A conduction time control circuit, a circuit board, and an electronic device

Abstract

The application discloses a conduction time control circuit, a circuit board and electronic equipment, and belongs to the field of electronic circuits. The conduction time control circuit comprises a conversion module, a current mirror module, a generation module and a control module. The conversion module outputs a related first current according to an external load input voltage. The current mirror module mirrors the first current to generate a second current. The generation module comprises a charging unit and a charging control unit. The charging unit receives the second current for charging. The charging control unit controls the charging process and ensures that the charging voltage is not zero according to the voltage across the charging unit and the external load output voltage. The control module adjusts the charging time of the charging unit by the external output reference voltage and the output voltage, thereby controlling the conduction time of the current mirror module. The application can reduce the undershoot voltage of the output voltage during load transients and improve the stability of the power supply under high load conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electronic circuits, and in particular to a turn-on time control circuit, a circuit board and an electronic device. BACKGROUND

[0002] With the rapid development of the field of artificial intelligence, CPUs (Central Processing Units) and GPUs (Graphics Processing Units) often work under high load conditions, and multiphase control power management chips must quickly handle transient changes in the load. TON (Turn-On Time) refers to the time required for a switching element (such as a transistor, MOSFET, etc.) in an electronic circuit to switch from an off state to an on state. Due to the slow feedback loop rate and the instability of the TON control algorithm of existing multiphase control power management chips, the output voltage exhibits large fluctuations, and in severe cases, there is a risk of damaging the CPU and GPU. TON is directly calculated and determined through the proportional relationship between the load output voltage and the output voltage, but when the load is transient, the adjustment speed of TON is slower than the transient change speed, resulting in a large undershoot and rebound of the output voltage. Therefore, how to reduce the undershoot voltage of the output voltage when the load is transient to improve the stability of the power supply under high load conditions is a technical problem that needs to be solved. SUMMARY

[0003] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application provides a turn-on time control circuit, a circuit board and an electronic device, which can reduce the undershoot voltage of the output voltage when the load is transient, and improve the stability of the power supply under high load conditions.

[0004] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0005] In a first aspect, the present application provides a turn-on time control circuit, comprising:

[0006] a conversion module, configured to output a first current related to an external load input voltage according to the external load input voltage;

[0007] a current mirror module, an input end of the current mirror module being connected to an output end of the conversion module, the current mirror module being configured to mirror the first current to generate a second current related to the first current;

[0008] The generating module comprises a charging unit and a charging control unit, an input end of the charging unit is connected to an output end of the current mirror module, a first input end of the charging control unit is connected to the input end of the charging unit, a second input end of the charging control unit is connected to an external load output voltage, a third input end of the charging control unit is connected to an external enable signal, an output end of the charging unit and an output end of the charging control unit are both connected to a ground end, and the charging control unit is used to control the charging unit to charge and control the voltage across the charging unit not to drop to zero according to the voltage across the charging unit, the external load output voltage and the external enable signal.

[0009] The control module comprises a first input end connected to an external output reference voltage, a second input end connected to an external load output voltage, and an output end connected to an input end of the charging unit, and the control module is used to control the charging time of the charging unit according to the external output reference voltage and the external load output voltage, so as to control the on time of the current mirror module.

[0010] The on time control circuit according to the first aspect of the present application has at least the following beneficial effects: the external load input voltage is converted into a first current by the conversion module, wherein the first current is related to the external load input voltage; the first current is mirrored by the current mirror module, and a second current related to the first current is output for charging the charging unit; when the voltage across the charging unit is lower than the external load output voltage, the charging unit is controlled to charge according to the external enable signal by the charging control unit; when the voltage across the charging unit is higher than the external load output voltage, the charging unit is controlled to make the voltage across the charging unit not drop to zero according to the voltage across the charging unit and the external load output voltage by the charging control unit; when the load is output, when the external output reference voltage is greater than the external output voltage, the control module does not work; when the external output reference voltage is less than the external output voltage, the charging time of the charging unit is controlled according to the external output reference voltage and the external load output voltage by the control module, and when the external load output voltage continuously decreases, the charging time of the charging unit is shortened, so that the on time of the current mirror module is prolonged. The on time of the current mirror module is TON. Compared with the prior art, when the load is transient, the present application prolongs TON to reduce the undershoot voltage of the output voltage, thereby improving the stability of the power supply in the high load state. Therefore, the present application solves the technical problem of how to reduce the undershoot voltage of the output voltage when the load is transient to improve the stability of the power supply in the high load state.

