Control circuit applied to a lifting platform and method for controlling the same

Abstract

A control circuit (1) applied to a lifting platform (200) configured to control a motor (100) to adjust the height of a platform (200A), the control circuit (1) comprising: a conversion circuit (10) configured to receive an input voltage (Vin) and provide an output voltage (Vout) to control the motor (100), the conversion circuit (10) comprising: an AC / DC conversion circuit (102) configured to convert the input voltage (Vin) into a DC voltage (Vdc), and a DC / DC conversion circuit (104) configured to convert the DC voltage (Vdc) into the output voltage (Vout), a detection unit (20) configured to detect an output end of the AC / DC conversion circuit (102) and to provide a detection signal (Ss), and a control unit (30) configured to supply a PWM signal (PWM) according to the detection signal (Ss) to control the DC / DC conversion circuit (104) so ​​that the DC / DC conversion circuit (104) converts the DC voltage (Vdc) into the output voltage (Vout), wherein the control unit (30) sets a power supply threshold; when the control unit (30) realizes, according to the detection signal (Ss), that the DC voltage (Vdc) or a DC power (Pdc) supplied by the AC / DC conversion circuit (102) is less than the power supply threshold, the control unit (30) reduces a duty cycle of the PWM signal (PWM) to reduce a rotational speed of the motor (100) and maintains the DC voltage (Vdc) or the DC power (Pdc) greater than or equal to the power supply threshold, wherein the power supply threshold is a power threshold and the AC / DC conversion circuit (102) supplies a DC current (Idc) to the DC / DC conversion circuit (104); the detection unit (20) detects the DC voltage (Vdc) and the DC current (Idc) and supplies the detection signal (Ss) to the control unit (30); the control unit (30) calculates the DC power (Pdc) according to the detection signal (Ss) and sets a maximum output power as the power threshold when the DC power (Pdc) is at the maximum output power, and reduces the duty cycle when the DC power (Pdc) is less than or equal to the maximum output power, or wherein the power supply threshold is a voltage threshold; the detection unit (20) detects the DC voltage (Vdc) and supplies the detection signal (Ss) to the control unit (30); the control unit (30) compares the detection signal (Ss) with the voltage threshold and reduces the duty cycle if the DC voltage (Vdc) corresponding to the detection signal (Ss) is less than or equal to the voltage threshold.

Description

BACKGROUNDTechnical field

[0001] The present disclosure relates to a control circuit applied to an elevator platform and a method of controlling the same, and more particularly to a control circuit for maintaining maximum output power and a method of controlling the same. Description of the state of the art

[0002] The statements in this section merely provide background information related to the present disclosure and do not necessarily constitute prior art.

[0003] Modern people need a new tool to improve the poor circulation caused by sedentary sitting. Therefore, to meet the needs of personal work comfort and ergonomic design, the use of adjustable table heights is becoming increasingly popular. In the application of lifting tables, manual, pneumatic, or electric methods are usually used to adjust the height of the table body. In particular, since the electric control method for adjusting the height of the table body is more precise and the adjustment effect is better, the application range of electric lifting tables is wider.

[0004] However, when the load of the conventional electric lift table increases, and if the maximum output power of the converter is exceeded, the output power of the converter always decreases, resulting in poor load capacity. When the load is heavy (i.e., the lift table operates under heavy-duty conditions), the electric lift table cannot rise either. Therefore, the prior art solution is usually to use a converter with a larger output power to increase the output power of the converter, allowing it to drive a heavier load. However, this solution increases the cost of the electric lift table, and the circuitry is bulky.

[0005] US 2012 / 0 181 968 A1 relates to a method for controlling the operation of an electric motor in a height-adjustable furniture arrangement, wherein the operation of the electric motor provides a height adjustment function in the height-adjustable furniture arrangement.The method comprises the steps of providing an input power comprising an input current and an input voltage by a power supply unit connected to the electric motor, converting the input current and the input voltage into a motor supply current and a motor supply voltage supplied to the electric motor, measuring a load on the electric motor and, if the measured load requires a current higher than the input current to provide the height adjustment function, adjusting the levels of the motor supply current and / or the motor supply voltage such that the motor supply current is higher than the input current and the motor supply voltage is lower than the input voltage.

