Inverter DC bus capacitor charging circuit

Abstract

This utility model discloses a DC bus capacitor charging circuit for a frequency converter, comprising: a slow charging unit, a controllable fast charging unit, a control signal input unit, a controller, and a capacitor charging unit. The input terminals of both the slow charging unit and the controllable fast charging unit are connected to the positive output terminal of the DC power supply in the elevator system. The output terminals of both the slow charging unit and the controllable fast charging unit are connected to the positive terminal of the capacitor charging unit. The output terminal of the capacitor charging unit is grounded. The control terminal of the controllable fast charging unit is connected to the controllable signal input unit, and the control terminal of the control signal input unit is connected to the output terminal of the controller. This DC bus capacitor charging circuit for a frequency converter solves the problem in existing capacitor charging circuits that cannot control the charging speed.

Description

Technical Field

[0001] This utility model relates to capacitor charging circuits, specifically to a DC bus capacitor charging circuit for a frequency converter. Background Technology

[0002] In the prior art, the capacitor charging circuit includes: a charging capacitor, the positive terminal of which is connected to the output terminal of the power supply, and the negative terminal of which is grounded. When the power supply is powered, the charging capacitor is charged, and when the power supply is not powered, the charging capacitor can discharge.

[0003] The elevator system includes: a DC power supply, a frequency converter, a motor, a controller, and a capacitor charging circuit. The DC input terminal of the frequency converter is connected to the DC power supply, the AC output terminal of the frequency converter is connected to the motor power supply, the control terminal of the frequency converter is connected to the output terminal of the controller, and the controller controls the rotation speed of the motor by controlling the operation of the frequency converter. The positive terminal of the capacitor charging circuit is connected to the positive voltage output terminal of the DC power supply.

[0004] Although a capacitor charging circuit with only a charging capacitor can be used to charge the elevator system, if there is a short circuit between the DC input and AC output terminals of the frequency converter, and the capacitor charging circuit cannot control the charging speed, the capacitor charging circuit is also prone to damage. Utility Model Content

[0005] This utility model provides a DC bus capacitor charging circuit for a frequency converter, which solves the problem that existing capacitor charging circuits cannot control the charging speed.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: The present invention discloses a DC bus capacitor charging circuit for a frequency converter, comprising: a slow charging unit, a controllable fast charging unit, a control signal input unit, a controller, and a capacitor charging unit; the input terminals of the slow charging unit and the controllable fast charging unit are both connected to the positive output terminal of the DC power supply in the elevator system, the output terminals of the slow charging unit and the controllable fast charging unit are both connected to the positive terminal of the capacitor charging unit, the output terminal of the capacitor charging unit is grounded, the control terminal of the controllable fast charging unit is connected to the controllable signal input unit for control, and the control terminal of the control signal input unit is connected to the output terminal of the controller.

[0007] Preferably, the control signal input unit includes: a light-emitting part and a first controllable switch part, the positive terminal of the light-emitting part is connected to the first output terminal of a low-voltage power supply, the negative terminal of the light-emitting part is grounded through the first controllable switch part, and the control terminal of the first controllable switch part is the control terminal of the control signal input unit.

[0008] Preferably, the controllable fast charging unit is provided with a second controllable switch, and the second controllable switch and the light-emitting part constitute a first optocoupler U1.

[0009] Preferably, the first optocoupler U1 is a switching transistor type optocoupler.

[0010] Preferably, the controllable fast charging unit further includes: a diode D1, the anode of the diode D1 being the input terminal of the controllable fast charging unit, the cathode of the diode D1 being connected to the collector of the second controllable switch, and the emitter of the second controllable switch being the output terminal of the controllable fast charging unit.

[0011] Preferably, the slow charging unit includes: a resistor R1, the first end of which is the input terminal of the slow charging unit, and the second end of which is the output terminal of the slow charging unit.

[0012] Preferably, the first controllable switch is a switching transistor Q1, the base of the switching transistor Q1 is the control terminal of the first controllable switch, the collector of the switching transistor Q1 is connected to the negative terminal of the light-emitting part, and the emitter of the switching transistor Q1 is grounded.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] In this application, a slow charging unit and a controllable fast charging unit are connected in parallel. Both the slow charging unit and the controllable fast charging unit can charge the capacitor charging unit. The slow charging unit uses a resistor R1 with a large resistance value, and the current through the slow charging unit is small. This allows the slow charging unit to slowly charge the capacitor charging unit before the controllable fast charging unit is closed. The controllable fast charging unit has a small resistance value, and the controllable fast charging power supply can be closed or not under the control of the controller. This allows the controller to control whether fast charging is performed, thus enabling the entire capacitor charging unit to be fast or slow charged under the control of the controller. The controller's control can protect the capacitor charging unit and extend its service life.

[0015] Other advantages, objectives and features of this invention will be partly apparent from the following description, and partly understood by those skilled in the art through study and practice of this invention. Attached Figure Description

[0016] Figure 1 Circuit diagram of the DC bus capacitor charging circuit for the frequency converter. Detailed Implementation

[0017] To make the technical means, creative features, achieved objectives and functions of this utility model clearer and easier to understand, the utility model will be further described below with reference to the accompanying drawings and specific embodiments:

[0018] like Figure 1As shown, this utility model discloses a DC bus capacitor charging circuit for a frequency converter, including: a slow charging unit, a controllable fast charging unit, a control signal input unit, a controller (which can use an AT89C52 control chip, or other control chips), and a capacitor charging unit; the input terminals of the slow charging unit and the controllable fast charging unit are both connected to the positive output terminal of the DC power supply in the elevator system, the output terminals of the slow charging unit and the controllable fast charging unit are both connected to the positive terminal of the capacitor charging unit, the output terminal of the capacitor charging unit is grounded, the control terminal of the controllable fast charging unit is connected to the control signal input unit, and the control terminal of the control signal input unit is connected to the output terminal of the controller.