[0011] According to some embodiments of the first aspect of the present application, the control module comprises a trans-impedance amplifier and a diode, a positive input terminal of the trans-impedance amplifier is the first input terminal of the control module, a negative output terminal of the trans-impedance amplifier is the second input terminal of the control module; a positive input terminal of the trans-impedance amplifier is connected to an external reference voltage, a negative input terminal of the trans-impedance amplifier is connected to an external load output voltage, an output terminal of the diode is connected to an output terminal of the trans-impedance amplifier, an input terminal of the diode is connected to an input terminal of the charging unit, the trans-impedance amplifier is configured to control a charging time of the charging unit according to the external load output voltage and the external output reference voltage, thereby controlling a turn-on time of the current mirror module.

[0012] According to some embodiments of the first aspect of the present application, the charging control unit comprises a comparator, a flip-flop, a first resistor and a first switch tube, a positive input terminal of the comparator is the first input terminal of the charging control unit, a negative input terminal of the comparator is the second input terminal of the charging control unit; the negative input terminal of the comparator is connected to an external load output voltage, the positive input terminal of the comparator is connected to an input terminal of the charging unit, a reset terminal of the flip-flop is connected to an output terminal of the comparator, a set terminal of the flip-flop is connected to an external enable signal, a control terminal of the first switch tube is connected to an inverted output terminal of the flip-flop, a first terminal of the first resistor is connected to the positive input terminal of the comparator, a second terminal of the first resistor is connected to an input terminal of the first switch tube, output terminals of the first switch tube are both connected to a ground terminal, the control terminal of the first switch tube is configured to control a turn-on state of the input terminal and the output terminal of the first switch tube according to a signal output by the inverted output terminal, the flip-flop is configured to control the charging unit to charge or the turn-on state of the input terminal and the output terminal of the first switch tube according to the external enable signal or a signal output by the comparator, the comparator is configured to control an output signal of the inverted output terminal of the flip-flop according to a voltage across the charging unit and the external load output voltage, thereby controlling the turn-on state of the input terminal and the output terminal of the first switch tube, and the first resistor is configured to prevent the voltage across the charging unit from dropping to zero to compensate for a transmission delay of the comparator.

[0013] According to some embodiments of the first aspect of the present application, the charging unit comprises a capacitor, a first terminal of the capacitor is connected to an output terminal of the current mirror module, and a second terminal of the capacitor is connected to a ground terminal.

[0014] According to some embodiments of the first aspect of the present application, the conversion module comprises an operational amplifier, a second resistor, a third resistor, a fourth resistor and a second switch tube, the first end of the second resistor is connected with the input end of the current mirror module and is used to access an external load input voltage, the first end of the third resistor is connected with the second end of the second resistor, the second end of the third resistor is connected with a ground terminal, the positive input end of the operational amplifier is connected with the first end of the third resistor, the negative input end of the operational amplifier is connected with the output end of the second switch tube, the output end of the operational amplifier is connected with the control end of the second switch tube, the input end of the second switch tube is connected with the input end of the current mirror module, the first end of the third resistor is connected with the output end of the operational amplifier, and the second end of the third resistor is connected with the ground terminal.

[0015] According to some embodiments of the first aspect of the present application, the current mirror module comprises a third switch tube and a fourth switch tube, the input end of the third switch tube and the input end of the fourth switch tube are both connected with the first end of the second resistor, the control end of the third switch tube and the control end of the fourth switch tube are both connected with the input end of the second switch tube, the output end of the third switch tube is connected with the input end of the second switch tube, and the output end of the fourth switch tube is connected with the input end of the charging unit.

[0016] According to some embodiments of the first aspect of the present application, the first switch tube is an NMOS tube.

[0017] According to some embodiments of the first aspect of the present application, the second switch tube is an NMOS tube, and the third switch tube and the fourth switch tube are both PMOS tubes.

[0018] In a second aspect, the present application provides a circuit board comprising the turn-on time control circuit according to the first aspect of the present application.