[0006] US 2021 / 0 159 811 A1 relates to a power converter arrangement comprising a first and a second power converter, each comprising a voltage intermediate circuit and a load-side power converter. SUMMARY

[0007] The object of the present invention is achieved by the subject matter of the independent claims. Advantageous embodiments are specified in the subclaims. To solve the above-mentioned problems, the present disclosure provides a control circuit applied to a lifting platform that controls a motor to adjust the height of a platform. The control circuit includes a conversion circuit, a detection unit, and a control unit.

[0008] The conversion circuit receives an input voltage and provides an output voltage to control the motor. The conversion circuit includes an AC / DC conversion circuit and a DC / DC conversion circuit. The AC / DC conversion circuit converts the input voltage into a DC voltage. The DC / DC conversion circuit converts the DC voltage into the output voltage. The detection unit detects an output end of the AC / DC conversion circuit and provides a detection signal. The control unit provides a PWM signal according to the detection signal to control the DC / DC conversion circuit, so that the DC / DC conversion circuit converts the DC voltage into the output voltage. The control unit sets a power supply threshold.When the control unit realizes according to the detection signal that the DC voltage or DC power supplied by the AC / DC conversion circuit is less than the power supply threshold, the control unit decreases a duty cycle of the PWM signal to decrease a speed of the motor and keeps the DC voltage or DC power greater than or equal to the power supply threshold.

[0009] To solve the above-mentioned problems, the present disclosure provides a method for controlling an aerial platform. The method includes the steps of: setting a power supply threshold and controlling a DC / DC conversion circuit to convert a DC voltage supplied by an AC / DC conversion circuit into an output voltage to control a motor; detecting an output end of the AC / DC conversion circuit to provide a detection signal, and adjusting a PWM signal to control the DC / DC conversion circuit according to the detection signal;Decreasing a duty cycle of the PWM signal to decrease a speed of the motor when the DC voltage or DC power supplied by the AC / DC conversion circuit is less than the power supply threshold according to the detection signal, and maintaining the DC voltage or DC power greater than or equal to the power supply threshold;

[0010] The main purpose and effect of the present disclosure are to use the control unit to detect the maximum output of the AC / DC conversion circuit to maintain the load capacity of the conversion circuit, and to solve the poor load capacity and platform inability to lift in the prior art. Therefore, when the lifting platform operates under heavy load conditions, the speed of the lifting table can still be controlled faster than the speed of the lifting table in the prior art.

[0011] It should be understood that both the foregoing general description and the following detailed description are exemplary and are intended to provide further explanation of the present disclosure as claimed. Other advantages and features of the present disclosure will be apparent from the following description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The present disclosure can be more fully understood by reading the following detailed description of the embodiment, with reference to the accompanying drawings, in which: Fig. 1 is a block diagram of a control circuit applied to an aerial platform according to the present disclosure; Fig. 2 is a diagram of a power-load curve of a converter according to the present disclosure; Fig. 3A is a flowchart of a method for controlling the aerial platform according to the present disclosure; Fig. 3B is a flowchart of the method when a power supply threshold is a voltage threshold, according to the present disclosure; and Fig.3C is a flowchart of the method when the power supply threshold is a power threshold, according to the present disclosure. DETAILED DESCRIPTION

[0013] Reference will now be made to the drawings to describe the present disclosure in detail. It should be understood that the drawings and the illustrated embodiments of the present disclosure are not limited to the details thereof.

