Circuit for term / recharge comparator multiplexing

Abstract

The application discloses a circuit suitable for Term / Recharge comparator multiplexing, which comprises a Term judgment subcircuit and a Recharge judgment subcircuit. The application adopts a comparator multiplexing structure of Term / Recharge controlled by a linear charging loop, controls the charging state of the chip by detecting the voltage condition on the sampling circuit and the battery voltage condition, and realizes the effect of safely and efficiently charging the lithium ion battery. The comparator multiplexing structure can reduce one comparator, simplify the structure, simplify the logic circuit, reduce the chip cost, and improve the working efficiency of the circuit.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of CMOS analog integrated circuits, in particular to a circuit suitable for Term / Recharge comparator multiplexing. BACKGROUND

[0002] With the continuous development of science and technology, mobile communication technology has become an indispensable part of people's life, and the application of portable electronic products is also more and more widespread, and the requirement for battery performance is also gradually increased. Lithium ion battery is widely used in portable electronic products due to its advantages of light weight, small size, high voltage and large energy density compared with other secondary batteries. With the development of intelligentization of portable electronic equipment, the power consumption of the equipment is also increasing, and various electronic manufacturers have to increase the battery capacity to meet the endurance requirements of the equipment. However, the increase of battery capacity will inevitably affect the charging time, which seriously affects the user experience. And the battery is limited by the material and cannot produce a technological breakthrough, so the most suitable solution at present is to improve the user experience by adopting more advanced charging methods.

[0003] However, due to the limitations of physical structure and electrical characteristics in the design of lithium ion battery charging products, there are often many strict requirements. Because the voltage, current and temperature requirements of lithium ion battery charging and discharging are very high. In order to improve the safety factor of charging and protect the service life of lithium ion battery, lithium ion charging management chip needs to monitor the battery voltage in real time, improve the utilization efficiency of battery capacity, and provide overvoltage protection, overtemperature protection, short circuit protection and other protections for the charging process, which is undoubtedly a challenge for chip designers.

[0004] When the charging current is reduced to a certain extent, we will stop charging the battery because we think the battery is full, and this stage is usually called Term stage, and the power tube will be turned off after entering this stage. There is a loss after the battery stops charging, even if the battery is not used, there will be a slight leakage, when the battery voltage is reduced to a certain extent, it will be considered that the battery needs to be recharged, at this time the power tube will be restarted to charge the battery in the CV stage. This stage is usually called Recharge stage. The circuit structure for determining the two stages in the traditional lithium ion linear charging management chip is to use two comparators to determine the sampling current and battery voltage respectively, which results in low circuit working efficiency, complex circuit structure and logic, and increased chip cost. SUMMARY

[0005] In view of the above shortcomings in the prior art, the circuit suitable for Term / Recharge comparator multiplexing provided by the present application solves the problems of low circuit working efficiency, complex circuit structure and logic, and high chip cost in the traditional lithium ion linear charging management chip.

[0006] To achieve the aforementioned objectives, the present invention employs the following technical solution: a circuit suitable for Term / Recharge comparator multiplexing, the circuit comprising a Term determination sub-circuit and a Recharge determination sub-circuit. The Term determination sub-circuit includes RS flip-flop X1, RS flip-flop X2, transmission gate TG1, transmission gate TG3, and comparator CMP. The non-inverting input of comparator CMP is connected to the output of transmission gate TG1, and the input of transmission gate TG1 is connected to the sampled voltage V. ISEN The control terminal C of the RS flip-flop X1 is connected to the Q output terminal of the RS flip-flop X1, and its control terminal C' is connected to the Q output terminal of the RS flip-flop X1. The output terminals are connected as follows: the R input terminal of RS flip-flop X1 is connected to the output terminal of comparator CMP, its S input terminal is connected to the output terminal of NOT gate X3, the input terminal of NOT gate X3 is connected to the output terminal of comparator CMP, the R input terminal of RS flip-flop X2 is connected to the output terminal of comparator CMP, its S input terminal is connected to the output terminal of NOT gate X4, the input terminal of NOT gate X4 is connected to the output terminal of comparator CMP, and the Q output terminal of RS flip-flop X2 is connected to the control terminal C of transmission gate TG3. The output terminal is connected to the control terminal C' of the transmission gate TG3, and the input terminal of the transmission gate TG3 is connected to the reference voltage divider V. REF_TERM The output terminal of the comparator is connected to the inverting input terminal of the comparator CMP, and the output terminal of the comparator CMP is connected to the grounding capacitor C1.

