TWI739258B - Pre-charge control circuit and method of controlling the same - Google Patents

Abstract

A pre-charge control circuit includes a control unit, a conversion unit, and a pre-charge switch. The control unit provides a control signal to the conversion unit according to a PWM signal, and the conversion unit provides a ramp voltage according to the control signal. The pre-charge switch gradually turns on an input path of an electronic circuit according to the ramp voltage.

Description

Precharge control circuit and control method thereof

The present invention relates to a precharge control circuit and a control method thereof, in particular to a precharge control circuit and a control method thereof that only use a transistor to couple the input path of an electronic circuit.

Nowadays, in the technical field of electronic circuits, more and more attention is paid to the power consumption and efficiency requirements of electronic circuits. Therefore, more and more circuit designs are aimed at reducing power consumption and improving efficiency of electronic circuits. Especially the suppression of inrush current is the focus of circuit design. The reason is that, in addition to causing extra power consumption of the electronic circuit, if the peak current is too high, the internal components of the electronic circuit will break down and be damaged, causing the electronic circuit to fail to operate normally. Especially in applications where the input is high voltage (for example, but not limited to, the input power is above 1000V), the surge current causes additional power consumption and breakdown of the components is even more significant.

The reason for the inrush current is that the input capacitor of the electronic circuit will be close to short circuit at the moment when the power is turned on. Therefore, when the input power source is just coupled to the electronic circuit, an instantaneously large current is poured into the input capacitor, and this current is the surge current. Therefore, a resistor is usually added to the input path of the electronic circuit to suppress the peak value of the inrush current caused by this situation. However, after the electronic circuit is operating normally (that is, when there is no inrush current), if this resistor is not bypassed, it will cause additional Problems such as power consumption and increased environmental temperature inside electronic circuits. Therefore, in the conventional electronic circuit, a switch is connected in parallel with the resistor, and after the electronic circuit operates normally, the switch is turned on to bypass the resistor, thereby saving power consumption.

However, when the electronic circuit is operating and the switch is damaged, the damage of the switch is usually difficult to detect and all current flows through the resistor. The reason is that simple detection can only know the increase in power consumed by the electronic circuit, but it is not easy to detect what causes the increase in power consumption. As a result, additional power consumption is generated and the overall efficiency of the circuit is low.

Therefore, how to design a pre-charge control circuit and its control method that only use the pre-charge switch coupled to the input path of the electronic circuit to control the pre-charge of the electronic circuit so as to achieve the effect of suppressing the peak surge current is An important subject that the inventor intends to study in this case.

In order to solve the above-mentioned problems, the present invention provides a pre-charge control circuit to overcome the problems of the prior art. Therefore, the pre-charge control circuit of the present invention includes a control unit that receives the pulse width modulation signal. The conversion unit is coupled to the control unit. And a pre-charge switch, coupled to the conversion unit and the input path of the electronic circuit. Wherein, the control unit provides a control signal to the conversion unit according to the pulse width modulation signal, and the conversion unit provides a ramp voltage according to the control signal; the precharge switch gradually turns on the input path according to the ramp voltage.

In order to solve the above-mentioned problems, the present invention provides a control method of a pre-charge control circuit to overcome the problems of the prior art. Therefore, the control method of the pre-charge control circuit of the present invention includes the following steps: providing a pre-charge switch coupled to the input path of the electronic circuit. Modulate the signal according to the pulse width Provide control signals to the conversion unit. The conversion unit provides a ramp voltage according to the control signal. And the pre-charge switch gradually turns on the input path according to the ramp voltage.

In order to have a better understanding of the technology, means and effects adopted by the present invention to achieve the intended purpose, please refer to the following detailed description and drawings of the present invention. I believe that the purpose, features and characteristics of the present invention can be obtained from this in depth and For specific understanding, however, the accompanying drawings are only provided for reference and illustration, and are not intended to limit the present invention.

