Charge pump voltage detection circuit

Abstract

The invention relates to a charge pump voltage detection circuit, which comprises a first PMOS tube, a second PMOS tube, a third PMOS tube, a fourth PMOS tube, a first resistor and a second resistor, the source electrode of the first PMOS tube and the source electrode of the second PMOS tube are connected with the output voltage of a charge pump, the grid electrode and the drain electrode of the first PMOS tube, the grid electrode of the second PMOS tube and the first end of the first resistor are mutually connected, and the drain electrode of the third PMOS tube and the second end of the second resistor are mutually connected. The second end of the first resistor and the grid electrode of the third PMOS tube are connected with the power supply voltage of the motor driving chip, the drain electrode of the second PMOS tube is connected with the source electrode of the third PMOS tube, and the drain electrode of the third PMOS tube is connected with the source electrode of the fourth PMOS tube to form the output end of the charge pump voltage detection circuit; the grid electrode and the drain electrode of the fourth PMOS tube are connected with the first end of the second resistor, and the second end of the second resistor is grounded.

Description

Technical Field

[0001] The present invention relates to the technical field of motor driving, and more particularly to a charge pump voltage detection circuit. Background Art

[0002] The motor driver chip is the core component for controlling the operation of the motor. The design of its drive solution directly affects the performance, efficiency and reliability of the motor. Common motor drive solutions include high-side and low-side drive. In the high-side drive solution, NMOS tubes are the mainstream choice due to their low on-resistance and high switching speed.

[0003] However, when the NMOS tube is used on the high side, its gate voltage needs to be higher than the source voltage, and the difference between the two needs to be greater than a threshold voltage, which increases the complexity of the drive circuit. To solve this problem, a charge pump is widely used in motor driver chips. It is connected to the gate of the high-side NMOS tube and is used to output a voltage higher than the source voltage to the gate of the high-side NMOS tube, thereby ensuring the reliable conduction of the high-side NMOS tube.

[0004] However, in actual applications, the output voltage of the charge pump may be affected by various factors (such as capacitor aging, load changes, power supply fluctuations, etc.) and become unstable. This instability may cause incomplete conduction of the high-side NMOS tube and generate additional power loss, or even cause the motor drive to fail.

[0005] Therefore, there is an urgent need in the art for a charge pump voltage detection circuit to detect whether the output voltage of the charge pump can turn on the high-side NMOS transistor. Summary of the invention

[0006] The object of the present invention is to provide a charge pump voltage detection circuit to ensure that the output voltage of the charge pump can make the high-side NMOS tube fully turned on, so that the motor drive chip can operate stably.

[0007] Based on the above purpose, the present invention provides a charge pump voltage detection circuit, including a first PMOS tube, a second PMOS tube, a third PMOS tube, a fourth PMOS tube, a first resistor and a second resistor, the source of the first PMOS tube and the source of the second PMOS tube are both connected to the output voltage of the charge pump, the gate and drain of the first PMOS tube, the gate of the second PMOS tube and the first end of the first resistor are connected to each other, the second end of the first resistor and the gate of the third PMOS tube are both connected to the power supply voltage of the motor drive chip, the drain of the second PMOS tube is connected to the source of the third PMOS tube, the drain of the third PMOS tube is connected to the source of the fourth PMOS tube and forms the output end of the charge pump voltage detection circuit; the gate and drain of the fourth PMOS tube and the first end of the second resistor are connected to each other, and the second end of the second resistor is grounded.

[0008] Further, the first PMOS tube, the second PMOS tube and the fourth PMOS tube are the same low-voltage PMOS tubes, and the third PMOS tube is a high-voltage PMOS tube.

[0009] Furthermore, the first resistor and the second resistor have the same resistance value.

[0010] Furthermore, the output end of the charge pump voltage detection circuit is used to output the difference between the output voltage of the charge pump and the power supply voltage of the motor driving chip.

[0011] Furthermore, the first PMOS tube is replaced by a first PNP tube, the second PMOS tube is replaced by a second PNP tube, and the fourth PMOS tube is replaced by a third PNP tube; the emitter of the first PNP tube and the emitter of the second PNP tube are both connected to the output voltage of the charge pump, the base and collector of the first PNP tube, the base of the second PNP tube and the first end of the first resistor are connected to each other, the second end of the first resistor and the gate of the third PMOS tube are both connected to the power supply voltage of the motor drive chip, the collector of the second PNP tube is connected to the source of the third PMOS tube, the drain of the third PMOS tube is connected to the emitter of the third PNP tube and forms the output end of the charge pump voltage detection circuit, the base and collector of the third PNP tube and the first end of the second resistor are connected to each other, and the second end of the second resistor is grounded.

