Control circuit for a lifting platform and control method thereof

Abstract

The present application provides a control circuit for a lifting platform and a control method thereof, wherein the control circuit is used to control a motor to adjust the height of the platform, and the control circuit comprises an AC / DC conversion circuit, a DC / DC conversion circuit, a detection unit and a control unit. The detection unit detects the output end of the AC / DC conversion circuit to provide a detection signal, and the control unit provides a pulse width modulation signal to control the DC / DC conversion circuit according to the detection signal, so that the DC / DC conversion circuit converts a DC voltage into an output voltage. When the control unit knows that the DC voltage or the DC power provided by the AC / DC conversion circuit is less than a power threshold value through the detection signal, the duty cycle of the pulse width modulation signal is reduced to maintain the DC voltage or the DC power greater than or equal to the power threshold value, so as to improve the load capacity of the lifting platform.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of automation control technology, and in particular, to a control circuit for maintaining maximum output power of a lifting platform and a control method thereof. BACKGROUND

[0002] Modern people need a new tool to improve the poor circulation caused by sitting for a long time. Therefore, in order to meet the comfort and ergonomic design of personal work, the application of height-adjustable lifting table is becoming more and more popular. In the application of lifting table, manual, pneumatic or electric methods are usually used to adjust the height of the table body. The control method of adjusting the height of the table body by the electric method is more precise, and the adjustment effect is better, so the application range of the electric lifting table is more extensive.

[0003] However, when the load of the conventional electric lifting table is increased, if the maximum output power of the converter is exceeded, the output power of the converter will always decrease, resulting in poor load capacity, and the electric lifting table will not rise when the load is heavy. Therefore, the solution of the prior art is usually to replace the converter with a larger output power to increase the output power of the converter, so as to be able to push a heavier load. However, such a solution will increase the cost of the electric lifting table, and the circuit will be bulky.

[0004] Therefore, how to design a control circuit for a lifting platform and a control method thereof, which uses a conversion circuit to control the lifting table to maintain the load capacity of the conversion circuit, and solves the problem of poor load capacity of the lifting table of the prior art and the lifting table not rising when the load is heavy, is a major research topic for the present inventor. SUMMARY

[0005] In order to solve the above problems, the present application provides a control circuit for a lifting platform, which controls the height of the platform by a motor. The control circuit comprises a conversion circuit, a detection unit and a control unit. The conversion circuit receives an input voltage and provides an output voltage to control the motor. The conversion circuit comprises an AC / DC conversion circuit and a DC / DC conversion circuit. The AC / DC conversion circuit converts the input voltage into a DC voltage, and the DC / DC conversion circuit converts the DC voltage into the output voltage. The detection unit detects the output end of the AC / DC conversion circuit to provide a detection signal. The control unit provides a pulse width modulation signal to control the DC / DC conversion circuit according to the detection signal, so that the DC / DC conversion circuit converts the DC voltage into the output voltage. The control unit sets a power threshold value. When the control unit knows through the detection signal that the DC voltage or the DC power provided by the AC / DC conversion circuit is less than the power threshold value, the duty cycle of the pulse width modulation signal is reduced to reduce the speed of the motor, and the DC voltage or the DC power is maintained to be greater than or equal to the power threshold value.

[0006] As another embodiment of the present application, the power threshold is a power threshold, and the AC / DC conversion circuit provides a DC current to the DC / DC conversion circuit; the detection unit detects the DC voltage and the DC current to provide the detection signal to the control unit, the control unit calculates the DC power according to the detection signal, and tracks the DC power at a maximum output power, sets the maximum output power as the power threshold, to reduce the duty cycle according to the DC power less than or equal to the maximum output power.

[0007] As another embodiment of the present application, the power threshold is a voltage threshold; the detection unit detects the DC voltage to provide the detection signal to the control unit, and the control unit compares the detection signal with the voltage threshold, to reduce the duty cycle according to the DC voltage corresponding to the detection signal less than or equal to the voltage threshold.

[0008] As another embodiment of the present application, the DC voltage and the AC / DC conversion circuit providing a DC current form a power load curve, and the control unit sets the DC voltage corresponding to a maximum output power in the power load curve as the voltage threshold.