100: electronic circuit

102: first end

104: second end

Cin: Input capacitance

Vin: input power

1. 1’: Pre-charge control circuit

12, 12’: Control unit

14, 14’: Conversion unit

142, 142’: Switching unit

Q1: Upper bridge switch

Q2: Lower bridge switch

144: filter unit

L: Inductance

C: Capacitance

Rg: current limiting resistor

Q: Pre-charge switch

D, C: Input terminal

S, E: output

G: Control terminal

Vgs, Vge: control terminal voltage

Vds, Vce: voltage difference

Vth: critical voltage

Ids, Ice: current

PWM: Pulse width modulation signal

Sc1, Sc2: control signal

Sc1: upper bridge control signal

Sc2: Lower bridge control signal

Vr: ramp voltage

Vcc: working voltage

I1: Inductor current

WA: work area

Fig. 1A is a circuit block diagram of the first embodiment of the electronic circuit of the present invention with a pre-charge control circuit; Fig. 1B is a circuit block diagram of the second embodiment of the electronic circuit of the present invention with a pre-charge control circuit; Fig. 2 is the pre-charge switch of the present invention Fig. 3A is a circuit block diagram of the first embodiment of the pre-charge control circuit of the present invention; Fig. 3B is a circuit block diagram of the second embodiment of the pre-charge control circuit of the present invention; and Fig. 4 is the pre-charge control circuit of the present invention Flow chart of the control method of the control circuit.

The technical content and detailed description of the present invention are described as follows in conjunction with the drawings:

Please refer to FIG. 1A for the circuit block diagram of the first embodiment of the electronic circuit combined with the precharge control circuit of the present invention, and FIG. 1B is the circuit block diagram of the second embodiment of the electronic circuit combined with the precharge control circuit of the present invention. The electronic circuit 100 receives the input power Vin, and precharges the input capacitor Cin, so that the input The capacitor Cin can provide the voltage required for the operation of the electronic circuit 100. Among them, the input power Vin is, for example, but not limited to, provided by devices such as solar panels, batteries, or the DC parallel side of a modular power converter. The precharge control circuit 1 is coupled to the input path of the electronic circuit 100 to control the precharge of the electronic circuit 100. Specifically, when the input power source Vin is not yet coupled to the electronic circuit 100, the input capacitor Cin has not yet stored energy and is close to a short circuit. Therefore, when the input power source Vin is just coupled to the electronic circuit 100, a large surge will be generated. The current may cause the internal components of the electronic circuit 100 to be broken down and damaged. Therefore, the pre-charge control circuit 1 must be used to control the pre-charge of the electronic circuit 100 at the moment when the input power source Vin is just coupled to the electronic circuit 100 to reduce the peak value of the inrush current and avoid the above-mentioned situation. Wherein, as shown in FIG. 1A, the precharge control circuit 1 can be coupled to the first terminal 102 of the input path of the electronic circuit 100 (that is, between the positive terminal of the input power Vin and the input capacitor Cin). Or, as shown in FIG. 1B, the precharge control circuit 1 may be coupled to the second terminal 104 of the input path of the electronic circuit 100 (that is, between the negative terminal of the input power source Vin and the input capacitor Cin). Both of the above two coupling positions can control the pre-charging of the input capacitor Cin when the input power source Vin starts to charge the input capacitor Cin to achieve the effect of reducing the peak value of the inrush current.

Furthermore, the main purpose of the present invention is that the precharge control circuit 1 only uses the precharge switch Q to be coupled to the input path of the electronic circuit 100 to control the precharge of the electronic circuit 100. It uses the working area of the pre-charge switch Q as the control of the conduction degree of the pre-charge switch Q, so that the pre-charge switch Q of the present invention does not need a parallel resistor as in the prior art. Therefore, the voltage at both ends of the precharge switch Q can be completely isolated, and it is easy to detect whether the precharge switch Q is damaged. Among them, the precharge switch Q can be a semiconductor-type switching element, such as but not limited to a semiconductor-type switching element such as a metal oxide half field effect transistor (MOSFET) or an insulated gate bipolar transistor (IGBT). For the convenience of description, FIG. 1A and Figure 1B takes the pre-charge switch Q as an example of a metal-oxygen half-field effect transistor (MOSFET). In addition, since the pre-charge control circuit 1 of the present invention does not include a parallel resistor, it will not be caused by the damage of the pre-charge switch Q. When power flows through the resistor, additional power consumption of the electronic circuit 100 occurs, or conditions such as an increase in the internal ambient temperature of the electronic circuit 100 occur.