[0019] In a third aspect, the present application provides an electronic device comprising the turn-on time control circuit according to the first aspect of the present application.

[0020] The present application will be further described below in conjunction with the accompanying drawings and embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 FIG. 1 is a schematic diagram of an embodiment of the turn-on time control circuit according to the first aspect of the present application;

[0022] Figure 2 FIG. 2 is a diagram of the corresponding relationship between the upper tube turn-on time and the error voltage of an embodiment of the turn-on time control circuit according to the first aspect of the present application;

[0023] Figure 3Fig. 1 is a diagram showing the effect comparison before and after processing for one embodiment of the on-time control circuit of the present application.

[0024] Reference numerals:

[0025] The conversion module 100, the current mirror module 200, the generation module 300, the charging unit 310, the charging control unit 320, the control module 400. DETAILED DESCRIPTION

[0026] Embodiments of the present application are described in detail below with reference to examples illustrated in the accompanying drawings, in which the same or similar components are denoted by the same or similar reference numerals throughout. The embodiments described below by reference to the drawings are exemplary and are for the purpose of explanation only, and are not to be understood as limiting the present application.

[0027] In the description of the present application, the meaning of several is one or more, the meaning of multiple is two or more, greater than, less than, more than, etc. are understood as not including the number, above, below, etc. are understood as including the number. If it is described as first, second, it is only for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features or the order of indicated technical features.

[0028] The embodiments of the present application are further described below with reference to the accompanying drawings.

[0029] Reference Figure 1As shown in the figure, VIN is the external load input voltage, EN is the external enable signal, VOUT is the external load output voltage, I2 is the first current, Ion is the second current. The on-time control circuit includes a conversion module 100, a current mirror module 200, a generation module 300 and a control module 400. The conversion module 100 is used to output the first current related to the external load input voltage according to the external load input voltage; the input end of the current mirror module 200 is connected to the output end of the conversion module 100, and the current mirror module 200 is used to mirror the first current to generate the second current related to the first current; the generation module 300 includes a charging unit 310 and a charging control unit 320, the input end of the charging unit 310 is connected to the output end of the current mirror module 200, the first input end of the charging control unit 320 is connected to the input end of the charging unit 310, the second input end of the charging control unit 320 is connected to the external load output voltage, the third input end of the charging control unit 320 is connected to the external enable signal, and the output end of the charging unit 310 and the output end of the charging control unit 320 are both connected to the ground. The charging control unit 320 is used to control the charging of the charging unit 310 and the voltage across the charging unit 310 not to drop to zero according to the voltage across the charging unit 310, the external load output voltage and the external enable signal; the first input end of the control module 400 is connected to the external output reference voltage, the second input end of the control module 400 is connected to the external load output voltage, and the output end of the control module 400 is connected to the input end of the charging unit 310. The control module 400 is used to control the charging time of the charging unit 310 according to the external output reference voltage and the external load output voltage, so as to control the on-time of the current mirror module 200.

[0030] In the above embodiment, the load input voltage from outside is converted into a first current by the conversion module 100, wherein the first current is related to the load input voltage from outside. The first current is mirrored by the current mirror module 200, and a second current related to the first current is outputted for charging the charging unit 310. When the voltage across the charging unit 310 is lower than the load output voltage from outside, the charging unit 310 is controlled to charge by the charging control unit 320 according to the enable signal from outside; when the voltage across the charging unit 310 is higher than the load output voltage from outside, the charging unit 310 is controlled by the charging control unit 320 according to the voltage across the charging unit 310 and the load output voltage from outside so that the voltage across the charging unit 310 will not drop to zero. When the output reference voltage from outside is greater than the load output voltage from outside during the output loading, the control module 400 does not work; when the output reference voltage from outside is less than the load output voltage from outside, the charging time of the charging unit 310 is controlled by the control module 400 according to the output reference voltage from outside and the load output voltage from outside, and when the load output voltage from outside continuously decreases, the charging time of the charging unit 310 is shortened, so that the on time of the current mirror module 200 is prolonged. The on time of the current mirror module 200 is the on time of the upper transistor. Compared with the prior art, the on time of the upper transistor is prolonged to reduce the undershoot voltage of the output voltage during the load transient, so that the stability of the power supply under high load state is improved.