[0009] As another embodiment of the present application, the control unit sets the DC / DC conversion circuit according to a maximum output parameter, so that the DC / DC conversion circuit provides the output voltage and an output current corresponding to the maximum output parameter to the motor.

[0010] As another embodiment of the present application, when the control unit knows that the DC voltage or the DC power is greater than the power threshold through the detection signal, the control unit increases the duty cycle to increase the rotation speed.

[0011] As another embodiment of the present application, the lifting platform is a lifting table, and the motor is a DC motor.

[0012] To solve the above problems, the present application also provides a control method for a lifting platform to overcome the problems of the known art. Therefore, the control method for a lifting platform of the present application comprises the following steps: setting a power threshold, and controlling a DC / DC conversion circuit to convert a DC voltage provided 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 pulse width modulation signal for controlling the DC / DC conversion circuit according to the detection signal. And when it is known through the detection signal that the DC voltage or the DC power provided by the AC / DC conversion circuit is less than the power threshold, reducing the duty cycle of the pulse width modulation signal to reduce the rotation speed of the motor, and maintaining the DC voltage or the DC power greater than or equal to the power threshold.

[0013] As another embodiment of the present application, the power threshold is a power threshold, and the AC / DC conversion circuit provides a direct current to the DC / DC conversion circuit, the control method further comprises: detecting the direct voltage and the direct current to provide the detection signal; calculating the direct power according to the detection signal, and tracking the direct power at a maximum output power, setting the maximum output power as the power threshold; and reducing the duty cycle according to the direct power being less than or equal to the maximum output power.

[0014] As another embodiment of the present application, the power threshold is a voltage threshold, the control method further comprises: detecting the direct voltage to provide the detection signal; and obtaining the direct voltage through the detection signal, and comparing the direct voltage with the voltage threshold, to reduce the duty cycle according to the direct voltage being less than or equal to the voltage threshold; wherein the direct voltage and the change of the direct current provided by the AC / DC conversion circuit constitute a power load curve, and the direct voltage corresponding to a maximum output power in the power load curve is set as the voltage threshold.

[0015] As another embodiment of the present application, the control method further comprises: setting the DC / DC conversion circuit according to a maximum output parameter, so that the DC / DC conversion circuit provides the output voltage and an output current corresponding to the maximum output parameter to the motor.

[0016] As another embodiment of the present application, the control method further comprises: when the direct voltage or the direct power obtained through the detection signal is greater than the power threshold, increasing the duty cycle to increase the rotating speed.

[0017] The main purpose and effect of the present application is to detect the maximum output power of the AC / DC conversion circuit by the control unit, to maintain the load capacity of the conversion circuit, and to solve the poor load capacity and the problem that the lifting platform cannot be raised in the prior art. Therefore, the speed of the lifting table can be controlled to be faster than that of the lifting table in the prior art when the lifting platform is under heavy load.

[0018] In order to further understand the technology, means and effects taken by the present application to achieve the predetermined purpose, please refer to the following detailed description of the present application and the accompanying drawings, and it is believed that the purpose, features and characteristics of the present application can be understood in depth and specifically from the drawings. The accompanying drawings are provided for reference and illustration only, and are not intended to limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 Block diagram of the control circuit for the lifting platform of the present application;

[0020] Figure 2 Power load curve of the converter in the present application;

[0021] Figure 3A Method flowchart for the control method of the lifting platform of the present application;

[0022] Figure 3B Method flowchart for the control method of the present application when the power threshold is a voltage threshold; and

[0023] Figure 3C Method flowchart for the control method of the present application when the power threshold is a power threshold.

[0024] Explanation of symbols in the drawings:

[0025] 1… Control circuit

[0026] 10… Conversion circuit

[0027] 102… AC / DC conversion circuit

[0028] 104… DC / DC conversion circuit

[0029] 20… Detection unit

[0030] 30… Control unit

[0031] 100… Motor

[0032] 200… Lifting platform

[0033] 200A… Platform

[0034] Vin… Input voltage

[0035] Vdc… DC voltage

[0036] Idc… DC current

[0037] Pdc… DC power

[0038] Vout… Output voltage

[0039] Io… Output current

[0040] Ss… Detection signal

[0041] PWM… Pulse width modulation signal

[0042] A, B… Curve

[0043] S100-S770… Step DETAILED DESCRIPTION

[0044] Now, the technical content and detailed description of the present application are explained as follows in conjunction with the drawings:

