Low-leakage-current high-voltage selection circuit applied to voltage sampling of multiple batteries connected in series

Abstract

The invention discloses a low-leakage-current high-voltage selection circuit applied to voltage sampling of multiple serially-connected batteries, which comprises a high-voltage selection circuit for battery voltage sampling, a high-voltage switch HSWITCH1 and a high-voltage switch HSWITCH2, the high-voltage selection circuit for battery voltage sampling is composed of multiple serially-connected lithium batteries, the voltage of the first battery and the voltage of the second battery are selected by a group of high-voltage switches, and the high-voltage switch HSWITCH2 is connected with the high-voltage switch HSWITCH2. The voltage of the third battery is matched with a battery positive and negative end matching circuit for selection, and N batteries correspond to N + 4 sampling switches. The problems that in the prior art, when an LDMOS serves as a high-voltage selection switch for battery voltage sampling in the BCD technology, a pull-down or pull-up current provided by the battery voltage exists in a typical structure, so that the consistency of the electric quantity of a battery is affected, and the use efficiency and the service life of the battery are further affected are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of battery management chips, and in particular relates to a low leakage current high voltage selection circuit applied to voltage sampling of multiple series-connected batteries. Background Art

[0002] With the popularization and development of new energy technologies, lithium-ion batteries play an important role in applications such as automotive electronics, portable devices, and intelligent logistics equipment. Usually, several lithium batteries are connected in series as the power source of these products, but overcharging and over-discharging of lithium batteries will cause irreversible and serious damage to lithium batteries, affecting the normal use and life of lithium batteries. In order to improve battery efficiency and extend the service life, a battery management system (BMS) is required to monitor whether the voltage of a single battery cell is over-voltage or under-voltage and trigger corresponding protection.

[0003] In order to save chip area and power consumption, the battery voltage sampling circuit usually selects the voltage of a single battery through a high-voltage selection circuit, and then uses a level shift circuit to convert the voltage signal in the high-voltage domain into a voltage signal in the low-voltage domain with a certain conversion coefficient. Finally, the converted voltage signal is sent to the analog-to-digital converter (ADC) for quantization.

[0004] Since multiple lithium batteries are connected in series, the maximum battery voltage can reach tens of volts. Battery management chips usually use Bipolar-CMOS-DMOS (BCD) technology, in which LDMOS has the characteristics of gate-drain voltage resistance but gate-source voltage resistance. Therefore, when LDMOS is used as a high-voltage switch, a gate-source voltage bias circuit is required to make it linearly conductive. Figure 1 This is a typical LDMOS circuit diagram for high-voltage switching. When EN is at a high level, a pull-down current will be generated and a voltage drop will be generated on R1, causing DM P1 The gate-source voltage is biased at a suitable value. However, there are two problems with this circuit: 1. Due to the presence of the substrate diode D1, the high-voltage switch cannot be used in cascade. 2. When the high-voltage switch is working normally, there will always be a pull-down current provided by Vbat_in. When the high-voltage switch selects different batteries, due to the different Vbat_in, it will affect the consistency of the battery power, further affecting the battery efficiency and life. Summary of the invention

[0005] The purpose of the present invention is to provide a low leakage current high voltage selection circuit for voltage sampling of multiple series-connected batteries, which solves the problem in the prior art that when LDMOS is used as a high voltage selection switch for battery voltage sampling in a BCD process, a pull-down or pull-up current provided by the battery voltage will exist in the typical structure, thereby affecting the consistency of the battery power and further affecting the battery's use efficiency and life.

[0006] The technical solution adopted by the present invention is a low leakage current high voltage selection circuit applied to voltage sampling of multiple series-connected batteries, including a high voltage selection circuit for battery voltage sampling, a high voltage switch HSWITCH1 and a high voltage switch HSWITCH2.

[0007] The present invention is also characterized in that: The high-voltage selection circuit for battery voltage sampling is composed of multiple lithium batteries connected in series. The voltages of the first and second batteries are selected by a group of high-voltage switches, and the voltage of the third battery is selected by matching the positive and negative terminals of the battery. N batteries correspond to N+4 sampling switches.