[0014] Fig.1 shows a block diagram of a control circuit applied to an elevating platform according to the present disclosure. The control circuit 1 controls a motor 100 to adjust the height of a platform 200A. The platform 200A may be a desk body (for example, but not limited to, an office desk, a tea table, etc., which are not used to support heavy machine tools or large construction materials), and therefore, the elevating platform 200 is a elevating table. The control circuit 1 includes a conversion circuit 10, a detection unit 20, and a control unit 30. In some embodiments, the conversion circuit 10 may be an isolated or non-isolated DC-DC converter.Conversion circuit 10 includes an AC / DC conversion circuit 102 for receiving an AC voltage input Vin and a DC / DC conversion circuit 104 for receiving a DC voltage Vdc. Motor 100 may be a DC motor characterized by easy speed adjustment, smooth speed control, and large overload capacity. It is particularly suitable for electric desk structures used for personal offices or reading.

[0015] With further reference to Fig.1, the AC / DC conversion circuit 102 receives the input voltage Vin, converts the input voltage Vin into the DC voltage Vdc, and supplies the DC voltage Vdc to the DC / DC conversion circuit 104. The DC / DC conversion circuit 104 receives the DC voltage Vdc, converts the DC voltage Vdc into the output voltage Vout, and supplies the output voltage Vout to control the motor 100. The detection unit 20 is coupled to an output end of the AC / DC conversion circuit 102 and provides a detection signal Ss according to the detection results.The control unit 30 is coupled to a power switch (not shown) of the DC / DC conversion circuit 104 and the detection unit 20, and supplies a pulse width modulation (PWM) signal PWM to control the switching of the power switch according to the detection signal Ss, so that the DC / DC conversion circuit 104 converts the DC voltage Vdc into the output voltage Vout by switching the power switch. During the operation of the DC / DC conversion circuit 104, the control unit 30 adjusts the output voltage Vout by adjusting the duty cycle of the PWM signal PWM according to the detection signal Ss at any time to adjust the speed of the motor 100 by adjusting the output voltage Vout (the output voltage Vout corresponds to the speed of the motor 100).

[0016] Fig.2 shows a diagram of a power-load curve of a converter according to the present disclosure, see also Fig. 1 and Table 1 below. Curve A in Fig. 2 is drawn from Table 1 below: the DC power curve Pdc is plotted through points of the input voltage Vin (100 V / 50 Hz). Curve B is drawn from Table 1 below: the DC power curve Pdc is plotted through points of the input voltage Vin (240 V / 50 Hz). In Fig. 2, only the parameters of two different types of conversion circuits 10 are shown as examples, but are not limited to these parameters. Since the control circuit of the lifting platform in the prior art is heavier than the load of the platform 200A, the control unit 30 continuously increases the output current I O the DC / DC conversion circuit 104 to drive the platform 200A. When the output current I Ocontinuously increases until the DC power Pdc that the AC / DC conversion circuit 102 can deliver exceeds the maximum output power, causing the increase in the output current I O only that the DC power Pdc, instead of increasing, decreases. Under this condition, the DC current Idc of the AC / DC conversion circuit 102 continuously increases, but the DC voltage Vdc continuously decreases, so that the 200A platform cannot rise due to the low DC voltage Vdc and poor load capacity when the load of the 200A platform is under the heavy load condition.

[15] Table 1 (the output voltage and output current of the conversion circuit) Direct current Idc DC voltage Vdc Input voltage Vin (100 V / 50 Hz) Input voltage Vin (240 V / 50 Hz) 0 32,7 32,7 1 32,6 32,7 2 32,6 32,6 3 32,5 32,6 4 32,4 32,4 5 32,4 32,4 6 32,3 32,3 7 31,9 32,2 8 24,7 30,3 9 17,8 24,5 10 12,1 19,2 11 0 14,6 12 10,5 13 6 14 0

[0017] The main purpose and effect of the present disclosure are that: the control unit 30 detects the maximum output power of the AC / DC conversion circuit 102 to maintain the load capability of the conversion circuit 10 and solves the problem that the platform 200A cannot rise when the load of the platform 200A operates under the heavy load condition. Specifically, the control unit 30 sets the power supply threshold of the output end of the AC / DC conversion circuit 102.When the control unit 30 detects, according to the detection signal Ss, that the DC voltage Vdc or the DC power Pdc is less than the power supply threshold, the control unit 30 reduces the duty cycle of the PWM signal PWM to reduce the speed of the motor 100 and maintains the DC voltage Vdc or the DC power Pdc greater than or equal to the power supply threshold. When the control unit 30 detects, according to the detection signal Ss, that the DC voltage Vdc or the DC power Pdc is greater than or equal to the power supply threshold, the control unit 30 increases the duty cycle of the PWM signal PWM to increase the speed of the motor 100, thereby increasing the setting speed of the platform 200A.

