mirror of the current detection module 260 flows through the current of the first switch module 210 through R2, and then is filtered by RC to obtain the average current I IN The representation reflects the current flowing through the first switch module 210 in real time.

[0084] It should be noted that Fig. 9 In the figure, it is exemplarily shown that the first input terminal of the current mirror amplifier OTA is the non-inverting input terminal, and the second input terminal is the inverting input terminal, which is not a limitation of the present invention. In other embodiments, the first input terminal of the current mirror amplifier OTA can also be set as the inverting input terminal, and the second input terminal can be set as the non-inverting input terminal. Similarly, the first input terminal of the comparator COMP is the non-inverting input terminal, and the second input terminal is the inverting input terminal, or the first input terminal of the comparator COMP is the inverting input terminal, and the second input terminal is the non-inverting input terminal.

[0085] Fig.10 A circuit diagram of a controllable load provided by an embodiment of the present invention. Fig.10In one embodiment of the present invention, the controllable load 270 optionally includes an edge detection module and a load. The control end of the edge detection module serves as a control end 271 of the controllable load 270; the control end of the load is electrically connected to the output end of the edge detection module, the first end of the load serves as a second end 272 of the controllable load 270; and the third end of the load serves as a second end 273 of the controllable load 270.

[0086] For example, the edge detection module can generate a start signal of a certain fixed time according to the signal input by the control terminal 271, which is used to control the load and pull the first terminal 272 of the edge detection module 270. It is used to make the input drop faster when there is no input power, and it is easier to turn off the BUCK step-down circuit.

[0087] Fig.11 A circuit diagram of a PWM drive module provided by an embodiment of the present invention. Fig.11In one embodiment of the present invention, optionally, the PWM driving module 240 includes: a first NAND gate NAND1, a second NAND gate NAND2, a first inverter NOT1, a second inverter NOT2, a third inverter NOT3, a fourth inverter NOT4, a fifth inverter NOT5 and a sixth inverter NOT6. Among them, the first NAND gate NAND1 includes a first input terminal, a second input terminal, a third input terminal and an output terminal, the first input terminal of the first NAND gate NAND1 is electrically connected to the enable input terminal, and the second input terminal of the first NAND gate NAND1 is electrically connected to the PWM input terminal; the second NAND gate NAND2 includes a first input terminal, a second input terminal and an output terminal, the first input terminal of the second NAND gate NAND2 is electrically connected to the PWM input terminal; the input terminal of the first inverter NOT1 is electrically connected to the output terminal of the first NAND gate NAND1; the input terminal of the second inverter NOT2 is electrically connected to the output terminal of the first inverter NOT1, and the output terminal of the second inverter NOT2 serves as the PWM driving module 24. 0; the input end of the third inverter NOT3 is electrically connected to the output end of the second NAND gate NAND2; the input end of the fourth inverter NOT4 is electrically connected to the output end of the third inverter NOT3; the output end of the fourth inverter NOT4 serves as the first output end of the PWM driving module 240; the input end of the fifth inverter NOT5 is electrically connected to the output end of the first inverter NOT1; the output end of the fifth inverter NOT5 is electrically connected to the second input end of the second NAND gate NAND2; the input end of the sixth inverter NOT6 is electrically connected to the output end of the fourth inverter NOT4, and the output end of the sixth inverter NOT6 is electrically connected to the third input end of the first NAND gate NAND1. In this way, the first switch module 210 and the second switch module 220 are driven. Different from the second NAND gate NAND2, the first NAND gate NAND1 includes three input ends, so that the enable signal can be used to control the output signal of the second output end.