[0008] Two back-to-back series-connected P-LDMOS are used as a low leakage current high voltage switch HSWITCH1. In the HSWITCH1, the P-LDMOS tube DM P1 The source of the DM is connected to the input battery voltage Vbat_in. P1 The drain of the P-LDMOS tube DM is connected P2 The drain of DM forms a back-to-back high-voltage switch. P2 The source of the current source is connected to the output battery voltage Vbat_out; the current source generating circuit is R1, and R1 is connected to the low voltage NMOS tube M N1 The gate-drain terminal and the low-voltage NMOS tube M N2 、M N3 、M N4 The gate of the resistor R2 is used as a current mirror to copy the current; one end of the resistor R2 is connected to the input battery voltage Vbat_in, and the other end is connected to the N-LDMOS tube DM N2 The drain, DM N2 The source connection M N3 The drain electrode forms DM P1 Bias circuit; Current source I3 connects resistor R3 and P-LDMOS tube DM P5 The source, DM P5 The drain of R3 is grounded, and the other end of R3 is connected to the N-LDMOS tube DM N3 The drain and DM P2 The gate, DM N3 The source connection M N4 The drain electrode forms DM P2 Bias circuit of N-LDMOS tube DM N1 The source connection M N2 The drain, DM N1 The drain of the P-LDMOS tube DM is connected P3 The gate-drain and P-LDMOS tube DM P4 The gate, DM P3 The source of the low voltage PMOS tube M P1 Gate drain and low voltage PMOS tube MP2 The gate, M P2 The drain connection DM P4 The source of forms a current compensation circuit.

[0009] In HSWITCH1, let I BACK1 =I1, so that the pull-down current is provided by the highest battery voltage VCC instead of the input battery voltage Vbat_in; Two N-LDMOS connected in series back to back are used as a low leakage current high voltage switch HSWITCH2. In the HSWITCH2, the N-LDMOS tube DM N1 The drain terminal of DM is connected to the input battery voltage Vbat_in. N1 The source of the N-LDMOS tube DM is connected N2 The source of DM forms a back-to-back high-voltage switch. N2 The drain outputs the battery voltage Vbat_out; the current source generation circuit is R1, which is connected to the low-voltage NMOS tube M N1 The gate-drain terminal and the low-voltage NMOS tube M N2 Gate of N-LDMOS tube DM N3 The source connection M N2 The drain, DM N3 The drain of the P-LDMOS tube DM is connected P1 The gate-drain and P-LDMOS tube DM P2 The gate, DM P1 The source of the low voltage PMOS tube M P1 The gate and drain of the PMOS tube M P2 The gate, M P2 The drain connection DM P2 The source, DM P2 The drain of the resistor R2 is connected, and the other end of R2 is connected to the DM N1 and DM N2 The source of forms the bias circuit of the high voltage switch.

[0010] N-LDMOS tube DM N4 The drain connection DM N1 and DM N2 The source, DM N4 The source of the low voltage NMOS tube M N3 The drain of the circuit forms a current compensation circuit.

[0011] In HSWITCH2, let I BACK2 =I2, so that the pull-down current provided by VCC flows into the ground instead of the input terminal.

[0012] The beneficial effect of the present invention is that the low leakage current high voltage selection circuit applied to the voltage sampling of multiple series-connected batteries is compared with the traditional high voltage switch applied to the voltage sampling of multiple series-connected lithium batteries. The present invention uses current compensation to enable LDMOS to generate a pull-up or pull-down current provided by the highest battery voltage instead of the input battery voltage of each battery when used as a high voltage switch, thereby avoiding the potential safety hazard of overvoltage or undervoltage of the battery caused by inconsistent power of each battery. The designed high voltage switches HSWITCH1 and HSWITCH2 are applied to the battery high voltage selection circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a typical circuit diagram of LDMOS used as a high-voltage switch; Figure 2 The present invention is a high voltage selection circuit applied to voltage sampling of multiple series-connected batteries; Figure 3 Two back-to-back series-connected P-LDMOSs of the present invention serve as a low leakage current high-voltage switch HSWITCH1; Figure 4 Two N-LDMOS connected in series back to back in the present invention serve as a low leakage current high voltage switch HSWITCH2; Figure 5 This is a schematic diagram of the control signals of a low leakage current high voltage selection circuit used for voltage sampling of multiple series-connected lithium batteries. DETAILED DESCRIPTION

[0014] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0015] The present invention is applied to a low leakage current high voltage selection circuit for voltage sampling of multiple series-connected batteries, and the structure is as follows: Figure 2 As shown, it includes a high-voltage selection circuit for battery voltage sampling, a high-voltage switch HSWITCH1 and a high-voltage switch HSWITCH2. The high-voltage selection circuit for battery voltage sampling is composed of multiple lithium batteries connected in series. The voltages of the first and second batteries are selected by a group of high-voltage switches, and the voltage of the third battery is selected by matching the positive and negative terminals of the battery. N batteries correspond to N+4 sampling switches.