[0018] As in Fig. 1 and Fig.2, the control unit 30 provides two control and setting modes. One of the modes is that the control unit 30 sets the power supply threshold according to the Fig.2. Specifically, the power-load curve is a DC power Pdc curve formed by the product of the DC voltage Vdc and the DC current Idc. The control unit 30 previously sets the voltage value of the DC voltage Vdc corresponding to the DC power Pdc at the maximum output power point as the power supply threshold (the power supply threshold is the voltage threshold). After that, the detection unit 20 detects the DC voltage Vdc and outputs a detection signal Ss representing the amplitude of the DC voltage Vdc. The control unit 30 receives the detection signal Ss representing the amplitude of the DC voltage Vdc to realize the amplitude of the DC voltage Vdc. The control unit 30 then compares the DC voltage Vdc and the voltage threshold to determine whether the duty cycle of the PWM signal PWM should be limited.

[0019] In particular, when the DC voltage Vdc is greater than the voltage threshold, the control unit 30 increases the duty cycle of the PWM signal PWM to increase the output current I O of the DC / DC conversion circuit 104, thereby increasing the speed of the motor 100. When the DC voltage Vdc is less than or equal to the voltage threshold, the control unit 30 reduces the duty cycle of the PWM signal PWM to increase the output current I O of the DC / DC conversion circuit 104, thereby reducing the speed of the motor 100. Since the output current I Ois reduced, the DC voltage Vdc no longer continuously decreases to maintain the DC power Pdc of the AC / DC conversion circuit 102 at the maximum output. Under this condition, although the lifting speed of the platform 200A slows down, the phenomenon that the platform 200A cannot be lifted as in the conventional technology does not occur. Therefore, compared with the prior art, the lifting table of the present disclosure can increase the lifting speed of the platform 200A under the heavy load condition.

[0020] The other type is that the detection unit 20 detects the DC voltage Vdc and the DC current Idc to provide the detection signal Ss representing the DC voltage Vdc and the DC current Idc. The control unit 30 receives the detection signal Ss representing the amplitude of the DC voltage Vdc and the DC current Idc to detect the amplitude of the DC voltage Vdc and the DC current Idc. After that, the control unit 30 calculates the DC power Pdc according to the DC voltage Vdc and the DC current Idc and continuously tracks the increase and decrease of the DC power Pdc as the DC current Idc increases. When the DC current Idc increases but the DC power Pdc decreases, the control unit 30 sets the previous DC power Pdc as the maximum output power and sets this DC power Pdc as the power threshold (ie,the power supply threshold is a power threshold.) Then, the control unit 30 compares the current DC power Pdc with the power threshold to adjust the duty cycle of the PWM signal PWM accordingly.

[0021] When the DC power Pdc is greater than the power threshold, the control unit 30 increases the duty cycle of the PWM signal PWM to increase the output current I O of the DC / DC conversion circuit 104, thereby increasing the speed of the motor 100. When the DC power Pdc is less than the power threshold, the control unit 30 reduces the duty cycle of the PWM signal PWM to increase the output current I O of the DC / DC conversion circuit 104, thereby reducing the speed of the motor 100. Since the output current I Ois reduced, the DC voltage Vdc no longer continuously decreases to maintain the DC power Pdc of the AC / DC conversion circuit 102 at the maximum output. Under this condition, although the lifting speed of the platform 200A slows down, the phenomenon that the platform 200A cannot be lifted as in the conventional technology does not occur. Therefore, compared with the prior art, the lifting table of the present disclosure can increase the lifting speed of the platform 200A under the heavy load condition.