Please refer to FIG. 2 for a schematic diagram of the waveform of the working area of the precharge switch Q of the present invention, and refer to FIGS. 1A and 1B for complex cooperation. Taking the pre-charge switch Q as a MOSFET as an example, the working area WA of the pre-charge switch Q is the saturation region (Saturation), and the horizontal axis is the voltage from the input terminal D to the output terminal S of the MOSFET Q差Vds. The vertical axis is the current Ids flowing from the input terminal D of the MOSFET to the output terminal S. Each curve represents the relationship curve between the voltage difference Vds between the input terminal D and the output terminal S and the current Ids when different voltages are applied to the control terminal G of the MOSFET. When the voltage of the control terminal G of the MOSFET is lower than the threshold value (meaning that the control terminal voltage Vgs is lower than the threshold voltage Vth), the precharge switch Q does not establish a channel so that the input terminal D and the output terminal of the precharge switch Q S is an open circuit, and no current can flow (Ids is equal to 0). When the voltage of the control terminal G of the precharge switch Q gradually rises (meaning that Vgs gradually rises above the threshold voltage Vth), a channel begins to be established between the input terminal D and the output terminal S of the precharge switch Q, and the channel gradually becomes larger ( This means that Vgs is gradually increased from 5V to 10V), so that the current Ids that can flow through the input terminal D and the output terminal S gradually increases.

Through the gradual conduction of the precharge switch Q, the current Ids that can flow through the input terminal D and the output terminal S of the precharge switch Q can be controlled to gradually increase, so that the precharge control circuit 1 is at the moment when the input power source Vin is just coupled to the electronic circuit 100 The current flowing through the input terminal D and the output terminal S of the precharge switch Q can be limited, thereby reducing the peak value of the inrush current. Moreover, after the input capacitor Cin is charged, the pre-charging switch Q is completely turned on so that the current Ids can all flow through the pre-charging switch Q, so as to save the power loss of the electronic circuit 100. And, when the pre-charge switch Q is damaged, the input path of the electronic circuit 100 is open, and it can be known that the pre-charge switch Q is damaged through simple detection. It is worth mentioning that if the pre-charging switch Q uses an insulated gate bipolar transistor (IGBT), the working area of the pre-charging switch Q is an active area (Active). The horizontal axis is the voltage difference Vce from the input terminal C to the output terminal E of the insulated gate bipolar transistor. The vertical axis is the current Ice flowing from the input terminal C of the insulated gate bipolar transistor to the output terminal E. Each curve represents the control terminal of the insulated gate bipolar transistor When different voltages are applied to G, the relationship curve between the voltage difference Vce between the input terminal C and the output terminal E and the current Ice. The effect and control method are also to use the voltage of the control terminal G (meaning Vge) to control the current Ice that can flow through the input terminal C and the output terminal E, which will not be repeated here.

Please refer to FIG. 3A for the circuit block diagram of the first embodiment of the pre-charge control circuit of the present invention, and refer to FIGS. 1A~2 for multiple cooperation. The pre-charge control circuit 1 includes a control unit 12, a conversion unit 14 and a pre-charge switch Q, and the conversion unit 14 is coupled to the control unit 12 and the pre-charge switch Q. The control unit 12 receives the pulse width modulation signal PWM, and provides control signals Sc1 and Sc2 to the conversion unit 14 according to the pulse width modulation signal PWM. The conversion unit 14 receives the control signals Sc1 and Sc2, and converts the operating voltage Vcc into the ramp voltage Vr to the precharge switch Q according to the control signals Sc1 and Sc2. The precharge switch Q is coupled to the input path of the electronic circuit 100 (the first terminal 102 or the second terminal 104 of the input path), and the control terminal G receives the ramp voltage Vr whose voltage value gradually increases to gradually establish a channel to gradually turn on Enter the path. It is worth mentioning that, in an embodiment of the present invention, the operating voltage Vcc can be provided by the electronic circuit 100 or provided by an external electronic device.