[0016] Two back-to-back series-connected P-LDMOS are used as a low leakage current high voltage switch HSWITCH1. In the HSWITCH1, the P-LDMOS tube DM P1 The source of the DM is connected to the input battery voltage Vbat_in. P1 The drain of the P-LDMOS tube DM is connected P2 The drain of DM forms a back-to-back high-voltage switch. P2 The source of the current source is connected to the output battery voltage Vbat_out; the current source generating circuit is R1, and R1 is connected to the low voltage NMOS tube MN1 The gate-drain terminal and the low-voltage NMOS tube M N2 、M N3 、M N4 The gate of the resistor R2 is used as a current mirror to copy the current; one end of the resistor R2 is connected to the input battery voltage Vbat_in, and the other end is connected to the N-LDMOS tube DM N2 The drain, DM N2 The source connection M N3 The drain electrode forms DM P1 Bias circuit.

[0017] Current source I3 connects resistor R3 and P-LDMOS tube DM P5 The source, DM P5 The drain of R3 is grounded, and the other end of R3 is connected to the N-LDMOS tube DM N3 The drain and DM P2 The gate, DM N3 The source connection M N4 The drain electrode forms DM P2 Bias circuit of N-LDMOS tube DM N1 The source connection M N2 The drain, DM N1 The drain of the P-LDMOS tube DM is connected P3 The gate-drain and P-LDMOS tube DM P4 The gate, DM P3 The source of the low voltage PMOS tube M P1 Gate drain and low voltage PMOS tube M P2 The gate, M P2 The drain connection DM P4 The source of forms a current compensation circuit.

[0018] In HSWITCH1, let I BACK1 =I1, so that the pull-down current is provided by the highest battery voltage VCC instead of the input battery voltage Vbat_in.

[0019] Two N-LDMOS connected in series back to back are used as a low leakage current high voltage switch HSWITCH2. In the HSWITCH2, the N-LDMOS tube DM N1 The drain terminal of DM is connected to the input battery voltage Vbat_in. N1 The source of the N-LDMOS tube DM is connected N2 The source of DM forms a back-to-back high-voltage switch. N2 The drain outputs the battery voltage Vbat_out; the current source generation circuit is R1, which is connected to the low-voltage NMOS tube M N1 The gate-drain terminal and the low-voltage NMOS tube M N2Gate of N-LDMOS tube DM N3 The source connection M N2 The drain, DM N3 The drain of the P-LDMOS tube DM is connected P1 The gate-drain and P-LDMOS tube DM P2 The gate, DM P1 The source of the low voltage PMOS tube M P1 The gate and drain of the PMOS tube M P2 The gate, M P2 The drain connection DM P2 The source, DM P2 The drain of the resistor R2 is connected, and the other end of R2 is connected to the DM N1 and DM N2 The source of forms the bias circuit of the high voltage switch.

[0020] N-LDMOS tube DM N4 The drain connection DM N1 and DM N2 The source, DM N4 The source of the low voltage NMOS tube M N3 The drain of the circuit forms a current compensation circuit.

[0021] In HSWITCH2, let I BACK2 =I2, so that the pull-down current provided by VCC flows into the ground instead of the input terminal.

[0022] Example 1 The present invention is applied to a low leakage current high voltage selection circuit for voltage sampling of multiple series-connected batteries, and the structure is as follows: Figure 2 As shown, it includes a high-voltage selection circuit for battery voltage sampling, a high-voltage switch HSWITCH1 and a high-voltage switch HSWITCH2. The high-voltage selection circuit for battery voltage sampling is composed of multiple lithium batteries connected in series. The voltages of the first and second batteries are selected by a group of high-voltage switches, and the voltage of the third battery is selected by matching the positive and negative terminals of the battery. N batteries correspond to N+4 sampling switches.