[0007] The beneficial effects of the above solution are: by combining the two different state determination structures of Term and Recharge, the chip charging state is converted through the output of the comparator CMP, which simplifies the circuit structure and logic structure to a certain extent, improves the circuit efficiency, reduces the chip area, and reduces the chip cost.

[0008] Furthermore, the Recharge determination sub-circuit includes RS flip-flop X1, RS flip-flop X2, transmission gate TG2, transmission gate TG4, and comparator CMP. The non-inverting input of comparator CMP is connected to the output of transmission gate TG2, and the input of transmission gate TG2 is connected to the reference voltage divider V. REF_RECH The connection is made between its control terminal C and RS flip-flop X1. Output terminal connection, its control end C' is connected with the Q output terminal of RS trigger X1, the R input terminal of RS trigger X1 is connected with the output terminal of comparator CMP, its S input terminal is connected with the output terminal of non gate X3, the input terminal of non gate X3 is connected with the output terminal of comparator CMP, the R input terminal of RS trigger X2 is connected with the output terminal of comparator CMP, its S input terminal is connected with the output terminal of non gate X4, the input terminal of non gate X4 is connected with the output terminal of comparator CMP, the Q output terminal of RS trigger X2 is connected with the control end C' of transmission gate TG4, and the input terminal of transmission gate TG4 is connected with the output terminal of comparator CMP Output terminal is connected with the control end C of transmission gate TG4, and the input terminal of transmission gate TG4 is connected with the battery voltage V BAT Connection, its output terminal is connected with the inverting input terminal of comparator CMP, and the output terminal of comparator CMP is connected with ground capacitor C1.

[0009] The beneficial effects of the above further scheme are: through the above technical scheme, the recharge determination circuit is realized, which is used in combination with the Term circuit structure to complete the charging of the lithium ion battery.

[0010] Further, in the circuit, the reference voltage V REF_TERM As the determination standard of the full battery, the sampling voltage V ISEN And the reference voltage V REF_TERM Are compared, and the specific determination conditions are as follows:

[0011] (1) When the sampling voltage V ISEN ≥ The reference voltage V REF_TERM , the comparator CMP outputs high level, it is considered that the battery is not full, and the present situation continues to charge the battery;

[0012] (2) When the sampling voltage V ISEN < The reference voltage V REF_TERM , it is considered that the battery is full, and the comparator CMP outputs low level, at this time, the Q end output of RS trigger X1 and RS trigger X2 is 0, the transmission gate TG1 and the transmission gate TG3 cannot be turned on, the End output of RS trigger X1 and RS trigger X2 is 1, and the transmission gate TG2 and the transmission gate TG4 are turned on, and the recharge determination of the battery is started.

[0013] The beneficial effects of the above further scheme are: by comparing the sampling voltage V ISEN And the reference voltage V REF_TERM , it is determined whether the battery needs to be charged, and whether the comparator starts the recharge determination.

[0014] Further, the recharge determination specific conditions are as follows:

[0015] (1) When the reference voltage V REF_RECH ≤ battery voltage V BAT , the comparator CMP outputs low, and it is considered that the battery is fully charged and does not need to be recharged, and the status is maintained.

[0016] (2) When the reference voltage V REF_RECH > battery voltage V BAT , the comparator CMP outputs high, the battery voltage drops, and needs to be recharged, at this time, the R end of the RS flip-flop X1 and the R end of the RS flip-flop X2 are high, and the Q end outputs high, the transmission gate TG1 and the transmission gate TG3 are turned on, the comparator CMP starts to determine Term, and the process is repeated to determine the state of the battery.