[0045] Please refer to Figure 1A block diagram of a control circuit for a lift platform. The control circuit 1 controls a motor 100 to adjust the height of a platform 200A, and the platform 200A can be a table body (such as, but not limited to, an office table, a coffee table, etc. that is not used to carry heavy tools or large building materials), so the lift platform 200 is a lift table. The control circuit 1 includes a conversion circuit 10, a detection unit 20, and a control unit 30, and the conversion circuit 10 can be an isolated or non-isolated DC converter. Among them, the conversion circuit 10 includes an AC / DC conversion circuit 102 receiving an AC input voltage Vin and a DC / DC conversion circuit 104 receiving a DC voltage Vdc. The motor 100 can be a DC motor, which has the characteristics of easy speed regulation, smooth speed regulation, and large overload capacity, and is particularly suitable for use in electric table structures for personal office or reading.

[0046] Referring back to Figure 1 , the AC / DC conversion circuit 102 receives the input voltage Vin, and converts the input voltage Vin into a DC voltage Vdc to provide the DC voltage Vdc to the DC / DC conversion circuit 104. The DC / DC conversion circuit 104 receives the DC voltage Vdc and converts the DC voltage Vdc into an output voltage Vout to provide the output voltage Vout to control the motor 100. Among them, the DC / DC conversion circuit 104 also provides an output current Io to control the motor 100. The detection unit 20 is coupled to the output end of the AC / DC conversion circuit 102, and provides a detection signal Ss according to the detection result. The control unit 30 is coupled to the power switch (not shown in the figure) of the DC / DC conversion circuit 104 and the detection unit 20, and provides a pulse width modulation 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 through the switching of the power switch. During the operation of the DC / DC conversion circuit 104, the control unit 30 adjusts the duty cycle of the pulse width modulation signal PWM according to the detection signal Ss to adjust the output voltage Vout, so as to adjust the speed of the motor 100 by adjusting the output voltage Vout (the size of the output voltage Vout corresponds to the speed of the motor 100).

[0047] Further, please refer to Figure 2 The power load curve of the converter in the present application, and please refer to Figure 1 and Table 1 below. Among them, Figure 2The curve A is plotted by the points of the DC power Pdc curve in Table 1 for the input voltage Vin (100 V / 50 Hz), and the curve B is plotted by the points of the DC power Pdc curve in Table 1 for the input voltage Vin (240 V / 50 Hz), which are only examples of the parameters of the two different types of conversion circuit 10, but not limited to these parameters. Since the prior art boost-buck platform control circuit continuously increases the output current Io of the DC / DC conversion circuit 104 to push the platform 200A when the load of the platform 200A is heavier, when the output current Io continuously increases to the point that the DC power Pdc provided by the AC / DC conversion circuit 102 exceeds the maximum output power, the increase of the output current Io only causes the DC power Pdc provided by the AC / DC conversion circuit 102 to decrease instead of increasing, resulting in the DC current Idc of the AC / DC conversion circuit 102 continuously increasing, but the DC voltage Vdc continuously decreasing, so that the boost-buck platform control circuit 1 causes the load of the platform 200A to fail to rise when the load of the platform 200A is heavy due to the poor load capacity caused by the continuously decreasing DC voltage Vdc.

[0048] Table 1: Output voltage and output current relationship table of the conversion circuit

[0049]

[0050] However, the main purpose and effect of the present application is that the control unit 30 detects the maximum output power of the AC / DC conversion circuit 102 to maintain the load capacity of the conversion circuit 10 and solve the condition that the load of the platform 200A fails to rise when the load of the platform 200A is heavy. Specifically, the control unit 30 of the present application sets a power threshold value at the output end of the AC / DC conversion circuit 102, and when the control unit 30 learns from the detection signal Ss that the DC voltage Vdc or the DC power Pdc is less than the power threshold value, the duty cycle of the pulse width modulation signal PWM is adjusted to reduce the speed of the motor 100, and the DC voltage Vdc or the DC power Pdc is maintained to be greater than or equal to the power threshold value. When the control unit 30 learns from the detection signal Ss that the DC voltage Vdc or the DC power Pdc is greater than or equal to the power threshold value, the duty cycle of the pulse width modulation signal PWM is adjusted to increase the speed of the motor 100 to speed up the adjustment speed of the lift platform 200.