[0023] Example 2 The present invention is applied to a low leakage current high voltage selection circuit for voltage sampling of multiple series-connected batteries, and the structure is as follows: Figure 2 As shown, it includes a high-voltage selection circuit for battery voltage sampling, a high-voltage switch HSWITCH1 and a high-voltage switch HSWITCH2. The high-voltage selection circuit for battery voltage sampling is composed of multiple lithium batteries connected in series. The voltages of the first and second batteries are selected by a group of high-voltage switches, and the voltage of the third battery is selected by matching the positive and negative terminals of the battery. N batteries correspond to N+4 sampling switches.

[0024] Two back-to-back series-connected P-LDMOS are used as a low leakage current high voltage switch HSWITCH1. In the HSWITCH1, the P-LDMOS tube DM P1 The source of the DM is connected to the input battery voltage Vbat_in. P1 The drain of the P-LDMOS tube DM is connected P2 The drain of DM forms a back-to-back high-voltage switch. P2 The source of the current source is connected to the output battery voltage Vbat_out; the current source generating circuit is R1, and R1 is connected to the low voltage NMOS tube M N1 The gate-drain terminal and the low-voltage NMOS tube M N2 、M N3 、M N4 The gate of the resistor R2 is used as a current mirror to copy the current; one end of the resistor R2 is connected to the input battery voltage Vbat_in, and the other end is connected to the N-LDMOS tube DM N2 The drain, DM N2 The source connection M N3 The drain electrode forms DM P1 Bias circuit.

[0025] Example 3 The present invention is applied to a low leakage current high voltage selection circuit for voltage sampling of multiple series-connected batteries, and the structure is as follows: Figure 2 As shown, it includes a high-voltage selection circuit for battery voltage sampling, a high-voltage switch HSWITCH1 and a high-voltage switch HSWITCH2. The high-voltage selection circuit for battery voltage sampling is composed of multiple lithium batteries connected in series. The voltages of the first and second batteries are selected by a group of high-voltage switches, and the voltage of the third battery is selected by matching the positive and negative terminals of the battery. N batteries correspond to N+4 sampling switches.

[0026] Two back-to-back series-connected P-LDMOS are used as a low leakage current high voltage switch HSWITCH1. In the HSWITCH1, the P-LDMOS tube DM P1 The source of the DM is connected to the input battery voltage Vbat_in. P1 The drain of the P-LDMOS tube DM is connected P2 The drain of DM forms a back-to-back high-voltage switch. P2 The source of the current source is connected to the output battery voltage Vbat_out; the current source generating circuit is R1, and R1 is connected to the low voltage NMOS tube M N1 The gate-drain terminal and the low-voltage NMOS tube M N2 、M N3 、M N4 The gate of the resistor R2 is used as a current mirror to copy the current; one end of the resistor R2 is connected to the input battery voltage Vbat_in, and the other end is connected to the N-LDMOS tube DM N2 The drain, DM N2The source connection M N3 The drain electrode forms DM P1 Bias circuit.

[0027] Two N-LDMOS connected in series back to back are used as a low leakage current high voltage switch HSWITCH2. In the HSWITCH2, the N-LDMOS tube DM N1 The drain terminal of DM is connected to the input battery voltage Vbat_in. N1 The source of the N-LDMOS tube DM is connected N2 The source of DM forms a back-to-back high-voltage switch. N2 The drain outputs the battery voltage Vbat_out; the current source generation circuit is R1, which is connected to the low-voltage NMOS tube M N1 The gate-drain terminal and the low-voltage NMOS tube M N2 Gate of N-LDMOS tube DM N3 The source connection M N2 The drain, DM N3 The drain of the P-LDMOS tube DM is connected P1 The gate-drain and P-LDMOS tube DM P2 The gate, DM P1 The source of the low voltage PMOS tube M P1 The gate and drain of the PMOS tube M P2 The gate, M P2 The drain connection DM P2 The source, DM P2 The drain of the resistor R2 is connected, and the other end of R2 is connected to the DM N1 and DM N2 The source of forms the bias circuit of the high voltage switch.

[0028] N-LDMOS tube DM N4 The drain connection DM N1 and DM N2 The source, DM N4 The source of the low voltage NMOS tube M N3 The drain of the circuit forms a current compensation circuit.