[0022] Furthermore, the relationship between the output voltage Vo and the PWM signal PWM may be, for example, as shown in Table 2 below, but is not limited thereto. As shown in Table 1 and Fig. 2 when the output current I Ois increased sufficiently, the DC voltage Vdc inevitably drops. The control unit 30 controls the PWM signal PWM to decrease according to the decrease in the DC voltage Vdc, so that the output voltage Vo decreases accordingly and the speed of the motor 100 is reduced. As the speed of the motor 100 decreases, the output current I Oalso decreases, causing the DC voltage Vdc to increase. With this circuit characteristic and the setting of the power supply threshold, the load capacity of the conversion circuit 10 can be maintained, and the situation where the 200A platform cannot increase when the load of the 200A platform is under the heavy load condition can be resolved. The main control method is to maintain the DC voltage Vdc output by the AC / DC conversion circuit 102 above a specific voltage, and the output voltage Vo changes within a specific interval when the PWM signal PWM is adjusted (for example, but not limited to, 0 to 33 volts).

[22] Table 2 the output voltage and the PWM signal) PWM signal PWM Output voltage Vo 100 % 32 V 70 % 32 V*0,7 30 % 32 V* 0,3 10% 32 V*0,1

[0023] As again in Fig.As shown in Figure 2, when the power supply threshold is the power threshold, two modes for operating a maximum output parameter can be implemented. Mainly, for the user to operate the control circuit 1, the control circuit 1 can directly lift the lifting platform 200 with the maximum power, and then the PWM signal PWM is adjusted according to the detection unit 20 to detect the actual operating condition of the conversion circuit 10, in order to save the time of lifting the platform 200A. One of the modes is that before the actual operation of the control circuit 1, the control unit 30 performs a preload (gradually increasing the output current I OThe DC / DC converter 104 performs a continuous measurement (through an internal memory or manual operation) to capture the corresponding changes in the DC voltage Vdc and the DC current Idc. After that, the maximum output power is calculated during the process of their change; that is, parameters corresponding to the DC voltage Pdc that begins to decrease are stored. Therefore, during the actual operation of lifting the platform 200A, the DC / DC conversion circuit 104 is directly controlled according to the stored maximum output parameter, and the duty cycle of the PWM signal PWM is adjusted according to the current detection signal Ss and the comparison of the power supply threshold.

[0024] The other operation is that when the AC / DC conversion circuit 102 operates at the maximum output, the corresponding parameter (namely, the maximum output parameter) is set in advance in the control unit 30, so that the control unit 30 can directly control the DC / DC conversion circuit 104 according to the maximum output parameter when the control unit 30 wants to control the lifting of the platform 200A. Specifically, the parameters, i.e., the maximum output parameter (when the AC / DC conversion circuit 102 operates at the maximum output), can usually be acquired from the specifications of the AC / DC conversion circuit 102.Thereafter, the control unit 30 compares the feedback generated by the DC voltage Vdc or the DC power Pdc with the power supply threshold to adjust the duty cycle of the PWM signal PWM accordingly.

[0025] In particular, the speed adjustment of the motor 100 can have a variety of humanized designs. In particular, since the lifting speed of the platform 200A that is too fast or too slow causes inconvenience to the user during use and even the possibility of accidents, the control unit 30 can set the platform 200A to have a step-by-step or speed limit function to slow down the adjustment speed of the platform 200A and prevent the platform 200A from lifting too quickly.

[0026] Fig.3A shows a flowchart of a method for controlling the lifting platform according to the present disclosure, see also Fig. 1 to Fig.2. The control method is applied to control the motor 100 to adjust the height of the platform 200A. The platform 200A may be a desk body (for example, but not limited to, an office desk, a tea table, etc., which are not used to support heavy machine tools or large construction materials). The control method includes the steps of setting a power supply threshold and controlling a DC / DC conversion circuit to convert a DC voltage supplied by an AC / DC conversion circuit into an output voltage to control a motor (S100).In one embodiment, the control unit 30 sets the power supply threshold and provides the PWM signal PWM to control the switching of a power switch, so that the DC / DC conversion circuit 104 converts the DC voltage Vdc to the output voltage Vout by switching the power switch.