[0051] Referring back to Figures 1-2 , the control unit 30 includes two control and setting methods. One of them is that the control unit 30 adjusts the speed of the motor 100 according to the DC voltage Vdc or the DC power Pdc detected by the detection signal Ss, and the other is that the control unit 30 adjusts the speed of the motor 100 according to the DC current Idc detected by the detection signal Ss. Figure 2The power source load curve shown sets a power source threshold. Specifically, the power source load curve is a direct current power Pdc curve formed by the product of a direct current voltage Vdc and a direct current Idc. The control unit 30 sets the voltage value of the direct current voltage Vdc corresponding to the maximum output power point of the direct current power Pdc as the power source threshold (the power source threshold is a voltage threshold) in advance. Then, the detection unit 20 detects the direct current voltage Vdc to provide a detection signal Ss representing the magnitude of the direct current voltage Vdc. The control unit 30 receives the detection signal Ss representing the magnitude of the direct current voltage Vdc to learn the magnitude of the direct current voltage Vdc. Then, the control unit 30 compares the direct current voltage Vdc with the voltage threshold to determine whether to limit the duty cycle of the pulse width modulation signal PWM.

[0052] Specifically, when the direct current voltage Vdc is greater than the voltage threshold, the control unit 30 increases the duty cycle of the pulse width modulation signal PWM to increase the output current Io output by the direct current / direct current conversion circuit 104, thereby increasing the rotation speed of the motor 100. When the direct current voltage Vdc is less than or equal to the voltage threshold, the control unit 30 decreases the duty cycle of the pulse width modulation signal PWM to decrease the output current Io output by the direct current / direct current conversion circuit 104, thereby decreasing the rotation speed of the motor 100. Since the output current Io is decreased, the direct current voltage Vdc no longer continuously decreases to maintain the direct current power Pdc of the alternating current / direct current conversion circuit 102 at the maximum output power, so that the speed of the lifting platform 200A is slowed down but the platform 200A does not fail to rise as in the known art. Therefore, the lifting table of the present application can improve the lifting speed of the platform 200A under heavy load conditions compared with the prior art.

[0053] Another control and setting method is that the detection unit 20 detects the direct current voltage Vdc and the direct current Idc to provide a detection signal Ss representing the direct current voltage Vdc and the direct current Idc. The control unit 30 receives the detection signal Ss representing the magnitudes of the direct current voltage Vdc and the direct current Idc to learn the magnitudes of the direct current voltage Vdc and the direct current Idc. Then, the control unit 30 calculates the direct current power Pdc according to the direct current voltage Vdc and the direct current Idc, and continuously tracks the rising and falling conditions of the direct current power Pdc when the direct current Idc rises. When the direct current Idc rises but the direct current power Pdc decreases instead, the control unit 30 sets the direct current power Pdc of the previous pen as the maximum output power, and sets this direct current power Pdc as a power threshold (the power threshold is a power threshold). Then, the control unit 30 compares the current direct current power Pdc with the power threshold to correspondingly adjust the duty cycle of the pulse width modulation signal PWM.

[0054] When the DC power Pdc is greater than the power threshold, the control unit 30 adjusts the duty cycle of the pulse width modulation signal PWM to increase the output current Io outputted by the DC / DC conversion circuit 104, and thus to increase the rotation speed of the motor 100. When the DC power Pdc is less than or equal to the power threshold, the control unit 30 adjusts the duty cycle of the pulse width modulation signal PWM to decrease the output current Io outputted by the DC / DC conversion circuit 104, and thus to decrease the rotation speed of the motor 100. As the output current Io is decreased, the DC power Pdc will not continuously decrease, so as to maintain the DC power Pdc outputted by the AC / DC conversion circuit 102 at the maximum output power. Thus, the speed of the lifting platform 200A is slowed down, but the platform 200A will not be stuck as in the prior art. The speed of the lifting platform 200A under heavy load is also improved.