[0017] The beneficial effect of the further scheme is that by comparing the reference voltage V REF_RECH and the battery voltage V BAT , it is determined whether the battery needs to be charged, and whether the comparator starts to determine Term.

[0018] Further, the comparator CMP adopts a two-stage operational amplifier structure.

[0019] The beneficial effect of the further scheme is that the two-stage operational amplifier structure has a large gain, which can increase the accuracy of the comparator. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 A circuit suitable for Term / Recharge comparator multiplexing.

[0021] Figure 2 A state transition diagram suitable for Term / Recharge comparator multiplexing structure.

[0022] Figure 3 A simulation waveform suitable for Term / Recharge comparator multiplexing structure. DETAILED DESCRIPTION

[0023] The application will be further described below in conjunction with the drawings and specific embodiments.

[0024] As shown in Figure 1 , a circuit suitable for Term / Recharge comparator multiplexing, the circuit includes a Term determination sub-circuit and a Recharge determination sub-circuit, the Term determination sub-circuit includes an RS flip-flop X1, an RS flip-flop X2, a transmission gate TG1, a transmission gate TG3 and a comparator CMP, the non-inverting input end of the comparator CMP is connected with the output end of the transmission gate TG1, the input end of the transmission gate TG1 is connected with a sampling voltage V ISENThe control terminal C is connected to the Q output terminal of RS flip-flop X1, and its control terminal C' is connected to the Q output terminal of RS flip-flop X1. The output terminals are connected as follows: the R input terminal of RS flip-flop X1 is connected to the output terminal of comparator CMP, its S input terminal is connected to the output terminal of NOT gate X3, the input terminal of NOT gate X3 is connected to the output terminal of comparator CMP, the R input terminal of RS flip-flop X2 is connected to the output terminal of comparator CMP, its S input terminal is connected to the output terminal of NOT gate X4, the input terminal of NOT gate X4 is connected to the output terminal of comparator CMP, and the Q output terminal of RS flip-flop X2 is connected to the control terminal C of transmission gate TG3. The output terminal is connected to the control terminal C' of the transmission gate TG3, and the input terminal of the transmission gate TG3 is connected to the reference voltage divider V. REF_TERM The output terminal of the comparator is connected to the inverting input terminal of the comparator CMP, and the output terminal of the comparator CMP is connected to the grounding capacitor C1.

[0025] The essence of the Term decision sub-circuit structure is to select two signals from the non-inverting and inverting inputs of the comparator for comparison, and then use the output signal of the comparator to control the selection of different signals for comparison.

[0026] The recharge determination subcircuit includes RS flip-flop X1, RS flip-flop X2, transmission gate TG2, transmission gate TG4, and comparator CMP. The non-inverting input of comparator CMP is connected to the output of transmission gate TG2, and the input of transmission gate TG2 is connected to the reference voltage divider V. REF_RECH The connection is made between its control terminal C and RS flip-flop X1. The output terminal is connected, and its control terminal C' is connected to the Q output terminal of RS flip-flop X1. The R input terminal of RS flip-flop X1 is connected to the output terminal of comparator CMP, and its S input terminal is connected to the output terminal of NOT gate X3. The input terminal of NOT gate X3 is connected to the output terminal of comparator CMP. The R input terminal of RS flip-flop X2 is connected to the output terminal of comparator CMP, and its S input terminal is connected to the output terminal of NOT gate X4. The input terminal of NOT gate X4 is connected to the output terminal of comparator CMP. The Q output terminal of RS flip-flop X2 is connected to the control terminal C' of transmission gate TG4. The output terminal is connected to the control terminal C of the transmission gate TG4, and the input terminal of the transmission gate TG4 is connected to the battery voltage divider V. BAT The output terminal of the comparator is connected to the inverting input terminal of the comparator CMP. The output terminal of the comparator CMP is connected to the grounding capacitor C1 and is used as an output signal in the subsequent logic control circuit.