[0029] Example 4 The present invention is applied to a low leakage current high voltage selection circuit for voltage sampling of multiple series-connected batteries, and the structure is as follows: Figure 2 As shown, it includes a high-voltage selection circuit for battery voltage sampling, a high-voltage switch HSWITCH1 and a high-voltage switch HSWITCH2. The high-voltage selection circuit for battery voltage sampling is composed of multiple lithium batteries connected in series. The voltages of the first and second batteries are selected by a group of high-voltage switches, and the voltage of the third battery is selected by matching the positive and negative terminals of the battery. N batteries correspond to N+4 sampling switches.

[0030] Two N-LDMOS connected in series back to back are used as a low leakage current high voltage switch HSWITCH2. In the HSWITCH2, the N-LDMOS tube DM N1 The drain terminal of DM is connected to the input battery voltage Vbat_in. N1 The source of the N-LDMOS tube DM is connected N2 The source of DM forms a back-to-back high-voltage switch. N2 The drain outputs the battery voltage Vbat_out; the current source generation circuit is R1, which is connected to the low-voltage NMOS tube M N1 The gate-drain terminal and the low-voltage NMOS tube M N2 Gate of N-LDMOS tube DM N3 The source connection M N2 The drain, DM N3 The drain of the P-LDMOS tube DM is connected P1 The gate-drain and P-LDMOS tube DM P2 The gate, DM P1 The source of the low voltage PMOS tube M P1 The gate and drain of the PMOS tube M P2 The gate, M P2 The drain connection DM P2 The source, DM P2 The drain of the resistor R2 is connected, and the other end of R2 is connected to the DM N1 and DM N2 The source of forms the bias circuit of the high voltage switch.

[0031] N-LDMOS tube DM N4 The drain connection DM N1 and DM N2 The source, DM N4 The source of the low voltage NMOS tube M N3 The drain of the circuit forms a current compensation circuit.

[0032] In HSWITCH2, let I BACK2 =I2, so that the pull-down current provided by VCC flows into the ground instead of the input terminal.

[0033] Example 5 The present invention is applied to a low leakage current high voltage selection circuit for voltage sampling of multiple series-connected batteries, and the structure is as follows: Figure 2 As shown, it includes a high-voltage selection circuit for battery voltage sampling, a high-voltage switch HSWITCH1 and a high-voltage switch HSWITCH2. The high-voltage selection circuit for battery voltage sampling is composed of multiple lithium batteries connected in series. The voltages of the first and second batteries are selected by a group of high-voltage switches, and the voltage of the third battery is selected by matching the positive and negative terminals of the battery. N batteries correspond to N+4 sampling switches.

[0034] Two back-to-back series-connected P-LDMOS are used as a low leakage current high voltage switch HSWITCH1. In the HSWITCH1, the P-LDMOS tube DM P1 The source of the DM is connected to the input battery voltage Vbat_in. P1 The drain of the P-LDMOS tube DM is connected P2 The drain of DM forms a back-to-back high-voltage switch. P2 The source of the current source is connected to the output battery voltage Vbat_out; the current source generating circuit is R1, and R1 is connected to the low voltage NMOS tube M N1 The gate-drain terminal and the low-voltage NMOS tube M N2 、M N3 、M N4 The gate of the resistor R2 is used as a current mirror to copy the current; one end of the resistor R2 is connected to the input battery voltage Vbat_in, and the other end is connected to the N-LDMOS tube DM N2 The drain, DM N2 The source connection M N3 The drain electrode forms DM P1 Bias circuit.

[0035] Current source I3 connects resistor R3 and P-LDMOS tube DM P5 The source, DM P5 The drain of R3 is grounded, and the other end of R3 is connected to the N-LDMOS tube DM N3 The drain and DM P2 The gate, DM N3 The source connection M N4 The drain electrode forms DM P2 Bias circuit of N-LDMOS tube DM N1 The source connection M N2 The drain, DM N1 The drain of the P-LDMOS tube DM is connected P3 The gate-drain and P-LDMOS tube DM P4 The gate, DM P3 The source of the low voltage PMOS tube M P1 Gate drain and low voltage PMOS tube M P2 The gate, M P2 The drain connection DM P4 The source of forms a current compensation circuit.