[0055] Further, the relationship between the output voltage Vo and the pulse width modulation signal PWM can be, for example but not limited to, as shown in Table 2. When the output current Io is large enough, the DC voltage Vdc will decrease according to Table 1 and Figure 2 It can be seen that the DC voltage Vdc will decrease. The control unit 30 controls the pulse width modulation signal PWM to decrease according to the decrease of the DC voltage Vdc, so as to decrease the output voltage Vo and thus decrease the rotation speed of the motor 100. As the rotation speed of the motor 100 decreases, the output current Io also decreases, so as to increase the DC voltage Vdc. Through the circuit characteristics and the setting of the power threshold, the load capacity of the conversion circuit 10 can be maintained, and the situation that the platform 200A is stuck under heavy load can be solved. The main control method is to maintain the DC voltage Vdc outputted by the AC / DC conversion circuit 102 above a certain voltage, and the output voltage Vo is adjusted within a certain range (for example but not limited to, 0V~33V) according to the pulse width modulation signal PWM.

[0056] Table 2: Relationship table of output voltage and pulse width modulation signal

[0057] Pulse width modulation signal PWM Output voltage Vo 100% 32V 70% 32V * 0.7]]> 30% 32V * 0.3]]> 10% 32V * 0.1]]>

[0058] Referring back to Figure 2, the power threshold value, the control circuit 1 can directly control the maximum power lifting platform 200, and then adjust the pulse width modulation signal PWM according to the detection unit 20 to detect the actual operation of the conversion circuit 10, so as to save the time of the lifting platform 200. One of them is that the control unit 30 performs preloading (gradually increases the output current Io) before the control circuit 1 actually operates, so as to obtain the change of the corresponding DC voltage Vdc and DC current Idc (which can be memorized by an internal memory or manually operated). Then, the maximum output power calculated in the process of its change (i.e. the parameter corresponding to the DC power Pdc before the memory starts to change when the DC power Pdc starts to change is the maximum output parameter), so as to directly control the DC / DC conversion circuit 104 according to the memorized maximum output parameter in the actual lifting operation of the platform 200A, and adjust the duty cycle of the pulse width modulation signal PWM according to the comparison between the detection signal Ss and the power threshold value at that time.

[0059] Another way is to pre-set the parameter corresponding to the maximum output power of the AC / DC conversion circuit 102 (i.e. the maximum output parameter) 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 it wants to control the lifting of the platform 200A. Among them, the parameter of the AC / DC conversion circuit 102 when it is at the maximum output power (i.e. the maximum output parameter) can usually be obtained from the specification of the AC / DC conversion circuit 102. Then, the control unit 30 adjusts the duty cycle of the pulse width modulation signal PWM according to the comparison between the feedback generated by the DC voltage Vdc or the DC power Pdc and the power threshold value.

[0060] It is worth mentioning that the speed of the motor 100 can be designed in many ways. Specifically, if the lifting speed of the platform 200A is too fast or too slow, it will cause inconvenience to the user in use, and even cause accidents. Therefore, the control unit 30 can set the lifting (or lowering) of the platform 200A to have a step-by-step or speed-limited function, so as to slow down the speed of the platform 200A, and avoid the lifting (or lowering) of the platform 200A being too fast.

[0061] Please refer to Figure 3A The method flowchart of the control method for the lifting platform of the present application, and Figures 1-2The control method for the lifting platform is to adjust the height of the platform 200A by controlling the motor 100, and the platform 200A can be a table body (such as but not limited to an office table, a tea table, etc. which is not used to carry heavy tools or large building materials). The control method first includes: setting a power threshold, and controlling the DC / DC conversion circuit to convert the DC voltage provided by the AC / DC conversion circuit into an output voltage to control the motor (S100). In a preferred embodiment, the control unit 30 sets the power threshold, and provides a pulse width modulation signal PWM to control the switching of the power switch, so that the DC / DC conversion circuit 104 converts the DC voltage Vdc into the output voltage Vout through the switching of the power switch.

[0062] Then, the output end of the AC / DC conversion circuit is detected to provide a detection signal, and the pulse width modulation signal for controlling the DC / DC conversion circuit is adjusted according to the detection signal (S200). During the operation of the conversion circuit 10, the control unit 30 adjusts the duty cycle of the pulse width modulation signal PWM according to the detection signal Ss detected at the output end of the AC / DC conversion circuit 102 to adjust the output voltage Vout, so as to adjust the rotating speed of the motor 100 by adjusting the output voltage Vout.