[0027] The Term determination circuit and the Recharge determination circuit share RS flip-flop X1, RS flip-flop X2 and comparator CMP. The Recharge determination circuit basically reuses the Term determination circuit structure, except that the signal to be compared is selected by a two-to-one selector, thus achieving different functions.

[0028] The reference voltage V is divided in the circuit. REF_TERM As a criterion for determining whether the battery is fully charged, the sampling voltage V ISEN and reference voltage divider V REF_TERM The comparison is as follows:

[0029] (1) When the sampling voltage V ISEN ≥ Reference voltage V REF_TERM If the comparator CMP outputs a high level, it indicates that the battery is not fully charged and continues to charge the battery while maintaining the current state.

[0030] (2) When the sampling voltage V ISEN <Reference voltage V REF_TERM If the battery is fully charged, the comparator CMP output is low. At this time, the Q outputs of both RS flip-flops X1 and X2 are 0, and transmission gates TG1 and TG3 cannot conduct. The RS flip-flops X1 and X2... All terminal outputs are 1, and both transmission gates TG2 and TG4 are turned on, initiating the recharge determination for the battery.

[0031] The specific circumstances for determining Recharge are as follows:

[0032] (1) When the reference voltage V REF_RECH ≤ Battery voltage divider V BAT If the comparator CMP outputs a low level, it is considered that the battery is fully charged and does not need to be recharged, and the current state is maintained.

[0033] (2) When the reference voltage V REF_RECH Battery voltage divider V BAT If the comparator CMP outputs a high level, the battery voltage drops and needs to be recharged. At this time, the R terminals of RS flip-flops X1 and X2 are both high, and the Q terminals both output a high level. Transmission gates TG1 and TG3 are turned on, and the comparator CMP starts performing Term determination, continuing the process to determine the battery status.

[0034] like Figure 2 As shown, point A is the output signal of comparator CMP. When point A is 0, the battery is considered fully charged. If the reference voltage V... REF_RECH Less than the battery voltage divider V BAT, it is considered that the battery is still full and needs no recharge, so the present state is kept and the battery voltage is detected in real time; at this time, if the reference voltage V REF_RECH is greater than the battery voltage V BAT , it is considered that the battery is in a large loss state and needs recharge to ensure that the battery is full, so the A point is converted to 1, at this time, the chip control starts to charge the battery. When the A point is 1, it is considered that the battery is being charged, at this time, the sampling voltage V ISEN and the reference voltage V REF_TERM are compared, if the sampling voltage V ISEN is greater than the reference voltage V REF_TERM , it is considered that the battery is still being charged, the present state is kept and the sampling voltage is detected in real time; if the sampling voltage V ISEN is less than the reference voltage V REF_TERM , it is considered that the battery is full, the A point is converted to 0, and the state of the reference voltage V REF_RECH and the battery voltage V BAT is detected under the condition that the battery is full.

[0035] The comparator CMP adopts a two-stage operational amplifier structure, the MOS tube gate length of the transmission gates TG1, TG2, TG3 and TG4 is selected to be small size and appropriate width-length ratio, the capacitor size needs to be adjusted according to the actual circuit to prevent oscillation due to false triggering; the determination reference voltage of the battery entering the Term and Recharge states should be selected according to the actual situation to prevent damage to the battery due to overcharging.

[0036] In an embodiment of the present application, the two signals in the Term state determination circuit structure are respectively a sampling voltage V ISEN generated by the sampling current passing through an external resistor and a reference voltage V REF_TERM , the outputs of the two RS flip-flops X1 and X2 are controlled through the output of the comparator, the Q end, of the RS flip-flops X1 and X2 control whether the connected transmission gates TG1 and TG3 are turned on, so that the same phase input end of the comparator CMP is the sampling voltage V ISEN and the opposite phase input end is the reference voltage V REF_TERM . If the sampling voltage V ISEN is greater than the reference voltage V REF_TERM , the output end of the comparator CMP is high level, at this time, the R input end of the two RS flip-flops X1 and X2 is high level and the S input end is low level, since the RS flip-flop is composed of a NAND gate and realizes falling edge triggering, so the Q end of the two RS flip-flops outputs high level, the transmission gates TG1 and TG3 are kept turned on, and the sampling voltage V ISEN and the reference voltage V REF_TERMA comparison is made. At this point, it is assumed that the charging current is insufficient and the battery is not fully charged, so the sampling voltage V is maintained. ISEN and reference voltage divider V REF_TERM The comparison status is then used to continue detecting the magnitude of the charging current.