Furthermore, the pulse width modulation signal PWM can be provided by a controller inside the electronic circuit 100 or provided by an externally coupled electronic device, and the pulse width modulation signal PWM can be provided by an analog controller or Provided by a digital controller. The pulse width modulation signal PWM is a signal that gradually increases the duty ratio, so that the duty ratios of the control signals Sc1 and Sc2 provided by the control unit 12 to the conversion unit 14 are gradually increased. As the duty ratios of the control signals Sc1 and Sc2 gradually increase, the voltage value of the ramp voltage Vr output by the conversion unit 14 also gradually increases. Therefore, the ramp voltage Vr whose voltage value gradually increases can gradually turn on the precharge switch Q. Among them, the best way to increase the duty cycle is to increase with equal magnification. The increase of the same magnification method can make the voltage value of the ramp voltage Vr also increase in the same magnification manner. The best embodiment is that the duty ratios of the control signals Sc1 and Sc2 are increased by 1%, but it is not limited to this. In this way, the best surge current suppression effect is achieved, and the conduction speed of the precharge switch Q is not too slow, which prolongs the start-up time of the electronic circuit 100, or the precharge switch Q is turned on. The speed is too fast to effectively suppress the peak value of the surge current. Therefore, the present invention utilizes the operating characteristic of the precharge switch Q as the transistor, so that the precharge control circuit 1 only needs to control the duty cycle of the pulse width modulation signal PWM to control the effect of the current flowing through the precharge switch Q.

Specifically, the conversion unit 14 includes a switching unit 142 and a filtering unit 144, and the control unit 12, the switching unit 142, and the filtering unit 144 constitute a buck converter. The switching unit 142 includes an upper bridge switch Q1 and a lower bridge switch Q2, the upper bridge switch Q1 is coupled to the operating voltage Vcc and the control unit 12, and the lower bridge switch Q2 is coupled to the output of the upper bridge switch Q1, the control unit 12 and the precharge switch Q End (S, E). The filter unit 144 includes an inductor L and a capacitor C. One end of the inductor L is coupled to the contact point between the upper bridge switch Q1 and the lower bridge switch Q2, and the other end of the inductor L is coupled to one end of the capacitor C and the control of the precharge switch Q End G. The other end of the capacitor C is coupled to the output terminals (S, E) of the pre-charge switch Q to establish a ramp voltage that gradually turns on the pre-charge switch Q between the control terminal G and the output terminal (S, E) of the pre-charge switch Q Vr. It is worth mentioning that in an embodiment of the present invention, the control unit 12, the switching unit 142, and the filtering unit 144 may also constitute, for example, but not limited to, a switching converter such as a boost converter. All of them can generate the ramp voltage Vr by controlling the switching of the switch. The only difference lies in the circuit cost of the circuit structure and the difficulty of the control method. That is, the circuit structure of the step-down converter is simple and low in cost, and the control method is the simplest.