[0027] Next, detecting an output end of the AC / DC conversion circuit to provide a detection signal, and adjusting a PWM signal to control the DC / DC conversion circuit according to the detection signal (S200). During operation of the conversion circuit 10, the control unit 30 adjusts the duty cycle of the PWM signal PWM to adjust the output voltage Vout according to the detection signal Ss of the output end of the detection AC / DC conversion circuit 102 at any time, thereby adjusting the speed of the motor 100.

[0028] Then, when the DC voltage or DC power is less than the power supply threshold according to the detection signal, the duty cycle of the PWM signal is reduced to reduce the speed of the motor, and the DC voltage or DC power is maintained at greater than or equal to the power supply threshold (S300). When the control unit 30 detects that the DC voltage Vdc or the DC power Pdc is less than the power supply threshold according to the detection signal Ss, the control unit 30 reduces the duty cycle of the PWM signal PWM to reduce the speed of the motor 100 and maintains the DC voltage Vdc or the DC power Pdc at greater than or equal to the power supply threshold.Therefore, it can solve the phenomenon that the platform 200A cannot rise due to the low DC voltage Vdc or DC power Pdc when the load of the platform 200A is under the heavy load condition. Then, when the DC voltage or DC power is greater than the power supply threshold, the duty cycle is increased to increase the speed according to the detection signal (S400). When the control unit 30 realizes, according to the detection signal Ss, that the DC voltage Vdc or DC power Pdc is greater than or equal to the power supply threshold, the control unit 30 increases the duty cycle of the PWM signal PWM to increase the speed of the motor 100, thereby increasing the setting speed of the lifting of the platform 200A.

[0029] If the control unit 30 wants to adjust the height of the 200A platform, the control unit 30 can control the DC / DC conversion circuit according to the specified maximum output parameter (S500). The maximum output parameter operating mode can be implemented: the control unit 30 performs a preload (gradually increasing the output current I OThe controller performs a process (e.g., through an internal memory or manual operation) to capture the corresponding changes in the DC voltage Vdc and DC current Idc. After that, the maximum output power is calculated during the process of their change; that is, parameters corresponding to the DC voltage Pdc that begins to decrease are stored. Therefore, during the actual operation of lifting the 200A platform, the DC / DC conversion circuit 104 is directly controlled according to the stored maximum output parameter, and the duty cycle of the PWM signal PWM is adjusted according to the current detection signal Ss and the power supply threshold comparison.

[0030] Alternatively, when the AC / DC conversion circuit 102 operates at the maximum output power, the corresponding parameter (namely, the maximum output parameter) is set in advance in the control unit 30, so that the control unit 30 can directly control the DC / DC conversion circuit 104 according to the maximum output parameter when the control unit 30 wants to control the lifting of the platform 200A. Specifically, the parameters, i.e., the maximum output parameter (when the AC / DC conversion circuit 102 operates at the maximum output power), can usually be acquired from the specifications of the AC / DC conversion circuit 102.Thereafter, the control unit 30 compares the feedback generated by the DC voltage Vdc or the DC power Pdc with the power supply threshold to adjust the duty cycle of the PWM signal PWM accordingly.

[0031] In particular, the speed adjustment of the motor 100 can have a variety of humanized configurations, and therefore, step (S500) is an optional step. In particular, since a lifting speed of the platform 200A that is too fast or too slow causes inconvenience to the user during use and even poses the possibility of accidents, the control unit 30 can set the platform 200A to have a step-by-step or speed limit function to slow down the adjustment speed of the platform 200A and prevent the platform 200A from lifting too quickly.