[0036] Example 6 The present invention is applied to a low leakage current high voltage selection circuit for voltage sampling of multiple series-connected batteries, and the structure is as follows: Figure 2As shown, it includes a high-voltage selection circuit for battery voltage sampling, a high-voltage switch HSWITCH1 and a high-voltage switch HSWITCH2. The high-voltage selection circuit for battery voltage sampling is composed of multiple lithium batteries connected in series. The voltages of the first and second batteries are selected by a group of high-voltage switches, and the voltage of the third battery is selected by matching the positive and negative terminals of the battery. N batteries correspond to N+4 sampling switches.

[0037] Two N-LDMOS connected in series back to back are used as a low leakage current high voltage switch HSWITCH2. In the HSWITCH2, the N-LDMOS tube DM N1 The drain terminal of DM is connected to the input battery voltage Vbat_in. N1 The source of the N-LDMOS tube DM is connected N2 The source of DM forms a back-to-back high-voltage switch. N2 The drain outputs the battery voltage Vbat_out; the current source generation circuit is R1, which is connected to the low-voltage NMOS tube M N1 The gate-drain terminal and the low-voltage NMOS tube M N2 Gate of N-LDMOS tube DM N3 The source connection M N2 The drain, DM N3 The drain of the P-LDMOS tube DM is connected P1 The gate-drain and P-LDMOS tube DM P2 The gate, DM P1 The source of the low voltage PMOS tube M P1 The gate and drain of the PMOS tube M P2 The gate, M P2 The drain connection DM P2 The source, DM P2 The drain of the resistor R2 is connected, and the other end of R2 is connected to the DM N1 and DM N2 The source of forms the bias circuit of the high voltage switch.

[0038] N-LDMOS tube DM N4 The drain connection DM N1 and DM N2 The source, DM N4 The source of the low voltage NMOS tube M N3 The drain of the circuit forms a current compensation circuit.

[0039] In HSWITCH2, let I BACK2 =I2, so that the pull-down current provided by VCC flows into the ground instead of the input terminal.

[0040] Figure 1This is a typical circuit diagram of LDMOS used as a high-voltage switch. Vbat_in is the input battery voltage. When the control signal EN is at a high level, a pull-down current is generated and a voltage drop is generated on the resistor R1. In this way, the P-LDMOS tube DM P1 V SG is biased within a certain range so that it can be turned on linearly. D1 is DM P1 However, the pull-down current generated is provided by the input battery voltage Vbat_in. When the high-voltage switch selects different batteries as input, the average pull-down current of each battery is not equal, which will cause the voltage of each battery to be inconsistent, thus affecting the battery efficiency and life.

[0041] Figure 2 This is a high-voltage selection circuit for voltage sampling of multiple lithium batteries in series. In combination with the proposed battery voltage sampling method, in order to save the number of switches to the greatest extent, the high-voltage sampling circuit structure is designed. The voltages of the first and second batteries are selected by a group of high-voltage switches, and the voltage of the third battery is selected by matching the positive and negative terminals of the battery. In traditional high-voltage selection circuits, sampling N batteries requires 2N sampling switches, while this method only requires N+4 sampling switches. For 5 or more batteries in series, this method can significantly reduce the number of switches.

[0042] Under normal circumstances, the voltage range of a single battery is 1.5V-4.5V. According to the different battery voltages, select the appropriate high-voltage switches HSWITCH1 and HSWITCH2. If the voltage of a single battery is 1.5V, then the positive terminal voltage of the second battery is 3V. If HSWITCH1 is used as the high-voltage selection switch for the second battery, it is difficult to make M N3 It works in the saturation region, so the positive terminal voltage of the second battery selects HSWITCH2 as the high-voltage switch. The positive terminal voltage of the second battery is also the negative terminal voltage of the third battery. When the voltage of the third battery is selected, the switch S B1 , S B2 conduction, where S B1 The negative terminal voltage of the third battery is selected, so HSWITCH2 is selected as the high-voltage switch. When the voltage of the fourteenth battery is selected (the highest battery voltage), the switch S 13 , S 14 , S A1 , S A2 When it is turned on, HSWITCH1 is used as a high-voltage switch, so that VCC does not need an additional charge pump circuit to drive it.