The upper bridge switch Q1 receives the upper bridge control signal Sc1 of the control signals Sc1 and Sc2, the lower bridge switch Q2 receives the lower bridge control signal Sc2 of the control signals Sc1 and Sc2, and the upper bridge control signal Sc1 and the lower bridge control signal Sc2 are complementary controls Signal. When the upper bridge control signal Sc1 controls the upper bridge switch Q1 to turn on, the lower bridge control signal Sc2 controls the lower bridge switch Q2 to not turn on. At this time, under the transient condition where the duty cycle is constant, the operating voltage Vcc stores energy to the inductor L through the high-bridge switch Q1, so that the inductor current I1 generated by the inductor L charges the capacitor. Therefore, the voltage value of the ramp voltage Vr across the capacitor C starts to increase. Then, when the upper bridge control signal Sc1 controls the upper bridge switch Q1 to turn off, the lower bridge control signal Sc2 controls the lower bridge switch Q2 to turn on. At this time, the inductor L, the capacitor C, and the lower bridge switch Q2 form a closed loop, and the inductor current I1 on the inductor L gradually decreases to release the capacitor C. Then in the steady state, the fixed Vr can be obtained according to the volt-second balance law The voltage value. As the duty ratios of the control signals Sc1 and Sc2 gradually increase, the switching unit 142 gradually increases the conduction time to switch conduction, thereby causing the ramp voltage Vr to increase accordingly. It is worth mentioning that in one embodiment of the present invention, the slope of the ramp voltage Vr's rising slope is related to the duty cycle control of the control signals Sc1 and Sc2, but the voltage value of the ramp voltage Vr is not limited to a fixed slope. It can also be increased in a non-fixed slope manner (for example, exponential or logarithmic).

The conversion unit 14 further includes a current-limiting resistor Rg, and the current-limiting resistor Rg is coupled between the upper bridge switch Q1, the lower bridge switch Q2 and the inductor L. When the conversion unit 14 is not working, the capacitor C does not yet have any voltage and is close to a short circuit. Therefore, when the conversion unit 14 starts to operate and the upper bridge switch Q1 is turned on, an instantaneous large current will flow to the filter unit 144, which causes the voltage value of the ramp voltage Vr to be instantaneously too high and the precharge switch Q is turned on by mistake. Therefore, the current-limiting resistor Rg can limit the conduction current from the working voltage Vcc through the high-bridge switch Q1, the inductor L to the capacitor C when the high-bridge switch Q1 is turned on, so as to avoid the above-mentioned pre-charge switch Q misoperation and conduction. Furthermore, it also protects the upper bridge switch Q1 from being damaged by a large current. It is worth mentioning that the current-limiting resistor Rg can also be called a driving resistor.

Please refer to FIG. 3B for a circuit block diagram of the second embodiment of the precharge control circuit of the present invention, and refer to FIGS. 1A to 3A for complex cooperation. The precharge control circuit 1'of this embodiment is different from the precharge control circuit 1 of FIG. 3A in that the switching unit 142' only has the lower bridge switch Q2, and the control unit 12' also only provides the control signal Sc2 (ie, the lower bridge control signal ) To the lower bridge switch Q2. The lower bridge switch Q2 is coupled to the working voltage Vcc, the inductor L and the output terminals (S, E) of the precharge switch Q, and receives the lower bridge control signal Sc2 to switch on. When the low-bridge control signal Sc2 is at the first level (meaning low level), the low-bridge switch Q2 is not turned on, and the operating voltage Vcc stores energy in the inductor L, so that the inductor current I1 generated by the inductor L charges the capacitor C. Therefore, the voltage value of the ramp voltage Vr across the capacitor C starts to increase. Then, when the lower bridge control signal Sc2 is at the second level (meaning high level), the lower bridge switch Q2 is turned on. At this time, the inductor L, the capacitor C, and the low-bridge switch Q2 form a closed loop, and the inductor current I1 on the inductor L decreases slowly to discharge the capacitor C. The detailed operation process is as described in the previous paragraph, and finally the ramp voltage Vr becomes The voltage value can be stably controlled to a fixed value. It is worth mentioning, Yu Ben In an embodiment of the invention, the circuit coupling method and control method not mentioned in FIG. 3B are the same as those in FIG. 3A, and will not be repeated here.