[0032] Fig.3B shows a flowchart of the control method when a power supply threshold is a voltage threshold, according to the present disclosure, see also Fig. 1 to Fig.3A. If the power supply threshold is the voltage threshold, and the control unit 30 wants to control the motor 100 to adjust the height of the platform 200A, it controls the DC / DC conversion circuit to provide the output voltage and current corresponding to the maximum output parameter (S600). Then, it detects the DC voltage (S620). The control unit 30 receives the detection signal Ss representing the amplitude of the DC voltage Vdc to realize the amplitude of the DC voltage Vdc. It then determines whether the DC voltage is greater than or equal to the voltage threshold (S640). If the DC voltage Vdc is greater than or equal to the voltage threshold, it controls the motor to accelerate (S650). The control unit 30 increases the duty cycle of the PWM signal PWM to control the DC / DC conversion circuit 104 to increase the output current I Oto increase the DC voltage Vdc to control the motor 100 to accelerate. If the DC voltage Vdc is not greater than or equal to the voltage threshold, determine whether the DC voltage is less than the voltage threshold (S660). If the DC voltage Vdc is less than the voltage threshold, control the motor to decelerate (S670). The control unit 30 decreases the duty cycle of the PWM signal PWM to control the DC / DC conversion circuit 104 to increase the output current I O to control the motor 100 to decelerate. Finally, return to step (S620) if the determination result in step (S660) is "NO".

[0033] Please see Fig. 3C, which shows a flowchart of the control method when a power supply threshold is a power threshold, and see also Fig. 1 to Fig.3A. If the power supply threshold is the power threshold, and the control unit 30 wants to control the motor 100 to adjust the height of the platform 200A, control the DC / DC conversion circuit to provide the output voltage and current corresponding to the maximum output parameter (S700). Then, detect the DC power (S720). The control unit 30 calculates the DC power Pdc based on the DC voltage Vdc and the DC current Idc and continuously monitors the increase and decrease of the DC power Pdc. Then, determine whether the DC power is not decreasing (S740). If the DC power Pdc is not decreasing, control the motor to accelerate (S750). The control unit 30 increases the duty cycle of the PWM signal PWM to increase the output current I Oof the DC / DC conversion circuit 104, thereby increasing the speed of the motor 100. If the DC power Pdc is decreased, determine whether the DC power is decreased (S760). If the DC power Pdc is decreased, control the motor to decelerate (S770). The control unit 30 decreases the duty cycle of the PWM signal PWM to increase the output current I O of the DC / DC conversion circuit 104, thereby reducing the speed of the motor 100. Finally, return to step (S720) if the determination result in step (S760) is "NO".