[0031] It can be understood that, as shown in Figure 1 The control module 400 includes a transconductance amplifier and a diode, the positive input terminal of the transconductance amplifier is the first input terminal of the control module 400, and the negative output terminal of the transconductance amplifier is the second input terminal of the control module 400; the positive input terminal of the transconductance amplifier is connected to the reference voltage from outside, the negative input terminal of the transconductance amplifier is connected to the load output voltage from outside, the output terminal of the diode is connected to the output terminal of the transconductance amplifier, and the input terminal of the diode is connected to the input terminal of the charging unit 310. The transconductance amplifier is used to control the charging time of the charging unit 310 according to the load output voltage from outside and the output reference voltage from outside, so as to control the on time of the current mirror module 200.

[0032] The nonlinear on time control of the upper transistor is realized by the cooperation of the transconductance amplifier and the diode.

[0033] For example, as shown in Figure 1As shown in the diagram, VREF is the external output reference voltage, VOUT is the external load output voltage, GM is the transconductance amplifier, D1 is the diode, Ion is the first current, and I1 is the output current. When VOUT is higher than VREF-20mV, the path containing D1 is cut off due to the presence of D1, and I1 = 0; when VOUT is lower than VREF-20mV, the transconductance is gm, and I1 is (VREF-20mV-VOUT)*gm. When the load changes transiently, VOUT fluctuates. As VOUT decreases, I1 increases, reducing the charging current of the charging unit 310 and thus extending the conduction time of the upper transistor. The maximum output current of I1 is limited to Ion / 2, so the maximum conduction time of the upper transistor is twice the conduction time during normal operation. This ensures that even with an infinitely extended conduction time in the event of an output short circuit, an excessive second current will not be generated, thus preventing the current mirror module 200 from burning out. This improves the stability and safety of the circuit and extends its service life.

[0034] For example, such as Figure 1 and 2 As shown, VREF represents the external output reference voltage, VOUT represents the external load output voltage, and Vus is the error voltage. Nonlinear on-time control of the upper transistor is achieved through the cooperation of a transconductance amplifier and a diode. It can be seen that the on-time of the upper transistor only begins to extend after the value of Vus exceeds 20mV. This ensures that under steady-state conditions, VOUT does not affect the on-time of the upper transistor, and therefore does not affect the stability of the system.

[0035] Understandably, referring to Figure 1As shown, the charging control unit 320 includes a comparator, a flip-flop, a first resistor and a first switch tube. The positive input terminal of the comparator is the first input terminal of the charging control unit 320, and the negative input terminal of the comparator is the second input terminal of the charging control unit 320. The negative input terminal of the comparator is connected to the external load output voltage, and the positive input terminal of the comparator is connected to the input terminal of the charging unit 310. The reset terminal of the flip-flop is connected to the output terminal of the comparator, and the set terminal of the flip-flop is connected to the external enable signal. The control terminal of the first switch tube is connected to the inverting output terminal of the flip-flop. The first terminal of the first resistor is connected to the positive input terminal of the comparator, and the second terminal of the first resistor is connected to the input terminal of the first switch tube. The output terminals of the first switch tube are connected to the ground terminal. The control terminal of the first switch tube is used to control the conduction state of the input terminal and the output terminal of the first switch tube according to the signal output by the inverting output terminal. The flip-flop is used to control the charging of the charging unit 310 or the conduction state of the input terminal and the output terminal of the first switch tube according to the external enable signal or the signal output by the comparator. The comparator is used to control the output signal of the inverting output terminal of the flip-flop according to the voltage across the charging unit 310 and the external load output voltage, so as to control the conduction state of the input terminal and the output terminal of the first switch tube. The first resistor is used to prevent the voltage across the charging unit 310 from being reduced to zero to compensate for the transmission delay of the comparator.

[0036] As shown in the example, Figure 1 As shown, CMP is a comparator, Q1 is a flip-flop, R4 is a first resistor, M4 is a first switch tube, VOUT is an external load output voltage, and EN is an external enable signal. Q1 is an RS flip-flop, and M4 is an NMOS tube. When the voltage across the charging unit 310 is lower than VOUT, EN will send an enable pulse, so that the non-inverting output terminal of Q1 outputs a high level and the inverting output terminal outputs a low level, and the charging unit 310 starts charging. When the voltage across the charging unit 310 is higher than VOUT, CMP outputs a high level, and M4 is in a conduction state. At this time, R4 reduces the voltage across the charging unit 310 to a lower value that is not zero, thereby effectively compensating for the influence of the transmission delay of CMP.