The conversion unit 14' further includes a current-limiting resistor Rg, and the current-limiting resistor Rg is coupled between the working voltage Vcc, the low-bridge switch Q2 and the inductor L, and its function is equivalent to the current-limiting resistor Rg in FIG. 3A. Wherein, the coupling position of the current limiting resistor Rg in FIG. 3A can also be the same as the coupling position in FIG. 3B. That is, the current-limiting resistor Rg is coupled between the operating voltage Vcc and the high-bridge switch Q1, and the effect is equivalent to that the current-limiting resistor Rg is coupled between the high-bridge switch Q1, the low-bridge switch Q2 and the inductor L. It is worth mentioning. The current-limiting resistor Rg can also be called a driving resistor. In addition, the pulse width modulation signal PWM, the control units 12, 12', the upper-bridge switch Q1 and the lower-bridge switch Q2 in Figs. 3A and 3B can be included in a driving IC in practice.

Please refer to FIG. 4 for a flow chart of the control method of the pre-charge control circuit of the present invention, and refer to FIGS. 1A to 3B for complex cooperation. The control method of the precharge control circuit 1 first includes providing a precharge switch coupled to the input path of the electronic circuit (S100). The precharge switch Q can be coupled to the first end 102 of the input path of the electronic circuit 100 or the second end 104 of the input path, so as to control the precharge of the electronic circuit 100 at the moment when the input power source Vin is just coupled to the electronic circuit 100 . Then, the control signal is provided to the conversion unit according to the pulse width modulation signal (S200). The control unit 12 receives the pulse width modulation signal PWM, and provides control signals Sc1 and Sc2 to the conversion unit 14 according to the pulse width modulation signal PWM. The pulse width modulation signal PWM can be provided by the internal controller of the electronic circuit 100, or provided by an externally coupled electronic device, and the pulse width modulation signal PWM can be provided by an analog controller or digitally controlled Provided by the device. The pulse width modulation signal PWM is a signal that gradually increases the duty ratio, so that the duty ratios of the control signals Sc1 and Sc2 provided by the control unit 12 to the conversion unit 14 are gradually increased.

Then, the conversion unit provides a ramp voltage according to the control signal (S300). The conversion unit 14 receives the control signals Sc1 and Sc2, and converts the operating voltage Vcc into the ramp voltage Vr to the precharge switch Q according to the control signals Sc1 and Sc2. As the duty ratios of the control signals Sc1 and Sc2 gradually increase, the voltage value of the ramp voltage Vr output by the conversion unit 14 also gradually increases. Among them, the best way to increase the duty cycle It is improved by means of equal magnification. The increase of the same magnification method can make the voltage value of the ramp voltage Vr also increase in the same magnification manner. The best embodiment is that the duty ratios of the control signals Sc1 and Sc2 are increased by 1%. In this way, the best inrush current suppression effect is achieved, and the conduction speed of the precharge switch Q is not too slow to prolong the startup time of the electronic circuit 100, or the conduction speed of the precharge switch Q is too fast to effectively suppress the inrush. The effect of the peak value of wave current.

The conversion unit 14 may include at least two circuit structures and control methods, one of which is that the conversion unit 14 is a buck converter and includes an upper bridge switch Q1 and a lower bridge switch Q2. The upper bridge switch Q1 receives the upper bridge control signal Sc1 of the control signals Sc1 and Sc2, the lower bridge switch Q2 receives the lower bridge control signal Sc2 of the control signals Sc1 and Sc2, and the upper bridge control signal Sc1 and the lower bridge control signal Sc2 are complementary controls Signal. When the upper bridge control signal Sc1 controls the upper bridge switch Q1 to turn on, the lower bridge control signal Sc2 controls the lower bridge switch Q2 to not turn on. At this time, the operating voltage Vcc stores energy to the inductor L through the high-bridge switch Q1, so that the inductor current I1 generated by the inductor L charges the capacitor. Therefore, the voltage value of the ramp voltage Vr across the capacitor C starts to increase. Then, when the upper bridge control signal Sc1 controls the upper bridge switch Q1 to turn off, the lower bridge control signal Sc2 controls the lower bridge switch Q2 to turn on. At this time, the inductor L, the capacitor C, and the low-bridge switch Q2 form a closed loop, and the inductor current I1 on the inductor L gradually decreases to discharge the capacitor C, so that the voltage value of the ramp voltage Vr can be stably controlled to a fixed value.