[0012] Further, the first PNP transistor, the second PNP transistor and the third PNP transistor are the same PNP transistor.

[0013] Furthermore, the amplification factors of the first PNP tube, the second PNP tube and the third PNP tube are all greater than 50.

[0014] The charge pump voltage detection circuit of the present invention can accurately detect the difference between the output voltage of the charge pump and the power supply voltage of the motor driver chip using a relatively simple circuit, thereby ensuring that the output voltage of the charge pump can make the NMOS tube fully conductive and enable the motor driver chip to operate stably. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural schematic diagram of the first existing charge pump voltage detection circuit; Figure 2 is a structural schematic diagram of a second existing charge pump voltage detection circuit; Figure 3 is a structural schematic diagram of a charge pump voltage detection circuit according to an embodiment of the present invention; Figure 4 FIG. 4 is a schematic diagram of a charge pump voltage detection circuit according to another embodiment of the present invention. DETAILED DESCRIPTION

[0016] The preferred embodiments of the present invention are given below in conjunction with the accompanying drawings and described in detail.

[0017] like Figure 1 As shown, the first existing charge pump voltage detection circuit includes two identical low-voltage PMOS tubes 101 and 102, two identical resistors 103 and 104, and a high-voltage PMOS tube 105. The source of the PMOS tube 101 is connected to the output voltage VCP of the charge pump, the gate of the PMOS tube 101, the drain of the PMOS tube 101, the first end of the resistor 103, and the gate of the PMOS tube 102 are connected to each other, the source of the PMOS tube 102 is connected to the output voltage VCP of the charge pump, the drain of the PMOS tube 102 is connected to the source of the PMOS tube 105, the gate of the PMOS tube 105 and the second end of the resistor 103 are both connected to the power supply voltage VM of the motor driving chip, the drain of the PMOS tube 105 is connected to the first end of the resistor 104 and forms the output end of the charge voltage detection circuit for outputting the voltage Vx, and the second end of the resistor 104 is grounded.

[0018] According to the circuit deduction, the current I1 flowing through the PMOS tube 101 = (VCP-VM-Vgs1) / R1, Vgs1 is the gate-source voltage of the PMOS tube 101 (i.e., the difference between the gate voltage and the source voltage), so the current I2 flowing through the resistor 104 = (VCP-VM-Vgs1) / R1, Vx = (VCP-VM-Vgs1) / R1×R2, where R1 is the resistance value of the resistor 103, and R2 is the resistance value of the resistor 104. After simplification, Vx = VCP-VM-Vgs1.

[0019] In actual use, the gate of the high-side NMOS tube of the motor driver chip is connected to VCP, and the source is connected to VM. Therefore, VCP-VM is the gate-source voltage of the high-side NMOS tube, which needs to be greater than the threshold voltage Vth. There is a difference of Vgs1 between the voltage detected here and VCP-VM, so it is impossible to directly judge whether the high-side NMOS tube meets the conduction condition through Vx, and the value of Vgs1 will change under the influence of different temperatures and processes. If Vx+Vgs1 is used to judge whether the high-side NMOS tube meets the conduction condition, the judgment result will also be biased.

[0020] In order to solve the above problems existing in the first charge pump voltage detection circuit, the prior art provides the following Figure 2 The second charge pump voltage detection circuit shown in the figure includes resistors 201 and 202, PMOS tubes 203-207, NMOS tubes 208 and 209, current sources 210 and 211, and resistor 212. The first end of the resistor 201 is connected to the output voltage VCP of the charge pump, the first end of the resistor 202 is connected to the power supply voltage VM of the motor drive chip, the second end of the resistor 201 is respectively connected to the source of the PMOS tube 203 and the source of the PMOS tube 205, the second end of the resistor 202 is connected to the source of the PMOS tube 202, the drain of the PMOS tube 203, the gate of the PMOS tube 203, the gate of the PMOS tube 204, and the source of the PMOS tube 206 are connected to each other, and the drain of the PMOS tube 204, the gate of the PMOS tube 205, and the gate of the PMOS tube 206 are connected to each other. The gate and the source of the PMOS tube 207 are connected to each other, the drain of the PMOS tube 206, the gate of the PMOS tube 206, the gate of the PMOS tube 207 and the drain of the NMOS tube 208 are connected to each other, the drain of the PMOS tube 207 is connected to the drain of the NMOS tube 209, the gate of the NMOS tube 208 is connected to the gate of the NMOS tube 209, the source of the NMOS tube 208 is connected to one end of the current source 210, and the other end of the current source 210 is grounded, the source of the NMOS tube 209 is connected to one end of the current source 211, and the other end of the current source 211 is grounded, the drain of the PMOS tube 205 is connected to the first end of the resistor 212 and forms the output end of the charge pump detection circuit for outputting the voltage Vx, and the second end of the resistor 212 is grounded. The PMOS tubes 203 and 204 have the same size, the PMOS tubes 205, 206 and 207 are all high-voltage PMOS tubes, the NMOS tubes 208 and 209 are high-voltage NMOS tubes, the currents of the current sources 210 and 211 are the same, and the resistances of the resistors 201, 202 and 212 are the same. The negative feedback circuit regulation ensures that the source voltages of the PMOS tubes 203 and 204 are equal.