[0063] Then, when the DC voltage or DC power is less than the power threshold through the detection signal, the duty cycle of the pulse width modulation signal is adjusted to reduce the rotating speed of the motor, and the DC voltage or DC power is maintained to be greater than or equal to the power threshold (S300). When the control unit 30 knows through the detection signal Ss that the DC voltage Vdc or the DC power Pdc is less than the power threshold, the duty cycle of the pulse width modulation signal PWM is adjusted to reduce the rotating speed of the motor 100, and the DC voltage Vdc or the DC power Pdc is maintained to be greater than or equal to the power threshold. In this way, the phenomenon that the platform 200A cannot be lifted due to the DC voltage Vdc or the DC power Pdc being too low when the load of the platform 200A is heavy can be solved. Then, when the DC voltage or DC power is greater than the power threshold through the detection signal, the duty cycle is adjusted to increase the rotating speed (S400). When the control unit 30 knows through the detection signal Ss that the DC voltage Vdc or the DC power Pdc is greater than or equal to the power threshold, the duty cycle of the pulse width modulation signal PWM is adjusted to increase the rotating speed of the motor 100, so as to speed up the adjustment speed of the lifting platform 200.

[0064] When the control unit 30 intends to adjust the height of the platform 200A, the control unit 30 can control the DC / DC conversion circuit 104 according to the preset maximum output parameter (S500). The operation mode of the maximum output parameter can be preloaded by the control unit 30 (gradually increase the output current Io) to obtain the corresponding changes of the DC voltage Vdc and the DC current Idc (which can be memorized by the internal memory or manually operated). Then, the maximum output power calculated in the process of the changes (i.e. the parameter corresponding to the last DC power Pdc when the DC power Pdc starts to change is the maximum output parameter) is used to control the DC / DC conversion circuit 104 according to the memorized maximum output parameter in the actual lifting operation of the platform 200A, and the duty cycle of the pulse width modulation signal PWM is adjusted according to the comparison between the detection signal Ss and the power threshold value.

[0065] Alternatively, the control unit 30 can preset the parameters corresponding to the maximum output power of the conversion circuit 10 (i.e. the maximum output parameter) 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 it intends to control the lifting of the platform 200A. The parameters of the AC / DC conversion circuit 102 when it is at the maximum output power (i.e. the maximum output parameter) can be obtained from the specification of the AC / DC conversion circuit 102. Then, the control unit 30 adjusts the duty cycle of the pulse width modulation signal PWM according to the comparison between the feedback of the DC voltage Vdc or the DC power Pdc and the power threshold value.

[0066] It is worth mentioning that the speed-up of the motor 100 can have various humanized designs, so step (S500) is not necessary. Specifically, if the lifting speed of the platform 200A is too fast or too slow, it will cause inconvenience to the user in use, and even the possibility of an accident. Therefore, the control unit 30 can set the step-by-step or speed-limited function of the platform 200A to slow down the speed of the platform 200A to avoid the platform 200A from being lifted (or lowered) too fast.

[0067] Please refer to Figure 3B For the control method flow chart of the power threshold value as the voltage threshold value in the present application, please refer to Figures 1-3BWhen the power threshold is the power threshold and the control unit 30 wants to control the motor 100 to adjust the height of the platform 200A, first, the DC / DC conversion circuit is controlled to provide the output voltage and the output current corresponding to the maximum output parameter (S600). Then, the DC voltage is detected (S620). The control unit 30 receives the detection signal Ss representing the size of the DC voltage Vdc to know the size of the DC voltage Vdc. Then, it is confirmed that the DC voltage is greater than or equal to the voltage threshold (S640). When the DC voltage Vdc is greater than or equal to the voltage threshold, the motor is controlled to accelerate (S650). The control unit 30 increases the duty cycle of the pulse width modulation signal PWM to control the DC / DC conversion circuit 104 to increase the output current Io and control the motor 100 to accelerate. When the DC voltage Vdc is not greater than or equal to the voltage threshold, it is confirmed that the DC voltage is less than the voltage threshold (S660). When the DC voltage Vdc is less than the voltage threshold, the motor is controlled to decelerate (S670). The control unit 30 decreases the duty cycle of the pulse width modulation signal PWM to control the DC / DC conversion circuit 104 to decrease the output current Io and control the motor 100 to decelerate. Finally, when the judgment of step (S660) is "No", return to step (S620).