The other is: the conversion unit 14' is a buck converter and only includes the low-bridge switch Q2. The control unit 12' only provides the lower bridge control signal Sc2 to the lower bridge switch Q2. The lower bridge switch Q2 is coupled to the working voltage Vcc, the inductor L and the output terminals (S, E) of the precharge switch Q, and receives the lower bridge control signal Sc2 to switch on. When the low-bridge control signal Sc2 is at the first level (meaning low level), the low-bridge switch Q2 is not turned on, and the operating voltage Vcc stores energy in the inductor L, so that the inductor current I1 generated by the inductor L charges the capacitor. Therefore, the voltage value of the ramp voltage Vr across the capacitor C starts to increase. Then, when the lower bridge control signal Sc2 is at the second level (meaning high level), the lower bridge switch Q2 is turned on. At this time, the inductor L, the capacitor C, and the lower bridge switch Q2 form a package The loop is closed, and the inductor current I1 on the inductor L gradually decreases to release the energy of the capacitor C, so that the voltage value of the ramp voltage Vr can be stably controlled to a fixed value.

The above-mentioned two conversion units 14, 14' may include a current limiting resistor Rg. When the conversion units 14, 14' start to operate, the conduction current of the path from the operating voltage Vcc through the inductor L to the capacitor C is limited to avoid precharging. The switch Q malfunctions and turns on. Finally, the pre-charge switch gradually turns on the input path according to the ramp voltage (S400). The precharge switch Q gradually establishes a channel through the control terminal G receiving the ramp voltage Vr whose voltage value gradually increases, so as to gradually turn on the input path.

To sum up, the main advantages and effects of the embodiments of the present invention are that the pre-charge control circuit of the present invention only uses the pre-charge switch to couple to the input path of the electronic circuit to control the pre-charge of the electronic circuit. It uses the working area of the pre-charge switch as the control of the conduction degree of the pre-charge switch, so that the pre-charge switch of the present invention does not need parallel resistors like the prior art. Therefore, the voltage at both ends of the pre-charge switch can be completely isolated, and it is easy to detect whether the pre-charge switch is damaged.

However, the above are only detailed descriptions and drawings of the preferred embodiments of the present invention. However, the features of the present invention are not limited to these, and are not intended to limit the present invention. The full scope of the present invention should be referred to the following application The scope of the patent shall prevail. All embodiments that conform to the spirit of the scope of the patent application of the present invention and similar variations should be included in the scope of the present invention. Anyone familiar with the art in the field of the present invention can easily think of it. Changes or modifications can be covered in the following patent scope of this case. In addition, the features mentioned in the scope of the patent application and the specification can be implemented individually or in any combination.

100: electronic circuit

102: first end

104: second end

Cin: Input capacitance

Vin: input power

1: Precharge control circuit

Q: Pre-charge switch

Claims (16)