[0043] Figure 3The present invention uses two back-to-back series-connected P-LDMOS as a low leakage current high-voltage switch HSWITCH1. In order to increase the isolation between the high-voltage switches, two back-to-back series-connected P-LDMOS are used, and their substrate diodes D1 and D2 are reverse biased; R2, DM N2 、M N3 、M N1 and R1 form DM P1 Bias circuit of M N4 DM N3 , R3, DM P5 and current source I3 form DM P2 Bias circuit of M N2 DM N1 DM P3 DM P4 、M P1 、M P2 The current compensation circuit is formed. Its working principle is: when the control signal EN is high, the current source I=5V / R1,M N1 and M N3 A current mirror is formed to copy the generated current I to current I1. R2 and I1 produce a voltage drop, making V SG,DMP1 =Vbat_in-I1R2;M N2 and M N1 The current mirror is formed, and the copied current is I2, DM P5 and current source I3 form a source follower, and I3 must be greater than I2, V SG,DMP2 =I2R3-V SG,DMP5 ;M N2 and M N1 Forming a current mirror, M P1 、M P2 DM P3 and DM P4 The cascode current mirror is formed, and the copied current is I back1 , let I back1 =I1, through current compensation, the current I2 is provided by the highest battery voltage VCC instead of the input battery voltage Vbat_in, ensuring the consistency of battery power. When the highest battery positive terminal voltage is selected, VCC=Vbat_in, although M P2 and DM P4 The short circuit makes the current compensation circuit invalid, but the pull-down current is still provided by the highest battery cell voltage and will not affect the consistency.

[0044] Figure 4The present invention uses two back-to-back series-connected N-LDMOS as a low leakage current high-voltage switch HSWITCH2. Similarly, in order to increase the isolation between the high-voltage switches, two back-to-back series-connected N-LDMOS are used, and their substrate diodes D1 and D2 are reverse biased; N2 DM N3 DM P1 DM P2 、M P1 、M P2 and R2 form DM N 1 and DM N2 Bias circuit of DM N4 and M N3 The transistor Q1 is used to protect the DM when the control signal EN is at a low level. N1 and DM N2 The gate-source voltage will not be broken down. Its working principle is: when the control signal EN is high, the current I=5V / R1 is generated, M N1 and M N2 Forming a current mirror, M P1 、M P2 DM P1 and DM P2 The cascode current mirror is formed, and the copied current is I2. R2 and I2 produce a voltage drop, making V GS,DMN1 =V GS,DMN2 =I2R2, this bias voltage makes DM N1 and DM N2 Can be linearly turned on; M N3 and M N1 The current mirror is formed, and the copied current is I back2 , let I back2 =I2, so that the current flows from VCC into the ground instead of the input battery voltage, ensuring the consistency of the battery charge.

[0045] Figure 5 This is a schematic diagram of a low leakage current high voltage selection circuit for voltage sampling of multiple series lithium batteries. When S1 is high, HSWITCH2 controlled by S1 is turned on and the voltage of the first battery is selected; when S1 and S2 are high, HSWITCH2 controlled by S1 is turned on and HSWITCH2 controlled by S2 is turned on and the voltage of the second battery is selected; when S2, S3, S B1 and S B2 When the level is high, S2, S B1 The controlled HSWITCH2 is turned on, S3, S B2 The controlled HSWITCH1 is turned on; the remaining battery selections are similar.

[0046] The present invention is applied to a low leakage current high voltage selection circuit for voltage sampling of multiple series-connected batteries. It improves the problem that when a typical LDMOS tube is used as a high voltage switch, its gate-source clamping circuit will generate a pull-up or pull-down current provided by the input battery voltage, affecting the consistency of the power of each battery, and further affecting the battery efficiency and life. The present invention uses a current compensation circuit to compensate for two back-to-back series-connected P-LDMOS used as high voltage switches and two back-to-back parallel-connected N-LDMOS used as high voltage switches, so that the pull-down or pull-up current generated by the gate-source clamping circuit is all provided by the highest battery voltage, thereby ensuring the consistency of the battery power. The two designed low leakage current high voltage switches are used in a specific high voltage selection circuit for voltage sampling.

Claims

1. A low leakage current high voltage selection circuit for voltage sampling of multiple series-connected batteries, characterized in that: It includes a high-voltage selection circuit for battery voltage sampling, a high-voltage switch HSWITCH1 and a high-voltage switch HSWITCH2.