[0068] Please refer to Figure 3C For the control method flowchart when the power threshold is the power threshold in the present application, please also refer to Figures 1-3A When the power threshold is the power threshold and the control unit 30 wants to control the motor 100 to adjust the height of the platform 200A, first, the DC / DC conversion circuit is controlled to provide the output voltage and the output current corresponding to the maximum output parameter (S700). Then, the DC power is detected (S720). The control unit 30 calculates the DC power Pdc according to the DC voltage Vdc and the DC current Idc, and continuously tracks the rising and falling of the DC power Pdc. Then, it is confirmed that the DC power does not become smaller (S740). When the DC power Pdc does not become smaller, the motor is controlled to accelerate (S750). The control unit 30 increases the duty cycle of the pulse width modulation signal PWM to increase the output current Io output by the DC / DC conversion circuit 104, thereby increasing the speed of the motor 100. When the DC power Pdc becomes smaller, it is confirmed that the DC power becomes smaller (S760). When the DC power Pdc becomes smaller, the motor is controlled to decelerate (S770). The control unit 30 decreases the duty cycle of the pulse width modulation signal PWM to decrease the output current Io output by the DC / DC conversion circuit 104, thereby decreasing the speed of the motor 100. Finally, when the judgment of step (S760) is "No", return to step (S720).

[0069] The above merely describes the preferred embodiments of the present application in detail and with reference to the drawings, but the features of the present application are not limited thereto, and are not intended to limit the present application. The scope of the present application should be based on the following patent claims, and any embodiments similar to the spirit of the present application should be included in the scope of the present application. Any changes or modifications in the field of the present application can be covered by the patent scope of the present application.

Claims

1. A control circuit for a lifting platform, characterized in that it controls a motor to adjust the height of a platform. The control circuit includes: A conversion circuit receives an input voltage and provides an output voltage to control the motor. The conversion circuit includes: An AC / DC converter circuit converts the input voltage into a DC voltage; and A DC / DC converter circuit that converts the DC voltage to the output voltage; A detection unit detects the output of the AC / DC conversion circuit and provides a detection signal; and A control unit provides a pulse width modulation signal based on 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 threshold. When the control unit detects through the detection signal that the DC voltage or the DC power provided by the AC / DC conversion circuit is less than the power threshold, it reduces the duty cycle of the pulse width modulation signal to reduce the speed of the motor and maintain the DC voltage or the DC power greater than or equal to the power threshold. The power threshold is a power threshold, and the AC / DC conversion circuit provides DC current to the DC / DC conversion circuit. The detection unit detects the DC voltage and the DC current and provides the detection signal to the control unit. The control unit calculates the DC power based on the detection signal and tracks the DC power. When the DC power reaches a maximum output power, it sets the maximum output power as the power threshold, and reduces the duty cycle when the DC power is less than or equal to the maximum output power.

2. The control circuit according to claim 1, characterized in that, The control unit sets the DC / DC converter circuit according to a maximum output parameter, so that the DC / DC converter circuit provides the output voltage and an output current corresponding to the maximum output parameter to the motor.

3. The control circuit according to claim 1, characterized in that, When the control unit detects through the detection signal that the DC voltage or DC power is greater than the power supply threshold, the control unit increases the duty cycle and thus increases the speed.

4. The control circuit according to claim 1, characterized in that, The lifting platform is a lifting table, and the motor is a DC motor.

5. A control circuit for a lifting platform, characterized in that it controls a motor to adjust the height of a platform. The control circuit includes: A conversion circuit receives an input voltage and provides an output voltage to control the motor. The conversion circuit includes: An AC / DC converter circuit converts the input voltage into a DC voltage; and A DC / DC converter circuit that converts the DC voltage to the output voltage; A detection unit detects the output of the AC / DC conversion circuit and provides a detection signal; and A control unit provides a pulse width modulation signal based on 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 threshold; when the control unit detects through the detection signal that the DC voltage or the DC power provided by the AC / DC conversion circuit is less than the power threshold, it reduces a duty cycle of the pulse width modulation signal to reduce a speed of the motor, while maintaining the DC voltage or the DC power greater than or equal to the power threshold; and The power supply threshold is a voltage threshold; the detection unit detects the DC voltage and provides the detection signal to the control unit, and the control unit compares the detection signal with the voltage threshold to reduce the duty cycle based on the DC voltage corresponding to the detection signal being less than or equal to the voltage threshold.