[0019] like Figure 1 As shown, the capacitor charging unit includes: a charging capacitor C1, with the positive terminal of the charging capacitor C1 being the positive terminal and the negative terminal of the charging capacitor C1 being the negative terminal. Of course, the capacitor charging unit may also include other electrical components.

[0020] In this application, the control signal input unit includes a light-emitting part and a first controllable switch part. The positive terminal of the light-emitting part is connected to the first output terminal of a low-voltage power supply, and the negative terminal of the light-emitting part is grounded through the first controllable switch part. The control terminal of the first controllable switch part is the control terminal of the control signal input unit. The first output terminal of the low-voltage power supply outputs a 5V voltage. The light-emitting part is a light-emitting diode.

[0021] Preferably, the controllable fast charging unit includes a second controllable switch section, which, together with the light-emitting section, forms a first optocoupler U1. This allows the light-emitting section to control whether the second controllable switch section is closed, with the light-emitting section and the second controllable switch section positioned opposite each other.

[0022] Preferably, the first optocoupler U1 is a switching transistor type optocoupler. Of course, the first optocoupler U1 can also be other optocoupler types. This application uses a first optocoupler composed of a second controllable switch section and a light-emitting section, which isolates the branch where the light-emitting section is located from the branch where the second controllable switch section is located. Since the voltage connected to the second controllable switch section is higher, while the output voltage of the controller is lower, the controller cannot be connected to a high voltage. Therefore, the light-emitting section and the second controllable switch section are isolated to achieve low voltage connection in the branch where the light-emitting section is located and high voltage connection in the second controllable switch section, so that they do not affect each other and protect the light-emitting section, the first controllable switch section, and the controller.

[0023] In this application, the controllable fast charging unit further includes a diode D1. The anode of diode D1 is the input terminal of the controllable fast charging unit, the cathode of diode D1 is connected to the collector of the second controllable switch, and the emitter of the second controllable switch is the output terminal of the controllable fast charging unit. The addition of diode D1 is to limit the current direction and prevent backflow of current when the capacitor charging unit discharges through the second controllable switch.

[0024] Preferably, the slow charging unit includes a resistor R1, with its first end serving as the input terminal and its second end serving as the output terminal. Using a resistor R1 with a relatively large resistance value allows for a smaller current flow through the slow charging unit, thus enabling slow charging of the capacitor-type charging unit under normal circumstances. Of course, other resistors with larger resistance values ​​can also be used to charge the capacitor-type charging unit.

[0025] Preferably, the first controllable switch is a switching transistor Q1. The base of the switching transistor Q1 is the control terminal of the first controllable switch, the collector of the switching transistor Q1 is connected to the negative terminal of the light-emitting part, and the emitter of the switching transistor Q1 is grounded. The capacitor charging unit uses an NPN type switching transistor, which enables the first controllable switch to close when the controller outputs a high level. At this time, the light-emitting part is turned on and emits light. The second controllable switch closes, and the controllable fast charging unit is turned on. The controllable fast charging unit has a small resistance and provides a high current to the capacitor charging unit, realizing fast charging of the capacitor charging unit. Thus, the charging speed of the capacitor charging unit can be controlled under the control of the controller.

[0026] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model and are not intended to limit it. Although this utility model has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this utility model without departing from the spirit and scope of the technical solutions of this utility model, and all such modifications or substitutions should be covered within the scope of the claims of this utility model.

Claims

1. A capacitor charging circuit for a DC bus of a frequency converter, characterized in that include: Slow charging unit, controllable fast charging unit, control signal input unit, controller, and capacitor charging unit; The input terminals of the slow charging unit and the controllable fast charging unit are both connected to the positive output terminal of the DC power supply in the elevator system. The output terminals of the slow charging unit and the controllable fast charging unit are both connected to the positive terminal of the capacitor charging unit. The output terminal of the capacitor charging unit is grounded. The control terminal of the controllable fast charging unit is connected to the controlled signal input unit for control. The control terminal of the control signal input unit is connected to the controller output terminal.

2. The frequency converter DC bus capacitor charging circuit of claim 1, wherein, The control signal input unit includes a light-emitting part and a first controllable switch part. The positive terminal of the light-emitting part is connected to the first output terminal of a low-voltage power supply, and the negative terminal of the light-emitting part is grounded through the first controllable switch part. The control terminal of the first controllable switch part is the control terminal of the control signal input unit.

3. The frequency converter DC bus capacitor charging circuit of claim 2, wherein, The controllable fast charging unit is provided with a second controllable switch section, which together with the light-emitting section forms a first optocoupler U1.

4. The frequency inverter DC bus capacitor charging circuit of claim 3, wherein, The first optocoupler U1 is a switching transistor type optocoupler.

5. The frequency inverter DC bus capacitor charging circuit of claim 4, wherein, The controllable fast charging unit also includes a diode D1, the anode of which is the input terminal of the controllable fast charging unit, the cathode of which is connected to the collector of the second controllable switch, and the emitter of the second controllable switch is the output terminal of the controllable fast charging unit.

6. The inverter DC bus capacitor charging circuit according to claim 5, characterized in that, The slow charging unit includes: resistor R1, the first end of resistor R1 is the input terminal of the slow charging unit, and the second end of resistor R1 is the output terminal of the slow charging unit.

7. The frequency inverter DC bus capacitor charging circuit of claim 6, wherein, The first controllable switch section is a switching transistor Q1. The base of the switching transistor Q1 is the control terminal of the first controllable switch section, the collector of the switching transistor Q1 is connected to the negative terminal of the light-emitting section, and the emitter of the switching transistor Q1 is grounded.

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