[0037] As shown in the example, Figure 1 As shown, C1 represents a capacitor. The charging unit 310 includes a capacitor, and the first terminal of the capacitor is connected to the output terminal of the current mirror module 200, and the second terminal of the capacitor is connected to the ground terminal. The charging time of the capacitor is used to control the conduction time of the upper tube, and the charging process of the capacitor is used to accurately control the conduction time of the upper tube. In some embodiments, the capacitor can be an electrolytic capacitor, a tantalum capacitor, a ceramic capacitor or a thin film capacitor.

[0038] As shown in the example, Figure 1As shown, the conversion module 100 includes an operational amplifier, a second resistor, a third resistor, a fourth resistor, and a second switch tube. The first end of the second resistor is connected to the input end of the current mirror module 200 and is used to access the external load input voltage. The first end of the third resistor is connected to the second end of the second resistor, and the second end of the third resistor is connected to the ground. The positive input end of the operational amplifier is connected to the first end of the third resistor. The negative input end of the operational amplifier is connected to the output end of the second switch tube. The output end of the operational amplifier is connected to the control end of the second switch tube. The input end of the second switch tube is connected to the input end of the current mirror module 200. The first end of the third resistor is connected to the output end of the operational amplifier, and the second end of the third resistor is connected to the ground. Precise conversion from the external input voltage to the first current is realized through the cooperation of the operational amplifier, the second resistor, the third resistor, the fourth resistor, and the second switch tube.

[0039] As shown in the example, Figure 1 As shown, OPA is an operational amplifier, R1 is a second resistor, R2 is a third resistor, R3 is a fourth resistor, M1 is a second switch tube, and VIN is an external load input voltage. M1 is an NMOS tube. R1, R2, OPA, and M1 constitute a buffer with a gain of 1, which can generate a voltage related to VIN at the source of M1. This voltage is converted into a first current related to VIN through R3.

[0040] As shown in the example, Figure 1 M2 is a third switch tube, and M3 is a fourth switch tube. The current mirror module 200 includes the third switch tube and the fourth switch tube. The input end of the third switch tube and the input end of the fourth switch tube are both connected to the first end of the second resistor. The control end of the third switch tube and the control end of the fourth switch tube are both connected to the input end of the second switch tube. The output end of the third switch tube is connected to the input end of the second switch tube, and the output end of the fourth switch tube is connected to the input end of the charging unit 310. A current mirror is formed by the third switch tube and the fourth switch tube, which can accurately copy the first current and output a second current, providing a stable mirror current for driving subsequent circuits, thereby realizing precise current control. In addition, the current mirror structure is simple, occupies a small chip area, has low power consumption, and has good linearity and temperature stability, which can effectively improve the stability and consistency of the system.

[0041] As shown in the example, Figure 1 M4 represents a first switch tube, CMP represents a comparator, and C1 represents a capacitor. The first switch tube is an NMOS tube. The NMOS tube has strong driving capability, high efficiency, and low power consumption. Using an NMOS tube for M4 can easily match the output logic of the comparator, thereby realizing fast and accurate capacitor discharge.

[0042] As shown in the example, Figure 1As shown, M1 represents the second switch tube, M2 represents the third switch tube, and M3 represents the fourth switch tube. The second switch tube is an NMOS tube, and the third and fourth switch tubes are PMOS tubes. The NMOS tube has the characteristics of low on-resistance, fast switching speed, strong current driving capability, and low voltage operation, so using an NMOS tube for M1 can work more efficiently, quickly, and stably during signal transmission and buffering. Using PMOS tubes for M2 and M3 can better adapt to high-voltage environments, provide more accurate current replication, and have lower leakage current, ensuring the performance and stability of the circuit.