[0021] According to the circuit deduction, the current flowing through the resistor 212 is [VCP-VM+I1×R1-I2×R2) / R1=(VCP-VM) / R1, so Vx=(VCP-VM) / R1×R3=VCP-VM. In other words, the output Vx of the second circuit pump voltage detection circuit is the difference between the gate voltage and the source voltage of the high-side NMOS tube of the motor driver chip. Through Vx, it can be accurately determined whether the output voltage VCP of the charge pump can turn on the high-side NMOS tube.

[0022] Although the detection result of the second charge pump voltage detection circuit is more accurate than that of the first one, its circuit structure is more complicated.

[0023] Based on this, an embodiment of the present invention provides a charge pump voltage detection circuit to accurately detect the difference between VCP and VM through a simple circuit structure.

[0024] like Figure 3 As shown, the charge pump voltage detection circuit of the embodiment of the present invention includes a first PMOS tube PM1, a second PMOS tube PM2, a third PMOS tube PM3, a fourth PMOS tube PM4, a first resistor R1 and a second resistor R2. The source of the first PMOS tube PM1 and the source of the second PMOS tube PM2 are both connected to the output voltage VCP of the charge pump, the gate of the first PMOS tube PM1, the drain of the first PMOS tube PM1, the gate of the second PMOS tube PM2 and the first end of the first resistor R1 are connected to each other, the second end of the first resistor R2 and the gate of the third PMOS tube PM3 are both connected to the power supply voltage VM of the motor driving chip, the drain of the second PMOS tube PM2 is connected to the source of the third PMOS tube PM3, the drain of the third PMOS tube PM3 is connected to the source of the fourth PMOS tube PM4 and forms the output end of the charge pump voltage detection circuit for outputting the voltage Vx, the gate and drain of the fourth PMOS tube PM4 and the first end of the second resistor R2 are connected to each other, and the second end of the second resistor R2 is grounded.

[0025] The first PMOS transistor PM1 , the second PMOS transistor PM2 and the fourth PMOS transistor PM4 are all low-voltage PMOS transistors with the same size. The third PMOS transistor PM3 is a high-voltage PMOS transistor. The first resistor R1 and the second resistor R2 have the same resistance value.

[0026] Through circuit deduction, it can be known that the current flowing through the first PMOS tube PM1 and the second PMOS tube PM2 is the same and is (VCP-VM-Vgs1) / R1, Vx=(VCP-VM-Vgs1) / R1×R2+Vgs4, wherein Vgs1 is the difference between the gate voltage and the source voltage of the first PMOS tube PM1, and Vgs4 is the difference between the gate voltage and the source voltage of the fourth PMOS tube PM4. Since the first PMOS tube PM1 and the fourth PMOS tube PM4 are the same PMOS tubes, Vgs1=Vgs4, and combined with R1=R2, Vx=VCP-VM can be obtained. Therefore, the output of the charge pump voltage detection circuit is the accurate voltage difference between the output voltage of the charge pump and the power supply voltage of the motor driver chip. Vx can be used to determine whether the output voltage VCP of the charge pump can turn on the high-side NMOS tube.

[0027] The charge pump voltage detection circuit of the embodiment of the present invention can detect the difference between the charge pump voltage and the power supply voltage of the motor driver chip using only three low-voltage PMOS tubes, two resistors and one high-voltage PMOS tube. Compared with the prior art, the structure is simpler and the circuit area is smaller.

[0028] like Figure 4 As shown, another embodiment of the present invention provides a charge pump voltage detection circuit, which is Figure 3 The difference between the charge pump voltage detection circuit and the charge pump voltage detection circuit is that the first PMOS tube PM1, the second PMOS tube PM2 and the fourth PMOS tube PM4 are replaced by three identical high β (i.e., amplification factor) PNP tubes, that is, the first PMOS tube PM1 is replaced by the first PNP tube Q1, the second PMOS tube PM2 is replaced by the second PNP tube Q2, and the fourth PMOS tube PM4 is replaced by the third PNP tube Q3. The first PNP tube Q1, the second PNP tube Q2 and the third PNP tube Q3 are three identical PNP tubes; the emitter of the first PNP tube Q1 and the emitter of the second PNP tube Q2 are both connected to the output voltage VCP of the charge pump. The base and collector of the first PNP tube Q1, the base of the second PNP tube Q2 and the first end of the first resistor R1 are connected to each other, the second end of the first resistor R1 and the gate of the third PMOS tube PM3 are both connected to the motor drive chip power supply voltage VM, the collector of the second PNP tube Q2 is connected to the source of the third PMOS tube PM3, the drain of the third PMOS tube PM3 is connected to the emitter of the third PNP tube Q3 and forms an output end of the charge pump voltage detection circuit, which is used to output the voltage Vx, the base and collector of the third PNP tube Q3, and the first end of the second resistor R2 are connected to each other, and the second end of the second resistor R2 is grounded.