6. The control circuit according to claim 5, characterized in that, The change in DC voltage and the DC current provided by the AC / DC conversion circuit constitute a power load curve, and the control unit sets the DC voltage corresponding to a maximum output power in the power load curve as the voltage threshold.

7. The control circuit according to claim 5, characterized in that, The control unit sets the DC / DC converter circuit according to a maximum output parameter, so that the DC / DC converter circuit provides the output voltage and an output current corresponding to the maximum output parameter to the motor.

8. The control circuit according to claim 5, characterized in that, When the control unit detects through the detection signal that the DC voltage or DC power is greater than the power supply threshold, the control unit increases the duty cycle and thus increases the speed.

9. The control circuit according to claim 5, characterized in that, The lifting platform is a lifting table, and the motor is a DC motor.

10. A control method for a lifting platform, characterized in that, Includes the following steps: A power threshold is set, and a DC / DC converter is controlled to convert the DC voltage provided by an AC / DC converter into an output voltage to control a motor. The output of the AC / DC converter circuit is detected and a detection signal is provided, and a pulse width modulation signal controlling the DC / DC converter circuit is adjusted according to the detection signal. When the detection signal indicates that the DC voltage or the DC power provided by the AC / DC converter circuit is less than the power supply threshold, the duty cycle of the pulse width modulation signal is reduced to decrease the speed of the motor, while maintaining the DC voltage or the DC power greater than or equal to the power supply threshold; wherein the power supply threshold is a power threshold, and the AC / DC converter circuit provides DC current to the DC / DC converter circuit, the control method further includes: The detection signal is provided by detecting the DC voltage and the DC current. The DC power is calculated based on the detected signal, and the DC power is tracked to a maximum output power, at which point the maximum output power is set as the power supply threshold; and The duty cycle is reduced based on the DC power being less than or equal to the maximum output power.

11. The control method according to claim 10, characterized in that, The control method also includes: The DC / DC converter circuit is configured according to a maximum output parameter, so that the DC / DC converter circuit provides the output voltage and an output current corresponding to the maximum output parameter to the motor.

12. The control method according to claim 10, characterized in that, The control method also includes: When the detection signal indicates that the DC voltage or DC power is greater than the power supply threshold, the duty cycle is increased to increase the rotational speed.

13. A control method for a lifting platform, characterized in that, Includes the following steps: A power threshold is set, and a DC / DC converter is controlled to convert the DC voltage provided by an AC / DC converter into an output voltage to control a motor. The output of the AC / DC converter circuit is detected and a detection signal is provided, and a pulse width modulation signal controlling the DC / DC converter circuit is adjusted according to the detection signal. When the detection signal indicates that the DC voltage or the DC power provided by the AC / DC conversion circuit is less than the power supply threshold, the duty cycle of the pulse width modulation signal is reduced to reduce the speed of the motor, while maintaining the DC voltage or the DC power greater than or equal to the power supply threshold. Wherein, the power supply threshold is a voltage threshold, and the control method further includes: The detection signal is provided by detecting the DC voltage; and The DC voltage is obtained through the detection signal, and the DC voltage is compared with the voltage threshold. The duty cycle is reduced if the DC voltage is less than or equal to the voltage threshold. The DC voltage and the change in DC current provided by the AC / DC conversion circuit constitute a power load curve, and the DC voltage corresponding to a maximum output power in the power load curve is set as the voltage threshold.

14. The control method according to claim 13, characterized in that, The control method also includes: The DC / DC converter circuit is configured according to a maximum output parameter, so that the DC / DC converter circuit provides the output voltage and an output current corresponding to the maximum output parameter to the motor.

15. The control method according to claim 13, characterized in that, The control method also includes: When the detection signal indicates that the DC voltage or DC power is greater than the power supply threshold, the duty cycle is increased to increase the rotational speed.

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