[0043] The following refers to Figures 1 to 3 The on-time control circuit of one embodiment of the present application is described as follows:

[0044] As Figure 1As shown, R1 represents a second resistor, R2 represents a third resistor, R3 represents a fourth resistor, R4 represents a first resistor, M1 represents a second switch tube, M2 represents a third switch tube, M3 represents a fourth switch tube, M4 represents a first switch tube, OPA represents an operational amplifier, CMP represents a comparator, Gm represents a transconductance amplifier, Q1 represents an RS flip-flop, S represents a set terminal, R represents a reset terminal, Q represents a positive output terminal, Q represents a negative output terminal, C1 represents a capacitor, VIN represents an external load input voltage, VOUT represents an external load output voltage, VREF represents an external output reference voltage, EN represents an external enable signal, C1 represents a capacitor, I1 represents an output current, I2 represents a first current, Ion represents a second current. A buffer with a gain of 1 composed of R1 and R2, OPA and M1 can generate a voltage related to VIN at the source of M1. This voltage is converted to I2 related to VIN by R3. Then, I2 is mirrored to Ion by the current mirror composed of M2 and M3 for charging C1. When the voltage on C1 is lower than VOUT, the EN signal will send a start pulse, so that the Q output of the RS flip-flop is high and the Q output is low, so that the capacitor is charged. When the voltage on C1 is higher than VOUT, the comparator outputs a high level, triggering M4 to conduct. At this time, R4 reduces the voltage on C1 to a lower value, rather than directly to 0, effectively compensating for the effects of comparator transmission delay. When the output is loaded, D1 and Gm form a nonlinear TON control structure. When VOUT is higher than VREF-20mV, I1 is 0 due to the existence of D1, which cuts off the path where D1 is located; when VOUT is lower than VREF-20mV, I1 is (VREF-20mV-VOUT)*gm. As VOUT decreases, I1 increases, reducing the charging current of C1, thereby extending TON. The maximum output current capability of I1 is limited to Ion / 2, so the maximum value of TON is twice the TON under normal working conditions to avoid excessive current when the output is short-circuited, which may cause M3 to burn out.

[0045] As shown in Figure 2 Vus represents an error voltage, VREF represents an output reference voltage, VOUT represents a load output voltage, and TON represents a turn-on time of the upper tube. After adding the nonlinear TON control, it can be seen that TON will start to widen only when the value of Vus exceeds 20mV. Under steady-state conditions, VOUT voltage does not affect TON, so it does not affect the stability of the system.

[0046] As shown in Figure 3As shown, the black curve represents the changes of the output current and the load output voltage after the nonlinear TON control processing; the green curve represents the changes of the output current and the load output voltage before the nonlinear TON control processing; and the orange curve represents the changes of the load demand current. IL represents the output current, Iload represents the load demand current, and VOUT represents the load output voltage. The on-time control circuit of the embodiment of the present application enables the output current to reach the demand value of the load more quickly, the undershoot voltage of the load output voltage is smaller, and the stability of the power supply in the high load state is improved.

[0047] The circuit board of the second aspect embodiment of the present application comprises the on-time control circuit of the first aspect embodiment of the present application, which can reduce the undershoot voltage of the output voltage during load transients and improve the stability of the power supply in the high load state.

[0048] The electronic device of the third aspect embodiment of the present application comprises the on-time control circuit of the first aspect embodiment of the present application, which can reduce the undershoot voltage of the output voltage during load transients and improve the stability of the power supply in the high load state.

[0049] The embodiments of the present application are described in detail above in combination with the drawings, but the present application is not limited to the above embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the purpose of the present application.

Claims

1. A conduction time control circuit, characterized in that, include: A conversion module, the conversion module being used to output a first current related to the external load input voltage based on the external load input voltage; A current mirror module, wherein the input terminal of the current mirror module is connected to the output terminal of the conversion module, and the current mirror module is used to mirror the first current to generate a second current related to the first current; The generation module includes a charging unit and a charging control unit. The input terminal of the charging unit is connected to the output terminal of the current mirror module. The first input terminal of the charging control unit is connected to the input terminal of the charging unit. The second input terminal of the charging control unit is connected to the external load output voltage. The third input terminal of the charging control unit is connected to an external enable signal. The output terminals of the charging unit and the charging control unit are both connected to ground. The charging control unit is used to control the charging unit to charge and prevent the voltage across the charging unit from dropping to zero based on the voltage across the charging unit, the external load output voltage, and the external enable signal. The control module has a first input terminal connected to an external output reference voltage, a second input terminal connected to an external load output voltage, and an output terminal connected to the input terminal of the charging unit. The control module is used to control the charging time of the charging unit based on the external output reference voltage and the external load output voltage, thereby controlling the conduction time of the current mirror module.