A pre-charge control circuit, the pre-charge control circuit includes: a control unit, receiving a pulse width modulation signal; a conversion unit, coupled to the control unit; and a pre-charge switch, coupled to the conversion unit and an electronic circuit Wherein the control unit provides a control signal to the conversion unit according to the pulse width modulation signal, and the conversion unit provides a ramp voltage according to the control signal; the precharge switch gradually turns on the The input path is input, and the final voltage value of the ramp voltage is stably controlled at a fixed value that enables the precharge switch to turn on. For the pre-charge control circuit described in claim 1, wherein a duty cycle of the control signal is gradually increased, so that the conversion unit provides the ramp voltage according to the control signal of the duty cycle that is gradually increased. For the precharge control circuit described in item 2 of the scope of patent application, the duty cycle is increased by an equal rate, so that a voltage value of the ramp voltage is increased by an equal rate. According to the pre-charge control circuit described in claim 1, wherein the conversion unit includes: a switching unit coupled to the control unit; and a filter unit coupled to the switching unit and the pre-charge switch; wherein, the The switching unit is switched on according to the control signal, so that the filter unit generates the ramp voltage according to the switching on of the switching unit. The precharge control circuit described in item 4 of the scope of patent application, wherein the filter unit includes: An inductor, coupled to the switching unit; and a capacitor, coupled to the inductor and the precharge switch; wherein, through the switching of the switching unit, a working voltage stores energy to the inductor, or the inductor discharges energy to the capacitor , So that the two ends of the capacitor pass through the energy storage and discharge of the inductor to generate the ramp voltage. The pre-charge control circuit described in item 5 of the scope of patent application, wherein the switching unit includes: an upper bridge switch, which is coupled to the operating voltage and the control unit; and a lower bridge switch, which is coupled to the upper bridge switch and the control unit Unit; wherein, the control signal includes a complementary upper bridge control signal and a lower bridge control signal; when the upper bridge control signal turns on the upper bridge switch, the lower bridge switch is not conductive, and the operating voltage passes through the upper bridge switch pair The inductor and the capacitor store energy; when the lower bridge control signal turns on the lower bridge switch, the upper bridge switch is not turned on, and the inductor discharges energy to the capacitor. For the precharge control circuit described in item 6 of the scope of patent application, the conversion unit further includes: a current limiting resistor coupled to the upper bridge switch, the lower bridge switch and the inductor; wherein, when the upper bridge switch is turned on , The current-limiting resistor limits the magnitude of a conduction current flowing from the operating voltage through the high-bridge switch, the inductor to the capacitor path. For the precharge control circuit described in item 5 of the scope of patent application, the switching unit includes: a lower bridge switch, which is coupled to the operating voltage and the control unit; wherein, the control signal is a lower bridge control signal; the lower bridge control When the signal does not turn on the low-bridge switch, the operating voltage stores energy to the inductor, and when the low-bridge control signal turns on the low-bridge switch, the inductor discharges energy to the capacitor. As described in item 8 of the scope of patent application, the conversion unit further includes: a current-limiting resistor coupled to the operating voltage, the lower bridge switch and the inductor; wherein, when the lower bridge switch is not conducting , The current-limiting resistor limits the magnitude of a conduction current flowing from the operating voltage through the inductor to the capacitor path. A control method of a precharge control circuit, the control method comprising the following steps: providing a precharge switch coupled to an input path of an electronic circuit; providing a control signal to a conversion unit according to a pulse width modulation signal; the The conversion unit provides a ramp voltage according to the control signal; and the precharge switch gradually turns on the input path according to the ramp voltage, and the final voltage value of the ramp voltage is stably controlled to a fixed value that turns on the precharge switch. For the control method of the precharge control circuit described in item 10 of the scope of patent application, wherein a duty ratio of the control signal is gradually increased, so that the conversion unit provides the ramp according to the control signal of the gradually increasing duty ratio Voltage. For the control method of the precharge control circuit described in item 11 of the scope of patent application, the duty cycle is increased by an equal rate, so that a voltage value of the ramp voltage is increased by an equal rate. For the control method of the precharge control circuit described in item 10 of the scope of patent application, the control signal includes a complementary upper bridge control signal and a lower bridge control signal; the upper bridge control signal makes a working voltage for the conversion unit An inductor stores energy, and the lower bridge control signal enables the inductor to discharge energy to a capacitor of the conversion unit; the capacitor generates the ramp voltage through the energy storage and discharge of the inductor. For example, the control method of the precharge control circuit described in item 13 of the scope of patent application further includes: limiting the magnitude of a conduction current flowing from the operating voltage through the inductor to the capacitor path. For the control method of the pre-charge control circuit described in item 10 of the scope of patent application, a first level of the control signal enables an operating voltage to store energy on an inductance of the conversion unit, and a second level of the control signal The level enables the inductor to discharge energy to a capacitor of the conversion unit; the capacitor generates the ramp voltage through the energy storage and discharge of the inductor. For example, the control method of the precharge control circuit described in item 15 of the scope of patent application further includes: limiting the magnitude of a conduction current from the operating voltage flowing through the inductor to the capacitor path.

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