2. The low leakage current high voltage selection circuit for voltage sampling of multiple series-connected batteries according to claim 1, characterized in that: The high-voltage selection circuit for battery voltage sampling is composed of multiple lithium batteries connected in series. The voltages of the first and second batteries are selected by a group of high-voltage switches, and the voltage of the third battery is selected by matching the positive and negative terminals of the battery. N batteries correspond to N+4 sampling switches.

3. The low leakage current high voltage selection circuit for voltage sampling of multiple series-connected batteries according to claim 1, characterized in that: Two back-to-back series-connected P-LDMOS are used as a low leakage current high voltage switch HSWITCH1. In the HSWITCH1, the P-LDMOS tube DM P1 The source of the DM is connected to the input battery voltage Vbat_in. P1 The drain of the P-LDMOS tube DM is connected P2 The drain of DM forms a back-to-back high-voltage switch. P2 The source of the current source is connected to the output battery voltage Vbat_out; the current source generating circuit is R1, and R1 is connected to the low voltage NMOS tube M N1 The gate-drain terminal and the low-voltage NMOS tube M N2 、M N3 、M N4 The gate of the resistor R2 is used as a current mirror to copy the current; one end of the resistor R2 is connected to the input battery voltage Vbat_in, and the other end is connected to the N-LDMOS tube DM N2 The drain, DM N2 The source connection M N3 The drain electrode forms DM P1 Bias circuit.

4. The low leakage current high voltage selection circuit for voltage sampling of multiple series-connected batteries according to claim 3, characterized in that: Current source I3 connects resistor R3 and P-LDMOS tube DM P5 The source, DM P5 The drain of R3 is grounded, and the other end of R3 is connected to the N-LDMOS tube DM N3 The drain and DM P2 The gate, DM N3 The source connection M N4 The drain electrode forms DM P2 Bias circuit; N-LDMOS tube DM N1 The source connection M N2 The drain, DM N1 The drain of the P-LDMOS tube DM is connected P3 The gate-drain and P-LDMOS tube DM P4 The gate, DM P3 The source of the low voltage PMOS tube M P1 Gate drain and low voltage PMOS tube M P2 The gate, M P2 The drain connection DM P4 The source of forms a current compensation circuit.

5. The low leakage current high voltage selection circuit for voltage sampling of multiple series-connected batteries according to claim 4, characterized in that: In the HSWITCH1, let I BACK1 =I1, so that the pull-down current is provided by the highest battery voltage VCC instead of the input battery voltage Vbat_in.

6. The low leakage current high voltage selection circuit for voltage sampling of multiple series-connected batteries according to claim 5, characterized in that: Two N-LDMOS connected in series back to back are used as a low leakage current high voltage switch HSWITCH2. In the HSWITCH2, the N-LDMOS tube DM N1 The drain terminal of DM is connected to the input battery voltage Vbat_in. N1 The source of the N-LDMOS tube DM is connected N2 The source of DM forms a back-to-back high-voltage switch. N2 The drain outputs the battery voltage Vbat_out; the current source generation circuit is R1, which is connected to the low-voltage NMOS tube M N1 The gate-drain terminal and the low-voltage NMOS tube M N2 Gate of N-LDMOS tube DM N3 The source connection M N2 The drain, DM N3 The drain of the P-LDMOS tube DM is connected P1 The gate-drain and P-LDMOS tube DM P2 The gate, DM P1 The source of the low voltage PMOS tube M P1 The gate and drain of the PMOS tube M P2 The gate, M P2 The drain connection DM P2 The source, DM P2 The drain of the resistor R2 is connected, and the other end of R2 is connected to the DM N1 and DM N2 The source of the high voltage switch forms a bias circuit.

7. The low leakage current high voltage selection circuit for voltage sampling of multiple series-connected batteries according to claim 6, characterized in that: The N-LDMOS tube DM N4 The drain connection DM N1 and DM N2 The source, DM N4 The source of the low voltage NMOS tube M N3 The drain of the circuit forms a current compensation circuit.

8. The low leakage current high voltage selection circuit for voltage sampling of multiple series-connected batteries according to claim 7, characterized in that: In the HSWITCH2, let I BACK2 =I2, so that the pull-down current provided by VCC flows into the ground instead of the input terminal.

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