2. The conduction time control circuit according to claim 1, characterized in that, The control module includes a transconductance amplifier and a diode. The positive input terminal of the transconductance amplifier is the first input terminal of the control module, and the negative output terminal of the transconductance amplifier is the second input terminal of the control module. The positive input terminal of the transconductance amplifier is connected to an external reference voltage, and the negative input terminal of the transconductance amplifier is connected to an external load output voltage. The output terminal of the diode is connected to the output terminal of the transconductance amplifier, and the input terminal of the diode is connected to the input terminal of the charging unit. The transconductance amplifier is used to control the charging time of the charging unit according to the external load output voltage and the external output reference voltage, thereby controlling the conduction time of the current mirror module.

3. The conduction time control circuit according to claim 1, characterized in that, The charging control unit includes a comparator, a trigger, a first resistor, and a first switching transistor. The positive input terminal of the comparator is the first input terminal of the charging control unit, and the negative input terminal of the comparator is the second input terminal of the charging control unit. The negative input terminal of the comparator is connected to the external load output voltage, and the positive input terminal of the comparator is connected to the input terminal of the charging unit. The reset terminal of the trigger is connected to the output terminal of the comparator, and the set terminal of the trigger is connected to an external enable signal. The control terminal of the first switching transistor is connected to the inverting output terminal of the trigger. The first terminal of the first resistor is connected to the positive input terminal of the comparator, and the second terminal of the first resistor is connected to the input terminal of the first switching transistor. The output terminals of the first switching transistor are all connected to ground. The control terminal of the first switching transistor is used to control the conduction state of the input and output terminals of the first switching transistor according to the signal output by the inverting output terminal. The trigger is used to control the charging unit to charge and the conduction state of the input and output terminals of the first switching transistor according to the external enable signal and the signal output by the comparator. The comparator is used to control the output signal of the inverting output terminal of the trigger according to the voltage across the charging unit and the external load output voltage, thereby controlling the conduction state of the input and output terminals of the first switching transistor. The first resistor is used to prevent the voltage across the charging unit from dropping to zero to compensate for the propagation delay of the comparator.

4. The conduction time control circuit according to claim 1, characterized in that, The charging unit includes a capacitor, with the first end of the capacitor connected to the output terminal of the current mirror module and the second end of the capacitor connected to ground.

5. The conduction time control circuit according to claim 1, characterized in that, The conversion module includes an operational amplifier, a second resistor, a third resistor, a fourth resistor, and a second switching transistor. The first end of the second resistor is connected to the input terminal of the current mirror module and is used to connect an external load input voltage. The first end of the third resistor is connected to the second end of the second resistor, and the second end of the third resistor is connected to ground. The positive input terminal of the operational amplifier is connected to the first end of the third resistor, the negative input terminal of the operational amplifier is connected to the output terminal of the second switching transistor, the output terminal of the operational amplifier is connected to the control terminal of the second switching transistor, the input terminal of the second switching transistor is connected to the input terminal of the current mirror module, the first end of the third resistor is connected to the output terminal of the operational amplifier, and the second end of the third resistor is connected to ground.

6. The conduction time control circuit according to claim 5, characterized in that, The current mirror module includes a third switch and a fourth switch. The input terminals of the third switch and the fourth switch are both connected to the first terminal of the second resistor. The control terminals of the third switch and the fourth switch are both connected to the input terminal of the second switch. The output terminal of the third switch is connected to the input terminal of the second switch, and the output terminal of the fourth switch is connected to the input terminal of the charging unit.

7. The conduction time control circuit according to claim 3, characterized in that, The first switching transistor is an NMOS transistor.

8. The conduction time control circuit according to claim 6, characterized in that, The second switch is an NMOS transistor, while the third and fourth switches are both PMOS transistors.

9. A circuit board, characterized in that, Includes the conduction time control circuit as described in any one of claims 1-8.

10. An electronic device, characterized in that, Includes the circuit board as described in claim 9.

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