[0037] If the sampling voltage V ISEN Less than the reference voltage V REF_TERM When the comparator CMP output is low, the R inputs of the two RS flip-flops X1 and X2 are low, the S inputs are high, and the Q outputs of both RS flip-flops are low. When the terminal outputs a high level, transmission gates TG1 and TG3 are turned off, while transmission gates TG2 and TG4 are turned on, thus realizing the reference voltage divider V. REF_RECH and battery voltage divider V BAT A comparison is made. At this point, the battery's charging current is small enough that it is considered fully charged. Therefore, the detection state is changed to determine whether the fully charged battery needs to discharge further and requires recharging. If the reference voltage V... REF_RECH Less than the battery voltage divider V BAT When the comparator CMP outputs a low level, the R inputs of both RS flip-flops are low, ensuring that both RS flip-flops maintain a low level. The terminal outputs a high level, maintaining the reference voltage divider V. REF_RECH and battery voltage divider V BAT The comparison is performed. At this point, it is assumed that the battery voltage is still high and does not require further charging. Therefore, the current detection state is maintained, and the battery is judged in real time whether it needs to be recharged.

[0038] If the reference voltage V REF_RECH Greater than the battery voltage divider V BAT When the comparator CMP outputs a high level, the R inputs of both RS flip-flops are also high. Both RS flip-flops ensure a high Q output, thus enabling transmission gates TG1 and TG3 to conduct and achieve the sampling of voltage V. ISEN and reference voltage divider V REF_TERM The comparison is then performed. At this point, the battery is considered degraded and needs recharging. Therefore, the system checks whether the charging current is sufficiently low, i.e., whether the battery is fully charged. This forms a closed-loop logical judgment, using a comparator to determine the Term / Recharge states and generate an output signal.

[0039] like Figure 3 As shown, after trickle charging, constant current charging, and constant voltage charging, the lithium-ion battery voltage tends to saturate, and the charging current gradually decreases under the action of the loop. When the sampled voltage value is lower than the reference voltage V... REF_TERMWhen the battery is gradually discharged in the air until it is lower than 4V, it is considered to need recharging, at this time, the Term / Recharge output is high, and the judgment of whether the battery is full is re-performed.

[0040] The application uses a comparator, two output states of the battery are indicated by a signal, thereby improving the energy conversion efficiency of the system, reducing the system loss, simplifying the circuit structure and circuit logic, using a comparator multiplexing structure can reduce the chip area, to a certain extent, reduce the cost of the chip, increase the competitiveness of the chip, the comparator uses a two-stage amplifier structure, improves the response speed and comparison accuracy of the design, a capacitor is connected to the ground at the output end of the comparator to prevent false triggering, and the accuracy of state determination is increased.

[0041] Those skilled in the art will realize that the embodiments described herein are for the purpose of helping the reader understand the principles of the application and should be understood as not limiting the scope of protection of the application to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations according to the technical inspiration disclosed in the application without departing from the essence of the application, and these modifications and combinations are still within the scope of protection of the application.