Claims

[1] A control circuit (1) applied to a lifting platform (200) configured to control a motor (100) to adjust the height of a platform (200A), the control circuit (1) comprising: a conversion circuit (10) configured to receive an input voltage (Vin) and provide an output voltage (Vout) to control the motor (100), the conversion circuit (10) comprising: an AC / DC conversion circuit (102) configured to convert the input voltage (Vin) into a DC voltage (Vdc), and a DC / DC conversion circuit (104) configured to convert the DC voltage (Vdc) into the output voltage (Vout), a detection unit (20) configured to detect an output end of the AC / DC conversion circuit (102) and to provide a detection signal (Ss), and a control unit (30) configured to supply a PWM signal (PWM) according to the detection signal (Ss) to control the DC / DC conversion circuit (104) so ​​that the DC / DC conversion circuit (104) converts the DC voltage (Vdc) into the output voltage (Vout), wherein the control unit (30) sets a power supply threshold; when the control unit (30) realizes, according to the detection signal (Ss), that the DC voltage (Vdc) or a DC power (Pdc) supplied by the AC / DC conversion circuit (102) is less than the power supply threshold, the control unit (30) reduces a duty cycle of the PWM signal (PWM) to reduce a rotational speed of the motor (100) and maintains the DC voltage (Vdc) or the DC power (Pdc) greater than or equal to the power supply threshold, wherein the power supply threshold is a power threshold and the AC / DC conversion circuit (102) supplies a DC current (Idc) to the DC / DC conversion circuit (104); the detection unit (20) detects the DC voltage (Vdc) and the DC current (Idc) and supplies the detection signal (Ss) to the control unit (30); the control unit (30) calculates the DC power (Pdc) according to the detection signal (Ss) and sets a maximum output power as the power threshold when the DC power (Pdc) is at the maximum output power, and reduces the duty cycle when the DC power (Pdc) is less than or equal to the maximum output power, or wherein the power supply threshold is a voltage threshold; the detection unit (20) detects the DC voltage (Vdc) and supplies the detection signal (Ss) to the control unit (30); the control unit (30) compares the detection signal (Ss) with the voltage threshold and reduces the duty cycle if the DC voltage (Vdc) corresponding to the detection signal (Ss) is less than or equal to the voltage threshold. [2] The control circuit (1) according to claim 1, wherein a power-load curve is formed by the DC voltage (Vdc) and the DC current (Idc) supplied by the AC / DC conversion circuit (102), and the control unit (30) sets the DC voltage (Vdc) corresponding to the maximum output power of the power-load curve to the voltage threshold value. [3] The control circuit (1) according to claim 1, wherein the control unit (30) sets the DC / DC conversion circuit (104) according to a maximum output parameter, so that the DC / DC conversion circuit (104) supplies the output voltage (Vout) corresponding to the maximum output parameter and an output current to the motor (100). [4] The control circuit (1) according to claim 1, wherein when the control unit (30) realizes that the DC voltage (Vdc) or the DC power (Pdc) is greater than the power supply threshold, the control unit (30) increases the duty cycle to increase the rotational speed. [5] Control circuit (1) according to claim 1, wherein the lifting platform (200) is a lifting table and the motor (100) is a DC motor. [6] Method for controlling a lifting platform (200) comprising the steps: Setting a power supply threshold and controlling a DC / DC conversion circuit (104) to convert a DC voltage (Vdc) supplied by an AC / DC conversion circuit (102) into an output voltage (Vout) to control a motor (100), Detecting an output end of the AC / DC conversion circuit (102) to provide a detection signal (Ss), and setting a PWM signal (PWM) for controlling the DC / DC conversion circuit (104) according to the detection signal (Ss), and Reducing a duty cycle of the PWM signal (PWM) to reduce a speed of the motor (100) when the DC voltage (Vdc) or a DC power (Pdc) supplied by the AC / DC conversion circuit (102) is less than the power supply threshold according to the detection signal (Ss), and maintaining the DC voltage (Vdc) or the DC power (Pdc) greater than or equal to the power supply threshold, wherein the power supply threshold is a power threshold and the AC / DC conversion circuit (102) supplies a DC current (Idc) to the DC / DC conversion circuit (104), the control method further comprising the steps of: Detecting the DC voltage (Vdc) and the DC current (Idc) to provide the detection signal (Ss), Calculating the DC power (Pdc) according to the detection signal (Ss) and setting a maximum output power as the power supply threshold when the DC power (Pdc) is tracked at the maximum output power, and Reducing the duty cycle when the DC power (Pdc) is less than or equal to the maximum output power, or wherein the power supply threshold is a voltage threshold and the control method further comprises the steps of: Detecting the DC voltage (Vdc) to provide the detection signal (Ss), and Realizing the DC voltage (Vdc) according to the detection signal (Ss) and comparing the DC voltage (Vdc) with the voltage threshold to reduce the duty cycle when the DC voltage (Vdc) is less than or equal to the voltage threshold, wherein a power-load curve is formed by the DC voltage (Vdc) and the DC current (Idc) supplied by the AC / DC conversion circuit (102), and the DC voltage (Vdc) corresponding to a maximum output power of the power-load curve is set to the voltage threshold value. [7] The method of claim 6, wherein the control method further comprises a step: Setting the DC / DC conversion circuit (104) according to a maximum output parameter such that the DC / DC conversion circuit (104) supplies the output voltage (Vout) corresponding to the maximum output parameter and an output current to the motor (100). [8] The method of claim 6, wherein the control method further comprises a step: Increasing the duty cycle to increase the speed when the DC voltage (Vdc) or the DC power (Pdc) is greater than the power supply threshold, according to the detection signal (Ss).

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