[0029] Through circuit derivation, it can be obtained that the current flowing through Q1 and Q2 is the same and is (VCP-VM-Veb1) / R1, where Veb1 is the voltage difference between the emitter and base of Q1. Since the β of Q1 and Q2 is high enough (for example, greater than 50, when β=50, the voltage detected by Vx will have an error of 3.85%), the influence of the base current can be ignored, and finally Vx=(VCP-VM-Veb1) / R1×R2+Veb3=VCP-VM is obtained, where Veb3 is the voltage difference between the emitter and base of Q3, and Veb3=Veb1. Therefore, its output voltage Vx is also the voltage difference between the accurate output voltage of the charge pump and the power supply voltage of the motor driver chip. Vx can be used to determine whether the output voltage VCP of the charge pump can turn on the high-side NMOS tube.

[0030] The charge pump voltage detection circuit of the embodiment of the present invention can accurately detect the difference between the output voltage of the charge pump and the power supply voltage of the motor driver chip using a relatively simple circuit, thereby ensuring that the output voltage of the charge pump can make the NMOS tube fully turned on and enable the motor driver chip to operate stably.

[0031] The above is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. The above embodiment of the present invention can also be modified in various ways. That is, all simple, equivalent changes and modifications made according to the claims and the description of the present invention fall within the scope of protection of the claims of the present invention. The contents not described in detail in the present invention are all conventional technical contents.

Claims

1. A charge pump voltage detection circuit, characterized in that: It includes a first PMOS tube, a second PMOS tube, a third PMOS tube, a fourth PMOS tube, a first resistor and a second resistor, the source of the first PMOS tube and the source of the second PMOS tube are both connected to the output voltage of the charge pump, the gate and drain of the first PMOS tube, the gate of the second PMOS tube and the first end of the first resistor are connected to each other, the second end of the first resistor and the gate of the third PMOS tube are both connected to the power supply voltage of the motor drive chip, the drain of the second PMOS tube is connected to the source of the third PMOS tube, the drain of the third PMOS tube is connected to the source of the fourth PMOS tube and forms the output end of the charge pump voltage detection circuit; the gate and drain of the fourth PMOS tube and the first end of the second resistor are connected to each other, and the second end of the second resistor is grounded.

2. The charge pump voltage detection circuit according to claim 1, characterized in that: The first PMOS tube, the second PMOS tube and the fourth PMOS tube are the same low-voltage PMOS tubes, and the third PMOS tube is a high-voltage PMOS tube.

3. The charge pump voltage detection circuit according to claim 1, characterized in that: The first resistor and the second resistor have the same resistance value.

4. The charge pump voltage detection circuit according to claim 1, characterized in that: The output end of the charge pump voltage detection circuit is used to output the difference between the output voltage of the charge pump and the power supply voltage of the motor driving chip.

5. The charge pump voltage detection circuit according to claim 1, characterized in that: The first PMOS tube is replaced by a first PNP tube, the second PMOS tube is replaced by a second PNP tube, and the fourth PMOS tube is replaced by a third PNP tube; the emitter of the first PNP tube and the emitter of the second PNP tube are both connected to the output voltage of the charge pump, the base and collector of the first PNP tube, the base of the second PNP tube and the first end of the first resistor are connected to each other, the second end of the first resistor and the gate of the third PMOS tube are both connected to the power supply voltage of the motor drive chip, the collector of the second PNP tube is connected to the source of the third PMOS tube, the drain of the third PMOS tube is connected to the emitter of the third PNP tube and forms the output end of the charge pump voltage detection circuit, the base and collector of the third PNP tube and the first end of the second resistor are connected to each other, and the second end of the second resistor is grounded.

6. The charge pump voltage detection circuit according to claim 5, characterized in that: The first PNP transistor, the second PNP transistor and the third PNP transistor are the same PNP transistors.

7. The charge pump voltage detection circuit according to claim 5, characterized in that: The amplification factors of the first PNP tube, the second PNP tube and the third PNP tube are all greater than 50.

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