[0088] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A lithium battery BUCK synchronous buck charging anti-reverse boost circuit, characterized in that: include: A first output terminal of a power supply, a second output terminal of a power supply, a first output terminal of a load, and a second output terminal of a load; the second output terminal of the power supply and the second output terminal of the load are both grounded; A first switch module, comprising a control end, a first end and a second end, wherein the first end of the first switch module is electrically connected to the first output end of the power supply; A second switch module, comprising a control end, a first end, and a second end, wherein the first end of the second switch module is electrically connected to the second end of the first switch module, and the second end of the second switch module is electrically connected to the second output end of the load; An energy storage module, wherein the energy storage module is connected in series between the second end of the first switch module and the first output end of the load; An input capacitor connected in parallel between the first output terminal of the power supply and the second output terminal of the power supply; a current detection module, comprising a first detection input terminal, a second detection input terminal and an enable output terminal, wherein the first detection input terminal is electrically connected to the first terminal of the first switch module, and the second detection input terminal is electrically connected to the second terminal of the first switch module; The current detection module is used to detect the current flowing through the first switch module, and generate an enable signal when the output current is less than the current comparison threshold; A controllable load, comprising a control end, a first end, and a second end, wherein the control end of the controllable load is electrically connected to the enable output end of the current detection module, the first end of the controllable load is electrically connected to a power supply, and the second end of the controllable load is grounded; A controller module, the controller module comprising a PWM output terminal for obtaining a PWM control signal according to an input-output voltage ratio; A PWM driving module, comprising a first input terminal, an enable input terminal, a first output terminal and a second output terminal, wherein the first input terminal is electrically connected to the PWM output terminal of the controller module; the enable input terminal is electrically connected to the enable output terminal of the current detection module; the first output terminal is electrically connected to the control terminal of the first switch module; the second output terminal is electrically connected to the control terminal of the second switch module; the PWM driving module is used to generate a PWM driving signal according to the enable signal and the PWM control signal to control the opening and closing of the first switch module and the second switch module; The current detection module comprises: A current mirror amplifier, wherein the first input end of the current mirror amplifier serves as the first detection input end of the current detection module, and the second input end of the current mirror amplifier serves as the second detection input end of the current detection module; a first resistor, wherein a first end of the first resistor is electrically connected to an output end of the current mirror amplifier; a second resistor, a first end of the second resistor being electrically connected to an output end of the current mirror amplifier; a first capacitor, wherein a first end of the first capacitor is electrically connected to a second end of the second resistor; The first capacitor and the second resistor form an RC filter circuit for averaging the output current of the current mirror amplifier; A comparator, wherein a first input terminal of the comparator is used to access a reference signal, a second input terminal of the comparator is electrically connected to a second end of the second resistor, and an output terminal of the comparator serves as an enable output terminal of the current detection module; The controllable load includes: An edge detection module, the edge detection module comprising a control end and an output end, the control end of the edge detection module being electrically connected to the control end of the controllable load; A load, wherein the load comprises a control end, a first end, and a second end, wherein the load control end is electrically connected to the output end of the edge detection module, the load first end is electrically connected to the controllable load first end, and the load second end is electrically connected to the controllable load second end; The control end of the edge detection module serves as the control end of the controllable load, the first end of the load serves as the first end of the controllable load, and the second end of the load serves as the second end of the controllable load.

2. The lithium battery BUCK synchronous buck charging anti-reverse boost circuit according to claim 1, characterized in that: The PWM driving module comprises: A first NAND gate, comprising a first input terminal, a second input terminal, a third input terminal and an output terminal, wherein the first input terminal of the first NAND gate is electrically connected to the enable input terminal, and the second input terminal of the first NAND gate is electrically connected to the output terminal of the controller module; A second NAND gate, comprising a first input terminal, a second input terminal and an output terminal, wherein the first input terminal of the second NAND gate is electrically connected to the output terminal of the controller module; A first inverter, wherein an input terminal of the first inverter is electrically connected to an output terminal of the first NAND gate; A second inverter, wherein an input end of the second inverter is electrically connected to an output end of the first inverter, and an output end of the second inverter serves as a second output end of the PWM driving module; a third inverter, wherein an input terminal of the third inverter is electrically connected to an output terminal of the second NAND gate; a fourth inverter, wherein the input end of the fourth inverter is electrically connected to the output end of the third inverter; and the output end of the fourth inverter serves as the first output end of the PWM driving module; a fifth inverter, wherein an input terminal of the fifth inverter is electrically connected to an output terminal of the first inverter; and an output terminal of the fifth inverter is electrically connected to a second input terminal of the second NAND gate; A sixth inverter, wherein an input terminal of the sixth inverter is electrically connected to an output terminal of the fourth inverter, and an output terminal of the sixth inverter is electrically connected to a third input terminal of the first NAND gate.

3. The lithium battery BUCK synchronous buck charging anti-reverse boost circuit according to claim 1, characterized in that: The energy storage module includes an inductor, and the inductor is connected in series between the second end of the first switch module and the first output end of the load.

4. The lithium battery BUCK synchronous buck charging anti-reverse boost circuit according to claim 1, characterized in that: Also includes: An output capacitor is connected in parallel between the first output terminal of the load and the second output terminal of the load.

5. The lithium battery BUCK synchronous buck charging anti-reverse boost circuit according to claim 1, characterized in that: The first switch module includes a first power tube, a gate of the first power tube serves as a control end of the first switch module, a first electrode of the first power tube serves as a first end of the first switch module, and a second electrode of the first power tube serves as a second end of the first switch module; The second switch module includes a second power tube, a gate of the second power tube serves as a control end of the second switch module, a first pole of the second power tube serves as a first end of the second switch module, and a second pole of the second power tube serves as a second end of the second switch module.

6. The lithium battery BUCK synchronous buck charging anti-reverse boost circuit according to claim 5, characterized in that: The first power tube is a P-type power tube, the first electrode of the first power tube is a source electrode, and the second electrode of the first power tube is a drain electrode; The second power tube is an N-type power tube, the first electrode of the second power tube is a drain, and the second electrode of the second power tube is a source.

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