Claims

1. A circuit suitable for Term / Recharge comparator multiplexing, characterized by, The circuit includes a Term determination subcircuit and a Recharge determination subcircuit. The Term determination subcircuit includes RS flip-flops X1 and X2, transmission gates TG1 and TG3, and a comparator CMP. The non-inverting input of the comparator CMP is connected to the output of the transmission gate TG1, and the input of the transmission gate TG1 is connected to the sampled voltage V. ISEN The control terminal C of the RS flip-flop X1 is connected to the Q output terminal of the RS flip-flop X1, and its control terminal C' is connected to the Q output terminal of the RS flip-flop X1. The output terminals are connected as follows: the R input terminal of RS flip-flop X1 is connected to the output terminal of comparator CMP, its S input terminal is connected to the output terminal of NOT gate X3, the input terminal of NOT gate X3 is connected to the output terminal of comparator CMP, the R input terminal of RS flip-flop X2 is connected to the output terminal of comparator CMP, its S input terminal is connected to the output terminal of NOT gate X4, the input terminal of NOT gate X4 is connected to the output terminal of comparator CMP, and the Q output terminal of RS flip-flop X2 is connected to the control terminal C of transmission gate TG3. The output terminal is connected to the control terminal C' of the transmission gate TG3, and the input terminal of the transmission gate TG3 is connected to the reference voltage divider V. REF_TERM The circuit is connected to the following: its output terminal is connected to the inverting input terminal of comparator CMP, and the output terminal of comparator CMP is connected to ground capacitor C1; the Recharge determination sub-circuit includes RS flip-flop X1, RS flip-flop X2, transmission gate TG2, transmission gate TG4, and comparator CMP. The non-inverting input terminal of comparator CMP is connected to the output terminal of transmission gate TG2, and the input terminal of transmission gate TG2 is connected to the reference voltage divider V. REF_RECH The connection is made between its control terminal C and RS flip-flop X1. The output terminal is connected, and its control terminal C' is connected to the Q output terminal of RS flip-flop X1. The R input terminal of RS flip-flop X1 is connected to the output terminal of comparator CMP, and its S input terminal is connected to the output terminal of NOT gate X3. The input terminal of NOT gate X3 is connected to the output terminal of comparator CMP. The R input terminal of RS flip-flop X2 is connected to the output terminal of comparator CMP, and its S input terminal is connected to the output terminal of NOT gate X4. The input terminal of NOT gate X4 is connected to the output terminal of comparator CMP. The Q output terminal of RS flip-flop X2 is connected to the control terminal C' of transmission gate TG4. The output terminal is connected to the control terminal C of the transmission gate TG4, and the input terminal of the transmission gate TG4 is connected to the battery voltage divider V. BAT The circuit is connected such that its output is connected to the inverting input of comparator CMP, and the output of comparator CMP is connected to ground capacitor C1; the Term determination subcircuit and the Recharge determination subcircuit share RS flip-flop X1, RS flip-flop X2 and comparator CMP; the circuit divides the reference voltage V REF_TERM As a criterion for determining that the battery is full, the sampled voltage V ISEN is compared with the reference divided voltage V REF_TERM , and the situation is determined as follows: (1) When the sampling voltage V ISEN ≥ reference voltage V REF_TERM , the comparator CMP outputs a high level, and it is considered that the battery is not fully charged, and the present state is maintained to continue charging the battery; (2) When the sampling voltage V ISEN <Reference voltage V REF_TERM The battery is considered full, and the comparator CMP outputs a low level. At this time, the Q outputs of the RS flip-flop X1 and the RS flip-flop X2 are both 0, the transmission gates TG1 and TG3 cannot be turned on, the Q outputs of the RS flip-flop X1 and the RS flip-flop X2 are both 1, and the transmission gates TG2 and TG4 are turned on, starting the Recharge determination of the battery. ​ The Recharge determination specific circumstances as follows: (1) When the reference voltage V REF_RECH ≤ battery voltage V BAT , the comparator CMP outputs low, and it is considered that the battery is fully charged and does not need to be charged, and the status is maintained. (2) When the reference voltage V REF_RECH > battery voltage V BAT The comparator CMP outputs high level, the battery voltage drops, and needs to be recharged. At this time, the R end of the RS flip-flop X1 and the R end of the RS flip-flop X2 are high level, the Q end outputs high level, the transmission gate TG1 and the transmission gate TG3 are turned on, the comparator CMP starts to determine Term, and the process is repeated to determine the battery state.

2. The circuit suitable for Term / Recharge comparator multiplexing according to claim 1, characterized in that, The comparator CMP adopts two level operational amplifier structure.

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